• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3638-3654
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• 2014

Cognitive Radio (CR) users need to sense the environment or channel at regular time interval for sharing the spectrum band of the primary users (PUs). Once find the spectrum idle, CR users start their transmission through it. Even while transmitting, they need to continue the sensing process so that they can leave the spectrum immediately whenever find a PU wanting to use the band. Therefore, detecting PUs is one of the main functions of cognitive radio before transmission and higher the detection probability ensures better protection to the primary users. However, it is not possible to attain a high detection probability (or a low miss detection probability) and low false alarm probability simultaneously as there is a tradeoff between false alarm probability ($P_{fa}$) and the probability of detection ($P_d$). In this paper, the author has provided a comprehensive study on different sensing techniques and discussed their advantages and disadvantages. Moreover, it is expected that, with this article, readers can have a through understanding of sensing techniques in CR and the current research trends in this area.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.155-161
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• 2014

Mobility can lead to continual loss of data and service interruptions during communications in multi-hop cognitive radio networks. Mobility of primary users (PUs) or cognitive users (CUs) requires adjustment of multi-hop communications among CUs to avoid any interference to PUs. To provide durable and reliable data routing that ensures continuous network service, we propose mobility-aware cognitive routing (MCR) for multi-hop cognitive radio networks. MCR examines the risk level of each node against interference regions and selects the most reliable path for data delivery using a Markov predictor. Through simulation, we verify that the proposed scheme can avoid route destruction preemptively and achieve reliable data delivery.

• ETRI Journal
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• v.31 no.6
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• pp.709-716
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• 2009

In this paper, we propose a novel reconfigurable processor using dynamically partitioned single-instruction multiple-data (DP-SIMD) which is able to process multimedia data. The SIMD processor and parallel SIMD (P-SIMD) processor, which is composed of a number of SIMD processors, are usually used these days. But these processors are inefficient because all processing units (PUs) should process the same operations all the time. Moreover, the PUs can process different operations only when every SIMD group operation is predefined. We propose a processor control method which can partition parallel processors into multiple SIMD-based processors dynamically to enhance efficiency. For performance evaluation of the proposed method, we carried out the inverse transform, inverse quantization, and motion compensation operations of H.264 using processors based on SIMD, P-SIMD, and DP-SIMD. Experimental results show that the DP-SIMD control method is more efficient than SIMD and P-SIMD control methods by about 15% and 14%, respectively.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.1-10
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• 2018

In cognitive radio (CR), secondary users (SUs) are able to sense the absence of primary users (PUs) in the spectrum. Then, SUs use this information to opportunistically access the licensed spectrum in the PUs' absence. In this paper, we present an implementation of real-time video transmission with spectrum-sensing between two points using GNU Radio and a National Instruments 2900 Universal Software Radio Peripheral (USRP). In our project, spectrum-sensing is implemented at both transmitter and receiver. The transmitter senses the channel, and if the channel is free, a video signal (which could be a real-time signal from a video file) will be modulated and processed by GNU Radio and transmitted using a USRP. A USRP receiver also senses the channel, but in contrast, if the channel is busy, the signal is demodulated to reproduce the transmitted video signal. This project brings in several challenges, like spectrum-sensing in the devices' environment, and packets getting lost or corrupted over the air.

• Journal of KIISE
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• v.43 no.12
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• pp.1412-1419
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• 2016

In cognitive radio sensor networks (CRSNs), secondary users (SUs) can occupy licensed bands opportunistically without causing interferences to primary users (PUs). SUs perform spectrum sensing to detect the presence of PUs. Sensing time is a critical parameter for spectrum sensing that can yield a tradeoff between sensing performance and secondary throughput. In this study, we investigate new approaches for spectrum sensing by exploring the tradeoff from a) spectrum sensing for PU detection (SSPD) and b) spectrum sensing for secondary throughput (SSST). In the proposed scheme, the first sensing result of the current frame determines the dynamic performance of the second spectrum sensing. Energy constraint in CRSNs leads to maximized network energy efficiency via optimization of sensing time. Simulation results show that the proposed scheme of SSPD and SSST improves network performance in terms of energy efficiency and secondary throughput, respectively.

• International journal of advanced smart convergence
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• v.7 no.3
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• pp.23-36
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• 2018

In wireless communication, efficient spectrum usage is an issue that has been an attractive research area for many technologies. Recently new technologies innovations allow compact radios to transmit with power efficient communication over very long distances. For example, Low-Power Wide Area Networks (LPWANs) are an attractive emerging platform to connect the Internet-of-Things (IoT). Especially, LoRa is one of LPWAN technologies and considered as an infrastructure solution for IoT. End-devices use LoRa protocol across a single wireless hop to communicate to gateway(s) connected to the internet which acts as a bridge and relays message between these LoRa end-devices to a central network server. The use of the (ISM) spectrum sharing for such long-range networking motivates us to implement spectrum sensing testbed for cognitive radio network based on LoRa and GNU radio. In cognitive radio (CR), secondary users (SUs) are able to sense and use this information to opportunistically access the licensed spectrum band in absence of the primary users (PUs). In general, PUs have not been very receptive of the idea of opportunistic spectrum sharing. That is, CR will harmfully interfere with operations of PUs. Subsequently, there is a need for experimenting with different techniques in a real system. In this paper, we implemented spectrum sensing for cognitive radio networks based on LoRa and GNU Radio, and further analyzed corresponding performances of the implemented systems. The implementation is done using Microchip LoRa evolution kits, USRPs, and GNU radio.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.1
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• pp.47-55
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• 1994

Post operative maxillary cyst may arise after the surgical treatment for maxillary sinusitis with the symtoms of swelling, pain, and pus discharge in the buccal region. It is examined by Waters' view, panoramic view and other intraoral radiographs, but quite variable radiologically. Most of the cyst is seen round or ovoid shape radiolucency, destruction, expansion and thinning of the lateral wall or posterior wall, and roots of the adjacent teeth may be resorbed. We studied about 117 cases of the post operative maxillary cysts which diagnosed in department of oral and maxillofacial radiology, Seoul National University Hospital. We analyzed and obtained following results. 1. These cysts occured more frequently in male than in female and the incidence is highest in the 4th and 5th decade. 2. Initial radical operation of maxillary sinus were performed mainly between the age of 10 and 45 years, and about 60% of the patients were 15 to 25 years. 3. Pain and swelling on buccal area, pus discharge, and toothache are most chief compaints, seven cases were found at routine examination without symtoms. 4. Most of these cysts were unilocular with smooth and well-defined border. 5. The majority of the cysts occurred in the anterolateral wall of maxillary sinus. 6. Dental changes of the lesional area were loss of lamina dura and root resorption, but about 55% were not changed.

• Journal of Gastric Cancer
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• v.16 no.3
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• pp.195-199
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• 2016

Phlegmonous gastritis is a rare and rapidly progressive bacterial infection of the stomach wall, with a high mortality rate. Antibiotics with or without surgical treatment are required for treatment. We present a case in which phlegmonous gastritis occurred during the diagnostic evaluation of early gastric cancer. The patient showed improvement after antibiotic treatment, but attempted endoscopic submucosal dissection failed because of submucosal pus. We immediately applied argon plasma coagulation since surgical resection was also considered a high-risk procedure because of the submucosal pus and multiple comorbidities. However, there was local recurrence two years later, and the patient underwent subtotal gastrectomy with lymph node dissection. Considering the risk of incomplete treatment immediately after recovery from phlegmonous gastritis and that recurrent disease can be more difficult to manage, delaying treatment and evaluation until after complete recovery of PG might be a better option in this particular clinical situation.

• Journal of Chest Surgery
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• v.23 no.4
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• pp.750-757
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• 1990

Empyema with bronchopleural fistula is an uncommon, but serious problem. Early diagnosis and adequate drainage of the empyema cavity are well established principles for the initial management of this condition and will enable patient to recover from the toxic effects of loculated pus. 37 patients of empyema with bronchopleural fistula were treated at the department of the chonbuk National University Hospital between 1981 and 1988. The age group of fifty and sixty decades occupied 64.8%. Bacteriologic cultures of the pus were postive in 56.8%. The most common organism of the culture was staphylococci(42.9%). And the others were Pseudomonas(19%). Klebsiella(14.3%), and E. doli. No growth of pathologic organism was reported 43.2%. 24 patients of empyema with bronchopleural fistula were nonoperative causes : There were 10 pulmonary tuberculosis, 3 abscess, 9 ascending infection, one bronchiectasis and one tumor, respectively. The remaining 13 were occurred as postoperative complications ; pneumonectomy in 6, lobectomy in 4, decortication in 2, and lobectomy with segmentectomy in 1. When used as the initial mode of drainage, closed thoracostomy was performed to almost all of the patients, but 4 patients were died during this treatment. Main operations were performed except 4 died patients ; open thoracostomy in 21, open thoracostomy with myoplasty in 3, decortication in 5, decortication with resection in 3, and completion pneumonectomy in 1. Open thoracostomy was performed in 21 patients which results were favorable except one death. Permanent open thoracostomy is an old but still useful minor operation in patients with empyema with bronchopleural fistula. The overall mortality rate was 15% (6 patients) and the causes of the death were respiratory insufficiency or sepsis, or both.

• Korean Journal of Veterinary Service
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• v.35 no.1
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• pp.63-67
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• 2012

An 8-months-old young Maltese bitch was presented for investigation of anorexia and occasional vomiting. The body weight was 2 kg. Abdominal sonography demonstrated abnormal enlargement of uterus. The dog had been clinically and pathologically examined. Also, ovariohystectomy was performed. Staphylococcus aureus was identified in the pus-like materials of the uterine lumen. This case was confirmed as pyometra induced by Staphylococcus aureus. Gross examination of the dissected uterus revealed enlarged uterine horn, which had yellowish or brownish pus-like materials in the lumen. Also, there was several segments formation between the enlarged areas of left and right uterine horns. Histopathologically, endometritis and necrosis were present in uterine wall. The bitch made a complete recovery following an ovariohystectomy. This case was spontaneous pyometra induced by Staphylococcus species. On our knowledge, this is a very rare report of pyometra occurrence in young dog and Staphylococcus species-induced pyometra. This study may provide a valuable data on the study of canine pyometra.