• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.284-294
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• 2008

In this paper, we describe an implementation of small mobile robot that can be used at research and application of mobile sensor networking. This robot that will constitute the sensor network, as a platform of multi-robot system for each to be used as sensor node, has to satisfy restrictions in many aspects in order to perform sensing, communication protocol, and application algorithms. First, the platform must be designed with a robust structure and low power consumption since its maintenance after deployment is difficult. Second, it must have flexibility and modularity to be used effectively in any structure so that it can be used in various applications. Third, it must support the technique of wireless network for ubiquitous computing environment. At last, to let many nodes be scattered, it must be cost-effective and small. Considering the above restrictions of the mobile platform for sensor network, we designed and implemented robots control the current of actuator by using additional circuit for power efficiency. And we chose MSP430 as MCU, CC2420 as RF transceiver, and etc, that have the strength in the aspect of power. For flexibility and modularity, the platform has expansion ports. The results of experiments are described to show that this robot can act as sensor node by RF communication process with Zigbee standard protocol, execute the navigation process with simple obstacle avoidance and the moving action with RSSI(Received Signal Strength Indicator), operate at low-power, and be made with approx. $100.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.788-794
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• 2007

The policy of US DoD is moving towards implementation of Network Centric Warfare(NCW) concepts. NCW is commonly described as the integration and synchronization of four key interdependent elements such as command and control, sensor system, engagement systems and the network. Therefore the military policy of Korea military is needed to access and examine the policy of NCW communication environment and crypto communication, which is able to apply it. In this case study, We are reviewed the security framework of the concept of network centric warfare in the centering around the US. It is introduced the core technology in the network centric warfare, and it is reviewed the security framework such as, the requirements of security, the characteristics security of global information grid, joint tactical radion system, net centric enterprise services, transformational communication satellite, in the basis of core technology, and analysis the effect of crypto communication relay between command node and surbornate node in NCW environment. This report support the assistance, which is considered the elements of surrounding effects in the varied crypto communication research area of NCW.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3213-3230
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• 2016

Sensor node (SN) is a crucial part in any remote monitoring system. It is a device designed to monitor the particular changes taking place in its environs. Wireless sensor network (WSN) is a system formed by the set of wirelessly connected SNs placed at different geographical locations within a target region. Precise placement of SNs is appreciated, as it affects the efficiency and effectiveness of any WSN. The manual placement of SNs is only feasible for small scale regions. The task of SN placement becomes tedious, when the size of a target region is extremely large and manually unreachable. In this research article, an automated mechanism for fast and precise deployment of SNs in a large scale target region has been proposed. It uses an assembly of rotating cannons to launch the SNs from a moving carrier helicopter. The entire system is synchronized such that the launched SNs accurately land on the pre-computed desired locations (DLs). Simulation results show that the proposed model offers a simple, time efficient and effective technique to place SNs in a large scale target region.

• Journal of KIISE:Databases
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• v.33 no.3
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• pp.271-281
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• 2006

Recently the need for Location-Based Service (LBS) has increased due to the development and widespread use of the mobile devices (e.g., PDAs, cellular phones, labtop computers, GPS, and RFID etc). The core technology of LBS is a moving-objects database that stores and manages the positions of moving objects. To search for information quickly, the database needs to contain an index that supports both real-time position tracking and management of large numbers of updates. As a result, the index requires a structure operating in the main memory for real-time processing and requires a technique to migrate part of the index from the main memory to disk storage (or from disk storage to the main memory) to manage large volumes of data. To satisfy these requirements, this paper suggests a unified index scheme unifying the main memory and the disk as well as migration policies for migrating part of the index from the memory to the disk during a restriction in memory space. Migration policy determines a group of nodes, called the migration subtree, and migrates the group as a unit to reduce disk I/O. This method takes advantage of bulk operations and dynamic clustering. The unified index is created by applying various migration policies. This paper measures and compares the performance of the migration policies using experimental evaluation.

• Journal of Gastric Cancer
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• v.15 no.3
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• pp.159-166
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• 2015

Purpose: Laparoscopic total gastrectomy (LTG) is more complicated than laparoscopic distal gastrectomy, especially during a surgeon's initial experience with the technique. In this study, we evaluated the short-term outcomes of and learning curve for LTG during the initial cases of a single surgeon compared with those of open total gastrectomy (OTG). Materials and Methods: Between 2009 and 2013, 134 OTG and 74 LTG procedures were performed by a single surgeon who was experienced with OTG but new to performing LTG. Clinical characteristics, operative parameters, and short-term postoperative outcomes were compared between groups. Results: Advanced gastric cancer and D2 lymph node dissection were more common in the OTG than LTG group. Although the operation time was significantly longer for LTG than for OTG ($175.7{\pm}43.1$ minutes vs. $217.5{\pm}63.4$ minutes), LTG seems to be slightly superior or similar to OTG in terms of postoperative recovery measures. The operation time moving average of 15 cases in the LTG group decreased gradually, and the curve flattened at 54 cases. The postoperative complication rate was similar for the two groups (11.9% vs. 13.5%). No anastomotic or stump leaks occurred. Conclusions: Although LTG is technically difficult and operation time is longer for surgeons experienced in open surgery, it can be performed safely, even during a surgeon's early experience with the technique. Considering the benefits of minimally invasive surgery, LTG is recommended for early gastric cancer.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.5
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• pp.488-495
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• 2012

The real-time indoor location technology using radio waves has been studied in a variety of environments. One of them, a ship which consists of steel structure has high reception rate but causes significant ranging error due to the reflection of radio waves. In order to reduce location measurement errors that occurs in such a environment, this paper, based on CSS of IEEE 802.15.4a, presents compensation algorithm for localization using modified bilateration and pyroelectric sensor in a ship. The proposed system reduces the number of fixed nodes by estimating the appropriate reception distance between mobile node and fixed node through the analysis of CSS characteristic in a narrow passage such as ship corridors. Also, in the corner section which the ranging errors are significantly fluctuated due to the reflection and diffraction of radio waves, we recognize the location by tracking the a moving section using modified bilateration technique and pyroelectric sensor. The experimental results show that the location accuracy and efficiency of the proposed algorithm are improved 86.2 % compared to general method.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1320-1327
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• 2013

In this paper, two different electromagnetic energy harvesters using bulk micromachined silicon spiral springs and Polydimethylsiloxane (PDMS) packaging technique have been fabricated, characterized, and compared to generate electrical energy from ultra-low ambient vibrations under 0.3g. The proposed energy harvesters were comprised of a highly miniaturized Neodymium Iron Boron (NdFeB) magnet, silicon spiral spring, multi-turned copper coil, and PDMS housing in order to improve the electrical output powers and reduce their sizes/volumes. When an external vibration moves directly the magnet mounted as a seismic mass at the center of the spiral spring, the mechanical energy of the moving mass is transformed to electrical energy through the 183 turns of solenoid copper coils. The silicon spiral springs were applied to generate high electrical output power by maximizing the deflection of the movable mass at the low level vibrations. The fabricated energy harvesters using these two different spiral springs exhibited the resonant frequencies of 36Hz and 63Hz and the optimal load resistances of $99{\Omega}$ and $55{\Omega}$, respectively. In particular, the energy harvester using the spiral spring with two links exhibited much better linearity characteristics than the one with four links. It generated $29.02{\mu}W$ of output power and 107.3mV of load voltage at the vibration acceleration of 0.3g. It also exhibited power density and normalized power density of $48.37{\mu}W{\cdot}cm-3$ and $537.41{\mu}W{\cdot}cm-3{\cdot}g-2$, respectively. The total volume of the fabricated energy harvesters was $1cm{\times}1cm{\times}0.6cm$ (height).

• Journal of KIISE:Information Networking
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• v.33 no.4
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• pp.333-342
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• 2006

The cdma2000 lxEV - DO mobile communication system provides broadcast and multicast services (BCMCS) to meet an increasing demand from multimedia data services. The servicing of video streams over a BCMCS network must, however, face a challenge from the unreliable and error-prone nature of the radio channel. The BCMCS network uses Reed-Solomon coding integrated with the MAC protocol for error recovery. We analyze this coding technique and show that it is not effective in the case of slowly moving mobiles. To improve the playback quality of an MPEG-4 FGS video stream, we propose the Hybrid error recovery scheme, which combines Reed-Solomon with ARQ, using slots which are saved by reducing the Reed-Solomon coding overhead. The target packets to be retransmitted are prioritized by a utility function to reduce the packet error rate in the application layer within a fixed retransmission budget. This is achieved by considering of the map of the error control block at each mobile node. The proposed Hybrid error recovery scheme also uses the characteristics of MPEG-4 FGS (fine granularity scalability) to improve the video quality even when conditions are adverse: slow-moving nodes and a high error rate in the physical channel.