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Emission components characteristics of a bi-fuel vehicle at idling condition

Sameh M. METWALLEY, Shawki A. ABOUEL-SEOUD, Abdelfattah M. FARAHAT

《能源前沿（英文）》 2011年第5卷第3期页码 322-329 doi: 10.1007/s11708-011-0158-6

摘要： Natural gas (NG) represents today a promising alternative to conventional fuels for road vehicles propulsion, since it is characterized by a relatively low cost, better geopolitical distribution than oil, and lower environmental impact. This explains the current spreading of compressed natural gas (CNG) fuelled spark ignition (SI) engine, above all in the bi-fuel version, which is able to run either with gasoline or with NG. However, the aim of the present investigation is to evaluate the emission characteristics at idling condition. The vehicle engine was converted to bi-fueling system from a gasoline engine, and operated separately either with gasoline or CNG. Two different fuel injection systems (i.e., multi-point injection (MPI)-sequential and closed-loop venturi-continuous) are used, and their influences on the formation of emissions at different operating conditions are examined. A detailed comparative analysis of the engine exhaust emissions using gasoline and CNG is made. The results indicate that the CNG shows low air index and lower emissions of carbon monoxide (CO), carbon dioxide (CO ), and total hydrocarbon (THC) compared to gasoline.

关键词： road vehicle engine fuel injection systems carbon monoxide (CO) carbon dioxide (CO₂) total hydrocarbon (THC) vehicle idle conditions air index

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Accelerated life-time test of MEA durability under vehicle operating conditions in PEM fuel cell

Tian TIAN, Jianjun TANG, Wei GUO, Mu PAN

《能源前沿（英文）》 2017年第11卷第3期页码 326-333 doi: 10.1007/s11708-017-0489-z

摘要： In this paper, a novel accelerated test method was proposed to analyze the durability of MEA, considering the actual operation of the fuel cell vehicle. The proposed method includes 7 working conditions: open circuit voltage (OCV), idling, rated output, overload, idling-rated cycle, idling-overload cycle, and OCV-idling cycle. The experimental results indicate that the proposed method can effectively destroy the MEA in a short time (165 h). Moreover, the degradation mechanism of MEA was analyzed by measuring the polarization curve, CV, SEM and TEM. This paper may provide a new research direction for improving the durability of fuel cell.

关键词： polymer electrolyte membrane fuel cell accelerated life-time test load cycling test durability

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Changes of ecological conditions induced by rock tunneling in Laoshan Mountain area

LI Xiaozhao, ZHAO Xiaobao, WANG Zhongsheng

《结构与土木工程前沿（英文）》 2008年第2卷第4期页码 366-370 doi: 10.1007/s11709-008-0056-0

摘要： Through field investigation, this paper examined the changes of ecological conditions induced by tunnel construction in Laoshan Mountain area, Nanjing, Jiangsu Province, P. R. China. The effects of habitat fragmentation and edge effect are examined and discussed. It is found that the environmental factors and vegetation situation have been influenced by the tunneling activity, and the disturbed area is approaching the sampling patch centre. The changed ecological conditions are beneficial for the settlement and growth of some herb and shrub species, and are unfavorable for the existence and growth of saplings, especially for the predominant species (e.g., robur) in this area. If the time of habitat fragmentation is long enough and there is no supplement from external areas, some vegetation species in the engineering influencing area will deteriorate, or even diminish in the future. The results can be used as a reference for the long-term ecological study in this area.

关键词： supplement fragmentation reference tunneling activity vegetation situation

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Assessing artificial neural network performance for predicting interlayer conditions and layer modulus

Lingyun YOU, Kezhen YAN, Nengyuan LIU

《结构与土木工程前沿（英文）》 2020年第14卷第2期页码 487-500 doi: 10.1007/s11709-020-0609-4

摘要： The objective of this study is to evaluate the performance of the artificial neural network (ANN) approach for predicting interlayer conditions and layer modulus of a multi-layered flexible pavement structure. To achieve this goal, two ANN based back-calculation models were proposed to predict the interlayer conditions and layer modulus of the pavement structure. The corresponding database built with ANSYS based finite element method computations for four types of a structure subjected to falling weight deflectometer load. In addition, two proposed ANN models were verified by comparing the results of ANN models with the results of PADAL and double multiple regression models. The measured pavement deflection basin data was used for the verifications. The comparing results concluded that there are no significant differences between the results estimated by ANN and double multiple regression models. PADAL modeling results were not accurate due to the inability to reflect the real pavement structure because pavement structure was not completely continuous. The prediction and verification results concluded that the proposed back-calculation model developed with ANN could be used to accurately predict layer modulus and interlayer conditions. In addition, the back-calculation model avoided the back-calculation errors by considering the interlayer condition, which was barely considered by former models reported in the published studies.

关键词： asphalt pavement interlayer conditions finite element method artificial neural network back-calculation

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Influence of initial curing conditions and exposure environments on chloride migration in concrete using

Wen XUE, Weiliang JIN, Hiroshi YOKOTA,

《结构与土木工程前沿（英文）》 2010年第4卷第3期页码 348-353 doi: 10.1007/s11709-010-0077-3

摘要： To investigate the influence of initial curing conditions and exposure environments on chloride ions’ migration in concrete, the specimens that were cured in different conditions and placed in several marine environments were studied. The amount of chloride ions passing through the specimen’s section was monitored in the accelerated chloride migration test. The effective chloride diffusion coefficients () were calculated from the steady-state on the basis of Nernst-Planck’s equation. The results indicated that the initial curing conditions and the wet-dry interval of external environments have coupling influence on effective diffusion coefficient of chloride ion significantly. reflected the density and pore connectivity of concrete. The co-effects of the initial curing condition and following exposure environment should be taken into account in durability design for concrete structure located in marine environment.

关键词： durability effective diffusion coefficient steady-state migration test

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长征三号系列运载火箭

龙乐豪

《中国工程科学》 1999年第1卷第1期页码 11-18

摘要：

论述了长征三号系列运载火箭诞生的背景、设计思路、总体技术方案、应用发射结果及其在技术与研制工作方面的特点，展望了其发展前景，指出该系列运载火箭是我国目前性能先进的大型主力商业应用发射火箭群体。

关键词：航天大型运载火箭发射服务长征三号系列

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Boundary conditions for axisymmetric piezoelectric cylinder

Baosheng ZHAO, Di WU, Xi CHEN

《机械工程前沿（英文）》 2013年第8卷第4期页码 401-408 doi: 10.1007/s11465-013-0272-8

摘要：

For axisymmetric piezoelectric cylinder, the reciprocal theorem and the axisymmetric general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the cylinder of general edge geometry and loadings. A decay analysis technique developed by Gregory and Wan is converted into necessary conditions on the end-data of axisymmetric piezoelectric circular cylinder, and the rapidly decaying solution is established. The prescribed end-data of the circle cylinder must satisfy these conditions in order that they could generate a decaying state within the cylinder. When stress and mixed conditions are imposed on the end of cylinder, these decaying state conditions for the case of axisymmetric deformation of piezoelectric cylinder are derived explicitly. They are then used for the correct formulation of boundary conditions for the theory solution (or the interior solution) of axisymmetric piezoelectric cylinder. The results of the present paper enable us to establish a set of correct boundary conditions, most of which are obtained for the first time.

关键词： solid and structures the axisymmetric deformation the piezoelectric circular cylinder the refined theory Bessel’s Function

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Influence of boundary conditions and turntable speeds on the stability of hydrostatic oil cavity

Zhaomiao LIU, Chengyin ZHANG, Feng SHEN

《机械工程前沿（英文）》 2011年第6卷第3期页码 359-368 doi: 10.1007/s11465-011-0222-2

摘要：

The flow, bearing, and carrying capacity of the cycloidal hydrostatic oil cavity in hydrostatic turntable systems are numerically simulated, considering the rotation speeds of a turntable from 0 to 5 m/s and different boundary conditions. The vortex effect is weakened, and the stability of the oil cavity is enhanced with the increase in lubricant viscosity. However, the increase in inlet speed, depth, and inlet radius of the oil cavity causes the vortex effect to increase and the stability of oil cavity to reduce. With the increase in the oil film thickness, the carrying capacity of the oil cavity diminishes. The oil cavity pressure increases along the direction of the motion of the turntable; it is distributed unevenly because of the rotation of the turntable. With the increase in turntable speed, the location and size of the vortex scope in the oil cavity flow field and the strength of the vortex near the entrance gradually weaken and move away from the entry. The distribution of pressure is determined by the locations of the vortex. When the vortex is close to the wall, the wall pressure increases at its location. Otherwise, the wall pressure decreases first and then increases after the center of the vortex.

关键词： hydrostatic oil cavity flow state oil cavity pressure stability vortex

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Performance design of a cryogenic air separation unit for variable working conditions using the lumped

Jinghua XU, Tiantian WANG, Qianyong CHEN, Shuyou ZHANG, Jianrong TAN

《机械工程前沿（英文）》 2020年第15卷第1期页码 24-42 doi: 10.1007/s11465-019-0558-6

摘要： Large-scale cryogenic air separation units (ASUs), which are widely used in global petrochemical and semiconductor industries, are being developed with high operating elasticity under variable working conditions. Different from discrete processes in traditional machinery manufacturing, the ASU process is continuous and involves the compression, adsorption, cooling, condensation, liquefaction, evaporation, and distillation of multiple streams. This feature indicates that thousands of technical parameters in adsorption, heat transfer, and distillation processes are correlated and merged into a large-scale complex system. A lumped parameter model (LPM) of ASU is proposed by lumping the main factors together and simplifying the secondary ones to achieve accurate and fast performance design. On the basis of material and energy conservation laws, the piecewise-lumped parameters are extracted under variable working conditions by using LPM. Takagi–Sugeno (T–S) fuzzy interval detection is recursively utilized to determine whether the critical point is detected or not by using different thresholds. Compared with the traditional method, LPM is particularly suitable for “rough first then precise” modeling by expanding the feasible domain using fuzzy intervals. With LPM, the performance of the air compressor, molecular sieve adsorber, turbo expander, main plate-fin heat exchangers, and packing column of a 100000 Nm O /h large-scale ASU is enhanced to adapt to variable working conditions. The designed value of net power consumption per unit of oxygen production (kW/(Nm O )) is reduced by 6.45%.

关键词： performance design air separation unit (ASU) lumped parameter model (LPM) variable working conditions T–S fuzzy interval detection

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Identification of structural parameters and boundary conditions using a minimum number of measurement

Ali KARIMPOUR, Salam RAHMATALLA

《结构与土木工程前沿（英文）》 2020年第14卷第6期页码 1331-1348 doi: 10.1007/s11709-020-0686-4

摘要： This article proposes a novel methodology that uses mathematical and numerical models of a structure to build a data set and determine crucial nodes that possess the highest sensitivity. Regression surfaces between the structural parameters and structural output features, represented by the natural frequencies of the structure and local transmissibility, are built using the numerical data set. A description of a possible experimental application is provided, where sensors are mounted at crucial nodes, and the natural frequencies and local transmissibility at each natural frequency are determined from the power spectral density and the power spectral density ratios of the sensor responses, respectively. An inverse iterative process is then applied to identify the structural parameters by matching the experimental features with the available parameters in the myriad numerical data set. Three examples are presented to demonstrate the feasibility and efficacy of the proposed methodology. The results reveal that the method was able to accurately identify the boundary coefficients and physical parameters of the Euler-Bernoulli beam as well as a highway bridge model with elastic foundations using only two measurement points. It is expected that the proposed method will have practical applications in the identification and analysis of restored structural systems with unknown parameters and boundary coefficients.

关键词： structural model validation eigenvalue problem response surface inverse problems

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Recent developments in passive interconnected vehicle suspension

Wade A. SMITH, Nong ZHANG,

《机械工程前沿（英文）》 2010年第5卷第1期页码 1-18 doi: 10.1007/s11465-009-0092-z

摘要： This paper presents an overall review on the historical concept development and research advancement of passive hydraulically interconnected suspension (HIS) systems. It starts with an introduction to passive HIS systems and their various incarnations developed over many decades. Next, a description is provided of a recently proposed multidisciplinary approach for the frequency-domain analysis of vehicles fitted with an HIS. The experimental validation and applications of the method to both free and forced vibration analysis are discussed based on a simplified, roll-plane half-car model. A finite-element-method-based approddach for modelling the transient dynamics of an HIS vehicle is also briefly outlined. In addition, recent work on the investigation of NVH associated with HIS-equipped vehicles is mentioned. Discussion is then provided on future work to the further understanding of HIS and its applications. The paper concludes that interconnected suspension schemes can provide much greater flexibility to independently specify modal stiffness and damping parameters – a characteristic unique among passive suspensions. It points out that there is a need for system optimisation, and there are troublesome NVH issues that require solutions. It suggests that further research attention and effort be paid to NVH issues and system level optimisation to gain a greater understanding of HIS and to broaden its applications.

关键词： interconnected suspensions rollover prevention vehicle dynamics ride comfort multibody system dynamics hydraulic system dynamics

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考虑电池放电特性的动态电压调节策略研究

许参,胡晨

《中国工程科学》 2008年第10卷第2期页码 79-85

摘要：

电池寿命是移动设备的关键设计参数之一。由于电池容量消耗的非线性和与负载轮廓相关的特性，最大化电池寿命是个相当困难的问题。研究了在考虑电池放电特性情况下动态电压调节策略（DVS, dynamic voltage scaling）最小化电池容量消耗的问题。针对现有考虑电池放电特性的DVS策略中空闲时间分配不合理的缺陷，提出了空闲时间分布调整过程，用于优化空闲时间分布从而减少电池容量消耗，并分析了该过程对任务调度的影响。实验结果表明对现有考虑电池放电特性的DVS策略形成的任务调度进行空闲

关键词：电池优化动态电压调节空闲时间分布调整

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2023年度机械与运载工程前沿

机械与运载工程项目组

《全球工程前沿》 2023年第7卷第1期页码 7-34

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of preozonation on the bioactivity and biodiversity of subsequent biofilters under low temperature conditions—A

Jiaxuan YANG, Jun MA, Dan SONG, Xuedong ZHAI, Xiujuan KONG

《环境科学与工程前沿（英文）》 2016年第10卷第4期 doi: 10.1007/s11783-016-0844-z

摘要： The bioactivity was enhanced by preozonation under low temperature conditions. Higher level of BDOC/AOC and DO may enhance the nitrifying performance. High level of biodiversity and bioactivity may help maintain the stability of filters. Water quality and DO could selectively enhance different microbial communities. The combination of preozonation and subsequent biological granular activated carbon (O /BAC) filtration is well known as a promising method for the removal of many pollutants. Temperature and nutrients are the dominant factors in external conditions to influence the biological communities. To explore the influence of preozonation under low temperature, the factors such as dissolved oxygen (DO), dissolved organic carbon (DOC) and NH -N were analyzed from the sampling ports every week; triphenyl tetrazolium chloride-dehydrogenase activity (TTC-DHA) and the nitrifying activity were detected along the bed height of biofilter at four levels (10, 40, 70 and 110 cm) on the 90th, 110th, and 130th day; microbial community, based on 16S rRNA gene-denaturing gradient gel electrophoresis (DGGE), was monitored on the 130th day of the operation. The observed microbial property showed that preozonation had a positive influence on bioactivity, biomass and nitrifying activity. Community analysis showed no significant difference on the biodiversity of nitrifying bacteria between the parallel filters in the inlet end based on the method employed. This result showed that biofilters’ performance is not correlated well with microbial biodiversity. The elevated functionality in O /BAC filters can be a result of increased microbial activity, which was promoted by preozonation.

关键词： Preozonation BAC filtration High ammonia level Bacterial activity Microbial community structure Pilot scale study

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加快制定适合我国国情的智能制造技术战略

延建林,董景辰,古依莎娜,杨晓迎

《中国工程科学》 2018年第20卷第4期页码 9-12 doi: 10.15302/J-SSCAE-2018.04.002

摘要：

当前，新一轮科技革命和产业变革不断加速，全球制造业进入新的发展阶段。美国、德国、日本等发达国家都制定了本国智能制造技术发展战略。中国智能制造正处于加速发展的关键期，发展不平衡不充分的矛盾非常突出，必须要按照前瞻性、阶段性、实用性、开放性相结合的原则，抓紧制定适合我国国情的智能制造技术发展战略，以指导和推动我国制造业科学地实现智能升级。

关键词：中国国情智能制造技术战略