Large Range Research Articles

Autonomous Alignment and Docking Control for a Self-Reconfigurable Modular Mobile Robotic System

This paper presents the path planning and motion control of a self-reconfigurable mobile robot system, focusing on module-to-module autonomous docking and alignment tasks. STORM, which stands for Self-configurable and Transformable Omni-Directional Robotic Modules, features a unique mode-switching ability and novel docking mechanism design. This enables the modules that make up STORM to dock with each other and form a variety configurations in or to perform a large array of tasks. The path planning and motion control presented here consists of two parallel schemes. A Lyapunov function-based precision controller is proposed to align the target docking mechanisms in a small range of the target position. Then, an optimization-based path planning algorithm is proposed to help find the fastest path and determine when to switch its locomotion mode in a much larger range. Both numerical simulations and real-world experiments were carried out to validate these proposed controllers.

Thermal creep properties of virgin and irradiated cladding tubes made of Ti-stabilised DIN 1.4970 (15-15Ti) austenitic stainless steel

ABSTRACT This paper presents assessments performed on a large database of virgin material and irradiated material thermal creep data from uniaxial and pressurised DIN 1.4970 Ti-stabilised austenitic stainless steel i.e. EN X10NiCrMoTiB15–15 or ‘15-15Ti’ cladding tubes. The data base incorporates multi-heat data from uniaxial and bi-axial (internal pressure) creep tests conducted during the fast reactor R&D program of the DeBeNe (Deutschland-Belgium-Netherlands) consortium between the 1960s to the late 1980s together with more recent data, for example, from the European projects MATTER and PATRICIA and the EERA JPNM pilot project TASTE. The data comprises of a virgin material data base and a data base with irradiated creep data. The virgin material data comprises of time-to-rupture and time-to-0.2% creep strain in a temperature range of 600–800°C and covers a large range of stresses. The irradiated data base has less data and does not cover all material heats tested for the virgin material properties. The irradiation conditions are also different depending on the test reactor specifics and the irradiation campaign targets. The attained ‘irradiation damage’ in displacements per atom (DPA) for the irradiated materials range from 0.1 up to 38.1. Un-irradiated ‘reference material’ models for tensile strength and creep strength are constructed from the current-state of the art literature data and more recent results from the Sandvik 24% cold worked 1515–Ti cladding tube currently used as the main material batch studied at SCK CEN. The tensile strength model is used throughout the paper for normalizing creep strengths by the tensile properties, needed when applying the Wilshire (WE) creep model. Time factors (TF), stress factors (SF) and temperature ratio factors (TRF) are calculated for different material states for describing the impact of heat treatments, (virgin and irradiated) and irradiation conditions. This initial study targets to give estimates for the thermal creep properties of cladding tubes with a cold work range of 16–24% in a non-annealed state, as it is the preferred option for future designs according to the state-of-the art knowledge base. However, the main bulk of the available data on irradiated material is on claddings with a cold work range of 0-16% with and without annealing and at various levels of irradiation damage, thus leading to the need for estimation by interpolation and extrapolation assuming that irradiation damage levels and trends, e.g. time reduction factors found on a lower cold worked material can also be applied on materials with higher cold work levels. The results of the assessments clearly show relative strength differences between chosen material heats and heat treatments and has enabled constructing simple multilinear models for estimating the life of irradiated material. The models show that low creep test temperatures (and irradiation temperatures), low stress levels, low levels of cold work and high irradiation doses are increasing the detrimental difference between the specific material condition and the reference material. Also, it was found that the general level of life reduction (time factor TF and stress factor SF) for irradiation damaged material failure, in relation to the reference material failure, roughly coincides the corresponding values of time to 0.2% creep strain for virgin material. The estimated ‘failure creep temperature limits’ for 30 000 hours of service are studied and compared for both virgin and irradiated materials at a reference stress level of 1/3 of the tensile strength (at temperature).

Minimally invasive surgical therapies for benign prostatic hyperplasia in the geriatric population: A systematic review.

Geriatric patients, prone to adverse events (AEs) and low compliance with drugs, may benefit from minimally invasive surgical therapies (MISTs) for managing benign prostatic hyperplasia (BPH). We evaluated the efficacy, safety, and procedural characteristics of MISTs in geriatric patients with BPH. PubMed/MEDLINE database was systematically searched for relevant articles through October 1, 2023. Eligible studies focused on geriatric patients (≥65 years) with BPH who were treated with MISTs and evaluated follow-up surgical, micturition, and/or sexual outcomes. Studies were included if there was separate reporting for age subgroups ≥65 years, or if the mean age minus standard deviation was ≥65 years, or if the first quartile was ≥65 years. Out of 292 screened studies, 32 (N = 3972 patients) met inclusion criteria and assessed prostatic artery embolization (PAE), Rezum, GreenLight, holmium laser enucleation of the prostate (HoLEP), thulium laser enucleation of the prostate (ThuLEP), diode laser enucleation of the prostate (DiLEP), and Aquablation. Except for Rezum, all MISTs required a planned overnight stay. While PAE and Rezum could be performed under local anesthesia, the other MISTs needed general or spinal anesthesia. Postoperative catheterization duration was longest for PAE (median 14 days) and Rezum (21 days) and shortest for GreenLight (1.9 days). At 12 months postoperatively, all MISTs exhibited significant percent changes in International Prostate Symptom Score (median -69.9%) and quality of life (median -72.5%). Clavien-Dindo Grade 1 AEs ranged widely, with PAE (5.8%-36.8%), Rezum (0%-62.1%), and GreenLight (0%-67.6%) having the largest range, and HoLEP (0%-9.5%), ThuLEP (2%-6.9%), and DiLEP (5%-17.5%) having the smallest. PAE, Rezum, DiLEP, and Aquablation reported no significant changes in the International Index of Erectile Function. Although all the MISTs reviewed in this study effectively treat BPH in geriatric patients, differences in procedural characteristics and safety profiles across MISTs were considerable. Physicians should use shared decision-making processes, considering risks and patient characteristics, when choosing a suitable treatment option for their patients.

Experiment investigation on the local scour around circular and square piles in open wharf

Open wharves often rely on pile structures for stability, but these can cause local scouring, risking structural integrity and safety. Understanding scour mechanisms induced by propeller jet flow is crucial for effective scour protection, yet research on square piles and double piles is limited. This study presents a series of flume tests to investigate the local scour mechanisms around square piles and circular piles under propeller jet flow. The experiments consist of seven different configurations, including single square piles, double square piles, single circular piles, double circular piles, and a control case without any piles. The main focus of this research is to understand the development and variations of scour depth and scour pit dimensions induced by propeller jet flow. Additionally, the scour mechanisms of square piles are compared with those of circular piles, and the influence of double piles and pile spacing is examined. It can be found that substituting circular piles with square piles in practical engineering will generally lead to an increase in the overall scouring range of the foundation. The horizontal scouring range of double piles is significantly influenced by the pile spacing, resulting in a larger range with increased spacing. However, the variation in pile spacing has minimal impact on the vertical scouring range of the double piles. The shape of piles significantly impacts scour depth in both single and double-pile setups, with square piles resulting in deeper scour. Furthermore, increased pile numbers and narrower spacing contribute to higher scour depths. The results of this study enhance understanding of scour characteristics and offer valuable insights for designing and maintaining pile-supported open wharves, ensuring the safety and durability of waterfront structures through effective scour protection measures.

Feasibility of Using Survey Data and Semi‐variogram Kriging to Obtain Bespoke Indices of Neighborhood Characteristics: A Simulation and a Case Study

Data on neighborhood characteristics are not typically collected in epidemiological studies. They are however useful, for example, in the study of small‐area health inequalities and may be available in social surveys. We propose to use kriging based on semi‐variogram models to predict values at nonobserved locations with the aim of obtaining indicators of neighborhood characteristics of epidemiological study participants. The spatial data available for kriging is usually sparse at small distance and therefore we perform a simulation study to assess the feasibility and usability of the method as well as a case study using data from the RECORD study. Apart from having enough observed data at small distances to the non‐observed locations, a good fitting semi‐variogram, a larger range and the absence of nugget effects for the semi‐variogram models are factors leading to a higher reliability. Recommendations on the required number of observations within the neighborhood range are given.

Intelligent robotic arm for human pose recognition based on teleoperation system

With the rapid development of skeleton recognition, machine learning and other technologies, we will find that there are great drawbacks in the control of manipulators. Robot teleoperation refers to the inclusion of human operation in the control loop of robot control. When robots deal with complex perception and a large number of tasks, teleoperation is far superior to intelligent programming when making decisions quickly and dealing with extreme situations. The goal of this paper is to build a robotic arm teleoperation system for human motion capture, so as to solve the problems that the control accuracy of the end of the robotic arm is not high and the motion of the robotic arm is greatly affected by the difference between the human arm in the current related research, the master-slave human motion mapping algorithm is designed and extended with machine learning algorithms. We use inertial motion capture to realize teleoperation, so as to avoid the use of the terminal position and orientation control method of the hand controller to form the control command of the remote robot after tedious calculation, and it is convenient for the operator to complete the attitude tracking task in real time. The obtained attitude information has a larger range, higher sensitivity and better dynamic performance.

Investigating the Mechanical Behaviour of Unbound Granular Material (UGM) for Road Pavement Construction Applications: A Western Victoria Case Study

The behaviour of unbound granular materials (UGMs) used in road construction is crucial in determining the longevity and performance of road pavement. Geotechnical analysis can assist engineers in selecting suitable materials and designing road pavements that meet industry standards. This paper presents the results of laboratory geotechnical tests conducted on unbound granular materials (UGMs) collected from three sites (Roses Gap, Rules East, and Polkemmet Road) in Horsham, Victoria, Australia. UGMs were investigated for their mechanical behaviour and suitability as subgrade materials for road pavements. The study utilised laboratory geotechnical tests, including particle size distribution (PSD), Atterberg limits, compaction (Proctor) test, unconfined compressive strength (UCS), California Bearing Ratio (CBR), and repeated load triaxial (RLT) tests, to evaluate the physical and mechanical properties of the UGM samples. The study indicates that UGM samples collected from different locations displayed variations in their geotechnical properties, such as particle size distribution, water absorption, and CBR strength. Roses Gap samples showed weak cohesion properties, and significant vertical displacements after repeated triaxial tests. However, among the samples in this site, samples with higher clay content (RG21) demonstrated the most promise in triaxial tests. Similarly, the Rules East samples were found to be suitable for low-traffic subgrades due to their satisfactory CBR and RLT testing results, albeit with little cohesion from clay content. Out of three locations, Polkemmet samples were identified as potential subgrade applications, with PR12 being the top recommendation overall. It satisfied PSD, CBR, and RLT test conditions due to acceptable particle size in the largest range, highest CBR strength value, and lowest permanent displacement. The study's findings provide useful information for the design of road pavements using these materials and the characterisation of rural materials around the Horsham region for future use in various other contexts.

Improving Low Mathematics Achievers’ Number Sense via Number Line Training with Board Games

The current study investigated the effect of a number line training via board games with specific contents, namely numerical and figural, on students’ number line estimation skill, arithmetic performance, and mathematics achievement. A total of 30 first graders (15 in experimental and 15 in control group) participated in the study. There were 2 SLD students, one in each, in the experimental and control groups. Number line training with a board game, Sahibingo® was implemented in the experimental group, while a non-numerical board game, Animalbingo, was used in the control group. Training lasted for 30 minutes a day, one day a week, and 4 weeks (2 hours in total).
 Results showed that students, including the SLD, in the experimental group improved their number line estimation skills in 0-10 and 0-20 number range, but not in the 0-100 range. Improvements did not reflect in arithmetic performance and mathematics achievement scores. Although there are some improvements in small range number line estimations possibly because of the familiarity there is no improvement in the larger range and in terms of mathematics achievement scores, possibly because of the shorter period of training. It can be concluded that low mathematics achievers’ number sense can be improved via board games with numerical content. Future research may investigate the effect of longer periods and may include other students with special needs.

Effect of maximum packing fraction of powders on the rheology of metakaolin-based geopolymer pastes

In this work, we study the effect of maximum packing fraction of powders on the rheology of geopolymer pastes. A large range of metakaolin powders is generated either by blending or grinding powders. Blends of metakaolin with quartz and limestone are also studied. We show that the compressive packing model is able to predict correctly over a wide range of values the maximum packing fraction of these powders. We show that an increase of the maximum packing of powders leads to a decrease of the viscosity of geopolymer suspension at a constant solid volume fraction. We finally show that the viscosity of studied geopolymer suspensions can be well predicted by the Krieger Dougherty relation. We suggest that the highest potential degree of freedom allowing for the control of the viscosity of geopolymer pastes without modifying the composition of the suspension lies in the maximum packing fraction of the solid powders.

An event-oriented diffusion-refinement method for sparse events completion

Event cameras or dynamic vision sensors (DVS) record asynchronous response to brightness changes instead of conventional intensity frames, and feature ultra-high sensitivity at low bandwidth. The new mechanism demonstrates great advantages in challenging scenarios with fast motion and large dynamic range. However, the recorded events might be highly sparse due to either limited hardware bandwidth or extreme photon starvation in harsh environments. To unlock the full potential of event cameras, we propose an inventive event sequence completion approach conforming to the unique characteristics of event data in both the processing stage and the output form. Specifically, we treat event streams as 3D event clouds in the spatiotemporal domain, develop a diffusion-based generative model to generate dense clouds in a coarse-to-fine manner, and recover exact timestamps to maintain the temporal resolution of raw data successfully. To validate the effectiveness of our method comprehensively, we perform extensive experiments on three widely used public datasets with different spatial resolutions, and additionally collect a novel event dataset covering diverse scenarios with highly dynamic motions and under harsh illumination. Besides generating high-quality dense events, our method can benefit downstream applications such as object classification and intensity frame reconstruction.

Northwestern Mediterranean Heavy Precipitation Events in a Warmer Climate: Robust Versus Uncertain Changes With a Large Convection‐Permitting Model Ensemble

AbstractTaking advantage of a large ensemble of Convection Permitting‐Regional Climate Models on a pan‐Alpine domain and of an object‐oriented dedicated analysis, this study aims to investigate future changes in high‐impact fall Mediterranean Heavy Precipitation Events at high warming levels. We identify a robust multi‐model agreement for an increased frequency from central Italy to the northern Balkans combined with a substantial extension of the affected areas, for a dominant influence of the driving Global Climate Models for projecting changes in the frequency, and for an increase in intensity, area, volume and severity over the French Mediterranean. However, large quantitative uncertainties persist despite the use of convection‐permitting models, with no clear agreement in frequency changes over southeastern France and a large range of plausible changes in events' properties, including for the most intense events. Model diversity and international coordination are still needed to provide policy‐relevant climate information regarding precipitation extremes.

The effect of musical expertise on whistled vowel identification

In this paper, we looked at the impact of musical experience on whistled vowel categorization by native French speakers. Whistled speech, a natural, yet modified speech type, augments speech amplitude while transposing the signal to a range of fairly high frequencies, i.e. 1 to 4 kHz. The whistled vowels are simple pitches of different heights depending on the vowel position, and generally represent the most stable part of the signal, just as in modal speech. They are modulated by consonant coarticulation(s), resulting in characteristic pitch movements. This change in speech mode can liken the speech signal to musical notes and their modulations; however, the mechanisms used to categorize whistled phonemes rely on abstract phonological knowledge and representation. Here we explore the impact of musical expertise on such a process by focusing on four whistled vowels (/i, e, a, o/) which have been used in previous experiments with non-musicians. We also included inter-speaker production variations, adding variability to the vowel pitches. Our results showed that all participants categorize whistled vowels well over chance, with musicians showing advantages for the middle whistled vowels (/a/ and /e/) as well as for the lower whistled vowel /o/. The whistler variability also affects musicians more than non-musicians and impacts their advantage, notably for the vowels /e/ and /o/. However, we find no specific training advantage for musicians over the whole experiment, but rather training effects for /a/ and /e/ when taking into account all participants. This suggests that though musical experience may help structure the vowel hierarchy when the whistler has a larger range, this advantage cannot be generalized when listening to another whistler. Thus, the transfer of musical knowledge present in this task only influences certain aspects of speech perception.

Nonlocal, Flat-Band Meta-Optics for Monolithic, High-Efficiency, Compact Photodetectors.

Miniaturized photodetectors are becoming increasingly sought-after components for next-generation technologies, such as autonomous vehicles, integrated wearable devices, or gadgets embedded on the Internet of Things. A major challenge, however, lies in shrinking the device footprint while maintaining high efficiency. This conundrum can be solved by realizing a nontrivial relation between the energy and momentum of photons, such as dispersion-free devices, known as flat bands. Here, we leverage flat-band meta-optics to simultaneously achieve critical absorption over a wide range of incidence angles. For a monolithic silicon meta-optical photodiode, we achieved an ∼10-fold enhancement in the photon-to-electron conversion efficiency. Such enhancement over a large angular range of ∼36° allows incoming light to be collected via a large-aperture lens and focused on a compact photodiode, potentially enabling high-speed and low-light operation. Our research unveils new possibilities for creating compact and efficient optoelectronic devices with far-reaching impact on various applications, including augmented reality and light detection and ranging.

Prandtl number effects on extreme mixing events in forced stratified turbulence

Relatively strongly stratified turbulent flows tend to self-organise into a ‘layered anisotropic stratified turbulence’ (LAST) regime, characterised by relatively deep and well-mixed density ‘layers’ separated by relatively thin ‘interfaces’ of enhanced density gradient. Understanding the associated mixing dynamics is a central problem in geophysical fluid dynamics. It is challenging to study LAST mixing, as it is associated with Reynolds numbers $Re := UL/\nu \gg 1$ and Froude numbers $Fr :=(2{\rm \pi} U)/(L N) \ll 1$ ( $U$ and $L$ being characteristic velocity and length scales, $\nu$ the kinematic viscosity and $N$ the buoyancy frequency). Since a sufficiently large dynamic range (largely) unaffected by stratification and viscosity is required, it is also necessary for the buoyancy Reynolds number $Re_{b} := \epsilon /(\nu N^{2}) \gg 1$ , where $\epsilon$ is the (appropriately volume-averaged) turbulent kinetic energy dissipation rate. This requirement is exacerbated for oceanically relevant flows, as the Prandtl number $Pr := \nu /\kappa = {O}(10)$ in thermally stratified water (where $\kappa$ is the thermal diffusivity), thus leading (potentially) to even finer density field structures. We report here on four forced fully resolved direct numerical simulations of stratified turbulence at various Froude ( $Fr=0.5, 2$ ) and Prandtl ( $Pr=1, 7$ ) numbers forced so that $Re_{b}=50$ , with resolutions up to $30\,240 \times 30\,240 \times 3780$ . We find that, as $Pr$ increases, emergent ‘interfaces’ become finer and their contribution to bulk mixing characteristics decreases at the expense of the small-scale density structures populating the well-mixed ‘layers’. However, extreme mixing events (as quantified by significantly elevated local destruction rates of buoyancy variance $\chi _0$ ) are always preferentially found in the (statically stable) interfaces, irrespective of the value of $Pr$ .

A survey of water chemistry used in zebrafish facilities and their effects on early zebrafish development

Background There are a variety of published standard methods and water chemistry recommendations for zebrafish (Danio rerio) husbandry, but empirical evidence for their justification is often lacking, as is information on some variables that have important biological effects on fish. Importantly, these different recommendations could contribute to variability in results and fish welfare between or within institutions. Methods Here we document the current range of water chemistry used by various research institutions around the world and report initial findings on their effects on the development and growth of zebrafish. Over 40 institutes responded to a survey that revealed a large variation in water chemistry used for zebrafish husbandry including differences in the set-points and acceptable ranges for temperature, pH and conductivity. In subsequent experiments, zebrafish (D. rerio, WIK) embryos/larvae exposed to a large range of salt concentrations (50μM to 10mM Na+ or 30 – 2500 μS/cm) and CO2 levels (400 – 8,000 μatm). Results Larvae exposed to the lowest salt concentration (5 μM Na+ or < 30μS/cm) had a slower response to touch and their swim bladders were not inflated. Larvae exposed to 5-100 μM Na+ were 5 % shorter in total body length than those exposed to higher salt concentrations (>100 μM Na+). Zebrafish embryo/larvae exposed to intermediate pCO2 values (~2000 μatm) were 1 to 3.5% longer than those exposed to either ambient (400 μatm) or higher (4000 μatm) pCO2, but pCO2 did not affect developmental endpoints up to 4 dpf. Conclusions Overall, we highlight the magnitude of variation in water chemistry used within zebrafish research and provide some empirical evidence to show that not all of these water conditions might be optimal for developing zebrafish and reproducibility of research, although further research is necessary to determine longer-term effects of water chemistry on older larvae, juveniles and adults.

Highly‐Linear and Wavelength‐Tunable Frequency‐Modulated Continuous‐Wave Hybrid‐Integrated Laser

AbstractFrequency‐sweeping laser sources play a critical role in the accurate 3D mapping of frequency‐modulated continuous‐wave (FMCW) LiDAR systems, whose chirp linearity greatly impacts the measurement precision. Although various pre‐distortion algorithms have been proposed to reduce chirp nonlinearity, these open‐loop methods can rapidly suppress the chirp nonlinearity but they are susceptible to environmental variations and often exhibit subpar performance in long‐range detection scenarios. In contrast, the electro–optical phase‐locked loop (EO‐PLL) serves as a real‐time linearizing solution for FMCW LiDAR, enabling high‐precision, high‐resolution, and long‐distance measurement capabilities. In this study, a III/V‐Si3N4 hybrid‐integrated external cavity laser (ECL) is used to generate an FMCW signal over a large wavelength tuning range of 68 nm. The maximum output optical power is 15.8 mW, and the intrinsic linewidth is 0.9 kHz. By modulating the phase shifter, an FMCW signal with a chirp bandwidth of 0.7 GHz is generated at a repetition rate of 1 kHz. The pre‐distortion algorithm is combined with the gain‐tunable EO‐PLL system to suppress the chirp nonlinearity and frequency noise across multiple wavelengths, leading to a remarkable improvement in range precision from 202 to 4.2 cm when targeting a distance of 200 m.

Enhancing Performances of the VOXES Bragg Spectrometer for XES Investigations

Utilizing a dispersive crystal for X-ray Emission Spectroscopy (XES) significantly enhances the energy resolution when compared with spectroscopy performed with just silicon drift detectors. This high resolution is particularly valuable for studying metals, as it offers essential insights into their electronic structures and chemical environments. Conducting such experiments in the laboratory, as opposed to synchrotron light sources, presents challenges due to the reduced intensities of X-ray tubes and, consequently, low signal rates, with the effect of increasing the acquisition time. In this study, we demonstrate that XES spectra can be acquired within a few hours for a CuNiZn metallic sample alloy while still maintaining a good energy resolution and a large dynamic range. This is achieved with the VOXES spectrometer, developed at INFN National Laboratories of Frascati (LNF), along with a background reduction procedure that enhances the signal from emission lines under study. This study is a showcase for improving the efficiency of XES in tabletop setup experiments.

Force analysis of a soft-rigid hybrid pneumatic actuator and its application in a bipedal inchworm robot

AbstractThis paper systematically investigates a soft-rigid hybrid pneumatic actuator (SRHPA), which consists of a rigid-foldable twisting skeleton capable of a large range of helical motion and a soft bellows muscle with high linear driving force. Considering the unique varying-pitch helical motion of the foldable skeleton, the analytical model mapping the input force generated by the bellows muscle and output forces of the actuator is revealed and verified with a simulation of the force analysis. Prototypes of the actuator are developed by fabricating the twisting skeleton with multilayered aluminum composite panels and 3D-printing the bellows muscle with thermoplastic polyurethane (TPU) 95A filament. The static and dynamic performances of the prototypes are tested to validate the analytical modeling of output forces. Using the actuator as a module, a novel bipedal inchworm robot with four modules is developed and tested to demonstrate its adaptability in confined space by switching between the going-straight, the turning-around, and the rotating gaits. The hybrid actuator and the inchworm robot with zero onboard electronics have the potential to be deployed in extreme environments where pneumatically actuated systems are preferred over electrical machines and drives, such as in nuclear and explosive environments.

Determining optimal range of reduction rates for nitrogen fertilization based on responses of vegetable yield and nitrogen losses to reduced nitrogen fertilizer application

Vegetable production is commonly accompanied by high nitrogen fertilizer rates but low nitrogen use efficiency in China. Reduced fertilization has been frequently recommended in existing studies as an efficient measurement to avoid large amount of nutrient loss and subsequent nonpoint source pollution. However, the reported responses of vegetable yield and nitrogen losses to reduced fertilization rates varied in a large range, which has resulted into large uncertainties in the potential benefits of those recommended reduction rates. Thus, we constructed the relationship between responses of nitrogen losses and vegetable yield to reduced nitrogen fertilization rates to determine the optimal range of reduction rates for nitrogen fertilization in a proportional form based on data reported in literatures across China's mainland, and evaluated the roles of greenhouse, managing options, and vegetable species on the responses. The relationships were constructed separately for 4 subregions: Northern arid and semiarid, loess plateau regions (NSL), Temperate monsoon zone (TMZ), Southeast monsoon zone (SMZ), Southwest zone (SWZ). The optimal nitrogen fertilizer reduction range for the TMZ, SMZ and SWZ were 51 % to 67 %, 40 % to 66 % and 54 % to 80 %, respectively and no reduction for NSL. Vegetable yields were not be sacrificed when fertilizations were reduced within the optimal ranges. Greenhouse and managing options showed no significant effect on the responses of both vegetable yield and nitrogen losses by the optimal reduction range but vegetable species played a relatively important role on the responses of vegetable yield. This indicated that the optimal reduction rates can be effective on reducing nitrogen loss in both open-field and greenhouse conditions across China's mainland without extra managing options. Therefore, the optimal reduction rates can still serve as a good starting point for making regional plans of nitrogen reduction that help balancing the chasing of high vegetable yield and low nitrogen loss.

A generalized data assimilation architecture of digital twin for complex process industrial systems

As one of the critical cores of digital twin (DT), data assimilation (DA) can maintain consistency and synchronization between DT and physical system. Kalman filtering is a common DA method, but its estimation performance is deteriorated by factors such as model inaccuracy and time-varying noise covariance in practical applications. The errors caused by these multiple uncertainties are all coupled to the measurements, which augments the difficulty for DT to obtain physical system information. In order to tackle the DA problem with multiple uncertainties, this paper proposes a generalized DA architecture for DT in sophisticated process industry. First, by combining Stein variational gradient descent and nonlinear Bayesian filtering paradigm, a recursive estimation framework is established, which has higher accuracy in estimating the noise covariance compared to traditional methods. Second, to effectively deal with model inaccuracy by using filtering residuals containing time-varying noise, we propose a neural network and modified wavelet-based model error compensation (NNMW-MEC) block. Based on the modified wavelet technique, the filtering residual denoising built in NNMW-MEC can better cope with time-varying noise compared to existing wavelets, and extract the low-frequency signal involving model error information from noisy residual smoothly. In addition, because of the neural network-based state-compensation subblock, NNMW-MEC has more outstanding ability in compensating the state deviations with large changing range. Finally, we take the boiler system in a coal-fired power plant as an example to verify the effectiveness of our architecture. Experimental results show that the DA architecture proposed in this paper can improve the estimation performance of DT under inaccurate models and uncertain noise statistics.