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Sensor-related indoor localization has attracted considerable attention in recent years. The accuracy of conventional fingerprint solutions based on a single sensor, such as a Wi-Fi sensor, is affected by multipath interferences from other electronic devices that are produced as a result of complex indoor environments. Light sensors and magnetic (i.e., geomagnetic) field sensors can be used to enhance the accuracy of a system since they are less vulnerable to disturbances. In this paper, we propose a deep feedforward (DFF)-neural-network-based method, termed DFF-WGL, which integrates the data from the embedded Wi-Fi sensor, geomagnetic field sensor, and light sensor (WGL) in a smart device to localize the device in an indoor environment. DFF-WGL does not require complex and expensive auxiliary equipment, except for basic fluorescent lamps and low-density Wi-Fi signal coverage, conditions that are easily satisfied in modern offices or educational buildings. The proposed system was implemented on a commercial off-the-shelf android device, and performance was evaluated through an experimental analysis conducted in two different indoor testbeds, one measuring 60.5 m2 and the other measuring 38 m2, with 242 and 60 reference points, respectively. The results indicate that the model prediction with an input consisting of the combination of light, a magnetic field sensor, and two Wi-Fi RSS signals achieved mean localization errors of 0.01 m and 0.04 m in the two testbeds, respectively, compared with any subset of combination of sensors, verifying the effectiveness of the proposed DFF-WGL method. [ABSTRACT FROM AUTHOR]

Aging is a significant contributor to changes in sleep patterns, which has compounding consequences on cognitive health. A modifiable factor contributing to poor sleep is inadequate and/or mistimed light exposure. However, methods to reliably and continuously collect light levels long-term in the home, a necessity for informing clinical guidance, are not well established. We explored the feasibility and acceptability of remote deployment and the fidelity of long-term data collection for both light levels and sleep within participants' homes. The original TWLITE study utilized a whole-home tunable lighting system, while the current project is an observational study of the light environment already existing in the home. This was a longitudinal, observational, prospective pilot study involving light sensors remotely deployed in the homes of healthy adults (n = 16, mean age: 71.7 years, standard deviation: 5.0 years) who were co-enrolled in the existing Collaborative Aging (in Place) Research Using Technology (CART) sub-study within the Oregon Center for Aging and Technology (ORCATECH). For 12 weeks, light levels were recorded via light sensors (ActiWatch Spectrum), nightly sleep metrics were recorded via mattress-based sensors, and daily activity was recorded via wrist-based actigraphy. Feasibility and acceptability outcomes indicated that participants found the equipment easy to use and unobtrusive. This proof-of-concept, feasibility/acceptability study provides evidence that light sensors can be remotely deployed to assess relationships between light exposure and sleep among older adults, paving the way for measurement of light levels in future studies examining lighting interventions to improve sleep. [ABSTRACT FROM AUTHOR]

This work reports on the synthesis of small molecular semiconductor 2-(1H-pyrrol-1-yl)-anthracene-9,10-dione (PAD) via wet chemical precipitation route method for its possible potential applications in sensors. Thin film characterization of the synthesized PAD is carried out by studying its surface morphology, bond dynamics, and optical properties. For studying sensing characteristics of the PAD, its 100 nm thick film is thermally deposited on pre-patterned silver (Ag) electrodes over glass substrate having ~45 µm inter-electrode gaps to prepare Ag/PAD/Ag sensor. The effects of humidity (%RH), temperature (T), and illumination of light (Ev) on the fabricated Ag/PAD/Ag sensor are studied by changing one of the three (%RH, T, and Ev) parameters at a time and measuring the corresponding variations in capacitance (C) and capacitive reactance (X) of the device. As C and X also depend on frequency, sensing properties of the Ag/PAD/Ag sensor are measured at two different frequencies (120 Hz and 1 kHz) to find the optimum sensitivity conditions. To investigate reproducibility and repeatability of Ag/PAD/Ag sensor, each measurement is taken several times and also hysteresis loops of %RH vs. C are plotted at 120 Hz and 1 kHz to find the percent errors in each cycle of measurements. The sensor is active to sense humidity, temperature, and illumination within a broad range, i.e., from 15–93%RH, 293–382 K, and 1500–20,000 lx, respectively. Other key parameters of the sensor i.e., the humidity response time (TRes) and recovery time (TRec), are measured, which are 5 and 7 s, respectively, whereas for light sensing the values of TRes and TRec are measured to be 3.8 and 2.6 s, respectively. The measured values of TRes and TRec for the fabricated Ag/PAD/Ag sensor are shorter and better as compared to those of previously reported for similar kind of small molecular based sensors. The sensing properties of Ag/PAD/Ag device exhibit the potential of PAD for humidity, temperature, and light sensing applications. [ABSTRACT FROM AUTHOR]

In this paper, a new wireless sensor, designed for a 0.35 μm CMOS technology, is presented. The microchip was designed to be placed on an object for the continuous remote monitoring of its temperature and illumination state. The temperature sensor is based on the temperature dependence of the I-V characteristics of bipolar transistors available in CMOS technology, while the illumination sensor is an integrated p-n junction photodiode. An on-chip 2.5 GHz transmitter, coupled to a mm-sized dipole radiating element fabricated on the same microchip and made in the top metal layer of the same die, sends the collected data wirelessly to a radio receiver using an On-Off Keying (OOK) modulation pattern. [ABSTRACT FROM AUTHOR]

One critical point of dairy farm management is calving and neonatal first care. Timely calving assistance is associated with the reduction of calf mortality and postpartum uterine disease, and with improved fertility in dairy cattle. This study aimed to evaluate the performance and profitability of an intravaginal sensor for the prediction of stage II of labor in dairy farms, thus allowing proper calving assistance. Seventy-three late-gestating Italian Holstein cows were submitted to the insertion of an intravaginal device, equipped with light and temperature sensors, connected with a Central Unit for the commutation of a radio-signal into a cell phone alert. The remote calving alarm correctly identified the beginning of the expulsive phase of labor in 86.3% of the monitored cows. The mean interval from alarm to complete expulsion of the fetus was 71.56 ± 52.98 min, with a greater range in cows with dystocia (p = 0.012). The sensor worked correctly in both cold and warm weather conditions, and during day- or night-time. The intravaginal probe was well tolerated, as any cow showed lesions to the vaginal mucosa after calving. Using sex-sorted semen in heifers and beef bull semen in cows at their last lactation, the economic estimation performed through PrecisionTree™ software led to an income improvement of 119 € and 123 €/monitored delivery in primiparous and pluriparous cows, respectively. Remote calving alarm devices are key components of "precision farming" management and proven to improve animal welfare, to reduce calf losses and to increase farm incomes. [ABSTRACT FROM AUTHOR]

Sunlight incident on the Earth's atmosphere is essential for life, and it is the driving force of a host of photo-chemical and environmental processes, such as the radiative heating of the atmosphere. We report the description and application of a physical methodology relative to how an ensemble of very low-cost sensors (with a total cost of <$20, less than 0.5% of the cost of the reference sensor) can be used to provide wavelength resolved irradiance spectra with a resolution of 1 nm between 360–780 nm by calibrating against a reference sensor using machine learning. These low-cost sensor ensembles are calibrated using machine learning and can effectively reproduce the observations made by an NIST calibrated reference instrument (Konica Minolta CL-500A with a cost of around USD 6000). The correlation coefficient between the reference sensor and the calibrated low-cost sensor ensemble has been optimized to have R 2 > 0.99. Both the circuits used and the code have been made publicly available. By accurately calibrating the low-cost sensors, we are able to distribute a large number of low-cost sensors in a neighborhood scale area. It provides unprecedented spatial and temporal insights into the micro-scale variability of the wavelength resolved irradiance, which is relevant for air quality, environmental and agronomy applications. [ABSTRACT FROM AUTHOR]

Two-dimensional materials, including molybdenum disulfide (MoS 2 ), present promising sensing and detecting capabilities thanks to their extreme sensitivity to changes in the environment. Their reduced thickness also facilitates the electrostatic control of the channel and opens the door to flexible electronic applications. However, these materials still exhibit integration difficulties with complementary-MOS standardized processes and methods. The device reliability is compromised by gate insulator selection and the quality of the metal/semiconductor and semiconductor/insulator interfaces. Despite some improvements regarding mobility, hysteresis and Schottky barriers having been reported thanks to metal engineering, vertically stacked heterostructures with compatible thin-layers (such as hexagonal boron nitride or device encapsulation) variability is still an important constraint to sensor performance. In this work, we fabricated and extensively characterized the reliability of as-synthesized back-gated MoS 2 transistors. Under atmospheric and room-temperature conditions, these devices present a wide electrical hysteresis (up to 5 volts) in their transfer characteristics. However, their performance is highly influenced by the temperature, light and pressure conditions. The singular signature in the time response of the devices points to adsorbates and contaminants inducing mobile charges and trapping/detrapping carrier phenomena as the mechanisms responsible for time-dependent current degradation. Far from being only a reliability issue, we demonstrated a method to exploit this device response to perform light, temperature and/or pressure sensors in as-synthesized devices. Two orders of magnitude drain current level differences were demonstrated by comparing device operation under light and dark conditions while a factor up to 10 5 is observed at vacuum versus atmospheric pressure environments. [ABSTRACT FROM AUTHOR]

We propose a novel approach to measure photosynthetically active radiation (PAR) in the form of photosynthetic photon flux density with an inexpensive, small multi-channel spectrometer sensor, with integrated optical filters and analog-to-digital converter. Our experiments prove that the combination of eight spectral channels with different optical sensitivities, such as the sensorchip in use (AS7341, ams), derive the PAR with an accuracy of 14 μ m − 2 s − 1 . Enabled by the sensor architecture, additional information about the light quality can be retrieved which is expressed in the reduced light quality index. A calibration method is proposed, and exemplary measurements are performed. Moreover, the integration in a solar-powered wireless sensor node is outlined, which enables long-term field experiments with high sensor densities and may be used to obtain important indexes, such as the gross primary production. [ABSTRACT FROM AUTHOR]

This paper describes a new class of light transducer-based poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer doped with 50% wt. phosphor particles that enables to efficiently transform light energy into an electrical signal. Broadband dielectric characterization together with experimental results on photo-electric conversion demonstrated high capacitance variation of the proposed composite under light exposure, confirming promising potential of our sensor device for application in retinal prostheses where the converted electrical signal can affect the biological activity of the neuron system. In addition to the benefit of being light-weight, having ultra-flexibility, and used in a simple process, the proposed photodetector composite leads to fast response and high sensibility in terms of photoelectrical coupling where significant increases in capacitance change of 78% and 25% have been recorded under blue and green light sources, respectively. These results demonstrated high-performance material design where phosphor filler contributes to promote charge-discharge efficiency as well as reduced dielectric loss in P(VDF-TrFE-CTFE), which facilitate the composite for flexible light transducer applications, especially in the medical environment. [ABSTRACT FROM AUTHOR]

We successfully fabricated a planar nanocomposite film that uses a composite of silver nanoparticles and titanium dioxide film (Ag-TiO2) for ultraviolet (UV) and blue light detection and application in ozone gas sensor. Ultraviolet-visible spectra revealed that silver nanoparticles have a strong surface plasmon resonance (SPR) effect. A strong redshift of the plasmonic peak when the silver nanoparticles covered the TiO2 thin film was observed. The value of conductivity change for the Ag-TiO2 composite is 4–8 times greater than that of TiO2 film under UV and blue light irradiation. The Ag-TiO2 nanocomposite film successfully sensed 100 ppb ozone. The gas response of the composite film increased by roughly six and four times under UV and blue light irradiation, respectively. We demonstrated that a Ag-TiO2 composite gas sensor can be used with visible light (blue). The planar composite significantly enhances photo catalysis. The composite films have practical application potential for wearable devices. [ABSTRACT FROM AUTHOR]

Solar energy is considered the greatest source of renewable energy. In this paper, a case study was performed for a single-axis solar tracking model to analyze the performance of the solar panels in an office building under varying ambient temperatures and solar radiation over the course of one year (2018). This case study was performed in an office building at the College of Engineering at Shaqra University, Dawadmi, Saudi Arabia. The office building was supplied with electricity for a full year by the designed solar energy system. The study was conducted across the four seasons of the studied year to analyze the performance of a group of solar panels with the total capacity of a 4 kW DC system. The solar radiation, temperature, output DC power, and consumed AC power of the system were measured using wireless sensor networks (for temperature and irradiance measurement) and a signal acquisition system for each hour throughout the whole day. A single-axis solar tracker was designed for each panel (16 solar panels were used) using two light-dependent resistors (LDR) as detecting light sensors, one servo motor, an Arduino Uno, and a 250 W solar panel installed with an array tilt angle of 21°. Finally, an artificial neural network (ANN) was utilized to estimate energy consumption, according to the dataset of AC load power consumption for each month and the measurement values of the temperature and irradiance. The relative error between the measured and estimated energy was calculated in order to assess the accuracy of the proposed ANN model and update the weights of the training network. The maximum absolute relative error of the proposed system did not exceed 2 × 10−4. After assessment of the proposed model, the ANN results showed that the average energy in the region of the case study from a 4 kW DC solar system for one year, considering environmental impact, was around 8431 kWh/year. [ABSTRACT FROM AUTHOR]

The interior space of large-scale buildings, such as hospitals, with a variety of departments, is so complicated that people may easily lose their way while visiting. Difficulties in wayfinding can cause stress, anxiety, frustration and safety issues to patients and families. An indoor navigation system including route planning and localization is utilized to guide people from one place to another. The localization of moving subjects is a critical-function component in an indoor navigation system. Pedestrian dead reckoning (PDR) is a technology that is widely employed for localization due to the advantage of being independent of infrastructure. To improve the accuracy of the localization system, combining different technologies is one of the solutions. In this study, a multi-sensor fusion approach is proposed to improve the accuracy of the PDR system by utilizing a light sensor, Bluetooth and map information. These simple mechanisms are applied to deal with the issue of accumulative error by identifying edge and sub-edge information from both Bluetooth and the light sensor. Overall, the accumulative error of the proposed multi-sensor fusion approach is below 65 cm in different cases of light arrangement. Compared to inertial sensor-based PDR system, the proposed multi-sensor fusion approach can improve 90% of the localization accuracy in an environment with an appropriate density of ceiling-mounted lamps. The results demonstrate that the proposed approach can improve the localization accuracy by utilizing multi-sensor data and fulfill the feasibility requirements of localization in an indoor navigation system. [ABSTRACT FROM AUTHOR]

This paper presents a fully integrated photodiode-based low-power and low-mismatch stimulator for a subretinal prosthesis. It is known that a subretinal prosthesis achieves 1600-pixel stimulators on a limited single-chip area that is implanted beneath the bipolar cell layer. However, the high-density pixels cause high power dissipation during stimulation and high fabrication costs because of special process technologies such as the complementary metal-oxide semiconductor CMOS image sensor process. In addition, the many residual charges arising from the high-density pixel stimulation have deleterious effects, such as tissue damage and electrode corrosion, on the retina tissue. In this work, we adopted a switched-capacitor current mirror technique for the single-pixel stimulator (SPStim) that enables low power consumption and low mismatch in the subretinal device. The customized P+/N-well photodiode used to sense the incident light in the SPStim also reduces the fabrication cost. The 64-pixel stimulators are fabricated in a standard 0.35-μm CMOS process along with a global digital controller, which occupies a chip area of 4.3 × 3.2 mm2 and are ex-vivo demonstrated using a dissected pig eyeball. According to measured results, the SPStim accomplishes a maximum biphasic pulse amplitude of 143 μA, which dissipates an average power of 167 μW in a stimulation period of 5 ms, and an average mismatch of 1.12 % between the cathodic and anodic pulses. [ABSTRACT FROM AUTHOR]