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Homotopy Analysis Method for Portfolio Optimization Problem Under the 3/2 Model

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Journal of Systems Science & Complexity 2021年第3期34卷 1087-1101页

作者： YANG Shuquan JIA Zhaoli wu qianqian wu Huojun School of Mathematics Hefei University of TechnologyHefei 230009China

This paper considers the Merton portfolio optimization problem for an investor that aims at maximizing the expected power utility of the terminal wealth and intermediate *** the homotopy analysis method,an analytical solution for value function as well as optimal strategy under the 3/2 model is derived,*** with the existing explicit solutions for Merton problem under the 3/2 model,the formulas provide certain parameters with less requirement since the homotopy analysis method does not depend on the existence of small parameters in the ***,numerical examples are examined with the approach,and the proposed solution provides more accurate approximation as the number of terms in infinite series increases.

关键词： HJB equation homotopy analysis method optimal portfolio strategy power utility stochastic volatility

Computational Studies of Porous Head Protection Structures for Human Cranium under Impact Loading

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Acta Mechanica Solida Sinica 2021年第4期34卷 477-493页

作者： qianqian wu Zongbing Chen Jian Xiong Zhenyu Wang Chenglin Yang Center for Composite Materials and Structures Harbin Institute of TechnologyHarbin150001China Neurosurgery Department The Second Affiliated Hospital of Harbin Medical UniversityHarbin150001China Orthopedic Department The First Affiliated Hospital of Harbin Medical UniversityHarbin150001China

This paper looks into the effects of various porous structures used in the construction of the shell of a protective helmet on the energy absorption capacity and their efficacy in protecting the head/skull against impact *** is well known that porous structures are very effective for energy absorption;hence,they have been widely used to reduce the negative effects of impact and explosion loads on the human *** shell structures,made from titanium alloy(Ti–6Al–4V)and,comprised of several periodic topological configurations,namely the more common rectangle and hexagonal honeycomb,as well as those having auxetic properties,namely the concave honeycomb and double-arrow,are studied by means of numerical *** reliability of the numerical model is validated with the published experimental *** the double-arrow configurations,the study involves three different densities,and the structural energy absorption capacity of the double-arrow shells increases with *** the same density,the energy absorption capacity of the rectangular shell is the best,and that of the honeycomb is the *** superior performance of the rectangular configuration is partly derived from the fact that the orientation of the struts in this structure is aligned along the direction of the impact *** comparison of energy absorption capacity is made between the porous shell and a shell having a traditional titanium *** severe plastic deformation in the solid titanium shell(traditional monolayer shell)is detrimental to the overall effectiveness of head protection *** from this,compared with the Kevlar composite laminated shell of the same mass,both the solid and porous titanium shells provide considerable protection to the human *** comprehensive comparisons show that the porous design on the titanium shell is beneficial for mitigating the risks of traumatic brain injuries(TBIs).

关键词： Protective helmet Porous shell structures Negative Poisson’s ratio effect Impact resistance Numerical simulation

Pre-judgment and Incomplete Allocation Approach for Query Result Cache

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Chinese Journal of Electronics 2016年第6期25卷 1101-1108页

作者： QIAN Libing JI Zhenzhou FU Zhongchuan wu qianqian SONG Guangjia School of Computer Science and Technology Harbin Institute of Technology

Query result caching is a crucial technique employed in search engines, reducing the response time and load of the search engines. As search engines continuously update their indexes, the query results in long-lived cache entries may become stale. It is important to provide the refresh mechanism to enhance the degree of freshness of cached results. We present a pre-judgment approach to improve the freshness of the result cache and design an incomplete allocation algorithm. We introduce the queryTime-to-live(TTL) and term-TTL structure to pre-judge the result cache. The query-TTL is used to pre-check the likelihood of a cache hit and term-TTL is applied to maintain all terms of the latest posting list. For the cache structure, we design a Queue-Hash structure and develop the corresponding incomplete allocation algorithm. The preliminary results demonstrate that our approaches can improve the freshness of cached results and decrease processing overhead compared with no pre-judgment approaches.

关键词： Time-to-live(TTL) Caching freshness Pre-judgment Result cache Cache structure

Construction of NiCo_(2)O_(4) nanoflake arrays on cellulose-derived carbon nanofibers as a freestanding electrode for high-performance supercapacitors

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Frontiers of Chemical Science and Engineering 2023年第6期17卷 691-703页

作者： Xuepeng Ni Kunming Li Changlei Li qianqian wu Chenglin Liu Huifang Chen Qilin wu Anqi Ju College of Materials Science and Engineering&State Key Laboratory for Modification of Chemical Fibers and Polymer Materials Donghua UniversityShanghai 201620China Key Laboratory of High-Performance Fibers&Products Ministry of EducationDonghua UniversityShanghai 201620China Weifang Xinlong Biomaterial Co. Ltd.Weifang 261000China

Cellulose has a wide range of applications in many fields due to their naturally degradable and low-cost characteristics,but few studies can achieve cellulose-nanofibers by conventional ***,we demonstrate that the freestanding cellulose-based carbon nanofibers are successfully obtained by a special design of electrospinning firstly,pre-oxidation and high-temperature carbonization(1600℃),which display a superior electrical conductivity of 31.2 S·cm^(-1)and larger specific surface area of 35.61 m^(2)·g^(-1)than that of the polyacrylonitrile-based carbon nanofibers(electrical conductivity of 18.5 S·cm^(-1),specific surface area of 12 m^(2)·g^(-1).The NiCo_(2)O_(4)nanoflake arrays are grown uniformly on the cellulose-based carbon nanofibers successfully by a facile one-step solvothermal and calcination *** as-prepared cellulose-based carbon nanofibers/NiCo_(2)O_(4)nanoflake arrays are directly used as electrodes to achieve a high specific capacitance of 1010 F·g^(-1)at 1 A·g^(-1)and a good cycling stability with 90.84%capacitance retention after 3000 times at 10 A·g^(-1).Furthermore,the all-solid-state symmetric supercapacitors assembled from the cellulose-based carbon nanofibers/NiCo_(2)O_(4)deliver a high energy density of 62 W·h·kg(-1) at a power density of 1200 W·kg^(-1).Six all-solid-state symmetric supercapacitors in series can also power a‘DHU’logo consisted of 36 light emitting diodes,confirming that the cellulose-based carbon nanofiber is a promising carbon matrix material for energy storage devices.

关键词： cellulose carbon nanofibers NiCo_(2)O_(4) supercapacitors

Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag

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Journal of Environmental Sciences 2016年第8期28卷 63-71页

作者： Chong Han Yanan Jiao qianqian wu Wangjin Yang He Yang Xiangxin Xue School of Metallurgy Northeastern University

Basic oxygen furnace slag（BOFS） has the potential to remove hexavalent chromium（Cr（VI））from wastewater by a redox process due to the presence of minerals containing Fe2＋. The effects of the solution p H, initial Cr（VI） concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr（VI） was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope（SEM） equipped with an energy dispersive spectrometer（EDS）system and X-ray diffractometer（XRD）. The results show that Cr（VI） in wastewater can be efficiently removed by Fe2＋released from BOFS under appropriate acidic conditions. The removal of Cr（VI） by BOFS significantly depended on the parameters mentioned above. The reaction of Cr（VI） with BOFS followed the pseudo-second-order kinetic model. Fe2＋responsible for Cr（VI） removal was primarily derived from the dissolution of Fe O and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum（Ca SO4·2H2O）could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe2＋and the removal of Cr（VI）. Finally, the main mechanism of Cr（VI） removal by BOFS was described using several consecutive reaction steps.

关键词： Hexavalent chromium Basic oxygen furnace slag Fe2+ Redox process Kinetics

XO(X=Ti,Mn)decorated hollow multi-channel carbon sub-micro fiber networks as freestanding cathode for LieS batteries

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Journal of Materiomics 2023年第1期9卷 215-222页

作者： qianqian wu Tianbao Yan Kunming Li Xuepeng Ni Fanlong Zeng Anqi Ju State Key Laboratory for Modification of Chemical Fibers and Polymer Materials&College of Materials Science and Engineering Donghua UniversityShanghai201620China Center for Civil Aviation Composites&Shanghai Collaborative Innovation Center of High-Performance Fibers and Composites(Province-Minitry Joint) Donghua UniversityShanghai201620China

Lithium-sulfur(Lisingle bondS)batteries are considered as one of the most promising high-energy storage devices due to the high theoretical capacity(1675 mA·h·g^(-1))and large energy density(2600 W·h·kg^(-1)).However,the poor conductivity of sulfur and“shuttle effect”of soluble polysulfide intermediates limit practical applications of Lisingle bondS ***,four kinds of carbon sub-micro fibers with different structures were designed and prepared,the effect of structure on Lisingle bondS battery was *** this basis,the XO(X=Ti,Mn)decorated hollow multi-channel carbon sub-micro carbon fibers(HMCMFs)were prepared by electrospinning and *** HMCMFs can not only supply nanopores for relieving the expansion of sulfur but also served as high conductivity freestanding substrate for sulfur loading,meanwhile the decorated XO(X=Ti,Mn)can provide powerful chemical adsorption to polysulfide intermediates and limit“shuttle effect”Therefore,the TiO-HMCMFs/S composite shows high specific capacity of 900 mA·h·g^(-1)and maintain stable specific capacities up to∼600 mA·h·g^(-1)over 300 cycles at 0.1 A·g^(-1).This work offers a facile method to build efficient sulfur cathode to acquire Lisingle bondS batteries with high performance.

关键词： Lithium-sulfur batteries TiO MnO Carbon sub-miacro fibers

Design,fabrication,and dynamic mechanical responses of fiber-reinforced composite lattice materials

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International Journal of Mechanical System Dynamics 2023年第3期3卷 213-228页

作者： Jian Xiong Cheng Gong qianqian wu Li Ma Jinshui Yang Linzhi wu Center for Composite Materials and Structures Harbin Institute of TechnologyHarbinChina National Key Laboratory of Science and Technology on Advanced Composites in Special Environments Harbin Institute of TechnologyHarbinChina

Fiber-reinforced composites are a popular lightweight materials used in a variety of engineering applications,such as aerospace,architecture,automotive,and marine construction,due to their attractive mechanical *** lattice materials from fiber-reinforced composites is an efficient approach for developing ultra-lightweight structural systems with superior mechanical proper-ties and multifunctional *** contrast to corrugated,foam,and honeycomb core materials,composite lattice materials can be manufactured with various architectural designs,such as woven,grid,and truss ***,lattice materials with open-cell topology provide multifunctional advantages over conventional closed-cell honeycomb and foam structures and are thus highly desirable for developing aerospace systems,hypersonic vehicles,long-range rockets and missiles,ship and naval structures,and protective *** objective of this study is to review and analyze dynamic mechanical behavior performed by different researchers in the area of composite lattice materials and to highlight topics for future research.

关键词： fiber-reinforced composite lattice structures sandwich structures dynamic mechanical behavior

InP quantum dots-based electroluminescent devices

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Chinese Physics B 2019年第11期28卷 18-24页

作者： qianqian wu Fan Cao Lingmei Kong Xuyong Yang School of Material Science and Engineering Shanghai UniversityShanghai 200072China Key Laboratory of Advanced Display and System Applications of Ministry of Education Shanghai UniversityShanghai 200072China

Indium phosphide(InP) quantum dots(QDs) have shown great potential to replace the widely applied toxic cadmiumcontaining and lead perovskite QDs due to their similar emission wavelength range and emission peak width but without intrinsic toxicity. Recently, electrically driven red and green InP-based quantum-dot light-emitting diodes(QLEDs) have achieved great progress in external quantum efficiency(EQE), reaching up to 12.2% and 6.3%, respectively. Despite the relatively poor device performance comparing with cadmium selenide(CdSe)-and perovskite-based QLEDs, these encouraging facts with unique environmental friendliness and solution-processability foreshadow the enormous potential of InP-based QLEDs for energy-efficient, high-color-quality thin-film display and solid-state lighting applications. In this article, recent advances in the research of the InP-based QLEDs have been discussed, with the main focus on device structure selection and interface research, as well as our outlook for on-going strategies of high-efficiency InP-based QLEDs.

关键词： indium phosphide quantum dots light-emitting diodes external quantum efficiency

Plant vs. Animal Prototype for Designing Bio-inspired PEMFC Flow Fields: Corn Veins or Murray’s Law?

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Journal of Bionic Engineering 2022年第3期19卷 761-776页

作者： Wenxuan Fan Taotao Zhao Ke Jiang Lei Sun Saisai Jia qianqian wu Guolong Lu Zhenning Liu Key Laboratory of Bionic Engineering(Ministry of Education) College of Biological and Agricultural EngineeringJilin UniversityChangchun130022China

Designing bio-inspired flow fields holds great potential in improving the performance of Proton Exchange Membrane Fuel Cell(PEMFC).Two kinds of biological prototypes are widely used:plant prototype and animal *** remains a question which one of these prototypes is more appropriate for the scenario of ***,a comparative study was conducted to compare bionic flow fields based on animal and plant ***,a Corn Leaf Vein Mathematical Model(CLMM)was established by extracting structural parameters from corn leaves of two growth *** the obtained CLMM and well-known Murray’s law were employed to design bionic flow fields corresponding to the plant and animal prototypes,respectively,which have been subsequently compared by numerical *** results demonstrate that the flow field guided by Murray’s law outperforms the counterpart based on the structural parameters of CLMM in terms of PEMFC net output power,mass transport,water management and pressure drop,suggesting that animal circulation system is more suitable to the bionic flow field design of PEMFC than plant leaf *** work may also offer valuable insights into the design of other flow fields related to electrochemical energy conversion.

关键词： Proton exchange membrane fuel cell Flow field Biological prototypes Corn leaf vein Murray’s law Comparative study