Second-order Direct Analysis of Steel Structures made of tapered members

[EN] Mild steel hot-rolled sections are commonly prismatic because of the rolling process with a furnace, but welded sections made from steel plates do not have such a constraint, especially when robotic welding machines are used. The weight saving could be very significant by, say, using wide flanged section at mid-span and a small flanged section at ends of a simply supported beam. However, design codes do not provide formulae for buckling check of tapered members. This paper proposes a code-free second-order direct analysis for stabilty design of steel frames made of tapered members. The design is further applied to a single layered mega space frame of 136m span. In the whole design process based on the concept of Second-order Direct Analysis, no uncertain effective length and independent member buckling checking are required.The authors are grateful to the financial supports by the Research Grant Council of the Hong Kong SAR Government on the project “Second-Order Analysis of Shallow Dome Structures Made of Tapering Members (PolyU 152047/17E)” and Second-Order Analysis of Flexible Steel Cable Nets Supporting Debris (PolyU 152008/15E)” and support by Innovation and Technology Fund of the Hong Kong SAR Government for the project “Development of an energy absorbing device for flexible rock-fall barriers (ITS/059/16FP)” and by the Hong Kong Branch of Chinese National Engineering Research Centre for Steel Construction of The Innovation and Technology Fund of the Hong Kong SAR Government for the project Advanced Numerical Analysis for Building Structures using High Performance Steel Materials".Chan, S.; Liu, S.; Liu, Y. (2018). Second-order Direct Analysis of Steel Structures made of tapered members. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 75-82. https://doi.org/10.4995/ASCCS2018.2018.7221OCS758

Common-Mode Noise Cancellation in Switching-Mode Power Supplies Using an Equipotential Transformer Modeling Technique

Electromagnetic interference (EMI) is a significant challenge in the design of high-efficiency switching-mode power supplies due to the presence of common-mode (CM) noise. In many power-supply designs, a variety of noise suppression schemes must be implemented in order to meet EMI requirements. Most of these schemes create power loss that lead to efficiency and thermal issues. In this paper, a transformer construction technique is proposed that effectively reduces the CM noise current injecting across the isolated primary and secondary windings. This technique is based on the zero equipotential line theory. A transformer design with the proposed CM noise cancellation technique can achieve high conversion efficiency as well as substantial CM noise rejection.published_or_final_versio

Sliding stability analysis of a retaining wall constructed by soilbags

Model tests were conducted to analyse the sliding stability of a retaining wall constructed by soilbags. The aim was to obtain an equation that calculates the active resultant earth pressure of sand acting on the wall in the ultimate state. Additionally, shear tests on multi-layers of vertically stacked soilbags were designed to investigate how the interlayer friction resistance varied with the height of the wall. The results show that the active earth pressure acting on the soilbag-constructed retaining wall in the ultimate state is non-linear, but it can be calculated from the force equilibrium of a differential element. The interlayer friction resistance of soilbags is found to be related to the shape of the sliding surface. Based on the obtained equation and the unique shear test results, the sliding stability of the retaining wall constructed by soilbags could be appropriately analyse

The interactive bending wrinkling behaviour of inflated beams

ArticleA model is proposed based on a Fourier series method to analyse the interactive bending wrinkling behaviour of inflated beams. The whole wrinkling evolution is tracked and divided into three stages by identifying the bifurcations of the equilibrium path. The critical wrinkling and failure moments of inflated beam are then able to be predicted. The global-local interactive buckling pattern is elucidated by the proposed theoretical model and also verified by non-contact experimental tests. The effects of geometric parameters, internal pressure and boundary conditions on the buckling of inflated beams are investigated in the end. Results reveal that the interactive buckling characteristics of inflated beam under bending are more sensitive to the dimensions of the structure and boundary conditions. We find that beams which are simply supported at both ends or clamped and simply supported boundary conditions may prevent the wrinkling formation. The results provide significant support for our understanding of the bending-wrinkling behaviour of inflated beams.This work is supported by National Natural Science Foundation of China, 11172079 and 11572099; Program for New Century Excellent Talents in University, NCET-11-0807; Natural Science Foundation of Heilongjiang Province of China, A2015002; the Fundamental Research Funds for the Central Universities, HIT.BRETIII.201209 and HIT.MKSTISP.2016 29

CS 3180/5180: Comparative Languages

This course will introduce fundamental concepts and paradigms underlying the design of modern programming languages. For concreteness, we study the details of an object-oriented language (e.g. Java, C#, C++), a functional language (e.g., Scheme, and get introduced to multiparadigm languages (e.g., Python, Scala). The overall goal is to enable comparison and evaluation of existing languages. The programming assignments will largely be coded in Java and in Scheme, and optionally in Python or Scala

Exploration of the Survival Probability and Shape Evolution of Crushable Particles during One-Dimensional Compression Using Dyed Gypsum Particles

Observing the fragmentation of individual particles within granular assemblies is a subject of evident theoretical and practical importance. A new technique using dyed gypsum particles (DGPs) to match the broken particles to their parents was adopted in this study. An image-based method of acquiring the shape information of particles from two orthogonal views was proposed. The mass survival probability and shape characteristics of the children particles were analyzed after a series of one-dimensional compression tests on the DGPs. It was found that medium-sized particles in the polydisperse samples underwent more breakage than the other particles, and this might have been attributed to the combined effects of the particle crushing strength and the coordination number. The shape evolution of broken particles and surviving particles showed opposite trends. Because the particles after the test within a given size range consisted of both the broken and surviving particles, their overall shape characteristics did not show a consistent trend. Furthermore, individual particle crushing tests on the children particles suggested that the breakage-induced shape irregularity did not change the Weibull modulus, but had a substantial effect on the magnitude of the survival probability

Promoting green residential buildings in China: Bridging the gap between design and operation to improve occupants' residential satisfaction

© 2019 by the authors. While many studies have examined the supply of green residential buildings (GRBs), few have focused on the demand and living experience of them. This paper explores the antecedents of existing residents' repurchase intention and the effect of their residential satisfaction through a questionnaire survey in Sino-Singapore Tianjin Eco-city, China. Structural equation modeling was used to examine the role of proposed determinants. Multi-group analysis tested the moderating role of residential satisfaction. Results show that residents' satisfaction with respect to their homes in GRBs was heterogeneous with dissatisfied residents account for 55%. Residents' knowledge about GRBs, their environmental attitudes and perceived usefulness of GRB were key determinants of repurchase intentions but trust in relevant institutions was not. Residential satisfaction played a moderating role in predicting repurchase intentions. This study enlightens practitioners in both private and public sectors to improve occupancy experiences of existing residents and to understand the repurchase behaviors of existing customers, by bridging the gap between strong green design and construction and weak operation and maintenance of GRBs

A low cost and reliable dimmable ballast topology with inherent power regulation and insensitivity to lamp characteristics

The output power of the proposed dimmable ballast topology is self-regulated and insensitive to the lamp characteristics. Accurate dimming operation with rather constant filament power can be realized simply by open loop control of the switching frequency of the converter. It can provide reliable operation during lamp ignition with fault conditions or even short circuit without the need of current sensing circuits. Prototype was built for experimental verifications. For completeness, a simple ultra low dimming method is also proposed together with the theoretical dimming limit considered. © 2005 IEEE.published_or_final_versio

In situ loading and delivery of short single- And double-stranded dna by supramolecular organic frameworks

Short DNA represents an important class of biomacromolecules that are widely applied in gene therapy, editing, and modulation. However, the development of simple and reliable methods for their intracellular delivery remains a challenge. Herein, we describe that seven water-soluble, homogeneous supramolecular organic frameworks (SOFs) with a well-defined pore size and high stability in water that can accomplish in situ inclusion of single-stranded (ss) and double-stranded (ds) DNA (21, 23, and 58 nt) and effective intracellular delivery (including two noncancerous and six cancerous cell lines). Fluorescence quenching experiments for single and double endlabeled ss- and ds-DNA support that the DNA sequences can be completely enveloped by the SOFs. Confocal laser scanning microscopy and flow cytometry reveal that five of the SOFs exhibit excellent delivery efficiencies that, in most of the studied cases, outperform the commercial standard Lipo2000, even at low SOF-nucleic acid ratios. In addition to high delivery efficiencies, the watersoluble, self-assembled SOF carriers have a variety of advantages, including convenient preparation, high stability, and in situ DNA inclusion, which are all critical for practical applications in nucleic acid delivery

Experimental study of subcooled flow boiling heat transfer on micro-pin-finned surfaces in short-term microgravity

The flow boiling heat transfer of subcooled air-dissolved FC-72 on micro-pin-finned surfaces was studied in microgravity by utilizing the drop tower facility in Beijing. The micro-pin-fins with the dimension of 30 x 30 x 60 mu m(3) (width x thickness x height), named PF30-60, were fabricated on a silicon chip by using the dry etching technique. For comparison, experiments of flow boiling heat transfer in terrestrial gravity were also conducted. The effects of inlet velocity on both flow boiling heat transfer and bubble behavior were explored. It was found that gravity has nearly no effect on flow boiling heat transfer for the departure of the inertial-force dominant bubbles in the low and moderate heat fluxes regions. In contrast, in the high-heat-flux region, the flow boiling heat transfer deteriorates and the critical heat flux (CHF) decreases due to the bubble accumulation in the channel. For PF30-60 at V = 0.5 m/s, the CHF point can be inferred to be between 20.8 and 24.5 W/cm(2), which is 63.0-74.2% of that in normal gravity. Regarding PF30-60 at V = 1.0 m/s, the CHF point can be inferred to be between 25.4 and 31.6 W/cm(2), which is 67.6-84.0% of that in normal gravity. The impact of gravity on CHF is closely linked to the channel geometry parameter and surface modification. The dimensionless numbers, Ch (Channel number) and Sf (Surface number), were proposed to describe the effect of the channel geometry and surface modification on the ratio of CHF in microgravity to that in normal gravity (CHF mu g/CHF1g). An empirical correlation based on We (Weber number), Ch and Sf was proposed to predict the value of CHF mu g/CHF1g ratio in good agreement with the experimental data. This study provides a new perspective to determine the threshold inlet velocity of inertial-force-dominant flow boiling under different experimental conditions at different gravity levels