Search

Traditional tool was difficult to achieve digitisation and precision in manufacturing high-speed train panels. Thus, multi-point tooling was proposed as a novel and flexible manufacturing equipment. In this paper, the principle and implementation of multi-point tooling were described, and the key techniques in stretching and trimming process were discussed. To verify the feasibility and manufacturing effects in application, typical high-speed train panels forming process was carried out with multi-point tooling and commercial finite-element software, respectively. Comparison and analysis of strain distribution, thinning rate in thickness and shape errors were made between simulation results and experimental results. The results show consistency and may provide instructive guidance on high-speed train panels manufacturing.

Background:Some studies demonstrated that physical activity may have beneficial effect on cognitive function. The objective of the study was to estimate the association between physical activity and cognitive function in community-dwelling elderly Chinese in Hong Kong (HK) and Guangzhou (GZ).Methods:In the neighborhood of HK and GZ, a convenience sample of 557 (260 in HK and 297 in GZ) older persons without dementia aged over 60 years (73.4 ± 6.5) was recruited. Physical activity was measured using a checklist. Information on physical activity participation, cognitive function, and other variables were collected. Multivariate linear regression analyses were performed to evaluate the association between physical activity and cognitive function.Results:Total number of physical activities showed significant association with the delayed recall test (p < 0.01) and category verbal fluency test (CVFT) (p < 0.01). However, with further adjustment for participation in intellectual activity, the coefficients were no longer statistically significant (p > 0.05)Conclusion:Physical activity may not be associated with better cognitive function among elderly Chinese independently of other factors.

Denti-strip inclusion is a new type reinforcement that consists of conventional strip type reinforcement and vertical inclusions which are installed on the strip in spacing. A series of laboratory model tests were carried out on a physical model of reinforced sloped embankment with strip inclusions and denti-strip inclusions under surcharge. Compared with strip reinforcement, it is found that due to the existence of vertical reinforcing elements which provided passive resistances against shearing and enhanced soil strength, denti-strip inclusions are more effective in improving the ultimate surcharge, reducing the settlement and restricting the lateral displacement of the slope. Furthermore, the shear bands in the embankment reinforced with two-layer inclusions under the condition without cutting of reinforcements are separated into several discontinuous arc bands by the inclusions unlike the single continuous arc in unreinforced embankment; the inclination angles of the shear bands are greater than that of unreinforced embankment and the position of the lower arc is close to the mid-height of embankment.

Background Gum chewing has been reported to enhance bowel motility and reduce postoperative ileus (POI). However, the efficacy remains imprecise for women following caesarean section. Objectives To summarise and evaluate the current evidence for postoperative gum chewing on the recovery of bowel function following caesarean section. Search strategy We searched studies from the following electronic databases: PubMed, EMBASE, SCOPUS and Cochrane Library from inception to 30 May 2013. Selection criteria We included randomised controlled trials (RCTs) of women after caesarean section; these RCTs should compared gum chewing with no gum chewing and reported on at least one of the outcomes: time to flatus, time to bowel sound, time to passing stool and length of hospital stay (LOS). Data collection and analysis Study outcomes were presented as mean differences (for continuous data) with 95% confidence interval (95% CI). The risk of bias in the study results was assessed using the assessment tool from the Cochrane Handbook. Main results Six RCTs including 939 women were included in our meta-analysis. The pooled results demonstrated that gum chewing is superior to no gum chewing with a reduction of 6.42 hours (95% CI −7.55 to −5.29) for time to first flatus, 3.62 hours (95% CI −6.41 to −0.83) for time to first bowel sound, 6.58 hours (95% CI −10.10 to −3.07) for time to first stool and 5.94 hours (95% CI −9.39 to −2.49) for LOS. In addition, no evidence emerged for any side effects caused by gum chewing. Conclusions The current evidence suggests that gum chewing is associated with early recovery of bowel motility and shorter LOS for women after caesarean section. This safe and inexpensive intervention should be included in routine postoperative care following a caesarean section.

In this study, algae and microcystins (MC-LR and MC-RR) were studied in 6 reservoirs in the northeastern part of Haihe River Basin. The results indicate that the eutrophication degree of most reservoirs has been obviously improved, but Yuqiao reservoir and Yanghe reservoir are still in the state of eutrophication. The MC-LR and MC-RR were also detected in Yuqiao reservoir and Yanghe reservoir. In addition, cyanobacteria were dominant spices in the eutrophic reservoirs, and the concentration of microcystins was positively correlated with algae density. Although the concentration of MC-LR is lower than the concentration limits of sanitary standard for drinking water. It is suggested that it should be monitored during the outbreak of cyanobacteria, especially in the later stage of outbreak considering a risk for the health of the water supply population.

The band offsets of the ZnO/anatase TiO2 and GaN/ZnO heterojunctions are calculated using the density functional theory/generalized gradient approximation (DFT/GGA)-1/2 method, which takes into account the self-energy corrections and can give an approximate description to the quasiparticle characteristics of the electronic structure of semiconductors. We present the results of the ionization potential (IP)-based and interfacial offset-based band alignments. In the interfacial offset-based band alignment, to get the natural band offset, we use the surface calculations to estimate the change of reference level due to the interfacial strain. Based on the interface models and GGA-1/2 calculations, we find that the valence band maximum and conduction band minimum of ZnO, respectively, lie 0.64 eV and 0.57 eV above those of anatase TiO2, while lie 0.84 eV and 1.09 eV below those of GaN, which agree well with the experimental data. However, a large discrepancy exists between the IP-based band offset and the calculated natural band offset, the mechanism of which is discussed. Our results clarify band alignment of the ZnO/anatase TiO2 heterojunction and show good agreement with the GW calculations for the GaN/ZnO heterojunction.

A non-intrusive method is proposed in this study with details showing the steps to convert rail pad into a load sensor for train wheel damage detection applications. The fabrication process is simple, requiring only the addition of a thin PVDF-based multilayered sensing device (approximately 0.7 mm) beneath the rail pad. An alternating-strip configuration is adopted in the multilayered sensing device, comprising active strips for sensing the vertical forces acting on the rail pad and dummy strips for resisting the potential lateral forces together with the baseplate shoulder. To validate the performance of the proposed rail pad sensor, both laboratory and field tests have been conducted. The tests results highlight the feasibility and potential of the rail pad sensor for train wheel condition monitoring. Unlike conventional strain gauge-based wheel load monitoring system, the rail pad sensor does not have blind zone problem.

This randomized, double-blind, placebo-controlled study evaluated whether lamivudine given during late pregnancy can reduce hepatitis B virus (HBV) perinatal transmission in highly viraemic mothers. Mothers were randomized to either lamivudine 100 mg or placebo from week 32 of gestation to week 4 postpartum. At birth, infants received recombinant HBV vaccine with or without HBIg and were followed until week 52. One hundred and fifty mothers, with a gestational age of 26-30 weeks and serum HBV DNA >1000 MEq/mL (bDNA assay), were treated. A total of 141 infants received immunoprophylaxis at birth. In lamivudine-treated mothers, 56 infants received vaccine + HBIg (lamivudine + vaccine + HBIg) and 26 infants received vaccine (lamivudine + vaccine). In placebo-treated mothers, 59 infants received vaccine + HBIg (placebo + vaccine + HBIg). At week 52, in the primary analyses where missing data was counted as failures, infants in the lamivudine + vaccine + HBIg group had a significant decrease in incidence of HBsAg seropositivity (10/56, 18%vs 23/59, 39%; P = 0.014) and in detectable HBV DNA (11/56, 20%vs 27/59, 46%; P = 0.003) compared to infants in the placebo + vaccine + HBIg group. Sensitivity analyses to evaluate the impact of missing data at week 52 resulting from a high dropout rate (13% in the lamivudine + vaccine + HBIg group and 31% in the placebo + vaccine + HBIg group) remained consistent with the primary analysis in that lower transmission rates were still observed in the infants of lamivudine-treated mothers, but the differences were not statistically significant. No safety concerns were noted in the lamivudine-treated mothers or their infants. Results of this study suggest that lamivudine reduced HBV transmission from highly viraemic mothers to their infants who received passive/active immunization.

Previous dual-frequency lasers mainly made use of artificial birefringence for frequency splitting, which were of a limited-frequency difference stability and complex construction. In this paper, we invented a novel Zeeman-birefringence He-Ne dual-frequency laser without any artificial devices, but by hole drilling in the cavity mirror. The laser-frequency difference (LFD) ranging from kilohertz to tens of megahertz was realized and the relationship between the LFD and the hole geometric sizes was investigated. Theoretical analyses were carried out. Characteristics of the LFD were explored for both the indium-sealed and hard-sealed lasers with a frequency stabilization system. The results showed the LFD with hole-drilling, indium-sealed lasers is maintained at 30 kHz within 2 h, which is better than the hard-sealed ones with a stability of 200 kHz within 2 h. The hole-drilling Zeeman-birefringence He-Ne lasers may make significant progress for the light source of the interferometers and Doppler velocimeters.

Summary Aim: CYP1A2, a constitutive enzyme expressed in the liver, is among the phase I enzymes responsible for polycyclic aromatic hydrocarbons metabolism. Phenacetin O-de-ethylation is a marker for CYP1A2 activity. This study investiagtes the metabolism of phenacetin in patients with hepatocellular carcinoma (HCC). Methods: The phenacetin test was performed in 56 normal subjects and 92 HCC patients. The test was repeated in HCC patients after treatment with transcatheter arterial chemoembolization (TACE). The recovery of phenacetin’s urinary metabolites was studies in 12 normal subjects and 14 patients with HCC. Results: Compared with normal controls, the recovery of phenacetin O-de-ethylated metabolites decreased by 42·5% (P

This paper, presents a robust spacer technology for definition of deca-nanometer gate length MOSFETs. Conformal deposition, selective anisotropic dry-etching and selective removal of sacrificial layers enabled patterning of an oxide hard mask with deca-nanometer lines combined with structures defined with I-line lithography on a wafer. The spacer gate technology produces negligible topographies on the hard mask and no residual particles could be detected on the wafer. The line-width roughness of 40nm poly-Si gate lines was 4nm and the conductance of 200@mm long lines exhibited a standard deviation of 6% across a wafer. nMOSFETs with 45nm gate length exhibited controlled short-channel effects and the average maximum transconductance in saturation was 449@mS/@mm with a standard deviation of 3.7% across a wafer. The devices exhibited a cut-off frequency above 100GHz at a drain current of 315@mA/@mm. The physical and electrical results show that the employed spacer gate technology is robust and can define deca-nanometer nMOSFETs with high yield and good uniformity.

Ni-salicided MOSFETs with a gate stack of ALD Al2O3/HfO2/Al2O3 high-x dielectric and poly-SiGe gate electrode were fabricated. The Si pMOSFETs with an EOT of 1.7 nm showed an expected gate leakage ...

Low-frequency noise was characterized in Si0.7Ge0.3 surface channel pMOSFETs with ALD Al2O3/HfO2/Al2O3 stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and ...

The temporal and spatial distribution of PAHs in surface-water from the typical rivers of North China was investigated. PAHs in typical rivers ranged from n.d. to 1.98 ng/L. LMW PAHs (2 and 3-ring) were abundant in surface water with high detection frequencies in Beisanhe River, while HMW PAHs (4 and 6-ring) were abundant in Luanhe River. Specific PAHs with its ratios were measured in order to deduce the possible sources of PAHs contaminant. The results indicate that the PAHs were from combustion processes in Beisanhe River, while PAHs were from petroleum products in Luanhe River.

Using comprehensive density functional theory calculations, the structural, electronic, and optical properties of novel fluorosilicene/chlorosilicene (F-silicene/Cl-silicene) heterobilayer are investigated. Our results unveil that the presence of hetero-halogen bonding (Si-F···Cl-Si) has a remarkable influence on the F-silicene/Cl-silicene bilayer. The F-silicene/Cl-silicene heterostructure in the most stable pattern has a moderate band gap of 0.309 eV, lower than that of isolated halogenated silicene. Encouragingly, F-silicene/Cl-silicene heterobilayers all have a direct band gap nature, irrespective of the stacking pattern, thickness and external electric fields (E-fields), which is an advantage over MoS2 layers. In addition, applying appropriate E-field leads to a significant enhancement of binding strength of the F-silicene/Cl-silicene heterobilayer. Especially, the band gap of the F-silicene/Cl-silicene heterobilayer can be effectively modulated by E-fields, even a semiconductor–metal transition occu...

Threshold voltage control for PMOSFETs using an undoped epitaxial Si channel and a p+-SixGe1-x gate

In this work, the formation of TiSi/sub 2/ from Ti/Mo bilayers on both blanket and patterned poly-Si substrates during rapid thermal annealing (RTA) was first studied by means of electrical measurements on van der Pauw test structures. Then, ohmic contacts between the silicide and both p- and n-type Si, as well as electrical shorts between the gate and source/drain electrodes were investigated.

A two-peak photoluminescence (PL) spectrum of ${\mathit{p}}^{\mathrm{\ensuremath{-}}}$-type porous silicon (PS) has been observed in atmospheric stored samples. According to different spectral characteristics, especially linewidth, and different effects induced by storage and illumination of samples, the low- and high-energy peaks are identified as due to emission caused by quantum confinement effects of remnant Si walls of PS and siloxene and/or ${\mathrm{SiO}}_{2}$ on PS surfaces, respectively. A light-emitting mechanism accounting for the two-peak PL spectrum is discussed.

The silicide growth over the spacers (bridging) in the conventional self-aligned silicide process using titanium disilicide is dominated by the lateral diffusion of Si atoms from the gate and source/drain areas. A TiN cap layer, which has been suggested to minimize the bridging problem was studied. The influence of such a capping layer on the reaction between Ti and Si, on the lateral diffusion of Si, and on the electrical properties of the TiSi 2 -Si contact was investigated.

A self-aligned titanium disilicide MOS process was investigated. Sputter deposited titanium films on silicon and silicon dioxide were heated in a Heatpulse rapid thermal annealing system either in nitrogen or in argon atmosphere. The silicidation-nitridation of titanium was carried out in two temperature steps; the behaviour was monitored by means of Rutherford backscattering and X-ray diffraction. Bridging over silicon dioxide spacers, which is known to create severe problems for self-aligned technique, was studied. In particular, the stability of titanium on silicon dioxide for the first temperature step was investigated in the temperature range 650–800°C. In this case, ellipsometry was used to study the reduction in the silicon dioxide thickness as a function of annealing time. The annealing atmosphere was found to have a large impact on the titanium-silicon dioxide interaction. Different wet etching solutions were examined and optimized for realistic MOS processing. Finally, MOS devices were fabricated and electrical measurements were performed to fully characterize the self-aligned process.

ZnO is a promising material for optoelectronic devices because of its wide bandgap and large exciton binding energy. However, majority of studies of ZnO nanostructures have been focusing on the study of their optical and structural properties. For device applications of ZnO, other factors besides ZnO material quality also play a significant role. For example, a typical ZnO nanorod based light emitting diode (LED) contains a polymer insulating layer and a top contact. The device performance is dependent on the insulating layer and top contact quality. In this work, the effect of different insulating polymers on the performance of p-GaN/n-ZnO LED was investigated. The structure of LED was: Au/ Ni/p-GaN/ZnO nanorods/insulating polymers/Ag. The ZnO nanorods were fabricated by hydrothermal method, and the length of the nanorods was 250 nm. In this work, we investigated absorption spectra, electroluminescence (EL) properties, and I-V curves to characterize the performance of the devices fabricated using spin-on glass (SOG), poly(vinylalcohol) (PVA), polymethyl methacrylate (PMMA) and polystyrene (PS) as insulating layers. Finally, the comparison of the performance of the devices with different polymers was discussed.

This works demonstrates a novel approach using Si implantation prior to Pt deposition and PtSi formation to control the underlap length between the PtSi source/drain regions to the gate in Schottky-Barrier (SB-) MOSFETs. Dopant segregation at the PtSi/Si interface is used to enhance device performance. With the lon /Ioff current ratio as an indicator, optimized Si implant doses are found for both n- and p-channel SB-MOSFETs. Through an effective barrier width, the underlap length has direct implication on the leakage current.

We study the variability of the electrical characteristics of silicon-on-insulator (SOI) SB-MOSFETs. A new method by extracting the variation of the threshold voltage from a large number of devices with different SOI thicknesses enables determining the main sources of variability and distinguishing between them. It is found that the device-to-device variability is mainly due to the inherent variation of the Schottky barrier (SB) height. An additional but smaller contribution stems from fluctuations of the SOI body thickness itself. However, scaling the SOI thickness down our measurements suggest that the SB inhomogeneity increases with decreasing tsi. Furthermore, employing dopant segregation during silicidation to realize low SB heights leads to an increase of the variability, too. Using the measured spread of PhiB we discuss on the base of simulations the influence of this variation on the on-current of SB-MOSFETs. The improved electrostatic gate control in multi-gate devices reduces the sensitivity of carrier injection on an inhomogeneous PhiB and thus suppresses the variability.

We present electronic band structure, Gibbs free energy of formation, and electric field modulation calculations for silicane nanoribbons (NRs), i.e., completely hydrogenated or fluorinated silicene NRs, using density functional theory. We find that although the completely hydrogenated silicene (H-silicane) sheet in the chair-like configuration is an indirect-band-gap semiconductor, a direct band gap can be achieved in the zigzag H-silicane NRs by using Brillouin-zone folding. Compared to H-silicane NRs, the band gaps of completely fluorinated silicene (F-silicane) NRs reduce at least by half. For all silicane NRs considered here, the Gibbs free energy of formation is negative but shows different trends by changing the ribbon width for H-silicane NRs and F-silicane NRs. Furthermore, by analyzing the effect of transverse electric fields on the electronic properties of silicane NRs, we show that an external electric field can make the electrons and holes states spatially separated and even render silicane NRs self-doped. The tunable electronic properties of silicane NRs make them suitable for nanotechnology application.

A significant reduction of negative oxide charges is observed in strained SiGe channel pMOSFETs, utilizing ALD high-k-gate dielectrics, after low temperature water vapor annealing. The negative charges may originate from non-bridging oxygen bonds in the dielectrics, which are passivated after the water vapor annealing. However, the subthreshold slope is not changed with the 300/spl deg/C annealing, which indicates that interface states are not affected.

The formation of Ni germanosilicides during solid-state interaction between Ni and heavily B-doped strained epitaxial Si1-xGex films with x=0.18, 0.32 and 0.37 is studied. No NiSi2 is found in these samples even after annealing at 850 °C, which can be compared to the formation of NiSi2 at 750 °C on Si(100). Resistance and diffraction studies for the Si0.82Ge0.18 sample indicate that NiSi0.82Ge0.18 forms and the NiSi0.82Ge0.18/Si0.82Ge0.18 structure is stable from 400 to 700 °C. For the NiSi1-uGeu formed in all Si1-xGex samples, where u can be different from x, a strong film texturing is observed. When the Ge fraction is increased from 18 at.% to 32–37 at.%, the morphological stability of the film is degraded and a substantial increase in sheet resistance occurs already at 600 °C. The contact resistivity for the NiSi0.8Ge0.2/Si0.8Ge0.2 interface formed at 550 °C is determined as 1.2×10-7 Ωcm2, which satisfies the RS contact resistivity requirement for the 70 nm technology node.

A previous investigation revealed that during annealing at high temperatures a CoSi 2 /polysilicon bilayer breaks down, resulting in an inverted bilayer structure because of silicon grain growth and cobalt redistribution. The present paper is devoted to the electrical effects of the observed phenomena. MOS capacitors were subjected to heat treatments in the range 750–900°C prior to the evaluation of breakdown statistics. The electrical results were compared with Rutherford backscattering spectrometry. It is concluded that the effects on gate oxide integrity are slight and reproducible even after partial inversion of the bilayer structure.

Contactless and accurate measurement of the temperature is an important issue in rapid thermal processing. In this letter we report on the variation of the emissivity of the surface during chemical vapor deposition of polycrystalline silicon onto oxidized silicon wafers. The observed periodic change in the emissivity of the polycrystalline silicon/silicon dioxide/silicon structure is due to interference phenomena in the growing layer. In these experiments the silicon wafers were heated by direct absorption of microwaves in a single wafer reactor. It is shown that with this method of heating, the change of emissivity does not influence the actual temperature of the substrate.

In an intensity modulated direct-detection (IMDD) optical communication system an external modulator is often used to avoid the effect of laser diode chirping. Even so, the phase noise of the laser diode at the transmitter can be converted into intensity noise by the chromatic dispersion of the single-mode fiber and therefore cause a power penalty.1,2 Equations for calculating this phase to intensity noise conversion have been given previously.3 In this paper, we use these results to assess the effect of such noise on an IMDD system using an erbium-doped fiber amplifier (EDFA) as a receiver preamplifier. The power penalty caused by this noise is presented so that it may be used in system design.

Erbium-doped fiber amplifiers(EDFAs) can be used to amplify solitons for long- haul transmission[1] or to reshape solitons[2]. When a very-short soliton evolves through an EDFA, if the gain per soliton period(GPSP) of the EDFA is large, before the nonlinearity takes effect the amplitude of the soliton pulse is amplified whilst the shape remains unchanged. After passing through some distance, the increase in amplitude renders the effect of non-linearity significant so that the amplified soliton pulse(ASP) becomes narrower and at the same time the amplitude increases even faster. Comparing the shape of the ASP with that of the fundamental soliton with the same amplitude(FSWSA), we may find that for a certain length of the EDFA the shape of the ASP best fits the shape of the FSWSA. This paper shows that such a length of the EDFA does indeed exist and analyses are provided of how this length and the shape of the ASP changes with the gain and the gain dispersion of an EDFA are also provided.

Mass fabrication of directly accessible, ultralong, uniform Si nanowires is realized by employing a controllable and reproducible method based on standard Si technology. High-conductivity polycrystalline Ni-silicide nanowires around 30 nm by 30 nm in cross section, able to support extremely high currents at ∼108A∕cm2, are obtained by means of solid-state reaction of the Si nanowires with subsequently deposited Ni films. By properly adjusting the Ni film thickness, NiSi, Ni2Si, and Ni31Si12 nanowires characterized with distinct resistivity and temperature coefficient of resistance are obtained. Upon annealing, the electrical continuity of the nanowires breaks at temperatures about 0.7 times the melting points of the silicides.

Lateral growth of Ni silicide towards the channel region of metal-oxide-semiconductor transistors (MOSFETs) fabricated on ultrathin silicon-on-insulator (SOI) is characterized using SOI wafers with a 20-nm-thick surface Si layer. With a 10-nm-thick Ni film for silicide formation, p-channel MOSFETs displaying ordinary device characteristics with silicided p+ source/drain regions were demonstrated. No lateral growth of NiSix under gate isolation spacers was found according to electron microscopy. When the Ni film was 20 nm thick, Schottky contact source/drain MOSFETs showing typical ambipolar characteristics were obtained. A severe lateral encroachment of NiSix into the channel region leading to an increased gate leakage was revealed, while no detectable voiding at the silicide front towards the Si channel was observed.

This paper describes a proof-of-concept work on implementing a polycrystalline p+-SixGe1-x gate electrode in both n- and p-channel metal-oxide semiconductor field-effect-transistors (MOSFETs). The process utilised for the fabrication of the MOSFETs only involved the use of two photo-lithographic masks. The device metallisation was realised using a self-aligned silicide process. The SixGe1-x film, deposited by the in situ B doping technique with 45?at.% of Si and 55?at.% of Ge, was found to be degenerately doped with a resistivity of 1?m?cm. It has been shown that the p+-Si0.45Ge0.55 gate controlled both types (n- and p-channel) of well functioning transistors at about the same threshold voltages (absolute values). This symmetrically controlled transistor characteristics was anticipated, since the work function of the p+-Si0.45Ge0.55 film is known to be close to the mid-bandgap value of Si.

We report microscopic photoluminescence images and corresponding spectra of epitaxial GaAs on Si substrates, prepared by molecular beam epitaxy. High magnification (3000×) images directly reveal dislocations present in the epilayer. Several substrate orientations are investigated including nominal (001) tilted 4° toward 〈110〉. The GaAs samples include structures grown with and without superlattice buffer layers. Some samples were annealed at several temperatures from 650 to 850 °C. The dislocation density versus depth is studied by varying the optical probe wavelength and by studying samples that had been beveled and etched. In addition, the images and spectra are studied over a wide temperature range.