The occurrence of shear failure in a rock mass, resulting from the sliding of joint surfaces, is primarily influenced by the surface roughness and contact area of these joints. Furthermore, since joints serve as crucial conduits for the movement of water, oil, gas, and thermal energy, the aperture and geometric complexity of these joints have a significant impact on the hydraulic properties of the rock mass. This renders them critical factors in related industries. Therefore, to gain insights into the mechanical and hydraulic behavior of a rock mass, it is essential to identify the key morphological characteristics of the joints mentioned above. In this study, we quantified the morphological characteristics of tensile fractures in granitic rocks using X-ray CT imaging. To accomplish this, we prepared a cylindrical sample of Hwang-Deung granite and conducted splitting tests to artificially create tensile fractures that closely resemble rough joint surfaces. Subsequently, we obtained 2D sliced X-ray CT images of the fractured sample with a pixel resolution of approximately 0.06 mm. By analyzing the differences in CT numbers of the rock components (e.g., fractures, voids, and rock matrix), we isolated and reconstructed the geometric information of the tensile fracture in three dimensions. Finally, we derived morphological characteristics, including surface roughness, contact area, aperture, and fracture volume, from the reconstructed fracture.

It is crucial to understand the hydro-mechanical behavior of rock mass to assess the performance of natural barriers. As rock fractures serve as both mechanically weak planes and prominent pathways for hydraulic flow, they significantly influence the hydro-mechanical behavior of the rock mass. Hence, understanding the characteristics of rock fractures is necessary to analyze the long-term behavior of natural barriers. In particular, fracture apertures are crucial parameters directly associated with groundwater flow and consequently hold significant importance in determining the hydro-mechanical behavior of natural barriers. Fracture apertures are defined as mechanical and hydraulic apertures, and various studies have been conducted to measure and analyze them. However, direct measurement of mechanical aperture according to changes in normal stress is known to be a challenging task. For this reason, there has been a scarcity of direct comparative findings between mechanical and hydraulic apertures under various normal stress conditions. This study aims to analyze the characteristics of the mechanical and hydraulic apertures according to changes in normal stress based on experimental results. A digital analysis technique using a pressure film image was applied to analyze the mechanical aperture characteristics of the fracture. This technique can be applied by performing a pressure film compression test and a normal stiffness test on a fracture specimen, and has the advantage of being able to derive mechanical apertures under various normal stress conditions. The hydraulic aperture characteristics of the fracture were analyzed based on Cubic law after measuring the flow rate by performing a constant pressure injection test under triaxial compression conditions. By applying various confining pressures, it was possible to examine the hydraulic apertures according to changes in normal stress conditions. Through the experimental results, the relationship between the mechanical and hydraulic apertures of the fracture was summarized under various normal stress conditions. In addition, the experimental results were used to examine the applicability of various empirical equations for mechanical and hydraulic apertures proposed in previous studies. The characteristics of the fracture aperture resulting from this study are significant because they are required in the hydro-mechanical model of natural barriers. Future studies will entail further experiments, with the objective of establishing novel relationships based on the accumulation of experimental data.

Rock discontinuities in underground rock behave as weak planes and affect the safety of underground structures, such as high-level radioactive waste disposal and underground research facilities. In particular, rock discontinuities can be a main flow path of groundwater and induce large deformation caused by stress disturbance or earthquakes. Therefore, it is essential to investigate the characteristics of rock discontinuities considering in-situ conditions when constructing highlevel radioactive waste disposal, which needs to assure the long-term safety of the structure. We prepared Hwang-Deung granite rock block specimens, including a saw-cut rock surface, to perform multi-stage direct shear tests as a preliminary study. In the multi-stage direct shear tests, we can exclude possible errors induced by different specimens for obtaining a full failure envelope by using an identical specimen. We applied the initial normal stress of 3 MPa on the specimen and increased the normal stress to 5 and 10 MPa step by step after peak shear stress observation. We obtained the mechanical properties of saw-cut rock surfaces from the experiments, including friction coefficient and cohesion. Additionally, we investigated the effect of filling material between rock discontinuities, assuming the erosion and piping phenomenon in the buffer material of the engineering barrier system. When the filling material existed in the rock surfaces, the shear characteristics deteriorated, and the effect of bentonite was dominant on the shear behavior.

Buffer materials play an important role in preventing the leakage of radionuclides from the residue. The mineralogical properties of these buffer materials are critical in repository design. This study presents the fundamental properties of Na-type MX80 and a novel Ca-type Bentonil- WRK. The CaO to MgO ratio in Bentonil-WRK was approximately 1:1, and the CaO to Na2O ratio was approximately 2.8:1. These results suggest that Bentonil-WRK demonstrates a lower swelling index compared to Gyeongju bentonite due to its CaO-to-MgO ratio’s proximity to 1:1, despite having a higher montmorillonite content than Gyeongju bentonite. The results of this research can provide useful foundational data for the evaluation of the thermal-hydraulic-mechanical-chemical behavior of buffer materials.

Nuclear fuel assemblies are exposed to high temperature and high pressure environments underwater for long periods of time in a reactor, leading to deterioration of the assembly structure. These assembly consists of fuel rods, grids, a top nozzle, a bottom nozzle and guide tubes. In particular, the integrity of the guide tube made of Zircaloy-4 is a very important part in handling the assembly. In the Post Irradiation Examination Facility (PIEF), there are 14×14 Westinghouse STD assemblies that have lost their handleability due to the top nozzle being removed for damaged fuel rod test. To handle these assemblies, it is reasonable to use cut guide tubes whenever possible. Therefore, it is necessary to determine the irradiation embrittlement state of the guide tube before designing or manufacturing parts that can connect the top nozzle and the guide tubes. Therefore, in this paper, the location for installing the top nozzle-guide tube connection parts was selected in the height range of 3,460 to 3,713 mm, and guide tube specimens were made within that range. Offset strain was derived from the load-displacement curve obtained through compression testing to confirm whether the ductility of guide tubes was maintained. As a result, there was no significant difference in strength and ductility of the guide tube within the above length range. In addition, it was confirmed that the ductility was maintained enough to install the top nozzle-guide tube connection parts. Therefore, it is judged that there will be no problem even if the top nozzle-guide tube connection parts are installed in the guide tube to restore the handleability of the assemblies.

In nuclear fuel development research, consideration of the back-end cycle is essential. In particular, a review of an in-reactor performance of nuclear fuel related to the various degradation phenomena that can occur during spent fuel dry storage is an important area. The important factors affecting the degradation of zirconium-based cladding during dry storage are the cladding’s hydrogen concentration and rod internal pressure after irradiation. In this study, a preliminary analysis of the in-reactor behavior of the HANA cladding, which has been developed and is currently undergoing licensing review, was performed, and based on this result, a comparative analysis between nuclear fuel with HANA cladding and current commercial fuel under storage conditions was performed. The results show that the rod internal pressure of nuclear fuel with HANA cladding is not significantly different from that of commercial cladding, and the hydrogen concentration in the cladding tends to reduce due to the increased corrosion resistance, so fuel integrity in a dry storage conditions is not expected to be a major problem. Although the lack of cladding creep data under dry storage conditions, the results from the Halden research reactor test comparing in-reactor creep behavior with Zircaloy-4 showed that there is sufficient margin for degradation due to creep during storage.

Globally, the operation of nuclear power plants results in the production of a tremendous quantity of spent nuclear fuel. The methods for handling spent nuclear fuel can be categorized into three: storage, direct disposal and recycling. A technology designed to recycle accumulated spent nuclear fuel is pyropocessing. In pyroprocessing, various fission products (FPs) such as C-14, H-3, I-129 and Cs-137 are generated. Among these FPs, technetium (Tc-99) is a gaseous nuclear isotope with a long half-life and high mobility in the form of TcO4 - in aqueous solutions, making it essential to capture strictly in order to prevent radioactive contamination of the environment. In previous studies, ion-exchange or adsorption using MOFs (Metal Organic Frameworks) have been used to remove Tc-99. These methods, however, involve separation in aqueous solutions, not in the gaseous state. In this study, we developed a CaO-based adsorbent for capturing Re as a surrogate for radioactive Tc-99. Isopropyl alcohol (IPA) was employed as a pore-forming agent during the preparation of the adsorbents, and its effects on characteristics and adsorption performance were investigated. The size of the pores were analyzed from nitrogen (N2) adsorption isotherm analysis and mercury (Hg) intrusion curves. As a result, it was confirmed that the addition of IPA had a significant impact on the formation of macro-pores. Furthermore, this macroporous structure was found to enhance the adsorption performance of Re.

Hydride reorientation is widely known as one of the major degradation mechanisms in Zirconium cladding during dry storage. Some previous theoretical models for hydride reorientation used assumption of an ideal radial basal pole orientation for HCP structure of Zirconium cladding. Under this assumption, circumferential hydride was considered to precipitate in the basal plane while radial hydride was considered to precipitate in the prismatic plane, thereby giving energetical penalty on thermodynamical precipitation of radial hydrides. However, in reality, reactor-grade Zirconium cladding exhibits average 30° tilted texture, adding complexity to the hydride precipitation mechanism. In this study, reactor-grade Zirconium cladding was charged with hydrogen and hydride reorientation -treated specimens were fabricated. Microstructural characterization of hydrides was conducted via following three methods in terms of interface and stored energy. And this study aimed to compare these characteristics between circumferential and radial hydrides. Using Electron Back Scattered Diffraction (EBSD), the interface was investigated assuming that interface lies parallel to the axial axis of the tube. These were further validated with Transmission Electron Microscope (TEM). In addition, Differential Scanning Calorimetry (DSC) analysis was conducted to calculate the stored energy. This investigation is expected to establish fundamental understanding of how hydrides precipitate in Zirconium cladding with different orientations. And it will also increase the predictability of radial hydride formation and help understanding the mechanical behavior of Zirconium cladding with radial hydrides.

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.

When an earthquake occurs, the severity of damage is determined by natural factors such as the magnitude of the earthquake, the epicenter distance, soil properties, and type of the structures in the affected area, as well as the socio-economic factors such as the population, disaster prevention measures, and economic power of the community. This study evaluated the direct economic loss due to building damage and the community’s recovery ability. Building damage was estimated using fragility functions due to the design earthquake by the seismic design code. The usage of the building was determined from the information in the building registrar. Direct economic loss was evaluated using the standard unit price and estimated building damage. The standard unit price was obtained from the Korean Real Estate Board. The community’s recovery capacity was calculated using nine indicators selected from regional statistical data. After appropriate normalization and factor analysis, the recovery ability score was calculated through relative evaluation with neighboring cities.

Non-structural elements, such as equipment, are typically affixed to a building’s floor or ceiling and move in tandem with the structure during an earthquake. Seismic forces acting upon non-structural elements traverse the ground and the building’s structure. Considering this seismic load transmission mechanism, it becomes imperative to account for the interactions between soil, structure, and equipment, establishing seismic design procedures accordingly. In this study, a Soil-Structure-Equipment Interaction (SSEI) model is developed. Through seismic response analysis using this model, how the presence or absence of SSEI impacts equipment behavior is examined. Neglecting the SSEI aspect when assessing equipment responses results in an overly conservative evaluation of its seismic response. This emphasizes the necessity of proposing an analytical model and design methodology that adequately incorporate the interaction effect. Doing so enables the calculation of rational seismic forces and facilitates the seismic design of non-structural elements.

In the automotive information display device industry, products with high reliability and wide temperature conditions are required, and interest in products that do not cause lighting defects even under extremely low temperature conditions is increasing. In this experiment, we produced an LED backlight unit for car navigation in a cryogenic environment. And to make this backlight unit, we used 12 side-emitting white LEDs with 3[W] high power LEDs. This backlight unit emits up to 18,000[nits] at a power consumption of 36[W] and has a startup voltage time of less than 1[ms] at -50° ambient temperature.

This study aims to analyze the variations in online clothing purchasing patterns based on demographic attributes and purchasing behavior. The survey subjects comprised individuals in their 10s to 50s who had prior experience with online shopping. The survey was conducted in Gyungnam from May to June 2022. A total of 397 questionnaires were analyzed using the χ2-test statistical method. The analysis of clothing purchase type based on demographic characteristics revealed differences in terms of gender, marital status, age, monthly income, and occupation. Notably, when analyzed by demographic characteristics and clothing purchase types, monthly online purchase frequency displayed significant differences in marital status, age, and occupation. Similarly, monthly purchase amounts through online platforms exhibited significant variations based on marital status, age, monthly income, and occupation. The online fashion platforms, when examined in relation to demographic characteristics and purchase types, showed significant differences across all variables. Clothing purchases by consumers seeking individuality and differentiation exhibited significant differences in age, occupation, and purchase types. Furthermore, the reasons for choosing online platforms for clothing purchases varied significantly based on age and occupation. These findings indicate diverse purchasing behaviors on online platforms influenced by demographic characteristics. These findings can be valuable for effectively segmenting the online fashion market.

자생식물은 관상용, 약용, 식량자원으로 활용될 수 있는 잠재력을 지닌 고유 유전자원이다. 돌부추(Allium koreanum H.J. Choi & B.U. Oh)는 우리나라 해안 암반지대에 분포하는 자생식물 중 하나로, 기후변화와 서식지 감 소로 인해 보전 가치가 높은 식물이다. 이번 연구는 온도와 과산화수소가 돌부추의 발아에 미치는 영향을 조사하기 위해 수행되었다. 종자를 무처리(대조군) 또는 1% 과산화수소(H2O2)로 90분간 처리한 종자를 준비해 15, 20, 25°C 로 설정된 식물 생장 챔버에 배치하였다. 그 결과, 파종 23일 후 15°C에서 42%인 발아율이 20°C와 25°C에서 각각 18%와 0%인 발아율보다 2배 이상 높았으며, H2O2 처리 여부와 관계없이 15°C에서 발아율이 42%로 가장 높았다. H2O2 처리와 관계없이 최종 발아율 50%(T50)에 도달하는 일수는 20°C에서 가장 짧았지만, 일평균 발아율(MDG)은 15°C에서 가장 높았다. 따라서 1%의 H2O2 처리는 돌부추의 발아율에 큰 영향을 미치지 않았으며, 15°C의 온도가 돌부추의 발아율을 높이는 데 최적인 것으로 판단된다. 본 연구 결과는 돌부추의 발아를 위한 기초 연구 자료로 활 용될 수 있을 것으로 기대된다.

Fulvic acid, a humic substance with unique properties, has sparked interest due to its potential applications in the treatment of allergic diseases, Alzheimer's disease, and as a microplastic adsorbent. However, conventional extraction methods produce insufficient quantities for commercial use, which has prompted research to enhance fulvic acid production. In this study, we investigated the impact of Saccharomyces cerevisiae fermentation on the yield and spectral characteristics of fulvic acid extracted from white peat. Fulvic acid was extracted from both S. cerevisiae-treated and untreated white peats using acid precipitation. The yield of fulvic acid from the S. cerevisiae treated group reached its highest at 3.5 % after 72 hr of fermentation, which was significantly higher than the untreated group (1.1 %). Fourier Transform Infrared (FTIR) analysis revealed similarities in functional groups and characteristic absorption bands between the treated and untreated fulvic acid samples. These findings suggest that S. cerevisiae fermentation can increase the yield of fulvic acid extracted from white peat, providing a promising approach for enhancing the commercial viability of fulvic acid production.

이 연구는 핵무기 폭발 시 발생하는 효과 변인을 토대로 북한이 언제, 어떤 방법으로 핵무기를 운용할 것이며, 핵폭발 시 생성되는 방사성 물 질이 자연환경과 인공물의 영향에 따라 도심지에서 어떤 거동 현상을 보 이는가와 이를 고려한 국민 방호의 대비 방향에 관한 것이다. 연구 결과 핵무기는 폭발 고도에 따라 그 효과가 달라지며, 북한은 이를 활용하여 개전 초부터 가장 효과적인 공격을 할 것으로 예측되었다. 즉, 북한은 개 전 초 한미연합군과 정부의 지휘‧통제‧통신체계를 무력화하기 위해 저위 력핵무기로 지하 폭발을, 전쟁 도중 결정적인 목표 확보를 위해 전술핵 무기로 저공 폭발을, 전쟁 말기 패색이 짙어지는 위기 시에는 전술핵무 기로 지표면 폭발을 시도할 것이다. 북한의 핵무기 공격 후 발생되는 방 사성 물질은 낙진의 형태로 일정 지역을 오염시킬 것이며, 방사성 물질 이 도심지로 유입된다면 공기역학 또는 유체역학적 거동을 보임으로써 다양한 형태의 오염과 위험이 존재할 것으로 분석되었다. 이에 따라 국 민 방호를 위해서는 북한의 핵무기 공격 양상을 고려 최악의 상황을 가 정한 대비가 평시에 완료되어야 하며, 전쟁 개시 이후에는 당시의 공격 유형에 부합한 대응 및 복구가 뒤따라야 한다. 아울러 방사능 낙진의 거 동을 세밀히 분석하고 이를 고려하여 핵폭발 초기 효과에 대비하는 주민 대피와 이를 후속하는 낙진에 대응하기 위한 주민 소개는 분리되어야 한다.

In this study, when Butyl ether, a type of diether-based oxygenated fuel, is mixed in each volume ratio in a naturally aspirated direct injection diesel engine, the exhaust gas emission characteristics of the oxygenated component in the fuel affect each operating area of the engine I wanted to investigate the effect on. For comparative measurement of engine performance and exhaust emissions, commercial diesel and butyl ether mixed fuels were classified into 4 types according to the mixing ratio and tested. As the content of butyl ether in fuel increases, soot emission reduction increases, and when the maximum mixing amount of butyl ether (diesel 80vol-% + BE 20vol%) is applied, compared to the case of using only diesel as fuel, at 2500 rpm and no load, 39%, and about 32% of smoke reduction effect at full load was confirmed.

It is essential to select materials with excellent mechanical properties to prevent chemical and mechanical damage to the surfaces of materials used in machines and structures and to extend their lifespan. Co-based stellite alloy, which has wear resistance, heat resistance, and corrosion resistance, is essential for products used in harsh environments. However, due to the problem of enormous costs, research on hard facing, which uses a stellite coating layer only on the contact surface, is urgently required. Currently, high-facing research on Stellite coating layers is focused on powder, and GMAW research using wire is relatively lacking. In this study, welding experiments were performed to form stable weld beads using stellite 6 welding wire, and the correlation between parameters and weld beads was analyzed. A CMT welder was used to minimize the heat effect on the base material.

이 연구의 목적은 예비 지구과학 교사들이 선다형 문항 제작 실습 프로그램에 참여하는 과정에서 드러나는 문 항 제작 역량의 발달 양상을 이해하는 것이다. 이를 위해 예비 지구과학 교사 15명이 선다형 문항 제작 과정 중 공동 검토 과정에서 나타나는 논의에 초점을 맞춰 그 특징을 분석하였다. 구성주의 근거 이론을 토대로 3단계의 코딩을 수 행한 결과, 36개의 초기 코드, 12개의 초점 코드, 5개의 이론적 코드가 도출되었다. 코딩 범주에 근거하여 논의의 특징 을 규정하는 검토 문화와 문항에 대한 관점을 두 축으로 설정하였으며, 이로부터 수험생의 문제풀이, 조심스레 한 걸음 떼기, 짙어지는 담화를 주제로 하는 세 가지 이야기를 구성하였다. 또한 프로그램 동안 일관되게 드러나는 문항 제작 역량의 한계를 다다르지 못한 노정에 대한 네 번째 이야기로 서술하였다. 문항 제작 과정에서 드러나는 평가 전문성은 예비교사의 정체성 발달과 관련되어 있으며, 본 연구에서 적용한 개발한 프로그램의 효과와 의의 및 프로그램의 개발과 개선을 위한 시사점을 논의하였다.