• Title/Summary/Keyword: Tooth Impact

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Detent Force Analysis in Permanent Magnet Linear Synchronous Motor Considering Longitudinal End Effects

  • Li, Liyi;Ma, Mingna;Chan, C.C.
    • Journal of international Conference on Electrical Machines and Systems
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    • v.2 no.1
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    • pp.9-15
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    • 2013
  • This paper presents a uniform analytical model by energy method and Fourier series expansion to analyze detent force in uneven magnetic field for permanent magnet linear synchronous motor (PMLSM). The model reveals that detent force in long-primary type is mainly influenced by non-ideal distribution of permanent magnet magnetic motive force, while nounified air-gap permeance makes a great impact on detent force of short-primary type. Hence, magnetic field similarity of motor design techniques referring rotary counterpart are adopted. For long-primary type novel method of splitting edge magnets is proposed to reduce end effects force, and optimal widths of edge tooth in short-primary type also verify the effectiveness of magnetic field similarity. The experimental results validate finite element analysis results.

Impact of Socioeconomic, Behavioral and Psychological Factors for Children's Self-Reported Oral Symptoms

  • Kwak, Seon-Hui;Shin, Bo-Mi
    • Journal of dental hygiene science
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    • v.17 no.3
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    • pp.257-266
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    • 2017
  • This study investigated factors affecting the subjective experience of oral symptoms among 2,285 elementary school students in the fourth and sixth grades using the Korean survey on the Health of Youth and Children in 2010. After conducting chi-square and Mann-Whitney U tests, we performed multiple logistic regression analysis to determine the factors affecting children's experience of oral symptoms. We found that the factors most frequently associated with the subjective experience of more oral symptoms were lower tooth brushing frequency, greater intake of foods that cause dental caries, higher stress levels, and lower levels of support from friends. In conclusion, determinants of children's oral health, such as children's oral health behaviors and psychological factors must be considered in a multifaceted approach to developing programs to promote oral health among children.

WATER INDUCED MECHANICAL EFFECT ON THE DENTAL HARD TISSUE BY THE SHORT PULSED LASER

  • Kwon,Yong-Hoon;Kim, You-Young
    • Journal of Photoscience
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    • v.5 no.1
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    • pp.33-37
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    • 1998
  • One macroscopic effect in the free-running Er:YAG laser is an accumulation of microscopic effects. Understanding of the exogenous water induced mechanical effect on the dental hard tissue by the Qswitched Er:YAG laser has an important impact on the further understanding of the free-running Er:YAG laser ablation on the dental hard tissue. The Q-switched Er:YAG laser (1-$\mu$s-long pulse width) was used in the recoil pressure measurement with an aid of water-jet system and a pressure transducer. The amplitude of the recoil pressure depends on the tooth surface conditions (dry and wet) and the volume of the water upon it. Wet surfaces yielded higher recoil pressure than that of dry, surface, and as the volume of the exogenous water drop increased, the amplitude of the recoil pressure increased also.

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Numerical Modeling to Evaluate Rear Crashworthiness for Round Recliner of Automotive Seats (자동차 시트용 라운드 리클라이너의 후방 충돌 성능 평가를 위한 수치해석 모델링)

  • Kim, Jung-Min;Lee, Kyoung-Taek;Kim, Heon-Young
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.1
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    • pp.64-71
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    • 2009
  • The development of more safe recliners is an important issue in the automotive industry. However, the development of new recliners is costly and take much time because it is typically based on experimental evaluation using prototypes. This study presents the evaluation of rear crashworthiness for round recliner using finite element method. That reduces the number of repeating test and gives an information about stiffness. To evaluate rear crashworthiness, the FMVSS 301 simulation and pendulum impact simulation were performed. The load path on two simulations was observed and compared each other in this paper. Also stress, strain and internal energy was compared. It is attempted the tooth strength simulation using a substructure option on PAM-CRASH.

Numerical Modeling of Short-Time Scale Nonlinear Water Waves Generated by Large Vertical Motions of Non-Wallsided Bodies (Non-Wallsided 물체의 연직운동에 의해 발생된 파의 비선형 해석을 위한 수치해석 모형의 연구)

  • Park, Jong-Hwan;;Troesch, Armin W.
    • Journal of Ocean Engineering and Technology
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    • v.7 no.1
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    • pp.33-55
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    • 1993
  • 선수충격파의 문제를 푸는데 있어서 Boundary Integral Method(BIM)의 여러가지 수치 해석방법이 검토되었으며, 특히 여러가지 Time stepping scheme, Green function, far-field 조건등에 따른 수치해석안정성과 정확성의 상관관계가 연구되었다. von Neumann 안정성해석과 matrix 안정성해석 등을 이용한 선형 안정성해석을 기초로하여, 수치해석방법의 안정성 여부를 체계적으로 조사할 수 있는 parameter(Free Surface Stability number)를 설정하고, 이 parameter의 변화에 따른 비선형 운동해석을 연구하였다. 그 결과 비선형성이 심하지 않은 기진파의 경우에서는 비선형 운동해석의 수치해석 안정성의 선형 수치해석 안정성과 큰 차이가 없음을 알 수 있게 된다.

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Impact on the Health Behaviors of Children by High Risk Alcohol Drink Behavior of Parent (부모의 고위험 음주 행동이 자녀의 건강행동에 미치는 영향)

  • Jang, Ju-Dong;Han, Song-Yi;Lee, Moo-Sik
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.8
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    • pp.3858-3865
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    • 2013
  • This study was performed to examine the impact on the health behaviors of the children by their parents' drinking behaviors. We used the data from a community health survey in 2009. The subjects were selected the household that had a child older than 19, and then among them, chose those 916 parents of highly risky drinking exposition among 16,383 control parents. The collected data was analyzed by frequency, chi-square test, and logistic regression analysis, using SPSS 18.0k program. Parent's high risk drinking behavior was independently associated with children's high risk drinking behavior after adjusting covariates(p<0.01). According to the result of the study, high risk drinking behavior of parents impact highly on the children's high risk alcohol drinking, nutritional behaviors, influenza vaccination, and tooth brushing, so it's necessary to consider a systematic family health education to the high risk drinkers.

Effects of auditory feedback and task difficulty on the cognitive load and virtual presence in a virtual reality dental simulation

  • Kim, Byunggee;Yang, Eunbyul;Choi, Namki;Kim, Seonmi;Ryu, Jeeheon
    • The Journal of the Korean dental association
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    • v.58 no.11
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    • pp.670-682
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    • 2020
  • This research examined the difference in cognitive load and the virtual presence depending on auditory feedback and task difficulty in haptic-based dental simulation. In the field of dental education, practice-centered training using handpiece has been crucial because a practitioner's psychomotor experience has a significant impact on the mastery of treatment skills. For the novice, it is necessary to reduce errors in dental treatment to enhancing skill acquisition in the haptic practice. In the training process, the force-feedback is crucial to elaborate subtle movement to guide what to do and how it should be hard or soft. However, It is not easy to add force-feedback to generate kinetic experience training. As an alternative method, we examined that auditory feedback can help learners' skill training. In this study, we analyzed how the presence/absence of auditory feedback at the different levels of task difficulty impacts learners' psychological demand and virtual presence in the virtual reality simulation. For this study, 29 dental college students participated in a dental simulation. The participants were grouped into two conditions that are with and without auditory feedback. Additionally, two consecutive tooth preparation tasks with different levels of difficulty were used in the simulation. The auditory feedback condition gives alarms to a learner when he treats a non-targeted tooth with a virtual handpiece. The user's cognitive load and virtual presence were measured to examine the effects of auditory feedback. The results revealed that the main effect was found in cognitive loads. Also, a significant interaction effect was shown in the virtual presence. We discussed the effective design methods for the virtual reality-based dental simulation through the result of this study.

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Ankylosed Primary Molar and Eruption Guidance of Succeeded Permanent Premolar : Case Reports (유착된 유구치와 후속 영구 소구치의 맹출 유도 : 증례보고)

  • Jang, Hayoung;Oh, Sohee
    • Journal of the korean academy of Pediatric Dentistry
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    • v.44 no.1
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    • pp.99-107
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    • 2017
  • In the management of ankylosed primary molars, early diagnosis, proper treatment, and thorough follow-ups are very important. Untreated infraocclusion due to ankylosis has a negative impact on normal occlusal development, and may cause problems. There are many treatment options on infraoccluded deciduous molars, such as periodic observation, conservative method, restoration, and space regaining via extraction of the teeth. In this case report, two 6-year-old girls were diagnosed with ankylosed maxillary second primary molar and displaced tooth germ of the second premolar. Early surgical removal of the ankylosed primary molar was considered as a treatment approach. The long-term follow-up shows normal eruption of a succeeded permanent premolar.

A Study on Application of Radix Asari Main Blended Prescription From Dongeubogam (동의보감(東醫寶鑑) 중(中) 세신(細辛)이 주약(主藥)으로 배오(配伍)된 방제(方劑)의 활용(活用)에 대한 고찰(考察))

  • Jeon Ho-Cheol;Rho Euy-Joon;Kim Hyung-Rul;Yun Young-Gab
    • Herbal Formula Science
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    • v.12 no.2
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    • pp.57-76
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    • 2004
  • This report describes the remedial fields, symptoms, pathology, dosage, prescriptional constitution of 69 studies related to the use of Radix Asari main blended prescriptions from Dongeubogam. The following conclusions were reached through investigations on the prescriptions that use Radix Asari as a key ingredient. Radix Asari blended prescriptions are utilized for 14 therapeutic purposes, for example, in symptoms of tooth, eye, paralysis, ear-nose, skin infection and carbuncle. In particular, 14.49% of the prescriptions appear in the chapter of tooth, and 10.14% of those appear in the chapter of eye. Prescriptions that utilize Radix Asari as the main ingredient are used in the treatment of dental disease, othalmology, nose and ear disease, throat disease, common cold, dermothology, paralysis, musculoskeletal disease, disease of the head, asthma, genital disease, the injury of the cuts and they are also used for treating 50 different types of diseases. Radix Asari is used in Six pathogenic factors such as wind, wind-cold, wind-heat, wind-dampness heat, wind-dampness, dampness, paralysis, cold-chill, cold, dryness, in visceral pathogenic factors such as stomach, kidney, liver-kidney, liver and in chi-blood pathogenic factors such as chi-blood deficiency, chi-blood stagnation and in extravasated blood pathogenic factors such as impact injury, an injury such as cuts, blood accumulation as well as weakness-cold and parasites. The actual amount of Radix Asari blended has ranged at a wide variety of amounts from 2.5pun(about 0.94gram) to 3don(about 11.25gram). 26.09% of the prescriptions used 1don(about 3.75gram). The function of Radix Asari is to calm down, to get the consciousness back, to bore through, to warm up the meridians and to run it smoothly, to discharge of phlegm from the combination of drugs and prescriptions.

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Analysis of Dynamic Characteristics of a Piston for a Linear Compressor Considering Changes in Groove Geometry (리니어 압축기에서 그루브 형상 변화에 따른피스톤의 동특성 해석)

  • Noh, Sangwan;Oh, Wonsik;Park, Kyeongbae;Rhim, Yoonchul
    • Tribology and Lubricants
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    • v.31 no.5
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    • pp.221-228
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    • 2015
  • It is possible to prevent a piston from contacting the cylinder by changing the shape of the piston or by applying micro-textures, such as micro-grooves or micro-holes, over the piston surface. Usually, the minimum radial clearance reaches its minimum value at the beginning of the suction stroke because the pressure around the piston is low and almost axisymmetric such that the net pressure force on the piston is not sufficiently high to support the piston from touching the cylinder. In this study, we apply a series of saw-tooth-shaped grooves on the piston surface, and numerically investigate the effects of groove depth, groove angle, and the number of grooves with radial clearance variations using a finite difference method. We conduct a dynamic analysis of the piston for various changes in groove geometries to obtain the minimum radial clearance variation for the entire compression cycle. The minimum radial clearance increases while friction loss decreases when we apply the series of saw-tooth-shaped grooves on the piston. In addition, we analyze the impact of the change in the groove shape variable due to changes in radial clearance. Leakage variations are relevant to radial clearance, but have almost no effect on the groove parameters.