• 한국지하수토양환경학회지:지하수토양환경
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• 제18권1호
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• pp.129-136
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• 2013

This research was conducted to investigate effects of acid buffering capacity and soil component in treatment of phenanthrene using electrokinetic-Fenton process. In Hadong clay of high acid buffering and low iron oxide content, it was difficult to oxidize phenanthrene due to shortage of iron catalyst and scavenger effect of carbonate minerals. The desorbed phenanthrene conductive to Fenton oxidation was transported toward cathode by electroosmotic flow. However, in Youngdong illitic clay, oxidation of phenanthrene near anode readily occurred compared to Hadong clay due to high iron content and low acid buffering capacity.

• Bulletin of the Korean Chemical Society
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• 제35권5호
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• pp.1343-1348
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• 2014

A cholesterol-bridge-naphthopyran dyad (NP-MCB) was designed and synthesized. NP-MCB can readily self-assemble into gels under ultrasound-radiation in several organic solvents and the formed gels easily transfer to solution by heat. This reversible process can be repeated many times. Scanning Electron Microscopy results showed that the morphologies of all formed xerogels in different solvents have fibrillar microstructure. The gels formation was due to energy and pressure afforded by the ultrasonic process, resulting in formation of molecular hydrogen bonding and molecular aggregation. NP-MCB displayed the normal photochromism both in solution and gel states. The kinetic results confirm that the colored merocyanine in gels show a slower fading speed than that in solution due to the compact aggregation of NP-MCB molecules in gels. The xerogel film formed in polar gelling solvent had large surface wettability than that in nonpolar gelling solvent.

• 천문학회지
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• 제37권5호
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• pp.483-491
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• 2004

Clusters of galaxies are storage rooms of cosmic rays. They confine the hadronic component of cosmic rays over cosmological time scales due to diffusion, and the electron component due to energy losses. Hadronic cosmic rays can be accelerated during the process of structure formation, because of the supersonic motion of gas in the potential wells created by dark matter. At the shock waves that result from this motion, charged particles can be energized through the first order Fermi process. After discussing the most important evidences for non-thermal phenomena in large scale structures, we describe in some detail the main issues related to the acceleration of particles at these shock waves, emphasizing the possible role of the dynamical backreaction of the accelerated particles on the plasmas involved.

• 한국기계가공학회지
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• 제14권6호
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• pp.69-76
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• 2015

This study investigates the thermal efficiency and the efficiency of heat transfer through thermal analysis when the same heat is applied to a mortar frame by firing with various configurations of mortar. As the inside diameter of the mortar increases, the additional material must be reinforced. In comparison with the extent of getting cold due to models, a mortar with the strut under the gun barrel becomes cooler than one with no strut. The thermal deformation at firing becomes different. According to the configuration of mortar and its inside diameter, the extent of getting cold becomes different. This study result can be effectively applied for improving the efficiency of the heat transfer of mortar.

• 한국기계가공학회지
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• 제19권9호
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• pp.9-14
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• 2020

In this study, CFX analyses were performed with flow models to minimize the flow resistance due to the windscreen on the front of a car body. The results indicated that the greater the slant angle of the windshield, the greater the maximum pressure area. The lower the slant angle of the windscreen, the smaller the area in which the air collides with the front of the car body and the more smoothly the air moves. The results of this study can be applied to increase fuel economy under driving conditions by changing the slant angle of the vehicle's windscreen.

• 한국생산제조학회지
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• 제4권2호
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• pp.18-24
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• 1995

In order to achieve the autimation and untended system of manufacturing process, it is necessary that the monitoring system check up the disorder of machine tool or the conditions of tool wear for the maximum use of cutting tool. In the metal cutting Process, AE signal is detected by AE sensor, then amplified and transmitted to an Locan-AT. The experiment was performed to SM25C and STS304 steels at uniform feedrate, cutting speed and depth of cut, The results of experimental data apparently showed emission intensity vary due to increasing of tool wear at the 165kHz, 200kHz in the SM25C and 140kHz, 165kHz, 200kHz, in the STS304 respectively Therefore, it is possible to predict the tool wear. This study is intended to suggest the way to the automation and untended system of machine tool through the system monitoring tool wear by using AE signal.

• 대한기계학회논문집A
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• 제31권7호
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• pp.732-738
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• 2007

Effects of melt-mixing conditions on fracture properties of hydroxyapatite filled bioabsorbable poly(L-lactic acid)(HA/PLLA) composites was investigated by measuring the firacture toughness value of HA/PLLA composites prepared under different mixing time and rotor speed. The fracture surface morphology was also examined by profile measurement and scanning electron microscopies. It was found that the fracture toughness of HA/PLLA composites decreases due to decrease of ductile deformation of PLLA matrix and debonding of interfaces with increase of the rotor speed and mixing time. Effect of mixing process on neat PLLA was also assessed, and it was found that the fracture toughness of PLLA decreases due to disappearance of multiple craze formation and increase of defects. Such thermal and shear-stress degradation were found to be the primary mechanisms of the degradation of HA/PLLA composites during melt-mixing process.

• 한국소음진동공학회논문집
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• 제22권1호
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• pp.3-8
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• 2012

In an attempt to improve adhesion strength between glass and metal due to use of Pb-free solder as a sealant between glass and metal in the manufacturing process of vacuum insulation window glass to maintain the vacuum volume, ultrasonic energy is often applied during the process of Pb-free sealing. In this study, we propose an ultrasonic vibrator with a 4 mm end tip radius which performs resonance frequency of 60 kHz and 14 um or higher vibration displacement. A frequency variation due to applied pressure on piezo disks, which was excluded in the computer simulation, was verified experimentally, and we have demonstrated a 17 um vibration displacement at 50 V input through the performance test of a vibrator constructed with our specification.

• 한국정밀공학회지
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• 제17권4호
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• pp.173-180
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• 2000

In the process of grinding a long slender type workpiece, such as ballscrew, by the external cylindrical grinding machine, the cylindricity of the workpiece depends on the distance of rests, the stiffness of supports, the diameter and material of workpiece. Conventionally the process needs to be supported by one or more rests to prevent static deflection and vibration. In this paper, the optimal position of the rests was investigated in order to minimize the cylindricity due to the static deflection, by taking compliance of the workpiece and structure into account. In order to obtain the optimal position of rests, a new modeling that is considering the spring effect of all support elements was established. Since it is so complicated to obtain the optimal position analytically for various conditions due to discontinuity, a genetic algorithm u as utilized.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2005년도 춘계공동학술대회 발표논문
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• pp.517-522
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• 2005

This paper addresses scheduling heuristics for an assembly job-shop that includes at least an assembly process throughout its processes. The assembly job shop has certain characteristics not only considering the precedence relationship between the processes but also considering the processing progress between the parts. In addition, it probably presents a different processing time for the same product according to the order of processes and the point of workable time, due to the difference in the availability of equipments. The paper proposes several priority-based dispatching rules that consider these characteristics of the assembly job-shop, aiming to minimize the total tardiness of products in the shop floor. Computational tests showed that job due date based priority rules significantly outperform existing priority rules in terms of total tardiness.