采用冲击加速度指标评价安全帽抗侧向冲击性能的研究

安全帽是应用最为广泛的一种重要的劳动作业人员头部安全防护用品,广泛使用在机械、建筑、矿山、交通、冶金、电力等行业中。在实际工作中,作业人员除可能受到来自顶部的坠落冲击外,还切实存在着受到侧面冲击的可能。现行安全帽国家标准主要采用头部受到的冲击力数值大小作为依据评价安全帽防护性能的优劣,此种方法无法用来考察安全帽的抗侧向冲击性能。本文讨论引入冲击加速度作为新的评价指标,以达到科学评价安全帽抗侧向冲击防护性能的目的。     

Benzoate degradation by Rhodococcus opacus 1CP after dormancy: Characterization of dioxygenases involved in the process

The process of benzoate degradation by strain Rhodococcus opacus 1CP after a five-year dormancy was investigated and its peculiarities were revealed. The strain was shown to be capable of growth on benzoate at a concentration of up to 10 g L^?1. The substrate specificity of benzoate dioxygenase (BDO) during the culture growth on a medium with a low (200–250 mg L^?1) and high (4 g L^?1) concentration of benzoate was assessed. BDO of R. opacus 1CP was shown to be an extremely narrow specificity enzyme. Out of 31 substituted benzoates, only with one, 3-chlorobenzoate, its activity was higher than 9% of that of benzoate. Two dioxygenases, catechol 1,2-dioxygenase (Cat 1,2-DO) and protocatechuate 3,4-dioxygenase (PCA 3,4-DO), were identified in a cell-free extract, purified and characterized. The substrate specificity of Cat 1,2-DO isolated from cells of strain 1CP after the dormancy was found to differ significantly from that of Cat 1,2-DO isolated earlier from cells of this strain grown on benzoate. By its substrate specificity, the described Cat 1,2-DO was close to the Cat 1,2-DO from strain 1CP grown on 4-methylbenzoate. Neither activity nor inhibition by protocatechuate was observed during the reaction of Cat 1,2-DO with catechol, and catechol had no inhibitory effect on the reaction of PCA 3,4-DO with protocatechuate.     

Development and Testing of a Physically Based Model of Streambank Erosion for Coupling with a Basin‐Scale Hydrologic Model SWAT

A comprehensive streambank erosion model based on excess shear stress has been developed and incorporated in the hydrological model Soil and Water Assessment Tool (SWAT). It takes into account processes such as weathering, vegetative cover, and channel meanders to adjust critical and effective stresses while estimating bank erosion. The streambank erosion model was tested for performance in the Cedar Creek watershed in north‐central Texas where streambank erosion rates are high. A Rapid Geomorphic field assessment (RAP‐M) of the Cedar Creek watershed was done adopting techniques developed by the Natural Resources Conservation Service (NRCS), and the stream segments were categorized into various severity classes. Based on the RAP‐M field assessment, erosion pin sites were established at seven locations within the severely eroding streambanks of the watershed. A Monte Carlo simulation was carried out to assess the sensitivity of different parameters that control streambank erosion such as critical shear stress, erodibility, weathering depth, and weathering duration. The sensitive parameters were adjusted and the model was calibrated based on the bank erosion severity category identified by the RAP‐M field assessment. The average observed erosion rates were in the range 25‐367 mm year^?1. The SWAT model was able to reasonably predict the bank erosion rates within the range of variability observed in the field (R² = 0.90; E = 0.78). Editor's note : This paper is part of the featured series on SWAT Applications for Emerging Hydrologic and Water Quality Challenges. See the February 2017 issue for the introduction and background to the series.     

从相关国际标准的要求谈振动试验台校准

近十年来,振动试验的相关国际标准已经多次修订,对振动试验台提出了新的要求;国内振动试验台产业得到了长足的发展,振动参数认知也更加深入;现行检定规程都是上世纪九十年代制定,亟待修订。本文谈一谈振动试验台校准中的失真度、均匀度、横向振动、频率等几个主要参数。     

侧部点式排烟隧道火灾临界风速研究

为得到侧部点式排烟模式隧道火灾临界风速无量纲计算式,针对隧道侧部点式排烟模式,根据π定理和相似理论,采用量纲分析方法分析影响临界风速的相关因素,推导出影响临界风速3个因素的无量纲函数关系式;采用数值模拟方法,确定临界风速与火灾热释放速率、排烟量、排烟口距火源距离的量化关系.研究结果表明:当无量纲排烟口距火源距离小于2....     

Real-time reverse transcription PCR analysis of trichloroethylene-regulated toluene dioxygenase expression in Pseudomonas putida F1

Toluene dioxygenase (tod) is a multicomponent enzyme system in Pseudomonas putida F1. Tod can mediate the degradation of Trichloroethylene (TCE), a widespread pollutant. In this study, we try to explore the TCE-regulated tod expression by using real-time qRT-PCR. The minimal culture media were supplemented with glucose, toluene, or a mixture of glucose/toluene respectively as carbon and energy sources. The TCE was injected into each medium after a 12-hour incubation period. The TCE injection severely affected bacterial growth when cultured with toluene or toluene/glucose mixtures. The cell density dropped 61 % for bacteria growing in toluene and 36 % for bacteria in the glucose/toluene mixture after TCE injection, but the TCE treatment had little effect on bacteria supplied with glucose alone. The decrease in cell number was caused by the cytotoxicity of the TCE metabolized by tod. The results from the real-time qRT-PCR revealed that TCE was capable of inducing tod expression in a toluene-dependent manner and that the tod expression level increased 50 times in toluene and 3 times in the toluene/glucose mixture after 6 hours of TCE treatment. Furthermore, validation of the rpoD gene as a reference gene for P. putida F1 was performed in this study, providing a valuable foundation for future studies to use real-time qRT-PCR in the analysis of the P. putida F1 strain.     

环境因子对脱氯功能念珠藻Nostoc PD-2降解多氯联苯过程中基因表达的影响

以分离筛选自多氯联苯污染水稻田中的脱氯功能蓝藻Nostoc PD-2为材料,两种典型的三氯代多氯联苯PCB28和PCB30为目标污染物,在不同的氮源、碳源和培养温度条件下,研究了脱氯功能藻种Nostoc PD-2中双加氧酶基因和细胞色素b6f复合体铁硫蛋白基因的表达情况及两种基因对脱氯作用的影响.结果显示,以硝酸钠作为氮源时,与氮气氮源组相比,PCB28和PCB30降解组中的两种基因均显著上调表达,双加氧酶基因的上调倍数分别为1.9和5.7倍,铁硫蛋白基因的上调倍数分别为1.1和1.7倍;添加碳酸钠时,与对照相比,双加氧酶基因最高上调了2.2倍,铁硫蛋白基因最高上调了3.4倍;提高温度对双加氧酶基因和铁硫蛋白基因的表达均有促进作用.相较于铁硫蛋白,双加氧酶基因相对表达量与PCB28和PCB30的脱氯百分比之间的相关系数分别为0.872和0.832,表明双加氧酶基因活性与功能藻种PD-2脱氯降解PCBs的相关性更高.本研究结果表明,不同环境因子可引起脱氯功能藻种Nostoc PD-2降解PCBs过程中双加氧酶基因和铁硫蛋白基因的差异表达,添加碳源对降解效果的促进作用最明显,脱氯功能藻种在工程应用中采用优化的环境条件有利于提高降解效率.     

中日规范中关于液化和侧向扩流场地桥梁桩基抗震设计考虑之比较

评述了我国液化场地和侧向扩流场地桥梁桩基抗震设计规范.总结了中日两国液化场地和侧向扩流场地桥梁桩基的抗震设计方法与技术细节,阐述了日本规范中液化场地和侧向扩流场地桥梁桩基抗震设计中的液化地基土反力折减系数的确定方法,以及土体液化侧向扩流对桩作用力的计算模式.指出我国规范中在液化和侧向扩流场地桩的抗震分析方法、不同土层分...     

Predicting River Floodplain and Lateral Channel Migration for Salmon Habitat Conservation1

Abstract: In this article, we describe a method for predicting floodplain locations and potential lateral channel migration across 82,900 km (491 km² by bankfull area) of streams in the Columbia River basin. Predictions are based on channel confinement, channel slope, bankfull width, and bankfull depth derived from digital elevation and precipitation data. Half of the 367 km² (47,900 km by length) of low‐gradient channels (≤ 4% channel slope) were classified as floodplain channels with a high likelihood of lateral channel migration (182 km², 50%). Classification agreement between modeled and field‐measured floodplain confinement was 85% (κ = 0.46, p < 0.001) with the largest source of error being the misclassification of unconfined channels as confined (55% omission error). Classification agreement between predicted channel migration and lateral migration determined from aerial photographs was 76% (κ = 0.53, p < 0.001) with the largest source of error being the misclassification of laterally migrating channels as non‐migrating (35% omission error). On average, more salmon populations were associated with laterally migrating channels and floodplains than with confined or nonmigrating channels. These data are useful for many river basin planning applications, including identification of land use impacts to floodplain habitats and locations with restoration potential for listed salmonids or other species of concern.     

Investigating the influence on safety of retrofitting Italian motorways with barriers meeting a new EU standard

Objective: A new European Union (EU) regulation for safety barriers, which is based on performance, has encouraged road agencies to perform an upgrade of old barriers, with the expectation that there will be safety benefits at the retrofitted sites. The new class of barriers was designed and installed in compliance with the 1998 (European Norm) EN 1317 standards for road restraint systems, which lays down common requirements for the testing and certification of road restraint systems in all countries of the European Committee for Standardization (CEN). Both the older and new barriers are made of steel and are installed in such a way as to avoid vehicle intrusion, but the older ones are thought to be only effective at low speeds and large angles of impact. The new standard seeks to remedy this by providing better protection at higher speeds. This article seeks to quantify the effect on the frequency of fatal and injury crashes of retrofitting motorways with barriers meeting the new standards.

Methods: The estimation of the crash modification was carried out by performing an empirical Bayes before–after analysis based on data from the A18 Messina–Catania motorway in Italy. The methodology has the great advantage to account for the regression to the mean effects. Besides, to account for time trend effects and dispersion of crash data, a modified calibration methodology of safety performance was used.

Results: This study, based on data collected on 76 km of motorway in the period 2000–2012, derived Crash Modification Factor point estimates that indicate reductions of 72% for run-off-road fatal and injury crashes and 38% in total fatal and injury crashes that could be expected by upgrading an old safety barrier by complying with new EU 1317 standards. The estimated benefit-cost ratio of 5.57 for total crashes indicates that the treatment is cost effective.

Conclusions: The magnitude of this benefit indicates that the retrofits are cost-effective even for total crashes and should continue in any European country inasmuch as the estimated Crash Modification Factors are based on treatment sites that are reasonably representative of all European motorways.