• KIPS Transactions on Computer and Communication Systems
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• v.5 no.12
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• pp.491-498
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• 2016

Recently leakages of confidential information and internal date have been steadily increasing by using booting technique on portable OS such as Windows PE stored in portable storage devices (USB or CD/DVD etc). This method allows to bypass security software such as USB security or media control solution installed in the target PC, to extract data or insert malicious code by mounting the PC's storage devices after booting up the portable OS. Also this booting method doesn't record a log file such as traces of removable storage devices. Thus it is difficult to identify whether the data are leaked and use trace-back technique. In this paper is to propose method to help facilitate the process of digital forensic investigation or audit of a company by collecting and analyzing BIOS firmware images that record data relating to BIOS settings in flash memory and finding traces of portable storage devices that can be regarded as abnormal events.

• Journal of KIISE
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• v.42 no.2
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• pp.169-176
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• 2015

The atomic write technique is a good solution to solve the problem of the double write buffer. The atomic write technique needs modified I/O subsystems (i.e., file system and I/O schedulers) and a special SSD that guarantees the atomicity of the write request. In this paper, we propose the writing unit aligned block allocation technique (for EXT4 file system) and the merge prevention of requests technique for the CFQ scheduler. We also propose an atomic write-supporting SSD which stores the atomicity information in the spare area of the flash memory page. We evaluate the performance of the proposed atomic write scheme in MariaDB using the tpcc-mysql and SysBench benchmarks. The experimental results show that the proposed atomic write technique shows a performance improvement of 1.4~1.5 times compared to the double write buffer technique.

• IEMEK Journal of Embedded Systems and Applications
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• v.16 no.4
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• pp.153-161
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• 2021

Real-time access is required to handle continuous and unstructured data and should be flexible in management under dynamic state. Platform can be built to allow data collection, storage, and processing from local-server or multi-server. Although the former centralize method is easy to control, it creates an overload problem because it proceeds all the processing in one unit, and the latter distributed method performs parallel processing, so it is fast to respond and can easily scale system capacity, but the design is complex. This paper provides data collection and processing on one platform to derive significant insights from various data held by an enterprise or agency in the latter manner, which is intuitively available on dashboards and utilizes Spark to improve distributed processing performance. All service utilize dockers to distribute and management. The data used in this study was 100% collected from Kafka, showing that when the file size is 4.4 gigabytes, the data processing speed in spark cluster mode is 2 minute 15 seconds, about 3 minutes 19 seconds faster than the local mode.

• Spatial Information Research
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• v.2 no.2
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• pp.107-116
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• 1994

Choropleth map is a type of thematic maps in which areal units are shaded with a color or pattern that symbolizes some characteristic of the mapped unit. CMS was first developed to produce choropleth maps on ordinary microcomputer environments in 1988. Since then there have been significant technological developments and enhancements in user environments, which have affected the field of choropleth mapping systems posi¬tively. A new version of CMS was developed in accordance with these changes. CMS II requires an IBM PC, or compatible, with the minimum 640KB memory and VGA graphic board. It supports HP laser jet printers to output a high resolution map. The program can use Hangul letters for main menu, map title, and legend. And dBase file format (DEW) was implemented to exchange attribute files effectively.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.3
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• pp.181-190
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• 2009

Module is an object file that can be loaded into operating system dynamically and has complete privileged access to all resources in kernel. Therefore trivial misuses in a module may cause critical system halts or deadlock situations. In this paper, we propose Kernel Resource Protector(KRP) scheme to reduce the various problems caused by module. KRP provides protections of a variety of kernel resources such as memory, major number and work queue resource. We implement the scheme onto linux kernel 2.6.18, and experimental results show that our scheme can protect kernel resources effectively.

• Journal of the Korea Computer Graphics Society
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• v.19 no.1
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• pp.11-20
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• 2013

This paper introduces a user interface for large 3D meshes in mobile systems, which have limited memory, screen size and battery power. A large 3D mesh is divided into partitions and simplified in multi-resolutions so a large file is transformed into a number of small data files and saved in a PC server. Only selected small files specified by the user are hierarchically transmitted to the mobile system for 3D browsing and rendering. A 3D preview in a pop-up shows a simplified mesh in the lowest resolution. The next step displays simplified meshes whose resolutions are automatically controlled by the user interactions. The last step is to render a set of detailed original partitions in a selected range. As a result, while minimizing using mobile system resources, our interface enables us to browse and display 3D meshes in mobile systems through real-time interactions. A mobile 3D viewer and a 3D app are also presented to show the utility of the proposed user interface.

• The Transactions of the Korea Information Processing Society
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• v.4 no.2
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• pp.325-337
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• 1997

This paper introduces the basic concepts and requirements of database system based on the object-oriented paradigm,and presents the overview of the design of an object-oriented data base system which refects those conceprs and requirements . The system imolemented on C++,consists of three structure layers.The inner layer, which is in fact a storage system,performs file I/O,while the inermediate layer is responisible for most of the functions except the ones rerated to the user interface, such as the transaction management,the schema manage-ment,and the management of buffers in main memory etc.The outer layer,designed mainly for the uwerunteface,mot only privides the functions for graphical user interface,preprocessor,and interpreter etc,but also supports extended SQL for object-oriented features.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.3
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• pp.193-204
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• 2006

In most existing distributed Web systems, incoming requests are distributed to servers via Domain Name System (DNS). Although such systems are simple to implement, the address caching mechanism easily results in load unbalancing among servers. Moreover, modification of the DNS is necessary to load considering the server's state. In this paper, we propose a new dynamic load balancing method using dynamic DNS update and round-robin mechanism. The proposed method performs effective load balancing without modification of the DNS. In this method, a server can dynamically be added to or removed from the DNS list according to the server's load. By removing the overloaded server from the DNS list, the response time becomes faster. For dynamic scheduling, we propose a scheduling algorithm that considers the CPU, memory, and network usage. We can select a scheduling policy based on resources usage. The proposed system can easily be managed by a GUI-based management tool. Experiments show that modules implemented in this paper have low impact on the proposed system. Furthermore, experiments show that both the response time and the file transfer rate of the proposed system are faster than those of a pure Round-Robin DNS.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.186-193
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• 2019

This paper presents and implements a simple programmable PCM encoder structure uisng the commutation method. In the telemetry system, information is required to assign each data to the channel in order to generate a frame format the data acpuired from the sensor. In this case, when the number of state information is large or the data type is various, there is a necessity to input a large amount of information to each channel. However, the more the number of channels and data, the more probability the error will occur. Therefore, in this paper, the channel information is created using the program. And PCM encoder was implemented to store channel information in ROM. The proposed PCM encoder architecture reduces the likelihood of errors. And it can improve the development speed. The validity of proposed structure is proved by simulation.

• The KIPS Transactions:PartA
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• v.12A no.2 s.92
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• pp.151-160
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• 2005

The exponential growth of Web users requires the web serves with high expandability and reliability. It leads to the excessive transmission traffic and system overload problems. To solve these problems, cluster systems are widely studied. In conventional cluster systems, when the request size is large owing to such types as multimedia and CGI, the particular server load and response time tend to increase even if the overall loads are distributed evenly. In this paper, a cluster system is proposed where each Web server in the system has different contents and loads are distributed efficiently using the Web server resource information such as CPU, memory and disk utilization. Web servers having different contents are mutually connected and managed with a network file system to maintain information consistency required to support resource information updates, deletions, and additions. Load unbalance among contents group owing to distribution of contents can be alleviated by reassignment of Web servers. Using a simulation method, we showed that our method shows up to $50\%$ about average throughput and processing time improvement comparing to systems using each LC method and RR method.