• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.2
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• pp.505-513
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• 1996

In this paper the dual-mode bandpass filters with a Chebyshev response are designed and manufactured at Ku-band as well as K-band. Manufactured filters are resonated by two independent orthogonal $TE_{113}$ circular-cavity modes and characterized by 4-pole Chebyshev function. One is operating at a center frequency of 12.5GHz with a bandwidth of 100MHz and the other, a center frequency of 19.25GHz with 120MHz, respectively. The measureed experimental results of a 12.5GHZ dual-mode filter ahve a 1.2dB intertion loss in the passband and 65dB out-of-rejection, and a 19.25GHz filter has a 1.55dB insertion loss and 70dB out-of-rejection. These experimantal results shoults show good agreements with the design specifications.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4E
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• pp.14-20
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• 1996

The double mode SAW resonator filters have the serious shortcoming that out-of-band rejection above the passband is quite poor. Hence a new structure of the double mode filter is designed with the COM (Coupling Of MOdes) theory with better out-of-band rejection characteristics while keeping all the beauties of the conventional type. The second goal of the design is to reduce the planar size of the structure so that mass productivity of low frequency devices can be improved. For those purposes, several IDT's and relfector gratings are added to or subtracted from the conventional structure so that the modification can lead to better overall performance as a filter. As results of the investigation, several new double mode SAW resonator filter structures are developed. A new structure shows 10dB more out-of-band rejection that the conventional type with 25% reduced device size. Good agreement is demonstrated between the analytical results and experimental results for an illustrative 325MHz four pole resonator filter on 64°YX LiNbO3.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.10
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• pp.3371-3380
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• 1996

Low resolution spectral modeling of water vapor is carried out by applying the weighted-sum-of-gray-gases model (WSGGM) to a narrow band. For a given narrow band, focus is placed on proper modeling of gray gas absorption coefficients vs. temeprature relation used for any solution methods for the Radiative Transfer Equation(RTE). Comparison between the modeled emissivity and the "true" emissivity obtained from a high temperatue statistical narrow band parameters is made ofr the total spectrum as well as for a few typical narrow bands. Application of the model to nonuniform gas layers is also made. Low resolution spectral intensities at the boundary are obtained for uniform, parabolic and boundary layer type temeprature profiles using the obtained for uniform, parabolic and boundary layer type temperature profiles using the obtained WSGGM's with 9 gray gases. The results are compared with the narrow band spectral intensities as obtained by a narrow band model-based code with the Curtis-Godson approximation. Good agreement is found between them. Local heat source strength and total wall heat flux are also compared for the cases of Kim et al, which again gives promising agreement.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.359-362
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• 2002

The increase in the number of PCS base station and repeater has increased the level of interference between PCS carriers. In this paper, interference of singular PCS repeater out-of-band noise power on mobile phone is analysed and compared with that of unified PCS repeater for multiple PCS carriers. It is shown that unified PCS repeater provide about 2∼3dB signal gain in comparison with conventional PCS repeater. As a result, the interference of out-of-band noise power on mobile phone is reduced. It is expected that PCS carriers are able to build an environmentally-friendly communications infrastructure and reduce the cost by using unified PCS revealer and apply it for the deployment of IMT-2000 network.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.693-696
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• 2008

The systems for mobile communication services of fourth generation use OFDM (Orthogonal Frequency Division Multiplexing) scheme that ran transmit large amounts of data to support the multimedia services, and consist of several types of cell, such as Macro Cell, Pico Cell, Femto Cell to improve the qualify of service. According to subdivision of communication region, superposition of cells in co-channel different from conventional single cell is used, but it cause inter band interference between systems. In particular, an OFDM signal consists of a number of independently modulated subcarriers, and superposition of these subcarriers causes a problem that ran give a large PAPR. Increased PAPR induces signal distortion passing through components such as power amplifier so that inter band interference is caused by out-of-band spectrum radiation. In order to minimize the inter band interference, this paper applies PAPR reduction scheme and analyzes the out-of-band spectrum radiation when the signal passes through nonlinear components such an power amplifier.

• Nuclear Engineering and Technology
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• v.42 no.6
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• pp.690-703
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• 2010

Sampling based uncertainty analysis was carried out to quantify uncertainty in predictions of best estimate code RELAP5/MOD3.2 for a thermal hydraulic test (10% hot leg break LOCA) performed in the Large Scale Test Facility (LSTF) as a part of an IAEA coordinated research project. The nodalisation of the test facility was qualified for both steady state and transient level by systematically applying the procedures led by uncertainty methodology based on accuracy extrapolation (UMAE); uncertainty analysis was carried out using the Latin hypercube sampling (LHS) method to evaluate uncertainty for ten input parameters. Sixteen output parameters were selected for uncertainty evaluation and uncertainty band between $5^{th}$ and $95^{th}$ percentile of the output parameters were evaluated. It was observed that the uncertainty band for the primary pressure during two phase blowdown is larger than that of the remaining period. Similarly, a larger uncertainty band is observed relating to accumulator injection flow during reflood phase. Importance analysis was also carried out and standard rank regression coefficients were computed to quantify the effect of each individual input parameter on output parameters. It was observed that the break discharge coefficient is the most important uncertain parameter relating to the prediction of all the primary side parameters and that the steam generator (SG) relief pressure setting is the most important parameter in predicting the SG secondary pressure.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.37.1-37.1
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• 2019

The faint quasars with M1450 > -24 mag are known to hold the key to the determination of the ultraviolet emissivity for the cosmic reionization. But only a few have been identified so far because of the limitations on the survey data. Here we present the first results of the z ~ 5 faint quasar survey with the Infrared Medium-deep Survey (IMS), which covers ${\sim}100deg^2$ areas in J band to the depths of $J_{AB}$ ~ 23 mag. To improve selection methods, the medium-band follow-up imaging has been carried out using the SED camera for QUasars in Early uNiverse (SQUEAN) on the Otto Struve 2.1 m Telescope. The optical spectra of the candidates were obtained with 8 m class telescopes. We newly discovered 10 quasars with -25 < $M_{1450}$ < -23 at z ~ 5, among which three have been missed in a previous survey using the same optical data over the same area, implying the necessity for improvements in high-redshift faint quasar selection. We derived photometric redshifts from the medium-band data and found that they have high accuracies of ${\langle}{\mid}{\Delta}z{\mid}/(1+z){\rangle}=0.016$. The medium-band-based approach allows us to rule out many of the interlopers that contaminate ${\geq}20%$ of the broadband-selected quasar candidates. These results suggest that the medium-band-based approach is a powerful way to identify z ~ 5 quasars and measure their redshifts at high accuracy (1%-2%). It is also a cost-effective way to understand the contribution of quasars to the cosmic reionization history.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.229-234
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• 2002

OFDM(Orthogonal Frequency Division Multiplexing) 전송방식은 SCM(Single Carrier Modulation)에 비해 우수한 여러 가지 장점들을 가지며, 방송시스템들 중 Eureka 147 DAB(Digital Audio Broadcasting) 시스템에 가장 먼저 채택되었다. 그러나 OFDM 신호의 높은 PAPR(Peak-to-Average Power Ratio) 특성은 D/A, A/D 변환기의 복잡도를 높이고, 고출력 증폭기의 효율성을 감소시키는 원인이 된다. 이를 개선하기 위한 방법 중에, SDT(Signal Distortion Technique)는 전송시스템의 규격 및 수신기의 변경 없이도 적용 가능하다는 장점을 갖는다. 본 논문에서는 SDT에 속하는 companding 기법을 Eureka 147 DAB 시스템에 적용하여 PAPR 개선정도에 따른 시스템의 요구 $E_2/N_0$ 및 out-of-band의 PSD 열화 정도를 분석하였으며, 이를 clipping 기법의 성능과 비교하였다. 모의실험 결과, $\mu$값이 2인 경우, companding 기법이 PAPR, $E_2/N_0$, out-of-band의 PSD 특성 모두에서 clipping 기법에 비해 우수한 성능을 나타냈다. 또한 $\mu$ 값을 고정시킨 경우, 정규화 값이 증가할수록 신호왜곡 정도가 줄어들어 $E_2/N_0$, out-of-band의 PSD 성능개선 정도는 증가하지만, 이와는 반대로 PAPR 값은 개선 정도가 줄어들었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.85-91
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• 1986

Fatigue life is an important consideration for the design of offshore structures in deep sea and in hostile environments. In this paper, the effect of the bandwidth of random stresses on the fatigue life estimation of fixed offshore structures is investigated. The dynamic analysis is carried out in the frequency domain by using the equivalent linearization technique. Fatigue damages are calculated by two stress cycle counting methods; i.e., the narrow band method and the wide band method using rainflow counting technique. Example studies are carried out for two different structures. Numerical results indicate that the wide band approach, which is more complex but theoretically more appropriate pridicts smaller values of fatigue damages compared with those by the narrow band approach for all seastate conditions. Such trend becomes more apparent for the cases of severe seastates where the bandwidth of random stresses becomes large.

• Journal of Broadcast Engineering
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• v.24 no.2
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• pp.299-305
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• 2019

In ISO MPEG, MPEG-H has been standardized to smoothly deliver huge volume of ultra-high resolution videos over heterogeneous network environments for the consumers. In the MPEG-H standard, MMT(MPEG Media Transport) protocol is the next generation MPEG media transport technology to provide hybrid media delivery over heterogeneous environments. It is important to sustain accurate media synchronization to provide ultra-high resolution video services over heterogeneous network environments. In this paper, we propose and verify an in-band media synchronization scheme to circumvent the problem of additional session setup and excessive traffic problems of the conventional out-of-band media synchronization supported by the MMT technology.