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期刊论文 17

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临界风速 1

地铁隧道 1

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斯托克斯流 1

水稻 1

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流动塑形 1

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Numerical study on natural convection in a square enclosure containing a rectangular heated cylinder

Jianhua LU, Zhaoli GUO, Zhenhua CHAI, Baochang SHI,

《能源前沿（英文）》 2009年 第3卷 第4期   页码 373-380 doi: 10.1007/s11708-009-0078-x

摘要： In this paper, the natural convection in a square enclosure with a rectangular heated cylinder is investigated via the lattice Boltzmann method. A detailed study is conducted on the effect of the cylinder width and the Rayleigh number on the fluid flow and heat transfer. The flow structures and heat transfer patterns are classified into eight buoyant regimes, i.e., four steady regimes, two periodic regimes, one multiple periodic regime, and one chaos regime, two of which are reported for the first time.

关键词： natural convection     buoyant regime     heated cylinder     lattice Boltzmann    

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Experimental study on combined buoyant-thermocapillary flow along with rising liquid film on the surface

Manuel J. GOMES, Ning MEI

《能源前沿（英文）》 2020年 第14卷 第1期   页码 114-126 doi: 10.1007/s11708-017-0483-5

摘要： Temperature distribution and variation with time has been considered in the analysis of the influences of the initial level of immersion of a horizontal metallic mesh tube in the liquid on combined buoyant and thermo-capillary flow. The combined flow occurs along with the rising liquid film flow on the surface of a horizontal metallic mesh tube. Three different levels of immersion of the metallic mesh tube in the liquid have been tested. Experiments of 60 min in duration have been performed using a heating metallic tube with a diameter of 25 mm and a length of 110 mm, sealed outside with a metallic mesh of 178 mm by 178 mm, and distilled water. These reveal two distinct flow patterns. Thermocouples and infrared thermal imager are utilized to measure the temperature. The level of the liquid free surface relative to the lower edge of the tube is measured as angle . The results show that for a smaller angle, or a low level of immersion, with a relatively low heating power, it is possible to near fully combine the upwards buoyant flow with the rising liquid film flow. In this case, the liquid is heated only in the vicinity of the tube, while the liquid away from the flow region experiences small changes in temperature and the system approaches steady conditions. For larger angles, or higher levels of immersion, a different flow pattern is noticed on the liquid free surface and identified as the thermo-capillary (Marangoni) flow. The rising liquid film is also present. The higher levels of immersion cause a high temperature gradient in the liquid free surface region and promote thermal stratification; therefore the system could not approach steady conditions.

关键词： rising liquid film     combined flow     thermo-capillary flow     buoyant flow     metallic mesh tube     horizontal tube    

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Investigation of bubble diameter and flow regime between water and dilute aqueous ethanol solutions in

Baharak SAJJADI, Mostafa Keshavarz MORAVEJI, Reza DAVARNEJAD

《化学科学与工程前沿（英文）》 2011年 第5卷 第2期   页码 194-202 doi: 10.1007/s11705-010-1019-2

摘要： In this study, the effect of ethanol addition into pure water and its concentration on bubble diameter, gas hold-up and flow regimes were investigated in an airlift reactor. Air and water with ethanol (concentration ranging from 0%–1%, v/v) were as dispersed and continuous phases, respectively. Superficial gas velocity was considered as an effective parameter. Bubble size distribution was measured by photography and picture analysis at various concentrations of ethanol and various velocities of gas. Alcohol concentration enhancement caused bubble diameter to decrease. Furthermore, the bubbles diameter in pure water was nearly 4 times higher than that of ethanol with concentration of 1% (v/v) and also was 3.4 times higher than that of ethanol with concentration of 0.25% (v/v) at the highest aeration gas velocity inlet. For ethanol solutions in lower superficial gas velocity, a homogenous flow regime was observed. This trend continued to inlet gas velocity of about 0.4 cm/s. The transition flow regime occurred after this datum although in pure water, a homogenous flow regime was observed up to a superficial gas velocity of 0.7 cm/s. The gas hold-up in dilute ethanol solutions were more than (around 2 times) that of pure water and increased with increasing concentration of ethanol in those solutions.

关键词： airlift rector     bubble diameter     gas hold-up     flow regime     ethanol    

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Calculation of collision frequency function for aerosol particles in free molecule regime in presence

Xiaowei LUO, Yannick BENICHOU, Suyuan YU

《能源前沿（英文）》 2013年 第7卷 第4期   页码 506-510 doi: 10.1007/s11708-013-0275-5

摘要： The collision frequency function for aerosol particles has already been calculated for the free molecule regime and for the continuum range. The present work, taking into account the influence of internal force fields such as magnetic force, electric force and molecular forces, created by particles themselves, recalculated the collision frequency in the case of particles much smaller than the mean free path of the gas (free molecule regime). Attractive forces increase naturally the collision frequency, while repulsive forces decrease it. The calculation was performed for all types of central forces deriving from a potential, including Coulomb forces and Van der Waals forces.

关键词： aerosol particles     collision frequency function     coagulation    

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Kinetic roughening transition and missing regime transition of melt crystallized polybutene-1 tetragonal

Motoi YAMASHITA

《化学科学与工程前沿（英文）》 2009年 第3卷 第2期   页码 125-134 doi: 10.1007/s11705-009-0001-3

摘要： The morphology and lateral growth rate of polybutene-1 ( -PB1) have been investigated for crystallization from the melt over a wide range of crystallization temperatures from 50 to 110°C. The morphology of -PB1 crystals is a rounded shape at crystallization temperatures lower than 85°C, while lamellar single crystals possess faceted morphology at higher crystallization temperatures. The kinetic roughening transition occurs around 85°C. The nucleation and growth mechanism for crystallization does not work below 85°C, since the growth face is rough. However, the growth rate shows the supercooling dependence derived from the nucleation and growth mechanism. The nucleation theory seems still to work even for rough surface growth. Possible mechanisms for the crystal growth of this polymer are discussed.

关键词： isotactic polybutene-1     tetragonal phase (form Ⅱ)     melt crystallization     growth rate     kinetic roughening     morphology    

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Study of two-phase flow regime identification in horizontal tube bundles under vertical upward cross-flow

HUANG Xinghua, WANG Li, JIA Feng

《能源前沿（英文）》 2008年 第2卷 第3期   页码 333-338 doi: 10.1007/s11708-008-0043-0

摘要： A wavelet-transform based approach for flow regime identification in horizontal tube bundles under vertical upward cross-flow condition was presented. Tests on two-phase flow pattern of R134a were conducted under low mass velocity and flow boiling conditions over ranges of mass flux 4–25 kg/ms, vapor quality 0.02–0.90. Time series of differential pressure fluctuations were measured and analyzed with discrete wavelet transform. Different time-scale characteristics in bubbly flow, churn flow and annular flow were analyzed. The wavelet energy distributions over scales were found to be appropriate for flow regime identification. Based on the wavelet energy distribution over characteristic scales, a criterion of flow regime identification was proposed. The comparison with experiment results show that it is feasible to use the discrete wavelet transform as the tool of flow regime identification in horizontal tube bundles under vertical upward cross-flow condition.

关键词： two-phase     discrete     appropriate     wavelet-transform     criterion    

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Experimental study for the stratified to slug flow regime transition mechanism of gas-oil two-phase flow

LIU Yiping, YANG Weilin, WANG Jing

《能源前沿（英文）》 2008年 第2卷 第2期   页码 152-157 doi: 10.1007/s11708-008-0012-7

摘要： Theoretical relations that predict the transition from a stratified pattern to a slug pattern, including a one-dimensional wave model that contains less empiricism than the commonly used Taitel-Dukler model, and the ideal model for stratified flow for the gas-liquid flow in horizontal pipes are presented. Superficial velocities of each phase, as the onset of slugging occurs, were predicted, and theoretical analysis was conducted on the stratified to slug flow regime transition. The friction, existing between the fluid and pipe wall, and on the interface of two phases, was especially taken into account. A theoretical model was applied to an experiment about air-oil two-phase flow in a 50 mm horizontal pipe. The effect of pipe diameter on the transition was also studied. The results show that this approach gives a reasonable prediction over the whole range of flow rates, and better agreement has been achieved between predicted and measured critical parameters.

关键词： two-phase     Superficial     reasonable prediction     one-dimensional     gas-liquid    

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photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime

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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Is atmospheric oxidation capacity better in indicating tropospheric O formation?

《环境科学与工程前沿（英文）》 2022年 第16卷 第5期 doi: 10.1007/s11783-022-1544-5

摘要：

● This study summarizes and evaluates different approaches that indicate O3 formation.

关键词： O3     AOC     O3 formation regime    

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Burnett simulations of gas flow and heat transfer in microchannels

Fubing BAO, Jianzhong LIN

《机械工程前沿（英文）》 2009年 第4卷 第3期   页码 252-263 doi: 10.1007/s11465-009-0037-6

摘要： In micro- and nanoscale gas flows, the flow falls into the transition flow regime. There are not enough molecule collisions and the gas deviates from the equilibrium. The Navier-Stokes equations fail to describe the gas flow in this regime. The direct simulation Monte Carlo method converges slowly and requires lots of computational time. As a result, the high-order Burnett equations are used to study the gas flow and heat transfer characteristics in micro- and nanoscale gas flows in this paper. The Burnett equations are first reviewed, and the augmented Burnett equations with high-order slip boundary conditions are then used to model the gas flow and heat transfer in Couette and Poiseuille flows in the transition regime.

关键词： micro- and nanoscale gas flow     slip-transition flow regime     Burnett equations     numerical simulation    

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EFFECTS OF SUBSTITUTION OF MINERAL NITROGEN WITH ORGANIC AMENDMENTS ON NITROGEN LOSS FROM SLOPING CROPLAND OF PURPLE SOIL

《农业科学与工程前沿（英文）》 2022年 第9卷 第3期   页码 396-406 doi: 10.15302/J-FASE-2022456

摘要：

● Interflow acts as the dominant pathway for N loss loadings.

关键词： improved fertilization regime     interflow     nitrogen forms     nitrogen leaching     purple soil     sloping cropland    

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水稻节水灌溉及其对环境的影响

茆智

《中国工程科学》 2002年 第4卷 第7期   页码 8-16

摘要：

水稻是中国最主要的粮食作物之一，其产量约占粮食作物总产量的40%；在全国约11×108hm2的粮食作物总面积中，稻田面积约占28%。20世纪80年代以来，水稻产区的水资源短缺已成为当地农业生产中的重要问题，各地试验、开发、应用与推广了许多种水稻节水灌溉模式。文章根据这些新的水稻灌溉模式试验结果与推广经验，将我国水稻节水灌溉主要模式归纳为浅、湿、晒结合，间歇淹水，半旱栽培和蓄雨型等4类。阐述了这些模式的田间水分控制标准以及节水、增产和提高水分生产率的潜力；提出了该4类模式的选择原则以及应用这些模式时应注意的问题；分析、讨论了推广这些模式能够持续节水与提高水分生产率的机理以及对环境的影响。

关键词： 水稻     节水灌溉     灌溉模式     节水潜力     环境影响    

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纵向通风水平隧道火灾烟气流动特性研究

卢平,丛北华,廖光煊,范维澄,厉培德

《中国工程科学》 2004年 第6卷 第10期   页码 59-64

摘要：

地铁隧道火灾烟气控制是城市公共安全的一个重要组成部分。在分析地铁隧道火灾烟气流动主要影响因素的基础上，将地铁隧道通风和排烟系统作为一个整体考虑，引入地铁隧道火灾烟气的浮力效应和热阻效应，建立了隧道通风网络火灾模拟的数学模型，分析了地铁隧道火灾烟气逆流的临界条件、临界流速、隧道风流及烟流流速与火灾强度的变化关系，为地铁隧道火灾烟气控制和事故应急处理提供科学依据。

关键词： 地铁隧道     火灾烟气     浮力效应     热阻效应     临界风速    

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Photochemical indicators of ozone sensitivity: application in the Pearl River Delta, China

Lyumeng Ye,Xuemei Wang,Shaofeng Fan,Weihua Chen,Ming Chang,Shengzhen Zhou,Zhiyong Wu,Qi Fan

《环境科学与工程前沿（英文）》 2016年 第10卷 第6期 doi: 10.1007/s11783-016-0887-1

摘要： The distribution of NO - and VOC-sensitive regimes in the PRD are identified. The effectiveness of six popular chemical indicators for discriminating O sensitivity regimes is evaluated. Threshold levels for HCHO/NO , H O /HNO , O /NO , O /NO , O /HNO were derived and verified. The indicators H O /HNO and H O /NO performed best and maintained relatively stable threshold levels. Surface O production has a highly nonlinear relationship with its precursors. The spatial and temporal heterogeneity of O -NO -VOC-sensitivity regimes complicates the control- decision making. In this paper, the indicator method was used to establish the relationship between O sensitivity and assessment indicators. Six popular ratios indicating ozone-precursor sensitivity, HCHO/NO , H O /HNO , O /NO , O /NO , O /HNO , and H O /NO , were evaluated based on the distribution of NO - and VOC-sensitive regimes. WRF-Chem was used to study a serious ozone episode in fall over the Pearl River Delta (PRD). It was found that the south-west of the PRD is characterized by a VOC-sensitive regime, while its north-east is NO -sensitive, with a sharp transition area between the two regimes. All indicators produced good representations of the elevated ozone hours in the episode on 6 November 2009, with H O /HNO being the best indicator. The threshold sensitivity levels for HCHO/NO , H O /HNO , O /NO , O /NO , O /HNO , and H O /NO were estimated to be 0.41, 0.55, 10.2, 14.0, 19.1, and 0.38, respectively. Threshold intervals for the indicators H O /HNO , O /NO , O /NO , O /HNO , and H O /NO were able to identify more than 95% of VOC- and NO -sensitive grids. The ozone episode on 16 November 16 2008 was used to independently verify the results, and it was found that only H O /HNO and H O /NO were able to differentiate the ozone sensitivity regime well. Hence, these two ratios are suggested as the most appropriate indicators for identifying fall ozone sensitivity in the PRD. Since the species used for indicators have seasonal variation, the utility of those indicators for other seasons should be investigated in the future work.

关键词： Ozone     Pearl River Delta (PRD)     Sensitivity regime     Photochemical indicator     Threshold levels    

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Option-like properties in the distribution of hedge fund returns

Katharina DENK, Ben DJERROUD, Luis SECO, Mohammad SHAKOURIFAR, Rudi ZAGST

《工程管理前沿（英文）》 2020年 第7卷 第2期   页码 275-286 doi: 10.1007/s42524-020-0095-3

摘要： Hedge funds have recently become popular because of their low correlation with traditional investments and their ability to generate positive returns with a relatively low volatility. However, a close look at those high-performing hedge funds raises the questions on whether their performance is truly superior and whether the high management fees are justified. Incurring no alpha costs, passive hedge fund replication strategies raise the question on whether they can similarly perform by improving efficiency at reduced costs. Therefore, this study investigates two different model approaches for the equity long/short strategy, where weighted segmented linear regression models are employed and combined with two-state Markov switching models. The main finding proves a short put option structure, i.e., short equity market volatility, with the put structure present in all market states. We obtain an evidence that the hedge fund managers decrease their short-volatility profile during turbulent markets.

关键词： hedge funds     hedge fund index     segmented linear regression models     regime-switching models     mimicking portfolios     single factor-based hedge fund replication     equity long–short strategy    

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标题 作者 时间 类型 操作

Numerical study on natural convection in a square enclosure containing a rectangular heated cylinder

Jianhua LU, Zhaoli GUO, Zhenhua CHAI, Baochang SHI,

期刊论文

Experimental study on combined buoyant-thermocapillary flow along with rising liquid film on the surface

Manuel J. GOMES, Ning MEI

期刊论文

Investigation of bubble diameter and flow regime between water and dilute aqueous ethanol solutions in

Baharak SAJJADI, Mostafa Keshavarz MORAVEJI, Reza DAVARNEJAD

期刊论文

Calculation of collision frequency function for aerosol particles in free molecule regime in presence

Xiaowei LUO, Yannick BENICHOU, Suyuan YU

期刊论文

Kinetic roughening transition and missing regime transition of melt crystallized polybutene-1 tetragonal

Motoi YAMASHITA

期刊论文

Study of two-phase flow regime identification in horizontal tube bundles under vertical upward cross-flow

HUANG Xinghua, WANG Li, JIA Feng

期刊论文

Experimental study for the stratified to slug flow regime transition mechanism of gas-oil two-phase flow

LIU Yiping, YANG Weilin, WANG Jing

期刊论文

photogeneration and extraction dynamics of polymer solar cells probed by a transient photocurrent nearby the regime

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

期刊论文

Is atmospheric oxidation capacity better in indicating tropospheric O formation?

期刊论文

Burnett simulations of gas flow and heat transfer in microchannels

Fubing BAO, Jianzhong LIN

期刊论文

EFFECTS OF SUBSTITUTION OF MINERAL NITROGEN WITH ORGANIC AMENDMENTS ON NITROGEN LOSS FROM SLOPING CROPLAND OF PURPLE SOIL

期刊论文

水稻节水灌溉及其对环境的影响

茆智

期刊论文

纵向通风水平隧道火灾烟气流动特性研究

卢平,丛北华,廖光煊,范维澄,厉培德

期刊论文

Photochemical indicators of ozone sensitivity: application in the Pearl River Delta, China

Lyumeng Ye,Xuemei Wang,Shaofeng Fan,Weihua Chen,Ming Chang,Shengzhen Zhou,Zhiyong Wu,Qi Fan

期刊论文

Option-like properties in the distribution of hedge fund returns

Katharina DENK, Ben DJERROUD, Luis SECO, Mohammad SHAKOURIFAR, Rudi ZAGST

期刊论文