• Proceedings of the Korea Concrete Institute Conference
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• 1989.10a
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• pp.53-58
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• 1989

Thicknesses of the base concrete blocks for large machines were estimated by analyzing the resonance modes of mechanical vibrations. The vibration was produced by the mechanical impact and detected by a wideband conical transcuder. There signals were analyzed by FET and thicknesses were obtained by the peaks of frequency spectrum. The estimated thickness upto 100cm are in good agreement with the real ones. For the layered concrete block, the estimated thickness is dependent on the acoustic reflective index at the boundary of the two layers.

• International Journal of Highway Engineering
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• v.18 no.6
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• pp.123-130
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• 2016

OBJECTIVES : The objective of this research is to determine the moisture resistance of the freeze-thaw process occurring in low-noise porous pavement using either hydrated-lime or anti-freezing agent. Various additives were applied to low-noise porous asphalt, which is actively paved in South Korea, to overcome its disadvantages. Moreover, the optimum contents of hydrated-lime and anti-freezing agent and behavior properties of low-noise porous asphalt layer are determined using dynamic moduli via the freeze-thaw test. METHODS : The low-noise porous asphalt mixtures were made using gyratory compacters to investigate its properties with either hydrated-lime or anti-freezing agent. To determine the dynamic moduli of each mixture, impact resonance test was conducted. The applied standard for the freeze-thaw test of asphalt mixture is ASTM D 6857. The freeze-thaw and impact resonance tests were performed twice at each stage. The behavior properties were defined using finite element method, which was performed using the dynamic modulus data obtained from the freeze-thaw test and resonance frequencies obtained from non-destructive impact test. RESULTS : The results show that the coherence and strength of the low-noise porous asphalt mixture decreased continuously with the increase in the temperature of the mixture. The dynamic modulus of the normal low-noise porous asphalt mixture dramatically decreased after one cycle of freezing and thawing stages, which is more than that of other mixtures containing additives. The damage rate was higher when the freeze-thaw test was repeated. CONCLUSIONS : From the root mean squared error (RMSE) and mean percentage error (MPE) analyses, the addition rates of 1.5% hydrated-lime and 0.5% anti-freezing agent resulted in the strongest mixture having the highest moisture resistance compared to other specimens with each additive in 1 cycle freeze-thaw test. Moreover, the freeze-thaw resistance significantly improved when a hydrated-lime content of 0.5% was applied for the two cycles of the freeze-thaw test. Hence, the optimum contents of both hydrated-lime and anti-freezing agent are 0.5%.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.487-497
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• 2005

Purpose: Resonance frequency analysis (RFA) , a non-invasive technique for the clinical measurement of implant stability, was investigated. Peri-implant bony defect may contribute to implant failure. This in vitro study evaluated the resonance frequencies according to various bony defects and determined whether the directional bone defect can affect the value of frequency analysis. Material and Method: Fifteen 3.75 mm in diameter and 10 mm in length, machined self-tapping implant future were used. Twelve types of bone defects that have different horizontal and vertical dimensions were simulated. Embedded implants were attached to the dental surveyor. Then, the transducer was connected with the implant fixture and the ISQ value was measured at four different directions. Two-way analysis of variance and post hoc $Sch\`{e}ffe'$ test were performed at the 95% significance level. Results: The control group showed the highest ISQ value and 5 thread-$360^{\circ}$ group had the lowest one. As the vertical exposure of implants in each angle was increased, the ISQ value was decreased. Although the horizontal exposure in each thread was increased, the ISQ value was not significantly decreased. Conclusion : Although the simulated defect type was different from each other, the ISQ value was similar among groups.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.925-931
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• 2012

The air-conditioner for railway vehicle should have vibration durability in order to operate normally in vehicle running situation. KS R 9144(vibration test methods for railway vehicle parts) is used to verify the vibration durability. The specifications of compressor, condenser and evaporator for air-conditioner in railway vehicle are standardized, but the shape and structure of pipe lines are not specified. Because the air-conditioner handler produces the pipe line arbitrarily, sometimes the pipe line is broken during the vibration durability test. In this research the cause identification and solution of pipe line breaking problem in during the vibration durability test were studied for air-conditioner of railway vehicle(diesel multiple unit). It was found that the natural frequency of pipe line is related to the pipe line breaking by experiment. A new pipe line shape was introduced by using FEA in order to avoid the resonance. The prototype new pipe line was applied to air-conditioner and the natural frequency was measured by experiment in order to verify the resonance avoidance. The vibration reduction of air-conditioner with new pipe line was reviewed by comparing to the air-conditioner with original one.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.1320-1325
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• 2006

When the train running on the high-speed track, there is a speed band which track distortion is unusually increased according to the condition of track and roadbed. This speed is called critical velocity and physical parameter values are increased greatly. These phenomenon happened as high-speed train were developed, studied regularly through TGV 100 running test in France. As research result until now, the main reason is soft roadbed's bearing capacity. Wave propagation and track support capacity is varied by the ground characteristics. This paper achieved theoretical examination about resonance band(speed and frequency) that occurred in roadbed on the base rock in point of geotechnical engineering. The examination of resonance divides with ground response analysis, critical band analysis by the shear wave velocity of roadbed and train critical speed through the ground stratum.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.3
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• pp.17-27
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• 2016

In the high-frequency characterizations of planar circuit components, measurement data may not be physical. It is mainly due to resonance effects concerned with discontinuities which are inevitable for a planar component characterization. In this paper, a novel accurate transmission line characterization method is presented that excludes the resonance effects based on measurement data reconfirmation. For the physically obvious data acquisition near the resonance frequencies of a transmission line, the additional lines with different line lengths are fabricated on the same substrate. The test transmission lines are characterized by using vector network analyzer (VNA) in 100 MHz to 26.5 GHz. It is shown that an accurate transmission line characterization can be achieved with the proposed measurement data reconfirmation technique.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.1-8
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• 2015

When the line and switchgear of the substation system are disconnected, ferro-resonance can occur. This happens even if the capacitive reactance and inductive reactance are not equal, which are not common resonance conditions. Resonance conditions vary depending on the busbar configuration environment. Although the damping resistance method applying the existing saturable reactor to cope with ferro-resonance has been successfully applied on site, there can be loss of normal function during long-term operation. The reason is because the rise in the operating frequency of saturable reactors means the saturation number is increased. Therefore, it can no longer function as saturable reactor since the resistor having inadequate capacity is burned out. To address this problem, in this paper, an EMTP-based simulation test was performed by designing and applying a dual reactor method, which adds an extended divergence reactor to the 1st side of the VT. The test result confirms that when the divergence reactor is inserted, the voltage and current values obtained at the 1st side and 2nd side of the VT as well as current values of divergence reactor part were stabilized from the transient phenomena and return to normal values. When compared with existing measures, although this method is similar in adding having a reactor added to a system regarding ferro-resonance, it has the advantage of being able to prevent ferro-resonance in advance since the reactor is added before the system is saturated. In addition, because it does not use damping resistance, it can extend the equipment life and stabilize its operation. Therefore, there are a lot of differences in terms of its operating characteristics and achivement of goal between the conventional method and new divergence reactor method.

• Journal of Biosystems Engineering
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• v.28 no.3
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• pp.253-260
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• 2003

In this study, the feasibility of magnetic resonance techniques for nondestructive internal quality evaluation of Korean red ginseng was examined. Relaxation time constants were measured using various grades of red ginsengs. Solid state magnetic resonance imaging technique was applied to image dried red ginsengs which have low moisture contents (about 13%). A 7 tesla magnetic resonance imaging system operating at a proton resonant frequency of 300 ㎒ was used for acquiring MR images of dried Korean red ginseng. The comparison test of cross cut digital images and magnetic resonance images of heaven grade, good grade with cavity inside, and good grade with white part inside red ginseng suggested the feasibility of the internal quality evaluation of Korean red ginsengs using MRI techniques. A good grade red ginseng included abnormal tissues such as cavities or white parts inside was observed by the signal intensity of MR image based on magnetic resonance properties of proton nucleus. Analysis on an one dimensional profile of acquired MR image of Korean red ginseng showed easy discrimination of normal and abnormal tissues. MR techniques suggested ways to detect internal defects of red ginsengs effectively.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.26 no.2
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• pp.113-118
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• 2020

Due to the rapid increase in cyber shopping mall of agricultural products, the parcel delivery service industry also increased, making it necessary to design an optimum packaging for agricultural products. And Due to the recent increase in strawberry consumption, there is also a need for a packaging system for parcel delivery service. In order to establish the criteria for optimum cushioning packaging design of strawberries, the bioyield strength of strawberries by storage time was measured through the ASABE test standards, and the peak acceleration in the resonance frequency and resonance frequency bands of strawberries was measured through the vibration test regulated in the ASTM test specifications. Tray cup pad and corrugated fiberboard box of delivery strawberries were designed using FEM theoretical analysis of contact stress and resonant frequency. In addition, an optimum packaging system was developed with a cushioning and vibration design considering the impact characteristics when distributing agricultural products. Through the performance evaluation and on-site evaluation of the optimum packaging system of strawberries for parcel delivery service, the random PSD test results of the delivery showed a 74% reduction in the acceleration level, and the actual distribution test of the delivery showed that the damage rate of strawberries was not more than 6.7%, indicating that it was possible to use the optimum packaging of strawberries for delivery.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.178.2-178.2
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• 2010

The wind turbine gearbox is important rotating part to transmit torque from turbine blade to generator. Generally, gear shaft which rotates causes vibration by influence of stiffness and mass with gear shaft. Root cause of this vibration source is well known to gear transmission error that is decided from gear tooth property. Transmission error excites a gear, and makes excitation force that is vibrated shaft. This vibration of shaft is transmitted to gearbox housing through gearbox bearing. If the resonance about which the natural frequency of the gearbox accords with shaft exciting frequency occurs, a wind turbine can lead to failure. The gearbox for wind turbine should be considered influence of vibration as well as the fatigue life and its performance by such reason. The cause to vibration should be closely examined to reduce influence of such vibration. In this paper, the cause of the vibration which occurs by a gearbox is closely examined and the method which can reduce the vibration which occurred is shown. It is compared with vibration test outcome of a 3MW gearbox for verification of the method shown by this paper.