• Title/Summary/Keyword: cut-off frequency

Search Result 406, Processing Time 0.024 seconds

Development of a High-Performance Bipolar EEG Amplifier for CSA System (CSA 시스템을 위한 양극 뇌파증폭기의 개발)

  • 유선국;김창현;김선호;김동준
    • Journal of Biomedical Engineering Research
    • /
    • v.20 no.2
    • /
    • pp.205-212
    • /
    • 1999
  • When we want to observe and record a patient's EEG in an operating room, the operation of electrosurgical unit(ESU) causes undesirable artifacts with high frequency and high voltage. These artifacts make the amplifiers of the conventional EEG system saturated and prevent the system from measuring the EEG signal. This paper describes a high-performance bipolar EEG amplifier for a CSA (compressed spectral array ) system with reduced ESU artifacts. The designed EEG amplifier uses a balanced filter to reduce the ESU artifacts, and isolates the power supply and the signal source of the preamplifier from the ground to cut off the current from the ESU to the amplifier ground. To cancel the common mode noise in high frequency, a high CMRR(common mode rejection ratio) diffferential amplifier is used. Since the developed bipolar EEG amplifier shows high gain, low noise, high CMRR, high input impedance, and low thermal drift, it is possible to observe and record more clean EEG signals in spite of ESU operation. Therefore the amplifier may be applicable to a high-fidelity CSA system.

  • PDF

The Development of a Simple Evaluation Questionnaire for Screening the Overweight-type Dietary Pattern in 30 to 49 Year Old Adults (한국 장년 성인의 과체중 예방을 위한 식생활 간이평가표 개발)

  • 박영숙;한재라;이정원;조한석;구재옥;김정희;윤진숙
    • Korean Journal of Community Nutrition
    • /
    • v.7 no.4
    • /
    • pp.495-505
    • /
    • 2002
  • A study was performed to develop as a screening tool the Simple Evaluation Questionnaire for Screening the Over-weight-type Dietary Pattern in 30 to 49 Year Old Adults. We used the data from the 30 to 49 year old subjects who participated in the three surveys - the health behavior survey, the dietary habit survey and the food intake survey - as the National Health and Nutrition Survey 1998. The 3,598 adults were classified into to two body fatness groups of normal (including underweight) and overweight (including obese) on the basis of their relative body weight (RBW) When comparing variables between the two groups, significant differences were found in gender, education, job, employment status, perceived health status, sadness / depression state, stress level, age, number of diseases, age when overweightedness started, maximum body weight, sleep length, drinking pattern (yes/no) , amount of alcoholic drinks, frequency of intoxication or drunkeness, amount of alcoholic drinks when drunk, intensity of exercise, frequency of exercise, exercise duration, skipped meals, small meals and drug supplements. In terms of food intake, there were significant differences in the daily food intake in terms of breakfast, dinner, daily kimchi and dairy products. In terms of mealtimes, we found differences in the amount of cooked rice at breakfast, kimchi at lunch, soup / kuk at dinner, fresh vegetables for snacks, fried foods for snacks between breakfast and lunch, and fruits /juices for snacks between lunch and dinner. After developing questions with indicators and analyzing the indicators by logistic regression analysis three times, we chose 10 questions for a simple evaluation of dietary patterns for the overweight-type category in order to give one point each. Among them we selected two questions to add one additional point and one question to add two additional points. The average scores of the overweight and normal groups, as shown by the developed questionnaire, were $5.97 \pm 2.36 \pm 7.36 \pm 2.21$, respectively. A score of seven points was selected as the cut-off point. We examined the sensitivity, specificity and positive predictive value of the questionnaire to the results of 67%, 59% and 62%, respectively.

Extended Slip-Weakening Model and Inference of Rupture Velocity (Slip-Weakening 모델의 확장과 단층 파열속도의 추정)

  • Choi, Hang;Yoon, Byung-Ick
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.24 no.5
    • /
    • pp.219-232
    • /
    • 2020
  • The slip-weakening model developed by Ohnaka and Yamashita is extended over the breakdown zone by equating the scaling relationships for the breakdown zone and the whole rupture area. For the extension, the study uses the relationship between rupture velocity and radiation efficiency, which was derived in the theory of linear elastic fracture mechanics, and the definition of fmax given in the specific barrier model proposed by Papageorgiou and Aki. The results clearly show that the extended scaling relationship is governed by the ratio of rupture velocity to S wave velocity, and the velocity ratio can be determined by the ratio of characteristic frequencies of a Fourier amplitude spectrum, which are corner frequency, fc, and source-controlled cut-off frequency, fmax, or vice versa. The derived relationship is tested by using the characteristic frequencies extracted from previous studies of more than 130 shallow crustal events (focal depth less than 25 km, MW 3.0~7.5) that occurred in Japan. Under the assumption of a dynamic similarity, the rupture velocity estimated from fmax/fc and the modified integral timescale give quite similar scale-dependence of the rupture area to that given by Kanamori and Anderson. Also, the results for large earthquakes show good agreement to the values from a kinematic inversion in previous studies. The test results also indicate the unavailability of the spectral self-similarity proposed by Aki because of the scale-dependent rupture velocity and the rupture velocity-dependent fmax/fc; however, the results do support the local similarity asserted by Ohnaka. It is also remarkable that the relationship between the rupture velocity and fmax/fc is quite similar to Kolmogorov's hypothesis on a similarity in the theory of isotropic turbulence.

Wireless Communication at 310 GHz using GaAs High-Electron-Mobility Transistors for Detection

  • Blin, Stephane;Tohme, Lucie;Coquillat, Dominique;Horiguchi, Shogo;Minamikata, Yusuke;Hisatake, Shintaro;Nouvel, Philippe;Cohen, Thomas;Penarier, Annick;Cano, Fabrice;Varani, Luca;Knap, Wojciech;Nagatsuma, Tadao
    • Journal of Communications and Networks
    • /
    • v.15 no.6
    • /
    • pp.559-568
    • /
    • 2013
  • We report on the first error-free terahertz (THz) wireless communication at 0.310 THz for data rates up to 8.2 Gbps using a 18-GHz-bandwidth GaAs/AlGaAs field-effect transistor as a detector. This result demonstrates that low-cost commercially-available plasma-wave transistors whose cut-off frequency is far below THz frequencies can be employed in THz communication. Wireless communication over 50 cm is presented at 1.4 Gbps using a uni-travelling-carrier photodiode as a source. Transistor integration is detailed, as it is essential to avoid any deleterious signals that would prevent successful communication. We observed an improvement of the bit error rate with increasing input THz power, followed by a degradation at high input power. Such a degradation appears at lower powers if the photodiode bias is smaller. Higher-data-rate communication is demonstrated using a frequency-multiplied source thanks to higher output power. Bit-error-rate measurements at data rates up to 10 Gbps are performed for different input THz powers. As expected, bit error rates degrade as data rate increases. However, degraded communication is observed at some specific data rates. This effect is probably due to deleterious cavity effects and/or impedance mismatches. Using such a system, realtime uncompressed high-definition video signal is successfully and robustly transmitted.

EBG Structure Using Bridge Line in the Signal Transmission Plane (신호 전달 평면의 브릿지 라인을 이용한 EBG 구조)

  • Kim, Byung-Ki;Ha, Jung-Rae;Lee, June-Sang;Bae, Hyeon-Ju;Kwon, Jong-Hwa;Nah, Wan-Soo
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.21 no.7
    • /
    • pp.786-795
    • /
    • 2010
  • In this paper, we propose a new EBG structure that the two unit cells are connected by the bridge line in signal transmission plane. The SSN of the power plane is reduced effectively by via holes and bridge lines connecting the unit cells. The superior signal transfer characteristic is shown between the signal lines in the signal transmission plane. The proposed EBG structure contains 1.2 GHz cut-off frequency and less than -30 dB suppression in the 8.3 GHz broad bandwidth. In addition, To improve the SI(Signal Integrity) in signal transmission plane keeping the same bandstop frequency range, the optimized location of the reference plane is proposed.

Condition Monitoring Technique for Heating Cables by Detecting Discharge Signal (방전신호 검출에 의한 히팅 케이블의 상태감시기술)

  • Kim, Dong-Eon;Kim, Nam-Hoon;Lim, Seung-Hyun;Kil, Gyung-Suk
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.34 no.2
    • /
    • pp.136-141
    • /
    • 2021
  • Heating cables, widely used in office buildings, factories, streets and railways, deteriorate in electrical insulation during operation. The insulation deterioration of heating cables leads to electric discharges that can cause electrical fires. With this background, this paper dealt with a condition monitoring technique for heating cables by the analysis of discharge signals to prevent electrical fires. Insulation deterioration was simulated using an arc generator specified in UL1699 under AC operation, and the characteristic and propagation of discharge signals were analyzed on a 100 meter-long heating cable. Discharge signals produced by insulation deterioration were detected as a voltage pulse because they are as small as a few mV and they are attenuated through propagation path. The frequency spectrum of discharge signals mainly existed in the range from 70 kHz to 110 kHz, and the maximum attenuation of the signal was 84.8% at 100 meters away from the discharge point. Based on the experimental results, a monitoring device, which is composed of a high pass filter with the cut-off frequency of 70 kHz, a comparator, a wave shaper and a microprocessor, was designed and fabricated. Also, an algorithm was designed to discriminate the discharge signal in the presence of noise, compared with the pulse repetition period and the number of pulse counts per 100ms. In the experiment, the result showed that the prototype monitoring device could detect and discriminate the discharge signals produced at every discharge point on a heating cable.

Design of acoustic meta-material silencer based on coiled up space (지그재그 구조 메타물질을 이용한 음향 소음기 설계)

  • Shim, Ki-Hwoon;Jang, Jun-Young;Kwon, Ho-Jin;Song, Kyungjun
    • The Journal of the Acoustical Society of Korea
    • /
    • v.40 no.1
    • /
    • pp.31-37
    • /
    • 2021
  • In this paper, we design an acoustic meta-material silencer that operates at low frequency to reduce noise in duct. A high refractive index meta-material silencer is demonstrated with a combination of zigzag structured thin waveguide and helmholtz resonator, which reduces the speed of sound. Finite Element Method (FEM) analysis via thermo-viscous acoustic mesh is performed in order to calculate thermo-viscous dissipation in sub-wavelength waveguide. Sound power reflection, transmission and absorption coefficients are obtained utilizing 4-Microphone Method. The results show that cut-off frequency and transmission loss can be controlled through adjusting intervals of the zigzag structures. A wide-band acoustic silencer is also suggested by connecting meta-materials in series or parallel.

Detection of a Surface-Breaking Crack Using the Surface Wave of a Laser Ultrasound (레이저 초음파의 표면파를 이용한 표면결함 측정)

  • Park, Seung-Kyu;Jung, Hyun-Kyu;Baik, Sung-Hoon;Lim, Chang-Hwan;Joo, Young-Sang;Kang, Young-June
    • Journal of the Korean Society for Nondestructive Testing
    • /
    • v.26 no.2
    • /
    • pp.84-89
    • /
    • 2006
  • A laser ultrasonic inspection system is a non-contact inspection device which generates and measures ultrasounds by using laser beams. A laser ultrasonic inspection system provides a high measurement resolution because the ultrasonic signal generated by a pulse laser beam has a wide-band spectrum and the ultrasonic signal is measured from a small focused spot of a measuring laser beam. In this paper, we have investigated the detection techniques of a surface-breaking crack by using the laser ultrasonic surface waves. A crack acts as a low pass filter whose cut-off frequency is lowered in proportion to the depth of a crack. And, the center frequency value of a spectrum is decreased in proportion to the depth of a crack. In this paper, we extracted the crack information by using the frequency attenuation from the normalized transfer function spectrum of a surface-breaking crack. Also, we effectively measured the crack depth by using the decreasing value of the center frequency from a crack passed ultrasonic signal. The proposed measuring techniques of crack depths provided more precise information than the amplitude measuring technique.

Evaluation of dietary behavior and nutritional status of elementary school students in Jeju using nutrition quotient (어린이 영양지수 (nutrition quotient)를 이용한 제주 지역 일부 초등학생의 식습관 및 영양 상태 평가)

  • Boo, Mi Na;Cho, Su Kyung;Park, Kyong
    • Journal of Nutrition and Health
    • /
    • v.48 no.4
    • /
    • pp.335-343
    • /
    • 2015
  • Purpose: The aim of this study was to evaluate the food behavior and nutritional status of elementary school students in the Jeju area using Nutrition Quotient (NQ). Methods: The subjects were 440 students (235 boys and 205 girls) in the fifth and sixth grade at four elementary schools located in Jeju. Demographic, lifestyle, and environmental information was collected using a self-reported questionnaire. The food behavior checklist for children's Nutrition Quotient (NQ), consisting of 19 items, and nutrition education related information were also obtained. Results: The mean score of the children's NQ was poor, reaching 60.3 points. The percentage distribution of NQ grade was 19.8% (lowest), 18.6% (low), 45.0% (medium), 10.7% (high), and 5.9% (highest) and the factor scores for balance, diversity, abstinence, regularity, and practice were 56.6, 68.4, 71.3, 57.4, and 54.8 points, respectively. Compared with the NQ cut-off points for defining malnutrition (balance; 57, diversity; 87, abstinence; 66, regularity; 69, and practice; 67 point), average score of abstinence factor was only above the cut-off point and scores of the other factors were below the cut-off point. Subjects with higher NQ scores tended to have higher levels of exercise activity (p < 0.001), frequency of family meals (p < 0.01), and father's educational levels (p < 0.01) compared to those with lower NQ score. NQ score showed positive association with nutrition education experience and practice (p < 0.001). Conclusion: NQ score of elementary school students residing in Jeju was lower than the national average. More opportunities should be provided for participation in nutrition education, which incorporates a range of program strategies, as well as communication and education activities.

Dielectric Properties of Sardine-Starch Paste at Low Moisture Contents 1, Effect of Moisture Content and Frequency (정어리 마쇄육의 저수분에서의 유전특성 1. 수분함량과 주파업에 따른 유전특성)

  • LEE Byeong-Ho;KIM Chang-Yang
    • Korean Journal of Fisheries and Aquatic Sciences
    • /
    • v.16 no.2
    • /
    • pp.125-132
    • /
    • 1983
  • Dielectric properties of sardine-starch paste with moisture content of 4 to $13\%$ were investigated as functions of moisture and frequency. And the effects of the levels of fat and starch of the mixtures upon dielectric permittivity, critical moisture, were also mentioned. In addition, a theoretical prediction of frequency dependence of dielectric constant which was computed by the lumped circuit of two layer condenser model was evaluated. For the preparation of sardine-starch paste, comminuted sardine meat was washed thoroughly several times in chilled water by soaking and decanting, and finally centrifuged. This procedure was extended longer to provide a low fat sample. The centrifuged meat was mixed with adequate amounts of starch and salt, and ground for 25 minutes in a stone mortar, moulded in the form of disk with 7cm diameter and 1.2cm thickness and then freeze dried. Dried meat disks were cut off for the size of 5.5cm diameter and 1.0cm thickness and their moisture contents were controlled in humidified desiccators with saturated solutions. Dielectric constants of sardine-starch paste tended to decrease frequency was increased showing a critical charge at the moisture called critical moisture content. In case of the sample with $20\%$ starch and $2\%$ salt an average complex permittivity($\epsilon^{\ast}$) at 7 to $8\%$ morsture as the critical moisture content was presented; $\epsilon^{\ast}$=3.37+j 0.39 at 0.1 MHz, $\epsilon^{\ast}$=2.54+j 0.19 at 15 MHz, and $\epsilon^{\ast}$=2.15+j 0.08 at 1.8 GHz, respectively. The theoretically obtained complex permittivity values from the two layer condoner model were in close agreement with these actual measurements under the same conditions, that appeared as $\epsilon^{\ast}$=2.53+i 0.09 at 0.1 MHz and $\epsilon^{\ast}$=2.28+j 0.06 at 15 MHz, respectively. The fast level of the mixture also revealed an influence on dielectric property that defatted neat with $1.0\%$ fat showed a higher hc and $\epsilon^{\ast}$ value than the meat with $4.8\%$ fat. Complex permittivity being related to the moisture level remained nearly unchanged or slightly changed at the moisture range of 4 to $8\%$ but was dispersed widely at higher moisture contents.

  • PDF