• 한국구조물진단유지관리공학회 논문집
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• 제23권6호
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• pp.45-52
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• 2019

이산화탄소 농도가 높은 도심지의 경우 탄산화로 인한 철근부식이 발생하기 쉬우며 이는 콘크리트 구조물의 내구수명을 감소시킨다. 콘크리트 구조물의 경우 다양한 구속조건을 가지며 항상 외부의 재하하중을 받고 있다. 도입된 응력수준은 이산화탄소와 같은 유해인자의 확산을 변화시키며 탄산화 깊이의 변동성을 야기한다. 본 연구에서는 응력재하수준에 따른 탄산화 변동성을 정량화하였으며, 이를 이용하여 탄산화 예측식을 도출하였다. 내구성 설계인자인 피복두께, 이산화탄소 확산계수, 탄산화 반응 수화물, 그리고 외부 이산화탄소 농도를 확률변수로 정의하였으며, MCS을 통하여 영향인자의 변동성에 따른 내구수명을 도출하였다. 또한 응력수준에 따라 변화하는 내구수명을 도출하였으며, 이를 결정론적인 방법의 결과와 비교하였다. 피복두께 및 내부 수화물 생성이 내구수명 변동성에 가장 큰 영향을 미쳤으며, 응력수준을 고려한 내구수명평가는 유지관리 우선순위 설정에 합리적으로 적용할 수 있다.

• Journal of Periodontal and Implant Science
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• 제29권1호
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• pp.41-49
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• 1999

The purpose of this study was to evaluate the relationship between osteoporosis and periodontal condition in postmenopausal women. Twenty-eight patients who have been treated at Chonnam national university hospital with osteoporosis(osteoporotic group, mean $age62.2{\pm}6.6$) and 21 normal postmenopausal women with periodontitis(control group, mean $age60.4{\pm}3.7$) were examined. Bone mineral density(BMD) of lumbar spine(L2-L4) was measured by dual energy X-ray absorptiomemtry(DEXA). Percentage to peaked bone mass in osteoporotic group was 70.9% which had lower BMD than in control group(p<0.05). The number of present teeth were 23.6 in osteoporotic group and 23.1 in control group. Percentage of bleeding on probing was 41% in osteoporotic group and 37% in control group. probing depth and attachment level were shown 3.18 mm, 3.63 mm in osteoporotic group and 2.85mm, 3.11mm in control group, respectively. Probing depth and attachment level were significantly greater in osteoporotic group than in control group(p<0.05). The significant negative correlation was found between BMD level and periodontal attachment level(p<0.001, ${\gamma}=-0.56$). These results suggest that osteoporosis may be associated with periodontal breakdown.

• 대한기계학회논문집
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• 제7권4호
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• pp.425-433
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• 1983

Fatigue tests by axial loading (R=0.1) were carried out to investigate fatigue crack growth properties of small surface cracks in mild steel at room temperature, 250.deg. C and 400.deg. C, by using flat specimens with a small artificial pit. All the data of the fatigue crack growth rate obtained in the present tests are determined as a function of the stress intensity factor range, so that the applicability of liner fracture mechanics to the fatigue crack growth of surface cracks at elevated temperatures is investigated and discussed in comparison with the data of type 304 stainless steel at room temperature and elevated temperature. The obtained results are as follows: 1) Relations of both surface fatigue crack length and its depth to cycle ratio fall within a narrow scatter band in spite of different stress levels. 2) The .DELTA. .sigma. .root. .pi. a-da/dN relation of surface fatigue crack growth at room temperature is independent of the stress level and can be plotted as a straight line at log-log diagram, but the relation at 400.deg. C depends partly on the stress level. 3) Relations of the fatigue crack growth into depth d(2b)/dN and is stress intensity factor range .DELTA. $K_{I}$, accounted for the aspect ratio variation, fall within a narrow scatter band for wide range of the applied stress levels. And .DELTA. $K_{I}$E-d(2b)/dN relations of mild steel at different stress level coincide relatively well with the data of type 304 stainless steel. 4) The value of aspect ratio obtained by a beach mark method and a temper coloring method approaches about 0.9 in common with crack growth and it is independent of stress level and temperatures. 5) The equi-crack length curve is parallel to S-N$_{f}$ curve at elevated temperatures.s.s.s.

• The Journal of Advanced Prosthodontics
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• 제6권5호
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• pp.325-332
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• 2014

PURPOSE. The aim of this review was to analyze the evaluation criteria on mandibular implant overdentures through a systematic review and suggest standardized evaluation criteria. MATERIALS AND METHODS. A systematic literature search was conducted by PubMed search strategy and hand-searching of relevant journals from included studies considering inclusion and exclusion criteria. Randomized clinical trials (RCT) and clinical trial studies comparing attachment systems on mandibular implant overdentures until December, 2011 were selected. Twenty nine studies were finally selected and the data about evaluation methods were collected. RESULTS. Evaluation criteria could be classified into 4 groups (implant survival, peri-implant tissue evaluation, prosthetic evaluation, and patient satisfaction). Among 29 studies, 21 studies presented implant survival rate, while any studies reporting implant failure did not present cumulative implant survival rate. Seventeen studies evaluating peri-implant tissue status presented following items as evaluation criteria; marginal bone level (14), plaque Index (13), probing depth (8), bleeding index (8), attachment gingiva level (8), gingival index (6), amount of keratinized gingiva (1). Eighteen studies evaluating prosthetic maintenance and complication also presented following items as evaluation criteria; loose matrix (17), female detachment (15), denture fracture (15), denture relining (14), abutment fracture (14), abutment screw loosening (11), and occlusal adjustment (9). Atypical questionnaire (9), Visual analog scales (VAS) (4), and Oral Health Impact Profile (OHIP) (1) were used as the format of criteria to evaluate patients satisfaction in 14 studies. CONCLUSION. For evaluation of implant overdenture, it is necessary to include cumulative survival rate for implant evaluation. It is suggested that peri-implant tissue evaluation criteria include marginal bone level, plaque index, bleeding index, probing depth, and attached gingiva level. It is also suggested that prosthetic evaluation criteria include loose matrix, female detachment, denture fracture, denture relining, abutment fracture, abutment screw loosening, and occlusal adjustment. Finally standardized criteria like OHIP-EDENT or VAS are required for patient satisfaction.

• The Journal of Korean Physical Therapy
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• 제22권6호
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• pp.77-83
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• 2010

Purpose: The aim of this study was to do numerical analysis of the wavelength dependence in low level laser therapy (LLLT) using a finite element method (FEM). Methods: Numerical analysis of heat transfer based on a Pennes' bioheat equation was performed to assess the wavelength dependence of effects of LLLT in a single layer and in multilayered tissue that consists of skin, fat and muscle. The three different wavelengths selected, 660 nm, 830 nm and 980 nm, were ones that are frequently used in clinic settings for the therapy of musculoskeletal disorders. Laser parameters were set to the power density of 35.7 W/$cm^2$, a spot diameter of 0.06 cm, and a laser exposure time of 50 seconds for all wavelengths. Results: Temperature changes in tissue based on a heat transfer equation using a finite element method were simulated and were dominantly dependent upon the absorption coefficient of each tissue layer. In the analysis of a single tissue layer, heat generation by fixed laser exposure at each wavelength had a similar pattern for increasing temperature in both skin and fat (980 nm > 660 nm > 830 nm), but in the muscle layer 660nm generated the most heat (660 nm ${\gg}$ 980 nm > 830 nm). The heat generation in multilayered tissue versus penetration depth was shown that the temperature of 660 nm wavelength was higher than those of 830 nm and 980 nm Conclusion: Numerical analysis of heat transfer versus penetration depth using a finite element method showed that the greatest amount of heat generation is seen in multilayered tissue at = 660 nm. Numerical analysis of heat transfer may help lend insight into thermal events occurring inside tissue layers during low level laser therapy.

• 수산해양기술연구
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• 제26권1호
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• pp.14-19
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• 1990

동지나해의 초음파산란층에 대한 기초적 연구로서, 산란층의 주야간에 대한 수직이동상태와 Echo 신호의 변동특성에 관하여 검토한 결과, 수심 20m~80m에 형성된 상\ulcorner하한의 수온차가 약 11$^{\circ}C$인 수온약층부에서 일몰 전에는 산란층의 Echo 신호가 뚜렷하지 않았으나, 일몰 후부터 수심 35m~45m 구간에서 산란층이 강하게 나타내기 시작하여, 시간이 경과할수록 수직적으로 신장되면서 표층을 향해 점차 부상하는 경향을 나타내었다. 한편, 일출 전에 초음파산란층의 상부는 수온약층의 상부까지 부상하였고, 또 전 수심에서 상당히 강한 Echo 신호가 돌발적으로 출현하는 현상이 확인되었으며, 이것은 저층에 분포하고 있던 어군이 부상하여 발생한 것으로 생각된다. 일출 후에는 산란층이 급속히 하강함과 동시에 Echo level도 급격히 낮아지는 경향을 나타내었고, 그 하강속도는 일몰 후 산란층의 부상속도에 비해 현저하게 빠른 현상을 나타내었으며, 일출전후 약 30분간에 가장 강한 Echo 신호가 관측되었다. 또 Echo 신호의 진폭빈도분포는 일몰전에는 전 수층에 걸쳐 Echo level이 매우 낮으므로 낮은 level에 많이 집중되는 지수분포형을 나타내고, 일출전후에는 Echo 신호가 높은 level에 많이 집중되는 정규분포형을 나타내었다.

• 한방안이비인후피부과학회지
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• 제25권3호
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• pp.88-96
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• 2012

Objectives : We investigated the skin properties on the periorbital region and cheek of Korean female according to age pattern by 7year based on Sang Go Cheun Jin Ron (上古天眞論) in So Moon (素問,) Methods : 49 Korean females, aged 21-56 years ($39.54{\pm}10.04$ years) were participated in this study. We measured the skin properties of periorbital region and cheek with SkinTouch (Amorepacific, Korea). Skin moisture, sebum, elasticity, lightness, roughness, area of wrinkle, depth of wrinkle were assessed. Results : Differences were noticed depending on the site and age. The level of moisture was higher on the eyelid than crow's feet. The level of lightness and elasticity were lower on the periorbital region than cheek. Skin lightness was highest on group1(under 28y) and lowest on group5(over 49y). Skin roughness was highest on group1(under 28y) and lowest on group4(over 42y under 49y). The level of wrinkle are was lowest on group1(under 28y) and highest on group 5(over49y). The level of wrinkle depth was lowest on group1(under 28y) and highest on group 4(over 42y under 49y). Conclusion : Unique aging pattern by 7 years of female is reflected to diverse skin properties of eyes. It can be possible to apply the theory on Sang Go Cheun Jin Ron (上古天眞論) to practical use in dermatology and cosmetic.

• 대한조선학회논문집
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• 제59권5호
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• pp.288-295
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• 2022

In this study, the force and moment acting on a Joubert BB2 submarine model at depths near the free surface were measured through a captive model test with the scale ratio of 1/15. Based on the experiment, the pitch moment and heave force due to the "Tail suction effect", including the change in surge force with depth near the free surface, were quantitatively analyzed. The change of force and moment according to the relative position of the sail and the free surface was reviewed with the free surface waves generated for each depths. As a result, the angle of attack of the hull to counteract the pitch moment induced by the tail suction effect was derived. The effect of the hydrostatic moment component according to the angle of attack on the equilibrium of pitch moment was also taken into account. The control plane performance tests for the X-type rudder and sail plane were conducted in snorkel and surface depth conditions to figure out the control plane angles for the neutral level flight of the submarine at near free surface. The results of this study are expected to be used as a reference data for the neutral level flight of the submarine at near free surface operation in the free running model test as well as numerical studies.

• 인간식물환경학회지
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• 제24권5호
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• pp.469-483
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• 2021

Background and objective: If the Nelumbo nucifera spreads in a wetland at a high density, it can have considerable positive and negative ecological effects on habitats. For this reason, it is necessary to precisely investigate the impacts of its rapid proliferation. This study was conducted to propose the distribution and management of N. nucifera, which can cause the degradation of wildlife habitats due to the rapid spread of internal and external environmental factors that may affect the Junam wetland ecosystem. Methods: For the investigation and analysis of physical and ecological characteristics, factors of the abiotic environment such as general weather conditions, topography and water depth structure, and soil and water quality analysis, and bioenvironment characteristics such as changes in the N. nucifera community distribution were evaluated. To assess whether the differences in the soil depth and physicochemical characteristics between the N. nucifera community and the aquatic plant community are statistically significant, a One-way ANOVA was executed. Results: N. nucifera was presumably introduced in approximately 2007 and observed at a prevalence of only 0.8% in 2009, but had expanded to 11.1% in 2014. After that, the area was increased to 19.3% in 2015 and 40.0% in 2017, about twice that of the previous survey year. The rapid diffusion of an N. nucifera colony can have adverse effects on wildlife habitats and biodiversity at Junam Wetland. To solve these problems, four management methods can be proposed; water level management, mowing management, installation of posts and removal of lotus roots. Control of the N. nucifera community using these methods was judged to be suitable for cutting and water level management when considering expansion rate, water level variation, and wildlife habitat impacts. Conclusion: As the biotic and abiotic environmental factors are different for each wetland, it is necessary to determine the timing and method of management through a detailed investigation.

• 수산해양기술연구
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• 제22권1호
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• pp.19-23
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• 1986

This paper describes that air noise and underwater noise in the Somjin Estuary are measured and analysed to get the basic data to find out the influence of environment on the underwater. The results obtained are summerized as follows: 1. The spectrum level of air noise in the Somjin Estuary increases until 500Hz, and decreases a little over 2KHz. 2. The spectrum level of underwater noise in the Somjin Estuary increases from 50 Hz to 1 KHz, but it decreases over 1 KHz as the depth is deeper. 3. When the influence of other factors is scarce but the influence of flowing speed is significant, the noise level seems to be higher at speedy layer than at slower layer. 4. The underwater sound level seems to be wider at speedy layer than at slower layer.