Convex formulations for optimal selection of controlled variables and measurements using Mixed Integer Quadratic Programming

The appropriate selection of controlled variables is important for operating a process optimally in the presence of disturbances. Self-optimizing control provides a mathematical framework for selecting the controlled variables as combinations of measurements, c = Hy, with the aim to minimize the steady state loss from optimal operation. In this paper, we present (i) a convex formulation to find the optimal combination matrix H for a given measurement set and (ii) a Mixed-Integer Quadratic Programming (MIQP) methodology to select optimal measurement subsets that result in minimal loss. The methods presented in this paper are exact for quadratic problems with linear measurement relations. The MIQP methods can handle additional structural constraints compared to the branch and bound (BAB) methods reported in literature. The MIQP methods are evaluated on a toy test problem, an evaporator example, a binary distillation column example with 41 stages and a Kaibel column with 71 stages.     

Improving software security with static automated code analysis in an industry setting

Software security can be improved by identifying and correcting vulnerabilities. In order to reduce the cost of rework, vulnerabilities should be detected as early and efficiently as possible. Static automated code analysis is an approach for early detection. So far, only few empirical studies have been conducted in an industrial context to evaluate static automated code analysis. A case study was conducted to evaluate static code analysis in industry focusing on defect detection capability, deployment, and usage of static automated code analysis with a focus on software security. We identified that the tool was capable of detecting memory related vulnerabilities, but few vulnerabilities of other types. The deployment of the tool played an important role in its success as an early vulnerability detector, but also the developers perception of the tools merit. Classifying the warnings from the tool was harder for the developers than to correct them. The correction of false positives in some cases created new vulnerabilities in previously safe code. With regard to defect detection ability, we conclude that static code analysis is able to identify vulnerabilities in different categories. In terms of deployment, we conclude that the tool should be integrated with bug reporting systems, and developers need to share the responsibility for classifying and reporting warnings. With regard to tool usage by developers, we propose to use multiple persons (at least two) in classifying a warning. The same goes for making the decision of how to act based on the warning. Copyright © 2012 John Wiley & Sons, Ltd.     

A longitudinal study of VDT work and health

A longitudinal study on the use of visual display terminals (VDTs) was conducted with questionaire data obtained 1981 and in 1987–1988 from a cohort of office workers. The use of VDTs became more widespread in these offices during the intervening time period, but the time spent by individuals working at VDTs showed no general increase. The data suggested that VDT use was related to the risk of developing eye discomforts and hand and wrist problems. For skin problems and headache, risks for VDT and non‐VDT users were fairly similar, but indications of increased risks were found for certain groups and situations. The risks of developing neck, shoulder, shoulder joint, or upper arm problems were high for both VDT and non‐VDT users, but there were, in this study, no convincing suggestions that these risks were higher for VDT users compared to nonusers.     

Domain‐specific design of user interfaces

The use of graphical user interfaces in a computerized work environment is often considered to substantially improve the work situation. The outcome can, however, often be the opposite. Inappropriate use of windowing techniques, scrolling, and colors can result in tedious and confusing interaction with the computer. Today's standards and style guides define basic design principles but are insufficient for design of interfaces to end‐user applications. Here detailed domain knowledge is indeed essential. A domain‐specific style guide (DSSG) is an extension of today's standard with domain‐specific primitives, interface elements, and forms, together with domain‐specific guidelines. Careful dedicated analysis of information utilization in a domain is the development basis for a DSSG. The development is performed with an object‐oriented approach to facilitate the reuse of interface components and to support consistency and structure. Using a DSSG, the development of applications can be performed with a simplified information analysis. Therefore a more effective design process is possible, one in which end users can participate in the design using their own familiar domain‐related terminology. Time and costs for the development process can be drastically reduced if domain‐specific style guides, design guidelines, and development tools are used.     

Note: fast and reliable fracture strain extraction technique applied to silicon at nanometer scale

Simple fabrication process and extraction procedure to determine the fracture strain of monocrystalline silicon are demonstrated. Nanowires/nanoribbons in silicon are fabricated and subjected to uniaxial tensile stress along the complete length of the beams. Large strains up to 5% are measured for nanowires presenting a cross section of 50 nm × 50 nm and a length of 2.5 μm. An increase in fracture strain for silicon nanowires (NWs) with the downscaling of their volume is observed, highlighting the reduction of the defects probability as volume is decreased.     

Verifying Programs with Unreliable Channels

We consider the verification of a particular class of infinite-state systems, namely systems consisting of finite-state processes that communicate via unbounded lossy FIFO channels. This class is able to model, e.g., link protocols such as the Alternating Bit Protocol and HDLC. For this class of systems, we show that several interesting verification problems are decidable by giving algorithms for verifying (1) thereachability problem—is a finite set of global states reachable from some other global state of the system ? (2)safety properties over tracesformulated as regular sets of allowed finite traces, and (3)eventuality properties—do all computations of a system eventually reach a given set of states? We have used the algorithms to verify some idealized sliding-window protocols with reasonable time and space resources. Our results should be contrasted with the well-known fact that these problems are undecidable for systems with unboundedperfectFIFO channels.     

Characterization of triacylglycerols in the seeds ofAquilegia vulgaris by chromatographic and mass spectrometric methods

The online version of the original article can be found at     

A chemometric strategy for the classification of lecithins according to process performance

Lecithins are widely used as multipurpose additives in the pharmaceutical and food industries. This implies the need for an analytical means for the assessment of process performance prior to full-scale processing. A general methodology was developed for the classification of lecithins with respect to this property. The strategy developed utilizes pattern recognition methods, fatty acid composition of the phospholipid classes(phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol) and lipid class analysis by high performance liquid chromatography to identify the lecithins with acceptable performance, e.g., emulsifying behavior.     

Ester content evaluation in biodiesel from animal fats and lauric oils

A modified method for the determination of ester contents of biodiesel based on EN 14103 has been developed. The method includes natural contents of heptadecanoic acid ester, which are found in animal fats and interfere with the standard method, into the calculation of ester content values. As a result, biodiesel samples prepared from waste animal fats and oils showed an increase in ester content between 2 and 7 wt‐% compared to values measured according to EN 14103. Furthermore, modifications of the GC temperature program made it possible to include also short‐chain fatty acid esters C₈–C₁₂, which can be found in coconut and palm kernel oil, into the calculation. Measurements showed that the ester content of such biodiesel differs by more than 40 wt‐% compared to EN 14103 determinations. However, also the stability of the internal standard solution methyl heptadecanoate influences the values of ester content. It can be demonstrated that after a period of 7 days, an ester content decrease of about 2 wt‐% can be observed. Therefore, the use of almost freshly prepared standard solutions should be recommended.     

Thermodynamic Assessment of the CaO–MgO–Al2O3 System

The system CaO–MgO–Al₃O₃ has been assessed with the Calphad technique using a computerized optimization procedure called parrot . The rather meager experimental information, mainly on liquidus relations, is described reasonably well, but the lack of data, especially on solid-phase relations, implies that the present assessment should be regarded as provisional. The system contains one stable ternary phase with the stoichiometry 3CaO·2Al₂O₃·MgO.