Strip Structure Research Articles

Quantitative evaluation of alteration and exfoliation in Jurassic sandstone, Chongqing Danzishi rock carvings, China

Historical relics of Jurassic sandstones in southwest China have been subjected to weathering damage. Exfoliation, characterized by the detachment of multiple thin stone layers sub-parallel to the stone surface, is common in sandstone heritage sites. However, its mechanism of action remains poorly understood. In this study, a conceptual model of exfoliation is drawn from the literature and field investigations. To quantitatively determine the exfoliation mechanism, a range of non-destructive field-based methods (surface hardness, water absorption test, roughness, and amplitude of residual spalling layers) and laboratory analyses (scanning electron microscopy (SEM) and X-ray diffraction (XRD)) are adopted as weathering agents for separated detachments. In addition, the grain and pore sizes of weathering products are analyzed using digital image techniques. The results show that the roughness, water absorption coefficient, and pore size in sandstone surfaces increase from the inner layer to the outer layer, and their hardness and grain size decrease, respectively. The proportions of quartz, dolomite, and illite increases from the interior to the exterior, whereas the proportion of feldspar decreases correspondingly. The residual column strip structure derived from feldspar alteration and a mixed montmorillonite-illite mineral layer can be observed in the SEM images. It can be inferred from surviving environmental analysis that comprehensive actions from solar radiation, acid rain attack and capillary rise lead to sandstone exfoliation. In addition, the alteration of feldspar plays an important role during sandstone exfoliation. The results of this study enhance our understanding of the exfoliation of the Jurassic sandstone of the Chongqing Danzishi rock carvings in China.

Si-capping-induced surface roughening on the strip structures of Ge selectively grown on an Si substrate

Si-capping-induced surface roughening, accompanying Si–Ge alloying, is reported for strip structures of Ge selectively grown on Si via ultrahigh vacuum chemical vapor deposition. A 0.7-μm-wide strip structure of Ge running in the [110] direction, as well as a 100-μm-wide mesa structure, is selectively grown on an Si (001) surface exposed in an SiO2-masked Si substrate. In contrast to a wide mesa structure with a Ge thickness of 0.5 μm, composed of a (001) plane at the top and {113} facet planes at the sidewalls, the (001) top plane almost disappears for the narrow strip structure. The strip is mainly surrounded with inclined {113} planes near the top and adjacent {111} planes at the side, while the structure near the bottom edges depends on the growth temperature (600/700 °C). An Si cap layer with a thickness of 10 nm or larger is subsequently grown at 600 °C to protect the fragile Ge surface. The scanning electron microscopy observations reveal a roughened surface on the {113} planes, with depressions specifically induced near the boundary with the {111} planes. The Raman spectra indicate that an SiGe alloy is formed on the strip and the wide mesa sidewalls due to the Si–Ge interdiffusion. There is no such SiGe alloy on the (001) plane of the wide mesa top. The Si cap layer with a misfit strain probably works as a stressor for the underlying Ge, applying stress concentrated around the facet boundaries and inducing a mass transport alongside the Si–Ge interdiffusion for strain relaxation. In terms of the fabrication of practical devices, it is important to suppress the roughening and alloying significantly by decreasing the growth temperature for the Si cap layer from 600 to 530 °C.

Study on THz SPPs excitation and field distributions of graphene microribbons

Surface plasmon polaritons have wide applications in sensing, biasing, absorption, and beam splitting, etc. because they can break diffraction limits and have strong field localization. So far, most of the research on terahertz surface plasmon polaritons is in the far-field spectrum, and exploring near-field properties is further needed. In this paper, based on the graphene strip structure, the excitation and field distribution characteristics of terahertz surface plasmon polaritons were studied. Specifically, the graphene microribbons that could excite surface plasmon polaritons by terahertz waves were designed, and the field distribution was calculated. Then, we experimentally fabricated the designed structure and measured its surface plasmon polaritons by terahertz near-field microscope. Finally, the effects of resonance detuning on surface plasmon polaritons field distribution were investigated. Our results provide a research basis for the application of graphene surface plasmon polaritons components in terahertz detection, biomedicine, safety detection, and high data rate communication.

Effects of cooling method and elements segregation on the martensite-pearlite banded structure of high carbon bearing steel

In this study, the effects of the cooling method and alloying element segregation on the abnormal zonal structure of high-carbon bearing steel were investigated by reheating, controlled rolling, and controlled cooling of the sample. The microstructure and alloy segregation characteristics of the abnormal strip structure in the hot-rolled plate of the steel were revealed by optical microscopy, scanning electron microscopy, transmission electron microscopy, and electron probe x-ray microanalysis. The JMatPro thermodynamic software was used to examine the relationship between the alloy elements and banded structure defects of the hot-rolled sheet and analyse the causes of the defects and their elimination methods. The results show distinct positive segregation of Cr/Mn and negative segregation of C in martensite–pearlite banded structure defects in hot-rolled plates. The martensite–pearlite banded structure is formed by the interaction between the cooling rate and the segregation of alloying elements after hot rolling. Studies have found that segmented cooling (slow cooling–air cooling) can eliminate the martensite–pearlite banded structure.

Electronic Blood Vessel

Summary Advances in bioelectronics have great potential to address unsolved biomedical problems in the cardiovascular system. By using poly(L-lactide-co-ϵ-caprolactone), which encapsulates liquid metal to make flexible and biodegradable electrical circuitry, we develop an electronic blood vessel that can integrate flexible electronics with three layers of blood-vessel cells, to mimic and go beyond the natural blood vessel. It can improve the endothelialization process through electrical stimulation and can enable controlled gene delivery into specific parts of the blood vessel via electroporation. The electronic blood vessel has excellent biocompatibility in the vascular system and shows great patency 3 months post-implantation in a rabbit model. The electronic blood vessel would be an ideal platform to enable diagnostics and treatments in the cardiovascular system and can greatly empower personalized medicine by creating a direct link of the vascular tissue-machine interface.

Dual-polarization wave-front manipulation with high-efficiency metasurface

In recent years, plentiful works have focused on anomalous reflections, but only few works achieved dual-polarized reflection with high efficiency. In this paper, we present a reflection-type metasurface based on a dual-layer metallic structure at microwave frequency. By designing various periods of metallic structures, the metasurface can achieve high-efficiency anomalous reflections with a wide deflected angle range for orthogonal linearly polarized plane waves (x and y). By arranging distinct periods of units, various scattering angles of the reflected beam are achieved in two orthogonal directions. Besides, there is little interference between x-polarization and y-polarization reflected waves. To realize the aforementioned functionality, a unit cell with a stacked strip structure is employed. Based on the specific elements, we propose and simulate four metasurface schemes. Two of them are fabricated and measured, the measured results of which show good agreement with simulations validating our design. The high performance potentially makes this work diverse and intriguing with applications such as focusing reflectors and holograms.

Zigzag reflective multifunctional metamaterial absorber and polarization rotator with horizontal strip structure

In this paper, we design and investigate a zigzag reflective multifunctional metamaterial (ZRMM) made by folding a planar metamaterial with horizontal strip structure. It has better absorption and polarization conversion performance compared to planar structures, which can achieve multiple absorption, broad-band cross-polarization conversion, broad-band linear-to-circular and circular-to-linear polarization conversion at different frequencies. Simulation results show that the absorption of the proposed design at 4.48 GHz, 10.54 GHz and 21.02 GHz are 94.76%, 97.90% and 99.60%, respectively. In 14.43 GHz–20.32 GHz, cross-polarization conversion can be achieved well. Similarly, excellent linear-to-circular and circular-to-linear polarization conversion have been achieved at 10.98 GHz–13.96 GHz. This metamaterial can be used as an absorber and polarization rotator. It can be used for antennas to change the polarization of radiated waves, as a frequency selective surface, or to reduce the radar cross section. Our work has made illuminating explorations for the multifunctional integration of metamaterials.

Experimental study on shock and turbulent boundary layer interactions under different incident shock waves

In this paper, the interactions between shock wave and the turbulent boundary layer of an incoming wall were experimentally studied. The experiments were performed in a Mach 3.4 supersonic low-noise wind tunnel at the unit Reynolds number of 6.30×106 m−1. Under different incident shock wave conditions, fine flow field structure, wall pressure, and wall temperature distribution were determined. Relationship was also analyzed. Instantaneous fine structures of typical flow fields with shock wave and turbulent boundary layer interactions were investigated using the nano-tracer planar laser scattering technique, and the transient flow images were analyzed statistically. The oscillation position of the induced shock wave satisfies a normal distribution. Simultaneously, the wall pressure distribution under different incident shockwave conditions of the interaction region was determined using the flush air data sensing system, and the relationship between flow the structure of the separation region and the wall pressure distribution with different incident shock wave intensities is analyzed. Using a temperature sensitive paint technology, the wall temperature distribution under different incident shockwave conditions of the interaction region model was determined. Also, the relationship between the strip structure caused by Gortler vortices and the incident shock wave intensity in the shockwave/turbulent boundary layer interaction was analyzed.

Wideband Circularly Polarized Antenna Using Single-Arm Coupled Asymmetric Dipoles

This article presents a novel design concept to realize a wideband circularly polarized (CP) antenna by using single-arm coupled asymmetric dipoles (SCADs). First, an impedance compensation method is developed to obtain flat antenna input impedance by designing different arm lengths of the asymmetric dipole. Then, a single-arm coupling method is introduced to improve the antenna bandwidth. Four asymmetric dipoles are bent and sequentially coupled to each other among the long arms of the dipoles. By elaborately adjusting the coupling among the long arms, improved bandwidth and compact radiator size are achieved simultaneously. In addition, to further enhance and optimize the operating bandwidth of the antenna implementation, impedance matching strip and interdigital structure are introduced into SCADs. To verify the design concept, a prototype of the SCAD antenna was designed, fabricated, and measured. Experimental results agree well with the simulations, showing a wide impedance bandwidth of 108% (1.53-5.12 GHz) and an axial ratio (AR) bandwidth of 96% (1.78-5.06 GHz). To the best of our knowledge, the proposed design concept of SCADs is first used to design a wideband CP antenna. Both the simulated and measured results prove that the proposed antenna is a promising candidate for modern broadband CP applications.

Preparation and high temperature tribological properties of laser in-situ synthesized self-lubricating composite coating on 304 stainless steel

An in-situ synthesized self-lubricating anti-wear composite coating was prepared with mixed Ni60-TiC-WS2 precursor powders on the surface of 304 stainless steel by high-energy laser beam. The microstructure and microhardness of the composite coating and substrate were characterized by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDS), and Vickers hardness test. The tribological properties and the related wear mechanisms of the composite coating and the substrate were systematically studied at RT, 300, 600 and 800 °C, respectively. The correlative results reveal that solid solution Cr0.19Fe0.7Ni0.11, self-lubricating sulfides Ti2CS/CrS/WS2 and hard ceramic particle Fe2C/Cr7C3 are in-situ synthesized in molten pool during laser process. Microstructure of the upper area of the coating is primarily composed of long strip structure, continuous matrix, white granular structure and rod structure. However, the cellular dendrites that formed during the solidification process were aggregated in the bottom area of the coating, which deteriorate the mechanical properties of the coating. The average microhardness of the composite coating (302.0 HV0.5) is slightly higher than that of the substrate (257.2 HV0.5), this is due to the more sulfides and iron compounds were in-situ synthesized in the molten pool, which was formed by the irradiation of the high-energy laser beam. At all test temperatures, the coefficient of friction (COF) and wear rate of the coating are lower than that of the substrate. The minimum COF of the coating (0.3031) appears at 300 °C, and the wear resistance of the coating is the best at 600 °C, with a wear rate of 9.699 × 10−5 mm3/Nm.

Influence of long-term thermal ageing (＞10,000h) on low stress creep deformation of P92 heat-resistant steels

ABSTRACTMicrostructure evolution of P92 heat-resistant steel during long-term service has high influence on the creep property. In this paper, P92 heat-resistant steel samples were aged at 898 K for 10,000 h, 15,000 h and 25,000 h. The effect of thermal ageing on microstructure was analysed through optical microscopy and scanning electron microscopy. The creep behaviour at specific shear stresses (14.7 MPa, 20 MPa, 25.6 MPa, 41 MPa) was investigated through helicoid-spring creep testing. The relationship between microstructure evolution and creep properties was discussed. The results demonstrated that the basic morphology of P92 heat-resistant steel samples following long-term thermal ageing was martensite strip structure, while the precipitated phases were MX, Laves and M23C6. The coarsening of M23C6 carbide was slower than Laves phase during thermal ageing of 15,000 ~ 25,000 h. Precipitation strengthening for the grain interior was corresponding to the Orowan mechanism. In the regions of high shear stresses (14.7 MPa, 20 MPa), the Laves phases played an important role in dislocation motion inhibition at grain boundaries, while in the regions of low shear stresses (25.6 MPa, 41 MPa), the M23C6 phases played a significant role in dislocation motion inhibition at grain boundaries. Moreover, the main precipitate which affected the creep of P92 heat-resistant steels under the lower shear stresses of 14.7 MPa and 20 MPa was Laves phase and the higher shear stresses of 25.6 MPa and 41 MPa was mainly M23C6 phase.

Electrothermally Driven Hydrogel-on-Flex-Circuit Actuator for Smart Steerable Catheters.

This paper reports an active catheter-tip device functionalized by integrating a temperature-responsive smart polymer onto a microfabricated flexible heater strip, targeting at enabling the controlled steering of catheters through complex vascular networks. A bimorph-like strip structure is enabled by photo-polymerizing a layer of poly(N-isopropylacrylamide) hydrogel (PNIPAM), on top of a 20 × 3.5 mm2 flexible polyimide film that embeds a micropatterned heater fabricated using a low-cost flex-circuit manufacturing process. The heater activation stimulates the PNIPAM layer to shrink and bend the tip structure. The bending angle is shown to be adjustable with the amount of power fed to the device, proving the device’s feasibility to provide the integrated catheter with a controlled steering ability for a wide range of navigation angles. The powered device exhibits uniform heat distribution across the entire PNIPAM layer, with a temperature variation of <2 °C. The operation of fabricated prototypes assembled on commercial catheter tubes demonstrates their bending angles of up to 200°, significantly larger than those reported with other smart-material-based steerable catheters. The temporal responses and bending forces of their actuations are also characterized to reveal consistent and reproducible behaviors. This proof-of-concept study verifies the promising features of the prototyped approach to the targeted application area.

Design and simulation of a germanium multiple quantum well metal strip nanocavity plasmon laser

In order to achieve electrically pumped plasmon nano lasers, several structures, materials and methods, have been proposed recently. However, there is still a long way to find out a reliable appropriate on-chip plasmon source for commercial plasmonic integrated circuits. In this paper, a new integrated nanocavity plasmon laser is proposed, analyzed and simulated for 1550 nm free-space wavelength. Due to its significant field confinement resulted by the metal strip structure and strong interaction of plasmonic modes with the germanium quantum wells this structure has a remarkable output performance. Purcell factor of this nanocavity is about 291. Using semi-classical rate equations in combination with finite difference time domain (FDTD) cavity mode analysis, the output performance measures are estimated and confirmed with respect to various physical models and simulation tools. Simulation results for this structure which has 0.073 µm2 area show a 2.8 µW output power with 10 µA injection current and about 4.16 mW output power with the threshold pump current of 27 mA, while maintaining its performance in a wide spectral bandwidth about 1.46 THz. It also can be electrically modulated by the pump current up to 5.7 GHz.

Transition of cellulose supramolecular structure during concentrated acid treatment and its implication for cellulose nanocrystal yield

Cellulose nanocrystals with cellulose I and II allomorphs (CNC-I and CNC-II) were prepared from eucalyptus cellulose I substrate by controlling the sulfuric acid hydrolysis conditions, including acid concentration (56–64 wt%), reaction temperature (45 or 60 °C) and time (10–120 min). The crystalline structures were verified by XRD and 13C-NMR. CNC-II only appeared at very restricted reaction conditions. The rapid cellulose supramolecular structure transition under sulfuric acid concentration of around 60 wt% resulted in an abrupt change in CNC yield. A maximal CNC yield of 66.7% was obtained at acid concentration of 58 wt% and reaction temperature of 60 °C. CNC-I exhibited spindle-shape, while CNC-II showed a twisted strip structure. The state of order in cellulose during the acid hydrolysis process has been studied using a coagulation method. A tentative model of CNC-I and CNC-II formation was then proposed. This work provided significant knowledge for the production of CNCs with high yield and controllable allomorph.

Extraction, characterization and antioxidant activity of polysaccharide from Pouteria campechiana seed

In this study, the seed polysaccharides (PCSP) was ultrasonic-assisted extracted from Pouteria campechiana and optimized by response surface method (RSM). After separation and purification by DEAE-52 cellulose column and Sephadex G-75 glucan gel column, the pure polysaccharide component of PCSPa-1 was obtained, and its structure and antioxidant activity were analyzed. The results showed that the optimal parameters of PCSP with maximum yields (15.94%) were ultrasonic temperature of 79 °C, ultrasonic time of 69 min, and liquid to material ratio of 41 mL/g. The molecular weight of PCSPa-1 was 67900 Da. PCSPa-1 consisted of glucose and mannose with a molar ratio of 86.65:4.62, and the glycosidic bond mainly included →4)-α-d-Glc(1→ and →6)-α-d-Glc(1→. Scanning electron microscopy showed that PCSPa-1 was a strip structure with a smooth surface. In addition, PCSPa-1 had strong scavenging capacity to 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis- (3-ethylbenzthiaz oline-6-sulphonic acid) (ABTS), hydroxyl radical, and superoxide radical. Polysaccharides of Pouteria campechiana seeds could be exploited as a natural antioxidant.

Linewidth dependence of NbN-based microwave kinetic inductance detectors

We analysed, fabricated, and characterised niobium nitride (NbN)-based microwave kinetic inductance detectors (MKIDs) with a rewound strip structure (spiral-MKIDs). To control resonance characteristics precisely, the linewidth (w) dependence of rewound spiral resonators varying between w = 10, 20, and 40 μm was analysed using an electromagnetic field simulator; the resonance frequencies (f0’s) were obtained as 4.42, 4.58, and 5.15 GHz respectively, proving that the inductance decreases as the w increases. To verify the simulation results experimentally, NbN-based MKID arrays with different linewidths were fabricated on 10×10 mm2 sapphire substrates, and cooled down to 3 K. The microwave characteristics with a vector network analyser, and f0’s were found to be 4.11, 4.23, and 4.85 GHz for the MKIDs with w = 10, 20, and 40 μm, respectively. These values are in agreement with the simulation results within 7.6% accuracy. The other resonance characteristics such as the scattering-matrix element (S21) and loaded quality factor (QL) showed the similar w dependence with the simulation. Spiral-MKIDs with narrower w is expected to have better detector performance owing to shallower S21 and higher QL.

Putative spin-nematic phase in BaCdVO(PO4)2

We report neutron scattering and AC magnetic susceptibility measurements of the 2D spin-1/2 frustrated magnet BaCdVO(PO$_{4}$)$_{2}$. At temperatures well below $T_{\sf N}\approx 1K$, we show that only 34 % of the spin moment orders in an up-up-down-down strip structure. Dominant magnetic diffuse scattering and comparison to published $\mu$sr measurements indicates that the remaining 66 % is fluctuating. This demonstrates the presence of strong frustration, associated with competing ferromagnetic and antiferromagnetic interactions, and points to a subtle ordering mechanism driven by magnon interactions. On applying magnetic field, we find that at $T=0.1$ K the magnetic order vanishes at 3.8 T, whereas magnetic saturation is reached only above 4.5 T. We argue that the putative high-field phase is a realization of the long-sought bond-spin-nematic state.

Performance of a two-dimensional position sensitive MRPC prototype with adjustable transmission line impedance

The free streaming readout concept of the CBM experiment imposes to the Multi-Strip Multi-Gap RPCs (MSMGRPCs) developed for the CBM-TOF wall a very good matching of the characteristic impedance of the signal transmission line (corresponding to a single strip) to the input impedance of the front-end electronics in order to reduce fake signals produced by reflections. The design of the MSMGRPC prototype described here exploits in an innovative way the advantage of a strip structure for the readout and the high voltage electrodes, the impedance of the signal transmission line being adjusted independent of the detector granularity. The new design allows to built MSMGRPCs with the impedance corresponding to a single strip matched to the input impedance of the front end electronics. The prototype was tested in-beam at CERN-SPS with reaction products of a 30⋅A GeV Pb beam colliding onto a Pb target, in conditions rather similar in terms of energy and multiplicity with those expected at SIS100/FAIR. The obtained performance of 62 ± 3 ps system time resolution and 97% efficiency shows that the new developed prototype meets the challenging requirements for the inner zone of the CBM-TOF wall.

N-type Bi-doped SnSe Thermoelectric Nanomaterials Synthesized by a Facile Solution Method.

An n-type Bi-doped SnSe was synthesized by a facile solution method followed by spark plasma sintering. We used bismuth(III) 2-ethyhexanoate as a cationic dopant precursor, which can absorb on the powder surface and then diffuse into the lattice to realize the substitution of Sn by Bi. A strip structure with low-angle boundary was constructed for effective phonon scattering. With increasing content of Bi, the carrier concentration decreased from 1.35 × 1019 cm-3 (p-type) in undoped SnSe to 4.7 × 1014 cm-3 (n-type) in Sn0.99Bi0.01Se and then increased to 1.3 × 1015 cm-3 (n-type) in Sn0.97Bi0.03Se. The Seebeck coefficient changed from positive to negative and presented n-type conducting behavior in the whole measured temperature range from 300 to 773 K, reaching a maximum absolute value of ∼900 μV K-1 at room temperature and ∼300 μV K-1 at 773 K. Considering the rich variety of metal 2-ethylhexanoates, higher thermoelectric performance is expected by different cationic doping in solution-synthesized nanomaterials.

EFFECT OF ANNEALING AT DIFFERENT TEMPERATURES ON THE STRUCTURE AND HARDNESS OF AL85Y8NI5CO2 ALLOY AMORPHOUS STRIPS

Aluminum-based metallic glasses are the new promising family of materials. However, the effect of heat treatment on the structure and properties of Al–Y–Ni–Co amorphous alloys has not been widely studied so far. In this paper, Al85Y8Ni5Co2 amorphous alloy strips were obtained by hardening on a rotary copper wheel. The effect of vacuum annealing at temperatures ranging from 100 to 500 °C for 30 minutes on the structure and hardness of these strips was investigated. Transmission electron microscopy, X-ray diffraction analysis, and differential scanning calorimetry were used to study changes in the structure of strips after heat treatment. Vickers microhardness was measured to investigate the effect of annealing on the mechanical properties of strips. The results obtained allowed for the conclusions made about changes in hardness depending on the Al85Y8Ni5Co2 alloy strip structure. It was found that as the temperature rises, strip microhardness increases reaching a maximum value of 575±7 HV after annealing at 350 °C, then it decreases with a further increase in the annealing temperature. It was shown that the Al85Y8Ni5Co2 alloy strips remain completely amorphous and no crystalline phases are detected in their structures after annealing at temperatures up to 250 °C for 30 minutes. A sharp increase in hardness after annealing at 350 °C is associated with 10–30 nm nanocrystals of an aluminum solid solution formed in the amorphous matrix and surrounded by a residual amorphous matrix, while further hardness decrease is associated with the increasing sizes of these crystals and Al3Y and Al19Ni5Y3 intermetallics formed in the structure.