• Journal of the Korean School Mathematics Society
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• v.15 no.4
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• pp.673-698
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• 2012

In this study, we suggest the standards for future mathematics classroom from environment, teachers, and students aspects. Future mathematics classroom should have the three environmental standards that perform responsible roles and appropriate functions of physical resources and classroom space. In the teacher standards' domain, we presented as a total of eight kinds. Concretely, we proposed the four standards for improvement of mathematical teacher's instructional expertise and the four standards for improvement of abilities of learners. The students standards consist of 4 domain a such as 3 standards of mathematical investigation and problem solving, 3 standards of cooperation and communication, 1 standard of utilization and operation of mathematical technologies and learning support systems, 2 standard of digital ethics and citizenship. Also, we developed the mathematical convergence instruction model and reported the results of its application after the lessons conducted in the classroom equipped with advanced environmental and technologies. We presented the convergence instruction model and scenarios focused on thoughts and actions of teachers and students in the future mathematics classroom.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.2
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• pp.98-107
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• 2013

This work describes a 13b 100 MS/s 0.13 um CMOS four-stage pipeline ADC for 3G communication systems. The proposed SHA-free ADC employs a range-scaling technique based on switched-capacitor circuits to properly handle a wide input range of $2V_{P-P}$ using a single on-chip reference of $1V_{P-P}$. The proposed range scaling makes the reference buffers keep a sufficient voltage headroom and doubles the offset tolerance of a latched comparator in the flash ADC1 with a doubled input range. A two-step reference selection technique in the back-end 5b flash ADC reduces both power dissipation and chip area by 50%. The prototype ADC in a 0.13 um CMOS demonstrates the measured differential and integral nonlinearities within 0.57 LSB and 0.99 LSB, respectively. The ADC shows a maximum signal-to-noise-and-distortion ratio of 64.6 dB and a maximum spurious-free dynamic range of 74.0 dB at 100 MS/s, respectively. The ADC with an active die area of 1.2 $mm^2$ consumes 145.6 mW including high-speed reference buffers and 91 mW excluding buffers at 100 MS/s and a 1.3 V supply voltage.

• Journal of Information Processing Systems
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• v.8 no.3
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• pp.495-520
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• 2012

A secure Electronic Payment System (EPS) is essential for the booming online shopping market. A successful EPS supports the transfer of electronic money and sensitive information with security, accuracy, and integrity between the seller and buyer over the Internet. SET, CyberCash, Paypal, and iKP are the most popular Credit Card-Based EPSs (CCBEPSs). Some CCBEPSs only use SSL to provide a secure communication channel. Hence, they only prevent "Man in the Middle" fraud but do not protect the sensitive cardholder information such as the credit card number from being passed onto the merchant, who may be unscrupulous. Other CCBEPSs use complex mechanisms such as cryptography, certificate authorities, etc. to fulfill the security schemes. However, factors such as ease of use for the cardholder and the implementation costs for each party are frequently overlooked. In this paper, we propose a Web service based new payment system, based on ANSI X9.59-2006 with extra features added on top of this standard. X9.59 is an Account Based Digital Signature (ABDS) and consumer-oriented payment system. It utilizes the existing financial network and financial messages to complete the payment process. However, there are a number of limitations in this standard. This research provides a solution to solve the limitations of X9.59 by adding a merchant authentication feature during the payment cycle without any addenda records to be added in the existing financial messages. We have conducted performance testing on the proposed system via a comparison with SET and X9.59 using simulation to analyze their levels of performance and security.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.6
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• pp.189-196
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• 2014

Though the plagiarism is illegal and should be avoided, it still occurs frequently. Particularly, the plagiarism of source codes is more frequently committed than others since it is much easier to copy them because of their digital nature. To prevent code plagiarism, there have been reported a variety of studies. However, previous studies for plagiarism detection techniques on source codes do not consider the data structures although a source code consists both of data structures and algorithms. In this paper, a plagiarism detection technique for source codes considering data structures is proposed. Specifically, the data structures of two source codes are represented as sets of trees and compared with each other using Hungarian Method. To show the usefulness of this technique, an experiment has been performed on 126 source codes submitted as homework results in an object-oriented programming course. When both the data structures and the algorithms of the source codes are considered, the precision and the F-measure score are improved 22.6% and 19.3%, respectively, than those of the case where only the algorithms are considered.

• The Transactions of the Korea Information Processing Society
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• v.4 no.10
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• pp.2562-2570
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• 1997

This paper deals with the design and performance of the adaptive equalizer using high order statistics in order to improve the transmission characteristics of multipath fading channel. The multipath propagational phenomenon occurred in digital radio transmission causes the distortion and ISI of receiving signal. These are main reasons to increase the bit error rate and degrade the performance of receivers. In this paper, the adaptive equalization algorithm using high order statistics of received signal is used instead of CMA algorithm, Bussgang and Godard which are known widely. The performance of this algorithm (residualisi, recovered constellation, calculation) is presented varing SNR. As the result of the computer simulation, equalizer algorithm using high order statistics is better than CMA in the range of low SNR, $10{\sim}20dB$. Therefore, considering the actual communication systems which use the range of $14{\sim}20$ SNR, the adaptive equalizer using high order statistics can be used in the real multipath fading environment.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.235-249
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• 2006

In this paper, SER(Symbol Error Rate) variation and effects on SER by phase noise at various frequency offset of the local oscillator in digital communication systems are gerneralyzed for QPSK(Quadrature Phase Shift Keying), MQAM(M-ary Quadrature Amplitude Modulation), OFDM(Orthogonal Frequency Division Multiplex)-MQAM, OFDM-QPSK and 8-VSB(Vestigal Side Bands) modulation methods and compared those with the ideal cases, which have no phase noise, through the MATLAB simulation. And the ration between modulation bandwidths and the SER on the various frequency offsets on the above modulation methods have been analyzed for the system requirement of minimum phase noise characteristics. From this study, we have confirmed that the most sensitive modulation method on the phase noise is OFDM-MQAM and that the relatively insensitive method 8-VSB.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.10
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• pp.377-382
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• 2014

Analysis techniques of the data over time from the mobile environment and IoT, is mainly used for extracting patterns from the collected data, to find meaningful information. However, analytical methods existing, is based to be analyzed in a state where the data collection is complete, to reflect changes in time series data associated with the passage of time is difficult. In this paper, we introduce a method for analyzing multi-block streaming data(AM-MBSD: Analysis Method for Multi-Block Stream Data) for the analysis of the data stream with multiple properties, such as variability of pattern and large capacitive and continuity of data. The multi-block streaming data, define a plurality of blocks of data to be continuously generated, each block, by using the analysis method of the proposed method of analysis to extract meaningful patterns. The patterns that are extracted, generation time, frequency, were collected and consideration of such errors. Through analysis experiments using time series data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.87-98
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• 2008

Electronic Navigational Charts (ENCs) are digital charts encoded in S-57 format, which contain navigational informations such as coastlines, depth areas, and nautical marks. Although they have been successfully used for the safe navigation of ships, they have limited usages and applications because of their specialized data format and access systems. To cope with such drawbacks, S-57 ENCs need to be transformed into more generalized format such as Geography Markup Language (GML). The transformed GML ENCs can be kept in a database for efficiency, and can be accessed through Internet for usability. This paper proposes a new method for transforming and managing ENCs with XML database. S-57 ENCs are lust transformed into GML format, and then stored in a XML database. On the database, users can query for their needs. To validate the feasibility of the proposed method, we developed a protype system, and then conducted several test runs. The system can provide users with easy access to the marine information contained in ENCs. It also provides compatibility and efficiency by virtue of GML and XML database, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1641-1647
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• 2018

In this paper, we describe a portable potentiostat which is capable of cyclic voltammetry(CV) and amperometry for electrochemical dissolved oxygen sensor. In addition, this portable potentiostat can also transmit the measured data wirelessly to android devices such as smart phone, tablet, etc. through Bluetooth. The potentiostat system consists of three parts; a voltage generator circuit which is controlled by Arduino nano and 12-bit DAC(digital to analog converter) to generate necessary electric potential for operating the electrochemical sensor, an oxidation/reduction current measurement circuit, and a Bluetooth module to transmit data wirelessly to an android device. Once measurements are carried out with the android application, the measured data is transmitted to the android device via Bluetooth and displayed using the android app. in real time. In this paper, we report the measured reduction current with a fabricated dissolved oxygen sensor in both saturated-oxygen state and zero-oxygen states. The results of the developed portable potentiostat system are in good agreement with those of the commercial portable potentiostat (${\mu}stat200$, Dropsens inc.). The measured peak reduction currents using the developed potentiostat and the commercial ${\mu}stat200$ potentiostat were $-0.755{\mu}A$ and $-0.724{\mu}A$, respectively. The reduction currents measured at zero-oxygen state were $-0.005{\mu}A$ and $-0.004{\mu}A$. The discrepancy between those two systems seems very small, which implies successful development of a portable and wireless potentionstat.

• Journal of Korea Multimedia Society
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• v.22 no.5
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• pp.613-625
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• 2019

The rise of the Internet of Things (IoT) devices have greatly influenced many industries and one of them is healthcare where wearable devices started to track all your daily activities for better health monitoring accuracy and even down to tracking daily food intake in some cases. With the amounts of data that are being tracked and shared between from these devices, questions were raised on how to uphold user's data privacy when data is shared between these IoT devices and third party. With the blockchain platforms started to mature since its inception, the technology can be implemented according to a variety of use case scenarios. In this paper, we present a system architecture based on the healthcare system and IoT network by leveraging on multiple blockchain networks as the medium in between that should enable users to have direct authority on data accessibility of their shared data. We provide proof of concept implementation and highlight the results from our testing to show how the efficiency and scalability of the healthcare system improved without having a significant impact on the performance of the Electronic Medical Record (EMR) that mostly affected by the previous solution since these solutions directly connected to a public blockchain network and which resulted in significant delays and high cost of operation when a large amount of data or complicated functions are involved.