Design, Meshing Characteristics and Stress Analysis of Cylindrical Gears with Curvilinear Tooth Profile

Curvilinear tooth gears are commonly produced on a face milling cutter and a hob cutter. However, this paper proposes a kind of curvilinear tooth gear which is processed by a parallel linkage with a single blade cutter. For the purpose of identifying the meshing and contact characteristics of curvilinear tooth gears, the paper covers the following: (i) equations of tooth surfaces are deduced from the meshing theory, and a parameterized geometric model is developed by applying computer graphics; (ii) an investigation into meshing characteristics for an ideal assembly condition is performed, and an instantaneous contact curve is obtained from the developed tooth contact algorithm; (iii) based on the application of the finite element method, the evolution of contact and bending stresses during the cycle of meshing and between different arc radii of the curvilinear tooth is illustrated by numerical examples. The result shows that curvilinear tooth gear drives possess a higher contact ratio, severe contact stresses on the top edge of the tooth, and lower contact and bending stresses between appropriate arc radii, hence they may replace spur gears in the future

Motor Noise and Vibration Test Research

Some factors, such as friction, vibration, and so on, can result in the fault and abnormal noise in the motor. Based on the detection and analysis of noise and vibration, we can identify and eliminate the faults of the motor. This is helpful not only to ensure the completion of production tasks, but also to prevent accidents. In this paper, we briefly introduce the motor noise generation principle. A laptop computer and LabVIEW software are used to design the experiment system to detect and analysis the noise and vibration of motor. External microphone and computer with sound card constitute noise detection system hardware. Vibration sensor and the data acquisition card constitute vibration detection system hardware. LabVIEW software combined with FFT analysis is used to realize the noise signal acquisition, recording and spectral analysis. Detecting and analyzing the noise of the permanent magnet DC motor and three-phase asynchronous motor proves that the motor noise and vibration detecting experimental platform is fully meet the requirements of motor test and research. This detection and analysis system has a good man-machine interface and strong operability

Dynamic modeling and analysis of oscillatory bioreactors

Dynamic modeling of bioreactors is a challenging problem. The complexity of first principle models also make model validation and analysis very difficult and model-based controller design practically intractable. This thesis has focused on finding an effective tool for model dynamic analysis, construction of low-dimension model and simple and effective controller design. The validity of a biochemical reactor model often is evaluated by comparing transient responses to experimental data. Dynamic simulation can be rather inefficient and ineffective for analyzing bioreactor model. Bifurcation analysis is found to be a powerful tool for obtaining a more efficient and complete characterization of the model behavior. Dynamic behaviors of three low-dimension continuous bioreactor models consisting of a small number of ordinary differential equations are investigated. Several important features, as well as potential limitations, that are difficult to ascertain via dynamic simulation are disclosed through the bifurcation analysis. Bifurcation analysis is also successfully used for analysis and validation of more complex population balance models for yeast cultures. Saccharomyces cerevisiae exhibits sustained oscillations over a wide range of operating conditions when produced in a continuous bioreactor. Transient cell population balance models consist of nonlinear partial differential-integro equations. An accurate discretized approximation which typically requires a large number of nonlinear ordinary differential equations is not well suited for dynamic analysis and controller design purpose. Proper orthogonal decomposition is used to construct nonlinear reduced-order models from spatiotemporal data sets obtained via simulations of an accurate discretized yeast cell population model. The short-term and long-term behaviors of the reduced-order models are evaluated by comparison to the full-order model. Dynamic simulation and bifurcation analysis results demonstrate that reduced-order models with a comparatively small number of differential equations yield accurate predictions over a wide range of operating conditions. Feedback linearizing control of the yeast bioreactor is also studied. The controller design is based on a low dimensional moment representation of the PBE model. Satisfactory oscillation attenuation results have been achieved. The performance of nonlinear controllers using different input/output variable pairings is also investigated

Relationship between intrinsic viscosity, thermal, and retrogradation properties of amylose and amylopectin

The relationships between intrinsic viscosity and some properties of amylose and amylopectin were investigated. The intrinsic viscosities determined by Ubbelohde viscometer for rice, maize, wrinkled pea and potato amyloses were 46.28 ± 0.30, 123.94 ± 0.62, 136.82 ± 0.70, and 167.00 ± 1.10 ml/g, respectively; and the intrinsic viscosities of rice, maize, wrinkled pea and potato amylopectins were 77.28 ± 0.90, 154.50 ± 1.10, 162.56 ± 1.20 and 178.00 ± 1.00 ml/g, respectively. The thermal and retrogradation properties of amylose and amylopectin were investigated by differential scanning calorimeter (DSC). Results showed that the thermal enthalpy (ΔHg) was positively correlated with intrinsic viscosity, however, the onset and peak temperatures were not related to the intrinsic viscosity. The amylose and amylopectin retrogradation enthalpy values were negatively related to intrinsic viscosity, while the onset and peak temperature values of retrograded amylose and amylopectin were not related to the intrinsic viscosity during storage (except one-day storage). Furthermore, the onset and peak temperatures and retrogradation enthalpy of amylose and amylopectin changed slowly during storage at 4°C

Modeling of gas generation from the Cameo coal zone in the Piceance Basin, Colorado

The gas generative potential of the Cretaceous Cameo coal in the Piceance Basin, northwestern Colorado, was evaluated quantitatively by sealed gold tube pyrolysis. The H/C and O/C elemental ratios show that pyrolyzed Cameo coal samples follow the Van Krevelen humic coal evolution pathway, reasonably simulating natural coal maturation. Kinetic parameters (activation energy and frequency factor) for gas generation and vitrinite reflectance (Ro) changes were calculated from pyrolysis data. Experimental Ro results from this study are not adequately predicted by published Ro kinetics and indicate the necessity of deriving basin-specific kinetic parameters when building predictive basin models. Using derived kinetics for Ro evolution and gas generation, basin modeling was completed for 57 wells across the Piceance Basin, which enabled the mapping of coal-rank and coalbed gas potential. Quantities of methane generated at approximately 1.2% Ro are about 300 standard cubic feet per ton (scf/ton) and more than 2500 scf/ton (in-situ dry-ash-free coal) at Ro values reaching 1.9%. Gases generated in both low- and high-maturity coals are less wet, whereas the wetter gas is expected where Ro is approximately 1.4–1.5%. As controlled by regional coal rank and net coal thickness, the largest in-place coalbed gas resources are located in the central part of the basin, where predicted volumes exceed 150 bcf/mi^2, excluding gases in tight sands

Application of complicated floating-bed for pre-reservoir non-point sources pollution control project

Proceedings of the Seventh International Conference on Hydroscience and Engineering, Philadelphia, PA, September 2006. http://hdl.handle.net/1860/732The complicated floating-bed technique is an effective method for the non-point sources(NPS) pollution control. Suitable aquatic plants are selected and used to build the complicated floating-beds. They were applied for controlling NPS pollution in the pre-reservoir project in Lake Tai basin of China. Colocasia esculenta(Linn.) Schott, Sagittaria sagittifolia Linn, Eleocharis dulcis Trin.ex Henschel,Oenantha javanica(Blume)DC, Ipomoea aquatica Forst, and Ganna generalis Balier are the common aquatic vegetable, ornamental flower in the area of Taihu lake. The removal rate of nitrogen and phosphorus by those plants at light eutrophicated level in summer and autumn was studied. They were selected as floating-bed plants for pre- reservoir project. This paper proves that the Ipomoea aquatica Forst has better removal effect on total phosphorous (TP)(30-81%) and Colocasia esculenta(Linn.) Schott on total nitrogen (TN)(62-67%). The floating-bed was applied in the pre-reservoir non-point pollution control project in the plain river network at Yixing County in Lake Tai basin. The effect of purification was very obvious. The complicated floating-bed was more effective than the previous plane floating-bed in the removal of TN and TP. This study can provide the useful information in the non-point sources pollution control and the ecological rehabilitation of rivers and lakes in genera

How Does Targeted Poverty Alleviation Policy Influence Residents' Perceptions of Rural Living Conditions? A Study of 16 Villages in Gansu Province, Northwest China

Rural living conditions (RLCs) in China are influential on the overall development and stability of regions, particularly for populations in distant poverty-stricken villages. This paper takes 16 villages of Chedao town in Gansu province, Northwest China (NWC) as our case study. Using data from the Poverty Alleviation and Assistance (PAA) project launched by Lanzhou University in June 2017, and the perceptions of residents of Chedao, we pinpoint RLC changes in the targeted poverty alleviation (TPA) process. The three main results show that: (1) From the residents' perceptions, the impact of alleviation measures on RLC is mainly reflected in improved housing conditions, infrastructure, and public services. We find no significant effect on cultural conditions. However, eco-environmental conditions have obviously weakened. (2) Housing size, accessibility, distance to shops, and safe drinking water are the most significant factors in housing conditions, infrastructure, public services, and eco-environmental conditions, respectively. (3) Out of the different levels of rural poverty households (RPHs), severe rurality villages are more strongly aware of the positive changes in RLC than residents of mild rurality villages. Moreover, in residents' view, housing conditions are most improved in severe rurality villages, infrastructure is most improved in moderate rurality villages, and public services are most improved in mild rurality villages. Eco-environmental conditions worsen across all levels. Our findings shed light on the perceptions of residents on changes occurring in rural living conditions, and provide a basis for subsequent studies of RLC in Northwest China