• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2153-2164
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• 1998

This paper has presented the parameters for the coexistence between two systems in macro/microcell ovelaid W-CDMA WLL (wideband CDMA wireless local loop) and has calculated the capacity of forward/reverse link in microcell. To produce the capacity for analyzing system interference effects, we have shown tables and graphs with the parameters sucyh as RF channel bandwidth of WLL(W), the transmission rate of service message(R), the required signal power to noise power ratio( $E_{b/}$ $N_{0}$) for achieving accepatable error rate, te user number ( $N_{W1}$, $N_{W2}$) of the neighboring system, the signal power to interference power ratio(.GAMMA.$_{C1B}$, .GAMMA.$_{C2B}$) of the neighboring system, the normalized distance(d) between microcell and macrocell base-station, and microcell to macrocell radius ratio ( $R_{d}$). From the results, we have convinced that the capacity of microcell diminishes as increasing the user number ( $N_{W2}$) in macrocell, increasing the microcell radius, and decreasing the normalized distance(d) between microcell and macrocell base-station. Especially, we have known that when $R_{d}$=0.1, $N_{W2}$ must be below 24 at .GAMMA.$_{C2B}$ = 0 dB and below 8 at .GAMMA.$_{C2B}$ = 4 dB for the acceptable capacity raito to be over 80%. Therfore, this paper is usefult to design microcell W-CDMA WLL for accommodating more user number under the interference effects of macrocell W-CDMA WLL and is expected to be reference in power control if base-station.ation.ion.ation.ation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.202-208
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• 2010

The performance of upstream transmission in SCM-PON is generally limited by the presence of OBI which is caused by the beating of two or more lasers. In this paper, we propose a novel approach for reducing OBI problem by using heterodyne detection with an additional LD as a local oscillator, resulting that the RF signal is shifted to the other spectal band. In addition, it is possible that the proposed method can provide the cost-effective solution thanks to the loop-back mechanism using R-SOA in ONUs. The performance is superior when the spectral width of LD is smaller and the power difference between the transmission LD and the oscillation LD is bigger. System configuration and design consideration are discussed. Performance of the systems is evaluated by simulator called OptSim. It is expected to provide WDM/SCM-PON system not only cost-effective but also efficient in increasing the number of subscribers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.134-139
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• 2004

A clock recovery circuit for a 40 Gb/s optical receiver has been designed and implemented. The clock recovery circuit consists of pre-amplifiers, a nonlinear circuit with diodes, a bandpass filter and a clock amplifier. Before implementing the 40 Gb/s clock recovery circuit, a 10 Gb/s clock recovery circuit has been successfully implemented and tested. With the 40 Gb/s clock recovery circuit, when a 40 Gb/s signal of -10 dBm was applied to the input of the circuit, the 40 GHz clock was recovered with the -20 dBm output power after passing through the nonlinear circuit. The output signal from the nonlinear circuit passes through a narrow-band filter, and then amplified. The implemented clock recovery circuit is planned to be used for the input of a phase locked loop to further stabilize the recovered clock signal and to reduce the clock jitter.

• Nuclear Engineering and Technology
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• v.30 no.5
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• pp.403-415
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• 1998

The CANDU 6 reactor assembly consists of an array of 380 pressure tubes, which are installed horizontally in a large cylindrical vessel, the Calandria, containing the low pressure heavy water moderator. The pressure tube is located inside the calandria tube and the annulus between these tubes, which forms a closed loop with $CO_2$ gas recirculating, is called the Annulus Gas System(AGS). It is designed to give an alarm to the operator even for a small pressure tube leak by a very sensitive dew point meter so that he can take a preventive action for the pressure tube rupture incident. To judge whether the operator action time is enough or not in the design of Wolsong 2,3 & 4, the Leak Before Break(LBB) assessment is required for the analysis of the pressure tube failure accident. In order to provide the required data for the LBB assessment of Wolsong Units 2, 3, 4, a series of leak detection capability tests was performed by injecting controlled rates of heavy water vapour. The data of increased dew point and rates of rise were measured to determine the alarm set point for the dew point rate of rise of Wolsong Unit 2. It was found that the response of the dew point depends on the moisture injection rate, $CO_2$ gas flow rate and the leak location. The test showed that CANDU 6 AGS can detect the very small leaks less than few g/hr and dew point rate of rise alarm can be the most reliable alarm signal to warn the operator. Considering the present results, the first response time of dew point to the AGS $CO_2$ flow rate is approximated.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.523-533
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• 2015

Three-dimensional flow phenomena in a wire-wrapped 37-pin fuel assembly mock-up of a Japanese loop-type sodium-cooled fast reactor, Monju, were investigated with a numerical analysis using a general-purpose commercial computational fluid dynamics code, CFX. Complicated and vortical flow phenomena in the wire-wrapped 37-pin fuel assembly were captured by a Reynolds-averaged Navier-Stokes flow simulation using a shear stress transport turbulence model. The main purpose of the current study is to understand the three-dimensional complex flow phenomena in a wire-wrapped fuel assembly to support the license issue for the core design. Computational fluid dynamics results show good agreement with friction factor correlation models. The secondary flow in the corner and edge subchannels is much stronger than that in an interior subchannel. The axial velocity averaged in the corner and edge subchannels is higher than that averaged in the interior subchannels. Three-dimensional multiscale vortex structures start to be formed by an interaction between secondary flows around each wire-wrapped pin. Behavior of the large-scale vortex structures in the corner and edge subchannels is closely related to the relative position between the hexagonal duct wall and the helically wrapped wire spacer. The small-scale vortex is axially developed in the interior subchannels. Furthermore, a driving force on each wire spacer surface is closely related to the relative position between the hexagonal duct wall and the wire spacer.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.952-964
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• 2016

The prototype generation IV sodium-cooled fast reactor (PGSFR) has been developed by the Korea Atomic Energy Research Institute. This reactor uses sodium as a reactor coolant to transfer the core heat energy to the turbine. Sodium has chemical characteristics that allow it to violently react with materials such as a water or steam. When a sodium-water reaction (SWR) occurs due to leakage or breakage of steam generator tubes, high-pressure waves and corrosive reaction products are produced, which threaten the structural integrity of the components of the intermediate heat-transfer system (IHTS) and the safety of the primary heat-transfer system (PHTS). In the PGSFR, SWR events are included in the design-basis event. This event should be analyzed from the viewpoint of the integrities of the IHTS and fuel rods. To evaluate the integrity of the IHTS based on the consequences of the SWR, the behaviors of the generated high-pressure waves are analyzed at the major positions of a failed IHTS loop using a sodium-water advanced analysis method-II code. The integrity of the fuel rods must be consistently maintained below the safety acceptance criteria to avoid the consequences of the SWR. The integrity of the PHTS is evaluated using the multidimensional analysis of reactor safety-liquid metal reactor code to model the whole plant.

• Journal of the Korea Society of Computer and Information
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• v.13 no.1
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• pp.143-151
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• 2008

Execute IP traceback at this paper as target an intruder's attacking that Bypass Attack in order to avoid an exposure of own Real IP address Design IP traceback server and agent module, and install in Internet network system for Real IP traceback. Set up detection and chase range aggressive loop around connection arbitrariness, and attack in practice, and generate Real IP data cut off by fatal attacks after data and intrusion detection accessed general IP, and store to DB. Generate the Forensic data which Real IP confirms substance by Whois service, and ensured integrity and the reliability that buy to early legal proof data, and was devoted to of an invader Present the cyber criminal preventive effect that is dysfunction of Ubiquitous Information Society and an effective Real IP traceback system, and ensure a Forensic data generation basis regarding a judge's robe penalty through this paper study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.135-145
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• 2005

Geotechnical design routinely requires that in-situ strength, stiffness of the ground be determined. In the working stress conditions, the strain level in a ground experienced by existing structures and during construction is less than about 0.1%~1%. In order to analyze the deformational behavior accurately, the in-situ testing technique which provides the reliable deformational characteristics at small strains, needs to be developed. Cone pressuremeter tests were performed on the western off-shore region of korea, and analyzed using cavity expansion theory and curve fitting technique to obtain the shear modulus at small strain level of $10^{-1}%$. The value of $E_u/S_u$ ratio for the marine clay shows about 589 at the small strain. However the value of $E_u/S_u$ estimated by lab tests are much smaller values ranged from 81 to 91. It is indicated that the curve fitting technique from CPM tests results can be used to obtain the shear modulus at small strain.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.101-104
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• 2000

Nowadays, the issue of congestion control in high-speed communication networks becomes critical in view of the bandwidth-delay products for efficient data flow. In particular, the fact that the congestion is often accompanied by the data flow from the high-speed link to low-speed link is important with respect to the stability of closed-loop congestion control. The Virtual-Connection Network (VCN) in Gigabit Ethernet networks is a packet-switching based network capable of implementing cell- based connection, link-by-link flow-controlled connection, and single- or multi-destination virtual connections. VCN described herein differ from the virtual channel in ATM literature in that VCN have link-by-link flow control and can be of multi-destination. VCNs support both connection-oriented and connectionless data link layer traffic. Therefore, the worst collision scenario in Ethernet CSMA/CD with virtual collision brings about end-to-end delay. Gigabit Ethernet networks based on CSMA/CD results in non-deterministic behavior because its media access rules are based on random probability. Hence, it is difficult to obtain any sound mathematical formulation for congestion control without employing random processes or fluid-flow models. In this paper, an analytical method for the design of a congestion control scheme is proposed based on Smith＇s principle to overcome instability accompanied with the increase of end-to-end delays as well as to avoid cell losses. To this end, mathematical analysis is provided such that the proposed control scheme guarantees the performance improvement with respect to bandwidth and latency for selected network links with different propagation delays. In addition, guaranteed bandwidth is to be implemented by allowing individual stations to burst several frames at a time without intervening round-trip idle time.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.6
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• pp.20-26
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• 2002

This paper deals with the guaranteed cost control problems for a class of discrete-time linear uncertain systems with time-varying delay. The uncertain systems under consideration depend on time-varying norm-bounded parameter uncertainties. We address the existence condition and the design method of the memoryless state feedback control law such that the closed loop system not only is quadratically stable but also guarantees an adequate level of performance for all admissible uncertainties. Through some changes of variables and Schur complement, It is shown that the sufficient condition can be rewritten as an LMI(linear matrix inequality) form in terms of all variables.