Wetting on Lines and Lattices of Cylinders

This paper discusses wetting and capillary condensation transitions on a line and a rectangular array of cylinders using an interface potential formalism. For a line of cylinders, there is a capillary condensation transition followed by complete wetting if the cylinders are sufficiently close together. Both transitions disappear as the cylinder separation is increased. The dependence of the wetting phase diagram of a rectangular array of cylinders is discussed as a function of the chemical potential, substrate--fluid interaction strength and surface tension.Comment: 17 pages in total: 11 pages of Latex document and 6 pages of figures, Latex Version 2.09, OUTP-93-40

Effect of casing treatment of overall performance of axial-flow transonic fan stage with pressure ratio of 1.75 and tip solidity of 1.5

The effect of a number of casing treatments on the overall performance of a 1.75-pressure-ratio, 423-m/sec-tip-speed fan stage was evaluated. The skewed slot configuration with short-open slots over the midportion of the rotor had a stall margin of 23.5 percent, while the solid casing had a stall margin of 15.0 percent. The skewed slot configuration with long open slots extending ahead of and over portion of rotor displaced the stall line to the lowest flow at all speeds tested. At design speed, the peak efficiency for the long, forward open slots was 1 point less than that for the short midopen slots and 3 points less than that for the solid casing

Does Seasonality Change over the Business Cycle? An Investigation using Monthly Industrial Production Series

This paper examines the proposition that the business cycle affects seasonality in industrial production, with output being switched to the traditionally low production summer months when recent (annual) growth has been strong. This is investigated through the use of a restricted threshold autoregressive model for the monthly growth rate in a total of 74 industries from 16 OECD countries. Approximately one third of the series exhibit significant nonlinearity, with this nonlinearity predominantly associated with changes in the seasonal pattern. Estimates show that the summer slowdown in many European countries is substantially reduced when recent growth has been high.

Forecasting UK Industrial Production Over the Business Cycle

This paper examines the information available through leading indicators for modelling and forecasting the UK quarterly index of production (seasonally adjusted). The emphasis is on one-quarter ahead prediction, especially over the 1990s recession. Linear specifications considered are univariate autoregressive models together with dynamic single indicator and multiple indicator models. Both univariate and leading indicator versions of nonlinear Markov switching specifications are also examined. In the latter case, the transition probabilities are modelled as logistic functions of the leading indicators, allowing the lead times to differ for the expansion to expansion and recession to recession probabilities. Despite general evidence that the term structure of interest rates helps regime classification in the Markov switching models, these models perform relatively poorly in forecasting the 1990s production recession. It is suggested that this poor performance may be due to the nature of that recession, which differed from previous major UK postwar recessions in having no single quarter where industrial production declined substantially. However, a three indicator linear specification does well. The leading indicator variables in this latter model are a short-term interest rate, the stock market dividend yield and the optimism balance from the quarterly survey conducted by the Confederation of British Industry.

Leading-edge vortex research: Some nonplanar concepts and current challenges

Some background information is provided for the Vortex Flow Aerodynamics Conference and that current slender wing airplanes do not use variable leading edge geometry to improve transonic drag polar is shown. Highlights of some of the initial studies combining wing camber, or flaps, with vortex flow are presented. Current vortex flap studies were reviewed to show that there is a large subsonic data base and that transonic and supersonic generic studies have begun. There is a need for validated flow field solvers to calculate vortex/shock interactions at transonic and supersonic speeds. Many important research opportunities exist for fundamental vortex flow investigations and for designing advanced fighter concepts

Seasonal adjustment and the detection of business cycle phases

To date, there has been little investigation of the impact of seasonal adjustment on the detection of business cycle expansion and recession regimes. We study this question both analytically and through Monte Carlo simulations. Analytically, we view the occurrence of a single business cycle regime as a structural break that is later reversed, showing that the effect of the linear symmetric X-11 filter differs with the duration of the regime. Through the use of Markov switching models for regime identification, the simulation analysis shows that seasonal adjustment has desirable properties in clarifying the true regime when this is well underway, but it distorts regime inference around turning points, with this being especially marked after the end of recessions and when the one-sided X-11 filter is employed. JEL Classification: E32, C22, C80business cycles, Markov switching models, Seasonal adjustment

Effects of tip clearance on overall performance of transonic fan stage with and without casing treatment

The overall performance of a transonic fan stage is presented for various tip clearances, with and without casing treatment. The stage was tested with a solid casing, and with open skewed slots and closed skewed slots in the casing over the rotor blade tips. Four nominal nonrotating rotor blade tip clearances from 0.061 to 0.178 centimeter were used. For all three casings, the pressure ratio and efficiency decreased with increasing tip clearance. The stall margin for a given casing also decreased with increasing clearance. At design speed and a given tip clearance, the highest stall margin was obtained with the open-slot casing, and the lowest stall margin was obtained with the solid casing

Performance of a 1.15-pressure-ratio axial-flow fan stage with a blade tip solidity of 0.5

The overall and blade-element performance of a low-solidity, low-pressure-ratio, low-tip-speed fan stage is presented over the stable operating range at rotative speeds from 90 to 120 percent of design speed. At design speed a stage peak efficiency of 0.836 was obtained at a weight flow of 30.27 kilograms per second and a pressure ratio of 1.111. The pressure ratio was less than design pressure ratio, and the design energy input into the rotor was not achieved. A mismatch of the rotor and stator blade elements resulted due to the lower than design pressure ratio of the rotor

Development of an innovative method for the evaluation of fungal contamination of surfaces

The objective of this technical report is to compare the ability to capture fungal spores through samples performed with three different methods: Rodac contact plates, cotton pad and a pad prepared with a dusting cloth (DC pads) selected from those available on the market. The tests were conducted using a suspension of Aspergillus niger conidia equal to 0.5 MacFarland diluted 1/30, 1/40, 1/50, 1/100. With each of these dilutions 3 sterile tiles of stainless steel were contaminated, each divided into 16 small squares, in the center of which 0.1 ml of the dilution chosen was placed and left to dry (for a total of 12 sheets). In addition, we have used other 6 tiles to repeat the experience with dilutions 1/40 and 1/50. A total of 288 squared surfaces were contaminated: 96 of these were sampled with Rodac contact plates, 96 with cotton pads and 96 with DC and then inseminated in Petri plates. Sabouraud dextrose agar was used as culture medium for the first 12 plates, while, for the other 6 plates Sabouraud dextrose agar added with lecithin and polysorbate 80 was used. All plates were incubated at 37 degrees for 18 hours. To estimate the differences among the sampling methods and the dilutions tested, multiple linear regression was used. The analysis showed that the number of colonies harvested at dilution 1/40 is 13% higher (P = 0.09) than the number harvested at dilution 1/50 and the number of colonies harvested at dilution 1/30 is 6% higher than dilution 1/50 (P = 0.52). With regard to the comparison between the number of colonies harvested with Rodac contact plates, with cotton pads and DC pads, regression analysis shows that cotton pads harvest a number of fungal cfu 5 times higher than those detected with Rodac plates, while DC pads harvest a number of fungal ufc 6 times higher than those detected with Rodac plates (P < 0.00005). These results, although preliminary, indicate that DC pads are a sensitive and simple approach for the environmental control of fungal contamination