• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1D
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• pp.1-6
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• 2011

The Context-Awareness technology which can provide the appropriate information to the human after estimating a lot of information exceeds the time and space in the ubiquitous environment is being developed now. GIS (Geographic Information System) and LBS (Location Based Services) based context awareness is one of these kinds of technology. The context awareness based transfer guide service which can provide useful information, according to the different information which was got from different sensors which were set in different places, to the pedestrian who is using the transfer center will be introduced in this paper. About the result of the service prototype which was tested in test-bed, the context awareness information such as the inside location and density calculation's accuracy is 90%, and the response time of the service is in 10 seconds, and also, the reliability will be higher if more advanced based infra will be used, so it is consider that it can be used to provide service enough.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.777-787
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• 2012

The transient analysis for the output voltage of a piezoresistive microaccelerometer takes a relatively high computation time because at least two iterations are required to calculate the piezoresistive-structural coupled response at each time step. In this study, the high computational cost for calculating the transient output voltage is considerably reduced by an approach integrating the mode superposition method and the least square method. In the approach, data on static displacement and output voltage calculated by piezoresistive-structural coupled simulation for three acceleration inputs are used to develop a quadratic regression model, relating the output voltage to the displacement at a certain observation point. The transient output voltage is then approximated by a regression model using the displacement response cheaply calculated by the mode superposition method. A high-impact microaccelerometer subject to several types of acceleration inputs such as 100,000 G shock, sine, step, and square pulses are adopted as a numerical example to represent the efficiency and accuracy of the suggested approach.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.121-127
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• 2017

From the perspective of commercializing rotating machines equipped with magnetic bearings, maintaining the error between the mechanical center and the magnetic center within an acceptable level is crucial. The existing method of measuring the center error is to adjust the position references that minimize the current imbalance present in levitation control outputs. However, this method can be applied only after all the components of the system are operational. In this paper, we present a new method of estimating the center error by using only the position sensors and a current source. A force model that relates the position of the rotor with the coil currents is set up. Using this model, the center error is estimated by minimizing the difference between the force angles and the contact angles measured in a pull test. The feasibility of the method is numerically and experimentally validated.

• The Journal of Society for e-Business Studies
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• v.23 no.2
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• pp.97-110
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• 2018

With the advent of the 4-th industrial revolution, manufacturing companies have increasing interests in the realization of smart manufacturing by utilizing their accumulated facilities data. However, most previous research dealt with the structured data such as sensor signals, and only a little focused on the unstructured data such as text, which actually comprises a large portion of the accumulated data. Therefore, we propose an association rule mining based facility error pattern extraction framework, where text data written by operators are analyzed. Specifically, phrases were extracted and utilized as a unit for text data analysis since a word, which normally used as a unit for text data analysis, is unable to deliver the technical meanings of facility errors. Performances of the proposed framework were evaluated by addressing a real-world case, and it is expected that the productivity of manufacturing companies will be enhanced by adopting the proposed framework.

• Journal of IKEEE
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• v.24 no.2
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• pp.468-474
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• 2020

This paper describes the hardware implementation of SPECK, a lightweight block cipher algorithm developed for the security of applications with limited resources such as IoT and wireless sensor networks. The block cipher SPECK crypto-core supports 8 block/key sizes, and the internal data-path was designed with 16-bit for small gate counts. The final round key to be used for decryption is pre-generated through the key initialization process and stored with the initial key, enabling the encryption/decryption for consecutive blocks. It was also designed to process round operations and key scheduling independently to increase throughput. The hardware operation of the SPECK crypto-core was validated through FPGA verification, and it was implemented with 1,503 slices on the Virtex-5 FPGA device, and the maximum operating frequency was estimated to be 98 MHz. When it was synthesized with a 180 nm process, the maximum operating frequency was estimated to be 163 MHz, and the estimated throughput was in the range of 154 ~ 238 Mbps depending on the block/key sizes.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.1
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• pp.67-73
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• 2017

An analysis of thermal degradation of epoxy based adhesive performed by thermogravimetry tests are presented in this study. Six different heating rates were employed for the weight change measurements. Based on the data, an Arrhenius type modeling equation was developed by calculating activation energies and proportional constants, and $n^{th}$ polynomial function was adopted to predict the weight change rates. The prediction results by the modeling was compared with the data using the average activation energy. It was found that the activation energy at the each heating rate was not same due to the different degradation kinetics, especially at the high heating rate. To overcome this pitfall, a new approach using exponential function series was introduced and employed. The calculation results showed very good agreements with the test data regardless of the heating rates.

• The Journal of Korean Association of Computer Education
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• v.14 no.1
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• pp.137-146
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• 2011

Edward de Bono's six thinking hats is effective to increase the excellence of the thinking and cultivate divergent thinking. In particular, this method is effective in finding a reasonable solution through analyzing issue from a variety of perspective. In this paper, we developed the system for an effective debate learning that student's own ideas based on six thinking hats are shared and expressed in speech and images through Android devices sensors. We analyzed the tools and guidelines by making design structural model for system design. The developed system was evaluated by the teacher through demonstration and practice and we analyzed through evaluation results the effectiveness and the improvement of the system. The evaluation results were analysed that the developed system is more effective improve motivation and debate ability than web based debate learning system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.5
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• pp.12-20
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• 2008

RFID(Radio frequency indentification) technology, that the reader detect the tag information attached on the objects without contact, is considered the kernel of realizing tile Ubiquitous Sensor Network. Particularly, because there are lots of tags(which the reader have to detect) in the UHF RFID system(that is applied at the Logistic & Distribution industry). In the UHF RFID system the negative effects, we called the tag-collision, may occur and we should solve these effects. So, in the EPCglobal Gen2 protocol they present the Slotted Random Anti-collision algorithm to prevent the tag-collision effect. In this paper, in order to minimize the tag-collision effect and bring on the system efficiency, we propose the Power Increasing Method that controls the transmission power of the reader depending on the environment and verily the improved performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.1013-1022
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• 2010

In this paper, we propose a C-band radiometer for remote sensing of land surface temperature and present its experiment results using asphalt as target. Total power type is selected for high sensitivity and low power consumption, super-heterodyne type is selected for stable high gain. A radiometer designed at 5.1 GHz to have operating bandwidth of 110 MHz has system gain of 59 dB, noise figure of 2.7 dB and receiving sensitivity of 0.45 K. We have measured surface temperature on asphalt by using implemented system and thermometer. Analysis data of each measurement results show that a radiometer operates linearly with output voltage variation rate of 6 $mV/^{\circ}C$. As a result, we verified validity of a developed C-band radiometer for remote sensing of land surface temperature.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.361-365
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• 2010

In recent years, social networks come into the spotlight as the important ways to find people or share information. Especially, existing social network services based on the Internet, such as Facebook.com and Cyworld.com, are now extended into the mobile environment. A mobile phone easily collects the personal information since it is carried by the user at all times, and various types of data can be gathered together with the advance of sensor technologies. These features differentiate the mobile social network services from the previous Internet-based services. In this paper, we estimate the user's mobile social contexts like closeness and relationship between the user and surrounding people using Bayesian networks. The mobile social contexts can be employed as important information for providing mobile social network services, and experimental results on real world data have verified their possibilities.