2019, Vol.14, No.3

Journal of Knowledge Information Technology and Systems 2023 KCI Impact Factor : 0.89

pISSN : 1975-7700 / eISSN : 2734-0570
https://journal.kci.go.kr/kkits

Various bypass techniques have been developed to hide malicious code in image files among non-executable files. It is difficult to detect by reputation or signature-based antivirus methods when unknown malware is hidden. In this paper, we proposed a neutralizing method of hidden malicious code to analyze the structure of the original image file format and disable the malicious code through image data area conversion even if there is no prior information about the signatures or characteristics of malicious codes. The proposed method consists of image file extraction phase, file format analysis phase, file transformation phase, and management phase of transformation image file. In the image file transformation phase, header information transformation, specific string filtering transformation for additional information, and image pixel data transformation using nonlinear transfer function are performed. In order to prove the effectiveness of the proposed method, 10 malicious code - hidden image files among 48,220 of the latest malicious code (paid API) purchased from Virus Total Company were used in the experiment. After the file extraction phase, the format analysis phase, and the image file conversion phase for the neutralizing method, the experimental results show that the virus detection amount is reduced quantitatively and thus the effectiveness of the proposed method is verified. In addition, by using the non-linear transfer function, the converted image file was able to neutralize the malicious code while maintaining the same quality as the original image, which could not be distinguished by the naked eye.

This study aimed to fine the effects of learner’s trait factors on discussion flow and satisfaction degree, focusing on self-regulated learning strategy and smartphone addiction. The research data was collected from the 46 discussion learners. After discussion, the data was analyzed through multivariate analysis of variance. The results of this study were summarized as follows : Firstly, the learner's self-regulated learning strategy affects the learner's discussion flow degree. That is, the high self-regulated learning strategy group was more effective than the low self-regulated learning strategy in the discussion flow degree. Secondly, the learner's self-regulated learning strategy affects the learner's discussion satisfaction degree. That is, the high self-regulated learning strategy group was more effective than the low self-regulated learning strategy in the discussion satisfaction degree. Thirdly, the learner's smartphone addiction affects the learner's discussion flow degree. That is, the general user group was more effective than the smartphone addiction group in the discussion flow degree. Lastly, the learner's smartphone addiction affects the learner's discussion satisfaction degree. That is, the general user group was more effective than the smartphone addiction group in the discussion satisfaction degree. Based on these research results, it was suggested that the high self-regulated learning strategy and the prevention of smartphone addiction should be considered in order to improve the discussion outcomes.

In recent years, the potential technology for short distance and high-data wireless communication systems has been grown. Ultra-wideband (UWB) technology has emerged as a considerable interest and new technology. According to a proposed standard, the UWB system is assigned to operate over 3.1 - 5 GHz or 3.1 - 10.6 GHz. Most of the proposed applications allow transmission of signals between 3.1 and 10.6 GHz. In this paper, a wideband CMOS Low Noise Amplifier (LNA) is proposed with a inverter structure using inductor peaking technique and broadband matching techniques, which meets stringent requirements of UWB system in the proposed specifications. The proposed LNA has the inverter structure and cascode structure with shunt feedback. Measurement results show the maximum power gain (S21) of 17.4 dB with the 3-dB band and input/output reflection coefficient (S11, S22) of less than –9.7 dB from 3.1 to 9.6 GHz. In addition, the fabricated LNA achieves the minimum noise figure (NF) of 3.5 dB from the operating frequency, which value is much lower than previously reported state-of-the-art wideband amplifiers. The input-referred IIP3 and the input-referred P1dB of the proposed LNA are achieved as 0 dBm and –10 dBm, respectively, while consuming 27 mW in 0.18- RF CMOS process.