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Enhancement of the maximum proton energy using a funnel-geometry target is demonstrated through particle simulations of laser–plasma interactions. When an intense short-pulse laser illuminate a thin foil target, the foil electrons are pushed by the laser ponderomotive force, and then form an electron cloud at the target rear surface. The electron cloud generates a strong electrostatic field, which accelerates the protons to high energies. If there is a hole in the rear of target, the shape of the electron cloud and the distribution of the protons will be affected by the protuberant part of the hole. In this paper, a funnel-geometry target is proposed to improve the maximum proton energy. Using particle-in-cell 2-dimensional simulations, the transverse electric field generated by the side wall of four different holes are calculated, and protons inside holes are restricted to specific shapes by these field. In the funnel-geometry target, more protons are restricted near the center of the longitudinal accelerating electric field, thus protons experiencing longer accelerating time and distance in the sheath field compared with that in a traditional cylinder hole target. Accordingly, more and higher energy protons are produced from the funnel-geometry target. The maximum proton energy is improved by about 4 MeV compared with a traditional cylinder-shaped hole target. The funnel-geometry target serves as a new method to improve the maximum proton energy in laser–plasma interactions. [ABSTRACT FROM AUTHOR]

Abstract: To improve the interfacial properties between carbon fibers and epoxy matrix, the fibers were treated by an ammoniac medium, which consisted of supercritical water, ethanol and triethylene tetramine. The images of atomic force microscopy and scanning electron microscope indicate that coating layers are formed on the surfaces of treated fibers. The results of X-ray photoelectron spectroscopy demonstrate that N content on the surfaces of carbon fibers increases and the main ammoniac groups of the coating layers are amino and imino groups. The mechanical measurements indicate that both interlaminar and interface shear strength of carbon fibers are significantly increased after amination. [Copyright &y& Elsevier]

Abstract: Fast steering mirror (FSM) system is a precise beam steering mechanism which modulates the beam between a light source and a receiver using its reflecting surface. High bandwidth is an important property of FSM, which is associated with the response speed and stable precision. It is difficult to design the closed-loop bandwidth for FSM, which relies on the open-loop frequency response of the system and the design of the controller. A theoretical analysis, simulation, and testing method to determine an appropriate bandwidth designation for a two-axis FSM are developed in this paper. An ideal open-loop plant frequency response is compared to a final closed-loop bandwidth requirement, and then, stiffness of elastic support in each direction is researched and idea of stiffness design of elastic support is put forward. An integrated mechanical control simulation (IMCS) method is introduced to simulate the structural response and controller design synchronously to predict the final closed-loop control performance of the two-axis FSM system. Finally, the open-loop plant frequency response and closed-loop bandwidth of the assembled two-axis FSM system are tested with the results confirming the general validity of the analysis and simulation method presented in this paper. [Copyright &y& Elsevier]

Abstract: In order to improve the interfacial properties between carbon fibers and epoxy matrix, supercritical water and hydrogen peroxide were used as oxidation medium for the oxidation treatment for carbon fibers. Analysis results of X-ray photoelectron spectroscopy suggest that the oxygen content on the carbon fibers’ surfaces increases by these oxidation treatments. Scanning electron microscope and atomic force microscopy images indicate that the surface appearance of oxidized carbon fibers obviously changed. The maximal interlaminar shear strength and interface shear strength of carbon fiber/epoxy resin composite in which the fibers were treated by the supercritical water and hydrogen peroxide systems reaches 70.46MPa and 106.66MPa, increases by 13.4% and 29.6% respectively compared with untreated carbon fibers. [Copyright &y& Elsevier]

Abstract: The polyacrylonitrile-based (PAN-based) carbon fibers with progressive amounts of the oxidation treatment have been investigated using a number of surface analytical methods. The chemical content and structure of oxidated fibers have been interrogated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), then compared to the untreated ones. The value of oxygen content increased from 4.71% to 18.84%, meanwhile, the grooves on the surfaces of the carbon fibers were deepened gradually after treatments. The results of dynamic contact angle (DCA) measurements suggest that the increase in carbon fiber surface tension is mainly because of the polar component of surface tension. After treated with increasing amounts of oxidants, the monofilament tensile strength decreased less than 3.1%. [Copyright &y& Elsevier]

Abstract: Four kinds of polyacrylonitrile-based carbon fibers were cleaned by three methods and were characterized by X-ray photoelectron spectroscopy, monofilament tensile strength test and atomic force microscopy (AFM). Experimental results of these tests reveal that the method using supercritical acetone or subcritical potassium hydroxide aqueous solution act as the processing medium shows a better cleaning effect compared to the traditional method, Soxhlet extraction with acetone. The method using supercritical acetone is more appropriate to wipe off the oxygenated contaminants on carbon fibers’ surfaces and causes a relatively smaller damage to the bulk strength of each carbon fiber. As far as treating method using the subcritical alkali aqueous solution, it can thoroughly remove silicious contaminants on the surfaces of treated fibers. [Copyright &y& Elsevier]

The quasi-zero stiffness (QZS) mechanism can rely on the combination of negative and positive stiffness elements to achieve very low dynamic stiffness while obtaining high static stiffness to support the isolated payload. It is a nonlinear shock isolation method with good shock isolation performance. In this paper, a new QZS compliant shock isolator is designed for shock isolation under strong acceleration shock excitation(>1000g), by paralleling a fixed-guided beam with negative stiffness and a Roberts configuration compliant beam with positive stiffness. The force-displacement characteristics of the QZS compliant shock isolator is analyzed and calculated theoretically using an elliptic integration method, and are verified by comparison using finite element simulation. The dynamic time-domain response characteristics of the QZS compliant shock isolator under the excitation of ideal shock excitation with different amplitudes, different periods, different payloads, and actual shock excitation are calculated, and compared with the performance of a general positive stiffness compliant shock isolator under the same excitation. The results show that the proposed QZS compliant shock isolator can be applied to shock isolation under strong shock excitation, and exhibits good constant force characteristics in the whole stroke during the shock isolation process, and is less affected by the amplitude and period of shock excitation. Compared with the general positive stiffness compliant shock isolator, the proposed QZS compliant shock isolator can significantly reduce the peak of the shock, reduce the maximum acceleration ratio and improve the shock isolation performance. It can provide some theoretical guidance for the design of the QZS compliant shock isolator under strong shock excitation. • A quasi-zero stiffness shock isolator suitable for strong shock excitation is proposed. • The isolator has a constant force characteristics almost in the whole stroke more than 8 mm. • Compared the performance with the general positive stiffness shock isolator. • The feasibility of using QZS compliant mechanism under strong excitation isolator is verified theoretically. [ABSTRACT FROM AUTHOR]

This article presents a design principle of a novel small-sized compliant optical micro-scanner with two translational (X, Y) and a rotational (θz) degree of freedoms (3-DOFs). A novel normal-stress electromagnetic actuator system is proposed to provide 3-DOFs actuating forces with the working strokes of hundreds of microns for the optical micro-scanner within a very compact structural envelope. The electromagnetic actuator system can not only generate high actuating force density which is similar to solenoid, but also has linear force-current relations along three actuating axes by adopting magnetic configuration design strategy. The theoretical analysis model of the actuator system is derived by using equivalent magnetic circuit method and the actuating force is analyzed through energy store method. Permanent magnet flux leakage and magnetic saturation of stator core in excitation situation are taken into consideration to improve the modelling accuracy. Finite element analysis (FEA) software is utilized to investigate the critical characteristics of the micro-scanner. By FEA comparison, both the theoretical and FEA results show that the actuating force generated by the designed electromagnetic actuator system has a linear relationship with the excitation current. Compare with the normal optical micro-scanner actuated by voice coil motors (VCMs) or piezoelectric (PZT) actuators, the normal-stress based micro-scanner can not only offer movements with three degrees of freedom within a very compact structural envelope, but also achieve high actuating forces which are over 6 times higher than the same sized VCM-actuated micro-scanners. The workspace of this scanner is more than 800 × 800 μm2, which is more than 8 times larger than that of PZT-actuated scanner. The volume of this stage is 60 * 60 * 14 mm3, resulting in a high area-ratio of 1.2%. The cross-axis coupling motion is less than 24 μm at the full primary motion. The resonant frequencies of the two working axes are about 184 Hz. [ABSTRACT FROM AUTHOR]

Electro-optical detection systems face numerous challenges due to the complexity and difficulty of targeting controls for "low, slow and tiny" moving targets. In this paper, we present an optimal model of an advanced n-step adaptive Kalman filter and gyroscope short-term integration weighting fusion (nKF-Gyro) method with targeting control. A method is put forward to improve the model by adding a spherical coordinate system to design an adaptive Kalman filter to estimate target movements. The targeting error formation is analyzed in detail to reveal the relationship between tracking controller feedback and line-of-sight position correction. Based on the establishment of a targeting control coordinate system for tracking moving targets, a dual closed-loop composite optimization control model is proposed. The outer loop is used for estimating the motion parameters and predicting the future encounter point, while the inner loop is used for compensating the targeting error of various elements in the firing trajectory. Finally, the modeling method is substituted into the disturbance simulation verification, which can monitor and compensate for the targeting error of moving targets in real time. The results show that in the optimal model incorporating the nKF-Gyro method with targeting control, the error suppression was increased by up to 36.8% compared to that of traditional KF method and was 25% better than that of the traditional nKF method. [ABSTRACT FROM AUTHOR]

Purpose of study: There is ongoing controversy as to the risk of paraplegia from segmental artery ligation during anterior spinal fusion. While somatosensory evoked potentials have been used to test indirectly for spinal cord ischemia after temporary segmental artery occlusion, the potential for a false-negative finding is high, because the SSEP is dorsal column mediated. The purpose of this study was to determine if transcranial electrical motor-evoked potentials (TCEMEPs) could provide a more sensitive, direct test for identifying nutrient-feeding segmental arteries that are critical to anterior spinal motor tract function before vessel ligation. Methods used: TCEMEPs (Digitimer, Ltd., Garden City, UK) were recorded from bilateral quadriceps, tibialis anterior and/or abductor hallucis muscles as well as from an upper extremity control muscle group, both before and 2 to 3 minutes after test occlusion of each candidate segmental artery. If postocclusion TCEMEP amplitudes did not change, the vessel was permanently ligated. If, however, response amplitude over one or more lower extremity muscles was diminished by more than 50%, the clamp was released until complete amplitude recovery. If on subsequent reclamping, TCEMEP amplitudes again diminished (more than 50%), no permanent ligation was performed. of findings: Significant TCEMEP changes after temporary vessel occlusion were noted in 8 (6.0%) of 150 pediatric patients in this series. In two patients, the TCEMEP changes were correlated with hypotension (MAP< 55 mm Hg), which resolved upon elevating the MAP to 90 mm Hg, thereby allowing for permanent vessel ligation. For the remaining six patients (4.0%), however, TCEMEPs could be restored only by removal of the test clamp. Consequently, no permanent ligation was performed to avoid postoperative motor deficit. No patient emerged with new motor deficit after surgery, as predicted by unchanged TCEMEPs at closing. Relationship between findings and existing knowledge: TCEMEPs provide a rapid, valid and reliably sensitive technique for identifying segmental arteries that may be nutrient feeders to the anterior spinal cord. If ligated, such segmental vessels may predispose the patient to anterior spinal cord ischemic injury, particularly during a single-stage anterior-posterior spinal fusion for scoliosis correction. Overall significance of findings: These data suggest that, in select patients, there are segmental arteries that represent critical feeding vessels to the anterior spinal artery for maintenance of adequate spinal cord perfusion during the application of strong corrective spinal forces. Disclosures: Device or drug: Digitimer D-185 Multi-Pulse Motor Evoked Potential Stimulator. Status: investigational. Conflict of interest: No conflicts. [ABSTRACT FROM AUTHOR]

Posttraumatic tendon adhesion limits the motion of the limbs greatly. Biomimetic tendon sheaths have been developed to promote tendon healing and gliding. However, after introduction of these biomaterials, the associated inflammatory responses can decrease the anti-adhesion effect. Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) that can decrease inflammation responses. We blended hyaluronic acid and poly( l -lactic acid)–polyethylene glycol (PELA) with microgel electrospinning technology to form an inner layer of a bi-layer biomimetic sheath using sequential electrospinning of an outer celecoxib–PELA layer. Electrospun bi-layer fibrous membranes were mechanically tested and characterized by morphology, surface wettability, and drug release. The tensile strength showed a decreased trend and water contact angles were 114.7 ± 3.9°, 103.6 ± 4.4°, 116.3 ± 5.1°, 122.8 ± 4.7°, and 126.5 ± 4.2° for the surface of PELA, hyaluronic acid–PELA, 2, 6, and 10% celecoxib–PELA electrospun fibrous membranes, respectively. In vitro drug release studies confirmed burst release and then sustained release from the fibrous membranes containing celecoxib for 20 days. In a chicken model of flexor digitorum profundus tendon surgery, the outer celecoxib/PELA layer offered advanced anti-adhesion roles compared to the outer PELA layer and the inner hyaluronic acid-loaded PELA layer still offered tendon healing and gliding. Thus, celecoxib-loaded anti-adhesive tendon sheaths can continuously offer bi-layer biomimetic tendon sheath effects with celecoxib release from the outer layer to prevent tendon adhesion. [ABSTRACT FROM AUTHOR]

Abstract: Carbon fiber reinforced composite materials can be enhanced by introducing oxygen-containing groups on the surface of the reinforcing fibers to improve the interface bonding strength between carbon fibers and polymer matrix. While the addition of oxygen-containing groups has been shown to effectively increase the interfacial interaction between fibers and matrix, the treatments tend to consume the carbon fiber tensile strength. In this work, the surface of carbon fibers is oxidized by a chemical oxidation method which employs a strong oxidant of K2S2O8 and a catalyst of AgNO3 to effectively creating carboxyl and hydroxy functionalized surface and the reaction is shown that it can preserve the tensile strength and morphology of the carbon fibers. The surface oxidation is investigated by X-ray photoelectron spectroscopy, which shows that the relative surface coverage by oxygen atoms is increased from an initial 4.49% up to a maximum of 14.11% while the results of single fiber tensile strength tests demonstrate that the reaction did not lead to any obvious decrease in the fiber tensile strength. After oxidation, the interfacial shear strength (IFSS) improved from 59.52 to 96.73MPa, with a increase of 62.5%. [Copyright &y& Elsevier]

Highlights: [•] A new chemical grafting method for carbon fibers was proposed. [•] The oxidation system adopts K2S2O8 and AgNO3. [•] The interfacial shear strength (IFSS) of carbon fiber increased by 61%, and the interfacial adhesion increased with dendritic generation number. [•] The tensile strength of carbon fiber does not decrease distinctly. [•] The treatment conditions are mild and convenient. [ABSTRACT FROM AUTHOR]

• The PLA oligomer was grafted on the surface of biomass by in situ polymerization. • Improved photo-oxidative resistance of PLA was obtained by the biomass addition. • The interface constructed was proved available to alleviate the irradiation shielding effect of biomass. • A dual mechanism of PLA/biomass composites was proposed by the surface analysis during the irradiation. Based on the improved performance by interface construction, poly-lactic acid (PLA)/biomass composites have attracted much attention and received wide application as a completely degradable material. This work aims to study the effect of biomass components and the designed interface on the photo-degradation behavior of PLA/biomass composites exposed to the simulated sunlight irradiation, which could further alleviate the restriction caused by the poor ultraviolet (UV) stability of PLA. The biomass shows a significant delay effect in the degradation rate of the PLA matrix by the absorption of visible and UV ranges, acting as a photo-oxidative stabilizer during the irradiation. The investigation of the surface chemical changes reveals a dual mechanism for the degradation of the composites, consisting of a typical Norrish II photochemical and photo-oxidation mechanism. The interface in the composites is constructed by the surface treatment of biomass through the in situ polymerization of lactic acid, which could effectively alleviate the shielding effect of biomass. In our view, this work provides a novel strategy to prepare the PLA/biomass composites that possessed excellent photo-oxidative stabilization provided by biomass, adjustable degradation cycle offered by the interface construction, and potential application in more advanced packaging and agriculture fields. [Display omitted] [ABSTRACT FROM AUTHOR]

• Systematic analysis of PLA ablated by femtosecond laser was first explored. • The surface microstructure displayed a dependence on the fs laser parameters. • The photo-thermal oxidation was proved as the dominant reaction on the surface. • The degradation in PLA matrix was also observed during the surface ablation. The effects of femtosecond laser ablation on the surface morphology, surface chemical composition, and matrix properties of poly-lactic acid (PLA) were explored in this paper, since the analysis of the different energy density range is crucial in evaluating to what extent material properties change during the micromachining. Scanning electron microscopy (SEM) analysis found that different surface microstructures, i.e., the convex microstructure and the through hole, were generated by single and multiple pulses femtosecond laser ablations, respectively. The photo-thermal features appeared on the PLA surface displayed a dependence on the femtosecond laser pulse number or fluence. The surface affected by femtosecond laser ablation was also analyzed using Fourier transforms infrared (FTIR) as well as X-ray photoelectron spectroscopy (XPS), which indicated that an oxidation reaction had occurred during the micromachining. The ablation of PLA surface resulted in a decreased molecular weight and an increase of polydispersity, which was consistent with a drop in transition temperature (T m). Therefore, the substrate also degraded although the micromachining process was only performed on the surface. The variation in PLA surface microstructures, chemistry, and matrix performance resulted from different laser parameters were related to the laser-matter interaction effects. [ABSTRACT FROM AUTHOR]

This paper investigates the pre-pressure's influence on the key performance of a traveling wave ultrasonic motor (TRUM) using simulations and experimental tests. An analytical model accompanied with power dissipation is built, and an electric cylinder is first adopted in regulating the pre-pressure rapidly, flexibly and accurately. Both results provide several new features for exploring the function of pre-pressure. It turns out that the proportion of driving zone within the contact region declines as the pre-pressure increases, while a lower power dissipation and slower temperature rise can be achieved when the driving zones and the braking zones are in balance. Moreover, the shrinking speed fluctuations with the increasing pre-pressures are verified by the periodic-varying axial pressure. Finally, stalling torque, maximum efficiency, temperature rise and speed variance are all integrated to form a novel optimization criterion, which achieves a slower temperature rise and lower stationary error between 260 and 320 N. The practical speed control errors demonstrate that the proportion of residual error declines from 2.88% to 0.75% when the pre-pressure is changed from 150 to 300 N, which serves as one of the pieces of evidence of the criterion's effectiveness. [ABSTRACT FROM AUTHOR]

Background: With the exception of normal anatomic changes in the medial collateral ligament and radial head, other factors related to carrying angle changes have not been systematically studied. We reviewed patients who underwent open arthrolysis of the elbow, and evaluated if open arthrolysis could change carrying angle. We then identified factors associated with carrying angle changes.Methods: Fifty patients with a minimum of 24 months of follow-up after open arthrolysis were evaluated retrospectively. Preoperative and postoperative carrying angles were compared.Results: The carrying angles of 36 elbows in 36 patients were unchanged after surgery (Group A), while the carrying angles of 14 elbows in 14 patients increased postoperatively (Group B). In Group A, mean postoperative extension and flexion were 7° (range 0-24°) and 125° (range 10-135°) respectively, while mean postoperative pronation and supination were 60° (range 50-80°) and 65° (range 30-85°), respectively. In Group B, mean postoperative extension and flexion were 25° (range 0-40°) and 128° (range 60-138°), while mean postoperative pronation and supination were 65° (range 45-85°) and 60° (range 45-75°), respectively. No significant difference in range of motion and Mayo Elbow Performance Score was observed between the two groups.Conclusions: During open arthrolysis, humeral trochlea debridement and techniques for improving forearm rotation could increase carrying angle. However, this had no impact on elbow functional recovery. [ABSTRACT FROM AUTHOR]

Fibrous carbon materials have been attracted many researchers' attentions. Carbon fibers have been developed as one of the most important industrial materials for modern science and technology since 1960s [1] . Due to the superior mechanical properties including high-specific strength and modulus, low density and thermal expansion, heat resistance, and chemical stability, carbon fibers as reinforcement materials have provided the impetus for researchers in developing high-performance composite materials. Nowadays, carbon fiber reinforced plastics (CFRP) are widely applied in the industries of aeronautic, aerospace, sporting goods, as well as new energy. The region between the fibers and matrix, contains unique micromechanical properties, is characteristically called the interphase and influence the bulk composite properties. Interface between fibers (reinforcements) and matrix is an important component for CFRP which may govern the CFRP performances [2] . For example, the interphase determines the off-axis strength and impact toughness of CFRP, environmental stability of CFRP and functional performance of CFRP. The effect of interface on composite can be achieved by regulating the composition, structure and distribution of the interface [3] . It has been proved that there has an optical interface for polymer based composite through the match of composite interface, reinforcement and polymer matrix. However, in terms of the smooth surface and chemical inertness of carbon fiber, the interface between carbon fiber and resin matrix is unsatisfactory. The interface should be modified and carefully controlled, which can be through by increasing the surface polarity of carbon fiber, improving the wettability between carbon fiber and resin, as well as promoting the chemical reaction. Obey these principles, the interfacial modification methods have been well developed. The universality of carbon fiber and polymer matrix, and the variability of the composite material forming process result in the complexity of polymer-based composites interface problems. Meanwhile the scale of the interface region is very small, it has great difficulty in characterizing the chemical structure, physical properties and mechanical characteristics. Recently, a series of effective characterization methods have been developed and initial interface characterization system is always being improved. With interface characterization techniques, the interfacial composition, structure morphology and micro-mechanical characteristics of interface can be researched easily, which can provide the basis for studying the interface physical and chemical properties. Hence interface characterization techniques not only are theory researches, but also have important practical significance for solving practical application problems of carbon fiber composites. Interface characterization techniques have become an important research direction of interface engineering research. In this paper, the researches in this field of carbon fiber interface were described, such as carbon fiber composite material characterization methods, interface control, and interfacial modification methods. With reference to the research achievements of a large number of scholars at present, so their current development trend were systemic concluded. [ABSTRACT FROM AUTHOR]

A facile and efficient approach is developed to simultaneously functionalize and reduce graphene oxide (GO) containing isocyanate groups with toluene-2,4-diisocyanate (TDI). In this approach, the reaction between some isocyanate groups of TDI and oxygen containing functional groups of GO has occurred, with the GO reducing. The result can be found that others active isocyanate groups of TDI remain upon surface of GO, and the surface of GO changes from hydrophile to hydrophobic. In order to obtain the largest amount of isocyanate groups on surface of TDI-rGO, appropriate temperature and equilibrium time of the reaction are determined to be 75 °C and 5 h. [ABSTRACT FROM AUTHOR]