• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.9
• /
• pp.1193-1200
• /
• 2001

There are many regulation test methods to be related with engine emissions such as CVS-75, D-13, ECE-15 modes and so on. Most of these modes are consisted of lots of transient conditions that have rapid acceleration, deceleration and cranking modes. In this experimental research, the engine characteristics of cranking, accelerating and power output in a S.I. engine were studied to compare with neat gasoline and alternative fuels of M30 (methanol 30%, aromatic series 32%, non-aromatic 38%) and M50 (methanol 50%, aromatic 30%, non-aromatic 20%) for performance and exhaust emissions. The results show that reformulated methanol fuels are better emissions reduction of 15.7% over than that of neat gasoline fuel especially in HC and CO emissions at cranking mode. And the accelerating performances coincide with the results of distillation curve. CO concentration for M50 fuel is varied in a just little for the condition of slow acceleration. At wide-open throttle condition, brake specific energy consumption of reformulated fuels is increased and thermal efficiency is some what lower than that of gasoline fuel.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.17 no.1
• /
• pp.182-189
• /
• 2009

The noise from the sunroof can be divided into the low frequency buffeting noise and the high frequency turbulence noise generated when a car runs at the high driving speed. The wind deflector suppresses the buffeting noise generation by accelerating the vortex shedding from the front edge of sunroof opening, and guides the flow direction so that air can pass smoothly over the sunroof opening. To reduce the buffeting noise and the high frequency noise, it is very important to locate a deflector in a proper position depending on the driving speed and the sunroof opening width. The deflector's sectional shape also plays an important role in efficiently reducing the buffeting and high frequency noise. In this paper, we determined the optimum deflector's sectional shape and examined the flow characteristics behind a sunroof deflector through CFD analysis with changing the deflector height, the driving speed and the sunroof opening width. It is found that the deflector needs to be located in the higher location to control the buffeting noise by shedding the higher frequency vortices to accelerating vortices from the sunroof front edge. The deflector may act as a new noise source at the high driving speed, then it is desirable to put the deflector at the proper height to reduce the flow fluctuations and the noise generation. We also made a road test to verify CFD analysis results in this study.

• Geomechanics and Engineering
• /
• v.27 no.5
• /
• pp.527-535
• /
• 2021

The creep characteristics of rock is of great significance for the study of long-term stability of engineering, so it is necessary to carry out indoor creep test and creep model of rock. First of all, in different water-bearing state and different positive pressure conditions, the granite is graded loaded to conduct indoor shear creep test. Through the test, the shear creep characteristics of granite are obtained. According to the test results, the stress-strain isochronous curve is obtained, and then the long-term strength of granite under different conditions is determined. Then, the fractional-order calculus software element is introduced, and it is connected in series with the spring element and the nonlinear viscoplastic body considering the creep acceleration start time to form a nonlinear viscoplastic creep model with fewer elements and fewer parameters. Finally, based on the shear creep test data of granite, using the nonlinear curve fitting of Origin software and Levenberg-Marquardt optimization algorithm, the parameter fitting and comparative analysis of the nonlinear creep model are carried out. The results show that the test data and the model curve have a high degree of fitting, which further explains the rationality and applicability of the established nonlinear visco-elastoplastic creep model. The research in this paper can provide certain reference significance and reference value for the study of nonlinear creep model of rock in the future.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.5
• /
• pp.13-24
• /
• 2012

In this study, the in-situ model test has been conducted and used to estimate and analyze consolidation behavior of the ground by using the miniature test that reconstructs economically geotechnical behavior of in-situ full scale structure. To analogize the relation among effective stress, void ratio and coefficient of permeability at the self-weight consolidation stage, the low stress seepage consolidation test has been conducted and the involution function of constitutive equation had been obtained from the result of the curve fitted seepage consolidation test result. As a result of the numerical analysis that had been conducted on the representative section using a constitute equation, final settlement was similar with those of self-weight consolidation of the centrifugal model test. But, it was more or less smaller. It seems that these trends are caused by the difference between estimated values.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.5
• /
• pp.29-36
• /
• 2008

The shotcrete is a NATM technique as a major tunnel support for ground stability after tunnel excavation. Instead of a general concrete lining method, it is a trend for curtail of construction periods and reduction of construction expenses that required to use of the permanent shotcrete lining. This high-strength shotcrete is required to use as a permanent shotcrete lining. This brought out the solution of environmental pollution and harmfulness to human. Accordingly, in this study specimens for strength measurement were made to develop shotcrete possible to develop materials in early with cement mineral accelerator as NATM method construction. It was compared with existing shotcrete material, unconfined compression test, flexural strength test, antiwashout underwater test were experimented. The fish poison test was experimented to evaluate an influence of environment. As a results of the test, unconfined compressive strength and flexural strength were equivalent with 28-curing day strength of existing material. An antiwashout of research subject material was revealed excellently in antiwashout Underwater test. As a results of the fish poison, an evaluation research subject material was founded more environmentally friendly than existing shotcrete.

• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.1558-1560
• /
• 2004

Liquid-immersed pole transformers have utilized an insulation system consisting of natural cellulose-based materials and mineral oil for many years. If the transformers are installed with the abruptly changing load over limitation, its insulation materials are apt to unexpected aging with high temperature. Therefore we have been conscious of developing a transformer that is more thermally stable then conventional types. To measure temperature distribution in the winding of conventional and newly designed transformers, temperature sensors were installed fordirect reading of oil and conductor temperatures at transformers. And we conducted accelerating aging test for these transformers. The measuring data had made use of the design to hybrid insulation system. Also we could find the possibility of this insulation system to apply in pole mounted transformers.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.997-1002
• /
• 2001

There are two types of chloride in concrete; one is added as concrete materials' chloride when concrete's mixing, and .the other is penetrated from the air and sea water in the sea-shore area. These chlorides penetrate into concrete, and they are accumulated inside the concrete with aging. This study aimed to evaluate the chloride ion penetration resistance of concrete containing GGBFS in the sea-shore area. Therefore, the specimens made with the replacement ratios(0, 0.30, 0.45, 0.60) of GGBFS were put into 3% NaCl solution according to the chloride accelerating test of JCI-SC3, and then investigated the weight changes, compressive strength, chloride ion with the depths of the specimens by aging. The result is that the diffusion coefficient of chloride ion is decreased with the increase of replacement ratios when compared to OPC

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.357-360
• /
• 2005

Hyundai Motor Company developed the second generation of fuel cell hybrid electric vehicle based on Tucson SUV in 2004. This vehicle has cold start capability below -10C and its driving performances including maximum speed and accelerating time are almost similar to conventional Tucson SUV's performances without any sacrifice in terms of cabin space. Especially. the cold start capability was realized by utilizing only internal power sources such as fuel cell power and high voltage lithium ion polymer battery. In this paper, we will briefly introduce specifications of Tucson FCEV and its driving performances based on field test and simulations.

• International Journal of Automotive Technology
• /
• v.5 no.4
• /
• pp.311-319
• /
• 2004

There are many methods to test engine emissions depending on the regulations used such as FTP-75(CYS-75) mode, 10-15 mode and ECE-15 mode. Most of these modes consist of transient conditions such as cranking, rapid acceleration or deceleration modes. In this experimental research, the transient characteristics including cranking and accelerating mode in SI engines were studied to compare pure gasoline with methanol-reformulated fuels for performance and exhaust emissions. The results show that methanol-reformulated fuels have a better emissions reduction rate than that of pure gasoline especially for HC, CO and NOx emissions during cranking mode. The acceleration performances conform to the results of the distillation curve and the CO concentration for RM50 varies slightly in acceleration mode.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.05a
• /
• pp.201-206
• /
• 2002

The purpose of this study is to improve the anti-corrosive properties of coated reinforcing bar using polymer cement slurry. Poymer cement slurry are prepared with three types of polymer dispersions and corrosion inhibiting admixture. And tested for corrosion accelerating tests such as immersion in NaCl 10% solution NaCl 10% solution spray, high temperature and pressure steam in condition of 8cycles, carbonation before and after, penetration of NaCl solution. From the test results, it is concluded that the anti-corrosive properties are considerably improved by coating using polymer cement slurry at surface of reinforcing bar. And this trend is marked by adding of corrosion inhibiting admixture. The difference of the anti-corrosive properties is hardly recognized according to types of polymer dispersions. The anti-corrosive properties of coated reinforcing bar using polymer foment slurry are improved to a great extent compared to those of plain reinforcing bar accordiy to increasing content of chloride ion in cement concrete.