• Structural Engineering and Mechanics
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• 제88권4호
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• pp.389-403
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• 2023

In order to explore the influence of tooth root cracks on the dynamic characteristics of multi-stage planetary gear transmission systems, a concentrated parameter method was used to construct a nonlinear dynamic model of the system with 30-DOF in bending and torsion, taking into account factors such as crack depth, length, angle, error, time-varying meshing stiffness (TVMS), and damping. In the model, the energy method was used to establish a TVMS model with cracks, and the influence of cracks on the TVMS of the system was studied. By using the Runge- Kutta method to calculate the differential equations of system dynamics, a series of system vibration diagrams containing cracks were obtained, and the influence of different crack parameters on the vibration of the system was analyzed. And vibration testing experiments were conducted on the system with planetary gear cracks. The results show that when the gear contains cracks, the TVMS of the system will decrease, and as the cracks intensify, the TVMS will decrease. When cracks appear on the II-stage planetary gear, the system will experience impact effects with intervals of rotation cycles of the II-stage planetary gear. There will be obvious sidebands near the meshing frequency doubling, and the vibration trajectory of the gear will also become disordered. These situations will become more and more obvious as the degree of cracks intensifies. Through experiments, the theoretical results are in good agreement with experimental results, verifying the correctness of the theoretical model. This provides a theoretical basis for fault diagnosis and reliability research of the system.

• 핵의학기술
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• 제18권2호
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• pp.8-16
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• 2014

간담도 스캔에서 GBEF의 산출은 정적영상법과 동적영상법으로 가능하다. 이번 연구를 통해 영상수집 방법에 따른 GBEF 차이를 알아보고, 정확한 GBEF를 산출하기 위한 방법을 강구하고자 한다. 본원의 환자 27명을 대상으로 하였으며, $^{99m}Tc$-mebrofenin을 정맥주사한 후 60분 동안은 정적영상법으로 영상을 수집하고 담낭이 잘 관찰되면 지방식(우유 $200m{\ell}$, 삶은 계란 1개)을 섭취하도록 하였다. 지방식 섭취 후 동적 영상법으로 60 sec/frame, 30분간 영상을 수집하고, 종료 후 60분 영상과 같은 조건으로 90분 영상을 수집하였다. 정적 GBEF는 지방식 전 후 정적 영상의 담낭계수를 이용하여 산출하고, 동적 GBEF는 시간-방사능곡선 상에 $T_{max}$와 $T_{min}$의 담낭계수를 이용하여 산출하였다. 또한 정적영상법의 지방식 전 영상과 동적영상법의 1분째 영상을 이용하여 지방식을 섭취하는 동안의 담즙배출량(초기담즙배출량)을 산출하였다. 결과는 $T_{max}$가 1분 이하인 경우는 20 case였으며, 정적영상법이 평균 $11.4{\pm}6.7%$ 높게 산출되었다(동적 : $40.1{\pm}21.7%$, 정적 : $51.5{\pm}23.6%$). $T_{max}$가 1분을 초과한 경우는 7 case였으며, 동적영상법이 평균 $-9.7{\pm}4.9%$ 높게 산출되었다(동적 : $31.0{\pm}19.7%$, 정적 : $21.3{\pm}19.4%$). 정확한 비교를 위해 영상법에 따른 담즙배출차이와 초기배출량을 지방식 전 담낭계수와의 비율로 부터 산출하였다. $T_{max}$가 1분 이하인 경우, 영상법간 차이는 평균 $16.7{\pm}13.6%$, 초기배출량은 평균 $12.7{\pm}13.8%$로, 오차범위 이내에서 일치하였다. 이는 영상법간 GBEF의 차이가 동적영상법이 시작되기 전에 이미 배출된 담즙때문이라는 것을 의미한다. $T_{max}$가 1분을 초과한 경우, 영상법간 차이는 평균 $-14.3{\pm}7.3%$, 초기배출량은 $-5.9{\pm}3.9%$로, 8.4% 차이가 났다. 이는 지방식 섭취를 시작한 시점부터 동적영상법을 시작한 후 일정 시점($T_{max}$)까지 계속 담즙이 집적되고 있음을 의미하며, 이 때문에 영상법간에 GBEF가 차이가 나는 것으로 판단된다. 정확히 30분 동안의 GBEF 산출하기 위해서, $T_{max}$가 9.5분 이상인 4 case를 추세 분석하여 GBEF를 산출한 결과, 평균 $57.2{\pm}20.4%$로, 정적영상법 (평균 $37.8{\pm}20.9%$) 보다는 20%정도, 동적영상법(평균 $42.0{\pm}16.2%$) 보다는 15% 정도 높게 산출되었다. 정적영상법은 비교적 간단하게 GBEF을 산출할 수 있으며, 환자의 움직임 등 여러 가지 오류로부터 영향을 적게 받는다는 장점이 있다. 반면에 $T_{max}$ 이전에 담낭자극을 시행한 경우이거나 환자의 상태에 따라서 담낭자극에 반응이 느린 경우엔 GBEF가 낮게 산출된다. 동적영상법은 담낭에서 담즙이 배출되는 양상을 분석할 수 있다는 장점이 있다. 배출이 지연되는 경우에도 T-A curve를 통해 $T_{max}$ 시점을 알 수 있기 때문에 정확한 GBEF를 산출할 수 있다. 하지만 지방식을 섭취한 후에 검사가 시작되기 때문에 지방식을 섭취하는 동안에 배출되는 답즙이 제외되어 GBEF가 낮게 산출된다. 연구 결과 간담도 스캔을 통해 정확한 GBEF를 산출하기 위해서는 우선적으로 동적영상법을 시행하여 T-A curve를 통해 담즙배출양상($T_{max}$의 시점)을 확인한 후에 두 영상법 중 적합한 GBEF를 선택하는 것이 바람직하다고 본다.

• 대한핵의학회지
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• 제30권1호
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• pp.35-46
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• 1996

Dopamine transporter concentrations have been known to decrease in Parkinson's disease (PD) or increase in Tourette's disorder. The purpose of this study was to evaluate the effectiveness of [I-123]N-(3-iodopropene-2-yl)-$2{\beta}$-carbomethoxy-$3{\beta}$-(4-chlorophenyl) tropane (IPT) as an imaging agent for measuring changes in transporter concentrations with PD. IPT labelled with 6.69+/-0.64 mCi(247.53+/-23.68 MBq) of I-123 was intravenously injected into ten patients(age: 55+/-11) with PD, and six normal controls(NC)(age: 46+/-14) as a bolus. Dynamic SPECT scans of the brain were then performed for 5 minutes each over 120 minutes on a triple headed camera. Time activity curves were generated for the left basal ganglia(LBG), right basal ganglia(RBC), and occipital cortex(OCC). The statistical parameters included the time to peak activity, the contrast ratio of LBG and RBG to OCC at several time points, and the accumulated specific binding counts/mCi/pixel(ASBC) from 0 to 115 minutes. The uptake of IPT in the brains of PD and NC peaked within 10 minutes of injection in all subjects. The maximum target to background ratio in the basal ganglia of PD and NC occurred at 85+/-20 min and 110+/-6 min of injection, respectively. The BG/OCC ratios at 115 minutes for PD and NC were 2.15+/-0.54 and 4.26+/-0.73, respectively. The ASBC at 115 minutes for PD and NC were 152.91+/-50.09 and 289.51+/-49.00, respectively. The ratio of BG/OCC for the NC was significantly higher than the ratio for PD. SPECT data matched with clinical diagnosis for PDs. The ratio between BG and OCC and the ASBC for PD were clearly separated from NC and may be useful outcome measures for clinical diagnosis. The findings suggest that IPT may be a very useful tracer for early diagnosis of PD and study of dopamine reuptake site.

• Investigative Magnetic Resonance Imaging
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• 제19권4호
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• pp.231-236
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• 2015

A 17-year-old girl presented with complaints of headache and decreasing vision of one month's duration, without any history of fever, weight loss, or any evidence of an immuno-compromised state. Her neurological examination was normal, except for papilledema. Laboratory investigations were within normal limits, except for a slightly increased Erythrocyte Sedimentation Rate (ESR). Non-contrast computerized tomography of her head revealed complex mass in left frontal lobe with a concentric, slightly hyperdense, thickened wall, and moderate perilesional edema with mass effect. Differential diagnoses considered in this case were pilocytic astrocytoma, metastasis and abscess. Magnetic resonance imaging (MRI) obtained in 3.0 Tesla (3.0T) scanner revealed a lobulated outline cystic mass in the left frontal lobe with two concentric layers of T2 hypointense wall, with T2 hyperintensity between the concentric ring. Moderate perilesional edema and mass effect were seen. Post gadolinium study showed a markedly enhancing irregular wall with some enhancing nodular solid component. No restricted diffusion was seen in this mass in diffusion weighted imaging (DWI). Magnetic resonance spectroscopy (MRS) showed increased lactate and lipid peaks in the central part of this mass, although some areas at the wall and perilesional T2 hyperintensity showed an increased choline peak without significant decrease in N-acetylaspartate (NAA) level. Arterial spin labelling (ASL) and dynamic susceptibility contrast (DSC) enhanced perfusion study showed decrease in relative cerebral blood volume at this region. These features in MRI were suggestive of brain abscess. The patient underwent craniotomy with excision of a grayish nodular lesion. Abundant acid fast bacilli (AFB) in acid fast staining, and epithelioid cell granulomas, caseation necrosis and Langhans giant cells in histopathology, were conclusive of tubercular abscess. Tubercular brain abscess is a rare manifestation that simulates malignancy and cause diagnostic dilemma. MRI along with MRS and magnetic resonance perfusion studies, are powerful tools to differentiate lesions in such equivocal cases.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 1999년도 추계학술대회-지능형 정보기술과 미래조직 Information Technology and Future Organization
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• pp.269-279
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• 1999

본 연구는 Web상에서 원격 협력 학습을 위한 수준별 학습자 모집 스케줄링 에이전트의 설계와 구현에 관해 제안한다. 본 시스템의 구조는 원격 교사 모듈과 여러 명의 학습자, 그리고 이를 연결해 주는 스케줄링 Agents, 학습자를 진단할 수 있는 진단 Agent로 구성된다. 컴퓨터가 분산환경으로 발전됨에 따라서 교육의 변화도 가속화되었고, 지식의 공유와 정보의 공유가 원격 협력학습에 의하여 절실히 필요하게 되었다. 원격 협력 학습에서의 학습자는 동일한 과목과 주제에 흥미를 느끼는 여러 명의 아동이 동시에 학습할 수 있는 상황이 필요하며, 선행 지식 또한 비슷한 수준이어야 동일한 주제로 학습의 효과가 있다. 이런 학습자를 판단하기 위해서 진단 Agent가 학습자를 진단하며 스케줄링 Agents의 학습자 지식에 추가한 후 스케줄링 Agents가 학습자의 기본 사항과 요구 내용을 추론하여 비슷한 수준의 학습자를 연결한다. 교사 모듈은 전통적인 ITS의 구조의 교수 학습 모듈, 전문가모듈로 구성되어 교수 학습을 할 수 있다. 이렇게 여러 명의 학습자를 연결하여 협력학습을 하기 위해서는 학습자간의 요구사항과 지식 수준 그리고 학습 가능한 시간이 같아야 하는데 이를 위해 시간을 자원으로 하는 동적 자원 스케줄링(Dynamic Resource Scheduling)으로 모델링 하였다. 본 연구에서 도형학습을 기반으로 하는 실험을 통해 구현한 원격 협력학습을 위한 지능형 스케줄링 에이전트를 평가하였다.

• 대한치과의사협회지
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• 제50권1호
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• pp.22-30
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• 2012

The methods for the occlusal force measurement have long been developed. The occlusal analyzing equipment utilizing the pressure-sensitive film (Prescale) is useful for the assessment and comparison among large group of patients. On the other hand, the apparatus which uses the grid-based sensor sheet (T-scan) can be a useful assistant for acquiring the well-balanced occlusion. The device that can process the electrical input from the strain gauge which is attached to the tooth surface can collect the dynamic data of actual masticatory force. This device has been developed for the measurement of actual mastication with the food bolus and it can be a useful method for the comparison before and after the restorative treatment. Occlusal force measurement can be applied for the analysis of therapeutic action, diagnosis of crack- tooth syndrome, temporomandibul ar disease, and idiopathic implant loosening.

• 한국지능시스템학회논문지
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• 제26권2호
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• pp.135-140
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• 2016

비동기 순차 회로를 위한 교정 제어기는 회로를 재설계하지 않고도 회로 내에 존재하는 여러 고장을 탐지하고 극복하는 능력을 보인다. 이번 논문에서는 교정 제어기의 크기를 줄이기 위한 방법으로서 정적 교정 제어기(static corrective controller)를 제안한다. 동적 제어기에 비해 정적 제어기는 제어기 상태가 필요 없으므로 조합 회로(combinational circuit)만으로 구현 가능하다. 본 논문에서는 상태 천이 고장에 대한 정적 내고장성 교정 제어기가 존재할 조건과 설계 과정을 규명한다. 또한 제안된 제어 기법을 FPGA로 구현된 SEU 오류 카운터에 적용하여 그 효용성을 실험적으로 검증한다.

• 대한기계학회논문집A
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• 제30권4호
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• pp.435-441
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• 2006

The anterior cruciate ligament(ACL) is an important stabilizer of knee joint. The ACL injury of knee is common and a serious ACL injury leads to ligament reconstruction surgery. Gait analysis is essential to identify knee condition of patients who display abnormal gait. The purpose of this study is to evaluate and classify knee condition of ACL deficient patients using a nonlinear dynamic method. The nonlinear method focuses on understanding how variations in the gait pattern change over time. The experiments were carried out for 17 subjects(l2 healthy subjects and five subjects with unilateral deficiency) walking on a motorized treadmill for 100 seconds. Three dimensional kinematics of the lower extremity were collected by using four cameras and KWON 3D motion analysis system. The largest Lyapunov exponent calculated from knee joint flexion-extension time series was used to quantify knee stability. The results revealed the difference between healthy subjects and patients. The deficient knee was significantly unstable compared with the contralateral knee. This study suggests an evaluation scheme of the severity of injury and the level of recovery. The proposed Lyapunov exponent can be used in rehabilitation and diagnosis of recoverable patients.

• 대한후두음성언어의학회지
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• 제20권2호
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• pp.118-125
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• 2009

Bilateral vocal fold immobility (BVFI) is a challenging condition which may result from diverse etiologies including vocal fold paralysis, synkinesis, cricoarytenoid joint fixation, and interarytenoid scar. Most patients present with dyspnea and stridor, but sometimes with a breathy dysphonia. Careful history taking, laryngoscopic evaluation under general anesthesia or awaken status, laryngeal EMG, and imaging studies with CT and/or MRI are helpful for providing a precise diagnosis and planning appropriate managements. In children, congenital neurological disorder is one of the most common etiologies, and spontaneous recovery has been reported in more than 50% of cases. Therefore, observation for more than 6 months while securing the upper airway with tracheostomy if needed is a generally accepted rule before deciding any destructive procedure to be undertaken. In children with advanced posterior glottic stenosis, laryngotracheal reconstruction with rib cartilage graft should be considered. In contrast to children, BVFI most commonly occurs as sequalae of surgical complication in adults. Diverse static or dynamic procedures can be applied; posterior cordotomy, vocal fold lateralization, endoscopic or open arytenoidectomy, arytenoid abduction, and reinnervation, electrical laryngeal pacing, which need to be carefully selected according to each patient's needs and pathophysiology of BVFI.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.307-309
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• 2004

In this study, we have evaluated and classified arthritic pathology using the auscultation of knee joint sound. Six normal persons and 11 patients with knee problem were enrolled. Six patients of Group 1 needed an orthopeadic surgery because of the ruptured wounds of meniscus or ACL(Anterior Cruciate Ligament) and 5 patients of Group 2 diagnosed as osteoarthritis. Subjects were taken knee flexion and extension being seated in a chair for 20 seconds which repeated 3 times. Also subjects stood up and sit down repeatedly in the same way. After the movement of knee was divided into 18 degrees, the pitch perturbation according to partial degrees was analyzed and the DTW(Dynamic Time Warping) method was applied for normalizing a time-axis and unpaired t-test was used for statistic results among groups. As a result, the amplitude and frequency perturbations of group 2 was higher than group 1(p<0.05) and showed a characteristic 'w-shape' in angle-amplitude graph. These results suggest that the analysis of knee joint sound might assist in early diagnosis of knee joint disease.