Showing papers by "Pusan National University published in 1993"
TL;DR: In this article, the optimality of Scarf's ordering rule for the newsboy problem with only the mean and the variance of the demand are known is analyzed, and the analysis is extended to the fixed ordering cost case, where a fixed cost is charged for placing an order, and to the case of random yields.
Abstract: We present here a new, very compact, proof of the optimality of Scarf's ordering rule for the newsboy problem where only the mean and the variance of the demand are known. We then extend the analysis to the recourse case, where there is a second purchasing opportunity; to the fixed ordering cost case, where a fixed cost is charged for placing an order; to the case of random yields; and to the multi-item case, where multiple items compete for a scarce resource.
762 citations
TL;DR: In this article, the authors presented a new method to solve the problem of economic power dispatch with piecewise quadratic cost function using the Hopfield neural network, which is much simpler and the results are very close to those of the numerical method.
Abstract: The authors present a new method to solve the problem of economic power dispatch with piecewise quadratic cost function using the Hopfield neural network. Traditionally one convex cost function for each generator is assumed. However, it is more realistic to represent the cost function as a piecewise quadratic function rather than one convex function. In this study, multiple intersecting cost functions are used for each unit. Through case studies, the possibility of the application of the Hopfield neural network to the economic load dispatch problem with general nonconvex cost functions was shown. The proposed approach is much simpler and the results are very close to those of the numerical method. >
422 citations
TL;DR: In this article, the authors examined the shear band microstructure of a tempered martensitic HY-100 steel and found that the thermodynamic stability of the original micro-structure can influence the tendency toward shear localization under dynamic loading conditions.
Abstract: Dynamic torsion experiments have been conducted on thin-walled tubular specimens of a tempered martensitic HY-100 steel, causing adiabatic shear bands to form. The strain rates imposed were ∼ 10 3 s −1 and local temperature increases up to 600°C within the shear bands were measured. The shear band microstructure was examined by transmission electron microscopy (TEM), revealing two distinct microstructures. In some regions, highly elongated narrow subgrains extended in the shear direction, while in other regions, fine equiaxed cells were characteristic. The proportions of the two microstructures varied for different specimens, and the observations were interpreted to indicate that a process of dynamic recovery accompanying large deformation and a high temperature rise occurred within the shear band. Although thermal effects were apparent, there was no evidence to support a phase transformation to austenite followed by martensite formation. On the basis of present findings, it appears that the thermodynamic stability of the original microstructure can influence the tendency toward shear localization under dynamic loading conditions.
145 citations
TL;DR: The volatile concentrate obtained from the edible Korean chamchwi plant (Aster scaber Thunb) by a distillation-extraction system was separated into hydrocarbon and oxygen-containing fractions, and the latter was further separated into eight subfractions by silica gel column chromatography.
Abstract: The volatile concentrate obtained from the edible Korean chamchwi plant (Aster scaber Thunb) by a distillation-extraction system was separated into hydrocarbon and oxygen-containing fractions, and the latter was further separated into eight subfractions by silica gel column chromatography. Gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) were utilized to identify 119 volatile compounds in the fractions. The volatile compounds included 55 hydrocarbons, 37 alcohols, 11 aldehydes, 5 oxides, 4 esters, 4 ketones, 2 acids, and 1 phenol. Myrcene, a monoterpene hydrocarbon, was the most abundant volatile compound identified in chamchwi (18.80%). Chamchwi oil was found to possess a woody or herbaceous aroma following sensory evaluation of each fraction and individual volatile component using a GC-sniff apparatus.
111 citations
TL;DR: Highly concentrated fructo-oligosaccharides up to 90 % was obtained by the mixed-enzyme system.
Abstract: A technique to produce high-content fructo-oligosaccharides by the mixed- enzyme system of fructosyltransferase and glucose oxidase was investigated. The mixed-enzyme reaction was carried out in a stirred tank reactor containing 40 %(w/v) sucrose with 10 unit of fructosyltransferase and 10 unit of glucose oxidase per gram sucrose for 25 h, at 40 °C and pH 5.5. Highly concentrated fructo-oligosaccharides up to 90 % was obtained by the mixed-enzyme system.
77 citations
TL;DR: In this article, the authors presented an optimum simple step-stress accelerated life test for the Weibull distribution under Type I censoring, which minimizes the asymptotic variance of the maximum likelihood estimator of a stated percentile at design stress.
Abstract: This article presents an optimum simple step-stress accelerated life test for the Weibull distribution under Type I censoring. It is assumed that a log-linear relationship exists between the Weibull scale parameter and the (possibly transformed) stress and that a certain cumulative exposure model for the effect of changing stress holds. The optimum plan—low stress and stress change time—is obtained, which minimizes the asymptotic variance of the maximum likelihood estimator of a stated percentile at design stress. For selected values of the design parameters, nomographs useful for finding the optimum plan are given, and the effects of errors in preestimates of the parameters are investigated. As an alternative to the simple step-stress test, a three-level compromise plan is proposed, and its performance is studied and compared with that of the optimum simple step-stress test. © 1993 John Wiley & Sons. Inc.
74 citations
TL;DR: In this article, a generalized vector variational inequality (GVVI) is considered and the existence theorem is established under assumptions of C -pseudomonotonicity and V -hemicontinuity.
73 citations
TL;DR: In this article, the effect of a blending sequence in acrylonitrile-butadiene-styrene terpolymer(ABS)/nylon-6 blend modified by poly(styrene-co-maleic anhydride) (SMA) on the dynamic mechanical and rheological properties, and morphology was studied.
60 citations
TL;DR: In this article, polypropylene powder was extruded in the presence of peroxide and multifunctional monomers at varying concentrations, and the results were interpreted in terms of decreased molecular weight and its distribution by chain scission.
Abstract: Polypropylene (PP) powder was extruded in the presence of peroxide and multifunctional monomers at varying concentrations. With increasing peroxide concentration, MFI increased almost linearly, whereas hardness, modulus, and impact strength decreased, and the results were interpreted in terms of decreased molecular weight and its distribution by chain scission. On the other hand, triacrylate type multifunctional monomers (PETA and TMPTA) reduced the MFI of PP upon extrusion, and led to increase of Tm and Tc followed by increased modulus, yield strength, and elongation as well. TAIC and PBQ exerted effects smaller than triacrylate type. When the multifunctional monomers were added to the 0.01 phr peroxide containing system, MFI decreased below that of peroxide, and increased above that of multifunctional monomer of the same concentration, and synergistic physical properties were generally obtained, especially at low content of coagent. However, at higher peroxide concentration (0.05 and 0.1 phr) MFI increased with PETA and TMPTA, and decreased with PBQ. In general, increase and decrease of MFI were respectively followed by the decrease and increase of modules, strength, and impact strength as well. © 1993 John Wiley & Sons, Inc.
59 citations
TL;DR: In this paper, an EOQ model which relaxes the assumption of the infinite planning horizon is studied, and the discounted cash flow approach is used to properly recognize the financial implication of the cash flows in an inventory analysis.
Abstract: The Economic Order Quantity (EOQ) model and its variations have received a lot of attention by researchers for a long time However, an infinite planning horizon in practice is of rare occurrence because of changes in product specifications and design or its abandonment or substitution by another product due to rapid development of technology This paper studies an EOQ Model which relaxes the assumption of the infinite planning horizon In addition, the discounted cash flow (DCF) approach is used to properly recognize the financial implication of the cash flows in an inventory analysis We derive the general expression of the expected present value for the inventory carrying and ordering costs, and investigate the characteristics of the function for the exponential distribution
56 citations
TL;DR: The effect of peroxide and coagent, alone and together, on the crosslinking of HDPE during melt extrusion was studied in this paper, and the most significant improvement was obtained with impact strength.
Abstract: The effect of peroxide and coagent, alone and together, on the crosslinking of HDPE during melt extrusion was studied. The melt flow index decreased rapidly with peroxide (1,3-bis (t-butylperoxy-isopropyl) benzene), and smoothly with trimethylolpropanetriacrylate (TMPTA), but showed a small increase with parabenzoquinone (PBQ).
Melt viscosity of 0.3 phr peroxide-treated PE responded elastically, whereas that of 0.3 phr TMPTA showed yield behavior. Tm (crystalline melting temperature) and Tc (crystallization temperature) increased with peroxide, Tm decreased, and Tc increased with TMPTA. ΔHf (heat of fusion) increased at 0.05 phr followed by a sharp drop, more with peroxide and less with TMPTA. Hardness and preyield properties increased with TMPTA, and peroxide (except hardness) with the loss of elongation at break. The most significant improvement was obtained with impact strength, over 5 times with peroxide and 7 times with TMPTA.
When the TMPTA was used in combination with peroxide, more redution in MI, followed by a further increase of hardness, modulus, and strength, was obtained, but impact strength was decreased below that of TMPTA alone. © 1993 John Wiley & Sons, Inc.
TL;DR: In this article, gas chromatography and mass spectrometry were used to identify 99 volatile compounds in headspace samples of peanut oil heated to 50, 100, 150, or 200 o C for 5 h.
Abstract: Gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) were used to identify 99 volatile compounds in headspace samples of peanut oil heated to 50, 100, 150, or 200 o C for 5 h. There were 42 hydrocarbons, 22 aldehydes, 11 fatty acids, 8 alcohols, 8 ketones, 4 furans, 2 esters, and 2 lactones identified. Identification of formaldehyde, acetone, acetaldehyde, propanal, 2-pentanone, butanal, and 2-hexanone was achieved only after their transformation to corresponding thiazolidine derivatives. The total amount of all identified volatiles increased as the temperature of the oil was increased
TL;DR: In this paper, a ternary blend of polypropylene (PP) / rubber / CaCO3 composites was prepared in a twin-screw extruder, where the dispersed phase formed a reticulate structure with reduced size.
Abstract: Ternary blends of PP (80) /rubber (EPM, EPDM) (10) / PE (10) and PP (80) / rubber (10) / CaCO3 (10) composites were prepared in a twin-screw extruder. With polyethylene (PE) viscosity comparable to, or higher than that of rubber, the dispersed phase formed a reticulate structure with reduced size. On the contrary, when the viscosity of PE was significantly lower than that of rubber, the dispersed phase formed almost homogeneous morphology. With reticulate morphology, PE crystallinity content, hardness, modulus, and elongation at break of the ternary blend increased. In polypropylene (PP) / rubber / CaCO3 composites, better dispersion of CaCO3 in the PP matrix was obtained when the viscosity of rubber was significantly higher than that of matrix. With better dispersion, hardness and tensile properties were improved, but the impact strength more or less decreased. © 1993 John Wiley & Sons, Inc.
TL;DR: In this article, the authors used three types of ABS having different acrylonitrile (AN) content, and PMMAs with different MWs, and found that ABSs containing 24 and 27 wt % AN were miscible, while immiscible ones gave positive and negative deviations from the additivity.
Abstract: Melt blends of ABS and PMMA were prepared using three types of ABS having different acrylonitrile (AN) content, and PMMAs with different MW. From TEM micrographs, it was found that ABSs containing 24 and 27 wt % AN were miscible, and the one containing 35 wt % AN was immiscible with PMMA. Morphologically miscible blends showed welldefined semicircles in Cole—Cole plots, whereas immiscible ones showed immiscible drifts from the semicircle. In addition, as the compounding temperature increases, the dispersed PMMA phase became stratified, and more rubber particles, especially larger ones, migrated toward the PMMA phase. Miscible blends gave viscosities lower than additivity would predict, whereas immiscible ones gave positive (ABS-rich phase) and negative (PMMA-rich phase) deviations from the additivity. © 1993 John Wiley & Sons, Inc.
TL;DR: Findings imply that the functional significance of Fos activation on circadian rhythms and mechanism of FLI induction in IGL would be different from that in SCN.
TL;DR: Data suggest that the endogenous glibenclamide-sensitive K+ channel opener is involved in the modulation of cerebral microvascular autoregulation in vivo.
TL;DR: A tetrameric proanthocyanidin named davallin (1) and two new phenolic glycosides, 5-O-β-D-(6-Ovanilloylglucopyranosyl)gentisic acid (6) and 4-O-, β-, β-D-, 4-β,D-, 6-O, vanilloy lg-lg-polygonyl)vanillic acid, have been isolated from the rhizomes of Davallia mariesii MOORE together with six
Abstract: A new tetrameric proanthocyanidin named davallin (1) and two new phenolic glycosides, 5-O-β-D-(6-O-vanilloylglucopyranosyl)gentisic acid (6) and 4-O-β-D-(6-O-vanilloylglucopyranosyl)vanillic acid (7), have been isolated from the rhizomes of Davallia mariesii MOORE together with six known compounds, procyanidin B-2 (2) and B-5 (3), epicatechin-(4β→8)-epicatechin-(4β→6)-epicatechin (4), epicatechin-(4β→6)-epicatechin-(4β→8)-epicatechin-(4β→6)-epicatechin (5), protocatechuic acid (8), and 1-naphthol-β-D-glucopyranoside (9). Structures of the three new compounds (1, 6, and 7) were determined by means of spectroscopic methods including two-dimensional NMR techniques.Among the compounds obtained, 1 and 2 inhibited protein kinase C with IC50 values of 3.5 and 8.6 μM, respectively.
TL;DR: In this paper, the effect of transdermal absorption enhancing compounds on the barrier function of the stratum corneum lipid liposome (SCLL) has been investigated and the results of differential scanning thermograms of the SCLL suggest that the pyrrolidone derivatives had incorporated into the lipid layer in the lipid bilayer and increased the fluidity of the lipid surface.
TL;DR: Results suggest that inhibition of MDR1 gene expression by H-87 is associated with circumvention of drug resistance in MDR cells.
TL;DR: Inventory-related cost as well as material-handling cost is considered to determine the space requirement and the storage location of each item simultaneously and an improvement heuristic algorithm is developed for the problem.
Abstract: We study the problem of clustering inventory items to assigned storage locations. Inventory-related cost as well as material-handling cost is considered to determine the space requirement and the storage location of each item simultaneously. An improvement heuristic algorithm is developed for the problem. We provide a numerical example to illustrate the algorithm developed. The performance of the algorithm is evaluated through numerical experimentation.
TL;DR: In this paper, the flow field characteristics of a two-dimensional wall-attaching offset jet (WAOJ) are experimentally investigated by comparing with those of a turbulent plane wall jet(PWJ).
Abstract: The flow field characteristics of a two-dimensional wall-attaching offset jet (WAOJ) are experimentally investigated by comparing with those of a turbulent plane wall jet(PWJ). The mean velocity, the turbulent stresses and triple velocity correlations are measured with a split film probe and anX wire probe. Even with the strong influence of the suction pressure field in the recirculation bubble at the lower corner, it is found that the WAOJ in the wall jet region has a close similarity with the PWJ. Especially, the decay of maximum velocity and the upper jet spread along the maximum velocity line of the WAOJ are virtually the same as those of the PWJ. The mean velocity profile of the WAOJ attains similarity after the jet impingement onto the lower plate. However the profiles of second and third-order moments of fluctuating velocities vary rapidly before the impingement and then relax very slowly to the similarity profiles of the PWJ.
TL;DR: In this article, the authors investigated the effect of particle entrainment on the heat transfer past particles entrained in an oscillating flow with and without a steady velocity in the gas phase.
TL;DR: In this paper, the authors investigated the properties of injection-molded specimens for miscible and immiscible blends of ABS with PMMA and found that the surface properties are governed by miscibility and the viscosity ratio of the components.
Abstract: Mechanical and surface properties of injection-molded specimens for miscible and immiscible blends of ABS with PMMA were investigated. Regardless of miscibility, hardness, modulus, and strength of the blends generally showed a smooth variation with composition, with the possible exception of impact strength. In miscible blends, impact strength decreased smoothly with PMMA; however, in immiscible blends, a drastic drop to less than the half that of ABS was obtained at 10 wt % PMMA. Compounding at higher temperature gave decreased modulus and strength and increased impact strength. Surface gloss decreased with PMMA addition in the miscible system and increased in the immiscible system up to 50 wt % PMMA. From contact-angle and FTIR measurements, it is suggested that the surface properties are governed by miscibility and the viscosity ratio of the components. © 1993 John Wiley & Sons, Inc.
TL;DR: In this article, the effects of an oscillating flow induced by a high intensity acoustic field on heat and mass transfer to and from particles and droplets such as pulverized coal particles and coal-water slurry fuel droplets are investigated.
TL;DR: In this article, the microstructural development of the adiabatic shear band in an HY-100 steel was studied, and three typical micro-structural features were observed: elongated grain structure at the boundary between the shear bands and matrix, fine equiaxed grain structure with high dislocation densities in the middle of the hear band, and relatively coarse-grained structure located between the above two structures.
Abstract: This article presents a study of the microstructural development of the adiabatic shear band in an HY-100 steel. The steel was deformed at a high strain rate by ballistic impact, and subsequent metallographic observations along with electron microscopy were performed. A number of white- etched shear bands were found near the perforated region, and three typical microstructural features of the adiabatic shear band were observed: elongated grain structure at the boundary between the shear band and matrix, fine equiaxed grain structure with high dislocation densities in the middle of the shear band, and relatively coarse-grained structure located between the above two structures. These microstructures might be formed in an extremely short time by the combined effects of the large temperature rise and the highly localized deformation. Since very complex phenomena might occur within the shear band, possible mechanisms, such as dynamic recovery and strain-induced dynamic phase transformation, are suggested to explain the micro- structural development of the adiabatic shear band.
TL;DR: In this paper, the authors present a counter example which disproves their claim that the objective functions developed by Kim, Philippatos and Chung are concave and give clarifying explanations that the unique inflection point is a global maximum even though the objective function is not concave.
Abstract: Recently, Roumi and Schnabel wrote an addendum to attempt to fill gaps found in the article by Kim, Philippatos and Chung. They claimed that the objective functions developed by Kim, Philippatos and Chung are concave. However, we present a counter example which disproves their claim. In addition, we give clarifying explanations that the unique inflection point is a global maximum even though the objective functions are not concave. Consequently, we justify the optimally of solutions derived from the first order conditions in Kim, Phillippatos and Chung.
TL;DR: In this article, a new kinematically-admissible velocity field is proposed to determine the final-stage extrusion load and the average extruded height in the backward extrusion of internally non-axisymmetric tubes from round billets.
TL;DR: A copper-sensitive chemically modified electrode (CME) was constructed by incorporating di(2-imino-cyclopentylidine mercaptomethyl) disulfide (didd) into the carbon paste composed of graphite powder and Nujol oil as discussed by the authors.
Abstract: A copper-sensitive chemically modified electrode (CME) has been constructed by incorporating di(2-imino-cyclopentylidine mercaptomethyl) disulfide (didd) into the carbon paste composed of graphite powder and Nujol oil. Copper(I) ion was chemically deposited on the CME by immersing it in the Cu(I) solution. The resulting surfaces were characterized by cyclic and differential pulse voltammetry. The CME's surface could be regenerated by applying more positive potential than the stripping potential of the Cu(I) ion and then used for another deposition. After seven deposition/measurement/ regeneration cycles, the peak current of voltammograms of the analyte decreases slightly. The differential pulse technique was also applied to the above system. In this case, the detection limit for Cu(I) ion was 5 × 10−11 M for 30 minutes of deposition time. After reduction of Cu(II) ion to Cu(I) in the sample solution with hydroxylamine, satisfactory results were obtained for the determination of copper in certified standard urine reference material SRM's 2670 (trace elements in urine).
TL;DR: Forogold retrograde transport combined with CGRP immunofluorescence demonstrates that CGRPI neurons in the IGL constitute a part of IGL reciprocal connections, which supports the hypothesis of differences in the content of neuroactive substances in the circadian clock between mammalian species.