The variable-speed rotor has proven to be a promising means to improve helicopter performance. Previous investigations on the aeromechanics of the variable-speed rotor are scarce. This work studies the mechanism of the variable-speed rotor affecting the rotor aerodynamic performance by means of dimensionless parameter analysis and reveals the various effect mechanisms under the various flight speeds and take-off weights. The current work shows that, during hover, the variable-speed rotor improves the rotor aerodynamic performance by reducing the blade dynamic pressure, while the non-uniform thrust distribution is attributed to the reduced rotor speed suppresses the performance improvement. In slow forward flight, the blade dynamic pressure reduction improves the rotor aerodynamic performance. In cruise and fast forward flight, both the blade dynamic pressure and advancing blade tip compression loss reductions improve the rotor aerodynamic performance. The study also shows that in forward flight, the rotor loading is smaller, and the effect of reducing the advancing blade tip compression loss through the variable-speed rotor is greater. Full article

This study was initiated to evaluate the performance of asphalt binders and mixtures incorporating linear low-density polyethylene- calcium carbonate (LLDPE-CaCO₃) pellet, either with or without titanate coupling agent. The detailed manufacturing process of modifier pellets was displayed. The coupling agent was used to enhance the cross-linking between materials by means of winding up covalent bonds or molecule chains, thus improving the performance of composites. In the preparation of modified bitumen, the preheated asphalt binder was mixed with the modifiers using a high shear mixer at 5000 rpm rotational speed for 45 min. Experimental works were conducted to evaluate the performance of asphalt binders in terms of volatile loss, viscosity, rutting potential, and low temperature cracking. Meanwhile, the asphalt mixtures were tested using the flow number test and tensile strength ratio (TSR) test. The addition of LLDPE-CaCO₃ modifiers and coupling agent does not significantly affect the volatile loss of modified asphalt binders. The addition of modifiers and coupling agent has significantly improved the resistance to permanent deformation of asphalt binders. Even though, the addition of LLDPE-CaCO₃ modifier and coupling agent remarkably increased the mixture stiffness that contributed to lower rutting potential, the resistance to low temperature cracking of asphalt binder was not adversely affected. The combination of 1% coupling agent with 3% PECC is optimum dosage for asphalt binder to have satisfactory performance in resistance to moisture damage and rutting. Full article

Rail surface defects seriously affect the safety of railway systems. At present, human inspection and rail vehicle inspection are the main approaches for the detection of rail surface defects. However, there are many shortcomings to these approaches, such as low efficiency, high cost, and so on. This paper presents a novel visual inspection approach based on unmanned aerial vehicle (UAV) images, and focuses on two key issues of UAV-based rail images: image enhancement and defects segmentation. With regards to the first aspect, a novel image enhancement algorithm named Local Weber-like Contrast (LWLC) is proposed to enhance rail images. The rail surface defects and backgrounds can be highlighted and homogenized under various sunlight intensity by LWLC, due to its illuminance independent, local nonlinear and other advantages. With regards to the second, a new threshold segmentation method named gray stretch maximum entropy (GSME) is presented in this paper. The proposed GSME method emphasizes gray stretch and de-noising on UAV-based rail images, and selects an optimal segmentation threshold for defects detection. Two visual comparison experiments were carried out to demonstrate the efficiency of the proposed methods. Finally, a quantitative comparison experiment shows the LWLC-GSME model achieves a recall of 93.75% for T-I defects and of 94.26% for T-II defects. Therefore, LWLC for image enhancement, in conjunction with GSME for defects segmentation, is efficient and feasible for the detection of rail surface defects based on UAV Images. Full article

To understand complex biological processes, scientists must gain insight into the function of individual living cells. In contrast to the imaging of fixed cells, where a single snapshot of the cell’s life is retrieved, live-cell imaging allows investigation of the dynamic processes underlying the function and morphology of cells. Label-free imaging of living cells is advantageous since it is used without fluorescent probes and maintains an appropriate environment for cellular behavior, otherwise leading to phototoxicity and photo bleaching. Quantitative phase imaging (QPI) is an ideal method for studying live cell dynamics by providing data from noninvasive monitoring over arbitrary time scales. The effect of drugs on migration, proliferation, and apoptosis of cancer cells are emerging fields suitable for QPI analysis. In this review, we provide a current insight into QPI applied to cancer research. Full article

This study reports the application of an optoacoustic method for evaluating the bonding strength of ultrasonically bonded joints in a non-destructive and non-contact fashion. It is proposed that the bonding strength is correlated with the resonant frequency of bonded joints. The bonding strength measured with a destructive tensile test roughly increased with the vibration time, however, it varied, causing the transitional and dispersed formation of micro-bonds at the bonding interface. Scanning Electron Microscopic observation of the fractured surface suggested that the bonding strength depends on the total bonded area of micro-bonds. Frequency response of the bonded joint was examined with a non-destructive method using a piezo-electric vibrator. The experiment revealed that the resonant frequency exponentially increased with the bonding strength. In addition, this vibration behavior was dynamically visualized with electronic speckle pattern interferometry (ESPI). The correlation between the bonded area and the resonant frequency is discussed based on finite element analysis. The results indicate the possibility for in-situ evaluation of the ultrasonic bonding strength. Full article

Bentonite is widely used as a waterproof material in civil engineering. The swelling capacity and impermeability will be reduced in saline water conditions. A polymer-modified bentonite was used in this study, and the swelling characteristic and hydraulic conductivity in saline water were investigated. Results show that: the modified bentonite (MB) has good swelling characteristics and low permeability in saline water conditions; the unload swelling strain of MB in saline water conditions increased with rising swelling time; the final unload swelling strain of MB decreased with the increase of vertical pressure and increased with increasing initial dry density; and, as the swelling time increased, the swelling pressure increased rapidly at first and then decreased. Based on experimental results, this study obtained a linear relationship between the ratio of time to unload swelling strain and swelling time, a formula for load swelling strain that was related to initial dry density and vertical pressure, a linear relationship between the ratio of time to swelling pressure and swelling time, and an exponential relationship between swelling pressure and initial dry density. The MB can be used as a waterproof material in seepage-prone applications under saline environmental conditions in civil engineering works. Full article

This paper investigates the problem of global asymptotic stabilization of underactuated surface vessels (USVs) whose dynamics features off-diagonal inertia and damping matrices. By using input and state transformations, the dynamic model of USV is converted into an equivalent system consisting of two cascade connected subsystems. For the transformed system, a continuous fractional power control framework is given to achieve global asymptotic stabilization of USVs. Then, the convergence under this framework is analyzed showing that the rate can be improved by adjusting the fractional power term. Finally, a continuous control algorithm is proposed to guarantee the global convergence rate of the USV system. Simulations are given to demonstrate the effectiveness of the presented method. Full article

Sensor networks are handicapped by limited resources in the form of energy, processing, and memory. This paper proposes a new multi-hop energy efficient protocol, namely a routing algorithm using the ring-zone (RARZ) model. The protocol is lightweight, takes routing decisions based on the remaining energy of nodes, and performs location-based routing without the need for the nodes to know their respective positions. The protocol partitions the network into concentric rings around the base station. Each node assigns itself to a particular ring, known by a ringID. Multi-hop routing is performed and nodes within inner rings carry data for the outer rings towards the base station. Simulation results show that RARZ outperforms the address-light integrated MAC routing protocol (AIMRP), ad hoc on-demand distance vector (AODV) and Flooding in terms of end-to-end delay, average hop count, and energy consumption. Full article

Characteristic mass fragmentation of 20 phenethylamine/tryptamine standards were investigated and compared by means of matrix assisted laser desorption/time-of-flight mass spectrometry (MALDI/TOFM), gas chromatography–electron ionization–mass spectrometry (GC-EI/MS) and liquid chromatography–electrospray ionization/mass spectrometry (LC-ESI/MS) methods. As a result, three characteristic peaks ([M]⁺ and fragments from the C_β-C_α bond breakage) were found to be unique and contained information useful in identifying 2C series compounds based on the GC-EI/MS method. We found that the protonated molecular ion ([M+H]⁺) and two types of fragments produced from the α-cleavage and β-cleavage processes were useful mass spectral information in the rapid screening and confirmation of phenethylamine and tryptamine derivatives when ESI/MS and MALDI/TOFMS methods were applied. This assay was successfully used to determine samples that contain illicit drugs. Full article

We report the preparation of a series of spacer-incorporated, tetra-amino cobalt (II) phthalocyanine (CoPc)-immobilized bacterial cellulose (BC) functional nanocomposites (CoPc@s-BC). Four kinds of flexible spacers with different lengths—diethylenetriamine (DT), triethylenetetramine (TT), tetraethylenepentamine (TP) and pentaethylenehexamine (PH)—were covalently attached onto pre-oxidized BC for the synthesis of the spacer-attached BC, and the attached spacers’ contents were carefully quantified. Using glutaraldehyde as a cross-linker, the CoPc catalyst was covalently immobilized onto the spacer-attached BC, and the immobilization steps were optimized by monitoring both the residual spacer contents and the resulting immobilized CoPc. All of the functionalization processes were characterized and confirmed by X-ray photoelectron spectroscopy (XPS). The series of spacer-incorporated, CoPc-immobilized BC nanocomposites, CoPc@s-BC, were used for the decoloration of dye wastewater. Both the adsorption capacity and adsorption rate were increased after the incorporation of spacers. When H₂O₂ was employed as an oxidant, dye molecules were catalytically oxidized with these nanocomposites. Electron paramagnetic resonance (EPR) spin-trapping results showed that the highly reactive hydroxyl radical (·OH) was involved in the catalytic oxidation process. The spacer length had a direct effect on the catalytic efficiency of CoPc@s-BC—the decoloration rate for CoPc@TP-BC was as high as 41 μmol·min⁻¹·g⁻¹, which was more than 50% higher than that without spacer. Full article

Nanotechnology is a potential and emerging field with multiple applications in different areas of study. The beneficial effects of the use of nanoparticles in agriculture have already been proven. The objective of this research was to determine if the foliar application of Cu nanoparticles (NPs) could increase the content of the bioactive compounds in tomato fruits. Our study considered four treatments with different concentrations of Cu nanoparticles (50, 125, 250, 500 mg L⁻¹, diameter 50 nm) applied twice during the development of the culture. The effects on the fruit quality and the contents of the antioxidant compounds were determined. The application of the Cu nanoparticles induced the production of fruits with greater firmness. Vitamin C, lycopene, and the ABTS antioxidant capacity increased compared to the Control. In addition, a decrease in the ascorbate peroxidase (APX) and glutathione peroxidase (GPX) enzymatic activity was observed, while the superoxide dismutase (SOD) and catalase (CAT) enzymes showed a significant increase. The application of Cu NPs induced a greater accumulation of bioactive compounds in tomato fruits. Full article

Rice husk and cotton straw were used to produce biochar under 300, 400, 500, 600, and 700 °C pyrolysis conditions, and the physicochemical properties of the obtained biochar samples were characterised. The effects of various adsorbent amounts, initial pH, and adsorption time on the Cd²⁺ adsorption performance were studied. The results showed that, at increasing pyrolysis temperatures, the biochar yield decreased, the ash content increased, the pH transitioned from acidic/neutral to basic/strongly basic, the biochar aromaticity gradually increased, and the biochar structure became more stable. In contrast, the hydrophilicity and polarity decreased, the specific surface area increased, and the number of oxygen-containing functional groups decreased. All these factors resulted in differences in the Cd²⁺ adsorption by the biochar samples. With increasing adsorbent content, the rate of Cd²⁺ adsorbed on the biochar gradually increased. The adsorption performance was optimal when the initial solution pH of the rice-husk and cotton-straw biochar samples was 5 and 6, respectively. The shortest time to achieve equilibrium was 30 min for rice-husk biochar, and 20 min for cotton-straw biochar. The Cd²⁺ adsorption data for both types of biochar were very well fitted with a pseudo-second-order kinetic model. Ion exchange and cation–π interactions may be the main factors influencing the Cd²⁺ adsorption by biochar. At the same time, the large specific surface area of biochar also plays a role in the Cd²⁺ adsorption. Full article

Acid stratification is a common issue in lead-acid batteries. The density of the electrolyte rises from the top to the bottom and causes inhomogeneous current distribution over the electrodes. The consequences are unequal aging processes provoking earlier battery failure. In stationary applications electrolyte circulation pumps are sporadical installed in the battery to mix the acid. For automotive applications passive mixing systems are implemented by some battery manufacturers against stratification. Stratification does not show any distinct voltage-current profile to be recognizable online. However, it increases the voltage and affects the impedance, which both are essential information for diagnostic purpose. Impedance spectra were performed here on lead-acid test cells with adjusted stratification levels to analyze the influence on the impedance in details. It is observed, that the high-frequency impedance is decreased in the stratified cell and that in contrast to this the charge-transfer resistance is increased. Based on simulations with a spatially-resolved equivalent electrical circuit the increased charge-transfer resistance could be explained with an inhomogeneous State-of-Charge resulting in an accumulation of sulfate crystals in the bottom part of the electrodes. These sulfate crystals further affected recorded impedance spectra after the electrolyte was homogenized. Full article

Background: Ex vivo computer controlled circulatory reactors are advantageous for the investigation of circulatory systems. So far, most of the models have dealt with laminar or pulsatile flow. This study aimed to monitor blood vessel and vessel graft compliance continuously under physiological flow in real time. Methods: Human common iliac arteries and silicon tubes served as interposition grafts. Changes in wall diameter and displacement were analyzed. The artificial circulatory system (ACM) presented an “artificial heart” able to simulate various ejection pressures, ejection volumes (EV), and frequencies of pulsation (FP). ACM was validated by comparing medical data reconstructed with the 2D-speckle-tracking-technique (2DSTT). Results: Silicon tubes were more rigid compared to iliac arteries, as changes in diameter were approximately 48% lower (0.56 ± 0.007 mm vs. 0.83 ± 0.016 mm, p < 0.0001, for EV = 70 mL and FP = 60 min⁻¹). Wall displacement was 2.3-fold less pronounced in silicon tubes (1.45 ± 0.032 mm vs. 5.79 ± 0.043 mm for iliac arteries (p < 0.0001)). FP and EV did not further increase differences in wall displacement between both types of grafts. There were no significant changes between results gathered from ACM and 2DSTT. Conclusions: The ACM was successfully validated by 2DSTT with the use of selected grafts. It may become a useful tool to investigate different types of vascular grafts. Full article

Purpose: In the light of decarbonizing the passenger car sector, several technologies are available today. In this paper, we distinguish plug-in hybrid electric vehicles (PHEV), electric vehicles (EV) with a modest battery capacity of 40 kWh, and long-range EVs with 90 kWh installed. Given that the average motorist only rarely performs long-distance trips, both the PHEV and the 90 kWh EV are considered to be over-dimensioned for their purpose, although consumers tend to perceive the 40 kWh EV’s range as too limiting. Therefore, in-life range modularity by means of occasionally using a range-extender trailer for a 40 kWh EV is proposed, based on either a petrol generator as a short-term solution or a 50 kWh battery pack. Method: A life cycle assessment (LCA) is presented for comparing the different powertrains for their environmental impact, with the emphasis on local air quality and climate change. Therefore, the combination of a 40 kWh EV and the trailer options is benchmarked with a range of conventional cars and EVs, differentiated per battery capacity. Next, the local impact per technology is discussed on a well-to-wheel base for the specific situation in Belgium, with specific attention given to the contribution of non-exhaust emissions of PM due to brake, tyre, and road wear. Results: From a life cycle point of view, the trailer concepts outperform the 90 kWh EV for the discussed midpoint indicators as the latter is characterized by a high manufacturing impact and by a mass penalty resulting in higher contributions to non-exhaust PM formation. Compared to a petrol PHEV, both trailers are found to have higher contributions to diminished local air quality, given the relatively low use phase impact of petrol combustion. Concerning human toxicity, the impact is proportional to battery size, although the battery trailer performs better than the 90 kWh EV due to its occasional application rather than carrying along such high capacity all the time. For climate change, we see a clear advantage of both the petrol and the battery trailer, with reductions ranging from one-third to nearly sixty percent, respectively. Conclusion: Whereas electrified powertrains have the potential to add to better urban air quality, their life cycle impact cannot be neglected as battery manufacturing remains a substantial contributor to the EV’s overall impact. Therefore, in-life range modularity helps to reduce this burden by offering an extended range only when it is needed. This is relevant to bridge the years up until cleaner battery chemistries break through, while the energy production sector increases the implementation of renewables. Petrol generator trailers are no long-term solution but should be seen as an intermediate means until battery technology costs have further dropped to make it economically feasible to commercialize battery trailer range-extenders. Next, active regulation is required for non-exhaust PM emissions as they could dominate locally in the future if more renewables would be applied in the electricity production process. Full article