Hole Cleaning Prediction in Foam Drilling Using Artificial Neural Network and Multiple Linear Regression

Foam drilling is increasingly used to develop low pressure reservoirs or highly depleted mature reservoirs because of minimizing the formation damage and potential hazardous drilling problems. Prediction of the cuttings concentration in the wellbore annulus as a function of operational drilling parameters such as wellbore geometry, pumping rate, drilling fluid rheology and density and maximum drilling rate is very important for optimizing these parameters. This paper describes a simple and more reliable artificial neural network (ANN) method and multiple linear regression (MLR) to predict cuttings concentration during foam drilling operation. This model is applicable for various borehole conditions using some critical parameters associated with foam velocity, foam quality, hole geometry, subsurface condition (pressure and temperature) and pipe rotation. The average absolute percent relative error (AAPE) between the experimental cuttings concentration and ANN model is less than 6%, and using MLR, AAPE is less than 9%. A comparison of the ANN and mechanistic model was done. The AAPE values for all datasets in this study were 3.2%, 8.5% and 10.3% for ANN model, MLR model and mechanistic model respectively. The results show high ability of ANN in prediction with respect to statistical methods.

Outcomes of 4 surgical adjuvants used for internal limiting membrane peeling in macular hole surgery: a systematic review and network Meta-analysis

AIM:To compare the outcomes of four adjuvants used for internal limiting membrane(ILM)peeling in macular hole surgery,including indocyanine green(ICG),brilliant blue G(BBG),triamcinolone(TA)and trypan blue(TB),through systematic review and random-effects Bayesian network Meta-analysis.METHODS:PubMed,Cochrane library databases and Web of Science were searched until August 2018 for clinical trials comparing the above four adjuvants.ORs for postoperative best corrected visual acuity(BCVA)improvement and primary macular hole closure rates were compared between the different adjuvants.RESULTS:Twenty-seven eligible articles were included.For postoperative BCVA improvement,results of BBGassisted peeling were significantly more favorable than those of ICG(WMD 0.08,95%credible interval 0.01-0.16)and TA ranked highest.No significant differences were found between any other two groups in postoperative BCVA improvement.For postoperative primary macular hole closure rates,BBG ranked highest.However,no significant differences were shown between any two groups.CONCLUSION:TA and BBG are the optimum adjuvants for achieving postoperative BCVA improvement macular hole surgery with adjuvant-assisted ILM peeling.Among all adjuvants,the use of BBG is associated with the highest postoperative macular hole closure rate.

A Proposal for Mitigating Multiple Black-Hole Attack in Wireless Mesh Networks

The Network Layer in wireless mesh networks is responsible for routing packets making it a prime target for intruders and hackers. Black-hole attack is a type of denial-of-service attack which when carried out can disrupt the services of this layer. This paper takes a look at some important detection and mitigation techniques and presents the drawbacks. After analysis of current mechanisms, the paper proposes RID-AODV, a security solution for multiple black-hole attack in wireless mesh networks. Based on the backbone of AODV, RID-AODV combines the ability of route skipping of IDSAODV and route failure correction using reverse route establishment of RAODV. The enhanced protocol RID-AODV, AODV, IDSAODV, and RAODV are implemented in a simulated environment using ns-2.35 simulator. The networks for each protocol are bombarded with up to ten black-hole nodes starting from zero. The results obtained are then analyzed and compared and a discussion is presented.

韧性视角下城市洪涝灾害应急管理协同网络研究

近年来,极端天气气候事件频发,城市洪涝灾害对社会安全构成严重威胁。为有效处置紧急灾害事件,该文从协同视角出发,以“7·31北京暴雨”作为研究案例,采用结构洞与社会网络分析方法,将参与救援的相关职能部门作为研究对象,构建部门间2-模灾害应急协同网络。通过分析得出:市级应急组织的凝聚力较强,获取资源信息途径较多,拥有更多运用结构洞的能力。相较而言,县-区级应急组织的整体协同能力相对薄弱,其节点关系的衔接程度较松散。基于此提出:强化区县级政府的应急统筹协调能力、深化边缘组织与核心部门之间的合作、提升市-区资源信息的传递效率。为减轻灾害损失、厘清应急网络中的组织协同关系以及完善协同联动机制提供参考。

Structure of Chinese City Network as Driven by Technological Knowledge Flows

Based on patent cooperation data,this study used a range of city network analysis approaches in order to explore the structure of the Chinese city network which is driven by technological knowledge flows.The results revealed the spatial structure,composition structure,hierarchical structure,group structure,and control structure of Chinese city network,as well as its dynamic factors.The major findings are:1) the spatial pattern presents a diamond structure,in which Wuhan is the central city;2) although the invention patent knowledge network is the main part of the broader inter-city innovative cooperation network,it is weaker than the utility model patent;3) as the senior level cities,Beijing,Shanghai and the cities in the Zhujiang(Pearl) River Delta Region show a strong capability of both spreading and controlling technological knowledge;4) whilst a national technology alliance has preliminarily formed,regional alliances have not been adequately established;5) even though the cooperation level amongst weak connection cities is not high,such cities still play an important role in the network as a result of their location within ′structural holes′ in the network;and 6) the major driving forces facilitating inter-city technological cooperation are geographical proximity,hierarchical proximity and technological proximity.

Effects of Network Closure on Cooperative Innovation: Evidence from Dongying's Petroleum Equipment Industry in China

There are two opposing viewpoints on which kind of network configuration provides a more competitive advantage, namely,network closure or structural holes, with the latter occupying the dominant position in the literature. Using social network analysis and negative binomial regression methods, we graph the co-patent network of Dongying's petroleum equipment industry in China and explore its impact on enterprise innovation. The analysis is based on 17 face-to-face interviews, 31 enterprise questionnaires, and 354 co-patent records from the China State Intellectual Property Office identifying cooperative innovation for the years 1988–2013. We find that this network is closed, controlled by state-owned enterprises, and its closure has positive effects on enterprise innovation performance. This may be related to China's unique industrial development history, state system and policies, regional culture and circumstances, and enterprise characteristics. Therefore, for some industries in specific regions, the advantages usually attributed to structural holes and open innovation may not necessarily apply.

数据引流下异构传感器网络能量空洞防护算法

异构传感器网络在工作时,靠近传感器基站位置的节点会由于接收转发次数较多而出现能量空洞现象。为有效对此现象实施防护,保障网络安全运行,提出数据引流下异构传感器网络能量空洞防护算法。构建网络节点部署模型,对传感器网络节点实施节点优化部署;计算网络节点能耗对网络实施能量均衡控制,获取异构传感器网络节点的簇内传输跳数;结合获取的节点簇内跳数以及能量均衡结果开展节点接收数据的的引流分配,平衡传感器网络层内节点能量消耗,实现传感器网络的能量空洞防护。实验结果表明,使用上述方法开展传感器网络能量空洞防护时,数据转发接收能耗较低,防护方法性能高,防护效果好。

A Void Avoidance Scheme for Grid-Based Multipath Routing in Underwater Wireless Sensor Networks

This work proposes a geographic routing protocol for UWSNs based on the construction of a 3D virtual grid structure, called Void-Avoidance Grid-based Multipath Position-based Routing (VA-GMPR). It consists of two main components, the multipath routing scheme and the grid-based void avoidance (GVA) mechanism for handling routing holes. The multipath routing scheme adopts node-disjoint routes from the source to the sink in order to enhance network reliability and load balancing. While the GVA mechanism handles the problem of holes in 3D virtual grid structure based on three techniques: Hole bypass, path diversion, and path backtracking. The performance evaluation of the VA-GMPR protocol was compared to a recently proposed grid-based routing protocol for UWSNs, called Energy-efficient Multipath Geographic Grid-based Routing (EMGGR). The results showed that the VA-GMPR protocol outperformed the EMGGR protocol in terms of packet delivery ratio, and end-to end-delay. However, the results also showed that the VA-GMPR protocol exhibited higher energy consumption compared to EMGGR.

Getting the Balance Right in Intercultural Groups: A Dynamic Social Network Perspective

Problem: A common assumption is that students prefer to select their friends for group-work. The prime goal of this study was to understand the impact of two group selection methods on how students from diverse cultural backgrounds build learning and work relations. Method: Social Network Analysis in a pre-post test manner in a quasi-experimental design of 81 vs. 70 third-year students. Solution: In this study, we “disrupted” this group selection process after Day 1 by balancing students from different parts of the social network together. In one condition the students were “balanced” into groups by staff to encourage structural hole formation, and in the other condition students were allowed to self-select their group members to encourage network closure. Results: Students in the self-selected condition primarily selected their friends from a similar cultural background. In both conditions the learning networks after 11 weeks were primarily predicted by the group allocation and initial friendships. However, students in the balanced condition developed more cross-cultural learning links. These results indicate that teachers can actively intervene in the cross-cultural dynamics in- and outside the classroom.

数字化转型提升企业创新效率的网络机制——合作和知识双重创新网络结构洞的中介作用

企业数字化转型不仅拓展和优化了创新网络,也使创新网络在创新驱动发展中的作用日益重要。基于网络结构洞理论,从创新合作网络和创新知识网络(双重创新网络)角度分析数字化转型通过增强企业在创新网络中的“桥梁”作用来提升企业创新效率的机制,并采用沪深A股制造业上市公司2013—2021年的数据进行实证检验,结果发现:制造业企业数字化转型能够显著提升其创新效率,该作用在非国有企业中更为显著;双重创新网络结构洞是数字化转型影响企业创新效率的中介变量,即存在“数字化转型水平提高→双重创新网络结构洞增加→创新效率提升”的影响路径;企业组织韧性提高能够强化数字化转型对网络结构洞的正向影响,但对网络结构洞影响创新效率没有显著的调节作用。因此,应积极推进企业数字化转型,通过拓展和优化创新网络来促进企业创新效率提升,并不断提高企业的组织韧性以有效化解转型风险。

一种基于空洞节点检测的可靠无人机自组网路由协议

针对高动态无人机自组网中节点之间链路生存时间(Link Live Time,LLT)短和节点遭遇路由空洞次数多的问题,提出了一种基于空洞节点检测的可靠无人机自组网路由协议——GPSR-HND(Greedy Perimeter Stateless Routing Based on Hollow Node Detection)。GPSR-HND协议中,转发节点通过空洞节点检测机制检测邻居节点状态,将有效邻居节点加入待选邻居节点集;然后基于层次分析法(Analytic Hierarchy Process,AHP)的多度量下一跳节点选择机制从待选邻居节点集中选择权重最大的邻居节点贪婪转发数据;如果待选邻居节点集为空,则从空洞邻居节点集中选择权重最大的空洞节点启动改进的周边转发机制,寻找可恢复贪婪转发模式的节点。与GPSR-NS协议和GPSR协议相比,GPSR-HND协议表现出了更好的性能,包括平均端到端时延和丢包率的改善,以及吞吐量的提高。

WSN中融合优选机制和变螺旋策略的自适应黑洞覆盖策略

在无线传感器网络节点覆盖优化过程中,黑洞算法往往会陷入局部最优解,导致节点分布不均,后期收敛缓慢。因此提出一种融合优选机制和变螺旋策略的自适应黑洞算法,建立具有最优解的黑洞种群,引入黑洞优选机制,使星体种群在迭代过程中不再围绕一个黑洞进行寻优,经过多次迭代,黑洞种群数量减少,即最优解所在区域更加精确,算法不易陷入局部最优,并围绕最优解附近进行局部搜索,从而实现全局和局部优化能力的平衡。其次,动态调整星体位置更新过程中的螺旋形状,黑洞种群规模不断减小的同时螺旋形状也逐渐变小,即星体能够在更靠近最优解的区域进行开采,提高优化精度。仿真结果显示,改进后的黑洞算法能使节点覆盖率显著提升,覆盖盲区和重叠区域面积大幅减少,节点的移动距离也明显缩减。

A Distributed Trust Based Secure Communication Framework for Wireless Sensor Network

The wireless sensor network is an emerging technology, which is used to sense and monitor the environment. As the nodes are deployed in an open environment, the security is one of the essential factors. The cryptography techniques can ensure confidentiality, integrity and authentication. However, wireless sensor network also needs to deal with inside and outside attackers. To deal with outside attackers, attacks by compromised or malicious nodes, trust management system is suggested by many researchers in the area of wireless sensor network. Trust management system can be implemented in various applications for security management such as secure data aggregation, secure cluster head selection, trusted routing, access control, etc. Many researchers provide different kind of solutions for these secure applications based on trust management. However, to incorporate, all such applications on a single sensor node in the network, it is essential to design and develop a trust management system, which considers various aspects and applications of wireless sensor network. As a result, in this paper, we would like to propose a parameter and trust factor based secure communication framework and design a trust management system for wireless sensor networks. Our main contribution is to identify various parameters and trust factors which influences on trust in wireless sensor network and developing a framework for a trust management system based on various parameters and trust factors. The working of the proposed model is shown by simulation experiments conducted in MATLAB for the application of secure communication, data aggregation and intrusion detection in wireless sensor networks.

Real Time Vehicular Traffic Simulation for Black Hole Attack in the Greater Detroit Area

Vehicular Ad-hoc Networks (VANETs) technology has recently emerged, and gaining significant attention from the research because it is promising technologies related to Intelligent Transportation System (ITSs) and smart cities. Wireless vehicular communication is employed to improve traffic safety and to reduce traffic congestion. Each vehicle in the ad-hoc network achieves as a smart mobile node categorized by high mobility and forming of dynamic networks. As a result of the movement of vehicles in a continuous way, VANETs are vulnerable to many security threats so it requisites capable and secure communication. Unfortunately, Ad hoc networks are liable to varied attacks like Block Hole attacks and Grey Hole attacks, Denial of service attacks, etc. Among the most known attacks are the Black Hole attacks while the malicious vehicle is able to intercept the data and drops it without forwarding it to the cars. The main goal of our simulation is to analyze the performance impact of black hole attack in real time vehicular traffic in the Greater Detroit Area using NS-2 and SUMO (Simulation of Urban). The simulation will be with AODV protocol.

基于加权组合算法的点云孔洞修补

为了对无人机航测数据中的点云孔洞进行修补,将最小二乘支持向量机算法LS-SVM和遗传算法GA优化的反向传播神经网络算法BP进行线性组合,构建一种加权组合模型,用于散乱点云数据中的孔洞修补。通过两种修补方法的误差进行两者的加权组合,建立出与两种修补方法误差相关的加权组合模型,并将加权组合模型的修补结果与单一使用最小二乘支持向量机、遗传算法优化的BP神经网络两种修补方法的修补结果进行残差和内外符合精度的比较与分析。结果表明:采用加权组合模型得到的点云修补结果内外符合精度较高,且具有更强的稳定性,为无人机获取的点云数据提供了一种有效的孔洞修补方法。

基于SPH露天台阶的爆破优化

针对露天深孔台阶爆破容易出现块度不均匀、大块率高等问题,运用经验公式法对台阶爆破参数进行计算并确定爆破方案,建立基于光滑粒子流体动力学(SPH)的台阶数值模型,对深孔台阶爆破孔排距共同作用下的岩体损伤情况及孔间应力大小进行研究。结果表明:孔排距会影响炮孔间的应力叠加作用,模拟过程中SPH粒子能良好地模拟出爆破过程中岩石运动状态和岩石损伤范围,当孔间距为8.5 m、排间距为5.0 m,爆破效果最佳。将模拟结果应用于现场试验,大块率较优化前降低了10.3%,块度平均合格率提高了5.2%,现场试验与模拟结果最优爆破方案效果高度一致,说明利用SPH的数值模拟方法研究台阶爆破是合理可行的。研究结果可为相关台阶爆破孔排距选择提供依据和参考。

基于Voronoi图的无线传感网络覆盖盲区检测方法

传感网络的空洞暴露程度较少,在检测网络覆盖情况时更容易出现误差,影响盲区的检测效果。为此,提出基于Voronoi图的无线传感网络覆盖盲区检测方法。根据节点分布关系推测无线传感网络覆盖情况,在Voronoi图的指导下排除已覆盖区域,获取具备检测条件的未覆盖无线传感网络空洞。计算网络空洞的暴露程度和节点能量,作为特征样本输入粒子群分离器中,根据分类器的输出结果,实现无线传感网络覆盖盲区检测。仿真结果表明,所提方法不同覆盖盲区数量下的检测时长低于0.2 s、不同节点数量下的检测能耗低于20 J、不同空洞圆心距下的覆盖盲区差异度最高为0.24,证明所提方法具有较好的无线传感网络覆盖盲区检测效果。

基于交叉导线网的隧道洞内测量新方法

交叉导线网是隧道洞内控制网的常用网形,具有精度高、可靠性好等特点,但存在测量强度大、边角联合平差精度不理想等问题。在分析交叉导线网测距、测角观测量对联合平差精度影响基础上,结合工程实践提出了一种基于交叉导线网的洞内测量新方法,即单边测距交叉导线法。该方法避免了交叉导线网边角精度不匹配、测边测角网相对扭曲、测距内部定权不准等造成的联合平差精度不理想问题。仿真实验表明,该方法较传统方法各项贯通指标值更接近真实值;工程实践表明,采用该方法,横向贯通精度和贯通方位精度较传统方法分别提升51.5%、9.8%,且布网测量工作量减少约30%。

基于集成正交实验与CNN方法的微细电火花微孔加工精度

针对改善微细电火花微孔加工精度问题,提出一种集成正交试验与卷积神经网络的方法。首先,利用正交试验研究进给速度、主轴转速、脉冲占空比和脉冲频率4个因素对微细电火花加工H62黄铜微孔入口过切(En-OV)、出口过切(ExOV)和锥度(TA)的影响规律及其最优加工工艺参数。然后,采用基于PyTorch框架的卷积神经网络对试验结果进行预测。结果表明:对于微孔加工入口过切,各因素按影响程度由高到低依次为脉冲占空比、脉冲频率、进给速度和主轴转速;对于微孔加工出口过切,各因素按影响程度由高到低依次为进给速度、主轴转速、脉冲占空比和脉冲频率;对于微孔加工锥度,各因素按影响程度由高到低依次为进给速度、脉冲占空比、主轴转速和脉冲频率。综合考虑并分析各因素之间关系,通过验证实验得到微孔加工精度最优组合参数:进给速度为0.02mm/s、主轴转速为1000r/min、脉冲占空比为60%、脉冲频率为3000Hz。微孔加工入口过切、出口过切和锥度的预测值与试验真实值吻合程度较高,两者相对误差均小于12%。基于PyTorch框架的卷积神经网络(CNN)具有较高的预测准确性,满足实际生产加工需求,为微细电火花微孔加工精度预测研究提供了新方法,也为实际生产加工指导提供了依据。