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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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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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Stress induced polarization switching and coupled hysteretic dynamics in ferroelectric materials

Linxiang WANG, Roderick MELNIK, Fuzai LV

《机械工程前沿（英文）》 2011年 第6卷 第3期   页码 287-291 doi: 10.1007/s11465-011-0230-2

摘要：

The dynamic responses of ferroelectric materials upon external mechanical and electrical stimulations are inherently nonlinear and coupled. In the current paper, a macroscopic differential model is constructed for the coupled hysteretic dynamics via modeling the orientation switching induced in the materials. A non-convex potential energy is constructed with both mechanic and electric field contributions. The governing equations are formulated as nonlinear ordinary differential equations by employing the Euler-Lagrange equation, and can be easily recast into a state space form. Hysteresis loops associated with stress induced polarization switching and butterfly-shaped behavior in ferroelectric materials are also successfully captured. The effects of mechanical loadings on the electrically induced switching are numerically investigated, as well as the mechanically-induced switching with various bias electric fields.

关键词： differential model     state space     electromechanical switching     butterfly effects     hysteresis    

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Experimental investigation of a novel micro gas turbine with flexible switching function for distributed

Xiaojing LV, Weilun ZENG, Xiaoyi DING, Yiwu WENG, Shilie WENG

《能源前沿（英文）》 2020年 第14卷 第4期   页码 790-800 doi: 10.1007/s11708-020-0691-2

摘要： Micro gas turbine (MGT) is widely used in small-scale distributed power systems because of its low emissions and fuel flexibility. However, the under-utilization of its exhaust heat and the low electric efficiency are the main bottlenecks that restrict its application. Additionally, the flexible switching between the power generated by the MGT and the power grid is also a key factor for keeping the secure operation of a distributed power station. Therefore, this paper conducted some experimental investigations of a 30 kW MGT to provide reference solutions for the above issues. This MGT is located at Shanghai Jiao Tong University (SJTU), which is designed by the Gas Turbine Research Institute of SJTU, and is manufactured by a turbo-machinery factory in Chongqing, China. The demonstration prototype is mainly composed of a single stage centrifugal compressor, a radial turbine, a combustor, a high-speed permanent magnet generator, and a control system. The results show that the MGT can achieve steady operation at a low rotational speed from 10000 r/min to 34000 r/min in the case of using oil lubricated bearings, which can greatly reduce the economic cost compared with the use of air bearings. At the same time, the ignition success rate of combustion chamber (CC) reaches 98% at a low rotational speed, and a wide range of stable combustion area can be obtained, because of the novel design method of combustor by referencing the way applied in an axial flow aero-engine. The MGT generating set can achieve functions, such as starting up, ignition, stable operation, loaded operation, grid-connection and stopping. This system also can realize flexibly switching from the start motor mode to the generator mode, and from grid-connected mode to off-grid mode, because the innovative multi-state switching control system is adopted. The above research work can make our state master independent intellectual property rights of micro gas turbine, rather than continue to be subject to the technological monopoly of the developed states, which can provide theoretical and experimental support for the industrialization of MGT in China.

关键词： gas turbine     flexible switching system     control system     distributed power system     emission test    

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An improved delta-star switching scheme for reactive power saving in three-phase induction motors

P. RAJA,N. KUMARESAN,M. SUBBIAH

《能源前沿（英文）》 2014年 第8卷 第3期   页码 364-370 doi: 10.1007/s11708-014-0324-8

摘要： It is proposed that a capacitor can be connected permanently across each phase winding of a three-phase induction motor along with the conventional delta-star switching, for further saving in VARh at reduced loads on the motor. The method of choosing a suitable value for the capacitor and the criteria to be adopted for calculating the power output at which the star to delta switching is to be made are also explained. The experimental results on a 3-phase, 4-pole, 415 V, 50 Hz, 3.3 kW induction motor verify the advantages in adding the capacitor to the phase winding of the motor. Compared to using only a single delta connected stator winding or a delta-star switching, the advantages of the proposed addition of a capacitor, are also demonstrated through a case study conducted on a 400 V, 250 kW motor. Any further improvement in grid side power factor can be achieved by employing a static synchronous compensator (STATCOM) of reduced VAR rating.

关键词： delta-star switching     induction motor     power factor     steady-state analysis    

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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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A novel soft-switching twin arc pulse MAG welding inverter

WANG Zhenmin, XUE Jiaxiang, WANG Fuguang, HUANG Shisheng

《机械工程前沿（英文）》 2007年 第2卷 第2期   页码 224-227 doi: 10.1007/s11465-007-0039-1

摘要： The high-speed double wire pulse metal gas arc (MAG) welding process possesses advantages of automation and high efficiency and quality. Thus, it attracts much more attention nowadays. To meet the requirements of the double wire pulse MAG welding process, a novel double wire pulse MAG welding inverter integrated with technologies, such as soft-switching, double closed loop control, and synchronic control, is produced. A complete performance test was done for the pulsed MAG welding power supply by using a computer testing platform. The results of the experiment indicate that the novel welding inverter has an excellent performance both in the dynamic and the static characteristics. Also, the synchronic control between the master inverter and the slave inverter is reliable.

关键词： high-speed     control     computer     experiment indicate     platform    

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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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国内首台ATM交换机研制及其组网实践

雷振明

《中国工程科学》 2000年 第2卷 第2期   页码 53-55

摘要：

国内首台ATM（异步转送方式）交换机BTC-9500的研制于1995年完成，并配合国内宽带试验网络的建设，进行了大量的组网试验、设计改进和发展工作。目前，该设备已经由国内最大的电信设备制造商之一——上海贝尔公司生产销售，并且用于装备中国电信宽带骨干网的全部核心节点。根据组网实践中发现的问题，提出了在同一个交换结构内同时实现ATM信元交换和IP数据报交换的方案，并在BTC-9500中予以实现，达到了大大节省设备、简化网络和提高网络速度的多重目的，将研究范围逐渐拓宽到更大的宽带通信领域，提出了对于新一代电信网络发展的一些看法。

关键词： 通信     交换     异步转送方式（ATM）    

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A review on different theoretical models of electrocaloric effect for refrigeration

《能源前沿（英文）》 2023年 第17卷 第4期   页码 478-503 doi: 10.1007/s11708-023-0884-6

摘要： The performance parameters for characterizing the electrocaloric effect are isothermal entropy change and the adiabatic temperature change, respectively. This paper reviews the electrocaloric effect of ferroelectric materials based on different theoretical models. First, it provides four different calculation scales (the first-principle-based effective Hamiltonian, the Landau-Devonshire thermodynamic theory, phase-field simulation, and finite element analysis) to explain the basic theory of calculating the electrocaloric effect. Then, it comprehensively reviews the recent progress of these methods in regulating the electrocaloric effect and the generation mechanism of the electrocaloric effect. Finally, it summarizes and anticipates the exploration of more novel electrocaloric materials based on the framework constructed by the different computational methods.

关键词： electrocaloric effect     effective Hamiltonian     phase-field modeling     different theoretical models    

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Predictive models on photolysis and photoinduced toxicity of persistent organic chemicals

Qing ZHANG

《环境科学与工程前沿（英文）》 2013年 第7卷 第6期   页码 803-814 doi: 10.1007/s11783-013-0547-7

摘要： Photodegradation is a major abiotic transformation pathway of toxic chemicals in the environment, which in some cases might lead to photoinduced toxicities. The data on photodegradation kinetics and photoinduced toxicities of organic chemicals are essential for their risk assessment. However, the relevant data are only available for a limited number of chemicals, due to the difficulty and high cost of experimental determination. Quantitative structure-activity relationship (QSAR) models that relate photodegradation kinetics or photoinduced toxicity of organic chemicals with their physicochemical properties or molecular structural descriptors may enable simple and fast estimation of their photochemical behaviors. This paper reviews the QSAR models on photodegradation quantum yields and rate constants for toxic organic chemicals in different media including liquid phase, gaseous phase, surfaces of plant leaves, and QSAR models on photoinduced toxicity of organic chemicals to plants, bacteria, and aquatic invertebrates. Further prospects for QSAR model development on photodegradation kinetics and photoinduced toxicity of refractory organic chemicals are proposed.

关键词： quantitative structure-activity relationship (QSAR) models     photodegradation     persistent organic pollutants     environmental media     mechanisms    

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A pulsed switching peroxi-coagulation process to control hydroxyl radical production and to enhance 2,4

Yaobin Lu, Songli He, Dantong Wang, Siyuan Luo, Aiping Liu, Haiping Luo, Guangli Liu, Renduo Zhang

《环境科学与工程前沿（英文）》 2018年 第12卷 第5期 doi: 10.1007/s11783-018-1070-7

摘要：

• A new pulsed switching peroxi-coagulation (PSPC) system was developed.

• The ECT for 2,4-D removal in the PSPC was lower than that in the EF.

• The iron consumption for 2,4-D removal in the PSPC was lower than that in the PC.

关键词： Pulsed switching peroxi-coagulation system     Energy consumption     Hydroxyl radical production     2     4- Dichlorophenoxyacetic acid    

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Gained switching-based fuzzy sliding mode control for a discrete-time underactuated robotic system with

Hui LI, Ruiqin LI, Jianwei ZHANG

《机械工程前沿（英文）》 2021年 第16卷 第2期   页码 353-362 doi: 10.1007/s11465-020-0620-4

摘要： This study proposes a gained switching-based discrete-time sliding mode control method to address the chattering issue in disturbed discrete-time systems, which suffer from various unknown uncertainties. Through the new structure of the designed reaching law, the proposed method can effectively increase the convergence speed while guaranteeing chattering-free control. The performance of controlling underactuated robotic systems can be further improved by the adoption of fuzzy logic to perform adaptive online hyper-parameter tuning. In addition, an underactuated robotic system with uncertainties is studied to validate the effectiveness of the proposed reaching law. Results reveal the dynamic performance and robustness of the proposed reaching law in the studied system and prove the proposed method’s superiority over other state-of-the-art methods.

关键词： sliding-mode control     robot control     discrete-time uncertain systems     fuzzy logic    

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标题 作者 时间 类型 操作

Option-like properties in the distribution of hedge fund returns

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

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

Stress induced polarization switching and coupled hysteretic dynamics in ferroelectric materials

Linxiang WANG, Roderick MELNIK, Fuzai LV

期刊论文

Experimental investigation of a novel micro gas turbine with flexible switching function for distributed

Xiaojing LV, Weilun ZENG, Xiaoyi DING, Yiwu WENG, Shilie WENG

期刊论文

An improved delta-star switching scheme for reactive power saving in three-phase induction motors

P. RAJA,N. KUMARESAN,M. SUBBIAH

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

A novel soft-switching twin arc pulse MAG welding inverter

WANG Zhenmin, XUE Jiaxiang, WANG Fuguang, HUANG Shisheng

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

国内首台ATM交换机研制及其组网实践

雷振明

期刊论文

A review on different theoretical models of electrocaloric effect for refrigeration

期刊论文

Predictive models on photolysis and photoinduced toxicity of persistent organic chemicals

Qing ZHANG

期刊论文

A pulsed switching peroxi-coagulation process to control hydroxyl radical production and to enhance 2,4

Yaobin Lu, Songli He, Dantong Wang, Siyuan Luo, Aiping Liu, Haiping Luo, Guangli Liu, Renduo Zhang

期刊论文

Gained switching-based fuzzy sliding mode control for a discrete-time underactuated robotic system with

Hui LI, Ruiqin LI, Jianwei ZHANG

期刊论文