Steel plate shear walls (SPSWs) have been recognized as an effective seismic-force resisting systems due to their excellent strength and stiffness characteristics. The infill steel plate in a SPSW is constrained by a boundary frame consisting of vertical and horizontal structural members. The main purpose of this study was to investigate deformation modes and hysteretic characteristics of steel plate shear walls (SPSWs) to consider the effects of their aspect ratios and width-to-thicness ratios. The finite element model (FEM) was establish in order to simulate cyclic responses of SPSWs which have the two-side clamped boundary condition and made of conventional steel grade. The stress distribution obtained from the FEA results demonstrated that the principal stresses on steel plate with large thickness-to-width ratio were more uniformly distributed along its horizontal cross section due to the formation of multiple struts.

Since the decrease of skid resistance of the road surface due to the effects of hydroplaning increases the ratio of vehicle crashes significantly, it is important to predict water film thickness (WFT). Tined is one of the widely used textures for concrete pavements. Since previous WFT models have been developed based on the asphalt pavement texture and broom concrete, it may not give reliable predictions for Water film thickness for tinned concrete. Furthermore, surface flow on tined texture may show hydraulically different characteristics due to the geometric characteristics of tined texture. This study aims to propose a reliable water film thickness prediction model for tined concrete. Three test slabs including a smooth surface, a tined surface with 16mm spacing, and a tined surface with 25mm spacing were prepared. WFTs of the test slab were measured for various conditions such as pavement slope (0-10%), rainfall intensity (0-130mm/h), and drainage path length (0-5m). A statistical model was proposed to predict water film thickness (WFT) as a function of pavement slope, rainfall intensity, drainage path length, and mean texture depth. This model exhibits strong agreement with the experimental test results. The GWNU prediction model consistently provides reliable predictions with the actual WFT for tined concrete pavement. Conversely, the previous equation consistently underestimated the water film thickness, notably on tined surfaces with 16 mm and 25 mm spacing, due to the occurrence of viscous flow along the tined lines.

여름철은 타 계절에 비해 장마와 불안정한 대기 등으로 인하여 빗길 교통사고의 위험성이 크게 증대될 수 있으며, 최근 5년 (2018~2022)간 여름철 빗길 교통사고는 전체 빗길 교통사고의 39%를 차지할 정도로 높은 수준이다. 이러한 빗길 운전은 노면의 배수 불량 및 미끄럼 저항 감소 등으로 인하여 수막현상을 발생시키게 된다. 이에 본 연구에서는 우천 시 도로의 안전성 강화 및 사고 위 험을 최소화하기 위한 요소인 수막두께를 산정하기 위하여 Manning의 평균 유속식을 기반으로 콘크리트 노면의 조도계수 예측 모델을 개발하는 것을 목표로 하였다. 조도계수의 영향인자를 고려하기 위하여 실외 강우 모의 장비를 이용하여 콘크리트를 타설한 뒤 실험 인자로 포장 경사, 배수거리, 강우강도, 노면 조직 특성을 고려하였으며, 이 중 노면 조직 특성은 타이닝 처리를 하지 않은 구간만 고 려한 타 연구의 기존 예측 모델 단점을 보완하기 위하여 16, 25mm 간격의 타이닝 표면 처리한 구간을 추가로 고려하였다. 수막두께 측정은 측정 범위 0.3~5mm의 수막두께 측정 게이지를 제작하여 강우가 모사된 조건에서 배수 거리 1~5m 이내 지점의 노면 조직 상 단과 수면이 접하는 수직 높이를 총 3회 측정하여 평균값을 사용하였다. 실측된 수막두께 데이터베이스를 기반으로 Manning 공식을 이용하여 조도계수를 역산한 결과, 강우강도가 증가함에 따라 조도계수는 감소하였으며, 이는 강우의 증가로 인해 물의 흐름과 콘크리 트 노면 사이의 마찰 저항 감소에 기인한 것으로 판단되었다. 또한 포장 경사가 높고 배수 거리가 짧을수록 배수성이 증가하여 마찰 저항의 지표인 조도계수가 증가하는 것으로 확인되었다. 평균 조직 깊이에 따른 조도계수 영향의 경우, 평균 조직 깊이가 증가할수록 콘크리트 표면에 노출되는 표면적이 증가하여 수막두께가 얕게 생성되고, 얕은 수심으로 인해 물의 흐름 저항이 감소하여 조도계수는 감소하는 것으로 산정되었다. 이후 135개의 데이터를 종합하여 조도계수를 종속변수로 하고 강우강도, 포장경사, 배수거리, 평균 조직 깊이, 수막두께를 독립변수로 하는 회귀분석을 수행하여 조도계수 산정식을 개발하였다.

The Derived Concentration Guideline Level (DCGL) is required to release the facility from the nuclear safety act at the stage of site restoration of the decommissioning nuclear power plant. In order to evaluate DCGL, there are various requirements, and among them, the selection of input parameters based on the application scenario is the main task. Especially, it is important to select input parameters that reflect site characteristics, and at this time, a single deterministic value or a probabilistic distribution can be applied. If it is inappropriate to apply a particular single value, it may be reasonable to apply various distributions, and the RESRAD code provides for evaluation using probabilistic methods. Therefore, this study aims to analyze the difference between the application of the deterministic method and the application of the probabilistic method to the area and thickness of the contaminated zone among the site characteristics data. This study analyzed the thickness and area of the contaminated zone, and in the case of thickness, the deterministic method was applied by changing the thickness at regular intervals from the minimum depth considered by MARSSIM to the thickness of the unsaturated zone identified in previous research data. In addition, a probabilistic analysis was performed by applying a distribution to the thickness of contaminated zone. Second, for the area of the contaminated zone, the dose was evaluated for each area in consideration of the areas to be considered when deriving Area Factor (AF), and the resulting change in DCGL was observed. As a result, the DCGL tends to decrease as the thickness increases, and it seems to be saturated when the thickness exceeds a certain thickness. Therefore, It was confirmed that the level of saturated values is similar to that of entering a probabilistic distribution, and in the case of a parameter that is reasonable to enter as a distribution rather than as a single value, it is sufficiently conservative to perform a probabilistic evaluation. In the case of area change, the DCGL evaluation result showed that the DCGL increased as the scale decreased. The magnitude of the change varies depending on the characteristics of each radionuclide, and in the case of radionuclides where external exposure gamma rays have a major exposure effect, the change is relatively small. It can be seen that the change in DCGL according to the area has the same tendency as the AF applicable to the survey unit for small survey units applied in the final status survey.

The types of fuel loaded and burned in domestic nuclear power plants are WH-type and OPR/ APR-type nuclear power plants, with a total of 19 types. In the case of spent nuclear fuel released in Korea, the low combustion level of 45,000 MWD/MTU or less accounts for about 75%. In terms of fuel type, WH 17×17 and CE 16×16 fuels account for about 85% of all spent nuclear fuels. The thickness of the oxide film of the fuel cladding can make the fuel rod vulnerable during reactor operation, directly affecting the integrity of the fuel rods. so, it is a very important design factor in design. Therefore, the fuel rod design code that predicts and evaluates this has also been developed to accurately predict fuel rod corrosion. And it’s being applied to the design. In this study, the ECT probe measured by inserting it between fuel rods. The thickness of the fuel cladding oxide film was measured for spent nuclear fuel. When reloading operational nuclear fuel, the IAEA recommends an oxide film thickness of up to 100 micrometers. In this study, it was confirmed that spent nuclear fuels keeping integrity burned for 2-3 cycles were sufficiently maintained within the limit. However, the difference could be confirmed according to the characteristics of the coating material, the combustion cycle, and the use of poison rods. For the reliability of the data, symmetrical to the quadrant fuels were selected, and the fuel burned at the same period was measured. The method of selecting the target fuel can produce meaningful results.

PURPOSES : This study provides fundamental information on the temperature variations in tunnel structures during severe fire events. A fire event in a tunnel can drastically increase the internal temperature, which can significantly affect its structural safety. METHODS : Numerical simulations that consider various fire conditions are more efficient than experimental tests. The fire dynamic simulator (FDS) software, based on computational fluid dynamics (CFD) and developed by the National Institute of Standards and Technology, was used for the simulations. The variables included single and multiple accidents involving heavy goods vehicles carrying 27,000 liters of diesel fuel. Additionally, the concrete material characteristics of heat conductivity and specific heat were included in the analysis. The temperatures of concrete were investigated at various locations, surfaces, and inside the concrete at different depths. The obtained temperatures were verified to determine whether they reached the limits provided by the Fire Resistance Design for Road Tunnel (MOLIT 2021). RESULTS : For a fire caused by 27,000 liters of diesel, the fire intensity, expressed as the heat release rate, was approximately 160 MW. The increase in the carrying capacity of the fire source did not significantly affect the fire intensity; however, it affected the duration of the fire. The maximum temperature of concrete surface in the tunnel was approximately 1400 ℃ at some distance away in a longitudinal direction from the location of fire (not directly above). The temperature inside the concrete was successfully analyzed using FDS. The temperature inside the concrete decreased as the conductivity decreased and the specific heat increased. According to the Fire Resistance Design for Road Tunnel (MOLIT 2021), the internal temperatures should be within 380 ℃ and 250 ℃ for concrete and reinforcing steel, respectively. The temperatures were found to be approximately 380 ℃ and 100 ℃ in mist cases at depths of 5 cm and 10 cm, respectively, inside the concrete. CONCLUSIONS : The fire simulation studies indicated that the location of the maximum temperature was not directly above the fire, possibly because of fire-frame movements. During the final stage of the fire, the location of the highest temperature was immediately above the fire. During the fire in a tunnel with 27,000 liters of diesel, the maximum fire intensity was approximately 160 MW. The capacity of the fire source did not significantly affect the fire intensity, but affected the duration. Provided the concrete cover about 6 cm and 10 cm, both concrete and reinforcing steel can meet the required temperature limits of the Fire Resistance Design for Road Tunnel (MOLIT 2021). However, the results from this study are based on a few assumptions. Therefore, further studies should be conducted to include more specific numerical simulations and experimental tests that consider other variables, including tunnel shapes, fire sources, and locations.

목적 : 본 연구는 RGP 렌즈 착용 상태에서 렌즈후면과 각막전면에 존재하는 눈물층의 두께와 눈물의 굴절력을 측정하였다. 방법 : 본 연구의 대상자는 20명(평균연령 23.02±1.89세)이 참여하였다. 각 참여자는 각막곡률의 측정값에 따 라 피팅상태가 flat fit, alignment fit, steep fit이 되도록 3개의 다른 BC의 RGP를 피팅하였다. RGP렌즈를 착 용한 상태에서 OCT로 눈물층 두께 측정, 자동굴절계를 이용하여 눈물렌즈의 굴절력을 측정하였다. 결과 : 측정결과 베이스 커브에 따라 발생한 렌즈 후면과 각막 간의 눈물층 높이의 평균값은 플랫한 피팅 상태 에서는 6.20±1.06 μm, 정렬된 피팅상태에서는 9.10±1.55 μm, 스팁한 피팅상태에서는 12.5±1.50 μm으로 통 계적으로 유의한 차이가 나타났다(F(2, 57)=103.05, p<0.010). 피팅상태에 따라 생성된 눈물렌즈의 굴절력은 플 랫 피팅인 경우 –0.85±0.75 D, 정렬된 경우 –0.48±0.85 D, 스팁 피팅인 경우 +1.56±0.77 D로 통계적 으로 유의하게 나타났다(F(2, 57)=53.71,p<0.010). 3가지 피팅에 따라서 RPG 렌즈 후면과 각막전면의 있는 눈 물 렌즈의 두께와 눈물 렌즈로 생성된 굴절력과의 상관관계 분석에서 r=0.58로 다소 높은 상관관계를 보였다. 결론 : 본 연구에서는 정렬된 피팅이 된 경우, 최소의 굴절력 조정이 요구되며, 반면 스팁한 피팅인 경우 더 많 은 조정이 필요하다.

Background: People these days use smartphone extensively as a means of diverse social activities, but excessive use of it has also created increasing forward head posture (FHP) with neck pain. To improve this FHP, neck stabilization exercise is necessary. Objectives: This study was to investigate the effects of stabilization exercise using biofeedback on FHP subjects with neck pain. Design: A non-randomized, controlled intervention study. Methods: This study chose 18 college students in their 20s whose neck disability index (NDI) was equal to or higher than 10 and cranio-vertebral angle indicated FHP as experimental group. The control group selected 18 persons with no neck pain and a normal range of cranio-vertebral angle. The stabilization movement was performed by applying three phases of pressure, with low of 20 mmHg, intermediate of 25 mmHg, and high of 30 mmHg, using the Stabilizer. To check the effects of stabilization exercise according to pressure, the circumference of deep neck muscles was measured with ultrasonic waves, and the activity of surface muscle of sternocleidomastoid (SCM) was measured using electromyography (EMG). Results: When the circumference of the deep neck flexor was analyzed according to the pressure change during stabilization exercise, the experimental group showed increase at all pressures. The activity of the SCM of the surface muscle increased in both groups as the pressure increased. Conclusion: The application of stabilization exercise was found to be more effective on forward head posture subjects with neck pain at lower pressures.

Background: For the elderly, masticatory function is one of the most important oral functions and the masticatory ability is related to the wearing of dentures. Many older people wear dentures for their masticatory function, but a significant number of older people who use dentures have found that they feel uncomfortable when performing their daily activities, such as performing masticating functions or talking. Objects: The purpose of this study is to investigate how the forward head posture (FHP), respiratory function and thickness of masseter (MS), and sternocleidomastoid (SCM) are affected by the presence or absence of dentures in the elderly, and what kind of correlation there is between these variables. Methods: The study was conducted on 11 patients in the normal group and 13 in the denture group. The participant’s cognitive ability was evaluated using Mini-Mental State Examination Korean (MMSE-K), and the FHP was evaluated by measuring the craniovertebral angle (CVA). The thickness of the MS and SCM muscles were measured using ultrasound, and respiration was measured with a spirometry. As for the statistical method, the correlation of each variable was investigated using Spearman’s correlation coefficient. Results: In the normal group, there was a significant correlation between forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) (p < 0.001), and in the denture group, FVC and FEV1 (p < 0.001), maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) (p < 0.001), CVA and Lt. MS (p = 0.012). Conclusion: CVA and Lt. MS of the denture group have a high negative correlation, it is related that the thickness of MS may be thick when the elderly wearing dentures are FHP.

For deep geological repository of the spent nuclear fuel, the fuel assemblies loaded in the storage cask are transferred to the disposal cask and the operation is performed in the fuel handling hot cell at the fuel re-packaging facility. As the fuel handling hot cell shielding is accomplished by the concrete wall and the viewing glass window, the required shielding thickness was evaluated for both materials. The ordinary concrete is applied to hot cell wall and two kinds of glasses, i.e., single layer of lead glass and double layer of lead glass and borosilicate glass, are considered for the viewing glass window. A bare spent PWR fuel assembly exposed to the environment in the hot cell was considered as the neutron and gamma radiation sources. The neutron and gamma transport calculations were performed using the MAVRIC program of the SCALE code system for the dose rate evaluation. The dose limit of 10 μSv/h is applied as the target dose to establish the required shielding thickness. The concrete wall of 94 cm thickness reduces the total dose rate to 6.9 μSv/h, which is the sum of neutron dose and gamma dose. Penetrating the concrete wall, both of the neutron dose and the gamma dose decrease constantly with shield thickness and the gamma dose is always dominant through whole penetrating distance. Single layer lead glass of 74 cm thickness reduces total dose rate to 6.2 μSv/h. Applying double layer shield glass combined of lead glass and borosilicate glass, the total dose rate reduces to 3.6 μSv/h at same shield thickness of 74 cm. Through the shield glass, gamma dose decreases rapidly and neutron dose decreases slowly compared with those for concrete wall. In result, neuron dose becomes dominant on the window glass shielding. The more efficient dose reduction of double layer glass is achieved by the borosilicate glass’s superior neutron shielding power. Thus, the use of double layer glass of lead glass and borosilicate glass is recommended for the viewing glass of the fuel handling hot cell. Finally, it is concluded that about 1 m thick concrete wall and 75 cm thick viewing glass window are sufficient for the radiation shielding of the hot cell at the spent fuel repackaging facility.