基于安全换道理论高架出口匝道地面附加车道长度研究

随着我国城市化进程趋向大城市化与城市郊区化发展,城市跨度逐渐增大。城市高架快速路作为城市道路路网的重要组成部分,是城市道路路网的“大动脉”。针对目前我国大都将出口匝道落地点距离交叉口较近的位置,本文建立路段型出口匝道建设模型,并对模型长度指标进行研究。

基于仿真分析的快速路左入加速车道长度取值研究

随着交通量的迅猛增长,快速路匝道影响区成为交通运行效率和安全的主要瓶颈。快速路出入口匝道通常采用右侧布置的形式,但受地面路况与施工可行性制约,也会采用左侧布置形式,对交通设计参数提出了更高要求。通过航拍实地采集南京机场快速路的相关交通流数据,研究车道数量、加速段长度及渐变段长度等对合流区交通运行效率和安全的影响,得到左入加速车道长度推荐值。结果表明:双车道匝道布置形式虽能弥补设计通行能力不足的问题,但出于安全性考虑,仍建议采取单车道匝道;主路限速为80 km/h的左入加速车道最小长度应不小于260 m,若进一步增加车道长度,对交通冲突数的影响变化不大,但可进一步降低车辆平均行程延误,合流区交通运行效率在车道长度增加至380 m后基本达到最高。

广西铁山港跨海大桥长度对环境影响的研究

为研究兴建铁山港跨海大桥对水文环境的影响，科学地确定大桥的合理长度，采用二维潮流数值模型对潮位、流场及纳潮量等的变化进行了数值计算，经优化提出推荐方案。

纳米级钼制品发展迅速

纳米级钼制品是以0.1-100纳米为长度研究钼分子世界的高科技产品。纳米钼科技包括三个研究领域:纳米级钼材料、纳米级钼器件。

An Experimental Investigation on Solid Acceleration Length in the Riser of a Long Circulating Fluidized Bed

Systematic experimental work was conducted to investigate the solid acceleration length in a 16m long circulating fluidized bed riser with fluid cracking catalyst particles over a wide range of operating conditions. A more feasible method is proposed to determine the acceleration length from the measured axial profiles of pressure gradient (or apparent solid holdup). With this new method and large amount of experimental data, a clear picture on the variation of the acceleration length with both solid circulating rate and superficial gas velocity is obtained.It is found that the acceleration length increases generally with increasing solid flow rate and/or decreasing gas velocity. However, the trend in variation of the acceleration length with operating conditions are quite different in different operation ranges. Reasonable explanations are suggested for the observed variation patterns of acceleration length.

Development of Liquid Slug Length in Gas-Liquid Slug Flow along Horizontal Pipeline: Experiment and Simulation

The liquid slug length distribution is crucial for designing the downstream processing system with mul-tiphase pipeline. Experiments were conducted in a 133m long horizontal test loop. The measurements were per-formed by conductivity probes to determine the liquid slug length distribution. The data covered both the slug and plug flow regimes. From experimental results, the mean liquid slug lengths were relatively insensitive to gas and liquid flow rates in the higher mixture velocity range. But in the lower mixture velocity range, the mean liquid slug length decreased and then increased with mixture velocity. It shows that the development length of slug flow was longer than x/D=1157. A slug tracking model was adapted to study the evolution of liquid slug length distribution in a horizontal pipeline. In the present model, the wake effect of elongated bubble and the pressure drop due to accel-eration are taken into account and random slug lengths are introduced at the entrance. The results of the model are compared with the measured slug length distributions of slug flow regime. It shows that the predicted mean and maximum slug lengths are in agreement with the experimental data at x/D=1157 and the form of the slug length distributions is also predicted well by the model.

Solar light,seawater temperature,and nutrients,which one is more important in affecting phytoplankton growth?

Based on research results on the impacts of solar light,seawater temperature,and nutrient available to phytoplankton growth and changes in phytoplankton physiology and assemblage,we discussed the order of influence of these factors.By clarifying the mechanisms and processes of the impacts by these factors,we have determined the rising order of the importance as solar light,seawater temperature,and nutrient silicon (Si).Therefore,for human interests in sustaining economic development,the first thing to be considered is the input of nutrient Si into the ocean,followed by seawater temperature change.

Immunohistochemical evaluation of vitamin D receptor(VDR) expression in cutaneous melanoma tissues and four VDR gene polymorphisms

Objective:Vitamin D receptor(VDR)mediates vitamin D activity.We examined whether VDR expression in excised melanoma tissues is associated with VDR gene(VDR)polymorphisms.Methods:We evaluated VDR protein expression(by monoclonal antibody immunostaining),melanoma characteristics,and carriage of VDR-Fok I-rs2228570(C>T),VDR-Bsm I-rs1544410(G>A),VDR-ApaI-rs7975232(T>G),and VDR-TaqI-rs731236(T>C)polymorphisms(by restriction fragment length polymorphism).Absence or presence of restriction site was denoted by a capital or lower letter,respectively:"F"and"f"for Fok I,"B"and"b"for Bsm I,"A"and"a"for ApaI,and "T"and"t"for TaqI endonuclease.Seventy-four Italian cutaneous primary melanomas(52.1±12.7 years old)were studied;51.4% were stage Ⅰ,21.6% stage Ⅱ ,13.5% stage Ⅲ,and 13.5% stage Ⅳ melanomas.VDR expression was categorized as follows:100% positive vs.<100%;over the median 20%(high VDR expression)vs.≤20%(low VDR expression);absence vs.presence of VDR-expressing cells.Results:Stage I melanomas,Breslow thickness of<1.00 mm,level II Clark invasion,Aa heterozygous genotype,and AaTT combined genotype were more frequent in melanomas with high vs.low VDR expression.Combined genotypes BbAA,bbAa,AATt,BbAATt,and bbAaTT were more frequent in 100%vs.<100%VDR-expressing cells.Combined genotype AATT was more frequent in melanomas lacking VDR expression(odds ratio=14.5;P=0.025).VDR expression was not associated with metastasis,ulceration,mitosis>1,regression,tumor-infiltrating lymphocytes,tumoral infiltration of vascular tissues,additional skin and non-skin cancers,and melanoma familiarity.Conclusions:We highlighted that VDR polymorphisms can affect VDR expression in excised melanoma cells.Low VDR expression in AATT carriers is a new finding that merits further study.VDR expression possibly poses implications for vitamin D supplementation against melanoma.VDR expression and VDR genotype may become precise medicinal tools for melanoma in the future.

Numerical investigation on critical length of impermeable plate below underwater pipeline under steady current

This study proposes a new approach in which an impermeable plate is placed under the pipeline to prevent the local scour around the pipeline.In order to understand the performance of this approach,the finite volume method(FVM) and volume of fluid(VOF) method are adopted to simulate the flow field around the pipeline.The pressure distribution along the sandy bed surface is obtained by considering the variation of water surface.Furthermore,the effects of water depth,unidirectional and bidirectional impermeable plates on pressure difference are discussed.The seepage flow field of sandy bed near underwater pipeline is numerically simulated using the laminar and porous media model.On this basis,the effect of the impermeable plate length on hydraulic gradient is investigated and the critical length of impermeable plate is obtained.The simulated results show that when the water depth is smaller than 5.00D(D is the diameter of pipeline),the effect of the water depth on the pressure difference is remarkable.The pressure differences between two endpoints of both the unidirectional and bidirectional plates decrease with the increase of the plate length.The variations of the pressure differences for both the unidirectional and bidirectional plates are similar.With the increase of plate length,the hydraulic gradient decreases and the piping at the seepage exit is avoided effectively as long as it reaches a certain length.Such a critical length of the plate decreases with the increase of the water depth.When water depth is larger than 4.00D,the effect of the water depth on the critical length is small.For the same water depth,the critical length of impermeable plate increases with the increase of the dimensionless flow parameter.Numerical simulation results are in good agreement with the available experimental measurements.