Ambient oxygen ingress rate method—an alternative method to Ox‐Tran for measuring oxygen transmission rate of whole packages

The ambient oxygen ingress rate method (AOIR) is an alternative method to Ox‐Tran for measuring the oxygen transmission rates (OTR) of whole packages. The objective of the present work was (a) to compare OTR values obtained by the two methods, and (b) to evaluate the use of the AOIR method for measuring OTR at realistic food storage temperatures and humidity levels. The AOIR method gave equal OTR values compared to the Ox‐Tran method for the five different types of whole packages used in the experiment, with OTR values in the range 0.06–1.48 ml O₂/day. The repeatability of the AOIR method measured on an HDPE bottle was ±2.6% of the measured value in this experiment. This is slightly higher than the general specifications of the Ox‐Tran method (1% of reading for packages). However, the AOIR method can be considered to be a reliable, precise and cheap alternative method to the Ox‐Tran method for measuring OTR of whole packages. The capacity of the method is also high. The AOIR method showed satisfactory results when comparing OTR for packages tested under realistic food storage conditions covering 23°C/50% relative humidity (RH) and at 4°C/60% RH on the outside, combined with water (100% RH) or dry air inside the packages. Copyright © 2000 John Wiley & Sons, Ltd.     

The power of gifts: organizing social relationships in open source communities

Abstract. In writings on the open source software development model, it is often argued that it is successful as a result of the gift economy that embraces activities in online communities. However, the theoretical foundations for this argument are seldom discussed and empirically tested. Starting with the 'classic' theories of gift giving, we discuss how they need to be developed in order to explain gift-giving practices in digital domains. In this paper, we argue that the gift economy is important, not only because it creates openness, but also because it organizes relationships between people in a certain way. Open source software development relies on gift giving as a way of getting new ideas and prototypes out into circulation. This also implies that the giver gets power from giving away. This power is used as a way of guaranteeing the quality of the code. We relate this practice to how gifts, in the form of new scientific knowledge, are given to the research community, and how this is done through peer review processes.     

Accuracy analysis of a covariance matching approach for identifying errors-in-variables systems

A system identification method for errors-in-variables problems based on covariance matching was recently proposed. In the first step, a small amount of covariances of noisy input–output data are computed, and then a parametric model is fitted to these covariances. In this paper, the method is further analyzed and the asymptotic accuracy of the parameter estimates is derived. An explicit algorithm for computing the asymptotic covariance matrix of the parameter estimates is given, and the identification method is shown to be asymptotically statistically efficient assuming that the given information is the computed covariances. As an important byproduct, an efficient algorithm is presented for computing the covariance matrix of the computed input–output covariances.     

Improving yield and shape in a crushing plant

There is increasing demand to optimise yield and increase capacity of crushing plants. Research in this area has resulted in the development of numerous optimisation tools, and resent research has shown that the economic aspects of production have great influence on the optimisation results. The profitability of a product is influenced by several parameters, and control of all these parameters is necessary to use some sort of optimisation software.In this paper, we present a case study of a typical crushing plant, with the goal of reducing the number of crusher while keeping the plant capacity and quality. By reducing the number of crusher the plant will need less maintenance which will decrease the operating costs. The article presents a method to combine crushing plant simulation and optimisation with quality and economic considerations in order to successfully study alternative configurations of the plant.     

Algorithm for dynamic cone crusher control

Cone crushers are used in the mineral, mining, and aggregate industry for fragmentation of rock materials. Control systems for cone crusher settings are widely used for compensating for wear and protecting the machines from high pressure. However, these systems focus on the crusher and not the crushed products.By applying measurement devices on the process the crusher can be run optimally from the saleable products point of view (unlike most existing systems which only protect the machine) in each time. The measurement devices can be mass flow meters, e.g. conveyor belt scales. To analyze data from the process and convert them to a desired CSS value, an algorithm was developed.The developed algorithm is tested and evolved at a real crushing plant for aggregates. The algorithm was loaded into a computer which could communicate with the crusher control system, read data from three mass flow meters, and also interact with the operators. The computer was reachable over the Internet by the researchers at Chalmers and the algorithm was tuned and improved on-line.The result is an algorithm which was capable of providing CSS set-points to the automatic setting regulation system. The amount of saleable product from the crushing stage improved 3.5%, when not limited by the hydraulic pressure, compared to when a fixed closed side setting is used. The use of the algorithm automatically compensates for changes in the feed material and it also decreases the need for calibration of the underlying system.     

Automatic Generation of Persistent Formations for Multi-agent Networks Under Range Constraints

In this paper we present a collection of graph-based methods for determining if a team of mobile robots, subjected to sensor and communication range constraints, can persistently achieve a specified formation. What we mean by this is that the formation, once achieved, will be preserved by the direct maintenance of the smallest subset of all possible pairwise inter-agent distances. In this context, formations are defined by sets of points separated by distances corresponding to desired inter-agent distances. Further, we provide graph operations to describe agent interactions that implement a given formation, as well as an algorithm that, given a persistent formation, automatically generates a sequence of such operations. Experimental results are presented that illustrate the operation of the proposed methods on real robot platforms.     

On the calculation of the quasi-bound-state energies and lifetimes in inverted MOS structures with ultrathin oxides and its application to the direct tunneling current

We discuss the inverted MOS structure with extremely thin oxides as a quasi-bound-state system. Its energy subbands can be regarded as resonances of a quantum mechanical system with a continuum of eigenstates. We derive an analytical calculation to extract the defining parameters of the Lorentzian peaks associated with the relative probability of localizing an electron in the confining potential region at the Si/dielectric interface and propose an algorithm that allows to estimate the energy levels and the lifetimes of these states, provided the solution of the approximate bound state system is known. This new method has the advantage of not being affected by computational errors, avoiding the time consuming scanning procedure usually employed in previously reported works. Furthermore, a comparison with semiclassical calculation of the lifetimes is performed and direct tunneling current is calculated, which allows it to fit experimental gate-leakage curves with high accuracy.     

A Novel internally heated Au/TiO2 carbon-carbon composite structured reactor for low-temperature CO oxidation

A compact, internally heated, catalytic reactor is demonstrated for the low-temperature oxidation of carbon monoxide. Carbon nanofibres were grown on carbon felt and used as a support material for Au/TiO₂ catalysts. The carbon composite plays two roles; as a support material for the catalyst and for providing heat to the reaction by the Joule effect. The internal heating offers a stable reactor system with quick temperature response at relatively low energy input. Comparison between external and internal heating shows higher conversion of CO in the low-temperature range when using internal heating. The Au/TiO₂ catalyst supported on the carbon-carbon composite shows good stability at 250°C.     

Synergistic gelation of solutions of isotactic polypropylene and bis-(3,4-dimethyl benzylidene) sorbitol and its use in gel-processing

We report the synergistic, rapid gelation of solutions of isotactic polypropylene (i-PP) and the nucleating agent 1,3:2,4-bis-(3,4-dimethyl benzylidene) sorbitol (DMDBS) in decalin. Cooling to room temperature of a solution comprising, for instance, 3.0 wt% of a moderately high molecular weight i-PP (M_v=1.3×10⁶ g/mol) and as little as 0.0075 wt% DMDBS (0.25 wt% based on the polymer) resulted in the fast formation of highly ductile gels. In reference experiments without DMDBS, often ‘mud-cracked’, brittle polymer films were obtained, and decaline solutions of DMDBS alone at the above concentration did not form macroscopically coherent gels. In the present work we employed this useful occurrence for gel-processing/drawing of i-PP, yielding material with Young's moduli of 35 GPa, tensile strengths of approximately 1 GPa and melting temperatures measured for constrained samples as high as 228 °C.     

The Minimal Structure and Motion Problems with Missing Data for 1D Retina Vision

In this paper we investigate the structure and motion problem for calibrated one-dimensional projections of a two-dimensional environment. The theory of one-dimensional cameras are useful in several areas, e.g. within robotics, autonomous guided vehicles, projection of lines in ordinary vision and vision of vehicles undergoing so called planar motion. In a previous paper the structure and motion problem for all cases with non-missing data was classified and solved. Our aim is here to classify all structure and motion problems, even those with missing data, and to solve them. In the classification we introduce the notion of a prime problem. A prime problem is a minimal problem that does not contain a minimal problem as a sub-problem. We further show that there are infinitely many such prime problems. We give solutions to four prime problems, and using the duality of Carlsson these can be extended to solutions of seven prime problems. Finally we give some experimental results based on synthetic data.