In this paper, we developed the hydraulic leveling jack(HLJ) with double-tube type structure which could be applicable to excessive lateral load area. In order to develop HLJ, the design requirements, such as the vertical and lateral loads where applied to hydraulic jack, were selected. To verify the structural stability of the HLJ, the structure analysis was performed. In order to verify the operational performance and structural stability of the developed HLJ, test bench was designed. The performance of HLJ was verified via various test using test bench.

The coating of solid lubricant on the part of fixed or orbiting scroll wrap in a scroll compressor can not only reduce friction loss, noise & vibration and time cost for surface finishing but also improve efficiency and performance of the compressor. In this study, we found the most appropriate combination of the solid lubricant by carrying out many measurements and tests such as coefficient of friction, surface structure, the coating thickness and surface roughness for the various cases. We have come to conclusion that the most appropriate solid lubricant can be obtained by adding WS2 3% to Base(SM 3901) without any solvent and filler.

바이오디젤은 세계 화석연료의 흐름을 변화시킬 수 있는 환경 친화적 대체물질로 관심의 대상이 되고 있으며 대체연료 외에도 다양한 분야에서 수많은 응용 연구가 진행되고 있다. 최근에는 원유의 정제로부터 얻어진 석유제품을 대체하려는 다양한 움직임이 활발하게 진행되고 있다. 그 중 윤활기유로서의 식물성 오일은 급속도로 발전된 석유산업으로 인해 상용화 되지 못했던 오일로 관심의 대상이 되고 있으며 자연친화적 생분해성과 무독성, 윤활유로서의 낮은 휘발성과 우수한 계면윤활 등 대체 오일로써 충분한 가능성을 지니고 있다. 하지만 우수한 윤활 및 마모성능에도 불구하고 윤활연구에 넓게 활용되지 못했던 이유 중에는 지방산메틸에스테르가 갖는 열악한 산화안정성(oxidation stability) 및 열화안정도(thermal stability) 때문으로 보고되고 있다. 따라서 바이오디젤을 윤활기유 내 일정비율로 혼합하여 윤활성능 및 산화안정성의 변화를 확인하였으며 사구식 내마모 성능시험 후 발생되는 산화 및 열화현상을 알아보았다. 또한 산화에 따른 혼합 오일의 윤활특성 변화를 분석하였으며 이러한 결과를 바탕으로 윤활유 또는 윤활 향상제로서의 가능성을 살펴보았다.

PURPOSES : This study is to develop a method to evaluate lubrication of asphalt binder using WMA additives and compare their lubrication effects on two types of WMA additives and three types of asphalt film thicknesses. METHODS : This study is based on laboratory experiments and rheological analysis of the experimental results. Testing materials are aggregate diskes, asphalt, and WMA additives. The main testing method is stress sweep test by using dynamic shear rheometer (DSR). RESULTS : Sasobit gives more lubrication effects on film thicknesses 0.2mm and under but LEADCAP does on film thicknesses over 0.3mm. CONCLUSIONS : LVE-Limit is a better parameter to discern the lubrication effects on the thin film asphalt thickness. Both Sasobit and LEADCAP WMA additives provide effective lubrication at the compaction temperature.

The synovial tissues are a valuable MSCs source for cartilage tissue engineering because these cells are easily obtainable by the intra-articular biopsy during diagnosis. In this study, we isolated and characterized the canine MSCs derived from synovial fluid of female and male donors. Synovial fluid was flushed with saline solution from pre and post-puberty male (cM1-sMSC and cM2-sMSC) and female (cF1-sMSC and cF2-sMSC) dogs, and cells were isolated and cultured in advanced-DMEM (A-DMEM) supplemented with 10% FBS in a humidified 5% atmosphere at . The cells were evaluated for the expression of the early transcriptional factors, such as Oct3/4, Nanog and Sox2 by RT-PCR. The cells were induced under conditions conductive for adipogenic, osteogenic, and chondrogenic lineages, then evaluated by specific staining (Oil red O, von Kossa, and Alcian Blue staining, respectively) and analyzed for lineage specific markers by RT-PCR. All cell types were positive for alkaline phosphatase (AP) activity and early transcriptional factors (Oct3/4 and Sox2) were also positively detected. However, Nanog were not positively detected in all cells. Further, these MSCs were observed to differentiate into mesenchymal lineages, such as adipocytes (Oil red O staining), osteocytes (von Kossa staining), and chondrocytes (Alcian Blue staining) by cell specific staining. Lineage-specific genes (osteocyte; osteonectin and Runx2, adipocytes; PRAR-, FABP and LEP, and chondrocytes; collagen type-2 and Sox9) were also detected in all cells. In this study, we successfully established synovial fluid derived mesenchymal stem cells from female and male dogs, and determined their basic biological properties and differentiation ability. These results suggested that synovial fluid is a valuable stem cell source for cartilage regeneration therapy, and it is easily accessible from osteoarthritic knee.

In general, a valve body of the automatic transmission(AT) is controlled by the clutch, the brake and lubricating oil flow in a hydraulic system and lubricant flow for each valve can be adjusted independently. To increase the lifetime of AT, the lubrication flow rate in a valve body for a 6 speed AT based parallel hybrid electric vehicle must be provided with proper oil distribution and control. In this study, we carried out several experiments without the inner parts of AT and with a AT assembly. The variation of the flow rate on oil temperature and pressure between an oil supply port and the outlets of the lubrication port was evaluated and analyzed. In the case of AT without the inner parts, it was evident that as the oil required for an operation of the clutch and brake was discharged from the outlet port, the flow rate from each lubrication port is decreased. However, the flow rate of the AT assembly was slightly increased. In addition, the lubrication flow rate was increased with increasing the oil temperature, and also it was reduced with increasing the oil pressure. Details of the resulting data are discussed.

We developed functional synthetic lubricant for internal combustion engine oil, which would improve engine oil performance for internal combustion engine and extend engine life. We made base oil by synthesizing nonanoic acid, 1.1.1-trimethylol propane (which has good bio-degradability) and pentaerythrytol ester. We synthesized catalyst using p-toluene sulfonic acid 0.15 wt% and coloring-prevention agent hypo-phosphorus acid 0.18 wt% at 180-190℃. Reaction temperature was increased at the rate of 10℃ for every 1 hour. When acid value reached below 3, reaction was completed. After cooling and deoxidization, we washed it by distilled water two times. After dehydration and filtering, we obtained trimethylol propane tripelargonate (TMTP) and pentaerythrytol tetrapelargonate (PETP) at yields of 96 % and 98 % respectively.

Conventional additives were added to a newly synthesized base oil to create synthetic lubricants. Commercial polyol ester prepared in this laboratory were obtained as esterification of 1,1,1-trimethylol propane and respectively. This newly synthesized base oil had a variable chemical structure that could achieved the following properties; oxidation or thermal stability, low temperature fluidity, and higher flash points. When compared with commercial mineral lubricants, the synthetic lubricants show superior thermal and oxidation stability, and anti-wear properties.

Lubricant-based nanofluids were prepared by dispersing carbon nanoparticles in gear oil. In this study, the effects of the particle size, shape and dispersity of the particles on the tribological properties of nanofluids were investigated. Dispersion experiments were conducted with a high-speed bead mill and an ultrasonic homogenizer, and the surfaces of the nanoparticles were simultaneously modified with several dispersants. The effective thermal conductivity of the nanofluids was measured by the transient hot-wire method, and the tribological behaviors of the nanofluids were also investigated with a disk-on-disk tribo-tester. The results of this study clearly showed that the combination of the nanoparticles, the deagglomeration process, the dispersant and the dispersion solvent is very important for the dispersity and tribological properties of nanofluids. Lubricant-based nanofluids showed relatively low thermal conductivity enhancement, but they were highly effective in decreasing the frictional heat that was generated. For nanofluids containing 0.1vol.% graphite particles in an oil lubricant, The friction coefficient in the boundary and fluid lubrication range was reduced to approximately 70% of the original value of pure lubricant.

Oil-based nanofluids were prepared by dispersing Ag, graphite and carbon black nanoparticles in lubricating oil. Agglomerated nanoparticles were dispersed evenly with a high-speed bead mill and/or ultrasonic homogenizer, and the surfaces of the nanoparticles were modified simultaneously with several dispersants. Their tribological behaviors were evaluated with a pin-on-disk, disk-on-disk and four-ball EP and wear tester. It is obvious that the optimal combination of nanoparticles, surfactants and surface modification process is very important for the dispersity of nanofluids, and it eventually affects the tribological properties as a controlling factor. Results indicate that a relatively larger size and higher concentration of nanoparticles lead to better load-carrying capacity. In contrast, the use of a smaller size and lower concentration of particles is recommended for reducing the friction coefficient of lubricating oil. Moreover, nanofluids with mixed nanoparticles of Ag and graphite are more suitable for the improvement of load-carrying capacity and antiwear properties.

Nanoscale Cu-Ni alloy nanopowders have been produced by a pulsed wire evaporation method in an inert gas. The effect of Cu-Ni alloy nanopowders as additives to motor oil on the tribological properties was studied at room temperature. The worn surfaces were characterized by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Cu-Ni alloy nanopowders as additives lowered coefficient of friction and wear rate. It was found that a copper containing layer on the worn surface was formed, and deposited layers of the metal cladding acted as lubricant on the worn surface, reducing the friction coefficient. It was clearly demonstrated that Cu-Ni alloy nanopowders as additives are able to restore the worn surface and to preserve the friction surfaces from wear

Engine valve seat is a functionally important part for maintaining engine performance. The progress of automotive technology has increased the severity of conditions to which it is exposed, especially as regards LPG fuel engines and turbocharger. Therefore, it requires excellent heat and wear resistance to meet the severe condition inside the engine. In the present study, effects of solid lubricants such as CaF, MnS and MoS on microstructure and mechanical properties of sintered Fe alloys for valve srats have been investigated for the development of valve seat material with high temerature wear resistance. As a results of engine simulation test, 0.5 wt% CaF specimen showed the most excellent property, but in the overall aspect of view valve recession has increased with increasing the amount of solid lubricants.