Active and passive microwave measurements in Hurricane Allen

The NASA Langley Research Center analysis of the airborne microwave remote sensing measurements of Hurricane Allen obtained on August 5 and 8, 1980 is summarized. The instruments were the C-band stepped frequency microwave radiometer and the Ku-band airborne microwave scatterometer. They were carried aboard a NOAA aircraft making storm penetrations at an altitude of 3000 m and are sensitive to rain rate, surface wind speed, and surface wind vector. The wind speed is calculated from the increase in antenna brightness temperature above the estimated calm sea value. The rain rate is obtained from the difference between antenna temperature increases measured at two frequencies, and wind vector is determined from the sea surface normalized radar cross section measured at several azimuths. Comparison wind data were provided from the inertial navigation systems aboard both the C-130 aircraft at 3000 m and a second NOAA aircraft (a P-3) operating between 500 and 1500 m. Comparison rain rate data were obtained with a rain radar aboard the P-3. Evaluation of the surface winds obtained with the two microwave instruments was limited to comparisons with each other and with the flight level winds. Two important conclusions are drawn from these comparisons: (1) the radiometer is accurate when predicting flight level wind speeds and rain; and (2) the scatterometer produces well behaved and consistent wind vectors for the rain free periods

Vibration Suppression of a Spacecraft Flexible Appendages Using Smart Material

The article of record as published may be found at http://dx.doi.org/10..1088/0964-1726/7/1/011This paper presents the results of positive position feedback (PPF) control and linear–quadratic Gaussian (LQG) control for vibration suppression of a flexible structure using piezoceramics. Experiments were conducted on the US Naval Postgraduate School’s flexible spacecraft simulator (FSS), which is comprised of a rigid central body and a flexible appendage. The objective of this research is to suppress the vibration of the flexible appendage. Experiments show that both control methods have unique advantages for vibration suppression. PPF control is effective in providing high damping for a particular mode and is easy to implement. LQG control provides damping to all modes; however, it cannot provide high damping for a specific mode. LQG control is very effective in meeting specific requirements, such as minimization of tip motion of a flexible beam, but at a higher implementation cost.This paper presents the results of positive position feedback (PPF) control and linear–quadratic Gaussian (LQG) control for vibration suppression of a flexible structure using piezoceramics. Experiments were conducted on the US Naval Postgraduate School’s flexible spacecraft simulator (FSS), which is comprised of a rigid central body and a flexible appendage. The objective of this research is to suppress the vibration of the flexible appendage. Experiments show that both control methods have unique advantages for vibration suppression. PPF control is effective in providing high damping for a particular mode and is easy to implement. LQG control provides damping to all modes; however, it cannot provide high damping for a specific mode. LQG control is very effective in meeting specific requirements, such as minimization of tip motion of a flexible beam, but at a higher implementation cost.This paper presents the results of positive position feedback (PPF) control and linear–quadratic Gaussian (LQG) control for vibration suppression of a flexible structure using piezoceramics. Experiments were conducted on the US Naval Postgraduate School’s flexible spacecraft simulator (FSS), which is comprised of a rigid central body and a flexible appendage. The objective of this research is to suppress the vibration of the flexible appendage. Experiments show that both control methods have unique advantages for vibration suppression. PPF control is effective in providing high damping for a particular mode and is easy to implement. LQG control provides damping to all modes; however, it cannot provide high damping for a specific mode. LQG control is very effective in meeting specific requirements, such as minimization of tip motion of a flexible beam, but at a higher implementation cost

The Scattering of Electromagnetic Waves from Two-Dimensional Randomly Rough Penetrable Surfaces

An accurate and efficient numerical simulation approach to electromagnetic wave scattering from two-dimensional, randomly rough, penetrable surfaces is presented. The use of the M\"uller equations and an impedance boundary condition for a two-dimensional rough surface yields a pair of coupled two-dimensional integral equations for the sources on the surface in terms of which the scattered field is expressed through the Franz formulas. By this approach, we calculate the full angular intensity distribution of the scattered field that is due to a finite incident beam of $p$-polarized light. We specifically check the energy conservation (unitarity) of our simulations (for the non-absorbing case). Only after a detailed numerical treatment of {\em both} diagonal and close-to-diagonal matrix elements is the unitarity condition found to be well-satisfied for the non-absorbing case (${\mathcal U}>0.995$), a result that testifies to the accuracy of our approach.Comment: Revtex, 4 pages, 2 figure

What unites Europe and what divides it? Solidarity and the European heritage reconsidered

Despite the on-set on new divisions, there is a strong case to be made for the view that ultimately Europe is more united than divided. There is still significant continuity with the post-war project of reconstruction and peace and that this common ground that constitutes the European heritage needs to be given greater recognition. One of the defining features of European self-understanding is opposition to war

Roger Blackman 1941-2022 an appreciation

Dr Roger Laurence Blackman (Fig. 1) passed away on 17 March 2022, after more than 50 years dedicated to advances in aphid science. There can be very few scientists studying any aspect of aphids whose papers have not cited the works of Roger Blackman. To his name, we add that of Victor Eastop (1924–2012), for the two of them formed an inspirational, complementary and indefatigable pair at London’s Natural History Museum. Together they were responsible for, amongst many other seminal works, the three testaments of the aphidologists’ bible: Aphids on the World’s Crops, Aphids on the World’s Trees and Aphids on the World’s Herbaceous Plants and Shrubs, now brought together and regularly updated by Roger until very recently in the online version, Aphids on the World’s Plants (www.aphidsonworldsplants.info). Victor was an out-and-out taxonomist, absolutely amongst the best the world has known, whilst being very familiar with most aspects of aphidology. Roger’s contributions were broader as we shall see

Astrometric Methods and Instrumentation to Identify and Characterize Extrasolar Planets: A Review

I present a review of astrometric techniques and instrumentation utilized to search for, detect, and characterize extra-solar planets. First, I briefly summarize the properties of the present-day sample of extrasolar planets, in connection with predictions from theoretical models of planet formation and evolution. Next, the generic approach to planet detection with astrometry is described, with significant discussion of a variety of technical, statistical, and astrophysical issues to be faced by future ground-based as well as space-borne efforts in order to achieve the required degree of measurement precision. After a brief summary of past and present efforts to detect planets via milli-arcsecond astrometry, I then discuss the planet-finding capabilities of future astrometric observatories aiming at micro-arcsecond precision. Lastly, I outline a number experiments that can be conducted by means of high-precision astrometry during the next decade, to illustrate its potential for important contributions to planetary science, in comparison with other indirect and direct methods for the detection and characterization of planetary systems.Comment: 61 pages, 8 figures, PASP, accepted (October 2005 issue

Nearby low-mass triple system GJ795

We report the results of our optical speckle-interferometric observations of the nearby triple system GJ795 performed with the 6-m BTA telescope with diffraction-limited angular resolution. The three components of the system were optically resolved for the first time. Position measurements allowed us to determine the elements of the inner orbit of the triple system. We use the measured magnitude differences to estimate the absolute magnitudes and spectral types of the components of the triple: $M_{V}^{Aa}$=7.31$\pm$0.08, $M_{V}^{Ab}$=8.66$\pm$0.10, $M_{V}^{B}$=8.42$\pm$0.10, $Sp_{Aa}$ $\approx$K5, $Sp_{Ab}$ $\approx$K9, $Sp_{B}$ $\approx$K8. The total mass of the system is equal to $\Sigma\mathcal{M}_{AB}$=1.69$\pm0.27\mathcal{M}_{\odot}$. We show GJ795 to be a hierarchical triple system which satisfies the empirical stability criteria.Comment: 6 pages, 2 figures, published in Astrophysical Bulleti

Practical long-distance quantum key distribution system using decoy levels

Quantum key distribution (QKD) has the potential for widespread real-world applications. To date no secure long-distance experiment has demonstrated the truly practical operation needed to move QKD from the laboratory to the real world due largely to limitations in synchronization and poor detector performance. Here we report results obtained using a fully automated, robust QKD system based on the Bennett Brassard 1984 protocol (BB84) with low-noise superconducting nanowire single-photon detectors (SNSPDs) and decoy levels. Secret key is produced with unconditional security over a record 144.3 km of optical fibre, an increase of more than a factor of five compared to the previous record for unconditionally secure key generation in a practical QKD system.Comment: 9 page

Long distance decoy state quantum key distribution in optical fiber

The theoretical existence of photon-number-splitting attacks creates a security loophole for most quantum key distribution (QKD) demonstrations that use a highly attenuated laser source. Using ultra-low-noise, high-efficiency transition-edge sensor photodetectors, we have implemented the first version of a decoy-state protocol that incorporates finite statistics without the use of Gaussian approximations in a one-way QKD system, enabling the creation of secure keys immune to photon-number-splitting attacks and highly resistant to Trojan horse attacks over 107 km of optical fiber.Comment: 4 pages, 3 figure

Spatially heterogeneous land cover/land use and climatic risk factors of tick-borne feline cytauxzoonosis

Background: Feline cytauxzoonosis is a highly fatal tick-borne disease caused by a hemoparasitic protozoan, Cytauxzoon felis. This disease is a leading cause of mortality for cats in the Midwestern United States, and no vaccine or effective treatment options exist. Prevention based on knowledge of risk factors is therefore vital. Associations of different environmental factors, including recent climate were evaluated as potential risk factors for cytauxzoonosis using Geographic Information Systems (GIS). Methods: There were 69 cases determined to be positive for cytauxzoonosis based upon positive identification of C. felis within blood film examinations, tissue impression smears, or histopathologic examination of tissues. Negative controls totaling 123 were selected from feline cases that had a history of fever, malaise, icterus, and anorexia but lack of C. felis within blood films, impression smears, or histopathologic examination of tissues. Additional criteria to rule out C. felis among controls were the presence of regenerative anemia, cytologic examination of blood marrow or lymph node aspirate, other causative agent diagnosed, or survival of 25 days or greater after testing. Potential environmental determinants were derived from publicly available sources, viz., US Department of Agriculture (soil attributes), US Geological Survey (land-cover/landscape, landscape metrics), and NASA (climate). Candidate variables were screened using univariate logistic models with a liberal p value (0.2), and associations with cytauxzoonosis were modeled using a global multivariate logistic model (p<0.05). Spatial heterogeneity among significant variables in the study region was modeled using a geographically weighted regression (GWR) approach. Results: Total Edge Contrast Index (TECI), grassland-coverage, humidity conditions recorded during the 9th week prior to case arrival, and an interaction variable, “diurnal temperature range×percent mixed forest area” were significant risk factors for cytauxzoonosis in the study region. TECI and grassland areas exhibited significant regional differences in their effects on cytauxzoonosis outcome, whereas others were uniform. Conclusions: Land-cover areas favorable for tick habitats and climatic conditions that favor the tick life cycle are strong risk factors for feline cytauxzoonosis. Spatial heterogeneity and interaction effects between land-cover and climatic variables may reveal new information when evaluating risk factors for vector-borne diseases