• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.579-585
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• 2002

The investigation into the effect of various feedback errors on system performance can help the robust feedback channel design and transmission of exact feedback channel information as well. In this paper, we address the algorithm that determines space combining weight vector maximizing received signal power at mobile on frequency flat fading channel and investigate the performance degradation by feedback channel delay in the FDD/CDMA systems employing transmit beamforming. We observe the effect of feedback channel delay corresponding to the number of transmit antennas and the temporal/spatial correlation of channel. The results show that performance is more sensitive to feedback delay with the larger number of antennas when fadings at transmit antennas are not spatially correlated.

• Tunnel and Underground Space
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• v.4 no.2
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• pp.132-143
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• 1994

Many methods and techniques to reduce ground vibrations are well known. Some of them are to adopt electric millisecond detonators with a sequential blasting machine or an initiating system with an adequate number of delay intervals. The types of electric detonators manufactured in korea include instantaneous, decisecond and millisecond delays but numbers of delay intervals are only limited from No.1 to No.20 respectively. It is not sufficient to control accurately millisecond time with these detonators in tunnel excavation. Sequential fire time refers to adding an external time delay to a detonators norminal firing time to obtain sequential initiation and it is determined by sequential timer setting. To reduce the vibration level, sequential blasting machine(S.B.M) with decisecond detonators was adopted. A total of 134 blasts was recorede at various sites. Blast-to-structure distances ranged from 20.3 to 42.0 meter, where charge weight varied from 0.24 to 0.75 kg per delay. The results can be summarized as follow: 1. The effects of sequential blasting machine on the vibration level are discussed. The vibration level by S.B.M are decreased approximately 14.38~18.05% compare to level of conventional blasting and cycle time per round can be saved. 2. The empirical equations of particle velocity were obtained in S.B.M and conventional blasting. V=K(D/W1/3)-n, where the values for n and k are estimated to be 1.665 to 1.710 and 93.59 to 137 respectively. 3. The growth of cracks due to vibrations are found but the level fall to within allowable value.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.12
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• pp.5860-5876
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• 2018

A single snapshot data can only provide limited amount of information so that the rank of covariance matrix is not full, which is not adopted to complete the parameter estimation directly using the traditional super-resolution method. Aiming at solving the problem, a joint time delay and angle estimation using matrix pencil method based on information reconstruction vector for orthogonal frequency division multiplexing (OFDM) signal is proposed. Firstly, according to the channel frequency response vector of each array element, the algorithm reconstructs the vector data with delay and angle parameter information from both frequency and space dimensions. Then the enhanced data matrix for the extended array element is constructed, and the parameter vector of time delay and angle is estimated by the two-dimensional matrix pencil (2D MP) algorithm. Finally, the joint estimation of two-dimensional parameters is accomplished by the parameter pairing. The algorithm does not need a pseudo-spectral peak search, and the location of the target can be determined only by a single receiver, which can reduce the overhead of the positioning system. The theoretical analysis and simulation results show that the estimation accuracy of the proposed method in a single snapshot and low signal-to-noise ratio environment is much higher than that of Root Multiple Signal Classification algorithm (Root-MUSIC), and this method also achieves the higher estimation performance and efficiency with lower complexity cost compared to the one-dimensional matrix pencil algorithm.

• The Korean Journal of Air & Space Law and Policy
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• v.35 no.2
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• pp.197-224
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• 2020

This paper reviews and criticizes some issues as to the case of A and Others v. Finnair Oyj [2020] Case C-832/18 by examining EU Regulations and practical point of views. Under this case, the travellers brought an action against Finnair in light of the Air Passenger Regulation12, seeking compensation for both the first cancelled flight, and the delayed re-routed flight. Finnair had paid the first compensation, but refused to grant the second claim, arguing that the regulation did not set out that passengers were eligible for a second claim in those situations, and that the delay of the second flight was a consequence of 'extraordinary circumstances' under the regulation. The Court of Appeal in Helsinki has asked the CJEU whether an air passenger is entitled to a further compensation where a re-routed flight they have agreed to take is delayed, where both the original and rerouted flight are operated by the same air carrier. The CJEU held that the regulation does not in any way limit the rights of passengers where they find their flights being re-routed. As such, under earlier CJEU case law, the relevant travellers here were entitled to compensation for cancellation of the first flight and delay of the second flight. It also disagreed with Finnair's assessment that the technical failure in the re-routing flight was a matter of extraordinary circumstances.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.373-381
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• 2021

This paper details the result of flight experiment that examines performance of roll angle estimation algorithm of slowly rolling munition taking time delay of measurement into account when measurement comes in delayed fashion. As the measurement is passed through low pass filter for numerical stabilization and de-noising purpose which induces time delay, we design augmented state Kalman filter that incorporates distribution models of stochastic delay over time. Flight experiment was conducted to verify the algorithm at around 250m high AGL(Above Ground Level) conveying velocity of 28m/s from fixed-wing mother plane to the munition. Munition was made spun with respect to its roll axis using internal reaction wheel afterward. Numerical comparison of proposing method's roll estimation performance with that of commercial aerospace graded GPS/INS shows that proposed filter design can effectively compensate time delay of measurement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.7
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• pp.1188-1195
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• 2006

This paper presents an efficient design method of 2-D state-space digital filter based on an improved branch-and -bound algorithm. The resultant 2-D state-space digital filters whose coefficients are represented as the sum of two power-of-two terms, are attractive for high-speed operation and simple implementation. The feasibility of the proposed method is demonstrated by several experiments. The results show that the approximation error and group delay characteristic of the resultant filters are similar to those of the digital filters which designed in the continuous coefficient space.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.59.2-59.2
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• 2015

We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes of the late-type stars. These observations have been carried out at the K and Q bands using KVN since 2014 August and were scheduled to test the feasibility of multi-frequency phase referencing analysis on the maser lines. In order to increase the accuracy of group delay solution in the fringe search on the continuum source, the IF channels were randomly distributed within the available bandwidth of 500 MHz in each band. The positions of all maser spots are relatively described with respect to the position of the reference continuum source through the source frequency phase referencing technique, and this provides the astrometric position accuracy. Therefore, the relative locations of the H2O maser spots with respect to the SiO maser spots are determined from our observations, and the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the maser pumping mechanism around the late-type stars.

• Journal of the Korean Society of Systems Engineering
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• v.10 no.2
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• pp.71-79
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• 2014

To enhance success probability of a system development project, its overall risk level should be minimized through systematically managing schedules, costs, and technical performances. However, Attempts to manage technical performance compared to numerous efforts to control costs and schedules in such projects are deficient. Particularly, a space launch vehicle, a large complex system, development project is much less likely to meet its technical performance objectives due to its technological difficulty, along with schedule delay and cost overrun. The technical performance management (TPM) is a method for tracking and managing technical progress in order to achieve technical performance targets within schedule and budget. In this paper, we investigate applications of the TPM in several space launch vehicle development projects. Then we propose and validate the TPM process to achieve a successful mission in such projects.

• Journal of the Korean Society for Railway
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• v.2 no.2
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• pp.21-30
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• 1999

This study proposes the analysis and evaluation method of time series ultrasonic signal using the phase space-frequency domain. Features extracted from time series signal analyze quantitatively characteristics of weld defects. For this purpose, analysis objectives in this study are features of time domain and frequency domain. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics resulting from distance shifts such as parts of head and flange even though the types of defects are identified. These differences in characteristics of weld defects enables the evaluation of unique characteristics of defects in the weld zone. In quantitative fractal feature extraction, feature values of 3.848 in the case of part of head(crack) and 4.102 in the case of part of web(side hole) and 3.711 in the case of part of flange(crack) were proposed on the basis of fractal dimension. Proposed phase space-frequency domain method in this study can integrity evaluation for defect signals of rail weld zone such as side hole and crack.

• The Korean Journal of Pain
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• v.8 no.1
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• pp.156-158
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• 1995

Total spinal anesthesia is a well documented serious life threatening complication which results from an attempted spinal or epidural analgesia. We had an accidental total spinal anesthesia associated with a cranial nerve paralysis and an eventual unconsciousness during epidural analgesia. A 45-year-old female with an uterine myoma was scheduled for a total abdominal hysterectomy under the epidural analgesia. A lumbar tapping for the epidural analgesia was performed in a sitting position at a level between $L_{3-4}$, using a 18 gauge Tuohy needle. Using the "Loss of Resistance" technique to identify the epidural space, the first attempt failed; however, the second attempt with the same level and the technique was successful. The epidural space was identified erroneously. However, fluid was dripping very slowly through the needle, which we thought was the fluid from the normal saline which was injected from the outside to identify the space. Then 20 ml of 2% lidocaine was administered into the epidural space. Shortly after the spinal injection of lidocaine, many signs of total spinal anesthesia could be clearly observed, accompanied by the following progressing signs of intracrainal nerve paralysis: phrenic nerve, vagus nerve, glossopharyngeal nerve and trigeminal nerve in that order. Then female was intubated and her respiration was controlled without delay. The scheduled operation was carried out uneventfully for 2 hours and 20 minutes. The patient recovered gradually in th4e reverse order four hours from that time.