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This paper investigates the performance of hovering unmanned aerial vehicles (UAVs) using free space optical (FSO) communications with decode-and-forward (DF) relaying. Multi-hop UAV relays are considered. The channel is modeled considering the atmospheric attenuation due to the sandstorm and relative humidity (RH), in addition to the atmospheric turbulence, angle-of-arrival (AOA) fluctuations, and pointing errors (PE). We first obtain a simplified expression for end-to-end (E2E) outage probability considering atmospheric attenuation conditions, then the impact of various parameters such as transmitted power, field of view (FOV) and optical beamwidth on E2E outage probability is incorporated. We also derive a closed form expression for the ergodic capacity and characterize the effect of different system parameters. Monte Carlo simulation is utilized to prove the analytical results. The asymptotic bound for E2E outage probability is validated to offer insights into the effects of different channel coefficients. Analysis of the results indicates that the impact of low visibility due to sandstorms is comparable to that of high RH on FSO links.

A double Sagnac interferometer (DSI) and vernier effect sensor for relative humidity (RH) is proposed and experimentally implemented, in which two single Sagnac interferometers (SI1 and SI2) cascaded in parallel to construct the structure of the sensor. Owing to the approximate free spectral range (FSR) of the SI1 and SI2, the proposed sensor can produce fundamental and harmonic vernier effect. Theoretical analysis shows that the RH sensitivity of the sensor is only related to the lengths of polarization-maintaining fibers (PMFs). The experimental results show that in the range of 30∼80%RH, the RH sensitivities of the spectral envelope can reach −0.48 nm/%RH, which is 60 times higher than that measured by the single Sagnac interferometer sensor (8 pm/%RH). The experimental results are consistent with the theoretical analysis. The proposed sensor has the superiorities of high sensitivity, good repeatability, simple fabrication, and compact size, and it has potential applications in the areas of biopharmaceuticals, environmental monitoring, food processing, and microbial sensing.

Pigeon is a kind of poultry with high practicability and economic value, and humidity is an important indicator of the intensive breeding of pigeons, which is closely related to the healthy growth of pigeons. Humidity changes are complex, dynamic, and nonlinear. Accurately predicting humidity values and analyzing their changing trends is crucial to the growth of pigeons. Addressing low prediction accuracy and poor generalization of traditional humidity prediction methods, this paper proposes a combination based on partial least squares (PLS) data dimensionality reduction, Savitzky-Golay (SG) filter, and sparrow optimization algorithm (SSA) Predictive models to improve humidity forecast accuracy. First, the SG filter is used for data smoothing to remove abnormal noise in the data signal to enhance the feature learning ability of the prediction system. Next, the original data is selected through the PLS method to select information higher than the set threshold. Valuable information features are extracted for data dimensionality reduction. In addition, SSA is used to optimize key parameters and structure of the BiGRU model for improved prediction. Finally, a combined prediction model based on SG-PLS-SSA-BiGRU was built to simulate and predict the humidity of the pigeon house. The experimental results demonstrate the proposed model’s high accuracy and stability with minimal prediction error fluctuations, fast calculation speed, good feature extraction ability and generalization ability, and is very effective and reliable for predicting pigeon house breeding humidity.

In this letter, the attenuation by spheroidal sand particles under different relative humidity (RH) is investigated with consideration of contributions of water vapor and excess charges carried by particles, which is much closer to real conditions. The microwave (MW) attenuation will be enhanced when the sand particles are considered as the spheroids. The contributions of RH and excess charges to the MW attenuation are much greater by the spheroidal sand particles than that by the equal-volume spherical ones. The increasing effects of excess charges and RH on the MW attenuation are mutually reinforced. The contribution of water vapor to the MW attenuation by sand–dust storms is significant when the visibility is high, which makes up the gap between the experimental results and calculated results. An improved attenuation model by sand and dust storms is given with an incident wave frequency of 4–45 GHz. [ABSTRACT FROM AUTHOR]

Aqueous route is readily for fabricating oxide thin-film transistors (TFTs), but the relative humidity (RH) impacts evolution of oxide thin films. Herein, the effect of RH on the electronic performance and bias stability of aqueous-processed Tb-doped indium oxide (Tb:In2O3) TFTs is investigated. The mobility is sensitive to RH. By tuning the RH for desirable thickness and density of the obtained Tb:In2O3 films, the TFTs present optimized mobility of 13.0 cm2/Vs, with high ON/OFF ratio of 108. Notably, low threshold voltage shift of −0.35 V and 0.42 V under negative and positive gate bias stress are simultaneously obtained with a fabricating RH of 40%. Moreover, dry ambience (RH $\le23$ %) affords to abundant nanopores and defects, resulting in inferior performance and stability of the aqueous-processed oxide TFTs. And high humid ambience easily ruins the uniform of precursor films. This work indicates the strategy to fabricate highly stable oxide TFTs with high performance. [ABSTRACT FROM AUTHOR]

In ambient conditions, uncontrolled fluctuations of ambient temperature and relative humidity significantly reduce the accuracy of metal oxide semiconductor-based gas sensors. The main innovation of the work is an algorithmic self-correction method that employs a response from an auxiliary temperature sensor and a multivariable polynomial regression model to minimize the effect of such environmental fluctuations. Tin oxide (SnO2) MOS gas sensors were chosen for a sample study due to their fast response times and high resolution. Using the developed correction method, the study analyzes sensor accuracy while measuring a typical pollutant gas (carbon monoxide) over a temperature range from −10 to 40°C at relative humidity intervals of 35%, 65%, and 95%. On average, the corrected sensors measured a 40 ppm CO gas sample with 11 times more accuracy when compared to uncorrected sensors placed in the same variable ambient conditions. Corroborating ANOVA tests demonstrated that the prescribed correction algorithm reduced measurement variability with statistical significance. In the presence of CO2, CH4, ethanol, LPG, or smoke interference gas samples, sensors applying the correction method and temperature-based selectivity distinguished and measured CO concentrations with a maximum error of only ±2.0 ppm. Thus, the proposed technical solution is attractive for highly variable environments and field applications where low-cost drift stabilization is necessary. [ABSTRACT FROM AUTHOR]

Novel fiber Bragg grating (FBG) relative humidity (RH) sensors based on polyimide (PI) doped with graphene quantum dots (GQDs) are proposed and experimentally demonstrated. The effects of GQDs doping on the sensor performance were investigated. The sensitivity of the humidity sensor could be increased by 96.36% when the doping mass fraction of GQDs was optimized at 0.2%. The FBG humidity sensor based on PI-doped GQDs exhibited good linearity at different operating temperatures in the RH range of 10–90%. Moreover, the excellent linearity of the temperature sensitivity facilitates the temperature compensation of these sensors. GQDs-doped PI is an excellent moisture-sensitive material that significantly improves the sensitivity of FBG humidity sensors, making it a promising candidate for humidity sensing in various applications. [ABSTRACT FROM AUTHOR]

The measurement of soil moisture and air humidity is essential to many technological and environmental applications. Sensors provide information that is useful in order to effectively manage and control various processes. This study presents an energy-efficient, highly reliable, ultra-high frequency (UHF) capacitive sensor that can measure moisture/humidity, and liquid levels. As a sensitive part, an interdigital capacitor (IDC) is fed via a coplanar waveguide (CPW) for efficient power transfer. Aside from the sensitive part of the IDC, the structure of the sensor is insensitive to variations in surrounding permittivity, which reduces uncertainty in results and thus improves accuracy. The principle of sensing is based on a reactive phase variation of the input signal upon reflection, whereas its amplitude and phase are actively changing with variations in the dielectric constant of the test medium. Practical testing was conducted on the sensor to determine soil moisture, air humidity, and liquid level measurement. At a fixed UHF frequency of 915 MHz the sensor offers a capacitive sensitivity of 7.5 fF/%WC, 4.5 fF/%RH, and 13.4 fF/mm for soil moisture, air humidity, and water level detection respectively. This new sensor provides high reliability, good sensitivity, low power consumption, and can be implemented in a number of applications, including agriculture, oil, and gas industry, land and water treatment, medical equipment, and biotechnology. [ABSTRACT FROM AUTHOR]

A novel fusion algorithm is proposed based on Improved Adaptive Wavelet Threshold De-noising (IAWTD), C-means Support Vector Machine (CSVM) and Ensemble Empirical Mode Decomposition (EEMD) method to eliminate the humidity drift of MEMS gyroscope. Firstly, the IAWTD method is employed to decrease the humidity drift component in MEMS gyroscope output signal. Then, the humidity drift compensation model is established: the input elements are the relative humidity, the change rate of relative humidity and the humidity drift, and the output is the compensated MEMS gyroscope output signal by EEMD method. In order to verify the compensation effect of the fusion algorithm, the gyroscope outputs are collected and analyzed with the relative humidity ranged from 40% to 90% based on the temperature varying from 20°C to 60°C. The results show that the IAWTD-CSVM-EEMD method significantly reduces the influence of relative humidity drift on the gyroscope output, according to the quantitative analysis of Allan variance, the quantization noise of the gyroscope output decreases by 87.78%, 96.37%, 97.77%, 99.17% and 92.62% respectively under the relative humidity ranging from 40% to 90%, as the temperature rose from 20 °C to 60 °C at intervals of 10 °C. In addition, the bias stability decreases by 96.9%, 99.41%, 99.1%, 99.46%, and 99.78% respectively and the angle random walk decreases by 88.16%, 96.54%, 98.16%, 94.43%, and 92.05% respectively at different temperatures. It is worth mentioning that, to further verify the applicability of the fusion algorithm, a group of comparative experiments are added to consider the influence of temperature changes on the gyroscope output under different relative humidity. The experimental results show that the quantization noise, bias stability and angle random walk of the MEMS gyroscope are significantly reduced compared with the original output after processing by IAWTD-CSVM-EEMD. Therefore, the method proposed in this paper is beneficial to reduce the humidity drift in the MEMS gyroscope output.

A novel structure of photonic crystal fiber (PCF) Mach-Zehnder interferometer (MZI) for temperature and relative humidity measurement is proposed. The novel structure is composed of two sections of no core fiber (NCF) with a piece of PCF. The sensitivity of the proposed sensor is enhanced by adopting NCF coupling method. The results show that the sensitivities of temperature are 0.059 nm/°C, 0.074 nm/°C and 0.130 nm/°C in the range of 25 °C to 70 °C, and the sensitivities of relative humidity are 0.020 nm/%RH, 0.027 nm/%RH and 0.036 nm/%RH in the range of 30%RH to 70%RH. The sensor has the advantages of high stability, good linearity fit and simple structure, which indicates that the sensor has the potential of making an important contribution to the field of biology, chemistry, and medical.

In this paper, a novel platform for simultaneous measurement of relative humidity (RH) and temperature using dual Fabry–Perot interferometers (FPIs) based on C-shaped fiber was demonstrated. The sensor was composed by splicing two sections of C-shaped fiber between single mode fiber (SMF). Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) are filled in the two sections of C-shaped fibers to increase sensitivity to temperature and RH. This is the first demonstration that solid polymer materials can be added to the C-shaped fiber interferometers for sensing. In our experiment, RH sensitivities of -0.128 nm/%RH and 0.038 nm/%RH in the range of 20%RH to 45%RH, and temperature sensitivities of 0.022 nm/°C and -0.722 nm/°C in the temperature range of 15 °C to 45°C, were acquired for dual FPIs, respectively. We verified that it is possible to use the sensitivity matrix method to measure two parameters simultaneously. In addition, it has the benefits of simple structure, excellent stability and high sensitivity, and has a broad application prospect in agriculture, food processing and environmental measurement. [ABSTRACT FROM AUTHOR]

In this paper, a carboxymethyl cellulose (CMC)/graphene oxide (GO) composite film-coated humidity sensor was proposed based on thin-core fiber Mach-Zehnder interferometer (TCMZI). A segment of thin-core fiber (TCF) was spliced between two segments of single-mode fiber (SMF), and the TCF cladding was first corroded with hydrofluoric acid and then coated with a layer of CMC/GO film via optical driven deposition method. The relative humidity (RH) sensing characteristics of the sensor were experimentally investigated by observing the wavelength shift of resonant dips in the transmission spectrum, which showed that the CMC/GO composite film-coated TCMZI has good repeatability and stability in the measurement of humidity. A maximum average humidity sensitivity of −75.6 pm/%RH was obtained in the RH range of 35%-80%, nearly 2.048 and 3.237 times higher than that of CMC and GO single film coated ones. To the best of our knowledge, this is the first report on using the CMC/GO composite film for humidity measurement, and its excellent performance is expected to be extended to humidity sensitization of more fiber-optic sensors. The proposed sensor has the advantages of simple structure, easy fabrication, low cost, good stability and high performance, which can be applied to the fields of bio-chemical and medicine. [ABSTRACT FROM AUTHOR]

A new U-shape panda polarization-maintaining fiber (PPMF) based microfiber interferometer coated with graphene oxide (GO) film was proposed and experimentally demonstrated for relative humidity (RH) sensing. Experimental results show that the U-shape sensor has refractive index (RI) sensitivity of 1692.5 nm/RIU in the RI range of 1.33 when the diameter of the taper waist is 10.08 μm. The surface of the U-shape sensor was then modified chemically and coated with a thin layer of GO film (59.64 nm) for RH detection and the sensitivity is proportional to RH: as RH increases from 30% to 98%, the sensitivity increases from 0.111 to 0.361 nm/%RH and the response time is 0.28 s. In addition, the cross sensitivity to temperature, stability, reproducibility, and response/recovery time of the RH sensor were studied in detail. The proposed U-shape fiber RH sensor has advantage of high sensitivity, good reproducibility and fast response (0.28 s), which has potential application in areas requiring dynamic measurement of RH variations such as industrial product fabrication process control and breath state monitoring. [ABSTRACT FROM AUTHOR]

Atmosphere ion mobility is an important electrical parameter related to the filamentary ion flow field of high voltage direct current (HVDC) transmission lines and other characteristics of the glow and streamer corona discharge. Many machine learning (ML)-based algorithms have already been widely used in the prediction of air discharge. This article proposes a genetic algorithm (GA)-support vector regression (SVR) combined with kernel principal components analysis (PCA) to predict the ion mobility, involving dimensionality reduction, feature selection, parameter optimization of SVR. Kernel PCA could reduce the dimension of data and GA with adaptive probability parameters is employed to optimize the parameters of SVR model. An improved parallel-plates ion generator is employed to produce corona discharge and then measure the saturation ion current density and then obtain the training data and testing data of ion mobility. The prediction results show that the proposed algorithm outperforms the other methods in terms of mean relative error and mean squared error criteria. In addition, the parameters of model and data features have a major influence on the performance of the prediction algorithm. Based on the measured data and reference data, the prediction result obtained on ion mobility under different humidity shows a satisfactory generalization and effectiveness of proposed model for the prediction.

We report a dual-wavelength fiber laser sensor based on a uniform fiber Bragg grating (UFBG) and a Polyvinyl alcohol (PVA) film-coated long-period grating (LPG) as sensor probe for simultaneous detection of relative humidity (RH) and temperature. Two UFBGs and the LPG were inscribed in three single mode fibers utilizing phase/amplitude mask technology and mobile scanning technique via the 248 nm UV laser. In our experiment, the RH function based on the differential intensity measurement at dual-wavelength output from 30% to 85% is in a quadratic equation, and the RH sensitivity coefficient of 0.358 dB/% shows good linear relationship and stability from 55% to 85%. Meanwhile, the temperature sensitivity coefficients based on wavelength detection and differential intensity detection are 9.1 pm/°C and 0.21 dB/°C, respectively. The structure of dual-wavelength fiber laser sensor with high signal to noise ratio (SNR), narrow spectral width and good stability enables simultaneous measurement of the RH and temperature with high accuracy and good repeatability.

Subjective analysis of thermal comfort of occupants relates to the recording of the level of satisfaction or dissatisfaction of occupants with regard to indoor environmental conditions on a scale which ranges from -5 to +5. This requires recruitment of subjects and matching for gender, age etc. In this study, we have tried to predict the thermal comfort of occupants by observing their real behavior inside the test room fitted with a novel thermoelectric air duct (TE-AD) cooling system rather than a conventional air conditioning system. Firstly, real experimental data were collected for more than two months from the test room equipped with the TE-AD cooling system operated at an input power supply of 6 A and 5 V. After that, the ANN model was developed based on the Levenberg-Marquardt algorithm by taking experimental parameters such as air temperature, relative humidity, globe temperature, wind speed, metabolic rate, and clothing value as model input. The ANN model is optimized by developing different models with different data points as a starting input in the training and validation process. The neuron optimization has been carried out in these models to minimize the mean square error (MSE) for the ANN model. The result shows that among the three models M1, M2, and M3, the optimum predictive mean value (PMV) was obtained from M1 at 10 neurons with MSE of 0.07956, while for predicted percentage dissatisfied (PPD), M3 gives optimum accuracy at 10 neurons with MSE value of 5.1789. The ANN model is then generalized to predict thermal comfort for one week and then for one month. Finally, all the model results were validated with the experimental data.

Most relative humidity sensors are resistive or capacitive sensors. It’s a fact that the resistance and capacitance of a vast majority of such sensors also depend on the surrounding temperature and a change of temperature can cause significant errors in the final reading of relative humidity. This fact of temperature dependence is scarcely investigated in development of humidity sensors. In this work, a very simple temperature compensation method has been developed that automatically eliminates the effect of change in temperature from the final output without requiring separate measurement of temperature or any data processing. Amorphous polyethylene oxide (PEO) was used as the active material for humidity sensor owing to its high sensitivity and almost linear response. Interdigitated type sensor electrodes (IDE) were fabricated using reverse offset printing on glass substrate and the active layer was deposited through spin coating. An identical twin sensor was fabricated with the same parameters and was additionally encapsulated form the open environment. The dummy sensor was used as opposing pair with the active sensor in a bridge configuration to achieve temperature compensation. The bridge sensitivity was recorded to be ~2.9 mV/%RH that was further improved to 100 mV/%RH using a differential instrumentation amplifier based signal conditioning circuit. The sensor system was deployed in a real-life relative humidity measurement with changing temperature that returned a remarkable accuracy of 98.76%. The error due to temperature dependence reduced from 22.4% to just 1.24%. The transient response time of the sensor was found to be ~2.4 s. [ABSTRACT FROM AUTHOR]

It has been found that the introduction of nanoparticles (NPs) into transformer oil can alleviate the destructive effect of water on the insulation properties. Researchers have begun to explore the mechanism behind this phenomenon and try to provide possible explanations. However, the effect of water on the electrical properties of NF has not yet been explained definitively due to many factors, such as the NP concentration and external electric field. In this paper, mineral oil-based Al2O3 NFs with a wide range of NP concentrations and moisture content are prepared and tested to study the effects of their coexistence on the electrical properties of transformer oil. Diagnostic techniques (including ac breakdown voltage, thermally stimulated current, and dielectric spectroscopy) have been used to measure the dielectric properties of samples with varying relative humidity. The experimental results show that different NP concentrations and relative humidity can obviously affect the electrical performance of transformer oil. The breakdown voltage of the NF significantly improved compared with that of pure oil with the introduction of Al2O3 NPs at varying relative humidity. The shallow trap density in NF significantly increases due to the introduction of NPs with different relative humidity. The proper mechanisms of the water forms with different water contents are discussed based on the results of the experiment. The study of the electrical properties of NFs with different relative humidity is a good complement to current studies in this field.

The leakage current, which is influenced by the operating voltage, the surface contamination, and environmental variables, is one of the most basic online monitoring parameters for the surface contamination status of insulators. However, the impact of temperature and humidity on leakage current have not been expressed concisely nor distinguished according to sunny and rainy weather. In this paper, based on leakage current online monitoring data, the time-domain waveforms of leakage current of an insulator string in Shenzhen, China, were compared with those of the ambient temperature and humidity. Results indicate that the leakage current presents a saddle-shaped curve on days without rain, and that there is a remarkable positive correlation between leakage current and humidity as well as a negative correlation between leakage current and temperature. In a short period (several days) without rain, as long as the relative humidity keeps constant, the leakage current would vary insignificantly, whereas it may vary in a wide range at the same temperature. Moreover, the functional relation mathematical model I = a * eb*RH between the first harmonic component of leakage current and the relative humidity is presented, inferring that the insulator string leakage current depends mainly on the ambient relative humidity in a day without rain.

This article reports and discusses the results of impulse breakdown study of different insulating liquids under highly divergent electric field conditions. Samples of a natural ester (Envirotemp FR3), a synthetic ester (MIDEL 7131), and a naphthenic mineral oil (Shell Diala S4 ZX) at different levels of relative humidity were exposed to HV impulses with a nominal 7- $\mu \text{s}$ rise time and 150-kV peak voltage of both positive and negative polarity. A strong dependence of the breakdown voltage and time to breakdown of the investigated dielectric liquids was observed with respect to the polarity of the applied HV impulses. It was shown that the FR3 natural ester liquid has a higher dielectric strength when exposed to positive impulse than when under negative impulse stress. The opposite breakdown behavior was observed for the synthetic ester MIDEL 7131 and the naphthenic oil Shell Diala S4 ZX which exhibited lower breakdown voltage under positive energization as compared with the negative energization. The breakdown voltage and prebreakdown time obtained in the present tests of the naphthenic oil, Shell Diala S4 ZX, lie between that of the ester liquids irrespective of impulse polarity. It has been established that no statistically significant variations exist in the breakdown parameters (breakdown voltage and time to breakdown) of the studied dielectric liquids as their relative humidity is increased under either impulse polarity. The obtained results will help in coordination of practical applications of low environmental impact dielectric fluids in power and pulsed power systems and components. [ABSTRACT FROM AUTHOR]

An optical fiber tip interferometer for the measurement of relative humidity (RH) and temperature is proposed. The optical fiber structure used, a dual-cavity optical fiber Fabry-Perot interferometer (DFFPI), is simply-to-fabricate, compact, and robust. The reflectance ($\text{R}_{\sf DFFPI}$) of the interferometer is sensitive to the refractive index (RI) and temperature of the external medium. Consequently, when the cross-section of the fiber tip was coated with a SnO2 thin film, whose RI changes according to the humidity of the surrounding ambient, the measurement of the RH was possible. An increment of the RH produced a decrement of RI of the SnO2 thin film, then the reflectance of the fiber tip end-face diminished, and this produced a decrement of the visibility of the interference fringes. The analysis of the $\text{R}_{\sf DFFPI}$ was carried out in the Fourier domain, using a novel processing method it was possible to establish that the amplitude of two peaks of Fourier spectrum changed at a ratio of ${\sf 39.49}\times {\sf 10}^{- {\sf 3}}$ %RH−1 in the range of 40 to 90 RH%. On the other hand, the temperature of the humidity chamber was monitored, from 25 to 60 °C at a fixed RH%, by analyzing the phase shift of the interference pattern produced by the changes in the optical path length of the cavities. The good sensitivity, stability, reproducibility, and compactness of the fiber tip RH sensor make this proposal very appealing in a wide range of applications. [ABSTRACT FROM AUTHOR]

Modern silicon-based detectors for high-energy physics operate in an experimental environment with sub-zero temperatures. At those temperatures, even low traces of humidity will produce vapor condensation with damages to the detectors. Monitoring relative humidity is then a requirement for efficient detector operation. However, the performance of any relative humidity sensor operating in high-energy physics detectors is highly degraded in time due to high radiation doses. Therefore, this paper provides a comprehensive review of all the humidity sensors that have been tested so far for use in high-energy physics applications. Different working-principles of the tested humidity sensors are introduced as well as the description of the radiation effects on the sensing materials. Actually, there are only few publications in literature about humidity sensors as related to this novel and challenging application, while it becomes increasingly important to keep under control the performance-degradation of any silicon-based detector in most advanced high-energy physics. [ABSTRACT FROM AUTHOR]

Humidity detection has significant and extensive applications in various fields. Herein, a miniaturized integrated relative humidity (RH) sensing system from surface acoustic wave (SAW) sensor to circuits and software is described. Delay-line SAW devices were designed and fabricated to be used as sensor and reference device. Graphene oxide (GO) was deposited on the surface of SAW sensor between interdigitated transducers (IDTs) as ultra-thin and wrinkled sensitive film by the method of drop-cast. The well-matched circuits and software with excellent stability and accuracy were developed to form a miniaturized integrated relative humidity sensing system with SAW sensor. A linear variation of the frequency shift is obtained in an extremely wide detection range from 0 to 97.3 %RH. Besides, the system exhibits a high sensitivity of 3.33 kHz/%RH, rapid response time of 80 s and recovery time of 72 s, good dynamic response and excellent repeatability. These results demonstrate that the SAW sensing system not only realizes humidity detection at system level, but also has excellent performance, which shows great feasibility and tremendous potential for relative humidity measurement applications. [ABSTRACT FROM AUTHOR]

We demonstrate an ultra-compact optical fiber thermo-hygrometer on the base of a bilayer OA (Optical Adhesive, a kind of polymer) micro-cap covering the entire SMF (Single-Mode-Fiber) facet. In fabrication, two types of OA are dispensed to fiber facet successively and stratified distinctly forming the bilayer micro-cap, which contains a flat and 2 spherical interfaces reflecting emitted light. Hence, hybrid interference would occur. The experimental results show that the sensitivity for humidity and temperature reach −3.641deg/%RH and −4.527deg/°C when demodulating interference phase shift, and dual-parameter measurement could also be achieved. The proposed optical fiber thermo-hygrometer is integrated, robust and with high sensitivity, making it satisfy lab-on-tip measuring requirement. [ABSTRACT FROM AUTHOR]

Low-cost ultrasonic sensors are widely used for non-contact distance measurement problems. Speed of ultrasonic waves is greatly affected by environmental conditions such as temperature and relative humidity among a few other parameters. Presence of acoustic and electronic noise also influences an ultrasonic sensor based distance measurement system. Existing standard techniques assume that the temperature and relative humidity levels remain constant throughout the measurement medium. In our proposed system, we measure water level in storage tanks of different depths, which exhibits a gradient of temperature and relative humidity across the measurement medium. Hence, the standard ultrasonic measurement system (UMS) is not able to estimate distance accurately. In this article, we propose an algorithm based on modified neural network architecture to increase the accuracy of UMS and also to extend the standard operating range of the ultrasonic sensor used. This article presents a novel approach to reduce measurement error using Levenberg–Marquardt backpropagation artificial neural network (LMBP-ANN) architecture. The proposed model is validated by comparing the actual water level at various depths under different environmental conditions with the output of the trained neural network. The measurement error in the proposed model is bounded by ±1 cm in the distance measurements ranging from 2 to 500 cm. This model is able to extend the maximum standard operating range of the ultrasonic sensor (HC-SR04 model) from 400 to 500 cm. The proposed model is evaluated using mean squared error (MSE) and $R$ -values to establish the effectiveness. [ABSTRACT FROM AUTHOR]

The effect of relative humidity on LEDs and how the moisture incursion is associated to the color shift is studied. This paper proposes a different approach to describe the lumen degradation of LEDs due to the long-term effects of humidity. Using the lumen degradation data of different types of LEDs under varying conditions of relative humidity, a humidity based degradation model (HBDM) is developed. A practical estimation method from the degradation behaviour is proposed to quantitatively gauge the effect of moisture incursion by means of a humidity index. This index demonstrates a high correlation with the color shift indicated by the LED's yellow to blue output intensity ratio. Physical analyses of the LEDs provide a qualitative validation of the model, which provides good accuracy with longer periods of moisture exposure. The results demonstrate that the HBDM is an effective indicator to predict the extent of the long-term impact of humidity and associated relative color shift.

In this article, we demonstrate a “Fabry-Perot + Michelson” hybrid interferometer based on a polymer micro-cap located on asymmetric 2-core fiber (2CF) facet. Because the polymer micro-cap comprises a flat reflector and a concave reflector, the light propagating in the centric core will be reflected twice forming Fabry-Perot interference. Due to the bias angle between the eccentric core and the concave reflector, the light in the eccentric core reflects only once on the flat reflector and would interfere with the other reflected light in the 2CF. The experimental results show that Fabry-Perot and Michelson interference occur and are superimposed on the directly detected spectrum. Independent interferometric spectrums can be separated by Discrete Fourier Transform to achieve humidity-temperature simultaneous measurement based on coefficient matrix demodulation. Moreover, this new optical fiber sensing platform is all-solid, high-integration, and flexible, so it has potential in lab-on-fiber applications. [ABSTRACT FROM AUTHOR]

Hydrogel is a kind of functional cross-linked polymer material with 3-D network structure. When hydrogel is exposed to water environment, a mass of hydrophobic groups and hydrophilic residues existing in the cross linked netlike nano-structure is willing to combine with water molecules and expand, respectively. In this paper, a novel optical fiber probe based on hollow-core fiber and calcium alginate (CaAlg) hydrogel film is proposed and experimentally demonstrated. The experimental results of relative humidity (RH) and temperature sensing characteristics show that the proposed probe has a binomial response to RH in the range of 20%~90% RH and a linear response to temperature with the sensitivity of 121pm/°C. CaAlg is considered as an effective and potential as the humidity-sensitive material to optical fiber RH sensors. [ABSTRACT FROM AUTHOR]

The effect of relative humidity on LEDs and how the moisture incursion is associated to the color shift is studied. This paper proposes a different approach to describe the lumen degradation of LEDs due to the long-term effects of humidity. Using the lumen degradation data of different types of LEDs under varying conditions of relative humidity, a humidity based degradation model (HBDM) is developed. A practical estimation method from the degradation behaviour is proposed to quantitatively gauge the effect of moisture incursion by means of a humidity index. This index demonstrates a high correlation with the color shift indicated by the LED's yellow to blue output intensity ratio. Physical analyses of the LEDs provide a qualitative validation of the model, which provides good accuracy with longer periods of moisture exposure. The results demonstrate that the HBDM is an effective indicator to predict the extent of the long-term impact of humidity and associated relative color shift. [ABSTRACT FROM AUTHOR]

This study investigates experimentally the time lag (τ) characteristics of lightning impulse spark discharges in air with relative humidity (RH) over the range 20 to 80%. The experiment was conducted using a wire-plate electrode system with a 30 mm gap and with overvoltage of 30 to 50% of the DC sparking voltage. The statistical and formative time lags (τs and τf) are discussed relative to the effects of RH and overvoltage on electron attachment and detachment mechanisims. [ABSTRACT FROM AUTHOR]

A novel moisture sensor based on near field communication (NFC) is presented. The system consists of a battery-less sensing device that measures temperature, relative humidity, and the volumetric water content, and is powered from the magnetic field generated by the reader. In order to compute the sensed data, the system includes a microcontroller, which has been programmed to make the calculations and to send the processed data to the NFC chip through an I2C bus. These data are stored into the EEPROM memory of the NFC-integrated circuit in NFC data exchange format, which is read by the reader. An analysis of different methods to measure the soil moisture is presented in order to select the approach, which fits better with the constraints of an NFC energy harvested system. [ABSTRACT FROM AUTHOR]

A high-performance fiber-optic relative humidity (RH) sensor was prepared by layer-by-layer self-assembly of polycation, poly (4-vinylpyridinium chloride), and polyanion, sodium alginate, on the surface of a thin-core fiber modal interferometer. The process of layer-by-layer self-assembly was monitored by UV-vis spectroscopy and surface profilometer. The morphology of the fabricated multilayer film was characterized by atomic force microscopy and field emission scanning electron microscopy. A fast, reversible, and linear response to RH with a high resolution of 0.1 nm/1% RH has been experimentally demonstrated by the proposed fiber-optic sensor. [ABSTRACT FROM PUBLISHER]

The underlying cause of most electrostatic discharge is tribocharging. Thus, understanding tribocharging is essential to assess the likelihood of damages as they might occur in the production of liquid crystal display (LCD) screens. In this paper, a study of triboelectric charge build-up between the glass and rollers during the glass transfer process in display panel manufacturing is presented. A roller conveyor system was fabricated and two types of rollers materials, insulative and dissipative, with radii of 30 and 90 mm, were considered. To measure the triboelectric charge of the glass, a Faraday cup with an elevator system was mounted on the apparatus. Various parameters including transfer velocity, acceleration/deceleration, and relative humidity were investigated. For instance, it is observed that the average saturated charge density on the glass is 0.324 nC/cm2 after 320-m displacements if it transfers by small dissipative rollers with condition of 200 mm/s and 200 mm/s 2. In addition, a comprehensive study of the surface potential distribution on the glass and rollers by utilizing a two-dimensional automated scanner is presented. The experiments pointed out that the amount of charge accumulated on the glass for the dissipative rollers saturated faster with a smaller value than the insulative rollers. [ABSTRACT FROM PUBLISHER]

The development of a silicon-only capacitive dew point sensor is described in this paper. The principle of operation is based on the change in capacitance of an interdigitated parallel plate capacitor due to the condensation of water below dew point temperature. The proposed sensor element is simple in fabrication, with only one lithography step and no metal or polymer usage. The experiments show good repeatability and baseline stability, whereas detection accuracy needs to be further improved. The influence of condensed water on the capacitance is investigated at different frequencies and cooling rates. It is expected that replacing air with water increases the capacitance by a factor of 80, due to the ratio of relative permittivity of water to ambient air. However, at low frequencies, the conducting properties of water in combination with the ultra-thin oxide coating on the electrodes result in a more complex capacitance behavior and an increase of up to four orders of magnitude has been measured. This additional and more rapid increase in capacitance may be utilized for faster dew point detection. In the current stage of development, the accuracy of the dew point temperature reading is equal to or better than the reference sensor (± 2 °C), with a response time of < 40 s, and is expected to be further improved with a more accurate test setup. [ABSTRACT FROM PUBLISHER]

In addition to large path loss, non-line-of-sight (NLOS) optical wireless scattering communication suffers time dispersion due to the multipath nature of the NLOS scattering channel. In this paper, the channel pulse delay spreads over broad spectra \left[ 0.2,1.6 \right] μm in polydisperse aerosols are investigated based on the Monte Carlo ray-tracing method. It is shown that the pulse delay spread first rises and then falls as the wavelength increases from deep ultraviolet to near-infrared spectrum. A comparison of pulse delay spread and path loss distributions over broad spectra is performed, which implies a tradeoff of channel bandwidth and power loss in the wavelength selection of NLOS optical scattering communication. The effects of relative humidity (RH) variations on NLOS optical scattering communication link are also studied, which indicate that RH variations do not significantly change the ultraviolet NLOS optical scattering communication link, but for near infrared spectrum, high RH condition can alleviate the large path loss and time dispersion and thus improve the NLOS optical scattering communication performance. [ABSTRACT FROM PUBLISHER]

This paper presents a new sensor system for vibration and relative humidity measurements based on its interaction with the evanescent field of a microwire. The interrogation of the sensing head is carried out by monitoring the fast Fourier transform (FFT) phase of one of the FFT peaks of the microwire transmission signal. This technique is not dependent of the signal amplitude and also eludes the requisite of tracking the wavelength evolution in the spectrum, which can be a handicap when there are multiple interference frequency components with different sensitivities. The point sensor is able to measure a wide humidity range (20%–70% relative humidity) with a maximum sensitivity reached of 0.14πrad/% relative humidity. This microwire sensor is also operated within a frequency range from 320 to 1300 Hz with a sensitivity of around 0.0051 nm–1/Hz. Finally, due to the system uses an optical interrogator as unique active element, the system presents a cost-effective feature. [ABSTRACT FROM PUBLISHER]