• Applied Microscopy
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• v.29 no.4
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• pp.471-477
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• 1999

Microstructural observations on the pyrochlore-type $Lu_2Ti_2O_7$ and the similar type of compounds, $In_2(Ti_{1.7}Zn_{0.3})O_{6.7}$ and $In_2(Ti_{1.7}Mg_{0.3})O_{6.7}$ which were made by the isothermal heat-treatment at 1623K for 18 days in Pt tube, were carried out using a top-entry HRTEM working at 200 kV. The modulated structures were found in both compounds, however, not in $Lu_2Ti_2O_7$. From the electron diffraction pattern analysis, the modulated superlattices are incommensurate and are 2.69 times of sublattices along (220) direction. The high resolution TEM images have shown that the superlattices consist of alternate superlattices which are composed of two or three sublattices, resulting in the average of 2.7 times of sublattices in accordance with the analysis of electron diffraction patterns. The crystal structures of both compounds are found to quite similar to those of pyrochlore, however the evidence that the cubic axes are slightly deviated from right angle. The modulated structure has gradually changed to the unmodulated structure induced by electron irradiation.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.3
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• pp.549-554
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• 1998

The prevalence of the supernumerary tooth is $1{\sim}4%$. It usually occurs in the permanent dentition. It frequently occurs in the maxillary mid palatal area. The presence of the supernumerary tooth causes the following problems ; (1) interfering the eruption of successional tooth, (2) displacing the neighboring teeth, (3) resulting large diastema, (4) forming cystic change. So the supernumerary tooth should be removed as soon as possible. To extract the supernumerary tooth, the exact position must be noticed first. Radiographic techniques that were used in the past are tube shift technique, right angle technique, sterioradiography, using radiopaque contrast media and conventional tomography. But these methods include the subjective opinion of the operator. So, a technique eliminating the operator's opinion and showing the position 3-dimentionally can be used. 3-dimentional computed tomography equipped with dental softwares can show the position of the impacted supernumerally tooth in 3-dimentional position. It has an advantage to eliminate the subjective opinion of the operator. With a fast computer this techenique is done in a relatively short period of time. The rationale of this methods is relatively simple. After tacking X-ray and reconstructing the data 3-dimentionally, sequential removal of the soft tissue and hard tissue(bone) CT number leaves the teeth alone in 3-dimentional position. The image can be seen from anywhere, so the operator can see the image in front, rear, upper, and lower positions. In both cases 1 and 2, the position of the impacted supernumerary tooth is viewed by the 3-dimensional computed tomography. And it made the operator easy to figureout the exact position.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.5-5
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• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.

• Journal of the Korean Society of Radiology
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• v.6 no.4
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• pp.281-290
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• 2012

The difference of radiation dose of MDCT due to different protocols between hospitals was analyzed by CTDI, DLP, the number of Slice and the number of DLP/Slice in 30 cases of the head, the abdomen and the chest that have 10 cases each from MDCT examination of the department of diagnostic imaging of three general hospitals in Gyeongsangbuk-do. The difference of image quality, CTDI, DLP, radiation dose in the eye and radiation dose in thyroid was analyzed after both helical scan and normal scan for head CT were performed because a protocol of head CT is relatively simple and head CT is the most frequent case. Head CT was significantly higher in two-thirds of hospitals compared to A hospital that does not exceed a CTDI diagnostic reference level (IAEA 50mGy, Korea 60mGy) (p<0.001). DLP was higher in one-third of hospitals than a diagnostic reference level of IAEA 1,050mGy.cm and Korea 1,000mGy.cm and two-thirds exceeded the recommendation of Korea and those were significantly higher than A hospital that does not exceed a diagnostic reference level (p<0.001). Abdomen CT showed 119mGy that was higher than a diagnostic reference level of IAEA 25mGy and Korea 20mGy in one-third. DLP in all hospitals was higher that Korea recommendation of 700mGy.cm. Among target hospitals, C hospital showed high radiation dose in all tests because MPR and 3D were of great importance due to low pitch and high Tube Curren. To analyze the difference of radiation dose by scan methods, normal scan and helical scan for head CT of the same patient were performed. In the result, CTDI and DLP of helical CT were higher 63.4% and 93.7% than normal scan (p<0.05, p<0.01). However, normal scan of radiation dose in thyroid was higher 87.26% (p<0.01). Beam of helical CT looked like a bell in the deep part and the marginal part so thyroid was exposed with low radiation dose deviated from central beam. In addition, helical scan used Gantry angle perpendicularly and normal scan used it parallel to the orbitomeatal line. Therefore, radiation dose in thyroid decreased in helical scan. However, a protocol in this study showed higher radiation dose than diagnostic reference level of KFDA. To obey the recommendation of KFDA, low Tube Curren and high pitch were demanded. In this study, the difference of image quality between normal scan and helical scan was not significant. Therefore, a standardized protocol of normal scan was generally used and protective gear for thyroid was needed except a special case. We studied a part of CT cases in the local area. Therefore, the result could not represent the entire cases. However, we confirmed that patient's radiation dose in some cases exceeded the recommendation and the deviation between hospitals was observed. To improve this issue, doctors of diagnostic imaging or technologists of radiology should perform CT by the optimized protocol to decrease a level of CT radiation and also reveal radiation dose for the right to know of patients. However, they had little understanding of the situation. Therefore, the effort of relevant agencies with education program for CT radiation dose, release of radiation dose from CT examination and addition of radiation dose control and open CT contents into evaluation for hospital services and certification, and also the effort of health professionals with the best protocol to realize optimized CT examination.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.25-28
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• 2012

Purpose : It is important to reduce radiation dose associated with computed tomography (CT) scanning to as low as reasonably achievable (ALARA). With Dose Modulation Technic, user select a desired image quality and the system adapts tube current to obtain the desired image quality with greater radiation dose efficiency. In this paper, we presents a comprehensive description of fundamentals, clinical applications and radiation dose benefits of Dose Modulation Technic depending on Body Mass Index(BMI). Materials and Methods : In this study, 149 patients were examined(The mean age : $58{\pm}12.4$ years old). Biograph True Point 40 (Siemens, USA) and Gemini TF 64 (Philips. Cleveland) were used for equipment. When we used Care Dose 4D (Siemens, USA) and D-dom (Philips, Cleveland), we measured dose reduction and Computed Tomography Dose Index (CTDI) depending on BMI. Then we analyze data using SPSS Ver.18. Results : When we used Care Dose 4D, p-value is considered statistically significant by groups with the result that we compared Care Dose 4D with D-dom. On the other hand, p-value isn't considered statistically significant by groups using D-dom. Conclusion : Dose modulation based on the projection angle didn't affect degree of obesity. And When using Care Dose 4D, dose reduction rate in the normal patients were higher than the obese. In this study, there are errors on somato type. So I think more research have to be done. Then application of Dose Modulation technic can help in maintaining acceptable image quality while reducing radiation dose by 20-60% in most instances.

• Journal of Chest Surgery
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• v.43 no.2
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• pp.139-143
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• 2010

Background: Thoracic empyema remains a serious problem despite the availability of modern diagnostic methods and appropriate antibiotics. The condition presents in many different forms and stages that require different therapeutic options. Video-assisted thoracic surgery (VATS) has become increasingly popular for use in the treatment of empyema. Material and Method: From January 2005 to May 2009, VATS was performed in 36 patients with pleural empyema and for whom chest-tube drainage and antibiotic therapy had failed or the CT scan showed multiseptate disease. The perioperative clinical factors were analyzed for all the study patients. Result: All the patients underwent VATS, but it was necessary to convert to thoracotomy in one patient. The mean operation time was $90{\pm}38.5\;min$. For the operative evaluation, 11 patients were compatible with ATS stage III. The duration of chesttube insertion was $11.9{\pm}5.8$ (3~24) days. One patient did not improve and therefore this patient underwent additional open drainage. At discharge, costophrenic angle blunting was observed in 22 patients, pleural thickening was noted in 20 patients, both were noted in 17 patients and neither was noted in 11 patients. However, at follow-up, each of these changes was observed in 9, 7, 4 and 24 patients, respectively. All except one patient showed radiographic improvement. Conclusion: VATS is suitable for the treatment of early and fibrinopurulent thoracic empyema, and even in selected patients with stage III disease.