• 한국연소학회:학술대회논문집
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• 2000.05a
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• pp.178-188
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• 2000

In the present study, a systematic chemical kinetic calculations were made to investigate the augmentation of $NO-NO_{2}$ conversion due to the addition of various hydrocarbons (methane, ethylene, ethane, propene, propane) in the nonthermal plasma treatment. It is included in the present conclusion that the reaction between hydrocarbon and oxygen radicals induced by electron collision, is believed to be a primarily process for triggering the overall NO oxidation and the eventual NOx reduction. Upon the completion of the initiating step, various radicals (OH, $HO_{2}$ etc.) successively produced by hydrocarbon decomposition form the primary path of $NO-NO_{2}$ conversion. When the initiating step is not activated, hydrocarbon consumption rate appeared to be very low, thereby the targeted level of NO conversion can only be achieved by the addition of more input energy. Present study showed ethylene and propene to have higher affinity with 0 radical under all conditions, thereby both of these hydrocarbons show very fast and efficient $NO-NO_{2}$ oxidation. It was also shown that propene is superior to ethylene in the aspect of NOx removal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.729-739
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• 1994

In a centralized spread-spectrum packet radio network, a random assignment -transmitter-based spreading code protocol(RA-T) is proposed which permits the contention mode only in the trasmission of a preamble while avoiding collision during the data packet transmission by assigning near-orthogonal spreading codes to each user. Compared to the conventional transmitter-based code scheme, this scheme allows reduction in receiver complexity when only a small number of distinct spreading codes are employed for the preamble transmission. Throughout theoretical and simulation results, it is shown that the use of the RA-T scheme with just two or three distinct codes for the preamble packet achieves most of the performance gain.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.6
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• pp.711-720
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• 2015

Recently many studies of Radar systems mounted on ground vehicles for autonomous driving, SLAM (Simultaneous localization and mapping) and collision avoidance have been reported. Since several pixels per an object may be generated in a close-range radar application, a width of an object can be estimated automatically by various signal processing techniques. In this paper, we tried to attempt to develop an algorithm to estimate obstacle width using Radar images. The proposed method consists of 5 steps - 1) background clutter reduction, 2) local peak pixel detection, 3) region growing, 4) contour extraction and 5)width calculation. For the performance validation of our method, we performed the test width estimation using a real data of two cars acquired by commercial radar system - I200 manufactured by Navtech. As a result, we verified that the proposed method can estimate the widths of targets.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.4
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• pp.9-16
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• 2015

Quick and safe message transmission is an important research topic of vehicular ad hoc networks (VANET). Most studies assume that the periodic broadcast of beacon-frames between vehicles increases the safety of the driver. In this paper, we propose a medium access control (MAC) protocol and location-based clustering for the VANET to support reliable data transfer. In our proposal, the cluster heade (CH) manage the access and allocate the resources of the node. Our proposal uses simulation to confirm the reduction of the transmission delay and the collision rate of the signal.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1103-1114
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• 2000

Recent attempt to enhance the safety against collision reshaped the simple shell structures into the integrated complex shell structures. Moreover, due to various regulations continuously tightened for environment protection, weight reduction of automobiles becomes an increasingly important issue. Auto parts lightening is mainly accomplished by more reasonable design, adoption of lighter materials and miniaturization of the auto bodies. Focusing on the locally enhanced design approach among the above three ways, we here attempt to develop a patching optimization method, and also to determine the thicknesses of an integrated shell structure, both bringing a specified amount of stress relaxation. We first select a cross member as a patching optimization model. Based on the finite element stress calculations, we relieve the stress of cross member by patching in two ways-nonuniform thickness patching and optimized uniform thickness patching, the latter of which is more effective in a practical point of view for the preset amount of stress relaxation. Selecting a box type subframe as another finite element analysis model, we then determine the thickness of each part by axiomatic design approach for a preset amount of stress relaxation. The patching methodology and the axiomatic approach adopted in this work can be applied to the other complex shell structures such as center member and lower control arm.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.08a
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• pp.45-52
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• 2004

Continuing pressure for the weight reduction of vehicles and improvement of collision safety is driving the development of new high strength steel with excellent formability. The formable high strength steels which have excellent drawability have been developed and applied to the complicated inner panels. Although BH steel have mainly occupied the material market for outer panels, it is challenged by DP steel which have low yield strength and good bake hardenability. The advanced high strength steel, TRIP steels and DP steels which have excellent formability are new alternatives to conventional HSLA steel for structural parts such as members and pillars. HSLA steels also have been used for automotive bumper reinforcements due to their high yield ratio. Higher grade complex phase steel(CP) were developed for bumper reinforcements by addition of precipitation hardening to transformation strengthened steel. The usage of the advanced high strength steel ale increasing and will become the main material in structural parts near future. This paper describes the features of newly developed high strength cold rolled steels for automobiles.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2005.05a
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• pp.267-271
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• 2005

This experiment was carried out at 450"C, which is relatively lower than the temperature for supercritical water oxidation (600-650$^{\circ}C$). In this experiment, the decomposition rates of various incombustible organic substances were very high. In addition, it was confirmed that hetero atoms existed in organic compounds and chlorine was neutralized by sodium(salt formation).However, to raise the decomposition rate, relatively large amount of sodium nitrate(3-4 times the equivalent weight) was required. When complete oxidation is intended as in the case with PCB, the amount of oxidizer and decomposition cost is important. But when vaporization reduction is required as in the case with nuclear wastes, the amount of radioactive wastes increases instead. But as can be seen in the result of XRD measurement, unreacted sodium nitrate remained unchanged. If oxidation reaction of organic substance simply depends on collision frequency, unreacted sodium nitrate can be recovered and reused, then oxidation equivalent weight would be sufficient. In the gas generated, toxic gas was not found. As the supercritical water medium has high reactivity, it is difficult to generate relatively low energy level SO$_{X}$, and NO$_{X}$.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.3
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• pp.53-58
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• 2006

This study deals with the method of post-processing in the automatic tool path generation for 5-axis NC machining. The 5-axis NC machining cannot only cope with the manufacturing of complicated shapes, but also offers numerous advantages such as reasonable tool employment, great reduction of set-up process and so on. Thus 5-axis NC machining has been used for aircraft parts, mold and die as well as for complicated shapes such as impeller, propeller and rotor. However, most of the present CAM systems for 5-axis NC machining have limited functions in terms of tool collision, machine limits and post-processing. Especially 5-axis machine configurations are various according to the method which the rotational axes are adapted with the table and spindle. For that reason, In many cases the optimal numerical control (NC) data cannot be obtained or considerable time is consumed. To solve this problem, we applied a general post-processor for 5-axis NC machining. The validity of this post-processor should be experimentally confirmed by successfully milling to a helix shaped workpiece.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.364-369
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• 2012

Location information is a critical element of ubiquitous computing. Cricket is an indoor location-based system that transmits radio and ultrasonic signals in regular intervals to calculate the distance between nodes. However, the amount of signal interference and collisions increases in proportion with the number of nodes, losing the accuracy of the location-based system. This study proposes an algorithm based on the 802.15.2 MAC protocol for the wireless sensor network to reduce signal interference and collision by employing node numbers and the frequency reuse approach used in mobile telecommunication. We analyzed the performance of our algorithm. The obtained results showed that the algorithm is an effective for throughput and energy compared to the Cricket system.

• Journal of Surface Science and Engineering
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• v.45 no.1
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• pp.25-30
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• 2012

The galvanostatic tests for corrosion protection are conducted at various applied current densities during 93,600 sec, and evaluated in terms of the variations in current density with time and in the potential at the applied current density. In addition, the corrosion damage depth is analyzed with 3D analysis optical microscope after galvanostatic tests. In this study, it was investigated to decide condition of the corrosion protection gavalnostatic method for Cu-Al alloy that has an excellent corrosion resistance. In the galvanostatic test under the cavitation environment, the energy was reflected or cancelled out by the collision with the oxygen gas generated by the oxygen reduction action. The surface observation showed neither the cavitation damage nor the electrochemical damage in the current density over 0.01 $A/cm^2$ in the dynamic state under the cavitation environment.