• Journal of Powder Materials
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• v.30 no.6
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• pp.509-515
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• 2023

Lead-free perovskite ceramics, which have excellent energy storage capabilities, are attracting attention owing to their high power density and rapid charge-discharge speed. Given that the energy-storage properties of perovskite ceramic capacitors are significantly improved by doping with various elements, modifying their chemical compositions is a fundamental strategy. This study investigated the effect of Zn doping on the microstructure and energy storage performance of potassium sodium niobate (KNN)-based ceramics. Two types of powders and their corresponding ceramics with compositions of (1-x)(K,Na)NbO₃-xBi(Ni_2/3Ta_1/3)O₃ (KNN-BNT) and (1-x)(K,Na)NbO₃-xBi(Ni_1/3Zn_1/3Ta_1/3)O₃ (KNN-BNZT) were prepared via solid-state reactions. The results indicate that Zn doping retards grain growth, resulting in smaller grain sizes in Zn-doped KNN-BNZT than in KNN-BNT ceramics. Moreover, the Zn-doped KNN-BNZT ceramics exhibited superior energy storage density and efficiency across all x values. Notably, 0.9KNN-0.1BNZT ceramics demonstrate an energy storage density and efficiency of 0.24 J/cm³ and 96%, respectively. These ceramics also exhibited excellent temperature and frequency stability. This study provides valuable insights into the design of KNN-based ceramic capacitors with enhanced energy storage capabilities through doping strategies.

• Journal of architectural history
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• v.32 no.5
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• pp.81-94
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• 2023

Haeju was home to the Hwanghae-do Provincial Office and a hub for supporting the northwestern regions of Korea. Local commerce expanded in Haeju during the late Joseon period based on its abundant resources and regional products, leading it to evolve into a large city. King Seonjo temporarily resided in Haeju while seeking refuge from the Japanese Invasions of Korea, and Yi Yi (sobriquet: Yulgok) secluded himself in Seokdam in Haeju in his later years. King Seonjo's residence in Haeju and Yi Yi's retirement there boosted interest in the city among the literati and influenced its places of scenic beauty. The development of its local history and literary achievements were documented in a wide variety of historical records and visual materials. Eight scenic views in Haeju became famous through a poem written by Seong Su-ik in the late sixteenth century. Around the mid-eighteenth century, eight new scenic views became popular. Local officials and travelers from other regions produced a vast body of prose and poetry focusing on the landscape and society of Haeju, playing a crucial role in raising awareness of its scenic attractions. Most surviving visual materials related to Haeju were created in and after the nineteenth century. Many of them illustrate both landscapes and the everyday lives of people. Among them, paintings of scenic spots created by Jeong Seon (sobriquet: Gyeomjae), who never actually visited Haeju in person, raises some of the issues posed by relying on indirect materials. In contrast, Eight Scenic Views of Haeju, which is presumed to have been produced by a local painter, appears to have accurately highlighted the characteristics of each scenic spot. Moreover, Haejudo, a folding screen presenting a panoramic view of Haeju, incorporates content from paintings depicting eight scenic views, in this case Eight Scenic views of Haeju. This practice can be observed in visual materials of other provincial cities.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.74-77
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• 2015

The cure kinetics of a neat epoxy system and epoxy/silica composite were investigated by DSC analysis. A cycloaliphatic type epoxy resin was diglycidyl 1,2-cyclohexanedicarboxylate and curing agent was anhydride type. To estimate kinetic parameters, the Kissinger equation was used. The activation energy of the neat epoxy system was 88.9 kJ/mol and pre-exponential factor was 2.64×10¹² min⁻¹, while the activation energy and pre-exponential factor for epoxy/silica composite were 97.4 kJ/mol and 9.21×10¹² min⁻¹, respectively. These values showed that the silica particles have effects on the cure kinetics of the neat epoxy matrix.

• Transactions on Electrical and Electronic Materials
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• v.16 no.2
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• pp.82-85
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• 2015

Mechanical and electrical properties of epoxy/silica microcomposites were investigated. The cycloaliphatic- type epoxy resin was diglycidyl 1,2-cyclohexanedicarboxylate and the curing agent was of an anhydride type. To measure the glass transition temperature (Tg), dynamic differential scanning calorimetry (DSC) analysis was carried out, and tensile and flexural tests were performed using a universal testing machine (UTM). Electrical breakdown strength, the most important property for electrical insulation materials, and insulation breakdown strength were also tested. The microcomposite with 60 wt% microsilica showed maximum values in mechanical and electrical properties.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.3
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• pp.57-68
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• 2012

In this study, designs of the high efficiency composite propeller blade for a high speed turboprop aircraft, which will be used for a next generation regional commercial aircraft in Korea, are performed. Both the vortex theory and the blade element theory are used for preliminary aerodynamic design and performance analysis of the propeller. Then the aerodynamic design result is confirmed through performance analysis using a commercial CFD code, ANSYS. The carbon/epoxy composite materials is used, and the skin-spar-foam sandwich type structure is adopted for improvement of lightness and structural stability. Finally, it is investigated that the proposed propeller blade has high efficiency and structural safety through both aerodynamic and structural analysis and experimental test of a prototype propeller blade.

• Advances in concrete construction
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• v.10 no.1
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• pp.71-79
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• 2020

Ultra-high-performance concrete (UHPC) is recognized as a promising material in future civil engineering projects due to its outstanding mechanical and durability properties. However, the lack of local UHPC materials and official standards, especially for prestressed UHPC structures, has limited the application of UHPC. In this research, a large-scale prestressed bridge girder composed of nonproprietary UHPC is produced and investigated. This work has two objectives to develop the mixing procedure required to create UHPC in large batches and to study the flexural behavior of the prestressed girder. The results demonstrate that a sizeable batch of UHPC can be produced by using a conventional concrete mixing system at any precast factory. In addition, incorporating local aggregates and using conventional mixing systems enables regional widespread use. The flexural behavior of a girder made by this UHPC is investigated including flexural strength, cracking pattern and development, load-deflection curve, and strain and neutral axis behaviors through a comprehensive bending test. The experimental data is similar to the theoretical results from analytical methods based on several standards and recommendations of UHPC design.

• Journal of Chest Surgery
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• v.26 no.5
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• pp.343-348
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• 1993

Growth of suture line and anastomosis is required for long-term success after the tracheal and bronchial surgery in infant and pediatric patient. We used various suture materials in these cases, but the results were differ. To select the adequate suture material in tracheal surgery, we tried next. Tracheal anastomoses were performed in 150 Sprague Dawley rats, aged 4 to 8 [mean 5.8] weeks and weight 62 to 106[mean 83.6] gram, to compare polydioxanone[PDS] 7-0, polyglactin 910[Vicryl]7-0, and polypropylene [prolene] 8-0 suture materials. In 150 rats, only 29[20%] were lived over 300 days, and the weight was 250 to 320[mean 289.5]gram. Cross sectional area of the anastomoses and two or three tracheal rings below anastomosis site were measured under microscope, and calculated and compared as Hsieh`s equition. Cross-sectional area,anastomosis site/normal site 100, were 89.4 $\pm$ 5.34% in PDS group[n=9], 75.7 $\pm$ 6.06% in Vicrylgroup [n = 10], and 80.8$\pm$ 4.06% in Prolene group[n = 10]. Histopathologic studies were done for all autopsies or put in death around 300 days postoperatively. PDS absorblion was not seen 16 weeks after suture but disappeared over 24 weeks slide. Vicryl absorbtion was noted postoperative 8 to 16 weeks, with marked tissue reaction. Prolene showed least tissue reaction, but the suture material was persisted with regional fibrotic capsule.Causes of death were respiratory failure in 76 cases, tracheal rupture in 22 cases, hemorrhage, biting, starvation and etc. in 23 cases. With the brief review of literatures, we report the results.

• Computers and Concrete
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• v.13 no.1
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• pp.83-96
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• 2014

Accumulated annual reservoir sedimentation in Taiwan was 14.6 million m3 in 2010, seriously endangering reservoir safety and the water supply. In addition, the sintering temperature of reservoir-sediment aggregates (RSAs) is very high, and very energy consuming consequently. Therefore, to explore the effects of admixtures on sintering behavior and performance of the aggregates, two different admixtures are blended, waste-glass and municipal sewage sludge, into reservoir sediment to make artificial aggregates. Experimental results show that the lightweight characteristics of waste-glass/reservoir-sediment aggregates (WGRSAs) are more significant than those of sewage sludge/reservoir-sediment aggregates (SSRSAs). Moreover, as sintering temperature increases, the specific gravity of WGRSAs drops more apparently. The optimum sintering temperature of pure reservoir-sediment aggregates (PRSAs), SSRSAs, and WGRSAs was $1150^{\circ}C$, $1100^{\circ}C$, and $1050^{\circ}C$, respectively. The PRSAs are normal weight with better strength; the WGRSAs are lightweight and energy-saving; and the SSRSAs are lightweight with normal strength.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.42 no.5
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• pp.523-526
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• 2009

Biodegradable polybutylene succinate (BPS) multifilament were designed to degrade upon disposal by the action of afforestration of Ecklonia cava. Matured thalli of E. cava were collected at Jeju for zoospore collection and the substrate for zoospores were BPS multifilament (12 mm, 500 Td/96). The materials were made as nets of $1\;m^2$ with a cross stripes of 10 cm. The unit biodegradable nets bearing germlings of E. cava was moved into Wando where the place is conducting intensive seaweed cultivation in Korea for 5 months of nursery culture until they grew to 10 cm in length after which the nets were transplanted into the sea bed at Jeju at a depth of 12 m and the algal growth was monitored from May 2007 to December 2008. This is the first instance of using the BPS materials for seaweed afforestation to avoid any environmental problems.

• Fashion & Textile Research Journal
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• v.3 no.1
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• pp.53-60
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• 2001

The Miao nationality is one of China's major ethnic group. The Miao traditional costume, as an ideographic symbol of the Miao people, have preserved its unique characteristics up to the present time. Historically there were many old names given only for ciothings, still they have reflected the complexities of the ciothings of the Miao people. The southeast Guizhou (Qiandongnan) modal of dress and ornament are fashionable in countries in the valley of Qingshui River such as Taijiang, Kaili, Leishan, Jianhe, Huangping, Shibing, which are densely populated with the Miao nationality. Women's traditional wear for the most part consists of a short coat with straight sleeves and the left lapel of the collar overlaps the right one (In some areas, the right lapel overlaps the left one). For lower garments, they wear long or medium sized pleated skirts, broad waistbands and leggings. Their attire may be of the same style, but there exist marked regional differences and distinctive features in dress materials, workmanship, contents and variety of designs and colour matching, as evolved from tradition. Merely from the embroidering skill and the materials used, one can judge where the dress is made.