The effect of rubber dampers on engine’s NVH and thermal performance

Fins as extended surfaces are attached to the internal combustion engine surfaces for enhancing the heat transfer. However, these fins vibrate at various frequencies, which produce undesirable radiated noise. To mitigate this effect, automobile industry inserts rubber dampers between these fins. These rubber dampers reduce the fins’ amplitude of vibration and thus reduce the radiated noise from the fin surfaces. Investigations on the effect of rubber dampers on the engine’s NVH (Noise–Vibration–Harshness) and thermal performance using numerical (FEM and CFD) and experimental measurement have been presented in this paper. Experiments were conducted in the semi-anechoic chamber on an engine with and without rubber dampers to measure the radiated noise from the fins. It was found that rubber dampers assist in reducing engine high frequency noise signals at higher engine speeds. Modal and harmonic response analysis was carried out on various designs for NVH characteristics improvement. Prototypes of the final design was made and tested for the NVH performance. Computational fluid dynamics (CFD) simulations were performed on engine with and without rubber dampers to investigate the thermal performance. It was found that rubber dampers increase engine temperature by about 10%. Effect of rubbers dampers on the cost and environmental impact has also been discussed. This paper provides a systematic procedure to investigate the effect of rubber dampers and a method to eliminate these dampers from the engines with the same NVH and better thermal performances.     

The effect of an aircraft’s boundary layer on propeller noise

This study concerns the influence of the boundary layer at an aircraft??s fuselage, simulated by an infinite hard cylinder, on propeller noise in the acoustic far field. Also studied is the effect of the boundary layer on noise as a function of the thickness and profile of the mean velocity of the boundary layer, the Mach number of the incident flow, and the rotation speed of the propeller. It is shown that the boundary layer at the fuselage can substantially modify propeller noise in the far field and should therefore be taken into account in calculating community noise.     

The effect of conductor loss on half-wave voltage and modulation bandwidth of electro-optic modulators

In this paper, we theoretically deduce the expressions of half-wave voltage and 3-dB modulation bandwidth in which conductor loss is taken into account. The results suggest that it will affect the theoretical values of half-wave voltage and bandwidth as well as the optimized electrode's dimension whether considering the conductor loss or not. As an example, we present a Mach-Zehnder (MZ) type polymer waveguide amplitude modulator. The half-wave voltage increases by 1 V and the 3-dB bandwidth decreases by 30% when the conductor loss is taken into account. Besides, the effects of impedance mismatching and velocity mismatching between microwave and light wave on the half-wave voltage, and 3-dB bandwidth are discussed.     

Nature’s optics and our understanding of light

Optical phenomena visible to everyone have been central to the development of, and abundantly illustrate, important concepts in science and mathematics. The phenomena considered from this viewpoint are rainbows, sparkling reflections on water, mirages, green flashes, earthlight on the moon, glories, daylight, crystals and the squint moon. And the concepts involved include refraction, caustics (focal singularities of ray optics), wave interference, numerical experiments, mathematical asymptotics, dispersion, complex angular momentum (Regge poles), polarisation singularities, Hamilton’s conical intersections of eigenvalues (‘Dirac points’), geometric phases and visual illusions.     

The effect of laser surface treatment of Al-Si alloy on the surface hardness and structure

In this paper, some samples of Al-Si alloy with various silicon content were treated by laser beam. The effects on structure, hardness and substructure of samples were investigated. The experimental results show that the primary crystal Al and eutectic silicon in the laser treated samples is got thinning obviously, the mosaic dimension is decreased and the dislocation density is increased.     

The effect of vacuum annealing on the remediation abilities of iron and iron−nickel nanoparticles

Zero-valent iron nanoparticles are effective remediators of uranium from solution. It is postulated that the improved core crystallinity and the migration of impurity phases to the nanoparticle surfaces induced by annealing may improve their corrosion resistance and reactive lifespan. The ability of annealed and non-annealed Fe and FeNi nanoparticles to remediate a U-contaminated effluent from AWE, Aldermaston was investigated. Nanoparticles (of diameter typically between 0 and 100 nm) were introduced to the effluent and allowed to react for 7 days during which the liquid and nanoparticulate solids were periodically sampled. In all the systems, the maximum U-uptake occurred within 1 h of introduction, with variable efficiency. The Fe nanoparticles removed 98% of the total U from solution, resulting in a final U-concentration of <4 μg/L. A rapid release of Fe into solution was recorded early in the reaction period: attributed to limited partial dissolution of the nanoparticles. Annealing the Fe nanoparticles did not affect their efficiency but the dissolution of Fe was significantly reduced and X-ray Photoelectron Spectroscopy indicated slower progressive oxidation. The performance of the FeNi nanoparticles was significantly improved by annealing, with U-uptake increasing from 50 to 94%. Although the dissolution of Ni was completely inhibited by annealing, the Fe dissolution increased compared to that observed for the non-annealed FeNi nanoparticles, in contrast to behaviour exhibited by Fe-annealed nanoparticles. In all the systems, U was reduced to U(IV) and retained on the surfaces of the nanoparticulate solids for up to 48 h; the U-stability was not affected by annealing the Fe or the FeNi nanoparticles before use.     

The effect of high-frequency acoustic wave vibration pattern on HKUST’s multi-level pore structure

The physical properties of materials are critical to their functionality, and the ability to control these properties using external forces is a significant challenge. In this study, we investigate the effect of three high frequency acoustic wave vibration patterns on the structure and morphology of MOF particles. Our results indicate that while regular vibration patterns generated by SAW can alter particle morphology, hybrid waves and Lamb waves with irregular vibration patterns can synthesise MOF crystals with multi-level pores. The vibration pattern of acoustic waves is shown to be a critical factor in controlling the particle morphology process. These results provide new insights into the precise control of crystal structure and the theory of crystallisation by particle attachment (CPA).     

ΔThe effect of co-doping on the yttrium local environment and ionic conductivity of yttria-stabilised zirconia

The effect of co-doping yttria-stabilised zirconia with calcia and scandia has been investigated. Changes in the yttrium ion local environment have been monitored using solid-state magic angle sample spinning ⁸⁹Y nuclear magnetic resonance. The effect on the low-temperature (below 320 °C) bulk ionic conductivity has been observed using AC impedance spectroscopy. It was found that the number of oxygen vacancies in the nearest-neighbour sites to yttrium ions decreased on co-doping with scandia, correlating with an increase in conductivity, but increased on co-doping with calcia, correlating with a decrease in conductivity. This behaviour can be explained by proposing the trapping of oxygen vacancies in the nearest-neighbour yttrium ion sites so that they no longer contribute to the conduction mechanism.

The influence of pressure on the Mössbauer effect

A study was made of the pressure dependence of the intensity of the Mössbauer line, and the dependence of this quantity on the specific volume of the crystal, which has the same form for all these crystals in the first approximation, was derived for regular atomic crystals in the Grüneisen approximation. The change in intensity of the Mössbauer line due to pressure can be converted, except for a multiplication factor, to a change in intensity of this line caused by a change in temperature.     

Discussion notes on “Thoughts on some outstanding issues in the physics of equilibrium wetting and conceptual understanding of contact lines”, by K. Sefiane

Comments are provided for [10].     

The effect of Bi content on the thermal stability and crystallization of Se–Te chalcogenide glass

Glass formation and devitrification of intermediate alloys in the Se–Te–Bi system were studied by differential scanning calorimetry. A comparison of various simple quantitative methods to assess the level of stability of the glassy materials in the above-mentioned system is presented. All of these methods are based on characteristic temperatures, such as the glass transition temperature, T _g, the onset temperature of crystallization, T _in, the temperature corresponding to the maximum crystallization rate, T _p, or the melting temperature, T _m. In this work, a kinetic parameter, K _r(T), is added to the stability criteria. The thermal stability of several compositions of Se–Te–Bi was evaluated experimentally and correlated with the activation energies of crystallization by this kinetic criterion and compared with those evaluated by other criteria. All the results confirm that the thermal stability decreases with increasing Bi content in this glassy system. The crystallization results are analysed and the activation energy and mechanism of crystallization characterized.     

The effect of oil on the performance of heat pumps and refrigerators—II. Experimental results

The results of a prolonged investigation of the influence of the lubricating oil Shell Clavus 68 on the performance of an R12-based refrigeration-heat pump system are presented. The strategy is discussed for deciding if a given series of data collected at 10s intervals adequately represents the chosen experimental conditions and results are presented under both transient and steady state conditions. The effects of oil on evaporator capacity, coefficient of performance, heat transfer rates, evaporator outlet superheat stability, refrigerant mass flow rate, evaporator pressure drop and compressor discharge temperature are discussed, and the experimental results are compared with a theoretical analysis. Finally, it is shown that under certain (albeit unlikely) conditions, it is possible for both the evaporator and condensor to act as heat rejectors.     

The effect of HCP on the formation of twin boundaries and dislocations in Ni–Co alloys

In this study, molecular dynamics (MD) was used to simulate the rapid solidification process of Ni₄₇Co₅₃ and Ni₄₈Co₅₂ alloys at a cooling rate of 10¹² K/s. The effects of HCP on the formation of twin boundaries and dislocations in two Ni–Co alloys are studied. It is found that the difference of HCP clusters is the main effect that producing discrepancies on microstructure of two alloys. The number of HCP clusters accounted for 9.23% in Ni₄₇Co₅₃ alloy. They are regularly arranged to form the number of single-layer twin boundaries, and each twin boundary ends in a dislocation. The FCC and HCP structures coexist in the same atomic layers, which is easy to create dislocations. The relatively standard FCC crystal and only 0.32% HCP clusters are formed in Ni₄₈Co₅₂ alloy at 300 K. That small amount of HCP clusters are dispersed on the surface, and cause the formation of dislocation in the border with FCC clusters.     

The effect of metallic environment and low temperature on the 253Es α decay rate

In recent publications it has been pointed out that the α decay of transuranic elements in nuclear waste can be considerably speeded up by putting them into metals. The proposed mechanism is based on the effect of electron screening of radioactive nuclei (according to the Debye electron plasma model), which grows enhanced as temperature decreases. To verify the predicted phenomenon, half-lives of ²⁵³Es nuclei implanted in a metallic iron foil were measured at the temperature from 4 K to 50 mK. The results agree with the room-temperature data reported in the literature; no temperature dependence of the half-life was found within the error of ≈2%.     

The effect of SRS on pilot-tone detection technique in DWDM system

A math model that can describe the effect of stimulated Raman scattering (SRS) on pilot-tone detection technique is proposed.Through numerical simulation,it is shown that the effect of SRS could produce ghost-tones.The power of ghost-tones was larger for the channels separated further from the real-tone. The power ratio between real-tone and ghost-tones increases linearly with the increase of transmission length when propagation distance longer than 300 km.     

The effect of nitrobenzene on the Raman spectra of ribonuclease in aqueous solution

The Raman spectra of the native ribonuclease treated with nitrobenzene in aqueous solution have been obtianed. The conformation of the main chain and the side chain in ribonuclease were studied. Among the amide Ⅰ and amide Ⅲ bands, the characters of β-sheet and random coil structures are clear. The disulfide bridges assume the gauche-gauche-gauche conformation. The parts of tyrosine residue are buried. It indicates that nitrobenzene treatment on protein aqueous solution is an efficient means for obtaining better Raman spectra.     

The effect of the polytropic index γ on the structure of gaseous detonations

The present study aims to clarify the effect of the polytropic index (i.e., the ratio of specific heats in the context of a perfect gas) on the detonation structure. This is addressed by two-dimensional numerical simulations. To ease the clarification of the role of gasdynamics, a simple Arrhenius kinetic law is used for the chemical model. The activation energy, normalized by the shock temperature, is kept constant to obtain the same reaction rate sensitivity to temperature in all considered mixtures. This procedure dissociates the gasdynamic effects from the chemistry effects. The numerical results reveal that in mixtures with low polytropic indicies, the convective mixing is enhanced compared to mixtures with higher polytropic indicies. The mixing is evaluated using Lagrangian tracers. Moreover, mixtures with low polytropic indicies are found to have a shorter reaction length than mixtures with high polytropic indicies. Also, for the range of parameters considered in this study the results indicate that Mach stem bifurcation in detonations due to jetting is primarily a gasdynamic driven mechanism.     

The effect of perturbedk-selection and gap shrinkage on the optical transitions in III–V semiconductors

Optical transitions in direct semiconductors are governed according to simple one-electron treatment by ak-selection rule, which in doped or mixed crystals is but lifted to some extent (k) caused by 1) shallow impurities, 2) isoelectronic impurities or 3) alloy scattering. Values of k for these mechanisms are given and the implications for line shapes of optical spectra are discussed.Furthermore, as to the position of lines in the optical spectra of highly doped or highly excited crystals, gap shrinkage effects have to be considered, three main mechanisms of which can be distinguished: 1) Quadratic response of the band edges with respect to the fluctuating potential of the (screened) impurities, 2) polaron effects and 3) carrier exchange and correlation effects. Results of theoretical calculation are compared with experimental findings for GaAs and GaP. The practical importance of gap shrinkage effects for gain measurements and for the operation of (Ga, Al) As laser diodes is pointed out.From the Coulomb interaction of the carriers an additional mechanism for the lifting of thek-selection rule (especially valid for pure, but excited semiconductors) can be derived (plasmon coupling): Estimations show that the simplek-selection rule is almost never fulfilled within the energy range of emission spectra and that these spectra can be well explained simply assuming no-k-selection even for pure direct material.