• 제목/요약/키워드: Strength Index

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국내 연약지반의 신뢰성있는 비배수 전단강도 추정을 위한 flat DMT와 인공신경망 이론의 적용 (Application of Flat DMT and ANN for Reliable Estimation of Undrained Shear Strength of Korean Soft Clay)

  • 변위용;김영상;이승래;정은택
    • 한국지반공학회논문집
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    • 제20권5호
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    • pp.17-25
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    • 2004
  • DMT 시험은 연약지반의 공학적 특성을 파악하기 위한 현장 시험방법으로, 이 방법으로부터 구한 비배수 전단강도는 가장 신뢰성 있고 유용한 매개변수로 알려져 있다. 그러나 국외 다른 지역의 자료를 토대로 기존에 제안된 상관관계식들은 지역적인 특성에 의존한다. DMT 시험 결과는 3가지 중간 지수 - 재료지수, 수평응력지수, dilatometer modulus를 사용하여 해석이 이루어지며 특히 비배수 전단강도는 수평응력지수만을 이용하여 예측하고 있다. 본 논문에서는 먼저 DMT 시험의 국내 연약지반에서의 적용성을 살펴보았으며 DMT로부터 비배수 전단강도를 추정하기 위하여 $p_0, p_1, p_2, {\sigma '}_v$ 그리고 초기 간극수압을 바탕으로 인공신경망 모델을 개발하였다. 인공신경망 모델은 오차 역전파 알고리즘을 적용하였으며 국내 연약지반에서 수행된 DMT 시험 자료를 이용하여 훈련하였다. 인공신경망 모델의 적용성을 판단하기 위하여 훈련에 이용되지 않은 자료로부터 예측된 결과와 기존에 제안된 상관관계식으로부터 얻은 결과를 서로 비교하였다.

국내 연약지반의 신뢰성있는 비배수 전단강도 추정을 위한 flat DMT와 인공신경망 이론의 적용 (Application of flat DMT and ANN for reliable estimation of undrained shear strength of Korean soft clay)

  • 변위용;김영상;이승래;정은택
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2004년도 춘계학술발표회
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    • pp.154-161
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    • 2004
  • The flat dilatometer test(DMT) is a geotechnical tool to estimate in-situ properties of various types of ground materials. The undrained shear strength is known to be the most reliable and useful parameter obtained by DMT. However, the existing relationships which were established for other local deposits depend on the regional geotechnical characteristics. In addition, the flat dilatometer test results have been interpreted using three intermediate indicesmaterial index($I_p$), horizontal stres index($K_p$), and dilatometer modulus($E_p$) and the undrained shear strength is estimated only by using the horizontal stress index($K_D$). In this paper, an artificial neural network was developed to evaluate the undrained shear strength by DMT and the ANN, based on the $p_0,\;p_1,\;p_2,\;{\sigma}'_v_0$, and porewater pressure. The ANN which adopts the back-propagation algorithm was trained based on the DMT data obtained from Korean soft clay. To investigate the feasibility of ANN model, the prediction results obtained from data which were not used to train the ANN and those obtained from existing relationships were compared.

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지하광산용 근접경고시스템 개발을 위한 블루투스 비콘 신호의 수신 강도 분석 (Analysis of Received Signal Strength Index from Bluetooth Beacons to Develop Proximity Warning Systems for Underground Mines)

  • 백지은;서장원;최요순
    • 한국자원공학회지
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    • 제55권6호
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    • pp.604-613
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    • 2018
  • 본 연구에서는 블루투스 비콘이 송신하는 저전력 블루투스 신호의 세기와 전파 방향성에 따른 수신 강도(Received Signal Strength Index, RSSI) 변화를 분석하였다. 자수정 지하광산에서 스마트폰을 이용하여 저전력 블루투스 신호의 RSSI 변화를 조사한 결과, 무지향성 비콘의 경우 비콘과 스마트폰 사이의 거리가 감소할수록 신호 세기가 증가할수록 RSSI 평균이 점차 증가하였다. 지향성 비콘의 RSSI 평균은 비콘과 스마트폰이 마주 보는 각도와는 연관성 없이 변화하였다. 본 연구의 결과는 블루투스 비콘 기반의 지하광산 근접경고시스템 개발을 위한 기초자료로 활용될 수 있을 것이다.

섬유보강 고강도 콘크리트 구조설계지침(안)의 저감계수에 대한 신뢰도 분석 (Reliability Analysis of Reduction Factor for Structural Design Guideline(draft) of Fiber Reinforced High Strength Concrete)

  • 김아량;최정욱;백인열
    • 한국건설순환자원학회논문집
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    • 제9권1호
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    • pp.100-108
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    • 2021
  • 이 연구의 목적은 최근 국내에서 개발된 섬유보강 고강도 콘크리트 설계지침(안)의 저감계수를 적용하여 확보하는 설계의 신뢰도지수를 분석하는 것이다. 설계지침(안) 개발을 위하여 수행된 재료실험 및 부재실험 데이터를 수집하여 재료강도 통계특성 및 부재강도 해석식에 대한 통계특성을 구한다. 재료통계특성과 설계지침(안)의 부재 해석식을 적용한 시뮬레이션을 수행하고 해석식의 통계특성과 종합하여 단면강도에 대한 통계특성을 산출한다. 국내 도로교설계기준과 콘크리트구조기준의 하중조합을 적용한 신뢰도분석을 수행하였으며, 설계지침(안)에서 제시한 재료 및 부재에 대한 저감계수를 적용한 설계는 목표신뢰도 지수를 만족함을 확인하였다.

The Analysis of the Effects of Physical Activity on Impaired Fasting Glucose in Adults Over 20 Years of Age

  • Joo-Won Yoon
    • 대한통합의학회지
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    • 제11권2호
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    • pp.181-196
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    • 2023
  • Purpose : The purpose of this study was to investigate the effects of physical activity on impaired fasting glucose in adults aged 20 years or older. Methods : This study utilized raw data from the 8th National Health and Nutrition Examination survey (2019~2021). The subjects of this study were 5,344 adults aged 20 years or older who were confirmed to be free of diabetes. The control variables in this study model are health behavior characteristics (subjective health status, smoking, drinking), anthropometric characteristics (body mass index), and personal background characteristics (gender, age, income level, education level, marital status). As for the analysis method, the degree of physical activity was made into a dummy variable, and a probit model was used. Results : As a result of this study, compared to quartile 1 of the relative grip strength value obtained by dividing the grip strength by the body mass index (body mass index, kg, m2), fasting blood glucose levels were significantly higher in quartile 2 (.05, p<.01), quartile 3 (.04, p<.01), and quartile 4 (.04, p<.01). It was found that the probability of belonging to the normal category was higher than that of impaired fasting glucose. In addition, in the group of adults aged 20 or older who had a lot of aerobic and anaerobic physical activity, fasting blood sugar was more likely to be in the normal category. Conclusion : Based on the results of this study, it was suggested that diabetes should be managed through physical activity in the pre-diabetic stage, as prevention is important as well as treatment. From a practical point of view, muscle strength, such as grip strength, can be identified as a reliable indicator for identifying impaired fasting glucose.

Predictive model for the shear strength of concrete beams reinforced with longitudinal FRP bars

  • Alzabeebee, Saif;Dhahir, Moahmmed K.;Keawsawasvong, Suraparb
    • Structural Engineering and Mechanics
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    • 제84권2호
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    • pp.143-154
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    • 2022
  • Corrosion of steel reinforcement is considered as the main cause of concrete structures deterioration, especially those under humid environmental conditions. Hence, fiber reinforced polymer (FRP) bars are being increasingly used as a replacement for conventional steel owing to their non-corrodible characteristics. However, predicting the shear strength of beams reinforced with FRP bars still challenging due to the lack of robust shear theory. Thus, this paper aims to develop an explicit data driven based model to predict the shear strength of FRP reinforced beams using multi-objective evolutionary polynomial regression analysis (MOGA-EPR) as data driven models learn the behavior from the input data without the need to employee a theory that aid the derivation, and thus they have an enhanced accuracy. This study also evaluates the accuracy of predictive models of shear strength of FRP reinforced concrete beams employed by different design codes by calculating and comparing the values of the mean absolute error (MAE), root mean square error (RMSE), mean (𝜇), standard deviation of the mean (𝜎), coefficient of determination (R2), and percentage of prediction within error range of ±20% (a20-index). Experimental database has been developed and employed in the model learning, validation, and accuracy examination. The statistical analysis illustrated the robustness of the developed model with MAE, RMSE, 𝜇, 𝜎, R2, and a20-index of 14.6, 20.8, 1.05, 0.27, 0.85, and 0.61, respectively for training data and 10.4, 14.1, 0.98, 0.25, 0.94, and 0.60, respectively for validation data. Furthermore, the developed model achieved much better predictions than the standard predictive models as it scored lower MAE, RMSE, and 𝜎, and higher R2 and a20-index. The new model can be used in future with confidence in optimized designs as its accuracy is higher than standard predictive models.

Physical, Mechanical and Durability Properties of the Quartzite Units of Central Nepal Lesser Himalaya

  • Dinesh Raj Sharma;Naresh Kazi Tamrakar;Upendra Baral
    • 지질공학
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    • 제34권1호
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    • pp.67-105
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    • 2024
  • This study compares the quartzites of four quartzite units: The Fagfog Quartzite, Dunga Quartzite (member of the Robang Formation), Pandrang Quartzite (member of the Kalitar Formation) and the Chisapani Quartzite. The analysis shows variations in flakiness and elongation, as the Fagfog Quartzite displays low flakiness whereas the Pandrang and the Chisapani have moderate and the Dunga Quartzite has shown variations. The density values of the four quartzite units remain consistent, indicating uniform physical properties and porosity levels. However, bulk density values differ among the quartzites, suggesting variations in particle arrangement, porosity, and density. Regarding strength measures, the Pandrang and the Chisapani Quartzite have higher strength characteristics as compared to the Fagfog and the Dunga Quartzites. The Pandrang Quartzite has the highest average point load strength index, classifying it as "Extremely Strong". The resistance to impact and crushing forces varies among the quartzites, with lower Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) indicating higher strength and durability. Durability tests show that the Fagfog Quartzite has high durability against slaking, with a slight decrease observed after the fifth cycle. The Dunga Quartzite shows varying degrees of weathering, while the Pandrang and the Chisapani Quartzite have minimal weight changes, indicating strong resistance to weathering. Magnesium sulfate soundness tests indicate high durability and resistance to degradation for all four units. The Los Angeles abrasion value (LAAV) tests indicate favorable resistance to abrasion for the majority of the Fagfog, Dunga, and the Pandrang Quartzites samples, while Chisapani Quartzite shows more variability in LAAV values. The Pandrang Quartzite shows a higher proportion of elongated particles but lower flakiness index values as compared to Fagfog and Dunga Quartzites while Chisapani Quartzite stands out with a significantly higher presence of flaky particles and lower elongation index values. Mechanically, the Fagfog and Dunga Quartzite show higher strength and better resistance to abrasion and freeze and thaw. The Pandrang Quartzite shows moderate resistance to crushing and sudden effect, while the Chisapani Quartzite has variable resistance to effect. This comparative study emphasizes the diversity and complexity of quartzite rock types, showing the need for comprehensive characterization and assessment to determine their suitability for specific applications.

노인 대상 가상현실 기반 구강 근력 강화 훈련의 구강 기능 개선 효과 (Effectiveness of virtual reality-based oral muscle strength training on oral function in older adults)

  • Yoon-Young Choi;Eun-Seo Jung;Kyeong-Jin Lee;Hyun-Young Moon;Mi-Sook Yoon;Kyeong-Hee Lee
    • 한국치위생학회지
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    • 제24권2호
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    • pp.121-130
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    • 2024
  • 연구목적: 본 연구는 가상현실(VR) 기반 구강 근력 강화훈련 콘텐츠를 개발하고 노인에게 적용한 후 구강 기능의 개선 효과를 확인하고자 하였다. 연구방법: 구강근력 강화훈련은 2023년 8월 말부터 10월 초까지 6주 동안 총 12회를 적용하였다. 수행 장소는 참여 대상자의 소속기관이며, 1회당 소요시간은 약 60분으로 하였다. 연구결과: 가상현실 기반 구강근력 강화훈련 실시 후 치면세균막 지수(O'Leary index)는 0.42점 감소하였으며(p<0.01), 치은염 지수(Löe & Silness index)는 1.11점 감소하였다(p<0.01). 설태는 1.24점 감소하였고(p<0.01), 타액분비량은 0.55g 증가하였다(p<0.05). 사후 두 그룹 간의 비교에서도 치면세균막(p<0.001), 치은염(p<0.001), 설태(p<0.01)에서 유의한 차이를 보였다. 결론: 본 연구 결과, 가상현실 기반 구강근력 강화훈련은 노인층의 구강건강을 일부 향상하는 효과를 나타냈다. 이에 본 연구에서 개발한 가상현실 기반 구강근력 강화훈련 콘텐츠가 노인층을 대상으로 한 건강증진 프로그램에 유용하게 활용될 수 있을 거라 생각된다.

Strength Modeling of Mechanical Strength of Polyolefin Fiber Reinforced Cementitious Composites

  • Sakthievel, P.B.;Ravichandran, A.;Alagumurthi, N.
    • Journal of Construction Engineering and Project Management
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    • 제4권2호
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    • pp.41-46
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    • 2014
  • RCC consumes large quantities of natural resources like gravel stone and steel, and there is a need to investigate on an innovative material that utilizes limited quantities of natural resources but should have good mechanical strength. This study deals with the experimental investigation of strength evaluation of cementitious composites reinforced with polyolefin fibers from 0% to 2.5% (with interval of 0.5%), namely Polyolefin Fiber Reinforced Cementitious Composites (PL-FRCC) and developing statistical regression models for compressive strength, splitting-tensile strength, flexural strength and impact strength of PL-FRCC. Paired t-tests (for each PL fiber percentage 0 to 2.5%) bring out that there is significant difference in compressive and splitting-tensile strength when curing periods (3, 7, 28 days) are varied. Also, a strong relationship exists between the compressive and flexural strength of PL-FRCC. The proposed mathematical models developed in this study will be helpful to ascertain the mechanical strength of FRCC, especially, when the fiber reinforcing index is varied.

Optimal Use of MSWI Bottom Ash in Concrete

  • Zhang, Tao;Zhao, Zengzeng
    • International Journal of Concrete Structures and Materials
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    • 제8권2호
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    • pp.173-182
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    • 2014
  • An experimental investigation was carried out to evaluate the mechanical properties of concrete mixtures in which coarse aggregate was partially (30, 50 or 70 %) replaced with pre-washed municipal solid waste incineration (MSWI) bottom ash. Results indicated that bottom ash reduced the compressive strength, elastic modulus, and levels of heavy metals in leachate when used as a replacement for gravel, and that the maximum amount of MSWI bottom ash in concrete should not exceed 50 %. To analyze the effect mechanism of bottom ash in concrete, the degree of hydration and the following pozzolanic reaction characterized by the pozzolanic activity index, and the porosity distribution in cement mortar. The study indicates that improved properties of concrete are not solely later strength gain and reduced levels of heavy metals in leachate but also the progression of pozzolanic reactions, where a dense structure contains a higher proportion of fine pores that are related to durability.