• Structural Engineering and Mechanics
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• v.87 no.4
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• pp.317-332
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• 2023

Understanding and analysing the behaviour and response of historical structures in the face of climate changes and environmental conditions is of utmost significance for their preservation. There are several structural hazards associated with climate and hydrology changes in the region, including the settlement of piers, the rotation of piers, and temperature changes. The present study investigates the experimental and numerical structural behaviour of skewed and non-skewed Persian brick masonry barrel vaults under various conditions. The external loading conditions included pier rotation in five modes, settlement, and temperature variations in four states. Initially, the experiments extracted the mechanical properties of the scaled materials. Then, three semi-circular brick barrel vaults were tested with gravitational loads. The outcomes were used to develop and validate the finite element model. Following the development of the finite element model, numerical and parametric studies were conducted on the effect of the aforementioned structural hazards on the response of brick masonry barrel vaults with various Persian geometries (semi-circular, drop pointed, and four-centred), angles of skew (0, 15, 30, and 45 degrees), and dimensional ratios. According to the findings, the fragility of masonry materials makes historical structures susceptible to failure under different loading. A brick barrel vault fails in the presence of minor rotation and settlement of the piers. The four-centred geometric shape has the lowest performance among the seven Persian geometries; therefore, its health monitoring and retrofitting should be prioritised. In Isfahan, Iran, temperature variations, particularly during the warm seasons, cause critical conditions in such structures.

• Geotechnical Engineering
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• v.14 no.4
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• pp.177-204
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• 1998

In the present study, a method of quasi-three dimensional stability analysis is proposed for a systematic design of the GRS-RW(Geosynthetic-Reinforced Soil Retaining Wall) system based on the postulated three dimensional failure wedge. The proposed method could be applied to the analysis of the stability of both the straight-line and cove-shaped are. As with skew reinforcements. Maximum earth thrust expected to act on the rigid face wall is assumed to distribute along the depth, and wall displacements are predicted based on both the assumed compaction-induced earth pressures and one dimensional finite element method of analysis. For a verification of the procedure proposed in the present study, the predicted wall displacements are compared with chose obtained from the RMC tests in Canada and the FHWA tests in U.S.A. In these comparisons the wall displacements estimated by the methods of Christopher et at. and Chew & Mitchell are also included for further verification. Also, the predicted wall displacements for the convex-shaped zone reinforced with skew reinforcements are compared with those by $FLAC_{3D}$ program analyses. The assumed compaction-induced earth pressures evaluated on the basic of the proposed method of analysis are further compared with the measurements by the FHWA best wall. A parametric stduy is finally performed to investigate the effects of various design parameters for the stability of the GRS-RW system

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.5
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• pp.325-335
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• 2018

We herein present a study on the active phased array antenna for receiving satellite broadcasting that can electrically align its polarization to that of target transmitters in its moving condition or in the Skew angle arrangement of the broadcasting satellite receiver. Hence, we have developed an active phased array structure composed of the self-developed Vivaldi antenna and multifunction core (MFC) chip, receiving RF front end module, and control units. In particular, the new Vivaldi antenna designed in the Ku-band of 10.7 - 14.5 GHz to receive one desired polarization mode such as the horizontal or vertical by means of an MFC chip and other control units that can control the amplitude and phase of each antenna element. The test results verified that cross-polarization property is 20 dB or higher and the primary beam can be scanned clearly at approximately ${\pm}60^{\circ}$.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.243-248
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• 2014

The permanent magnet linear synchronous motors facilitate maintenance, for it is structurally simple compare to rotating machine and has lots of advantage such as a precision control, high speed, high thrust and so on. However, it causes an increase of material cost because of structural characteristics that need to arranges the armature on the full length of transportation lines. Thus, in order to resolve this problem, we propose the discontinuous arrangement method of the armature but the edge always exists due to the structure when the armature is arranged discontinuously. Due to this edge, the cogging force is greatly generated and it causes thrust force ripple generating noise, vibration and decline of performance. Therefore, in this paper, we examined the characteristic of end edge according to the skew angle through 3-D numerical analysis using finite element method(FEM) and improved the operation characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.4
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• pp.11-21
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• 1988

In twentieth century, a rigid pavement composed of a series of thin Portland Cement Concrete has been accepted due to the desirable structural strength of concrete, durability and economy. However, despite of precise design and construction of concrete highway pavements, some of concrete pavements (example : Interstate-l0 and 75 in U.S.A, 88 Olympic express highway and Jung-bu express highway in Korea) has already shown severe signs of longitudinal and transverse cracking, faulting, and pumping before the end of their intended service life. This highlights the need for better understanding of concrete pavement behavior using structural analysis program. For these reasons, this research was performed to study an analytical behavior of concrete pavements, especially for the effects of skewed joints on concrete pavements. Subsequently, this research should give better understanding of concrete pavement behavior to the highway engineers and provide effective remedies to the concrete highway pavements.

• Steel and Composite Structures
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• v.52 no.2
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• pp.237-248
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• 2024

In order to make the dynamic analysis and design of improved composite beam with corrugated steel web (CBGSCC) bridge more efficient and economical, the parametric self-cyclic analysis model (SCAM) was written in Python on Anaconda platform. The SCAM can call ABAQUS finite element software to realize automatic modeling and dynamic analysis. For the CBGSCC bridge, parameters were set according to the general value range of CBGSCC bridge parameters in actual engineering, the SCAM was used to calculate the large sample model generated by parameter coupling, the optimal value range of each parameter was determined, and the sensitivity of the parameters was analyzed. The number of diaphragms effects weakly on the dynamic characteristics. The deck thickness has the greatest influence on frequency, which decreases as the deck thickness increases, and the deck thickness should be 20-25 cm. The vibration frequency increases with the increase of the bottom plate thickness, the web thickness, and the web height, the bottom plate thickness should be 17-23mm, the web thickness should be 13-17 mm, and the web height should be 1.65-1.7 5 m. Web inclination and Skew Angle should not exceed 30°, and the number of diaphragms should be 3-5 pieces. This method can be used as a new method for structural dynamic analysis, and the importance degree and optimal value range of each parameter of CBGSCC bridge can be used as a reference in the design process.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.4
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• pp.405-420
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• 2003

Purpose : The purpose of this study was to compare the fracture resistance of the IPS Empress ceramic crown with 1.0mm width rounded shoulder, which is usually recommended in all ceramic crown. and 0.5mm width chamfer finish lines on the maxillary central incisor. Material and method : After 15 metal dies were made for each group, the IPS Empress all ceramic crowns were fabricated and cemented with resin cement(Bistite resin cement, Tokuyama Soda Co. LTD., Japan) on the metal die. The cemented crowns were mounted on the positioning jig and the universal testing machine(Zwick Z020, Zwick Co. Germany)was used to measure the fracture strength with loading on the incisal edge. And also, three-dimensional finite element stress analysis was used to measure the stress distribution with the various types of the finish lines(1.0mm width rounded shoulder, 0.5mm width chamfer), the loading site(incisal edge, incisal $\frac{1}{3}$) and the type of loading(concentration loading, distribution loading). Results and conclusion : 1. In the fracture resistance experiment according to the finish line, the mean fracture strength of rounded shoulder(876N) and the mean fracture strength of chamfer(882N) did not skew any significant difference between each other(p>0.05). 2. The stress distribution of all ceramic crown in three dimensional finite element analysis showed concentration aspect at loading point and cervical area or labial surface. 3. In metal die, there were no differences in stress distribution between finish lines, but in natural teeth model, chamfer finish line showed higher stress than rounded shoulder finish line. 4. When force was loaded on the incisal edge the stress was concentrated on the incisal edge and the cervical area of labial surface. When force was loaded on the incisal $\frac{1}{3}$, the stress concentrated on the cervical area of labial surface and the cingulum area. 5. Generally, natural teeth model showed higher and various stress than the metal die.

• Computers and Concrete
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• v.3 no.5
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• pp.301-312
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• 2006

Experimental research revealed that the spatial dispersion of aggregate grains exerts pronounced influences on the mechanical and durability properties of concrete. Therefore, insight into this phenomenon is of paramount importance. Experimental approaches do not provide direct access to three-dimensional spacing information in concrete, however. Contrarily, simulation approaches are mostly deficient in generating packing systems of aggregate grains with sufficient density. This paper therefore employs a dynamic simulation system (with the acronym SPACE), allowing the generation of dense random packing of grains, representative for concrete aggregates. This paper studies by means of SPACE packing structures of aggregates with a Fuller type of size distribution, generally accepted as a suitable approximation for actual aggregate systems. Mean free spacing $\bar{\lambda}$, mean nearest neighbour distance (NND) between grain centres $\bar{\Delta}_3$, and the probability density function of ${\Delta}_3$ are used to characterize the spatial dispersion of aggregate grains in model concretes. Influences on these spacing parameters are studied of volume fraction and the size range of aggregate grains. The values of these descriptors are estimated by means of stereological tools, whereupon the calculation results are compared with measurements. The simulation results indicate that the size range of aggregate grains has a more pronounced influence on the spacing parameters than exerted by the volume fraction of aggregate. At relatively high volume density of aggregates, as met in the present cases, theoretical and experimental values are found quite similar. The mean free spacing is known to be independent of the actual dispersion characteristics (Underwood 1968); it is a structural parameter governed by material composition. Moreover, scatter of the mean free spacing among the serial sections of the model concrete in the simulation study is relatively small, demonstrating the sample size to be representative for composition homogeneity of aggregate grains. The distribution of ${\Delta}_3$ observed in this study is markedly skew, indicating a concentration of relatively small values of ${\Delta}_3$. The estimate of the size of the representative volume element (RVE) for configuration homogeneity based on NND exceeds by one order of magnitude the estimate for structure-insensitive properties. This is in accordance with predictions of Brown (1965) for composition and configuration homogeneity (corresponding to structure-insensitive and structure-sensitive properties) of conglomerates.

• Journal of Internet Computing and Services
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• v.15 no.2
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• pp.87-94
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• 2014

Social media which includes Facebook enable users to construct relationships and networks as well as sharing of information. By enlisting Facebook users as proxy, this paper attempted to analyze the different emotional states experienced by social media users, specifically to gauge what effect their usage motivation and usage pattern had on the ambivalence level of the users. The quantitative survey result revealed that usage duration or the time of day when Facebook was accessed had no relevant impact on one's ambivalence level. However, there was a direct correlation between frequency of Facebook usage and the ambivalence level. The more the user logged onto Facebook the more suppressed his or her expression became due to fear of giving negative impressions to others and also receiving their negative feedbacks, which then subsequently added to the user's ambivalence. People's main reasons for using Facebook were identified as "chatting," "communicating," "maintaining relationships," "relationship building," "networking," and "finding information about friends," but only "maintaining relationships," "communicating," and "networking" had observable effect on ambivalence. There were no noticeable differences among genders with regards to ambivalence and usage levels, but there was a marked difference based on the user's age. For example, people in their forties showed higher levels of ambivalence than those in their twenties. This may be attributed to anxiety they face as they use Facebook primarily to expand their networks and to maintain relationships. As such, it is surmised that their fatigue level from using social media will only increase. Meanwhile, Korean Facebook user's emotional manifestation tended to skew toward relation-involved ambivalence rather than the self-defensive type. This relation-involved ambivalence might be something that can actually help prevent damage to relationships by limiting excessive emotional expressions. In other words, such ambivalence by Facebook users may be a positive element in a user's social media interaction.