Location recommendation plays an essential role in helping people find attractive places. Though recent research has studied how to recommend locations with social and geographical information, few ...of them addressed the cold-start problem of new users. Because mobility records are often shared on social networks, semantic information can be leveraged to tackle this challenge. A typical method is to feed them into explicit-feedback-based content-aware collaborative filtering, but they require drawing negative samples for better learning performance, as users' negative preference is not observable in human mobility. However, prior studies have empirically shown sampling-based methods do not perform well. To this end, we propose a scalable Implicit-feedback-based Content-aware Collaborative Filtering (ICCF) framework to incorporate semantic content and to steer clear of negative sampling. We then develop an efficient optimization algorithm, scaling linearly with data size and feature size, and quadratically with the dimension of latent space. We further establish its relationship with graph Laplacian regularized matrix factorization. Finally, we evaluate ICCF with a large-scale LBSN dataset in which users have profiles and textual content. The results show that ICCF outperforms several competing baselines, and that user information is not only effective for improving recommendations but also coping with cold-start scenarios.
Carbon monoxide (CO) gas sensors are widely used, especially for environmental monitoring in confined spaces such as the landscape of mining cave ruins in mining parks, which is essential for ...ensuring the health and safety of tourists and staff. In this paper, a flexible CO gas sensor based on polyimide, interdigital electrodes, and reduced graphene oxide (RGO)/cuprous chloride (CuCl) composite film is designed and manufactured for reliable room temperature detection of high-concentration CO gas. The structure size of RGO/CuCl gas-sensitive film is 5 × 5 mm. The RGO with a 62.65% C-C bond is prepared by the thermal reduction method. The test results show that the sensor has a high response in the range of 400–2000 ppm CO gas concentration, and the maximum response is 1.56. The linear correlation coefficient of the sensor is 0.981, which indicates that the sensor has good output response characteristics. The response time of the sensor for 400 ppm CO gas is 332 s, which indicates that the sensor has a fast response rate. Furthermore, compared with other gases, the sensor shows higher gas selectivity for CO gas. This sensor has the characteristics of small size and easy attachment; therefore, it can be installed on the shoulder or helmet of tourists’ safety suits, providing personalized real-time warning prompts for tourists’ physical health status.
Environmental monitoring plays an important role in the preventive protection of ancient buildings, although it is still in the prototype stage. In order to provide data support for the protection of ...ancient buildings, an environmental monitoring system with multi-sensor and multi-node for the interior and exterior of ancient buildings is designed and realized, based on ZigBee, TCP/IP, and intranet penetration technology. The new type of indoor node package box and outdoor package device are designed to meet the needs of different types of sensors. The monitoring platform is developed on the strength of the LabView so as to obtain real-time display, storage, and over-limit warning functions for local and remote monitoring data. It also proves that the monitoring system is stable and reliable by monitoring the actual ancient building with a brick (stone) structure.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Two sandwiched ZnO/Metal/ZnO transparent conductive thin films, 50nm ZnO/Cu/50nm ZnO (abbreviated as ZnO(Cu)) and 50nm ZnO/Ti/Cu/Ti/50nm ZnO (abbreviated as ZnO(Ti/Cu)) were deposited by magnetron ...sputtering technology. The comparative analysis of experiment results shows that the introduction of the Ti layer is beneficial to the overall properties of ZnO(Ti/Cu) thin film compared to ZnO(Cu) thin film with the same metal layer thickness. The effect of the annealing temperature on the performance of the two film systems was studied. Although the carrier concentration did not always increase with annealing temperature, the sheet resistances did decrease due to the obvious increase of mobility. The transmittance of ZnO(Cu) thin films increases with annealing temperature, while that of ZnO(Ti/Cu) films increases at first and then decreases. The optical band gap of ZnO(Cu) thin films increases with temperature, but is lower than that of ZnO(Ti/Cu) thin films, whose bandgap first increases with temperature and then decreases. The figure of merit of the ZnO(Ti/Cu) film is better than that of ZnO(Cu), which shows that the overall performance of ZnO(Ti/Cu) films is better, and annealing can improve the performance of the film systems.
With the rapid development and application of smart homes, sensors known as ‘neurons’ have become more and more important in this field. In response to the demand for relative humidity parameter in ...home monitoring, a flexible relative humidity sensor based on reduced graphene oxide (RGO) and interdigital electrode for smart homes was designed and prepared in this paper. The base of the interdigital electrode structure was polyimide, and the RGO film was prepared by a spraying process. A test system for the relative humidity sensor with different saturated salt solutions was also built. The test results show that the sensor resistance and relative humidity have a linear relationship in the range of 24.6% RH–82.9% RH, and the linearity is as high as 0.987. The sensitivity of the sensor is 0.51 kΩ/% RH. The relative humidity sensor with the characteristics of flexibility and high sensitivity will have broad application prospects and value in the field of smart homes.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract
Flexible sensors used to detect NO
2
gas generally have problems such as poor repeatability, high operating temperature, poor selectivity, and small detection range. In this work, a new ...spraying platform with a simple structure, low cost, and good film-forming consistency was designed and built to make a sensitive film (rGO/SnO
2
) for NO
2
gas sensors. The relationship between the solid content of rGO and SnO
2
nanoparticles, annealing temperature, and sensor performance was studied. The results show that the interdigital electrode-sensitive film formed by spraying 0.25 ml of a 0.4 wt% rGO/SnO
2
mixture and annealing at 250 °C exhibited the best comprehensive performance for NO
2
detection. The sensor’s response value for 100 ppm NO
2
gas was 0.2640 at room temperature (25 °C), and the response time and recovery time were 412.4 s and 587.3 s, respectively. In the range of 20–100 ppm, the relationship between the response and NO
2
concentration was linear, and the correlation coefficient was 0.9851. In addition, a soft-monitoring node module with an overlimit warning function for NO
2
gas was designed and manufactured based on flexible electronics. Finally, the flexible sensor and node module were embedded into woven fabric that could be used to make a mask or a watch that could detect NO
2
gas, realizing the practical application of flexible NO
2
gas sensors in the field of wearable electronics.
Extrinsic optical fiber Fabry–Perot (F–P) high temperature sensors using Al2O3 ceramic tubes were fabricated by a microscope equipped with a CCD whose scaleplate has been calibrated using a standard ...gauge block. The initial cavity length of the F–P sensor, which must be larger than 36 µm, whose output signal is demodulated by the multi-peak method is determined. The temperature measurement range of the sensor is 25 °C–1000 °C. Because the temperature sensitivity of the F–P temperature sensor made by Al2O3 ceramic tubes, whose thermal expansion coefficient is different from that of the fiber, is dependent on the initial cavity length, a low initial cavity length is beneficial in improving sensor sensitivity. Compared with the results of the quartz tube F–P sensor, the temperature sensitivity of the ceramic tube F–P sensor is 10 times larger than that of the quartz tube F–P sensor. Hence, it can be deduced that the ceramic tube F–P sensor is greatly improved compared with the quartz tube F–P sensor.
Reduced graphene oxide (rGO) fiber as a carbon-based fiber sensor has aroused widespread interest in the field of gas sensing. However, the low response value and poor flexibility of the rGO fiber ...sensor severely limit its application in the field of flexible wearable electronics. In this paper, a flexible and wearable nylon fiber sensor modified by rGO and ZnO quantum dots (QDs) is proposed for wide-range NO2 gas detection at room temperature. The response value of the nylon fiber sensor to 100 ppm NO2 gas is as high as 0.4958, and the response time and recovery time are 216.2 s and 667.9 s, respectively. The relationship between the sensor’s response value and the NO2 concentration value is linear in the range of 20–100 ppm, and the fitting coefficient is 0.998. In addition, the test results show that the sensor also has good repeatability, flexibility, and selectivity. Moreover, an early warning module was also designed and is proposed in this paper to realize the over-limit monitoring of NO2 gas, and the flexible sensor was embedded in a mask, demonstrating its great application potential and value in the field of wearable electronics.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
The intangible cultural heritage of Yangjiabu New Year woodblock paintings (YNYWPs) has numerous potential cultural, artistic, and economic values. The quantitative color characteristics of ...YNYWPs, which have always been disregarded, can offer evidence in support of their inheritance and conservation. Utilizing the principles and methods of color science and spectral imaging technology, the color characteristics, including spectral characteristics, colorimetric characteristics, and color combination regularity, were quantitatively investigated by measuring and capturing the representative works. The results show that the spectral reflectances of the seven colors (i.e., red, yellow, green, cyan, violet, black, and paper color) adopted in the selected paintings have no significant structured features and can be accurately described using the first six derived eigenvectors by principal component analysis. The Xuan paper and the yellow color have higher reflectance than the other five colors. Correspondingly, their Commission Internationale de l'Eclairage (CIE) 1964 XYZ stimulus values are also relatively high. The others cover a narrow range in the CIE XYZ system. When transformed into the CIELAB color space, the seven colors can be relatively uniformly distributed in the color space. With regards to the color combination regularity, red, yellow, and cyan tend to occupy a large area in the selected paintings. In contrast, the other colors, especially green, are not frequently used. The resulting data of the color combination regularity quantitatively verify the color combination knack that is transmitted by word of mouth from generation to generation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The optical fiber temperature and refractive index sensor combined with the hollow needle structure for medical treatment can promote the standardization of traditional acupuncture techniques and ...improve the accuracy of body fluid analysis. A double-parameter sensor based on fiber Bragg grating (FBG) is developed in this paper. The sensor materials are selected through X-ray diffraction (XRD) analysis, and the sensor sensing principle is theoretically analyzed and simulated. Through femtosecond laser writing pure silica fiber, a high temperature resistant wavelength type FBG temperature sensor is obtained, and the FBG is corroded by hydrofluoric acid (HF) to realize a high-sensitivity intensity-type refractive index sensor. Because the light has dual characteristics of energy and wavelength, the sensor can realize simultaneous dual-parameter sensing. The light from the lead-in optical fiber is transmitted to the sensor and affected by temperature and refractive-index; then, the reflection peak is reflected back to the lead-out fiber by the FBG. The high temperature response and the refractive index response of the sensor were measured in the laboratory, and the high temperature characteristics of the sensor were verified in the accredited institute. It is demonstrated that the proposed sensor can achieve temperature sensing up to 1150 °C with the sensitivity of 0.0134 nm/°C, and refractive sensing over a refractive range of 1.333 to 1.4027 with the sensitivity of -49.044 dBm/RIU. The sensor features the advantages of two-parameter measurement, compact structure, and wide temperature range, and it exhibits great potential in acupuncture treatment.
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