环孔雾化喷嘴设计参数的研究

根据对雾化气流流动的理论分析及环孔雾化喷嘴设计参数的研究,提出了环孔雾化喷嘴设计参数的定性解析和定量描述;导出了在环孔雾化喷嘴出口处雾化气体流速及质量流量取得极大值时,雾化喷嘴气流出口截面积与空腔截面积及雾化压力的解析表达式;建立了雾化气体流速与环孔雾化喷嘴节圆直径、环孔直径及喷射顶角的函数关系式;探讨了保障环孔雾化喷...     

敞开式水雾化喷嘴

水雾化喷嘴是水雾化法生产金属粉末的关键设备。对于常规喷嘴,增大雾化夹角及提高雾化压力均可提高金属粉末的细粉率,但也都会遇到堵嘴问题,从而导致雾化过程中断。本研究分析了雾化过程中的堵嘴机理,设计了一种新型敞开式水雾化喷嘴,对其进行强度计算,并进行雾化试验。结果表明,此新型敞开式雾化喷嘴可以有效避免水雾化金属粉末过程中气囊的形成,可从根本上解决以往生产中经常出现的堵嘴问题。而对单个敞开式喷嘴而言,提高雾化夹角,增加孔数,以及提高雾化压力,均可以显著提高细粉率。     

TiAl预合金粉末制备的研究进展

高品质的预合金粉末是以粉末冶金工艺制备高性能TiAl基合金材料的基础。介绍了目前可用于规模化生产TiAl预合金粉末的各种雾化制备技术,包括惰性气体雾化法、转盘雾化法和等离子旋转电极雾化法,其中惰性气体雾化法又分为等离子感应熔炼定向气雾化法和电极感应熔炼气雾化法。分析了各种雾化制备技术的特点,并对国内外TiAl预合金粉末制备的研究进展进行了综述。     

超声波雾化喷嘴的设计

在超声波雾化设计原理的基础上，将雾化喷嘴按照用途进行了分类，总结了三类超声渡雾化喷嘴。在研究雾化汽油等燃料类的喷嘴、雾化水类的喷嘴的基础上。着重叙述了制取微细金属粉末的超声波雾化喷嘴；在固体雾化技术研究的基础上。研制成一种新型的雾化喷嘴——双层固体技术雾化喷嘴，叙述了它的工作原理和雾化机理，并进行了简单的实验验证。     

雾化铜粉制备技术的研究进展

本文概述了雾化法制备铜粉的研究进展,阐述了雾化法制备铜粉各工序的基本原理,探讨了雾化介质、氧化还原、还原、雾化方式、熔炼、破碎球磨等工序的技术特点,提出了更加合理的低松装密度雾化铜粉的生产工艺流程.     

真空气雾化参数对粉末粒度及形貌的影响研究

对雾化压力、雾化气体温度等雾化参数对粉末粒度、形貌的影响进行了研究。试验结果表明,雾化压力在2.3~3.2MPa范围内对粉末粒度影响不大,当雾化压力超过3.5MPa时,粉末粒度开始变细小。雾化气体温度对粉末粒度影响最大,较高的雾化气体温度有利于获得较细小的粉末。     

超声波重油喷嘴雾化特性的研究

介绍了一种新型流体动力式超声波重油雾化喷嘴。为了研究其雾化特性,以压缩空气和水为介质,利用激光粒度分析仪对超声波重油雾化喷嘴的雾化特性进行了详细的研究,分析了该型喷嘴的工作特点,研究了不同供气压力、供水压力和气液比(ALR)对喷嘴雾化性能的影响,同时也分析了粒径沿程变化情况。研究表明:流体动力式超声波重油雾化喷嘴雾化索太尔平均粒径非常小,为10～20μm,具有较好的应用前景。     

大功率多雾化电弧喷枪的研制

设计二进四出多雾化电弧喷枪,改变雾化气流场和流速,使雾化气流场合理分布,提高了喷涂粒子的射流速度,改善了雾化效果,使雾化粒子更细小更均匀,降低了涂层孔隙率,获得更大喷涂幅宽。应用对比试验标明,其性能已达到甚至超过国际同类产品。     

雾化室内气压对Sn_(0.3)Ag_(0.7)Cu焊锡粉末雾化过程的影响

利用超音速气雾化装置制备了Sn0.3Ag0.7Cu无铅焊锡粉末,研究了雾化室内不同气压状态对粉末雾化过程的影响。结果表明:随着雾化室内部气压的逐渐增大,锥形雾化区由稳定逐渐趋于紊乱,锥形雾化区范围逐渐变大,气液流量比也随之增大,粉末球形度先变好后变差。当雾化室内部气压为0.05 MPa时,锥形雾化区稳定且雾化区范围大,粉末球形度最好。     

雾化气体和熔滴速度的研究

从理论与实验两方面研究了雾化气体流速场和雾化熵滴与气体流场的交互作用,建阙雾化气体和熔滴流速的数学模型,探讨了雾化熵滴对雾化气体流速的影响。     

金属粉末气体雾化制备技术的研究现状与进展

气体雾化技术是生产金属及合金粉末的主要方法。本文依据气体雾化中喷嘴的结构特征，分析了国外几种具有工业实用意义的雾化技术的原理、性能与发展状况，评述了其优缺点和应用情况。     

Symptoms and characteristics of individuals with different types of recovery from DSM-IV alcohol dependence

This paper describes the psychological and psychosocial aspects of prenatal care, which are believed to be of particular importance for medical/psychological practice. The emotional changes that "normally" take place during pregnancy are surveyed and evidence is provided linking these changes with potential adverse effect on pregnancy and labour. The salience of anxiety and life stresses in pregnancy research is highlighted as well as their intricate inverse relationship with social support. Antenatal classes are offered as an example of social support provision. The different kinds of such classes and evaluation of their effectiveness are briefly presented, as well as a number of controlled trials of enhanced support during pregnancy. Finally, the effect provision of prenatal care has on women as well as their role in their own care are raised. The need is stressed for further sophisticated longitudinal and multivariate research exploring further the causative links between quality of prenatal care, pregnancy outcome, and subsequent child development.     

The contribution of fathers to the individuation process in adolescence

Numerous studies have shown fathers to be less engaged and less involved with their children and adolescents. This paper discusses the possible function that fathers' lower involvement may play in the development of their children. Data from two studies conducted on adolescents show that on the one hand fathers spend less time and are less engaged with their adolescents, but when they are together, the nature of their interaction is distinctive. For example, fathers are more engaged in play-like activities. This apparently distant and distinctive model is what adolescents need at this period of separation--a model of a "close enough" parent that allows and respects separation and support strivings for individuation. As results show, adolescents are satisfied with the role fathers play in their lives. Moreover, fathers are perceived as models for subsequent developmental goals such as marital life. It is suggested that fathers in their natural attitude are more capable of balancing closeness and separateness than mothers do and as such they are more flexible in response to varying developmental goals of their adolescent offspring.     

Niobium and tantalum: State of the world market, fields of application, and raw sources. Part I

Niobium and tantalum are rare refractory metals of important industrial value. Their reserves are a “critical” raw material, which leads to the necessity of evaluating the risks associated with the presence of primary and industrial raw-material sources of niobium and tantalum, as well as the influence of these factors on the supply and demand for these metals and their compounds allowing for their traditional and new application regions. In this article we analyze the world reserves of niobium and tantalum, and the dynamics of varying the raw-material base and industrial solutions implemented and proposed for their processing is considered. A modern market of niobium-based and tantalum-based materials is described, the main players on this market are listed, and the tendencies in the variation in the structure of consuming functional materials based on these metals are considered.     

Association of Risk Attitude with Market Diversification in the Construction Business

In construction, many large firms are diversified, and their diversification is recognized as a corporate strategy for growth and risk management. Diversification indicates extended competition into a different market sector. It is a departure from a firm’s experience base, and it can be riskier than improving performance in the currently operating market. Then, contractors’ diversification and their aggregate pattern in the market, if there is any, are realized outcomes through competition among contractors over different market sectors. The competing contractors may have different risk attitudes, which are the subconscious but critical basis of their risk-taking behaviors in competition. This study investigates the association of contractors’ organizational risk attitudes with their diversification on the basis of simulated competition among multiple contractors. The simulation replicates the actual diversification pattern of large U.S. construction contractors. The results provide new insight on the relationship between contractors’ risk attitude and their diversification as well as their competitive success.     

Molecular and biotechnological aspects of microbial proteases

Proteases represent the class of enzymes which occupy a pivotal position with respect to their physiological roles as well as their commercial applications. They perform both degradative and synthetic functions. Since they are physiologically necessary for living organisms, proteases occur ubiquitously in a wide diversity of sources such as plants, animals, and microorganisms. Microbes are an attractive source of proteases owing to the limited space required for their cultivation and their ready susceptibility to genetic manipulation. Proteases are divided into exo- and endopeptidases based on their action at or away from the termini, respectively. They are also classified as serine proteases, aspartic proteases, cysteine proteases, and metalloproteases depending on the nature of the functional group at the active site. Proteases play a critical role in many physiological and pathophysiological processes. Based on their classification, four different types of catalytic mechanisms are operative. Proteases find extensive applications in the food and dairy industries. Alkaline proteases hold a great potential for application in the detergent and leather industries due to the increasing trend to develop environmentally friendly technologies. There is a renaissance of interest in using proteolytic enzymes as targets for developing therapeutic agents. Protease genes from several bacteria, fungi, and viruses have been cloned and sequenced with the prime aims of (i) overproduction of the enzyme by gene amplification, (ii) delineation of the role of the enzyme in pathogenecity, and (iii) alteration in enzyme properties to suit its commercial application. Protein engineering techniques have been exploited to obtain proteases which show unique specificity and/or enhanced stability at high temperature or pH or in the presence of detergents and to understand the structure-function relationships of the enzyme. Protein sequences of acidic, alkaline, and neutral proteases from diverse origins have been analyzed with the aim of studying their evolutionary relationships. Despite the extensive research on several aspects of proteases, there is a paucity of knowledge about the roles that govern the diverse specificity of these enzymes. Deciphering these secrets would enable us to exploit proteases for their applications in biotechnology.     

Critical evaluation of currently recommended "reverence level" values

The guidelines of the committee on health protection in medical exposure contain, as required by the international commission on radiation protection, the requirement for the determination of values for reference levels for medical exposure, their use, and their fulfillment. Here we discuss the basis for their determination and point out that their control only appears to be meaningful in combination with quality requirements for which parameters are given in the guidelines of the German Medical Chamber and the European Guidelines.     

Significance of family relations for coping with psychological disorders--results of an empirical study of therapy prognosis of children and adolescents with psychological disorders

The importance of family relations for the therapy of psychiatric disorders in children and adolescents is discussed reporting results from an empirical study carried out in an inpatient sample of a child and adolescent psychiatric unit with regard to the quality of mother-child resp, father-child relation and its influence on coping processes. Whether adolescents suffering from a psychiatric disorder are able to cope with their problems during the course of a therapy, depends on their individual and social resources. Therapy outcome is to a great extent influenced by the emotional quality of their family relations. Hostility and rejection as well as unstructured and disorganized parental behavior contribute to a negative outcome. A differentiated analysis shows further that the relation between the adolescents and their fathers is particularly important for therapy prognosis. Nevertheless, one has to consider the respective relations with both parents for therapy prognosis, as problems with one parent may be partly compensated by a good relationship with the other parent. Finally, the cooperation between parents and clinical staff is discussed. Data and experiences show that interest and readiness of parents (mothers as well as fathers) for a close cooperation are higher than generally expected.     

Vulnerability and mother-child interactions. Illustration of the necessary but insufficient conditions for the efficacy of early intervention

The present study evaluates the impact of an early stimulation program for 24 mother-infant (0-6 months) vulnerable dyads from the Montérégie region. These dyads participate in a series of ten stimulation workshops. Twenty four other dyads form a witness group. The program's major objective aims at developing positive interactions for the mother and stimulative interactions for the infant. The hypotheses state that at the end of the program, the mother from the intervention group will feel less isolated, possess a higher level of knowledge on the development of their child, perceive more positively the temperament of their child and have behaviors that are more contingent to their infants as well as more functional to this development. The two first hypotheses are not confirmed. However, at the end of the program, the mothers of the intervention group perceive the temperament of their child as foreseeable. Also, they imitate more frequently the verbal and facial behaviors of their infant and emit more vocalizations when they are interacting with the child. The discussion of results bears on the importance of modifying conditions in which the parent-child interactions are held to prevent deficits in the development of the children.     

Glenohumeral arthroplasty: a critical review of indications and preoperative considerations

Total shoulder arthroplasty has become an effective treatment for advanced glenohumeral arthritis. The results depend, in part, on the underlying degenerative process. This article reviews the indications for glenohumeral arthroplasty, including important preoperative considerations. The different types of glenohumeral arthritides are discussed with respect to their clinical and radiographic manifestations, as well as their impact on preoperative planning.