• Korean Chemical Engineering Research
• /
• 제54권4호
• /
• pp.459-464
• /
• 2016

In this study, the electrochemical characteristics of porous silicon/carbon composite anode were investigated to improve the cycle stability and rate performance in lithium ion batteries. In this study, the effect of TEOS and $NH_3$ concentration, mixing speed and temperature on particle size of nano silica was investigated using $St{\ddot{o}}ber$ method. Nano porous Si/C composites were prepared by the fabrication processes including the synthesis of nano $SiO_2$, magnesiothermic reduction of nano $SiO_2$ to obtain nano porous Si by HCl etching, and carbonization of phenolic resin. Also the electrochemical performances of nano porous Si/C composites as the anode were performed by constant current charge/discharge test, cyclic voltammetry and impedance tests in the electrolyte of $LiPF_6$ dissolved inorganic solvents (EC:DMC:EMC=1:1:1vol%). It is found that the coin cell using nano porous Si/C composite has the capacity of 2,006 mAh/g and the capacity retention ratio was 55.4% after 40 cycle.

• KSBB Journal
• /
• 제19권3호
• /
• pp.178-186
• /
• 2004

The aim of this study was to investigate the skin-whitening effect of okyong-san and to develop new drug delivery carrier The extracts of okyong-san were found to have the whitening effect and Eudragit$\^$ⓡ/ L 100-55 (EUD) coated solid lipid nanoparticle (E-SLN) was prepared by solvent evaporation method and melt dispersion technique. As a result, E-SLN have a 144-170 nm of particle size, spherical shape, and 33-41% encapsulation efficiency, After release test in vitro, release profile of E-SLN depended on pH and temperature. Lastly, closed patch test and skin-whitening test was peformed clinically. In conclusion, test sample had non-stimulation and high % whiteness. The results suggest that okyong-san and E-SLN is useful as cosmeceuticals for whitening cosmetics.

• Journal of the Korean Recycled Construction Resources Institute
• /
• 제2권1호
• /
• pp.46-51
• /
• 2014

In this study, strength development properties of high volume fly ash concrete was evaluated through compressive strength of concrete with reduction of unit water content. And concrete specimens were prepared according to target strength 3 level and variation of unit water content. As a result, the improved fluidity were obtained as a result of the ball bearing action of the spherical, the electrostatic repulsion and the particle size distribution of fly ash particles in case of using more than 50% fly ash. Through this, the mixture of fly ash has been shown to reduce the amount of water required in concrete. Also, the early strength of high volume fly ash concrete with reduction of unit water content was improved more about 66% than general concrete mixture.

• Water for future
• /
• 제27권1호
• /
• pp.123-131
• /
• 1994

A plunge pool is often employed as an energy-dissipating device at the end of a spillway or a pipe culvert. A jet from spillways or pipes frequently generates a scour hole which threatens the stability of the hydraulic structure. Existing scour prediction formulas of plunge pool of spillways or pipe culverts give a wide range of scour depths, and it is, therefore, difficult to accurately predict those scour depths. In this study, a new experimental method and new scour prediction formulas under submerged circular jet for large bed materials with shallow tailwater depths were developed. A major variale, which was not used in previous scour prediction equations, was the ratio of jet size to bed material size. In this study, jet momentum acting on a bed particle and jet diffustion theory were employed to derive scour prediction formulas. Four theoretical formulas were suggested for the two regions of jet diffusion, i.e., the region of flow establishment and the region of established flow. The semi-theoretically developed scour prediction formulas showed close agreement with laboratory experiments performed on a movable bed made of large spherical particles.

• Journal of Powder Materials
• /
• 제24권5호
• /
• pp.364-369
• /
• 2017

Ceramic powder, such as MgO, is added as a binder to prepare the green compacts of molten salts of an electrolyte for a thermal battery. Despite the addition of a binder, when the thickness of the electrolyte decreases to improve the battery performance, the problem with the unintentional short circuit between the anode and cathode still remains. To improve the current powder molding method, a new type of electrolyte separator with porous MgO preforms is prepared and characteristics of the thermal battery are evaluated. A Spherical PMMA polymer powder is added as a pore-forming agent in the MgO powder, and an organic binder is used to prepare slurry appropriate for tape casting. A porous MgO preform with $300{\mu}m$ thickness is prepared through a binder burnout and sintering process. The particle size of the starting MgO powder has an effect, not on the porosity of the porous MgO preform, but on the battery characteristics. The porosity of the porous MgO preforms is controlled from 60 to 75% using a pore-forming agent. The batteries prepared using various porosities of preforms show a performance equal to or higher than that of the pellet-shaped battery prepared by the conventional powder molding method.

• Journal of Pharmaceutical Investigation
• /
• 제24권3호
• /
• pp.145-153
• /
• 1994

Ibuprofen is an effective non-steroidal anti-inflammatory drug (NSAID), but it has several limitations in clinical application because of low solubility in water and gastrointestinal irritation. A water-soluble salt of ibuprofen, ibuprofen Iysinate, has been synthesized to overcome these shortcomings, and it was formulated as suppository for rectal administration. Witepsol and polyethylene glycols were employed as suppository bases for either ibuprofen or ibuprofen Iysinate, in order to compare the bioavailability in rabbits. The plasma concentrations of ibuprofen were assayed by HPLC after a rectal administration of ibuprofen and ibuprofen Iysinate, respectively. In addition to the comparison of two suppository bases, the other factors which affect on rectal absorption were also evaluated, especially in the point of not only particle size and shape of ibuprofen Iysinate but also effects of additives such as stearic acid, cetyl alcohol and capric acid. And pharmacokinetic parameters such as AUC, $C_{max}$, and $T_{max}$ were also compared. In conclusion, spray-dried ibuprofen Iysinate which was polyporous and spherical shape gave an increased absorption from the rectal formulations with Witepsol Hl5 and stearic acid.

• Journal of Pharmacopuncture
• /
• 제23권1호
• /
• pp.30-36
• /
• 2020

Objectives: The objective of the study was to prepare Bauhinia variegata loaded nanoemulsion(formulation and determine the efficacy of herbal drug formulation against diabetic peripheral neuropathic pain through acupuncture technique. Methods: Nine different ba tches of nanoemulsion (NE1 NE9) of BVN was prepared by varying the S_mix ratio and the concentration of oil. BVN was characterized to determine particle size, shape, zeta potential, polydispersity index, optical transmittance, drug release profile and stora ge stability. The optimized formulation was subjected to plantar test, behavioral tests of neuropathic pain and Von Frey filament stimulation test. Diabetes was induced by intraperitoneal injection of freshly prepared solution of Streptozotocin (60 mg/kg) to the experimental rats. Animals were made diabetic divided into four groups, Group I was untreated normal control group, Group II was diabetic control group, Group III was Bauhinia variegata extract ( treated group (100 mg/kg/day, p.o) and Group IV was BVN treated groups (100 mg/kg/day, p.o) acute and chronically. Results: The prepared B. variegata loaded nanoemulsion was nanosized (124 nm), spherical, uniform and stable over the period of 180 days with no change in physiochemical properties. The bl ood glucose and body weight of animals was normalizing after four weeks of treatment that was significant with BVN in comparison to diabetic control group. The chronic administration of BVN significantly (P<0.001) decreased hind paw withdrawal latency an d attenuated mechanical allodynia as compared with diabetic rats. Conclusion: Thus, BVN may be an effective drug formulation against diabetic peripheral neuropathic pain.

• Journal of Microbiology and Biotechnology
• /
• 제15권2호
• /
• pp.254-258
• /
• 2005

We have conducted in vitro reconstitution study of ferritin from its subunits FerH and FerL. For the reconstitution, FerH was produced from an expression vector construct in Escherichia coli and was purified from a heat treated cell extract by using one-step column chromatography. FerL was expressed as inclusion bodies. The denatured form of FerL was obtained by a simple washing step of the inclusion bodies with 3 M urea. The reconstitution experiment was conducted with various molar ratios of urea-denatured FerH and FerL to make the ferritin nanoparticle with a controlled composition of FerH and FerL. SDS-PAGE analysis of the reconstituted ferritins revealed that the reconstitution required the presence of more than 40 molar$\%$ of FerH in the reconstitution mixture. The assembly of the subunits into the ferritin nanoparticle was confmned by the presence of spherical particles with diameter of 10 nm by the atomic force microscopic image. Further analysis of the particles by using a transmission electron microscope revealed that the reconstituted particles exhibited different percentages of population with dense iron core. The reconstituted ferritin nanoparticles made with molar ratios of [FerH]/[FerL]=l00/0 and 60/40 showed that 80 to $90\%$ of the particles were apoferritin, devoid of iron core. On the contrary, all the particles formed with [FerH]/[FerL]=85/ 15 were found to contain the iron core. This suggests that although FerH can uptake iron, a minor portion of FerL, not exceeding $40\%$ at most, is required to deposit iron inside the particle.

• Explosives and Blasting
• /
• 제22권4호
• /
• pp.7-15
• /
• 2004

An explosion modeling technique was developed by using the spherical discrete element code, PFC3D, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a PFC3D particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). According to this concept, the explosion pressure is applied to the wall particles by the scheme of radius expansion/contraction of inner-hole particles. The output wall force is compared to the input hole pressure in every time step, and a correction routine is activated to control the radius multiplier of the inner-hole particles. A comparative blast simulation far a cement mortar block of $80\times90\times80mm$ was conducted by using the conventional explosion modeling method and the new one. The results of the simulation are presented in a qualitative fashion.

• Korean Chemical Engineering Research
• /
• 제46권6호
• /
• pp.1069-1074
• /
• 2008

In this work, we made a study for the 3D SAM formation of octanethiol, decanethiol, and dodecanethiol on copper nanoparticles and we verified stability of the copper particle depending on the ratio of dodecanethiol to copper. The reaction was performed in a one-phase system under nitrogen atmosphere and the thiolated copper particles could be obtained by centrifugation. We could confirm that the nanoparticles consisted of a spherical shape of 3~6 nm from TEM images. FT-IR, XPS and TGA results showed that alkanethiols were chemisorbed via thiol group and the packing density of the alkanethiols on copper surface increased with the alkyl chain lengths. XRD patterns gave us useful information about superlattice formations. Finally, $Cu_2O$ was formed when the molar ratio of dodecanethiol to copper is less than unity and copper nanoparticles formed more compact 3D SAMs when the molar ratio of dodecanethiol to copper was 1.25.