• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.44-44
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• 2010

In this presentation, noise control materials will be discussed from several points-of-view. First, materials will be categorized in terms of their intended function: i.e., as dissipative materials, as barriers, and as media intended to modify some aspect of the sound field. Within each category, example implementations will be described as will modeling procedures. In the context of barrier materials, recent developments in the area of metamaterials will be described briefly, and problems with some recently suggested approaches will be highlighted. Acoustical cloaking will be described as a method of modifying a sound field in such a way that a sensitive area is shielded from noise exposure; the practical difficulties of this approach will also be described. Finally, within each category of material and approach, a series of suggested research challenges will be described.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.5-14
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• 1998

In this paper we propose a new approach to the development of the automatic vision system to examine and repair the steam generator tubes at remote distance. In nuclear power plants, workers are reluctant of works in steam generator because of the high radiation environment and limited working space. It is strongly recommended that the examination and maintenance works be done by an automatic system for the protection of the operator from the radiation exposure. Digital signal processors are used in implementing real time recognition and examination of steam generator tubes in the proposed vision system. Performance of proposed digital vision system is illustrated by simulation and experiment for similar steam generator model.

• Journal of the Semiconductor & Display Technology
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• v.6 no.3
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• pp.25-33
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• 2007

A computationally efficient and accurate Monte Carlo (MC) simulator of electron beam lithography process, which is named SCNU-EBL, has been developed for semiconductor nanometer pattern design and fabrication. The simulator is composed of a MC simulation model of electron trajectory into solid targets, an Gaussian-beam exposure simulation model, and a development simulation model of photoresist using a string model. Especially for the trajectories of incident electrons into the solid targets, the inner-shell electron scattering of an target atom and its discrete energy loss with an incident electron is efficiently modeled for multi-layer resists and heterogeneous multi-layer targets. The simulator was newly applied to the development profile simulation of ZEP520 positive photoresist for NGL(Next-Generation Lithography). The simulation of ZEP520 for electron-beam nanolithography gave a reasonable agreement with the SEM experiments of ZEP520 photoresist.

• Toxicological Research
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• v.25 no.1
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• pp.9-15
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• 2009

Historically, research in toxicology has utilized non-human mammalian species, particularly rats and mice, to study in vivo the effects of toxic exposure on physiology and behavior. However, ethical considerations and the overwhelming increase in the number of chemicals to be screened has led to a shift away from in vivo work. The decline in in vivo experimentation has been accompanied by an increase in alternative methods for detecting and predicting detrimental effects: in vitro experimentation and in silico modeling. Yet, these new methodologies can not replace the need for in vivo work on animal physiology and behavior. The development of new, non-mammalian model systems shows great promise in restoring our ability to use behavioral endpoints in toxicological testing. Of these systems, the zebrafish, Danio rerio, is the model organism for which we are accumulating enough knowledge in vivo, in vitro, and in silico to enable us to develop a comprehensive, high-throughput toxicology screening system.

• Journal of Korean Association for Spatial Structures
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• v.20 no.4
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• pp.101-110
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• 2020

In case of stone pagoda structures, the various construction types appear, and various damages occur due to exposure to the outdoors for a long time. Such damages can be classified into non-structural damages and structural damages. However, studies for the effects of structural damages on stone pagoda structures are insufficient. Accordingly, this study intends to perform structural modeling and structural analysis according to structural damages of stone pagoda structure, and to perform risk analysis through the fragility curve. So, we expects that this study gives a great contribution to the preservation and maintenance of stone pagoda structures under the various structural damages.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.48.3-49
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• 2021

We study the process of panspermia in Milky Way-like galaxies by modeling the probability of successful travel of organic compounds between stars harboring potentially habitable planets. To this end, we apply the modified habitability recipe of Gobat & Hong (2016) to a model galaxy from the MUGS suite of zoom-in cosmological simulations. We find that, unlike habitability, which only occupies narrow dynamic range over the entire galaxy, the panspermia probability can vary be orders of magnitude between the inner (R, b = 1~4 kpc) and outer disk. However, only a small fraction of star particles have very large values of panspermia probability and, consequently, the fraction of star particles where the panspermia process is more effective than prebiotic evolution is much lower than from naïve expectations based on the ratio between panspermia probability and natural habitability. The lunar surface progressively darkens and reddens as a result of sputtering from solar wind particles and bombardment of micrometeoroids. The extent of exposure to these space weathering agents is frequently calculated as the location in a diagram of reflectance at 750 nm

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.1015-1024
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• 2019

In the medical field, X-rays are essential in the diagnosis and treatment of diseases, and the use of X-rays continues to increase with the development of imaging technology, but X-rays have the disadvantage of radiation exposure. Although lead protection tools are used in clinical practice to protect against radiation exposure, lead is classified as a heavy metal and can cause harmful reactions such as lead poisoning. Therefore, the purpose of this study is to investigate the usefulness of the shield fabricated using materials of FDM (Fused Deposition Modeling) 3D printer. In order to confirm the filament's line attenuation factor, phantoms were fabricated using PLA, XT-CF20, Wood, Glow and Brass, and CT scan was performed. And the shielding sheet of 100 × 100 × 2 mm size was modeled, the dose and shielding rate was measured by using a diagnostic X-ray generator and irradiation dose meter, and the shielding rate with lead protection tools. As a result of the experiment, the CT number of the brass was measured to be the highest, and the shielding sheet was manufactured by using the brass. As a result of confirming with the diagnostic X-ray generator, the shielding rate was increased in the shielding sheet having a thickness of 6 mm upon X-ray irradiation under the condition of 100 kV and 40 mAs. It measured by 90% or more, and confirmed that the shielding rate is higher than apron 0.25 mmPb. As a result of this study, it was confirmed that the shield fabricated by 3D printing technology showed high shielding rate in the diagnostic X-ray region. there was.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.3
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• pp.299-305
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• 2019

This study was initiated to solve the difficulties of aged and female workers in agriculture society due to aging and demise of young people. In the case of the conventional elevated lift, the risk of exposure to uneven road or work environment, not the difficulty of professional qualification and operation, and the risk of exposure to the uneven road or working environment, were also studied based on previous researches so that women could easily and efficiently perform productive agriculture. First, the simulation was carried out through the prediction model of traction performance using the object of agricultural forklift, and the soil of the Kimhae city in Gyeongnam (34.125kPa, internal friction angle 35.294deg, external friction angle 13.620deg, Adhesion force 5.750 kPa, average cone index 0-15 cm cl, 1001.8 kPa). In the case of the forklift for simulation, the driving force and the kinetic resistance prediction modeling of the agricultural electric forklift are modeled. Based on this model, the motor control drive adopts the 1232E model, which is a drive dedicated to AC motor, and divides the two drivers into master and slave And the model for the simulation was designed to control motor drive, hydraulic drive, and various outputs on the main PCB. The simulation model is undergoing continuous simulation, modification and supplementation. Based on this research, we will continue research for development of safer and more efficient agricultural electric forklift.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.4
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• pp.348-356
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• 2014

To understand the relationship between road-traffic noise and urban components such as population, building, road-traffic and land-use, the city of Cheongju that already has road-traffic noise maps of daytime and nighttime was selected for this study. The whole area of the city is divided into square cells of a uniform size and for each cell, the urban components are estimated. A spatial representative noise level for each cell is determined by averaging out population-weighted facade noise levels for noise exposure population within the cell during nighttime. The relationship between the representative noise level and the urban components is statistically modeled at the cell level. Specially, we introduce a spatial auto regressive model and a spatial error model that turns out to explain above 85 % of the noise level. These findings and modeling methods can be used as a preliminary tool for environmental planning and urban design in modern cities in consideration of noise exposure.

• Safety and Health at Work
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• v.10 no.1
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• pp.109-113
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• 2019

Background: In both developed and developing countries, noise is regarded as the most common occupational hazard in various industries. The present study aimed to examine the effect of sound pressure level (SPL) on serum cortisol concentration in three different times during the night shift. Methods: This case-control study was conducted among 75 workers of an industrial and mining firm in 2017. The participants were assigned to one of the three groups (one control and two case groups), with an equal number of workers (25 participants) in each group. Following the ISO 9612 standard, dosimetry was adopted to evaluate equivalent SPL using a TES-1345 dosimeter. The influence of SPL on serum cortisol concentration was measured during the night shift. The serum cortisol concentration was measured using a radioimmunoassay (RIA) test in the laboratory. Repeated measure analysis of variance and linear mixed models were used with ${\alpha}=0.05$. Results: The results indicated a downward trend in the serum cortisol concentration of the three groups during the night shift. Both SPL and exposure time significantly affected cortisol concentration (p < 0.0001, p < 0.0001). Conversely, age and body mass index had no significant influence on cortisol concentration (p = 0.360, p = 0.62). Conclusion: Based on the obtained results, increasing SPL will lead to enhancement of serum cortisol concentration. Given that cortisol concentration varies while workers are exposed to different SPLs, this hormone can be used as a biomarker to study the effect of noise-induced stress.