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.

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.

게임을 구현하는 동안 주기성을 보장해야될 필요성이 있는 경우가 많이 있다. 예를 들어 많은 경우에 캐릭 터의 충돌은 주기적으로 처리되어야 될 필요성이 있는데 주기적으로 처리하지 못하는 경우 게임에서 충돌 을 감지하지 못하는 경우가 발생할 수 있다. 또한 슈팅 게임에서는 많은 경우에 사용자의 편의를 위하여 특 정 버튼을 누르면 무기를 자동적으로 발사하는 기능을 포함하고 있어 주기적으로 무기를 발사해야될 필요 성이 있다. 한편 유니티를 사용하여 게임을 구현할 때 이러한 주기성을 보장하기 위해서 WaitForSeconds로 지연을 발생시킨 코루틴, InvokeRepeating, FixedUpdate, .NET의 Timers.Timer가 사용될 수 있다. 그러나 이러한 다양한 방법들로 인하여 방법의 선택에 어려움이 있어 연구를 진행하였다. 본 연구에서는 1분 동안 6000번 메서드를 주기적으로 실행하고 주기성과 횟수를 측정하였다. 또한 다양한 환경에서의 실험을 위하여 추가의 모델 렌더링이 없는 경우와 렌더링을 추가한 경우, 다양한 해상도에서 주기성과 메서드 호출 횟수를 모두 측정했다. 실험 결과, 부하가 적은 환경에서는 InvokeRepeating이 가장 6000회에 가까웠으며 부하가 큰 환경 에서는 Timers.Timer가 가장 6000회에 가까웠으며 실행 주기의 편차가 가장 적었다. 이러한 실험들을 통하여 유니티를 통하여 게임을 구현할 때 일정 시간 내에 실행되는 횟수가 중요한 게임에서 성능 부하가 크지 않 은 경우 InvokeRepeating을, 성능 부하가 크다면 .NET의 Timer를 쓰는 것이 적합함을 알아내었다. 본 연구를 통하여 개발자는 유니티에서 제공되는 주기성 제공 방법들 중에서 적절한 방법을 선택할 수 있다.

In Korea, research on the introduction of dry storage facility is being conducted as an alternative to saturation of temporary storage facilities for spent nuclear fuel. The introduction of dry storage facilities requires a radiological impact assessment on the workers of the facility, and for this, an appropriate exposure scenario must be derived through work procedure analysis. In this study, the procedure for storing spent nuclear fuel in dry storage facilities was analyzed based on the case of evaluating the radiological impact of workers in dry storage facilities abroad. We investigated cases of radiological impact assessment on workers at on-site dry storage facilities by PNNL, Dominion, and P. F. Weck. PNNL and Dominion analyzed the storage work procedure of the VSC (Vertical Storage Cask) method using CASTOR V/21, TN-32, respectively, and conducted a radiological impact assessment. P. F. Weck analyzed the storage work procedure of various spent nuclear fuel casks for VSC and HSM (Horizontal Storage Module), conducted a radiological impact assessment. As a result of comparing the procedure for storing spent nuclear fuel by case, it was found that the storage procedure was determined by the storage method and the cask type. In the case of VSC method, canister-type casks and basket-type casks are used, and the storage procedure are partially different according to each. Canister-type cask requires repackaging from transfer overpack to storage overpack, but basket-type cask doesn’t require that procedure. In the case of the HSM method, only the canister type cask was found to be used. However, the storage procedure was different depending on the type of HSM system. Depending on the type of HSM system, the necessity of cask for on-site transport was different. In this study, we investigated and analyzed the work procedure according to the storage method of dry storage facilities abroad. It was found that the dry storage procedure of spent nuclear fuel different according to the storage method and type of cask. The results of this study can be used as basic when deriving the exposure scenario for spent nuclear fuel dry storage workers suitable for the domestic situation.

In this study, graphene was rapidly grown by chemical vapor deposition using a liquid cell for supplying methanol as a carbon source of graphene. To realize the rapid growth, methanol which is carbon-contained organic solvent was used instead of methane gas, a widely used carbon source for graphene growth. The graphene grown with the growth time as a variable was transferred to a SiO2/ Si substrate with an oxide thickness of 300 nm to confirm whether it was grown with full coverage with an optical microscope. The results confirmed a full coverage in 0.5 min of growth. The Raman spectra also confirmed the G-peak position at 1585.0 cm−1 and an intensity ratio of 2D/G at 2.3 or higher. Concerning electrical transport characteristics, at an induced carrier density of 1 × 1012 cm−2, the hole (μh) and electron (μe) mobilities were 1524 cm2 V−1 s−1 and 1528 cm2 V−1 s−1, respectively. Thus, our study confirmed that high-quality, large-area graphene can be grown within 0.5 min.