• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1522-1526
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• 2007

최근 영국의 Institute of Hydrology에서는 Generalized logistic (GL) 분포형을 홍수빈도해석시 GEV 분포형을 대체하는 분포형으로 추천한 바 있으며, 그로 인해 GL 분포형의 사용이 증가하고 있는 추세이다. 하지만 아직 그 사용빈도에 반하여 분포형 자체의 특성, 그 중에서도 확률홍수량의 근사적 분산에 관한 연구는 거의 이루어지지 않았다. 따라서 본 연구에서는 최우도법을 이용하여 GL 분포형의 확률홍수량에 대한 근사적 분산에 관한 연구를 수행하였으며, 이를 표본 크기, 재현기간, 매개변수들의 함수로 나타내었다. 또한 확률홍수량의 근사적 분산의 적용성을 검토하기 위해 Monte Carlo 모의실험을 수행하였으며, 모의실험은 형상 매개변수$(\beta)$가 $\pm0.5$이면 gamma function으로 인하여 표본 크기에 관계없이 분산값이 무한대에 가까워지므로 형상매개변수의 범위는 $-0.5{\leq}{\beta}{\leq}+0.5$로 제한하였다. 모의결과 최우도법에 의해 계산된 분산식은 형상매개변수 $-0.25{\leq}{\beta}{\leq}+0.5$의 범위에서 비교적 잘 맞는 것을 확인할 수 있었으며, 기존에 알려진 대로 표본크기가 크면 클수록 정확해지는 것을 알 수 있다. 또한 표본크기가 작은 경우 형상매개변수 전 범위에서 정확도가 떨어지는 것을 확인할 수 있으며, 최우도법의 경우 표본크기가 작은 경우를 제외하고 $-0.25{\leq}{\beta}{\leq}+0.5$ 범위에서 quantile 산정시 quantile이 약간 과다추정되는 경향이 있는 것을 알 수 있으며, 이는 분산이 과다 추정되는 결과를 초래하며 이로 인해 해석해보다 약간씩 큰 값을 나타내는 것으로 판단되었다..이 극단적인 선정적인 폭력성에 탐닉하게 되는 경향이 있다. 현실은 결코 아름답지 못하고, 행복하게 살 수 없다는 것에 대한 깨달음에서 기인한다. 욕구불만의 강도가 심해질수록 폭력성은 더욱 강하게 나타나는데 개인에게서 뿐만 아니라 가족, 동료, 사회 단체나 종교, 국가간에도 집단적으로도 발생하게 된다. 사회적으로 볼 때 폭력은 용인되는 것이 아니므로 도덕적으로 절제를 하거나 상대방과 적절한 타협과 조정을 필요로 한다. 그러나 절제의 한계를 넘어선다고 생각되거나, 조정의 노력이 불가능하거나, 실패했을 때 폭력적인 행동으로 나타나게 된다. 리차즈(I.A Richards)는 분노와 공포는 일단 겉잡을 수 없는 경향이 있다고 하면서 오늘날 폭력에 대한 요구가 일상의 정서 생활에 있어, 억압을 통한, 빈곤함을 반영하고 있지 않은지 생각해봐야 할 것이라고 충고한다. 조성 가이드라인(안)을 제시하였다.EX>$\ulcorner$세종실록$\lrcorner$(世宗實錄) $\ulcorner$지리지$\lrcorner$(地理志)와의 비교를 해보면 상 중 하품의 통합 9개소가 삭제되어 있고, $\ulcorner$동국여지승람$\lrcorner$(東國與地勝覽) 에서는 자기소와 도기소의 위치가 완전히 삭제되어 있다. 이러한 현상은 첫째, 15세기 중엽 경제적 태평과 함께 백자의 수요 생산이 증가하자 군신의 변별(辨別)과 사치를 이유로 강력하게 규제하여 백자의 확대와 발전에 걸림돌이 되었다. 둘째, 동기(銅器)의 대체품으로 자기를 만들어 충당해야할 강제성 당위성 상실로 인한 자기수요 감소를 초래하였을 것으로 사료된다. 셋째, 경기도 광주에서 백자관요가 운영되었으므로 지방인 상주지역에도 더 이상 백자를 조달받을 필요가 없이, 일반 지방관아와 서민들의

• Journal of Communications and Networks
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• v.16 no.2
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• pp.227-237
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• 2014

Throughput scaling laws for two coexisting ad hoc networks with m primary users (PUs) and n secondary users (SUs) randomly distributed in an unit area have been widely studied. Early work showed that the secondary network performs as well as stand-alone networks, namely, the per-node throughput of the secondary networks is ${\Theta}(1/\sqrt{n{\log}n})$. In this paper, we show that by exploiting directional spectrum opportunities in secondary network, the throughput of secondary network can be improved. If the beamwidth of secondary transmitter (TX)'s main lobe is ${\delta}=o(1/{\log}n)$, SUs can achieve a per-node throughput of ${\Theta}(1/\sqrt{n{\log}n})$ for directional transmission and omni reception (DTOR), which is ${\Theta}({\log}n)$ times higher than the throughput with-out directional transmission. On the contrary, if ${\delta}={\omega}(1/{\log}n)$, the throughput gain of SUs is $2{\pi}/{\delta}$ for DTOR compared with the throughput without directional antennas. Similarly, we have derived the throughput for other cases of directional transmission. The connectivity is another critical metric to evaluate the performance of random ad hoc networks. The relation between the number of SUs n and the number of PUs m is assumed to be $n=m^{\beta}$. We show that with the HDP-VDP routing scheme, which is widely employed in the analysis of throughput scaling laws of ad hoc networks, the connectivity of a single SU can be guaranteed when ${\beta}$ > 1, and the connectivity of a single secondary path can be guaranteed when ${\beta}$ > 2. While circumventing routing can improve the connectivity of cognitive radio ad hoc network, we verify that the connectivity of a single SU as well as a single secondary path can be guaranteed when ${\beta}$ > 1. Thus, to achieve the connectivity of secondary networks, the density of SUs should be (asymptotically) bigger than that of PUs.

• Journal of the Korean Society of Combustion
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• v.20 no.4
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• pp.34-41
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• 2015

Oxy-methane nonpremixed flames diluted with $CO_2$ were investigated to clarify impact of radiation heat loss and chemical effects of additional $CO_2$ to oxidizer stream on flame extinction. Flame stability maps were presented with functional dependencies of critical diluents mole fraction upon global strain rate at several oxidizer stream temperatures in $CH_4-O_2/N_2$, $CH_4-O_2/CO_2$, and $CH_4-O_2/CO_2/N_2$ counterflow flames. The effects of radiation heat loss on the critical diluent mole fractions for flame extinction are not significant even at low strain rate in nonpremixed $CH_4-O_2/N_2$ diffusion flame, whereas those are significant at low strain rate and are negligible at high strain rate (> $200s^{-1}$) in $CH_4-O_2/CO_2$ and $CH_4-O_2/CO_2/N_2$ counterflow flames. Chemical effects of additional $CO_2$ to oxidizer stream on the flame extinction curves were appreciable in both $CH_4-O_2/CO_2$ and $CH_4-O_2/CO_2/N_2$ flames. A scaling analysis based on asymptotic solution of stretched flame extinction was applied. A specific radical index, which could reflect the OH population in main reaction zone via controlling the mixture composition in the oxidizer stream, was identified to quantify the chemical kinetic contribution to flame extinction. A good correlation of predicted extinction limits to those calculated numerically were obtained via the ratio between radical indices and oxidizer Lewis numbers for the target and baseline flames. This offered an effective approach to estimate extinction strain rate of nonpremixed oxy-methane flames permitting air infiltration when the baseline flame was taken to nonpremixed $CH_4-O_2/N_2$ flame.

• Journal of Korean Society of Forest Science
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• v.90 no.5
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• pp.650-662
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• 2001

The growth and yield models for five different kinds of natural forest types were systemically developed in the natural Broadleaved-Korean pine Forests in Northeast China. The data were collected from 359 temporary plots and 58 permanent plots with area ranged from 0.06 ha to 1.0 ha, ranging in stand age from 43 to 364 years. The Site Class Index (SCI) was introduced to evaluate site quality and the Crown Competition Factor (CCF) was selected as a measure of stand density for the mixed natural forest. The Chapman-Richards function was adopted to develop SCI equation and height-diameter curve. The Schumacher growth function was selected as base model to develop the DBH, basal area, and stand volume growth models by using re-parameterized method. In modeling mean DBH and basal area growth, it was found that the asymptotic parameter A of Schumacher function was exponentially related to site quality (SCI) and stand density (CCF). The rate parameter k was related to stand density and it was independent of SCI. Several validation measures for predicted stand variables were evaluated in the growth and yield models using independent data sets. The results indicated that relative mean errors (RME) in predicted stand attributes were less than ${\pm}5%$ and the estimated precision values of the stand variables were all greater than 95%.

• Korean journal of applied entomology
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• v.40 no.4
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• pp.301-307
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• 2001

The pine needle gall midge (PNGM), Thecodiplosis japonensis Uchida et Inouye, is a serious pest in pine forests in Korea. Since the first report of PNGM infestation in Korea in 1929, the infestation area has been expanded gradually. In 1975 the distribution of PNGM and its parasitoids were surveyed throughout several infested areas in Korea. Annual survey has been made for the rates of gall formation by PNGM and parasitism by its parasitoids at the monitoring sites including newly infested area in 1975 since 1980. These data were used to examine the relationship between PNGM and its parasitoids for newly invaded areas. The gall forming rate of PNGM and the parasitism by the parasitoid were 34.8 and 1.9% in 1975, respectively, while the gall forming rate and the parasitism were 20.7 and 8.9% in 1985, respectively. The relationships of densities between PNGM and its parsitoid were weak in the early stage of dispersion, but the density of parasitoid was with an asymptotic increase along with PNGMs density increase during the observation period for 10 years.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.9-16
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• 2014

Using a level set method and topological derivatives, a topological shape optimization method that is independent of an initial design is developed for linearly elastic structures. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. The "Hamilton-Jacobi(H-J)" equation and computationally robust numerical technique of "up-wind scheme" lead the initial implicit boundary to an optimal one according to the normal velocity field while minimizing the objective function of compliance and satisfying the constraint of allowable volume. Based on the asymptotic regularization concept, the topological derivative is considered as the limit of shape derivative as the radius of hole approaches to zero. The required velocity field to update the H-J equation is determined from the descent direction of Lagrangian derived from optimality conditions. It turns out that the initial holes are not required to get the optimal result since the developed method can create holes whenever and wherever necessary using indicators obtained from the topological derivatives. It is demonstrated that the proper choice of control parameters for nucleation is crucial for efficient optimization process.

• Communications for Statistical Applications and Methods
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• v.15 no.3
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• pp.451-464
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• 2008

Six sigma is the rating that signifies "best in clas", with only 3.4 defects per million units or operations. Higher sigma quality level is generally perceived by customers as improved performance by assigning a correspondingly higher satisfaction score. The process capability indices and the sigma level $Z_{st}$ have been widely used in six sigma industries to assess process performance. Most evaluations on process capability indices focus on point estimates, which may result in unreliable assessments of process performance. In this paper, we consider statistical inference for process capability indices $C_p$, $C_{pk}$ and $C_{pm}$. Also, we study better testing procedure on assessing sigma level $Z_{st}$ and capability index $C_{pm}$, for practitioners to use in determining whether a given process is capable. The proposed method is easy to use and the decision making is more reliable. Whether a process is clearly normal or nonnormal, our bootstrap testing procedure could be applied effectively without the complexity of calculation. A numerical result based on our proposed method is illustrated.

• Journal for History of Mathematics
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• v.25 no.4
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• pp.53-67
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• 2012

Today, it is necessary to calculate orbits with high accuracy in space flight. The key words of Poincar$\acute{e}$ in celestial mechanics are periodic solutions, invariant integrals, asymptotic solutions, characteristic exponents and the non existence of new single-valued integrals. Poincar$\acute{e}$ define an invariant integral of the system as the form which maintains a constant value at all time $t$, where the integration is taken over the arc of a curve and $Y_i$ are some functions of $x$, and extend 2 dimension and 3 dimension. Eigenvalues are classified as the form of trajectories, as corresponding to nodes, foci, saddle points and center. In periodic solutions, the stability of periodic solutions is dependent on the properties of their characteristic exponents. Poincar$\acute{e}$ called bifurcation that is the possibility of existence of chaotic orbit in planetary motion. Existence of near exceptional trajectories as Hadamard's accounts, says that there are probabilistic orbits. In this context we study the eigenvalue problem in early 20th century in three body problem by analyzing the works of Darwin, Bruns, Gyld$\acute{e}$n, Sundman, Hill, Lyapunov, Birkhoff, Painlev$\acute{e}$ and Hadamard.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.170-179
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• 2019

In this study, the wave responses in a 'Y'shape water channel resonator for amplifying wave energy of a low density has been investigated. A water channel resonator is composed of the long channel and wave guider installed at the entrance. If the period of the incident waves coincides with the natural period of the fluid in a water channel resonator, resonance occurs and the internal fluid amplifies highly to a standing wave form. In order to analyze the wave response in a water channel resonator, we used the matched asymptotic expansion method and boundary element method. The both results were in good agreement with the results of the model test carried out in the two-dimensional wave tank of Jeju National University. Wave guider has an optimum length and installation angle according to the period of the incident wave, and especially effective in enhancing the amplification factor in a period range deviated from the resonance period. It is expected that the wave energy can be effectively extracted by placing the point absorber wave energy converter at the position of anti-node where the maximum wave height is formed by the internal fluid resonance.

• Journal of the Korean Geotechnical Society
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• v.25 no.10
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• pp.111-122
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• 2009

Dissolution of some of geo-materials may yield the loss of the soil strength and the settlement of earth structures. The goal of this study is to monitor the several physical behaviors of soluble mixtures during dissolution. Sand-salt mixtures are used to monitor the meso to macro response including the settlements and shear waves. The mixtures of photoelastic and ice disks are used to monitor micro to meso behavior of soluble mixture including the void ratio, force chain, coordination number and horizontal force changes. In the sand-salt mixtures, shear waves are measured by using bender elements in conventional oedometer cells. In the photoelastic disk - ice disk mixtures, micro to meso response are measured by digital images and load cells. The shear wave velocity decreases at the initial stage of the dissolution, and then increases and approaches to asymptotic value. The larger dissoluble particle and the more random packing produces the severe horizontal fore change. After dissolution, the void increases and the coordination number decreases. This study demonstrates that the particle level behavior such as the changes of the force chain, void ratio, and coordination number affects the global behavior such as the change of the shear wave velocity and horizontal force of the system.