• Smart Structures and Systems
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• v.21 no.2
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• pp.187-194
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• 2018

This paper focuses on the $H_{\infty}$ filter design problem for offshore steel jacket platforms. Its objective is to design a full-order state observer for offshore platforms in presence of unknown disturbances. To make the method more practical, it is assumed that the measured variables are available at discrete-time instants with time-varying sampling time intervals. By modelling the sampling intervals as a bounded time-varying delay, the estimation error system is expressed as a time-delay system. As a result, the addressed problem can be transformed to the problem of stability of dynamic error between the system and the state estimator. Then, based on the Lyapunov-Krasovskii Functional (LKF), a stability criterion is obtained in the form of Linear Matrix Inequalities (LMIs). According to the stability criterion, a sufficient condition on designing the state estimator gain is obtained. In the end, the proposed method is applied to an offshore platform to show its effectiveness.

• Smart Structures and Systems
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• v.26 no.3
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• pp.291-309
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• 2020

To study oceanic and meteorological problems related to climate change, Korea has been operating several ocean research stations (ORSs). In 2011, the Gageocho ORS was attacked by Typhoon Muifa, and its structural members and several observation devices were severely damaged. After this event, the Gageocho ORS was rehabilitated with 5 m height to account for 100-yr extreme wave height, and the vibration measurement system was equipped to monitor the structural vibrational characteristics including natural frequencies and modal damping ratios. In this study, a mass reallocation method is presented for structural model updating of the Gageocho ORS based on the experimentally identified natural frequencies. A preliminary finite element (FE) model was constructed based on design drawings, and several of the candidate baseline FE models were manually built, taking into account the different structural conditions such as corroded thickness. Among these candidate baseline FE models, the most reasonable baseline FE model was selected by comparing the differences between the identified and calculated natural frequencies; the most suitable baseline FE model was updated based on the identified modal properties, and by using the pattern search method, which is one of direct search optimization methods. The mass reallocation method is newly proposed as a means to determine the equivalent mass quantities along the height and in a floor. It was found that the natural frequencies calculated based on the updated FE model was very close to the identified natural frequencies. In conclusion, it is expected that these results, which were obtained by updating a baseline FE model, can be useful for establishing the reference database for jacket-type offshore structures, and assessing the structural integrity of the Gageocho ORS.

• Smart Structures and Systems
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• v.18 no.6
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• pp.1203-1215
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• 2016

When strain sensing cables are under long-term stress and cyclic loading, creep may occur in the jacket material and each layer of the cable structure may slide relative to other layers, causing fatigue in the cables. This study proposes a device for testing the fatigue characteristics of three types of cables operating under different conditions to establish a decay model for observing the patterns of strain decay. The fatigue characteristics of cables encased in polyurethane (PU), GFRP-reinforced, and wire rope-reinforced jackets were compared. The findings are outlined as follows. The cable strain decayed exponentially, and the decay process involved quick decay, slow decay, and stabilization stages. Moreover, the strain decay increased with the initial strain and tensile frequency. The shorter the unstrained period was, the more similar the initial strain levels of the strain decay curves were to the stabilized strain levels of the first cyclic elongation. As the unstrained period increased, the initial strain levels of the strain decay curves approached those of the first cyclic elongation. The tested sensing cables differed in the amount and rate of strain decay. The wire rope-reinforced cable exhibited the smallest amount and rate of decay, whereas the GFRP-reinforced cable demonstrated the largest.

• Journal of Fashion Business
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• v.9 no.3
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• pp.8-21
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• 2005

The purpose at this study was to analyze and to position the clothing images at women's formal wear brands carried by at least two department stores in Daejon, for providing data for a basic marketing strategy for fashion manufacturers and distributors. The results tram the study were as tallows; The brand that showed the highest classic image was 'BCBG'(83.6%), the brand that showed the highest feminine image was 'Obzee' (80.2%), the brand that showed the highest character image was 'Doho' (84.1%), and the brand that showed the highest mannish image was 'F.Station' (64.1%). On the brands image positioning map, brands, such as 'Deco', 'Mine', 'Time', and 'Anne Klein', lying on or near the point of intersection (where the vertical and horizontal axes meet) showed 4 types. They were 'smart & chic cluster', 'charming & luxury cluster', 'character elegance cluster', and 'sportive elegance cluster' that showed compound images. These clusters would be differentiated tram young casual lines by emphasizing the brands' shape and cut, higher quality fabrics and materials, and elegant and graceful colors. Analysis of target ages and tweed jacket prices for brands carried by at least two department stores showed that the target was between 23 and 50, and that the prices range from 198,000 won to 460,000 won.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2008.10a
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• pp.106-109
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• 2008

The aim of this study is to develop a model of layering system for future soldier system. Future soldier has been supposed to carry various digital devices embedded into the combat uniform. The combat uniform must be developed to be fit to soldier's body and movement, and can be felt comfortable to soldier. The Uniform must be studied in ergonomic and physiological component because it is different from the present one. It has many devices inside, so there are some unknown barriers to set the devices on to the body. For making the ergonomic aspect of future combat suits clear, the movement of the body was researched. The size of arms(3 parts), torsos(4 parts), and legs(3 parts) of people were measured by movement. Many dots were drawn on the testees' bodies every 3cm. Each time they made compulsory poses, the distances between dots be measured and analyzed. For making the physiological aspect of future combat suits clear, the thermo-map and sweating map of body were made. The 3 maps - movement, thermo and sweating- were overlapped. The devices for future soldier were arranged on the overlapped map considering relations between devices. The final layering system developed on the arrangement of devices.

• Smart Structures and Systems
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• v.33 no.3
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• pp.177-188
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• 2024

The fatigue-induced sequential failure of a structure having structural redundancy requires system-level analysis to account for stress redistribution. System reliability-based design optimization (SRBDO) for preventing fatigue-initiated structural failure is numerically costly owing to the inclusion of probabilistic constraints. This study incorporates the Branch-and-Bound method employing system reliability Bounds (termed the B³ method), a failure-path structural system reliability analysis approach, with a metaheuristic optimization algorithm, namely grey wolf optimization (GWO), to obtain the optimal design of structures under fatigue-induced system failure. To further improve the efficiency of this new optimization framework, an additional bounding rule is proposed in the context of SRBDO against fatigue using the B³ method. To demonstrate the proposed method, it is applied to complex problems, a multilayer Daniels system and a three-dimensional tripod jacket structure. The system failure probability of the optimal design is confirmed to be below the target threshold and verified using Monte Carlo simulation. At earlier stages of the optimization, a smaller number of limit-state function evaluation is required, which increases the efficiency. In addition, the proposed method can allocate limited materials throughout the structure optimally so that the optimally-designed structure has a relatively large number of failure paths with similar failure probability.

• Smart Structures and Systems
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• v.15 no.2
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• pp.355-373
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• 2015

An optimal sensor placement (OSP) method based on structural subsection technique (SST) and model reduction technique was proposed for modal identification of truss structures, which was conducted using genetic algorithm (GA). The constraints of GA variables were determined by SST in advance. Subsequently, according to model reduction technique, the optimal group of master degrees of freedom and the optimal objective function value were obtained using GA in a case of the given number of sensors. Correspondingly, the optimal number of sensors was determined according to optimal objective function values in cases of the different number of sensors. The proposed method was applied on a scaled jacket offshore platform to get its optimal number of sensors and the corresponding optimal sensor layout. Then modal kinetic energy and modal assurance criterion were adopted to evaluate vibration energy and mode independence property. The experiment was also conducted to verify the effectiveness of the selected optimal sensor layout. The results showed that experimental modes agreed reasonably well with numerical results. Moreover the influence of the proposed method using different optimal algorithms and model reduction technique on optimal results was also compared. The results showed that the influence was very little.

• Journal of Fashion Business
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• v.6 no.5
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• pp.27-40
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• 2002

The purpose of this thesis is presenting desirable design of uniform which could reflect high school girls' demands with the researches on their consciousness of fashion and actual state of uniforms. Methods to accomplish this research include first, examinationson characteristics of high school girls and their consciousness of fashion with relevant articles, second, interviews with designers from major domestic uniform brands - ELITE, IVY, SMART - and third, analysis on related internet sites. Practical researches are followed by design analysis and proposal of improvement on high school girls' uniform, accompanied by collection of photographs from field studies, major uniform brands' shops and uniform related internet sites. Korean high school girls in the digital era are able to express themselves in each different fashion with own individuality, preference or intention, as they are particularly interested in clothes or their appearances. Their consciousness of fashion became visible in a shape of negative attitude and dissatisfaction with uniforms due to its out-of-date design, lack of features and inconvenience in action. Besides more than half of high school girls already experienced reforming it for better looks. As a result of current analysis on references of uniform designs, various levels of refinement were noticed even in uniform of similar details, design, fabric textile and color due to differences on size & length of jacket collar, dart, cutting line, size of details, decorative line, easiness in fit, length of clothes, and etc. To provide students of more refined and desired designs which reflect their demands, current uniforms are to begin acquiring delicate changes with present vogue and feature such as size of details, silhouette, cutting line, decorative line and etc. In addition newly designed uniforms are to present desirable design with image of refinement and neat as they actively comprehend students' needs within its symbolic, functional, economic and aesthetic characteristics by nature.

• Fashion & Textile Research Journal
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• v.23 no.2
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• pp.273-289
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• 2021

This study aimed to examine the appearance of heated clothing in relation to fashion trends by analyzing constructive components of clothing using product images and actual products. A total of 91 images of domestic and foreign heated clothing products were collected, and a product analysis conducted with six parameters of item classification, namely, concept and image, silhouette, color, number of heating elements, and heating parts. In addition, an in-depth analysis was carried out with 11 products among them, while focusing on further detailed components of the design and heating system. As a result, the overall exterior design of domestic products has been changed from outdoor clothing to daily clothing reflecting the current design trend. Compared with domestic products, foreign products showed a diverse assortment and a greater number of heating regions per individual item of clothing. The current heating system commonly consists of a heating element, power source, controller board, and wires, although the existence and type of switches differed from product to product. To develop a more efficiently heated clothing to expand the market, the design, ease of use, safety, consumer preference, heating functionality, and durability should be considered. Along with design recommendations for future heated clothing, this study also provides a practical guide to the technical aspects of the design of the components of heated clothing.

• Smart Structures and Systems
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• v.29 no.5
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• pp.653-660
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• 2022

Gravel scattering that is generated during operation of high-speed railway vehicle is cause to damage of vehicle such as windows, axle protector and so on. Especially, those are frequently occurred in winter season when snow ice is generated easily. Above all, damage of vehicle windows has not only caused maintenance cost but also increased psychological anxiety of passengers. Various methods such as heating system using copper wire, heating jacket and heating air are applied to remove snow ice generated on the under-body of vehicle. However, the methods require much run-time and man power which can be low effectiveness of work. Therefore, this paper shows that large-area heating system was developed based on heating coat in order to fundamentally prevent snow ice damage on high-speed railway vehicle in the winter season. This system gives users high convenience because that can remotely control the heating system using IoT-based wireless communication. For evaluating the applicability to railroad sites, a field test on an actual high-speed railroad operation was conducted by applying these techniques to the brake cylinder of a high-speed railroad vehicle. From the results, it evaluated how input voltage and electric power per unit area of the heating specimen influences exothermic performance to draw the permit power condition for icing. In the future, if the system developed in the study is applied at the railroad site, it may be used as a technique for preventing all types of damages occurring due to snow ice in winter.