• 한국생산제조학회지
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• 제21권1호
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• pp.85-89
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• 2012

Conventional grinding of BK7 glass will normally result in brittle fracture at the surface, generating severe sub-surface damage and poor surface finish. The precision grinding of BK7 glass in parallel grinding modes has been investigated. Grinding process, maximum chip thickness, ductile/brittle regime, surface roughness and sub-surface damage have been addressed. Special attention has been given to the condition for generating a ductile mode response on the ground surface. Experiments reveal that the level of surface roughness and depth of sub-surface damage vary differently for different condition. This study gives an indication of the strategy to follow to achieve high quality ground surfaces on brittle materials.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 3차
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• pp.49-54
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• 2010

In order to study the performance of levees reinforced with steel sheet piles under high water condition, a series of model tests was conducted by simulating the high water condition before and after applying severe seismic loading history. As a result, the seepage behavior through the subsoil layers underlying the levee was not significantly affected by the seismic loading history. It was also verified that, irrespective of the seismic loading history, the sheet piles installed at the levee crest or shoulder are effective in preventing the breakage of levees caused by overflow. In addition, applicability of drainage works at the foot of the levee in preventing the seepage failure was confirmed.

• 한국구조물진단유지관리공학회 논문집
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• 제6권1호
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• pp.205-212
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• 2002

The deterioration rate of concrete structures in urban area is accelerated due to rapid urbanization and environmental pollution. Repair materials and methods newly introduced in Korea should be investigated whether they are appropriate for the urban environment in Korea. The creek concrete structures are exposed in severe environmental condition than others. Based on these background in mind, the study is focused on evaluation of performance on repair materials used to rehabilitate creek concrete structures. To evaluate the performance of repair materials, four kinds of repair materials were selected based on polymer emulsion. This experimental study was conducted on fundamental performance such as setting time, compressive strength, bending strength, bonding strength, thermal expansion coefficient, and durability performance such as chloride diffusion, carbonation, chemical attack, and steel corrosion rate. On the basis of this study, the optimal repair material which is proper to the environment condition can be selected and service life of creek concrete structures can be extended. As a result, the life cycle cost can be reduced and the waste of material resources will be cut down.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.766-771
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• 2001

The package used to transport radioactive materials, which is called by cask, must be safe under normal and hypothetical accident conditions. These requirements for the cask design must be verified through test or finite element analysis. Since the cost for FE analysis is less than one for test. the verification by FE analysis is mainly used. But due to the complexity of mechanical behaviors. the results depends on how users apply the codes and it can cause severe errors during analysis. In this paper, finite element analysis is carried out for the 9 meters free drop and the puncture condition of the hypothetical accident conditions using LS-DYNA3D and ABAQUS/Explicit. We have investigated the analyzing technique for the free drop impact test of the cask and found several vulnerable cases to errors. The analyzed results were compared with each other. We have suggested a reliable and relatively simple analysis technique for the drop test of spent nuclear fuel casks.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1093-1096
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• 2004

Bearings are elementary machinery component which loads and do rotating motion. Excessive loads or many other reasons can cause incipient faults to be created and grown in each component. Moreover, it happens that incipient faults which were caused by manufacturing or assembling process' errors of the bearings are created. Finding the incipient faults as early as possible is necessary to the bearings in severe condition: high speed or frequently varying load condition, etc. How early we can detect the faults has to do with how the detection algorithm finds the fault information from measured signal. Fortunately, the bearing fault signal makes periodic impulse train. This information allows us to find the faults regardless how much noise contaminates the signal. This paper shows the basic signal processing idea and experimental results that demonstrate how good the method is.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1048-1051
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• 2004

The environmental pollution by noise is recognized by the pollution source made it not only to carry out harm of the Quality of a life of people seriously in most countries, but was generated for most actual problems. The measure to such environmental noise must conduct first investigation which noise generating currently regarded as questionable says in what grade has resulted and the suitable measure by that is studied. The concern of the residents who demand such a comfortable living environment is increasing rapidly. Therefore, the three areas of Jeollabuk-Do judged that noise is comparatively severe was selected. It is going to grasp delicately the noise actual condition of a residential, semi-residential, commercial, industrial area.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제11권3호
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• pp.37-41
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• 2007

The semi-convexity for planar shapes has been recently introduced in [2]. As a generalization of the convextiy, semi-convexity is closed under the Minkowski sum. But the definition of semi-convexity requires that the shape boundary should satifisfy a differentiability condition $C^{1:1}$, which means that it should be possible to take the normal vector field along the domain's extended boundary. In view of the fact that the semi-convextiy is a most natural generalization of the convexity in many respects, this is a severe restriction for the semi-convexity, since the convexity requires no such a priori differentiability condition. In this paper, we generalize the semi-convexity to the closure of the class of semi-convex $\mathcal{M}$-domains for any Minkowski class $\mathcal{M}$, and show that this generalized semi-convexity is also closed under Minkowski sum.

• 로봇학회논문지
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• 제14권1호
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• pp.8-13
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• 2019

Visual place recognition is widely researched area in robotics, as it is one of the elemental requirements for autonomous navigation, simultaneous localization and mapping for mobile robots. However, place recognition in changing environment is a challenging problem since a same place look different according to the time, weather, and seasons. This paper presents a feature extraction method using a deep convolutional auto-encoder to recognize places under severe appearance changes. Given database and query image sequences from different environments, the convolutional auto-encoder is trained to predict the images of the desired environment. The training process is performed by minimizing the loss function between the predicted image and the desired image. After finishing the training process, the encoding part of the structure transforms an input image to a low dimensional latent representation, and it can be used as a condition-invariant feature for recognizing places in changing environment. Experiments were conducted to prove the effective of the proposed method, and the results showed that our method outperformed than existing methods.

• Nuclear Engineering and Technology
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• 제54권4호
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• pp.1355-1362
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• 2022

Nuclear fuel, including its fresh state, must be handled safely due to its critical and hazardous nature. Under normal transport conditions, several interactions take place among different components, such as transport cask used for loading the nuclear fuel and tie-down structure to attach with the vehicle. To ensure structural integrity of the nuclear fuel, vibrations and impacts transmitted from the vehicle must be sufficiently reduced. Therefore, in this study, we conducted two transportation tests from Daejeon to Kijang in Korea to verify the vehicle-induced vibrational characteristics of the KJRR-F fresh nuclear fuel when transported under normal transport conditions. The speed and location of the vehicle were obtained via GPS, and the accelerations between the vehicle and the KJRR-F fresh nuclear fuel were measured. Additionally, using the acceleration results, a structural analysis was conducted to confirm the structural integrity of the nuclear fuel under the most severe conditions during normal transport.

• Nuclear Engineering and Technology
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• 제55권1호
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• pp.180-189
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• 2023

We measured the heat load to a reactor vessel with and without the in-vessel debris bed under an IVR-ERVC condition. Mass transfer methodology was adopted based on heat and mass transfer analogy to achieve high Ra'_H of order ~10¹⁵ with compact test rigs. We postulated the in-vessel debris bed has a flat top and particulate debris was simulated as an identical diameter spheres. We conducted experiments varying the height of the debris bed and the results showed that Nusselt numbers decreased in both uppermost and curved surfaces with the increasing bed height. Once the debris bed is formed, it acts as an obstacle to the natural convective flow, which reduces the buoyancy. The reduction of driving force results in the impaired heat transfer in both upward and downward heat transfers.