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浅谈学生的“减负”与新上岗教师的“增压”
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作者 戴文智 《辽宁教育研究》 北大核心 2000年第11期74-75,共2页
关键词 学生 减负 上岗教师 “增压” 教学基本功 备课 责任心
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Compressive performance of innovative reinforced pillars in closed/abandoned mines
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作者 LI Jian BAI Jin-wen +6 位作者 FENG Guo-rui WANG Shan-yong ZHAO Hong-chao MI Jia-chen PAN Rui-kai SHI Xu-dong MA Jun-biao 《Journal of Central South University》 SCIE EI CAS CSCD 2024年第8期2780-2793,共14页
Pillar is closely related to the stability and reliability of underground spaces in closed/abandoned mines.The present research introduced a new technique to strengthen square cement mortar columns via fiber-reinforce... Pillar is closely related to the stability and reliability of underground spaces in closed/abandoned mines.The present research introduced a new technique to strengthen square cement mortar columns via fiber-reinforced polymer(FRP)strips to verify the strengthening effect of FRP on pillars.Compared to a fully wrapped FRP jacket,the advantages of FRP strip are cost-effective and easy-to-construct.A series of compression tests as well as theoretical analysis were carried out to explore the mechanical behavior of square cement mortar specimens partially strengthened with FRP strips.The results verified the effectiveness of FRP strips in enhancing the stress and strain of cement mortar.Different from unconfined cement mortar specimens,these FRP-strengthened cement mortar specimens are featured with the double-peaked behaviors,mainly attributed to the stress state transformation from a one-dimensional to a three-dimensional stress state.It also indicated that the enhancement of stress increased with the FRP strip width.Moreover,the brittle-ductile transition ductile failure characteristics were also observed in FRP-confined cement mortar specimens.The ultimate ductility of the cement mortar specimen decreases gradually with the growth of the FRP strip width.The main contribution of this research is to enrich the strengthening techniques for residual pillars. 展开更多
关键词 fiber-reinforced polymer uniaxial compression partially strengthening double-peaked behaviors brittle-ductile transition
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Combustion and pollutant emission characteristics of coal in a pressurized fluidized bed under O_2/ CO_2 atmosphere 被引量:4
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作者 段元强 段伦博 +1 位作者 胡海华 赵长遂 《Journal of Southeast University(English Edition)》 EI CAS 2015年第2期188-193,共6页
The pressurized combustion experiments of bituminous coal and lignite under air and O2/CO2 atmospheres were conducted to study the influences of pressure and atmosphere on combustion and the CO, NO, SO2 release proces... The pressurized combustion experiments of bituminous coal and lignite under air and O2/CO2 atmospheres were conducted to study the influences of pressure and atmosphere on combustion and the CO, NO, SO2 release process. Two indices, the maximum concentration and the total emission, were applied to quantitatively evaluate the influence of several different operating parameters such as pressure, atmosphere and temperature on the formation of NO and SO2 during coal combustion in the fluidized bed. The experimental results show that the releasing profiles of CO, NO and SO2 during coal combustion under a pressurized oxy- fuel atmosphere are similar to those under a pressurized air atmosphere, and the curves of measured gas components are all unimodal. Under the oxy-fuel condition, pressure increasing from 0.1 to 0.7 MPa can cause the inhibition of NO and SO2 emission. The elevation of temperature can lead to an increase in the maximum concentration and the total production of NO and SO2, and the increase under atmospheric pressure is higher than that under high pressure. 展开更多
关键词 pressurized oxy-fuel combustion fluidized bed SO2 emission NO emission
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Development of Turbocharger for Improving Diesel Engine Matching Performance 被引量:4
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作者 张虹 马朝臣 《Journal of Beijing Institute of Technology》 EI CAS 2002年第2期146-149,共4页
The two development ways of turbocharger technology to solve the problem of matching performance with diesel were presented. The ways of waste valve gate turbocharger and variable geometry turbocharger can solve the p... The two development ways of turbocharger technology to solve the problem of matching performance with diesel were presented. The ways of waste valve gate turbocharger and variable geometry turbocharger can solve the problem of engine’s low speed torque and achieve lower smoke level. Especially for variable geometry turbocharger, it covers all conditions of engine. It can not only improve the low engine’s speed torque and keep the power performance at high engine speed, but also cover wide engine speed performance that keeps lower fuel consumption and exhaust gas temperature in full load and part load matching. The results of theory analysis and experiment research showed that it’s the ideal solution to solve the matching problem of diesel engines. 展开更多
关键词 TURBOCHARGER match performance variable geometry turbocharger
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Numerical Simulation of Pressurized Spouted Fluidized Bed for Coal Semi-Gasification 被引量:2
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作者 周山明 金保升 章名耀 《Journal of Southeast University(English Edition)》 EI CAS 2002年第4期319-325,共7页
Numerical simulation study is conducted for a pressurized spouted fluidized bed coal carbonizer, in which hydrodynamics of pressurized spouted fluidized bed, chemical reactions and energy balance are taken into accoun... Numerical simulation study is conducted for a pressurized spouted fluidized bed coal carbonizer, in which hydrodynamics of pressurized spouted fluidized bed, chemical reactions and energy balance are taken into account. The effect of operating conditions such as bed pressure, air and steam mass flow ratio, temperature on product compositions in the bed is investigated. According to the calculated results, bed pressure and bed temperature have the key effects on coal semi gasification. 展开更多
关键词 pressurized spouted fluidized bed coal gasification numerical simulation
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Influence of FeCrAl fiber on microstructure and mechanical properties of FeCrAl(f)/HA composites 被引量:2
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作者 杨海林 李婧 +4 位作者 方华婵 张翔 周忠诚 童晓阳 阮建明 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2013年第3期711-717,共7页
FeCrAl fiber-reinforced hydroxyapatite(HA) biocomposites(FeCrAl(f)/HA) were fabricated by the hot pressing technique.The metallographic microscopy,X-ray diffractometry,scanning electron microscopy(SEM) and ene... FeCrAl fiber-reinforced hydroxyapatite(HA) biocomposites(FeCrAl(f)/HA) were fabricated by the hot pressing technique.The metallographic microscopy,X-ray diffractometry,scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS) were used to observe and analyze the microstructure and composition of FeCrAl(f)/HA composites,respectively.The mechanical properties of FeCrAl(f)/HA composites were measured by the three-point-bending test.The results show that the composite can be reinforced by FeCrAl fiber and enhanced gradually,and then declined with the increase of the content of FeCrAl fiber(0-11%,volume fraction) in the whole range of experiments.Both the HA matrix and FeCrAl fiber integrate very tightly and bit into each other very deeply and counter-diffusion takes place to some extent at two-phase interface.The optimum parameters of FeCrAl(f)/HA composite are diameter of 22 μm,length of 1-2 mm and of volume faction of about 7% for FeCrAl fibers. 展开更多
关键词 FeCrAl(f)/HA composites fiber reinforcement hot pressing technique mechanical properties
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FABRICATION OF DLC COATED COBALT-CEMENTED TUNGSTEN CARBIDE MICRO-DRILLS AND THEIR CUTTING PERFORMANCE 被引量:4
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作者 马玉平 陈明 +1 位作者 向道辉 孙方宏 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2007年第2期89-93,共5页
In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon (DLC) films are deposited on cobalt-cem... In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon (DLC) films are deposited on cobalt-cemented tungsten carbide micro-drills with two-step pretreatment method. Characteristics of DLC coated tools are investigated in bias-enhanced HFCVD system with the optimized hot filament arrangement. The optimization deposition technology is obtained and the wear mechanism of cutting tools is analyzed. The drilling performance of DLC coated tools is verified by the experiments of cutting particle reinforced aluminum based composite material (Si 15% in volume) compared with uncoated ones. Experimental results show that the two-step pretreatment method is appropriate for complex shaped cemented carbide substrates and ensures the good adhesive strength between the diamond film and the substrate. The cutting performance of DLC coated tool is enhanced 10 times when machining the Si particle reinforced aluminum based metal matrix composite compared with that of uncoated ones under the same cutting conditions. 展开更多
关键词 DLC film bias-enhanced HFCVD cobalt-cemented tungsten carbide cutting tool micro-drilling cutting performance
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A monolithic InGaP/GaAs HBT power amplifier for W-CDMA applications 被引量:1
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作者 黄继伟 王志功 +2 位作者 廖英豪 陈志坚 方志坚 《Journal of Southeast University(English Edition)》 EI CAS 2011年第2期132-135,共4页
A monolithic microwave integrated circuit (MMIC) power amplifier (PA) is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the... A monolithic microwave integrated circuit (MMIC) power amplifier (PA) is proposed. It adopts a new on-chip bias circuit, which not only avoids the instability of the direct current bias caused by the change in the power supply and temperature, but also compensates deviations caused by the increase in input power. The bias circuit is a current-mirror configuration, and the feedback circuit helps to maintain bias voltage at a constant level. The gain of the feedback circuit is improved by the addition of a non-inverting amplifier within the feedback circuit. A shunt capacitor at the base node of the active bias transistor enhances the linearity of the PA. The chip is fabricated in an InGaP/GaAs heterojunction bipolar transistor (HBT) process. Measured results exhibit a 26. 6-dBm output compression point, 33.6% power-added efficiency (PAE) and - 40.2 dBc adjacent channel power ratio (ACPR) for wide-band code division multiple access (W-CDMA) applications. 展开更多
关键词 power amplifier wide-band code division multipleaccess(W-CDMA) heterojunction bipolar transistor (HBT) bias circuit gain compression
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Design of voltage-controlled dynamic band-pass filter based on VCA810 被引量:1
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作者 张艳花 杨录 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2015年第2期147-152,共6页
In order to filter signal effectively according to selective center frequency, a voltage-controlled dynamic band-pass filter with gain compensation was designed based on voltage-controlled gain wideband amplifier VCA8... In order to filter signal effectively according to selective center frequency, a voltage-controlled dynamic band-pass filter with gain compensation was designed based on voltage-controlled gain wideband amplifier VCA810. The transfer function of the filter was analyzed and gain compensation voltages were given through tests; besides, a system was designed, including the gain compensation circuit and the control voltage circuit, etc. Center frequency will change from 1 kHz to 20 kHz according to control voltage on condition that bandwidth of the filter remains constant. The designed system has the advantages of simple structure, low noise, stable performance and convenient adjustment. 展开更多
关键词 VCA810 dynamic band-pass filter voltage-controlled gain compensation
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Neural network based online hypertension risk evaluation system 被引量:2
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作者 马光志 卢炎生 +3 位作者 宋恩民 聂绍发 靖伟峰 张廆 《Journal of Southeast University(English Edition)》 EI CAS 2008年第3期267-271,共5页
Since the previous research works are not synthetic and accurate enough for building a precise hypertension risk evaluation system,by ranking the significances for hypertension factors according to the information gai... Since the previous research works are not synthetic and accurate enough for building a precise hypertension risk evaluation system,by ranking the significances for hypertension factors according to the information gains on 2 231 normotensive and 823 hypertensive samples,totally 42 different neural network models are built and tested.The prediction accuracy of a model whose inputs are 26 factors is found to be much higher than the 81.61% obtained by previous research work. The prediction matching rates of the model for "hypertension or not","systolic blood pressure",and "diastolic blood pressure" are 95.79%,98.22% and 98.41%,respectively.Based on the found model and the object oriented techniques,an online hypertension risk evaluation system is developed,being able to gather new samples,learn the new samples,and improve its prediction accuracy automatically. 展开更多
关键词 hypertension prediction neural network information gain
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ISM Band Medium Power Amplifier 被引量:1
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作者 白大夫 刘训春 +1 位作者 袁志鹏 钱永学 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2004年第6期626-632,共7页
With the large-signal model extracted from the InGaP/GaAs HBT with three fingers,a three-stage,class AB power amplifier at ISM band is designed.Through the optimization of the traditional bias network,the gain compres... With the large-signal model extracted from the InGaP/GaAs HBT with three fingers,a three-stage,class AB power amplifier at ISM band is designed.Through the optimization of the traditional bias network,the gain compression at the low input power level is eliminated successfully.At 3.5V of supply voltage of the power amplifier after optimization exhibits 30dBm of maximum linear output power,43.4% of power added efficiency 109.7mA of a quite low quiescent bias current ,29.1dB of the corresponding gain,and -100dBc of the adjacent channel power rejection (ACPR) at the output power of 30dBm. 展开更多
关键词 heterojunction bipolar transistor power amplifier bias network gain compression quiescent bias current
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Influence of Device Narrowing on HALO-pMOSFETs' Degradation Under V_g= V_d/2 Stress Mode
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作者 胡靖 赵要 +1 位作者 许铭真 谭长华 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2003年第12期1255-1260,共6页
The degradation characteristics of both wide and narrow devices under V _g= V _d/2 stress mode is investigated.The width-enhanced device degradation can be seen with devices narrowing.The main degradation mechanism is... The degradation characteristics of both wide and narrow devices under V _g= V _d/2 stress mode is investigated.The width-enhanced device degradation can be seen with devices narrowing.The main degradation mechanism is interface state generation for pMOSFETs with different channel width.The cause of the width-enhanced device degradation is attributed to the combination of width-enhanced threshold voltage and series resistance. 展开更多
关键词 width-enhanced degradation pinch-off voltage current-crowding effect
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High-quality aluminum turbocharger impellers produced by thixocasting 被引量:3
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作者 G.WALLACE A.P.JACKSON +1 位作者 S.P.MIDSON Q.ZHU 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2010年第9期1786-1791,共6页
The thixocasting process was chosen to produce the impellers as it is capable of producing castings with extremely high internal quality.Slugs cut from the DC cast bars are re-heated to the semi-solid casting temperat... The thixocasting process was chosen to produce the impellers as it is capable of producing castings with extremely high internal quality.Slugs cut from the DC cast bars are re-heated to the semi-solid casting temperature, and a specially-designed runner and gating system is used to prevent oxide from the surface of the slugs from becoming incorporated into the impeller.The technology used to produce the semi-solid impellers is described in detail.The semi-solid cast impellers, produced from an Al-Si-Mg-Cu alloy, are heat treated to the T6 temper.Results from testing are presented demonstrating that the impellers are free of porosity and other internal defects.Both mechanical property and fatigue data are presented showing that the semi-solid impellers have better properties than impellers produced by conventional casting and similar properties to forged and machined impellers.A short study is also described which identified suitable processing parameters to minimize hot tearing in the complex-shaped turbocharger impellers semi-solid cast from alloy 201.The surfaces of the impellers were examined using penetrant testing, and the results of modifying processing parameters on the propensity for surface cracking are presented.An aging study was performed to identify optimum mechanical strength. 展开更多
关键词 semi-solid casting turbocharger impeller fatigue properties alloy 201
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CMOS Dual-Band Low Noise Amplifer
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作者 冯东 石秉学 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2004年第9期1055-1060,共6页
A CMOS dual-band low noise amplifer (LNA) design is presented.The purpose of th is work is intended to substitute only one LNA for two individual LNA's in dual -band transceivers for applications such as wireless ... A CMOS dual-band low noise amplifer (LNA) design is presented.The purpose of th is work is intended to substitute only one LNA for two individual LNA's in dual -band transceivers for applications such as wireless local area network complying with both IEEE 802.11a and 802.11b/g.Dua l-band simultaneous input power and noise matching and load shaping are discuss ed.The chip is implemented in 0.25μm CMOS mixed and RF process.The measured pe rformance is summarized and discussed. 展开更多
关键词 low noise amplifier dual- band receiver power matching noise matching power gain voltage gain
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Numerical forecasting surge in a piping of compressor shops of gas pipeline network 被引量:1
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作者 SELEZNEV V. E. PRYALOV S. N. 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2007年第11期1775-1788,共14页
This paper presents a method of forecasting stable operation of gas compressor unit (GCU) centrifugal supercharger (CFS) installed on a piping of compressor shops servicing gas pipelines. The stability of supercharger... This paper presents a method of forecasting stable operation of gas compressor unit (GCU) centrifugal supercharger (CFS) installed on a piping of compressor shops servicing gas pipelines. The stability of superchargers operation is assessed in relation to the phenomenon of surge. Solution of this problem amounts to the development and numerical analysis of a set of ordinary differential equations. The set describes transmission of gas through a compressor shop as a fluid dynamics model with lumped parameters. The proposed method is oriented to wide application by specialists working in the gas industry. The practical application of this method can use all-purpose programming and mathematical software available to specialists of gas companies. 展开更多
关键词 Gas pipelines Compressor station Centrifugal supercharger (CFS) SURGE Numerical simulation
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GPP Based Open Cellular Network Towards 5G 被引量:2
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作者 Jiang Wang Jing Xu +1 位作者 Yang Yang Haidong Xu 《China Communications》 SCIE CSCD 2017年第6期189-198,共10页
Due to 5G's stringent and uncertainty traffic requirements,open ecosystem would be one inevitable way to develop 5G.On the other hand,GPP based mobile communication becomes appealing recently attributed to its str... Due to 5G's stringent and uncertainty traffic requirements,open ecosystem would be one inevitable way to develop 5G.On the other hand,GPP based mobile communication becomes appealing recently attributed to its striking advantage in flexibility and re-configurability.In this paper,both the advantages and challenges of GPP platform are detailed analyzed.Furthermore,both GPP based software and hardware architectures for open 5G are presented and the performances of real-time signal processing and power consumption are also evaluated.The evaluation results indicate that turbo and power consumption may be another challengeable problem should be further solved to meet the requirements of realistic deployments. 展开更多
关键词 open 5G general purpose processor (GPP) real-time signal processing software defined network (SDN) network function virtualization (NFV)
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Shock resistance of supercharged boilers through integration with ship structure 被引量:1
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作者 YAO Xiong-liang FENG Lin-han ZHANG A-man ZHOU Qi-xin 《Journal of Marine Science and Application》 2007年第4期18-26,共9页
The non-linear finite element software ABAQUS was used to simulate the dynamic response of a marine supercharged boiler when subjected to impact loading. Shock resistance was analyzed by the time-domain simulation met... The non-linear finite element software ABAQUS was used to simulate the dynamic response of a marine supercharged boiler when subjected to impact loading. Shock resistance was analyzed by the time-domain simulation method. After exhaustive simulations,the effect of air pressure induced by different working conditions on the shock response of a supercharged boiler was reviewed,leading to conclusions about the variability of structural response with different loading parameters. In order to simulate the real impulsive environments of supercharged boilers,the integration of equipment and ship structure was then primarily used to analyze shock response. These distinctly different equipment shock test methods,run under equivalent work conditions,were compared and the causes of discrepancy were analyzed. The main purpose of this paper is to present references for the anti-shock design of marine supercharged boilers. 展开更多
关键词 supercharged boiler numerical simulation dynamic response shock resistance integrationof equipment and ship structure
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A Low-Voltage,Low-Power CMOS High Dynamic Range dB-Linear VGA for Super Heterodyne Receivers 被引量:3
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作者 董桥 耿莉 邵志标 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2007年第11期1690-1695,共6页
This paper presents a low-voltage low-power variable gain amplifier,which is applied in the automatic gain control loop of a super heterodyne receiver. Six stages are cascaded to provide an 81dB digitally controlled g... This paper presents a low-voltage low-power variable gain amplifier,which is applied in the automatic gain control loop of a super heterodyne receiver. Six stages are cascaded to provide an 81dB digitally controlled gain range in a 3dB step. The gain step error is less than 0.5dB. It operates at an intermediate frequency of 300kHz, and the power consumption is 1.35mW from a 1.8V supply. The prototype chip is implemented in a TSMC's 0.18μm 1P6M CMOS process and occupies approximately 0.24mm^2 . It is very suitable for portable wire- less communication systems. The measurement results agree well with the system requirements. 展开更多
关键词 variable gain amplifier low voltage low power super heterodyne receiver CMOS RF integratedcircuits
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Collaborative optimization of exhaust gas recirculation and Miller cycle of two-stage turbocharged marine diesel engines based on particle swarm optimization 被引量:1
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作者 TANG Xu-yang WANG Peng +3 位作者 ZHANG Zhong-yuan ZHANG Feng-li SHI Lei DENG Kang-yao 《Journal of Central South University》 SCIE EI CAS CSCD 2022年第7期2142-2156,共15页
To meet increasingly stringent emission standards and lower the brake-specific fuel consumption(BSFC)of marine engines,a collaborative optimization study of exhaust gas recirculation(EGR)and a Miller cycle coupled tur... To meet increasingly stringent emission standards and lower the brake-specific fuel consumption(BSFC)of marine engines,a collaborative optimization study of exhaust gas recirculation(EGR)and a Miller cycle coupled turbocharging system was carried out.In this study,a one-dimensional numerical model of the EGR,Miller cycle,and adjustable two-stage turbocharged engine based on WeiChai 6170 marine diesel engine was established.The particle swarm optimization algorithm was used to achieve multi-input and multi-objective comprehensive optimization,and the effects of EGR-coupled Miller regulation and high-pressure turbine bypass regulation on NO_(x)and BSFC were investigated.The results showed that a medium EGR rate-coupled medium Miller degree was better for the comprehensive optimization of NO_(x)and BSFC.At medium EGR rate and low turbine bypass rates,NO_(x)and BSFC were relatively balanced and acceptable.Finally,an optimal steady-state control strategy under full loads was proposed.With an increase in loads,the optimized turbine bypass rate and Miller degree gradually increased.Compared with the EGRonly system,the optimal system of EGR and Miller cycle coupled turbine bypass reduced NO_(x)by 0.87 g/(kW·h)and BSFC by 17.19 g/(kW·h)at 100%load.Therefore,the EGR and Miller cycle coupled adjustable two-stage turbocharging achieves NO_(x)and BSFC optimization under full loads. 展开更多
关键词 exhaust gas recirculation(EGR) Miller cycle NO_(x)emissions adjustable two-stage turbocharging particle swarm optimization
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Portal hypertension secondary to myelofibrosis with myeloid metaplasia:A study of 13 cases 被引量:10
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作者 Mohannad Abu-Hilal Jayant Tawaker 《World Journal of Gastroenterology》 SCIE CAS CSCD 2009年第25期3128-3133,共6页
AIM:To describe the clinical presentation and complications of portal hypertension (PH) secondary to myelofibrosis with myeloid metaplasia (MMM).METHODS: Medical records for 123 patients with MMM were reviewed.RESULTS... AIM:To describe the clinical presentation and complications of portal hypertension (PH) secondary to myelofibrosis with myeloid metaplasia (MMM).METHODS: Medical records for 123 patients with MMM were reviewed.RESULTS: Thirteen patients with PH secondary to MMM were identified. Median ages at time of MMM and PH diagnosis were 61 and 66 years, respectively. The interval from MMM diagnosis to presentation with one of the PH features ranged from 1 to 11 years. Variceal bleeding and ascites were the most common presentations. Of the eight patients who presented with variceal bleeding, six patients underwent endoscopic variceal ligation (EVL) with no variceal recurrence or hematological worsening during a 12-mo follow up period.CONCLUSION: Patients with MMM might develop PH. Exact mechanisms leading to PH in MMM are still controversial. As in other etiologies, variceal bleeding and ascites are the most common presentations. Anemia may correlate with, and/or predict, the severity of the PH presentation in these patients. EVL can successfully control variceal bleeding in MMM. Further clinical studies are required. 展开更多
关键词 Portal hypertension MYELOFIBROSIS Myeloid metaplasia ASCITES Variceal bleeding
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