• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.522-541
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• 2016

Network virtualization provides an effective way to overcome the Internet ossification problem. As one of the main challenges in network virtualization, virtual network embedding refers to mapping multiple virtual networks onto a shared substrate network. However, existing heuristic embedding algorithms evaluate the embedding potential of the nodes simply by the product of different resource attributes, which would result in an unbalanced embedding. Furthermore, ignoring the hops of substrate paths that the virtual links would be mapped onto may restrict the ability of the substrate network to accept additional virtual network requests, and lead to low utilization rate of resource. In this paper, we introduce and extend five node attributes that quantify the embedding potential of the nodes from both the local and global views, and adopt the technique for order preference by similarity ideal solution (TOPSIS) to rank the nodes, aiming at balancing different node attributes to increase the utilization rate of resource. Moreover, we propose a novel two-stage virtual network embedding algorithm, which maps the virtual nodes onto the substrate nodes according to the node ranks, and adopts a shortest path-based algorithm to map the virtual links. Simulation results show that the new algorithm significantly increases the long-term average revenue, the long-term revenue to cost ratio and the acceptance ratio.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.76-85
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• 2000

Stirling cycle was actualized as so called ‘hot air engine’. It has been focused again lately as one of measures for exhaust gas emission problem, but as small power engine because of its method of heat addition. Recently marine power plants commenced to meet a stringent environmental restrictions by international convention, Marpol so that diesel engines as main and auxiliarly power plants are urged to be reformed to reduce NOx emission. Author devised a compression ignition engine as a large marine power plants combined with turbo charger based on stirling cycle, and analyzed the performance by means of basic thermodynamic calculation. Analyzed in this paper, were theoretical efficiency, mean effective pressure, required equivalence ratio, gas turbine power ratio, maximum pressure, states of turbo-charger inlet gas and exhaust gas, manifesting that the engine could be proposed as one of the future power plants of marine use.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.707-714
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• 2001

This paper presents the fundamental study on rational manu(acture of Very High Strength(VHS) concrete using industrial by-products as like silica fume, slag and fly ash. In this study, we had tested various mixing cases to manufacture the VHS concrete(target compressive strength : over 1,000 kgf/$cm^{2}$) which is easily workable (target slump flow : 60$\pm$l0cm), The main variables studied are; 1) test variables to find the optimum replacement ratio of mineral admixture, 2) test variables to find a rational water-binder ratio, a proper binder content, 3) test variables to find the method for reduction of slump loss, 4) test variables to know the influence of air entrainment on frost resistance. From the test results, it is concluded that the rational mix design can be made by using 40% slag, 10% silica fume, and water reducing agent(slump loss reduction type). We found that it is unnecessary to entrain air for freeze-thawing resistance.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.175-180
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• 2014

Experimental investigations of the heat transfer and friction factors in the ribbed divergent rectangular channel with the channel exit hydraulic diameter to inlet hydraulic diameter ratio of 1.16 were performed. The surface heaters were mounted onto the two opposite walls. The main experimental parameter is the ratio of rib pitch (p) to height (e), at which the ratios (p/e) of 6, 10, and 14 are considered in the channel with ribs on one wall only. The straight ribbed square channel is also considered as a comparison. The major findings are that the ratio of p/e = 6 shows the highest values in the heat transfer and the ratio of p/e = 10 indicates the greatest friction factor in the ribbed divergent channel. Editor's note:No major changes or corrections needed. Well written.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.135-144
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• 2005

The Effects of intake swirl and combustion parameters on the performance and emission characteristics in a V8 type turbocharged intercooler D.I. diesel engine of the displacement $16.7\iota$ were studied experimentally in this paper. Generally the swirl in the combustion process of diesel engine promotes mixing of the injection fuel and the intake air. Also, TCI diesel engine is put to practically use intercooler in order to increase boost efficiency which is cooled boost air. As a result of steady flow test, when the swirl ratio is increased, the mean flow coefficient is decreased, whereas the Gulf factor is increased. And through engine test, its can be effected to meet performance and emission by optimizing the main parameters; the swirl ratio is 2.25, compression ratio is 17.5, combustion bowl is re-entrant $8.5^{\circ}$, nozzle hole diameter is $\phi0.33^{\ast}3+\phi0.35^{\ast}2$, injection timing is BTDC $12^{\circ}CA$ and turbocharger is T02 model which are compressor 0.6A/R+46trim and turbine 1.0A/R+57trim.

• Journal of the Korean Society of Combustion
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• v.10 no.2
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• pp.35-41
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• 2005

Behaviors of lean premixed flame of propane/air and methane/air flame anchored by a pilot flame in a tube were investigated experimentally varying the mean velocity from 10 to 140 cm/s and the equivalence ratio from 0.45 to 0.8. Behaviors of both flames are divided into five regions of stable, flash-back, tail-out, flickering and vibrating. General characteristics of each region and Le number effect are investigated. Two main instabilities, flickering and vibration, are both unstable but the instability mechanism, the frequency and the amplitude of pressure fluctuation are different. In the edge of the vibrating region, pressure fluctuation repeats generation and extinction. Repeated growth and decrease of the amplitude of pressure fluctuation are explained by Rayleigh#s index.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.1
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• pp.66-79
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• 1993

To construct the design back data for a lean-burn gas engine, we have designed a constant volume combustion chamber with sub-chamber. With constant volume ratio of main-sub combustion chamber and constant equivalence ratio of methane-air mixture, the influence of geometric configurations(diameter, injection angle, number, length) of passagehole upon combustion characteristics were studied. It was found that combustion characteristics in the main combustion chamber were greatly influenced by the injection angle and length of passagehole.

• Journal of Environmental Health Sciences
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• v.40 no.1
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• pp.38-46
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• 2014

Objectives: This study was carried out in order to estimate atmospheric polycyclic aromatic hydrocarbon (PAH) concentrations and sources using pine needles as a passive air sampler (PAS) in urban (Pyeongtaek), semirural (Anseong) and rural (Jincheon) sites. Methods: One-year-old pine needles were collected for analysis of their PAH concentrations ($C_{p,n}g/g$ dry) at the end of December. PAHs concentrations in the ambient air ($C_a$, $ng/m^3$) were calculated with a $Log(C_p/C_a)-LogK_{oa}$ correlational equation. Results: PAHs concentrations in ambient air ($C_a$) were high, in the order of urban ($114.03ng/m^3$), semirural ($105.17ng/m^3$) and rural ($61.91ng/m^3$) sites. However, distributions of PAH isomer concentrations were very similar. PAHs of which molecular weight is smaller than 228.30 (AcPy, Acp, Flu, Phen, Ant, Flt, Pyr, BaA, Chry) made up most of the PAHs in the ambient air (96.6-98.5%). Conclusion: At urban, semirural and rural sites, it was concluded that the main source of PAHs in the ambient air ratio of each PAH isomer concentration was cars, especially diesel vehicles.

• Wind and Structures
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• v.31 no.1
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• pp.15-20
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• 2020

The aircraft industry supports aviation by building aircraft and manufacturing aircraft parts for their maintenance. Fuel economization is one of the biggest concerns in the aircraft industry. The reduction in specific fuel consumption of aircraft can be achieved by a variety of means, simplest and more effective is the one to impose minor modifications in the aircraft main wing or the parts which are exposed to the air flow. This method can lead to a reduction in aerodynamic resistance offered by the air and have a smoother flight. The main objective of this study is to propose geometric design modifications on an existing aircraft wing which acts as a vortex generator and it can reduce the drag and increase lift to drag ratio, leading to lower fuel consumption. The NACA 2412 aircraft wing is modified and designed. Rigorous flow analysis is carried out using computational fluid dynamics based software Ansys Fluent. Results show that saw tooth modification to the main wing shows the best aerodynamic efficiency as compared to other modifications.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1069-1076
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• 2005

The oil crises in 1973 and 1979 caused considerable effort to decrease the fuel consumption. As a result, the main engine had been changed through the shape(from loop scavenging air system to uniflow scavenging air system), higher compression ratio, low speed and long stroke. It is difficult to make a various engine satisfied with all owner's request. So manufacturer could find a way that can change the rating through large range from the engine already manufactured. These ways are tried through large range to change rpm to 72% and engine's output to 48% of MCR with keeping the normal engine's shape almost. The important element considered in the process of derated output of the main engine is to recover the beginning overcapitalization as soon as possible through low SFOC. In this paper, it is compared and considered between rating and derating engine with several data about modifying rating which have been done by engine manufacturer so far. And the selection process of derating engine is studied also.