• Korean Journal of Materials Research
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• v.31 no.9
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• pp.481-487
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• 2021

ZnO particles are successfully synthesized at 150 ℃ for 30 min using zinc acetate as the Zn source and 1,4-butanediol as solvent using a relatively facile and convenient glycol process. The effect of ammonium hydroxide amounts on the growth behavior and the morphological evolution of ZnO particles are investigated. The prepared ZnO nanoparticle with hexagonal structure exhibits a quasi-spherical shape with an average crystallite size of approximately 30 nm. It is also demonstrated that the morphology of ZnO particles can be controlled by 1,4-butanediol with an additive of ammonium hydroxide. The morphologies of ZnO particles are changed sequentially from a quasi-spherical shape to a rod-like shape and a hexagonal rod shape with a truncated pyramidal tip, exhibiting preferential growth along the [001] direction with increasing ammonium hydroxide amounts. It is demonstrated that much higher OH^- amounts can produce a nano-tip shape grown along the [001] direction at the corners and center of the (001) top polar plane, and a flat hexagonal symmetry shape of the bottom polar plane on ZnO hexagonal prisms. The results indicate that the presence of NH⁴⁺ and OH^- ions in the solution greatly affects the growth behaviors of ZnO particles. A sharp near-band-edge (NBE) emission peak centered at 383 nm in the UV region and a weak broad peak in the visible region between 450 nm and 700 nm are shown in the PL spectra of the ZnO synthesized using the glycol process, regardless of adding ammonium hydroxide. Although the broad peak of the deep-level-emission (DLE) increases with the addition of ammonium hydroxide, it is suggested that the prominent NBE emission peaks indicate that ZnO nanoparticles with good crystallization are obtained under these conditions.

• Journal of Korean Medical classics
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• v.33 no.1
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• pp.61-80
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• 2020

Objectives : To clarify the construction, changes, and contents of the diagrams of spleen through comparison of 30 different diagrams originated from Mingtangzangfutu. Methods : The diagrams were analyzed in whole shape, ratio between width and height, shape of the lower part, and concavo-convex of the middle part, then matched to the characteristics of the section diagram. The contents of the diagram of the spleen were newly interpreted with comparison to the classical texts. Results : The whole shape is described to be a long sword, long stick, bottle gourd, western pear, sole of feet. The height to width ratio was mostly above 4.0:1, but those listed in the 『Bianquemaishunaning』 and 『Hehensancaituhui』 were 1.9:1~1.0:1, most similar to the numbers described in the 『Nanjing』. The shape of the lower part was narrow and sharp, narrow and flat or wide and flat. To analyze through affiliation characteristic, properties of other affiliations could be found. In comparison to classical texts, the diagrams could be found to be affected by 『Nanjing』 and Wangbing's annotations. The diagrams of the spleen should be composed of the spleen, the cord of spleen, and Sangao(散膏); but those which distinguish the spleen and the cord of spleen are twelve. The description of its shape as being similar to sword or sickle seems to come from Lichan's misunderstanding of the diagram in 『Zhenjiujuying』. Those that mention Sangao are merely two and their opinion on the position are different from each other; both did not identify it with the pancreas. Conclusions : In the process of the diagrams differentiating into 30 they were affected by the classical texts. The various changes seem to come from difference in understanding of the content composition of the diagram of the spleen.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.62-68
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• 2016

Laser welding has superior characteristic such as low distortion, high welding speed, easy automation and real time control. But it is easy to occur weld defects such as porosity, crater, humping bead in the area of welding start and end. These weld defects can be suppressed by applying the wave shape control. In this study CW fiber laser was used for welding of $0.5mm^t$ pure titanium. Penetration properties were evaluated with the time of slope up and down. After then the bead shape was observed, and the maximum depth and the area of crater were measured. The bead shape of welding start area changed to be sharp with increase of slope up time and non-weld area of welding start increased. The crater and humping bead were suppressed with slope down time. The cooling rate of crater area was understood through measure of the hardness. Also, The distribution tendency of alloying elements was observed by EPMA and EDS. When wave shape control didn't applied to weld, the hardness of end weld increased due to rapid cooling rate and the hardness of rear part in the crater was higher than that of fore part. On the other hand, when the wave shape control was used for end weld, the increase of hardness in the end weld couldn't be found due to gradual cooling rate.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.421-435
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• 2017

Recently, due to the saturation of ground structures and the overpopulation of pipeline facilities requires to development of underground structures as an alternative to ground structures. Thus, mechanized tunnel construction of the shield TBM method has been increasing in order to prevent vibration and noise problems in construction of the NATM tunnel for the urban infrastructure construction. Tunnel construction plan for the tunnel line should be formed in a sharp curve to avoid building foundation and underground structures and it is inevitable to develop a shield TBM technology that suits the sharp curve tunnel construction. Therefore, this study is about the structural stability technology of the articulation jack, shield jack and skin plate for the shield TBM thrust in case of the mechanized tunnel construction that is a straight and sharp curve line. The construction case study and shield TBM operation principle are examined and analyzed by the theoretical approach. The torque of the cutter head, the thrust of the articulation jack and the shield jack, the amount of over cutting for curve is important respectively in shield TBM construction of straight and sharp curve line. In addition, it is very important to secure the stability of the skin plate structure to ensure the safety of the inside worker. This study examines the general structure and construction of the equipment, experimental simulation was carried out through numerical analysis to examine the main factors and structural stability of the skin plate structure. The structural stability of the skin plate was evaluated and optimizes the shape by comparing the loads of the articulation jack by selecting the virtual soil to be applied in a straight and sharp curve line construction. Since the present structure and operation method of the shield TBM type in domestic constructions are very similar, this study will help to develop the localized shield TBM technology for the new equipment and the vulnerability and stability review.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.2
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• pp.208-229
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• 1996

Comprative osteology of the chum salmon Oncorhynchus keta, masu salmon O. masou and rainbow trout O. mykiss in Korea was studied. As a result, it was found that there were some differences in the structural features of the cranium and visceral skeleton among the species. Interspecific differencies in glossohyal, supraethmoid, parasphenoid and vomer were distinctive for the species. Chum salmon could be distinguished easily by some characters on form of glossohyal which is thin, long and sharp in shape. It has triangle shape supraethmoid while other two species have oval shape one. The shape of parasphenoid, preopercle, hyomandibular and the number of epurals were evaluated as new taxonomic criteria for the salmons.

• Korean Journal of Human Ecology
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• v.14 no.6
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• pp.995-1006
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• 2005

The purpose of this study was to investigate the wearing sensation and satisfaction of high school girls' winter uniform jackets according to the fabrics and the shapes. The fabrics were divided into four parts of stretch and non-stretch woven fabrics. The shapes were divided into two parts of tight and general types. The results were as followings: 1. In the aspect of the appearance evaluation for the uniform jackets, silhouette and length item showed significant differences in fabric and shape. The non-stretch woven fabric and tight type was more satisfying than the stretch fabric and general type because its silhouette and length were shorter and fitter than the stretch one and general type. The jackets of non-stretch woven fabric of tight type were evaluated as the thinnest in the silhouette and were evaluated as the shortest in the length. Conversely, the jackets of stretch woven fabric of general type were evaluated as the thickest and longest. 2. As for the wearing sensation of school uniform jacket, all test items showed significant differences in fabric and shape. The stretch fabric and general type was more satisfying than the non-stretch woven fabric and tight type because the jacket of stretch fabric and general type was felt more comfortable in activities, and wearing. Accordingly, the appearance evaluation for uniforms' jacket is in sharp contrast with that of wearing sensation.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.97-105
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• 2002

The use of rapid prototyping (RP) has reduced time to market, cut total costs and improved product quality by giving design and manufacturing teams the opportunity to verify and fine tune designs before committing them to expensive tooling and fabrication. In order to improve their unique characteristics according to the working principles, Variable Lamination Manufacturing process (VLM-ST) and corresponding CAD/CAM software (VLM-Slicer) is developed. The objective of this study is to improve the accuracy of VLM-ST process, and it can be done by offset fur cutting error correction, cutting path overrun fur sharp edge and reference shape generation for off-line stacking. It has been shown that, through the verification experiments for given practical shapes, the proposed algorithms are effective for diverse categories of three-dimensional shapes.

• Steel and Composite Structures
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• v.22 no.4
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• pp.777-796
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• 2016

In this paper, the behavior of woven E-glass fabric composite laminate was experimentally investigated under quasi-static indentation and high velocity impact by flat-ended, hemispherical, conical (cone angle of $37^{\circ}$ and $90^{\circ}$) and ogival (CRH of 1.5 and 2.5) cylindrical perforators. Moreover, the results are compared in order to explore the possibility of extending quasi-static indentation test results to high velocity impact test results in different characteristics such as perforation mechanisms, performance of perforators, energy absorption, friction force, etc. The effects of perforator nose shape, nose length and nose-shank connection shapes were investigated. The results showed that the quasi-static indentation test has a great ability to predict the high velocity impact behavior of the composite laminates especially in several characteristics such as perforation mechanisms, perforator performance. In both experiments, the highest performance occurs for 2.5 CRH projectile and the lowest is related to blunt projectiles. The results show that sharp perforators indicate lower values of dynamic enhancement factor and the flat-ended perforator represents the maximum dynamic enhancement factor among other perforators. Moreover, damage propagation far more occurred in high velocity impact tests then quasi-static tests. The highest damage area is mostly observed in ballistic limit of each projectile which projectile deviation strongly increases this area.

• Transactions of the Society of Information Storage Systems
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• v.6 no.1
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• pp.37-40
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• 2010

Fresnel lens is a kind of refractive optical lens with various advantages. It has nearly flat shaped optical lens that has small mass. Fresnel lens has number of applications in the compact optical systems. Recently, demands of high quality Fresnel lens for small size optical systems such as illumination units, compact imaging systems, display units, information storage systems, optical detecting units had increased rapidly. Conventional manufacturing process of high quality Fresnel lens is direct machining. However, it is not suitable for mass production because of high cost and long cycle time. Replication method can provide cost effective mass production process. However, there are various issues about replication of Fresnel lens. Fresnel lens has number of sharp blade shape prism. In the replication process, this blade shape causes defects that can affect optical efficiency. In this study, replication processes; injection molding process and UV imprinting process, were developed and evaluated using Fresnel lens that has maximum pattern height of $250\;{\mu}m$ and aspect ratio of 1.5.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.99-105
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• 2003

The influence of discharge conditions, including the resistance of the sparking circuit, the shape of the electrodes and the width of the falling dust on the ignitability of lycopodium streams were investigated. Discharge characteristics and the ignition phenomena were also explored. When a 100 ㏀ resistor was connected in series with the sparking circuit, the lowest level of minimum ignition energy (MIE) was attained for lycopodium streams. Simultaneously, the area where flammable gas generated increased and the duration of flammable gas generation decreased. That is, the ignita-bility of lycopodium streams depended strongly on the discharge power and discharge duration. Electrodes with sharp tips gave smaller MIEs than those with round tips in a capacitive-inductive sparking circuit, while shape made no difference in a capacitive-resistive circuit. Streams that were too narrow required a considerable amount of energy for ignition.