• Title/Summary/Keyword: frequency problem

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A 10b 200MS/s 75.6mW $0.76mm^2$ 65nm CMOS Pipeline ADC for HDTV Applications (HDTV 응용을 위한 10비트 200MS/s 75.6mW $0.76mm^2$ 65nm CMOS 파이프라인 A/D 변환기)

  • Park, Beom-Soo;Kim, Young-Ju;Park, Seung-Jae;Lee, Seung-Hoon
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.46 no.3
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    • pp.60-68
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    • 2009
  • This work proposes a 10b 200MS/s 65nm CMOS ADC for high-definition video systems such as HDTV requiring high resolution and fast operating speed simultaneously. The proposed ADC employs a four-step pipeline architecture to minimize power consumption and chip area. The input SHA based on four capacitors reduces the output signal range from $1.4V_{p-p}$ to $1.0V_{p-p}$ considering high input signal levels at a low supply voltage of 1.2V. The proposed three-stage amplifiers in the input SHA and MDAC1 overcome the low output resistance problem as commonly observed in a 65nm CMOS process. The proposed multipath frequency-compensation technique enables the conventional RNMC based three-stage amplifiers to achieve a stable operation at a high sampling rate of 200MS/s. The conventional switched-bias power-reduction technique in the sub-ranging flash ADCs further reduces power consumption while the reference generator integrated on chip with optional off-chip reference voltages allows versatile system a locations. The prototype ADC in a 65nm CMOS technology demonstrates a measured DNL and INL within 0.19LSB and 0.61LSB, respectively. The ADC shows a maximum SNDR of 54.BdB and 52.4dB and a maximum SFDR of 72.9dB and 64.8dB at 150MS/S and 200MS/s, respectively. The proposed ADC occupies an active die area of $0.76mm^2$ and consumes 75.6mW at a 1.2V supply voltage.

A Study on awareness of environmental management Knowledge and enviromental management behavior of Housewives (주부의 환경관리지식 인지도와 환경관리행동에 관한 연구)

  • 노남숙
    • Hwankyungkyoyuk
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    • v.7 no.1
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    • pp.106-122
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    • 1994
  • The purpose of this study to investigate the awareness of environmental management knowledge and behavior and the effect of independent variables (The environmental management behavior of housewives are composed of five activities-clothing, eating, housing, buying, family management. The independent variables are composed of objective variable and subjective variable). The Research Questions are as follows; 1. Are there significant differences in the housewife's awareness of the environmental management knowledge according to the objective variable and the subjective variable? 2. How much are the effects of related variables on the awareness of environmental management knowledge? 3. Are there significant differences in the housewife's environmental management behavior according to objective variable and subjective variable and awareness of environmental management knowledge? 4. How much are effects of related variables on the housewife's environmental management behavior? For these purpose, a theoretical framework was developed by literature review and applied to empirical test. The data was collected through the questionnaire those respondents were 477 housewives in seoul. It was analyzed by various statistical methods such as Frequency. Percentile, GLM, F-test, T-test, Duncan's Multiple Range Test, Pearson's Correlations Analysis Simple Regression Analysis, and Multiple Regression Analysis. The results of this research are as follows; 1. The awareness of environmental management knowledge had significant differences according to the variables such as housewife's age, husband's job, family number, education experience of environment, frequencies of contracting mass media, the perceived adequacy of resources, social-altruistic orientation. 2. Among all of these variables affecting the awareness of environmental management knowledge, the perceived adequacy of resources had the highest effects and the next were family number, social-altruistic, type of residence in order. 3. Total Environmental management behavior of housewives had significant differences according to the variables such of environment, frequencies of contracting mass media, the satisfaction of household labor, the perceived adequacy of resources, biospheric orientation, social-altruistic orientation, egoism orientation, the awareness of environmental management knowledge. The clothing, eating, housing, family management behavior had the high level, the buying management behavior had the average level. The clothing, eating, housing, buying, family management behavior had significant differences according to the variables such as the satisfaction of household labor, the perceived adequacy of resources, biospheric orientation, social-altruistic orientation, egoism orientation, the awareness of environmental management knowledge. In particular, the clothing, eating, housing, buying management behavior had significant differences according to the variables such as education experience of environment. And the housing, buying management behavior had significant differences according to the variables such as frequencies of contracting mass media. 4. Among all of theses variables affecting environmental management behavior, the most influence variables was awareness of environmental management knowledge and the next were influence of housewife's job, biospheric orientation, the satisfaction of household labor, education experience of environment, frequencies of contraction mass media, egoism orientation in order. Among all of theses variables effecting the clothing, eating, housing, buying management behavior the variables affecting the family management behavior, the most influences variables was housewife's job. In the result of analysing the housewife's environmental management behavior and awareness of environmental management knowledge, influences of education experience of environment had the highest effect and frequencies of contracting mass media may more influencial than other variables. And Concrete and systematic knowledge and technique of environmental education is requisite. The result of this study could be attributed to develop the efficient environmental information. More emphasis should be given to environmental education and a long range environmental policy. in particular, environmental education be effectively related to environmental behavior, life-education and systematic support must be provided. In addition, further study of environmental problem is needed for and application of various theoretical approaches and research method.

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A Study on the Health Care Satisfaction and Attitude of Elementary School Students - by the presence or absence of nurse teacher - (초등학생의 보건관리 만족도와 태도에 관한 연구 - 양호교사 유무를 중심으로 -)

  • Park, Dong-Kwon;Park, Young-Soo
    • The Journal of Korean Society for School & Community Health Education
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    • v.1 no.2
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    • pp.49-71
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    • 2000
  • The purpose of this study was to serve as a basis for school health care of better quality, by making a comparative analysis of the health care satisfaction and attitude of elementary school students in consideration of their general characteristics and the presence or absence of nurse teacher. The subjects in this study were 919 selected six graders in 16 elementary schools in the city of Tongduchun, Koyang and Euijungbu, Yangju-kun and Yeunchun-kun. A survey was conducted with questionnaire designed for measurement of health care satisfaction and attitude. As a result of analyzing the data collected from June 1 through 15, 2000, the conclusions were as follows. 1) As for the general characteristics of the students investigated, the subjects included 513 boys(55.8%) and 406 girls(44.2%). The schools where 390(42.4%) students attended were located in municipal area, and the schools where 529(57.6%) students attended were located in kun area. 608(66.2%) students had a nurse teacher at their schools, while 311(33.8%) students had no nurse teacher. 498(54.2%) had an experience to use the health room this year, but 421(45.8%) had no such an experience. Their mean school life satisfaction was scored $3.42{\pm}.71$, above the average. And their health condition was rated $3.81{\pm}.87$, which implied they tended to be in good health. 2) The mean satisfaction at the health room operation was scored $3.33{\pm}.71$, above the medium level. What they were most satisfied with($4.02{\pm}1.08$) was, among the health room facilities, that there were beds. But they expressed the least satisfaction($2.83{\pm}1.17$) at the location of health room. The presence or absence of nurse teacher made a significant difference to their satisfactionat health room operation, because the students in schools with nurse teacher showed greater satisfaction($3.42{\pm}.72$) than the others in schools with no nurse teacher did($3.15{\pm}.66$). 3) Concerning their attitude to use the health room in case of disease or accident occurrence, a lot of students in schools with a nurse teacher, who had ever suffered from indigestion, headache or traumatic injury, used the health room. In schools with no nurse teacher, there was a tendency to talk to their class teachers(p<.001). The recognition of the necessity for health counseling was generally on a medium level. The counselor whom they wanted to discuss health problem with was family or friend in the largest cases. Few students discussed with class teachers in case there was a nurse teacher in school. Instead, some of them discussed with friend, family or nurse teacher, and there was a significant difference between them(p<.001). 4) The mean satisfaction at health, sanitation and environmental management was rated $3.20{\pm}.90$, above the average. The classroom lighting gave them the best satisfaction with $3.67{\pm}1.07$, but the satisfaction at toilet cleanness and disinfection was not good with $2.83{\pm}1.19$. By the presence or absence of nurse teacher, those who had a nurse teacher expressed better satisfaction at water supply facilities including hot water than the others who had no nurse teacher did(p<.001). But no significant difference was observed in the other items. 5) The health education satisfaction was rated $3.19{\pm}.99$, which was on a medium level. By item, the mean satisfaction level was $3.36{\pm}1.19$ at nurse teacher's explanation about treatment, $3.13{\pm}1.15$ at the frequency of health education, and $3.08{\pm}1.16$ at the explanation on the cause of disease. By the presence or absence of nurse teacher, the students with nurse teacher showed significantly better satisfaction at every factor0(p<.001). 6) Regarding health education attitude, their recognition of the need for school health education was scored $3.89{\pm}.96$. Those who had a nurse teacher felt it more necessary($3.96{\pm}.92$), yet the others who had no nurse teacher felt its necessity a little less($3.74{\pm}1.01$). The most preferred thing for them to learn in health education was first aid, followed by sex education, obesity prevention, safety accident prevention in school and outdoors, smoking-related health, good use of leisure time, and environmental pollution cause in the order named. According to the presence or absence of nurse teacher, there was a significant difference in sex education(p<.01), but no significant disparities were found in the other factors. The most preferred person who would offer health education was a lecturer from the outside(45.8%) and nurse teacher(45.4%). Their preference for class teacher as a person in charge of health education was just 8.8%. But the presence or absence of nurse teacher didn't produce any differences to their preference for a person in charge of health education.

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A Study to Determine the Effectsiveness of Severance Hospice Home Care Program (호스피스케어에 대한 평가 연구 - 세브란스호스피스 중심으로)

  • Kingsley, Marian R.N.;Cho, Won-Jung;Kim, Cho-Ja;Lee, Won-Hee;Yoo, Ji-Soo
    • The Korean Nurse
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    • v.29 no.4
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    • pp.51-72
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    • 1990
  • The purpose of this study was to determine whether Severance Hospice Home Care Pro gram was able to meet its objectives. This was done in order to show in detail the effects of hospice home care on the quality of life of terminally ill patients and to provide rationale for setting up more hospice home care programs in korea. The results of the study were as follows: The subjects of the study were 100 terminally ill patients who hnd died 'while in the hospice program and 64 family members who were registered with Severance Hospice Home Care Program between march 1988 and Feb. 1990. The nursing needs of these terminally ill patients were assessed by the nursing records of these patients. The need for pain control(82%) was the highest nursing need so far as the physical aspects were concerned. This was followed by poor appetite(37%), 8 dyspnea(34%), nausea and vomiting(30%) in that order of frequency. In reqard to spiritual needs, the need for religious' support was also high at 72%. Their main psychological symptoms were anxiety and fear(34% ). Burn-out was a major problem for 44% of the family members. The psychological process experiencel by the terminal ill patients was compared to the dying process, described by Kiibler Ross. In comparison of the five stages outlined by kubler Ross with the dying process of the subjects it was found that the subjects not only experienced the five stages but also experienced denial and doubt-fulness or denial with acceptance or acceptance with the expectation of a miracle. But rather than acceptance of the dying process, giving up was a frequent end point of the psychological process, of the subjects. However, when the combination of states was observed, most of the patients reached the state of acceptance in the dying process. It was difficult to identify a definite pattern of change in the psychological process of the subjects. Also it was difficult to identify the factors that influenced the psychological process. The symptoms of the terminally j]] subjects just before dying, that is, 3-4 days before dying included apparent signs of dying. These were a reduction of intake(77%), reduction of the amount of urination(63%), increase in sleeping time (64%) and acceptance of dying by patients and their families who had been unaccepting be before that time(66%). The primary care givers(family member's) degree of satisfaction with the care given to the patient by the hospice was 88.7%. The results of this study show that Severance Hospice Home Care Program had a positie effeet on the quality of life of the terminally ill patients and their family members as they faced the death of the patient. It can be seen from this study that there is an urgent need to extend hospice programs - in order to provide quality of care for terminally ill patient and their families. Based upon the reesults of this study several suggestions are presente as follows: 1) A follow up study should be carried out to identify the dying process as it is unique to Korea. 2) A comparison should be made of other hospice care programs. 3) A comparison study should- be made with subjects who do not receive any hospice care as compared to those who do by use of an experimental and control group methodology. 4) There is a need to determine a scientific method to adequeto measure the interventions carried out to meet the hospice patients nursing care needs. 5) A study should be made using quality research methodology to evaluate effects of hospiec care from the patients, their family members and the nurrse's perspective.

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Evaluation of Indoor Air Quality in a Department of Radiation Oncology Located Underground (지하에 위치한 방사선종양학과에서의 실내공기 질 평가)

  • Kim, Won-Taek;Shin, Yong-Chul;Kang, Dong-Mug;Ki, Yong-Kan;Kim, Dong-Won;Kwon, Byung-Hyun
    • Radiation Oncology Journal
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    • v.23 no.4
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    • pp.243-252
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    • 2005
  • Purpose: Indoor air quality (IAQ) in the radiation treatment center which is generally located underground is important to the health of hospital workers and patients treated over a long period of time. this study was conducted to measure and analyze the factors related to IAQ and subjective symptoms of sick building syndrome, and to establish the causes influencing IAQ and find a solution to the problems. Methods and Materials : Self administrated questionnaire was conducted to check the workers' symptoms and understanding of the work environment. Based on a preliminary investigation, the factors related to IAQ such as temperature, humidity, fine particulate. carbon dioxide, carbon monoxide, formaldehyde, total volatile organic compounds (TVOC), and radon gas were selected and measured for a certain period of time in specific sites where hospital workers stay long in a day. And we also evaluated the surrounding environment and the efficiency of the ventilating system simultaneously, and measured the same factors at the first floor (outdoor) to compare with outdoor all quality, All collected data were assessed by the recommended standard for IAQ of the domestic and international environmental organizations. Results: Hospital workers were discontented with foul odors, humidity and particulate. They complained symptoms related to musculo-skeletal system, neurologic system, and mucosal-irritatation. Most of the factors were not greater than the recommended standard, but the level of TVOC was third or fourth times as much as the measuring level of some offices in the United States. The frequency and the amount of the ventilating system were adequate, however, the problem arising in the position of outdoor-air inlets and indoor-air outlets involved a risk of the indraft of contaminated air. A careful attention was a requirement in handling and keeping chemical substances including a developing solution which has a risk of TVOC emissions, and repositioning the ventilating system was needed to solve the contaminated-air circulation immediately Conclusion We verified that some IAQ-related factors and inadequate ventilating system could cause subjective symptoms in hospital workers. The evaluation of IAQ was surely needed to improve the underground working environments for hospital workers and patients. On the basis of these data, from now on, we should actively engage in designs of the department of radiation oncology or improvement in environments of the existing facilities.

Obstetric and Neonatal Outcomes of the Teenage Pregnancy (청소년 임신에 따른 임산부와 신생아의 주산기 문제점)

  • Shin, Jeong-Hee;Bauer, Siegfried;Yoon, Young-Sun;Jeong, Hyun-Chul;Rhie, Young-Jun;Lee, Jang-Hoon;Woo, Chan-Wook;Choi, Byung-Min;Kim, Hai-Joong;Park, Sang-Hee;Song, Ji-Won
    • Neonatal Medicine
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    • v.17 no.1
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    • pp.94-101
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    • 2010
  • Purpose:In recent years, Korea has showed a steady increase in the frequency of teenage birth, while the overall birth rate has declined. As the teenage birth is known as a high risk pregnancy itself, we examined perinatal complications of teenage mothers and whose neonates in aspects of medical problem, and social status and support. Methods:We examined the perinatal characteristics of teenage mothers and whose babies, who were hospitalized at Korea University Ansan Hospital from January 2004 to July 2009 using medical records retrospectively. Twenty-seven teenage mothers and their 28 babies were enrolled in this study. Results:Teenage mothers were all unmarried and showed high rates of preterm labor, maternal anemia, and unexpected delivery. Among them, 11 (40.7%) were from families that were separated. Eleven mothers (40.7%) did not have any antenatal care. There were high rates of prematurity and low birth weight (60.7% and 64.3%, respectively). The complication included: respiratory distress syndrome, patent ductus arteriosus and necrotizing enterocolitis. Fourteen babies (51.9%) were not going to be brought up by their biological parents. Conclusion:Teenage pregnancy had high rates of preterm labor and associated complications, often caused by the lack of proper antenatal care. Babies from unmarried mothers were likely to be adopted and this could be a social burden. Therefore, to reduce unplanned teenage pregnancy and births, sex education and social supports should be provided to all teenagers.

A study on optical coherence tomography system using optical fiber (광섬유를 이용한 광영상 단층촬영기에 관한연구)

  • 양승국;박양하;장원석;오상기;김현덕;김기문
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2004.04a
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    • pp.5-9
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    • 2004
  • In this paper, we studied the OCT(Optical Coherence Tomography) system which it has been extensively studied because of having some advantages such as high resolution cross-sectional images, low cost, and small size configuration. A basic principle of OCT system is Michelson interferometer. The characteristics of light source determine the resolution and the transmission depth. As a results, the light source have a commercial SLD with a central wavelength of 1,285 nm and FWHM(Full Width at Half Maximum) of 35.3 nm. The optical delay line part is necessary to equal of the optical path length with scattered light or reflected light from sample. In order to equal the optical path length, the stage which is attached to reference mirror is moved linearly by step motor And the interferometer is configured with the Michelson interferometer using single mod fiber, the scanner can be focused of the sample by using the reference arm. Also, the 2-dimensional cross-sectional images were measured with scanning the transverse direction of the sample by using step motor. After detecting the internal signal of lateral direction at a paint of sample, scanner is moved to obtain the cross-sectional image of 2-demensional by using step motor. Photodiode has been used which has high detection sensitivity, excellent noise characteristic, and dynamic range from 800 nm to 1,700 nm. It is detected mixed small signal between noise and interference signal with high frequency After filtering and amplifying this signal, only envelope curve of interference signal is detected. And then, cross-sectional image is shown through converting this signal into digitalized signal using A/D converter. The resolution of the OCT system is about 30$\mu\textrm{m}$ which corresponds to the theoretical resolution. Also, the cross-sectional image of ping-pong ball is measured. The OCT system is configured with Michelson interferometer which has a low contrast because of reducing the power of feedback interference light. Such a problem is overcomed by using the improved inteferometer. Also, in order to obtain the cross-sectional image within a short time, it is necessary to reduce the measurement time for improving the optical delay line.

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A Study on the Planning of Nationwide Indexing Services for Korea (전국색인지간행협동체제 편성방안에 관한 연구)

  • Choi Sung Jin
    • Journal of the Korean Society for Library and Information Science
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    • v.12
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    • pp.39-86
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    • 1985
  • The main purpose of the present study is to survey the major iudexing bulletins of national nature in Korea, to define such problem areas as lacunae, duplicates and limitation in coverage in the indexing services currently available in Korea, and to make some suggestions for action for improving the existing indexing services in the light of general principles and the tradition and constraints unique to Korea. The major findings and conclusions reached at this study are summarised as follows: (A) A new indexing bulletin of general nature covering the entire field needs to be created in each of the following fields without an established indexing service available for the outcome of research and development activities in Korea. (1) Philosophy (2) Religion (3) Pure sciences (4) Art (5) Language (6) Literature (7) History (B) A new specialised indexing bulletin needs to be created in each of the following fields where indexing services are heavily utilised but no, or only partial, indexing service is available. (1) Social sciences (a) Statistics (b) Sociology (c) Folklore (d) Military science (2) Pure sciences (a) Mathematics (b) Physics (c) Chemistry (d) Astronomy (e) Geology (f) Mineralogy (g) Life sciences (h) Botany (i) Zoology (3) Applied sciences (a) Medicine (b) Agriculture (c) Civil engineering (d) Architectural engineering (e) Mechanical engineering (f) Electrical engineering (g) Chemical engineering (h) Domestic science (C) Publication of the indexing bulletins suggested in A and B above may be ideally carried on by a qualified and dependable learned society established in the respective fields and designated by the Minister of Education, and should be financially supported from the public fund under the provisions of Art. 27 of the Scientific Research Promotion Act of 1979. (D) The coverage and contents of the four indexing bulletins in the field of banking and financing published by the Library of the Bank of Korea are similar and considerably duplicated. It is, therefore, suggested that the four indexing bulletins are combined in one to form a more comprehensive and efficient bibliographical tool in the field and it is further developed into a general guide to the literature produced in the entire field of economics in Korea by gradually expanding its subject coverage. (E) For the similar reasons stated in D, the Index to the Articles on North Korea and the Catalogue of Theses on North Korea, both publisheds by the Ministry of Unification Library, are suggested to make into one. The Index to the Articles of the Selected North Korean Journals and the Index to the Articles of the North Korean Journals in Microfilm Housed in the Ministry of Unification Library, both published by the same Library, are also suggested to be combined in one. (F) The contents of the Catalogue of the Reports Submitted by Government Officials Who Have Travelled Abroad, published by the National Archives are included in the Index to the Information Materials Related to Government Administration, published by the National Archives. The publication of the former is hardly justified. (G) The contents of the Index to Legal Literature published by the Seoul National University Libraries and those of the Law Section of the Index to Scholastic Works published by the National Central Library are nearly identical. One of the two indexes should cease to be published. (H) Though five indexes are being published in the field of political science and four in the field of public administration, their subject coverage is limited. Naturally, these indexes are little usable to many other researchers in the two fields. A comprehensive index covering all the specialised areas in each field needs to be developed on one or all the existing indexes. (I) It is suggested that the Catalogue of the Scholastic Works on Curricula published by the National Central Library expands its subject coverage to become a more usable and effective index to all the researchers in the field of education. (J) The bimonthly Index to Periodical Articles and the specialised index by subject series published by the National Assembly Library, and the Index to Scholastic Works published by the National Central Library are expected to increase their coverage and frequency of publication to be used more effectively and more efficiently by all users in all fields till the indexing bulletins suggested in this study will fully be available in Korea.

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Influence of implant diameter and length changes on initial stability (임플란트의 직경과 길이 변화가 초기 안정성에 미치는 영향)

  • Cho, Jae-Myoung;Cho, Uk;Yun, Mi-Jung;Jeong, Chang-Mo;Jeon, Young-Chan
    • The Journal of Korean Academy of Prosthodontics
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    • v.47 no.3
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    • pp.335-341
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    • 2009
  • Statements of problem: Adequate bone quality and quantity were important to achieve initial stability and to prevent early failures. However there were few published data available regarding the actual effect of dimensional change in implant geometry on initial stability. Purpose: The purpose of the current study was to investigate the influence of diameter and length changes on initial stability of implants. Material and methods: Four types of dummy bone (D1, D2, D3 and D4) consisted of cortical and cancellous layers with different thickness were simulated. Implants which had similar surface area to each other ($3.5{\times}13.0-mm$, $4.0{\times}11.5-mm$, $4.5{\times}10.0-mm$, $5.0{\times}8.5-mm$) were inserted in dummy bones. Implant stability as a function of peak insertion torque and resonance frequency values were recorded for each implant. Results: 1. Bone quality was a major influential factor to achieve initial stability (P <.05). 2. In D1, D2 and D3 dummy bones, implant stability quotient values were not significantly different to each other (P >.05), however insertion torques were increased with wider and shorter implants (P <.05). 3. In D4 dummy bone, implant stability quotient values and insertion torques were decreased with wider and shorter implants (P <.05). Conclusion: From a point of view of initial stability, it is suggested that use of wide and short implant may be helpful in avoiding bone augmentation procedures in area of adequate bone quality.

THE SECOND MESIOBUCCAL CANAL OF UPPER PRIMARY MOLAR : CASE REPORT (제 2근심협측근관이 존재하는 상악유구치의 치험례)

  • Kim, Chang-Gi;Hong, Seong-Soo;Ko, Sung-Back;Lee, Chang-Seop;Lee, Sang-Ho
    • Journal of the korean academy of Pediatric Dentistry
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    • v.29 no.2
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    • pp.139-145
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    • 2002
  • In a primary teeth, dental caries is rapidly advanced the pulp disease, because the primary teeth have the thinner and the weaker enamel layer and the wider pulp chamber than relatively the permanent teeth. And the pulps of primary teeth are exposed during caries removal or even they are exposed by unexpected movement of the children or by trauma. For successive pulp treatment in primary teeth, it is necessary to understand completely about multiple canal morphology, variation of root canal anatomy and specific problem related to root formation and resorption of primary teeth. In upper primary molar, canal configuration of mesial root has the most variation same as upper molar. If not canal treatment is completely, most of all endodontic treatment should be failed. In a clinical case report, upper primary molars existed persistent pain or bleeding during treatment were founded the second MB canal and were performed the endodontic treatment of theirs. As a result, the upper primary molars have no symptom and good prognosis. In the examination of extracted upper primary molar, we found that 8 of 35 teeth(22.8%) in the upper primary first molars and 22 of 33 teeth(66.6%) in the upper primary second molar had the second mesiobuccal canal. It has revealed the high prevalence of two canals in mesiobuccal roots of upper primary molars. The frequency of occurrence of the second mesiobuccal canal must be taken into consideration when endodontic treatment is planned and as a possible cause of otherwise un explained failure.

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