Nominal Cut Research Articles

A deep recession came with deep wage cuts

While economists historically have considered wages rigid downwards, recent studies have shown that cuts in nominal wages are more common than previously thought. The deep recession experienced in Iceland in 2008, coupled with Iceland’s flexible labor market provided an extreme example of a labor market that experienced widespread and deep cuts in nominal wages. Data covering two-fifths of the labor market showed that 80% of employees experienced a nominal cut in regular hourly wages between 2008 and 2010. The data was collected directly from organizations, and excluded the effects of a change in hours worked. Nominal hourly wages for full time work were cut by 9.3% on average, at the same time inflation measured 18%.

Analysis of chip formation mechanisms and modelling of slabber process

During the primary transformation in wood industry, logs are faced with conical rough milling cutters commonly named slabber or canter heads. Chips produced consist of raw materials for pulp paper and particleboard industries. The process efficiency of these industries partly comes from particle size distribution. However, chips formation is greatly dependent on milling conditions and material variability. Thus, this study aims at better understanding and predicting chips production in wood milling. The different mechanisms of their formation were studied through orthogonal cutting experiments at high cutting speed for beech and Douglas fir. Under these conditions, ejection of free water inside wood can be observed during fragmentation, particularly on beech. As previously seen in quasi-static experiments, chip thickness is proportional to the nominal cut thickness. Moreover, the grain orientation has a great influence on the cutting mechanisms, so as the nominal cut and the growth ring widths. This chip fragmentation study finally allows the improvement of the cutting conditions in rough milling. In order to optimize machine design as well as cutting geometry, a geometrical model of a generic slabber head was developed. This model allows the study of the effective cutting kinematics, the log-cutting edges interactions and the effective wood grain direction during cutting. This paper describes the great influence of the carriage position on cutting conditions. The results obtained here can be directly used by milling machine manufacturers.

Using ozone to reduce recalcitrant compounds and to enhance biodegradability of pulp and paper effluents

The effect of ozone based oxidation on removing recalcitrant organic matter (ROM) and enhancing the biodegradability of alkaline bleach plant effluent was investigated. A bubble column ozonation tower was used in the study. The experiments were carried out at different temperatures (20 degrees C and 60 degrees C) and pH (9 and 11), with a number of biological and chemical parameters being monitored including BOD5, COD, TC, pH, color, and molecular weight distribution of organics (nominal cut off of 1,000 Da). Biodegradability of the effluent was determined based on BOD5/COD of the wastewater throughout the process. For all the experiments, ozonation enhanced the biodegradability of the effluent by 30-40%, which was associated with noticeable removal of ROM including high molecular weight (HMW) and color-causing organics by about 30% and 60%, respectively. While the biodegradability of HMW fraction increased by about 50%, there was no biodegradability improvement for low molecular weight (LMW) portion, which was originally readily biodegradable (with BOD5/COD of about 0.5). Statistical analysis of variance (ANOVA) revealed neither pH nor temperature played significant role on the ozonation process at 95% confidence level.

Energy scaling transitions in machining of silicon by diamond

The existence of an energy scaling brittle-ductile transition in the machining of ceramics and glasses is now well established. We have examined the surface layers of silicon crystals machined in the ductile regime by two methods: (i) a dedicated highly stiff single point diamond turning facility (SPDT), using cut depths of the order of 100 nm (ii) high precision cup grinding using a nominal cut depth of 500 nm. Surfaces were profiled by AFM and subsurface damage was characterized by Rutherford ion backscattering and cross section TEM. The main results to date are: (a) The SPDT specimens possessed a surface quality corresponding to that achieved by optical polishing, the R a ⋍ 0.6 nm and R max (P-V) ⋍ 6 nm. (b) The R a values of the ground specimens ranged between 7 nm and 20 nm, with 64 < R max < 148 nm. There were significant differences between wheels bonded by resin and by cast iron. (c) The mean depths of surface damage were in the range 200–400 nm in all cases. (d) In the SPDT crystals the subsurface damage consisted of dislocation loops intersecting the surface. In any one region of the specimen these represented slip on a single close packed system. (e) In ground slices the permanent damage comprised sub-micron length cracks as well as a high density of dislocations on various systems. Local regions of amorphous silicon were also present. (f) In SPDT ductile machining diamond tool wear is effectively homogeneous and much less variable than in normal machining.

Recovery of β-galactosidase from a poly (ethylene glycol) solution by diafiltration

Cross-flow diafiltration was used for the recovery of β-galactosidase from a poly (ethylene glycol) (PEG) 4000 top phase, which was obtained during extraction of Escherichia coli cell disintegrate in a PEG 4000/potassium phosphate aqueous two-phase system. Two different filtration systems were used, an Amicon system containing a hollow fiber filter (nominal cut off 100,000, membrane area 2.65 · 10 −2 m 2) and a Millipore system containing a plate and frame filter (nominal cutoff 100,000, membrane area 0.5 m 2). To enhance filtration, the top phases were diluted 2.5×, 5×, and 10× with water prior to the filtration. By reducing the concentration of top phase before the filtration, the retention of β-galactosidase and PEG 4000 decreased and the flux increased in both systems. While the retention of β-galactosidase was high in both systems, the retention of PEG 4000 was much lower in the Amicon system. However, the system capacities, expressed as the volume of nondiluted top phase treated per membrane area and time, were not influenced by the extent of dilution of the top phase prior to the filtration. The system capacities were approximately 3.0 and 1.5 l m −2 h −1 for the Millipore and Amicon systems, respectively. The recoveries of β-galactosidase in the retentates were ≥ 95%.

Feasibility study for the production of narrow, closely fractionated lube oil cuts

1. In order to produce a 460–490°C cut that is 80% “pure,” i.e., with 80% distilling within the nominal cut points (15–18% light impurities, 2–5% heavy impurities), a column equivalent to 20 theoretical plates is required, along with a reflux ratio of 10; this cannot be achieved in the present state of the art in commercial vacuum distillation. 2. With the maximum number of actual channel or valve trays that can be used in a commercial vacuum tower, the best “purity” that can be achieved in segregating the 460–490°C cut is only 50–60% with respect to the nominal components (content of light impurities 30–35%, heavy 10–15%). 3. A linear model has been developed for the distillation of complex mixtures, and a corresponding program for the Minsk-22 computer. With small expenditures of machine time, polyvariant evaluation calculations can be performed for complex distillation units, through which the optimal variant can be selected on the basis of the index for the sharpness of fractionation.