• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.6
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• pp.157-162
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• 2023

A highly sensitive refractive index bio-sensor based on grating-assisted strip directional coupler (GASDC) is proposed. The sensor is designed using two asymmetric strip waveguides with a top-loaded grating structure in one of the waveguides. Maximum light couples from one waveguide to the other at the resonance wavelength satisfying phase-matching condition (PMC), and it shows that the change in phase-matching condition with the change in refractive index of the analyte medium in the cover region can be used as a measure of the sensitivity. The proposed sensor will be an on-chip device with a high refractive index sensitivity, and the sensor configuration offers a low propagation loss, thereby enhancing the sensitivity. Furthermore, variation of the sensitivity with the waveguide parameters of sensor is evaluated to optimize the design.

• Journal of Korean Neurosurgical Society
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• v.66 no.6
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• pp.735-742
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• 2023

Nephrotic syndrome (NS) is associated with cerebral venous sinus thrombosis (CVST), which is a rare cerebrovascular disorder in children. Systemic anticoagulation with heparin is the standard therapy for CVST, and mechanical thrombectomy (MT) has been described as a salvage treatment for adult anticoagulant refractory CVST, However, it has never been reported in children. We describe a case of MT for refractory CVST in a child with NS. A 13-year-old boy with newly diagnosed NS presented to an emergency department with acute headache. A head computed tomography showed acute thrombus in the superior sagittal sinus, straight sinus and transverse sinus. The child was started on heparin therapy, but clinically deteriorated and became unresponsive. In view of the rapid deterioration of the condition after anticoagulation treatment, the patient received intravascular treatment. Several endovascular technologies, such as stent retriever and large bore suction catheter have been adopted. After endovascular treatment, the patient's neurological condition was improved within 24 hours, and magnetic resonance venography of the head demonstrated that the CVST was reduced. The child recovered with normal neurological function at discharge. This case highlights the importance of considering MT for refractory CVST, and we suggest that MT may be considered for refractory CVST with NS in children.

• Journal of Korean Neurosurgical Society
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• v.42 no.1
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• pp.27-34
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• 2007

Objective : On the magnetic resonance image (MRI) of the infiltrating brain tumor, enhancement is usually higher in malignant tumor than in benign tumor, and tumor cells can invade into the peritumoral area without definite enhancement. In various pathological conditions, the blood brain barrier (BBB) becomes changed to pathological condition, allowing various materials extravasating into the interstitial space, and degree of enhancement is depend on the pathology. Authors performed dynamic MRI on enhancing and surrounding edematous area in order to evaluate the degrees of opening of BBB, to differentiate tumor from non-tumorous condition, and to determine its relationship with the recurrence of the tumor. Methods : Dynamic MRI was performed in 25 patients. Dynamic scans were done every 15 seconds after administration of Gd-DTPA on the enhancing and surrounding area for maximum 300 seconds, and the patterns of enhancement were ana lysed. The enhancement curve with initial steep increase followed by slow decrease was defined as "N pattern", those with initial steep increase followed by additional slow increase as "T pattern", and those with initial steep increase followed by plateau as "E pattern". Histopathological findings were compared with the dynamic scan. Results : The graphs taken from enhancing area showed "T pattern" regardless of pathology. In the surrounding area, "T pattern" was noticed in the malignant tumors, but "E pattern" or "N pattern" was noted in low-grade or benign tumors and non-tumorous condition. "T pattern" in the surrounding area was related to the malignant with tumor cell infiltration and recurrence. Conclusion : The results suggest that the malignant tumor infiltration changes the condition of BBB enough to extravasate the Gd-DTPA. Enhancement pattern in the surrounding edematous area may be a useful information to differentiate the malignant glioma with the low-grade and benign tumors or other non-tumorous conditions.

• Journal of Acupuncture Research
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• v.31 no.4
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• pp.109-119
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• 2014

Objectives : The aim of this study is to observe clinical characteristics and treatment outcomes of inpatients admitted to a Korean medicine hospital for shoulder pain based on magnetic resonance imaging(MRI) findings. Methods : 28 patients with MRI data were included. Data on MRI findings, duration of pain, and treatment effects were collected. To measure treatment outcomes, verbal numerical rating scale(VNRS), range of motion(ROM), and a clinical condition grading system were used. Results : 1. The patient population was 75.0 % female and 39.3 %(n=11) belonged to the 51~60-year-old age group. In the under 40 population, 1 or less MRI findings were found. 2. As for the type of disorder, 82.1 % of the patients were diagnosed with 'Supraspinatus lesion', 39.3 % with 'subacromial-subdeltoid(SA-SA) bursitis', and 28.6 % with 'Adhesive capsulitis' 3. Numerous correlations could be made between duration of pain and MRI findings. 'rotator cuff full thickness tear' was more prevalent in acute shoulder pain patients, and 'Adhesive capsulitis' in chronic patients. 4. VNRS and ROM at the time of discharge had significantly improved as compared to VNRS and ROM at the time of admission. 5. As for correlation between MRI findings and clinical condition grade, patients diagnosed with 'rotator cuff partial tear' reported to be in 'good' condition or better whereas those with 'rotator cuff full thickness tear' reported to be in 'fair' condition or worse. Conclusions : Patients admitted to a Korean Medicine hospital for shoulder pain had varying degrees of severity as shown on MRI. Almost all lesions responded well to Korean medicine treatment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.68-76
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• 2021

Storage racks have suffered huge losses due to earthquakes, but related research and regulations are relatively insufficient non-structural elements compared to the structural elements. In this study, we tried to experimentally analyze the behavioral characteristics of storage racks due to external force according to the fixing conditions of the column-foundations connection of storage racks. In general, the column-foundations connection of storage racks is installed according to the user's convenience without installation standards and regulations. For this reason, this study conducted a behavior analysis test on four full-scale storage racks with the condition of column-foundations connection of four typical storage racks. The behavior characteristics analysis test was performed by two-direction of the shake table with El-Centro seismic wave. To confirm the behavior characteristics according to the magnitude of the seismic load, 50% ~ 150% of the seismic waves were increased by 50% for each test. In addition, a resonance search test was conducted to confirm the natural frequency of each storage racks foundations fixing condition. Among the data obtained through the test, the displacement of the top layer and the permanent displacement after the test were compared for each condition to analyze the behavior characteristics of the column-foundations fixed conditions of the storage racks. As a result, the change of natural frequency was small in storage racks due to the change of the conditions of the foundations, and the behavior characteristics were changed due to the difference of the restoring force due to the change of the storage racks foundations condition rather than the influence of the natural frequency of the input load.

• International Journal of Automotive Technology
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• v.4 no.1
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• pp.21-30
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• 2003

In this paper a systematic test procedure for evaluation of road-induced noise of a vehicle and guidelines for each test are presented. Also, a practical application of the test procedure to a small SUV is presented. According to the test procedure, all the tests were performed to evaluate road-induced booming noise that is in low frequency range. First of all the information on characteristics of road-induced noise was obtained through baseline test. Coupling effects between body structure and acoustic cavity of a compartment were obtained by means of modal tests for a structure and an acoustic cavity. Local stiffness of joint areas between chassis system and car-body was determined by test for measurement of input point inertance. Noise sensitivities of body joints to operational forces were obtained through test for measurement of noise transfer functions. Operational deflection shapes made us analyze behaviors of chassis system under running condition and then find sources of noise due to resonance of the chassis system. Finally, Principal Component Analysis and Transfer Path Analysis were utilized to investigate main paths of road-induced noise. In order to evaluate road-induced booming noise exactly, all of tests mentioned above should be performed systematically.

• Advances in nano research
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• v.9 no.3
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• pp.133-145
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• 2020

In this study, nonlinear vibrations and dynamic instabilities of a smart embedded micro shell conveying varied fluid flow and subjected to the combined electro-thermo-mechanical loadings are investigated. With the aim of designing new hydraulic sensors and actuators, the piezoelectric materials are employed for the body and the effects of applying electric field on the stability of the system as well as the induced voltage due to the dynamic behavior of the system are studied. The nonlocal piezoelasticity theory and the nonlinear cylindrical shell model in conjunction with the energy approach are utilized to mathematically modeling of the structure. The fluid flow is assumed to be isentropic, incompressible and fully develop, and for more generality of the problem both steady and time dependent flow regimes are considered. The mathematical modeling of fluid flow is also carried out based on a scalar potential function, time mean Navier-Stokes equations and the theory of slip boundary condition. Employing the modified Lagrange equations for open systems, the nonlinear coupled governing equations of motion are achieved and solved via the state space problem; forth order numerical integration and Bolotin's method. In the numerical results, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence, flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or vibration amplitude controller in the micro electro mechanical systems.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.2
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• pp.221-228
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• 1997

A strong combustion-driven sound from a surface burner made of a perforated metal fiber plate for premixed gas was investigated to clarify the physical mechanism of its generation. A simple model was developed for the acoustic power generation in terms of the heat transfer response function and the acoustic impedance of the burner. The acoustic impedance of the perforated metal fiber placed on the open exit was measured and the heat release response of the burner to the oscillating flow associated with the acoustic disturbance was expressed in terms of a response function. It was found that the power is generated by the heat release in response to the downstream particle velocity, in contrast to the upstream velocity in the case of the Rijke oscillation driven by a heater placed in the lower half of a columm with upstream flow. The measured frequencies of the oscillation were in agreement with the estimated resonance frequencies and their excitation was varied with the combustion conditions. For the same fuel rate, the excited frequency increases with the air ratio if it is low but decreases with the ratio if not so low. Such frequency characteristics were explained by assuming a heat release response function with a time constant and it was shown that the excited frequency decreases as the time constant increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.426-426
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• 2009

Diagnostic X-ray system is general and basic medical equipment to be used in mostly medical organizations, but being bombed of radioactivity is a big weak point when irradiates a X-ray to the human body so that ICRP restricted the radiation exposure tolerance of the human body. In order to reduce being bombed, the many research and development is now advanced. A lots of diagnostic X-ray machines have currently used due to the increase of occurrence efficiency of X-ray and precisely the output control by using the inverter which is a high speed switching semiconductors. For getting the confidence of the X-ray machine, the same radiation occurrence, same evaluation, and same irradiation condition are necessary when evaluates X-ray irradiation. It is the most important part for the accuracy of the test result and the patient safety. This paper has produced the high voltage occurrence system of full-wave rectification method by using the LC resonance inverter, and evaluated the irradiation reproducibility in order to use it in diagnosis of the patient.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.119-122
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• 2002

The vibration qualification test of satellite antenna is required to verify that there will be no structural damage due to the severe vibration caused by the launch of satellite. For the qualification test, reasonable test load condition needs to be introduced by dynamic analysis. The present work has been performed to provide an understanding how the qualification test load can be evaluated by the results of both normal mode and sine vibration analyses with notching technique for a composite Ka-band antenna structure.