Pre-research on Enhanced Heat Transfer Method for Special Vehicles at High Altitude Based on Machine Learning

The performance of an integrated thermal management system signi?cantly in?uences the stability of special-purpose vehicles;thus,enhancing the heat transfer of the radiator is of great signi?cance.Common research methods for radiators include?uid mechanics numerical simulations and experimental measurements,both of which are time-consuming and expensive.Applying the surrogate model to the analysis of the?ow and heat transfer in louvered?ns can effectively reduce the computational cost and obtain more data.A simpli?ed louvered-?n heat transfer unit was established,and computational?uid dynamics(CFD)simulations were conducted to obtain the?ow and heat transfer characteristics of the geometric structure.A three-factor and six-level orthogonal design was established with three structural parameters:angleθ,length a,and pitch L_p of the louvered?ns.The results of the orthogonal design were subjected to a range analysis,and the effects of the three parametersθ,a,and L_p on the j,f,and JF factors were obtained.Accordingly,a proxy model of the heat transfer performance for louvered?ns was established based onthe arti?cial neural network algorithm,and the model was trained with the data obtained by the orthogonal design.Finally,the?n structure with the largest JF factor was realized.Compared with the original model,the optimizedmodel improved the heat transfer factor j by 2.87%,decreased the friction factor f by 30.4%,and increased the comprehensive factor JF by 15.7%.

Preparation of Lightweight Alumina-silica Castables by Replacing Closed-cell Perlite Aggregates with Coal Gangue Ceramsites

Lightweight alumina-silica castables were prepared using closed-cell perlite(2-4 mm),open-cell perlite(4-6 mm)and coal gangue ceramsites(2-5 mm)as aggregates,floating beads(0.3-0.5 mm),sinking beads(0.6-0.8 mm),silica micropowder,α-Al_(2)O_(3) micropowder,zirconia and zircon micropowder as fines,and Secar 71 cement(calcium aluminate cement)as the binder.The effects of the coal gangue ceramsites addition(0,6%,12%,18%and 24%,by mass)on the properties of the as-prepared lightweight alumina-silica castables were investigated.The results show that:(1)the addition of coal gangue ceramsites can reduce the sintering shrinkage of the specimens and help to improve the strength and thermal shock resistance;(2)the samples with the addition of coal gangue ceramsites can produce pores in the matrix of the sintered samples,which provides enough space for the growth of CA6 complex solid solution and expands the irregular lamellar structure;(3)with the addition of coal gangue ceramsites increasing,the linear shrinkage of the samples heat treated at 1000 or 1200℃firstly reduces and then increases,the bulk density increases and the apparent porosity decreases;the cold compression strength and the thermal shock resistance of the specimens heat treated at 1200℃firstly increase and then decrease.Thus,the optimal addition of coal gangue ceramsites is 18%.

Research on utilizing recycled plastic to make environment-friendly plywood

In our study, we replaced traditional adhesives with compounds made with recycled plastic shopping bags in order to make hot-melt plywood using various amounts of plastic film, different hot-pressing temperatures and hot-pressing times. All three variables have an effect on the intensity and water-resistance of plywood. The results show that the bonding strength of plywood does not increase with increasing amounts of plastic film. When the hot-pressing temperature is increased to 150℃, the bonding strength does not necessarily increase any further. At a hot-pressing time of 6 min, the bonding strength reaches a maximum, after which it will decrease. The optimum hot-pressing parameters are as follows： 100 g·m^-2 of recycled plastic, a hot-pressing temperature of 150℃ and a hot-pressing time of 6 min. This study puts forward a new idea of making use of plastic waste, which, ultimately, may solve the problem of formaldehyde emission without damaging the environment. It has enormous potential market applications.

Similarity evaluation of stratum anti-drilling ability and a new method of drill bit selection

Considering the stratum anti-drilling ability,drill bit working conditions,drill bit application effect and drill bit economic benefits,the similarity of stratum anti-drilling ability was evaluated by grey relational analysis theory to screen out candidate drill bits with reference values.A new comprehensive performance evaluation model of drill bit was established by constructing the absolute ideal solution,changing the relative distance measurement method,and introducing entropy weight to work out the closeness between the candidate drill bits and ideal drill bits and select the reasonable drill bit.Through the construction of absolute ideal solution,improvement of relative distance measurement method and introduction of entropy weight,the inherent defects of TOPSIS decision analysis method,such as non-absolute order,reverse order and unreasonable weight setting,can be overcome.Simple in calculation and easy to understand,the new bit selection method has good adaptability to drill bit selection using dynamic change drill bit database.Field application has proved that the drill bits selected by the new drill bit selection method had significant increase in average rate of penetration,low wear rate,and good compatibility with the drilled formations in actual drilling.This new method of drill bit selection can be used as a technical means to select drill bits with high efficiency,long life and good economics in oilfields.

The Relationship Between Online Participation and Academic Achievements for Students Majoring in Business English

The quantitative method here was applied to study the correlation between online participation and academic achievement.The online participation in this study was represented by the frequency with which students raise their hands in four business English reading classes over a single semester,while academic achievements were measured by the scores of the students in the final examination.The results showed a moderate positive correlation in two of the four classes of students between their online participation and scores on class level.Otherwise,there was no correlation in the other two classes.Since there was no strong correlation between online participation and comprehensive performance in this study,it can be inferred that online participation may not likely cause better comprehensive performance in the final examination.

An Evaluation Method for Automotive Technical and Comprehensive Performance

An objective evaluation scheme for automotive technical and comprehensive performance could provide critical and instructive insights for academic research,engineering practice,and commercial marketing of vehicles.In this paper,the technical performance index A=S∕T_(1)⋅T_(2)(m∕(s^(2)⋅L))and comprehensive performance index F=M⋅S∕T_(1)⋅T_(2),(kN⋅L^(−1),where M is the vehicle mass)are formulated by incorporating the vehicle 0–100 km⋅h^(−1) acceleration duration T_(1),100–0 km⋅h^(−1) braking duration T_(2),and fuel economy S(mileage per liter fuel at constant speed)to assess the vehicle’s longitudinal dynamic performance.A and F offer a clear physical implication of a vehicle’s acceleration capability and traction efficiency acquired per unit of fuel consumption,respectively.These indexes are used for wide case studies of popular market sedans and SUVs of joint ventures(JVs)and domestic brands in China over the last 17 years.The findings prove that this approach could be effectively and reliably utilized for the objective evaluation and analysis of the technical and comprehensive performance of automotive models.

Multiple indicators and analytic hierarchy process(AHP)for comprehensive performance evaluation of exhaust hood

Indicators are the basis for judging the working performance of exhaust hood and capture performance are usually used as the only indicator.An evaluation index system including three factors of cooking oil fumes(COF)instantaneous capture,health risk impact and thermal comfort was proposed to assess the comprehensive performance of exhaust hood in the present study.The primary capture efficiency(PCE)of formaldehyde,the PCE of particulate matter with the diameter less than or equal to 2.5μm(PM_(2.5)),the incremental lifetime cancer risk(ILCR)of formaldehyde,the ILCR of PM_(2.5)and the predicted mean vote(PMV),which can all be quantified with the aid of computational fluid dynamics(CFD),were selected as the indicators.And the analytic hierarchy process(AHP)method was introduced to perform the comprehensive performance evaluation of exhaust hood.The performance of two exhaust hood structures(grille and orifice type)with three exhaust rates(3000,4000,and 5000 m^(3)/h)in two cooking zones of a university canteen kitchen were evaluated.The result showed that the reduction of ILCR of COF exposure is the most important to the performance of exhaust hood.The comprehensive performance of orifice exhaust hood with exhaust rate of 4000 and 5000 m^(3)/h are optimal;the orifice exhaust hood with exhaust of 3000 m^(3)/h and grille exhaust hood with exhaust rate of 5000 m^(3)/h are moderate;the grille exhaust hood with exhaust rate of 3000 and 4000 m^(3)/h are low.Decision-making priorities based on comprehensive and individual performance are not exactly the same in the two cooking zones.It is necessary to use the index system to evaluate the comprehensive performance of exhaust hood that considers the impact on human health and thermal comfort.

A comparative study of different online model parameters identification methods for lithium-ion battery

Precise states estimation for the lithium-ion battery is one of the fundamental tasks in the battery management system(BMS),where building an accurate battery model is the first step in model-based estimation algorithms.To date,although the comparative studies on different battery models have been performed intensively,little attention is paid to the comparison among different online parameters identification methods regarding model accuracy,robustness ability,adaptability to the different battery operating conditions and computation cost.In this paper,based on the Thevenin model,the three most widely used online parameters identification methods,including extended Kalman filter(EKF),particle swarm optimization(PSO),and recursive least square(RLS),are evaluated comprehensively under static and dynamic tests.It is worth noting that,although the built model’s terminal voltage may well follow a measured curve,these identified model parameters may significantly out of reasonable range,which means that the error between measured and predicted terminal voltage cannot be seen as a gist to determine which model is the most accurate.To evaluate model accuracy more rigorously,battery state-of-charge(SOC)is further estimated based on identified model parameters under static and dynamic tests.The SOC prediction results show that EKF and RLS algorithms are more suitable to be used for online model parameters identification under static and dynamic tests,respectively.Moreover,the random offset is added into originally measured data to verify the robustness ability of different methods,whose results indicate EKF and RLS have more satisfactory ability against imprecisely sampled data under static and dynamic tests,respectively.Considering model accuracy,robustness ability,adaptability to the different battery operating conditions and computation cost simultaneously,EKF is recommended to be adopted to establish battery model in real application among these three most widely used methods.

A new method for performance evaluation of decision-making units with application to service industry

The decision-making units(DMUs)in the modern service industries may produce desirable outputs and undesirable outputs.For the decision makers,some outputs may be more desired than others although all of them are desirable.Considering these characteristics,this work combines the data envelopment analysis(DEA)and the multiple attributes decision-making(MADM)method,to make a reasonable and comprehensive performance evaluation for DMUs.Specifically,three DEA-based models are modified to obtain more reasonable efficiency scores for DMUs.The MADM method is used to determine the weights of outputs based on the preference ratings within the outputs.The efficiency scores are then multiplied by the aggregated outputs quantities to obtain the comprehensive performance scores for evaluation.The effectiveness of the proposed models is demonstrated by extensive numerical experiments.