• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4467-4486
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• 2016

Discrete cosine transform (DCT) based JPEG standard significantly improves the coding efficiency of image compression, but it is unacceptable event in serious blocking artifacts at low bit rate and low efficiency of high-definition image. In the light of all phase digital filtering theory, this paper proposes a novel transform based on discrete sine transform (DST), which is called all phase discrete sine biorthogonal transform (APDSBT). Applying APDSBT to JPEG scheme, the blocking artifacts are reduced significantly. The reconstructed image of APDSBT-JPEG is better than that of DCT-JPEG in terms of objective quality and subjective effect. For improving the efficiency of JPEG coding, the structure of JPEG is analyzed. We analyze key factors in design and evaluation of JPEG compression on the massive parallel graphics processing units (GPUs) using the compute unified device architecture (CUDA) programming model. Experimental results show that the maximum speedup ratio of parallel algorithm of APDSBT-JPEG can reach more than 100 times with a very low version GPU. Some new parallel strategies are illustrated in this paper for improving the performance of parallel algorithm. With the optimal strategy, the efficiency can be improved over 10%.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.2
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• pp.179-185
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• 2016

In this study, the RDII predictions were compared using two methodologies, i.e., the RTK-based and regression methods. Long-term (1/1/2011~12/31/2011) monitoring data, which consists of 10-min interval streamflow and the amount of precipitation, were collected at the domestic study area (1.36 km2 located in H county), and used for the construction of the RDII prediction models. The RTK method employs super position of tri-triangles, and each triangle (called, unit hydrograph) is defined by three parameters (i.e., R, T and K) determined/optimized using Genetic Algorithm (GA). In regression method, the MovingAverage (MA) filtering was used for data processing. Accuracies of RDII predictions from these two approaches were evaluated by comparing the root mean square error (RMSE) values from each model, in which the values were calculated to 320.613 (RTK method) and 420.653 (regression method), respectively. As a results, the RTK method was found to be more suitable for RDII prediction during extreme rainfall event, than the regression method.

• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.77-87
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• 2007

This paper sets a goal at developing an intelligent advertising system that displays only an advertisement in which interests passers by collecting their RFID information and analysing it in order to improve the defect of outdoor advertising boards which unilaterally advertise regardless of people's interest. For this purpose, we propose a RFID contents middleware which generates a meaningful event and streams an advertising content corresponding with the passers' interest after filtering and analysing the recognized RFID data. We implemented the RFID middleware with Sun Java RFID software and made an experiment by designing a RFID emulator. As a result of the experiment. we found that this system displays the advertisement according to the passers' information.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1533-1556
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• 2017

The concept of trust in vehicular ad hoc networks (VANETs) is usually utilized to assess the trustworthiness of the received data as well as that of the sending entities. The quality of safety applications in VANETs largely depends on the trustworthiness of exchanged data. In this paper, we propose a self-organized distributed trust computing framework (DTCF) for VANETs to compute the trustworthiness of each vehicle, in order to filter out malicious nodes and recognize fully trusted nodes. The proposed framework is solely based on the investigation of the direct experience among vehicles without using any recommendation system. A tier-based dissemination technique for data messages is used to filter out non authentic messages and corresponding events before even going farther away from the source of the event. Extensive simulations are conducted using Omnet++/Sumo in order to investigate the efficiency of our framework and the consistency of the computed trust metrics in both urban and highway environments. Despite the high dynamics in such networks, our proposed DTCF is capable of detecting more than 85% of fully trusted vehicles, and filtering out virtually all malicious entities. The resulting average delay to detect malicious vehicles and fraudulent data is showed to be less than 1 second, and the computed trust metrics are shown to be highly consistent throughout the network.

• Proceedings of the KSPS conference
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• 2007.05a
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• pp.207-210
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• 2007

As the Internet is prevalent in our life, harmful contents have been increasing on the Internet, which has become a very serious problem. Among them, pornographic video is harmful as poison to our children. To prevent such an event, there are many filtering systems which are based on the keyword based methods or image based methods. The main purpose of this paper is to devise a system that classifies the pornographic videos based on the audio information. We use Mel-Cepstrum Modulation Energy (MCME) which is modulation energy calculated on the time trajectory of the Mel-Frequency cepstral coefficients (MFCC) and MFCC as the feature vector and Gaussian Mixture Model (GMM) as the classifier. With the experiments, the proposed system classified the 97.5% of pornographic data and 99.5% of non-pornographic data. We expect the proposed method can be used as a component of the more accurate classification system which uses video information and audio information simultaneously.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.19-21
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• 2005

EPCglobal은 RFID와 관련된 다양한 분야의 표준화를 주도하고 있으며 응용 표준으로써 Tag 정보의 운용을 위한 미들웨어 표준인 ALE Specification을 제시하였다. ALE의 ECSpec은 애플리케이션이 미들웨어에 등록하는 이벤트 필터링을 위한 스펙으로써 일정 시간동안 반복적으로 수행되는 연속 질의와 유사한 특성을 가진다. ECSpec을 연속질의로 변환할 때 해당질의의 WHERE절이 가지는 Predicate는 매우 긴 길이를 가지는 Long Interval이 된다. 이러한 특성은 기존의 질의 색인들의 삽입과 검색 성능을 저하시키는 문제점을 가진다. 이 논문에서는 ECSpec을 연속 질의의 형태로 변환하고 해당 질의가 기지는 Predicate인 2D Interval의 특성을 반영한 새로운 질의 색인 구조로써 TLC-Index를 제안한다. 색인 구조는 그리드 방식의 큰 크기를 가지는 셀 분할 구조와 선분 모양의 가상 분할 구조를 병행하는 하이브리드 구조이다. 색인에서 Long Interval의 정의는 셀 분할 구조의 길이보다. 크거나 같은 길이를 가지는 interval이다. 제안하는 색인은 Long Interval을 큰 크기를 가지는 셀 분할 구조로 분할 삽입함으로써 저장 공간의 소모를 줄이고 삽입 성능을 향상시킨다. 또한 Short Interval들을 짧은 길이를 가지는 가상 분할 구조들로 분할 삽입함으로써 그리드 방식이 가질 수 있는 부분적 겹침을 제거하여 검색 성능을 향상시킨다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.619-622
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• 2004

For recent years, hacking is in the trends of making excessive traffic unnecessarily to obstruct the service by getting a system's performance down. And we can also see systems paralyzed in service ability due to the flash crowds of normal traffic to a popular website. This is an important problem certainly solved in the point of QoS guarantee for the clients. It is known that the former is DDoS(Distributed Denial of Service) attack and the latter is FE(Flash Event). These two are samely anomalous traffic because these make excessive congestion on the network or system and downgrade the system's service ability. In this paper, we propose a scheme for protecting the system against anomalous traffic and for guaranteeing the QoS. For this, a server records and maintains the information of clients accessed more than one time before when it is in normal condition. When it falls into the congestion, the records are used for filtering the spoofed IP. We send and receive the ICMP request/reply packet to know whether the IP is spoofed. And we also propose for applying the object spliting of CDN to guarantee the QoS in the initial FE situation.

• Journal of the Korea Society for Simulation
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• v.11 no.2
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• pp.1-16
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• 2002

The need for network security is being increasing due to the development of information communication and internet technology. In this paper, firewall models, operating system models and other network component models are constructed. Each model is defined by basic or compound model, referencing DEVS formalism. These models and the simulation environment are implemented with MODSIM III, a general purpose, modular, block-structured high-level programming language which provides direct support for object-oriented programming and discrete-event simulation. In this simulation environment with representative attacks, the following three attacks are generated, SYN flooding and Smurf attack as an attack type of denial of service, Mail bomb attack as an attack type of e-mail. The simulation is performed with the models that exploited various security policies against these attacks. The results of this study show that the modeling method of packet filtering system, proxy system, unix and windows NT operating system. In addition, the results of the simulation show that the analysis of security performance according to various security policies, and the analysis of correlation between availability and confidentiality according to security empowerment.

• 전자공학회논문지 IE
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• v.47 no.4
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• pp.18-27
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• 2010

This paper is designed the efficient Data Acquisition System for an vibration of rotatory machines. The Data Acquisition System is consist of the analog logic having signal filer and amplifier, and digital logic with ADC, DSP, FPGA and FIFO memory. The vibration signal of rotatory machines acquired from sensors is controlled by the FPGA device through the analog logic and is saved to FIFO memory being converted analog to digital signal. The digital signal process is performed by the DSP using the vibration data in FIFO memory. The vibration factor of the rotatory machinery analysis and diagnosis is defined the RMS, Peak to Peak, average, GAP, FFT of vibration data and digital filtering by DSP, and is need to follow as being happened the event of vibration and make an application to an warning system. It takes time to process the several analysis step of all vibration data and the event follow, also special event. It should be continuously performed the data acquisition and the process, however during processing the input signal the DSP can not be performed to the acquisited data after then, also it will be lose the data at several channel. Therefore it is that the system uses efficiently the DSP and FPGA devices for reducing the data lose, it design to process a part of the signal data to FPGA from DSP in order to minimize the process time, and a process to parallel process system, as a result of design system it propose to method of faster process and more efficient data acquisition system by using DSP and FPGA than signal DSP system.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.33-42
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• 1999

AVO and complex trace analyses mainly used to characterize natural gas reservoir were tested in this paper for a possible application to detection of major geological discontinuities such as fracture zones. The test data used in this study were calculated by utilizing a viscoelastic numerical program which was based on the generalized Maxwell body for a horizontal fracture model. In AVO analysis of a horizontal fracture zone, p-wave reflection appears to be variant depending upon the acoustic-impedence contrast and the offset distance. The fracture zone is also effectively clarified both in gradient stack and range-limited stack in which fracture zone reflection is attenuated with the increasing offset distance. In complex attribute plots (instantaneous amplitude, frequency, and phase), the top and bottom of the fracture Tone are characterized by a zone of strong amplitudes and an event of the same phase. Low frequency characteristics appear at the fracture zone and the underneath. Amplitude attenuation and waveform dispersion are dependent on Q-contrast between the fracture zone and the surrounding media. They were properly compensated by optimum inverse Q-filtering.