• Structural Engineering and Mechanics
• /
• v.74 no.4
• /
• pp.533-545
• /
• 2020

An optimal design method for a spoke double-layer cable-net structure (SDLC) is proposed in this study. Simplified calculation models of the SDLC are put forward to reveal the static responses under vertical loads and wind loads. Next, based on an energy principle, the relationship among the initial prestress level, cross-sectional areas of the components, rise height, sag height, overall displacement, and relative deformation is proposed. Moreover, a calculation model of the Foshan Center SDLC is built and optimized. Given the limited loading cases, material properties of the components, and variation ranges of the rise height and sag height, the self-weight and initial prestress level of the entire structure can be obtained. Because the self-weight of the cables decreases with increasing of the rise height and sag height, while the self-weight of the inner strut increases, the total weight of the entire structure successively exhibits a sharp reduction, a gradual decrease, a slow increase, and a sharp increase during the optimization process. For the simplified model, the optimal design corresponds to the combination of rise height and sag height that results in an appropriate prestress level of the entire structure with the minimum total weight.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.521-522
• /
• 2007

A new high strength conductor was designed for long span transmission line with a high nitrogen steel having high tensile strength and non-magnetic properties and high strength AI alloy. The tensile strength of conductor is very important to reduce the sag. The height of electric tower depend on the sag also. More than 36% less of sag was achieved by using ACHR(Aluminum conductor stranded high-nitrogen steel reinforced) instead of conventional ACSR.

• Molecules and Cells
• /
• v.42 no.9
• /
• pp.661-671
• /
• 2019

Adipose tissue-derived mesenchymal stem cells (ADSCs) are promising for regenerating degenerated intervertebral discs (IVDs), but the low efficiency of nucleus pulposus (NP)-specific differentiation limits their clinical applications. The Sonic hedgehog (Shh) signaling pathway is important in NP-specific differentiation of ADSCs, and Smoothened Agonist (SAG) is a highly specific and effective agonist of Shh signaling. In this study, we proposed a new differentiation strategy with the use of the small molecule SAG. The NP-specific differentiation and extracellular matrix (ECM) synthesis of ADSCs were measured in vitro, and the regenerative effects of SAG pretreated ADSCs in degenerated IVDs were verified in vivo. The results showed that the combination of SAG and transforming growth factor-${\beta}3$ ($TGF-{\beta}3$) is able to increase the ECM synthesis of ADSCs. In addition, the gene and protein expression levels of NP-specific markers were increased by treatment with SAG and $TGF-{\beta}3$. Furthermore, SAG pretreated ADSCs can also improve the disc height, water content, ECM content, and structure of degenerated IVDs in vivo. Our new differentiation scheme has high efficiency in inducing NP-specific differentiation of ADSCs and is promising for stem cell-based treatment of degenerated IVDs.

• Journal of Korean Association for Spatial Structures
• /
• v.17 no.1
• /
• pp.31-40
• /
• 2017

The objective of this study is to analysis the mechanical characteristics and nonlinear behaviors on the geometric nonlinear behavior of a cable spoke wheel roof system for long span lightweight roof structures. The weight of a cable spoke wheel roof dramatically can reduce and the cable roof system can easily make the required rigidity and shape by the sag ratio and pretension forces. Determining the pretension and initial sag of cable roof system is essential in a design process and the shape of roof is changed by pretension. The nonlinear behavior of flexible cable system has greatly an affect on the sag and pretension. This paper will be carried out analyzing and comparing the tensile forces and deflection of a cable spoke wheel system for the large span retractable roof, and analyzed to deflections and tensile forces by the post height of center hub. The double arrangement of a spoke wheel system with reverse curvature works more effectively as a load bearing system, the pretension can easily increase the structural stiffness. The cable truss system can carry vertical load in up and downward direction, and act effectively as load bearing elements.

• Korean Journal of Optics and Photonics
• /
• v.34 no.1
• /
• pp.13-21
• /
• 2023

We have investigated the acceptance angle and imaging performance of a curved artificial compound eye (ACE), depending on the sag height of the microlens array to maximize its sensitivity to light. When the h/r values increased from 0.22 to 0.37, the acceptance angle of the curved ACE was expanded from 28.70° to 49.02°, which is an enhancement by 70.8%. With the designed optical system, it was demonstrated that a microlens located at the 23rd position from the center of the main lens could still focus an incident beam tilted at 56.35°, so that the letter F was clearly observed.

• Journal of the Korean Society of Industry Convergence
• /
• v.20 no.5
• /
• pp.431-439
• /
• 2017

Since the power transmission line(PTL) passes through the high mountain and heavy snowfall region, it is necessary to keep the stability of the PTL. In this study, PTL is modeled as a mass-spring-damper system by using RecurDyn. The lumped mass model is verified by calculated from the simulation comparing the deflection analysis according to the sag and tension. In order to analyze the dynamic behavior of PTL, a damping coefficient for a multi-body model is derived by using the free vibration test and Rayleigh damping theory. Sleet jump simulation according to the region is performed. The maximum jump height, icing sag and amount of jump are confirmed. Also, the amount of jump and the reaction force at the supporting point according to the tension and load of ice are analyzed, respectively. As a result, it is noted that the amount of jump and reaction force are influenced more by the load of ice than by the tension of PTL.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.644-647
• /
• 2003

Resulting from reproducibility and possibility of mass production. many researches to fabricate micro lens array using lithography have been developed. However, it still remains the level of fabricating compensation lens. Therefore, to realize the fabrication of lens having high numerical aperture can be the key technology of ultra slim optical system. Reflow phenomenon have been researched to make lens having high refractive power. And through those researches, the possibility to fabrication of high refractive power lens has been investigated. In this paper, we analyze the effect of many parameters in reflow process to get an aspheric shape with high repeatability. And we make possible to estimate shape error, through we give direct information about decrease in volume of photoresist.

• Structural Engineering and Mechanics
• /
• v.60 no.4
• /
• pp.595-614
• /
• 2016

By taking the Runyang Highway Bridge over the Yangtze River with 1490 m main span as example, structural response of the bridge under the horizontal and vertical seismic excitations is investigated by the response spectrum and time-history analysis of MIDAS/Civil software respectively, the seismic behavior and the influence of structural nonlinearity on the seismic response of the bridge are revealed. Considering the aspect of seismic performance, the suitability of employing the suspension bridge in super long-span bridges is investigated as compared to the cable-stayed bridge and cable-stayed-suspension hybrid bridge with the similar main span. Furthermore, the effects of structural parameters including the span arrangement, the cable sag to span ratio, the side to main span ratio, the girder height, the central buckle and the girder support system etc on the seismic performance of the bridge are investigated by the seismic response spectrum analysis, and the favorable earthquake-resistant structural system of suspension bridges is also discussed.

• Structural Engineering and Mechanics
• /
• v.71 no.3
• /
• pp.271-282
• /
• 2019

The span record of cable-stayed bridges has exceeded 1,000 m, which makes research on the maximum possible span length of cable-stayed bridges an important topic in the engineering community. In this paper, span limit is discussed from two perspectives: the theoretical span limit determined by the strength-to-density ratio of the cable and girder, and the engineering span limit, which depends not only on the strength-to-density ratio of materials but also on the actual loading conditions. Closed form equations of both theoretical and engineering span limits of cable-stayed bridges determined by the cable and girder are derived and a detailed parametric analysis is conducted to assess the engineering span limit under current technical conditions. The results show that the engineering span limit of cable-stayed bridges is about 2,200 m based on materials used available today. The girder is the critical member restricting further increase in the span length; its compressive stress is the limiting factor. Approaches to increasing the engineering span limit are also presented based on the analysis results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.79-83
• /
• 2007

We have developed a compact and cost-effective camera module on the basis of wafer-scale replication technology. A multiple-layered structure of several aspheric lenses in a mobile camera module is first assembled by bonding multiple glass-wafers on which 2-dimensional replica arrays of identical aspheric lenses are UV-embossed, followed by dicing the stacked wafers and packaging them with image sensor chips. We have demonstrated a VGA camera module fabricated by the wafer-scale replication processing with various UV-curable polymers having refractive indices between 1.4 and 1.6, and with three different glass-wafers of which both surfaces are embossed as aspheric lenses having 200 um sag-height and aspheric-coefficients of lens polynomials up to tenth-order. We have found that precise compensation in material shrinkage of the polymer materials is one of the most technical challenges, in order to achieve a higher resolution in wafer-scaled lenses for mobile camera modules.