Quantitative determination of sulfisoxazole and its three N-acetylated metabolites using HPLC-MS/MS, and the saturable pharmacokinetics of sulfisoxazole in mice

Oh, K.,Baek, M.C.,Kang, W. Pergamon Press ; Elsevier Science Pub. Co 2016 Journal of pharmaceutical and biomedical analysis Vol.129 No.-

Sulfisoxazole (SFX) is still used in combination with trimethoprim in cattle despite adverse drug reactions (e.g., urolithiasis). Recently, SFX is known to be a promising repositioned drug candidate for pulmonary hypertension and cancer. We developed a simultaneous determination method of SFX and its N-acetylated metabolites (N<SUP>1</SUP>-acetyl SFX, N1AS; N<SUP>4</SUP>-acetyl SFX, N4AS; diacetyl SFX, DAS) using HPLC-MS/MS for the first time, and examined the pharmacokinetics of SFX in mice. N1AS and DAS were converted rapidly to SFX and N4AS, respectively, in mouse plasma. The time courses of plasma SFX and N4AS concentrations were well-characterised following the oral administration of SFX to mice. The absorption, metabolism, and/or excretion of SFX given at >700mg/kg may be saturable, and in contrast to humans and rats, the extent of systemic exposure of mice to N4AS was much greater than that of SFX. Interestingly, the acetyl groups at both N1- and N4-positions were degraded during the ionisation required to generate precursor ions. In additional experiments the carboxyl group of N-acetyl-5-aminosalicylic acid (NA5AS) was lost instead of the acetyl group during the ionisation, and acetaminophen (AAP) appeared. As the acetyl and carboxyl groups of some substances can be degraded during ionisation in the mass spectrometer, caution is appropriate when it is sought to simultaneously quantify similar structures containing these moieties; chromatographic separation is essential.

Numerical study of thermal stresses in high-temperature proton exchange membrane fuel cell (HT-PEMFC)

Oh, K.,Chippar, P.,Ju, H. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.6

The purpose of this work is to numerically examine the thermal stress distributions in a high-temperature proton exchange membrane fuel cell (HT-PEMFC) based on a phosphoric acid doped polybenzimidazole (PBI) membrane. A fluid structure interaction (FSI) method is adopted to simulate the expansion/compression that arises in various components of a membrane electrode assembly (MEA) during the HT-PEMFC assembly processes, as well as during cell operations. First, three-dimensional (3-D) finite element method (FEM) simulations are conducted to predict the cell deformation during cell clamping. Then, a nonisothermal computational fluid dynamic (CFD)-based HT-PEMFC model developed in a previous study [1] is applied to the deformed cell geometry to estimate the key species and temperature distributions inside the cell. Finally, the temperature distributions obtained from these CFD simulations are employed as the input load for 3-D FEM simulations. The present numerical study provides a fundamental understanding of the stress-temperature interaction during HT-PEMFC operations and demonstrates that the coupled FEM/CFD HT-PEMFC model presented in this paper can be used as a useful tool for optimizing HT-PEMFC clamping and operating conditions.

Salient object detection using recursive regional feature clustering

Oh, K.,Lee, M.,Lee, Y.,Kim, S. Elsevier science 2017 Information sciences Vol.387 No.-

<P>In the past decade, contrast features, which focus on rarity and uniqueness, have been widely used in the saliency-detection field, but the extreme dependency on the most highlighted region remains as a limitation for the detection of multiple and complex objects. In particular, the difficulties are commonly observed when a high inter-object dissimilarity exists. Based on this observation, we present a new paradigm for the detection of the salient-object region, whereby only the spatial-saliency clues are interpreted from a multiple-level clustering framework; for this reason, in contrast to the previous methods, the proposed model is not dependent upon the contrast features. The proposed model can be roughly decomposed into the following four main phases: regional feature extraction, homogeneous-region clustering, saliency-score computation, and recursive processing. In particular, a recursive processing for which the salient region is optimized through the improvement of its clustering results is introduced. According to the experiment results, the proposed scheme outperforms the state-of-the-art methods on various benchmark datasets consisting of single, multiple, and complex object images; furthermore, the proposed model is more effective for the detection of multiple objects. To validate the contributions of this study, a multiple salient-object dataset (MSOD) that contains 100 images with more than two objects with a higher dissimilarity was also constructed. (C) 2017 Elsevier Inc. All rights reserved.</P>

EFFICIENCY MEASUREMENT AND ENERGY ANALYSIS FOR A HEV BENCH TESTER AND DEVELOPMENT OF PERFORMANCE SIMULATOR

OH K.,KIM D.,KIM T.,KIM C.,KIM H. The Korean Society of Automotive Engineers 2005 International journal of automotive technology Vol.6 No.5

This paper presents the efficiency measurement and energy analysis for a parallel HEY. Using the HEV test rig, the efficiency of each powertrain component is measured for a given driving cycle including the regenerative braking system. Accompanied by the efficiency measurements, a detailed energy analysis is performed. Based on the efficiency measurement and energy analysis, a HEV performance simulator is developed. Using the simulator, the HEV performance is evaluated for a mild hybrid system. It is expected that the HEV simulator developed can be used to obtain further optimization potentials.

MPC-based approach to optimized steering for minimum turning radius and efficient steering of multi-axle crane

Oh, K.,Seo, J.,Kim, J. G.,Yi, K. Korean Institute of Electrical Engineers 2017 International Journal of Control, Automation, and Vol.15 No.4

<P>In a conventional steering system for a multi-axle crane, the steering angle of each axle is determined according to Ackernianns steering principle,'which assumes the slip angles of the tires are negligible. The role of optimal steering control in improving a driver's steering efficiency is hardly considered in Ackermann's principle. To address this problem, this paper proposes a control strategy for determining the optimal steering angles for a multi-axle crane and thereby improving a driver's steering efficiency by applying the model predictive control (MPC) algorithm and defining a driver's intentions. A simplified crane model for the steering system was developed using a bicycle model, and a comparative study was carried out via simulation to analyze steering performance for the conventional (Ackermann) and proposed steering control systems for the cases of all-wheel steering and road steering modes. The simulation results show that both the minimum turning radius and the driver's steering effort are decreased more by the proposed steering control system than by conventional system and that the proposed control strategy therefore yields better steering performance.</P>

Gear ratio and shift schedule optimization of wheel loader transmission for performance and energy efficiency

Oh, K.,Yun, S.,Ko, K.,Ha, S.,Kim, P.,Seo, J.,Yi, K. Elsevier ; Elsevier Science Pub. Co 2016 AUTOMATION IN CONSTRUCTION - Vol.69 No.-

This paper presents gear ratio and shift schedule optimization strategies to improve energy efficiency for the dynamic simulation of a wheel loader equipped with dual clutch transmission (DCT) and automated manual transmission (AMT). A conventional wheel loader uses torque converter (T/C) based automotive transmission, and the torque converter causes heavy energy loss during the V-pattern working cycle. To improve fuel economy while maintaining working performance in the V-pattern working cycle, automated manual transmission (AMT) and dual clutch transmission (DCT) have been suggested to substitute the clutch for the torque converter. In addition, the optimization strategies for the gear ratio and shift schedule for AMT and DCT have been proposed for improving fuel economy. Gear ratios have been determined by a nonlinear optimization method based on the standard V-pattern working cycle which is obtained from experimental test data by a skilled driver. Then, the gear-shift schedule for clutch-type transmission has been derived by using a determined gear ratio and optimization strategy. Simulations have been conducted to investigate working performance and energy efficiency by using three developed wheel loader simulation models equipped with T/C, AMT, and DCT, respectively, with the driver model for the V-pattern working cycle. Simulation results show that AMT- and DCT-based wheel loaders are more fuel efficient for the V-pattern working cycle than the T/C-based wheel loader.

Design of a Dual and Wide Band Aperture Stacked Antenna with Double-Sided Notches

Oh, K.,Kim, B.,Choi, J. IEEE 2004 Digest Vol.2004 No.3

Optimization of control strategy for a single-shaft parallel hybrid electric vehicle

Oh, K.,Min, J.,Choi, D.,Kim, H. Professional Engineering Publishing Ltd 2007 Proceedings of the Institution of Mechanical Engin Vol.221 No.5

Seismic performance evaluation of Korean column-tree steel moment connections

Oh, K.,So, J.,Ha, H.,Lee, K. Springer Science + Business Media 2016 International Journal of Steel Structures Vol.16 No.4

<P>The purpose of this study was to evaluate the seismic performance of existing Korean column-tree connection type in steel moment frames. The column-tree connection has frequently been used in steel moment frames because it is well known to provide high quality and economy with shop-welding and field-bolting in Korea and Japan. However, there have been no studies on the design details and ductility of column-tree connections. Therefore, in this paper, the seismic performance of non composite and composite column-tree specimens was evaluated to investigate their problems. Full-scale specimens were fabricated with non-composite/composite strong axis and weak axis column-tree connections, respectively. The testing results showed that, although non-composite column-tree specimens reached a 5% story drift ratio, tiny cracks occurred at beam-to column connections. In the case of composite specimens, the expected brittle fracture at the bottom flange was not detected. However, severe crushing of concrete slab occurred, and the bottom flange underwent great stress. Therefore, composite action should be considered when composite structures are designed because bottom flanges may fracture.</P>

A CO poisoning model for high-temperature proton exchange membrane fuel cells comprising phosphoric acid-doped polybenzimidazole membranes

Oh, K.,Jeong, G.,Cho, E.,Kim, W.,Ju, H. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.36

We present herein a carbon monoxide (CO) poisoning model for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) comprising phosphoric acid-doped polybenzimidazole membranes. In the model, the adsorption/desorption processes of CO and hydrogen on the anode Pt catalysts, and subsequent electrochemical oxidation are rigorously considered. The CO poisoning model is incorporated into a previously developed three-dimensional HT-PEMFC model, and then both numerical simulations and experimental measurements are conducted for a comparative study. The simulation results generally agree well with the experimental data under various current density conditions, highlighting that it is necessary to consider the variable hydrogen adsorption kinetics as a function of CO fractional coverage to achieve better agreement with the experimental data. Furthermore, detailed key contours for hydrogen/CO fractional coverage, anode overpotential, temperature, and current density are provided to derive greater insights into the CO poisoning mechanisms and characteristics in HT-PEMFCs.