In an attempt to find the most cost effective design of a multipurpose hoisting device that can be easily mounted on and removed from a regular farm vehicle, cost optimisation including both material and manufacturing expenditure, is performed on the main frame supporting the device. The optimisation is constrained by local and global buckling and fatigue conditions. Implementation of Snyman’s gradient-based LFOPC optimisation algorithm to the continuous optimisation problem, results in the economic determination of an unambiguous continuous solution, which is then utilised as the starting point for a neighbourhood search within the discrete set of profiles available, to attain the discrete optimum.
This optimum is further investigated for a different steel grade and for the manufacturing and material cost pertaining to different countries. The effect of variations in the formulation of the objective function for optimisation is also investigated. The results indicate that considerable cost benefits can be obtained by optimisation, that costing in different countries do not necessarily result in the same most cost effective design, and that accurate formulation of the objective function, i.e. realistic mathematical modelling, is of utmost importance in obtaining the intended design optimum. 相似文献
Radiotracer experiments confirm that neutral carrier ion-selective electrodes made from plasticized PVC are low-capacity selective ion-exchangers. The ion-exchange selectivity is closely correlated to potentiometric selectivity. 相似文献
We study the relationship between transfinite diameter, Chebyshev constant and Wiener energy in the abstract linear potential
analytic setting pioneered by Choquet, Fuglede and Ohtsuka. It turns out that, whenever the potential theoretic kernel satisfies
the maximum principle, then all these quantities are equal for all compact sets. For continuous kernels even the converse
statement is true: if the Chebyshev constant of any compact set coincides with its transfinite diameter, the kernel must satisfy
the maximum principle. An abundance of examples is provided to show the sharpness of the results.
Dedicated to the memory of Professor Gustave Choquet (1 March 1915–14 November 2006). 相似文献
During the second half of the 20th century, Molecular Computations have reached to a level that can revolutionize chemistry. The next target will be structural biology, which will be followed soon by Molecular Medicine. The present paper outlines where we are at, in this field, at the end of the 20th century, and in what direction the development may take in the new millennium. In view of the gigantic nature of the problem, it is suggested that a suitably designed cooperative Millennial Mega-project might accelerate our schedule. 相似文献
Bergenia species (Saxifragaceae) are important sources of herbal medicines in Asia, mainly in Russia. Various plant parts are valued for their antibacterial, anti-inflammatory, antioxidant sand adaptogenic effect, and used for the dissolution of kidney and bladder stones. In this study a rapid reversed phase liquid chromatography (RP-HPLC) method has been developed for rapid screening and identifying of the main active components in leaf samples of Bergenia accessions. The main goal of this study was to develop an efficient method for the simultaneous identification and detection of arbutin, bergenin and gallic acid from Bergenia leaf samples, which were extracted with a methanolic solvent mixture [methanol:water = 1:1 (v/v)]. Chromatographic separations were performed on a reversed phase Luna C18(2)-HST HPLC column. This chromatographic system provided increased speed and efficiency for separations, without the need for ultra-high pressures. Reversed phase HPLC coupled with diode array detector method was used for the analysis. The method was validated using ICH guidelines. The level of gallic acid was significantly higher in Bergenia crassifolia samples compared to Bergenia cordifolia. However, the samples of the two Bergenia species did not differ substantially regarding the concentrations of arbutin and bergenin. The novel method proved to be fast and allowed sufficient separation and quantification of arbutin, bergenin and gallic acid, the most important bioactive compounds of Bergenia leaves; thus facilitating rapid screening and quality assessment of Bergenia samples of various botanical and geographical origins.
The activation parameters and optimized structures of the reactants and transition states in the S(N)2 reactions of substituted pyridines and N,N-dimethylanilines with methyl iodide were computed at the DFT level in different solvents. The measured and calculated deltaG/deltaH/deltaS versus sigma plots proved to be linear, and their slopes, the deltadeltaG, deltadeltaH, and deltadeltaS reaction constants, were determined. The least solvent-dependent deltadeltaG reaction constants can be computed with acceptable accuracy. The calculated deltadeltaS data decrease only very slightly with the jointly increasing electron-withdrawing effect of the substituents and tightness of the transition states. The measured deltadeltaS values are influenced mainly by the change of solvation in the reactions, and deltadeltaH is also influenced by the reorganization of the solvent. Consequently, the experimental and calculated deltadeltaS and deltadeltaH reaction constants may deviate considerably from each other. In dipolar aprotic solvents the measured deltadeltaS was less than zero, and in protic solvents it was greater than zero. The ordering of the solvent molecules around the transition state with increasing charge is increased in the former but decreased in the latter media, as compared to the bulk of the solvents. The calculated deltaG(o), deltaH(o), and deltaS(o) parameters of the unsubstituted compounds agree relatively well with the experimental data for reactions of neutral molecules in dipolar aprotic solvents (e.g., XC6H4N(CH3)2 + CH3I). On the other hand, the measured and calculated activation parameters may show considerable deviations for reactions of ions (e.g., XC5H4NCH3+ + I-) and for any reaction in protic solvents. 相似文献
We consider shock measures in a class of conserving stochastic particle systems on ℤ. These shock measures have a product
structure with a step-like density profile and include a second class particle at the shock position. We show for the asymmetric
simple exclusion process, for the exponential bricklayers’ process, and for a generalized zero range process, that under certain
conditions these shocks, and therefore the second class particles, perform a simple random walk. Some previous results, including
random walks of product shock measures and stationary shock measures seen from a second class particle, are direct consequences
of our more general theorem. Multiple shocks can also be handled easily in this framework. Similar shock structure is also
found in a nonconserving model, the branching coalescing random walk, where the role of the second class particle is played
by the rightmost (or leftmost) particle. 相似文献
Journal of Thermal Analysis and Calorimetry - A simple synthetic method was developed to prepare 4[Agpy2ClO4]·[Agpy4]ClO4 in a low-temperature decomposition process of [Agpy4]ClO4. A detailed... 相似文献