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91.
C. D. Evans G. R. List Helen A. Moser J. C. Cowan 《Journal of the American Oil Chemists' Society》1973,50(6):218-222
Commercially prepared and packaged soybean and cottonseed salad oils from several different processors were evaluated periodically
during storage for 12 months. Partially hydrogenated and winterized soybean oils, as well as unhydrogenated soybean salad
oils, were stored in bottles and cans at 78 and 100 F. Control samples of all oils were held at 0 F during the entire test.
Some lots in bottles and cans were packaged under nitrogen to improve storage stability. Agreement was good between organoleptic
and oxidative evaluation of aged oils. After 26 weeks of storage at 100 F, the flavor of partially hydrogenated-winterized
oils packaged under nitrogen showed a minimum loss. These same oils did not exhibit much, if any, reduction in their oxidative
stability as indicated by storage peroxide values (active oxygen method). Soybean oil not protected with nitrogen demonstrated
progressive flavor deterioration at 100 F. After 10 weeks of storage, the deterioration became marked and the flavor score
was below 5. From limited observations, bottled oils appear to have a better stability than oils packaged in screw-cap tin
cans. Hydrogenated oils packaged under nitrogen in cans had good oxidative stability, but some lowering of the flavor score
was observed. Nonhydrogenated soybean oils packaged in tin cans not under nitrogen exhibited the most rapid flavor deterioration
of all lots of oil investigated.
Presented in part at the AOCS meeting, New York, October 1968
ARS, USDA 相似文献
92.
The Oxidation of NdFeB Magnets 总被引:10,自引:0,他引:10
The oxidation kinetics in air of a commercial NdFeB magnet have been investigated over the temperature range 335–500°C. The oxide microstructure has been characterized by SEM, XRD and cross-sectional TEM. The results show that the external scale formed consists of an outer layer of Fe2O3 and an inner layer of Fe3O4 but that the principal degradation process is the formation of an extensive zone of internal oxidation. HREM has been used to show that this zone contains NdO particles embedded in an -Fe matrix. These particles are discrete and very small, approximately 2 nm in diameter, and have an amorphous structure. The -Fe matrix has a columnar grain structure with a grain width of approximately 100 nm. It is argued that the high rates of internal oxidation arise because the external-oxide layers are not protective at the oxidation temperature, and oxygen penetrates to the zone front by fast diffusion along the columnar -Fe grain boundaries. 相似文献
93.
On the mechanical performance of closed cell Al alloy foams 总被引:8,自引:0,他引:8
Y. Sugimura J. Meyer M.Y. He H. Bart-Smith J. Grenstedt A.G. Evans 《Acta Materialia》1997,45(12):5245-5259
The mechanical properties of three different commercially available closed cell Al alloys all made by foam casting are examined. The objective is to assess the roles of cell morphology and of imperfections in governing the basic properties: stiffness, yield strength and fracture resistance. This assessment provides goals for manufacturing strategies that enable attainment of good mechanical performance with affordable process technologies. A prevalent role of curves and wiggles in the cell walls on stiffness and strength (anticipated by models) is affirmed by the present measurements. Systematically larger stiffnesses and yield strengths found in tension than in compression are consistent with a prominent role exerted by such imperfections. Moreover, foam casting is apparently capable of cell morphologies that impart properties approaching the best achievable values for an isotropic closed cell solid, devoid of imperfections. There are associated implications for performance and affordability. Fracture measurements indicate crack growth occurring along the cell walls by a mechanism analogous to the plastic tearing of thin sheets. The crack growth resistances are in the range of 1 kJm−2. This mechanism infers a toughness that scales with the cell wall thickness and its yield strength. 相似文献
94.
Eggbeer D Evans P 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2011,225(1):94-99
This case study presents a method of utilizing computer-aided design technologies to provide bespoke, external breast prostheses. The technique is illustrated through a case study of a mastectomy patient. Photogrammetry methods were used to capture the breast form when supported by a brassiere and the unsupported breast and defect side. Computer-aided design techniques were used to generate a digital prosthesis based upon the supported breast shape and with a fitting surface that matched the defect side. Furthermore, a two-part mould was designed and fabricated using rapid prototyping methods. A colour-matched prosthesis was then fabricated in a gel-based, platinum-cured silicone. 相似文献
95.
96.
David Evans, BCS government relations, looks at what it couldtake to convince kids that the hard stuff is worth doing. 相似文献
97.
Model-based 3-D segmentation of multiple sclerosis lesions in magnetic resonance brain images 总被引:2,自引:0,他引:2
Kamber M Shinghal R Collins DL Francis GS Evans AC 《IEEE transactions on medical imaging》1995,14(3):442-453
Human investigators instinctively segment medical images into their anatomical components, drawing upon prior knowledge of anatomy to overcome image artifacts, noise, and lack of tissue contrast. The authors describe: 1) the development and use of a brain tissue probability model for the segmentation of multiple sclerosis (MS) lesions in magnetic resonance (MR) brain images, and 2) an empirical comparison of the performance of statistical and decision tree classifiers, applied to MS lesion segmentation. Based on MR image data obtained from healthy volunteers, the model provides prior probabilities of brain tissue distribution per unit voxel in a standardized 3-D "brain space". In comparison to purely data-driven segmentation, the use of the model to guide the segmentation of MS lesions reduced the volume of false positive lesions by 50-80% 相似文献
98.
S. A. Matar M. J. Edirisinghe J. R. G. Evans E. H. Twizell J. H. Song 《Journal of Materials Science》1995,30(15):3805-3810
A shrinking undegraded core and a porous outer layer result, if the organic vehicle used for shaping ceramic or metal powder mouldings recedes in the interparticle space of the moulded body during pyrolysis. In the present work, a numerical model has been used which simulates the undegraded shrinking core situation and quantifies degradation of the organic vehicle and the diffusion of the resulting products in solution in the organic phase during pyrolysis of a ceramic moulding. This model is extended to include gaseous mass transport in the porous outer layer for a moulding in the shape of an infinite cylinder. The effect of resistance to gaseous mass transport in the porous outer region on defects originating in inner regions was estimated. It is shown that the greatest obstruction to mass transport is diffusion of degradation products in solution in the organic phase. However, the permeability coefficient for gas transport in the outer region begins to affect the critical heating rate required for avoidance of defects only when it is less than 10–15m2.Nomenclature
C
Concentration,C=C (r, t), based on the total volume of ceramic suspension
-
d
Effective molecular diameter of alphamethylstyrene
-
D
Diffusion coefficient,D=D (C, T)
-
e
Porosity of powder
-
E
Activation energy for thermal degradation
-
h
Remaining weight fraction of polymer
- Hvap
Enthalphy of vaporization
-
i
Node number
-
I
Pre-exponential constant in Equation 13
-
j
Time step
-
K
p
Permeability coefficient
-
K
0
Specific rate constant
-
m
Mass of monomer displaced
-
M
Mass of one alphamethylstyrene molecule
-
P
Monomer vapour pressure
-
P
s
Monomer vapour pressure at outer surface of the cylinder
-
P
1
0
Vapour pressure of monomer over its pure liquid
-
Q
Rate of production of monomer, based on the total volume of ceramic suspension
-
r
Radius of the cylinder
-
r
j
Distance from central axis to the inner surface of the porous layer at time stepj
-
r
0
Initial radius of the cylinder
-
R
Universal gas constant
-
S
0
Specific surface area of powder per unit solid volume
-
t
Time
-
T
Absolute temperature
-
T
c
Temperature at maximum vapour pressure of monomer and atZ
c
-
V
Volume of monomer
-
V
c
Ceramic volume fraction
-
V
p
Polymer volume fraction
-
w
Mass of monomer stored in the porous annulus
-
Z
Heating rate
-
Z
c
Critical heating rate
- 1
Volume fraction of monomer in the polymer-monomer solution
-
Viscosity of the monomer vapour
- p
Density of the polymer
-
Polymer-monomer interaction constant 相似文献
99.
Energy Storage: Confined Assembly of Hollow Carbon Spheres in Carbonaceous Nanotube: A Spheres‐in‐Tube Carbon Nanostructure with Hierarchical Porosity for High‐Performance Supercapacitor (Small 19/2018) 下载免费PDF全文
100.
Professor F. T. Evans 《AI & Society》1998,12(3):185-213
Instead of seeing technology as outside ourselves, it is argued that it is an innate human function and the main driving force in human evolution. Opportunistic thing using, long before stone tools appeared, was the likeliest cause of bipedalism. It also forced brain development and the emergence of creativity. The neural basis for this creative technical activity later provided the brain functions on which language could develop. This simple unifying hypothesis has interesting implications for the way that we see technology in history, and for determinist theories of the future. It also bears on the way engineers are trained, and more important, the human faculties which need to be fostered in children. 相似文献