• Tribology and Lubricants
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• v.10 no.2
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• pp.39-42
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• 1994

This paper deals with the distributions of the contact stress in oil seals. The distributions of the contact stress due to the temperature effects are analyzed for various values of the interference for a nitrile rubber seal. The calculated FEM results show that the relative maximum stresses occur at the contacting area against the shaft, the flex zone, and the contacting area of the garter spring grooves. Using the coupled temperature-stress FEM a nalysis, the contact force of a radial lip seal with and without the garter spring are studied as a function of shaft diameter. The calculated results of mechanical analysis show good correspondence with those of the coupled thermal-mechanical analysis method except small values of the interference. And the calculated results indicated that the thermal stresses only have a very minor influence on the deformed shape of the lip seal as the interference increases. But the coupled temperature-stress analysis will be very useful tool to predict the contact behaviors of rubber lip seals for small values of the interference.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1997.04a
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• pp.198-203
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• 1997

This paper deals with a numerical study of the tribological contact stress distributions of elastomeric lip seah for oscillating shafts when the sealing interference and band width between the lip edge of contact seals the shaft are present. Using the finite element method, the contact stress and band width of scraper seals rare analyzed for the sealing interference including some nonlinearities such as geometrical nonlinearity, material nonlinearity and nonlinear contact boundary condition. The FEM results showed that the contact stress concentrated on the contacting lip zone between the contacting edge of lip and the shaft for the increased interference. In double lip scraper seals, the maximum contact stress of the dust lip, which is used to exclude foreign contaminants, is six times higher than that of the primary sealing lip, which is used to contain lubricants.

• Journal of Plant Biology
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• v.25 no.1
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• pp.37-53
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• 1982

Pollen analysis from lake districts, Youngnangho, Wolhamji and Bangeojin, revealed vegetational patterns in Korea. The pollen stratigraphy was divided into five zones, zone L, I, II, IIIa and IIIb for the past 15,000 years. During zone L (earlier than 10,500 yr BP), late-glacial period, Youngnangho was vegetated with a coniferous forest dominated by spruce, larch, haploxylon pine and fir with considerable amount of herbs. Zone I(10,500~7500 yr BP) was predominantly herbaceous vegetationj with significant amount of oak and diploxylon pine. It suggests that the overall environment became milder and drier than late-glacial period. Zone II(7,500~4,000 yr BP), hypsithermal period, showed significant warming condition, indicated by high pollen concentrations of oak, diploxylon pine and hornbeam, and by more diverse flora of deciduous broad-leaved trees than before. Herbs were not an important part of vegetation. Zone III$^a$(4,000~1,500 yr BP) had pine and oak as main elements. Birch increased slightly while hornbeam decreased in this time. It indicates cooling condition. Zone III$^b$(1,5000-present) which can be called pine period showed obvious human interference. Following forest clearance, agriculture was intensified. The beginning of logging and agriculture was discernible by a sudden decline of arboreal species and by considerable amount of rice, buckwheat, sorrel and plantain. Numerous charcoal fragments were observed in zone I and zone III$^b$.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.6
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• pp.797-805
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• 2003

This paper describes experimental investigations of helium-air exchange flow through single opening and partitioned opening. Such exchange flows may occur following rupture accident of stand pipe in high temperature gas cooled reactor. A test vessel with a small opening on top of test cylinder is used for experiments. An estimation method of mass increment is developed and applied to measure the exchange flow rate. A technique of flow visualization by Mach-Zehnder interferometer is provided to recognize the exchange flows. Flow measurements are made with the opening, for partition ratios H_p/H$_1$$ in the range 0 to 1. where H_p$ and H$_1$ are partition length and height of the opening. respectively. In the case of H_p/H$_1$$ of 0, flow passages of upward flow of the helium and downward flow of the air within the opening are unseparated (bidirectional), and the two flows interfere within the opening. The unseparated flow increases strength of flow resistance and therefore, the exchange flow rate is minimum through range of the partition ratios. Two flow zones, i.e., separated (unidirectional) flow zone and unseparated (bidirectional) flow zone, exist with increasing the partition length. The exchange flow rate increases with increasing the separated flow zone. It is found that a maximum exchange flow rate exists at H_p/H$_1$$ of 1. As a result of comparison of the exchange flow rates by changing the partition ratio, the fluids Interference in the unseparated zone is found to be an important factor on the helium-air exchange flow rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.43-51
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• 2015

Upcoming cellular networks such as LTE-advanced and IEEE 802.16m are enhanced by relay stations to support high data rate multimedia services and minimize the shadow zone with low cost. Enhancing the relay stations, however, divides the multihop cellular network into smaller microcells and the distance between microcells is closer, which intends large intra-cell and inter-cell interference. Especially the access link on downlink in the OFDMA cellular network is the throughput bottleneck due to the severe interference caused by base stations and relay stations transmitting large data to mobile stations simultaneously. In this paper, we present interference aware channel allocation algorithm to avoid severe interference on multihop cellular networks with random topology. Proposed algorithm increases SINR(signal to interference plus noise ratio) and decreases number of required control messages for channel allocation, so that increases overall throughput on the networks.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1408-1415
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• 2007

To operate Platform Screen Door (PSD) automatically, the operational data of PSD and the train must be interfaced properly. PSD and train are operated together by the signaling system in Automatic Train Operation (ATO) signaling system zone where interfaces are provided between PSD and train. However, the additional PSD interface system with train is required in train operating zone without the interface between PSD and train. For the PSD interface, the wireless communication system or the train status (train correct stop status / train door status) detection system has been used. Seoul Metro line No.2. has the PSD wireless communication system using 447MHz band RF. For the safety of PSD operation, it is required to prevent RF interference in the subway environment where many frequencies exist. In this paper, the PSD wireless communication system is developed using 2.4GHz band RF to prevent the interference of the wireless communication and increase the traffic of the PSD interface. Furthermore, the improved system can store, manage and display the PSD and train operational data using Human Machine Interface (HMI) in the train's driver cab.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.10a
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• pp.157-160
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• 2000

This study is concerned with how to optimize the Input sequence of product models with sequence -dependent setup time in Mixed-Model Assembly Line (MMAL) using conveyor system. Usually MMAL consists of a number of stations linked by conveyor belt and each station has a work zone limited by upstream and downstream boundaries. To avoid improper interference between operators in the adjacent stations and excess of machine moving range, operators are forced to complete their operations within their predetermined work zone. In this study, our goal is to determine sequence of models for minimizing the total work unfinished within their work zone. A generalized formulation of the product sequencing problem in MMAL is presented and we developed an optimal procedure using Branch & Bound. Also we developed a heuristic procedure using local search.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1171-1177
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• 2011

A high power laser beam focused on a small area accelerates a thin material that flies and hits other target material in which a shock wave may be induced. This laser induced shock experimental method is more repeatable and cheaper but worse than other experimental method using gas gun or other apparatus. An optical system including a phase zone plate reduces the interference and also makes the focused-beam-intensity distribution uniform. We wrote a computer code that calculates light ray traces. Using the code we designed and fabricated an optical system including a phase zone plate and improved the laser-beam uniformity. We introduce preliminary experimental results of laser induced shock of the samples such as aluminum and other materials.

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.1
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• pp.29-37
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• 2016

We propose vehicular spread spectrum (SS) radar robust to mutual interference using zero correlation zone (ZCZ) code. SS radar schemes have been employed for vehicular radar systems due to their outstanding correlation property. However, this superiority is based on a premise that timing among codes is completely synchronized. In the practical driving environment, timing mismatch among radar signals is inevitable because the radar signals of several vehicles are independently transmitted at each different location and each timing and thus each radar signal is received at different timing. This timing offset is the main cause of orthogonality destruction among codes and thus radar signals from other vehicles become mutual interference. In order to solve this problem, we find out the new property of ZCZ code which maintains the complete orthogonality except to timing offset corresponding to chips (pulses) of multiple of 4 and employ ZCZ code to SS radar systems. Simulation results show the proposed scheme achieve better performance compared with the conventional SS radar scheme using pseudo code or gold code.

• Journal of Advanced Navigation Technology
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• v.22 no.4
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• pp.295-301
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• 2018

Recently, GPS(Global Positioning System) array antenna technology is generally used and widely adopted as a national infrastructure structure and aero-vehicles for protection the GPS signal reception. Until now, the 2-dimensional planar array is universally used for its applications in the array antenna signal processing, however relatively higher altitude air vehicles such as UAV experiences additional null zones induced by low altitude GPS interferences which is located in a symmetry zone of antenna horizontal plane and this could make the receiving antenna pattern coverage reduction. In this paper, we improved 20% of the beam pattern receiving performance and 13 dB correlation value improvement by eliminating the interference mirror images.