Wireless sensor network applications range from industrial automation and control, agricultural and environmental protection, to surveillance and medicine. In most applications, data are highly ...sensitive and must be protected from any type of attack and abuse. Security challenges in wireless sensor networks are mainly defined by the power and computing resources of sensor devices, memory size, quality of radio channels and susceptibility to physical capture. In this article, an embedded sensor node microcontroller designed to support sensor network applications with severe security demands is presented. It features a low power 16-bitprocessor core supported by a number of hardware accelerators designed to perform complex operations required by advanced crypto algorithms. The microcontroller integrates an embedded Flash and an 8-channel 12-bit analog-to-digital converter making it a good solution for low-power sensor nodes. The article discusses the most important security topics in wireless sensor networks and presents the architecture of the proposed hardware solution. Furthermore, it gives details on the chip implementation, verification and hardware evaluation. Finally, the chip power dissipation and performance figures are estimated and analyzed.
The aim of this research was to investigate the density, thermal conductivity, and viscosity of dispersions of agricultural biomass particles in ionic liquid HMIMNTf2 used as a base fluid. This ...research is a continuation of the development of IoBioFluids, a new class of dispersions obtained by suspending particles produced from agricultural biomass, as a sustainable alternative to IoNanoFluids. Dispersions with different mass concentration of particles (0, 0.5, 1, 2.5, and 5 wt%) were studied at different temperatures (20°C, 30°C, 40°C, and 50°C). Agricultural biomass, namely sunflower stalks, was used for particle production. The dispersion was prepared by applying the commonly used two-step method. In the first step, particles were produced as dry powder from hydrothermal carbonization and heat treatment in the inert atmosphere oven. In the second step, the particles were dispersed into ionic liquid. A rheological investigation showed that dispersions exhibited Newtonian behavior for shear rates over 10 s−1. Density, thermal conductivity, and dynamic viscosity of dispersions increased with greater mass concentration of particles. Two applied merit criteria suggested a lack of any currently benefit of using the dispersions for heat transfer in the laminar flow regime due to high viscosity of dispersion. The results of criterial analysis showed that experimental data are relatively close to the limit values. Indications are suggesting the possibility of further improvement of IoBioFluid properties as a new heat transfer fluid.
This paper presents an overview of semiconductor materials used in gas sensors, their technology, design, and application. Semiconductor materials include metal oxides, conducting polymers, carbon ...nanotubes, and 2D materials. Metal oxides are most often the first choice due to their ease of fabrication, low cost, high sensitivity, and stability. Some of their disadvantages are low selectivity and high operating temperature. Conducting polymers have the advantage of a low operating temperature and can detect many organic vapors. They are flexible but affected by humidity. Carbon nanotubes are chemically and mechanically stable and are sensitive towards NO and NH
, but need dopants or modifications to sense other gases. Graphene, transition metal chalcogenides, boron nitride, transition metal carbides/nitrides, metal organic frameworks, and metal oxide nanosheets as 2D materials represent gas-sensing materials of the future, especially in medical devices, such as breath sensing. This overview covers the most used semiconducting materials in gas sensing, their synthesis methods and morphology, especially oxide nanostructures, heterostructures, and 2D materials, as well as sensor technology and design, application in advance electronic circuits and systems, and research challenges from the perspective of emerging technologies.
The appearance of pest insects can lead to a loss in yield if farmers do not respond in a timely manner to suppress their spread. Occurrences and numbers of insects can be monitored through insect ...traps, which include their permanent touring and checking of their condition. Another more efficient way is to set up sensor devices with a camera at the traps that will photograph the traps and forward the images to the Internet, where the pest insect’s appearance will be predicted by image analysis. Weather conditions, temperature and relative humidity are the parameters that affect the appearance of some pests, such as Helicoverpa armigera. This paper presents a model of machine learning that can predict the appearance of insects during a season on a daily basis, taking into account the air temperature and relative humidity. Several machine learning algorithms for classification were applied and their accuracy for the prediction of insect occurrence was presented (up to 76.5%). Since the data used for testing were given in chronological order according to the days when the measurement was performed, the existing model was expanded to take into account the periods of three and five days. The extended method showed better accuracy of prediction and a lower percentage of false detections. In the case of a period of five days, the accuracy of the affected detections was 86.3%, while the percentage of false detections was 11%. The proposed model of machine learning can help farmers to detect the occurrence of pests and save the time and resources needed to check the fields.
The efficient conversion of solar radiation into heat at high temperature levels requires the use of concentrating solar collectors. The goal of this paper is to present the optical and the thermal ...analysis of a parabolic dish concentrator with a spiral coil receiver. The parabolic dish reflector consists of 11 curvilinear trapezoidal reflective petals constructed by PMMA with silvered mirror layer and has a diameter of 3.8 m, while its focal distance is 2.26m. This collector is designed with commercial software SolidWorks and simulated, optically and thermally in its Flow Simulation Studio. The optical analysis proved that the ideal position of the absorber is at 2.1m from the reflector in order to maximize the optical efficiency and to create a relative uniform heat flux over the absorber. In thermal part of the analysis, the energetic efficiency was calculated approximately 65%, while the exergetic efficiency is varied from 4% to 15% according to the water inlet temperature. Moreover, other important parameters as the heat flux and temperature distribution over the absorber are presented. The pressure drop of the absorber coil is calculated at 0.07bar, an acceptable value.
Introduction. When receiving anesthesia, patients with obstructive sleep apnea (OSA) are more likely to experience perioperative difficulties than those without this diagnosis. Aim. The aims of the ...paper were to highlight the correlation between OSA and increased risk of perioperative complications and present possible complications and pathophysiological mechanisms that may condition them in the perioperative environment; to review available preoperative screening methods of OSA and treatment planning strategies that should be considered as part of the perioperative care of these patients. Methodology. Standard databases were searched to identify qualified studies that included adult surgical patients without, suspected or diagnosed OSA. Results. Anesthesia method selection, airway management, and patient monitoring are all part of the customized care plan that must be used for each patient who is at risk for or has been diagnosed with OSA. Conclusion. The rising prevalence and heterogeneity of OSA, as well as the lack of solid risk predictors and well-documented evidence-based studies on the effectiveness of perioperative interventions, pose a challenge for future research in order to implement an appropriate strategy for perioperative care of OSA patients and prevent life-threatening consequences.
Modern agriculture necessitates the use of techniques and tools that pollute the environment less and improve the safety of food and feed production. In the field of plant protection, drones are ...attracting increasing attention due to their versatility and applicability in a variety of environmental and working conditions. Drone crop spraying techniques offer several advantages, including increased safety and cost effectiveness through autonomous and programmed operations based on specific schedules and routes. One of the main advantages of using drones for plant protection is their ability to monitor large areas of crops in a short amount of time. In addition to crop protection management, using drones for augmentative biocontrol facilitates the distribution of beneficial organisms to the exact locations where they are required, which can increase the effectiveness of biocontrol agents while reducing distribution costs. In this context, given the very limited commercial use of drones in the Western Balkans’ agri-food sector, the use of drones in the agri-food industry is a topic that needs to be elaborated on and highly promoted. Additionally, the specific legal regulations in Serbia that currently limit the use of drones in agriculture must be outlined. Conventional crop production is still significantly more prevalent in Serbia, but given the region’s continuous technological progress, there is no doubt that farmers’ education and future investments in precision agriculture will most likely increase the use of state-of-the-art technologies and drones in agriculture.
The main aim of the paper is to provide effective and accurate solutions for the calculation of the support region of the μ-law logarithmic companding quantizers. A new solution for the starting ...point of iterative methods will be proposed, that provides very accurate value of the support region (being the main parameter needed for the design of the quantizer) only after one iteration of the iterative method. Based on this new starting point, an accurate closed-form approximate expression for the calculation of the support region will be derived, as one of the main contributions of the paper. To significantly simplify implementation of the μ-law companding quantizer, piecewise linearization is performed. A new linearization method is presented, based on the optimization of the last segments. Derivation of an accurate closed-form formula for the support region of the linearized quantizer is done, as an important contribution. The obtained linearized μ-law companding quantizer is very simple to design (due to closed-form formulas) and to implement (due to linearization), providing at the same time very high performance (due to optimization of the last segments). Due to these and other advantages (robustness, adjustability to the statistical distribution of the input signal), the proposed quantizer can be used in many topical applications, such as in receivers of 5G wireless systems or in neural networks for quantization of weights and activations. The paper provides an application of the designed quantizers for quantization of weights of a neural network, showing significant decreasing of the bit-rate compared to the standard full-precision representation (from 32 bits to just 5 bits), with the same prediction accuracy of the network.
•A very accurate closed-form expression for the support region of the µ-law logarithmic quantizer is provided.•Implementation complexity of the µ-law logarithmic quantizer is drastically reduced by optimized linearization.•Weights of neural networks can be drastically compressed if they are quantized with the proposed quantizer.
Serbia is one of the leading producers and exporters of raspberry in the world, and considering the short shelf life of raspberry, the processing, storage, and transport are some of the main issues ...to be addressed.
A comparative experiment was conducted in order to find the suitable process parameters for convective drying that may be considered as the alternatives to freeze‐drying, which is a widely used preservation method for raspberry even though it is a costly and energy‐consuming method. Twelve convective drying regimens were applied with a combination of three influencing factors: air temperature (60°C, 70°C, and 80°C), air rate (0.5 and 1.5 m·s−1), and stage of raspberry (fresh and frozen). The final product, a dried raspberry, was assessed for chemical, physical, and mechanical properties and rehydration capacity. Deep ranking analysis by power eigenvectors (DRAPE) and sum of ranking differences (SRD) were used to uncover the differences and similarities between the applied drying methods.
SRD showed that convective drying of fresh raspberries proved to be more similar to freeze‐dried raspberries than convective drying of frozen ones. Fresh samples dried at 60 °C air temperature and 1.5 m·s−1 air flow proved to be the most similar to the reference freeze‐drying method. This convective regimen gives samples with the lowest color change, shrinkage, and shape deformation. With the mechanical and chemical properties of these samples being observed, statistical Duncan's test show that there is no significant difference (P < .05) in terms of hardness, shear force resistance, total phenolic, and total flavonoid preservation, compared with freeze‐dried samples. DRAPE gave similar results, but it added the variable importance in ranking as well, and total phenol reduction was defined as the most important variable. These results can help practitioners to develop cheaper and simpler drying methods that would replace the freeze‐drying but keep the same quality of the dried products.
The aim of this article is to find the suitable alternative to freeze‐drying of raspberry. Twelve convective drying regimens were applied with a combination of three influencing factors: air temperature (60°C, 70°C, and 80°C), air rate (0.5 and 1.5 m·s−1), and stage of raspberry (fresh and frozen). The sum of ranking differences (SRD) showed that convective drying of fresh raspberries at 60°C air temperature and 1.5 m·s−1 air flow proved to be the most similar to the reference freeze‐drying method.
Raspberries are one of Serbia's best-known and most widely exported fruits. Due to market fluctuation, producers are looking for ways to preserve this fresh product. Drying is a widely accepted ...method for preserving berries, as is the case with freeze-drying. Hence, the aim was to evaluate convective drying as an alternative to freeze-drying due to better accessibility, simplicity, and cost-effectiveness of Polana raspberries and compare it to a freeze-drying. Three factors were in experimental design: air temperature (60, 70, and 80 °C), air velocity (0,5 and 1,5 m · s
), and state of a product (fresh and frozen). Success of drying was evaluated with several quality criteria: shrinkage (change of volume), color change, shape, content of L-ascorbic acid, total phenolic content, flavonoid content, anthocyanin content, and antioxidant activity. A considerable influence of convective drying on color changes was not observed, as ΔE was low for all samples. It was obvious that fresh raspberries had less physical changes than frozen ones. On average, convective drying reduced L-ascorbic acid content by 80.00-99.99%, but less than 60% for other biologically active compounds as compared to fresh raspberries. Convective dried Polana raspberry may be considered as a viable replacement for freeze-dried raspberries.
PDF
