bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of computer vision for the prediction of cutting conditions in milling operations
Authors: Gadelmawla E S , Eladawi A E , Abouelatta O B , Elewa I M
Published: March 2009

Machining conditions such as speed, feed, and depth of cut significantly affect tool wear, which in turn affects the surface quality and thus this is an area of research interest. With the growing emphasis on industrial automation in manufacturing, vision techniques play an important role in many applications. One of these applications is texture analysis. Although this technique has been extensively researched it has only infrequently been used to predict the cutting conditions of machined surfaces. This paper introduces an application of computer vision to predict the cutting conditions in milling operations (feed, speed, and depth of cut) using grey-level co-occurrence matrix texture features. A software, named the Cutting Conditions Prediction in Milling has been developed in order to predict the cutting conditions from the captured images of machined surfaces. Three modules were developed to perform the prediction process and they are presented in this paper. The system was verified by predicting cutting conditions for various specimens and the maximum error between the predicted and the actual cutting conditions did not exceed ± 10.6 per cent.
Statistical numerical modelling of sub-surface initiated spalling in bearing contacts
Authors: Raje N , Sadeghi F
Published: March 2009

Sub-surface-initiated spalling, which is the classical mode of failure in rolling element bearings is significantly influenced by the inhomogeneous and stochastic nature of the material microstructure. This microstructural disorder is one of the primary reasons for scatter in fatigue lives for a seemingly identical batch of bearings. In this study, a stochastic fatigue model that takes the material microstructure explicitly into account is used to investigate dispersion in spalling lives for rolling element bearings. Material microstructures are generated stochastically using the process of Voronoi tessellation. Input parameters to the fatigue model are obtained from torsional fatigue tests. Spalling lives are found to follow a three-parameter Weibull distribution more closely compared with the conventionally used two-parameter Weibull distribution. The stress-life results generated using the model are found to correlate well with the Lundberg-Palmgren theory. Based on parametric studies, a new statistical life equation for bearing life is proposed which is similar in structure to the Lundberg-Palmgren equation with a modification term. Parameters in the life equation are functions of torsional fatigue parameters for the material.
Efficient calculation of the inertia terms in floating frame of reference formulations for flexible multibody dynamics
Authors: Lugrís U , Naya M A , Luaces A , Cuadrado J
Published: March 2009

One of the characteristics of floating frame of reference (FFR) formulations for flexible multibody dynamics is the fact that the inertia terms are highly non-linear. At every time-step, both the mass matrix and the velocity-dependent forces vector must be updated, and this can become the most CPU intensive task. This work studies the efficiency of two different methods for performing this operation, when applied to both a formulation in absolute coordinates and another in relative coordinates.

The first method calculates the inertia terms by projecting the finite element (FE) mass matrix into the generalized coordinates, by means of a variable projection matrix. The second one calculates the inertia shape integrals at a preprocessing stage and uses them for obtaining the inertia terms in a more efficient way, at the cost of a more involved implementation. Both methods have been tested when used in combination with either the FFR absolute or relative formulation, by simulating a vehicle with 12 flexible elements. The results show that the performance can be considerably increased by means of the preprocessing method, especially in the case of large FE models, whereas, for small models, the projection method can be more convenient due to its simplicity.
Initiation of ribosome degradation during starvation in Escherichia coli
Authors: Zundel Michael A. , Basturea Georgeta N. , Deutscher Murray P.
Published: March 2009

Ribosomes are known to be degraded under conditions of nutrient limitation. However, the mechanism by which a normally stable ribosome becomes a substrate for the degradation machinery has remained elusive. Here, we present in vitro and in vivo data demonstrating that free ribosome subunits are the actual targets of the degradative enzymes, whereas 70S particles are protected from such degradation. Conditions that increase the formation of subunits both in vitro and in vivo lead to enhanced degradation, while conditions favoring the presence of intact 70S ribosomes prevent or reduce breakdown. Thus, the simple formation of free 50S and 30S subunits is sufficient to serve as the initiation mechanism that allows endoribonuclease cleavage and subsequent ribosome breakdown.
Intravenous Administration of Low Molecular Weight and Unfractionated Heparin Elicits a Rapid Increase in Serum Pregnancy-Associated Plasma Protein A
Authors: Tertti Risto , Wittfooth Saara , Porela Pekka , Airaksinen K E , Metsärinne Kaj , Pettersson Kim
Published: March 2009

Background: Pregnancy-associated plasma protein A (PAPP-A) has been suggested as a useful diagnostic and prognostic marker in acute coronary syndromes. Because low molecular weight heparin (LMWH) and unfractionated heparin (UFH) are commonly used in these cases, we analyzed the effects of intravenous administration of these heparins on serum PAPP-A concentrations.

Methods: Serum concentrations of total and free PAPP-A were analyzed in 14 patients on chronic hemodialysis and in 10 coronary angiography patients. Ten of the dialysis patients received standard LMWH anticoagulation at the start of dialysis, and 4 were treated with a heparin-free method. Two of the patients on heparin-free hemodialysis received a reduced LMWH bolus 2 h after the start of dialysis. All angiography patients received UFH at the start of the procedure, and 1 patient received 2 extra boluses of UFH. Serum PAPP-A concentrations were analyzed before and during the dialysis session and during the coronary angiography examination.

Results: A rapid increase in total PAPP-A (median, 25-fold) was seen in all patients within 5 min of administration for both LMWH and UFH boluses. This response was due to an increase in free PAPP-A in the serum. PAPP-A did not increase significantly in the patients who underwent heparin-free hemodialysis. Repeated heparin boluses induced a new PAPP-A release. In vitro addition of heparins to samples of whole blood did not increase PAPP-A concentrations.

Conclusions: Intravenous administration of heparin induces an intense and rapid increase in free PAPP-A in the serum. We recommend that this effect be considered when PAPP-A is assessed as a biomarker in acute coronary syndromes.
Urinary Excretion of Buprenorphine, Norbuprenorphine, Buprenorphine-Glucuronide, and Norbuprenorphine-Glucuronide in Pregnant Women Receiving Buprenorphine Maintenance Treatment
Authors: Kacinko Sherri L , Jones Hendree E , Johnson Rolley E , Choo Robin E , Concheiro-Guisan Marta , Huestis Marilyn A
Published: March 2009

Background: Buprenorphine (BUP) is under investigation as a medication therapy for opioid-dependent pregnant women. We investigated BUP and metabolite disposition in urine from women maintained on BUP during the second and third trimesters of pregnancy and postpartum.

Methods: We measured BUP, norbuprenorphine (NBUP), buprenorphine glucuronide (BUP-Gluc), and NBUP-Gluc concentrations in 515 urine specimens collected thrice weekly from 9 women during pregnancy and postpartum. Specimens were analyzed using a fully validated liquid chromatography-mass spectrometry method with limits of quantification of 5 μg/L for BUP and BUP-Gluc and 25 μg/L for NBUP and its conjugated metabolite. We examined ratios of metabolites across trimesters and postpartum to identify possible changes in metabolism during pregnancy.

Results: NBUP-Gluc was the primary metabolite identified in urine and exceeded BUP-Gluc concentrations in 99% of specimens. Whereas BUP-Gluc was identified in more specimens than NBUP, NBUP exceeded BUP-Gluc concentrations in 77.9% of specimens that contained both analytes. Among all participants, the mean BUP-Gluc:NBUP-Gluc ratio was significantly higher in the second trimester compared to the third trimester, and there were significant intrasubject differences between trimesters in 71% of participants. In 3 women, the percent daily dose excreted was higher during pregnancy than postpregnancy, consistent with other data indicating increased renal elimination of drugs during pregnancy.

Conclusions: These data are the first to evaluate urinary disposition of BUP and metabolites in a cohort of pregnant women. Variable BUP excretion during pregnancy may indicate metabolic changes requiring dose adjustment during later stages of gestation. .
Removal of Steroid Estrogens from Wastewater Using Granular Activated Carbon: Comparison between Virgin and Reactivated Carbon
Authors: Rowsell Victoria Francesca , Pang Dawn Sok Cheng , Tsafou Foteini , Voulvoulis Nikolaos
Published: March 2009

This research was set up in response to new European legislation to identify cost‐effective treatment for removal of steroid estrogens from effluent. This study aimed to compare estrogen removal of two types of granular activated carbon: virgin (F400) and reactivated (C401) carbon. Rapid, small‐scale column tests were conducted with a total bed volume of 24.9 cm 3 over three columns, and analysis was carried out using high‐performance liquid chromatography. Results demonstrated that C401 performed more efficiently with greater than or equal to 81% estrogen removal in wastewater compared to F400 which produced greater than or equal to 65% estrogen removal. Estrogen removal can be affected by competitive adsorption from natural organic matter present in wastewater. In addition, the physical properties of each carbon had the potential to influence adsorption differently, thus resulting in the observed varied adsorption capability of the two carbons.
Comparison of the Modeling Approach between Membrane Bioreactor and Conventional Activated Sludge Processes
Authors: Jiang Tao , Sin Gürkan , Spanjers Henri , Nopens Ingmar , Kennedy Maria D. , van der Meer Walter , Futselaar Harry , Amy Gary , Vanrolleghem Peter A.
Published: March 2009

Activated sludge models (ASM) have been developed and largely applied in conventional activated sludge (CAS) systems. The applicability of ASM to model membrane bioreactors (MBR) and the differences in modeling approaches have not been studied in detail. A laboratory‐scale MBR was modeled using ASM2d. It was found that the ASM2d model structure can still be used for MBR modeling. There are significant differences related to ASM modeling. First, a lower maximum specific growth rate for MBR nitrifiers was estimated. Independent experiments demonstrated that this might be attributed to the inhibition effect of soluble microbial products (SMP) at elevated concentration. Second, a greater biomass affinity to oxygen and ammonium was found, which was probably related to smaller MBR sludge flocs. Finally, the membrane throughput during membrane backwashing/relaxation can be normalized and the membrane can be modeled as a continuous flow‐through point separator. This simplicity has only a minor effect on ASM simulation results; however, it significantly improved simulation speed.
Offensive and defensive adaptation in distributed multimedia systems
Authors: Tusch Roland , Böszörményi László , Goldschmidt Balázs , Hellwagner Hermann , Schojer Peter
Published: March 2009

Adaptation in multimedia systems is usually restricted to defensive, reactive media adaptation (often called stream-level adaptation). We argue that offensive, proactive, system-level adaptation deserves not less attention. If a distributed multimedia system cares for overall, end-to-end quality of service then it should provide a meaningful combination of both. We introduce an adaptive multimedia server (ADMS) and a supporting middleware which implement offensive adaptation based on a lean, flexible architecture. The measured costs and benefits of the offensive adaptation process are presented. We introduce an intelligent video proxy (QBIX), which implements defensive adaptation. The cost/benefit measurements of QBIX are presented elsewhere [1]. We show the benefits of the integration of QBIX in ADMS. Offensive adaptation is used to find an optimal, user-friendly configuration dynamically for ADMS, and defensive adaptation is added to take usage environment (network and terminal) constraints into account.
The multi-courses tutoring system design
Authors: Simic Goran
Published: March 2009

This paper describes architecture, design, and implementation of Multitutor a Web-based environment for the development the e-learning courses and for the use of them by the students. Multitutor is designed as a Web-classroom client-server system, ontologically founded, and is built using modern intelligent and Web-related technologies. Experience with Multitutor so far shows that both teachers and learners have positive feelings about using them as a support tool for creating and learning different courses. In order to illustrate the design of the system, this paper presents some details of Multitutor architecture.
Composing transformations of compiled Java programs with Jabyce
Authors: Lenglet Romain , Coupaye Thierry , Bruneton Eric
Published: March 2009

This article introduces Jabyce, a software framework for the implementation and composition of transformations of compiled Java programs. Most distinguishing features of Jabyce are 1) its interaction orientation, i.e. it represents elements of transformed programs as interactions (method calls) which generally consumes less memory and CPU time than representing programs as graphs of objects; and 2) its component orientation, i.e. it allows for the design and composition of transformers as software components based on the Fractal component model. This latter point is strongly connected to infra-structural and architectural issues, and software engineering aspects such as composing, scaling, maintaining and evolving transformers. Jabyce is compared with other existing compiled Java programs transformation systems using an extension of a previous well-known categorization of program transformation systems.
FP-outlier: Frequent pattern based outlier detection
Authors: He Zengyou , Xu Xiaofei , Huang Zhexue , Deng Shengchun
Published: March 2009

An outlier in a dataset is an observation or a point that is considerably dissimilar to or inconsistent with the remainder of the data. Detection of such outliers is important for many applications and has recently attracted much attention in the data mining research community. In this paper, we present a new method to detect outliers by discovering frequent patterns (or frequent itemsets) from the data set. The outliers are defined as the data transactions that contain less frequent patterns in their itemsets. We define a measure called FPOF (Frequent Pattern Outlier Factor) to detect the outlier transactions and propose the FindFPOF algorithm to discover outliers. The experimental results have shown that our approach outperformed the existing methods on identifying interesting outliers.
A case study on research assistant system: From knowledge management perspective
Authors: Yang David , Tsai Chun-Yen , Huang Jey
Published: March 2009

The purpose of this study is to develop a web-based Research Assistant System (RAS), a Knowledge Management System by community of practice, to improve the group performance of Research Assistants (RAs). Knowledge management is concerned with effective and efficient access to internal and external knowledge that enable an organization to be informed of its environment. The methodology of this study consists of system analysis/design. This study focuses on the implementation of such a system, a system based on free software-PhpBB that allows people to add special features to meet RAS's requirements. The testing phase in this study was also obtained from RAs' feedbacks. Two contributions of RAS are: (a). With shared memory, the RAS exposes to an interest in how research performance being not merely a function of an individual's achievement, but in a way that tasks and problems are being shared; the organization memory implies an emphasis on how individual insights are combined in a group, and how the structure and dynamics of such group thought processes; (b). The RAS plays as an organizational learning support system that individual problem solving is inspired by how groups of experts can come together and solve problems in a way that the individuals could not do on their own. Finally, the implications of RAS in terms of Knowledge Management are also discussed.
Machine learning models of problem space navigation: The influence of gender
Authors: Stevens Ron , Soller Amy
Published: March 2009

We have developed models of how problem spaces are navigated as male and female secondary school, university, and medical students engage in repetitive complex problem solving. The strategies that students used when solving problem-solving simulations were first classified with self-organizing artificial neural networks resulting in problem solving strategy maps. Next, learning trajectories were developed from sequences of performances by Hidden Markov Modeling that stochastically described students' progress in understanding different domains. Across middle school to medical school there were few gender differences in the proportion of cases solved; however, six of the seven problem sets showed significant gender differences in both the strategies used (ANN classifications) as well as the in the HMM models of progress. These results were extended through a detailed analysis of one problem set. For this high school / university problem set, gender differences were seen in how the problems were encoded consolidated and retrieved. These studies suggest that strategic problem solving differences are common across gender, and would be masked by simply looking at the outcome of the problem solving event.
A structure editor for the program composing assistant
Authors: Suvajdzin Zorica , Hajdukovic Miroslav
Published: March 2009

The Program Composing Assistant is an interactive generic development environment dedicated to programming languages. It provides a structure editor with graphical user interface as a main feature. The structure editor is based on an intuitive approach, and aims to integrate important practical aspects of structure editing.
User profiling for the web
Authors: Grcar Miha , Mladenic Dunja , Grobelnik Marko
Published: March 2009

This paper addresses a problem of personalized information delivery related to the Web, that is based on user profiling. Different approaches to user profiling have been developed. When the user profiling is used for personalization in the context of Web, we can talk about Web personalization. There are three main groups of approaches: content-based filtering collaborative filtering and Web usage mining. We provide an overview of them including recent research results in the area with especial emphases on user profiling in the perspective of Semantic Web applications.
No cure no pay: How to contract for software services
Authors: Gilb Tom
Published: March 2009

Contractual motivation is needed to avoid costly project failures and improve the delivery of stakeholder value. Only if the supplier management is made to feel the pain of project failure will it strive to avoid it. The current culture of rewarding failure, by paying for systems development work regardless of the product delivered, must be altered. Such contractual motivation must be supported by quantitative requirements and evolutionary delivery. Quantitative requirements allow project progress and success to be measured enabling monitoring and testing for contractual compliance Evolutionary delivery (that is, delivering early high value in small increments and using feedback from deliverables to determine future increments) allows early reporting of the ability of systems development to deliver and so enables any required corrective actions. Note: This paper specifically addresses the software problem, but the ideas most likely apply to the wider systems engineering problem to some interesting degree as well .
Developing a new color model for image analysis and processing
Authors: Rasras Rashad , El Emary , Skopin Dmitriy
Published: March 2009

The theoretical outcomes and experimental results of new color model implemented in algorithms and software of image processing are presented in the paper. This model, as it will be shown below, may be used in modern real time video processing applications such as radar tracking and communication systems. The developed model allows carrying out the image process with the least time delays (i.e. it speeding up image processing). The proposed model can be used to solve the problem of true color object identification Experimental results show that the time spent during RGI color model conversion may approximately four times less than the time spent during other similar models. .
A generator of SQL schema specifications
Authors: Aleksic Slavica , Lukovic Ivan , Mogin Pavle , Govedarica Miro
Published: March 2009

IIS*Case is an integrated CASE tool that supports the automation and intelligent support of complex and highly formalized design and programming tasks in the development of an information system. IIS*Case, as a tool from the class of domain oriented design environments, generates relational database schemas in 3rd normal form with all relevant data constraints. SQL Generator is an IIS*Case tool that generates the implementation specification of a database schema according to ANSI SQL:2003 standard. The generator may also produce a database schema specification for Microsoft SQL Server or Oracle DBMSs. The paper describes SQL Generator's traits, considers aspects of its application, and shows its use in the implementation of a complex database constraint using procedural mechanisms of a particular relational DBMS. SQL Generator is implemented in Java and Oracle JDeveloper environment.
Functional approach to the adaptation of languages instead of software systems
Authors: Kollár Ján , Porubän Jaroslav , Václavík Peter , Bandáková Jana , Forgác Michal
Published: March 2009

From the viewpoint of adaptability, we classify software systems as being nonreflexive, introspective and adaptive. Introducing a simple example of LL(1) languages for expressions, we present its nonreflexive and adaptive implementation using Haskell functional language. Multiple metalevel concepts are an essential demand for a systematic language approach, to build up adaptable software systems dynamically, i.e. to evolve them. A feedback reflection loop from data to code through metalevel data is the basic implementation requirement and the proposition for semi-automatic evolution of software systems. In this sense, practical experiment introduced in this paper is related to the base level of language, but it illustrates the ability for extensions primarily in horizontal but also in vertical direction of an adaptive system.
On the application of artificial neural network in analyzing and studying daily loads of Jordan power system plant
Authors: Najim Salam , Al-Omari Zakaria , Said Samir
Published: March 2009

In this paper, we propose a neural network approach to forecast AM/PM Jordan electric power load curves based on several parameters (temperature, date and the status of the day). The proposed method has an advantage of dealing with not only the nonlinear part of load curve but also with rapid temperature change of forecasted day, weekend and special day features. The proposed neural network is used to modify the load curve of a similar day by using the previous information. The suitability of the proposed approach is illustrated through an application to actual load data of Electric Power Company in Jordan. The results show an acceptable prediction for Short-Term Electrical Load Forecasting (STELF), with maximum regression factor 90%.
From Lisp S-expressions to Java source code
Authors: Leitão António
Published: March 2009

The syntax of Lisp languages is based on S-expressions, an extremely simple form of structured data representation that is nevertheless fundamental to the development of Lisp syntactic extensions. By adopting a more conventional syntax, the Java language placed itself in a difficult position in regard to user-defined syntax extensions. In spite of the many efforts to provide mechanisms for such extensions, they continue to be more difficult to use than S-expression- based ones. In this paper, we will describe the use of the S-expression syntax in a Java code generation environment. By providing an S-expression based program representation for Java source code, we are able to reuse and extend Lisp macro-expansion techniques to significantly simplify the construction of Java programs. .
Anion/Cation Layers at Electrified Interfaces: A Comprehensive STM, XRD and XPS Case Study
Authors: Pham Duc T. , Keller Hubert , Breuer Stephan , Huemann Sascha , Hai Nguyen T.N. , Zoerlein Caroline , Wandelt Klaus , Broekmann Peter
Published: March 2009

Charged organic adsorbates play an important role in a number of electrochemical reactions, e.g. as additives for metal plating relevant for device fabrication in the semiconductor industry. Fundamental investigations are mandatory in order to acquire profound knowledge of the
structural and electronic properties of these layers parallel and perpendicular to the surface, and to finally achieve a deeper mechanistic understanding of the kinetics of involved charge transfer reactions taking place at these complex metal/organic/electrolyte interfaces. A key structural
motif of these interfaces consists in 'paired' (inorganic)anion/(organic)cation layers that can have an enormous stability even during an ongoing charge transfer reaction. In this contribution we present and discuss a selected case study on the co-adsorption of halide anions and cationic
organic molecules that exhibit a pronounced redox activity. It will be demonstrated that their phase behavior at the interface crucially depends on both their particular redox-state and the surface concentration of the halide counter ions. The subtle balance between adsorbate–adsorbate
and adsorbate–substrate interaction of the poly-cationic organic layer can be carefully controlled by potential dependent anion adsorption and desorption processes through the organic layer. This process can be followed by in situ high-resolution scanning tunnelling microscopy,
while additional information about the structural and chemical state of the respective phase is obtained from in situ X-ray diffraction and ex situ photoelectron spectroscopy.
Cyclization of Cyclopropyl Carbonyls and the Homo-Nazarov Reaction
Authors: De Simone Filippo , Waser Jérôme
Published: March 2009

Ring strain confers exceptional reactivity to the cyclopropane ring. Nevertheless, activation of the cyclopropane ring is usually needed to allow ring-opening reactions under mild conditions. The introduction of one or several carbonyl functionalities on cyclopropanes is often used
to enhance their electrophilic reactivity. When a donor group is also present at the vicinal position to the carbonyl, more reactive donor–acceptor systems are obtained, which are ideally suited for homo-conjugate addition or cycloaddition reactions. This short review focuses on the
special case of intramolecular cyclization reactions. Particular emphasis is devoted to the cyclization of vinyl- and aryl-cyclopropyl ketones for the formation of six-membered rings. This process corresponds to a formal homo-Nazarov cyclization and has been only used rarely in the past. Recently,
the scope of the reaction was greatly expanded by the use of a silyl group as cation-stabilizing group and by the first catalytic method for the synthesis of vinyl-cyclopropyl ketones. With these new developments, the basis is now set for the application of this special class of cationic cyclizations
to the synthesis of more complex synthetic and natural products.
Exploiting Fluorescent Reporter Molecules for Process Analytical Technology (PAT)
Authors: Broger Tobias , Odermatt Res P. , Ledergerber Pablo , Sonnleitner Bernhard
Published: March 2009

Process Analytical Technology (PAT) launched by the U.S. Food and Drug Administration (FDA) aims to ensure the quality of pharmaceutical products. One important tool to obtain a deeper process understanding is the use of modern real-time process sensors and analyzers. In this context
an industrially accepted optical probe for turbidity measurement (Aquasant probe) has been adapted for on-line and real-time fluorescence measurement in (bio-)reactors. By tagging product proteins with fluorescent reporter molecules (e.g. GFP) it was possible to quantify product concentrations
during a fermentation process with the new probe. The on-line obtained signal showed a high correlation to the off-line signal. This new method has remarkable advantages compared to classical off-line product lab analyses and can serve as a platform-independent quantification method of products
to be used in either up- or downstream processing.
Basic equations of mass transfer through biocatalytic membrane layer
Authors: Nagy Endre
Published: March 2009

The diffusive and convective mass transport through biocatalytic membrane layer (membrane bioreactor), without and with biochemical reactions, have been investigated. Similarly to the two‐film theory for gas‐liquid system with diffusive mass transport, only, mass transfer rates have been developed for the biocatalytic membrane layer and for the concentration boundary layer on the feed side of the membrane. Overall mass transfer coefficient has also been defined involving the two‐layer, simultaneous mass transfer, namely the mass transfer through the concentration boundary layer and biocatalytic membrane layer. The effect of the convective velocity (Pe number) and the biochemical reaction rate, namely first‐order and zero‐order reactions as limiting cases of the Monod kinetics, are demonstrated on the mass transfer coefficients accompanied by chemical reaction and on the concentration profiles. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Möglichkeiten zur Energierückgewinnung aus Wasserstoff bei der Chlor‐Alkali‐Elektrolyse
Authors: Moussallem I. , Pinnow S. , Turek T.
Published: March 2009

Wasserstoff entsteht als Koppelprodukt bei der Chlor‐Alkali‐Elektrolyse und wird, sofern eine Verwendung für chemische Synthesen nicht möglich ist, in der Regel thermisch durch Verbrennung in Feuerungsanlagen genutzt. Im vorliegenden Beitrag werden alternative Möglichkeiten zur Energierückgewinnung aus Wasserstoff energetisch und wirtschaftlich bewertet. Dabei zeigt sich, dass die Vermeidung der Entstehung von Wasserstoff mit Hilfe von so genannten Sauerstoffverzehrkathoden energetisch und wirtschaftlich vorteilhaft ist. Dies gilt insbesondere bei zukünftig weiter steigenden Strompreisen. Demgegenüber ist die Verstromung von Wasserstoff in Brennstoffzellen wegen des geringeren Wirkungsgrads erst dann ähnlich attraktiv, wenn sich die Kosten für Brennstoffzellen‐Systeme im Zuge einer zukünftigen Massenfertigung signifikant verringern lassen.
Mixing between a round jet and a transverse turbulent pipe flow
Authors: Rathgeber D. E. , Becker H. A.
Published: March 2009

A light‐scatter technique, marker nephelometry, was used to obtain air‐in‐air mixing data on the system resulting from the injection, at right angles through a port in the wall, of a round subsonic jet into a fully developed turbulent pipe flow. Though the pipe Reynolds number was also varied, the important input variables were the port to pipe mean speed ratio of the input streams (2.5–12.5), and the port to pipe diameter ratio (0.020–0.058). Jet trajectories were measured and the associated mixing field was characterized in terms of both the jet source fluid mean concentration and concentration fluctuations. The process was also studied as to concentration fluctuation spectral density, integral scale, and intermittency.
Redox kinetics of benzene oxidation to maleic anhydride
Authors: Cordova Victor Rangel , Gau Georges
Published: March 2009

Steady state kinetics of the oxidation reaction have been determined with the help of a gradientless semi‐differential, fixed‐bed reactor. The Mars and van Krevelen phenomenological model satisfactorily correlates the experimental data but a modification of the Langmuir‐Hinshelwood model taking into account partial coverage of the catalyst surface with reaction intermediates is preferred.

Transient kinetics have been studied with a new automated periodic‐pulse reactor, directly connected to a gas chromatograph. The response of a catalyst (essentially V2O5–MoO3) to reduction and oxidation has been investigated. The rate of bulk (lattice) oxygen utilization as well as the degree of carbon coverage are estimated by this technique. Selectivity is dependent on the oxidation state of the catalyst: high partial pressure of either benzene or oxyen and high temperatures are detrimental to selectivity.
Pressure distribution in spout‐fluid bed reactors
Authors: Heil C. , Tels M.
Published: March 2009

The occurrence of several flow regimes in spout‐fluid beds was investigated. Four different flow regimes, viz. a packed bed flow regime, a bubbling and a fluctuating spouted bed flow regime and a stable spouted bed flow regime, were found to exist. Pressure distributions in a spout‐fluid bed were measured in several of these flow regimes by means of a moveable pressure probe. A theoretical model that describes the flow pattern in spout‐fluid beds was developed from fundamental relationships that govern the flow of gases through porous media. Pressure distributions calculated from this model agree fairly well with measured values.
Spouting with a porous draft‐tube
Authors: Claflin J. K. , Fane A. G.
Published: March 2009

Particle motion and gas distribution have been measured in 0.3 m spouted beds with porous and solid wall draft‐tubes. Particle velocity in the annulus varied with gas rate and bed geometry. Narrow particle residence time distributions were observed under all conditions. Annular gas flow with the porous tubes exhibited a characteristic maximum in the lower part of the bed. A computer model has successfully simulated this phenomenon. The porous tube had a higher annular airflow than the solid tube at low separation distances, and a lower pressure drop for a given annular flow. A composite porous and solid wall tube offers improved performance.
Gas jets in fluidized beds and spouts: A comparison of experimental behavior and models
Authors: Filla M. , Massimilla L. , Vaccaro S.
Published: March 2009

Experimental data reviewed include pressure profiles, gas and solids axial and radial velocity profiles, and solids concentration in the jet and spout. Similarities and differences from experimental evidence available for spouts in spouted beds and jets in fluidized beds are discussed. Modelling procedures are compared.
Visual observations of spouted bed gas combustion modes and their flow regimes
Authors: Khoe G. K. , Weve D.
Published: March 2009

A study of a spouted bed combustion through direct visual observation in a half cylindrical bed (9 cm ID x 50 cm height, flat based) is reported. The different combustion modes are described as a function of the massflow of the gas mixture entering the bed and of the ratio of air to combustible. These combustion modes have been analyzed and documented with the aid of colour cinematography and photography. Bed temperatures have also been registered. Various bed heights of sand and different sizes of the orifice have been used.
Hydrodynamics and mass transfer characteristics of co‐current downflow packed tube columns
Authors: Patil V. K. , Sharma M. M.
Published: March 2009

Hydrodynamics and effective interfacial area in a 25 mm i.d. packed tube column were studied over a wide range of operating conditions for demister pad packings (DPP). Flow maps have been prepared. Values of effective interfacial area as high as 1880 m−1 in the spray flow regime were obtained. Data on pressure drop and effective interfacial area have been correlated for different flow regimes. Values of liquid side volumetric mass transfer coefficient, kL a, were measured by absorption and desorption of oxygen in different packed tube columns containing Pall rings (standard and low height to dia. ratio), multifilament wire gauge packings (MFWGP) and DPP. kL a was found to vary from 0.017 to 0.34 s−1 for DPP.

Values of wall side solid‐liquid mass transfer coefficient, kSL, were obtained in a 25 mm i.d. copper tube column packed with MFWGP by the dissolution of copper in acidic dichromate solutions. Values of wall side heat transfer coefficient could be obtained by analogy.
Mass transfer characteristics of low H/D bubble columns
Authors: Gopal J. S. , Sharma M. M.
Published: March 2009

The mass transfer characteristics of 0.2, 0.6 and 1.0 m diameter bubble columns having a low height to diameter ratio (0.6 < H/D < 4) and operated at low superficial gas velocities (0.01 < VG < 0.08 m/s) were investigated. Different types of spargers were used to study their effect on the column performance.

The values of effective interfacial area, a, and volumetric mass transfer coefficient, kLa, were measured by using chemical methods. The values of a and kLa were found to vary from 40 to 420 m2/m3 of clear liquid volume and from 0.01 to 0.16 s−1, respectively, in the range of VG, and VL covered in this investigation. The value of the liquid‐side mass transfer coefficient, kL, was found to vary from 3 × 10−4 to 7 × 104 m/s. The effect of the physical properties of the system on the values of a was also investigated. The height to diameter ratio and the column diameter did not have significant effect on the values of gas holdup, a and kLa. It was found that the sparger design is not of critical importance, provided multipoint/multiorifice gas spargers are used.

The comparative performance of bubble columns having low H/D with horizontal sparged contactors and tall bubble columns has been considered.
A method for determining the settling behavior of dense suspensions
Authors: Al Taweel A. M. , Farag H. A. , Fadaly O. , Mackay G. D. M.
Published: March 2009

An accelerated method for evaluating the compaction behavior of dense suspensions is presented, in which centrifugal force is used to enhance settling rates and a highly‐compensated compound pendulum is used to detect the resultant small shifts in centre of gravity.

The results obtained by following the temporal variation in suspension characteristics indicate that a Richardson and Zaki type of equation can describe the subsidence of very concentrated suspensions. The exponent n, and the ultimate sediment compaction density were found to be strongly influenced by small changes in the physicochemical characteristics of the suspended solids.
The effect of air distribution on the induced air flotation of fine oil in water emulsions
Authors: Van Ham Niel J. M. , Behie Leo A. , Svrcek William Y.
Published: March 2009

The induced air flotation (IAF) of a highly stabilized oil in water (o/w) emulsion has been studied experimentally in a batch column 10 cm in diameter and 150 cm in height. Column performance was strongly affected by the method of air distribution. The main variables investigated were the type of air distributor (either porous plate, single hole plate, or multi‐hole plate), initial oil concentraton (30‐600 mg/L), oil drop size distribution of feed (1.0‐30 μm), surfactant type, and gas superficial velocity. Results were successfully analyzed in terms of a first order kinetic rate model which yielded a removal rate constant (K1) that varied from 2.0 to 60.0 h−1. Corresponding total organic carbon (TOC) removal efficiencies went from 20 to 99.9 percent, illustrating the wide performance range for the flotation cell.
Low temperature oxidation of athabasca bitumen
Authors: Babu D. Ram , Cormack Donald E.
Published: March 2009

The kinetics of low temperature oxidation in the Athabasca oil sands were investigated over the temperature range 373 K to 459 K. Oxidation experiments, in which the sand‐free bitumen was vigorously stirred to obtain a homogeneous oxygen concentration throughout the bitumen, were carried out. It was concluded that the oxidation reaction is governed by three different kinetic expressions depending on temperature and past oxidation history. These are: (i) a high rate first order regime which is obeyed at low extents of oxidation and at temperatures below approximately 423 K; (ii) a second order regime, obeyed at low extents of oxidation and at temperatures greater than 423 K; and (iii) a low rate first order regime, obeyed for extents of oxidation greater than 1.7 moles O2/kg bitumen over the entire temperature range investigated.

The partial molar enthalpy of low temperature oxidation was also evaluated, and was found to be constant over the range of oxidation extents studied.
Model experiments on sliding friction for application in hydraulic conveying of solids
Authors: Briscoe B. J. , Radwan H. , Streat M.
Published: March 2009

This paper describes a preliminary experimental study of the sliding friction of sand‐water mixtures when continuously propelled over glass surfaces by a potential energy gradient. The particle contact density at the glass wall and the work dissipated are estimated. These experiments are compared with the process of hydraulic conveying of sand‐water mixtures under a hydraulic gradient. It is argued that there is a unique correlation between the surface particle density and the frictional work irrespective of the nature of the driving force. This argument allows a realistic estimate of the frictional work in hydraulic conveying to be made from the measurement of surface particle velocity during flow. In an example cited, the dynamic coefficient of sliding fraction for a particular case of sand‐water flow is found to be a function of mean velocity and decreases from about 0.65 to 0.22 for velocities of 0.47 and 1.07 m/s respectively.
The effect of moisture on the rheology of brown coal‐oil suspensions
Authors: Low G. S. , Bhattacharya S. N.
Published: March 2009

The rheological properties of brown coal‐oil suspensions were investigated using both a Contraves rheometer and a Weissenberg rheogoniometer. The aging characteristic of the suspensions was found to be due to the moisture in the coal and the presence of large numbers of micropores. Moisture in the suspension caused aggregation of coal particles and diffusion of oil in the pores was responsible for the reduction in the volume fraction of free carrier oil. Both the yield stress and apparent viscosity were found to increase sharply if the coal contained more than 10 wt% moisture. Photomicrographs were also used to identify the cause of aggregation in brown coal‐oil suspensions.
Oxygen enrichment in rotary lime kilns
Authors: Watkinson A. P. , Brimacombe J. K.
Published: March 2009

The operation of a pilot‐scale rotary lime kiln, fired with natural gas, was studied to determine the effects of enriching the combustion air with oxygen. The variables of interest were the temperature, calcination and heat flow patterns within the kiln as functions of the fuel rate, oxgyen concentration and limestone feed rate. All tests were conducted with essentially a stoichiometric fuel/oxygen ratio and employed two different limestones. Data are presented to show the increase in kiln throughput that can be achieved using oxygen enrichment. The results are interpreted using detailed measurements of axial solids, gas and wall temperatures and axial calcination profiles. These permit the evaluation of the driving forces for the various heat exchange processes, and of local heat flow to the solids bed.
Optimal control of a continuous two valves in series letdown flow system
Authors: Oǧuztöreli M. Namik , Özüm Baki
Published: March 2009

In the present work, the dynamics of two interacting valves‐in‐series letdown flow system subjected to the optimal control of the liquid levels in two vessels and of simultaneous distribution of the total pressure drop amongst the valves has been studied. The controllers of the process (the valve constants) have been obtained as functions of the input and output liquid volumetric flow rates and process characteristics, assuming no time‐lags in the measurement of the state variables and of the controllers' actions.
Penetration theory solution for gas absorption and chemical reaction in cocurrent and countercurrent flow wetted‐wall columns
Authors: Datta Ravindra , Rinker Robert G.
Published: March 2009

Penetration theory solutions are provided for gas absorption with or without a (pseudo) first‐order irreversible chemical reaction in cocurrent and countercurrent flow wetted‐wall columns, taking into account a constant gas‐film resistance as well as the axial decrease in gas composition due to absorption, while assuming non‐rippling laminar flow for the liquid phase and plug flow for the gas phase. Limiting solutions are also obtained for situations when either the gas phase resistance or the axial variation of gas composition is negligible. The results are suitable for ϕ ≥ 3 and can be used for both Newtonian and non‐Newtonian liquids.
Measurement, correlation and prediction of binary vapor‐liquid equilibria for alcohol‐tetrachloroethene systems
Authors: Venkateswara Rao K. , Ravi Prasad A.
Published: March 2009

Experimental isobaric vapor‐liquid equilibria of binary mixtures of tetrachloroethene with ethanol, 2‐propanol, 2‐butanol and 2‐pentanol have been measured at 101.08 kPa. The UNIFAC (Fredenslund et al., 1975), a group contribution model and the activity coefficient models of Margules and Van Laar (as presented by Carlson and Colburn, 1942), Wilson (1964), NRTL (Renon and Prausnitz, 1968) and UNIQUAC (Abrams and Prausnitz, 1975) have been used to predict the vapor composition from measured T‐x data of ten binary mixtures of alcohol‐tetrachloroethene including these four systems. The average absolute deviation between the experimental and the predicted vapor composition with the UNIFAC model ranges from 0.006 to 0.023 mole fraction and that with the activity coefficient models ranges from 0.003 to 0.038. The maximum deviation in both the cases occurred in the data of 1‐propanol (Venkateswara Rao et al., 1980).
Particle—gas dispersion effects in a round jet
Authors: Subramanian Viswanath , Ganesh Raman
Published: March 2009

The fully developed region for a two‐phase jet exhibits similarity for velocity and concentration. A power law expression approximates the velocity distribution and the square root of this profile coincides with the concentration distribution. Measurements show that particle dispersion decreases with increase in particle concentration and the gas mixing rate is lower than the particle mixing rate. The turbulent Schmidt Number remains constant at a value equal to 0.47.
Sectionalised bubble column: Gas hold‐up and wall side solid—Liquid mass transfer coefficient
Authors: Patil V. K. , Joshi J. B. , Sharma M. M.
Published: March 2009

The effect of gas sparger type, clear liquid height, liquid viscosity and addition of electrolyte on fractional gas hold‐up in a 0.38 m i.d. sectionalised bubble column (SBC) was studied for superficial gas velocities ranging from 0.03 to 0.15 m s−1. A study of the wall side solid–liquid mass transfer coefficient, kSL, has been made by considering the dissolution of copper in acidic dichromate solutions. The variation of kSL with axial distance in a section for different gas velocities has been explained. A comparison between the performance of sectionalised bubble columns and conventional bubble columns has been presented. In some cases, the SBC may prove to be superior to bubble columns in practice.