• Structural Engineering and Mechanics
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• v.43 no.3
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• pp.395-410
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• 2012

The visualizing energy flow and control in vibrating stiffened plates with a cutout are studied using finite element method. The vibration intensity, vibration energy and strain energy distribution of stiffened plates with cutout at different excitation frequencies are calculated respectively and visualized for the various cases. The cases of different size and boundaries conditions of cutouts are also investigated. It is found that the cutout or opening completely changes the paths and distributions of the energy flow in stiffened plate. The magnitude of energy flow is significantly larger at the edges near the cutout boundary. The position of maximum strain energy distribution is not corresponding to the position of maximum vibrational energy. Furthermore, the energy-based control using constrained damping layer (CDL) for vibration suppression is also analyzed. According to the energy distribution maps, the CDL patches are applied to the locations that have higher energy distribution at the targeted mode of vibration. The energy-based CDL treatments have produced significant attenuation of the vibration energy and strain energy. The present energy visualization technique and energy-based CDL treatments can be extended to the vibration control of vehicles structures.

• Investigative Magnetic Resonance Imaging
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• v.16 no.2
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• pp.173-176
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• 2012

We report the radiological findings of regional enhancement of the liver adjacent to the right adrenal pheochromocytoma. CT and MRI showed focal strong enhancement of adjacent liver tissue in the arterial phase. However during the delayed phase, the lesion showed iso-attenuation with normal hepatic parenchyma and not delineated. The lesion did not show abnormal signal intensity on neither T1 nor T2 weighted images and indistinguishable from normal parenchyma. The enhancing hepatic lesion was spontaneously regressed on postoperative follow up CT which was taken several months after the adrenalectomy.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.21-29
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• 2004

The flow characteristics of a swirl injector were investigated with the variation of the flow condition and geometric dimensions, such as orifice length for considering the viscous effect and tangential entry port area for considering the swirl intensity. The liquid film thickness strongly influencing on the formed drop size of the spray was measured using a new technique. The film thickness measurement technique proposed here, used the attenuation of fluorescence signal near the injector exit. The breakup length that is important for the flame location as well as the spray cone angle which influences on the ignition performance was measured using a backlit stroboscopic photography technique. From the experimental results, it is found that an increase in injection pressure decreased the film thickness and breakup length, and also enlarged the spray cone angle. A decrease in orifice length and tangential entry port area has a similar tendency of thinner film thickness, shorter breakup length and larger spray cone angle. In the present study, we proposed empirical models of the flow characteristics of the swirl injectors.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.4
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• pp.398-407
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• 2013

Optical tomography was used to measure the pattern of spray cross-section. The maximum-likelihood estimation (MLE) algorithm was used to reconstruct the spray cross-section from the measured transmission rate of the spray. A swirl-type injector was used to form an optically dense spray, and the test was carried out in a high-pressure chamber, to control the pressure condition of the test site. Before the experiment, the reliability of the MLE-based reconstruction algorithm was verified, by comparing it with a conventional filtered back projection reconstruction (FBP) method. The MLE algorithm showed superior reconstruction of the image. In the spray patternation experiment, the results of the optical tomography and optical line patternator, which uses Mie scattering signal information, were compared. While measuring the cross-section of optically dense spray, the intensity of the scattering signal had attenuated to an uncorrectable level, which led to incorrect spray pattern measurement by the optical line patternator. However, reliable results were obtained by optical tomography, under the same condition. Finally, the pattern of the optically dense spray was measured at various chamber pressures, of up to 3 MPa. As the chamber pressure increased, the hollow cone-shaped swirl spray shrank, and the attenuation coefficient value of the inner region increased.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.2
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• pp.93-102
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• 2003

A technique for the seismic reliability evaluation of electric power transmission network system(EPTS) was developed to evaluate reliability indices corresponding to the whole network system and to each node within. A network model with nodes and links for EPTS was established, and a seismic substation fragility curve obtained from seismic fragilities of power system facilities was derived. A point source model, the doubly truncated Gutenberg-Richter relationship, and earthquake intensity attenuation formula was applied to simulate seismic events. Using Monte-Carlo simulation method, the seismic reliability of EPTS was evaluated and, it appeared that seismic effect on EPTS of korea has to be considered.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.6
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• pp.656-664
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• 1997

This paper introduces a fixed radio-relay link design simulator with which we can select the station site and the frequency and can predict the performance of the radio-relay links. The simulator analyzes the path profile, the fading effects, the availability, the rain attenuation and the interference of the cosidered radio path using the digital terrain data and the rain intensity data. The calculation algorithms used in this simulator are mostly from the recommendations of the ITU-R. All the modules of the simulator are performed in full GUI mode and the input and output parameters are displayed interactively. This simulator could be used to the fixed radio-relay link design and the LMDS design.

• Imaging Science in Dentistry
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• v.36 no.3
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• pp.163-168
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• 2006

A 60-year-old female, who complained of delayed healing and swelling after extraction of left lower second molar during chemotherapy, visited our department. She had a history of a resection surgery of breast cancer and postoperative radiotherapy. The conventional radiographs showed diffuse permeative bone destruction in posterior mandibular body, which gave the first radiologic impression of osteonecrosis associated with radiotherapy or chemotherapy. And bone metastasis from the breast cancer was also considered in the differential diagnosis. On the enhanced computed tomography (ECT) the posterior mandibular body was occupied by a large expansile lesion showing central low attenuation with peripheral rim enhancement. Magnetic resonance images revealed that the low attenuated area on ECT did not show as high signal intensity as water on T2 weighted image and indicated solid component of a tumor. The final diagnosis was central squamous cell carcinoma. We present the diagnostic imaging features of the patient with special emphasis on the differential diagnosis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.501-505
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• 2013

It is well known that monolithic glass has specific coincidence dip allowing transmittance of noise around the critical frequency. Laminated glass, made of a polyvinyle butyral(PVB) interlayer sandwiched by two panes of glass sheet, has long served for the advantage in noise attenuation properties as well as the safety purpose. More research on the improvement of sound insulation performance is needed, considering much of the noise is still transmitted through the glass. As a preliminary study, authors have made several test specimens, varied combinations of glass and interlayer film, to optimize the acoustic performance. Experimental investigation was carried out to study the sound transmission loss of test specimens in the reverberation chamber by using sound intensity method. Several new applications, instead of the existing PVB laminated glass, show better results in sound transmission loss and low temperature have a bad influence on the acoustic performance.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.860-866
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• 2019

The lead element or its salts are good radiation shielding materials. However, their toxic effects are high. Due to less toxicity of bismuth salts, the radiation shielding properties of the bismuth salts have been investigated and compared to that of lead salts to establish them as a better alternative to radiation shielding material to the lead element or its salts. The transmission geometry was utilized to measure the mass attenuation coefficient (${\mu}/{\rho}$) of different salts containing lead and bismuth using a high-resolution HPGe detector and different energies (between 81 and 1333 keV) emitted from point sources of $^{133}Ba$, $^{57}Co$, $^{22}Na$, $^{54}Mn$, $^{137}Cs$, and $^{60}Co$. The experimental ${\mu}/{\rho}$ results are compared with the theoretical values obtained through WinXCOM program. The theoretical calculations are in good agreement with their experimental ones. The radiation protection efficiencies, mean free paths, effective atomic numbers and electron densities for the present compounds were determined. The bismuth fluoride ($BiF_3$) is found to have maximum radiation protection efficiency among the selected salts. The results showed that present salts are more effective for reducing the intensity of gamma photons at low energy region.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.20 no.2
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• pp.119-125
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• 1987

Optical properties of sea water were studied in the Sagami Bay, Japan, based on the data obtained from six oceanographic stations in June, 1985. The observation of surface irradiance and underwater irradiance of sea water for eight kind of wavelengths (378, 422, 481, 513, 570, 621, 653, 677 nm) of sun light was conducted using the underwater irradiameter $(Isigawa\;\#\;SR-8)$. The mean attenuation coefficient of the sea water was appeared to be 0.166 $(0.061\~0.644)$ and the attenuation coefficient of the sea water for wavelength appeared such as 0.121 for 378 nm, 0.105 for 422 nm, 0.097 for 481 nm, 0.099 for 513 nm, 0.138 for 570 nm, 0.253 for 621 nm, 0.258 for 653 nm, 0.253 for 677 nm. The transparency was 12.9 m $(7.2\~18m)$, water color was $(5\~10m)$ in the study area and the sun altitude was $70.79^{\circ}\;(57.44^{\circ}\~78.42^{\circ}C)$ The relationship between attenuation coefficient (K) ana transparency (D) was $K=2.87/D(1.06/D\~5.48/D)$. The rates of light penetration for eight kind of wavelenths (378, 422, 481, 513, 570, 621, 653, 677 nm) were computed with reference to the surface light intensity respectively, The mean rate of light penetration in proportion to depths were $77.93\%\;(52.52\~94.06\%)$ in 1 m layer, $35.46\%\;(4.00\~73.64\%)$ in 5m layer, $18.71\%\;(0.24\~54.23\%)$ in 10m layer and $7.00\%\;(0.007\~27.58\%)$in 20m layer. The rate of light penetration at the transparency layer with reference to the surface light intensity was shown as $13.02\%\;(0.42\~34.78\%)$.