• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.753-757
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• 2011

The possibility of implementing nonuniform residual dispersion per span (RDPS) in optical links with net residual dispersion (NRD) controlled by precompensation and postcompensation for 960 Gbps WDM transmissions is studied and discussed. The fiber optic communication links investigated in this paper consist of inline dispersion management (DM) for each fiber spans and optical phase conjugator (OPC) at mid-way of total transmission length in order to compensate for WDM signal distortions due to group velocity dispersion (GVD) and nonlinearities. It is confirmed that the effect of nonuniform RDPS distribution on system performance is not significant. It is also confirmed that the optimal NRD is obtained to be one of two values of +10 ps/nm or -10 ps/nm, which depend on the deciding of NRD controlled by precompensation or postcompensation, and the exact RDPS configurations. The effective NRD ranges resulting eye opening penalty (EOP) below 1 dB are independent on the exact RDPS distribution for relative low launch power. Therefore, results show the possibility of implementing the flexible optical links to expand network construction for WDM transmission of high bit-rate capability.

• Structural Engineering and Mechanics
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• v.53 no.4
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• pp.703-723
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• 2015

In this paper optimization of volume fraction distribution in a thick hollow cylinder with finite length made of two-dimensional functionally graded material (2D-FGM) and subjected to steady state thermal and mechanical loadings is considered. The finite element method with graded material properties within each element (graded finite elements) is used to model the structure. Volume fractions of constituent materials on a finite number of design points are taken as design variables and the volume fractions at any arbitrary point in the cylinder are obtained via cubic spline interpolation functions. The objective function selected as having the normalized effective stress equal to one at all points that leads to a uniform stress distribution in the structure. Genetic Algorithm jointed with interior penalty-function method for implementing constraints is effectively employed to find the global solution of the optimization problem. Obtained results indicates that by using the uniform distribution of normalized effective stress as objective function, considerably more efficient usage of materials can be achieved compared with the power law volume fraction distribution. Also considering uniform distribution of safety factor as design criteria instead of minimizing peak effective stress affects remarkably the optimum volume fractions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1566-1574
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• 2010

This paper presents an in-depth review for current status for demand-side management (DSM) investment of energy supplier and an useful prospect on the introduction of Energy Efficiency Resource Standards (EERS). According to the Article 9 of Rational Energy Utilization Act, Energy suppliers-Korea Electric Power Corporation (KEPCO), Korea Gas Corporation (KOGAS) and Korea District Heat Corporation (KDHC) prescribed by Presidential Decree-must establish and implement annual demand-side management investment plan to improve energy efficiency in production, transformation, transportation, storage and usage of corresponding energy and to reduce demand and green house gas emissions. In this paper, we examine the DSM programs of energy suppliers and the results of DSM investment in 2009, then we propose a reasonable solution for the development of DSM investment. Furthermore, in order to compare our situation, the case studies were conducted on EERS issues in England, Italy, France and U.S, such as establishing the energy saving target, selecting the target energy supplier, and penalty and incentive mechanisms. Throughout the case studies, this paper suggests the directions to the DSM investment planning of energy suppliers and the major issues to prepare EERS in Korea.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.9
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• pp.11-17
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• 2006

We have theoretically investigated the effects of the interplay between the driving voltage of Mach-Zehnder(MZ) modulators and the bandwidth of low-pass filters(LPF) in 10[Gb/s] duobinary modulation systems. For the change of driving voltage ratios(driving voltage/switching voltage), the transmission performance has been evaluated over 200[km] of single-mode fiber(SMF) systems. For driving voltage ratios with smaller than 100[%], the transmission performance has been maintained and greatly affected by the bandwidth of LPFs than the driving voltage. For driving voltage ratios with larger than 100[%], the transmission performance has been degraded and is not sensitive to the bandwidth of LPFs. To see the limitation of driving voltage, we have reduced the driving voltage ratio to 50[%]. Our results suggest that 10[Gb/s] duobinary signals with driving voltage ratio with smaller than 100[%] have been transmitted over 200[km] SMF within 2[dB] power penalty without dispersion compensation. For the driving voltage ratio with 50[%], we have verified that the transmission performance was maintained.

• Korean Journal of Optics and Photonics
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• v.12 no.3
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• pp.212-218
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• 2001

We experimentally investigated the dependence of extinction ratio and chirp on bias current which was injected into DFB-LD in a directly modulated 2.5 Obitls transmitter. Through the abnormal dispersion transmission, we found that transmission power penalty is minimized at 8-10 dB extinction ratio (bias current at 1.5-1.8 fold above threshold current). Also, we discussed the relation between extinction ratio and self phase modulation (SPM) through the 240 km abnormal dispersion transmission. When SPM takes effect, we obtained the best receiver sensitivity for specific system configuration at 10.4 dB and 8.4 dB extinction ratio, below and above 200km transmission distance, respectively. ively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.106-112
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• 1997

We demonstrate a novel wavelength -division add/drop multiplexer employing fiber bragg gratings and polarization beam splitters. the multiplexer is easy to fbricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5Gbps-per-channel WDM transmission system. We find that the rejection of adjacent channels is more than -6dB, and the signal leakage through output port is less than -34dB.

• Journal of Computing Science and Engineering
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• v.4 no.3
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• pp.189-206
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• 2010

It is generally accepted that dynamic voltage scaling (DVS) is one of the most effective techniques of energy minimization for real-time applications in embedded system design. The effectiveness comes from the fact that the amount of energy consumption is quadractically proportional to the voltage applied to the processor. The penalty is the execution delay, which is linearly and inversely proportional to the voltage. According to the granularity of tasks to which voltage scaling is applied, the DVS problem is divided into two subproblems: inter-task DVS problem, in which the determination of the voltage is carried out on a task-by-task basis and the voltage assigned to the task is unchanged during the whole execution of the task, and intra-task DVS problem, in which the operating voltage of a task is dynamically adjusted according to the execution behavior to reflect the changes of the required number of cycles to finish the task before the deadline. Frequent voltage transitions may cause an adverse effect on energy minimization due to the increase of the overhead of transition time and energy. In addition, DVS needs to be carefully applied so that the dynamically varying chip temperature should not exceed a certain threshold because a drastic increase of chip temperature is highly likely to cause system function failure. This paper reviews representative works on the theoretical solutions to DVS problems regarding inter-task DVS, intra-task DVS, voltage transition, and thermal-aware DVS.

• Journal of the Korean Institute of Navigation
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• v.5 no.1
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• pp.1-23
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• 1981

As far as transportation problems are concerned, the minimization of transportation cost is the most prevailing object. But in some cases, the cargo delivery time is the utter problem rather than the cost. For instance, we may imagine the case that the delivery of the construction materials is delayed behind the schedule and this makes the construction cost increased because of idle time of other materials and man power, in addition to the indemnity. Therefore the allocation of ships, in marine transportation which is now the main route of overseas trade, to the needed area on the required time is to be appropriately performed. However, there are several restrictions for cargo delivery to meet the demand, such as ship's size, number to be employed and cargo handling capacity of the ports, etc. And there are some other factors to be considered, that is, the degree of necessities of commodities, on their kinds, amount, and the time of arrival, etc. This paper deals with the problem of optimum allocation of ships emphasizing the cargo delivery time adopting Linear Programming technique with those cargo delivery restrictions and factors transformed by introducing the multi-speed conception, the conversion of multi-commodity to a single commodity, allowable delivery time, weight penalty number and nominating priority. This paper presents a case of optimum allocation of ships in the light of cargo delivery time for a construction company which has two different construction places and analyzes the result. This study will give a planner a good tool for optimum planning of maring transportation and be used for decision of schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1654-1675
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• 2014

In practical wireless systems, the erroneous channel state information (CSI) sometimes deteriorates the performance drastically. This paper focuses on robust design of coordinated set planning of coordinated multi-point (CoMP) transmission, with respect to the feedback delay and link error. The non-ideal channel models involving various uncertainty conditions are given. After defining a penalty factor, the robust net ergodic capacity optimization problem is derived, whose variables to be optimized are the number of coordinated base stations (BSs) and the divided area's radius. By the maximum minimum criterion, upper and lower bounds of the robust capacity are investigated. A practical scheme is proposed to determine the optimal number of cooperative BSs. The simulation results indicate that the robust design based on maxmin principle is better than other precoding schemes. The gap between two bounds gets smaller as transmission power increases. Besides, as the large scale fading is higher or the channel is less reliable, the number of the cooperated BSs shall be greater.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.90-99
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• 2007

We demonstrate an 80km-reach 64-channel DWDM-PON based on wavelength-locked F-P LDs by changing the position of the C-band BLS for upstream channels from the CO to the RN. It mitigates the necessity of the high power C-band BLS and its handling problems. It also reduces back scattering induced penalty. We obtained less than $10^{-6}$ PLRs in all 128channels through 80km SMF. We also demonstrate a 240km-reach DWDM-PON based on wavelength-locked F-P LDs by adding a bidirectional erbium-doped fiber amplifier(EDFA). We show packet-loss-free transmission in all 128channels at 125 Mb/s per channel over 240km SMF We report the detuning effect of arrayed waveguide gratings(AWGs) and crosstalk effect in the implemented system. We Propose an architecture of a next generation defense wire communication system with the demonstrated long-reach DWDM-PON.