715 research outputs found
Control mechanisms in protein synthesis and turnover with special reference to liver ferritin
Abstract Not Provided
Minimum-weight triangulation is NP-hard
A triangulation of a planar point set S is a maximal plane straight-line
graph with vertex set S. In the minimum-weight triangulation (MWT) problem, we
are looking for a triangulation of a given point set that minimizes the sum of
the edge lengths. We prove that the decision version of this problem is
NP-hard. We use a reduction from PLANAR-1-IN-3-SAT. The correct working of the
gadgets is established with computer assistance, using dynamic programming on
polygonal faces, as well as the beta-skeleton heuristic to certify that certain
edges belong to the minimum-weight triangulation.Comment: 45 pages (including a technical appendix of 13 pages), 28 figures.
This revision contains a few improvements in the expositio
Linear angular momentum multiplexing-conceptualization and experimental evaluation with antenna arrays
Linear Angular Momentum Multiplexing is a new method for providing highly spectrally efficient short range communication between a transmitter and receiver, where one may move at speed transverse to the propagation. Such applications include rail, vehicle and hyperloop transport systems communicating with fixed infrastructure on the ground. This paper describes how the scientific concept of linear angular momentum multiplexing evolves from orbital angular momentum multiplexing. The essential parameters for implementing this concept are: a long array at least at one of the ends of the link; antenna element radiation characteristics; and the array element spacing relative to the propagation distance. These parameters are also backed by short range measurements carried out at 2.4GHz used to model the Rice fading channel and determine resilience to multipath fading
The Effect of Model Parameters on the Simulation of Fire Dynamics
Peer-reviewed article published in the Proceedings of the 9th International Symposium on Fire Safety Science, Karlsruhe, 2008.The sensitivity of computer fire modelling using results from NIST’s Fire Dynamics Simulator (FDS) to a set of input parameters
related to fire growth has been analyzed. The scenario simulated is the real-scale Dalmarnock Fire Test One and the modelling
results are compared to the measurements. Fire size and location, convection, radiation and combustion parameters were varied in order to determine the associated degree of sensitivity. Emphasis is put in the prediction of secondary ignition and time to flashover. In this context and while keeping the HRR constant, simulations of fire growth are significantly sensitive to location of the heat release rate (HRR), fire area, flame radiative fraction, and material thermal and ignition properties. The simulations are relatively insensitive to the heat of combustion (while keeping the HRR constant), the soot yield and the heating from the smoke layer. The results indicate that the future development of successful fire forecast methodologies of fire growth using CFD must focus on the
global HRR as well as the important parameters identified here
The Suaineadh Project : a stepping stone towards the deployment of large flexible structures in space
The Suaineadh project aims at testing the controlled deployment and stabilization of space web. The deployment system is based on a simple yet ingenious control of the centrifugal force that will pull each of the four daughters sections apart. The four daughters are attached onto the four corners of a square web, and will be released from their initial stowed configuration attached to a central hub. Enclosed in the central hub is a specifically designed spinning reaction wheel that controls the rotational speed with a closed loop control fed by measurements from an onboard inertial measurement sensor. Five other such sensors located within the web and central hub provide information on the surface curvature of the web, and progression of the deployment. Suaineadh is currently at an advanced stage of development: all the components are manufactured with the subsystems integrated and are presently awaiting full integration and testing. This paper will present the current status of the Suaineadh project and the results of the most recent set of tests. In particular, the paper will cover the overall mechanical design of the system, the electrical and sensor assemblies, the communication and power systems and the spinning wheel with its control system
Fire Size and Fire Spread in Tunnels with Longitudinal Ventilation Systems.
The results and findings of three previous research projects are combined with new research to estimate the overall influence of longitudinal ventilation on fire size and spread in tunnels. Each of the three previous projects is briefly described. Combining the results of these three projects, together with knowledge of HGV fire behaviour in an experimental test, enables the estimation of the maximum fire size of a fire in a tunnel and the conditions under which it might spread to an adjacent vehicle, for a given longitudinal ventilation velocity. These results have been combined into a single computer model. Results are presented and discussed. It is concluded that, although it may greatly increase the heat release rate of a fire in a tunnel, increasing the ventilation velocity will tend to reduce the likelihood of the fire spreading to an adjacent vehicle, assuming no flame impingement
Diagnosing air quality changes in the UK during the COVID-19 lockdown using TROPOMI and GEOS-Chem
The dramatic and sudden reduction in anthropogenic activity due to lockdown measures in the UK in response to the COVID-19 outbreak has resulted in a concerted effort to estimate local and regional changes in air quality, though changes in underlying emissions remain uncertain. Here we combine satellite observations of tropospheric NO_{2} from TROPOspheric Monitoring Instrument and the Goddard Earth Observing System (GEOS)-Chem 3D chemical transport model to estimate that NO_{x} emissions declined nationwide by ~20% during the lockdown (23 March to 31 May 2020). Regionally, these range from 22% to 23% in the western portion of the country to 29% in the southeast and Manchester, and >40% in London. We apply a uniform 20% lockdown period emission reduction to GEOS-Chem anthropogenic emissions over the UK to determine that decline in lockdown emissions led to a national decline in PM_{2.5} of 1.1 μg m^{−3}, ranging from 0.6 μg m^{−3} in Scotland to 2 μg m^{−3} in the southwest. The decline in emissions in cities (>40%) is greater than the national average and causes an increase in ozone of ~2 ppbv in London and Manchester. The change in ozone and PM_{2.5} concentrations due to emission reductions alone is about half the total change from 2019 to 2020. This emphasizes the need to account for emissions and other factors, in particular meteorology, in future air pollution abatement strategies and regulatory action
Masonry components
Masonry is a non-homogeneous material, composed of units and mortar, which can be of different types, with distinct mechanical properties. The design of both masonry units and mortar is based on the role of the walls in the building. Load-bearing walls relate to structural elements that bear mainly vertical loads, but can serve also to resist to horizontal loads. When a structural masonry building is submitted to in-plane and out-of-plane loadings induced by an earthquake for example, the masonry walls are the structural elements that ensure the global stability of the building. This means that the walls should have adequate mechanical properties that enable them to resist to different combinations of compressive, shear and tensile stresses.The boundary conditions influence the resisting mechanisms of the structural walls under in-plane loading and in a buildings the connection at the intersection walls are of paramount importance for the out-of-plane resisting mechanism. However, it is well established that the masonry mechanical properties are also relevant for the global mechanical performance of the structural masonry walls. Masonry units for load-bearing walls are usually laid so that their perforations are vertically oriented, whereas for partition walls, brick units with horizontal perforation are mostly adopted
Use of non-steroidal anti-inflammatory drugs and risk of death from COVID-19:an OpenSAFELY cohort analysis based on two cohorts
The question of access to the Japanese market
This survey focuses on the question of how market structure and different
corporate organisational forms might affect access to the Japanese market for industrial goods. The question is how and whether keiretsu corporate structures in Japan constitute an important unofficial barrier in access to the Japanese market for manufactured goods
- …