• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.649-656
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• 2004

Hypersonic wind tunnel test of the rectangular variable geometry intake is performed. For realization of a Precooled turbojet engine, development of a hypersonic ramjet engine is planned. To investigate performance of the intake of the hypersonic ramjet engine, wind tunnel test is done with freestream Mach number of 5.1. The total pressure recovery was 18 % with 12.9 % of ramp bleed. Several reasons for low total pressure recovery are shown. Supersonic internal compression is not enough. Then, the throat Mach number is high (M2.61) and total pressure losses at the terminal shock is large. Supersonic flow at the throat and position of the terminal shock is sensitive to a difference of the second ramp's throat height and the third ramp's throat height. Flow separations at the second ramp's trailing edge and the third ramp's leading edge are seen those could result in the trigger of unstart. The seal mechanism between the ramps and the sidewalls is important.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.226-229
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• 2001

To achieve ZnO layer with a high resistance, a new sputtering method with a Ramp method and cycled power process mode was developed. The specific resistance of the layers was in rang of 3*10$\^$10/Ωcm to 2*10$\^$11/Ωcm. The characteristics of ZnO thin films changed with working pressure and Ramp method were investigated by XRD(x-ray diffractometer), and SEM (scanning electron microscopy) analyses. This paper presents calculated and measured results for structures with thin ZnO layers. Measurements of SAW Properties using thin ZnO layered structures will be shown. Also presented are results on the quality of ZnO films and specifics of the deposition process.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.2
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• pp.9-21
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• 2011

The ramp metering strategy is one of the effective ways to solve the freeway traffic congestion in peak time periods. The study was initiated with assurance that the traffic conditions of ramp and mainline that mitigate the congestion would exist. Under the moderate traffic volume levels, ramp metering is expected to improve the quality of freeway operation. To derive a range of traffic condition, three operation strategies(Do nothing, ramp metering, minimum ramp control) were set up and the ALINEA algorithm was implemented with microscopic traffic simulator "VISSIM". The volumes of mainline and ramp are key parameters for the simulation scenarios. Measures of effectiveness for the study include mainline density and average vehicle speed. Operation boundaries in terms of traffic volume were proposed for operating ramp metering strategy. The results show that under the proposed traffic conditions the ramp metering was more successful to increase average vehicle speeds. Traffic controls under the operation boundaries of traffic levels give significant effects for density and average vehicle speed. The outcomes of this study would be useful to improve the performance of ramp metering strategies.

• 한국기계연구소 소보
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• v.4 no.1
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• pp.43-50
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• 1981

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.780-785
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• 2004

The work presented here deals with controller design by graphical method based on proportional control ramp response. The design aims at the improvement of transient response, disturbance rejection capability, steady-state error reduction with stability preservation. The first step is to generate tracking-error curve with proportional control only and decide the added error signal shape on the error curve. The effectiveness of the proposed controller is confirmed through the simulation and experiment.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.219-227
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• 2021

In the present study, the effect of command signals of the flow control valve on performance of underwater discharge systems using a linear pump was investigated numerically. For that, the improved mathematical model was developed. The improvement is to calculate the flow leakage between the water cylinder and the piston. Also the model of the hydraulic cylinder is simplified. To validate the improved model, calculation results were compared with experiment results. The results of the study is as follows: Double ramp command signals of the flow control valve had an advantage over single ramp signals. The parametric study on the effect of double ramp command signals on performance of the system was performed. In case of using double ramp signals, the maximum acceleration of the underwater vehicle was reduced by approximately 50 % compared with using single ramp signals.

• Journal of Korean Port Research
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• v.14 no.2
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• pp.175-185
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• 2000

Today freeway is experiencing a severe congestion with incoming or outgoing traffic through freeway ramps during the peak periods. Thus, the purpose of this study is to identify the traffic characteristics, analyze the relationships between the traffic characteristics and finally construct the delay predictive models on the rap junctions of freeway with 70mph speed limit. From the traffic analyses, and model construction and verification for delay prediction on the ramp junctions of freeway, the following results were obtained : ⅰ) Traffic flow showed a big difference depending on the time periods. Especially, more traffic flows were concentrated on the freeway junctions in the morning peak period. ⅱ) The occupancy also showed a big difference depending on the time periods, and the downstream occupancy(Od) was especially shown to have a higher explanatory power for the delay predictive model construction on the ramp junctions of freeway. ⅲ) The delay-occupancy curve showed a remarkable shift based on the occupancies observed : O$\_$d/〈9% and O$\_$d/$\geq$9%. Especially, volume and occupancy were shown to be highly explanatory for delay prediction on the ramp junctions of freeway under O$\_$d/$\geq$9%, but lowly for delay prediction on the ramp junctions of freeway under O$\_$d/〈9%. Rather, the driver characteristics or transportation conditions around the freeway were thought to be a little higher explanatory for the delay prediction under O$\_$d/〈9%. ⅳ) Integrated delay predictive models showed a higher explanatory power in the morning peak period, but a lower explanatory power in the non-peak periods.

• Journal of The Korea Institute of Healthcare Architecture
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• v.26 no.2
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• pp.31-38
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• 2020

Purpose: The ramp is an important facility for the barrier free access and vertical circulation of users of various buildings, including users of walker, wheelchair users, stroller users, and baggage carriers. The installation standards for ramps in Korea have various problems during construction and BF certification. It is necessary to improve the criteria for ensuring practical mobility and safety. Method: Korean standard, International Standard(ISO 21542, 2011), German Standard(DIN 18040-1, 2010), Austrian Standard(OENORM B 1600, 2017), Swiss Standard(Norm SIA 500, 2009), Canadian Standard(Building Standards Guide, 2017), American Standard(ADA Standards, 2010) were investigated and analyzed. A comprehensive improvement of the ramp installation standards is proposed. Results: The ramp is a necessary facility for the barrier free access and vertical circulation of the disabled. It shall be installed with comprehensive consideration of the appropriate slope of the ramp, the distance of the continuous slope, the handle and upstand for pedestrian safety. In order to improve convenience, setting the proper slope and limiting the length of the slope are very important, and improvements are required to the levels presented by international and foreign standards. The unclear standards of Korean law and BF certification standards should be clearly improved so as not to be misinterpreted in construction and Barrier Free Certification. Implication: International and foreign standards should be reviewed to ensure practical mobility and safety. And comprehensive improvement measures should be presented through continuous research.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.329-332
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• 2005

Cross rolling process is one of incremental forming processes to form an axi-symmetric shaped metal component. It can be classified into two types according to the shape of dies, which are a drum type (roll type) and a plate type (straight type). It can also be classified into a wedge type and a ramp type processes according to deformation characteristics of a material. The ramp type die is applied to plate type cross rolling process in cold forming process for forming of teeth of gear or bolt, while the wedge type die is generally utilized to drum type and plate type cross rolling processes in hot forming process. A shape of the ramp type die is usually same as final shape of a product at every section of a progressing direction, while the shape of the wedge type die has different shapes in a progressing direction. In this paper, a rolling of neck part in a ball stud component has been carried out using the plate type cross rolling process with a ramp shaped die. Forming characteristics have been performed using finite element analysis in order to obtain a proper preform for the ramp type plate cross rolling process.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.13-15
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• 1999

A Josephson sampler circuit using high-Tc superconductor (HTS) ramp-edge junctions has been designed, fabricated, and experimentally tested. It consists of five ramp-edge junctions with a stacked groundplane and is based on single-flux-quantum (SFQ) operations. The sampler was used to measure current waveforms at picosecond and microampere resolutions. We are developing a system based on the sampler for measuring the current waveform in a room-temperature sample. And measuring current flowing through wiring in a semiconductor large-scale integrated circuit is a promising application for the HTS sampler system.