Coupled IEEE 802.11ac and TCP Goodput Improvement Using Aggregation and Reverse Direction

This paper suggests a new model for the transmission of Transmission Control Protocol (TCP) traffic over IEEE 802.11 using the new features of IEEE 802.11ac. The paper examines the first step in this direction and as such we first consider a single TCP connection, which is typical in a home environment. We show that when the IEEE 802.11ac MAC is aware of QoS TCP traffic, using Reverse Direction improves the TCP Goodput in tens of percentages compared to the traditional contention based channel access. In an error-free channel this improvement is 20% while in an error-prone channel the improvement reaches 60% also using blind retransmission of frames. In our operation modes we also assume the use in Two-Level aggregation scheme, the Automatic Repeat-Request (ARQ) protocol of the IEEE 802.11ac MAC layer, the data rates and the four Access Categories defined in this standard.

Time-lapse videography reveals different morphokinetic profiles of human embryos displaying direct or reverse cleavage at different stages of development: A retrospective sibling embryo study

Objective:To investigate morphokinetic characteristics of embryos displaying either reverse cleavage or direct cleavage during the first,second or third cleavage cycle.Methods:A total of 167 in vitro fertilization and/or intracytoplasmic sperm injection treatment cycles undertaken by 167 women[aged(35.0±4.6)years]were included for reverse cleavage analysis,and a total of 167 in vitro fertilization and/or intracytoplasmic sperm injection treatment cycles undertaken by 167 women[aged(33.8±4.3)years]were included for direct cleavage analysis in this study.Using a sibling-embryo design,morphokinetic profiles(both before and after the onset of abnormal event)of embryos displaying reverse cleavage(n=241)or direct cleavage(n=244)were compared with their unaffected siblings(the controls)in the first,second and third cell cycles(n=32,n=142,n=562;n=195,n=412,n=205,respectively),at different developmental stages up to day 3.Results:Direct cleavage embryos demonstrated significantly delayed cleavage rates prior to the event regardless of developmental stage of the occurrence,while reverse cleavage embryos showed similar cleavage rates to their unaffected siblings.Post event,direct cleavage embryos sped up cleavage rates while reverse cleavage embryos slowed down.Conclusions:Altered morphokinetic profiles are displayed by direct cleavage embryos both before and after their occurrence and reverse cleavage embryos after the occurrence,which could potentially confound morphokinetic comparisons if not separated from their unaffected sibling embryos.Further study is warranted in order to fully understand the biological mechanisms of such events.

Direct and Reverse Carleson Conditions on Generalized Weighted Bergman-Orlicz Spaces

Let D be the open unit disk in the complex plane C. For a〉 -1, let dAa（z）=（1 ＋a） （1 -｜z}^2） ^a da（z）be the weighted Lebesgue measure on ]D. For a positive function ω ∈ L^1（D,dAa）, the generalized weighted Bergman-Orlicz spaceA^ψω（D,dAa）is｜｜f｜｜ω^ψ=∫Dψ｜F（z）｜ω（z）dA^（z） 〈 ∞,where q; is a strictly convex Orlicz function that satisfies other technical hypotheses. Let G be a measurable subset of D, we say G satisfies the reverse Carleson condition for A^ψω （D, dAa） if there exists a positive constant C such that ∫Gψ（f（z））ω（z）dAa（z）≥C∫Dψ（｜f（z）dAa（z）.for all f ∈ .A^ψω （D,dAa）. Let μ be a positive Borel measure, we say μ satisfies the direct Carleson condition if there exists a positive constant M such that for all f∈Aψ^ω （D,dAa）,∫Dψ（｜f（z）｜）dμ（z）≤M∫Dψ（｜f（z）｜）ω（z）dAa（a）.In this paper, we study the direct and reverse Carleson condition on the generalized weighted Bergman-Orlicz space Aω^ψ（D,dAa）.We present conditions on the set G such that＇the reverse Carleson condition＇holds. ＂Moreover, we give a sufficient condition for the finite positive Borel measure μ to satisfy the direct carleson condition on the generalized weighted Bergman-Orlicz spaces.

Differential interformational velocity analysis as an effective direct hydrocarbon indicator under velocity reversal conditions,an example from the anomalously high temperature and over-pressured DF1-1 Gas Field in the Yinggehai Basin,South China Sea

In the DF1-1 Gas Field in the Yinggehai Basin, South China Sea, the velocity-depth plot and velocity spectra show significant variations from a linear trend, exhibiting a distinct reversal phenomenon. Velocity parameters derived from velocity spectral analysis of the seismic data and sonic logs indicate that the interval velocity reverses below 2,100 m (2.2 s two-way time (TWT)) in the DF1-1 Gas Field. Some direct hydrocarbon indicators (DHIs) models developed for the shallow strata cannot be simply applied to the moderately to deeply buried strata for direct exploration target recognition because the velocity reversal has caused the middle-deep gas reservoirs to exhibit a moderate or weak seismic amplitude. The hydrocarbon indicator method of “Differential Interformational Velocity Analysis (DIVA)” with the aid of other hydrocarbon indicating techniques was employed to effectively identify DHIs in the middle-deep strata under velocity inversion. The result has shown that the DIVA technique can be effectively used as a DHI in both the shallow and the middle-deep strata in the study area with the shallow strata characterized by Type I DIVA anomaly and the middle-deep strata characterized by the Type II DIVA anomaly.

Reversal of radial glow distribution in helicon plasma induced by reversed magnetic field

In this work, the reversal of radial glow distribution induced by reversed magnetic field is reported. Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction, it seems such a phenomenon in theory appears impossible. However, according to the diagnostic of the helicon waves by magnetic probe, it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves, i.e., the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field. It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution. The appearance of the traveling wave does not only improve the discharge strength, but also determines the transition of the discharge mode.

Progress on direct assembly approach for in situ fabrication of electrodes of reversible solid oxide cells

Reversible solid oxide cells(SOCs)are very efficient and clean for storage and regeneration of renewable electrical energy by switching between electrolysis and fuel cell modes.One of the most critical factors governing the efficiency and durability of SOCs technology is the stability of the interface between oxygen electrode and electrolyte,which is conventionally formed by sintering at a high temperature of~1000–1250℃,and which suffers from delamination problem,particularly for reversibly operated SOCs.On the other hand,our recent studies have shown that the electrode/electrolyte interface can be in situ formed by a direct assembly approach under the electrochemical polarization conditions at 800℃and lower.The direct assembly approach provides opportunities for significantly simplifying the cell fabrication procedures without the doped ceria barrier layer,enabling the utilization of a variety of high-performance oxygen electrode materials on barrier layer–free yttria-stabilized zirconia(YSZ)electrolyte.Most importantly,the in situ polarization induced interface shows a promising potential as highly active and durable interface for reversible SOCs.The objective of this progress report is to take an overview of the origin and research progress of in situ fabrication of oxygen electrodes based on the direct assembly approach.The prospect of direct assembly approach in the development of effective SOCs and in the fundamental studies of electrode/electrolyte interface reactions is discussed.

INDEX OF DIRECTION CHANGE OF ZONALLY AVERAGED WIND AND CHANGE OF SEASON

In this paper, a Wind Direction Change Index (WI), which can describe four-dimensional spatiotemporal changes of the atmospheric circulation objectively and quantitatively, is defined to study its evolution and seasonal variation. The first four modes can be obtained by EOF expansion of the zonally averaged WI. The first mode reveals the basic spatial distribution of the annually averaged WI. The second mode reflects the quasi-harmonic parts of the WI deviations. Tropical, subtropical and extratropical monsoon areas can be clearly reflected by this mode. The third mode reflects the non-harmonic parts of the WI deviations. It shows the so-called February reverse in stratospheric atmosphere as well as the asymmetric seasonal changes from spring to fall and from fall to spring due to both the land-sea distribution contrast between the Northern and Southern Hemispheres and the nonlinear effect of atmospheric and ocean fluids. The fourth mode reveals the northward advancing of the global reversed wind fields from spring to summer and their southward withdrawal from summer to autumn.

时间反转直扩通信系统及性能分析

时间反转传输技术的空时聚焦特性能够有效地提升通信系统的性能.本文设计了一种将时间反转技术应用于直扩通信系统的方案,并对多径衰落信道下单用户和多用户系统的接收信干噪比、系统容量、误比特率等性能进行了理论分析与仿真验证.理论与仿真结果表明,通过时间反转预处理,直扩通信系统的性能得到了改善,且优于复杂度较高的多通道Rake接收的系统,且多径数目越多,优势越明显.

“一带一路”倡议下对外直接投资对国内产业结构升级的影响

对外直接投资是推进高水平对外开放的重要内容,其促进母国产业结构升级的积极作用对构建双循环发展新格局具有重要意义。利用我国2003—2020年的省级面板数据的实证检验表明,对外直接投资在总体上显著促进了我国产业结构的升级。而异质性分析发现,这一效应在“一带一路”倡议提出以后和西部地区尤为明显;分位数检验表明,对外直接投资促进国内产业结构升级的边际效应会受产业结构发展水平的影响呈现“M型”特征。因此,应增强技术溢出吸收能力和要素优化配置能力,加快形成“走出去”和“引进来”双向互促的高水平开放新格局,最大化对外直接投资促进国内产业结构升级的效应。

服务业进出口、OFDI和全要素生产率的动态关系研究——基于VAR模型的实证分析

研究服务业贸易、投资与服务业之间的影响关系,对提升我国服务行业国际竞争力、促进其高质量发展具有重要意义。论文使用我国2000—2021年数据,构建VAR模型对服务业进出口、服务业对外直接投资(OFDI)和全要素生产率的动态交互关系进行实证分析。研究结果显示,服务业进出口对服务业对外直接投资具有正相关关系,且长期支持效果明显;服务业进出口对OFDI、全要素生产率提升具有促进作用;在短期内,全要素生产率与OFDI之间存在双向促进作用,从长期来看则存在一定负向影响。基于实证研究结论,文中提出制定政策鼓励服务企业参与国际化竞争、发挥服务业进出口对OFDI的促进效应、提升服务企业自主创新能力等相关对策建议。

基于Geomagic Design Direct的残缺数据实体重构

面向实物的逆向工程技术是近几年来研究和发展的热点,已广泛应用于产品设计、文物保护和零件修复等领域。报告了对模型的残缺表面数据进行曲面和实体重构的研究现状,以及结合正向和逆向建模软件进行实体模型重构的局限性。介绍了应用软件Geomagic Design Direct进行实体模型重构的优势以及对残缺表面数据实体模型重构的一般流程。提出了基于软件Geomagic Design Direct的特征识别与提取功能,对残缺表面数据进行实体重构的解决方案,并以某一零部件的残缺表面数据为例进行实体重构验证了该方案的可行性和便利性。

基于Geomagic Design Direct的截面特征提取与逆向建模

当前逆向工程已成为一种消化、吸收先进技术,实现产品的创新设计和快速开发的重要技术手段。随着各种特征技术的不断发展和引进,基于特征的逆向建模方法逐渐成为逆向工程新的发展方向。根据已有的建模方法,提出一种在二维草图模式下截面特征轮廓线提取与参数化设计的逆向建模新思路。并以Geomagic Design Direct软件为平台,实现了二维草图模式下特征轮廓线的提取与参数化再设计的逆向建模方法,为产品的快速建模和创新设计提供了一种新的途径。

基于改进帝王蝶算法的最大似然DOA估计

针对传统最大似然波达方向(maximum likelihood direction of arrival,ML-DOA)估计存在计算量大、估计精度差等问题,本文提出一种采用改进帝王蝶优化算法(improved monarch butterfly optimization algorithm,IMBO)的ML-DOA估计方法。IMBO算法通过精英反向学习策略对初始帝王蝶种群进行优化,得到适应度值较优的初始帝王蝶个体,进而能够改善帝王蝶种群的多样性;引入差分进化算法启发的变异操作以及自适应策略对帝王蝶个体的寻优方式进行改进,扩大了算法的搜索空间;引入了高斯-柯西变异算子,自适应调整变异步长,避免算法陷入局部最优。将IMBO应用于ML-DOA,实验表明,与传统的DOA估计算法相比,在不同信源数目、信噪比以及种群数量下,本文提出的算法收敛性能更好,均方根误差更低,运算量更小。

基于深度学习的二进制变种协议字段划分方法

为提高二进制变种协议字段格式划分的准确率,提出一种基于深度学习的方法,能够自动挖掘协议报文序列的深层字段特征完成协议的字段格式划分。引入一种字段列特征数据集的提取方法,在传统的双向长短期记忆条件随机场网络模型的基础上增加协议字段列特征提取模块,搭建一种专门解决二进制变种协议字段格式划分的神经网络PRO-BILSTM-CRF。与二进制未知协议字段格式划分方法以及几种主流网络模型的对比实验结果表明,在变种协议字段格式划分任务上,提出模型能够取得更高准确率。

不同膨胀潜势等级的膨胀土残余强度环剪试验研究

为探讨不同膨胀潜势等级的膨胀土残余强度与其成分特征的相关性,采用经自主改装的环剪仪开展Denver强膨胀土、荆门中、弱膨胀土环剪试验研究,并与排水反复直接剪切试验结果进行系统对比分析,在此基础上,用实测结果探讨残余强度与土成分特征相关关系的适用性。结果表明:(1)环剪试验测得Denver强膨胀土、荆门中、弱膨胀土有效残余强度内摩擦角分别为11.3°,12.3°,23.7°,比排水反复直接剪切试验测得的低1.7°~3.3°,并无应力相关性且具很好精度,更适于在工程中应用。(2)相关经验关系和公式存在高估或者低估膨胀土有效残余强度内摩擦角的情况。(3)残余强度与土成分特征间定性关系非常明确,上述经验关系对一般土性状况下残余强度预测较为准确;但在土成分复杂状况下,定量准确预测较为困难,这也反映出实测的重要性与必要性。

Transient Stability Analysis of Grid-connected Converters in Wind Turbine Systems Based on Linear Lyapunov Function and Reverse-time Trajectory

As the proportion of converter-interfaced renewable energy resources in the power system is increasing,the strength of the power grid at the connection point of wind turbine generators(WTGs)is gradually weakening.Existing research has shown that when connected with the weak grid,the stability of the traditional grid-following controlled converters will deteriorate,and they are prone to unstable phenomena such as oscillation.Due to the limitations of linear analysis that cannot sufficiently capture the stability phenomena,transient stability must be investigated.So far,standalone time-domain simulations or analytical Lyapunov stability criteria have been used to investigate transient stability.However,the time-domain simulations have proven to be computationally too heavy,while analytical methods are difficult to formulate for larger systems,require many modelling assumptions,and are often conservative in estimating the stability boundary.This paper proposes and demonstrates an innovative approach to estimating the transient stability boundary via combining the linear Lyapunov function and the reverse-time trajectory technique.The proposed methodology eliminates the need of time-consuming simulations and the conservative nature of Lyapunov functions.This study brings out the clear distinction between the stability boundaries with different post-fault active current ramp rate controls.At the same time,it provides a new perspective on critical clearing time for wind turbine systems.The stability boundary is verified using time-domain simulation studies.

OFDI与区域碳排放的非线性关系——基于技术创新的门槛效应研究

随着我国外部市场的扩大和经济对外开放政策的推进,对外直接投资(OFDI)呈现出迅猛增长的趋势。然而,由于过去采用粗放式增长模式,生态环境发展不充分,且由于“双碳”目标政策的实施,碳排放已成为对环境产生重大影响的关键因素,并被纳入总排放控制体系。基于此,本文选取中国2005—2019年30个省份(西藏、港澳台地区除外)的面板数据进行分析。结果表明,在不考虑技术创新作为门槛变量的情况下,整体上我国OFDI对本地碳排放具有显著的抑制作用。然而,在引入技术创新作为门槛变量后,处于技术创新水平较高的地区通过加大OFDI带来的逆向技术溢出效应可以降低本地区碳排放水平;中等技术创新水平的地区增大OFDI反而会增加地区碳排放;较低技术创新水平的地区对外直接投资的碳减排效应则不显著,OFDI对区域碳减排效应存在门槛。文章提出建议:技术创新水平较高地区进一步加大对外开放力度,充分发挥OFDI的逆向技术溢出效应;技术创新水平较低地区扩大OFDI规模,优化调整OFDI结构,坚持绿色导向型OFDI,积极引进国外先进技术、管理经验等,缓解全球温室效应等问题。

我国制造业对外直接投资逆向技术溢出效应--基于行业层面吸收能力

从行业层面构建了反映行业特性的七个吸收能力指标,实证检验了行业吸收能力对制造业ODI逆向技术溢出效应的影响。制造业整体检验结果表明,产业集聚度和行业资本密集度对ODI逆向技术溢出无显著正向调节作用,研发强度、人力资本水平、市场集中度、行业盈利能力和行业信息化水平均不同程度地增强了ODI逆向技术溢出效应。不同技术层次行业检验结果表明:研发强度、人力资本水平和市场集中度除对低技术行业ODI逆向技术溢出效应无显著调节作用之外,对中低、中高和高技术行业均有显著调节作用。产业集聚度、行业盈利能力和行业资本密集度对低技术和中低技术行业ODI逆向技术溢出效应无显著调节作用,但对中高和高技术行业均有显著调节作用。行业信息化水平对各技术层次行业ODI逆向技术溢出效应均有显著调节作用。门槛检验表明不同技术层次行业的各吸收能力指标是否达到门槛条件是导致上述差异的重要原因。

爆炸荷载下反向弧形裂纹扩展规律的实验研究

为了研究爆炸荷载作用下预制反向弧形裂纹的动态断裂特性,采用数字激光动态焦散线实像-虚像综合实验系统分析爆炸应力波作用下和斜入射爆生运动裂纹作用下预制弧形裂纹尖端实像和虚像焦散斑变化特征、预制弧形裂纹尖端应力强度因子变化特征以及爆生裂纹与翼裂纹运动扩展特征。结果表明:通过实像光路和虚像光路可以定量分析裂纹尖端拉剪应力和压剪应力的动态变化过程,从而获得爆炸荷载与预制弧形裂纹作用的全过程;爆生主、次裂纹能量具有大小之分,且其动态应力强度因子变化趋势具有一致性;定向爆生运动裂纹与预制弧形裂纹贯通位置是造成预制弧形裂纹上下端点应力强度因子差异性的主要原因。