• Journal of Advanced Navigation Technology
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• v.21 no.4
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• pp.353-358
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• 2017

In order to reduce the size of the previous stepped slot antenna for UWB applications(3.1 ~ 10.6 GHz) to half, an open ended stepped slot antenna is proposed. The proposed antenna consists of a stepped slot etched on the ground plane as radiation part and a microstrip feed-line with rectangular patch on the top plane for wideband impedance matching. The proposed antenna is designed and fabricated on the FR4 substrate with dielectric constant of 4.3, thickness of 1.6 mm and size of $28.5{\times}32mm^2$. The measured impedance bandwidth (${\mid}S_{11}{\mid}{\leq}-10dB$) of the fabricated antenna is 7.99 GHz(3.01~11 GHz) which is sufficient to cover UWB band (3.1 ~ 10.6 GHz). In particular, it has been observed that antenna has a good omnidirectional radiation patterns and high gain over the entire frequency band of interest even though the size of the proposed antenna is reduced to half when compared with the previous antenna.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.4
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• pp.345-358
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• 2018

The high altitude scientific balloon has been used for decades in advanced aerospace countries such as United States, France, and Japan to carry out various research objectives. Since the initial cost for development and operation is enormous, it has been conducted by national research institutes. Recently, the advent of open source software/hardware ecosystems with low-cost yet high-performance have lowered barriers to enter into scientific balloon research and development. In this study, a zero pressure balloon prototype was designed considering the cost, usability, compatibility, and development period by using commercial off the shelf (COTS) items. In addition, the flight operation experience was accumulated through eight times of the flight tests, and operational reliability of the balloon system was verified. Finally, the foundation for the operation of the large zero pressure balloon was established.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.91-91
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• 2015

반도체 공정의 발전에 의해 최근 생산되는 메모리 등은 십 수 나노미터까지 좁아진 선 폭을 갖게 되었다. 이러한 이유로, 기존에는 큰 문제를 발생시키지 않던 나노미터 영역의 입자들이 박막 증착 공정과 같은 반도체 제조공정 수율을 저감시키게 되었다. 따라서 오염입자의 유입을 막거나 제어하기 위해 transmission electron microscopy (TEM)나 scanning electron microscopy (SEM)과 같은 전자현미경을 활용한 비 실시간 입자 측정 방법 및 광원을 이용하는 in-situ particle monitor (ISPM) 및 전기적 이동도를 이용한 scanning mobility particle sizer (SMPS) 등 다양한 원리를 이용한 실시간 입자 측정방법이 현재 사용중에 있다. 이 중 진공 내 입자의 수농도를 측정하기 위해 개발된 particle beam mass spectrometer (PBMS) 기술은 박막 증착 공정 등 chemical vapor deposition (CVD) 방법을 이용하는 진공공정에서 활용 가능하여 개발이 진행되어 왔다. 본 연구에서는 PBMS의 한계점인 입자 밀도, 형상 등의 특성분석이 용이하도록 PBMS와 scanning electron microscopy (SEM), 그리고 energy dispersive spectroscopy (EDS) 기술을 결합하여 입자의 직경별 개수농도, 각 입자의 형상 및 성분을 함께 측정 가능하도록 하였다. 협소한 반도체 제조공정 내부 공간에 적용 가능하도록 기존 PBMS 대비 크기 또한 소형화 하였다. 각 구성요소인 공기역학 집속렌즈, electron gun, 편향판, 그리고 패러데이 컵의 설치 및 물리적인 교정을 진행한 후 입자발생장치를 통해 발생시킨 sodium chloride 입자를 상압 입자 측정 및 분류장치인 SMPS 장치를 이용하여 크기별로 분류시켜 압력차를 통해 PBMS로 유입시켜 측정을 진행하였다. 나노입자의 입경분포, 형상 및 성분을 측정결과를 토대로 장치의 측정정확도를 교정하였다. 교정된 장치를 이용하여 실제 박막 증착공정 챔버의 배기라인에서 발생하는 입자의 수농도, 형상 및 성분의 복합특성 측정이 가능하였으며, 최종적으로 실제 공정에 적용가능하도록 장치 교정을 완료하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.1
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• pp.36-44
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• 2010

The accurate prediction of dynamic characteristics of high speed rotors, such as gas turbines, is important to avoid the possibility of operating the machinery near the critical speeds or unstable speed regions. However, the dynamic analysis methods and softwares for gas turbines have been developed in the process of producing many gas turbines by manufacturers and most of them have seldom been disclosed to the public. Recently, commercial FEM softwares, such as SAMCEF, ANSYS and NASTRAN, started supporting some rotordynamics analysis modules based on 3-D finite elements. In this paper, the dynamic analysis method using commercial S/W, especially ANSYS, is attempted for the small-size gas turbine engine rotor, and the analysis capability and limitations of its rotordyamics module are evaluated for further improvement of the module. As the preliminary procedure, the rotordyamic analysis capability of ANSYS was tested and evaluated with the reference models of the well-known dynamics. The limitations in application of the rotordynamics module were then identified. Under the current capability and limitations of ANSYS, it is shown that Lee diagram, a new frequency-speed diagram enhanced with the concept of $H{\infty}$ in rotating machinery, can be indirectly obtained from FRFs computed from harmonic response analysis of ANSYS. Finally, it is demonstrated based on the modeling and analysis method developed in the process of the S/W verification that the conventional Campbell diagram, Lee diagram, mode shapes and critical speeds of the small-size gas turbine engine rotor can be computed using the ANSYS rotordynamics module.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2010.04a
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• pp.385-386
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• 2010

The ship's seakeeping performance in the pitching and roll motion was felt tired. These gives structural loads to loaded with cargo and hull facilities. Be to improve, small catamaran power yacht designed a data for ship research and ship's hull form to be decided. In this study, based on domestic release for coastal marine environment in the interpretation criteria were chosen based on the exercise performance. The seakeeping performance of marine leisure catamaran was based on voyage speed. The seakeeping performance estimates based on the encounter angle, the wave of the encounter frequency response amplitude ratio for exercise was assessed in the high performance area.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.42 no.4 s.304
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• pp.1-10
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• 2005

Recently, most of PLC has been using widely in automation equipment that is needed for field of industry automation. HMI is essential system for effective Control of many numbers of PLC. Even though early HMI system was consists of simple analog devices, however, HMI system could control or supervise PLC through display screen since it embeds various digital parts by development of technology in these days. HMI system consists of three parts as HMI hardware, an operating program for HMI equipment and a HMI screen editor. Among these elements, a Program for editing screen of HMI should provide various screen elements that helps users to edit each screens displayed on HMI. In this study, we design and implement screen edit program by object-oriented method for small HMI equipment and propose Prototype of embedded HMI system.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.534-539
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• 2008

This paper is about intelligent hexapod robot for the support walking of the aged person. The robot using various sensors and small camera has various abilities of forward backward walking, turing left or right, control the speed of walking, avoiding the obstacles and detecting risky situation of fire or gas. To let the aged feel soft and safe walking, we used special servo motor and developed hexapod walking mechanism and effective algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.529-537
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• 2006

Multi-layer PCBs are of ien used In compact microwave circuit design as density of PCB layout is increased. In this paper, the crosstalk between coupled lines connected with vias in a 4-layer PCB is investigated theoretically based on the circiuit-concept approach. Coupled lines connected with vias in a 4-layer PCB are divided into three sections, which are coupled microstrip lines and upper via section, center via section, and lower via and coupled microstrip lines section, respectively. Each section is represented by ABCD matrix. By cascading these three ABCD matrices crosstalk between coupled lines connected with vias in a 4-layer PCB is approximately calculated. The validity of this theoretical approach is verified by comparing the calculated results with the simulated ones using HFSS.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.379-388
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• 2007

This paper presents a real-time respiration and heartbeat detector comprised of a 1.6 GHz single-channel Doppler sensor and analog/digital signal processing block for remote vital sign detection. The RF front end of the Doppler sensor consists of an oscillator, mixer, low noise amplifier, branch-line hybrid and patch antenna. We apply artificial transmission lines(ATLs) to the branch-line hybrid, which leads to a size reduction of 40 % in the hybrid, while its performance is very comparable to that of a conventional hybrid. The analog signal conditioning block is implemented using second order Sallen-Key active filters and the digital signal processing block is realized with a LabVIEW program on a computer. The respiration and heartbeat detection is demonstrated at a distance of 50 cm using the developed system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.1995-2001
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• 2001

In this study, a small punch creep(SP-Creep) test using miniaturized specimen(10${\times}$10${\times}$0.5mm) is described to develop the new creep test method for high temperature structural materials. The SP-Creep test is applied to 2.25Cr-lMo(STBA24) steel which is widely used as boiler tube material. The test temperatures applied for the creep deformation of miniaturized specimens are between 550∼600$^{\circ}C$. The SP-Creep curves depend definitely on applied load and creep temperature, and show the three stages of creep behavior like in conventional uniaxial tensile creep curves. The load exponent of miniaturized specimen decreases with increasing test temperature, and its behavior is similar to stress exponent behavior of uniaxial creep test. The creep activation energy obtained from the relationship between SP-Creep rate and test temperature decreases as the applied load increases. A predicting equation or SP-Creep rate for 2.25Cr-lMo steel is suggested. and a good agreement between experimental and calculated data has been found.