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The traditional rolling process for large ring part is to forge a large ring blank from a large cast ingot firstly and then ring rolling it to a large ring. However, large ingots are more likely to produce casting defects such as voids and composition segregation. The casting defects will bring hereditation to the final ring product, especially for super-large ring whose dimeter is more than ten meters. In this paper, a novel constructive hot ring rolling method to manufacture the high performance large ring is proposed. In this process, ring blank units are forged by high-quality small ingots firstly. Then the ring blank units are assembled together to a large ring blank and surface welded along the unit interface. Finally, the large assembled ring blank is heated and ring rolled to a large seamless ring. To verify the feasibility of the constructive hot ring rolling process, an experiment of constructive hot ring rolling process was carried out in the laboratory condition. Two separated rings are machined firstly. Then cleaning the surface of the two rings and assembling them together. Follow on, the upper and lower interfaces of the assembled ring are welded in the surface areas. Finally, the ring blank is heated to high temperature and deformed by radial ring rolling. The microstructure status and mechanical properties of the forming ring are tested. It is found that the interface is healed after high temperature rolling. The tensile strength of the constructive rolling ring is close to the ring rolled from a seamless ring blank. The research work can provide a new idea for the manufacturing technology of high performance large ring.

The application of a coordination container in biomedicine is hindered by single binding domains and unsatisfactory biostability and biocompatibility. Herein, we designed a sulfonylcalix[4]arene-based decahexanuclear zinc(II) coordination container employing a flexible tetracarboxylate ligand as a linker and utilized it as a novel drug delivery system. The coordination container consisting of one endo and four exo cavities provides multiple binding domains for efficient encapsulation of drug molecules as clearly revealed by systematic host-guest studies using NMR techniques of 1H NMR titration experiments and 2D NOESY and diffusion-ordered NMR spectroscopy studies. Incorporation of a flexible p-phenylene-bis(methanamino) spacer into the container via the carboxylate linker allowed a stepwise drug loading process through sequential binding at endo and exo cavities, as well as enabling pH-responsive stepwise drug release. The drug-loaded coordination container not only exhibits excellent biostability and biocompatibility but also provides encouraging therapeutic efficiency toward inflammatory macrophages as revealed by in vitro studies. The novel strategy for engineering the endo cavity of a coordination container provides a new approach to achieving controlled drug delivery and opens up new opportunities for designing novel functional supramolecular materials.

AlGaN/GaN E/D-mode GaN inverters are successfully fabricated on a 150-mm Si wafer. P-GaN gate technology is applied to be compatible with the commercial E-mode GaN power device technology platform and a systematic study of E/D-mode GaN inverters has been conducted with detail. The key electrical characters have been analyzed from room temperature (RT) to 200 °C. Small variations of the inverters are observed at different temperatures. The logic swing voltage of 2.91 V and 2.89 V are observed at RT and 200 °C at a supply voltage of 3 V. Correspondingly, low/high input noise margins of 0.78 V/1.67 V and 0.68 V/1.72 V are observed at RT and 200 °C. The inverters also demonstrate small rising edge time of the output signal. The results show great potential for GaN smart power integrated circuit (IC) application.

A flexible Ti/Cr/Ti multilayer strain gauge have been successfully developed based on polyimide substrate. The pure Ti metal strain gauge have shown the hysteresis phenomenon at the relationship between resistance and strain during tensile test. The experimental results of multilayer strain gauge show that adding Cr interlayer can improve the recovery and stability of the sensing electrode. When the interlayer Cr thickness was increased from 0 to 70 nm, the resistance decreased from 27 to 8.8 kΩ. The gauge factor (GF) value also decreased from 4.24 to 2.31 with the increase in the thickness of Cr interlayer from 30 to 70 nm, and the hysteresis phenomenon disappeared gradually. The multilayer Ti/Cr/Ti film has feasible application for strain sensor.

Graphite oxide (GO), often being used as a precursor of graphene-based materials, can be prepared through a modified Hummers' method. The last step of GO synthesis, i.e. the removal of hydrogen chloride (HCl), is generally time-consuming, costly and polluting. Herein, the HCl-containing graphite oxide (H-GO) and pure GO aqueous suspensions were respectively hydrothermally treated followed by freeze-drying, leading to two graphene aerogels (H-GA and GA). Characterization results show that the two aerogels possess similar microstructure but distinct surface chemistry properties. When used as the active electrode materials in supercapacitors, GA and H-GA show comparable electrochemical properties in KOH aqueous electrolyte. In EMIMBF4 ionic liquid electrolyte, H-GA shows larger specific capacitance (243 F g−1 at 1 A g−1), better rate capability, and higher energy density (135 Wh kg−1 at 1 kW kg−1) compared with GA (216 F g−1, 120 Wh kg−1), which is attributed to its higher O/C ratio and better electrolyte wettability. We propose that it is not always necessary to conduct the HCl removal, and H-GO could be directly used as a precursor, which not only saves the time and cost remarkably but also may open up a relatively facile route to fabricate some graphene-based functional bulk materials.

Four new sulfonylcalix[4]arene-supported coordination containers have been designed and synthesized through the self-assembly of Co(II)/Ni(II), p-tert-butylsulfonylcalix[4]arene, and ortho-dicarbox...

To reduce the structure vibration caused by changes of working directions, this study proposes a ball-screw inerter with two mechanical diodes, which divides the rotary motion of the flywheel used in the ball-screw inerter into two unidirectional rotations. And the dynamical model and equivalent electrical model of a ball-screw inerter with two mechanical diodes are established and analyzed. Moreover, considering dissipation of energy caused by mechanical diodes, there is a damper in parallel with the inerter. And the damping factor of the damper is in direct proportion to the angular frequency of the exciting harmonic force, when one terminal is fixed and the amplitude of the exciting harmonic force is almost constant. On account of the model and analysis, a ball-screw inerter with two flywheels and two mechanical diodes is designed, manufactured, assembled and installed on the experiment rig. By analyzing the experimental data gathered by force sensor, acceleration sensor and laser displacement sensor, the conclusions that the ball-screw inerter with two mechanical diodes is able to reduce the impulse caused by changes of working directions and there is variable damper caused by mechanical diodes in parallel with the inerter are proved.

Aiming at the complex structure of cross-linked polyethylene(XLPE) power cable joints and the characteristics of partial discharge(PD) easily caused by insulation defects, the paper designs and develops an improved built-in coupling sensor based on capacitive coupling effect. Firstly, by constructing the equivalent circuit model of the sensor, the transfer function of the sensor is calculated, and the factors affecting the detection performance of the sensor are comprehensively analyzed. Secondly, based on the analysis of the detection performance of the sensor, the design scheme of the effective detection frequency band of the sensor is determined, and the structural size of the sensor is determined, including the width of the ring electrode and the thickness of the insulating cushion of the sensor. Finally, the key performance test experiments are carried out on the developed sensor. The test results show that the effective detection frequency band of the sensor is $1 \sim 300$ MHz, and the effective detection sensitivity is 5pC, which can effectively detect the internal PD signal of the cable joint.

Color tunable electroluminescence is obtained from devices having a spin-coated single emitting layer with a novel EuIII-tetrakis-β-diketonate complex NBu4[EuL4] (L− = 4-(4′-carbazol-9-yl-biphenyl-4-yl)-1,1,1-trifluoro-4-oxo-but-2-en-2-ol anion) doped with CBP (4,4′-N,N′-dicarbazolebiphenyl)–OXD7 (1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene) blend. An external quantum efficiency (EQE) as high as 2.8%, maximum brightness (L) of 1547 cd m−2, current efficiency (ηc) of 5.14 cd A−1 and power efficiency (ηp) of 2.53 lm W−1 were shown by a device having the structure ITO/PEDOT:PSS (50 nm)/CBP (56%):OXD7 (24%):NBu4[EuL4] (20%) (50 nm)/TPBI (50 nm)/LiF (1.5 nm)/Al (120 nm). The newly designed β-diketonate ligand containing hole-transporting carbazole group and π-spacer extends the excitation window of the EuIII-complex to 450 nm and also improves the carrier transport properties. The modification in the ligands results in a low turn-on voltage of the devices (

Electrical discharge grinding is part of the most widely used methods to machine polycrystalline cubic boron nitride cutting tool. Polycrystalline cubic boron nitride compact samples processed in domestic with different grain size are the research object. Electrode running speed, peak current, and pulse width are selected as the main process parameters. The material removal volume and electrode loss set as the evaluation index of productive efficiency; workpiece surface roughness value sets as an evaluation standard of processing quality. Through electrical discharge grinding experiments, combined with scanning electron microscopy observation, energy spectrum analyzer and roughness tester, the influences of the main process parameters on electrical discharge grinding are analyzed, polycrystalline cubic boron nitride compact electrical discharge grinding technics & mechanism are summarized.

High speed turn-milling has superiority on the productivity and the quality of work pieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. In this papers adopting orthogonal experiment method cutting experiments of orthogonal turn-milling Aluminum alloy have been done. The relation between turn-milling regimes (cutter rotate speed, axial feed, feed per tooth etc.) and machined surface roughness has been ascertained. Finally, primary and secondary order of cutting regimes impacting surface roughness has more been confirmed through orthogonal experiments variance analysis, the rotate speed of cutter (cutting speed) influence greatly on surface roughness. Through 2-dimension surface topography diagram and 3-dimension surface topography of processed surface, it can be seen that high speed turn-milling processing technology can process micro miniature component of high surface quality, and features excellent development prospect and application value.

Owing to outstanding properties of two-dimensional electron gas (2DEG) and GaN-base material, such as high electron mobility and high critical electric field, AlGaN/GaN high electron mobility transistors (HEMTs) have been considered as the next-generation power semiconductor devices with high power conversion efficiency, high switching frequency and high-temperature operation capability. For power switching applications, enhancement mode (e-mode, or say normally-off) transistors are desired for fail-safe operation and silicon-compatible gate drive circuit. However, e-mode operation is difficult for AlGaN/GaN-based HEMTs because of the natural existence of 2DEG. To achieve e-mode operation, several approaches have been reported, including gate recess structure, fluorine plasma ion implantation, p-type gate structure and selective channel regrowth, etc. This paper reports normally-off AlGaN/GaN HEMTs with a recessed MOS-gate. After mesa isolation and Source and drain metal, the gate recess process used inductively coupled plasma (ICP). In order to avoid severe etching damage and obtain high drain current density, etching power was carefully optimized. The etching rate is slow for accurate etching depth control to leverage the current density and threshold voltage. After that, an O2 plasma treatment was applied using a plasma asher to oxidize the damaged semiconductor surface. The oxide layer was then removed in HCl: DI-water (1: 3). The next step is an atomic layer deposition (ALD) of Al 2 O 3 as the gate dielectric to increase the breakdown voltage. Follow after that, gate metal and pad metal. By the process, our team made three kinds of HEMTs with different recessed gate depths. The first one, which has been report before, exhibits a high threshold voltage of +4.6V, a specific on-resistance of 4mΩ-cm⁁2 and a drain current density of 108 mA/mm. This paper will show the others fabricated in the later researches. The device transfer curves show that this normally-off recessed MOS-gate AlGaN/GaN HEMTs exhibit threshold voltage of +0.9V and +2.1V, respectively. Additionally, the specific on-resistance and saturation drain current density of the device with 0.9V threshold voltage are 2.26mΩ-cm⁁2 and 326mA/mm, while 2.1V-Threshold Voltage-device are 3.03mΩcm⁁2 and 173mA/mm. Both of the two HEMTs have a breakdown voltage over 400V.

Highly phosphorescent (Ph4 P)2 [MnBr4 ] as a low-cost and environmentally benign emitting material achieves peak current efficiency of 25.4 cd A-1 and external quantum efficiency (EQE) of 7.2% for nondoped organic light-emitting diodes, and peak current efficiency of 32.0 cd A-1 and EQE of 9.6% for doped devices with 20% (Ph4 P)2 [MnBr4 ]:27% TCTA:53% 6DCZPPY as a doping emitting layer.

In this work, the thermal bistability of magnons in yttrium iron garnet microspheres was experimentally characterized. Using high quality factor optical whispering gallery modes in the microsphere, the temperature change caused by the microwave pump is precisely measured by probing the optical resonance wavelength shift. It is found that temperature change also induces the magnonic frequency shift and the frequency shift depends on the crystal axis direction of the material. With some appropriate alignment of the magnetic field and the microsphere, the magnonic frequency shift induced by the thermal bistability from the microwave can be suppressed. Our results show its potential use in future experiments on magnon-based transducers.

Controlled drug delivery systems employing microparticles offer lots of advantages over conventional drug dosage formulations. Microencapsulation technique have been conducted with biodegradable polymers such as poly(lactic-co-glycolic acid) (PLGA) and poly(lactic acid) (PLA) for its adjustable biodegradability and biocompatibility. In this study, we evaluated two techniques, oil-in-water (o/w) emulsion solvent evaporation and spray drying, for preparation of polymeric microparticles encapsulating a newly synthesized drug, SS-AG20, for the long-term drug delivery of this low-molecular-weight drug with a very short half-life. Drug-loaded microparticles prepared by the solvent evaporation method showed a smoother morphology; however, relatively poor encapsulation efficiency and drastic initial burst were discovered as drawbacks. Spray-dried drug-loaded microparticles had an imperfect surface with pores and distorted portions so that its initial burst was critical (70.05-87.16%) when the preparation was carried out with a 5% polymeric solution. By increasing the concentration of the polymer, the morphology was refined and undesirable initial burst was circumvented (burst was reduced to 35.93-74.85%) while retaining high encapsulation efficiency. Moreover, by encapsulating the drug with various biodegradable polymers using the spray drying method, gradual and sustained drug release, for up to 2 weeks, was achieved.

Bone marrow stimulation techniques (BSTs) are widely used in clinics to treat cartilage defects, but yet have a critical limitation from the loss of blood clots. In this work, a novel cartilage extracellular matrix (CECM) membrane is developed to protect blood clots after BSTs. The CECM membrane was made of ECM fabricated naturally by cultured porcine chondrocytes, and then decellularized and multi-layered to confer optimal mechanical strength. Highly compatible with cells, the CECM membrane did not show any cytotoxicity or immune responses in vivo. The CECM membrane was very thin (30–60 μm thick) and bendable, but had good tensile strength (85.64 N), suitable for protecting blood clots from leakage in rabbit cartilage defect. Moreover, the CECM membrane showed low but enough diffusion coefficient to allow delivery of small proteins in synovial fluid into the repaired tissue. In a beagle model, covering the cartilage defect with the CECM membrane after BST generated more hyaline cartilage-like tissues than the BST alone in histology and chemical analyses at 18 weeks. Its ICRS score was approximately 2.5 times higher than that of the BST alone. Therefore, the CECM membrane is proposed as a useful tool that can improve the outcome of BSTs to treat cartilage defects.

Turn-milling technology can replace turning with milling to high speed machining rotationally body parts. So, micro-turn-milling has superiority on the productivity and the quality of workpieces, and is more suitable to machine micro-shaft parts and desirable miniature parts based on the turn-milling technology. Micro-turn-milling can be used for the machining of micro-parts in its hardened state. In this paper, the influence of cutting parameters on surface topography and tool wear is presented in micro-turn-milling of micro-screw. The interaction effect of parameters to surface topography and tool wear is investigated. The results show that micro-turn-milling technology has its peculiar advantages in realizing high-speed cutting and ensuring machining quality.

We synthesized biodegradable b-PEIS (branched poly(ethylenimine sulfide)) by crosslinking linear PEIS. We controlled the degree of crosslinking and molecular weight by adjusting the amount of the crosslinker, bisepoxide. The b-PEIS was readily degradable under reductive conditions (5mm glutathione solution) and the degradation time was dependent on the degree of crosslinking. We controlled the molecular weights of the b-PEIS by regulating the amount of crosslinker and thus, the degree of crosslinking. Our titration data showed that there was almost no loss in buffering ability before or after bisepoxide crosslinking. We verified the degradation of this polymer by MALLS and gel electrophoresis, and confirmed that there was a high transfection efficiency and low cytotoxicity based on cellular data. Intracellular trafficking was observed by image restoration microscopy, demonstrating that b-PEIS does not accumulate in the cell interior.

The interaction effect of parameters to surface topography and cutting forces is investigated, and the magnitudes of these parameters are determined in the micro-milling of AISI D2 steel. The results show that the feed per tooth has a prominent impact on the surface topography. Due to the low feed per tooth to cutting edge radius ratio, a high surface roughness and a high amount of burrs are obtained in micro-milling. In micro cutting, the cutting forces present are small; in addition, the radial thrust cutting forces are greater than the principal cutting forces. This research proves that the micro-milling process can be applied to the manufacturing of AISI D2 steel micro parts and presents experimental evidence and possible solutions to the cutting parameters.

Surface treatment of glass bead (GB) was carried out by using γ-glycidoxypropyltrimethoxy silane (GPTES) and γ-methacryloxypropyltrimethoxy silane (MPTMS) as coupling agents, respectively. The steady viscosity and yield stress of the GB/hydroxyl terminated polybutadiene (HTPB) suspensions were determined by Brookfield R/S rheometer. The effect of surface treatment on the viscosity and yield stress of GB/HTPB suspension was investigated. The results indicate that the viscosity of the pristine GB/HTPB suspension increases with increasing GB, and the relationship between its viscosity and volume fraction of GB depends on the shear rate. The modification of GB by MPTMS changes the viscosity of the MPTMS@GB/HTPB suspension, and its viscosity is the minimum at the MPTMS dosage of 0.3 g per 1 g GB. Additionally, the modification of GB by MPTMS increases the yield stress of the GB/HTPB suspension, and its yield stress is the maximum at the MPTMS dosage of 0.1 g per 1 g GB. The GPTES modified GB/HTPB suspension behaves lower viscosity and weaker shear thinning than the MPTMS modified GB/HTPB suspension within the range of experimental shear rate.

We report a selective area growth (SAG) method to define the p-GaN gate of AlGaN/GaN high electron mobility transistors (HEMTs) by metal-organic chemical vapor deposition. Compared with Schottky gate HEMTs, the SAG p-GaN gate HEMTs show more positive threshold voltage (V th) and better gate control ability. The influence of Cp2Mg flux of SAG p-GaN gate on the AlGaN/GaN HEMTs has also been studied. With the increasing Cp2Mg from 0.16 μmol/min to 0.20 μmol/min, the V th raises from −0.67 V to −0.37 V. The maximum transconductance of the SAG HEMT at a drain voltage of 10 V is 113.9 mS/mm while that value of the Schottky HEMT is 51.6 mS/mm. The SAG method paves a promising way for achieving p-GaN gate normally-off AlGaN/GaN HEMTs without dry etching damage.

BACKGROUND: Calcium phosphate cement (CPC) can be molded or injected to form a scaffold in situ, which intimately conforms to complex bone defects. Bioactive glass (BG) is known for its unique ability to bond to living bone and promote bone growth. However, it was not until recently that literature was available regarding CPC-BG applied as an injectable graft. In this paper, we reported a novel injectable CPC-BG composite with improved properties caused by the incorporation of BG into CPC. MATERIALS AND METHODS: The novel injectable bioactive cement was evaluated to determine its composition, microstructure, setting time, injectability, compressive strength and behavior in a simulated body fluid (SBF). The in vitro cellular responses of osteoblasts and in vivo tissue responses after the implantation of CPC-BG in femoral condyle defects of rabbits were also investigated. RESULTS: CPC-BG possessed a retarded setting time and markedly better injectability and mechanical properties than CPC. Moreover, a new Ca-deficient apatite layer was deposited on the composite surface after immersing immersion in SBF for 7 days. CPC-BG samples showed significantly improved degradability and bioactivity compared to CPC in simulated body fluid (SBF). In addition, the degrees of cell attachment, proliferation and differentiation on CPC-BG were higher than those on CPC. Macroscopic evaluation, histological evaluation, and micro-computed tomography (micro-CT) analysis showed that CPC-BG enhanced the efficiency of new bone formation in comparison with CPC. CONCLUSIONS: A novel CPC-BG composite has been synthesized with improved properties exhibiting promising prospects for bone regeneration.

A cell-derived extracellular matrix (ECM) scaffold was constructed using cultured porcine chondrocytes via a freeze-drying method, and its ability to promote cartilage formation was evaluated in vitro. Scanning electron microscope (SEM) revealed that the scaffold had highly uniform porous microstructure. Then, rabbit chondrocytes were seeded dynamically on ECM scaffold and cultured for 2 days, 1, 2, and 4 weeks in vitro for analysis. Polyglycolic acid (PGA) scaffold was used as a control. On gross observation of neocartilage tissue, a silvery white cartilage-like tissue was observed after 1 week of culture in ECM scaffold, while similar morphology was seen only after 4 weeks in PGA scaffold. The volume of neocartilage-like tissue was significantly increased in both ECM and PGA groups. The compressive strength was gradually increased with time in ECM group, while gradually decreased in PGA group. DNA, glycosaminoglycan (GAG) and collagen contents also increased gradually with time in both groups, but showed more significant increase in ECM group. Histological staining for GAG (Safranin O staining) and type II collagen (immunohistochemistry) showed sustained accumulation of ECM molecules with time, which gradually and uniformly filled porous space in ECM scaffold. On the contrary, they accumulated only at the peripheral area of PGA scaffold. These results suggest that a novel cell-derived ECM scaffold can provide a promising environment for generating a high quality cartilage in vitro.