• Journal of Satellite, Information and Communications
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• v.12 no.4
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• pp.141-145
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• 2017

Spectrum sensing is a critical functionality of Cognitive Radio(CR) systems and the CR systems can be applied to RF energy harvesting systems to improve an energy harvesting rate. There are number of spectrum sensing techniques. One of techniques is energy detection. Energy detection is the simplest detection method and is the most commonly used. But, energy detection has a hidden terminal problem in real wireless communication, because of secondary user (SU) can be affected by frequency fading and shadowing. Cooperative spectrum sensing can solve this problem using spatial diversity of SUs. But it has a problem of increasing data by processing multiple secondary. So, we propose the system model using adaptive spectrum sensing algorithm and system model is simulated. This algorithm chooses sensing method between single energy sensing and cooperative energy according to the received signal's Signal to Noise Ratio (SNR) from Primary User (PU). The simulation result shows that adaptive spectrum sensing has an efficiency and improvement in CR systems.

• Journal of Astronomy and Space Sciences
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• v.22 no.2
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• pp.139-146
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• 2005

A model of advection-dominated accretion flows has been highlighted in the last decade. Most of calculations are based on self-similar solutions of equations governing the accreting flows. We revisit self-similar solutions of the simplest form of advection-dominated accretion flows. We explore the parameter space thoroughly and seek another category of self-similar solutions. In this study we allow the parameter f less than zero, which denotes the fraction of energy transported through advection. We have found followings: 1. For f > 0, in real ADAF solutions the ratio of specific heats ${\gamma}$ satisfies 1 < ${\gamma}$ < 5/3 for O ${\leq}$ f ${\leq}$ 1. On the other hands, in wind solutions a rotating disk does not exist. 2. For f < 0, in real ADAF solutions with ${\epsilon}$ greater than zero ${\gamma}$ requires rather exotic range, that is, ${\gamma}$ < 1 or ${\gamma}$ > 5/3. When -5/2 < ${\epsilon}$' < 0, however, allowable ${\gamma}$ can be found in ${\gamma}$ < 5/3, in which case 4{\Omega}_0$,_ is imaginary. 3. For a negative $u_0$,+ with f > 0, solutions are only allowed with exotic ${\gamma}$, that is, 1 < ${\gamma}$ or ${\gamma}$ > (5f/2-5/3)/(5f/2-1)when O < f < 2/5, (5f/2-5/3)/(5f/2-1) < ${\gamma}$ < 1 when f > 2/5. Since ${\epsilon}$' is negative, 4{\Omega}_0$,+ is again an imaginary quantity. For a negative $u_0$,+ with f < 0, ${\gamma}$ is allowed in 1 < 7 < (5|f|/2 + 5/3)/(5|f|/2 + 1). We briefly discuss physical implications of what we have found.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.869-879
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• 1995

The new field of learning control develops controllers that learn to improve their performance at executing a given task, based on experience performing this task. The simplest forms of learning control are based on the same concept as integral control, but operating in the domain of the repetitions of the task. In the previous paper, I had studied the use of such controllers in a decentralized system, such as a robot with the controller for each link acting independently. The basic result of the paper is to show that stability of the learning controllers for all subsystems when the coupling between subsystems is turned off, assures stability of the decentralized learning in the coupled system, provided that the sample time in the digital learning controller is sufficiently short. In this paper, we present two examples. The first illustrates the effect of coupling between subsystems in the system dynamics, and the second studies the application of decentralized learning control to robot problems. The latter example illustrates the application of decentralized learning control to nonlinear systems, and also studies the effect of the coupling between subsystems introduced in the input matrix by the discretization of the system equations. The conclusion is that for sufficiently small learning gain, and sufficiently small sample time, the simple learning control law based on integral control applied to each robot axis will produce zero tracking error in spite o the dynamic coupling in the robot equations. Of course, the results of this paper have much more general application than just to the robotics tracking problem. Convergence in decentralized systems is seen to depend only on the input and output matrices, provided the sample time is suffiently small.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1105-1116
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• 2008

Cognitive radio is one of the most effective techniques to improve the spectrum utilization efficiency. To implement the cognitive radio, spectrum sensing is considered as the key functionality because only counting on it, can the secondary users identify the spectrum holes and utilize them efficiently without causing interference to primary users. Generally, there are several spectrum sensing methods; the most common and simplest method is energy detection. However, the conventional energy detection has some disadvantages, which are caused by noise, especially, uncertain noise power leads to degradation of energy detector. In this paper, to solve this problem, we proposed sliding window-based energy detection method which can devide the frequency band of primary signal and noise using sliding window to estimate the power of primary user without the noise effect and achieve the better performance. It can calculate the energy of primary user only and can detect the primary signal. The simulation result shows that our proposed method outperforms conventional one.

• Journal of Digital Contents Society
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• v.4 no.1
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• pp.11-21
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• 2003

In computer vision, the goal of stereopsis is to determine the surface structure of real world form two or more perspective views of scene. It is similar to human visual system. We can avoid obstacles, recognize objects, and manipulate machine using three-dimensional information. Until recently, only gray-level images have been used as input to computation for depth determination, but the availability of color can further enhance the performance of computational stereopsis. There are many models to provide efficient color system. The simplest model, RGB model treats color as if it were composed of separate entities. Each color channel is processed individually by the same stereopsis module as used in the gray-level model. His Model decouples intensity component from color information. So it can deal with color properties without defect intensity information. Opponent color model is based on human visual system. In this model, the red-green-blue colors are combined into three opponent channels before further processing.

• Journal of the Korea Fashion and Costume Design Association
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• v.15 no.4
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• pp.101-112
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• 2013

The purpose of this study was to evaluate the differences of the visual image on the variations in the waist position and the width of the wide pants. The stimuli were 9 samples: 3 variations of the waist position and 3 variations of the width of hem line. The data was obtained from 56 fashion students and analyzed by using Factor Analysis, Anova, Scheffe's Test and the MCA method. The results of this study are as follows; 1. The visual evaluation by the waist position and the width of the wide pants is composed of 4 factors: attractiveness, physical characteristics, modesty, and personality. Among these factors, the attractiveness was the most important. 2. The high waist pants showed the most characteristic and soft under the condition that the width of the hem line was 98cm at the third stage, while the natural waist pants showed no characteristics and stiff in case the width of the hem line was 66cm at the first stage. 3. The first stage pants were simplest and modest in case the waist position was low, while the third stage pants were the most complicated and untidiest in case the waist position was natural. 4. The waist position and the width of the wide pants interacted with the physical characteristics and the modesty. 5. According to the MCA on the attractiveness and the personality, the width affected to the visual image of the wide pants than the waist position did.

• Physical Therapy Korea
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• v.17 no.4
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• pp.41-48
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• 2010

The WeeFIM is an outcome measure used worldwide to evaluate the functional abilities of children. The aim of this study was to evaluate the psychometric properties of WeeFIM in Korean children with cerebral palsy (CP) using the Rasch model. The mean age of the participants (92 boys and 53 girls) was 10.6 years (SD=2.3, range 5~15 years). The Winsteps software was used for analyzing the internal construct validity and reliability of WeeFIM. For analyzing the internal validity the motor and cognitive area items of the WeeFIM were analyzed both together and separately. When all 18 items were analyzed 4 were considered to be misfits; upper extremity dressing, lower extremity dressing, toileting, and comprehension. When only the 13 motor items were analyzed, toileting, bladder management, and bowel management were considered misfits. In addition, only comprehension was considered as a misfit among the 5 cognitive items. The most difficult motor items were stair climbing, and bathing. The simple ones were eating, bowel management, and bladder management. The most difficult cognitive item was problem solving, and the simplest one was comprehension. The person separation indexes and reliability for combined and divided instruments were reported as excellent. These results demonstrated the applicability of WeeFIM to Korean CP children with satisfactory reliability and validity. Further studies should include young children with CP and compare item difficulty among the different types of CP. In addition, the Korean normative data of nondisabled children should be used to compare the cultural differences between Korea and other countries.

• Journal of the Korean Home Economics Association
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• v.38 no.1
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• pp.25-38
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• 2000

This study focuses on the Russian Constructivist Textile Design in the post-revolutionary period, of the early 20th century. Russian textile of the time is highly valued in the west in terms of innovative changes in aesthetic directions, which has become one of the most important centers for the development of new textiles, or the origin of industrial design. Most of brilliant mass-production patterns were produced specially by the pioneers of constructivists such as Stepanova and Popova who were influenced by 'Maxism' through the Revolution regarded themselves as productivists for the proletariat. They were inspired by the avant-garde movements, which were involved with traditionalism, futuristic mechanism, stylization of nature, pure geometrical and abstract form. Early textile design was based on the relationship between the graphic methods of design and the technology because they regarded art as physical, intellectual and technical production. They created all the excitement made from the primary simplest forms of precise mathmatical shapes, such as the circle, the triangle, the rectangle and horizontle and vertical lines. These geometric design can be interpreted as the mechanization of the artists'labor, or methods in line with the technology of mass production, however partly roots in the rich tradition of Russian decorative art. On the other hand, stable crystalline construction on the surface reflect urban architectural complex, and the world of industry in graphic form. They were interested in illusion of movement, cinematic movement of vertical linear rhythms, optical formations and vibrations, by composing a multi-leveled constructions by several spatial planes, or color-field, and combining structures of several intersecting matrices, and superimposing parts of the forms on each other. All these characteristics of the Russian textile designs reflect the complex interactions between 'art and society' of Constructivist's idea and represent the traits of the epoch.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.105-111
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• 2017

In this paper, the analysis results are shown about several weights of Weighted K-Nearest Neighbor method, Recently, it is employed for the indoor positioning technologies using WiFi fingerprint which has been actively studied. In spite of the simplest feature, the W-KNN method shows comparable performance to another methods using WiFi fingerprint technology. So W-KNN method has employed in the existing indoor positioning system. It shows positioning error performance according to data preprocessing and weight factor, and the analysis on the weight is very important. In this paper, based on the real measured WiFi fingerprint data, the estimation error is analyzed and the performances are compared, for the case of data processing methods, of the weight of average, variance, and distance, and of the averaging several position of number K. These results could be practically useful to construct the real indoor positioning system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.61-66
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• 2005

Location Positioning is a major technology for ubiquitous computing. Recently the research on Location Positioning using UWB is on going. In order to construct an in-door location network, synchronization of base stations is very important. NTP is Popularly used as clock synchronization protocol ranging from LAN to WAN. Also Master-Slave scheme is the simplest method to synchronize in-door network. We compare and analyze NTP and Master-Slave schemes according to the statistical channel model for indoor multipath propagation environment. In this paper, error ranges are calculated at various circumstances that in-door network expands from one primary base station into several base stations. We compared the correctness of NTP and Master-Slave synchronization methods. NTP is more reasonable synchronization protocol in in-door environment.