• Macromolecular Research
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• v.11 no.5
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• pp.375-381
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• 2003

Silver salt complex membranes with glassy poly(methyl methacrylate) (PMMA) unexpectedly showed higher propylene permeance than those with rubbery poly(butyl methacrylate) (PBMA) where as neat PMMA is much less permeable to propylene than that of neat PBMA. Such unusual facilitated olefin transport has been systematically investigated by changing the side chain length of polymethacrylates (PMAs) from methyl, ethyl to butyl. The ab initio calculation showed almost the same electron densities of the carbonyl oxygens in the three PMAs, expecting very similar intensity of the interaction between carbonyl oxygen and silver ion. However, the interaction intensity decreases with the length of the alkyl side chain: PMMA > PEMA > PBMA according to wide angle X-ray scattering and FT-Raman spectroscopy. The difference in the interaction intensity may arise from the difference in the hydrophilicity of the three PMAs, as confirmed by the contact angle of water, which determines the concentrations of the ionic constituents of silver salts: free ion, contact ion pair and higher order ionic aggregate. However, propylene solubilities and facilitated propylene transport vary with the side chain length significantly even at the same concentration of the free ion, the most active olefin carrier, suggesting possible difference in the prohibition of the molecular access of propylene to silver ion by the side chains: the steric hindrance. Therefore, it may be concluded that both the hydrophilicity and the steric hindrance associated with the side chain length in the three PMAs are of pivotal importance in determining facilitated olefin transport through polymer/silver salt complex membranes.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.382-382
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• 2010

$TaO_2$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility in achieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFETchannel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. The atomic structure of amorphous and crystalline Tantalum oxide ($TaO_2$) gate dielectrics thin film on Si (100) were grown by utilizing atomic layer deposition method was examined using Ta-K edge x-ray absorption spectroscopy. By using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy (REELS) the electronic and optical properties was obtained. In this study, the band gap (3.400.1 eV) and the optical properties of $TaO_2$ thin films were obtained from the experimental inelastic scattering cross section of reflection electron energy loss spectroscopy (REELS) spectra. EXAFS spectra show that the ordered bonding of Ta-Ta for c-$TaO_2$ which is not for c-$TaO_2$ thin film. The optical properties' e.g., index refractive (n), extinction coefficient (k) and dielectric function ($\varepsilon$) were obtained from REELS spectra by using QUEELS-$\varepsilon$(k, $\omega$)-REELS software shows good agreement with other results. The energy-dependent behaviors of reflection, absorption or transparency in $TaO_2$ thin films also have been determined from the optical properties.

• Archives of Pharmacal Research
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• v.18 no.2
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• pp.84-89
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• 1995

The complexation and physical characteristics of egg phosphatidylcholine (PC) liposome containing amphotericin B(AmB) were investigated through circular dichrosim(CD) spectra, the size distribution, the turbidity change, and the calcein release. CD spectra of AmB-containing egg PC mxture exhibited a positive peak around 330 nm indicative of complexation of AmB and four negative peaks. The positive peak increased up to $2.2{\;}millidegree/{\mu}g$ AmB as AmB contents increased up to 12% (w/w), suggesting that AmB-phospholipid complexation was promoted by the antibiotics. The effective diameter of liposomesa by dynamic light scattering decreased from 450 nm to 220 nm as the amount of AmB in liposomes increased from o to 30% (w/w). The complexation may be responsible for the reduction in size. On the other hand, at around 1 mN deoxycholate (DOC), the reltive turbidities of 5 and 10% (w/w) AmB-containing liposome suspension were less than 1 probably due to the soblubilization of the complex, while those of pure PC liposome suspension were larger than 1 at the same concentration. Deoxycholate-induced release of liposomes, indicating the intercalation of the drug into the bilayers. Therefore, it is concluded that in AmB/eggPC/water system, AmB-phospholipid complexcoexists with AmB-containing liposomes.

• Progress in Medical Physics
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• v.31 no.3
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• pp.54-62
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• 2020

Dose calculation algorithms play an important role in radiation therapy and are even the basis for optimizing treatment plans, an important feature in the development of complex treatment technologies such as intensity-modulated radiation therapy. We reviewed the past and current status of dose calculation algorithms used in the treatment planning system for radiation therapy. The radiation-calculating dose calculation algorithm can be broadly classified into three main groups based on the mechanisms used: (1) factor-based, (2) model-based, and (3) principle-based. Factor-based algorithms are a type of empirical dose calculation that interpolates or extrapolates the dose in some basic measurements. Model-based algorithms, represented by the pencil beam convolution, analytical anisotropic, and collapse cone convolution algorithms, use a simplified physical process by using a convolution equation that convolutes the primary photon energy fluence with a kernel. Model-based algorithms allowing side scattering when beams are transmitted to the heterogeneous media provide more precise dose calculation results than correction-based algorithms. Principle-based algorithms, represented by Monte Carlo dose calculations, simulate all real physical processes involving beam particles during transportation; therefore, dose calculations are accurate but time consuming. For approximately 70 years, through the development of dose calculation algorithms and computing technology, the accuracy of dose calculation seems close to our clinical needs. Next-generation dose calculation algorithms are expected to include biologically equivalent doses or biologically effective doses, and doctors expect to be able to use them to improve the quality of treatment in the near future.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.2
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• pp.96-104
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• 2000

By using the offshore type submersible platform, Artificial sea floor anchored at a depth of forty meters several experimental studies have been conducted successfully during 1996. The facility consists of an artificial sea floor that floats at 7 meters below the surface, a machinery hut that projects above the surface at the center of the structure and a balance weight beneath the structure. The facility can be surfaced easily by using a water discharging pump in the water tank which is located at the center of it. To find out the behavioral character and the gathering factor of fishes around the artificial sea floor, investigations were carried out during the daytime and nighttime by direct observation and by echo-sounder. Around the testing reefs and artificial sea floor, six kinds of fishes were found by diving observation and the dominants were Scomber japonicus, Sebastes thompsoni and Oplegnathus fascitus. As Scomber japonicus was distributed around the artificial sea floor in dense small school, they were not seen elsewhere in the survey area. The artificial sea floor was concluded to act as a schooling ground far Scomber japonicus, Sebastes thompsoni and Oplegnathus fascitus. were close to the testing reefs(within 10m) in the daytime, and were thought to settle on the testing reefs at nighttime, To examine the distribution of 7shes around the artificial sea floor, an acoustic survey over a 1$\times$1km area, 0-50m in depth during the all day. Around the artificial sea floor many thin scattering fish echo(TS-54.5~ -51.5dB) and dense fish echo(TS-41~-38dB) were mainly distributed. Many scattering fish echoes, which were thought to be a mixture of small squid, pelegic crustacea and ethers, were distributed over the whole survey area. A dense fish school stayed beneath the artificial sea floor for a short duration. These phenomena were concluded to show an attraction and detention function of the artificial sea floor.

• Progress in Medical Physics
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• v.20 no.2
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• pp.51-61
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• 2009

A Compton camera, which is based on the geometrical interpretation of Compton scattering, is a very promising gamma-ray imaging device considering its several advantages over the conventional gamma-ray imaging devices: high imaging sensitivity, 3-D imaging capability from a fixed position, multi-tracing functionality, and almost no limitation in photon energy. In the present study, a Monte Carlo-based, user-friendly Compton imaging simulator was developed in the form of a graphical user interface (GUI) based on Geant4 and $MATLAB^{TM}$. The simulator was tested against the experimental result of the double-scattering Compton camera, which is under development at Hanyang University in Korea. The imaging resolution of the simulated Compton image well agreed with that of the measured image. The imaging sensitivity of the measured data was 2~3 times higher than that of the simulated data, which is due to the fact that the measured data contains the random coincidence events. The performance of a stacking-structure type Compton camera was evaluated by using the simulator. The result shows that the Compton camera shows its highest performance when it uses 4 layers of scatterer detectors.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.478-485
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• 2014

This study is to form the self assembly of cubic crystalline phase to penetrate into the skin epidermis. The various performance synthesized diglyceryl phytylacetate (DGPA) having hydroxyl group (-OH) and 4 methyl chains with phytyl group was carried out as an amphoteric lipid such as emulsifying power, self assembly. Emulsifying activity of DGPA was very stabilized on only 1% of small content, it could make a W/O emulsion containing high internal phase incorporated with water. Cubic liquid crystal structure with DGPA on three-phase diagram was formed, when mixed DGPA, dimethicone (2CS), and water. Through three-phase diagram forming the cubic liquid crystal area, hexagonal structure zone, and mixing water phase and hexagonal structure area, reversed micelle area were respectively certified. Its structure was proved by the SAXS (small angled x-ray scattering) analysis. As an application, formation of cubosome containing 10% of magnesium ascorbylphosphate and 5% of pyridoxine tris-hexyldecanoate was encapsulated. Occlusive effect of cubosome had above 1.7 times better than reversed micelle. From using poloxamer of dispersing agent, phase structure recovered from W/O emulsion to cubic liquid crystal phase when storage in $33^{\circ}C$ incubator. Therefore, our this study is expected to be as epidermal-dermal skin absorbers in skin care cosmetics and pharmaceuticals industries as raw materials to form a cubic crystal phase through a more in-depth research to DGPA having amphoteric lipid property.

• Korean Journal of Remote Sensing
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• v.38 no.3
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• pp.283-298
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• 2022

As Synthetic Aperture Radar (SAR) image can be acquired regardless of the weather and day or night, it is highly recommended to be used for Automatic Target Recognition (ATR) in the fields of surveillance, reconnaissance, and national security. However, there are some limitations in terms of cost and operation to build various and vast amounts of target images for the SAR-ATR system. Recently, interest in the development of an ATR system based on simulated SAR images using a target model is increasing. Attributed Scattering Center (ASC) matching and template matching mainly used in SAR-ATR are applied to target classification. The method based on ASC matching was developed by World View Vector (WVV) feature reconstruction and Weighted Bipartite Graph Matching (WBGM). The template matching was carried out by calculating the correlation coefficient between two simulated images reconstructed with adjacent points to each other. For the performance analysis of the two proposed methods, the Synthetic and Measured Paired Labeled Experiment (SAMPLE) dataset was used, which has been recently published by the U.S. Defense Advanced Research Projects Agency (DARPA). We conducted experiments under standard operating conditions, partial target occlusion, and random occlusion. The performance of the ASC matching is generally superior to that of the template matching. Under the standard operating condition, the average recognition rate of the ASC matching is 85.1%, and the rate of the template matching is 74.4%. Also, the ASC matching has less performance variation across 10 targets. The ASC matching performed about 10% higher than the template matching according to the amount of target partial occlusion, and even with 60% random occlusion, the recognition rate was 73.4%.

• Journal of Pharmaceutical Investigation
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• v.41 no.2
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• pp.103-109
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• 2011

The objective of the study was to prepare self-microeulsifying drug delivery system (SMEDDS) incorporating atorvastatin calcium and evaluate its properties and oral bioavailability. Solubility of atorvastatin in various vehicles was determined. Pseudo-ternary phase diagrams were constructed to identify the good self-emulsification region. The droplet size distributions of the resultant emulsions were determined by dynamic light scattering measurement. The mean droplet size of chosen formulation (20% ethyl oleate, 40% tween-80, 40% Carbitol$^{(R)}$) was $23.4{\pm}1.3$ nm. The SMEDDS incorporating atorvastatin calcium appeared to be associated with better performance in dissolution and pharmacokinetic studies, compared with raw atorvastatin calcium. In dissolution test, the release percentage of atorvastatin from SMEDDS mixture could rapidly reach more than 95% within 3 min. Oral $AUC_{0{\rightarrow}8hr}$ values in SD rats was $1994{\pm}335\;ng{\cdot}hr/mL$, which significantly increased (P<0.05) compared with raw atorvastatin calcium. The SMEDDS formulation was relatively stable when stored at $4^{\circ}C$ during 3 months. Our studies illustrated the potential use of SMEDDS for the delivery of hydrophobic compounds, such as atorvastatin, by the oral route.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.258-262
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• 2016

The effect of zirconium dioxide ($ZrO_2$) on the properties of color conversion glasses was examined in the $BaO-ZnO-B_2O_3-SiO_2$ system. The difference in refractive index between glass and phosphor affect the optical properties of the color conversion glass because of light scattering. Reducing the difference in refractive index is a method to improve the luminous efficacy of color conversion glasses. As a reference, a type of glass that contains 25 mol% of each component was used. To increase the refractive index of the glass samples, the BaO content was increased from 25 to 40 mol%, and $ZrO_2$ was added at levels of 1, 3, and 5 mol%. Color conversion glasses were prepared by sintering a mixture of glass and 5 wt% $YAG:Ce^{3+}$ phosphor. As a result, the refractive index of the glass was found to be dependent on the BaO and $ZrO_2$ contents in the BaO-ZnO-$B_2O_3-SiO_2$ system. As the BaO and $ZrO_2$ contents were increased, the luminous efficacy of the color conversion glass was improved because the refractive index difference between the glass and the $YAG:Ce^{3+}$ phosphor decreased.