• 한국산학기술학회논문지
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• 제17권3호
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• pp.218-223
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• 2016

본 논문에서는 광통신시스템의 수신기에서 Butterworth 필터의 차수가 수신기의 감도에 미치는 상관관계에 대해 연구를 수행하였다. 일반적인 경우에는 필터의 차수가 증가하면 할수록 수신기의 감도가 증대된다. 이는 필터의 차수가 증가할수록 필터의 규격화 주파수의 응답이 구형파와 비슷해지기 때문이다. 그러한 이유로 수신기의 감도를 증가시키기 위해서 필터의 차수를 높이는 방법을 이용한다. 그러나 필터의 차수를 높이는 방법을 사용하면 시스템이 복잡해지고 시스템의 단가를 상승시키는 요인이 된다. 따라서 본 논문에서는 시스템을 간단히 구성하여 시스템의 단가를 낮추기 위한 방법을 모색하기 위해 수신기의 감도와 필터의 차수와의 상관관계에 대해 연구를 수행하였다. 시뮬레이션 결과 필터의 차수를 증가시키면 수신기의 감도가 상승하는 것을 확인 할 수 있었다. 또한 수신기의 감도를 감소시키지 않는 범위의 버터워스 필터의 차수는 2로 확인되었다. 따라서 본 논문의 결과를 사용한다면 저렴한 광시스템의 수신기를 구현이 가능하리라 사료된다.

• Korea-Australia Rheology Journal
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• 제14권2호
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• pp.57-62
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• 2002

The sensitivity of the final filament to the ongoing sinusoidal disturbances has been Investigated in the viscoelastic spinning using frequency response method. Amplification ratios or gains of the spinline cross-sectional area at the take-up to any disturbances show resonant peaks along the frequency regime, where the frequencies at theme points directly correspond to the imaginary parts of the successive leading eigenvalues from the linear stability analysis. As shown in Jung et al. (1999) and Lee et al (2001), the sensitivity results on the effect of various process conditions such as spinline cooling and fluid viscoelasticity, obtained by dynamic transient simulation have been corroborated in this study. That is, increasing spinline cooling makes the system less sensitive to disturbances, thus stabilizes the spinning. Also, an increasing viscoelasticity for extension-thickening fluids decreases the sensitivity of the spinning. i.e., stabilizing the system, where, as it increases the sensitivity of the spinning of extension-thinning fluids. Furthermore, it has been found in the present study that the inertia force as one of secondary forces causes the system to be more stabile or less sensitive to process disturbances.

• Transactions on Electrical and Electronic Materials
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• 제15권4호
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• pp.182-188
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• 2014

When the windowed DFT algorithm is applied in harmonic measurements, the problem of initial-phase sensitivity will be encountered, this has an effect on harmonic amplitude accuracy. In this paper, the origin of initial-phase sensitivity is analyzed and the main factors that influence the level of initial-phase sensitivity are demonstrated. A method of reducing initial-phase sensitivity is proposed to increase the stability of harmonic measurements. We found that initial-phase sensitivity is determined by the side lobe peak level of the window functions when synchronous deviation is fixed. In addition, increasing the length of the time recorded can be used to remove initial-phase sensitivity. The correctness and validity of our conclusions have been confirmed through numerical results and field tests.

• Journal of Preventive Medicine and Public Health
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• 제40권4호
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• pp.297-304
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• 2007

Objectives : We investigated the validity of the dipstick method (Mossman Associates Inc. USA) and the expired CO method to distinguish between smokers and non-smokers. We also elucidated the related factors of the two methods. Methods : This study included 244 smokers and 50 ex-smokers, recruited from smoking cessation clinics at 4 local public health centers, who had quit for over 4 weeks. We calculated the sensitivity, specificity and Kappa coefficient of each method for validity. We obtained ROC curve, predictive value and agreement to determine the cutoff of expired air CO method. Finally, we elucidated the related factors and compared their effect powers using the standardized regression coefficient. Results : The dipstick method showed a sensitivity of 92.6%, specificity of 96.0% and Kappa coefficient of 0.79. The best cutoff value to distinguish smokers was 5-6ppm. At 5 ppm, the expired CO method showed a sensitivity of 94.3%, specificity of 82.0% and Kappa coefficient of 0.73. And at 6 ppm, sensitivity, specificity and Kappa coefficient were 88.5%, 86.0% and 0.64, respectively. Therefore, the dipstick method had higher sensitivity and specificity than the expired CO method. The dipstick and expired CO methods were significantly increased with increasing smoking amount. With longer time since the last smoking, expired CO showed a rapid decrease after 4 hours, whereas the dipstick method showed relatively stable levels for more than 4 hours. Conclusions : The dipstick and expired CO methods were both good indicators for assessing smoking status. However, the former showed higher sensitivity and specificity and stable levels over longer hours after smoking, compared to the expired CO method.

• Structural Engineering and Mechanics
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• 제68권5호
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• pp.549-561
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• 2018

Sobol method is applied as a powerful variance decomposition technique in the field of global sensitivity analysis (GSA). The paper is devoted to increase convergence speed of the extracted Sobol indices using a new proposed sampling technique called genetic based Latine hypercube sampling (GBLHS). This technique is indeed an improved version of restricted Latine hypercube sampling (LHS) and the optimization algorithm is inspired from genetic algorithm in a new approach. The new approach is based on the optimization of minimax value of LHS arrays using manipulation of array indices as chromosomes in genetic algorithm. The improved Sobol method is implemented to perform factor prioritization and fixing of an uncertain comprehensive high speed rotor-bearing system. The finite element method is employed for rotor-bearing modeling by considering Eshleman-Eubanks assumption and interaction of axial force on the rotor whirling behavior. The performance of the GBLHS technique are compared with the Monte Carlo Simulation (MCS), LHS and Optimized LHS (Minimax. criteria). Comparison of the GBLHS with other techniques demonstrates its capability for increasing convergence speed of the sensitivity indices and improving computational time of the GSA.

• 한국통신학회논문지
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• 제38C권7호
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• pp.643-649
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• 2013

본 논문에서는 무선통신기기에서 필수적으로 사용되는 안테나의 근접 전자기장 변화에 의한 반사계수의 변화를 토대로 하여 사람의 심박신호를 검출한다. 반사되는 신호를 검출하기 위하여 20 dB의 directional coupler를 사용하여 송신신호에 영향을 주지 않고 안테나의 반사계수를 검출하는 회로를 사용하였다. 사람의 심박에 의한 다이폴 안테나의 반사계수는 약 0.07 dB 가량 변하게 되어 검출하기 어려우므로, 민감도를 향상시키는 방법을 적용하여 심박신호를 깨끗하게 잡아내었다. Discrete한 소자의 사용으로 오차가 발생하는 것을 감안하여 안테나의 위치를 움직여 최적 지점에서 더 좋은 심박신호의 결과를 나타내는 것을 확인하였고, 일반적인 통신신호에서도 가능한지 확인하기 위하여 4 MHz 대역의 FM신호를 사용하여 잘 동작하는 것을 검증하였다.

• 센서학회지
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• 제30권1호
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• pp.47-50
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• 2021

Human hearing sensitivity is frequency-dependent. The sensitivity is low at both ends of the audible frequency, and the sensitivity is the highest in the middle band at 3000 Hz. The heart sound of a healthy person is concentrated at a low frequency of 200 Hz or less, and despite using a stethoscope, the hearing sensitivity of the human body is low, and the stethoscope sound is low. Amplifying the sound of the stethoscope is not effective in distinguishing heart sounds in noisy environments because it maintains the same signal-to-noise ratio. In this study, a method of enhancing auditory stimulation was developed by applying a method of moving the spectrum of auscultation sounds into a high-frequency region where the human body is highly sensitive to hearing. The spectrum of the auscultation sound was moved up by 500 Hz in the frequency domain, and an inverse fast Fourier transform (FFT) was performed to reconstruct the auscultation sound. The heart sounds reconstructed by moving the spectra were divided into the first heart and second heart sound components, as in the original heart sound, and it was confirmed that the intensity was large in the cochleagram representing auditory stimulation. Therefore, this study suggested that spectral shift is a method to enhance auditory stimulation during auscultation without increasing the intensity of the auscultation sound.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.436-439
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• 2007

This paper describes the optimization of PGS(Patterned Ground Shield) of 5.5 turns rectangular spiral inductor using Taguchi's method. PGS is decrease method of parasite component by silicon substrate among dielectric loss reduction method. By using the taguchi's method, each parameter is fixed upon that PGS high poison(A), slot spacing(B), strip width(C) and overlap turn number(D) of PGS design parameter. Then we verified that percentage contribution and design sensitivity analysis of each parameter and level by signal to noise ratio of larger-the-better type. We consider percentage contribution and design sensitivity of each parameter and level, and then verify that model of optimization for PGS is lower inductance decreasing ratio and higher Q-factor increasing ratio by EM simulation.

• 전기학회논문지P
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• 제64권4호
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• pp.333-336
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• 2015

Recently, the power load is growing larger and because of the environmental limitation of generation, the expansion of generation facilities are becoming more difficult. For that reason the importance of the demand-side resources come to be higher. One method of the demand-side resource, the DLC Program, has executed, and moreover, the loads which are available to be controlled are increasing. It should be considered of some kinds of power system components such as DLCs, because the fact that using the demand resources will be an important part of the power system. This paper considers the power factor of the load-bus which is shedded in the direct load control program. and then analyze the power system using flow sensitivity and voltage sensitivity. In this paper, we assumed two scenarios through the rank of the load power factor at each bus and to compare and evaluate each case, we used Power World for the simulation.

• 대한전기학회논문지
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• 제43권7호
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• pp.1144-1151
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• 1994

The humidity-sensitive specimens-(BaS11T-S1xTCaS1xT)TiOS13T, x=0, 0.1, 0.2, 0.3, 0.4, 0.5-were fabricated by a solid-state reaction method which is easy in process control of microstructure and good in mass production, and their humidity-sensitive characteristics were examined. Ca inhibits grain growth and the open porosity increases with Ca substitution, and the specimens at x=0.5 show the best humidity sensitivity. Their humidity sensitivity is higher at the lower frequencies, and drift phenomenon in humidity sensitivity is exhibted with aging in the air, which disappears by a heat treatment. The electrical conduction with water adsorption is dominated by the ions, and the activation energy decreases with increasing relative humidity.