• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.4A
• /
• pp.377-386
• /
• 2008

In this paper, a new handover management scheme has been proposed to reduce handover latency and to support fast handover without packet losses, so that it may be applicable to the wireless mobile Internet system such as IPv6-based WiBro system. To minimize the handover latency in processing of movement detection, we propose the handover management scheme which simplifies the handover message exchanging procedure between mobile subscriber station (MSS) and network by integrating layer 2 and layer 3 handovers efficiently based on the layer2 information. To reduce the processing delay from new care-of-address (NCoA) configuration during handover, we propose that NCoA is created, distributed and managed by new access control router (NACR). In addition, in order to minimize the packet transmission delay and eliminate the packet losses, the proposed scheme employs a crossover router (CR) which is upper network located over PACR and NACR and employs the packet buffering for MSS. The simulation study shows that the proposed scheme achieves loss-free packet delivery and low latency in the environment of narrow overlapped cell area or high velocity of the MSS, comparing the performance with the conventional schemes.

• Korea Journal of Hospital Management
• /
• v.23 no.1
• /
• pp.65-77
• /
• 2018

The purpose of this study is to examine the structural causal relationships between service image, service satisfaction, affective commitment, and customer loyalty to customers who have experienced hospital medical services, and to identifies the mediating effect of relationship proneness in explaining the effects of service image, service satisfaction, and affectivel commitment on customer loyalty. For this study, 250 respondents were surveyed and data were analyzed using SPSS 21.0 and AMOS 20.0 statistical package. Statistical analysis tools, such as SPSS 21.0 and AMOS 20.0 were utilized for ensuring the validity and the reliability, whereas the SEM method was used for testing the research hypothesis. The results of study are as follows. Service image had significant influence on service satisfaction and emotional commitment. First, Service satisfaction was significant for emotional commitment and customer loyalty, and emotional commitment had a significant effect on customer loyalty. Therefore, the path relations between variables were all statistically significant. Second, there was differences the moderating effect of the relationship proneness in the effects of service satisfaction, service image and affective commitment on customer loyalty. In other words, the moderating effect of the relationship tendency was consistent with the research hypothesis and the adjustment effect was significant in the relationship between service satisfaction and customer loyalty. However, there was no control effect in relation to service image and customer loyalty and affective commitment and customer loyalty. Therefore, In order to secure long-term and stable profits by establishing a relationship with their customers, the medical service marketing strategies of hospitals should be promoted to enhance customer loyalty by raising the level of service satisfaction to high relationship proneness group and by raising the the level of affective commitment to low relationship proneness group.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.11 no.3
• /
• pp.245-250
• /
• 2006

The effects of aliphatic hydrocarbons (n-hexadecane and n-dodecane) on the volumetric oxygen mass transfer coefficient $(k_L\;a)$ were studied in flat alveolar airlift reactor and continuous stirred tank reactors (CSTRs). In the flat alveolar airlift reactor, high aeration rates (>2vvm) were required in order to obtain efficient organic-aqueous phase dispersion and reliable $k_La$ measurements. Addition of 1% (v/v) n-hexadecane or n-dodecane increased the $k_La$ 1.55- and 1.33-fold, respectively, compared to the control (superficial velocity: $25.8{\times}10^{-3}m/s$, sparger orifice diameter: 0.5 mm). Analysis of the gas-liquid interfacial area a and the liquid film mass transfer coefficient $k_L$ suggests that the observed $k_La$ increase was a function of the media's liquid film mass transfer. Addition of 1% (v/v) n-hexadecane or n-dodecane to analogous setups using CSTRs led to a $k_La$ increase by a factor of 1.68 and 1.36, respectively (superficial velocity: $2.1{\times}10^{-3}m/s$, stirring rate: 250 rpm). These results propose that low-concentration addition of oxygen-vectors to aerobic microbial cultures has additional benefit relative to incubation in purely aqueous media.

• 한국생물공학회:학술대회논문집
• /
• 2005.10a
• /
• pp.434-438
• /
• 2005

Nitrification characteristics and performance of wastewater treatment plants depend on not only temperature, pH, and dissolved oxygen of the wastewater but also species, distribution, and their metabolic stages of nitrifying bacteria. Due to their low specific growth rate, nitrifying bacteria are easy to wash out of the reactor and need long time to start-up and recover from damaged nitrifiers community. In order to overcome this limitation, nitrifying bacteria were coated on a polyurethane-based media. Laboratory and pilot-scale reactor had been designed and operated to compare the effect of coated nitrifying bacteria on wastewater nitrification efficiency and performance. Furthermore, the species and quantitative distribution of nitrifying bacteria were also investigated in the suspension and on the media. The results showed that nitrifier-coated reactor had better nitrification efficiency and performance than the control experiments. It also demonstrated that the amounts of total nitrifying bacteria of a coated reactor was higher than other reactors and it increased with operation time and wastewater temperature.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.1
• /
• pp.18-28
• /
• 2001

The present study investigates flow dynamics between two dimensional compliant plates under sinusoidal flow conditions in order to understand influence of wall motion, impedance phase angle (time delay between pressure and flow waveforms), and non-Newtonian fluid on wall shear stress using computational fluid dynamics. The results showed that wall motion induced additional terms in the streamwise velocity profile and the pressure gradient. These additional terms due to wall motion reduced the amplitude of wall shear stress and also changed the mean wall shear stress. The trend of the changes was very different depending on the impedance phase angle. As the impedance phase angle was changed to more negative values, the mean wall shear stress decreased while the amplitude of wall shear stress increased. As the phase angle was reduced from 0°to -90°under $\pm$4% wall motion, the mean wall shear stress decreased by 12% and the amplitude of wall shear stress increased by 9%. Therefore, for hypertensive patients who have large negative phase angles, the ratio of amplitude and mean of the wall shear stress is raised resulting in a more vulnerable state to atherosclerosis according to the low and oscillatory shear stress theory. We also found that non-Newtonian characteristics of the blood protect atherosclerosis by decreasing the oscillatory shear index.

• Fisheries and Aquatic Sciences
• /
• v.18 no.1
• /
• pp.57-63
• /
• 2015

Effects of rearing density on growth and survival of the polychaete rockworm Marphysa sanguinea have been investigated in order to develop rearing techniques for this species. This study was examined over a nine-month period in the Fisheries Science and Technology Center of Pukyong National University. Three rockworm densities, 500, 1,000 and $2,000worms{\cdot}m^{-2}$ with weight ranges of < 0.5 g, 0.6-1.5 g, and 1.6-2.5 g, and the no feed control treatment, were stocked in triplicate $0.10m^2$ boxes with sand bottoms. Growth rates were checked with 15 randomly sampled rockworms from each box at months 3, 6 and 9. Results showed that SGRs in all treatments were higher during the first period (0-3 months) than the second (3-6 months) and third periods (6-9 months) for all treatment densities, while SGRs decreased with increasing density. However, survival and growth of worms at high density was not better than low density, but daily biomass production in medium and high density groups was $6.28gm^{-2}day^{-1}$ for the rockworms of 0.6-1.5 g with $2,000inds{\cdot}m^{-2}$, and $12.6gm^{-2}day^{-1}$ for group between 1.6-2.5 g with $2,000inds{\cdot}m^{-2}$, and $14.7gm^{-2}day^{-1}$ for the group of individuals <0.5 g with $1,000inds{\cdot}m^{-2}$. Results showed that M. sanguinea can be one of the most suitable species to commercially exploit in a farming system. In particular, specified densities permit elevated pure production.

• The Journal of the Korea Contents Association
• /
• v.15 no.10
• /
• pp.587-596
• /
• 2015

3D scanners are applied to many industries, such as manufacturing, construction, and shipbuilding. Recently, 3D scanner is used in 3D imaging of worksite in order to control and guide earthmoving heavy equipments, which provides basic information for intelligent excavation. This study compares the accuracy and productivity between total stations and high-resolution 3D scanners. The analysis results show that 3D scanner has high accurate rate of greater than 99 percent and has low error rate of less than 2.0mm compared to total stations. In terms of productivity, 3D scanner saves 71 percent of measuring time compared to the total station. This study confirms that 3D scanner can measure the earthwork sites with high accuracy and better productivity.

• 한국태양에너지학회:학술대회논문집
• /
• 2012.03a
• /
• pp.108-112
• /
• 2012

Crystalline silicon solar cell remains the major player in the photovoltaic marketplace with 90 % of the market, despite the development of a variety of thin film technologies. Silicon's excellent efficiency, stability, material abundance and low toxicity have helped to maintain its position of dominance. However, the cost of silicon photovoltaic remains a major barrier to reducing the cost of silicon photovoltaics. Using the crystalline silicon wafer with thinner thickness is the promising way for cost and material reduction in the solar cell production. However, the thinner thickness of silicon wafer is, the worse bow phenomenon is induced. The bow phenomenon is observed when two or more layers of materials of different temperature expansion coefficiencies are in contact, in this case silicon and aluminum. In this paper, the solar cells were fabricated with different thicknesses of Al layer in order to reduce the bow phenomenon. With lower paste applications, we observed that the bow could be reduced by up to 40% of the largest value with 130 micron thickness of the wafer even though the conversion efficiency decrease of 0.5 % occurred. Since the bowed wafers lead to unacceptable yield losses during the module construction, the reduction of bow is indispensable on thin crystalline silicon solar cell. In this work, we have studied on the counterbalance between the bow and conversion efficiency and also suggest the formation of enough back surface field (BSF) with thinner Al paste application.

• Journal of the Korea Society for Simulation
• /
• v.21 no.2
• /
• pp.79-90
• /
• 2012

In this paper, a feature signal extraction method is proposed in order to enhance the low performance of fault detection caused by unbalanced data which denotes the situations when severe disparity exists between the numbers of class instances. Most of the cyclic signals gathered during the process are recognized as normal, while only a few signals are regarded as fault; the majorities of cyclic signals data are unbalanced data. SOM(Self-Organizing Map)-based feature signal extraction method is considered to fix the adverse effects caused by unbalanced data. The weight neurons, mapped to the every node of SOM grid, are extracted as the feature signals of both class data which are used as a reference data set for fault detection. kNN(k-Nearest Neighbor) and SVM(Support Vector Machine) are considered to make fault detection models with comparisons to Hotelling's $T^2$ Control Chart, the most widely used method for fault detection. Experiments are conducted by using simulated process signals which resembles the frequent cyclic signals in semiconductor manufacturing.

• Applied Chemistry for Engineering
• /
• v.10 no.4
• /
• pp.599-602
• /
• 1999

Chitosan was depolymerized by using nitrous acid. In order to synthesize new fluorinated chitosan oligomer(FCO) derivative, free amine groups of resulting low molucular weight chitosan oligomers were reacted with trifluoroacetic anhydride. The structure changes in the samples were conformed by using FT-IR, $^{1}H\;NMR$, $^{13}C\;NMR$ and $^{19}F\{^{1}H\}NMR$. Antiviral activity of FCO was studied by measuring DAN amounts of the replication viruses at 36 hr after the cells were infected with the viral solution containing FCO of various concentrations. The viral replications in the cells infected with the viral solution containing FCO were proportionally decreased with the FCO does, compared to those of the control groups, indicating that FCO efficiently inhibits viral infection. In particular, viral replication was decreased to 40% in the 1% FCO-treated cells.