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261.
A methodology for systematic geometric error compensation in five-axis machine tools 总被引:8,自引:8,他引:0
Abdul Wahid Khan Wuyi Chen 《The International Journal of Advanced Manufacturing Technology》2011,53(5-8):615-628
To enhance the accuracy, an efficient methodology was developed and described for systematic geometric error correction and their compensation in five-axis machine tools. The methodology is capable of compensating the overall effect of all position-dependent and position-independent errors which contribute to volumetric workspace. It was implemented on a five-axis grinding machine for error compensation and for the check of its effectiveness. Error compensation algorithm was designed, and a routine was written in Matlab software. The developed technique and software are based on an error table which interprets the function of axis through cubic spline technique and synthesis modeling of a machine tool. Recursive compensation methodology was used to remove the machine errors from the actual tool path and inverse technique was implemented to find the corrected positions of prismatic and rotary joints. Moreover, it can convert the corrected tool paths into practical compensated NC codes. The generated, corrected and modified NC codes directly fed to the controller of a five-axis machine tool. Validation of the technique was preceded by repeated experimentation of measurement and through machining of typical standard workpieces with some additional specific features. Experimental results exhibit effective compensation and remarkable improvement in the parametric and volumetric-workspace accuracy of the five-axis machine tool. 相似文献
262.
Mohd Ragib Badaruddin Muhamad Rasat Muhamad Saadah Abdul Rahman 《Thin solid films》2011,519(15):5082-5085
In this work, Silicon Carbon Nitride (Si-C-N) thin films were deposited by Hot Wire Chemical Vapour Deposition (HWCVD) technique from a gas mixture of silane (SiH4), methane (CH4) and nitrogen (N2). Six sets of Si-C-N thin films were produced and studied. The component gas flow rate ratio (SiH4:CH4:N2) was kept constant for all film samples. The total gas flow-rate (SiH4 + CH4 + N2) was changed for each set of films resulting in different total gas pressure which represented the deposition pressure for each of these films ranging from 40 to 100 Pa. The effects of deposition pressure on the chemical bonding, elemental composition and optical properties of the Si-C-N were studied using Fourier transform infrared (FTIR) spectroscopy, Auger Electron Spectroscopy (AES) and optical transmission spectroscopy respectively. This work shows that the films are silicon rich and multi-phase in structure showing significant presence of hydrogenated amorphous silicon (a-Si:H) phase, amorphous silicon carbide (a-SiC), and amorphous silicon nitride (a-SiN) phases with Si-C being the most dominant. Below 85 Pa, carbon content is low, and the films are more a-Si:H like. At 85 Pa and above, the films become more Si-C like as carbon content is much higher and carbon incorporation influences the optical properties of the films. The properties clearly indicated that the films underwent a transition between two dominant phases and were dependent on pressure. 相似文献
263.
264.
Woven hybrid composites: Tensile and flexural properties of oil palm-woven jute fibres based epoxy composites 总被引:1,自引:0,他引:1
M. JawaidH.P.S. Abdul Khalil A. Abu Bakar 《Materials Science and Engineering: A》2011,528(15):5190-5195
In this research, tensile and flexural performance of tri layer oil palm empty fruit bunches (EFB)/woven jute (Jw) fibre reinforced epoxy hybrid composites subjected to layering pattern has been experimentally investigated. Sandwich composites were fabricated by hand lay-up technique in a mould and cured with 105 °C temperatures for 1 h by using hot press. Pure EFB and woven jute composites were also fabricate for comparison purpose. Results showed that tensile and flexural properties of pure EFB composite can be improved by hybridization with woven jute fibre as extreme woven jute fibre mat. It was found that tensile and flexural properties of hybrid composite is higher than that of EFB composite but less than woven jute composite. Statistical analysis of composites done by ANOVA-one way, it showed significant differences between the results obtained. The fracture surface morphology of the tensile samples of the hybrid composites was performed by using scanning electron microscopy. 相似文献
265.
K. C. Amanul Alam Rifat Ara Rouf Bidyut Baran Saha M. Abdul Hakim khan Francis Meunier 《传热工程》2016,37(7-8):640-649
This study investigates the performance of an adsorption chiller driven by thermal heat collected from solar collectors’ panels with heat storage. The heat is reserved in a storage tank and the reserved heat is used to drive the adsorption chiller. The investigation was carried on the climatic conditions of Dhaka, Bangladesh. Heat transfer fluid goes from the collectors to the adsorption cooling unit, then from the adsorption cooling unit to the storage tank. It is seen that heat storage is more effective than direct solar coupling; however, it requires more collectors, depending on the size of the storage tank. The analysis shows that cycle time is one of the most influential parameters for the solar-driven adsorption cooling system. It is seen that the size of the collector can be reduced if the proper cycle time is adjusted. The analysis also revealed that the system with 22 collectors (each of 2.415 m2) along with 1000 s cycle time provides better performance for the base run conditions. It is also seen that the solar-driven adsorption chiller with heat storage works well beyond the sunset time. 相似文献
266.
Nondestructive in situ measurement of tomato fruits is essential to determine growing stages and to assist in automatic picking of fruits. This study evaluates the applicability of visible and near-infrared (Vis-NIR) spectroscopy for in situ determination of growing stages and harvest time of three cultivars of tomato fruits. A mobile fiber-type AgroSpec Vis-NIR spectrophotometer (Tec5 Co., Germany) with a spectral range of 350-2200 nm was used to measure tomato spectra in reflection mode. A new growing stage (GS) index defined as the ratio of the current growing age in days to the on-vine duration before harvest in days was proposed. After dividing spectra into a calibration set (70%) and an independent prediction set (30%), spectra in the calibration set were subjected to a partial least squares regression (PLSR) with leave-one-out cross-validation to establish calibration models relating GS to the spectra of tomato fruits. Separate models were developed for each tomato cultivar and compared with a general model that used combined spectra of all three cultivars. The results show that PLSR based on the new GS is successful and robust in predicting the growing stages and harvest time of tomato fruits. Validation of calibration models on the independent prediction set indicates that successful prediction of GS can be achieved using the three models developed separately for each cultivar with a coefficient of determination (R(2)) of 0.91-0.92, root mean square error of prediction (RMSEP) of 0.081-0.097, and residual prediction deviation (RPD) of 3.29-3.70. General calibration using the combined spectra produces good prediction performance, although less accurate than that for the three individual cultivar models. The analysis of regression coefficient plots resulting from PLSR analysis indicates consistent assignment of important wavelengths for individual cultivar spectra and combined spectra. It is concluded that the Vis-NIR PLSR based on GS index can be adopted successfully for in situ determination of growing stages and harvest time of on-vine tomato fruits, which allows for automatic picking of fruits by a horticultural robot. 相似文献
267.
Microwave dielectric ceramics in the Sr1−xCaxLa4Ti5O17 (0 ≤ x ≤ 1) composition series were prepared through a solid state mixed oxide route. All the compositions formed single phase ceramics within the detection limit of in-house X-ray diffraction when sintered in the temperature range 1450-1580 °C. Theoretical density and molar volume decreased due to the substitution of Ca2+ for Sr2+ which was associated with a decrease in the dielectric constant (?r) and temperature coefficient of resonant frequency (τf) but an increase in quality factor, Qfo. Optimum properties were achieved for Sr0.4Ca0.6La4Ti5O17 which exhibited, ?r ∼ 53.7, Qfo ∼ 11,532 GHz and τf ∼ −1.4 ppm/°C. 相似文献
268.
Su Kong Chong Boon Tong GohZarina Aspanut Muhamad Rasat MuhamadBinni Varghese Chorng Haur SowChang Fu Dee Saadah Abdul Rahman 《Thin solid films》2011,520(1):74-78
In this study, the fabrication of Si nanostructures by Au and SiH4 co-deposition technique using hot-wire chemical vapor deposition was demonstrated. A high deposition rate of 2.7 nm/s and a high density of silicon nanostructures with a diameter of about 140 nm were obtained at Ts of 250 °C. An increase in Ts led to a significant reduction in the size of the nanostructures. However, coalescence on the nanostructures was observed at Ts of 400 °C. The Si nanostructures exhibited a highly crystalline structure, which was induced by Au crystallites. The crystallite size and crystallinity of the Si nanostructures amplified with the increase in Ts. The presence of nanostructures enhanced the surface roughness of the samples and clearly reduced the reflection, especially in the visible region. 相似文献
269.
Maisara Othman Richard Ritikos Noor Hamizah Khanis Nur Maisarah Abdul RashidSaadah Abdul Rahman Siti Meriam Ab GaniMuhamad Rasat Muhamad 《Thin solid films》2011,519(15):4981-4986
Carbon nitride (CNx) thin films were deposited by radio frequency plasma enhanced chemical vapour deposition (rf PECVD) technique from a gas mixture of methane (CH4), hydrogen (H2) and nitrogen (N2). The effects of rf power on the structural properties of CNx thin films were discussed in this paper. It was found that rf power had significant effects on the growth rate, structural and morphological properties of the deposited films. The point of transition of the growth rate trend marked the equilibrium condition for primary and secondary reactions in growth kinetics of the film with respect to rf power. The films grown at this optimum rf power were most ordered in structure with high surface roughness and had the lowest N incorporation. This work showed that H etching effects and ion bombardment effects increase with increase in rf power and strongly influenced the structure of the CNx films. 相似文献
270.
The zero-equation turbulence model for indoor airflow applications proposed by Chen and Xu [4] has obtained immense popularity amongst the CFD practitioners in HVAC industry. A uniform turbulent intensity of 10% has been assumed in their model. In this paper, following the analogy of Chen and Xu [4] in deriving the coefficient of their zero-equation turbulence model (0.03874) which is indeed expressed as a function of turbulent intensity, the effect of turbulent intensity value assumed in the model towards the solution accuracy is investigated in this paper. Three indoor airflow cases, i.e. forced convection, natural convection and mixed convection problems are studied. It has been discovered that as the assumed uniform turbulent intensity Ti is reduced, the solution accuracy is significantly improved and the prediction comes closer to those of the two-equation standard k-? model, LES model as well as the experimental data. 相似文献