A heuristic technique for inventory replenishment policy with increasing demand pattern and shortage allowance

In the growth stage of a product life cycle, the demand rate is usually unstable and follows an increasing pattern. The traditional inventory policies, which have been developed for stationary demand pattern, are not appropriate to this situation. Although there exist some researches in the past dealing with inventory policy for the case of increasing demand pattern, most of them focused on the inventory systems in which shortages are not allowed. In reality, the presence of shortages is sometimes economically preferable when holding cost is significant as compared with shortage cost. The aim of the research presented in this paper is, therefore, to develop a replenishment policy for inventory systems with nonlinear increasing demand pattern and shortage allowance in such a way that the total demand during a predefined planning horizon can be exactly met. A heuristic technique to help determine the operational parameters for the inventory policy is then developed. In the proposed heuristic technique, the consecutive improvement method developed by Wang (Comput Oper Res, 29:1819–1825, 2002) will first be used to help determine replenishment times. And then, a new concept of reduction cost, which is defined as the difference between the holding cost when shortage is allowed and the incurred shortage cost, is introduced and applied to help find the optimal shortage starting point in each replenishment cycle. Numerical experiments are also conducted to illustrate the applicability of the proposed technique.     

Visualization of vortex core polarity in NiFe nanodots by tilted Fresnel images

We illustrate an approach which allows determining the out-of-plane component of the vortex core (polarity) in NiFe nanodots using Fresnel imaging in Lorentz electron microscopy. Using tilted Fresnel images, contribution of the polarity is introduced into the Fresnel image. However, this contribution is relatively small and a difference image from two symmetrically tilted Fresnel images must be used to eliminate the strong contribution from the in-plane curling magnetization and non-magnetic contrast. The sense of the polarity appears as a bipolar white-black contrast in the difference image on the tilt axis. A vortex core with a diameter of 16.5±2.5 nm is experimentally measured. Image tilting, displacement and geometrical distortion may disturb the difference image, and hence subtraction of the difference image must be aligned by cross-correlation. The method is also justified by a study of the observed contrast characteristic due to misalignment. The method is confirmed to be superior to similar approach with direct interpretation of information and more information subtracted.     

Effect of Supports and Promoters on the Performance of Ni-Based Catalysts in Ethanol Steam Reforming

Ethanol steam reforming (ESR) is one of the potential processes to convert ethanol into valuable products. Hydrogen produced from ESR is considered as green energy for the future and can be an excellent alternative to fossil fuels with the aim of mitigating the greenhouse gas effect. The ESR process has been well studied, using transition metals as catalysts coupled with both acidic and basic oxides as supports. Among various reported transition metals, Ni is an inexpensive material with activity comparable to that of noble metals, showing promising ethanol conversion and hydrogen yields. Additionally, different promoters and supports were utilized to enhance the hydrogen yield and the catalyst stability. This review summarizes and discusses the influences of the supports and promoters of Ni-based catalysts on the ESR process.     

Pull-Down of Metalloproteins in Their Native States by Using Desthiobiotin-Based Probes

One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn²⁺-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated.     

Stabilization of anthocyanins on thermally processed red D'Anjou pears through complexation and polymerization

Stabilization of red anthocyanins on the surface of thermally processed red pears (D'Anjou) through complexation with metallic ions and polymerization was investigated. Pears were treated briefly in an aqueous solution containing stannous (Sn) ion, hydrochloric acid, formaldehyde, and tannic acid prior to steaming and canning processes. Polymerization capacity of the treatment solutions was investigated by monitoring the haze formation of the solutions. Aqueous acetone extracts of the peels from fresh and treated pears at major processing steps (pre-treatment, steam-heating, and canning) were subjected to HPLC qualitative analysis on anthocyanins. The total phenolics (TP) and anthocyanin content (ACN) of the peels were measured by Folin-Ciocalteu assay and pH-differential method, respectively. Polymerization capacity of the solution was influenced by the composition, setting-time, and the time of Sn addition into the formulated solutions. The pre-treatment along with steam-heating resulted in stable red pigments on the peels of canned pears. The new pigments are believed to be the complexes of stannous and phenolics, including anthocyanins. No major newly formed anthocyanins or small phenolics were detected in treated pears. Although developed treatment formula did not represent a commercial application yet, this study revealed an effective approach of retaining red anthocyanins on thermally processed fruits.     

Nusselt number correlations for a microchannel heat exchanger hot water supplier with S-shaped fins

Using 3D-CFD code, Nusselt number correlations for a microchannel heat exchanger (MCHE) with S-shaped fins used for hot water suppliers are obtained through numerical experiments and then validated. The supercritical carbon dioxide working fluid is assumed to operate around the pseudo-critical point, where fluid properties change radically. Calculations with 20 different temperatures are executed to produce Nusselt number correlations for each side. The fluid inlet temperature in each calculation is defined as 2 °C lower or higher than the constant wall temperature, respectively, for cold and hot side simulations. The small temperature difference of 2 °C is sufficiently small to regard thermal–hydraulic properties as constant. A new integrating method using the correlations to calculate the heat-transfer-performance is proposed. The resultant heat-transfer-performance is compared with that of another numerical result, which is reduced from large geometry and integration. The results agree within 3% error; the calculation accuracy of the method is confirmed. Experimental results with MCHE verify the correlations. The difference is approximately 5%. Using few computer resources, these Nusselt number correlations and the heat-transfer-performance calculation methods using correlation information are sufficiently accurate to evaluate heat exchangers.     

In-channel electrochemical detection for microchip capillary electrophoresis using an electrically isolated potentiostat

A new electrode configuration for microchip capillary electrophoresis (CE) with electrochemical (EC) detection is described. This approach makes it possible to place the working electrode directly in the separation channel. The "in-channel" EC detection was accomplished without the use of a decoupler through the utilization of a specially designed, electrically isolated potentiostat. The effect of the working electrode position on the separation performance (in terms of plate height and peak skew) of poly(dimethylsiloxane)-based microchip CEEC devices was evaluated by comparing the more commonly used end-channel configuration with this new in-channel approach. Using catechol as the test analyte, it was found that in-channel EC detection decreased the total plate height by a factor of 4.6 and lowered the peak skew by a factor of 1.3. A similar trend was observed for the small, inorganic ion nitrite. Furthermore, a fluorescent and electrochemically active amino acid derivative was used to directly compare the separation performance of in-channel EC detection to that of a widely used laser-induced fluorescence (LIF) detection scheme. In this case, it was found that the plate height and peak skew for both detection schemes were essentially equal, and the separation performance of in-channel EC detection is comparable to LIF detection.     

Practical issues on the projection of polyhedral sets

Projection of polyhedral sets is a fundamental operation in both geometry and symbolic computation. In most cases, however, it is not practically feasible to generate projections as the size of the output can be exponential in the size of the input. Even when the size of the output is manageable, we still face two serious problems: overwhelming redundancy and degeneracy. Here, we address these problems from a practical point of view. We discuss three algorithms based on algebraic and geometric techniques and we compare their performance in order to assess the feasibility of these approaches.     

A PWM method for reduction of switching loss in a full-bridgeinverter

This paper presents the “hybrid pulsewidth modulation” (HPWM) method which requires only two of the four switches in a full-bridge inverter to be pulsewidth-modulated at high frequency, thus significantly reducing the switching losses in the other two switches. For triangular carriers, HPWM has the same frequency spectrum and switching losses as the conventional unipolar PWM (UPWM). A low-frequency model for a fast-switching HPWM full-bridge inverter with high-quality output is described, and is substantiated by experimental data