Meshfree Local Radial Basis Function Collocation Method with Image Nodes

백승기,백승기 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.1

We numerically solve two-dimensional heat diffusion problems by using a simple variant of the meshfree local radial-basis function (RBF) collocation method. The main idea is to include an additional set of sample nodes outside the problem domain, similarly to the method of images in electrostatics, to perform collocation on the domain boundaries. We can thereby take into account the temperature profile as well as its gradients specified by boundary conditions at the same time, which holds true even for a node where two or more boundaries meet with different boundary conditions. We argue that the image method is computationally efficient when combined with the local RBF collocation method, whereas the addition of image nodes becomes very costly in case of the global collocation. We apply our modified method to a benchmark test of a boundary value problem, and find that this simple modification reduces the maximum error from the analytic solution significantly. The reduction is small for an initial value problem with simpler boundary conditions. We observe increased numerical instability, which has to be compensated for by a sufficient number of sample nodes and/or more careful parameter choices for time integration.

Internal Energy Density of the Critical Three-state Potts Model on the Kagome Lattice

백승기,Harri M¨akel¨a 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.6

The internal energy density of the Potts model on a semi-infinite strip with a width L has beenconjectured to have no finite-size corrections at the critical point K = Kc. By factorizing thetransfer matrix for the kagome lattice with larger widths, we have found that this conjecture is notcorrect in that the internal energy density varies slightly with L at the critical point. From this sizedependence of the internal energy density, we obtain an upper bound as Kc < 1.0565615, which isclose to a recent estimate KJSc = 1.0565600(7) by Jacobsen and Scullard [J. Phys. A 45, 494003(2012)]. We also obtain a lower bound as Kc > 1.0560 by calculating the correlation length alongthe strips.

UV 램프 폐형광체 수은 열적처리 및 잔류물 용출 특성

백승기,정법묵,이은송,성진호,이선재,박용준,서용칠 한국폐기물자원순환학회 2017 한국폐기물자원순환학회지 Vol.34 No.2

This study investigates leaching and thermal treatment characteristics of mercury in waste phosphor powder from UV lamp for industrial use. Waste phosphor powder contaminated with mercury compounds requires proper treatment for final disposal. A sequential extraction procedure was conducted in order to estimate the stability of mercury compounds in waste phosphor powder. The fraction of mercury compounds leached in initial steps by ion-exchangeable and low acidic solutions was 62%, which would be unstable. Finally 36% of mercury compounds was left as a strongly stable form before last step of acid digestion by aqua regia. Mercury was decomposed rapidly during initial period in thermal treatment. However, the decomposition rate reached in steady later. Correlation of mercury content in residues with concentration of leaching extract was attempted in order to set a thermal treatment condition. When mercury content in residue of phosphor powder could be lowed up to about 13 mg-Hg/kg by thermally with satisfying the Korean leaching standard limit of 0.005 mg-Hg/L.

단계적 용출법을 이용한 산업시설 부산물의 수은 안정도 평가

백승기,정법묵,성진호,장하나,서용칠,정다위,김기헌 한국폐기물자원순환학회 2016 한국폐기물자원순환학회지 Vol.33 No.5

This study focused on the evaluation of stability of mercury compounds in byproducts from industrial facilities. Stability testing was conducted using a 5-step sequential extraction procedure using six kinds of byproducts. The mercury compounds extracted were categorized as ion-exchangeable (F1), acid soluble (F2), organic matter-bound (F3), strong complex (F4), and residual (F5) mercury compounds. The amount of mercury in each step was calculated and compared with total mercury amount; a 51% to 92% recovery rate was estimated. Hg-extracted F1, F2, and F3 were easily released into environment. It is necessary to apply an appropriate method to handle byproducts that contain these portions of mercury. On the other hand, mercury in F4 and F5 fraction is relatively more stable. F4 fraction means strong complex and elemental mercury. Byproduct from metal production facility has a higher elemental mercury fraction. It was found that 89% and 65% of mercury were contained in F4 fractions from fly ash and sludge, respectively. The goal of this study is to investigate stability of Hg compounds in different byproducts to suggest appropriate treatment methods for each byproduct on its Hg compound characteristics.

경쟁시장에서 컨조인트분석에 기초한 제품포지셔닝에 대한 연구:온라인 게임을 중심으로

백승기,임호순,박명섭 한국경영과학회 2006 한국경영과학회지 Vol.31 No.3

We introduce a two-stage game theoretic model to support decision making processes for product positioning and pricing in competitive environment. In the first stage, firms decide on entry and product position; in the second stage, firms compete with price. ‘Alpha rule' is used as a choice model. Demand parameters of the choice model are estimated by conjoint analysis. We investigate conditions for the existence of Nash price equilibria in the pricing game. Nash equilibria in the entry and positioning game are produced using a concept of stable sets. An example of the online game industry in Korea is examined.

비산재를 활용한 해수 알칼리도 증대 및 흡수액의 알칼리도가 탈황 효율에 미치는 영향

백승기,조현호,서용칠,김성헌,정현태,홍정희 한국폐기물자원순환학회 2014 한국폐기물자원순환학회지 Vol.31 No.8

Among many types of flue gas desulfurization (FGD) facilities, wet type FGD using lime or limestone is most popular in the world because of its simplicity of operation and availability of lime and limestone. Seawater desulfurization utilizes the alkalinity of seawater, thus requires no addition of lime and limestone. The efficiency of seawater desulfurization depends on the variation of alkalinity of seawater at different locations. This study presents the effect of gas-water ratio and total alkalinity of absorbing solution on the removal efficiency of sulfur dioxide from the flue gas by means of seawater. Also this study provides an alternative way to increase total alkalinity of seawater by utilizing fly ash from coal-fired power plants. The increase of removal efficiency with increase of alkalinity was measured as 0.26 ± 0.01% per ppm of bicarbonate alkalinity from the set of experiments using seawater, underwater, and distilled water, the alkalinity of which were 111 ppm, 38 ppm, and 1 ppm, respectively. Capability to increase total alkalinity of seawater using fly ash was confirmed.

효사상과 국민총화

백승기 한국국민윤리학회 1979 倫理硏究 Vol.8 No.1

활강 압박고 나사와 전자부 고정 금속판을 이용한 대퇴골 전자부 분쇄골절의 치료

백승기,최영준,김정환,안형선,황재광,김유진,안현태,박경준,조재우 대한골절학회 2002 대한골절학회지 Vol.15 No.2

목적 : 대퇴골 전자부 분쇄 골절기 활강 압박고 나사만으로 치료한 결과와 활강 압박고 나사와 전자부 고정화 금속판을 함께 사용하여 치료한 결과를 비교 관찰하고자 하였다. 연구 대상 및 방법 : 1997년 6월부터 2000년 8월까지 대퇴골 전자부 골절로 입원하였던 환자로 전자 관통 골절(A2)과 대 전자부 하외측 피질골에 골절선이 동반된 전자간 골절(A3) 환자 중 대전자부 골절이 동반된 환자로 32명을 대상으로 하였으며 활강 압박고 나사만 사용한 활강 압박고 나사군 과 전자부 고정화 금속판을 같이 사용한 전자부 고정화 금속판군을 나누어서 단순 방사선 사진상 지연나사의 활강 정도와 대전자의 외측 전위 정도 및 골유합 기간을 추시하였다. 결과 : 모든 예에서 골유합이 되었으며 추시 단순 방사선 사진상으로 골유합이 되었을 때 측정한 지연 나사 활강 정도는 활강 압박고 나사군에서는 14.5mm, 전자부 고정화 금속판 군에서는 12.6mm이었다. 대퇴 대전자 평균 외측 전위 정도는 활강 압박고 나사군에서는 9.8mm, 전자부 고정화 금속판군에서는 1.2mm이었다. 결론 : 활강 압박고 나사와 전자부 고정화 금속판을 이용하여 대퇴골 전자간 분쇄 골절과 함께 대전자부 골절이 동반되어있는 경우의 치료시 방사선학적 추시상 지연나사의 활강 정도 및 대전자 외측 전위가 적었으며, 기존의 압박고 나사를 단독으로 사용하는 것에 비하여 수술시 얻은 골절 정복 및 내고정의 위치를 계속 유지하여 골유합을 시킬 수 있는 좋은 방법이라 사료된다. Purpose : The purpose of this study is to evaluate the results of treatment of comminuted femoral trochanteric fracture using dynamic hip screw(DHS) with trochanteric stabilizing plate(TSP) and DHS only. Materials and Methods : we analysed retrospectively 32 cases that has fracture extends over two or more levels of medial cortex(A2 of AO classification) and fracture extends through lateral cortex of femur(A3 of AO classicification) of femoral trochanteric fractures between 1997 and 2000. On simple AP radiograph of the DHS with TSP(n=16) and DHS only group(n=16), we reviewed bony union, slippage of lag screw, lateral displacement of greater trochanter. Result : Bony union was observed in all cases. When bony union is done in follow up radiograph, Mean slippage of lag screw is 14.5mm in DHS only group, 12.6㎜ in DHS with TSP group and mean lateral displacement of greater trochanter is 9.8㎜ in DHS only group, 1.2mm in DHS with TSP group. Conclusion : Use of DHS with TSP in comminuted femoral trochanteric fracture is lesser slippage of lag screw and lateral displacement of greater trochanter than DHS only used, and that is better method to maintain fracture reduction and internal fixation in treatment of comminuted femoral trochanteric fractures than DHS only.

Torus Instability in an Extended Medium

백승기,문희태 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.II

We investigate the dynamics of quasiperiodic solution in a real flow. Here, a two-mode truncation of the Ginzburg-Landau equation is considered entailing a four-dimensional phase space. We analyze, in particular, the evolution and the instability of single-lobed tori observed in the phase space. One-dimensional return maps are used to investigate the basic characteristics of the dynamics.1

옹호연합모형(ACF: Advocacy Coalition Framework)에 의한 의료보험 통합정책에 관한 비교 연구: 한국과 대만의 사례를 중심으로

백승기 한국행정학회 2010 韓國行政學報 Vol.44 No.4

본 연구는 한국과 대만의 의료보험 통합과정을 옹호연합모형(ACF: Advocacy Coalition Framework)을 적용하여 살펴보고자 한다. 먼저 외적 조건을 보면, 문제영역의 속성(basic attributes of the problem area)에서 대만이 한국에 비해 의보통합에 유리한 구조를 가지고 있음을 알 수 있다. 기회구조(opportunity structures)에서는 대만이 한국보다 행정부의 제안이 효과적으로 정책으로 전환될 수 있는 집행환경을 가지고 있었다. 정책하위체제(policy subsystem) 내의 옹호연합의 활동을 보면, 의보통합이 신념체계의 문제임에 따라 양국 모두 정책 중개가 잘 이루어지지 않았다. 정책산출(policy outputs)을 보면, 한국은 외부충격에 의한 산출이 많은 반면, 대만에서는 ‘협의에 의한 정책산출(negotiated agreements)’이 상당히 많음을 알 수 있다. 마지막으로 대만은 의보통합 이후 한국에 비해 적극적으로 개선 대책을 진행했다. 2001년 行政院二代健保規劃小組가 설립되어 ‘二代健保規劃’이라 불리는 개혁 작업을 통해 전민건강보험의 전반적인 개선책을 강구하고 있는 것이 그 예이다.