Closed-form inverse kinematics of 6R milling robot with singularity avoidance

For a 6R milling robot, it is necessary to convert the postprocessing cutter locations (CL) into the robot’s revolute joint variables. This paper introduces an algorithm for calculating the forward and inverse kinematics of a 6R robot according to the CL data generated by conventional CAD/CAM systems. A redundant mechanism is analyzed to avoid the singular configurations and joint limits. The Denavit–Hartenberg (D–H) convention is referred to for developing the forward kinematics, and a closed-form solution of the inverse kinematics is presented by means of kinematic decoupling. A fundamental approach with modifying factor for avoiding singularity are developed with regard to three-axis and five-axis CL data. A gap bridging strategy is applied to reduce the jerk motion caused by tool retraction and cut paths connection. Finally, the result is conducted to simulation and machining test to verify the algorithms.     

Water�CGas Shift and CO Methanation Reactions over Ni�CCeO2(111) Catalysts

X-ray and ultraviolet photoelectron spectroscopies were used to study the interaction of Ni atoms with CeO₂(111) surfaces. Upon adsorption on CeO₂(111) at 300 K, nickel remains in a metallic state. Heating to elevated temperatures (500?C800 K) leads to partial reduction of the ceria substrate with the formation of Ni²⁺ species that exists as NiO and/or Ce_1?xNi_xO_2?y. Interactions of nickel with the oxide substrate significantly reduce the density of occupied Ni 3d states near the Fermi level. The results of core-level photoemission and near-edge X-ray absorption fine structure point to weakly bound CO species on CeO₂(111) which are clearly distinguishable from the formation of chemisorbed carbonates. In the presence of Ni, a stronger interaction is observed with chemisorption of CO on the admetal. When the Ni is in contact with Ce⁺³ cations, CO dissociates on the surface at 300 K forming NiC_x compounds that may be involved in the formation of CH₄ at higher temperatures. At medium and large Ni coverages (>0.3 ML), the Ni/CeO₂(111) surfaces are able to catalyze the production of methane from CO and H₂, with an activity slightly higher than that of Ni(100) or Ni(111). On the other hand, at small coverages of Ni (<0.3 ML), the Ni/CeO₂(111) surfaces exhibit a very low activity for CO methanation but are very good catalysts for the water?Cgas shift reaction.     

A Review on the Effects of Supercritical Carbon Dioxide on Enzyme Activity

Different types of enzymes such as lipases, several phosphatases, dehydrogenases, oxidases, amylases and others are well suited for the reactions in SC-CO₂. The stability and the activity of enzymes exposed to carbon dioxide under high pressure depend on enzyme species, water content in the solution and on the pressure and temperature of the reaction system. The three-dimensional structure of enzymes may be significantly altered under extreme conditions, causing their denaturation and consequent loss of activity. If the conditions are less adverse, the protein structure may be largely retained. Minor structural changes may induce an alternative active protein state with altered enzyme activity, specificity and stability.     

Hydroisomerization of Fischer�CTropsch Wax on Pt/AlSBA-15 and Pt/SAPO-11 Catalysts

A Pt/AlSBA-15 catalyst was investigated in the selective isomerisation of Fischer?CTropsch wax, which type of catalyst have not been studied in detail in this reaction system yet. Its hydroconversion activity was compared with that of the Pt/SAPO-11 catalyst. Based on the results it was concluded that the selective isomerization of the Fischer?CTropsch wax can be a new application of the Pt/AlSBA-15 catalyst.     

Process Optimisation of In Situ H2 Generation From Ammonia Using Ni on Alumina Coated Cordierite Monoliths

A catalyst of Ni supported on alumina coated monolith has been prepared, characterized and tested in NH₃ decomposition. The characterization of the catalyst by XPS and TPR showed that there is no formation of aluminates after catalyst use. It is studied the effect of the space velocity, by varying the feed flow rate and the catalyst??s length. Some evidences are shown about the reaction inhibition by produced H₂ and about the reasons for the better performance of the monolith than packed bed catalyst.     

Comparison of the Determination of Eight Cholesterol Oxides in Dry�CCured Shoulder by GC�CFID, GC�CMS, and GC Tandem Mass Spectrometry

The analysis of eight cholesterol oxidation products: 7α–hydroxycholesterol, 7β–hydroxycholesterol, α–epoxycholesterol, β–epoxycholesterol, 20α–hydroxycholesterol, cholestanetriol, 25–hydroxycholesterol, and 7–ketocholesterol in dry–cured shoulder was carried out. The extraction of lipids was performed by using the Bligh and Dyer method (1959). Interferences were removed by solid-phase extraction (SPE) in two steps with silica and aminipropylsilica SPE columns. The separation of the eight cholesterol oxidation products was done by gas chromatography, and the detection was performed by flame ionization detection (FID) and mass spectrometry (MS). The results obtained from the use of both systems of detection were compared. The results showed that gas chromatography-mass spectrometry (GC–MS) was the most suitable technique to obtain reliable quantitative data, and significant differences (p < 0.05) between FID and MS determining 7α–hydroxycholesterol, 20α–hydroxycholesterol, and 25–hydroxycholesterol were observed. For the determination of cholesterol oxidation products, it was necessary to apply gas chromatography-tandem mass spectrometry to increase the sensitivity and to avoid interference from other compounds.     

Urban scene understanding from aerial and ground LIDAR data

We present a framework to segment cultural and natural features, given 3D aerial scans of a large urban area, and (optionally) registered ground level scans of the same area. This system provides a primary step to achieve the ultimate goal of detecting every object from a large number of varied categories, from antenna to power plants. Our framework first identifies local patches of the ground surface and roofs of buildings. This is accomplished by tensor voting that infers surface orientation from neighboring regions as well as local 3D points. We then group adjacent planar surfaces with consistent pose to find surface segments and classify them as either the terrain or roofs of buildings. The same approach is also applied to delineate vertical faces of buildings, as well as free-standing vertical structures such as fences. The inferred large structures are then used as geometric context to segment linear structures, such as power lines, and structures attached to walls and roofs from remaining unclassified 3D points in the scene. We demonstrate our system on real LIDAR datasets acquired from typical urban regions with areas of a few square kilometers each, and provide a quantitative analysis of performance using externally provided ground truth.     

Native and Biotechnologically Engineered Plant Proteases with Industrial Applications

Proteases occupy the most relevant position among industrial enzymes. Plant proteases have been used in medicine, detergent manufacturing, and food science for many years, but their production is diminishing in favor of those of microbial origin because lower production costs. Papain, bromelain, and ficin are the most frequently employed plant proteases, although new proteases with new and more appealing physicochemical properties for industry are still emerging. DNA technology and genetic engineering shall play, without a doubt, an important role for the production of these proteases at the industrial level. The present review focuses on the applications of traditional plant proteases as well as new proteases discovered during the last 20 years, some of which have already been genetically engineered either to increase production or to strengthen some of their physicochemical properties. The review also refers to the protease classification, action pattern, and main characteristics.