• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.355-358
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• 2004

최근 웨이블릿 변환을 이용하여 저주파수 부대역 신호를 반복적으로 분해하고 삽입된 워터마크 비트에 따라 특정 부대역 신호에 두개의 다른 반향 중 하나를 삽입하는 반향 삽입 기법을 제안하였다. 이 기법은 오디오 신호의 주파수 특성을 고려했기 때문에 시간 영역에서의 기존의 반향 삽입 기법에 비해 비가청성(inaudibility), 워터마크의 강인성(robustness) 및 용적성(capacity)을 모두 증가시킬 수 있다. 기존의 부대역 신호 기반 반향 삽입 기법이 단일 반향 커널만을 이용하였으나, 본 논문에서는 부대역 신호에 다중 반향 커널을 이용한 반향 삽입 기법을 제안한다. 이 기법은 주관적 왜곡(perceptibility)과 SNR(signal to Noise Ratio)과 같은 객관적인 왜곡 면에서, 원본 오디오 신호의 왜곡을 줄일 수 있다. 실험 결과를 통하여 기존의 방법에 비해 제안된 방법이 SNR과 DR(Detection Rate) 모두 좋은 성능을 보여 제안된 방법의 유효성을 입증하였다.

• Korean Journal of Head & Neck Oncology
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• v.8 no.2
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• pp.91-96
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• 1992

The efficacy of the fine needle aspiration biopsy and cytological examination(FNABC) under ultrasonographic(US) guides for the diagnosis of cervical tuberculous lymphadenitis was assessed. There were one hundred and one patients whose neck masses were proven to be tuberculous lymphadenites with cytologic and/or histologic diagnosis. The physical characteristics shown by US revealed that all the cases were multiple lesions. Multiregional lesions were found in 80 cases(79.1%) and 19 cases(18.8%) were the bilateral lesion. The region V was the most prevalent site(n=69, 68.3%). US findings revealed 92 cases(90.9%) showed hypoechoic lesions and 9(9.1%) showed mixed echo patterns. There was no hyperechoic lesion (p<0.05). The sensitivity of FNABC was 77.2% and specificity was 99.0%. Diagnostic accuracy was 85.0%. There was no complication during the procedures. FNABC for the diagnosis of cervical tuberculous lymphadenitis is a safe, convinient procedure and has a high specificity. The pitfall of FNABC the low sensitivity, seemed to be compensated by US evaluations.

• 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.

• Journal of Korean Neurosurgical Society
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• v.29 no.7
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• pp.891-898
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• 2000

Objective : It is difficult to differentiate intramedullary spinal cord tumors preoperatively from non-neoplastic pathologies in patients presenting as non-compressive myelopathies in magnetic resonance imaging(MRI). In this report, the authors reviewed nonneoplastic intramedullary spinal cord lesions preoperatively diagnosed as tumors and discussed their clinical and radiological characteristics and usefulness of surgical intervention. Methods : From January, 1985 to January, 1999, authors experienced eight non-neoplastic pathologies mimicking intramedullary spinal cord tumors and analysed their medical records, radiological findings and histopathological specimens retrospectively. Results : There were five males and three females and the duration of symptoms were from two to 20 months(mean, 9.8 months). The location of lesions were four cervical, one cervicothoracic and three thoracic. All patients manifested sensory abnormality, seven motor weakness, and six bladder symptom. All cases had swollen spinal cords and increased signal intensities in spin-echo sequences. Six cases showed contrast enhancement : four cases were focal and two diffuse. Under the impression of intramedullary tumors, the patients were operated upon. Final diagnoses on the base of clinical and pathologic finding were : three subacute necrotizing myelopathies, two multiple scleroses, two myelopathy of unknown etiology. One case showed no gross abnormality in surgical field in spite of adequate exposure of the lesion, so biopsy was not performed. In that case, postoperative MRI revealed spontaneous resolution of the lesion. Conclusion : MRI is invaluable diagnostic tool in screening myelopathies. However, its high sensitivity and lack of specificity make difficulty in preoperative differential diagnosis of non-compressive myelopathies. Although no surgical morbidity occurred in our series, we sometimes failed to confirm definite diagnosis even with biopsy. In such a circumstance, long-term follow up is needed.

• Journal of Intelligence and Information Systems
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• v.17 no.2
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• pp.97-107
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• 2011

Nowadays there are a lot of issues about copyright infringement in the Internet world because the digital content on the network can be copied and delivered easily. Indeed the copied version has same quality with the original one. So, copyright owners and content provider want a powerful solution to protect their content. The popular one of the solutions was DRM (digital rights management) that is based on encryption technology and rights control. However, DRM-free service was launched after Steve Jobs who is CEO of Apple proposed a new music service paradigm without DRM, and the DRM is disappeared at the online music market. Even though the online music service decided to not equip the DRM solution, copyright owners and content providers are still searching a solution to protect their content. A solution to replace the DRM technology is digital audio watermarking technology which can embed copyright information into the music. In this paper, the author proposed a new audio watermarking algorithm with two approaches. First, the watermark information is generated by two dimensional barcode which has error correction code. So, the information can be recovered by itself if the errors fall into the range of the error tolerance. The other one is to use chirp sequence of CDMA (code division multiple access). These make the algorithm robust to the several malicious attacks. There are many 2D barcodes. Especially, QR code which is one of the matrix barcodes can express the information and the expression is freer than that of the other matrix barcodes. QR code has the square patterns with double at the three corners and these indicate the boundary of the symbol. This feature of the QR code is proper to express the watermark information. That is, because the QR code is 2D barcodes, nonlinear code and matrix code, it can be modulated to the spread spectrum and can be used for the watermarking algorithm. The proposed algorithm assigns the different spread spectrum sequences to the individual users respectively. In the case that the assigned code sequences are orthogonal, we can identify the watermark information of the individual user from an audio content. The algorithm used the Walsh code as an orthogonal code. The watermark information is rearranged to the 1D sequence from 2D barcode and modulated by the Walsh code. The modulated watermark information is embedded into the DCT (discrete cosine transform) domain of the original audio content. For the performance evaluation, I used 3 audio samples, "Amazing Grace", "Oh! Carol" and "Take me home country roads", The attacks for the robustness test were MP3 compression, echo attack, and sub woofer boost. The MP3 compression was performed by a tool of Cool Edit Pro 2.0. The specification of MP3 was CBR(Constant Bit Rate) 128kbps, 44,100Hz, and stereo. The echo attack had the echo with initial volume 70%, decay 75%, and delay 100msec. The sub woofer boost attack was a modification attack of low frequency part in the Fourier coefficients. The test results showed the proposed algorithm is robust to the attacks. In the MP3 attack, the strength of the watermark information is not affected, and then the watermark can be detected from all of the sample audios. In the sub woofer boost attack, the watermark was detected when the strength is 0.3. Also, in the case of echo attack, the watermark can be identified if the strength is greater and equal than 0.5.

• Journal of Yeungnam Medical Science
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• v.22 no.1
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• pp.43-51
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• 2005

Background: To examine the ultrasonographic and magnetic resonance (MRI) imaging findings of a cervical mass type cervical pregnancy. Materials and Methods: The ultrasonographic and MRI findings of 5 patients pathologically confirmed as having a cervical pregnancy were analyzed retrospectively. On ultrasonography, the size and echo pattern of the uterine cervix, the shape and echo pattern of the lesion, the degree and the pattern of blood flow on the color Doppler study and the spectral Doppler pattern were analyzed. The shape, signal intensity, and degree and pattern of enhancement of the lesion were evaluated on MRI. Results: The uterine cervix was enlarged and the size of the lesion was 6.1 to 7.1 (average, 6.5) cm. The endocervical canal was irregularly dilated and showed heterogeneous echogenicity in all 5 cases. Four of the 5 lesions were heterogeneously hyper- or mixed echoic and remaining one was relatively homogeneous echogenic. Doppler ultrasonography revealed an increased vascularity of the peritrophoblastic flow pattern. In all 4 cases where MRI performed, the lesion was irregular in shape and the margin was not sharply demarcated. The T2-weighed image showed that the lesions were mixed signal intensity. Three of the 4 lesions contained high signal intensity nodular portions and a low signal intensity rim was observed along the margin of the nodular portions. The T1-weighted image revealed multiple signal voids along the periphery of the lesions and high signal intensity portions as a result of hemorrhage were noted. The dynamic enhanced study showed that the high signal intensity portions on the T2-weighted image were strongly enhanced similar to the vessels on the early phase and the contrast enhancement gradually decreased with time. Conclusion: A cervical mass type cervical pregnancy can be correctly diagnosed using the patient's clinical symptom, the elevation in the serum ${\beta}$-HCG level, and characteristic ultrasonographic and MRI findings.

• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.3
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• pp.160-174
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• 2014

The purpose of this paper is to develop a meso-scale grid-based continuous hydrological model and apply to assess the future watershed hydrology by climate change. The model divides the watershed into rectangular cells, and the cell profile is divided into three layered flow components: a surface layer, a subsurface unsaturated layer, and a saturated layer. Soil water balance is calculated for each grid cell of the watershed, and updated daily time step. Evapotranspiration(ET) is calculated by Penman-Monteith method and the surface and subsurface flow adopts lag coefficients for multiple days contribution and recession curve slope for stream discharge. The model was calibrated and verified using 9 years(2001-2009) dam inflow data of two watersheds(Chungju Dam and Soyanggang Dam) with 1km spatial resolution. The average Nash-Sutcliffe model efficiency was 0.57 and 0.71, and the average determination coefficient was 0.65 and 0.72 respectively. For the whole Han river basin, the model was applied to assess the future climate change impact on the river bsain. Five IPCC SRES A1B scenarios of CSIRO MK3, GFDL CM2_1, CONS ECHO-G, MRI CGCM2_3_2, UKMO HADGEMI) showed the results of 7.0%~27.1 increase of runoff and the increase of evapotranspiration with both integrated and distributed model outputs.

• Journal of Yeungnam Medical Science
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• v.2 no.1
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• pp.87-93
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• 1985

Intraabdommal abscess usually causes distress with fever, leukocytosis, pain and toxicity. Diagnosis of intraabdominal abscess is occasionally difficult and It has high morbidity. However radiologic method, such as ultrasonography, CT scan, or RI scan are helpful to early detection of intraabdominal abscess. Among these methods, ultrasonography is a non-invasive technique and performed without discomfort to patient. And also differential diagnosis between cystic and solid lesion is very easy and sequential ultrasonography in same patient is valuable for the evaluation of treatment effect. We analyzed the ultrasonic features of 48 cases with intra-abdominal abscesses and the results are as follows; 1. In total 48 cases, the intra-abdominal abscesses were 30 cases, the retroperitoneal abscesses, 5 cases, and the visceral abscesses, 13 cases. 2. The causes of the intra-abdominal abscesses were perforating appendicitis (25 cases), postoperative complications (5 cases), pyogenic and amebic hepatic abscesses (13 cases), and the others (5 cases). 3. Round or oval shaped lesions were 26 cases (54%), irregular shape, 18 cases (38%), and multiple abscess formation in 4 cases (8 %). 4. The size of the lesions were between 5 and 10cm in diameter in 54% of total 48 cases, and the most frequent feature of the echo-pattern of the lesions was cystic with or without internal echogenicity (69%).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.3
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• pp.186-194
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• 2017

In this paper, we analyze the main performance of satellite's Synthetic Aperture Radar system for high resolution and wide swath. We have used the radiation pattern of reflector antenna with array feed and comparison between the conventional ScanSAR mode and SweepSAR mode has been carried out. The SweepSAR mode is a high-resolution wide-swath mode that transmits beams over a wide range and receives echo signals through sequential beamforming based on SCORE(SCan On REceive). In this paper, we analyzed the operating principle and characteristics of satellite's SweepSAR mode and simulate system performances. In addition, in order to increase the utilization of image, performances analysis for multiple frequency bands(C-band, X-band) has been considered.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1242-1249
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• 2017

In this paper, we propose a new algorithm for the performance analysis of the sidelobe blanker (SLB) in radar system, which is based on the matrix pencil method (MPM). In general, the SLB in radar is composed of the main antenna, the auxiliary antenna, and the processing unit. The auxiliary antenna with wide beamwidth receives interference signals such as jamming or clutter signals. The main antenna with high gain receives the target signal in the main beam and the interference signals in the sidelobe. In this paper the Swerling model is used as the target echo signal by considering a probabilistic radar cross section (RCS) of the target. To estimate the SLB performance it needs to calculate the probability of target detection and the probability of blanking the interference by using the signals received from the main and auxiliary antennas. The detection probability and the blanking probability include multiple summations of infinite series with infinite integrations, of which convergence rate is very slow. Increase of summation range to improve the calculation accuracy may lead to an overflow error in computer simulations. In this paper, to resolve the above problems, we used the MPM to calculate a summation of infinite series and improved the calculation accuracy and the convergence rate.