Evolutionary algorithms(EAs)have been used in high utility itemset mining(HUIM)to address the problem of discover-ing high utility itemsets(HUIs)in the exponential search space.EAs have good running and mining perform...Evolutionary algorithms(EAs)have been used in high utility itemset mining(HUIM)to address the problem of discover-ing high utility itemsets(HUIs)in the exponential search space.EAs have good running and mining performance,but they still require huge computational resource and may miss many HUIs.Due to the good combination of EA and graphics processing unit(GPU),we propose a parallel genetic algorithm(GA)based on the platform of GPU for mining HUIM(PHUI-GA).The evolution steps with improvements are performed in central processing unit(CPU)and the CPU intensive steps are sent to GPU to eva-luate with multi-threaded processors.Experiments show that the mining performance of PHUI-GA outperforms the existing EAs.When mining 90%HUIs,the PHUI-GA is up to 188 times better than the existing EAs and up to 36 times better than the CPU parallel approach.展开更多
A new type of liquid desiccant water chiller for applications on air-conditioning and refrigeration is introduced.The system can be driven by low-grade heat sources with temperatures of 60 to 80 ℃,which can be easily...A new type of liquid desiccant water chiller for applications on air-conditioning and refrigeration is introduced.The system can be driven by low-grade heat sources with temperatures of 60 to 80 ℃,which can be easily obtained by a flat plat solar collector,waste heat,etc.A numerical model is developed to study the system performance.The effects of different parameters on performance are discussed,including evaporating temperature,regenerating temperature,ambient condition,and mass flow rates of closed moist air and regenerating air.The results show that an acceptable performance of a cooling capacity of 2.5 kW and a coefficient of performance of 0.37 can be achieved in a reference case.The regenerating temperature and the humidity ratios of ambient air are two main factors affecting system performance,while the temperature of ambient air functions less.In addition,the mass flow rate of regenerating air and closed moist air should be carefully determined for economical operation.展开更多
For the joint time difference of arrival(TDOA) and angle of arrival(AOA) location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved pe...For the joint time difference of arrival(TDOA) and angle of arrival(AOA) location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.展开更多
Updates to traffic signal timing plans are expected to either improve operations or mitigate the effects of increased volumes. Longitudinal before-after studies are important when validating changes to traffic signal ...Updates to traffic signal timing plans are expected to either improve operations or mitigate the effects of increased volumes. Longitudinal before-after studies are important when validating changes to traffic signal systems, but they have historically required field data collection as well as deployment of extensive detection and communication equipment. These infrastructure-based techniques are costly and hard to scale. This study utilizes commercially available connected vehicle (CV) trajectory data to assess the change in performance between August 2020 and August 2021 on a 22-intersection corridor associated with the implementation of a semi-automated adaptive control system. Approximately 1 million trajectories and 13.5 million GPS points are analyzed for weekdays in August 2020 and August 2021. The vehicle trajectory data is used to compute corridor travel times and linear referenced relative to the far side of each intersection to generate Purdue Probe Diagrams (PPD). Using the PPDs, operational measurements such as arrivals on green (AOG), split failures (SF), and downstream blockage (DSB) are calculated. Additionally, traditional Highway Capacity Manual (HCM) level of service (LOS) is estimated. Even though there was a 35% increase in annual average daily traffic (AADT), the weighted average vehicle delay only increased by two seconds, LOS did not change, AOG improved by 1%, and SF and DSB remained the same. Based on the small changes in operational performance and considering the increase in traffic volume it is concluded that the implementation of the semi-automated adaptive control system had a significant positive impact in the corridor. The presented framework can be utilized by agencies to use CV data to perform before-after studies to evaluate the impact of signal timing plan changes. The presented methodology can be applied to any location where CV trajectory data is available.展开更多
ZA27 alloy has the best performance and the widest applications in high aluminum zinc based die casting alloy series. One of its main applica-tions is used as abrasion resistant alloy,instead of nonferrous alloys such...ZA27 alloy has the best performance and the widest applications in high aluminum zinc based die casting alloy series. One of its main applica-tions is used as abrasion resistant alloy,instead of nonferrous alloys such as copper alloy.The frictional wear p展开更多
Based on a two-qubit isotropic Heisenberg XY model under a constant external magnetic field,we construct a four-level entangled quantum heat engine(QHE).The expressions for the heat transferred,the work,and the effi...Based on a two-qubit isotropic Heisenberg XY model under a constant external magnetic field,we construct a four-level entangled quantum heat engine(QHE).The expressions for the heat transferred,the work,and the efficiency are derived.Moreover,the influence of the entanglement on the thermodynamic quantities is investigated analytically and numerically.Several interesting features of the variations of the heat transferred,the work,and the efficiency with the concurrences of the thermal entanglement of two different thermal equilibrium states in zero and nonzero magnetic fields are obtained.展开更多
Cyclic spectral correlation above the bifrequency plane for the received signal was calculated by the strip spectral correlation algorithm (SSCA)and then was normalized. The result was expressed by matrix. The sum o...Cyclic spectral correlation above the bifrequency plane for the received signal was calculated by the strip spectral correlation algorithm (SSCA)and then was normalized. The result was expressed by matrix. The sum of error-square was computed between corresponding elements for the theoretical sampling matrix of all kinds of modulated signals and calculated matrix. The modulation type was recognized by exploiting the minimum value of the sum of error-square. No extracted characteristic parameter and prior information are needed for identifying the modulation type compared to the conventional methods. In addition, the new method extends the recognition scope and has high recognition probability at low SNR. The simulation results obtained by means of Monter-Carlo method proved the presented algorithm.展开更多
This paper developed a short-term stock exchange prediction model using the Box-Jenkins approach. In this study, monthly data from Ghana Stock Exchange market report that spans from March 2013 to February 2018 were us...This paper developed a short-term stock exchange prediction model using the Box-Jenkins approach. In this study, monthly data from Ghana Stock Exchange market report that spans from March 2013 to February 2018 were used to develop the model. ARIMA (0, 2, 1) model was fitted to the data based on the Bayesian Information Criterion (BIC) for model selection. Diagnostic checks showed that the residuals of the fitted model were uncorrelated. The developed model was used for forecasting for a period of six months. The trend of the forecasted values showed a significant increase in the Ghana Stock Exchange performance for the next six months.展开更多
GPUs are of increasing interests in the multi-core era due to their high computing power. However, the power consumption caused by the rising performance of GPUs has been a general concern. As a consequence, it is bec...GPUs are of increasing interests in the multi-core era due to their high computing power. However, the power consumption caused by the rising performance of GPUs has been a general concern. As a consequence, it is becoming an imperative demand to optimize the GPU power consumption, among which the power consumption estimation is one of the important and useful solutions. In this work, we present a novel statistical model that is capable of dynamically estimating the power consumption of the AMD's integrated GPU (iGPU). Precisely, we adopt the linear regression for power consumption modeling and propose a mechanism called kernel extension to lengthen the kernel execution time so that we can sample system data for model evaluation. The results show that the median absolute error of our model is less than 3%. Furthermore,to reduce the latency of power consumption estimation, we conduct a study to explore the possibility to simplify our statistical model. The results suggest that the accuracy and stability is still acceptable in the simplified model. This provides a desirable option to reduce our model latency when it is applied to the iGPU power consumption optimization in the real world.展开更多
To examine the effect of sleep deprivation (SD) on eye movement be- havior in flight task, four subjects who were skilled in flight simulator participated in the experiment, which were asked to perform a level fligh...To examine the effect of sleep deprivation (SD) on eye movement be- havior in flight task, four subjects who were skilled in flight simulator participated in the experiment, which were asked to perform a level flight task in a flight simulator. Eye movement data and flight performance data were measured at the following hours: 11:00, 15:00, 04:00, 11:00, 15:00. The subjects workload and fatigue were assessed with the method of national aeronautics and space administration-task load index (NASA-TLX) and rating of perceived exertion (RPE). Eye movement indices of average pupil area, av- erage saceade amplitude and average saccade velocity decreased during the 32 h of SD and they all showed significantly change in the final SD while the index of average fixa- tion time increased in the final SD. Flight performance deteriorated during the 32 h of SD, but not significantly. The feeling of fatigue and workload reported by subjects both increased during the 32 h of SD. Daily rhythm effects on the measured indices were also found, there were a obviously change at the hour of 04:00. 32 h of SD has obvious effect on eye movement behaviors which have close relation to fatigue because of SD. The eye movement measurement can be served as a tool to continually monitor fatigue online.展开更多
Atmospheric ice accretion on transmission lines is of great danger to the security of service of electrical power system. This paper reviews the progress in research dealing with the formation of ice accretions on tra...Atmospheric ice accretion on transmission lines is of great danger to the security of service of electrical power system. This paper reviews the progress in research dealing with the formation of ice accretions on transmission lines and the effects of ice on the mechanical and electrical performance of transmission lines. The results show that ice accretions on transmission lines can be categorized into five types: glaze, hard rime, soft rime, hoar frost, and snow and sleet. In all types of ice accretions, glaze grown in a wet regime is of the greatest danger to the transmission lines. Meteorological conditions, terrain and geographic conditions, and some other factors significantly influence the ice accumulation speed and the ice amount. Drastic decrease of mechanical property and electric property as a result of severe icing is the main reason for ice accidents. The amount of ice, the asymmetrical ice accretion, and the asynchronous ice shedding can considerably change the conductor strain, conductor sag, variation amount of the span, displacement of the insulator string, and the tension difference. The amount and type of ice, the uniformity of ice accumulation, and the con- ductivity of freezing water have significant influence on the flashover voltage of ice-covered insulators.展开更多
Ecdysteroid hormone 20-hydroxyecdysone plays fundamental roles in in- sect postembryonic development and reproduction. Several cytochrome P450 mono- oxygenases (CYPs), encoded by the Halloween genes, have been docum...Ecdysteroid hormone 20-hydroxyecdysone plays fundamental roles in in- sect postembryonic development and reproduction. Several cytochrome P450 mono- oxygenases (CYPs), encoded by the Halloween genes, have been documented to be involved in ecdysteroidogenesis in representative insects in Diptera, Lepidoptera and Orthoptera. Here the putative Halloween gene Phantom (Phm, cyp306al) from a hemipteran insect species, the small brown planthopper Laodelphax striatellus, was cloned. LsPHM shows five insect conserved P450 motifs, that is, Helix-C, Helix-I, Helix-K, PERF and heme- binding motifs. Temporal and spatial expression patterns of LsPhm were evaluated by quantitative polymerase chain reaction. Through the fourth-instar and the early fifth-instar stages, LsPhm showed two expression peaks in day 2 and days 4-5 fourth-instar nymphs, and three troughs in day 1 and 3 fourth instars and day 1 fifth instars. On day 5 of the fourth-instar nymphs, LsPhm clearly had a high transcript level in the thorax where the prothoracic glands were located. Dietary introduction of double-stranded RNA (dsRNA) of LsPhm at the nymph stage successfully knocked down the target gene, decreased expres- sion level ofecdysone receptor (LsEcR) gene and caused a higher nymphal mortality rate and delayed development. Ingestion of 20-hydroxyecdysone on LsPhm-dsRNA-exposed nymphs did not increase LsPhm expression level, but almost completely rescued the LsEcR mRNA level, and relieved the negative effects on survival and development. Thus, our data suggest that the putative LsPhm encodes a ftmctional 25-hydroxylase that catalyzes the biosynthesis of ecdysteroids in L. striatellus.展开更多
The competence of fresh graduates of architecture has been continuously criticized by the industry for inadequate knowledge. This is often blamed on the poor standard of education evidenced by poor performances in pro...The competence of fresh graduates of architecture has been continuously criticized by the industry for inadequate knowledge. This is often blamed on the poor standard of education evidenced by poor performances in professional and degree/diploma examinations conducted by various schools of architecture in the country. Although, factors responsible for the scenario are wetl documented in the literature, most of these works are based on testimonial and circumstantial evidences relating to management of architectural education only. The aim of this paper is to investigate the relationship between entry qualifications and the performance of architecture students in Nigerian Polytechnics with a view to determining the relevance of current admission policy to architectural education in Nigeria. Data were obtained from official records in the Department of Architecture in four randomly selected polytechnics in the southwestern part of Nigeria. Pearson Product Moment Corretation (r) was used to test the hypotheses. Findings reveal weak relationship between the two variables (physics and mathematics). This is contrary to the expectations of most schotars and policy makers who opine that studentst proficiency in these subjects would enhance their performance at higher LeveLs. The paper traces the contradiction to the poor handling of public examinations and misconception of architecture as being pure science. It holds that if these requirements are still relied upon for the admission of students into schools of architecture, wrong candidates wouldcontinue to gain entry into the profession. The paper concludes by recommending certain measures that are capable of reversing the trend.展开更多
Forecasts of industrial emissions provide a basis for impact assessment and development planning. To date, most studies have assumed that industrial emissions are simply coupled to production value at a given stage of...Forecasts of industrial emissions provide a basis for impact assessment and development planning. To date, most studies have assumed that industrial emissions are simply coupled to production value at a given stage of technical progress. It has been argued that the monetary method tends to overestimate pollution loads because it is highly influenced by market prices and fails to address spatial development schemes. This article develops a land use-based environmental performance index (L-EPI) that treats the industrial land areas as a dependent variable for pollution emissions. The basic assumption of the method is that at a planning level, industrial land use change can represent the change in industrial structure and production yield. This physical metric provides a connection between the state-of-the-art and potential impacts of future devel- opment and thus avoids the intrinsic pitfalls of the industrial Gross Domestic Product-based approach. Both methods were applied to examine future industrial emissions at the planning area of Dalian Municipality, North-west China, under a development scheme provided by the urban master plan. The results suggested that the L- EPI method is highly reliable and applicable for the estimation and explanation of the spatial variation associated with industrial emissions.展开更多
The authors performed ionic liquid-based microwave-assisted liquid-liquid microextraction(IL-based MALLME) coupled with high performance liquid chromatographic separation for the determination of 6 sulfonamides (SA...The authors performed ionic liquid-based microwave-assisted liquid-liquid microextraction(IL-based MALLME) coupled with high performance liquid chromatographic separation for the determination of 6 sulfonamides (SAs) from animal oils. The target analytes were extracted from animal oil samples with sodium hydroxide solution containing 1-butyl-3-methylimidazolium tetrafluoroborateand as the extraction solvent under microwave irradiation. The experimental parameters of the IL-based MALLME, including types of ILs, volume of IL, amount of ion-pairing agent(NHaPF6), pH value of sample solution, and extraction temperature and time were evaluated. The limits of detection and quantification obtained were in a range of 0.4--0.5μg/kg and a range of 1.2--1.8μg/kg, respectively. The accuracy of the method was evaluated by analyzing five spiked animal oil samples at two fortified levels(5 and 50μg/kg), and the recoveries of SAs varied from 81.4% to 114.5% with relative standard deviations ranging from 0.8% to 9.0%.展开更多
This article shows experimentally the thermal performance of two test cells with different coverage systems, Ught Green Roof (LGR) and ceramic roof by analyzing internal surface temperatures (IST) in the ceiling a...This article shows experimentally the thermal performance of two test cells with different coverage systems, Ught Green Roof (LGR) and ceramic roof by analyzing internal surface temperatures (IST) in the ceiling and dry bulb temperatures (DBT). The objective was to evaluate the spatial distnbution of temperatures in buildings according to spatial and temporal Dynamic CUmato[ogy approaches. An experimental, typical day for heat conditions was determined. The data of the main climatic vari- ables provided by an automatic weather station and temperatures inside the test cells were collected using thermocouples installed such that the entire space is included. The results led to the conclusion that the LGR has a balanced IST and DBT spatial distribution compared with ceramic roofs. Nevertheless, the analysis of the thermal performance is only one of the variables that must be considered when developing a construction proposal that is adapted to the context. The manner in which the thermocouples were placecl inside the test cells also showed the importance of specifying the location of the sensors in experimental studies on the behavior and thermal performance of buildings.展开更多
基金This work was supported by the National Natural Science Foundation of China(62073155,62002137,62106088,62206113)the High-End Foreign Expert Recruitment Plan(G2023144007L)the Fundamental Research Funds for the Central Universities(JUSRP221028).
文摘Evolutionary algorithms(EAs)have been used in high utility itemset mining(HUIM)to address the problem of discover-ing high utility itemsets(HUIs)in the exponential search space.EAs have good running and mining performance,but they still require huge computational resource and may miss many HUIs.Due to the good combination of EA and graphics processing unit(GPU),we propose a parallel genetic algorithm(GA)based on the platform of GPU for mining HUIM(PHUI-GA).The evolution steps with improvements are performed in central processing unit(CPU)and the CPU intensive steps are sent to GPU to eva-luate with multi-threaded processors.Experiments show that the mining performance of PHUI-GA outperforms the existing EAs.When mining 90%HUIs,the PHUI-GA is up to 188 times better than the existing EAs and up to 36 times better than the CPU parallel approach.
基金The National Natural Science Foundation of China(No.50976021)the National Key Technology R&D Program of China during the 11th Five-Year Plan Period(No.2007BA000875)
文摘A new type of liquid desiccant water chiller for applications on air-conditioning and refrigeration is introduced.The system can be driven by low-grade heat sources with temperatures of 60 to 80 ℃,which can be easily obtained by a flat plat solar collector,waste heat,etc.A numerical model is developed to study the system performance.The effects of different parameters on performance are discussed,including evaporating temperature,regenerating temperature,ambient condition,and mass flow rates of closed moist air and regenerating air.The results show that an acceptable performance of a cooling capacity of 2.5 kW and a coefficient of performance of 0.37 can be achieved in a reference case.The regenerating temperature and the humidity ratios of ambient air are two main factors affecting system performance,while the temperature of ambient air functions less.In addition,the mass flow rate of regenerating air and closed moist air should be carefully determined for economical operation.
基金supported by the National Natural Science Foundation of China(6107210761271300)+4 种基金the Shaanxi Industry Surmount Foundation(2012K06-12)the Arm and Equipment Pre-research Foundationthe Fundamental Research Funds for the Central Universities of China(K0551302006K5051202045K50511020024)
文摘For the joint time difference of arrival(TDOA) and angle of arrival(AOA) location scene,two methods are proposed based on the rectangular coordinates and the polar coordinates,respectively.The problem is solved perfectly by calculating the target position with the joint TDOA and AOA location.On the condition of rectangular coordinates,first of all,it figures out the radial range between target and reference stations,then calculates the location of the target.In the case of polar coordinates,first of all,it figures out the azimuth between target and reference stations,then figures out the radial range between target and reference stations,finally obtains the location of the target.Simultaneously,simulation analyses show that the theoretical analysis is correct,and the proposed methods also provide the application of the joint TDOA and AOA location algorithm with the theoretical basis.
文摘Updates to traffic signal timing plans are expected to either improve operations or mitigate the effects of increased volumes. Longitudinal before-after studies are important when validating changes to traffic signal systems, but they have historically required field data collection as well as deployment of extensive detection and communication equipment. These infrastructure-based techniques are costly and hard to scale. This study utilizes commercially available connected vehicle (CV) trajectory data to assess the change in performance between August 2020 and August 2021 on a 22-intersection corridor associated with the implementation of a semi-automated adaptive control system. Approximately 1 million trajectories and 13.5 million GPS points are analyzed for weekdays in August 2020 and August 2021. The vehicle trajectory data is used to compute corridor travel times and linear referenced relative to the far side of each intersection to generate Purdue Probe Diagrams (PPD). Using the PPDs, operational measurements such as arrivals on green (AOG), split failures (SF), and downstream blockage (DSB) are calculated. Additionally, traditional Highway Capacity Manual (HCM) level of service (LOS) is estimated. Even though there was a 35% increase in annual average daily traffic (AADT), the weighted average vehicle delay only increased by two seconds, LOS did not change, AOG improved by 1%, and SF and DSB remained the same. Based on the small changes in operational performance and considering the increase in traffic volume it is concluded that the implementation of the semi-automated adaptive control system had a significant positive impact in the corridor. The presented framework can be utilized by agencies to use CV data to perform before-after studies to evaluate the impact of signal timing plan changes. The presented methodology can be applied to any location where CV trajectory data is available.
文摘ZA27 alloy has the best performance and the widest applications in high aluminum zinc based die casting alloy series. One of its main applica-tions is used as abrasion resistant alloy,instead of nonferrous alloys such as copper alloy.The frictional wear p
基金Project supported by the National Natural Science Foundation of China (Grant No. 11065008)
文摘Based on a two-qubit isotropic Heisenberg XY model under a constant external magnetic field,we construct a four-level entangled quantum heat engine(QHE).The expressions for the heat transferred,the work,and the efficiency are derived.Moreover,the influence of the entanglement on the thermodynamic quantities is investigated analytically and numerically.Several interesting features of the variations of the heat transferred,the work,and the efficiency with the concurrences of the thermal entanglement of two different thermal equilibrium states in zero and nonzero magnetic fields are obtained.
文摘Cyclic spectral correlation above the bifrequency plane for the received signal was calculated by the strip spectral correlation algorithm (SSCA)and then was normalized. The result was expressed by matrix. The sum of error-square was computed between corresponding elements for the theoretical sampling matrix of all kinds of modulated signals and calculated matrix. The modulation type was recognized by exploiting the minimum value of the sum of error-square. No extracted characteristic parameter and prior information are needed for identifying the modulation type compared to the conventional methods. In addition, the new method extends the recognition scope and has high recognition probability at low SNR. The simulation results obtained by means of Monter-Carlo method proved the presented algorithm.
文摘This paper developed a short-term stock exchange prediction model using the Box-Jenkins approach. In this study, monthly data from Ghana Stock Exchange market report that spans from March 2013 to February 2018 were used to develop the model. ARIMA (0, 2, 1) model was fitted to the data based on the Bayesian Information Criterion (BIC) for model selection. Diagnostic checks showed that the residuals of the fitted model were uncorrelated. The developed model was used for forecasting for a period of six months. The trend of the forecasted values showed a significant increase in the Ghana Stock Exchange performance for the next six months.
文摘GPUs are of increasing interests in the multi-core era due to their high computing power. However, the power consumption caused by the rising performance of GPUs has been a general concern. As a consequence, it is becoming an imperative demand to optimize the GPU power consumption, among which the power consumption estimation is one of the important and useful solutions. In this work, we present a novel statistical model that is capable of dynamically estimating the power consumption of the AMD's integrated GPU (iGPU). Precisely, we adopt the linear regression for power consumption modeling and propose a mechanism called kernel extension to lengthen the kernel execution time so that we can sample system data for model evaluation. The results show that the median absolute error of our model is less than 3%. Furthermore,to reduce the latency of power consumption estimation, we conduct a study to explore the possibility to simplify our statistical model. The results suggest that the accuracy and stability is still acceptable in the simplified model. This provides a desirable option to reduce our model latency when it is applied to the iGPU power consumption optimization in the real world.
基金Aviation Science Foundation of Chinagrant number:20115551025
文摘To examine the effect of sleep deprivation (SD) on eye movement be- havior in flight task, four subjects who were skilled in flight simulator participated in the experiment, which were asked to perform a level flight task in a flight simulator. Eye movement data and flight performance data were measured at the following hours: 11:00, 15:00, 04:00, 11:00, 15:00. The subjects workload and fatigue were assessed with the method of national aeronautics and space administration-task load index (NASA-TLX) and rating of perceived exertion (RPE). Eye movement indices of average pupil area, av- erage saceade amplitude and average saccade velocity decreased during the 32 h of SD and they all showed significantly change in the final SD while the index of average fixa- tion time increased in the final SD. Flight performance deteriorated during the 32 h of SD, but not significantly. The feeling of fatigue and workload reported by subjects both increased during the 32 h of SD. Daily rhythm effects on the measured indices were also found, there were a obviously change at the hour of 04:00. 32 h of SD has obvious effect on eye movement behaviors which have close relation to fatigue because of SD. The eye movement measurement can be served as a tool to continually monitor fatigue online.
文摘Atmospheric ice accretion on transmission lines is of great danger to the security of service of electrical power system. This paper reviews the progress in research dealing with the formation of ice accretions on transmission lines and the effects of ice on the mechanical and electrical performance of transmission lines. The results show that ice accretions on transmission lines can be categorized into five types: glaze, hard rime, soft rime, hoar frost, and snow and sleet. In all types of ice accretions, glaze grown in a wet regime is of the greatest danger to the transmission lines. Meteorological conditions, terrain and geographic conditions, and some other factors significantly influence the ice accumulation speed and the ice amount. Drastic decrease of mechanical property and electric property as a result of severe icing is the main reason for ice accidents. The amount of ice, the asymmetrical ice accretion, and the asynchronous ice shedding can considerably change the conductor strain, conductor sag, variation amount of the span, displacement of the insulator string, and the tension difference. The amount and type of ice, the uniformity of ice accumulation, and the con- ductivity of freezing water have significant influence on the flashover voltage of ice-covered insulators.
文摘Ecdysteroid hormone 20-hydroxyecdysone plays fundamental roles in in- sect postembryonic development and reproduction. Several cytochrome P450 mono- oxygenases (CYPs), encoded by the Halloween genes, have been documented to be involved in ecdysteroidogenesis in representative insects in Diptera, Lepidoptera and Orthoptera. Here the putative Halloween gene Phantom (Phm, cyp306al) from a hemipteran insect species, the small brown planthopper Laodelphax striatellus, was cloned. LsPHM shows five insect conserved P450 motifs, that is, Helix-C, Helix-I, Helix-K, PERF and heme- binding motifs. Temporal and spatial expression patterns of LsPhm were evaluated by quantitative polymerase chain reaction. Through the fourth-instar and the early fifth-instar stages, LsPhm showed two expression peaks in day 2 and days 4-5 fourth-instar nymphs, and three troughs in day 1 and 3 fourth instars and day 1 fifth instars. On day 5 of the fourth-instar nymphs, LsPhm clearly had a high transcript level in the thorax where the prothoracic glands were located. Dietary introduction of double-stranded RNA (dsRNA) of LsPhm at the nymph stage successfully knocked down the target gene, decreased expres- sion level ofecdysone receptor (LsEcR) gene and caused a higher nymphal mortality rate and delayed development. Ingestion of 20-hydroxyecdysone on LsPhm-dsRNA-exposed nymphs did not increase LsPhm expression level, but almost completely rescued the LsEcR mRNA level, and relieved the negative effects on survival and development. Thus, our data suggest that the putative LsPhm encodes a ftmctional 25-hydroxylase that catalyzes the biosynthesis of ecdysteroids in L. striatellus.
文摘The competence of fresh graduates of architecture has been continuously criticized by the industry for inadequate knowledge. This is often blamed on the poor standard of education evidenced by poor performances in professional and degree/diploma examinations conducted by various schools of architecture in the country. Although, factors responsible for the scenario are wetl documented in the literature, most of these works are based on testimonial and circumstantial evidences relating to management of architectural education only. The aim of this paper is to investigate the relationship between entry qualifications and the performance of architecture students in Nigerian Polytechnics with a view to determining the relevance of current admission policy to architectural education in Nigeria. Data were obtained from official records in the Department of Architecture in four randomly selected polytechnics in the southwestern part of Nigeria. Pearson Product Moment Corretation (r) was used to test the hypotheses. Findings reveal weak relationship between the two variables (physics and mathematics). This is contrary to the expectations of most schotars and policy makers who opine that studentst proficiency in these subjects would enhance their performance at higher LeveLs. The paper traces the contradiction to the poor handling of public examinations and misconception of architecture as being pure science. It holds that if these requirements are still relied upon for the admission of students into schools of architecture, wrong candidates wouldcontinue to gain entry into the profession. The paper concludes by recommending certain measures that are capable of reversing the trend.
文摘Forecasts of industrial emissions provide a basis for impact assessment and development planning. To date, most studies have assumed that industrial emissions are simply coupled to production value at a given stage of technical progress. It has been argued that the monetary method tends to overestimate pollution loads because it is highly influenced by market prices and fails to address spatial development schemes. This article develops a land use-based environmental performance index (L-EPI) that treats the industrial land areas as a dependent variable for pollution emissions. The basic assumption of the method is that at a planning level, industrial land use change can represent the change in industrial structure and production yield. This physical metric provides a connection between the state-of-the-art and potential impacts of future devel- opment and thus avoids the intrinsic pitfalls of the industrial Gross Domestic Product-based approach. Both methods were applied to examine future industrial emissions at the planning area of Dalian Municipality, North-west China, under a development scheme provided by the urban master plan. The results suggested that the L- EPI method is highly reliable and applicable for the estimation and explanation of the spatial variation associated with industrial emissions.
文摘The authors performed ionic liquid-based microwave-assisted liquid-liquid microextraction(IL-based MALLME) coupled with high performance liquid chromatographic separation for the determination of 6 sulfonamides (SAs) from animal oils. The target analytes were extracted from animal oil samples with sodium hydroxide solution containing 1-butyl-3-methylimidazolium tetrafluoroborateand as the extraction solvent under microwave irradiation. The experimental parameters of the IL-based MALLME, including types of ILs, volume of IL, amount of ion-pairing agent(NHaPF6), pH value of sample solution, and extraction temperature and time were evaluated. The limits of detection and quantification obtained were in a range of 0.4--0.5μg/kg and a range of 1.2--1.8μg/kg, respectively. The accuracy of the method was evaluated by analyzing five spiked animal oil samples at two fortified levels(5 and 50μg/kg), and the recoveries of SAs varied from 81.4% to 114.5% with relative standard deviations ranging from 0.8% to 9.0%.
文摘This article shows experimentally the thermal performance of two test cells with different coverage systems, Ught Green Roof (LGR) and ceramic roof by analyzing internal surface temperatures (IST) in the ceiling and dry bulb temperatures (DBT). The objective was to evaluate the spatial distnbution of temperatures in buildings according to spatial and temporal Dynamic CUmato[ogy approaches. An experimental, typical day for heat conditions was determined. The data of the main climatic vari- ables provided by an automatic weather station and temperatures inside the test cells were collected using thermocouples installed such that the entire space is included. The results led to the conclusion that the LGR has a balanced IST and DBT spatial distribution compared with ceramic roofs. Nevertheless, the analysis of the thermal performance is only one of the variables that must be considered when developing a construction proposal that is adapted to the context. The manner in which the thermocouples were placecl inside the test cells also showed the importance of specifying the location of the sensors in experimental studies on the behavior and thermal performance of buildings.