Solar energy fixation of carbon dioxide via cadmium sulphide and other semiconductor photocatalysts

Aqueous carbon dioxide is photochemically reduced in the presence of semiconductor suspensions and colloids. Experiments have been performed using CdS, ZnO, SiC, Ba TiO₃, and SrTiO₃, dispersions. Product analysis showed the formation of formic acid formaldehyde, sometimes methanol and in the presence of tetramethylammonium chloride, two-carbon products such as glyoxylic and acetic acids and sometimes acetaldehyde. Product yields and photochemical yields were studied as a function of pH, solution composition, added sacrifical electron donors and catalysts, irradiation intensity and irradiation time. A demonstration experiment with a flat-bed solar collector showed the formation of formic acid and formaldehyde using direct sunlight.     

The incapacitative effects of exposure to the thermal decomposition products of polyurethane foams

The mechanisms of incapacitation resulting from exposures to the thermal decomposition products of flexible and rigid polyurethane foams (PUF) were studied over a range of different temperatures under pyrolytic or non-flaming oxidative decomposition conditions. Individual cynomolgus monkeys were exposed to atmospheres increasing in separate experiments from very low concentrations until early physiological signs of incapacitation were detected. When flexible PUF was pyrolysed at 900°C and rigid PUF was oxidized at 600°C, clear atmospheres containing CO and HCN were produced and the signs of toxicity were very similar to those produced by HCN gas alone, consisting of an episode of hyperventilation followed by a semi-conscious state. Pyrolysis of flexible PUF at 600°C and 300°C produced a dense yellow smoke but no HCN. The signs, consisting of hyperventilation throughout exposure and dyspnoea afterwards, were consistent with pulmonary irritation, Since TDI monmer is not present at 600⁰ C it is concluded that some as-yet unidentified but highly irritant chemical species is present in smoke from flexible PUF.     

Object technology. A virtual roundtable

Heralded by many as a promising solution to software complexity, object technology is coming into its own. This article explores some recent trends, including distributed objects, object-oriented databases (OODBs), parallel computing, software testing and theoretical foundations     

Analyzing the feasibility of building a new mass storage system on distributed resources

The average PC now contains a large and increasing amount of storage with an ever greater amount left unused. We believe there is an opportunity for organizations to harness the vast unused storage capacity on their PCs to create a very large, low‐cost, shared storage system. What is needed is the proper storage system architecture and software to exploit and manage the unused portions of existing PC storage devices across an organization and make it reliably accessible to users and applications. We call our vision of such a storage system Storage@desk (SD). This paper describes our first step towards the realization of SD—a study of machine and storage characteristics and usage in a model organization. We studied 729 PCs in an academic institution for 91 days, monitoring the configuration, load and usage of the major machine subsystems, i.e. disk, memory, CPU and network. To further analyze the availability characteristics of storage in an SD system, we performed a trace‐driven simulation of some basic storage allocation strategies. This paper presents the results of our data collection efforts, our analysis of the data, our simulation results and our conclusion that an SD system is indeed feasible and holds promise as a cost‐effective way to create massive storage systems. Copyright © 2007 John Wiley & Sons, Ltd.     

Resource management in Legion

The recent development of gigabit networking technology, combined with the proliferation of low-cost, high-performance microprocessors, has given rise to metacomputing environments. These environments can combine many thousands of hosts, from hundreds of administrative domains, connected by transnational and world-wide networks. Managing the resources in such a system is a complex task, but is necessary to efficiently and economically execute user programs.

In this paper, we describe the resource management portions of the Legion metacomputing system, including the basic model and its implementation. These mechanisms are flexible both in their support for system-level resource management but also in their adaptability for user-level scheduling policies. We show this by implementing a simple scheduling policy and demonstrating how it can be adapted to more complex algorithms.     

Variance of Load Estimates Derived by Piecewise Linear Interpolation

Piecewise linear interpolation (PLI) is used frequently in environmental studies to estimate missing data. However, to evaluate the reliability of these estimates, the variances of these interpolated values must be quantified. We propose a procedure to quantify this PLI variance, which involves establishing a semivariogram with coefficients that are calibrated using a cross-validation technique. Estimated values are written as a linear combination of neighboring data points and the variance is calculated with the help of the variogram. Such interpolated values are unaffected by the variance quantification procedure. We then use the PLI model to calculate the variance of a yearly nutrient load under the assumption that only the nutrient concentrations contained missing values. When these results were compared with those from an arithmetic mean, a flow-weighted mean, and a linear regression model, the PLI model was found to be comparable with the other three models in terms of variance. Selection of an appropriate model depends on the characteristics of the data set. Knowing the variance of estimated loads can help regulatory agencies make better decisions to determine whether water quality in the environment is in compliance with established standards or criteria.     

The role of context in decision making: some implications for database design

With increasing integration of computer systems through local and wide area communication networks, there exists the capability in many organizations to retrieve information from databases to support ad hoc decision making by many different users. The idea that information is a corporate resource is now something more than business school hype. But the implications of sharing data are only just dawning on the corporate mind. How do managers interpret data? Where decision making is carried out by several people, perhaps in several different locations for different purposes the same data is used in multiple decision contexts. This paper explores the role of context as a way of adding value to information from databases. Two types of context are defined and discussed in relation to some examples of decisions where the role of context is vital. These examples are taken from some empirical research conducted with users of spatial decision support systems. Here the use of background information on maps, for example roads, add context to maps which otherwise simply display statistical data. The paper concludes by suggesting a model of context based on the notion that context acts as a filter between user and database.