氧化铝生产过程中弹簧式安全阀的维护及故障排除

目前在氧化铝生产过程中弹簧式安全阀被广泛地使用在各种压力容器设备和压力管道系统上。它是确保压力容器及压力管道安全正常运行的最为重要的安全附件之一。如果弹簧式安全阀在使用过程中出现的故障不能及时消除,就不能对设备及管道系统起到安全保护作用,甚至发生事故。安全阀工作的可靠与否直接关系到设备及人身的安全,所以必须给予重视。本文就弹簧式安全阀出现的常见主要故障从5个方面分别进行分析,并给出消除故障保证弹簧式安全阀正常运行的解决方法。     

水管网带压合叉技术与应用

在有色冶炼企业，由于生产工艺连续性以及新水阀门易损坏关不严等原因，应用带压合叉技术显得尤为重要，本简要介绍了带压开孔器的技术原理和安全使用方法。并对在实际应用中的突发情况提出了相应的预防措施，在水、风等能源管网连接中，具有一定的参考价值。     

原子荧光光谱法测定土壤中的铅、铬、镉、汞、砷、锌、铜、镍等元素研究

土壤无机污染物铅、铬、镉、汞、砷、锌、铜、镍这八大重金属,是一般土壤检测中的必检项目。金属元素在土壤中积累富集后,有可能通过雨水迁移,造成地下水,地表水污染,或者通过农作物进入食物链,进而影响食品安全和人体健康,因此,对这些元素的检测显得尤为重要。本文采用原子荧光光谱法对土壤中的金属元素进行测量,同时结合微波消解技术对样品进行处理,确保测量数据的准确性。     

A general framework illustrating an approach to quantitative microbial food safety risk assessment

Hazard analysis critical control point (HACCP), risk assessment, predictive microbiology, and dose-response modeling have been recognized as important tools for the assessment and management of health risks posed by food-borne pathogens. Unfortunately, the biology of both the food chain and food poisoning is complex and dynamic. Therefore, mathematical modeling of microbial risk from food production through to consumption and illness is difficult. Nevertheless, previous authors have made impressive progress in modeling specific pathogen-food-consumer combinations. In this study a framework for a Monte Carlo model of a generic food system was developed. It links together food ingredients, batch processing, cross contamination, microbial growth, cooking, recontamination, consumption, human exposure to pathogens, the dose-response relationship, and the biologic and economic impact components of such risks. This framework is presented to illustrate one potential approach to quantitative risk assessment for microbial food safety. It requires refinement with appropriate distributions and mathematical relationships before it can be applied to a specific pathogen-food-consumer situation.     

轧钢高压水除鳞喷射阀启闭特性分析

轧钢高压水喷射除鳞对提高钢材轧制表面质量效果明显 ,除鳞喷射阀结构特殊 ,由气压驱动 ,其启闭特性与一般水阀不同。分析了其阀芯所受水压力 ,液流力及密封的摩擦力 ,从而给出了启闭喷射阀所需气压作用力的计算式 ,并以研制的喷射阀的实际数据作为例子计算了该阀的启闭特性 ,解决了阀门流量大 ,压力高启闭难的问题。     

Salmonellae and food safety

Salmonella is one of the most important foodborne pathogens around the world. The knowledge that very low numbers of Salmonella cells can be infectious emphasizes the need for stringent food safety measures Traditional methods for isolating and identifying Salmonella in food rely on preenrichment, selective enrichment in selective and differential media, biochemical tests, and serological confirmation. Recent advances in diagnostic technology have considerably altered testing methods for foodborne Salmonella. Many commercial assay systems and kits that use newer technologies are available to facilitate the identification of Salmonella in foods. These systems include miniaturized biochemical tests, new media formulations, automated instrumentation, DNA/RNA probes, antibody-dependent assays, and polymerase chain reaction. The technologies used for these systems are described, and the various kit formats are compared. Among the limitations of detection methods in terms of food safety are timeliness, limits of detection, and differentiation of virulent and nonvirulent isolates. Current efforts of prevention measures and strategies at different links of the food chain such as consumer education and hazard analysis and critical control point (HACCP) programs are reviewed, Global approaches to food safety are needed..     

Reasoning and food and contamination.

Examines strategies that are used to reason about food and contamination. In Exp 1, Ss refrained from choosing a substance that had been given a "poison" label when the intent of the labeler was ambiguous or malicious but preferred this substance when a rationale was provided that dispelled the implication that there once might have been contaminants present. Exp 2 was designed to compare the effects of safety on conditional reasoning in food and food-irrelevant contexts. When the safety issue was relevant to food in the form of contamination, Ss were most likely to use formal logic in reasoning. A similar pattern of responses was found in Exp 3 on tasks for which Ss' ratings of their experience of contexts were matched for plausibility, experience, and danger. Results are discussed in terms of an adaptive constraint that facilitates rationality in reasoning within the food domain (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intensive (pasture) beef cattle operations: the perspective of New Zealand

Beef production in New Zealand has characteristics typical of a temperate climate and pasture-based animal husbandry. The specific pathogens which may contaminate fresh beef and which are empirically considered to be of public health importance are similar to those in other countries with temperate climates, i.e. Salmonella, Campylobacter, Escherichia coli O157:H7, Listeria monocytogenes and Toxoplasma gondii. With the exception of T. gondii, it is likely that almost all transmission of these hazards through consumption of beef results from unseen microbial cross-contamination from gastrointestinal sources during slaughter, dressing and further processing. Gaining comprehensive information on carcass contamination levels is an essential first step in establishing food safety objectives for a particular beef production system, and in designing risk-based hazard analysis and critical control point (HACCP) plans. It is likely that the lower mean and maximum numbers of indicator micro-organisms on New Zealand carcasses (when compared with other countries) are in part due to the pre-slaughter cleanliness status of cattle reared under temperate, pasture conditions. Similarly, the failure to detect specific pathogens of gastrointestinal origin in a comprehensive baseline survey most probably reflects the limited pathway for faecal contamination during slaughter and dressing under processing conditions in New Zealand. The New Zealand example provides strong evidence for the need to design HACCP plans according to the specific national (or regional) situation. Reducing all pathways for faecal contamination of products to the maximum extent practicable will be the most important factor in achieving desired food safety objectives for fresh beef. Variable densities of microbial pathogens in gastrointestinal contents are also likely to have a significant effect on subsequent contamination levels of beef carcasses: however, effective controls for limiting the presence of most pathogens of concern in the live animal have yet to be identified.     

Prevalence of Staphylococcus aureus among food handlers from a metropolitan university in Chile

BACKGROUND: An important agent of food intoxication is Staphylococcus aureus, that is able to produce enterotoxins. AIM: To detect Staphylococcus aureus contamination in cafeteria food handlers of a Chilean University. SUBJECTS AND METHODS: Nose, throat, hands and nail samples from 87 food handlers were obtained for microbiological examination. RESULTS: Fifty seven subjects (65.5%) were carriers of Staphylococcus aureus. Enterotoxigenic Staphylococcus aureus was found in 36 subjects (41%). The most frequently found enterotoxin was type B (18 samples) followed by type D (12 samples). Men bad a higher frequency of contamination than women (83 and 57% of positive samples respectively). CONCLUSIONS: The frequency of Staphylococcus aureus contamination among food handlers is high and should prompt personal and environmental hygienic measures.     

液压系统在高压状态下保压控制的设计

液压系统在高压下的保压控制很重要，本文介绍了采用光导卸荷控制保压，自动补压系统的工作原理及特点，此系统克服了溢流阀保压控制使油温升高的弊病。     

Planimetric quantification of aortic valve stenoses using multiplanar transesophageal echocardiography

Standard techniques used in order to quantify the severity of aortic valve stenoses in clinical practice comprise: transthoracic echocardiography, namely, by determining maximum and mean transvalvular gradients and evaluating aortic valve areas, as well as invasive techniques which quantify aortic valve areas through hemodynamic pressure measurements and application of the Gorlin formula. Since the introduction of the multiplane TEE technique, it has become feasible to scan the aortic valve in a strictly horizontal plane and quantify the aortic valve orifice by planimetry. In this study, we investigated 23 patients with various degrees of aortic valve stenoses. We compared aortic valve areas, which had been planimetrically determined by multiplane TEE scans, and mean aortic valve gradients (standard TEE technique) with pressure gradients and valve areas derived from hemodynamic measurements obtained during cardiac catheterization, and have found that the valve areas as well as the mean pressure gradients correlate well.     

Posture-related overdrainage: comparison of the performance of 10 hydrocephalus shunts in vitro

OBJECTIVE: Approximately 10 to 30% of shunt revisions may be attributed to posture-related overdrainage. The susceptibility of various hydrocephalus shunts to overdrainage of cerebrospinal fluid requires independent laboratory evaluation. METHODS: Shunts were tested in vitro by using precise computer-controlled equipment that was able to evaluate pressure-flow performance curves under various conditions. Hydrodynamic resistance and opening, closing, and operational pressures were evaluated for at least 28 days with normal (atmospheric) and decreased (-23 mm Hg, based on the International Standard Organization/Draft International Standard 7197 standard, which simulates conditions in upright body positions) outlet pressures. RESULTS: Ten different models of valves have been tested to date (Medtronic PS Medical Delta valve, flow-control valve, and lumboperitoneal shunt, Heyer-Schulte in-line, low-profile, and Pudenz flushing valves, Codman-Medos programmable and nonprogrammable valves, Sophy programmable valve, and Cordis Orbis-Sigma valve). The majority of these valves produced significantly negative (less than -10 mm Hg) average intracranial pressures in vertical body positions. In conjunction with nonphysiologically low hydrodynamic resistance (with the exception of the Orbis-Sigma valve, Medtronic PS Medical lumboperitoneal shunt, and Heyer-Schulte in-line valve), this may result in overdrainage related to body posture. The clinically reported rate of complications related to overdrainage is probably reduced by the long distal catheter, which increases the resistance of these valves by 100 to 200%. A few shunts (the Delta valve, low-profile valve, and Pudenz flushing valve with anti-siphon devices) offer reasonable resistance to negative outlet pressure, preventing complications related to overdrainage, but all valves with siphon-preventing devices may be blocked by increased subcutaneous pressure. CONCLUSION: Shunts without mechanisms preventing very low intracranial pressure in vertical body positions should be identified and avoided for patients likely to develop complications related to cerebrospinal fluid overdrainage.     

Environmental urban lead exposure and blood lead levels in children of Mexico City

Lead contamination is now a leading public health problem in Mexico. However, there are few data on the lead content of various environmental sources, and little is known about the contribution of these sources to the total lead exposure in the population of children residing in Mexico City. We conducted a cross-sectional study in a random sample of 200 children younger than 5 years of age who lived in one of two areas of Mexico City. Environmental samples of floor, window, and street dust, paint, soil, water, and glazed ceramics were obtained from the participants' households, as well as blood samples and dirt from the hands of the children. Blood lead levels ranged from 1 to 31 micrograms/dl with a mean of 9.9 micrograms/dl (SD 5.8 micrograms/dl). Forty-four percent of the children 18 months of age or older had blood lead levels exceeding 10 micrograms/dl. The lead content of environmental samples was low, except in glazed ceramic. The major predictors of blood lead levels were the lead content of the glazed ceramics used to prepare children's food, exposure to airborne lead due to vehicular emission, and the lead content of the dirt from the children's hands. We conclude that the major sources of lead exposure in Mexico City could be controlled by adequate public health programs to reinforce the use of unleaded gasoline and to encourage production and use of unleaded cookware instead of lead-glazed ceramics.     

Effect of Crack Inclination and Residual Stress on the Stress Intensity Factor of Semi-elliptical Crack in a Pressure Vessel

Transactions of the Indian Institute of Metals - Pressure vessels are widely used in products ranging from consumer artifacts to engineering components. Ensuring safety and reliability of pressure...     

高炉炉顶放散阀泄漏的原因分析及防范措施

当高炉休风或顶压冒尖时,炉顶放散阀打开关闭后出现的泄漏称为高炉炉顶放散阀泄漏。炉顶放散阀泄漏给维护人员人身安全带来较大威胁,同时也影响生产,污染环境。通过分析高炉炉顶放散阀泄漏的原因(包括放散阀阀盖圆周不同步下压和阀盖在使用过程中产生的缺陷),改进放散阀结构和密封形式,加强日常维护,提高了放散阀的密封性能。     

Once in Contact, Always in Contact: Contagious Essence and Conceptions of Purification in American and Hindu Indian Children.

Cultural and age differences in responses to contamination and conceptions of purification were examined in Hindu Indian (N = 125) and American (N = 106) 4- to 5-year-olds and 8-year-olds, who were provided with stories of juice contaminated by contact with a cockroach, a human hair, and a stranger (via sipping). Children who rejected the juice as being fit to drink were probed to determine whether their rejection was based on material essence (reduced by boiling), association (reduced by color change), or spiritual essence (reduced by sipping by the mother). A majority of 4- to 5-year-olds showed some form of contamination response, as did the great majority of 8-year-olds. Younger children's judgments were often based on spiritual essence or association, whereas material essence was more important for the older children, particularly Americans. However, for many children in both cultures, no purifiers were effective. In keeping with Hindu culture, the Indian children responded significantly more strongly to stranger or cockroach contamination and, with increasing age, viewed contamination as more impervious to any kind of purification. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

试析锌冶炼企业安全风险和管控途径

锌冶炼企业是我国社会主义市场经济体系当中一个很重要的组成部分,金属锌作为诸多工业产品深加工的原材料,占有重要地位,但是对锌冶炼行业来说,冶炼生产存在一定的安全风险,在生产过程如管理不善往往会形成一些安全隐患最终引发生产安全事故,因此需要加强冶炼生产风险管控,杜绝发生生产安全事故。     

高炉布袋防爆装置的改进

针对高炉布袋除尘器防爆泄压安全板安全性差、更换时间长的问题进行了改进,用安全阀代替了防爆板,取得良好的效果。     

Intracoronary stent implantation using a single high-pressure perfusion balloon catheter

INTRODUCTION: A factory producing lead ingots, located in Ca?apava, caused lead and cadmium contamination of the environment, in the Paraiba Valley region of Southeastern, Brazil, through the discharge of industrial waste and the recycling of batteries. The factory, set in a rural, dairy cattle breeding area, worried sanitary authorities who envisaged the possibility of these metals' having entered the food chain. For the purpose of assessing the levels of contamination of the milk produced in the region, due to the cattle's possible consumption of contaminated grass and water, the amounts of cadmium and lead present in the milk were verified. MATERIAL AND METHOD: Major producers, covering an area of up to 20 km from the contaminated source, authorized collection of 218 samples of both pasteurized and non-pasteurized milk, which were analysed. Lead and cadmium levels were determined by flame atomic absorption spectrophotometry, the lead being pre-concentrated by complexation with APDC (ammonium 1-pyrrolidinecarbodithioate) and further extraction with isobutyl methylketone. RESULTS AND CONCLUSIONS: Of the total number of samples, 43 presented lead levels over the maximum limit of 0.05 mg/kg established by Brazilian legislation. The median value found for lead was 0.04 mg/L. The variance analysis, with 95% confidence level, found no significant difference among the types of milk studied with regard to lead levels. As for cadmium, all samples showed levels below the 0.02 mg/L quantification limit of the method. In spite of the environmental contamination, the levels of cadmium found in the milk were below the 1.0 mg/kg limit established by Brazilian legislation.