• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.439-441
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• 1996

A simple coupling method between APD(avalanche photodiode) arrays and SMF(single mode fiber) arrays on a Silicon carrier composed of V-grooves is proposed and carried out. Jacketed fibers embedded in V-grooves are used as alignment marks instead of patterned pedestals or solder bumps and a optical receiver module are packaged.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.105-106
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• 2005

The impact ionization MOS (I-MOS) transistor with 50nm channel length is presented by using 2-D device simulator ISE-TCAD. The subthreshold slope cannot be steeper than kT/q since the subthreshold conduction is due to diffusion current. As MOSFETs are scaled down, this problem becomes significant and the subthreshold slope degrades which leads an increase in the off-current and off-state power dissipation. The I-MOS is based on a gated p-i-n structure and the subthreshold conduction is induced by impact ionization. The simulation results show that the subthreshold slope is 11.7 mV/dec and this indicates the I-MOS improves the switching speed and off-state characteristics.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.100-101
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• 2003

본 논문은 초고속 광통신용 검출기로 사용되고 있는 InP／InGaAs Avalanche Photodiode (APD)에 대한 연구로서 구조 변화에 따른 APD의 특성에 대해 연구하였다. 채택된 APB의 기본 구조는 Separated Absorption, Grading, Charge and Multiplication (SAGCM)구조로 u-InP 의 두께 3.5$\mu\textrm{m}$에~2.9$\mu\textrm{m}$ 만큼 Zn diffusion 하였으며, u-InGaAs 의 흡수층 두께는 0.8$\mu\textrm{m}$ 로 하였다. charge sheet 층의 도핑 농도는 ~ 3.5 $\times$ 10／sup 12／／cm／sup 2／ 이고, 전극 구조는 back side illumination type이다. (중략)

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.58.3-58.3
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• 2019

Optical intensity interferometry, developed in the 1950s, is a simple and inexpensive method for achieving angular resolutions on microarcsecond scales. Its low sensitivity has limited intensity interferometric observations to bright stars so far. Substantial improvements are possible by using avalanche photodiodes (APDs) as light detectors. We present here the results of laboratory measurements with a prototype astronomical intensity interferometer using APDs in continuous ("linear") detection mode - arguably, the first of its kind. We used two interferometer configurations, one with zero baseline and one with variable baseline. Using a superluminous diode as light source, we unambiguously detected Hanbury Brown-Twiss photon-photon correlations at very high significance. From measuring the correlation as function of baseline, we measured the angular diameter of the light source, in analogy to the measurement of the angular diameter of a star. Our results demonstrate the possibility to construct large astronomical intensity interferometers that can address a multitude of astrophysical science cases.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.8 no.4
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• pp.3-20
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• 1998

해쉬 함수는 임의의 길이를 갖는 메세지를 규정된 길이의 값으로 압축하는 알고리듬으로 메시지 정보의 무결정 , 사용자 인증, 바이러스 침투 예방에 응용될 수 있는 핵심 보안 알고리듬이다. 또한 안전한 해쉬 함수는 일방향성, 충돌회피성, 고속 동작성 등의 특성을 지녀야 한다. 본 노눈에서는 응용에 따라 128, 160, 192, 224, 256 비트 길이로 출력을 생성하고 암호학적으로 강력한 안전성을 지닌 해쉬 알고리듬(HAVES: Hash Algorithm with Variable IEngth Speed)을 제안한다. 이 해쉬 알고리듬은 메시지 블록을 1024비트 단뒤로 처리하고 연산의 효과적인 배열을 통해 비교적 빠른 속도로 동작한다. 제안하는 해쉬 알고리듬은 0-1 균형성(Balancedness), 높은 비선형성(Nonlinearity), 구조적인 선형 비등가성 (Linearly Inequivalent), 상호 출력 무상관성(Mutually Output Uncorrelated), SAC(Strict Avalanche Criterion)를 모두 만족함으로서 효율성과 안전성을 도모한다. 더불어 안전성이 요구되는 실용적인 응용에 맞게 출력 길이를 가변적으로 선택할 수 있도록 했다.

• Current Optics and Photonics
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• v.6 no.1
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• pp.39-43
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• 2022

Underwater optical wireless communication (UOWC) is a good candidate for high-speed underwater wireless communication. In this work, we compare the performance of several modulation techniques for a UOWC system consisting of a light-emitting diode (LED) with an operating wavelength of 405 nm and a Si avalanche photodiode (APD). In this work, we consider six modulation schemes: 4-quadrature amplitude modulation (QAM), 8-QAM, quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), on-off keying (OOK), and 4-pulse amplitude modulation (PAM). We also consider the cases of pure water and seawater for the working conditions. Our results show that 4-QAM and 8-QAM perform the best, in terms of communication distance and transmission power efficiency, for all water types considered.

• Computers and Concrete
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• v.34 no.1
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• pp.79-91
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• 2024

In symmetric cryptography, a cryptographically secure Substitution-Box (S-Box) is a key component of a block cipher. S-Box adds a confusion layer in block ciphers that provide resistance against well-known attacks. The generation of a cryptographically secure S-Box depends upon its generation mechanism. In this paper, we propose a novel framework for the construction of cryptographically secure S-Boxes. This framework uses a combination of linear fractional transformation and permutation functions. S-Boxes security is analyzed against well-known security criteria that include nonlinearity, bijectiveness, strict avalanche and bits independence criteria, linear and differential approximation probability. The S-Boxes can be used in the encryption of any grayscale digital images. The encrypted images are analyzed against well-known image analysis criteria that include pixel changing rates, correlation, entropy, and average change of intensity. The analysis of the encrypted image shows that our image encryption scheme is secure.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.45-45
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• 2003

The aim of this study was the characterization and performance validation of new prototype avalanche photodiode (APD) arrays for positron emission tomography (PET). Two different APD array prototypes (noted A and B) developed by Radiation Monitoring Device (RMD) have been investigated. Principal characteristics of the two APD array were measured and compared. In order to characterize and evaluate the APD performance, capacitance, doping concentration, quantum efficiency, gain and dark current were measured. The doping concentration that shows the impurity distribution within an APD pixel as a function of depth was derived from the relationship between capacitance and bias voltage. Quantum efficiency was measured using a mercury vapor light source and a monochromator used to select a wavelength within the range of 300 to 700 nm. Quantum efficiency measurements were done at 500 V, for which the APD gain is equal to one. For the gain measurements, a pencil beam with 450 nm in wavelength was illuminating the center of each pixel. The APD dark currents were measured as a function of gain and bias. A linear fitting method was used to determine the value of surface and bulk leakage currents. Mean quantum efficiencies measured at 400 and 450 nm were 0.41 and 0.54, for array A, and 0.50 and 0.65 for array B. Mean gain at a bias voltage of 1700 V, was 617.6 for array A and 515.7 for type B. The values based on linear fitting were 0.08${\pm}$0.02 nA 38.40${\pm}$6.26 nA, 0.08${\pm}$0.0l nA 36.87${\pm}$5.19 nA, and 0.05${\pm}$0.00 nA, 21.80${\pm}$1.30 nA in bulk surface leakage current for array A and B respectively. Results of characterization demonstrate the importance of performance measurement validating the capability of APD array as the detector for PET imaging.

• Composites Research
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• v.32 no.6
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• pp.301-306
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• 2019

Triboelectric nanogenerator (TENG) is one of the energy harvesting methods in spotlight that can convert mechanical energy into electricity. As TENGs produce high electrical output, previous studies have shown TENGs that can power small electronics independently. However, recent studies have reported limitations of TENG due to air breakdown and field emission. In this study, we developed a triboelectric nanogenerator that utilizes the metal-to-metal surface contact to induce ion-enhanced field emission and electron avalanche for electrons to flow directly between two electrodes. The average peak open-circuit voltage of this TENG was measured as 340 V, and average peak closed-circuit current was measured as 10 mA. The electrical output of this TENG has shown different value depending on the surface charge of surface charge generation layer. The TENG developed in this study have produced RMS power of 0.9 mW, which is 2.4 times higher compared to conventional TENGs. The TENG developed in this study can be utilized in charging batteries and capacitors to power portable electronics and sensors independently.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4A
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• pp.291-300
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• 2002

In this paper, a way of constituting optimized S box and G function was suggested in the block cipher whose structure is similar to SEED, which is KOREA standard of 128-bit block cipher. S box can be formed with nonlinear function and an affine transform. Nonlinear function must be strong with differential attack and linear attack, and it consists of an inverse number over GF(2$\^$8/) which has neither a fixed point, whose input and output are the same except 0 and 1, nor an opposite flexed number, whose output is one's complement of the input. Affine transform can be constituted so that the input/output correlation can be the lowest and there can be no fixed point or opposite fixed point. G function undergoes diffusive linear transform with 4 S-box outputs using the matrix of 4$\times$4 over GF(2$\^$8/). G function can be constituted so that MDS(Maximum Distance Separable) code can be formed, SAC(Strict Avalanche Criterion) can be met, there can be no weak input, where a fried point, an opposite fried point, and output can be two's complement of input, and the construction of hardware can be made easy. The S box and G function suggested in this paper can be used as a constituent of the block cipher with high security, in that they are strong with differential attack and linear attack with no weak input and they are excellent at diffusion.