• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.3
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• pp.245-252
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• 2016

In this study, an alternative bend design is proposed to overcome the aging problem in piping bends. In this design, the foam pad is not included. Finite element analysis was performed based on the total pipe diameter. From this analysis, the shape of the Shear Control Ring (SCR) was determined. Temperature, stress, and other data of the proposed reinforced pipe were acquired and analyzed after the test was performed. The value of the thermal stress for the reinforced steel pipe satisfied the required standard without the foam pad based on the manufacturing of the reinforced fitting and construction site of the test. The reinforcement provided a shear strength level for the foam pad that resulted in maximum shear stress less than stress based on the original foam pad applied at the pipe bend. Additionally, an increasing factor of safety effect for the reinforced fitting application was discovered.

• Membrane Journal
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• v.28 no.3
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• pp.169-179
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• 2018

The purposes of this paper were to improve both fouling and chlorine resistance by increasing the hydrophilicity of the reverse osmosis membrane. In order to improve chlorine resistance, the surface of RO membrane was activated by ultraviolet irradiation, and then it was modified by the sol-gel method using Octyltriethoxysilane (OcTES) such as the silane coupling agent to low sensitivity to chlorine, thereby the polyamide active layer was protected and chlorine resistance was improved. In addition, polyglycerol polyglycidyl ether (PGPE) and sorbitol polyglycidyl ether (SPE) coating with different number of epoxides, ring opening reaction of epoxide improved the anti-fouling resistance. The surface modification condition was optimized by FT-IR, XPS, and contact angle analysis. As a result, the permeability reduction rate of the silane-epoxy modified membrane after the fouling test was decreased about 1.5 times as compared with that of the commercial membrane. And the salt rejection was maintained over 90% at $20,000ppm{\times}hr$ even after chlorine resistance test.

• Journal of the Korean Home Economics Association
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• v.39 no.8
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• pp.107-120
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• 2001

The purpose of this study is to characterize the preference for fashion design according to fashion value of Net generation's. This study has 824 samples of individuals aged from 13 to 24. These sampling data are analyzed by frequency analysis, cross-tabs analysis, T-test, LSD-test, MANOVA and ANOVA utilizing SPSS WIN package. The results of this study are as follows; Net generation's is economic value higher than other fashion value and prefer for ring cuffs, mandarin sleeves, shirt collar, round neckline, tailored pants, blue color, check pattern according to economic value. It is proved that in case of shirt, people prefer ring cuffs, raglan sleeves, shirt collar, for jacket, prefer coat cuffs, mandarin sleeves, tailored collar, for jumper, they prefer single cuffs, set in sleeves, soutien collar and for T-shirt, prefer round neckline. For the design and length of pants, people prefer long tailored pants, color of blue and check designed one. It is proved that women haute a higher degree of preference for sleeve-design, neckline-design and color than men do.1318 teenagers have a higher preference for sleeve-design, neckline-design and color than semi-adult. Above university educational-course Net generation has a higher degree of preference for sleeve-design, neckline-design and color than high school educational-course Net generation does. A class of average monthly income of 2-3 million won has a higher degree of preference for neckline-design and color than other lasses do. And there is no difference at the preference for the fashion design when considered classes of average monthly expenditure on purchasing clothes.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.3
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• pp.186-193
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• 2018

Modern manufacturing industries is to produce both precise and robust mechanical parts without failure while they are in service. In order to prevent a part failure for its lifetime, a mechanical design for a part should be examined on a basis of mechanical simulation. A nozzle plate, being a key part in steam engines, changes flow directions of steam in a turbine used in power plant. This paper is to the design and test for part safety and durability. Currently, nozzle plates are fabricated by welding nozzles to their plates. Welding causes some defects on the used materials while they are being manufactured. Another major defect is un-even pitches between welded nozzles. Welding causes phase changes because of high melting temperature of metal. This leads to decay on the welding spots, which weakens their structural strength and then, may lead to early damages on mechanical structures. This research proposes assembly-typed nozzle plate without welding. From the beginning, nozzle and plate are designed for insertion-typed assembly. Nozzle head and foot are designed in accordance with the grooves on outer ring and inner ring of a plate to make mating surfaces. Then the nozzle plate should be proved for structural and fatigue safety before they are put in manufacturing. This research adopts commercial softwares for modeling and mechanical simulation. The test result shows that the design with smaller mating area and deeper insertion produces higher safety in terms of structure and durability. From the conclusion, this paper proposes the assembly-typed nozzle plate to replace the welding typed.

• Structural Engineering and Mechanics
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• v.66 no.3
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• pp.343-351
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• 2018

Brazilian disc test is one of the most widely used experiments in the literature of geo-mechanics. In this work, the pre-holed concrete Brazilian disc specimens are numerically modelled by a two-dimensional discrete element approach. The cracks initiations, propagations and coalescences in the numerically simulated Brazilian discs (each containing a single cylindrical hole and or multiple holes) are studied. The pre-holed Brazilian discs are numerically tested under Brazilian test conditions. The single-holed Brazilian discs with different ratios of the diameter of the holes to that of the disc radius are modelled first. The breakage load in the ring type disc specimens containing an internal hole with varying diameters is measured and the crack propagation mechanism around the wall of the ring is investigated. The crack propagation and coalescence mechanisms are also studied for the case of multi-holes' concrete Brazilian discs. The numerical and experimental results show that the breaking mechanism of the pre-holed disc specimens is mainly due to the initiation of the radially induced tensile cracks which are growth from the surface of the central hole. Radially cracks propagated toward the direction of diametrical loading. It has been observed that for the case of disc specimens with multiple holes under diametrical compressive loading, the breaking process of the modelled specimens may occur due to the simultaneous cracks propagation and cracks coalescence phenomena. These results also show that as the hole diameter and the number of the holes increases both the failure stress and the crack initiation stress decreases. The experimental results already exist in the literature are quit agree with the proposed numerical simulation results which validates this simulation procedure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.9
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• pp.979-984
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• 2012

An antiroll-bar assembly is a precision component that is designed to control the rolling of railway cars. It is important for ensuring a safe and comfortable ride. A torsion bar is the main part of the antiroll-bar assembly. Now, this part is classified as a consumable, and it is imported into Korea from France. Therefore, there is a strong need to domestically develop a torsion bar suitable for Korean conditions and to reduce cost and improve quality. In this study, an antiroll bar is developed, and it is analyzed and tested by using a road histogram measured on Korean railroads. This bar shows satisfactory results in a comparison with the imported bar. It has a novel design featuring a ring cover made of SUS steels to prevent the corrosion of the torsion bar. Its safety is examined through CAE analysis and wear tests. It is found that its design does not result in a significant difference in static and fatigue safety. Two different SUS steels were investigated in terms of their wear resistance, and the best one was adopted.

• Journal of Advanced Navigation Technology
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• v.23 no.1
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• pp.69-76
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• 2019

In this paper, a design method for an enhanced-sensitivity microwave sensor based on microstrip defected ground structure was studied for the permittivity measurement of planar dielectric substrates. The proposed sensor was designed by modifying the ridge structure of an H-shaped aperture into the shape of a capacitor symbol. The sensitivity of the proposed sensor was compared with that of a conventional sensor based on a double-ring complementary split ring resonator(DR-CSRR). Two sensors were designed and fabricated on a 0.76-mm-thick RF-35 substrate so that the transmission coefficient would resonate at 1.5 GHz in the absence of the substrate under test. Five types of taconic substrates with a relative permittivity ranging from 2.17 to 10.2 were selected asthe substrate under test. Experiment results show that the sensitivity of the proposed sensor, which is measured by the shift in the resonant frequency of the transmission coefficient, is 1.31 to 1.62 times higher than that of the conventional DR-CSRR-based sensor.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.415-423
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• 2019

In this paper, a design method for a high-sensitivity microstrip patch sensor antenna (MPSA) loaded with a bent-slot was studied for the permittivity measurement. The bent-slot similar to a single-ring complementary split ring resonator was added along a radiating edge of the patch in order to enhance the sensitivity to the permittivity. The sensitivity of the proposed MPSA was compared with that of a conventional rectangular MPSA and a thin rectangular-slotted MPSA. Three MPSAs were designed and fabricated on a 0.76-mm-thick RF-35 substrate so that the input reflection coefficient would resonate at 2.5 GHz in the absence of the superstrate under test. When five different Taconic substrates with a relative permittivity ranging from 2.17 to 10.2 were used as the superstrate under test, experiment results show that the sensitivity of the proposed MPSA, which is measured by the shift in the resonant frequency of the input reflection coefficient, is 4.1 to 6.1 times higher than that of the conventional MPSA.

• Smart Structures and Systems
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• v.30 no.3
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• pp.327-332
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• 2022

In building envelope, transparent components play an important role. The structural glazing systems are the weak element of the casing in terms of mechanical resistance, thermal and acoustic insulation. In the present work, new structural glass panels with granular aerogel in interspace were investigated from different points of view. In particular, the mechanical characterization was carried out in order to assess the resistance to bending of the single glazing pane. To this end, a special instrument system was built to define an alternative configuration of the coaxial double ring test, able to predict the fracture strength of glass large samples (400 × 400 mm) without overpressure. The thermal and lighting performance of an innovative double-glazing façade with granular aerogel was evaluated. An experimental campaign at pilot scale was developed: it is composed of two boxes of about 1.60 × 2 m² and 2 m high together with an external weather station. The rooms, identical in terms of size, construction materials, and orientation, are equipped with a two-wing window in the south wall surface: the first one has a standard glazing solution (double glazing with air in interspace), the second room is equipped with the innovative double-glazing system with aerogel. The indoor mean air temperature and the surface temperature of the glass panes were monitored together with the illuminance data for the lighting characterization. Finally, a brief energy characterization of the performance of the material was carried out by means of dynamic simulation models when the proposed solution is applied to real case studies.

• Composites Research
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• v.22 no.3
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• pp.1-8
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• 2009

In this paper, we present the results of experimental and analytical investigations on the structural behavior of GFRP pipes used in the water supply pipeline system. Cross-section of the pipe is consisted with two GFRP tubes and polymer mortar between the tubes. Due to the advantages such as light-weight, corrosion resistance, smooth surface, flexibility, etc., use of GFRP pipe in the water supply pipeline system is ever increasing trend. Therefore, more optimized structural design methodology should be developed. In the investigation, we conducted theoretical and analytical studies on the load versus radial deformation characteristics of GFRP pipes. In addition, ring stiffness test is also performed. Test results are compared with theoretical and analytical results and it was found that the results are agreed well within 5% of radial deformation. Finally, it was also found that the GFRP pipes used in the water supply pipeline system are strong enough to satisfy the industrial requirements.