Comparison of grinding media - Cylpebs versus balls

Cylpebs are slightly tapered cylindrical grinding media with a ratio of length to diameter of unity. The manufactures have made conflicting claims regarding the milling performance of Cylpebs in comparison with balls. One major point of interest is which one grinds finer at the same operating conditions. The difficulty in comparison is due to the shape difference. The two grinding media have different surface area, bulk density and contact mechanisms in grinding action. Comparative tests were conducted using the two types of grinding media in a laboratory Bond ball mill at various conditions of equality such as media mass, size distribution, surface area and input specific energy. The laboratory results indicate that at the same specific energy input level the Cylpebs produce a product with slightly less oversize due to their greater surface area, but essentially the same sizing at the fine end as that produced with the balls. The reason may be that the advantage of greater surface area is balanced by the line contact and area contact grinding actions with the Cylpebs. A new ball mill scale-up procedure [Man, Y.T., 2001. Model-based procedure for scale-up of wet, overflow ball mills, Part 1: outline of the methodology. Minerals Engineering 14 (10), 1237-1246] was employed to predict grinding performance of an industrial mill from the laboratory test results. The predicted full scale operation was compared with the plant survey data. Some problems in the original scale-up procedures were identified. The scale-up procedure was therefore modified to allow the predicted ball mill performance to match the observed one. The calibrated scale-up procedure was used to predict the Cylpebs performance in the full scale industrial mill using the laboratory tests results. (C) 2004 Elsevier Ltd. All rights reserved.

Business communication in interactions between mainland Chinese and western firms through Hong Kong Chinese intermediaries

Purpose-The paper aims to analyse the nature of business communication and its influence on relationships development between Hong Kong Chinese intermediaries sourcing from Mainland Chinese sellers involved in manufacturing for sale to Western buyer firms. Design/methodology/approach-A case study-driven methodology with purposeful sampling is applied to yield maximum variation in the sampling to elicit underlying tendencies and generative mechanisms that exist within and across the multiple cases of relationships. Findings-The paper finds that Mainland Chinese sellers and Hong Kong Chinese intermediaries tend not to have the close ties that might be expected. Mainland Chinese sellers constrained their use of social information, requiring Hong Kong Chinese intermediaries to use commercial information transfers to evaluate the trustworthiness of their Mainland Chinese partners. An ingroup/outgroup bias exacerbates the modesty bias of the Mainland Chinese and also hinders learning through the transfer of technical information within these Chinese interactions. On the other hand, Western buyers tend not to prefer social information interactions with their Hong Kong Chinese intermediaries, requiring these intermediaries to emphasise commercial information interactions to evaluate the trustworthiness of their Western buyers. Research limitations/implications-This research uses a restricted sample of case study respondents. Representative sampling across multiple contexts will assist in testing the generality of the findings. Practical implications-For the West to source increasingly attractive manufactures from Mainland China, Hong Kong intermediaries will remain fundamentally important even though this creates further interactions. The aggregate of these multiple exchange arrangements is less problematic than would be the case if Western business were to deal directly with the Mainland Chinese. Originality/value-This article sheds light on the nature of business communication interactions in a group of relationships between Hong Kong Chinese intermediaries and Mainland sellers, and buyers from the West. Implications for relationships development among the Chinese and Western actors are identified with propositions framed to guide further investigation.