• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.2038-2040
• /
• 2000

The main objective of this paper is to design and test a new type of polymer ZnO surge arrester for AC power system of railroad vehicles. Metal oxide surge arrester for most electric power system applications, electric train and subway are now being used extensively to protect overvoltage due to lightning. Surge arresters with porcelain housing must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of ZnO elements in a surge arrester occurs due to flashover, fault short current flows through the arrestor and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock, pressure rise. etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion. The main research works are focused on the structure design by finite element method, pressure relief of module, and studies of performance of surge arrester for electric railway vehicle.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1545-1547
• /
• 2000

The mechanical and electrical properties of the hot-pressed and annealed $\beta$-Sic-$TiB_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_{2}O_{3}+Y_{2}O_3$. Phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_{5}Y_{3}O_{12}$). The relative density and the mechanical properties of composites were increased with increasing $Al_{2}O_{3}+Y_{2}O_3$ contents because YAG of reaction between $Al_{2}O_3$ and $Y_{2}O_3$ was increased. The Flexural strength showed the highest value of 432.5MPa for composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. Owing to crack deflection, crack bridging, phase transition and YAG of fracture toughness mechanism. the fracture toughness showed 7.1MPa${\cdot}m^{1/2}$. For composites added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature The electrical resistivity and the resistance temperature coefficient respectively showed the lowest of 6.0${\sim}10^{-4}{\Omega}{\cdot}$ cm and 3.1${\times}10^{-3}/^{\circ}C$ for composite added with l2wt% $Al_{2}O_{3}+Y_{2}O_3$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of 25$^{\circ}C$ to 700$^{\circ}C$.

• Korean Chemical Engineering Research
• /
• v.53 no.3
• /
• pp.401-406
• /
• 2015

Getter is a class of materials used in absorbing gases such as hydrogen and moisture in microelectronics or semiconductor devices to operate properly. In this study, we developed a new device structure consisting of porous anodized alumina films on textured silicon wafer, which have cost efficiency in materials and processing aspects. Anodic aluminum oxide (AAO) with controlled pore sizes can be applied to a high-efficiency moisture absorber due to the high surface area and OH- saturated surface property. The moisture sorption capacity was 2.02% (RH=35%), obtained by analyzing isothermal adsorption/desorption curve.

• Journal of the Korean Chemical Society
• /
• v.36 no.3
• /
• pp.460-465
• /
• 1992

The structure of th 5S rRNA isolated from Xanthomonas citri was determined by enzymatic and chemical degradation methods. It consists of 119 nucleotides and contains no modified nucleosides. As does the 5S rRNA of X. maltophilia, it contains an additional uridine residue on the 5'-terminus. The secondary structure of the 5S rRNA from X. citri was almost identical to the generalized models proposed by many other workers [De Wachter et al., Biochimie, 64, 311 (1982); Specht et al., Nucleic Acids Res., 18, 2215 (1990); Cho et al., Proceedings of the First Symposium on Biomolecules, p. 9 (1991)]. The secondary structure of 5S rRNA from X. citri consists of five helices, five loops and two bulges. This 5S rRNA has a uridine residue at position 66 as a bulge.

• Korean Journal of Biological Psychiatry
• /
• v.17 no.1
• /
• pp.44-48
• /
• 2010

Objectives : Social phobia is frequently accompanied with autonomic nerve system symptoms. QT dispersion(QTd) is the maximum inter-lead difference in QT interval, an indicator of the autonomic nerve system(ANS) disparity of the heart itself. The objective of this study is to investigate the ANS disparity, which is measured by QTd, is associated with pathophysiology of social phobia. Methods : This research have compared QT dispersion of 25 physically healthy social phobia outpatients(16 men, 9 women, the average age $35.5{\pm}12.9$) and age and sex matched control group of mentally and physically healthy 25 volunteers(16 men, 9 women, the average age $34.83{\pm}12.7$). QTd was measured by previously described method. Results : QTd and rate-corrected QTd were significantly higher on the patient group than the control group[QTd(patients vs. controls : $52.60{\pm}27.63ms$ vs. $27.53{\pm}14.29ms$, p<0.0001), QTd(patients vs. controls : $55.79{\pm}27.98ms$ vs. $29.10{\pm}14.24ms$, p<0.0001)]. Conclusion : Our study showed that the patients with social phobia have higher QTd than the normal controls. These results suggest that the ANS disparity, which is measured by QTd, is associated with pathophysiology of social phobia.

• Korean Journal of Biological Psychiatry
• /
• v.14 no.2
• /
• pp.106-114
• /
• 2007

Objective : It is suggested that disturbance of dopaminergic system might be related to the possible mechanism of social phobia. The aim of this study was to investigate the possible association of DRD2 TaqI polymorphism and social phobia. Method : Fifty-one patients with social phobia and 200 comparison subjects were tested for DRD2 TaqI A polymorphism. The severity of social phobic symptoms was measured by self-report version of the Liebowitz Social Anxiety Scale(LSAS-SR) and Hamilton anxiety scale(HAM-A). Results : There was no signigicant difference in the genotype, allele frequency, A1 carrier frequency, and heterozygote frequency DRD2 TaqI A polymorphism between the social phobia patients and the control groups. However, we found significant decrease in somatic anxiety of the HAM-A in the patients having A2A2 homozygotes(p=0.014). In addition, patients having A1A2 heterozygotes showed more anxiety in two subscales (p=0.042 in anxiety, p=0.019 in performance) of the LSAS-SR. Conclusion : These results suggest that DRD2 A2 homozygote might have a protective role against somatic anxiety, and molecular heterosis of DRD2 TaqI A polymorphism might be related with more severe anxiety in social phobia.

• Korean Journal of Biological Psychiatry
• /
• v.14 no.3
• /
• pp.194-200
• /
• 2007

Objectives:This study was performed to investigate the differences of the clinical feature between panic disorder with agoraphobic patients and panic disorder without agoraphobic patients. Methods:Two hundred nine patients meeting the criteria of DSM-IV panic disorder were recruited. One group was panic disorder with agoraphobia(n=78, 42 male(53.8%), mean age $37.6{\pm}9.9$ years), another was panic disorder without agoraphobia(n=131, 81 male(61.8%), mean age $40.5{\pm}10.3$ years). The numbers and frequency of panic symptoms were compared between two groups with t-test, and the logistic regression analysis were used for predicting panic disorder with agoraphobia. Results:The number of panic symptoms during panic attack was significantly higher in the group of panic disorder with agoraphobia than the group of panic disorder without agoraphobia(p<0.05).'Sweating','nausea or abdominal distress','fear of losing control of going crazy','chills or hot flushes'were more frequent in the group of panic disorder with agoraphobia(p<0.05). Among panic symptoms on logistic regression analysis,'sweating',' nausea or abdominal distress','fear of losing control or going crazy'turned out to correlate significantly with risk of development of agoraphobia in panic disorder. Conclusion:These results suggest that the frequency of some symptoms during panic attack may be a predictor of agoraphobia in patients with panic disorder.

• Journal of computational fluids engineering
• /
• v.16 no.3
• /
• pp.66-74
• /
• 2011

A fluid in an enclosure can be heated by electric heating, chemical reaction, or fission heat. In order to remove the volumetric heat of the fluid, the walls surrounding the enclosure must be cooled. In this case, a natural convection occurs in the pool of the fluid, and it has a dominant role in heat transfer to the surrounding walls. It can augment the heat transfer rates tens to hundreds times larger than conductive heat transfer. The heat transfer by a natural convection in a regular shape such as a square cavity or semi-circular pool has been studied experimentally and numerically for many years. A pool of an inverted triangular shape with 10 degree inclined bottom walls has a good cooling performance because of enhanced boiling critical heat flux (CHF) compared to horizontal downward surface. The coolability of the pool is determined by comparing the thermal load from the pool and the maximum heat flux removable by cooling mechanism such as radiative or boiling heat transfer on the pool boundaries. In order to evaluate the pool coolability, it is important to correctly expect the thermal load by a natural convection heat transfer of the pool. In this study, turbulence models with modifications for buoyancy effect were validated for unsteady natural convections by volumetric heating. And natural convection in the triangular pool was evaluated by using the models.

• Anxiety and mood
• /
• v.12 no.1
• /
• pp.1-6
• /
• 2016

Objective : This study was performed to confirm the hypothesis that the more one applies positive thinking, the less severe the symptoms of stress and the better the therapeutic responsein panic disorder and major depressive disorders. Methods : The study included 50 subjects with confirmed diagnoses of panic disorder or major depressive disorders. Positive thinking was assessed using Positive thinking scale. Beck Depression Inventory was used as a subjective measure for depression, and to ensure an objective measure for depression and anxiety, the Hamilton Depression and Hamilton Anxiety rating scales were implemented. Results : The positive thinking scale measured at the initial visit had shown a strong negative correlation with objective depression. Although patients with a high level of positive thinking had shown a tendency to respond better to the treatment, as compared with those with a lower level, the differences were not statistically significant. Conclusion : Positive thinking is likely to ameliorate major depressive disorder, panic disorder-induced depression, and anxiety. Nevertheless, it was not possible to confirm the effects of positive thinking on the patients' treatment responses.

• Anxiety and mood
• /
• v.8 no.2
• /
• pp.146-152
• /
• 2012

Objective : Individuals with anxiety disorders experience a wide range of time to seeking treatment (TST) as well as various comorbid mental disorders. The present study examined the TST in social anxiety disorder (SAD) and panic disorder. This study aimed to find out the influence of comorbid mental disorder on TST of anxiety disorder through the comparison of SAD and panic disorder. Methods : This study included 311 SAD and 378 panic disorder patients at the initial visit of psychiatric clinic. Contribution of clinical (number of comorbidity, comorbid type and onset age) and demographic (current age) factors to TST were investigated by multivariate analysis. Results : The median length of TST was 14.03 years in SAD and 2.26 years in panic disorder. In social anxiety disorder, fewer comorbidity, younger onset age, and older age were factors associated with delayed TST. In panic disorder, only younger onset age was associated with delayed TST. In both disorders, comorbid depressive disorder was associated with shorter TST. Conclusion : Our data provided the differences in illness behavior needing help based on comorbid mental disorders between SAD and panic disorder. In addition to comorbid disorder, factors affecting TST of anxiety disorder requires future investigation.