Flexible guidepath design for automated guided vehicle systems

We address the problem of unidirectional guidepath layout design for automated guided vehicle systems- A two-step layout design method to consider both loaded and empty vehicle movements is developed to guarantee a complete layout design. First, the flow path selection (FPS) problem is formulated to design guidepath layout with the objective of minimizing loaded vehicle movements. Both a mathematical model and a heuristic algorithm for FPS are presented. Since AGV guidepath layouts are used by both loaded and empty vehicles, the FPS does not guarantee a closed or complete layout design. For the case when an incomplete or unclosed layout is produced from the first step, a complementary layout design (CLD) approach to convert the incomplete layout into complete one with the consideration of empty vehicle movements is considered in the second step. A heuristic for the CLD problem is developed. An example problem is used to illustrate the whole design approach.     

Combinatorial investigation of Pt–Ru–M as anode electrocatalyst for direct methanol fuel cell

The addition of Au/TiO₂ and zeolites as active components to PtRu/C electrode in DMFC was investigated by using combinatorial high-throughput-screening test. Addition of Au/TiO₂ to PtRu/C electrode, especially in the ratio of PtRu/C: Au/TiO₂ 9:1, 8:2, 7:3, were effective to improve the performance of direct methanol fuel cell. The electrochemical properties of the prepared electrodes were compared using cyclic voltammetry, impedance spectroscopy and a single cell performance test of a direct methanol fuel cell (DMFC). The adsorbed CO on Pt might be easily oxidized on the surface of Au/TiO₂ by interaction between PtRu/C and Au/TiO₂. The addition of the solid acid proton conducting materials (ZSM-5) on PtRu/C anode leads to the high temperature operation. The cell performance was maintained over the cell temperature 120 °C (maximum current density was 200 mA/cm² at 160 °C) by the addition of ZSM-5 as proton conducting materials.     

A simple construction of OFDM-CDMA signals with low peak-to-average power ratio

This paper investigates the peak-to-average power ratio (PAR) reduction scheme employing a simple symbol transform in OFDM-CDMA systems. This approach is very simple because of no additional complexity and works without restriction on the allocation of spreading code, maintaining the original transmission efficiency. Simulation results show that the investigated scheme gives the PAR reduction gain of 2 /spl sim/ 3 dB compared to the original OFDM and OFDM-CDMA signals, and can provide the further PAR reduction by combining the selective mapping (SLM) and partial transmit sequence (PTS) schemes, which are less complex compared to the ordinary SLM and PTS approaches, respectively.     

Characteristics of intermetallic NdNi5 as an unsupported catalyst in thiophene hydrodesulfurization

A systematic research is carried out on intermetallic NdNi₅ for the hydrodesulfurization (HDS) of thiophene. The effect of calcination and presulfidation of intermetallic NdNi₅ on thiophene HDS was examined and property changes of the catalyst during calcination, presulfidation, and reaction were observed by XRD, SEM, and surface area techniques. The intermetallic compound of NdNi₅ is disintegrated to fine powder and recrystallized to Nd/Ni oxide and sulfide by calcination, presulfidation, and reaction. A model for the surface area increase of the catalyst during calcination, presulfidation, and reaction was proposed and the role of neodymium was explained.     

Metformin-induced encephalopathy without lactic acidosis in a patient with contraindication for metformin

A 51-year-old Korean man with end-stage renal disease and who was on intermittent hemodialysis was admitted with progressive dysarthria, gait disturbance, and myoclonus. The liver function tests and the electrolyte and arterial gas analyses were normal. The Magnetic resonance imaging scan showed a diffuse symmetric high signal intensity in the basal ganglia on the T2-weighted image. After a thorough history taking, we knew that he had been treated with metformin for 3 months at other hospital without our hospitals staff's knowledge. After stopping the metformin, the patient's neurologic signs and symptoms disappeared and the Magnetic resonance imaging findings after 20 days were markedly improved.     

In-situ detection of C-reactive protein using silicon nanowire field effect transistor

Label-free, sensitive, and real-time c-reactive protein (CRP) sensor was fabricated using p-type silicon nanowire (SiNW) based structures configured as field effect transistors (FET) using the conventional 'top-down' semiconductor processes. The width of SiNWs were distributed 80 nm to 400 nm. Among them to improve signal-to-noise ratio and sensitivity of SiNW FET, 221 nm-SiNW was chosen for biosensing of CRP. Antibody of c-reactive protein (anti-CRP) was immobilized on the SiNW surface through polydimethylsiloxane (PDMS) microfluidic channel for detection of CRP. Specific binding of CRP with anti-CRP on the SiNW surface caused a conductance change of SiNW FET and various injections from 10 and 1 microg/ml to 100 ng/ml solutions of CRP resulted in the conductance changes from 39 and 25 to 16%, respectively. Label-free, in-situ and very sensitive electrical detection of CRP was demonstrated with the prepared SiNW FET.     

Advances in J‐integral estimation of circumferentially surface cracked pipes

This paper describes enhanced J‐integral estimation schemes for pipes with circumferential semi‐elliptical cracks subjected to tensile loading, global bending and internal pressure. These schemes are given in two different forms to cover the wide ranges of geometries and material parameters; the modified GE/EPRI method and the modified reference stress method. In the former method, new plastic influence functions for fully plastic J‐integral estimation are developed based on extensive three‐dimensional finite element calculations. In the latter method, new optimized reference loads are suggested and utilized to predict the J values. To verify the feasibility of these two schemes, J‐integral values obtained from further detailed FE analyses are compared to those from the proposed schemes. Because the estimated J‐integrals agree fairly well with the detailed FE analysis results, the new solutions can be applied for accurate structural integrity assessment of different size pipes with a circumferential surface crack.     

Flux Optimization During Tapping in BOF Process

An integrated Plate Mill has started it’s operation on July 7, 2010 in Gwangyang Steelworks, POSCO. The production capability is about 2.5 million tons per year and the main stream consists of Blast Furnace, Hot metal pretreatment (KR), Converter, Bubbling Station, RH/VTD and Continuous Casting. Particularly, it is possible to control sulfur concentration at excellent level in BOF without any further treatment in LF or VTD, which is attained by unique KR process and scrap usage strategy in BOF. In this paper, desulfurization efficiency and steel cleanliness was introduced by optimizing flux amount during tapping in BOF process. In addition, the effect of the flux addition on the refractory of ladle was investigated based on EPMA analyses with the viewpoint of phase diagram. The cleanliness of each sample was examined using optical emission spectrometry and oxygen nitrogen determinator.     

Orientational control of liquid crystal molecules by reformed poly(dimethylsiloxane) alignment layer via ion-beam irradiation

We introduce an alternative approach to making a reformed PDMS layer as a pretilt controllable alignment layer, which can be used in the vertical alignment (VA) and twisted nematic (TN) modes, by varying the ion beam (IB) energy. Depending on different the dielectric anisotropy of surfaces, PDMS layers have been demonstrated to align LC molecules homogeneously and homeotropically. The electro-optic characteristics of aligned VA and TN-LCD based on PDMS layer were comparable to those of VA and TN-LCD based on polyimide, showing good potential of PDMS film as an alignment layer.