Background Subtraction Based on Perception-Contained Piecewise Memorizing Framework

A key issue for full-time video surveillance is to search or establish a reference image of background which corresponds to current video frame. However, background that was ever in presence long time ago is enclosed or discarded due to background forgetting assumption. How to rapidly pick up or even rebuild long-term background needs to be discussed. This paper aims to present a framework for background maintenance in order to solve the problem. A piecewise memorizing framework is proposed for matching, updating and even rebuilding long-term background. Based on the metaphors of psychological selective attention theory, the framework is composed of a prior piecewise perception processor for intensity stationary test. Besides, a hierarchical memorizing mechanism constitutes the other part of the framework for overcoming the exponential forgetting of long period background appearances. Applied to Gaussian mixture model (GMM), this framework is capable of maintaining short-term background states, identifying long period background appearances, and rapidly adjusting to new background states according to different expressions derived from the prior perception of scene intensity changes. Its effectiveness can be demonstrated by experimental results for solving various typical problems

A High Performance Sensor for Triaxial Cutting Force Measurement in Turning

This paper presents a high performance triaxial cutting force sensor with excellent accuracy, favorable natural frequency and acceptable cross-interference for high speed turning process. Octagonal ring is selected as sensitive element of the designed sensor, which is drawn inspiration from ring theory. A novel structure of two mutual-perpendicular octagonal rings is proposed and three Wheatstone full bridge circuits are specially organized in order to obtain triaxial cutting force components and restrain cross-interference. Firstly, the newly developed sensor is tested in static calibration; test results indicate that the sensor possesses outstanding accuracy in the range of 0.38%–0.83%. Secondly, impacting modal tests are conducted to identify the natural frequencies of the sensor in triaxial directions (i.e., 1147 Hz, 1122 Hz and 2035 Hz), which implies that the devised sensor can be used for cutting force measurement in a high speed lathe when the spindle speed does not exceed 17,205 rev/min in continuous cutting condition. Finally, an application of the sensor in turning process is operated to show its performance for real-time cutting force measurement; the measured cutting forces demonstrate a good accordance with the variation of cutting parameters. Thus, the developed sensor possesses perfect properties and it gains great potential for real-time cutting force measurement in turning

An Improved 1D-VAR Retrieval Algorithm of Temperature Profiles from an Ocean-Based Microwave Radiometer

In this study, a one-dimensional variational algorithm that combines brightness temperatures (BTs), measured by ocean-based microwave radiometers (MWR), with reanalysis data was developed to generate high accuracy temperature profiles. A forward radiative transfer model was used to simulate the BTs. For the V band (50–70 GHz), there is a good agreement between observations and simulations, but for K band (20–30 GHz), which is more affected by water vapor, large errors are observed. To reduce the errors, a combined temperature and water vapor background error covariance matrix is applied to the 1D-Var algorithm. In addition, a correction factor is added to the 1D-Var iterative equation to improve retrieval accuracy. The results of the improved 1D-Var method have been compared with the MWR built-in neural network (NN) method, original 1D-Var method, and radiosonde data, which shows that the retrievals of the combined 1D-Var method showed significant improvements between 0 to 10 km. The statistical results show that the maximum mean absolute error of the combined 1D-Var method is less than 2 K in clear sky and cloudy conditions. This paper demonstrates that the proposed combined 1D-Var method has better performance than many known retrieval methods

A review of fracture mechanic behaviors of rocks containing various defects

The existence of defects in a rock mass is a vital factor complicating the mechanical response of the rock mass under stress. The characteristics of defects control the rock mass’s mechanical behaviors. This report reviews the experimental studies on the influence of simulating the internal defects of rock mass’s mechanical properties. The effects of preexisting defects (shape, size, number, angle, and other factors) on the mechanical properties and failure modes of the rock are investigated from the perspectives of rock failure and fracture mechanics. The fracture propagation mechanisms of different defective rock masses are analyzed by studying the stress state of different defective rock masses under uniaxial compression. After the defective rock samples with varying inclination angles are destroyed, the relationship among the compressive strength, the fracture propagation, and the failure characteristics is explored. The primary findings are as follows. The increase in the size and number of defects rapidly damages the mechanical properties of the rock and intensifies defect penetration and expansion. The rock mechanics characteristics of fissured rocks with different inclination angles show two primary variations: one is a continuous increase, and the other is a decrease followed by an increase. This result is strongly related to the failure pattern of rocks with preexisting fissures. This investigation is crucial for further studying the failure modes of complex defective rock masses and the geotechnical engineering related to defective rocks

Performance Improvement of Recycled Concrete Aggregates and Their Potential Applications in Infrastructure: A Review

In the construction industry, natural aggregates (NA) can be replaced by recycled concrete aggregates (RCA), which can address the issue of construction-waste disposal and resolve the dilemma between demand and supply. This paper aims to systematically review the modification of RCA techniques and their application in producing recycled aggregate concrete (RAC). First, the pretreatment approaches for enhancing the properties of RCA are introduced. Next, the improved efficiency of these approaches and their influences on the workability, mechanical strengths, and permeability of RAC are analyzed and discussed. Subsequently, the effectiveness of different techniques and their cost/environmental impact are compared. Finally, some case studies of the application of RCA in infrastructure are presented, and the remaining challenges and perspectives are discussed. The results of this review work can extend the knowledge of RCA and RAC, as well as serving as a source of inspiration for further studies

Experimental Study on Rock-Like Specimens with Single Flaw under Hydro-Mechanical Coupling

In order to study the mechanical characteristics and cracking behavior of jointed rock mass under hydro-mechanical coupling, a series of uniaxial compression tests and triaxial compression tests were carried out on cylinder gypsum specimens with a single pre-existing flaw. Under different confining pressures, water pressure was injected on the pre-existing flaw surface through a water injection channel. The geometrical morphology and tensile or shear properties of the cracks were determined by X-ray computed tomography (CT) and scanning electron microscope (SEM). Based on the macro and micro observation, nine types of cracks that caused the specimen failure are summarized. The results of mechanical properties and crack behavior showed that the confining pressure inhibited the tensile cracks, and shear failure occurred under high confining pressure. The water pressure facilitated the initiation and extension of tensile crack, which made the specimens prone to tensile failure. However, under the condition of high confining pressure and low water pressure, the lubrication effect had a significant effect on the failure pattern, under which the specimens were prone to shear failure. This experimental research on mechanical properties and cracking behavior under hydro-mechanical coupling is expected to increase its fundamental understanding

Fecal microbiota transplantation for irritable bowel syndrome: a systematic review and meta-analysis of randomized controlled trials

ObjectiveWhether fecal microbiota transplantation (FMT) in patients with irritable bowel syndrome (IBS) is effective in improving outcomes remains controversial. We assessed the safety and efficacy of FMT for patients with IBS.MethodsIn this systematic review and meta-analysis, we searched PubMed, Embase, Web of Science, the Cochrane Library, the clinicaltrials.gov and International Clinical Trials Registry Platform (ICTRP) up to February 25, 2022, updated to March 28, 2023. Randomized controlled trials (RCTs) compared the stool and capsule FMT with placebo in patients with IBS were included. Two authors independently assessed study eligibility, extracted the data, and assessed risk of bias. We did meta-analysis with RevMan, and the Stata software was used for sensitivity analysis and meta-regression. The GRADE system was used to assess the quality of evidences. Mean difference (MD) or standardized Mean difference (SMD) with 95% CI for continuous data, and risk ratios (RR) with 95% CI for dichotomous data were used with random-effects models. The primary outcomes included the clinical response rate and IBS-SSS score. This study is registered with PROSPERO: CRD42022328377.ResultsNineteen reports from nine RCTs were included finally. Compared with the placebo, a single stool FMT could significantly decrease the IBS-SSS score at 1 month (MD=-65.75, 95%CI [-129.37, -2.13]), 3 months (MD=-102.11, 95% CI [-141.98, -62.24]), 6 months (MD=-84.38, 95%CI [-158.79, -9.97]), 24 months (MD=-110.41, 95%CI [-145.37, -75.46]), and 36 months (MD=-104.71, 95%CI [-137.78, -71.64]). It also could improve the clinical response rate at 3 months (RR=1.91, 95% [1.12, 3.25]), 24 months (RR=2.97, 95% [1.94, 4.54]), and 36 months (RR=2.48, 95% [1.65, 3.72]), and increase the IBS-QoL score at 3 months, 24 months, and 36 months. FMT did not increase the serious adverse event. The risk of bias was low, and the quality of evidence based on GRADE system was moderate in the stool FMT group. However, we did not find positive effect of capsule FMT on patients with IBS based on the current available data.ConclusionA single stool FMT is effective and safe for patients with IBS. However, some factors may affect the effectiveness of FMT, and the relationship between the gut microbiome and the effect of FMT for IBS is still unclear.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/, identifier CRD42022328377

Photocatalytic Degradation of Microcystins-LR over Mesoporous graphitic Carbon Nitride (mpg-CN)

Mesoporous graphitic carbon nitrides (mpg-CN) were synthesized by a templating method using Ludox (SiO2) as hard template and guanidine hydrochloride (GndCl) as precursor, and were used as metal-free photocatalysts for microcystin-LR (MC-LR) degradation in aqueous solution. By tuning the mass ratio of SiO2 to GndCl, mpg-CN with varied surface areas and condensation degrees were obtained. Catalytic results showed that sample prepared at mass ratio equals 0.4, i.e., mpg-CN(0.4), exhibits the best activity, with above 98% MC-LR conversion obtained at 120 min. Mechanism studies suggested that the reaction obeys the pseudo first-order equation and the produced superoxide anion radicals (•O2−) is the major reactive intermediates contributing to the reaction. Stability tests showed that no appreciable loss of activity is observed even the catalyst is recycled for five times, indicating that the material is stable in the reaction