• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.299-305
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• 2013

The complexity and severe nonlinearity of multi-machine power systems make it difficult to design a control input for voltage regulation using modern control theory. This paper presents a model-based PID control scheme for the regulation of the bus voltage to a desired value. To this end, a fourth-order linear system is constructed using input and output data obtained using the TSAT (Transient Security Assessment Tool); the input is assumed to be applied to the grid through the STATCOM (STATic synchronous COMpensator) and the output from the grid is a bus voltage. On the basis of the model, it is identified as to which open-loop poles of the system make the response to a step input oscillatory. To reduce this oscillatory response effectively, a model-based PID control is designed in such a way that the oscillatory poles are no longer problematic in the closed loop. Simulation results show that the proposed PID control dampens the response effectively.

• The Journal of Korean Association of Computer Education
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• v.13 no.5
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• pp.103-110
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• 2010

If an exterior computer wants to join the Grid/cloud computing platform for a while, all of the related firewalls' filtering rule should be immediately updated. As the platform of Internet application is gradually evolving into the Grid/Cloud environment, the R&D requirement for the dynamic traversing of the multiple firewalls by a single try is also increasing. In this paper, we introduce the new mechanism for the dynamic traversing of the multiple firewalls using the concept of the one-time master key that can dynamically unlock the tiers of firewalls simultaneously instead of the existed filtering rule based method like a lock management at each firewall. The proposed master keys are like one-time password, consisted of IP addresses, port numbers, and TCP's initial sequence numbers, and generated by end users not administrators. They're exchanged mutually in advance and used to make a hole at local-side firewalls for the other's packet incoming. Therefore, the proposed mechanism can function regardless of the number or type of firewalls.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.736-748
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• 2013

In this paper, we analyse the vulnerabilities of KL scheme which is an ID-based authentication scheme for AMI network, and propose two kinds of authentication schemes which satisfy forward secrecy as well as security requirements introduced in the previous works. In the first scheme, we use MDMS which is the supervising system located in an electrical company for a time-synchronizing server, in order to synchronize smart grid devices in home, and we process device authentication with a new secret value generated by OTP function every session. In the second scheme, we use a secret hash-chain mechanism for authentication process, so we can use a new secret value every session. The proposed two schemes have strong points and weak points respectively and those depend on the services area and its environment, so we can select one of them efficiently considering real aspects of AMI environment.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1682-1691
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• 2018

Natural ester is a suitable substitute for mineral oil and has been widely used in AC transformer in many countries. In order to further application of natural ester in direct current (DC) equipment, it is needed to investigate its long term insulation property under DC condition. In this paper, a thermal ageing experiment was conducted for both mineral oil-paper and natural ester-paper insulation. The DC breakdown and space charge characteristics of insulation paper impregnated with natural ester and mineral oil was compared. Results show that the resistivity of the paper immersed in natural ester and mineral oil both increase as the ageing goes on. While insulation paper impregnated with natural ester has higher resistivity and DC breakdown voltage than the paper impregnated with mineral oil. The DC breakdown voltage for the oil impregnated insulation paper being DC pre-stressing is higher than that without pre-stressing. The average DC breakdown field strength difference between the test with pre-stressing and without pre-stressing clearly shows that there is an apparent enhancement effect for the homo-charge injection on the DC breakdown.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.560-564
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• 2007

Korea Basic Science Institute(KBSI) has three general electron microscopes including High Voltage Electron Microscope(HVEM) which is the only one in Korea. Observed images through an electron microscope are what they are tilted by each step and saved, offering the more better circumstances for observers, a reconstruction to 3D could be a essential process. In this process, a warping method decreases distortions maximumly of avoided parts of a camera's focus. All these image treatment processes and 3D reconstruction processes are based on an accompaniment of a highly efficient computer, a number of Grid Node Personal computers share this process in a short time and dispose of it. Grid Node Personal computers' purpose is to make an owner can share different each other and various computing resources efficiently and also Grid Node Personal computers is applying to solve problems like a role scheduling needed for a constructing system, a resource management, a security, a capacity measurement, a condition monitoring and so on. Grid Node Personal computers accomplish roles of a highly efficient computer that general individuals felt hard to use, moreover, a image treatment using the warping method becomes a foundation for reconstructing to more closer shape with an real object of observation. Construction of the electron microscope volume 랜더링 system based on Grid Node Personal computer through the warping process can offer more convenient and speedy experiment circumstances to observers, and makes them meet with experiment outcome that is similar to real shapes and is easy to understand.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.8-14
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• 2020

Recently, there was an increasing demand for an integrated access control system which is capable of user recognition, door control, and facility operations control for smart buildings automation. The market available door lock access control solutions need to be improved from the current level security of door locks operations where security is compromised when a password or digital keys are exposed to the strangers. At present, the access control system solution providers focusing on developing an automatic access control system using (RF) based technologies like bluetooth, WiFi, etc. All the existing automatic door access control technologies required an additional hardware interface and always vulnerable security threads. This paper proposes the user identification and authentication solution for automatic door lock control operations using camera based visible light communication (VLC) technology. This proposed approach use the cameras installed in building facility, user smart devices and IoT open source controller based LED light sensors installed in buildings infrastructure. The building facility installed IoT LED light sensors transmit the authorized user and facility information color grid code and the smart device camera decode the user informations and verify with stored user information then indicate the authentication status to the user and send authentication acknowledgement to facility door lock integrated camera to control the door lock operations. The camera based VLC receiver uses the artificial intelligence (AI) methods to decode VLC data to improve the VLC performance. This paper implements the testbed model using IoT open-source based LED light sensor with CCTV camera and user smartphone devices. The experiment results are verified with custom made convolutional neural network (CNN) based AI techniques for VLC deciding method on smart devices and PC based CCTV monitoring solutions. The archived experiment results confirm that proposed door access control solution is effective and robust for automatic door access control.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.10
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• pp.3607-3623
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• 2014

The increasing demand in promoting cloud computing in either business or other areas requires more security of a cloud storage system. Traditional cloud storage systems fail to protect data integrity information (DII), when the interactive messages between the client and the data storage server are sniffed. To protect DII and support public verifiability, we propose a data integrity verification scheme by deploying a designated confirmer signature DCS as a building block. The DCS scheme strikes the balance between public verifiable signatures and zero-knowledge proofs which can address disputes between the cloud storage server and any user, whoever acting as a malicious player during the two-round verification. In addition, our verification scheme remains blockless and stateless, which is important in conducting a secure and efficient cryptosystem. We perform security analysis and performance evaluation on our scheme, and compared with the existing schemes, the results show that our scheme is more secure and efficient.

• Convergence Security Journal
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• v.14 no.7
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• pp.65-73
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• 2014

Recently, the Internet of things has become issue as the new techniques the cloud computing and the grid computing etc. The Internet of Things is can grow even more that utilization of the range with the development of smart devices. and it has a lot of interest in several industries. In these circumstances, By analyzing the technologies and trends in the Internet of Things, I think you are ready to adapt to future IT field when needed. therefore, this paper are analyzed a various technologies and a case studies of the Internet of things, and it is expected to be used as the road map and material to build environment of the Internet of things in the future.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1899-1904
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• 2017

This paper presents a new one-time password approach generated based on $4{\times}4$ pattern schedule. It demonstrates generation of passkey from initial seed of random codes and mapping out in table pattern schedule which will produce a new form of OTP scheme in protecting information or data. The OTP-2FA has been recognized by many organizations as a landmark to authentication techniques. OTP is the solution to the shortcomings of the traditional user name/password authentication. With the application of OTP, some have benefited already while others have had second thoughts because of some considerations like cryptographic issue. This paper presents a new method of algorithmic approach based on table schedule (grid authentication). The generation of OTP will be based on the random parameters that will be mapped out in rows and columns allowing the user to form the XY values to get the appropriate values. The algorithm will capture the values and extract the predefined characters that produce the OTP codes. This scheme can work in any information verification system to enhance the security, trust and confidence of the user.

• International Journal of Computer Science & Network Security
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• v.22 no.1
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• pp.225-233
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• 2022

The recent outbreak of corona virus (COVID-19) infectious disease had made its forecasting critical cornerstones in most scientific studies. This study adopts a machine learning based time series model - Auto Regressive Integrated Moving Average (ARIMA) model to forecast COVID-19 confirmed cases in Botswana over 60 days period. Findings of the study show that COVID-19 confirmed cases in Botswana are steadily rising in a steep upward trend with random fluctuations. This trend can also be described effectively using an additive model when scrutinized in Seasonal Trend Decomposition method by Loess. In selecting the best fit ARIMA model, a Grid Search Algorithm was developed with python language and was used to optimize an Akaike Information Criterion (AIC) metric. The best fit ARIMA model was determined at ARIMA (5, 1, 1), which depicted the least AIC score of 3885.091. Results of the study proved that ARIMA model can be useful in generating reliable and volatile forecasts that can used to guide on understanding of the future spread of infectious diseases or pandemics. Most significantly, findings of the study are expected to raise social awareness to disease monitoring institutions and government regulatory bodies where it can be used to support strategic health decisions and initiate policy improvement for better management of the COVID-19 pandemic.