• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.1
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• pp.33-41
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• 1998

The response characteristics of the PZT transducers during glass capillary breakage were studied at the epicenter of the glass plate. The PZT transducers had been made by using EC-65 PZT ceramics(supplied by Edo co.) with a constant area and a various thickness. The theoretical displacement and velocity at the epicenter of glass plate with an air boundary condition were calculated by assuming the point load of 1N force strength and a rise time of 280 ns with a ramped functional dependence, and the 1st pulses of the PZT transducer may be considered as the vertical velocity incident on the electrode of the PZT ceramic. The responses of the PZT transducer may be depended on the thickness mode of the PZT ceramic below 0.33 in the ratio of the thickness to the diameter of PZT ceramic, but the reponse of the PZT transducer may be depended on the other modes of PZT transducer in the addition of the thickness mode of the PZT ceramic above 0.33. The full time of half maximum at the 1st pulse was nearly 280 ns without a variation of applied breakage load and the resonant frequency of the PZT transducer, and then may be considered as the rise time of a AE source. The maximum amplitude of the 1st pulse depended on the incident vertical velocity and capacitance of the PZT transducer. Therefore, the full time of half maximum and maximum amplitude of the 1st pulse may be considered as the rise time and strength of acoustic emission source respectively.

• Korean Journal of Environment and Ecology
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• v.33 no.3
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• pp.266-279
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• 2019

We investigated the characteristics of fish communities and habitat status of endangered species Rhodeus pseudosericeus in Heuk Stream, a tributary of the Han River, from April to October 2018. During this period, we collected 47 species of 14 families from 10 survey stations using kick nets, cast nets, and long bag set nets. The dominant and subdominant species were Zacco platypus (37.6%) and Z. koreanus (13.8%), respectively. The next most abundant species were Squalidus gracilis majimae (11.1%), Pungtungia herzi (7.7%), Rhodeus pseudosericeus (5.0%), Microphysogobio yaluensis (4.3%), and Hemibarbus longirostris (3.0%). Among the fish collected, 19 species (40.4%) were Korean endemic species. Endangered species were R. pseudosericeus and Acheilognathus signifer while exotic species were Micropterus salmoides and Oncorhynchus mykiss, and land-locked species were Plecoglossus altivelis and Rhinogobius brunneus. The community analysis showed that the dominance and evenness indexes were mostly low and that the diversity and richness indexes were high. Moreover, the river health (index of biological integrity) was mostly excllent (1 site is good, 9 sites are very good). R. pseudosericeus inhabited widely from St. 3 to St. 9 in Heuk Stream, and its population size was large. Age groups for R. pseudosericeus estimated by the frequency distribution of total length in spawning season (April) indicated the 32~45 mm group as 1-year old, the 46~59 mm group as 2-years old, 60~69 mm group as 3-years old, and the 70~89 mm group as 4-years or older. Total length range of male and female was similar, and the sex ratio of female (426) to male (394) was 1 : 0.95. A. signifer, which had been released in Heuk Stream, inhabited from St. 4 to St. 5, but its population size was small. Lastly, this paper discusses a conservation plan for fish in Heuk Stream.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.882-889
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• 2003

This paper presents the method for structure borne noise analysis of a flexible body in multibody system. The proposed method is the superposition method using the flexible multibody dynamic analysis and the finite element one. This method is executed in 3 steps. In the 1st step, time dependent quantities such as dynamic loads, modal coordinates and gross body motion of the flexible body are calculated through a flexible multibody dynamic analysis. And frequency response functions of those time dependent quantities are computed through Fourier transforms. In the 2nd step, acoustic pressure coefficients are obtained through structure-acoustic coupling analyses by the finite element method. In the final step, frequency responses of acoustic pressure at the acoustic nodes are recovered through linear superposition of frequency response functions with acoustic pressure coefficients. The accuracy of the proposed method is verified in the numerical example of a simple car model.

• Journal of the Institute of Convergence Signal Processing
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• v.13 no.1
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• pp.26-31
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• 2012

The highest frequency band of wavelet decomposition band is divided into 4 equal subbands and by the minimum power of the subbands and by the monotonic transform, the level adapted threshold is obtained. The adapted threshold is applied to the soft threshold technique to denoise high and middle frequency band noise of image signals. And the results of PSNRs are compared with the results obtained by the VisuShrink technique and by the technique using the monotonic transform and the weight value. The results showed the validity of this technique.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1554-1560
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• 2017

Prepare a lose of 765kV transmission route in power system operation condition, there are some Special Protection Scheme(SPS)s in Korean power system. These SPS can make some preselected generators are tripped to avoid generator overspeed. Because of many of the new large power plants are installed to existing power generation sites due to the siting problem, the number of generator tripped by SPS should be increased. But that can be a cause of system frequency change under the Under Frequency Relay(UFR) 1st pickup level 59.0Hz. Therefore generation constraint should be considered until new transmission lines are installed. In this paper, we propose the ESS application for generation constraint mitigation by frequency damping control of ESS. To analysis an effect of ESS application, we use PSS/E dynamic simulation tool, CBEST model and controller model. The proposed ESS application is applied to the empirical Korean power system.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.45-54
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• 2011

A vehicle suspension system performs two functions, the ride quality and the stability, which conflict with each other. Among the various suspension systems, an active suspension system has an external energy source, from which energy is always supplied to the system for continuous control of vehicle motion. In the process of the linearization for the nonlinear active suspension system, the frequency dependent damping method is used for the exact modelling to the real model. The pressure control valve which is controlled by proportional solenoid is the most important component in the active suspension system. The pressure control valve has the dynamic characteristics with 1st order delay. Therefore, It's necessary to adopt the lead compensator to compensate the dynamics of the pressure control valve. The sampling time is also important factor for the control performances. The sampling time value is proposed to satisfy the system performances. After the modelling and simulation for the pressure control valve and vehicle dynamic, the performances of the vehicle ride quality and the stability are enhanced.

• Research in Community and Public Health Nursing
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• v.32 no.4
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• pp.467-476
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• 2021

Purpose: The purpose of this study is to understand the social perceptions of nurses in the context of the COVID-19 outbreak through analysis of media articles. Methods: Among the media articles reported from January 1st to September 30th, 2020, those containing the keywords '[corona or Wuhan pneumonia or covid] and [nurse or nursing]' are extracted. After the selection process, the text mining and topic modeling are performed on 454 media articles using textom version 4.5. Results: Frequency Top 30 keywords include 'Nurse', 'Corona', 'Isolation', 'Support', 'Shortage', 'Protective Clothing', and so on. Keywords that ranked high in Term Frequency-Inverse Document Frequency (TF-IDF) values are 'Daegu', 'President', 'Gwangju', 'manpower', and so on. As a result of the topic analysis, 10 topics are derived, such as 'Local infection', 'Dispatch of personnel', 'Message for thanks', and 'Delivery of one's heart'. Conclusion: Nurses are both the contributors and victims of COVID-19 prevention. The government and the nurses' community should make efforts to improve poor working conditions and manpower shortages.

• Neonatal Medicine
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• v.16 no.1
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• pp.89-93
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• 2009

Maternal diabetes is known to have teratogenic effects which increase the risk for congenital anomalies, such as caudal dysplasia, cardiac defects, hydronephrosis, and small left colon syndrome. Infants of diabetic mothers have a 10-fold higher frequency of anomalies in the central nervous system and a 5-fold higher frequency of congenital heart defects. However, jejunal atresia combined with multiple anomalies of the face, ears, and hands has rarely been reported. Herein we report a neonate born to a diabetic mother, who had hemifacial microsomia, displacement of the lacrimal ducts, polydactyly of the right hand, microtia of the right ear and proximal jejunal atresia presenting as bile regurgitation on the 1st day of life.

• Journal of Korean Academy of Nursing
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• v.41 no.1
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• pp.26-35
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• 2011

Purpose: This study was done to compare the effects of abdominal aroma massage and meridian massage on constipation and stress in college women with functional constipation. Methods: The participants were 38 college women, 18 were in the aroma group and 20 in the meridian group. The aroma massage was given using aroma oil which was a mixture of lemon, lavender, rosemary, and cyprus. The meridian massage was given at 9 accupoints which influence intestinal functions. The treatment was given 5 days a week for 4 weeks. A constipation severity score, weekly defecation frequency, and a stress response score were measured before and every week of 4 weeks of the experiment. Results: While there was no significant difference between two groups, there was a significant difference within the groups in the constipation severity (aroma group: 1st week, meridian group: except 4th week), defecation frequency (aroma group: 3rd week, meridian group: 2nd and 3rd week), and stress (aroma group: all weeks, meridian group: except 4th week) after different duration of experiment. Conclusion: Based on these results, both abdominal massages relieved constipation and stress. Resorting to either types of massage will contribute to the reduction of use of stool softeners, suppositories, or enemas.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.237-244
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• 2016

This paper, presents the characteristics of electromagnetic fields radiated from a pole-transformer. The cylindrical cavity is used to measure electromagnetic fields radiated from a pole-transformer when partial discharge occures inside the pole-transformer. The theoretical analysis is conducted by a finite difference time domain (FDTD) method. As a result, frequency characteristics of the radiated electromagnetic waves emitted from the inside the cavity to the outside through the 1st and 2nd bushings could be observed for the configuration of the cylindrical cavity with a radiation window. The frequency characteristics of electromagnetic field are also studied according to the enclosure structure of the cylindrical cavity. To verify the theoretical analysis, computed results are compared to experimental results.