• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.1
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• pp.24-31
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• 2015

A differential codebook using M-ary phase shift keying (M-PSK) constellation as its codeword elements, is proposed for Long term evolution (LTE), LTE-Advanced (LTE-A), and/or WiMAX systems. Due to the temporal correlation of the adjacent channel, the consecutive precoding matrices are likely to be similar. This approach quantize only the differential information of the channel instead of the whole channel subspace, which virtually increase the codebook size to realize more accurate quantization of the channel. Especially, the proposed codebook has the same properties of LTE release-8 codebook that is, constant modulus, complexity reduction, and nested property. The mobile station can be designed by using a less expensive non-linear amplifier utilizing the constant modulus property. Computer simulations show that the capacity of the proposed codebook performs better than LTE release-8 codebook with the same amount of feedback information.

• Journal of Digital Convergence
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• v.17 no.9
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• pp.127-133
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• 2019

A callable product is one of service derivatives using options to generate demand and reduce risk. This paper compares two booking admission controls for callable products, the online and the batch admission controls. To this end, the paper computes the optimal booking policy by using the backward dynamic programming and the stochastic optimization method. Intuitively, the provider should outperform under the batch control by utilizing demand information. The contribution of the paper is to show that the two controls are equivalent in terms of the booking strategy and the expected profit, which enables the provider to keep its current control method. The paper develops the closed-form solutions for the three fare classes. The future work is to extend the result to the model with complicated fare structures.

• Korean Association of Arts Management
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• no.56
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• pp.275-304
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• 2020

This paper discusses a way to differentiate contents and enhance the competitiveness of art spaces in rural regions through place assets, noting the growing number of rural art spaces and their great potential as cultural spaces in recent years. First, we surveyed existing research and resources to understand the current status and roles of rural art spaces in the context of theoretical discussions on place assets. Based on this, we classified place assets into physical, human, and symbolic elements. After that, we conducted two case studies that apply this classification. For the case studies on the Ami Art Museum and the Potato Flower Studio, we investigated the sites and conducted in-depth interviews with the directors following a qualitative research method. Our findings through the case studies show that Ami Art Museum and Potato Flower Studio remodeled closed school buildings, which are known as physical place assets in rural areas. However, there was a difference in utilizing other place asset elements, and this resulted in different types of differentiated contents. We found three types of rural art spaces from two case studies: inhabitant-friendly, artist-friendly, and tourist-friendly. Finally, in our research, we presented a method of utilizing place assets that differentiate rural art places along with a method for developing differentiated contents. To conclude, the significance of our study is that it attempted to find out a way to make rural art spaces sustainable, and sought cultural regeneration in rural areas through revitalization of rural art spaces.

• Composites Research
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• v.32 no.6
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• pp.301-306
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• 2019

Triboelectric nanogenerator (TENG) is one of the energy harvesting methods in spotlight that can convert mechanical energy into electricity. As TENGs produce high electrical output, previous studies have shown TENGs that can power small electronics independently. However, recent studies have reported limitations of TENG due to air breakdown and field emission. In this study, we developed a triboelectric nanogenerator that utilizes the metal-to-metal surface contact to induce ion-enhanced field emission and electron avalanche for electrons to flow directly between two electrodes. The average peak open-circuit voltage of this TENG was measured as 340 V, and average peak closed-circuit current was measured as 10 mA. The electrical output of this TENG has shown different value depending on the surface charge of surface charge generation layer. The TENG developed in this study have produced RMS power of 0.9 mW, which is 2.4 times higher compared to conventional TENGs. The TENG developed in this study can be utilized in charging batteries and capacitors to power portable electronics and sensors independently.