• Wind and Structures
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• v.23 no.2
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• pp.109-125
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• 2016

Flow interference is investigated between two tripped cylinders of identical diameter D at stagger angle ${\alpha}=0^{\circ}{\sim}180^{\circ}$ and gap spacing ratio $P^*$ (= P/D) = 0.1 ~ 5, where ${\alpha}$ is the angle between the freestream velocity and the line connecting the cylinder centers, and P is the gap width between the cylinders. Two tripwires, each of diameter 0.1D, were attached on each cylinder at azimuthal angle ${\beta}={\pm}30^{\circ}$, respectively. Time-mean drag coefficient ($C_D$) and fluctuating drag ($C_{Df}$) and lift ($C_{Lf}$) coefficients on the two tripped cylinders were measured and compared with those on plain cylinders. We also conducted surface pressure measurements to assimilate the fluid dynamics around the cylinders. $C_D$, $C_{Df}$ and $C_{Lf}$ all for the plain cylinders are strong function of ${\alpha}$ and $P^*$ due to strong mutual interference between the cylinders, connected to six interactions (Alam and Meyer 2011), namely boundary layer and cylinder, shear-layer/wake and cylinder, shear layer and shear layer, vortex and cylinder, vortex and shear layer, and vortex and vortex interactions. $C_D$, $C_{Df}$ and $C_{Lf}$ are very large for vortex and cylinder, vortex and shear layer, and vortex and vortex interactions, i.e., the interactions where vortex is involved. On the other hand, the interference as well as the strong interactions involving vortices is suppressed for the tripped cylinders, resulting in insignificant variations in $C_D$, $C_{Df}$ and $C_{Lf}$ with ${\alpha}$ and $P^*$. In most of the (${\alpha}$, $P^*$ ) region, the suppressions in $C_D$, $C_{Df}$ and $C_{Lf}$ are about 58%, 65% and 85%, respectively, with maximum suppressions 60%, 80% and 90%.

• Journal of IKEEE
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• v.24 no.2
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• pp.372-377
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• 2020

This paper is based on the triangular inset patch antenna as the basic structure, and the array structure is the twin tree form to improve the antenna's main lobe gain and reduce the side lobe gain. A twin tree structure was implemented by placing two identical trees of 2-4-6 arrays of triangular inset patches side by side. The parametric analysis confirmed that the gap between tree structures arranged side by side is most effective for impedance matching. The fabricated antenna has a gain of 16.74 dBi at 24.15 GHz, and the beam width of the main lobe is 22° in the E-plane and 6° in the H-plane. The antenna size was 125 mm × 50 mm, and a Taconic TLC substrate with a dielectric constant of 3.2 was used. Although the main lobe gain is improved over the twin tree structure, The directivity in the beam pattern due to the mutual interference of the two tree array structure can be improved.

• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.529-540
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• 2020

The mechanical properties of timber construction have drawn more attention after the 2013 Lushan earthquake. A strong desire to preserve this ancient architectural styles has sprung up in recent years, especially for residential buildings of the mountainous areas. In the column-and-tie timber construction, continuous-tenon joints are the most common structural form to connect the chuanfang (similar to the beam in conventional structures) and the column. To study the cyclic performance of the continuous-tenon joints in column-and-tie timber construction, the reversed lateral cyclic loading tests were carried out on three 3/4 scale specimens with different section heights of the chuanfang. The mechanical behavior was assessed by studying the ultimate bending capacity, deformation ductility and energy dissipation capacity. Test results showed that the slippage of chuanfang occurred when the specimens entered the plastic stage, and the slippage degree increased with the increase of the section height of chuanfang. An obvious plastic deformation of the chuanfang occurred due to the mutual squeezing between the column and chuanfang. A significant pinching was observed on the bending moment-rotation curves, and it was more pronounced as the section height of chuanfang increased. The further numerical investigations showed that the flexural capacity and initial stiffness of the continuous-tenon joints increased with the increase of friction coefficient between the chuanfang and the column, and a more obvious increasing of bending moment occurred after the material yielding. The compressive strength perpendicular to grain of the material played a more significant role in the ultimate bending capacity of continuous-tenon joints than the compressive strength parallel to grain.

• The KIPS Transactions:PartB
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• v.14B no.3 s.113
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• pp.183-190
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• 2007

VoiceXML is new markup language which is designed for web resource navigation via voice based on XML. An application using VoiceXML is classified into mutual-controlled and machine-controlled form dialog structure. Such dialog structures can't construct service which provide free navigation of web resource by user because a scenario is decided by application developer. In this paper, we propose VoiceXML application structure using user-controlled form dialog system which decide service scenario according to user's intention. The proposed application automatically detects recognition candidates from requested information by user, and then system uses recognition candidate as voice-anchor. Also, system connects each voice-anchor with new voice-node. An example of proposed system, we implement news service with IT term dictionary, and we confirm detection and registration of voice-anchor and make an estimate of hit rate about measurement of an successive offer from information according to user's intention and response speed. As the experiment result, we confirmed possibility which is more freely navigation of web resource than existing VoiceXML form dialog systems.

• Proceedings of the KAIS Fall Conference
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• 2003.11a
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• pp.223-230
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• 2003

Feature-based similarity retrieval has become an important research issue in multimedia database systems. The features of multimedia data are useful for discriminating between multimedia objects (e 'g', documents, images, video, music score, etc.). For example, images are represented by their color histograms, texture vectors, and shape descriptors, and are usually high-dimensional data. The performance of conventional multidimensional data structures(e'g', R- Tree family, K-D-B tree, grid file, TV-tree) tends to deteriorate as the number of dimensions of feature vectors increases. The R＊-tree is the most successful variant of the R-tree. In this paper, we propose a SOM-based R＊-tree as a new indexing method for high-dimensional feature vectors.The SOM-based R＊-tree combines SOM and R＊-tree to achieve search performance more scalable to high dimensionalities. Self-Organizing Maps (SOMs) provide mapping from high-dimensional feature vectors onto a two dimensional space. The mapping preserves the topology of the feature vectors. The map is called a topological of the feature map, and preserves the mutual relationship (similarity) in the feature spaces of input data, clustering mutually similar feature vectors in neighboring nodes. Each node of the topological feature map holds a codebook vector. A best-matching-image-list. (BMIL) holds similar images that are closest to each codebook vector. In a topological feature map, there are empty nodes in which no image is classified. When we build an R＊-tree, we use codebook vectors of topological feature map which eliminates the empty nodes that cause unnecessary disk access and degrade retrieval performance. We experimentally compare the retrieval time cost of a SOM-based R＊-tree with that of an SOM and an R＊-tree using color feature vectors extracted from 40, 000 images. The result show that the SOM-based R＊-tree outperforms both the SOM and R＊-tree due to the reduction of the number of nodes required to build R＊-tree and retrieval time cost.

• Earthquakes and Structures
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• v.10 no.1
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• pp.53-71
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• 2016

Unconventional computer vision and image processing techniques offer significant advantages for experimental applications to shaking table testing, as they allow the overcoming of most typical problems of traditional sensors, such as encumbrance, limitations in the number of devices, range restrictions and risk of damage of the instruments in case of specimen failure. In this study, a 3D motion optical system was applied to analyze shake table tests carried out, up to failure, on a natural-scale masonry structure retrofitted with steel reinforced grout (SRG). The system makes use of wireless passive spherical retro-reflecting markers positioned on several points of the specimen, whose spatial displacements are recorded by near-infrared digital cameras. Analyses in the time domain allowed the monitoring of the deformations of the wall and of crack development through a displacement data processing (DDP) procedure implemented ad hoc. Fundamental frequencies and modal shapes were calculated in the frequency domain through an integrated methodology of experimental/operational modal analysis (EMA/OMA) techniques with 3D finite element analysis (FEA). Meaningful information on the structural response (e.g., displacements, damage development, and dynamic properties) were obtained, profitably integrating the results from conventional measurements. Furthermore, the comparison between 3D motion system and traditional instruments (i.e., displacement transducers and accelerometers) permitted a mutual validation of both experimental data and measurement methods.

• Journal of Korean society of Dental Hygiene
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• v.18 no.6
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• pp.1013-1023
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• 2018

Objectives: The purpose of this study is to evaluate dental hygiene students' recognition of safety management and phantom practice in dental radiology. Methods: The study subjects were 409 students in six regions who completed a dental radiology practice course and had on-job experience more than once. After understanding the study purpose and contents, they answered a questionnaire. The main jobs in dental radiology were analyzed. Results: As a result, regarding the most difficult aspects of dental radiology practice, "it is impossible to irradiate the mouth directly with X-rays" was the most common response (29.1%). Regarding the question "what is the main role of students in dental radiology practice?", the answer "it is shooting simulations using phantoms" accounted for 59.7% of responses. The most difficult regions in bisecting and paralleling radiography with a phantom were found to be the maxillary & mandibular molars and premolars. The most difficult technique was reported to be locating XCP maintenance to fit inside the mouth for both molars and premolars. The most difficult region to perform bitewing radiography using the phantom was the molar region (2.87), and the most difficult to perform occlusal radiography approaches were maxillary anterior general occlusal radiography (2.92) and mandibular cross-sectional occlusal radiography (3.00). Conclusions: The most technically difficult point in bitewing and occlusal radiography was the correct positioning of the vertical and horizontal angles. Radiography practice was considered to be more effective than previous mutual practice in terms of analysis of anatomical structures and patient treatment methods. Therefore, it will be necessary to improve policy regarding dental radiography practice at the department of dental hygienics and revise the necessary laws and regulations.

• Advances in materials Research
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• v.8 no.1
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• pp.47-73
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• 2019

Joining of Mg/Ti hybrid structures by welding for automotive and aerospace applications has attracted great attention in recent years due mainly to its potential benefit of energy saving and emission reduction. However, joining them has been hampered with many difficulties due to their physical and metallurgical incompatibilities. Different joining processes have been employed to join Mg/Ti, and in most cases in order to get a metallurgical bonding between them was the use of an intermediate element at the interface or mutual diffusion of alloying elements from the base materials. The formation of a reaction product (in the form of solid solution or intermetallic compound) along the interface between the Mg and Ti is responsible for formation of a metallurgical bond. However, the interfacial bonding achieved and the joints performance depend significantly on the newly formed reaction product(s). Thus, a thorough understanding of the interaction between the selected intermediate elements with the base metals along with the influence of the associated welding parameters are essential. This review is timely as it presents on the current paradigm and progress in welding and joining of Mg/Ti alloys. The factors governing the welding of several important techniques are deliberated along with their joining mechanisms. Some opportunities to improve the welding of Mg/Ti for different welding techniques are also identified.

• Korean Journal of Heritage: History & Science
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• v.36
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• pp.227-239
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• 2003

Korea and China can find the common feature derived from the mutual cultural exchanges, belonging to the same cultural sphere of the East Asia. It also applies to the stone figures of the palace gardens of both countries. In case of Korea in the stone figures of the palace gardens, there are few of them existing in Kyungbok Palace, Changduk Palace, and Changkyung Palace of the Chosun Dynasty, and most of them were washed away, there are hardly any records remaining and transmitted, and there are hardly any materials of drawings and pictures of them. On the contrary, in case of China, although there are those washed away, there are vast numbers of real objects, and records and materials of them. Therefore, for the study on the stone figures of Korea, the method to analogize the research lacking regarding the stone figures of the palace gardens of Korea from those of China after conducting the comparative study between those existing and those of China, may be available. I consider that although the restoration of the palaces of Chosun Dynasty of Korea had been the restoration project oriented toward the buildings until now, it will be the phase where one should have more interest toward the restoration of the palace gardens in the future, and that the restoration of the palace gardens should be made centered on the landscape architectural structures, deviated from the restoration project attaching weight to the restoration of the trees. Above all, I consider that the interest should be turned to the restoration of the stone figures where the view toward the nature of the Orientals are expressed well. For the restoration of the stone figures in the Changduk and Changkyung Palaces, it is considered that the restoration of the rough locations and shapes is possible based on the Dongkwol Drawings being transmitted, and that the research on the shapes, characters, pedestals, characteristics, etc. of the specific stone figures is possible as far as it is based on the study of the stone figures of the palace gardens of China.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3745-3765
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• 2022

The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20-70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.