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The most effective way to protect data in remote stores is to adopt cryptographic schemes, so that all of the delegated data are ciphertext. In order to share these encrypted data with others, the Proxy Re-Encryption ( $PRE$ ) technique is proposed. It allows a proxy to convert a ciphertext encrypted under one key into an encryption of the same message under another key, while placing as little trust and reveal to the proxy as necessary to allow it to perform its translations. $PRE$ turns out to be the most suitable scheme for remote data sharing and becomes popular with the spread of cloud computing. However, in reality, it is difficult for users to manage their secret keys by themselves and not to authorize others by generating the re-encryption keys. In this proposal, we introduce a distributed key management system ( $DKMS$ ) to manage user keys and handle data sharing requests. The $DKMS$ is an honest authority that does not provides any encryption or re-encryption services, thus it is of zero-knowledge to the data. Moreover, the $DKMS$ will not store the intact secret keys, which will only appear in runtime environment and be destroyed after lifecycle.

We present the data analysis pipeline, commissioning observations and initial results from the GREENBURST fast radio burst (FRB) detection system on the Robert C. Byrd Green Bank Telescope (GBT) previously described by Surnis et al. which uses the 21~cm receiver observing commensally with other projects. The pipeline makes use of a state-of-the-art deep learning classifier to winnow down the very large number of false positive single-pulse candidates that mostly result from radio frequency interference. In our observations totalling 156.5 days so far, we have detected individual pulses from 20 known radio pulsars which provide an excellent verification of the system performance. We also demonstrate, through blind injection analyses, that our pipeline is complete down to a signal-to-noise threshold of 12. Depending on the observing mode, this translates to peak flux sensitivities in the range 0.14--0.89~Jy. Although no FRBs have been detected to date, we have used our results to update the analysis of Lawrence et al. to constrain the FRB all-sky rate to be $1140^{+200}_{-180}$ per day above a peak flux density of 1~Jy. We also constrain the source count index $\alpha=0.83\pm0.06$ which indicates that the source count distribution is substantially flatter than expected from a Euclidean distribution of standard candles (where $\alpha=1.5$). We discuss this result in the context of the FRB redshift and luminosity distributions. Finally, we make predictions for detection rates with GREENBURST, as well as other ongoing and planned FRB experiments., Comment: 9 pages, 7 figures, submitted to MNRAS

Objectives: To systematically evaluate the clinical effect of intraoperative goal-directed fluid therapy (GDFT) in gastrointestinal surgery within an enhanced recovery after surgery (ERAS) program. Methods: EMBASE, MEDLINE, Cochrane Library, PubMed, OVID, CNKI and other databases were searched for randomized controlled trials (RCTs) from the inception dates to December 2018. These studies included patients undergoing elective gastrointestinal surgery comparing regular fluid therapy versus GDFT within ERAS. The meta-analysis was carried on with RevMan 5.3. Results: A total of 10 RCT studies were included with 1216 patients. Compared with the regular fluid therapy group, the GDFT group reduced the rate of readmission [odds ratio, OR = 1.67, 95% CI (1.05, 2.65), P = 0.03] in gastrointestinal surgery patients within ERAS. However, there was no significant decrease in length of hospital stay (LOHS) [mean difference, MD = -0.11, 95% CI (-1.22, 1.00), P = 0.85], postoperative morbidity [OR = 0.78, 95% CI (0.55, 1.11), P = 0.17], postoperative mortality [OR = 0.86, 95% CI (0.30, 2.49), P = 0.78], postoperative ileus [OR = 1.24, 95% CI (0.70, 2.19), P = 0.45], anastomotic leaks [OR= 0.66, 95% CI (0.29, 1.49), P = 0.31] and the first gastrointestinal motility time [MD = -0.37, 95% CI (-1.07, 0.33), P = 0.30]. Conclusions: The current evidence demonstrates that, in gastrointestinal surgery within ERAS, GDFT decreased the rate of readmission. However, there was no advantage over regular fluid therapy in the reduction of LOHS, postoperative morbidity, postoperative mortality, postoperative ileus and anastomotic leaks.

As the number of array elements and bandwidth increase, the design challenges of the Phased Array Feed (PAF) front-end and its signal processing system increase. Aiming at the ng-PAF of the 110 m radio telescope, this article introduces the concept of fully digital receivers and attempts to use Radio Frequency System-on-Chip (RFSoC) technology to digitize close to the feed array, reduce the complexity and analog components of the front-end, and improve the fidelity of the signals. The article discusses the digital beamforming topology and designs a PAF signal processing experimental system based on RFSoC+GPU hybrid architecture. The system adopts a ZCU111 board to design RF-direct digitization and preprocessing front-end, which can sample eight signals up to 2.048 GSPS, 12 bit, channelize the signals into 1024 chunks, then reorder into four data streams and select one of the 256 MHz frequency bands to output through four 10 Gb links. A GPU server is equipped with four RTX 3090 GPUs running four HRBF_HASHPIPE instances, each receiving a 64 MHz bandwidth signal for high-throughput real-time beamforming. The experimental system uses a signal generator to emulate Sa-like signals and propagates through rod antennas, which verifies the effectiveness of the beamforming algorithm. Performance tests show that after algorithm optimization, the average processing time for a given 4 ms data is less than 3 ms in the four-GPU parallel processing mode. The RFSoC integrated design shows significant advantages in power consumption and electromagnetic radiation compared with discrete circuits according to the measurement results.

White light scanning interferometry (WLSI) has been an extremely powerful technique in precision measurements. In this work, a phase noise estimation based surface recovery algorithm is proposed, which can significantly improve the measurement accuracy by decreasing the noise level in phase map coming from the systemic and environmental disturbances. The noise existed in phase map is firstly researched in spectrum domain and defined as the linear combination of complex terms at each angular wavenumber. Afterwards, based on the theoretical linearity of the phase distribution, the surface features can be redefined through establishing the function with respect to phase noise. By applying least square estimation (LSE), a spectral coefficient is defined to determine the optimal estimation of phase noise that represents the best statistical consistency with the actual case, from which a more accurate surface after removing most phase noise will then be generated. In order to testify the noise elimination ability of the proposed method, a nano-scale step height standard (9.5nm±1.0nm) is scanned, and the measurement result 9.49nm with repeatability 0.17nm is successfully achieved. Moreover, a leading edge of an aero-engine blade is also tested to investigate the potential of this method in industrial inspections. The measurement comparison with AFM is also displayed.

Morus spp. leaves (MSLs) show various beneficial effects in the treatment of metabolic-related diseases, which have created a growing interest in MSL development as dietary supplements and functional foods. The illustration of chemical compositions and screening of high-quality MSL resources are therefore necessary for further application. This study developed a new UHPLC-ESI-QTOF-MS/MS strategy of in-source collision-induced dissociation (IS-CID) and target collision-cell CID (TCC-CID) to quickly capture analogues with consistent skeleton, and combined global natural product social molecular networking (GNPS) to efficiently annotate bioactive phytochemicals in MSLs. For the results, 49 bioactive ingredients, including quercetin-type flavonoids, kaempferol-type flavonoids, chlorogenic acid isomers, 1-deoxynojirimycin, γ-aminobutyric acid, amino acids, and unsaturated fatty acids, were systematically identified in MSLs for the first time. Quantification for the typical components was simultaneously carried out in MSLs of 90 Morus resources collected from different locations. Partial least squares discriminant analysis (PLS-DA) indicated that quercetin-3-O-(6″-O-malonyl)-glucoside, rutin, kaempferol-3-O-(6″-O-malonyl)-glucoside, kaempferol-3-O-rutinoside, and chlorogenic acid showed high variable importance in the project (VIP > 1) that were significant constituents for the differences between MSL species. Then, high-quality MSLs were comprehensively screened in multiple Morus cultivars based on the criteria importance through intercriteria correlation (CRITIC) method. This study presented an efficient strategy to annotate bioactive compounds, revealed the difference of bioactive components in MSLs, and provided important information for the high-value production of Morus cultivars in food and supplement fields.

This paper proposed a multi-scale measurement methodology for turbine blade, which is able to evaluate the geometrical features of turbine surface in different scales. A turbine blade measurement system is designed by using LED illuminators in this work. To ensure the efficiency and the accuracy of our system during the scale transition, a fast light source calibration method is introduced with a special designed calibration target, where with only one camera snapshot, the position and the orientation of a LED can be calibrated precisely and simultaneously. A surface reconstruction algorithm via iteration is improved by analyzing the LED radiant intensity distribution. The simulation is carried out with a synthetic hyperboloid structure, where the root mean square error (RMSE) of rebuilding is lower than 1.7 µm, and the mean angular error(MAE) of normal estimation is 0.5°. System calibration is performed by using a USAF 1951 calibration target with 3 different scales with the minimum deviation below 4 µm. Experiments are implemented on the concave and the tenon of a turbine blade from civil aero engine, where the profile, the size of the cooling hole and the roughness are retrieved successfully in different scales, which shows the great potential of the proposed methodology in blade inspection applications.

In this study, the interactions of magnesium (Mg) atom and Mg(001) surface with different metal-atom-doped graphene were investigated using a density functional theory (DFT) method. For the interactions of magnesium with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene, it was found that the magnesium atoms were physisorbed into the hollow sites of the intrinsic graphene with only the smallest interaction energy (approximately −1.900 eV). However, the magnesium atoms tended to be chemisorbed on the doped graphene, which exhibited larger interaction energies and charge transfers. Additionally, the Zn-doped graphene displayed the largest interaction energy with the Mg atom (approximately −3.833 eV). For the interactions of Mg(001) with Al-, Mn-, Zn-, and Zr-doped and intrinsic graphene (intrinsic and doped graphene/Mg interface), doped atoms interacted with a Mg layer to make graphene wrinkle, resulting in a higher specific surface area and better stability. Mg–C chemical bonds were formed at the Al-, Zn-, and Zr-doped interface, and Mg–Mn chemical bonds were formed at the Mn-doped interface. This study provided the fundamental research for future research into doped atoms on graphene reinforced magnesium matrix composites.

The toxicity of polystyrene nano/microplastics with diameter sizes of 50um and 100 nm and concentrations of 100 and 1000 μg/mL on gut microbiota, antioxidant activity and innate immune response in zebrafish was investigated. After exposure to polystyrene plastics particle, the pathological morphological changes of intestine and gills were observed, and the injury severity was related to the concentration and particle size of plastics. Significant changes in the richness and diversity of gut microbiota were observed after polystyrene plastics-exposed in zebrafish. The plastics-treated groups exhibited more substantial oxidative stress than the control group. In addition, the mRNA expression level of most pro- and anti-inflammatory factors, including IL-8, NF-κb, and IL-10, increased while the mRNA expression of TNF-α, a pro-inflammatory factor, decreased. Our results suggest that polystyrene nano/microplastics may represent a potential threat to the gut microbiota, oxidative status, and innate immunity. These results indicated that polystyrene nano/microplastics exerted size and concentration-dependent toxicity on zebrafish. The findings provide new evidence for the toxicity of polystyrene plastics on zebrafish.

The first-principles tensile simulation was carried out to investigate the Al(111)/Al3Ti(112) interface tensile properties and failure mechanism through the calculated tensile stress, deformation energy, bond length, bond angle, lattice constant, and charge distribution. Results showed that the maximum tensile strength of the Al(111)/Al3Ti(112) interface is 14.38 GPa and the deformation energy is mainly absorbed by the interface and Al side. When the tensile strain exceeds 25%, partial Al–Ti and Al–Al chemical bonds at the interface break and the tensile model is destroyed. As a result of the increasing tensile strain, the lattice constant b (the side length along the [010] direction) decreases continuously and rapidly, and electron holes appear in a large area at the interface and sub-interface, which severely weakens the interaction between atoms. These phenomena indicate that the Al/Al3Ti interface and sub-interface are weak links and fail easily.

Multiphase composite solid-state electrolytes (CSEs), with excellent customizability and combing the advantages of the inorganic solid electrolyte and solid polymer electrolyte (SPE), have been considered as a promising candidate electrolyte for commercial all-solid-state lithium metal batteries (ASLMBs). Since the performance of CSEs is largely governed by the morphology and structure of the filler, a highly efficient filler material is the key point for achieving high-performance CSEs. Herein, utilizing the super-dispersibility of hectorite (Ht) in water, 2D Ht nanolayers were prepared and combined with poly(ethylene glycol) (PEO) to work as high-performance CSEs. Benefiting from the high specific surface area and surface electronegativity, obtained nanoscale 2D Ht has shown effectively enhanced ionic conductivity and contributed to the mechanical robustness of the composite electrolyte. When 10 wt% of 2D Ht is applied, the ionic conductivity of the composite solid electrolyte reaches up to 1.08 × 10−4 S∙cm−1 at 30 °C, and the tensile modulus and elongation at break rise up to 1.88 MPa and 1270%, respectively. The facile solution-processed filler, consuming lower energy than high-temperature calcination, can provide an efficient strategy for developing advanced ASLMBs.

This study presents a joint analysis of daytime and nighttime crash frequencies at the zone level with consideration of spatial correlations. Crash data from 131 traffic analysis zones in Hong Kong...

In this paper, we seek to investigate the spatiotemporal impacts of traffic incident on urban road networks. The theoretical lens of a complex network leads us to expect that incident impacts are associated with the functionality that an intersection acts in a network, and also, the location of incident sites. Incident impacts are measured in both temporal and spatial dimension through mining the large-scale traffic flow data in conjunction with the incident record. In the complex network context, the urban road network can be converted into a weighted direct graph with intersections as nodes and road segments as edges with their geographic information. Four network features, i.e., Betweenness Centrality, weighted PageRank, Hub, and K-shell are assigned to each intersection to measure its functionality. Temporally, we find out significant correlations between incident delay and two network features by applying hazard-based models. Spatially, the micro impact and the macro impact are found to be strongly associated with three network features through estimating a Bayesian Negative-binomial Conditional Autoregressive model and a generalized linear model, respectively. Our study provides the basis of leveraging urban road network context to evaluate incident impacts, with some explanations, insights and possible extensions that would assist traffic administrations to guide the post-incident resilience and emergency management.

Cooperative driving around intersections has aroused increasing interest in the last five years. Meanwhile, driving safety in non-signalized intersections has become an issue that has attracted attention globally. In view of the potential collision risk when more than three vehicles approach a non-signalized intersection from different directions, we propose a driving model using cooperative game theory. First, the characteristic functions of this model are primarily established on each vehicle’s profit function and include safety, rapidity and comfort indicators. Second, the Shapley theorem is adopted, and its group rationality, individual rationality, and uniqueness are proved to be suitable for the characteristic functions of the model. Following this, different drivers’ characteristics are considered. In order to simplify the calculation process, a zero-mean normalization method is introduced. In addition, a genetic algorithm method is adopted to search an optimal strategy set in the constrained multi-objective optimization problem. Finally, the model is confirmed as valid after simulation with a series of initial conditions.

Posttraumatic stress disorder (PTSD) is a disabling psychological condition associated with significant physical comorbidities. There has been growing evidence to support the relationship between PTSD and cardiometabolic disease. Disordered eating behaviors often seen in people with PTSD symptoms may explain increased cardiometabolic risk. This systematic review aimed to assess the quality of evidence surrounding dietary intake of individuals with symptoms or a diagnosis of PTSD and their associated risk with cardiometabolic health outcomes. Online databases Scopus, ProQuest (Health), Embase, Medline, PsycINFO, and CINAHL with Full Text were searched for peer-reviewed English articles prior to December 2017 that examined dietary intake and cardiometabolic health outcomes in adults with PTSD symptoms or diagnosis. The quality of each study was graded based on the design and methodology using adapted quality assessment tools. Seven studies with five unique participant samples were included in the review. Study methods, design, populations, and outcomes were inconsistent across studies. Dietary intake was considerably varied and limited associations were demonstrated between dietary intake and cardiometabolic risk factors in the PTSD cohorts. Due to the variability of measures and study outcomes, there was insufficient evidence to determine the relationship between dietary intake and PTSD-related cardiometabolic health outcomes. Future studies are needed to examine these associations in individuals with PTSD: specifically higher quality descriptive studies are necessary to confirm a link between diet and cardiometabolic disease in PTSD.

We analyze in detail the effects of the intermode nonlinearity (IEMN) and intramode nonlinearity (IRMN) on modulation instability (MI) in randomly birefringent two-mode optical fibers (RB-TMFs). In the anomalous dispersion regime, the MI gain enhances significantly as the IEMN and IRMN coefficients increases. In the normal dispersion regime, MI can be generated without the differential mode group delay (DMGD) effect, as long as the IEMN coefficient between two distinct modes is above a critical value, or the IRMN coefficient inside a mode is below a critical value. This critical IEMN (IRMN) coefficient depends strongly on the given IRMN (IEMN) coefficient and DMGD for a given nonlinear RB-TMF structure, and is independent on the input total power, the power ratio distribution and the group velocity dispersion (GVD) ratio between the two modes. On the other hand, in contrast to the MI band arising from the pure effect of DMGD in the normal dispersion regime, where MI vanishes after a critical total power, the generated MI band under the combined effects of IEMN and IRMN without DMGD exists for any total power and enhances with the total power. The MI analysis is verified numerically by launching perturbed continuous waves (CWs) with wave propagation method.

The dried roots of Rehmannia glutinosa Libosch. (Scrophulariaceae) are of both medicinal and nutritional importance. Our previous study has found that the 80% ethanol extract of R. glutinosa (RGEE) produced antidepressant-like activities in mouse behavioral despair depression models. However, its mechanisms are still unclear. The present study aimed to observe the antidepressant-like mechanisms of RGEE on a rat chronic unpredictable mild stress (CUMS) model by involving monoaminergic neurotransmitters and brain-derived neurotrophic factor (BDNF). CUMS-stressed rats were orally given RGEE daily (150, 300, and 600 mg/kg) or fluoxetine hydrochloride (FH) for 3 weeks after starting the CUMS procedure. Sucrose preference test was carried out to observe depression-like behavior, and serum and brain tissues were used for neurochemical and fluorescent quantitative reverse transcription PCR analysis. Results demonstrated that CUMS induced depression-like behavior, whereas RGEE and FH administration inhibited this symptom. Furthermore, CUMS caused excessively elevated levels of serum corticosterone (CORT), an index of hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, in a manner attenuated by RGEE and FH administration. RGEE administration also further elevated monoamine neurotransmitters and BDNF levels, up-regulated the mRNA expression of BDNF and tropomyosin-related kinase B (TrkB) in hippocampus of rats suffering CUMS. Together, our findings suggest that RGEE can improve CUMS-evoked depression-like behavior, and indicate its mechanisms may partially be associated with restoring HPA axis dysfunctions, enhancing monoamineergic nervous systems, and up-regulating BDNF and TrkB expression.

Purpose This paper aims to solve the lubrication failures in the turning arm bearing of RV reducer, give some help in perfecting the bearing structure design and provide theoretical basis for the reducer’s performance improvement. Design/methodology/approach The paper establishes a mixed lubrication analysis model to study performance parameters. According to the discretization of parameters and iteration of equations, numerical simulation and theoretical analysis are achieved in computational process. Findings Considering influences of contact load, real rough surface and realistic geometry of RV reducer turning arm roller bearing, the mixed lubrication analysis model is established to study the ratio of oil film thickness, pressure distribution and maximum von Mises stress in different speeds, temperatures and fillets. The results of mixed lubrication show that reasonable round corner modification, increase in temperature and speed, decrease of surface roughness and lubricant types can improve the lubrication performance. Originality/value The mixed lubrication analysis model is established to study the influences of contact load, real rough surface and realistic geometry of RV reducer turning arm roller bearing. Different speed, temperature, lubricant and fillet modification are also considered in the research to analyze oil film thickness, pressure distribution and maximum von Mises stress. These studies can optimize structural design of bearing and direct engineer operations.

Baefrutones A-F (1-6), six new meroterpenoids with rare triketone-phloroglucinol-monoterpene/sesquiterpene frameworks, together with their biosynthetically related intermediate (±)-baeckenon B (7), were isolated from the aerial part of Baeckea frutescens under the guidance of HPLC-Q/TOF-MS2 investigation. Compounds 1-4 represent the first examples of natural meroterpenoids existing as four pairs of inseparable diastereomeric atropisomers (2 : 1, 1H NMR integration) caused by the restricted rotation around the C-6-C-7-C-1' bonds arising from the intramolecular hydrogen bond between C-1 carbonyl and 2'-OH. The discovery of these architectures not only largely enriched the chemodiversity of the meroterpenoid and atropisomer library, but also might be exciting and challenging for asymmetric organic synthesis. Their structures and absolute configurations were established by extensive spectroscopic analysis, X-ray diffraction, and ECD calculations. Compounds 5 and 6 were biomimetically synthesized from 7 and β-caryophyllene via a regioselective oxidative hetero-Diels-Alder reaction, thus providing access to the construction of the 6/6/9/4 tetracyclic ring system. The anti-inflammatory activities of these meroterpenoids were also discussed.

Purpose To evaluate the difference in prostate-specific antigen (PSA) recurrence–free, distant metastasis–free, overall, and cancer-specific survival between PSA bounce (PSA-B) and non-bounce patients treated with dose-escalated external beam radiation therapy (DE-EBRT). Methods and Materials During 1990-2010, 1898 prostate adenocarcinoma patients were treated with DE-EBRT to ≥75 Gy with ≥5 years follow-up. Patients receiving neoadjuvant/concurrent androgen-deprivation therapy (n=1035) or with fewer than 4 PSA values obtained 6 months or more after post-EBRT completion (n=87) were excluded. The evaluable 776 patients were treated (median, 81.0 Gy). Prostate-specific antigen bounce was defined as a ≥0.2-ng/mL increase above the interval PSA nadir, followed by a decrease to nadir or below. Prostate-specific antigen relapse was defined as post–radiation therapy PSA nadir + 2 ng/mL. Median follow-up was 9.2 years (interquartile range, 6.9-11.3 years). Results One hundred twenty-three patients (15.9%) experienced PSA-B after DE-EBRT at a median of 24.6 months (interquartile range, 16.1-38.5 months). On multivariate analysis, younger age ( P =.001), lower Gleason score ( P =.0003), and higher radiation therapy dose ( P =.0002) independently predicted PSA-B. Prostate-specific antigen bounce was independently associated with decreased risk for PSA relapse (hazard ratio [HR] 0.53; 95% confidence interval [CI] 0.33-0.85; P =.008), distant metastatic disease (HR 0.34; 95% CI 0.12-0.94; P =.04), and all-cause mortality (HR 0.53; 95% CI 0.29-0.96; P =.04) on multivariate Cox analysis. Because all 50 prostate cancer–specific deaths in patients without PSA-B were in the non-bounce cohort, competing-risks analysis was not applicable. A nonparametric competing-risks test demonstrated that patients with PSA-B had superior cancer-specific survival compared with patients without PSA-B ( P =.004). Conclusions Patients treated with dose-escalated radiation therapy for prostate adenocarcinoma who experience posttreatment PSA-B have improved PSA recurrence-free survival, distant metastasis–free survival, overall survival, and cancer-specific survival outcomes.

ALFABURST has been searching for Fast Radio Bursts (FRBs) commensally with other projects using the Arecibo L-band Feed Array (ALFA) receiver at the Arecibo Observatory since July 2015. We describe the observing system and report on the non-detection of any FRBs from that time until August 2017 for a total observing time of 518 hours. With current FRB rate models, along with measurements of telescope sensitivity and beam size, we estimate that this survey probed redshifts out to about 3.4 with an effective survey volume of around 600,000 Mpc$^3$. Based on this, we would expect, at the 99% confidence level, to see at most two FRBs. We discuss the implications of this non-detection in the context of results from other telescopes and the limitation of our search pipeline. During the survey, single pulses from 17 known pulsars were detected. We also report the discovery of a Galactic radio transient with a pulse width of 3 ms and dispersion measure of 281 pc cm$^{-3}$, which was detected while the telescope was slewing between fields., 11 pages, 11 figures, accepted to MNRAS

Currently, the lubricated interface contact stiffness of driving system is regard as steady-state without considering the effect of load and speed fluctuation. However, the multi-directional mechanical vibration of driving system is universal and inevitable in the practical engineering, which is accompanied by noteworthy normal load fluctuation and tangential speed fluctuation. It is of great significance to predict and understand the dynamic contact stiffness evolution for the design and dynamic simulation of transmission mechanism. While the research on the dynamic contact stiffness in transient mixed lubrication caused by fluctuation load and speed hasn't been reported yet. In this manuscript, a comprehensive study about the lubricated dynamic contact stiffness in point contact and spiral bevel gears (SBG) under periodic fluctuation load and velocity was performed. The results emerge some unusual and unprecedented characteristics. There is an obvious hysteresis loop of load-displacement when the phase of the coupled periodic load and velocity is 90° or 270°. And the hysteresis loop expands as speed fluctuation amplitude rises. The dynamic contact stiffness of SBG is sensitive to load and speed fluctuation especially in the stable engagement period. In addition, due to the competitive relationship between dynamic load and contact area/ radius, the reversals of positive and negative stiffness would occur at certain fluctuation amplitudes, which can lead to extremely low (even zero) stiffness or extremely high stiffness.

We proposed and experimentally demonstrate a calibration method to estimate the position and the orientation of the anisotropic near point LED light source from a single view. In this work, a Lambertian sphere is used as the calibration target, where the reflection model of the Lambertian sphere under the illumination of LED with given radiant intensity distribution is analyzed theoretically to establish the relationship between the recorded image intensity and the observed surface. Based on this relationship, the geometrical principle of the calibration is researched and an iteration method is presented to calculate the LED position and orientation with a cost function through minimizing the estimation error. The accuracy of the proposed method is verified by simulations with the mean estimation error lower than 5.8mm and 1.7deg for near field lighting. The experiments are performed by measuring the plaster models using the presented system, which proves the effectiveness of the proposed calibration approach.