• Journal of Internet Computing and Services
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• v.9 no.6
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• pp.99-107
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• 2008

Wireless sensor networks (WSN) based on low-power technologies become important portion of ubiquitous systems. In this paper, we introduce a WSN-based welfare management system as one of the WSN applications. Especially, we implement S-MAC (Sensor Medium Access control) protocol on our system that saves both cost and power consumption, and we evaluate system performances using the TOSSIM simulator. Sensors and a small database server are placed in the house of participant, which collects and stores some environment conditions of the house. The small servers are connected to each others by wireless ad-hoc network.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.1-11
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• 2000

This study is aimed to develop a proto-type LPG engine for medium-duty commercial vehicles in order to substitute for conventional diesel engine. Recently, it is recognized that diesel engines are main cause for smoke pollution in urban site. So, it is expected to reduce this environmental emission by developing and substituting LPG engine which has the advantage of practical use in a short development period in aspects of infrastructures. For that, after analysing the specifications and performance characteristics of a base diesel engine, parts of combustion chamber, intake system, fuel supply and ignition systems suitable for LPG combustion were re-designed and manufactured. And and engine controller for fuel supply and ignition distributions was matched by feedback mapping based on the speed-load conditions. The torque and power of LPG engine were increased by 6∼12% on the overall driving conditions compared to the base diesel engine, and fuel consumption rate marked the similar level based on the fuel price. Exhaust emissions such as THC, CO, NOx recorded the same order with conventional LPG engine for passenger car.

• Journal of Communications and Networks
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• v.17 no.3
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• pp.247-255
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• 2015

In this paper, we propose an adaptive time division multiple access based medium access control (MAC) protocol, called bitmap-assisted shortest job first based MAC (BS-MAC), for hierarchical wireless sensor networks (WSNs). The main contribution of BS-MAC is that: (a) It uses small size time slots. (b) The number of those time slots is more than the number of member nodes. (c) Shortest job first (SJF) algorithm to schedule time slots. (d) Short node address (1 byte) to identify members nodes. First two contributions of BS-MAC handle adaptive traffic loads of all members in an efficient manner. The SJF algorithm reduces node's job completion time and to minimize the average packet delay of nodes. The short node address reduces the control overhead and makes the proposed scheme an energy efficient. The simulation results verify that the proposed BS-MAC transmits more data with less delay and energy consumption compared to the existing MAC protocols.

• Membrane Journal
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• v.2 no.2
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• pp.122-128
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• 1992

A study on the citric acid production was performed in various size dual hollow fiber bioreactors with immobilized Aspergillus niger (KCTC 1232). The final dry cell mass density reached 300g/l based on the space volume available for cell growth. Under air and oxygen aeration the volumethe productivity reached 0.63 and 1.02g/l.h, which cormsponded to 10 and 16 fold over those of batch fermentation, respectively. The initial pH of the medium was a critical factor and the lower value resulted in higher citric acid yield. The increase in the feeding rate of medium or the number of reactor unit resulted in the improvement of the productivity due to higher consumption rate of substrate.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.75-83
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• 2016

In this paper, we propose a multi-channel medium access control (MAC) protocol, named underwater multi-channel MAC protocol (UMMAC), for underwater acoustic networks (UANs). UMMAC is a split phase and reservation based multi-channel MAC protocol which enables hosts to utilize multiple channels via a channel allocation and power control algorithm (CAPC). In UMMAC, channel information of neighboring nodes is gathered via exchange of control packets. With such information, UMMAC allows for as many parallel transmissions as possible while avoiding using extra time slot for channel negotiation. By running CAPC algorithm, which aims at maximizing the network's capacity, users can allocate their transmission power and channels in a distributed way. The advantages of the proposed protocol are threefold: 1) Only one transceiver is needed for each node; 2) based on CAPC, hosts are coordinated to negotiate the channels and control power in a distributed way; 3) comparing with existing RTS/CTS MAC protocols, UMMAC do not introduce new overhead for channel negotiation. Simulation results show that UMMAC outperforms Slotted floor acquisition multiple access (FAMA) and multi-channel MAC (MMAC) in terms of network goodput (50% and 17% respectively in a certain scenario). Furthermore, UMMAC can lower the end-to-end delay and achieves a lower energy consumption compared to Slotted FAMA and MMAC.

• International Journal of Computer Science & Network Security
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• v.22 no.9
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• pp.327-333
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• 2022

Wireless Sensor Networks (WSNs) plays an important role in our everyday life. WSN is distributed in all the places. Nowadays WSN devices are developing our world as smart and easy to access and user-friendly. The sensor is connected to all the resources based on the uses of devices and the environment [1]. In WSN, Quality of Service is based on time synchronization and scheduling. Scheduling is important in WSN. The schedule is based on time synchronization. Min-Max data size scheduling is used in this proposed work. It is used to reduce the Delay & Energy. In this proposed work, Two-hop neighboring node is used to reduce energy consumption. Data Scheduling is used to identify the shortest path and transmit the data based on weightage. The data size is identified by three size of measurement Min, Max and Medium. The data transmission is based on time, energy, delivery, etc., the data are sent through the first level shortest path, then the data size medium, the second level shortest path is used to send the data, then the data size is small, it should be sent through the third level shortest path.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.1
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• pp.124-133
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• 1996

A herbivorous copepod, Tigriopus japonicus, was tested to study its acute and chronic responses to Cd tonicity. Under $20^{\circ}C,\;96hr-LC_{50}$ of T. japonicus in medium with $32\%_{\circ},\;26\%_{\circ},\;and\;18\%_{\circ}$ salinity were 11.1 ppm, 13.7 ppm, and 9.7 ppm, respectively. The $96hr-LC_{50}$ in medium with $32\%_{\circ},\;26\%_{\circ},\;and\;18\%_{\circ}$ salinity increased to 21.6 ppm, 15.0 ppm, and 11,0 ppm, respectively under $10^{\circ}C$ condition. Oxygen consumption rates during 96hrs exposure to Cd toxicity decreased more sharply at $20^{\circ}C$ than those at $10^{\circ}C$. Survival rate and $250dys-LC_{50}$ of T. japonicus in medium with $32\%_{\circ}$ salinity, in concentration of Cd 4 ppm were $5\%$ and 0.05 ppm, respectively under $10^{\circ}C$, and $0\%$ and 0.20 ppm under $20^{\circ}C$. It was that the copepod selectively feed on Skeletonema costatum, Nitzschia pungens, N. seriata, and Rhizosolenia hebetata f. semispina.

• Horticultural Science & Technology
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• v.30 no.4
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• pp.432-436
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• 2012

This study was conducted to determine the optimal aeration rate for mass propagation of ever-bearing strawberry by bioreactor culture. The aeration rate was treated in four levels: 0.1 vvm (air volume/medium volume/min), 0.2 vvm, 0.3 vvm, and 0.4 vvm. In 0.2 vvm conditions, shoot length was the longest at 9.03 cm in bioreactor culture, leave numbers were 40.4 ea and fresh weight was 6,106 mg. Plant growth rate at 0.2 vvm condition was faster than other treatments. In the aeration condition, 0.2 vvm was most effective to increase aerial part growth and to decrease medium consumption. As the culture periods increased, the fresh weight also increased rapidly. After six weeks of cultivation, shoots were emerged with 10.4 ea per plantlet, resulting in developing a complete plant. As a result, the bioreactor culture system for mass propagation of strawberry is required to continuously supply the air by 0.2 vvm speed and cultivate at least for six weeks.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.1342-1350
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• 2009

In accordance with the development of broadcasting, the style of using medium by users has been personalized in the propensity to consume. Recent advent of media convergence allowed users of medium to decide the received environment for their needs, thereby the position of users has become more important in the medium consumption. IPTV has the most advanced form of personalized information media. However, IPTV was made by media convergence, which has relation with a variety of interested parties, so there are a few troubles among them in the way of commercializing IPTV. As a matter of fact, although users play a leading role in the IPTV industry, there are still few discussions on the welfare of users. IPTV should be remained the characteristic of the medium of personalized information, and it should include the welfare of users in various fields of media convergence. That is Universal Service. It is necessary to be guaranteed the access right and the variety of contents in using IPTV. Moreover, in terms of telecommunication, IPTV should insure the reasonable fare system as a pay-services. On the basis of the analysis in local and international IPTV circumstances, in terms of content as a medium of personalized information, in terms of fares as a pay-services, and in terms of digital literacy as a new medium of digital access, policies for welfare of users are suggested.

• Journal of Korea Trade
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• v.26 no.6
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• pp.20-40
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• 2022

Purpose - In recent times, the international trade environment has been changing rapidly, centering on the online market. In the post-COVID-19 era, small and medium-sized trading companies are facing the problem of not being properly provided with overseas market research, market trend analysis, and trade-related information. Cloud-based digital trade is being sought as an alternative to solve these problems; however, there is a lack of research on the intention to switch to digital trade among small and medium-sized trading companies. Therefore, this study empirically analyzes the intention to switch to digital trade based on the migration theory, and through this, attempts to identify each factor that affects the intention to switch to digital trade. Design/methodology - In this study, in order to identify factors influencing intention to switch to digital trade and innovation resistance of small and medium-sized trading companies, through previous research on migration theory and the PPM (Push, Pull, Mooring) model, each variable was selected for the purpose of the study. Based on this, a research model was established for the factors affecting switching to digital trade of small and medium-sized trading companies and empirically analyzed. In addition, considering the differences in the innovation propensity and maturity of information infrastructure of trading companies as the recipients of innovation, this study analyzes the moderating effect of the mooring effect and seeks ways to establish specific strategies according to the degree. Findings - As a result of empirical analysis, the pull effect was found to have the greatest influence on intention to switch to digital trade. However, the pull factor was found to have an effect on user resistance, and it was confirmed that it was a factor simultaneously inducing positive and negative consumption behaviors among users. In addition, it was found that the higher the company's innovation propensity, the higher the pull effect's influence on the intention to switch, and analysis showed that the push effect had no influence. In addition, companies with high information infrastructure maturity were expected to have a relatively high level of intention to switch compared to companies with low information infrastructure maturity, and the difference between the two groups was found not to be statistically significant. Originality/value - This study is a timely study in that it demonstrated the effect on the switching to cloud-based digital trade for small and medium-sized trading companies and that the cloud system related to digital trade is in full swing. There are academic implications in that it revealed that the pull effect is an important factor in the intention to switch to cloud service. Practical implications were presented in that small and medium-sized trading companies suggested ways to increase the value of the cloud system for switching to digital trade and a way to increase the switching ratio by minimizing the mooring effect. In addition, the study argues that active institutional support from the government is needed to activate cloud service.