• Journal of Species Research
• /
• 제2권2호
• /
• pp.159-166
• /
• 2013

Typical of large, oligotrophic lakes, Lake H$\ddot{o}$vsg$\ddot{o}$l, Mongolia, exhibits complex morphometry which should support a spatially heterogeneous community of benthic macroinvertrates. The lake also exhibits a broad range of land uses. Based on the variation in land use and complex physical habitat of the lake (e.g. substrate variation and presence of affluent streams in bays), we asked two questions. First, does density of total benthic macroinvertebrates vary between different bays in Lake H$\ddot{o}$vsg$\ddot{o}$l? Second, does density of individual benthic taxa vary by bay? Samples collected in 1997, the last year for benthic sampling of the lake, were designed to test for variation in macroinvertebrate density between bays and can now be used to establish baseline variation in density for future studies. A total of 56 Ponar grab samples were analyzed from six bays in Lake H$\ddot{o}$vsg$\ddot{o}$l. Results of a general linear model analysis of variance showed that total density of macroinvertebrates varied only slightly between bays of the lake, but that most individual taxa showed significant variation between bays. Variation in density for most taxa was linked to substrate composition rather than other geographic or physical variables in the lake. Recent increases in grazing intensity and ecotourism along the shores should be managed to reduce the nutrient load into the lake to avoid impairment of the benthic biota of this unique, ancient ecosystem.

• 한국통신학회논문지
• /
• 제35권1B호
• /
• pp.1-7
• /
• 2010

본 논문에서는 편향 자기 경로 제어 방법을 사용하는 새로운 고성능 고장 감내 스위칭 망을 제시한다. 기반이 되는 델타 망의 위상적 구조를 대수적 기법을 사용하여 해석한 결과로 부터, 편향 자기 경로 제어 알고리즘을 사용하는 다중 경로 스위칭 망인 다차원 링-델타 망을 유도한다. 제시된 스위칭 망에서는 델타 망의 링크들을 포함하는 모든 링크들이 결함 혹은 혼잡이 생긴 링크들을 우회하는 대체 경로들로써 사용된다. 본 연구에서 비균일 주소 분포를 가진 부하를 가했을 경우의 이 망의 성능을 시뮬레이션을 사용하여 분석하였다. 입력 셀의 도착률이 0.9이고, Hot Ratio가 0.8인 경우, $1024\;{\times}\;1024$ 크기의 제안된 스위칭 망의 통과율은 사이클릭 벤얀 망에 비해서 36.5% 우수하고, 2차원 링-벤얀 망에 비해서 13.3% 우수하다. 또한, $64\;{\times}\;64$ 크기의 제안된 스위칭 망의 신뢰도 는 Hui의 망에 비해 2.2배, 2차원 링-벤얀 망에 비해 46.6% 높다.

• Structural Engineering and Mechanics
• /
• 제74권2호
• /
• pp.157-173
• /
• 2020

In the finite element modelling of long-span cable-stayed bridges, there are a lot of uncertainties brought about by the complex structural configuration, material behaviour, boundary conditions, structural connections, etc. In order to reduce the discrepancies between the theoretical finite element model and the actual static and dynamic behaviour, updating is indispensable after establishment of the finite element model to provide a reliable baseline version for further analysis. Traditional sensitivity-based updating methods cannot support updating based on static and dynamic measurement data at the same time. The finite element model is required in every optimization iteration which limits the efficiency greatly. A convenient but accurate Kriging surrogate model for updating of the finite element model of cable-stayed bridge is proposed. First, a simple cable-stayed bridge is used to verify the method and the updating results of Kriging model are compared with those using the response surface model. Results show that Kriging model has higher accuracy than the response surface model. Then the method is utilized to update the model of a long-span cable-stayed bridge in Hong Kong. The natural frequencies are extracted using various methods from the ambient data collected by the Wind and Structural Health Monitoring System installed on the bridge. The maximum deflection records at two specific locations in the load test form the updating objective function. Finally, the fatigue lives of the structure at two cross sections are calculated with the finite element models before and after updating considering the mean stress effect. Results are compared with those calculated from the strain gauge data for verification.

• Restorative Dentistry and Endodontics
• /
• 제43권2호
• /
• pp.26.1-26.12
• /
• 2018

Objective: The purpose of this study was to investigate the degree of conversion (DC) and mechanical properties of a microhybrid Filtek Z250 (3M ESPE) resin composite after aging. Method: The specimens were fabricated using circular molds to investigate Vickers microhardness (Vickers hardness number [VHN]) and DC, and were prepared according to ISO 4049 for flexural strength testing. The initial DC (%) of discs was recorded using attenuated total reflectance-Fourier transforming infrared spectroscopy. The initial VHN of the specimens was measured using a microhardness tester under a load of 300 g for 15 seconds and the flexural strength test was carried out with a universal testing machine (crosshead speed, 0.5 mm/min). The specimens were then subjected to thermocycling in $5^{\circ}C$ and $55^{\circ}C$ water baths. Properties were assessed after 1,000-10,000 cycles of thermocycling. The surfaces were evaluated using scanning electron microscopy (SEM). Data were analyzed using 1-way analysis of variance followed by the Tukey honest significant difference post hoc test. Results: Statistical analysis showed that DC tended to increase up to 4,000 cycles, with no significant changes. VHN and flexural strength values significantly decreased upon thermal cycling when compared to baseline (p < 0.05). However, there was no significant difference between initial and post-thermocycling VHN results at 1,000 cycles. SEM images after aging showed deteriorative changes in the resin composite surfaces. Conclusions: The Z250 microhybrid resin composite showed reduced surface microhardness and flexural strength and increased DC after thermocycling.

• 한국도로학회논문집
• /
• 제15권5호
• /
• pp.91-99
• /
• 2013

PURPOSES : This study aims at proposing the methodology for benefit evaluations in pavement maintenance methods and timings using KoPMS(Korean Pavement Management System) software which was developed for efficient pavement management. METHODS : This study classified pavement sections into 4 clusters considering AADT(Annual Average Daily Traffic) and ESAL(Equivalent Single-Axle Load) using cluster analysis and used the deterioration models in each cluster. Increased user costs due to pavement deterioration as time goes by and agent costs for maintenance were estimated. Based on deterioration model and KoPMS software, Methodology for benefit evaluation was proposed in pavement maintenance methods and with/without implementation using real pavement section data. RESULTS : This study verified that considering agent costs only would be constrained to decide pavement maintenance methods and timings, and ascertained that decision making with agent and user costs would be effective. In addition, this study revealed that pavement maintenance methods and timings can be affected by AADT and ESAL and frequent pavement maintenances can be more efficient for benefits in pavement sections with more AADT and ESAL. Also this study found that user costs would be more affected to decision making than agent costs. Moreover, Delay of conducting pavement maintenance caused increased vehicle operating costs and environmental costs because of poor conditions of pavements. CONCLUSIONS : This study proposed LCCA and benefit estimation methodology of pavement with considering agent and user costs. The results of this study can be used for baseline data of efficient pavement asset management.

• 국제물리치료학회지
• /
• 제10권4호
• /
• pp.1889-1896
• /
• 2019

Background: Because of the lack of accurate values for applied forces in manual therapy, manual therapists relies on the magnitude of the individual's perception during applying the force. However, excessive loading maneuvers carry risks for patients. Objective: To establish the relationship between the maximal force applied to swine skin with the specific region, sex, and baseline parameters of the subject. Design: Ex-vivo Study and laboratory Experimental research Methods: 3.5 kg of Korean pork sirloin that is a piece of swine was handled and it was set 3 dimensions; #A; #B; #C. Forty-seven participants who has no experience in physical therapy randomly carried out the experiment, indicated to push each place of the pressure spots with same posture and process under supervision from the instructor who has over 15 years of manual therapy, and we measured the pressure force in each time. Results: The biggest pressure force was recorded in spot #A, and #B was represented after #C. Pressure on #A showed certain statistic relation with height (r=.317, p<.05) and weight (r=.434, p<.01); pressure on #B showed certain relation which has statistical meaning with only height (r=.401, p<.01); pressure on #C emerged to have statistic relationship with height (r=.308, p<.05)and weight (r=.428, p<.01). The age aspect revealed relation with pressure on #A, #B and #C, but that was not statistically significant. Conclusions: It can be inferred that there is the most loss of pressure in the area where cartilage is like an island in the middle.

• Smart Structures and Systems
• /
• 제6권5_6호
• /
• pp.579-593
• /
• 2010

Low-power radio frequency (RF) chip transceiver technology and the associated structural health monitoring platforms have matured recently to enable high-rate, lossless transmission of measurement data across large-scale sensor networks. The intrinsic value of these advanced capabilities is the allowance for high-quality, rapid operational modal analysis of in-service structures using distributed accelerometers to experimentally characterize the dynamic response. From the analysis afforded through these dynamic data sets, structural identification techniques can then be utilized to develop a well calibrated finite element (FE) model of the structure for baseline development, extended analytical structural evaluation, and load response assessment. This paper presents a case study in which operational modal analysis is performed on a three-span prestressed reinforced concrete bridge using a wireless sensor network. The low-power wireless platform deployed supported a high-rate, lossless transmission protocol enabling real-time remote acquisition of the vibration response as recorded by twenty-nine accelerometers at a 256 Sps sampling rate. Several instrumentation layouts were utilized to assess the global multi-span response using a stationary sensor array as well as the spatially refined response of a single span using roving sensors and reference-based techniques. Subsequent structural identification using FE modeling and iterative updating through comparison with the experimental analysis is then documented to demonstrate the inherent value in dynamic response measurement across structural systems using high-rate wireless sensor networks.

• 한국지반공학회논문집
• /
• 제38권8호
• /
• pp.75-84
• /
• 2022

현재 인장형 지반앵커는 그 사용목적, 사용기간에 따라 가설과 영구로 구분하여 성능평가를 별도로 제시하고 있다. 현재의 성능평가 상한선과 하한선 기준을 실무에 적용하는 데 있어 타당한 것으로 보인다. 하지만, 압축형 지반앵커는 주로 영구로 사용되어 온 점으로 인해 가설과 영구의 구분 없이 영구에 해당하는 기준이 제시되어 있어 제거형과 같이 가설로 사용하는 지반앵커에 있어서는 엄격한 기준이 되고 있다. 기존 성능평가 기준선을 고찰해 본 결과, 하한 기준선은 가설과 영구 구분 없이 적용할 수 있는 것으로 판단되나 상한 기준선은 가설과 영구를 구분하여 제시하는 것이 바람직한 것으로 판단된다. 압축형 지반앵커에서 상한선 기준의 적용에 있어서 앵커의 정착지반상태(암반 또는 토사), 사용기간, 특히 하중-변위 곡선의 탄성상태 유지 여부 등을 고려하여 상한선을 조정할 필요성이 있다.

• Journal of Nutrition and Health
• /
• 제53권5호
• /
• pp.464-475
• /
• 2020

본 연구에서는 한국인이 평소 섭취하는 일반식사와 유사한 수준의 당부하량을 가진 high GL 식사와 당부하량이 낮게 설계된 low GL 식사를 섭취한 후 체중, 체지방, 혈압 및 혈액 내 생활습관병 위험 지표 등의 변화를 분석 및 비교하였다. 20대 성인남녀를 대상으로 체중 감량을 위해 wash-out 기간인 중간 2주를 제외하고 개인 필요 열량의 30%를 줄인 low GL 식사와 high GL 식사를 각 2주간 제공하였다. Low GL 식사와 high GL 식사의 효과를 비교한 결과 low GL 식사가 high GL 식사에 비해 체중 (p < 0.001), 체지방량 (p = 0.024), 체질량지수 (p < 0.001)에서 유의적으로 감소량이 더 컸다. 하지만 혈압, 혈액 내 비만 질환 위험 지표에서는 유의한 차이가 없었다. Low GL 식사의 전·후를 비교한 결과 체중, 체지방량, 체질량지수, 체지방률, 이완기 혈압, 중성지방, 총콜레스테롤, HDL-콜레스테롤, LDL-콜레스테롤, 공복혈당, C-peptide HOMA 지수가, high GL 식사에서는 체중, 체지방량, 체질량지수, 총콜레스테롤, HDL-콜레스테롤, 공복혈당, C-peptide, C-peptide HOMA 지수에서 각 식사 전보다 후에 유의적으로 감소되었다. 또한 실험 식사 섭취 전과 섭취 후를 비교한 결과 체중, 체지방량, 체질량지수, 체지방률, 혈압 (수축기, 이완기), 총콜레스테롤, HDL-콜레스테롤, LDL-콜레스테롤, 공복혈당, 당화혈색소, C-peptide, C-peptide HOMA 지수가 모두 유의적으로 감소되었다. 본 연구 결과 체중감량 및 생활습관병 위험을 줄이기 위해서는 단순히 섭취 열량을 낮추기보다는 열량과 함께 당부하량을 고려하여 섭취하는 것이 체중을 감소시키는 데에 더 효과적일 것으로 사료된다.

• 구강회복응용과학지
• /
• 제31권4호
• /
• pp.301-309
• /
• 2015

목적: 무치악 부위를 임플란트 보철로 수복하면 기능저하 상태였던 대합치는 생리적인 자극을 받게 된다. 본 연구는 하악 구치부 임플란트에 대합되는 상악치아의 골변화를 평가하였다. 연구 재료 및 방법: 보철물 장착시(기준점) 및 3, 6개월 후에 방사선 사진을 채득하였다. 맞춤형 필름유지기구를 제작하여 대합치의 연속적인 방사선 사진에 대한 투사를 표준화하였다. 디지털사진에서 관심부위에 대한 그레이수치를 시간별로 측정하여 95% 유의수준으로 반복측정분산분석으로 통계적 유의성을 검증하였다. 결과: 대합치의 그레이수치는 시간이 흐름에 따라 증가하였다. 치조정부위보다 중앙부위의 변화가 더 컸으나 근심과 원심의 그레이수치는 큰 차이를 나타내지 않았다. 그레이수치의 변화는 하중을 가하지 않았던 기간에 따라 다른 양상을 나타내었다. 결론: 기능저하였던 치아주변의 골조직에 기능적 하중이 가해지면 골조직의 변화가 발생할 수 있는 것으로 사료된다.