• Title/Summary/Keyword: depth level

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Probabilistic Service Life Evaluation for OPC Concrete under Carbonation Considering Cold Joint and Induced Stress Level (콜드조인트 및 재하 응력을 고려한 탄산화에 노출된 OPC 콘크리트의 확률론적 내구수명평가)

  • Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.6
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    • pp.45-52
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    • 2019
  • Steel corrosion due to carbonation in RC (Reinforced Concrete) structures easily occurs in urban cities with high CO2 concentration. RC structures are always subjected to external loading with various boundary conditions. The induced stress level causes changes in diffusion of harmful ion like CO2. In this work, a quantification of carbonation progress with stress level is carried out and carbonation prediction is derived through the relations. Determining the design parameters like cover depth, CO2 diffusion coefficient, carbonatable materials, and exterior CO2 concentration as random variables, service lifes under carbonation with design parameter's variation are obtained through MCS(Monte Carlo Simulation). Additionally the service life with different stress level is derived and the results are compared with those from deterministic method. Cover depth and cement hydrates are evaluated to be very effective to resist carbonation, and the proposed method which can consider the effect of stress on service life can be applied to maintenance priority determination.

Periodontal status in patients with osteoporosis (골다공증 환자의 치주조직 상태)

  • Park, Seong-Pyo;Park, Byung-Ju;Kim, Young-Jun;Chung, Hyun-Ju
    • Journal of Periodontal and Implant Science
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    • v.29 no.1
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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.

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A Study on Propagation Behavior of Surface-Fatigue-Crack in the Mild Steel at Elevated Temperatures (軟鋼의 高溫 表面渡勞균열 成長擧動에 관한 硏究)

  • ;;北川英夫
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.7 no.4
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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.

Standardizing the evaluation criteria on treatment outcomes of mandibular implant overdentures: a systematic review

  • Kim, Ha-Young;Shin, Sang-Wan;Lee, Jeong-Yol
    • The Journal of Advanced Prosthodontics
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    • v.6 no.5
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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.

Numerical Analysis of the Wavelength Dependence in Low Level Laser Therapy (LLLT) Using a Finite Element Method

  • Yoon, Jin-Hee;Park, Ji-Won;Youn, Jong-In
    • The Journal of Korean Physical Therapy
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    • v.22 no.6
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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.

동지나해의 초음파 산란층에 관한 연구 ( 1 ) ( Acoustic Scattering Layers in the East China Sea ( 1 ) )

  • Lee, Dae-Jae;Shin, Hyeong-Il;Park, Jung-Hee
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.26 no.1
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    • pp.14-19
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    • 1990
  • This paper describes on the characteristics of the acoustic echoes from the scattering layers by the aggregation of marine organisms which was measured by using a 50kHz echo sounder on board of the training ship SAEBADA belong to National Fisheries University of Pusan during the summer, 1989 in the East China Sea. A data acquisition system was used to record digitally the envelope of the echoes and the frequency distribution of echo amplitudes on the whole water column was examined as a function of time during the sunrise and sunset periods. Acoustic data showed that the abundance distribution of marine organisms according to depth in the servery area changed with time and that the organisms were most active during the twilight of morning, and the echo strength on the water column or scattering layer was also strongest during this time. Additional results of this survey suggest that other interest, such as the relationship between environmental conditions and biomass depth distribution, could be also investigated in hydroacoustic method.

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Analysis the skin physical properties of periorbital region and cheek based on female's aging pattern by 7 years (한국 성인 여성의 눈가 피부 특성 분석)

  • Cho, Ga-Young;Kim, Jee-Yeun;Yeom, Myung-Hun;Cho, Jun-Cheol;Kim, Yoon-Bum
    • The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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    • v.25 no.3
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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.

A Captive Model Test on Hydrodynamic Force and Neutral Level Flight of BB2 Submarine in Straight Operation at Near Free Surface with Different Depths (자유수면 근처에서 직진하는 BB2 잠수함의 심도별 유체력과 중립운항에 대한 구속모형시험 연구)

  • Kwon, Chang-Seop;Kim, Dong-Jin;Yun, Kunhang;Kim, Yeon-Gyu
    • Journal of the Society of Naval Architects of Korea
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    • v.59 no.5
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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.

Characteristics and Management Plan for the Distribution of Nelumbo nucifera community in Junam Wetland

  • Lee, Soo-Dong;Kim, Han;Cho, Bong-Gyo;Lee, Gwang-Gyu
    • Journal of People, Plants, and Environment
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    • v.24 no.5
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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.

Ambient Underwater Noise in the Somjin Estuary (섬진강 하구에서의 수중 환경 소음)

  • 박해훈
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.22 no.1
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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.

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