• Steel and Composite Structures
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• v.48 no.3
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• pp.305-320
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• 2023

The mechanical properties of polymeric composites are degraded under elevated temperatures due to the effect of temperature on the mechanical behavior of the resin and resin fiber interfaces. In this study, the effect of temperature on the impact response of the carbon fiber reinforced plastics (CFRP) was investigated at low-velocity impact (LVI) using a drop-weight impact tester machine. All the composite plates were fabricated using a vacuum infusion process with a stacking sequence of [45/0_2/-45/90_2]s, and a thickness of 2.9 mm. A group of the specimens was exposed to an environment with a temperature cycling at the range of -30 ℃ to 65 ℃. In addition, three other groups of the specimens were aged at ambient (28 ℃), -30 ℃, and 65 ℃ for ten days. Then all the conditioned specimens were subjected to LVI at three energy levels of 10, 15, and 20 J. To assess the behavior of the damaged composite plates, the force-time, force-displacement, and energy-time diagrams were analyzed at all temperatures. Finally, radiography, optical microscopy, and scanning electron microscopy (SEM) were used to evaluate the effect of the temperature and damages at various impact levels. Based on the results, different energy levels have a similar effect on the LVI behavior of the samples at various temperatures. Delamination, matrix cracking, and fiber failure were the main damage modes. Compared to the samples tested at room temperature, the reduction of temperature to -30 ℃ enhanced the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. The temperature increasing to 65 ℃ increased the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. Applying 200 thermal cycles at the range of -30 ℃ to 65 ℃ led to the formation of fine cracks in the matrix while decreasing the absorbed energy. The maximum contact force is recorded under cyclic temperature as 5.95, 6.51 and 7.14 kN, under impact energy of 10, 15 and 20 J, respectively. As well as, the minimum contact force belongs to the room temperature condition and is reported as 3.93, 4.94 and 5.71 kN, under impact energy of 10, 15 and 20 J, respectively.

• Nuclear Engineering and Technology
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• v.38 no.5
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• pp.449-454
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• 2006

Neutron imaging technique was used to investigate the water distribution and movement in Polymer Electrolyte Membrane Fuel Cell (PEMFC) at HANARO, KAERI. The Feasibility tests were performed in the first and second exposure rooms at the neutron radiography facility (NRF) at HANARO in order to check the ability of each exposure room, respectively. The feasibility test apparatus was composed of water and pressurized air before making up the actual test apparatus. Due to the low neutron intensity in the second exposure room, the exposure time was too long to investigate the transient phenomena of PEMFC. Although the exposure time was improved to 0.1 sec in the first exposure room, it was difficult to discriminate detail water movement at the channel due to the high noise level. Therefore, the experimental setup must be optimized according to the test conditions. Water discharge characteristics were investigated under different flow field geometries by using feasibility test apparatus and the neutron imaging technique. The water discharge characteristics of a 3-parallel serpentine are superior to those of a 1-parallel serpentine, but water at Membrane Electrode Assembly (MEA) was not removed, regardless of the flow field type.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.212-218
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• 2013

A transfer method of neutron radiography was developed to measure the size of the end plug and a gap of an intact K102L-2, the irradiated fuel of a ballooned K174L-3, a ballooned and ruptured K98L-3. A typical irradiation time of 25 min. was determined to obtain a film density of between 2 and 3 of SR X-ray film with neutrons of $1.5{\times}10^{11}n{\cdot}cm^{-2}$. To validate and calibrate the results, a RISO fuel standard sample, Cd plate and ASTM-BPI/SI were used. An activated latent image formed in the $100{\mu}m$ Dy foil was subsequently transferred in a dark room for more than 8 hours to the SR film which is a maximum of three half-lives. Due to the L/D ratio an unsharpness of $9.82-14{\mu}m$ and a magnification of 1.0003 were given. After digitizing an image of SR film, the ballooning gap of the plug was discernible by an H/V filter of image processing. The gap size of the ballooned element, K174L-3, is equal to or greater than 1.2 mm. The development of a transfer method played a pivotal role in developing high burn-up of Wolsung and PWR nuclear fuel type.

• Journal of the Korean Society of Radiology
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• v.16 no.2
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• pp.177-184
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• 2022

The purpose of this study is surveyed diagnostic radiography (DR) examination in veterinary hospital (VC) including non-ionization radiation such as ultra-sonography and magnetic resonance imaging. From June 1 to June 20. 2021, we surveyed the VC in 00 metropolitan city by using a structural questionnaire which are location of VC and X-ray unit et al.. Data are expressed as a mean with standard deviation for continuous variable or percent for categorical variable using SPSS ver. 26.0. As the first animal to be visited, dogs were the highest with 61.9%, followed by cats with 12.9%. In 87.1% fo cases, DR units were used, and 4 VCs did not. In 27 VCs using DR units, 48.1% separated examination room and control room, 19.8% examined in animal visited, protective clothing was in all VCs, 55.6% were measured radiation exposure dose, 92.6% was responded a necessary for examination education. From the above results, it will help to revise the guidelines for DR units and examination in korea VCs.

• Journal of Korean Critical Care Nursing
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• v.13 no.1
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• pp.15-26
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• 2020

Purpose : This study aimed to examine factors affecting radiation protective behaviors among emergency room nurses by assessing knowledge, attitude, and environment for radiation protection. Methods : The study employed a cross-sectional design. Subjects were a convenience sample of 129 nurses working in emergency rooms of three general hospitals. Data were collected using self-report questionnaires and analyzed using t-test, ANOVA, Pearson correlation coefficients, and multiple regression. Results : The more the nurses received radiation safety education (t=2.26, p=.026), used protective gear (t=4.40, p<.001), and took health screenings (t=2.65, p=.009), the higher their levels of radiation protection behavior. There were significant relations between radiation protective behaviors and attitude (r=.27, p=.002), and radiation protective behaviors and environment for radiation protection (r=.55, p<.001). The factors affecting radiation protective behaviors were protective environment (β=.53, p<.001), protective attitude (β=.32, p<.001), and the use of protective gear (β=.24, p=.002). Conclusions : The government, hospital administrators, and radiation protection-related organization should adopt the following measures to protect emergency room nurses from radiation: research and development of shield instrument, medical examination for emergency room nurses, protocol development of radiation protection behaviors, extension of education chances of radiation protection, and encouraging the use of protective equipment.

• Journal of radiological science and technology
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• v.46 no.1
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• pp.53-61
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• 2023

The aim of this study analyzed the important level (IL) and understanding level (UL) including the Borich's need for students preparing of the national examination for radiological technologists at online open chatting room. A total of 254 survey were collected from a total of 1,016 students who used open chatting room from December 13 to December 16, 2022. A general characteristics were the age, gender, curriculum (3 or 4 years), grade and area. The IL, UL, learning satisfaction (LS), learning achievement (LA) and intention to continue using (ICU) were analyzed by using the 5 point Likert scale. There was no significant difference the LS, LA, and ICU according to general characteristics (p>0.05). There was a statistically significant difference a total of sixteen subjects based on the t-test results of the response values from the IL and UL (p<0.05). The total of ten subjects with the highest priority in the Locus for Focus models were the Ultrasonography, Human anatomy, Magnetic resonance imaging, Radiation therapy, Cardiovascular and intervention, Computed tomography, Human physiology, Radiographic imaging, Fluroscopic radiography, and Nuclear medicine) that the Borich's need was also the same as the top 10 ranked subjects. The LS (4.23±0.72), LA (4.18±0.73), and ICU (4.15±0.78) for open chatting room were high. This study identified the subjects most needed by college students by the Borich's need analysis. First, it is necessary to provide intensive education on subjects with high scores that are most needed by college students. Second, it is necessary to improve the teaching method for subjects with low need and low level of understanding.

• Korean Journal of Digital Imaging in Medicine
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• v.3 no.1
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• pp.52-58
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• 1997

Before entering 21st Century, modern medical science is requiring more precise display which is highly estimated in diagnostic value as radial science technology is achieving sharp development. And it is also trying to contribute to improve national health and to offer better service by reducing radial exposure. General projection and Fluoroscopy which are most difficult to be displayed in digital tend to change their way ; from analog to digital with development of Electronic Engineering and Computer Technology, Introducing to CR system in 1994, SMC have displayed General projection and Fluoroscopy 100% in digital using CR system. This study searched differences between repeat rate, repeat type in the exam using Film/Screen and those in the exam using CR system. According to the analysis of repeat types and repeat rate of Film which was reused by using CR system in general projection room and Fluoroscopy room of SMC, we found that total 192,813 films were used and 2,097 films, 1.09% of total were reused. However, actual repeat covers 0.76% to 1,461 sheets with the exception of 636sheets. As above, display process using CR system is 0.76% much lower than general repeat rate 2$\sim$4% of Film/Screen exam. Besides decreased under/over exposure, it is appeared that position failure rate in repeat rate 0.76% covers relatively high 31%. Noticing that repeat caused unskilled devices handing was found many times, sufficient understanding seems to be required to reduce repeat.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.174-179
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• 2001

In order to investigate the fracture behaviors(perforation modes) and resistance to perforation during ballistic impact of aluminum alloy plate, ballistic tests were conducted. Depth of penetration experiments with 5.56mm-diameter ball projectile launched into 25mm-thickness Al 5052-H34 targets were conducted. A powder gun launched the 3.55g projectiles at striking velocities between 0.6 and 1.0 km/s. radiography of the damaged targets showed different penetration modes as striking velocities increased. Resistance to perforation is determined by the protection ballistic limit($V_{50}$), a statistical velocity with 50% probability for complete perforation. Fracture behaviors and ballistic tolerance, described by perforation modes, are respectfully observed at and above ballistic limit velocities, as a result of $V_{50}$ test and Projectile Through Plates (PTP) test methods. PTP tests were conducted with $0^{\circ}$ obliquity at room temperature using 5.56mm ball projectile. $V_{50}$ tests with $0^{\circ}$ obliquity at room temperature were conducted with projectiles that were able to achieve near or complete perforation during PTP tests. The effect of various impact velocity are studied with depth of penetration.

• Journal of Chest Surgery
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• v.31 no.12
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• pp.1243-1246
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• 1998

Tracheobronchial injuries are uncommon. Except for the cervical region, most tracheobronchial injuries are due to blunt chest trauma in Korea. The depth of the tracheobronchial trees renders these structures relatively safe from stab wound. We experienced a case of left main bronchial laceration with azygos vein tear following stab wound in the back of right chest firstly in Korea. The patient was a 24 years old male. A routine chest radiography showed a knife in chest at emergency room. We didn't remove the knife at emergency room. This patient was carried to operation room in 30 minutes after arrival of our hospital without computed tomography and bronchoscopy. The operation was performed through standard right posterolateral thoracotomy and then the knife was removed. The left main bronchus and azyos vein were lacerated obliquely. The penetrated azygos vein was ligated and the laceration of the left main bronchus was repaired. Postoperative course was uneventful.

• Tuberculosis and Respiratory Diseases
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• v.72 no.2
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• pp.140-148
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• 2012

Background: Detection and treatment of tuberculosis (TB) infection with contact investigation is a key component of TB control program. I evaluated the prevalence and risk factors for TB infection among contacts of recently diagnosed pulmonary TB patients in a tertiary hospital in Korea. Methods: 206 contacts of 90 adult pulmonary TB patients underwent tuberculin skin tests (TST) and chest radiography. The TST results were considered positive with an induration of 10 mm or more, suggesting TB infection. A standardized questionnaire was used to assess risk factors associated with TB infection. Results: TST was positive in 97 of 206 contacts of TB patients (47.1%) and positive rate of TST increased with age. The risk of TB infection was significantly associated with close contact with TB patients (sleeping in the same room) (odd ratio [OR], 4.94; 95% confidence interval [CI], 1.43~17.00). Conclusion: TB infection rate was higher in the elderly, and the risk of TB infection was significantly increased with close contact of TB patients.