• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.439-454
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• 2013

Hollow cylindrical tubes with a prismatic sandwich lining designed to replace the solid cross-sections are studied in this paper. The sections are divided by a number of revolving periodic unit cells and three topologies of unit cells (Square, Triangle and Kagome) are proposed. Some types of multiple-topology designed materials are also studied. The feasibility and accuracy of a homogenization method for obtaining the equivalent parameters are investigated. As the curved elements of a unit cell are represented by straight elements in the method and the ratios of the lengths of the curved elements to the lengths of the straight elements vary with the changing number of unit cells, some errors may be introduced. The frequencies of the first five modes and responses of the complete and equivalent models under an internal static pressure and an internal step pressure are compared for investigating the scope of applications of the method. The lower bounds and upper bounds of the number of Square, Triangular and Kagome cells in the sections are obtained. It is shown that treating the multiple-topology designed materials as a separate-layer structure is more accurate than treating the structure as a whole.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1724-1732
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• 2001

In this paper, a technique for increasing the bandwidth of microstrip array antennas using the parallel coupled lines on a single layer is presented. Four types of wideband microstrip array antenna are designed and the characteristics of each type are analyzed. In addition, an iterative method using a distributed network is proposed to design the parallel coupled lines as a wideband impedance matching network. Measurements show that the proposed antennas provide wider bandwidths ∼1.7 times those of conventional microstirp array antennas, while the sizes of proposed antennal are the same as that of a conventional array. And low cross-polarization level can be obtained through symmetrical locations of the parallel coupled lines section

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.371-372
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• 2006

This study was carried out to analyze the effect of wind load on the structural stability of a container crane according to the change of the boom shape using wind tunnel test and provide a container crane designer with data which can be used in a wind resistance design of a container crane assuming that a wind load 75m/s wind velocity is applied in a container crane. Data acquisition conditions for this experiment were established in accordance with the similarity. The scale of a container crane dimension, wind velocity and time were chosen as 1/200, 1/13.3 and 1/15. And this experiment was implemented in an Eiffel type atmospheric boundary layer wind tunnel with $11.52m^2$ cross-section area. Each directional drag and overturning moment coefficients of a container crane according to the change of the boom shape were investigated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.10a
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• pp.87-94
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• 2006

In this study we carried out to analyze the effect of wind load on the structural stability of a container crane according to the change of the boom shape using wind tunnel test and provided a container crane designer with data which can be used in a wind resistance design of a container crane assuming that a wind load at 75m/s wind velocity is applied on a container crane. Data acquisition conditions for this experiment were established in accordance with the similarity. The scale of a container crane dimension, wind velocity and time were chosen as 1/200, 1/13.3 and 1/15. And this experiment was implemented in an Eiffel type atmospheric boundary-layer wind tunnel with $11.52m^2$ cross-section area. Each directional drag and overturning moment coefficients were investigated and uplift forces at each supporting point due to the wind load were analyzed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1224-1231
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• 2018

Automatic age estimation has been used in many social network applications, practical commercial applications, and human-computer interaction visual-surveillance biometrics. However, it has rarely been explored. In this paper, we propose an automatic age estimation system, which includes face detection and convolutional deep learning based on an inception module. The latter is a 22-layer-deep network that serves as the particular category of the inception design. To evaluate the proposed approach, we use 4,000 images of eight different age groups from the Adience age dataset. k-fold cross-validation (k = 5) is applied. A comparison of the performance of the proposed work and recent related methods is presented. The results show that the proposed method significantly outperforms existing methods in terms of the exact accuracy and off-by-one accuracy. The off-by-one accuracy is when the result is off by one adjacent age label to the above or below. For the exact accuracy, the age label of "60+" is classified with the highest accuracy of 76%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.838-841
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• 2005

This study was carried out to analyze the effect of wind load on the structural stability of a 50ton articulation type container crane using wind tunnel test and provide a container crane designer with data which can be used in a wind resistance design of an articulation type container crane assuming that a wind load 75m/s wind velocity is applied in an articulation type container crane. Data acquisition conditions for this experiment were established in accordance with the similarity. The scale of an articulation type container crane dimension, wind velocity and time were chosen as 1/200, 1/13.3 and 1/15. And this experiment was implemented in an Eiffel type atmospheric boundary layer wind tunnel with $11.52m^2$ cross-section area. Each directional drag and overturning moment coefficients were investigated and uplift forces at each supporting point due to the wind load were analyzed.

• Steel and Composite Structures
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• v.18 no.2
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• pp.357-374
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• 2015

Orthotropic decks composed of deck plate, ribs, cross beams and wearing surface are frequently used in industry to span long distances due to their light structures and load carrying capacities. As a result they are broadly preferred in industry and there are a lot of bridges of this type exist in the world. Nevertheless, some of them cannot sustain the anticipated service life and damages in form of cracks develop in steel components and wearing surface. Main reason to these damages is seen as the repetitive wheel loads, namely the fatigue loading. Solutions to this problem could be divided into two categories: qualitative and quantitative. Qualitative solutions may be new design methodologies or innovative materials, whereas quantitative solution should be arranging dimensions of deck structure in order to resist wheel loads till the end of service life. Wearing surface on deck plate plays a very important role to avoid or mitigate these damages, since it disperses the load coming on deck structure and increases the bending stiffness of deck plate by forming a composite structure together with it. In this study the effect of Elastic moduli, Poisson ratio and thickness of wearing surface on the stresses emerged in steel deck and wearing surface itself is investigated using a FE-model developed to analyze orthotropic steel bridges.

• Journal of Information Processing Systems
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• v.15 no.4
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• pp.833-852
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• 2019

In real time applications, due to their effective cost and small size, wireless networks play an important role in receiving particular data and transmitting it to a base station for analysis, a process that can be easily deployed. Due to various internal and external factors, networks can change dynamically, which impacts the localisation of nodes, delays, routing mechanisms, geographical coverage, cross-layer design, the quality of links, fault detection, and quality of service, among others. Conventional methods were programmed, for static networks which made it difficult for networks to respond dynamically. Here, machine learning strategies can be applied for dynamic networks effecting self-learning and developing tools to react quickly and efficiently, with less human intervention and reprogramming. In this paper, we present a wireless networks survey based on different machine learning algorithms and network lifetime parameters, and include the advantages and drawbacks of such a system. Furthermore, we present learning algorithms and techniques for congestion, synchronisation, energy harvesting, and for scheduling mobile sinks. Finally, we present a statistical evaluation of the survey, the motive for choosing specific techniques to deal with wireless network problems, and a brief discussion on the challenges inherent in this area of research.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.3
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• pp.175-183
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• 2008

In wireless sensor networks with ad hoc networking capability, sensor nodes are battery operated and are usually disposable once deployed. As a result, each sensor node senses and communicates with limited energy and, thus, energy efficiency has been studied as a key design factor which determines lifetime of a wireless sensor network, and it is more improved recently by using so-called cross-layer optimization technique. In this paper, we propose and implement a new energy saving mechanism that reduces energy consumption during data collection by controlling transmission power at sensor nodes and then measure its performance in terms of lifetime improvement for the wireless sensor network platform ZigbeX. When every sensor node transmits sensed data to its clusterhead, it controls its transmission power down to as low level as communication is possible, resulting in energy saving. Each sensor node controls its transmission power based on RSSI(Received Signal Strength Indicator) of the packet received from its clusterhead. In other words, the sensor node can save energy by controlling its transmission power down to an appropriate level that its clusterhead safely receives the packet it transmits. According to the repetitive experiment of the proposed scheme on the ZigbeX platform using the packet analyzer developed by us, it is observed that the network lifetime is prolonged by up to 21.9% by saying energy during the data collection occupying most amount of network traffic.

• Fire Science and Engineering
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• v.25 no.3
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• pp.78-84
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• 2011

In this study, we have measured the charring rate of solid sawn timber as a preceding step for develop performance based fire safety design method of wood framed building structures. The follows are the summary of fire test results carried out with $400{\times}400$ mm cross-section Douglas-fir in varied of thickness and grain directions. I) When the timber thickness increase under same dimension, the charring rate decreases gradually. It is seemed the charring layer up on a thickness roles as a insulation, gives combustion delaying time to specimen. 2) The charring rates measured at different depths (10, 20, 30, 40 mm) in timber which varying thickness (20, 40, 80, 120 mm) when exposed maximum 1 hour standard fire increase by 30 mm depth, but decrease at 40 mm. It is seemed the minimum charr layer should be 30 mm for having role of insulation. 3) The charring rate of cross section surface (direction of perpendicular to grain) was more high than that of grain direction. It can be explained by the cracks and gaps from greater charr contraction made more heat flux incident into timber.