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The flow behavior of a high‐strength Ti alloy (Ti‐55511) in the β region is studied by hot compressive experiments. A dislocation density–based constitutive equation, together with processing maps, is established to describe the flow behavior and hot workability of the studied Ti alloy. It is found that the strain rate (ε˙) and temperature (T) distinctly influence the hot compressive deformation behavior. The flow stress increases distinctly with a rising ε˙ or reducing T. The main softening mechanism in the β region is dynamic recovery (DRV). The established constitutive equation based on the work hardening (WH) and DRV mechanisms has the desired prediction accuracy, and the correlation coefficient between the predicted and experimental results is 0.9912. The processing maps indicate that a high strain rate (0.4–10 s−1) easily causes unstable deformation, whereas low and medium strain rates (0.001–0.2 s−1) are suitable for hot compressive deformation of the studied alloy. [ABSTRACT FROM AUTHOR]

It is known that electroreflectance of surface-intrinsic-n[sup +]-type-doped GaAs has exhibited many Franz–Keldysh oscillations to enable the application of fast Fourier transform to separate the heavy- and light-hole transitions. However, each peak still contains two components, which belong to F+δF/2 and F-δF/2, respectively, where F is the electric-field strength in the undoped layer and δF is the modulating field of applied ac voltage (V[sub ac]). In order to resolve the heavy- and light-hole transitions, δF was kept much smaller than F in the previous works. In this work, we have used a larger V[sub ac] and, hence, a larger δF, to further separate the peaks. The peaks can be divided into two groups which belong to F+δF/2 and F-δF/2, respectively. The peak belonging to the heavy-hole transition and F-δF/2 can be singled out to compare with the Airy function theory. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The frequency dependence of the first molecular hyperpolarizability β of a thiophene based charge-transfer chromophore has been measured by using a number of excitation wavelengths emitted from an optical parametric amplifier pumped by a 1 KHz 130 fs Ti/sapphire laser. The excitation wavelength covers the resonance and nonresonance region of the charge transfer chromophore. β shows a maximum on the red side of the charge transfer electronic absorption band. A comparison of the experimental result with a recent proposed calculation involving the Kramers–Kronig transformation of the charge-transfer absorption spectrum is made. It is found that while the Kramers–Kronig transformation analysis predicts a correct position of the β maximum, it does not yield an agreement in the resonance region of the frequency dependent first molecular hyperpolarizability. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Up to now, there are few reports on the yield behavior of Ni-based superalloy during plastic deformation. However, an accurate yield stress model is significant for simulating the plastic forming process by cellular automaton or finite element methods. Therefore, the yield behavior of a solution-treated Ni-based superalloy is studied by hot compression tests. In order to evaluate yield stresses from the measured flow stress curves, the yield process is analyzed in terms of dislocation theory. Then, yield stresses at different deformation temperatures and strain rates are clearly determined. The experimental results show that the yield stresses are highly sensitive to deformation temperature and strain rate. The determined yield stress almost linearly increases with the increase of the logarithm of strain rate or the reciprocal of deformation temperature. A yield stress model is developed to correlate the yield behavior of the studied solution-treated Ni-based superalloy with deformation temperature, strain rate, and strengthening effect of alloying elements. The developed model can well describe the yield behavior of the studied solution-treated Ni-based superalloy. [ABSTRACT FROM AUTHOR]

The effects of stress-aging processing on corrosion resistance of an Al–Zn–Mg–Cu alloy were investigated. It is found that the one-stage stress-aged alloy is strongly sensitive to the electrochemical corrosion. The poor corrosion resistance of the one-stage stress-aged alloy can be attributed to fine intragranular aging precipitates and continuous distribution of grain boundary precipitates. Meanwhile, the incomplete precipitation of solute atoms results in high electrochemical activity of aluminum matrix. However, when the alloy is two-stage stress-aged, the corrosion resistance is greatly improved. Furthermore, the corrosion resistance decreases firstly and then increases with increasing the first stage stress-aging temperature. Increasing external stress can enhance the corrosion resistance of the two-stage stress-aged alloy. These phenomena are mainly related to aging precipitates within grains and along grain boundaries. The coarse and relatively low-density intragranular aging precipitates, as well as the discontinuously distributed grain boundary precipitates can enhance the corrosion resistance of the stress-aged alloy. [ABSTRACT FROM PUBLISHER]

Generally, the obvious work hardening, dynamic recrystallization (DRX), and dynamic recovery behaviors can be found during hot deformation of Ni-based superalloys. In the present study, the classical dislocation density theory is improved by introducing a new dislocation annihilation item to represent the influences of DRX on dislocation density evolution for a Ni-based superalloy. Based on the improved dislocation density theory, the peak strain corresponding to peak stress and the critical strain for initiating DRX can be determined, and the improved DRX kinetics equations and grain size evolution models are developed. The physical framework and algorithmic idea of the improved dislocation density theory are clarified. Moreover, the deformed microstructures are characterized and quantitatively correlated to validate the improved dislocation density theory. It is found that the improved dislocation density-based models can precisely characterize hot deformation and DRX behaviors for the studied superalloy under the tested conditions. [ABSTRACT FROM PUBLISHER]

The effects of pre-treatments on the precipitate microstructures of an Al–Zn–Mg–Cu alloy are investigated. Meanwhile, the creep-rupture behavior of the under-aged and peak-aged alloys are comparatively analyzed. Additionally, the effects of pre-treatment on the fracture mechanisms are discussed. It is found that the precipitate microstructures are sensitive to pre-treatments. The intragranular precipitates of the peak-aged alloy are larger than those of the under-aged. The precipitate free zone of the peak-aged alloy is wider than that of the under-aged. Some large intergranular precipitates appear on the grain boundaries of the under-aged alloy, and induce the nucleation of microvoids. Eventually, the creep fracture of the under-aged alloy is accelerated. Therefore, the differences in microstructures lead to the shorter creep-rupture life of the under-aged alloy, compared to the peak-aged alloy. [ABSTRACT FROM PUBLISHER]

The strain hardening effect and dynamic recovery behavior of a Ni-based superalloy are studied by isothermal compressive tests. A new unified dislocation-density based constitutive model is developed to characterize the strain hardening effect and dynamic recovery behavior of the studied superalloy. In the developed constitutive model, some material parameters (yield stress, strain hardening coefficient, and dynamic recovery coefficient) are assumed as functions of initial grain size, deformation temperature, and strain rate. An iterative algorithm is designed to predict the high-temperature deformation behaviors under time-variant hot working conditions. The hot deformation parameters and material parameters can be updated in each strain increment. Comparisons between the experimental and calculated flow stresses indicate that the developed constitutive model can accurately describe the high-temperature deformation behavior of the studied superalloy. Furthermore, the developed constitutive model is also successfully used for analyzing time-variant hot working processes. [ABSTRACT FROM PUBLISHER]

Apparent digestibility coefficients of dry matter, crude protein, lipid and energy, and amino acids availability in white fish meal, brown fish meal, meat meal, fermented soybean meal, soybean meal and rapeseed meal were determined for loach ( Misgurnus anguillicaudatus) (12.05 ± 0.21 g), using a reference diet with 5 g kg−1 chromic oxide and test diets that contained 700 g kg−1 reference diet, by weight, and 300 g kg−1 of the test feed ingredients. The juvenile loach was held in 300-l tanks at a density of 30 fish per tank. White fish meal, brown fish meal, meat meal and fermented soybean meal had highest apparent digestibility coefficients ( ADCs) of dry matter, crude protein and gross energy among ingredients tested, ranged from 50.4% to 60.9% for dry matter, from 64.6% to 88.4% for crude protein and from 57.9% to 79.0% for gross energy. The apparent digestibility coefficients of dry matter ranged from 61.0% to 66.9% for animal products and 50.4% to 60.7% for plant products. For crude protein, apparent digestibility coefficients of protein exceeding 80% were observed for white fish meal, brown fish meal, meat meal and fermented soybean meal, and the apparent digestibility coefficients of protein in rapeseed meal were the lowest among all the treatments. Lipids from both animal and plant feedstuffs were poorly digested by loach, ranging from 64.0% to 77.6%. The apparent digestibility coefficients of energy were similar to those of dry matter and protein, and the highest and lowest ADCs of energy were found in WFM and RM, respectively. The loach used dietary phosphorus from the animal feedstuffs more efficiently than from plant feedstuffs (soybean meal and rapeseed meal), with ADC-values ranging from 42.3% to 53.1% and from 25.1% to 32.7%, respectively. For the animal products, the availabilities of amino acids in white fish meal and brown fish meal were higher than that in meat meal, expect for Met, Asp, Pro, Gly, and Cys. Among all the plant products, the availabilities of amino acids in fermented soybean meal were higher than in soybean meal and rapeseed meal, and thus had a greater potential to be used as a dietary replacement of fish meal in loach diets. [ABSTRACT FROM AUTHOR]

This study assessed the oral health disparities and oral health care needs of children whose parents are Southeast Asian immigrant women in arranged transnational marriages. We used the baseline data of the Lay Health Advisor Approach to Promote Oral Health Program (LHA-POHP) to explore the disparities in oral health between immigrant and native children, and the factors associated with their oral health. A cross-sectional community-based study was conducted to collect data from mothers and their preschool children in Southern Taiwan in 2011. A total of 590 (440 natives, 150 immigrants) children aged 4-6 years and their mothers completed the questionnaire and oral examination. Multiple regression models were used to analyze the association between children's oral health and their related factors. The caries index was 6.05 in immigrant children and 3.88 in native children (p < 0.001). The caries prevalence of maxillary anterior teeth in the labial surfaces was higher among immigrants, ranging from 14.7 to 22%. The factor associated with children's caries index was maternal tooth brushing frequency (adjusted odds ratio [aOR] = 8.95, 95% confidence interval [CI] 1.95-41.05). When the mothers did not direct children to brush teeth after eating sweets, their children were more likely to have decayed teeth (aOR = 3.54, 95% CI 1.04-12.03). Children's filled teeth were related to their dental regular check-ups (aOR = 2.28, 95% CI 1.26-4.10). Disparities in oral health among immigrant and native children were observed. The findings suggest that culturally adequate oral health promotion intervention programs should be implemented for immigrants. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

A total of 630 juvenile Chinese sucker, with an average initial weight of 1.72 ± 0.05 g, were fed seven diets for 56 days to study the effect of dietary methionine levels on growth, feed utilization, body composition and haematological parameters on juvenile Chinese sucker. Diet 1 using fish meal as the sole protein source and diets 2-7 using fish meal and fermented soybean meal as intact protein sources supplemented with crystalline amino acids contained six levels of l-methionine ranging from 6.4 to 18.9 g kg−1 of dry diet at a constant dietary cystine level of 3.7 g kg−1. Each diet was randomly assigned to three aquaria. Results indicated that the highest weight gain, specific growth rate ( SGR), feed efficiency ratio, protein efficiency ratio and protein productive value occurred at 13.9 g methionine kg−1 diet among the methionine supplemented dietary groups, beyond which they showed declining tendency. The whole body and muscle protein contents of juvenile Chinese sucker were positively correlated with dietary methionine level, while muscle lipid content was negatively correlated with it. The total essential amino acids content of muscle was increased significantly with increasing dietary methionine level from 6.4 to 13.9 g kg−1 ( P < 0.05). Apparent digestibility coefficients of dietary protein were significantly affected by dietary treatments. Serum protein, cholesterol and triacylglycerol increased with increasing dietary methionine levels, but showed a relatively lower value for fish fed the 18.9 g methionine kg−1 diet. Quadratic regression analysis of SGR against dietary methionine level indicated that optimal dietary methionine requirement for juvenile Chinese sucker was 14.1 g kg−1 of the diet in the presence of 3.7 g kg−1 cystine (corresponding to 32.0 g kg−1 of dietary protein on a dry-weight basis). [ABSTRACT FROM AUTHOR]

Two feeding experiments were conducted to evaluate the potential of fermented soybean meal ( FSBM), corn gluten meal ( CGM) and cottonseed meal ( CSM) with or without lysine ( L) and iron ( Fe) to replace fish meal ( FM) in practical diets of juvenile Chinese sucker. In experiment I, four experimental diets (430 g kg−1 crude protein on dry matter basis) were formulated. Diet containing FM as the main protein source was used as a control ( Diet 1). Diets 2-4 had 300 g kg−1 FM protein replaced with FSBM, CGM or CSM protein without iron or lysine supplement. Fish (average weight, 1.82 ± 0.01 g) were hand-fed twice daily for 8 weeks. In experiment II, juvenile Chinese sucker (average weight, 3.40 ± 0.08 g) were fed one of five experimental diets twice daily for 8 weeks. Diet 1 in experiment I was used as a control and Diet 4 in experiment I, with ferrous sulphate, with lysine or with both ferrous sulphate and lysine were used as the experimental diets (designated as FM, CSM, CSM+ Fe, CSM+ L and CSM+ Fe& L, respectively). Results from the two feeding trials indicated that about 300 g kg−1 of FM protein can be replaced by FSBM, CGM or CSM with lysine supplement in Chinese sucker diets without adversely affecting growth. CSM with iron could not improve the growth performance. CSM without lysine supplement significantly affected the growth performance, body composition and digestive enzyme activities. [ABSTRACT FROM AUTHOR]

The study was designed to investigate the influence of fermented soybean meal ( FSBM) on the growth and feed utilization of juvenile Chinese sucker, Myxocyprinus asiaticus. Seven isonitrogenous and isolipidic diets were formulated with 0%, 15%, 25%, 35%, 45%, 55% or 65% replacement of fish meal with FSBM on a protein basis. Each diet was fed to three replicate groups of fish with an initial weight 4.59 ± 0.2 g for 8 weeks. Weight gain ( WG) and specific growth rate ( SGR) was significantly lower when FSBM inclusion was 391 g kg−1 or greater, replacing more than 45% fish meal protein. A significant negative relationship was observed between growth response and the level of fish meal protein replacement with FSBM. Methionine and Lysine content decreased as FSBM inclusion levels increased, consequently compromising growth performance. Feed intake ( FI) were unaffected by dietary FSBM levels. The feed conversion ratio ( FCR) of fish fed D-0, D-15, D-25 and D-35 diets was significantly lower than those fed other diets. The protein efficiency ratio ( PER) was highest at the lowest FSBM inclusion level. Experimental diets D-0, D-15, D-25 and D-35 had apparent dry matter digestibility ranging from 71.2% to 72.6% and apparent protein digestibility ( ADPs) from 89.1% to 90.1%, while the diets with higher FSBM inclusion ( D-45 to D-65) had a significantly lower apparent dry matter digestibility range (69.7-70.3%) and ADPs range (88.5-88.9%). It is concluded that FSBM is an acceptable alternative plant protein source that can replace up to 35% of fish meal protein in diets without significant adverse effects on growth, survival, FCR, PER and body composition. [ABSTRACT FROM AUTHOR]

Six isonitrogenous diets (420 g kg−1 crude protein on dry matter basis) with six levels of soybean meal ( SBM) inclusion (0, 112, 225, 336, 449 and 560 g kg−1) in substitution of fish meal (0%, 20%, 40%, 60%, 80% and 100%) were evaluated in Chinese sucker of 1.81 ± 0.01 g initial weight for 8 weeks. There existed a significant difference ( P < 0.001) in fish weight gain, feed conversion ratio, feed intake, protein efficiency ratio and specific growth rate when the replacement level for fish meal protein was increased from 40% to 60%, indicating that up to 40% of fish meal protein could be replaced with SBM protein without causing reduction in growth and protein utilization. Lipid contents in the Chinese sucker body decreased significantly ( P < 0.001) as dietary SBM increased. Digestive enzyme activities in the intestine and hepatopancreas of the fish were significantly different ( P < 0.001) as the SBM protein replacement level was increased. Results of the present study appear to indicate that 40% FM can be replaced by SBM in practical feeds of Chinese sucker. [ABSTRACT FROM AUTHOR]

In this study, the microstructural evolution of Sn-3Ag-0.5Cu/Au/Pd(P)/Ni(P) microbumps during isothermal aging was examined by electron probe microanalysis and scanning electron microscopy equipped with electron backscatter diffraction. The Au/Pd(P)/Ni(P) trilayer was deposited on 85- μm (opening diameter) Cu pads with a thickness combination of 0.15 μm/0.2 μm/8 μm. The reaction of the Au/Pd(P) dual layer with the molten solder yielded plenty of AuSn and PdSn grains in the solder matrix after reflow, which has never been observed previously in the literature. At the interface, discontinuous, facet-type CuSn [or (Cu,Ni)Sn] nucleated. Interestingly, the CuSn transformed into layered NiSn after subsequent aging for 250 h at 180°C. Moreover, the AuSn and PdSn agglomerated with each other and resettled to the region neighboring the interface. This configuration changed significantly when a pronounced corrosion occurred in the as-plated Ni(P) metallization pad. In the corroded Ni(P) case, CuSn rarely appeared at the interface immediately after reflow, but a large quantity of PdSn formed in the solder region near the corroded Ni(P) layer. AuSn in this case distributed uniformly throughout the entire solder joint. Isothermal aging treatment drove the PdSn and AuSn to deposit onto the corroded Ni(P) surface, where they merged with each other as a dense layer of (AuPdNi)Sn (250 h). The formation of the (Au,Pd,Ni)Sn layer over the corroded Ni(P) substrate provided a crack initiation site, deteriorating the mechanical reliability of the solder joint. The results of this study show that appropriate deposition of Au/Pd(P)/Ni(P) is very important for the thermal/mechanical reliability of microbumps. [ABSTRACT FROM AUTHOR]

Here, we present the characteristics of a novel GaN- based ultraviolet (UV) photodiode (PD) with a low-temperature (LT) AIN cap layer. The dark leakage current for the PD with the LT-AIN cap layer was shown to be about four orders of magnitude smaller than that for the conventional PDs. It was found that we could achieve larger UV to visible rejection ratio by inserting an LT-AIN cap layer. It was also found that we could improve minimum noise equivalent power and maximum normalized detectivity of the PD by inserting an LT-AIN cap layer. [ABSTRACT FROM PUBLISHER]

GaN-based ultraviolet photodiodes with a semi-insulating Mg-doped GaN cap layer were fabricated and characterized. Dark leakage current of the aforementioned photodiodes was much smaller than that of the conventional ones without the Mg-doped GaN cap layer due to a thicker and higher potential barrier and less amounts of interface states after inserting the Mg-doped GaN cap layer. The ultraviolet to visible rejection ratio is 3.44 x 103 by inserting a semi-insulating Mg-doped GaN cap layer with a -IV applied bias. In this study, we also discuss the noise characteristics. It was found that minimum noise equivalent power and maximum detectivity of our photodiode were 1.2 x 10-12 W and 9.34 x 1011 cmHz0.5 W-1, respectively. [ABSTRACT FROM PUBLISHER]

Mechanical properties of thin films on substrates can be evaluated directly through nanoindentation. For a comprehensive study, thin films should be characterized via Young’s modulus, yield stress and strain-hardening exponent at constant temperature. In this paper, we evaluate these effects of thin films on silicon substrate through finite element analysis. Thin films, from soft to hard relative to the silicon substrate, are investigated in three categories: soft films on hard substrates, soft to hard films on no elastic mismatch substrates, and hard films on soft substrates. In addition to examining the load-displacement curve, the normalized hardness versus normalized indentation depth is checked as well to characterize its substrate effect. We found that the intrinsic film hardness can be acquired with indentation depths of less than 12% and 20% of their film thickness for soft films on hard substrates and for soft to hard films on no elastic mismatch substrates, respectively. Nevertheless, nanoindentation of hard films on soft substrates cannot determine the intrinsic film hardness due to the fact that a soft substrate cannot support a hard film. By examining the von Mises stresses, we discovered a significant bending phenomenon in the hard film on the soft substrate. [ABSTRACT FROM AUTHOR]

Anomalous hot-carrier degradation phenomenon was observed in a 0.5-mum 12-V n-type drain-extended MOS transistors (N-DEMOS) with various n-type drain-drift (NDD) implant dosage. Under the same stress condition, the device with a higher NDD dosage produces a higher substrate current, a slightly higher transconductance degradation, but a lower ON-resistance (RON) degradation. Two degradation mechanisms are identified from the analysis of the electrical data and two-dimensional device simulations. The first mechanism is hot-electron injection in the accumulation region near the junction of the channel and accumulation regions. The second mechanism is hot-hole injection in the accumulation region near the spacer. This injection of hot holes creates a positive-charge trapping in the gate oxide, resulting in negative mirror charges in the accumulation region that reduces RON. The second mechanism is identified to account for the anomalous lower RON degradation [ABSTRACT FROM PUBLISHER]

Flip-chip p(GaN)-i(GaN)-n(AlGaN) photosensors with extremely low dark currents were fabricated and characterized. It was found that the sensor with a 0.5-mum-thick Si-doped n+-Al0.15Ga 0.85N layer could only detect optical signals with wavelength in between 325 and 360 nm. With an incident wavelength of 355 nm, the authors achieved a peak responsivity of 0.16 A/W at zero bias, which corresponds to an external quantum efficiency of 56% [ABSTRACT FROM PUBLISHER]

Nitride-based p-i-n sensors with indium-tin-oxide electrodes on Mg-doped AlGaN/GaN strain layer superlattice structure were fabricated and characterized. It was found that the fabricated sensors exhibit small dark current and large reverse breakdown voltage. With an incident wavelength of 355 nm, we achieved a peak responsivity of 0.17 A/W which corresponds to 59% external quantum efficiency for sensors with 500°C annealed ITO(70 nm) p-contacts. [ABSTRACT FROM PUBLISHER]