Preparation and characterization of porous chitosan–tripolyphosphate beads for copper(II) ion adsorption

Porous chitosan–tripolyphosphate beads, prepared by the ionotropic crosslinking and freeze‐drying, were used for the adsorption of Cu(II) ion from aqueous solution. Batch studies, investigating bead adsorption capacity and adsorption isotherm for the Cu(II) ion, indicated that the Cu(II) ion adsorption equilibrium correlated well with Langmuir isotherm model. The maximum capacity for the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, deduced from the use of the Langmuir isotherm equation, was 208.3 mg/g. The kinetics data were analyzed by pseudo‐first, pseudo‐second order kinetic, and intraparticle diffusion models. The experimental data fitted the pseudo‐second order kinetic model well, indicating that chemical sorption is the rate‐limiting step. The negative Gibbs free energy of adsorption indicated a spontaneous adsorption, while the positive enthalpy change indicated an endothermic adsorption process. This study explored the adsorption of Cu(II) ion onto porous chitosan–tripolyphosphate beads, and used SEM/EDS, TGA, and XRD to examine the properties of adsorbent. The use of porous chitosan–tripolyphosphate beads to adsorb Cu(II) ion produced better and faster results than were obtained for nonporous chitosan–tripolyphosphate beads. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Medium-term multi-plant capacity planning problems considering auxiliary tools for the semiconductor foundry

The foundry is an industry whose demand varies rapidly and whose manufacturing process is quite complicated. This paper explores issues on mid-term capacity planning in the foundry. First, issues on capacity planning of the foundry are categorized. Second, focusing on multi-site planning, an increment strategy for the number of auxiliary tools—“photo mask”—is proposed to increase the flexibility of production. The related decisions include how to allocate appropriately the forecast demands of products among multiple sites and how to decide on the production quantities of products in each site after receiving customer-confirmed orders. By constructing the mathematical programming model of capacity planning, the rates of capacity utilization and customer order fulfillment are found to be effectively enhanced by adding new masks to increase production flexibility. Furthermore, from the sensitivity analysis, the importance of customers is shown to influence significantly the amount of reserved capacity of customers. Increasing the number of certified factories is also an indirect way to increase capacity. For long life cycle products, the verification of products in multiple factories in order to increase capacity utilization rate effectively is suggested.     

An analytical subthreshold current model for pocket-implanted NMOSFETs

An analytical subthreshold current model for metal oxide semiconductor field effect transistors (MOSFETs) with pocket implantation is presented. The model is developed based on considering an averaged localized pileup of channel dopants near the source and drain ends of channel to account for the pocket implantation effect and to derive the channel potential using a pseudo-two-dimensional (2-D) method. This, together with the conventional drift-diffusion theory, leads to the development of a subthreshold current model for pocket-implanted MOS devices. Model verification is carried out using data measured from a set of pocket-implanted NMOSFETs fabricated from a 0.17-/spl mu/m, DRAM process. Very good agreement is obtained between the model calculations and measurement results.     

Mapping knowledge to rules for scheduling expert systems

Although the theoretical framework of expert systems has been well established, the process of developing a non-trivial expert system is still considered a difficult task. The main reason for this is that the nature of expert systems is knowledge-intensive. Also, it is usually difficult for domain experts to explain or communicate their expertise to the system professionals. Many methodologies have been proposed to overcome this domain knowledge representation problem. Most of them require the assistance of an expert system shell (tool). However, with a purpose of helping the system development in mind, most of them were not satisfactory. This research takes the experience of implementing a course scheduling expert system, and suggests two analysis methods to describe the characteristics of course scheduling knowledge. It is shown that these methods provide assistance on clarifying the complicated scheduling problem. Another favorable advantage of this method is its capability helping the transferring of domain knowledge to rules in the knowledge base.     

A new method for extracting the effective channel length of MOSFETs

A new and simple method to extract the effective channel length L_eff of metal-oxide superconductor field effect transistor (MOSFET)s is presented. The method, which is developed based on an auxiliary integral function, has the advantage of determining the value of L_eff not influenced by the series resistances of the MOSFET. The method is tested in the environments of device simulation and measurements. In addition, comparison is made between the results obtained from the present method and a widely used L_eff extraction method.     

有机电致发光材料的研发现状

有机电致发光器件 (OLED)具有驱动电压低、主动发光等优势 ,在平板显示领域具有极大的应用前景而引起了广泛的关注。与此同时有机电致发光材料的研发也取得了很大的进展。本文介绍了近年来有机电致发光材料 (包括小分子发光材料和聚合物发光材料 )的研发状况     

Numerical analysis on determining the physical mechanisms contributing to the abnormal base current in post-burn-in AlGaAs/GaAs HBTs

An abnormal base current behavior with an ideality of about 3 is often observed in the AlGaAs/GaAs HBT after it is subjected to a high temperature/electrical burn-in condition. Using a two-dimensional device simulator, this paper studies and determines the main physical mechanisms contributing to such an abnormality. Data measured from two post-burn-in HBTs are included in support of the finding.     

A novel dual-polarity device with symmetrical/asymmetrical S-type I-V characteristics for ESD protection design

A novel and compact device with adjustable forward and reverse conductions and symmetrical/asymmetrical I-V characteristics for ESD (electrostatic discharge) applications is presented. The device allows for the dual-polarity conduction with the proper selection of blocking junction configurations. This design enables high-level ESD protections for various mixed-signal integrated circuits operating under a wide range of symmetrical and asymmetrical bias conditions.