• Korean Journal of Optics and Photonics
• /
• v.20 no.3
• /
• pp.143-147
• /
• 2009

We propose an asymmetrical 2.5 Gbps / 622 Mbps bidirectional optical subscriber network with Manchester coded downstream and NRZ (Non-Return-to-Zero) upstream remodulation. The proposed system has important characteristics in the optical network unit (ONU): it does not require a light source or the usual control circuits such as wavelength control and output power control, and it is possible to use a synchronization scheme between upstream and downstream data. We theoretically analyze BER(Bit Error Rate) performance of upstream data remodulated with Manchester coded downstream according to the types of NRZ downstream data and perform simulations with MATLAB. The BER performance and the receiver sensitivity have been improved by 3 dB by adjusting threshold levels compared to the conventional receiver. The results have shown the remodulation scheme with Manchester coded downstream could be a useful technology for asynchronous and asymmetric optical subscriber networks with low cost and simple structures.

• Journal of the Korean Chemical Society
• /
• v.42 no.6
• /
• pp.657-663
• /
• 1998

New asymmetric dimer, 7,7'-substituted (or H)-4-oxo-2,2'- dialkyl-l,l',2,2'-dibenzothiazine-3,3'dicarboxylic acid methyl ester-1,1,1',1'-tetraoxide 3,4'-yl ethers 2a-d were synthesized through the oxidative dimerization of 7-substituted (or H)-4-hydroxy-2-alkyl-1,2-benzothiazine-3-carboxylic acid methyl ester 1,1-dioxides la-d using silver oxide($Ag_2O$). 4-Oxo-2,2'-dialkyl-1,1'2,2'-dibenzothiazine-3,3'-dicarboxylic acid methyl ester-1,1,1',l'-tetraoxide 3,4'-yl ether 2c was identified by X-ray crystal structure determination.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.8
• /
• pp.684-692
• /
• 2016

In this paper, a non-offset longitudinal shunt slot excited by an asymmetry compound iris on the broad wall of a rectangular waveguide is presented as an element for a waveguide slot-array antenna(WSAA). By properly adjusting the iris dimension, a resonance of the slot at a desired frequency can be achieved. The proposed resonant slot has some advantageous properties, such as a wide range of normalized resonant conductance, and minimum change of phase in the waveguide at the resonance. In addition, when the slots are arrayed for a waveguide slot antenna, the unwanted cross-polarization level can be reduced because each slot is placed in a straight line. A $8{\times}1$ WSAA with -20 dB side-lobe level(SLL) is designed, fabricated, and tested experimentally. The measured results are well agreed with the simulated ones and have an SLL of -18.13 dB and a cross-polarization level of -48.85 dB at 9.41 GHz, which was improved by about 15 dB of that of the conventional longitudinal slot array antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.6
• /
• pp.586-594
• /
• 2013

This paper proposes a new coupling element of microwave slot coupler for designing waveguide slot array which can reduce the effect of undesired higher order mode coupling between coupling and radiating slots in the branch waveguide. The proposed device is composed of a centered longitudinal shunt-series coupling slot at the center of broad wall shared by two crossed rectangular waveguides and an asymmetric compound iris that excites the coupling slot. We first have obtained scattering parameters for the proposed coupler by use of EM S/W tool HFSS and then extracted the parameters of T- network equivalent circuit for the coupling slot. We also have analyzed the resonant properties such as resonant length and normalized admittance by changing the geometrical dimensions. The measured results for the fabricated coupler with short-circuited block ${\lambda}_g/4$ away from the coupling slot are well agreed with the simulated ones.

• Journal of the Korean Geographical Society
• /
• v.46 no.4
• /
• pp.425-441
• /
• 2011

Ridge traversing trail in Mount Jiri National Park is classified as flat, gully-like, unilateral, and asymmetric bilateral, paths based on a location and gradient of paths. These types are interchangeable due to a drainage condition of trail surfaces. Using a rapid survey, the trail is 135.9 cm wide, 23.6 cm deep and $5.1^{\circ}$ in a gradient, respectively. All treads have been compacted due to human trampling. The path width is affected by a slope aspect and a distribution of Sasa borealis. An asymmetric path is wider than a symmetric path. A soil erosion rate is equivalent to $68.9cm^2/year$ for the period from 1960 to 2009, suggesting that the trail has been widened 2.7 cm/year and the tread lowered 0.4 cm/year. Trampling and needle ice action combined with rainwash induced by a pipeflow are dominant erosion processes contributing to the trail expansion.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.12
• /
• pp.970-978
• /
• 2002

The differential equations governing free vibrations of the elastic arches with unsymmetric axis are derived in Cartesian coordinates rather than in polar coordinates. in which the effect of rotatory inertia is included. Frequencies and mode shapes are computed numerically for parabolic arches with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported, with and without the rotatory inertia, as functions of three non-dimensional system parameters the rise to chord length ratio. the span length to chord length ratio, and the slenderness ratio. Also typical mode shapes of vibrating arches are presented.

• 한국해양학회지
• /
• v.30 no.2
• /
• pp.125-137
• /
• 1995

CTD, light transmission and tidal current data obtained off the Keum estuary in August, 1991 and 1992 were analyzed to look into the plume movement and the vertical structure of the plume changing with tidal currents. When the river plume was developed by a localized torrential downpour, the initial plume showed a surface lens of low salinity in the section south of the Yeon-Do. The axis of surface lens moved with tidal currents which flows mainly northeastward and southwestward tn the study area and the excursion of the lens axis reached 7 km. The plume during the ebb period showed a symmetric lens structure of low salinity which extends vertically to 3 m below the surface. During the flood period the plume deepened to 6 m below the surface in its northen side forming a sharp salinity front, which results in an asymmetric lens. We suggest that the salinity front with deepened plume moved to the north repeatedly, resulting in temperature increase and salinity decrease in the northern region off the estuary. When the river discharged continuously the large volume over 20 days, the plume forming surface lens extended to the Sybidongpa-Do and deflected to the north.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.4
• /
• pp.341-348
• /
• 2017

This study examined the effects of the location and direction of the scolioti curve on postural balance in patients with idiopathic scoliosis. Fifteen subjects were divided into three groups: right thoracic curve group, left lumbar curve group, and double curve group. The dynamic trunk motion (angle variation in the lumbar, thoracolumbar, lower thoracic and upper thoracic region) and plantar pressure distribution (maximum force and peak pressure) were assessed using an ultrasound-based motion analysis system and Emed-at platform system. From the results, it was confirmed that patients with idiopathic scoliosis showed postural imbalance with an increased angle and pressure asymmetry according to the location and direction of the scoliotic curve for dynamic trunk motion and plantar pressure distribution. In addition, there were differences in the postural balance pattern between the single curve and double curve groups. Further studies for developing a rehabilitation training device will be conducted to improve the postural control ability and trunk balance as well as treat scoliosis based on the results of this study.

• Korean Journal of Optics and Photonics
• /
• v.3 no.3
• /
• pp.183-190
• /
• 1992

Luminescence properties of asymmetric double quantum well structure composed of $Al_x/Ga_{1-x}$ /As AIAs/GaAs have been studied by steady state and time-resolved photoluminescence and phtoluminescence excitation spectroscopy at low temperature. Two quantum well samples with different barrier thickness (15$\AA$ and 150$\AA$) were prepared to investigate the dependence of tunneling characteristics on barrier thickness. The abscence of excitonic recombination peak from $Al_x/Ga_{1-x}$As well for the 15$\AA$ barrier sample indicates a very fast electron tunneling to GaAs well. Meanwhile, T-X transition between well and barrier is supposed to be a major route for the fast decay of luminescence from $Al_x/Ga_{1-x}$As well in the 150$\AA$ barrier sample. Time-resolved photduminescence from GaAs well of 15$\AA$ sample shows the exsitence of the rise with 100 ps which is attributed to the hole tunneling.

• Journal of the Korean Chemical Society
• /
• v.48 no.1
• /
• pp.85-93
• /
• 2004

The purpose of this research was to investigate the change of argumentation of middle school students when they participated in argument tasks with CASE(Cognitive acceleration through science education) programs. Students argumentations were divided into two categories; 'explanatory argumentation' and 'dialogic argumentation'. Several argumentation components were used in their argumentation. Among argumentation components, claim and ground took place more than half of argumentation components. The percentage of 'dialogic argumentation' was lower than the percentage of 'explanatory argumentation'. The percentage of 'dialogic argumentation' was getting higher during CASE intervention. CASE programs had more effect on symmetric group than asymmetric group, however it was unstable. In general, participation ratio in argumentation of the formal operational student was high and the ratio in argumentation of the transitional student was getting higher.