MODELING VACUUM-CONTACT DRYING OF WOOD: THE WATER POTENTIAL APPROACH

ABSTRACT

A two-dimensional mathematical model for vacuum-contact drying of wood is presented. The moisture and heat equations are based on the water potential concept whereas the pressure equation is formulated considering unsteady state conservation equation of dry air. Most of the model parameters were determined during independent experiments. The set of equations is then solved in a coupled form using the finite element method. The validation of the model is performed using experimental results obtained during vacuum-contact drying of sugar maple sapwood. The experimental and calculated data are in good agreement. Nevertheless, some discrepancies are observed which can be attributed to the boundary conditions used and to the fact that heat transfer by convection was neglected.     

ANALYSIS OF BATCH DRYING DATA USING SAS

An analysis technique is described which uses the nonlinear curve fitting capabilities of the Statistical Analysis System (SAS) to analyze batch drying data. The technique does not require any apriori assumptions about whether a constant rate period exists. Rather, the only assumptions necessary are the possible forms of the equations which can be used to describe the drying phenomenon. The program will then determine, based upon statistical techniques, where each equation should be used during the drying process in order to best describe the overall drying process. Two examples are given; the first analyzes the drying of. sand, a material having a constant rate period; the second analyzes the data describing the drying of French fried potato pieces.     

光通信技术的最新发展动态

本文在报告了美国光通信市场格局之后,介绍了未来高速大容量数据传输系统ＤＷＤＭ的发展状况,并预测ＤＷＤＭ的市场规模将从１９９９年的４０亿美元扩大到５年后的２１５亿美元。在文章第二部分介绍了新型光通信元件,凶手对应波长１４５０ｎｍ～１６５０ｎｍ的宽带光通信单向波导管、无需温控的２．５Ｇｂｉｔ／ｓ半导体激光元件、１０Ｇｂｉｔ／ｓ光信号传输器和５００Ｍｂｉｔ／ｓ光收发信器。     

Impact response of a cracked soft ferromagnetic medium

A solution is given for the problem of an infinite soft ferromagnetic solid containing a central crack subjected to normal impact load. The solid is permeated by a uniform magnetostatic field normal to the crack surface. Laplace and Fourier transforms are employed to reduce the transient problem to the solution of integral equations in the Laplace transformed plane. A numerical Laplace inversion technique is used to compute the values of the dynamic stress-intensity factor, and the results are compared with the corresponding elastodynamic values to reveal the influence of magnetic field on the dynamic stress-intensity factor. The dynamic stress intensity factor is found to increase with increasing values of the magnetic field.With 4 Figures     

西班牙电信跨国经营的经验及启示

西班牙电信(Telefonica)是西班牙和葡萄牙语国家主要的电信运营商，并在资本运作方面是欧洲地区第二大电信运营商．同时它还是全世界具有最大海外市场的电信运营商。其跨国经营的经验包括：与世界上大型电信运营商结成战略联盟，以发展跨国经营业务；强化在关键业务和核心市场的竞争地位；以收购、合资等多种方式进入国际市场；实现融资渠道多样化；适时进行业务重组以适应不斯变化的市场；遵循审慎的财务管理原则等。     

FINITE ELEMENT SIMULATION OF ROUGH RICE DRYING

Milled, brown and rough rice samples were dried in the laboratory with heated air and diffusivities of the endosperm, bran and husk were evaluated with a search technique using the finite element method. The endosperm had the highest diffusivity. The husk had a slightly higher diffusivity than the bran because the trapped air inside the husk was considered as an integral part of the husk. The finite element method predicted rough rice drying that was in good agreement with experimental results.     

Improving Through-Flight Schedules

In the wake of airline deregulation, most carriers have been forced to reexamine both their pricing strategies and operating schedules. With reference to the latter, one of the factors that has been largely overlooked as a source of additional revenue is the convenience of a through flight over a connecting flight. The purpose of this paper is to explore this issue by developing an algorithm that can be used to effectively pair inbound and outbound routes at hub cities over the course of the day. We take the view that if demand is dependent from one period to the next then significantly higher revenues can be realized by making appropriate adjustments in the scheduling algorithm.

The methodology is based on a forward looking heuristic designed to skirt the combinatorial difficulties that arise in problems of this magnitude. The algorithm is first demonstrated on a 6 city, 3 period problem, and then applied to the Dallas/Fort Worth hub, the home base of American Airlines who supplied the data. In the full analysis, 62 cities were scheduled over 10 time periods. The results yielded benefits of up to 60% over current procedures and confirmed the value in trying to quantify the model's underlying parameters.