• Wind and Structures
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• v.30 no.4
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• pp.405-421
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• 2020

Quayside container cranes are important delivery machineries located in the most frontiers of container terminals, where strong wind attacks happen occasionally. Since the previous researches on quayside container cranes mainly focused on the mean wind load and static response characteristics, the fluctuating wind load and dynamic response characteristics require further investigations. In the present study, the aerodynamic wind loads on quayside container cranes were obtained from wind tunnel tests. The probabilistic and spectral models of the fluctuating aerodynamic loads were established. Then the joint probabilistic distributions of dynamic wind-induced responses were derived theoretically based on a series of Gaussian and independent assumption of resonant components. Finally, the results were validated by time domain analysis using wind tunnel data. It is concluded that the assumptions are acceptable. And the presented approach can estimate peak dynamic sliding force, overturning moments and leg uplifts of quayside container cranes effectively and efficiently.

• Journal of Information Processing Systems
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• v.8 no.4
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• pp.669-684
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• 2012

Discrete wavelet transforms are extensively preferred in biomedical signal processing for denoising, feature extraction, and compression. This paper presents a new denoising method based on the modeling of discrete wavelet coefficients of ECG in selected sub-bands with Kernel density estimation. The modeling provides a statistical distribution of information and noise. A Gaussian kernel with bounded support is used for modeling sub-band coefficients and thresholds and is estimated by placing a sliding window on a normalized cumulative density function. We evaluated this approach on offline noisy ECG records from the Cardiovascular Research Centre of the University of Glasgow and on records from the MIT-BIH Arrythmia database. Results show that our proposed technique has a more reliable physical basis and provides improvement in the Signal-to-Noise Ratio (SNR) and Percentage RMS Difference (PRD). The morphological information of ECG signals is found to be unaffected after employing denoising. This is quantified by calculating the mean square error between the feature vectors of original and denoised signal. MSE values are less than 0.05 for most of the cases.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.3
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• pp.894-907
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• 2022

The features extracted by convolutional neural networks are more descriptive of images than traditional features, and their convolutional layers are more suitable for retrieving images than are fully connected layers. The convolutional layer features will consume considerable time and memory if used directly to match an image. Therefore, this paper proposes a feature weighting and region integration method for convolutional layer features to form global feature vectors and subsequently use them for image matching. First, the 3D feature of the last convolutional layer is extracted, and the convolutional feature is subsequently weighted again to highlight the edge information and position information of the image. Next, we integrate several regional eigenvectors that are processed by sliding windows into a global eigenvector. Finally, the initial ranking of the retrieval is obtained by measuring the similarity of the query image and the test image using the cosine distance, and the final mean Average Precision (mAP) is obtained by using the extended query method for rearrangement. We conduct experiments using the Oxford5k and Paris6k datasets and their extended datasets, Paris106k and Oxford105k. These experimental results indicate that the global feature extracted by the new method can better describe an image.

• Journal of Information Processing Systems
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• v.18 no.6
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• pp.813-821
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• 2022

Intelligent monitoring, life entertainment, medical rehabilitation, and other fields are only a few examples where visual image technology is becoming increasingly sophisticated and playing a significant role. Recognizing Wushu, or martial arts, movements through the use of visual image technology helps promote and develop Wushu. In order to segment and extract the signals of Wushu movements, this study analyzes the denoising of the original data using the wavelet transform and provides a sliding window data segmentation technique. Wushu movement The Wushu movement recognition model is built based on the hidden Markov model (HMM). The HMM model is trained and taught with the help of the Baum-Welch algorithm, which is then enhanced using the frequency weighted training approach and the mean training method. To identify the dynamic Wushu movement, the Viterbi algorithm is used to determine the probability of the optimal state sequence for each Wushu movement model. In light of the foregoing, an HMM-based martial arts movements recognition model is developed. The recognition accuracy of the HMM model increases to 99.60% when the number of samples is 4,000, which is greater than the accuracy of the SVM (by 0.94%), the CNN (by 1.12%), and the BP (by 1.14%). From what has been discussed, it appears that the suggested system for detecting martial arts acts is trustworthy and effective, and that it may contribute to the growth of martial arts.

• Geophysics and Geophysical Exploration
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• v.13 no.1
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• pp.51-60
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• 2010

To determine subglacial topography and internal features of the Fourcade Glacier on King George Island in Antarctica, helicopter-borne and ground-towed ground-penetrating radar (GPR) data were recorded along four profiles in November 2006. Signature deconvolution, f-k migration velocity analysis, and finite-difference depth migration applied to the mixed-phase, single-channel, ground-towed data, were effective in increasing vertical resolution, obtaining the velocity function, and yielding clear depth images, respectively. For the helicopter-borne GPR, migration velocities were obtained as root-mean-squared velocities in a two-layer model of air and ice. The radar sections show rugged subglacial topography, englacial sliding surfaces, and localised scattering noise. The maximum depth to the basement is over 79m in the subglacial valley adjacent to the south-eastern slope of the divide ridge between Fourcade and Moczydlowski Glaciers. In the ground-towed profile, we interpret a complicated conduit above possible basal water and other isolated cavities, which are a few metres wide. Near the terminus, the GPR profiles image sliding surfaces, fractures, and faults that will contribute to the tidewater calving mechanism forming icebergs in Potter Cove.

• Journal of the Korean Society of Safety
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• v.12 no.4
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• pp.214-219
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• 1997

The mechanical seals, which are installed in rotating machines like pump and compressor, are generally used as sealing devices in the many fields of industries. The failure of mechanical seals such as leakage, crack, breakage, fast and severe wear, excessive torque, and squeaking results in big problems. To identify abnormal phenomena on mechanical seals and to propose the proper monitoring parameter for the failure of mechanical seals, sliding wear experiments were conducted. Acoustic emission, torque, and temperature were measured during experiments. Optical microstructure was observed for the wear processing after every 10 minute sliding at rotation speed of 1750 rpm and scanning electron microscopy was also observed. Except for the initial part of every experiment, the variation of acoustic emission was well coincided with torque variation during the experiments. This study concludes that acoustic emission and torque are proper monitoring parameters for the failure of mechanical seals. The intensity of acoustic emission signals is measured in root mean square voltage. Temperature of sealing face will be used as a parallel parameter for increasing the reliability of monitoring system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.162-168
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• 2006

Understanding of propagation characteristics is very important for the wireless communication system design and wireless communication service construction. In this paper, propagation characteristics is measured and analyzed at 2.45Ghz frequency band under curved subway tunnel environment. We constituted channel measurement system with sliding correlation and five different kind of antennas. The purpose of five different type of antennas is to compare propagation characteristics according to beam shape of antennas. The path loss under tunnel environment is average $4.38^{\sim}14.41dB$ lower than free space and circular polarization antenna marked smallest path loss. Also, path loss is smallest when the receiver antenna located outside of tunnel in th curved section. 90% of delay components of all antennas measured within 20ns and directional antenna has more wide coherence bandwidth than omni-directional antenna. According to measured result, when we consider path loss and delay characteristics, circular polarization antenna is most suitable under tunnel environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2581-2589
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• 2002

In this research, fretting tests were conducted in air to investigate the wear characteristics of fuel cladding materials with the fretting parameters such as normal load, slip amplitude, frequency and the number of cycles. A high frequency fretting wear tester was designed for this experiment by KAERI. After the experiments, the wear volume and the shape of wear contour were measured by the surface roughness tester. Tribologically transformed structures(TTS) were analysed by means of optical and scanning electron microscopes to identify the main wear mechanisms. The results of this study showed that the wear volume were increased with increasing slip amplitude, and the shape of wear contour was transformed V-type to W-type. Also, it was found that the critical slip amplitude was 168${\mu}{\textrm}{m}$. These phenomena mean that wear mechanism transformed partial slip to gross slip to accelerate wear volume. The wear depth increased with an increase of friction coefficient due to increase of normal load and frequency. The fretting wear mechanisms were believed that, after adhesion and surface plastic deformation occurred by relative sliding motion on the contact between two specimens, TTS creation was induced by surface strain hardening and wear debris were detached from the contact surface which were produced by the micro crack propagation and creation.

• Structural Engineering and Mechanics
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• v.61 no.4
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• pp.527-538
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• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.

• Journal of Korea Foundry Society
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• v.14 no.5
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• pp.471-479
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• 1994

Al-2%Si-2%Mg alloy containing SiC particle in 20, $70{\mu}m$ were prepared by mean of squeeze casting with various pressure 50, 100, 150 and 220MPa respectively. The specimens were made by casting into $50{\Phi}{\times}100{\ell}$ mold under various squeeze conditions(pressures, pressurizing temperature, particle sizes). Mechanical properties(hardness, tensile strength, elongation and wear characteristics) were evaluated at room temperature with those various fabrication factors. It became feasible to make favorable Al-SiCp composite free from casting defects by the injection of Ar gas during melting and 100MPa pressure squeeze casting. However, pressure of 50MPa was not sufficient to avoid completely porosity formation as a result of precessing and shrinkage during solidification. As the particle size is smaller and the squeeze pressure is higher, the hardness and tensile strength at room temperature are higher. Cell size became smaller gradually with increase of squeeze pressure. With increase of squeeze pressure(MPa), wear behaviors of those composites were changed from adhesive into abrasive wear, and the tendency of above behavior became outstanding with increasing sliding speed. The chemical reaction(4Al＋3SiC${\rightarrow}$$Al_4C_3+3Si$) is more accelerated at interface between SiCp and matrix with increase of squeeze pressure. Therefore $Al_4C_3$ intercompound and Si peak intensity is increased at interface.