• Proceedings of the Korea Information Processing Society Conference
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• 2020.05a
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• pp.582-584
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• 2020

기호 실행 (symbolic execution)은 프로그램을 특정 상태로 구동하는 입력 값을 찾는 코드 분석기법이다. 이를 사용하면 자동화 소프트웨어 테스트 기법인 퍼징 (fuzzing)을 훨씬 효율적으로 사용하여 더 많은 보안 취약점을 찾을 수 있지만, 기호 실행의 한계점으로 인하여 쉽게 적용할 수 없었다. 이를 해결하기 위해 인공 지능을 활용한 방법을 소개하겠다.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.290-292
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• 2021

양자 컴퓨터 기술의 발전에 따라 현재 사용되고 있는 암호 알고리즘과 시스템들이 위협받고 있다. 이러한 시대적 흐름에 따라 양자 컴퓨터로도 쉽게 해결할 수 없는 양자내성암호의 개발이 요구되고 있으며, 미국 NIST 에서는 양자내성암호의 표준화를 위한 공모전을 진행하고 있다. 본 논문에서는 공모전 최종 후보 중 하나인 NTRU 알고리즘을 가속화하기 위한 성능 분석을 진행하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2023.05a
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• pp.212-214
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• 2023

동형암호는 주목받는 차세대 프라이버시 보존 기술이다. 많은 기업들이 이를 활용한 서비스들을 제공하고 있다. 비록 동형암호가 수학적으로 안전성을 인정받았지만, 실행되는 프로그램으로써 동형암호는 부채널공격들에 취약하다는 연구 결과들이 보고되고 있다. 이 논문은 이런 부채널공격들에 대해 본석, 일반화하여 사용 가능한 gadget을 소개하며, 대응기법에 대한 가이드라인을 제안하고 그 효과와 한계에 대해 분석한다.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.174-179
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• 2017

We designed the CMOS analog integrate and fire (I&F) neuron circuit for driving memristor based on resistive-switching random access memory (RRAM). And we fabricated the RRAM device that have $HfO_2$ switching layer using atomic layer deposition (ALD). The RRAM device has gradual set and reset characteristics. By spice modeling of the synaptic device, we performed circuit simulation of synaptic device and CMOS neuron circuit. The neuron circuit consists of a current mirror for spatial integration, a capacitor for temporal integration, two inverters for pulse generation, a refractory part, and finally a feedback part for learning of the RRAM. We emulated the spike-timing-dependent-plasticity (STDP) characteristic that is performed automatically by pre-synaptic pulse and feedback signal of the neuron circuit. By STDP characteristics, the synaptic weight, conductance of the RRAM, is changed without additional control circuit.

• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.2
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• pp.115-120
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• 2008

Carrier velocity in the MOSFET channel is the main driving force for improved transistor performance with scaling. We report measurements of the drift velocity of electrons and holes in silicon inversion layers. A technique for extracting effective carrier velocity which is a more accurate extraction method based on the actual inversion charge measurement is used. This method gives more accurate result over the whole range of $V_{ds}$, because it does not assume a linear approximation to obtain the inversion charge and it does not limit the range of applicable $V_{ds}$. For a very short channel length device, the electron velocity overshoot is observed at room temperature in 37 nm MOSFETs while no hole velocity overshoot is observed down to 36 nm. The electron velocity of short channel device was found to be strongly dependent on the longitudinal field.

• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.234-239
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• 2010

We have developed and reported several micro-spikes for minimally invasive biopsy. This paper presents a diagnosis protocol for micro-spike biopsy using paraffin-based tissue collecting tool. Using the proposed tissue collecting tool, which has a negative micro-spike structure in a porous chamber, the biopsied tissue in a micro-spike is effectively detached. The proposed diagnosis protocol prevents the loss of tissues in a paraffin embedding and sectioning process. Hence, it is compatible with conventional histopathology without additional reagents and processes. The gastro-intestinal tissue of a pig is biopsied in an in vivo environment, and then it is detached from a micro-spike using the paraffin-based tissue collecting tool. A histopathological photomicrograph of the detached tissue is acquired with the proposed diagnosis protocol. The acquired image offers clinical quality. This result shows that the paraffin-based tissue collecting tool is applicable to the medical practice.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.679-682
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• 2005

Negative-differential conductance (NDC) characteristics as well as negative-differential trans-conductance (NDT) characteristics have been observed in the room temperature I-V characteristics of Field-induced Inter-band Tunneling Effect Transistors (FITETs). These characteristics have been explained with inter-band tunneling physics, from which, inter-band tunneling current flows when the energy bands of degenerately doped regions align, and it does not flow when they don't. FITET is an SOI device and the body region is not directly connected to the external terminal. Therefore, Fermi energy in the body region is determined by electrical coupling among four regions - gate, source, drain and substrate. So, a quasi Fermi energy of the majority carriers in the floating body region can be changed by external voltages, and this causes the energy band movements in the body region, which determine whether the energy bands between degenerately doped junctions aligns or not. This is a key point for an explanation of NDT and NDC characteristics. In this paper, a quasi Fermi energy movement in the floating body region of FITET was investigated by a device simulation. This result was applied for the description of relation between quasi Fermi energy in the body region and external gate bias voltage.

• Journal of Information Display
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• v.2 no.3
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• pp.66-71
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• 2001

MCFEDs (MOSFET-Contoolled Field Emission Displays) were fabricated to evaluate the validity of MCFEA for display application. The electrical properties of FEAs (Field Emitter Arrays), HVMOSFETs (High-Voltage MOSFETs), and MCFEAs (MOSFET-Controlled Field Emitter Arrays) were measured. The extraction gate voltage of the FEAs to obtain the anode current of 10 nA/tip was around 71 V. The breakdown voltages of the HVMOSFETs were above 81 V for all the samples. The I-V characteristics of the MCFEAs showed that the emission currents of the FEAs were well controlled depending on the control gate voltages of the HVMOSFETs. To avoid the harmful effects during the packaging process, the performance of the MCFEDs was evaluated in a high vacuum chamber. The emission images of the MCFEDs were controlled through very-through operation. From the comparison with a conventional FED, it was proven that the poor uniformity of FED could be improved through the integration with HVMOSFET.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.6
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• pp.658-663
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• 2015

In the previous work, we have proposed an integrate-and-fire neuron circuit and synaptic device based on the floating body MOSFET [1-3]. Integrate-and-Fire(I&F) neuron circuit emulates the biological neuron characteristics such as integration, threshold triggering, output generation, refractory period using floating body MOSFET. The synaptic device has short-term and long-term memory in a single silicon device. In this paper, we connect the neuron circuit and the synaptic device using current mirror circuit for summation of post synaptic pulses. We emulate spike-timing-dependent-plasticity (STDP) characteristics of the synapse using feedback voltage without controller or clock. Using memory device in the logic circuit, we can emulate biological synapse and neuron with a small number of devices.

• Journal of Electrical Engineering and information Science
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• v.2 no.6
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• pp.212-216
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• 1997

A new metal tip fabrication process for low voltage operation is reported in this paper. The key element of the fabrication process is that isotropic silicon etching and oxidation process used in silicon tip fabrication is utilized for gate hole size reduction and gate oxide layer. A metal FEA with 625 tips was fabricated in order to demonstrate the validity of the new process and submicron gate apertures were successfully obtained from originally 1.7$\mu\textrm{m}$ diameter mask. The emission current above noise level was observed at the gate bias of 50V. The required gate voltage to obtain the anode current of 0.1${\mu}\textrm{A}$/tip was 74V and the emission current was stable above 2${\mu}\textrm{A}$/tip without any disruption. The local field conversion factor and the emitting area were calculated as 7.981${\times}$10\ulcornercm\ulcorner and 3.2${\times}$10\ulcorner$\textrm{cm}^2$/tip, respectively.