Atomic Ordering on PtNi Alloy Surfaces

한원근 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.2

We have studied the relation between surface segregation and surface ordering for PtNi alloy through a Monte Carlo simulation of an Ising model. Our results explain well the surface segregation on the (100) and the (111) surfaces, as previously observed in experimental studies. Furthermore, we conclude that the (100) surface shows surface-induced ordering while the (111) surface shows surface-induced disordering.

낚시어선 안전관리 개선방안 연구: 낚시어선 관련자 인식도를 중심으로

한원근,장덕종 한국해양경찰학회 2023 한국해양경찰학회보 Vol.13 No.4

최근 수년간 낚시 이용객과 낚시어선의 급증은 동시에 안전사고를 증가시키는 요인으로 작용하고 있다. 그동안 정부에서는 낚시어선의 안전사고를 절감하고자 선장의 승선경력 요건과 안전요원 승선 추가 등 낚시어선 안전관리 개선방안을 지속적으로 마련하여 시행하고 있다. 그러나 현행 낚시어선은 다중이용 선박임에도 선박안전관리 측면에서 기준이 완화되어있는 「어선법」을 적용받고 있기에 낚시어선에 대한적극적인 안전관리를 시행하는 데 한계가 있다. 본 연구는 낚시 관련자들을 대상으로 설문조사를 통해 현장의 문제점들을 파악하고 실효성 있는 낚시어선 안전관리 방안을 도출하는 것이 목적이며 연구결과는 다음과 같다. 제도적인 측면에서는 낚시어선 사업진입을 현행 신고제에서 면허제로 변경하여여객선이나 유·도선 수준의 안전기준을 마련하고, 현행 낚시어선의 승선인원 산정방식을 유·도선 등의 다중이용선박에 준하여 시행할 필요가 있다. 또한 선박 간의 과도한 경쟁의 해결 방안으로 지역별 낚시어선 허가정수를 마련하여 시행할 필요가 있다. 또한 낚시어선의 안전운영 측면에서는 선장의 휴식시간 보장을 위한 낚시어선 휴식일제 도입과 낚시 이용객들의 기본교육 시행을 제도화할 것을 제안한다. The sharp increase in fishing users and fishing boats in recent years is acting as a factor in increasing safety accidents at the same time. Accordingly, in order to reduce safety accidents on fishing boats, the government continues to improve the safety management of fishing boats, such as adding to the various fishing rules. However, even though the current fishing boat is a multi-use ships, there is a limit in implementing the active safety management for fishing boats because applied the「 Fishing Vessels Act」. The results of the study are as follows. The institutional point of view, it is necessary to change the entry into the fishing boat business from the current reporting system to the license system to prepare safety standards at the level of passenger ships or excursion ships. It is necessary to implement the method of calculating the fixed number of persons on board for general fishing boats applied to current fishing boats in accordance with multi-use ships such as guided and excursion ships. In addition, to prevent excessive competition and to systematically manage fishing boats, it is proposed to establish and operate a limited number of fishing boats permitted in each region. In terms of safe operation of fishing boats, it is necessary to implement a fishing boat rest system to ensure the captain's rest time, and to make it mandatory to provide minimum basic safety education for fishing users.

FeCo 합금의 표면 편석과 질서도

한원근,Han, Wone-Keun 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.3

The surface segregation and surface order near the order-disorder phase transition of FeCo alloy was studied through Monte Carlo simulation of an Ising type model Hamiltonian. The results showed that the proper choice of Hamiltonian parameters could reproduce the recent observation of surface order above the transition temperature and that the field term played dominant role.

Surface Ordering and Segregation on Cu_3Au(100) and Ni_3Pt(100)

한원근 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.1

We simulate the thermodynamic behaviors of Cu_3Au(100) and Ni_3Pt(100) surfaces, focusing on the segregation and ordering. Through Monte Carlo simulations of a short-range Ising model Hamiltonian, we develop a phase digram to distinguish surface behaviors. We can explain the bulk phase transition and surface segregation on a quantitative level in good agreement with previous experimental observations. Further, we reveal that Cu_3Au(100) (100) shows a surface-induced disordering behavior, as suggested in previous works, but Ni_3Pt(100) shows a surface-induced ordering, which awaits further experimental testing.

이차원 모형계의 상전이 : 이차원의 합금의 편석 Segregation of Two Dimensional Alloy

韓原根 弘益大學校 科學技術硏究所 2002 科學技術硏究論文集 Vol.13 No.-

Through Monte-Carlo simulation of two-dimensional Ising model which is equivalent to a lattice gas model, we study the phase transition of two-dimensional alloys and the edge segregation. We found that the edge segregation occurs as a function of temperature as well as the competing atomic interactions. This results can be useful to understand the various ordering on the terrace of a surface.

Structure and Energetics of Half-monolayer Hydrogen on W(110)

한원근,Mei-Yin Chou 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.1

We have studied the hydrogen ordering on the W(110) surface by using the first-principles pseudopotential approach based on the local density approximation. The calculations for a halfmonolayer coverage of hydrogen indicate that the three-fold hollow site is favored for this coverage, similar to the full-coverage case. A p(1 × 2) ordering is found to have the lowest energy, in agreement with low-energy electron diffraction(LEED) results. However, another type of ordering, p(2 × 1), is also close in energy. The possibility of a phase coexistence and a subsequent change in the diffraction pattern are discussed. We find small displacements that are in opposite directions for two inequivalent surface W atoms in one unit cell. Without a uniform lateral shift of surface atoms, the LEED intensities calculated using the theoretical structure parameters still exhibit an asymmetry in integer spots at this coverage, resulting from the ordering of hollow-site hydrogen.

A new method of surface dynamics

韓源根 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.5 No.-

We developed a new method of studying surface dynamics of metal surfaces by combining the analytic and simulational methods. In this formalism, the vibrational motion of bulk atoms are considered to be harmonic using a central force model, however, that of surface atoms is considered to be anharmonic in order to explain the surface structural change. We show that the dynamical structure factor can be expressed as a continued fraction and its expansion parameters are equilibrium thermodynamic averages, which can be evaluated through Monte Carlo simulation. Therefore, we conclude that the static behaviors and surface dynamics which are anhamonic and critical can be studied more systematically at the same time.

In-Plane Modulated Phases on Metal Surfaces

韓源根 弘益大學校 科學技術硏究所 1993 科學技術硏究論文集 Vol.3 No.-

체심입방 금속의 (100) 표면 상에서의 변조된 상과 그 상전이를, 이차 원상 격자의 동역학적 모형 해밀토니안을 이용하여 계수 공간 상에서, 풍부한 종류의 변조된 상들이 나타났다. 이 결과는 금속 표면 상에서의 다양한 표면 재구성을 설명하는 데 적용될 수 있다.

FeCo 합금의 상전이

한원근 弘益大學校 科學技術硏究所 2000 科學技術硏究論文集 Vol.11 No.-

We studied the surface properties of FeCo alloys near the phase transition via Monte Carlo simmulation of Ising model Hamiltonians. We concluded that the surface field induced by surface segregation of Fe atoms is the surface induced order behavior observed in a recent experiment.

PtNi(110)에서 표면편석과 질서 - 무질서

韓源根,徐芝根 弘益大學校 科學技術硏究所 1993 科學技術硏究論文集 Vol.3 No.-

PtNi(110) 합금에서의 표면 편석 현상과 질서-무질서 상전이 현상을 몬테 카를로 시뮬레이션 방법을 통하여 고찰하였다. 간단한 Ising 모델로 PtNi 합금의 질서 무질서 상전이 현상을 잘 보여줄 수 있었고, 실험에서 관측된 (110)표면에서 나타나는 편석 역전 현상, 그리고 편석되는 정도, 층별 농도 분포를 양적으로도 잘 설명할 수 있었다. 치환형 합금에서 편석은 표면과 bulk 사이의 질서 차이로 발현됨을 보았고, 편석량도 이 질서 현상에 깊게 의존하는 것을 보았다. 질서-무질서 상전이를 표면 편석과 동시에 고려함으로서 이 두가지 현상이 보다 완전히 이해될 수 있음을 보였다. We investigated the surface segregation and order-disorder phase transition on PtNi(110) alloy through Monte Carlo simulation. We reproduced the order-disorder phase transition with a simple Ising model and explained the segregation reversal, amount of segregation, and concentration depth profile as observed on its (110) surface on a good quantitative level. We demonstrated that the segregation in a substitutional alloy appeared due to the difference between the degree of order of a bulk and that of the surface and the amount of segregation also depends on the degree of order. We finally showed that the order-disorder phase transition and the surface segregation are to be considered at the same time for a better understanding.