Influence of span-to-depth ratio on dynamic response of vehicle-turnoutbridge system in high-speed railway

For high-speed railways,the smoothness of the railway line significantly affects the operational speed of trains.When the train passes through the turnout on a long-span bridge,the wheel-rail impacts caused by the turnout structure irregularities,and the instability arising from the bridge's flexural deformation lead to a strong coupling effect in the vehicle-turnout-bridge system.This significantly affects both ride comfort and operational safety.For addressing this issue,the present study considered a long-span continuous rigid-frame bridge as an example and established a train-turnout-bridge coupled dynamic model of high-speed railway.Utilizing a selfdeveloped dynamic simulation program,the study analysed the dynamic response characteristics when the train passes through the turnouts on the bridge.It also investigated the influence of different span-to-depth ratios of the bridge on the vehicle dynamic response when the train passes through the main line and branch line of turnouts and then proposed a span-to-depth ratio limit value for a long-span continuous rigid-frame bridge.The research findings suggest that the changes in the span-to-depth ratio have a relatively minor impact on the train’s operational performance but significantly affect the dynamic characteristics of the bridge structure.Based on the findings and a comprehensive assessment of safety indicators,it is advisable to establish a span-to-depth ratio limit of 1/4500 for a long-span continuous rigid-frame bridge.

Migration and population structure characteristics of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea

Monthly fishery survey data of the small yellow croaker Larimichthys polyactis in the southern Yellow Sea from2003 and 2013 were employed to evaluate the variation in the resource distribution and biological characteristics（especially body length and sex ratio） in the population on a decadal scale.The results indicated that the small yellow croaker migrated from the Shawai fishing ground to the Dasha fishing ground in spring and was mainly distributed in the central and western parts of the Dasha fishing ground in April and May.Larimichthys polyactis in the Dasha fishing ground migrated eastward to offshore wintering grounds in autumn and reached the central Dasha fishing ground in October and November.The small yellow croaker entered the western waters of the Shawai fishing ground in winter.A large number of age 0＋ fish occurred in the Shawai and Jiangwai fishing grounds in October of 2003 and 2013.The body lengths of the spawning stock and wintering stock in 2013 were larger than those in 2003,and the monthly sex ratios（female to male） were significantly less than 1 in both years.The monthly distribution of this fish in the southern Yellow Sea was consistent with a previous finding that ＂the stock migrated between the wintering grounds in the west of Jeju Island and the Lüsi spawning grounds＂ but tended to move more northward,with the spawning grounds extending outward.In the past decade,body length variation experienced a decline after an increase,rather than a steady decrease.The sex ratio in the single-stick stow net showed a tendency to increase over the decade,but was either less than or more than 1 depending on the fishing gear;therefore,further studies should be conducted to determine the sex structure.

FATIGUE DAMAGE CALCULATED BY RATIO-METHOD TO METALLIC MATERIALS WITH SMALL CRACK UNDER UNSYMMETRIC CYCLIC LOADING

Based on the standpoint to take for the crack size also to be a damage variable like the damage variable, by means of the two-directions coordinate system, several new calculation equations on the small crack growth rate are suggested for describing the elastic-plastic behavior of some metallic materials. And the estimation formulas of life are also suggested relative to varied small crack size at each loading history, which is unsymmetric cyclic loading. In the calculation method, as a loaded stress-strain parameter to adopt the ratio with plastic strain range to elastic strain range, and as the material constants using the typical material parameters in damage calculation expression, a new concept of the compositive material constant, which has functional relation with the typical material constants, average stress, average strain, critical loading time is given out. In addition, the fatigue damage of a part of car is put up to calculate as an example, its calculation results are accordant with the Landgraf＇s equation, and calculation precision is more rigorous, so could avoid unnecessary fatigue tests and will be of practical significance on saving times, manpower and capitals, as well as the convenience for engineering applications.

小口径弹丸侵彻双箭头负泊松比蜂窝夹芯结构的弹道特性

通过有限元仿真的方法研究双箭头负泊松比蜂窝夹芯结构的抗侵彻性能,利用小口径弹丸侵彻9种双箭头负泊松比蜂窝夹芯结构,获得双箭头负泊松比蜂窝夹芯结构的弹道特性.通过仿真得到弹丸侵彻过程中姿态变化,建立弹丸侵彻双箭头胞元的动力学仿真模型.仿真模拟表明:当上下面层厚度不变,仅增大芯层双箭头夹角,蜂窝夹芯结构的弹道极限随之降低.对于相同蜂窝夹芯结构,子弹初始速度与结构动能吸收率存在非线性关系,存在某一速度区间使得蜂窝夹芯结构抗侵彻性能最佳.侵彻过程中弹丸周向存在应力分布不均现象,产生非对称作用使弹丸受力环境变化,导致弹丸姿态角改变,最终引起弹丸的侵彻弹道失稳.

构网型与跟网型变流器混联并网系统配比关键影响因素分析

跟网型变流器在弱电网下存在次同步振荡失稳风险,构网型变流器可以改善混联系统在弱电网下次同步频段的稳定性。在新能源场站中可以适当配置构网型单元提高系统稳定性,故构网型/跟网型变流器的配比是影响系统稳定性的关键因素。文中针对构网型与跟网型变流器混联并网系统小干扰稳定性问题,研究了变流器控制系统特性对构网型变流器配比边界条件的影响。首先,建立了构网型与跟网型变流器混联并网系统的状态空间模型,在此基础上分析了构网型/跟网型变流器控制系统各关键参数以及构网型变流器中电压环控制结构对系统稳定性的影响。从保证系统次同步频段小干扰稳定的角度出发,分析了混联系统中构网型变流器配比下限的关键影响因素,得到了各影响因素约束下配比的稳定边界,并利用频域阻抗法对各影响因素的影响机理进行了解释。最后,基于RT-LAB半实物平台验证了理论分析的准确性。

构网型变流器宽短路比范围适应性分析与提升

随着新能源渗透率的增大,电网的复杂度也随之增加,基于构网控制的并网变流器面临电网短路比宽范围变化的并网环境。为了研究构网型变流器并网时潜在的稳定性问题,并提升其在宽短路比范围电网下的适应性,文中建立了考虑功率控制、坐标变换以及电压-电流控制的阻抗模型,通过分析降阶阻抗模型揭示了构网型变流器与强网交互时的失稳机理。进而,提出了混合虚拟阻抗法,在全频段内提升了构网型变流器的并网稳定性以及在复杂电网环境下的适应性。最后,通过实验验证了阻抗特性分析的正确性与所提控制策略的有效性。

阳性淋巴结比率对M_0期非小细胞肺癌患者的预后影响

目的研究阳性淋巴结比率对M_0期非小细胞肺癌的预后影响。方法分析2010—2015年间SEER数据库中M_0期非小细胞肺癌患者的临床数据,应用X-file软件选取阳性淋巴结比率的最佳截断值,运用Cox回归比例风险模型探讨阳性淋巴结比率在M_0期非小细胞肺癌患者中的预后价值,Kaplan-Meier法绘制生存曲线分析两组的生存情况。结果从数据库中提取37001例M_0期非小细胞肺癌患者的数据,X-file筛选出阳性淋巴结比率的最佳截断值为阳性淋巴结比率≤0.07和阳性淋巴结比率>0.07,通过Cox回归比例风险模型得到年龄、性别、人种、T分期、N分期、Grade分级、诊断到治疗的时间(月)、收入、肿瘤大小、肿瘤所在肺叶、有无系统治疗是同时影响M_0期非小细胞肺癌患者总体生存期和肿瘤特异性生存期的独立风险因素,Kaplan-Meier生存曲线显示阳性淋巴结比率≤0.07组的预后要明显优于阳性淋巴结比率>0.07组(P<0.05)。结论阳性淋巴结比率>0.07是M_0期非小细胞肺癌患者预后的独立危险因素,预后预测价值高。

Data processing of small samples based on grey distance information approach

Data processing of small samples is an important and valuable research problem in the electronic equipment test. Because it is difficult and complex to determine the probability distribution of small samples, it is difficult to use the traditional probability theory to process the samples and assess the degree of uncertainty. Using the grey relational theory and the norm theory, the grey distance information approach, which is based on the grey distance information quantity of a sample and the average grey distance information quantity of the samples, is proposed in this article. The definitions of the grey distance information quantity of a sample and the average grey distance information quantity of the samples, with their characteristics and algorithms, are introduced. The correlative problems, including the algorithm of estimated value, the standard deviation, and the acceptance and rejection criteria of the samples and estimated results, are also proposed. Moreover, the information whitening ratio is introduced to select the weight algorithm and to compare the different samples. Several examples are given to demonstrate the application of the proposed approach. The examples show that the proposed approach, which has no demand for the probability distribution of small samples, is feasible and effective.

Influence of filler-bitumen ratio on performance of modified asphalt mortar by additive

When the filler-bitumen ratio of asphalt mortar changes, its adhesion and viscoelasticity will also change, as well as its performance at the high and low temperatures, fatigue durability, and ductility. Thus, the appropriate fillerbitumen ratio directly affects the asphalt mortar＇s performance. This paper tested the physical indexes of the No. 70 matrix asphalt mortar modified by additive Sasobit （SB） and Sasowam （SW） through dynamic shear rheometer and bending beam rheometer under different temperature conditions, and comprehensively analyzed the high-temperature anti-rutting and fatigue performance, low-temperature crack resistance performance, and ductility of asphalt mortar. The results show that ore powder not only can increase the antirutting factor but also can increase the aging resistance of asphalt. SB has better performances than SW at high temperatures. As for the filler-bitumen ratio of asphalt mortar with additive SB, the recommended value is between 0.8 and 1.2, and the value may be a little larger for that with SW.

Graft-to-recipient weight ratio lower to 0.7% is safe without portal pressure modulation in right-lobe living donor liver transplantation with favorable conditions

BACKGROUND: The low graft-to-recipient weight ratio(GRWR) in adult-to-adult living donor liver transplantation(LDLT) is one of the major risk factors affecting graft survival. The goal of this study was to evaluate whether the lower limit of the GRWR can be safely reduced without portal pressure modulation in right-lobe LDLT. METHODS: From 2005 to 2011, 317 consecutive patients from a single institute underwent LDLT with right-lobe grafts without portal pressure modulation. Of these, 23 had a GRWR of less than 0.7%(group A), 27 had a GRWR of ≥0.7%, 【0.8%(group B), and 267 had a GRWR of more than and equal to 0.8%(group C). Medical records, including recipient, donor, operation factors, laboratory findings and complications were reviewed retrospectively. RESULTS: The baseline demographics showed low model for end-stage liver disease score(mean 16.3±8.9) and high percentage of hepatocellular carcinoma(231 patients, 72.9%). Three groups by GRWR demonstrated similar characteristics except recipient body mass index and donor gender. For smallforsize syndrome, there were 3(13.0%) in group A, 1(3.7%) in group B, and 2 patients(0.7%) in group C(P【0.001). Hepatic artery thrombosis was more frequently observed in group A than in groups B and C(8.7% vs 3.7% vs 1.9%, P=0.047). However, among the three groups, graft survival rates at 1 year(100% vs 96.3% vs 93.6%) and 3 years(91.7% vs 73.2% vs 88.1%) were not different(P=0.539). In laboratory measurements,there was no group difference in total bilirubin and albumin. However, prothrombin time was longer in group A within postoperative 1 week and platelet count was lower in groups A and B within postoperative 1 month. CONCLUSION: A GRWR lower to 0.7% is safe and does not need to modulate portal pressure in adult-to-adult LDLT using the right-lobe in favorable conditions including low model for end-stage liver disease score.

Harmonic stochastic resonance-enhanced signal detecting in NW small-world neural network

The harmonic stochastic resonance-enhanced signal detecting in Newman-Watts small-world neural network is studied using the Hodgkin-Huxley dynamical equation with noise. If the connection probability p, coupling strength gsyn and noise intensity D matches well, higher order resonance will be found and an optimal signal-to-noise ratio will be obtained. Then, the reasons are given to explain the mechanism of this appearance.

A High-performance Small Signal Amplifier

According to questions in the design of high quality small signal amplifier, this paper gave a new-type high performance small signal amplifier. The paper selected the operational amplifier of ICL Company and designed a new-type circuit with simple, low cost and excellent performance,

Outcomes of adult patients adopting small-for-size grafts in living donor liver transplantation: A systematic review and meta-analysis

Background: Small-for-size graft(SFSG) has emerged as one of the very contentions in adult-to-adult living donor liver transplantation(LDLT) as a certain graft size is related to recipients’ prognosis. Graftto-recipient weight ratio(GRWR)≥0.8% was considered as a threshold to conduct LDLT. However, this also has been challenged over decades as a result of technique refinements. For a better understanding of SFSG in practice, we conducted this meta-analysis to compare the perioperative outcomes and long-term outcomes between patients adopting the grafts with a lower volume(GRWR < 0.8%, SFSG group) and sufficient volume(GRWR ≥ 0.8%, non-SFSG group) in adult-to-adult LDLT. Data sources: The studies comparing recipients adopting graft with a GRWR < 0.8% and ≥ 0.8% were searched by three authors independently in Pub Med, Web of Science, Embase, the Cochrane Library, MEDLINE and Google Scholar databases until September 2018 and data were analyzed by RevMan 5.3.5. Results: Sixteen studies with a total of 3272 subjects were included in this meta-analysis. In terms of small-for-size syndrome(SFSS), no significant difference was found in subjects enrolled after year 2010(before 2010, OR = 3.00, 95% CI: 1.69–5.35, P = 0.0002;after 2010, OR = 1.23, 95% CI: 0.79–1.90, P = 0.36;P for interaction: 0.02). There was no significant difference in operative duration, blood loss, cold ischemia time, biliary complications, acute rejection, postoperative bleeding, hospitalization time, perioperative mortality, and 1-, 3-and 5-year overall survival rates between two groups. Conclusions: This meta-analysis suggested that adopting SFSG in adult LDLT has comparable outcomes to those with non-SFSG counterparts since 2010.

Assessment of Sedimentation Impacts on Small Dams—A Case of Small Reservoirs in the Lotsane Catchment

Sedimentation is a major problem for agricultural dams in Botswana, as it reduces the storage capacity and life span of the reservoirs. The process of sedimentation starts from day one of the impounding of water in any given reservoir. Even though a provision is made for every reservoir during planning for a certain storage capacity, specifically for sediment deposition, called dead storage, a major portion of the sediment gets deposited for many years of the reservoir’s life in areas other than the dead storage, and this trend cannot be reversed at easy cost. This study is aimed at the analysis of prevailing sedimentation processes in the nearby dozens of dams found in the Lotsane catchment located within the Limpopo Basin of Botswana, and focuses on assessment of annual sedimentation rate. A spatial analysis and modelling study was conducted based on the Revised Universal Soil Loss Equation and GIS to determine sediment yield and degree of impact of each reservoir for a given landscape, rainfall and catchment heterogeneity. Field observations and soil sampling were carried out in order to determine the factors that lead to reservoir sedimentation. Spatial data on the dams in Lotsane catchment were also collected from Ministry of Agriculture, which were used for ground-truthing, GIS-based calculations and model validation. The average sediment rate and sediment delivery ratio were found to be 1.74 t/ha/year and 81%, respectively. These are useful parameters to estimate service life of the dams and plan remedial measures related to sedimentation problems.

Analysis of Factors That Affect the Long-Term Survival of Small Businesses in Pretoria, South Africa

The paper is based on a 5-year follow-up study (2007 to 2012) of a random sample of 349 small business enterprises that operate in and around the city of Pretoria in South Africa. Data weregathered from each of the businesses on socio economic factors that were known to affect the long-term survival of small businesses. The objective of the study was to identify and quantify key predictors of viability and long-term survival. Pearson’s chi-square tests of associations, binary logistic regression analysis and the Cox Proportional Hazards Model were used for screening of variables, and for estimating odds ratios and hazard ratios of key predictors of viability and long-term survival. The study found that 188 of the 349 businesses that took part in the study (54%) were not viable, and that the long-term survival and viability of small businesses were adversely affected by lack of entrepreneurial skills, lack of supervisory support to newly established businesses, and inability to operators running newly established businesses to acquire relevant vocational skills.

Optimal Deployment Density for Maximum Coverage of Drone Small Cells

With the proliferation of small and mini drones, Drone Small Cells(DSCs) can cooperative multiple drones to provide communication service for ground users as emergency means or supplementary ones of traditional terrestrial cellular networks. In this paper, we study the fundamental problem of optimizing the deployment density of DSCs to achieve the maximum coverage performance. Most related works do not consider cumulative inter-cell interference when studying the coverage performance of DSCs. First, we derive an approximate and closed-form expression of the cumulative inter-cell interference which comes from both probabilistic Line-of-Sight(Lo S) and Non-Line-of-Sight(NLo S) links. Then, we analyze the coverage performance of DSCs and derive the transcendental function of optimal deployment density to obtain the maximum coverage. Last, we propose an algorithm to get the optimal deployment density with low complexity. We conduct both field experiments and Matlab simulations to verify the correctness of theoretical analysis. In addition, we show the impact of some factors on the relation between the deployment density and coverage performance through extensive numerical simulations.

Rosuvastatin Reduces Plasma Small Dense Ldl-Cholesterol Predominantly in Non-Diabetic Hypercholesterolemic Patients

Aims: Small dense LDL (sdLDL) cholesterol is considered a cardiovascular risk. Our purpose in this study was to evaluate the efficacy of rosuvastatin in reducing sdLDL and large buoyant LDL (lbLDL-C) in hypercholesterolemia. Methods: Fifty-six patients with a mean baseline LDL-cholesterol (LDL-C) concentration of 173.9 ± 40.5 mg/dL were treated with rosuvastatin 2.5 mg/day for 12 weeks. LDL-C, sdLDL-C, and apolipoprotein (apo) B were assessed and l lbLDL-C was calculated (LDL-C minus sdLDL-C). Results: After 12-week treatment with rosuvastatin 2.5mg, sdLDL-C and lbLDL-C were significantly reduced from 62.1 ± 23.8 mg/dL to 34.0 ± 13.4 mg/dL, p <0.001 and 112.7 ± 34.9 mg/dL to 77.2± 29.2 mg/dL, p < 0.001 respectively, and sdLDL-C/lbLDL-C ratio and apo B also decreased significantly, from 0.36 ± 0.02 to 0.32 ± 0.02, p < 0.005 and 134.2 ± 4.3 to 93.6 ± 3.5 mg/dl, p < 0.001, respectively. In diabetic subjects there was significant correlation between percent reductions in the plasma triglyceride and sdLDL-C/ lbLDL-C ratio (r = 0.58, p < 0.005), but not between the percentage decrease in plasma triglyceride and sdLDL-C. Conclusions: Treatment with rosuvastatin is associated with significant reduction in sdLDL, lbLDL and sdLDL/lbLDL ratio.

Effects of Bearing Type on Seismic Response of Small Base Isolation System Using Friction Bearings

In this study, dynamic characteristics of the small base isolation system using new friction bearings are investigated by excitation experiment, and compared to other one using previous bearings. Peak amplitude of the acceleration response waves on the small base isolation system is decreased to about 10%-25% compared to the input waves. Also root mean square amplitude is decreased to about 10%-40%. In case of the ball embedded a cylindrical sponge, the new bearing, the damping ratio increases with increasing width of the cylindrical sponge. The natural frequency does not change. On the other hand, in case of the marble plate that is previous bearing, the damping ratio increases with increasing curvature radius of the marble plate, the natural frequency also increases. Therefore, the small base isolation system using new friction bearing provides better performance. The responses of the base isolation system indicate nonlinier effects by friction force.

Piketty’s Capital-Income Theory Reconsidered for a Small Open Economy with Increasing Savings Rate

Since Piketty offered a new view of capital/income ratio, numerous attempts have been made to examine the relationship between return on capital, economic growth and the capital/income ratio. This paper attempts to shed new light on this field. More precisely, following recent literatures that pay attention to dynamics of external balance sheets of countries, we examine if Piketty’s results for large countries are robust for a country that takes the world rate of return on capital as given and whose savings rate increases gradually from negative value. It is revealed that for such a country, (1) Kuznets curve is drawn and (2) capital/income ratio decreases in accordance with a rise in savings rate and return on capital.

颗粒表面粗糙度对材料小应变动力特性的影响

土体的小应变剪切模量和阻尼比是表征土体动力学特性的重要参数,不仅受到土体密实度和应力状态的影响,还受到土体颗粒级配、形状等颗粒特征的影响。颗粒表面粗糙度是重要的土体颗粒特征之一,然而关于颗粒表面粗糙度对土体小应变动力特性影响的研究较为匮乏。利用能量注入式虚拟质量共振柱设备,系统地测试了颗粒表面粗糙度不同的玻璃珠所成试样的小应变剪切模量和阻尼比;采用三维干涉显微镜测量了玻璃珠的表面粗糙度,并量化表征粗糙度对试样小应变剪切模量和阻尼比的影响。试验结果表明,在相同孔隙比和有效应力条件下,试样的小应变剪切模量随颗粒表面粗糙度增大而减小,而小应变阻尼比受颗粒表面粗糙度影响的规律不明显。研究结果表明,当材料的颗粒形状、级配等因素相近时,颗粒表面粗糙度对材料小应变剪切模量的影响不应被忽略。