• Wind and Structures
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• v.19 no.5
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• pp.541-563
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• 2014

This paper investigates the topographic effects on wind characteristics over hilly terrain, based on wind data recorded at a number of meteorological stations in or near complex terrain. The multiply data sources allow a more detailed investigation of the flow field than is normally possible. Vertical profiles of mean and turbulent wind components from a Sodar profiler were presented and then modeled as functions of height and wind speed. The correlations between longitudinal and vertical wind components were discussed. The phenomena of flow separation and generation of vortices were observed. The distance-dependence of the topographic effects on gust factors was revealed subsequently. Furthermore, the canyon effect was identified and discussed based on the observations of wind at a saddle point between two mountain peaks. This study aims to further understanding of the characteristics of surface wind over rugged terrain. The presented results are expected to be useful for structural design, prevention of pollutant dispersion, and validation of CFD (computational fluid dynamics) models or techniques over complex terrains.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.2
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• pp.133-141
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• 1990

In the operation of an electric power system, the voltage security of the system has acquired more significant importance after the occurrence of large system black-outs caused by voltage collapse several times. This paper describes a fast contingency screening method concerning voltage security. The method defines a voltage-sensitive buses where significant voltage changes would occur as a result of the contingency to reduce the number of bus voltages to be solved for continngency screening. This method is based on the observation that it is not necessary to solve the entire network in most contingency cases because boltage changes actually occur around the contingency. The P-Q decoupled linearized model and the fast error correction method are also adopted in the method to define voltage-sensitive buses and to calculate voltage magnitude on the selected voltage-sensitive buses fastly and reliably. The method suggested in this papaer has been tested in IEEE 30-bus model system and KEPCO 130-bus actual system and its effectiveness for practical use has also been confirmed.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.129-132
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• 1987

This paper presents an emergency control algorithms for viability crisis following abnormal condition as well as a sudden major supply outage and line outage. The algorithm considers the effect of voltage-reactive power control for determining the load shedding quantities and generation reallocation. The problem is decomposed into a P-problem and a Q-problem. The former minimizes system frequency deviation from nominal value and the latter minimizes voltages violation of load buses. The optimization problem is solved by a reduced gradient technique which can handle a great number of inequality constraints very efficiently. It has been found that the use of the proposed algorithm for 6-Bus system restore the abnormal system during the viability crisis to the normal state.

• Animal cells and systems
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• v.10 no.2
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• pp.65-71
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• 2006

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is one of the most common inherited renal disorders in the world. Mutations in PKD1 located on chromosome 16p13.3 are responsible for 85% of all the ADPKD patients whereas mutations in PKD2 on chromosome 4q21-23 are responsible for the rest of the cases. Genetic heterogeneity and the problems of mutation detection in PKD1 suggest that linkage analysis is an important approach to study the genetics of ADPKD. To evaluate the availability of six (CA)n microsatellite markers for the linkage analysis of ADPKD in the Korean population, we examined the allele frequencies and heterozygosities of the markers. With the exception of KG8, five markers were highly informative, with PIC values over 0.5, but the PIC value of KG8 marker was less informative than other five markers because of the low number of alleles. Therefore, this study will be useful in linkage analysis for ADPKD families in the Korean population.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1472-1473
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• 2006

During normal machine operation, partial discharge(PD) measurements were peformed with turbine generator analyzer(TGA) in two high voltage motors(rated 6.6 kV). These high voltage motors were installed with 80 pF capacitive couplers at the terminal box. TGA summarizes each plot with two quantities such as the normalized quantity number(NQN) and the peak PD magnitude (Qm). The trend analyses of NQN and $Q_m$ value are available for monitoring of the insulation condition in stator windings of high voltage motors.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.49-50
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• 2002

In micro-channels, the electro-viscous effect is caused by the electrical double layer on pressure-driven liquid flow. Velocity fields of flow inside micro-channels were measured using micro-PIV system for investigating the electro-viscous effect. De-ionized water and aqueous NaCl solutions with four different concentrations were used as working fluid in a PDMS micro-channel of $100{\mu}m$ width and $66{\mu}m$ height. The pressure gradient, dP/dx, was determined from the pre-determined input flow rate Q of syringe pump. The mean velocity $u_m$ used for calculating Reynolds number was obtained from the PIV velocity field data. These are used to plot the pressure gradient as a function of Reynolds numbers. The pressure gradient far lower concentration solution $(10^{-5}\;M)$ was higher than that for the higher concentration solution. The increase of flow resistance was about $30\%\;and\;37.5\%$ at Re=0.02 and 0.06, respectively.

• The Pure and Applied Mathematics
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• v.16 no.2
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• pp.199-212
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• 2009

We investigate the multiplicity of the nontrivial periodic solutions for a class of the system of the nonlinear suspension bridge equations with Dirichlet boundary condition and periodic condition. We show that the system has at least two nontrivial periodic solutions by the abstract version of the critical point theory on the manifold with boundary. We investigate the geometry of the sublevel sets of the corresponding functional of the system and the topology of the sublevel sets. Since the functional is strongly indefinite, we use the notion of the suitable version of the Palais-Smale condition.

• Journal of the Korean Mathematical Society
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• v.56 no.2
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• pp.507-521
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• 2019

For any $m{\times}n$ nonbinary Boolean matrix A, its spanning column rank is the minimum number of the columns of A that spans its column space. We have a characterization of spanning column rank-1 nonbinary Boolean matrices. We investigate the linear operators that preserve the spanning column ranks of matrices over the nonbinary Boolean algebra. That is, for a linear operator T on $m{\times}n$ nonbinary Boolean matrices, it preserves all spanning column ranks if and only if there exist an invertible nonbinary Boolean matrix P of order m and a permutation matrix Q of order n such that T(A) = PAQ for all $m{\times}n$ nonbinary Boolean matrix A. We also obtain other characterizations of the (spanning) column rank preserver.

• Journal of applied mathematics & informatics
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• v.37 no.1_2
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• pp.149-156
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• 2019

Let G be a (p, q) graph. Let $f:V(G){\rightarrow}\{1,2,{\ldots},k\}$ be a map where $k{\in}{\mathbb{N}}$ and k > 1. For each edge uv, assign the label gcd(f(u), f(v)). f is called k-Total prime cordial labeling of G if ${\mid}t_f(i)-t_f(j){\mid}{\leq}1$, $i,j{\in}\{1,2,{\ldots},k\}$ where $t_f$(x) denotes the total number of vertices and the edges labelled with x. A graph with a k-total prime cordial labeling is called k-total prime cordial graph. In this paper we investigate the 4-total prime cordial labeling of some graphs.

• Korean Journal of Microbiology
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• v.49 no.4
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• pp.424-428
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• 2013

To identify risk factors for Legionella contamination, water quality variables routinely measured in examination of natural and city waters were meta-analyzed for significance of correlation to Legionella incidences. For evaluation of abundance of Escherichia coli as a risk factor, which is currently used as an indicator of Legionella contamination in an official guideline in Korea, odds ratio (OR) of above-cutoff total coliform counts for Legionella presence/absence was used as the effect size in the meta-analysis. The OR was estimated as 1.05 (0.36-3.12, 95% CI), and the probability of having identical odds reached 0.92. Also, ORs from individual studies showed significant heterogeneity (P=0.008), which contributed to 63% of total variance of the ORs. In the case of heterotrophic plate count (HPC), the OR for Legionella presence/absence was 2.72 (2.04-3.63) with highly significant deviation from identical odds (P<0.0001). ORs from different studies were seemingly homogeneous ($Q_{df=8}$=12.7, P=0.12). Turbidity and concentrations of chlorine, iron ion and cupper ion were other routine variables that could be considered as risk factors. However, statistical measures from different studies were not uniform enough to develop an appropriate effect size while the number of studies reporting the variables was also small (3-5). In conclusion, HPC appeared to be appropriate as indicator of Legionella contamination, rather than fecal bacteria contamination. HPC may imply abundance of habitats (amoebas and biofilms) of Legionella in water. This result warrants further studies for standardizing protocols and cutoff values to infer Legionella risks from HPC.