绿化带对交通噪声衰减效果对比分析

选取福州市三环路的绿化带进行实验,主要以樟树与灌木、黄槐与灌木、刺桐与灌木、羊蹄甲与灌木绿化带作为研究对象,研究不同树种的郁闭度,在不同噪声强度下,各树种搭配衰减效果,进一步分析郁闭度与单位长度绿化带衰减效果的相关性。结果表明:刺桐与樟树绿化带郁闭度较高,黄槐次之,羊蹄甲郁闭度最低;黄槐的降噪效果最为明显,其次是樟树与刺桐,羊蹄甲的降噪效果最差,且噪声声级越高,绿化带衰减效果也越理想;郁闭度与噪声衰减值关系相关性较差,郁闭度需结合树木枝叶相关特征来分析整个树木的空间立体结构,进而建立与衰减效果之间关联。     

An innovative model to estimate the accessibility of a destination by public transport

Accessibility is a valuable indicator for assessing the effectiveness of a transport network. Nevertheless, its analysis can lead to very heterogeneous results depending on the method adopted, thus still struggling to be considered by policy makers and in planning processes. This article contributes to the development of an accessibility analysis as a planning tool, by proposing an alternative model to estimate the relative accessibility of a destination by public transport (PT). Indeed, PT is a mobility paradigm that has been supported to reduce the negative externalities produced by private transport, especially in environmentally fragile contexts. The model includes a set of eleven factors affecting public transport operation which refer to four macro topics: connectivity, multimodality, tariff/ticketing, and info-mobility. They are integrated into a Public Transport Accessibility index which analyses a series of nodes along a route and detects the progressive variation of accessibility. Eventual shifts are highlighted, including information about the factors feeding them. The model is tested for the Lana-Zurich (IT-CH) connection, showing how the most relevant issues are caused by difficulties in the transnational and transregional integration of the services. Through this process, the model aims at backing policy makers in the detection and understanding of public transport barriers and related causes.     

路面平整度对标线逆反射测试的静态影响

为了明确路面平整度对道路交通标线逆反射亮度系数测试的静态影响机理，减小工程应用中的误差，针对手持式逆反射测量仪和车载式逆反射测量仪，在忽略仪器测量基准平面偏差的前提下，参考公路工程质量检验评定标准中路面平整度“最大间隙”的要求，分析路面平整度影响下的现场测试几何条件，提出逆反射标线板设计方案及其参考值赋值方法，开展手持式逆反射测量仪和车载式逆反射测量仪的测量偏差试验。在逆反射标线板参考值赋值过程中发现，反射照度随着入射角的增大而降低，同逆反射亮度系数随入射角变化产生的变化趋势呈非线性关系。手持式逆反射测量仪和车载式逆反射测量仪无法识别入射角产生的偏差，仅通过测得的反射信号强度计算得到逆反射亮度系数，因此其变化趋势和反射照度随入射角变化的趋势相近。入射角偏差对车载式逆反射测量仪测量结果引入的相对不确定度u_r22为4.8%，对开放光路的手持式逆反射测量仪测量结果引入的相对不确定度u_r12为7.4%。研究结果表明：入射角偏差对道路交通标线逆反射亮度系数的现场测量结果影响较大，在现场测量时应注意调整仪器的放置位置；车载式逆反射测量仪较手持式逆反射测量仪抗干扰的能力更强，在路面平整度较差的路段选用车载式逆反射测量仪并进行数据修正能够提高测量结果的可信度；建议车载式逆反射测量仪选取9 m内最大高程差不超过7 mm的路段进行现场自校准。     

A meta-analysis of Western European external costs estimates

This paper analyses the external transport cost estimates that have been found in various European studies. These estimates seem at first glance to be highly dispersed, a fact which raises questions about their reliability. The article offers a list of the possible reasons for discrepancies between the various studies; differences in the specific situations studied, in the type of cost calculated, in the physical laws relating to emissions, in the measurement of values of external costs. It assesses the relative magnitude of each of these causes through a meta-analysis. It turns out that the main differences come from the specificity of the situation under review and the type of cost calculated. In comparison, differences in the laws and in the values methods have a lower importance. The conclusion is that the estimates of external costs are reliable for decision-making policies.     

板桩码头的有限元解法及计算机处理

介绍采用竖向弹性地基梁法计算板桩码头的要点。     

多功能程控心脏起搏器120例临床应用

本文总结我院自1984年来使用的120例多功能程控心脏起搏器,其中VVI114例,DDD5例,DVI1例。通过对其中95例进行的162决程控,认为在置入术后适时地合理地程控,可以纠正起搏器的部分合并症、消除症状、节约电能、延长起搏器的使用寿命、减少更换起搏器次数。相信这类起搏器定会得到更加广泛的临床应用。     

Parametrical studies of a new numerical model for controlled ship motions in extreme astern seas

Parametrical studies based on numerical simulations were carried out for very steep regular waves to assess possible improvements in the state-of-the art numerical modelling of the control and capsizing behaviour of ships in following and quartering seas. A nonlinear 6-DOF numerical model has been developed with the inclusion of frequency-dependent terms, the so called memory effects, and a flexible axis system that allows straightforward combination of seakeeping and manoeuvring models while accounting for extreme motions. The previously undertaken validation analyses using extensive model test data provided qualitatively good agreement, whereas the comparison with numerical models without coupling of the vertical motions and frequency-dependent hydrodynamic terms embodied in radiation forces identified improvements in the accuracy. However, to broaden the assessment of the numerical model, further parametrical numerical analyses were carried out using two ships, which had previously been tested in the validation analyses, for various operational and environmental conditions. These parameters were changed in accordance with the recommendations from international organisations and experience from model tests to realise and avoid dangerous conditions that often result in capsizing, such as broaching associated with surf riding and low-cycle resonance. As a result of the parametric analysis, we discuss the sensitivity of the improvements in the numerical model for various critical operational and design parameters and its possible use to provide a link between the ship's behavior and these parameters.     

南沙地区真空预压法加固软土地基效果分析

全面分析南沙某真空预压区的监测成果,从土体的变形、孔隙水压的消散、水位的变化加固前后土层土工参数的变化、十字板试验等各方面评价了真空预压加固超软地基的效果,监测结果说明真空预压加固后,土体强度得到明显提高,工后沉降大大减少。     

圆弧形检定断面超限点位置及货物超限程度确定方法的研究

根据圆弧形检定断面和各级限界的特点，分析了它们之间的位置关系，建立了确定计算点位置及计算最小距离的数学模型，并编制了相应的计算机程序进行求解；地于准确判定货物超限等级和确定超限车运行条件具有重要意义。     

公路建设中的水土保持措施

以茂湛高速公路观珠至坡心段工程为例，阐述了公路建设中水土保持的必要性、所采取的水土保持技术措施、以及该工程水土保持防治效果，对类似工程有一定的借鉴作用。