Pressure venting of dust explosions in large vessels

The validity of the dust explosion venting nomograph D in NFPA 68 was examined in tests with vessels having volumes from 2.4 to 250 cubic meters and with dusts of classes St 1 and St 2.     

Design example: Explosion protection selected for a spray drying installation

A new spray drying installation must withstand a probable dust explosion without endangering personnel. Explosion venting and suppression are considered as well as the reasoning behind the design requirements.     

A heuristic algorithm for a multi-product dynamic lot-sizing and shipping problem

This paper analyzes a dynamic lot-sizing problem, in which the order size of multiple products and a single container type are simultaneously considered. In the problem, each order (product) placed in a period is immediately shipped by some containers in the period and the total freight cost is proportional to the number of containers used. It is also assumed that backlogging is not allowed. The objective of this study is to simultaneously determine the lot-sizes and the transportation policy that minimizes the total costs, which consist of production cost, inventory holding cost, and freight cost. Because this problem is NP-hard, a heuristic algorithm with an adjustment mechanism is proposed based on the optimal solution properties. The computational results from a set of simulation experiment are also presented.     

Enhancing Concept Test Validity by Using Expert Consumers

In standard concept testing practice, consumers may be invited to participate in a test if they use or possess the product. However, merely using or possessing a product is no guarantee that a consumer has the level of product knowledge that is necessary for judging the concept. Conducting a concept test with consumers who lack the necessary product knowledge may jeopardize the validity of the test results. That is, the results of such a concept test may not accurately indicate how consumers will evaluate the real product. To ensure the validity of concept test results, Jan Schoormans, Roland Ortt, and Cees de Bont suggest that consumers who are invited to participate in a concept test should possess a degree of product knowledge. When a consumer is asked to evaluate a concept, their product expertise allows them to understand product information faster, fill in missing information, and learn more easily. Consumers with product expertise are better able to discriminate between important and unimportant aspects of a product. They are also better able to infer benefits from a product's physical attributes. To explore the effects of consumer expertise on the quality of the evaluations provided by concept tests, the authors conducted two experiments, both of which resemble actual concept tests. The first experiment examines the effect of consumer expertise on the results of a concept test for a major innovation, Videotext. This experiment tests the hypothesis that the similarity between the evaluations of a concept and an actual product will be greater for consumers with a high level of product-category expertise than for consumers with low product-category expertise. The results of the experiment clearly support the idea that product-category expertise enhances a respondent's ability to evaluate concepts in a test of major innovations. From this, it is concluded that only respondents with high product-category expertise should be used for concept tests of major innovations. The second experiment explores the effects of product expertise on consumers' evaluations of a minor innovation, a redesigned coffee maker. This experiment tests two hypotheses. First, it is proposed that consumers with high product expertise give more consistent evaluations in a concept test than consumers with low product expertise. Second, it is suggested that consumers with product expertise generate more stable evaluations over time than consumers without product expertise. The results of this experiment clearly indicate that using consumers with moderate to high levels of product expertise is beneficial to the validity of the results from concept tests of minor innovations.     

Analysis of diers venting tests: Validation of a tool for sizing emergency relief systems for runaway chemical reactions

A one-dimensional computer model of multiphase, chemically reacting flow has been used to analyze a number of DIERS Phase III venting tests.     

Dust entrainability and its effect on explosion propagation in elongated structures

Two apparatuses have been developed to characterize the entrainability of dust deposits. The minimum aerodynamic wall shear stress required for dust removal (Critical Shear Stress), measured by the first apparatus, is an indicator of the ease with which dust particles can be removed from a layer. The second apparatus measures the settling velocity distribution of dust clouds, which is an important factor controlling the extent of dispersion as well as the time period during which the entrained dust cloud can remain suspended. Testing has shown that the critical shear stress depends not only on the nature of the dust, but on the way the dust deposit is formed. Therefore, a portable version of this apparatus was developed to allow field testing of dust deposits. This methodology has also been used to evaluate the effect of oil treatment sometimes used in the grain handling industry to reduce dust emission. Simulated explosion tests have demonstrated the importance of critical shear stress on dust entrainability. A simple model calculating unsteady dust concentration in elongated structures has been developed. The model shows that flammable dust concentrations induced in a gallery by a primary explosion exist over a finite length and time period. Therefore, the probability of a secondary explosion depends not only on the dust and layer properties, but on the details of the primary explosion and of the enclosure geometry. A simple criterion for transmission of a primary explosion into an adjoining elongated structure is discussed in the paper.     

基于天然气放空系统的水力计算软件开发

高压天然气放空系统由放空干线管段气体、放空管线及外界大气组成。放空管路属于非稳定流动,其水力计算不能采用一般站场管路的达西公式。以Fano方程为基础,运用流体力学及输气管路流动基础理论进行程序编写,计算软件可实现对各时刻放空所对应的瞬时放空量、累计放空时间、截面压力及温度、储气量的求解。计算结果与图解法进行对比,误差控制在2%以内,弥补了图解法仅可求得瞬时放空量而无法得到其他参数的缺陷,并利用东河伴生气管线下沉工程现场放空数据与本计算软件对比,计算结果吻合度高,符合现场工程实际。     

Optimal inventory control of empty containers in inland transportation system

In this paper, we deal with an inventory control problem of empty containers in an inland transportation system. In inland container transportation, freights (containers) are transported between terminal and the customer’s location by trucks, trains and barges. Empty containers are an important logistic resource and shipping companies try to operate and manage empty containers efficiently. Because of the trade imbalance between hub ports, empty containers should be periodically repositioned from surplus areas to shortage areas. However, it is not easy to exactly forecast the demand of empty containers, and we therefore need to build an efficient way to reposition the empty containers. In this paper, we consider a shortage area and propose an efficient inventory policy to control empty containers. We assume that demands per unit time are independent and identically distributed random variables. To satisfy the demand of empty containers, we reposition empty containers from other hubs based on the (s, S) inventory policy, and also consider the lease of empty containers with zero lead time. For the leased containers, we should return the number of empty containers leased to the leaser after the specified period. For a given policy, simulation is used to estimate the expected cost rate and we use the optimization tool, OptQuest^® in Arena to obtain the near optimal (s, S) policy in numerical examples.     

Laboratory and large-scale dust explosion research

This paper describes dust explosibility research in full-scale experimental mines and a 20-L laboratory chamber at the U.S. Bureau of Mines and in a 1-m³ laboratory chamber at Fike Corporation. The purpose of this research is to improve safety in mining and other industries that manufacture, process, or use combustible dusts. As part of this work, carbonaceous dusts with a wide range of volatilities and various particle size distributions were studied. Laboratory data on the minimum explosible concentrations of predispersed dusts were comparable to mine data for nominal dust loadings that were dispersed by the aerodynamic disturbance from a gas ignition zone. Recommendations are given on the limitations of small-scale testing such as “overdriving” by too strong of an ignitor. The effect of dust particle size on explosibility data is illustrated for coal and aluminum dusts. For both dusts, the finest sizes were the most hazardous. The inerting requirements for preventing explosions were also measured in both laboratory and large-scale systems. All the data show relatively good agreement between the laboratory and the large-scale tests.     

Disengagement predictions via drift flux correlation vertical,horizontal and spherical vessels

The behavior of an open system is modeled. Thus, for special cases, the void fraction is predicted as a function of location and time. The open system may be an open vessel or a vessel with an open relief device. A single governing equation is derived based on combining the material and energy balances with the churn-turbulent drift flux relationship and assuming no radial gradients. This partial differential equation is not solved. It is, however, bounded by homogeneous and all vapor venting. These special cases are solved. In homogeneous venting the key variable is time. In all vapor venting under pseudo-steady-state conditions the key variable is location. The solution of the partial differential equation is also discussed. Under pseudo-steady-state and churn-turbulent conditions, the open system is modeled. The minimum void fractions (corresponding to a maximum liquid inventory) with all vapor venting, for vertical, horizontal, and spherical vessels are predicted and compared. Analytical expressions for the local and average void fractions in a vertical vessel and non-unity distribution parameters are presented. Void fraction profiles are compared for three cases: 1. vertical cylinders with distribution parameters (Co values) of unity and 1.5, 2. horizontal and vertical cylinders with varying L/D ratios, and 3. spheres with inscribed vertical cylinders having constant gas production to bubble rise ratio (Ψ′ value). The vertical cylinder average void fraction for non-unity distribution parameters can now be calculated analytically. The horizontal cylinder average void fraction predicted by turning it upright results in an over prediction of at most 4%. The sphere average void fraction predicted via an inscribed vertical cylinder, with the same Ψ′ value, is consistenly high by at most 8%.     

The storage location assignment problem for outbound containers in a maritime terminal

This paper addresses the storage location assignment problem for outbound containers. The problem is decomposed into two stages. The yard bays and the amount of locations in each yard bay, which will be assigned to the containers bounded for different ships, are determined in the first stage. The exact storage location for each container is determined in the second stage. The problem in the first stage is solved by a mixed integer programming model, while a hybrid sequence stacking algorithm is applied to solve the problem in the second stage. Experimental results show that the proposed approach is effective and efficient in solving the storage location assignment problem for outbound containers.     

The Predictive Power of Internet-Based Product Concept Testing Using Visual Depiction and Animation

One critical step in new product development is selecting from among multiple possible product concepts the one that the firm will carry forward into the marketplace. There is a need for low‐cost, parallel testing of the appeal of new product concepts, the results of which closely mirror ultimate market performance. In this article, the authors first describe an Internet‐based product concept testing method they developed that incorporates virtual prototypes of new product concepts, substituting them for physical prototypes. The method can be used with either static representations of the products or with dynamic representations that demonstrate how the product works through a simulated video clip of its operation. The objective of this method is to allow design teams to select the best of several new concepts within a product category with which to proceed, without having to develop physical prototypes. The authors then provide a rigorous test of both virtual prototype methods against tests using both physical prototypes and attribute‐only (i.e., no visuals), full‐profile conjoint analysis. Nine concepts compete against two actual products in the tests. Market shares from the test using the physical prototypes are defined as the “actual” market shares. Predicted market shares for the attribute‐only, full‐profile conjoint analysis and each of the two virtual prototype methods are compared to those obtained for the physical prototypes. Both static and animated virtual prototype tests produced market shares that closely mirrored those obtained with the physical products, outperforming the set of predictions across the full range of products produced in the attribute‐only conjoint analysis. Interestingly, the attribute‐only conjoint analysis identified the top three products, in correct order. It was unable to differentiate performance below these top three products. Furthermore, it predicted market shares for the top three products to be well below those achieved using physical prototypes. As virtual prototypes cost considerably less to build and test than their physical counterparts, design teams using Internet‐based product concept research may be able to afford to explore a much larger number of concepts. Virtual prototypes and the testing methods associated with them may help reduce the uncertainty and cost of new product introductions by allowing more ideas to be concept tested in parallel with target consumers.     

Knowledge sharing and strategic fit in integrated product development proejcts: An empirical study

While product strategy has been approached from a variety of perspectives, the role of strategic fit as a critical linkage of knowledge sharing practices and new product development outcomes have not been adequately explored. This paper discusses how strategic fit is instrumental for cross-functional teams to integrate product development outcomes. This paper identifies critical knowledge sharing components that enhances the extent of strategic fit that in turn improves the success of product development efforts. Strategic fit or alignment requires knowledge sharing practices of the product development team. Teams with a shared knowledge base are more capable of thinking strategically, adapting their actions to their project environment and accordingly engaging in innovative problem-solving while ultimately achieving project goals of time, cost and value. This paper presents and tests a research model using a sample of 285 product development projects of firms from USA, Canada and Spain. The results suggest that strategic fit is associated with greater knowledge sharing and enhance product development outcomes in both small and large firms as well as diverse regions (i.e., USA, Canada and Spain).     

The Moderating Roles of Prior Experience and Behavioral Importance in the Predictive Validity of New Product Concept Testing

Concept testing has long been recognized as an important new product development (NPD) activity. As one of the widely used concept testing techniques, the method of intentions surveys relies on the purchase intentions of the potential buyers of new products and helps firms assess the viabilities of their new products before making major financial and nonfinancial commitments to their development. Despite the importance of intentions‐based new product concept testing and its widespread use by firms, the correspondence between initial behavioral intentions and subsequent purchase behaviors has been relatively low and heterogeneous, making it very difficult for firms to draw any useful conclusions from intentions surveys. Focusing on the predictive validity of intentions‐based new product concept testing and addressing several calls for future research to identify specific conditions making it more effective, this paper tests the moderating roles of prior experience and behavioral importance in the predictive validity of intentions‐based new product concept testing. It also tests whether people who state a positive intention and people who state a negative intention are equally accurate in their intentions. Finally, it tests the relative moderating roles of prior experience and behavioral importance in the intentions–behavior relationship. The results based on two longitudinal surveys first suggested that people's prior experience moderates the relationship between behavioral intentions and actual behaviors in a way that the relationship is stronger when prior experience is high as opposed to when it is low. Second, they showed that the level of importance that people attach to a behavior also moderates the relationship between behavioral intentions and actual behaviors such that the relationship is stronger when behavioral importance is high as opposed to when it is low. Third, they indicated that the behavioral intentions of people who state that they will not perform a behavior are more accurate than are those of people who state that they will perform it. Finally, the results suggested that the impact of behavioral importance is greater than that of prior experience. This study offers several implications. Most notably, the results can help firms better understand different factors affecting the predictive validity of intentions‐based new product concept testing and hence make more accurate new product decisions.     

石家庄市冬季大气颗粒物中元素组分的特征分析

为研究石家庄市大气颗粒物的污染特征及其来源,于2013年2月选取石家庄市6个点位,分别采集大气中TSP,PM10和PM2.5的样品,采用ICP-MS法测定颗粒物中20种元素的浓度,并采用相关性分析、t检验法和富集因子法分析探讨石家庄市冬季大气颗粒物中元素污染特征。结果表明,石家庄市城区Al,Ca,Si,S元素在不同粒径颗粒物中含量都较高。根据标识元素分析,颗粒物中无机元素主要来源于燃煤尘、建筑尘和土壤尘,TSP,PM10和PM2.5中无机元素具有较好地统计相关性和同源性。通过富集因子分析,石家庄市大气颗粒物中的元素受人为因素影响的主要污染来源为燃煤、交通排放和冶金化工尘。     

New Product Development Performance and the Interaction of Cross-Functional Integration and Knowledge Management

Previous research on cross-functional integration between research and development (R&D) and marketing has focused on the development of appropriate structural modes and levels of integration and cooperation across the R&D–marketing interface. A gap in the previous research in this area has been the failure to investigate the integration of information from past related product development projects (i.e., knowledge management). In this investigation of R&D–marketing integration, variables from the emerging research literature on organizational learning and knowledge management are examined. By simultaneously investigating the effects of knowledge management variables and R&D–marketing integration, this gap in the literature is addressed. The results demonstrate that the combined effects of R&D–marketing integration and knowledge management in the form of recording, retrieving, and reviewing information from past projects results in interaction effects. In 8 of 18 tests interactions were found. In 6 of 18 tests these resulted in the form of amplification effects with dependent variables such as product prototype development proficiency, product launch proficiency, technological core competency fit, and design change frequency.     

Hydrodynamic aspects of venting for vessels containing viscous fluids

Nine depressurization experiments for vessels containing water, freon-114 and high viscosity fluids have been analyzed. These experiments were carried out at different plants and provide information about the dependence of the depressurization process on the size of the vessel, the type of vent installed, and the initial conditions. The differences of venting into the atmosphere or venting into a catch tank have been also examined. The accuracy of the two-phase flow model used for the analysis of these experiments has been demonstrated by comparisons with steady state data referring to co-current liquid/vapor flow as well as to batch type of flows, where the liquid phase is stagnant.     

Operationalizing and testing Galbraith's center of gravity theory

This paper develops and tests an expanded model of relatedness and firm performance, based on Galbraith's (1983) center of gravity concept. Traditional empirical approaches to relatedness have focused primarily on product similarities. This research operationalizes and tests a managerial dimension of relatedness, based on a firm's historical center of gravity, which assumes that businesses in the same vertical stage of the value chain are more similar to manage than those in different stages. Empirical results support Galbraith's hypothesis that this managerial dimension of relatedness may be more important than constrained product relatedness in achieving high performance. This finding suggests that diversified firms should operate in lines of business that are managerially similar in order to minimize complexity and apply core skills appropriately. Interestingly, while managerial relatedness was positively associated with firm performance in two out of three samples, constrained product relatedness was negatively associated with performance in two of the three samples. Taken together, these results suggest that optimal relatedness profiles may be industry specific, and that corporate relatedness may be more important in managing diversity than product relatedness. Future research should seek a better understanding of the specific dimensions which underlie both product and managerial relatedness.