High-power microwave optics for flexible power transmission systems

A large concave microwave mirror near the transmitter can magnify the apparent size of the Earth as seen from a phased array, and vice versa, permitting a small phased array to be coupled to a small rectenna while preserving the transmission efficiency (the reflection loss is slight) and peak power densities characteristic of the reference system. This augmentation of the phased array aperture with a large mirror gives the system greater resolution (in the optical sense), and opens new degrees of freedom in SPS design. The consequences of such an approach for a prototype satellite were explored. Its consequences for a mature SPS are discussed

Path-Length-Resolved Dynamic Light Scattering: Modeling the Transition From Single to Diffusive Scattering

Dynamic light-scattering spectroscopy is used to study Brownian motion within highly scattering samples. The fluctuations of the light field that is backscattered by a suspension of polystyrene microspheres are measured as power spectra by use of low-coherence interferometry to obtain path-length resolution. The data are modeled as the sum of contributions to the detected light weighted by a Poisson probability for the number of events that each component has experienced. By analyzing the broadening of the power spectra as a function of the path length for various sizes of particles, we determine the contribution of multiple scattering to the detected signal as a function of scattering anisotropy

The Effect of Credit Insurance on Liquidity Constraints and Default Rates: Evidence From a Governmental Intervention

Understanding the extent to which interventions in financial markets can reduce liquidity constraints is of crucial importance to researchers and policymakers. Even though there is consensus that limited access to financing can reduce the number of profitable projects undertaken by entrepreneurs, there is little research on how well governmental interventions address this problem. In this paper we use Partial Credit Guarantee Schemes in Chile to study how such a government intervention in the financial system can affect the access that entrepreneurs have to the formal financial system. We also explore how these schemes affect the default rates on the guaranteed loans. We find that partial credit guarantee schemes increase the number of loans and the aggregate amount lent to small and medium size businesses. In addition, we find that credit guarantees increase the debt capacity of individual entrepreneurs, holding assets fixed. We also find that Credit Guarantees increase default rates, but the evidence suggests that this result is explained mainly by misalignment of bank incentives rather than moral hazard in the context of client practices.

Rolling and sliding of a nanorod between two planes: Tribological regimes and control of friction

The motion of a cylindrical crystalline nanoparticle sandwiched between two crystalline planes, one stationary and the other pulled at a constant velocity and pressed down by a normal load, is considered theoretically using a planar model. The results of our model calculations show that, depending on load and velocity, the nanoparticle can be either rolling or sliding. At sufficiently high normal loads, several sliding states characterized by different friction forces can coexist, corresponding to different orientations of the nanoparticle, and allowing one to have low or high friction at the same pulling velocity and normal load.Comment: 5 figure

Footbridge

Tato práce se zabývá návrhem a posouzením lávky pro pěší ze dřeva. Lávka je navržena pro oblast Loučná nad Desnou přes řeku Desná. Rozpětí lávky je 30m, šířka 4m. Lávka je zastřešená sedlovou střechou. Hlavním nosným prvkem lávky jsou dva trojkloubový oblouky s mezilehlou mostovkou. Mostovka je z dvou hlavních nosníků a z devíti příčníků, mezi kterými jsou vždy dva podélníky. Zastřešení lávky je z devíti příčných vazeb, které jsou propojeny vaznicemi a vrcholovou vaznicí. Stabilita celé konstrukce je zabezpečena vodorovnými podélnými ztužidly ve spodní a horní rovině a svislým podélným ztužidlem ve střeše. Hlavní nosné prvky jsou z lepeného lamelového dřeva, ostatní prvky jsou z rostlého dřeva. Ztužidla jsou z ocelových táhel.This thesis deals with the design and assessment of the wooden footbridge. The structure is designed for the locality of the village Loučná nad Desnou acrros the river Desná. Span of the footbridge is 30m, and the width is 4m. The footbridge is covered with a saddle roof. The main supporting elements are two triple joint arcs with intermediate bridge deck. The bridge deck is made of two main beams and nine cross members, with always two longitudinal members in between them. Roofing is of nine cross-bindings, which are connected by purlins and top purlin. The stability of the whole structure is stiffened by the horizontal longitudinal stiffeners in the top and bottom surface and vertical longitudinal stiffener in the roof. The main load-bearing elements are made of glued laminated timber, the other elements are made of solid timber. Stiffeners are made of steel rods.

Introduction to Nuclear Propulsion: Lecture 15 - Nuclear Test Operations

The test operation of nuclear power plants, specifically nuclear rockets, bears some interesting similarities to the operation of chemical rocket tests as well as, of course, many differences. A significant feature common to both nuclear and chemical rocket tests is that all the fuel for the entire operation is loaded at the start of the test. As a direct consequence of this fact, the operation of nuclear power plants must be surrounded with adequate safety precautions, as is indeed the case in the operation of chemical rockets, A second direct consequence is that in both types of testing a very thorough and complete checkout is made before starting the test

Prototype solar power satellite options

The choice of options for the prototype solar power satellite is addressed relative to risk and cost. Emphasis is placed on the reduction of the risk of failure. Risk is the program cost multiplied by the reduction in probability of program success due to the risky action. Four classes of risk are identified. It is suggested that prototyping would reduce the technical risk as well as reduce the effects of the other three types of risk by allowing them to be quantified earlier. Prototype demonstration requirements addressed include electromagnetic power link feasibility demonstration, component integration verification, construction technology verification, and cost performance verification. Specific prototype requirements are listed and prototyping options are given in tabular form