• Journal of Korean Neurosurgical Society
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• 제62권4호
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• pp.458-466
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• 2019

Objective : We retrospectively assessed the efficacy of stereotactic radiosurgery (SRS) for dural arteriovenous fistulas (DAVFs) involving the transverse-sigmoid sinus and analyzed the angiographic and clinical results with our 8-year experience. Methods : Nine patients with intracranial DAVFs involving the transverse-sigmoid sinus underwent SRS using a Gamma $Knife^{(R)}$ (Elekta Inc., Atlanta, GA, USA) between 2009 and 2016. Five patients underwent SRS for residual DAVFs after embolization and four patients were treated with SRS alone. The median target volume was $1.9cm^3$ (range, 0.8-14.2) and the median radiation dose of the target was 17 Gy (range, 16-20). The median follow-up period was 37 months (range, 7-81). Results : Pulsating tinnitus (33%) was the most common symptom. DAVFs were completely obliterated in four patients (44%) and subtotally obliterated in five (56%). Six patients (67%) showed complete recovery of symptoms or signs, and three (33%) showed incomplete recovery. One patient experienced a recurrent seizure. Adverse radiation effects after SRS occurred in one patient (11%). The total obliteration rates after SRS were 16.7%, 37.5%, and 68.7% at 1, 2, and 3 years, respectively. The median interval from SRS to total obliteration of the fistula was 31 months (range, 12-38). The rates at which the symptoms started to improve were 40% at 1 month and 80% at 2 months after SRS. Symptoms started to improve at a median of 5 weeks after SRS (range, 3-21). Conclusion : SRS with or without embolization is a safe and effective treatment to relieve symptoms and obliterate DAVFs on the transverse-sigmoid sinus.

• 전자공학회논문지 IE
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• 제44권3호
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• pp.12-22
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• 2007

본 논문에서는 잉여수체계(Residue Number System)를 이용하여 고속의 디지털 신경회로망을 제안하고 이를 구현하기 위한 중요연산부인 고속의 디지털 뉴런프로세서를 설계하였다. 설계된 디지털 뉴런프로세서는 잉여수계를 이용한 MAC 연산기와 혼합계수 변환을 이용한 시그모이드 함수 연산 부로 구성되며, 설계된 회로는 VHDL로 기술하였고 Compass 툴로 합성하였다. 실험결과, 본 논문에서 설계한 디지털 뉴런프로세서는 19.2nsec의 속도를 보였으며, 실수연산기로 설계한 뉴런프로세서에 비하여 약 50%정도 하드웨어 크기를 줄일 수 있었다. 본 논문에서 설계한 뉴런프로세서는 실시간 처리를 요하는 병렬분산처리 시스템에 적용될 수 있을 것으로 기대된다.

• 전자공학회논문지C
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• 제35C권2호
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• pp.56-64
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• 1998

Multi-layered perceptrons that are a nonlinear neural network model, have been widely used for various applications mainly thanks to good function approximation capability for nonlinear fuctions. However, for digital hardware implementation of the multi-layere perceptrons, the quantization scheme using "look-up tables (LUTs)" is commonly employed to handle nonlinear signmoid activation functions in the neworks, and thus requires large amount of storage to prevent unacceptable quantization errors. This paper is concerned with a new effective methodology for digital hardware implementation of multi-layered perceptrons, and proposes a "piecewise affine approximation" method in which input domain is divided into (small number of) sub-intervals and nonlinear sigmoid function is linearly approximated within each sub-interval. Using the proposed method, we develop an expression and an error backpropagation type learning algorithm for a multi-layered perceptron, and compare the performance with the quantization method through Monte Carlo simulations on XOR problems. Simulation results show that, in terms of learning convergece, the proposed method with a small number of sub-intervals significantly outperforms the quantization method with a very large storage requirement. We expect from these results that the proposed method can be utilized in digital system implementation to significantly reduce the storage requirement, quantization error, and learning time of the quantization method.quantization method.

• Advances in pediatric surgery
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• 제10권2호
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• pp.145-149
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• 2004

A 12-year-old boy with severe periumbilical pain visited the emergency room. Physical examination, abdominal ultrasonography, colonoscopy and CT, identified a lesion of sigmoid colon. Endoscopic biopsy showed a signet ring cell carcinoma of the sigmoid colon. On explorative laparotomy, cancer invasions of the adjacent structures and metastases on peritoneal wall were noticed. We performed palliative loop-ileostomy. He underwent chemotherapy and radiotherapy for 3 months. The second case was a 16-year-old boy with abdominal pain and hematochezia, transferred to our hospital with the diagnosis of acute appendicitis with periappendiceal abscess. Although he underwent appendectomy, the abdominal pain persisted. Digital rectal examination revealed a lumen-obstructing fungating mass in the rectum. Endoscopic biopsy revealed a adenocarcinoma. Cancer invasion of the adjacent structures and metastases involving the mesentery of the small intestine were found at laparotomy. A palliative procedure, a Hartmann's operation and end-colostomy at the sigmoid colon were performed. The patient died 8 month later due to pneumonia and sepsis. Chemotherapy was not applied.

• Journal of Trauma and Injury
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• 제30권4호
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• pp.216-219
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• 2017

Laparoscopy has been one of the most effective modalities in various surgical situations, although its use in trauma patients has some limitations. The benefits of laparoscopy include cost-effectiveness, shorter length of hospital stay, and less postoperative pain. This report describes diagnostic laparoscopy and laparoscopic diverting sigmoid loop colostomy in penetrating extraperitoneal rectal injury. A 41-year-old male presented with perineal pain following penetrating trauma caused by a tree limb. Computed tomography showed air density in the perirectal space and retroperitoneum. As his vital signs were stable, we performed diagnostic laparoscopy and confirmed no intraperitoneal perforation. Therefore, laparoscopic diverting sigmoid loop colostomy was performed. He was discharged without any complications despite underlying hepatitis C-related cirrhosis. Colostomy closure was performed 3 months later.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2005년도 추계 종합학술대회 논문집
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• pp.649-653
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• 2005

눈 모형이 닫혀있는 등화 초기에 축소 신호점을 적용한 시그모이드 비선형성으로 오차신호를 추정하면, 기존 연판정의거 알고리즘의 문제점인 고차 신호점을 적용 시 계산 복잡도가 증가하고 수렴속도가 저하되는 단점을 개선할 수 있다. 시그모이드 함수는 평균과 분산 파라미터로 특성이 조절되므로, 분산 값을 조절함에 따라 축소 신호점의 값$(\gamma)$이+$\gamma$와-$\gamma$ 사이의 범위를 가질 수 있다. 본 논문에서는 등화가 올바르게 진행하여 각 신호점에서 군집의 크기가 줄어들 때 분산 값을 가변함으로써 정상상태 성능을 개선할 수 있는 가변 모듈러스 알고리즘(Variable Modulus Algorithm: VMA)을 제안한다.

• Journal of Korean Neurosurgical Society
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• 제30권9호
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• pp.1144-1149
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• 2001

Schwannomas of the jugular foramen, originating from the glossopharyngeal nerve, vagus and accessory nerve represent approximately 0.17-0.72% of all intracranial tumor, and consists of 1.4-2.9% of all intracranial schwannomas. The clinical presentation of these tumors varies significantly according to originated nerve and it's growth pattern. Magnetic resonance(MR) image and temporal bone computed tomography(CT) scan have a major role for diagnosis of such tumor. The treatment of choice is total resection whenever possible. Generally, suboccipital approach is sufficient for the removal of the tumor, but in case with large size, combination of resection of petrous part of temporal bone with or without transection of sigmoid sinus is may be necessory. We have recently experienced one case of giant jugular foramen schwannoma and postoperative fatal complication in a 34-year-old male who was treated with combined posterior petrous and suboccipital approach with transection of sigmoid sinus

• 한국자동차공학회논문집
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• 제22권3호
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• pp.220-227
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• 2014

This paper presents about multi-rate sensors' synchronization and filter fusion via a sigmoid function of the Kalman filter. To synchronize multi-rate sensors, the estimation states of the Kalman filter is modified. A specific matrix that makes the filter choose sensor values only updated is multiplied to measurement matrix. For the filter that has weak points on some criteria, filter fusion is suggested by using sigmoid function. Modified kalman filter is tested with practical case. A sigmoid function was designed for the test and the performance of the modified function is estimated with respect to conventional Kalman filter. Unscented Kalman filter is used to the base filter of the suggested filter because of its stability.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.20-20
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• 2000

Back-propagation neural network (BPNN) is the most prevalently used paradigm in modeling semiconductor manufacturing processes, which as a neuron activation function typically employs a bipolar or unipolar sigmoid function in either hidden and output layers. In this study, applicability of another linear function as a neuron activation function is investigated. The linear function was operated in combination with other sigmoid functions. Comparison revealed that a particular combination, the bipolar sigmoid function in hidden layer and the linear function in output layer, is found to be the best combination that yields the highest prediction accuracy. For BPNN with this combination, predictive performance once again optimized by incrementally adjusting the gradients respective to each function. A total of 121 combinations of gradients were examined and out of them one optimal set was determined. Predictive performance of the corresponding model were compared to non-optimized, revealing that optimized models are more accurate over non-optimized counterparts by an improvement of more than 30%. This demonstrates that the proposed gradient-optimized teaming for BPNN with a linear function in output layer is an effective means to construct plasma models. The plasma modeled is a hemispherical inductively coupled plasma, which was characterized by a 24 full factorial design. To validate models, another eight experiments were conducted. process variables that were varied in the design include source polver, pressure, position of chuck holder and chroline flow rate. Plasma attributes measured using Langmuir probe are electron density, electron temperature, and plasma potential.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권5호
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• pp.525-536
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• 2017

Course keeping is hard to implement under the condition of the propeller stopping or reversing at slow speed for berthing due to the ship's dynamic motion becoming highly nonlinear. To solve this problem, a practical Maneuvering Modeling Group (MMG) ship mathematic model with propeller reversing transverse forces and low speed correction is first discussed to be applied for the right-handed single-screw ship. Secondly, a novel PID-based nonlinear feedback algorithm driven by bipolar sigmoid function is proposed. The PID parameters are determined by a closed-loop gain shaping algorithm directly, while the closed-loop gain shaping theory was employed for effects analysis of this algorithm. Finally, simulation experiments were carried out on an LPG ship. It is shown that the energy consumption and the smoothness performance of the nonlinear feedback control are reduced by 4.2% and 14.6% with satisfactory control effects; the proposed algorithm has the advantages of robustness, energy saving and safety in berthing practice.