Showing papers by "Dong-Wook Kim published in 2009"

Occurrence of Both Unipolar Memory and Threshold Resistance Switching in a NiO Film

Abstract: We observed two types of reversible resistance switching (RS) effects in a NiO film: memory RS at low temperature and threshold RS at high temperature. We were able to control the type of RS effects by thermal cycling. These phenomena were explained using a new dynamic percolation model that can describe the rupture and formation of conducting filaments. We showed that the RS effects are governed by the thermal stability of the filaments, which arise from competition between Joule heating and thermal dissipation. This work provides us understandings on basic mechanism of the RS effects and their interrelation.

Photophysical, Photoelectrochemical, and Photocatalytic Properties of Novel SnWO4 Oxide Semiconductors with Narrow Band Gaps

Abstract: Novel SnWO4 visible-light active photocatalysts with two polymorphs (orthorhombic α and cubic β phases) were prepared by a conventional solid-state reaction method, and their optical properties, electronic band structure, and photocatalytic activities were investigated. It was found that the low-temperature phase, α-SnWO4 with corner-shared WO6 octahedra, exhibited a dark-red color and indirect band gap of 1.64 eV, whereas the high-temperature phase, β-SnWO4 with unshared WO4 tetrahedra, exhibited a light-yellow color and direct band gap of 2.68 eV. The Mott−Schottky plots obtained using a thick film electrode in 1 M NaCl electrolyte revealed the n-type semiconductive properties of the SnWO4 polymorphs; i.e., the flat-band potential values of α- and β-SnWO4 were −0.61 and −0.66 V (SCE), respectively. From the electronic band structure calculations performed using density functional theory, the Sn 5p and O 2p orbitals were hybridized to construct the valence band in both SnWO4 polymorphs. However, the cons...

Personally customized electronic furniture and method of implementing the same

Abstract: An apparatus which provides various functions for physical and/or mental relaxation, as well as for health care of a user, and a method of implementing the apparatus, include downloading personal data of the user from a user terminal to a personally customized bed and controlling one or more functions of the personally customized bed based on the personal data.

Design of an Adaptive Cruise Control / Collision Avoidance with lane change support for vehicle autonomous driving

Abstract: This paper presents an Adaptive Cruise Control (ACC) and Collision Avoidance (CA) system for vehicle autonomous driving. The control scheme is designed to improve drivers' comfort during multi-vehicle driving situations and to completely avoid rear-end collision using severe braking and lane change maneuver. In order to create such an application, the proposed system consists of a longitudinal control strategy for multi-vehicle ACC with severe braking, a lateral control strategy for lane change, and a decision unit for integration of two strategies. The longitudinal control strategy was used to achieve comfort behavior of subject vehicle in normal-driving situations and to achieve safe behavior in sever-braking situations. The lateral control strategy is used to generate a trajectory for lane change and follow the generated trajectory in order to avoid collision. Finally, the decision unit is used to recognize the current driving situation and select a behavior of the subject vehicle. The performance and safety benefits of the proposed control system are investigated via simulations using various driving scenarios. The simulation results show that the proposed control system performs longitudinal and lateral control strategy depending on the driving situations.

Development of novel mucoadhesive pellets of metformin hydrochloride.

Abstract: Mucoadhesive polymer-coated pellets containing metformin hydrochloride were prepared by the powder-layering technique using a centrifugal fluidizing (CF)-granulator. Four high-viscosity polymers were applied to make the pellets: 1) hydroxymethylcellulose (HPMC), 2) sodium alginate (Na-Alg), 3) HPMC/Carbopol, and 4) sodium carboxylmethylcellulose (Na-CMC). The physical crushing test, mucoadhesive test, zeta-potential test, in vitro release study and observation of gastroretention state of the dosage form were performed to investigate the pellets. The strong adhesive interaction between the Na-CMC-coated pellets and the mucin disc was obtained by mucoadhesive test. Na-Alg was most effective among the polymers used in changing the value of zeta potential of the mucin solution by the interaction between a polymer and a mucin particle. Results from drug dissolution study showed that over 95% of the drug from all the four pellets was released before 2 h, while Na-CMC- and Na-Alg-coated pellets showed a moderate sustained-release in SGF (simulated gastric fluid) and SIF (simulated intestine fluid), respectively. In conclusion, Na-CMC and Na-Alg seem to be promising candidates for mucoadhesive formulation and further studies to improve the sustained-release property are underway for achieving the ultimate goal of once-a-day formulation of metformin hydrochloride.

Interfacial reactions and resistive switching behaviors of metal/NiO/metal structures

Abstract: Ag/NiO/Pt structures did (did not) exhibit reproducible resistive switching when a positive bias was applied to the Pt (Ag) electrode. X-ray photoemission spectra revealed that ultrathin NiO films on Pt (Ag) layers did (did not) undergo reversible chemical state change during heat treatment in a vacuum and oxygen ambient. Such differences in interfacial chemical interaction may affect filament formation and rupture processes near the electrode and hence alter the resistive switching behaviors.

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

Abstract: 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.

Inhomogeneous barrier and hysteretic transport properties of Pt/SrTiO 3 junctions

Abstract: We investigated the temperature-dependent transport properties of Pt/Nb-doped SrTiO3 junctions, exhibiting rectifying and hysteretic behaviours. The conventional Schottky diode model failed to explain the current–voltage characteristics, since the estimated Richardson constant was too small. The temperature dependence of the barrier height and the ideality factor showed that the inhomogeneous barrier model described the experimental data well. The estimated interfacial potential fluctuation was dependent on the resistance states. This suggested that the spatial inhomogeneity could affect the resistive switching phenomena.

Photoluminescence induced by thermal annealing in SrTiO3 thin film

Abstract: We have grown SrTiO3 thin films by rf-sputtering and studied its photoluminescence (PL) property after postannealing treatments. While the as-grown film does not show any PL signal, visible frequency PL emissions are induced by high temperature (T>550 °C) annealing. When subsequent low-T (50 °C) and long term (>8 months) annealing was made, the PL-spectra evolved into another pattern in which four distinct luminescence peaks appear simultaneously at λ=1.8, 2.2, 2.7, and 3.1 eV. We propose that these remarkable room temperature PL effects are due to both metastable and energetically stabilized defect states formed inside the band gap.

Magnetic properties of insulating RTiO3 thin films

Abstract: The magnetic properties of epitaxial RTiO3 (R = Y, Eu) thin films are reported. The films were grown on various substrates with different lattice mismatches using the pulsed laser deposition technique. Ferromagnetic YTiO3 thin films could only be grown on LaAlO3 (110) substrates, while EuTiO3 films could be grown on various substrates. The magnetic properties of the grown films are discussed in light of the structural characterization.

Robust stabilisation of sampled-data control systems with non-linear perturbations via digital redesign

Abstract: This study addresses a new digital redesign (DR) problem for a linear time-invariant (LTI) system with a perturbation that is an uncertain non-linear time-varying function but linearly bounded. Given a continuous-time linear controller robustly stabilising the origin of the perturbed system for all admissible perturbations, the concerned DR problem is to design the sampled-data linear controller making trajectories of the continuous-time and the sampled-data non-linear control systems close, or at least robustly stabilising the perturbed system. The proposed approach interprets the DR problem as the stabilisation problem considering the convergence rate for error dynamics between the continuous-time and the sampled-data non-linear control systems. Sufficient conditions for the stabilisation are derived and formulated in the form of linear matrix inequalities (LMIs). A numerical example is used to demonstrate the effectiveness of the proposed design technique.

Abnormal resistance switching behaviours of NiO thin films: possible occurrence of both formation and rupturing of conducting channels

Abstract: We report a detailed study on the abnormal resistance switching behaviours observed in NiO thin films which show unipolar resistance switching phenomena. During the RESET process, in which the NiO film changed from a low resistance state to a high resistance state, we sometimes observed that the resistance became smaller than the initial value. We simulated the resistance switching by using a random circuit breaker network model. We found that local conducting channels could be formed as well as ruptured during the RESET process, which result in the occurrence of such abnormal switching behaviours.

Molecular Genetic Characterization of the Merozoite Surface Protein 1 Gene of Plasmodium vivax from Reemerging Korean Isolates

Abstract: Plasmodium vivax merozoite surface protein 1 (PvMSP-1) has been considered a major candidate for the development of an antimalaria vaccine, but the molecule exhibits antigenic diversity among isolates. The extent of genetic polymorphism in the region between interspecies conserved blocks 4 and 5 (ICB4 and ICB5) of the PvMSP-1 gene was analyzed for 30 Korean isolates. Two genotypes, SK-A and SK-B, were identified on the basis of amino acid substitution. Almost all the amino acid sequences of the Korean isolates were nearly identical to those of the Solomon Island isolate Solo-83 (97.8 to 99.9% similarity) and Philippine isolates Ph-79, Ph-52-2, and Ph-49 (97.3 to 99.8% similarity). Also, we report two sequences in the isolates that were characterized on the basis of restriction fragment length polymorphism (RFLP). The RFLP profiles following digestion with the DraI restriction enzyme produced two distinguishable patterns. This study might be the first report of the region between ICB4 and ICB5 of the MSP-1 gene of P. vivax in South Korea.

Advanced preparation method of organic-transition metal hydride complexes as hydrogen storage materials

Abstract: The present invention relates to an advanced preparation method of organic-transition metal hydride used as hydrogen storage materials, the method including: preparing organic-transition metal-aluminum hydride complexes by reacting the organic-transition metal halide with metal aluminum hydride compounds; and preparing the organic-transition metal hydride by reacting the organic-transition metal aluminum hydride complexes with Lewis bases. Since the preparation method of the organic-transition metal hydride according to the present invention does not use catalysts, it has advantages that it does not cause problems due to poisoning and can prepare the organic-transition metal hydride at high yield under less stringent conditions. The hydrogen storage materials containing the organic-transition metal hydride prepared from the preparation method can safely and reversibly store a large amount of hydrogen.

A Case of Zosteriform Kaposi's Sarcoma after Prednisolon Treatment

Abstract: Kaposi's sarcoma is a rare lympho-angioproliferative neoplasm with four types of variants: classic, iatrogenic immunosuppressive drug-associated, AIDS-related and Africa-endemic Kaposi's sarcoma Most immunosuppressive drugassociated Kaposi's sarcomas usually occur after a kidney transplant or after receiving immunosuppressive therapy A 64-year-old female patient showed numerous purpuric nodules and smaller erythematous plaques on the right lower leg for three months Previously, the patient was treated with an immunosuppressive drug for rapidly progressive glomerulonephritis for a five-week period A skin biopsy was performed under the clinical diagnosis of Kaposi's sarcoma We performed immunohistochemical staining and polymerase chain reaction to detect human herpes virus 8 (HHV-8) We report a case of iatrogenic immunosuppressive drug-associated zosteriform Kaposi's sarcoma that rapidly occurred five weeks after prednisolon therapy in a rapidly progressive glomerulonephritis patient

Improved method for producing organic-transition metal hydride as hydrogen storage substance

Abstract: PROBLEM TO BE SOLVED: To improve a method for producing an organic-transition metal hydride used as a hydrogen storage substance. SOLUTION: The method of producing the organic-transition metal hydride comprises a step of producing an organic-transition metal-aluminum hydride complex by reacting an organic-transition metal halide with a compound of the aluminum hydride series; and a step of producing the organic-transition metal hydride by reacting the organic-transition metal-aluminum hydride complex with a Lewis base. The production method does not use any catalyst and thus causes no problems involving catalyst poisoning and has an advantage of producing the organic-transition metal hydride under milder conditions in a high yield. The hydrogen storage substance comprising the organic-transition metal hydride produced by the method can safely and reversibly store a high volume of hydrogen. COPYRIGHT: (C)2009,JPO&INPIT

Personalized article of domestic electronic equipment, and a method for implementing the same

Abstract: The present invention relates to a device for providing diverse functions for relaxation and health monitoring, and to a method for implementing the same. The invention is arranged in such a way as to optimize, for separate individuals, diverse functions for the user's mental relaxation and health monitoring. It does this by downloading the user's individual information from a user terminal, and controlling at least one function provided by a bed personalized on the basis of the said individual information.

Effects of Onion and Naringin Extract Mixed Products on Antihyperlipidemic Levels of Bio FIB Hamster

Abstract: This study investigated the effects to lowering hyperlipidemic levels in hamsters by feeding them naringin and onion extracts. The hyperlipidemic levels on all of the hamsters were raised by feeding them with high fat atherogenic diet (HFAD) containing 10% coconut oil and 0.05% cholesterol. The experimental groups were randomly assigned to 5 groups (normal, control, OEN, OES, and OESN) each 6 hamsters over a 40 days period. The control group (HFAD) received a 10% coconut oil and 0.05% cholesterol with basal diet, the OEN group which received an onion extract mixture contaning 50% water and 50% onion extract, the OES group which received 100% onion extract, the OESN group which received 100% onion extract combined with 1% naringin. Serum cholesterol and triglyceride levels significantly decreased in the naringin treated group while the HDL cholesterol level increased. On the other hand, the morphology of the mitochondria and nuclei found in the livers of the treated group given naringin were siginficantly different when compared to those group given high fat diets. In conclusion, onion extract with naringin decreased cholesterol levels in hamster’s livers.

Condensation and Annealing Effects of Polymer Gate Insulator on Organic Thin-Film Transistor Characteristics

Abstract: Performances of organic thin-film transistors (TFTs) can be detrimentally affected by the state of gate dielectric layer. In this study, we report the condensation and annealing effects of a polymer gate dielectric layer. For the observations of the effect of condensation, the spin-coated polymer layers with various deposition conditions were fabricated and kept under low vacuum condition for several days. It is observed that the thickness of polymer layer and the electrical characteristics of organic TFTs vary with the condensation time, and the appropriate additional annealing process could stabilize the gate dielectric layer and even improve the device characteristics consequently.

A Study on the Electrical and Mechanical Properties of a Epoxy Powder for Compact Bus Duct

Abstract: Insulated methods of compact bus duct has been applied a way of coating Epoxy powder. The problem which is caused by degradation during operation is very important in severe environment. Therefore, this study compared and verified many kind of properties ; electrical breakdown by thermal and water aging, v-t characteristic, arc discharge, mechanical properties, bending test and cross cut. Sample D was stable before the to be about decrease in the breakdown test according to temperature change. In case of V-t and arc discharge, it had been kept up suitable characteristic. Also, in case of electrical and mechanical characteristic, both sample D and A have excellent capacity.

Preparation method of organic-transition metal hydride complexes and their use as hydrogen storage materials

Abstract: The present invention relates to an advanced preparation method of organic-transition metal hydride used as hydrogen storage materials, the method including: preparing organic-transition metal-aluminum hydride complexes by reacting the organic-transition metal halide with metal aluminum hydride compounds; and preparing the organic-transition metal hydride by reacting the organic-transition metal aluminum hydride complexes with Lewis bases. Since the preparation method of the organic-transition metal hydride according to the present invention does not use catalysts, it has advantages that it does not cause problems due to poisoning and can prepare the organic-transition metal hydride at high yield under less stringent conditions. The hydrogen storage materials containing the organic-transition metal hydride prepared from the preparation method can safely and reversibly store a large amount of hydrogen.