scholarly journals SEISMIC RESISTANCE INVESTIGATION OF A LARGE-PANEL BUILDING WITH SUPER-WIDE WALL SPACING 

2016 ◽  
Author(s):  
П.А. Реквава
Keyword(s):  
High Frequency ◽  
Vertical Component ◽  
Source Zone ◽  
High Frequency Component ◽  
Traditional Use ◽  
Urbanized Territory ◽  
Large Panel ◽  
Instrumental Records ◽  
Wall Spacing ◽  
Wide Wall

В работе рассмотрена проблема сейсмического прогноза и его эффективности. Проведен анализ ситуации при реализации среднесрочного прогноза разрушительного Тбилисского землетрясения 25 апреля 2002 года в Грузии. Рассмотрены инженерно-геологические, геоморфологические и гидрогеологические условия г. Тбилиси. Показаны изосейсты 5‑ти бального форшока и 7‑ми бального основного толчка. В данной статье рассматриваются записи ряда разрушительных землетрясений, очаг которых находился вблизи урбанизированной территории. Проведен анализ инструментальных записей. Показано, что нахождение урбанизированной территории в ближней зоне источника обуславливает наличие высокочастотной вертикальной составляющей, предваряющей основные колебания. Хорошо известно, что поглощение сейсмических волн прямо пропорционально частоте колебаний, что предполагает быстрое затухание высокочастотной составляющей сигнала. При этом, за редким исключением, большинство записей производится станциями, достаточно удаленными от места событий. Традиционное использование инерционных сейсмоприемников при этом исключает регистрацию указанных высокочастотных сигналов. Исходя из того обстоятельства, что землетрясения расположены непосредственно под территорией г. Тбилиси использование соответствующих записей должно позволить получать реакции зданий и сооружений на подобные воздействия максимально приближенными к реальным условиям. В этой связи исследована эффективность применения в жилых зданиях конструктивной схемы с супершироким шагом на примере 5‑этажного крупнопанельного дома. Был произведен динамический расчет методом конечных элементов The problem of earthquake prediction and its effectiveness is discussed. The analysis of the situation with the implementation of the medium-term forecast of devastating earthquake April 25, 2002, Tbilisi, Georgia was held. Engineering-geological, geomorphological and hydrogeological conditions of Tbilisi are reviewed. 5‑point forshock and 7‑point main shock isoseists are shown. This article discusses a number of devastating earthquakes records, which source was close to the urbanized territory. The analysis of instrumental records was held. It is shown that the near-source zone urbanized territory determines the availability of high-frequency vertical component, anticipating major fluctuations. It is well known that absorption of seismic waves is directly proportional to the frequency of the oscillations, which involves rapid attenuation of signal high-frequency component. Thus, with few exceptions, most of the records produced by stations, quite remote from the scene. Traditional use of inertial seismic detectors excludes the registration of these high frequency signals. Earthquakes are located directly beneath the territory of Tbilisi so the use of appropriate records should enable to receive buildings and structures reactions to such impact closest to real conditions. In this context, we investigated the efficacy of residential design concept with super-wide wall spacing on the example of 5‑storeyed large-panel building. Dynamic calculation using finite element was produced. 

Laser-Generated Ultrasonic Technique for Inspecting Delamination in CFRP

2006 ◽  
Vol 321-323 ◽  
pp. 968-971
Author(s):  
Won Su Park ◽  
Sang Woo Choi ◽  
Joon Hyun Lee ◽  
Kyeong Cheol Seo ◽  
Joon Hyung Byun
Keyword(s):  
High Frequency ◽  
Ultrasonic Method ◽  
Piezoelectric Sensor ◽  
Frequency Component ◽  
Guided Wave ◽  
Center Frequency ◽  
High Frequency Component ◽  
Ultrasonic Technique ◽  
Non Destructive Evaluation ◽  
Non Destructive

For improving quality of a carbon fiber reinforced composite material (CFRP) by preventing defects such as delamination and void, it should be inspected in fabrication process. Novel non-contacting evaluation technique is required because the transducer should be contacted on the CFRP in conventional ultrasonic technique during the non-destructive evaluation and these conventional contact techniques can not be applied in a novel fiber placement system. For the non-destructive evaluation of delamination in CFRP, various methods for the generation and reception of laser-generated ultrasound are applied using piezoelectric transducer, air-coupled transducer, wavelet transform technique etc. The high frequency component of laser-generated guided wave received with piezoelectric sensor disappeared after propagating through delamination region. Air-coupled transducer was tried to be adopted in reception of laser-generated guided wave generated by using linear slit array in order to generate high frequency guided wave with a frequency of 1.1 MHz. Nevertheless, it was failed to receive high frequency guided wave in using air-coupled transducer and linear slit array. Transmitted laser-generated ultrasonic wave was received on back-wall and its frequency was analyzed to establish inspecting technique to detect delamination by non-contact ultrasonic method. In a frequency spectrum analysis, intensity ratio of low frequency and center frequency was approvable parameter to detect delamination.

Hierarchal Predefined Codebook for High-Frequency Component Augmentation Image Enlargement

2010 ◽  
Author(s):  
Hakaru Tamukoh ◽  
Hideaki Kawano ◽  
Noriaki Suetake ◽  
Masatoshi Sekine ◽  
Byungki Cha ◽  
...  
Keyword(s):  
High Frequency ◽  
Frequency Component ◽  
High Frequency Component ◽  
Image Enlargement

Abstract 13243: Diminished Daily Fluctuation of Heart Rate Variability in Patients with Chronic Kidney Disease

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Hisaki Makimoto ◽  
Katsuhito Fujiu ◽  
Kohei Shimizu ◽  
Eisuke Amiya ◽  
Kazuo Asada ◽  
...  
Keyword(s):  
Chronic Kidney Disease ◽  
Regression Analysis ◽  
Kidney Disease ◽  
High Frequency ◽  
High Frequency Component ◽  
Control Group ◽  
Holter Monitor ◽  
Significant Difference ◽  
High Incidence ◽  
Circadian Fluctuation

Introduction: Autonomic dysfunction is well known in patients with chronic kidney disease (CKD) and linked with cardiac death. In spite of a high incidence of morning death in CKD patients, circadian fluctuation in parasympathetic activation have not been studied in CKD. Hypothesis: We assessed the hypothesis that the cardiac autonomic circadian fluctuation is impaired in patients with CKD. Methods: The study population consisted of consecutive 101 patients (54 males, 70±10 years old) with CKD who underwent 24-hour Holter monitor. As a control group, 134 age and sex matched cases (66 males, 68±10 years old) without CKD who also underwent Holter monitor were recruited. Patients with diabetes orβ-blocker therapy were excluded. The high frequency component (HF), which reflected parasympathetic activity, and the low frequency to high frequency ratio (L/H ratio), which reflected, in part, sympathetic activity, were evaluated. To evaluate the contribution of CKD and other parameters to the cardiac autonomic fluctuation, the night (6PM-6AM) to day (6AM-6PM) ratio of HF and L/H ratio were analyzed utilizing a regression analysis. Results: The L/H ratio showed no significant difference during the night between the two groups, in contrast to the significant difference during the daytime. Patients with CKD showed significantly lower HF during the night as compared to control cases (P<0.05), although the daytime HF was not significantly different between the groups (Figure). Multivariate regression analysis demonstrated that CKD was independently associated with a lower night-to-day ratio of the HF and a higher night-to-day ratio of the L/H ration, even with the adjustment of age and comorbid hypertension. Conclusions: Our findings suggest that cardiac autonomic fluctuation is impaired in CKD patients. Whether a deterioration of autonomic activation might explain the high incidence of morning death in CKD patients needs to be clarified in future studies.

Force fluctuations are modulated by alternate muscle activity of knee extensor synergists during low-level sustained contraction

2004 ◽  
Vol 97 (6) ◽  
pp. 2121-2131 ◽  
Author(s):  
Motoki Kouzaki ◽  
Minoru Shinohara ◽  
Kei Masani ◽  
Tetsuo Fukunaga
Keyword(s):  
Correlation Coefficient ◽  
Muscle Activity ◽  
High Frequency ◽  
Vastus Lateralis ◽  
Frequency Component ◽  
Knee Extension ◽  
Voluntary Contraction ◽  
High Frequency Component ◽  
Knee Extensors ◽  
Force Fluctuations

The study examined the hypothesis that altered synergistic activation of the knee extensors leads to cyclic modulation of the force fluctuations. To test this hypothesis, the force fluctuations were investigated during sustained knee extension at 2.5% of maximal voluntary contraction force for 60 min in 11 men. Surface electromyograms (EMG) were recorded from the rectus femoris (RF), vastus lateralis (VL), and vastus medialis (VM) muscles. The SD of force and average EMG (AEMG) of each muscle were calculated for 30-s periods during alternate muscle activity. Power spectrum of force was calculated for the low- (≤3 Hz), middle- (4–6 Hz), and high-frequency (8–12 Hz) components. Alternate muscle activity was observed between RF and the set of VL and VM muscles. The SD of force was not constant but variable due to the alternate muscle activity. The SD was significantly greater during high RF activity compared with high VL and VM activity ( P < 0.05), and the correlation coefficient between the SD and AEMG was significantly greater in RF [0.736 (SD 0.095), P < 0.05] compared with VL and VM. Large changes were found in the high-frequency component. During high RF activity, the correlation coefficient between the SD and high-frequency component [0.832 (SD 0.087)] was significantly ( P < 0.05) greater compared with other frequency components. It is suggested that modulations in knee extension force fluctuations are caused by the unique muscle activity in RF during the alternate muscle activity, which augments the high-frequency component of the fluctuations.

scholarly journals High Frequency Resonance Damping Method for Voltage Source Converter Based on Voltage Feedforward Control

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1591
Author(s):  
Bo Pang ◽  
Feng Li ◽  
Hui Dai ◽  
Heng Nian
Keyword(s):  
High Frequency ◽  
Feedforward Control ◽  
Frequency Component ◽  
Voltage Source ◽  
High Frequency Component ◽  
Voltage Source Converter ◽  
Frequency Resonance ◽  
Significant High Frequency ◽  
Resonance Damping ◽  
High Frequency Resonance

High frequency resonance (HFR) is a subsistent problem which affects the operation of the voltage source converter (VSC) connected to the parallel compensated grid. The appearance of HFR introduces a significant high frequency component in the grid voltage, thereby the operation of VSC system will be seriously affected. For enhancing the operation capability of VSC system, an HFR damping method based on the voltage feedforward control is proposed in this paper, which can reshape the VSC system impedance effectively in a wideband range. Besides, different with the existing HFR damping methods, the proposed method introduces a correction factor instead of the series virtual impedance with fixed value, so that the effect of impedance reshaping is irrelevant to the parameters of controlled object. In addition, this paper analyzes the fundamental control performance of VSC system after equipping the proposed method, for verifying that the proposed method will not worsen the fundamental control. Experimental results are given to validate the effectiveness of the proposed damping method.

Enhancing Signal-to-Noise Ratios of High-Frequency Rayleigh Waves Extracted from Ambient Seismic Noises in Topographic Region

2020 ◽  
Vol 110 (2) ◽  
pp. 793-802
Author(s):  
Ping Ping ◽  
Risheng Chu ◽  
Yu Zhang ◽  
Jun Xie
Keyword(s):  
Free Surface ◽  
Correlation Functions ◽  
High Frequency ◽  
Rayleigh Waves ◽  
Vertical Component ◽  
Noise Correlation ◽  
Surface Boundary ◽  
Elastic Wedge ◽  
Signal To Noise ◽  
Surface Boundary Conditions

ABSTRACT High-frequency Rayleigh waves can be extracted from ambient seismic noises through noise correlation functions (NCFs), which provides a useful tool to image shallow structures in topographic regions, for example, landslides. Topography may affect signal-to-noise ratios (SNRs) of extracted Rayleigh waves. It is necessary to investigate the propagation features of Rayleigh waves passing a 3D topography. Based on the incident and scattered waves satisfying the free surface boundary conditions, we first derive the displacement responses of Rayleigh waves across a 3D elastic wedge. The results show that the particle motions of Rayleigh waves are an ellipse whose longer axis is always perpendicular to the topographic free surface. Therefore, the Qg component, perpendicular to the topographic free surface, is a better choice to extract high-frequency Rayleigh waves than the conventional vertical component. To verify the choice, we carry out numerical simulations to extract high-frequency NCFs for a typical 3D massif model. Finally, we apply this approach to extract high-frequency Rayleigh-wave NCFs on the Xishancun landslide in southwestern China. The NCFs obtained using the Qg component have more coherent waveforms and higher SNRs than those using the vertical component. We conclude that the Qg component has advantages in extracting high-frequency Rayleigh waves over the conventional vertical component.

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