The openers are the planter components that interact with soil and several researchers studied openers characteristics and behaviour in different conditions, but few explored the effects on crop ...emergence, growth and yield. The aim of this study is to evaluate and quantify any effects of openers on crop de-velopment and yield. The performance of three planters equipped with five different openers were compared on maize in a field test: double disc (DD), punch planter (PP), horizontal furrow with winged opener (HW), vertical furrow with winged opener (VW), vertical furrow with shank opener (SO). Seed spacing, depth, penetration resistance and plant emergences, root dry mass and yield were measured respectively on seeding slots and during crop development to evaluate openers effects. The results showed low variability in seed depth and spacing when DD and PP openers were used despite higher level of compaction on DD slot. High variability was found on maize plants when VW and HW openers were used. SO obtained relevantly lower yield in absolute value -35% (1.7 Mg ha-1) compared to other openers. However, the high variability observed in the different replicates and plant adaptability to stress conditions could explain the absence of significant differences in crop yield.
Unlike most double-disc grinding processes, which use forced workpiece rotation, some double-disc processes rely on workpiece self-rotation driven by non-uniform shear forces resulting from partial ...wheel-workpiece coverage. This self-rotation is poorly understood, with workpiece angular frequency remaining unknown despite its importance. This paper investigates the kinematics of self-rotation via analytical modelling of the moment-equilibrium conditions, derived from experimentally determined specific-energy values. The model showed that workpiece coverage ratio is the dominant factor governing workpiece angular frequency, allowing for the choice of optimal workpiece coverage ratios that avoid (i) workpiece-stoppage and (ii) excessive frictional heat generation. The predicted velocity was validated with acoustic-emission measurements.
This research work investigates the erosion effect on the surfaces of SS (Stainless Steel) 201, SS 304, SS 316 and SS 420 under different operating conditions. Beside this, the novelty of this work ...is to observe the combined effects of different percentage of SiC- Al2O3-Fe2O3 solid particles on the surfaces of these materials and significant findings are obtained.
The results collected from this study are validated with the morphological analysis of erosive surfaces which is attributed to the real wear mechanism. To characterize the eroded surfaces, this mechanism is associated with the micro-cutting, micro-plowing, plastic deformation and several other materials removal processes.
During the experiments, the impact angles are maintained at 15°, 30°, 45°, 60°, 75° and 90°. The erosion rate is higher at 60° impact angle and then the abrasion is sharply decreased up to up to 90°. However, the erosion varies differently with the variation of impact angles for different tested materials. The erosion rates under impact velocity 40, 50 and 60 m/s are tested. The higher the impact velocity, the higher the erosion rate is noted despite the levels of erosion changes are different for different materials. The enhancement of erosion with the impact velocity is linked with the increase of kinetic energy which in turn is responsible for the increase of temperature. The combined impact of kinetic energy and temperature effects the location of the examined surfaces of stainless steels. But as the stainless steels have the better mechanical and physical properties, these show better erosion resistance in comparison of other polymer and composite materials.
It is also observed the higher test duration and larger particle size have some role to increase the erosion rate. The results of this work are compared with the works of other researchers and the trends of these results are explained with the possible causes. The results of this work can be used as a reliable source for the applications of advanced technology in industry.
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•The combined effects of SiC- Al2O3-Fe2O3 solid particles on erosion of stainless steels.•Erosion rates are observed on the basis of % variation of silica sand (SiC), Al2O3 and Fe2O3.•The relation between different operating parameters with erosion is evaluated.•Obtained results can be used for future mechanical and tribological processes.
Background: Pseudomonas aeruginosa (P. aeruginosa) is a ubiquitous gram-negative rod shaped bacteria and a significant nosocomial opportunistic pathogen. Current study aimed at the investigation and ...determination of extended-spectrum beta-lactamase (ESBL) positive P. aeruginosa from clinical samples. Materials and methods: A total of 150 catheter tubes, pus, blood, and sputum samples were collected from three different hospitals in the twin cities of Rawalpindi and Islamabad. The isolates were identified by using standard microbiology procedures. Antibiotic susceptibility of the isolates was done through the disc diffusion method as per the protocol given by CLSI guidelines. Phenotypic characterization of ESBL producers was performed by combination disc test (CDT), double disc synergy test (DDST) and through PCR. Results: A total of 77/218 isolates were identified as P. aeruginosa. Among them 47 were resistant to different drugs, while 28 were identified as multidrug resistant. They were resistant to 9 different drugs including Cefotaxime (49%), Cefipime (41%), Cephradine (32%), Cefotetan (62%), Azetronam (50%), Cofaclor (42%), Ticarcillin (57%), Ciproflaxacin (45%), and Imipenem (36%). CDT and DDST showed that 7/29 isolates produce ESBL. One isolate was positive for VEB and 3 were positive for SHV ESBL genotype. Conclusion: The phenomenon of ESBL production does not only remain in Klebsiella pneumonia and Escherichia coli but could also be found in P. aeruginosa. Moreover, SHV genotype is prevalent in local isolates of P. aeruginosa.
The double-disc straight-groove (DDSG) grinding method is a new precision machining method for the rolling surface of bearing cylindrical rollers by using a flat grinding disc and a straight-groove ...grinding disc as machining tools. The machining principle of bearing cylindrical rollers based on the DDSG grinding method is experimentally investigated in this study. A circulating grinding platform has been constructed. The grinding test of the cylindrical rollers was performed with W40 white corundum abrasive. Under the experimental conditions of the grinding disc rotation speed of 7.5 rpm, the machining load of 110 N, and the eccentricity of the straight groove of 6 mm, 2000 cylindrical rollers (AISI 52100) were synchronously ground by the DDSG grinding method. The average diameter, surface roughness, and roundness of the ground rollers were investigated. Experimental results show that the material removal rate of the rollers is uniform. After 270 grinding cycles, the average diameter decreased from 5.99082 to 5.94135 mm, with an average material removal rate of 0.183 microns per cycle. The average roundness of ground cylinders reduced from 9.64 to 2.78 μm. The diameter variation decreased significantly from 14.5 to 6.0 μm. The average roughness reduced from 0.258 to 0.137 μm, and the fluctuation range of the roughness decreased from 0.143 to 0.033 μm. Experimental results demonstrate that the DDSG grinding method can improve the bearing cylindrical rollers’ dimensional consistency, roundness, and surface quality.
Present paper demonstrates the application of double disc magnetic abrasive finishing (DDMAF) process, on planar paramagnetic workpieces (copper alloy and stainless steel) of different mechanical ...properties like flow stress, hardness, shear modulus, etc. The copper alloy and stainless steel work pieces have been finished using DDMAF process. The experiments were performed based on a response surface methodology. The results obtained after finishing have been analyzed to determine the effect of different process parameters like working gap, rotational speed, percentage weight of abrasive, abrasive mesh size and feed rate for individual work material and to study various interaction effects that may significantly affect the finishing performance of the process. The outcomes of the analysis so obtained for the two different work materials have been critically compared to understand the effect of the considered process parameters based on mechanical properties. The scanning electron microscopy was also conducted on the work piece surface to understand the possible mechanism of material removal and the surface morphology produced.
We explored and evaluated for the first time colorimetric nitrocefin assay in conjunction with the double disc test and PCR assay. We suggested the use of nitrocefin assay for rapid screening of ...ESBL-production by Enteroaggregative Escherichia coli.
The double-disc straight-groove (DDSG) grinding method is a new precision machining approach employed for the rolling surface of bearing rollers. The friction coefficient and wear resistance of ...grinding disc materials affect the grinding performance due to the operation on the workpiece. However, relevant research on DDSG is rather limited currently. Therefore, we analyzed the friction principles of the DDSG method and conducted friction and wear experiments to facilitate appropriate material selection for grinding discs. The optimal friction conditions for grinding disc materials were determined to ensure steady rotation of cylindrical rollers. In addition, the friction coefficients, wear resistance, and clogging resistance of various materials such as PTFE, PMMA, cast iron, brass, and fixed abrasives were measured by friction and wear experiments under grinding conditions. The friction pairs of PMMA-AISI 52100 and PTFE-AISI 52100 exhibited sliding friction coefficients of 0.14 and 0.03, respectively, along with a high grinding efficiency and excellent wear resistance. The friction pairs of both bearing steel-fixed abrasive and bearing steel-brass were easily clogged, leading to dramatic changes in the sliding friction coefficients, and neither fixed abrasive nor brass was found to be a suitable material for grinding discs. Thus, PMMA and PTFE were selected as the materials for upper and lower grinding discs. Moreover, a verification platform was built to implement the DDSG grinding method where a continuous rotation of ground roller was observed. Overall, this study provides a basis for feasible material selection and an appropriate material combination for designing a grinding machine based on DDSG.
Mechanical pulp for printing paper can be produced with a process that involve much less equipment and that require much lower specific energy compared to conventional processes. Even though common ...evaluation methods, e.g. handsheet testing, have shown that the pulp quality is similar for the simplified and the conventional processes, it is not known how fibre properties, at the microscopic level, is developed with the simplified process. In this mill scale study, the fibre properties attained with an “intensified” mechanical pulping process, consisting of single stage high consistency double disc refining followed by two stage low consistency refining and no reject treatment was investigated. The simplified process was compared to a process with a reject system. The simplified process rendered fibres with higher degree of fibrillation, higher share of axial splits, lower fibre wall thickness but slightly lower length than the conventional process. The fibrillar fines size distribution of the two processes was different. The conventional process generated more of small fibrillar fines which probably explains the higher tensile index at given density for that process. The results show that it is possible to simplify the production process for mechanical pulp and reduce the specific energy with over 700 kWh/adt.
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