• ETRI Journal
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• v.23 no.4
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• pp.177-189
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• 2001

Multicarrier DS-CDMA is an effective approach to combat fading and various kinds of interference. In this paper, we present an overlapped multicarrier DS-CDMA system, wherein each of the rate 1/M convolutionally-encoded symbols is also repetition coded and transmitted using overlapped multicarriers. However, since the frequency spectrums of successive carriers are allowed to overlap, the transmission bandwidth is more efficiently utilized. The effect of the overlapping percentage between successive carriers of a multicarrier DS-CDMA system on the performance is investigated to determine the overlapping percentage showing the best performance. We suggest two methods for sub-band overlapping variation. One is to allow variation of sub-band overlapping percentage when the total number of subcarriers is fixed. The other is to increase the number of sub-bands (the number of repetitions R) with fixed sub-band bandwidth. Given a total number of subcarriers MR, we show that the BER variation is highly dependent on the roll-off factor ${\beta}$ of a raised-cosine chip wave-shaping filter irrespective of convolutional encoding rate 1/M and repetition coding rate 1/R. We also analyze the possibility of reduction in total multi-user interference by considering the variation of both the roll-off factor ($0<{\beta}{\leq}1$) and the sub-band overlapping factor ($0<{\lambda}{\leq}2$), and show that the proposed system may outperform the multicarrier DS-CDMA system in [3].

• Journal of Ocean Engineering and Technology
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• v.36 no.1
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• pp.61-81
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• 2022

The available underwater acoustic spectrum is limited. Therefore, it is imperative to avoid frequency interference from overlapping frequencies of underwater acoustic equipment (UAE) for the co-existence of the UAE. Cognitive technology that senses idle spectrum and actively avoids frequency interference is an efficient method to facilitate the collision-free operation of multiple UAE with overlapping frequencies. Cognitive technology is adopted to identify the frequency usage of UAE to apply cognitive technology. To this end, we investigated two principle underwater acoustic sources: UAE and marine animals. The UAE is classified into five types: underwater acoustic modem, acoustic positioning system, multi-beam echo-sounder, side-scan sonar, and sub-bottom profiler. We analyzed the parameters of the frequency band, directivity, range, and depth, which play a critical role in the design of underwater acoustic cognitive technology. Moreover, the frequency band of several marine species was also examined. The mid-frequency band from 10 - 40 kHz was found to be the busiest. Lastly, this study provides useful insights into the design of underwater acoustic cognitive technologies, where it is essential to avoid interference among the UAE in this mid-frequency band.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.227-235
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• 2003

The WSGG-based narrow band model was employed to solve the radiative transfer equations along isothermal and non-isothermal paths through $CO_2-H_2O-N_2$ gas mixtures at 1 atm. When the WSGGM is applied for arbitrary gas mixtures by considering the multiplication property of transmissivity in overlapping bands, the number of gray gases is significantly increased. To reduce the computation time, three different regrouping methods for the gray gases are tested in obtaining the mean absorption coefficient for each gray gas group. Among them, the regrouping method by minimizing the regrouping error shows the best results. For the isothermal media, 10 gray gases show fairly good agreement with the results by statistical narrow band(SNB) model which are regarded as reference solutions. For non-isothermal media, 20 gray gases show good agreement with reference solutions.

• The Research Journal of the Costume Culture
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• v.18 no.6
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• pp.1228-1241
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• 2010

This study aims to help understanding on design of basic pattern of shirt collars and to suggest schemes to raise completeness of shape by reviewing problems shown in finished products after sewing. From March 2009 to August 2009, 12 patterns for education and firms were collected centering on basic shirt collar form respectively. There are four problems generally raised from a completed shirt collar. In case of overlapping shirt collar on front neck point, the sewing point of shirt collar should be drawn at front neck point of collar band at a distance of about 0.2~0.3cm, and the center front of band and one of bodice should be arranged in a straight line. In case of the problem about right and left length difference of shirt collar, it is raised by closing so the problem was solved by prolonging about 0.2 cm of the center front of left collar. It was evaluated that adjusting notch point when sewing would be more rational solution than solving something on patterns for distance difference problem of shirt collar between right and left part at center front. And a problem about getting loose of front garment between collar band below and the first button was also raised. It was designed 0.2cm cut of collar band. Around basic shirt collar form, above mentioned solutions are applied to the patterns for education and manufacture experimental clothing. So as a result of sensory evaluation, generally good ratings on all items were received.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1707-1714
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• 2016

This paper presents the effect of spectrum sharing/overlapping in a heterogeneous OFDM system with nonlinear High Power Amplifier (HPA). According to the spectrum sharing strategies, the achievable rate performances are analyzed. In the non-orthogonal spectrum sharing, we address how the portion of the overlapped or overlaid spectrum band and the nonlinear properties of HPA affect the system performance and accordingly, propose the optimized spectrum sharing strategies.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.193-198
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• 2006

Among 242 Hyperion bands, there are 46 bands that contain completely no information and some other bands with various kinds of noise. It is mainly due to the atmosphenc absorption and the low signal-to-noise ratio. The visual inspection for selecting clean and stable bands is a simple practice, but is a manual, inefficient, and subjective Process. Though uncalibrated, overlapping, and all deep water absorption bands are removed, there still exist noisy bands. In this paper, we propose that the extrema ratio be measured for noise estimation and the unsupervised band selection be performed using the Expectation-Maximization algorithm. The Hyperion data were classified into 5 categories according to the image quality by visual inspection, and used as the reference data. The accuracy of the proposed method was compared with signal-to-noise ranking and entropy ranking. As a result, the proposed mettled was effective as preprocessing step for band selection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.1939-1946
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• 2012

USNs (Ubiquitous Sensor Networks) such as IEEE 802.15.4 ZigBee network share ISM (Industrial, Scientific, and Medical) frequency band with WiFi networks. Once both networks operate in a region, packet collision may happen because of frequency overlapping. To assure this possibility, we conducted experiments where WiFi and ZigBee communication networks had been installed in an area. As a result of the test, successful data transmission rate were reduced due to the frequency overlapping between a WiFi communication channel and a ZigBee communication band. To cope with this problem, we propose a collision avoidance algorithm. In the proposed algorithm, if frequency collision is sensed, new communication channel with different frequency band is allocated to each node. Performance of the proposed frequency collision avoidance algorithm was tested and the results were described.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.6
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• pp.445-452
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• 2002

The goal of this paper Is to characterize the vibration damping induced in a main structure by a large number of sub-oscillators. A simple expression is obtained for the substructure impedance when the number of sub-oscillators approaches Infinity. It is found that the induced damping depends on the total mass of the sub-oscillators resonating in a frequency band of interests and nearly independent of their Individual loss factors. A modal overlapping condition. which corresponds to bandwidths that exceed the spacing of those natural frequencies, is required for the sub-oscillators to have such effects. An impulse response of the system is also considered. When the sub-oscillators lack damping and do not satisfy the modal overlapping condition, the vibratory energy is returned from the sub-oscillators to the main structure at later times. The result of this paper is consistent with that found with the fuzzy structure and SEA framework.

• Smart Structures and Systems
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• v.8 no.2
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• pp.219-237
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• 2011

This paper presents novel research into the source localization of multiple impacts. Source localization technology for single impact loads in a plate structure has been used for health monitoring. Most of research on source localization has been focused only on the localization of single impacts. Overlapping of dispersive waves induced by multiple impacts and reflection of those waves from the edge of the plate make it difficult to localize the sources of multiple impacts using traditional source localization technology. The method solving the overlapping problem and the reflection problem is presented in the paper. The suggested method is based on pre-signal processing technology using band pass filter and optimal filter. Results from numerical simulation and from experimentation are presented, and these verify the capability of the proposed method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.133-133
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• 2008

Recently, as the down-scailing of field-effect transistor devices continues, Schottky-barrier field-effect transistors (SB-FETs) have attracted much attention as an alternative to conventional MOSFETs. SB-FETs have advantages over conventional devices, such as low parasitic source/drain resistance due to their metallic characteristics, low temperature processing for source/drain formation and physical scalability to the sub-10nm regime. The good scalability of SB-FETs is due to their metallic characteristics of source/drain, which leads to the low resistance and the atomically abrupt junctions at metal (silicide)-silicon interface. Nevertheless, some reports show that SB-FETs suffer from short channel effect (SCE) that would cause severe problems in the sub 20nm regime.[Ouyang et al. IEEE Trans. Electron Devices 53, 8, 1732 (2007)] Because source/drain barriers induce a depletion region, it is possible that the barriers are overlapped in short channel SB-FETs. In order to analyze the SCE of SB-FETs, we carried out systematic studies on the Schottky barrier overlapping in short channel SB-FETs using a SILVACO ATLAS numerical simulator. We have investigated the variation of surface channel band profiles depending on the doping, barrier height and the effective channel length using 2D simulation. Because the source/drain depletion regions start to be overlapped each other in the condition of the $L_{ch}$~80nm with $N_D{\sim}1\times10^{18}cm^{-3}$ and $\phi_{Bn}$ $\approx$ 0.6eV, the band profile varies as the decrease of effective channel length $L_{ch}$. With the $L_{ch}$~80nm as a starting point, the built-in potential of source/drain schottky contacts gradually decreases as the decrease of $L_{ch}$, then the conduction and valence band edges are consequently flattened at $L_{ch}$~5nm. These results may allow us to understand the performance related interdependent parameters in nanoscale SB-FETs such as channel length, the barrier height and channel doping.