基元事件分析法

航空事故的发生是航空系统存在缺陷的反映。为了发现、分析系统的缺陷，人们发展了一些事故分析统计方法。“基元事件分析法”不仅分析了事故的原因，而且指出了预防这类事故的办法，文章论述了该方法的结构特点。

克雷伯氏杆菌代谢网络的基元模式优化分析!

对克雷伯氏杆菌代谢甘油产1,3-丙二醇的代谢网络进行了基元模式分析,并结合不同发酵阶段下的胞外代谢产物积累速率,以生物量最大化为目标函数,应用线性规划对其微氧和厌氧条件下的代谢网络进行优化分析,得出不同发酵阶段各基元模式的通量值。结果表明:微氧条件下不同发酵阶段生物量合成的最优基元模式相同;厌氧条件下延迟期和稳定期的最优基元模式相同,对数期的最优基元模式不同;各最优基元模式对1,3-丙二醇合成贡献较大;氧化磷酸化途径在维持NAD+/NADH2和ATP/ADP平衡中起重要作用,更有利于生物量和1,3-丙二醇的合成。

基于基元自相关图的图像检索

提出一种新颖的颜色特征描述子,它能够在基元的基础上表达颜色信息的空间相关性。首先将彩色图像量化为64种颜色,并且对图像进行基元分析,最后利用统计信息来描述图像特征。实验结果表明,基元自相关图的性能优越于颜色直方图和颜色自相关图;基元自相关图的计算复杂度和特征维数均明显地小于颜色自相关图。

航空人为差错事故/事件分析(ECAR)模型研究

为深入研究航空人为差错事故/事件的影响因素,以人为差错相关理论为基础,对比分析几种典型的人为差错分析模型;通过借鉴ECCAIRS分析框架,并在基元事件分析(EEAM)逻辑和CCAR396部的分类方法基础上,构建航空人为差错事故/事件分析(ECAR)模型,它从事件层、描述层、原因层和组织因素与改进建议层,分析航空事故和不安全事件的人为差错。此外,还将组织因素概念引入该模型。

任意波面的基元波分解

提出了对任意波面以不同波数 (长 )基元波叠加表出的方法 ,在数学上它可归于函数展开或逼近 .当给定 K个点上的波面值后 ,利用所提出的基元波分解形式 ,可以由最小二乘法确定相应的系数值 .通过对几种典型问题 (其中包括水下点源兴波 )的算例表明此方法是有效的 .

基于事故/事件的大型客机“飞行员操作程序”分析

收集近20年国内外大型客机事故/事件信息,设计筛选流程,确定与飞行员操作程序相关的事故/事件,在此基础上,采用基元事件分析法对这些事故/事件进行分解,并对国内外事故致因进行对比分析,试图发现其中可能蕴藏的深层次原因,为设计大型客机飞行员操作程序和提升民航安全运行水平提供支持。

小球藻产三酰甘油过程的代谢途径分析

以基因工程强化微藻三酰甘油(TAG)积累是实现微藻生物柴油应用化的途径之一。为进行有效的基因工程操作,研究分析了微藻代谢网络,以找出其中对TAG合成重要的反应。构建了异养及自养条件下小球藻产TAG过程核心代谢网络。采用改进CASOP(Computational approach for strain optimization aiming at high productivity)法分析网络中各反应的重要度。结果表明,主要的关键反应包括脂肪酸和TAG的合成反应以及提供NADPH的反应,特别是将NADH转化为NADPH的反应。此外,分析结果也部分解释了环境压力对TAG积累的作用。

基于ISM—CRITIC法的通用航空可控飞行撞地影响因素分析

为了研究通用航空可控飞行撞地的影响因素,提出针对性的预防措施,采用基元事件分析法对中国民航安全办公室不安全数据库中2006—2015年间发生的30起通用航空可控飞行撞地事件进行分析,建立通用航空可控飞行撞地影响因素体系;运用解释结构模型对影响因素进行两两对比分析,建立3层阶梯有向模型;运用CRITIC法计算各影响因素权重并排序。结果表明:影响通用航空可控飞行撞地事件的表层直接原因分别是注意力分配不当、违反标准运行程序、安全意识淡薄、应急能力弱、导航设备失效、发动机失效、其他天气意外、飞行保障不利和组织混乱;中层间接原因分别是驾驶技能不足、航前准备不足、机组资源管理欠缺、地形复杂、能见度和光线刺激;深层根本原因分别是疲劳驾驶、公司违规和违法组织飞行;影响通用航空可控飞行撞地事件发生的主要因素分别是飞行保障不利和组织混乱、航前准备不足、安全意识淡薄、驾驶技能不足和违反标准运行程序。

Discrimination for minimal hepatic encephalopathy based on Bayesian modeling of default mode network

In order to classify the minimal hepatic encephalopathy （MHE） patients from healthy controls, the independent component analysis （ICA） is used to generate the default mode network （DMN） from resting-state functional magnetic resonance imaging （fMRI）. Then a Bayesian voxel- wised method, graphical-model-based multivariate analysis （GAMMA）, is used to explore the associations between abnormal functional integration within DMN and clinical variable. Without any prior knowledge, five machine learning methods, namely, support vector machines （SVMs）, classification and regression trees （ CART ）, logistic regression, the Bayesian network, and C4.5, are applied to the classification. The functional integration patterns were alternative within DMN, which have the power to predict MHE with an accuracy of 98%. The GAMMA method generating functional integration patterns within DMN can become a simple, objective, and common imaging biomarker for detecting MIIE and can serve as a supplement to the existing diagnostic methods.

Specific HLA-DQB1 alleles associated with risk for development of hepatocellular carcinoma:A meta-analysis

AIM:To evaluate the association of human leukocyte antigen(HLA)-DQB1 alleles with hepatocellular carcinoma(HCC) through meta-analysis of published data.METHODS:Case-control studies on HLA-DQB1 allele association with HCC published up to January 2010 were included in the analyses.The odds ratios(ORs) of HLADQB1 allele distributions in HCC patients were analyzed and compared with healthy controls.The meta-analysis software REVMAN 5.0 was applied for investigating heterogeneity among individual studies and for summarizing all the studies.A meta-analysis was performed using fixed-effect or random-effect methods,depending on the absence or presence of significant heterogeneity.Seven case-control studies containing 398 cases and 594 controls were included in the final analysis.RESULTS:Among the five family alleles,two(DQB1*02 and DQB1*03) were found to be significantly associated with the risk of HCC.The combined OR for the association of DQB1*02 and DQB1*03 allele with the risk for HCC was 1.78(95% CI:1.05-3.03,P = 0.03) and 0.65(95% CI:0.48-0.89,P = 0.007),respectively.Among the 13 specific alleles,two(DQB1*0502 and DQB1*0602) were significantly associated with risk of HCC.The combined OR for the association of DQB1*0502 and DQB1*0602 allele with the risk for HCC was 1.82(95% CI:1.14-2.92,P = 0.01) and 0.58(95% CI:0.36-0.95,P = 0.03),respectively.No significant association was established for other HLA-DQB1 family alleles and specific alleles.CONCLUSION:Our results support the hypothesis that specific HLA-DQB1 allele families and alleles might influence the susceptibility or resistance to HCC,although it needs further investigations.

Failure of circular shaft subjected to hydraulic uplift: Field and numerical investigation

A working shaft for pipe-jacking is going to be excavated into a sand stratum with high hydraulic pressure in Guangzhou, China. A newly assembled pre-stressed retaining system has been proposed to support the shaft for its efficiency, safety and sustainability. Full-scale field tests and numerical analysis were conducted to analyze the base failure of the circular shaft with confined water. The failure process of the shaft was observed on site. The construction process of step-by-step excavation of shaft and layer-by-layer assembly of pre-stressed structure was simulated in detail. Simulation results agree well with the phenomenon on site. The base failure modes present that tensile damage generates at the center of the base due to non-uniform uplift and shear failure occurs along the soil-structure interface. The effects of shaft size and confined water head were also discussed. As a result, a critical ratio of diameter to shaft depth is put forward to assess the size effect of circular shaft. A conclusion that the soil strength should be partially considered in anti-inrushing safety factor calculation is drawn by analysis and comparison of various calculation methods. This research provides a reference for the base stability evaluation of similar shaft subjected to hydraulic uplift.

FE Analysis of Longitudinal Dynamic Response of Subgrade in Bridge-Subgrade Transition of Heavy Haul Railway

With the increase of axle load and the train speed, dynamic interaction of train-track system becomes so exacerbated that the deformation and dynamic response of subgrade are more aggravated. The differential settlement will be created in bridge-embankment transition section under such dynamic action, and an adverse effect on the train operation safety can be caused. Meanwhile, differential settlement will produce additional dynamic effect when high-speed trains go through the transition between bridge-embankment. Such dynamic action will aggravate the differential settlement and subgrade damage. This paper applies the methods of field test and finite-element to systematically study the dynamic response characteristics of subgrade in bridge-embankment transition section of heavy haul railway under dynamic load for the first time. This research is focused on the analysis of influence of the different axle load, train speed, filled soil modulus, etc.. At last, the dynamic response rules are systematically summarized.

Aseismic strengthening techniques of Chinese typical stele relics:A case study of Xi'an Beilin

In order to improve the seismic performance of Chinese traditional stele relics, a suitable aseismic strengthening method of Chinese traditional stele relics is proposed. Taking the typical stele relic in Xi＇an Beilin as an example, the on-site investigations were carried out to obtain the actual geometric size and damage state of the stele relic. Then, the structural performance of the stele relic was analyzed by the finite element software ANSYS. Finally, the two different aseismic strengthening methods of the traditional stele relic are proposed and comparatively analyzed. The results show that in addition to the common problems, such as weathering, and cracks, etc, earthquakes seriously threaten the structural safety of stele relics. Under the rarely-occurring earthquake of eight degree, the unstrengthened stele relic will be overturned, and many cracks will occur at the connection area of stele body and stele pedestal. When the stele relic is strengthened by the stainless angle steel strengthening method, the stele relic will not be overturned, but some cracks will occur at the connection area of stele body and stele pedestal. When the stele relic is strengthened by the base isolation strengthening method, the stele relic will not be overturned, and no cracks will occur at the connection area of stele body and stele pedestal. Therefore, the aseismic strengthening effect of the base isolation strengthening method is obviously better than that of the stainless angle steel strengthening method, and this method is a suitable aseismic strengthening method of Chinese traditional stele relics.

Three-dimensional finite element analysis on effects of tunnel construction on nearby pile foundation

A three-dimensional finite element simulation was carried out to investigate the effects of tunnel construction on nearby pile foundation.The displacement controlled model (DCM) was used to simulate the tunneling-induced volume loss effects.The numerical model was verified based on the results of a centrifuge test and a set of parametric studies was implemented based on this model.There is good agreement between the trend of the results of the centrifuge test and the present model.The results of parametric studies show that the tunnelling-induced pile internal force and deformation depend mainly on the pile?tunnel distance,the pile length to tunnel depth ratio and the volume loss.Two different zones are separated by a 45° line projected from the tunnel springline.Within the zone of influence,the pile is subjected to tensile force and large settlement;whereas outside the zone of influence,dragload and small settlement are induced.It is also established that the impact of tunnelling on a pile group is substantially smaller as compared with a single pile in the same location with the rear pile in a group,demonstrating a positive pile group effect.

Analysis model for deformation mechanism of strip foundation of building:Considering shear effect of down-crossing tunnel under excavation

When the tunnel underpasses through the building,it will cause deformation and even damage to the buildings above,and the deformation of building foundation is the key to building safety.Based on the engineering case,the theoretical analysis was employed to evaluate the influence of shield tunnel underpass construction on the stability of the building,and the optimal tunneling parameters in the field construction have been obtained through the verified theoretical model and parameter analysis.First,the strip foundation of the building was simplified to the Timoshenko beam,which was taken into account the shear effect,and then the deformation displacement of the soil at the same place of strip foundation was applied to the simplified Timoshenko beam.Finally,the numerical solution of the displacement of the strip foundation was obtained by using the finite element method and verified its reliability using Euler-Bernoulli beam theoretical model,field monitoring data,and numerical simulation.Parameters analysis for the deformation and internal force of strip foundation under different types of shield machine tunneling parameters showed that the influence of the pressure of shield excavation chamber,thrust of shield,and driving speed played an important role in the deformation of the building’s strip foundation and internal force.

Empirical Analysis on Influence Mechanism of Cohesiveness and Collective Efficacy of Virtual Community Based on Triadic Reciprocal Determinism

The virtual community has become a new life style as for human,but the public's acceptance is relatively low at present.So the research about the mechanism of the influence on the cohesiveness and the collective efficiency in virtual community has an important theoretical value and practical value.In the paper,the key variables that affect virtual community cohesiveness are extracted from two aspects—self-perception of community members and community environment,and the influence mechanism model of virtual community cohesiveness and community collective efficiency is established based on Triadic Reciprocal Determinism.By means of the questionnaire on the community members and the empirical analysis,the key factors influencing cohesiveness of virtual community are brought up,as well as the mechanism that the four dimensions of cohesiveness work,on collective efficiency.According to the results,it is practically meaningful that the problems and insufficiency in the operation of existing virtual community are discovered,which guides the operating managers of the virtual community to formulate operation policy of the virtual community for operating managers to develop strategies.

Estimation of Heights of Soil Plug Inside Bucket Foundations During Suction Penetration by Deformable Discrete Element Modeling

The soil plug phenomenon involving the rising of the surface soil inside the bucket chamber under the suction pressure and seepage forces was simulated and calculated by deformable discrete element method (DDEM) models. The seepage forces, the effective gravity of soil, the friction on the chamber wall and the suction inside the chamber are considered as the main external forces of DDEM specimen. Three typical types of soil (silty clay, silt and sand) in the Bohai Sea are set as the main environmental conditions in the formation process of soil plug. It is found that the heights of soil plug simulated by DDEM models are 161.85 mm in silty clay, 125.22 mm in silt and 167.56 mm in sand, which are close to model test results and higher than those estimated by discrete element method (DEM). DDEM is an effective method to estimate and predict the heights of soil plug before suction penetration of bucket foundations on site.

Distribution of stress and strain between adjacent particles in particulate reinforced metal matrix composites

The distribution of stress and strain between adjacent particles in particulate reinforced metal matrix composites wasinvestigated using cohesive zone models. It is found that the strain of the composite is concentrated in the matrix, and there is aregion with higher strain along the loading path, which can promote the formation of a void near the particles pole. The stress andstrain in matrix near the particles gradually decrease with the increase of the distance between particles. And it is calculated that thereis a critical distance within which the stress and strain fields of the neighboring particles can influence with each other. This criticaldistance increases with the increase of particle size. It is also found that the angle between the tensile direction and the center line ofparticles plays an important role in the stress and strain distribution. The model with the angle of 0° has the greatest influence on thedistribution of stress and strain in the matrix, while the model with the angle of 45° has the least influence on the distribution of stressand strain in the matrix.

3D finite elements analysis of vertically loaded composite piled raft

In recent years,a new type of foundation named composite piled raft foundation (also called long short composite piled raft) has been developed.Where designing shallow foundations would mean unacceptable settlement,or other environmental risks exist which could impair the structure in the future,composite piled raft foundations could be used.Finite element method was applied to study the behavior of this type of foundation subjected to vertical loading.In order to determine an optimal pile arrangement pattern which yields the minimum settlement,various pile arrangements under different vertical stress levels were investigated.Results show that with increasing the vertical stress on the raft,the effectiveness of the arrangements of short and long piles become more visible.In addition,a new factor named "composite piled raft efficiency" (CPRE) has been defined which determines the efficiency of long short piles arrangement in a composite piled raft foundation.This factor will increase when short piles take more axial stresses and long piles take less axial stresses.In addition,it is found that the changes in settlements for different long short piles arrangement are in a well agreement with changes in values of CPRE ratio.Thus,CPRE ratio can be used as a factor to determine the efficiency of piles arrangements in composite piled raft foundation from the view point of reducing raft settlements.

Differential uplift and settlement between inner column and diaphragm wall in top-down excavation

Top structure and basement will confront the risk of being damaged on account of large stress and strain fields incurred by differential uplift and settlement between inner column and diaphragm wall in top-down method. Top-down excavation of the Metro Line 10 in Shanghai was modeled with finite element analysis software ABAQUS and parameters of subsoil were obtained by inverse analysis. Based on the finite element model and parameters, changes in the following factors were made to find more effective methods to restrain differential uplift and settlement: length of diaphragm wall, thickness of jet-grouting reinforcement layer, ways of subsoil reinforcement, sequence of pit excavation, connection between slabs and diaphragm wall or column and width of pit. Several significant results are acquired. The longer the diaphragm wall is, the greater the differential uplift between column and diaphragm wall is. Rigidity of roof slab is in general not strong enough to keep diaphragm wall and column undergoing the same uplift during excavation; Uplift at head of column and differential uplift between column and diaphragm wall decrease when subsoil from-16.6 to-43 m in pit is reinforced through jet-grouting. But, as excavation proceeds to a lower level, benefit from soil reinforcement diminishes. During the process applying vertical load, the larger the depth of diaphragm wall is, the smaller the settlement is at head of column and diaphragm wall, and the greater the differential settlement is between column and diaphragm wall. When friction connection is implemented between column, diaphragm wall and floor slabs, uplifts at head of column and diaphragm wall are larger than those of the case when tie connection is implemented, and so does differential uplift between column and diaphragm wall. The maximum deflection of diaphragm wall decreases by 58% on account of soil reinforcement in pit. The maximum deflection of diaphragm wall decreases by 61.2% when friction connection is implemented instead of tie connection.