Can energy prices predict stock returns? An extreme bounds analysis

We assess the predictive abilities of energy prices for future US stock market returns using Sala-i-Martin's (1997) extreme bounds analysis (EBA). The EBA results reveal that the predictive power of energy prices varies substantially across the regression models with different combinations of conditioning variables. Energy prices are not robust predictors for the stock returns in the whole sample period from June 1987 to April 2015. However, before the 2008 global financial crisis, energy prices exerted a moderate negative effect on future stock returns and their effects have become strongly positive afterwards. In general, the predictive power declines with the increase in forecast horizon and it varies considerably over time.     

High-temperature stability of Mg(Al,Cr)2O4 spinel co-existing with calcium aluminates in air

Cr₂O₃ is a well-known corrosion resistant oxide used in refractory applications. However, it can oxidize into toxic and water-soluble Cr(VI) compounds upon reaction with calcium aluminate cement phases in the presence of oxygen, which subsequently causes disposal problems after use. This study describes the extent to which chromium in the spinel Mg(Al,Cr)₂O₄ phase can be oxidized to Cr(VI) when it reacts with the calcium aluminate cement phases C₁₂A₇, CA, CA₂ and free CaO at 1300 °C in air, using XRD, XPS and leaching tests (TRGS 613 standard) as analytical tools. On reaction with CaO, the Mg(Al,Cr^III)₂O₄ spinel mainly transformed into hauyne (Ca₄Al₆Cr^VIO₁₆) and Ca₅Cr₃O₁₂ which contains both Cr(IV) and Cr(VI). The reaction of C₁₂A₇ and CA with the spinel phase also resulted in the formation of Ca₄Al₆CrO₁₆. Conversely, the reaction of Mg(Al,Cr^III)₂O₄ spinel with CA₂ resulted in the formation of only a trace amount of Cr(VI). Water-soluble Cr(VI) leached in large quantities (>100 mg/L) from samples where the Mg(Al,Cr^III)₂O₄ reacted with either C₁₂A₇ or CA. Almost no Cr(VI) leached from the sample when Mg(Al,Cr^III)₂O₄ reacted with CaO, using the standard TRGS 613 leach test, but a significant amount of Cr(VI) was released into solution when leached with a HCl solution for 12 h. Both Cr(IV) and Cr(VI) present in the Ca₅Cr₃O₁₂ dissolved into acidic solution. Only a small amount of Cr(VI) leached from the sample that resulted when spinel was reacted with CA₂, even after a prolonged HCl leach. Cr(III) in spinel Mg(Al,Cr)₂O₄ is very stable and does not leach in either distilled water or acidic solution.     

The influence of Mgon the formation of calcareous deposits on a freely corroding low carbon steel in seawater

The purpose of this study was to determine how magnesium in seawater influences the corrosion behaviour of freely corroding steel. This was done by studying if Mg(OH)₂ is formed and if calcite and aragonite differ in their protective properties. No Mg(OH)₂ was detected after immersion of steel in a Mg²⁺-containing artificial seawater. Magnesium seems to influence the corrosion behaviour of freely corroding steel by causing calcium carbonate to precipitate as aragonite. Aragonite is more effective in covering the surface than calcite and is therefore more functional in preventing oxygen from reaching the steel surface, thereby lowering the corrosion rate.     

Activity-composition relations of MnO in MnO-CrO x -CaO-SiO2-containing melts

The MnO activities in (MnO-CrO _x -CaO-SiO₂)-containing melts, which were saturated with the (Mn, Cr)₃O₄ spinel phase, were determined at 1500 °C under an oxygen partial pressure of 10^−8.99 atm. This was done by equilibrating the samples with platinum. The activity of MnO in the melt was then calculated from the activity coefficient of manganese in the resultant Pt-Cr-Mn alloy. Darken’s quadratic formalism for ternary metallic solutions was used to calculate the activity coefficient of manganese in the Pt-Cr-Mn system, in which platinum was considered to be the solvent. It was found that an increase in the concentration of MnO in the melt increases both the MnO activity and the activity coefficient of MnO. For a constant MnO concentration in the (MnO-CrO _x -CaO-SiO₂)-containing melts, the activity of MnO can be increased by increasing the basicity of the melt. In order to obtain high-manganese recoveries from (MnO-CrO _x -CaO-SiO₂)-containing melts into an alloy phase, basic slags in which the activity coefficient of MnO is high should therefore be used.     

The use of probability theory in fracture mechanics—A case study

A probabilistic approach to fracture mechanics in the form of a typical case study is described wherein the integrity of a high-pressure water pipeline is assessed. An analysis methodology is discussed incorporating the probability density functions of defect sizes, the statistics of defect occurrences and the statistical distribution of material properties. This method enables the analyst to supply a very simple assessment of safety, based on the probability of failure (a single number) which may be compared to accepted industrial standards (e.g. 10⁻⁶ for nuclear applications). It is argued that this method often offers the only way to scientifically and economically assess the integrity of fracture prone structures.     

Nanoscale research in South Africa: A mapping exercise based on scientometrics

This article reports the findings of a scientometric analysis of nanoscale research in South Africa during the period 2000–2005. The ISI databases were identified as the most appropriate information platform for the objectives of the investigation and have been interrogated for the identification of South African authors publishing in the field. The article identifies trends over time, major institutional contributors, journals in which South African authors publish their research, international collaborators and performance in comparison to four comparator countries (India, Brazil, South Korea and Australia). The major findings of the investigation are as follows: nanoscale research in South Africa is driven by individual researchers interests up to date and it is in its early stages of development; the country’s nanoscale research is below what would one expect in light of its overall publication output; the country’s nano-research is distributed to a number of Universities with subcritical concentration of researchers.     

Extended Helmholtz–Weyl decompositions

The Helmholtz–Weyl decomposition in which a vector field is decomposed into the curl of a vector potential and the gradient of a scalar potential, is extended to situations where function-objects somewhat different from vector fields are considered. This is done by creating, in the spirit of Hermann Weyl, a Hilbert space framework from which the classical as well as some new decompositions can be obtained. Because of the Hilbert space setting, functions in classes of square integrable functions are in the background. In applications to hydrodynamics, decomposition of the velocity field has to be brought into line with the decomposition of the time derivative of this field. For this purpose we introduce the derived decomposition which is what is really used in fluid mechanics. In addition there is the matter of dimensional correctness of decompositions to which attention is also paid. Applications of the theory to problems in fluid mechanics which involve dynamic boundary conditions are also given.     

Laboratory and Field Consumer Evaluation Relationships for Menu Items Processed in Retortable Trays for Quantity Foodservice

Problems associated with provision of food in quantity foodservices prompted the development and use of prepared food items processed in retortable trays. Consumer acceptance of such foods was required so that the items could be screened for foodservice application. Consumer tests, using small portion samples and sensory testing under laboratory conditions, gave a relatively reliable prediction of acceptability of most of the items under extended-use consumer testing during a field trial. Final field acceptance of some items was influenced by external factors not accounted for in laboratory testing.     

Comparing orthogonal force and unidirectional strain component processing for tool condition monitoring

Signal processing using orthogonal cutting force components for tool condition monitoring has established itself in literature. In the application of single axis strain sensors however a linear combination of cutting force components has to be processed in order to monitor tool wear. This situation may arise when a single axis piezoelectric actuator is simultaneously used as an actuator and a sensor, e.g. its vibration control feedback signal exploited for monitoring purposes. The current paper therefore compares processing of a linear combination of cutting force components to the reference case of processing orthogonal components. Reconstruction of the dynamic force acting at the tool tip from signals obtained during measurements using a strain gauge instrumented tool holder in a turning process is described. An application of this dynamic force signal was simulated on a filter-model of that tool holder that would carry a self-sensing actuator. For comparison of the orthogonal and unidirectional force component tool wear monitoring strategies the same time-delay neural network structure has been applied. Wear-sensitive features are determined by wavelet packet analysis to provide information for tool wear estimation. The probability of a difference less than 5 percentage points between the flank wear estimation errors of above mentioned two processing strategies is at least 95 %. This suggests the viability of simultaneous monitoring and control by using a self-sensing actuator.