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초음파 위상 어레이를 이용한 가상 음원 합성 구경 기법의 해석
윤창한 서강대학교 일반대학원 2009 국내석사
합성구경 기법은 양방향 집속을 가능하게 하여 우수한 측방향 해상도를 제공하지만 낮은 프레임율(frame rate)과 낮은 신호 대 잡음비(SNR)을 갖는 단점이 있다. 이를 개선하기 위한 방법으로 가상 음원(virtual source)을 이용한 합성구경 기법(synthetic aperture technique)이 제안되었다. 가상 음원을 이용한 합성구경 기법은 일반적인 수신 동적집속과 같은 프레임율을 가지면서 양방향 집속이 가능하며 높은 SNR을 얻을 수 있다. 본 논문에서는 가상 음원을 이용한 합성구경 기법을 빔의 편향(steering)이 고려된 섹터 주사로 확장하여 해석하였다. 이를 위해 가상 음원을 이용한 합성구경 기법에 대한 송수신 모형을 제시하고 수학적 해석을 통해 최적화된 가상 음원의 위치와 위상 어레이를 이용한 가상 음원 합성구경기법의 빔 패턴 식을 유도하였다. 일반적으로 선형 주사에서는 빔 패턴의 향상을 위해 합성할 수 있는 주사선의 개수가 많아지도록 송신 초점을 변환자와 가까이 위치시켜야 한다. 하지만 섹터 주사의 경우에 가상 음원이 변환자로부터 멀리 위치하거나 합성하는 인접 주사선의 개수가 늘어날수록 빔 패턴이 좋아지는 것을 수식을 통해 확인하였다. 해석된 결과는 컴퓨터 모사실험과 실제 RF 데이터를 사용하여 검증하였다. 그 결과 모든 영상점에서 해상도가 개선됨을 확인할 수 있었다. 또한 가상 음원이 변환자로 멀어지거나 합성하는 주사선의 수가 늘어날수록 빔 패턴이 향상되는 것을 확인하였다.
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Today, the national development has been pursued by means of speeding up the economic growth, and the bureaucratic role has been thought as being important for the development. It seems that the bureaucratic ethics should be considered as essential and powerful effect on the bureaucratic behaviors and on the process of the development. In this situation one of the most impeding factors to our sincere target is the bureaucratic corruption. In general, it is common that the bureaucratic corruption is widely spread in underdeveloped countries. The effects of corruption include: wasting the national resources, weakening the smooth function of government,-disobedience of law and order, and undermining the security of the present government. The corruption might have indirectly contributed to the economic growth, however, its dysfunction is greatly harmful to the national development. Korean government has made considerable efforts for the establishment of bureaucratic ethics and the control of bureaucratic corruption. However, the results have not been satisfactory. The purpose of this study is to analyze the behaviors of corruption and to suggest the methods of improving the control of corruption. The present study is composed of six chapters: In chapter 1, the purpose, scope and method of the study are explained. In chapter 2, theoretical background of corruption as concepts, types, effects are enumerated. In chapter 3, a management of corruption control and its problems in Korean history are argued. In chapter 4, the behavior of bureaucratic corruption in historical, personal, administrative-cultural, economic, politico-administrative aspect are analyzed. In chapter 5, through the result of the behavioral analysis, the improvement for the control of corruption are suggested. Finally in chapter 6, conclusion of the study are made.
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Beamforming methods for enhancing photoacoustic image quality : breast cancer study
윤창한 서강대학교 일반대학원 2013 국내박사
Photoacoustic (PA) imaging based on PA effect is a hybrid functional imaging modality that combines strong optical contrast with high ultrasonic spatial resolution. It showed great potentials in diagnosis of cancer due to its high extrinsic optical contrast such as hemoglobin and melanin. In PA imaging, non-ionizing laser energy is delivered in biological tissue and acoustic waves (i.e., PA signals) are generated only inside a target that absorbs the incident laser pulses due to thermo-elastic expansion. The PA signals are detected by an ultrasound (US) transducer and then an image of initial pressure distribution is reconstructed. Among various PA imaging system configurations, the cross-sectional PA imaging can provide real-time imaging and be used in clinical applications with minimal modification of a current ultrasound (US) scanner. However, a suitable image reconstruction method for the cross-sectional PA imaging was not investigated and a reconstruction method used in US imaging was employed. Thus, to fully take advantages of PA imaging and widely accepted in clinical practice, an adequate reconstruction method for the cross-sectional PA imaging should be explored In this thesis, we have developed new beamforming methods for enhancing image quality of PA imaging based on a commercial one-dimensional (1D) array transducer. First, for precise calculation of time-of-flight, a method for estimating optimal sound speed was developed. Since the method could minimizes the phase distortion stemming from disparity between a true sound speed and assumed one in beamformation, the best beamforming performance was achieved, leading to improvement of the lateral resolution and signal-to-noise ratio (SNR). In addition, adequate image reconstruction method for PA imaging, i.e., display pixel based focusing (DPBF), was proposed with viable computational complexity. The method was further extended to three-dimensional (3D) imaging, i.e., display voxel based focusing (DVBF). In the method, poor elevational resolution poor elevation resolution due to the fixed focusing by an acoustic lens was retrieved by using synthetic aperture technique. For this, mathematical analysis was performed and appropriate synthetic focusing delay was proposed. The developed methods were evaluated through simulation, in vitro, and ex vivo experiments with microcalcification contained breast specimens. From the results, it was learned that the proposed method can enhance the image quality of PA imaging based on a 1D array transducer and may useful for the clinical use.
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근관와동 가봉재는 근관치료중 근관이 이물질에 오염되는 것을 방지하기 위하여 근관와동을 폐쇄시키는데 사용되며, 특히 가봉재의 변연폐쇄성은 근관치료의 성패에 지대한 영향을 미친다. 본 연구는 근관와동 가봉재의 변연폐쇄성을 평가하기 위하여 임상에서 많이 사용되고 있는 Caviton^�(G-C International Corp., Japan), IRM^�(The L.D. Caulk Co., U.S.A), 산화아연-유지놀 시멘트에 대한 변연누출과 가봉재의 변연폐쇄성에 영향을 주는 수분 흡수율을 측정 비교하였다. 변연누출은 각 치아의 교합면에 표준 근관와동을 형성한 후 3종의 근관와동 가봉재로 충전한 다음 9V의 정전압을 가하고 각각 2주 동안 전기화학적 방법으로 측정하여 변연누출량을 관찰하였고, 또한 각 근관와동 가봉재의 수분 흡수율을 측정하여 근관와동 가봉재의 변연폐쇄성을 비교 분석한 바 다음과 같은 결과를 얻었다. 1. 변연누출은 6일 후부터 Caviton^� 충전군이 산화아연-유지놀 시멘트나 IRM^� 충전군보다 낮았으며, 6일부터 12일까지는 IRM^� 충전군이 산화아연-유지놀 시멘트 충전군보다 낮았으나 13일 후에는 유의한 차이가 없었다. 2. Caviton^�, IRM^�, 산화아연-유지놀 시멘트등 3종의 근관와동 가봉재는 시간의 경과에 따라 변연누출도 증가하였으며 가봉재로는 5일 이내에서 사용하는 것이 효과적이다. 3. 수분 흡수율은 Caviton^�, IRM^�, 산화아연-유지놀 시멘트 순으로 낮아 수분 흡수율과 가봉재의 변연누출은 밀접한 관계가 있는 것으로 나타났으며 수분 흡수율이 높은 가봉재의 변연누출이 낮았다. The roles of temporary sealing materials used in endodontics are important. Especially, its marginal sealing properties affect endodontic success and failure in endodontic tretment. The purpose of this in vitro study was to compare and evaluate the marginal sealing properties of various temporary restorative materials used in endodontic access cavity by using electrochemical method. Standard endodontic access cavities were prepared in extracted human molar teeth and filled with Caviton, IRM, zinc oxide-eugenol cement. Each specimen was immersed in 1% solution of KCl, and applied a potential of 9V external power supply. Margianl microleakage and water sorption were measured for marginal sealing effect evaluation in comparison with each group. A comparative study of the obtained results have led to the following conclusions. 1. The Caviton group showed lower marginal microleakage value than the zinc oxide-eugenol cement and IRM group the 6th day after. The IRM group showed lower marginal microleakage value than the zinc oxide-eugenol cement group from the 6th day to the 12th day. But there was no significant difference between zinc oxide-eugenol cement and IRM group after the 13th day. 2. As time went by, marginal microleakage value was increased in Caviton, IRM, and zinc oxide-eugenol cement. But, they had effective marginal sealing property within the 5th day. 3. The water sorption showed the highest value in Caviton and the lowest in zinc oxide-eugenol cement. There was evidence of correlation between the water sorption and marginal microleakage of temporary sealing material, and then, high water sorption was the cause of low marginal microleakage value in temporary sealing materials.
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This experiment was carried out in order to study the effect of seasonal changes, location differences and fertilizer application on the feed value of reed(Phragmites corrm- unis Trinius). The samples of the reed were taken at about 30-days intervals from May to October, 1982, on the open field of the reclaimed land, the river bank and the tideland in Chonnam area, and measured the yield, the feed compositions and in vitrodry-matter digestibility (IVD), The results are summarized as follows, 1. Plant height was rapidly heightened in May to June, and the number of leaves rapidly increased in May to August. Dry-matter yield increased in May to September and gradually decreased afterwards. 2. In general, the content of crude protein and the In vitro dry-matter digestibility decreased with ageing, and the content of fiber increased. 3. Considerable difference, by location in the chemical composition including SiO₂, Ca and P was observed. 4. There was a significant negative correlation(p<0.05) between the content of crude protein and that of crude fiber. There was a significant positive correlation(p<0.05) between the in vitro dry-matter digestibility(IVD) by two- stage method and the content of crude protein, and was a significant negative correlation(p<0,05) with the content of fiber. 5.Plant height, the content of crude protein and the in vitro dry-matter digestibility(IVD) were significantly increased, and significantly decreased by fertilizer application. 6.There was a significant negative correlation (P<0.05) between the in vitro dry-matter digestibility(IVD) of the fraction and growing period, plant height, the content of crude fiber and that of acid detergent fibers. and was a significant positive correlation (P<0.05) with the content of crude protein and that of crude fat. 7.In the one-stage in vitro dry-matter digestibility(IVD) using rumen liquor procedure of the whole sample, the variation of the IVD after 48 hr. and 72 hr. fermentation was found in some growing period.(P<0.05) 8. The rumen microbial nitrogen was increased as the in vitro dry-matter digestibility (IVD) increased.
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飼料作物內 窒酸鹽 축적과 窒酸鹽 섭취수준이 緬羊의 第1胃液 및 血液性狀에 미치는 影響
本 硏究는 飼料作物內 窒酸鹽 含量이 緬羊에 있어서 질산염 急性中毒의 强度에 미치는 영향을 관찰하기 위하여 窒素施肥水準(10, 20 및 40kgN/10a)을 달리하여 재배한 Italian ryegrass 및 靑刈 옥수수의 生育時期別 窒酸態 窒素 含量의 變化 정도를 測定하였으며, 緬羊 12頭를 供試하여 飼料作物을 급여한 후 緬羊의 血液中 methemoglobin(MHb), hemoglobin(Hb) 및 packed cell volume(PCV)을 측정하였다. 또한 窒酸鹽 投與水準에 따른 緬羊의 第1胃液 및 血液性狀의 변화를 관찰하기 위하여 NaNO₃를 頭當 體重 kg當 0.34g(低水準), 0.45g(中水準) 및 0.56g(高水準)으로 3처리 4반복으로 배치하고, NaNO₃를 30%(w/v) 수용액으로 하여 第1胃 內에 fistula를 통하여 1회 주입한 後, 第1胃液 및 血液의 몇가지 成分을 經時的으로 측정하였다. 한편 窒酸鹽 中毒으로 인한 病理組織學的 변화를 究明하기 위하여, 高水準 投與區에서 窒酸鹽 急性中毒을 일으켜 斃死한 緬羊의 斃死體를 病理解剖 및 組織學的으로 관찰하였다. 窒素施肥水準 및 生育時期別 Italian ryegrass와 靑刈 옥수수의 NO₃-N 含量은 窒素施肥水準에 따라 有意的으로 증가(p<0.05)했으며, 窒素多肥栽培에 의한 植物體內의 NO₃-N含量은 Italian ryegrass가 靑刈 옥수수보다 더 높은 경향이었다. 緬羊에 對한 窒酸鹽 給與 試驗에서는, 40kgN/10a를 施用하여 栽培한 Italian ryegrass를 섭취한 緬羊의 血液中 MHb濃度는 他區(10kgN 및 20kgN/10a)에 비해 有意的으로 높아서 (p<0.05) 窒酸鹽 中毒의 發生 가능성이 충분히 엿보였고, 靑刈 옥수수를 섭취한 緬羊의 血液中 MHb濃度의 최고치는 매우 낮아서 총 Hb의 7%이하로 處理水準間에 統計的 有意性은 없었다. 窒酸鹽 投與 試驗에서 緬羊의 第1胃 內에 窒酸鹽 投與에 따른 第1胃液 內 亞窒酸鹽 濃度 및 血液中 MHb濃度는 高水準區에서 가장 높아서 그 최고치는 각각 6.9mg/100ml, 47%로 나타났고, 第1胃 內 pH는 약 5.8∼7.0범위로 處理水準間에 큰 차이는 나타나지 않고 飼料攝取에 따른 畵間的 變化樣相을 보였다. 血液中 Hb 含量 및 PCV는 高水準區에서 약간 增加하는 경향이었으나 有意差는 없었고, NaNO₃ 投與水準(低, 中, 高水準)에 따른 MHb 最高濃度는 각각 19.2, 22.0 및 47.0%에 달했으며 血漿內 NO₂-N 및 血液中 MHb濃度는 個體間에 큰 차이 가 있었다. 0.56g NaNO₃/kgBW 投與區(高水準)에서 供試畜의 25%인 3頭가 斃死하였는데, 이 때 總Hb에 對한 MHb濃度는 각각 67.0, 80.8 및 87.8%에 달했고, 血液凝固時間은 MHb濃度가 높아짐에 따라 有意的으로 단축되었으며(p<0.05), 血漿內 Na^+ 및 K^+의 平均濃度는 窒酸鹽 投與水準間에 두드러진 차이가 나타나지 않았다. 斃死한 緬羊의 病理解剖 및 組織學的 檢査결과 臨床的으로 急性中毒症에 있어서는 可視粘膜의 cyanosis, 頻尿, 호흡곤란, 血液의 심한 암적색으로의 변화 및 全身臟器의 충혈 등 循環障碍의 소견이 인정되었고, 病理組織學的으로는 肝小葉 中心性 壞死 및 腎臟細尿管上皮의 壞死가 인정되었다. Four experiments were conducted to investigate the influence of the level of nitrate as well as the effect of roughage intake on the nitrate metabolism including methemoglobin formation in blood. In experiment I, Italian ryegrass and forage corn were applied with three different levels of nitrogen fertilization (10, 20 and 40kg N/l0a). Significant difference was observed in N0₃-N concentration in Italian ryegrass nitrogen fertilized (p<0.05). In experiment II, 12 Corriedale wethers were fed Italian ryegrass and forage corn applied with three different levels of nitrogen fertilization (10, 20, 40kgN/l0a). The results obtained were summarized as follows; 1. A significant difference was observed in the changing pattern of methemoglobin formation in blood of sheep fed Italian ryegrass(p<0.05). 2. No significant difference was observed in the changing pattern of methemoglobin formation in blood of sheep fed forage corn(p<0. 05). In experiment III, 12 Corriedale wethers(average body wt. 33kg) fed on concentrates and Italian ryegrass hay were administered intraruminally three different levels of sodium nitrate (0.34g, 0.45g and 0.56g per kg body weight) as 30% (w/v) aqueous solution via ruminal fistula. Rumen fluid and blood samples were taken at 1, 2 or 3hour intervals, and then time courses of ruminal pH, nitrate and nitrite concentrations in the rumen fluid and packed cell volume(PCV), hemoglobin(Hb) and methemoglobin(MHb) content in blood were det ermined. The results obtained were summarized as follows; 1. The concentration of nitrite in rumen fluid after administration of sodium nitrate was highest in the group fed 0.56g sodium nitrate, showing the highest methemoglobin formation in blood. 2. No significant difference was observed in the changing pattern of ruminal pH by the different levels of sodium nitrate application. 3. The concentration of hemoglobin and PCV in blood were increased when 0.56g sodium nitrate per kg body weight was given. 4. Sodium nitrate(0.34g, 0.45g and 0.56g per kg body weight) administered into the rumen resulted in methemoglobin formation corresponding to 19.2%, 22.0% and 47.0% conversion of the total hemoglobin. 5. There were large variations among the test animals in the capacity of methemoglobin formation and NO₂-N concentration in blood plasma after sodium nitrate administration. 6. Three wethers died when administered 0.56g sodium nitrate per kg body weight, and maximum methemoglobin concentrations recorded at the point of death were 67.0%, 80.8% and 87.8%, respectively. 7. Significant differences were observed in coagulation time with the formation of methemoglobin in blood(b<0.05). 8. Na^+ and K^+ concentrations in blood plasma affected by sodium nitrate adminstration were statistically not significant. In experiment IV, in order to clarify the histopathological changes resulting from nitrate poisoning sheep were experimentally poisoned by the ruminal administration of 0.56g sodium nitrate per kg body weight. Microscopic findings in lung, heart, liver and kidney were studied. The results obtained were summarized as follows; 1. Main findings observed from the acute cases which died after the administration were severe cyanosis of visible mucosa, frequent urination, and dyspnea. 2. Main gross appearances observed in acute cases were dark red discoloration of blood, syanosis of mucosa, and hyperemia of internal organs. 3. Main microscopic appearances observed in acute cases were hemorrhage and congestion of various organs, centrilobular necrosis of hepatic parenchyma, and necrosis of renal convoluted tubules.
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