• Journal of Communications and Networks
• /
• 제16권5호
• /
• pp.568-577
• /
• 2014

We consider a mobile content delivery network (mCDN) in which special mobile devices designated as caching servers (caching-server device: CSD) can provide mobile stations with popular contents on demand via device-to-device (D2D) communication links. On the assumption that mobile CSD's are randomly distributed by a Poisson point process (PPP), an optimization problem is formulated to determine the probability of storing the individual content in each server in a manner that minimizes the average caching failure rate. Further, we present a low-complexity search algorithm, optimum dual-solution searching algorithm (ODSA), for solving this optimization problem. We demonstrate that the proposed ODSA takes fewer iterations, on the order of O(log N) searches, for caching N contents in the system to find the optimal solution, as compared to the number of iterations in the conventional subgradient method, with an acceptable accuracy in practice. Furthermore, we identify the important characteristics of the optimal caching policies in the mobile environment that would serve as a useful aid in designing the mCDN.

• 산업식품공학
• /
• 제15권3호
• /
• pp.221-229
• /
• 2011

Optimization study of the hot water extraction for enhancing antioxidative activity from Auricularia auricula was performed by Taguchi approach using orthogonal matrix $L_9(3^4)$ method. The correlation between DPPH radical scavenging activity and the components of samples extracted from different extraction conditions were also analyzed. The correlation coefficient between DPPH radical scavenging activity and melanin content of A. auricula were 0.93, indicating 'good correlation'. The optimum extraction conditions was obtained at the extraction time of 1 hr. temperature of $85^{\circ}C$, solid: water ratio of 1: 40(w/v) and frequency of 2 times. Under these conditions, values of maximum DPPH free radical scavenging activity and melanin contents of A. auricula were $67.21{\pm}2.17$ and $52.94{\pm}2.10 mg/g$, respectively. Melanin content of 1.6 times and DPPH free radical scavenging effect of 130% were enhanced by optimization.

• Journal of Applied Biological Chemistry
• /
• 제56권2호
• /
• pp.119-129
• /
• 2013

Thirteen different Streptomyces isolates were evaluated for their ability to produce keratinase using chicken feather as a sole carbon and nitrogen sources under solid state fermentation (SSF). Streptomyces sp. NRC 13S produced the highest keratinase activity [1,792 U/g fermented substrate (fs)]. The phenotypic characterization and analysis of 16S rDNA sequencing of the isolate were studied. Optimization of SSF medium for keratinase production by the local isolate, Streptomyces sp. NRC13S, was carried out using the one-variable-at-a-time and the statistical approaches. In the first optimization step, the effect of incubation period, initial moisture content, initial pH value of the fermentation medium, and supplementation of some agro-industrial by-products on keratinase production were evaluated. The strain produced about 2,310 U/gfs when it grew on chicken feather with moisture content of 75% (w/w), feather: fodder yeast ratio of 70:30 (w/w), and initial pH 7 using phosphate buffer after 8 days. Based on these results, the Box-Behnken design and response surface methodology were applied to find out the optimal conditions for the enzyme production. The corresponding maximal production of keratinase was about 2,569.38 U/gfs.

• 폴리머
• /
• 제38권1호
• /
• pp.16-23
• /
• 2014

A novel poly(AM-DMDAAC)/MMT superabsorbent nanocomposites are prepared by radical polymerization using ammonium persulfate (APS) and anhydrous sodium sulfite as a free radical initiator and N,N-methylene bisacrylamide (MBA) as a crosslinker. In this paper, an optimization study on the synthesis of superabsorbent nanocomposites is carried out. Orthogonal array experiment indicates that the optimized conditions is acrylamide (AM) content 23 wt%, diallyl dimethyl ammonium chloride (DMDAAAC) content 6 wt%, montmorillonite (MMT) content 4 wt%, initiator content 0.2 wt% and crosslinker content 0.02 wt%. Under the optimization syntheses conditions concluded, the maximum water absorbency in distilled water is $659.53g{\cdot}g^{-1}$ and in 2 wt% sodium chloride solution is $116.25g{\cdot}g^{-1}$. Compared with the range values of different factors ($R_j$), the order of significance factors in distilled water is C (MMT) > B (DMDAAC) > A (AM) > D (crosslinker) > E (initiator). MMT is intercalated during polymerization reaction and a nanocomposite structure is formed as shown by TEM analysis and XRD analysis.

• 한국식품조리과학회지
• /
• 제26권5호
• /
• pp.617-626
• /
• 2010

The purpose of this study was to determine the optimal mixing conditions of three different amounts of seatangle powder, sugar, and butter in germinated brown rice cookie prepared with seatangle powder. The experiment was designed according to the Central Composite Design of response surface, which showed 16 experimental points including 2 replicates for seatangle powder, sugar and butter. The mechanical and sensory properties of each test were measured, and these values were applied to the mathematical models. A canonical form and perturbation plot showed the influence of each ingredient on the final product mixture. The L value, a value and b value decreased with increasing seatangle powder content and increased with sugar content. The a value and b value increased with increasing butter content, whereas the L value decreased with increasing butter content. Hardness decreased with increasing butter content. The results of sensory evaluation showed very significant values for texture (p<0.001), taste (p<0.01), and overall quality (p<0.05). As a result, the optimum formulation by numerical and graphical methods was calculated to be seatangle powder 4.25 g, sugar 49.86 g, and butter 58.23 g.

• Natural Product Sciences
• /
• 제27권3호
• /
• pp.187-192
• /
• 2021

Cordycepin is a characteristic bioactive compound of Cordyceps militaris with various beneficial effects. Cordyceps grows on both grains and insects, and the content of cordycepin varies depending on the cultivation conditions. In this study, the effect of culture conditions on the cordycepin content was analyzed and the extraction conditions were optimized. Analysis of cordycepin content in Pupae-Cordyceps found that it was highly affected by temperature in culture conditions. In the case of mycelium, it grows well at 20 and 25 ℃, but not at 30 ℃. However, the content of cordycepin was highest at 30℃ and less at 20 ℃. The fruiting body also showed a similar tendency: growth was 20 ℃ > 25 ℃ > 30 ℃, but the cordycepin content was 30 ℃ > 25 ℃ > 20 ℃. The content of cordycepin decreased after the fruiting bodies were produced. Next, extraction conditions such as solvent and time were optimized for maximum cordycepin content using response surface methodology (RSM). There was a large difference in the content of cordycepin according to the content of ethanol and the extraction temperature. Through RSM, it was confirmed that the optimum condition for extraction of cordycepin was 48.9 ℃ using 49.0% ethanol, and 160.9 mg/g extract could be obtained under this condition. In conclusion, this study suggested the optimized conditions for the cultivation and extraction of Pupae-Cordyceps for maximizing the content of cordycepin, and this may be applied to the discovery of materials using cordycepin.

• Journal of Biosystems Engineering
• /
• 제7권1호
• /
• pp.42-52
• /
• 1982

This study was intended to develop a cost function for the natural air in-bin drying: system which could lead to an optimization of the drying system cost. Based on the cost function developed, a series of simulated drying tests were conducted with 10-year weather data (1970~1979) for 7 different regions by applying an appropriate levels of system factors. System performance factors treated in this study were initial moisture content, airflow rate, bin diameter and grain depth. An optimization procedure to find the least cost system was developed as follows: First, the worst year of the past decade was determined in consideration of the dryiang time and maximum dry matter loss. Second, the minimum airflow rate for a fixed bin diameter and grain depth was determined. Third, the optimum grain depth was found for the minimum airflow rate with different initial moisture contents and bin diameters. The results obtained in this study are summarized as follows: 1. The optimization procedure developed in this study was able to reduce the time and efforts significantly. 2. Optimum values of drying parameters including airflow rate, grain depth, and fan size were determined for different initial moisture contents and bin diameters in each region. The results are shown in Tables 3 to 9. 3. Optimum grain depths decreased as the initial moisture content and airflow rate increased. 4. Drying time for the least cost system should be reduced with higher initial moisture content and lower drying potential to prevent grain spoilage. 5. The fixed cost was 65 to 75 percent of the total system cost and the variable cost was 25 to 35 percent. To reduce the fixed cost it is desirable to use a drying bin 2 or 3 times a year.

• 한국멀티미디어학회논문지
• /
• 제20권9호
• /
• pp.1541-1550
• /
• 2017

The increasing number of multimedia content offered to the user demands content recommendation. In this paper, we propose a system for recommending content related to the content that user is watching. In the proposed system, relationship information between content is generated using relationship information between representative keywords of content. Relationship information between keywords is generated by analyzing keyword collocation frequencies in Internet news corpus. In order to handle big corpus data, we design an architecture that consists of a distributed search engine and a distributed data processing engine. Furthermore, we store relationship information between keywords and relationship information between keywords and content in NoSQL to handle big relationship data. Because the query optimizer of NoSQL is not as well developed as RDBMS, we propose query optimization techniques to efficiently process complex queries for recommendation. Experimental results show that the performance is improved by up to 69 times by using the proposed techniques, especially when the number of requested related keywords is small.

• Natural Product Sciences
• /
• 제24권3호
• /
• pp.199-205
• /
• 2018

To determine the optimum extraction conditions that give the highest yield of isoquercitrin and caffeic acid from Aster scaber, the effects of four extraction variables (solvent concentrations, extraction time, number of repeated extraction, and solvent volumes) on isoquercitrin and caffeic acid yield was examined via HPLC-UV. Our results showed that the highest extract and isoquercitrin yield were observed when A. scaber was extracted with 450 mL distilled water for 8 hr repeatedly for three times. In case of caffeic acid, the content was higher in the two repeated extracts. Also, content analysis of isoquercitrin in Aster species was performed in which A. fastigiatus, A. ageratoides, and A. scaber exhibited the highest isoquercitrin content at 6.39, 5.68, and 2.79 mg/g extract, respectively. In case of caffeic acid, the highest content of A. scaber and A. glehni was 0.64 and 0.56 mg/g extract, respectively. This study reports an optimized method for extraction of isoquercitrin and caffeic acid from A. scaber and evaluates potential sources of the compounds.

• 한국식품조리과학회지
• /
• 제32권6호
• /
• pp.704-715
• /
• 2016

Purpose: This study was conducted to optimize the conditions of manufacturing the wet noodle added with Aloe powder. Methods: The I-optimal design of response surface methodology (RSM) was used for the optimization of added amount of Aloe powder, water content, and kneading time as the independent variables. The quality characteristics (color, texture, water absorption ratio, volume, turbidity) and sensory characteristics (color, flavor, taste, mouth feel, overall acceptance) were analyzed as dependent variables. Results: The lightness, redness, and yellowness of the Aloe noodle were all lowered with the addition of Aloe powder. All texture characteristics such as hardness, elasticity and chewiness of Aloe noodle showed the tendency to increase with increasing amount of Aloe added and kneading time. The water uptake and the volume expansion tended to increase with increasing aloe addition and water addition. As the kneading time increased, the dissolution of solids decreased and the turbidity tended to decrease. Aloe powder content influenced the color, flavor and taste of the noodles most among independent variables, and the mouthfeel of the noodle influenced by the water addition and the kneading time. Conclusion: Aloe noodle showed the best desirability with 3.03% of Aloe powder, 43.56% of water content and 13.06 min of kneading time by RSM analysis. Aloe noodles prepared under these optimized conditions are expected to be able to manufacture and utilize functional Aloe noodles by meeting the content of isobarbaloin, which helps the intestinal functional activity.