共查询到18条相似文献，搜索用时 187 毫秒
1.
A set of compressed natural gas (CNG) multi-point direct injection system of spark-ignited engines and the corresponding measurement and data acquisition systems were developed in this paper. Based on different injection modes, the mixture formation and combustion of CNG low-pressure direct injection (LPDI) engines were studied under varying factors such as air/ fuel ratio, injection timing. Meanwhile, three-dimensional simulations were adopted to explain the mixture formation mechanisms of CNG low-pressure compound direct injection (LPCDI) mode. On the basis of test results and simulation of the mixture homogeneous degree, the conception of injection window was proposed, and the LPCDI mode was proved to be more beneficial to the mixture concentration stratification formation in cylinder under lean-burning conditions, which resulted in effective combustion and stability. 相似文献
2.
Application of developed Grid-GA distributed hydrologic model in semi-humid and semi-arid basin 总被引：1，自引：0，他引：1
A grid and Green-Ampt based(Grid-GA)distributed hydrologic physical model was developed for flood simulation and forecasting in semi-humid and semi-arid basin. Based on topographical information of each grid cell extracted from the digital elevation model (DEM) and Green-Ampt infiltration method, the Grid-GA model takes into consideration the redistribution of water content, and consists of vegetation and root interception, evapotranspiration, runoff generation via the excess infiltration mechanism, runoff concentration, and flow routing. The downslope redistribution of soil moisture is explicitly calculated on a grid basis, and water exchange among grids within runoff routing along the river drainage networks is taken into consideration. The proposed model and Xin’anjiang model were applied to the upper Lushi basin in the Luohe River, a tributary of the Yellow River, with an area of 4 716 km2 for flood simulation. Results show that both models perform well in flood simulation and can be used for flood forecasting in semi-humid and semi-arid region. 相似文献
3.
Numerical simulation of a gas pipeline network using computational fluid dynamics simulators 总被引：1，自引：0，他引：1
SELEZNEV Vadim 《浙江大学学报(A卷英文版)》2007,8(5):755-765
This article describes numerical simulation of gas pipeline network operation using high-accuracy computational fluid dynamics (CFD) simulators of the modes of gas mixture transmission through long, multi-line pipeline systems (CFD-simulator). The approach used in CFD-simulators for modeling gas mixture transmission through long, branched, multi-section pipelines is based on tailoring the full system of fluid dynamics equations to conditions of unsteady, non-isothermal processes of the gas mixture flow. Identification, in a CFD-simulator, of safe parameters for gas transmission through compressor stations amounts to finding the interior points of admissible sets described by systems of nonlinear algebraic equalities and inequalities. Such systems of equalities and inequalities comprise a formal statement of technological, design, operational and other constraints to which operation of the network equipment is subject. To illustrate the practicability of the method of numerical simulation of a gas transmission network, we compare computation results and gas flow parameters measured on-site at the gas transmission enter-prise. 相似文献
4.
ZHAN Liang-tong CHEN Ping NG C.W.W. 《浙江大学学报(A卷英文版)》2007,8(5):699-706
A laboratory study was carried out on both natural and compacted specimens to investigate the complex soil-water interaction in an unsaturated expansive clay. The laboratory study includes the measurement of soil-water characteristic curves, 1D free swelling tests, measurement of swelling pressure and shrinkage tests. The test results revealed that the air-entry value of the natural specimen was quite low due to cracks and fissures present. The hydraulic hysteresis of the natural specimen was relatively insignificant as compared with the compacted specimen. Within a suction range 0 to 500 kPa, a bilinear relationship between free swelling strain (or swelling pressure) and initial soil suction was observed for both the natural and compacted specimens. As a result of over-consolidation and secondary structures such as cementation and cracks, the natural specimens exhibited significant lower swelling (or swelling pressure) than the compacted specimen. The change of matric suction exerts a more significant effect on the water phase than on the soil skeleton for this expansive clay. 相似文献
5.
A dynamic velocity feed-forward compensation control (DVFCC) approach with RBF neural network (RBF-NN) dynamic model identification was presented for the adaptive trajectory tracking of industrial robots.The proposed control approach combined the advantages of traditional feedback closed-loop position control and computed torque control based on inverse dynamic model.The feed-forward compensator used a nominal robot dynamics as accurate dynamic model and on-line identification with RBF-NN as uncertain part to improve dynamic modeling accuracy.The proposed compensation was applied as velocity feed-forward by an inverse velocity controller that can convert torque signal into velocity in the standard industrial controller.Then,the need for a torque control interface was avoided in the real-time dynamic control of industrial robot.The simulations and experiments were carried out on a gas cutting manipulator.The results show that the proposed control approach can reduce steady-state error,suppress overshoot and enhance tracking accuracy and efficiency in joint space and Cartesian space,especially under highspeed condition. 相似文献
6.
A mathematic model of two-phase flow and a physical model of two-dimensional (2D) vertical section for the plate-type structured packing Mellapak 250.Y were set up and verified. The models were used to study the influence of packing’s surface microstructure on the continuity of liquid film and the amount of liquid holdup. Simulation results show that the round corner shape and micro wavy structure are favorable in remaining the continuity of liquid film and increasing the amount of liquid holdup. The appropriate liquid flow rate was determined by investigating different liquid loadings to obtain an unbroken liquid film on the packing surface. The pressure difference between inlet and outlet for gas phase allowed gas and liquid to flow countercurrently in a 2D computational domain. The direction change of gas flow occurred near the phase interface area. 相似文献
7.
During the last four decades, reinforced-concrete structure failures have been happening widely for many reasons, such as increased service loads, war accidents, fire, and durability problems. The economic losses due to those failures are very high. An expert system is an interactive computer-based decision tool that uses both facts and heuristics to solve difficult problems based on knowledge acquired from experts. To realize these requirements, a logic programming visual basic language is used together with visual diagnosis. The expert system, Diagnosis of Fire-Caused Damages to Reinforced-Concrete Tunnel Lining (DFCDRCTL) was developed in this work for diagnosing the annual damages caused by fire. The program is used as an alternative of a human expert to make annual technical decisions in diagnosing fire damages at the second reinforced-concrete tunnel lining segment. It is concluded that the proposed DFCDRCTL expert system is easy to use, and is fast and helpful for engineers. 相似文献
8.
Fiber Bragg grating(FBG) is used as a wavelength reference device to calibrate the position of gas absorption peak in the intracavity absorption gas sensor(ICAGS) based on erbium-doped fiberring laser.This system can detect both the reflectance spectrum of FBGs and absorption spectrum of measured gas during a single wavelength sweeping process by linearly varying the driving voltage of optic filter.The voltages corresponding to center wavelength positions of four FBGs in the spectrum are determined through ... 相似文献
9.
魏季和 《上海大学学报(英文版)》2002,6(1):1-23
The available studies in the literature on physical and mathematical modeling of the argon-oxygen decarburization(AOD) process of stainless ssteel have briefly been reviewed.The latest advances made by the author with his research group have been summarized.Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18t AOD vessel,as well as the “back-attack” action of gas jfets and its effects on the erosion and wear of the refractory lining,with sufficiently full kinematic similarity.The non-rotating and rotating gas jets blown through two annular tuyeres,respectively of straight-tube and spiral-flat tube type.Were employed in the experiments.The geometric similarity ratio between the model and its prototype(including the straighttube type tuyeres)was 1:3 ,The influences of the gas flow rate,the angle included between the two tuyeres and other operating parameters,and the suitability of the spiral tuyere as a practical application,were examined.These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back-attack phenomena of gas jfets during the blowing.nd have offered a better understanding of the refining process.Besides,mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed.The model performs the rate calculations of the refining and the mass and heat balances of the system.Also,the effects of the operating factors,including adding the salg materials.crop ends,and scrap,and alloy agents;the non-isothermal conditions;the changes in the amounts of metal and slag materials,crop ends,and scrap,and alloy agents;the non-isothermal conditions;the changes in the amounts of metal and slag during the refining;and other factors were all considered.The model was used to deal with and analyze the austenitic stainless steel making (including ultra-low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18t AOD vessel.The changes in the bath compostion and temperature during the refining process with time can be accurately predicted using this model.The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real-time and online. 相似文献
10.
Education is the backbone for the development of society. With the advent of technology, it is becoming necessary and being used for the advancement of society. Technology is being used for education as being used in other important fields of life. Usage of technology for education can play a big part in bringing improvement in education For this purpose, this research aims to explore the usage and effects of technology for education. While using the survey method, a questionnaire was constructed for data collection. The sample of the study consists of graduate and postgraduate students from both ODL and regular universities and the sample size would be of 300 respondents （150 from each type of university） who were selected by using simple random sampling. The present study concluded that technology is widely used by both regular and ODL students. This study further concluded that ODL students are more dependent on technology as compared to regular students. 相似文献
11.
为实现混合有机废弃物的资源化处理与综合利用,以安徽农业大学为例,对该校各学生食堂产生的餐厨废弃物及农业园温室生产有机废弃物等为原料,以沼气工程厌氧发酵技术为核心,将混合有机废弃物转化为清洁可再生能源及高品质有机肥原料;方案设计日处理量3t,需建设全混式厌氧反应器（CSTR）225m3;可实现年处理混合有机废弃物约800t,年产沼气约4.8万m3,沼渣、沼液有机肥原料约400t;所产沼气用于厌氧工程加热、保温,沼液沼渣用作农业园温室生产有机肥料;本方案的实施可改善校园环境,形成生态、环保的校园氛围,建立循环农业基本模式。 相似文献
12.
采用电沉积的方式将纳米金固载在玻碳电极表面,制得纳米金修饰玻碳电极(NG/GCE)。研究了去甲肾上腺素(NE)在NG/GCE的电化学行为,发现NG/GCE不仅对NE有良好的催化和富集作用,而且能将NE和抗坏血酸(AA)的循环伏安氧化峰很好地区分开,可在抗坏血酸共存下选择性测定NE。 相似文献
13.
以蚕豆叶片为材料,借助药理学实验和共聚焦技术结合一氧化氮（N0）探针DAF-2DA证明光下乙烯合成前体1-氨基环丙烷-1-羧酸（ACc）和乙烯气体均能显著诱导气孔关闭,且均表现明显浓度依赖效应。另外,一氧化氮合酶（NOS）抑制荆NG-氮-L-精氨酸-甲酯能够逆转ACC和乙烯气体诱导气孔关闭的效应,并能阻断ACC和乙烯气体诱导的气孔保卫细胞内NO水平的提高。结果表明乙烯可能通过NO$途径诱导的蚕豆保卫细胞内NO水平的提高导致气孔关闭。 相似文献
14.
Carolin Kreber Heather Castleden Nina Erfani Joan Lim Tarah Wright 《Teaching in Higher Education》2013,18(3):431-445
We explore the utility of George Kelly's Personal Construct Theory, specifically his repertory grid technique, to the assessment of student learning in undergraduate science courses. We provide an in-depth review of the assumptions underlying Personal Construct Theory and how these were reflected in the repertory grid technique Kelly developed. We explain how an adapted version of the repertory grid, sharing some yet not all of Kelly's assumptions, was utilised as a research tool in a recent study involving science instructors and their students. We argue that as well as having applicability as an innovative research tool, an adapted version of Kelly's repertory grid is a useful heuristic for university teachers when used as a classroom assessment technique (CAT) and indicate several features it shares with the more widely-known conceptual mapping technique, which has been used in the study of science teaching and learning for many years. We conclude by highlighting several advantages the use of repertory grids has for both students and instructors. 相似文献
15.
MVC模式能克服二层体系结构的局限,被广泛地用于大型软件的开发。网格技术和web服务被用于解分布式资源的共享。在研究传统的MVC模式的基础上,提出一种基于网格的MVC模型(GM-VC),并分析和讨论该模型的结构及其设计。GMVC模型能较好地解决网格系统中业务逻辑混合的问题。 相似文献
16.
旨在为秸秆类木质纤维素沼气工业化奠定科学基础,以滤纸作为纤维素材料对不同发酵原料和发酵时期的沼气池菌系进行驯化和筛选,并研究其中温条件下对麦秸、玉米秸和滤纸的降解特性.采用减重法、分光光度法和蒸馏法分别测定复合菌系在发酵过程中的纤维素降解能力、复合菌系生物量和发酵液中挥发性有机酸.结果显示：发酵原料和发酵时期的菌源纤维素降解能力有较大差异,来自粪便池源的复合菌系在发酵前期纤维素降解力强,而秸秆池源的复合菌系在发酵后期纤维素降解力强.粪源产气稳定期的复合菌系F6的降解能力最强,对纤维素降解能力由高到低依次为滤纸、麦秸和玉米秸. 相似文献
17.
Two squirrel monkeys searched for a reward buried in 1 of 144 holes that formed a 12×12 grid (48×50 cm). An array of vertical, colored landmarks was placed on the grid, and their locations on the grid were changed from trial to trial. During training trials, the mealworm reward was placed either in the center of a square array of landmarks (Experiments 1 and 3) or midway between two landmarks (Experiment 2). On nonrewarded test trials, the monkeys searched among landmarks placed in the same arrays as those used in training and among landmarks placed in an expanded array (Experiments 1 and 2) or in an array intermediate between the two arrays used in training (Experiment 3). Distributions of searches on test trials indicated that the monkeys searched mostly within the configuration of the landmarks but that they had not coded the location of the reward as being either in the middle of the landmarks or at a fixed distance and direction from an individual landmark. 相似文献
18.
Chun-yu Li Zhe-wei Wang Can Tu Jia-bo Wang Bing-qian Jiang Qi Li Ling-na Zeng Zhi-jie Ma Ping Zhang Yan-ling Zhao Ya-ming Zhang Dan Yan Rui Tan Xiao-he Xiao 《Journal of Zhejiang University. Science. B》2014,15(10):888-899
Insulin is widely used in treating diabetes, but still needs to be administered by needle injection. This study investigated a new needle-free approach for insulin delivery. A portable powder needleless injection (PNI) device with an automatic mechanical unit was designed. Its efficiency in delivering insulin was evaluated in alloxan-induced diabetic rabbits. The skin irritation caused by the device was investigated and the results were analyzed in relation to aerodynamic parameters. Inorganic salt-carried insulin powders had hypoglycemic effects, while raw insulin powders were not effective when delivered by PNI, indicating that salt carriers play an important role in the delivery of insulin via PNI. The relative delivery efficiency of phosphate-carried insulin powder using the PNI device was 72.25%. A safety assessment test showed that three key factors (gas pressure, cylinder volume, and nozzle distance) were related to the amount of skin irritation caused by the PNI device. Optimized injection conditions caused minimal skin lesions and are safe to use in practice. The results suggest that PNI has promising prospects as a novel technology for delivering insulin and other biological drugs. 相似文献