A comprehensive test method for inline flame arresters

The certification test standards that presently exist for flame arresters are highly inadequate for inline applications. A proper flame arrester test method should ensure that a unit will work with any flame front conditions that it could be exposed to in actual use. When evaluating flame arrester performance, it is just as dangerous to neglect deflagration testing as detonation testing. The comprehensive inline flame arrester test method outlined here involves exposing a unit to the entire flame propagation pressure spectrum. This includes low, medium and high pressure deflagrations as well as overdriven and stable detonations. The test method also takes into account the following factors: flow restriction on the protected side of the flame arrester, flame propagation through a flowing gas, initial system pressure and temperature, and specified gas mixture. Flow restriction on the protected side of the flame arrester has a very significant effect on performance and has not previously been given consideration in flame arrester testing. Besides moving flame front test, endurance burn testing and hydrostatic pressure testing are also discussed here. Major regulatory organizations have recently adopted these findings as the basis for new standards proposed to cover an inline flame arrester test method.     

Design practice for extinguishing barrier systems

An extinguishing barrier comprises an optical flame sensor and a HRD-Suppressor located downstream of the detected flame front. The effectiveness of an extinguishing barrier is based on its ability to detect an explosion in a pipeline by means of an optical flame detector whose tripping signal is amplified and then very quickly actuates the detonator-actuated valves of the pressurized HRD-Suppressors. Extensive practice-related tests in pipelines, having different cross sections and length, in pipelines connected with different vessels, have shown that extinguishing barriers can be used without reservation to halt or stop an explosion in practice. The amount of suppressant agent required depends on the nature of the combustible dusts, the nominal diameter of the protected pipeline, the explosion velocity and the maximum reduced explosion overpressure in the vessel. Most significantly, the theoretical understanding of explosion propagation and extinguishing has led to computer design guidance which has simplified system design. Explosions can be combated effectively in pipelines up to diameter 2500 mm.     

University‐industry collaboration and front‐end success: the moderating effects of innovativeness and parallel cross‐firm collaboration

Collaboration with science‐based and/or market‐based partners is a promising means for firms’ R&D groups to leverage complementary expertise and resources to generate innovative results. However, R&D managers face the dilemma which partner type to choose in different innovative contexts and whether to focus on one partner type or to integrate both types in early stage R&D. Using survey data from 166 heads of R&D groups, this study investigates university–industry collaboration’s impact on front‐end success depending on the degree of innovativeness and the interaction with other industry partners. The results confirm an overall positive relationship between university–industry collaboration and front‐end success. However, innovativeness increases complexity in this relationship. Parallel collaboration with firms and universities can have a mixed impact on front‐end success depending on the degree of innovativeness. This simultaneous collaboration with firms and universities strengthens front‐end success for more radical innovations, while parallel collaboration activities for more incremental innovations do not necessarily strengthen front‐end success. These findings imply that both collaboration types should be used simultaneously in the front end of radical innovation and that firms could reduce complexity by focusing on either firms or universities as partners for incremental innovations.     

Market Share Instability and the Dynamics of Competition: a Panel Data Analysis of Japanese Manufacturing Industries

This paper explores market share instability as a measure of market mobility. Using a newly constructed panel data set, we examine the determinants of the market share instability of leading firms in Japanese manufacturing industries. The findings suggest that there is a significant relationship between concentration and market share instability, and the market shares of leading firms are more stable in highly concentrated industries. We also provide evidence that industry growth has a significantly positive effect on market share instability.     

A method for determining the flammable limits of gases in a spherical vessel

The current method for determining the flammable limits for a gas in a closed spherical vessel is based on a specification of the maximum pressure increase during the combustion, usually from 5 to 10% of the initial ambient pressure. This approach is completely arbitrary and is not fundamentally based. For most hydrocarbons this pressure boundary and hence the flammable limits are easy to determine experimentally since an abrupt pressure drop occurs at the flammable limits as the fuel concentration in air is adjusted. However, for some species, particularly hydrogen mixed with air, the drop in maximum combustion pressure is not very abrupt and the fuel concentration can range several percentage points depending on the arbitrary criterion used for the flammable limits. This article will discuss a new approach for determining the flammable limits for a gas in a spherical vessel. The approach is based on the maximum second derivative of pressure rise. The second derivative is indicative of an acceleration of the combustion process and is, hence, fundamentally based. Furthermore, we have identified a new approach to determine the downward propagating flammable limits based on the combustion time, that is, the time that the gas actually burns in the vessel. Experimental data for methane and hydrogen show that the second derivative flammable limit criterion produces slightly conservative values for combustion in air. Visual inspection of the combustion during the tests showed that no visual combustion was observed at the second derivative criterion. For methane, the second derivative criterion resulted in a flammable range in air from 4.6 to 15.8% methane. For hydrogen these limits are 3.6–75.2%. We believe that this method will provide a much more fundamentally based method to determine both the upper and lower flammable limits of upward flame propagation and also provide a means to determine the downward propagation limits in a spherical combustion vessel. © 2009 American Institute of Chemical Engineers Process Saf Prog, 2009     

具有异质性扩散率的传染病模型分析

为了刻画大尺度空间范围内的个体移动对疾病传播的影响,主要研究了异质集合种群网络的传染病传播过程。由于城市之间存在规模以及交通发达程度等方面的异质性,扩散率也存在一定的异质性。以城市作为节点,建立了具有异质性扩散率的传染病动力学模型,更加准确地刻画了网络结构以及人们的出行对疾病传播的影响。通过对系统进行定性及稳定性分析,发现系统存在一个无病平衡点,并得到了无病平衡点不稳定的阈值条件。当达到疾病爆发的阈值条件时,系统存在唯一的地方病平衡点,并且地方病平衡点是局部渐近稳定的。通过数值模拟验证了理论的正确性。研究表明,增大扩散率能加快疾病的流行速度,因此,通过有效控制大城市的人口出行率可以在一定程度上控制疾病的爆发。     

Customer segments as moving targets: Integrating customer value dynamism into segment instability logic

Segmentation is a mature concept in marketing strategy that continues to receive significant attention from managers and scholars alike. The key goal in segmentation is identifying and reaching profitable segments with products and services that meet the common needs of these customers. However, a fundamental issue needing rigorous attention is that customers' needs are dynamic and can induce segment instability. The purpose of this paper is to draw focus to segment instability in business-to-business markets by conceptually exploring its theoretical underpinnings and integrating related theory on customer value change to propose an agenda for future research.     

表面喷丸处理对轴用42CrMo钢弯曲疲劳性能的影响

根据轴类零件的实际工况,选用缺口棒状试样作为研究对象,分析了经表面喷丸处理的调质态42CrMo钢在常温空气环境下的旋转弯曲疲劳性能。结果表明,试样经表面喷丸工艺处理后,抗弯曲疲劳性能显著提高,疲劳极限提高约90MPa;表面喷丸试样疲劳裂纹产生和扩展速度缓慢,宏观断口呈现出塑性断裂特征。     

Beyond listening: the distinct effects of proactive versus responsive customer orientation on the reduction of uncertainties at the fuzzy front end of innovation

The extent to which the intensity of R&D employees' interaction with market-oriented employees, proactive customer orientation, and responsive customer orientation affect the ability to reduce product-related uncertainties at the fuzzy front end of innovation was analyzed. They investigated 160 product innovation projects in various high-tech industries and identified proactive customer orientation as an important moderator of the link between R&D employees' interaction with market-oriented employees and the reduction of product-related uncertainties at the fuzzy front end. They also found that responsive customer orientation diminishes the ability to reduce product-related uncertainties at the fuzzy front end. The theoretical and managerial implications of the results are discussed.     

基于GWR模型的长三角区域经济增长主导因素研究

本文运用地理加权回归(geographical weighted regression,GWR)方法,对2003年、2008年两个年度的长三角区域经济增长主导因素的空间非稳定性进行了实证分析。传统的OLS只是对参数进行平均或全局估计,不能反映参数在不同空间的空间非稳定性;GWR是一种简单、有效的技术,可以反映参数在不同空间的空间非稳定性。研究结果表明,在对长三角经济增长各主要因素进行参数估计时,GWR模型与OLS模型有显著的差异;经济增长的主导因素存在空间变异。     

Global sourcing strategy and sustainable competitive advantage

Global sourcing strategy has been one of the most hotly debated management trends in the last 20 years. In its early years, global sourcing was examined mostly from “in-house” development and procurement perspectives; and in the last several years, research focus has shifted to “outsourcing” activities. Along with this shift from internal to external focus on global sourcing, many researchers and business practitioners have applied a core competency argument to justify increased levels of outsourcing activities on a global basis. Although the beneficial aspects of outsourcing are assumed in most cases, no consensus exists in reality as to the effect of outsourcing. Furthermore, the increased instability of the exchange rate environment in the last several years has also led to increased difficulties in managing globally scattered operations that were once fashionable in the 1980s-90s under the rubric of global strategy. In this article, the authors explore potential limitations and negative consequences of outsourcing strategy on a global scale.     

Thermal stability and deflagration of ethylene oxide

Some initiating causes of ethylene oxide decomposition are examined. Experimental data are presented for thermal decomposition limits, autoignition temperature and minimum ignition energy. It is shown that flame propagation through liquid filled lines may occur via decomposition of a vapor pocket. Insulation fires are discussed in terms of a series of exothermic reactions initiated by low tempertaure formation of polyethylene glycols. Some case histories are reviewed.     

垂直列管内低沸点物料的沸腾传热

以水-邻苯二甲酸二丁酯为测试物系,研究了垂直列管内水在沸腾状态下对其传热膜系数的影响,考察了温度、物料组成、进料速度等因素对传热膜系数的影响。实验结果表明沸点差和低沸点物料的相对进料速度对传热膜系数的影响较大,据此提出了低沸点组分沸腾状态下两相流传热膜系数随沸点差和相对进料速度的计算式。     

SRC柱和CFST柱在车辆撞击下的动力响应分析

为了研究框架柱在冲击荷载作用下的抗撞击性能,基于非线性有限元软件LS-DYNA建立了精细化车辆-框架柱碰撞模型。首先,根据轴压承载力相同的原则设计2类框架柱：钢骨混凝土(SRC)柱和钢管混凝土(CFST)柱;其次,对轴压比、撞击角度、撞击速度和车型等影响方形框架柱抗撞击性能有关因素进行参数化分析,探讨框架柱在汽车撞击下的塑性损伤以及破坏模式;最后,比较SRC柱和CFST柱的抗撞击性。结果表明,SRC柱在柱顶受到斜向剪切破坏,在柱底受到弯剪破坏,而CFST柱的破坏模式是弯曲破坏。在车辆侧向撞击下,角度为15°撞击SRC柱时更危险,而CFST柱在正面撞击时更危险。车辆速度和车辆质量的增大,使得框架柱受到的碰撞损伤增大。CFST柱的抗撞击性能优于SRC柱。研究结果证明SRC柱和CFST柱具有优越的抗撞击性能,可为国家相关标准的修订提供参考。     

Combustion hazards of silane and its chlorides

This paper addresses the unusual combustion hazards of silane and its chlorides, comprising the homologous chlorosilane series SiH_nCl_4-n. The literature on silane is briefly reviewed and new experimental data presented showing the effects of sudden releases into free air. New data are presented for ignition sensitivities and deflagration rates of chlorosilane mixtures with air. Specific hazardous reactions of this group of materials are described and contrasted with those of the analogous alkanes. Mechanisms for flame acceleration and transition to detonation are discussed.     

2009香港玩具展1月5日开幕

依托香港得天独厚的地理、经济、文化等优势,香港玩具展一直都被业界称之为新年世界玩具发展“风向标”。受金融风暴影响,全球经济持续低述,玩具行业在此环境下面临重大挑战。2009年新年第一周在香港举办的第35届香港玩具展,将是玩具业界同仁展望2009年玩具发展新趋势、把握世界玩具市场新动向的重要平台,是不容错过的玩具盛会。     

管道内高速传播火焰传感器的研制及应用

研制了管道内高速传播火焰检测用的光电传感器,并应用于溶解乙炔干式回火防止器回火性能测试仪。传感器具有结构简单,灵敏度高,可靠性好等特点。     

K?nnen sich erneuerbare Energien langfristig auf wettbewerblich organisierten Stromm?rkten finanzieren?

In this paper we address the issue of whether renewable energy sources can be integrated into power markets if the use of renewable energies is extended at the desired speed. Market integration means that renewable energy sources have to cover their full costs from revenues on competitive markets. In the first part of this paper, we evaluate the long-term revenues of intermittent renewable energy sources using a high resolution power market model. Considering the renewable targets of the German lead study of 2010, we show that due to the merit order effect, intermittent renewable energy sources, such as wind power and photovoltaic, cannot be financed through power markets alone, even if their full costs fall below those of conventional power plants. This is also true for scenarios with high CO₂-prices and increasing spot market prices. In the second part of this paper, we discuss whether in the long run additional instruments such as green certificates or capacity markets would allow for a more competitive financing of renewable energy sources. Center stage in the discussion is the question under which circumstances these instruments increase competitive pricing and decentralised market decisions.     

Communities of Practice versus Organizational Climate: Which One Matters More to Dispersed Collaboration in the Front End of Innovation?*

Dispersed collaboration provides many benefits such as members' closeness to local cultures and markets and reachability of talent worldwide. Hence, it is no surprise that dispersed collaboration is frequently being used by product development teams. A necessary but not sufficient condition for innovation performance is the sharing of tacit, non‐codified and explicit, codified knowledge by the team. Situated learning theory, however, predicts that tacit knowledge sharing will be largely prevented by “decontextualization.” Therefore, increasing usage of dispersed collaboration will decrease levels of tacit knowledge—crucial to innovation and organizational performance—in the business unit. This research investigates the moderating role of mechanisms believed to enable tacit knowledge transfer in the front end of innovation. Using data from 116 business units, the moderating role of communities of practice and organizational climate on the relationship between the proficiency of dispersed collaboration and front end of innovation performance is investigated. Encouragement of communities of practice is found to moderate the relationship between proficiency of dispersed collaboration and front end of innovation performance on the business unit level. More specifically, proficiency of dispersed collaboration is not related at all to front end of innovation performance in business units with low support for communities of practice; but a positive relationship exists in business units with high support for communities of practice. This study does not provide support for the moderating effect of organizational climate on the relationship between proficiency in dispersed collaboration and front end of innovation performance. However, supportiveness of climate has a significant direct effect on front end of innovation performance. The findings of this study suggest that managers should simultaneously invest in increasing proficiency in dispersed collaboration and supporting communities of practice. Either one by itself is insufficient. Because of its significant direct effect, managers should also nurture an open climate favoring risk taking, trust, and open interaction.