Influence of magnetically constricted arc traverse speed (MCATS) on tensile properties and microstructural characteristics of welded Inconel 718 alloy sheets

The magnetically constricted arc technique was implemented to mitigate the heat input related metallurgical problems in Gas Tungsten Arc Welding(GTAW)of Inconel 718 alloy particularly Nb segregation and subsequent laves phase evolution in fusion zone.This paper reports the direct effect of magnetically constricted arc traverse speed(MCATS)on bead profile,tensile properties and microstructural evolution of Inconel 718 alloy sheets joined by Gas Tungsten Constricted Arc Welding(GTCAW)process.The mechanism amenable for the microstructural modification and corresponding influence on the tensile properties of joints is investigated both in qualitative and quantitative manner related to the mechanics of arc constriction and pulsing.It is correlated to the solidification conditions during welding.The relationship between MCATS and Arc Constriction Current(ACC)was derived.Its interaction effect on the magnetic arc constriction and joint performance was analysed.Results showed that the joints fabricated using CATS of 70 mm/min exhibited superior tensile properties(98.39% of base metal strength with 31.50% elongation).It is attributed to the grain refinement in fusion zone microstructure leading to the evolution of finer,discrete laves phase in interdendritic areas.

Study on Key Techniques for Multi-scale Expression of Laneway Traverse Data in MGIS

The multi-scale expression of enormously complicated laneway data requires differentiation of both contents and the way the contents are expressed. To accomplish multi-scale expression laneway data must support multi-scale transformation and have consistent topological relationships. Although the laneway data generated by traverse survey-ing is non-scale data it is still impossible to construct a multi-scale spatial database directly from it. In this paper an al-gorithm is presented to first calculate the laneway mid-line to support multi-scale transformation; then to express topo-logical relationships arising from the data structure; and,finally,a laneway spatial database is built and multi-scale ex-pression is achieved using components GIS-SuperMap Objects. The research result is of great significance for improv-ing the efficiency of laneway data storage and updating,for ensuring consistency of laneway data expression and for extending the potential value of a mine spatial database.

Recent Russian remote sensing investigations in Antarctica within the framework of scientific traverses

This paper includes a short historical review of Russian and Soviet scientific traverses to study the Antarctic inland. The first traverse left on April 2, 1956. It resulted in the opening of the first Russian inland research station named Pionerskaya and provided the first geophysical and glaciological data on regions inland of the Antarctic coast. By 1965, a number of regional inland scientific traverses had been completed and. the first Atlas of Antarctica was published in 1966. The atlas presented the main achievements of that time. After the discovery of Lake Vostok, Russian scientists commenced remote sensing investigations to study this unique natural phenomenon. The propagation of acoustic and electromagnetic waves in the glacier near Vostok Station were measured to provide important geophysical data. Radio-echo sounding data showed that Lake Vostok is isolated and separated from the rest of the Antarctic subglacial hydrosphere. The total area of the lake is 15 790 km2, excluding 365 km^2 occupied by 11 islands. Reflection seismic soundings of Lake Vostok estimated a total volume of about 6 100 km^3, an average depth of about 400 m, and a maximum depth of 1 200 m. Since 2008, there have been a number of scientific traverses between Mirny and Vostok stations and between Progress and Vostok stations. The data collected during the traverses have provided new insights into sub-ice topography and ice sheet structure, and have led to the discovery of subglacial lakes near Komsomolskaya Station and under Pionerskaya Station.

Antarctic Traverses from Zhongshan Station to Dome-A and the Result Analysis for the GPS Points along the Expedition Route

Some GPS points were set up and occupied and reoccupied along the traverse route from Zhongshan Station to DomeA.The result analysis for the GPS data processed by GAMIT/GLOBK package was presented in this paper.It was indicated that the ice along the traverse route flowed with an 825 m/a velocity to the northwest in the last three years,which was the direction of the edge of the ice sheet.The maximum horizontal flow velocity is about 100 m/a.Moreover,due to the ice flow,a 0.21 m/a sedimentation rate is achieved.Finally,a 15 m/a 2 horizontal acceleration is achieved from the GPS data of the three different stages.

Gravity Survey along the Mizuho Traverse Routes, East Antarctica: SEAL Seismic Exploration in 1999-2000

A gravity survey was conducted along the Mizuho traverse routes in austral summer of 1999-2000 by the 41st Japanese Antarctic Research Expedition (JARE-41). The main purpose of the survey was to obtain detail gravity anomaly along the traverse routes, where deep seismic exploration was simultaneously conducted in order to obtain a fine crustal structure of the Mizuho Plateau. By using SCINTREX (CG-3M) gravity meter, the survey was carried out at 160 sites with about 1 km interval in a distance of 190 km from S16 to Z20 on the traverse routes. Free-air and Bouguer anomalies were calculated using precise locations by GPS measurements, by taking into account an effect of the thick icesheet. The furrowed negative Free-air anomalies are identified around H192, where middle points of the whole traverse routes. Two bedrock elevation models derived both by seismic refraction analyses and radio-echo sounding might correspond to the bottom and the top of a mixture layer composed from ice-moraine rocks over the bedrock surface. Thickness of the crust estimated by Bouguer anomalies is 0.5 - 1 km larger toward inland at the terminal point of Z20 along the profile.

EFFECTS OF S86019, AN ACTIVE COMPONENT FROM PURALIA LOB AT A, ON CELL DIFFERENTIATION AND CELL CYCLE TRAVERSE OF HL-60 CELLS

The effects of S86019, an active component from Puralia lobata, on the induction of cell differentiation and cell cycle traverse of HL-60 cells were described. It was shown that cell proliferation of HL-60 cells was inhibited by S86019 in vitro. Under the action of S86019 the HL-60 cells were induced to differentiate into metamyelocytes, myelocytes and much matured cells with banded or segmented nucleus. Flow cytometry demonstrated that the cell population of HL-60 cells was blocked at G1 phase which resulted in the elevation of percentage of G1 cells and decrease of percentage of cells in S phase. Experimental results demonstrated that S86019 is an active inducer of cell differentiation in HL-60 cells.

Comprehensive Study on the Estimation of the Variance Components of Traverse Nets

This paper advances a new simplified formula for estimating variance components ,sums up the basic law to calculate the weights of observed values and a circulation method using the increaments of weights when estimating the variance components of traverse nets,advances the charicteristic roots method to estimate the variance components of traveres nets and presents a practical method to make two real and symmetric matrices two diagonal ones.

The Road Traversed by Lhumao

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Exploration of Traversable Wormholes Sustained by an Extra Spatial Dimension

The main goal of this paper is to determine the effect of an extra dimension on a traversable wormhole. Here an earlier study by the author [Phys. Rev. D 98, 064041 (2018)] is extended in several significant ways. To begin with, the extra spatial dimension is assumed to be time dependent, while the redshift and shape functions, as well as the extra dimension, are functions of both r and l, the respective radial and extra coordinates;the last of these is therefore a function of r, l, and t. The main objective is to determine the conditions that allow the throat of the wormhole to be threaded with ordinary matter (by respecting the null energy condition) and that the same conditions lead to a violation of the null energy condition in the fifth dimension, which is therefore responsible for sustaining the wormhole. The dependence of the extra dimension on l and t is subject to additional conditions that are subsequently analyzed in this paper. Finally, the extra dimension may be extremely small or even curled up.

图计算体系结构和系统软件关键技术综述

图计算作为分析事物之间关联关系的重要工具,近年来已成为各国政府及公司争夺的关键技术.学术界和工业界在图计算体系结构和系统软件关键技术方面取得了一定进展.然而,现实场景图计算大多具有动态变化、应用需求复杂多样等特征.这给图计算在基础理论、体系架构和系统软件关键技术方面提出了新的需求,同时也带来了新的挑战.为应对这些挑战,科研人员提出了一系列图计算系统或图计算加速器,通过高性能计算、并行计算等技术来优化图计算过程.综述国内外图计算体系结构和系统软件关键技术的研究发展现状,对国内外研究的最新进展进行归纳、比较和分析,并结合国家发展战略和重大应用需求,选取与我国国计民生密切相关的领域,从典型应用分析总结图计算相关技术的行业进展.最后,就未来的技术挑战和研究方向进行展望.

基于改进蚁群算法的农业机器人多田块路径规划方法与试验

[目的]针对丘陵地区因田块碎片化和障碍物影响农业机器人作业的情况,提出一种基于改进蚁群算法和A算法相结合的多田块路径规划方法。[方法]通过无人机构建农田遥感影像,利用栅格法对农田进行环境建模,再进行子区的划分与合并,在蚁群算法中引入区域启发函数,对不同区域内的移动代价作区分,通过人工增加最优路径中的信息素浓度并建立自适应信息素挥发系数,对信息素更新方法进行改进,以此求解作业子区间的最优遍历顺序,利用具有启发式搜索功能的A算法进行子区连接路径规划,最终实现多田块路径规划。[结果]MATLAB仿真试验结果表明,在子区数量为40时,采用改进蚁群算法进行规划的平均路径长度比传统的蚁群算法减少了3.19%,平均迭代收敛次数减少了79.5%;在路径遍历仿真试验中,农业机器人遍历路径覆盖率能达到100%,路径重复率为6.48%。利用农田无人机遥感影像和田间作业参数进行自然环境的仿真试验,进一步验证了该方法的有效性。[结论]本研究提出的方法能有效解决丘陵地区农业机器人多田块路径规划问题,可为丘陵地区农业机器人大面积作业提供路径参考与技术支持。

可抗穷举攻击的射频识别群组证明协议

针对孙达志等提出的群组证明协议进行重点分析,指出协议存在无法抗穷举攻击的安全缺陷,并在此基础上给出一个改进的协议。协议采用遍历取反运算对信息加密,遍历取反运算将根据加密参量自身汉明重量大小不同而进行对不同参量的取反操作,增加破解难度;协议将信息加密之后再发送,同时信息加密时确保多个参量攻击者无法知晓,以此来抵抗穷举攻击。从安全性角度分析协议,表明协议具有较好的安全性能;从仿真实验角度分析协议,表明协议具有计算量低的优势。

高速公路桥梁变宽段曲线横移架梁技术研究

在桥梁工程中,对于既处在曲线段又是变宽段的预制梁安装路段往往不可避免,此时一般采用架桥机常规直线横移轨道进行架梁铺设,随之带来的问题是需要令架桥机前、中支腿错位排布,如此一来施工的精度、难度都有所提升,并且存在一定的安全隐患。依托于江西宜遂高速公路桥梁某路段,提出了使用曲线横移轨道为架桥机在曲线变宽段进行架梁作业时平稳过渡到支腿错位分布提供条件,以达到缩短工期、保障安全和提高经济效益的目的。

基于相对强度算法和参数遍历试验的地震预测回溯性检验——以中国川滇地区为例

探索地震活动的时空分布对于地震风险评估,尤其是对于中国川滇地区这样的地震频发区和强震危险区而言具有重要意义。相对强度算法(RI)基于统计学理论,使用过去的地震强度评估预测同一地点的未来地震强度。其原理简单,已多次在国内外强震预测的实践应用中取得了良好的效果。目前,经过多年的发展完善,该方法的预测性能愈加突出。为了辅助川滇地区的地震活动性预测工作,文中使用相对强度算法(RI)和参数遍历试验(PTT)进行了全面的参数分析,深入研究了RI算法在中国川滇地区的适用性,结果表明:由于参数选择合理(包括网格大小、异常学习时间窗长度、预测时间窗起始时间和预测时间窗长度),RI和PTT的组合研究表现出了明显优于随机猜测的预测效果,揭示了川滇地震危险区地震预测的有效参数区间。相对强度算法能够对川滇地区的地震活动进行预测,文中成果丰富了地震危险区地震趋势预测的参考依据。

支持访问行为身份追踪的跨域密文共享方案

作为在云环境下被广泛应用的密文数据授权访问机制,密文策略属性基加密(ciphertext-policy attribute-based encryption,CP-ABE)具有细粒度、1对多和拥有者可控的特点.由于多个用户可能拥有相同属性集合,传统属性基加密机制难以追溯到滥用解密权限的恶意授权用户身份.虽然现有研究解决了恶意用户的特定解密权限滥用行为(白盒攻击与黑盒攻击)的身份追踪问题,但仍难以实现针对授权用户访问行为的身份追踪,这将导致潜在的安全风险和数据访问知情权合规性问题.为了在现实应用场景中实现密文数据访问行为身份追踪,方案基于密文策略属性基加密机制构造跨域密文共享方法,通过数字签名和交互式外包解密流程将可追踪密钥和授权用户访问行为绑定为访问请求,并利用区块链的不可篡改性实现访问请求的完整性保护.为了解决引入区块链所导致的访问行为身份追踪效率低下问题,方案引入加密倒排索引结构以优化区块遍历效率,并通过BLS签名和隐私集合交集思想实现索引查询的隐私保护.理论分析和实验验证表明所提方案是实用与高效的.

面向测控专业的非线性数据结构算法实验设计

数据结构是软件设计领域的重要课程,对于测控专业的学生来说,掌握数据结构知识尤为重要。然而,在教学过程中,如何将通用的数据结构知识与测控专业面临的实际工程问题相结合,以及如何选择恰当的非线性结构问题案例,以便学生在知识理解和实践应用两个层面加深对课程内容的掌握,是教学中需要解决的关键问题。为此,在教学实践中,以测控领域科研中常用的自动测试命令解析程序设计为例,设计了非线性数据结构算法实验。通过科教融合的方式拓展教学的深度和广度,使学生能够将理论知识与实践技能相结合,有效提升他们解决实际工程问题的能力。

基于图结构的空间同位模式挖掘

空间同位模式反映了不同地理要素分布的依存关系,是地理学第一定律的体现,也符合空间大数据分析重在揭示事物关联特征的目标。空间同位模式挖掘需要顾及空间分布耦合机制,探测空间邻近关系及基于支持度等指标分析高频共生模式。现有方法多在判定邻近关系的同时搜索共生模式,导致在挖掘高阶共生模式时需要实时修正几何邻近关系,在复杂系统下丧失计算过程的灵活性。考虑到图数据蕴含的拓扑连接信息与空间同位模式相契合,本文提出一种基于图结构的空间同位模式挖掘方法。该方法一步完成几何上的邻近关系探测,然后在图数据库中通过子图搜索完成逻辑上的同位模式判别。首先,基于Delaunay三角网构建自适应邻接图,利用自适应邻接过滤器删除无效连接。然后,通过候选子图的不断连接、剪枝、生长,逐步从N元递推获取N+1元候选同位模式。最后,通过计算支持度指标并与预定义阈值比较以确定空间同位模式。本文基于不断生长迭代的图遍历思想提升了空间同位模式挖掘面向更复杂的空间场景的普适性。试验表明本文方法具备高效的挖掘能力,相较传统算法,在多元空间同位模式的挖掘任务中效果更优。

高带宽压电片变形镜的动力学仿真与优化方法研究

为进一步提高压电波前校正器的响应速度和轻量化程度,对面向高动态形状控制的压电片变形镜的动力学仿真与优化方法进行了研究。首先,基于压电片变形镜的参数化有限元模型,提出了高效、高精度的电-力耦合动力学仿真分析方法。然后,通过正交遍历多维设计参数(光学反射镜与压电陶瓷的材料类型、几何尺寸和固定方式等),探究了不同参数对压电片变形镜动态形状控制性能的影响规律。最后,优化得到具有预期响应带宽和驱动位移性能的压电片变形镜设计方案,并通过制备压电片变形镜的原理样件来验证其性能。实验结果表明,所研制的压电片变形镜的固有频率和镜面驱动位移幅值符合预期,验证了所提出的动力学仿真与优化方法的有效性,这可为高带宽压电片变形镜的高效研制提供科学的理论方法。

负载横移扰动下人体步态频率变化特性

为了研究人体行走时适应负载横向动态干扰的机制,从而设计可靠的穿戴式机器人辅助策略,提出采用基于双自由度受迫振动模型构建人-负载耦合系统。基于机械振动原理分析人-负载耦合系统特性,给出不同行走频率对人和负载位移的影响,提出人体通过调节行走频率适应负载横移扰动影响的假设;搭建负载横向动态干扰人体行走实验平台,获得实验对象无负重行走以及负载横向扰动下的肌肉协同特征及腿部激励频率,并与仿真结果进行对比分析。实验结果表明:负载横移扰动下人体行走是一个适应性调整并最后进入动态稳定的过程。其中,在负重情况下的人体上肢躯干摆动幅度比无负重情况下摆动增幅大60%,人体通过调整行走频率以及相关肌群肌肉协同策略来减少负载横向动态干扰带来的上肢躯干摆动影响。在负重情况下,不同行走速度的步态频率均趋向于人-负载耦合系统的固有频率,设定常速频率与固有频率相同,慢速下行走到达稳态时腿部激励频率上升4.30%,快速下腿部激励频率下降2.71%,负重下的行走控制策略与无负重下的行走控制策略相比发生了改变,以适应负载横移扰动带来的影响。