Prepreg is an abbreviation of Preimpregnated Materials. It is a sheet-type product in which a matrix is ​​impregnated with reinforced fiber. The prepreg has very different properties depending on the orientation of the fibers and the weaving method, and the orientation of the fibers plays an important role in determining the mechanical strength of CFRP. Short and randomly oriented reinforcing fibers show isotropy, while long, unidirectional reinforcing fibers exhibit anisotropic behavior and are strongest when the applied load is parallel to the reinforcing fibers. Classification by the direction of the fiber is divided into unidirectional, orthogonal, multiaxial, and the like. Uni-directional refers to a state in which almost all fibers in the fabric are aligned in one direction. When the fibers used as reinforcing materials are aligned in one direction, the fibers are used in a straight line without twisting during the fabric production process, and there is an advantage in that the amount of fibers used as a whole can be minimized. A uni-directional prepreg exhibits different cutting forces depending on the stacking orientation angle. In this experiment, the optimal cutting conditions for a uni-directional prepreg 45 degree orientation angle specimen are presented.

강진은 적절한 내진 설계 기술이 적용되지 않으면 건물 붕괴로 인하여 극심한 피해가 발생할 수 있다. 이를 해결할 수 있는 면진 기술은 구조물과 지반 사이에 베어링 장치를 적용하여 지진 에너지를 흡수하고 건물에 전달되는 진동을 감쇠한 다. 본 연구는 고무 마찰 베어링 장치의 구조물 적용성을 검증하고 지진으로부터 안전성을 확보하기 위하여 고무 마찰 베어링 프레임 구조물에 대한 수치해석을 수행하였다. 수치해석 결과로써 최대 지붕 가속도와 총 밑면 전단력이 감소되어 내진 성능을 확인하였다. 또한, 최대 층간 변위 및 최대 잔류 층간 변위에 대한 분석 결과로 프레임 구조물을 경제적 복구 수준의 결과를 도 출하여 고무 마찰 베어링 장치의 우수한 내진 성능을 확인하였다.

Demand for CFRP with new characteristics is increasing in various industrial fields, from parts materials to daily necessities, and research on this is also being actively conducted. CFRP is a material that realizes properties suitable for multiple functions that cannot be seen in a single material by physically combining two or more materials with different shapes and chemical compositions. When machining CFRP using a high-speed steel (HSS) drill or a TiAlN-coating drill with different rotation speed and feed speed, the cutting force was experimentally analyzed and the optimal tool material and cutting conditions were selected. The cutting force according to the change in rotation speed of the high-speed steel drill and the TiAlN-coating drill is compared.

The objective of this study is to propose a simple and accurate analytical model for HSS braces. For this purpose, a physical theory model is adopted. Rectangular hollow section steel (HSS) braces are considered in this study. To accurately simulate the cyclic behavior of braces using the physical theory model, empirical equations calculating constituent parameters are implemented on the analytical model, which were proposed in the companion paper. The constituent parameters are cyclic brace growth, cyclic buckling load, and the incidence of local buckling and fracture. The analytical model proposed in this study was verified by comparing actual and simulated cyclic curves of brace specimens. It is observed that the proposed model accurately simulates the cyclic behavior of the braces throughout whole response range.

The cyclic behavior of braces is complex due to their asymmetric properties in tension and compression. For accurately simulating the cyclic curves of braces, it is important to predict the major parameters such as cyclic brace growth, cyclic buckling load, incidence local buckling and fracture with good precision. For a given brace, the most accurate values of these parameters can be estimated throughout experiments. However, it is almost impossible to conduct experiments whenever an analytical model has to be established for many braces in building structures due to enormous cost and time. For avoid such difficulties, empirical equations for predicting constituent parameters are proposed from regression analyses based on test results of various braces. This study focuses on rectangular hollow structural section(HSS) steel braces, which have been popularly used in construction practice owing to its sectional efficiency.

In this present investigation, Metal Injection Moulding (MIM) of M2 High Speed Steel (HSS) parts using a wax-High Density Polyethylene (HDPE) binder is shown. The elimination of organic binder was carried out by thermal debinding under inert atmosphere. In order to keep carbon in the sample that could improve the sintering process, incomplete debinding was performed between 450 and . The specimens were sintered at temperatures between 1210 and in high vacuum atmosphere, obtaining the 98% of the theoretical density. In the samples with higher residual carbon content, the sintering window was extended up to 20 degrees and the optimum temperature was lower.

In recent times the potential application of the high speed steel produced by HIP process for wear resistant and cutting materials are increasing. In this work the microstructure of Anval 30 produced by HIP process was investigated and the effect of WC, TiC addition on microstructure formation and wear properties were studied. After HIP process at 1150 , the original feature of spherical raw powders was not removed and consequently, nonuniform microstructure was formed. However the WC added by simple powder mixture incereased the sinterbility of high speed steel and uniform microstructure formed. The wear characteristics of Anval 30 with carbide addition were tested at RT and . The uniform microstructure played an more important role in wear resistance as compared with the hardness.

Background : Cynanchum wilfordii and Cynanchum auriculatum belong to the Asclepiadaceae family and appear morphologically similar. In order to discriminate them, it is needed to find the presence of sap and the leaf shapes: C. auriculatum has a blade ovate leaf comparing to C. wilfordii. However, in the herbal medicine market, they have been handled as cut and dried roots. Due to their similar morphology, it is limited to distinguish the roots of C. wilfordii and C. auriculatum. Recently in Korea, it has been a critical issue to misuse these two roots in the herbal market and food industry. Thus, it is required to establish a robust tool for the discrimination and quality control of them. Methods and Results : To separation and characterization of flavor compounds, C. wilfordii and C. auriculatum samples were analyzed by head space solid phase micro extraction (HSS) fiber coupled with gas chromatography-mass spectrometry using Rtx-5MS (30 m x 0.25 mm x 0.25 μm) column. As a result, We have identified compounds of a few hundred in aliphatic aldehydes and aliphatic alcohols, alkenes and acids, aromatic compounds, aromatic compounds containing nitrogen & sulfur, etc,. In particular, The aliphatic and aromatic compounds had been clearly separated on the second dimensional direction by using two-dimensional GC. Conclusion : The volatile flavor compounds of C. wilfordii and C. auriculatum could easily analyzed without pre-treatment with improved resolution and sensitivity using HSS-GCxGC-TOFMS. We have identified compounds of a few hundred in C. wilfordii and C. auriculatum sample. And It was more accurately qualitative confirmed with separation of GCxGC and TSD. We have confirmed the PCA and PLS-DA Plot that was classified depending on C. wilfordii and C. auriculatum through multivariate statistical analysis of the identified flavor compounds.