• 한국수학사학회지
• /
• 제25권2호
• /
• pp.23-34
• /
• 2012

2014년 8월 13일에서 21일까지 서울에서 ICM(국제수학자대회) 이 열린다. 100년이 넘는 역사를 갖고 있는 ICM은 4년에 한 번씩 열린다. 클라인 (Klein) 에 의하여 ICM이 시작된 것으로 알려져 있으나, 사실은 칸토어 (Cantor) 가 먼저 국제수학자대회와 국제수학자연합체를 꿈꾸고 씨앗을 뿌렸다. 이 논문에서는 ICM이 시작된 계기와 ICM 초기인 1회부터 5회까지의 회의 발전 과정을 자세히 알아본다. 특히 ICM의 공식언어의 변화, 참석자들의 수의 변화, 논문발표의 수, 기조강연자의 구성, 수학 분과의 변화등을 통하여 20세기 초반 수학의 발전상을 함께 연구 한다.

• 복식문화연구
• /
• 제17권4호
• /
• pp.600-615
• /
• 2009

$21^{st}$ century post digital society orients co-existence, fusion, and blurring boundary than conflict, differentiation, and boundary, and makes a try liberal combination of various different objects. Furthermore, radical development of science and digital equipments offer technical possibility that could combine various fields. Hence, many different departments demolish their boundary, and combine for development of multi-functional and complex shape's products. For job-nomads, fashion attempts to combine with architecture, furniture, daily necessities, and digital equipments spontaneously. This paper aims at consideration about the blurring phenomena expressed in complex fashion space of $21^{st}$ century throughout empirical fashion photographs analysis, which show combination among fashion and various different fields. Blurring boundary phenomena of complex fashion space are classified with 4 parts as follows as: 1) furniturizing, 2) wearable dwelling, 3) lumiduct, 4) becoming fashion. Each parts are examined 8 aesthetical characteristics such as movement and lightness, hyper-link and openness, immateriality and inter-activeness, and diversity and ambiguity. $21^{st}$ century fashion has changed more simple and light, and creates new form throughout combination with many other fields, and enlarges its function and sphere. I think this paper would help certificating practical use of fashion space as multiple and complex space, and makes contribution to forecast about fashion development of the future and offer inspiration about creative and innovative fashion design.

• 한국통신학회논문지
• /
• 제38C권7호
• /
• pp.595-604
• /
• 2013

공개된 네트워크 상에서 통신하는 두 참여자를 위한 안전한 인증된 키 동의 프로토콜(AKA)을 고안하는 것은 중요한 연구이다. McCullagh등은 단일 도메인과 두 개의 도메인을 위해 사용될 수 있는 제 3자 키 기탁(escrow)과 제 3자 키기탁이 필요없는 두가지 속성을 지원하는 두 참여자간 식별자 기반 인증된 키동의 프로토콜을 제안하였다. 본 논문은 McCullagh등의 두 개의 도메인을 위한 프토토콜이 가장 공격(masquerading attack)에 취약함으로서 주장하는 보안을 만족하지 않음을 보인다. McCullag등의 기법에 존재하는 가장 공격은 충분한 개체 인증과 무결성 보증의 부족 때문에 발생한다. McCullagh등의 프로토콜 문제점을 해결하기 위해서 인증절차에 서명 원리가 포함된 효율적인 검증가능한 키 동의 프로토콜을 제안한다.

• IEIE Transactions on Smart Processing and Computing
• /
• 제2권3호
• /
• pp.168-175
• /
• 2013

Key escrow is a default property that is inherent in identity-based cryptography, where a curious private key generator (PKG) can derive a secret value shared by communicating entities in its domain. Therefore, a dishonest PKG can encrypt and decrypt ciphers or can carry out any attack on the communicating parties. Of course, the escrow property is not completely unwanted but is acceptable in other particular applications. On the other hand, in more civil applications, this key escrow property is undesirable and needs to be removed to provide maximum communication privacy. Therefore, this paper presents an escrow-free identity-based key agreement protocol that is also applicable even in a distinct PKG condition that does not use pairings. The proposed protocol has comparable computational and communicational performance to many other protocols with similar security attributes, of which their security is based on costly bilinear pairings. The protocol's notion was inspired by McCullagh et al. and Chen-Kudla, in regard to escrow-free and multi-PKG key agreement ideas. In particular, the scheme captures perfect forward secrecy and key compromise impersonation resilience, which were lacking in McCullagh et al.'s study, as well as all other desirable security attributes, such as known key secrecy, unknown key-share resilience and no-key control. The merit in the proposed protocol is the achievement of all required security requirements with a relatively lower computational overhead than many other protocols because it precludes pairings.

• International Journal of Fluid Machinery and Systems
• /
• 제3권4호
• /
• pp.342-351
• /
• 2010

During the operation of a hydro turbine the fluid mechanical pressure loading on the turbine blades provides the driving torque on the turbine shaft. This fluid loading results in a structural load on the component which in turn causes the turbine blade to deflect. Classically, these mechanical stresses and deflections are calculated by means of finite element analysis (FEA) which applies the pressure distribution on the blade surface calculated by computational fluid dynamics (CFD) as a major boundary condition. Such an approach can be seen as a one-way coupled simulation of the fluid structure interaction (FSI) problem. In this analysis the reverse influence of the deformation on the fluid is generally neglected. Especially in axial machines the blade deformation can result in a significant impact on the turbine performance. The present paper analyzes this influence by means of fully two-way coupled FSI simulations of a propeller turbine utilizing two different approaches. The configuration has been simulated by coupling the two commercial solvers ANSYS CFX for the fluid mechanical simulation with ANSYS Classic for the structure mechanical simulation. A detailed comparison of the results for various blade stiffness by means of changing Young's Modulus are presented. The influence of the blade deformation on the runner discharge and performance will be discussed and shows for the configuration investigated no significant influence under normal structural conditions. This study also highlights that a two-way coupled fluid structure interaction simulation of a real engineering configuration is still a challenging task for today's commercially available simulation tools.

• Journal of Communications and Networks
• /
• 제13권5호
• /
• pp.499-510
• /
• 2011

Any server offering a routing service in the Internet would naturally be in competition for clients, and clients may need to utilize service from a specific server in order to achieve a desired result. We study the various properties of this competition, such as the fraction of route requests handled by a routing service provider and the fraction of total revenue obtained. As the routing service providers (i.e., servers or routers in this context) compete, they may alter behavior in order to optimize one of the above properties. For example, a service provider may lower the price charged for its service, in order to increase the number of clients served. Our models are based on servers offering a routing service to clients within representative network topologies based on actual Internet sub-graphs. These models provide, a framework for evaluating competition in the Internet. We monitor key aspects of the service, as several variables are introduced into the models. The first variable is the fraction of client requests that will pay more for a better quality route. The remaining requests are normal client requests that are satisfied by the most economical route. The second variable is the fraction of servers who choose to lower service prices in order to maximize the number of client requests served. As this fraction increases, it is more likely that a server will lower the price. Finally, there are some resource constraints applied to the model, to increase the difficulty in providing a routing solution, i.e., to simulate a realistic scenario. We seek to understand the effect on the overall network, as service providers compete. In simple cases, we show that this competition could have a negative impact on the overall efficiency of a service. We show that the routing variety present in the larger models is unable to mask this tendency and the routing service performance is decreased due to competition.

• Nuclear Engineering and Technology
• /
• 제48권2호
• /
• pp.482-494
• /
• 2016

The Feshbache-Kermane-Koonin (FKK) multi-step direct (MSD) theory of pre-equilibrium reactions has been used to compute the single-step cross-sections for some (p,${\alpha}$) reactions using the knock-on and pick-up reaction mechanisms at two incident proton energies. For the knock-on mechanism, the reaction was assumed to have taken place by the direct ejection of a preformed alpha cluster in a shell-model state of the target. But the reaction was assumed to have taken place by the pick-up of a preformed triton cluster (also bound in a shell-model state of the target core) by the incident proton for the pick-up mechanism. The Yukawa forms of potential were used for the proton-alpha (for the knock-on process) and proton-triton (for the pick-up process) interaction and several parameter sets for the proton and alpha-particle optical potentials. The calculated cross-sections for both mechanisms gave satisfactory fits to the experimental data. Furthermore, it has been shown that some combinations of the calculated distorted wave Born approximation cross-sections for the two reaction mechanisms in the FKK MSD theory are able to give better fits to the experimental data, especially in terms of range of agreement. In addition, the theory has been observed to be valid over a wider range of energy.

• 대한기계학회논문집A
• /
• 제37권12호
• /
• pp.1503-1512
• /
• 2013

본 논문에서는 cohesive zone 모델을 이용한 유한요소해석에 기초해 압입 파괴인성 평가식을 제시한다. 먼저 Vickers 압입균열해석에 기초해 다양한 물성변수(항복변형률 ${\varepsilon}_o$, 푸아송비 ${\nu}$, 영률 E)의 들이 균열크기에 미치는 영향을 분석하고, 파괴인성을 압입 시 측정되는 최대하중과 균열길이로 나타낼 수 있는 수식을 회귀로 얻었다. 아울러 접촉길이 a, E/H (H: 경도) 등을 추가 압입변수로 선정해 다양한 형태의 파괴인성평가법을 제시했다. 이후 동일 압입하중에서 압입자각 및 압입자 형태와 균열 크기의 관계를 분석해 Vickers 압입 파괴인성평가법을 다양한 압입자 형태로 확장했다. 본 연구에서 제안된 평가식을 이용하면 압입시험으로 얻어지는 데이터로부터 바로 취성재료의 파괴인성을 예측할 수 있다.

• Archives of Plastic Surgery
• /
• 제48권5호
• /
• pp.518-523
• /
• 2021

Epignathus is a rare congenital orofacial teratoma that arises from the sphenoid region of the palate or the pharynx. It occurs in approximately 1:35,000 to 1:200,000 live births representing 2% to 9% of all teratomas. We present the case of a newborn of 39.4 weeks of gestation with a tumor that occupied the entire oral cavity. The patient was delivered by cesarean section. Oral resection was managed by pediatric surgery. Plastic surgery used virtual 3-dimensional models to establish the extension, and depth of the tumor. Bloc resection and reconstruction of the epignathus were performed. The mass was diagnosed as a mature teratoma associated with cleft lip and palate, nasoethmoidal meningocele that conditions hypertelorism, and a pseudomacrostoma. Tridimensional technology was applied to plan the surgical intervention. It contributed to a better understanding of the relationships between the tumor and the adjacent structures. This optimized the surgical approach and outcome.

• Wind and Structures
• /
• 제32권4호
• /
• pp.355-369
• /
• 2021

Shape optimization of tall buildings is an efficient approach to mitigate wind-induced effects. Several studies have demonstrated the potential of shape modifications to improve the building's aerodynamic properties. On the other hand, it is well-known that the cross-section geometry has a direct impact in the floor area availability and subsequently in the building's profitability. Hence, it is of interest for the designers to find the balance between these two design criteria that may require contradictory design strategies. This study proposes a surrogate-based multi-objective optimization framework to tackle this design problem. Closed-form equations provided by the Eurocode are used to obtain the wind-induced responses for several wind directions, seeking to develop an industry-oriented approach. CFD-based surrogates emulate the aerodynamic response of the building cross-section, using as input parameters the cross-section geometry and the wind angle of attack. The definition of the building's modified plan shapes is done adopting the reduced basis approach, advancing the current strategies currently adopted in aerodynamic optimization of civil engineering structures. The multi-objective optimization problem is solved with both the classical weighted Sum Method and the Weighted Min-Max approach, which enables obtaining the complete Pareto front in both convex and non-convex regions. Two application examples are presented in this study to demonstrate the feasibility of the proposed strategy, which permits the identification of Pareto optima from which the designer can choose the most adequate design balancing profitability and occupant comfort.