HYBRID SCHEME FOR COMPRESSIBLE TURBULENT FLOW AROUND CURVED SURFACE BODY

A hybrid central-upwind scheme is proposed. Two sub-schemes, the central difference scheme and the Roets flux difference splitting scheme, are hybridized by means of a binary sensor function. In order to examine the capability of the proposed hybrid scheme in computing compressible turbulent flow around a curved surface body, especially the flow involving shock wave, three typical eases are investigated by using detached-eddy simulation technique. Numerical results show good agreements with the experimental measurements. The present hybrid scheme can be applied to simulating the compressible flow around a curved surface body involving shock wave and turbulence.

Defending Against Link Failure in Virtual Network Embedding Using a Hybrid Scheme

Nowadays network virtualization is utterly popular.As a result,how to protect the virtual networks from attacking on the link is increasingly important.Existing schemes are mainly backup-based,which suffer from data loss and are helpless to such attacks like data tampering.To offer high security level,in this paper,we first propose a multipath and decision-making(MD) scheme which applies multipath simultaneously delivery and decision-making for protecting the virtual network.Considering different security requirement for virtual link,we devise a hybrid scheme to protect the virtual links.For the critical links,MD scheme is adopted.For the other links,we adopt the Shared Backup Scheme.Our simulation results indicate the proposed scheme can significantly increase the security level of the critical link high in the loss of less acceptance ratio.

A New Hybrid WENO Scheme with the High-Frequency Region for Hyperbolic Conservation Laws

In this paper,a new kind of hybrid method based on the weighted essentially non-oscillatory(WENO)type reconstruction is proposed to solve hyperbolic conservation laws.Comparing the WENO schemes with/without hybridization,the hybrid one can resolve more details in the region containing multi-scale structures and achieve higher resolution in the smooth region;meanwhile,the essentially oscillation-free solution could also be obtained.By adapting the original smoothness indicator in the WENO reconstruction,the stencil is distinguished into three types:smooth,non-smooth,and high-frequency region.In the smooth region,the linear reconstruction is used and the non-smooth region with the WENO reconstruction.In the high-frequency region,the mixed scheme of the linear and WENO schemes is adopted with the smoothness amplification factor,which could capture high-frequency wave efficiently.Spectral analysis and numerous examples are presented to demonstrate the robustness and performance of the hybrid scheme for hyperbolic conservation laws.

A High Resolution Low Dissipation Hybrid Scheme for Compressible Flows

In this paper, an efficient hybrid shock capturing scheme is proposed to obtain accurate results both in the smooth region and around discontinuities for compressible flows. The hybrid algorithm is based on a fifth-order weighted essentially non-oscillatory （WENO） scheme in the finite volume form to solve the smooth part of the flow field, which is coupled with a characteristic-based monotone upstream-centered scheme for conservation laws （MUSCL） to capture discontinuities. The hybrid scheme is intended to combine high resolution of MUSCL scheme and low dissipation of WENO scheme. The two ingredients in this hybrid scheme are switched with an indicator. Three typical indicators are chosen and compared. MUSCL and WENO are both shock capturing schemes making the choice of the indicator parameter less crucial. Several test cases are carried out to investigate hybrid scheme with different indicators in terms of accuracy and efficiency. Numerical results demonstrate that the hybrid scheme in the present work performs well in a broad range of problems.

A Stability Analysis of Hybrid Schemes to Cure Shock Instability

The carbuncle phenomenon has been regarded as a spurious solution produced by most of contact-preserving methods.The hybrid method of combining high resolution flux with more dissipative solver is an attractive attempt to cure this kind of non-physical phenomenon.In this paper,a matrix-based stability analysis for 2-D Euler equations is performed to explore the cause of instability of numerical schemes.By combining the Roe with HLL flux in different directions and different flux components,we give an interesting explanation to the linear numerical instability.Based on such analysis,some hybrid schemes are compared to illustrate different mechanisms in controlling shock instability.Numerical experiments are presented to verify our analysis results.The conclusion is that the scheme of restricting directly instability source is more stable than other hybrid schemes.

A HYBRID FINITE ELEMENT SCHEME FOR INVISCID SUPERSONIC FLOWS

A hybrid monotonous finite element algorithm is developed in the present paper, based on a second-order-accurate finite element scheme and a first-accurate monotonous one derived from the former by a unilateral lumping procedure in one dimensional case. The switch functions for the two dimensional Euler equation system are constructed locally, based on the gradient of the flow field, with special consideration on the information from neighboring elements. Examples show that the new scheme can eliminate oscillations near strong shocks obviously.

A TVD-WAF-based hybrid finite volume and finite difference scheme for nonlinearly dispersive wave equations

A total variation diminishing-weighted average flux （TVD-WAF）-based hybrid numerical scheme for the enhanced version of nonlinearly dispersive Boussinesq-type equations was developed. The one-dimensional governing equations were rewritten in the conservative form and then discretized on a uniform grid. The finite volume method was used to discretize the flux term while the remaining terms were approximated with the finite difference method. The second-order TVD-WAF method was employed in conjunction with the Harten-Lax-van Leer （HLL） Riemann solver to calculate the numerical flux, and the variables at the cell interface for the local Riemann problem were reconstructed via the fourth- order monotone upstream-centered scheme for conservation laws （MUSCL）. The time marching scheme based on the third-order TVD Runge- Kutta method was used to obtain numerical solutions. The model was validated through a series of numerical tests, in which wave breaking and a moving shoreline were treated. The good agreement between the computed results, documented analytical solutions, and experimental data demonstrates the correct discretization of the governing equations and high accuracy of the proposed scheme, and also conforms the advantages of the proposed shock-capturing scheme for the enhanced version of the Boussinesq model, including the convenience in the treatment of wave breaking and moving shorelines and without the need for a numerical filter.

Likelihood Inference under Generalized Hybrid Censoring Scheme with Comp eting Risks

Statistical inference is developed for the analysis of generalized type-Ⅱ hybrid censoring data under exponential competing risks model. In order to solve the problem that approximate methods make unsatisfactory performances in the case of small sample size,we establish the exact conditional distributions of estimators for parameters by conditional moment generating function(CMGF). Furthermore, confidence intervals(CIs) are constructed by exact distributions, approximate distributions as well as bootstrap method respectively,and their performances are evaluated by Monte Carlo simulations. And finally, a real data set is analyzed to illustrate all the methods developed here.

HHR:Hierarchical Hybrid Routing Scheme for Information-Centric Network

Publish/subscribe(pub/sub) paradigm is the main communication model for Information-Centric Network(ICN) proposals.A key issue for pub/sub system is how to route the content objects to the correct subscribers,and ICN is no exception.ICN network would be divided into core domain and many edge domains as today's internet does.HHR(Hierarchy Hybrid Routing scheme) is presented for ICN:A Chord-like routing scheme is used in core domain,while edge domains routing structure can be classified into three categories,Local Routing(LR),Delivery of Local Publication to Core domain(DLPC),and Remote Publication Routing into edge domain(RPR).LR can be decided by each edge domain,which determined by many factors,such as locality characteristic for pub/sub information and local policies.A hierarchical routing algorithm is proposed to solve DLPC and RPR simultaneously.Simulation results demonstrate that HHR can be fast deployed,and can be applied in large scale network or dynamic subscription environment.

Hybrid Mapping Scheme for Recent Orthogonal FDMA Schemes

Single-carrier frequency-division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA) systems are new orthogonal multiple access systems. They have been adopted in the 3GPP long term evolution (3GPP-LTE). In these systems, there are only two types of subcarrier mapping schemes which are the interleaved and the localized. So, introducing a new subcarrier mapping scheme is an important issue, which is the main objective of this paper. In this paper, a hybrid subcarrier mapping scheme is proposed and examined for the SC-FDMA system. Monte Carlo simulations are performed to compare the performance of the proposed scheme with that of the interleaved and the localized schemes. It is shown that a hybrid scheme provides better performance than that of the localized and the same performance as that of the interleaved scheme and increased robustness to carrier frequency offset (CFO) at the expense of increased envelope fluctuations.

带有预验证机制的区块链动态共识算法

委员会共识和混合共识通过选举委员会来代替全网节点完成区块验证,可有效加快共识速度,提高吞吐量,但恶意攻击和收买易导致委员会发生腐败问题,严重时将影响共识结果甚至造成系统瘫痪.现有工作虽引入信誉机制降低委员会节点腐败的可能性,但开销大、可信度低且无法降低腐败问题对系统的影响.提出一种带有预验证机制的区块链动态共识算法(DBCP),通过预验证机制在较小开销的前提下对委员会进行可靠的信誉评估,及时淘汰委员会中的恶意节点.若腐败问题已影响到共识结果,DBCP会通过动态共识将区块验证权转移到全网节点,并淘汰给出错误意见的委员会节点,避免系统瘫痪.若委员会通过迭代达到高可信状态,则DBCP会将区块验证权交由委员会,全网节点将认同委员会的共识结果,并不再对区块进行验证,进而加快共识速度.经实验验证,DBCP的吞吐量与比特币相比提升了两个数量级,且与Byzcoin相近,可在一个出块周期内快速应对委员会腐败问题,安全性优于Byzcoin.

基于改进的多元宇宙算法的晶圆生产调度算法

针对以最小化最大完工时间为目标的晶圆生产制造系统的调度问题,提出了改进的多元宇宙算法。根据晶圆生产制造系统的特征,构建了一个整数规划模型。针对原始多元宇宙算法的局限性,分别从使用启发式规则生成初始种群、重新定义向最优宇宙移动策略和宇宙更新策略三个方面对算法进行改进。将原始多元宇宙算法、遗传算法、NEH启发式算法、迭代贪婪算法以及通过不同策略改进的多元宇宙算法进行对比实验,结果表明,所提方法可以高效地解决晶圆制造过程中的复杂现象。

不同解码方案下的星地融合网络混合多址接入性能分析

该文针对地面中继辅助的星地融合网络(ISTNs),分析了卫星采用不同解码方案时系统性能的差异。首先,提出一种新颖的用户配对方案,通过位置信息将卫星波束覆盖范围内的多个用户分为若干个组。接着,为了提高传输可靠性以及频谱利用率,用户采用混合多址接入技术与卫星进行通信。进一步,在考虑用户-地面中继链路服从Nakagami-m分布,地面中继-卫星链路服从相关阴影莱斯分布的情况下,分别推导出基于连续干扰消除(SIC)和联合解码(JD)两种解码方案的系统中断概率和吞吐量的闭合表达式。最后,计算机仿真验证了理论分析的正确性和所提方案相比正交多址(OMA)方案的优越性,并揭示了JD解码技术在ISTNs中的可行性。

A density-functional-theory-based and machine-learning-accelerated hybrid method for intricate system catalysis

Being progressively applied in the design of highly active catalysts for energy devices,machine learning(ML)technology has shown attractive ability of dramatically reducing the computational cost of the traditional density functional theory(DFT)method,showing a particular advantage for the simulation of intricate system catalysis.Starting with a basic description of the whole workflow of the novel DFT-based and ML-accelerated(DFT-ML)scheme,and the common algorithms useable for machine learning,we presented in this paper our work on the development and performance test of a DFT-based ML method for catalysis program(DMCP)to implement the DFT-ML scheme.DMCP is an efficient and user-friendly program with the flexibility to accommodate the needs of performing ML calculations based on the data generated by DFT calculations or from materials database.We also employed an example of transition metal phthalocyanine double-atom catalysts as electrocatalysts for carbon reduction reaction to exhibit the general workflow of the DFT-ML hybrid scheme and our DMCP program.

高超声速带奇性轴外形热流准确预示的混合算法研究与应用

准确的热流预示在超/高超声速复杂流动数值模拟是一个难点问题。当计算网格中出现奇性轴时,进一步增加了准确流场模拟、热流计算的难度。本文针对奇性轴在有限差分计算中出现的流场结构不稳定、热流预测误差大等难题,在通量重构方法的基础上,结合基于守恒变量的重构方法,提出了一种采用高精度格式计算带奇性轴问题的混合算法。该算法在奇性轴附近使用基于守恒变量的重构方法,有效反映奇性轴附近流场分布对奇性轴计算的影响,能够有效解决奇性轴问题。采用该混合算法并对比应用WENO3‑JS和高分辨率WENO3‑PRM^(2)_(1,1)格式,本文对高超声速球头、HB‑2、球钝锥及Apollo等外形绕流问题进行了数值模拟,结果表明:新方法能够有效解决含奇性轴问题计算中的流场结构不稳定问题,并且可以实现准确的热流预示。

作战仿真混合实验方案设计研究

作战仿真实验方案设计指的是基于基准的作战想定,利用各种实验设计方法对实验因子的取值进行抽样,形成一组实验方案,供后续仿真使用。作战仿真的复杂性包括实验因子数目众多,因子类型多样,既有连续数值类型,又有离散数值类型,这对高效的混合实验设计方法提出了迫切的需求。针对这些需求,对作战仿真混合实验方案设计技术展开了研究。对实验设计方法做了简单的分类和综述,给出了3种混合实验方案设计方法的流程及其优缺点分析;介绍了一个面向作战仿真的实验设计系统,包括软件架构设计、功能组成及实验设计流程;以一个作战想定为例,演示和分析了3种混合实验方案设计方法的具体应用。上述方法和工具将有效指导复杂作战仿真中具有离散和混合类型因子的实验设计问题,并在多个仿真项目得到了应用和验证。

煤矿人员精确定位系统数据存储方案设计

为了满足基于UWB等新型定位技术的煤矿人员精确定位系统数据存储与访问需要,分析了人员精确定位系统的数据结构、操作频率、数据量及存储占用空间大小等的数据情况,总结了系统数据生成与使用的主要特征,提出了基于Redis、MySQL和文件分别存储热数据、温数据和冷数据的混合数据存储架构,并详细阐述了Redis、MySQL、文件的存储关键设计,以及数据加密和基于Web API数据交互服务的数据查询方法。模拟数据测试结果表明:该存储方案具有较高的数据访问效率,能够满足数据存储与业务功能数据查询需要。

混合驱动绞车方案设计及现场试验

为了解决现有煤矿运输绞车普遍存在的操作困难,调速性能差的问题,设计了一种混合驱动绞车。首先,根据实际生产需求,结合现有绞车技术,提出了混合驱动绞车的总体设计。然后,对各部位分别进行结构与原理设计。最后,根据方案设计,通过现场试验验证设计的绞车各种性能,为以后的实际生产提供理论依据。

基于重传错误率估计的自适应HARQ

自适应混合自动重传请求(hybrid automatic repeat request,HARQ)系统的性能与每次传输中的调制与编码方案(modulation and coding scheme,MCS)、发送功率选择密切相关,通过优化重传时的MCS及发送功率可以提升HARQ系统的吞吐率并降低能耗。由于不同MCS传输合并后的译码性能没有闭式解,这导致自适应HARQ优化问题不易解决。首先基于译码的判决域半径给出了一种HARQ合并后译码错误率的近似公式,进而提出了多种能权衡吞吐率和能耗性能的自适应HARQ优化策略。仿真结果验证了所提错误率估计方法的可靠性以及所提自适应HARQ的性能。与传统HARQ方案相比,所提方案能同时提高吞吐率、降低能耗,实现更好的吞吐率与能耗的性能折中。

基于串联式混合动力的无人车功率控制系统设计

介绍了串联式混合动力的无人车辆功率控制系统设计方案,分析了车辆在不同行驶工况下的功率匹配方案和控制策略,针对降速和制动中容易出现的功率匹配性问题提出了解决措施,整体方案已成功在实车上进行了应用。