饱和层状尾砂动力特性研究

为探究动力作用下尾砂液化破坏特性,基于某矿山尾矿库坝体分层尾砂,开展不同固结应力和层状结构条件下动三轴试验,分析层状尾砂动弹性模量、阻尼比及动剪应力比等动力参数与动孔压的变化规律.结果表明:固结应力对层状尾砂力学特性和动孔压变化趋势有较大影响,固结应力越大,动孔压增长越明显,初始增长斜率随固结应力增大而下降;尾粉土厚度...     

Physicochemical substance properties as indicators for unreliable exposure in microplate-based bioassays

In the last years many efforts were made to transform standardized algal test protocols into low-cost microplate assays. While advantages were pointed out frequently, limitations are not systematically addressed, thus hindering a widespread utilisation. In this study a group of organic substances with a wide distribution of volatility (log K_AW from −6.53 to −2.13) and lipophilicity (log K_OW from 1.26 to 4.92) was investigated with respect to the influence of these physicochemical properties on their algal toxicity in different assays. Therefore the EC₅₀ values were determined with a microplate assay based on ISO 8692 protocol and the results were compared with those of an established algal growth inhibition test conducted in air tight glass vessels. Using the ratio of the EC₅₀ values, a clear connection between biological response and volatility as well as lipophilicity of test substances could be detected. Chemicals with a log K_OW higher than 3 or a Henry coefficient log K_AW higher than −4 were identified as less effective in the microplate assay than in the comparative assay. The loss in nominal concentration due to physicochemical properties could be shown to contribute to this using HPLC analysis. Consequently, when using microplate assay’s one should be aware that lipophilic and volatile chemicals might be underestimated in their toxicity, which could be indicated from evaluating related physicochemical properties modelled from structural information prior to an experimental investigation.     

‘A powerful alternative to Williams’ test with application to toxicological dose-response relationships of normally distributed data

The comparison of increasing doses of a treatment to a negative control is frequently part of toxicological studies. For normally distributed data Williams (1971, 1972) introduced a maximum likelihood test under total order restriction. But until now there seems to have been no solution for the arbitrary unbalanced case. According to the idea proposed by Robertson et al. (1988) we will apply in this article the basic concept of Williams on the class of multiple contrast tests for the general unbalanced parametric set-up. Simulation results for size and power and two examples for estimating the minimal toxic dose (MTD) are given.     

旱地长期定位施肥对土壤剖面硝态氮分布与累积的影响

在 １５ ａ长期定位试验基础上研究了黄土高原旱地长期施用不同用量和配比的氮、磷肥对土壤剖面中硝态氮分布和累积的影响。结果表明：长期大量施用氮肥,在土壤剖面 １００～１８０ ｃｍ之间形成硝态氮累积层,峰值出现在 １４０ ｃｍ处,最大值为 ６７．９２ｍｇ／ｋｇ（单施 Ｎ １８０ ｋｇ／ｈｍ~２）; 配合施用磷肥可以降低土壤剖面硝态氮质量分数,根据试验,提出了旱地合理施肥的氮磷肥用量。     

基于分段式电压采集法的天线绝缘检测技术研究

如今,短波发信伸缩天线、插拔鞭天线等大量应用于通信台站与舰船上,天线绝缘性能是其重要的考核指标,该参量关乎到天线的持久性与通信的稳定性。以天线绝缘电阻检测技术为研究对象,分析了天线绝缘检测手段的必要性与存在的不足,在普通绝缘检测技术的基础上,提出了一种基于分段电压采集法的绝缘检测方法,对信台站与舰艇上天线的设计、施工、调试、维修、以及现场系统联调等环节起到保障作用,改善了天线绝缘性能检测技术智能化、模块化、高精度等问题。     

金属材料海水腐蚀试验方法的编制及标准解读

为了使相关人员更好地理解标准,更好地完成试验,回顾了我国金属材料海水腐蚀试验方法和标准的编制历程,对金属材料海水腐蚀试验的两个现行国家标准进行了解读和比较。     

汽车整车自然暴露试验评价方法前期研究

主要介绍汽车整车自然暴露试验评价方法,基于整车厂长期进行汽车整车自然暴露试验,对整车进行表观检测、性能检查及其他项目检测,通过分析试验结果,归纳汽车内外饰件常见缺陷,按照失效程度和不同部件类型,为整车耐候性进行等级划分,建立整车系统化评价方法。     

一种高压油管焊接质量评价方法

阐述了高压油管疲劳破坏的原理及危害,建立高压油管焊接质量评价力学模型,通过有限元分析技术对其许用位移输入进行计算,并结合应变测量技术,利用电动振动台,对高压油管焊接处的疲劳特性进行了试验验证。结果表明,此高压油管焊接质量评价方法是可行的,有限元分析技术和应变测量技术的结合使用,保证了试验的安全性和结果准确性,此外,利用电动振动台进行疲劳耐久试验,操作方便简单,成本相对较低,具有通用性。     

北斗导航终端设备可靠性加速试验与快速评价技术研究

针对北斗导航终端设备开展传统可靠性试验时间长、成本高,难以实现在短期内完成高可靠性指标考核的现状,借鉴加速试验建模技术和相关标准的加速模型参数,进行北斗导航整机可靠性加速建模,设计加速试验剖面和方案,预先评估出北斗导航终端设备的加速因子,通过一组样品即可完成北斗导航的加速试验,实现对北斗导航终端设备高可靠性指标的快速评估。     

热真空试验系统温度均匀度试验研究

热真空试验是航天器研制过程中非常重要的一项试验,作为满足热真空试验必不可少的工具,好的热真空试验系统可以保证试验件在不失真的情况下试验,使试验受控,而热真空试验系统温度均匀度不好,会造成过试验或欠试验的产生。文中以某型热真空试验设备为例,通过试验研究分析其温度均匀度,可以提高热真空试验的精度。