• Journal of Satellite, Information and Communications
• /
• v.9 no.4
• /
• pp.20-25
• /
• 2014

In this paper, we provide efficient spectrum sensing technology for smooth use of frequency and energy charge of multi-copter. The proposed structures focus on improving performance of spectrum sensing that is based on Ad-hoc network. First, we explain basic principles and disadvantages of cooperative spectrum sensing and ad-hoc based spectrum sensing. To solve these problems, in this paper, we employ the beamforming technology that guarantees higher transmit primary users' signal power to secondary users in ad-hoc network. The performance of proposed algorithm is analyzed in terms of detection probabilities, and the results of this paper can be applied to the various ad-hoc based Cognitive Radio system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.05a
• /
• pp.250-253
• /
• 2010

Underwater sensor network has attracted more and more attention from the networking research community recently. Most of traditional studies focus on the topology with a single gateway. Underwater sensor network consists of a variable number of sensors and multi-gateway to ensure the reliability of the network. In this paper, we propose a new MAC protocol that can reduce collisions among sensor nodes and improve QoS(Quality of Service) for underwater sensor network with multi-gateway. We evaluate the performance of the proposed scheme through simulation. Simulation results show that the proposed scheme outperforms the existing MAC protocol.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.11 no.8
• /
• pp.3766-3788
• /
• 2017

A blockchain is an underlying technology and basic infrastructure of the Bitcoin system. At present, blockchains and their applications are developing rapidly. However, the basic research of blockchain technology is still in the early stages. The efficiency and reliability of blockchain communication is one of the research problems that urgently need to be studied and addressed. Existing algorithms may be less feasible for blockchain-based communication because they only consider a single communication factor (node communication capability or node trust degree) and only focus on a single communication performance parameter(communication time or communication reliability). In this paper, to shorten the validation time of blockchain transactions and improve the reliability of blockchain-based communication, we first establish a multi-link concurrent communication model based on trust degree, and then we propose a novel integrated factor communication tree algorithm (IFT). This algorithm comprehensively considers the node communication link number and the node trust degree and selects several nodes with powerful communication capacity and high trust as the communication sources to improve the concurrency and communication efficiency. Simulation results indicate that the IFT algorithm outperforms existing algorithms. A blockchain communication routing scheme based on the IFT algorithm can increase communication efficiency by ensuring communication reliability.

• Journal of Information Technology Applications and Management
• /
• v.25 no.4
• /
• pp.79-114
• /
• 2018

Although former scholarly studies mostly focus on exploring leadership effectiveness under the traditional hierarchical leader-subordinate relationship, the research of leadership performance for non-hierarchical organizational structures, particularly the mediating factors of higher-order goals, trust-in-leader, and self-efficacy have been ignored. This study, therefore, makes an attempt to ascertain the impacts of transformational leadership on the performance of subordinates through the mediating effects of higher-order goals, trust-in-leader, and self-efficacy and the differences of these effects in the context of multi-level marketing (MLM). Like the small-sample studies adopted by Barling, Weber, and Kelloway [1996], Barling, Slater, and Kelloway [2000] and Bass, Avolio, Jung, and Berson [2003], this study adopts a sample of 123 MLM distributors of an MLM company in Hong Kong, with a high response rate of 80.4%. The results indicate that the mediating effect of self-efficacy between transformational leadership and performance is significant under non-hierarchical organizational structures such as MLM in China.

• Composites Research
• /
• v.31 no.6
• /
• pp.355-364
• /
• 2018

Flexible energy-storage devices (FESDs) have been studied and developed extensively over the last few years because of demands in various fields. Since electrochemical performance and mechanical flexibility must be taken into account together, different framework from composition of conventional energy-storage devices (ESDs) is required. Numerous types of electrodes have been proposed to implement the FESDs. Herein, we review the works related to the FESDs so far and focus on free-standing electrodes and, especially substrate-based ones. The way to utilize carbon woven fabric (CF) or carbon cloth (CC) as flexible substrates is quite simple and intuitive. However, it is meaningful in the point of that the framework exploiting CF or CC can be extended to other applications resulting in multifunctional composites. Therefore, summary, which is on utilization of carbon-based material and conductive substrate containing CF and CC for ESDs, turns out to be helpful for other researchers to have crude concepts to get into energy-storage multi-functional composite. Moreover, polymer electrolytes are briefly explored as well because safety is one of the most important issues in FESDs and the electrolyte part mainly includes difficult obstacles to overcome. Lastly, we suggest some points that need to be further improved and studied for FESDs.

• Journal of Information Processing Systems
• /
• v.17 no.3
• /
• pp.556-570
• /
• 2021

The existing video expression recognition methods mainly focus on the spatial feature extraction of video expression images, but tend to ignore the dynamic features of video sequences. To solve this problem, a multi-mode convolution neural network method is proposed to effectively improve the performance of facial expression recognition in video. Firstly, OpenFace 2.0 is used to detect face images in video, and two deep convolution neural networks are used to extract spatiotemporal expression features. Furthermore, spatial convolution neural network is used to extract the spatial information features of each static expression image, and the dynamic information feature is extracted from the optical flow information of multiple expression images based on temporal convolution neural network. Then, the spatiotemporal features learned by the two deep convolution neural networks are fused by multiplication. Finally, the fused features are input into support vector machine to realize the facial expression classification. Experimental results show that the recognition accuracy of the proposed method can reach 64.57% and 60.89%, respectively on RML and Baum-ls datasets. It is better than that of other contrast methods.

• Current Optics and Photonics
• /
• v.7 no.5
• /
• pp.545-556
• /
• 2023

This paper introduces volume-sharing multi-aperture imaging (VMAI), a potential approach proposed for volume reduction in space-borne imagers, with the aim of achieving high-resolution ground spatial imagery using deep learning methods, with reduced volume compared to conventional approaches. As an intermediate step in the VMAI payload development, we present a phase-1 design targeting a 1-meter ground sampling distance (GSD) at 500 km altitude. Although its optical imaging capability does not surpass conventional approaches, it remains attractive for specific applications on small satellite platforms, particularly surveillance missions. The design integrates one wide-field and three narrow-field cameras with volume sharing and no optical interference. Capturing independent images from the four cameras, the payload emulates a large circular aperture to address diffraction and synthesizes high-resolution images using deep learning. Computational simulations validated the VMAI approach, while addressing challenges like lower signal-to-noise (SNR) values resulting from aperture segmentation. Future work will focus on further reducing the volume and refining SNR management.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.24 no.1
• /
• pp.49-54
• /
• 2024

Data imbalance is a common issue encountered in classification problems, stemming from a significant disparity in the number of samples between classes within the dataset. Such data imbalance typically leads to problems in classification models, including overfitting, underfitting, and misinterpretation of performance metrics. Methods to address this issue include resampling, augmentation, regularization techniques, and adjustment of loss functions. In this paper, we focus on loss function adjustment, particularly comparing the performance of various configurations of loss functions (Cross Entropy, Balanced Cross Entropy, two settings of Focal Loss: 𝛼 = 1 and 𝛼 = Balanced, Asymmetric Loss) on Multi-Class black-box video data with imbalance issues. The comparison is conducted using the I3D, and R3D_18 models.

• Journal of the Korean housing association
• /
• v.24 no.4
• /
• pp.1-8
• /
• 2013

Recently international marriage has been increasing steadfastly in Korea and its diversity of nationality has been expanding also. Korean government and academic circles are actively studying on such trends in population to find out proper measures to cope with such social changes. But their studies on improving the residential environment that is the base of the essential three factors of life, clothing, food and housing are not sufficient enough. Therefore it is necessary to study in depth and diversity about the residential environments of multi-culture families that are the base of their life. It is necessary to comparatively study the residential status and demands of these immigrants by marriage. The purpose of this study is to comparatively study the residential status and demand of immigrant women by marriage according to their nationalities. The objects of this study are the immigrant women by marriage from China, Vietnam and Cambodia who take the high portion of immigrant women in Jeonju-si and survey was used as study method. The result of this study revealed that the general characteristics, residential status and demands of immigrant women showed certain differences and the direction of residential plans for them in future based on these differences was proposed. This study is meaningful as basic information to improve the residential conditions of the multi-culture families in order to enhance their quality of life in preparation for the coming society of multi-culture.

• The Journal of the Korea Contents Association
• /
• v.11 no.12
• /
• pp.742-752
• /
• 2011

Multi-Level Marketing distribution process to reduce occurs in a number of the distribution costs to consumers of reducing its profits outside the area subject to the non-store or stores is the way to a special sale. Japan for the multi-level marketing Article 33 of the Act on Specified Commercial Transactions at or below the regulatory chain is defined as dealers. However, unlike other legislative attention two -dimensional chain for sales transactions are regulated. A chain of Japanese regulations on sales transactions, the definition is very specific and detailed regulations, and the chain is specifically for sales transactions in detail how to take regulatory and regulatory relief of pre- and post- regulatory focus, and the streamlining of regulatory aimed at restrictions on how the implications of such a large country.