• Elastomers and Composites
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• v.51 no.3
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• pp.195-205
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• 2016

A series of aromatic poly(hydroxyamide)s (PHAs) containing varying oligo(oxyethylene) substituents and 1,3-phenylene imide ring unit in the main chain were synthesized by the direct polycondensation reaction. The inherent viscosities of the PHAs exhibited in the range of 0.89~1.12 dL/g in DMAc or DMAc/LiCl solution. The PH-2~5 copolymers were easily soluble in strong aprotic solvents: DMAc, NMP, DMSO etc. and the PH-5 copolymer was soluble in less polar solvents such as m-creasol and pyridine with LiCl salt on heating. However, all PBOs were quite insoluble in other solvents, but only partially soluble in sulfuric acid. All copolymers (PH-2~5) could afford the flexible and tough films by solution casting. We identified that the PHAs were converted to the PBOs by the thermal cyclization reaction in the range of $200{\sim}380^{\circ}C$. The 10% weight loss temperatures and char yields of the PBOs were recorded in the range of $382{\sim}647^{\circ}C$ and 38.7~73.1% values at $900^{\circ}C$. The tensile strength and initial modulus of the PH-5 in the copolmers showed the highest values of 2.46 GPa and 49.55 MPa, respectively. The LOI values of the PHAs were in the range 26.6~29.0%, and increased with increasing 1,3-phenylene imide ring unit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.1005-1012
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• 2005

An OHT(Over Head Transportation) vehicle is an example of the industrial monorail vehicle, and it is used in the automobile, semiconductor, LCD manufacturing industries. OHT vehicle is moved by main wheels and guide rollers. The major function of the main wheel is to support and drive the OHT vehicle. The roles of the guide roller is the inhibition of derailment and steering of the OHT vehicle. Since the required vehicle velocity becomes faster and the required load capacity is increased, the durability characteristics of the wheel and roller, which was made of urethane, need to be increased. So it is necessary to estimate the fatigue life cycle of the wheel and roller. In this study, OHT dynamic model was developed by using the multi body dynamic analysis program ADAMS. Wheel and roller are modeled by the 3-D surface contact module. Especially, motor cycle tire mechanics is used in the wheel contact model. The OHT dynamic model can analyze the dynamic characteristic of the OHT vehicle with various driving conditions. And the result was verified by a vehicle traveling test. As a result of this study, the developed model is expected to predict wheel dynamic load time history and makes a contribution to design of a new monorail vehicle.

• Applied Chemistry for Engineering
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• v.20 no.2
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• pp.177-185
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• 2009

The failure analysis of scales deposited on automotive thermostat housing has been carried out. Observations using energy dispersive spectroscopy and electron probe micro analyzer indicate that the main components of scales are some of additives of coolant used. For a detailed investigation of organic matters pyrolysis-GC/MS is employed. The result shows that the main organic component is benzoic acid and furthermore, a small amount of acetophenone, benzene and phenyl group is detected. Based on the results of failure analysis performed, the scales on automotive thermostat housing appear due to the deposition of coolant components, followed by crevice corrosion, into gap between housing and rubber horse. New accelerated test methodology, which could mimic the scale formation and the crevice corrosion on thermostat housing, is developed considering the above results. In order to reproduce the real operating conditions, the accelerating factors, i.e. temperature and humidity, are changed and programmed. The reproducibility of the accelerated test proposed is confirmed after analyzing the scales obtained from the accelerated test.

• Elastomers and Composites
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• v.44 no.4
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• pp.436-441
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• 2009

Semi flexible polyesters containing aromatic rings and pentamethylene groups in the main chain were synthesized by direct polycondensation reaction. The structures of these polymers were investigated by $^1H$-NMR and FT-IR and the phase transition behavior was characterized with DSC, TGA and crossed polarizing microscope. Inherent viscosities ($\eta_{inh}$) of polymers measured in phenol/p-chlorophenol/1,1,2,2-tetrachloroethane were between 0.46 and 1.30 dL/g. As increasing the linearlity of rigid moieties in polyster, melting transition temperatures ($T_m$) increased and solubilities in organic solvents decreased. P-H, P-mH and P-4H of the polymers formed turbid melts that showed stir-opalescence and nematic phase at the broad anisotropic region, However, P-R, P-C and P-2B did not exhibit any textures related to the liquid crystallinity.

• Elastomers and Composites
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• v.54 no.4
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• pp.359-367
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• 2019

Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified with various co-monomers, such as N-vinyl pyrrolidone (NVP), glycidyl methacrylate (GMA), and glycerol monomethacrylate (GMMA), were prepared to investigate the effect of adding a co-monomer on the water contents, surface wettability, and tensile modulus. These polymers were synthesized by thermal- and photo-polymerization in the presence of azobisisobutyronitrile (AIBN) and diphenyl(2,4,6-trimethylbenzoyl)-phosphineoxide (TPO) as the initiators. The characteristics of the hydrogels were analyzed via FTIR and UV/Vis spectroscopies, contact angle measurements, and tensile modulus measurements with UTM. Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). The effects of adding the co-monomers on the water content, surface wettability, and tensile modulus for soft contact lenses were also investigated. In the case of p(HEMA-co-NVP) hydrogels, the increase in the equilibrium water content (EWC) was primarily due to the increase in the bound water content. For p(HEMA-co-GMMA) hydrogels, an increase in free water content was the main reason for the increased EWC. In contrast, in the case of p(HEMA-co-GMA) hydrogels, a decrease in bound water content was observed to be the main factor that reduced the EWC. Photo-polymerized PHEMA hydrogels showed enhanced surface wettability and tensile modulus as compared to those produced via thermal polymerization.

• Economic and Environmental Geology
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• v.32 no.6
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• pp.633-644
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• 1999

Gully pot is a part of urban darainage system to butter the runoff water fluxes from road to rivers and to minimize environmental pollution by prevending over the surrounding area. A series of studies have been carried out concerning the physicochemical characteristics of the sewage sludge sediments sttling down in such a gully pot in order to over to evaluate the contamination for heavy metals such as pb, Zn, Cu and Cd. The roadside soil and sewage sludge samples from gully pots were characterized by XRD analyses and sequential extraction : Zn 2595.7$\mu$g/g; Cd9.8$\mu$/g; Cu602.5$\mu$g/g; Pb260.0$\mu$g/g),because of a long-term accumulation of vehicle- and industrial-related pollutants. Mean Zn concentration in Yeouido (3873$\mu$g/g) and Junggu(3262$\mu$g/g)areas are 4-5 times higher than those in Dobonggu area, suggesting that Zn may be derived from automobile traffic (including the rubber of automobile tires). The mean concentrations of Cu and Cr are very significantly high in Junggu and Gurogu areas, possibly due to the industrial activities in these areas. The low Pb levels throughtotut the whole study areas in Seoul can be accounted for the use of unleaded gasoline since 1987. Sequential extraction experiments illustrate that a major part of Zn is bound to FII and FIII, representing about 88% of the total Zn concentration. Fraction IV, related to orgnic matter, is mostly significant for Cu accounting for 60% of the total Cu, and FII is next in importance. The main carriers of Pb are the fractions III, II and FIV, and in that order. The behavior of Cd is quite different from other elements (Zn, Cu, Pb), and most of the Cd is associated with FV. Changes in the physicochemical environments (such as acidification) may result in severe environmental pollution of surface water and rivers with respect to heavy metals (especially Zn and Cu).

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.745-752
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• 2011

Light Rail Vehicle(LRT) is "New Transit System" that has transportation capacity as well as physical size of vehicle is in-between bus and subway. The demand of LRT system is increasing rapidly; both domestically and internationally. Reason being is that it is more economical and eco-friendly compare to existing heavy rail vehicle. Especially, Busan Subway Line 4 K-AGT (Rubber-tired LRT) being the first of its kind to start revenue service in Korea, it is very much likely that application of its demand will continue to increase. Considering its trend, study to reduce implementation cost of LRT is being pursued in many different aspects; reducing construction cost is one that aspect. In this study, on-site application of 'Up-Down Turnout System' implementation research has been carried out which can replace existing 'Left-Right Turnout System'. When safety of its type gets verified, application of this system to line which intends to use K-AGT, Shin-Lim Line and Dong-Book Line, expects to save its construction cost. This thesis paper reports ongoing research of AGT 'Up-Down Turnout System' development and main component design factors, fundamental principle, performance test result.

• Asian-Australasian Journal of Animal Sciences
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• v.6 no.3
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• pp.389-394
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• 1993

A study on housing and management of dairy cows was conducted in three villages. All activities of husbandry related to the housing and the condition of the cows were observed and farmers were interviewed using a questionnaire. The main type of housing was a tie stall mostly in the back yard area with a gable or shed type roof. Inside the shed the temperature ranged from 17 to $29^{\circ}C$ and the relative humidity ranged from 62 to 73%. Drainage and manure handling was poor which lead to poor cleanliness of the stables and animal skins. The floor space was mostly wide and the roof level was low (less than 2.5 m). The slope of the floor (1-3%) was sufficient, the roughness of the floor was of medium quality. The shape and size of the feed trough was good with a surface of mostly irregular forms. Concentrate was mixed with water and offered in liquid form in pails made from plastic or from parts of rubber car tires. Hoof length was too long which could lead to unstable position and self injury. It is concluded that the housing conditions of dairy cattle need to be improved in order to improve the condition of the animals and the production performance.

• Earthquakes and Structures
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• v.10 no.2
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• pp.293-311
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• 2016

A parametric study on the nonlinear seismic response of isolated reinforced concrete structural frame is presented. Three prototype frames designed according to the 1954 Hellenic seismic code, with number of floor ranging from 1 to 3 were considered. These low rise frames are representative of many existing reinforced concrete buildings in Greece. The efficacy of the implementation of both lead rubber bearings (LRB) and friction pendulum isolators (FPI) base isolation systems were examined. The selection of the isolation devices was made according to the ratio $T_{is}/T_{fb}$, where Tis is the period of the base isolation system and $T_{bf}$ is the period of the fixed-base building. The main purpose of this comprehensive study is to investigate the effect of the isolation system period on the seismic response of inadequately designed low rise buildings. Thus, the implementation of isolation systems which correspond to the ratio $T_{is}/T_{fb}$ that values from 3 to 5 is studied. Nonlinear time history analyses were performed to investigate the response of the isolated structures using a set of three natural seismic ground motions. The evaluation of each retrofitting case was made in terms of storey drift and storey shear force while in view of serviceability it was made in terms of storey acceleration. Finally, the maximum developed displacements and the residual displacements of the isolation systems are presented.

• Journal of Biosystems Engineering
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• v.29 no.5 s.106
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• pp.433-440
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• 2004

Worldwide consumption of vegetable soybean has been increasing recently, but in the process of vegetable soybean production, threshing and separation work accounts fur about $80\%$ of overall labor. Therefore, developing of the vegetable soybean thresher is necessary to reduce the cost of labor. The main objective of this study is to acquire the basic in-formations for design of the vegetable soybean thresher which is suitable for domestic circumstances. We made the experimental system to investigate the threshing and separating performance at the several speeds of threshing cylinder and separating blower according to the kinds of threshing tooth. The result are as follows; Threshing performance of vegetable soybean thresher was shown as the best in case the threshing tooth made of rubber which has the 80 of Shore hardness was used at the circumference speed of cylinder of 5.8$\~$8.1m/s. Also separating cleaning performance of vegetable soybean thresher was shown as the best at more than 1,300 rpm of blower speed and $60\~80\%$ of opening ratio of suction port.