• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.4
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• pp.331-339
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• 2018

The IEEE 1588, commonly known as a precision time protocol (PTP), is a standard for precise clock synchronization that maintains networked measurements and control systems. The best master clock (BMC) algorithm is currently used to establish the master-slave hierarchy for PTP. The BMC allows a slave clock to automatically take over the duties of the master when the slave is disconnected due to a link failure and loses its synchronization; the slave clock depends on a timer to compensate for the failure of the master. However, the BMC algorithm does not provide a fast recovery mechanism in the case of a master failure. In this paper, we propose a technique that combines the IEEE 1588 with network bonding to provide a faster recovery mechanism in the case of a master failure. This technique is implemented by utilizing a pre-existing library PTP daemon (Ptpd) in Linux system, with a specific profile of the IEEE 1588 and it's controlled through bonding modes. Network bonding is a process of combining or joining two or more network interfaces together into a single interface. Network bonding offers performance improvements and redundancy. If one link fails, the other link will work immediately. It can be used in situations where fault tolerance, redundancy, or load balancing networks are needed. The results show combining IEEE 1588 with network bonding enables an incredible shorter recovery time than simply just relying on the IEEE 1588 recovery method alone.

• Journal of Korea Multimedia Society
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• v.7 no.7
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• pp.944-955
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• 2004

The modern society as a high-level information-oriented society lays a great emphasis on lifelong education. It emphasizes all the learners' creative learning ability and various teaching-learning methods as well. We need the self-directed learning to meet these requirements, and one of the solutions is the self-directed teaching-learning process employing the web. Though many educators, so far, developed a number of teaching materials, they are no more than web-based teaching materials for simple learning activities or simple item-bank systems. So, this paper suggests an problem-solving based and self-directed learning system on web in order to overcome such simplicities, and it shows design and implementation of the system. Suggested learning system enables learners to get thinking skill though self-directed control of learning level after they learn the basic concepts and principles on the web as self-directed learning. For example, the system was applied to mathematics education for a middle school students. It supports a test of questions chosen from the item bank in a self-directed way, and helps learners to understand their learning levels for themselves and to solve their questions through on-line discussions with their instructor. The system can also be helpful in improving the learners' learning effects by sharing mutual information through the data room or the Q&A between learners and learners or between learners and instructors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.420-426
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• 2020

In this study, an assistive device for BVM (Bag Valve Mask) was developed. When emergencies occur, rescuers must perform artificial respiration within four minutes utilizing suitable BVM. If not, the patient can suffer serious damage within their brain and body systems. The rescuer must execute artificial respiration until the patient arrives at the hospital. In the process of artificial respiration, the rescuer can feel fatigued in their forearm muscles, particularly those who may have smaller hands or weaker muscle strength. Many products have been developed to solve these problems, but these products are difficult to market and commercialize because of their volume, size, and difficulty of use. In this paper, the BVM assistive device that has been previously manufactured was improved, and an attempt was made to devise a new method that reduces the burden on the user. The BVM assistive device can be divided into three-parts: a head part for compressing the air bag, which can control the amount of air; the body part for coupling with BVM; and finally, the handle that can rotate for better use on various postures of patients. Throughout the experiment, the assistive device could inject an equal amount of air into the patients. As a result, the rescuer could feel less fatigue and inject a suitable amount of air to emergency patients during artificial respiration.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.8
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• pp.1199-1208
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• 2005

Abatement of greenhouse gas emitted from ruminants and promotion of biogas energy from animal effluent were comprehensively examined in each anaerobic fermentation reactor and animal experiments. Moreover, the energy conversion efficiency of biomass energy to power generation were evaluated with a gas engine generator or proton exchange membrane fuel cell (PEMFC). To mitigate safely rumen methanogenesis with nutritional manipulation the suppressing effects of some strains of lactic acid bacteria and yeast, bacteriocin, $\beta$1-4 galactooligosaccharide, plant extracts (Yucca schidigera and Quillaja saponarea), L-cysteine and/or nitrate on rumen methane emission were compared with antibiotics. For in vitro trials, cumulative methane production was evaluated using the continuous fermented gas qualification system inoculated with the strained rumen fluid from rumen fistulated Holstein cows. For in vivo, four sequential ventilated head cages equipped with a fully automated gas analyzing system were used to examine the manipulating effects of $\beta$1-4 galactooligosaccharide, lactic acid bacteria (Leuconostoc mesenteroides subsp. mesenteroides), yeast (Trichosporon serticeum), nisin and Yucca schidigera and/or nitrate on rumen methanogenesis. Furthermore, biogas energy recycled from animal effluent was evaluated with anaerobic bioreactors. Utilization of recycled energy as fuel for a co-generator and fuel cell was tested in the thermophilic biogas plant system. From the results of in vitro and in vivo trials, nitrate was shown to be a strong methane suppressor, although nitrate per se is hazardous. L-cysteine could remove this risk. $\beta$1-4 galactooligosaccharide, Candida kefyr, nisin, Yucca schidigera and Quillaja saponarea are thought to possibly control methanogenesis in the rumen. It is possible to simulate the available energy recycled through animal effluent from feed energy resources by making total energy balance sheets of the process from feed energy to recycled energy.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.139-151
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• 2010

A quasi-two-dimensional unsteady flow model was developed for simulating the flow in a river system including artificial storage pockets with side weirs. It is a multiply-connected network which combines channels and storage pockets. The channel flow is described by the one-dimensional Saint Venant equations, and the weir overflow flow by the cell continuity and stage-discharge relations. The model was applied to the Imjin river system including six artificial storage pockets. Design flood peak reduction due to storage pockets is not sensitive to the side weir discharge coefficient. Storage pockets downstream are less effective than upstream ones in reducing peak stage as the backwater effect becomes more dominant. Simulated flood control effect is highly sensitive to the roughness coefficient. The uncertainty due to the roughness coefficient increases as the weir crest elevation gets higher. Because the best design alternative varies with the roughness coefficient, proper estimation of it is essential to the design of side weirs. Moreover, uncertainty of the estimation needs to be considered in the design process.

• Journal of Korea Spatial Information System Society
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• v.8 no.1 s.16
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• pp.93-106
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• 2006

A Grid Database is a database management system to process effectively and use the distributed data in a grid computing environment. Spatial data is more important than other general data according to the local characteristics and requires a large storage. The grid database can be used as the optimal system for the management of the spatial data. However, contrary to the conventional distributed database systems, the Grid Database which guarantees the local autonomy has a possibility not to provide an effective system, or it is impossible to use a centralized management environment. In order to allow flexible responses to a dynamically changing environment, it is required to use effectively reorganized method. In this paper, hierarchical reorganization method is presented for dynamic reorganization in a grid database. When the reorganization is conducted, an organizer is created to collect the information of databases. In addition, the organizer which is constructed by the hierarchical structure supports information communication and reorganization, and then it allows the support of regional reorganization operation and effective balance control. The performance assessment of the proposed method shows that the processing capacity is increased after the reorganization.

• Geophysics and Geophysical Exploration
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• v.3 no.2
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• pp.53-60
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• 2000

The server/client systems using the web protocol and distribution computing environment by network was applied to the MT data processing based on the Java technology. Using this network based system, users can get consistent and stable results because the system has standard analysing methods and has been tested from many users through the internet. Users can check the MT data processing at any time and get results during exploration to reduce the exploration time and money. The pure/enterprised Java technology provides facilities to develop the network based MT data processing system. Web based socket communication and RMI technology are tested respectively to produce the effective and practical client application. Intrinsically, the interpretation of MT data performing the inversion and data process requires heavy computational ability. Therefore we adopt the MPI parallel processing technique to fit the desire of in situ users and expect the effectiveness for the control and upgrade of programing codes.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.8
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• pp.261-270
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• 2014

As Internet traffic increases recently, much effort has been put on improving the performance of a web server. In addition to hardware side solutions such as replacement by high-end hardware or expansion of the number of servers, there are software side solutions to improve performance. Recent studies on these software side solutions have been actively performed. In this paper, we identify performance degradation problems occurring in a conventional TCP networking reception process and propose a way to solve them. We improve performance by combining three kinds of existing methods for Linux Networking Performance Improvement and two kinds of newly proposed methods in this paper. The three existing methods include 1) an allocation method of a packet flow to a core in a multi-core environment, 2) ITR(Interrupt Throttle Rate) method to control excessive interrupt requests, and 3) sk_buff data structure recycling. The two newly proposed methods are fd data structure recycling and epoll_event data structure recycling. Through experiments in a web server environment, we verify the effect of our two proposed methods and its combination with the three existing methods for performance improvement, respectively. We use three kinds of web servers: a simple web server, Lighttpd generally used in Linux, and Apache. In a simple web server environment, fd data structure recycling and epoll_event data structure recycling bring out performance improvement by about 7 % and 6%, respectively. If they are combined with the three existing methods, performance is improved by up to 40% in total. In a Lighttpd and an Apache web server environment, the combination of five methods brings out performance improvement by up to 36% and 20% in total, respectively.

• Journal of Korean Society on Water Environment
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• v.34 no.4
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• pp.375-381
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• 2018

The monitoring of phytoplankton biomass and community structure is essential as a first step to control the harmful cyanobacterial blooms in freshwater systems, such as seen in rivers and lakes, due to the process of eutrophication and climate change. In order to quantify the biomass of phytoplankton with a wide range in size and shape, the measurement of cell biovolume along with cell density is required for a comprehensive review on this issue. However, most routine monitoring programs preserve the gathered phytoplankton samples before analysis using chemical additives, because of the constraint of time and the number of samples. The purpose of this study was to investigate the cell biovolume change characteristics of six cyanobacterial species, which are common bloom-causing cyanobacteria in the Nakdong River, after the preservation with Lugol's iodine solution. All species showed a statistically significant difference after the addition of Lugol's iodine solution compared to the live cell biovolume, and the cell biovolume decreased to the level of 34.0 ~ 56.3 % at maximum in each species after the preservation. The nonlinear regression models for determining the shrinkage ratio by a preservation period were derived by using the cell biovolume measured until 180 days preservation of each target species, and the equation to convert the cell biovolume measured after preservation for a certain period to the cell biovolume of viable cell was derived using that formula. The conversion equation derived from this study can be used to estimate the actual cell biovolume in the natural environment at the time of sampling, by using the measured biovolume after the preservation in the phytoplankton monitoring. Moreover this is expected to contribute to the final interpretation of the water quality and aquatic ecosystem impacts due to the cyanobacterial blooms.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.1
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• pp.67-77
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• 2008

Seismic isolation has been studied continuously as a solution of the seismic engineering to reduce the sectional forces and the damages of structures caused by earthquakes. To certify reliable design and installation of the seismic isolation systems, seismic isolation bearings should be fabricated under well planned quality control process, and proper evaluation tests for their seismic performance should be followed. In this study, shear property evaluation tests for the lead rubber bearings(LRB) and the rubber bearings(RB) were implemented and the temperature dependency tests were also implemented to evaluate the changes of shear properties according to the changes of temperature. After evaluation tests, the measured shear properties were compared to their design values and their deviation was analyzed comparing with the allowable error ranges specified in Highway Bridge Design Specifications. These results showed that a considerable number of isolation bearings have so large deviations from their design values that their error ranges were over or very close to the allowable ranges. And the test results for temperature dependency showed that the shear properties of isolation bearings would be changed in great degree by the change of temperature during their service period. If these two types of changes in their shear properties are superposed, it would possible that the changes of shear properties from their original design values are over than 50%.