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The formation mechanism of the metastable M2-phase VO2, which is believed to be a true Mott insulator, has attracted great attention for understanding the intriguing physics of the metal–insulator ...

A correct understanding of the effects of dopants and the electric field on the metal–insulator transition of VO2 remains a challenge. Herein, theoretical and experimental studies are performed to elucidate the role of W dopants and the electric field on the transition. W dopants are found to introduce additional localized electrons in d bands, which induce the splitting of d// orbitals and the V–V dimerization of local V ions in W-doped R-VO2. The experiments on electric-field-driven MIT of VO2 nanofilms indicate that the conductivity of W-doped R-VO2 increases with increasing applied voltage; however, for the pure R-VO2, the conductivity is independent of applied voltages. The phenomena evidence that the electric field would excite the localized d electrons to the conduction band and result in the closure of the d// orbital splitting. This work gives an insight into electric-field-driven MIT and doping engineering of VO2, which would offer opportunities for improving and promoting the applications of VO...

A self-designed single-axle vehicle is used to detect the bridge frequencies from its rocking motion, caused by wheels moving over an uneven surface. To include both the rocking and vertical motions, the single-axle vehicle is modeled as a two degree-of-freedom (DOF) system, unlike the previous single-DOF model. The rocking frequency, an inborn property of the vehicle, may pollute the frequency extraction of bridges in the test. The sensors mounted near the wheels (called the wheel sensors) for catching the rocking are of higher fidelity than the central sensor for the vertical motion. Both the vertical and rocking frequencies of the vehicle will be eliminated in the newly derived responses of the wheel-bridge contact points (CPs). In the flat road test, the vertical frequency of the test vehicle is identified from the average of the two wheel sensors responses, and rocking frequency from the angular response calculated. From the field test conducted on a two-span girder bridge, it is concluded that: (1) the new formulas for the CPs are reliable for scanning the bridge frequencies, while removing vehicle’s frequencies; (2) the present model enables us to look into the mechanism of the wheel-bridge contact for uneven surface roughness; and (3) temporary stop of the test vehicle on the bridge can help sharpen the bridge frequencies identified.

Bobbin tool friction stir welding (BT–FSW) is a novel and effective welding method for aluminum alloys, but microvoid defects are usually formed in the nugget zones (NZ). Therefore, it is important to understand the formation mechanism of microvoid defects and their effect on the fracture behavior of joints. In the present study, 6 mm thick 2219–T8 aluminum alloy plates were subjected to BT–FSW under a constant rotation rate of 300 rpm and welding speeds of 150–500 mm min–1 with the objective of analyzing the evolution of microvoid defects and their effect. The results showed that, lower welding speeds resulted in microvoid defects in the band pattern structure on the retreating side (RS) of the NZ, and the size of the defects decreased with increasing the welding speed, while sound joints were obtained under higher welding speeds. In contrast to conventional FSW precipitation–hardened aluminum alloys with the lowest hardness zone (LHZ) at the heat affected zone (HAZ), the LHZs of the BT–FSW 2219–T8 joints were located at the thermal–mechanically affected zone (TMAZ). Digital image correlation (DIC) of large tensile samples showed that the microvoid defects exhibited an obvious effect on the tensile deformation and fracture behavior of the joints due to the decrease in the maximum strain and lack of necking. Mini-samples in different layers further confirmed that cracks initiated from the microvoid defects in the NZ. However, the sound BT–FSW 2219–T8 joints fractured along the LHZs on the RS, with a maximum joint strength coefficient of 78.1% being achieved.

Finding appropriate structures of cathode materials is crucial to the development of sodium-ion batteries (SIBs). A novel NASICON-related structure (R-32 space group) of Na4MnAl(PO4)3 is synthesized, which exhibits a high specific capacity (116.8 mAh g−1) with two voltage plateaus of ~ 3.56 V and ~ 4.10 V for Mn3+/Mn2+ and Mn4+/Mn3+ redox couples, respectively. The sodium ion storage mechanism and diffusion mechanism are investigated by ex-situ XRD and ex-situ XPS, with the aid of first principle calculations. Both two-phase and solid solution reactions take place in the charge/discharge process, and the diffusion path along Na(1) ↔ Na(2) ↔ Na(3) is revealed for the first time in NASICON-structured materials. In addition, a voltage plateau of ~ 4.48 V of the Mn5+/Mn4+ redox couple is suggested by the DFT calculations in Na4MnAl(PO4)3, which may be more easily accessed than that of other compounds such as Na3MnTi(PO4)3 and Na3MnZr(PO4)3 reported in literature, leaving great potential in elevating the voltage and specific capacity for Na4MnAl(PO4)3 cathode. Because of high theoretical specific capacity, high voltage plateaus and low cost, Na4MnAl(PO4)3 is a strong contender in cathode material for SIBs.

A new lower tungsten divertor has been developed and installed in the EAST superconducting tokamak to replace the previous graphite divertor with power handling capability increasing from −2 to ∼10 MW m−2, aiming at achieving long-pulse H-mode operations in a full metal wall environment with the steady-state divertor heat flux of ∼10 MW m−2. A new divertor concept, ‘corner slot’ (CS) divertor, has been employed. By using the ‘corner effect’, a strongly dissipative divertor with the local buildup of high neutral pressure near the corner can be achieved, so that stable detachment can be maintained across the entire outer target plate with a relatively lower impurity seeding rate, at a separatrix density compatible with advanced steady-state core scenarios. These are essential for achieving efficient current drive with low-hybrid waves, a low core impurity concentration and thus a low loop voltage for fully non-inductive long-pulse operations. Compared with the highly closed small-angle-slot divertor in DIII-D, the new divertor in EAST exhibits the following merits: (1) a much simpler geometry with integral cassette body structure, combining vertical and horizontal target plates, which are more suitable for actively water-cooled W/Cu plasma facing components, facilitating installation precision control for minimizing surface misalignment, achieving high engineering reliability and lowering the capital cost as well; (2) it has much greater flexibility in magnetic configurations, allowing for the position of the outer strike point on either vertical or horizontal target plates to accommodate a relatively wide triangularity range, δ l = 0.4–0.6, thus enabling to explore various advanced scenarios. A water-cooled copper in-vessel coil has been installed under the dome. Five supersonic molecular beam injection systems have been mounted in the divertor to achieve faster and more precise feedback control of the gas injection rate. Furthermore, this new divertor allows for double null divertor operation and slowly sweeping the outer strike point across the horizontal and vertical target plates to spread the heat flux for long-pulse operations. Preliminary experimental results demonstrate the ‘corner effect’ and are in good agreement with simulations using SOLPS-ITER code including drifts. The EAST new divertor provides a test-bed for the closed divertor concept to achieve steady-state detachment operation at high power. Next step, a more closed divertor, ‘sharp-cornered slot’ divertor, building upon the current CS divertor concept, has been proposed as a candidate for the EAST upper divertor upgrade.

The properties for group IA and VA atoms doped BeS are studied by using the first-principles method. Our studies show BeS is a transparent semiconductor. The visible light transmittances could reach 80.0 %, as the thickness increases to 60.0 nm. The holes effective mass along the Г-X and Г-L directions are 0.56 and 1.34 m0 (m0 is electron’s static mass). The defective behaviors for group IA and VA atoms in BeS show that N substituting S, together with the Li and Na substituting Be are shallow acceptors, and the corresponding ionization energy levels e(0/-), compared to the valence band maximum, are 0.166, 0.177 and 0.25 eV, respectively. Formation energies imply under S-rich condition, NS, LiBe and NaBe defects can be realized experimentally by using the equilibrium growth conditions, while the detrimental hole killers, such as, VS, Bei, Nint, Liint and Naint would be inhibited as samples fabrication. These properties indicate N, Li and Na doped BeS may offer new opportunities in transparent electronics and optoelectronic applications.

In order to investigate the dynamic behavior of medium-fine-grained Huashan granite treated by different temperatures, the splitting tests on the granite specimens are carried out using an improved split Hopkinson pressure bar (SHPB). The dynamic force equilibrium condition in the specimen is basically satisfied. The results show that with increasing treatment temperature, the ultrasonic P-wave velocity decreases, while thermal damage accordingly increases. The damage evolution follows the logistic curve model. For a temperature at or below 500 °C, all the specimens break diametrically into two halves at relatively low impact velocities. As the impact velocity rises, the triangular crushed zones are observed at the two loading ends of the specimen. When the temperature exceeds 500 °C, the damage of the specimen becomes severe, and even completely pulverized under high impact velocity. There are good correlations between the splitting strength and the treatment temperature, the ultrasonic P-wave velocity as well as the thermal damage. In addition, the splitting strength is slightly abnormal at 100 °C, namely the strength becomes lower than that at room temperature with increasing impact velocity. Overall, the decay of the splitting strength with thermal damage for the treatment temperatures over 100 °C accords with the power function. Moreover, the splitting strength of specimen is sensitive to strain rate at high temperature, but the increasing rates are different under different ranges of temperature.

A magnetically tunable magnetoelectric transducer vibrator made of ring-type Pb(Zr,Ti)O 3 (PZT)/Terfenol-D (TDF) composite has been developed. We investigated the size effects of the vibrator resonance frequency. The relative effective permittivity and relative effective permeability of magnetoelectric composite are related to the size of ferromagnetic material. Improvements of about 469%, 176% and 696% of magnetoimpedance, magnetoinductance and magnetocapacitance have been achieved at anti-resonance of the vibrator, respectively. The dramatic change in the magnitude of capacitive type magnetoimpedance, magnetoinductance and magnetocapacitance shows that their responses depend on the size of the magnetostrictive ring in the transducer composite vibrator. The capacitive type magnetoimpedance effect can be substantially enhanced via properly designing the inner radius of magnetostrictive ring, which providing an alternative avenue for increasing magnetically tunable sensitivity.

A low-pass Ka-band MEMS tunable filter based on the high-resistivity silicon substrate with Electromagnetic-Bandgap Structure (EBG) is presented. The tunable filter consists of multiple MEMS switches fabricated by a CMOS-compatible surface micromachining process. The equivalent circuit model of the tunable EBG bandstop filter was derived based on the circuit analysis theory. The dispersion characteristics obtained are useful for describing and understanding the propagation characteristics of the EBG and the MEMS bridges. The performance of the single MEMS bridges is discussed. The measurement results of the tunable MEMS filter showsa 3-dB cutoff frequency tunable from 34.25 GHz to 26.60 GHz, while the average insertion loss varies from 0.25 dB to 0.22 dB. The whole chip size is 3.6 mm × 1.6 mm. This work demonstrates a high-performance miniaturized tunable low-pass filters at mm-waves frequency bands using Electromagnetic-Bandgap Structure.

The near-surface mounted (NSM) fibre-reinforced polymer (FRP) strengthening technique has become a viable strengthening method for reinforced concrete (RC) beams. Premature debonding failure of the NSM FRP strips is a common failure mode though that severely limits the effectiveness of the FRP intervention that results in reduced beam strength and deformability. The application of FRP U-jackets near the ends of the NSM strips offers a potential solution to the debonding problem. This paper presents the first systematic experimental investigation on the use of FRP U-jackets for delaying or preventing debonding failure in RC beams strengthened in flexure with tension face NSM FRP strips. A total of 11 large-scale RC beams were tested, with the investigated parameters being (i) arrangement of NSM carbon FRP (CFRP) strips, (ii) U-jacket material type, (iii) layout, width and inclination angle of FRP U-jackets. Failure modes, load-deflection and strain distribution responses of all tested beams were recorded. The test results bring clarity and understanding to the tested parameters and they also demonstrate the effectiveness of the U-jacket intervention.

A case of a woman with twin pregnancy having placenta percreta involving the colon, showed hematochezia symptoms, experienced bleeding which caused the patient's mortality. Placenta percreta with bowel involvement is a very serious complication of pregnancy. Symptoms are very atypical and it is very difficult to diagnose.

We obtain the geodesics for the simplest possible stealth defect which has a flat spacetime. We, then, discuss the lensing properties of such a defect, and the corresponding image formation. Similar lensing properties can be expected to hold for curved-spacetime stealth defects., Comment: 17 pages, v5: published version

The white wax insect Ericerus pela Chavannes (Hemiptera: Coccoidea) is an economically valuable insect species that has been used for over a thousand years in China. The present study focuses on assessing the genetic variability in different populations of E. pela collected from seven Chinese provinces. The amplified fragment length polymorphism technique was used to generate DNA fingerprints of individuals from each population using nine primer combinations (EcoRI-MseI). A total of 435 polymorphic loci were generated; fragment sizes ranged from 200 to 1000 bp. The percentage of polymorphic loci was 85.29%. Nei's genetic diversity and Shannon index indicated consistency in the results, which showed that the Sichuan population had the highest diversity, followed by Yunnan and Zhejiang populations. Dendrogram analysis showed the shortest genetic distance between the Sichuan and Yunnan populations, suggesting that they probably form sister groups. High genetic differentiation between population values among all sampled populations indicated a low degree of genetic variability within each population (40.85%) and higher variation among populations (59.15%). Gene flow estimate values were low in all samples, suggesting low gene flow from events such as interbreeding and migration. Low gene flow values also suggested that populations among species of E. pela might become genetically heterogeneous, due to counteracting forces such as strong differential selection. Our data support the probability that E. pela will remain localized, and has a low potential to spread beyond current habitats.

The aim of this study is to investigate the effects of working fluid (nitrogen, argon and oxygen) on the performance of adsorption cryocooler in the range 77–100 K. A thermodynamic model of adsorption cryocooler with two-stage compressor has been constructed. The model is based on quasi-static conditions without considering the temperature profiles and pressure drops across the compressor. It is then analyzed with an optimization toolbox to determine the optimum operating conditions to obtain the optimum performance of adsorption cryocooler. The Coefficient of Performance (COP) for each working fluid in the range 77–100 K is obtained and compared. It is found that working fluid has larger effects on adsorption compressor than on cold stage, and the optimum selection of working fluid depends on the operating parameters.

We process a 230-km-long MCS section and a coincident OBS refraction profile acquired across the Spratly Islands south of the SW SCS oceanic basin. By joint interpretation between MCS profile and OBS derived P-wave velocity field, we identify pre-rift units, two stages of syn-rift and post-rift sediments in the basins. Normal faults tilting pre-rift units root in a shallow decollement south of the profile. This shallow decollement is directly imaged by a thick band of reflectivity and also identified by a velocity contrast in the refraction derived P-wave velocity model. Deeper down (~7s twt), significant reflectivity may be interpreted as the top of the lower crust with ~7 km/s velocities. Even deeper reflectors around 10-11s may be related to the Moho or mantle. The images show moderate finite extension in the pre-rift sedimentary infill, although large faults penetrate the basement. Syn-rift units show that the tertiary rifting of the SW SCS may be characterized by rapid and short-lived activity of the faults or more subaerial conditions. Deeper, we infer that multiple heterogeneities present in the continental crust are used as decollement levels at different depths down to the ductile lower crust.

This paper presents the measurement results of bridge frequencies by a test vehicle in non-moving and moving states. The self-made test vehicle fitted with vibration sensors is a two-wheel trailer, intentionally used to simulate the theoretical single degree-of-freedom system. The two-span bridge selected is located in the Chongqing University campus. For the purpose of comparison, the bridge frequencies were firstly measured by direct deployment of vibration sensors on the bridge. The dynamic properties of the test vehicle in the non-moving state, including the transmissibility, are examined in detail. Based on the measured car-body response, the contact-point response of the vehicle with the bridge was calculated by a backward procedure that allows the vehicle frequency to be eliminated. It was found that the vehicle in the non-moving state can catch more bridge frequencies than in the moving state. Both the car-body and contact-point responses agree well the results by direct measurement. But the contact-point response performs better than the car-body response, which can be used to detect the first few frequencies of the bridge, including the torsional frequency.

A B S T R A C T Macromolecular polymers can effectively improve soil structure, increase soil penetration and control runoff and erosion on hillslopes. Simulated rainfall experiments on a bare soil investigated the impact of natural polymer derivatives (NPD) on soil properties and the characteristics of runoff and sediment yield of sheet erosion on experimental loessial hillslopes. A control (without NPD) and three concentrations of polymers (1, 3 and 5 g/m 2 ) were tested at rainfall intensities of 1, 1.5 and 2 mm/min and a slope gradient of 158. NPD effectively altered the onset, volume and sediment content of the runoff. Higher concentrations of NPD provided earlier onsets, lower depth and lower sediment contents of the runoff. Compared with control, cumulative runoffs decreased by 49–68%, 61–70% and 69–79% at concentrations of 1, 3 and 5 g/m 2 NPD, respectively, while cumulative erosion modulus decreased by 31–37%, 39–47%, 56–61%, respectively. Additionally, NPDs significantly increased the shear strength and the composition of aggregates from soil surface. Shear strength was 2.71, 3.24 and 4.01 times higher at 1, 3 and 5 g/m 2 , respectively, than in the controls. The percent mass of aggregates >0.25 mm increased to 52.5%, 62.65% and 73.0% from 8.9% in the control at the three respective concentrations. More research is needed to confirm the utility of NPDs in helping to control sheet erosion.

A tunable bandstop filter applying the micromachined technology is designed, simulated and fabricated. The filter is realized by incorporating defected ground structures structures with the micromachined switches. The surface micromachining fabrication process is employed on the high resistivity silicon substrate to fabricate the filter. The measured 3-dB cut-off frequency changes of the reconfigurable low-pass filter for four different states has been analyzed. The measured insertion loss is very lower in four tuning range of the filter. This work demonstrates the possibility of high-performance compact-size reconfigurable filters at mm-waves using multiple-contact micromachined switches. Simulated and measured results of the proposed filter show good agreements. The entire reconfigurable filter was realized in a small chip size of 1.2 mm × 1.5 mm.

The oxidation resistance of ultrafine diamonds (UFDs) was improved by encapsulating UFDs into silica shells forming core/shell structures with a PVP-aided method. Meanwhile, the dispersion stability of the UFDs in the inorganic salt aqueous solution was also improved greatly. In addition, adopting the silica-coated UFD aqueous suspension including multi-component inorganic salts, the coated UFDs–vitrified bond composite powders with higher homogeneity were obtained by using a polyacrylamide gel method, which was used for manufacturing the vitrified-bonded UFD wheels. The porous specimens of the UFD grinding wheels were fabricated with the above composite powders at low temperature in the air and in a muffle furnace. The results suggested that the porosity, bulk density and bending strength of the specimens were 36.3%, 1.71 g/cm − 3 and 62.9 MPa, respectively. Moreover, no obvious aggregation and degradation of UFDs were observed in the above UFD specimens. These results demonstrate a new pathway of preparing multifunctional nanostructure with a low-aggregation and high oxidation resistance that can be applied for manufacturing vitrified-bonded UFD wheels.

The lithium-ion battery can be reasonably abused by using it at a higher temperature than the general recommendation of 60 °C depending on the situation, such as in a car in the summer season. In this investigation, the material damage mechanisms of an isothermally exposed lithium-ion battery containing LiPF6 salt in the liquid electrolyte were investigated after exposure to 60 °C and 85 °C for up to 14 days, respectively. The chemical reaction product on the anode surface and microcrack in the cathode material were microscopically observed when exposed to 85 °C, while no such damage was observed for the battery exposed to 60 °C. These microscopic damages were in-situ monitored by applying electrochemical impedance spectroscopy (EIS) and acoustic emission (AE) technique, respectively. The possible mechanisms of these damages were discussed in relation to the role of the thermally decomposed LiPF6 salt and resulting products. The highly accelerated capacity degradation after exposure to 85 °C was attributed to the observed microscopic material damages.

This paper presents a novel approach in order to construct low-loss reconfigurable impedance matching networks and tuners using MEMS series-contact switches and periodic defected-ground-structures (DGSs) implemented on coplanar waveguide (CPW) transmission lines. The application of DGSs results in an improved insertion loss and power handling capability compared to the conventional RF MEMS impedance tuning networks. The proposed structure consists of 12 DGSs and RF MEMS series-contact switches. The tunable matching network was fabricated on a silicon substrate and is only 1.4×̃˾̈˰̽̽˰̹̾˰̵̹̓͊˾˰̸̵̤˰̵̵̴̱̽̓͂ͅ˰̼̿̓̓˰̶̿˰̸̵̈́˰̵͇̻̾̈́̿͂˰̸̵͇̾˰̵̴̓ͅ˰̈́̿˰̸̱̳̽̈́˰̱˰́̀˰Ω˰̴̼̱̿˰̈́̿˰̅̀˰Ω˰̶͂̿m 5GHz up to 40 GHz is only 0.8 dB. The results show that the tuner can achieve a broadband impedance match for a wide variety of loads that are either purely resistive or that have a large reactance as well.

In this paper, fully monolithic tunable millimeter-wave filters using defected ground structures (DGS) are proposed using the CPW-based periodic structures with novel multiple-contact MEMS switches. Millimeter-wave low-pass filters were designed, fabricated, and tested. The cascaded CPW-based periodic structures, with low-pass intrinsic filtering characteristics, are reconfigured into a self-similar single unit cell by the operation of the novel multiple-contact MEMS switches with single actuation. In the first order tuning, the 3-dB cut-off frequency changes from 8.2GHz to10.5GHz, and the second order tuning is 8.2GHz to 16.8GHz. The tested results show that the pass-band ripple is less than 1.2dB and the maximal out-of-band rejection is better than 27dB. The chip size of the low-pass filter is 2.5mm×1.2mm.

By observation of the phenological phase, the growth and bearing habits, biological characteristics of three Chinese jujube cultivars 'Zanhuangdazao', 'Xinledazao' and 'Hupingzao' were revealed. The results indicated that budbreak, leaf expansion, flowering and fruit set were earlier in 'Zanhuangdazao' than in the other two cultivars. The fruit of 'Hupingzao' was spindle-shaped and the largest one among the three cultivars, with smooth fruit surface, thin skin and dark red fruit color. Its flesh was thick, crisp and sweet. Budbreak, leaf expansion, flowering and fruit set of 'Xinledazao' were later than those of the other two cultivars and its bearing branch growth, leaf length and width increase were also slower.

The importance of gelcasting process is related to producing strong de-mouldable complex shape green bodies through polymerization of monomer in colloidal suspensions. As such, research in modeling of viscosity, stability, casting, polymerization, dispersion and toxicity of colloidal suspension is of particular importance as these factors affect the resultant green bodies. The current study uses a low toxicity gelling systems based on 2-hydroxypropyl methacrylate (HPMA), 2-hydroxyethyl methacrylate (HEMA), and N,N-dimethylacrylamide (DMAA) in the synthesis of copper green bodies through a non-aqueous gelcasting process. The monomers are polymerized in 1,2-propanediol and cross-linked by diethylene glycol diacrylate to form three dimensional network structures that hold the copper particles. Viscosity, polymerization time, flexural strength, and relative density of the resultant colloidal suspension having copper particles suspension are investigated in details. Their flexural strength and density values strongly depend on optimum gelcasting process parameters and the chemical character of the monomer used.