Iron ore tailings filled polypropylene (PP) composites were produced using the compo-indirect squeeze casting (C-ISC) process. Particle sizes 150, 212 and 300 μm where considered for different volume fractions of 5% ...Iron ore tailings filled polypropylene (PP) composites were produced using the compo-indirect squeeze casting (C-ISC) process. Particle sizes 150, 212 and 300 μm where considered for different volume fractions of 5% to 30% at intervals of 5%. The tensile and impact behavior of the produced composites were investigated, experimentally, by carrying out uniaxial tensile and izod impact tests to obtain tensile strength, elongation at break, modulus of elasticity and impact strength. Empirical data were compared with results obtained from models proposed by Nielsen, Bigg and Einstein. The experimental results show that elongation at break for iron ore tailings filled PP reduces with increasing 150 μm particle size. Tensile strength reduces with increasing filler. The Bigg equation exhibited improved predictability with decreasing particle size of filler in PP;while the Einstein equation which assumes poor adhesion gives the best prediction of modulus of elasticity with increasing particle size in PP. Izod impact strength decreases with particle size but increases with increasing volume content of iron ore tailings from 5% to 25% for each particle size considered.展开更多
By using instrumental micro-indentation technique, the microhardness and Young＇s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro- compression-tester （MCT）. The micro-inde...By using instrumental micro-indentation technique, the microhardness and Young＇s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro- compression-tester （MCT）. The micro-indentation experiments were performed with different max- imum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young＇s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions （maximum load and loading speed） and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increas- ing. During the analysis, the effect of loading conditions on Young＇s modulus and microhardness were explained. Besides, the elastic-plastic properties of matrix were analyzed. The validity of cal- culated results was identified by finite element simulation. And the simulation results had been pre- liminarily analyzed from statistical aspect.展开更多
Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites(AMCs)to enhance selective properties and reduce the cost of fabrication.However,poor machinability of such AMC...Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites(AMCs)to enhance selective properties and reduce the cost of fabrication.However,poor machinability of such AMCs limits their application.The present study focuses on the preparation of cenosphere fly ash reinforced Al6061alloys by compo casting method.X-ray diffraction analysis of the prepared AMCs exposes the presence of cenosphere particles without any formation of other intermetallic compounds.In this study,electrical discharge machining(EDM)was engaged to examine the machinability of the prepared metal matrix composite(MMCs).The measured performance characteristics for the various combinations of input process parameters were considered to be MRR,EWR and SR.Face centered central composite design(CCD)of response surface method(RSM)was employed to design the number of experimental trials required and a hybrid approach of grey-based response surface methodology(GRSM)was imposed for predicting the optimal combination of processing parameter in EDM process.Generous improvement was observed in the performance characteristics obtained by employing both the optimal setting of machining parameters.The optical3D surface profile graphs of the ED machined surface also revealed the improvement in surface quality and texture employing the optimal processing conditions proposed by hybrid GRSM approach.展开更多
A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance, such as low friction coefficient and low wear rate. Al2...A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance, such as low friction coefficient and low wear rate. Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure. Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear. Al2O3/TiC ceramic was also cold pressed and sintered for comparison. Friction analysis of the two ceramics was then conducted via a wear-and-tear machine. Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum, respectively. Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite. Under the friction load, the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits. This process formed a smooth, self-lubricating film, which led to better anti-wear properties. Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.展开更多
<span style="font-family:Verdana;">In this study, two Cu</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-fami...<span style="font-family:Verdana;">In this study, two Cu</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">based catalysts with and without N doped carbon matrix, named N-Cu/CuO/C and Cu/CuO were synthesized via calcination of melamine-cupper acetate complex and cupper acetate at 500<span style="white-space:nowrap;">°</span>C under an inert atmosphere. The catalysts were characterized by X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and </span><span><span style="font-family:Verdana;">CHNS </span><span><span style="font-family:Verdana;">elemental analyzer</span><i><span style="font-family:Verdana;">.</span></i></span></span><span style="font-family:Verdana;"> The catalytic activity of both catalysts was evaluated</span><span style="font-family:Verdana;"> through the NaBH</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> associated reduction of commercial textile dye named reactive black 5 (RB5). The kinetics of the reduction of reactive black 5 was also described by the pseudo-first-order kinetic equation. For the studied reduction, N-Cu/CuO/C exhibited enhanced catalytic activity both in conversion and kinetics (97% conv. in 315 sec) compared to that of by Cu/CuO/C (25% conv. in 1500 sec). Besides, N-Cu/CuO/C also demonstrated good reusability up to four consecutive cycles.</span></span></span></span>展开更多
Internet of things(IoT) imposes new challenges on service composition as it is difficult to manage a quick instantiation of a complex services from a growing number of dynamic candidate services. A cross-modified Arti...Internet of things(IoT) imposes new challenges on service composition as it is difficult to manage a quick instantiation of a complex services from a growing number of dynamic candidate services. A cross-modified Artificial Bee Colony Algorithm(CMABC) is proposed to achieve the optimal solution services in an acceptable time and high accuracy. Firstly, web service instantiation model was established. What is more, to overcome the problem of discrete and chaotic solution space, the global optimal solution was used to accelerate convergence rate by imitating the cross operation of Genetic algorithm(GA). The simulation experiment result shows that CMABC exhibited faster convergence speed and better convergence accuracy than some other intelligent optimization algorithms.展开更多
The high performance magnesium alloy was investigated by adding B2O3 in magnesium and magnesium alloys. Experiments include adding B2O3 in Mg, Mg-Al and Mg-RE alloys, respectively, studying the effects of B2O3 on the ...The high performance magnesium alloy was investigated by adding B2O3 in magnesium and magnesium alloys. Experiments include adding B2O3 in Mg, Mg-Al and Mg-RE alloys, respectively, studying the effects of B2O3 on the microstructure, were studied measuring the change of grain size and microhardness of the materials, discussing the change of grain size, morphology and distribution. The results show that adding 3% or 6%(mass fraction) B2O3 in Mg can bring twinning in Mg, adding B2O3 in Mg-Al alloys and Mg-RE alloys can refine the alloy grain size. Adding 3%B2O3 in Mg-6Al alloys can refine the average grain size by about 5μm, with the average hardness increased by 13.3% (53.3-60.4 HV0.03); adding 6%B2O3 in Mg-6Al alloys can refine the average grain size by about 13μm, with the average hardness increased by 15.8% (53.3-61.73 HV0.03); adding 3% and 6%B2O3 into Mg-6RE alloys can refine the grain size by about 5 and 9μm, respectively, with the average hardness decreased to HV0.03 64.66 and HV0.03 57.86, respectively from HV0.03 88.57. In the Mg-6Al alloy the content of aluminum is increased, while in the Mg-6RE alloy the content of oxygen is decreased. It can be concluded that it is beneficial to develop Mg-Al-B-O particle reinforce composite alloys, and it is feasible to develop nanometer crystallization of block material by Mg-B-O-RE.展开更多
There are two intermetallic compounds of AgZr and AgZr2 in the Ag-Zr system,and six intermetallic compounds of Cu9Zr2, Cu7Zr2, Cu52, CuZr and CuZr2 in the Cu-Zr system.The Ag-Cu system is an entectic system with solid...There are two intermetallic compounds of AgZr and AgZr2 in the Ag-Zr system,and six intermetallic compounds of Cu9Zr2, Cu7Zr2, Cu52, CuZr and CuZr2 in the Cu-Zr system.The Ag-Cu system is an entectic system with solid solubility.Although,展开更多
地下水管漏水普遍,造成水资源和经济损失。有效的漏水探测技术缺乏,尤其因供水管道埋设在地下,难以及时发现漏水。长波极化SAR信号穿透能力强,可记录次地表含水量信息,为漏水探测提供了新机遇。本研究利用SAOCOM数据,通过Singh七分量极...地下水管漏水普遍,造成水资源和经济损失。有效的漏水探测技术缺乏,尤其因供水管道埋设在地下,难以及时发现漏水。长波极化SAR信号穿透能力强,可记录次地表含水量信息,为漏水探测提供了新机遇。本研究利用SAOCOM数据,通过Singh七分量极化分解方法提取城区地表散射能量,结合地面实测数据,训练了随机森林、多层感知机和XGBoost三种机器学习模型预测漏点。最后构建集成模型,通过投票机制提高漏点检测准确性,准确率达81.20%。通过DBSCAN(density-based spatial clustering of applications with noise)密度聚类方法优化预测结果,将潜在漏点减少至1 265个,发现所有真实漏点均位于疑似漏点的150 m缓冲区内。本研究展示了利用PolSAR数据结合机器学习技术在城市水管漏损检测中的潜力,并为未来相关研究提供了有价值的方法和经验。展开更多
It is well recognized that the voltage stability of a power system is affected by the load model and hence, to effectively analyze the reactive power compensation of an isolated hybrid wind-diesel based power system, ...It is well recognized that the voltage stability of a power system is affected by the load model and hence, to effectively analyze the reactive power compensation of an isolated hybrid wind-diesel based power system, the loads need to be considered along with the generators in a transient analysis. This paper gives a detailed mathematical modeling to compute the reactive power response with small voltage perturbation for composite load. The composite load is a combination of the static and dynamic load model. To develop this composite load model, the exponential load is used as a static load model and induction motors （IMs） are used as a dynamic load model. To analyze the dynamics of IM load, the fifth, third and first order model of IM are formulated and compared using differential equations solver in Matlab coding. Since the decentralized areas have many small consumers which may consist large numbers of IMs of small rating, it is not realistic to model either a single large rating unit or all small rating IMs together that are placed in the system. In place of using a single large rating IM, a group of motors are considered and then the aggregate model of IM is developed using the law of energy conservation. This aggregate model is used as a dynamic load model. For different simulation studies, especially in the area of voltage stability with reactive power compensation of an isolated hybrid power system, the transfer function AQ/AV of the composite load is required. The transfer function of the composite load is derived in this paper by successive derivation for the exponential model of static load and for the fifth and third order IM dynamic load model using state space model.展开更多
<正> Let H be a complex Hilbert space, and T be a linear bounded operator on H. T is called a quasihyponormal operator if there exists a strict monotone continuous function φ(t) on [0, + ∞) with φ(0)= 0 (stan...<正> Let H be a complex Hilbert space, and T be a linear bounded operator on H. T is called a quasihyponormal operator if there exists a strict monotone continuous function φ(t) on [0, + ∞) with φ(0)= 0 (standard function) such that φ(T~*T)-φ(TT~*) D_φ ≥ 0. T is called a complete hyponormal operator if D_≥ 0 is true for every standard function. T is called a θ-class operator if [T~* + T, T~*T] = 0. T is called a BN-class operator if [T~*T,TT~*] = 0. T is called a strong complete hyponormal operator展开更多
该研究以不同年份(0~10年)浓酱兼香型白酒为研究对象,通过单因素试验对液液萃取(LLE)前处理条件进行优化后,通过气相色谱-质谱联用(GC-MS)技术对其挥发性风味成分进行检测,并结合香气活力值(OAV),利用主成分分析(PCA)分析不同年份浓酱...该研究以不同年份(0~10年)浓酱兼香型白酒为研究对象,通过单因素试验对液液萃取(LLE)前处理条件进行优化后,通过气相色谱-质谱联用(GC-MS)技术对其挥发性风味成分进行检测,并结合香气活力值(OAV),利用主成分分析(PCA)分析不同年份浓酱兼香型白酒挥发性风味物质的变化规律。结果表明,最佳LLE条件为添加75 g NaCl,采用二氯甲烷萃取3次,每次萃取5 min。从不同年份浓酱兼香型白酒中共鉴定出65种挥发性风味物质,包括醇类12种、醛类6种、酸类9种、酮类3种、酯类31种、其他类4种。PCA可有效区分不同年份酒样挥发性风味的差异,己酸乙酯、辛酸乙酯、丁酸乙酯、苯乙酸乙酯、3-苯丙酸乙酯等14种挥发性风味成分为0~1年酒样主要风味影响组分,十六酸乙酯、丁酸、己酸为2~4年酒样的主要风味影响组分,丁酸为5年和7年酒样的主要风味影响组分,己酸为6年和9~10年酒样的主要风味影响组分,异丁酸乙酯为8年酒样的主要风味影响组分。展开更多
文摘Iron ore tailings filled polypropylene (PP) composites were produced using the compo-indirect squeeze casting (C-ISC) process. Particle sizes 150, 212 and 300 μm where considered for different volume fractions of 5% to 30% at intervals of 5%. The tensile and impact behavior of the produced composites were investigated, experimentally, by carrying out uniaxial tensile and izod impact tests to obtain tensile strength, elongation at break, modulus of elasticity and impact strength. Empirical data were compared with results obtained from models proposed by Nielsen, Bigg and Einstein. The experimental results show that elongation at break for iron ore tailings filled PP reduces with increasing 150 μm particle size. Tensile strength reduces with increasing filler. The Bigg equation exhibited improved predictability with decreasing particle size of filler in PP;while the Einstein equation which assumes poor adhesion gives the best prediction of modulus of elasticity with increasing particle size in PP. Izod impact strength decreases with particle size but increases with increasing volume content of iron ore tailings from 5% to 25% for each particle size considered.
基金the support received from the National Natural Science Foundation of China (No. 51275414)the Aeronautical Science Foundation of China (No. 2011ZE53059)
文摘By using instrumental micro-indentation technique, the microhardness and Young＇s modulus of SiC particles reinforced aluminum matrix composites were investigated with micro- compression-tester （MCT）. The micro-indentation experiments were performed with different max- imum loads, and with three loading speeds of 2.231, 4.462 and 19.368 mN/s respectively. During the investigation, matrix, particle and interface were tested by micro-indentation experiments. The results exhibit that the variations of Young＇s modulus and microhardness at particle, matrix and interface were highly dependent on the loading conditions （maximum load and loading speed） and the locations of indentation. Micro-indentation hardness experiments of matrix show the indentation size effects, i.e. the indentation hardness decreased with the indentation depth increas- ing. During the analysis, the effect of loading conditions on Young＇s modulus and microhardness were explained. Besides, the elastic-plastic properties of matrix were analyzed. The validity of cal- culated results was identified by finite element simulation. And the simulation results had been pre- liminarily analyzed from statistical aspect.
文摘Fly ash has congregated considerable attention as a potential reinforcement for aluminum matrix composites(AMCs)to enhance selective properties and reduce the cost of fabrication.However,poor machinability of such AMCs limits their application.The present study focuses on the preparation of cenosphere fly ash reinforced Al6061alloys by compo casting method.X-ray diffraction analysis of the prepared AMCs exposes the presence of cenosphere particles without any formation of other intermetallic compounds.In this study,electrical discharge machining(EDM)was engaged to examine the machinability of the prepared metal matrix composite(MMCs).The measured performance characteristics for the various combinations of input process parameters were considered to be MRR,EWR and SR.Face centered central composite design(CCD)of response surface method(RSM)was employed to design the number of experimental trials required and a hybrid approach of grey-based response surface methodology(GRSM)was imposed for predicting the optimal combination of processing parameter in EDM process.Generous improvement was observed in the performance characteristics obtained by employing both the optimal setting of machining parameters.The optical3D surface profile graphs of the ED machined surface also revealed the improvement in surface quality and texture employing the optimal processing conditions proposed by hybrid GRSM approach.
基金supported by the National Natural Science Foundation for Young Scholars of China(No.51005100)China Postdoctoral Science Foundation(No.20110491572)Scientific and Technologic Development Program of Shandong Province(No.2012GGX10324)
文摘A novel laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite was fabricated through cold pressing and sintering to achieve better anti-wear performance, such as low friction coefficient and low wear rate. Al2O3/TiC/CaF2 and Al2O3/TiC composites were alternatively built layer-by-layer to obtain a sandwich structure. Solid lubricant CaF2 was added evenly into the Al2O3/TiC/CaF2 layer to reduce the friction and wear. Al2O3/TiC ceramic was also cold pressed and sintered for comparison. Friction analysis of the two ceramics was then conducted via a wear-and-tear machine. Worn surface and surface compositions were examined by scanning electron microscopy and energy dispersion spectrum, respectively. Results showed that the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite has lower friction coefficient and lower wear rate than those of Al2O3/TiC ceramic alone because of the addition of CaF2 into the laminated Al2O3/TiC/CaF2-Al2O3/TiC sandwich ceramic composite. Under the friction load, the tiny CaF2 particles were scraped from the Al2O3/TiC/CaF2 layer and spread on friction pairs before falling off into micropits. This process formed a smooth, self-lubricating film, which led to better anti-wear properties. Adhesive wear is the main wear mechanism of Al2O3/TiC/CaF2 layer and abrasive wear is the main wear mechanism of Al2O3/TiC layer.
文摘<span style="font-family:Verdana;">In this study, two Cu</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">based catalysts with and without N doped carbon matrix, named N-Cu/CuO/C and Cu/CuO were synthesized via calcination of melamine-cupper acetate complex and cupper acetate at 500<span style="white-space:nowrap;">°</span>C under an inert atmosphere. The catalysts were characterized by X-ray powder diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and </span><span><span style="font-family:Verdana;">CHNS </span><span><span style="font-family:Verdana;">elemental analyzer</span><i><span style="font-family:Verdana;">.</span></i></span></span><span style="font-family:Verdana;"> The catalytic activity of both catalysts was evaluated</span><span style="font-family:Verdana;"> through the NaBH</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> associated reduction of commercial textile dye named reactive black 5 (RB5). The kinetics of the reduction of reactive black 5 was also described by the pseudo-first-order kinetic equation. For the studied reduction, N-Cu/CuO/C exhibited enhanced catalytic activity both in conversion and kinetics (97% conv. in 315 sec) compared to that of by Cu/CuO/C (25% conv. in 1500 sec). Besides, N-Cu/CuO/C also demonstrated good reusability up to four consecutive cycles.</span></span></span></span>
基金supported by a grant from the Project "Multifunctional mobile phone R & D and industrialization of the Internet of things" supported by the Project of the Provincial Department of research (2011A090200008)partly supported by National Science and Technology Major Project (No. 2010ZX07102-006)+3 种基金the National Basic Research Program of China (973 Program) (No. 2011CB505402)the Major Program of the National Natural Science Foundation of China (No. 61170117)the National Natural Science Foundation of China (No.61432004)the National Key Research and Development Program (No.2016YFB1001404)
文摘Internet of things(IoT) imposes new challenges on service composition as it is difficult to manage a quick instantiation of a complex services from a growing number of dynamic candidate services. A cross-modified Artificial Bee Colony Algorithm(CMABC) is proposed to achieve the optimal solution services in an acceptable time and high accuracy. Firstly, web service instantiation model was established. What is more, to overcome the problem of discrete and chaotic solution space, the global optimal solution was used to accelerate convergence rate by imitating the cross operation of Genetic algorithm(GA). The simulation experiment result shows that CMABC exhibited faster convergence speed and better convergence accuracy than some other intelligent optimization algorithms.
文摘The high performance magnesium alloy was investigated by adding B2O3 in magnesium and magnesium alloys. Experiments include adding B2O3 in Mg, Mg-Al and Mg-RE alloys, respectively, studying the effects of B2O3 on the microstructure, were studied measuring the change of grain size and microhardness of the materials, discussing the change of grain size, morphology and distribution. The results show that adding 3% or 6%(mass fraction) B2O3 in Mg can bring twinning in Mg, adding B2O3 in Mg-Al alloys and Mg-RE alloys can refine the alloy grain size. Adding 3%B2O3 in Mg-6Al alloys can refine the average grain size by about 5μm, with the average hardness increased by 13.3% (53.3-60.4 HV0.03); adding 6%B2O3 in Mg-6Al alloys can refine the average grain size by about 13μm, with the average hardness increased by 15.8% (53.3-61.73 HV0.03); adding 3% and 6%B2O3 into Mg-6RE alloys can refine the grain size by about 5 and 9μm, respectively, with the average hardness decreased to HV0.03 64.66 and HV0.03 57.86, respectively from HV0.03 88.57. In the Mg-6Al alloy the content of aluminum is increased, while in the Mg-6RE alloy the content of oxygen is decreased. It can be concluded that it is beneficial to develop Mg-Al-B-O particle reinforce composite alloys, and it is feasible to develop nanometer crystallization of block material by Mg-B-O-RE.
文摘There are two intermetallic compounds of AgZr and AgZr2 in the Ag-Zr system,and six intermetallic compounds of Cu9Zr2, Cu7Zr2, Cu52, CuZr and CuZr2 in the Cu-Zr system.The Ag-Cu system is an entectic system with solid solubility.Although,
文摘地下水管漏水普遍,造成水资源和经济损失。有效的漏水探测技术缺乏,尤其因供水管道埋设在地下,难以及时发现漏水。长波极化SAR信号穿透能力强,可记录次地表含水量信息,为漏水探测提供了新机遇。本研究利用SAOCOM数据,通过Singh七分量极化分解方法提取城区地表散射能量,结合地面实测数据,训练了随机森林、多层感知机和XGBoost三种机器学习模型预测漏点。最后构建集成模型,通过投票机制提高漏点检测准确性,准确率达81.20%。通过DBSCAN(density-based spatial clustering of applications with noise)密度聚类方法优化预测结果,将潜在漏点减少至1 265个,发现所有真实漏点均位于疑似漏点的150 m缓冲区内。本研究展示了利用PolSAR数据结合机器学习技术在城市水管漏损检测中的潜力,并为未来相关研究提供了有价值的方法和经验。
文摘It is well recognized that the voltage stability of a power system is affected by the load model and hence, to effectively analyze the reactive power compensation of an isolated hybrid wind-diesel based power system, the loads need to be considered along with the generators in a transient analysis. This paper gives a detailed mathematical modeling to compute the reactive power response with small voltage perturbation for composite load. The composite load is a combination of the static and dynamic load model. To develop this composite load model, the exponential load is used as a static load model and induction motors （IMs） are used as a dynamic load model. To analyze the dynamics of IM load, the fifth, third and first order model of IM are formulated and compared using differential equations solver in Matlab coding. Since the decentralized areas have many small consumers which may consist large numbers of IMs of small rating, it is not realistic to model either a single large rating unit or all small rating IMs together that are placed in the system. In place of using a single large rating IM, a group of motors are considered and then the aggregate model of IM is developed using the law of energy conservation. This aggregate model is used as a dynamic load model. For different simulation studies, especially in the area of voltage stability with reactive power compensation of an isolated hybrid power system, the transfer function AQ/AV of the composite load is required. The transfer function of the composite load is derived in this paper by successive derivation for the exponential model of static load and for the fifth and third order IM dynamic load model using state space model.
文摘<正> Let H be a complex Hilbert space, and T be a linear bounded operator on H. T is called a quasihyponormal operator if there exists a strict monotone continuous function φ(t) on [0, + ∞) with φ(0)= 0 (standard function) such that φ(T~*T)-φ(TT~*) D_φ ≥ 0. T is called a complete hyponormal operator if D_≥ 0 is true for every standard function. T is called a θ-class operator if [T~* + T, T~*T] = 0. T is called a BN-class operator if [T~*T,TT~*] = 0. T is called a strong complete hyponormal operator
文摘该研究以不同年份(0~10年)浓酱兼香型白酒为研究对象,通过单因素试验对液液萃取(LLE)前处理条件进行优化后,通过气相色谱-质谱联用(GC-MS)技术对其挥发性风味成分进行检测,并结合香气活力值(OAV),利用主成分分析(PCA)分析不同年份浓酱兼香型白酒挥发性风味物质的变化规律。结果表明,最佳LLE条件为添加75 g NaCl,采用二氯甲烷萃取3次,每次萃取5 min。从不同年份浓酱兼香型白酒中共鉴定出65种挥发性风味物质,包括醇类12种、醛类6种、酸类9种、酮类3种、酯类31种、其他类4种。PCA可有效区分不同年份酒样挥发性风味的差异,己酸乙酯、辛酸乙酯、丁酸乙酯、苯乙酸乙酯、3-苯丙酸乙酯等14种挥发性风味成分为0~1年酒样主要风味影响组分,十六酸乙酯、丁酸、己酸为2~4年酒样的主要风味影响组分,丁酸为5年和7年酒样的主要风味影响组分,己酸为6年和9~10年酒样的主要风味影响组分,异丁酸乙酯为8年酒样的主要风味影响组分。
