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991.
Resistance of 19 mold and 6 yeast species to 15 commercial disinfectants was investigated by using a suspension method in which the fungicidal effect and germination time were determined at 20 degrees C. Disinfectants containing 0.5% dodecyldiethylentriaminacetic acid, 10 g of chloramine-T per 1, 2.0% formaldehyde, 0.1% potassium hydroxide, 3.0% hydrogen peroxide, or 0.3% peracetic acid were ineffective as fungicides. The fungicidal effect of quaternary ammonium compounds and chlorine compounds showed great variability between species and among the six isolates of Penicillium roqueforti var. roqueforti tested. The isolates of P roqueforti var. carneum, P. discolor, Aspergillus versicolor, and Eurotium repens examined were resistant to different quaternary ammonium compounds. Conidia and vegetative cells were killed by alcohols, whereas ascospores were resistant. Resistance of ascospores to 70% ethanol increased with age. Both P. roqueforti var. roqueforti and E. repens showed great variability of resistance within isolates of each species. 相似文献
992.
993.
994.
V. P. Kostov 《Journal of Dynamical and Control Systems》1996,2(1):125-155
In this paper we consider the following problem: For what choice of the (p+1)-tuple of conjugacy classesC 1,…,C p+1 in GL(n,?),p≥2, do there exist irreducible (p+1)-tuples of matricesM j ∈C j such that the productM 1,…,M p+1 equals identity? We present the necessary and sufficient conditions for the existence of such tuples in the case whereM j are unipotent. 相似文献
995.
Forward displacement solutions are presented for a class of spatial parallel manipulators. In particular, considered are manipulators consisting of a platform supported through passive spherical joints by three branches, each branch having three-revolute joints forming its main arm. Solutions are described for arbitrary main-arm layouts and for all possible cases of redundant (nine, eight, and seven sensors) and non-redundant (six sensors) sensing of branch main-arm joint displacements. It is demonstrated that closed-form forward displacement solutions can be found for all cases of redundant sensing. Furthermore, it is shown that a closed-form solution can be obtained for one of the two possible cases of non-redundant sensing of the main-arm joint displacements. The only case of joint displacement sensing not allowing a closed-form forward displacement solution is two joints sensed per branch, a case that can be expressed as a 16th-order polynomial of a single variable. Due to the importance of having efficient and failure-safe solutions for the forward displacement problem, it is suggested that appropriate redundancy in displacement sensing should be an important consideration in the design of parallel manipulation devices. © 1994 John Wiley & Sons, Inc. 相似文献
996.
Neurocomputing strategies in structural design — on analysing weights of feedforward neural networks
The sequel of two papers explores the applicability of selected neurocomputing strategies in the optimization of structural systems. The present paper describes the use of interconnection weights of a multilayer, feedforward neural network to extract information pertinent to a design space modelled by such a network. It is shown that aweights analysis provides a technique to assess the effect of all input quantities on a given output. Such dependencies are expressed in the form of atransition matrix, and their evaluation is reduced to the inspection of elements of a matrix row. Explicit formulae are derived for networks with one and two hidden layers and can easily be generalized to networks with an arbitrary number of hidden layers. In addition to its use as a tool to partition design spaces, the weights analysis may be employed to assist in determining the size of hidden layers and an adequate number of training patterns (input-output pairs). Several numerical examples from the field of structural analysis are provided, and the paper underscores the utility of the present technique in decomposition driven optimal design; such optimization is treated in full in the companion paper. 相似文献
997.
ADS Expert is an integrated system that (a) provides suggestions about suitable optimization algorithms for a particular structural optimization problem, (b) it offers explanations and guide lines, in the form of hypertext, that refer to the optimization strategy, optimizer and one dimensional search method, (c) it produces the required gradients for the objective function and the constraints using symbolic differentiation, (d) establishes a direct linking with ADS routines and (e) it monitors the evolution of the optimization process. The system can be used as an educational tool for structural optimization and as an efficient integrated system for small to medium size optimization problems for which the objective function and the constraints are given in the form of explicit functions of the design variables. The system is a Windows application and runs quite satisfactorily on PCs. 相似文献
998.
Reconstruction of an original continuous curve and the estimation of its parameters from the digitized version of the curve
is a challenging problem, as quantization always causes some loss of information. In this paper, we have developed a scheme
for reconstruction which is applicable to a class of curves having at the most two parameters. The class of curves for which
the scheme works has also been characterized. We have shown that for one-parameter curves the exact domain of values of the
parameter can be obtained. But in the two-parameter case, only the smallest rectangle containing the domain can be realised.
The distinctive feature of our scheme is that it provides a unified approach to solve the reconstruction and the domain-finding
problem for a class of curves. 相似文献
999.
The effect of a weld line on the tensile, tensile impact and environmental stress cracking properties of a number of polyethylene (PE) and polypropylene (PP) samples has been investigated. The observed mechanical behaviour has been correlated to material properties, and also to the weld line morphology. PE samples differed in branching, molar mass (Mw) and molar mass distribution (MWD), whereas the PP samples differed in nucleation. The morphology of the weld line formed in injection moulding was analysed by optical microscopy and transmission electron microscopy. The mechanical strength was studied by tensile, tensile impact and constant tensile stress methods. In polyethylene samples with a high Mw, the weld line area was seen through the skin layer to the shear layer, and even down to the beginning of the core layer. The effect of a high Mw on morphological changes was diminished by a broad MWD. Short chain branching limited the morphological change solely to the skin layer. Both PP samples were morphologically rather homogeneous. The weld line created a V-notch on the surface that acted as a crack initiator in mechanical tests and thus reduced the mechanical strength of the weld line samples. The V-notch mainly hid the effect of the morphology on the mechanical properties. © 1998 Chapman & Hall 相似文献
1000.