• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.486-492
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• 2004

Flow patterns around a rotating circular cylinder having square dimpled surface were visualized by the hydrogen bubble technique at velocity ratios from a=0 to 4.8 and Reynolds number of Re=1.0${\times}$10$^4$. The wake region of the cylinder was reduced as the velocity ratios increase and was smaller than that of the smooth cylinder without dimples at the same velocity ratio. The hydrodynamic characteristics on the cylinder was investigated by measuring of lift and drag at velocity ratios from a=0 to 4.1 and Reynolds number from Re=1.2${\times}$10$^4$ to Re=2.0${\times}$10$^4$. As the velocity ratios increase, the average lift and drag coefficients were increased and at the same velocity ratio, the average lift was larger but the average drag was smaller than that of the smooth cylinder.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.48
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• pp.269-277
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• 1998

In this study, a traditional concept of sampling inspection plan for the quality assurance system is extended to a consideration of economic aspects in total production system by representing and analyzing the effects between proceding/succeeding production process including inspection. This approach recognizes that the decision to be made at one manufacturing process (or assembly process) determine not only the cost and the average outgoing quality level of that process but also the input parameters of the cost and the incoming quality to the succeeding process. By analyzing the effects of the average incoming and outgoing quality, manufacturing/assembly quality level and sampling inspection plan on the production system, mathematical models and solution technique to minimize the total production cost for a single product manufacturing system with specified average outgoing quality limit (AOQL) are suggested.

• Journal of the Optical Society of Korea
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• v.20 no.2
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• pp.228-233
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• 2016

In this paper, we propose a nonlinear maximum average correlation height (MACH) filter for information authentication of photon counting double random phase encryption (DRPE). To enhance the security of DRPE, photon counting imaging can be applied because of its sparseness. However, under severely photon-starved conditions, information authentication of DRPE may not be implemented successfully. To visualize the photon counting DRPE, a three-dimensional imaging technique such as integral imaging can be used. In addition, a nonlinear MACH filter can be utilized for helping the information authentication. Therefore, in this paper, we use integral imaging and nonlinear MACH filter to implement the information authentication of photon counting DRPE. To verify our method, we implement optical experiments and computer simulation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.10
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• pp.1198-1205
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• 1999

This study is focused on the reliability evaluation for distribution system based on deterministic evaluation technique. Average failure rates, average outage time, and average annual outage time of electrical parts and load points are calculated through network reduction method and failure mode & effective analysis method. And reliability indices of distribution system are calculated. Finally, by employing analytic hierarchy process method, unique index which evaluates and improves the distribution system is calculated. As a result, finding weak points and expansion schedule of the system is possible. The usefulness of this method is verified by applying it to the Inchon International Airport.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4872-4891
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• 2015

Orthogonal frequency division multiplexing (OFDM) signals suffer from the problem of high peak-to-average power ratio (PAPR), which complicates the design of analog front-end of the system. Companding is a well-known PAPR reduction technique that involves transforming signal amplitudes using a deterministic function. OFDM signal amplitude, on average, is Rayleigh distributed but the distribution can vary significantly from symbol to symbol, especially when constellation size increases. In this paper, a new adaptive companding scheme is proposed along with its design methodology aiming at optimizing the compander performance by accommodating this variation in its design. This is achieved by designing compander parameters separately for statistically dissimilar symbols in OFDM waveform and making the compander select from these parameters, during run-time, according to the features of input symbols.

• Speech Sciences
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• v.10 no.4
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• pp.137-147
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• 2003

Speech synthesis can classify by synthesis way, that is waveform coding, source coding and mixture coding. Specially, waveform coding is suitable for high quality synthesis. However, it is not desirable by synthesis techniques of syllable or phoneme unit because it do not separate and handles excitation and formant part. Therefore, there is a need for pitch alteration method applied in synthesis by the rule in waveform coding. This study propose about pitch alteration method that use spectrum scaling after do to flatten spectra by subband linear approximation to minimize spectrum distortion. This paper show evaluation whether show excellency of some measure compared with LPC, Cepstrum, lifter function and method that propose. estimation method seeks distribution of each flattened signal and measured degree of flattened spectra Signal flattened is normalized, So that highest point amounts to zero, and distribution of signal ,whose average is zero, is calculated. this show result that measure the spectrum distortion rate to estimate performance of method that propose. The average spectrum distortion rate was kept below the average 2.12%, so the method that propose is superiors than existent method.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.3
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• pp.432-437
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• 1996

This paper describes a diagnostic technique of power transformers by on-line detection of ultrasonic signals. A trend of partial discharge variation in a real transformer was estimated by counting the number of ultrasonic signals until insulation paper in the point-to-plane electrode is punctured. The number of electrical signals is closely related to the ultrasonic signals generated by partial discharge. The trend of the ultrasonic signal number could easily be distinguished by taking moving average. The insulation failure due to partial discharge in transformers can be predicted based on the trend analysis of ultrasonic signal number caused by partial discharge. (author). 14 refs., 10 figs.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.46
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• pp.119-125
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• 1998

In this study, a traditional concept of sampling inspection plan for the quality assurance system is extended to a consideration of economic aspects in total production system by representing and analyzing the effects between proceeding / succeeding production process including inspection. This approach recognizes that the decision to be made at one manufacturing process (or assembly process) determine not only the cost and the average outgoing quality level of that process but also the input parameters of the cost and the incoming quality to the succeeding process. By analyzing the effects of the average incoming and outgoing quality, manufacturing / assembly quality level and sampling inspection plan on the production system, mathematical models and solution technique to minimize the total production cost for a single product manufacturing system with specified average outgoing quality limit(AOQL) are suggested.

• Journal of Audiology & Otology
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• v.25 no.4
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• pp.224-229
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• 2021

Background and Objectives: The United Kingdom (UK) national standard for the closure rate for myringoplasty is 89.5% (90.6% and 84.2% for primary and revision surgeries, respectively). The average hearing gains for primary and revision myringoplasty are 9.14 dB and 7.86 dB, respectively. This study compared the myringoplasty outcomes for a single surgeon over 5 years. Subjects and Methods: Data for 68 cases were analyzed retrospectively. The outcome measures were achievement of the tympanic membrane closure and the average hearing gain or loss. Results: The overall and primary closure rates were 97% and 98%, respectively and significantly higher than the UK national standard (p=0.0210 and p=0.0287, respectively). The revision closure rate was 93%; however, it was not significantly higher than the national standard (p=0.1872). The average hearing gain was 5.18 dB. The gains for primary and revision surgeries were 5.15 dB and 5.25 dB, respectively. Conclusions: We propose that these outcomes are a result of our surgical technique, including the simultaneous use of cortical mastoidectomy in ears with discharge.

• Korean Journal of Audiology
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• v.25 no.4
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• pp.224-229
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• 2021

Background and Objectives: The United Kingdom (UK) national standard for the closure rate for myringoplasty is 89.5% (90.6% and 84.2% for primary and revision surgeries, respectively). The average hearing gains for primary and revision myringoplasty are 9.14 dB and 7.86 dB, respectively. This study compared the myringoplasty outcomes for a single surgeon over 5 years. Subjects and Methods: Data for 68 cases were analyzed retrospectively. The outcome measures were achievement of the tympanic membrane closure and the average hearing gain or loss. Results: The overall and primary closure rates were 97% and 98%, respectively and significantly higher than the UK national standard (p=0.0210 and p=0.0287, respectively). The revision closure rate was 93%; however, it was not significantly higher than the national standard (p=0.1872). The average hearing gain was 5.18 dB. The gains for primary and revision surgeries were 5.15 dB and 5.25 dB, respectively. Conclusions: We propose that these outcomes are a result of our surgical technique, including the simultaneous use of cortical mastoidectomy in ears with discharge.