• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.73-78
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• 2000

On this study, the fatigue crack propagation of super duplex stainless steel is investigated in conditions of various volume fraction of austenite phase by changing heat treatment temperature. And we analysed acoustic emission signals during the fatigue test by time-frequency analysis methods. As the temperature of heat treatment increased, volume fraction of austenite decreased and coarse grain was obtained. The specimen heat treated at $1200^{\circ}C$ had longer fatigue life and slower rate of crack growth. As a result of time-frequency analyze of acoustic emission signals during fatigue test, main frequency was $200{\sim}300kHz$ having no correlation with heat treatment and crack length, and 500kHz was obtained by dimple and separate of inclusion

• 한국분말재료학회지
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• 제26권5호
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• pp.421-431
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• 2019

In this study, the formation, microstructure, and wear properties of Colmonoy 88 (Ni-17W-15Cr-3B-4Si wt.%) + Stellite 1 (Co-32Cr-17W wt.%) coating layers fabricated by high-velocity oxygen fuel (HVOF) spraying are investigated. Colmonoy 88 and Stellite 1 powders were mixed at a ratio of 1:0 and 5:5 vol.%. HVOF sprayed self-fluxing composite coating layers were fabricated using the mixed powder feedstocks. The microstructures and wear properties of the composite coating layers are controlled via a high-frequency heat treatment. The two coating layers are composed of ${\gamma}-Ni$, $Ni_3B$, $W_2B$, and $Cr_{23}C_6$ phases. Co peaks are detected after the addition of Stellite 1 powder. Moreover, the WCrB2 hard phase is detected in all coating layers after the high-frequency heat treatment. Porosities were changed from 0.44% (Colmonoy 88) to 3.89% (Colmonoy 88 + ST#1) as the content of Stellite 1 powder increased. And porosity is denoted as 0.3% or less by inducing high-frequency heat treatment. The wear results confirm that the wear property significantly improves after the high-frequency heat treatment, because of the presence of well-controlled defects in the coating layers. The wear surfaces of the coated layers are observed and a wear mechanism for the Ni-based self-fluxing composite coating layers is proposed.

• 전력전자학회논문지
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• 제16권6호
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• pp.554-560
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• 2011

단일 주파수로 유도가열에 의한 표면 경화 열처리 공정에서 생기는 설비의 이중 투자 문제 및 열처리 공정시간을 단축할 수 있도록 하기 위해 하나의 공정에서 두가지 공정을 동시에 처리할 수 있도록 해주는 동시 이중 주파수(Simultaneous dual frequency: SDF) 구동기법 기술에 대해 설명한다. 본 논문에서는 듀얼 방식의 인버터를 제안하여 이중 주파수(Dual frequency) 구동기법을 구현하였으며 시뮬레이션과 실험을 통해 제안된 인버터의 이중 주파수제어 및 전력제어를 검증하였다.

• 대한물리의학회지
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• 제4권4호
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• pp.241-247
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• 2009

Purpose：The purpose of this study is to investigate the effect of transcutaneous electrical stimulation on autonomic nervous system using heart rate variability analysis. Methods：31 subjects were evaluated with HRV before and after a single high-frequency TENS for 15minutes treatment. The standard deviation of all the normal RR-interval(SDNN) and lower frequency/high frequency ratio(LF/HF ratio) were recorded with TAS-9. Results：After single TENS treatment, autonomic adaptation as analyzed by SDNN was increased from $42.47\pm12.96$ to $4.43\pm16.76$(p>0.05) and autonomic balance as analyzed by LF/HF ratio was increased from $1.4\pm0.45$ to $1.45\pm0.41$(p>0.05). Conclusion：In this study, SDNN and LF/HF ratio changed in health young students as a result of single TENS treatment. But there is no significant difference between pre-treatment and post-treatment of SDNN and LF/HF ratio.

• 대한한방부인과학회지
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• 제33권1호
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• pp.36-58
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• 2020

Objectives: We conducted a literature study on the treatment trends in China to find out the possibility of Oriental medicine treatment of atypical hyperplasia of breast (AHB). Methods: RCTs (randomized controlled trial) on AHB were collected from CNKI (China National Knowledge Infrastructure). The search words were "乳腺增生", "乳腺囊性增生", "乳癖", "中医", "中药" and "中西医结合". The search period was limited from July 2006 to May 2017. Finally, we selected 107 RCTs which were clinical studies to find out the effectiveness of Chinese herbal medicine in comparison with Western medicine. After reviewing, we investigated Chinese herbal medication guide, Chinese treatment method and prescriptions. And the correlation between the treatments and the medicinal herbs was investigated to be useful in the clinical practice. Results: 1. The administration of herbal medicine was 58.9 percent in 63 cases, followed by menstrual cycles, and 41.1 percent in 44 cases, regardless of menstrual cycles. 2. In the basic frequency analysis between the treatment and the medicinal herb, the frequency of dissipate binds (散結) was the highest. Next, there was a high frequency of therapies such as activating blood-activating (活血), relieve pain (止痛), soothe the liver (疏肝), regulate qi (理氣), resolve phlegm (化痰), soften hardness (軟堅), resolve depression (解鬱), move qi (行氣) of frequency was high. In herbal medicine, bupleuri radix (柴胡), cyperi rhizoma (香附子), angelicae gigantis radix (當歸), fritillaria thunbergii bulb (貝母), paeoniae radix alba (白芍藥), prunellae spica (夏枯草), corydalis rhizoma (玄胡索) showed high frequency. 3. We finded out the correlation between the frequent treatment methods and the medicinal herbs using Text Mining. Conclusions: These findings are thought to help implement Korean traditional medicine treatments for AHB.

• Journal of Acupuncture Research
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• 제25권5호
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• pp.27-42
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• 2008

Objectives : The purpose of this study was to observe the effects of acupuncture and electro-acupuncture at $LR_3$ on intestinal motility in rat. Methods : We made over-activated state of intestinal motility with carbachol and suppressed state of intestinal motility with loperamide in rat and carried out needle retention acupuncture and high frequency electro-acupuncture at $LR_3$ in rat devided into pre-treatment group and post-treatment group. The charcoal travel rate was measured to evaluate the intestinal motility. Results : 1. High frequency electro-acupuncture at $LR_3$ have significant influences on intestinal motility of rat in normal state. 2. Pre-treatment of needle retention acupuncture, high frequency electro-acupuncture significantly decreased intestinal motility in rat which over-activated with carbachol. 3. Post-treatment of high frequency electro-acupuncture significantly increased intestinal motility in rat which suppressed with loperamide. Conclusions : These results suggest that acupuncture and electro-acupuncture at $LR_3$ are effective on intestinal motility in rat.

• 한국기계가공학회지
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• 제9권6호
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• pp.7-15
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• 2010

Recently, with the high performance and efficiency of machine, there have been required the multi-functions in various machine parts, such as the heat resistance, the abrasion resistance and the stress resistance as well as the strength. Fatigue crack growth tests were carried out to investigate the fatigue characteristics of high carbon steel (SM53C) experienced by high-frequency induction treatment. The Cam nose part of the Automobile's Cam shaft is strongly bumped with rocker arm or valve-lift. Therefore abnormal wear such as unfair wear and early wear occur in the surface. This abnormal wear causes a defect that bad timing open and close actions of the engine valve happen in the combustion chamber so the fuel gas will be combustion imperfect. Therefore, the cam shaft demands high hardness and wear resistance. In this study, high frequency heat treatment has been accomplished while wear test for material SM53C.

• 한국산업융합학회 논문집
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• 제24권3호
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• pp.295-300
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• 2021

This study investigated the dominant frequency of the elastic waves from the tensile test. The specimen was rolled with five different rolling degrees (10, 22, 33, 42 and 50%), which was treated subzero. The specimen was rolled at room temperature, which was transformed from austenite to martensite (only α'-martensite). The dominant frequency increased with an increase in the rolling degree regardless of the subzero temperature, and decreased after 33% of the rolling degree. On the other hand, higher frequency band was obtained at lower temperature and long time. The dominant frequency increased when the amount of α'-martensite increased and decreased with the α'-martensite amount between 50-65%. The lower subzero treatment temperature increased the amount of α'-martensite, which resulted in the higher dominant frequency. The longer treatment time at the same subzero temperature led to an increase in the amount of α'-martensite, leading to high dominant frequency.

• 한국정밀공학회지
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• 제32권6호
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• pp.563-570
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• 2015

In this paper, Finite Element Analysis (FEA) for gear heat treatment using simultaneous dual frequency (SDF) induction heating is conducted. To do this, thermal-electromagnetic coupled FE model is built. A two dimensional FE model of gear and heater is introduced to reduce computation time. For more time-efficient analysis, harmonic analysis for electromagnetic model is adopted and transient analysis model, for heat transfer model. Through the coupled analysis, it can be found that the proposed FE model can solve for SDF induction heating of gear and heat treatment parameters can also be determined.

• 대한의생명과학회지
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• 제27권2호
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• pp.99-104
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• 2021

Treatment techniques that affect homeostasis by non-invasive regulation in peripheral organs will advance disease research. Here, we demonstrate a non-invasive method of conditioning within an organ using a low-frequency stimulator superposition of alternating microcurrent wave in stages. It is first applied to the inflammatory response in H3N2-infected sinusitis mice. To check the progress of the treatment, mice were sacrificed every week for 3 weeks, nasal tissue was removed, and the inflammatory response was investigated through H & E staining. The low-frequency stimulation treatment group was found to alleviate the proliferation of epithelial cells and invasion of inflammatory cells compared to the control group as the passage of treatment time. The reduction of inflammatory cytokines in the nasal lavage fluid was observed in H3N2-infected sinusitis mice treated with of low-frequency stimulation using superposition of alternating microcurrent wave compared to H3N2-infected sinusitis mice after 3 weeks. These data demonstrate that low-frequency stimulation device in the form of using alternating current wave superposition on within organs provides a new method to regulate specific physiological functions. Therefore, it is necessary to prove the inhibitory effect of low-frequency stimulation using alternating current wave superposition on inflammatory diseases by various methods through further studies and clinical studies.