• Steel and Composite Structures
• /
• 제1권4호
• /
• pp.441-458
• /
• 2001

We analyzed the experimental and theoretical behavior of a particular type of steel joint designed to connect beam to beam and able to transfer both shear forces and bending moments. This joint is characterized by the use of steel plates and bolts enclosed in the width of the beams. The experimental investigation was carried out characterizing the constituent materials and testing in flexure beams constituted by two portions of beams connected in the middle with the joint proposed. Connections having different characteristics in terms of thickness of plates, number and type of bolts were utilized. Flexure tests allow one to determine the loaddeflection curves of the beam tested and the moment-rotation diagrams of the connections, highlighting the strength and the strain capacity of the joints. The proposed analytical model allows one to determine the moment-rotation relationship of the connections, pointing out the influence of the principal geometrical and mechanic characteristics of single constituents on the full properties of the joint.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.1722-1723
• /
• 2007

This paper describes a simple method to reduce rotation angle error of mobile robot using omni-wheel[3](omni-bot). This method can be applied to not only omni-bot, but also other robot with a large number of servo motor. Robot using many servo motor as omni-bot is complicated for hardware and software, each servo motor has difficulty in synchronizing. Three servo motor, three omni-wheel and three serial servo motor controller is used, PC or Micro Processor interface with the serial servo controller through "SSC100" protocol. In order to check the improvement of the proposed serial servo synchronization compared to existing sequential communication method. comparing object is rotation angle error of omni-bot. The results of this make building of omni-bot system easy and decrease rotation angle error.

• 대한전자공학회논문지
• /
• 제23권3호
• /
• pp.340-344
• /
• 1986

This paper shows that we can design a vector-coordinate rotation processor and obtain the approximate evaluations of sine and cosine based upon the use of residue number systems. The algorithm results in the considerable improvement of the computation speed when compared to CORDIC algorithm. The results from computer simulation show that the mean error of sine and cosine is 0.0025 and the mean error of coordinate rotation arithmatic is 0.65. Also, the proposed processor has the efficiency for the design and fabrication of integrated circuit, because it consists of the array of idecntially structured look-up tables.

• 대한기계학회논문집B
• /
• 제30권11호
• /
• pp.1074-1083
• /
• 2006

In the present study, the effect of blade rotation on blade heat transfer is investigated by comparing with the heat transfer results for the stationary blade. The experiments are conducted in a low speed annular cascade with a single stage turbine and the turbine stage is composed of sixteen guide vanes and blades. The chord length and the height of the tested blade are 150 mm and about 125 mm, respectively. The blade has a flat tip and the mean tip clearance is 2.5% of the blade chord. A naphthalene sublimation method is used to measure detailed mass transfer coefficient on the blade. For the experiments, the inlet Reynolds number is $Re_c=1.5{\times}10^5$, which results in the blade rotation speed of 255.8 rpm. Blade rotation induces a relative motion between the blade and the shroud as well as a periodic variation of incoming flow. Therefore, different heat/mass transfer patterns are observed on the rotating blade, especially near the tip and on the tip. The relative motion reduces the tip leakage flow through the tip gap, which results in the reduction of the tip heat transfer. However, the effect of the tip leakage flow on the blade surface is increased because the tip leakage vortex is formed closer to the surface than the stationary case. The overall heat/mass transfer on the shroud is not affected much by the blade rotation.

• 천문학회보
• /
• 제45권1호
• /
• pp.60.3-61
• /
• 2020

We perform disk-halo decomposition of the Large Magellanic Cloud (LMC) using a novel HI velocity field extraction method, aimed at better deriving its HI kinematics and thus the dark matter density profile. For this, we use two newly developed galaxy kinematic analysis tools, BAYGAUD and 2DBAT which have been used for the kinematic analysis of resolved galaxies from Australian Square Kilometre Array (ASKAP) observations like WALLABY which is an all-sky HI galaxy survey in southern sky. By applying BAYGAUD to the combined HI data cube of the LMC taken with the Australia Telescope Compact Array (ATCA) and Parkes radio telescopes, we decompose all the line-of-sight velocity profiles into an optimal number of Gaussian components based on Bayesian MCMC techniques. From this, we disentangle turbulent non-circular gas motions from the overall rotation of the galaxy. We then derive the rotation curve of the LMC by applying 2DBAT to the separated circular motions. The rotation curve reflecting the total kinematics of the LMC, dark and baryonic matters is then be combined with the mass models of baryons, mainly stellar and gaseous components in order to examine the dark matter distribution. Here, we present the analysis of the extracted HI gas maps, rotation curve, and J, H and K-band surface photometry of the LMC.

• Geomechanics and Engineering
• /
• 제37권4호
• /
• pp.383-393
• /
• 2024

Monopile foundations of offshore wind turbines embedded in soft clay are subjected to the long-term cyclic lateral loads induced by winds, currents, and waves, the vibration of monopile leads to the accumulation of pore pressure and cyclic strains in the soil in its vicinity, which poses a threat to the safety operation of monopile. The researchers mainly focused on the hysteretic stress-strain relationship of soft clay and kinds of stiffness degradation models have been adopted, which may consume considerable computing resources and is not applicable for the long-term bearing performance analysis of monopile. In this study, a modified cyclic stiffness degradation model considering the effect of plastic strain and pore pressure change has been proposed and validated by comparing with the triaxial test results. Subsequently, the effects of cyclic load ratio, pile aspect ratio, number of load cycles, and length to embedded depth ratio on the accumulated rotation angle and pore pressure are presented. The results indicate the number of load cycles can significantly affect the accumulated rotation angle of monopile, whereas the accumulated pore pressure distribution along the pile merely changes with pile diameter, embedded length, and the number of load cycles, the stiffness of monopile can be significantly weakened by decreasing the embedded depth ratio L/H of monopile. The stiffness degradation of soil is more significant in the passive earth pressure zone, in which soil liquefaction is likely to occur. Furthermore, the suitability of the "accumulated rotation angle" and "accumulated pore pressure" design criteria for determining the required cyclic load ratio are discussed.

• 한국잡초학회지
• /
• 제17권2호
• /
• pp.157-162
• /
• 1997

답전윤환(畓田輪換)에 따른 잡초발생 양상(樣相)을 구명하여 환경보존형(環境保全型) 잡초방제(雜草防除) 기술(技術)의 기초자료를 얻고자 수행한 결과 다음의 결과를 얻었다. 1. 답전윤환(畓田輪換)에 따른 초종별 우점도(優占度)를 보면 밭을 논으로 윤환(輪換)함으로서 방동사니, 피, 마디꽃, 밭뚝외풀, 여뀌 순으로 우점도(優占度)가 높았으며 반대로 논을 밭으로 윤환(輪換)함으로서 피, 바랭이, 방동사니, 밭뚝외풀 순으로 우점도(優占度)가 높았다. 2. 답전윤환(畓田輪換)에 의한 잡초방제(雜草防除) 효과(效果)는 74-78%로 밭을 논으로 윤환(輪換)함으로서 명아주, 바랭이, 환삼덩굴, 메꽃, 닭의장풀 등이 반대로 논을 밭으로 윤환(輪換)함으로서 마디꽃, 올챙이고랭이, 피 등이 감소(減少)하였다. 3. 답전윤환(畓田輪換)에 따른 초종별 유사성(類似性) 계수(係數)는 밭을 논으로 윤환(輪換)함으로서 8, 반대로 논을 밭으로 윤환(輪換)함으로서 64를 나타내었으며 Simpson index로 0.34-0.35로 나타나 답전윤환(畓田輪換)에 의해 군락내 초종이 매우 다양화(多樣化)되었다.

• 한국정보통신학회논문지
• /
• 제19권10호
• /
• pp.2367-2372
• /
• 2015

탁월한 에러 정정 능력으로 인해 최근 통신 표준에서 많이 채택되고 있는 low-density parity-check(LDPC) 코드중, quasi-cyclic LDPC(QC-LDPC) 코드는 복호기 복잡도가 비교적 낮아서 많이 사용되고 있다. QC-LDPC 코드의 복호기 설계에 있어서 중요한 블록 중 하나가 여러 가지 크기의 rotation을 수행할 수 있는 multi-size circular shifter(MSCS)이다. MSCS의 여러 구현 방법 중 많이 사용되는 Benes 네트워크는 일반적인 MSCS 동작에는 효율적이나 rotation 크기 등의 특징을 이용할 수 없는 단점이 있다. 이 논문에서는 Benes 네트워크의 제어 신호 생성을 수정하여서 rotation 크기 특징을 이용할 수 있는 방법을 제시한다. 제안된 제어 신호 생성법을 IEEE 802.16e WiMAX 표준의 QC-LDPC 코드 복호기에 적용하여, MUX의 개수를 줄이고 지연 시간을 단축하였다.

• 문화기술의 융합
• /
• 제8권2호
• /
• pp.53-58
• /
• 2022

일반적인 가정용 선풍기는 단 하나의 좌우 회전 구간을 갖기 때문에 회전 각도를 조절할 수 없어 불필요한 영역까지 바람이 가거나 바람이 필요한 공간에 바람이 가지 않는 구간이 발생한다. 본 논문에서는 에너지 낭비를 줄이면서 필요한 공간에 선택적으로 바람을 보낼 수 있도록 회전 구간을 효율적으로 조절하는 방법을 제시하고자 한다. 정지 풍향각 측정 실험을 통해 최소 회전 각도를 구하였으며 최적의 회전 단계수를 선정하기 위해 바람이 도달하는 공간을 적절히 분할하였다. 이를 통해 선풍기가 45°의 최소 회전 각도와 3단계의 회전 구간을 가지면서 각 단계마다 정지 풍향각의 2배씩 회전 각도가 증가할 때 바람이 효율적으로 분배되는 것을 확인하였다. 따라서 본 논문에서 제시한 선택적 회전 구간 조절 방법은 선풍기 구조에 큰 변형 없이 에너지 낭비를 최소화 할 수 있을 것으로 사료된다.

• Journal of Mechanical Science and Technology
• /
• 제17권4호
• /
• pp.562-570
• /
• 2003

This experimental study concerns the characteristics of vortex flow in a concentric annulus with a diameter ratio of 0.52, whose outer cylinder is stationary and inner one is rotating. Pressure losses and skin friction coefficients have been measured for fully developed flows of water and of 0.4% aqueous solution of sodium carboxymethyl cellulose (CMC), respectively, when the inner cylinder rotates at the speed of 0～600 rpm. Also, the visualization of vortex flows has been performed to observe the unstable waves. The results of present study reveal the relation of the bulk flow Reynolds number Re and Rossby number Ro with respect to the skin friction coefficients. In somehow, they show the existence of flow instability mechanism. The effect of rotation on the skin friction coefficient is significantly dependent on the flow regime. The change of skin friction coefficient corresponding to the variation of rotating speed is large for the laminar flow regime, whereas it becomes smaller as Re increases for the transitional flow regime and. then, it gradually approach to zero for the turbulent flow regime. Consequently, the critical (bulk flow) Reynolds number Re$\_$c/ decreases as the rotational speed increases. Thus, the rotation of the inner cylinder promotes the onset of transition due to the excitation of Taylor vortices.