Strength and behaviour of cold-formed steel offset trusses

Thirteen full-scale truss specimens fabricated with cold-formed steel C-sections were tested to study various practical strengthening techniques in order to achieve a desired behaviour and an increased capacity. Specimens were subjected to concentrated panel point loading simulating the realistic loading condition of a roof truss. Results revealed that local buckling of the top chord (LBTC) adjacent to the heel plate was the predominant failure mechanism. In instances where the heel plate was not adequately stiffened, the distortion or crippling of the plate occurred at failure. For the investigated pitches, an increase in specimen pitch resulted in an increase in the capacity. Strengthening both the top chord adjacent to the heel plate and the heel connection with both a shallow member and a heel plate stiffener resulted in the most significant increase in the capacity compared with the original truss configuration. Beam-column analysis of the top chords in the failure region was performed using both the conventional interaction design equations and the direct strength method as suggested in CSA S136-07.     

Downhole Heating: Productivity Ratio Improvements—Dangers of Misconceptions

Stimulating the well productivity of reservoirs that contain viscous oil is initially often carried out by heating the near-wellbore region. Heating lowers the oil viscosity so that the oil can flow faster under the same pressure differential, but for maximum rewards how much of the reservoir must be heated and to what temperature should it be heated? This paper presents a boundary condition approach to give guidance to these questions. We examine the effectiveness of downhole heating on the productivity using a simple radial model with viscosity changes. We find that for the same temperature rise the productivity improvement is greater for high viscosity oils than for low viscosity ones. We also find that there is a maximum beneficial temperature rise for a given radius of heating, and that for the same energy input it is probably more beneficial to heat deeper into the reservoir at a lower temperature than high heating for a smaller radius. If only 17% of the reservoir radius is heated, then the maximum productivity increase is typically no more than a factor of around 4 no matter how large is the temperature increase in the heated zone. The exact improvement depends on the initial oil viscosity, the initial oil temperature, and its temperature dependence.     

A new quantitative method for the analysis of monoacylglycerol isomers using13C nuclear magnetic resonance spectroscopy

Current methods for determining the regiochemistry of monoacylglycerols are lengthy, tedious and aggravated by the ready isomerization of 2-acyl-sn-glycerols. A new method employs a very rapid adsorption chromatography step in which isomerization is kept to a minimum, followed by formation of the isopropylidene derivatives using mild procedures. These cyclic derivatives of 1- and 3-acyl-sn-glycerols and 2-acyl-sn-glycerols are stable thermally and display certain characteristic¹³C NMR resonances. Integration of these resonances yields directly the proportion of monoacylglycerol isomers in the mixture. The method was applied to the analysis of monoacylglycerols produced by enzymatic hydrolysis of synthetic and naturally occurring triacylglycerols. NRCC No. 28475.     

Measurement technique for the on-line detection of fines in a fluidized bed

In many industrial applications knowledge of the particle size distribution in a fluidized bed and in particular knowledge of the proportion of fines, is extremely important in order to maintain good fluidization quality in the bed, and to prevent too many particles from leaving the cyclones in the gas stream. A common method of monitoring particle size in a laboratory situation is to take a sample of particles from the fluidized bed and use equipment such as a laser diffraction device to analyze the sample, which can be a cumbersome procedure. The objective of this study was to develop an online tool to monitor the proportion of fines in a fluidized bed. A novel online measurement technique for the detection of fines in fluidized beds was developed, which includes a correlation that relates the triboelectric signal to the proportion of fines in the bed.     

Study of horizontal sonic gas jets in gas–solid fluidized beds

Existing jet penetration correlations have all been developed for sub‐sonic gas jets and have been found to perform poorly when employed in sonic and supersonic regimes. In the present study, triboelectric probes were used to measure both the penetration depth and expansion angle of sonic gas jets. Experiments were conducted using nozzles of different size and geometry, different particle types, different injection gases, and different fluidization velocities. All these data were used to develop a new, general correlation to predict the penetration depth of sonic gas jets. The effects of these variables on jet expansion angle were also studied.     

Multiple widespread eruptive Spitz naevi

A 19-year-old man presented with a widespread eruption of several hundred Sptiz naevi. He is still developing new lesions, 4 years after the problem began. No treatment to date has been satisfactory. The literature on prognosis and treatment of this condition is reviewed.     

Spline finite strip analysis of the buckling and vibration of composite prismatic plate structures

A spline finite strip capability is described for predicting the buckling stresses and natural frequencies of vibration of prismatic plate structures which may be of composite laminated construction with arbitrary lay-ups. The plate structures may have general boundary conditions. The capability embraces analyses based on the use of first-order shear deformation plate theory and of classical plate theory, and utilizes substructuring procedures which include the use of superstrips. The theoretical development is not detailed since the present paper reports a very direct extension of a theoretical study developed for the analysis of single plates in an earlier paper in this Journal. A considerable range of buckling and vibration applications is documented and comparison of spline finite strip numerical values of buckling stresses and frequencies is made with results generated using the semi-analytical finite strip method and, in some cases, the finite element method. Buckled and vibrational mode shapes are presented for some applications.     

Vapex—Gravity-assisted Film Drainage for Heavy Oil Recovery

Abstract

Reservoir heavy oils of viscosity higher than 20 cp are difficult to recover efficiently. A new vapor extraction process called Vapex which uses horizontal wells and volatile solvents is being developed, primarily in Canada. This process lowers the viscosity of the oil by dilution and the oil is produced by gravity drainage (vertical movement of fluids) to horizontal wells placed low in the reservoir. More oil should be produced at lower production and energy costs. The Vapex process is outlined in this article and followed by some experimental work demonstrating gravity drainage flow in films at the macro- and micro-scale.