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In this work, an air-cooled, single effect solar-driven absorption system is being evaluated from the point of view of 1 st and 2 nd thermodynamic principles for two different applications: absorption chiller and heat pump. One of the most widely used working pairs, LiBr-H 2 O, is applied in this study due to its high performance in the absorption cycle. Their performance is compared with another working pair Carrol-H 2 O (Carrol contains LiBr and EG -Ethylene glycol- with a mass ratio of 4.5:1). The Carrol solution has the advantage of reducing the crystallization risk at the high concentration solution which enters the absorber. The numerical modelling was implemented on a modular object-oriented simulation platform (NEST platform tool), which allows linking different components, considered objects. In the simulations performed, the heat source temperature in the system is in the range of 70-90 ∘ C, and the inlet temperature at evaporator secondary circuit at chiller application is fixed in two values, 9 ∘ C and 14 ∘ C, and for heat pump application in 0 ∘ C and -5 ∘ C. Moreover, EG is added to the evaporator at heat pump application to prevent the refrigerant water from freezing below zero. The studied mass concentration range of EG of 10-40%. The result shows the C O P of an absorption chiller and heat pump are around 0.7 and 1.6, respectively, and the C O P EX values are 0.2-0.6 at chiller application and 0.5-1.5 at heat pump application. When compared with LiBr system, Carrol system has about 6.4% higher C O P , about 6.3% higher C O P EX , and a decrease of about 19% of cooling capacity. In the heat pump application, the heat source temperature should be lower than 90 ∘ C, and EG concentration at evaporator has been chosen as 30% as an optimal value. According to the operation condition, this EG concentration has been determined to avoid freezing in the evaporator in the studied working range. However, too much EG significantly decreases the pressure in the evaporator and increases the viscosity, hence will increase the maintenance of equipment as more vacuum tightness is required.

The ejector driven by the high-pressure gas potential energy from the hydrogen storage tank can reliably recirculate the unconsumed hydrogen in the proton exchange membrane fuel cell (PEMFC) system. However, the fixed-geometry ejector cannot maintain consistently high performance among the whole power output range in the PEMFC system due to its shortage of limited operating range. In this paper, a coaxial two-nozzle ejector, satisfying the requirements of the PEMFC system under different power outputs, is developed for hydrogen recirculation. The proposed ejector is investigated numerically based on an experimentally verified simulation model to reveal the flow distribution and predict its performance. The simulation results show that the proposed ejector can work in a wide power range of 17.90–84.00 kW within a suitable supply hydrogen pressure range of 4–7 bar. More importantly, the ejector can not only maintain a recirculation ratio above 0.9 in the wide output power range but a high recirculation ratio greater than 2.0 in the low power output. The proposed ejector broadens the working range of a single ejector used in the PEMFC system, which significantly promotes the development of fuel cell being widely adopted in automobiles.

Flexible strain sensors have received intensive attention owing to their wide application prospects in the fields of wearable, personal electronics, and intelligent robotic systems. But it is a huge challenge for them to possess high sensitivity, fast response, wide sensing range, and superior durability synergistically. In order to solve these issues, we prepared a new type of buckypaper with excellent mechanical properties (elongation at break of about 22%) and electrical conductivity (33 S/cm) by filtering carbon nanotube (CNT) aqueous dispersion mixed with a small amount of natural rubber latex (NR), named natural rubber-buckypaper (N-BP). By taking advantage of the robust N-BP, an NR/N-BP/NR strain sensor was creatively constructed by sandwiching the N-BP with two NR layers using the casting-curing method. The NR/N-BP/NR sandwich strain sensor showed a very high gauge factor value (2280), ultrashort response time (21 ms), very large sensing range (500%), and satisfactory sensing stability (2000 cycles at 100% strain). As for practical application, this NR/N-BP/NR strain sensor could accurately capture large or subtle human body movements, such as limb joint movements and facial movements, and could even distinguish the pronunciation of different English words. As a whole, the NR/N-BP/NR sandwich strain sensor exhibited promising applications in wearable electronics. The NR/N-BP/NR sandwich strain sensor with wide working range and high sensitivity based on the excellent performance of N-BP.

Wearable strain and temperature sensors are desired for human-machine interfaces, health monitoring, and human motion monitoring. Herein, the fibrous mat with aligned nanofibers of ionic liquid (IL)/thermoplastic polyurethane (TPU) ionogels is fabricated via an electrospinning technique. The resultant fibrous mat is cut into a rectangle specimen and electrodes are loaded along the direction perpendicular to the nanofiber orientation to design a high-performance multimodal sensor based on an ionic conducting mechanism. As a strain sensor, the obtained sensor exhibits a wide strain working range (0-200%), a fast response and recovery (119 ms), a low detection limit (0.1%), and good reproducibility because of the reversible and deformable ionic conductive pathways of the sensor. Moreover, the sensor also exhibits excellent temperature-sensing behaviors, including a monotonic thermal response, high sensitivity (2.75% °C-1), high accuracy (0.1 °C), a fast response time (2.46 s), and remarkable repeatability, attributable to the negative temperature coefficient behavior of the IL/TPU fibrous mat. More interestingly, the IL/TPU fibrous sensor possesses good breathability, which is desired for wearable electronics. Because of these excellent sensing capabilities in strain and temperature, the sensor can not only monitor tiny and large human motions but also detect respiration and proximity, exhibiting enormous potential in wearable electronics.

This paper presents a position sensor based on a novel configuration of linear variable differential transformer. Design and optimization of the position sensor using finite element method are presented. The measurements are also conducted to validate experimentally the sensor performance. The sensor has short air core coils and long magnetic armatures. The axis of the rectangular excitation coil and two antiserially connected rectangular pick up coils is perpendicular to the motion direction of the position sensor. The coils are located between two parallel silicon steel laminations serving as the armatures. The position sensor is optimized with compromise between minimization of nonlinearity error and maximum sensitivity. The main advantage of the proposed position sensor is the small ratio of coils dimensions to the working range. The position sensor is operated for excitation frequencies of 500 Hz, 1000 Hz, and 2000 Hz. The maximum nonlinearity error is less than 1.5% for the theoretical results and it is less than 2% for the measured results in ±90 mm position range.

The mechanism of the fluorescence quenching of the CQDs by warfarin was determined and based on this study a simple, low cost and highly sensitive nanosensor was developed for determination of Warfarin in plasma samples. The carbon quantum dots with 3.5 µs lifetime (halflife of 2.4 µs) were synthesized by hydrothermal method and characterized. The fluorescence rate constant of 4.5 × 104 s−1 and quenching rate constant of 6.18 × 104 s−1 (from 10 μM warfarin that result in 17% lifetime reduction) was calculated. High quenching efficiency results in 21.63 L mmol−1 Stern–Volmer constant and the study of pH and temperature also confirm the dynamic quenching mechanism. The second order rate constant of 6.18 × 104 L mmol−1 s−1 was obtained for collisions between CQDs and warfarin. Based on this mechanism, a simple, low cost and very sensitive warfarin nanosensor was developed with calibration sensitivity of 21.63 L mmol−1, working range of 0.10 – 12.00 μM and detection limit of 0.01 μM.

Microstructures play a dominant role in flexible electronics to improve the performance of the devices, including sensitivity, durability, stretchability, and so on. However, the complicated and expensive fabrication process of these microstructures extremely hampers the large-scale application of high-performance devices. Herein, we propose a novel method to fabricate flexible graphene-based sensors with a 3D microstructure by generating laser-induced graphene (LIG) on the 3D printed polyether ether ketone corrugated substrate, which is referred to as CLIG. Based on that, two integrated piezoresistive sensors are developed to monitor the precise strain and pressure signals. Contributed to the 3D corrugated graphene structure, the sensitivities of strain and pressure sensors can be up to 2203.5 and 678.2 kPa-1, respectively. In particular, the CLIG-based strain sensor exhibits a high resolution to the microdeformation (small as 1 µm or 0.01% strain) and remarkable durability (15,000 cycles); meanwhile, the pressure sensor presents a remarkable working range (1-500 kPa) and fast response time (24 ms). Furthermore, the CLIG-based sensors provide a stable data source in the applications of human-motion monitoring, pressure array, and self-sensing soft robotic systems. High accuracy allows CLIG sensors to recognize more subtle signals, such as pulse, swallowing, gesture distinction of human, and movement status of soft robotics. Overall, this technology shows a promising strategy to fabricate high-performance sensors with high efficiency and low cost.

The demand of ultra-precision micro-machine tools is growing day by day due to exigent requirements of miniaturized components. High accuracy, good dimensional precision and smooth surface finish are the major characteristics of these ultra-precision machine tools. High-speed machining has been adopted to increase the productivity using high-speed spindles. However, machine tool vibration is a major issue in high-speed machining. Vibration significantly deteriorates the quality of micro-machining in terms of dimensional precision and surface finish. This article describes a design methodology of a closed type machine structure for vibration minimization of a high-speed micro-milling center. The rigid machine structure has provided high stiffness and the damping capability to the machine tool without utilizing vibration absorbers. The models of the machine structures have been generated and assembled in AutoCAD 3D. The performance of the integrated micro-milling machine tools was determined by finite element analysis. The best model has been selected and proposed for manufacturing. Additionally, simulation results were validated by comparing with experimental results. Eventually, after manufacturing and assembly, experiments have been performed and it was observed that the amplitude of vibration was approaching towards nanometer level throughout the working range of the high-speed spindle. The machine tool was capable to fabricate miniaturized components with smooth surface finish.

In this study, we proposed a Base S-type, long-period, fiber grating (Base S-type LPFG) coated with graphene oxide (GO) for sensing relative humidity based on the micro-electro-mechanical systems (MEMS) process and piezoelectric inkjet technology. The single mode optical fiber was etched to three different diameters (37, 42 and 60 μm) which were evaluated in the Base S-type LPFG. According to the experimental results, the diameter of 37 μm yielded the best sensitivity. Humidity sensor experiments showed that the Base S-type LPFG exhibited a high humidity sensitivity in a wide range from 20% RH to 80% RH. These experiments were repeated three times and the results showed that the average value of transmission loss sensitivity was −0.1824 dB/% RH and the average linear response had a correlation coefficient of 95.68%. The sensor exhibits good linearity, high stability, and reversibility in a wide working range. Therefore, the proposed graphene oxide-coated Base S-type LPFG humidity sensor has the potential for monitoring the relative humidity.

PurposeThe purpose of the experimental investigation was to optimize the process parameters of the fused deposition modeling (FDM) technique. The optimization of the process was performed to identify the relationship between the chosen factors and the tensile strength of acrylonitrile butadiene styrene (ABS) and carbon fiber polylactic acid (PLA) thermoplastic material, FDM printed specimens. The relationship was demonstrated by using the linear experimental model analysis, and a prediction expression was established. The developed prediction expression can be used for the prediction of tensile strength of selected thermoplastic materials at a 95% confidence level.Design/methodology/approachThe Taguchi L9 experimental methodology was used to plan the total number of experiments to be performed. The process parameters were chosen as three at three working levels. The working range of chosen factors was the printing speed (60, 80 and 100mm/min), 40%, 60% and 80% as the infill density and 0.1mm, 0.2mm and 0.3mm as the layer thickness. The fused deposition modeling process parameters were optimized to get the maximum tensile strength in FDM printed ABS and carbon fiber PLA thermoplastic material specimens.FindingsThe optimum condition was achieved by the process optimization, and the desired results were obtained. The maximum desirability was achieved as 0.98 (98%) for the factors, printing speed 100mm/min, infill density 60mm and layer thickness 0.3mm. The strength of the ABS specimen was predicted to be 23.83MPa. The observed strength value was 23.66MPa. The maximum desirability was obtained as 1 (100%) for the factors, printing speed 100mm/min, infill density 60mm and layer thickness 0.2mm. The strength of the carbon fiber PLA specimen was predicted to be 26.23MPa, and the obtained value was 26.49MPa.Research limitations/implicationsThe research shows the useful process parameters and their suitable working conditions to print the tensile specimens of the ABS and carbon fiber PLA thermoplastics by using the fused deposition modeling technique. The process was optimized to identify the most influential factor, and the desired optimum condition was achieved at which the maximum tensile strength was reported. The produced prediction expression can be used to predict the tensile strength of ABS and carbon fiber PLA filaments.Practical implicationsThe results obtained from the experimental investigation are useful to get an insight into the FDM process and working limits to print the parts by using the ABS and carbon fiber PLA material for various industrial and structural applications.Social implicationsThe results will be useful in choosing the suitable thermoplastic filament for the various prototyping and structural applications. The products that require freedom in design and are difficult to produce by most of the conventional techniques can be produced at low cost and in less time by the fused deposition modeling technique.Originality/valueThe process optimization shows the practical exposures to state an optimum working condition to print the ABS and carbon fiber PLA tensile specimens by using the FDM technique. The carbon fiber PLA shows better strength than ABS thermoplastic material.

The flexible strain sensor is of significant importance in wearable electronics, since it can help monitor the physical signals from the human body. Among various strain sensors, the foam-shaped ones have received widespread attention owing to their light weight and gas permeability. However, the working range of these sensors is still not large enough, and the sensitivity needs to be further improved. In this work, we develop a high-performance foam-shaped strain sensor composed of Ti3C2Tx MXene, multiwalled carbon nanotubes (MWCNTs), and thermoplastic polyurethane (TPU). MXene sheets are adsorbed on the surface of a composite foam of MWCNTs and TPU (referred to as TPU/MWCNTs foam), which is prefabricated by using a salt-templating method. The obtained TPU/MWCNTs@MXene foam works effectively as a lightweight, easily processable, and sensitive strain sensor. The TPU/MWCNTs@MXene device can deliver a wide working strain range of ∼100% and an outstanding sensitivity as high as 363 simultaneously, superior to the state-of-the-art foam-shaped strain sensors. Moreover, the composite foam shows an excellent gas permeability and suitable elastic modulus close to those of skin, indicating its being highly comfortable as a wearable sensor. Owing to these advantages, the sensor works effectively in detecting both subtle and large human movements, such as joint motion, finger motion, and vocal cord vibration. In addition, the sensor can be used for gesture recognition, demonstrating its perspective in human-machine interaction. Because of the high sensitivity, wide working range, gas permeability, and suitable modulus, our foam-shaped composite strain sensor may have great potential in the field of flexible and wearable electronics in the near future.

Wire Electrical Discharge Machining (WEDM) has been recently used to fabricate ultra-thin silicon wafers for applications in solar cells. However, the slicing of wafers induce thermal damage and deteriorate the surface of wafers, thereby requiring polishing to eliminate the damage. In order to reduce the polishing time, laser surface modification using nanosecond pulses is explored as a potential pre-treatment technique before polishing to reduce thermal damages incurred during the WEDM process. The process relies on the selection of appropriate parameters. Therefore, this work attempts at understanding the effect of various laser parameters on the surface to optimize the process for a nanosecond pulsed laser. Since the range of parameters to be used is entirely unknown, a numerical model is developed using the Finite Volume Method to arrive at a preliminary range of parameters to carry out the experimental work. The temperature profile obtained from the numerical model is then used to select the working range of laser power for the experiments. Experiments were carried out on WEDM sliced silicon wafers using the range of laser power obtained. Based on scanning electron microscope images, it was observed that the surface thermal damage depth reduced up to 50 % after laser processing. The thermal damage depth was observed to decrease with an increase in pulse repetition rate with a minimum at 50 kHz and increases thereafter. Besides, it was also observed that the residual stresses also reduced significantly at lower values of laser power and pulse repetition rate.

Significant efforts have been devoted to enhancing the sensitivity and working range of flexible pressure sensors to improve the precise measurement of subtle variations in pressure over a wide detection spectrum. However, achieving sensitivities exceeding 1000 kPa−1 while maintaining a pressure working range over 100 kPa is still challenging because of the limited intrinsic properties of soft matrix materials. Here, we report a magnetic field-induced porous elastomer with micropillar arrays (MPAs) as sensing materials and a well-patterned nickel fabric as an electrode. The developed sensor exhibits an ultrahigh sensitivity of 10,268 kPa−1 (0.6–170 kPa) with a minimum detection pressure of 0.25 Pa and a fast response time of 3 ms because of the unique structure of the MPAs and the textured morphology of the electrode. The porous elastomer provides an extended working range of up to 500 kPa with long-time durability. The sophisticated sensor system coupled with an integrated wireless recharging system comprising a flexible supercapacitor and inductive coils for transmission achieves excellent performance. Thus, a diverse range of practical applications requiring a low-to-high pressure range sensing can be developed. Our strategy, which combines a microstructured high-performance sensor device with a wireless recharging system, provides a basis for creating next-generation flexible electronics.

Accurate engine performance models are important for model-based performance evaluation of aero engine. The accuracy of the model often depends on engine component maps, so there is a need for a method that can accurately correct the component maps of the model over a wide range. In this paper, a new method for modifying component maps is proposed, this method combines the correction of the scaling factors with the solution process of the off-design working point, and uses the adjustment of the variable geometric parameters of the engine to change the position of the working line, in order to obtain more correction results and guarantee high accuracy in a wider range. The method is validated by taking the main fan of the Adaptive Cycle Engine (ACE), an ideal power unit for a new generation of multi-purpose and ultra-wide working range aircraft, as an example. The results show that the maximum error between the corrected component maps and the target maps is less than 1%. New possibility for more precise component maps can be realized in this paper.

Wind energy plays an increasingly important role in alleviating the shortage of fossil fuel energy because of the emerging promising technologies such as electromagnetic generators (EMGs), triboele...

Air leakage in underground coal mines presents a serious hazard for coal production and the safety of miners. Coating technology is commonly used as an efficient means for preventing air leakage. To address existing problems with high dust concentrations in large operations involving complex processes and the high cost of traditional coating technology, a novel coating technology that ensures intrinsic safety by utilizing water pressure and wind pressure was developed. This new coating technology was designed to suction and spray, and the technical parameters of its spray performance was also studied. The experimental tests and evaluation indicated the optimum working range is 0.3–0.7 MPa of wind pressure, 1.2–10.2 L/min of water quantity, and 1.0–3.5 m of spraying distance. Moreover, this novel coating technology was tested in the Dashuitou Coal Mine in Gansu Province of China. Compared with conventional counterparts, the proposed new technology is safe, efficient, and convenient to operate. During spraying, dust concentrations were kept at less than 10 mg/m3, and the average rebound ratio resilient rate of solid materials was below 13%. After spraying, the average leakage every 100 m was 4 m3/min, and the oxygen volume fraction in the adjacent goaf was approximately 4%, demonstrating excellent air leakage prevention.

Introduction of novel statistical technique for computing the interaction of lomefloxacin (LOME) and lanthanum (Ln) was the main purpose of this research. Moreover, using lanthanum as example of lanthanides for such interaction had not been exploited before. Screening of four factors affecting the interaction as metal volume, pH, temperature and reaction time was executed applying Plackett–Burman design where Pareto plots and ANOVA testing were used to pool off the insignificant factor. Accordingly, the imperative factors were optimized using Box–Behnken design after fine-tuning of the upper and lower levels values. 3-D surface plots and 2-D contour plots were chosen to evaluate the interaction between factors, followed by optimization plots to obtain the best blend of factors harmonized together and model confirmation was verified with three target points. Responses were measured as maximum absorbance; Y1 for technique (A) and maximum fluorescence intensity; Y2 for technique (B) using the resulted optimal conditions. Determination of LOME was applied with successful wide working range of (0.900–15.520, 0.070–1.552 µg/mL) for Y1 and Y2, respectively, with LOD and LOQ figured as 0.252, 0.763 µg/mL for Y1 and 0.0177, 0.0536 µg/mL for Y2. High degree of accuracy and precision was maintained in both pure and dosage forms findings. The techniques were found to be robust and adequate. Selectively of the models were proven by satisfactory % recovery calculations in interference tests. Statistical screening and optimization of the factors affecting the absorbance and fluorescence intensities of complexation of Lomefloxacin with lanthanum were achieved, followed by model confirmation and determinations in pure and dosage forms of the drug.

Summary Objectives The pharmaceutical industry and the National Regulatory Authorities (NRAs) are now focusing on the dissolution of multi-component drugs for quality control testing and predicting in vivo results to further consolidation of the biowaiver concept. The mixed formulation of Ciprofloxacin hydrochloride (CIP) and Metronidazole (MET) have been used as a model for simultaneous determination and obtaining in vitro dissolution profiles by using green analysis method namely (UV-CWT(Db4, a=490)). Material and methods The proposed method (UV-CWT(Db4, a=490)) includes UV detection combined with Continuous Wavelet Transform (CWT) with Daubechies family and the order of fourth at the scaling factor (a = 490) has been used and validated for analyzing and obtaining the dissolution profiles of the fixed-dose combination (CIP-MET). Results The proposed method (UV-CWT(Db4, a=490)) has been validated effectively in accordance with ICH rules, regarding linearity, specificity, rigor, and preciseness of the working range (3.0–16.0 μg/mL) for both (CIP) and (MET), respectively. As well as figures of merit were concluded. The dissolution profiles of CIP-MET tablets were acquired by the proposed (UV-CWT (Db4, a=490)) and HPLC reported methods were conveniently compared using the indicators f1 and f2 (“difference” and “similarity”) the results ensured that there were no statistically differences between the methods. In addition, the green assessment tool, namely analytical eco-scale, evaluated and compared the greenness of the suggested method (UV-CWT(Db4, a=490)) and HPLC reported one. Conclusion The suggested process (UV-CWT(Db4, a=490)) was considered as an excellent green, rapid, accurate, economical and minimum-steps method for simultaneously resolve and construct the dissolution curves of a fixed-dose combination drug (CIP-MET) in a short time and without the use of organic solvents, enabling significant labor and resource savings.

We propose a vertical linear motor (VLM) for semiconductor manufacturing equipment that compensates for the weight of the moving part by using the balance of magnetic and elastic forces. The developed VLM achieves zero stiffness with a constant upward force over a working range. The magnetic circuit of the VLM is designed to provide a linear negative stiffness over a ±2 mm stroke, with an upward force of 14 N at a 0 mm stroke. The negative stiffness is compensated for by the positive stiffness of elastic component-like springs. The upward force is then constant over the working range and corresponds to the weight of the moving part. The proposed VLM is designed to minimize the coupling effects of stiffness and gravity compensation forces by using magnetic flux saturation and magnetic flux path design. We investigate the effects of each design parameter on VLM operation through finite element analysis. Finally, the simulated forces in the proposed VLM are experimentally verified, indicating a linear negative stiffness of approximately −13.5 N/mm and a gravity compensation force of 14.9 N.

Wearable and highly sensitive pressure sensors are of great importance for robotics, health monitoring and biomedical applications. For simultaneously achieving high sensitivity within a broad working range, fast response time (within a few milliseconds), minimal hysteresis and excellent cycling stability are critical for high performance pressure sensors. However, it remains a major challenge. Herein, we report a conceptual micro-cliff design of a graphene sensor with a record high sensitivity of up to 72 568 kPa−1 in a broad working range of 0–255 kPa, which is one order of magnitude higher than the state-of-the-art reported sensitivity. In addition, the detection limit can be as low as 0.35 Pa and the fast response time is less than 5 ms. The sensor also has a minimal hysteresis and an outstanding cycling stability of 5000 cycles, all of which meet the requirements of an ideal pressure sensor. More interestingly, the micro-cliff graphene sensor is made by the fast and scalable flash reduction of graphene oxide using a single flashlight pulse within 150 ms and has been integrated into a wearable smart insole and an E-glove prototype for demonstration of health monitoring applications. This micro-cliff graphene pressure sensor achieves record-high sensitivity, which brings new possibilities in sensor research and promises broad applications.

Exploration of wearable strain sensors in diverse application scenarios is one global requirement for shaping the future of our intelligent community. However, state-of-the-art wearable devices still face challenges such as interference under humid conditions and chemical/mechanical fragility. Here, a facile and fluorine-free approach is introduced to realize a sensitive, robust and superhydrophobic strain sensor via the in situ formation of microcilia on the PDMS surface, followed by a two-step swelling process. The swelling process facilitates the penetration of carbon black nanoparticles into the PDMS matrix to render the conductive network suitable for strain sensing, while the decoration of silica nanoparticles along with the microcilia forms a hierarchical architecture for water repellency. The sensing performance was optimized, including the sensitivity (gauge factor of 354), working range (up to 250%), and long-term stability (>10 000 cycles). The superhydrophobic surface exhibits excellent resistance to mechanical abrasion, chemical corrosion, and high-speed water impact, etc. Demonstrations, such as body motion perception, wireless and underwater communications, Morse code generation, underwater jet impact, reveal the potential of the sensor as a robust platform for broad applications not only in air but also for underwater or under harsh condition uses.

The rapid development of human–machine interfaces and artificial intelligence is dependent on flexible and wearable soft devices such as sensors and energy storage systems. One of the key factors for these devices is the design of a flexible electrode with high sensitivity, fast response time, and a wide working range. Here, we report the fabrication of strain sensors and all-solid-state flexible supercapacitors using Co@N-CNT/MXenes as an electrode material. The manufactured sensor shows a high tensile range (strain up to 200%) and high stability. The resistance change caused by the fingers touching the sensor can be used to transmit the Morse code information. Flexible supercapacitors serving as power supply demonstrate excellent cycling stability (85 000 cycles) and coulombic efficiency (99.7%) for their high surface area and pseudocapacitance. A self-powered integrated system composed of the strain sensor and flexible supercapacitor is fabricated and operates stably in a wide strain sensing test range. Moreover, the flexible solar-charging self-powered integrated system could be attached to the human body for stable human motion detection. This study clearly shows that appropriate selection of a single functional material to enable it to be used in multi-functional sensors and supercapacitors can simplify the process and reduce the cost of manufacturing wearable devices.

Water sources are vulnerable to intentional and inadvertent human pollution with thousands of synthetic and geogenic trace contaminants, posing long-term effects on the aquatic ecosystem and human health. Thus, early and rapid detection of water pollutants followed by corrective and preventive actions can lead to the reduction of the overall polluting impact to safeguard public health. This study presents a generic sensing assay for the label-free detection of copper contaminants in environmental water samples using multilayered polyethylenimine (PEI) functionalized porous silicon Fabry-Pérot interferometers. The selective chelating activity of PEI thin-films was monitored in real-time by reflective interferometric Fourier transform spectroscopy (RIFTS) while assessing the improved optical responses. The optimized scaffold of two sequential PEI layers depicted a linear working range between 0.2 and 2 ppm while presenting a detection limit of 0.053 ppm (53 ppb). The specificity of the developed platform was cross-validated against various metallic pollutants and cations commonly found in water bodies (i.e., Cd2+, Pb2+, Cr3+, Fe3+, Mg2+, Ca2+, Zn2+, K+ and Al3+). Finally, as a proof of concept, the analytical performance of the porous interferometers for real-life scenarios was demonstrated in three water samples (tap, ground and irrigation), presenting sufficient adaptability to complex matrix analysis with recovery values of 85-106%. Overall, the developed sensing concept offers an efficient, rapid and label-free methodology that can be potentially adopted for routine on-site detection using a simple and portable device.

The effect of temperature on negatively charged nitrogen-vacancy (NV) centers in diamond is interesting owing to their high precision and high spatial resolution. In addition, this thermal effect has many applications, such as in magnetic imaging, materials science, and fundamental physics. Temperature sensitivity varies for different magnetic field directions. In this letter, a temperature working range of 260–500 K and sensitivity of 10 mK/√Hz were achieved. This could be a novel approach to study the thermal processes and thermodynamics of nanostructures.

Shaddock peel, a crop by-product mainly composed of cellulose, hemicellulose, lignin, and pectin, was developed as a flexible sensitive material for detecting environmental external pressure. Firstly, a natural carbon framework (C-SPF) with high conductivity was prepared using hydrothermal treatment followed by carbonization. Then, the PDMS elastomer was coated on the C-SPF instead of dense filling to convert the brittle C-SPF into elastic porous materials (M-SPF). Benefiting from the large deformation space of the porous framework and the stable interactions between PDMS and C-SPF, M-SPF exhibited ultrahigh coercibility (up to 99.0% strain) and high elasticity (99.4% height retention for 10 000 cycles at 50.0% strain). The M-SPF-based pressure sensor also exhibited a quick response (loading and unloading times were 20 ms and 30 ms), high sensitivity (63.4 kPa−1), wide working range (from 0 to 800 kPa), and stable stress-electric current response (10 000 cycles). These advantages open a door to a variety of applications, such as flexible wearable devices, which demonstrated human physiological signal monitoring. The low cost, simple design and portable use of piezoresistive sensors highlight the potential application of the crop by-product shaddock peel as a high-value material.

Intelligent flexible sensors that are comfortable to wear and have self-powered properties are primary candidates for next-generation wearable electronics. Nevertheless, most current flexible sensors cannot work independently, they have to rely on external power. Herein, we report a flexible sensing device that is able to reliably and stably monitor human motion with successive self-powering. The device consists of a supercapacitor as a power source and a strain sensor. An ionic hydrogel was used either as the electrolyte for the supercapacitor or as the functional element for the sensor. Thanks to the superior electromechanical and electrochemical properties of the hydrogel, when used as the electrolyte, the supercapacitor delivers over a wide voltage window (0–2.5 V), and exhibits superior energy density (81.46 mW h cm−2), and power density (2500 mW cm−2). The ionic hydrogel electrolyte also exhibits environmental durability and strain-resistance, demonstrating its reliability under deformation. Strain sensors based on such ionic organohydrogels operate over a wide working range (0–1000%), with high sensitivity (gauge factor = 6.04), and durability. Such a compact wearable sensing system presents potential applications in health monitoring by detecting motion precisely and rapidly. When machine learning is combined into a wearable sensing system, the intelligent device offers new prospects for tackling challenges in wearable electronics.

The implementation of precision engineering principles in the design of precision systems is fundamental to achieve high accuracy. Although these principles may be independent of the system working range, their implementation is not. The working range, the accuracy, and the load of the system limit, for instance, the selection of materials, the structural design, or the positioning system. This article analyzes the applicability of precision engineering design principles depending on the working range of the system in order to establish their scalability or lack of it in small, medium, and large range machines and instruments.

The question of the use of vortex flowmeters with different versions of the flow body (TO) under operating conditions on the technological lines of pulp and paper production is considered. It is shown that when using different TO in vortex flowmeters, an error occurs in the working range of speeds (flow rates). The observed error arises due to a change in the Strouhal number (Sh) and is associated with the measurement method. In this case, the Strouhal number begins to depend not only on the TO used as a vortex generator, but also on the flow velocity and the concentration of the fibrous suspension. As the main comparative factor for the investigated TOs, the force action on the sensitive element (flexible electrode) located inside the TO was taken. The study was carried out in several stages using numerical modeling and experimental design method. According to the results of a numerical study, the dependence of the Strouhal number (Sh) on the flow rate (V) and the concentration of the suspension (c) is presented. In a comparative analysis of the deviation of the Strouhal number from the average values, it was revealed that MOT No. 1 has a minimal effect on the concentration of the suspension in the working range of flow rates (± 0.5%). This circumstance makes it possible to verify and test flow meters with such maintenance in conventional pouring installations. The analysis of the maintenance with respect to the signal-to-noise ratio shows that the purest signal is generated by the cylindrical maintenance (maintenance No. 3), and maintenance No. 2 and No. 1 have noticeably large noise. The differences are explained by the absence on the surface of a cylindrical TO of extra protrusions, faces, which leads to a smoother flow of a suspension around its surface, as well as to a decrease in internal spurious noise.

As a rule, the width of a spectral line in atomic emission spectral analysis with arc sources is much smaller than the hardware function of the spectral device. Thus, the spectral line contour is determined by the hardware function of the device and can be approximated, e.g., by the Voigt function. However, when reference samples with a wide range of element concentrations are analyzed, there is a frequent problem of self-absorption that causes one to change the analytical line, which is not always possible. It is proposed to modify the Voigt function by adding a factor that describes self-absorption, by analogy with the Bouguer–Lambert law. The possibility of using the proposed function is evaluated during the analysis of reference samples of rocks, ores, and sandstones in a Grand-Potok spectral system with a MAES analyzer and BLPP-2000 photodetector arrays. The use of the proposed approximating function has provided an increase in the working range of the calibration curves of Cu 327.3954 nm, Cu 324.7532 nm, Pb 287.3311 nm, Ni 305.0818 nm, and Mo 313.2594 nm by 1–3 orders of magnitude.

With the continuous development of power automation and smart grids, online monitoring equipment has been utilized more widely for inspection of the state of high-voltage ac transmission lines. To ensure the stable and effective work of the monitoring device, the problem of power supply needs to be solved urgently. Although the inductive energy harvester penetrated through line has been extensively researched, the practical process has been greatly hindered caused by the core materials, which cannot simultaneously combine two advantages of both high permeability and high saturation. Based on the inherent contradiction of the inductive energy harvester, the structure of compound cores with different intrinsic properties is adopted. In addition, three optimization topologies for the structure are proposed. Theoretical analysis and experimental results show that the proposed structures and topologies have certain advantages over the conventional structure in terms of effective start-up sensitivity, saturation performance, and gained power. The proposed energy harvesters also broaden the effective working range by enduring the primary current fluctuation. The simulation and experimental results verify the correctness of the theoretical analysis and the validity of the topologies.

The optimisation methodology was applied to design a specific geometry for a ring-shaped clip gauge as a quasi-static displacement measurement. The gauge was designed to maximise sensitivity under various types of constraints, including working range, strength, and installation. The analytical expressions of the ring gauge’s responses and constraints were derived to formulate an optimisation problem. The optimal solution was determined by an optimisation solver in the MathCAD Prime 4 program. The sensitivity of the objective function with respect to the parameters in the optimisation problem evaluated at the optimal solution was also determined. The sensitivity and linearity of the designed ring gauge is in the range of commercial gauges. The accuracy of the ring gauge was better than 0.1%, complying with ASTM standard E1820. Performance of the ring gauge, i.e. its linearity, hysteresis, and repeatability, was better than the DCB gauge reproduced from the standard. Applying the ring gauge to a tensile test with a cracked specimen yielded an accurate displacement measurement. Limitations of the analytical formulation are highlighted and recommendations for improving the formulation are discussed.

This manuscript reports, a novel, integrated on-chip sample-to-answer platform capable of detecting lead ions (Pb+2) directly in sediment samples. As sediment is one of the main sources of hazardous heavy metals in aquatic ecosystems, rapid and real-time detection of heavy metals in sediment is crucial in the field of environmental monitoring. Electrochemical sensors can provide rapid detection capability, but in-situ measurement of heavy metals with such sensors has been limited by complicated pretreatment steps. To overcome this drawback, an integrated system was developed consisting of a porous matrix for purification and extraction of Pb+2 onto a graphene oxide thin film that serves as an active sensing material. The integrated sensor with a 3D porous matrix was used as an in-situ platform to detect lead directly in complex sediment samples. The proposed electrochemical sensor has a detection limit of 4 ppb and a linear working range. The ability to directly detect lead in sediment samples with minimal pretreatment agents and time makes this system a promising solution for on-site monitoring of heavy metals in environmental samples. Although the current study focused on lead for platform validation, the proposed sensing platform can be further developed for the detection of a wide panel of toxic metals.

As a novel conductive elastomer, magnetorheological elastomers (MREs) featuring both high sensitivity and wide working range have been employed as a new sensing material for flexible tactile sensors. Their sensing mechanism, that is, the spatial distribution rearrangement of particles under compression, completely differs from their conventional counterparts. The piezo-capacitive effect of MREs resulting from the unique mechanism of particles rearrangement is actually a response to the microscopic mechanical movement of particles. This nature brings a core concern on the intrinsic relationship between their mechanical and electrical properties. This study illuminates them from the perspective of electrical creep and recovery behavior of MREs. We give a meaningful analysis for the capacitance creep-recovery mechanism. The experimental fact strongly demonstrated that the particles rearrangement was the direct cause, while the strain creep was an indirect cause. All the behaviors were well interpreted by an evolution mechanism of the particles rearrangement driven by the mechanical strain creep of the flexible matrix under constant pressure. In simpler terms, the electrical creep was induced by the mechanical creep. We further explored the creep effect in practical applications and found a “self-healing” behavior, which indicated that the MRE sensors could obtain a stable sensing capability after a pre-processing.

The design, fabrication, and testing of soft sensors that measure elastomer curvature and mechanical finger bending are described in this study. The base of the soft sensors is polydimethylsiloxane (PDMS), which is a translucent elastomer. The main body of the soft sensors consists of three layers of silicone rubber plate, and the sensing element is a microchannel filled with galliumindium-tin (Ga-In-Sn) alloy, which is embedded in the elastomer. First, the working principle of soft sensors is investigated, and their structure is designed. Second, the relationship between curvature and resistance is determined. Third, several sensors with different specifications are built in accordance with the structural design. Experiments show that the sensors exhibit high accuracy when the curvature changes within a certain range. Lastly, the soft sensors are applied to the measurement of mechanical finger bending. Experiments show that soft curvature sensors can effectively reflect mechanical finger bending and can be used to measure the bending of mechanical fingers with high sensitivity within a certain working range.

In this paper, a new no-reference image quality assessment (NR-IQA) metric is proposed. This method is based on the probability coefficients and modified entropy. The probability coefficients are used to capture the significant features and represent the important dynamics of an image. Moreover, it is used to quantify the possible loss of naturalness in a distorted image. The proposed approach has been tested on synthetic images with blurring effects and under noisy conditions. It is observed that the proposed focus measure is invariant to contrast and noisy conditions. The effectuality of the proposed approach is tested on various experimentations carried out on real-time images. The performance of proposed focus measure is better as compared to the existing image focus metrics. It also shows a good consistency and a better response under blurring effects and noises at different levels. Moreover, it exhibits a good working range, unimodality and monotonicity properties and hence satisfying the conditions of a good focus measure. Further, the various experiments on image datasets such as LIVE, TID2008 and CSIQ have shown the effectiveness of proposed NR-IQA metric. It is also observed that the presented approach has good correlation with the human opinion score as compared to the existing methods.

Conductive textiles have a range of applications including sports, military, automobiles and healthcare. In this study, textile-based piezoresistive sensors were designed and developed using flexible conductive threads stitched on fabric. The sensor is a multi-layer structure, including fabric, a flexible conductive sheet and a semi-rigid material. This work aimed to create new knowledge in the field of e-textiles using stitching as a new scalable fabrication technique to develop wearable piezoresistive sensors. Unlike other methods, stitching has the advantage to create free-form sensor designs. The sensors were developed using different thread lengths and stitch designs to study their impact on sensitivity, working range and response time. Replicability was assured by developing and testing several sensors with the same physical characteristics. Each sensor was characterized by gradually loading and unloading pressure from 0 kPa to 14 kPa. The sensor was also subjected to cyclic loading for 3000 cycles to evaluate its fatigue behavior. After the extensive characterization, the developed sensor was embedded inside a garment and used to measure small pressure changes exerted by human muscles. Experiments showed that the piezoresistive sensor is capable of monitoring breathing rate through ribcage and step counting through hamstring muscle. This wearable, low cost and easy to develop sensor was then machine washed for ten cycles to check its performance after washing. The characteristics of high sensitivity, repeatability, excellent response time and flexibility provide a high possibility for the developed sensor to fit on various wearable applications.

Zinc is an essential trace element for animals in several biological processes, particularly in energy production, and it is acquired from food ingestion. In this context, a microplate-based fluorimetric assay was developed for simple, fast, and low-cost determination of zinc in pet food using 2,2′-((4-(2,7-difluoro-3,6-dihydroxy-4aH-xanthen-9-yl)-3-methoxyphenyl)azanediyl)diacetic acid (FluoZin-1) as fluorescent probe. Several aspects were studied, namely, the stability of the fluorescent product over time, the FluoZin-1 concentration, and the pH of reaction media. The developed methodology provided a limit of detection of 1 μg L−1 in sample acid digests, with a working range of 10 to 200 μg L−1, corresponding to 100–2000 mg of Zn per kg of dry dog food samples. Intraday repeatability and interday repeatability were assessed, with relative standard deviation values μg L−1) and μg L−1). Sample analysis indicated that the proposed fluorimetric assay provided results consistent with ICP-MS analysis. These results demonstrated that the developed assay can be used for rapid determination of zinc in dry dog food.

Permanent-magnetic Synchronous Frequency-convertible (PSF) compressor as a new technology has been widely used in heating, ventilation and air conditioning. In this paper, a PSF centrifugal compressor was designed and developed. Some key technologies such as large working range 3-Dimensional impeller, 360° circular refrigerant injection port, two-stage impeller directly driven by PSF motor and high-speed inverter were adopted to improve the compressor efficiency. The theoretical comparison of conventional frequency-convertible centrifugal compressor and PSF centrifugal compressor was conducted to show the performance improvement. Then, a comprehensive experimental investigation was carried out to evaluate operating characteristics of the developed compressor. Experimental results showed that the adiabatic efficiency of PSF compressor reached 75.9%~88.5%. The mechanical efficiency, motor efficiency and inverter efficiency of PSF compressor was also greatly improved. Rated COP of PSF centrifugal chiller reached 7.0, and IPLV reached 11.7. The PSF centrifugal chiller has excellent system performances under both rated and partial load conditions.

This work describes a novel and portable pressure-based point-of-care (POC) testing strategy for the sensitive and rapid detection of carcinoembryonic antigen (CEA) via a flexible pressure sensor constructed by three-dimensional (3D) polypyrrole (PPy) foam. Initially, platinum nanoparticles (PtNPs) were conjugated to the detection antibodies, which were used to form sandwich-type immunocomplexes with targets and capture antibodies in the reaction cell. Then, the carried PtNPs catalyzed the dissociation of hydrogen peroxide (H2O2) for the generation of oxygen (O2) in a sealed device, translating the biomolecule recognition event into gas pressure. With the increase of pressure, a flexible pressure sensor with 3D polypyrrole foam as the sensing layer was used to sensitively monitor the pressure variations in this system. Thus, the concentration of the target could be quantitatively determined by the pressure response. Under optimal conditions, the pressure-based immunosensor showed good sensing performance for CEA in the dynamic working range from 0.2 to 60 ng/mL with a detection limit of 0.13 ng/mL. The reproducibility, specificity, and accuracy compared with commercial enzyme-linked immunosorbent assay (ELISA) kit were also acceptable. Therefore, this work provides a promising approach for developing portable and sensitive POC testing in the future.

Wearable textile pressure sensors with piezoelectric properties are a very effective way of detecting movements of the human body based on the force exerted by the sensor. Owing to the merits of flexibility and breathability, the textile pressure sensor finds potential application in biomedical monitoring and human-machine interaction. The textile pressure sensor works on the principle of piezoelectricity where an electrode of conductive woven fabric forms the outer layer and a semi-conductive material such as ZnO is sandwiched between two conductive layers. ZnO is prepared using a simple hydrothermal method and SEM, XRD are two effective methods to detect the presence of ZnO on the conductive fabric. The pressure applied on the fabric is translated into voltage and the output voltages are compared using two samples of ZnO nanostructures. The effect of the seed layer is investigated under identical growth and measurement which influences the output performance of voltage. This property can be used to change the sensitivity and working range of pressure sensor for specific applications. The pressure sensor designed can be sewn directly onto the clothing which conforms to the human body’s flexible curved surface.

The ability of perceiving external pressures and conducting corresponding signals is one of the important functions of flexible electronics, which has been widely studied in electronic skin, prosthetics, robotics, healthcare, human-machine interfaces, etc. Pressure sensor should not be limited to the detection of unidirectional pressure. Here, a leather-based electronic pressure sensor and corresponding arrays with bidirectional sensing capability are demonstrated. The sensor/arrays consisting of two pieces of stacked leather both modified with acidified carbon nanotubes (a-CNTs) can achieve multi-level response to pressure over a broad working range and sense pulling force opposite to pressure. With polyurethane mixed with ferriferrous oxide (Fe3O4) powder being applied to their upper surface, the resistive sensor/individual units of arrays can also detect the magnetic field because of the contactless pulling force generated by the magnetized Fe3O4. Being able to sense pressure, pulling force and magnetic field, the leather-based electronic bidirectional pressure sensor and corresponding arrays with good performance not only exhibit potential for mass production and their broad application prospects, but also provide a new insight for the development of flexible electronics.

A piezoelectric platform using function module actuator is presented to achieve nano-positioning and high frequency scanning in large working range. A function module actuator is designed to produce a pair of orthogonal bending deformations and a longitudinal deformation through partition exciting. The bending deformations are used to actuate the planar motion, while the longitudinal deformation is utilized to dynamically adjust the driving force and broaden the scanning frequency. The dynamic model of the platform system is developed. The open-loop performances of a prototype are first tested: a scan frequency of 308 Hz in a scanning range of 3.368 µm×3.396 µm is measured in direct actuation mode, and the displacement resolution is measured to be 16 nm; maximum speed is measured to be 3.38 mm s−1 in the inertial actuation mode. Furthermore, the closed-loop experiments are carried out and a switching strategy is proposed to obtain the switching of the inertial and direct actuation modes automatically; the platform achieves the scanning with frequency of 300 Hz at the set position.

In this paper, a novel immersion liquid pressure sensor based on the fiber Bragg grating (FBG)is introduced. Two FBGs are encapsulated in polymer in different forms, according to the deformation principle of the polymer under special constraints which is immersed in liquid, we can get the information of pressure in the liquid. Due to the use of a new packaging method, the proposed sensor can achieve distributed measurement on a single axis, which is difficult for liquid pressure sensor based on FBG to realize and is important for the measurement of pressure in special liquid environments. The sensing principle and mathematical model analysis of the sensor were first introduced and its sensing characteristics were analyzed by numerical simulation and the finite element simulation. The experimental result shows that the sensitivity of two sensors are 51.296 pm/MPa and 46.117 pm/MPa, it is consistent with the theoretical value within the working range of 0~15.5 MPa. The temperature compensation scheme is also considered in the designed sensor. Through the temperature calibration experiment, it is shown that the maximum average difference value is only 4.887 pm at a wide working temperature range 0~44.8° during the measurement.

The article presents the results of a study of the concept of a distributed calorimetric fiber dosimeter based on the effect of stimulated–Brillouin scattering. The sensor design comprises one or several thermally insulated spherical sensing elements made of a material with a high γ-radiation attenuation coefficient fixed with a certain distance on an optical fiber. The change in the temperature of the sensor due to interaction with ionizing radiation is monitored using a stimulated Brillouin scattering analyzer, which allows temperature measurement over the entire length of the optical fiber at distances of up to several tens of kilometers. The results of model calculations of the efficiency of spherical sensor elements made of various materials are presented. The sensitivity range of the proposed dosimeter is estimated and the results of a preliminary experiment on the interaction of the sensor with γ-radiation are given. It is shown that the working range of the dosimeter is approximately 130 Gy/h–700 kGy/h.

Purpose This paper aims to propose a method for manufacturing multi-material monolithic structures with flexible materials to construct the elastic body by using a dual-nozzle three-dimensional printer to develop a piezoelectric (PZT)-driven micropositioning stage with three degrees of freedom (3-DOF) and flexure hinges. Design/methodology/approach Polylactic acid (PLA) and nylon were used for the lever structure’s frame and flexure hinge, respectively. Additionally, the stage consisted of three PZT actuators for fine movement in the nanometer scale in 3-DOF (x, y and θ-directions). For the design of the stage, the kinematic analysis model and the finite element method (FEM) analysis was undertaken for comparing between PLA with nylon (multi-material), PLA (single material) and aluminum (conventional-material). In addition, two verification experiments were implemented for the fabricated prototype stage. First, to evaluate various assessments (lever ratio, hysteresis, coupling error and resolution), a measurement is carried out using the three capacitive sensors. Then, a two-camera-vision measurement experiment was performed to verify the displacement and lever ratio over the full-scale working range of the fabricated positioning stage, and the results from the experimentation and the FEM analysis were compared. Findings The authors confirmed enhancements in the properties of the lever structure frame, which requires stiffness and of the hinge, which requires flexibility for elastic deformation. Comparing FEM analysis and experimental results, although the performance as shown by experimental results was lower: the maximum difference being 3.4% within the end-point working range; this difference was sufficient to be a plausible alternative for the aluminum-based stage. Originality/value Multi-material monolithic-structure fabrication has an effective advantage in improving the performance of the stage, by using a combination of materials capable of reinforcing the desired characteristics in the necessary parts. It was verified that the fabricated stage can substitute the aluminum-based stage and can achieve a higher performance than single-material stages. Thus, precise-positioning stages can be manufactured in many kinds of structures with various properties and contribute to weight reduction and low costs for application equipment.

The performance curve of the compressor is limited by the surge boundary, so it is of great significance to increase the stable working range of the compressor. The self-circulating casing treatment is an effective way to improve the stable working range of the compressor. In this paper, the study of the influence of the injector position of the self-circulating casing treatment on the transonic axial flow compressor rotor performance is carried out by using the numerical simulation. The influence mechanism of the injector position on the enhancing stability effect of the self-circulating casing treatment is revealed. It is found that the self-circulating casing treatment can reduce the blade tip blockage by restraining the blade tip clearance leakage flow and changing the trajectory of the tip clearance leakage vortex, thus delaying the deterioration of the rotor tip flow field and improving the rotor stability. When the injector position of the self-circulating casing treatment moves from the upstream of the leading edge of the blade tip to the trailing edge of the blade tip, the enhancing stability effect of the self-circulating casing treatment increases first and then decreases. But the high-velocity jet from the injector of the self-circulating casing treatment aggravates the mixing loss of the rotor tip flow field, so that the rotor efficiency slightly decreases after using the self-circulating casing treatment.

We constructed a compact single-beam atomic magnetometer operated in a transverse magnetic-modulation mode or a DC-offset mode. By coupling the laser beam into a polarization maintaining fiber, with a vapor cell of the dimensions 4 mm $\times4$ mm $\times4$ mm, a sensitivity of 30 fT/Hz1/2 has been achieved in the single-beam configuration. In addition to the experimental study of the sensitivity, we perform a theoretical analysis of the single-beam atomic magnetometer in the transverse magnetic-modulation mode and the DC-offset mode. The results indicate both of two modes have almost the same scale factor. We also studied the dynamic working range of the sensor and found, experimentally, that our sensor reaches a dynamic response range of ± 3 nT, with a nonlinear error of 1%. The frequency responses of the transverse magnetic-modulation mode and the DC-offset mode are 125 Hz and 65 Hz, respectively. This sensor will be particularly suitable for applications that require high sensitivity, low cost and compact size, e.g., magnetoencephalography (MEG) and magnetocardiography (MCG).

Electrochemical low-level detection of l-tryptophan (l-Trp), a precursor to the neurotransmitter serotonin, was performed at a practical sensor based on pencil graphite electrode. The electrode chosen is disposable, economical, and eco-friendly as well as sensitive and selective when used for adsorptive stripping differential pulse voltammetry (DPAdSV) in the presence of uric acid and also in urine samples. The electrochemical oxidation of l-Trp was found to be partly adsorption controlled under diffusion conditions. The optimum values for the pH (3.0), accumulation potential (+ 0.3 V), and accumulation time (5.0 s) were investigated and used in the voltammetric analysis. Under the optimum conditions, the anodic DPAdSV peak current of l-Trp linearly increased with the concentration of l-Trp in the presence of uric acid and also in urine. The electrode used exhibited a wide working range from 0.154 to 200.0 µM with a detection limit of 0.046 µM. The method developed was applied to the analysis of l-Trp in the human urine sample with acceptable recoveries.

An HPLC-UV procedure is proposed for identifying processing impurities and determining the contents of active ingredient in the drug substance of the promising non-narcotic analgesic (2R,4R,4aR,7R,8aR)- 4,7-dimethyl-2-(thiophen-2-yl)octahydro-2H-chromen-4-ol (1). Processing impurities including the starting reagents thiophene-2-carbaldehyde and (–)-isopulegol, a related stereoisomer of 1, and intermediates and dehydration products of 1 could be present as a result of the synthesis and isolation. The developed chromatography conditions could separate possible impurities and analyte 1 with the required resolution. The contents of the studied processing impurities were below the established detection limits of 0.056 μg/mL for thiophene-2-carbaldehyde; 0.32, (–)-isopulegol; 0.22, the stereoisomer; and 0.18, 0.22, and 0.37, for the dehydration products. The working range of concentrations for the procedure was 0.50 – 10 μg/mL. The recovery varied from 98.9 to 101.2% in the accuracy evaluation. The procedure was demonstrated to have sufficient accuracy. The average relative standard deviation in the intraday precision evaluation was 0.7%; in the interday precision assessment, 0.8%, which were below the acceptance criteria of 2.0 and 3.0%, respectively.

In this article, we fabricate a flexible pressure sensor based on the honeycomb-like graphene network (HGN). The HGN is fabricated by mixing cube sugar, graphene oxide solution, and polydimethylsiloxane. Attributing to the structure, the pressure sensor shows a high sensitivity of 3.54 kPa−1 in the low-pressure regime (