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Both the physical features and social functions of urban green spaces (UGSs) are crucially important to the ecological and social benefits of urban residents. Increasing attention has been focused on exploring how UGS social functions affect the ecological and social benefits of urban residents, but the social functional classification of UGSs has rarely been studied, and related efficient classification methods are urgently needed. Thus, a novel methodological framework for accurately mapping UGS social functional zones was proposed by integrating remote sensing images, crowd-sourced geospatial data (i.e. point of interest data, the OpenStreetMap road network, and Baidu Map boundary), and a deep learning algorithm. A sequence of combination experiments and ablation experiments were designed for performance validation and for quantifying the contributions of individual crowd-sourced geospatial data to UGS social functional classification. The results showed that the proposed methodological framework can precisely and effectively map UGS social functional zones and that all kinds of crowd-sourced geospatial data contributed to improving the accuracy of UGS social functional classification. This study can assist planners and government departments in the rapid monitoring, effective management, and scientific planning of UGS social functional zones by providing accurate data sources and an effective mapping tool.

Abstract Under transient greenhouse warming, El Niño-Southern Oscillation (ENSO) is projected to increase pre-2100, accompanied by an easier establishment of atmospheric convection in the equatorial eastern Pacific, where sea surface temperature (SST) warms faster than surrounding regions. After 2100, how ENSO variability may change remains unknown. Here we find that under a high emission scenario, ENSO variability post-2100 reverses from the initial increase to an amplitude far smaller than that of the 20th century. The fast eastern warming persists and shrinks the equatorial Pacific non-convective area, such that establishing convection in the non-convective area, as during an El Niño, requires smaller convective anomaly, inducing weaker wind anomalies leading to reduced ENSO SST variability. The nonlinear ENSO response is thus a symptom of the persistent El Niño-like warming pattern. Therefore, the oscillatory ENSO impact could be replaced by that from the permanent El Niño-like mean condition with cumulative influences on affected regions.

In this study, a kind of in-fiber Mach–Zehnder interferometer (MZI) is designed and experimentally examined. The MZI is composed of two in-fiber S-shaped cores (SSCs), which enhance strain sensitivity. To prepare the SSCs, a high-frequency CO2 laser is first utilized to polish grooves on the symmetrical surface of a single-mode fiber (SMF). The polished area is then subjected to arc-discharging by a commercial fusion splicer, and the core of the fiber bends towards the polished grooves due to the self-roundness of the cladding and the heating effect of discharge. The results of the experiments demonstrate that the sensor achieves high strain sensitivities of −66.5 pm/με and −40.1 pm/με within the strain range of 0 με to 350 με. By solving the matrix equation, simultaneous online measurements of temperature and strain can be performed. With the advantages of easy fabrication, low cost, high sensitivity, and compactness, the proposed sensor is a competitive candidate in strain sensing.

As the global population ages, improving health statuses and quality of life has become crucial. Healing spaces enhance older adults’ (OA) physical and mental health and well-being. However, the current research status and development trends must be systematically reviewed to guide future research directions. This study systematically examines the role of healing spaces in improving the health and well-being of OA through a bibliometric analysis. Results reveal three developmental stages: slow start, steady development, and in-depth refinement. Highly cited articles emphasize physical and environmental factors. The main research foundations encompass physical, chemical, biological, and ecological aspects of healing spaces and OA mental health. The research frontier is shifting towards a more comprehensive understanding of OA needs. Keyword analysis indicates a transition from a single physical environment focus to a holistic approach considering psychological, social, and spiritual needs across various disciplines. The field is progressing toward interdisciplinary integration, personalized demand, and systematic development. Future research should prioritize OA spiritual needs, develop scientific evaluation systems for spiritual healing, optimize personalized treatment environments using innovative technologies, and address diverse health and well-being needs. Strengthening international cooperation and integrating global research efforts are also essential for advancing the field.

To obtain high-resolution magnetic force microscopy (MFM) images, it is essential to have a cantilever with a high-quality factor. However, conventional vibrating cantilevers typically have quality factor values in the range of a few hundred, which limits their sensitivity for MFM measurements. To address this limitation, numerous studies have explored methods to enhance the quality factor in different environments, including vacuum, air, and liquid. This study introduces a novel approach for improving the quality factor using flowing helium gas. By selecting helium gas with a low viscosity coefficient, we successfully achieved a higher quality factor (Q-factor) of MFM microcantilever oscillations at room temperature in one atmosphere compared with the Q-factor in air. This provides a potential approach for achieving high-resolution MFM measurements under room temperature conditions. By optimizing the gas flow rate at room temperature in one atmosphere, we successfully obtained a higher MFM cantilever oscillation Q-factor and clearer MFM images compared with the air. The experimental results revealed a long and narrow resonant curve, and the quality factor significantly increased to 778.2, which is 3.8 times higher than that observed in air 205.4. Furthermore, systematic investigations demonstrated the capability of this approach to produce high-resolution MFM images of videotape track patterns under the optimized helium gas flow rate of 60 mm/s.

Under global warming, increased variability in El Niño sea surface temperature was projected to be detectable by about 2070. Here the authors show that the increased variability of a type of more impactful El Niño events is likely detectable by 2030.

Abstract El Niño/Southern Oscillation (ENSO) exhibits evident amplitude asymmetry with stronger El Niño than La Niña events. Equatorial submesoscale eddies act as an important damper of ENSO via their induced upward heat flux (Qeddy,vsub) from the subsurface to the surface ocean. Yet their effect on ENSO amplitude asymmetry remains unexplored. Using a high‐resolution global climate simulation, we found that strengthening of Qeddy,vsub in the Niño3.4 region during La Niña is more evident than weakening of Qeddy,vsub during El Niño, resulting in stronger damping of La Niña than El Niño events. This asymmetric response of Qeddy,vsub to ENSO is primarily ascribed to that of the temperature fronts associated with larger‐scale processes. Using a recharge oscillator model modified to include the effects of Qeddy,vsub, we show that the asymmetric damping of ENSO by Qeddy,vsub contributes importantly to the ENSO amplitude asymmetry.

The leakage of subsea oil and gas pipelines can have adverse impacts on production progress and the ecological environment. Investigating the sound source and near-field sound propagation of pipeline leaks is essential for understanding the acoustic characteristics of and variations in these leaks. Such understanding is significant for the accurate detection and location of small leaks in pipelines. In this study, we designed an experimental system to study the characteristics of leakage sound signals. We introduced the formation mechanism of leakage sound sources and reviewed corresponding theoretical research. The leakage sound signal’s characteristic frequency range was determined to be between 1 kHz and 2 kHz. We examined the effects of pipeline pressure, leakage aperture, and detection distance on the acoustic signal characteristics. The results show that as internal pipe pressure increases, the leakage sound signal intensity first increases and then decreases. As the leakage aperture increases, the intensity of the leakage sound signal increases. Within a short distance, the intensity remains consistent regardless of detection distance. The results of this experimental study can guide the acoustic internal detection of pipelines. This study has practical significance in the timely detection of small leaks in pipelines and preventing leakage accidents from occurring.

Material perception is one of the several essential abilities required by robots, and it also poses significant challenges in real-world field applications. In harsh environments, the existing material recognition methods have the problem of low accuracy. In this paper, ultrasonic technology is applied to the field of material recognition, which is derived from the predatory strategy of echolocation animals. We propose a novel noncontact material recognition method of surrounding objects for robots based on ultrasonic echo signals, which can be used in external extreme environments. This method primarily adopts the 16-dimensional feature vector extracted from intrinsic mode functions that we gain from empirical mode decomposition as inputs of machine learning algorithms to recognize different materials, and we use K-nearest neighbor, decision tree, and support vector machine algorithms on the feature vector set to decide the best classifier, and its acoustic theoretical model is established additionally. The experimental results validate the accuracy of the acoustic theoretical model and the effectiveness of the proposed method. Compared with the existing methods, the proposed method improves the low accuracy and the poor recognition effect in ultrasonic material recognition. This method provides a new idea for robots to recognize and perceive materials in extreme environments.

In radiation measurement, optical fiber sensors (OFS) have many advantages compared to commercial dosimeters, including high spatial resolution. Due to the OFS measurement principle (fluorescence), the recorded measurement results differ from the standard dose value, such as that obtained using an ionization chamber. In this study, a physical correction function is established to considerably reduce the difference. This function quantifies the over-response of OFS to low-energy scattered photons and low-energy electrons. The specific expression of the function is derived from experimental measurement results obtained using the OFS and a commercial standard dosimeter when subject to two different radiation field sizes irradiated using a clinical linac. Following the application of the correction of the function, the measurement difference between the OFS and the standard dosimeter is greatly reduced for a range of radiation fields, in which case the maximum difference decreased from 42.2% to 1.5%. The dose correction method is based on existing quality assurance (QA) protocols used in radiotherapy and is simple and convenient to apply. This research has further promoted the application of OFSs in radiation dose measurement, including radiotherapy QA and in-patient use.

The global navigation satellite system (GNSS) is developing rapidly, and the related market applications and scientific research are increasing. Studies based on large low Earth orbit (LEO) satellite constellations have become research hotspots. The global coverage of the LEO constellation can reduce the dependence of navigation satellites on ground-monitoring stations and improve the precise orbit determination (POD) accuracy of navigation satellites. In this paper, we simulate various LEO satellite constellations (with 12, 30, and 60 satellites), along with ground stations’ observation data, to examine the impact of LEO satellites on the precision of the BeiDou-3 Global Navigation Satellite System (BDS-3) in terms of its POD accuracy. Using the simulated observation data of both LEO satellites and ground-monitoring stations, we analyze the integrated orbit determination for the LEO and BDS-3 satellites. The findings reveal that the 3D orbital accuracy of BDS-3 is 9.51 dm by using only seven ground-monitoring stations, and it is improved to a centimeter level after adding the LEO constellations. As the number of LEO constellation satellites increases, the impact on improving accuracy gradually diminishes. In terms of time synchronization accuracy in the BDS-3, compared to the results of clock offset using only ground stations, the addition of 12 LEO satellites resulted in an improvement of 49% for RMS1(root mean square) and 52% for RMS2 (standard deviation), the addition of 30 LEO satellites resulted in an improvement of 66% for RMS1 and 70% for RMS2, and the addition of 60 LEO satellites resulted in an improvement of 87% for RMS1 and 90% for RMS2. The integrated orbit determination of the LEO and BDS-3 satellites constellation greatly improves the accuracy of time synchronization. In addition, we also use simulated inter-satellite link (ISL) data to perform enhanced BDS-3 satellites POD and time synchronization experiments. The experiments showed that the orbit determination accuracy of the seven sta (seven stations) and ISL scheme is comparable to that of the seven sta and LEO12 scheme, and that the time synchronization accuracy of the seven sta and ISL scheme is slightly worse. The preliminary experiments showed that the LEO satellite could enhance the orbit determination accuracy of BDS-3 and obtain a higher time synchronization accuracy.

We present a novel homebuilt scanning tunneling microscope (STM) with atomic resolution integrated into a cryogen-free superconducting magnet system with a variable temperature insert. The STM head is designed as a nested structure of double piezoelectric tubes (PTs), which are connected coaxially through a sapphire frame whose top has a sample stage. A single shaft made of tantalum, with the STM tip on top, is held firmly by a spring strip inside the internal PT. The external PT drives the shaft to the tip–sample junction based on the SpiderDrive principle, and the internal PT completes the subsequent scanning and imaging work. The STM head is simple, compact, and easy to assemble. The excellent performance of the device was demonstrated by obtaining atomic-resolution images of graphite and low drift rates of 30.2 pm/min and 41.4 pm/min in the X–Y plane and Z direction, respectively, at 300K. In addition, we cooled the sample to 1.6 K and took atomic-resolution images of graphite and NbSe2. Finally, we performed a magnetic field sweep test from 0 T to 9 T at 70 K, obtaining distinct graphite images with atomic resolution under varying magnetic fields. These experiments show our newly developed STM’s high stability, vibration resistance, and immunity to high magnetic fields.

In this work, the feasibility of solid-surface three-dimensional fluorescence (SSTF) in combination with chemometrics to rapidly and directly determine three PAHs in drill cuttings recycling products was studied for the first time. Due to the nondestructive characteristics of SSTF and the “mathematical separation” of chemometric three-way calibration, neither time-consuming sample pretreatments nor toxic organic reagents were involved in the determination. By using the smart “mathematical separation” function of the parallel factor analysis (PARAFAC) algorithm, clear spectral profiles together with reasonable quantitative results for the three target PAHs were successfully extracted from the total SSTF signals of drill cuttings recycling products without the need for chromatographic separation. The linearity of the calibration models was good (R2 > 0.96) and the average spiked recoveries of three target PAHs were between 88.1–102.7% with a relative standard deviation less than 20%. Nevertheless, given the green, fast, low-cost, and nondestructive advantages of the proposed strategy, it has the potential to be used as a fast screening approach and allow for a quick survey of PAHs in drill cuttings recycling products.

Abstract The westerly wind burst (WWB) is an important triggering mechanism of El Niño and typically occurs in the western Pacific Ocean. The Fourier spectrum of the wind field over the western tropical Pacific is characterised by a large variety of peaks distributed from intra-seasonal to decadal time scales, suggesting that WWBs could be a result of nonlinear interactions on these time scales. Using a combination of observations and simulations with 15 coupled models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), we demonstrate that the main drivers initiating WWBs are quantifiable physical processes rather than atmospheric stochastic signals. In this study, ensemble empirical mode decomposition (EEMD) from the Holo-Hilbert spectral analysis (HHSA) is used to decompose daily zonal winds over the western equatorial Pacific into seasonal, interannual and decadal components. The seasonal element, with prominent spectral peaks of less than 12 months, is not ENSO related, and we find it to be strongly associated with the East Asian monsoon (EAM) and cross-equatorial flow (CEF) over the Australian monsoon region. The CEF is directly related to the intensity of the Australian subtropical ridge (STR-I). Both the EAM and CEF are essential sources of these high-frequency winds over the western Pacific. In contrast, the interannual wind component is closely related to El Niño occurrences and usually peaks approximately two months prior to a typical El Niño event. Finally, the decadal element merely represents a long-term trend and thus has little to no relation to El Niño. We identified EAM- and CEF-induced westerly wind anomalies in December–January–February (DJF) and September–October–November (SON). However, these anomalies fade in March–April–May (MAM), potentially undermining the usual absence of WWBs in the boreal spring. Similar results are found in CMIP6 historical scenario data.

Transistors in three-phase voltage-source inverter often suffer from open-circuit failures due to the lifting of bonding wires caused by thermic cycling, resulting in performance degradation with ripple torque and current harmonics. Current-spectral-analysis based methods are widely applied to failure diagnosis; however, high calculation consumption and complex implementation limit their application in some real-time occasion. In this paper, a simplified Fourier series method is proposed by the product between reconstructed phase currents and reference signals. Meanwhile, a novel normalized method for DC and fundamental components of simplified Fourier series are proposed to locate twenty-one transistor open-circuit faults. Numerical results show that the proposed Fourier series method coincides with that of Fast Fourier Transform. Experimental results and the comparison with previous methods show high efficiency and merits of its application to transistor open-circuit fault location in the voltage-source inverter.

Accumulating observational studies suggested that hypercholesterolemia is associated with vascular dementia (VaD); however, the causality between them remains unclear. Hence, the aim of this study is to infer causal associations of circulating lipid-related traits [including high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), apolipoprotein A-I (apoA-I), and apolipoprotein B (apoB)] with VaD jointly using univariable MR (uvMR), multivariable MR (mvMR) and bidirectional two-sample MR methods. Then, the summary-data-based MR (SMR) and two-sample MR analysis were conducted to investigate the association of lipid-lowering drugs target genes expression (including HMGCR, PCSK9, NPC1L1, and APOB) and LDL-C level mediated by these target genes with VaD. The results of forward MR analyses found that genetically predicted HDL-C, LDL-C, TG, apoA-I, and apoB concentrations were not significantly associated with the risk of VaD (all p > 0.05). Notably, there was suggestive evidence for a causal effect of genetically predicted VaD on HDL-C via reverse MR analysis [odds ratio (OR), 0.997; 95% confidence interval (CI), 0.994–0.999; p = 0.022]. On the contrary, the MR results showed no significant relationship between VaD with LDL-C, TG, apoA-I, and apoB. The results for the SMR method found that there was no evidence of association for expression of HMGCR, PCSK9, NPC1L1, and APOB gene with risk of VaD. Furthermore, the result of MR analysis provided evidence for the decreased LDL-C level mediated by gene HMGCR reduced the risk of VaD (OR, 18.381; 95% CI, 2.092–161.474; p = 0.009). Oppositely, none of the IVW methods indicated any causal effects for the other three genes. Using genetic data, this study provides evidence that the VaD risk may cause a reduction of HDL-C level. Additionally, the finding supports the hypothesis that lowering LDL-C levels using statins may be an effective prevention strategy for VaD risk, which requires clinical trials to confirm this result in the future.

Frozen fractured rock mass is often encountered during the implementation of geotechnical engineering in cold regions. The tensile strength parameters of frozen rock play an important role in the construction of rock slopes involving tensile failure. In order to study the tensile characteristics of a frozen fractured rock mass in a cold region, original rock specimens were mined and processed in the Yulong Copper Mine, and artificial, frozen fractured marble specimens were made. The effects of different ice-filled crack angles, lengths, and widths on the force–displacement curve and the tensile strength of frozen rock were studied by laboratory Brazilian splitting experiments and RFPA3D, and the evolution law of the tensile strength of frozen rock was revealed. At the same time, wing crack initiation and cracking mode after tensile failure were analyzed by high-speed camera; the whole process of the Brazilian splitting of frozen rock was reconstructed, and the development of microcrack initiation in frozen rock was analyzed. The following conclusions were drawn from the test results: the frozen rock specimens have typical brittle-failure characteristics. The tensile strength of frozen rock decreases gradually with the increase in the width and length of ice-filled cracks, and decreases first and then increases with the increase in the angle of the ice-filled crack. The ice-filled crack incurs damage first, and then the wing cracks start from the tip of the ice-filled crack and extend continuously. The tensile strength of frozen rock is significantly affected by the angle and length of ice-filled cracks.

Magnetic Force Microscopy (MFM) is among the best techniques for examining and assessing local magnetic characteristics in surface structures at scales and sizes. It may be viewed as a unique way to operate atomic force microscopy with a ferromagnetic tip. The enhancement of magnetic signal resolution, the utilization of external fields during measurement, and quantitative data analysis are now the main areas of MFM development. We describe a new structure of MFM design based on a cryogen-free superconducting magnet. The piezoelectric tube (PZT) was implemented with a tip-sample coarse approach called SpiderDrive. The technique uses a magnetic tip on the free end of a piezo-resistive cantilever which oscillates at its resonant frequency. We obtained a high-quality image structure of the magnetic domain of commercial videotape under extreme conditions at 5 K, and a high magnetic field up to 11 T. When such a magnetic field was gradually increased, the domain structure of the videotape did not change much, allowing us to maintain the images in the specific regions to exhibit the performance. In addition, it enabled us to locate the sample region in the order of several hundred nanometers. This system has an extensive range of applications in the exploration of anisotropic magnetic phenomena in topological materials and superconductors.

Paurocephala sauteri (Enderlein, 1914) (Hemiptera: Psyllidae) is a species of a psyllid distributed in Asia. Mulberry is the only known host for P. sauteri until now. The complete mitogenome of P. sauteri (accession number: MT759765) 14,963 bp in size, including 13 protein-coding genes, 22 transfer RNAs, and two ribosomal RNAs genes. The base composition of the whole P. sauteri mitogenome is 40.26% for A, 7.86% for G, 34.07% for T, and 11.81% for C, with a high AT bias of 80.33%. The mitochondrial genome of P. sauteri was sequenced and annotated as the first representative of family Paurocephalidae. The present data could contribute to a detailed phylogeographic analysis of this valuable economic insect for further study in differentiating closely related species.

The broadcast ionospheric model is one of the main methods for eliminating ionospheric delay errors for the Global Navigation Satellite Systems (GNSS) single-frequency users. GPS Klobuchar model (GPSK8) is the widely used broadcast ionospheric model for GPS, while BDS usually implements the BDS Klobuchar model (BDSK8) and BeiDou Global Broadcast Ionospheric Delay Correction Model (BDGIM). Geomagnetic storms may cause interference within the ionosphere and near-Earth space, compromising the accuracy of ionospheric models and adversely affecting the navigation satellite systems. This paper analyzes the static Standard Point Positioning (SPP) accuracy of GPS and BDS by implementing the broadcast ionospheric models and then investigates the impact of strong geomagnetic storms occurring in 2021 on positioning accuracy. The results show that the global 3D positioning accuracy (95%) of GPS + GPSK8, BDS + BDSK8, and BDS + BDGIM are 3.92 m, 4.63 m, and 3.50 m respectively. BDS has a better positioning accuracy in the northern hemisphere than that of the southern hemisphere, while the opposite is valid for GPS. In the mid-latitude region of the northern hemisphere, BDS + BDSK8 and BDS + BDGIM have similar positioning accuracy and are both better than GPS + GPSK8. The positioning accuracy after applying those three broadcast ionospheric models shows the superior performances of winter and summer over spring and autumn (based on the northern hemisphere seasons). With the exception of during winter, nighttime accuracy is better than that of daytime. The strong geomagnetic storm that occurred on the day of year (DOY) 132, 2021 has an impact on the positioning accuracy for only a small number of stations; however, the global average positioning accuracy is not significantly affected. The strong geomagnetic storms that occurred in DOY 307 and DOY 308 have a significant impact on the positioning accuracy of dozens of stations, and the global average positioning accuracy is affected to a certain extent, with some stations experiencing a serious loss of accuracy. Decreased degrees in positioning accuracy is proportional to the intensity of the geomagnetic storm. Of the 33 IGS Multi-GNSS Experiment (MGEX) stations worldwide, those located in the low and mid-latitudes are more significantly affected by the geomagnetic storms compared with higher latitudes. Evident fluctuations of the positioning errors existed during the strong geomagnetic storms, with an increase in extreme values, particularly in the up direction.

A novel sensor structure has been proposed and experimentally investigated for simultaneous strain and temperature measurement. The structure is fabricated by weak power modulation of CO2 laser exposure on tapered long period fiber grating (LPFG). Compared with the transmission spectrum of the tapered LPFG, two peaks appear in the transmission spectrum of the novel structure. These resonance peaks exhibit different sensitivity responses; thus, simultaneous measurement of strain and temperature is realized by monitoring the wavelength shift of the two peaks. Experiment results indicate that strain sensitivities of the two peaks are 1.82 pm/με and 8.17 pm/με, and temperature sensitivities are 47.9 pm/°C and 65 pm/°C, respectively.

The grid-connected inverter is a vital power electronic equipment connecting distributed generation (DG) systems to the utility grid. The quality of the grid-connected current is directly related to the safe and stable operation of the grid-connected system. This study successfully constructed a robust control system for a grid-connected inverter through a dynamic recurrent fuzzy-neural-network imitating sliding-mode control (DRFNNISMC) framework. Firstly, the dynamic model considering system uncertainties of the grid-connected inverter is described for the global integral sliding-mode control (GISMC) design. In order to overcome the chattering phenomena and the dependence of the dynamic information in the GISMC, a model-free dynamic recurrent fuzzy-neural-network (DRFNN) is proposed as a major controller to approximate the GISMC law without the extra compensator. In the DRFNN, a Petri net with varied threshold is incorporated to fire the rules, and only the parameters of the fired rules are adapted to alleviate the computational workload. Moreover, the network is designed with internal recurrent loops to improve the dynamic mapping capability considering the uncertainties in the control system. In addition, to assure the parameter convergence in the adaptation and the stability of the designed control system, the adaptation laws for the parameters of the DRFNN are deduced by the projection theorem and Lyapunov stability theory. Finally, the experimental comparisons with the GISMC scheme are performed in an inverter prototype to verify the superior performance of the proposed DRFNNISMC framework for the grid-connected current control.

The characteristics and performance of satellite clocks are important to the positioning, navigation, and timing (PNT) services of Global Navigation Satellite System (GNSS) users. Although China’s BeiDou-3 Navigation Satellite System (BDS-3) has been fully operational for more than one year, there is still a lack of comprehensive research on the onboard clocks of the entire BDS-3 constellation. In this study, the precise clock products of GeoForschungsZentrum (GFZ) from day-of-year (DOY) 1, 2021 to DOY 300, 2021 were used to analyze the characteristics and performance of BDS-3 onboard clocks from the following aspects: clock bias, frequency, drift rate, fitting residuals, periodicity, and frequency stability. Compared with BDS-2, the clock quality of BDS-3 satellites has been greatly improved, but there are still jumps in the clock offsets and frequency series of BDS-3 clocks. The drift rate of BDS-3 clocks varies within the range between −2×10−18 and 2×10−18 s/s2. The daily model fitting residuals of passive hydrogen masers (PHM) on BDS-3 medium Earth orbit (MEO), inclined geosynchronous orbit (IGSO), and geostationary (GEO) satellites are 0.15, 0.28, and 0.46 ns, respectively. The overlapping Allan deviation (OADEV) of BDS-3 MEO clocks is 4.0 × 10−14 s/s at a time interval of 1000 s. The PHMs on BDS-3 MEO satellites exhibit fewer periodic signals than those of Rb clocks. In addition, the precise clock offsets of the BDS-3 PHMs carried on the MEO, IGSO, and GEO satellites show different periodicities, which are similar to those of the corresponding types of BDS-2 satellites.

A new type of Mach-Zehnder interferometer (MZI) is proposed to measure twist and temperature. The sensor contains a pretwisted taper and a ball. The pretwisted taper is made by pretwisted, and then, thermally tapering along a single-mode fiber, to induce permanent spiral distortion in the fiber. The experimental results indicate that the sensor has higher twist sensitivity. Twisting the sensor for counterclockwise and clockwise direction, the twist sensitivities of Dip 1584 nm are -0.378 and 0.083 nm/(rad/m), respectively, and the twist sensitivities of Dip 1685 nm are -0.117 and 0.089 nm/(rad/m), respectively. Meanwhile, the twist direction can be determined by the value of the twist sensitivities. The temperature sensitivities of Dip 1584 and Dip 1685 nm are 63 pm/°C and 74 pm/°C, respectively. The feasibility of measuring the torsion and temperature characteristics has been experimentally confirmed. Thus, the proposed MZI sensor can be used to measure twist and temperature and discriminate twist direction.

With the rapid development and gradual perfection of GNSS in recent years, improving the real-time service performance of GNSS has become a research hotspot. In GNSS single-point positioning, broadcast ephemeris is used to provide a space–time reference. However, the orbit parameters of broadcast ephemeris have meter-level errors, and no mathematical model can simulate the variation of this, which restricts the real-time positioning accuracy of GNSS. Based on this research background, this paper uses a BP (Back Propagation) neural network and a PSO (Particle Swarm Optimization)–BP neural network to model the variation in the orbit error of GPS and BDS broadcast ephemeris to improve the accuracy of broadcast ephemeris. The experimental results showed that the two neural network models in GPS can model the broadcast ephemeris orbit errors, and the results of the two models were roughly the same. The one-day and three-day improvement rates of RMS(3D) were 30–50%, but the PSO–BP neural network model was better able to model the trend of errors and effectively improve the broadcast ephemeris orbit accuracy. In BDS, both of the neural network models were able to model the broadcast ephemeris orbit errors; however, the PSO–BP neural network model results were better than those of the BP neural network. In the GEO satellite outcome of the PSO–BP neural network, the STD and RMS of the orbit error in three directions were reduced by 20–70%, with a 20–30% improvement over the BP neural network results. The IGSO satellite results showed that the PSO–BP neural network model output accuracy of the along- and radial-track directions experienced a 70–80% improvement in one and three days. The one- and three-day RMS(3D) of the MEO satellites showed that the PSO–BP neural network has a greater ability to resist gross errors than that of the BP neural network for modeling the changing trend of the broadcast ephemeris orbit errors. These results demonstrate that using neural networks to model the orbit error of broadcast ephemeris is of great significance to improving the orbit accuracy of broadcast ephemeris.

Abstract Background The primary aim of this study was to evaluate the safety of a novel dendritic cell (DC) vaccine pulsed with survivin and MUC1, silenced with suppressor of cytokine signaling 1 (SOCS1), and immune stimulated with flagellin for patients with stage I to IIIA non-small cell lung cancer (NSCLC) in a phase I open-label, uncontrolled, and dose-escalation trial. Moreover, we evaluate the potential efficacy of this modified DC vaccine as secondary aim. Methods The patients were treated with the vaccine at 1 × 106, 1 × 107and the maximum dose 8 × 107 at day 7, 14, and 21 after characterization of the vaccine phenotype by flow cytometry. The safety of the vaccine was assessed by adverse events, and the efficacy by the levels of several specific tumor markers and the patient quality of life. Results The vaccine was well tolerated without dose-limiting toxicity even at higher doses. The most common adverse event reported was just grade 1 flu-like symptoms without unanticipated or serious adverse event. A significant decrease in CD3 + CD4 + CD25 + Foxp3+ T regulatory (Treg) cell number and increase in TNF-α and IL-6 were observed in two patients. Two patients showed 15% and 64% decrease in carcino-embryonic antigen and CYFRA21, respectively. The vaccination with the maximum dose significantly improved the patients’quality of life when administered at the highest dose. More importantly, in the long-term follow-up until February 17, 2017, 1 patient had no recurrence, 1 patients had a progressive disease (PD), and 1 patient was died in the low dose group. In the middle dose group, all 3 patients had no recurrence. In the high dose group, 1 patient was died, 1 patient had a PD, and the other 7 patients had no recurrence. Conclusions We provide preliminary data on the safety and efficacy profile of a novel vaccine against non-small cell lung cancer, which was reasonably well tolerated, induced modest antitumor activity without dose-limiting toxicity, and improved patients’ quality of life. Further more, the vaccine maybe a very efficacious treatment for patients with resected NSCLC to prevent recurrence. Our findings on the safety and efficacy of the vaccine in this phase I trial warrant future phase II/III clinical trial.

Abstract Human serum albumin (HSA) is an intrinsic protein and important carrier that transports endogenous as well as exogenous substances across cell membranes. Herein, we have designed and prepared resveratrol (RV)-loaded HSA nanoparticles conjugating RGD (arginine–glycine–aspartate) via a polyethylene glycol (PEG) “bridge” (HRP–RGD NPs) for highly effective targeted pancreatic tumor therapy. HRP–RGD NPs possess an average size of 120 ± 2.6 nm with a narrow distribution, a homodisperse spherical shape, a RV encapsulation efficiency of 62.5 ± 4.21%, and a maximum RV release ratio of 58.4.2 ± 2.8% at pH 5.0 and 37 °C. In vitro biocompatibility of RV is improved after coating with HSA and PEG. Confocal fluorescence images show that HRP–RGD NPs have the highest cellular uptake ratio of 47.3 ± 4.6% compared to HRP NPs and HRP–RGD NPs with free RGD blocking, attributing to an RGD-mediated effect. A cell counting kit-8 (CCK-8) assay indicates that HRP–RGD NPs without RV (HP–RGD NPs) have nearly no cytotoxicity, but HRP–RGD NPs are significantly more cytotoxic to PANC-1 cells compared to free RV and HRP NPs in a concentration dependent manner, showing apoptotic morphology. Furthermore, with a formulated PEG and HSA coating, HRP–RGD NPs prolong the blood circulation of RV, increasing approximately 5.43-fold (t1/2). After intravenous injection into tumor-bearing mice, the content of HRP–RGD NPs in tumor tissue was proven to be approximately 3.01- and 8.1-fold higher than that of HRP NPs and free RV, respectively. Based on these results, HRP–RGD NPs were used in an in vivo anti-cancer study and demonstrated the best tumor growth suppression effect of all tested drugs with no relapse, high in vivo biocompatibility, and no significant systemic toxicity over 35 days treatment. These results demonstrate that HRP–RGD NPs with prolonged blood circulation and improved biocompatibility have high anti-cancer effects with promising future applications in cancer therapy.

Satellite chip shape distortions lead to signal tracking errors in pseudorange measurements, which are related to the receiver manufacturers, called receiver-related pseudorange biases. Such biases will lead to adverse effects for differential code bias (DCB) and satellite clock estimation, single point positioning (SPP) and precise point positioning (PPP) applications with pseudoranges. In order to assess the characteristics of receiver-related pseudorange biases for global positioning system (GPS), Galileo navigation satellite system (Galileo) and BeiDou navigation satellite system (BDS), seven short baselines from the Multi-GNSS experiment (MGEX) network are tested. The results demonstrate that there are significant inconsistences of pseudorange biases according to satellites, frequencies, receiver and antenna types. For the baselines using the same receivers of TRIMBLE, pseudorange biases are within ±0.2 ns with the same antennas, while they increase to ±0.6 ns with the different antennas. As for baselines with mixed receiver types, pseudorange biases can reach up to 2.5 ns. Among GPS/Galileo/BDS, Galileo shows the smallest pseudorange biases, and the obvious inconsistences of pseudorange biases are observed between BDS-2 and BDS-3, and Galileo in-orbit validation (IOV) satellites and full operational configuration (FOC) satellites. In order to validate receiver-related pseudorange biases, we carry out relative positioning experiments using short baselines. The results show that the RMS values of position errors are reduced 12.6% and 11.4% in horizontal and vertical components with biases correction. The impacts of receiver-related pseudorange biases on wide-lane (WL) ambiguity are also discussed. The results indicate that the percentage of the fractional parts within ±0.1 cycles have an obvious increase with the pseudorange biases correction, and RMS values of the fractional parts are reduced 28.9% and 67.6% for GPS and BDS, respectively.

A structure made of tapered three-core fiber and CO2 laser notch long-period fiber grating is proposed in this paper. By adjusting the taper waist diameter of a three-core fiber, this structure is made suitable for simultaneous strain and temperature measurements. The effectiveness of the proposed structure in realizing simultaneous measurement sensitivity is verified by measuring the sensitivities of the two peaks at the variation of the wavelength and the depth difference. Experimental results indicate that the wavelength sensitivities of the two peaks are -2.96 nm mε-1, 42.9 pm °C-1 and -1.52 nm mε-1, 47.4 pm °C-1 for strain and temperature, respectively, and the depth sensitivities of two peaks can reach 2.5 dB mε-1, 0.007 dB °C-1 and -2.8 dB mε-1, -0.013 dB°C-1. It can therefore be concluded that the proposed structure can be realized by adjusting the taper waist diameter of a three-core fiber for simultaneous strain and temperature measurements.

Dual one-way inter-satellite link (ISL) pseudoranges of BDS-3 satellites can be introduced as an additional measurement along with L-band pseudoranges and phases to improve the accuracy of precise orbit determination (POD). In the existing research, although the clock-free or geometry-free ISL observables are derived from the raw two one-way pseudoranges, only the clock-free observables are adopted for the ISL joint POD (Joint 1 POD) without considering the geometric-free observables. An improved joint (Joint 2 POD) strategy making full use of the clock-free and geometry-free observables is applied in this contribution. The orbits of ground-only POD, ISL-only POD, Joint 1 POD, and Joint 2 POD are comprehensively compared by the orbit overlapping differences, the Satellite Laser Ranging (SLR) residuals, and the characteristics of the satellite clock offsets estimated simultaneously. The comparisons prove that the performance of the Joint 2 POD strategy is better than that of the other three POD strategies regardless of the types of satellites. Moreover, this paper discusses ISL’s contribution to the station selection strategy in terms of the number and distribution. The experimental results show that, when there are more than 20 stations, each additional 10 stations contributes to a maximum of 7.5%, 3.9%, and 2.8% improvement on MEO, IGSO, and GEO satellites 3D accuracy, respectively. When the number of stations reaches 50, the precise orbits achieve similar accuracy to the results using 80 stations. In addition, after adding ISL data, the orbits estimated using 10 regional stations and 10 global stations are greatly improved, and the accuracy between them is only 0.9 cm in 3D errors.

Coir fiber (CF), an eco-friendly and renewable natural fiber, was introduced into magnesium phosphate cement (MPC) mortar to improve its crack resistance. A total of 21 specimens were employed to investigate the failure pattern, compressive strength, stress–strain curve, and energy absorption of MPC with varying CF lengths (0, 5, 10, 15, 20, 25, and 30 mm) after a curing period of 28 days through a static compressive test. The results demonstrated that compressive strength, elastic modulus, and secant modulus decreased with the increase in CF length. However, energy absorption presented a convex curve, which increased to the maximum value (77.0% relative to the value of the specimen without CF) with a CF length of 20 mm and then declined. A series of modern micro-tests were then carried out to analyze the microstructure and composition of specimens to explain the properties microscopically.

For single-frequency Global Navigation Satellite Systems (GNSSs) users, ionospheric delay is the main error source affecting the accuracy of positioning. Applying a broadcast ionospheric correction model to mitigate the ionospheric delay is essential for meter-to-decimeter-level accuracy positioning. To provide support for real-time single-frequency operations, particularly in the China area, we assessed the performance of three broadcast ionospheric correction models, namely, the Neustrelitz total electron content (TEC) broadcast model (NTCM-BC), the BeiDou global broadcast ionospheric delay correction model (BDGIM), and the Klobuchar model. In this study, the broadcast coefficients of Klobuchar and BDGIM are obtained from the navigation data files directly. Two sets of coefficients of NTCM-BC for China and global areas are estimated. The slant total electron contents (STEC) data from more than 80 validation stations and the final vertical TEC (VTEC) data of the Center for Orbit Determination in Europe (CODE) are used as independent benchmarks for comparison. Compared to GPS STEC during the period of Day of Year (DOY) 101~199, 2019, the ionospheric correction ratio of NTCM-BC, BDGIM, and Klobuchar are 79.4%, 64.9%, and 57.7% in China, respectively. For the global area, the root-mean-square (RMS) errors of these three models are 3.67 TECU (1 TECU = 1016 electrons/m2), 5.48 TECU, and 8.92 TECU, respectively. Compared to CODE VTEC in the same period, NTCM-BC, BDGIM, and Klobuchar can correct 72.6%, 69.8%, and 61.7% of ionospheric delay, respectively. Hence, NTCM-BC is recommended for use as the broadcast ionospheric model for the new-generation BeiDou satellite navigation system (BDS) and its satellite-based augmentation system.

We have proposed a novel tapered-single mode-no core-single mode (TSNS) fiber refractometer based on multimode interference. The TSNS structure exhibits a high contrast ratio (>15 dB) and a uniform interference fringe. The influence of different lengths and diameters of the TSNS on the refractive index unit (RIU) sensitivity was investigated. The experimental investigations indicated a maximum sensitivity of 1517.28 nm/RIU for a refractive index of 1.417 and low-temperature sensitivity (

The international GNSS monitoring and assessment system (iGMAS) tracking network has been established by China to track multi-GNSS satellites. A key feature of iGMAS stations is the capability to fully track new navigation signals from the recently deployed BDS-3 satellites. In addition to the B1I and B3I signals inherited from BDS-2 satellites, the BDS-3 satellites are capable of transmitting new open service signals, including B1C at 1575.42 MHz, B2a at 1176.45 MHz, and B2b at 1207.14 MHz. In this contribution, we present a comprehensive analysis and characterization of GNSS signals tracked by different receivers and antennas equipped in the iGMAS network, especially as they relate to BDS-3 signals. Signal characteristics are analyzed in terms of the carrier-to-noise density ratio for the different signals as measured by the receiver, as well as pseudo-range noise and multipath. Special attention is given to discussion of the satellite-induced code bias, which has been identified to exist in the code observations of BDS-2, and the inter-frequency clock bias (IFCB), which has been observed in the triple-frequency carrier phase combinations of GPS Block IIF and BDS-2 satellites. The results indicate that the satellite-induced code bias is negligible for all signals of BDS-3 satellites, while small IFCB variations with peak amplitudes of about 1 cm can be recognized in BDS-3 triple-carrier combinations.

The characteristics of the improved Atomic Frequency Standard (AFS) operated on the latest BeiDou-3 experimental satellites are analyzed from day-of-year (DOY) 254 to 281, of the year 2017, considering the following three aspects: stability, periodicity, and prediction precision. The two-step method of Precise Orbit Determination (POD) is used to obtain the precise clock offsets. We presented the stability of such new clocks and studied the influence of the uneven distribution of the ground stations on the stability performance of the clock. The results show that the orbit influence on the Medium Earth Orbit (MEO) clock offsets is the largest of three satellite types, especially from 3 × 10 3 s to 8.64 × 10 4 s. Considering this orbit influence, the analysis shows that the Passive Hydrogen Maser (PHM) clock carried on C32 is approximately 2.6 × 10 − 14 at an interval of 10 4 , and has the best stability for any averaging intervals among the BeiDou satellite clocks, which currently achieves a level comparable to that of the PHM clock of Galileo, and the rubidium (Rb) clocks of Global Positioning System (GPS) Block IIF. The stability of the improved Rb AFS on BeiDou-3 is also superior to that of BeiDou-2 from 3 × 10 2 s to 3 × 10 3 s, and comparable to that of Rb AFS on the Galileo. Moreover, the periodicity of the PHM clock and the improved Rb clock are presented. For the PHM clock, the amplitudes are obviously reduced, while the new Rb clocks did not show a visible improvement, which will need further analysis in the future. As expected, the precision of the short-term clock prediction is improved because of the better characteristics of AFS. The Root Mean Square (RMS) of 1-h clock prediction is less than 0.16 ns.

Currently, ultra-rapid orbits play an important role in the high-speed development of global navigation satellite system (GNSS) real-time applications. This contribution focuses on the impact of the fitting arc length of observed orbits and solar radiation pressure (SRP) on the orbit prediction performance for GPS, GLONASS, Galileo and BeiDou. One full year’s precise ephemerides during 2015 were used as fitted observed orbits and then as references to be compared with predicted orbits, together with known earth rotation parameters. The full nine-parameter Empirical Center for Orbit Determination in Europe (CODE) Orbit Model (ECOM) and its reduced version were chosen in our study. The arc lengths of observed fitted orbits that showed the smallest weighted root mean squares (WRMSs) and medians of the orbit differences after a Helmert transformation fell between 40 and 45 h for GPS and GLONASS and between 42 and 48 h for Galileo, while the WRMS values and medians become flat after a 42 h arc length for BeiDou. The stability of the Helmert transformation and SRP parameters also confirmed the similar optimal arc lengths. The range around 42–45 h is suggested to be the optimal arc length interval of the fitted observed orbits for the multi-GNSS joint solution of ultra-rapid orbits.

Aiming at how precise to track by LOS, a method is proposed. The method combines the advantages of LOS simplicity and intuition, easy parameter setting and good convergence, with the features of GPC softening, multi-step prediction, rolling optimization and excellent controllability and robustness. In order to verify the effectiveness of the method, the method is simulated by Matlab. The simulation’s results show that it makes ship tracking highly precise.

Delayed healing or non-union of skeletal fractures are common clinical complications. Ibandronate is a highly potent anti-catabolic reagent used for treatment of osteopenia and fracture prevention. We hypothesized that local application of ibandronate after fracture fixation may improve and sustain callus formation and therefore prevent delayed healing or non-union. This study tested the effect of local application of an ibandronate/gelatin sponge composite on osteotomy healing. A right-side distal-femoral osteotomy was created surgically, with fixation using a k-wire, in forty adult male rabbits. The animals were divided into four groups of ten animals and treated by: (i) intravenous injection of normal saline (Control); (ii) local implantation of absorbable gelatin sponge (GS); (iii) local implantation of absorbable GS containing ibandronate (IB+GS), and (iv) intravenous injection of ibandronate (IB i.v.). At two and four weeks the affected femora were harvested for X-ray photography, computed tomography (CT), biomechanical testing and histopathology. At both time-points the results showed that the calluses in both the ibandronate-treated groups, but especially in the IB+GS group, were significantly larger than in the control and GS groups. At four weeks the cross sectional area (CSA) and mechanical test results of ultimate load and energy in the IB+GS group were significantly higher than in other groups. Histological procedures showed a significant reduction in osteoclast numbers in the IB+GS and IB i.v. groups at day 14. The results indicate that local application of an ibandronate/gelatin sponge biomaterial improved early osteotomy healing after surgical fixation and suggest that such treatment may be a valuable local therapy to enhance fracture repair and potentially prevent delayed or non-union.

Fiber optic biosensor has a great potential to meet the need for rapid, sensitive,and real-time microbial detection systems. We developed an antibody-based fiber-opticbiosensor to rapidly detect low levels of Escherichia coli O157:H7 cells in ground beef. Theprinciple of the sensor is a sandwich immunoassay using an antibody which is specific forE. coli O157:H7. A polyclonal antibody was first immobilized on polystyrene fiberwaveguides through a biotin-streptavidin reaction that served as a capture antibody. AnAlexa Fluor 647 dye-labeled antibody to E. coli O157:H7 was used to detect cells andgenerate a specific fluorescent signal, which was acquired by launching a 635 nm laser-lightfrom an Analyte-2000. Fluorescent molecules within several hundred nanometers of thefiber were excited by an evanescent wave, and a portion of the emission light fromfluorescent dye transmitted by the fiber and collected by a photodetector at wavelengths of670 to 710 nm quantitatively. This immunosensor was specific for E. coli O157:H7compared with multiple other foodborne bacteria. In addition, the biosensor was able todetect as low as 103 CFU/ml pure cultured E. coli O157:H7 cells grown in culture broth.Artificially inoculated E. coli O157:H7 at concentration of 1 CFU/ml in ground beef couldbe detected by this method after only 4 hours of enrichment.

Recent outbreaks of food borne illnesses continue to support the need for rapidand sensitive methods for detection of foodborne pathogens. A method for detecting Listeriamonocytogenes in food samples was developed using an automated fiber-optic-basedimmunosensor, RAPTORTM. Detection of L. monocytogenes in phosphate buffered saline(PBS) was performed to evaluate both static and flow through antibody immobilizationmethods for capture antibodies in a sandwich assay. Subsequent detection in frankfurtersamples was conducted using a flow through immobilization system. A two stage blockingusing biotinylated bovine serum albumin (b-BSA) and BSA was effectively employed toreduce the non-specific binding. The sandwich assay using static or flow through mode ofantibody immobilization could detect 1

Since 2015, China has successfully launched five experimental BeiDou global navigation system (BDS-3) satellites for expanding the regional system to global coverage. An initial performance assessment and characterization analysis of the BDS-3 is presented. Twenty days of tracking data have been collected from eleven monitoring stations. The tracking characteristics and measurement quality are analyzed and compared with the regional BDS (BDS-2) in terms of observed carrier-to-noise density ratio, pseudo-range multipath, and noise. The preliminary results suggest that the measurement quality of BDS-3 outperforms the BDS-2 for the same type of satellites. In addition, the analysis of multipath combinations reveals that the problem of satellite-induced code biases found in BDS-2 seems to have been solved for BDS-3. Precise orbit and clock determination are carried out and evaluated. The orbit overlap comparison show a precision of 2–6 dm in 3D root mean square (RMS) and 6–14 cm in the radial component for experimental BDS-3 satellites. External validations with satellite laser ranging (SLR) show residual RMS on the level of 1–3 dm. Finally, the performance of the new-generation onboard atomic clocks is evaluated and results confirm an increased stability compared to BDS-2 satellite clocks.

Host-pathogen interactions are complex processes and it is a central challenge to reveal these interactions. Fungal infection of silkworm, Bombyx mori, may induce a variety of responsive reaction. However, little is known about the molecular mechanism of silkworm immune response against the fungal infection. To obtain an overview of the interaction between silkworm and an entomopathogenic fungus Beauveria bassiana, Digital Gene Expression profiling, a tag based high-throughput transcriptome sequencing method, was employed to screen and identify differentially expressed genes (DEGs, FDR ≤ 0.001, ∣log2ratio∣ ≥ 1) of silkworm larvae during early response against B. bassiana infection. Total 1430 DEGs including 960 up-regulated and 470 down-regulated ones were identified, of which 627 DEGs can be classified into GO categories by Gene Ontology (GO) analysis. KEGG pathways analysis of these DEGs suggested that many biological processes, such as defense and response, signal transduction, phagocytosis, regulation of gene expression, RNA splicing, biosynthesis and metabolism, protein transport etc. were involved in the interaction between the silkworm and B. bassiana. A number of differentially expressed fungal genes were also identified by mapping the sequencing tags to B. bassiana genome. These results provided new insights to the molecular mechanism of silkworm immune response to B. bassiana infection.

In order to satisfy the requirement of high-rate high-precision applications, 1 Hz BeiDou Navigation Satellite System (BDS) satellite clock corrections are generated based on precise orbit products, and the quality of the generated clock products is assessed by comparing with those from the other analysis centers. The comparisons show that the root mean square (RMS) of clock errors of geostationary Earth orbits (GEO) is about 0.63 ns, whereas those of inclined geosynchronous orbits (IGSO) and medium Earth orbits (MEO) are about 0.2–0.3 ns and 0.1 ns, respectively. Then, the 1 Hz clock products are used for BDS precise point positioning (PPP) to retrieve seismic displacements of the 2015 Mw 7.8 Gorkha, Nepal, earthquake. The derived seismic displacements from BDS PPP are consistent with those from the Global Positioning System (GPS) PPP, with RMS of 0.29, 0.38, and 1.08 cm in east, north, and vertical components, respectively. In addition, the BDS PPP solutions with different clock intervals of 1 s, 5 s, 30 s, and 300 s are processed and compared with each other. The results demonstrate that PPP with 300 s clock intervals is the worst and that with 1 s clock interval is the best. For the scenario of 5 s clock intervals, the precision of PPP solutions is almost the same to 1 s results. Considering the time consumption of clock estimates, we suggest that 5 s clock interval is competent for high-rate BDS solutions.

Human walking is a dynamic, partly self-stabilizing process relying on the interaction of the biomechanical design with its neuronal control. The coordination of this process is a very difficult problem, and it has been suggested that it involves a hierarchy of levels, where the lower ones, e.g., interactions between muscles and the spinal cord, are largely autonomous, and where higher level control (e.g., cortical) arises only pointwise, as needed. This requires an architecture of several nested, sensori-motor loops where the walking process provides feedback signals to the walker's sensory systems, which can be used to coordinate its movements. To complicate the situation, at a maximal walking speed of more than four leg-lengths per second, the cycle period available to coordinate all these loops is rather short. In this study we present a planar biped robot, which uses the design principle of nested loops to combine the self-stabilizing properties of its biomechanical design with several levels of neuronal control. Specifically, we show how to adapt control by including online learning mechanisms based on simulated synaptic plasticity. This robot can walk with a high speed (>3.0 leg length/s), self-adapting to minor disturbances, and reacting in a robust way to abruptly induced gait changes. At the same time, it can learn walking on different terrains, requiring only few learning experiences. This study shows that the tight coupling of physical with neuronal control, guided by sensory feedback from the walking pattern itself, combined with synaptic learning may be a way forward to better understand and solve coordination problems in other complex motor tasks.