La génération de solides divisés par fluides supercritiques

Processes using crystallisation from a supercritical medium constitute a new route to obtain finely divided solids. By using the pressure as an operating parameter, these processes allow to obtain fine and monodisperse powders. There exist two types of processes, according to whether supercritical fluid — usually carbon dioxide — is used as a solvent or an anti‐solvent: RESS or SAS. In the first case it is the drop in density due to the brutal decompression of the fluid which is the driving force of nucleation, in the second it is the reciprocal dissolution of an organic solvent in the supercritical fluid. Industrial applications are expected in many sectors, even if it is the pharmaceutical industry which seems best armed to gather a majority of its developments.     

Gedanken zur Qualitätssicherung beim Bau von Chemieanlagen

Thoughts on quality assurance in the construction of chemical plant . To be able to operate a chemical plant free of hazards and breakdowns, a wide variety of measures have to be taken to assure quality during planning, during construction and in operation. These measures are outlined with the aid of an example, namely a large reactor. Particular attention is paid to the individual building phases and the intermediate non-destructive tests. The paper also touches on quality planning, quality assurance in operation and the organization of quality systems. The example is intended to show that, however much quality documentation there may be, it cannot replace the willingness of the people involved to adopt a quality-conscious approach to their work and be responsible for the quality of their own workmanship. Educating the employees to think in terms of quality is an important aspect of quality assurance.     

Radioaktive Indikatormethode in der chemischen Verfahrenstechnik

The radioactive tracer method in the chemical industry. In the chemical industry the radioactive tracer method has become a method of analysis with a variety of applications, which range from determining traces of biologically active substances to process analysis in production plants. Process analysis, for instance the determination of residence-time distributions or of intermingling of streams of different substances, can be carried out under widely varying operating conditions. If the streams of material are labelled with gamma-ray emitters the distribution of the tracers can be determined by means of detectors outside the plant. To demonstrate the possible applications of the method to process analysis, measurements in three different plants are described. Exhaust gases were labelled with Ar-41 to determine the residence-time distribution in plant for the combustion of waste residues consisting of a rotary tube furnace, an afterburn chamber, and a waste-heat boiler. The waste water entering the activation tank of sewage-treatment plant was labelled with Na-24 to determine its residence-time distribution. Individual particles labelled with Mn-56 were used to investigate mixing of the powder in the stirred-bed reactor of a polypropylene plant. The knowledge gained from these measurements has contributed to optimization of existing and planned plant.     

Lecithin-cholesterol acyltransferase: Inhibition by local anesthetics in plasma from man and experimental animals in vitro

Lecithin-cholesterol acyltransferase (LCAT, EC 2.3.1.43) was assayed in vitro in plasma from normal man, rat, rabbit and dog by following the formation of¹⁴C-cholesteryl esters subsequent to labeling the plasma with¹⁴C-cholesterol in vitro. In all species examined, various local anesthetics were found to inhibit LCAT when studied over the concentration range of 1 to 5 mM. The order of inhibition was dibucaine>benzocaine>tetracaine>lidocaine>procaine. Since LCAT activity represents the combined effect of a deacylation step and an esterification step, inhibition of LCAT by local anesthetics could theoretically involve either or both steps.     

Topology Aware Data‐Driven Inverse Kinematics

Creating realistic human movement is a time consuming and labour intensive task. The major difficulty is that the user has to edit individual joints while maintaining an overall realistic and collision free posture. Previous research suggests the use of data‐driven inverse kinematics, such that one can focus on the control of a few joints, while the system automatically composes a natural posture. However, as a common problem of kinematics synthesis, penetration of body parts is difficult to avoid in complex movements. In this paper, we propose a new data‐driven inverse kinematics framework that conserves the topology of the synthesizing postures. Our system monitors and regulates the topology changes using the Gauss Linking Integral (GUI), such that penetration can be efficiently prevented. As a result, complex motions with tight body movements, as well as those involving interaction with external objects, can be simulated with minimal manual intervention. Experimental results show that using our system, the user can create high quality human motion in real‐time by controlling a few joints using a mouse or a multi‐touch screen. The movement generated is both realistic and penetration free. Our system is best applied for interactive motion design in computer animations and games.     

Integrating information systems: case studies on current challenges

Integration of information systems is a prerequisite for efficient collaboration within and between organizations. Despite intensive research on integration issues in Information Systems research, companies nowadays still encounter considerable challenges in integration projects. The question for the reasons still engages researchers and practitioners. The paper at hand investigates current integration problems by deriving a framework for integration problems from literature research and applying it for the analysis of concrete cases from business practice. The examples are described in detail in explorative case studies examining three integration projects from different industries and with different objectives. From the comparison of theoretically derived and practically proven integration problems, the paper identifies integration problems that have been insufficiently addressed so far and discusses open challenges of integration in the Information Systems discipline.     

DBD lamp converter design using an electrical model of the load

This paper presents a design process of the power supply for a dielectric barrier discharge (DBD) lamp; this design is based on an electrical model of DBD lamps. An identification algorithm is used to find the values of the parameters of the model, on the basis of several experimental waveforms. With the identified model, the design phase of the power supply is simplified and improved, thanks to the simulation of the entire system: the converter along with the lamp. This model also helps to correlate the UV radiation with the current which actually flows into the gas: the latter, being a variable which is not directly measurable, is calculated offline.     

Stainless Steels for Exhaust Lines

Exhaust lines of cars have been strongly evolving during the last decade to meet the various requirements of the automotive industry and the new environment regulations. This development tends to favour stainless steel grades to replace cast iron for the exhaust manifold and aluminized low carbon steel for pipes and mufflers. Among the various stainless steel grades, the proportion of ferritic grade increases for the hot part of the exhaust system as its price is lower and more stable than austenitic or refractory grades, and as it exhibits a better resistance to cyclic oxidation. A large and rapid development of stainless ferritic grades has been based on Ti and Nb stabilization. Adding niobium presents many advantages for corrosion resistance, deep‐drawability, and mainly creep resistance at high temperature. The paper is focused on stainless steel with 14 wt% chromium, stabilized with Nb. Intermetallic precipitation is studied after a 100 h holding time at different temperatures (sag tests). It is shown that, depending on the test temperature and on the chemical composition of the steel, Fe₂Nb or Fe₂Nb₃ intermetallic particles can precipitate, which affects the creep resistance: Fe₂Nb₃ being more stable at higher temperature. Some impacts on the alloy design dedicated to exhaust line application are presented as a conclusion of the study.     

Measurements and comparison of saltation and pickup velocities in wind tunnel

This work presents experimental results of the pickup velocity measurements for variety of particulate solids. The experiments were carried out in a horizontal wind tunnel. The influence of three initial arrangements of particle(s) on pickup velocity was investigated. Particle(s) were placed either on the bottom surface of the tunnel or on the horizontal layer of particles or the heaps of particles with various heights were created in the wind tunnel. A high-speed video camera was used to visualize the particle entrainment. However, the pickup velocity was defined in a qualitative manner by extrapolating the carried weight of particles as a function of air velocity. Comparison between the saltation velocity in dilute phase flow and the pickup velocity, both measured in the horizontal wind tunnel, provide an insight and guideline how the minimum operating air velocity in a pneumatic conveying line could be defined and determined.Authors would like to thank Mr. Rhye Hamey and Mr. Milorad Djomlija for their valuable comments and proofreading.