Brazing of A5056 aluminium alloy with the aid of ultrasonic vibration using Ag filler metal

In order to produce a high strength brazed joint of A5056 aluminium alloy containing magnesium of about 5 mass%, the authors applied a flux-free brazing method with the aid of ultrasonic vibration to the aluminium alloy by selecting pure Ag foil as brazing filler metal and examined the effect of brazing conditions on the joint properties. The main results obtained in this study are as follows.

At a brazing temperature of 570°C, just above the eutectic point of Al–Ag binary system, application of ultrasonic vibration for 4.0 s provided the brazed joint with the maximum tensile strength and the strength decreased with the application time. When the brazing temperature was varied from 550 to 580°C and the application time of ultrasonic vibration was kept constant at 4.0 s, the joint brazed at 560°C attained the maximum tensile strength and fractured in the base metal. It was found that using a pure Ag foil as brazing filler metal successfully brazed A5056 aluminium alloy and the joint strength was equivalent to that of the base metal. Fracture of the joint was prone to occur along the (Al₃Mg₂ + Al solid solution) phase with high hardness formed at the grain boundary of the base metal. The amount of the hard (Al₃Mg₂ + Al solid solution) phase increased with the ultrasonic application time and the brazing temperature. It seemed that the increase of the hard (Al₃Mg₂ + Al solid solution) phase mainly caused the brazed joint strength to decrease.     

Impulsive responses of functionally graded material bars due to collision

We investigated the ability of functionally graded materials (FGMs) to absorb impact energy by mathematically analyzing the impulsive responses of functionally graded (FG) bars colliding with a homogeneous bar on the basis of Laplace transformation and calculated by using numerical transformation and its inversion. Young’s modulus in the FG bar was assumed to be proportional to the square of its density, which was similar to foam materials. Results showed that maximum impact loads were not strongly dependent on the distribution of material property in the FG bar. In the FG bar with increasing modulus from the impact end to the fixed end, much larger compressive stress and even large tensile stress occurred near the fixed end compared with the ones in the homogeneous bar. In the FG bar with decreasing modulus from the impact end, the compressive stress was approximately the same as the one in the homogeneous bar, and the history of the stress varied regularly.     

Reverse-reward learning in squirrel monkeys (Saimiri sciureus): Retesting after 5 years, and assessment on qualitative transfer.

Seven squirrel monkeys (Saimiri sciureus) previously trained on reverse-reward tasks were presented with the original “1-versus-4” task after a 5-year interval without reverse-reward experience (Experiment 1). None of them reliably selected the smaller food array; however, at around chance level, their performance was superior to when they were first exposed to the task almost 6 years previously, suggesting some long-term memory retention. One naive monkey consistently selected the larger array, as expected. In Experiment 2, trials consisting of 1 versus 1 piece of two qualitatively different types of food were interspersed among familiar 1-versus-4 trials. None of five monkeys tested reliably selected the less-preferred food to get the more preferred food as the reward, and one monkey scored below chance. However, when one piece of low-preference food was paired with four pieces of high-preference food (Experiment 3), all four monkeys tested avoided reaching for the latter and thereby obtained it as the reward; two monkeys obtained perfect scores on these trials. These two monkeys were trained on a specific qualitative reverse-reward pairing and then again tested on new pairings (Experiment 4), but transfer was incomplete. Compound trials that pit quantity against quality in novel ways appear taxing for squirrel monkeys, despite competence in reverse-reward on both dimensions separately. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Highly polarized single-c-domain single-crystal Pb(Mn,Nb)O(3)-PZT thin films

In-plane unstrained single-c-domain/single-crystal thin films of PZT-based ternary ferroelectric perovskite, ξPb(Mn,Nb)O3-(1 - ξ)PZT, were grown on SrRuO(3)/Pt/MgO substrates using magnetron sputtering followed by quenching. The sputtered unstrained thin films exhibit unique ferroelectric properties: high coercive field, Ec > 180 kV/cm, large remanent polarization, P(r) = 100 μC/cm(2), small relative dielectric constants, ε* = 100 to 150, high Curie temperature, Tc = ~600 °C, and bulk-like large transverse piezoelectric constants, e31,f = -12.0 C/m(2) for PZT(48/52) at ξ = 0.06. The unstrained thin films are an ideal structure to extract the bulk ferroelectric properties. Their micro-structures and ferroelectric properties are discussed in relation to the potential applications for piezoelectric MEMS.     

A 1.9 $e^{-}$ Random Noise CMOS Image Sensor With Active Feedback Operation in Each Pixel

A 1.9 e^- random noise CMOS image sensor has been developed by applying an active feedback operation (AFO), which uses a capacitive feedback effect to floating diffusion (FD) by a gate-source capacitance of a pixel source follower (SF), in a CMOS image sensor with a lateral overflow integration capacitor (LOFIC) technology. It is described that the AFO is suitable for CMOS image sensors with LOFIC because the design of the full well capacity and the FD can be independently optimized. The AFO theory is found to be explored to a large signal voltage in detail, as well as the conventional analysis of the capacitive feedback effect of the pixel SF for a small signal voltage. A 1/4-in 5.6- mum-pitch 640(H) times 480(V) pixel sensor chip in a 0.18-mum two-poly-Si three-metal CMOS technology achieves about 1.7 times the sensitivity with AFO compared with the case where the feedback operation is not positively used, resulting in an input-referred conversion gain of 210 muV/e^- and an input-referred noise of 1.9 e^-. A high well capacity of 130 000 e^- is also achieved.     

The effect of video game competition and violence on aggressive behavior: Which characteristic has the greatest influence?

Objective: This study is the first to our knowledge to isolate the effect of video game violence and competitiveness on aggressive behavior. Method: In Pilot Study 1, a violent and nonviolent video game were matched on competitiveness, difficulty, and pace of action, and the effect of each game on aggressive behavior was then compared using an unambiguous measure of aggressive behavior (i.e., the Hot Sauce Paradigm) in Experiment 1. In Pilot Study 2, competitiveness was isolated by matching games on difficulty and pace of action, and systematically controlling for violence. The effect of video game competition on aggressive behavior was then examined in Experiment 2. Results: We found that video game violence was not sufficient to elevate aggressive behavior compared with a nonviolent video game, and that more competitive games produced greater levels of aggressive behavior, irrespective of the amount of violence in the games. Conclusion: It appears that competition, not violence, may be the video game characteristic that has the greatest influence on aggressive behavior. Future research is needed to explore the mechanisms through which video game competitiveness influences aggressive behavior, as well as whether this relation holds in the long-term. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Changes in Ovulation-Related Gene Expression during Induced Ovulation in the Amur Sturgeon (Acipenser schrenckii) Ovarian Follicles

The luteinizing hormone (LH) and maturation-inducing steroids (MIS), such as 17α,20β-dihydroxy-4-pregnen-3-one, regulate the final oocyte maturation in teleosts. Oocyte maturational competence (OMC) and ovulatory competence measure the sensitivity to MIS for oocyte maturation and ovulation, respectively. However, the molecular mechanisms underlying the acquisition of ovulatory competence remain unknown. Sturgeons are an excellent research model for investigating these mechanisms. We examined the seasonal profiles of OMC and ovulatory competence in vitro and the expression of 17 ovulation-related gene candidates using quantitative PCR in Amur sturgeon ovarian follicles. The ovulatory competence was induced by the LH-releasing hormone analog (LHRHa) priming injection after acquiring the OMC, which was spontaneously induced in spring or autumn. Seven genes, including the tissue-type plasminogen activator (plat), were enhanced following the LHRHa priming injection in ovarian follicles sampled from anovulated and ovulated fish. The activin receptor type 1 (acvr1) and prostaglandin G/H synthase 2 (ptgs2) were only upregulated in ovulated fish. Our results suggest that plat/plasmin and prostaglandin (PG)/PG receptor systems are essential for sturgeon ovulation, similar to other vertebrates. Notably, successful ovulation depends on a sufficient PG synthesis, and mediators activating the PG/PG receptor system are essential for acquiring the ovulatory competence. We provide the first report of ovulation-related gene alterations in the ovarian follicles of Amur sturgeons.     

New Pb-Based 1222 Cuprates, (Pb0.5B0.5)Sr2(RE2−x−y Ce x Sr y )Cu2O z (RE = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y)

New Pb-based layered cuprates with the 1222 structure have been synthesized in the (Pb_0.5B_0.5)Sr₂ (RE_2−x−y Ce _x Sr _y )Cu₂O _z (RE = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Y) systems. The almost-single-phase samples in the systems can be obtained for a nominal composition of x=0.7 and y=0.1. The crystal structure of the samples has a tetragonal symmetry, the lattice parameters of a and c are increasing with increasing the ionic radius of RE element. Despite treatment under high O₂ pressure of 100 atm, the samples are semiconductors with the transport process characteristic of three-dimensional variable range hopping conduction.     

Loads carrying capacity map for the surface texture design of SiC thrust bearing sliding in water

Water lubricated silicon carbide is expected to be widely used for sliding bearings and mechanical seals in hydraulic systems since it is environmentally friendly and saves energy. The purpose of this study is to find the optimum surface texture to improve the load carrying capacity of SiC bearings working in water. Micro-pits, evenly distributed in a square array, were selected as the texture pattern, and formed on one of the contact surfaces by reactive ion etching. Experiments, which simulate the working condition of thrust bearings, were carried out to evaluate the effects of the micro-pits on the critical load of the transition of the lubrication mode from hydrodynamic to mixed. The results are summarized in the form of a load carrying capacity map. It was found that an optimum geometric and distributive range of micro-pits exists, where the load carrying capacity can be increased at least twice over that of an untextured surface.