Showing papers by "Kyungpook National University published in 1991"
TL;DR: In this article, a series of ZrO2-SiO2 catalysts with various molar ratios of ZRO2 and SiO2 were prepared by a coprecipitation method.
79 citations
TL;DR: In this article, the correlation between the band frequency of the silanol bending vibration in TiO{sub 2}-SiO(sub 2) catalysts and acid catalytic activity was reported.
69 citations
TL;DR: In this article, the α-Fe 2 O 3 -based thick film gas sensors were made by a screen printing technique and the microstructure of the raw material was affected by the hydrogen ion concentration which was controlled during the process of raw material preparation.
49 citations
TL;DR: In this article, the authors examined the stoichiometric growth of SiC in the MTS + H2 system, and obtained SiC films without Si or excess C phases at a temperature of 1500 °C, but excess Si phase was always observed at <1500 °C.
Abstract: Silicon carbide (SIC) has some oustanding properties such as high hardness, chemical inertness and thermal stability. These properties have attracted great interest in its structural and device use, especially at high temperature. Since Pring and Fielding [1] synthesized SiC by chemical vapour deposition (CVD) using C6H 6 and SiC14 as a precursor, many efforts [2-5] have been made to investigate the precursors of Si and C. Recently methyltrichlorosilane (MTS; CH3SiC13)has been the most frequently used precursor [6-8], because MTS contains the same number of Si and C atoms and thus can easily produce stoichiometric SiC. From thermodynamic calculations on the CVD of SiC in the MTS + H2 system, Kingon et al. [9] developed CVD phase diagrams and reported that only SiC single phase can be deposited in a wide range of temperature and MTS molar fraction. However, in experimental works by others it has been reported that excess Si [10] or excess C [11] is codeposited with SiC under some conditions, and relatively strict control in the deposition conditions is required for the stoichiometric growth of SiC. In this work we examined the stoichiometric growth of SiC in the MTS + H2 system, and obtained SiC films without Si or excess C phases at a temperature of 1500 °C, but excess Si phase was always observed at <1500 °C. For the deposition experiment we used a conventional horizontal cold-walled reactor which consisted of a quartz tube (inside diameter 26 mm) and a SiC-coated graphite susceptor heated by r.f. induction. The MTS vapour was carried by H2 from an MTS container which was maintained at 0 °C. The molar fraction of MTS was controlled by adjusting the flow rate of carrier gas. The temperature of the substrate, located on a tilted susceptor, was measured with an optical pyrometer calibrated with SiC emissivity [12]. The detailed experimental conditions are listed in Table I. The film thickness was measured by gravimetry and identified by optical
37 citations
TL;DR: The activity of AlaAT-2 was found to increase markedly during leaf greening in parallel with the increase of immunochemically titrated protein, and it is suggested to function in the C4 photosynthetic cycle.
34 citations
TL;DR: In this article, the authors present computer-simulation results of self-avoiding walks (SAW's) on a percolation cluster for a square lattice performed very close to the per-colation threshold.
Abstract: We present computer-simulation results of self-avoiding walks (SAW's) on a percolation cluster for a square lattice performed very close to the percolation threshold. We specifically consider the disorder averages of SAW's on all clusters supporting one or more N-step walks and those on a backbone of an infinite cluster and estimate the critical exponents \ensuremath{
u} and \ensuremath{\gamma} that characterize the disorder averages of the end-to-end distance and the number of SAW's, respectively. Our results for \ensuremath{\gamma} indicate a behavior rather similar to SAW's on fully occupied lattices for both cases, while for \ensuremath{
u} one of two cases shows different behavior.
31 citations
TL;DR: Fracture toughness and bending properties of three types of dental composite resins (macrofilled type, microfilled type and hybrid type) were determined and fracture toughness was calculated quantitatively by a critical strain criterion based on a microscopic fracture model.
24 citations
University of California, Davis1, CINVESTAV2, University of Colorado Boulder3, Fermilab4, University of Illinois at Urbana–Champaign5, Indiana University6, Korea University7, Kyungpook National University8, University of Milan9, University of North Carolina at Chapel Hill10, University of Puerto Rico at Mayagüez11, University of South Carolina12, University of Tennessee13, Vanderbilt University14, University of Wisconsin-Madison15
TL;DR: In this paper, the D 0 and D + meson lifetimes were measured using approximately 7500 fully reconstructed D 0 → K − π +, K − ε + π+ π −, D + → ε − δ +, and charge conjugate decays.
15 citations
TL;DR: Fracture toughness, critical stress intensity factor, and bending strength of 3 types of commercially available dental composite resins (macrofilled, hybrid and microfilled type) were determined using three point bend specimens.
Abstract: Fracture toughness (KIC), critical stress intensity factor, and bending strength of 3 types of commercially available dental composite resins (macrofilled, hybrid and microfilled type) were determined using three point bend specimens. Acoustic Emission (AE), which is the generation of elastic wave due to the release of energy from the localized sources in material, was also detected during the fracture toughness test. Fracture surfaces were examined by scanning electron microscope. The fracture toughness values, AE patterns, and the nature of fracture surface were analyzed to understand fracture behavior of dental composite resins and fracture mechanism for each dental composite resin are proposed.
13 citations
TL;DR: The field-dependent self-energy operators are obtained, which show that the collisional broadening appears in both weak and high fields, while the intracollisional field effect is observed only in high field, as predicted by Barker.
Abstract: On the basis of Tani's formalism for nonlinear response, a closed-form expression of the field-dependent dc conductivity is introduced. The field-dependent dc conductivity of electron-background (impurity and phonon) systems is evaluated by using the Mori-type projection technique. We also obtain the field-dependent self-energy operators, which show that the collisional broadening appears in both weak and high fields, while the intracollisional field effect is observed only in high field, as predicted by Barker. The results are compared with the work of some other authors.
12 citations
TL;DR: Etude de l'influence du traitement par TiCl 4 du catalyseur Mg(OEt) 2 /C 6 H 5 COCl sur son aire superficielle, son activite catalytique et son isospecificite dans la polymerisation du propene.
Abstract: Etude de l'influence du traitement par TiCl 4 du catalyseur Mg(OEt) 2 /C 6 H 5 COCl sur son aire superficielle, son activite catalytique et son isospecificite dans la polymerisation du propene. Les resultats montrent que des traitements repetes par TiCl 4 transforment completement Mg(OEt) 2 en MgCl 2 et que le catalyseur supporte obtenu a une efficacite comparable a celle du catalyseur supporte sur MgCl 2 usuel
TL;DR: In this article, a mechanism of π-complex formation of the halogen moiety of the pyridinium ring with the phenyl ring is suggested for the reactive pyrinium salt.
23 Jun 1991
TL;DR: In this paper, an enhanced bandwidth balancing (BWB) mechanism of the distributed queue dual bus (DQDB) protocol has been proposed to solve the drawbacks of the priority scheme and unfairness in the multiple priority implementation.
Abstract: The bandwidth balancing (BWB) mechanism of the distributed queue dual bus (DQDB) protocol has several drawbacks, such as inefficiency of the priority scheme and unfairness in the multiple priority implementation. An enhanced BWB mechanism is proposed here to solve these problems. In the proposed mechanism, a separate BWB is applied to each priority level. Simulation indicates that the enhanced version not only may provide more efficient priority transmissions but may also offer fairer access opportunities among nodes. >
23 Jun 1991
TL;DR: Simulation results show that the proposed dynamic bandwidth balancing mechanism may offer better performance than the bandwidth balancing and the symmetric bandwidth balancing mechanisms in terms of fairness, delay, and utilization.
Abstract: The protocol of the distributed queue dual bus (DQDB) may not work as a perfect scheduler and, as a result, may cause such problems as unfairness and bandwidth wastage. A dynamic bandwidth balancing mechanism to solve these problems is proposed. Simulation results show that the proposed mechanism may offer better performance than the bandwidth balancing and the symmetric bandwidth balancing mechanisms in terms of fairness, delay, and utilization. >
TL;DR: The dependence of catalytic activity on acid strength was reported by numerous investigators as mentioned in this paper, and it has been shown that the NiO-TiOO{sub 2} and NiOZrO{Sub 2} modified with sulfate ion is very active for the isomerization of n-butane, which has been proved to be of a proton donor-acceptor type.
18 Nov 1991
TL;DR: Multilayer neural networks using the modified backpropagation learning algorithm are applied to achieve identification and orientation estimation of different classes of aircraft in a variety of 3-D orientations.
Abstract: Multilayer neural networks using the modified backpropagation learning algorithm are applied to achieve identification and orientation estimation of different classes of aircraft in a variety of 3-D orientations 2-D distortion-invariant (L, Phi ) feature space was introduced for describing an aircraft image and used as the input of the neural network classifier The optimum structure of the neural network was studied to obtain a high-performance classifier, and the reliability measure of the designed neural network classifier is introduced >
TL;DR: In this article, the catalysts Mg(OC2H5)2/benzoyl chloride (BC)/TiCl4 and Mg (OC 2H5/BC/TiCl 4) were prepared for the polymerization of propene and the reaction with triethylaluminium (TEA) was studied.
Abstract: The catalyst systems Mg(OC2H5)2/benzoyl chloride (BC)/TiCl4 and Mg(OC2H5)2/ethyl benzoate (EB)/TiCl4 were prepared for the polymerization of propene. In case of the Mg(OC2H5)2/BC/TiCl4 catalyst, BC changes into the internal donor EB during the in situ preparation of the catalyst and the unchanged BC acts as additional donor after reaction with triethylaluminium (TEA). Catalyst activity and isospecificity were also studied for the two catalysts by changing the amounts of BC or EB in the polymerization of propene cocatalyzed with TEA.
TL;DR: The present results suggest that Yongyang area still remains endemic with Clonorchis sinensis and Metagonimus sp.
Abstract: The present study was undertaken to determine the endemicity of trematode infections in Yongyang County, Kyungpook Province, Korea. One hundred and seventy-seven out of 955 residents examined were found to be infected with one or more kinds of helminths. The prevalence rate was 18.5%. Among them, 70 were found to be infected with Clonorchis sinensis, 74 with Metagonimus sp. and 24 with both flukes. The eggs of Fasciolidae were demonstrated from two specimens. The prevalence rate of clonorchiasis in males was 12.6%, while that in females was 3.6% (p less than 0.05). The prevalence of metagonimiasis in males was 12.0% and was also significantly higher than 6.1% in females (p less than 0.05). The intensity of both infections was significantly heavier in males than in females. The prevalence of both flukes was higher in residents of over 30 years of age than in those below that age. No correlation was found between the intensity and the age group. Among eight species of the fresh-water fish collected at the Panbyon River, Zacco temmincki was found to be the most frequently and heavily infested with metacercariae of Metagonimus sp., and Gnathopogon atromaculatus alone was found to be infested with metacercariae of Clonorchis sinensis. The present results suggest that Yongyang area still remains endemic with Clonorchis sinensis and Metagonimus sp. infection.
18 Nov 1991
TL;DR: Improvements on the error-correcting effect of these two models can be achieved by introducing a feedback structure which returns autoassociative image outputs and classification tag fields into the network's inputs.
Abstract: Autoassociative single-layer neural networks (SLNNs) and multilayer perceptron (MLP) models have been designed to achieve English-character image recall and classification. These two models are trained on the pseudoinverse algorithm and backpropagation learning algorithms, respectively. Improvements on the error-correcting effect of these two models can be achieved by introducing a feedback structure which returns autoassociative image outputs and classification tag fields into the network's inputs. The two models are compared in terms of character image recall and classification capabilities. Experimental results indicative that the MLP network required longer learning time and a smaller number of weights, and showed more stable variations in noise-correcting capability and classification rate with respect to the change of the numbers of stored patterns than the SLNN. >
TL;DR: It can be concluded that topical application of fibronectin has a beneficial effect on wound healing during its early phase, but no significant influence on wound contraction.
Abstract: In order to evaluate the effects of a topical application of homologous fibronectin on the healing of skin wounds, we made 2 excisional wounds on the back skin of each rat, applied ointment with or without fibronectin purified from citrated homologous plasma, and evaluated the effect according to wound size and microscopic findings. Excised lesions treated with carrier alone, but the difference was significant only in the early phase of wound healing, 2 and 3 days, according to wound size and microscopic changes. A significant decrease in wound size could be found in both groups, treated with ointment containing and not containing fibronectin, between day 4 and 9 when wound contraction was a major contributor to wound closure. Therefore it can be concluded that topical application of fibronectin has a beneficial effect on wound healing during its early phase, but no significant influence on wound contraction.
TL;DR: It is likely that PEC and sera of nude or DS mice which are deficient, at least partially, in the cellular immune system are unable to transfer immunity against C. sinensis to syngeneic recipients.
Abstract: The effects of peritoneal exudate cells(PEC) and sera of athymic nude and DS mice infected with Clonorchis sinensis metacercariae or sensitized by injection of metabolic products into footpad on transfer of immunity against the fluke to the syngeneic mice were studied. There was no significant difference in eggs per gram pattern between the sensitized and control groups, and between nude and DS mice. However, the worm burdens were slightly greater in nude mice than in DS mice. Also, a few plaque forming cells were found in only DS mice given PEC and serum from Group II DS mice. In the light of these results, it is likely that PEC and sera of nude or DS mice which are deficient, at least partially, in the cellular immune system are unable to transfer immunity against C. sinensis to syngeneic recipients. Key wordy: Clonerchis sinensis, nude mouse, DS mouse, immunity transfer, peritoneal exudate cells, serum
TL;DR: In this article, the coordination-site exchange mechanism, involving chelate ring opening and closing in the ion, is proposed, and the solid-state 13C NMR spectra of the oxalato complexes, (NH4)3[VO2(C2O4)2]·2H2O and K3[V2C2C4]·3H2 O, are also discussed in relation to the structures.
Abstract: Activation parameters were determined for the exchange between the two types of carboxylate groups which are cis and trans to the VO bonds in the bis(oxalato)dioxovanadate(V) ion, [VO2(C2O4)2]3−. Kinetic data were obtained from the 13C NMR spectra at eleven temperatures between 268 and 306 K by the total line-shape method. The coordination-site exchange mechanism, involving chelate ring opening and closing in the ion, is proposed. The solid-state 13C NMR spectra of the oxalato complexes, (NH4)3[VO2(C2O4)2]·2H2O and K3[VO2(C2O4)2]·3H2O, are also discussed in relation to the structures.
23 Jun 1991
TL;DR: Simulation results show that both the D QDB and the FDDI can provide satisfactory priority transmission service, and it is shown that the DQDB is more favorable than the F DDI in terms of data throughput, while the FddI has little advantage over the DZDB for transmission of low priority data in termsof transmission delay time.
Abstract: The effectiveness of priority schemes of the DQDB (distributed-queue dual-bus) and the FDDI (fiber distributed data interface) is evaluated. The DQDB offers three levels of priority by the use of three request bits and the FDDI provides eight levels of priority by the timed token rotation protocol. Simulation results show that both the DQDB and the FDDI can provide satisfactory priority transmission service. It is also shown that the DQDB is more favorable than the FDDI in terms of data throughput, while the FDDI has little advantage over the DQDB for transmission of low priority data in terms of transmission delay time. >
TL;DR: In this article, non-compact conformally flat manifolds with constant scalar curvature and Kaehler manifold with vanishing Bochner curvature are studied and classified.
Abstract: Non-compact conformally flat manifolds with constant scalar curvature and non-compact Kaehler manifolds with vanishing Bochner curvature are studied and classified.
TL;DR: In this article, a study on natural convection from a horizontal ice surface melting in pure water was conducted experimentally for the ambient water temperature from 2▿C to 10°C.
Abstract: A study on natural convection from a horizontal ice surface melting in pure water was conducted experimentally for the ambient water temperature from 2▿C to 10°C. Natural convection flow around upward-or downward-facing horizontal ice plate was divided into three regions according to the temperature variation of ambient water. The flow patterns of three regions were no flow, two-dimensional steady laminar flow and unsteady flow. Mean Nusselt number for the upward-facing surface had its maximum value at about 3°C of ambient water temperature. However, in the case of the downward-facing surface it increased as the ambient water temperature increased.
11 Jun 1991
TL;DR: A new neural network model, called the input driven multilayer perceptron (IDMLP), and its learning algorithm for binary input and output patterns, in contrast to the back propagation algorithm (BPA), hidden layers develop by themselves as the learning algorithm proceeds.
Abstract: Proposes a new neural network model, called the input driven multilayer perceptron (IDMLP), and its learning algorithm for binary input and output patterns. In contrast to the back propagation algorithm (BPA), hidden layers develop by themselves as the learning algorithm proceeds. The learning speed is much faster than the BPA. Hard limiters as the activation functions of neurons and integer connection weights are used. Accurate hardware implementation of trained networks can be easily realized using readily available digital CMOS VLSI technology. As practical applications IDMLPs are trained to recognize sets of randomly chosen printed Chinese characters after a feature extraction process. Discussions on actual digital CMOS VLSI implementation of trained IDMLPs are are also included. >
TL;DR: Five phenolic compounds from the cultural filtrate of the fungus grown in the broth of apple branch were isolated, and identified as phloroglucinol, 3-(p-hydroxyphenyl) propionic acid, p-hydroxyacetophenone, p -hydroxybenzoic acid and protocatechuic acid.
Abstract: Several researchers have repeatedly asserted that the necrotic toxin produced by Valsa ceratosperma (Tode ex Fr.) Maire., the causal fungus of apple Valsa canker, may have a possible role in symptom development. Natsume et al.2) isolated five phenolic compounds from the cultural filtrate of the fungus grown in the broth of apple branch, and identified them as phloroglucinol, 3-(p-hydroxyphenyl) propionic acid, p-hydroxyacetophenone, p-hydroxybenzoic acid and protocatechuic acid. All these toxic substances except p-hydroxyacetophenone were also detected in canker tissue. Koganezawa and Sakuma1) also isolated three toxic substances, phloretic acid, p-hydroxybenzoic acid and protocatechuic acid from cultural filtrate of the fungus. When the toxic substances were applied to apple shoots, necrosis similar to that of the bark infected by the pathogen were produced2). Therefore, it was supposed that the toxic substances
TL;DR: In this paper, a mechanism of π-complex formation of the halogen moiety of the pyridinium ring with the phenyl ring is suggested for the reactive pyrinium salt.
Abstract: Various N-[(2-haloaryl)methyl]pyridinium, N-(arylmethyl)-2-halopyridinium and N-(2-halobenzyl)iso-quinolinium salts have been synthesized and their intramolecular photocyclization reactions studied. Upon irradiation the aqueous solution of N-[(2-haloaryl)methyl]pyridinium, and N-arylmethyl-2-halopyridinium salts 1, 2 were cyclized to give isoindolium salts. In contrast to the pyridinium salts 1, 2, the aqueous solution of N-(2-halobenzyl)isoquinolinium salts 3 appear not to undergo photocyclization. N-Benzyl-2-chloropyridinium salts 1c is more reactive than N-(2-chlorobenzyl)pyridinium salt 1a in the photocyclization. N-(2-Chlorobenzyl)-2-chloropyridinium salt 1d is three times more reactive than 1c. A mechanism of π-complex formation of the halogen moiety of the pyridinium ring with the phenyl ring is suggested for the reactive pyridinium salt. The triplet energy of the isoquinolinium salts 3 is tool low to photocyclize.
TL;DR: It is concluded that endotoxin induces structural and enzymatic changes in the myocardial capillary endothelium and an increase of capillary permeability.
Abstract: A study was carried out to investigate changes in myocardial capillaries induced by endotoxin, in order to clarify the pathogenesis of myocardial damage in endotoxemia. Wis-tar rats were injected intraperitoneally with 100 mg/kg Escherichia coli lipopolysaccharide and then sacrificed at 1, 2, 3,4, 5,6,8, and 24 h after injection. The myocardium was observed by electron microscopy with histochemistry using horseradish peroxidase and immunocytochemistry for Na+, K+ ATPase. The earliest evident endothelial alterations were swelling, increased numbers of pinocytotic vesicles, and formation of cytoplasmic projections. Interstitial edema and focal detachment of the endothelial cells from the basement membrane occurred with time. Vascular permeability was increased after endotoxin injection. Activity of Na+, K+-ATPase was reduced on the plasma membrane of the endothelial cells. It is concluded that endotoxin induces structural and enzymatic changes in the myocardial capillary endothelium and an increase of capillary permeability. Acta Pathol Jpn 41: 12–18, 1991.
28 Sep 1991
TL;DR: In this paper, a microactuator with a PZT bar, two silicon pads, and a silicon substrate is presented, with a maximum speed of 16 mu m/sec/volt at the three phase input pulse power of 13.3 kHz.
Abstract: A microactuator as a linear controllable movement device fabricated by solid state technology is introduced. It is composed of a PZT bar, two silicon pads, and a silicon substrate. It moves linearly forward and backward with a maximum speed of 16 mu m/sec/volt at the three phase input pulse power of 13.3 kHz. The size of the pad and oxide layer are determined by the coefficient of friction between base material (SiO/sub 2//Si) and the required pulling force. As the force pulling the pad becomes bigger, the size of the pad increases. From the experimental test of the device the static frictional coefficient between base (SiO/sub 2//Si) and pad surface (SiO/sub 2//Si) is determined as 0.64 under vacuum at 30 volts for clamping force. Basic information is presented in order to design an electrostatic or piezoelectric motor using solid state technology. >