• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2887-2900
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• 2020

Cladding failure in a fuel rod during operation in a BWR is analyzed using a FALCON code-based model. Comparative calculation with a neighbouring, intact rod is presented, as well. A considerable 'hot spot' effect in cladding temperature is predicted with the SLICE-DO model due to a thermal barrier caused by the localized crud deposition. Particularly significant overheating is expected to occur on the affected side of the cladding of the failed rod, in agreement with signs of significant localized crud deposition as revealed by Post Irradiation Examination. Different possibilities (criteria) are checked, and Pellet-Cladding Mechanical Interaction (PCMI) is shown to be one of the plausible potential threats. It is shown that PCMI could lead to discernible concentrated inelastic deformation in the overheated part of the cladding. None of the specific mechanisms considered can be experimentally or analytically identified as an only cause of the rod failure. However, according to the current calculation, a possibility of cladding failure by PCMI cannot be excluded if the crud thickness exceeded 300 ㎛.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.50.1-50.1
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• 2010

We have analyzed times of minima for of 6 binary systems. Three binary systems show period decrease at rate $3.19{\times}10-5$ yr -1 for SV Cen, $1.35{\times}10-7$ yr -1 for RT Scl and $1.14{\times}10-7$ yr -1 for AD Phe. Two systems show period increase $5.696{\times}10-8$ yr -1 for SX Aur and $6.93{\times}10-8$ yr -1 for GO Cyg. One system shows cyclic period variation. We estimated the mass transfer rate for 5 binary systems. Four systems show asymmetric light curves. Two asymmetric light curves (SV Cen and RT Scl) are due to hot spot caused by mass transfer. And two asymmetric light curves (AD Phe and TY Boo) are due to cool spot caused by magnetic activities on the cooler component. We also obtain absolute dimensions from photometric solution and spectroscopic solution by analyzing their light curves and radial velocity curves, which are collected from literatures, using 2007 version Wilson and Deviney computer code.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.32.3-32.3
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• 2010

We have analyzed times of minima for six eclipsing binary systems which show asymmetric light curves. We found that five binary systems show period decrease and one system shows cyclic period variation. Three asymmetric light curves (SV Cen, RT Scl and VW Boo) are due to hot spot caused by mass transfer. Other three asymmetric light curves (AD Phe,, EZ Hya and TY Boo) are due to cool spot on the cooler component caused by magnetic activities. We also obtain absolute dimensions from photometric solution and spectroscopic solution by analyzing their light curves and radial velocity curves, collected from literatures, using 2007 version Wilson and Devinney computer code.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.24.2-24.2
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• 2009

We present the results of new CCD photometry for the contact binary BX Peg, made during three successive months beginning on September 2008. As do historical light curves, our observations display an O'Connell effect and the November data by themselves indicate clear evidence for very short-time brightness disturbance. For these variations, model spots are applied separately to the two data set of Group I (Sep.--Oct.) and Group II (Nov.). The former is described by a single cool spot on the secondary photosphere and the latter by a two-spot model with a cool spot on the cool star and a hot one on either star. These are generalized manifestations of the magnetic activity of the binary system. Twenty light-curve timings calculated from Wilson-Devinney code were used for a period study, together with all other minimum epochs. The complex period changes of BX Peg can be sorted into a secular period decrease caused dominantly by angular momentum loss due to magnetic stellar wind braking, a light-travel-time (LTT) effect due to the gravitational effect of a low-mass third companion, and a previously unknown short-term oscillation. This last period modulation could be produced either by a second LTT orbit with a period of about 16 yr due to the existence of a fourth body or by the effect of magnetic activity with a cycle length of about 12 yr.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.86.2-86.2
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• 2014

We present a new ray-tracing code, "Odyssey", for the Kerr spacetime accelerated by the Graphics Processing Unit (GPU). Taking advantage of the ability of nVidia graphic cards to evaluate trajectories of a large amount of photon simultaneously, the code is two orders of magnitude as fast as the previous CPU-based code corresponding to the speed of few nanoseconds per photon per time step. In the light of the Graphic User Interface (GUI) powered by the GPU-enhanced 2D/3D displaying technique, DirectX, it is feasible for users to manipulate diverse results such as rotating and zooming in/out the trajectories of photon instantly near the black hole. Thus the Odyssey can serve as a tool not only for scientific but also for the educational purpose. We discuss possible applications in detail in light of several results such as the shape of the silhouette of a black hole, the shape of a hot spot orbiting a black hole, and 3D photon trajectories.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.1
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• pp.38-47
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• 2001

PDM is an integrated solution for managing various kinds of document and information for a whole life~cycle of product management. PDM system spans a huge and complex area and requires so many efforts and budgets for development. A framework has been considered a promising way to improve productivity by reusing the software architecture, not just one part of the design or just source code. This was the reaSon why we developed PDM (Product Data Management) framework. Framework can reduce the time and efforts to develop a new PDM application. However, it also requires supporting environment since a framework is a big set of classes where their interactions are so complex. With this supporting environment, it is easy to understand the framework at a glance and easy to identify what hot spots to be refined to meet new requirements. In this paper, a new framework-supporting reuse environment based on the meta-repository was constructed for easy and convenient reuse.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.731-741
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• 2009

Optical repeater is often installed at the isolated area. Spatial separation makes it possible to reduce the inter-code interference when secondary scrambling codes are used for traffic connected through repeater. In this paper, we propose five secondary scrambling code usage scenarios with the aids of optical repeater to maximize the user capacity. In order to evaluate the performance, dynamic system level simulation is performed. We also propose a base station-repeater switching where each active users can change access points by comparing the channel condition from base station and repeater thorough secondary common pilot channel (S-CPICH) signal to noise-interference ratio (SINR). Moreover, primary-secondary scramble code replacing scheme is proposed which replaces secondary scramble code with primary scramble code when a call using primary scramble code is ended and its corresponding OVSF code is available to users using the secondary scramble code

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.64.1-64.1
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• 2017

접촉쌍성 EK Com은 0.2667일의 짧은 주기를 가진 만기형 식쌍성으로 광도곡선의 변화로 인해 연구자마다 이계의 하위 유형을 다르게 언급하여 하위유형의 혼동이 있는 천체이다. 우리는 소백산천문대에서 2009년 5월 VR 필터로, 2013년 2 ~ 5월 사이 BVRI 필터로, 2016년 1 ~ 4월 사이 R 필터로 CCD 측광 관측하여 3개의 새로운 광도곡선을 획득하였다. 우리의 관측 자료와 SuperWASP의 공개된 자료로부터 40개의 새로운 극심시각을 산출하였다. 이 극심시각을 포함하여 155개의 극심시각을 여러 문헌에서 수집하여 주기 연구를 수행한 결과, EK Com의 공전주기는 영년 주기 증가와 더불어 8.2년의 주기적인 변화가 겹쳐 변화함을 발견하였다. 이러한 주기 변화 원인에 대하여 살펴본 결과, 영년주기변화는 질량이 작은 별에서 큰 별로의 질량이동에 의하여 일어나고, 주기적인 변화는 질량이 큰 주성의 자기 활동에 의해 발생할 수 있음을 보였다. Wilson-Devinney code를 이용한 광도곡선 분석을 통하여 EK Com은 개기식이 부식에 있는 하위 유형 A라기 보다 주식에 있는 W형에 속하며, 모든 광도곡선에서 1개의 Hot spot과 1개의 Cool spot을 가진 모형이 가장 관측치를 잘 설명한다. W UMa형 별들의 HR도, 온도비, 질량의 그래프에서 EK Com은 W형 Group들이 있는 위치에 존재한다. 이는 광도곡선에서 유추한 EK Com의 하위 유형과도 일치한다.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.97-109
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• 2022

Multi-dimensional coupling analysis is a research hot spot in nuclear reactor thermal hydraulic study and both the full-scale system transient response and local key three-dimensional thermal hydraulic phenomenon could be obtained simultaneously, which can achieve the balance between efficiency and accuracy in the numerical simulation of nuclear reactor. A one-dimensional to three-dimensional (1D-3D) coupling platform for the nuclear reactor multi-dimensional analysis is developed by XJTU-NuTheL (Nuclear Thermal-hydraulic Laboratory at Xi'an Jiaotong University) based on the CFD code Fluent and system code RELAP5 through the Dynamic Link Library (DLL) technology and Fluent user-defined functions (UDF). In this paper, the International Standard Problem (ISP) No. 43 is selected as the benchmark and the rapid boron dilution transient in the nuclear reactor is studied with the coupling code. The code validation is conducted first and the numerical simulation results show good agreement with the experimental data. The three-dimensional flow and temperature fields in the downcomer are analyzed in detail during the transient scenarios. The strong reverse flow is observed beneath the inlet cold leg, causing the de-borated water slug to mainly diffuse in the circumferential direction. The deviations between the experimental data and the transients predicted by the coupling code are also discussed.

• Journal of KIISE:Software and Applications
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• v.29 no.1_2
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• pp.65-79
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• 2002

Object-oriented frameworks need to be systematically tested because they are reused in developing many applications software. They also need additional testing whenever they are extended for reuse. Frameworks, however, have properties that make it difficult to control and observe the testing of the parts that were modified and extended. In this paper, we describe the method of embedding test components as BIT(Built-In Test) into the framework's hot spots in order to efficiently detect the faults through testing that occurred while implementing application programs by modifying and extending the framework. The test components embedded into a framework make it easy to control and observe testing the framework, and thereby improve the testability of frameworks. Test components designed by the method proposed in this paper can be dynamically attached and detached to/from hot spots of a framework without changes or intervention to the framework code.