• Journal of the Optical Society of Korea
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• v.20 no.2
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• pp.257-262
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• 2016

A two-dimensional optical code division multiple access (OCDMA) en/decoder composed of four double-ring resonator add/drop filters and three delay waveguides is designed, and a transfer matrix method combined with fast Fourier transform is implemented to provide numerical simulations for the en/decoder. The auto-correlation peak level over the maximum cross-correlation level is larger than 3 at the center of the correctly decoded pulse for most of wavelength hopping and spectral phase code combinations, which assures the BER lower than 10^-3 which corresponds to the forward error correction limit.

• The Journal of Engineering Research
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• v.3 no.1
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• pp.171-180
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• 1998

The low cost fiber ring laser can be tuned by controlling polarization states within the loop. In this paper, we investigate its operating principle and verify the performance through an experiment. This ring laser consists of a polarization controller and an intracavity polarizer for the wavelength tuner and semiconductor optical amplifier for the gain medium. It is seen that the lasing wavelength may be tuned through the range of 1540~1560 nm as a polarization controller and a polarizer are adjusted.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.856-862
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• 2013

A cavity-backed two-arm spiral antenna for partial discharge diagnosis is presented. The proposed antenna consists of a two-arm Archimedean spiral, a tapered microstrip balun as spiral antenna feed, and a ring-shaped absorber-loaded cavity. The Archimedean spiral antenna is designed for the operating frequency band of 0.3 GHz to 1.5 GHz and fed by the tapered microstrip balun. The cavity is utilized to transform the bidirectional beam into a unidirectional beam, thereby enhancing gain. The ring-shaped absorber is stacked in the cavity to reduce the reflected waves from the cavity wall. The proposed antenna is designed and simulated using CST Microwave Studio. A prototype of the proposed antenna is likewise fabricated and tested. The measured radiation patterns are directional to the positive z-axis, and the measured peak gain is 8.13 dBi at a frequency of 1.1 GHz.

• Korean Journal of Agricultural and Forest Meteorology
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• v.7 no.4
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• pp.289-295
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• 2005

This paper reports on the dendrochronological investigation of tree ring growth of Pinus densiflora in the Gyeongbuk region. Tree ring growth was analysed using basic statistical value and correlation analysis to evaluate the relative contribution of climatic factors. Ta extract age-related trends and nonclimatic signals, each measurement series was standardized using a negative exponential growth function. In the Gyeongbuk region, tree ring growth was positively correlated with the current year in February, March and April, January, February, and March precipitation showed a positive correlation with the current growth year. This suggests that climatic factors (monthly average temperature, precipitation) limit breaking of dormancy and promotion of growth of Pinus densiflora in the Gyeongbuk region.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.3
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• pp.213-223
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• 2004

We consider the traffic grooming problem for the design of SONET/WDM(Synchronous Optical NETwork/Wavelength Division Multiplexing) ring networks. Given a physical network with ring topology and a set of traffic demands between pairs of nodes, we are to obtain a stack of rings with the objective of minimizing the number of ADMs installed at the nodes. This problem arises when a single ring capacity is not large enough to accommodate all the demands. As a solution method, an efficient algorithm based on the branch-and-price approach has been reported in the literature for the problem in which only unidirecional path switched ring (UPSR) was considered. In this study, we suggest integer programming models and the algorithms based on the same approach as the above one, considering two-fiber bidirectional line switched ring(BLSR/2), and BLSR/4 additionally. Using the results, we compare the number of required ADMs for all types of the ring architecture.

• Communications of the Korean Mathematical Society
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• v.18 no.4
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• pp.615-620
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• 2003

Semi-meet-prime projective modules and fully invariant meet-prime submodules of a projective module are studied. Actually a generalization of the Schur's lemma and semi-prime endmorphism rings of projective modules are considered.

• Bulletin of the Korean Chemical Society
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• v.30 no.7
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• pp.1531-1534
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• 2009

(2S,3R)-3-Hydroxy-2-(hydroxymethyl)-3,6-dihydro-2H-pyridine 8, an important precursor for the synthesis of polyhydroxylated piperidine azasugars, has been prepared from L-serine. Highly stereoselective nucleophilic addition to amino aldehyde 5 gave the corresponding allylic alcohol 6 which proceeded to give dihydro-2H-piridine 7a via a Grubbs II catalyzed RCM. Stereoselective H-bond directed epoxidation of allylic alcohol led to the oxiranyl alcohol 9 which was easily converted to L-deoxyaltronojirimycin by regioselective ring opening.

• Bulletin of the Korean Chemical Society
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• v.9 no.3
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• pp.164-166
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• 1988

7-Dithiocarboxy-3-phenyl-5,6-dihydro imidazo[2,1-b]thiazolium-betaine (2) was prepared by treatment of 3-phenyl-5,6-dihydro imidazo[2,1-b]thiazole (1) with carbon disulfide in acetone at room temperature. On the reaction of 2 with para-substituted phenacyl bromides (4) having the electron withdrawing property by virtue of (+) resonance (R) < (-) inductive (I) or (-) resonance (R), (-) inductive (I) effect, ring transformation product p-substituted-2-[2-[7-(p-substituted benzoyl)-5-thioxo-2,3-dihydro-1H-imidazo[1,2-c] thiazol-1-yl]-2-phenylvinylthio] acetophenone (6) was obtained; however, when R is electron donating grops with (+) resonance (R) > (-) inductive (I) effect the quarternary ammonium salt 7-(p-substituted phenyl) carbonyl methyl-3-phenyl-5,6-dihydro imidazo [2,1-b] thiazolium bromide (8) is formed. The reaction of 2 with unsubstituted-phenacyl bromide (R = H), on the other hand, gives 6a and 8a to the similar ratio, respectively.

• ETRI Journal
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• v.31 no.5
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• pp.631-633
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• 2009

We introduce an improved Ethernet ring protection method, selective filtering database (FDB) advertisement, to minimize traffic overshoot in the event of a failure or recovery. On the protection switching event, the proposed method makes all ring nodes perform an FDB flush except the FDB entries associated with their client subnets. Then, ring nodes rapidly exchange their client MAC address lists so that their FDBs are immediately updated by indirect MAC address learning. The proposed scheme guarantees fast and reliable protection switching over the standard scheme.

• Communications of the Korean Mathematical Society
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• v.33 no.3
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• pp.711-719
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• 2018

In this paper we define and study a new kind of dimension called, semisimple dimension, that measures how far a module is from being semisimple. Like other kinds of dimensions, this is an ordinal valued invariant. We give some interesting and useful properties of rings or modules which have semisimple dimension. It is shown that a noetherian module with semisimple dimension is an artinian module. A domain with semisimple dimension is a division ring. Also, for a semiprime right non-singular ring R, if its maximal right quotient ring has semisimple dimension as a right R-module, then R is a semisimple artinian ring. We also characterize rings whose modules have semisimple dimension. In fact, it is shown that all right R-modules have semisimple dimension if and only if the free right R-module ${\oplus}^{\infty}_{i=1}$ R has semisimple dimension, if and only if R is a semisimple artinian ring.