주파수 의존성을 고려한 등가선형해석기법의 검증

정창균,곽동엽,박두희 한국지반공학회 2008 한국지반공학회논문집 Vol.24 No.12

One-dimensional site response analysis is widely used to simulate the seismic site effects. The equivalent linear analysis, which is the most widely used type of site response analysis, is essentially a linear method. The method applies constant shear modulus and damping throughout the frequency range of the input motion, ignoring the dependence of the soil response on the loading frequency. A new type of equivalent linear analysis method that can simulate the frequency dependence of the soil behavior via frequency-strain curve was developed. Various forms of frequency-strain curves were proposed, and all curves were asserted to increase the accuracy of the solution. However, its validity has not been extensively proven and the effect of the shape of the frequency-strain curve is not known. This paper used two previously proposed frequency-strain curves and three additional curves developed in this study to evaluate the accuracy of the frequency-dependent equivalent linear method and the influence of the shape of the frequency-strain curves. In the evaluation, six recordings from three case histories were used. The results of the case study indicated that the shape of the frequency-strain curve has a dominant influence on the calculated response, and that the frequency dependent analysis can enhance the accuracy of the solution. However, a curve that results in the best match for all case histories did not exist and the optimum curve varied for each case. Since the optimum frequency-strain curve can not be defined, it is recommended that a suite of curves be used in the analysis.

Evaluation of Frequency-Dependent On-Resistance of GaN Devices at High Frequency

Kangping Wang,Bingyang Li,Zhiyuan Qi,Laili Wang,Xu Yang,Aici Qiu 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

The switching frequency of GaN-based power converters has been pushed to several MHz and even higher. At such high frequencies, this paper finds that the onresistance of GaN devices may be much higher than their DC values, especially for the devices with low on-resistance. The frequency-dependent characteristics of on-resistance are studied through electrical and thermal experiments for the first time in this paper. A simplified finite-element-simulation model is proposed to illustrate the mechanism of the frequency-dependent characteristics. The results show that the frequency-dependent characteristics of the on-resistance are closely related to the current distribution inside the GaN device and affected by the layout. In addition, two same GaNbased 10MHz DC-DC converters were designed to operate under the same conditions, and the only difference comes from the layout of GaN devices. The experimental results show that the efficiency of the converter with optimized layout is improved by 2% compared to that with conventional layout.

Frequency Dependent Properties of Tris(8-Hydroxyquinoline) Aluminum Thin Films

Lee, Yong-Soo,Park, Jae-Hoon,Choi, Jong-Sun The Korean Institute of Electrical Engineers 2001 KIEE International Transactions on Electrophysics Vol.11C No.3

Admittance or impedance spectroscopy is one of the powerful tools to study dielectric relaxation and loss processes in organic and inorganic materials. In this study, the frequency dependent properties of an indium tin oxide/tris(8-hydroxyquinoline) aluminum($Alq_3$)/aluminum structure have been studied. The conductance of the $Alq_3$ film increases with the DC applied voltage up to 4V and decreases above 4V in the low frequency region. This indicates that the resistance of the device decreases with the applied bias due to the carrier injection enhancement, thereafter the injected carriers form the space charge and the additional injection of carriers is prevented. The Cole-Cole plot of the admittance takes a one-semicircle shape, which means that the device can be modeled as a parallel resistor-capacitor network. The resistance and capacitance were estimated as 8.62k${\Omega}$ and 2.7nF, respectively, at 3V in the low frequency region. The dielectric constant ( ${\epsilon}'$ ) of the $Alq_3$ film is independent of the frequency in the low frequency region below 100kHz, while the frequency dependency was observed at above 100kHz. The dielectric loss factor ( ${\epsilon}"$ ) of the $Alq_3$ film shows the dielectric dispersion below 100kHz and dielectric absorption in higher frequency domain. The dispersion is thought to be related to the hopping process of the carriers. The ${\epsilon}"$ is proportional to the reciprocal of the frequency. The dielectric relaxation time was extracted to about 0.318${\mu}s$ from the dielectric absorption spectrum.

Investigation of Frequency Dependency of Residential Loads in Modern Power Systems: An Experimental Approach

Qiucen Tao,Johanna Geis-Schroer,Maeva Courcelle,Thomas Leibfried,Giovanni De Carne 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

The increasing penetration of power electronic-based or -interfaced resources and loads leads to a reduction in the overall system inertia. As a result, the modern power network can experience faster and larger frequency changes under power imbalances. This highlights the importance of a better assessment of network parameters, such as the frequency dependency of loads and active resources. So far, studies on load behavior have mainly focused on voltage dependency, and very few have investigated frequency dependency. The frequency dependency parameters used in recent publications are still mainly results obtained between 1940 and 1980. Load technology has changed since. Therefore, this paper focuses on the identification of the frequency dependency of modern passive residential loads and active resources through experiments on real appliances. For this purpose, the perturbation-based identification method is used: an apartment-like laboratory is supplied by a three-phase voltage amplifier to create artificial frequency variations. The frequency dependency is then calculated from the recorded power responses.

Effects of Different Physical Frequency on Food-Dependent Exercise Induced Allergy Anaphylaxis (FDEIA) and Related Mechanisms

Cheol Woo Kim(김철우),Yi Sub Kwak(곽이섭) 한국생명과학회 2012 생명과학회지 Vol.22 No.7

본 연구에서는 적절하게 알레르기가 유발되는 운동강도인 50분간의 강도를 선정한 후 운동빈도를 서로 달리하여 통제 그룹(S) 저빈도 그룹(F2, 주2회), 중빈도 그룹(F3, 주 3회) 및 고빈도 그룹(F5, 주5회)으로 나누어 훈련을 부여하고 OVA알부민으로 감작한 후 OVA로 challenge를 하였을 때, 알레르기 아나플락시스의 변화 양상 차이를 살펴보고 동시에 기전변화를 함께 규명하고자 하였다. 본 연구를 위해 그룹당 25마리씩 통제군(S; control sensitized, n=25), 저빈도 훈련군(F2, n=25), 중빈도 훈련군(F3, n=25) 및 고빈도 훈련군(F5, n=25)으로 구분하여 수영훈련 빈도에 따른 알레르기를 유도하였을 때, 알레르기 아나플락시스를 조사하고 아울러 비장지수, 림프구의 수, 복강 ROS, ASAS, 및 싸이토카인(INF-γ, IL-4)의 변화를 함께 측정하였다. 이 때, 알러지 아나플락시스 테스트는 그룹당 10마리를 사용하였고, 나머지는 세포분석과 ROS 측정을 위하여 사용하였다. 본 연구결과 일반 감작군에 비하여 운동 감작군에서 알러지가 더 잘 유도됨을 알 수 있었고, 같은 운동강도 부여시 저빈도의 운동군에 비하여 고빈도 운동군에서 알러지 반응이 더 잘 일어남을 확인 할 수 있었다. 이는 고빈도 운동군에서 현저히 증가되는 IL-4 반응과 ASAS 반응으로 알 수 있었고, 특히 이러한 반응이 고빈도 운동그룹에서 현저히 증가하는 ROS반응과 일치함을 확인하였다. 한편 저빈도 그룹에서는 오히려 INF-γ의 증가와 ROS 반응이 감소하였고, ASAS 반응이 통제군보다 오히려 줄어들어 운동의 빈도가 알레르기반응과 밀접한 연관이 있음을 확인할 수 있었다. 추후 이러한 원인에 대한 면밀한 분석이 요구되며, 알레르기 반응의 cross training 및 detraining 효과도 함께 규명되어야 할 것으로 여겨진다. Food allergies have become a serious health concern in the past two decades, especially in developed countries. Foods associated with allergies include vegetables, some fruits, shellfish, wheat, egg, chicken, and nuts. To describe the specific fundamentals, etiological factors, and clinical manifestations, we analyzed the different physical frequency on spleen index in sensitized and regular exercise-trained mice. We also conducted a proliferation assay of lymphocytes to OVA, ROS, ASAS, and we determined the cytokine levels. Female BALB/c mice were bred in the animal laboratory of the P and D university under controlled conditions (22±2oC, RH 45-55%, and a 12-hour photoperiod). The animals were 6 weeks old at the start of the study and were fed a standard commercial chow diet from 09:00 to 15:00 for the 8-week study period. All animals had access to distilled deionized water ad libitum. They were divided into four groups: a control group (S; control sensitized, n=25), a low-frequency training group (F2, n=25), a mid-frequency training group (F3, n=25), and a high-frequency training group (F5, n=25) following the treatment of exercise time per week. The results were as follows: The mice spleen index showed the highest grade in the F5 group compared with the other groups; this level showed in an exercise frequency-dependent manner. In the proliferation assay of OVA, the F5 group showed the highest grade compared with the other groups; this level was also showed in an exercise frequency-dependent manner. Peritoneal ROS and ASAS showed a statistically significant increase in the F5 group and decreased in the F2 group compared with the S group. However, there were no significant differences in the F3 group. The highest level of IL-4 was found in the F5 group compared with the other groups. However, the highest level of INF-γ was in the F2 group. The results suggest that FDEIA is positively correlated with the frequency of exercise due to the direct effect of physical exercise on peritoneal ROS and the cytokine profile. Further research is needed on the specific mechanism underlying the combined effects of exercise intensity and frequency on physical-induced allergy anaphylaxis.

Brain Regional Homogeneity Changes in Cirrhotic Patients with or without Hepatic Encephalopathy Revealed by Multi-Frequency Bands Analysis Based on Resting-State Functional MRI

Gaoyan Zhang,Yue Cheng,Wen Shen,Baolin Liu,Lixiang Huang,Shuangshuang Xie 대한영상의학회 2018 Korean Journal of Radiology Vol.19 No.3

Objective: To investigate brain regional homogeneity (ReHo) changes of multiple sub-frequency bands in cirrhotic patients with or without hepatic encephalopathy using resting-state functional MRI. Materials and Methods: This study recruited 46 cirrhotic patients without clinical hepatic encephalopathy (noHE), 38 cirrhotic patients with clinical hepatic encephalopathy (HE), and 37 healthy volunteers. ReHo differences were analyzed in slow-5 (0.010−0.027 Hz), slow-4 (0.027−0.073 Hz), and slow-3 (0.073−0.198 Hz) bands. Routine analysis of (0.010−0.080 Hz) band was used as a benchmark. Associations of abnormal ReHo values in each frequency band with neuropsychological scores and blood ammonia level were analyzed. Pattern classification analyses were conducted to determine whether ReHo differences in each band could differentiate the three groups of subjects (patients with or without hepatic encephalopathy and healthy controls). Results: Compared to routine analysis, more differences between HE and noHE were observed in slow-5 and slow-4 bands (p < 0.005, cluster > 12, overall corrected p < 0.05). Sub-frequency band analysis also showed that ReHo abnormalities were frequency-dependent (overall corrected p < 0.05). In addition, ReHo abnormalities in each sub-band were correlated with blood ammonia level and neuropsychological scores, especially in the left inferior parietal lobe (overall corrected p < 0.05 for all frequency bands). Pattern classification analysis demonstrated that ReHo differences in lower slow-5 and slow-4 bands (both p < 0.05) and higher slow-3 band could differentiate the three groups (p < 0.05). Compared to routine analysis, ReHo features in slow-4 band obtained better classification accuracy (89%). Conclusion: Cirrhotic patients showed frequency-dependent changes in ReHo. Sub-frequency band analysis is important for understanding HE and clinical monitoring.

Analysis of frequency dependence on short-term annoyance of conventional railway noise using sound quality metrics in a laboratory context

Yoon, Kiseop,Gwak, Doo Young,Chun, Chanil,Seong, Yeolwan,Hong, Jiyoung,Lee, Soogab Elsevier 2018 Applied acoustics Vol.138 No.-

<P><B>Abstract</B></P> <P>Since the early 20th century, many studies have been conducted about the noise characteristics of trains, particularly in regards to annoyance. However, none of the studies considered the frequency dependence of short-term annoyance of railway noise. Moreover, none of the studies was performed to observe the change of the annoyance using sound quality metrics when the frequency component of railway noise was modified. Thus, in the current study, after experimentally confirming the validity of using sound quality metrics as assessment units, the frequency dependence of short-term annoyance was investigated that included sound quality metrics based on frequency-modified ‘conventional’ railway noise. Three experiments were conducted on the study. In the first experiment, 50 participants determined the words most suitable to represent the quantity of railway noise, and the metrics that were expected to be most relevant to railway noise were identified. Using the results from the first experiment, 50 participants estimated the magnitude of subjective loudness, subjective sharpness, and the annoyance of the railway noise to verify the reasonability of using sound quality metrics as the assessment units of estimating the frequency dependence. From the results of the second experiment, it was determined that the subjective factors and the calculated factors had clear linear relationships, and it was identified that sound quality metrics can be used to determine the frequency dependence of short-term annoyance of the railway noise. In the third experiment, 50 participants estimated the upper and lower limits of hearing perception of subjective loudness of the railway noise to identify the frequency sensitivity of participants to the railway noise. Finally, case studies were conducted on short-term annoyance model using multiple regression method, which confirmed the frequency dependence of the annoyance of the railway noise.</P>

수평으로 매설된 도선의 접지임피던스의 주파수의존성을 계산하는 기법

조성철(Sung-Chul Cho),이복희(Bok-Hee Lee) 대한전기학회 2016 전기학회논문지 Vol.65 No.5

The parameters of Debye’s equation were applied to analyze the frequency-dependent ground impedance of horizontally-buried wires. We present a new method, based on Debye’s equation, of analyzing the effect of polarization on frequency-dependent ground impedance. The frequency-dependent ground impedances of a horizontally-buried wire are directly measured and calculated by applying sinusoidal current in the frequency range of 100 Hz to 10 MHz. Also, the results obtained in this work were compared with the data calculated from empirical equations and commercial programs. A new methodology using the delta-gap source model is proposed in order to calculate frequency-dependent ground impedance when the ground current is injected at the middle-point of the horizontal ground electrode. The high frequency ground impedance of horizontal electrodes longer than 30 m is larger or equal to its low frequency ground resistance. Consequently, the frequency-dependent ground impedance simulated with the proposed method is in agreement with the experimental data, and the validity of the computational simulation approach is confirmed.

반구형 전극계에서 물의 저항률을 이용한 접지시스템의 등가회로 구성

이복희(Bok-Hee Lee),최종혁(Jong-Hyuk Choi),배성배(Sung-Bae Bae) 한국조명·전기설비학회 2008 조명·전기설비학회논문지 Vol.22 No.8

현재 우리나라의 접지시스템의 설계기준은 낮은 주파수에서 측정된 저항값을 기반으로 한다. 고주파 성분을 포함하는 뇌서지가 접지시스템에 인가되면 접지임피던스는 정상상태의 저항과 매우 다르게 된다. 이 논문은 접지시스템의 고주파 성능에 대한 물의 저항률의 영향을 파악하기 위하여 대지를 모의하는 수조를 이용하여 물의 저항률에 따른 어드미턴스의 주파수 의존성을 기술하였다. 500[Ωㆍm] 이상의 높은 물의 저항률에서 용량성 효과에 의해 주파수가 증가함에 따라 어드미턴스와 컨덕턴스가 증가하는 것으로 나타났다. 반면에, 500[Ωㆍm] 미만의 낮은 저항률에서는 유도성 효과에 의해 주파수가 증가함에 따라 어드미턴스와 컨덕턴스가 감소하는 것으로 나타났다. 또한 200[㎑]에서 5[㎒]에 이르는 주파수 범위에서 전류와 전압의 위상차가 증가하는 것으로 나타났다. 결론적으로, 접지시스템의 주파수 의존성은 대지의 저항률과 밀접한 관계가 있으며, 주파수와 대지저항률이 접지시스템의 성능에 미치는 영향에 대한 고려가 필요하다. A design criterion of grounding systems is commonly based on the ground resistance measured with low frequency in Korea. When lightning grus which have high frequency components are injected into the grounding system, the grounding impedance is greatly different morf the static grounding resistance. In order to investigate the effect of water resistivity on the high frequency performance of grounding systems, this paper presents the frequency-dependent admittance using water tank simulating the grounding system in different water resistivities. As a result, because of capacitive effect admittances and conductance are increased with increasing frequency in higher water resistivity of greater than 500[Ωㆍm]. On the other hand, admittances and conductances are decreased with increasing frequency due to inductive effect in lower water resistivity of less than 500[Ωㆍm]. The phase difference between the current and voltage increases in the range of 200[㎑] to 5[㎒]. Consequently, frequency-dependent performance of grounding systems is closely taler to the soil resistivity, it is necessary to consider the effect of grounding system performance on the frequency and soil resistivity.

An Investigation on the Frequency Dependence of Soil Electrical Parameters

이복희,김기복 한국조명.전기설비학회 2015 조명·전기설비학회논문지 Vol.29 No.4

This paper presents the results of an investigation into the frequency-dependent electrical parameters for different types of soil as a function of moisture content. The frequency dependence of soil electrical parameters is very important in the design of grounding systems. In fact, the performance of grounding systems is greatly dependent upon various factors such as soil type, particle size, water content, temperature, frequency, and the like. The resistivity and relative permittivity for four different soils were measured and analyzed in the frequency range of 1kHz – 1MHz. Soil resistivity declined as moisture content and frequency increased. In particular, the frequency dependence of soil resistivity was significant as the moisture content was low. In contrast, the relative permittivity of soil dramatically declined at the frequency of 10kHz or below as the moisture content increased, showing the opposite pattern in terms of variation patterns, compared to resistivity.