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101.
Harald Nottebohm 《化学,工程师,技术》1983,55(5):346-352
Automation in the chemical industry – scope and limitations . Tempestuous developments in semiconductor technology centering upon the microprocessor open up new possibilities of automation in chemical engineering. The traditional appearance of process control rooms is changing drastically. A few video display units with uniform keyboards suffice to monitor and control an extensive chemical plant. In spite of all technical perfection, automation has its limitations wherever unavoidable irregularities require human intervention. This in turn requires that one is in command of both the process and the function of the automatic mechanism. 相似文献
102.
The N-acylethanolamine phospholipids (NAPE) are precursors for N-acylethanolamines (NAE), including anandamide (20∶4-NAE), which is a ligand for the cannabinoid receptors. Previously, NAPE
were believed to be found only in injured tissue, e.g., after neurodegenerative insults. Neuronal injury may occur in response
to seizure activity. Therefore, we investigated the effect of pentylenetetrazol (PTZ)-induced seizures in PTZ-kindled mice
on the level of NAPE in the brain. Male NMRI mice were kindled with PTZ injections 3 times/wk, thereby developing clonic seizures
in response to PTZ. Mice were killed within 30 min after the clonic seizure on the test day (12th injection) and the brains
were collected. Eight species of NAPE were analyzed as the glycerophospho-N-acylethanolamines by high-performance liquid chromatography-coupled electrospray ionization mass spectrometry. No effect
of the PTZ kindling on the NAPE levels in murine brains was observed. Total NAPE in control mice cortex (n=4) was 16.4±3.0 μmol/g wet weight of which 20∶4-NAPE accounted for 3.6 mol%, and the major species was 16∶0-NAPE, accounting
for 52.1 mol%. Determination of the activity of NAPE-hydrolyzing phospholipase D and of N-acyltransferase in brain membrane preparations from adult and 3-d-old mice revealed an enzyme pattern in the adult mice that
was favorable for NAE accumulation as opposed to NAPE accumulation. Thus, there was no difference in NAPE levels; at present,
however, this does not exclude that NAE may accumulate during seizure. 相似文献
103.
Structural Superplasticity at High Strain Rates of Super Duplex Stainless Steel Fe‐25Cr‐7Ni‐3Mo‐0.3N
The fine‐grained super duplex stainless steel Fe‐25Cr‐7Ni‐3Mo‐0.3N consisting of two phases (δ‐ferrite/austenite) exhibits structural super‐plasticity at higher strain rates of ? ≈ 10?2s?1 in the temperature range between 975 and 1100°C. The equiaxed microstructure with an average grain size of was produced by thermomechanical processing. Maximum strain‐rate‐sensitivity exponents of m ≈ 0.5 and elongations to failure of more than 500% were achieved. From thermal activation analysis an activation energy for superplastic flow of Q = 310 ± 20 kJ/mole was derived. The superplastic behaviour at higher strain rates is quantitatively described by a deformation model where grain or interphase boundary sliding is accommodated by sequential steps of dislocation glide and climb. The high strain‐rate‐sensitivity exponent and the observed dislocation density indicate that dislocation climb in the slightly solid solution strengthened austenite is the rate controlling step for superplastic flow. The deformation mechanism reveals that the investigated super duplex stainless steel exhibits superplastic behaviour that is typical for class II solid solution alloys. 相似文献
104.
105.
Harald Hruschka 《OR Spectrum》2007,29(4):579-595
Clusterwise pricing is characterized by prices of each brand of a category being equal in stores belonging to the same cluster.
Expected sales necessary to compute profits are estimated using coefficients of a multilayer perceptron which performs better
than several parametric models. Store-specific coefficients of sales response models are estimated by a MCMC method. Both
assignment of stores to clusters and prices of each cluster are determined by means of improving hit-and-run, a stochastic
optimization method. The objective function to be optimized includes both profits and adherence to the usual price level at
individual stores. Based on empirical data on sales, prices and marginal costs of a retail chain it is demonstrated that for
a moderate level of risk aversion clusterwise pricing leads to higher expected utility than micromarketing pricing with different
prices of each brand across individual stores. Clusterwise pricing attains a high percentage of the profits generated by micromarketing
pricing and entails lower menu costs than micromarketing pricing.
H. Hruschka thanks two anonymous reviewers for their interest and their detailed helpful comments. 相似文献
106.
Erik Benkler Andreas G. Steffan Harald R. Telle 《Photonics Technology Letters, IEEE》2007,19(5):267-269
We demonstrate a novel synchronization scheme for optical sampling which is based on a nonstandard phase-locked loop (PLL). Phase comparison is performed at a 10-GHz optical time-division-multiplexing (OTDM) base rate, thus avoiding ultrafast detectors and electronics. The employed frequency-offset PLL allows synchronous sampling of OTDM signals (or any other signals with bit rates given by integer multiples of the base rate), which would be impossible using a standard PLL. This provides a higher degree of flexibility for problem-specific sweeping than asynchronous sampling 相似文献
107.
Juan M. Carrillo Miguel A. Montecelo Harald Neubauer Hans Hauer J. Francisco Duque-Carrillo 《Analog Integrated Circuits and Signal Processing》2007,53(2-3):63-69
This paper deals with the implementation of a second-order ΣΔ modulator in 0.18-μm CMOS technology. The analog-to-digital converter structure combines a 1-bit approach along with a high oversampling ratio (OSR). A silicon circuit prototype, including the modulator itself, a current reference, and the clock signals generator, was designed to operate with a 1.8-V supply, fabricated and tested. Measured values of 87 dB and 91 dB were obtained for the signal-to-noise-plus-distortion ratio (SNDR) and the dynamic range (DR), respectively, for a clock frequency of 8 MHz and an OSR of 256. The effective number of bits (ENOB) was above 14. The experimental performance of the ΣΔ modulator maintains a good level over a modulator clock range higher than 16 MHz, featuring an ENOB equal to 13 at 16 MHz. 相似文献
108.
109.
By varying cross-linking intensity, the effect of microbial transglutaminase on acid gels made from casein solution and raw milk was studied. To avoid any impact of heating, N-ethylmaleimide was used for enzyme inactivation after appropriately checking its efficiency. Up to a specific degree of oligomerisation gel stiffness and firmness increased and tan δ, time at gelation onset and syneresis decreased. Above approximately 70% and 25% of cross-linked protein in casein solution and raw milk, respectively, these parameters showed an opposite behaviour, and weak gels with high syneresis were obtained. Substrate differences, such as preferred cross-linking of adjoining κ-caseins on the surface of the micelle enhanced the effect of steric hindrance in raw milk and impaired proper rearrangements upon acidification at a much lower level of oligomerised protein. It is mainly dimeric and trimeric casein that successfully contributed to the enhanced properties of milk protein gels. 相似文献
110.
The refractory lining in steel ladles is exposed to chemical and mechanical loads during the heats. Mechanical loads develop from the thermal expansion of the refractories which is confined either by the steel construction or by regions of different temperature within the refractory material. The aim of this work was the investigation of factors influencing the mechanical durability of refractory steel ladle linings and the clarification of failure mechanisms. Especially irreversible strains at the hot face of the working lining caused by compressive stresses induce an opening of joints at the hot face. The irreversible strains reduce the compressive stresses in circumferential direction and increase the probability of tensile failure. A further effect of the irreversible strains is a reduced stability of the working lining. Of special interest in this context is a possible controlled expansion of bricks to counterbalance the irreversible compressive strains. 相似文献