• Journal of KIISE:Software and Applications
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• v.37 no.12
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• pp.936-941
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• 2010

CMMI is composed of 22 process areas by 5 maturity levels and each process area consists of specific goals and generic goals. Since there are many relations among process areas, organizational standard processes tend to contain overlapped contents. In this paper we demonstrated that 60 out of 528 specific goals are highly related (11% relationship) in CMMI maturity level 3 process areas by using pearson correlation analysis and proposed to a scheme for defining organizational standard processes based on the results. As a result of defining organizational standard processes by using proposed a scheme, we achieved a significant improvement of 25% in process defining productivity.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.280-289
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• 2010

The H.264/AVC standard uses efficient inter prediction technologies improving the coding efficiency by reducing temporal redundancy between images. However, since H.264/AVC does not efficiently encode a video sequence that occurs a local illumination change, the coding efficiency of H.264/AVC is decreased when a local illumination change happens in video. In this paper, we propose an improved motion compensation using adjacent pixels and motion vector refinement to efficiently encode local illumination changes. The proposed method always improves the BD-PSNR (Bj$\o$ntegaard Delta Peak Signal-to-Noise Ratio) of 0.01 ~ 0.21 dB compared with H.264/AVC.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.2
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• pp.29-36
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• 2003

This paper proposes a new 3D image transmission technique using digital watermarking for compatibility with conventional 2D digital TV. To transmit 3D images effectively, generally, we use image sequence transmission using temporal-spatial redundancy between stereo images. It is difficult for users with conventional digital TV to watch the transmitted 3D image sequence because of effectivity of 3D image compression. To improve such problem, in this paper, we perceive the concealment of new information of digital watermarking and conceal information of the other stereo image into three channels of the reference image. So we can watch the image with 3D TV as well as conventional digital TV when it is decoded.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.12
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• pp.117-126
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• 2005

In this paper, we present a new method for the reduction of the PAPR (peak to average power ratio) of OFDM signals. The idea behind the proposed method is that IFFT is implemented often with software for a digital signal processor such that we may avoid the repeated calculations to reduce the computational operations: we define sub-sequences in the IFFT process and then multiply the optimum phase rotation factors to them to minimize the PAPR. The PAPR reduction performance of the proposed method is equal to that of the interleaved partition scheme of the PTS (partial transmit sequence) method with only 1/3 computational operations of it.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.222-227
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• 1995

A single mode, 100-mW diode laser was injection-locked by the master laser which was spectrally narrowed with Littman-type grating feedback. In the incomplete-injection-locking, we observed that two frequencies were simultaneously generated from the slave laser. The power ratio and frequency shift of two frequency components were proportional to the square of injected laser intensity. When the ratio of the injection intensity to the slave laser intensity was about $10^{-3}$, the injection-locking bandwidth was to be about 1.4 GHz. The bandwidth proportionally increased to the square root of the injection intensity, which was in good agreement with the theoretical predictions. The Iinewidth of the locked-laser was about 2.5 MHz, which was five times as narrow as that of free-running operation. ation.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.346-350
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• 2010

Since sensor nodes have restriction of using resources in Zigbee network, number of study on improving efficiency is currently ongoing[1]. Clustering mechanism based on hierarchy structure provides a prevention of duplicated information and a facility of a network expansion[2]. however overheads can occurs when the cluster header is elected and the election of a incorrect cluster header causes to use resources inefficiently. In this paper, we propose that the cluster header election mechanism using distances between nodes and density of nodes in accordance with the operation of the central processing system in which the sync nodes are having information of location and energy with respect to general nodes based on hierachy clustering mechanism.

• Journal of KIISE:Information Networking
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• v.34 no.3
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• pp.218-225
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• 2007

As the research on home network technologies, sensor network technologies, and ubiquitous network technologies makes rapid progresses, wireless ad-hoc network have attracted a lot of attention. A wireless mobile ad-hoc network is a temporary network formed by a collection of wireless mobile nodes without the aid of any existing network infrastructure or centralized administration, and it is suitable for ubiquitous computing environments. In this paper, we suggest an extension scheme of a wireless mobile ad-hoc network based on limited multiple paths source routing protocol. This scheme reduces the overhead of route re-establishment and re-registration by maintaining link/node non-disjoint multiple paths between mobile hosts in a wireless mobile ad-hoc network or a mobile host in a wireless mobile ad-hoc network and a base station supporting fixed network services. By maintaining multiple paths, our scheme provides short end-to-end delay and is reliable extension scheme of a wireless mobile ad-hoc network to a fixed network. In this paper, our simulations show that our scheme outperforms existing schemes with regards to throughput and end-to-end delay. Also we show that our scheme outperforms multi-paths approach using disjoint routes with regards to routing overhead.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.10
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• pp.752-760
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• 2009

Emerging peer-to-peer systems benefit from the large amount of resources provided by many peers. However, many peer-to-peer systems or applications suffer from malicious peers and it is not guaranteed that peers are always online. Micropayment systems are accounting and charging mechanism for buying services, so we can apply them to solve these problems. In the past the majority of micropayment system uses a centralized broker but the problem with most existing micropayment system is a heavy load on the broker. For instance, when an owner of the coin is offline, the broker delegates the owner and handles payment messages. It occurs frequently because of characteristic of peer-to-peer system and is another load of the broker. In this paper we introduce DPay, a peer-to-peer micropayment system that uses distributed hash table (DHT) for storing encrypted payment messages and increases scalability and reduces the load of broker by removing downtime protocol. We show the idea of real-time double spending detection in DPay and report the results of several evaluations in order to compare DPay and other payment scheme. In simulation result, the load of broker in DPay is reduced by 30% on average of other previous payment scheme. We expect that DPay can apply various peer-to-peer systems because it provides a real-time double spending detection and stores more secure payment messages.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.83-92
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• 2004

Gene expression profile is numerical data of gene expression level from organism measured on the microarray. Generally, each specific tissue indicates different expression levels in related genes, so that we can classify cancer with gene expression profile. Because not all the genes are related to classification, it is needed to select related genes that is called feature selection. This paper proposes a new gene selection method using forward selection method in regression analysis. This method reduces redundant information in the selected genes to have more efficient classification. We used k-nearest neighbor as a classifier and tested with colon cancer dataset. The results are compared with Pearson's coefficient and Spearman's coefficient methods and the proposed method showed better performance. It showed 90.3% accuracy in classification. The method also successfully applied to lymphoma cancer dataset.

• KIISE Transactions on Computing Practices
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• v.24 no.3
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• pp.129-137
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• 2018

NVMe(Non-Volatile Memory Express) SSD(Solid State Drive) is a high-performance storage that makes use of flash memory as a storage cell, PCIe as an interface and NVMe as a protocol on the interface. It supports multiple I/O queues which makes it feasible to process parallel-I/Os on multi-core environments and to provide higher bandwidth than SATA SSDs. Hence, NVMe SSD is considered as a next generation-storage for data-center and cloud computing system. However, in the virtualization system, the performance of NVMe SSD is not fully utilized due to the bottleneck of the software I/O stack. Especially, when it uses I/O stack of the hypervisor or the host operating system like Xen and KVM, I/O performance degrades seriously due to doubled-I/O stack between host and virtual machine. In this paper, we propose a new I/O engine, called Direct-AIO (Direct-Asynchronous I/O) engine, that can access NVMe SSD directly for I/O performance improvements on QEMU emulator. We develop our proposed I/O engine and analyze I/O performance differences between the existed I/O engine and Direct-AIO engine.