• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.332-335
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• 2007

The superplastic forming (SPF) has been widely used in the automotive and aerospace industry because it has great advantages to produce very light and strong components. Finite element method (FEM) is used to model the process of superplastic forming/diffusion bonding (SPF/DB), to predict the pressure-time curve and to analyze the process parameter. In this study, process design of SPF/DB is carried out a 3-sheet sandwich part. SPF/DB process with pressure control was analyzed by using finite element method. For obtaining proper shape, step-by-step pressurization is proposed. The first step of SPD/DB process is obtained by applying of pressure in patches. From the next step it applied pressure to all regions (between inner sheets, between inner and face sheets). By using the proposed pressurization scheme, deficit in part shape is found to be eliminated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.395-397
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• 2002

Dielectric thin films of Pb$\_$0.72/La$\_$0.28/Ti$\_$0.93/O$_3$(PLT(28)) have been deposited on Pt(111)/Ti/SiO$_2$/Si(100) substrates in-situ by pulsed laser deposition using different annealing and deposition processes. We have investigated the effect of hydrogen annealing on the ferroelectric properties of PLT thin films and found that the annealing process causes the diffusion of hydrogen into the ferroelectric film resulting in the destruction of polarization. Two-step process to grow PLT films was adopted and verified to be useful to enlarge the grain size of the film. Structural properties including dielectric constant, and ferroelectric characteristics of PLT thin films were shown to be strongly influenced by grain size. The film deposited by using two-step process including pre-annealing treatment has a strong (111) orientation. However, the films deposited by using single-step process with hydrogen annealing process shows the smallest grain size.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.2
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• pp.727-746
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• 2018

The hash function RIPEMD-160 is a worldwide ISO/IEC standard and the hash function HAS-160 is the Korean hash standard and is widely used in Korea. On the basis of differential meet-in-the-middle attack and biclique technique, a preimage attack on 34-step RIPEMD-160 with message padding and a pseudo-preimage attack on 71-step HAS-160 without message padding are proposed. The former is the first preimage attack from the first step, the latter increases the best pseudo-preimage attack from the first step by 5 steps. Furthermore, we locate the linear spaces in another message words and exchange the bicliques construction process and the mask vector search process. A preimage attack on 35-step RIPEMD-160 and a preimage attack on 71-step HAS-160 are presented. Both of the attacks are from the intermediate step and satisfy the message padding. They improve the best preimage attacks from the intermediate step on step-reduced RIPEMD-160 and HAS-160 by 4 and 3 steps respectively. As far as we know, they are the best preimage and pseudo-preimage attacks on step-reduced RIPEMD-160 and HAS-160 respectively in terms of number of steps.

• Journal of Industrial Technology
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• v.35
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• pp.3-8
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• 2015

A study has been made on defects which are formed in manufacturing processes of engine bearing and also on fatigue crack growth behavior in each step of bearing metal manufacturing. After the first step(sinter brass powder on steel plate ; Series A) many voids are made on brass surface and its size is decreased by the second step(rolling process of sintered plate ; Series B). After the third step(re-sintering step of brass powder and rolling ; Series C) the number of voids is decreased and its type shows line. The time of fatigue crack initiation and the growth rate of fatigue crack are in order of Series A, Series B, Series C. These reasons are that void fosters the crack initiation and growth, and residual stress made by rolling process effects on the crack growth rate in Series B, C. In forming and machining processes by use of final bearing metal, crack was observed at internal corner of flange and peeling off was observed at junction between steel and brass. Owing to the above crack and peeling off, it is considered that there is a possibility of fatigue fracture during the application time.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.6-8
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• 2005

The optical and electrical properties of indium tin oxide (ITO) thin films deposited at room temperature can be substantially enhanced by adopting a two-step process. In the first step, the films (50 nm thick) were grown by pulsed laser deposition (PLD) on glass substrate at room temperature and quickly annealed at $400^{\circ}C$ in nitrogen ambient for 1 minute by using rapid thermal annealing method. The process was completed by additional deposition (150 nm thick) on annealed film at room temperature. High quality ITO films grown by two-step process at room temperature could be obtained with the resistivity of $3.02{\times}10^{-4}{\Omega}cm$, the carrier mobility of 32.07 $cm^2/Vs$, and the transparency above 90 % in visible region mainly due to the enhancement of the film crystallinity and the increase of grain size.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.737-743
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• 1995

Two step RTD(Rapid Thermal Diffussion) of P into silicon wafer using tungsten halogen lamp was used to fabricated very shallow n$^{+}$p junction. 1st RTD was performed in the temperature range of 800.deg. C for 60 see and the heating rate was in the 50.deg. C/sec. Phosphrous solid source was transfered on the silicon surface. 2nd RTD process was performed in the temperature range 1050.deg. C, 10sec. Using 2 step RTD we can obtain a shallow junction 0.13.mu.m in depth. After RTD, the Ti-silicide process was performed by the two step RTA(Rapid Thermal Annealing) to reduced the electric resistance and to improve the n$^{+}$p junction diode. The titanium thickness was 300.angs.. The condition of lst RTA process was 600.deg. C of 30sec and that of 2nd RTA process was varied in the range 700.deg. C, 750.deg. C, 800.deg. C for 10sec-60sec. After 2 step RTA, sheet resistance was 46.ohm../[]. Ti-silicide n+p junction diode was fabricated and I-V characteristics were measured.red.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.53-57
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• 2010

Low-density parity-check (LDPC) codes with belief-propagation (BP) algorithm achieve a remarkable performance close to the Shannon limit at reasonable decoding complexity. Conventionally, each iteration in decoding process contains two steps, the horizontal step and the vertical step. In this paper, an efficient implementation of the adaptive offset min-sum (AOMS) algorithm for decoding LDPC codes using the single-step method is proposed. Furthermore, the performances of the AOMS algorithm compared with belief-propagation (BP) algorithm are investigated. The algorithms using the single-step method reduce the implementation complexity, speed up the decoding process and have better efficiency in terms of memory requirements.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.555-556
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• 2006

In this paper, we have proposed a novel process using two-step electron beam lithography to fabricate 20 nm T-gates for high performance MODFETs. Two-step lithography reduces electron forward scattering by defining the foot on a thin (100 nm) bottom-layer of polymethyl methacrylate (PMMA) at the second step, the T-gate head having been developed at the first step. Adopting a low temperature development technique for the second step reduces the detrimental effect of head exposure on foot definition. We have shown that 20 nm T-gate can be patterned with this process.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.1
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• pp.33-40
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• 2010

Because sampling interval for data collection tends to be short compared with the overall processing time, in chemical process, instrumental process related tanks or furnace collected data have a significant autocorrelation. Insufficient control technique and frequent control actions cause unstable condition of the process. Traditional control charts which were developed based on iid (independently and identically distributed) among data cannot be applied on the existence of autocorrelation. Also unstable process is difficult to identity or diagnose. Because large-scale process has a lot of measurable variables and multi-step-structures among data, it is difficult to find relation between measurable variables and nonconformity. In this paper, we suggested an appicable model to diagnose the process and to find relation between measurable variables (CTQ) and nonconformity in the process having autocorrelation, unstable condition frequently, a lot of measurable variables, and multi-step-structure. And we applied this model to real process, to verify that the process engineers could easily and effectively diagnose the process and control the nonconformity.

• Journal of the Korea Safety Management & Science
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• v.15 no.1
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• pp.283-292
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• 2013

This paper aims to propose a new steps of hypothesis testing using analysis process and improvement process in the six sigma DMAIC. The six sigma implementation models proposed in this paper consist of six steps. The first step is to establish a research hypothesis by specification directionality and FBP(Falsibility By Popper). The second step is to translate the research hypothesis such as RHAT(Research Hypothesis Absent Type) and RHPT(Research Hypothesis Present Type) into statistical hypothesis such as $H_0$(Null Hypothesis) and $H_1$(Alternative Hypothesis). The third step is to implement statistical hypothesis testing by PBC(Proof By Contradiction) and proper sample size. The fourth step is to interpret the result of statistical hypothesis test. The fifth step is to establish the best conditions of product and process conditions by experimental optimization and interval estimation. The sixth step is to draw a conclusion by considering practical significance and statistical significance. Important for both quality practitioners and academicians, case analysis on six sigma projects with implementation guidelines are provided.