A new synthesis of tetrachlorofluorodibenzo‐p‐dioxin

Abstract

The 1,2,3,4‐tetrachloro‐7‐fluorodibenzo‐p‐dioxin has been synthesized via condensation of 4‐fluorocatechol and pentachloronitrobenzene. This compound could be used as an internal standard for the analysis of 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin by Chromatographic methods.     

化学需氧量现有2种标准分析方法若干问题研究

《水质化学需氧量的测定重铬酸盐法》(HJ 828—2017)和《高氯废水化学需氧量的测定氯气校正法》(HJ/T 70—2001)是测定水中COD_(Cr)现有有效的2种标准方法。针对这2种方法存在的问题,通过实验给出操作建议。指出,对高氯废水稀释后采用《HJ 828—2017》方法测定水中COD_(Cr)时,稀释倍数太大或稀释后COD_(Cr)质量浓度20 mg/L,将降低测定结果的准确度;采用《HJ/T 70—2001》方法测定高氯废水中COD_(Cr)时,硫酸亚铁铵浓度应为0.10 mol/L;《HJ 828—2017》方法中高、低质量浓度分界点建议从50 mg/L改为60 mg/L,试验结果可行且对部分行业排放标准适用性更好;鉴于低浓度样品的精密度结果相对偏大,建议按照COD_(Cr)的浓度大小分级设定精密度的质控要求,更加科学合理。     

子密钥数据库安全加密算法研究

探讨数据库的加密特点及其加密方法,并详细介绍一种类似DES(数据加密标准)的分组加密算法———子密钥数据库加密算法;同时分析和讨论如何实现数据库加密、解密以及更新;以微软数据库SQLServer2000为例,介绍数据库加密算法的实现过程,该实例应用广泛,在信息管理系统安全、电子商务等领域有很大的借鉴作用。     

Pushing,pulling and manoeuvring an industrial cart: a psychophysiological study

One of the most frequent manual occupational tasks involves the pushing and pulling of a cart. Although several studies have associated health risks with pushing and pulling, the effects are not clear since occupational tasks have social, cognitive and physical components. The present work investigates a real case of a pushing and pulling occupational task from a manufacturing company. The study initially characterizes the case in accordance with Standard No. ISO 11228-2:2007 as low risk. An experiment with 14 individuals during three modalities of pushing and pulling was performed in order to further investigate the task with the application of electrophysiology. At the end, a simple questionnaire was given. The results show electrophysiological differences among the three modalities of pushing and pulling, with a major difference between action with no load and fully loaded with a full range of motions on the cart to handle.     

Effect of turbulence spatial distribution on the deflagration index: Comparison between 20 L and 1 m3 vessels

In this work, the effect of spatial distribution and values of the turbulent kinetic energy on the pressure-time history and then on the explosion parameters (deflagration index and maximum pressure) was quantified in both the standard vessels (20 L and 1 m³).The turbulent kinetic energy maps were computed in both 20 L and 1 m³ vessels by means of CFD simulations with validated models. Starting from these maps, the turbulent flame propagation of cornstarch was calculated, by means of the software CHEMKIN. Then, the pressure-time history was evaluated and from this, the explosion parameters.Calculations were performed for three cases: not uniform turbulence level as computed from CFD simulations, uniform turbulence level and equal to the maximum value, uniform profile and equal to the minimum value. It was found that the cornstarch in the 20 L vessel get variable classes (St-1, St-2, St-3) with respect to the 1 m³ (St-1). However, simulations performed on increasing the ignition delay time, shown that the same results can be attained only using 260 ms as ignition delay time in the 20 L vessel.     

手传振动的危害及防护

综述了手传振动危害的现状及为减少振动危害开展的工作。对国内关于振动危害调查报告进行了汇总分析;研究了按行业、工种的分布情况并对常见的手持工具进行了振动测试及评价;对防振方面采取的措施进行了调查及分析;回顾及介绍了涉及手传振动的法规及标准     

略论环境管理模式的重大变革——ISO14000系列标准剖析

国际标准化组织（ＩＳＯ）根据环发大会的决议，１９９３年６月正式成立“环境管理技术委员会”（ＩＳＯ／ＣＴ２０７），负责环境管理工具及体系方面国际标准化工作。文章通过对ＩＳＯ－１４０００系列标准的背景和内容的介绍与分析，阐述了目前在我国实施ＩＳＯ－１４０００系列标准的意义和对策。建议。     

室内空气质量指数评价模式的研究

提出室内空气质量的三级评价标准和五个评价等级,建议依据评价目的,选择相应污染物质作为评价因子。分析常用指数评价模式的特点,建立适用于室内空气质量评价的综合指数模式,该模式是一种客观有效的评价方法。     

中国有机食品的开发

有机农业运动已在我国兴起,我国在有机食品的开发上有着潜在的巨大市场及有利条件,应遵循“先易后难、逐步发展、建立基地、开发市场”的原则,严格按有关标准进行。     

环境管理体系ISO14000的产生及其实施

ISO14000是国际标准化组织（ISO）为推动可持续发展，统一协调各国环境管理标准，减少世界贸易中的非关税贸易壁垒而制定的环境管理系列标准。由于实施系列标准具有保护环境和消除贸易技术壁垒的双重作用，因此受到世界各国的广泛关注。本文就ISO14000系列标准的产生背景、制定基础及实施情况进行了简单介绍，希望能引起有关企业的重视，推动ISO14000在我国的认证工作，以减少工业企业的环境污染，推进可持续发展战略在我国的实施。