• Structural Monitoring and Maintenance
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• v.9 no.3
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• pp.237-258
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• 2022

This paper studies detecting and locating loose bolts using nonlinear guided waves. The 3D Finite Element (FE) simulation is used for the prediction of guided waves' interactions with loose bolted joints. The numerical results are verified by experimentally obtained data. The study considers bolted joints consisting of two bolts. It is shown that the guided waves' interaction with surfaces of a loose bolted joint generates Contact Acoustic Nonlinearity (CAN). The study uses CAN for detecting and locating loose bolts. The processed experimentally obtained data show that the CAN is able to successfully detect and locate loose bolted joints. A 3D FE simulation scheme is developed and validated by experimentally obtained data. It is shown that FE can predict the propagation of guided waves in loose bolts and is also able to detect and locate them. Several numerical case studies with various bolt sizes are created and studied using the validated 3D FE simulation approach. It is shown that the FE simulation modeling approach and the signal processing scheme used in the current study are able to detect and locate the loose bolts in imperfect bolted joints. The outcomes of this research can provide better insights into understanding the interaction of guided waves with loose bolts. The results can also enhance the maintenance and repair of imperfect joints using the nonlinear guided waves technique.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.91-98
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• 2010

At present, advanced countries are focusing on the study of Demilitarization Method of Conventional Ammunitions. In this paper, we will report the current trends of Demilitarization of Conventional and Guided Missile ammunitions, and present the efficient Demilitarization Methods of new development of Guided Missile ammunitions in Korea.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.2
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• pp.114-121
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• 2009

Ultrasonic guided waves have been widely utilized for long range inspection of structures. Especially, development of array guided waves techniques and its application for long range gas pipe lines(length of from hundreds meters to few km) were getting increased. In this study, focusing algorithm for array guided waves was developed in order to improve long range inspectability and accuracy of the array guided waves techniques for long range inspection of gas pipes, and performance of the developed techniques was verified by experiments using the developed array guided wave system. As a result, S/N ratio of array guided wave signals obtained with the focusing algorithm was increased higher than that of signals without focusing algorithm.

• Environmental Engineering Research
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• v.18 no.3
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• pp.117-121
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• 2013

For underpasses in Yeongjong Sky City business district, the guided drainage system, as a buoyancy prevention system has been designed, and is under construction. This paper investigates the safety of the guided drainage system for underpass structures being constructed in Yeongjong Sky City business district. This paper also calculates the amount of outflowing groundwater generated by the guided drainage system, and proposes alternative usages of the water. In order to investigate safety and field applicability of the guided drainage system for underpasses, characteristics of the surface flow for the area of interest have been analyzed, and the flow change of groundwater following the underpass structure construction has been evaluated using the 3-dimensional groundwater program MODFLOW. The influence of ground water on safety of the underpass structures has been calculated by FLAC2D analysis. For alternative usages for the outflowing groundwater generated by the guided drainage system, utilization methods of the outflowing groundwater in national and international resources have been researched. The amount of an outflowing groundwater to be generated in the area of interest has been analyzed, and efficient potential usages of this groundwater have been researched. When guided drainage technique is applied, the change in flow of groundwater must be evaluated and considered as safety factor relating to the buoyancy of the structure. As a result, safety factor demonstrated more than 1.2, meaning that the underpass structure is safe. The amount of subsoil drain generated by the guided drainage system was also analyzed. The quality and amount of water satisfied the standards and volume requirements, so as to make it applicable for a number of uses, such as X, Y, and Z, and should prove to be a valuable resource as the circumstances of the neighboring area change over time. These resources can be used as basic data for future urban water circulation studies, as well as generating research of alternative water usages.

• Journal of Broadcast Engineering
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• v.20 no.5
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• pp.718-727
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• 2015

In this paper, we present a novel segmentation method that can extract new foreground objects from a current frame in real-time. It is performed by detecting differences between the current frame and reference frame taken from a fixed camera. We minimize computing complexity for real-time video processing. First DCT (Discrete Cosine Transform) is utilized to generate rough binary segmentation maps where foreground and background regions are separated. DCT shows better result of texture analysis than previous methods where texture analysis is performed in spatial domain. It is because texture analysis in frequency domain is easier than that in special domain and intensity and texture in DCT are taken into account at the same time. We maximize run-time efficiency of DCT by considering color information to analyze object region prior to DCT process. Last we use Guided filter for natural matting of the generated binary segmentation map. In general, Guided filter can enhance quality of intermediate result by incorporating guidance information. However, it shows some limitations in homogeneous area. Therefore, we present an additional method which can overcome them.

• Korean Journal of Head & Neck Oncology
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• v.15 no.2
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• pp.189-193
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• 1999

Objectives: Fine needle aspiration cytology(FNAC) is a well established preoperative diagnostic procedure in the thyroid nodules. However, diagnostic accuracy of FNAC varies according to the size and the structural characteristics of thyroid nodule. We performed the ultrasound guided FNAC(US-guided FNAC) for impalpable thyroid nodule, and estimated the sampling accuracy rate through a comparison study between the cytologic diagnosis and the final histologic diagnosis of the postoperative specimens in order to determine clinical efficacy of the US-guided FNAC. Materials and Methods: We evaluated 117 patients underwent US-guided FNAC from January 1997 to December 1998. These patients had 129 thyroid nodules to need cytologic examination. Whereas the nodules were so no graphically classified into cystic, solid, and mixed type according to echo pattern, the aspirated thyroid specimens were classified into benign, malignant, suspicious, and insufficient. Results: Positive sampling for diagnositc examination was achieved in 75 nodules(58.1%), and US-guided FNAC in our study showed the accuracy rate of 95.2%, false positivity rate of 0%, and false negativity rate of 5.5%. Conclusions: US-guided FNAC is a powerful techniques for evaluating cytologic characterics and allowing a reliable diagnositc result in the impalpable thyroid nodule. However, the experienced technique is recommanded in order to obtain the sufficient samples for reliable results.

• Journal of Korean Academy of Nursing Administration
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• v.10 no.3
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• pp.311-316
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• 2004

Purpose: The purpose of this study was to identify the effects of Guided Imagery on the stress and anxiety of nursing students in clinical practice. Method: The research design was a nonequivalent control group pretest-posttest design. The data were collected from the 20th of June to the 11th of July 2003. The objects of this study were 32 nursing students of college(16 for the experimental group, 16 for the control group). The instruments used in this study were State Trait Anxiety Inventory, the stress scale developed by Choi(1991). The guided imagery was provided through audiotapes to the subjects for 8 minutes, a time for 5 days. The pretest was given before the therapy to measure variables for both groups and the posttest was performed after intervention. The data were analyzed by the SAS program using t-test. Result: The results of this study are as follows. The stress scores of students were decreased in the experimental group, but were not significantly different between the experimental group and the control group after the guided imagery. The anxiety scores of students were significantly different between the experimental group and the control group after the guided imagery. Conclusion: The guided imagery can be suggested as an effective nursing intervention to reduce the anxiety. Further studies to identify the effects of stress reduction according to the frequency of the guided imagery can be needed.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.339-346
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• 2003

MRI provides anatomical structure information with superb spatial resolution that can be utilized in clinical surgeries. Advanced image processing techniques in conjunction with the MRI-guided surgery is expected to be of great importance in brain surgeries in the near future. In this paper, we introduce an image-guided surgery technique using the stereo matching method. To perform image-guided biopsy operations, we made MRI markers, camera markers and a detection probe marker. To evaluate the accuracy of the image-guided system. we made a silicone phantom. Using the phantom and markers, we have performed MRI-guided experiments with a 1.5 Tesla MRI system. It has been verified from phantom experiments that our system has a positioning error less than 1.5%. Compared with other image guided surgery system, our system shows better positioning accuracy.

• Journal of Advanced Navigation Technology
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• v.25 no.4
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• pp.293-298
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• 2021

In general, the guided weapon seeker and the guided control device process the target, search, recognition, and capture information to indicate the state of the guided missile, and play a role in controlling the operation and control of the guided weapon. The signals required for guided weapons are gaze change rate, visual signal, and end-stage fuselage orientation signal. In order to process the complex and difficult-to-process missile signals of recent missiles in real time, it is necessary to increase the data processing speed of the missiles. This study showed the processing speed after applying the stop and go and inverse enumeration algorithm among the parallel algorithm methods of PINQ and comparing the processing speed of the signal data required for the guided missile in real time using the guided missile inspection program. Based on the derived data processing results, we propose an effective method for processing missile data when applying a parallel processing algorithm by comparing the processing speed of the multi-core processing method and the single-core processing method, and the CPU core utilization rate.

• Journal of Chest Surgery
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• v.55 no.6
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• pp.442-451
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• 2022

Background: This meta-analysis was conducted to evaluate the effect of fractional flow reserve (FFR) on clinical outcomes after coronary artery bypass grafting (CABG). Methods: Five online databases were searched for studies that (1) enrolled patients who underwent isolated CABG or CABG with aortic valve replacement and (2) demonstrated the effect of an FFR-guided strategy on major adverse cardiac events (MACE) after surgery based on a randomized controlled trial or adjusted analysis. MACE included cardiac death, acute myocardial infarction (MI), and repeated revascularization. The primary outcomes were all MACE outcomes and a composite of all-cause death and MI, and the secondary outcomes were the individual MACE outcomes. Publication bias was assessed using a funnel plot and the Egger test. Results: Six articles (3 randomized and 3 non-randomized studies: n=1,027) were selected. MACE data were extracted from 4 studies. The pooled analyses showed that the risk of MACE was not significantly different between patients who underwent FFR-guided CABG and those who underwent angiography-guided CABG (hazard ratio [HR], 0.80; 95% CI, 0.57-1.12). However, the risk of the composite of death or MI was significantly lower in patients undergoing FFR-guided CABG (HR, 0.62; 95% CI, 0.41-0.94). The individual MACE outcomes were not significantly different between FFR-guided and angiography-guided CABG. Conclusion: FFR-guided CABG might be beneficial in terms of the composite outcome of death or MI compared with angiography-guided CABG although data are limited.