• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
• /
• pp.163-172
• /
• 1997

This paper is a study on the deformation behavior of the reinforced concrete circular section column carrying bi-axial bending moment and axial force. That is, this is to clarify the deformation behavior of the reinforced concrete circular section column carrying bi-axial bending moment and axial force by analytic methods. The deformation behavior of circular section column under bi-axial uni-axial bending moment and axial force are compare with those of a square section column under the same conditions. Those of circular section column under bi-axial bending moment are decreased as compared with those of circular section column under uni-axial bending moment. The results mentioned above are the same under the axial force of 7tons and 11tons.

• 한국생산제조학회지
• /
• 제9권3호
• /
• pp.48-54
• /
• 2000

In this study the characteristics of chip formation of the cold drawn Bi-S free machining steels were assessed. And for comparison those of the cold drawn Pb-S free machining steel the hot rolled low carbon steel which has MnS as free machining inclusions and the conventional steels were also investigated. During chip formation the cold drawn free machining steels show relatively little change in thickness and width of chip compare to those of the conventional carbon steels. And a single parameter which indicates the degree of deformation during chip formation chip cross-section area ratio is introduced. The chip cross-section area ratio is defined as chip cross-section area is divided by undeformed chip cross-section area. The variational patters of the chip cross-section area ratio of the materials cut are similar to those of the shear strain values. The shear stress however seems to be dependent on the carbon content of the materials. The cold drawn Bi-S and Pb-S steels show nearly the same chip forming behaviors and the energy consumed during chip formation is almost same. A low carbon steel without free machining aids shows poor chip breakability due to its high ductility. By introducing a small amount of free machining inclusions such as MnS Bi, Pb or merely increasing carbon content the chip breakability improves significantly.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1999년도 추계학술대회 논문집 - 한국공작기계학회
• /
• pp.351-356
• /
• 1999

In this study, the characteristics of chip formation of the cold drawn Bi-S free machining steels were assessed. And for comparison, those of the cold drawn Pb-S free machining steel, the hot rolled low carbon steel which has MnS as free machining inclusions and the conventional steels were also investigated. During chip formation, the cold drawn free machining steels show relatively little change in thickness and width of chip compare to those of the conventional carbon steels. And a single parameter which indicates the degree of deformation during chip formation, 'chip cross-section area ratio' is introduced. The chip cross-section area. The variational patterns of cross-section area is divided by undeformed chip cross-section area. The variational patterns of the chip cross-section area ratio of the materials cut are similar to those of the shear strain values. The shear stress, however, seems to be dependent on the carbon content of the materials. The cold drawn BiS and Pb-S steels show nearly the same chip forming behaviors and the energy consumed during chip formation is almost same. A low carbon steel without free machining aids shows poor chip breakability due to its high ductility. By introducing a small amount of non-metallic inclusions such as MnS, Bi, Pb or merely increasing carbon content the chip breakability improves significantly.

• 한국해안·해양공학회논문집
• /
• 제34권4호
• /
• pp.109-118
• /
• 2022

정점 표층 수온 관측 데이터 중 결측 구간의 데이터를 양방향 순환신경망(Bidirectional Recurrent Neural Network, BiRNN) 기법을 이용하여 보간하였다. 인공지능 기법 중 시계열 데이터에 일반적으로 활용되는 Recurrent Neural Networks(RNNs)은 결측 추정 위치까지의 시간 흐름 방향 또는 역방향으로만 추정하기 때문에 장기 결측 구간에는 추정 성능이 떨어진다. 반면, 본 연구에서는 결측 구간 전후의 양방향으로 추정을 하여 장기 결측 데이터에 대해서도 추정 성능을 높일 수 있다. 또한 관측점 주위의 가용한 모든 데이터(수온, 기온, 바람장, 기압, 습도)를 사용함으로써, 이들 상관관계로부터 보간 데이터를 함께 추정하도록 하여 보간 성능을 더욱 높이고자 하였다. 성능 검증을 위하여 통계 기반 모델인 Multivariate Imputation by Chained Equations(MICE)와 기계학습 기반의 Random Forest 모델, 그리고 Long Short-Term Memory(LSTM)을 이용한 RNN 모델과 비교하였다. 7일간의 장기 결측에 대한 보간에 대해서 BiRNN/통계 모델들의 평균 정확도가 각각 70.8%/61.2%이며 평균 오차가 각각 0.28도/0.44도로 BiRNN 모델이 다른 모델보다 좋은 성능을 보인다. 결측 패턴을 나타내는 temporal decay factor를 적용함으로써 BiRNN 기법이 결측 구간이 길어질수록 보간 성능이 기존 방법보다 우수한 것으로 판단된다.

• 전자공학회논문지S
• /
• 제35S권9호
• /
• pp.19-27
• /
• 1998

본 연구에서는 E-GSM 단말기용 RF Transceiver 칩의 송신부에 대한 회로설계 및 시뮬레이션, 공정 및 제작, 평가를 수행하였다. AMS社의 0.8${\mu}m$ BiCMOS 공정으로 제작된 RF-IC 칩은 $10 {\times} 10mm$ 크기의 80 pin TQFP로 제작되었으며, 3.3V에서 동작하고 양호한 RF 특성을 보였다. 본 논문에서는 IF/RF 상향변조 주파수 혼합기, IF/RF polyphase, 전치증폭기 등을 포함하는 송신부의 개발 결과를 서술하고자 한다. 송산단의 측정결과 E-GSM RF 송신단 주파수인 880~915MHz에서 양호하게 동작하며, 소비전류는 71mA이고 총출력은 8.2dBm으로 측정되었다.

• 전자공학회논문지S
• /
• 제35S권9호
• /
• pp.9-18
• /
• 1998

본 논문에서는 E-GSM 단말기용 Transceiver RFIC 칩 수신단의 회로설계, 제작 및 특성측정을 수행하였다. AMS사의 0.8${\mu}m$ 실리콘 BiCMOS 공정을 사용하여 $10 {\times} 10 mm$ 크기를 갖는 80핀 TQFP 패키지로 제작하였으며, 동작전압 3.3V에서 우수한 RF 성능을 얻었다. 제작된 RFIC의 수신단에는 LNA, Down Conversion Mixer, AGC, SW-CAP 및 Down Sampling Mixer를 포함하고 있으며, 제작된 RFIC의 사용 주파수 범위는 925 ~ 960MHz, 전류소모는 67mA, 최소검출레벨은 -105dBm의 특성을 얻었다.

• 한국주조공학회지
• /
• 제25권1호
• /
• pp.40-50
• /
• 2005

A series of heavy section ductile cast iron ingots with the cube length of 250mm were systematically investigated as functions of casting parameters of sand casting. Abnormal graphite formation was specially observed with the variation of Si content and Bi or Sb addition. Effects of chilling during casting and adaptation of riserless system were also examined, and proved to be effective for the prevention of both shrinkage and abnormal graphite such as chunky one. The formation of chunky graphite was effectively prevented by low Si content despite the promotion of pearlite matrix structure. The ferritic matrix was encouraged to form by high Si content and chunky graphite formation was effectively suppressed by the addition of Bi and Sb. Bi addition, however, was not good enough to control the microstructure owing to the sensitive cooling rate dependent inoculation behavior and relative low ability of nodulization. Sb addition, on the other hand, was proved to be effective for the microstructural control and enhancement of various mechanical properties such as strength, elongation, and impact energy. It may be suggested that optimized casting parameters should be applied to produce heavy section ductile cast iron with reliability.

• KIEE International Transactions on Power Engineering
• /
• 제3A권4호
• /
• pp.222-230
• /
• 2003

This paper presents reference designs for vapor-cooled HTS/Copper leads rated at 25 kA and 40 kA and that satisfy a protection criterion. Each HTS section is cooled by the effluent helium vapor boiling from a 4.2-K bath. Each HTS section is based on a design concept in which a short portion of its warm end (77.3 K) operates in the current-sharing mode; such operation results in a considerable saving for HTS materials required in the HTS section. Two designs of "fully superconducting" vapor-cooled HTS sections, one rated at 25 kA and the other at 40 kA are also presented as comparison bases for the new HTS sections. Each warm end of HTS sections is coupled to an optimal vapor-cooled copper lead rated at the same current as that for the HTS section. The extra coolant required at 77.3 K at the coupling station, an optimal length of the copper section will be shorter than that optimized for helium-vapor cooling between 4.2 K and room temperature.mperature.

• 한국기계가공학회지
• /
• 제4권2호
• /
• pp.3-9
• /
• 2005

In this study, the chip breaking characteristics of S, PbS and BiS free machining steels have been assessed. PbS free machining steel shows the lowest value of chip thickness ($t_c$) under the same cutting conditions. SM10C steel has the largest value of the chip cross-section area ratio ($R_{CA}$). As the feed rate becomes larger the chip breaking cycle time ($T_B$) decreases and the chip breaking index ($C_B$) increases. The properly controlled-C type chip has been obtained with the value of $C_B$ between 0.05 and 0.2. Free machining steel, PbS produces the properly controlled-C type chip in a wider feed rate range than other steels.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
• /
• pp.282-283
• /
• 2014

An active study on UHPC, which has been recently used in high-rise building and bridges, is in progress. However, research on adhesion strength of normal concrete and UHPC is required to be studied due to the lack of information. In this study, experimental research progress for adhesion strength (shear strength of adhesive surface) evaluation of Bi-compressive strength concretes (UHPC, Normal concrete) is proceeded. First, specimens using glue are produced and surface treatment methods of concrete bonded section are considered. Second, Direct Shear test is applied on concrete bonded section of UHPC (80~180MPa) and Normal Concrete (NC). As a result of this study, it is confirmed that bond strength is deteriorated as the difference of intensity ration of NC and UHPC increases.