Multi-damage detection in composite structure

In this paper a pre-stack reverse-time migration concept of signal processing techniques is developed and adapted to guided-wave propagation in composite structure for multi-damage imaging by experimental studies. An anisotropic laminated composite plate with a surface-mounted linear piezoelectric ceramic (PZT) disk array is studied as an example. At first, Mindlin Plate Theory is used to model Lamb waves propagating in laminates. The group velocities of flexural waves are also derived from dispersion relations and validated by experiments. Then reconstruct the response wave fields with reflected data collected by the linear PZT array. Reverse-time migration technique is then performed to back-propagate the reflected energy to the damages using a two-dimensional explicit finite difference algorithm and damages are imaged. Stacking these images together gets the final image of multiple damages. The results show that the pre-stack migration method is hopeful for damage detection in composite structures

Both Efficiency and Effectiveness! A Large Scale Pre-ranking Framework in Search System

In the realm of search systems, multi-stage cascade architecture is a prevalent method, typically consisting of sequential modules such as matching, pre-ranking, and ranking. It is generally acknowledged that the model used in the pre-ranking stage must strike a balance between efficacy and efficiency. Thus, the most commonly employed architecture is the representation-focused vector product based model. However, this architecture lacks effective interaction between the query and document, resulting in a reduction in the effectiveness of the search system. To address this issue, we present a novel pre-ranking framework called RankDFM. Our framework leverages DeepFM as the backbone and employs a pairwise training paradigm to learn the ranking of videos under a query. The capability of RankDFM to cross features provides significant improvement in offline and online A/B testing performance. Furthermore, we introduce a learnable feature selection scheme to optimize the model and reduce the time required for online inference, equivalent to a tree model. Currently, RankDFM has been deployed in the search system of a shortvideo App, providing daily services to hundreds of millions users

Text Classification Using Novel Term Weighting Scheme-Based Improved TF-IDF for Internet Media Reports

With the rapid development of the internet technology, a large amount of internet text data can be obtained. The text classification (TC) technology plays a very important role in processing massive text data, but the accuracy of classification is directly affected by the performance of term weighting in TC. Due to the original design of information retrieval (IR), term frequency-inverse document frequency (TF-IDF) is not effective enough for TC, especially for processing text data with unbalanced distributions in internet media reports. Therefore, the variance between the DF value of a particular term and the average of all DFs , namely, the document frequency variance (ADF), is proposed to enhance the ability in processing text data with unbalanced distribution. Then, the normal TF-IDF is modified by the proposed ADF for processing unbalanced text collection in four different ways, namely, TF-IADF, TF-IADF+, TF-IADFnorm, and TF-IADF+norm. As a result, an effective model can be established for the TC task of internet media reports. A series of simulations have been carried out to evaluate the performance of the proposed methods. Compared with TF-IDF on state-of-the-art classification algorithms, the effectiveness and feasibility of the proposed methods are confirmed by simulation results

Performance Analysis of Multi-Antenna Hybrid Satellite-Terrestrial Relay Networks in the Presence of Interference

Abstract—The integration of cooperative transmission into satellite networks is regarded as an effective strategy to increase the energy efficiency as well as the coverage of satellite communications. This paper investigates the performance of an amplifyand-forward (AF) hybrid satellite-terrestrial relay network (HSTRN), where the links of the two hops undergo Shadowed- Rician andRayleigh fadingdistributions, respectively.By assuming that a single antenna relay is used to assist the signal transmission between the multi-antenna satellite and multi-antenna mobile terminal, and multiple interferers corrupt both the relay and destination, we first obtain the equivalent end-to-end signal-to-interference-plus-noise ratio (SINR) of the system. Then, an approximate yet very accurate closed-form expression for the ergodic capacity of the HSTRN is derived. The analytical lower bound expressions are also obtained to efficiently evaluate the outage probability (OP) and average symbol error rate (ASER) of the system. Furthermore, the asymptotic OP and ASER expressions are developed at high signal-to-noise ratio (SNR) to reveal the achievable diversity order and array gain of the considered HSTRN. Finally, simulation results are provided to validate of the analytical results, and show the impact of various parameters on the system performance

Elemental data for Gonghai Lake sediments show significant effects of human activities on weathering processes after 1550 CE

The international Anthropocene Working Group has recognized the mid-20th centrury (ca. 1950 CE) as the onset of the Anthropocene, but human activities in China altered the land cover and influenced weathering processes much earlier. Changes in the elemental composition of sediment since 1000 CE from Gonghai Lake were studied, using X-ray Fluorescence element scanning (average time-resolution 3 years), to investigate the human impacts on weathering over time. We found that aluminum (Al) and calcium (Ca) containing minerals vary in the resistance to chemical weathering, and the concentrations of Al and Ca provide insights into the intensities of mechanical and chemical weathering respectively. The correlations between Al and Ca concentrations in these two periods, 1000–1550 CE and 1550–1950 CE changed from negative to positive, owing to that agricultural activities evidently enhanced both mechanical and chemical weathering during the latter stage. In addition, the Al and Ca concentrations recorded a border reclamation project in the 16th century and two catastrophic population decreases from 1630s to 1640s and 1850s–1870s. After 1950 CE, the concentrations of Al and Ca became uncorrelated, because weathering processes around Gonghai Lake were impacted by the enhanced anthropogenic perturbations in the Anthropocene

Re-Fracturing vs. CO2 Huff-n-Puff Injection in a Tight Shale Reservoir for Enhancing Gas Production

Field production data indicate that the shale gas production rate decreases sharply after a few years of the first fracking. Feasible enhanced gas recovery (EGR) approaches are very necessary to be investigated. In this study, we compared re-fracturing with a huff-n-puff gas injection scheme in a shale gas reservoir for EGR. A fully compositional simulation approach coupled with a dual porosity and dual permeability model is used. The gas production performances by using different fracturing fluids (i.e., slickwater and supercritical CO2) are evaluated. The effects of huff-n-puff parameters and matrix permeability on the gas production rate and carbon sequestration are investigated. The results show that using a re-fracturing approach yields a better recovery performance than the huff-n-puff gas injection method. Re-fracturing using supercritical CO2 performs better than using slickwater because the former can create complex three-dimensional fracture networks. Huff-n-puff CO2 injection can enhance the gas recovery effectively in ultra-tight formations. In a relatively high permeable formation, viscous flow instead of adsorption-desorption isotherms becomes the primary mass transfer mechanisms, resulting in a lower gas recovery. Both the re-fracturing treatment and huff-n-puff CO2 injection are profitable from a long-term cash flowback perspective

Energy Cost of Reclining, Sitting, and Standing Activities in Chinese Adults

International Journal of Exercise Science 15(7): 1202-1211, 2022. The 2011 Compendium presents MET values for sedentary behaviors (SBs) and light-intensity physical activities (LIPAs). Some entries have estimated METs, others have multiple activities in a single entry, and newer activities are not in the Compendium. Accurate MET values are needed to increase the validity and generalizability of the Compendium. This study measured and analyzed SBs and LIPAs’ energy costs in reclining, sitting, standing postures, and fidgeting. Indirect calorimetry measured the energy costs (VO2, ml.kg-1.min-1) in 11 males and seven females (30.7 ± 7.6 y). Two groups of 9 participants each completed 17 randomly assigned activities (9 in group 1; 8 in group 2) for 5 minutes with a 2-minute rest between tasks. Standard METs were calculated as VO2 ml.kg-1.min-1/3.5 ml.kg-1.min-1. Results showed mean MET values for doing nothing (recline: 1.3, sit: 1.3. stand: 1.3); Watching TV on a mobile phone (recline: 1.3, sit: 1.3); Reading (recline; 1.5, sit: 1.0); Writing (recline: 1.5, sit: 1.3, stand: 1.3); Texting or viewing websites on a mobile phone (recline: 1.3, sit: 1.3, stand: 1.3); Fidgeting (sit hands only: 1.5, sit feet only: 1.8, stand hands and feet: 2.0); Typing (stand: 1.3). Measured vs. Compendium METs were the same for five SBs and LIPAs, higher for three SBs and LIPAs (by 0.2 METs), and lower for one SB (by 0.3 METs). In conclusion, the activities ranged from 1.0 to 2.0 METs, categorized as sedentary and light-intensity. Increasing the accuracy of Compendium MET values increases its utility for the correct classification of SB and LIPAs

PO-222 The Influence of Different Route Randomness on Energy Contributions of College Students' Badminton Running Practice with Change of Direction at Two Frequencies

Objective Badminton four-corner running practice with change of direction commonly includes fix route and random route. However, the study of the energy contributions characteristics of these two training methods was very limited. The aim of this study was to investigate the influence of different route randomness on energy contributions of college students' badminton running practice with change of direction at two frequencies.   Methods 15 college badminton player whom from Shanghai University of Sport (Male, N=15, 22.9±1.4 yrs, 175.7±6.0 cm, 68.0±6.4kg, badminton training experience 2.2±0.5 yrs) volunteered to perform one test for maximal oxygen uptake （VO2max） on treadmill and four field tests with two route randomness (fix route and random route, F and R ) and two frequencies (24 times per 1min and 24 times per 1min, H and L ) of change of direction. A portable spirometric system (K4b2, Cosmed, Italy) was utilized to measure the ventilator information during the test, and capillary blood was taken from earlobe and analyzed prior and post the tests. The energy contributions was calculated with the method based on the fast component of oxygen debt (WAla) , accumulated blood lactate (WLa) and VO2 (WAer)during the tests. Results Higher frequency significantly increased the energy contributions from the three pathways both with F and R (WAla:26.2±6.3 kJ vs. 39.5±12.6 kJ, WLa: 5.7±2.4kJ vs. 23.1±9.3 kJ, WAer: 27.1±6.5kJ vs. 33.3±5.7kJ, P<0.01), and significantly increased the WLa (F: 23.9±8.1% vs. 9.6±3.4%, P<0.01; R: 30.5±6.6% vs. 11.7±5.2%, P<0.01), whereas significantly reduced the WAer% (F: 35.2±6.5% vs. 46.0±8.5%, P<0.01; R: 35.7±5.4 % vs. 50.4±10.2%, P<0.01). The R significantly reduced the WLa% both in L (44.4±8.5% vs. 38.0±8.6% , P<0.05) and H (40.9±10.5% vs. 33.8±8.6%, P<0.05), significantly increased the WLa (23.1±9.3kJ vs. 28.9±7.3kJ, P<0.05) and WLa% (23.9±8.1% vs. 30.5±1.7%) in H. Conclusions The route randomness of badminton running practice with change of direction at two frequencies has different effects on the energy contributions. The R will reduce the stimulation to the WAla and increase the stimulation to the WLa ; the H will increase the intensity of the running with change of direction as a whole, and will reducing the stimulation to the WAer and increasing the stimulation to the WLa. It is recommended that the coaches can change the stimulation of the WLa by changing the frequency of the change of direction and the randomness of the route when design the badminton four-corner running practice with change of direction. &nbsp

PO-211 Reliability and Validity of Measuring Energy Expenditure in Inline and Shuttle Running with Honor and Lifesense Fitness Wristbands

Objective Energy expenditure is an indicator that comprehensively reflects the amount of physical activity. Fitness wristbands are used to monitor the energy expenditure of human activities in the fitness field. Among the fitness wristbands popular in China, Honor and Lifesense rank in the top list. However, there was no research on the reliability and validity of these two wristbands in measuring the energy expenditure. This study aims to evalute the reliability and validity of the two fitness wristbands (Honor and Lifesense) in measuring the energy expenditure in inline and shuttle running. Methods 18 male collegiate students (age: 22.4±2.5yrs, height: 177±7cm, mass: 69.3.±8.4kg) volunteered to participate in two four-stage incremental inline running tests (8km/h, 10km/h, 12km/h, 14km/h) and two 20m four-stage incremental shuttle running test (6km/h, 8km/h, 10km/h, 12km/h). The duration of each stage was 5 min, and intermittent per stage was 1 min. Honor B3（GMN-BX9, Honor, China） and Lifesense Mombo2（LS417-B, Lifesense, China）fitness wristbands was utilized to measure the energy expenditure of each stage in incremental inline and shuttle running. A portable spirometric system (K4b2, Cosmed, Italy) was utilized to measure the ventilator information during the test. The energy expenditure was converted into equivalent units (kcal) according to the measured respiratory quotient coefficient. The repeat measuremented reliability test was carried out on the energy expenditure indicators measured by the fitness wristbands in the twice incremental inline running and the shuttle running. The energy expenditure calculated by the portable gas metabolic instrument was comparedwith those  measured by Honor and Lifesense fitness wristbands. Results The result test-retest reliability found that the Honor and Lifesense fitness wristbands had well correlations between the two tests at a speed of 8km/h, 10km/h, 12km/h in inline running, and 8km/h, and 10km/h in shuttle running (r=0.44~0.93, P<0.05), but the correlation was not well at 6km/h in shuttle running (r<0.43, P>0.05). The Honor wristband correlation (r=0.83~0.93, P<0.05) was higher than the Lifesense fitness wristbands (r=0.44~0.60, P<0.05) at 8km/h, 10km/h, and 12km/h in inline running and at 8km/h, and 10km/h in shuttle running. The correlation coefficients of the two fitness wristbands at 8km/h and 10km/h in inline running (r=0.52~0.93, P<0.05) were both higher than those in shuttle running (r=0.44~0.83, P<0.05). The energy expenditure measured by K4b2 and the two kinds fitnees wristband was significantly different (P<0.05), except at 12km/h in inline running and 10km/h in shuttle running (P > 0.05).  Conclusions Honor and Lifesense wristbands have acceptable reliability in measuring energy expenditure at 8, 10, 12km/h in inline and shuttle running, with the fore slightly higher than the after. The two wristbands have higher reliability in measuring the energy expenditure in inline running than in shuttle running. The validity of measuring the energy expenditure with the two fitness wristbands is acceptable at 12km/h in inline running and at 10km/h in shuttle running, but not at other speed

PO-226 Effect of Trunk Resistance Vest on Running Economy at Different Speed in Male Collegiate Students

Objective Wearable resistance training is a common method ultilzed by athletic and fitness population during running. This method is demonstrated to have multiple athletic and health benefits despite of its potential risk for running technique. Running economy is a measure for running technique, which is defined as the oxygen uptake (VO2) at a given sub-maximal speed. The purpose of this study is to evaluate the effect of wearable resistance on running economy at different running speed in male collegiate students. Methods 18 male collegiate students from Shanghai University of Sports (age: 22.4±2.4yrs, height: 177.4±7.5cm, body mass: 69.3±8.2kg, training experience: 4.6±1.6yrs, body fat: 13.3±4.7%) volunteered to perform one two four-stage incremental tests (8km/h, 10km/h, 12km/h, 14km/h) with and without a trunk resistance vest (10% of individual body mass). The duration of each stage was 5 min, and intermittent per stage was 1 min. A portable spirometric system (K4b2, Cosmed, Italy) was utilized to measure the ventilator and heart rate index during the test. The running economy was calculated as the averaged VO2 in the last minute of each stage. The capillary blood was collected from the earlobe after each stage IBM SPSS Statistics 19（SPSS Statistics 19, IBM Corporation, USA）was used to carry out a one-way repeated measurement ANOVA analysis on the physiological results at different speeds, and Paired-T test was to statistical analysis the normal and trunk vest test at the same speed. P<0.05 was set as the significant level. Results Along with the increase of speed, VO2, heart rate, blood lactate concentration and RPE was increased significantly (P<0.05, except  12km/h and 14km/h without vest, and 8km/h and 10km/h with vest). The running economy was slightly lower in running with vest at each running speed compared with without vest (P>0.05). However, the blood lactic concentration with vest was higher than that without vest at all speed, with the difference significant at 14km/h(9.3±2.9 vs. 7.6±2.2mM, P>0.05). The RPE was significant higher with vest than without vest at each speed (P<0.05, except at 8km/h). Conclusions Running with trunk resistance vest of 10% body mass is characterized with slightly better economy, although it induces a significant higher  blood lactic concentration and RPE. &nbsp