• Title/Summary/Keyword: Structural Weight

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The Structural Equivalence and Role Equivalence of Container Ports in Asia-Europe Container Shipping Networks (아시아-유럽 컨테이너 해운 네트워크 구성 항만의 구조적 등위성과 역할 등위성)

  • Lee, Sang-Yoon
    • Journal of Korea Port Economic Association
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    • v.32 no.2
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    • pp.105-122
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    • 2016
  • Numerous studies have evaluated the status of seaports. However, the majority of the research has approached this topic from the view-point of port capabilities, including locational advantage, infrastructure, productivity, and competitiveness. The position and/or role of a port can be understood more precisely and comprehensively by considering the interconnectivity among ports making up enormous global transportation networks. The main objective of this study is to compare the status of 82 container ports on the trunk shipping routes between Asia and Europe by applying the concepts of structural equivalence and role equivalence proposed by the social network analysis method. Network similarities and differences among competing ports in the regions are assessed by analysing their structural equivalence. Furthermore, the hierarchical structures of the ports located on the trunks between Asia and Northwest Europe and between Asia and the Mediterranean are constructed by evaluating their role equivalence. The results of this empirical research shows that Singapore and Rotterdam possess the most significant positions on the ocean corridors between Asia and Northwest Europe. Singapore also holds a leading position on the Asia-Mediterranean shipping route. Lastly, no ports located in the Middle East or Mediterranean regions have an equivalent weight to those of Rotterdam, Hamburg, Antwerp on the Asia-Northwest Europe route.

The Structural Safety Diagnosis of Three-Story Pagoda in Bulkuk Temple Using the Probability of Failure. (암석의 파괴 확률 분석을 통한 불국사 삼층석탑 구조 안전 진단)

  • Seo, Man-Cheol;Song, In-Seon;Choe, Hui-Su
    • Journal of the Korean Geophysical Society
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    • v.4 no.1
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    • pp.57-69
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    • 2001
  • We have carried out a nondestructive close examination for the purpose of the structural safety diagnosis of the Three-Story Pagoda(Seokga Pagoda) in Bulkuk temple in the city of Kyungju, Kyungbuk, Korea. Ultrasonic wave velocities were measured at 456 points of the pagoda comprising 44 blocks to estimate the mechanical properties of rock blocks constituting the pagoda. The measured velocities have the range of 1217 to 4403 m/sec with the average of 3227 m/sec. The empirical relationship between the ultrasonic velocity and the uniaxial compressive strength yielded the estimation of strength of each block, ranging from 134 to 844 kg/cm^2 and averaging 463 kg/cm^2. With an assumption that the strength of each block is described as a random variables having a normal distribution, we calculated the probability of failure of rock blocks of the pagoda. Our investigation revealed that the probability of the structural failure due to the weight of higher blocks is very low. However, the probability of partial failure around contact area is substantial, which is consistent with the appearance that edges and the corners of some blocks were broken off. The platform under the body of the pagoda appeared to be structurally weak as the probability of tensile failure of the lower platform is up to 18%, and diagonal fractures are shown where the probability of failure is high.

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Reliability-Based Design Optimization of 130m Class Fixed-Type Offshore Platform (신뢰성 기반 최적설계를 이용한 130m급 고정식 해양구조물 최적설계 개발)

  • Kim, Hyun-Seok;Kim, Hyun-Sung;Park, Byoungjae;Lee, Kangsu
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.34 no.5
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    • pp.263-270
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    • 2021
  • In this study, a reliability-based design optimization of a 130-m class fixed-type offshore platform, to be installed in the North Sea, was carried out, while considering environmental, material, and manufacturing uncertainties to enhance its structural safety and economic aspects. For the reliability analysis, and reliability-based design optimization of the structural integrity, unity check values (defined as the ratio between working and allowable stress, for axial, bending, and shear stresses), of the members of the offshore platform were considered as constraints. Weight of the supporting jacket structure was minimized to reduce the manufacturing cost of the offshore platform. Statistical characteristics of uncertainties were defined based on observed and measured data references. Reliability analysis and reliability-based design optimization of a jacket-type offshore structure were computationally burdensome due to the large number of members; therefore, we suggested a method for variable screening, based on the importance of their output responses, to reduce the dimension of the problem. Furthermore, a deterministic design optimization was carried out prior to the reliability-based design optimization, to improve overall computational efficiency. Finally, the optimal design obtained was compared with the conventional rule-based offshore platform design in terms of safety and cost.

Evaluation of Structural Performance of 3D Printed Composite Rudder according to Internal Topology Shape (내부 위상 형상에 따른 3D 프린트 복합재 방향타의 구조 성능 평가)

  • Young-Jae Cho;Hyoung-Seock Seo;Hui-Seung Park
    • Composites Research
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    • v.36 no.6
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    • pp.454-460
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    • 2023
  • Recently, regulations on greenhouse gas emissions have been strengthened, and the International Maritime Organization (IMO) has been strengthening greenhouse gas regulations with a goal of net 'zero' emissions by 2050. In addition, in the shipbuilding/offshore sector, it is important to reduce operating costs, such as improving propulsion efficiency and lightening structures. In this regard, research is currently being conducted on topology optimization using 3D printed composite materials to satisfy structural lightness and high rigidity. In this study, three topology shapes (hexagonal, square, and triangular) were applied to the interior of a rudder, a ship structure, using 3D printed composite materials. Structural analysis was performed to determine the appropriate shape for the rudder. CFD analysis was performed at 10° intervals from 0° to 30° for each rudder angle under the condition of 8 knots, and the load conditions were set based on the CFD analysis results. As a result of the structural analysis considering the internal topology shape of the rudder, it was confirmed that the triangular, square, and hexagonal topology shapes have excellent performance. The rudder with a square topology shape weighs 78.5% of the rudder with a triangular shape, and the square topology shape is considered to superior in terms of weight reduction.

Structural Optimization and Improvement of Initial Weight Dependency of the Neural Network Model for Determination of Preconsolidation Pressure from Piezocone Test Result (피에조콘을 이용한 선행압밀하중 결정 신경망 모델의 구조 최적화 및 초기 연결강도 의존성 개선)

  • Kim, Young-Sang;Joo, No-Ah;Park, Hyun-Il;Park, Sol-Ji
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.3C
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    • pp.115-125
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    • 2009
  • The preconsolidation pressure has been commonly determined by oedometer test. However, it can also be determined by insitu test, such as piezocone test with theoretical and(or) empirical correlations. Recently, Neural Network (NN) theory was applied and some models were proposed to estimate the preconsolidation pressure or OCR. It was already found that NN model can come over the site dependency and prediction accuracy is greatly improved when compared with present theoretical and empirical models. However, since the optimization process of synaptic weights of NN model is dependent on the initial synaptic weights, NN models which are trained with different initial weights can't avoid the variability on prediction result for new database even though they have same structure and use same transfer function. In this study, Committee Neural Network (CNN) model is proposed to improve the initial weight dependency of multi-layered neural network model on the prediction of preconsolidation pressure of soft clay from piezocone test result. Prediction results of CNN model are compared with those of conventional empirical and theoretical models and multi-layered neural network model, which has the optimized structure. It was found that even though the NN model has the optimized structure for given training data set, it still has the initial weight dependency, while the proposed CNN model can improve the initial weight dependency of the NN model and provide a consistent and precise inference result than existing NN models.

Strength Properties of Porous Concrete Containing Natural Fine Aggregate and Bottom Ash Aggregate (천연 잔골재와 바텀애시 골재를 활용한 다공성 콘크리트의 강도 특성)

  • Seung-Tae Jeong;Ji-Hun Park;In-Hwan Yang
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.11 no.3
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    • pp.192-201
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    • 2023
  • In this paper, the strength properties of porous concrete containing natural fine aggregates and bottom ash aggregates were investigated, The material properties of natural fine aggregates and bottom ash were identified then used as aggregates for porous concrete. The water-binder ratio was constant at 0.25, and the com paction level of 0.5, 1.5, and 2.5 MPa was applied to produce a porous concrete specimen. Test of unit weight, ultrasonic velocity, compressive strength, and flexural tensile strength were perform ed and analyzed. The unit weight, ultrasonic velocity, com pressive strength, and flexural tensile strength increased as the compaction level increased and also the replacement rate of bottom ash with sand(fine aggregate) increased. In addition, through regression analysis, the correlation between the unit weight, compressive strength, and flexural tensile strength of bottom ash porous concrete was presented. Unit weight and strength properties are proportional to each other and showed an increasing correlation. In addition, the correlation coefficient (R2) value of regression analysis was calculated based on the experimental results of this study and those of other research papers.

Biodegradation effect of cross-cultivated fungi and edible mushrooms on plastic films (식용버섯과 진균 교차 배양을 활용한 플라스틱 필름의 생물학적 분해효과)

  • Doo-Ho Choi;Eunji Lee;Gi-Hong An;Kang-Hyo Lee
    • Journal of Mushroom
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    • v.22 no.1
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    • pp.31-36
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    • 2024
  • Plastics are widely used in industries in human society and because of their structural stability, degradation is a serious global issue. To estimate the degradation of plastic, 31 edible mushrooms were cultured with the selected plastic films (polyethylene [PE], polystyrene [PS], and poly(ethylene terephthalate) [PET]) for 3 months at 25 ℃. Measuring the weight of the films showed that four species of mushrooms, namely Porostereum spadiceum, Ganoderma lucidum, Coprinellus micaceus, and Pleurotus ostreatus, exhibited the highest degrees of plastic degradation. In addition, the mushrooms and fungi that exhibited the most significant plastic degradation were cross-cultured to promote this degradation. As a result, cross-cultivation of G. lucidum and Aspergillus niger showed a weight loss of 2.49% for the PET film. For the PS film, Aspergillus nidulans showed a weight loss of 4.06%. Cross-cultivation of A. nidulans and C. micaceus, which showed a weight loss of 2.95%, was noted as an alternative for PS biodegradation, but is harmful to humans. These bio-degradation effects of edible mushroom will contribute to the development of alternatives for eco-friendly plastic degradation.

Study on Bullet-Proof Performance of Multi-Layered Hybrid Armor Against 9mm FMJ Projectile (9mm 권총탄 위협을 받는 적층구조의 방탄성능 연구)

  • Lee, Jong-Gu;Kim, Siho;Kim, Gunin;Cho, Maenghyo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.6
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    • pp.487-495
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    • 2012
  • In order to prevent the high velocity bullet from penetration, aluminum alloy and RHA(Rolled Homogeneous Armour) steel, which have a high tensile and compressive strength, are usually used as the bullet-proof armor material. Although these materials have a good bullet proof performance, but not an area density which is a weight increasing factor of bullet-proof armor. Therefore, Mg(magnesium) alloy is a promising substitute for the traditional bullet-proof armor material due to the relatively low areal density. The spatial efficiency of Mg alloy, however, is inferior to the traditional material's, which is a volume(thickness) increasing factor of bullet-proof armor. In this study, we select the multi-layered hybrid armor which consist of Ceramic, with a high strength; Mg alloy, with a low areal density; Kevlar, with a high tensile strength-to-weight ratio; in order to make up for the poor spatial efficiency of Mg alloy. By predicting V50 of the multi-layered armor against 9mm FMJ(Full Metal Jarket). we show that the multi-layered armor have the capability in improving bullet-proof performance in the respect of the areal density, but also the spatial efficiency.

Elaborate Image Quality Assessment with a Novel Luminance Adaptation Effect Model (새로운 광적응 효과 모델을 이용한 정교한 영상 화질 측정)

  • Bae, Sung-Ho;Kim, Munchurl
    • Journal of Broadcast Engineering
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    • v.20 no.6
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    • pp.818-826
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    • 2015
  • Recently, objective image quality assessment (IQA) methods that elaborately reflect the visual quality perception characteristics of human visual system (HVS) have actively been studied. Among those characteristics of HVS, luminance adaptation (LA) effect, indicating that HVS has different sensitivities depending on background luminance values to distortions, has widely been reflected into many existing IQA methods via Weber's law model. In this paper, we firstly reveal that the LA effect based on Weber's law model has inaccurately been reflected into the conventional IQA methods. To solve this problem, we firstly derive a new LA effect-based Local weight Function (LALF) that can elaborately reflect LA effect into IQA methods. We validate the effectiveness of our proposed LALF by applying LALF into SSIM (Structural SIMilarity) and PSNR methods. Experimental results show that the SSIM based on LALF yields remarkable performance improvement of 5% points compared to the original SSIM in terms of Spear rank order correlation coefficient between estimated visual quality values and measured subjective visual quality scores. Moreover, the PSNR (Peak to Signal Noise Ratio) based on LALF yields performance improvement of 2.5% points compared to the original PSNR.

Evaluation on the Effect of Depth Buried Pipeline and Refilling Materials on Pavement Performance (도로하부 매설관의 매설심도 및 되메우기 재료가 포장체에 미치는 영향 평가)

  • Baek, Cheolmin;Kim, Yeong Min;Kwon, Soo-Ahn;Hwang, Sung Do;Kim, Jin Man
    • International Journal of Highway Engineering
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    • v.15 no.2
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    • pp.105-112
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    • 2013
  • PURPOSES : Compared to the criteria from advanced countries, Korea has conservative criteria for the buried depth of pipeline (about 30~70cm deeper) causing the waste of cost and time. Therefore, this research investigated the effect of various buried depths of pipeline on pavement performance in order to modify the criteria to be safe but economical. In addition, a recycled aggregate which is effective in economical and environmental aspect was evaluated to be used as a refilling material. METHODS : In this study, total 10 pilot sections which are composed with various combinations of pavement structure, buried depth of pipeline, and refilling material were constructed and the telecom cable was utilized as a buried pipeline. During construction, LFWD (Light Falling Weight Deflectometer) tests were conducted on each layer to measure the structural capacity of underlying layers. After the construction is completed, FWD (Falling Weight Deflectometer) tests and moving load tests were performed on top of the asphalt pavement surface. RESULTS : It was found from the LFWD and FWD test results that as the buried depth decrease, the deflections in subbase and surface layer were increased by 30% and 5~10%, respectively, but the deflection in base layer remained the same. In the moving load test, the longitudinal maximum strain was increased by 30% for 120mm of buried depth case and 5% for 100mm of buried depth case. Regarding the effect of refilling material, it was observed that the deflections in subbase and surface layer were 10% lager in recycled aggregate compared to the sand material. CONCLUSIONS : Based on the testing results, it was found that the change in buried depth and refiliing material would not significantly affect the pavement performance. However, it is noted that the final conclusion should be made based on an intensive structural analysis for the pavement under realistic conditions (i.e., repeated loading and environmental loading) along with the field test results.