• Journal of Korea Water Resources Association
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• v.42 no.8
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• pp.607-617
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• 2009

Radar beam blocking which is partially or entirely interrupted by obstacles like a mountain causes underestimation of the rainfall. In this paper, partially blocked radar reflectivity is retrieved using the ARM(Accumulated Reflectivity Map). ARM is made by accumulation of the radar reflectivity and very useful product to analyze the beam blockage. The blockage correcting map could be obtained by assuming the spatially uniform reflectivity field in the ARM. This method is applied to the cases of typhoon and Changma, and we obtain the MFE(Mean Fractional Error) from two radar data, the one is objective radar data which is affected by blockage and the other is comparative radar data which is not affected by blockage. Before blocking correction, MFE is 20-35%. However, after correction, MFE decreases to 7-10%.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.637-642
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• 2020

In this study, the SLB(Sidelobe Blanking)/BLB(Blacklobe Blanking) design of the VHF band radar using the low-frequency band having a relatively larger beam width than the S-band or X-band radar. The antenna of the VHF band has a relatively large beam width, so it is reflected from the side lobe. If the reflected target signal is not processed into sidelobe, the false alarm rate of the radar increases by recognizing it from the main lobe signal. This method of SLB blocking is the elimination of the side lobe signal in the front of the array antenna using the central radiating element of the array antenna, and the blocking of side lobe signal from the antenna rear through BLB receiver block. After completed the radar implementation, The function of blocking of side lobe signals was confirmed through the system unit test by Simulated signal generator. Through this study, it will be used in the implementation of the side-lobe blocking technology of the array antenna for low-frequency band radar with large antenna size and beam width in the future.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.305-306
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• 2008

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8B
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• pp.730-738
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• 2004

In this paper, System performance parameters such as throughput, blocking probability and delay have been analyzed and expressed as a function of demanding traffic and service termination, probability, and we centers our discussion at particular downlink port of satellite switch which is capable of switching the individual spot beam and processing the information signals in the packet satellite communications with demand assigned multiple access technique. Delay versus throughput as a function of traffic parameters with several service termination probability can be derived via mathematical formulation and the relative differences of transmission delay is also compared.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.84-90
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• 2010

In focused ion beam (FIB) fabrication processes the ion beam intensity with Gaussian profile has a drawback for high resolution machining. In this paper, the fabrication method to modify the beam profile at substrate using silt mask is proposed to increase the machining resolution at high current. Slit mask is utilized to block the part of beam and transmit only high intensity portion. A nano manipulator is utilized to handle the silt mask. Geometrical analysis on fabricated profile through silt mask was conducted. By utilizing proposed method, improvement of machining resolution was achieved.

• Polymer(Korea)
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• v.29 no.6
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• pp.588-592
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• 2005

For the purpose of obtaining polycarbonate film which blocks ultra-violet ion beam was irradiated onto the surface of PC film. This method has gotten several advantages compared with the techniques, such as the protection of changes in film thickness and UV blocking material deposited onto a base film. In order to investigate UV blocking PC film, the optical and chemical characteristics, surface morphology and lightfastness were confirmed by UV/Vis, FTIR(ATR) spectroscopy, AFM, and Q-UV fasoess analyses. As a result, it was shown that the modified PC film was able to block almost all of UV region and easily control the degree of UV block. The optical changes in the film were attributed to chemical changes in PC surface by ion beam irradiation. Moreover, we expect that the modified PC film can durably block UV due to no changes in colour and UV transmittance after UV fastness test.

• Journal of Internet Computing and Services
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• v.21 no.6
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• pp.1-12
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• 2020

Low-Orbit satellite mobile networks can provide services through miniaturized terminals with low transmission power, which can be used as reliable means of communication in the national public disaster network and defense sector. However, the high traffic environment in the emergency preparedness situation increases the new call blocking probability and the handover failure probability of the satellite network, and the increase of the handover failure probability affects the QoS because low orbit satellites move in orbit at a very high speed. Among the channel allocation methods of satellite communication, the FCA shows relatively better performance in a high traffic environment than DCA and is suitable for emergency preparedness situations, but in order to optimize QoS when traffic increases, the new call blocking and the handover failure must be minimized. In this paper, we propose LEO-DBC (LEO satellite dynamic beam width control) technique, which improves QoS by adaptive adjustment of beam width of low-orbit satellites and call time of terminals by improving FCA-QH method. Through the LEO-DBC technique, it is expected that the QoS of the mobile satellite communication network can be optimally maintained in high traffic environments in emergency preparedness situations.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.149-152
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• 2000

In this paper, the reverse link performance of an imperfect power controlled DS/CDMA cellular system that uses a base station array antenna which can effectively remove the multiple access interference is analyzed considering both beam forming algorithm and power control error in shadowing. The blocking probability of the DS/CDMA cellular system based on array parameters, Eb/No and statistics of interference is derived, and then the system capacity corresponding to a certain blocking probability is calculated. On the assumption that the blocking probability is set 1 ％, the system capacity using MCGM algorithm with 12 antenna arrays is increased about 59 % than that using 8 antenna arrays when power control error is 2.5 ㏈.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.1
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• pp.51-54
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• 2002

Polymer EL devices of glass/ITO/PI/MEH-PPV/Al structure were fabricated using spin coating and the Ionized Cluster Beam deposition technique. PMDA-ODA type thin polyimide films which can be used as a impurity blocking layer of EL device were deposited by ICB. According to our previous results, the packing densities of polyimide films were subject to change and depend on their deposition condition. By inserting a Pl layer with various thickness and packing density, I-V characteristics and life time of the devices were investigated to determine the role of a interlayer. The blocking of impurity diffusion from ITO to luminescent layer were confirmed by XPS.

• Proceedings of the Korean Nuclear Society Conference
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• 2004.10a
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• pp.719-720
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• 2004

A multi-megawatt long pulse ion source (LPIS) of neutral beam injector was developed for the KSTAR. Beam extraction experiments of the LPIS were carried out at the neutral beam test stand (NBTS). Design requirements for the ion source were 120 kV/65 A deuterium beam and a 300 s pulse length. A maximum ion density of $9.1310^{11}$ $cm^{-3}$ was measured by using electric probes, and an optimum arc efficiency of 0.46 A/kW was estimated with ion saturation current of the probes, arc power, and total beam area. An arcing problem, caused by the structural defect of decelerating grid supporter, in the third gap was solved by the blocking of backstream ion particles, originated from the plasma in the neutralizer duct, through the unnecessary spaces on the side of grid supporter. A maximum drain power of 1.5 MW (i.e. 70 kV/21 A) with hydrogen was measured for a pulse duration of 0.5 s. Optimum beam perveance was ranged from 0.75 to 0.85. An improved design of accelerator for the effective control of beam particle trajectory should provide higher beam perveance.