Validation and application of three-dimensional discontinuous deformation analysis with tetrahedron finite element meshed block

In the last decade, three dimensional discontinuous deformation analyses (3D DDA) has attracted more and more attention of researchers and geotechnical engineers worldwide. The original DDA formulation utilizes a linear displacement function to describe the block movement and deformation, which would cause block expansion under rigid body rotation and thus limit its capability to model block deformation. In this paper, 3D DDA is coupled with tetrahedron finite elements to tackle these two problems. Tetrahedron is the simplest in the 3D domain and makes it easy to implement automatic discretization, even for complex topology shape. Furthermore, element faces will remain planar and element edges will remain straight after deformation for tetrahedron finite elements and polyhedral contact detection schemes can be used directly. The matrices of equilibrium equations for this coupled method are given in detail and an effective contact searching algorithm is suggested. Validation is conducted by comparing the results of the proposed coupled method with that of physical model tests using one of the most common failure modes, i.e., wedge failure. Most of the failure modes predicted by the coupled method agree with the physical model results except for 4 cases out of the total 65 cases. Finally, a complex rockslide example demonstrates the robustness and versatility of the coupled method.

Kinetic Model and Simulation Analysis for Toluene Disproportionation and C9-Aromatics Transalkylation

A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.

Repetitive transcranial magnetic stimulation for hallucination in schizophrenia spectrum disorders A meta-analysis

OBJECTIVE:This study assessed the efficacy and tolerability of repetitive transcranial magnetic stimulation for treatment of auditory hallucination of patients with schizophrenia spectrum disorders.DATA SOURCES:Online literature retrieval was conducted using PubMed,ISI Web of Science,EMBASE,Medline and Cochrane Central Register of Controlled Trials databases from January1985 to May 2012.Key words were"transcranial magnetic stimulation","TMS","repetitive transcranial magnetic stimulation",and"hallucination".STUDY SELECTION:Selected studies were randomized controlled trials assessing therapeutic efficacy of repetitive transcranial magnetic stimulation for hallucination in patients with schizophrenia spectrum disorders.Experimental intervention was low-frequency repetitive transcranial magnetic stimulation in left temporoparietal cortex for treatment of auditory hallucination in schizophrenia spectrum disorders.Control groups received sham stimulation.MAIN OUTCOME MEASURES:The primary outcome was total scores of Auditory Hallucinations Rating Scale,Auditory Hallucination Subscale of Psychotic Symptom Rating Scale,Positive and Negative Symptom Scale-Auditory Hallucination item,and Hallucination Change Scale.Secondary outcomes included response rate,global mental state,adverse effects and cognitive function.RESULTS:Seventeen studies addressing repetitive transcranial magnetic stimulation for treatment of schizophrenia spectrum disorders were screened,with controls receiving sham stimulation.All data were completely effective,involving 398 patients.Overall mean weighted effect size for repetitive transcranial magnetic stimulation versus sham stimulation was statistically significant(MD=–0.42,95%CI:–0.64 to–0.20,P=0.000 2).Patients receiving repetitive transcranial magnetic stimulation responded more frequently than sham stimulation(OR=2.94,95%CI:1.39 to 6.24,P=0.005).No significant differences were found between active repetitive transcranial magnetic stimulation and sham stimulation for positive or negative symptoms.Compared with sham stimulation,active repetitive transcranial magnetic stimulation had equivocal outcome in cognitive function and commonly caused headache and facial muscle twitching.CONCLUSION:Repetitive transcranial magnetic stimulation is a safe and effective treatment for auditory hallucination in schizophrenia spectrum disorders.

Thermal Analysis and Optimization for Cryopanel of NBI Cryocondensation Pump

Excellent vacuum performance ensures a high beam transmission efficiency of theneutral beam injector (NBI).The vacuum performance is mainly determined by the cryoperfor-mance of the cryopanel of the cryocondensation pumps which are the main vacuum pumps of NBI.In order to optimize the cryoperformance,the requirements for the temperature distribution andthe heat load of tire cryopanel are analysed and the factors that affect the cryopanel's temperaturedistribution are studied.The results indicate that.tire temperature difference of the cryopanel canbe reduced by fabricating the eryopanel with high thermal conductivity material,increasing itsthickness and cutting the distance between the two upward cooling pipes.The results may beapplied to a cryopanel cooled by forced flow liquid helium.

Public Transit Performance Evaluation Using Data Envelopment Analysis and Possibilities of Enhancement

This study evaluates the operational performance of all routes of Sajha Bus Yatayat operating inside Kathmandu valley using Data Envelopment Analysis (DEA) in terms of efficiency and effectiveness score. This approach allows us to access the relative performance of transit system in absence of historical data and research to compare with. To explore the possibility of enhancing the performance, scenarios were created for relatively underperforming routes and long route problem by changing the most important input variable and output variables accordingly with regression model where it was relevant. Partial Least Squares (PLS) regression was used to determine the most influential input variables to the output variables. DEA was conducted to access the performance of all routes under these scenarios. Underperforming routes except the longest route under the first set of scenarios, emerge to be better performing efficiently without considerable negative deviation in effectiveness. The result of second set of scenarios for long route problem suggests that the longest route’s performance can be enhanced significantly upon proper route alignment. Scenarios development and evaluation can help lead transit companies to explore the strategies to facilitate operational performance enhancement.

Quantitative volumetric analysis of the optic radiation in the normal human brain using diffusion tensor magnetic resonance imaging-based tractography

To attain the volumetric information of the optic radiation in normal human brains, we performed diffusion tensor imaging examination in 13 healthy volunteers. Simultaneously, we used a brain normalization method to reduce individual brain variation and increase the accuracy of volumetric information analysis. In addition, tractography-based group mapping method was also used to investigate the probability and distribution of the optic radiation pathways. Our results showed that the measured optic radiation fiber tract volume was a range of about 0.16% and that the fractional anisotropy value was about 0.53. Moreover, the optic radiation probability fiber pathway that was determined with diffusion tensor tractography-based group mapping was able to detect the location relatively accurately. We believe that our methods and results are helpful in the study of optic radiation fiber tract information.

Geochemical Properties and StratigraphicalCorrelation of Frasnian-Famennian TransitionalStrata in Wuzhishan Section

The qualities of petrology and paleobiology in Wuzhishan Section are studied. Several geo-chemical anomalies are recognized, such as: high rare earth element content, high pyrite content and Ni anomalies. It could be correlated with Nandong Section in Xiangzhou County and the F/F boundary could be determined according to Ni anomalies. The results of the study indicate that the geochemical anomaly plays an important role in stratigraphic correlation in non-fossil stratum.

Thermodynamic analysis and combined cycle research on recoverable pressure energy in natural gas pipeline

Current research and ways of capturing mechanical energy are discussed in this paper.By the aid of the comprehensive thermodynamic analysis and Aspen simulation tool,the amount of available work that can be produced from capturing the pressure energy has been calculated.Based on the comprehensive thermodynamic analysis,two systems have been proposed to capture pressure energy of natural gas to generate electricity.In this study,the expression of exergy is given which can be used in evaluating purposes.A problem with this multidisciplinary study is the complicated boundary condition.In conclusion,a technical prospect on recoverable natural gas pressure energy has been presented based on total energy system theory.

Mathematical theory of signal analysis vs. complex analysis method of harmonic analysis

We present recent work of harmonic and signal analysis based on the complex Hardy space approach.

微振动模拟与主被动隔振一体化实验平台

针对遥感卫星地面微振动实验的复杂要求,设计了一种同时具备微振动模拟与主被动隔振功能的一体化微振动实验平台,并对该平台的主、被动隔振性能以及微振动模拟效果分别进行了仿真分析和实验测试。其中,被动隔振由气浮支撑实现,主动隔振采用主动阻尼方法抑制共振峰,微振动模拟采用基于线性系统频响函数的控制策略。实验结果表明,平台前六阶的模态频率分布均小于10 Hz,被动隔振系统能大幅抑制10~200 Hz频段内的地面微振动;主动隔振能够实现14 dB的隔振系统共振峰衰减效果。微振动模拟功能能够有效产生接近星上的单频和多频真实扰动线谱,在特定频谱的扰动模拟实验中,幅值最大误差为5.9%,在误差允许范围内。该多功能一体化实验平台的各项功能均能满足地面模拟实验需求。

Modeling Cyber Loss Severity Using a Spliced Regression Distribution with Mixture Components

Cyber losses in terms of number of records breached under cyber incidents commonly feature a significant portion of zeros, specific characteristics of mid-range losses and large losses, which make it hard to model the whole range of the losses using a standard loss distribution. We tackle this modeling problem by proposing a three-component spliced regression model that can simultaneously model zeros, moderate and large losses and consider heterogeneous effects in mixture components. To apply our proposed model to Privacy Right Clearinghouse (PRC) data breach chronology, we segment geographical groups using unsupervised cluster analysis, and utilize a covariate-dependent probability to model zero losses, finite mixture distributions for moderate body and an extreme value distribution for large losses capturing the heavy-tailed nature of the loss data. Parameters and coefficients are estimated using the Expectation-Maximization (EM) algorithm. Combining with our frequency model (generalized linear mixed model) for data breaches, aggregate loss distributions are investigated and applications on cyber insurance pricing and risk management are discussed.

冷端管径对高压节流型涡流管性能影响分析

冷端管径(D_(c))是影响涡流管性能的重要因素之一,基于12 MPa的高压节流工况,以CH_(4)为计算工质,建立物理模型,改变D_(c)为36、38、40、42和44 mm。对比发现:随着D_(c)增大,冷端内旋气体温度逐渐下降,制冷效果提升;热端外旋气体温度先增加后下降,D_(c)=40 mm时制热效果最佳。反映出D_(c)与制冷效果呈正相关,但对制热效果存在最佳值。当D_(c)增大时,内旋气体总压下降幅度逐渐平缓,利于节流;在D_(c)≥40 mm时,外旋气体总压下降幅度变大,且变化不规律,节流时有损调节阀使用寿命。另外D_(c)=44 mm时,外旋气体速度变化规律异常。所以根据工况需求,可控制D_(c)尺寸来调节涡流管制冷制热效果。

全程信息化管理在提高医院检验分析前阶段质量中的应用效果

目的分析在医院检验分析前阶段实施全程信息化管理,对提升检验质量的应用价值。方法选取2022年4月—2023年3月陕西航天医院检验科的21名医护人员进行常规管理模式,为对照组,2023年4—7月进行全程信息化管理模式,为观察组,其间涉及的医护人员为同一批,比较两组管理效果。结果观察组时效性、实用性、专业性、服务性等维度评分高于对照组,差异有统计学意义(P均<0.05)。观察组样本采样至送出时间、样本送出至抵达实验室时间均短于对照组,差异有统计学意义(P均<0.05)。两组抗凝样本凝固、标本丢失、样本容器错误、血培养污染、样本溶血检验前不良事件发生率比较,差异无统计学意义(P均>0.05)。观察组医护人员对管理的满意度为100.00%,高于对照组的80.95%,差异有统计学意义(P<0.05)。结论在提高医院检验分析前阶段,实施全程信息化管理对于提高医院的整体运营效率和患者满意度有着重要作用。

五年制高等职业教育学校教师教科研现状调查与分析——基于南通卫生高职校近5年教科研成果数据统计

通过对南通卫生高等职业技术学校近5年教科研数据的统计,找出五年制高职学校教师在教科研方面存在的问题并分析其原因,从合理处理教学与科研的关系、提升教科研培育培训质量、促进教科研团队成长、健全学校教科研保障体系等方面提出五年制高职学校教师科研能力提升的策略与措施。

中国樱桃不同品种(优系)果实品质分析

对中国樱桃果实品质进行分析,有利于选育适合区域发展的樱桃品种,为中国樱桃种质资源的保护奠定理论基础。本研究结合主成分分析、相关性分析和聚类分析,选取相同栽培条件下30个不同品种(优系)的中国樱桃果实进行内、外品质分析。结果表明:在相同的栽培条件下,不同品种(优系)的中国樱桃果实品质存在显著差异,综合性状评价得分排名依次为C78、C6、C14、C34和C32,C20(贵州玛瑙红)这一品种在各地栽培均表现优异,本次综合评价排名为11。9个果实内在品质指标存在不同程度的变异,变异系数为11.27%~36.32%。果实品质指标间存在相关系数,其中12项在0.01水平下极显著相关,17项在0.05水平下显著相关。主成分分析结果显示,前7个主成分的累计贡献率为88.196%,能够反映数量性状的基本特征。欧氏聚类分析结果显示,30个不同的中国樱桃品种(优系)初步聚为4大类。该研究得到的果实品质分析结果可以初步探索中国樱桃资源的遗传变异图谱,同时也可以作为新品种选育的参考依据。

青海湖流域植被覆盖时空变化特征及驱动力分析

【目的】探索青海湖流域植被动态变化格局及其对气候变化和人类活动的响应。【方法】采用趋势分析、多元回归残差分析、偏相关分析等方法,以MOD13Q1遥感数据和气象数据为基础,分析2001-2019年流域植被覆盖时空变化特征及其驱动力。【结果】(1)2001-2019年青海湖流域植被覆盖度(FVC)增长率为2.1%/10 a,呈显著波动上升趋势(P<0.05),FVC改善面积约为1.21×10^(4) km^(2),占总面积的48.77%;(2)气候变化和人类活动对植被覆盖变化的贡献率分别为57.83%和41.52%;(3)降水和温度与FVC变化呈显著正相关的面积占比分别为7.93%和4.15%。【结论】近19 a年青海湖流域FVC整体改善显著,显著改善区域主要分布于流域西部和青海湖北岸区域;气候变化是流域FVC变化的主导因素,但人类活动对局地FVC变化具有显著的抑制作用;降水对流域FVC变化的影响力更高,局地FVC变化对温度响应更强烈。

强制对流对高压套管油介质中乙炔分子传质过程的影响

为优化对高压套管进行油中溶解气体分析时的取样质量,提升分析结果的代表性和准确性,提出一种对高压套管中的绝缘油施加强制对流的方法,通过向绝缘油施加速度场促进油中溶解气体的传质过程,进而改善油中溶解气体分析的取样质量。从仿真计算和实验验证2个方面对绝缘油中溶解乙炔气体传质过程进行研究。首先分析无强制对流情况下气体的传质过程,并测量气体从故障源到取样口的时间;然后分析在强制对流情况下气体的传质过程并测量了传质时间,在此基础上讨论气体传质时间缩短的原因;最后探究不同强制对流动作周期对传质过程影响的程度。研究成果能够为高压套管在线监测装置的研发提供参考。

一种变自由度单回路机构的变拓扑结构设计及拓扑分析

特殊单回路机构通过一些特殊位置后会发生自由度变化,从而使其拓扑学、运动学/动力学性能发生变化,并适用于不同的应用背景。研究设计了一种由8个转动副(R)组成的单回路并联机构,它有3种运动模式,分别为2自由度、4自由度以及3自由度驱动,对应3个机构;然后,分析计算了3种运动模式下机构的方位特征集、自由度、耦合度3个主要拓扑特性,并分析了3种机构变拓扑结构的稳定性及可转变性;同时,对运动模式1、模式3下机构的位置正反解进行了分析。为基于这种变自由度单回路机构单元的可重构并联机构的研究提供了基础。

传统交流线路保护在换流器并网系统中的适应性分析

提出了一种继电保护适应性评估方法,基于对换流器并网系统电气量特性的分析,对工程中常配备的纵联差动保护、保护辅助元件和距离保护在换流器并网系统中的适应性进行了评估,并分析了换流器控制策略、故障场景、系统拓扑参数等因素对保护适应性的影响,给出了保护适应边界,针对部分存在适应性问题的保护,提出了性能优化方案。最后利用PSCAD/EMTDC仿真验证了保护适应性分析的正确性和优化方案的有效性,所得结论可以为我国新型电力系统中继电保护的适应性研究以及优化配置提供理论指导。

计及硅橡胶应力松弛的电缆接头界面压力演变仿真研究

高压电缆中间接头的电气性能与其硅橡胶-交联聚乙烯界面压力的大小密切相关。为探究实际电缆接头界面压力的演变规律,开展了考虑老化过程中硅橡胶应力松弛现象的220 kV电缆中间接头界面压力仿真研究。首先综合电缆接头处物理场特点建立有限元模型,确定了电缆中间接头硅橡胶-交联聚乙烯界面的初始压力分布情况;其次通过力学理论计算的解析解以及预置压力传感器的实测结果对有限元分析结果进行验证;之后结合硅橡胶的热机械老化实验结果,提出一种将老化过程中硅橡胶应力松弛转化为过盈量变化的方法,得到了考虑老化过程中应力松弛与弹性模量变化的多参量有限元分析方法,并成功应用于电缆中间接头绝缘硅橡胶-交联聚乙烯界面压力的分析。分析认为,硅橡胶的老化同时导致应力松弛和弹性模量增大。综合考虑弹性模量和应力松弛的仿真结果表明:对中间接头硅橡胶在100℃、125℃、150℃下分别经过2040 h、1680 h、1200 h热机械老化后,界面压力从0.156 MPa分别下降到0.129 MPa、0.125 MPa、0.107 MPa。这说明应力松弛对于界面压力的影响更显著,界面压力随着老化时间的增加而下降,同时温度升高会显著加快中间接头界面压力的衰减过程。该文研究结果可为提升电缆中间接头设计与运行可靠性提供理论依据。