A BiCMOS Differential Amplifier and Timing Discriminator for the Receiver of a Laser Radar

A differential BiCMOS amplifier channel with gain control circuitry and a timing discriminator has been designed for a pulsed time-of-flight laser radar. The measured bandwidth of the amplifier channel is 160 MHz and its gain can be controlled with a variable R-2R ladder attenuator in 7 discrete steps from 0.44 to 23. A peak detector, used for gain control, can detect the peak of a single 10 ns pulse, the amplitude of which varies from 50 mV to 3.5 V. The timing discriminator produces accurately timed logic level pulses from noisy analog output pulses of the amplifier channel. The distance measurement result of the designed timing discriminator varies +/– 4 mm with an input amplitude range of 55 mV – 3.3 V. The single shot resolution with SNR = 250 is better than 6 mm. Measurement results suggest that a cm-level distance measurement accuracy can be realized using integrated ASICs.     

On the design of a hierarchical BTC-VQ compression system

In the present paper we study the use of vector quantization in the BTC-VQ image compression system. We propose an inverted order of proceeding in the BTC-VQ algorithm, so that the interaction of coding the bit-plane and the quantization data will be taken into consideration. The quality of the image depends radically on the codebook used in VQ. The use of frequencies in the selection of the initial codebook turns out to be superior to random selection.     

The effect of the impingement air drying on print mottle and other coated paper properties

The objective of this work is to study the influence of effective initial impingement drying (one-sided high intensity air impingement drying) on the quality of blade-coated paper and to compare it with IR (infrared) drying. A specially designed 1.31 m-long impingement air dryer unit was installed 2 m downstream of the coating station of the pilot coater for more efficient paper drying. Different drying strategies using different combinations of three impingement temperatures (300, 450 and 550 °C) and three impingement velocities (25, 40 and 60 m/s) were tested in the impingement dryer unit to determine the influence of drying on paper quality. Drying effects are compared with those obtained with two rows of an electrical IR at same position. The results of the investigation indicate that backtrap (BT) mottle was reduced with increasing drying power of the impingement dryer. The paper quality parameters, gloss and smoothness of the coated samples were better with air-drying than IR drying. The interesting finding of this study is the improvement of mottle with a high drying rate in the consolidation phase for coated WF (wood-free) paper. Drying section configuration with effective impingement drying unit directly after the coating station showed good performance and is proposed as a possible solution for the future dryer designs.     

Successful use of special stainless steels in nitrogen-based fertilizer plants

The modern urea plants are using a stripping process to reduce the energy consumption. The potential, very severe corrosion problems have been mastered by special grades and strict process control. The different grades are reviewed. After more than 20 years operation the results are very satisfying. In ammonia plants, an often forgotten corrosion problem is found in the heat exchangers. After about 3–6 years failures caused by chloride continuing cooling water may appear on carbon steel or low alloyed austenitic stainless steels. Corrosion mechanism is reviewed. Duplex stainless steels has been used with success and the properties are presented. An example of life-cycle cost shows that duplex stainless steel is an inexpensive way to solve chloride related corrosion problems. Condensation and evaporation of nitric acid in heat exchangers in nitric acid plants cause severe corrosion on conventional stainless steel grades. Low impurity in combination with high chromium content has proved to result in stainless steel with improved corrosion resistance.     

Product category description for web-shopping in e-commerce

In this paper, we focus on the web-shopping activity and on ways to improve the quality of the information available to consumers. We describe a tool, called a product space map, for the presentation of information about a product category which can help consumers in making purchasing decisions. Using this tool we first provide a clustering or segmentation of a product line, that is, 27-inch televisions, into price categories such as low end, moderate and high end. Once having this partitioning we then use the idea of linguistic summaries to describe the properties of each category with respect to relevant features. An example of such a summary is “Most TV's in the high price category provide extremely high resolution.” With the aid of such information it becomes much easier for consumers to understand the product line, see what they are getting for their money, and more easily and confidently locate products that are of particular value for the money. Considerable use is made of fuzzy set technology to provide the ability to describe the information in a way, using linguistic expressions, that is particularly consumer friendly. © 2001 John Wiley & Sons, Inc.     

Bringing Knowing-When and Knowing-What Together: Periodically Tuned Categorization and Category-Based Timing Modeled with the Recurrent Oscillatory Self-Organizing Map (ROSOM)

The study addresses the cyclically temporal aspect of sequence recognition, storage and recall using the Recurrent Oscillatory Self-Organizing Map (ROSOM), first introduced by Kaipainen, Papadopoulos and Karhu (1997). The unique solution of the network is that oscillatory States are assigned to network units, corresponding to their `readiness-to-fire'. The ROSOM is a categorizer, a temporal sequence storage system and a periodicity detector designed for use in an ambiguous cyclically repetitive environment. As its external input, the model accepts a multidimensional stream of environment-describing feature configurations with implicit periodicities. The output of the model is one or a few closed cycles abstracted from such a stream, mapped as trajectories on a two-dimensional sheet with an organization reminiscent of multi-dimensional scaling. The model's capabilities are explored with a variety of workbench data.     

Modelling mass transfer in an aerated 0.2 m vessel agitated by Rushton, Phasejet and Combijet impellers

We assembled a set of models that allows investigation of local variables that are difficult to measure, validation of mechanistic physical models, and comparison of different numerical solutions. Population balances (PB) for bubbles were combined with local flow modelling in order to investigate G–L mass transfer in an air–water system. Performance of three different impeller geometries was investigated: Rushton (RT), Phasejet (PJ) and Combijet (CJ). Simulations were compared against experimental mixing intensity, gas hold-up, vessel-averaged volumetric mass transfer rates (k_La), and local bubble size distributions (BSDs).The simulations qualitatively predict k_La's with different impellers at the fully dispersed flow region and gave new insight on how k_La is formed and distributed in the stirred vessels. The used bubble breakage and coalescence models are able to describe both air–water and viscous non-Newtonian G–L mass transfer. Difference between experimental mass transfer rates of the three impellers was within experimental error, even trough the flow patterns, gas distribution, and local BSDs differ considerably. The population balance for bubbles was modelled in two different ways, with multiple size groups (MUSIGs) and with the bubble number density (BND) approach. MUSIG calculations took over twice as much computational time than BND, but there was little difference in the results. The Rushton turbine k_La was described with best accuracy, which is not surprising since most phenomenological models are fitted based on RT experiments. We suggest that these models should be validated over a wider range of vessel geometries and operating conditions.     

Analysis of stirred tanks with two‐zone models

Stirred tank turbulence and fluid flow characteristics are analyzed based on a two‐zone model. Instead of using the zonal model for stirred tank performance prediction as often proposed in the literature, the zoning is used here as a tool for mixing analysis. A systematic zoning approach is proposed, where the tank is divided into two nested regions. By gradually increasing the inner zone volume, continuous curves can be obtained for turbulent energy dissipation distribution and pumping numbers between the zones as functions of the zone sizes. It is shown here that these curves can be used as a powerful tool for visualizing stirred tank performance. They can be used, e.g., in impeller performance comparisons and analysis of mixing characteristics with changing rheology, or to examine various numerical aspects related to stirred tank CFD modeling. © 2009 American Institute of Chemical Engineers AIChE J, 2009