• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.2
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• pp.101-108
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• 2011

Climate change could have a pronounced impact on natural and agricultural ecosystems. To assess the impact of climate change, projected climate data have been used as inputs to models. Because such studies are conducted occasionally, it would be useful to employ Cloud computing, which provides multiple instances of operating systems in a virtual environment to do processing on demand without building or maintaining physical computing resources. Furthermore, it would be advantageous to use open source geospatial applications in order to avoid the limitations of proprietary software when Cloud computing is used. As a pilot study, Amazon Web Service ? Elastic Compute Cloud (EC2) was used to calculate the number of days with rain in a given month. Daily sets of climate projection data, which were about 70 gigabytes in total, were processed using virtual machines with a customized database transaction application. The application was linked against open source libraries for the climate data and database access. In this approach, it took about 32 hours to process 17 billion rows of record in order to calculate the rain day on a global scale over the next 100 years using ten clients and one server instances. Here I demonstrate that Cloud computing could provide the high level of performance for impact assessment studies of climate change that require considerable amount of data.

• Journal of the Korea Computer Graphics Society
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• v.22 no.3
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• pp.11-20
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• 2016

This paper introduces an effective method for generating 3D stereoscopic images that gives immersive 3D experiences to viewers using mobile-based binocular HMDs. Most of previous AR systems with monocular cameras have a common limitation that the same real-world images are provided to the viewer's eyes without parallax. In this paper, based on the assumption that viewers focus on the marker in the scenario of marker based AR, we recovery the binocular disparity about a camera image and a virtual object using the pose information of the marker. The basic idea is to generate the binocular disparity for real-world images and a virtual object, where the images are placed on the 2D plane in 3D defined by the pose information of the marker. For non-marker areas in the images, we apply blur effects to reduce the visual discomfort by decreasing their sharpness. Our user studies show that the proposed method for 3D stereoscopic image provides high depth feeling to viewers compared to the previous binocular AR systems. The results show that our system provides high depth feelings, high sense of reality, and visual comfort, compared to the previous binocular AR systems.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.2
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• pp.102-110
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• 2009

The memory wall is the growing disparity of speed between CPU and memory outside the CPU chip. An economical solution is a memory hierarchy organized into several levels, such as processor registers, cache, main memory, disk storage. We introduce a novel memory hierarchy optimization technique in Linux based embedded systems using on-chip SRAM for the first time. The optimization technique allocates On-Chip SRAM to the code/data that selected by programmers by using virtual memory systems. Experiments performed with nine applications indicate that the runtime improvements can be achieved by up to 35%, with an average of 14%, and the energy consumption can be reduced by up to 40%, with an average of 15%.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.7
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• pp.636-645
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• 2008

OneNAND flash is a high-performance hybrid flash memory that combines the advantages of both NAND flash and NOR flash. OneNAND flash has not only all virtues of NAND flash but also greatly enhanced read performance which is considered as a downside of NAND flash. As a result, it is widely used in mobile applications such as mobile phones, digital cameras, PMP, and portable game players. However, most of the general purpose operating systems, such as Linux, can not exploit the read performance of OneNAND flash because of the restrictions imposed by their virtual memory system and block I/O architecture. In order to solve that problem, we suggest a new approach called virtual I/O segment. By using virtual I/O segment, the superior read performance of OneNAND flash can be exploited without modifying the existing block I/O architecture and MTD subsystem. Experiments by implementations show that this approach can reduce read latency of OneNAND flash as much as 54%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.7
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• pp.2325-2349
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• 2014

Network virtualization technology plays a key role in cloud computing, which serves as an effective approach for provisioning a flexible and highly adaptable shared substrate network to satisfy the demands of various applications or services. Recently, the problem of mapping a virtual network (VN) onto a substrate network has been addressed by various algorithms. However, these algorithms are typically efficient for unicast service-oriented virtual networks, and generally not applicable to multicast service-oriented virtual networks (MVNs). Furthermore, the survivable MVN mapping (SMVNM) problem that considers the survivability of MVN has not been studied and is also the focus of this work. In this research, we discuss SMVNM problem under regional failures in the substrate network and propose an efficient algorithm for solving this problem. We first propose a framework and formulate the SMVNM problem with the objective of minimizing mapping cost by using mixed integer linear programming. Then we design an efficient heuristic to solve this problem and introduce several optimizations to achieve the better mapping solutions. We validate and evaluate our framework and algorithms by conducting extensive simulations on different realistic networks under various scenarios, and by comparing with existing approaches. Our simulation experiments and results show that our approach outperforms existing solutions.

• Journal of KIISE:Computer Systems and Theory
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• v.35 no.12
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• pp.552-559
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• 2008

Computing technologies are extending the means by which people communicate. Especially, virtual worlds have recently become successful, due to rapidly improving Information Technologies. Chat is a crucial function in current virtual worlds. We need a realistic and efficient communication framework for multi-agents participating in a virtual world. The main contribution of our work is twofold. First, we propose a realistic communication framework which enables 'Complete Talk' and 'Partial Talk' in terms of spatial relationships between avatar agents. Second, our system reconstructs a dialogue graph which maintains all transcripts in the form of directed graphs with temporal(dialogue sequences) and spatial information(physical positions) about communicating agents.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.452-458
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• 2010

In case of an embedded system with computing resource restrictions such as system power and cpu, the overhead due to displaying data on the computer screen may have a significant influence on the system performance. This paper describes an initialization method for LCD-driving components such as an ARM Core, an LCD controller, and an SPI(serial peripheral interface). It also introduces a pixel display function and a panel display method using virtual screen for reducing the display overhead for an LN2440SBC system with an ARM9-based S3C2440A microprocessor. A virtual screen is a large space of computer memories allocated much larger than those needed for one-time display of an image. Displaying a specific region of a virtual screen is done by assigning it as a view-port region. Such a display is useful in an embedded system when concurrently running tasks produce and display their respective results on the screen; it is especially so when the execution result of each task is partially modified, instead of being totally modified, on its turn and displayed. If the tasks running on such a system divide and make efficient use of the region of the virtual screen, the display overhead can be minimized. For the performance comparison with and without using the virtual screen, two different images are displayed in turn and the amount of time consumed for their display is measured. The result shows that the display time of the former is about 5 times faster than that of the latter.

• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.4
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• pp.195-205
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• 2010

The popularity of Smartphones makes new fields of applications based on location based service easily feasible with a new user interface called augmented reality (AR). It presents a particularly powerful user interface to context-aware computing environments. AR on Smartphones integrates virtual information into a person's physical environment by overlaying information on an image taken through Smartphone's camera and motion sensors. Mobile augmented reality systems provide this service without constraining the individual's whereabouts to a specially equipped area. This work presents an overview of handheld augmented reality focusing on applications with introducing the basic issues of them. For this purpose, an example system, Studierstube ES (embedded system), is cited, which introduces the most significant problems and various methods of solving them through the experience of converting existing PC-based AR system into handheld AR.

• Journal of Information Processing Systems
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• v.5 no.2
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• pp.69-76
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• 2009

Self healing systems are considered as cognation-enabled sub form of fault tolerance system. But our experiments that we report in this paper show that self healing systems can be used for performance optimization, configuration management, access control management and bunch of other functions. The exponential complexity that results from interaction between autonomic systems and users (software and human users) has hindered the deployment and user of intelligent systems for a while now. We show that if that exceptional complexity is converted into self-growing knowledge (policies in our case), can make up for initial development cost of building an intelligent system. In this paper, we report the application of AHSEN (Autonomic Healing-based Self management Engine) to in OKKAM Project infrastructure backbone cluster that mimics the web service based architecture of u-Zone gateway infrastructure. The 'blind' load division on per-request bases is not optimal for distributed and performance hungry infrastructure such as OKKAM. The approach adopted assesses the active threads on the virtual machine and does resource estimates for active processes. The availability of a certain server is represented through worker modules at load server. Our simulation results on the OKKAM infrastructure show that the self healing significantly improves the performance and clearly demarcates the logical ambiguities in contemporary designs of self healing infrastructures proposed for large scale computing infrastructures.

• Korean Journal of Remote Sensing
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• v.32 no.6
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• pp.617-627
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• 2016

Many kinds of OGC-based web standards have been utilized in the lots of geo-spatial application fields for sharing and interoperable processing of large volume of data sets containing satellite images. As well, the number of cloud-based application services by on-demand processing of virtual machines is increasing. However, remote sensing applications using these two huge trends are globally on the initial stage. This study presents a practical linkage case with both aspects of OGC-based standard and cloud computing. Performance test is performed with the implementation result for cloud detection processing. Test objects are WPS 2.0 and two types of geo-based service environment such as web server in a single core and multiple virtual servers implemented on OpenStack cloud computing environment. Performance test unit by JMeter is five requests of GetCapabilities, DescribeProcess, Execute, GetStatus, GetResult in WPS 2.0. As the results, the performance measurement time in a cloud-based environment is faster than that of single server. It is expected that expansion of processing algorithms by WPS 2.0 and virtual processing is possible to target-oriented applications in the practical level.