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This paper is concerned with the design and the analysis of a semi-active suspension controller. In the recent years different kinds of semi-active control strategies, like two-state Skyhook, LQ-clipped or model-predictive control...
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This paper is concerned with the design and the analysis of a semi-active suspension controller. In the recent years different kinds of semi-active control strategies, like two-state Skyhook, LQ-clipped or model-predictive control, have already been developed in the literature. In this paper, a new semi-active suspension control strategy that a priori satisfies the principal limitations of a semi-active suspension actuator (dissipative constraint and force bounds) is introduced using the tools of the linear parameter varying (LPV) theory. This new approach exhibits some interesting advantages (implementation, performance flexibility, robustness, etc.) compared to already existing methods. Both industrial criterion based evaluation and simulations on a nonlinear quarter vehicle model are performed to show the efficiency of the method and to validate the theoretical approach.
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Mixtures of wastes were prepared to improve on the characteristics of the individual ingredients as Technosols, with special attention given to heavy metal extractability. An anaerobic digested sewage sludge and a CaO-treated aero...
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Mixtures of wastes were prepared to improve on the characteristics of the individual ingredients as Technosols, with special attention given to heavy metal extractability. An anaerobic digested sewage sludge and a CaO-treated aerobic sludge were used. A mixture of the two sludges (50:50 DW basis) was also prepared to provide a third type of sludge. The residues were mixed with other types of waste, such as fly ash, Linz-Donowitz slag, foundry sand, shot blasting machine scrap, fettling and barley straw. Extractability of Cu, Cr, Ni, and Zn by 0.01 M CaCl_2 extraction (Me_(CaCl_2)) was carried out, and leachability of these elements was estimated by acidification of an aqueous suspension of the mixtures with 0.5 N acetic acid (Me_(acetic)). The total concentrations of the metals were also determined (Me_T). The Me_(CaCl_2)/Me_T ratios for Cu and Ni (means: 4.0% and 3.1%) were higher than those for Cr and Zn (means: 0.07% each). The mean Me_(acetic)/Me_T ratios followed the order Ni, Zn, Cu, and Cr (19.5%, 4.1%, 3.7%, and 0.09%, respectively). The results highlight the existence of complex interactions among organic matter solubility, pH and heavy metal extractability.
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A comprehensive numerical study of the equivalent thermal conductivity of a multi-holed clay brick with the size of 240 × 115 × 90 (in mm) has been conducted, and 50 kinds of combination of holes and arrangements are examined. T...
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A comprehensive numerical study of the equivalent thermal conductivity of a multi-holed clay brick with the size of 240 × 115 × 90 (in mm) has been conducted, and 50 kinds of combination of holes and arrangements are examined. The indoor-outdoor temperature difference varies from 50 ℃ to 20 ℃. The effects of following factors are studied in details: the hole surface radiation, the width-wise and length-wise hole numbers, and the indoor-outdoor temperature difference. The major findings are as follows: (1) the radiation between hole surfaces has some effect on the equivalent thermal conductivity, thus it should be taken into account; (2) the hole number and arrangement affect the thermal conductivity in a rather complicated manner. Analysis shows that depending on the relative importance of natural convection, surface radiation and heat conduction through the clay solid, the thermal conductivity may decrease with the hole number or increase with the hole number and (3) among the 50 kinds of combination, the optimum configuration is found which has five length-wise holes, four width-wise holes and all the holes are from bottom to top in the depth direction of a brick. Its equivalent thermal conductivity is 0.419 W/(m K), which is only 53.1% of solid clay of which it is made, showing great energy-saving possibility if it is adopted in the construction of building wall.
Detailed discussion of the simulated results is conducted and flow field and temperature distributions are also provided for some typical configurations.
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Self-assembled 2D structures on thin films of block copolymers/Fe hybrid materials were fabricated on Si/Ta substrates, either by wet chemistry or laser irradiation at 157 nm. The polymer exhibits micelle-like structures with aver...
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Self-assembled 2D structures on thin films of block copolymers/Fe hybrid materials were fabricated on Si/Ta substrates, either by wet chemistry or laser irradiation at 157 nm. The polymer exhibits micelle-like structures with average dimensions of 5-10 nm and 30-50 nm for light and chemically reduced films respectively. For the laser processed films, SQUID measurements reveal a ferromagnetic response at 5 K, and 100 Oe coercivity was obtained for 2:1 iron concentration. For chemically reduced films, on the other hand, a superparamagnetic response with near zero coercivity at 5 K was obtained.
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The relationship between band gap and biaxial stress in wurtzite ZnO thin films has been investigated by side-inclination x-ray diffraction technique and optical absorbance spectrum as well as ab initio calculation. The experiment...
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The relationship between band gap and biaxial stress in wurtzite ZnO thin films has been investigated by side-inclination x-ray diffraction technique and optical absorbance spectrum as well as ab initio calculation. The experimental result shows that differing from other semiconductor thin films with hexagonal structure, such as GaN, the band gap of ZnO thin films increases with the increase in biaxial tensile stress. For explaining the difference, ab initio calculation is performed to simulate the relationship between band gap and biaxial stress of wurtzite ZnO and GaN. The calculated result indicates that the band gap of ZnO increases under biaxial tensile stress but GaN is opposite, supporting our experimental result. The band offset calculation shows that the conduction-band minimum (CBM) and the valence-band maximum (VBM) of ZnO and GaN offset to low energy under biaxial tensile stress. The VBM offset of ZnO is larger than the CBM, responsible for the increase in band gap. The VBM offset of GaN is smaller than the CBM, responsible for the decrease in band gap. The difference between ZnO and GaN is attributed to the strong p-d coupling in valence band of ZnO, but strong p-p coupling in valence band of GaN.
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A summary of analyses of critical behavior in both the ac susceptibility and dc magnetization in single crystal Pr_(1-x)Ca_xMnO_3 (x=0.27, and 0.29) is presented supplemented by magnetotransport data. The magnetic data indicate th...
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A summary of analyses of critical behavior in both the ac susceptibility and dc magnetization in single crystal Pr_(1-x)Ca_xMnO_3 (x=0.27, and 0.29) is presented supplemented by magnetotransport data. The magnetic data indicate that both single crystals exhibit a continuous/second-order paramagnetic to ferromagnetic phase transition but with marginally different critical exponents. Estimates of the latter for the x=0.27 sample yield δ=4.81 ±0.02, γ=1.36 ±0.02, and β=0.36 ±0.02 (consistent with both the predictions for the nearest-neighbor three-dimensional-Heisenberg model and with those reported for its double exchange-dominated metallic counterparts) with T_C=127±0.5 K; whereas at x=0.29, δ=4.62±0.05, γ= 1.38 ±0.01, and β =0.37 ± 0.02 with T_C= 114 ± 0.5 K. The absence of metallicity-and by inference, the suppression of charge fluctuations-does not, therefore, appear to influence the universality class of the transition. No evidence for a Griffiths-type phase was found in either specimen. These single crystals also display comparable values of the acoustic spin-wave stiffness D ～ 70 meV A~2 well below that found in the charge-ordered field-induced metallic regime of the same system. These samples remain insulators below ferromagnetic ordering temperature T_C in fields up to 90 kOe; they display nonabiabatic small polaron mediated transport behavior in the paramagnetic regime in zero field characterized by activation energies comparable to those reported previously for a range of doped perovskites.
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The damage and fracture behaviors of high purity polycrystalline zinc with two grain sizes during tension were investigated experimentally at different strain rates. It was found that specimens with coarse grains (～1 mm) showed s...
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The damage and fracture behaviors of high purity polycrystalline zinc with two grain sizes during tension were investigated experimentally at different strain rates. It was found that specimens with coarse grains (～1 mm) showed serrated flow behavior and failed in intermittent brittle cleavage fracture, while specimens with fine grains (～70μm) showed no cleavage crack initiation before necking even at high strain rate. It was observed that the fracture process of the fine-grained specimen was highly related to strain rates. With the strain rate increasing, the damage mechanism transformed from formation of tearing cracks along interfaces (including grain boundaries, twin boundaries and kink band boundaries) and cavity coalescence into abrupt quasi-cleavage fracture. Based on the observation, the inter-crystalline fracture of zinc was investigated, and the damage and fracture behaviors of
polycrystalline zinc during tension at room temperature were discussed in general.
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Out-of-equilibrium photoinduced switching from the low-spin to the high-spin state has been investigated on the iron(II) complex [Fe~(II)(DPEA)(NCS)_2] by both optical reflectivity and magnetic measurements under continuous light ...
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Out-of-equilibrium photoinduced switching from the low-spin to the high-spin state has been investigated on the iron(II) complex [Fe~(II)(DPEA)(NCS)_2] by both optical reflectivity and magnetic measurements under continuous light irradiation at low temperature. The photoinduced HS state can be observed up to 47 K and the relaxation process has been followed. Structural changes of both the temperature- and the photoinduced spin-state switching have been analyzed in detail by x-ray diffraction indicating no change of symmetry. Short intermolecular contacts and intramolecular deformations associated with the change of molecular spin state have been quantified. Actually a crossover behavior is observed at thermal equilibrium with however a qua-siabrupt shape indicating significant cooperative effects. These aspects are compared between the temperature-and photoinduced spin crossovers.
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High strength, amorphous or partly nanocrystalline, multiphase intermetallic alloys with average composition of Al_(65)Cu_(20)Ti_(15) have been processed by mechanical alloying of the elemental powders followed by consolidation us...
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High strength, amorphous or partly nanocrystalline, multiphase intermetallic alloys with average composition of Al_(65)Cu_(20)Ti_(15) have been processed by mechanical alloying of the elemental powders followed by consolidation using high-pressure (8GPa) sintering either at room temperature or at 300-450℃ for 1 min. Examination of the microstructural constituents using X-ray diffraction and transmission electron microscopy shows that the alloy pressed at 400℃ is primarily amorphous, while nanocrystalline intermetallic phases, Al_2Cu, Al_4Cu_9 and Al_5CuTi_2 evolve from the amorphous matrix on pressing at 450℃. The pressing temperature of 400 ℃ appears most promising, leading to products with negligible porosity, increment in the Young's modulus by about 85% with respect to that of Al alloys, as well as impressive hardness (7.9 GPa) and compressive strengths (1490MPa). However, absence of ductility and poor fracture toughness (3.8±0.8MPa m~(1/2)) appear as the major challenges to be met for widespread application of these alloys.
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Germanium Quantum Dots (Ge QDs) were formed in SiO_2 by RT magnetron sputtering co-deposition of Ge and SiO_2 and subsequent annealing. Films were deposited in the form of alternating (Ge + SiO_2) layers (40:60 molar ratio) and pu...
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Germanium Quantum Dots (Ge QDs) were formed in SiO_2 by RT magnetron sputtering co-deposition of Ge and SiO_2 and subsequent annealing. Films were deposited in the form of alternating (Ge + SiO_2) layers (40:60 molar ratio) and pure SiO_2 layers, serving as spacers. Grazing incidence small angle x-ray scattering (GISAXS) was applied for structural characterization of the QDs synthesized in the SiO_2 amorphous matrix. The chemical composition and phase of the QDs were determined by Raman spectroscopy, and the spatial distribution and concentration of the Ge atoms by Rutherford Backscattering.
The 2D GISAXS patterns, besides giving information on the layered structure, were used to reveal the onset of the synthesis of Ge QDs in SiO_2 and to determine the average size and shape of QDs. It has been shown that the insertion of spacer SiO_2 layers between (Ge + SiO_2) layers transforms the 3D growth of Ge QDs into a preferentially 2D growth, within each 7 nm thick (Ge + SiO_2) layer. This resulted in a considerably smaller average size of Ge QDs in the layered films. The synthesis of well crystallized, moderately sized, spherical Ge QDs was achieved by post-deposition annealing in the 700-800 ℃ range.
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