[en] As one of the alternative to conventional sintering, the application of electrical fields during sintering has aroused interest since decades, aiming at reducing the sintering time as well as improving the targeted material properties. Field assisted sintering (FAST) has undergone rapid development in the last years, as it provides a platform for manufacturing materials which are difficult or even impossible to be produced by conventional sintering. More recently, strong focus is put on 'flash sintering' in the academia, where the densification completes within seconds. However, the governing principles behind the field assisted sintering are still unveiled. In this work, the sintering of yttria-doped ceria samples (10 mol % yttrium doped ceria, 10YDC, and 0.1 mol % yttrium doped ceria, 01YDC) was studied under alternating electrical fields with a frequency of 50 Hz and field strengths significantly weaker than those required for the ‘flash regime’. For the first time, the dependence of sintering parameters on the applied electrical fields was investigatedwith constant sample temperatures, which was ensured by direct temperature measurement inside the sample and by thermo-electric finite element simulations. This excluded the macroscopic Joule heating and allowed to investigate the occurring mechanisms. In addition, the symmetric behavior under compressive and tensile loading could be experimentally verified for the first time. This part of study was done during a research stay in National Institute for Materials Science (NIMS), Japan. Under AC electric fields, yttrium doped ceria is deformed more easily, as shown by a lower uniaxial sintering viscosity, and the driving force for densification during sintering becomes larger, as revealed by a higher uniaxial sintering stress. This points to the existence of other mechanisms because the macroscopic thermal effects were excluded beforehand. In order to gain a deeper understanding of the experimental results, activation energies of the material system were measured under AC electric fields with a frequency of 50 Hz. The activation energies for the densification decrease by the increase of electrical field strengths, exerting larger effects for 10YDC. The activation energy for the densification of 10YDC decreased very significantly from 502±40 kJ/mol without electrical fields to 311±25 kJ/mol under E${}_{rms}$=28 V/cm; it also reduced, but moderately, for 01YDC from 485±39 kJ/mol to 439±37 kJ/mol for the same conditions. In addition, ionic conductivities were measured to find out whether grain boundaries and related space charge layers are irreversibly modified by the electrical fields. The grain boundary conductivity of 10YDC decreased slightly after a longer holding time during fieldless sintering; it increased under the application of a non-contacting electrical field during sintering. On the other hand, the grain boundary conductivity of 01YDC did not change under the same conditions. The electrical fields applied during sintering did not change the activation energy for the ionic conductivities of neither bulk nor grain boundary even for 10YDC, but decreased the grain boundary effective capacitances which is the origin of the higher grain boundary conductivity for 10YDC sintered under electrical field. As the effect of macroscopic Joule heating was excluded in the experiments the following two possible mechanisms for the observed field effect are proposed: either microscopic Joule heating at the sintering necks and grain boundaries or a direct effect of the field on the grain boundary diffusion processes. The latter is favored, because the above mentioned increase of the grain boundary conductivities were observed together with a change of the valence state of the cerium ions in the vicinity of the grain boundary as analysed by transmission electron microscopy. It is worth mentioning that these changes were observed ex-situ at a low temperature. A quantification of the in-situ grain boundary structure during sintering remains an open and challenging investigation. Nevertheless, these phenomena could not exclude the microscopic Joule heating effect completely, therefore, characterization methods with high spatial and temporal resolution as well as the in-situ techniques are essential for further research of field assisted sintering.

[en] Rat stroke model with middle cerebral artery occlusion (MCAO) is easy, safe, and less affective to the nature progress of cerebral edema and intracranial pressure, and has been widely used in the study of cerebral ischemia. MCAO model has been used in studies with diffusion tensor imaging (DTI), which is enable assessment of the spatial and temporal patterns of functional and structural changes inside and outside ischemic areas in vivo to elaborate pathophysiological process after stroke. The traditional DTI allows estimation of the structural integrity and connectivity of white matter tracts. Some new DTI technologies, such as diffusion spectral imaging (DSI), the Q-ball imaging, and diffusion kurtosis imaging (DKI), extend the benefits of conventional DTI. Using these new imaging methods and the MCAO model provides a unique mean to discover the dynamic structural and functional changes after onset of stroke and to predict outcome and evaluate drug efficacy. This article outlines the methods and the latest progress of DTI and functional MRI based on the rat's MCAO model. (authors)

No abstract available

[en] Highlights: • A novel phenomenological model was established based on test data. • A global kinetic submodel and an original parametric submodel were included. • Dilution temp, exhaust temp, sulfur content and space velocity were considered. • The model serves as a useful tool for PM reduction and air pollution control. -- Abstract: Particle number is a key index for evaluating particulate emissions, and diesel oxidation catalysts (DOCs) are one of the most important technologies for controlling the particulate emissions of a diesel engine. In this paper, a novel phenomenological one-dimensional model was established to predict particle number and size distributions at a DOC outlet with the aim of investigating the effects of DOC on particle number emissions. The phenomenological model consisted of two submodels: submodel-1, a global kinetic model for calculating particle size in particle number and size distributions after particles had passed through the DOC, and submodel-2, an original global parametric model for calculating the particle number at the DOC outlet. The effects of the sampling process, fuel properties, and the engine operating condition were considered in submodel-2. An 8.8 L, direct-injection, heavy-duty diesel engine was tested. The particle number and size distributions at the DOC inlet and outlet were determined using an engine exhaust particle sizer. The test data, coupled with literature results, were used to calibrate and validate the phenomenological model. This model was then applied to investigate the influence of various factors on particle number and size distributions at the DOC outlet. It was found that dilution temperature, fuel sulfur content, exhaust gas temperature, and gas hourly space velocity (GHSV) played a key role in the particle number after DOC oxidation. The particle number concentration at the DOC outlet increased as fuel sulfur content and exhaust gas temperature increased and decreased as GHSV and dilution temperature increased. In general, results proved that this phenomenological model was accurate enough to predict particle number and size distributions at a DOC outlet under most operating conditions. It may serve as a useful tool for research and development focusing on PM reduction of diesel engines and air pollution control.

[en] The charge transfer potential barrier (CTPB) formed beneath the transfer gate causes a noticeable image lag issue in pinned photodiode (PPD) CMOS image sensors (CIS), and is difficult to measure straightforwardly since it is embedded inside the device. From an understanding of the CTPB formation mechanism, we report on an alternative method to feasibly measure the CTPB height by performing a linear extrapolation coupled with a horizontal left-shift on the sensor photoresponse curve under the steady-state illumination. The theoretical study was performed in detail on the principle of the proposed method. Application of the measurements on a prototype PPD-CIS chip with an array of 160 × 160 pixels is demonstrated. Such a method intends to shine new light on the guidance for the lag-free and high-speed sensors optimization based on PPD devices. (paper)

[en] A design of an inverse U-shape buried doping in a pinned photodiode (PPD) of CMOS image sensors is proposed for electrical crosstalk suppression between adjacent pixels. The architecture achieves no extra fill factor consumption, and proper built-in electric fields can be established according to the doping gradient created by the injections of the extremely low P-type doping buried regions in the epitaxial layer, causing the excess electrons to easily drift back to the photosensitive area rarely with a diffusion probability; the overall junction capacitance and photosensitive area extensions for a full well capacity (FWC) and internal quantum efficiency (IQE) improving are achieved by the injection of a buried N-type doping. By considering the image lag issue, the process parameters of all the injections have been precisely optimized. Optical simulation results based on the finite difference time domain method show that compared to the conventional PPD, the electrical crosstalk rate of the proposed architecture can be decreased by 60%–80% at an incident wavelength beyond 450 nm, IQE can be clearly improved at an incident wavelength between 400 and 600 nm, and the FWC can be enhanced by 107.5%. Furthermore, the image lag performance is sustained to a perfect low level. The present study provides important guidance on the design of ultra high resolution image sensors. (semiconductor devices)

[en] A novel analytical model of pinch-off voltage for CMOS image pixels with a pinned photodiode structure is proposed. The derived model takes account of the gradient doping distributions in the N buried layer due to the impurity compensation formed by manufacturing processes; the impurity distribution characteristics of two boundary PN junctions located in the region for particular spectrum response of a pinned photodiode are quantitative analyzed. By solving Poisson's equation in vertical barrier regions, the relationships between the pinch-off voltage and the corresponding process parameters such as peak doping concentration, N type width and doping concentration gradient of the N buried layer are established. Test results have shown that the derived model features the variations of the pinch-off voltage versus the process implant conditions more accurately than the traditional model. The research conclusions in this paper provide theoretical evidence for evaluating the pinch-off voltage design. (semiconductor devices)

[en] A quantum efficiency analytical model for complementary metal—oxide—semiconductor (CMOS) image pixels with a pinned photodiode structure is developed. The proposed model takes account of the non-uniform doping distribution in the N-type region due to the impurity compensation formed by the actual fabricating process. The characteristics of two boundary PN junctions located in the N-type region for the particular spectral response of a pinned photodiode, are quantitatively analyzed. By solving the minority carrier steady-state diffusion equations and the barrier region photocurrent density equations successively, the analytical relationship between the quantum efficiency and the corresponding parameters such as incident wavelength, N-type width, peak doping concentration, and impurity density gradient of the N-type region is established. The validity of the model is verified by the measurement results with a test chip of 160 × 160 pixels array, which provides the accurate process with a theoretical guidance for quantum efficiency design in pinned photodiode pixels. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

[en] We present a stellar population synthesis study of a type II luminous infrared galaxy, IRASF21013-0739. Optical images show clear characteristics of a merger remnant. The H-band absolute magnitude is M_H = -25.1, which is ∼2 times as luminous as L* galaxies. Stellar populations are obtained through the stellar synthesis code STARLIGHT. We find that it experienced a recent starburst (SB) phase ∼ 100 Myr ago. By reconstructing the ultraviolet-to-optical spectrum, and adopting Calzetti et al. and Leitherer et al.'s extinction curves, we estimate the past infrared (IR) luminosities of the host galaxy and find it may have experienced an ultraluminous infrared galaxy phase which lasted for about 100 Myr. Its i-band absolute magnitude is M_i = -22.463, and its spectral type shows type 2 active galactic nucleus (AGN) characteristics. The mass of the supermassive black-hole is estimated to be M_BH = 1.6 x 10⁷ M_o-dot (lower-limit). The Eddington ratio L_bol/L_Edd is 0.15, which is typical of Palomar-Green (PG) quasars. Both the nuclear SB and AGN contribute to the present IR luminosity budget, and the SB contributes ∼67%. On the diagram of IR color versus IR/optical excess, it is located between IR quasars and PG quasars. These results indicate that IRASF21013-0739 has probably evolved from a ULIRG, and it can possibly evolve into an AGN. (invited review)

[en] In this paper, the millimeter wave radar amplification device is designed using the MWG303 power amplifier chip of Milliway Electronic Technology Co., Ltd. The whole device comprises an input waveguide microstrip transition structure based on Rogers 5880 and an output waveguide microstrip transition structure based on quartz. And waveguide structures such as waveguide turn and waveguide lift, in this design, the waveguide microstrip transition circuit is designed and simulated in the 3D electromagnetic field simulation software HFSS of Ansoft Company, and then the parts are combined, and the micro-assembly test is carried out after CAD processing. The results show that the gain can reaches more than 10dB. The design has the advantages of high gain, good flatness, practical structure and so on. (paper)