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.     

Testing protocols in Internet of Things by a formal passive technique

In recent years, Extensible Messaging and Presence Protocol （XMPP） is gaining momentum in Internet of Things （IoT）. It has been widely used in chatting, message exchanging and unique addressing. As a matter of course, it raises an interesting issue： how to formally test the conformance and performance of XMPP in IoT environment. While conformance testing of communicating protocols is a functional test that verifies whether the behaviors of the protocol satisfy defined requirements, performance testing is a qualitative and quantitative test that aims at checking whether the performance requirements of the protocol are satisfied under certain conditions. In this paper, we present a logic-based passive testing approach that can test both the conformance and the performance of XMPP protocol through real execution traces and formally specified properties. To evaluate and assess our methodology, we present a developed prototype and the experiments with a set of XMPP properties. Finally, the relevant verdicts and conclusions are provided.     

MoSi2-Based Sandwich Composite Made by Tape Casting

The mechanical properties of a novel laminar composite made by tape casting have been studied. The composite consists of three layers in which an inner core of pure molybdenum disilicide (MoSi₂) is sandwiched between two layers of MoSi₂ reinforced with alumina platelets. Monolithic MoSi₂ exhibits poor room-temperature strength and a brittle indentation strength response, indicative of the absence of R -curve behavior. The flexural behavior of the sandwich composite (both strength and toughness) is dominated by the properties of the outer layer, so long as the thickness of this layer exceeds a critical value. A model has been developed which successfully predicts the critical thickness required.     

The interpersonal privacy identity (IPI): development of a privacy as control model

The Internet and social computing technology have revolutionized our ability to gather information as well as enabled new modes of communication and forms of self-expression. As the popularity of social computing technologies has increased, our society has begun to witness modifications in socialization behaviors. Social psychology theory suggests that technological changes can influence an individual’s expectation of privacy, through adaptive behaviors resulting from use (Laufer and Wolfe in J Soc Issues 33(3): 22–42 (1977)). We adapt traditional privacy theory to explore the influence of developmental and environmental factors on the individual’s inner privacy identity, which is comprised of the individual’s belief in his or her right to control (1) personal information and (2) interactions with others, and is continuously shaped by privacy experiences. We then use the inner privacy identity to examine interpersonal behaviors in the online context. We find that individuals’ belief in their right to control their information impacts their information disclosure practices when consequences are implied and that their belief in their right to control the interaction impacts their online information sharing practices. We do not find support for a relationship between the interaction management component of the IPI and online interaction behavior, which considered in the presence of the relationship between interaction management and online information sharing, suggests that interaction behavior is more complicated in the online context. Insights from the model developed in this study can inform future studies of situational privacy behaviors.     

Nonlinear MPC based on a Volterra series model for greenhouse temperature control using natural ventilation

Suitable environmental conditions are a fundamental issue in greenhouse crop growth and can be achieved by advanced climate control strategies. In different climatic zones, natural ventilation is used to regulate both the greenhouse temperature and humidity. In mild climates, the greatest problem faced by far in greenhouse climate control is cooling, which, for dynamical reasons, leads to natural ventilation as a standard tool. This work addresses the design of a nonlinear model predictive control (NMPC) strategy for greenhouse temperature control using natural ventilation. The NMPC strategy is based on a second-order Volterra series model identified from experimental input/output data of a greenhouse. These models, representing the simple and logical extension of convolution models, can be used to approximate the nonlinear dynamic effect of the ventilation and other environmental conditions on the greenhouse temperature. The developed NMPC is applied to a greenhouse and the control performance of the proposed strategy will be illustrated by means of experimental results.     

Determination of the fracture toughness by automatic image processing

We determine the fracture toughness of a duplex stainless steel using the COD-concept (crack tip opening displacement). The COD_i values are obtained by stereophotogrammetric reconstruction of fracture surfaces. This is done by analyzing stereoscopic scanning electron microscope (SEM) images of the surfaces with an automatic image processing system. This system allows the automatic generation of a digital elevation model (DEM) with approximately 50000 points for each fracture surface image. Height-profiles at the point of crack initiation can be obtained from this DEM. The examination of corresponding profiles from both specimen-halves leads to COD_i.     

Pre-integrated volume rendering with non-linear gradient interpolation

Shading is an important feature for the comprehension of volume datasets, but is difficult to implement accurately. Current techniques based on pre-integrated direct volume rendering approximate the volume rendering integral by ignoring non-linear gradient variations between front and back samples, which might result in cumulated shading errors when gradient variations are important and / or when the illumination function features high frequencies. In this paper, we explore a simple approach for pre-integrated volume rendering with non-linear gradient interpolation between front and back samples. We consider that the gradient smoothly varies along a quadratic curve instead of a segment in-between consecutive samples. This not only allows us to compute more accurate shaded pre-integrated look-up tables, but also allows us to more efficiently process shading amplifying effects, based on gradient filtering. An interesting property is that the pre-integration tables we use remain two-dimensional as for usual pre-integrated classification. We conduct experiments using a full hardware approach with the Blinn-Phong illumination model as well as with a non-photorealistic illumination model.     

Self‐adaptation of service level in distributed systems

Modern distributed systems are diverse and dynamic, and consequently difficult to manage using traditional approaches, which rely on an extensive initial knowledge of the system. On the performance front, these systems often offer multiple opportunities for dynamically degrading or improving service level based on workload intensity, to avoid overload and underload. In this context, we propose a novel approach for building distributed systems capable of autonomously deciding when and how to adapt service level. Our approach limits the knowledge that must be provided manually to a component‐based representation of the system. From this representation, we build and maintain a performance profile, which allows us to (1) identify the most promising adaptations based on workload type and (2) dynamically characterize the intrinsic efficiency of each adaptation based on past attempts. We have successfully implemented and evaluated a prototype of our approach in the context of multi‐tiered application servers. Copyright © 2010 John Wiley & Sons, Ltd.     

A contribution to vision-based autonomous helicopter flight in urban environments

A navigation strategy that exploits the optic flow and inertial information to continuously avoid collisions with both lateral and frontal obstacles has been used to control a simulated helicopter flying autonomously in a textured urban environment. Experimental results demonstrate that the corresponding controller generates cautious behavior, whereby the helicopter tends to stay in the middle of narrow corridors, while its forward velocity is automatically reduced when the obstacle density increases. When confronted with a frontal obstacle, the controller is also able to generate a tight U-turn that ensures the UAV’s survival. The paper provides comparisons with related work, and discusses the applicability of the approach to real platforms.