275,131 research outputs found
Sustainability in design: now! Challenges and opportunities for design research, education and practice in the XXI century
Copyright @ 2010 Greenleaf PublicationsLeNS project funded by the Asia Link Programme, EuropeAid, European Commission
Recommended from our members
Research on the performance of radiative cooling and solar heating coupling module to direct control indoor temperature
The energy crisis and environmental pollution pose great challenges to human development. Traditional vapor-compression cooling consumes abundant energy and leads to a series of environmental problems. Radiative cooling without energy consumption and environmental pollution holds great promise as the next generation cooling technology, applied in buildings mostly in indirect way. In this work, a temperature-regulating module was introduced for direct summer cooling and winter heating. Firstly, the summer experiments were conduct to investigate the radiative cooling performance of the module. And the results indicated that the maximum indoor temperature reached only 27.5 °C with the ambient temperature of 34 °C in low latitude areas and the air conditioning system was on for only about a quarter of the day. Subsequently, the winter experiments were performed to explore the performance of the module in cooling and heating modes. The results indicated that indoor temperature can reach 25 °C in the daytime without additional heat supply and about a quarter of the day didn't require heating in winter. Additionally, the transient model of the module and the building revealed that the electricity saving of 42.4% (963.5 kWh) can be achieved in cooling season with the module, and that was 63.7% (1449.1 kWh) when coupling with energy storage system. Lastly, further discussion about the challenges and feasible solutions for radiative cooling to directly combine with the buildings were provided to advance the application of radiative cooling. Furthermore, with an acceptable payback period of 8 years, the maximum acceptable incremental cost reached 26.2 $/m2. The work opens up a new avenue for the application mode of the daytime radiative cooling technology
Topology of modified helical gears
The topology of several types of modified surfaces of helical gears is proposed. The modified surfaces allow absorption of a linear or almost linear function of transmission errors. These errors are caused by gear misalignment and an improvement of the contact of gear tooth surfaces. Principles and corresponding programs for computer aided simulation of meshing and contact of gears have been developed. The results of this investigation are illustrated with numerical examples
Torque and temperature dependence of the hysteretic voltage-induced torsional strain in tantalum trisulfide
We have measured the dependence of the hysteretic voltage-induced torsional
strain (VITS) in crystals of orthorhombic tantalum trisulfide on temperature
and applied torque. In particular, applying square-wave voltages above the
charge-density-wave (CDW) threshold voltage, so as to abruptly switch the
strain across its hysteresis loop, we have found that the time constant for the
VITS to switch (at different temperatures and voltages) varied as the CDW
current. Application of torque to the crystal could also change the VITS time
constant, magnitude, and sign, suggesting that the VITS is a consequence of
residual torsional strain in the sample which twist the CDW. Application of
voltage changes the pitch of these CDW twists, which then act back on the
lattice. However, it remains difficult to understand the sluggishness of the
response.Comment: 20 pages, including 7 figures, to be published in PR
Generation of a crowned pinion tooth surface by a surface of revolution
A method of generating crowned pinion tooth surfaces using a surface of revolution is developed. The crowned pinion meshes with a regular involute gear and has a prescribed parabolic type of transmission errors when the gears operate in the aligned mode. When the gears are misaligned the transmission error remains parabolic with the maximum level still remaining very small (less than 0.34 arc sec for the numerical examples). Tooth contact analysis (TCA) is used to simulate the conditions of meshing, determine the transmission error, and determine the bearing contact
Recommended from our members
Mechanical performance of auxetic polyurethane foam for antivibration glove applications
In this study the static and dynamic characteristics of conventional open cell
polyurethane (PU), of auxetic (negative Poissonâs ratio) and of iso-density foams
were analysed. The specimens were produced from conventional gray open-cells
polyurethane foam with 30-35 pores/inch and 0.0027 g/cm3 density, by means of
process which has been previously defined by the authors. Poissonâs ratio
measurements were performed under quasi-static conditions using an MTS 858 servohydraulic
test machine and a video image acquisition system. For the auxetic foams
the results suggested similar behaviour to that previously reported in the literature,
with significant increases in stiffness during compressive loading, and a significant
dependence of the Poissonâs ratio on the applied strain. Transmissibility tests,
performed in accordance with the ISO 13753 procedure for antivibration glove
materials, suggested a strong dependence of the transmissibility on the foam
manufacturing parameters. Within the frequency range from 10 to 31.5 Hz the
transmissibility was found to be greater than 1, while it was less than 1 at all
frequencies greater than 31.5 Hz. The transmissibility results were similar to the mean
values for 80 resilient materials tested by Koton et. al., but were higher than the five
best materials (not all polymeric) identified by the same researchers. In this study it
has been suggested that the resilient behaviour of glove isolation materials should also
be evaluated in terms of the indentation characteristics. A simple, linear elastic, Finite
Element simulation was therefore performed, and the indentation results suggested
that auxetic foams offer a significant decrease in compressive stresses with respect to
conventional PU foams
- âŠ