Feature Extraction Method Based on Pseudo-Wigner-Ville Distribution for Rotational Machinery in Variable Operating Conditions

In the case of fault diagnosis for roller bearings, the conventional diagnosis approaches by using the time interval of energy impacts in time-frequency distribution or the pass-frequencies are based on the assumption that machinery operates under a constant rotational speed. However, when the rotational speed varies in the broader range, the pass-frequencies vary with the change of rotational speed and bearing faults cannot be identified by the interval of impacts. Researches related to automatic diagnosis for rotational machinery in variable operating conditions were quite few. A novel automatic feature extraction method is proposed based on a pseudo-Wigner-Ville distribution （PWVD） and an extraction of symptom parameter （SP）. An extraction method for instantaneous feature spectrum is presented using the relative crossing information （RCI） and sequential inference approach, by which the feature spectrum from time-frequency distribution can be automatically, sequentially extracted. The SPs are considered in the frequency domain using the extracted feature spectrum to identify among the conditions of a machine. A method to obtain the synthetic symptom parameter is also proposed by the least squares mapping （LSM） technique for increasing the diagnosis sensitivity of SP. Practical examples of diagnosis for bearings are given in order to verify the effectiveness of the proposed method. The verification results show that the features of bearing faults, such as the outer-race, inner-race and roller element defects have been effectively extracted, and the proposed method can be used for condition diagnosis of a machine under the variable rotational speed.

Boosting lithium batteries under harsh operating conditions by a resilient ionogel with liquid-like ionic conductivity

New chemistries are being developed to increase the capacity and power of rechargeable batteries. However, the risk of safety issues increases when high-energy batteries using highly active materials encounter harsh operating conditions. Here we report on the synthesis of a unique ionogel electrolyte for abuse-tolerant lithium batteries. A hierarchically architected silica/polymer scaffold is designed and fabricated through a facile soft chemistry route, which is competent to confine ionic liquids with superior uptake ability (92.4 wt%). The monolithic ionogel exhibits high conductivity and thermal/mechanical stability, featuring high-temperature elastic modulus and dendrite-free lithium cycling. The Li/LiFePO_(4) pouch cells achieve outstanding cyclability at different temperatures up to 150 ℃, and can sustain cutting, crumpling, and even coupled thermal–mechanical abuses. Moreover, the solid-state lithium batteries with LiNi_(0.60)Co_(0.20)Mn_(0.20)O_(2), LiNi_(0.80)Co_(0.15)Al_(0.05)O_(2), and Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2) cathodes demonstrate excellent cycle performances at 60 ℃. These results indicate that the resilient and high-conductivity ionogel electrolyte is promising to realize high-performance lithium batteries with high energy density and safety.

Effects of Operating Conditions on the Catalytic Performance of HZSM-5 Zeolites in n-Pentane Cracking

In this work,n-pentane catalytic cracking over HZSM-5 zeolites was studied at 650°C under atmosphere pressure.A particular attention was paid to the measurement of n-pentane conversion,light olefins production,product distribution,coke deposit,etc.Several indexes were defined to evaluate the effects of operating conditions on the catalytic performance of HZSM-5 zeolites.It was found that decreasing the weight hourly space velocity,increasing the reactant partial pressure,and increasing the carrier gas flow rate could inhibit C-H bond breaking and enhance the C-C bond breaking and hydride transfer reactions,leading to reduced alkenes selectivity,which suppressed the formation of external coke and alleviated the deactivation of HZSM-5 zeolites.It was deduced that the catalytic stability of HZSM-5 zeolites was improved at the cost of alkenes selectivity.Compared with decreasing the weight hourly space velocity and increasing the reactant partial pressure,increasing the carrier gas flow rate could enhance the diffusion process and protect alkenes from being consumed in coke formation in order to improve the catalytic stability of HZSM-5 zeolites with less reduction of alkenes selectivity.

Influences of fluid physical properties,solid particles,and operating conditions on the hydrodynamics in slurry reactors

Slurry reactors are popular in many industrial processes,involved with numerous chemical and biological mixtures,solid particles with different concentrations and properties,and a wide range of operating conditions.These factors can significantly affect the hydrodynamic in the slurry reactors,having remarkable effects on the design,scale-up,and operation of the slurry reactors.This article reviews the influences of fluid physical properties,solid particles,and operating conditions on the hydrodynamics in slurry reactors.Firstly,the influence of fluid properties,including the density and viscosity of the individual liquid and gas phases and the interfacial tension,has been reviewed.Secondly,the solid particle properties(i.e.,concentration,density,size,wettability,and shape)on the hydrodynamics have been discussed in detail,and some vital but often ignored features,especially the influences of particle wettability and shape,as well as the variation of surface tension because of solid concentration alteration,are highlighted in this work.Thirdly,the variations of physical properties of fluids,hydrodynamics,and bubble behavior resulted from the temperature and pressure variations are also summarized,and the indirect influences of pressure on viscosity and surface tension are addressed systematically.Finally,conclusions and perspectives of these notable influences on the design and scale-up of industrial slurry reactors are presented.

Performance of Nonwoven Filter Materials Based on the Operating Condition

The practical condition of needle-punched filters applied in coal-fired power plants is investigated. According to the actual operating conditions, two common filters (glass fiber filter and polyphenylene sulfide (PPS) filter) are selected for experiment. The performance of these two kinds of filter is compared based on a series of tests such as resistance to the acid and alkali, oxidation resistance,hydrolysis resistance,and wear resistance. Experimental results show that PPS filter materials have better properties than those of glass filter material except oxidation resistance. Composite filter mixed glass fiber and PPS is recommended for polluters because of its good properties in all aspects.

Fault diagnosis of diesel engine valve clearance under variable operating condition based on soft interval SVM

The fault detection and diagnosis of diesel engine valve clearance can effectively improve the availability and safety of diesel engine and have extremely important value and significance.Diesel engines generally operate in various stable operating conditions,which have important influence on the fault diagnosis.However,many fault diagnosis methods have been put forward under specific stable operating condition based on vibration signal.As the result of great impact caused by operating conditions,corresponding diagnosis models cannot deal with the fault diagnosis under different operating conditions with required accuracy.In this paper,a fault diagnosis of diesel engine valve clearance under variable operating condition based on soft interval support vector machine(SVM)is proposed.Firstly,the fault features with weak condition sensitivity have been extracted according to the influence analysis of fault on vibration signal.Moreover,soft interval constraint has been applied to SVM algorithm to reduce the random influence of vibration signal on fault features.In addition,different machine learning algorithms based on different feature sets are adopted to conduct the fault diagnosis under different operating conditions for comparison.Experimental results show that the proposed method is applicable for fault diagnosis under variable operating condition with good accuracy.

Operating conditions combination analysis method of optimal water management state for PEM fuel cell

The water content of proton exchange membrane fuel cells(PEMFCs)affects the transport of reactants and the conductivity of the membrane.Effective water management measures can improve the performance and extend the lifespan of the fuel cell.The water management state of the stack is influenced by various external operating conditions,and optimizing the combination of these conditions can improve the water management state within the stack.Considering that the stack's internal resistance can reflect its water management state,this study first establishes an internal resistance-operating condition model that considers the coupling effect of temperature and humidity to determine the variation trend of total resistance and stack humidity with single-factor operating conditions.Subsequently,the water management state optimization method based on the ANN-HGPSO algorithm is proposed,which not only quantitatively evaluates the influence weights of different operating conditions on the stack's internal resistance but also efficiently and accurately obtains the optimal combination of five operating conditions:working temperature,anode gas pressure,cathode gas pressure,anode gas humidity,and cathode gas humidity to achieve the optimal water management state in the stack,within the entire range of current densities.Finally,the response surface experimental results of the stack also validate the effectiveness and accuracy of the ANN-HGPSO algorithm.The method mentioned in this article can provide effective strategies for efficient water management and output performance optimization control of PEMFC stacks.

Parametric Study of Operating Conditions on Performances of a Solid Oxide Electrolysis Cell

The operating conditions greatly affect the electrolysis performance and temperature distribution of solid oxide electrolysis cells(SOECs).However,the temperature distribution in a cell is hard to determine by experiments due to the limitations of in-situ measurement methods.In this study,an electrochemical-flow-thermal coupling numerical cell model is established and verified by both current-voltage curves and electrochemical impedance spectroscopy(EIS)results.The electrolysis performance and temperature distribution under different working conditions are numerically analyzed,including operating temperature,steam and hydrogen partial pressures in the fuel gas,inlet flow rate and inlet temperature of fuel gas.The results show that the electrolysis performance improves with increasing operating temperature.Increasing steam partial pressure improves electrolysis performance and temperature distribution uniformity,but decreases steam conversion rate.An inappropriately low hydrogen partial pressure reduces the diffusion ability of fuel gas mixture and increases concentration impedance.Although increasing the flow rate of fuel gas improves electrolysis performance,it also reduces temperature distribution uniformity.A lower airflow rate benefits temperature distribution uniformity.The inlet temperature of fuel gas has little influence on electrolysis performance.In order to obtain a more uniform temperature distribution,it is more important to preheat the air than the fuel gas.

Thermal Performance of a Micro Heat Pipe Array for Battery Thermal Management Under Special Vehicle-Operating Conditions

The thermal management of battery systems is critical for maintaining the energy storage capacity,life span,and thermal safety of batteries used in electric vehicles,because the operating temperature is a key factor affecting battery performance.Excessive temperature rises and large temperature differences accelerate the degradation rate of such batteries.Currently,the increasing demand for fast charging and special on-vehicle scenarios has increased the heat dissipation requirements of battery thermal management systems.To address this demand,this work proposes a novel micro heat pipe array(MHPA)for thermal management under a broadened research scope,including high heat generation rates,large tilt angles,mild vibration,and distributed heat generation conditions.The experimental results indicate that the temperature difference is maintained 3.44°C at a large heat generation of 50 W for a limited range of tilt angles.Furthermore,a mild vehicle vibra-tion condition was found to improve temperature uniformity by 3.3°C at a heat generation of 10 W.However,the use of distributed heat sources results in a temperature variation of 3.88°C,suggesting that the heat generation distribution needs to be considered in thermal analyses.Understanding the effects of these special battery-operating conditions on the MHPA could significantly contribute to the enhancement of heat transfer capability and temperature uniformity improvement of battery thermal management systems based on heat pipe technologies.This would facilitate the realization of meeting the higher requirements of future battery systems.

Effects of operating conditions and pre-densification on the torrefaction products of sorghum straw

The effects of operating conditions and pre-densification on the torrefaction performance parameters and the properties of the torrefied sorghum straw were studied.A full-factor experiment was performed on a fixed tube furnace,in which sorghum straw powder and pellets were heated to 230℃,260℃,280℃ and 300℃ at 2.5℃/min,5℃/min and 7.5℃/min,respectively.The pyrolysis characteristics of the sorghum straw torrefied under various operating conditions were complemented by thermogravimetric analysis.It was observed that the high temperature led to the high calorific value of the torrefied sorghum straw with an acceptable mass and energy yield.The sorghum straw torrefied at a temperature above 280℃ had a higher heating value(HHV)that was comparable to that of the low rank coal while maintaining its energy yield above 85%.The results suggested that temperature was an important factor determining the properties of the torrefied products,and the heating rate would affect the internal temperature of the torrefied biomass by affecting the heat transfer during the torrefaction.The energy densification index of the pellets decreased uniformly as the heating rate increased proportionally,indicating that pre-densification can be used as a potential method to solve the heat transfer delay in the fixed reactors at high heating rates,especially for high temperatures.

Agglomeration behavior of petal-shaped cerium carbonate with different operating conditions

Agglomeration phenomenon can often be observed during the fabrication process of petal-shaped, nano-sized Ce2（CO3）3 powders. This kind of powder was produced by liquid-phase precipitation method with the template agent of polyallylamine hydrochloride （PAH）. In this study, the effects of the polymer concentration, pH value, and stirring speed on the agglomeration phe- nomenon of cerium carbonate were investigated. On the condition that the concentration of PAH is 0.9 g·L^-1, the pH value of the adjusting solution is 3-4, the final pH value is 8-10, and the stirring speed is 300-400 r·min^-1, it is found that the agglomeration phenomenon of Ce2（CO3）3 particles can be greatly prevented and the regular petal- shaped particles are formed.

Elimination of Partial Overloading of Generators Under Unbalanced Operating Conditions of Power Systems

Unbalanced operating condition in a power system can cause partial overloading of the generators in the network,a condition where one or two of the three phases of the generator become overloaded even if the total 3-phase power output of the generator is within its specified limit.Partial overloading of generators beyond certain limits is undesirable and must be avoided.Distribution systems are often subjected to highly unbalanced operating conditions.Introduction of distributed generations(DGs),therefore,has rendered today’s distribution systems quite susceptible to this problem.Mitigation of this problem requires the issue to be addressed properly during analysis,operation and planning of such systems.Analysis,operation and planning of power networks under unbalanced operating condition require 3-phase load flow study.The existing methods of 3-phase load flow are not equipped to take into account any limit on the loadings of the individual phases of the generators.In the present work,a methodology based on NewtonRaphson(N-R)3-phase load flow with necessary modifications is proposed.The proposed methodology is able to determine the safe loading limits of the generators,and,can be adopted for operation and planning of power networks under unbalanced operating conditions to overcome the above difficulties.Test results on IEEE-37 bus feeder network are presented to demonstrate the effectiveness of the proposed method.

Robust Damage Detection and Localization Under Complex Environmental Conditions Using Singular Value Decomposition-based Feature Extraction and One-dimensional Convolutional Neural Network

Ultrasonic guided wave is an attractive monitoring technique for large-scale structures but is vulnerable to changes in environmental and operational conditions(EOC),which are inevitable in the normal inspection of civil and mechanical structures.This paper thus presents a robust guided wave-based method for damage detection and localization under complex environmental conditions by singular value decomposition-based feature extraction and one-dimensional convolutional neural network(1D-CNN).After singular value decomposition-based feature extraction processing,a temporal robust damage index(TRDI)is extracted,and the effect of EOCs is well removed.Hence,even for the signals with a very large temperature-varying range and low signal-to-noise ratios(SNRs),the final damage detection and localization accuracy retain perfect 100%.Verifications are conducted on two different experimental datasets.The first dataset consists of guided wave signals collected from a thin aluminum plate with artificial noises,and the second is a publicly available experimental dataset of guided wave signals acquired on a composite plate with a temperature ranging from 20℃to 60℃.It is demonstrated that the proposed method can detect and localize the damage accurately and rapidly,showing great potential for application in complex and unknown EOC.

An Experimental Study on Optimization of Large-volume Airgun Source Excitation Conditions in a Reservoir

Through manual pickup of seismic phases,the number of recording stations,the farthest observation distance of station and received energy are determined,then optimal operating condition processing software is developed to evaluate the excitation effect of operating conditions. The optimal operating conditions in the Mianhuatan Reservoir are determined using this software. They are: optimal water depth 25 m,airgun array sink depth 9m and airgun array size 7m × 7m. At the same time,accumulative stacking results for every 10 times are analyzed for 300 fixed-point excitations. It is concluded that the excitation effect shows a rapidly rising trend at 10 to 90 times stacking,a slowly rising trend at 100 to 150 times stacking,a rapidly rising trend at 160 to 240 times stacking,and a slowly rising trend at 250 to 300 times stacking. As the number of stacking increases,the propagation distance and the number of recording stations also increase gradually.

Effects of preparation and operation conditions on precipitated iron nickel catalysts for Fischer-Tropsch synthesis

Iron nickel oxide catalysts were prepared using co-precipitation procedure and studied for the conversion of synthesis gas to light olefins.In particular,the effects of a range of preparation variables such as Fe/Ni molar ratios of the precipitation solution,precipitate aging times,calcination conditions,different supports and loading of optimum support on the structure of catalysts and their catalytic performance for the tested reaction were investigated.It was found that the catalyst containing 40%Fe/60%Ni/40wt%Al 2O3 ,which was aged for 180 min and calcined at 600 ℃ for 6 h was the optimum modified catalyst.The catalytic performance of optimal catalyst has been studied in different operation conditions such as reaction temperatures,H2 /CO molar feed ratios and reaction total pressure.Characterization of both precursors and calcined catalysts was carried out by powder X-ray diffraction（XRD）,scanning electron microscopy（SEM）,Brunauer-Emmett-Teller（BET） surface area measurements,thermal analysis methods such as thermal gravimetric analysis（TGA） and differential scanning calorimetry（DSC）.

Lifetime Evaluating and the Effects of Operation Conditions on Automotive Fuel Cells

Lifetime isone of the important indicators of automotive proton exchange membrane fuel cells. People used to evaluate the lifetime of vehicular fuel cells by laboratory tests or road tests that usually take thousands hours even years. In order to achieve a rapid evaluation technique and to seek lifetime extension methods, a lifetime calculation formation was drawn out in consideration of the vehicle driving cycle and the working condition factors. Bench experiments were individually carried out on two fuel-cell stacks same as ones applied on vehicle, and the performance decay rates of the two stacks were obtained under four operation conditions of changing load cycle, start-stop cycle, idling and heavy load. As a result, the predicted lifetimes rather conform to the actual running status in road test. And the research on the fuel cell performance decay rates under different load conditions was also done. Consequently, an unexpected finding was discovered that operating under micro-current has an effect on recovering fuel cell performance. The vehicle fuel cell rapid assessment method only requires four laboratory tests of driving cycle, load cycle, idle operating conditions and heavy load conditions, and the whole process merely lasts less than 250 h. These experimental results can be used to predict the vehicular fuel cell lifetimes on various utility models or driving cycles, therefore to optimize the application model to prolong the fuel cell lifetime. Actually in the experiment, it has already been proved successfully that the fuel cell lifetime could be extended from 1 100 h to 2 600 h by optimizing operating mode. The quick evaluation method is helpful to develop extended life fuel cell and to deplete fuel cell for a longer time.

Effects of Operation Conditions on Service Life of Ladle Lining

Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermittent operation, and different refining equipment on service life of ladle lining refractories were researched. The following conclusions are drawn ： （1） molten steel temperature rising, remaiaing time prolonging, slag oxidation ability enhancing, slag viscosity and basicity decreasing can aecelerate the corrosion of ladle lining ; （2） ultra-high temperature and vacuum treatment of ladle not only acceler- ate the fusion corrasion of ladle lining, but also make the carbon containing refractories react forming gases leading to more corrosion, so carbon containing refractories are not stdtable.for the smelting conditions of long term vacuum treatment and ultra-high temperature, especially carbon containing refractories added with conventional additives such as A1 and Si powders ; （ 3 ） argon blowing does not accelerate the corrosion of ladle lining obvioasly, but oxygen blowing does; （4） the corrosion degree of refractories varies with the refining equipment, and the service life of ladle lining decreases according to a certain proportion with the refining ratio increasing.

Programming with Conditionals: Epistemic Programming for Scientific Discovery

In order to provide scientists with a computational methodology and some computational tools to program their epistemic processes in scientific discovery, we are establishing a novel programming paradigm, named ‘Epistemic Programming’, which regards conditionals as the subject of computing, takes primary epistemic operations as basic operations of computing, and regards epistemic processes as the subject of programming. This paper presents our fundamental observations and assumptions on scientific discovery processes and their automation, research problems on modeling, automating, and programming epistemic processes, and an outline of our research project of Epistemic Programming.

Study of Intelligent Approaches to Identify Impact of Environmental Temperature on Ultrasonic GWs Based SHM:A Review

Structural health monitoring(SHM)is considered an effective approach to analyze the efficient working of several mechanical components.For this purpose,ultrasonic guided waves can cover long-distance and assess large infrastructures in just a single test using a small number of transducers.However,the working of the SHM mechanism can be affected by some sources of variations(i.e.,environmental).To improve the final results of ultrasonic guided wave inspections,it is necessary to highlight and attenuate these environmental variations.The loading parameters,temperature and humidity have been recognized as the core environmental sources of variations that affect the SHM sensing mechanism.Environmental temperature has the most significant influence on SHM results.There is still a need for extensive research to develop such a damage inspection approach that should be insensitive to environmental temperature variations.In this framework,the current research study will not only illuminate the effect of environmental temperature through different intelligent approaches but also suggest the standard mechanism to attenuate it in actual ultrasonic guided wave based SHM.Hence,the work presented in this article addresses one of the open research challenges that are the identification of the effect of environmental and operating conditions in practical applications of ultrasonic guided waves and impedance-based SHM.

Pre-Compression Volume on Flow Ripple Reduction of a Piston Pump

Axial piston pump with pre-compression volume（PCV） has lower flow ripple in large scale of operating condition than the traditional one. However, there is lack of precise simulation model of the axial piston pump with PCV, so the parameters of PCV are difticult to be determined. A finite element simulation model for piston pump with PCV is built by considering the piston movement, the fluid characteristic（including fluid compressibility and viscosity） and the leakage flow rate. Then a test of the pump flow ripple called the secondary source method is implemented to validate the simulation model. Thirdly, by comparing results among the simulation results, test results and results from other publications at the same operating condition, the simulation model is validated and used in optimizing the axial piston pump with PCV. According to the pump flow ripples obtained by the simulation model with different PCV parameters, the flow ripple is the smallest when the PCV angle is 13~, the PCV volume is 1.3 ~ I0-4 m3 at such operating condition that the pump suction pressure is 2 MPa, the pump delivery pressure 15 MPa, the pump speed 1 000 r/min, the swash plate angle 13~. At the same time, the flow ripple can be reduced when the pump suction pressure is 2 MPa, the pump delivery pressure is 5 MPa,15 MPa, 22 MPa, pump speed is 400 r/min, 1 000 r/rain, 1 500 r/rain, the swash plate angle is ll~, 13~, 15~ and 17~, respectively. The finite element simulation model proposed provides a method for optimizing the PCV structure and guiding for designing a quieter axial piston pump.