• Wind and Structures
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• v.13 no.2
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• pp.95-108
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• 2010

This review paper discusses research from the last few years relating to windborne debris risk models and the essential elements of engineering damage prediction models. Generic types of windborne debris are discussed. The results of studies of debris trajectories that are relevant to damage models are described - in particular the horizontal component of debris velocity as a function of distance travelled. The merits of impact momentum versus impact kinetic energy as a relevant parameter for predicting damage are considered, and how published data from generic cannon Impact tests can be used in risk models. The quantitative variation of debris impact damage with wind speed is also discussed. Finally the main elements of previously-proposed debris damage models are described.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.202-206
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• 2001

In this study, the risk assessment of small reservoir by collapse using GIS is evaluated. Direct damage distance from collapsed reservoir is estimated by empirical USBR equations and submerged area is calculated by USBR's idea. The amount of damage by collapsed reservoir is figured out by damage assessment of National Institute for Disaster Prevention.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.37
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• pp.30.1-30.7
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• 2015

Background: The inferior alveolar nerve (IAN) may be injured during extraction of the mandibular third molar, causing severe postoperative complications. Many methods have been described for evaluating the relative position between the mandibular third molar and the inferior alveolar canal (IAC) on panoramic radiography and computed tomography, but conventional radiography provides limited information on the proximity of these two structures. The present study assessed the benefits of three-dimensional computed tomography (3D-CT) prior to surgical extraction of the mandibular third molar, to prevent IAN damage. Methods: This retrospective study included 4917 extractions in 3555 patients who presented for extraction of the mandibular third molars. The cases were classified into three groups, according to anatomical relationship between the mandibular third molars and the IAC on panoramic radiography and whether 3D-CT was performed. Symptoms of IAN damage were assessed using the touch-recognition test. Data were compared using the chi-square test and Fisher's exact test. Results: Among the 32 cases of IAN damage, 6 cases were included in group I (0.35 %, n = 1735 cases), 23 cases in group II (1.1 %, n = 2063 cases), and 3 cases in group III (0.27 %, n = 1119 cases). The chi-square test showed a significant difference in the incidence of IAN damage between groups I and II. No significant difference was observed between groups I and III using Fisher's exact test. In the 6 cases of IAN damage in group I, the mandibular third molar roots were located lingual relative to the IAC in 3 cases and middle relative to the IAC in 3 cases. The overlap was ${\geq}2mm$ in 3 of 6 cases and 0-2 mm in the remaining 3 cases. The mean distance between the mandibular third molar and IAC was 2.2 mm, the maximum distance 12 mm, and the minimum distance 0.5 mm. Greater than 80 % recovery was observed in 15 of 32 (46.8 %) cases of IAN damage. Conclusions: 3D-CT may be a useful tool for assessing the three-dimensional anatomical relationship and proximity between the mandibular third molar and IAC in order to prevent IAN damage during extraction of mandibular third molars.

• Current Optics and Photonics
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• v.7 no.1
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• pp.1-14
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• 2023

Wavefront-coding imaging can achieve high-quality imaging along with a wide range of defocus. In this paper, the anti-laser detection and damage performance of wavefront-coding imaging systems using different asymmetric phase masks are studied, through modeling and simulation. Based on FresnelKirchhoff diffraction theory, the laser-propagation model of the wavefront-coding imaging system is established. The model uses defocus distance rather than wave aberration to characterize the degree of defocus of an imaging system. Then, based on a given defocus range, an optimization method based on Fisher information is used to determine the optimal phase-mask parameters. Finally, the anti-laser detection and damage performance of asymmetric phase masks at different defocus distances and propagation distances are simulated and analyzed. When studying the influence of defocus distance, compared to conventional imaging, the maximum single-pixel receiving power and echo-detection receiving power of asymmetric phase masks are reduced by about one and two orders of magnitude respectively. When exploring the influence of propagation distance, the maximum single-pixel receiving power of asymmetric phase masks decreases by about one order of magnitude and remains stable, and the echodetection receiving power gradually decreases with increasing propagation distance, until it approaches zero.

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.42-45
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• 2007

This paper is estimation of structure damage caused by VCE(Vapor Cloud Explosion) in enclosure. As we estimate the influence of damage which occur at gas facility in factory. We can utilize it the elementary data of safety distance. In this study, the influence of explosion over-pressure caused by VCE in enclosure was calculated by using the Hopkinson's scaling law and the accident damage was estimated by applying the influence on the adjacent structure into the probit model. As a result of the damage estimation conducted by using the probit model, both the damage possibility of explosion overpressure to structures 20 meters away and that of overpressure to glass bursting 80m meters away showed nothing.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.39-39
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• 2011

This study presents an effective vision-based system for cable bridge damage detection. In theory, cable bridges need to be inspected the outer as well as the inner part. Starting from August 2010, a new research project supported by Korea Ministry of Land, Transportation Maritime Affairs(MLTM) was initiated focusing on the damage detection of cable system. In this study, only the surface damage detection algorithm based on a vision-based system will be focused on, an overview of the vision-based cable damage detection is given in Fig. 1. Basically, the algorithm combines the image enhancement technique with principal component analysis(PCA) to detect damage on cable surfaces. In more detail, the input image from a camera is processed with image enhancement technique to improve image quality, and then it is projected into PCA sub-space. Finally, the Mahalanobis square distance is used for pattern recognition. The algorithm was verified through laboratory tests on three types of cable surface. The algorithm gave very good results, and the next step of this study is to implement the algorithm for real cable bridges.

• Analytical Science and Technology
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• v.27 no.3
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• pp.147-152
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• 2014

RUVIS(Reflective Ultraviolet Imaging System) is an effective equipment that detects the location of latent fingerprint at crime scene using short wavelength ultraviolet of 254 nm. In this study, the degree of DNA damage in biological samples was compared depending on the distance and time of processing using four commonly used RUVIS. 50% of DNA was damaged by treating 10 seconds at 10 cm distance in 3 types of RUVIS such as Police RUVIS, SIRCHIE mini light and SIRCHIE RUVIS. In addition, the degree of DNA damage was increased as the distance was closer and the treatment time was longer. It showed that short wavelength UV could cause DNA damage when used close to the samples at crime scene. Therefore, it was suggested to use RUVIS at a distance of at least 1 m. The degree of DNA damage was not significant by Polilight which used long wavelength ultraviolet of 350 nm. As a result, the choice and usage of which UV light and RUVIS were critical for detection of fingerprint and successful DNA typing.

• Korean journal of applied entomology
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• v.47 no.2
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• pp.127-131
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• 2008

Ambrosia beetle, Platypus koryoensis, is a vector of oak wilt disease caused by Raffaelea sp. in Korea. The degree of damage by oak wilt disease was dependent on the density of the beetles in the oak trunk, a relationship between the degree of damage by oak wilt disease and the density of beetle on the basis of the number of entry hole was studied. Entry hole distribution within tree trunk was analyzed by the nearest neighbor method. Thirty four oak trees (Quercus mongolica) located in survey area were selected and then degree of damage, the number of attack hole/$623cm^2$ in upper (50cm from the surface) and lower (surface) trunk and the nearest neighbor distance between the holes were measured. The number of hole and the nearest neighbor distance in upper and lower part were positively correlated with each other. As the degree of damage was severer, the number of the holes increased, whereas the nearest neighbor distance decreased. The distribution pattern of the hole was changed from clumped one to uniform as the severity of damage increased. These results suggested that Platypus koryoensis attacked the oak tree in concentrative manner at initial stage of attack but at final stage, it distributed uniformly to reduce intraspecific competition between the beetles.

• Smart Structures and Systems
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• v.3 no.2
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• pp.201-217
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• 2007

An active damage detection technique is introduced to locate damage in an isotropic plate using Lamb waves. This technique uses a time-domain energy model of Lamb waves in plates that the wave amplitude inversely decays with the propagation distance along a ray direction. Accordingly the damage localization is formulated as a least-squares problem to minimize an error function between the model and the measured data. An active sensing system with integrated actuators/sensors is controlled to excite/receive $A_0$ mode of Lamb waves in the plate. Scattered wave signals from the damage can be obtained by subtracting the baseline signal of the undamaged plate from the recorded signal of the damaged plate. In the experimental study, after collecting the scattered wave signals, a discrete wavelet transform (DWT) is employed to extract the first scattered wave pack from the damage, then an iterative method is derived to solve the least-squares problem for locating the damage. Since this method does not rely on time-of-flight but wave energy measurement, it is more robust, reliable, and noise-tolerant. Both numerical and experimental examples are performed to verify the efficiency and accuracy of the method, and the results demonstrate that the estimated damage position stably converges to the targeted damage.

• Journal of the Korean Society of Safety
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• v.25 no.1
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• pp.44-49
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• 2010

This paper is estimation of structure damage caused by Explosion in LPG(Liquefied Petroleum Gas) filling station. As we estimate the influence of damage which occur at gas storage tank in filling station. We can utilize the elementary data of safety distance. In this study, the influence of over-pressure caused by VCE(Vapor Cloud Explosion) in filling station was calculated by using the Hopkinson's scaling law and the accident damage was estimated by applying the influence on the adjacent structure into the probit model. As a result of the damage estimation conducted by using the probit model, both the damage possibility of explosion overpressure to structures of max 265 meters away and to glass bursting of 1150 meters away was nearly zero in open space explosion.