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A 16-competitive algorithm for hierarchical median problem

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Science China(Information Sciences) 2014年第3期57卷 147-153页

作者： dai wenQiang School of Management and Economics University of Electronic Science and Technology of China

The hierarchical median problem consists of finding a hierarchical assignment function sequence of solutions to the well-known k-median problems with growing *** sequence is said to be rcompetitive if the cost of each solution is at most r-times of the optimum cost of median problem with a same cardinality,where r is called the competitive *** the best algorithm available for this problem has competitive ratio *** this paper an improved algorithm is proposed with competitive ratio factor 16.

关键词： hierarchical location median algorithm competitive ratio

Gene therapy for spinal muscular atrophy:perspectives on the possibility of optimizing SMN1 delivery to correct all neurological and systemic perturbations

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Neural Regeneration Research 2025年第7期20卷 2011-2012页

作者： Sharon j.Brown Rafael j.Yáñez-Muñoz Heidi R.Fuller School of Pharmacy and Bioengineering Keele UniversityKeeleUK wolfson Center for Inherited Neuromuscular Disease TORCH BuildingRJAH Orthopaedic HospitalOswestryUK *** Center of Gene and Cell TherapyDepartment of Biological SciencesSchool of Life Sciences and the EnvironmentRoyal Holloway University of LondonEghamUK

Spinal muscular atrophy(SMA)is a genetic condition that results in selective lower motor neuron loss with concomitant muscle weakness and *** genetic cause of SMA was understood in 1995 when loss or impairment of the survival motor neuron 1(SMN1)gene was identified as the main contributing factor(Lefebvre et al.,1995).This,in combination with the discovery that humans have a“back-up”gene,SMN2,which can produce low levels(approximately 10%)of the full-length functional SMN protein,has led to the generation of SMA-specific gene *** was traditionally classified according to age of symptom onset and developmental milestones achieved,with life expectancy and severity varying between ***,SMN2 copy number is used as a proxy for the prediction of disease severity,with higher SMN2 copy number typically being associated with reduced severity of SMA,although this relationship is not absolute:some individuals with low SMN2 copy number have less severe SMA phenotypes and vice ***,the etiology of SMA is further complicated by other factors,such as non-typical nucleotide variants and SMN2-independent modifiers of disease severity.

关键词： atrophy traditionally absolute

Methods and advances in the study of aeroelasticity with uncertainties

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Chinese journal of Aeronautics 2014年第3期27卷 461-474页

作者： dai Yuting Yang Chao School of Aeronautic Science and Engineering Beihang University

Uncertainties denote the operators which describe data error, numerical error and model error in the mathematical methods. The study of aeroelasticity with uncertainty embedded in the subsystems, such as the uncertainty in the modeling of structures and aerodynamics, has been a hot topic in the last decades. In this paper, advances of the analysis and design in aeroelasticity with uncertainty are summarized in detail. According to the non-probabilistic or probabilistic uncer- tainty, the developments of theories, methods and experiments with application to both robust and probabilistic aeroelasticity analysis are presented, respectively. In addition, the advances in aeroelastic design considering either probabilistic or non-probabilistic uncertainties are introduced along with aeroelastic analysis. This review focuses on the robust aeroelasticity study based on the structured singular value method, namely the ~t method. It covers the numerical calculation algo- rithm of the structured singular value, uncertainty model construction, robust aeroelastic stability analysis algorithms, uncertainty level verification, and robust flutter boundary prediction in the flight test, etc. The key results and conclusions are explored. Finally, several promising problems on aeroelasticity with uncertainty are proposed for future investigation.

关键词： Polynomial chaos expansion Probabilisticity Robustness Structured singular value Uncertainty

Numerical simulation of flow and heat transfer in a random packed bed

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Particuology 2010年第3期8卷 293-299页

作者： Xueyan Guo Ren dai School of Energy and Power Engineering University of Shanghai for Science and Technology S 16Jun Gong Road Shanghai 200093 China

Random packed beds have more complex interior structure than structured beds and are widely used in industry and engineering. CFD simulation was carried out to investigate and analyze the local flow and heat transfer in a 120-sphere random packed bed. 3D Navier-Stokes equation was solved with a finite volume formulation based on the Chimera meshing technique. Investigation was focused on low Reynolds number flow （Re=4.6-56.2）, which typically occurs in packed bed reactors in bio-chemical fields. Detailed temperature field information was obtained. Inhomogeneity of flow and heat transfer due to the non-uniform distribution of void fraction was discussed and analyzed.

关键词： Packed bed Heat transfer Chimera grid Numerical simulation Low Reynolds number

Synergistic and interference effects in coaxial mixers: Numerical analysis of the power consumption

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Chinese journal of Chemical Engineering 2018年第4期26卷 684-694页

作者： juan Huang Gance dai School of Perfume and Aroma Technology Shanghai Institute of Technology State Key Laboratory of Chemical Engineering East China University of Science and Technology

This paper is concerned with the design and application of coaxial mixers with the aid of analysis of interaction between each individual impeller. Two types of coaxial mixers pitched blade turbine(PBT)-helical ribbon(HR)and inner-outer HR operated in laminar regime were studied experimentally and numerically. The interaction implies synergistic and interference effects, which was revealed through the investigation of axial circulation rate, energy dissipation rate and power consumption. The influence factors including rotational speed ratio,rotating mode and impeller configuration were explored systematically. Quantitative analysis of power consumption involves three parameters: rate of variation in power consumption, interactive mode and ratio of power consumption. Analysis indicated that some important properties were embodied in the power *** properties are one-way and two-way interactions, critical speed ratio and dominant impeller. Finally, a new suggestion for power estimation was given.

关键词： Numerical simulation Mixing Laminar flow Coaxial mixers Power consumption Interaction

Attitude synchronization for multiple spacecraft with input constraints

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Chinese journal of Aeronautics 2014年第2期27卷 321-327页

作者： Lyu jianting Gao dai School of Mathematical Sciences Heilongjiang University School of Mechanical and Electrical Engineering Harbin Institute of Technology

The attitude synchronization problem for multiple spacecraft with input constraints is investigated in this paper. Two distributed control laws are presented and analyzed. First, by intro- ducing bounded function, a distributed asymptotically stable control law is proposed. Such a con- trol scheme can guarantee attitude synchronization and the control inputs of each spacecraft can be a priori bounded regardless of the number of its neighbors. Then, based on graph theory, homoge- neous method, and Lyapunov stability theory, a distributed finite-time control law is designed. Rig- orous proof shows that attitude synchronization of multiple spacecraft can be achieved in finite time, and the control scheme satisfies input saturation requirement. Finally, numerical simulations are presented to demonstrate the effectiveness and feasibility of the oroDosed schemes.

关键词： Attitude synchronization Cooperative control Finite,time control Input constraints Multiple spacecraft

Multiple air route crossing waypoints optimization via artificial potential field method

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Chinese journal of Aeronautics 2021年第4期34卷 279-292页

作者： Bizhao PANG wei dai Xinting HU Fuqing dai Kin Huat LOw School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore Air Traffic Management Research Institute Nanyang Technological UniversitySingapore 637460Singapore School of Air Traffic Management Civil Aviation University of ChinaTianjin 300300China

Air route crossing waypoint optimization is one of the effective ways to improve airspace utilization,capacity and resilience in dealing with air traffic congestion and ***,research is lacking on the optimization of multiple Crossing waypoints(CwPs)in the fragmented airspace separated by Prohibited,Restricted and Dangerous areas(PRDs).To tackle this issue,this paper proposes an Artificial Potential Field(APF)model considering attractive forces produced by the optimal routes and repulsive forces generated by *** optimization framework based on the APF model is proposed to optimize the different airspace topologies varying the number of CwPs,air route segments and *** on the framework,an adaptive method is developed to dynamically control the optimization process in minimizing the total air route *** proposed model is applied to a busy controlled *** the obtained results show that after optimization the safety-related indicators:conflict number and controller workload reduced by 7.75%and 6.51%*** for the cost-effectiveness indicators:total route length,total air route cost and non-linear coefficient,declined by 1.74%,3.13%and 1.70%*** the predictability indicator,total flight delay,saw a notable reduction by 7.96%.The proposed framework and methodology can also provide an insight in the understanding of the optimization to other network systems.

关键词： Adaptive method Air route network Air traffic control Potential field Structure optimization

Reliability index algorithm of a sub-domain interconnection large communication network

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journal of Systems Engineering and Electronics 2010年第2期21卷 339-348页

作者： Fusheng dai Aijun Liu College of Information Engineering Harbin Institute of Technology (Welhai Campus) Weihai 264209 P. R. China

The normalized weighted capacity reliability index of a sub-domain interconnection large scale communication network is defined and a new algorithm to calculate the reliability index is proposed, The proposed algorithm can be performed using logical or algebraic operation by means of computer-aided programming and the correctness of each key step is validated in detail. This paper takes the sub-domain interconnection symmetrical topologi- cal network for a typical example to calculate the network reliability index and verifies the correctness of the proposed algorithm us- ing the real measured statistical data. The real measured results are well in accordance with the results obtained by the proposed algorithm. The result shows that the proposed algorithm is a valid means to estimate the reliability index of a sub-domain intercon- nection large-scale communication network.

关键词： communication network reliability sub-domain inter- connection transmission capacity.

Onset and Direction of Shear Banding Instability in Metallic Glasses

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journal of Materials Science & Technology 2014年第6期30卷 616-621页

作者： Yan Chen Lanhong dai State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences

The shear banding instability occurs as the homogenous deformation in metallic glasses （MGs） develops to a critical point, at which the discontinuity in deformation rate is incipient across nano-scale shear bands. when and where the shear instability takes place is an important issue for understanding the shear band origin. However, such condition and direction of shear localization concerning the unique properties of MGs is still lacking for general stress state. In this paper, a new constitutive is introduced for MGs accounting for the pressure sensitivity, dilatancy and structural evolution; the shear banding is regarded as the appearance of instability in the constitutive description of inelastic deformation. Tying the bifurcation theory to the new constitutive, the general condition of deformation localization is derived. The shear band orientation corresponding to the easiest direction of shear instability is then obtained in dependence on pressure sensitivity, dilatancy and Poisson＇s ratio for MGs. The range of the predicted shear band angles is consistent with the experimental observations.

关键词： Metallic glasses Shear banding instability Bifurcation