• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권10호
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• pp.5056-5078
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• 2018

In this work we propose a compression technique that makes use of linear and perceptually uniform CIE $La^*b^*$ color space in the JPEG image compression framework to improve its performance at lower bitrates. To generate quantization matrices suitable for the linear and perceptually uniform CIE $La^*b^*$ color space, a novel linear Contrast Sensitivity Function (CSF) is used. The compression performance in terms of Compression Ratio (CR) and Peak Signal to Noise Ratio (PSNR), is further improved by utilizing image dependent, variable and non-uniform image sub-blocks generated using a proposed histogram-based merging technique. Experimental results indicate that the proposed linear CSF based quantization technique yields, on an average, 8% increase in CR for the same reconstructed image quality in terms of PSNR as compared to the conventional YCbCr color space. The proposed scheme also outperforms JPEG in terms of CR by an average of 45.01% for the same reconstructed image quality.

• 대한교통학회지
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• 제29권2호
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• pp.7-14
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• 2011

본선 교통류 제어 방안 중 가변속도제어 모형을 제시하고 서울 내부순환로를 중심으로 효과를 검증하였다. 차량 검지기로부터 수집된 데이터 보정 및 평활화 수행후 패턴분석을 통해 도시고속도로의 평일 상태를 4가지로 분류하고 중심 값을 산출하였다. 그리고 분석단위의 상태를 판단하기 위한 상태변수로 전이교통량, 평균밀도, 평균속도를 설정하였으며 제시된 모형과 시나리오에 근거하여 검증한 결과 안전성 및 효율성을 향상시킬 수 있었다. 또한 유입교통량에 따라 가변속도제어의 감속 정도와 유효 적용시간을 산출하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제20권1호
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• pp.28-35
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• 2015

In this study, the mechanisms on ultrasonication enhanced metals extraction were investigated compared with the conventional washing technique. We hypothesized the mechanisms on enhanced extraction of ultrasonication: ultrasonication increased the temperature of soil slurry and decreased average particle size of soil due to breakdown of soil aggregate. Actually, the ultrasonication increased the temperature of soil slurry to $60^{\circ}C$ in this study, and the increase in the temperature enhanced the metal extraction to 15-20% even in the conventional simple mixing. The conventional washing technique decreased average size of soil particles because of breakdown of soil aggregate, and the ultrasonication decreased the size more than that of washing. The breakdown of soil aggregate improved the contact between metals and washing agent, which enhanced the extraction of metals in the ultrasonication. Therefore, we concluded that the main mechanisms of ultrasonication are increase in the temperature and breakdown of the soil aggregate. Finally, the ultrasonicaiton increased the extractability of metals upto 40% compared to conventional washing technique.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.914-917
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• 2005

The paper proposes a new sonic resonance test for a dynamic elastic constant measurement which is based on time-average electronic speckle pattern interferometry(TA-ESPI)and Euler-Bernoulli equation. Previous measurement technique of dynamic elastic constant has the limitation of application for thin film or polymer material because contact to specimen affects the result. TA-ESPI has been developed as a non-contact optical measurement technique which can visualize resonance vibration mode shapes with whole-field. The maximum vibration amplitude at each vibration mode shape is a clue to find the resonance frequencies. The dynamic elastic constant of test material can be easily estimated from Euler-Bernoulli equation using the measured resonance frequencies. The TA-ESPI dynamic elastic constant measurement technique is able to give high accurate elastic modulus of materials through a simple experiment and analysis.

• ETRI Journal
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• 제43권2호
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• pp.209-220
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• 2021

The filtered orthogonal frequency division multiplexing (F-OFDM) system has been recommended as a waveform candidate for fifth-generation (5G) communications. The suppression of out-of-band emission (OOBE) and asynchronous transmission are the distinctive features of the filtering-based waveform frameworks. Meanwhile, the high peak-to-average power ratio (PAPR) is still a challenge for the new waveform candidates. Partial transmit sequence (PTS) is an effective technique for mitigating the trend of high PAPR in multicarrier systems. In this study, the PTS technique is employed to reduce the high PAPR value of an F-OFDM system. Then, this system is compared with the OFDM system. In addition, the other related parameters such as frequency localization, bit error rate (BER), and computational complexity are evaluated and analyzed for both systems with and without PTS. The simulation results indicate that the F-OFDM based on PTS achieves higher levels of PAPR, BER, and OOBE performances compared with OFDM. Moreover, the BER performance of F-OFDM is uninfluenced by the use of the PTS technique.

• Clinics in Orthopedic Surgery
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• 제10권4호
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• pp.479-483
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• 2018

Background: We developed a modified proximal scarf osteotomy technique for moderate to severe hallux valgus in an attempt to obtain better correction of the deformity. In addition, we compared the clinical and radiographic results of this modified technique with those of the classic scarf osteotomy reported in other studies. Methods: Between December 2004 and July 2009, 44 cases of modified proximal scarf osteotomy was performed in 35 patients with moderate hallux valgus. The American Orthopedic Foot and Ankle Society (AOFAS) score, visual analogue scale (VAS) score, range of motion of the first metatarsophalangeal joint, and radiographic results were evaluated. Results: The mean hallux valgus angle and the mean first intermetatarsal angle improved from an average of $32.2^{\circ}$ and $14.3^{\circ}$, respectively, to an average of $12.5^{\circ}$ and $8.6^{\circ}$, respectively. The distal metatarsal articular angle improved from an average of $18.7^{\circ}$ to $12.4^{\circ}$. The preoperative mean AOFAS and VAS scores were 47 points and 7 points, respectively, which improved to 86 points and 1 point, respectively, at the final follow-up. Limited range of motion occurred in two cases postoperatively. The height of the first metatarsal-cuneiform joint, which was an average of 15.9 mm preoperatively, did not change. The first metatarsal-talus angle increased from an average of $4.1^{\circ}$ to $7.1^{\circ}$. Conclusions: The modified proximal scarf osteotomy for the treatment of moderate hallux valgus showed similar results with the classic scarf osteotomy with regard to changes in the first intermetatarsal angle and postoperative satisfaction. Therefore, we suggest the modified proximal scarf osteotomy be considered as well as other proximal osteotomy in the treatment of moderate to severe hallux valgus.

• 대한족부족관절학회지
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• 제10권1호
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• pp.37-41
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• 2006

Purpose: To investigate the early results of limited open repair technique of Achilles tendon ruptures, and to describe the surgical technique. Materials and Methods: From October 2004 to February 2005, a total of 10 patients with Achilles tendon rupture underwent limited open repair. The average age of the patients was 39.3 years, and the average follow-up period was 9 months. The causes of injury were sports injuries in 8 cases, and slip down in 2. The mean interval between the injury and the operation was 9 days. The clinical results were assessed by patient's satisfaction, incision length, hospitalization, the ankle-hindfoot scale of American Foot and Ankle Society (AOFAS), and complications. Results: Of 10 patients, 8 were very satisfied, and the remaining 2 were satisfied. The mean incision length was 2.0 cm, and the mean hospitalization was 2 days. The mean AOFAS score was 97 points, and there was no complications such as infection, rerupture, or nerve injury. All patients returned to work at approximately 2 months, and resumed light exercise such as jogging at approximately 3 months. Conclusion: Limited open repair technique of Achilles tendon ruptures is provided for better cosmetic results, high patient's satisfaction, and functionally successful results without postoperative complications.

• 한국통신학회논문지
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• 제27권1B호
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• pp.56-65
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• 2002

본 논문에서는 IS-2000 시스템에 적합한 심볼 분할 OTD (orthogonal transmit diveristy)를 제안하였다. 심볼 분할 OTD는 Meyer가 제안한 심볼 분할과 OTD를 결합하여 최대 경로 다이버시티 및 시간 다이버시티 이득을 얻기에 IS-2000 순방향 성능을 개선시킬 수 있다. 이를 IS-2000 표준의 순방향 fundamental 채널에 대하여 시뮬레이션을 통해 확인하였다. 그리고, 그 결과를 기존의 IS-2000 표준에서 채택된 OTD와 STS (space-time spreading)의 성능과 비교하였다. 본 논문에서 제안한 방법을 IS-2000 시스템에 적용할 경우, 1% FER (frame error rate)을 얻기 위한 송신전력이 OTD의 경우보다 0.5-7.7dB 정도 감소되어 STS의 성능과 거의 일치하였다. 뿐만 아니라, 송신신호의 PAR(peak-to-average power ratio)가 STS보다 적으므로, 기지국 전력증폭기와 같은 RF 회로의 복잡도를 감소시킬 수 있는 장점이 있다.

• 한국통신학회논문지
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• 제33권6C호
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• pp.480-486
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• 2008

전송 신호의 높은 PAPR (Peak-to-Average Power Ratio)은 OFDM (Orthogonal Frequency Division Multiplexing)의 주된 문제점중의 하나이다. PTS (Partial Transmit Sequences) 기법은 OFDM 신호의 PAPR의 통계를 개선하는 기법이다. 그러나 PTS 기법에서 위상 가중치의 선택을 위한 계산 복잡도는 서브블록의 수에 따라 지수적으로 증가한다. 본 논문에서는 ${\mu}$-GA (micro-Genetic Algorithm) 기반의 위상 가중치 탐색 알고리즘을 적용한 낮은 계산 복잡도를 갖는 PTS 기법을 제안한다. 위상 가중치의 탐색은 랜덤하게 생성한 5 개체의 개체군으로부터 시작한다. 이 중에서 적합도가 가장 큰 엘리트와 토너먼트 선택 방법에 의해 나머지 4 개체를 선택하고 교배 연산을 통해 다음 세대를 구성한다. 만일 생성된 세대가 수렴한다면 엘리트를 제외한 나머지 개체를 다시 랜덤하게 생성한다. 일정 세대 이상 PAPR이 개선되지 않거나 사전에 정해진 최대 세대수까지 진행하면 탐색을 종료한다. 제안하는 PTS 기법의 성능을 평가하기 위해 PAPR의 CCDF (Complementary Cumulative Distribution Function)를 이전의 PTS 기법과 비교한다.

• 치과방사선
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• 제16권1호
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• pp.103-112
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• 1986

75명의 치과대학 4학년생들이 촬영한 300예의 구내전악표준방사선사진들을 촬영법과 필름의 유지법에 다라 필름을 피촬영자의 엄지나 검지로 유지하고 등각법으로 촬용한 경우 (Ⅰ군), 필름을 Rinn Sanp-A-Ray 기구로 유지하고 등각법으로 촬영한 경우 (Ⅱ군), 필름을 Rinn XCP기구로 유지하고 Short cone에서 평행법으로 촬영한 경우(Ⅲ군), 필름을 Rinn XCP기구로 유지하고 Long cone에서 평행법으로 촬영한 경우(Ⅳ군)으로 분류하여 75예의 구내전악표준방사선사진으로 구성된 각 군의 재촬영을 조사하여 각 군에서 가장 많이 나타난 실책의 종류와 부위, 그리고 구내전악표준방사선사진 1회당 평균재촬영매수에 대해 아래의 결과를 얻었다. Ⅰ군 : Incorrect film placement(47.8%)와 상악 견치부(26.9%)였으며 0.89매였다. Ⅱ군 : Incorrect film placement(44.0%)와 상악 대구치부(28.6%)였으며 1.12매였다. Ⅲ군 : Incorrect film placement(79.1%)와 상악 대구치부(32.0%)였으며 2.05매였다. Ⅳrns : Incorrect film placement(67.7%)와 상악 대구치부(30.7%)였으며 1.69매였다. 평균재촬영매수에서는 같은 촬영법인 Ⅰ군과 Ⅱ군간에서와, Ⅲ군과 Ⅳ군간에서는 유의한 차가 나타나지 않았으나 (P>0.05), 등각촬영법의 군 (Ⅰ＋Ⅱ)보다 평행촬영법의 군(Ⅲ＋Ⅳ)에서 0.86매 많았다 (P<0.01)