• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.6
• /
• pp.627-634
• /
• 2018

Gallium-based liquid metal, e.g., eutectic gallium-indium (EGaIn), is highly attractive as an electrode material for flexible and stretchable devices. On the liquid metal, oxide layer is spontaneously formed, which has a wide band-gap, and therefore is electrically insulating. In this paper, we fabricate a capacitor based on eutectic gallium-indium (EGaIn) liquid metal and investigate its cyclic voltammetry (CV) behavior. The EGaIn capacitor is composed of two EGaIn electrodes and electrolyte. CV curves reveal that the EGaIn capacitor shows the behavior of electric double-layer capacitors (EDLC), where the oxide layers on the EGaIn electrodes serves as the dielectric layer of EDLC. The oxide thicker than the spontaneously-formed native oxide decreases the capacitance of the EGaIn capacitor, due to increased voltage loss across the oxide layer. The EGaIn capacitor without oxide layer exhibits unstable CV curves during the repeated cycles, where self-repair characteristic of the oxide was observed. Finally, the electrolyte concentration is optimized by comparing the CV curves at various electrolyte concentrations.

• Tribology and Lubricants
• /
• v.38 no.1
• /
• pp.22-26
• /
• 2022

A 1.7-ton grade small excavator is a construction equipment that can perform various functions in limited spaces where heavy equipment cannot enter easily. Owing to the recent acceleration of urbanization, it has been used increasingly in drainage and gas pipes, as well as for road repair works in urban areas. The power train of a traveling reducer for a 1.7-ton grade small excavator utilizes a complex planetary gear system. Complex planetary gears are vital to the power train of a traveling reducer as it mitigates the fatigue strength problem. In the present study, the specifications of a complex planetary gear train are calculated; furthermore, the gear bending and compressive stresses of the complex planetary gears are analyzed to achieve an optimal design of the latter in terms of cost and reliability. In this study, the actual gear bending and compressive stresses of a planetary gear system are analyzed using a self-developed gear design program based on the Lewes and Hertz equation. Subsequently, the calculated specifications of the complex planetary gears are verified by evaluating the results with the data of allowable bending and compressive stress based on curves of stress vs. number of cycles of the gears.

• Journal of The Korean Association For Science Education
• /
• v.27 no.2
• /
• pp.105-119
• /
• 2007

Several studies have attempted to test students' misconceptions of physics and to provide teaching strategies in order to repair them. The results from these studies have revealed that the diagnosis of students' misconception is crucial, although they often failed to grasp the practice of its implementation. In terms of being a type of methodology for science education, the Internet allows large-scale surveys and investigations to be carried out in a relatively short period of time. This paper reports the results of the development, implementation, and evaluation of a WEb-based SYStem for TEsting students' Misconceptions in physics (WEBSYSTEM) aimed at three groups (science educational researchers who study students' physics conceptions using the system as a detector, school science teachers who practice it as an instructional material, and students who benefit from it for their self-directed learning). The web-based testing system is based on a review of the instructional development strategies of ADDIE (Gustafson, Branch, 2002; Rha, Chung, 2001). Results showed that WEBSYSTEM could work effectively as a multi-purposed tool for the three target groups with a further partial revision, providing educational researchers with resourceful data to study students' misconceptions in physics. Issues of administrative strategies, reexamination of questionnaires, and international collaboration via WEBSYSTEM are discussed.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.2
• /
• pp.146-154
• /
• 2017

Recently, self-healing concrete has been researched as maintenance and repair of concrete structures are important challenges we face. This paper focused on possibility of ion exchange resin as a novelty material directly and actively controlling harmful ions of concrete, whereas most self-healing concrete researches have been focused on methods to automatically filling and repairing internal crack of concrete. Because equilibrium properties between ion exchange resin and harmful ion is important before design of cement mixing proportion, it was conducted to remove chloride or sulfate in saturated $Ca(OH)_2$ solutions containing NaCl or $Na_2SO_4$. The removal performance was analyzed using kinetic equation and isothermal equation. Consequently, the removal properties of anion exchange resin were relatively more dependent on pseudo second reaction equation and Langmuir equation than pseudo first reaction equation and Freundlich equation. And it was concluded that each chloride and sulfate can be removed to the maximum 1068 ppm and 1314 ppm.

• Clean Technology
• /
• v.17 no.2
• /
• pp.85-96
• /
• 2011

Self-healing materials are a class of smart materials that have the structurally incorporated ability to repair damage caused by mechanical usage over time. A material (polymers, ceramics, metals, etc.) that can intrinsically correct damage caused by normal usage could lower production costs of a number of different industrial processes through longer part lifetime, reduction of inefficiency over time caused by degradation, as well as prevent costs incurred by material failure. The recent announcement from Nissan on the commercial release of scratch healing paints for use on car bodies has gained public interest on such a wonderful property of materials. This article is a second part of healing materials dealing with inorganic engineering materials such as metals, ceramics, and concrete. The healing mechanisms developed for the inorganic materials are to be discussed with the future prospect.

• Elastomers and Composites
• /
• v.44 no.3
• /
• pp.196-208
• /
• 2009

Sophisticated polymeric materials with 'responsive' properties are beginning to reach the market. The use of reversible, noncovalent interactions is a recurring design principle for responsive materials. Recently developed hydrogen-bonding units allow this design principle to be taken to its extreme. Supramolecular polymers, where hydrogen bonds are the only force keeping the monomers together, form materials whose (mechanical) properties respond strongly to a change in temperature or solvent. In this review, we describe some examples of hydrogen-bonded supramolecular polymers that can be utilized for self-healing materials. Synthesis of a rubber-like material that can be recycled might not seem exciting. But one that can also repeatedly repair itself at room temperature, without adhesives, really stretches the imagination. Autonomic healing materials respond without external intervention to environmental stimuli in a nonlinear and productive fashion, and have great potential for advanced engineering systems.

• Journal of Korea Multimedia Society
• /
• v.14 no.11
• /
• pp.1450-1457
• /
• 2011

Currently most of leak detection monitoring systems use digital maps with paying royalties, and this increases the cost of system construction and financial burdens on local self-governing bodies that manage such systems. Moreover, they have inefficiencies in repair and maintenance, functional expansion, and compatibility with other systems. Thus, this study developed a waterworks pipe network monitoring system that pursues low cost and high efficiency using general-purpose maps on the Internet such as google maps. As this system uses highly compatible free maps, it costs less in construction and its hardware requirements are lower than existing systems, and consequently, overall monitoring performance is enhanced and the cost of construction goes down sharply. This study also proposed a method for pipeline DB construction, which can be started together with the construction of the monitoring system, in order to improve the field applicability of the system.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.50 no.2
• /
• pp.114-121
• /
• 2013

As the weight of embedded memory within Systems-On-Chips(SoC) rapidly increases to 80-90% of the number of total transistors, the importance of testing embedded memory in SoC increases. This paper proposes IEEE std. 1500 wrapper based Programmable Memory Built-In Self-Test(PMBIST) architecture which can support various kinds of test algorithm. The proposed PMBIST guarantees high flexibility, programmability and fault coverage using not only March algorithms but also non-March algorithms such as Walking and Galloping. The PMBIST has an optimal hardware overhead by an optimum program instruction set and a smaller program memory. Furthermore, the proposed fault information processing scheme guarantees improvement of the memory yield by effectively supporting three types of the diagnostic methods for repair and diagnosis.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.14 no.3
• /
• pp.21-31
• /
• 1987

The overuse in the outdoor recreation lands has been deteriorating the natural resources and landscapes. So this study was executed to measure the users'impacts on vegetation and soil at Hwaum Temple District Campsite in the Mt. Jiri National Park, the southern part of Korea. Five sites were sampled in the study area according to the extent of impact observed. Then the users'densities and impacts on vegetation and soil were measured at each site. According to the result of this study, the numbers of species and individuals and the coverage of lower-layer vegetation showed outstanding changes by only light use. The numbers of species and individuals of middle-layer vegetation, species diversity indices, change rate in species composition of lower and middle-layer vegetation, damage rate of forces, contents of clay, soil moisture and organic matters, exchangeable base ions, soil hardness, organic matter depth and bare area of the campsite showed conspicuous changes from the site 4(19.6men / 1,000㎡). Especially, the self-repair of vegetation was impossible as the result of analysis of soil hardness and the formation of natural vegetation was expected to be difficult as the result of vegetation sturcture analysis over the users'average density of 19.6men /1,000㎡. The campsite management of this area shall be proposed as follows to prevent serious deterioration of natrual environment. A limitation of the present use and a conservation on soil and vegetation should be required at the site 4 and 5. Specially, prevention of camping recreation and artificial rehabilitation are necessary at the site 5(24. 3 men/1000㎡)

• Journal of the Korean housing association
• /
• v.22 no.4
• /
• pp.133-142
• /
• 2011

The purpose of this study was to gather baseline data to be used for improving housing environments and developing welfare policies for low-income groups by identifying the similarities and differences in housing environmental conditions and in the usages of community welfare services between the dwellers of Da-Ka-Gu rental housing and those of permanent rental apartment. This multifaceted diagnosis currently being undertaken can be utilized through the lowincome housing planning and welfare policies as the basis for future policy formulation. Self-administered questionnaires and interviews were carried out by 212 dwellers in Da-Ka-Gu rental housing (104) and permanent rental apartments (108) in the city of Gwangju from July to October of 2010. The main findings are as follows: 1. The dwellers living in both Da-Ka-Gu rental housing and permanent rental apartments are satisfied with their housing environment. Specifically, a higher satisfaction with transportation and a lower satisfaction with neighbor's inter-relationships were evident. The dwellers of Da-Ka-Gu rental housing appear to be more satisfied with community spaces and housing management than those of the permanent rental apartments, whereas the latter appear to be less satisfied with the noise of the housing complex than the former. 2. Of the community welfare service programs, a higher usage is shown for meals service, free health screenings, home repair, and after-school learning programs among all residents in the two housing types. In particular, for the residents of Da-Ka-Gu rental housing, the children's education and parent education programs are more popular, whereas for those of the permanent rental apartments, the housekeeping services and health services utilization are highest.