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A gas-kinetic theory based multidimensional high-order method for the compressible Navier–Stokes solutions

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Acta Mechanica Sinica 2017年第4期33卷 733-741页

作者： Xiaodong Ren kun xu Wei Shyy Key Laboratory for Thermal Science and Power Engineeringof Ministry of Education Department of Thermal Engineering Tsinghua University Beijing 100084 China Department of Mathematics School of Science The Hong Kong University of Science and Technology Hong KongChina Department of Mechanical and Aerospace Engineering School of Engineering The Hong Kong University of Scienceand Technology Hong Kong China

This paper presents a gas-kinetic theory based multidimensional high-order method for the compressible Naiver–Stokes solutions. In our previous study, a spatially and temporally dependent third-order flux scheme with the use of a third-order gas distribution function is ***, the third-order flux scheme is quite complicated and less robust than the second-order scheme. In order to reduce its complexity and improve its robustness, the secondorder flux scheme is adopted instead in this paper, while the temporal order of method is maintained by using a two stage temporal discretization. In addition, its CPU cost is relatively lower than the previous scheme. Several test cases in two and three dimensions, containing high Mach number compressible flows and low speed high Reynolds number laminar flows, are presented to demonstrate the method capacity.

关键词： compressible Stokes Navier Reynolds discretization laminar robustness spatially dimensions instead

单纯疱疹病毒1型脑炎临床特点及预后影响因素分析

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中国现代神经疾病杂志 2024年第4期24卷 224-229页

作者：徐坤榕王晓娟张弥兰薛红飞徐佳佳李玮河南省人民医院郑州大学人民医院神经内科450003

目的分析单纯疱疹病毒1型(HSV-1)脑炎的临床特点及预后影响因素。方法纳入2018年1月至2023年9月河南省人民医院诊断与治疗的51例HSV-1脑炎患者,记录其临床资料、实验室和影像学检查结果。采用改良Rankin量表(mRS)评估患者预后及脑损伤... 详细信息

目的分析单纯疱疹病毒1型(HSV-1)脑炎的临床特点及预后影响因素。方法纳入2018年1月至2023年9月河南省人民医院诊断与治疗的51例HSV-1脑炎患者,记录其临床资料、实验室和影像学检查结果。采用改良Rankin量表(mRS)评估患者预后及脑损伤后神经功能恢复情况,单因素和多因素逐步法Logistic回归分析筛查HSV-1脑炎预后不良的危险因素。结果共51例患者主要症状为发热、头痛;血清学检查可见血常规白细胞计数增加(14例),中性粒细胞计数增加(14例),淋巴细胞计数减少(8例),血清钠水平降低(17例);腰椎穿刺脑脊液压力升高(18例),白细胞计数增加(28例),蛋白定量升高(32例),葡萄糖水平升高(15例);有48例患者进行头部MRI检查,43例(89.58%)MRI显示有明显的脑区受累,其中35例(72.92%)MRI阳性病例均表现为典型的HSV-1脑炎单侧或双侧颞叶、额叶受累,软脑膜强化影增多8例(16.67%)。出院后6个月内有66.67%(34/51)患者完全康复,21.57%(11/51)遗留后遗症,病死率为11.76%(6/51);34例(66.67%)患者预后良好,17例(33.33%)患者预后不良。多因素Logistic回归分析显示,年龄增大(OR=1.090,95%CI:1.020~1.200;P=0.023)和脑脊液葡萄糖水平升高(OR=23.800,95%CI:23.800~1250.000;P=0.030)是HSV-1脑炎患者预后不良的危险因素。结论年龄增大和脑脊液葡萄糖水平升高是HSV-1脑炎患者预后不良的危险因素。临床实践中须掌握HSV-1脑炎的临床特点,做到早发现、早诊断、早治疗。

关键词：脑炎单纯疱疹预后危险因素 Logistic模型

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深层套管开窗技术在渤海S井的应用

化工设计通讯 2024年第7期50卷 27-29页

作者：马宏伟徐鲲中海石油(中国)有限公司天津分公司天津300451

为满足地质油藏对地层的评价需求,同时节省钻井工期,勘探井的侧钻比例、侧钻深度也随之逐年增加[1-4]。以S井Φ244.47 mm套管一趟式开窗作业为例,将从侧钻点优选、作业准备、开窗作业程序、裸眼钻进等方面对渤海油田深层套管开窗技术及... 详细信息

为满足地质油藏对地层的评价需求,同时节省钻井工期,勘探井的侧钻比例、侧钻深度也随之逐年增加[1-4]。以S井Φ244.47 mm套管一趟式开窗作业为例,将从侧钻点优选、作业准备、开窗作业程序、裸眼钻进等方面对渤海油田深层套管开窗技术及关键点进行阐述,针对深井、超深井在开窗作业程序阶段提出在井口摆好斜向器导斜面方位,下钻全程锁紧转盘,再使用陀螺复测确认的方式可以大大节省时间,为后续深层套管开窗作业提供技术指导。

关键词：侧钻比例侧钻深度一趟式开窗深层套管开窗技术关键点

Dynamics and Wheel's Slip Ratio of a Wheel-legged Robot in Wheeled Motion Considering the Change of Height

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Chinese Journal of Mechanical Engineering 2012年第5期25卷 1060-1067页

作者： DING Xilun LI Kejia xu kun School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China

The existing research on dynamics and slip ratio of wheeled mobile robot （WMR） are derived without considering the effect of height, and the existing models can not be used to analyze the dynamics performance of the robot with variable height while moving such as NOROS- Ⅱ. The existing method of dynamics modeling is improved by adding the constraint equation between perpendicular displacement of body and horizontal displacement of wheel into the constraint conditions. The dynamic model of NOROS- Ⅱ in wheel motion is built by the Lagrange method under nonholonomic constraints. The inverse dynamics is calculated in three different paths based on this model, and the results demonstrate that torques of hip pitching joints are inversely proportional to the height of robot. The relative error of calculated torques is less than 2% compared with that of ADAMS simulation, by which the validity of dynamic model is verified, Moreover, the relative horizontal motion between fore/hind wheels and body is produced when the height is changed, and thus the accurate slip ratio can not be obtained by the traditional equation. The improved slip ratio equations with the parameter of the vertical velocity of body are introduced for fore wheels and hind wheels respectively. Numerical simulations of slip ratios are conducted to reveal the effect of varied height on slip ratios of different wheels. The result shows that the slip ratios of fore/hind wheels become larger/smaller respectively as the height increases, and as the height is reduced, the reverse applies. The proposed research of dynamic model and slip ratio based on the robot height provides the effective method to analyze the dynamics of WMRs with varying height.

关键词： wheel-legged robot dynamics slip ratio change of height nonholonomic constraints

列线图风险评估模型在慢阻肺合并肺栓塞患者中的应用

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宁夏医学杂志 2024年第9期46卷 773-776页

作者：连军姚兰许坤宁夏回族自治区第五人民医院石嘴山中心医院呼吸与危重症医学科宁夏石嘴山753200

目的本研究旨在探究慢阻肺(COPD)合并肺栓塞(PE)患者的风险预测因素及其量化评估方法。方法选取COPD合并PE患者96例(PE组),另选取本院同期COPD未合并PE患者96例(非PE组)。收集2组患者性别、年龄、吸烟史、合并基础病等一般资料以及动脉... 详细信息

目的本研究旨在探究慢阻肺(COPD)合并肺栓塞(PE)患者的风险预测因素及其量化评估方法。方法选取COPD合并PE患者96例(PE组),另选取本院同期COPD未合并PE患者96例(非PE组)。收集2组患者性别、年龄、吸烟史、合并基础病等一般资料以及动脉血二氧化碳分压(PaCO_(2))、血氧分压(PaO_(2))、N端脑钠肽前体(NT-proBNP)、D-二聚体(D-dimer)、血清血红蛋白(Hb)及白蛋白(Alb)水平等临床指标。采用单因素及多因素logistic回归分析探讨COPD合并PE的相关影响因素,并构建列线图风险评估模型,同时验证模型的拟合度。结果2组患者卧床时间≥7 d、伴静脉血栓、COPD分级、PaO_(2)、D-dimer、NT-proBNP、Alb指标比较,差异有统计学意义(P<0.05)。卧床时间≥7 d、COPD分级、D-dimer及NT-proBNP是COPD合并PE的独立危险因素。卧床时间越久、COPD分级越高、PaO_(2)越低、D-dimer水平越高、NT-proBNP水平越高,发生COPD合并PE的风险越高。验证模型表明,偏差校准曲线与理想曲线吻合良好,该模型的AUC值为0.947,灵敏度为87.5%、特异度为87.5%。结论长时间卧床、高COPD分级、低PaO_(2)、高D-dimer水平以及高NT-proBNP水平是COPD合并PE的独立危险因素,建立的列线图模型能有效评估患者COPD合并PE的风险。

关键词：慢阻肺肺栓塞多因素分析列线图风险评估

A Survey of Image Synthesis and Editing with Generative Adversarial Networks

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Tsinghua Science and Technology 2017年第6期22卷 660-674页

作者： Xian Wu kun xu Peter Hall TNList and the Department of Computer Science and Technology Tsinghua UniversityBeijing 100084China the Department of Computer Science University of BathBathUK

This paper presents a survey of image synthesis and editing with Generative Adversarial Networks（GANs）. GANs consist of two deep networks, a generator and a discriminator, which are trained in a competitive way. Due to the power of deep networks and the competitive training manner, GANs are capable of producing reasonable and realistic images, and have shown great capability in many image synthesis and editing *** paper surveys recent GAN papers regarding topics including, but not limited to, texture synthesis, image inpainting, image-to-image translation, and image editing.

关键词： image synthesis image editing constrained image synthesis generative adversarial networks imageto-image translation

A unified gas-kinetic scheme for multiscale and multicomponent flow transport

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Applied Mathematics and Mechanics(English Edition) 2019年第3期40卷 355-372页

作者： Tianbai XIAO kun xu Qingdong CAI Department of Mechanics and Engineering Science College of EngineeringPeking University Department of Mathematics Hong Kong University of Science and Technology Department of Mechanical and Aerospace Engineering Hong Kong University of Science and Technology Shenzhen Research Institute Hong Kong University of Science and Technology

Compressible flows exhibit a diverse set of behaviors, where individual particle transports and their collective dynamics play different roles at different scales. At the same time, the atmosphere is composed of different components that require additional degrees of freedom for representation in computational fluid dynamics. It is challenging to construct an accurate and efficient numerical algorithm to faithfully represent multiscale flow physics across different regimes. In this paper, a unified gas-kinetic scheme(UGKS) is developed to study non-equilibrium multicomponent gaseous flows. Based on the Boltzmann kinetic equation, an analytical space-time evolving solution is used to construct the discretized equations of gas dynamics directly according to cell size and scales of time steps, i.e., the so-called direct modeling method. With the variation in the ratio of the numerical time step to the local particle collision time(or the cell size to the local particle mean free path), the UGKS automatically recovers all scale-dependent flows over the given domain and provides a continuous spectrum of the gas dynamics. The performance of the proposed unified scheme is fully validated through numerical *** UGKS can be a valuable tool to study multiscale and multicomponent flow physics.

关键词： unified gas-kinetic scheme(UGKS) multiscale modeling multicomponent flow

The synergism of sequential paired electrosynthesis with halogen bonding activation for the cyclization of organochlorides with olefins

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Science China Chemistry 2023年第2期66卷 540-547页

作者： Fei Lian kun xu Chengchu Zeng Faculty of Environment and Life Beijing University of TechnologyBeijing100124China

Reported herein is the design of a new catalytic paradigm by synergistically combining sequential paired electrosynthesis with halogen-bonding(XB)activation for the cyclization of organochlorides with *** dual activation strategy enables rapid access to densely functionalized 2-alkylidene-tetrahydrofurans with exclusive Z-selectivities,which are challenging to be synthesized by other methods.4,4′-Di-tert-butyl-2,2′-bipyridine(dtbbpy)showed an unprecedented reactivity as a XB acceptor to activate C-Cl bond by shifting its reduction potential positively by 220 m *** different from previous electroreductions of C-Cl bonds relying upon high electrode potentials or matched redox properties between mediators and organochlorides,the XB activator employed herein has no limit on the abovementioned redox property matching but can lower the applied electrode *** decreased operating potential allows broad functional group tolerance,which was highlighted by the late-stage functionalization of 11 examples of drugs and natural products-derived alkenes.

关键词： electrochemistry cross-electrophile coupling electrocatalysis paired electrolysis

Properties and Iterative Methods for the Lasso and Its Variants

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Chinese Annals of Mathematics,Series B 2014年第3期35卷 501-518页

作者： Hong-kun xu Department of Applied Mathematics National Sun Yat-Sen University Department of Mathematics King Abdulaziz University

The lasso of Tibshirani （1996） is a least-squares problem regularized by the l1 norm. Due to the sparseness promoting property of the l1 norm, the lasso has been received much attention in recent years. In this paper some basic properties of the lasso and two variants of it are exploited. Moreover, the proximal method and its variants such as the relaxed proximal algorithm and a dual method for solving the lasso by iterative algorithms are presented.

关键词： Lasso Elastic net Smooth-lasso l1 regulaxization Sparsity Proximalmethod Dual method Projection Thresholding