Lag Problem Research Articles

Experimental investigation and confinement model of composite confined concrete using steel jacket and prestressed steel hoop

This paper presents the results of an experimental study of the uniaxial compression behavior of circular section concrete columns confined by composite confinement (CC). The composite confinement includes prestressed steel hoops (PSH) active confinement and steel jackets (SJ) passive confinement. PSH can solve the problem of passive confinement stress lag, whereas SJ retains the prestressing well and prevents the PSH from penetrating the concrete or causing stress loss. The composite confined concrete specimens were tested with the variations of different initial prestress levels and steel hoop centerline spacing. Their behavior was compared with different types of confinement forms, including unconfined concrete (UC), active confined concrete (PSH confined concrete, PC), passive confined concrete (SJ confined concrete, SC). The results of the experiment show the composite confined concrete (CCC) had a higher bearing capacity and deformation ductility than the other groups of specimens. The initial prestress level increased from 0.3 to 0.4, the bearing capacity increased by 5.1%. As the distance between the centerlines of the steel hoop was reduced from 132 mm to 88 mm, the bearing capacity increased by 10.63%. The capacity of CCC is 1.61–1.78 times that of UC, 1.13–1.24 times that of SC, and 1.53–1.69 times that of PC. Based on the transverse reinforcement-confined concrete model of Mander, a composite confined concrete analysis model is proposed. Then the formula of bearing capacity of CCC column was established. The formula calculation results agree well with the experimental results. Compared with the SJ confined concrete, due to the presence of external PSH, the failure mode is changed, and the shear capacity of the composite confined concrete column is improved, thereby limiting the deformation of concrete and overcoming the tendency of diagonal cracks formation. This paper analyzes the shear failure mechanism of CCC based on the force balance model.

Decision-making Technology Based on Big Data

The paper investigates the issues of building decision support systems based on Big Data. The emphasis is on solving a number of relevant problems, including delayed decision-making, unification of system architectures, and reducing the cost of their development. It is shown that the main reason for the delay is a large number of data sources and a massive amount of information required for synthesizing solutions presented in different languages. For a comprehensive solution to the lag problem, a unified multi-agent architecture and software system are proposed, which, at the user’s request, automatically analyzes text in different languages from thousands of heterogeneous sources in different countries and synthesizes a relevant result to the query. An example of using the system to for decision making on the purchase of goods based on an analysis of customer opinions in different countries is presented.

Trend Analysis of Small Sample Operation and Maintenance Data Based on Function Fitting

After years of informatization construction, the State Grid Corporation’s data centers have reached a very large scale in the headquarters and provincial company’s network companies, providing good support for the deployment of various business systems. Compared with the rapid development of the data center infrastructure construction, the data center-related operation and maintenance management work concept is relatively lagging behind, the data center generates a large amount of operation and maintenance data every day, and relevant analysis and processing work of the data was ignored. In response to the overall requirements of the State Grid Corporation to build a ubiquitous power Internet of Things, the operation and maintenance of the computer room has been upgraded to a new level, and the operation and maintenance work will be transformed from the traditional lag problem solving problem to the forward-looking work of predicting the operation and maintenance risk in advance. Through the analysis and processing of operation and maintenance data, this paper establishes the functional relationship between operation and maintenance indicator data and time, so as to predict the events that may cause system downtime in the future.

ПРОЕКТНЫЙ ПОДХОД К УПРАВЛЕНИЮ ВНЕДРЕНИЕМ БЕРЕЖЛИВОГО ПРОИЗВОДСТВА

The article highlights methodical approaches to building a mechanism for effective management of the implementation of the lean production, as a factor in solving the problem of Russia's lag behind developed countries in productivity. The issues related to differences in the ideology of Japanese, American and Russian lean production systems, analysis of historical experience of implementation, trends and effectiveness of var-ious management options for the implementation of lean production are considered for Russia and developed countries; the reasons for the lack of efficiency of implementation in the dynamics are considered; An assess-ment of expected performance under the national project «Productivity and employment support”; methodical recommendations have been proposed to form an effective mechanism for implementing lean production based on a combination of project management and quality management.

State-Estimator-Integrated Robust Adaptive Tracking Control for Flexible Air-Breathing Hypersonic Vehicle With Noisy Measurements

In this paper, a novel state-estimator-integrated robust adaptive tracking control law is proposed for flexible air-breathing hypersonic vehicle (FAHV), with consideration of noisy measurements, parametric uncertainties, and unknown flexible dynamics. First, to reconstruct the states contaminated by the measurement noises, a continuous-model-based state estimator is designed, which can avoid severe phase lag problem brought by low-pass filter and greatly improve the estimation accuracy in the transition process. Then, based on noise-free measurements, an ideal state feedback robust adaptive tracking controller is formulated to deal with the parametric uncertainties as well as unknown flexible dynamics, where interval type-2 fuzzy logic systems are employed to approximate the unknown dynamics of FAHV online. Lyapunov theorem is utilized to analyze the stability properties of the state estimator and the ideal state feedback tracking controller. By synthesizing the above two parts, the whole state-estimator-integrated robust adaptive tracking control law is finally developed. Comparative numerical simulations of four scenarios demonstrate the effectiveness and superiority of the proposed integrated control law.

Novel docking controller for autonomous aerial refueling with probe direct control and learning-based preview method

Abstract Autonomous aerial refueling (AAR) has always been a hot research area due to its significant application and complicated control problem. In order to improve the docking precision of AAR, a novel docking controller with probe direct control and learning-based preview method is proposed. Firstly, the controlled object is transformed from receiver barycenter to probe tactfully. Then, a suitable probe direct controller designed via the combination of reference-observer-based tracking control method and the high order sliding mode control method is proposed for the probe direct control. Furthermore, a learning-based preview method is introduced to solve the tracking lag problem. The prediction of drogue motion is considered in the reference signal. Then, a novel learning algorithm, named deep learning and reinforcement learning (DLRL), which combines deep learning (DL) and reinforcement learning (RL) spatially rather than structurally like deep reinforcement learning (DRL) is proposed to generate the preview time adaptively. And a novel preview index is proposed to adapt for it. Through the combination of probe direct controller and learning-based preview method, the proposed docking controller could improve the tracking precision largely. Effectiveness of the proposed method is demonstrated by the simulations.

Assessment of nitrogen application limits in agro-livestock farming areas using quantile regression between nitrogen loadings and groundwater nitrate levels

The excessive application of nitrogen in agro-livestock farming areas has led to serious groundwater contamination around the world; thus, the efficient control of N loads is crucial to manage nitrate contamination of groundwater. In this study, to suggest an optimal N application limit as a key guideline of N management, we examine the impact of anthropogenic N loading on nitrate levels of shallow groundwater, using a large dataset (n = 4,000) collected in 2012–2014 from 100 agro-livestock farming districts in South Korea. Not considering the time lag and legacy problem, quantile regression is performed to overall assess the relationship between nitrate contamination and anthropogenic N input across the full range of conditional distribution of groundwater nitrate concentrations because of heteroscedasticity. As a result, positive gradients (βτ) meaning the rates of changes are found between groundwater nitrate concentrations and land-derived N loads at all quantiles; βτ increases as the quantile is higher and is as large as 36.48 ± 10.73 mg NO3−/L per land-derived N input (on a log scale) at the 90% quantile. The quantile map indicates that the high gradient (i.e., the large sensitivity to N loading) is related to agricultural land use, low elevation, and low topographic slopes. In fact, groundwater nitrate concentrations increase as the percentage of agricultural land increases but the percentage of forest, elevation and slope angle decreases, which suggests that land use, elevation, and slope should be considered when attempting to evaluate N application limits. This study suggests the N limits below 170 kg ha-1 year-1 based on the drinking water standard (44.3 mg/L as NO3−) at the quantiles higher than 70% which mostly occur in flat agricultural lowland areas. Our method used in this study can be applied elsewhere to establish efficient management practices for groundwater nitrate contamination, considering local environmental factors.

Voltage fluctuation smoothing in distribution systems with RES considering degradation and charging plan of EV batteries

Recently, the use of renewable energy sources (RES) and electric vehicles (EVs) has been rapidly increased worldwide. As a result of the highly fluctuating nature of RES, the charging and discharging rates of EVs significantly have to be increased, and so the lifespan of EV batteries decreases. In this paper, an optimization-based method is proposed to smooth voltage fluctuations due to various RES types by optimally controlling the charging and discharging power of EVs and the reactive power of the RES inverters. To extend the lifespan of the EV battery, EV power fluctuations and their minimum preset state of charge (SOC) are considered in the proposed optimization model. For this purpose, a new multi-objective function is formulated, including (1) voltage fluctuations, (2) EV power fluctuations, and (3) the deviation of SOC of EVs from their minimum desired level. The use of the hull moving average (HMA) is proposed to mitigate voltage fluctuations, which eliminates the lag problem of the widely used moving average methods. The gravitational search algorithm (GSA) is utilized to accurately solve the optimization model. The simulation results demonstrate the effectiveness of the proposed method to smooth voltage fluctuations while considering degradation and charging plan of EV batteries.

Application of Convolution of Daubechies Wavelet in Solving 3D Microscale DPL Problem

In this work, the triple convolution of Daubechies wavelet is used to solve the three dimensional (3D) microscale Dual Phase Lag (DPL) problem. Also, numerical solution of 3D time-dependent initial-boundary value problems of a microscopic heat equation is presented. To generate a 3D wavelet we used the triple convolution of a one dimensional wavelet. Using convolution we get a scaling function and a sevenfold 3D wavelet and all of our computations are based on this new set to approximate in 3D spatial. Moreover, approximation in time domain is based on finite difference method. By substitution in the 3D DPL model, the differential equation converts to a linear system of equations and related system is solved directly. We use the Lax-Richtmyer theorem to investigate the consistency, stability and convergence analysis of our method. Numerical results are presented and compared with the analytical solution to show the efficiency of the method.

Correction of torque transfer lag in magnetic coupling rheological test system.

In this study, a mathematical model for the magnetic coupling transmission process was set up to solve the problem of torque transfer lag in magnetic-coupled rheological testing systems. This model was developed on the basis of torque balance in a magnetic coupling rotatory rheometer test system, which considered friction loss for the jewel bearing, as well as the inertia of both the motor and fixture. Taking the HAAKE-MARS60 high-pressure rheometer as an example, the rheological properties of Newtonian fluid at the initial measuring stage under controlling constant stress conditions were tested to verify the accuracy of the model and using the model to modify the rheological test results. The results show that the load torque mainly influences the alternating frequency of the rotational speed and the hysteresis degree of the inner and outer magnetic rings, the larger the load torque, the greater the deviation of the magnetic coupling test results of the rotational rheometer. The results of the apparent viscosity test are modified under different loading conditions, and the rheological curves of the initial shear phase of the Newtonian fluid are coincident with the steady-state test results, showing the true viscosity of the Newtonian fluid, which conforms to the cognition of Newtonian fluid rheology being independent of time. The results of the initial start test of gelling crude oil were modified, the yield stress and yield time were reduced, and the lower the test temperature and the higher the shear rate, the more obvious the correction effect was. Under different shear rate conditions, the yield strain corresponding to the modified yield stress was close and the yield strain was approximately not changed with the shear rate. The results can provide a basis for understanding the rheological properties of materials in the start-up transient process under high pressure conditions.

USING BAIDU INDEX TO NOWCAST MOBILE PHONE SALES IN CHINA

Most of the official data are released with a lag period, which increases the difficulties for decision-makers assessing the situation. To solve the problem of data lag, we used real-time Baidu Index to nowcast the Chinese consumer behavior of buying the best-selling smartphone, Huawei Mate 7. We introduced keywords like “Mate 7” and “Huawei” in Baidu Index search queries to examine whether the introduction of real-time data can improve the efficiency of benchmark model. Overall, our finding is that the introduction of Baidu Index, both in-sample and out-of-sample, can improve the prediction accuracy of the model significantly. The extended model provided a 55.2% outperformance relative to benchmark one. This can not only make up for official data release lag, but also help firms gain near-real-time insight into the consumer demand trends and reduce inventory costs. The findings suggest that firms can improve marketing performance by use of search engine promotion campaign.

A shear model for unsteady state for viscoelastic fluids, based on the correction of torque transfer lag

In this study, a mathematical model for the magnetic coupling transmission process was set up to solve the problem of torque transfer lag in magnetic-coupled rheological testing systems. This model was developed on the basis of torque balance in a magnetic coupling rotatory rheometer test system, which considered friction loss for the jewel bearing, as well as the inertia of both the motor and fixture. The reliability of the mathematical model was fully confirmed by a constant stress no-load start-up experiment conducted using a HAAKE-MARS60 high pressure rheometer. Based on the mathematical model for simultaneous magnetic coupling transmission and a constitutive equation of viscoelastic thixotropic fluid, a model, put forward for the unsteady mathematical shear of viscoelastic fluids, was designed to correct torque transfer lag. Changes in real stress and strain on the rotator surface were then obtained under the initial unsteady-state shear phase of the rheometer. The results showed that magnetic coupling intensifies the unsteady shear flow of fluids. The bigger the elastic modulus and viscosity of the material, the larger the deviation of test results between rotational rheometers and magnetic couple rheometers will be. The results obtained in this study could facilitate a better understanding of the rheological properties of materials in the transient start-up process under high pressure conditions in later research.

Research on Dynamic Coordination Active Mode Switching Control Strategy for Hybrid Electric Vehicle Based on Traffic Information

In traditional hybrid-vehicle mode switching, a switch when it changes in road conditions is sensed. Because of the delays in the control system, lags in switching and large impacts on the switching process occur, in what is referred to as “passive mode switching.” Via a combination of an intelligent networked hybrid vehicle with environmental sensing, “passive mode switching” can be converted into “active mode switching,” reducing the impact degree during the switching process and increasing ride comfort. Combined with the application of intelligent transportation system in current traffic, an intelligent traffic scene with optimal traffic-light control (OTLC) is established. The OTLC algorithm determines the future driving-state information of the hybrid vehicle in a built scenario and predicts the driving mode of the hybrid vehicle for the next moment. The current mode and future mode are compared, active control of key components, such as the engine, motor, clutch, and electric-mechanical continuously variable transmission (EMCVT), under the premise of different conditions, is made possible, and corresponding dynamic coordinate active-mode-switching control strategies are developed. The proposed control strategy is simulated and verified on a built-in hardware-in-the-loop (HIL) test platform based on traffic scenarios. The results show that the dynamic coordinated active-mode-switching control strategy presented in this paper is superior to the traditional mode-switching control strategy and that it can overcome the problem of switching lag due to delays in the control system and the large impact during the switching process, reducing the impact degree by about 21.2%, which improves ride comfort.

Image Lag Elimination Algorithm for Pulse-Sequence-Based High-Speed Image Sensor

When the pulse-sequence-based image sensor films high-speed moving objects, the image lag problem may appears as blurring in reconstructed images. In this paper, an algorithm is proposed to suppress lags by distinguishing the lag area and calculating ratio of bright to dark part in one trigger interval. The algorithm bases on the sensor's characteristics and image lag principle that the change of light intensity cannot be immediately reflected on the pulse generated from photoelectric accumulation. The effectiveness of the algorithm is verified both on the sensor's behavior-level model and the real image sensor. In both experiments the curves of LSF (line spread function) and MTF (modulation transfer function) show the reconstructed edges after lag elimination algorithm are similar to the real edges both in sharpness and position. The indexes to evaluate image similarity including LMD (location mean deviation), PSNR (peak signal to noise ratio) and SSIM (structural similarity index) improve respectively. In the experiment on sensor's model, when the simulation velocity of edge is low, the algorithm can reconstruct the perfect edges as input images. As velocity increases, the reconstructed edges are still sharp but with slight shifts. In the real experiment to film a turntable with a rotation speed of 6000r/min, the LMD, PSNR and SSIM improve from 22.2833 to 2.5167, 18.2485 to 21.8603 and 0.8345 to 0.9364 respectively. These results show that the algorithm can suppress image lag and improve reconstructed image quality.

Shared Bottleneck Detection Based on Congestion Interval Variance Measurement

The key technical issue of bottleneck fairness-based multipath congestion control is to detect whether two flows share a common bottleneck or not. Previous approaches perform poorly when the delay of the two paths from the shared bottleneck to the common receiver differs significantly (named the path lag problem). In this letter, we propose and implement a shared bottleneck detection scheme based on congestion interval variance measurement (SBDV). Our scheme uses only one-way delay measurement within each flow to detect whether two flows share a bottleneck or not. If the variance of time interval between the two flows experiencing congestion is smaller than a threshold, which is determined by the duration of congestion, the two flows can be considered to share a common bottleneck. Otherwise, they are considered to have different bottlenecks. Our simulation shows that the accuracy of SBDV is high in most of the experiments, even when the bottlenecks are partially overlapped, and our scheme is robust to the troublesome Path lag problem, as compared to other state-of-the-art techniques.

Motion analysis and system response of fertilizer feed apparatus for paddy Variable-Rate fertilizer spreader

Precision agriculture and variable-rate technology have gained increasing public interest. To improve the rapid response ability of the control system of a variable-rate fertilization and reduce the errors corresponding to the feed fertilizer system in a centrifugal variable-rate spreader, three devices that could adjust the application rate using different actuators were developed; these involved the gear and rack structure A, electric handspike structure B, and screw slider structure C. Mechanism motion analysis models were established based on vector equations, the response analysis of system delay was performed according to the model of lag fertilization, and subsequently, performance tests were executed to calibrate the lag distance of falling fertilizer, as well as the response time of actuators and the error of feed fertilization flow. The test results indicated that for actuators A, B, and C, the average lag distance of falling fertilization was in the order LA > LC > LB, with the respective values being 3.56, 2.72, and 1.85 m; the corresponding lag correction times were 1.99, 1.74, and 1.48 s, respectively. A positive proportional relation was noted between the application increment and response time of apparatus execution, and TBi > TCi > TAi (i denotes the corresponding feed fertilization flow). Furthermore, the error of fertilization flow first decreased and then increased with the increasing application rate; the extremum appeared between 250g/s and 380g/s, and γBi > γAi > γCi. The feed fertilizer with structure C was optimized and integrated field validation tests, and incorporating the corresponding correction time of lagging response Tlag = 1.74 s into the control system, the mean error of variable-rate fertilization system was determined as 9.67%, and the average lag distance of fertilization was 0.37 m. This indicated that the control system of variable-rate fertilization with correction response time alleviated the problem of lag falling fertilizing, improved the response speed of variable-rate fertilization for rice, and helped achieved better fertilization accuracy.

Adaptive and ADRC information fusion method for high speed train braking system

Aiming at the problem of poor adaptability and lag of traditional braking control methods of high-speed train, a high-speed train braking information fusion method based on adaptive linear auto disturbance rejection is proposed to arrange the transition process for

Backstepping control based on L1 adaptive theory for large transport aircraft heavy load airdrop

A study of the L1 adaptive controller is conducted based on the backstepping method for the model of large transport aircraft with drastic changes appearing in heavy load airdrop process. The system is divided into an attitude subsystem and a velocity subsystem. For the attitude subsystem, the backstepping control is used to design the virtual control of path angle and the pitch angle in external loop with the L1 adaptive controller designed in internal loop to estimate the uncertainties and disturbances in the subsystem and to compensate them. In the stability analysis, the uniform boundedness of all signals in the closed-loop system is proven. Simulation results show that the proposed control method preserves the quick dynamic torque response, high efficiency, and robustness in heavy load airdrop; to some extent it can alleviate the control switch lead or lag problem and ensure the safety of the transport aircraft to fulfill the complete airdrop mission.

Jet lag: Heuristics and therapeutics

Jet lag is one of those common medical problems, to which most people don’t give a serious thought. However, it is intricately intertwined with our normal circadian rhythm. It is classified as a sleep disorder. There is also a dearth of good scientific literature, not to mention clinical trials on the subject. Slowly but steadily, the scientific community is realizing the various deleterious health effects of jet lag and is devising innovative methods to counter them. This narrative review touches upon the etiopathogenesis, clinical manifestations and therapeutic strategies effective against the nagging problem of jet lag.

Design, Modeling, and Experiment of a Piezoelectric Pressure Sensor Based on a Thickness-Shear-Mode Crystal Resonator

This paper presents the design, modeling, and experimental demonstration of a novel pressure sensor using an AT-cut quartz crystal resonator with beat frequency analysis-based temperature compensation technique. The combination of a compact design of the proposed pie-zoelectric crystal resonator structure and temperature compensation technique has advantages such as high accuracy, low cost, and good performance attributes. The sensor measures pressure and temperature simultaneously with a single AT-cut quartz resonator, thus avoiding the thermal lag problem in the commercial multiresonator-based pressure sensors. The pressure sensor is designed using computer-aided design software and CAE software (COMSOL Multiphysics). Finite-element analysis (FEA) of the pressure sensor is performed to analyze the stress–strain of the sensor's mechanical structure. A 3-D-printing prototype of the sensor was fabricated, and the sensing principle was verified using a force–frequency analysis apparatus. Subsequently, a full-up pressure sensor was fabricated with a stainless steel housing and a built-in crystal oscillator circuit. Based on the FEA and experimental results, we have determined that the maximum pressure the sensor can safely measure is 45 psi. Test results performed on the stainless steel product show a good linear relationship between the input (pressure) and the output (frequency).