• Journal of Magnetics
• /
• v.20 no.1
• /
• pp.11-20
• /
• 2015

In this work, Monte Carlo simulation was employed to model the stretchable Ising monolayer film to investigate the effect of the spatial distance variation among magnetic atoms on magnetic behavior of the film. The exchange interaction was considered as functions of initial interatomic distance and the stretched distance (or the strain). Following Bethe-Slater picture, the magnetic exchange interaction took the Lennard-Jones potential-like function. Monte Carlo simulations via the Wolff and Metropolis algorithms were used to update the spin systems, where equilibrium and dynamic magnetic profiles were collected. From the results, the strain was found to have strong influences on magnetic behavior, especially the critical behavior. Specifically, the phase transition point was found to either increase or decrease depending on how the exchange interaction shifts (i.e. towards or away from the maximum value). In addition, empirical functions which predict how the critical temperatures scale with initial interatomic distance and the strain were proposed, which provides qualitatively view how to fine tune the magnetic critical point in monolayer film using the substrate modification induced strain.

• The KIPS Transactions:PartB
• /
• v.13B no.5 s.108
• /
• pp.525-532
• /
• 2006

This paper proposes a new class of image restoration on the Ising modeled binary 'Takbon' image by the flexible line-fitting ICM(Iterated conditional modes) method. Basically 'Takbon' image need be divided into two extreme regions, information and background one due to its stroke combinations. The main idea is the line process, comparing with the conventional ICM approaches which were based on partially rectangular structured point process. For calculating geometrical mechanism, we have defined line-fitting functions at each current pixel array which form the set of linear lines with gradients and lengths. By applying the Bayes' decision to this set, the region of the current pixel is decided as one of the binary levels. In this case, their statistical reiteration for distinct tracking between intra and extra region offers a criterion to decide the attachment at each step. Finally simulations using the binary 'Takbon' image are provided to demonstrate the effectiveness of our new algorithm

• Journal of Integrative Natural Science
• /
• v.1 no.1
• /
• pp.36-40
• /
• 2008

본 논문은 자바 에플릿(Java applet)을 이용하여 보존모형과 비보존모형의 온도에 따른 손상확산(damage spreading)의 특성을 분석하였다. 보존모형인 아이징(Ising)모형과 비보존 모형인 격자기체(lattice gas) 및 Driven Diffusive System(DDS)을 다양한 전이확률(transition probability)을 사용하여 온도에 따라 물질내부에서 손상확산이 어떻게 발전하는지를 자바 에플릿 프로그램을 이용하여 시각화하여 손상확산을 명확히 이해하고자 하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.3
• /
• pp.240-244
• /
• 2010

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.

• Bulletin of the Korean Chemical Society
• /
• v.14 no.4
• /
• pp.485-487
• /
• 1993

The critical behavior of the classical D-dimensional spin model (D${\ge}$2), which is intermediate model that link up the Ising (D = 1) and the spherical model (D = ${\infty}$), is studied for the case of constant coupling interaction independent of the spin-spin distance (Curie-Weiss model). Analytical results show that the critical behavior of the present model is in quantitative agreement with the prediction of the phenomenological mean-field theory independent of D. Critical temperature is calculated to be T$_c$=k/JD. This gives a quantitative explanation of the relationship between the spin degree of freedom and the critical temperature.

• Journal of the Korean Electrochemical Society
• /
• v.5 no.2
• /
• pp.79-85
• /
• 2002

The present article is concerned with the application of the Monte Carlo simulation to electrochemistry of lithium intercalation from the thermodynamic view point. This article first introduced the fundamental concepts of the ensembles, and Ising and lattice gas models in statistical thermodynamics for the Monte Carlo simulation in brief. Finally the Monte Carlo method based upon the lattice gas model was employed to analyse thermodynamics of the lithium intercalation into the transition metal oxides. Especially we dealt with the thermodynamic properties as the electrode potential curve and the partial molar internal energy and entropy of lithium ion in the case of the $LiMn_2O_4$ electrode, and consequently confirmed the utility of the Monte Carlo method in the field of electrochemistry of the lithium intercalation.

• Current Applied Physics
• /
• v.18 no.11
• /
• pp.1248-1254
• /
• 2018

Magnetization versus temperature and magnetic-field measurements, M(T, $H_a$), have been carried out to study the magnetic and critical properties of polycrystalline $La_{1-x}Ba_xCoO_3$ (x = 0.3 and 0.5) cobaltites. These compounds with the density of ${\sim}6.2g/cm^3$ crystallized in the $R{\bar{3}}c$ rhombohedral and $Pm{\bar{3}}m$ cubic structures, respectively. With an applied field $H_a=200Oe$, M(T) data have revealed that the samples with x = 0.3 and 0.5 exhibit the ferromagnetic-paramagnetic (FM-PM) phase transition at the Curie temperature points $T_C=202$ and 157 K, respectively. At 4.2 K, the saturation magnetization ($M_{sat}$) decreases from 35.9 emu/g for x = 0.3-26.1 emu/g for x = 0.5. Particularly, the critical-behavior analyses in the vicinity of $T_C$ reveal all samples undergoing a second-order phase transition, with critical exponent values (${\beta}=0.328$ and ${\gamma}=1.251$ for x = 0.3, and ${\beta}=0.331$ and ${\gamma}=1.246$ for x = 0.5) close to those expected for the 3D Ising model. This proves short-range magnetic order existing in $La_{1-x}Ba_xCoO_3$. We believe that magnetic inhomogeneities due to the mixture of hole-rich FM regions (confined in the trivalent-cobalt hole-poor anti-FM matrix) and uniaxial anisotropy prevent long-range order in $La_{1-x}Ba_xCoO_3$.

• Korean Journal of Psychosomatic Medicine
• /
• v.29 no.2
• /
• pp.121-127
• /
• 2021

Objectives : The characteristics of depressive symptoms in patients with cancer is different from those in control group. However, few research has focused on the association between depressive symptoms in cancer patients. The aim of this study was to compare the network structure of depressive symptoms between patients with cancer and normal control. Methods : This study was based on cohort data from Korea National Health and Nutrition Examination Survey in 2016-2018. The Patient health Quetionnaire-9 (PHQ-9) was used to assess depressive symptoms in 599 patients with cancer and 599 age-sex matched controls. We estimated network structure of depressive symptom using Isingfit model. Results : There was no significant difference of each PHQ-9 item score. There were strong associations between symptoms were concentration problem-psychomotor activity, anhedonia-depressed mood, and depressed mood-suicidal ideation in both groups. Strength centrality of worthlessness was significantly higher in patients with cancer. Conclusions : These results suggest that worthless is associated with other depressive symptoms more tightly in patients with cancer. Worthless can serve as important treatment targets for intervention of depression in patients with cancer.

• Korean Journal of Psychosomatic Medicine
• /
• v.30 no.2
• /
• pp.172-178
• /
• 2022

Objectives : Although subclinical depression symptoms are associated with suicidal idea, most research have focused on clinical depression such as major depressive disorder or dysthymia. The aim of this study is to investigate network structure of depressive symptom and to reveal which symptoms are associated with suicidal ideation. Methods : We used part of data from the seventh Korea National Health and Nutrition Examination Survey. Participants were between 19 and 65 years of age (N=8,741). Network analysis with Isingfit model is used to reveal network structure of depressive symptoms and most central symptom and edges assessed by patient health questionnaire (PHQ-9). Results : The most two central symptoms were psychomotor activity and suicidal ideation. The strongest edge was psychomotor activity-suicidal ideation. Suicidal ideation also has strong association with depressive mood and worthlessness. Conclusions : These results suggest that psychomotor activity and suicidal ideation can serve as treatment target for subclinical depression and psychomotor activity, worthlessness and depressed mood may be important factor for early intervention of suicidal ideation.