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Numerical simulation of charge stratifications to improve combustion and NO formation of lean-burn SI

Zhijun PENG ,

《能源前沿（英文）》 2009年 第3卷 第3期   页码 353-358 doi: 10.1007/s11708-009-0035-8

摘要： The influences of charge stratification on spark ignition (SI) engine combustion and NO emission were analyzed using a phenomenological model. The mixture in the cylinder was divided spherically into three parts: a central core with a stoichiometric air-fuel charge, a dilution region without any combustible charge, and a mixing region lying between the core and the dilution region. Three mixture stratification parameters such as the extent of dilution in the mixing region, the extent of combustible charge in the mixing region, and the gradient of stratification in the mixing region were investigated. The results indicate that the extent of combustible charge in the mixing region could reduce in-cylinder NO formation significantly, compared with the extent of dilution in the mixing region. As long as the degree of dilution in the mixing region is within the dilution limit of the combustible charge, the gradient of dilution has little effect on combustion and NO formation.

关键词： charge stratification     SI engine     lean-burn combustion     NO emission    

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A methodology for regulating fuel stratification and improving fuel economy of GCI mode via double main-injection

《能源前沿（英文）》 2023年 第17卷 第5期   页码 678-691 doi: 10.1007/s11708-022-0859-z

摘要： Gasoline compression ignition (GCI) combustion faces problems such as high maximum pressure rise rate (MPRR) and combustion deterioration at high loads. This paper aims to improve the engine performance of the GCI mode by regulating concentration stratification and promoting fuel-gas mixing by utilizing the double main-injection (DMI) strategy. Two direct injectors simultaneously injected gasoline with an octane number of 82.7 to investigate the energy ratio between the two main-injection and exhaust gas recirculation (EGR) on combustion and emissions. High-load experiments were conducted using the DMI strategy and compared with the single main-injection (SMI) strategy and conventional diesel combustion. The results indicate that the DMI strategy have a great potential to reduce the MPRR and improve the fuel economy of the GCI mode. At a 10 bar indicated mean effective pressure, increasing the main-injection-2 ratio (Rm-2) shortens the injection duration and increases the mean mixing time. Optimized Rm-2 could moderate the trade-off between the MPRR and the indicated specific fuel consumption with both reductions. An appropriate EGR should be adopted considering combustion and emissions. The DMI strategy achieves a highly efficient and stable combustion at high loads, with an indicated thermal efficiency (ITE) greater than 48%, CO and THC emissions at low levels, and MPRR within a reasonable range. Compared with the SMI strategy, the maximum improvement of the ITE is 1.5%, and the maximum reduction of MPRR is 1.5 bar/°CA.

关键词： gasoline compression ignition     injection strategy     fuel stratification     high efficiency     high load    

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Comparison of prechilling stratification and sulfuric acid scarification on seed germination of

Nan WANG, Jing GAO, Suiqi ZHANG, Feng YAN

《农业科学与工程前沿（英文）》 2017年 第4卷 第2期   页码 220-227 doi: 10.15302/J-FASE-2017146

摘要： In semi-arid regions of the Loess Plateau, water deficiency restricts plant performance. (switchgrass), which is a highly versatile grass, had been introduced to the Plateau as a restoration species. To determine if prechilling stratification (PCS) and sulfuric acid scarification (SAS) can optimize establishment, cvs Pathfinder, Trailblazer and Alamo were tested under different ambient water potentials by measuring germination and root and shoot growth along water potential gradients under laboratory conditions. Both PCS and SAS improved total germination percentage (TGP), with PCS being more beneficial. The effect of PCS and SAS on mean germination time (MGT) weakened gradually with increasing drought stress. Both PCS and SAS showed no obvious effect on promoting root and shoot growth. Both PCS and SAS reduced base water potential requirement for reaching 50% germination of Pathfinder and Trailblazer, with this effect greater for PCS. These results indicate that embryo dormancy may be a major factor limiting germination of under drought conditions. Pathfinder appears to be more suitable for a semi-arid environment, whereas Alamo appears to be unsuitable for drought conditions. Given the large difference between predicted value and measured value, the reliability and applicable scope of linear regression estimated Y needs further investigation, specification and optimization.

关键词： base water potential     data analysis method     embryo growth     germination    

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Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrentnearby the regime of the space charge-limited current

Boa Jin, Hyunmin Park, Yang Liu, Leijing Liu, Jongdeok An, Wenjing Tian, Chan Im

《化学科学与工程前沿（英文）》 2021年 第15卷 第1期   页码 164-179 doi: 10.1007/s11705-020-1976-z

摘要： To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells, the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages, and a wide range of excitation intensities are analyzed. For this purpose, conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used. After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current, the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility. By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers, the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained. Subsequently, the charge-carrier concentration-dependent mobility values were obtained, and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.

关键词： charge-carrier photogeneration     transient photocurrent     polymer solar cells     charge-carrier extraction     space charge-limited current    

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Risk stratification system for skin and soft tissue infections after allogeneic hematopoietic stem cell

《医学前沿（英文）》 2022年 第16卷 第6期   页码 957-968 doi: 10.1007/s11684-021-0910-1

摘要： Skin and soft tissue infections (SSTIs) refer to infections involving the skin, subcutaneous tissue, fascia, and muscle. In transplant populations with hematological malignancies, an immunocompromised status and the routine use of immunosuppressants increase the risk of SSTIs greatly. However, to date, the profiles and clinical outcomes of SSTIs in hematopoietic stem cell transplantation (HSCT) patients remain unclear. This study included 228 patients (3.67%) who developed SSTIs within 180 days after allogeneic HSCT from January 2004 to December 2019 in Peking University People’s Hospital. The overall annual survival rate was 71.5%. We compared the differences between survivors and non-survivors a year after transplant and found that primary platelet graft failure (PPGF), comorbidities of acute kidney injury (AKI), and hospital-acquired pneumonia (HAP) were independent risk factors for death in the study population. A PPGF–AKI–HAP risk stratification system was established with a mortality risk score of 1×PPGF+1×AKI+1×HAP. The areas under the curves of internal and external validation were 0.833 (95% CI 0.760–0.906) and 0.826 (95% CI 0.715–0.937), respectively. The calibration plot revealed the high consistency of the estimated risks, and decision curve analysis showed considerable net benefits for patients.

关键词： skin and soft tissue infections     hematopoietic stem cell transplantation     risk stratification system     mortality    

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Charge and separation characteristics of nanofiltration membrane embracing dissociated functional groups

Zhun MA,Meng WANG,Xueli GAO,Congjie GAO

《环境科学与工程前沿（英文）》 2014年 第8卷 第5期   页码 650-658 doi: 10.1007/s11783-013-0605-1

摘要： The current work focused on the investigation of charge and separation characteristics of nanofiltration (NF) membrane embracing dissociated functional groups under different electrolyte solutions. The electro-kinetic method was carried out to assess the membrane volume charge density ( ) with different salt concentrations ranging from 0.1 to 10 mol·m and different electrolyte species, such as type 1–1, type 2–1 and type 3–1. The Donnan steric pore model-dielectric exclusion (DSPM-DE) model was employed to evaluate the separation characteristics of the NF membrane for wide range of electrolyte concentration (from 25.7 to 598.9 mol·m ). The results indicated that the dissociation of the hydrophilic functional groups and the specific adsorption contributed to charge formation on membrane surface. The former played a dominant role in type 1–1 and type 2–1 electrolytes at dilute aqueous solutions (0.1–0.5 mol·m ). However, for type 3–1 electrolyte, specific adsorption should contribute to the charge effect to a large extent. Moreover, the correlation between the volume charge density and feed concentration was in accordance with Freundlich isotherm. Furthermore, it was found that the separation characteristic of NF membrane could be evaluated well by DSPM-DE model coupling with electro-kinetic method in a whole concentration range.

关键词： Sulfonated polyethersulfone nanofiltration membrane     charge characteristics     electro-kinetic method     volume charge density     separation behavior    

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Visible-light-driven heterostructured g-CN/Bi-TiO floating photocatalyst with enhanced charge carrier

《环境科学与工程前沿（英文）》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1417-3

摘要：

• Bi doping in TiO2 enhanced the separation of photo-generated electron-hole.

关键词： Bi doping     Visible light     Algal removal     Charge carrier separation    

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Chaotic behavior of LNG after stratification in main stream region of storage tank

WANG Jingjing, MA Xiaoqian

《能源前沿（英文）》 2008年 第2卷 第4期   页码 514-518 doi: 10.1007/s11708-008-0076-4

摘要： A study of the chaotic behavior of liquefied natural gas (LNG) after stratification in the main stream region of a storage tank was conducted. Based on non-linear dynamics, a 2-dimensional Rayleigh-Benard convection model was developed to simulate the convection, Lorenz equations of LNG convection were deduced from conservation equations, and the Runge-Kutta method was used to solve the equations. The results showed that when = 1.33, 106 < < 1470, chaos was obtained, which meant that the velocity field and the temperature field were highly unsteady. In addition, the influence of temperature and scale factor on the solutions and the corresponding range of parameters were studied. The results revealed that the chaos in LNG convection resulted from the interaction of buoyancy and viscid forces. A small quantity of heat impacting the storage tank would lead to a strong and unstable convection of LNG in the main stream region.

关键词： Runge-Kutta     non-linear     corresponding     temperature     addition    

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membranes using SPES as a hydrophilic polymer for the effective removal of dyes via steric hindrance and charge

《化学科学与工程前沿（英文）》 2023年 第17卷 第10期   页码 1555-1567 doi: 10.1007/s11705-023-2338-4

摘要： Herein, polyethersulfone (PES) and sulfonated polysulfone (SPSf) blend membranes were prepared with addition of sulfonated polyethersulfone (SPES) as a hydrophilic polymer and adipic acid as a porogen via non-solvent induced phase separation method for effective fractionation of dyes based on the influence of steric hindrance and charge effect. Raman spectroscopy and molecular dynamic simulation modeling confirmed that hydrogen bonds between PES, SPSf, SPES, and adipic acid were crucial to membrane formation and spatial arrangement. Further addition of hydrophilic SPES resulted in a membrane with reduced pore size and molecular weight cut-off as well as amplified negative charge and pure water permeance. During separation, the blend membranes exhibited higher rejection rates for nine types of small molecular weight (269.3–800 Da) dyes than for neutral polyethylene glycol molecules (200–1000 Da). This was attributed to the size effect and the synergistic effect between steric hindrance and charge repulsion. Notably, the synergistic impact decreased with dye molecular weight, while greater membrane negative charge enhanced small molecular dye rejection. Ideal operational stability and anti-fouling performance were best observed in M2 (PES/SPSf/SPES, 3.1 wt %). Summarily, this study demonstrates that SPES with –SO3‒ functional groups can be applied to control the microstructure and separation of membranes.

关键词： adipic acid     loose nanofiltration membrane     dye/salt selective separation     steric hindrance     charge effect    

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真实空气中TNT装药爆炸近区冲击波传播特性研究

周丰峻,郑磊,孙云厚,张鏖,夏明

《中国工程科学》 2017年 第19卷 第6期   页码 18-26 doi: 10.15302/J-SSCAE-2017.06.004

摘要：

本文基于点源爆炸理论，建立了面源、线源和点源TNT装药强爆炸解，填补了面源与线源强爆炸解的空白；采用真实空气状态方程进行分析计算，研究了真实空气条件下球形TNT装药爆炸近区冲击波的传播特性。通过算例分析，计算结果与已有文献资料数据吻合较好。本文的研究成果对爆炸力学和防护工程研究起到了重要的参考作用。

关键词： TNT装药爆炸     真实空气状态方程     面源装药     线源装药     点源装药     抗爆防护    

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Effects of operating conditions on membrane charge property and nanofiltration

Li XU, Li-Shun DU, Jing HE

《化学科学与工程前沿（英文）》 2011年 第5卷 第4期   页码 492-499 doi: 10.1007/s11705-011-1143-7

摘要： The effects of the operating pressure, cross flow velocity, feed concentration, and temperature on the streaming and Zeta potential of the membranes were studied. The permeate flux and the retention rate under different nanofiltration operating conditions were also investigated. The results show that the higher pressure, feed concentration, temperature, and lower cross flow velocity lead to the higher absolute value of streaming and Zeta potential. The permeate flux of the nanofiltration decreases with the feed concentration and increases with not only the pressure but also the cross flow velocity and temperature. The higher the pressure and the cross flow velocity, the higher the retention rate. The lower feed concentration and higher temperature leads to lower retention rate. The effects of the operating conditions on the permeate flux and the retention rate were explained by the variation of the membrane charge property.

关键词： nanofiltration membrane     streaming potential     Zeta potential     permeate flux     retention rate    

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一种新型聚能破甲战斗部及其发展趋势探讨

安二峰,沈兆武,周听清,王德润

《中国工程科学》 2004年 第6卷 第6期   页码 85-90

摘要：

针对当前以单罩聚能效应为主的聚能破甲战斗部，提出一种新型多罩复合聚能装药结构，探讨了其成型机理和联合破甲原理，系统研究了主要装药结构参数对破甲效果的影响。实验结果表明，该聚能装药结构比EFP装药结构，在保持穿孔孔径相当和同等装药条件下，可以提高穿深50%左右。在此基础上，进一步提出反反应装甲目标新型聚能装药结构，深化了聚能效应的内涵，丰富了打击目标的手段。

关键词： 聚能战斗部     爆炸成型弹丸     聚能射流     反应装甲     侵彻    

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Effect of ligand chain length on hydrophobic charge induction chromatography revealed by molecular dynamics

Lin ZHANG, Yan SUN

《化学科学与工程前沿（英文）》 2013年 第7卷 第4期   页码 456-463 doi: 10.1007/s11705-013-1357-y

摘要： Hydrophobic charge induction chromatography (HCIC) is a mixed-mode chromatography which is advantageous for high adsorption capacity and facile elution. The effect of the ligand chain length on protein behavior in HCIC was studied. A coarse-grain adsorbent pore model established in an earlier work was modified to construct adsorbents with different chain lengths, including one with shorter ligands (CL2) and one with longer ligands (CL4). The adsorption, desorption, and conformational transition of the proteins with CL2 and CL4 were examined using molecular dynamics simulations. The ligand chain length has a significant effect on both the probability and the irreversibility of the adsorption/desorption. Longer ligands reduced the energy barrier of adsorption, leading to stronger and more irreversible adsorption, as well as a little more unfolding of the protein. The simulation results elucidated the effect of the ligand chain length, which is beneficial for the rational design of adsorbents and parameter optimization for high-performance HCIC.

关键词： adsorption     desorption     irreversibility     protein conformational transition     molecular dynamics simulation    

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Effects of compression ratio on the combustion characteristics of a homogeneous charge compression ignition

SONG Ruizhi, ZHOU Longbao, LIU Shenghua, LI Wei, HU Tiegang

《能源前沿（英文）》 2007年 第1卷 第4期   页码 463-467 doi: 10.1007/s11708-007-0068-0

摘要： The effects of homogeneous charge compression ignition (HCCI) engine compression ratio on its combustion characteristics were studied experimentally on a modified TY1100 single cylinder engine fueled with dimethyl ether. The resul

关键词： homogeneous     cylinder     combustion     compression     dimethyl    

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Effects of BTA2 as the third component on the charge carrier generation and recombination behavior of

Leijing Liu, Hao Zhang, Bo Xiao, Yang Liu, Bin Xu, Chen Wang, Shanpeng Wen, Erjun Zhou, Gang Chen, Chan Im, Wenjing Tian

《化学科学与工程前沿（英文）》 2021年 第15卷 第1期   页码 127-137 doi: 10.1007/s11705-020-1936-7

摘要： Effects of a benzotriazole (BTA)-based small molecule, BTA2, as the third component on the charge carrier generation and recombination behavior of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7):[6,6]-phenyl-C -butyric acid methyl ester (PC BM) organic solar cells (OSCs) were investigated by optical simulation of a transfer matrix model (TMM), photo-induced charge extraction by linearly increasing voltage (photo-CELIV) technique, atomic force microscope (AFM), and the Onsager–Braun model analysis. BTA2 is an A A D A A -type non-fullerene small molecule with thiazolidine-2,4-dione, BTA, and indacenodithiophene as the terminal acceptor (A ), bridge acceptor (A ), and central donor (D), respectively. The short-circuit current density of the OSCs with BTA2 can be enhanced significantly owing to a complementary absorption spectrum. The optical simulation of TMM shows that the ternary OSCs exhibit higher internal absorption than the traditional binary OSCs without BTA2, resulting in more photogenerated excitons in the ternary OSCs. The photo-CELIV investigation indicates that the ternary OSCs suffer higher charge trap-limited bimolecular recombination than the binary OSCs. AFM images show that BTA2 aggravates the phase separation between the donor and the acceptor, which is disadvantageous to charge carrier transport. The Onsager-Braun model analysis confirms that despite the charge collection efficiency of the ternary OSCs being lower than that of the binary OSCs, the optimized photon absorption and exciton generation processes of the ternary OSCs achieve an increase in photogenerated current and thus improve power conversion efficiency.

关键词： third component     organic solar cells     charge carrier generation     charge carrier recombination     bimolecular recombination    

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标题 作者 时间 类型 操作

Numerical simulation of charge stratifications to improve combustion and NO formation of lean-burn SI

Zhijun PENG ,

期刊论文

A methodology for regulating fuel stratification and improving fuel economy of GCI mode via double main-injection

期刊论文

Comparison of prechilling stratification and sulfuric acid scarification on seed germination of

Nan WANG, Jing GAO, Suiqi ZHANG, Feng YAN

期刊论文

Charge-carrier photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrentnearby the regime of the space charge-limited current

Boa Jin, Hyunmin Park, Yang Liu, Leijing Liu, Jongdeok An, Wenjing Tian, Chan Im

期刊论文

Risk stratification system for skin and soft tissue infections after allogeneic hematopoietic stem cell

期刊论文

Charge and separation characteristics of nanofiltration membrane embracing dissociated functional groups

Zhun MA,Meng WANG,Xueli GAO,Congjie GAO

期刊论文

Visible-light-driven heterostructured g-CN/Bi-TiO floating photocatalyst with enhanced charge carrier

期刊论文

Chaotic behavior of LNG after stratification in main stream region of storage tank

WANG Jingjing, MA Xiaoqian

期刊论文

membranes using SPES as a hydrophilic polymer for the effective removal of dyes via steric hindrance and charge

期刊论文

真实空气中TNT装药爆炸近区冲击波传播特性研究

周丰峻,郑磊,孙云厚,张鏖,夏明

期刊论文

Effects of operating conditions on membrane charge property and nanofiltration

Li XU, Li-Shun DU, Jing HE

期刊论文

一种新型聚能破甲战斗部及其发展趋势探讨

安二峰,沈兆武,周听清,王德润

期刊论文

Effect of ligand chain length on hydrophobic charge induction chromatography revealed by molecular dynamics

Lin ZHANG, Yan SUN

期刊论文

Effects of compression ratio on the combustion characteristics of a homogeneous charge compression ignition

SONG Ruizhi, ZHOU Longbao, LIU Shenghua, LI Wei, HU Tiegang

期刊论文

Effects of BTA2 as the third component on the charge carrier generation and recombination behavior of

Leijing Liu, Hao Zhang, Bo Xiao, Yang Liu, Bin Xu, Chen Wang, Shanpeng Wen, Erjun Zhou, Gang Chen, Chan Im, Wenjing Tian

期刊论文