• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.05a
• /
• pp.77-80
• /
• 2017

One of the fundamental limits of Bluetooth Low Energy(BLE) is that the data transmission is available via singlehop connection. In this research, we suggested the stable multihop transmission method to overcome this limitation. In multihop connection situation, multiple singlehop connection should be made and disconnected dynamically. Therefore, we stored the data within the GATT layer and tried to send it dynamically. We divided whole process as 4 states, and let each nodes transfers around each states to make data connection safely. Also, we set the transfer policy between each states during the transmission to make a robust system. From the experiment in real-time environment, we proved that our method showed high rate of packet delivery in a multihop network, which consists of more than 3 nodes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.4B
• /
• pp.258-268
• /
• 2012

Wireless Sensor Network(WSN) is constituted by low-cost and low-energy, So the most important issue is that the task of the sensor performs successfully by using less energy. In previous WSN, determination of the header and gathering sensor data solution by header give great affection to the performance of network. In this paper, we propose a Hybrid transmission method which considers the direction of data collections. In the proposed hybrid routing method, all of the sensors determine that transmission the data to the sink node directly or indirectly using the head node depend on the location of the head node in the cluster. The performance is compared with the LEACH(Low Energy Adaptive Clustering Hierarchy) by experimental analysis. The results show that the preposed method can reduce the communication distance and energy consumption by avoiding the detour direction of transmission of the data.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.26 no.5
• /
• pp.1211-1221
• /
• 2016

In IoT environment, making sure of trust of IoT devices is the most important one than others. The security threats of nowadays almost stay at exposure or tampering of information. However, if human life is strongly connected to the Internet by IoT devices, the security threats will probably target human directly. In case of devices, authentication is verified using the device-known private key. However, if attacker can modify the device physically, knowing the private key cannot be the evidence of trust any more. Thus, we need stronger verification method like code attestation. In this paper, we use software-based code attestation for efficiency. We also suggest secure code attestation method against copy of original code and implement it on embedded device and analyze its performance.

• Applied Chemistry for Engineering
• /
• v.23 no.2
• /
• pp.125-130
• /
• 2012

In these days, there has been increased focus on global warming and the exhaustion of resources recently caused by the heavy consumption of fossil resources. In order to resolve these problems, biomass is increasingly gaining international attention as a renewable energy source. Biogas derived from various biomass is environmental friendly alternative fuel for power generation, heating and vehicle fuel. Large amounts of sewage sludge, food waste and manure are generated from human activity, but these organic wastes contain high levels of organic matter and thus they are potential substrates for producing methane of biogas. The biogas contains 60% of highly concentrated methane, which is expected to be used effectively as energy. In this paper, we investigate the status of biogas in Korea as an alternative energy.

• Journal of Advanced Navigation Technology
• /
• v.17 no.6
• /
• pp.736-748
• /
• 2013

In this paper, we analyse the vulnerabilities of KL scheme which is an ID-based authentication scheme for AMI network, and propose two kinds of authentication schemes which satisfy forward secrecy as well as security requirements introduced in the previous works. In the first scheme, we use MDMS which is the supervising system located in an electrical company for a time-synchronizing server, in order to synchronize smart grid devices in home, and we process device authentication with a new secret value generated by OTP function every session. In the second scheme, we use a secret hash-chain mechanism for authentication process, so we can use a new secret value every session. The proposed two schemes have strong points and weak points respectively and those depend on the services area and its environment, so we can select one of them efficiently considering real aspects of AMI environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.10a
• /
• pp.517-520
• /
• 2009

Healthcare application system has been actively researched to apply WSN technology to healthcare area with a mobile sensor node of low cost, low power, and small size. Sensor node has the problem for transmission range of RF power and time delay of the wireless routing connectivity between sensor nodes. In this paper, we proposes a new method utilizing mobile sensor nodes with relay sensor nodes for quick network routing changing using query technique in healthcare system. A query processor to control and manage the routing changing of sensor nodes in a wireless sensor network was designed and implemented. The user's PC transmits the beacon message which will change the quick link routing according to activity status of patient in wireless sensor network. We describe the implementation for query protocol that is very effective of power saving between sensor nodes.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.19 no.1
• /
• pp.77-83
• /
• 2019

Major causes of industrial accidents include falls and gas leak. The existing safety helmet and smart device combination products are focused on convenience, so the functions to prevent such accidents are insufficient. We developed a smart helmet focusing on fall accident detection and gas leak detection. We also developed management system to manage workers efficiently. Its core function is to detect dangerous conditions of employees, to communicate with managers and to confirm the situations of workers. The effectiveness of the combustible gas measurement capability was verified through experiments. However, since a significant amount of power consumption is founded due to continuous operation of the board and the sensor, countermeasures such as replacing with a large capacity battery are required.

• Journal of IKEEE
• /
• v.24 no.4
• /
• pp.1074-1080
• /
• 2020

This paper proposes a digitally controlled buck converter insensitive to process, voltage and temperature and capable of three modes of operation depending on the state of the output voltage. Conventional digital-controlled buck converters utilized A/D converters, counters and delay line circuits for accurate output voltage control, resulting in increasing the number of counter and delay line bits. This problem can be resolved by employing the 8-bit and 16-bit bidirectional shift registers, and this design technique leads a buck converter to be able to control duty ratio up to 128-bit resolution. The proposed buck converter was designed and fabricated with a CMOS 180 nano-meter 1-poly 6-metal process, generating an output voltage of 0.9 to 1.8V with the input voltage range of 2.7V to 3.6V, a ripple voltage of 30mV, and a power efficiency of up to 92.3%. The transient response speed of the proposed circuit was measured to be 4us.

• The Journal of Korean Institute of Information Technology
• /
• v.17 no.11
• /
• pp.17-26
• /
• 2019

RAID-5 technology is one of the choice for flash storage device to enhance its reliability. However, RAID-5 has inherent parity update overhead, especially, parity overhead for partial stripe write is one of the crucial issues for flash-based RAID-5 technologies. In this paper, we design efficient parity log architecture for RAID-5 to eliminate runtime partial parity overhead. During runtime, partial parity is retained in buffer memory until full stripe write completed, and the parity is written with full strip write. In addition, parity log is maintained in memory until whole the stripe group is used for data write. With this parity log, partial parity can be recovered from the power loss. In the experiments, the parity log method can eliminate partial parity writes overhead with a little parity log writes. Hence it can reduce write amplification at the same reliability.

• Plant Journal
• /
• v.18 no.1
• /
• pp.43-49
• /
• 2022

In this study, the operational characteristics of the 7.48 MW fuel cell power plant consisting of 17 units of 440 kW Phosphoric Acid Fuel Cell (PAFC) in operation since its commercial operation in December 2017 were explained and the heat recovery process of the plat using Organic Rankine Cycle (ORC)was simulated. The fuel cell system performance improvement and economic assessment were analyzed by calculating the amount of heat recovery and electric power available when connecting a 125 kW XLT Model ORC for hot water heat sources with 105℃, 40.8 t/h. The result of the study shows that integrating the 125 kW ORC to PAFC power plant would improve generating efficiency by about 0.6% through annually 851,472 kWh of electricity produced by ORC, and fuel cell and ORC integrated systems were calculated to have a 0.35% higher Internal Return Ratio and more Net Present Value of 1,249 million KRW than not installing ORC despite installation costs.