• Journal of Pharmaceutical Investigation
• /
• v.41 no.2
• /
• pp.67-73
• /
• 2011

Ion exchange resins can be one of the good carriers for sustained drug release. However, the sustained release may not be enough only with themselves and hence film coating with rate controlling polymers can be applied to have a further effect on the drug release. Due to the environmental and economic issues of organic solvent for the polymer coating, aqueous polymeric systems were selected to develop dosage forms. Among the many aqueous polymeric dispersions for the film coating, EC (ethylcellulose) based polymers such as Aquacoat$^{(R)}$ ECD and Surelease$^{(R)}$ were evaluated.A fluid-bed coating was applied as a processing method. The drug release rate was quite dependent on the coating level so the release rate could be modified easily by changing different levels of the coating. The drug release rate in the Aquacoat$^{(R)}$ coated resin particles was strongly dependent on curing, which is a thermal treatment to make homogeneous films and circumvent drug release changes during storage. After dissolution test using the compressed tablets in which the coated resin particles are contained, inhomogeneous coating and even pores could be observed showing that the mechanical properties of EC were not resistant to granulation and compaction process. However, when tablets were prepared in different batches, the release profiles were almost identical showing the feasibility of the coated resin particle as incorporated into the tablet formulation.

• Restorative Dentistry and Endodontics
• /
• v.28 no.2
• /
• pp.134-145
• /
• 2003

Mechanical properties and microleakage of two composites [conventional hybrid type DenFil (VERICOM Co., Anyang, Korea) / micro matrix hybrid type Esthet X (Dentsply Caulk, Milford, DE, U.S.A.)] were evaluated to assess whether variable light intensity curing is better than conventional curing technique. Curing was done for 40 seconds in two ways of 2 step soft-start technique and 5 step ramping technique. Three kinds of light intensities of 50, 100, $200{\;}mW/\textrm{cm}^2$ were initially used for 10, 20, 30 seconds each and the maximum intensity of $600 {\;}mW/\textrm{cm}^2$ was used for the rest of curing time in a soft-start curing tech nique. In a ramping technique, curing was done with the same initial intensities and the light intensity was increased 5 times with the same rate to the maximum intensity of $600{\;}mW/\textrm{cm}^2$. After determining conditions that showed no different mechanical properties with conventional technique, Esthet X composite was filled in a class V cavity, which dimension was $4{\times}3{\times}1.5{\;}mm$ and cured under those conditions. Microleakage was evaluated in two ways of dye penetration and maximum gap estimation through SEM observation. ANOVA and Spearman's rho test were used to confirm any statistical significance among groups. The results were as follows : 1 Several curing conditions of variable light intensities resulted in the similar mechanical properties with a conventional continuous curing technique, except conditions that start curing with an initial light intensity of $50{\;}mW/\textrm{cm}^2$. 2. Conventional and ramping techniques were better than soft-start technique in mechanical properties of microhardness and compressive strength. 3. Soft-start group that started curing with an initial light intensity of $100{\;}mW/\textrm{cm}^2$ for 10 seconds showed the least dye penetration. Soft-start group that started curing with an initial light intensity of $200{\;}mW/\textrm{cm}^2$ for 10 seconds showed the smallest marginal gap, if there was no difference among groups. 4. Soft-start technique resulted in better dye-proof margin than conventional technique(p=0.014) and ramping technique(p = 0.002). 5. There was a very low relationship(p=0.157) between the methods of dye penetration and marginal gap determination through SEM evaluation. From the results of this study, it was revealed that ramping technique would be better than conventional technique in mechanical properties, however, soft-start technique might be better than conventional one in microleakage. It was concluded that much endeavor should be made to find out the curing conditions, which have advantages of both aspects or to solve these kinds of problems through a novel idea of polymerization.

• Journal of the Korea Computer Industry Society
• /
• v.3 no.12
• /
• pp.1747-1758
• /
• 2002

In order to study the electrical properties of silicone gel due to the curing condition, AC breakdown test is researched. For experiment, we have made up several samples cured during each 30[Min], 1[H], 2[H] at 100[$^{\circ}C$], 125[$^{\circ}C$], 150[$^{\circ}C$], 160[$^{\circ}C$], 170[$^{\circ}C$], 180[$^{\circ}C$]. The equipment for this test can measure the dipole output voltage to 50[kV], with increasing rate of about 3[kV] per second. A material of electrode using to the breakdown test is a copper(purity : 99%), the gap between electrodes is to 1[mm]~3[mm], and it thickness is 0.2[mm]. As a result of the experiment, the electrical properties of specimen cured at 170[$^{\circ}C$] for 2[H] is superior.

• Design & Manufacturing
• /
• v.17 no.2
• /
• pp.27-32
• /
• 2023

Liquid silicon rubber (LSR) has fine thermal compatibility and is widely used in various fields such as medical care and automobiles because it is easy to implement products with good fluidity. With the recent development of flexible sensors, the focus has been on manufacturing conductive elastomers, such as silicone as elastic materials, and carbon black, CNT, and graphene are mainly used as nanomaterials that impart conductive phases. In this study, mechanical behavior and curing behavior were measured and analyzed to manufacture a CB-LSR complex by adding Carbon Black to LSR and to identify properties. As a result of the compression test, the elastic modulus tended to increase as carbon black was added. When the swelling test and the compression set test were conducted, the swelling rate tended to decrease as the content of carbon black increased, and the compression set tended to increase. In addition, DSC measurements showed that the total amount of reaction heat increased slightly as the carbon black content increased. It is considered that carbon black was involved in the crosslinking of LSR to increase the crosslinking density and have a positive effect on oil resistance reinforcement.

• Journal of Mechanical Science and Technology
• /
• v.19 no.2
• /
• pp.649-654
• /
• 2005

This paper presents fabrication and drive test of a peristaltic PDMS micropump actuated by the thermopneumatic force. The micropump consists of the three peristaltic-type actuator chambers with microheaters on the glass substrate and a microchannel connecting the chambers and the inlet/outlet port. The micropump is fabricated by the spin-coating process, the two-step curing process, the JSR (negative PR) molding process, and etc. The diameter and the thickness of the actuator diaphragm are 2.5 mm and $30{\mu}m$, respectively. The meniscus motion in the capillary tube is observed with a video camera and the flow rate of the micro pump is calculated through the frame analysis of the recorded video data. The maximum flow rate of the micropump is about $0.36\;{\mu}L/sec$ at 2 Hz for the zero hydraulic pressure difference when the 3-phase input voltage is 20 V.

• The Journal of the Korean dental association
• /
• v.12 no.1
• /
• pp.37-42
• /
• 1974

To ascertain if the ultrasonic cleaning technique caused any dimensional changes in heat and cold curing and fluid resin denture bases and in addition to evaluate the dimensional changes of the resin denture bases stored in water and air, the author measured the distance between the outsides of two pins embedded in methyl methacrylate test denture bases by mean of 12 inch vernier caliper, accurate to 0.02mm. The results were as follows; (1) Ultrasonic cleaning didn't cause any permanent dimensional changes, but only affected temporary dimensional expansion in 16 test denture bases. (2) Temporary expansion rate caused by 10 minutes' ultrasonic cleaning was 0.29% and at the maximal temperature of the cleaning solution it was 0.64%. (3) The half of the denture bases stored in water showed the dimensional expansion rate of 0.47% while the others stored in air showed the dimensional shrinkage rate of 0.15% after 4 months.

• KIEAE Journal
• /
• v.7 no.4
• /
• pp.127-133
• /
• 2007

As a fundamental study on the corrosion resistance of reinforced concrete structures using Natural Inorganic Minerals exposed to carbonation environment, The test specimens were concrete(W/C=60%) with Natural Inorganic Minerals content of 0%, 10%. Accelerated carbonation and autoclave corrosion accelerated curing were then conducted with them. The corrosion resistance of steel in concrete with Natural Inorganic Minerals content of 0%, 10% was examined by corrosion form, half-cell potential, polarization resistance, corrosion area and weight loss after 24 hours of autoclave corrosion accelerated curing.The results of the study showed that as for steel in concrete with Natural Inorganic Minerals content of 10%, the corrosion resistance was more excellent than steel in concrete with Natural Inorganic Minerals content of 0%.

• Korean Journal of Materials Research
• /
• v.21 no.12
• /
• pp.650-654
• /
• 2011

In this paper, the effects of conventional and newly developed elastomer modified underfill materials on the mechanical shock reliability of BGA board assembly were studied for application in mobile electronics. The mechanical shock reliability was evaluated through a three point dynamic bending test proposed by Motorola. The thermal properties of the underfills were measured by a DSC machine. Through the DSC results, the curing condition of the underfills was selected. Two types of underfills showed similar curing behavior. During the dynamic bending reliability test, the strain of the PCB was step increased from 0.2% to 1.5% until the failure circuit was detected at a 50 kHz sampling rate. The dynamic bending reliability of BGA board assembly using elastomer modified underfill was found to be superior to that of conventional underfill. From mechanical and microstructure analyses, the disturbance of crack propagation by the presence of submicron elastomer particles was considered to be mainly responsible for that result rather than the shear strength or elastic modulus of underfill joint.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.43 no.4
• /
• pp.97-105
• /
• 2001

The ultrasonic pulse velocity test has a strong potential to be developed into a very useful and relatively inexpensive in-place test for assuring the quality of concrete placed in structure. The main problem in realizing this potential is that the relationship between compressive strength ad ultrasonic pulse velocity is uncertain and concrete is an inherently variable material. The objective of this study is to improve the reliability of in-place concrete strength predictions by ultrasonic pulse velocity method. Experimental cement content, s/a rate, and curing condition of concrete. Accuracy of the prediction expressed in empirical formula are examined by multiple regression analysis and linear regression analysis and practical equation for estimation the concrete strength are proposed. Multiple regression model uses water-cement ratio cement content s/a rate, and pulse velocity as dependent variables and the compressive strength as an independent variable. Also linear regression model is used to only pulse velocity as dependent variables. Comparing the results of the analysis the proposed equation expressed highest reliability than other previous proposed equations.

• The Research Journal of the Costume Culture
• /
• v.12 no.1
• /
• pp.1-11
• /
• 2004

This study was carried out on the process of natural dye substances which can flock ultraviolet rays without producing harmful substances by pollution, germs, etc. While making human body safe in contact, extracting Gardenia, Sappan wood, Radix scutellariae, Cromwell, Mugwort, Gallnut, Lac. Those are used for curing diseases, dyeing silk cloth with those extracts, and examining the color fastness, Ultraviolet protection. From this study, the following conclusion was produced. Brightness was lower in pre-mordanting than in post. And color difference showed that Radix scutellariae was the highest. Aluminum-mordanting showed a higher color difference than Fe. Colorfastness to washing was high in all samples, and the degree of color-changing by washing was the highest in the sample dyed by gardenia, pre-mordanted gallnut showed the highest degree. Colorfastness to perspiration was the highest in gardenia. UV-A test showed that all samples a high rate of 85% or higher compared with test white cloth. Especially, post-mordanted radix scutellariae, pre-mordanted gallnut and post-mordanted sappanwood showed a superior blocking rate.