Deformation processes in forging ceramics Progress report, 19 Jun. - 19 Sep. 1969

Deformation processes involved in forging of polycrystalline oxide ceramic

Deformation processes in forging ceramics Progress report, 19 Dec. 1969 - 19 Mar. 1970

Deformation processes in forging ceramic

High temperature compounds for turbine vanes

Fabrication and microstructure control studies were conducted on SiC, Si3N and composites based on Si3N. Charpy mode impact testing to 2400 F established that Si3N4/Mo composites have excellent potential. Attempts to fabricate composites of Si3N4 with superalloys, both by hot pressing and infiltration were largely unsuccessful in comparison to using Mo, Re, and Ta which are less reactive. Modest improvements in impact strength were realized for monolithic Si3N4; however, SiC strengths increased by a factor of six and now equal values achieved for Si3N4. Correlations of impact strength with material properties are discussed. Reduced MgO densification aid additions to Si3N4 were found to decrease densification kinetics, increase final porosity, decrease room temperature bend strength, increase high temperature bend strength, and decrease bend stress rupture properties. The decrease in bend strength at high temperature for fine grain size SiC suggested that a slightly larger grain size material with a nearly constant strength-temperature relation may prove desirable in the creep and stress rupture mode

Optical implementation of systolic array processing

Algorithms for matrix vector multiplication are implemented using acousto-optic cells for multiplication and input data transfer and using charge coupled devices detector arrays for accumulation and output of the results. No two dimensional matrix mask is required; matrix changes are implemented electronically. A system for multiplying a 50 component nonnegative real vector by a 50 by 50 nonnegative real matrix is described. Modifications for bipolar real and complex valued processing are possible, as are extensions to matrix-matrix multiplication and multiplication of a vector by multiple matrices

Potential of Interplanetary Torques and Solar Modulation for Triggering Terrestrial Atmospheric and Lithospheric Events

The Sun is forced into an orbit around the barycenter of the solar system because of the changing mass distribution of the planets. Solar-planetary-lunar dynamic relationships may form a new basis for understanding and predicting cyclic solar forcing functions on the Earth's climate.Comment: Invited Paper at the Fourth UN/ESA Workshop on Basic Space Science, Cairo, Egypt, July 1994. 7 pages LaTeX. Accepted for publication in the journal Earth, Moon, and Planet

Deformation processes in forging ceramics Summary report, Jun. 1969 - Aug. 1970

Deformation processes in forging polycrystalline oxide ceramic

Venture Capital Booms and Startup Financing

We review the growing literature on the relationship between venture capital booms and startup financing, focusing on three broad areas: First, we discuss the drivers of large inflows into the venture capital asset class, particularly in recent years -- which are related to but also distinct from macroeconomic business cycles and stock market fluctuations. Second, we review the emerging literature on the real effects of venture capital financing booms. A particular focus of this work is to highlight the potential impact that booms (and busts) can have on the types of firms that VCs choose to fund and terms at which they are funded, independent of investment opportunities -- thereby shaping the trajectory of innovation being conducted by startups. Third, an important insight from recent research is that booms in venture capital financing are not just a temporal phenomenon but can also be seen in terms of the concentration of VC investment in certain industries and geographies. We also review the role of government policy, exploring the degree to which it can explain the concentration of VC funding in the US over the past forty years in just two broad areas – information and communication technologies (ICT) and biotechnology. We conclude by highlighting promising areas of further research

Recent development in the design, testing and impact-damage tolerance of stiffened composite panels

Structural technology of laminated filamentary-composite stiffened-panel structures under combined inplane and lateral loadings is discussed. Attention is focused on: (1) methods for analyzing the behavior of these structures under load and for determining appropriate structural proportions for weight-efficient configurations; and (2) effects of impact damage and geometric imperfections on structural performance. Recent improvements in buckling analysis involving combined inplane compression and shear loadings and transverse shear deformations are presented. A computer code is described for proportioning or sizing laminate layers and cross-sectional dimensions, and the code is used to develop structural efficiency data for a variety of configurations, loading conditions, and constraint conditions. Experimental data on buckling of panels under inplane compression is presented. Mechanisms of impact damage initiation and propagation are described