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.     

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.     

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.     

III. Co-electrodeposition/removal of copper and nickel in a spouted electrochemical reactor

Results are presented of an investigation of co-electrodeposition of copper and nickel from acidic solution mixtures in a cylindrical spouted electrochemical reactor. The effects of solution pH, temperature, and applied current on metal removal/recovery rate, current efficiency, and corrosion of the deposited metals from the cathodic particles were examined under galvanostatic operation. The quantitative and qualitative behavior of co-electrodeposition of the two metals from their mixtures differs significantly from that of the individual single metal solutions. This is primarily attributed to the metal displacement reaction between Ni(0) and Cu(2+). This reaction effectively reduces copper corrosion, and amplifies that for nickel (at least at high concentrations). It also amplifies the separation of the deposition regimes of the two metals in time, which indicates that the recovery of each metal as a relatively pure deposit from the mixture is possible. It was also shown that nitrogen sparging considerably increases the observed net electrodeposition rates for both metals - considerably more so than from solutions with just the single metals alone. A numerical model of co-electrodeposition, corrosion, metal displacement, and mass transfer in the cylindrical spouted electrochemical reactor is presented that describes the behavior of the experimental copper and nickel removal data quite well.     

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.