Search results

The purpose of this paper is to study the effect of feeding scheme on melt flow and temperature field during the steady-state of level-pour direct-chill (DC) casting of A390 alloy hollow billet and optimize the design of feeding scheme.

Melt flow and temperature field are investigated by numerical simulation, which is based on a three-dimensional mathematical model and well verified by experiments.

The numerical results reveal that both melt flow and temperature field are obviously affected by the feeding scheme. The homogeneity of melt flow and temperature field in hollow billet with the feeding scheme of modified four inlets are better than the other feeding schemes. Experimental results show that crack can be eliminated by increasing the number of feeding inlets. The primary Si size appears unaffected while the distribution of primary Si particles is highly affected by the change of feeding scheme. Only with the feeding scheme of modified four inlets can fine and uniformly distributed primary Si particles be achieved.

The paper includes implications for the design of feeding scheme in level-pour DC casting of hollow billet for practical use.

This paper develops different feeding schemes for level-pour DC casting of hollow billet and optimizes the design of feeding scheme.

Performance prediction of a proton exchange membrane fuel cell (PEMFC) has been studied using a multiphysics-based numerical simulation. The simulated geometry was a simple channel, in which the multi species transportation in the porous electrodes and the coupled electrical current and potential distributions were modeled. The 3D simulations provide the cell performance curve and the fuel/oxidant concentration distributions along the feeding channel. To obtain the detailed flow field in the porous gas diffusion layer, a 2D simulation was also performed. The simulations were compared with the available experimental data for a single channel PEMFC and the comparisons are favorable.

With the twin screw extruder being widely used, there are a lot of parameters considered in the method, and the extruder’s volume is an important parameter of twin screw extruders among them. In this paper, some of the extruder parameters such as the impacting extruder volume are introduced, and the mathematical relationship in these parameters is interpreted. The minimum power consumption is the goal of the authors’ structural design.

This paper further applies genetic algorithm, a kind of intelligent optimization methods, to obtain the most optimized design dimension, and power consumption function related to unit output of extruder is used as the optimizing target. Meanwhile, this paper takes channel depth of feeding section, channel depth of extrusion section affecting the energy consumption, the width of flight top and helix angle as design variables.

By using genetic algorithm, the optimal structure size is obtained, and the power consumption is minimum.

With the use of optimizing the structure, the power of consumption is reduced. This method has important economic significance and important social significance on energy saving.

Cassava production surged noticeably in Southeastern Africa beginning in the 1990s. The purpose of this paper is to examine the commercial responses and food security consequences of cassava production growth in the region.

The paper incorporates a mix of quantitative analysis, based primarily on original analysis of national farm household survey data, together with key informant interviews with value chain participants in the three neighboring countries of Malawi, Mozambique and Zambia.

In the cassava production zones, cassava's high productivity translates into per kilogram carbohydrate costs 60 per cent to 70 per cent of the cost of cereals such as maize and wheat, thereby opening up a range of profitable opportunities for commercialization of cassava‐based foods, feeds and industrial products. Despite this potential, cassava commercialization in Southeastern Africa remains in its formative stages, with only 10 per cent to 30 per cent of production currently marketed. Unlike West Africa, where cassava commercialization has centered on marketing prepared cassava‐based convenience foods, the emerging cassava markets in Southeastern Africa have centered on fresh cassava, low value‐added cassava flour, and experiments in industrial processing of cassava‐based starches, biofuels and feeds. Strategic investment in a set of key public goods (breeding, training in food sciences and food safety, and research on in‐ground cassava storage) can help to shape this transition in ways that benefit both commercial interests and the food security of vulnerable households.

The paper compares cassava commercialization across differing agro‐climatic zones, policy environments and food staple zones.

Farm income in the agricultural sector is susceptible to natural and market risks. A large body of literature has studied the effects of cooperative membership on household welfare, technical efficiency, productivity and production behavior, yet little has been known about the impact of cooperative membership on farm income volatility. This paper aims to fill this research gap by investigating the relationship between cooperative membership and farm income volatility of Chinese pig farmers and drawing policy implications.

This paper examines the effect of cooperative membership on farm income volatility, using data from a two-round survey of pig farmers in China. The authors employ an endogenous switching regression model to address the selection bias issues associated with unobserved factors simultaneously affecting farmers' participation in agricultural cooperatives and income earning activities.

Using household panel from a two-round survey of 193 pig farmers in China, this analysis highlights two key findings: (1) agricultural cooperative membership has significant and positive effect on farm income stability and (2) the impact of cooperative membership on farm income stability varies with production scale.

This research makes two contributions to the literature. First, this study contributes to the scant literature exploring the relationship between agricultural cooperatives and farm income stability. Second, to the best of the authors' knowledge, this is the first study that explores such relationship in a livestock sector. The pig sector in China and around the developing world has been increasingly challenged by multifaceted risks (e.g. price fluctuations, epidemic diseases, environmental regulations), and understanding the role of agricultural cooperatives in farm income stability of pig farmers is of great practical and policy significance.

Over the last two decades, internal communications has developed considerably as a sub‐discipline of public relations. Some of this growth is due to the desire of managers to bypass trade union influence in the workplace. Additionally, during the 1970s there was considerable dispute in some workplaces about who actually owned the right to communicate with employees. However, recent studies, including one by the author, have shown that good trade union channels are a considerable asset in the communication manager's repertoire. This paper considers some of the evidence for this view, highlights the need to be clear about the purpose of involvement and of participation at work and poses some practical questions for communicators.

In Part I of this article equations have been developed describing the behaviour of general deterministic systems. These lines of thought are followed up below, and are especially applied to systems the elements of which exhibit linear behaviour. By applying Laplace transform theory, it is established that matrix products determining the system behaviour, the operations of which were to be interpreted symbolically in Part I, are no longer symbolic. It is also shown how a future system behaviour may be obtained as the convolution of vectors, depending on initial values, and a system weight function matrix, depending entirely on structural properties of the system and on element behaviour.

The purpose of this paper is to develop a concept and design to cast Al alloys/metal matrix composites (MMCs) by continuous casting process. The various steps involved in the evolution of the design have been reported and discussed in this study.

On the basis of developed design concept, initial prototype design has been prepared in this study. The casting process's melt flow pattern was studied via computer simulation, and the resulting changes were implemented in the original design. The single-phase fluid flow pattern through bottom feeding technique is studied. The equipment was fabricated based on computer simulation and water modelling studies. Finally, validation was performed for the preparation of Al alloys/ MMCs after parameter optimisation. The results were observed in the optical metallography to confirm the alloying and Al MMC preparation.

The developed continuous casting process with bottom feeding technique for the addition of constituent particles shows more efficiency in comparison to the existing batch processes. The final manufactured setup demonstrates effective Al alloy/MMC production as the basis for final fabrication has been accomplished by both computer simulation and water model test. In addition, the microstructure exhibits homogeneous distribution, validating the reliability of the setup.

Integrating continuous casting with continuous reinforcement or master alloy addition is novel in this area. The constraints that batch production had that have been rectified will also lower the contemporary cost of production.

Particle velocity is a critical factor that can affect the deposition quality in manufacturing processes involving the use of a laser source and a powder‐particle delivery nozzle. The purpose of this paper is to propose a method to detect the speed and trajectory of particles during a laser deposition process.

A low‐power laser light sheet technique is used to illuminate particles emerging from a custom designed powder delivery nozzle. Light scattered by the particles is detected by a high‐speed camera. Image processing on the acquired images was performed using both edge detection and Hough transform algorithms.

The experimental data were analyzed and used to estimate particle velocity, trajectory and the velocity profile at the nozzle exit. The results have demonstrated that the particle trajectory remains linear between the nozzle exit and the deposition plate and that the particle velocity can be considered a constant.

The use of low‐power laser light sheet illumination facilitates the detection of isolated particle streaks even in high‐powder flow rate condition. Identification of particle streaks in three subsequent images ensures that particle velocity vectors are in the plane of illumination, and also offers the potential to evaluate in a single measurement both velocity and particle size based on the observed scattered characteristics. The method provides a useful simple tool to investigate particle dynamics in a rapid prototyping application as well as other research fields involving the use of powder delivery nozzles.

This paper aims to describe how the experience feedback (EF) from building projects contributes to product platform development in house-building companies. House-building companies seek improvements to decrease costs, improve flow and decrease variability. Industrialised concepts using predefinitions in product platforms have provided a way of storing and reusing knowledge in project-based house-building organisations. However, the innovation in platforms is mainly incremental and based on EF from implementations in projects.

Qualitative data were gathered via interviews, archival studies and observations, and analysed to identify the underlying structures used to manage the incorporation of EF during platform development. Four different EF channels were studied at one Scandinavian house-builder. The data are explained using an analytical framework based on diffusion of innovation, product platforms and EF.

EF is distributed over the value chain to improve the platform over time. By using multiple channels with differing contents, it is possible to balance client demands and variation with production efficiency. Platform development using feedback channels provides opportunities for double-loop learning. Operative work on projects and the strategic decisions made by developers continuously improve the platform through a combination of knowledge pull and push.

A combination of different EF channels and strategies for developing knowledge pull are shown to be essential for the incremental development of product platforms in project-based house-building organisations. The development of product platforms requires a shift away from the construction industry’s dominant project focus towards a more product-oriented view of house-building. Integrating the design phase with the supply chain enables variety but also creates a need for continuous platform development.