国外高效连铸的发展

科学技术的进步必然促进工业生产向高效、优质方向发展。连铸技术近些年来又有很大进步,近终形连铸得到各国青睐,提高传统连铸的生产效率(高作业率、高拉速、高质量)在各工业发达国家取得了长足的进步,特别是高拉速技术已引起高度重视。大板坯的拉速(2.0～2.5m/min)在日本已较普遍。国外几个连铸专业公司纷纷推出高拉     

对连铸工艺和设备的要求研讨

探讨了全连续工艺对铸机拉速、连铸设备、铸坯质量的影响，介绍了高拉速对钢种设计的要求和宝钢高拉速薄板坯连铸技术特征。     

拉速对结晶器平均热流的影响

通过计算8088块板坯的平均热汉研究了拉速对板坯结晶器平均热流的影响结果表明：拉速对结晶器宽边的平均热流有显的影响,拉速在0．6－1．2m/min范围内,结晶器宽边平均热流随拉速提高而增加,当拉速超过1．2m/min后,结晶器宽边平均热流随拉速增加而提高的幅度变得很小;结晶器窄边的平均热流较宽边的热流约低0．2MW／m^2,当拉速超过1．2m/min后,结晶器窄边的平均热流仍可随拉速的进一步提高而增加。     

R9m方坯连铸二次冷却工艺的优化

为提高优钢铸坯质量,石横特钢厂对R9m方坯连铸二次冷却工艺进行了优化。依据拉速一定时,二冷配水冷却水量沿铸坯方向从上到下逐渐减少的配水原则,制定了不同钢种、不同拉速的配水丁艺模型。应用表明,铸坯低倍组织明显改善,杜绝了中间裂纹、鼓肚等现象,减少了铸坯脱方、疏松、缩孔等缺陷。     

宝钢圆坯连铸提高拉速生产实践

介绍了圆坯连铸提速的生产实践和取得的效果.对于包晶钢,尝试通过提高拉速来改善结晶器壁与坯壳间换热的均匀性,从而降低这类钢种的漏钢率.对于石油套管、钻杆类钢种,经过3个阶段的工作,成功将平均拉速提高到2.6 m/min,而且产品的内部质量有所提高.连铸拉速提高后,有了降低中间包过热度的可能,平均过热度下降达5 K.随着拉速的提高,VD成为产线生产的瓶颈.经试验,即使VD高真空时间缩短5 min,VD后的[H]仍可达到1.5×10-4%,同时发现,VD脱氮率与高真空保持时间无相关关系.于是VD处理时间成功缩短5 min,满足产线的节奏要求.     

研究连铸坯坏方和角裂成因的试验方法选择

在研究连铸坯脱方和角裂成因的试验方法选择上，走出了些弯路。最初制定的试验方案在实际衙不可行，经分析研究，又制定了试验方案。本试验方案是在实际生产过程中按常规生产工艺操作进行测试的，结果既没有影响生产，又找出了造成我厂铸坯脱方和角裂的成因，采取相应措施后，连铸坯脱方和角裂大为减少。     

连铸二冷区铸坯表面温度测量

介绍了ＣＩＴ－Ｍ型红外辐射测温系统的工艺特点,利用该系统实测了板坯连铸的典型钢种在不同拉速条件下的铸坯表面温度。分析了拉速和冷却强度对铸坯表面温度的影响,为攀钢板坯连铸二冷配水制度的优化提供了依据。     

高拉速方坯低倍缺陷的成因及分析

本文分析了小方坯加铸提高拉速后出现的铸坯低倍组织缺陷，就其表现形式进行了统计分析和讨论，并且采取了相应的具体工艺改进措施，使高拉速方坯低倍缺陷大幅度降低。     

薄板坯连铸二冷控制模型的研究

开发了动态跟踪程序和以虚拟拉速为控制参数的新型控制模型 ,应用二冷动态跟踪程序对鞍钢 16 2 0mm× 135mm板坯连铸机连铸变拉速过程进行仿真模拟。模拟结果得出 ,虚拟拉速和水量的变化滞后于实际拉速和水量的变化 ,两者变化连续平缓 ;虚拟拉速控制模型对变拉速的连铸过程的铸坯表面温度的控制效果要优于实际拉速控制模型     

减少方坯连铸脱方缺陷的途径

从生产管理及技术分析两方面对连铸方坯脱方缺陷进行攻关，并取得成功，使一炼钢方坯连铸脱方率降为０％。     

Considerations for Design Criteria for Lunar Structures

The development of design criteria for lunar structures must begin soon in order to establish adequate criteria. Some of the items that need consideration in such criteria are discussed. The categorization of the structures will provide designers with information on the purpose and level of complexity of the structure. Various construction materials and structure types that will be critical for the design of lunar structures, are considered. The environment of the moon and its possible effects on structures are presented and lead to the development of a few load cases that need to be considered in design. A probabilistic format for the criteria and design lifetimes are also discussed.     

Guidelines for Warranty Contracting for Highway Construction

This paper presents guidelines for implementing the construction warranty contracting method in the highway construction industry. A logical, step-by-step method for effectively applying the warranty contracting program for use in the highway construction industry is developed. Relevant issues that may present obstacles to the implementation are addressed, while the best practices, compiled from an evaluation of the current industry’s state-of-the-art practices, will assist an interested state highway agency in creating a warranty specification. In performing this research, the current use of warranty specifications among state highway agencies was examined, and an in-depth case study of the Wisconsin Department of Transportation’s warranty program was conducted.     

An argument for colloid resuscitation for shock

A focused review of the physiologic mechanisms of colloid and crystalloid fluid resuscitations for acute critical illness is presented. This review suggests that postresuscitation plasma volume, cardiac output, left ventricular mechanical performance, and global and microcirculatory O2 supplies are more favorable with colloid therapy. Conversely, crystalloid may adversely affect microcirculatory blood flow and resultant O2 supply and use by ischemic tissues in shock. Poor relief of global and regional hypoxia may persist in critically ill patients after resuscitation with crystalloid.     

NEHRP Provisions for 1994 for Nonstructural Components

The recently published 1994 National Earthquake Hazards Reduction Program (NEHRP) provisions include new and substantially improved provisions for the seismic design of nonstructural components, including architectural, mechanical, and electrical components. The provisions are a significant departure from the 1991 NEHRP provisions and other seismic provisions, such as those offered by the 1994 Uniform Building Code (UBC). The design-force provisions are rationally derived and consider actual in-structure acceleration data recorded in recent significant California earthquakes. Also considered in the design-force equations are the dynamic properties of the components, the location of the component within the supporting structure, the safety and operational importance of the component, and the component's anchorage ductility and energy-absorption capability. The resulting force requirements of the new recommendations are compared with the 1991 NEHRP provisions and the 1994 UBC requirements. In addition, explicit design displacement provisions are introduced and discussed.     

Ketamine used for anaesthesia in children for pneumoencephalography

The average blood pressure measured in a representative sample of 8th grade juveniles (14-16 years) was 120/70 mm Hg. Mean systolic pressure was 5 mm Hg higher in boys. The 90th percentile was 135/80 mm Hg for both sexes. Systolic and diastolic pressure rose with increasing body weight. Correlation with height was less obvious. Difference in weight could not account for all the sex difference in blood pressure. Association of sexual maturation with higher blood pressure values was more pronounced in boys.     

Evidence for a genetic predisposition for status epilepticus

The role of genetic factors in determining risk for status epilepticus (SE) was examined in twins identified using the population-based Virginia Twin Registry. Concordance rates for SE were 0.38 for monozygotic (MZ) and 0.00 for dizygotic (DZ) twins, with the rate in MZs being significantly increased over DZs. The prevalence of SE in MZ co-twins of affected individuals was as high as 0.55. Clinical presentation of SE was evaluated, and no association was found between occurrence of SE and age at onset or seizure etiology. Genetic factors contribute to risk for SE.     

Multilevel models for longitudinal variables prognostic for survival

The issue of modelling the joint distribution of survival time and of prognostic variables measured periodically has recently become of interest in the AIDS literature but is of relevance in other applications. The focus of this paper is on clinical trials where follow-up measurements of potentially prognostic variables are often collected but not routinely used. These measurements can be used to study the biological evolution of the disease of interest; in particular the effect of an active treatment can be examined by comparing the time profiles of patients in the active and placebo group. It is proposed to use multilevel regression analysis to model the individual repeated observations as function of time and, possibly, treatment. To address the problem of informative drop-out--which may arise if deaths (or any other censoring events) are related to the unobserved values of the prognostic variables--we analyse sequentially overlapping portions of the follow-up information. An example arising from a randomized clinical trial for the treatment of primary biliary cirrhosis is examined in detail.     

金属矿地震勘探钻孔方法研究

金属矿地震勘探一般位于复杂的山地和丘陵地区,而在这些地区开展地震数据采集工作有很大的难度。而这些问题产生的最根本的问题是激发成孔问题,只有成孔到合适的激发层位,才能获得较好的激发效果。本文主要依托某金属矿地震勘探研究项目,提出了一套经济、高效、便捷的钻孔方法。     

Evidence for clinical smoking cessation for adolescents.

Objective: This report reviews the evidence that informs the role of health and mental health care providers in addressing youth smoking cessation. Design: Qualitative literature review. Results: Physicians do not consistently screen adolescents for tobacco use and fail to provide recommended cessation advice. Challenges to addressing smoking cessation include the need for procedures to ensure confidentiality and the existence of competing demands to provide other services. Few published studies have specifically addressed the effectiveness of clinical interventions. Interventions that require return visits or follow-up phone contacts are technically difficult to implement in this population. Successful interventions may require resources not available in nonresearch settings. Most studies have used brief clinical intervention as a control condition, making it impossible to evaluate its effectiveness. Conclusion: There is little evidence that supports current clinical smoking cessation guidelines for adolescents. More research is needed to develop inexpensive, efficient clinical interventions that can provide youths access to smoking cessation help. Future challenges include reorganizing clinical systems to offer greater counseling by support staff or in electronic formats and to provide effective booster messages and follow-up care in a population that is difficult to track. (PsycINFO Database Record (c) 2010 APA, all rights reserved)