Computational Fluid Dynamics Study of Flow Induced by a Grooved High‐Shear Impeller in an Unbaffled Tank

A detailed hydrodynamic characterization in the transitional flow regime of two variants of the Norstone Polyblade® high‐shear impeller (HSI), of industrial relevance, is presented. The study was carried out on a simulated Newtonian fluid using computational fluid dynamics (CFD). Measurements of power number were carried out to validate the simulation results. Hydrodynamic parameters considered of key importance in powder dispersion processes (i.e., viscous dissipation and effective circulation) were used to assess the impellers' performance. Furthermore, their performances were compared with reported data for two ring‐style HSIs of two and four rings, and power number measurements of a sawtooth (Cowles‐type) impeller.     

Die Entwicklung der Chemie in Peru von den Anfängen bis zur Gegenwart

The evolution of chemistry in Peru begins in the high stages of civilizacion of the preincaic epoche. They is described for the incaic time by the chronicler Garcilaso de la Vega. After conquest of the country through Spanish colonizers follow the evolution of the chemistry under Spanish influence. She refers especially to applications in metallurgy and pharmacy. Additional impulses give the foundations of universities. Expedition travels of European scientists into the new continent increase the importance of chemistry in Peru. The south American natural world is made known in Europe simultaneously. In the 18/19th century influenced positively Jose Hipolito Unanue y Pavon, Mariano Eduardo de Rivera y Ustariz and Antonio Raimondi de Acqua the chemistry and mineralogy in Peru. Into the 20th century, the Sociedad Química del Perú together with the Departments of Chemistry of the universities have a coordinating and acting role. A first overall view of the history of chemistry in Peru was published by the Peruvian chemist Juan de Dios Guevara in 1993. The survey is completed by an analisis of fields of research, the chemistry training in the universities and considerations for chemical industry in Peru.     

The Friction-Reducing, Antiwear and Antioxidation Properties of an Organo-Molybdenum Lube Additive without Sulfur and Phosphorus

The engine oil specifications of ILSAC GF - 4 （ implemented 2004 ） and GF - 5 （ expected 2010 ） have in common three important OEM needs： （1） improved fuel economy and its retention, （2） emissions system compatibility （related to phosphorus and sulfur content）, and （3） improved oil robustness for extended oil life capability （e. g., reduced high temperature deposits and engine sludge, improved oxidative stability, and better valve train wear protec- tion）. For emission systems compatibility, there is a trend towards lower phosphorus and sulfur content in engine oils while maintaining high anti - oxidation and anti - wear performances. In this paper, the friction - reducing, antiwear and antioxidant properties of a sulfurfree and phosphorusfree molybdate ester compound as lubricant additive are discussed. The investigation showed that the molybdate ester enables good frictionreducing ability of the lubricant, and maintains low friction coefficients even after period of severe oil oxidation, which indicates the potential for excellent fuel economy retention in passenger car vehicles. For other organomolybdenum additives, the investigation showed their frictionreducing ability decreased greatly after oxidation of the oil, although the performance appeared to be very good with the fresh oil before aging. In addition, the molybdate ester demonstrated a synergistic effect in anti - wear protection with zinc dialkyl dithiophosphate （ZDDP）, a well- known commonly used additive in engine oils; this suggests that excellent wear protection is possible for an engine oil with reduced sulfur and phosphorus content. Moreover, the molybdate ester is also a strong synergist with arylamine antioxidants, which can retard its depletion in oxidized oil, extend its oxidative induction time, and reduce its high temperature deposit - forming tendency. Thus, this type of sulfur - free and phosphorus - free organo- molybdenum lubricant additive truly provides multifunctional performances, reducing friction, wear, and oxidation of an engine oil when combined with other suitable additives. Due to its phosphorus - free, sulfur- free and multifunctional properties, the molybdate ester compound can be extremely useful in formulat- ing modem engine oils with low phosphorus and sulfur content.     

Extending internal curing to concrete mixtures with W/C higher than 0.42

Internal curing (IC) is an effective method for improving performance of low W/C – low permeability concretes because they require additional water to hydrate the cementitious materials. Conventional concretes, on the other hand, contain enough water to hydrate the cementitious materials, but are frequently not properly cured, allowing drying and compromising strength gain and durability. The aim of this investigation is to assess the effect of IC as a complement to traditional curing in relatively high W/C concretes (W/C above 0.42) under drying conditions. Degree of hydration, compressive strength, and permeability were measured in concretes with IC and without IC. Results show that even under drying conditions, mixtures with IC exhibit 16% higher hydration, 19% higher compressive strength, and 30% lower permeability than their counterparts with no IC. This suggests that IC can be very useful for improving performance in concrete mixtures with relatively high W/C under poor curing conditions.     

Comparing different methods of analysing sewage sludge, dewatered sewage sludge and sewage sludge ash

The following article compares different ways of characterising sewage sludge. Against the background of sludge recycling in agriculture as well as treatment with subsequent phosphorus recovery in mind, the article starts by collating and evaluating the levels of phosphorus, heavy metals, chlorine and sulphur in sludge as reported in the literature. Sewage sludge from the sewage treatment plant at Kaditz in Dresden was analysed using standardised and adjusted methods, which produced different results. In the course of this analysis the results were produced by using elemental analysis, atomic absorption spectroscopy, X-ray fluorescence spectroscopy (X-RFA) and ion chromatography (IC). The second part of the article therefore seeks reasons for the differences in the findings and tries to give solution statements. The article closes by calculating transfer coefficients for selected parameters during the incineration process and solid-liquid separation and weighing up the analysis techniques compared. Basically this article will show significant differences in sludge composition and the effects on the specific elements by ashing or mechanical dewatering of the different sludges. An essential attention obtains the analysis by using the X-RFA.     

Numerical simulation of free surface flows on a fish bypass

A computational fluid dynamics (CFD) model is developed to better understand the complex flow field inside a free surface fish bypass constructed at Rocky Reach Dam. This facility consists of two identical parallel channels, with fish screens on the side walls of each channel, and a pump station recirculating 96% of incoming flows into the forebay. The model is based on the Reynolds-averaged Navier-Stokes (RANS) equations, with a standard κ-ε turbulence model. The volume of fluid (VOF) method is used to predict free surface elevations. A proportional controller is implemented in the model to achieve a target flow rate at the pump exits. The pressure drop in the fish screens is modeled using porous media. Quantitative validation and visualization of the flow field characteristics indicate that CFD modeling may be a useful tool for fish passage design.     

Simulation model for extended double-ended queueing

The purpose of this paper is to extend traditional double-ended queuing models using a simulation approach. Traditional double-ended queuing models assume that one supply queue should satisfy one demand queue through instantaneous pairing. Inter-arrival time is assumed to follow an exponential distribution, with arrivals to the system assumed to occur just one at a time. However, this assumption is frequently violated in many real-world situations. The pairing or batch size can either be multiple or a random variable, and the pairing processing time can be greater than 0. Inter-arrival time may follow distributions other than exponential. In some cases bulk arrivals may come at the same time, and pairing is not always guaranteed. Because the analytical approach has enormous difficulties obtaining performance measures under these relaxed situations, a simulation approach for extended double-ended queueing processes is presented. This includes an algorithm to find state probabilities and a newly developed simulation procedure. Using this new procedure, sensitivity analyses of performance measures were performed using various input conditions implemented using ProModel and SimRumnner simulation software. A business case is studied to demonstrate the versatility of the proposed approaches.     

THE EFFECT OF NETWORK STRUCTURE ON DYNAMIC TEAM FORMATION IN MULTI-AGENT SYSTEMS

Previous studies of team formation in multi-agent systems have typically assumed that the agent social network underlying the agent organization is either not explicitly described or the social network is assumed to take on some regular structure such as a fully connected network or a hierarchy. However, recent studies have shown that real-world networks have a rich and purposeful structure, with common properties being observed in many different types of networks. As multi-agent systems continue to grow in size and complexity, the network structure of such systems will become increasing important for designing efficient, effective agent communities.
We present a simple agent-based computational model of team formation, and analyze the theoretical performance of team formation in two simple classes of networks (ring and star topologies). We then give empirical results for team formation in more complex networks under a variety of conditions. From these experiments, we conclude that a key factor in effective team formation is the underlying agent interaction topology that determines the direct interconnections among agents. Specifically, we identify the property of diversity support as a key factor in the effectiveness of network structures for team formation. Scale-free networks, which were developed as a way to model real-world networks, exhibit short average path lengths and hub-like structures. We show that these properties, in turn, result in higher diversity support; as a result, scale-free networks yield higher organizational efficiency than the other classes of networks we have studied.     

Development and Characterization of Peptidic Fusion Inhibitors Derived from HIV‐1 gp41 with Partial D‐Amino Acid Substitutions

Interactions between C34 and N36 : Synthetic peptides with D ‐amino acid substitutions that mimic the human immunodeficiency virus (HIV) gp41 HR2 region may lead to new peptidic anti‐HIV‐1 drugs that retain potent antiviral activity while being more resistant to proteolytic degradation.

     

Mapping communication and collaboration in heterogeneous research networks

The aim of this mainly methodological paper is to present an approach for researching the triple helix of university-industry-government relations as a heterogeneous and multi-layered communication network. The layers included are: the formal scholarly communication in academic journals, the communication network based on project collaborations, and finally the communication of information over the 'virtual' network of web links. The approach is applied on typical 'Mode 2' fields such as biotechnology, while using a variety of data sources. We present some of the initial findings, which indicate the different structures and functions of the three layers of communication.