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51.
Texture analysis based on textons is extended by introducing a method for computing textons of arbitrary order. First-, second- and third-order textons are applied to classify screening mammograms as to indicate a low or high risk of breast cancer. First-order textons are found to provide better estimates of breast cancer risk than other orders on their own but the combination of first- and second-order textons outperforms first-order textons alone and other combinations of two orders. Combining all three orders of textons does not improve classification. This example indicates that including higher-order textons has the potential to improve classification performance.  相似文献   
52.
We analysed the length distributions of different types of ß-strandin a high resolution, non-homologous set of 500 protein structures,finding differences in their mean lengths. Antiparallel edgestrands in strand–turn–strand motifs show a preferencefor an even number of residues. This propensity is enhancedif the length is corrected for ß-bulges, which insertan extra residue into the strand. Residues in antiparallel edgeß-strands alternate between being in hydrogen bondedand non-hydrogen bonded rings. Antiparallel edges with an evennumber of residues are more likely to have their final ßresidue in a non-hydrogen bonded ring. This suggests that non-hydrogenbonded rings are intrinsically more stable than hydrogen bondedrings, perhaps because its side chain packing is closer. Therefore,we suggest that a simple way to increase ß-hairpinstability, or the stability of an antiparallel edge strand,is to have a non-hydrogen bonded ring at the end of the strand. Received June 19, 2003; revised October 25, 2003; accepted November 7, 2003  相似文献   
53.
Many Web portals allow users to associate additional information with existing multimedia resources such as images, audio, and video. However, these portals are usually closed systems and user-generated annotations are almost always kept locked up and remain inaccessible to the Web of Data. We believe that an important step to take is the integration of multimedia annotations and the Linked Data principles. We present the current state of the Open Annotation Model, explain our design rationale, and describe how the model can represent user annotations on multimedia Web resources. Applying this model in Web portals and devices, which support user annotations, should allow clients to easily publish and consume, thus exchange annotations on multimedia Web resources via common Web standards.  相似文献   
54.
Model-driven engineering introduces additional challenges for controlling and managing software evolution. Today, tools exist for generating model editors and for managing models with transformation, validation, merging and weaving. There is limited support, however, for model migration—a development activity in which instance models are updated in response to metamodel evolution. In this paper, we propose conservative copy—a style of model transformation that we believe is well-suited to model migration—and Epsilon Flock—a compact model-to-model transformation language tailored for model migration. The proposed structures are evaluated by comparing the conciseness of model migration strategies written in different styles of transformation language, using several examples of evolution taken from UML and the graphical modelling framework.  相似文献   
55.
The structure of traditional, linear phenol–resorcinol–formaldehyde (PRF) resins, urea‐branched PRF resins, and phenol–resorcinol–furfural (PRFuran) resins has been investigated in depth by both matrix‐assisted laser desorption/ionization time of flight (MALDI‐TOF) mass spectroscopy and 13C NMR. The structure of a variety of oligomers has been obtained, and the structures present in each of the three types of resins related to the very different percentages of resorcinol needed for their equal performance as adhesives. The oligomers type and species distribution appeared very different for each case. PRF resins performance is improved by maximizing either the proportion of resorcinol‐containing oligomers or methylol‐groups containing oligomers, even without any resorcinol, or both. It is equally obtained by the minimization of the relative proportion of the low reactivity Phenol (CH2 Phenol) species in which resorcinol is not present, this being the most important parameter. This can be obtained by more effective use of the resorcinol by just modifying the resin manufacturing procedure. This parameter instead does not appear to be determinant in PRFuran resins. In these, it is the higher molecular weight of furfural in relation to formaldehyde that engenders for the same manufacturing procedure a correspondingly lower proportion of resorcinol in the resin. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2665–2674, 2004  相似文献   
56.
Polymer‐ceramic composite coatings manufactured from calcium carbonate and ethylene‐methacrylic acid copolymer (EMAA) were prepared via a thermal spray process employing different CaCO3 filler sizes (average size of 2.8, 9 or 36 μm) and loading levels from about 2.5 to 7 wt%. The optimum filler feeding characteristics, deposition efficiency and deposition rate were obtained with a 36 μm sized CaCO3. Tensile properties, peel strength, and the erosion resistance of a pure EMAA and CaCO3‐EMAA composite coatings were investigated. It was found that the tensile strain at fracture of the composite coating decreased with the addition of filler to a greater degree than that observed in compression‐molded polymer composites. This is attributed to an inhomogenous distribution of the filler, with more being concentrated at the boundaries of the deposited polymer particles, thereby establishing a rigid framework within the coating. Only a small filler content is necessary to establish large changes in the mechanical properties of the coating. The peel strength of a composite coating decreases with filler content, both on a mild steel substrate and a previously sprayed polymer coating. Bonding to the latter is significantly higher and offers a possibility as a bonding layer between substrates and composite coatings. The coefficient of friction is lowered with the addition of a filler. Erosion testing has shown that the erosion resistance of PF111 is little improved overall with filler addition, although some increase is found for filler contents less than 5 vol%. Polym. Eng. Sci. 44:1448–1459, 2004. © 2004 Society of Plastics Engineers.  相似文献   
57.
The oxidative absorption of hydrogen sulfide (H2S) into a solution of ferric chelate of trans-1,2- diaminocyclohexanetetraacetate (CDTA) was studied in a counter-current laboratory column randomly packed with 15 mm plastic Ralu rings. The present investigation takes concern about the Kraft pulping situation where dilute H2S concentrations are omnipresent in large-volume gas effluents. A fractional two-level factorial approach was instigated to determine the significance of six operating variables, namely the solution's alkalinity (pH; 8.5-10.5), the liquid mass flow rate (L;1.73-), the solution's ionic strength (IC;0.01-), the gas mass flow rate (G;0.19-), the inlet H2S concentration (CH2S,0;70-430 ppm) and the initial ferric CDTA concentration (CFe,0;100 -). Initially, a Plackett-Burman design matrix of seven duplicated experiments revealed that pH is the leading factor controlling the H2S conversion rate while the ionic strength and ferric CDTA concentration effects remained negligible within the factorial domain. Surface response analysis based on 11 duplicated factorial experiments plus 10 central composite trials revealed that the H2S conversion significantly increases with liquid flow rate but decreases with growing H2S load up. Further examination about the influence of ferric CDTA on H2S absorption rate was set up over a broader concentration range (CFe,0;0- at pH of 9.5 and 10.5. It showed good potential at as H2S conversion increased by a significant 25% for both pH values in comparison to pure alkaline solutions containing no ferric CDTA.  相似文献   
58.
Safety aspects of charging bulk material into vessels or containers . The safe charging of bulk material requires a careful analysis of the potential sources of danger which can result from the physical properties of the materials and the design and construction material of plant and equipment. The method adopted in this analysis is illustrated and explained for selected examples. Criteria for safe charging methods are compiled and explained. A selection of proven charging equipment is listed and technically evaluated with respect to safety and operating criteria. Steps that must be taken to avoid charging errors are discussed. Special problems encountered on connecting pressureless charging devices to pressure vessels are outlined explained. The utilization of inert gas as a preferred method of explosion protection is discussed. Various methods are compared, and their application to special problems in charging bulk material is illustrated.  相似文献   
59.
Receptance coupling for end mills   总被引:3,自引:0,他引:3  
Identification of chatter free cutting conditions, the chatter stability lobes, requires a measurement of the frequency response function (FRF) of each tool mounted on the spindle. This paper presents a method of assembling known dynamics of the spindle–tool holder with an analytically modeled end mill using the receptance coupling technique. The classical receptance technique is enhanced by proposing a method of identifying the end mill–spindle/tool holder joint dynamics, which include both translational and rotational degrees of freedom. The method requires measurement of FRFs with impact tests applied on the spindle–tool holder assembly and blank calibration cylinders attached to the spindle. The spindle and tool holder characteristics are completely identified from the two experiments, and used for the mathematical prediction of FRF for end mills with arbitrary dimensions. The proposed method is experimentally proven and verified in cutting tests.  相似文献   
60.
The self-assembled monolayers (SAMs) of a series of substituted benzenethiol (BT) molecules, X-C6H4-SH (where X = meta-NH2, ortho-NH2, para-NH2, para-NHCOCH3, para-F, para-CH3 and para-CH(CH3)2), have been prepared by adsorption from a solution onto a fresh copper (Cu) surface pretreated by a nitric acid etch. The corrosion inhibition efficiency of the modified Cu surfaces in a sulfuric acid solution was investigated by electrochemical characterization. The protection afforded by the substituted functional groups on BT is strongly influenced by the type and the position of the substituent on the benzene ring. BT molecules without any substituent group on the ring are ineffective corrosion inhibitors, indicating that the chemical configuration is the key factor in determining the efficacy of the SAMs as barriers to electrochemically corrosive ions. It is further proposed that the steric hindrance offered by the substituted group in the SAMs plays a very important role in determining its barrier properties.  相似文献   
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