• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.36.2-36.2
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• 2011

In variable-speed variable-pitch wind turbines, the conventional approach for controlling power-production operation relies on a generator-torque controller and a rotor-collective blade-pitch controller. Both controllers use the generator speed measurement as the sole feedback input. In order to mitigate unwanted excitation of the control system, many filters are adopted. In this study, the characteristics of some filters for signal processing are investigated based on frequency response function. They include low-pass filters, band-pass filters, and notch filters. Especially, this study focuses on design parameters of their filters.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.850-856
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• 1998

The dynaamic fatigue behavior of alumina ceramics was observed at room temperature using four-point bending method. Dynamic fatigue fracture strength was observed as function of down speed and notch length. The crack growth exponent of the specimens was calculated from the fracture strength and lifetime in dynamic fatigue test. After loading the stresses in the range of 0% to 105% compared with the average in-ert strength the value of residual fracture strength was measured for unnotched and 0.5mm notched speci-mens at the 0.001 and 0.0005 mm/min down speed respectively. After the 95% stress of the average inert strength was applied repeatedly the value of rsidual fracture strength was measured for 0.5mm notched specimens at the 0.001 and 0.0005 mm/min down speed respectively. The material constant A was found to be almost the same and not to depend on the loading mode or the down speed for unnotched and notched specimen. The value of fracture strength with time calculated from the constants n and A was in good agreement with the measured value.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.956-958
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• 1996

The moving vehicle with disturbances has the 6 dof motion in the pitching, yawing and rolling directions of two independent axes. The control system in such a moving vehicle has to perform disturbance rejection well. The paper presents PID controller with disturbance rejection function, low sensitivity filter and notch filter for the bending frequency rejection. The performance of a designed system has been certified by the simulation and experiment results.

• International Journal of Concrete Structures and Materials
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• v.10 no.2
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• pp.163-175
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• 2016

This paper presents a revised procedure for computation of double-K fracture parameters of concrete split-tension cube specimen using weight function of the centrally cracked plate of finite strip with a finite width. This is an improvement over the previous work of the authors in which the determination of double-K fracture parameters of concrete for split-tension cube test using weight function of the centrally cracked plate of infinite strip with a finite width was presented. In a recent research, it was pointed out that there are great differences between a finite strip and an infinite strip regarding their weight function and the solution of infinite strip can be utilized in the split-tension specimens when the notch size is very small. In the present work, improved version of LEFM formulas for stress intensity factor, crack mouth opening displacement and crack opening displacement profile presented in the recent research work are incorporated. The results of the double-K fracture parameters obtained using revised procedure and the previous work of the authors is compared. The double-K fracture parameters of split-tension cube specimen are also compared with those obtained for standard three point bend test specimen. The input data required for determining double-K fracture parameters for both the specimen geometries for laboratory size specimens are obtained using well known version of the Fictitious Crack Model.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.1-6
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• 2007

This paper presents a new experimental Servo-Parameter tuning technique for a 6-axes articulated robot manipulator, especially considering robot's dynamics. First of all, investigation for proportional gain of velocity control loop by using a Dynamic Signal Analyzer(DSA) is performed. Using the FUNCTION characteristic of DSA based on the Bode plot, the Bode plot of open loop transfer function can be obtained. In turn, the integral gain of a servo controller can be found out by using the integration time constant extracted from the Bode plot of open loop transfer function. In the meanwhile, the positional gain of the servo controller can be obtained by using the Bode plot of the closed loop transfer function. Using the experimental gain tuning technique proposed in this paper, the testing linear motion of DR6-II robot has been shown to be more accurate rather than the motion with a conventional(empirical) gain tuning technique in Doosan Mecatec Co., Ltd., by improving the dynamic response of the robot as well as synchronizing each joint velocity according to the positional command of an end-effector.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1979.05a
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• pp.4.4-5
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• 1979

The degree of hearing impairment of chronic otitis media will indicate the nature and severity of middle ear pathology especially condition of ossicular chain, size of ear drum perforation and location of granulation tissue in the middle ear cavity. The subjects were 189 ears of tympanoplasty for chronic otitis media and divided into four groups as follows: Normal ossicular chain with only ear drum perforation (group I), normal ossicular chain with granulation tissue only around the ossicles regardless of any other region (group II), ossicular ankylosis or fixation of handle of malleus to promontory with or without granulation tissue around the ossicle (group III) and ossicular interruption by partial or complete destruction(groupf IV). The results were concluded as follows: 1) The average hearing threshold of chronic otitis media was 44.6 dB and hearing threshold was closely related to the condition of ossicular chain. Hearing threshold became greater in order of normal ossicular chain, ankylosis and interruption. 2) The average hearing threshold of ossicular interrupted group was 49.1 dB and it was greater in the cases of total destruction than that of partial destruction. 3) The hearing loss in the cases of normal ossicular chain with only tympanic membrane perforation was within 45 dB and this level was presumed to represent normal ossicular function. The degree of hearing loss was in proportion to the size of ear drum perforation and when over 45 dB, other middle ear pathology was suggested. 4) In the cases of small ear drum perforation with normal ossicular function, the hearing threshold was within 30 dB. 5) In the type of audiogram, flat type was 30.2% and ascending type 35.4%. Descending type was more frequent in the cases of normal ossicular mobility with granulation tissue around the ossicle and flat type was observed frequently in the cases of ossicular ankylosis. 6) Carhart's notch was seen in 14 cases (7.4%) and observed mainly in ossicular ankylosis. 7) There was no relation between hearing threshold and histopathological type of granulation tissue in chronic otitis media. However the degree of hearing impairment was related to the location of granulation tissue in the middle ear cavity. 8) Authors recognized the granulation tissue compensated the function of interrupted ossicular chain.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.4
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• pp.422-429
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• 2002

The identification of ultrasonic flaw signals is a truly difficult task in the angle beam testing of welded joints due to non-relevant signals from the geometric reflectors such as weld roots and counter bores. This paper describes a new approach called "technique for identification of flaw signal using deconvolution(TIFD)" in order to identify the flaw signals in such a problematic situation. The concept of similarity function based on the deconvolution is introduced in the proposed approach. The "reference" signals from both flaws and geometric reflectors and test signals are acquired and normalized. The similarity functions are obtained by deconvolution of test signals with reference signals. The flaw signals could be identified by the patterns of similarity function. The initiative results show great potential of TIFD to distinguish notch comer signals from the geometric reflections.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.E2
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• pp.66-73
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• 2007

The introduction of tracer gas techniques to ventilation studies in indoor environments provides valuable information that used to be unattainable from conventional testing environments. Data acquisition systems (DASs) containing analogue-to-digital (A/D) converters are usually used to function the key role that records signals to storage in digital format. In the testing process, there exist a number of components in the measuring equipment which may produce system-based inference to the monitored results. These unwanted fluctuations may cause significant error in data analysis, especially when non-linear algorithms are involved. In this study, a pre-processor is developed and applied to separate the unwanted fluctuations (noise or interference) in raw measurements and to reduce the uncertainty in the measurement. Moving average, notch filter, FIR (Finite Impulse Response) filters, and IIR (Infinite Impulse Response) filters are designed and applied to collect the desired information from the raw measurements. Tracer gas concentrations are monitored during leakage and ventilation tests in the model test room. The signal analysis functions are introduced to carry out the digital signal processing (DSP) work. Overall the FIR filters process the $CO_2$ measurement properly for ventilation rate and mean age of air calculations. It is found that, the Kaiser filter was the most applicable digital filter for pre-processing the tracer gas measurements. Although the IIR filters help to reduce the random noise in the data, they cause considerable changes to the filtered data, which is not desirable.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.867-880
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• 2015

Mechanical fastening is still one of the main methods used for joining components. Different techniques have been applied to reduce the effect of stress concentration of notches like fastener holes. In this work we evaluate the feasibility of combining laser shock peening (LSP) and cold expansion to improve fatigue crack initiation and propagation of open hole specimens made of 6061-T6 aluminum alloy. LSP is a new and competitive technique for strengthening metals, and like cold expansion, induces a compressive residual stress field that improves fatigue, wear and corrosion resistance. For LSP treatment, a Q-switched Nd:YAG laser with infrared radiation was used. Residual stress distribution as a function of depth was determined by the contour method. Compact tension specimens with a hole at the notch tip were subjected to LSP process and cold expansion and then tested under cyclic loading with R=0.1 generating fatigue cracks on the hole surface. Fatigue crack initiation and growth is analyzed and associated with the residual stress distribution generated by both treatments. It is observed that both methods are complementary; cold expansion increases fatigue crack initiation life, while LSP reduces fatigue crack growth rate.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.4
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• pp.499-504
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• 2017

A UHF CMOS variable gain low-noise amplifier (LNA) is designed for mobile digital TV tuners. The proposed LNA adopts a feedback topology to cover a wide frequency range from 474 to 868 MHz, and it supports the notch filter function for the interoperability with the GSM terminal. In order to handle harmonic distortion by strong interferers, the gain of the proposed LNA is step-controlled while keeping almost the same input impedance. The proposed LNA is implemented in a $0.11{\mu}m$ CMOS process and consumes 6 mA at a 1.5 V supply voltage. In the measurement, it shows the power gain of greater than 16 dB, NF of less than 1.7 dB, and IIP3 of greater than -1.7 dBm for the UHF band.