Abstract

Loop closure detection is one of the most important module in Simultaneously Localization and Mapping (SLAM) because it enables to find the global topology among different places. A loop closure is detected when the current place is recognized to match the previous visited places. When the SLAM is executed throughout a long-term period, there will be additional challenges for the loop closure detection. The illumination, weather, and vegetation conditions can often change significantly during the life-long SLAM, resulting in the critical strong perceptual aliasing and appearance variation problems in loop closure detection. In order to address this problem, we propose a new Robust Multimodal Sequence-based (ROMS) method for robust loop closure detection in long-term visual SLAM. A sequence of images is used as the representation of places in our ROMS method, where each image in the sequence is encoded by multiple feature modalites so that different places can be recognized discriminatively. We formulate the robust place recognition problem as a convex optimization problem with structured sparsity regularization due to the fact that only a small set of template places can match the query place. In addition, we also develop a new algorithm to solve the formulated optimization problem efficiently, which guarantees to converge to the global optima theoretically. Our ROMS method is evaluated through extensive experiments on three large-scale benchmark datasets, which record scenes ranging from different times of the day, months, and seasons. Experimental results demonstrate that our ROMS method outperforms the existing loop closure detection methods in long-term SLAM, and achieves the state-of-the-art performance.

Abstract

The \(\hbox {Sr}_{0.88}\hbox {Bi}_{0.12}\hbox {TiO}_{3}/\hbox {SrTi}_{0.92}\hbox {Mg}_{0.08}\hbox {O}_{3}\) (SBTO/STMO) heterostructure films were prepared on \(\hbox {p}^{+}\hbox {-Si}\) substrates by sol–gel spin-coating technique, and the films had good crystallinity and uniform grain distribution. The heterostructure films with a structure of Ag/SBTO/STMO/\(\hbox {p}^{+}\hbox {-Si}\) exhibited a bipolar, remarkable resistance-switching characteristic, and \(R_{\mathrm{HRS}}/R_{\mathrm{LRS}}\,\,{\sim }10^{4}\). More importantly, the heterostructure films showed rectifying characteristic in the low resistance state (LRS), and the rectification ratio can reach \(10^{2 }\) at \(\pm 1\hbox { V}\). The dominant resistive-switching conduction mechanism of high resistance state (HRS) was Ohmic behaviour, and the LRS changed to space charge-limited current (SCLC).

Abstract

This paper studies the optimization and implementation of human-machine dialog system based on cloud computing technology. Firstly, the coarse-perceived hash generation based on the formant frequency is studied, and the detail-aware hash generation based on the energy difference in the time domain is studied. Then, the combination of coarse-perceived hash and detail-aware hash is elaborated. Secondly, the algorithm is tested and emulated. The algorithm matches the coarse-perceived hash sequence with fewer bits, and returns the voice number with similar rough features to the index voice after matching successfully, and matches the detail-aware hash sequence of the corresponding number voice. Then, the exact match of the result is gotten. Finally, it is concluded that the algorithm in this paper can effectively recognize the human voice.

Abstract

‘Huangguan’ (HG) and ‘Whangkeumbae’ (HK) pears are two important Asian pear cultivars in China and South Korea, respectively. In practical production, ‘Huangguan’ pear is a drought-tolerant genotype while ‘Whangkeumbae’ pear is drought-sensitive. To uncover the mechanisms underlying pear tree tolerance to drought stress, a comprehensive transcriptome analysis was performed in this study. The results revealed a total of 1185 and 1667 differently expressed genes (DEGs) between control and treated plants of HG and HK pear, respectively. KEGG pathways enrichment analysis revealed that the DEGs were involved in the metabolism and signal transduction of various phytohormones. In HG, the DEGs annotated as ABA, gibberellic acid (GA), and salicylic acid (SA) were all upregulated, while those DEGs annotated as jasmonic acid (JA) were upregulated or downregulated. In HK, the DEGs annotated as ABA and JA were both upregulated or downregulated, but there were no DEGs annotated as GA and SA. In addition, there were 743 DEGs expressed in HG, but not in HK. Among them, there were 288 DEGs whose absolute values of log₂(fold-change ratio) were greater than 2. Eight of the 288 DEGs were selected randomly for validating the reproducibility and accuracy of the transcriptome RNA-Seq data by using quantitative-PCR. Our results will be helpful for breeding drought-tolerant pear cultivars.

Abstract

The arrangement of oligothiophenes is essential for understanding the relationship between structure and properties particularly in the organic electronic field. The self-assembly behaviors of helical (TMS)₂-[7]helicene (T1), naphthalene-cored double (TMS)₂-[7]helicene (T2), and saddle-shaped cyclooctatetrathiophene (T3), its derivative α,α,α,α-tetraphenyl-cyclooctatetrathiophene (T4) on solid surface are firstly investigated by using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) calculation. 1,3,5-Tris(10-carboxydecyloxy)-benzene (TCDB) is selected to build flexible host networks to immobilize these oligothiophenes in order to capture their molecular adsorption images successfully. The observed monodisperse or polydisperse filling and long-range alignment of oligothiophenes are described based on the non-covalent interactions and commensurate structure between olihothiophene and cavity. We speculate that those molecularly defined alignments could lead to significantly understanding the application of such ordered monolayer in organic electronic devices.

Abstract

The Internet of Things work by constantly sensing the physical properties in the vicinity of the user such as ambient light, sounds, motion and temperature. These sensors produce huge volumes of data that has to be efficiently sifted for relevant events required triggering certain actions. In addition, filtering has to be performed to ensure that privacy-sensitive confidential data is not leaked. Efficient and expressive pattern matching is thus a key enabling technology for the full realization of ambient and humanized computing. The bulk of research in this area has focused on the use of specialized hardware and reducing of the memory footprint. Unfortunately, there has been limited work if any on optimizing the core elements of pattern matching- the regular expression language and the compilation process that is responsible for converting patterns into internal data structures. The importance of writing good REs so that on compilation they do not lead to unrealizable data structures is relatively less understood. In the proposed research, we empirically compare different RE processing engines and practically demonstrate that the compilation phase is highly memory intensive and time-consuming as compared to the matching phase -and hence is worth exploring for new techniques and optimizations. As a second important contribution, we propose a novel technique for defining regular expressions by utilizing JavaScript Object Notation. Our evaluation with carefully created patterns shows that the performance of the proposed technique is at par with competing approaches. It is also less ambiguous, extensible, more expressive and much appropriate for defining large and complex patterns.

Abstract

Nanoparticles (NPs) tend to adsorb matrix molecules like proteins and lipids incubated with biological fluids, forming a biological corona. While the formation and functions of protein corona have been studied extensively, little attention has been paid to lipid adsorption on NPs. However, lipids are also abundantly present in biological fluids and play important roles in processes like cell signaling and angiogenesis. Therefore, in this study, we established the analytical procedure for study of lipid adsorption on three different types of NPs in two matrices: human serum and heavy cream, using nanoflow liquid chromatography-mass spectrometry (nanoflowLC-MS). Serum was chosen to represent the common environment the NPs would be present once entering human body, and heavy cream was the representative food matrix NPs may be added to improve the color or taste. Steps of liquid-liquid extraction were established and optimized to achieve maximum recovery of the adsorbed, standard lipids from the NPs. Then, the LC-MS/MS method was developed to attain base-line separation of the standard lipids that represent the major lipid classes. At last, the lipid adsorption profiles of the three NPs were compared. We found that the lipid adsorption profile on the same type of NP was significantly different between the two matrices. The established method will help us investigate lipid adsorption on additional NPs and reveal how it could be affected by the physiochemical properties of NPs and the presence of proteins and other components in the biological matrix.

Abstract

Injectable hydrogels are a potential therapy for mitigating adverse left ventricular (LV) remodeling after myocardial infarction (MI). Previous studies using magnetic resonance imaging (MRI) have shown that hydrogel treatment improves systolic strain in the borderzone (BZ) region surrounding the infarct. However, the corresponding contractile properties of the BZ myocardium are still unknown. The goal of the current study was to quantify the in vivo contractile properties of the BZ myocardium post-MI in an ovine model treated with an injectable hydrogel. Contractile properties were determined 8 weeks following posterolateral MI by minimizing the difference between in vivo strains and volume calculated from MRI and finite element model predicted strains and volume. This was accomplished by using a combination of MRI, catheterization, finite element modeling, and numerical optimization. Results show contractility in the BZ of animals treated with hydrogel injection was significantly higher than untreated controls. End-systolic (ES) fiber stress was also greatly reduced in the BZ of treated animals. The passive stiffness of the treated infarct region was found to be greater than the untreated control. Additionally, the wall thickness in the infarct and BZ regions was found to be significantly higher in the treated animals. Treatment with hydrogel injection significantly improved BZ function and reduced LV remodeling, via altered MI properties. These changes are linked to a reduction in the ES fiber stress in the BZ myocardium surrounding the infarct. The current results imply that injectable hydrogels could be a viable therapy for maintaining LV function post-MI.

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Abstract

To dispose the increasing oil pollution, tremendous effective ways have been proposed to deal with the oil/water mixture. In this study, polyphenylene sulfide (PPS) microfiber membrane was firstly employed as the substrate for separation. Polyethylene wax (PEW) powder and polytetrafluoroethylene (PTFE) ultrafine powder were simply and effectively introduced on the PPS membrane by employing one-step spray-coating method. The as-prepared membrane displayed excellent oil affinity and water-repellent behaviors. Significantly, the obtained membrane showed long-term stability under various extreme conditions such as strong acid, alkali, salt solutions and high temperature. Moreover, this membrane could maintain high oil flux (above 3500 L/m² h) and separation efficiency (above 98%) even after 20 cycles of oil/water separation and isolate a wide range of oil/water mixture effectively. The fabrication of superhydrophobic and superoleophilic PPS microfiber membrane presented here can be easily scaled up on a large scale, which will provide attractive potential in practical oil/water separation.

Abstract

Development of fan deltas alongside intrabasinal structural highs has been overlooked compared to those forming on basin margins. However, these fan deltas may provide important clues regarding the tectonic and climatic controls on deposition during rift development. This paper documents fan delta deposition alongside an intrabasinal structural high within the Early Cretaceous Xiagou Formation of the Jiuquan Basin, China, using subsurface geological and geophysical data. Deposits observed in drill core support fan delta deposition occurring almost exclusively through subaerial and subaqueous gravity flows. Subsurface mapping reveals a consistent decrease in the areal extent of fan deltas from lowstand to highstand system tracts, suggesting that deposition alongside the structural high is sensitive to lake-level changes. The temporal and spatial distribution of the fan deltas display retrogradational stacking patterns, where fan deltas exhibit a decreasing lateral extent up-sequence until fan delta deposition terminated and was replaced by deposition of fine-grained lacustrine deposits. The retrogradational stacking patterns observed alongside the intrabasinal structural high are not observed in fan deltas along the basin margin in the lower parts of the Xiagou Formation. Subsidence profiles also show differential subsidence across the basin during the earliest stages of this formation, likely resulting from border fault movements. These data suggest that non-uniform stacking patterns in the lower parts of the Xiagou Formation reflect basin-scale tectonic movements as the dominant control on synrift deposition patterns. However, later stages of Xiagou Formation deposition were characterized by uniform subsidence across the basin, and uniform retrogradational stacking patterns for fan deltas alongside the intrabasinal structural high and border fault. These observations suggest that basin-scale tectonic movements played a relatively limited role in controlling sediment deposition, and imply a potential change to regional-scale processes affecting fan delta deposition during later synrift stages. Climate change is favored here as the region-scale control on the uniform retrogradational fan delta stacking patterns. This assertion is supported by pollen assemblages, isotope signatures, and organic geochemical analyses, which collectively suggest a change from a humid to semi-arid environment during later synrift stages. We suggest that variations in stacking patterns between different fan delta systems can provide insights into the basin- and regional-scale processes that control rift basin deposition.

Abstract

Abstract

Toxicarioside N (Tox N), a natural product extract from Antiaris toxicaria, has been reported to induce apoptosis in human gastric cancer cells. However, the mechanism and actual role of autophagy in Tox N-induced apoptosis of human gastric cancer cells remains poorly understood. In the current study, we demonstrated that Tox N could induce autophagy by inhibiting the Akt/mTOR signaling pathway in SGC-7901 cells. Moreover, we found that the inhibition of autophagy by 3-methyladenine, an autophagy inhibitor, enhanced Tox N-induced apoptotic cell death. However, the stimulation of autophagy by rapamycin, an autophagy activator, remarkably suppressed Tox N-induced apoptosis, suggesting that autophagy plays a protective role in Tox N-induced apoptosis. Thus, the results from this study suggested that Tox N combination with an autophagy inhibitor might be a promising strategy to enhance the anticancer activity of Tox N for the treatment of human gastric cancer.

Abstract

Muddy baffles are one of the major geological factors controlling the underground fluid flow as well as the remaining oil distribution. This study used detailed drilling data from the E₁f₁ reservoir in the X Oilfield, Subei Basin, China, to investigate the hierarchical muddy baffles developed on lacustrine delta fronts and their precise cross-well correlation. According to the theories on allogenic and autogenic cycles as well as the genesis and scales of muddy baffles, five orders of muddy baffles were classified, which provided various degrees of difficulty when attempting interwell correlation. Under the guidance of a reliable stratigraphic model, the precise cross-well correlation of muddy baffles could be achieved and the key point of establishment of this stratigraphic model was to calculate foreset angles of hierarchical muddy baffles during deposition. During calculation, the relationships between sediment flow direction, higher-order strata dipping direction, well types and well trajectory direction should all be taken into consideration and some other angles (referred to here as θ₁, θ₂ and θ₃) should also be measured. Such new methods of cross-well correlation for hierarchical muddy baffles could greatly reduce the uncertainties and multiple solutions, which in turn would be significant for efficient development and oil recovery enhancement in the reservoirs.

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Abstract

Ag₃PO₄ and chitosan fiber (CF) composites were successfully fabricated using an in situ growth technique. The structure and properties of the obtained Ag₃PO₄/CF composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy, and UV–visible diffuse reflectance spectroscopy. SEM results suggested that the 50–500 nm Ag₃PO₄ particles grew on the CF surface into a spherical or dentate shape. Photocatalytic degradation of methyl orange (MO) solution was used as a typical reaction to evaluate the visible-light photocatalytic performance of the Ag₃PO₄/CF composites. The reaction results indicated that the Ag₃PO₄/CF composites-3 exhibited excellent photodegradation efficiency, with 93.8% removal of the MO solution. The effects of MO concentrations and cycling runs on the photocatalytic performance of the Ag₃PO₄/CF composites were evaluated as well.

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Abstract

By utilizing the concept of generalized order, we investigate the growth of Laplace–Stieltjes transform converging in the half plane and obtain one equivalence theorem concerning the generalized order of Laplace–Stieltjes transforms. Besides, we also study the problem on the approximation of this Laplace–Stieltjes transform and give some results about the generalized order, the error, and the coefficients of Laplace–Stieltjes transforms. Our results are extension and improvement of the previous theorems given by Luo and Kong, Singhal, and Srivastava.