• Journal of Powder Materials
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• v.21 no.1
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• pp.7-15
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• 2014

This study investigated the densification behavior of rhenium alloys including W-25 wt.%Re and Re-2W-1Ta (pure Re) during sintering. The dilatometry experiments were carried out to obtain the in-situ shrinkage in $H_2$ atmosphere. The measured data was analyzed through shrinkage, strain rate and relative density, and then symmetrically treated to construct the linearized form of master sintering curve (MSC) and MSC as a well-known and straightforward approach to describe the densification behavior during sintering. The densification behaviors for each material were analyzed in many respects including apparent activation energy, densification parameter, and densification ratio. MSC with a minimal set of preliminary experiments can make the densification behavior to be characterized and predicted as well as provide guideline to sinter cycle design. Considering the results of linearized form and MSC, it was confirmed that the W-25 wt.%Re compared to Pure Re is more easily densified at the relatively low temperature.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.1
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• pp.108-113
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• 2020

Pinions are generally heavy and integrated with a shaft. Thus, fabricating a pinion is a material- and machining-intensive task characterized by low productivity. Contact of the output pinion with a sliding surface or a cloud contact causes loss of power because of friction. Consequently, the output pinion undergoes considerable wear and tear at its ends, which adversely affects the overall transmission efficiency of decelerators. To improve transmission efficiency and extend gear life, an optimum output pinion design is required. To this end, in this study, an output pinion for worm gear decelerators was designed and optimized by means of product verification through prototyping and performance evaluation to improve gear life and productivity. The optimized design was validated and subjected to structural analysis.

• Elastomers and Composites
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• v.55 no.4
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• pp.347-353
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• 2020

Stearic acid (SA), polyethylene glycol (PEG), and malic acid (MA) have been used to modify the surface of waste gypsum to develop corresponding poly (butylene adipate-co-terephthalate) (PBAT) composites. According to the mechanical properties, MA-treated gypsum (MA-gypsum) showed the best performance, whereas SA-gypsum showed the worst performance. In contrast to SA and PEG (having -COOH and -OH as polar functional groups, respectively), the presence of both -OH and -COOH in MA is responsible for the superior surface treatment of gypsum and its better dispersion in the polymer matrix (as revealed by FE-SEM analyses). The presence of long aliphatic chain in SA is supposed to inhibit the dispersion of SA-gypsum. Further, the performance of MA-gypsum/PBAT was enhanced by adding polylactic acid (PLA). The maximum optimized contents of MA-gypsum and PLA are 20 and 7.5 wt% for developing a high-performance PBAT composite.

• Membrane and Water Treatment
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• v.14 no.1
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• pp.47-54
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• 2023

In this study, high concentrations of cadmium-containing wastewater were treated by electrodialysis (ED) with a channel stack. The limiting current density (LCD), cadmium removal efficiency, and current efficiency were investigated under each experimental condition according to the Reynolds number (Re), membrane area, and pH. With the increase in the film area to 111, 333, 555, and 777 cm² at Re (109.1), LCDs decreased to 408.11, 44.45, 35.32, and 13.64 A/m², respectively. The highest cadmium removal efficiency (99.6%) and current efficiency were obtained for the membrane area of 111 and 777 cm², respectively. Under changing Re in the pH range of 1 to 4, Re and LCD were proportional under the same pH condition, and pH and LCD tended to be inversely proportional under the same Re condition. Cadmium removal rate was the best at the pH range 3 - 4. It has been found that ED with channeled stacks can be successfully applied to treat wastewater containing high concentrations of cadmium.

• Computational Structural Engineering
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• v.11 no.1
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• pp.107-112
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• 1998

당 연구소는 회사의 비전인 E&C 21을 달성할 수 있도록 의식개혁(Re-Valuing), 구조개혁(Re-Structuring), 프로세스개혁(Re-Engineering)을 바탕으로 연구개발의 고도화, 연구관리의 선진화, 연구지원의 강화를 추진, 궁극적으로 고객만족(Customer-Satisfaction), 직원만족(Employee Satisfaction), 가족만족(Family Satisfaction)을 이룰 수 있는 초일류연구소(smart institute)를 그 비전으로 하고 있다. 이러한 비전을 달성하기 위한 단계별 목표는 제1기인 '97년까지 종합건설기술연구소 체제를 구축하고, 제2기(1998-2000)는 선진형 건설기술연구소 기반 구축을, 그리고 제3기(2001-2003)까지는 세계 초일류 종합건설기술연구소 달성을 목표로 하고 있다.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1202-1202
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• 2006

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.81-84
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• 2014

The bipolar resistive switching characteristics of resistive random access memory (ReRAM) based on $HfO_2$ thin films have been demonstrated by using Ag/$HfO_2$/Pt structured ReRAM device. MIcrowave irradiation (MWI) treatment at low temperature was employed in device fabrication with $HfO_2$ thin films as a transition layer. Compared to the as-deposited Ag/$HfO_2$/Pt device, highly improved uniformity characteristics of resistance values and operating voltages were obtained from the MWI treatment Ag/$HfO_2$/Pt ReRAM device. In addition, a stable DC endurance (> 100 cycles) and a high data retention (> $10^4$ sec) were achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.8
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• pp.491-496
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• 2014

The resistive switching characteristics of resistive random access memory (ReRAM) based on amorphous $Ge_{0.5}Se_{0.5}$ thin films have been demonstrated by using Ti/Ag nanocrystals/$Ge_{0.5}Se_{0.5}$/Pt structure. Ag nanocrystals (Ag NCs) were spread on the amorphous $Ge_{0.5}Se_{0.5}$ thin film and they played the role of metal ions source. As a result, comparing the conventional Ag/$Ge_{0.5}Se_{0.5}$/Pt structure, this Ti/Ag NCs/$Ge_{0.5}Se_{0.5}$/Pt ReRAM device exhibits the highly uniform bipolar resistive switching (BRS) characteristics, such as the operating voltages, and the resistance values. At the same time, a stable DC endurance(> 100 cycles), and the excellent data retention (> $10^4$ sec) properties were found from the Ti/Ag NCs/$Ge_{0.5}Se_{0.5}$/Pt structured ReRAM device.

• Korean Journal of Metals and Materials
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• v.46 no.1
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• pp.1-5
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• 2008

This study has been investigated the deformation behavior of a hot-extruded Mg-Zn-RE (RE: rare earth elements) alloy containing $Mg_{12}$(RE) particles at the elevated temperatures. The particles are intrinsically produced by breaking the eutectic structure of the alloy during the hot-extrusion process. The grain size of the extruded Mg-Zn-RE alloy developed via dynamic recrystallization is around $10{\mu}m$. Under the heat treatment at 200o C up to 48 hr, no change has been observed on the microstructure and mechanical properties due to the pinning effect of the thermally stable particles. Under the tensile test condition in the initial strain-rate range of $1\times10^{-3}s^{-1}$ and the temperature range up to $200^{\circ}C$, the alloy shows yield strength of 270 MPa and elongation to failure around 9% at room temperature and yield strength of 135 MPa at $200^{\circ}C$. Furthermore, although the alloy contains large amount of the second phase particles around 15%, it shows excellent hot-workability possibly due to the presence of the thermally stable interface between the particles and the matrix.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1664-1667
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• 2003

Aperture-coupled microstrip antenna is one type of microstrip antennas. This type of antenna has bandwidth wider than simple microstrip antenna. Herein, we use two substrates, that have the same dielectric constant 2.47 (PTFE-quartz) in which upper substrate is a rectangular patch. The microstrip patch is fed by a microstrip line which is printed on lower substrate, through an aperture or slot in the common ground plane of patch and microstrip feed. This antenna is analyzed by using Finite Difference Time Domain (FDTD) method the specific design frequency 10 GHz and match impedance is 50 ohms. The simulation results of its characteristics are input impedance, return loss, VSWR and radiation patterns respectively.