• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.847-853
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• 2016

Applications of Si have been increasingly exploited and extended to More-Moore, More-than-Moore, and beyond-CMOS approaches. Ge is regarded as one of the supplements for Si owing to its higher carrier mobilities and peculiar band structure, facilitating both advanced and optical applications. As an emerging metal-oxide device, the junctionless field-effect transistor (JLFET) has drawn considerable attention because of its simple process, less performance fluctuation, and stronger immunity against short-channel effects due to the absence of anisotype junctions. In this study, we investigated lateral field scalability, which is equivalent to channel-length scaling, in Si and Ge JLFETs. Through this, we can determine the usability of Si CMOS and hypothesize its replacement by Ge. For simulations with high accuracy, we performed rigorous modeling for ${\mu}_n$ and ${\mu}_p$ of Ge, which has seldom been reported. Although Ge has much higher ${\mu}_n$ and ${\mu}_p$ than Si, its saturation velocity ($v_{sat}$) is a more determining factor for maximum $I_{on}$. Thus, there is still room for pushing More-Moore technology because Si and Ge have a slight difference in $v_{sat}$. We compared both p- and n-type JLFETs in terms of $I_{on}$, $I_{off}$, $I_{on}/I_{off}$, and swing with the same channel doping and channel length/thickness. $I_{on}/I_{off}$ is inherently low for Ge but is invariant with $V_{DS}$. It is estimated that More-Moore approach can be further driven if Si is mounted on a JLFET until Ge has a strong possibility to replace Si for both p- and n-type devices for ultra-low-power applications.

• Investigative Magnetic Resonance Imaging
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• v.24 no.3
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• pp.95-122
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• 2020

In this article, we evaluated the performance of radiofrequency (RF) coils in terms of the signal-to-noise ratio (S/N) and homogeneity of magnetic resonance images when used for ultrahigh-frequency (UHF) 7T magnetic resonance imaging (MRI). High-quality MRI can be obtained when these two basic requirements are met. However, because of the dielectric effect, 7T magnetic resonance imaging still produces essentially a non-uniform magnetic flux (|B₁|) density distribution. In general, heterogeneous and homogeneous RF coils may be designed using electromagnetic (EM) modeling. Heterogeneous coils, which are surface coils, are used in consideration of scalability in the |B₁| region with a high S/N as multichannel loop coils rather than selecting a single loop. Loop coils are considered state of the art for their simplicity yet effective |B₁|-field distribution and intensity. In addition, combining multiple loop coils allows phase arrays (PA). PA coils have gained great interest for use in receiving signals because of parallel imaging (PI) techniques, such as sensitivity encoding (SENSE) and generalized autocalibrating partial parallel acquisition (GRAPPA), which drastically reduce the acquisition time. With the introduction of a parallel transmit coil (pTx) system, a form of transceiver loop arrays has also been proposed. In this article, we discussed the applications and proposed designs of loop coils. RF homogeneous coils for volume imaging include Alderman-Grant resonators, birdcage coils, saddle coils, traveling wave coils, transmission line arrays, composite right-/left-handed arrays, and fusion coils. In this article, we also discussed the basic operation, design, and applications of these coils.

• Journal of Advanced Navigation Technology
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• v.15 no.2
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• pp.204-212
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• 2011

Mobile P2P(Peer-to-Peer) protocols in MANET(mobile ad-hoc networks) have gained much attention recently. Existing P2P protocols can be categorized into structured and unstructured ones. In MANET, structured P2P protocols show large control traffic because they does not consider the locality of P2P data and unstructured P2P protocols have a scalability problem with respect to the number of nodes. Hybrid P2P protocols combine advantages of the structured and unstructured P2P protocols. Cluster-based P2P protocol is one of the hybrid P2P protocols. Our study makes an analysis of the cluster-based P2P protocol and derives the optimal cluster formation in MANET. In the derived optimal cluster formation, the cluster-based P2P protocol shows better performance than Gnutella protocol with respect to control traffic.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.728-731
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• 2008

Recently demands in construction of the stand-alone networks and interconnection between convergence devices have led an increase in research on IETF MANET working group, Bluetooth, and HomeRF working group and much attention has been paid to the application of MANET as a Ubiquitous network which is growing fast. With performance both as hosts and routers, easy network configuration, and fast response, mobile nodes participating in MANET are suitable for Embedded computing, but have vulnerable points, such as lack of network scalability and dynamic network topology due to mobility, passive attacks, active attacks, which make continuous security service impossible. For perfect MANET setting, routing is required which can guarantee security and efficiency through secure routing. In routing in this study, hashed AODV is used to protect from counterfeiting messages by malicious nodes in the course of path 'finding and setting, and disguising misrouted messages as different mobile nodes and inputting them into the network.

• Journal of KIISE
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• v.42 no.11
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• pp.1303-1313
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• 2015

MapReduce provides high levels of system scalability and fault tolerance for large-size data processing. A MapReduce-based k-nearest-neighbor(k-NN) join algorithm seeks to produce the k nearest-neighbors of each point of a dataset from another dataset. The algorithm has been considered important in bigdata analysis. However, the existing k-NN join query-processing algorithm suffers from a high index-construction cost that makes it unsuitable for the processing of bigdata. To solve the corresponding problems, we propose a new grid-based, k-NN join query-processing algorithm. Our algorithm retrieves only the neighboring data from a query cell and sends them to each MapReduce task, making it possible to improve the overhead data transmission and computation. Our performance analysis shows that our algorithm outperforms the existing scheme by up to seven-fold in terms of the query-processing time, while also achieving high extent of query-result accuracy.

• Journal of KIISE
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• v.42 no.4
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• pp.530-540
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• 2015

Industrial WSNs need great performance and reliable communication. In industrial WSNs, cluster structure reduces the cost to form a network, and the reservation-based MAC is a more powerful and reliable protocol than the contention-based MAC. Depth-based TDMA assigns time slots to each sensor node in a cluster-based network and it works in a distributed manner. DB-TDMA is a type of depth-based TDMA and guarantees scalability and energy efficiency. However, it cannot allocate time slots in parallel and cannot perfectly avoid a collision because each node does not know the total network information. In this paper, we suggest an improved distributed algorithm to reduce the end-to-end delay of DB-TDMA, and the proposed algorithm is compared with DRAND and DB-TDMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1933-1941
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• 2016

This paper compares the performance of wireless communication technologies to replace the wired networks by wireless networks on avionics intra-communication. Due to the drawbacks of wired network, such as complexity, weight, maintenance cost and scalability, it leads to the high data rate and network traffic demands of avionics systems. Therefore, in WAIC(Wireless Avionics Intra-Communications) system suggested by ITU(International Telecommunication Union), based on environment of avionics system and requirements of a wired network, wireless network structures are defined to solve the problems of wired networks. In this paper, we consider features, advantages and disadvantages of wireless communication technologies which can be used for wireless avionics network, and we propose suitable wireless communication technology candidates for wireless avionics networks in WAIC environments.

• Journal of KIISE:Computing Practices and Letters
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• v.13 no.6
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• pp.397-401
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• 2007

Recent applications on continuous queries on moving objects are extended quickly to various parts. These applications need not only 2-dimensional space data but also high-dimensional space data. If we use previous index for overlapped continuous range queries on high-dimensional space data, as the number of continuous range queries on a large number of moving objects becomes larger, their performance degrades significantly. We focus on stationary queries, non-exponential increase of storage cost and efficient processing time for large data sets. In this paper, to solve these problems, we present a novel query indexing method, denoted as PAB(Projected Attribute Bit)-based query index. We transfer information of high-dimensional continuous range query on each axis into one-dimensional bit lists by projecting technique. Also proposed query index supports incremental update for efficient query processing. Through various experiments, we show that our method outperforms the CES(containment-encoded squares)-based indexing method which is one of the most recent research.

• Journal of KIISE:Databases
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• v.35 no.4
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• pp.368-378
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• 2008

In recent years, publish-subscribe (pub-sub) systems based on XML document filtering have received much attention. In a typical pub-sub system, subscribed users specify their interest in profiles expressed in the XPath language, and each new content is matched against the user profiles so that the content is delivered to only the interested subscribers. As the number of subscribed users and their profiles can grow very large, the scalability of the system is critical to the success of pub-sub services. In this paper, we propose a fast and scalable XML filtering system called SFiST which is an extension of the FiST system. Sharable segments are extracted from twig patterns and stored into the hash-based Segment Table in SFiST system. Segments are used to represent user profiles as Terse Sequences and stored in the Compact Segment Index during filtering. Our experimental study shows that SFiST system has better performance than FiST system in terms of filtering time and memory usage.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.68-79
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• 2005

The popularity of Web service is ever increasing. As the number of services and clients continue to increase, the problem of providing a system that scales with this increase is becoming more difficult. A costly and ineffective method is to buy a new system that is more powerful every time the load becomes unbearable. h more cost effective solution is to expand the system as the need arises. This is the approach taken in Web cluster systems. However, providing effective scalability in a Web cluster system is stil1 an open issue. In this study, we implement a Web cluster system based on Layer 7 switching technique on Linux. The implementation is based on a design proposed and implemented by Aron et al., but on the FreeBSD. Though the design li the same, due to the vast difference between the FreeBSD and Linux, the implementation presented in this paper is totally new. We also propose the Dual Scheduling (DS) load distribution algorithm that distributes the requests to the system resources by observing the variations in the request rate. We show through measurement on our implementation that the DS alorithm performs considerably bettor than previous algorithms.