• Journal of the Korean Magnetics Society
• /
• v.5 no.1
• /
• pp.8-14
• /
• 1995

The magnetic properties of an $Fe_{87}Zr_{7}B_{5}Ag_{1}$(at.%) amorphous alloy have been investigated as a function of annealing temperatures to clarify its application potential as a core material for high-frequency use by adding a small amount of insoluble element of Ag. A new excellent soft magnetic material was developed. The amorphous alloy produced by relatively low temperature annealing at $T_{a}=400^{\circ}C$ exhibited very high initial permeability$(\mu_{i})$ of 288,000 at 1kHz and 2mOe, very low coercivity$(H_{c})$ of 15mOe and low core loss$(W_{c})$ of 50W/kg at 100kHz and 1,000G which is comparable with Co-based amorphous alloys, respectively. It is notable that the values obtained in the present study are the best magnetic properties among various kinds of Fe-based soft amorphous materials reported up to date. The reasons for the achievement of good soft magnetic properties are presumably due to the homogeneous formation of very fine $\alpha$-Fe clusters with the size of 2~3nm in an amorphous matrix, which can be deduced from the increase of resistivity and the TEM observation. The very fine $\alpha$-Fe clusters embedded in an amorphous matrix had a great influence on reduction of magnetostriction and refinement of magnetic domain.

• The Journal of the Petrological Society of Korea
• /
• v.14 no.1
• /
• pp.61-72
• /
• 2005

The granitoids in the Mt. Geumjeong, Busan can be divided into granodiorite, hornblende granite, adamellite, tonalite, biotite granite and micrographic granite. The geochemical characteristics of the Mt. Geumjeong granites indicate that they were crystallized from a calc-alkaline series and that they belong to Ⅰ-type granitic rocks which evolved from granodioritic magma into hornblende granite, adamellite, biotitie granite, and finally micrographic granite through fractional crystallization of plagioclase. The crystallization pressures and temperatures of the minimum melt compositions of the granitic rocks were estimated to about 1∼5 kbar and 720∼700℃. The trace element composition and REE patterns, characterized by a high LILE/HFSE ratio and enrichments in LREE, indicate typical continental margin arc calc-alkaline rocks produced in the subduction environment. The Rb-Sr isotopic data for the Mt. Geumjeong granites define a well-defined isochron yielding as age of 69.6±1.9 Ma with an initial Sr isotopic ratio of 0.70503.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.27 no.4
• /
• pp.58-66
• /
• 1990

A series of test was performed measuring the failure strength and failure mode of Gr/Pi, $[0^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}]_s$ laminate containing a single pin loaded hole. The finite element method is applied to calculate the stress distribution in the laminates, then the failure load and the failure mode were predicted by means of the characteristic length. 12 different geometric variations were developed to analyze the effects of the ratio of specimen width to hole diameter (W/d) and ratio of edge distance to hole diameter (L/d). X-Ray of NDE methods were utilized in finding out the initial defects, damage and the fracture mechanism, and SEM(Scanning Electron Microscopes) was used the evaluation of the fracture mechanism and crack propagation around hole under tension pin loading. $[0^{\circ}/45^{\circ}/90^{\circ}/-45^{\circ}]_s$ laminate are found to be most sensitive to W/d but not so influenced by L/d. The failure mode and tensile strength predicted by the model show agreement with experiment data for pin loading bolted jointed test except range of $L/d{\leqq}3$.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.6A
• /
• pp.417-424
• /
• 2011

This study focused on development of 60 m span PSC girder considering not only structural performance, but also economical efficiency and constructability including from the improvement of cross-section to the tendon profiles in sequence. Bulb-T type cross section was derived from optimization and actual possibilities to design a bridge were assessed through cross section evaluation. Tendons were also arranged efficiently so that the girder could resist the service load effectively. After developed girder was applied to a sample bridge, result of finite element analysis proved all load steps were satisfied with the allowable stress. Furthermore, it seemed that sufficient redundancy will be available to design a bridge safely. Based on these, a full-scale 60 m span girder was fabricated and 4 point bending test was performed. An initial crack occurred over twice of the service load in this experiment, which establishes adequate structural performance. 60 m span Half-Decked PSC girder developed in this study has a lower height for the given span which resulted from cross section improvement and efficient tendon layout. This girder also has not only the structural advantage, but also advantages in economical efficiency and constructability.

• Journal of the Korean Electrochemical Society
• /
• v.3 no.3
• /
• pp.131-135
• /
• 2000

In order to investigate the origin of capacity fading with charge/discharge cycling in $LiMn_2O_4$ thin film battery, impedance studies have been performed with increasing cycling in $LiMn_2O_4/1M\;LiClO_4-PC/Li$ cells. The fitted values obtained from impedance data show good agreements with the experimental results. Especially, the element of charge transfer resistance of $LiMn_2O_4/liquid$ electrolyte interface initially increased, and then saturated with increasing the charge/discharge cycles, which could explain the cause of initial abrupt capacity fading of $LiMn_2O_4$ thin film with cycling due to interfacial reaction. The steady capacity fading is caused by the increasing of Warburg resistance. The chemical diffusion coefficient of Li ions decreased from $5.15\times10^{-11}cm^2/sec$ at 1st cycles to $6.3\times10^{-12}cm^2/sec$ at 800th cycles, which attributed to the Jahn-Teller distortion/Mn dissolution which diminishes tetra hedral sites necessary for Li diffusion in $LiMn_2O_4$.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.15 no.3
• /
• pp.286-293
• /
• 1986

The purpose of this study was to investigate the effect of withering on mechanical properties for optimizing the condition of transportation and storage of fresh leafy vegetables which they would be easily able to be suffered the physical damage. Experimental material used were spinaches and leeks which were easily apt to be withered. The breaking stress, elastic modulus and viscosity were measured in the range of temperature $3{\sim}37^{\circ}C$ and water content $70{\sim}95%$ by the four element model, being used the creep tester made by author. As a result of this study, while water content was decreased, breaking stress was increased. The elastic modulus and viscosity of the specimens were not influenced on temperature, but on water content. In reversibility test of the withering, the appearance, water content and elastic modulus of the specimens were completely recovered to the initial freshness, but the viscosity was not.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.21 no.6
• /
• pp.8-14
• /
• 2017

Gearboxes for power transmission of a rotorcraft transfer power generated by an engine to the fan and the pusher for up, down and forward flight. The gearboxes are divided into the main gearbox and the sub-gearbox. The main goal of the gearbox design is to design the weight as light as possible within a range that satisfies all given requirements (transmission power, mounting space, etc.). In particular, the initial conceptual design is very important to reduce the weight of the gearbox, since the weight can vary greatly depending on the system configuration, even if it has the same function. In this study, various conceptual designs of the gearbox according to the installation position of the engine were presented. Also, the element parts such as gears and bearings in each concept design were designed by sizing for their life, and the estimated weights of the conceptual system configuration were compared.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.45 no.6
• /
• pp.171-184
• /
• 2017

The designers pursue the thoughtful and wide thinking through the accumulation of knowledge and cultivation of insights for making use of high-level design philosophy and language. The purpose of this study is to investigate characteristics of concept figuration types based on designer's 'memory' in landscape design. The results of this study are as follows. First, the design idea starts to be based on the language and image memory of the designer. The figuration types are composed of the verbal and visual view which are representative communication means. Second, the verbal concept figuration of landscape design consists of two types. The symbolic language of the title as a design theme can be a 'phrase', and it should have a hierarchial balance between the master and the sub. 'Descriptive shape of conceptual scenario' is a text that expresses the concept narratively in order that the reader virtually experiences designed landscapes. Third, visual concept figuration of landscape design is divided into three types. 'Simple visualization of a diagram' is easily embodied through a simple graphic using symbols, comments, images and key words. 'Concept sketch and shape of core idea' is useful to grasp the core of the idea such as physical element, form attribute of space and spatial relation at the initial phase of the concept. 'A collage and montage that create a new shape with a combination of images' are a collection of materials and images that provide a new perspective. These are tools to depict them in a compressed way after recording landscapes phenomenon.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.36 no.1
• /
• pp.67-77
• /
• 2018

This study investigated the recognition of Koreanesss, preference factors and the difference of recognition from adjacent Chinese and Japanese gardens for foreign visitors of Seoul gardens, a Korean traditional garden located within the Marzahn garden in Berlin, Germany. Overall, the Chinese garden and the Japanese garden were better known to most visitors than the Seoul garden due to their earlier construction. The awareness of the specialty to the Korean garden was at an average level indicating most visitors did not recognize the difference among the traditional gardens constructed from other countries. These less awareness on the Korean garden was because the traditional gardens of the three countries are located adjacent to the park in a continuous landscape with similar plant species created through natural planting techniques. This means the Korean garden is required for considering diversity and representativeness of planting species, uniqueness in space composition and recognition of Korean oriental garden culture in an initial design project stage. Visitors without prior information has better understanding on Korean garden and higher revisit intention resulting in increasing publicity and understanding of Korean traditional garden. Among the preference factors representing Koreaness of the Seoul gardens, the waterfall, stream, pavilion and natural stone within the water landscape were visitors favorite interests due to design concept with a representative Korean stream scenery of Dokrack-dang and Byeolseo garden resulting in differences from the landscape displaying technique for other oriental gardens. These stylistic differences in the dominant landscaping of garden architecture from surrounding the physical environments, the garden displaying technique derived from Korean natural landscape can be recognized as an unique garden element for foreign visitors.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.11
• /
• pp.7754-7760
• /
• 2015

The outer tie rod is one of the part of steering system, the optimization process was executed to find the lightweight design. The inner tie rod was considered in the optimum design of an outer tie rod. it could be closer to the test condition than in the case of considering outer tie rod only. The aluminum forging material was considered as a weight reduction proposal. The target of optimization was the shape of the minimum weight to resist at the load of buckling. RSM and Kriging interpolation method were applied as a optimization method to consider the nonlinear shape optimization problem. Then, 16.3%, 16.6% of weight reduction was obtained from the result comparing with that of the initial model. The results of meta model optimization was compared with that of finite element method. The error values of buckling load estimation were 2.6%, 2.04%. and those of weight estimation were 0.17%, 0.13%. Therefore, it seemed that the result of Kriging model could be obtained closer to optimum value than that of RSM model.