Optimal Control of Earthquake Response Using Semiactive Isolation

The responses of two, low-rise, 2-degree-of-freedom base isolated structures with different isolation periods to a set of near-field earthquake ground motions are investigated under passive linear and nonlinear viscous damping, two pseudoskyhook semiactive control methods, and optimal semiactive control. The structures are isolated with a low damping elastic isolation system in parallel with a controllable damper. The optimal semiactive control strategy minimizes an integral norm of superstructure absolute accelerations subject to the constraint that the nonlinear equations of motion are satisfied and is determined through a numerical solution to the Euler–Lagrange equations. The optimal closed-loop performance is evaluated for a controllable damper and is compared to passive viscous damping and causal pseudoskyhook control rules. Results obtained from eight different earthquake records illustrate the type of ground motions and structures for which semiactive damping is most promising.     

Strategy planning for collaborative humanoid soccer robots based on principle solution

Collaborative humanoid soccer robots are currently under the lime light in the rapidly advancing research area of multi-robot systems. With new functionalities of software and hardware, they are becoming more versatile, robust and agile in response to the changes in the environment under dynamic conditions. This work focuses on a new approach for strategy planning of humanoid soccer robot teams as in the RoboCup Standard Platform League. The key element of the approach is a holistic system model of the principle solution encompassing various strategies of a soccer robot team. The benefits of the model-based approach are twofold—it enables intuitive behavioral specification of the humanoid soccer robots in line with the team strategies envisaged by the system developers, and it systematizes the realization of their collaborative behaviors based on the principle solution. The principle solution is modeled with the newly developed specification technique CONSENS^® for the conceptual design of mechatronic and self-optimizing systems.     

Non-Evaporative Solvent Recovery Step in Deacidification of Used Frying Oil as Biodiesel Feedstock by Methanol Extraction

An alternative deacidification process combining a liquid–liquid extraction with a non-evaporative solvent recovery step was proposed for preparing used frying oil (UFO) as biodiesel feedstock. The liquid–liquid extraction step using methanol was simulated for obtaining refined UFO with a final residual free fatty acids (FFA) content ≤ 1%. Solvent recovery step of the process, which is based on the precipitation of FFA with Ca(OH)₂ as insoluble calcium soaps, was investigated experimentally. With the aim of maximizing the FFA removal from the methanol extract, the influence of process variables such as FFA concentration in the extract phase, Ca(OH)₂ amount, stirring rate and temperature were investigated by using model extract phases. Complete removal of FFA was achieved in 30, 20, and 15 min, from the extract phases containing 3.86, 7.78, and 11.58 wt% FFA, respectively, when the precipitation was carried out at a temperature of 65 °C, stirring rate of 250 rpm and by using 18 times the stoichiometric Ca(OH)₂ amount. The precipitate quickly settled down due to the agglomeration, thereby provided an efficient and easy separation of the methanol from the solids. Provided the final residual content of FFA in methanol was too low, recovered methanol can be recycled for more FFA extraction. Although the suggested process offers a feasible method for preparing UFO as biodiesel feedstock, the effect of other decomposition products in UFO must be investigated in depth for using such a process on an industrial scale.     

The dependence of tool overhang on surface quality and tool wear in the turning process

In the turning process, the importance of machining parameter choice is increased, as it controls the surface quality required. Tool overhang is a cutting tool parameter that has not been investigated in as much detail as some of the better known ones. It is appropriate to keep the tool overhang as short as possible; however, a longer tool overhang may be required depending on the geometry of the workpiece and when using the hole-turning process in particular. In this study, we investigate the effects of changes in the tool overhang in the external turning process on both the surface quality of the workpiece and tool wear. For this purpose, we used workpieces of AISI 1050 material with diameters of 20, 30, and 40 mm; and the surface roughness of the workpiece and tool wear were determined through experiments using constant cutting speed and feed rates with different depth of cuts (DOCs) and tool overhangs. We observed that the effect of the DOC on the surface roughness is negligible, but tool overhang is more important. The deflection of the cutting tool increases with tool overhang. Two different analytical methods were compared to determine the dependence of tool deflection on the tool overhang. Also, the real tool deflection values were determined using a comparator. We observed that the tool deflection values were quite compatible with the tool deflection results obtained using the second analytical method.     

Optical response of Ag-Au bimetallic nanoparticles to electron storage in aqueous medium

Composition and structure dependence of the shift in the position of the surface plasmon resonance band upon introduction of NaBH4 to aqueous solutions of gold and silver nanoparticles are presented. Silver and gold nanoalloys in different compositions were prepared by co-reduction of the corresponding salt mixtures using sodium citrate as the reducing agent. After addition of NaBH4 to the resultant nanoalloys, the maximum of their surface plasmon resonance band, ranging between that of pure silver (ca. 400 nm) and of pure gold (ca. 530 nm), is blue-shifted as a result of electron storage on the particles. The extent of this blue shift increases non-linearly with the mole fraction of silver in the nanoparticle, parallel to the trends reported previously for both the frequency and the extinction coefficient of the plasmon band shifts. Gold(core)@silver(shell) nanoparticles were prepared by sequential reduction of gold and silver, where addition of NaBH4 results in relatively large spectral shift in the plasmon resonance band when compared with the nanoalloys having a similar overall composition. The origin of the large plasmon band shift in the core-shell is related with a higher silver surface concentration on these particles. Hence, the chemical nature of the nanoparticle emerges as the dominating factor contributing to the extent of the spectral shift as a result of electron storage in bimetallic systems.     

The effect of MDP-based primer on shear bond strength of various cements to two different ceramic materials

The aim of this study was to determine the effect of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based primer on the shear bond strengths of thermally aged self-adhesive and conventional adhesive resin cements and zinc phosphate cement to zirconia and lithium disilicate substructures. Sixty zirconia (Z) and 60 lithium disilicate (L) disk specimens were cut from ceramic blocks. Each group was divided into six subgroups (n = 10). Half of the specimens of each ceramic group were treated with primer (P) and the other half was remained untreated. Three types of cement were applied: zinc phosphate cement [(ZPC) (Hoffmann Harmonic Shades)]; self-adhesive resin cement [(SAC) (RelyX U200)]; conventional adhesive resin cement [(CAC) (C&B)]. The specimens were subjected to thermal aging procedure for 1 week under 37 °C water bath. Shear bond strength (SBS) was determined using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with three-way (ANOVA). Pairwise comparisons and interactions between groups were analyzed by using Tukey’s simultaneous confidence intervals. There was no significant difference between the SBS values of SAC-Z (11,47 ± 0,47) and SAC-ZP (11,39 ± 0,42) (p > 0.05). However, the SBS values of SAC-L (12.34 ± 0,55) and SAC-LP (12,50 ± 0,49) were significantly higher than those of SAC-Z and SAC-ZP (p < 0.00). The use of primer significantly increased the SBS value of CAC-ZP (8,05 ± 0,55) when compared to the SBS value of CAC-Z (3,53 ± 0,41) (p < 0.00). Resin cement that contains methacrylate monomers with phosphoric ester functional groups exhibited reliable bond to zirconia. However, the use of an MDP-based primer may not further improve its bond strength.     

Disinfection Study with ClO<Subscript>2</Subscript> for Recycling Demijohns in Drinking Water Industry

The disinfection of recycling polymer based demijohns using in drinking water industry was targeted by using chlorine dioxide containing solutions. 1.5 L volume polyethylene terephthalate bottle was chosen as container to characterize the polymeric demijohn. Disinfection of the intentionally contaminated containers was performed with the 0.3–2 ppm range ClO₂ containing washing solutions which were prepared from the stock solution. Active matter concentration, washing time and the washing number were studied in gradient. Disinfection efficacy of ClO₂ on Escherichia coli ATCC 25922 and Enterococcus faecalis ATCC 29212 was investigated. The bacteria were chosen according to “Implementing Regulation on Water Intended for Human Consumption”. Viable bacterial cell was enumerated by membrane filtration method. The results were established as colony forming unit. The increasing of the concentration decreased the washing time is another determined result.     

Fixed-point analysis of a network of routers with persistent TCP/UDP flows and class-based weighted fair queuing

Fixed-point models have already been successfully used to analytically study networks consisting of persistent TCP flows only, or mixed TCP/UDP flows with a single queue per link and differentiated buffer management for these two types of flows. In the current study, we propose a nested fixed-point analytical method to obtain the throughput of persistent TCP and UDP flows in a network of routers supporting class-based weighted fair queuing allowing the use of separate queues for each class. In particular, we study the case of two classes where one of the classes uses drop-tail queue management and is intended for only UDP traffic. The other class targeting TCP, but also allowing UDP traffic for the purpose of generality, is assumed to employ active queue management. The effectiveness of the proposed analytical method is validated in terms of accuracy using ns-3 simulations and the required computational effort.     

Electrical and optical properties of p-type silicon based on polypyrrole-derivative polymer

The junction characteristics of the conducting polymer NpClPh PPy [N-(p-chloro phenyl) polypyrrole] on a p-type Si substrate have been studied at room temperature. A direct optical band gap energy value of conducting polymer (NpClPh PPy) was obtained as 2.94 eV. The ideality factor and barrier height of Al/NpClPh PPy/p-Si/Al structure were determined from the forward current–voltage characteristics in the dark and were found to be 1.41 and 0.78 eV, respectively. The ideality factor and barrier height values for the Al/NpClPh PPy/p-Si/Al structure are larger than that of conventional Al/p-Si Schottky diode. The contact parameters were calculated from Cheung's functions and modified Norde's function. The results found out from different methods were compared with each other. The barrier height value of 0.89 eV was obtained from capacitance–voltage characteristic. The different values of barrier height indicate the existence of barrier inhomogeneities. The conducting polymer (NpClPh PPy) modifies the effective barrier height of conventional Al/p-Si Schottky diode as the organic film forms a physical barrier between Al metal and p-Si.     

Incident radiation from a flare to a horizontal cylinder - Part II

The total radiative heat transfer from a pressure relief value to a rail tank car surface was calculated. The flame was regarded as a radiating surface. The variation of the incident heat flux on the cylindrical surface due to the inclination of the flare in cross-wind conditions was investigated. The results of full and 1/5-scale fire tests conducted on real tanks filled with LPG were utilized to compare the analytical results obtained here (Part II) and from Part I. Reasonable agreement was obtained between the analyses and experiments.