• Plant Journal
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• v.9 no.4
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• pp.31-36
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• 2013

In order to extend a hot gas parts replacement cycle of a gas turbine, blade row 1 from low pressure turbine, which has a significant impact on the cycle, has been selected from stored set after one cycle use. Taking into account the status of the first stage moving blade in LP turbine operated more than 27,000 equivalent operating hours(EOH) and the replacement cycle in the same type of gas turbine, the replacement of the high temperature components installed on the GT, a study subject, can be extended from 24,000 to 27,000 EOH.

• Clean Technology
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• v.5 no.2
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• pp.45-52
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• 1999

Recycling of red mud from the aluminium manufacturing process was investigated to be utilized as plastic fillers. High density polyethylene(HDPE), low density polyethylene(LDPE) and polypropylene(PP) were found to be the suitable plastic material for which red mud can be used as fillers. With the addition of red mud the plastic showed red brown color. As the ratio of amount of red mud to plastic increased, the tensile strength increased while the Izod impact strength decreased. About five percent of ethylene vinyl alcohol(EVA) was needed as an additive to prevent the lowering of impact strength. Maleic anhydride modified polypropylene was effective for reduction of impact strength lowering of PP. Mixed waste plastics containing LDPE, HDPE, PP, polystyrene and ABS could also accommodate red mud as fillers. In this case, significant loss in mechanical properties were observed due to immiscibility between the components. Ethylene propylene rubber(EPR) and styrene butadiene styrene block copolymer (SBS) could be used to improve the impact properties of the commingled waste plastics.

• Journal of Welding and Joining
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• v.26 no.4
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• pp.50-54
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• 2008

In this research, anode for SOFC has been manufactured from two different kinds of feedstock materials through thermal spraying process and the properties of the coatings were characterized and compared. One kind of feedstock was manufactured from spray drying method which includes nano-components of NiO, YSZ (300 nm) and graphite. And the other is manufactured by blending the micron size NiO coated graphite, YSZ and graphite powders as feedstock materials. Microstructure, mechanical properties and electrical conductivity of the coatings as-sprayed, after oxidation and after hydrogen reduction containing nano composite which is prepared from spray-dried powders were evaluated and compared with the same properties of the coatings prepared from blended powder feedstock. The coatings prepared from the spray dried powders has better properties as they provide larger triple phase boundaries for hydrogen oxidation reaction and is expected to have lower polarization loss for SOFC anode applications than that of the coatings prepared from blended feedstock. A maximum electrical conductivity of 651 S/cm at $800^{\circ}C$ was achieved for the coatings from spray dried powders which much more than that of the average value.

• Elastomers and Composites
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• v.51 no.1
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• pp.17-23
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• 2016

In this study, the reclaimed polypropylene (RPP) and waste ground rubber tire (WGRT) were used to simulate the thermoplastic vulcanizate (TPV) for cost reduction and resources recycling. Also, we examined the effects of dicumyl peroxide (DCP) and 2,5-dimethyl-2,5-di-(tert-butylperoxy)-hexane (DTBPH) as peroxide type cross-linking agents to enhance the properties of TPV's. The components of RPP and WGRT were fixed at 30 and 70 wt%, and DCP and DTBPH were added in the concentrations from 0.5 to 1.5 phr, respectively. RPP/WGRT composites with different contents of DCP and DTBPH were prepared by a modular intermeshing co-rotating twin screw extruder. The Young's modulus of composites were decreased with increasing peroxides contents. On the other hand, tensile strength, elongation at break, and impact strength of the composites were increased with peroxide contents. We also confirmed that interfacial adhesion between RPP and WGRT was considerably improved by adding the peroxides. Taken together, DTBPH added RPP/WGRT composites exhibited better mechanical properties rather than those of DCP added composites.

• The KSFM Journal of Fluid Machinery
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• v.20 no.1
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• pp.5-14
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• 2017

A fan-motor assembly in a vacuum cleaner is analyzed through system-level analysis method. This system consisted of three components, a fan, motor, and the flow resistance of the motor, or of the vacuum cleaner. System-level analysis method is characterized by the combination of torque matching at a constant throttling condition between the fan and the motor and the pressure drop at a constant flow rate due to the flow resistance of the motor, or of the vacuum cleaner. The performance characteristics of the fan-motor assembly and the vacuum cleaner system could be predicted over the whole range of operation, based on the characteristics of each component. The predicted performance of the vacuum cleaner system through system-level analysis agreed well with the experimental results within 4.5% difference of pressure and 6% difference of the efficiency. The effect of flow resistance of a motor is investigated and it is found that the efficiency decrease of fan-motor assembly at the constant flow rate due to the flow resistance of a motor is determined by the flow resistance ratio(FRR), which is defined as a ratio of flow resistance of motor and the flow resistance of a constant throttling condition of a given point. The fan-motor assembly(S2 model) was modified to reduce the FRR from 9.0% to 2.4% and the experimental result shows that the efficiency of S2 model was improved by about 3% at best efficiency point.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.45-56
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• 2015

This paper aims to develop a submerged propeller turbine for micro hydropower plant which allows to sustain high values of efficiency in a broad range of hydrological conditions (H=2~6 m, $Q=0.15{\sim}0.39m^3/s$). The two aspects to be considered in this development are mechanical simplicity and high-efficiency operation. Unlike conventional turbines that have spiral casing and gear box, this is directing driving and no spiral casing. A 10 kW class turbine which has the most high potential of the power generation has been developed. The most important element in the design of turbine is the runner blade. The initial blade is designed using inverse design method and then the runner geometry is modified by classical hydraulic method. The design process is carried out in two steps. First, the blade shape is fix and then other components of submerged propeller turbine are designed. Computational fluid dynamics analyses based on the Navier-Stokes equations have been used to obtain overall performance data for the blade and the full turbine, respectively. The results generated by performance parameters(head, guide vane opening angle and rotational speed) variations are theoretically analysed. The evaluation criteria for the blade and the turbine performances are the pressure distribution and flow's behavior on the runner blades and turbine. The results of simulation reveals an efficiency of 91.5% and power generation of 10.5kW at the best efficiency point at the head of 4m and a discharge of $0.3m^3/s$.

• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.4
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• pp.321-329
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• 2002

Bending moments results from offset overloading of dental implant, which may cause stress concentrations to exceed the physiological capacity of cortical bone and lead to various kinds of mechanical failures. The purpose of this study was to compare the distributing pattern of stress on the finite element models with the different angulated placement of dental implant in mandibular posterior missing areas. The three kinds of finite element model, were designed according to 3 main configurations: Model 1(parallel typed placement of 2 fixtures), Model 2(15. distal angulated placement of one fixture on second molar area), Model 3(15. mesial angulated placement of one fixture on second molar area). The cemented crowns for mandibular first and second molars were made on the two fixtures (4mm 11.5). Three-dimensional finite element models by two fixtures were constructed with the components of the implant and surrounding bone. A 200N vertical static load were applied to the center of central fossa and the point 2mm apart from the center of central fossa on each model. The preprocessing, solving and postprocessing procedures were done by using FEM analysis software NISA/DISPLAY IV Version 10.0((Engineering Mechanics Research Corporation, USA). Von Mises stresses were evaluated and compared in the supporting bone, fixtures, and abutment. The results were as following : (1) Under the point loading at the central fossa, the direction of angulated fixture affected the stress pattern of implants. (2) Under the offset loading, the position of loading affected more on the stress concentration of implants compare to the angulated direction of implants. The results had a tendency to increase the stress on the supporting bone, fixture and screw under the offset loads when the placement angulation of implant fixture is placed toward mesial or distal direction. In designing of the occlusal scheme for angulated placement, placing the occlusal contacts axially during chewing appears to have advantages in a biomechanical viewpoint.

• Journal of Ocean Engineering and Technology
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• v.10 no.2
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• pp.77-87
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• 1996

The estimation of the remaining life for the aged components in power plant as well as chemical and peroleum plants has been recently coberned. The raw materials used in this syudy are the 1Cr-1Mo-0.25V rotor steel which intensified P and S compositions along with the nominal compositions of ASTM A470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging teat treatment at $630^{\circ}C$ The mechanical properties and fatigue strength of virgin and aged 1Cr-1Mo-0.25V rotor steel have been inbestigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at room temperature. Thus, the data of aged specimens were compared with those of virgin specimen to evaluate the aging effects. The main results obtained in this study are as follows; The decrease of the hardness due to degradation was distinguished until 50, 000hrs simulated service time. And is was confirmed that the considerable amount of P, Mn, Cr and S was precipitated at the grain boundary of aged material through the SEM and EDS analysis. The fatigue strength of 25, 000, 50, 000, 75, 000 and 100, 000hrs aged material was decreased 29.5%, 24.4%, 28.6%, 35.7% than that of virgin material at $10^7$ cycles of room temperature. The major cracks of virgin and aged materials initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.

• Journal of IKEEE
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• v.18 no.2
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• pp.282-290
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• 2014

This paper presents the design of embedded electrical power control unit for Personal Electrical Vehicle(PEV). The embedded unit is designed using PIC18F8720 processor, 16Mb flash ROM, 32Mb SDRAM and signal condition circuits. The proposed PEV consists of 4KW in-wheel Brushless DC Motor(BLDCM), 3 phase voltage source inverter with the $180^{\circ}$ conduction space vector PWM method, PID speed controller and the embedded control unit. The PEV has mechanical manufacture of inverse 3 wheel system, which is applied by the in-wheel BLDCM and steering mechanism with tilting function. Also, the performances of the proposed embedded electrical power control unit are verified through the lab experiment and road driving test of PEV.

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.181-194
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• 1999

Both the chemical components and the physical and mechanical properties of the compacted and undisturbed weathered granite soils were estimated to investigate the influences of the degree of weathering and saturation on the shear strength. The weathered granite soils used in this study were taken from six different sites in Korea. The results showed that the shear strength of weathered granite soil decreased with increasing the degree of weathering and saturation. Under the normal stresses less that 40kPa, the shape of Mohr-Coulomb failure envelope followed curved or hyperbolic relationship and a half of cohesion value obtained by the common shear test was observed. Using the Sueoka's method, the values of CWI were ranged from 21.5 to 31.26 which can be characterized as a completely weathered granite soil. Large decrease in shear strength and remarkable variation in dilatancy were observed in saturated granite soil compared to unsaturated soil. It was also found that the shear strength of undisturbed weathered granite soil of Pungam site can be expressed approximately by the equation of ${(\tau)_{sat}= 1.0(\tau)_{unsat}-12.48}$ and this equation can be extended to the other sites considered in this study.