• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.3
• /
• pp.215-222
• /
• 2020

Metformin is a recommended first-line therapy drug for type 2 diabetes patients. However, compared to other oral antidiabetic drugs (OAD), metformin has a large unit dosage, with bioavailability of 40-60%. This limiting bioavailability is because metformin is absorbed only in the upper gastrointestinal tract as a BCS class 3 drug. Hence, we propose that applying the Gastroretentive Drug Delivery System (GRDDS) and extending drug release time in the stomach will result in improved bioavailability. We selected the swelling type delivery system, as it is considered the most stable gastroretention technology compared to other GRDDSs. We modified the swelling excipient by using a natural swelling excipient to form a swelling tablet made of carrageenan and hydroxypropyl methylcellulose (HPMC). Our results indicate that the swelling complex tablet made of carrageenan and HPMC has a good swelling ability and shows required sustained release in a dissolution pattern. In addition, the carrageenan complex has a better swelling ability than the marketed metformin tablet, as determined by the ratio, (swelling ability)/(excipient weight). Taken together, our results indicate that the carrageenan complex can be developed as a good swelling excipient. Further optimizations are required for the commercialization of the carrageenan complex.

• Korean Journal of Cognitive Science
• /
• v.26 no.3
• /
• pp.357-375
• /
• 2015

In our daily life, the probability of target prevalence in visual search varies from very low to high. However, most laboratory studies of visual search used a fixed probability of target prevalence at 50%. The present study examined the properties of information processing during visual search where the probability of target prevalence was manipulated to vary from low (20%), medium (50%), to high (80%). The search items were made of simple shape stimuli, and search accuracy, signal detection measures, and reaction times (RTs) were analyzed for characterizing the effect of target prevalence on the information processing strategies for visual search. The analyses showed that the rates of misses increased whereas those of false alarms decreased in the search condition of low target prevalence, whereas the pattern was reversed in the high prevalence condition. Signal detection measures revealed that the target prevalence shifted response criterion (c) without affecting sensitivity (d'). In addition, RTs for correct rejection responses in the target-absent trials became delayed as the prevalence increased, whereas those for hits in the target-present trials were relatively constant regardless of the prevalence. The RT delay in the target-absent trials indicates that increased target prevalence made the 'quitting threshold' for search termination more conservative. These results support an account that the target prevalence effect in visual search arises from a shift of decision criteria and the subsequent changes in search information processing, while rejecting the account of a speed-accuracy tradeoff.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.15 no.1
• /
• pp.1-8
• /
• 2012

To arrange effectively artificial reefs for marine afforestation, tidal currents were analyzed by numerical experiments, and particle tracking based upon tidal currents were carried out to clarify the path of algae spore. The experiments were carried out by EFDC (Environmental Fluid Dynamics Code), and water column was vertically divided 10 layers. Tidal current patterns showed to be affected by main current at outside of study area, and circle currents of two were observed from analysis of residual currents. Particle tracking were experimented for 15 days at 2 installation places in which artificial reefs for marine afforestation would be deployed. According to the results of particle tracking experiment, particle movement at St.1 showed belt type along coastal line, and St.2 showed ellipse type at 300~500 m distant from coastal line. It suggest that artificial reefs for marine afforestation should be installed belt zone at station of St.1 and ellipse zone at St.2. Modelling algae transport was also tested to account for local dispersion of algae spore due to the suspended materials.

• Korean Journal of Environmental Biology
• /
• v.38 no.1
• /
• pp.30-39
• /
• 2020

The changes in fish stock and biomass before and after fishway renovation located in a Korean estuary were studied and fluctuations in the economic value of the fish resources were estimated. The target fishway located in the east coast area in Korea was renovated in 2014 from the small fish ladder to the ice-harbor fishway. Monitoring was continued for five consecutive years after the renovation(2015 to 2019). Since the renovation of the fish passage, the economic values increased with increases in the fishery resources, except for in 2016 when the drought impact was severe. The yearly average incremental increase in the five years after the renovation was about 227%. The increase in economic value is believed to be due to the increased population of migratory fish as a result of habitat expansion. The exponential rise model showed an increase in economic value with increasing fishery resources (R²=0.896). The model coefficient contributing to economic analysis was 0.582 and the maximum economic value after the renovation was estimated at about 30.4 million. The economic value would be a useful index for quantitative comparison in terms of ecosystem services before and after renovation.

• Science of Emotion and Sensibility
• /
• v.18 no.2
• /
• pp.3-18
• /
• 2015

Numerosity perception is considered as an innate ability of human being where its sensivitiy may widely vary across each individual person. The present study explored the relationship between visual working memory (VWM), visual search efficiency, and numerosity sensitivity. To accomplish this, we calculated each participant's K-value from change detection performance representing one's storage capacity in VWM, slopes of search RTs representing the search efficiency, and discrimination sensitivity for a quantity difference across two sets of dot arrays representing the numerosity sensitivity. The correlational analysis across the measurements revealed that participants with a high VWM capacity better discriminated the numerosity difference in the arrays when the spatial information in the two dot arrays was preserved. In contrast, the participants with high search efficiency discriminated better the difference in the arrays when the spatial information in the arrays was not preserved. The results indicate high VWM-capacity individuals were presumably able to use a strategy of storing the dot arrays by grouping them into a smaller pattern of dot arrays while high search-efficiency individuals were able to use a strategy of rapidly switching their focused attention across the dots in the arrays to count each individual dot. These in sum suggest that individual differences in numerosity sensitivity rely on one's working memory capacity as well as their efficient use of switching focused attention.

• Korean Journal of Food Science and Technology
• /
• v.13 no.2
• /
• pp.107-113
• /
• 1981

Free sugars were isolated from ginseng root and its products and analyzed by using high performance liquid chromatogrphy. To isolate free sugars from aqueous sample solution fat-soluble components, crude saponin and protein were removed from the solution by extracting with benzene, water-saturated butanol and 80% ethanol, respectively. Free sugars found from both ginseng root and its products were fructose, glucose, sucrose and maltose, and the only sugar detected from red ginseng root and its products was rhamnose. Major sugar detected from fresh ginseng and white ginseng roots was sucrose, while sucrose and maltose were major sugars of red ginseng root.

• Applied Biological Chemistry
• /
• v.44 no.4
• /
• pp.219-223
• /
• 2001

Effects of hemoglobin (Hgb) concentration and degree of hydrolysis (DH) of Hgb on the separation of heme-iron were examined to produce highly enriched heme-iron from Hgb hydrolysate. Separation efficiency of Hgb hydrolysate with different DH was studied at wide pH range (pH $1.0{\sim}11.0$). Separation efficiency expressed as heme-iron/peptide ratio increased with decreasing Hgb concentration. When 5% Hgb (pH 10.0) was hydrolyzed using commercially available Esperase for 5 h at $50^{\circ}C$, DH was 25%. The precipitation of heme-iron-enriched peptides were remarkably high at pH range $3{\sim}6$. Optimal pH range for heme-iron with high heme-iron/peptide ratio shifted to acidic pH with increasing DHs of Hgb. The enriched heme-iron fraction in the precipitates showed a single band through urea-SDS-PAGE, with a molecular mass of 1 kDa. In the dry heme-iron product produced in a pilot bioreactor, content of heme-iron and heme-iron/peptide ratio were 27.1 and 38.7%, respectively, and production yield was 9.3%.

• Korean Journal of Applied Biomechanics
• /
• v.19 no.1
• /
• pp.77-85
• /
• 2009

This study is aimed at providing information on injury prevention and skill improvement by inducing the accurate movements in exercise as well as understanding the principles of badminton drive movements. Movement displacement of racket head showed the similar patterns among those surveyed but, it seemed that slight differences resulted from external factors such as height, length of brachial and forearm and individual trend of swing locus. Regarding upper joint angle per phase, the angles of shoulder joint, elbow joint and wrist joint were closely associated in taking drive movements and they supported the segment order theory that power was conveyed from proximal into distal. It was shown that angular velocity of upper joint became larger in follow through movement after impact among all those surveyed, which meant the importance of follow through in racket sports such as badminton. In conclusion, this follow through movement acts as an important factor in racket sports in terms of pose stability maintenance, pose correction of movements and injury prevention of joints. In summary, when swings are made according to segment order theory, efficient movements can be taken.

• Journal of Korean Society of Transportation
• /
• v.21 no.1
• /
• pp.91-102
• /
• 2003

There are two goals in this paper. The one is development of existing CA(Cellular Automata) model to explain more realistic deceleration process to stop. The other is the application of the updated CA model to forecasting simulation to predict short term link travel time that takes a key rule in finding the shortest path of route guidance system of ITS. Car following theory of CA models don't makes not response to leading vehicle's velocity but gap or distance between leading vehicles and following vehicles. So a following vehicle running at free flow speed must meet steeply sudden deceleration to avoid back collision within unrealistic braking distance. To tackle above unrealistic deceleration rule, “Slow-to-stop” rule is integrated into NaSch model. For application to interrupted traffic flow, this paper applies “Slow-to-stop” rule to both normal traffic light and random traffic light. And vehicle packet method is used to simulate a large-scale network on the desktop. Generally, time series data analysis methods such as neural network, ARIMA, and Kalman filtering are used for short term link travel time prediction that is crucial to find an optimal dynamic shortest path. But those methods have time-lag problems and are hard to capture traffic flow mechanism such as spill over and spill back etc. To address above problems. the CA model built in this study is used for forecasting simulation to predict short term link travel time in Kangnam district network And it's turned out that short term prediction simulation method generates novel results, taking a crack of time lag problems and considering interrupted traffic flow mechanism.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.358-359
• /
• 2012

최근 분극 특성이 상이한 무분극 GaN 에피성장에 관한 심도 있는 연구와 함께 전자-전공 캐리어의 주입 및 캐리어의 거동, 방출되는 편광 특성 및 다양한 물리적 특성들에 대해 보고되고 있으며, 광학적 특성 및 물리적 특성의 확보를 위한 많은 연구가 활발히 진행 중이다 [1]. GaN의 ohmic 접촉(ohmic contact)의 형성은 발광 다이오드(light emitting diode), 레이저 다이오드(Laser), 태양전지(solar cell)와 같은 고신뢰도, 고효율 광전자 소자를 제조하기 위해서는 매우 중요하다 [2]. 그러나 이와 함께 병행 되어야 할 무분극 p-GaN 의 ohmic contact에 관한 연구는 많이 이루어지고 있지 않는 실정이다. 따라서 본 논문에서는 r-plane 사파이어 기판 상에 성장된 p-GaN에서의 ohmic 접촉 형성 연구를 위하여 Ni/Au ohmic 전극의 접촉저항 특성을 연구하였다. 본 실험에서는 성장된 a-plane GaN의 Hole농도가 $3.09{\times}1017cm3$ 인 시편을 사용하였다. E-beam evaporation 장비를 이용하여 Ni/Au를 각각 20 nm 그리고80 nm 증착 하였으며 비접촉저항을 측정하기 위해 Circle-Transfer Length Method (C-TLM) 패턴을 사용하였다. 샘플은 RTA (Rapid Thermal Annealing)를 사용하여 $300^{\circ}C$에서 $700^{\circ}C$까지 온도를 변화시키며 전기적 특성을 비교하여 그림 1(a) 나타내었다. 그림에서 알 수 있듯이 $400^{\circ}C$에서 가장 낮은 비접촉저항 값인 $6.95{\times}10-3{\Omega}cm2$를 얻을 수 있음을 발견하였다. 이 때의 I-V curve 도 그림1(b)에 나타낸 바와 같이 열처리에 의해 크게 향상됨을 알 수 있다. 그러나, $500^{\circ}C$ 이상 온도를 증가시키면 다시 비접촉 저항이 증가하는 것을 관찰하였다. XRD (x-Ray Diffraction) 분석을 통하여 $400^{\circ}C$ 이상열처리 온도가 증가하면 금속 표면에 $NiO_2$가 형성되며, 이에 따라 오믹특성이 저하 된다고 사료된다. 또한 $Ni_3N$의 존재를 확인 하였으며 이는 nonpolar surface의 특성으로 인해 nitrogen out diffusion 현상이 동시에 발생하여 계면에는 dopant로 작용하는 질소 공공을 남기고 표면에 $Ni_3N$을 형성하여 ohmic contact의 특성이 저하되기 때문인 것으로 사료된다.