• 대한의용생체공학회:의공학회지
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• 제3권1호
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• pp.35-42
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• 1982

The objective of this phantom study is to develop a digital method for improving the lateral resolution of B-scan ultrasonographic images irs medical application of ultrasound. By utilizing a discrete state-space modeling approach and Kalman-Buch method for analysis of the transducer's beam profile and the measurement and sampling noise, a stable recursive restoration of the object image was obtained for improved lateral resolution. The point spread function (PSF) was measured for the reflective signals after scanning the small pins located along the depth of interest. One major advantage of the present recursive scheme over the transform method is in its applicability for the space-variant imaging, such as in the case of the rotational movement of transducer.

• International Journal of Aeronautical and Space Sciences
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• 제15권2호
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• pp.183-189
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• 2014

Pseudo-spectral method typically converges at an exponential rate. However, it requires a special set of fixed collocation points (CPs) to get highly accurate formulas for partial integration and differentiation. In this study, computational nodes for defining the discrete variables of states and controls are built independently of the CPs. The state and control variables at each CP, which are required to transcribe an NOCP into the corresponding NLP, are interpolated, using those variables allocated at each node. Additionally, Lagrange interpolation and spline interpolation are investigated, to provide a guideline for selecting a favorable interpolation method. The proposed techniques are applied to the solution of an NOCP using equally spaced nodes, and the computed results are compared to those using the standard PS approach, to validate the usefulness of the proposed methods.

• Structural Engineering and Mechanics
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• 제13권6호
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• pp.713-730
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• 2002

This paper presents a finite element approach for determining the natural frequencies for planar inclined arches of various shapes vibrating in three-dimensional space. The profile of inclined arches, represented by undeformed centriodal axis of cross-section, is defined by the equation of plane curves expressed in the rectangular coordinates which are : circular, parabolic, sine, elliptic, and catenary shapes. In free vibration state, the arch is slightly displaced from its undeformed position. The linear relationship between curvature-torsion and axial strain is expressed in terms of the displacements in three-dimensional space. The finite element discretization along the span length is used rather than the total are length. Numerical results for arches of various shapes are given and they are in good agreement with those reported in literature. The natural frequency parameters and mode shapes are reported as functions of two nondimensional parameters: the span to cord length ratio (e) and the rise to cord length ratio (f).

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.64-71
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• 2011

In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in a transonic flow region. The launch vehicle structural response are coupled with the transonic flow state transitions at the nose of the payload fairing. The developed fluid-structure coupled analysis system is applied for aeroelastic computations combining computational structural dynamics(CSD), finite element method(FEM) and computational fluid dynamics(CFD) in the time domain. It can give very accurate and useful engineering data on the structural dynamic design of advanced flight vehicles. For the nonlinear unsteady aerodynamics in high transonic flow region, Navier-Stokes equations using the structured grid system have been applied to the rocket configurations. Also, it is typically shown that the current computation approach can yield realistic and practical results for rocket design and test engineers.

• Spatial Information Research
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• 제18권2호
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• pp.45-55
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• 2010

Place based intervention has become an important strategy for the ubiquitous city initiative. However, the role of the ubiquitous built environment in determining urban quality of life has not investigated fully. Using place as a relational space where people access u-infrastructure, u-health and u-services, this paper examines the relationship between spatial variations in the provision of ICTs and the spatial reconfiguration of quality of life operating at different geographical scales across Australia. Based on a case study of the state of Queensland in Australia, we emphasize the need for a place based approach to ubiquitous technologies and infrastructure provision in different socio economic hierarchies of space and place.

• Journal of Astronomy and Space Sciences
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• 제39권2호
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• pp.59-65
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• 2022

In this paper we propose a new perspective for explaining galaxy rotation curves. We conjecture that there is a gravitational moment of inertia which, together with gravitational mass, contributes to the gravitational potential. We substantiate a formula for the potential created by the moment of inertia. We validate our model by computing orbital rotation velocities for several galaxies and showing that computed rotation velocities correspond to the observed ones. Our proposed approach is capable of accounting for constant gas velocities outside of a galactic disc without relying on the dark matter hypothesis. Furthermore, it addresses several problems faced by the application of the dark matter hypothesis, e.g., the absence of inward collapse of dark matter into a galaxy, the spherical distribution of dark matter around galaxies, and absence of traces of the effect of dark matter in two ultra-diffuse galaxies, NGC 1052-DF2, and NGC 1052-DF4.

• ETRI Journal
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• 제44권6호
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• pp.925-935
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• 2022

In this study, we propose a limited feedback-based frequency divided group beamforming with sparse space-frequency transmit diversity coded orthogonal frequency division multiplexing (OFDM) system for ultrareliable low latency communication (URLLC) scenario. The proposed scheme has several advantages over the traditional hybrid beamforming approach, including not requiring downlink channel state information for baseband precoding, supporting distributed multipoint transmission structures for diversity, and reducing beam sweeping latency with little uplink overhead. These are all positive aspects of physical layer characteristics intended for URLLC. It is suggested in the system to manage the multipoint transmission structure realized by distributed panels using a power allocation method based on cooperative game theory. Link-level simulations demonstrate that the proposed scheme offers reliability by achieving both higher diversity order and array gain in a nonline-of-sight channel of selectivity and limited spatial scattering.

• 한국과학교육학회지
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• 제33권1호
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• pp.144-160
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• 2013

본 논문은 '창의적 과학탐구 방법으로 철학의 비판적 사고가 어떤 기능을 하는지'를 신경학적으로 설명하려는 하나의 가설적 제안이다. 지금까지 창의적 과학연구 방법은 주로 포퍼(Popper), 쿤(Kuhn), 헴펠(Hempel), 라카토슈(Lakatos) 등 과학철학자들이 제안한 과학의 논리적 '탐구과정'과 관련된 가설적 주장들이었다. 그러한 주장들은 어떠한 연구과정 또는 접근법이 창의성을 발휘하게 하는지를 모색하게 한다. 본 연구자는 그러한 탐구 경향 혹은 접근법을 "창의성 과정 접근법(Process Approach of Creativity: PAC)"이라 부르겠다. 그러나 본 연구자의 관점에 따르면, PAC를 모색하는 연구자들은 실질적으로 창의적 이론이 어떻게 도출되는지에 관심을 두지 않는다. 반면에 본 논문은 서양에서 새로운 이론을 창안했던 과학자들의 '철학적 사고 능력'에 초점을 맞춘다. 그들은 과학 연구 이외에도 대부분 철학을 공부한 경험이 있으며, 자신의 학문에 대한 비판적 사고를 할줄 아는 학자들이었다. 본 연구자의 관점에 따르면, 철학의 비판적 사고는 자신이 갖는 (낡은) 과학이론에서 핵심적 기초 개념과 원리에 대한 회의와 의문을 제기하게 하여, 새로운 창의적 이론을 얻게 한다. 본 연구는 이것을 신경철학의 관점에서 설명하려 한다. 신경철학의 창시자인 처칠랜드 부부(Paul and Patricia Churchland)의 "상태공간 표상이론(the state space theory of representation)"의 관점에서 전망해보면, "창의적 이론"이란 새로운 포괄적 설명과 예측을 제공하는 새로운 국소 대응도(topographic maps)의 연결망이다. 그 전망에서, 철학의 비판적 질문의 태도는 낡은 국소대응도 연결망의 오류를 역전파(back-propagation) 또는 피드백(feedback)으로 수정하게 할 것이며, 따라서 새로운 대응도 연결망을 탐색하게 만들 원동력이라고 본 연구자는 가정한다. 이 가정에서, 과학자들은 특별히 비범한 창의성(extraordinary creativity)을 위해 자신의 학문적 기초 가정들을 철학적으로 돌아보는 것이 중요하다. 철학의 비판적 태도는 낡은 기초 가정들의 대응도를 흔들어 과학자들이 새로운 개념체계의 국소 대응도를 형성하도록 해주기 때문이다. 이러한 측면에서 본 연구자는 "창의성 비판적 사고 접근법(Critical Thinking Approach of Creativity: CTAC)"을 제안한다.

• 대한산업공학회지
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• 제36권3호
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• pp.193-202
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• 2010

The recommender system is a typical software solution for personalized services which are now popular in e-commerce sites. Most of the existing recommender systems are based on customers' explicit rating data on items (e.g., ratings on movies), and it is only recently that recommender systems based on implicit ratings have been proposed as a better alternative. Implicit ratings of a customer on those items that are clicked but not purchased can be inferred from the customer's navigational and behavioral patterns. In this article, a dimensionality reduction (DR) technique is newly applied to the implicit rating-based recommender system, and its effectiveness is assessed using an experimental e-commerce site. The experimental results indicate that the performance of the proposed approach is superior or at least similar to the conventional collaborative filtering (CF)-based approach unless the number of recommended products is 'large.' In addition, the proposed approach requires less memory space and is computationally more efficient.

• International Journal of Costume and Fashion
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• 제15권1호
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• pp.1-18
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• 2015

The ethnic dress of Germany's Black Forest, called Tracht, dates back to the 16th century. Although most people living within the Black Forest do not presently wear Trachten, some persistence in this tradition exists. This study explored the factors that have supported the persistence of the Trachten tradition, specifically related to the wearing and crafting of Trachten by women, in a contemporary society. A qualitative, ethnographic approach was adopted. Data were collected via observations and interviews in the Black Forest. Thematic analyses revealed that the maintenance of the Trachten tradition was linked to varied factors that revolved around the overarching themes of both persistence and change. Interpretations were supported by theory proposing that ethnic dress is not static, but rather, changes across space and time in ways that enable its persistence. The persistence of the Trachten tradition was linked to formalized practice, meaningful identities, and desires to preserve and promote local culture. Additionally, the persistence of the Trachten tradition was fostered by change in the tradition, including the conceptualization of Trachten as a "lived practice" and the negotiation of Trachten authenticity.