40 research outputs found
ECLSS advanced automation preliminary requirements
A description of the total Environmental Control and Life Support System (ECLSS) is presented. The description of the hardware is given in a top down format, the lowest level of which is a functional description of each candidate implementation. For each candidate implementation, both its advantages and disadvantages are presented. From this knowledge, it was suggested where expert systems could be used in the diagnosis and control of specific portions of the ECLSS. A process to determine if expert systems are applicable and how to select the expert system is also presented. The consideration of possible problems or inconsistencies in the knowledge or workings in the subsystems is described
A diagnostic prototype of the potable water subsystem of the Space Station Freedom ECLSS
In analyzing the baseline Environmental Control and Life Support System (ECLSS) command and control architecture, various processes are found which would be enhanced by the use of knowledge based system methods of implementation. The most suitable process for prototyping using rule based methods are documented, while domain knowledge resources and other practical considerations are examined. Requirements for a prototype rule based software system are documented. These requirements reflect Space Station Freedom ECLSS software and hardware development efforts, and knowledge based system requirements. A quick prototype knowledge based system environment is researched and developed
The ECLSS Advanced Automation Project Evolution and Technology Assessment
Viewgraphs on Environmental Control and Life Support System (ECLSS) advanced automation project evolution and technology assessment are presented. Topics covered include: the ECLSS advanced automation project; automatic fault diagnosis of ECLSS subsystems descriptions; in-line, real-time chemical and microbial fluid analysis; and object-oriented, distributed chemical and microbial modeling of regenerative environmental control systems description
Knight Shift Anomalies in Heavy Electron Materials
We calculate non-linear Knight Shift vs. susceptibility anomalies
for Ce ions possessing local moments in metals. The ions are modeled with the
Anderson Hamiltonian and studied within the non-crossing approximation (NCA).
The non-linearity diminishes with decreasing Kondo temperature
and nuclear spin- local moment separation. Treating the Ce ions as an
incoherent array in CeSn, we find excellent agreement with the observed Sn
data.Comment: 4 pages, Revtex, 3 figures available upon request from
[email protected]
Calculations of the Knight Shift Anomalies in Heavy Electron Materials
We have studied the Knight shift and magnetic susceptibility
of heavy electron materials, modeled by the infinite U Anderson model
with the NCA method. A systematic study of and for
different Kondo temperatures (which depends on the hybridization width
) shows a low temperature anomaly (nonlinear relation between and
) which increases as the Kondo temperature and distance
increase. We carried out an incoherent lattice sum by adding the of
a few hundred shells of rare earth atoms around a nucleus and compare the
numerically calculated results with the experimental results. For CeSn_3, which
is a concentrated heavy electron material, both the ^{119}Sn NMR Knight shift
and positive muon Knight shift are studied. Also, lattice coherence effects by
conduction electron scattering at every rare earth site are included using the
average-T matrix approximation. Also NMR Knight shifts for YbCuAl and the
proposed quadrupolar Kondo alloy Y_{0.8}U_{0.2}Pd_{3} are studied.Comment: 31 pages of RevTex, 22 Postscript figures, submmitted to PRB, some
figures are delete
Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}
Electrical resistivity , specific heat C, and magnetic susceptibility
measurements made on the filled skutterudite CeRu_4As_{12} reveal
non-Fermi liquid (NFL) T - dependences at low T, i.e., (T) T^{1.4}
and weak power law or logarithmic divergences in C(T)/T and (T).
Measurements also show that the T - dependence of the thermoelectric power S(T)
deviates from that seen in other Ce systems. The NFL behavior appears to be
associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than
a typical Kondo lattice scenario that would be appropriate for an integral Ce
valence of 3^+.Comment: 18 pages, 5 figure
Itinerancy and Hidden Order in
We argue that key characteristics of the enigmatic transition at in indicate that the hidden order is a density wave formed within
a band of composite quasiparticles, whose detailed structure is determined by
local physics. We expand on our proposal (with J.A. Mydosh) of the hidden order
as incommnesurate orbital antiferromagnetism and present experimental
predictions to test our ideas. We then turn towards a microscopic description
of orbital antiferromagnetism, exploring possible particle-hole pairings within
the context of a simple one-band model. We end with a discussion of recent
high-field and thermal transport experiment, and discuss their implications for
the nature of the hidden order.Comment: 18 pages, 7 figures. v2 contains added referenc
29-Si NMR and Hidden Order in URu2Si2
We present new 29-Si NMR spectra in URu2Si2 for varying temperature T, and
external field H. On lowering T, the systematics of the low-field lineshape and
width reveal an extra component (lambda) to the linewidth below T_N ~ 17 K not
observed previously. We find that lambda is magnetic-field independent and
dominates the low-field lineshape for all orientations of H with respect to the
tetragonal c axis. The behavior of lambda indicates a direct relationship
between the 29-Si spin and the transition at T_N, but it is inconsistent with a
coupling of the nuclei to static antiferromagnetic order/disorder of the U-spin
magnetization. This leads us to conjecture that lambda is due to a coupling of
29-Si to the system's hidden-order parameter. A possible coupling mechanism
involving charge degrees of freedom and indirect nuclear spin/spin interactions
is proposed. We also propose further experiments to test for the existence of
this coupling mechanism.Comment: 4 pages, 4 figures, submitted to PR
Use of group records of feed intake to select for feed efficiency in rabbit
Models for genetic evaluation of feed efficiency (FE) for animals housed in groups when they are either fed ad libitum (F) or on restricted (R) feeding were implemented. Definitions of FE on F included group records of feed intake (¯FI_F) and individual records of growth rate (GF) and metabolic weight (MF). Growth rate (GR) as FE measurement on R was used.
Data corresponded to 5,336 kits from a rabbit sire line, from 1,255 litters in 14 batches and 667 cages. A five-trait mixed model (also with metabolic weight on R, MR) was implemented including, for each trait, the systematic effects of batch, body weight at weaning, parity order and litter size; and the random effects of litter, additive genetic and individual. A Bayesian analysis was performed. Conditional traits such as ¯FI_F |M_F,G_F and G_F |M_F,¯FI_F were obtained from elements of additive genetics ( ( ¯FI_F |M_F,G_F )_g and ( G_F |M_F,¯FI_F )_g ) or phenotypic (( ¯FI_F |M_F,G_F )_p and ( G_F |M_F,¯FI_F )_p ) (co)variance matrices. In the first case, heritabilities were low (0.07 and 0.06 for ( ¯FI_F |M_F,G_F )_g and ( G_F |M_F,¯FI_F )_g, respectively) but null genetic correlation between the conditional and conditioning traits is guaranteed. In the second case, heritabilities were higher (0.22 and 0.16 for ( ¯FI_F |M_F,G_F )_p and ( G_F |M_F,¯FI_F )_p, respectively) but the genetic correlation between ( ¯FI_F |M_F,G_F )_p and G_F was moderate (0.58). Heritability of GR was low (0.08). This trait was negatively correlated with ( G_F |M_F,¯FI_F )_p and ( G_F |M_F,¯FI_F )_gof animals on F, which indicate a different genetic background. The correlation between GR and GF was also low to moderate (0.48) and the additive variance of GF was almost 4 times that of GR, suggesting the presence of a substantial genotype by feeding regimen interaction.info:eu-repo/semantics/acceptedVersio