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Cement-based sensors should exhibit accurate measurements of strain with high sensitivity and reliability under various environmental conditions. The ability of such sensors to perform in adverse situations needs to be well developed and critically examined. Cement-based sensors are generally embedded in structural/non-structural concrete components for health monitoring. This paper provides an in-depth study of the performance and response of Super Sensitive Carbon Nanofiber Aggregates (SSCNFA) under challenging and adverse environmental conditions, including different temperature, moisture/water exposure, and compressive forces. The SSCNFA detects changes in temperatures, moist environments, and compressive forces through changes in the electrical impedance. In this study, the change in the total impedance of SSCNFAs are experimentally examined by alternating current (AC) measurements (20 Hz–300 kHz) under various environmental conditions. The thermal tests (21 °C–120 °C) and the impedance recovery tests examine and elaborate the phenomenon of resistance and total impedance reduction. The waterproofing test identifies the suitable polymer to prevent moisture percolating through the SSNCFA. Also, compression tests examine the stress/strain sensing through piezoresistivity in the linear elastic limit of the SSCNFA. The effects of these external conditions in the selective frequency range are measured to monitor the stability, reliability, recovery, and performance of the SSCNFA. The research reveals that the SSCNFA exhibited a linear electrical response against the temperature at higher frequencies (higher or equal to 10 kHz) with a standard deviation of less than 5 %. The SSCNFA's porous structure absorbs moisture during concrete casting. This absorbed moisture will be influenced by the environmental temperature variations and mechanical stresses during the service period of the structure. Additionally, the impedance recovery test results of uncoated SSCNFAs provide insight into the frequency response against the moisture/water and the stability of electrical response at the higher frequencies (higher or equal to 100 kHz). The waterproofing of the SSCNFA using M-coat A and M-coat B (polymers) proves to be effective, with the waterproofed SSCNFA sensor embedded in concrete exhibiting stress-sensing ability due to piezoresistivity. The electrical response of the SSCNFAs is more sensitive to temperature, moisture/water, and compressive stresses at low frequencies with higher standard deviations than at higher frequencies. Therefore, the experiments performed on SSCNFAs show that the SSCNFA embedded in a concrete structure is suitable for structural health monitoring. Furthermore, this research offers various avenues for the application of the SSCNFA as a multifunctional tool for temperature sensing and moisture detection of concrete structures due to cracks at critical locations. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A super-sensitive carbon nanofiber aggregate (SSCNFA) sensor with 0.05% CNFs content has been developed. • The sensor's sensitivity is enhanced due to a well-defined conductive path between CNFs and steel mesh. • SSCNFA can detect forces as low as 0.28 N, making it suitable for stress/strain sensing and damage detection. • The sensor has a wide dynamic range, with any frequency from 1 Hz to 500 kHz available for various applications. A carbon nanofiber aggregate of exceptional sensitivity is developed. Our approach involves the development and utilization of a novel nanobrush structure of carbon nanofiber within the mortar matrix. The high number of nanostructures in the nanobrush, particularly near the electrodes, results in a greater number of nanogaps, leading to a substantial improvement in sensitivity. We are able to detect forces as small as 1 N using this sensor. The carbon nanofiber brush (CNFB) provides a well-defined conductive path for the piezoresistive functioning of the super-sensitive carbon nanofiber aggregate (SSCNFA) with significantly reduced cost. The influence of scanning frequency in impedance is rigorously investigated with alternating current (AC) based on two methods. SSCNFAs are tested in uniaxial compression to determine the highly sensitive face of cube sensor. An SSCNFA (0.05 % CNFs, dense electrodes) and a CNFA (0.5 % CNFs, wide-spaced electrodes) were tested in a sweep-frequency test under parallel compression to compare the super-sensitive performance of the new sensor. The gauge factors at various frequencies were determined. The electrical impedance measured at various frequencies provides versatility to the SSCNFA for stress monitoring. Four fixed-frequency tests were conducted to determine the resolution under uniaxial compression and examine repeatability. [ABSTRACT FROM AUTHOR]

• A high efficiency spectral linewidth narrowing structure is proposed. • A blue diode laser with 444.36 nm central wavelength and 0.18 nm spectral linewidth is achieved. • The 40 W class narrow-linewidth blue diode laser is the highest reported to date. An external cavity feedback structure based on volume Bragg grating is introduced to realise spectral stabilisation and linewidth narrowing of a blue diode laser, with a central wavelength of 444.36 nm and a spectral linewidth of 0.18 nm. Using spatial beam combining technology and fibre coupling technology, a blue diode laser source producing 40.3 W power from an output fibre (core diameter: 105 µm, numerical aperture: 0.22) is achieved at an operating current of 3 A. The external cavity feedback and fibre coupling efficiencies exceeded 101.8 % and 88 %, respectively. Such high-power narrow-linewidth blue diode lasers show potential applications in second-harmonic generation, high-resolution spectroscopy, medical treatment, and industrial processing. To the best of our knowledge, the 40 W class output power with the narrow-linewidth of a fibre-coupled blue diode laser is the highest reported to date. [ABSTRACT FROM AUTHOR]

A novel beam homogenisation system based on a micro-lens array and beam expansion structure is proposed to convert a Gaussian-distributed circular beam to a flat-top-distributed square beam of size 2–5 mm and a homogeneity degree exceeding 95%. The novel micro-lens array based on a cylindrical lens element can potentially be widely applied in practice because of the absence of the preparative limitations of size and focal length. By employing this beam homogenisation system, laser shock processing experiments were performed on 7050 titanium alloy. The laser shock processing parameters were optimised. When the laser repetition frequency was 1 Hz, pulse width was 15 ns, and laser energy was 20 J, a residual stress of > 400 MPa was achieved on the titanium alloy. The experimental results demonstrate the ability of this beam-homogenisation system to perform laser shock processing. [ABSTRACT FROM AUTHOR]

A diode-pumped alkali metal vapor laser (DPAL) combines the advantages of a solid laser and a gas laser. DPAL is useful in the industrial, medical, aerospace and military fields and can yield high output power while maintaining excellent beam quality. However, applications in many fields are limited due to the narrow absorption spectrum of the alkali metal vapor laser. In this study, a novel linewidth narrowing structure of the high-power diode laser based on volume Bragg gratings (VBGs) is proposed to match the absorption spectrum of the alkali metal vapor laser. With the combination of fast-axis collimating lens, beam transformation systems, slow-axis collimating lens, VBGs and metal ceramic heaters, the divergence angles of both fast and slow axis are compressed within 10 mrad. A high-power narrow linewidth diode laser source with a central wavelength of 780.044 nm, a spectral width of 0.138 nm, and an output power of 1090 W is achieved at an operating current of 50 A. Experimental results show that the effect of external cavity feedback based on VBG is improved and the multi-channel spectral linewidth is narrowed effectively by such a structure. The diode laser source based on this structure can be applied for pumping the rubidium alkali metal vapor laser. [ABSTRACT FROM AUTHOR]

[Display omitted] Magnesium rechargeable batteries are promising candidates for large-scale energy storage due to their -high safety, low material cost, and earthabundant materials. Many redox-active polymers have recently been reported to show excellent cycling stability with decent Mg-storage performance. However, compared to their Li counterparts, these polymers exhibit lower Mg-storage capacity, resulting in a low ratio of materials utilization (η Mg/ η Li) for the same polymer in two electrolyte systems (i.e., Mg vs. Li electrolytes). Herein, we present a sulfur-linked porous polymer, poly(hexaazatrinaphthalene sulfide) (PSHATN), which sets a record for material utilization of 98% among all polymer electrodes and delivers a reversible capacity of 196 mAh g−1 in Mg electrolytes. Based on electrochemical impedance spectroscopy and operando optical microscopy, we discover a strong correlation between specific capacity and degree of electrochemical swelling of polymers in both electrolytes. Importantly, the high ratio (η Mg/ η Li) of PSHATN is ascribed to sufficient electrochemical swelling due to its large pore volume and flexible polymer nature, in contrast to linear polymers and rigid covalent organic frameworks that swell less effectively. This work highlights the critical need for polymer swelling in promoting ion transport in redox polymers for high material utilization and offers important polymer structural design insights for multivalent ion-based energy storage. [ABSTRACT FROM AUTHOR]

Abstract: ZnO and graphene composites (ZnO/GR) were prepared by a simple and repeatable thermal evaporation process, and both the reduction of graphene oxide and the loading of ZnO were achieved. The structural and optical properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements. In the PL spectra, when the mass ratio of graphene to ZnO increased, a series of fluorescence quenching were found, and a regularly blue shift of the ultraviolet (UV) peak were also found, which might be attributed to the Burstein–Moss effect. [Copyright &y& Elsevier]

Abstract: In this paper, high-k LaAlO3 is proposed as tunnel dielectric for p-channel flash memory device application. The program/erase (P/E) injection current characteristic of p-channel flash memory cells with LaAlO3 tunnel dielectric is investigated compared to the cells with SiO2 tunnel dielectric by two-dimensional (2-D) device simulation, which shows that the bit line bias can be lowered from −5V to −3V during both P/E operations of flash memory cells with LaAlO3 tunnel dielectric, meanwhile retains the fast P/E speed and high injection efficiency. Our work also shows that drain disturb, one of the main issues for p-channel flash memory, is alleviated dramatically due to the lower P/E voltage. [Copyright &y& Elsevier]

• Ultra-high-performance carbon nanofiber aggreagate is proposed and developed. • The relationship between electrical response and stress–strain response are obtained. • The influence of scaning frequency and loading orientation are investigated. • The proposed sensor has compressive strength of 138 MPa to fit UHPC strength. Ultra-high-performance concrete (UHPC) is rapidly implemented to build robust, durable, and sustainable structures. This study presents the development of a robust self-sensing sensor with the motivation to monitor structures with high-performance construction material, such as UHPC. The ultra-high-performance carbon nanofiber aggregates (UHPCNFAs) are carbon nanofibers (CNFs) and UHPC-based smart aggregates. The newly developed UHPCNFAs are experimentally investigated in uniaxial compression. Sweep-frequency and fixed-frequency tests are adopted in alternating current measurements for determining the electrical behavior of the UHPCNFAs. UHPCNFAs are compressed in parallel and perpendicular loading orientations to understand the difference in the sensor's electrical sensitivity and mechanical behavior in each case. In addition, the robustness of the UHPCFNA is examined to the point of failure in both orientations. The relationship between stress, strain, and electrical impedance variation is established for eight different frequencies. Furthermore, the UHPCNFAs are compressed at a fixed frequency to verify the repeatable behavior. This paper examines the effect of loading orientations on electrical and mechanical response, robustness, and sensitivity of UHPCNFA in a wide range of frequency spectrum to check its suitability in real-time structural health monitoring. [ABSTRACT FROM AUTHOR]

• A comprehensive report of large-scale field tests for metamaterial-based barriers. • T -Rex mobile shaker at UT Austin is used to generate excitation. • Significant response reduction was observed for cases with metamaterial-based barriers. • Various excitations result in similar results of frequency response function. Seismic isolation systems protect structures and act as decoupling systems with the structure, which aims to uncouple the motion of the structure from incoming waves by reducing the kinetic energy of vibration transferred to structures. This research aims to study a non-invasive vibration isolation system using periodic barriers. A comprehensive field test program is completed to evaluate the wave isolation performance of empty trench and periodic barriers. The precast one-dimensional (1D) periodic barriers are arranged to form one long barrier and one short thick barrier to examine the influence of barrier length and the number of unit cells on the vibration isolation performance. The test program reported in this study is the P0 case (without periodic foundation), which serves as a reference group compared to previous test case P 1 (with periodic barrier and reinforced concrete foundation) and test case P 2 (with a combination of periodic barrier and periodic foundation). The triaxial (T -Rex) shaker truck generates excitation in three axis and the wave form include sine wave, sweep frequency and seismic waves. Each geophone sensor position records the triaxial soil response. The responses of soil along the direction of wave transfer, the normalized responses, and the frequency response function (FRF) are all provided and discussed. Various excitation inputs are comparable. It is found that the excitation directions influence the periodic barrier's effectiveness because of the dominant waveform. When FRF is compared between benchmark case and test cases, the periodic barriers' screening effectiveness can be determined in the attenuation zones. These attenuation zones are expected to be the frequency band gaps of the periodic barrier. When the incoming wave frequency falls in this frequency band gap, the periodic barrier can isolate the vibration propagating towards the protected region. [ABSTRACT FROM AUTHOR]

The Ni atom is difficult to occupy the Ti or Al site in TiAl, it exists in the form of NiTi phase at the grain boundary of TiAl alloy, which is detrimental to the ductility of the TiAl alloy. The Fe and Co atoms preferentially occupy the Al sites and can improve the electronic structures and elastic properties of TiAl, leading to the improvement of the ductility of TiAl alloy. With the addition of 3 at.% Fe and Co, the tested average fracture strain of TiAl alloy increases from 17.3% to 19.1% and 18.0%, respectively. [ABSTRACT FROM AUTHOR]

Nanomaterial additives have been broadly used in cement and concrete-based sensors to measure the stress and strain in the structure. Most of the studies focused on measuring the resistivity of sensors with Direct Current (DC) or relatively low-frequency. In this work, the impedance responses of enhanced Carbon Nano-Fiber Aggregates (CNFAs) at different frequencies are rigorously studied and utilized as a tool for real-time structural health monitoring (SHM). The CNFA impedance measurements at different measurement frequencies provide an extra dimension (frequency dimension) to allow the characterization of different phenomena and multimodal measurements simultaneously. First, a comprehensive physical model is established to understand the frequency responses of the CNFA impedance. Second, COMSOL Multiphysics is used to simulate the frequency responses of the CNFA impedance, which provides more insights into the electric field and current density distribution. The impedance of CNFAs decreased with the increased dosage of carbon nanofibers (CNFs). Third, experimental studies are reported in detail. The electrical impedance variation (EZV) of the CNFA in parallel orientation is 151% higher than that of perpendicular orientation at the frequency of 2612 Hz and uniaxial compression stress of 4.65 MPa. The strain-EZV curve obtained from the response spectrum is linear for frequencies ranging from 98 Hz to 463.9 kHz. The strain-EZV curve for 5625 Hz has a linear fit with the gauge factor of 147.78. At 1000 Hz, the CNFA exhibited a repeatable behavior up to 9.35 MPa and detection limit up to the stress of 18.62 MPa. [ABSTRACT FROM AUTHOR]

Abstract: A novel vertical channel dual-nitride-trapping-layer ROM (VDNROM) flash memory with oxide–nitride–oxide–nitride–oxide (ONONO) dielectrics stack is proposed and experimentally demonstrated. Compared with the conventional planar NROM cell, since the cell area of the proposed vertical structure is independent of the gate length, the VDNROM structure can relax the limitation of the gate length scaling, and can have high capability of cell area shrinking. The fabrication process of this VDNROM device is basically compatible with planar CMOS technology. The VDNROM cell can be programmed and erased by the hot carrier injection to the localized trapping dual-nitride layers, so it can achieve a four-physical-bits storage capability each cell. The reliability behaviors including the cycling endurance and the bake retention at 150°C have also been investigated and show the acceptable characteristics. The experiment results verify the VDNROM cell as a good candidate for high density applications. [Copyright &y& Elsevier]