In an assembly, there are two ways to control the deviation of critical dimensions. One is by keeping the deviation of the critical dimension small by tightening manufacturing tolerances and controlling aging and environmental effects. This approach is traditional and expensive, as it requires tighter manufacturing tolerances and protection from aging and the environment. The second is by moving the nominal values of the non-critical dimensions to a less sensitive portion. This approach is very helpful in improving the quality with no additional cost. One can analyze any number of designs very early in the concept development stage of a project. After the concept design the cost-based optimal tolerances for the corresponding dimensions are allocated. The continuous ants colony algorithm, a kind of meta-heuristic approach, is used as an optimization tool for minimizing the critical dimension deviation and allocating the cost- based optimal tolerances. 相似文献
Wireless Networks - The rapid escalation of user traffic and service innovation has made the deployment of small cell base stations essential for eventually decreasing energy consumption in future... 相似文献
AbstractIn this study, stability, density, rheology, and thermal conductivity of the Multi-wall carbon nanotubes (MWCNTs) based PCM nanocomposites were experimentally investigated. The PCM OM08 has been selected for the air-conditioning application with a phase change temperature of 8–10?°C. PCM nanocomposites (without surfactant) in various concentrations namely 0.05, 0.1, 0.3 and 0.5?vol. % were prepared using a typical two-step method and high homogenous stability is achieved using a mechanical mixing technique (ultra-sonication). The density of PCM nanocomposites was measured using two different types of standard volumetric flask approach and the experimental values confirmed good conformity with the Pak and Cho mixing theory. The highest thermal conductivity augmentation of 24.03%and 64.04% were achieved in liquid and solid states, respectively, with 0.5?vol. % of MWCNT. While, the addition of MWCNT resulted in a changeover of Newtonian to Non-Newtonian behaviors at a low shear rate, and the dynamic viscosity enhancement was increased by 130% with 0.5?vol. % of MWCNT. Further, the results were compared with existing correlations and it was found that the experimental values were in line with existing correlations. 相似文献
Recent research suggests that the cardiovascular diseases (CVDs), seem to be the foremost cause of mortality among the world populace. Three dimensional (3D) imaging modality such as computed tomography angiography(CTA) is a standard noninvasive imaging modality which has great potentials for the visualization of heart and coronary arteries. This article presents a fully automated method for coronary artery extraction using modified Frangi's vesselness measure and region based segmentation. In this article, grayness and gradient based measures are used while computing Frangi's vesselness measure to improve the extraction of coronary arteries. The obtained vesselness measures are utilized for automatically computing the location of ostia. The locations of ostia are then used as starting seed points in region growing segmentation to extract coronary arteries. Three major coronary arteries, namely the left anterior descending artery (LAD), left circumflex artery (LCX) and right coronary artery (RCA) are segmented using the proposed method and the centerlines are extracted for the main coronary branches. The performance of the proposed method is evaluated using 12 3D CCTA data set. The experimental results reveal that during the calculation of modified Frangi's vesselness measure the proposed method gives improved results. The qualitative results obtained during the segmentation stage are also convincing. The average segmentation accuracy and overlap measure of the proposed method are 97.4% and 77.86%, respectively. Hence, the proposed automated approach can detect and extract coronary arteries in CCTA images with high performance. 相似文献
Journal of Materials Science: Materials in Electronics - In this work, hydrogen-sensing characteristics of zinc oxide nanorods and reduced graphene oxide-incorporated zinc oxide nanorods are... 相似文献
Thermally and chemically stable perovskite-like layer structures have attracted extensively in the field of energy and environmental applications. In this study, La2Ti2O7 was synthesized by the solvothermal method at 180 °C. This method provides high pure and homogeneously dispersed nanorods of orthorhombic phase having length of 250 nm and width of 70 nm. Even though this is a low-temperature synthesis method, it yields high crystalline nature after calcination. The novelty of this work is its synthesis methodology by the solvothermal route to achieve lower weight loss of La2Ti2O7. Furthermore, they exhibit narrow absorption in the UV-region from 200 to 350 nm, makes it possible to fabricate it as UV photodetector at ambient condition. In presence of UV illumination at 390 nm, it shows sharp photocurrent response with the decay time of 1.7 s.
Optimization of cutting parameters is valuable in terms of providing high precision and efficient machining. Optimization
of machining parameters for milling is an important step to minimize the machining time and cutting force, increase productivity
and tool life and obtain better surface finish. In this work a mathematical model has been developed based on both the material
behavior and the machine dynamics to determine cutting force for milling operations. The system used for optimization is based
on powerful artificial intelligence called genetic algorithms (GA). The machining time is considered as the objective function
and constraints are tool life, limits of feed rate, depth of cut, cutting speed, surface roughness, cutting force and amplitude
of vibrations while maintaining a constant material removal rate. The result of the work shows how a complex optimization
problem is handled by a genetic algorithm and converges very quickly. Experimental end milling tests have been performed on
mild steel to measure surface roughness, cutting force using milling tool dynamometer and vibration using a FFT (fast Fourier
transform) analyzer for the optimized cutting parameters in a Universal milling machine using an HSS cutter. From the estimated
surface roughness value of 0.71 μm, the optimal cutting parameters that have given a maximum material removal rate of 6.0×103 mm3/min with less amplitude of vibration at the work piece support 1.66 μm maximum displacement. The good agreement between the
GA cutting forces and measured cutting forces clearly demonstrates the accuracy and effectiveness of the model presented and
program developed. The obtained results indicate that the optimized parameters are capable of machining the work piece more
efficiently with better surface finish. 相似文献
The cover image, by Aravindan Rajendran et al., is based on the Research Article Nutrient recovery from ethanol co‐products by a novel mycoalgae biofilm: attached cultures of symbiotic fungi and algae, DOI: 10.1002/jctb.5177 .