A linear programming approach for determining optimal advertising policy

^** Email: wkc{at}maths.hku.hk In this paper, we propose a new advertising model which cancapture the advertising wear out phenomenon. The objective hereis to maximize overall sales. We show how to derive the optimalpulsation advertising strategy. The optimization problem canbe formulated as a linear programming problem. Closed-form optimalsolution can also be obtained under some conditions. We presentnumerical examples to illustrate the proposed model and applythe model to practical sales data.     

气相吸附法制备复合载体TiO_2/γ-Al_2O_3及TiO_2在γ-Al_2O_3表面的分散状态

采用气相流动吸附法,以N_2为载气携带TiCl_4通过γ-Al_2O_3床,使TiCl_4吸附在γ-Al_2O_3表面上,经水解、干燥和焙烧制得TiO_2/γ-Al_2O_3复合载体。用XRD,LRS和TEM等表征手段研究了TiO_2在γ-Al_2O_3表面上的分散状态。结果表明,TiO_2在γ-A1_2O_3表面有一分散阈值(0.168 g TiO_2/g γ-Al_2O_3,在阈值以下TiO_2以单层或亚单层分散形式存在,在阈值以上则出现晶相,未发现有体相化合物生成。测定了TiCl_4穿透曲线和吹扫曲线,为用气相流动吸附法制备TiO_2/γ-Al_2O_3复合载体工艺条件的选择提供了基础。     

Micromechanical Analysis of Thermoplastic – Thermoset Interphase

The interfacial shear strength of a pull out model between a thermoplastic fiber and thermoset matrix was analyzed. The method to analyze the interfacial quality in this kind of composite was Photoelasticity. The interfacial shear strength was measured localizing the isocromatic fringes. The Isochromatic fringe corresponds to the points along the specimen in which the principal stresses have the same value.     

Recent developments in oriented polymers for biomedical and engineering applications

A review is presented of recent research at Leeds University which has been directed at devising novel methods for the production of oriented polymer structures. First, the new hot compaction process for oriented fibre and tapes is described, together with its applications to polyethylene and polypropylene where there are a number of practical developments. Secondly, there is the use of hydrostatic extrusion to make load bearing oriented products from hydroxyapatite filled polyethylenes. The production routes include the application of high pressure annealing prior to hydrostatic extrusion and the preparation of high modulus polyethylene fibre/hydroxyapatite billets as the starting point. Finally, recent progress on die-drawing as a means to producing oriented monofilaments and biaxially oriented tubes is described, where the applications include polymer ropes, pipes for gas and water distribution and transparent cans for packaging.