Flutter Control of a Two-dimensional Airfoil Using Wash-out Filter Technique

The wash-out filter （WF） technique is used to control the flutter of a two dimensional airfoil with cubic non-linearity in incompressible flow. Firstly, Hopf bifurcation theory is used to determine the point at which the nonlinear controller is introduced. The system is then transformed into Jordan canonical form, based on analysis of linearized eigenvalues of the system. Secondly, for the introduced WF controller, the linear control gain is determined according to Hopf bifurcation condition. The sym- bolic computing program of normal form direct method （NFDM） is also used to obtain the normal form of the controlled system. The non-linear control gain can be determined based on the relation of the type of bifurcation and the parameters of the normal form, to transform sub-critical Hopf bifurcation to be su- per-critical one. Lastly, numerical simulations are used to certify the validity of theoretical analysis, in which the amplitude of flutter or limit cycle of the controlled system is reduced greatly, comparing to the original system.

Two-dimensional gain cross-grating based on spatial modulation of active Raman gain

Based on the spatial modulation of active Raman gain,a two-dimensional gain cross-grating is theoretically proposed.As the probe field propagates along the z direction and passes through the intersectant region of the two orthogonal standingwave fields in the x-y plane,it can be effectively diffracted into the high-order directions,and the zero-order diffraction intensity is amplified at the same time.In comparison with the two-dimensional electromagnetically induced cross-grating based on electromagnetically induced transparency,the two-dimensional gain cross-grating has much higher diffraction intensities in the first-order and the high-order directions.Hence,it is more suitable to be utilized as all-optical switching and routing in optical networking and communication.

A novel method for sculptured surface subdivision

In this work, a novel method for sculptured surface subdivision to improve the machinery＇s ability and efficiency in 5-axis CNC machining complex surface is introduced. The method subdivides automatically a monolithic convex or concave or simultaneously complex sculptured surface into a number of surface patches and achieves the goal of similar normal directions and small difference between the curvatures in every patch by using weight fuzzy cluster algorithm which takes the curvatures and normal vectors of the sculptured surface into account simultaneously. The inclination angle variation between every two Cutter Contact Points （CC Points） is decreased in every patch to avoid large-angle rotation of tool to save machining time when a flat-end mill is used. This work contributes to automating 5-axis CNC tool path generation for sculptured part machining and forming a foundation for further research.

Development and comparison of local solar split models on the example ofCentral Europe

Solar radiation influences many and diverse fields like energy generation, agriculture and building operation.Hence, simulation models in these fields often rely on precise information about solar radiation. Measurementsare often restricted to global irradiance, whereby measurements of its single components, direct and diffuseirradiance, are sparse. However, information on both, the direct and diffuse irradiance, is necessary forsimulation models to work reliably. In this study, solar separation models are developed using 10-min trainingdata from two different locations in Austria. Direct horizontal irradiance is predicted via regressing the directfraction using several objective functions. The models are first trained on a data set including data from bothlocations, and evaluated regarding root mean squared deviation (RMSD), mean bias deviation (MBD), andcoefficient of determination (R2) on measured and estimated direct normal irradiance. The two best performing models are then selected for further analysis. This analysis comprises of an evaluation of the models per season,transferability of trained modes between two locations in Austria, a transferability and generalisability studyconducted for four more locations in Central Europe, and a comparison with the trusted Engerer model. Thesolar separation model with polynomial terms up to order three and Ridge regularisation outperforms thesecond model based a logistic term in combination with mixed quadratic terms as well as the Engerer model.

Experimental Studies on the Thermal Performance of a Parabolic Dish Solar Receiver with the Heat Transfer Fluids SiC+ Water Nano Fluid and Water

An experimental investigation has been carried out with aa point focusing dish reflector of 12 square meters aperture area, exposed to the average direct normal irradiations of 810 W/m^2. This work focuses on enhancinge the energy and exergy efficiencies of the cavity receiver by minimizing the temperature difference between the wall and heat transfer fluids. Two heat transfer fluids Water and SiC + water nano fluid have been prepared from 50 nm particle size and 1% of volume fraction, and experimented separately for the flow rates of 0.2 lpm to 0.6 lpm with an interval of 0.1 lpm. The enhanced thermal conductivity of nano fluid is 0.800115 W/mK with the k_(eff)/k_b ratio of 1.1759 determined by using the Koo and Kleinstreuer correlation. The maximum attained energy and exergy efficiencies are 29.14% and 24.82% for water, and 32.91% and 39.83% for SiC+water nano fluid. The nano fluid exhibits enhanced energy and exergy efficiency of 12.94% and 60.48% than that of water at the flow rate of 0.5 lpm. The result shows that the system with SiC+Water produces higher exergy efficiency as compared to energy efficiency; in the case of water alone, the energy efficiency is higher than exergy efficiency.

Automated extraction of corn leaf points from unorganized terrestrial LiDAR point clouds

Terrestrial LiDAR data can be used to extract accurate structure parameters of corn plant and canopy,such as leaf area,leaf distribution,and 3D model.The first step of these applications is to extract corn leaf points from unorganized LiDAR point clouds.This paper focused on an automated extraction algorithm for identifying the points returning on corn leaf from massive,unorganized LiDAR point clouds.In order to mine the distinct geometry of corn leaves and stalk,the Difference of Normal(DoN)method was proposed to extract corn leaf points.Firstly,the normals of corn leaf surface for all points were estimated on multiple scales.Secondly,the directional ambiguity of the normals was eliminated to obtain the same normal direction for the same leaf distribution.Finally,the DoN was computed and the computed DoN results on the optimal scale were used to extract leave points.The quantitative accuracy assessment showed that the overall accuracy was 94.10%,commission error was 5.89%,and omission error was 18.65%.The results indicate that the proposed method is effective and the corn leaf points can be extracted automatically from massive,unorganized terrestrial LiDAR point clouds using the proposed DoN method.

Viability of a concentrated solar power system in a low sun belt prefecture

Concentrating solar power(CSP)is considered as a comparatively economical,more efficient,and large capacity type of renewable energy technology.However,CSP generation is found restricted only to high solar radiation belt and installed where high direct normal irradiance is available.This paper examines the viability of the adoption of the CSP system in a low sun belt region with a lower direct normal irradiance(DNI).Various critical analyses and plant economics have been evaluated with a lesser DNI state.The obtained results out of the designed system,subjected to low DNI are not found below par,but comparable to some extent with the performance results of such CSP plants at a higher DNI.The analysis indicates that incorporation of the thermal energy storage reduces the levelized cost of energy(LCOE)and augments the plant capacity factor.The capacity factor,the plant efficiency,and the LCOE are found to be 32.50%,17.56%,and 0.1952$/kWh,respectively.

Non-uniformity effects of the inter-foil distance on GEM detector performance

The non-uniformity effect of the inter-foil distance has been studied using a gaseous electron multiplication（GEM） detector with sensitive area of 50mm×50mm. A gradient of the inter-foil distance is introduced by using spacers with different heights at the two ends of the foil gap. While the cluster size and the intrinsic spatial resolution show insignificant dependence on the inter-foil distance, the gain exhibits an approximately linear dependence on the inter-foil distance. From the slope, a quantitative relationship between the change of the inter-foil distance and the change of the gain is derived, which can be used as a method to evaluate the non-uniformity of the foil gap in the application of large-area GEM detectors.