• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제10권8호
• /
• pp.3551-3567
• /
• 2016

The Low Earth Orbit satellite network has the unique characteristics of the non-uniform and time-variant traffic load distribution, which often causes severe link congestion and thus results in poor performance for delay-sensitive flows, especially when the network is heavily loaded. To solve this problem, a novel adaptive routing algorithm, referred to as the delay-oriented adaptive routing algorithm (DOAR), is proposed. Different from current reactive schemes, DOAR employs Destination-Sequenced Distance-Vector (DSDV) routing algorithm, which is a proactive scheme. DSDV is extended to a multipath QoS version to generate alternative routes in active with real-time delay metric, which leads to two significant advantages. First, the flows can be timely and accurately detected for route adjustment. Second, it enables fast, flexible, and optimized QoS matching between the alternative routes and adjustment requiring flows and meanwhile avoids delay growth caused by increased hop number and diffused congestion range. In addition, a retrospective route adjustment requesting scheme is designed in DOAR to enlarge the alternative routes set in the severe congestion state in a large area. Simulation result suggests that DOAR performs better than typical adaptive routing algorithms in terms of the throughput and the delay in a variety of traffic intensity.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• 제45권10호
• /
• pp.836-843
• /
• 2017

In lunar exploration, the necessity of utilizing rover is verified by the examples of the Soviet Union and China and the similar Mars missions of the United States. In order to achieve the successful management of a lunar rover, a high precision navigation technique is required, and accordingly, high precision initial alignment is essential. Even though it is general to perform initial alignment in a steady state, a multiposition alignment technique is applied when high performance is needed. On the lunar surface, however, the performance of initial alignment decreases from that on Earth, and it cannot be improved by applying multiposition alignment method owing to certain constraints of lunar environment. In this paper, a sun sensor aided multiposition alignment technique is proposed. The measurement model for a sun vector is established, and its observability analysis is performed. The performance of the proposed algorithm is verified through computer simulations, and the results show the estimation performance is improved dramatically.

• Journal of Power Electronics
• /
• 제17권2호
• /
• pp.533-541
• /
• 2017

This paper presents a novel Parameter-Independent Fictive-Axis (PIFA) approach for the Voltage-Oriented Control (VOC) algorithm used in grid-tied single-phase inverters. VOC is based on the transformation of the single-phase grid current into the synchronous reference frame. As a result, an orthogonal current signal is needed. Traditionally, this signal has been obtained from fixed time delays, digital filters or a Hilbert transformation. Nevertheless, these solutions present stability and transient drawbacks. Recently, the Fictive Axis Emulation (FAE) VOC has emerged as an alternative for the generation of the quadrature current signal. FAE requires detailed information of the grid current filter along with its transfer function for signal creation. When the transfer function is not accurate, the direct and quadrature current components present steady-state oscillations as the fictive two-phase system becomes unbalanced. Moreover, the digital implementation of the transfer function imposes an additional computing burden on the VOC. The PIFA VOC presented in this paper, takes advantage of the reference current to create the required orthogonal current, which effectively eliminates the need for the filter transfer function. Moreover, the fictive signal amplitude and phase do not change with a frequency drift, which results in an increased reliability. This yields a fast, linear and stable system that can be installed without fine tuning. To demonstrate the good performance of the PIFA VOC, simulation and experimental results are presented.

• Journal of the Institute of Electronics and Information Engineers
• /
• 제54권4호
• /
• pp.10-15
• /
• 2017

Feedback burden of a full-digital energy beamforming, which is known as the optimal precoding scheme for radio frequency (RF) energy transfer, is huge because it uses a vector quantization for a channel feedback. To reduce the feedback burden, we consider a beam steering based wireless energy transfer, which uses a scalar quantization. Researches related to the beam steering based wireless energy transfer have been studied in special channel model with an assumption of full channel state information at the transmitter. In this paper, we analyze the beam steering scheme compared with the full-digital energy beamforming for practical channel models with channel estimation errors. According to characteristics of the millimeter wave channel, the number of antennas of the base station and the user, the distance between them, and channel estimation errors, we simulate the performance of the beam steering scheme and analyze reasons why.

• Journal of KIISE
• /
• 제44권3호
• /
• pp.306-313
• /
• 2017

Named entity recognition (NER) seeks to locate and classify named entities in text into pre-defined categories such as names of persons, organizations, locations, expressions of times, etc. Recently, many state-of-the-art NER systems have been implemented with bidirectional LSTM CRFs. Deep learning models based on long short-term memory (LSTM) generally depend on word representations as input. In this paper, we propose an approach to expand word representation by using pre-trained word embedding, part of speech (POS) tag embedding, syllable embedding and named entity dictionary feature vectors. Our experiments show that the proposed approach creates useful word representations as an input of bidirectional LSTM CRFs. Our final presentation shows its efficacy to be 8.05%p higher than baseline NERs with only the pre-trained word embedding vector.

• Publications of The Korean Astronomical Society
• /
• 제15권spc2호
• /
• pp.57-64
• /
• 2000

It is realized that the extraterrestrial matter is in ionized state, plasma, so the matter of this kind behaves as not expected because of its sensitiveness to electric and magnetic fields and its ability to carry electric currents. This kind of subtle change can be observed by an instrument for the magnetic field measurement, the magnetometer usually mounted on the rocket and the satellite, and based on the ground observatory. The magnetometer is a useful instrument for the spacecraft attitude control and the Earth's magnetic field measurements for the scientific purpose. In this paper, we present the preliminary design and the test results of the two onboard magnetometers of KARl's (Korea Aerospace Research Institute) sounding rocket, KSR­III, which will be launched during the period of 2001-02. The KSR-III magnetometers consist of the fluxgate magnetometer, MAG/AIM (Attitude Information Magnetometer) for acquiring the rocket flight attitude information, and of the search-coil magnetometer, MAG/SIM (Scientific Investigation Magnetometer) for the observation of the Earth's magnetic field fluctuations. With the MAG/AIM, the 3-axis attitude information can be acquired by the comparison of the resulting dc magnetic vector fields with the IGRF (International Geomagnetic Reference Field). The Earth's magnetic field fluctuations ranging from 10 to 1,000 Hz can also be observed with the MAG/SIM measurement.

• Physical Therapy Korea
• /
• 제23권1호
• /
• pp.87-93
• /
• 2016

Background: Posture balance control is the ability to maintain the body's center of gravity in the minimal postural sway state on a supportive surface. This ability is obtained through a complicated process of sensing the movements of the human body through sensory organs and then integrating the information into the central nervous system and reacting to the musculoskeletal system and the support action of the musculoskeletal system. Motor function, including coordination, motor, and vision, vestibular sense, and sensory function, including proprioception, should act in an integrated way. However, more than half of stroke patients have motor, sensory, cognitive, and emotional disorders for a long time. Motor and sensory disorders cause the greatest difficulty in postural control among stroke patients. Objects: The purpose of this study is to determine the effect of visual and somatosensory information on postural sway in stroke patients and carrying out a kinematic analysis using a tri-axial accelerometer and a quantitative assessment. Methods: Thirty-four subjects posed four stance condition was accepted various sensory information for counterbalance. This experiment referred to the computerized dynamic posturography assessments and was redesigned four condition blocking visual and somatosensory information. To measure the postural sway of the subjects' trunk, a wireless tri-axial accelerometer was used by signal vector magnitude value. Ony-way measure analysis of variance was performed among four condition. Results: There were significant differences when somatosensory information input blocked (p<.05). Conclusion: The sensory significantly affecting the balance ability of stroke patients is somatosensory, and the amount of actual movement of the trunk could be objectively compared and analyzed through quantitative figures using a tri-axial accelerometer for balance ability.

• Food Science of Animal Resources
• /
• 제38권2호
• /
• pp.362-375
• /
• 2018

This study proposed a rapid microscopic examination method for pork freshness evaluation by using the self-assembled hyperspectral microscopic imaging (HMI) system with the help of feature extraction algorithm and pattern recognition methods. Pork samples were stored for different days ranging from 0 to 5 days and the freshness of samples was divided into three levels which were determined by total volatile basic nitrogen (TVB-N) content. Meanwhile, hyperspectral microscopic images of samples were acquired by HMI system and processed by the following steps for the further analysis. Firstly, characteristic hyperspectral microscopic images were extracted by using principal component analysis (PCA) and then texture features were selected based on the gray level co-occurrence matrix (GLCM). Next, features data were reduced dimensionality by fisher discriminant analysis (FDA) for further building classification model. Finally, compared with linear discriminant analysis (LDA) model and support vector machine (SVM) model, good back propagation artificial neural network (BP-ANN) model obtained the best freshness classification with a 100 % accuracy rating based on the extracted data. The results confirm that the fabricated HMI system combined with multivariate algorithms has ability to evaluate the fresh degree of pork accurately in the microscopic level, which plays an important role in animal food quality control.

• The Journal of Internal Korean Medicine
• /
• 제27권1호
• /
• pp.27-39
• /
• 2006

Objectives : Induction of CYP2E1 by ethanol is believed to be one of the major mechanism by which ethanol generate a state of oxidative stress. Previous studies showed that treatment with Chungganhaeju-tang prevents hepatic inflammation and apoptosis in alcoholic liver disease. The purpose of our study is to determine if Chungganhaeju-tang can also protect against alcohol-induced cytotoxicity in CYP2E1-transfected HepG2 cells. Materials and Methods : CYP2E1-transfected HepG2 cells and control vector-transfected HepG2 cells were exposed for isx hours to Chungganhaeju-tang, and then 50 mM of ethanol was added and left for two days. Results : Ethanol significantly decreased cell viability in CYP2E1-transfected HepG2 cells and increased apoptosis. These alterations were attenuated by Chungganhaeju-tang. This was accompanied by an improvement of NF-${\kappa}B$ and Akt activation. Conclusion : These results suggest that Chungganhaeju-tang exerts inhibitory effect against the cytotoxicity induced by alcohol in CYP2E1-transfected HepG2 cells, and that this is a protective action due, at least in part, to an activation of NF-${\kappa}B$ that plays a key role in the protection mechanism, and in reducing hepatotoxic cytokine gene expression.

• Korean Journal of Applied Biomechanics
• /
• 제15권1호
• /
• pp.45-61
• /
• 2005

Stance is defined as any state in which the total mass of the body is supported by the feet. In order to maintain stance, the sum of gravito-inertial forces acting on the body must be registered by equal and opposite forces at the region of contact between the organism and the support surface. Balance is controlled by applying forces to the surface of support so as to maintain the body's center of mass vertically above the feet. for a muIti-segment organism, there can be a variety of ways in which balance can be controlled, since movements of different body segments can have similar effects on the control of balance. In general, the organism tends to have a body configuration that is aligned with gravito-inertial force when there are no external forces acting on it. If any segments of the body are not aligned with gravito-inertial force vector, a torque on that segment would tend to move the body's center of mass. The maintenance of postural stability is accomplished in humans by a complex neural control system. This requires organizing integrating and acting upon visual, vestibular, and somatosensory input, providing orientation information to the postural control system. The information necessary to control and coordinate movement is provided by the visual sense of eye position with respect to the surrounding surface layout, the vestibular sense of head orientation in the gravito-inertial space, and the somatic sense of body segment position relative to one another and to the support surface. In this study, perception and action capability was examined from various points of view. The underlying assumption of the study was that the change of postural configuration could be effected by organism, environment and task goal.