• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.7 s.361
• /
• pp.17-22
• /
• 2007

OFDM (Orthogonal Frequency Division Multiplexing) is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarrier. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. Unfortunately, an OFDM signal consists of a number of independently modulated subcarriers, which can give a large PAPR (Peak-to-Average Power Ratio) when added up coherently. In this paper, we investigate the performance of a simple PAPR reduction scheme, which requires no change of a receiver structure or no additional information transmission. The approach we employed is clipping in the time and frequency domains. The time-domain clipping is carried out with a predetermined clipping level while the frequency-domain clipping is done within EVM (Error Vector Magnitude). This approach is suboptimal with lower computational complexity compared to the optimal method. This evaluation is carried out on the OFDM system with an nonlinear amplifier. The simulation results demonstrated that the PAPR reduction algorithm is one of ways to reduce the effects of the nonlinear distortion of an HPA (High Power Amplifier).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.6 s.97
• /
• pp.586-593
• /
• 2005

It is very important to reduce the PAPR(Peak to Average Power Ratio) in the OFDM(Orthogonal Frequency Division Multiplexing) communication system. We propose an ACE(Active Constellation Extension) method that does not require the side information unlike the conventional PTS and SLM method. This ACE method is to clip the OFDM signal for the PAPR reduction. Then, the basic constellation actively moves into the higher level of M-QAM for the constellation extension due to the clipping. The already existing M-QAM system can be available so that it can be easily realized. So, we can get the target PAPR by the extension of the constellation level. In this paper, we can find the PAPR reduction of 4 dB by the 16-QAM extension, and can achieve the target PAPR by the 64-QAM ACE(Active Constellation Extension).

• The KIPS Transactions:PartB
• /
• v.11B no.1
• /
• pp.35-44
• /
• 2004

Web contents created for desktop screens give rise to problems when they are to be displayed on the small screens of mobile terminals. While in some cases some of the objects of a page may not be displayable due to the lack of browser capability, the entire page may not be displayable due to the incompatibility with the browser in other cases. In this paper, we introduce a new mobile content adaptation approach based on web clipping, which transforms an original page into one that is optimally displayed on a mobile terminal. In this method, a source page is automatically clipped and transformed according to the clip specification made by the content provider using a clip editing tool. The clip editing tool allows the user to specify group clips, multi-level cups and dynamic clips as well as simple clips, and the presentation layout through a graphic user interface. Based on the clip specifications, each clip is transformed into an intermediate meta-language document, which in turn is transformed into a presentation page in the target markup language. Transcoding of image objects in major image file formats is also supported.

• Asian Journal of Turfgrass Science
• /
• v.4 no.2
• /
• pp.125-131
• /
• 1990

This experiment was carried out in drder to study the changes of morphological characters and thatch weight on N-level and survey times N-levels were 0, 21, 28, 35, 42 and 49 g/m$^2$), respectively. The results are as follows. 1. Thatch weight was significantly different among survey times, and the interaction of survey time N-level. 2. The growth of Zoysia grass and thatch accumulation were incresed by higher N~level The highest value was obtained in all survey times. 3. Most survey characters and thatch accumulation was decreased by growth progressed. 4. Thatch increase rate(TIR) was the lowest at 28g Nm$^2$and T2-T3 period. 5. TIR was the positive significant correlated(P<0.05) with N-level, root weight, clipping weight and thatch weight.

• Proceedings of the Acoustical Society of Korea Conference
• /
• 1998.06c
• /
• pp.167-170
• /
• 1998

음성신호의 특징적인 성분인 피치를 검출하는 알고리즘 중 실시산 구현이 손쉬운 3단계를 클리핑 알고리즘을 PC상에서의 처리를 위하여 구현하였다. 이 알고리즘을 통하여 검출되는 피치의 안정성 및 정확성을 높이기 위해서 적용된 창함수, LPF, 클리핑 자기상관값계산, 비선형 감쇄, 등의 전처리 필터링과, 배수피치 검출 및 정정, 메디언 필터링을 사용하여 피치를 검출하였다. 또한 이 알고리즘을 이용하여 DSP의 도움을 얻지 않고 PC상에서 음성을 분석하여 스펙트로그램, 파형, 에너지, 피치 등을 출력하는 프로그램인 Visual Analysis Tool for sounds(VAT)의 출력화면을 통하여 피치검출을 나타내었다.

• Proceedings of the IEEK Conference
• /
• 2003.11a
• /
• pp.27-30
• /
• 2003

In this paper a new approach of digitalized ‘Takbon’ is introduced. By image signal processing, the letters which were written on stones can be deciphered. Epigraphic letter is detected by digital image device, digital camera. The two dimensional digital image is preprocessed because of sensor noise and detective turbulence. Color image is transformed into grey level. The letter image is analyzed in time/frequency domain. By the resultant analysis data decisive functions are calculated. Signal Processing techniques, such as scaling, clipping, digital negative, high/low filter, morphology and so on, provide algorithms that can extract letter from stones.

• Weed & Turfgrass Science
• /
• v.6 no.3
• /
• pp.272-281
• /
• 2017

This study was conducted to evaluate the effect of liquid fertilizer containing humic acid (LFHA) on changes of creeping bentgrass quality and growth. Treatments were designed as follows; control fertilizer (CF), HA-1 ($CF+1ml\;m^{-2}LFHA$ LFHA), HA-2 ($CF+2ml\;m^{-2}LFHA$ LFHA), and HA-3 ($CF+4ml\;m^{-2}LFHA$). As compared with CF, soil chemical properties and chlorophyll content of clipping of LFHA treatments were not significantly different. Visual quality in both of HA-2 and HA-3 treatments was higher than that of CF treatment from September to November, and clipping yield on October 27. Shoot density, root length, and the content of nitrogen, phosphorus or potassium were increased by application of LFHA. The clipping yield was positively correlated with phosphorus content, potassium content or shoot density. Similarly, LFHA level was proportionate to clipping yield of creeping bentgrass, and N, P, K contents in the leaf tissue. These results generally demonstrated that the application of LFHA improved the growth and quality of creeping bentgrass by increase of N content or P in leaf tissue.

• Journal of Korean Neurosurgical Society
• /
• v.62 no.4
• /
• pp.398-404
• /
• 2019

Objective : Recently, three-dimensional (3D) printed models of the intracranial vascular have served as useful tools in simulation and training for cerebral aneurysm clipping surgery. Precise and realistic 3D printed aneurysm models may improve patients' understanding of the 3D cerebral aneurysm structure. Therefore, we created patient-specific 3D printed aneurysm models as an educational and clinical tool for patients undergoing aneurysm clipping surgery. Herein, we describe how these 3D models can be created and the effects of applying them for patient education purpose. Methods : Twenty patients with unruptured intracranial aneurysm were randomly divided into two groups. We explained and received informed consent from patients in whom 3D printed models-(group I) or computed tomography angiography-(group II) was used to explain aneurysm clipping surgery. The 3D printed intracranial aneurysm models were created based on time-of-flight magnetic resonance angiography using a 3D printer with acrylonitrile-butadiene-styrene resin as the model material. After describing the model to the patients, they completed a questionnaire about their understanding and satisfaction with aneurysm clipping surgery. Results : The 3D printed models were successfully made, and they precisely replicated the actual intracranial aneurysm structure of the corresponding patients. The use of the 3D model was associated with a higher understanding and satisfaction of preoperative patient education and consultation. On a 5-point Likert scale, the average level of understanding was scored as 4.7 (range, 3.0-5.0) in group I. In group II, the average response was 2.5 (range, 2.0-3.0). Conclusion : The 3D printed models were accurate and useful for understanding the intracranial aneurysm structure. In this study, 3D printed intracranial aneurysm models were proven to be helpful in preoperative patient consultation.

• Korean Journal of Environmental Agriculture
• /
• v.41 no.3
• /
• pp.167-176
• /
• 2022

BACKGROUND: Nitrogen (N) is an important element for turfgrass (Zoysia matrella) growth; however, standard N application rate for turfgrass is not established yet. This study was conducted to evaluate the effect of N application rates on the growth and quality of turfgrass for establishment of standard N application rate. METHODS AND RESULTS: Treatments were as follows; control (0 N g/m²/month), 1N (1 N g/m²/month), 2N(2 N g/m²/month), 3N (3 N g/m²/month), 4N (4 N g/m²/month), and 5N (5 N g/m²/month). N application improved visual turfgrass quality. Compared with the control, clipping yield of all N treatments increased by 90~194%. The grass shoot weight of 3N, 4N, and 5N treatments increased by 52%, 43%, and 111%, respectively, and the stolon weight of 4N and 5N treatments increased by 412% and 201%, respectively, compared to the control. The N uptake amount and N recovery rate were estimated to be 4.10~6.28 g/m² and 14~58%, respectively. CONCLUSION(S): These results indicate that considering visual quality, clipping yield, N uptake amount, and N recovery, the application rate of 2~3 N g/m²/month was suggested to be suitable for Z. matrella production.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.10 no.8
• /
• pp.901-906
• /
• 2015

We presented a method for Vad(Voice Activity Detection) using Bi-level HMM. Conventional methods need to do an additional post processing or set rule-based delayed frames. To cope with the problem, we applied to VAD a Bi-level HMM that has an inserted state layer into a typical HMM. And we used posterior ratio of voice states to detect voice period. Considering MFCCs(: Mel-Frequency Cepstral Coefficients) as observation vectors, we performed some experiments with voice data of different SNRs and achieved satisfactory results compared with well-known methods.