期刊文献+
共找到5,438篇文章
< 1 2 250 >
每页显示 20 50 100
Effects of melatonin implantation on cashmere yield,fibre characteristics,duration of cashmere growth as well as growth and reproductive performance of Inner Mongolian cashmere goats 被引量:18
1
作者 Chunhui Duan Jianhai Xu +2 位作者 Changmian Sun Zhihai Jia Wei Zhang 《Journal of Animal Science and Biotechnology》 SCIE CAS CSCD 2015年第4期463-468,共6页
Background: Exogenous melatonin could induce cashmere growth. However, induced growth of cashmere fleece by melatonin implants cannot be combined with the typical growth, resulting in earlier shedding followed by ano... Background: Exogenous melatonin could induce cashmere growth. However, induced growth of cashmere fleece by melatonin implants cannot be combined with the typical growth, resulting in earlier shedding followed by another cycle of cashmere growth. To address this issue, we examine the effects on the cashmere yield, fibre characteristics, and the growth and reproductive performance of cashmere goats of planned administration of melatonin. Methods: Eighteen half-sib, female goats were assigned to two treatments (n = 9) including a control and a treatment where melatonin (2 mg/kg BW) was implanted at the end of April and end of June. Cashmere growth and shedding were observed for approximately ] year following implantation. Fibre samples were collected monthly to determine cumulative cashmere length. Initiation and cessation dates for cashmere growth as well as the rate of cashmere growth were calculated. Cashmere yield, weight gain of dam, kidding date, litter size, and birth weight were also recorded. Results: Melatonin implantation increased cashmere yield by 34.5 % (control 553.7 g vs. melatonin 745.0 g; P〈 0.01), cashmere length by 21.3 % (control 95.2 mm vs. melatonin 115.4 mm; P 〈 0.01), and decreased fibre diameter by 4.4 % (control 14.6 pm vs. melatonin 14.0 IJm; P 〈 0.03). In melatonin-treated goats, the average initiation date was earlier than in control goats (May 18, 2013 vs. July 2, 20]3; P〈 0.01) but there was a similar cessation date (March 22, 2014 vs. March 27, 2014). Consequently, the duration of cashmere growth was longer in melatonin-treated goats than in control goats (307 vs.270 days; P 〈 0.01). The final BW, average daily gain, kidding date, litter size, and birth weight were not influenced by melatonin implantation. Conclusions: These data indicate that melatonin implantation (2 mg/kg BW) on two occasions (late April and June) increased cashmere yield by combining the induced growth of cashmere fleece with the typical growth and decreased the fibre diameter without changing dam growth rate or reproductive performance. 展开更多
关键词 Cashmere goat Cashmere yield Fibre characteristics Growth performance Melatonin Reproductive performance
下载PDF
An Overview of Performance Characteristics, Experiencesand Trends of Aerospace Engine Bearings Technologies 被引量:28
2
作者 Ebert Franz-Josef 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2007年第4期378-384,共7页
In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, i... In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, integration design and reliability, are reviewed. The development history of aerospace engine bearing is recalled briefly at first. Then today's material technologies and the high bearing performances of the bearings obtained through the new materials are introduced, which play important roils in the aeroengine bearing developments. The integration design ideas and practices are explained to indicate its significant advantages and importance to the aerospace engine bearings. And the reliability of the shaft-bearing system is pointed out and treated as the key requirement with goals for both engine and bearing. Finally, as it is believed that the correct design comes from practice, the pre-qualification rig testing conducted by FAG Aerospace GmbH & Co. KG is briefly illustrated as an example. All these lead to the development trends of aerospace engine bearings from different aspects. 展开更多
关键词 aerospace engine bearing performance characteristic material technology integrated bearing design reliability system cost
下载PDF
Characteristics and Performance of Novel Water-Absorbent Slow Release Nitrogen Fertilizers 被引量:25
3
作者 HE Xu-sheng LIAO Zong-wen +4 位作者 HUANG Pei-zhao DUAN Ji-xian GE Ren-shan LI Hong-bo GENG Zeng-chao 《Agricultural Sciences in China》 CAS CSCD 2007年第3期338-346,共9页
In this article, a research on the characteristics and performance of water-absorbent slow release nitrogen fertilizer (WASRNF) using infrared spectroscopy (IR), scanning electronic microscopy (SEM), differentia... In this article, a research on the characteristics and performance of water-absorbent slow release nitrogen fertilizer (WASRNF) using infrared spectroscopy (IR), scanning electronic microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA), was present. The results indicate that the water absorbency and nitrogen analysis of WASRNF is 103 g g^-1 and 30%, respectively, and WASRNF exhibits approximately neutral pH and very low salt index. WASRNF is a copolymer of nitrogen fertilizer and super absorbent polymer (SAP) monomers which is formed through hydrogen bond interaction, and the molecule contains hydrophilic groups, which is responsible for the absorption and water retention capacity of the molecule. WASRNF is a gel that exhibits the ability to swell, but does not dissolve in water. WASRNF shows non-homogenous nature as a whole, but in local zone it is homogenous, the copolymer molecule shows chain network that is the physical structure responsible for absorption and retention of water in WASRNF. The water retained in WASRNF exists as free and nonfreezing bound and freezing bound water states, with the free and the nonfreezing water accounting for more than 95% of water retained in WASRNF, and the nonfreezing bound water for less than 5%. WASRNF functions in delaying the release of nitrogen from it, thereby serving a novel slow release nitrogenous fertilizer. 展开更多
关键词 water-absorbent slow release nitrogen fertilizer characteristics performance
下载PDF
Experimental study on atomization characteristics and dust-reduction performance of four common types of pressure nozzles in underground coal mines 被引量:5
4
作者 Han Han Pengfei Wang +1 位作者 Ronghua Liu Chang Tian 《International Journal of Coal Science & Technology》 EI 2020年第3期581-596,共16页
Pressure nozzle is commonly used in the dust-reduction techniques by spraying of underground coal mines.Based on the internal structure,the pressure nozzle can be divided into the following types:spiral channel nozzle... Pressure nozzle is commonly used in the dust-reduction techniques by spraying of underground coal mines.Based on the internal structure,the pressure nozzle can be divided into the following types:spiral channel nozzle,tangential flow-guided nozzle and X-swirl nozzle.In order to provide better guidance on the selection of nozzles for the coal mine dust-reduction systems by spraying,we designed comparing experiments to study the atomization characteristics and dust-reduction performance of four commonly used nozzles in the coal mine underground with different internal structures.From the experimental results on the atomization characteristics,both the tangential flow-guided nozzle and the X-swirl nozzle have high flow coefficients.The atomization angle is the largest in the spiral non-porous nozzle,and smallest in both the X-swirl nozzle and the spiral porous nozzle.The spraying range and the droplet velocity are inversely proportional to the atomization angle.When the water pressure is low,the atomization performance of the spiral non-porous nozzle is the best among the four types of nozzles.The atomization performance of the X-swirl nozzle is superior to other types when the water pressure is high.Under the high water pressure,the particle size of the atomized droplets is smallest in the X-swirl nozzle.Through the experiments on the dust-reduction performance of the four types of nozzles and the comprehensive analysis,the X-swirl nozzle is recommended for the coal mine application site with low water pressure in the dust-reduction system,while at the sites with high water pressure,the spiral non-porous nozzle is recommended,which has the lowest water consumption and obvious economic advantages. 展开更多
关键词 Pressure nozzle Atomization characteristics Dust-reduction performance Droplets DUST
下载PDF
Analysis of the design and performance characteristics of pumpable roof supports 被引量:4
5
作者 Batchler Timothy 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2017年第1期91-99,共9页
Pumpable roof supports are currently being used to provide a safe working environment for longwall mining. Because different pumpable supports are visually similar and installed fundamentally in the same manner as oth... Pumpable roof supports are currently being used to provide a safe working environment for longwall mining. Because different pumpable supports are visually similar and installed fundamentally in the same manner as other supports, there is a tendency to believe they all perform the same way. However, there are several design parameters that can affect their performance, including the cementitious material properties and the bag construction practices that influence the degree of confinement provided. A full understanding of the impact of these design parameters is necessary to optimize the support application and to provide a foundation for making further improvements in the support performance. This paper evaluates the impact of various support design parameters by examining full-scale performance tests conducted using the National Institute for Occupational Safety and Health(NIOSH) Mine Roof Simulator(MRS) as part of manufacturers' developmental and quality control testing. These tests were analyzed to identify correlations between the support design parameters and the resulting performance. Based on more than 160 tests over 7 years, quantifiable patterns were examined to assess the correlation between the support dimensions, cementitious material type, wire pitch, and single-wall vs. dualwalled bag designs to the support capacity, stiffness, load shedding events, and yield characteristics. 展开更多
关键词 Pumpable Roofsuppo performance characteristics Secondary support
下载PDF
Effects of the standardized ileal digestible lysine to metabolizable energy ratio on performance and carcass characteristics of growing-finishing pigs 被引量:3
6
作者 Pengfei Li Zhikai Zeng +3 位作者 Ding Wang Lingfeng Xue Rongfei Zhang Xiangshu Piao 《Journal of Animal Science and Biotechnology》 SCIE 2012年第1期42-50,共9页
A total of 2,121 growing-finishing pigs (Duroc × Landrace ×Large White) were utilized in six experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine (SID... A total of 2,121 growing-finishing pigs (Duroc × Landrace ×Large White) were utilized in six experiments conducted to determine the effects of different ratios of standardized ileal digestible lysine (SID-Lys) to metabolizable energy (ME) on the performance and carcass characteristics of growing-finishing pigs. Exps. 1 (30 to 50 kg), 2 (52 to 70 kg) and 3 (81 to 104 kg) were conducted to find an optimum ME level and then this level was used in Exps. 4 (29 to 47 kg), 5 (54 to 76 kg) and 6 (84 to 109 kg) to test the response of pigs to different ratios of SID-Lys:ME. In Exps.1 to 3, four treatments were used consisting of diets with a formulated ME content of 3.1, 3.2, 3.3 or 3.4 in Exps. I and 2 while Exp. 3 used 3.05, 3.1 S, 3.25 or 3.35 Mcal/kg. A constant SID-Lys:ME ratio of 2.6, 2.3 or 2.0 g/Mcal was used in Exps. 1, 2 and 3, respectively. Weight gain was significantly increased with increasing energy level in Exp.1 while weight gain was unaltered in Exps. 2 and 3. For all three experiments, feed intake was decreased (P 〈 0.05) and feed efficiency was improved (P 〈 0.05) with increasing energy level. Tenth rib back fat thickness linearly increased (P 〈 0.05) with increasing energy level, in Exps. 4 to 6, five treatments were used consisting of diets with a SID-Lys:ME ratio of 2.4, 2.6, 2.8, 3.0 or 3.2 in Exp. 1, 2.1, 2.3, 2.5, 2.7, 2.9 or 3.2 in Exp. 2 and 1.8, 2.0, 2.2, 2.4, or 2.6 in Exp. 3. A constant ME level 3.2, 3.2 and 3.05 Mcal/kg was used in Exps. 1, 2 and 3, respectively (selected based on the results of weight gain). For all three experiments, weight gain increased (P 〈 0.05) and feed efficiency improved linearly (P 〈 0.05) as the SID-Lys:ME ratio increased. Tenth rib back fat thickness linearly decreased (P 〈 0.0,5) as the SID-Lys:ME ratio increased. Based on a straight broken-line model, the estimated SID-Lys:ME ratio to maximize weight gain was 3.0, 2.43 and 2.2 for 29 to 47, 54 to76 and 84 to 109 kg of pigs, respectively. 展开更多
关键词 carcass characteristics performance growing-finishing pigs metabolizable energy standardized ilea diqestible lysine
下载PDF
Mechanical performances and microstructural characteristics of reactive MgO-carbonated silt subjected to freezing-thawing cycles 被引量:7
7
作者 Guanghua Cai Songyu Liu +3 位作者 Guangyin Du Zhen Chen Xu Zheng Jiangshan Li 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2021年第4期875-884,共10页
The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering per... The characteristics of reactive magnesia(MgO)-carbonated silt in respect to long-term stability have not been well understood in severely cold climate despite the usage of reactive MgO in enhancing the engineering performances.Under the binder content of 15%and initial water content of 25%,MgO-admixed silt specimens were carbonized for 3 h and 6 h and then subjected to different numbers of freezingthawing(F-T)cycles.After different F-T cycles,the physico-mechanical properties of MgO-carbonated silt were analyzed in comparison with Portland cement(PC)-stabilized silt through physical and unconfined compression tests.Besides,a series of micro tests on MgO-carbonated specimens was performed including X-ray diffraction(XRD),scanning electron microscopy(SEM)and mercury intrusion porosimetry(MIP)tests.The results demonstrate that both mass change ratio and moisture content of carbonated/stabilized silt decrease,and these values of MgO-carbonated silt are significantly lower while the density is higher compared to PC-stabilized silt.The strengths and moduli of MgO-carbonated silt are still two times higher than those of PC-stabilized specimens and the strength change ratio of keeps above0.8 after F-T cycles.There is no visible transformation between nesquehonite and dypingite/hydromagnesite,although the XRD peaks of nesquehonite decrease and the bonding and filling effects weaken slightly.After 6 and 10 F-T cycles,the pore-size characteristics changed from a unimodal distribution to a three-peak and bimodal distribution,respectively.The total,macro and large pore volumes increase obviously while the medium and small pore volumes decrease except for intra-aggregate pore.The findings show better F-T durability of MgO-carbonated silt,which would be helpful for facilitating the application of MgO carbonation in the soil treatment. 展开更多
关键词 Reactive magnesia(Mgo) Freezing-thawing(F-T)cycle Carbonated/stabilized silt Engineering performance Microstructural characteristics
下载PDF
Effects of different dietary energy and protein levels and sex on growth performance,carcass characteristics and meat quality of F1 Angus x Chinese Xiangxi yellow cattle 被引量:24
8
作者 Lingyan Li Yuankui Zhu +2 位作者 Xianyou Wang Yang He Binghai Cao 《Journal of Animal Science and Biotechnology》 SCIE CAS 2014年第4期485-496,共12页
Background:The experiment evaluated the effect of nutrition levels and sex on the growth performance,carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle.Methods:During the backg... Background:The experiment evaluated the effect of nutrition levels and sex on the growth performance,carcass characteristics and meat quality of F1 Angus × Chinese Xiangxi yellow cattle.Methods:During the background period of 184 d,23 steers and 24 heifers were fed the same ration,then put into a2×2×2 factorial arrangement under two levels of- dietary energy(TON:70/80%DM),protein(CP:11.9/14.3%DM)and sex(S:male/female) during the finishing phase of 146 d.The treatments were-(1) high energy/low protein(HELP),(2) high energy/high protein(HEHP),(3) low energy/low protein(LELP) and(4) low energy/high protein(LEHP).Each treatment used 6 steers and 6 heifers,except for HELP- 5 steers and 6 heifers.Results:Growth rate and final carcass weight were unaffected by dietary energy and protein levels or by sex.Compared with the LE diet group,the HE group had significantly lower dry matter intake(DMI,6.76 vs.7.48 kg DM/d),greater chest girth increments(46.1 vs.36.8 cm),higher carcass fat(19.9 vs.16.3%) and intramuscular fat content(29.9 vs.22.8%DM).The HE group also had improved yields of top and medium top grade commercial meat cuts(39.9 vs.36.5%).The dressing percentage was higher for the HP group than the LP group(53.4 vs.54.9%).Steers had a greater length increment(9.0 vs.8.3 cm),but lower carcass fat content(16.8 vs.19.4%) than heifers.The meat quality traits(shear force value,drip loss,cooking loss and water holding capacity) were not affected by treatments or sex,averaging 3.14 kg,2.5,31.5 and 52.9%,respectively.The nutritive profiles(both fatty and amino acid composition) were not influenced by the energy or protein levels or by sex.Conclusions:The dietary energy and protein levels and sex significantly influenced the carcass characteristics and chemical composition of meat but not thegrowth performance,meat quality traits and nutritive profiles. 展开更多
关键词 Carcass characteristics Energy F1 Angus × Chinese Xiangxi yellow cattle Growth performance Meat quality Protein Sex
下载PDF
Effect of working parameters on performance characteristics of hydrostatic turntable by using FSI-thermal model 被引量:3
9
作者 HU Jun-ping LIU Cheng-pei 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第11期2589-2600,共12页
Effects of working parameters on performance characteristics of hydrostatic turntable are researched by applying the fluid-structure-thermal coupled model.Fluid-structure interaction(FSI)technique and computational fl... Effects of working parameters on performance characteristics of hydrostatic turntable are researched by applying the fluid-structure-thermal coupled model.Fluid-structure interaction(FSI)technique and computational fluid dynamics(CFD)method are both employed by this new model,and thermal effects are also considered.Hydrostatic turntable systems with a series of oil supply pressures,various oil recess depth and several surface roughness parameters are studied.Performance parameters,such as turntable displacement,system flow rate,temperature rise of lubrication,stiffness and damping coefficients,are derived from different working parameters(rotational speed of turntable and exerted external load)of the hydrostatic turntable.Numerical results obtained from this FSI-thermal model are presented and discussed,and theoretical predictions are in good agreement with the experimental data.Therefore,this developed model is a very useful tool for studying hydrostatic turntables.The calculation results show that in order to obtain better performance,a rational selection of the design parameters is essential. 展开更多
关键词 hydrostatic turntable working parameters performance characteristics FSI-thermal coupled model
下载PDF
Aerodynamic Performance and Aeroacoustic Characteristics of Model Rotor with Anhedral Blade Tip in Hover 被引量:1
10
作者 Huang Shuilin Fan Feng +1 位作者 Yuan Mingchuan Sun Wei 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2018年第1期162-169,共8页
Experimental investigation on the aerodynamic performance and aeroacoustic characteristics of model rotors with different tip anhedral angles in hover are conducted in the paper.Three sets of model rotors with blade-t... Experimental investigation on the aerodynamic performance and aeroacoustic characteristics of model rotors with different tip anhedral angles in hover are conducted in the paper.Three sets of model rotors with blade-tip anhedral angle 0°(reference rotor),20°and 45°respectively are designed to analyze the influence of the anhedral angle on the hovering performance and aeroacoustics of rotor.In the environment of anechoic chamber,the hover experiments under the different collective pitch and blade numbers,are carried out to measure the figure of merit(FM),time history of sound pressure and sound pressure level(SPL)of the three rotor models.Based on test results,the comparison and analysis of hovering performance and aeroacoustic characteristics among the three rotor models have been done.Meanwhile,for the sake of analysis,the rotor wake and blade pressure distribution are simulated by means of computational fluid method(CFD).At last,some conclusions about the effects of blade-tip anhedral angle on the aerodynamic performance and aeroacoustic characteristics in hover are obtained.An anhedral blade tip can enhance the FM of the rotor,and decrease the rotor loads noise to some extent. 展开更多
关键词 HELICoPTER RoToR anhedral blade-tip aerodynacmic performance aero-acoustic characteristics
下载PDF
Ignition characteristics and combustion performances of a LO_2/GCH_4 small thrust rocket engine 被引量:2
11
作者 ZHANG Jia-qi LI Qing-lian SHEN Chi-bing 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第3期646-652,共7页
A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but th... A 500 N model engine filled with LO2/GCH4 was designed and manufactured.A series of ignition attempts were performed in it by both head spark plug and body spark plug.Results show that the engine can be ignited but the combustion cannot be sustained when head spark plug applied as the plug tip was set in the gaseous low-velocity zone with thin spray.This is mainly because flame from this zone cannot supply enough ignition energy for the whole chamber.However,reliable ignition and stable combustion can be achieved by body spark plug.As the O/F ratio increases from 2.61 to 3.49,chamber pressure increases from 0.474 to 0.925 MPa and combustion efficiency increases from 57.8%to 95.1%.This is determined by the injector configuration,which cannot produce the sufficiently breakup of the liquid oxygen on the low flow rate case. 展开更多
关键词 Lo2/GCH4 small thrust rocket engine ignition characteristic combustion performance
下载PDF
Performance characteristics of EZhou bentonite of Hubei province and its modification 被引量:1
12
作者 Long Wei Fan Zitian Hu Xueting 《China Foundry》 SCIE CAS 2009年第4期308-313,共6页
Both the chemical compositions and performance characteristics of the bentonite raw ores in Ezhou area of Hubei province and Honghuoshan area of Liaoning of these two kinds of bentonites were tested before and provinc... Both the chemical compositions and performance characteristics of the bentonite raw ores in Ezhou area of Hubei province and Honghuoshan area of Liaoning of these two kinds of bentonites were tested before and province were compared and analyzed. The properties after Na^+- and Li^+-modification. The results show that the Ezhou bentonite ore possesses higher montmorillonite content than the Honghuoshan bentonite ore, but the Ezhou Na-bentonite has weaker castability (e.g. wet compression strength and hot wet tensile strength) than the Honghuoshan Na-bentonite, while the performance of Ezhou Li-bentonite, such as colloid index, swelling value, swelling volume and mould coating performance, is equivalent to that of the Honghuoshan Na-bentonite. 展开更多
关键词 Ezhou bentonite Honghuoshan bentonite NA-BENToNITE Li-bentonite performance characteristic
下载PDF
Abrasive Wear Characteristics of Carbon and Low Alloy Steels for Better Performance of Farm Implements 被引量:2
13
作者 M.Kumar and R. C Gupta(Centre of Advanced Study, Dept. of Metallurgical Engineering, Institute of Technology,Banaras Hindu University, Vaanasi -221 005, India) 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 1995年第2期91-96,共6页
The low stress abrasion behaviours of heat treated mild, medium carbon and high C - low Cr steels, which are generally used in making farm implements, have been investigated. The simple heat treatment greatly improves... The low stress abrasion behaviours of heat treated mild, medium carbon and high C - low Cr steels, which are generally used in making farm implements, have been investigated. The simple heat treatment greatly improves the hardness, tensile strength and abrasion resistance of medium carbon and high C - low Cr steels. The results indicate that the material removal during abrasion is controlled by a number of factors, such as hardness, chemical composition, microstructure and heat treatment conditions. The conclusion is that the heat treated high C - low Cr steel and mild steel carburized by using coaltar pitch provide the best hardness and abrasion resistance and thus appear to be the most suitable materials for making agricultural tools. 展开更多
关键词 Abrasive Wear characteristics of Carbon and Low Alloy Steels for Better performance of Farm Implements MPA
下载PDF
Ballistic Performance and Damage Characteristics of Chemical Vapor Infiltration Quasi 3D-Cf/SiC Composites 被引量:1
14
作者 何旭道 程兴旺 +1 位作者 wang qi wang pei 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2016年第1期118-122,共5页
To investigate the ballistic performance and damage characteristics of quasi threedimensional(3D) needle-punched Cf/SiC composites prepared by chemical vapor infiltration(CVI),penetration experiments were conducte... To investigate the ballistic performance and damage characteristics of quasi threedimensional(3D) needle-punched Cf/SiC composites prepared by chemical vapor infiltration(CVI),penetration experiments were conducted by using 7.62 mm armor piercing incendiary(API).Macro and micro fracture morphologies were then observed on recycled targets.The results show that the protection coefficient of 3D Cf/SiC composites is 2.54.High porosity and many micro thermal stress cracks may directly lead to the lower ballistic performance.Flat fracture morphology was observed on the crater surface.The low dynamic fracture strength along layer direction may be attributed to the voids and microcracks caused by residual thermal stress.The damage characteristics of Cf/Si C composites include matrix cracking,fiber bundle cracking,interfacial debonding,fiber fracture,and fiber bundle pull-out.And interfacial debonding and fiber fracture may play major roles in energy absorption. 展开更多
关键词 CVI-Cf/SiC composites material ballistic performance damage characteristics
下载PDF
Performance Characteristics of an Irreversible Proton Exchange Membrane (PEM) Fuel Cell 被引量:1
15
作者 韦斐斐 黄跃武 《Journal of Donghua University(English Edition)》 EI CAS 2012年第5期393-398,共6页
A model of an irreversible proton exchange membrane (PEM) fuel cell working at steady-state was established, in which overpotenfials, internal currents, and crossover losses were taken into account. The expressions ... A model of an irreversible proton exchange membrane (PEM) fuel cell working at steady-state was established, in which overpotenfials, internal currents, and crossover losses were taken into account. The expressions of some key parameters of the fuel cell were derived from the point of electrochemistry and thermodynamics. Based on the irreversible model of the PEM fuel ceil, the influence of multi-irreversibilities on fuel cell performance were characterized and compared systematically. The general performance characteristic curves were generated. Moreover, when the electrical circuit was dosed with a load in it, the relations between the load resistance and power output density and efficiency were analyzed. The results provide a theoretical basis for both the operation and optimal design of real PEM fuel cells. 展开更多
关键词 proton exchange membrane PEM) fuel cell irreversible model performance characteristic leakage current load resistance
下载PDF
Performance characteristics of low-dissipative generalized Carnot cycles with external leakage losses
16
作者 黄传昆 郭君诚 陈金灿 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第11期171-179,共9页
Under the assumption of low-dissipation, a unified model of generalized Carnot cycles with external leakage losses is established. Analytical expressions for the power output and efficiency are derived. The general pe... Under the assumption of low-dissipation, a unified model of generalized Carnot cycles with external leakage losses is established. Analytical expressions for the power output and efficiency are derived. The general performance characteristics between the power output and the efficiency are revealed. The maximum power output and efficiency are calculated. The lower and upper bounds of the efficiency at the maximum power output are determined. The results obtained here are universal and can be directly used to reveal the performance characteristics of different Carnot cycles, such as Carnot heat engines, Carnot-like heat engines, flux flow engines, gravitational engines, chemical engines, two-level quantum engines, etc. 展开更多
关键词 generalized Carnot cycle low-dissipation unified model performance characteristic
下载PDF
Performance characteristics a nonlinear diode and optimal analysis of refrigerator
17
作者 Wang Xiu-Mei He Ji-Zhou Liang Hong-Ni 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第2期104-109,共6页
This paper establishes a model of a nonlinear diode refrigerator consisting of two diodes switched in the opposite directions and located in two heat reservoirs with different temperatures. Based on the theory of ther... This paper establishes a model of a nonlinear diode refrigerator consisting of two diodes switched in the opposite directions and located in two heat reservoirs with different temperatures. Based on the theory of thermal fluctuations, the expressions of the heat flux absorbed from the heat reservoirs are derived. After the heat leak between the two reservoirs is considered, the cooling rate and the coefficient of performance are obtained analytically. The influence of the heat leak and the temperature ratio on the performance characteristics of the refrigerator is analysed in detail. 展开更多
关键词 nonlinear diode refrigerator thermal fluctuations heat leak performance characteristics
下载PDF
Influence of Early Quantitative Feed Restriction on Performance and Carcass Characteristics of Broiler Chickens
18
作者 SHI Baoming SHAN Anshan CHAN Long 《Journal of Northeast Agricultural University(English Edition)》 CAS 2006年第2期140-144,共5页
An experiment was conducted to study the influence of eady quantitative feed restriction on the performance and carcass characteristics of broiler chickens. Two hundred 8-day-old commercial Avian male broiler chicks w... An experiment was conducted to study the influence of eady quantitative feed restriction on the performance and carcass characteristics of broiler chickens. Two hundred 8-day-old commercial Avian male broiler chicks were assigned to four groups randomly, with 50 broilers each. At the age of 8 days the broilers were restricted to 90%, 80% or 70% of the ad libitum intake for 7 days. When the restricion was finished, all birds received feed ad libitum again. The results showed that diet restriction resulted in a reduction in body weight and daily gain during the restriction period (P 〈0.05). The birds restricted to 90% of the ad libitum intake showed the occurring of growth compensation in the 3rd week. The birds restricted to 80% and 70% of the ad libitum intake had growth compensation in the 4th week. No significant differences between the effects of the restriction and the control on final body weight, growth rate, feed conversion efficiency and carcass characteristics (P 〈0.05). 展开更多
关键词 broiler early feed restriction performance carcass characteristics
下载PDF
Analysis on damage characteristics and detonation performance of solid rocket engine charge subjected to jet
19
作者 Song-lin Pang Xiong Chen +2 位作者 Jin-sheng Xu Ge-tu Zhaori Hong-Ying Du 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2022年第9期1552-1562,共11页
To further explore the damage characteristics and impact response of the shaped charge to the solid rocket engine(SRE) in storage or transportation, protective armor was designed and the shelled charges model(SCM)/SRE... To further explore the damage characteristics and impact response of the shaped charge to the solid rocket engine(SRE) in storage or transportation, protective armor was designed and the shelled charges model(SCM)/SRE with protective armor impacting by shaped charge tests were conducted. Air overpressures at 5 locations and axial acceleration caused by the explosion were measured, and the experimental results were compared with two air overpressure curves of propellant detonation obtained by related scholars. Afterwards, the finite element software AUTODYN was used to simulate the SCM impacted process and SRE detonation results. The penetration process and the formation cause of damage were analyzed. The detonation performance of TNT, reference propellant, and the propellant used in this experiment was compared. The axial acceleration caused by the explosion was also analyzed.By comprehensive comparison, the energy released by the detonation of this propellant is larger, and the HMX or Al particles contained in this propellant are more than the reference propellant, with a TNT equivalent of 1.168-1.196. Finally, advanced protection armor suggestions were proposed based on the theory of woven fabric rubber composite armor(WFRCA). 展开更多
关键词 Explosion mechanics Shaped charge jet Damage characteristics Detonation performance of propellant
下载PDF
Preventive Maintenance Characteristics towards Optimal Maintenance Performance: A Case Study of Office Buildings
20
作者 Cheong Peng Au-Yong Azlan Shah Ali Faizah Ahmad 《World Journal of Engineering and Technology》 2014年第3期1-6,共6页
Lack of preventive measure is currently the problem that implicates poor building maintenance performance and issue on sustainability of buildings in Malaysia. Whereby, preventive maintenance is an effective approach ... Lack of preventive measure is currently the problem that implicates poor building maintenance performance and issue on sustainability of buildings in Malaysia. Whereby, preventive maintenance is an effective approach to enhance the reliability and quality of a system and its components. This study seeks to investigate the characteristics of preventive maintenance towards the overall performance in building maintenance. Case study approach is adopted to identify the maintenance characteristics and aspects that lead to good performance. The research findings demonstrate that the most significant maintenance characteristics towards overall performance are skill and knowledge of maintenance labour, quality of spare parts and materials, length of predetermined maintenance interval, skill and knowledge of maintenance manager, capability to adopt maintenance equipment and technique, budget allocation for acquisition of maintenance data, reliability of maintenance data, as well as frequency of monitoring and inspection. As a conclusion, the significant maintenance characteristics must be taken into consideration to achieve optimal maintenance performance. In order to improve the effectiveness of maintenance strategy and the maintenance performance, the study recommends practice and provision of communication platform such as meeting and customer satisfaction survey that involves all the key participants from clients to customers. 展开更多
关键词 oFFICE BUILDING Maintenance Management PREVENTIVE Maintenance Maintenance characteristIC Maintenance performance
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部