• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12B
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• pp.1236-1243
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• 2010

The perimeter defense system was created and its characteristics were evaluated. It was designed to utilize the fiber sensing device, namely OTDR(Optical Time Domain Reflectometer) which has been used for the maintenance of the optical communication network. An OTDR was constituted by a pulse laser with the nature of 1310nm, +15dBm for the observation of 400 meter optical fence. The high-speed 32-bit processor(S3C2440) has applied to MPU(Main Processor Unit) which helps to improve the performance of OTDR algorithms. Consequently, the maximum error was 0.84 meter on the performance test of the 10km monitoring and the pass criteria of ${\pm}1m$ satisfied in all the sections. The alarm delay time was under 3 sec after detecting the disorder. For the case of secondary trespassing after primary trespassing, the optical switch was installed in OTDR to monitor the secondary trespassing and to measure the multi-point detection. Therefore, this paper shows that the detections of secondary trespassing and multi-point is possible by means of optical switch.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.6
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• pp.1083-1091
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• 2017

This paper describes a design of cryptographic processor supporting 224-bit elliptic curves over prime field defined by NIST. Scalar point multiplication that is a core arithmetic function in elliptic curve cryptography(ECC) was implemented by adopting the modified Montgomery ladder algorithm. In order to eliminate division operations that have high computational complexity, projective coordinate was used to implement point addition and point doubling operations, which uses addition, subtraction, multiplication and squaring operations over GF(p). The final result of the scalar point multiplication is converted to affine coordinate and the inverse operation is implemented using Fermat's little theorem. The ECC processor was verified by FPGA implementation using Virtex5 device. The ECC processor synthesized using a 0.18 um CMOS cell library occupies 2.7-Kbit RAM and 27,739 gate equivalents (GEs), and the estimated maximum clock frequency is 71 MHz. One scalar point multiplication takes 1,326,985 clock cycles resulting in the computation time of 18.7 msec at the maximum clock frequency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.88-92
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• 2017

Owing to the depletion of fossil energy, wind power is attracting attention as a promising environmentally friendly alternative energy source, because it is abundant, renewable, and non-polluting. Wind turbines are divided into horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs) according to the direction of the rotating shaft. VAWTs have a low power generation efficiency, but are not affected by the wind direction and, thus, no yaw system is required and their structure is simple. Small VAWTs are attracting much attention because they can generate power even at low wind speeds. In this study, the output voltages and output currents of small VAWTs with gyromill type, hinge type and double door type blades capable of generating power even at low wind speeds were analyzed at variable wind speeds in the range of 1~11 m/s. At the maximum wind speed of 11m/s, the application of the double door type blades achieved 67% and 9% higher wind turbine output voltages than that of the gyromill type and hinge type blades, respectively. As regards the wind turbine output currents, the application of the double door type blades gave rise to 93% and 5% higher results than that of the gyromill type and hinge type blades, respectively. Through this study, the excellent output characteristics and commercialization potential of the double door type blades, which can generate power both at low and high wind speeds, were confirmed.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.121-126
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• 2017

A technique for producing the ear shell for a hearing aid using DICOM (Digital Imaging and Communication in Medicine) image and a 3D printing was studied. It is a new application method, and is an application technique that can improve the safety and infection of hearing aid users and can reduce the production time and process stages. In this study, the effects on the shape surface were examined before and after the printing of the ear shell using a 3D printer based on the values obtained from the raw data of the DICOM images at the volumes of 0.5 mm, 1.0 mm, and 2.0 mm, respectively. Before the printing, relative relationship was compared with respect to the STL (STereoLithography) file structure; and after the printing, the intervals of the layered structure of the ear shell shape surface were compared by magnifying them using a microscope. For the STL file structure, the numbers of triangular vertices, more than five intersecting points, and maximum intersecting points were large in the order of 0.5 mm, 1.0 mm, and 2.0 mm, respectively; and the triangular structure was densely distributed in the order of the bending, angle, and crest regions depending on the sinuosity of the external auditory meatus shape. As for the ear shell shape surface examined by the digital microscope, the interval of the layered structure was thick in the order of 2.0 mm, 1.0 mm, and 0.5 mm. For the STL surface structure mentioned above, the intersecting STL triangular structure was denser as the sinuosity of the 3D ear shell shape became more irregular and the volume of the raw data decreased.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.10
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• pp.72-81
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• 2011

In this paper, we proposed and designed a novel floating point converter which supports single and double precisions of IEEE754 standard. The proposed convertor supports conversions between floating point number single/double precision and signed fixed point number(32bits/64bits) as well as conversions between signed integer(32bits/64bits) and floating point number single/double precision and conversions between floating point number single and double precisions. We defined a new internal format to convert various input types into one type so that overflow checking could be conducted easily according to range of output types. The internal format is similar to the extended format of floating point double precision defined in IEEE754 2008 standard. This standard specifies that minimum exponent bit-width of the extended format of floating point double precision is 15bits, but 11bits are enough to implement the proposed converting unit. Also, we optimized rounding stage of the convertor unit so that we could make it possible to operate rounding and represent correct negative numbers using an incrementer instead an adder. We designed single cycle data path and 5 cycles data path. After describing the HDL model for two data paths of the convertor, we synthesized them with TSMC 180nm technology library using Synopsys design compiler. Cell area of synthesis result occupies 12,886 gates(2 input NAND gate), and maximum operating frequency is 411MHz.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.1
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• pp.79-89
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• 2006

Particularly the photovoltaic systems are preferred because the output is extracted to the useful electric energy. However, the output characteristics of photovoltaic(PV) systems using solar cell or array depend on the weather conditions. The assistant equipment which emulates the solar cell characteristics that can be controlled arbitrarily by researcher is required to the researchers for reliable experimental data. To solve these problems, it is necessary to research a solar cell model of which output characteristics varied by setting the weather conditions such as insolation levels and temperatures. Therefore, this paper was presented that improved model which is based on interpolation model. To verified the improved model, it is confirmed using the simulation of MATLAB. Also, the experiment was performed by the characteristics of virtual implemented solar cell(VISC) system with the proposed solar cell model. It could be confirmed that there exists actual ewer within 5% between actual solar cell and VISC system.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1030-1035
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• 2012

In this research, we analysed design and CFD analysis of an inflow radial turbine for OTEC with an output power of 8kW using an working fluid of ammonia. The inflow radial turbine consists of scroll casing, vain nozzle with 18 blade numbers and rotor blade with 13 blade numbers. Mass flow rate, and inlet temperature are 0.5kg/s and $25^{\circ}C$ respectively, and variable rotational speeds were applied between 12,000 and 36,000 with 3,000 rpm intervals. As the results according to the rotational speeds, the designed speed is 24,000 rpm where maximum efficiency exists. The maximum efficiency and output power are 88.66% and 8.52kW, respectively. Through this study, we expect that the analysed results will be used as the design material for the composition of the turbine optimal design parameters corresponding to the target output power under various working material conditions.

• The Journal of the Korea Contents Association
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• v.8 no.6
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• pp.8-15
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• 2008

In this paper, in order to analyze property of frequency response in optical microphone, system was implemented. The capacitance microphone and fiber-optic transmission path type fiber-optic microphone (FOM) have weaknesses in directivity, size, weight, and price. However suggested optical microphone can be constituted by cheap devices, so it has many benefits like small size, light weight, high directivity, etc. Head part of optical microphone which is suggested in this paper is movable back and forth by sound pressure with the attached reflection plate. Operating point is determined by measuring the respond characteristics and choosing the point on which has maximum linearity and sensitivity while changing the distance between optical head and vibrating plate. We measured the output of the O/E transformed signal of the optical microphone while frequency of sound signal is changed using sound measurement/analysis program, Smaart Live and USBPre, which are based on PC, and compared the result from an existing capacitance microphone. The measured Optical microphone showed almost similar output characteristics as those of the compared condenser microphone, and its bandwidth performance was about 300[Hz]-3[kHz] at up to 3 [dB].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1208-1213
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• 2010

In this paper, a microstrip balun-BPF of slotted-square-patch type is proposed. The conventional balun-BPF has some drawbacks of narrow bandwidth and high insertion loss. In order to improve these weak points, we used a square patch in designing balun-BPF on which two slots intersecting perpendicularly and one corner-edge perturbation are adopted. This structure allows one of the most effective use of the patch space so that the insertion loss can be decreased. Changing the slot lengths is use to control the operating frequency and the bandwidth of the balun-BPF. A fabricated balun-BPF shows wide bandwidth of 300 MHz(12.7 %), small insertion loss of 0.56 dB, phase difference of $184^{\circ}{\pm}15^{\circ}$ and amplitude imbalances of within 1 dB between two output ports at 2.4 GHz band.

• Journal of Oral Medicine and Pain
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• v.26 no.4
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• pp.395-406
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• 2001

지난 수십년동안, 다양한 레이저기기를 이용하여 치아 경조직에 대한 응용 실험을 수행되었다. 그러나, 발생한 주요한 문제는 열발생과 플라즈마 형성과 같은 부작용이 지속된다는 점이었다. 실망스러운 실험결과에 따라 치아 삭제에 대한 레이저의 응용에 대한 연구가 거의 진행되지 못하였다. 본 연구의 목적은 국내에서 처음으로 개발된 얼비움레이저기기를 사용하여 다양한 에너지 수준과 다양한 펄스빈도에서 법랑질의 삭제율을 비교하고자 하였다. 본 연구에 사용된 레이저기기는 국내에서 최초로 개발된 $2.94{\mu}m$ 펄스를 $250{\mu}s$ 방출하는 얼비움야그레이저 기기이다. 기기의 에너지는 20 mJ에서 350 mJ까지 다양하게 방출하며, 최대 출력은 3.5 W이다. 22개의 치아를 에폭시 레진에 포매하고 경화하였다. 치아의 법랑질을 회전 다이아몬드 칼을 흐르는 물과 함께 사용하여 협측 또는 설측으로 평탄하게 삭제하였다. 제작된 법랑질표면은 6개의 구획으로 구분하여 에너지 수준과 펄스빈도에 따라 조사하였다. 본 연구에서 사용된 표본 수는 132개이며, 삭제율을 조사하기 위한 모든 표본은 22개의 실험 군으로 분류하였다. 실험결과는 다음과 같다. 1. 에너지 수준간에는 유의한 삭제율의 차이가 있었다. 2. 40 및 80 mJ로 조사한 경우에는 펄스빈도 간에 차이가 없었지만, 120 mJ의 출력으로 동일한 에너지를 조사한 경우에는 20 Hz가 40 또는 80 mJ로 조사한 경우 보다 가장 삭제효과가 높았다. 3. 연속조사 한 경우 조사시간 경과에 따라 법랑질의 삭제율은 증가되지 않았다. 결론적으로 효과적으로 법랑질을 삭제하기 위해서는 적절한 에너지와 펄스의 레이저를 사용해야 하며, 또한 항상 정확한 초점거리를 유지해야 할 것으로 사료된다.