A highly efficient, chemoselective synthesis of a library of polysubstituted pyrroles and tetrahydropyridines has been achieved through the one-pot, multicomponent reactions of ethyl (E)-3-(aryl/alkyl amino) acrylates, 2,2-dihydroxy-1-arylethan-1-ones, and malononitrile under solvent- and catalyst-free grinding conditions. The selective formation of pyrrole or tetrahydropyridines relied on subs...

background: based on contradictory findings concerning the use of lasers for enamel etching, the purpose of this study was to investigate the shear bond strength of teeth prepared for bonding with er-yag laser etching and compare them with phosphoric acid etching. materials and methods: in this in vitro study forty – eight premolars, extracted for orthodontic purposes were randomly divided in t...

This paper investigates the grinding performance of epoxy matrix composites reinforced by unidirectional carbon fibres, using an alumina grinding wheel. Emphasis was placed on understanding the effect of fibre orientations and grinding depths on the grinding force and surface integrity, and on understanding the grinding mechanisms, with a comparison to orthogonal cutting. It was found that grea...

recently, self-etching fissure sealants have been introduced to reduce technical sensitivity; however, their efficacy should be assessed. the aim of this study was to assess of the microshear bond strength of self-etching and conventional fissure sealants.thirty non-carious third molars were randomly divided into three groups (n=10). microcylinders of concise fissure sealant were bonded to prep...

Off-round grinding performed on CNC cylindrical grinding is a relatively new process. This paper takes a systems approach and discusses the various inputs and outputs and highlights the potential problems that production engineers face in implementing this new process. The effect of the inputs to the off-round grinding process such as the grinding machine, wheel, grinding fluid and the workpiec...

This study evaluated microstructural and crystallographic phase changes after grinding (G) and regeneration firing/anneling (R) of Y-TZP ceramics. Thirty five bars (LavaTM and Ice Zirkon) were divided: Y-TZP pre-sintered, control (C), regeneration firing (R), dry grinding (DG), dry grinding+regeneration firing (DGR), wet grinding (WG) and wet grinding+regeneration firing (WGR). Grinding was con...

Automation of grinding of metalcastings is desirable for many reasons. The major reasons are dangerous working conditions, low productivity, and inconsistency in human operations. As an approach to the automating grinding process, a gantrydriven grinding machine is proposed to manipulate an industrial hand grinder and control the grinding force applied to the work piece. To increase the materia...

background and aims. the aim of this study was to compare shear bond strength (sbs) of metal and ceramic brackets bonded to enamel using acid versus er:yag laser etching. materials and methods. eighty premolars were divided into 4 groups: am (acid etching/ metal brackets), ac (acid etching/ ceramic brackets), lm (laser etching/ metal brackets) and lc (laser etching/ ceramic brackets). enamel co...

cement powder size classification efficiency significantly affects quality of final product and extent of energy consumption in clinker grinding circuits. static and dynamic or high efficiency air separators are being used widely in closed circuit with multi-compartment tube ball mills, high pressure grinding rolls (hpgr) and more recently vertical roller mills (vrm) units in cement plants to c...

in this study; utilizing the elastic matrix ball has higher processing efficiency and better superficial quality than traditionalgrinding. the diversity of elastic abrasive tool characteristics contact with bend surface results in irregular wear abrasion，and abrasive tool machining status gets complicated. there is no theoretical interpretation of parameters affecting the grinding accuracy. bec...