Showing papers by "Kangwon National University published in 1995"

VSI-PWM rectifier/inverter system with a reduced switch count

Abstract: A current-controlled VSI-PWM rectifier and inverter with capacitor DC link is regarded as one of the most important structures for three-phase to three-phase power conversion. This type of power converter normally requires twelve switches for the rectifier and an inverter composed of self turnoff switch such as a bipolar transistor or an IGBT with an anti-parallel diode. In this paper, a new three-phase to three-phase AC/AC power converter for AC motor drives is proposed. The proposed power converter employs only eight switches and has the capability of delivering sinusoidal input currents with unity power factor and bidirectional power flow. This paper describes the feasibility and the operational limitations of the proposed structure. A mathematical model of the system is derived using the generalized modulation theory and experimental results for steady-state and dynamic behavior are presented to verify the developed model.

Implementation of hybrid short-term load forecasting system using artificial neural networks and fuzzy expert systems

Abstract: In this paper, a hybrid model for short-term load forecast that integrates artificial neural networks and fuzzy expert systems is presented. The forecasted load is obtained by passing through two steps. In the first procedure, the artificial neural networks are trained with the load patterns corresponding to the forecasting hour, and the provisional forecasted load is obtained by the trained artificial neural networks. In the second procedure, the fuzzy expert systems modify the provisional forecasted load considering the possibility of load variation due to changes in temperature and the load behavior of holiday. In the test case of 1994 for implementation in the short term load forecasting expert system of Korea Electric Power Corporation (KEPCO), the proposed hybrid model provided good forecasting accuracy of the mean absolute percentage errors below 1.3%. The comparison results with exponential smoothing method showed the efficiency and accuracy of the hybrid model. >

The final stages of spliceosome maturation require Spp2p that can interact with the DEAH box protein Prp2p and promote step 1 of splicing.

Abstract: Pre-mRNA processing occurs by assembly of splicing factors on the substrate to form the spliceosome followed by two consecutive RNA cleavage-ligation reactions. The Prp2 protein hydrolyzes ATP and is required for the first reaction (Yean SL, Lin RJ, 1991, Mol Cell Biol 11:5571-5577; Kim SH, Smith J, Claude A, Lin RJ, 1992, EMBO J 11:2319-2326). The Saccharomyces cerevisiae SPP2 gene was previously identified as a high-copy suppressor of temperature-sensitive prp2 mutants (Last RL, Maddock JR, Woolford JL Jr, 1987, Genetics 117:619-631). We have characterized the function of Spp2p in vivo and in vitro. Spp2p is an essential protein required for the first RNA cleavage reaction in vivo. Depletion of Spp2p from yeast cells results in accumulation of unspliced pre-mRNAs. A temperature-sensitive spp2-1 mutant accumulates pre-mRNAs in vivo and is unable to undergo the first splicing reaction in vitro. However, spliceosomal complexes are assembled in extracts prepared from the mutant. We show that Spp2p function is required after spliceosome assembly but prior to the first reaction. Spp2p associates with the spliceosome before the first RNA cleavage reaction and is likely to be released from the spliceosome following ATP hydrolysis by Prp2p. The Prp2 and Spp2 proteins are capable of physically interacting with each other. These results suggest that Spp2p interacts with Prp2p in the spliceosome prior to the first cleavage-ligation reaction. Spp2p is the first protein that has been found to interact with a DEAD/H box splicing factor.

Enhancement of solubility and dissolution rate of poorly water-soluble naproxen by complexation with 2-hydroxypropyl-β-cyclodextrin

Abstract: The solubility and dissolution rate of naproxen (NPX) complexed with 2-hydroxypropyl-β-cyclodextrin (2-HPβCD) using coprecipitation, evaporation, freeze-drying and kneading method were investigated. Solubility of NPX linearly increased (correlation coefficient, 0.995) as 2-HP-βCD concentration increased, resulting in AL type phase solubility curve. Inclusion complexes prepared by four different methods were compared by differential scanning calorimetry (DSC). The NPX showed sharp endothermic peak around 156°C but inclusion complexes by evaporation, freeze-drying and kneading method showed very broad peak without distinct phase transition temperature. In contrast, inclusion complex prepared by coprecipitation method resulted in detectable peak around 156°C which is similar to NPX, suggesting incomplete formation of inclusion complex. Dissolution rate of inclusion complexes prepared by evaporation, freeze-drying and kneading except coprecipitation method was largely enhanced in the simulated gastric and intestinal fluid when compared to NPX powder and commercial NAXEN® tablet. However, about 65% of NPX in gastric fluid still remained unreleased but most of NPX dissolved within 5 min in intestinal fluid. In case of inclusion complex prepared by coprecipitation method, formation of inclusion complex appeared to be incomplete, resulting in no marked enhancement of dissolution rate. From these findings, inclusion complexes of poorly water-soluble NPX with 2-HPβCD were useful to increase solubility and dissolution rate, resulting in enhancement of bioavailability and minimization of gastrointestinal toxicity of drug upon oral administration of inclusion complex.

Hyperthermal (10–500 eV) collisions of noble gases with Ni(100) surface Comparison between light and heavy atom collisions

Abstract: Collisional events between 10–500 eV atomic beams (He, Ne, Ar, Kr, and Xe) and a Ni(100) surface are investigated by the classical trajectory method. The calculation employs a molecular dynamics approach combined with a Langevin method for treating energy dissipation to infinite solid. We find that low energy collisions of heavy atoms (Xe and Kr) are characterized by extensive many-body interactions with top layer surface atoms. On the other hand, light atom (Ne and He) collisions can be approximated as a sequence of binary collisions even at these energies. Such a difference in the collisional nature gives rise to the following consequences. Low energy heavy atoms transfer energy mostly to the surface atoms during 45° angle collision. They scatter from the surface with a narrow angular distribution centered in a supraspecular direction. The ratio of the scattered to incident particle energy rapidly decreases with increasing beam energy of heavy atoms. The sputtering yield for Ni atoms by heavy atom bombardment increases quite linearly with beam energy, which is attributed to a linear proportionality between the beam energy and the energy transfered to a surface. Near the threshold energy sputtering can occur more efficiently by light atom bombardment. The energy transfer ratio to solid continuously increases with beam energy for light atoms. For heavy projectiles, on the other hand, this ratio reaches a maximum at the energy of ca, 100 eV, above which it stays nearly constant but slightly decreases.

Prediction of solid-state amorphizing reaction using effective driving force

Abstract: It is proposed that the nucleation and growth of the amorphous phase through the solid‐state amorphizing reaction in thin‐film diffusion couples can be predicted by using the concept of effective driving force. The effective driving force consists of two factors: (i) the thermodynamic driving force given by maximum free‐energy difference between the physical mixture of binary elements and the amorphous phase (ΔGmax), and (ii) the kinetic factor given by a ratio of the effective radius of the interstitial site in the host matrix to the atomic radius of the diffusing species (Rm/d). From the comparison of reported experimental results, it is shown that the criterion of effective driving force holds well for predicting the nucleation of the amorphous phase in metal/silicon systems as well as that of metal/metal systems. In addition, the concept of effective driving force holds well for predicting the growth tendency of the amorphous phase in metal/silicon systems.

Cloning of the 3'-terminal region encoding movement and coat proteins of a Korean isolate of odontoglossum ringspot virus

Abstract: The 3′-terminal 1855 nucleotides (nts) of a Korean isolate of odontoglossum ringspot tobamovirus (ORSV-Cy) were cloned and sequenced. The sequence contained two open reading frames, which encode the cell-to-cell movement protein (MP) and coat protein genes, and are 912 nts and 477 nts long, respectively. The MP gene contained a conserved sequence motif of tobamoviruses and putative assembly origin of the viral RNA locating between 1117 nts and 1292 nts from the 3′-end. The 3′ untranslated region (UTR) of the virus comprises 414 nts, includes nine pseudoknots and a tRNA-like structure domain containing aminoacyl acceptor arm and the anticodon hairpin loop coding for histidine.

Preparation and release characteristics of polymer-reinforced and coated alginate beads

Abstract: Polymeric reinforcement and coatings of alginate beads were carried out to control the release rate of drug from alginate beads A poorly water-soluble ibuprofen (IPF) was selected as a model drug A commercially available Eudragit® RS100 was also used as a polymer Effects of polymeric contents, the presence of plasticizers and amount of drug loading on the release rate of drug were investigated The release rate of drug from alginate beads in the simulated gastric fluid did not occur within 2 h but released immediately when dissolution media were switched to the simulated intestinal fluid No significant difference of release rate from polymer-reinforced alginate bead without plasticizers was observed when compared to plain (simple) beads However, the release rate of drug from polymer-reinforced alginate beads was further sustained and retarded when aluminium tristearate (AT) as a plasticizer was added to polymer However, polyethylene glycol 400 (PEG400) did not change the release rate of drug from alginate beads although PEG400 was used to improve dispersion of polymer and sodium alginate, and plasticize Eudragit® RS100 polymer The presence of plasticizer was crucial to reinforce alginate gel matrices using a polymer As the amount of drug loading increased, the release rate of drug increased as a result of decreasing effects of polymer contents in matrices The significantly sustained release of drug from polymer-coated alginate beads occurred as the amount of polymer increased because the thickness of coated membrane increased so that cracks and pores of the outer surface of alginate beads could be reduced The sustained and retarded action of polymer-reinforced and coated beads may result from the disturbance of swelling and erosion (disintegration) of alginate beads From these findings, polymeric-rein-forcement and coatings of alginate gel beads can provide an advanced delivery system by retarding the release rate of various drugs

A real time optimal load distribution for multiple cooperating robots

Abstract: An efficient solution algorithm of the optimal load distribution problem with joint torque constraints is presented. A multiple robot system where each robot is rigidly grasping a common object is considered. The optimality criterion used is the sum of weighted norm of the joint torque vectors. The maximum and minimum bounds of each joint torque in arbitrary form are considered as constraints, and the solution that reduces internal force to zero is obtained. The optimal load distribution problem is formulated as a quadratic optimization problem in R/sup l/, where l is the number of robots. The general solution can be obtained using any efficient numerical method for quadratic programming, and in particular, for dual robot case, the optimal solution is given in a simple and efficient closed form so that the solution scheme can easily be utilized in the real time control of the dual robot coordination.

Higher-order corrections to the eikonal phase shifts for heavy-ion elastic collision

Abstract: We present first- and second-order corrections to the eikonal phase shifts for heavy-ion elastic scattering based on Coulomb trajectories of colliding nuclei Including the first- and second-order corrections improves the agreement with the experimental data and the optical model result for the elastic scatterings in the [sup 16]O + [sup 40]Ca and [sup 16]O + [sup 90]Zr systems at [ital E][sub lab]=1503 MeV

Alterations in motor activity induced by high dose oral administration of dextromethorphan throughout two consecutive generations in mice

Abstract: To achieve a better understanding of the effects on behavioral safety caused by possible neuroprotective doses (50 mg/kg, p.o.) of dextromethorphan HBr (DM), several motor activity measures were monitored in two generations of mice through a long-term period of ten months. Adult male mice (G1), in the presence of DM, developed behavioral tolerance after an initial suppression period. Prenatally exposed, second generation (G2) mice formed two groups, prenatal exposure alone (G2C) and prenatally exposed with additional postnatal exposure (G2T). In the presence of DM, group G2T was characterized by significant behavioral impairment; while G2C exhibited behavioral activation. These results suggest that more attention should be given to the prenatal effects of DM on a developing organism.

Characteristics of a laccase over‐secreting mutant of Coprinus congregatus

Abstract: Coprinus congregatus has a membrane-associated laccase which is not secreted into the culture media. A mutant monokaryon has been generated by UV irradiation which shows slower radial growth than the wild-type (72.7%) but which secretes laccase. The laccase of the mutant was compared with that of wild-type by native PAGE analysis, and showed identical mobility.

The Chern-Simons Coefficient in Supersymmetric Yang-Mills Chern-Simons Theories

Abstract: We study one-loop correction to the Chern-Simons coefficient $\kappa=k/4\pi$ in $N=1,2,3$ supersymmetric Yang-Mills Chern-Simons systems. In the pure bosonic case, the shift of the parameter $k$ is known to be $k\rightarrow k + c_v$, where $c_v$ is the quadratic Casimir of the gauge group. In the $N=1$ case, the fermionic contribution cancels the bosonic contribution by half and the shift is $k \rightarrow k+ c_v/2$, making the theory anomalous if $c_v$ is odd. In the $N=2,3$ cases, the fermionic contribution cancels the bosonic contribution completely and there is no correction. We also calculate the mass corrections, showing the supersymmetry is preserved. As the matter fields decouple from the gauge field in the pure Chern-Simons limit, this work sheds some light on the regularization dependency of the correction in pure Chern-Simons systems. We also discuss the implication to the case when the gauge symmetry is spontaneously broken by the Higgs mechanism.

Statistical Mechanics of Non-Abelian Chern-Simons Particles

Abstract: We discuss the statistical mechanics of a two-dimensional gas of non-Abelian Chern-Simons particles which obey the non-Abelian braid statistics. The second virial coefficient is evaluated in the framework of the non-Abelian Chern-Simons quantum mechanics.

Effects of chronic dextromethorphan administration on the cellular immune responses in mice

Abstract: We examined the chronic effect of dextromethorphan (DM) on the cellular immune responses in mice. T cell stimulator, phytohemagglutinin did not show significant effect on lymphocyte proliferation. Costimulator of T and B cell, pokeweed mitogen, and B cell stimulator, lipopolysaccharide exhibited DM-induced decreased lymphocyte proliferation. Significantly suppressed natural killer (NK) cell cytotoxicity was evidenced following 6 months DM exposure. These results suggest that chronic DM administration perturb B cell functioning and NK cell cytotoxicity. In addition, prenatal DM exposure did not potentiate the immunomodulation in postnatal effect induced by chronic DM.

The optimization of serum-free medium for the production of the scu-PA by the addition of algal extracts.

Abstract: The addition of 2.8 μg/ml algal extracts enhanced both scu-PA production and cell growth in a serum-free medium, compared to a conventional serum-free medium for the cultivation of recombinant CHO cells. The growth rate and scu-PA production were relatively lower in the serum-free medium than 5% serum containing medium: however, specific scu-PA production rate was higher in the serum-free medium due to the long-term period of cultivation (3.66×10−4 vs. 2.48×10−4 IU/cell/day). Overall scu-PA production rate was also greater in an enforced serum-free medium as 25,000 IU/day over 50 d of perfusion cultivation. The conversion ratio of scu-PA to tcu-PA was greatly reduced in the serum-free medium during perfusion cultivation (10% compared to 20% conversion in a serum containing medium).

Pulsed-Light-Induced Metastable Defect Creation in Hydrogenated Amorphous Silicon

Abstract: We report the results of a study of metastable defect creation by pulsed light soaking in undoped hydrogenated amorphous silicon (a-Si:H). An illumination time dependence of the defect density, a saturated defect density, and light-induced annealing under pulsed laser light have been studied. Measurements show approximately a t1/2 time-dependence of the defect creation, which is independent of light intensity. It is observed that the saturation value of the defect density is about one order of magnitude higher than by cw illumination in device quality films. It has been suggested that these results would be due to the difference in the light-induced defect annealing rate between cw and pulsed lights, in which it is found that the light-induced annealing rate by pulsed light is lower than by cw light.

Communication protocol for virtual cellular network (VCN)

Abstract: A new wireless communication architecture, the 'virtual cellular network (VCN)' was proposed in order to improve the performance of conventional cellular networks. The advantage of the VCN includes increased throughput, easy placing of ports, no handover and simple wireless communications. A random access uplink (mobile-to-station) protocol, the multi-packet encoding (MPE) is proposed for the VCN in order to provide almost fair throughput independently of the position of the mobiles. Moreover, the MPE reduces the backoff delay by using an error correction code, and increases the downlink channel efficiency due to the minimized feedback (ack's). A minimum group (MG) protocol is proposed for the downlink. The MG protocol supports multicast (several ports send the same downstream packets) as well as unicast (only one port sends the packet to a mobile).