• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.9
• /
• pp.1209-1215
• /
• 2010

The effects of multi-walled carbon nanotube (MWCNT) content, carbon black (CB) content, atmospheric-pressure flame plasma (APFP) treatment, and acid treatment on the mechanical properties of elastomeric composites were investigated. For pure or filled rubbers with the given amount of CB (20 and 40 phr), the tensile strength and modulus of the elastomeric composites increase similarly with the MWCNT content. A composite with APFP-treated MWCNTs shows a hardening effect (high strength, high modulus, and high ductility) unlike the one with untreated MWCNTs. On the other hand, a composite with APFP-treated CB shows a softening effect (high strength, low modulus, and high ductility), which is unlike a composite with untreated CB. As the refluxing time increases from 1 h to 2 h and the sulfuric acid concentration increases from 60% to 90%, the tensile strength and modulus of a composite decrease. Thus, it is found that the MWCNT content, CB content, APFP treatment, sulfuric acid concentration, and refluxing time have an important effect on the mechanical properties of NBR composites.

• Korean Chemical Engineering Research
• /
• v.47 no.1
• /
• pp.31-37
• /
• 2009

A zwitterionic surfactant shows not only detergency but also mildness effect since it shows characteristics of a nonionic or an anionic surfactant above an isoelectric point, while showing characteristics of a cationic surfactant below an isoelectric point. Therefore, a zwitterionic surfactant can serve as a dual function surfactant by a single molecule through the interconversion of cleaning and softening effects depending on pH variations of the aqueous solution. In this study, physical properties of betaine surfactant such as CMC, surface tension, interfacial tension, contact angle and viscosity were measured and phase behavior study was performed. Also dual function characteristics of betaine zwitterionic surfactant were investigated by measuring an isoelectric point using QCM(quartz crystal microbalance) and zeta potential measurement. The CMC of betaine surfactant was near $10^{-4}mol/L$ and the surface tension at CMC was about 32 mN/m. The interfacial tension between 1 wt% aqueous solution and n-decane measured by spinning drop tensiometer at pH 2~10 resulted in an increase in interfacial tension until pH 5 and a decrease with pH after 5 and equilibration time showed the similar trend with an increase in pH. The isoelectric point of betaine surfactant measured by QCM experiment was found to exist between 3.0 and 3.3, which is the same as the result determined by zeta potential measurement.

• Journal of Korean Society of Forest Science
• /
• v.63 no.1
• /
• pp.12-20
• /
• 1984

This research was performed to estimate the properties of particleboard based on the press time and temperature which was made of chip of larch that grows in Korea. The results in this study were as follows: 1) Even though the chips, 1:1-35 ratio between length and thickness, are relatively bad condition, the surface smoothness that can easily spread the adhesive evenly and thoroughly and bonding ability of chips can give proper physical properties. 2) It shows more mechanical properties at the press time of 10 min. in MOR (Modulus of Rupture), MOE (Modulus of Elasticity) and SHA (Screw Holding Ability). 3) It is not significant according to the press time 20 min. in MOR, IBS (Internal Bonding Strength) and SHA, for the reciprocal actions between the accelerating aging effect of chip and the softening effect of adhesion are occured. 4) IBS is rising according to the increasing temp at the press time of 10 min. Because it needs to transfer the plate heat to make the proper hardening temp. In the layer. 5) The heat treatment effects have greatly influenced the stahility of dimension by falling the absorption, anisotropy and inhomegenity. As a result of these the values of thickness and linear expansion ratio were respectively dropped by the increase of press temp and the time and so did absorption.

• Horticultural Science & Technology
• /
• v.32 no.3
• /
• pp.303-309
• /
• 2014

The purpose of this study is to suggest indicators and proper standards to forecast the sensory quality of 'Hongisul' grape. Further, this study determines the optimum fruit load of 'Hongisul' grape reflecting consumer preference. Among several quality attributes, identified through instrumental and sensory evaluation, soluble solid-acid ratio was the most useful indicator of consumer preference for 'Hongisul' grapes. The ideal soluble solid-acid ratio for marketable grapes was found to be higher than 86.3. Analysis on the effects of fruit load control on fruit quality revealed a negative correlation where the latter increased as the former decreased. This trend is common for all grape species. The field with a fruit load of $1,400kg{\cdot}10a^{-1}$ exhibited a soluble solid-acid ratio of less than 86.3, uneven coloring and slow softening texture at the mature stage. However, fruit quality proved excellent in the field with a fruit load of $1,200kg{\cdot}10a^{-1}$ or less. It is therefore proposed that fruit load should be controlled to $1,200kg{\cdot}10a^{-1}$ or less when growing 'Hongisul' grapes to produce high quality grapes. We believe that this result can be used as a standard in judging harvest time and evaluating fruit quality.

• Korean Journal of Food Science and Technology
• /
• v.21 no.6
• /
• pp.869-875
• /
• 1989

For the evaluation of storage stability of kiwifruit, the conditions of CA storage were based on the following gas compositions; 2% oxygen and 2, 4, 6% carbon dioxide, respectively. The results obtained from the experiment were as follows; The flesh softening was considerably reduced at the storage atmospheres of 4% $CO_2$ plus 2% $O_2$, and fruit firmness of 3.0kg was marked in this CA condition after storage for 180 days. The concentration of $CO_2$ affected clearly on the respiration rate and organic acid compositions of kiwifruit during CA storage. The respiration rate at the storage condition of 6% $CO_2$ was lower than those at 2 and 4% $CO_2$. Quinic and succinic acid contents were obviously increased in the kiwifruit stored at all the CA conditions studied. In comparision of the developed amounts of off-flavor substances, ethanol and acetaldehyde, depended upon the concentration of $CO_2$ in the CA conditions, the larger amount were produced in the storage condition of higher concentration of $CO_3$. From the results mentioned above, it could be concluded that the optimum atmosphere combination for CA storage of kiwifruit was 4% $CO_2$ plus 2% $O_2$.

• Korean Journal of Medicinal Crop Science
• /
• v.28 no.2
• /
• pp.152-166
• /
• 2020

Background: Ginsenosides, which have various physiological activities, are known to be abundant in the leaves and roots of ginseng. Ginseng sprouts can be used as a fresh vegetable and roots, stems, and leaves of ginseng can be consumed. This study aimed to investigate the effect of carbon dioxide treatment and the modified atmosphere (MA) packaging method in suppressing quality deterioration during the distribution of ginseng sprouts. Methods and Results: Ginseng sprouts were packed using Styrofoam, barrier film + non gas treatment, barrier film + gas treatment, 15 ㎛ polyamide (PA) double film + non gas treatment, 15 ㎛ PA double film + gas treatment, 25 ㎛ PA film + non gas treatment, or 25 ㎛ PA film + gas treatment. Quality parameters including gas composition, relative humidity, chlorophyll SPAD (Soil Plant Analysis Development) value, firmness, and rate of quality loss in ginseng sprouts were monitored at the following temperatures: 20℃, and 10℃. Ginseng sprouts packaged with 25 ㎛ PA film showed loss in quality because of wilting owing to low relative humidity within the film. Chlorophyll and firmness did not differ between film and gas treatments. The time point at which the combined loss from softening and decay owing to fungal, and bacterial infection and wilt reached 20% was considered the limit of distribution. At 20℃, the packaging not included in the 20% distribution loss rate limit or up to 7 days was 15 ㎛ PA double film + gas treatment. At 10℃, the packaging not included in the 20% distribution loss rate limit for up to 18 days were barrier film + gas treatment and 15 ㎛ PA double film + gas treatment. Conclusions: The film packaging suitable for the distribution of ginseng sprouts was found to be the barrier film and PA film with low gas permeability and maintaining hygroscopicity at 95% relative humidity. To prevent the loss in quality of ginseng sprouts, gas treatment (8% of O₂ and 18% of CO₂) in the film was found to be more suitable than no gas treatment for inhibition of decay.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.36 no.2
• /
• pp.222-227
• /
• 2007

This study was carried out to investigate the influence of feeding eosungcho (Houttuynia cordata Thunb) powder on the meat quality of porks at chilled storage. Experimental groups were divided into control group (0%, C), 5% (T1) and 10% (T2) eosungcho powder feeding group, and then administered for 12 weeks. The results of sensory evaluation for softening value and scorched smell showed the highest preference in T1 group. Overall acceptability was also the highest in T1 group than the others. Physicochemical components were analyzed for pork loins that were stored at $4^{\circ}C$ for 23 days after vacuum packing. The moisture contents of pork loins were higher in T1 group than the others. Crude lipid contents were lower in T1 and T2 groups than the control group. The pH values were not significantly different in experimental groups during storage days. The Hunt L and a values increased significantly according to storage days. The Hunt b value was increased for the initial storage days but it did not change after 9 storage days. The Warmer-Bratzler share force of all experimental groups were greatly decreased between 2 and 9 storage days and then little exchanged afterwards.

• Korean Journal of Agricultural Science
• /
• v.37 no.2
• /
• pp.209-216
• /
• 2010

In order to understand the effects of a single or combined treatments of 1-MCP($1{\mu}L/L$) and $CO_2$(100%) on the firmness of melting type peach fruit(cv. Chunjungdo), fruit were harvested at commercial maturity and examined physiological changes including flesh firmness during 10 days of shelf-life. Firmness loss of fruit was delayed by both single and combined treatments of 1-MCP and $CO_2$. The treatment of 1-MCP was more effective than $CO_2$ treatment but no additive effective on firmness retention was found in the combined treatment. The upsurge of ethylene evolution occurred 5 days of shelf-life in air treated control but ethylene evolution gradually increased in fruit treated by 1-MCP and 1-MCP+$CO_2$. The suppression of ethylene evolution seemed stronger in $CO_2$ treatment. The respiration of fruit significantly inhibited up to 10 days except control where climacteric increase of respiration was found at 10 days of shelf-life. A molecular shift of pectic polymers(an increase of chelator soluble pectins and decrease of water soluble pectins) was induced by both 1-MCP and $CO_2$ treatments. An increase of water soluble pectins was coincident with firmness loss. The delay of firmness loss seemed to be associated with the migration of calcium to wall matrix, especially pectins, resulting in the increase of wall bound calcium. The polygalacturonase activity was significantly reduced by 1-MCP alone 1 day after treatment and increased to similar level of activity 5 days after treatment compared to other treatment except air treated control whereas pectin methylesterase activity seemed not to be affected by both 1-MCP and $CO_2$ treatments. Thus, the molecular shift of pectic polymers appeared not to be related with pectin methylesterase. Further study is required to clarify the softening mechanism associated with molecular shift of pectic polymers and the inter- or intra-cellular movement of calcium ions induced by postharvest treatments of 1-MCP and $CO_2$.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.4
• /
• pp.361-373
• /
• 2002

In this paper, we propose a channel normalization method to improve the performance of CMS (cepstral mean subtraction) which is widely adopted to normalize a channel variation for speech and speaker recognition. CMS which estimates the channel effects by averaging long-term cepstrum has a weak point that the estimated channel is biased by the formants of voiced speech which include a useful speech information. The proposed Formant-broadened Cepstral Mean Subtraction (FBCMS) is based on the facts that the formants can be found easily in log spectrum which is transformed from the cepstrum by fourier transform and the formants correspond to the dominant poles of all-pole model which is usually modeled vocal tract. The FBCMS evaluates only poles to be broadened from the log spectrum without polynomial factorization and makes a formant-broadened cepstrum by broadening the bandwidths of formant poles. We can estimate the channel cepstrum effectively by averaging formant-broadened cepstral coefficients. We performed the experiments to compare FBCMS with CMS, PFCMS using 4 simulated telephone channels. In the experiment of channel estimation, we evaluated the distance cepstrum of real channel from the cepstrum of estimated channel and found that we were able to get the mean cepstrum closer to the channel cepstrum due to an softening the bias of mean cepstrum to speech. In the experiment of text-independent speaker identification, we showed the result that the proposed method was superior than the conventional CMS and comparable to the pole-filtered CMS. Consequently, we showed the proposed method was efficiently able to normalize the channel variation based on the conventional CMS.

• Korean Journal of Food Science and Technology
• /
• v.31 no.6
• /
• pp.1596-1603
• /
• 1999

Dongchimi (Korean-style fermented radish with juice) products were frozen to prevent further acidification and softening of texture by restraining microbial growth and enzyme activity during storage. Dongchimi juice and radish were separated prior to freezing process. Dongchimi radish was frozen at $-20^{\circ}C,\;-70^{\circ}C$ and immersed in liquid nitrogen and dongchimi juice was frozen at $-20^{\circ}C\;and\;-70^{\circ}C$. Frozen dongchimi samples were thawed with ambient temperatures of $4^{\circ}C\;and\;27^{\circ}C$ and with 915 MHz-microwave, respectively. Dongchimi radish immersed in liquid nitrogen and thawed with 915 MHz-microwave showed the highest pectinesterase activity and hardness, and the lowest polygalacturonase activity and color change, indicating that this quick freezing-quick thawing method can be used for the long-term storage of dongchimi products. Dongchimi juice frozen at $-70^{\circ}C$ and thawed with 915 MHz-microwave retained its pH and titrable acidity, and showed a largest reduction in total aerobic count and lactic acid bacteria.