Ecological network analysis of urban metabolism based on input-output table

AbstractWith the increasing metabolic throughput, the city as a giant organism causes resource consumption and environmental pollution, which become a bottleneck for urban ecological systems to develop healthily. Using Beijing as an example, we adopt the material flow method to account for resource consumption and waste emissions during the urban metabolic process. Combined with a monetary input-output table (MIOT) for Beijing in 2002, we compile a physical input-output table (PIOT) and build an ecological network model of the urban metabolic system including 45 nodes and 1761 network paths. Using flow analysis and utility analysis methods of ecological network, we can study the complex relationships and hierarchical structure to reveal the crux that results in the disorder of the urban metabolic process; thus, it can provide a scientific basis for healthy development of urban ecological systems

Structure-Activity Relationship Analysis of the Thermal Stabilities of Nitroaromatic Compounds Following Different Decomposition Mechanisms

The decomposition behavior of energetic materi- als is very important for the safety problems concerning their production, transportation, use and storage, because molecular decomposition is intimately connected to their explosive properties. Nitroaromatic compounds, particularly nitrobenzene derivatives, are often considered as prototypi- cal energetic molecules, and some of them are commonly used as high explosives. Quantitative structure-activity rela- tionship (QSAR) represents a potential tool for predicting the thermal stability properties of energetic materials. But it is reported that constructing general reliable models to predict their stability and their potential explosive proper- ties is a very difficult task. In this work, we make our efforts to investigate the relationship between the molecular structures and corresponding thermal stabilities of 77 nitro- benzene derivatives with various substituent functional groups (in ortho , meta and/or para positions). The pro- posed best MLR model, developed by the new software QSARINS, based on Genetic Algorithm for variable selection and with various validation tools, is robust, stable and pre- dictive with R 2 of 0.86, Q LOO 2 of 0.79 and CCC of 0.90. The results indicated that, though difficult, it is possible to build predictive, externally validated QSAR models to estimate the thermal stability of nitroaromatic compound

Non-bar, anopticalcalibrationsystemforfive-axisCNCmachinetools

Five-axisCNCmachinetoolscomprisethreelinearaxesandtworotaryaxes,enablingthefabricationof complexworkpieces,suchasdies,turboblades,andcams.Improvedmeasurementmethodsare continuallybeingresearchedtoincreasetheaccuracyoffive-axisCNCmachinetools.Thispaper presentsanovelopticalcalibrationsystem,called non-bar, withnolinkagebars.Thesystemcomprises a masterdetectormodule,aballlensmodule,andasignalmodule.Theproposedmeasurementsystem was implementedaccordingtoISO/CD10791-6tomeasureA-type,B-type,andC-typefive-axisCNC machinetoolsfromthreedifferentmanufacturers.Theresultsdemonstratethattheproposed non-bar measurementschemeprovideshighaccuracy,highreproducibility,andsimultaneousmulti-axis measurement