The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricat...The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.展开更多
Lithium-sulfur battery(LSB)has brought much attention and concern because of high theoretical specific capacity and energy density as one of main competitors for next-generation energy storage systems.The widely comme...Lithium-sulfur battery(LSB)has brought much attention and concern because of high theoretical specific capacity and energy density as one of main competitors for next-generation energy storage systems.The widely commercial application and development of LSB is mainly hindered by serious“shuttle effect”of lithium polysulfides(Li PSs),slow reaction kinetics,notorious lithium dendrites,etc.In various structures of LSB materials,array structured materials,possessing the composition of ordered micro units with the same or similar characteristics of each unit,present excellent application potential for various secondary cells due to some merits such as immobilization of active substances,high specific surface area,appropriate pore sizes,easy modification of functional material surface,accommodated huge volume change,enough facilitated transportation for electrons/lithium ions,and special functional groups strongly adsorbing Li PSs.Thus many novel array structured materials are applied to battery for tackling thorny problems mentioned above.In this review,recent progresses and developments on array structured materials applied in LSBs including preparation ways,collaborative structural designs based on array structures,and action mechanism analyses in improving electrochemical performance and safety are summarized.Meanwhile,we also have detailed discussion for array structured materials in LSBs and constructed the structure-function relationships between array structured materials and battery performances.Lastly,some directions and prospects about preparation ways,functional modifications,and practical applications of array structured materials in LSBs are generalized.We hope the review can attract more researchers'attention and bring more studying on array structured materials for other secondary batteries including LSB.展开更多
This study presents the thermal comfort and hygrothermal performance of building envelope of the first certified passive single-family detached house in Estonia.Temperature and humidity conditions were measured from d...This study presents the thermal comfort and hygrothermal performance of building envelope of the first certified passive single-family detached house in Estonia.Temperature and humidity conditions were measured from different rooms and building envelopes.This article presents analysis of measurement results during the first year after construction.Results showed high room temperature,achieved mainly due to large windows with southern exposure and the small heat loss of the building envelope.High indoor temperature decreased the indoor RH(relative humidity)to quite low levels.Even the RH was low,the moisture excess was high indicating that the design of PH(passive houses)indoor humidity loads cannot be decreased.Humidity in the externally insulated cross-laminated timber panels was observed to be high,caused by drying out of the constructional moisture and the high diffusion resistance of the wood fibre sheathing board.That caused water vapour condensation and risk for mould growth.In conclusion,while planning buildings with high-energy efficiency,more focused attention should be paid to the performance of the building service systems and moisture safety already in the preliminary stages of design.展开更多
A significant proportion of urban crashes,especially serious and fatal crashes,occur at traffic signals.Many of the black-spots in both Australia and New Zealand cities occur at high volume and/or high-speed traffic s...A significant proportion of urban crashes,especially serious and fatal crashes,occur at traffic signals.Many of the black-spots in both Australia and New Zealand cities occur at high volume and/or high-speed traffic signals.Given this,crash reduction studies often focus on the major signalised intersections.However,there is limited information that links the phasing configuration,degree of saturation and overall cycle time to crashes.While a number of analysis tools are available for assessing the efficiency of intersections,there are very few tools that can assist engineers in assessing the safety effects of intersection upgrades and new intersections.Safety performance functions have been developed to help quantify the safety impact of various traffic signal phasing configurations and level of intersection congestion at low and high-speed traffic signals in New Zealand and Australia.Data from 238 signalised intersection sites in Auckland,Wellington,Christchurch,Hamilton,Dunedin and Melbourne was used to develop crash prediction models for key crash-causing movements at traffic signals.Different variables(road features)effect each crash type.The models indicate that the safety of intersections can be improved by longer cycle times and longer lost inter-green times,especially all-red time,using fully protected right turns and by extending the length of right turn bays.The exception is at intersections with lots of pedestrians where shorter cycle times are preferred as pedestrian crashes increase with longer wait times.A number of factors have a negative impact on safety including,free left turns,more approach lanes,intersection arms operating near or over capacity in peak periods and higher speed limits.展开更多
In order to improve the lightning protection performance of transmission lines, lightning protection management has been divided into every tower that lightning protection performance has been evaluated respectively. ...In order to improve the lightning protection performance of transmission lines, lightning protection management has been divided into every tower that lightning protection performance has been evaluated respectively. According to factors such as landform, span, tower type, grounding resistance, isolator type, and so on, relative ratio of tripping operation of every tower in the line has been calculated to evaluate its lightning protection safety performance, it is beneficial to operation maintenance and lightning reconstruction of transmission lines.展开更多
3-nitro-1,2,4-triazol-5-one(NTO)is the main component of insensitive munitions(IM)formulation because of its outstanding insensitive properties.In this paper,a series of NTO/HMX-based compositeexplosives were prepared...3-nitro-1,2,4-triazol-5-one(NTO)is the main component of insensitive munitions(IM)formulation because of its outstanding insensitive properties.In this paper,a series of NTO/HMX-based compositeexplosives were prepared and characterized.The study focuses on the effect of NTO on the perfommance of the formulations,especially the safety performance.The results revealed that the mechanical sensi-tivity of fomulations was associated with NTO content,as well as the thermal conductivity,specific heat capacity and Arrhenius parameters.Then,the high amount of NTO using in formulation was proved to be helpful for NTO/HMX-based formulation to exhibit good thermal safety.Besides,by accelerating rate calorimeter(ARC)and a modified cook-off equipment,the pressure and pressure rise rate were proved as the important indicator for judging the thermal safety performance in confined spaces.Finally,the numerical simulation was used as a credible method for predicting the respond temperature of cook-off experiment.展开更多
With the emergence of some solid electrolytes(SSEs)with high ionic conductivity being comparable to liquid electrolytes,solid-state lithium-sulfur batteries(SSLSBs)have been widely regarded as one of the most promisin...With the emergence of some solid electrolytes(SSEs)with high ionic conductivity being comparable to liquid electrolytes,solid-state lithium-sulfur batteries(SSLSBs)have been widely regarded as one of the most promising candidates for the next generation of power generation energy storage batteries,and have been extensively researched.Though many fundamental and technological issues still need to be resolved to develop commercially viable technologies,SSLSBs using SSEs are expected to address the present limitations and achieve high energy and power density while improving safety,which is very attractive to large-scale energy storage systems.SSLSBs have been developed for many years.However,there are few systematic discussions related to the working mechanism of action of various electrolytes in SSLSBs and the defects and the corresponding solutions of various electrolytes.To fill this gap,it is very meaningful to review the recent progress of SSEs in SSLSBs.In this review,we comprehensively investigate and summarize the application of SSEs in LSBs to determine the differences which still exist between current progresses and real-world requirements,and comprehensively describe the mechanism of action of SSLSBs,including lithium-ion transport,interfacial contact,and catalytic conversion mechanisms.More importantly,the selection of solid electrolyte materials and the novel design of structures are reviewed and the properties of various SSEs are elucidated.Finally,the prospects and possible future research directions of SSLSBs including designing high electronic/ionic conductivity for cathodes,optimizing electrolytes and developing novel electrolytes with excellent properties,improving electrode/-electrolyte interface stability and enhancing interfacial dynamics between electrolyte and anode,using more advanced test equipment and characterization techniques to analyze conduction mechanism of Li^(+)in SSEs are presented.It is hoped that this review can arouse people’s attention and enlighten the development of functional materials and novel structures of SSEs in the next step.展开更多
The numerical simulation for a new type of precast concrete barrier for viaducts is carried out systematically.To obtain an accurate representation of the damage state of the concrete barrier under the impact of a veh...The numerical simulation for a new type of precast concrete barrier for viaducts is carried out systematically.To obtain an accurate representation of the damage state of the concrete barrier under the impact of a vehicle,a stochastic damage-plasticity model of the concrete is adopted in the finite element model.Meanwhile,a simplified mathematical model of the impact between vehicles and the concrete barrier was established and the input energy was converted to the impact load to facilitate the investigation of the safety performance of the concrete barriers.On this basis,a refined finite element(FE)model of a precast concrete barrier was developed.The impact locations,impact load,boundary constraints,and reinforcement types were used as variables and the dynamic response of the precast concrete barrier was systematically analyzed under 36 working conditions.The simulated results indicated that the damage state of the concrete barrier and the stress of the reinforcing bars were accurately and quantitatively reflected.According to the computed results,some suggestions were put forward for selecting the appropriate reinforcement type of the precast concrete barrier and the connection between the superstructure and foundation.展开更多
Road safety performance function(SPF) analysis using data-driven and nonparametric methods, especially recent developed deep learning approaches, has gained increasing achievements. However, due to the learning mechan...Road safety performance function(SPF) analysis using data-driven and nonparametric methods, especially recent developed deep learning approaches, has gained increasing achievements. However, due to the learning mechanisms are hidden in a"black box" in deep learning, traffic features extraction and intelligent importance analysis are still unsolved and hard to generate.This paper focuses on this problem using a deciphered version of deep neural networks(DNN), one of the most popular deep learning models. This approach builds on visualization, feature importance and sensitivity analysis, can evaluate the contributions of input variables on model's "black box" feature learning process and output decision. Firstly, a visual feature importance(Vi FI) method that describes the importance of input features is proposed by adopting diagram and numerical-analysis. Secondly,by observing the change of weights using Vi FI on unsupervised training and fine-tuning of DNN, the final contributions of input features are calculated according to importance equations for both steps that we proposed. Sequentially, a case study based on a road SPF analysis is demonstrated, using data collected from a major Canadian highway, Highway 401. The proposed method allows effective deciphering of the model's inner workings and allows the significant features to be identified and the bad features to be eliminated. Finally, the revised dataset is used in crash modeling and vehicle collision prediction, and the testing result verifies that the deciphered and revised model achieves state-of-theart performance.展开更多
In order to achieve the old fence of reuse, improve the safety performance of guardrail, barrier structure does not meet the requirements, make full use of the old concrete guardrail on the basis of heightening, throu...In order to achieve the old fence of reuse, improve the safety performance of guardrail, barrier structure does not meet the requirements, make full use of the old concrete guardrail on the basis of heightening, through computer simulation experiment were analyzed, and optimization design, through the real car collision test, make the concrete guardrail after heightening structure satisfies the requirement of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">safety performance of current specification. The results show that the protective performance of the two guardrail schemes meets the requirements of the current guardrail evaluation standards through the computer simulation experiment. Through the optimized design of scheme 1, the actual car crash test proves that the enhanced structure of Minhua TYPE II concrete guardrail can meet the requirements of safety performance evaluation. The research results provide an important basis for the transformation of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">guardrail and the revision of the current design of expressway in China.展开更多
Total temporomandibular joint(TMJ)replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements.Several stock and custom-made TMJ impl...Total temporomandibular joint(TMJ)replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements.Several stock and custom-made TMJ implants have been made available;however,retrospective and comparative studies were unable to find significant differences between the two types of solutions.The introduction of additive manufacturing(AM)techniques in medical practice allows for a greater freedom of design and a higher degree of device customisation.The combination of AM with structural optimisation may streamline development and provide the key for fabricating biomechanic ally enhanced TMJ implants.In this study,structural optimis ation techniques were applied to develop and numerically validate a patient-specific TMJ implant.The biomechanical behaviour of each intermediate TMJ design was assessed under four different nominal and maximum biting tasks using finite element analyses.In addition,a new set of metrics were proposed to compare each design regarding biomechanical performance and implant safety.The results suggest that 55-82%of the natural/intact strain patterns can be recovered with the finally selected TMJ implant.This represents an increase of 15%in biomechanical performance for incisor biting,15%for right molar biting,17%for left molar biting and a decrease of 2%for left group biting compared with the initial design.The results also suggest that load transfer at the proximal ramus reduces the implant’s impact on the mandible’s strain patterns.Finally,structural optimisation allows for a volume reduction of up to 44%with a minimum loss of implant safety and biomechanical performance.展开更多
A number of studies conducted in Kenya </span><span style="font-family:Verdana;">and </span><span style="font-family:Verdana;">internationally indicate</span>...A number of studies conducted in Kenya </span><span style="font-family:Verdana;">and </span><span style="font-family:Verdana;">internationally indicate</span><span style="font-family:Verdana;">d</span><span style="font-family:""><span style="font-family:Verdana;"> that most of the construction firms and contractors do not seem to strictly observe safety administration in construction industry, hence compromised performance at implementation stage of projects and even later in the post implementation or post-delivery stage. The study aimed to examine the influence of contractors’ safety record on road performance. This is to create better understanding of how the safety record of contractors could either positively or negatively influence performance of roads during post-delivery stage. The study used both descriptive survey research design and correlation design based on a pragmatic mixed method approach. Through stratified sampling and proportionate sampling, a sample of 210 was drawn from a population of 460 comprising of registered contractors and Public Service Vehicles (PSV) drivers within Nairobi County in Kenya. Questionnaires were distributed using simple random sampling. The questionnaires returned were 153 in total representing 72.8% of all questionnaires distributed to the respondents. Data was descriptively analyzed using percentages, frequencies, means and standard deviations for measuring central tendency and variability. Inferential analysis was done by use of correlation and regression. The descriptive analysis revealed that safety policy management system, insurance policy, and adequacy of standards in addressing safety outcome are to some extent practiced and adhered to. However, compliance behavior to safety procedures is still weak and requires improvement. The null hypothesis was tested and the results obtained from a simple linear regression indicated that, R = 0.657, R</span><sup><span style="font-size:12px;font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> = 0.431, B = 0.359, t = 10.703, F (1,151) = 114.558, p = 0.000 < 0.05. This means that contractors’ safety record has a strong positive and significant relationship with road performance and that 43.1% of variation in performance is explained by safety record. This study recommends that contractors’ safety record should be part</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> and parcel of the evaluation criteria used in selection of a suitable road contractor to ensure road performance is achieved even after construction is completed. The study is significant in that it contributes to the body of knowledge by providing empirical data on the need for safety procedures in urban road construction and beyond.展开更多
Background: Beflex is an active fixation atrial and ventricular lead with a retractable screw;X-Fine is a passive fixation ventricular lead. These two bradycardia lead models were evaluated in the FINE study, an obser...Background: Beflex is an active fixation atrial and ventricular lead with a retractable screw;X-Fine is a passive fixation ventricular lead. These two bradycardia lead models were evaluated in the FINE study, an observational prospective trial conducted in France and Spain. Methods: Patients enlisted for pacemaker or defibrillator implants were enrolled. The primary objective was to assess acute dislodgement rates at the 3-month follow-up visit. Safety and electrical performances of the leads were assessed in acute conditions at implant and at the follow-up visit up to three months later. A handling questionnaire was submitted to implanting investigators immediately after implant. Results: A total of 2254 patients were enrolled in 95 centers;investigators implanted 1153 active atrial leads, mainly in the right atrium;1021 active right ventricular leads, mainly in the septum and 712 passive right ventricular leads, mainly in the apex. After a mean follow-up of 54.9 ± 37.6 days, dislodgement rates were 1.0% and 1.6% for atrial and ventricular active, and 3.2% for ventricular passive leads. No unexpected adverse reactions were observed during the course of the study and the electrical performances at implant and follow-up visits remained within normal ranges. Overall, most investigators (84%) rated leads’ handling as superior (better or best) to what observed with other bradycardia leads. Conclusion: Different bradycardia leads showed a dislodgement rate of 1.0% and 1.6% for atrial and ventricular active leads, and 3.2% for ventricular passive leads, at 3-month follow-up. Acute safety and electrical performances were within expected ranges and very good handling performances were observed.展开更多
With the gradual increase of car ownership in China and the continuous expansion of travel radius,traffic accidents caused by car safety are also increasing.As far as automobile safety itself is concerned,its evaluati...With the gradual increase of car ownership in China and the continuous expansion of travel radius,traffic accidents caused by car safety are also increasing.As far as automobile safety itself is concerned,its evaluation method is constantly evolving,but the safety of automobile textiles,which is an important part of it,is still in its infancy.The article starts from the factors that affect the safety performance of automobiles such as automobile safety theory,vehicle ergonomics and automobile textile performance.Then,the methods of expert investigation,analytic hierarchy process,fuzzy comprehensive evaluation and data analysis are used.In this way,we obtain a grade set for a multi-level index system and determine the weight of each index.Finally,we establish a comprehensive evaluation system for safety of the automobile textiles and select parameters under extreme conditions to verify the system,which proves to be effective and feasible.展开更多
A generalized mathematical model of human body current threshold for perception was established and the current flowing through human body could be arbitrary cyclical waveforms.The relationship between human body curr...A generalized mathematical model of human body current threshold for perception was established and the current flowing through human body could be arbitrary cyclical waveforms.The relationship between human body current threshold for perception and current frequency, true root mean square(RMS) value and influence factor was described.A test system was established based on electroencephalogram(EEG) to study the relationship between human body current threshold for perception and current waveform, frequency and duty cycle so that the data could be obtained objectively and reliably.At least 850 groups of current threshold for perception and 16-lead EEGs were acquired.The theoretical analysis are verified by experimental data, and an amendment proposal on leakage current evaluation limits specified in International Electro-Technical Commission(IEC) standards is suggested.展开更多
Background: The Occupational Safety and Health Council(OSHC) is committed to improve the safety performance of the high risk construction industry.In the past three years,about 40% of the fatal accidents in the constr...Background: The Occupational Safety and Health Council(OSHC) is committed to improve the safety performance of the high risk construction industry.In the past three years,about 40% of the fatal accidents in the construction industry were related to Renovation,Maintenance,Alteration and Addition(RMAA).Due to the poor safety record,some of the RMAA contractors have difficulty in obtaining the Employees' Compensation Insurance(ECI) cover in the market,or if they could obtain the ECI,the premium rate would be exceedingly high.In view of this,the OSHC,the Labour Department jointly launched"OSH Star Enterprise-Pilot Scheme on Safety Accreditation for the RMAA Industry",which prompts the industry to take practicable safety measures to improve the safety of working environment and reduce occupational injuries.The program also helps the stakeholders and insurers to identify safety-conscious contractors and thereby provide them with a favourable premium rate under the Employees' Compensation Insurance Residual Scheme(ECIRS).Objectives: The OSHC launches the Pilot Scheme to improve the safety performance of the RMAA industry through providing safety training,subsidizing enterprise to purchase safety equipment and providing safety audit.We also use financial incentive to encourage RMAA enterprises to join the Pilot Scheme-for those who are accredited as "OSH Star Enterprise"could receive a premium discount from the ERIRS when obtaining the ECI.The scheme also differentiates those safety-conscious and law-abiding enterprises from the poor performers,which helps the industry and public identifying the RMAA contractors who pay attention to work safety.Methods: The Pilot Scheme targets RMAA enterprises that employ less than 50 employees in Hong Kong.A three-pronged approach is used to improve the safety performance of the RMAA industry: the Pilot Scheme provides(1) financial support for the RMAA contractors to buy a transportable temporary anchor device and full body safety harness and its anchor system;(2) safety training on RMAA work safety and safety & health supervisor course;and(3) safety audit.Results: Enterprises that successfully pass the safety audit and satisfied the Scheme requirements will be accredited as"OSH Star Enterprise",which will be valid for two years.These enterprises can also be upgraded to"OSH Gold Star Enterprise"based on their continuous improvement in safety performance.OSHC will set up a register of OSH-accredited enterprises in RMAA works for reference of the public to facilitate their choosing of accredited contractors.The Employees' Compensation Insurance Residual Scheme Bureau will provide privileged premium rate for enterprises with OSH accreditation."OSH Star Enterprise"could enjoy 40% discounts when joining their insurance scheme.For example,a skilled worker's annual premium can be reduced by about HK $ 36,000.While,the "OSH Gold Star Enterprise"could enjoy 50% discounts when joining their insurance scheme,which means a skilled worker's annual premium can be reduced up to HK $ 45,000.Achievements: This Pilot Scheme offers practical assistance as well as attractive financial incentives for the RMAA industry to improve their safety performance.The Employees'Compensation Insurance Residual Scheme provides premium discounts for enterprises that have a good safety record.It provides incentive for RMAA contractors to actively participate in the Pilot Scheme.The Scheme demonstrates that by providing a safe working environment and appropriate personal protective equipment to workers,the enterprise not only helps to reduce the accident rate of the industry but also receive an economic return.The Pilot Scheme bridges stakeholders of RMAA industry,the government and the insurance industry creating an "all-win"situation.This partnership approach to prevent injuries and accidents in the construction industry could be an effective model for other industries.展开更多
The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper.The influences of their different roles in model construction of str...The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper.The influences of their different roles in model construction of structural topology optimization are also discussed.Furthermore,two structural topology optimization models,optimizing a performance index under the limitation of an economic index,represented by the minimum compliance with a volume constraint(MCVC)model,and optimizing an economic index under the limitation of a performance index,represented by the minimum weight with a displacement constraint(MWDC)model,are presented.Based on a comparison of numerical example results,the conclusions can be summarized as follows:(1)under the same external loading and displacement performance conditions,the results of the MWDC model are almost equal to those of the MCVC model;(2)the MWDC model overcomes the difficulties and shortcomings of the MCVC model;this makes the MWDC model more feasible in model construction;(3)constructing a model of minimizing an economic index under the limitations of performance indexes is better at meeting the needs of practical engineering problems and completely satisfies safety and economic requirements in mechanical engineering,which have remained unchanged since the early days of mechanical engineering.展开更多
This paper proposes a cruise control system(CCS)to improve an electric vehicle's range,which is a significant hurdle in market penetration of electric vehicles.A typical driver or a conventional adaptive cruise co...This paper proposes a cruise control system(CCS)to improve an electric vehicle's range,which is a significant hurdle in market penetration of electric vehicles.A typical driver or a conventional adaptive cruise control(ACC)controls an electric vehicle(EV)such that it follows a lead vehicle or drives close to the speed limit.This driving behaviour may cause the EV to cruise significantly above the average traffic speed.It may later require the EV to slow down due to the traffic ripples,wasting a part of the EV's kinetic energy.In addition,the EV will also waste higher speed dependent dissipative energies,which are spent to overcome the aerodynamic drag force and rolling resistance.This paper proposes a CCS to address this issue.The proposed CCS controls an EV's speed such that it prevents the vehicle from speeding significantly above the average traffic speed.In addition,it maintains a safe inter-vehicular distance from the lead vehicle.The design and simulation analysis of the proposed CCS were in a MATLAB simulation environment.The simulation environment includes an energy consumption model of an EV,which was developed using data collected from an electric bus operation in London.In the simulation analysis,the proposed system reduced the EV's energy consumption by approximately 36.6%in urban drive cycles and 15.4%in motorway drive cycles.Finally,the experimental analysis using a Nissan e-NV200on two urban routes showed approximately 30.8%energy savings.展开更多
Diamond interchanges are frequently used where a freeway intersects a two-way surface street. Most of the techniques to evaluate the performance of diamond interchanges rely on the Highway Capacity Manual (HCM), simul...Diamond interchanges are frequently used where a freeway intersects a two-way surface street. Most of the techniques to evaluate the performance of diamond interchanges rely on the Highway Capacity Manual (HCM), simulation, Automated Traffic Signal Performance Measures (ATSPMs), and historical crash data. HCM and simulation techniques require on-site data collection to obtain models’ inputs. ATSPMs need high-resolution controller event data acquired from roadway sensing equipment. Safety studies typically need 3 to 5 years of crash data to provide statistically significant results. This study utilizes commercially available connected vehicle (CV) data to assess the performance and operation of a three- and four-phase diamond interchange located in Indianapolis, Indiana, and Dallas, Texas, respectively. Over 92,000 trajectories and 1,400,000 GPS points are analyzed from August 2020 weekdays CV data. Trajectories are linear-referenced to generate Purdue Probe Diagrams (PPDs) from which arrivals on green (AOG), split failures, downstream blockage, and movement-based control delay are estimated. In addition, an extension of the PPD is presented that characterizes the complete journey of a vehicle travelling through both signals of the diamond interchange. This enhanced PPD is a significant contribution as it provides an analytical framework and graphical summary of the operational characteristics of how the external movements traverse the entire system. The four-phase control showed high internal progression (99% AOG) compared to the moderate internal progression of the three-phase operation (64% AOG). This is consistent with the design objectives of three- and four-phase control models, but historically these quantitative AOG measures were not possible to obtain with just detector data. Additionally, a graphical summary that illustrates the spatial distribution of hard-braking and hard-acceleration events is also provided. The presented techniques can be used by any agency to evaluate the performance of their diamond interchanges without on-site data collection or capital investments in sensing infrastructure.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 22275173)the Open Project of State Key Laboratory of Environment-friendly Energy Materials (Grant No. 22kfhg10)。
文摘The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.
基金This work was supported by the National Natural Science Foundation of China(52203066,51973157,61904123)the Tianjin Natural Science Foundation(18JCQNJC02900)+3 种基金the National innovation and entrepreneurship training program for college students(202310058007)the Tianjin Municipal college students’innovation and entrepreneurship training program(202310058088)the Science&Technology Development Fund of Tianjin Education Commission for Higher Education(Grant No.2018KJ196)the State Key Laboratory of Membrane and Membrane Separation,Tiangong University.
文摘Lithium-sulfur battery(LSB)has brought much attention and concern because of high theoretical specific capacity and energy density as one of main competitors for next-generation energy storage systems.The widely commercial application and development of LSB is mainly hindered by serious“shuttle effect”of lithium polysulfides(Li PSs),slow reaction kinetics,notorious lithium dendrites,etc.In various structures of LSB materials,array structured materials,possessing the composition of ordered micro units with the same or similar characteristics of each unit,present excellent application potential for various secondary cells due to some merits such as immobilization of active substances,high specific surface area,appropriate pore sizes,easy modification of functional material surface,accommodated huge volume change,enough facilitated transportation for electrons/lithium ions,and special functional groups strongly adsorbing Li PSs.Thus many novel array structured materials are applied to battery for tackling thorny problems mentioned above.In this review,recent progresses and developments on array structured materials applied in LSBs including preparation ways,collaborative structural designs based on array structures,and action mechanism analyses in improving electrochemical performance and safety are summarized.Meanwhile,we also have detailed discussion for array structured materials in LSBs and constructed the structure-function relationships between array structured materials and battery performances.Lastly,some directions and prospects about preparation ways,functional modifications,and practical applications of array structured materials in LSBs are generalized.We hope the review can attract more researchers'attention and bring more studying on array structured materials for other secondary batteries including LSB.
基金supported by the European Union through the European Regional Development Fundthe“Reducing the Environmental Impact of Buildings through Improvements of Energy Performance,AR12059”(financed by SA Archimedes)IUT1-15 project“Nearly-Zero Energy Solutions and Their Implementation on Deep Renovation of Buildings”(financed by the Estonian Research Council).
文摘This study presents the thermal comfort and hygrothermal performance of building envelope of the first certified passive single-family detached house in Estonia.Temperature and humidity conditions were measured from different rooms and building envelopes.This article presents analysis of measurement results during the first year after construction.Results showed high room temperature,achieved mainly due to large windows with southern exposure and the small heat loss of the building envelope.High indoor temperature decreased the indoor RH(relative humidity)to quite low levels.Even the RH was low,the moisture excess was high indicating that the design of PH(passive houses)indoor humidity loads cannot be decreased.Humidity in the externally insulated cross-laminated timber panels was observed to be high,caused by drying out of the constructional moisture and the high diffusion resistance of the wood fibre sheathing board.That caused water vapour condensation and risk for mould growth.In conclusion,while planning buildings with high-energy efficiency,more focused attention should be paid to the performance of the building service systems and moisture safety already in the preliminary stages of design.
文摘A significant proportion of urban crashes,especially serious and fatal crashes,occur at traffic signals.Many of the black-spots in both Australia and New Zealand cities occur at high volume and/or high-speed traffic signals.Given this,crash reduction studies often focus on the major signalised intersections.However,there is limited information that links the phasing configuration,degree of saturation and overall cycle time to crashes.While a number of analysis tools are available for assessing the efficiency of intersections,there are very few tools that can assist engineers in assessing the safety effects of intersection upgrades and new intersections.Safety performance functions have been developed to help quantify the safety impact of various traffic signal phasing configurations and level of intersection congestion at low and high-speed traffic signals in New Zealand and Australia.Data from 238 signalised intersection sites in Auckland,Wellington,Christchurch,Hamilton,Dunedin and Melbourne was used to develop crash prediction models for key crash-causing movements at traffic signals.Different variables(road features)effect each crash type.The models indicate that the safety of intersections can be improved by longer cycle times and longer lost inter-green times,especially all-red time,using fully protected right turns and by extending the length of right turn bays.The exception is at intersections with lots of pedestrians where shorter cycle times are preferred as pedestrian crashes increase with longer wait times.A number of factors have a negative impact on safety including,free left turns,more approach lanes,intersection arms operating near or over capacity in peak periods and higher speed limits.
文摘In order to improve the lightning protection performance of transmission lines, lightning protection management has been divided into every tower that lightning protection performance has been evaluated respectively. According to factors such as landform, span, tower type, grounding resistance, isolator type, and so on, relative ratio of tripping operation of every tower in the line has been calculated to evaluate its lightning protection safety performance, it is beneficial to operation maintenance and lightning reconstruction of transmission lines.
基金The authors are grateful to the National Defense Foundation of China(3090021322001,3090020221912,3090021211903.)for financial support of this work.
文摘3-nitro-1,2,4-triazol-5-one(NTO)is the main component of insensitive munitions(IM)formulation because of its outstanding insensitive properties.In this paper,a series of NTO/HMX-based compositeexplosives were prepared and characterized.The study focuses on the effect of NTO on the perfommance of the formulations,especially the safety performance.The results revealed that the mechanical sensi-tivity of fomulations was associated with NTO content,as well as the thermal conductivity,specific heat capacity and Arrhenius parameters.Then,the high amount of NTO using in formulation was proved to be helpful for NTO/HMX-based formulation to exhibit good thermal safety.Besides,by accelerating rate calorimeter(ARC)and a modified cook-off equipment,the pressure and pressure rise rate were proved as the important indicator for judging the thermal safety performance in confined spaces.Finally,the numerical simulation was used as a credible method for predicting the respond temperature of cook-off experiment.
基金supported by the National Natural Science Foundation of China(52203066,51973157,51673148,51678411)the Science and Technology Plans of Tianjin,China(19PTSYJC00010)+3 种基金the China Postdoctoral Science Foundation Grant(2019M651047)the Tianjin Research Innovation Project for Postgraduate Students,China(2020YJSB062)the Tianjin Municipal college student’innovation and entrepreneurship training program,China(202110058052)the National innovation and entrepreneurship training program for college students,China(202110058017)。
文摘With the emergence of some solid electrolytes(SSEs)with high ionic conductivity being comparable to liquid electrolytes,solid-state lithium-sulfur batteries(SSLSBs)have been widely regarded as one of the most promising candidates for the next generation of power generation energy storage batteries,and have been extensively researched.Though many fundamental and technological issues still need to be resolved to develop commercially viable technologies,SSLSBs using SSEs are expected to address the present limitations and achieve high energy and power density while improving safety,which is very attractive to large-scale energy storage systems.SSLSBs have been developed for many years.However,there are few systematic discussions related to the working mechanism of action of various electrolytes in SSLSBs and the defects and the corresponding solutions of various electrolytes.To fill this gap,it is very meaningful to review the recent progress of SSEs in SSLSBs.In this review,we comprehensively investigate and summarize the application of SSEs in LSBs to determine the differences which still exist between current progresses and real-world requirements,and comprehensively describe the mechanism of action of SSLSBs,including lithium-ion transport,interfacial contact,and catalytic conversion mechanisms.More importantly,the selection of solid electrolyte materials and the novel design of structures are reviewed and the properties of various SSEs are elucidated.Finally,the prospects and possible future research directions of SSLSBs including designing high electronic/ionic conductivity for cathodes,optimizing electrolytes and developing novel electrolytes with excellent properties,improving electrode/-electrolyte interface stability and enhancing interfacial dynamics between electrolyte and anode,using more advanced test equipment and characterization techniques to analyze conduction mechanism of Li^(+)in SSEs are presented.It is hoped that this review can arouse people’s attention and enlighten the development of functional materials and novel structures of SSEs in the next step.
基金supported by the Green Science Architecture Industry Development Co.,Ltd.,Guizhou,551400,China.XL Gao received the grant,http://www.gzslzkj.com.
文摘The numerical simulation for a new type of precast concrete barrier for viaducts is carried out systematically.To obtain an accurate representation of the damage state of the concrete barrier under the impact of a vehicle,a stochastic damage-plasticity model of the concrete is adopted in the finite element model.Meanwhile,a simplified mathematical model of the impact between vehicles and the concrete barrier was established and the input energy was converted to the impact load to facilitate the investigation of the safety performance of the concrete barriers.On this basis,a refined finite element(FE)model of a precast concrete barrier was developed.The impact locations,impact load,boundary constraints,and reinforcement types were used as variables and the dynamic response of the precast concrete barrier was systematically analyzed under 36 working conditions.The simulated results indicated that the damage state of the concrete barrier and the stress of the reinforcing bars were accurately and quantitatively reflected.According to the computed results,some suggestions were put forward for selecting the appropriate reinforcement type of the precast concrete barrier and the connection between the superstructure and foundation.
基金supported by the National Science and Engineering Research Council of Canada(NSERC)Ontario Research Fund–Research Excellence(ORF-RE)+3 种基金the Ministry of Transportation Ontario(MTO)through Its Highway Infrastructure Innovation Funding Program(HIIFP)Beijing Postdoctoral Science Foundation(ZZ-2019-65)Beijing Chaoyang District Postdoctoral Science Foundation(2019ZZ-45)Beijing Municipal Education Commission(KM201811232016)。
文摘Road safety performance function(SPF) analysis using data-driven and nonparametric methods, especially recent developed deep learning approaches, has gained increasing achievements. However, due to the learning mechanisms are hidden in a"black box" in deep learning, traffic features extraction and intelligent importance analysis are still unsolved and hard to generate.This paper focuses on this problem using a deciphered version of deep neural networks(DNN), one of the most popular deep learning models. This approach builds on visualization, feature importance and sensitivity analysis, can evaluate the contributions of input variables on model's "black box" feature learning process and output decision. Firstly, a visual feature importance(Vi FI) method that describes the importance of input features is proposed by adopting diagram and numerical-analysis. Secondly,by observing the change of weights using Vi FI on unsupervised training and fine-tuning of DNN, the final contributions of input features are calculated according to importance equations for both steps that we proposed. Sequentially, a case study based on a road SPF analysis is demonstrated, using data collected from a major Canadian highway, Highway 401. The proposed method allows effective deciphering of the model's inner workings and allows the significant features to be identified and the bad features to be eliminated. Finally, the revised dataset is used in crash modeling and vehicle collision prediction, and the testing result verifies that the deciphered and revised model achieves state-of-theart performance.
文摘In order to achieve the old fence of reuse, improve the safety performance of guardrail, barrier structure does not meet the requirements, make full use of the old concrete guardrail on the basis of heightening, through computer simulation experiment were analyzed, and optimization design, through the real car collision test, make the concrete guardrail after heightening structure satisfies the requirement of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">safety performance of current specification. The results show that the protective performance of the two guardrail schemes meets the requirements of the current guardrail evaluation standards through the computer simulation experiment. Through the optimized design of scheme 1, the actual car crash test proves that the enhanced structure of Minhua TYPE II concrete guardrail can meet the requirements of safety performance evaluation. The research results provide an important basis for the transformation of </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">guardrail and the revision of the current design of expressway in China.
基金funding from the Interreg 2 Seas program 2014-2020 co-funded by the European Regional Development Fund under subsidy contract no.2S04-014。
文摘Total temporomandibular joint(TMJ)replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements.Several stock and custom-made TMJ implants have been made available;however,retrospective and comparative studies were unable to find significant differences between the two types of solutions.The introduction of additive manufacturing(AM)techniques in medical practice allows for a greater freedom of design and a higher degree of device customisation.The combination of AM with structural optimisation may streamline development and provide the key for fabricating biomechanic ally enhanced TMJ implants.In this study,structural optimis ation techniques were applied to develop and numerically validate a patient-specific TMJ implant.The biomechanical behaviour of each intermediate TMJ design was assessed under four different nominal and maximum biting tasks using finite element analyses.In addition,a new set of metrics were proposed to compare each design regarding biomechanical performance and implant safety.The results suggest that 55-82%of the natural/intact strain patterns can be recovered with the finally selected TMJ implant.This represents an increase of 15%in biomechanical performance for incisor biting,15%for right molar biting,17%for left molar biting and a decrease of 2%for left group biting compared with the initial design.The results also suggest that load transfer at the proximal ramus reduces the implant’s impact on the mandible’s strain patterns.Finally,structural optimisation allows for a volume reduction of up to 44%with a minimum loss of implant safety and biomechanical performance.
文摘A number of studies conducted in Kenya </span><span style="font-family:Verdana;">and </span><span style="font-family:Verdana;">internationally indicate</span><span style="font-family:Verdana;">d</span><span style="font-family:""><span style="font-family:Verdana;"> that most of the construction firms and contractors do not seem to strictly observe safety administration in construction industry, hence compromised performance at implementation stage of projects and even later in the post implementation or post-delivery stage. The study aimed to examine the influence of contractors’ safety record on road performance. This is to create better understanding of how the safety record of contractors could either positively or negatively influence performance of roads during post-delivery stage. The study used both descriptive survey research design and correlation design based on a pragmatic mixed method approach. Through stratified sampling and proportionate sampling, a sample of 210 was drawn from a population of 460 comprising of registered contractors and Public Service Vehicles (PSV) drivers within Nairobi County in Kenya. Questionnaires were distributed using simple random sampling. The questionnaires returned were 153 in total representing 72.8% of all questionnaires distributed to the respondents. Data was descriptively analyzed using percentages, frequencies, means and standard deviations for measuring central tendency and variability. Inferential analysis was done by use of correlation and regression. The descriptive analysis revealed that safety policy management system, insurance policy, and adequacy of standards in addressing safety outcome are to some extent practiced and adhered to. However, compliance behavior to safety procedures is still weak and requires improvement. The null hypothesis was tested and the results obtained from a simple linear regression indicated that, R = 0.657, R</span><sup><span style="font-size:12px;font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> = 0.431, B = 0.359, t = 10.703, F (1,151) = 114.558, p = 0.000 < 0.05. This means that contractors’ safety record has a strong positive and significant relationship with road performance and that 43.1% of variation in performance is explained by safety record. This study recommends that contractors’ safety record should be part</span></span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> and parcel of the evaluation criteria used in selection of a suitable road contractor to ensure road performance is achieved even after construction is completed. The study is significant in that it contributes to the body of knowledge by providing empirical data on the need for safety procedures in urban road construction and beyond.
文摘Background: Beflex is an active fixation atrial and ventricular lead with a retractable screw;X-Fine is a passive fixation ventricular lead. These two bradycardia lead models were evaluated in the FINE study, an observational prospective trial conducted in France and Spain. Methods: Patients enlisted for pacemaker or defibrillator implants were enrolled. The primary objective was to assess acute dislodgement rates at the 3-month follow-up visit. Safety and electrical performances of the leads were assessed in acute conditions at implant and at the follow-up visit up to three months later. A handling questionnaire was submitted to implanting investigators immediately after implant. Results: A total of 2254 patients were enrolled in 95 centers;investigators implanted 1153 active atrial leads, mainly in the right atrium;1021 active right ventricular leads, mainly in the septum and 712 passive right ventricular leads, mainly in the apex. After a mean follow-up of 54.9 ± 37.6 days, dislodgement rates were 1.0% and 1.6% for atrial and ventricular active, and 3.2% for ventricular passive leads. No unexpected adverse reactions were observed during the course of the study and the electrical performances at implant and follow-up visits remained within normal ranges. Overall, most investigators (84%) rated leads’ handling as superior (better or best) to what observed with other bradycardia leads. Conclusion: Different bradycardia leads showed a dislodgement rate of 1.0% and 1.6% for atrial and ventricular active leads, and 3.2% for ventricular passive leads, at 3-month follow-up. Acute safety and electrical performances were within expected ranges and very good handling performances were observed.
基金National Natural Science Foundation of China(No.11804049)Fundamental Research Funds for the Central Universities,China(No.2232020G-01)+1 种基金Fundamental Research Funds for the Central Universities,China(No.2232019D3-14)Shanghai Technical Standards Projects,China(No.18DZ2205900)。
文摘With the gradual increase of car ownership in China and the continuous expansion of travel radius,traffic accidents caused by car safety are also increasing.As far as automobile safety itself is concerned,its evaluation method is constantly evolving,but the safety of automobile textiles,which is an important part of it,is still in its infancy.The article starts from the factors that affect the safety performance of automobiles such as automobile safety theory,vehicle ergonomics and automobile textile performance.Then,the methods of expert investigation,analytic hierarchy process,fuzzy comprehensive evaluation and data analysis are used.In this way,we obtain a grade set for a multi-level index system and determine the weight of each index.Finally,we establish a comprehensive evaluation system for safety of the automobile textiles and select parameters under extreme conditions to verify the system,which proves to be effective and feasible.
基金Supported by the Ministry of Science and Technology of China (No. NCSTE-2006-JKZX-167)Beijing Key Laboratory (Measurement and Control of Electro-mechanical Systems) (No. 82063005)
文摘A generalized mathematical model of human body current threshold for perception was established and the current flowing through human body could be arbitrary cyclical waveforms.The relationship between human body current threshold for perception and current frequency, true root mean square(RMS) value and influence factor was described.A test system was established based on electroencephalogram(EEG) to study the relationship between human body current threshold for perception and current waveform, frequency and duty cycle so that the data could be obtained objectively and reliably.At least 850 groups of current threshold for perception and 16-lead EEGs were acquired.The theoretical analysis are verified by experimental data, and an amendment proposal on leakage current evaluation limits specified in International Electro-Technical Commission(IEC) standards is suggested.
文摘Background: The Occupational Safety and Health Council(OSHC) is committed to improve the safety performance of the high risk construction industry.In the past three years,about 40% of the fatal accidents in the construction industry were related to Renovation,Maintenance,Alteration and Addition(RMAA).Due to the poor safety record,some of the RMAA contractors have difficulty in obtaining the Employees' Compensation Insurance(ECI) cover in the market,or if they could obtain the ECI,the premium rate would be exceedingly high.In view of this,the OSHC,the Labour Department jointly launched"OSH Star Enterprise-Pilot Scheme on Safety Accreditation for the RMAA Industry",which prompts the industry to take practicable safety measures to improve the safety of working environment and reduce occupational injuries.The program also helps the stakeholders and insurers to identify safety-conscious contractors and thereby provide them with a favourable premium rate under the Employees' Compensation Insurance Residual Scheme(ECIRS).Objectives: The OSHC launches the Pilot Scheme to improve the safety performance of the RMAA industry through providing safety training,subsidizing enterprise to purchase safety equipment and providing safety audit.We also use financial incentive to encourage RMAA enterprises to join the Pilot Scheme-for those who are accredited as "OSH Star Enterprise"could receive a premium discount from the ERIRS when obtaining the ECI.The scheme also differentiates those safety-conscious and law-abiding enterprises from the poor performers,which helps the industry and public identifying the RMAA contractors who pay attention to work safety.Methods: The Pilot Scheme targets RMAA enterprises that employ less than 50 employees in Hong Kong.A three-pronged approach is used to improve the safety performance of the RMAA industry: the Pilot Scheme provides(1) financial support for the RMAA contractors to buy a transportable temporary anchor device and full body safety harness and its anchor system;(2) safety training on RMAA work safety and safety & health supervisor course;and(3) safety audit.Results: Enterprises that successfully pass the safety audit and satisfied the Scheme requirements will be accredited as"OSH Star Enterprise",which will be valid for two years.These enterprises can also be upgraded to"OSH Gold Star Enterprise"based on their continuous improvement in safety performance.OSHC will set up a register of OSH-accredited enterprises in RMAA works for reference of the public to facilitate their choosing of accredited contractors.The Employees' Compensation Insurance Residual Scheme Bureau will provide privileged premium rate for enterprises with OSH accreditation."OSH Star Enterprise"could enjoy 40% discounts when joining their insurance scheme.For example,a skilled worker's annual premium can be reduced by about HK $ 36,000.While,the "OSH Gold Star Enterprise"could enjoy 50% discounts when joining their insurance scheme,which means a skilled worker's annual premium can be reduced up to HK $ 45,000.Achievements: This Pilot Scheme offers practical assistance as well as attractive financial incentives for the RMAA industry to improve their safety performance.The Employees'Compensation Insurance Residual Scheme provides premium discounts for enterprises that have a good safety record.It provides incentive for RMAA contractors to actively participate in the Pilot Scheme.The Scheme demonstrates that by providing a safe working environment and appropriate personal protective equipment to workers,the enterprise not only helps to reduce the accident rate of the industry but also receive an economic return.The Pilot Scheme bridges stakeholders of RMAA industry,the government and the insurance industry creating an "all-win"situation.This partnership approach to prevent injuries and accidents in the construction industry could be an effective model for other industries.
基金supported by the National Natural Science Foundation of China(Grant 11172013)
文摘The objective and constraint functions related to structural optimization designs are classified into economic and performance indexes in this paper.The influences of their different roles in model construction of structural topology optimization are also discussed.Furthermore,two structural topology optimization models,optimizing a performance index under the limitation of an economic index,represented by the minimum compliance with a volume constraint(MCVC)model,and optimizing an economic index under the limitation of a performance index,represented by the minimum weight with a displacement constraint(MWDC)model,are presented.Based on a comparison of numerical example results,the conclusions can be summarized as follows:(1)under the same external loading and displacement performance conditions,the results of the MWDC model are almost equal to those of the MCVC model;(2)the MWDC model overcomes the difficulties and shortcomings of the MCVC model;this makes the MWDC model more feasible in model construction;(3)constructing a model of minimizing an economic index under the limitations of performance indexes is better at meeting the needs of practical engineering problems and completely satisfies safety and economic requirements in mechanical engineering,which have remained unchanged since the early days of mechanical engineering.
基金partly supported by the UK Engineering and Physical Sciences Research Council(EPSRC)(EP/R035199/1)
文摘This paper proposes a cruise control system(CCS)to improve an electric vehicle's range,which is a significant hurdle in market penetration of electric vehicles.A typical driver or a conventional adaptive cruise control(ACC)controls an electric vehicle(EV)such that it follows a lead vehicle or drives close to the speed limit.This driving behaviour may cause the EV to cruise significantly above the average traffic speed.It may later require the EV to slow down due to the traffic ripples,wasting a part of the EV's kinetic energy.In addition,the EV will also waste higher speed dependent dissipative energies,which are spent to overcome the aerodynamic drag force and rolling resistance.This paper proposes a CCS to address this issue.The proposed CCS controls an EV's speed such that it prevents the vehicle from speeding significantly above the average traffic speed.In addition,it maintains a safe inter-vehicular distance from the lead vehicle.The design and simulation analysis of the proposed CCS were in a MATLAB simulation environment.The simulation environment includes an energy consumption model of an EV,which was developed using data collected from an electric bus operation in London.In the simulation analysis,the proposed system reduced the EV's energy consumption by approximately 36.6%in urban drive cycles and 15.4%in motorway drive cycles.Finally,the experimental analysis using a Nissan e-NV200on two urban routes showed approximately 30.8%energy savings.
文摘Diamond interchanges are frequently used where a freeway intersects a two-way surface street. Most of the techniques to evaluate the performance of diamond interchanges rely on the Highway Capacity Manual (HCM), simulation, Automated Traffic Signal Performance Measures (ATSPMs), and historical crash data. HCM and simulation techniques require on-site data collection to obtain models’ inputs. ATSPMs need high-resolution controller event data acquired from roadway sensing equipment. Safety studies typically need 3 to 5 years of crash data to provide statistically significant results. This study utilizes commercially available connected vehicle (CV) data to assess the performance and operation of a three- and four-phase diamond interchange located in Indianapolis, Indiana, and Dallas, Texas, respectively. Over 92,000 trajectories and 1,400,000 GPS points are analyzed from August 2020 weekdays CV data. Trajectories are linear-referenced to generate Purdue Probe Diagrams (PPDs) from which arrivals on green (AOG), split failures, downstream blockage, and movement-based control delay are estimated. In addition, an extension of the PPD is presented that characterizes the complete journey of a vehicle travelling through both signals of the diamond interchange. This enhanced PPD is a significant contribution as it provides an analytical framework and graphical summary of the operational characteristics of how the external movements traverse the entire system. The four-phase control showed high internal progression (99% AOG) compared to the moderate internal progression of the three-phase operation (64% AOG). This is consistent with the design objectives of three- and four-phase control models, but historically these quantitative AOG measures were not possible to obtain with just detector data. Additionally, a graphical summary that illustrates the spatial distribution of hard-braking and hard-acceleration events is also provided. The presented techniques can be used by any agency to evaluate the performance of their diamond interchanges without on-site data collection or capital investments in sensing infrastructure.