본 연구에서는 EBR 및 EBROG 기법으로 부착된 CFRP판과 콘크리트 모체 간 부착성능을 평가하였다. 실험 변수로는 콘크리 트 압축강도, 홈의 개수 및 깊이를 고려하였으며, 총 21개의 시편을 대상으로 단일 랩 전단 실험을 수행하였다. 실험 결과, EBROG 기법을 적용한 시편은 EBR 기법을 적용한 시편보다 최대 62% 높은 부착 강도를 보였다. 또한, 홈의 개수와 깊이가 증가할수록 부착강 도도 증가했으나, 홈이 3개일 때 가장 높은 증가율을 기록하였다. 한편, 콘크리트 압축강도가 증가할수록 부착강도도 상승했지만, 압축 강도가 가장 높은 시편에서는 오히려 부착강도 증가율이 가장 낮았다. 아울러, EBROG 기법으로 부착된 CFRP 판의 유효 변형률을 예측하는 모델을 개발하기 위해 실험 데이터를 기반으로 회귀 분석을 수행하였다. 제안된 모델의 예측값과 실험값의 비의 평균과 표준 편차는 각각 1.002 및 0.032로 나타나, 해당 모델이 유효 변형률을 정확하게 예측할 수 있음을 확인하였다.

국화도는 화성시 동쪽에 위치한 섬으로 지질학적으로는 경기육괴의 서부 가장자리에 속하나 최근 한반도 지체구 조구의 재정립에 따라 홍성-임진강대에 포함된다. 최근 보고된 국화도 일원의 분포 암석들에 대한 지질구조 및 연대측정 결과를 기초로 분포 암석 및 변형구조의 특성을 논의하고 학술적으로 가치 있는 다양한 지질유산을 보고하고자 한다. 국화도의 암상은 석영, 방해석, 장석으로 구성된 밝은색의 저변성 변성사질암과 규암, 각섬석-흑운모-사장석-티타나이트로 구성된 어두운색의 각섬암과 변성니질암, 그리고 석회질 편암 혹은 석회질 규산염암과 같이 3개 단위층으로 구분된다. 이들 암체는 후기 트라이아스기의 섬장암에 의해 관입되었다. 단위층들의 경계는 뚜렷한 호층구조와 함께 엽리 방향에 평행하며 습곡작용에 의하여 반복되어 산출한다. 저변성 변성사질암에는 사층리, 점이층리, 대칭연흔이 관찰되어 이 지역 의 퇴적환경이 조간대 혹은 호수환경을 지시한다. 단위층들의 퇴적시기(후기 데본기-전기 펜실베이니아아기)와 섬장암의 U-Pb 저어콘 연령(232 Ma)으로부터 국화도에 일원에 발생한 최소 2회의 강한 습곡작용의 시기는 펜실베이니아아기-후 기 트라이아스기로 판단된다. 국화도 대부분의 노두에서는 등사(isoclinal) 및 밀착(tight) 습곡이 횡와 내지 수직습곡의 형태로 관찰되며 이들 습곡의 날개부에는 전단에 의한 비대칭 습곡과 부딘구조가 발달한다. 또한 이들 단위층과 습곡구 조를 절단하는 충상단층도 발달한다. 따라서 국화도는 한반도 중서부지역의 변성 및 변형작용의 특징이 잘 보존된 지질 유산이 풍부한 지역으로 학술적 가치와 함께 학생과 교사들의 지질학습장으로 활용성도 뛰어난 명소이다.

최근 몇 년 동안 높은 감도, 빠른 응답 및 쉬운 제작 공정을 갖춘 습도 센서가 상당한 주목을 받고 있다. 여기서는 PET 기판의 깍지낀 전극(IDE)에 감지 층을 증착하여 길이 대 직경의 종횡비가 낮고 (PVP-ZnO-1), 높은(PVP-ZnO-2) PVP 개질 ZnO 나노막대 센서(PVP-ZnO)의 쉬운 제작 공정을 보고 한다. PVP-ZnO-2는 PVP-ZnO-1 센서(41,647%)에 비해 85% 상대 습도(RH)에서 99,397%의 더 높은 정전용량성 습도 감도를 보였다. PVP-ZnO-2 센서는 또한 순환 습도 조건에서 응답시간 7초 및 복구시간 10초를 나타냈다. PVP-ZnO-2의 높은 습도 감도 성능의 이점을 활용하여 다양한 호흡 정도의 정전용량 변화와 모스 부호 메시징을 시연하였다. 이 연구는 높은 표면적을 갖는 고성능 나노소재 기반 습도 센서의 엄청난 잠재력을 보여준다.

The International Maritime Organization (IMO) is promoting the transition to eco-friendly fuels such as hydrogen and ammonia, with the goal of achieving net-zero greenhouse gas emissions in the shipping sector by 2050. Hydrogen does not emit greenhouse gases, but it must be stored at an extremely low temperature of -253°C when stored as a liquid. 316L stainless steel is mainly used as a tank material to store liquid hydrogen. FCAW (Flux Cored Arc Welding) is known for its excellent weldability with 316L stainless steel, and it is particularly suited for welding thick metals efficiently, making it an ideal choice for storage tank welding. Finite Element Method (FEM) analysis can simulate the thermal and mechanical deformations occurring during welding with high precision, allowing for accurate prediction of deformation patterns and the derivation of optimal welding conditions. This ensures the stability and quality of the structure while reducing costs. In this study, FCAW butt welding was performed on 316L stainless steel, followed by cross-sectional observation and deformation measurement of the weld area. Based on the cross-sectional observation, a 3D FE model was designed, and heat transfer analysis was conducted. Subsequently, thermo-mechanical analysis was carried out to predict welding deformation.

The purpose of this study was to enhance the correlation between the dependent and independent variables in a prediction model of pavement performance for local roads on Jeju Island by applying K-means clustering for data preprocessing, thereby improving the accuracy of the prediction model. Pavement management system (PMS) data from Jeju Island were utilized. K-means clustering was applied, with the optimal K value determined using the elbow method and silhouette score. The Haversine formula was used to calculate the distances between the analysis sections and weather stations, and Delaunay triangulation and inverse distance weighting (IDW) were employed to interpolate the magnitude of the influencing factors. The preprocessed data were then analyzed for correlations between the rutting depth (RD) and influencing factors, and a prediction model was developed through multiple linear regression analysis. The RD prediction model demonstrated the highest performance with an R² of 0.32 and root-mean-square error (RMSE) of 1.48. This indicates that preprocessing based on the RD is more effective for developing an RD prediction model. The study also observed that the lack of pavement-age data in the analysis was a limiting factor for the prediction accuracy. The application of K-means clustering for data preprocessing effectively improved the correlation between the dependent and independent variables, particularly in the RD prediction model. Future research is expected to further enhance the prediction accuracy by including pavement-age data.

2022년 기준 국내 폐타이어 발생량은 약 37만톤으로 그 중 88.9% 인 약 32만 9천톤이 재활용되는 것으로 조사되었다. 하지만 이 중 약 75%가 시멘트소성로용 등 열이용 분야에 사용되었다. 폐타이어는 대부분 고무와 플라스틱으로 이루어져 있기 때문에, 고온에서 분 해되면서 다양한 유해가스와 오염물질이 발생할 수 있고, 이러한 공해물질은 적극적으로 관리되지 않으면 대기오염, 수질 오염 등 다 양한 환경문제를 발생시킬 수 있다. 때문에 친환경적이고 지속적인 재활용에 대한 필요성이 대두되고 있다. 폐타이어 고무 분말을 아스팔트 혼합물의 골재 일부로 치환하여 재활용하는 접근 방식은 환경에 미치는 영향을 완화할 뿐만 아니라 천연 자원의 고갈 측면에서도 긍정적인 영향을 미치는 것으로 판단된다. 따라서 타이어분말을 아스팔트 혼합물에 적용하는 것은 환경 문제를 해결하고 자원 효율성을 높이는 두 가지 이점을 가지고 있다. 폐타이어 분말을 아스팔트 바인더와 아스팔트 혼합물에 적용할 경우 미치는 영향을 평가하기 위하여 TTI의 반사균열 저항성 시험, FN Test를 진행하였다.

In this study, the performance evaluation of steel dampers was conducted based on existing research results. The test variables are cross-sectional shape and lateral deformation prevention details. As a result of performance tests according to cross-sectional shape, the circular cross-section was evaluated to be superior than the rectangular cross-section in terms of envelope, stiffness reduction, and energy dissipation capacity. In addition, it was evaluated that the rectangular cross-section where lateral deformation occurs can be restrained by lateral deformation prevention details, thereby improving strength and deformation capacity.

형상기억합금(SMA)-섬유 액추에이터는 소프트 로봇 공학 및 웨어러블 기술을 포함한 다양한 분야에서 큰 주목을 받아왔다. 이러 한 부드러운 액추에이터는 SMA와 단순 직물 섬유를 결합하여 개발되었으며, K 루프와 P 루프라는 두 가지 루프 패턴으로 편직되었 다. 두 루프 모두 루프 헤드 형상으로 인해 반대 굽힘 특성으로 구별된다. 그러나 이러한 액추에이터 시트의 편직 공정에는 전문 지식 과 시간이 필요하므로 편직 루프 작동 시트의 생산 비용이 높아진다. 이 논문에서는 전압을 가할 때 큰 변형이 발생하는 SMA 직물 기 반 액추에이터의 변형을 평가하는 새로운 방법을 소개하였다. SMA 재료의 매우 비선형적인 구성 방정식으로 인해 수치 분석을 위한 분석 모델을 개발하는 것은 어렵다. 따라서 본 연구에서는 SMA 재료의 대변형을 고려하면서 SMA-섬유 액추에이터의 초기 설계에 사용할 수 있는 선형 구성 방정식을 활용하는 새로운 접근 방식을 제안하였다. 전기-기계연성 효과를 모델링할 수 있는 선형구성방적 식은 ABAQUS의 UMAT을 사용하여 구현하였다. 이 등가 단위 셀 모델(EUC)은 K-루프와 P-루프의 실험적 굽힘 작동 결과와 비교하 여 검증하였다.

In the development of eco-friendly vehicles such as electric vehicles, weight reduction has become a very important design target. Seat weight reduction is very important in vehicle weight reduction. In this study, the energy absorption characteristics of Almag material, an alloy of aluminum and magnesium, and mild steel SAFH440, SAFH590, SAFC780, and SAFH980 were analyzed to obtain a true stress versus true strain curve that was correlated with the test. By performing the seat frame structure analysis using the obtained analysis material property, it was possible to compare the deformation between lightweight material, Almag and mild steel materials. In addition, it was confirmed that the weight reduction effect was 25.8% when applying Almag, an equivalent lightweight material that gives the same maximum deformation as SAFH980, a high-strength mild steel.

윌리엄 블레이크는 『로스의 서』와 『로스의 노래』에서 신화적 상상력으로 천지창조와 시민들의 자유에 대한 열망을 노래한다. 로스는 영원한 선지자로서 독자들에게 블레이크의 상상력의 원형을 인식하도록 만드는 역할을 한다. 독자들은 블레이크의 페르소나인 로스를 통해서 그의 신화적 상상력의 감성을 음미할 수 있다. 블레이크는 『로스의 서』에서 자신의 관점으로 천지창조와 인간의 창조를 노래하였고, 『로스의 노래』에서 인간이 창조된 이후에 인간의 정신문화가 어떻게 진화하고 발전하는지를 노래하면서, 인간이 본원적 가치를 회복하기 위한 노력으로 혁명을 통해 자유를 되찾는 과정을 맛깔스럽게 시로 노래한다. 그래서 현대인들은 블레이크의 시들을 읽으면서 인간의 자유와 정신문화를 숙고해보고, 인간의 진정한 가치가 무엇인지를 성찰하는 시간을 갖게 한다.

PURPOSES : Concrete, which is a construction material, is the most widely used compression material; however, unlike steel, it exhibits nonlinear material characteristics. Therefore, to examine the behavior of structures under the nonlinear conditions of concrete materials, one must select an appropriate numerical-analysis technique and a reasonable material model. When performing the nonlinear numerical analysis of a structure using general-purpose structural analysis software, the stress–strain curve or the Mohr–Coulomb failure criterion is typically employed to consider the nonlinear material characteristics. In this study, an efficient nonlinear numerical analysis is conducted by defining the stress–strain curves and Mohr–Coulomb parameters applicable to Strand7 to examine and design the stability of reinforced concrete structures. METHODS : This study was conducted by improving existing data. Based on the tensile region of the concrete stress–strain curve presented in a simple shape and the results of the splitting test, the proposed Mohr–Coulomb parameter was improved based on regulations stipulated in the design standards of concrete structures. The characteristics and usability of the improved material models were examined using concrete splitting tensile and bending models. RESULTS : A yield area distribution similar to that of the reference data is obtained when the Mohr–Coulomb material model is used in the numerical analysis of the concrete splitting tension, thus confirming the validity of the model. In the Mohr–Coulomb material model, nonlinear resistance continues even after the maximum reaction force occurs. However, when the stress–strain curve material model is applied, at the moment the maximum reaction force occurs, the material yields and begins to be damaged. In addition, by applying the Mohr–Coulomb material model to the bending numerical-analysis model, the magnitude of stress in the tensile region from the initial stage exceeds the yield stress defined in the stress–strain curve. CONCLUSIONS : Based on a series of examples, the usability of the proposed concrete stress–strain curve and Mohr–Coulomb parameters is confirmed. However, to obtain numerical-analysis results that are consistent with the nonlinear behavior of actual structures, nonlinear testing of reinforced concrete structures shall be conducted and material models shall be improved.

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.

Understanding the behavior of soil under cyclic loading conditions is essential for assessing its response to seismic events and potential liquefaction. This study investigates the effect of non-plastic fines content (FC) on excess pore pressure generation in medium-density sand-silt mixtures subjected to strain-controlled cyclic direct simple shear (CDSS) tests. The investigation is conducted by analyzing excess pore pressure (EPP) ratios and the number of cycles to liquefaction (Ncyc-liq) under varying shear strain levels and FC values. The study uses Jumunjin sand and silica silt with FC values ranging from 0% to 40% and shear strain levels of 0.1%, 0.2%, 0.5%, and 1.0%. The findings indicate that the EPP ratio increases rapidly during loading cycles, with higher shear strain levels generating more EPP and requiring fewer cycles to reach liquefaction. At 1.0% and 0.5% shear strain levels, FC has a limited effect on Ncyc-liq. However, at a lower shear strain level of 0.2%, increasing FC from 0 to 10% reduces Ncyc-liq from 42 to 27, and as FC increases further, Ncyc-liq also increases. In summary, this study provides valuable insights into the behavior of soil under cyclic loading conditions. It highlights the significance of shear strain levels and FC values in excess pore pressure generation and liquefaction susceptibility.

PURPOSES : This study was conducted to investigate the stress distribution and resulting effects in the joint between CRCP and JCP when temperature deformation occurs. METHODS : The tie bars, CRCP and JCP pavements, and lean concrete base were created as three-dimensional finite element models using ABAQUS, a general-purpose finite element analysis program. Contact stress analysis was performed between rebar and JCP and between JCP and lean concrete base layer. In the section where stress concentration occurred, the degree of damage was estimated using the CDP model. RESULTS : Since the domestic CRCP does not have a separation layer between the base layer and the surface layer, it was found that when connected to a JCP where the base layer and the surface layer are completely separated, stress concentration occurs around the tie bar at the connection point. Analysis results using the CDP model showed that 25 to 32 mm around the reinforcing bar exceeded the elastic range of concrete. CONCLUSIONS : At the point where CRCP and JCP are connected, local stress concentration is inevitable because the friction and bonding conditions with the base layer and the degree of curling deformation restraint by CRCP rebars are different, and design improvement is expected through life cycle cost and long-term measurement analysis.

This study reports an experimental and analytical exploration of concrete columns laterally confined with Fe-based shape-memory alloy (Fe-SMA) spirals. For performing experiments, Fe-SMA rebars with a 4% prestrain and diameter of 10 mm were fabricated and concrete columns with internal Fe-SMA spiral reinforcement were constructed with a diameter of 200 mm and height of 600 mm. An acrylic bar with an attached strain gauge was embedded in the center of the specimen to measure local strains. Experimental variables encompassed the Fe-SMA spiral reinforcement, spacing, and activation temperature. Uniaxial compression tests were conducted after applying active confinement to the concrete columns through electrical-resistance heating. Notably, as the Fe-SMA spiral spacing decreased, the local failure zone length and compressive fracture energy of the prepared specimens increased. Additionally, a model incorporating compressive fracture energy was proposed to predict the stress–strain behavior of the. This model, accounting for active and passive confinement effects, demonstrated accurate predictions for the experimental results of this study as well as for previously reported results.

The EV electric vehicle market is growing rapidly worldwide. Magnet fixing technology is important for mass production of driving motors, a key part of electric vehicles. The magnet fixing method was carried out by the PAM (Polyamide molding) method. This study conducted the injection of rotor core magnet PA of EV traction motor and is a study on the amount of rotor core deformation. In this study, the change in the outer diameter of the product after injection and the non-molding phenomenon were tested. An injection mold was made and the results and phenomena of product deformation types are discussed.

The most comprehensive and particularly reliable method for non-destructively measuring the residual stress of the surface layer of metals is the sin method. When X-rays were used the relationship of sin measured on the surface layer of the processing metal did not show linearity when the sin method was used. In this case, since the effective penetration depth changes according to the changing direction of the incident X-ray,  becomes a sin function. Since  cannot be used as a constant, the relationship in sin cannot be linear. Therefore, in this paper, the orthogonal function method according to Warren’s diffraction theory and the basic profile of normal distribution were synthesized, and the X-ray diffraction profile was calculated and reviewed when there was a linear strain (stress) gradient on the surface. When there is a strain gradient, the X-ray diffraction profile becomes asymmetric, and as a result, the peak position, the position of half-maximum, and the centroid position show different values. The difference between the peak position and the centroid position appeared more clearly as the strain (stress) gradient became larger, and the basic profile width was smaller. The weighted average strain enables stress analysis when there is a strain (stress) gradient, based on the strain value corresponding to the centroid position of the diffracted X-rays. At the 1/5 max height of X-ray diffraction, the position where the diffracted X-ray is divided into two by drawing a straight line parallel to the background, corresponds approximately to the centroid position.