In recent years, great development in sensor technologies have resulted in substantial progress in the construction efficiency and the degree of automation of construction machinery have made great ...progress. Applications of the sensor technologies, such as condition monitoring, autonomous construction and the Internet of Things (IoT), have been extensively studied for construction machinery. Firstly, this paper discusses the condition monitoring technology in construction machinery, which mainly involves the monitoring of oil pollution and leakage, vibration monitoring, emission monitoring and whole-system monitoring. Second, regarding autonomous construction technology, this paper conducts analysis and discussion on linear motion, rotary motion, navigation/positioning systems, and visual systems. Third, research on IoT technology in construction machinery is comprehensively discussed, especially in term of life cycle maintenance, construction management and safety management. Finally, higher reliability, the development of smart sensors and big data management of sensor information are described as prospective issues that must be addressed for future construction machinery.
Visible light communication(VLC)is a promising solution to the increasing demands for wireless connectivity.Gallium nitride micro-sized light emitting diodes(micro-LEDs)are strong candidates for VLC ...due to their high bandwidths.Segmented violet micro-LEDs are reported in this work with electrical-to-optical bandwidths up to 655 MHz.An orthogonal frequency division multiplexing-based VLC system with adaptive bit and energy loading is demonstrated,and a data transmission rate of 11.95 Gb/s is achieved with a violet micro-LED,when the nonlinear distortion of the micro-LED is the dominant noise source of the VLC system.A record 7.91 Gb/s data transmission rate is reported below the forward error correction threshold using a single pixel of the segmented array when all the noise sources of the VLC system are present.
The establishment of protected areas (PAs) is an effective way to biodiversity conservation while maintaining the multiple functions of ecosystem services. However, there is still a lack of ...comprehensive analysis on the relationship between PAs, biodiversity conservation, and ecological value in the field of research on prospects. Therefore, based on the research progress of literature content, this paper systematically reviews and evaluates domestic and international studies in terms of the biodiversity conservation and the ecological value of PAs. The results showed that relevant studies in recent years have mainly analyzed the spatial layout, area changes and conservation effectiveness of PAs in relation to biodiversity; By constructing the connotation system of ecological value concept of PAs, the research progress of ecological value accounting, ecological value realization and transformation, and ecological value types of PAs is further discussed, and the prospects of biodiversity conservation and ecological value research of PAs is proposed. This study provides a reference for the implementation of the Kunming-Montreal Global Biodiversity Framework and the construction and optimization of PAs system.
P(VDF-TrFE) is a promising material for flexible acoustic devices owing to its good piezoelectric performance and excellent stretchability. However, the high density of internal pores and large ...surface roughness of the conventional P(VDF-TrFE) results in a high propagation attenuation for acoustic waves, which limits its use in flexible acoustic devices. In this paper, a novel method based on two-step annealing is proposed to effectively remove the pores inside the P(VDF-TrFE) film and reduce its surface roughness. The obtained P(VDF-TrFE) film possesses excellent characteristics, including a high breakdown strength of >300 kV/mm, a high-purity β-phase content of more than 80%, and high piezoelectric coefficients (d
) of 42 pm/V. Based on the low-porosity β-phase P(VDF-TrFE) film, we fabricated flexible film bulk acoustic resonators (FBARs) which exhibit high sharp resonance peaks. The pressure sensor was made by sandwiching the FBARs with two PDMS microneedle patches. Heartbeat and respiration rate monitoring were achieved using the pressure sensor. This work demonstrates the feasibility of high-performance flexible piezoelectric acoustic resonators based on low-porosity P(VDF-TrFE) films, which could see wider applications in the wearable sensors for both physical and chemical sensing.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Measuring regional differences in agricultural green total factor productivity (AGTFP) provides a basis for policy guidance on agricultural green development in the Yangtze River Delta (YRD) region. ...By constructing a two-period Malmquist-Luenberger index under the carbon emission constraint, we measure the AGTFP of cities in the YRD region from 2001 to 2019. Furthermore, adopting the Moran index method and the hot spot analysis method, this paper analyzes the global spatial correlation and local spatial correlation of AGTFP in this region. Moreover, we investigate its spatial convergence. The results show that the AGTFP of 41 cities in the YRD region is on an increasing trend; the growth of AGTFP in the eastern cities is mainly driven by green technical efficiency, while this growth in the southern cities is mainly stimulated by green technical efficiency and green technological progress. We also find a significant spatial correlation between cities' AGTFP in the YRD region from 2001 to 2019, but with certain fluctuations, showing a U-shaped trend of "strong-weak-strong". In addition, absolute β convergence of the AGTFP exists in the YRD region, and this convergence speed is accelerated with the addition of spatial factors. This evidence provides support for implementing the regional integration development strategy and optimizing the regional agricultural spatial layout. Our findings offer implications for promoting the transfer of green agricultural technology to the southwest of the YRD region, strengthening the construction of agricultural economic belts and agricultural economic circles, and improving the efficiency of agricultural resource use.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The natural hazards caused by climate change have a significant impact on the production and life of urban residents, enhancing urban resilience is an important way to cope with climate disasters and ...ensure the safety of urban systems. Based on the “urban resilience” research relevant literature, the paper applies bibliometric analysis software to reveal the research hotspots and evolution trends of urban resilience in the perspective of climate change. The results indicate that the main research contents can be summarized into four aspects: ⅰ) influencing factors of urban resilience; ii) evaluation index and method of urban resilience; iii) the impact of climate change on urban resilience; ⅳ) Enhancing urban resilience in response to climate change. Finally, potential directions for future research on urban resilience were proposed, multi-dimensional research on urban resilience should be carried out from aspects of theoretical development, urban planning based on resilience mechanisms should be carried out from the perspective of planning practice, and innovation and reform should be carried out in policy implementation and urban management. Accurately understanding the conceptual connotation and construction mechanism of urban resilience is a crucial premise for climate mitigation and adaptation. Relevant research conclusions can provide useful reference for theoretical research and spatial planning of resilient cities.
The cardinality balanced multi-target multi-Bernoulli (CBMeMBer) filter developed recently has been proved an effective multi-target tracking (MTT) algorithm based on the random finite set (RFS) ...theory, and it can jointly estimate the number of targets and their states from a sequence of sensor measurement sets. However, because of the existence of systematic errors in sensor measurements, the CBMeMBer filter can easily produce different levels of performance degradation. In this paper, an extended CBMeMBer filter, in which the joint probability density function of target state and systematic error is recursively estimated, is proposed to address the MTT problem based on the sensor measurements with systematic errors. In addition, an analytic implementation of the extended CBMeMBer filter is also presented for linear Gaussian models. Simulation results confirm that the proposed algorithm can track multiple targets with better performance.
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The effect of cationic surfactants on the growth of gypsum was evaluated under conditions of a simulated production process of gypsum desulfurization. We used a laser particle size analyzer and a ...microscope to determine the particle size and morphology. The growth rate of gypsum was determined by the equation for the rate of chemical reaction of CaSO
·2H
O. The results showed that the growth rate at a supersaturation ratio of 2.4 increased by 50% with 30 mg/L of a dodecyldimethylbenzylammonium chloride. The gypsum morphology changed from needle-like in the absence of additives to tabular in the presence of cationic surfactants, indicating that relatively thicker and larger crystals were formed. Finally, the investigated cationic surfactants were beneficial to the normal operation of the desulfurization process.
In a humid environment, the stray current generated by subway operation will corrode the underground pipe network and the internal steel structure of the track plate, which will seriously affect the ...service life of the subway track plate and increase the maintenance cost later. Groundwater in subway projects mainly enters the concrete interior through capillary action and affects the concrete resistivity, and there is a lack of research on the mechanism of groundwater effect on concrete resistance. In this study, the variation of cement mortar resistivity with capillary water absorption time for cement mortar with different amounts of mineral admixtures (fly ash, ground-granulated blast furnace slag, and silica fume) was measured by the four-electrode method, and the mechanism of the influence of the electrical properties of cementitious materials under the effect of capillary water absorption was analyzed based on the mercury-pressure method (MIP) and thermogravimetric method (TG-DTG). The results show that with the increase in capillary water absorption time, the change curve of cement mortar resistivity can be divided into two stages; in the first stage, capillary water absorption leads to gel pores and transition pores quickly connecting to capillary pores and other large pores to form a water-saturated conductive pathway, resulting in a rapid decrease in resistivity, when the gel pores and excessive pores have a greater impact on resistivity. The second stage is that of capillary water absorption, to a certain extent, after the specimen’s internal water upward development rate slows down; at this time, the formation speed of the conductive pathway decreases, resulting in the rate of change in resistivity decreasing and gradually stabilizing. The incorporation of silica fume can effectively improve the resistivity of cementitious materials under the action of capillary water absorption, in which the resistivity of specimens incorporated with 15% silica fume after 36 days of capillary water absorption is 10.39 times that of the reference group, which is mainly due to its lower porosity and a higher percentage of gel pores.
The magnetic properties of a β-Mn-type alloy Co7Zn8Mn5, which is a chiral magnet hosting skyrmion phase, are comprehensively investigated, exhibiting a ferromagnetic transition around 184 K and a ...spin freezing near 20 K. The generated Rhodes–Wolfarth ratio equals 1.10, which indicates a weak itinerant character of the ferromagnetism in Co7Zn8Mn5. The spin dynamics of the spin freezing agrees with the universal scaling law of critical slowing down with τ0 = 1.7 × 10−5 s, Tg = 20.2 K, and zν = 3.92. Critical exponents β = 0.423(1) and γ = 1.366(4) are deduced by the modified Arrott plot, whereas δ = 4.22(2) is obtained by a critical isotherm analysis. The validity of the deduced critical exponents is verified by the Widom scaling relation and the scaling hypothesis. The boundary between the first-order and the second-order phase transition is evaluated by a scaling analysis. The magnetic interaction, obtained by a renormalization group theory, decays with distance r as J(r) ≈ r−4.9, lying between the mean-field model and the 3D Heisenberg model. The analyses on critical behavior could shed new light on the origin of ferromagnetism and topological Hall effect. Moreover, the magnetic entropy change −ΔSM exhibits a maximal value around TC, and the peak position gradually raises with an increasing fields, eliminating the mean-field model. The −ΔSMmax features a power-law behavior with n > 2/3, excluding any universal standard models of ferromagnetism. The −ΔSM(T, H) plots can be scaled into a universal curve, further verifying the reliability and accuracy of the yielded critical exponents.
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