• Transactions of the Korean hydrogen and new energy society
• /
• v.18 no.1
• /
• pp.60-66
• /
• 2007

In terms of the vehicle efficiency, a fuel cell hybrid system has advantages compared to a conventional internal combustion engine and a fuel cell alone-powered system. The efficiency of the fuel cell hybrid vehicle mainly depends on the maximum power of the fuel cell and therefore it is important to decide the design value of the fuel cell maximum power. In this paper, to estimate the performance of the fuel cell hybrid mini-bus in the design phase the simulator based on the models for the fuel cell stack, the electric battery, the fuel cell balance of plant, the controller, and the vehicle itself is proposed. Additionally, the hybrid mini-bus efficiencies with several different fuel cell powers are simulated for a city driving schedule and are compared on another. Consequently, the proposed simulation scheme is useful to determine the best design value of the fuel cell hybrid vehicles.

• Nuclear Engineering and Technology
• /
• v.50 no.3
• /
• pp.340-355
• /
• 2018

The methods and performance of a fast reactor multigroup cross section (XS) generation code EXUS-F are described that is capable of directly processing Evaluated Nuclear Data File format nuclear data files. RECONR of NJOY is used to generate pointwise XS data, and Doppler broadening is incorporated by the Gauss-Hermite quadrature method. The self-shielding effect is incorporated in the ultrafine group XSs in the resolved and unresolved resonance ranges. Functions to generate scattering transfer matrices and fission spectrum matrices are realized. The extended transport approximation is used in zero-dimensional calculations, whereas the collision probability method and the method of characteristics are used for one-dimensional cylindrical geometry and two-dimensional hexagonal geometry problems, respectively. Verification calculations are performed first for various homogeneous mixtures and cylindrical problems. It is confirmed that the spectrum calculations and the corresponding multigroup XS generations are performed adequately in that the reactivity errors are less than 50 pcm with the McCARD Monte Carlo solutions. The nTRACER core calculations are performed with the EXUS-F-generated 47 group XSs for the two-dimensional Advanced Burner Reactor 1000 benchmark problem. The reactivity error of 160 pcm and the root mean square error of the pin powers of 0.7% indicate that EXUF-F generates properly the broad-group XSs.

• Journal of the Optical Society of Korea
• /
• v.1 no.2
• /
• pp.110-115
• /
• 1997

We report effcient cascaded Raman generation and signal amplification at 1.3.mu.m achieved in a ring resonator constructed solely from fiber components, i.e. fusion WDM couplers. Low-loss single-mode fiber with moderate $GeO_2$ content (18 mole %) is used as an active medium and pumped by a Nd:YAG laser at 1.064.mu.m. In a resonant cascaded geometry, this generates the third Stokes line at 1.24.mu.m, which acts as a pump for signal wavelength around 1.3.mu.m. A DFB laser operating at 1.315.mu.m is used to provide an input signal. An output signal powers up to 20 dBm (100 mW) with a 28 dB Raman gain are attained, where the Nd:YAG pump power is 3.4 W. It is also shown experimentally that it is important to use optical filters to suppress feedback from the resonator, permitting high Raman gain and good signal quality.

• Bulletin of the Korean Mathematical Society
• /
• v.47 no.5
• /
• pp.997-1000
• /
• 2010

We prove that the reduced free product of $k\;{\times}\;k$ matrix algebras over abelian $C^*$-algebras is not the minimal tensor product of reduced free products of $k\;{\times}\;k$ matrix algebras over abelian $C^*$-algebras. It is shown that the reduced group $C^*$-algebra associated with a group having the property T of Kazhdan is not isomorphic to a reduced free product of abelian $C^*$-algebras or the minimal tensor product of such reduced free products. The infinite tensor product of reduced free products of abelian $C^*$-algebras is not isomorphic to the tensor product of a nuclear $C^*$-algebra and a reduced free product of abelian $C^*$-algebra. We discuss the freeness of free product $II_1$-factors and solidity of free product $II_1$-factors weaker than that of Ozawa. We show that the freeness in a free product is related to the existence of Cartan subalgebras in free product $II_1$-factors. Finally, we give a free product factor which is not solid in the weak sense.

• The Korean Journal of Food And Nutrition
• /
• v.28 no.2
• /
• pp.178-188
• /
• 2015

The purpose of this study was to investigate the association of interpersonal relationships with snack preference and the intake frequency of snacks with a primary focus on obesity index and snack preparations in upper grade (5~6th) elementary school students. A total of 719 students in Gyeongsangnam-do province were recruited and a questionnaire-based survey was conducted. Data were analyzed using the SPSS V18.0. The results were as follows : A total score of interpersonal relationships was 94.5 (full marks 125), and the scores of 7 factors consisting interpersonal relationships were over 3.50(full marks 5.00). Overweight group had the lowest score in interpersonal relationships (p<0.01) and purchase group by oneself had a low score than the other groups in snacks preparation (p<0.001). Most favorite snacks were ice cream. Additionally, the snack purchase group showed higher scores than the cook group by family in 8 types of snack and a total score of preference (p<0.05~p<0.001). Milk and dairy products had the highest score in frequency of snack intake. And purchase group by oneself or family was a higher than cook group by family (p<0.01). Interpersonal relationships showed a positive effect on preference and intake frequency of milk and dairy products but their explanation powers ($R^2$) were very low. The findings of this study provide fundamental information impact factor in snack preference and frequency of snack intake.

• The Southeast Asian review
• /
• v.28 no.1
• /
• pp.1-20
• /
• 2018

Southeast Asia witnessed a paradox of political stagnation and economic development in 2017. The 'dual order' of security dependence on America and economic dependence on China was sustained in East Asia. In this regard, Southeast Asia of two faces was quite similar to broader East Asia. On one hand, the old socialist group with totalitarian nostalgia lurked in the buffer zone between totalitarianism and authoritarianism, while the original capitalist group under democratic disguise roamed in the gray zone between authoritarianism and democracy. On the other, the old socialist group with the legacy of the planned economy succumbed to the temptation of the Beijing Consensus on state capitalism, while the original capitalist group with the myth of the market economy was exposed to the pressure of the Washington Consensus on liberal capitalism. The ASEAN Community representing the regional integration of Southeast Asia was caught in the strategic predicament of a looming 'new cold war' between the continental and maritime powers.

• Korean Journal of Biological Psychiatry
• /
• v.18 no.3
• /
• pp.134-140
• /
• 2011

Objectives Postpartum blues is known to be a major risk factor for postpartum depression and can be associated with the problems of language skills, behaviors or learning skills of their children. Therefore, it is very important for clinicians to evaluate precisely and control postpartum blues. Recent studies have found that music has an effect on depressive mood and the frontal EEG asymmetry of the patients with depression. The purpose of this study was to find out the effects of music on the frontal EEG asymmetry of the mothers with postpartum blues. Method Among one hundred and seventy mothers assessed with Korean version of the Edinburg Postnatal Depression Scale (EPDS), nine mothers with postpartum blues (EPDS ${\geq}$ 10) as postpartum blues group and nine non-depressive mothers (EPDS < 10) as non-depressive mother group were included. Ten non-labored, non-depressive women were also included as a normal control group. The subjects were evaluated with the State Trait Anxiety Inventory (STAI)-X1, the Visual Analogue Scale (VAS) and the Depression Adjective Checklist-Korean version (K-DACL) and EEG twice before and after the music sesssion with the length of twenty minutes and thirty two seconds. The statistical analyses were done for A1 score (log R - log L) which were computed from the alpha powers at F3 and F4. Results No significant difference was noted in demographic data among all three groups. The postpartum blues group had higher scores in the STAI-X1, the VAS and the K-DACL compared to the other groups at baseline, and their A1 scores were lower than those of only normal controls. There was a statistically significant increase of A1 score only in the postpartum blues group after the music session. Conclusion This study suggests that the mothers with postpartum blues may have a frontal EEG asymmetry which is possibly associated with their depressive mood, and the music session can affect the frontal asymmetry positively.

• Journal of the Korean Chemical Society
• /
• v.41 no.6
• /
• pp.292-298
• /
• 1997

An ICP(Inductively Coupled Plasma) emission spectrometer was developed with an axially viewed ICP source incorporated by a 5-turned induction coil and a torch, outer quartz tube of which was 50 mm longer than that used in conventional ICP/AES(Inductively Coupled Plasma Atomic Emission Spectrometry). The Optimization of the system has been performed in terms of the determination of signal-to-noise ratio and background intensity at various rf powers, sample flow rates, argon gas flow rates and cut-off gas flow rates. The spectro-analytical characteristics of the spectrum obtained between 200 and 500 nm was revealed to be similar compared with a vertically viewed ICP source. The detection limit of Pb(Ⅱ) at 220.35 nm was 11 ppb which was 5 times lower than that obtained with a vertically viewed ICP source.

• Korean Journal of Applied Biomechanics
• /
• v.25 no.3
• /
• pp.283-291
• /
• 2015

Objective : The purpose of this study was to determine the differences in the head and tibial acceleration signal magnitudes, and their powers and shock attenuations between flat-footed and normal-footed running. Methods : Ten flat-footed and ten normal-footed subjects ran barefoot on a treadmill with a force plate at 3.22m/s averaged from their preferred running speed using heel-toe running pattern while the head and tibial acceleration in the vertical axis data was collected. The accelerometers were sampled at 2000 Hz and voltage was set at 100 mv, respectively. The peak magnitudes of the head and tibial acceleration signals in time domain were calculated. The power spectral density(PSD) of each signal in the frequency domain was also calculated. In addition to that, shock attenuation was calculated by a transfer function of the head PSD relative to the tibia PSD. A one-way analysis of variance was used to determine the difference in time and frequency domain acceleration variables between the flat-footed and normal-footed groups running. Results : Peaks of the head and tibial acceleration signals were significantly greater during flat-footed group running than normal-footed group running(p<.05). PSDs of the tibial acceleration signal in the lower and higher frequency range were significantly greater during flat-footed running(p<.05), but PSDs of the head acceleration signal were not statistically different between the two groups. Flat-footed group running resulted in significantly greater shock attenuation for the higher frequency ranges compared with normal-footed group running(p<.05). Conclusion : The difference in impact shock magnitude and frequency content between flat-footed and normal-footed group during running suggested that the body had different ability to control impact shock from acceleration. It might be conjectured that flat-footed running was more vulnerable to potential injury than normal-footed running from an impact shock point of view.

• Journal of Korean society of Dental Hygiene
• /
• v.9 no.3
• /
• pp.319-328
• /
• 2009

The levels of psychosocial stresses of dental hygienist were analyzed to reveal the various factors related to them. The self-administered questionnaires were performed, to 276 dental hygienist in Daejeon City. Univariate analysis and multiple regression were performed with survey results, in which a degree of psychosocial stress was dependent variable and others were independent variable. 1. In terms of various levels of psychosocial stress according to the higher level of stress was found in the group of lower age, unmarried, and without spare times for hobby activities, the group with shorter-term job career, lower salary, and stress was found in the group who think that their job is considered as low position or their job is not high position in society or their prospect about job is discouraging, the group without regularly exercise, without regularly eating habits, in the group with higher level of job demand, lower job autonomy, and lower social support from colleagues in work than their respective counterparts. 2. Concerning correlation between psychosocial stress and various factors, while level of stress was negatively correlated with age, job career, salary, socioeconomic status of oneself, socioeconomic status of dental hygienist, future status of dental hygienist, job autonomy, social support from superiors, social support from colleagues, social support, but it was positively correlated with job demand. 3. Multiple regression revealed that the factors which influence on psychosocial stress included hobby activities, sleeping hours, job demand, which has explanatory powers of 29.9%. Therefore, to reduce of stress of dental hygienists, it is required to develop an effective strategy that institutional support for improvement of job environments and research for them be revitalized.