Effect of grinding wheel on the dynamic performance of high-speed spindle system with an improved FE model

The grinding wheel is a key factor which should be considered in the process of predicting the dynamic performance of the high-speed spindle system. Currently, most research is mainly focuses on shaft and bearing using Timoshenko’s beam and Jones’ bearing model. In this research, considering the effect of grinding wheel on the dynamic behavior of the high-speed motorized spindle system, a dynamic model of spindle system has been established by utilizing the finite element method (FEM). The model is improved by optimizing the relevant parameters of spindle system and validated by measuring FRF using impact hammer test. The reported results are well matched (maximum error is 5 %). Using the improved model, the effect of grinding wheel on the critical speeds, mode shapes, centrifugal force and gyroscopic effects of spindle system are analyzed. In addition, the impact of different diameters, materials and fixed methods of grinding wheel on the dynamic property of spindle system are also carried out. The result shows the affect of grinding wheel and design guideline of the spindle and grinding wheel

A thermodynamics coupled modeling approach for analysis and improvement of high-speed motorized spindle system

The performance of high-speed motorized spindle system is greatly affected by spindle’s thermal and dynamic behavior. So, it is very important to predict these properties in design stage of spindle system. However, the thermal and dynamic behaviour reacts upon each other for the high rotational speed and complex structure of the spindle system. To control and optimize the dynamic behaviour and the temperature rise of spindle, this paper developed a dynamic and thermal coupled model of the spindle system by using the finite element method (FEM). The shaft and rotor were modeled as Timoshenko’s beam, the rational interference fit between shaft and rotor was treated as mass-spring combinations, the bearings were modeled as nonlinear spring element. The thermal analysis procedure contained the calculation of heat generation and confirmation of boundary condition. The accuracy of this coupled model was validated by corresponding experiments. With this coupled model, the thermal and dynamic performance of the spindle system was studied. The effects of rotational speed, axial preload and material of bearing and the diameter of shaft on thermal and dynamic behavior were analyzed. The spindle system was optimized with the result of analyses above. After optimization, the temperature rise of spindle system falls significantly to 24.5°C, which was 30.2°C before, while the dynamic stiffness at working speed increases from 156 to 197 N/μm

Large-scale soil organic carbon mapping based on multivariate modelling: The case of grasslands on the Loess Plateau

The Loess Plateau is considered one of the world's regions with severe soil erosion. Grasslands are widely distributed on the Loess Plateau, accounting for approximately 40% of the total area. Soil organic carbon (SOC) plays an important role in the terrestrial carbon cycle in this region. We compiled more than 1,000 measurements of plant biomass and SOC content derived from 223 field studies of grasslands on the Loess Plateau. Combined with meteorological factors (precipitation and air temperature) and the photosynthetically active radiation factor, the topsoil SOC contents of grasslands were predicted using the random forest (RF) regression algorithm. Predicted grassland SOC content (1.70-40.34gkg(-1)) decreased from the southeast to the northwest of the Loess Plateau, with approximately 1/5 of the grassland exhibiting values lower than 4gkg(-1). Observed SOC content was positively correlated with observed plant biomass, and for predicted values, this correlation was strong in the desert steppe and the steppe desert of rocky mountains. Air temperature was the most important factor affecting SOC contents in the RF model. Moreover, the residual error of observations and predictions increased as the grazing intensity varied from none to very severe in the temperate desert steppe, and this RF model may not perform well in plains. The use of the RF model for SOC prediction in Loess Plateau grasslands provides a reference for C storage studies in arid and semi-arid regions, and aboveground biomass and temperature should receive more attention due to increasing C sequestration

Estimates of carbon storage in grassland ecosystems on the Loess Plateau

Grassland ecosystems play an important role in the carbon (C) balance of arid and semi-arid regions. These ecosystems provide C for grass growth and soil microbial activities and represent one of the main sources of atmospheric C. In this study, we estimated the C density and storage of 223 sampling sites in grassland ecosystems on the Loess Plateau using elevation, vegetation indexes, precipitation, air temperature, day and night land surface temperature (LSTd and LSTn, respectively), evapotranspiration (ET), percent tree cover and the non-vegetated area to build decision regression tree and generalized linear regression models (GLMs). The results showed that the C density decreased from south to north and ranged from 0.22 to 29.29 kg C/m(2). The average amount of C stored in the ecosystems was 1.46 Pg. The typical steppe and forest steppe stored the most C, and the steppe desert stored the least. The soil (0-1 m) stored most of the organic C, accounting for > 90%, and the belowground biomass (BGB) contained > 3 times the amount of C as the aboveground biomass (AGB). This study provides reference information for the loss of C and associated mitigation strategies on the Loess Plateau

Mycotoxigenic potentials of Fusarium species in various culture matrices revealed by mycotoxin profiling

In this study, twenty of the most common Fusarium species were molecularly characterized and inoculated on potato dextrose agar (PDA), rice and maize medium, where thirty three targeted mycotoxins, which might be the secondary metabolites of the identified fungal species, were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Statistical analysis was performed with principal component analysis (PCA) to characterize the mycotoxin profiles for the twenty fungi, suggesting that these fungi species could be discriminated and divided into three groups as follows. Group I, the fusaric acid producers, were defined into two subgroups, namely subgroup I as producers of fusaric acid and fumonisins, comprising of F. proliferatum, F. verticillioides, F. fujikuroi and F. solani, and subgroup II considered to only produce fusaric acid, including F. temperatum, F. subglutinans, F. musae, F. tricinctum, F. oxysporum, F. equiseti, F. sacchari, F. concentricum, F. andiyazi. Group II, as type A trichothecenes producers, included F. langsethiae, F. sporotrichioides, F. polyphialidicum, while Group III were found to mainly produce type B trichothecenes, comprising of F. culmorum, F. poae, F. meridionale and F. graminearum. A comprehensive picture, which presents the mycotoxin-producing patterns by the selected fungal species in various matrices, is obtained for the first time, and thus from an application point of view, provides key information to explore mycotoxigenic potentials of Fusarium species and forecast the Fusarium infestation/mycotoxins contamination

Carbon in Chinese grasslands : meta-analysis and theory of grazing effects

Unidad de excelencia María de Maeztu CEX2019-000940-MGlobally, livestock grazing is an important management factor influencing soil degradation, soil health and carbon (C) stocks of grassland ecosystems. However, the effects of grassland types, grazing intensity and grazing duration on C stocks are unclear across large geographic scales. To provide a more comprehensive assessment of how grazing drives ecosystem C stocks in grasslands, we compiled and analyzed data from 306 studies featuring four grassland types across China: desert steppes, typical steppes, meadow steppes and alpine steppes. Light grazing was the best management practice for desert steppes (< 2 sheep ha−1) and typical steppes (3 to 4 sheep ha−1), whereas medium grazing pressure was optimal for meadow steppes (5 to 6 sheep ha−1) and alpine steppes (7 to 8 sheep ha−1) leading to the highest ecosystem C stocks under grazing. Plant biomass (desert steppes) and soil C stocks (meadow steppes) increased under light or medium grazing, confirming the 'intermediate disturbance hypothesis'. Heavy grazing decreased all C stocks regardless of grassland ecosystem types, approximately 1.4 Mg ha−1 per year for the whole ecosystem. The regrowth and regeneration of grasslands in response to grazing intensity (i.e., grazing optimization) depended on grassland types and grazing duration. In conclusion, grassland grazing is a double-edged sword. On the one hand, proper management (light or medium grazing) can maintain and even increase C stocks above- and belowground, and increase the harvested livestock products from grasslands. On the other hand, human-induced overgrazing can lead to rapid degradation of vegetation and soils, resulting in significant carbon loss and requiring long-term recovery. Grazing regimes (i.e., intensity and duration applied) must consider specific grassland characteristics to ensure stable productivity rates and optimal impacts on ecosystem C stocks

Materials, Devices and Systems of Soft Bioelectronics for Precision Therapy

The potential applications of soft bioelectronics in biomedical research and clinical trials have inspired a great deal of research interest in the past decade. While there has been significant amount of work in the fabrication and characterization of soft and stretchable sensors for monitoring of physical conditions and vital signs of human body, the development of soft bioelectronics based medical treatment and intervention systems has just begun. In addition to health monitoring, active treatments are essential for disease control in the healthcare domain, and medical therapy and surgery realized by sophisticated soft bioelectronic systems are better demonstrations of their utility in healthcare. In this Research News, we summarize recent key research achievements in soft bioelectronics enabled precision therapy, with emphasis on drug delivery, therapeutic and surgical mechanisms and tools enabled by integrated systems. Challenges in technology development and prospects for commercialization are also discussed

Materials, Devices and Systems of Soft Bioelectronics for Precision Therapy

The potential applications of soft bioelectronics in biomedical research and clinical trials have inspired a great deal of research interest in the past decade. While there has been significant amount of work in the fabrication and characterization of soft and stretchable sensors for monitoring of physical conditions and vital signs of human body, the development of soft bioelectronics based medical treatment and intervention systems has just begun. In addition to health monitoring, active treatments are essential for disease control in the healthcare domain, and medical therapy and surgery realized by sophisticated soft bioelectronic systems are better demonstrations of their utility in healthcare. In this Research News, we summarize recent key research achievements in soft bioelectronics enabled precision therapy, with emphasis on drug delivery, therapeutic and surgical mechanisms and tools enabled by integrated systems. Challenges in technology development and prospects for commercialization are also discussed

Construct freeform surface directly in an initial layout of an off-axis reflective image system by seed curve extension and simulated annealing algorithm

In this paper, a method of how to construct a freeform surface directly in an off-axis reflective image system is proposed. The method includes both the seed curve extension algorithm and simulated annealing algorithm. Firstly, the sample points on the unkown freeform surface were be obtained quickly by the seed curve extension algorithm. Then the continuity of the freeform surface is evaluated by calculating the angle between the normal vectors at the adjacent sample points. At last the freeform surface was fitted to an extended polynomials using simulated annealing algorithm. The method is employed to construct a freeform surface directly which is used as a primary mirror in an initial layout of an off-axis two-mirror system