• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.189-202
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• 2023

In this study, the acoustic performance was analyzed by architectural shapes of the hall. There are four architectural shapes of halls. They are rectangular, horseshoe, surround, and fan-shape. Eight acoustic parameters were used to determine the acoustic performance. These are RT₆₀, EDT, C₈₀, BQI, LF, G_mid, G₁₂₅ and ITDG. First, measurement data of famous concert halls around the world were analyzed. The correlation coefficient R was obtained by regression analysis of the relationship between the subjective ranking of the halls and the acoustic parameters. It was found that BQI, G, and ITDG have higher correlation coefficients R. Also the average of acoustic parameters for each architectural shape were obtained. The total acoustic performance for each shape was calculated by using the correlation coefficient R as a weight for each acoustic parameters. As a result, rectangular halls and horseshoe halls showed good acoustical performances. Second, 3D models of each architectural shape were created and acoustic simulation had been performed. The simulation was performed by creating 3D models of each four shapes of concert halls with the same volume and sound absorption coefficient. Listening test was carried out using the sound source which is created from impulse responses of 3D model. As a result, rectangular hall and horseshoe hall showed the best performance however surround hall and fan-shaped hall showed relatively poor performance.

• Korean Journal of Heritage: History & Science
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• v.46 no.3
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• pp.68-77
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• 2013

This report is based on the investigation of potholes which are formed by fluvial erosion. A pothole is called so because it is a hole that looks like a coffeepot. The results of previous studies are applied to the 'Jakgwaecheon Porthole' of this study. The study is focused on the dimension and morphology of the Pothole and investigates the effects of stream sediments, river flow, geological structural lines, etc. on the formation of potholes. As a result of measuring 61 potholes in this area, we recognized that the elliptical dish-shaped cross sections are dominant and inferred that their longitudinal direction on the plain is affected by the direction of the stream flow. Also, 'Jakgwaecheon Pothole' is very characterized in terms of scale and morphology. Furthermore, it is harmonious with the beautiful landscape, humanity, and historical values and it can be suggested that it is qualified to be registered as a geoheritage structure.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.213-221
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• 2011

The purpose of this study is to clarify the characteristics of forms and distributions of Gapyoungchon potholes. Different sizes of 153 potholes were distributed in the upper stream marginal area that was 30×25m, and over 70 percent among them were egg-shaped potholes. A development of joint in pothole was not important to make potholes in the stream but the mean size of potholes with joint was larger than without joint. Moreover, the schistosity structure of the bedrock was more important factor to develop potholes in this area. Finally, four cross sectional faces were found in this study area. From the reason, Gapyoungchon potholes are distributed on the rock terraces.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.248-255
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• 2014

In this paper, we propose a pothole detection method in asphalt pavement using various features. Segmentation, candidate, and decision steps of pothole detection are processed according to the values which are derived from feature characteristics. Segmentation step, we use histogram and closing operation of morphology filter which extracts dark regions for pothole detection. Candidate step, we extract candidate regions of pothole using various features such as size, compactness, etc. Finally, decision step, candidate regions are decided whether pothole or not using comparison of pothole and background's features. Experimental results show that our proposed pothole detection method has better results than existing methods and good performance in discrimination of pothole and similar patterns.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.4
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• pp.249-255
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• 2022

Potholes are an important clue to the structural defects of asphalt pavement and cause many casualties and property damage. Therefore, accurate pothole detection is an important task in road surface maintenance. Many machine learning technologies are being introduced for pothole detection, and data preprocessing is required to increase the efficiency of deep learning models. In this paper, we propose a preprocessing method that emphasizes important textures and shapes in pothole datasets. The proposed preprocessing method uses intensity transformation to reduce unnecessary elements of the road and emphasize the texture and shape of the pothole. In addition, the feature of the porthole is detected using Superpixel and Sobel edge detection. Through performance comparison between the proposed preprocessing method and the existing preprocessing method, it is shown that the proposed preprocessing method is a more effective method than the existing method in detecting potholes.

• Tunnel and Underground Space
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• v.14 no.6 s.53
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• pp.411-422
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• 2004

Sinkhole subsidence occurs over abandoned mine workings and can be detrimental to human lives, damage to properties and other surface structures. In this study, simulation of sinkhole development process is performed using special finite element procedure. Especially, creation of mine voids due to roof falls and generation of goaf from broken rocks are simulated using active-passive-active finite elements. An active or solid element can be made passive or void once the tensile failure criterion is satisfied in the specified sinkhole formation zone. Upon completion of sinkhole development process, these passive elements in again be made active to simulate goal region. Several finite element models are analyzed to evaluate the relationships between sinkhole formation with width of gallery. depth of mine, roof condition and bulking factor of roof rocks. This study demonstrates that the concept of passive elements in numerical analysis can be used effectively for analyzing sinkhole formation or roof fall phenomenon in general.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.4
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• pp.104-114
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• 2016

Potholes have caused diverse problems such as wheel damage and car accident. A pothole detection technology is the most important to provide efficient pothole maintenance. The previous pothole detections have been performed by manual reporting methods. Thus, the problems caused by potholes have not been solved previously. Recently, many pothole detection systems based on video cameras have been studied, which can be implemented at low costs. In this paper, we propose a new pothole detection algorithm based on saliency map information in order to improve our previously developed algorithm. Our previous algorithm shows wrong detection with complicated situations such as the potholes overlapping with shades and similar surface textures with normal road surfaces. To address the problems, the proposed algorithm extracts more accurate pothole regions using the saliency map information, which consists of candidate extraction and decision. The experimental results show that the proposed algorithm shows better performance than our previous algorithm.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.161-168
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• 2013

Nowadays, one of the most interested area of automobile industry is the production of vehicle which has collision safety and ability to produce less amount of $CO_2$. The achievement of such a dual performance is done by choosing the materials like dual phase steel, ferrite bainite steel, etc. These steels have been used in automotive chassis and body parts, and also used to be formed by hole flanging to meet the goal of strength and design requirement. The formability of sheet material was experimented by hole expansion test and the judgement relies on human eye and his experience. This manual judgement involves many errors and large deviation. This paper develops the automatic crack recognition system which finds a crack based on CCD image to complement the problem of the current method depending on human's sense.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.6
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• pp.490-495
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• 2016

Pulsed eddy current (PEC) testing signals have typically been obtained from the electromotive force induced in a sensor coil. However, an increasing number of studies have elected to incorporate the Hall plate as a sensor. Thus, accurate numerical modeling of the Hall sensor signal is necessary. In this study, a PEC probe is designed and a numerical modeling program is written so that Hall sensor signals and coil sensor signals can be calculated simultaneously. First, a step current is used as the input current. The predicted Hall sensor signals show similar characteristics to those of the experimental signals reported by other researchers. The characteristics of the two types of signals are then analyzed and compared as the thickness of test object changes. The results show that the Hall sensor signal provides less information for evaluating the thickness of the test object than the coil sensor signal. The response signals from a pulsed input current are also calculated, and it is confirmed that an equivalent reversed signal pattern appeared after the pulse width at both signals.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.113-122
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• 2012

The geomorphic properties of potholes at Naerin River, Inje-gun are analyzed to discover the geosites of DMZ geopark in Gangwon-do. The furrow-type potholes along the river flow are mainly found in the P1 and P2 sites. The P3 site can be divided in to the zones where the furrow-type potholes densely distribute and various types of potholes are scattered, while the various types of small potholes are scattered in the P4 site. After measuring the 44 potholes, the potholes with a U-shaped cross-section, similar directivity with river flow and deposited gravels with in them show large values in length, width, depth and slope. Because the P1 and P2 sites are characteristic in the scales and forms of potholes and show beautiful scapes, it can be suggested that they are suitable for the geosite developments.