RSS 1.0Engineering
Recent Submissions
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Acoustic detection and mapping of submerged stone age sites with knapped flintThis chapter presents a non-destructive survey technique under development: acoustic detection and mapping of submerged Stone Age sites. While it has been experimentally established that reasonable amounts of man-knapped flint pieces can be excited by and respond to specific acoustic signal through meters of sea floor sediment, it is not yet known how small assemblages of knapped flint pieces one can obtain a response from and how deep in the sea floor this will be possible. It also remains to check experimentally if other knapped materials than flint (obsidian, quartzite, basalt, etc.) respond in a similar way given that some of their basic characteristics potentially differ from those registered for flint. This technique will facilitate a much more effective and cheap detection and mapping of submerged Stone Age sites with knapped lithics compared to the techniques available at present. Especially the deep sites down to the approximately 120 m deep coastlines of the glaciations, which are very difficult to localize today, represent an important research potential. In general, the highly productive coast lines must be assumed to have played an important economic role of human society from the Palaeolithic onwards, which means that we miss an important part of the picture of the human cultural development. In spite of the promising perspective of methodological improvement, one must be aware of the limitations of the acoustic method. It will not be able to map Stone Age sites lacking knapped lithics. This chapter presents and discusses the method’s basic technological principles and the experimental results obtained so far, elucidating its potential.
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On some problems related to the fabrication of a metallic micro-perforated panel for noise control applicationsMicro-Perforated Panels (MPP) are widely used nowadays as a noise control solution. Such materials present many interesting advantages and are considered to be among the latest innovative sound absorbing materials. For these reasons, many models are proposed in the literature to predict their acoustic behavior. However, the accuracy of these models depends on the assumptions under which they are derived and more often on the MPP samples built for their validation. Rigorous attention is therefore needed to insure convenient fabrication of samples for the MPP. This paper investigates some important problems related to the fabrication of metallic MPP samples used for noise control applications. Particular emphasis is given to the hole drilling effects. It is shown for instance that the presence of shavings inside the perforation may alter or change the MPP acoustic response. This work supports the design of optimum MPP for noise control applications such as duct mufflers, room acoustics, and transport domain and environment noise abatement.
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Progress in non-destructive 3D characterization and modelling of aerospace compositesThe route to lighter composite aerostructures requires advanced 3D non-destructive characterization methods to provide confidence that the as-built structures conform to the design expectations. Whilst X-ray Micro-CT imaging is an excellent non-destructive testing (NDT) method for 3D characterization, it can rarely be applied in production. In its place, ultrasound is an ideal vehicle for exploring the detailed local response of a composite structure, providing data that can be inverted to give 3D fiber direction, ply spacing, fiber volume fraction and 3D porosity distribution. The first material property that must be determined to enable full characterization and materials modelling of as-manufactured composite components is the vector field representing the fiber direction at every point. Inversion methods have been developed for converting 3D NDT data sets into 3D profiles of material properties. A study of ultrasonic analytic-signal propagation in composites has resulted in a novel method for tracking plies and ply drops, in ultrasonic full-waveform data sets. This paper presents methods for tracking the 3D orientation of fiber tows in the plies throughout a laminated composite structure and examples of finite-element models built directly from this NDT information.
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Visual SLAM for dynamic environments based on object detection and optical flow for dynamic object removalIn dynamic indoor environments and for a Visual Simultaneous Localization and Mapping (vSLAM) system to operate, moving objects should be considered because they could affect the system’s visual odometer stability and it is position estimation accuracy. vSLAM can use feature points or a sequence of images as it is only source of input in order to perform localization while simultaneously creating a map of the environment. A vSLAM system based on ORB-SLAM3 and on YOLOR was proposed in this paper. The newly proposed system in combination with an object detection model (YOLOX) applied on extracted feature points is capable of achieving 2-4% better accuracy as compared to VPS-SLAM and DS-SLAM. Static feature points such as signs and benches were used to calculate the camera position and dynamic moving objects were eliminated by using the tracking thread. A specific custom personal dataset that includes indoor and outdoor RGB-D pictures of train stations including dynamic objects and high density of people, ground truth data, sequence data, video recording with the train stations and X, Y, Z data was used to validate and evaluate the proposed method. The results show that ORB-SLAM3 with YOLOR as object detection achieves 89.54% of accuracy in dynamic indoor environments compared to previous systems such as VPS-SLAM.
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Visual SLAM algorithms and their application for AR, mapping, localization and wayfindingVisual simultaneous localization and mapping (vSLAM) algorithms use device camera to estimate agent’s position and reconstruct structures in an unknown environment. As an essential part of augmented reality (AR) experience, vSLAM enhances the real-world environment through the addition of virtual objects, based on localization (location) and environment structure (mapping). From both technical and historical perspectives, this paper categorizes and summarizes some of the most recent visual SLAM algorithms proposed in research communities, while also discussing their applications in augmented reality, mapping, navigation, and localization.
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Review of machine learning based fault detection for centrifugal pump induction motorsCentrifugal pumps are an integral part of many industrial processes and are used extensively in water supply, sewage, heating and cooling systems. While there are several review papers on machine learning-based fault diagnosis on induction motors, its application to centrifugal pumps has received relatively little attention. This work attempts to summarize and review recent research and development in machine learning-based pump condition monitoring and fault diagnosis. The paper starts with a brief explanation of pump operation including common pump faults and the main principles of the motor current signature analysis (MCSA) method. This is followed by a detailed explanation of various machine learning-based methods including the types of detected faults, experimental details and reported accuracies. The performances of different approaches are then presented systematically in a unified table. Finally, the authors discuss practical aspects and challenges related to data collection, storage and real-world implementation.
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A review of fuel cell technology for commercial vehicle applicationsThe demanding energy storage requirements of many commercial vehicle applications are extremely difficult to meet for pure battery electric vehicles (BEVs) due to the limited energy density of batteries. Fuel cells appear to be the only viable propulsion technology that is able to meet commercial vehicle powertrain requirements with zero local greenhouse gas emissions. Since almost all fuel cell vehicles (FCVs) contain a high voltage battery, some additional complexity is introduced since the hybrid energy storage system must be sized and controlled appropriately. An understanding of the strengths and weaknesses of each system is therefore essential in FCV design. The aim of this technology review is to provide an overview of fuel cell technologies in commercial vehicle applications including assessments of alternative powertrain and fuel cell types, advantages and disadvantages of fuel cell and battery systems and the implications of these on the powertrain sizing as well as control considerations of FCVs.
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Exploring the potential benefits of Ethanol Direct Injection (EDI) timing and pressure on particulate emission characteristics in a Dual-Fuel Spark Ignition (DFSI) engineNowadays, particulate matter emitted by vehicles severely impacts environmental quality and human health. In this paper, the potential benefits of Ethanol Direct Injection (EDI) timing and pressure on particulate emission characteristics in a Dual-Fuel Spark Ignition (DFSI) engine were initially and systematically explored. The experimental results illustrate that by delaying EDI timing from -340 ºCA to -300 ºCA, there is a significant benefit in both particulate number and mass concentration. Furthermore, the size distribution curve of particulate number changes from bimodal to unimodal, meantime size distribution curves of particulate mass consistently concentrate on the accumulation mode. By increasing EDI pressure from 5.5 MPa to 18 MPa, the droplet size of ethanol spray can be effectively reduced. The benefit of increasing EDI pressure is more apparent in reducing particulate number is than particulate mass. The concentration of number and mass for total particulates have a reduction of 51.15% and 22.64%, respectively. In summary, it was demonstrated that an appropriate EDI timing or high EDI pressure could be a practical and efficient way to reduce particulate emissions in a DFSI engine.
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Cell spreading behaviors on hybrid nanopillar and nanohole arraysAlthough nanopillars (NPs) provide a promising tool for capturing tumor cells, the effect of mixing NPs with other nanopatterns on cell behavior remains to be further studied. In this paper, a method of fabricating silicon nanoscale topographies by combining laser interference lithography with metal assisted chemical etching was introduced to investigate the behaviors and pseudopodia of A549 cells on the topologies. It was found that cells had a limited manner in spreading with small cell areas on the silicon nanopillar (SiNP) arrays, but a good manner in spreading with large cell areas on the silicon nanohole (SiNH) arrays. When on the hybrid SiNP/SiNH arrays, cells had medium cell areas and they arranged orderly along the boundaries of SiNPs and SiNHs, as well as 80% of cells displayed a preference for SiNPs over SiNHs. Furthermore, the lamellipodia and filopodia are dominant in the hybrid SiNP/SiNH and SiNP arrays, respectively, both of them are dominant in the SiNH arrays. In addition, the atomic force acoustic microscopy was also employed to detect the subsurface features of samples. The results suggest that the hybrid SiNP/SiNH arrays have a targeted trap and elongation effect on cells. The findings provide a promising method in designing hybrid nanostructures for efficient tumor cell traps, as well as regulating the cell behaviors and pseudopodia.
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Effect of different trypsin concentrations on SMCC-7721 cell adhesionIn this work, living human liver cancer cells (SMCC-7721) were exposed to the trypsin solution at the concentrations of 1.5 mg/ml, 2.0 mg/ml, 2.5 mg/ml, 3.0 mg/ml, 3.5 mg/ml and 4.0 mg/ml, respectively. After 2 min of dosing time, the physical and mechanical properties of the cells were detected by Atomic Force Microscope (AFM). With the increase of the trypsin concentration, the adhesion force between the cell and the probe gently decreased. The maximum lateral deflection voltage variation of the probe, which reflected the maximum external force that kept the cells attached to the substrate, was significantly reduced. This work indicates that we may change the cell morphology and regulate the mechanical properties of cells by controlling the concentration of trypsin solution to treat cells, which has important implications for bioengineering and cell manipulation.
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Laser interference field induced re-distribution of Ag nanoparticle arraysThe wide application of metal nanoparticle arrays has attracted much attention in the field of nanotechnology. Such as quantum dots, structural colors, sensors, metamaterials. In this work, we fabricated periodic micro-and nanostructures through the interference of two beams with the same frequency and vibration direction. By controlling the spot energy and light field energy distribution of Gaussian interference lithography, the various surface characteristics of Ag-Si material system (Ag@Si) are optimized, and the mass transfer brought by Oswald ripening is used to control the Rayleigh instability in the thermal dewetting process. To achieve the purpose of the periodic gradient Ag nanoparticle arrays (AgNPs) pattern can be controlled. The experimental results show that the periodic micro-and nanostructures can be obtained by optimizing the spot energy and the number of pulses.
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Fabrication of hierarchical Ti6Al4V structures by hydrothermal treatment and laser interference lithography with enhanced ice resistanceIcing widely exists in aerospace, transportation and electric power communication, causing great safety risks to people's production and life. Inhibiting icing is of great significance in practical engineering applications, and thus, employing an economical and efficient anti-icing method is a research hotspot. In this work, an anti-icing structured surface was fabricated by combining direct laser interference lithography (DLIL) with hydrothermal treatment. A micro-pillar array structure on the tc4 substrate was easily fabricated by DLIL, and a layer of nano-grass structure on the micro-pillar array was grown by hydrothermal treatment. These hierarchically textured surfaces exhibited low-temperature-adaptive water repellency (150° at −10°C, which delayed the frozen time (DT∼1h) and dropped frozen temperature. The above conditions were analyzed from the angle of wettability and heat conduction, and the influence of structure and wettability on ice resistance was discussed.
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Effect of astragalus polysaccharides on cancer cells studied by AFMAs a traditional Chinese medicine, astragalus and its products are used in cancer treatment aiming to reduce the side effects of chemotherapy. Cells are the most basic unit of living organisms, and AFM directly obtains information from living cells on the micro/nano scale. Therefore, the use of AFM to study the interaction between astragalus and cells is conducive to a full range of drug efficacy evaluation and provides a new way for drug development. In this paper, astragalus polysaccharides were extracted from astragalus, which were diluted into solutions of different concentrations. Combined with the MTT experiment, the effects of Astragalus polysaccharide on cancer cells and benign cells were studied by AFM.
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A dynamic feedback algorithm of AFM based on cell morphology changesThe atomic force microscope (AFM) used in biological research as a powerful tool has been for many years. However, the imaging of living cells is still a problem as the sample is too high and too soft to obtain their accurate morphologies. Especially in the high-speed scanning mode, AFM does not have enough judgments to make accurate measurements at the down part of the sample. In this study, we propose an improved control method to improve the image quality of living human colon cancer cells (SW480) especially in the down part during the scanning.
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Analysis of the mechanical properties of chromosomes in air and liquid by AFMChromosomes contain all the genomic information thus making the study of chromosomes practical and significant. Herein, the morphologies of chromosomes prepared with different methods were monitored by atomic force microscopy (AFM). Moreover, the mechanical properties of chromosomes in air and liquid were investigated quantitatively through AFM-based force spectroscopy. The differences of chromosome morphologies and mechanical properties caused by sample preparations indicated that the chromosome characterization in liquid was more meaningful to reveal the physiological characteristics of chromosomes.
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Study on the conductivity of DNA molecules under magnetic fieldsIn this work, the conductivity of DNA molecules under the effect of magnetic fields was studied by conductive atomic force microscopy (C-AFM). It is found that the self-assembly images of 7.5 ng/μL DNA aqueous solution on the bare mica and Au layer surfaces are quite different, and the DNA molecules are obviously stretched on the Au layer surface and single stretched DNA strands were obtained. In addition, the conductivity of single stretched DNA molecules in the horizontal stable magnetic field (SMF) and high frequency electromagnetic field (HFEF) were investigated in detail. The results showed that the conductivity of DNA was weakened by the effect of magnetic field.
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Effect of SMMC-7721-derived exosomes on hepatocytes studied by AFMExosomes play an important role in the early diagnosis and development of hepatocellular carcinoma (HCC). In the past, researchers mainly studied the contents of exosomes and the biological mechanism on cells, but the changes of mechanical properties of cells caused by exosomes are not clear. In this study, the changes of mechanical properties of hepatocytes (L-02) co-cultured with exosomes (7721-exos) derived from HCC (SMMC-7721) with low metastatic ability were studied. The 7721-exos were able to promote the proliferation and rearrange the cytoskeleton of L-02 cells. The atomic force microscopy measurement results showed that the height was increased, the adhesion and the elastic modulus were reduced. The effect was concentration dependent. The changes of cell mechanical properties induced by exosomes were of great significance for further studying the mechanism of exosomes.
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Tapping atomic force microscopy imaging at phase resonanceTapping atomic force microscope (TM-AFM) can measure soft samples, which has the advantages of low loss and high resolution, and has been widely used in the characterization of soft micro-nano materials by atomic force microscope (AFM). The phase image in TM-AFM contains sample properties, and it is an important method to characterize the sample by TM-AFM. At present, researchers usually select the frequency near the first resonance peak of the probe to drive its vibration to carry out scanning imaging. However, the phase sensitivity near the first-order resonance of the probe is not high. Therefore, the phase image of TM-AFM is also less sensitive to characterize micro-nano materials. In order to improve the phase sensitivity of the probe, the probe working at the phase resonance peak was selected in this paper to improve the phase sensitivity of the probe vibration and the imaging quality of TM-AFM phase image. The experimental results show that the phase image of phase resonance-atomic force microscope (PR-AFM) can provide not only the surface information but also the structure information of the sample subsurface. PR-AFM can be applied for better characterization of micro and nano materials.
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Growth behavior of SHSY5Y cells on hybrid micro-pit and nano-pillar arraysThe directional arrangement and extension of cells is of great significance in the tissue engineering field. Great efforts have been made to study the effects of micro- or nano- structures on cell behaviors, but they are still poorly understood. In this work, hybrid micro/nano structures prepared by combining laser marking technology with metal assisted chemical etching (MACE) were introduced to study their effect on the growth behavior of SHSY5Y cells. It was found that the cells on the silicon micro-pit arrays (SiMP arrays, unetched substrate) were arranged orderly along the edge of the micro-pits, stretched and connected with each other, while the cells on the hybrid silicon micro-pit and silicon nano-pillar arrays (hybrid SiMP/SiNP arrays, etched substrates) were also arranged in an orderly manner with a relatively short cell stretch, but displayed a preference for independent growth. In addition, about 90% of cells showed a preference for growing on the area of nano-pillars (NPs), and only 10% of cells on the area of micro-pits (MPs) on the etched substrate. The results showed that the hybrid SiMP/SiNP arrays trapped cells and restricted the cell spreading. Thus, this approach is of great significance for the study of independent growth behavior of cells on the substrate in the field of single neuron research.
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Multi-parameter AFM characterization of INS-1 cellsAFM-based single cell force spectroscopy has been employed wildly, while more work is needed for the mechanical detection of diabetes-related cells (INS-1 cells). In this study, a multi-parameter AFM characterization was performed to detect the mechanical properties of INS-1 cells in situ. High resolution topographies and concurrent mechanics were obtained by taking the advantage of the quantitatively imaging (QI) mode AFM. The analyses of force curves and force maps jointly presented the multiple parameters involved in the cell mechanics. The AFM force spectroscopy measurement provides full analysis and comprehensive understanding of cell mechanics.
