Exploiting the orbital motion of water particles for energy extraction from waves

In wave motion, the water particles are known to follow orbital paths. This orbital motion was used to drive five-bladed Savonius rotors. Experiments were performed on an array of four rotors placed in a two-dimensional (2-D) wave channel. The flow around the rotors was documented using particle image velocimetry measurements. The submergence of the rotors and the distance between them were varied, and the rotational speeds of the rotors (N_n) were recorded at different wave frequencies. It was found that rotational speeds increased with an increase in the wave frequency, as it amplified the wave height that increased the kinetic energy of the particles in their orbital motion. The rotational speeds decreased when the distance between the rotors increased. High rotational speeds are recorded when the array of the rotors is placed close to the water surface at the smallest centre-to-centre distance between the rotors.     

Effect of bipolar plate materials on the stress distribution and interfacial contact resistance in PEM fuel cell

In polymer electrolyte fuel cell (PEFC) system, ideal structural integrity design takes into account the end-to-end load transfer mechanism. Hence, structural durability of cell is dependent of individual layers response to the external clamp loading. Since failure modes of each layer differ from another, multidisciplinary approach is needed to innovative designs. Bipolar plate (BPP) of PEFC is multi-functional layer that has a significant potential for research to avoid its structural failure as well as neighboring layers. To this end, present work investigates the effect of BPP materials on the stress transfer as well as distribution in cell layers based on theoretical investigation for clamping load. Gas-diffusion layer (GDL) / BPP interface has drawn considerable interest among researchers due to its susceptibility for damage failure and other related losses. Hence, investigating the interfacial behavior and relating this to the electrical contact resistance is the key feature in proposed investigation.     

Eliminating weldlines of an injection-molded part with the aid of high-frequency induction heating

High-frequency induction is an efficient way to heat mold surface by non-contact electromagnetic induction. It has been recently applied to injection molding because of its capability to heat and cool mold surface rapidly. This study applies high-frequency induction heating to eliminate weldlines in an injection-molded plastic part. To eliminate or reduce weldlines, the mold temperature at the corresponding weld locations should be maintained higher than the glass transition temperature of the resin material. Through 3 s of induction heating, the maximum temperature of 143 °C is obtained on the mold surface around the elliptic coil, while the temperature of the mold plate is lower than 60 °C. An injection molding experiment is then performed with the aid of induction heating, and the effect of induction heating conditions on the surface appearance of the weldline is investigated. The weldline on the heated region is almost eliminated, from which we can obtain the good surface appearance of the part.     

Development of censored data-based robust design for pharmaceutical quality by design

Robust design techniques, which are based on the concept of building quality into products or processes, are increasingly popular in many manufacturing industries. In this paper, we propose a new robust design model in the context of pharmaceutical production research and development. Traditional robust design principles have often been applied to situations in which the quality characteristics of interest are typically time insensitive. In pharmaceutical manufacturing processes, time-oriented quality characteristics, such as the degradation of a drug, are often of interest. As a result, current robust design models for quality improvement which have been studied in the literature may not be effective in finding robust design solutions. To address such practical needs, this paper develops a robust design model using censored data, which is perhaps the first attempt in the robust design field. We then study estimation methods, such as the expectation–maximization algorithm and the maximum likelihood method, in the robust design context. Finally, comparative studies are discussed for model verification via a numerical example.     

Corrosion and inhibition process of carbon steel in LiBr-H2O solution

Journal of Mechanical Science and Technology - Lithium bromide (LiBr)-H2O triple-effect absorption chillers are supposed to have a much higher carbon steel corrosion rate under high temperature...     

Design of a slider-crank leg mechanism for mobile hopping robotic platforms

Legged locomotion has been widely researched due to its effectiveness in overcoming uneven terrains. Due to previous efforts there has been much progress in achieving dynamic gait stability and as the next step, mimicking the high speed and efficiency observed in animals has become a research interest. The main barrier in developing such a robotic platform is the limitation in the power efficiency of the actuator: the use of pneumatic actuators produce sufficient power but are heavy and big; electronic motors can be compact but are disadvantageous in producing sudden impact from stall which is required for high speed legged locomotion. As a new attempt in this paper we suggest a new leg design for a mobile robot which uses the slider-crank mechanism to convert the continuous motor rotation into piston motion which is used to impact the ground. We believe this new mechanism will have advantage over conventional leg mechanism designs using electronic motors since it uses the continuous motion of the motor instead of sudden rotation movements from stall state which is not ideal to draw out maximum working condition from an electronic motor. In order to control impact timing from the periodic motion of the piston a mechanical passive clutch trigger mechanism was developed. Dynamic analysis was performed to determine the optimal position for the mechanical switch position of the clutch trigger mechanism, and the results were verified through simulation and experiment. Development of a legged locomotion with two degrees of freedom, slider-crank mechanism for impact and additional actuation for swing motion, is proposed for future work.     

Numerical investigation of bolt fitting and fastening forces by elastoplastic finite element analysis

The bolt–flange fitting and detaching processes are numerically investigated by the updated Lagrangian elastoplastic finite element analysis. The elastoplastic behavior of the flange is modeled by the power-law plastic model with the isotropic strain hardening, while assuming the bolt to be rigid by virtue of the big difference in the material stiffness between bolt and flange. Through the parametric numerical analyses of the bolt–flange fitting and detaching processes with respect to the shape of the bolt cross-section, the characteristics of the bolt fitting and fastening forces are investigated. The validity of the simplified 2-D axisymmetric finite element model is examined through the comparison with the numerical results obtained by 3-D full finite element model. As well, the effects of the bolt petal number on these forces are investigated, and the experiment is performed to verify the numerical simulation.     

Qualitative verification of the dispersion level in nano-composite and its application to YD-128/MWCNT composite to assess the wear characteristics with respect to the dispersion level

We analyzed the wear characteristics according to dispersion level of MWCNT in YD-128/MWCNT composite. Specimens for this study were fabricated using mechanical stirrer after blending of YD-128 and MWCNT. To change the dispersion level, the mixture of YD-128/MWCNT was stirred using mechanical stirrer during different times, such as, 15, 30, 60, and 120 minutes. Because the direct measuring of dispersion level is difficult in the case of solid composite, we suggest an indirect method for checking qualitatively the dispersion level as follows. Firstly, using the AEH (asymptotic expansion homogenization) in-house code, we analyzed numerically the mechanical stiffness of composite using RVEs (representative volume elements) which are modeled with different dispersion level. According to the numerical results of RVEs, we verified that the mechanical stiffness is higher as the dispersion degree is better. Then, through the experimental tensile test of the fabricated specimens using UTM, we obtained that the mechanical stiffness is higher as the stirring time is longer. Consequently, we could ensure that the dispersion degree of the fabricated specimens is better as the mechanical stirring time is longer. Finally, we assessed the wear test using abrading machine with fabricated specimens. We confirmed that the abrasion loss is decreased according to the increasing of dispersion degree in the case of YD-128/MWCNT composites.     

Surface modification of rutile TiO2 by submerged arc discharge for improved photoreactivity

Titanium dioxide is well known for its photocatalytic activity, but it works effectively only in the ultraviolet (UV) range. Given the relatively low flux of solar UV that reaches earth, the potential of exploring its photocatalytic capacity for environmental protection applications is very limited. In this study, rutile, the least photocatalytic of the three existing titanium dioxide crystalline forms, was suspended in water or acetonitrile and treated with oxygen or argon plasmas, using a novel dense-medium plasma technology (submerged arc discharge). As a result of the plasma treatment, rutile particles were doped with various trace elements that originated in electrodes made of different metals. Subsequent analyses show that the photocatalytic capacity of plasma-modified rutile is comparable to or even better than that of unmodified anatase, the most photocatalytic form of titanium dioxides. The color change of TiO₂ samples after plasma treatment indicates that the modified rutile absorbs visible light and may therefore work as a photocatalyst in the visible range. Given the fact that rutile can be produced in large quantity more easily and cheaply than can anatase, these results are very encouraging and open up possibilities in using rutile for photocatalytic applications in the visible range. This paper was presented at the Third International Surface Engineering Congress and Exposition held August 2–4, 2004 in Orlando, FL.