• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.81-88
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• 2018

Spectrum sensing, the key technology of the cognitive radio networks, is used by a secondary user to determine the frequency state of a primary user. The energy detection in the spectrum sensing determines the presence or absence of a primary user according to the intensity of the allocated channel signal. Since this technique simply uses the strength of the signal for spectrum sensing, it is difficult to detect the signal of a primary user in the low SNR band. In this paper, we propose a way to combine spectrum sensing and support vector machine using wavelet packet decomposition to overcome performance degradation in low SNR band. In our proposed scheme, the sensing signals were extracted by wavelet packet decomposition and then used as training data and test data for support vector machine. The simulation results of the proposed scheme are compared with the energy detection using the AUC of the ROC curve and the accuracy according to the SNR band. With simulation results, we demonstrate that the proposed scheme show better determining performance than one of energy detection in the low SNR band.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.63-68
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• 2014

This paper related with the I-CMA (Improved-CMA) algorithm that is possible to compensates of phase in CMA adatpve equalizer which is used for the elemination of intersymbol interference in the multipath fading and band limit characteristics of channel. The new cost function is proposed for the eliminate the amplitude and phase simulataneous by modifying the cost fuction for get the error signal in present CMA algorithm. It has a merit to the algorithm simplicities and eliminats the PLL device for phase compensation after equalization. For proving this, the recovered signal constellation that is the output of equalizer output signal and the residual isi and Maximum Distortion charateristic learning curve that are presents the convergence performance in the equalizer and the overall frequency transfer function of channel and equalizer were used. As a result of computer simulation, the I-CMA has more good compensation capability of amplitude and phas in the recovered constellation. But the convergence time is slow due to the simultaneously phase compensation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.57-62
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• 2014

This paper proposes the improving the equalization performance using the adaptive modulus concept to the MCMA blind equalizer in order to the reduction of intersymbol interference which occurs in the band limited and time dispersive communication channel. In MCMA blind algorithm, it is possible to reducing the amplitude and phase rotation of intersymbol interference without training sequence, the fixed constant modulus of transmission signal is used. But in proposed algorithm, the modulus are adaptively varies according to the equalizer output signal, then the improved equalization performance were obtained by the computer simulation. For this, the recovered signal constellation that is the output of the equalizer, the convergence performance by MSE, MD (maximum distortion) and residual isi characteristic learning curve were used. The propose algorithm has fairly good performance compared to the traditional MCMA algorithm in the same adaptive equalization algorithm.

• Archives of Plastic Surgery
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• v.33 no.4
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• pp.454-457
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• 2006

Purpose: The anastomosis of hepatic artery to recipient vessel has a major role in a liver transplantation, so its occlusion is the most important cause of failure of liver transplantations. We made the study to reveal the peculiarities in pediatric liver transplantations compared with adult cases. Methods: From January 1999 to September 2005, we performed 99 cases of pediatric liver transplantation. The mean age at operation was 4.17 years of age. The hepatic vein and portal vein are anastomosed by the general surgeons and then the hepatic artery is anastomosed by the plastic surgeons. The Doppler ultrasonography and computed tomography were used for postoperative checkup for hepatic artery patency. Results: There were no immediate complications, but hepatic arterial occlusion was developed in 3 cases (2.8%). In pediatric patients, the anastomosis of hepatic artery is more difficult than adults because of the rapid respiratory and pulse rate, the small vascular diameter, and the large gap of diameter difference between the recipient and the donor vessels. Conclusion: We could confirm that pediatric liver transplantations are relatively safe but long learning curve was needed.

• Journal of Korean Neurosurgical Society
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• v.29 no.12
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• pp.1577-1583
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• 2000

Objectives : Among the various types of minimally invasive spine surgeries, thoracoscopic surgery is becoming more widely accepted and increasingly utilized. This report delineates our clinical experience using thoracoscopy to resect herniated thoracic discs in 16 patients who suffered from myelopathy or intolerable radiculopathy. Patients and Methods : Between Mar. 1997 and Sep. 1999, 16 consecutive patients underwent thoracoscopic discectomy for treatment of herniated thoracic discs. There were 12 men and 4 women(mean age 43.5 years ; range 18-61 years). Eleven patients presented with myelopathic signs and symptoms from spinal cord compression and 5 patients had incapacitating thoracic radicular pain without myelopathy. The surgical level was varied between T3 and T12. The pathology of specimen were 11 hard discs and 5 soft discs herniations. Thoracoscopic techniques were performed with long narrow spine instruments and high speed drill through 3 or 4 ports under one lung ventilated general anesthesia. During the operation three patients were converted to open thoracotomy due to intolerable one lung ventilation, excessive bleeding and inadequate operation field. The mean operation time was 264min.(range : 100-420min.), and postoperative mean admission period was 11 days. Results : Clinical and neurological outcomes were good in all patients(mean follow-up period 20 months). Among the eleven myelopathic patients, 8 improved neurologically, and 3 stabilized. Among the five radiculopathic patients, 4 recovered completely and no patient had worsened. Postoperative complications were pleural effusion in one case, intercostal neuralgia in one, delayed hemopneumothorax in one, prolonged air leakage in one and pneumonia in one case. Conclusions : Thoracoscopic discectomy needs a steep learning curve to be familiar to anatomical space and handling of endoscopic instruments. However, it is technically feasible and can be effectively performed with acceptable results.

• Clinics in Shoulder and Elbow
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• v.1 no.2
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• pp.160-166
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• 1998

The purpose of this study was to assess the results of arthroscopic subacromial decompression in patients with chronic impingement and to evaluate the results according to the rotator cuff pathology. We evaluated the clinical results of treatment for chronic impingement syndrome in 28 patients from Feb 1996 to Feb 1997. There were twenty men and eight women in age from 24 to 72 years (mean age 51) with dominant arm involvement in sixteen patients. Follow up evaluations averaged 15(range 12-24)months. The average duration of symptoms were 15(range 6­60)months. The final diagnoses which were based on the physical examination, plain radiographs and arthroscopic findings, were stage II impingement in 16 patients and stage ill impingement in 12 patients. We excluded the patients with acromioclavicular arthritis or glenohumeral instability in this study. All patients were managed non-operatively a minimum of six months. During the operation we performed contouring and smoothing the acromial undersurface and only resecting of the anterolateral band of the coracoacromial ligament. The clinical results were quantitated using UCLA shoulder rating score. Satisfactory results were obtained in 23(80%) patients. Unsatisfactory results were obtained in 5(18%) patients with posterior cuff tear. The average UCLA pain score showed significant improvement from 2.8(constant pain) to 7.2(present during heavy activities) at final follow up. The function and active forward flexion scores also increased from their preoperative value. There was no significant differences according to the surface and severity of tear and NeeI' stage (P>0.05). These results compared favorably with those reported following open acromioplasty. While arthroscopic subacromial decompression is a demanding technique with a learning curve, it is a reliable treatment for chronic impingement syndrome. A less aggressive approach to subacromial decompression and preserving the posteromedial band of the coracoacromialligament does not appear to compromise results.

• Journal of Educational Research in Mathematics
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• v.24 no.2
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• pp.125-143
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• 2014

In this study, we analyzed a mathematical discussion in the Calculus II course of the Gifted Science Academy and individual interviews to determine the relationship between cognitive conflicts and commognitive conflicts. The mathematical discussion began with a question from a student who seemed to have a cognitive conflict about the osculating plane of a space curve. The results indicated that the commognitive conflicts were resolved by ritualizing and using the socially constructed knowledge, but cognitive conflicts were not resolved. Furthermore, we found that the cause of the cognitive conflict resulted from the student's imperfect analogical reasoning and the reflective discourse about it could be a learning opportunity for overcoming the conflict. These findings imply that cognitive conflicts can trigger the appearance of commognitive conflicts, but the elimination of commognitive conflicts does not imply that cognitive conflicts are resolved.

• Journal of Gastric Cancer
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• v.10 no.4
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• pp.241-246
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• 2010

Purpose: Laparoscopy-assisted gastrectomy (LAG) has become a technically feasible and safe procedure for early gastric cancer treatment. LAG is being increasingly performed in many centers; however, there have been few reports regarding LAG at low-volume centers. The aim of this study was to report our early experience with LAG in patients with gastric cancer at a low-volume center. Materials and Methods: The clinicopathologic data and surgical outcomes of 39 patients who underwent LAG for gastric cancer between April 2007 and March 2010 were retrospectively reviewed. Results: The mean age was 68.3 years. Thirty-one patients had medical co-morbidities. The mean patient ASA score was 2.0. Among the 39 patients, 4 patients underwent total gastrectomy and 35 patients underwent distal gastrectomy. The mean blood loss was 145.4 ml and the mean operative time was 259.4 minutes. The mean time-to-first flatus, first oral intake, and the postoperative hospital stay was 2.8, 3.1, and 9.3 days, respectively. The 30-day mortality rate was 0%. Postoperative complications developed in 9 patients, as follows: anastomotic leakage, 1; wound infection, 1; gastric stasis, 2; postoperative ileus, 1; pneumonia, 1; cerebral infarction, 1; chronic renal failure, 1; and postoperative psychosis, 1. Conclusions: LAG is technically feasible and can be performed safely at a low-volume center, but an experienced surgical team and careful patient selection are necessary. Furthermore, for early mastery of the learning curve for LAG, surgeons need education and training in addition to an accumulation of cases.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.5
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• pp.55-63
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• 2011

This paper describes new moving target detection technique combining two algorithms to detect targets and reject clutters in video frame images for surveillance system: One obtains the region of moving target using phase correlation method using $N{\times}M$ sub-block images in frequency domain. The other uses adaptive threshold using learning weight for extracting target candidates in subtracted image. The block region with moving target can be obtained using the characteristics that the highest value of phase correlation depends on the movement of largest image in block. This technique can be used in camera motion environment calculating and compensating camera movement using FFT phase correlation between input video frame images. The experimental results show that the proposed algorithm accurately detects target(s) with a low false alarm rate in variety environment using the receiver operating characteristics (ROC) curve.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.1
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• pp.15-22
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• 2005

In this paper, we propose a face recognition system by using the CCD color image. We first get the face candidate image by using YCbCr color model and adaptive skin color information. And we use it initial curve of active contour model to extract face region. We use the Eye map and mouth map using color information for extracting facial feature from the face image. To obtain center point of Log-polar image, we use extracted facial feature from the face image. In order to obtain feature vectors, we use extracted coefficients from DCT and wavelet transform. To show the validity of the proposed method, we performed a face recognition using neural network with BP learning algorithm. Experimental results show that the proposed method is robuster with higher recogntion rate than the conventional method for the rotation and scale variant.