Tooling device design for vibration-assisted high speed shaping of PMMA

PMMA optical components that are used as one of the most important parts of high precision equipments and machines are increasingly replacing the glass due to the various advantages of PMMA. Especially in Light Guide Panels, the PMMA sheet that is used in Liquid Crystal Displays plays an important role in scattering the incident light and requires very fine machining as the sheet is directly related to the optical characteristics of the panels. The High Speed End milling and High Speed Shaping processes that are widely adopted and applied to the precise machining of Light Incident Plane still have quality problems, such as cracks, breakages, poor waviness, and straightness. This paper presents the tooling device design for machining a Light Incident Plane through vibration-assisted High Speed Shaping for increasing the optical quality by minimizing the above-mentioned problems. The cutting tool and the tool post presented in this paper are designed by the authors to increase the magnitude of the cutting stroke by adopting the resonant frequency without weakening the stiffness and to reduce vibrations during even high speed feeding. The dynamic characteristics of the cutting tool and the tool post are evaluated through simulation and experiment as well. The results reveal very appropriate dynamic characteristics for vibration-assisted High Speed Shaping.     

Analysis of water hammer in pipelines by partial fraction expansion of transfer function in frequency domain

Understanding water hammer is very important to the prevention of excessive pressure build-up in pipelines. Many researchers have studied this phenomenon, drawing effective solutions through the time- and frequency-domain approaches. For the purposes of enhancing the advantages of the frequency-domain approach and, thereby, rendering investigations of the dynamic characteristics of pipelines more effective, we propose partial fraction expansion of the transfer function between the unsteady flow source and a given section. We simulate the proposed approach using a vibration element inserted into a simple pipeline, deducing much useful physical information pertaining to pipeline design. We conclude that locating the resonance of the vibration element between the first and second resonances of the pipeline can mitigate the excessive pressure build-up attendant on the occurrence of water hammer. Our method of partial fraction expansion is expected to be useful and effective in analyses of unsteady flows in pipelines.     

Ultimate flexural strength of aluminum sections

A significant proportion of extruded aluminum sections have capacities beyond yield strength. In this study, the ultimate inelastic capacity is investigated for laterally supported aluminum flexural members symmetrical about bending axis. The topics studied include ultimate compressive stresses for component plate elements of flexural members, ultimate shape factors, and improvements to the existing weighted average strength approach. A parametric study using finite element analysis as well as physical tests was conducted to validate the approaches developed in this study. The study shows that the proposed approaches predict the ultimate inelastic flexural strength of aluminum members accurately.     

Enhanced transformation of triclosan by laccase in the presence of redox mediators

Triclosan (TCS), an antimicrobial agent, is an emerging and persistent environmental pollutant that is often found as a contaminant in surface waters and sediments; hence, knowledge of its degradability is important. In this study we investigated laccase-mediated TCS transformation and detoxification, using laccase (from the fungus Ganoderma lucidum) in the presence and absence of redox mediators. Transformation products were identified using HPLC, ESI-MS and GC-MS, and transformation mechanisms were proposed. In the absence of redox mediator, 56.5% TCS removal was observed within 24 h, concomitant with formation of new products with molecular weights greater than that of TCS. These products were dimers and trimers of TCS, as confirmed by ESI-MS analysis. Among the various mediators tested, 1-hydroxybenzotriazole (HBT) and syringaldehyde (SYD) significantly enhanced TCS transformation (∼90%). The presence of these mediators resulted in products with lower molecular weights than TCS, including 2,4-dichlorophenol (2,4-DCP; confirmed by GC-MS) and dechlorinated forms of 2,4-DCP. When SYD was used as the mediator, dechlorination resulted in 2-chlorohydroquinone (2-CHQ). Bacterial growth inhibition studies revealed that laccase-mediated transformation of TCS effectively decreased its toxicity, with ultimate conversion to less toxic or nontoxic products. Our results confirmed the involvement of two mechanisms of laccase-catalyzed TCS removal: (i) oligomerization in the absence of redox mediators, and (ii) ether bond cleavage followed by dechlorination in the presence of redox mediators. These results suggest that laccase in combination with natural redox mediator systems may be a useful strategy for the detoxification and elimination of TCS from aqueous systems.     

Optimal power system operation using parallel processing system and PSO algorithm

In recent studies, PSO algorithm is applied to solve OPF problem. However, population based optimization method requires higher computing time to find optimal point. This shortcoming is overcome by a straightforward parallelization of PSO algorithm. The developed parallel PSO algorithm is implemented on a PC-cluster system with 8 Intel Pentium IV 2 GHz processors. The proposed approach has been tested on the test systems. The results showed that computing time of parallelized PSO algorithm can be reduced by parallel processing without losing the quality of solution.     

Fiber-Laser-Pumped Er:YAG Lasers

Hybrid fiber-laser-pumped solid-state lasers exploit high-power cladding-pumped fiber lasers for direct (in-band) pumping of a crystal-based solid-state laser to reduce heating in the laser crystal, and hence allow scaling to higher power in both continuous-wave (CW) and pulsed modes of operation. In this paper, we briefly review the attractions of the hybrid laser approach for generation of output in the ~ 1.6 mum wavelength regime and consider the main design considerations for efficient operation of hybrid lasers based on Er:YAG in both CW and pulsed modes of operation. Examples of hybrid Er:YAG lasers, pumped by Er,Yb codoped fiber lasers at 1532 nm, with CW output powers up to 60 W at 1645 nm and 31 W at 1617 nm and slope efficiencies of 80% and 47% with respect to incident pump power, respectively, are described. In Q-switched mode of operation, pulse energies up to 30.5 mJ were obtained, limited by coating damage. Finally, the prospects for further increase in output power and improvement in overall performance in CW and Q-switched modes of operation will be discussed.     

GA-based decision support system for housing condition assessment and refurbishment strategies

Refurbishment work involves improvement, upgrading, renovation, retrofit, and repair of existing housing. With limited land usage and being aware of sustainability, the refurbishment market has faced increasing needs worldwide. During the long life cycle period of housing, most residents are undoubtedly faced with refurbishment requirements. However, it is not easy to make assessment and refurbishment related decisions due to the lack of knowledge and experience. This study presents Genetic algorithm-based on-line decision support system (DSS) to help residents easily conduct the housing condition assessment and offers optimal refurbishment actions considering the trade-off between cost and quality. Two refurbishment models are developed to explore the relationship among the life cycle cost, restoration cost and improved quality. The result reveals the proposed DSS solves the problems arising from asymmetric information and conflicting interests between residents and contractors, as well as improves traditional housing condition assessment to be more effective and efficient.     

Nanotube morphology changes for Ti-Zr alloys as Zr content increases

Nanotube morphology changes in Ti-Zr alloys as Zr content increases have been investigated. Ti-Zr (10, 20, 30 and 40 wt.%) alloys were prepared by arc melting and heat treated for 24 h at 1000 °C in an argon atmosphere. TiO₂ nanotubes were formed on the Ti-Zr alloys by anodization in H₃PO₄ containing 0.5 wt.% NaF. Electrochemical experiments were performed using a conventional three-electrode configuration with a platinum counter electrode and a saturated calomel reference electrode. Samples were embedded in epoxy resin, leaving an area of 10 mm² exposed to the electrolyte. Anodization was carried out using a scanning potentiostat, and all experiments were conducted at room temperature. Microstructures of the alloys were examined by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The Ti-Zr alloy microstructures observed by OM and FE-SEM changed from a lamellar structure to a needle-like structure with increasing Zr content. The microstructures also changed from β phase to increasing amounts of α phase as the Zr content increased. The number of large nanotubes formed by anodization decreased, and the number of small nanotubes increased, as the Zr content increased. The mean inner diameter ranged from approximately 150 to 200 nm with a tube-wall thickness of about 20 nm. The interspace between the nanotubes was approximately 60, 70, 100 and 130 nm for Zr contents of 10, 20, 30 and 40 wt.%, respectively.     

Equivalent multi-phase similitude law for pseudodynamic test on small scale reinforced concrete models

Small scale models have been frequently used to experimentally investigate the seismic performance of structures because capacities of testing facilities are limited and because they are more economically viable. However, not enough studies have been carried out on the development of similitude laws for accurately analogizing prototype structures with small scale models. Furthermore, conventional similitude requirements based on geometry may not be suitable in the inelastic range. When a small scale model of a prototype reinforced concrete structure is fabricated from a similar material to the prototype, an added mass would generally be required due to the volumetric variation, while the scale factor, as a ratio of the scale model to the prototype, cannot be sufficiently reduced due to the limitation of aggregate size. As an alternative, for small scale models it is desirable to use materials that are dissimilar to those of the prototype. Thus, a modified similitude law can be derived that depends on the geometric scale factor, equivalent modulus ratio and peak strain ratio. In this study, compressive strength tests were carried out to analyze the equivalent modulus ratio of micro-concrete to normal-concrete. The equivalent modulus ratios could then be divided into multi phases of strain level, which are basically dependent on the peak strain level at ultimate strength. An algorithm adaptable to the pseudodynamic test was therefore developed that considers an equivalent multi-phase similitude law based entirely on strain levels. Prior to carrying out the physical experiments, a numerical simulation was performed by idealizing the designed specimens to a single degree of freedom system with a bilinear model, and the pseudodynamic testing algorithm was numerically verified from seismic responses. A prototype and a 1/5 scale model of reinforced concrete columns as a test specimen was designed and fabricated based on the equivalent modulus ratios already defined. As a preliminary test, quasi-static tests on test specimens were carried out and their experimental results were compared using the constant and variable modulus ratios. Furthermore, in the pseudodynamic test on small scale models, it was verified that the modified pseudodynamic testing algorithm that considers the developed equivalent multi-phase similitude law may offer better simulation of the prototype structures than the conventional pseudodynamic testing algorithm. Therefore, it is found that the equivalent multi-phase similitude law would be applicable to the pseudodynamic test on small scale models.