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A GMDH-based estimation model for axial load capacity of GFRP-RC circular columns

  • Mohammed Berradia;El Hadj Meziane;Ali Raza;Mohamed Hechmi El Ouni;Faisal Shabbir
    • Steel and Composite Structures
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    • v.49 no.2
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    • pp.161-180
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    • 2023
  • In the previous research, the axial compressive capacity models for the glass fiber-reinforced polymer (GFRP)-reinforced circular concrete compression elements restrained with GFRP helix were put forward based on small and noisy datasets by considering a limited number of parameters portraying less accuracy. Consequently, it is important to recommend an accurate model based on a refined and large testing dataset that considers various parameters of such components. The core objective and novelty of the current research is to suggest a deep learning model for the axial compressive capacity of GFRP-reinforced circular concrete columns restrained with a GFRP helix utilizing various parameters of a large experimental dataset to give the maximum precision of the estimates. To achieve this aim, a test dataset of 61 GFRP-reinforced circular concrete columns restrained with a GFRP helix has been created from prior studies. An assessment of 15 diverse theoretical models is carried out utilizing different statistical coefficients over the created dataset. A novel model utilizing the group method of data handling (GMDH) has been put forward. The recommended model depicted good effectiveness over the created dataset by assuming the axial involvement of GFRP main bars and the confining effectiveness of transverse GFRP helix and depicted the maximum precision with MAE = 195.67, RMSE = 255.41, and R2 = 0.94 as associated with the previously recommended equations. The GMDH model also depicted good effectiveness for the normal distribution of estimates with only a 2.5% discrepancy from unity. The recommended model can accurately calculate the axial compressive capacity of FRP-reinforced concrete compression elements that can be considered for further analysis and design of such components in the field of structural engineering.

Diverse Chemo-Dynamical Properties of Nitrogen-Rich Stars Identified from Low-Resolution Spectra

  • Changmin Kim;Young Sun Lee;Timothy C. Beers;Young Kwang Kim
    • Journal of The Korean Astronomical Society
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    • v.56 no.1
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    • pp.59-73
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    • 2023
  • The second generation of stars in the globular clusters (GCs) of the Milky Way (MW) exhibit unusually high N, Na, or Al, compared to typical Galactic halo stars at similar metallicities. The halo field stars enhanced with such elements are believed to have originated in disrupted GCs or escaped from existing GCs. We identify such stars in the metallicity range -3.0 < [Fe/H] < 0.0 from a sample of ~36,800 giant stars observed in the Sloan Digital Sky Survey and Large Sky Area Multi-Object Fiber Spectroscopic Telescope survey, and present their dynamical properties. The N-rich population (NRP) and N-normal population (NNP) among our giant sample do not exhibit similarities in either in their metallicity distribution function (MDF) or dynamical properties. We find that, even though the MDF of the NRP looks similar to that of the MW's GCs in the range of [Fe/H] < -1.0, our analysis of the dynamical properties does not indicate similarities between them in the same metallicity range, implying that the escaped members from existing GCs may account for a small fraction of our N-rich stars, or the orbits of the present GCs have been altered by the dynamical friction of the MW. We also find a significant increase in the fraction of N-rich stars in the halo field in the very metal-poor (VMP; [Fe/H] < -2.0) regime, comprising up to ~20% of the fraction of the N-rich stars below [Fe/H] = -2.5, hinting that partially or fully destroyed VMP GCs may have in some degree contributed to the Galactic halo. A more detailed dynamical analysis of the NRP reveals that our sample of N-rich stars do not share a single common origin. Although a substantial fraction of the N-rich stars seem to originate from the GCs formed in situ, more than 60% of them are not associated with those of typical Galactic populations, but probably have extragalactic origins associated with Gaia Sausage/Enceladus, Sequoia, and Sagittarius dwarf galaxies, as well as with presently unrecognized progenitors.

Structural Analysis of Composite Wind Blade Using Finite Element Technique (유한요소기법을 이용한 복합재 풍력 블레이드 구조해석)

  • Unseong Kim;Kyeongryeol Park;Seongmin Kang;Yong Seok Choi;Kyungeun Jeong;Soomin Lee;Kyungjun Lee
    • Tribology and Lubricants
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    • v.40 no.4
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    • pp.133-138
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    • 2024
  • This study evaluates the structural safety of wind turbine blades, analyzes the behavior of composite laminate structures with and without defects, and assesses surface erosion wear. The NREL 5 MW standard is applied to assign accurate composite material properties to each blade section. Modeling and analysis of the wind turbine blades reveal stable behavior under individual load conditions (gravity, motor speed, wind speed), with the web bearing most of the load. Surface erosion wear analysis in which microparticle impacts are simulated on the blade coating shows a maximum stress and maximum displacement of 14 MPa and 0.02 mm, respectively, indicating good initial durability, but suggest potential long-term performance issues due to cumulative effects. The study examines defect effects on composite laminate structures to compare the stress distribution, strain, and stiffness characteristics between normal and cracked states. Although normal conditions exhibit stable behavior, crack defects lead to fiber breakage, high-stress concentration in the vulnerable resin layer, and decreased rigidity. This demonstrates that local defects can compromise the safety of the entire structure. The study utilizes finite element analysis to simulate various load scenarios and defect conditions. Results show that even minor defects can significantly alter stress distributions and potentially lead to catastrophic failure if left unaddressed. These findings provide valuable insights for wind turbine blade safety evaluations, surface protection strategies, and composite structure health management. The methodology and results can inform the design improvements, maintenance strategies, and defect detection techniques of the wind energy industry.

Effect of Pasture Mixtures on Forage Yields and Botanical Composition in Jeju at Altitude of 200 m (제주지역 표고 200 m에서 혼합조합별 초지 생산성 및 식생구성)

  • Chae, Hyun Seok;Kim, Nam Young;Woo, Jae Hoon;Park, Seol Hwa;Son, Jun Kyu;Back, Kwang Soo;Lee, Wang Shik;Kim, Si Hyun;Hwang, Kyung Jun;Kim, Young Jin;Park, Nam Gun
    • Journal of The Korean Society of Grassland and Forage Science
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    • v.36 no.4
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    • pp.325-332
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    • 2016
  • The objective of this study was to determine the growth characteristics of cool (C1) and warm season grasses (C2) in pastures mixed with C1 and C2 suitable for grazing horses and effect of pastures mixed with tall and short grasses on the intake characteristics of horses. C1 used in this study was Kentucky bluegrass, Redtop (short type grass) and tall type grasses were orchardgrass and tall fescue, respectively. The short type grass used as C2 was Bermudagrass. This study had the following four treatment groups: 1) Treatment 1 (Bermudagrass + Kentucky bluegrass + Redtop) 2) Treatment 2 (Bermudagrass + tall fescue + orchardgrass) 3) Treatment 3 (Kentucky bluegrass + Redtop) 4) Treatment 4 (tall fescue + orchardgrass). There was no winterkilling or lodging problem at an altitude of 200 m. Plant heights in mixed pasture of Treatment 1, 2, 3, and 4 were 53.9, 58.2, 57.5, and 78.1 cm, respectively. Plant height was the highest in Treatment 4. Dry matter yield was in the following order : Treatment 4 > Treatment 3 > Treatment 2 > Treatment 1. In the first investigation regarding vegetation distribution, Bermudagrass ratios among grasses in Treatment 1 and Treatment 2 were 70% and 66.7%, respectively. Overall, other grasses showed poor growth. In the second investigation of vegetation distribution, Bermudagrass ratios among grasses in Treatment 1 and Treatment 2 were 80% and 60.7%, respectively. Crude protein content, neutral detergent fiber content, acid detergent fiber content, digestibility value, and nutritive values were the lowest in Treatment 4, followed by those in Treatment 1, Treatment 2 and Treatment 3.

Conceptual Design of the Three Unit Fixed Partial Denture with Glass Fiber Reinforced Hybrid Composites (Glass fiber 강화 복합레진을 사용한 3본 고정성 국소의치의 개념 설계 연구)

  • Na, Kyoung-Hee;Lee, Kyu-Bok;Jo, Kwang-Hun
    • Journal of Dental Rehabilitation and Applied Science
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    • v.18 no.3
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    • pp.145-155
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    • 2002
  • The results of the present feasibility study are summarized as follows, 1. The three unit bridge of knitted material and UD fibre reinforcement has both the rigidity and the strength against a vertical occlusal load of 75N. 2. Stress concentration at the junctional area between the bridge and the abutments, i.e. between the pontic and the knitted caps was observed. In the case of the bridge with reinforcement straps, it was partly shown that the concentration problem could be improved by simply increasing the fillet size at the area. Further refining in the surface of the junctional area will be needed to ensure a further improvement in the stress distribution. This will require some trade off in the level of the stress and the available space. A parametric study will help to decide the appropriate size of the fillet. 3. Design refinement is a must to improve the stress distribution and realize the most favourable shape in terms of fabrication. The current straight bar with a constant cross section area can be redesigned to a tapered shape. The curve from the dental arch should also be placed on the pontic design. In accordance with design refinement, the resistance of the bridge frame to other load cases should be evaluated. 4. Although not included in the present feasibility study, it is estimated that bridges of the anterior teeth can be made strong enough with the knitted material without further reinforcement using unidirectional materials. In this regard, a feasibility study on design concepts and stress analysis for 3, 4, 5 unit bridge is suggested. 5. Two types of bridge were analysed in terms of fatigue. The safe life design concept, i.e. fatigue design concept, looks reasonable for the bridge where if cracks should form and propagate there is virtually nothing a dentist to do. The bridge must be designed so that no crack will be initiated during the life span. In the case of crowns, however, if constructed with composite resin with knitted materials, it might be possible to repair them, which in general is impossible for crowns of PFM or of metal. Therefore for composite resin crowns, a damage tolerance design concept can be applied and reasonably higher operational stresses can be allowed. In this case, of course, a periodic inspection program should be established in parallel. 6. Parts of future works in terms of structural viewpoint which need to be addressed are summarized as the following: 1) To develop processing technology to accommodate design concepts; 2) More realistic modelling of the bridge and analysis-geometry and loading condition. Thickness variation in the knitted material, taper in the pontic, design for anterior tooth bridge, the effect of combined loads, etc, will need to be included; 3) To develop appropriate design concepts and design goals for the fibre composite FPD aiming at taking the best advantage of knitted materials, including the damage tolerance design concept; 4) To develop testing method and perform test such as static ultimate load test, fatigue test, repair test, etc, as necessary.

On the Milled Wood Lignins Isolated from Hardwood by Progressive Milling (단계적(段階的) 분쇄법(粉碎法)에 의해 조제(調製)된 활엽수(闊葉樹) MWL에 관한 연구(硏究))

  • Cho, Nam Seok
    • Journal of Korean Society of Forest Science
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    • v.45 no.1
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    • pp.62-67
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    • 1979
  • Ultraviolet microscopy of ultrathin sections of wood has proved to be one of the useful means for determining the lignin distribution in the various regions of the cell wall. Also, spectral approach and quantitative analysis of isolated compound middle lamella fraction from birch xylem have revealed that the lignin associated with the vessel secondary wall and middle lamella is composed predominantly of gualacylpropane units. Lignin deposited in the fiber and ray parenchyma secondary walls is composed mostly of syringylpropane units. The middle lamella lignin around fibers and ray cells contains both guaiacyl and syringyl propane quits. On the basis of the results above, this research was carried out to clarify the origin of milled wood lignin (MWL) by analysing the chemical characteristics of ML MWLs extracted at various milling stages. The amount of phenolic hydroxyl-, α-carbonyl-, and methoxyl-group in the MWL's increases the milling time. And progressive mining contributes to the merease of ratio of syringylaldehyde to vanillin(S/V ratio) after nitrobenzene oxidation of MWL. Accordingly, It could be concluded that milled wood lignin extracted at the initial milling stage derives from compound middle lamella region of cell wall, whereas, with progressive milling, lignin of secondary wall of fiber is introduced gradually to milled wood lignin. These results are suggesting that heterogeneous chemical structure of lignins in hardwood exists. Although milled wood lignin at the initial stage seems to have lower molecular weight in comparison with milled wood lignin extracted at final milling stage from the result of Gel-filtration curves, further study would be required on molecular weight distribution of milled wood lignin in future.

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Effects of Green Tea, Cocoon Hydrolysates and Capsulated Components Mixture on Body Fat and Serum Lipid Composition in College Women in Terms of Supplemented Periods (녹차와 실크 펩타이드 및 캡슐 소재 함유 조성물이 여대생들의 복용 기간별 체지방 및 혈청 지질 성상 변화에 미치는 영향)

  • Lee, Sung-Hee;Cho, Byung-Nam;Hong, I-Jin;Lee, Min-Sook;Jew, Sang-Sup;Kim, Dong-Myung;Jin, Dong-Kyu;Rho, Sook-Nyung
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.32 no.5
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    • pp.715-722
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    • 2003
  • This study is to investigate effects of green tea and capsulated components mixture on body fat and serum lipid composition and fat distribution in college women students in terms of supplemented periods. During 3 months of this research, 34 college women students (average age 20.3 yr) were selected as subjects. Nutrient intake was investigated by questionnaire and 24-hr recall method. Anthropolatric assessments of the subjects were investigated by SBIA method (Segmental Bioimpedance Assay, Inbody 3.0). The results were as follows: mean body height was 162.5cm and mean body weight and mean BMI (Body Mass Index, kg/m2) were 57.9kg and 21.9, respectively. Status of carbohydrate intake decreased significantly (p<0.05) and dietary fiber intake increased significantly (p<0.001) after supplementation. WHR (waist-hip ratio) decreased significantly (p<0.05) and body fat and percent body fat decreased significantly after supplementation (p<0.05). Total cholesterol and triglyceride decreased significantly after supplementation (p<0.001). Above results of this study show that green tea, silk peptide and dietary fiber supplementation-added routine diet improves body fat distribution, total cholesterol, triglyceride. Especially, declination of abdominal fat and WHR was notable, since that means diminution of risk factors for obesity and chronic degenerative diseases.

On the High Yield Pulping of Fir by Pressurized Refining (가압(加壓)리화이닝법(法)에 의한 젓나무의 고수율(高收率)펄프 제조(製造)에 관한 연구(研究))

  • Cho, Nam Seok;Jo, Byoung Muk
    • Journal of Korean Society of Forest Science
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    • v.53 no.1
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    • pp.44-55
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    • 1981
  • Neutral sulfite precooked fir chips were refined in the Asplund Laboratory Defibrator at various temperature (20C, 120C and 180C). The effects of refining temperatures on the physical property and morphological structure of the resulting pulps were discussed. Yields of precooked chips (84%, 92% and 100%) and refining temperature affected remarkably the yield of refined pulp, its beatability, sheet strength and morhphological characteristics. Pulp yield and beatability decreased with increasing refining temperature. Fiber surface of unbeaten pulp from precooked chips of 84% yield was to some extent covered by the secondary wall, while that of the pulp form precooked yield of 92% by the compound middle lamella. In the case of uncooked chips, fibers were damaged heavily, and the exposed fiber surface resulted from the equal amount of the secondary wall and the compound middle lamella. In the case of pulps prepared from precooked chips of higher yields (92% and 100%), sheet strength increased linearly as sheet density increased. But at the same sheet density, pulp from lower precooked yield (84%) had better sheet strength after open discharge refining as compared to pressurized refining, because pulp from the former had much amounts of fines fraction of higher water retention value than the latters. And there was observed a little difference in fiber length distribution but nearly similar in its morphology with increasing refining temperature.

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The changed expression of CGRP immune-positive nerve in the periodontal ligament of rat molar during tooth movement (실험적 치아이동에 의한 백서 치주인대내 CGRP 면역 양성 신경섬유의 변화)

  • Sung, Jung-Ok;Park, Hyo-Sang;Bae, Yong-Chul;Sung, Jae-Hyun
    • The korean journal of orthodontics
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    • v.26 no.5 s.58
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    • pp.581-590
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    • 1996
  • Bone resorptiion was predominate in compression site, bone formation in tension site of periodontal ligament during tooth movement. The biologic response at compressiion site was different from tension site. Thus the CGHP immuno-positive nerve fiber will respond differently to mechanical force according to the area( compression or tension site). The purpose of this study was to investigate this response of CGRP immune-positive nerve fiber in the periodontal ligament according to the duration of applied force and the area (compression or tension site) during experimental tooth movement. The experimental animals were 7 week old male rat (approximately 200 gm). The orthodontic force was applied mesially to the right maxillary molar using the Ni-Ti coil spring during 12hours, 1, 3, 7, and 120days. Immunohistochemical staining using antibody against CGRP was performed after sacrifice. The results were as follows. The CGRP immune-positive nerve bundle showed reduced immunoreactivity and nerve fibers reduced in density after application of orthodontic force for 12 hours and 1day. The CGRP immune-positive nerve fibers showed many thin branches at the apical periodontal ligament after application of force for 3 days as compared with normal. The tension site in the apical periodontal ligament showed more branches than the compression site. In 7 day group, the CGRP immune-positive nerve fibers increased in terms of the number and had many thin branches in the apical periodontal ligament. The tension site had more branches than the compression site. In 12 day group, the CGRP immune-positive nerve fibers showed similar distribution to normal control at compression site of apical periodontal ligament, but the fibers at the tension site increased in number. The CGRP immuno-positive nerve fibers showed more increased at tension site than compression site after application of orthodontic force. Therefore it seems to have some relation to the bone remodeling besides the local inflammatory process.

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Nutritional Adequacy of Target Pattern in Dietary Guidance System - Dietary Reference Intakes for Koreans 2015 - (식사구성안 권장식사패턴의 영양 적정성 평가 - 2015 한국인 영양소 섭취기준 -)

  • Kim, Youngnam
    • Journal of Korean Home Economics Education Association
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    • v.29 no.3
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    • pp.77-88
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    • 2017
  • Nutritional adequacy of Target patterns in Dietary Guidance System were evaluated. Study subjects were 18 Target patterns designed for 2 children groups, 4 adolescent and 4 adult male and female groups in Dietary Reference Intakes for Koreans 2015. Nutrients examined were 4 macro-nutrients(protein, fat, carbohydrate, and dietary fiber), 5 minerals(Ca, P, Fe, Na, and K), and 5 vitamins(vitamin A, thiamin, riboflavin, niacin, and vitamin C). Energy and nutrients contents were calculated based upon assigned multiples of single serving in Target pattern and Representative Food Composition Table by Excel program. Among the 18 Target patterns, only 5 were mean adequacy ratio(MAR) of 1.0, fulfilled the expectations of Dietary Guidance System. Protein and Na contents were more than dietary reference intakes(DRI) in all 18 Target patterns. Dietary fiber, Ca, and K were deficient nutrient in 15, 10, and 9 Target patterns, respectively. The units of vitamin A were not same in Target pattern and DRI, retinol equivalent(RE) in Target pattern and retinol activity equivalent(RAE) in DRI. When calculate RE content of vitamin A in Target pattern to RAE content, 15 Target patterns did not reach to DRI of vitamin A. The Target pattern of elderly women showed the lowest mean adequacy ratio(MAR), 7 nutrients were less than DRI, need to be revised. Average energy contribution ratio of protein, fat, and carbohydrate were 16.04%, 24.35%, and 60.91%, respectively, fulfilled the adequate acceptable macro-nutrient distribution range(AMDR). To improve the nutritional inadequacy of dietary fiber, Ca, K, and vitamin A in Target pattern, effective mean may be the increasing vegetable group assignment. Also decreasing the meat fish egg legume group assignment in some Target pattern may be the way of preventing of protein overconsumption. The energy in adequate amount for condiment use also need to be considered.