• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.195-206
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• 2009

The deregulation of aviation markets in Europe and the United Sates had led airlines to reconfigure their networks into hub-and-spoke systems. Recent trends of "Open Skies" in the Asian aviation market are also expected to prompt the reformation of airlines' networks in the region. A significant connectivity index is a crucial tool for airlines and airport authorities to estimate the degree of hub-and-spoke operations. Therefore, this paper suggests a new index, Continuous Indirect Connectivity Index (CICI), for measuring the coordination of airlines' flight schedules, applying it to the Asian, European and the American aviation markets. CICI consists of three components：(i) temporal connectivity to identify the attractiveness between connection flights, (ii) spatial connectivity to differentiate the attractiveness by de-routing distance with continuous linear function, and (iii) relative intensity to reflect the effect of direct flight frequency on transfer routes. CICI is evaluated to examine a casual relationship through regression analyses with two dependent variables of the number of transfer passengers and transfer rates. Compared with Danesi's index and Doganis' index through evaluation processes, CICI has a higher coefficient value of determination, implying that it explains the relationship between connectivity and transfer passengers more precisely.

• Journal of radiological science and technology
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• v.28 no.4
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• pp.267-272
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• 2005

The effects of As addition in amorphous selenium (a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating (MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, jsc in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic (As) additions have been obtained. We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.2
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• pp.138-149
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• 2000

Various modeling techniques for ultrasonic wave propagation and scattering problems in finite solid media are presented. Elastodynamic boundary value problems in inhomogeneous multi-layered plate-like structures are set up for modal analysis of guided wave propagation and numerically solved to obtain dispersion curves which show propagation characteristics of guided waves. As a powerful modeling tool to overcome such numerical difficulties in wave scattering problems as the geometrical complexity and mode conversion, the Boundary Element Method(BEM) is introduced and is combined with the normal mode expansion technique to develop the hybrid BEM, an efficient technique for modeling multi mode conversion of guided wave scattering problems. Time dependent wave forms are obtained through the inverse Fourier transformation of the numerical solutions in the frequency domain. 3D BEM program development is underway to model more practical ultrasonic wave signals. Some encouraging numerical results have recently been obtained in comparison with the analytical solutions for wave propagation in a bar subjected to time harmonic longitudinal excitation. It is expected that the presented modeling techniques for elastic wave propagation and scattering can be applied to establish quantitative nondestructive evaluation techniques in various ways.

• Magazine of the Korean Society of Agricultural Engineers
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• v.22 no.3
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• pp.75-87
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• 1980

Most hydro]ogic phenomena are the complex and organic products of multiple causations like climatic and hydro-geological factors. A certain significant correlation on the run-off in river basin would be expected and foreseen in advance, and the effect of each these causual and associated factors (independant variables; present-month rainfall, previous-month run-off, evapotranspiration and relative humidity etc.) upon present-month run-off(dependent variable) may be determined by multiple regression analysis. Functions between independant and dependant variables should be treated repeatedly until satisfactory and optimal combination of independant variables can be obtained. Reliability of the estimated function should be tested according to the result of statistical criterion such as analysis of variance, coefficient of determination and significance-test of regression coefficients before first estimated multiple regression model in historical sequence is determined. But some error between observed and estimated run-off is still there. The error arises because the model used is an inadequate description of the system and because the data constituting the record represent only a sample from a population of monthly discharge observation, so that estimates of model parameter will be subject to sampling errors. Since this error which is a deviation from multiple regression plane cannot be explained by first estimated multiple regression equation, it can be considered as a random error governed by law of chance in nature. This unexplained variance by multiple regression equation can be solved by stochastic approach, that is, random error can be stochastically simulated by multiplying random normal variate to standard error of estimate. Finally hybrid model on estimation of monthly run-off in nonhistorical sequence can be determined by combining the determistic component of multiple regression equation and the stochastic component of random errors. Monthly run-off in Naju station in Yong-San river basin is estimated by multiple regression model and hybrid model. And some comparisons between observed and estimated run-off and between multiple regression model and already-existing estimation methods such as Gajiyama formula, tank model and Thomas-Fiering model are done. The results are as follows. (1) The optimal function to estimate monthly run-off in historical sequence is multiple linear regression equation in overall-month unit, that is; Qn=0.788Pn+0.130Qn-1-0.273En-0.1 About 85% of total variance of monthly runoff can be explained by multiple linear regression equation and its coefficient of determination (R2) is 0.843. This means we can estimate monthly runoff in historical sequence highly significantly with short data of observation by above mentioned equation. (2) The optimal function to estimate monthly runoff in nonhistorical sequence is hybrid model combined with multiple linear regression equation in overall-month unit and stochastic component, that is; Qn=0. 788Pn+0. l30Qn-1-0. 273En-0. 10+Sy.t The rest 15% of unexplained variance of monthly runoff can be explained by addition of stochastic process and a bit more reliable results of statistical characteristics of monthly runoff in non-historical sequence are derived. This estimated monthly runoff in non-historical sequence shows up the extraordinary value (maximum, minimum value) which is not appeared in the observed runoff as a random component. (3) "Frequency best fit coefficient" (R2f) of multiple linear regression equation is 0.847 which is the same value as Gaijyama's one. This implies that multiple linear regression equation and Gajiyama formula are theoretically rather reasonable functions.

• Journal of Physiology & Pathology in Korean Medicine
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• v.28 no.6
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• pp.630-635
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• 2014

The purpose of this study was to investigate the effects of Naeso-san in interstitial cells of Cajal (ICCs) in murine small intestine. First, we isolated ICCs from murine small intestine. After that, we cultured these cells for 1 days. The patch-clamp technique was applied on ICCs that formed network-like structures in culture (1 days). Spontaneous rhythms were routinely recorded from cultured ICCs under current-clamp conditions, and the ICCs within networks displayed more robust electrical rhythms (pacemaker potentials). To understand the relationship between Naeso-san and pacemaker activity in ICCs, we examined the effects of Naeso-san on pacemaker potentials of ICCs. In current clamp mode (I = 0), the addition of Naeso-san (10 mg/ml - 50 mg/ml) decreased the amplitude and frequency of the pacemaker potentials of ICCs in a dose dependent manner. However, these effects were blocked by intracellular $GDP{\beta}S$, a G-protein inhibitor, and glibenclamide, a specific ATP-sensitive K+ channels blocker. Pretreatment with SQ-22536, an adenylate cyclase inhibitor, did not block the Naeso-san induced effects, whereas pretreatment with ODQ, a guanylate cyclase inhibitor, or L-NAME, an inhibitor of nitric oxide (NO) synthase blocked the Naeso-san induced effects. Our findings provide insight into unraveling the modulation of Naeso-san in pacemaker potentials of ICCs and developing therapeutic agents against gastrointestinal motility disorders.

• Korean Journal of Veterinary Research
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• v.39 no.2
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• pp.247-256
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• 1999

A disease of young Holstein calves characterized by recurrent pneumonia, ulcerative and granulomatous stomatitis, enteritis with bacterial overgrowth, periodontitis, delayed wound healing, persistent neutrophilia and death at an early age had been originally described in 1983 and again in 1987. Most of these calves had stunted growth and a persistent, progressive neutrophilia (often exceeding 100,000/ml). By investigation of pedigrees, all of the affected calves have now been traced to a common sire and confirmed by polymerase chain reaction (PCR) diagnostic DNA testing to be homozygous carriers of a defective allele for bovine CD18. Neutrophils from these calves have several functional deficits and, most importantly, fail to adhere in a ${\beta}_2$-integrin dependent manner. The ${\beta}_2$-integrins represent a family of glycoproteins which participate in various leukocyte adhesion reactions during host defense. The presence or absence of ${\beta}_2$-integrin molecules can be demonstrated on the surface of neutrophils, monocytes and lymphocytes from normal or affected calves using specific monoclonal antibodies and flow cytometry, or by colloidal gold immunolabeling and scanning electron microscopy in backscatter mode. Deficiency of the ${\beta}_2$-integrins on all leukocyte types in Holstein calves is analogous to leukocyte adhesion deficiency (LAD) seen in humans. Neutrophils in bovine (BLAD) and human LAD patients are unable to adhere to the endothelial lining of the cardiovascular system thus interrupting egression of neutrophils into infected tissues. Other leukocytes, while still deficient in expression of the ${\beta}_2$-integrins, are still able to efficiently egress from the blood stream due to interactions of other adhesion molecules that are not as highly expressed on neutrophils. Both BLAD cattle and LAD children (who do not receive bone marrow transplants) often die at an early age as a result of the failure of neutrophils to extravasate into infected tissues. In 1991, Shuster, et $al^{27}$, identified two point mutations within the alleles encoding bovine CD18 in a Holstein calf afflicted with leukocyte adhesion deficiency. One mutation causes an aspartic acid to glycine substitution at amino acid 128 (D128G) in an extracellular region of this adhesion glycoprotein that is highly conserved (> 95% identity) between humans, cattle and mice. The other mutation is silent. Numerous calves with clinical symptoms of leukocyte adhesion deficiency have since been tested and all have been found homozygous for the D128G allele. In addition, calves homozygous far the D128G allele have been identified during widespread DNA testing in the United States. All cattle with the mutant allele are related to one bull, who through artificial insemination (A.I.), sired many calves in the 1950's and 1960's. The carrier frequency of the D128G CD18 allele among U.S. Holstein cattle had reached approximately 15% among active A.I. bulls and 8% among cows. By 1993, the organization of the dairy industry and the diagnostic test developed to genotype cattle, enabled virtually complete eradication of bovine leukocyte adhesion deficiency among current and future A.I. bulls.

• Journal of the Korean Society of School Health
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• v.19 no.1
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• pp.79-88
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• 2006

Purpose : To identify general characteristics of school personnel with recent fatigue which was the most frequent symptom among subjective symptoms and to explore fatigue-related factors by evaluating physical and perceived health status, life style, and symptoms through data mining techniques. Methods : We collected a data of the 1,147(male 545, female 602) who were elementary, middle, or high school personnel, answered a questionnaire, and received physical examination in Seoul School Health Center from September to November in 2000. And we investigated the differences between fatigue group and non-fatigue group for demographic characteristics, physical health status, perceived health status, symptoms, and laboratory values by frequency, chi-square test, t-test, or simple logistic regression analysis by SAS package 8.1, and then selected significant variables as input variables of a decision tree analysis of CART model by SAS E-miner. Results : In general characteristics, the fatigue consisted of 41.1%(male 35.2%, female 46.4%) among 1,147 school personnel. In classical statistics, factors related with fatigue were female, lower means of systolic and diastolic pressure, young age, personnel in middle school, irregular eating habit, no exercise a week or less than 30minutes exercise a day, perception of unhealthy status, and subjective symptoms including short of breath at exercise. In simple logistic regression to examine the relationship between selected independent variables and fatigue as a dependent variable, the odds ratio of gender (female vs male) was 1.58 times, and young age ( 20s vs 60s) 20.67 times, and middle vs high school personnel 1.86 times. However, we mined combined several characteristics by SAS-E miner. In CART model, if health perception was healthy, and age was >= 37.5 years, the proportion of the fatigue was only 19.3%. but if health perception was not healthy and symptom was severe 'short of breath' during exercise and age was < 53.5 years, and BMI was >= 22.69, the proportion of the fatigue was up to 84.8%. Conclusions : The fatigue consisted of 41.1%(male 35.2%, female 46.4%). In classical statistics, fatigue-related factors among school personnel were young age, female gender, perceived unhealthy status, subjective physical symptoms, poor life-style, and lower blood pressure rather than only physical health status. However, in data mining, if health perception was healthy and age was >= 37.5 years, the proportion of the fatigue was only 19.3%. but if health perception was not healthy and symptom was severe 'short of breath' during exercise and age was < 53.5 years, and BMI was >= 22.69, the proportion of the fatigue was up to 84.8%.

• Applied Chemistry for Engineering
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• v.19 no.4
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• pp.421-426
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• 2008

Multi-walled carbon nanotube/polystyrene (MWCNT/PS) composites with various MWCNT contents were prepared by using a solution process with an aid of surfactant. Particularly, PS's with 3 different molecular weights (${\bar{M}}_n$ = 101500 g/mole for PS-1, ${\bar{M}}_n$ = 89900 g/mole for PS-2, and ${\bar{M}}_n$ = 85000 g/mole for PS-3) were used in this study. Thermal behavior of these composites was examined by using an oscillator rheometer at $210^{\circ}C$ and $180^{\circ}C$, of above and below the critical flow temperature ($T_{cf}{\sim}195^{\circ}C$) of PS matrix, respectively. The storage and loss modulus, and the complex viscosity of these composites increased with increasing MWCNT content at both temperatures. Largest increases in the frequency-dependent moduli and complex viscosity were observed between 2 wt% and 5 wt% of MWCNTs at $210^{\circ}C$ and $180^{\circ}C$. Only the composite at $210^{\circ}C$ showed the rheological phase transition from a viscous-dominant to an elastic-dominant behavior of the composites at a certain MWCNT content. The MWCNT content at the rheological phase transition of MWCNT/PS composites generally increased with decreasing molecular weight of PS, and was measured to be 3.5 wt% for MWCNT/PS-1, 3.2 wt% for MWCNT/PS-2, and 3.0 wt% for MWCNT/PS-3 composites.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.615-621
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• 2016

This study examines whether there is agency cost in a public R&D subsidy program by applying agency theory. If there is agency cost, the composition ratio of the government subsidy and the firm's own R&D fund would have a significant (-) effect on technological performance. Companies that received a public R&D subsidy in Korea from 2000 to 2009 were selected as a sample. Frequency analysis and multiple regression analysis were used. The independent variables was the ratio of public R&D subsidy cost to the Firm's own R&D cost, and the dependent variables were the number of patent applications and the number of patents registered. The control variables were firm size and R&D cost. The results show that there are agency problems in the government-sponsored R&D system. A future study is needed to examine how much agency problems deteriorate the efficiency of the system.

• The Korean Journal of Physiology
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• v.28 no.1
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• pp.37-50
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• 1994

Synthetic potassium channel openers (KCOs) are agents capable of opening K-channels in excitable cells. These agents are known to have their maximal potency in the smooth muscle tissue, especially in the vascular smooth muscle. Much attention has been focused on the type of K-channel that is responsible for mediating the effects of KCOs. As the KCO-induced changes are antagonized by glibenclamide, an $K_{ATP}$ (ATP-sensitive K-channel) blocker in the pancreatic ${\beta}-cell,\;K_{ATP}$ was suggested to be the channel responsible. However, there also are many results in favor of other types of K-channel $$(maxi-K,\;small\;conductance\;K_{Ca,}\; SK_{ATP}) mediating the effects of KCOs. Effects of lemakalim, (-)enantiomer of cromakalim (BRL 34915), on the spontaneous contractions and slow waves, were investigated in the antral circular muscle of the guinea-pig stomach. Membrane currents and the effects on membrane currents and single channel activities were also measured in single smooth muscle cells and excised membrane patches by using the patch clamp method. Lemakalim induced hyperpolarization and inhibited spontaneous contractions in a dose-dependent manner. These effects were blocked by glibenclamide and low concentrations of tetraethyl ammonium (< mM). Glibenclamide blocked the effect of lemakalim on the membrane potential and slow waves. The mechanoinhibitory effect of lemakalim was blocked by pretreatment with glibenclamide. In a whole ceIl patch clamp condition, lemakalim largely increased outward K currents. These outward K currents were blocked by TEA, glibenclamide and a high concentration of intracelIular EGTA (10 mM). Volatage-gated Ca currents were not affected by lemakalim. In inside-out patch clamp experiments, lemakalim increased the opening frequency of the large conductance $Ca^{2+}-activated$ K channels $(BK_{Ca},\;Maxi-K).$ From these results, it is suggested that lemakalim induces hyperpolarization by opening K-channels which are sensitive to internal Ca and such a hyperpolarization leads to the inhibition of the spontaneous contraction.