• 한국항행학회논문지
• /
• 제4권2호
• /
• pp.191-200
• /
• 2000

최근, NORAD(북미방공사령부)의 발표에 따르면 10cm 이상의 우주물체로서 목록화 되어 관리가 되는 것 중의 단지 10%만이 임무와 관련된 것이고 나머지는 보조연료탱크, 그리고 인공위성의 잔해들로서 임무와는 상관이 없는 우주폐기물인 것으로 분석되었다. 우주폐기물의 대표적인 경우는 우주물체간의 충돌이나 폭발로 인해 발생된다. 그리고 임무 중인 인공위성에 큰 피해를 초래하게 된다. 현재 몇몇 국가에서는 지구 및 우주환경을 보호하고 인류의 안전을 위해 새로운 위성모델의 개발을 추진 중이다.

• 한방재활의학과학회지
• /
• 제25권4호
• /
• pp.75-81
• /
• 2015

Objectives To investigate the relationship between cervical intervertebral space narrowing in the X-ray and HIVD level of cervical spine in the CT image. Methods We studied 101 subjects who were taken cervical spine X-ray and CT. Intervertebral space were measured at the anterior, middle and posterior portion of each cervical disc in the X-ray. Considering individual difference, intervertebral space was set as value divided by upper width of lower vertebral body. We analyzed statistically adjusted intervertebral space of normal group and herniated disc group using student' t t-test. Results Intervertebral space of cervical spine was narrowed in the herniated disc group. But there was no significant difference at C2~C3. Conclusions We found that narrowing intervertebral space of cervical spine is associated with herniated disc. Further clinical observation is needed.

• Journal of Astronomy and Space Sciences
• /
• 제33권4호
• /
• pp.335-344
• /
• 2016

Scientific CubeSat with Instruments for Global Magnetic Fields and Radiations (SIGMA) is a 3-U size CubeSat that will be operated in low earth orbit (LEO). The SIGMA communication system uses a very high frequency (VHF) band for uplink and an ultra high frequency (UHF) band for downlink. Both frequencies belong to an amateur band. The ground station that communicates with SIGMA is located at Kyung Hee Astronomical Observatory (KHAO). For reliable communication, we carried out a laboratory (LAB) test and far-field tests between the CubeSat and a ground station. In the field test, we considered test parameters such as attenuation, antenna deployment, CubeSat body attitude, and Doppler frequency shift in transmitting commands and receiving data. In this paper, we present a communication performance test of SIGMA, a link budget analysis, and a field test process. We also compare the link budget with the field test results of transmitting commands and receiving data.

• Journal of applied mathematics & informatics
• /
• 제15권1_2호
• /
• pp.127-146
• /
• 2004

In this paper we consider a heat flow in an inhomogeneous. body without internal source. There exists special initial and boundary conditions in this system and we intend to find a convenient coefficient of heat conduction for this body so that body cool off as much as possible after definite time. We consider this problem in a general form as an optimal control problem which coefficient of heat conduction is optimal function. Then we replace this problem by another in which we seek to minimize a linear form over a subset of the product of two measures space defined by linear equalities. Then we construct an approximately optimal control.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 춘계학술대회논문집
• /
• pp.260-267
• /
• 2002

For an elastically suspended rigid body with the planes of symmetry in a three dimensional space, a novel analysis fur the vibration modes is presented. From the decompositions of the stiffness and inertia matrices, the conditions for the existence of pure translation and pure couple modes are analyzed for an elastically suspended rigid body with the planes of symmetry. From this analysis, it can be showed that how the structure of stiffness and inertia must be related in order to produce the pure translation and pure couple modes when an elastically suspended rigid body has one, two, or three planes of symmetry.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.464-466
• /
• 2014

The mechanism synthesis methods, graphical, analytical and computer-aided technique have been proposed for selecting and scaling mechanical system. According to developing computation tools, mechanism could be synthesized much faster and more correct than previous analytical ways by improved techniques. In this paper, the improved synthesis method is proposed to solve body guidance synthesis problem. To perform the mechanism synthesis for body guidance, a planar linkage is modeled as a set of free three bushings located in design space. The values of bushing stiffness and x, y position of bushings yielding a desired functional requirement related to input motion are found by using an optimization technique.

• ETRI Journal
• /
• 제37권3호
• /
• pp.439-449
• /
• 2015

Human body communication (HBC) is being recognized as a new communication technology for mobile and wearable devices in a body area network (BAN). This paper presents co-channel interference experienced by HBC supporting the physical layer in the IEEE 802.15.6 BAN standard. To analyze the co-channel interference, a co-channel interference model is introduced, and space-domain and time-domain parameters representing an interference environment are generated using the co-channel interference model. A new signal-to-interference ratio (SIR) parameter depending on the peak amplitudes of the data signals causing co-channel interference is defined; co-channel interference can be easily analyzed and modelled using the newly defined SIR. The BER degradation model derived using the co-channel interference model and SIR in this paper can be effectively used to estimate the performance.

• Structural Engineering and Mechanics
• /
• 제4권1호
• /
• pp.91-107
• /
• 1996

In Lagrangian mechanics, attention is directed at the body as it moves through space. Each body point is identified by the position it would have if the body were to occupy an arbitrary reference configuration. A result of this approach is that the analyst often describes the body by using quantities that may involve more than one configuration. This is particularly common in incremental calculations and in changes of the choice of reference configuration. With the rise of very powerful computing machinery, the popularity of numerical calculation has become great. Unfortunately, the mechanical theory has been evolved in a piecemeal fashion so that it has become a conglomeration of differently developed patches. The current work presents a unified development of the equilibrium principle. The starting point is the conservation of momentum. All details of configuration are shown. Finally, full dynamic and static forms are presented for total and incremental work.

• Journal of Multimedia Information System
• /
• 제8권2호
• /
• pp.111-120
• /
• 2021

As recent virtual reality technologies provide a more natural three-dimensional interactive environment, users naturally learn to explore space and interact with synthetic objects. The virtual reality researcher develops a technique that realizes realistic sensory feedback to get appropriate feedback to sense input behavior. Although much recent virtual reality research works extensively consider the human factor, it is not easy to adapt to all new virtual environment contents. Among many human factors, distance perception has been treated as very important in virtual environment interaction accuracy. We study the experiential virtual environment with the feature of the virtual object connected with the real object. We divide the three-dimensional interaction, in which distance perception and behavior have a significant influence, into two types (whole-body movement and direct manipulation) and analyze the real and virtual visual distance perception heterogeneity phenomenon. Also, we propose a statistical correction method that can reduce a near-body movement and manipulation error when changing the interaction location and report the experiment results proving its effectiveness.

• 로봇학회논문지
• /
• 제17권3호
• /
• pp.359-364
• /
• 2022

This study presents a nonlinear model predictive control (NMPC)-based obstacle avoidance and whole-body motion planning method for the mobile manipulators. For the whole-body motion control, the mobile manipulator with an omnidirectional mobile base was modeled as a nine degrees-of-freedom (DoFs) serial open chain with the PPR (base) plus 6R (arm) joints, and a swept sphere volume (SSV) was applied to define a convex hull for collision avoidance. The proposed receding horizon control scheme can generate a trajectory to track the end-effector pose while avoiding the self-collision and obstacle in the task space. The proposed method could be calculated using an interior-point (IP) method solver with 100[ms] sampling time and ten samples of horizon size, and the validation of the method was conducted in the environment of Pybullet simulation.