• International journal of advanced smart convergence
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• 제5권4호
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• pp.66-70
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• 2016

When tooth grinding occurs, electrical stimulation is given at the same time, and tooth grinding stops on such stimulation. Electromyography signals are used as control signals of electrical stimulation to disturb tooth grinding. However because of the electrical stimulation, the M-waves are generated and mixed with spontaneous electromyogram. In this study, we designed an optimal filter to remove M-wave and conserve spontaneous electromyogram simultaneously. The inverse power method (IPM) showed that the optimal filter coefficient is the eigenvector corresponding to the minimum eigenvalue of the input covariance matrix. In order to evaluate the performance of the optimal filter, we compared using a conventional band pass filter and adaptive filter using least mean square algorithm. The experimental results show that the optimal filter can effectively remove the M-wave compared to the previously studied prediction error filter.

• Journal of Oral Medicine and Pain
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• 제40권3호
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• pp.102-109
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• 2015

Purpose: The purpose of this study was to assess the association between sleep disturbances and personality type. Methods: Five hundred twenty-four college students in Gyeonggi-do completed the Myers-Briggs Type Indicator (MBTI) and a questionnaire and collected data were analyzed by SAS 9.4 program. Results: Extroversion (E) type, sensation (S) type, and perceiving (P) type had significantly higher prevalence of insomnia than introversion (I) type (p<0.05), intuition (N) type (p<0.05), and judging (J) type (p<0.001), respectively. Tooth grinding, snoring and insomnia appeared to occur more frequently in feeling (F) type than in thinking (T) type. Tooth clenching, tooth grinding and snoring seemed to occur more frequently in S type than in N type. Insomnia occurred significantly the most frequently in sensation-feeling (SF) type (p<0.05). Tooth grinding and snoring seemed to occur the most frequently in SF type. A significantly increased percentage of sensation-perceiving (SP) type demonstrated insomnia (p<0.001). Tooth clenching, tooth grinding and snoring seemed to occur the most frequently in sensation-judging (SJ) type. Sensitive or nervous type of personality had significantly higher prevalence of insomnia than relaxed or general type of personality (p<0.01). A significantly increased percentage of subjects with bad general health status showed insomnia (p<0.0001). Tooth clenching and snoring seemed to occur the most frequently in subjects with bad general health status. A significantly decreased percentage of normal weight subjects demonstrated tooth grinding (p<0.05). Snoring occurred significantly the most frequently in overweight subjects (p<0.001). Tooth clenching showed significant correlation with stress (p<0.01) and personality (p<0.05). Snoring showed significant correlation with stress (p<0.05) and body weight (p<0.001). Insomnia showed significant correlation with stress (p<0.0001), personality (p<0.01), and general health status (p<0.0001). Conclusions: Sleep disturbances including tooth clenching and insomnia were associated with personality type and it is desirable to manage them considering personality type.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.65-66
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• 2010

To improve the gear noise quality, gear tooth grinding machine are widely used in automotive industry. While using the gear profile grinding machine to improve the gear tooth quality of the transmission, several defects such as chattering, tooth waves that cause the gear noise occasionally happened. But it is very difficult to solve that problem, because there is no one who knows the setting up the optimal grinding condition appropriately. The abnormal manufacturing conditions which make the gear noise make the engineer to spend a lot of time, effort, and money. Due to demands for solving the serious abnormal gear noise happened in the new FF 6th stage automatic transmission in the mass product stage, the vibration checking process in the worm wheel axis, work rotation and fixed axis of the grinding machine were adapted to find the root causes. As a result, gear profile wave are affected by the work rotation axis's unbalance which is caused by worm wheel feeding speed. And a primary and the secondary grinding feeding speed, cutting oil, work fixed forces are also proved as the important factors. After setting up the grinding condition reported in this paper, it was adapted successfully to the grinding machine to manufacture the new FF 6th speed automatic transmissions' output gear. The gear noise was dramatically disappeared and the process and results will offer good guides to the engineers who manufacture the gear with the grinding machine.

• 한국소음진동공학회논문집
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• 제20권7호
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• pp.665-671
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• 2010

To improve the gear noise quality, gear tooth grinding machine are widely used in automotive industry. While using the gear profile grinding machine to improve the gear tooth quality of the transmission, several defects such as chattering, tooth waves that cause the gear noise occasionally happened. But it is very difficult to solve that problem, because there is no one who knows the setting up the optimal grinding condition appropriately. The abnormal manufacturing conditions which make the gear noise make the engineer to spend a lot of time, effort, and money. Due to demands for solving the serious abnormal gear noise happened in the automatic transmission in the mass product stage, the vibration checking process in the worm wheel axis, work rotation and fixed axis of the grinding machine were adapted to find the root causes. As a result, gear profile wave are affected by the work rotation axis's unbalance which is caused by worm wheel feeding speed. And a primary and the secondary grinding feeding speed, cutting oil, work fixed forces are also proved as the important factors. After setting up the grinding condition reported in this paper, it was adapted successfully to the grinding machine to manufacture the new automatic transmissions' gear. The gear noise was dramatically disappeared and the process and the results will offer good guides to the engineers who manufacture the gear with the grinding machine.

• 한국기계가공학회지
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• 제11권5호
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• pp.54-59
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• 2012

This study dealt with effect of the grinding in SCM420H planetary gears. The hardness, tooth profile, lead and roughness of the gear surface can be improved by grinding process. Therein, the grinding techniques are widely used especially as one of the physical surface improvement methods. As the results, the gear grinding process reduced vibration and noise, and increased the life of the gear. And the gear grinding improved the surface of gear tooth in a short time and low cost, thus, it is a very important process in manufacturing industry. But nowadays, it is hard to find the detail information of gear grinding process. The test piece is a planetary gear which is used in the industrial machine. The manufacture process of the test piece contains hobbing, shaving, carburizing and grinding. This study investigated the effect of the grinding process to the physiognomy and the fatigue strength of test piece which was made by SCM420H.

• Journal of Oral Medicine and Pain
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• 제45권1호
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• pp.1-11
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• 2020

Purpose: The purpose of this study was to assess influences of psychological factors on sleep disturbances in young adults through the revised version of the Minnesota Multiphasic Personality Inventory (MMPI-2). Methods: Two hundred and ninety nine college students in Gyeonggi-do completed the MMPI-2 and a questionnaire related to sleep disturbances and collected data were analyzed by logistic regression. Results: The odds of tooth grinding increased significantly with the increase of T-score of hysteria (Hy) scale. The increase of T-score of hypomania (Ma) and social introversion (Si) scale significantly contributed to the risk of insomnia. The occurrence of insomnia increased significantly as T-score of somatic complaints (RC1) and psychoticism (PSYC) scale increased. The odds of tooth grinding increased significantly as T-score of anxiety (ANX) and family problems (FAM) scale increased. The occurrence of insomnia decreased significantly with the increase of T-score of type A behavior (TPA) scale. The increase of T-score of dominance (Do) scale significantly contributed to the risk of tooth clenching. The odds of tooth grinding decreased significantly as T-score of MacAndrew alcoholism-revised (MAC-R) scale increased, whereas it increased significantly as T-score of addiction potential scale (APS) increased. No scale of MMPI-2 significantly affected the occurrence of snoring. Conclusions: T-scores of Hy, ANX, FAM, Do, MAC-R, and APS scales on MMPI-2 affected the risk of bruxism. T-scores of Ma, Si, RC1, PSYC, and TPA scales on MMPI-2 influenced the occurrence of insomnia. The psychometric instrument such as MMPI-2 is helpful in understanding and managing bruxism and insomnia.

• 한국기계가공학회지
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• 제17권3호
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• pp.87-92
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• 2018

As gas turbines for power generation become increasingly more important for high capacity and high efficiency, the technological development and investment of companies are increasing globally. Gas turbine manufacturing technology is only owned by a few companies such as GE, Siemens, and MHI, and our country currently depends on imports of processing technology and component parts. The core part of the gas turbine is curvic coupling tooth processing technology that improves turbine efficiency by smoothly transmitting power to the turbine rotor. Curvic coupling tooth machining and evaluation research is restricted overseas, and it is not underway in Korea. Therefore, in this study, roughing and finishing process technology for curvic coupling tooth machining is developed and a quantitative evaluation method is proposed. For the development of machining technology, the analysis of critical parameters was performed through C & E analysis. In the roughing process, the conditions considering the minimum machining time and tool load ratio were determined. Finishing process conditions were determined based on the contact ratio between the tooth surfaces. The image-processing method is presented for evaluation of the contact ratio and a verification test was performed.

• 소성∙가공
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• 제29권3호
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• pp.144-150
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• 2020

In this paper, we propose the generation of a double enveloping worm thread profile with a non-developable ruled surface. Thread surface machining cuts all the way from the tip to the tooth root at one time, like full-face contact machining, rather than cutting several times like point machining. This cutting can reduce the cutting duration and achieve the smooth surface that does not require a grinding process for the threaded surface. The mathematical model of the cutting process was developed from theoretical equations, and the tooth surface was generated using two parameters and modeled in the CATIA using the generated Excel data. Additionally, the machining process of the worm was simulated in a numerical control simulation system. To verify the validity of the proposed method, the deviation between the modeling and the workpiece was measured using a 3D measuring machine.

• 대한소아치과학회지
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• 제30권1호
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• pp.110-115
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• 2003

치외치(Dens evaginatus)는 조직 형태 분화기에 법랑기의 내측 법랑 상피가 외부로 과증식 되거나 치수 간엽 조직 이 국소적으로 과증식되어 나타난다. 치외치는 하악제 2소구치에서 가장 빈발하며 유전적 성향을 가지고 있다고 알려져 있다. 치아에 발생한 결절은 법랑질, 상아질, 치수 등의 정상 치아구조를 가지고 있으며 그 형태학적 특성으로 인해 저작에 의한 파절 또는 마모가 발생하여 미세한 치수노출이 발생할 수 있다. 이러한 치수노출에 의해서 치수염증, 치근단 병변, 치근 형성 중지 등이 생길 수 있으므로 조기에 발견하여 예방 및 조기치료를 시행하는 것이 중요하다. 만약 이미 감염이 진행되어 치근단 병변이 야기된 경우 적절한 근관 치료가 행해져야 하며 미완성 치근을 가지고 있는 경우가 대부분이므로 치근단 형성술을 병행해야 한다. 이에 저자는 치외치에 의한 치근단 병변을 주소로 내원하여 치근단 형성술을 시행한 언니의 증례와, 함께 내원하여 사전에 발견하고 점진적 삭제술을 시행하여 양호한 결과를 얻은 동생의 증례를 보고하는 바이다.

• Restorative Dentistry and Endodontics
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• 제19권1호
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• pp.231-254
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• 1994

Fracture of cusp, on posterior teeth, especially those carious or restored, is major cause of tooth loss. Inappropriate treatments, such as unnecessarily wide cavity preparations, increase the potential of further trauma and possible fracture of the remaining tooth structures. Fracture potential may be directly related to the stresses exerted upon the tooth during masticatory function. The purpose of this study is to evaluate the fracture resistance of tooth, restored with composite resin inlay. In this study, MOD inlay cavity prepared on maxillary first premolar and restored with composite resin inlay. Three dimensional finite element models with eight nodes isoparametric solid element, developed by serial grinding-photographing technique. These models have various occlusal isthmus and depth of cavity, 1/2, 1/3 and 1/4 of isthmus width and 0.7, 0.85 and 1.0 of depth of cavity. The magnitude of load was 474 N and 172 N as presented to maximal biting force and normal chewing force. These loads applied onto ridges of buccal and lingual cusp. These models analyzed with three dimensional finite element method. The results of this study were as follows : 1. There is no difference of displacement between width of occlusal isthmus and depth of cavity. 2. The stress concentrated at bucco-mesial comer, bucco-disal comer, pulpal line angle and the interface area between internal slopes of cusp and resin inlay. 3. The vector of stress direct to buccal and lingual side from center of cavity, to tooth surface going on to enamel. The magnitude of vector increase from occlusal surface to cervix. 4. The crack of tooth start interface area, between internal slop of buccal cusp and resin inlay. It progresses through buccopulpal line angle to cervix at buccomesial and buccodistal comer. 5. The influence with depth of cavity to fracture of tooth was more than width of isthmus. 6. It would be favorable to make the isthmus width narrower than a third of the intercuspal distance and depth of cavity is below 1 : 0.7.