• ETRI Journal
• /
• v.37 no.5
• /
• pp.951-960
• /
• 2015

For a conventional power metal-oxide-semiconductor field-effect transistor (MOSFET), there is a trade-off between specific on-state resistance and breakdown voltage. To overcome this trade-off, a super-junction trench MOSFET (TMOSFET) structure is suggested; within this structure, the ability to sense the temperature distribution of the TMOSFET is very important since heat is generated in the junction area, thus affecting its reliability. Generally, there are two types of temperature-sensing structures-diode and resistive. In this paper, a diode-type temperature-sensing structure for a TMOSFET is designed for a brushless direct current motor with on-resistance of $96m{\Omega}{\cdot}mm^2$. The temperature distribution for an ultra-low on-resistance power MOSFET has been analyzed for various bonding schemes. The multi-bonding and stripe bonding cases show a maximum temperature that is lower than that for the single-bonding case. It is shown that the metal resistance at the source area is non-negligible and should therefore be considered depending on the application for current driving capability.

• Journal of Sensor Science and Technology
• /
• v.8 no.4
• /
• pp.341-346
• /
• 1999

In general cases, compared with glass electrode, FET type electrolyte sensors have many advantages. But the drift, memory effect and the poor reproducibility of the FET type electrolyte sensor cause the decrease of the reliability in the measurement system. To improve the reliability, an ion-measuring system using FET type electrolyte sensor array with 8 sensors has been developed. Developed system employed the electronic switchs to connect a signal detecting circuit with 8 sensor array and the system can measure ion concentration of 4 different type electrolyte($H^+$, $Na^+$, $K^+$, $Ca^{2+}$). The signal processing algorithm with insertion sorting method was adopted to enhance the reliability. We measured 3 different ion($H^+$, $Na^+$, $K^+$) to evaluate the performance of developed system. The results show that the designed signal processing algorithm can reduce the error range in comparison with a simple arithmetic mean and the developed system has a good reliability over the previous single channel sensor system.

• Journal of KIISE:Computing Practices and Letters
• /
• v.16 no.8
• /
• pp.842-852
• /
• 2010

RFID applications use tags to identify objects, but recent applications tend to include diverse sensor devices such as light, temperature, and humidity sensors as well. RFID tag information is usually processed via the event driven model. However sensor devices are usually accessed via the functional call model. Therefore application developers have to deal with mixed data access models and device dependent interface functions. In this paper, we propose a sensor reader emulator that provides a consistent access interface to sensor devices regardless of the types of devices. SRE provides a more efficient way of developing RFID applications by providing a single application programmer's view to RFID tags and sensor devices. In applications where tags are fixed to a place, SRE can replace expensive sensor tags and sensor readers with inexpensive sensor devices reducing the total cost while providing the same functionality.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.9B
• /
• pp.811-820
• /
• 2006

In this paper, The correlation of the power consumption of sensor node is analyzed according to the analyze parameter in IEEE 802.15.4 star sensor network. And It is studied the influence on analysis parameter. The power consumption of sensor network in transmission process and average transmission power consumption drives to numerical formula. And CSEM WiseNET system measurement value is used. As a simulation result, The power consumption of sensor node in star network consist of 10 sensor nodes is more than 20 % that in single network in average. When beacon signal interval is 0.1 second in all frequency bands, the power consumption of sensor node in up-link is more than 2.5 times that in down-link in average. When beacon signal interval is 1 second and the number of sensor nodes increases to 100 and sensing data increases to 100 byte, the power consumption of sensor node increases to 2.3 times. And The superior performance of 2.4 GHz frequency band has than 868/915 MHz frequency band up to $6{\sim}12$ times.

• Journal of Intelligence and Information Systems
• /
• v.16 no.1
• /
• pp.45-56
• /
• 2010

Sensor Networks are composed of many sensor nodes, which are capable of sensing, computing, and communicating with each other, and one or more sink node(s). Sensor networks collect information of various objects' identification and surrounding environment. Due to the limited resources of sensor nodes, use of wireless channel, and the lack of infrastructure, sensor networks are vulnerable to security threats. Most research of sensor networks have focused on how to detect and counter one type of attack. However, in real sensor networks, it is impractical to predict the attack to occur. Additionally, it is possible for multiple attacks to occur in sensor networks. In this paper, we propose the Secure Routing Mechanism to Defend Multiple Attacks in Sensor Networks. The proposed mechanism improves and combines existing security mechanisms, and achieves higher detection rates for single and multiple attacks.

• Journal of the Korea Society of Computer and Information
• /
• v.12 no.6
• /
• pp.115-121
• /
• 2007

Recently, Location Based Service including tracking and way-finding services has been activated rapidly in the ubiquitous computing environment. According as the ubiquitous computing environment is developed, various types of sensor to acquire various data including location of the moving object are used widely, and acquired sensor data becomes abundant. However, the existing location management system based on a single location sensor is difficult to support LBS efficiently in the ubiquitous computing environment. In this paper, therefore, we propose the location management system in the ubiquitous computing environment that can manage the location data and the various sensor data efficiently. In addition, the location management system adopts the core technology for efficiently storing and transferring a large-volume of various data such as location data and for efficiently processing the various requests from a variety of servers and sensors. Especially, our architecture that is presented in this paper can support context-aware services and autonomous services efficiently in the ubiquitous computing environment.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.8
• /
• pp.1257-1262
• /
• 2008

A long-distance remote sensing of temperature and current based on a fiber Bragg grating (FBG) is proposed and demonstrated. The thermal expanding effect of the epoxy and the Er-doped fiber ring laser (EFRL) are applied to the sensor system to enhance the temperature and current sensitivity. An EFRL with a 5 km-single-mode fiber and a FBG shows a high extinction ratio of more than 60 dB and a low power fluctuation of less than 1 dB. The metal wires are used to supply the current to the sensors. When the NOA65 puts on the FBG as a thermal expanding material, the temperature and current sensitivity of the lasing wavelength shift are about $30\;pm/^{\circ}C$ and 3pm/mA, respectively. The proposed sensing scheme is useful for measurement of current or temperature at a distant object of more than several km.

• ETRI Journal
• /
• v.39 no.5
• /
• pp.683-694
• /
• 2017

Several studies have focused on multimedia transmission over wireless sensor networks (WSNs). In this paper, we propose a comprehensive and robust model to transmit images over cognitive radio WSNs (CRWSNs). We estimate the spectrum sensing frequency and evaluate its impact on the peak signal-to-noise ratio (PSNR). To enhance the PSNR, we attempt to maximize the number of pixels delivered to the receiver. To increase the probability of successful image transmission within the maximum allowed time, we minimize the average number of packets remaining in the send buffer. We use both single- and multi-channel transmissions by focusing on critical transmission events, namely hand-off (HO), No-HO, and timeout events. We deploy our advanced updating method, the dynamic parameter updating procedure, to guarantee the dynamic adaptation of model parameters to the events. In addition, we introduce our ranking method, named minimum remaining packet best channel selection, to enable us to rank and select the best channel to improve the system performance. Finally, we show the capability of our proposed image scrambling and filtering approach to achieve noticeable PSNR improvement.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.9
• /
• pp.3034-3055
• /
• 2014

Wireless Sensor Networks have extensively been utilized for ambient data collection from simple linear structures to dense tiered deployments. Issues related to optimal resource allocation still persist for simplistic deployments including linear and hierarchical networks. In this work, we investigate the case of dimensioning parameters for linear and tiered wireless sensor network deployments with notion of providing extended lifetime and reliable data delivery over extensive infrastructures. We provide a single consolidated reference for selection of intrinsic sensor network parameters like number of required nodes for deployment over specified area, network operational lifetime, data aggregation requirements, energy dissipation concerns and communication channel related signal reliability. The dimensioning parameters have been analyzed in a pipeline monitoring scenario using ZigBee communication platform and subsequently referred with analytical models to ensure the dimensioning process is reflected in real world deployment with minimum resource consumption and best network connectivity. Concerns over data aggregation and routing delay minimization have been discussed with possible solutions. Finally, we propose a node placement strategy based on a dynamic programming model for achieving reliable received signals and consistent application in structural health monitoring with multi hop and long distance connectivity.

• IEIE Transactions on Smart Processing and Computing
• /
• v.4 no.4
• /
• pp.216-223
• /
• 2015

The autonomous underwater vehicle (AUV) is being widely researched in order to achieve superior performance when working in hazardous environments. This research focuses on using image processing techniques to estimate the AUV's egomotion and the changes in orientation, based on image frames from different time frames captured from a single high-definition web camera attached to the bottom of the AUV. A visual odometry application is integrated with other sensors. An internal measurement unit (IMU) sensor is used to determine a correct set of answers corresponding to a homography motion equation. A pressure sensor is used to resolve image scale ambiguity. Uncertainty estimation is computed to correct drift that occurs in the system by using a Jacobian method, singular value decomposition, and backward and forward error propagation.