• Journal of the Korea Society for Simulation
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• v.18 no.2
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• pp.57-64
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• 2009

Stable and effective constraint enforcement system is one of the crucial components for physically-based dynamic simulations. This paper presents analysis and evaluation for traditional constraint enforcement systems(Lagrange Multiplier method, Baumgarte stabilization method, Post-stabilization method, Implicit constraint enforcement method, Fast projection method) to provide a guideline to users who need to integrate a suitable constraint enforcement system into their dynamic simulations. The mathematical formulations for traditional constraint enforcement systems are presented in this paper. This paper describes a summary of evaluation which consists of constraint error comparison, computational cost, and dynamic behavior analysis to verify the efficiency of each traditional constraint enforcement system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.2 no.1
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• pp.51-62
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• 2008

This paper proposes a second-order implicit constraint enforcement method which yields enhanced controllability compared to a first-order implicit constraints enforcement method. Although the proposed method requires solving a linear system twice, it yields superior accuracy from the constraints error perspective and guarantees the precise and natural movement of objects, in contrast to the first-order method. Thus, the proposed method is the most suitable for exact prediction simulations. This paper describes the numerical formulation of second-order implicit constraints enforcement. To prove its superiority, the proposed method is compared with the firstorder method using a simple two-link simulation. In this paper, there is a reasonable discussion about the comparison of constraints error and the analysis of dynamic behavior using kinetic energy and potential energy.

• Journal of Korea Multimedia Society
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• v.11 no.4
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• pp.516-524
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• 2008

This paper presents a new modeling technique for the simulation of cloth specific characteristics with a set of hard constraints using an implicit constraint enforcement scheme. A conventional explicit Baumgarte constraint stabilization method has several defects. It requires users to pick problem-dependent coefficients to achieve fast convergence and has inherent stabilization limits. The proposed implicit constraint enforcement method is stable with large time steps, does not require problem dependent feed-back parameters, and guarantees the natural physics-based motion of an object. In addition, its computational complexity is the same as the explicit Baumgarte method. This paper describes a formulation of implicit constraint enforcement and provides a constraint error analysis. The modeling technique for complex components of cloth such as seams, buttons, sharp creases, wrinkles, and prevention of excessive elongation are explained. Combined with an adaptive constraint activation scheme, the results using the proposed method show the substantial enhancement of the realism of cloth simulations with a corresponding savings in computational cost.

• Journal of Korea Multimedia Society
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• v.8 no.2
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• pp.211-224
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• 2005

With the wide acceptance of the Internet and the Web, volumes of information and related users have increased and companies have become to need security mechanisms to effectively protect important information for business activities and security problems have become increasingly difficult. This paper proposes a improved access control model for access control enforcement in enterprise environments through the integration of the temporal constraint character of the GT-RBAC model and sub-role hierarchies concept. The proposed model, called Extended GT-RBAC(Extended Generalized Temporal Role Based Access Control) Model, supports characteristics of GTRBAC model such as of temporal constraint, various time-constrained cardinality, control now dependency and separation of duty constraints(SoDs). Also it supports unconditional inheritance based on the degree of inheritance and business characteristics by using sub-roles hierarchies in order to allow expressing access control policies at a finer granularity in corporate enterprise environments.

• Journal of Internet Computing and Services
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• v.7 no.1
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• pp.17-30
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• 2006

With the wide acceptance of the Internet and the Web, volumes of information and related users have increased and companies have become to need security mechanisms to effectively protect important information for business activities and security problems have become increasingly difficult. This paper proposes a improved access control model for access control enforcement in enterprise environments through the integration of the temporal constraint character of the GT-RBAC model. sub-role hierarchies concept and PBDM(Permission Based Delegation Model). The proposed model. called Extended GT-RBAC(Extended Generalized Temporal Role Based Access Control) delegation Model. supports characteristics of GTRBAC model such as of temporal constraint, various time-constrained cardinality, control flow dependency and separation of duty constraints (SoDs). Also it supports conditional inheritance based on the degree of inheritance and business characteristics by using sub-roles hierarchies and supports permission based delegation, user to user delegation, role to role delegation, multi-step delegation and temporal delegation by using PBDM.

• Journal of Internet Computing and Services
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• v.4 no.1
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• pp.75-86
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• 2003

In this paper, we extended hierarchial structure of managed object class to support Role-Based Access Control, and described constraint conditions that have support dynamic temporal function as well as statical temporal function established by management process. And we defined about violation notifications should report to manager when rules violate constraint conditions. Also we presented system architecture that support RBAC with MIB(Management Information Base) of ITU-T recommendation. By access control enforcement and decision function, constraint conditions and activated translation procedure of each roles are described, our system presents dynamic temporal property systematically.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.68-70
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• 1998

본 논문에서는 클록들을 주기적으로 동기화하는 분산 실시간 시스템에서 주어진 태스크의 시간 제약(timing constraint)을 변환시는 구가지 기법을 제안한다. 전형적인 이산 클록 동기화(discrete clock synchronization)알고리즘은 클록의 값을 순간적으로 보정(correct)하여 클록의 시간이 불연속적으로 진행학 한다. 이러한 시간상의 불연속성은 태스크의 시작제한시간(release time)이나 종료시한(deadline)과 같은 이벤트를 잃어버리거나 다시 발생시키는 오류를 범하게 한다. 클록 시간의 불연속성을 피하기 위해 일반적으로 연속 클록 동기화(continuous clock synchronization) 기법이제안되었지만 소프트웨어적으로 구현되기에는 많은 오버헤드를 유발시키는 문제점이 있다. 이에 따라 연속 클록 동기화는 PLL (Phase-Locked Loop)을 이용한 별도의 하드웨어를 사용하는 것이 보통이다. 본 논문에서는 연속 클록 동기화 기법을 사용하는 대신, 태스크의 시간 제약을 동적으로 변환시키는 DCT (Dynamic Constraint Transformation) 기법을 제안하였다. DCT는 소프트웨어 으로 구현이 가능하여 새로운 하드웨어를 필요로 하지 않으며, 이를 통해 기존의 이산적으로 동기화된 시스템에서 클록 시간의 불연속성에 의한 문제점들을 해결할 수 있다. 또 다른 문제점으로서, 클록의 물리적인 특성으로 인해 동기화된 클록들이 상한된(bounded from the above)오차(skew)를 갖는다는 것이다. 이러한 오차는 지역 클록(local clock)에 대해 만족될 수 있는 임의의 실기간 제약 조건이 전역 클록(global clock)에 대해서는 만족되지 않을 수 있음을 의미한다. 본 논문에서는 이를 위해 먼저 두 가지의 스케줄링 가능성, 지역적 스케줄링 가능서(local schedulability)과 전역적 스케줄링 가능성(global schedulability)을 정의하고, 실시간 제약을 정적으로 변환시키는 SCT (Static Constraint Transformation)기법을 제안하였다. SCT를 통해 지역적으로 스케줄링 가능한 태스크는 전역적으로 스케줄링이 가능하므로, 단지 지역적 스케줄링 가능성만을 검사하면서 스케줄링 문제를 해결할 수 있도록 하였다.

• Journal of the Korea Society of Computer and Information
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• v.10 no.3 s.35
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• pp.45-54
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• 2005

The existing access control models have the demerits that do not provide the limit function of using resources by time constraint, the restricted inheritance function as a superior role in role hierarchy, the delicate delegation policy and the limit function of using resources by the location information about a user for the access control in ubiquitous environment. This paper proposes an Extended-GTRBAC model is suited to the access control in ubiquitous environment by applying to sub-role concept of GTRBAC model that the application of resources can be restricted by the period and time and PBDM and considering the location information about a user on temporal constraint. The proposal model can restrict the inheritance of permission in role hierarchy by using sub-role, provide the delicate delegation policy such as user-to-user delegation, role to role delegation, multi-level delegation. multi-step delegation, and apply diverse and delicate access control policy which is suited the characteristic of ubiquitous environment by considering the location information about a user on temporal constraint.

• Journal of Navigation and Port Research
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• v.32 no.7
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• pp.553-559
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• 2008

The lorry based transportation system in korea has many problems such as high domestic logistic cost, environment pollution and road damage etc. Hereupon, the necessity of improvement for national logistics system has been proposed continuously. Therefore we carried out this research through AHP(Analytic Hierarchy Process) to measure relative importance between effect factors and constraint factors and examined the possibility of Modal Shift from lorry transportation to coastal transportation. As the results of this research, the relative priority on modal shift policy enforcement (0.556) is higher than that of maintenance of the present transportation system(0.444).

• KDI Journal of Economic Policy
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• v.14 no.1
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• pp.191-212
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• 1992

This paper discusses the role of money in the process of capital accumulation where financial markets are impeded by contract enforcement problems in the context of overlapping generations framework. In particular, in less developed countries (LDCs) creditors may know little about the repayment capability of potential debtors due to incomplete information so that financial instruments other than money may not acceptable to them. In this paper the impediments to the operation of the private finanical markets are explicitly modelled. We argue that creditors cannot observe actual investment decisions made by the potential borrowers, and as a result, loan contracts may not be fully enforceable. Therefore, a laissez-faire regime may fail to provide the economy with the appropriate financial instruments. Under these circumstances, we introduce a government operated discount window (DW) that acts as an open market buyer of private debt. This theoretical structure represents the practice of governments of many LDCs to provide loans (typically at subsidized interest rates) to preferred borrowers either directly or indirectly through the commercial banking system. It is shown that the DW can substantially overcome impediments to trade which are caused by the credit market failure. An appropriate supply of the DW loan enables producers to purchase the resources they cannot obtain through direct transactions in the credit market. This result obtains even if the DW is subject to the same enforcement constraint that is responsible for the market failure. Thus, the DW intervention implies higher investment and output. However, the operation of the DW may cause inflation. Furthermore, the provision of cheap loans through the DW results in a worse income distribution. Therefore, there is room for welfare enhancing schemes that utilize the higher output to develop. We demonstrate that adequate lump sum taxes-cum-transfers along with the operation of the DW can support an allocation that is Pareto superior to the laissez-faire equilibrium allocation.