• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.196-213
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• 2001

A split beam ultrasonic transducer operating at a frequency of 70 kHz to use in the fish sizing echo sounder was developed and the acoustic radiation characteristics were experimentally analyzed. The amplitude shading method utilizing the properties of the Chebyshev polynomials was used to obtain side lobe levels below -20 dB and to optimize the relationship between main beam width and side lobe level of the transducer, and the amplitude shading coefficient to each of the elements was achieved by changing the amplitude contribution of elements with 4 weighting transformers embodied in the planar array transducer assembly. The planar array split beam transducer assembly was composed of 36 piezoelectric ceramics (NEPEC N-21, Tokin) of rod type of 10 mm in diameter and 18.7 mm in length of 70 kHz arranged in the rectangular configuration, and the 4 electrical inputs were supplied to the beamformer. A series of impedance measurements were conducted to check the uniformity of the individual quadrants, and also in the configurations of reception and transmission, resonant frequency, and the transmitting and receiving characteristics were measured in the water tank and analyzed, respectively. The results obtained are summarized as follows : 1. Average resonant and antiresonant frequencies of electrical impedance for four quadrants of the split beam transducer in water were 69.8 kHz and 83.0 kHz, respectively. Average electrical impedance for each individual transducer quadrant was 49.2$\Omega$ at resonant frequency and 704.7$\Omega$ at antiresonant frequency. 2. The resonance peak in the transmitting voltage response (TVR) for four quadrants of the split beam transducer was observed all at 70.0 kHz and the value of TVR was all about 165.5 dB re 1 $\mu$Pa/V at 1 m at 70.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The resonance peak in the receiving sensitivity (SRT) for four combined quadrants (quad LU+LL, quad RU+RL, quad LU+RU, quad LL+RL) of the split beam transducer was observed all at 75.0 kHz and the value of SRT was all about -177.7 dB re 1 V/$\mu$Pa at 75.0 kHz with bandwidth of 10.0 kHz between -3 dB down points. The sum beam transmitting voltage response and receiving senstivity was 175.0 dB re 1$\mu$Pa/V at 1 m at 75.0 kHz with bandwidth of 10.0 kHz, respectively. 3. The sum beam of split beam transducer was approximately circular with a half beam angle of $9.0^\circ$ at -3 dB points all in both axis of the horizontal plane and the vertical plane. The first measured side lobe levels for the sum beam of split beam transducer were -19.7 dB at $22^\circ$ and -19.4 dB at $-26^\circ$ in the horizontal plane, respectively and -20.1 dB at $22^\circ$ and -22.0 dB at $-26^\circ$ in the vertical plane, respectively. 4. The developed split beam transducer was tested to estimate the angular position of the target in the beam through split beam phase measurements, and the beam pattern loss for target strength corrections was measured and analyzed.

• Tuberculosis and Respiratory Diseases
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• v.61 no.3
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• pp.273-278
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• 2006

Endobronchial leiomyoma is a rare tumor that accounts for less than 2% of pulmonary benign tumors. A 32 year-old woman was admitted with fever, cough and sputum for a month. She had suffered from intermittent cough over three years. The chest X-ray and chest CT(computed tomography) showed a nodular lesion obstructing the proximal portion of the left lower lobar bronchus and atelectasis of the left lower lobe. Flexible Bronchoscopy detected a mass obstructing the distal portion of the left main bronchus and endobronchial biopsy showed benign smooth muscle cells. There was no abnormal finding in the uterine examination. Therefore this case was diagnosed as primary endobronchial leiomyoma. The lobectomy was performed due to intractable pneumonia and secondary parenchymal destruction. Postoperative course was uneventful and she was discharged in good health.

• The Journal of Internal Korean Medicine
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• v.26 no.4
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• pp.806-819
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• 2005

Objective : The purpose of this study is to investigate clinical characteristics and remedial value oriental medical therapy for sufferers of severe headache. Methods : On the authority of DongEuiBoCam, patients were classified into three groups: migraine, qi-syncope headache and phlegm-headache. All patients wert treated with acupuncture therapy and herb medicines. After that inquiry was made into the extent of improvement of headache. Results : 1. In accordance with the statistics, 56 cases(50.5%) had phlegm-syncope headache, 28 cases(25.2%) had qi-syncope headache and 27 cases(24.3%) had migraine. 2. The ratio between males and females was about 1:4. Most patients were in their forties. 3. 12 cases(31.6%) with migraine had pain only on the right side of the head, 20 cases(26.3%) with phlegm-syncope and 17 cases(45.6%) with qi-syncope headache suffered from the frontal lobe headache. 4. 8 cases(29.6%) with migraine had been suffering for a week or less, 12 cases(21.4%) with phlegm-syncope headache had been suffering for over six months and under one year and 6 cases(21.4%) with qi-syncupe headache had suffered over one year and under five. 5. Overwork and stress was deemed the main cause of migraine. Phlegm-syncope headache was also attributed to stress and tense situations. Qi-syncope headache was believed to be variously caused by traffic accident, noise, blood pressure and other reasons. 6. 46 cases(30%) felt dull headache and 32 cases(20.9%) felt dizzy. The common associated symptoms of migraine and qi-syncope headache included back, neck and shoulder pain and other pains. Dizziness was an especially prevalent symptom of phlegm-syncope headache. 7. After the oriental medical therapy, 12 cases(10.8%) almost entirely recovered, 50 cases(45%) were in about half as much pain, 45 cases(40.5%) improved little and 4 cases(3.6%) felt no improvement. Conclusions : The results support a role for oriental medical therapy in treatment of headache.

• Journal of Chest Surgery
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• v.25 no.3
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• pp.258-270
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• 1992

Benign lung tumors have been considered as relatively rare disease, which comprise approximately 8 to 15% of all solitary pulmonary lesions that are detected radiographically. We clinically analized 30 cases of benign lung tumors underwent the operation from Jan. 1970 to Aug.1991 in the department of thoracic and cardiovascular surgery, Catholic University Medical College. We adopted the classification presented by the World Health Organization[WHO], modified from Liebow, and added benign mesothelioma. There were 11 males & 19 females ranging in age from 2 years to 68 years old % the mean age was 38 years old. Of all 30 benign lung tumors, hamartomas [14 cases, 49%] were the most common & followed by hemangiomas [9 cases, 30%], 3 cases of benign mesotheliomas % a case of teratoma, papilloma, arteriovenous malformation and inflammatory pseudotumor. 14 cases of tumors were asymptomatic & were incidentally detected by plane chest x-ray In other cases, chief complaints at admission were coughing, chest discomfort, dyspnea, hemoptysis, and fever. Diagnosis were made by pathological examination; exploratory thoracotomy in 23 patients[76.7%], bronchoscopy in 4 patients and percutaneous needle aspiration biopsy in 3 patients. Precisely, preoperative diagnosis for confirmation of benign lung tumor was made only in 7 cases[23.6%]. Tumors were located on Rt.side[24 cases], especially Rt. middle lobe, and Lt.side[6 cases]. Operation methods were as follows: 21 cases [70%] of lobectomy, 2 cases of segmentectomy, 2 cases of wedge resection, 1 case of pneumonectomy, 1 case of bronchotomy, 2 cases of wedge resection, 1 case of pneumonectomy, 1 case of bronchotomy removal of the endobronchial hamartoma which located at the rt. main stem bronchus and 3 cases of complete resection in benign mesotheliomas. There were no operative death. The post operative complications were developed in 3 cases; post pneumonectomy empyema, wound infection and atelectasis. In conclusion, benign lung tumors must be histologically diagnosed to confirm of benignity and to provide limited resection for preservation of the lung tissue, whenever possible.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.7-16
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• 2015

The transmitter of quadrature multiplexed GMSK (QM-GMSK) is composed of two quadrature multiplexed GMSK modulators. QM-GMSK has a slightly increased spectrum main lobe compared with $Q^2PSK$ or QMSK, but it has highly suppressed side lobes. As a result, practical spectrum efficiency of QM-GMSK is achieved. By replacing the baseband elementary pulses of QM-GMSK with their approximate, the squared sinusoid of half-period, offset-$Q^2PSK$($OQ^2PSK$) is obtained. The $OQ^2PSK$ signal has similar spectral properties to QM-GMSK. The transmitter of $OQ^2PSK$ can be simply implemented without the Gaussian lowpass filter, which is required in QM-GMSK transmitter. In this paper, we propose an overlapped pulse shaping in $OQ^2PSK$ with RC(raised-cosine) or SRC(squared raised-cosine) pulses of length longer than the symbol period. Power spectrum of the proposed modulation scheme exhibits further suppressed side lobes, hence enhanced spectrum efficiency is obtained. Simulation results indicate that BER performance of the proposed scheme is comparable to that of $OQ^2PSK$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.337-346
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• 2014

This study aimed to understand the mode characteristics of a droplet subject to periodic forced vibration and the detachment of a droplet placed on a plate surface. An surface was coated with Teflon to clearly observe the behavior of a droplet. The contact angle between the droplet and surface and the hysteresis were found to be approximately $115^{\circ}C$ and within $25^{\circ}C$, respectively. The coating process was performed in a clean room that had an environment with a low level of contaminants and impurities such as air dust, detergents, and particles. To predict the resonance frequency of a droplet, theoretical and experimental approaches were applied. Two high-speed cameras were configured to acquire side and top views and thus capture different characteristics of a droplet: the mode shape, the detachment, the separated secondary droplet, and the waggling motion. A comparison of the theoretical and experimental results shows no more than 18 discrepancies when predicting the resonance frequency. These differences seem to be caused by contact line friction, nonlinear wall adhesion, and the uncertainty of the experiment. For lower energy inputs, the contact line of the droplet was pinned and the oscillation pattern was axisymmetric. However, the contact line of the droplet was de-pinned as the oscillation became more vigorous with increased energy input. The size of each lobe at the resonance frequency is somewhat larger than that at the neighboring frequency. A droplet in mode 2, one of the primary mode frequencies, exhibits vertical periodic movement as well as detachment and secondary ejection from the main droplet.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.227-237
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• 2014

Throughput scaling laws for two coexisting ad hoc networks with m primary users (PUs) and n secondary users (SUs) randomly distributed in an unit area have been widely studied. Early work showed that the secondary network performs as well as stand-alone networks, namely, the per-node throughput of the secondary networks is ${\Theta}(1/\sqrt{n{\log}n})$. In this paper, we show that by exploiting directional spectrum opportunities in secondary network, the throughput of secondary network can be improved. If the beamwidth of secondary transmitter (TX)'s main lobe is ${\delta}=o(1/{\log}n)$, SUs can achieve a per-node throughput of ${\Theta}(1/\sqrt{n{\log}n})$ for directional transmission and omni reception (DTOR), which is ${\Theta}({\log}n)$ times higher than the throughput with-out directional transmission. On the contrary, if ${\delta}={\omega}(1/{\log}n)$, the throughput gain of SUs is $2{\pi}/{\delta}$ for DTOR compared with the throughput without directional antennas. Similarly, we have derived the throughput for other cases of directional transmission. The connectivity is another critical metric to evaluate the performance of random ad hoc networks. The relation between the number of SUs n and the number of PUs m is assumed to be $n=m^{\beta}$. We show that with the HDP-VDP routing scheme, which is widely employed in the analysis of throughput scaling laws of ad hoc networks, the connectivity of a single SU can be guaranteed when ${\beta}$ > 1, and the connectivity of a single secondary path can be guaranteed when ${\beta}$ > 2. While circumventing routing can improve the connectivity of cognitive radio ad hoc network, we verify that the connectivity of a single SU as well as a single secondary path can be guaranteed when ${\beta}$ > 1. Thus, to achieve the connectivity of secondary networks, the density of SUs should be (asymptotically) bigger than that of PUs.

• Journal of Chest Surgery
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• v.35 no.3
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• pp.231-234
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• 2002

Moyamoya disease is an unusual cerebrovascular disorder characterized by occlusive intimal dysplasia of the distal internal carotid and proximal cerebral arteries as well as other collateral arteries. However, moyamoya diseases are recently being reported as a systemic process. We experienced one case of coronary artery occlusive disease affected by moyamoya disease. The patient was a 35-year-old female, experiencing intermittent NYHA class ll dyspnea and exertional chest pain for 6 months and right paresthesia for 1 month before admission. Cerebral artery angiogram showed abnormal cerebrovascular systems and confirmed moyamoya disease with cerebral infarction of the left frontal lobe. In coronary artery angiogram, left coronary artery was not visualized due to total occlusion of the left main ostium and left coronary blood flow was supplied from normal right coronary artery. CABG was performed with OPCAB. Both internal mammary arteries were used for LAD and LCx. Intraoperative coronary artery findings showed intimal hyperplasia and no definite thrombi, and nondiseased coronary arteries were good and patent. We concluded that this patient's coronary artery disease was affected by moyamoya disease, and moyamoya disease should be evaluated in the extracerebral cardiovascular system.

• Tuberculosis and Respiratory Diseases
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• v.72 no.1
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• pp.68-71
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• 2012

Untreated massive hemoptysis, especially in patients with tuberculous-destroyed lung, is a serious complication resulting in considerable morbidity and mortality. We report a case of a patient who had active tuberculosis and a destroyed left lung with massive bleeding. He was transferred to our clinic with intubation of a right-sided Robertshaw double lumen tube and right upper lobe collapse likely due to tube malposition that was presented on chest X-ray. Because hemoptysis had persisted after bronchial arterial embolizaton, we replaced the double lumen tube with a conventional endotracheal tube and inserted an endobronchial blocker into the left main bronchus through an endotracheal tube guided by bronchoscopy to prevent aspiration of blood into the right lung. Left pneumonectomy was performed and hemotpysis was ceased. We suggest that the use of an endobronchial blocker followed by surgery may be a safe and effective modality of treatment in patients with persistent bleeding after bronchial arterial embolization.

• The Journal of the Acoustical Society of Korea
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• v.43 no.3
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• pp.361-367
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• 2024

Ultrasound in the air is widely used in industry as a measurement technique to prevent abnormalities in the machinery. Recently, the use of airborne ultrasound imaging techniques, which can find the location of abnormalities using an array transducers, is increasing. A beamforming method that uses the phase difference for each sensor is used to visualize the location of the ultrasonic sound source. We exploit a random sparse ultrasonic array and obtain beamforming power distribution on the source in a certain distance away from the array. Conventional beamforming methods inevitably have limited spatial resolution depending on the number of sensors used and the aperture size. A high-resolution ultrasound imaging technique was implemented by applying functional beamforming as a method to overcome the geometric constraints of the array. The functional beamforming method can be expressed as a generalized beam forming method mathematically, and has the advantage of being able to obtain high-resolution imaging by reducing main-lobe width and side lobes. As a result of observation through computer simulation, it was verified that the resolution of the ultrasonic source in the air was successfully increased by functional beamforming using the ultrasonic sparse array.