• Therapeutic Science for Rehabilitation
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• v.7 no.3
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• pp.47-58
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• 2018

Objective : This study was conducted to investigate the effects of iPad applications on improvement of attention and short-term memory in mild dementia. Methods : A single-case experimental study using A-B-A design was conducted. A total of 20 sessions, including 5 each for baseline phase A and A' and 10 for the intervention phase, were provided to the subject. Interventions were only provided during the intervention phase and were iOS-based iPad applications named "Memorado-Moving Balls" and "Circles." "Fit Brains-Matching Pairs" and "Fit-Brains-Spot the Difference" were used for each session to evaluate attention and short-term memory. MMSE-K, K-TMT-e A and B, and DST assessment tools were used pre- and post-intervention to assess attention and memory. Result : Fit Brains scores indicated improvement in both attention and memory during the intervention phase. K-TMT-e A showed 3 increased correct points and 3 reduced error points, and B showed 7 increased correct points and 2 reduced error points in post-tests, but the DST and MMSE-K showed no meaningful change. Conclusion : This single-case study identified improvements in attention and short-term memory in a person with mild dementia using iPad applications. Further studies regarding different applications and larger samples with long-term designs are necessary.

• Journal of the Korean Society for Heat Treatment
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• v.2 no.4
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• pp.47-55
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• 1989

The effects of thermal cycle, aging heat treatment and Boron addition on the phase transformation characteristics and mechanical properties of the shape memory alloys of Cu-Zn-Al system, which was designed to operate about $80^{\circ}C$ by this research group, were studied. From the view point of the effects of thermal cycle on the phase transformation temperature change, it was found that up to 100 cycles Ms and Af points increased by $3-7^{\circ}C$ and Mf decreased a little bit and after that all of them were remain constant, and As point was not affected. All of the phase transformation temperatures were decreased $5-7^{\circ}C$ by aging heat treatment, at $140^{\circ}C$ for 24h however the effects of thermal cycle on aged alloys were same as on unaged alloys. As the thermal cycle increased the shape memory ability decreased a little up to 20 cycles, but above that it kept almost same ability. By Boron addition, grain size was refined from $1500{\mu}m$ to about $330{\mu}m$ and the hardness, fatigue property were improved but shape memory ability was lowered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.88-93
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• 2024

To evaluate the possibility as a multi-level memory medium for the Ge₂Sb₂Te₅/TiN/W-doped Ge₂Sb₂Te₅ cell structure, the crystallization rate and stabilization characteristics according to voltage (V)- and current (I)- pulse sweeping were investigated. In the cell structures prepared by a magnetron sputtering system on a p-type Si (100) substrate, the Ge₂Sb₂Te₅ and W-doped Ge₂Sb₂Te₅ thin films were separated by a barrier metal, TiN, and the individual thicknesses were varied, but the total thickness was fixed at 200 nm. All cell structures exhibited relatively stable multi-level states of high-middle-low resistance (HR-MR-LR), which guarantee the reliability of the multilevel phase-change random access memory (PRAM). The amorphousto-multilevel crystallization rate was evaluated from a graph of resistance (R) vs. pulse duration (T) obtained by the nanoscaled pulse sweeping at a fixed applied voltage (12 V). For all structures, the phase-change rates of HR→MR and MR→LR were estimated to be approximately t<20 ns and t<40 ns, respectively, and the states were relatively stable. We believe that the doublestack structure of an appropriate Ge-Sb-Te film separated by barrier metal (TiN) can be optimized for high-speed and stable multilevel PRAM.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.3
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• pp.363-369
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• 2017

Phase-change random access memory (PRAM) has been emerged as a potential memory due to its excellent scalability, non-volatility, and random accessibility. But, as the cell current is reducing due to cell size scaling, the read-sensing window margin is also decreasing due to increased variation of cell performance distribution, resulting in a substantial loss of yield. To cope with this problem, a novel adaptive read-sensing reference current generation scheme is proposed, whose trimming range and resolution are adaptively controlled depending on process conditions. Performance evaluation in a 58-nm CMOS process indicated that the proposed read-sensing reference current scheme allowed the integral nonlinearity (INL) to be improved from 10.3 LSB to 2.14 LSB (79% reduction), and the differential nonlinearity (DNL) from 2.29 LSB to 0.94 LSB (59% reduction).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.110-110
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• 2009

최근 차세대 비휘발성 메모리(NVM) 기술은 메모리의 성능과 기존의 한계점을 효과적으로 극복하며 활발한 연구를 통해 비약적으로 발전하고 있으며 특히, phase-change random access memory (PRAM)은 ferroelectric random access memory (FeRAM)과 magneto-resistive random access memory (MRAM)과 같은 다른 NVM 소자와 비교하여 기존의 DRAM과 구조적으로 비슷하고 상용화가 빠르게 진행될 수 있을 것으로 예상되는 바, PRAM에 사용되는 상변화 물질의 식각을 수행하고 X-ray photoelectron spectroscopy (XPS)를 통해 표면의 열화현상을 관찰하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.112-115
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• 2003

There is a growing need for a nonvolatile memory technology with faster speed than existing nonvolatile memories. $T_c$(crystallization temperature) is confirmed by measuring the conductivity with the varying temperature. The sample is heated on the hotplate and slow down to the room-temperature. We prepared Te based alloy bulk. The materials can be used for nonvolatile random access memory.

• Journal of Power Electronics
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• v.13 no.2
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• pp.264-274
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• 2013

A new sensorless position estimation method for switched reluctance motor (SRM) drives is presented in this paper. This method uses the change of the slope of the phase inductance to detect the aligned position. Since the aligned positions for successive electrical cycle of each phase are apart by a fixed mechanical angle $45^{\circ}$ in the case of 12/8 SRM, the speed of the machine can be calculated to estimate the rotor position. Since no prior knowledge of motor parameters is required, the method is easy for implementation without adding any additional hardware or memory. In order to verify the validity of this technique, effects such as changes in the advanced angle and phase lacking faults are examined. In addition, an inductance threshold based sensorless starting scheme is also proposed. Experimental results demonstrate the validity of the proposed method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.940-947
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• 2007

For the performance upgrade of a supersonic jet fighter, the processor and FLCC(Flight Control Computer) Architecture were upgraded from a baseline FLCC. Prior to the hardware implementation phase, the exact CPU throughput estimation is necessary. For this purpose, an experimental method for new FLCC throughput estimation was introduced in this study.　While baseline FLCC operating, the CPU address bus was collected with logic analyzer, and then decoded to get the exact access times to each memory-memory and the number of program Instruction branches. Based on these data, a throughput test in CPU demo-board of the new FLCC configuration was performed. From test results, the CPU-Memory architecture was design-changed before FLCC hardware implementation phase. To check the flight stability degradation due to power-interrupt problem due to CPU-Memory architecture change, the piloted HILS (Hardware-In-the Loop Simulator) test was conducted.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.982-987
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• 2011

In this study, $Ge_8Se_{(2+x)}Te_{(6-x)}$ thin film amorphous-to-crystalline phase-change rate was evaluated in using a nano-pulse scanner. The focused laser beam with a diameter <10 ${\mu}m$ was illuminated in the power (P) and pulse duration (t) ranges of 1-31 mW and 10-460 ns, respectively, with subsequent detection of the responsive signals reflected from the film surface. We also evaluated the material characteristics, such as optical absorption and energy gap, crystalline phases, and sheet resistance of as-deposited and annealed films. The result of experiments showed that the thermal stability of the Ge-Se-Te film is largely improved by adding Se.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.166-166
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• 2007

PRAM (phase-change random access memory)은 전류 펄스 인가에 따른 기록매질의 비정질-결정질 간 상변화와 그에 동반되는 저항변화를 이용하는 차세대 비휘발성 메모리 소자로서 연구되어지고 있다. 본 논문에서는 $(Ge_2Sb_2Te_5)_{1-x}Se_x$ (x=0,0.05,0.1,0.15) 조성에 대한 벌크 및 박막시료를 제작하고 각 조성에 대한 상변화 특성을 분석하였다. XRD를 통해 열처리 온도에 따른 구조적 분석을 실시하였고 UV-Vis-IR spectrophotometer를 사용하여 박막의 광학적 특성을 분석하였다. 또한 각 조성의 결정화 속도를 비교하기 위해 static tester를 사용하여 레이저 펄스 시간에 대한 반사도 변화를 측정하였고 DSC를 통해 결정화 온도를 측정하였다.