• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.369-375
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• 2002

The results of source location in terms of AE signal occurred by the spot exciting as suggested in this research, it has been confirmed that AE technique is quite fruitful in figuring out the location of the occurrence, form, size and direction of the defects. Thus, it is expected that the application of the experimental method suggested in this study would make it possible to identify, in the nondestructive way, the location of the defect in the material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.763-767
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• 1994

The measured vibration on a machine or a structure is shaped by the excitation waveform and the path transfer function. Mechanism diagnostics tends to focus on retrieving source featurce by minimzing the effects of the structural path, while in structural diagnostics we are more interested in minimizing source effects and retrieving path parameters. In structural diagnostics, therefore, there are experimental issues of gathering data that are independent source effects and finding a transfer function signature that reveals structural defects. This paper describes how the transfer function can be obtained more accurately by experiment using the compatibility relationship which is newly discovered.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.87-95
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• 2004

From the results of AE(Acoustic Emission) source location occurred by the spot exciting as suggested in this research, it has been confirmed that AE technique is quite fruitful in figuring out the location of the occurrence, form, size and direction of the defects. As the results of examining the distribution of event for the angle of crack $\alpha$ to Xs and Ys, as the increases from $0^{\circ}$ ~ $90^{\circ}$, gradually changes its width from the axis Xs to the axis Ys. So event appears approximately similar in its size at the angle of crack $\alpha$=$45^{\circ}$, yet opposite when $\alpha$ is lager. It is believed that this is a phenomenon where its crack legnth $\alpha$, assumed as a planar defect, is to be prcjected toward the direction with a larger size. Thus, it is expected that the application of the experimental method suggested in this study would make it possible to identify the location of the defect in the material in the nondestructive way.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.9 no.1
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• pp.35-41
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• 2023

Photodynamic therapy (PDT), in which a photosensitizer (PS), light, and molecular oxygen are essential components, is a non-invasive and highly effective cancer therapeutic method. However, PDT suffers from the penetration limit of light caused by attenuation and scattering of light through tissues constraining its use to skin and endoscopically accessible cancers. Cerenkov luminescence (CL) is defined as the light illuminated when charged particles move in a dielectric medium at a velocity greater than the phase velocity of light. It is known that medical radioisotopes in preclinical and clinical settings have enough energy to generate CL, and lately, CL has been exploited as an excitation source for PDT without external light illumination. This review introduces state of the art studies of radioisotope-based PDT for cancer, in which radioisotopes are utilized as a light source.

• Journal of Korean Society on Water Environment
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• v.39 no.1
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• pp.87-101
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• 2023

The constituents of a watershed control a wide range of ecosystem processes, such as, carbon sequestration, nutrient retention, and biodiversity preservation. Maintenance of a healthy watershed is advantageous to humans in many direct and indirect ways. Dissolved organic matter fluorescence analysis is one of the most commonly utilized parameters for water quality measurement, pollution source tracking, and determination of the ecological state of a watershed. Throughout the recent decades, the advancement in data processing, instrumentation, and methods has resulted in many improvements in the area of watershed study with fluorescence analysis. The current trend of coupling advanced instrumentations and new comparative parameters, such as, microplastics of different types, antibiotics, and specific bacterial contaminants have been reported in watershed studies. However, conventional methodologies for obtaining fluorescence excitation emission matrices and for calculating the fluorescence and spectral indices are preferred to advanced methods, due to their easiness and simple data collection. This review aims to gain a general understanding of the use of dissolved organic matter fluorescence analysis for diagnosis and source identification of watershed pollutions, by focusing on how the studies have utilized fluorescence analysis to improve existing knowledge and techniques in recent years.

• Progress in Superconductivity
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• v.7 no.1
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• pp.28-35
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• 2005

We propose a method to measure atrial arrhythmias (AA) such as atrial fibrillation (Afb) and atrial flutter (Afl) with a SQUID magnetocardiograph (MCG) system. To detect AA is one of challenging topics in MCG. As the AA generally have irregular rhythm and atrio-ventricular conduction, the MCG signal cannot be improved by QRS averaging; therefore a SQUID MCG system having a high SNR is required to measure informative atrial excitation with a single scan. In the case of Afb, diminished f waves are much smaller than normal P waves because the sources are usually located on the posterior wall of the heart. In this study, we utilize an MCG system measuring tangential field components, which is known to be more sensitive to a deeper current source. The average noise spectral density of the whole system in a magnetic shielded room was $10\;fT/{\surd}Hz(a)\;1\;Hz\;and\;5\;fT/{\surd}Hz\;(a)\;100\;Hz$. We measured the MCG signals of patients with chronic Afb and Afl. Before the AA measurement, the comparison between the measurements in supine and prone positions for P waves has been conducted and the experiment gave a result that the supine position is more suitable to measure the atrial excitation. Therefore, the AA was measured in subject's supine position. Clinical potential of AA measurement in MCG is to find an aspect of a reentry circuit and to localize the abnormal stimulation noninvasively. To give useful information about the abnormal excitation, we have developed a method, separative synthetic aperture magnetometry (sSAM). The basic idea of sSAM is to visualize current source distribution corresponding to the atrial excitation, which are separated from the ventricular excitation and the Gaussian sensor noises. By using sSAM, we localized the source of an Afl successfully.

• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.877-893
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• 2011

Response spectra of earthquake ground motions are important in the earthquake-resistant design and reliability analysis of structures. The formulation of the response spectrum in the frequency domain efficiently computes and evaluates the stochastic response spectrum. The frequency information of the excitation can be described using different functional forms. The shapes of the calculated response spectra of the excitation show strong magnitude and site dependency, but weak distance dependency. In this paper, to compare the effect of the earthquake ground motion variables, the contribution of these sources of variability to the response spectrum's uncertainty is calculated by using a stochastic analysis. The analytical results show that earthquake source factors and soil condition variables are the main sources of uncertainty in the response spectra, while path variables, such as distance, anelastic attenuation and upper crust attenuation, have relatively little effect. The presented formulation of dynamic structural response in frequency domain based only on the frequency information of the excitation can provide an important basis for the structural analysis in some location that lacks strong motion records.

• Smart Structures and Systems
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• v.16 no.2
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• pp.347-366
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• 2015

GPS and strong-motion sensors are broadly used for the monitoring of structural health and Earth surface motions, focusing on response of structures, earthquake characterization and rupture modeling. Several studies have shown the consistency of the two data sets within at certain frequency (e.g., 0.03

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.109-119
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• 1995

A driveline incorporating universal joints when driving through an angle can excite various components in a vehicle with second order excitation of torsional and bending vibrations, being transmitted either audibly(noise), or physically(vibration). For a certain range of vehicle dpeed noises can be radiated from the cab wall, in which resonances occur by the excitations transmitted from the driveline as a vibration source. In this paper, the excitation mechanism of cab noises is studied especially for the vehicle speed range of 65 .approx. 75 km/h through the simulation for torsional vibrations of the driveline and for bending vibrations of the cab of an 11 Ton grade Cargo Truck, and verified additionally by vibration and noise measurements. As a result, it is found that the uncomfortable noises in the cab are caused mainly by the abrupt increase of the joint angle of driveline near the axle differential resulted from the excessive clearance alignment of the leaf spring gate.

• Ocean Systems Engineering
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• v.1 no.1
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• pp.1-15
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• 2011

Offshore structures are subjected to wind loads, wind generated wave excitations, and current forces. In this paper we focus on the wind generated wave excitations as the main source for the external forces on the structure. The main objective of the paper is to provide a tool for using deck acceleration measurements to predict the value of the force and moment acting on the offshore structure foundation. A change in these values can be used as an indicator of the health of the foundation. Two methods of analysis are used to determine the relationship between the force and moment acting on the foundation and deck acceleration. The first approach uses neural networks while the other uses a Fokker-Planck formulation. The Fokker-Plank approach was used to relate the variance of the excitation to the variance of the deck acceleration. The total virtual mass of the equivalent SDOF of the structure was also determined at different deck masses.