Tilt response of pyranometers - studies at Pune

ABSTRACT. Pyranometers are normally used in a horizontal position to measure the global solar irradiance from the sun and sky. Because of the use of the pyranometers at sloping angles for determining the efficiency of the solar energy conversion installations, the effect of the tilled positions have to be quantified. Central Radiation Laboratory at Pune has made its own device and made measurements of the outputs of different pyranometers at different sloping angles. The results are discussed in the paper.

Photothermal Optical Beam Steering Using Large Deformation Multi-Layer Thin Film Structures

Photothermal actuation of microstructures remains an active area of research for microsystems that demand electrically isolated, remote, on-chip manipulation. In this study, large-deformation structures constructed from thin films traditional to microsystems were explored through both simulation and experiment as a rudimentary means to both steer and shape an incident light beam through photothermal actuation. A series of unit step infrared laser exposures were applied at increasing power levels to both uniformly symmetric and deliberately asymmetric absorptive structures with the intent of characterizing the photothermal tilt response. The results indicate that a small angle (<4° at ~74 W/cm2) mechanical tilt can be instantiated through central placement of an infrared beam, although directional control appears highly sensitive to initial beam placement. Greater responsivity (up to ~9° mechanical tilt at ~54 W/cm2) and gross directional control was demonstrated with an asymmetrical absorptive design, although this response was accompanied by a large amount (~5–10°) of mechanical tilt burn-in and drift. Rigorous device cycling remains to be explored, but the results suggest that these structures, and those similar in construction, can be further matured to achieve controllable photoactuation suitable for optical beam control or other applications.

Idealized Tropical Cyclone Responses to the Height and Depth of Environmental Vertical Wind Shear

Three sets of idealized, cloud-resolving simulations are performed to investigate the sensitivity of tropical cyclone (TC) structure and intensity to the height and depth of environmental vertical wind shear. In the first two sets of simulations, shear height and depth are varied independently; in the third set, orthogonal polynomial expansions are used to facilitate a joint sensitivity analysis. Despite all simulations having the same westerly deep-layer (200–850 hPa) shear of 10 m s−1, different intensity and structural evolutions are observed, suggesting the deep-layer shear alone may not be sufficient for understanding or predicting the impact of vertical wind shear on TCs. In general, vertical wind shear that is shallower and lower in the troposphere is more destructive to model TCs because it tilts the TC vortex farther into the downshear-left quadrant. The vortices that tilt the most are unable to precess upshear and realign, resulting in their failure to intensify. Shear height appears to modulate this tilt response by modifying the thermodynamic environment above the developing vortex early in the simulations, while shear depth modulates the tilt response by controlling the vertical extent of the convective vortex. It is also found that TC intensity predictability is reduced in a narrow range of shear heights and depths. This result underscores the importance of accurately observing the large-scale environmental flow for improving TC intensity forecasts, and for anticipating when such forecasts are likely to have large errors.

Tilt Response of Multi-Storey Building of Different Types due to Progressive Collapse of the Adjacent Underground Structure under Internal Blast Loading

This paper numerically investigates the tilt response of multi-storey buildings due to progressive collapse of the adjacent underground structure under internal blast loading. The software LS-DYNA is utilized to establish a three-dimensional coupled model composed of the underground structure, the soil around and the adjacent above-ground structure. In order to reduce the computational cost, an efficient computational method, Three-Stage Simulation Method (TSSM), is put forward. Three different methods, Alternative Path Load Method (APLM), Direct Simulation Method (DSM) and TSSM, are used to analyze the same model which illustrates the correctness of the model and the proposed method. By comparing tilt response of the above-ground structure of different types due to progressive collapse of underground structure under its internal blast loading, it is found that the tilt response of the above-ground structure of different types is related to the foundation of the structure. For example, compared with the frame structure with basement, the frame-shear wall structure with basement can prevent structure from great tilt response. However, the tilt response of the frame-shear wall structure with raft basis is larger than that of the frame.

Experimental Evaluation of a Hydraulically Actuated Tilt System for a Narrow Track Three-Wheeled Vehicle

The objective of the EU-funded CLEVER Project (Compact Low Emission VEhicle for uRban transport) is the design and development of a novel two-seat vehicle for individual urban transport providing car-like levels of comfort, safety and convenience with the lower emissions, noise levels and road footprints of motorcycles. A narrow three-wheeled tilting vehicle has been identified as the best method of achieving these goals. One problem with vehicles with a narrow track is the unstable roll moment created when cornering. To solve this issue, the vehicle's centre of gravity is moved towards the centre of the corner by tilting the vehicle in a similar manner to that of a motorcycle. An active tilting system using hydraulic actuation has been employed, allowing for car-like controls. A prototype vehicle has been built to test this active tilting system. Initial testing revealed that while basic steady state handling was good, transient response required improvement. The evidence indicating this poor response is examined, and the necessary methods employed within the control system to solve the issue are discussed. Improved results are presented following an increase in the system gain. The effects of different filter cutoff frequencies on the objective and subjective vehicle handling characteristics is also investigated and presented here. It is shown that when designing a three-wheeled tilting vehicle with the arrangement used in CLEVER, safe handling can only be achieved at the expense of fast tilt response. This is a result of fundamental limitations of the vehicle design.