• Electronic Materials Letters
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• v.14 no.6
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• pp.766-773
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• 2018

In this paper, temperature dependence of the excitonic bands in a mechanically exfoliated tungsten diselenide ($WSe_2$) monolayer is studied using photoluminescence and circular dichroic photoluminescence (PL) in the temperature range between 8 and 300 K. The peak energies associated with the neutral exciton (A), charged exciton (trion) and localized excitons are extracted from the PL spectra revealing a trion binding energy of around 30 meV. The circular dichroic PL measured at 8 K shows about 45% valley polarisation that sharply reduces with increasing temperature to 5% at 300 K with photoexcitation energy of 1.96 eV. A detailed analysis of the emission line-width suggests that the rapid decrease of valley polarisation with the increase of temperature is caused by the strong exciton-phonon interactions which efficiently scatter the excitons into different excitonic states that are easily accessible due to the supply of excess photoexcitation energy. The emission line-width broadening with the increase of temperature indicate residual exciton dephasing lifetime < 100 fs, that correlates with the observed rapid valley depolarisation.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.122-129
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• 2006

We propose the Fizeau-type phase shifting interferometer(FPSI) system for the performance test of high-order aspheric lenses. The proposed system is divided into two parts : optical part and signal processing part. Those two parts are operated by a program for hardware control. We also developed an analysis program adopting the phase shifting algorithm to analyze the obtained interferograms. We can confirm that the proposed system is efficient and adequate by direct comparison with the standard criterion in Mark IV interferometric system of Zygo. The peak-to-valley and RMS values of surface errors which are used to characterize high-order aspheric lenses are 0.845 wave and 0.1871 wave, respectively. The measurement errors between the proposed system and Mark IV are less than ${\lambda}/100$ and the repeatability is also calculated at less than ${\lambda}/100$.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.2
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• pp.279-284
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• 2010

The plane curve approach which was proposed by Boukharouba et. al. is a multi-threshold selection method through searching peak-valley based on histogram cumulative distribution function. However the method is required to select parameters to compose plane curve, and the shape of plane curve is affected according to parameters. Therefore detection of peak-valley is effected by parameters. In this paper, we propose an entropy maximizing-based method to select optimal plane curve parameters, and propose a multi-thresholding method based on the selected parameters. The effectiveness of the proposed method is demonstrated by multi-thresholding experiments on various images and comparison with other conventional thresholding methods based on histogram.

• The Transactions of the Korea Information Processing Society
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• v.6 no.2
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• pp.522-533
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• 1999

This paper proposes speaker recognition algorithm which includes both the pitch parameter and the fuzzy inference. This study proposes a pitch detection method PVPF(peak and valley pitch detection fuction) by means of comparing spectra which utilizes the transform characteristics between time and frequency. In this paper, makes reference pattern using membership function and performs vocal tract recognition of common character using fuzzy pattern matching in order to include time variation width for non-linear utterance time.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2267-2272
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• 2007

The present study investigates the two dimensional flow and heat/mass transfer characteristics of wavy duct with various corrugation angles. For the heat/mass transfer coefficients, a naphthalene sublimation technique is used. Numerical analysis and wall pressure measurement show detailed two dimensional flow features. The corrugation angles change from 145$^{\circ}$ to 100$^{\circ}$. The operating Reynolds numbers based on the duct hydraulic diameter vary from 700 to 3,000. The duct aspect ratio maintains 7.3. On the pressure wall, strong flow mixing enhances heat/mass transfer coefficients at the front position. In addition, the rear side of pressure wall, the near of peak, is affected by the acceleration and the shedding of main flow. On the suction wall, however, flow separation and reattachment lead to the valley and the peak of heat/mass transfer coefficient. Also, highly increasing boundary layer at the suction wall affects the decrease of heat/masst transfer. As decreasing corrugation angles, the spanwise average Sherwood number increases and the peak or the valley positions of the local Sherwood number are varied.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.12
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• pp.1281-1286
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• 2015

Fatigue cracks can be generated in aircraft as a result of the cumulative time spent during flight operations, which can extend for long periods of time and cover a variety of missions. If a crack occurs in an aircraft's main spar, it can generate many problems, including a lift time reduction. To solve this problem, it was necessary to perform an analysis of fatigue crack growth in the fatigue critical locations. Much time and expense is involved in generating the stress needed for a crack propagation analysis over a long period of time to obtain the amount of data required for an actual aircraft. In this paper, an algorithm is developed that can calculate the spectrum of stress over a long period of time for a mission by the Southwest Research Institute, which is based on the short-time load factor data produced using the peak-valley cycle counting method.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.185-194
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• 2014

One in every 10 persons suffer from chronic gastritis in Korea. Endoscopy is most commonly used to diagnose the chronic gastritis. Endoscopic diagnosis is precise but it is accompanied with pain and high cost. According to pulse diagnosis in Traditional East Asian Medicine, health problems in stomach can be diagnosed with radial pulse signals in 'Guan' location in the right wrist, which are non-invasive and cost-effective. In this study, we developed a classification model of chronic gastritis using pulse signals in right 'Guan' location. We used both linear discrimination method and logistic regression model with respect to pulse features obtained with a peak-valley detection algorithm and a Gaussian model. As a result, we obtained sensitivity ranged between 77%~89% and specificity ranged between 72%~83% depending on classification models and feature extraction methods, and the average classification rates were approximately 80%, irrespective of the models. Specifically, the Gaussian model were featured by superior sensitivities (89.1% and 87.5%) while the peak-valley detection method showed superior specificities (82.8% and 81.3%), and the average classification rate (sensitivity + specificity) of the Gaussian model was 80.9% which was 1.2% ahead of the peak-valley method. In conclusion, we obtained a reliable classification model for the chronic gastritis based on the radial pulse feature extraction algorithms, where the Gaussian model was featured by outperformed sensitivity and the peak-valley method was featured by outperformed specificity.

• Journal of Soil and Groundwater Environment
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• v.11 no.1
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• pp.37-44
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• 2006

This study summarizes advantages and disadvantages of numerical methods and compares ELLAM and LEZOOMPC to develop an efficient numerical modeling technique on contaminant transport. Eulerian-Lagrangian method and Eulerian method are commonly used numerical techniques. However Eulerian-Lagrangian method does not conserve mass globally and fails to treat boundary in a straightforward manner. Also, Eulerian method has restrictions on the size of Courant number and mesh Peclet number because of time truncation error. ELLAM (Eulerian Lagrangian Localized Adjoint Method) which has been popularly used for past 10 years in numerical modeling, is known for overcoming these numerical problems of Eulerian-Lagrangian method and Eulerian method. However, this study investigates advantages and disadvantages of ELLAM and suggests a change for the better. To figure out the disadvantages of ELLAM, the results of ELLAM, LEZOOMPC (Lagrangian-Eulerian ZOOMing Peak and valley Capturing), and visual MODFLOW are compared for four examples having different mesh Peclet numbers. The result of ELLAM generates numerical oscillation at infinite of mesh Peclet number, but that of LEZOOMPC yields accurate simulations. The simulation results suggest that the numerical error of ELLAM could be alleviated by adopting some schemes in LEZOOMPC. In other words, the numerical model which combines ELLAM with backward particle tracking, forward particle tracking, adaptively local zooming, and peak/valley capturing of LEZOOMPC can be developed for not only overcoming the numerical error of ELLAM, but also keeping the numerical advantage of ELLAM.

• Journal of Pharmacopuncture
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• v.10 no.2 s.23
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• pp.119-132
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• 2007

This study was performed to determine whether a pulse analyzer was useful 1) to characterize the variables of pulse wave of cerebral infarction patieno (CI), compared with those of healthy subjects, as well as 2) to determine Sasang Constitution in CI and healthy subjects. 1. Calibrated in Gwan, the amount of energy(Energy), height of main peak(H1), height of aorticvalley(H2), height of aortic peak(H3), total area of pulse wave(At), and area of main peak width(Aw) of the CI group were higher than those of the healthy group. 2. Calibrated in Cheek, Energy, H1, H2, H3, height of valve valley(H4), At, Aw, and main peak angle(MPA) of the CI group were higher than those of the healthy group. 3. Among the healthy (subjects) group, Taeumin showed the highest contact pressure(CP) and height of valve peak(H5) calibrated in Chon. The main peak width divided by whole time of pulse wave(MPW/T) calibrated in Gwan and Cheok, was highest in Soyangin and was lowest in Taeumin. The H3 divided by H1(H3/H1) and the time to valve valley minus the time to main peak and divided by T[(T4-T1)/T] calibrated in Cheek were highest in Soyangin. The time to main peak(T1) was longest in Soumin. 4. Among the CI group, At calibrated in Chon was widest in Taeumin and was narrowest in Soumin The time to aortic peak(T3) calibrated in Cheek was longest in Soumin and was shortest in Soyangin. The time to valve peak(T5) was shortest in Soyangin. 5. There were main effects of cerebral infarction in the area of systolic period(As) and area of diastolic period(Ad) calibrated in Chon, Energy calibrated in Cwan, and Energy, H1, H2, H3, (H4+H5)/Hl, and MPA calibrated in Cheek. 6. There were main effects of Sasang Constitution in (T4-T1)/T, area of systolic period(As), and Ad calibrated in Chon. 7. The interactions between the cerebral infarction and Sasang Constitution were observed in H5/H1 , T, At, As, Ad, and MPA calibrated in Chon, H4, T4, (T4-T1)/T, As, and Ad calibrated in Cwan, and 74,75, and MPW calibrated in Cheok. Therefore, we concluded that pulse analyzer was useful to determine the risk degree of cerebral infarction and Sasang Constitution.

• ETRI Journal
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• v.33 no.1
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• pp.99-109
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• 2011

This paper concerns a robust real-time voice activity detection (VAD) approach which is easy to understand and implement. The proposed approach employs several short-term speech/nonspeech discriminating features in a voting paradigm to achieve a reliable performance in different environments. This paper mainly focuses on the performance improvement of a recently proposed approach which uses spectral peak valley difference (SPVD) as a feature for silence detection. The main issue of this paper is to apply a set of features with SPVD to improve the VAD robustness. The proposed approach uses a weighted voting scheme in order to take the discriminative power of the employed feature set into account. The experiments show that the proposed approach is more robust than the baseline approach from different points of view, including channel distortion and threshold selection. The proposed approach is also compared with some other VAD techniques for better confirmation of its achievements. Using the proposed weighted voting approach, the average VAD performance is increased to 89.29% for 5 different noise types and 8 SNR levels. The resulting performance is 13.79% higher than the approach based only on SPVD and even 2.25% higher than the not-weighted voting scheme.