Use of active control systems to improve bending and rotor flapping response of a tilt rotor VTOL airplane

The results are summarized of an analytical study of the use of active control systems for the purpose of reducing the root mean square response of wing vertical bending and rotor flapping to atmospheric turbulence for a tilt-rotor VTOL airplane. Only the wing/rotor assembly was considered so that results of a wind tunnel test program would be applicable in a subsequent phase of the research. The capabilities and limitations of simple single feedback configurations were identified, and the most promising multiloop feedback configurations were then investigated. Design parameters were selected so as to minimize either wing bending or rotor flapping response. Within the constraints imposed by practical levels of feedback gains and complexity and by considerations of safety, reduction in response due to turbulence of the order of 30 to 50 percent is predicted using the rotor longitudinal cyclic and a trailing edge wing flap as control effectors

A study of the methods for the production and confinement of high energy plasmas

The injection of dense plasmas into a B sub z long magnetic field from both ends of the field coil was investigated. Deflagration plasma guns and continuous flow Z-pinch are discussed along with the possibility of a continuous flow Z-pinch fusion reactor. The injection experiments are described with emphasis on the synchronization of the two plasma deflagration guns, the collision of the two plasma beams, and the determination of plasma density

Preliminary core-engine noise abatement experimental results of a fluid injection nozzle on a JT-15D turbofan engine

Jet noise, as induced by shear stress, in an jet exhaust is investigated. Experiments were performed on a JT-15D fan jet to verify the inward momentum stress reduction concept. The experiments involved making fan air flow convergently around the high velocity core jet with a small angle. Ring airfoils were used as flow separators for the minimization of the thrust loss. Jet exhaust noise reduction of ll db at 30 deg from the jet axis was recorded and 8 db integrated overall noise reduction over a hemisphere was measured with only 4.6% thrust loss, or 152 db/percent thrust loss

Stellar mass versus stellar velocity dispersion: which is better for linking galaxies to their dark matter halos?

It was recently suggested that, compared to its stellar mass (M*), the central stellar velocity dispersion (sigma*) of a galaxy might be a better indicator for its host dark matter halo mass. Here we test this hypothesis by estimating the dark matter halo mass for central alaxies in groups as function of M* and sigma*. For this we have estimated the redshift-space cross-correlation function (CCF) between the central galaxies at given M* and sigma* and a reference galaxy sample, from which we determine both the projected CCF, w_p(r_p), and the velocity dispersion profile (VDP) of satellites around the centrals. A halo mass is then obtained from the average velocity dispersion within the virial radius. At fixed M*, we find very weak or no correlation between halo mass and sigma*. In contrast, strong mass dependence is clearly seen even when sigma* is limited to a narrow range. Our results thus firmly demonstrate that the stellar mass of central galaxies is still a good (if not the best) indicator for dark matter halo mass, better than the stellar velocity dispersion. The dependence of galaxy clustering on sigma* fixed M*, as recently discovered by Wake et al. (2012), may be attributed to satellite galaxies, for which the tidal stripping occurring within halos has stronger effect on stellar mass than on central stellar velocity dispersion.Comment: 4 pages, 4 figures, accepted for publication in ApJ Letters, minor revisions in the tex

Optimization of rotor blades for combined structural, performance, and aeroelastic characteristics

The strategies whereby helicopter rotor blades can be optimized for combined structural, inertial, dynamic, aeroelastic, and aerodynamic performance characteristics are outlined. There are three key ingredients in the successful execution of such an interdisciplinary optimization. The first is the definition of a satisfactory performance index that combines all aspects of the problem without too many constraints. The second element is the judicious choice of computationally efficient analysis tools for the various quantitative components in both the cost functional and constraints. The third element is an effective strategy for combining the various disciplines either in parallel or sequential optimizations

Detection of the large scale alignment of massive galaxies at z~0.6

We report on the detection of the alignment between galaxies and large-scale structure at z~0.6 based on the CMASS galaxy sample from the Baryon Oscillation Spectroscopy Survey data release 9. We use two statistics to quantify the alignment signal: 1) the alignment two-point correlation function which probes the dependence of galaxy clustering at a given separation in redshift space on the projected angle (theta_p) between the orientation of galaxies and the line connecting to other galaxies, and 2) the cos(2theta)-statistic which estimates the average of cos(2theta_p) for all correlated pairs at given separation. We find significant alignment signal out to about 70 Mpc/h in both statistics. Applications of the same statistics to dark matter halos of mass above 10^12 M_sun/h in a large cosmological simulation show similar scale-dependent alignment signals to the observation, but with higher amplitudes at all scales probed. We show that this discrepancy may be partially explained by a misalignment angle between central galaxies and their host halos, though detailed modeling is needed in order to better understand the link between the orientations of galaxies and host halos. In addition, we find systematic trends of the alignment statistics with the stellar mass of the CMASS galaxies, in the sense that more massive galaxies are more strongly aligned with the large-scale structure.Comment: 6 pages, 3 figures, accepted for publication in ApJ Letter

Recent advancement of turbulent flow measurement techniques

Advancements of the fluctuating density gradient cross beam laser Schlieren technique, the fluctuating line-reversal temperature measurement and the development of the two-dimensional drag-sensing probe to a three-dimensional drag-sensing probe are discussed. The three-dimensionality of the instantaneous momentum vector can shed some light on the nature of turbulence especially with swirling flow. All three measured fluctuating quantities (density, temperature, and momentum) can provide valuable information for theoreticians

Response-surface-model-based system sizing for nearly/net zero energy buildings under uncertainty

Properly treating uncertainty is critical for robust system sizing of nearly/net zero energy buildings (ZEBs). To treat uncertainty, the conventional method conducts Monte Carlo simulations for thousands of possible design options, which inevitably leads to computation load that is heavy or even impossible to handle. In order to reduce the number of Monte Carlo simulations, this study proposes a response-surface-model-based system sizing method. The response surface models of design criteria (i.e., the annual energy match ratio, self-consumption ratio and initial investment) are established based on Monte Carlo simulations for 29 specific design points which are determined by Box-Behnken design. With the response surface models, the overall performances (i.e., the weighted performance of the design criteria) of all design options (i.e., sizing combinations of photovoltaic, wind turbine and electric storage) are evaluated, and the design option with the maximal overall performance is finally selected. Cases studies with 1331 design options have validated the proposed method for 10,000 randomly produced decision scenarios (i.e., users’ preferences to the design criteria). The results show that the established response surface models reasonably predict the design criteria with errors no greater than 3.5% at a cumulative probability of 95%. The proposed method reduces the number of Monte Carlos simulations by 97.8%, and robustly sorts out top 1.1% design options in expectation. With the largely reduced Monte Carlo simulations and high overall performance of the selected design option, the proposed method provides a practical and efficient means for system sizing of nearly/net ZEBs under uncertainty