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Direct Formation of Structural Components Using a Martian Soil Simulant.
Martian habitats are ideally constructed using only locally available soils; extant attempts to process structural materials on Mars, however, generally require additives or calcination. In this work we demonstrate that Martian soil simulant Mars-1a can be directly compressed at ambient into a strong solid without additives, highlighting a possible aspect of complete Martian in-situ resource utilization. Flexural strength of the compact is not only determined by the compaction pressure but also significantly influenced by the lateral boundary condition of processing loading. The compression loading can be applied either quasi-statically or through impact. Nanoparticulate iron oxide (npOx), commonly detected in Martian regolith, is identified as the bonding agent. Gas permeability of compacted samples was measured to be on the order of 10-16 m2, close to that of solid rocks. The compaction procedure is adaptive to additive manufacturing
Imitation, local interaction, and efficiency: reappraisal
We revisit the model of Alos-Ferrer and Weidenholzer (2006) but under the assumption that risk-dominant equilibria are Pareto efficient. It is found that risk-dominant equilibria, non-risk-dominant equilibria, and some non-monomorphic states can emerge in the long run when players interact with their immediate neighbors only.Coordination game, imitation, local interaction
Cooling Load Calculations of Heat Gain for Buildings
Two recent papers [1,2] obtain formulas for temperature variations caused by the varying flow of solar heat through windows. These two works are used in the present study to develop a computer program for calculating the transient cooling load required to maintain the interior of a building at a given temperature. We assume that the building is standing by itself without surrounding radiating buildings or pavements. The heat gain through semi-transparent single or composite barriers is combined with the accompanying heat gain through the opaque walls; see Figure 1. The analytical solutions given in [1,2] cannot be represented directly as numerical terms in the cooling load. This is because the useful solutions in [1,2] exist as explicit solutions for the air temperature of the room; the solutions also exist in the form of a formal integral representation with the terms of the cooling load involved in the integrals. To obtain a solution of this part of the problem in numerical terms, two steps are involved: i. Numerical evaluations of the formal integral representation ii. Inversion of the indirect solutions to obtain the numerical results for the required cooling load. Two procedures can be followed to arrive at a· solution: One, we use the analytical solutions given in [1,2]; and two, we solve our problem directly from the differential formulation given in these references by numerical method. The mathematical representation of our problem was formulated into a computer program to perform the automatic calculations. This computer program is given in a separate volume available in the Department of Mechanical Engineering at South Dakota State University. Certain approximations are introduced in order to obtain the numerical results. The approximations associated with the numerical evaluations are discussed in Chapter III. The error induced due to the approximations can be reduced by using some of the more accurate approximation methods. However, the associated disadvantages in doing so are: 1. The flow chart for the automatic calculation system can be more complex in logic, and more difficult to understand. 2. The computer program associated with the flow chart can be more involved and larger in size to such an extent that it is not easily handled. Also, high accuracy can be attained by using smaller increments for each step of the calculations. But the required number of calculations will be greatly increased, and so will be the required computer time. For engineering applications, we prefer to have our methods simple and practical, so that they can be applied without difficulty by those who are interested
Ricci flow on open 3-manifolds and positive scalar curvature
We show that an orientable 3-dimensional manifold M admits a complete
riemannian metric of bounded geometry and uniformly pos- itive scalar curvature
if and only if there exists a finite collection F of spherical space-forms such
that M is a (possibly infinite) connected sum where each summand is
diffeomorphic to S2xS1 or to some mem- ber of F. This result generalises G.
Perelman's classification theorem for compact 3-manifolds of positive scalar
curvature. The main tool is a variant of Perelman's surgery construction for
Ricci flow.Comment: 65 page
Neutron flux mapping of the MSM reactor
This investigation presents a mean to determine thermal neutron flux of a reactor by irradiating copper wires inside the fuel elements. The activity recorded after decay correction, is the relative thermal neutron density. Thermal neutron flux is a measure of the neutron density at thermal energy, 0.025 ev.
Gold foils irradiated at National Bureau of Standards were used as the absolute neutron flux calibration standards. The average flux of the reactor with water as the reflector ranges from 7.24 x 1010 neutrons/cm2 - sec. to 7.87 x 1010 neutrons/cm2 - sec. as obtained from the calculations. This set of values compares favorably with the result as measured by the manufacturers.
In this investigation the thermal neutron flux in the MSM reactor was determined by irradiating copper wires inside the fuel elements --Abstract, page ii
Normalized Ricci flow on Riemann surfaces and determinants of Laplacian
In this note we give a simple proof of the fact that the determinant of
Laplace operator in smooth metric over compact Riemann surfaces of arbitrary
genus monotonously grows under the normalized Ricci flow. Together with
results of Hamilton that under the action of the normalized Ricci flow the
smooth metric tends asymptotically to metric of constant curvature for , this leads to a simple proof of Osgood-Phillips-Sarnak theorem stating that
that within the class of smooth metrics with fixed conformal class and fixed
volume the determinant of Laplace operator is maximal on metric of constant
curvatute.Comment: a reference to paper math.DG/9904048 by W.Mueller and K.Wendland
where the main theorem of this paper was proved a few years earlier is adde
Ricci flows with unbounded curvature
We show that any noncompact Riemann surface admits a complete Ricci flow
g(t), t\in[0,\infty), which has unbounded curvature for all t\in[0,\infty).Comment: 12 pages, 1 figure; updated reference
Two-charged non-extremal rotating black holes in seven-dimensional gauged supergravity: The single-rotation case
We construct the solution for non-extremal charged rotating black holes in
seven-dimensional gauged supergravity, in the case with only one rotation
parameter and two independent charges. Using the Boyer-Lindquist coordinates,
the metric is expressed in a generalized form of the ansatz previously
presented in [S.Q. Wu, Phys. Rev. D 83 (2011) 121502(R)], which may be helpful
to find the most general non-extremal two-charged rotating black hole with
three unequal rotation parameters. The conserved charges for thermodynamics are
also computed.Comment: 13 pages, elsarticle.cls, revised version with two typos removed and
three references adde
Spinor Fields and Symmetries of the Spacetime
In the background of a stationary black hole, the "conserved current" of a
particular spinor field always approaches the null Killing vector on the
horizon. What's more, when the black hole is asymptotically flat and when the
coordinate system is asymptotically static, then the same current also
approaches the time Killing vector at the spatial infinity. We test these
results against various black hole solutions and no exception is found. The
spinor field only needs to satisfy a very general and simple constraint.Comment: 19 page
Formal Verification of Real-Time Function Blocks Using PVS
A critical step towards certifying safety-critical systems is to check their
conformance to hard real-time requirements. A promising way to achieve this is
by building the systems from pre-verified components and verifying their
correctness in a compositional manner. We previously reported a formal approach
to verifying function blocks (FBs) using tabular expressions and the PVS proof
assistant. By applying our approach to the IEC 61131-3 standard of Programmable
Logic Controllers (PLCs), we constructed a repository of precise specification
and reusable (proven) theorems of feasibility and correctness for FBs. However,
we previously did not apply our approach to verify FBs against timing
requirements, since IEC 61131-3 does not define composite FBs built from
timers. In this paper, based on our experience in the nuclear domain, we
conduct two realistic case studies, consisting of the software requirements and
the proposed FB implementations for two subsystems of an industrial control
system. The implementations are built from IEC 61131-3 FBs, including the
on-delay timer. We find issues during the verification process and suggest
solutions.Comment: In Proceedings ESSS 2015, arXiv:1506.0325
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