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Polyvinylidene fluoride (PVDF) thin films with high β-phase content exhibit excellent piezoelectric and dielectric properties. In this work, PVDF–NaCl composite film with high β-phase content was prepared by near-electric-field three-dimensional (3D) printing. The mechanism of the influence of NaCl on the nucleation and phase transition of the PVDF thin films was revealed based on the synergistic effect of the electric field and salt addition. The composite films were characterized by scanning electron microscopy, fourier transform infrared spectroscopy, x-ray diffraction analysis, and measurements of electrical properties. The results showed that NaCl can increase the density of the membrane, while the β-phase content and dielectric properties of the PVDF composite membrane are positively correlated with the amount of NaCl added. The β-phase content reached a maximum value of 52.68% when the amount of NaCl added was 0.05% by weight. The dielectric constant of the PVDF composite film increased with increasing NaCl content. The electrical properties also indicated that PVDF composite film with higher NaCl content showed higher electrical output voltage, while the response voltage of the composite film with 0.05 wt.% NaCl was higher than that of pure PVDF film.

Smart energy monitors (SEMs), which enable householders to measure electricity usages of different appliances in real-time, have been widely deployed by utilities across many different countries. However, the actual electricity saving effects of smart information interventions via the SEM connected to the smart energy management system (SEMS) remain inconclusive, due to failures of the existing statistical models in capturing non-linear relationships. To address the non-linearity challenge and to observe the effects of smart information interventions on electricity savings among the public housing householders in Hong Kong, we initiate a longitudinal electricity consumption behavioural study in Hong Kong. We propose a machine-learning approach to capture any non-linearity identified from our SVR machine learning model. In particular, we identify the correlation between the different combinations of three smart information interventions and the percentage of electricity savings at the household-level in Hong Kong. Smart Energy Management System (SEMS), consisting of a smartphone app and a SEM installed respectively on the smartphone and the participant household of our participants in a public housing estate in Hong Kong, have been developed and deployed by the HKU AI-WiSe team. An innovative technological intervention cum environmental behavioural study was conducted on representative of 14 households residing in a public housing estate in Hong Kong, across a one-year period, from 2018 to 2019. Three types of smart information interventions were introduced to our household participants, including their (1) current electricity consumption profile (2) historical electricity consumption profile, and (3) ranking in electricity savings as compared to other participating households. Our study concludes that the overall average electricity savings across all 14 households is 7.1%. However, as different households have displayed different electricity consumption characteristics, the electricity savings vary significantly across 14 households, from slightly negative or almost zero savings, to significantly positive savings. Our results show that with respect to the three types of smart information interventions, Type (1) and Type (2) display a stronger electricity saving effect when compared to the ranking-based smart information intervention. We conclude our study by identifying the right electricity policies for the HKSAR Government to promote household electricity savings via SEMs and SEMS in HK. To the best of our understanding, our study represents the very first attempt to capture the non-linear statistical correlation between smart information interventions and household electricity savings via the machine-learning SVR approach. Our approach is generic and scalable; it can be applicable to other related electricity consumption experimental studies, across any geographical scale and sample size.

In the past two decades, the supratidal wetland in the Yellow River Delta experienced severe saline-alkalization and vegetation degradation. Restoration with enclosure-freshwater release mode has prevailed since 2002. This method presented some positive effects, but need a massive freshwater supply. Furthermore, the subsequent formed single Phragmites australis vegetation weakened the bird habitation function. In this study, we developed another restoration mode based on microtopography modification. The core idea of the mode is to enhance micro-habitat heterogeneity thus improve the water resource temporal-spatial distribution and shape more niches. An ecological restoration program was designed and implemented since May, 2015. The monitoring data from July, 2015 to December 2017 showed that, with no extra artificially drained freshwater released, the soil salinity decreased by 15.4% to 30.8%. The area of bare land decreased while that vegetation and water surface increased, resulting in relative even land cover composition, habitat heterogeneity increased and thus the bird biodiversity improved. This mode is more ecological and water cost-effective and is suitable to restore the degraded saline-alkalized supratidal wetlands. However, long-term comprehensive monitoring is essential to evaluate the restoration effect. Many detailed parameters for topography modification need further optimized.

Orthogonal anisotropic sensing plays an important role in determining driver and sensor properties, while the fiber diameter directly affects the sensitivity of piezoelectric fiber composites. However, few studies have been carried out on fibers at the micron level. Here, well-aligned piezoelectric fiber arrays approximately 10 μm in diameter were prepared using an activated carbon template. A 1-3 lead zirconate titanate (PZT) piezoelectric microfiber composite was obtained by infiltrating epoxy resin into fibers. The microfibers were embedded orderly and well distributed in the epoxy matrix. The orthogonal anisotropy of the sensing and actuating performance was investigated and evaluated. The 1-3 PZT piezoelectric microfiber composite was clearly anisotropic with a much better piezoelectric sensitivity along the longitudinal direction of the fibers. The highest output voltage in the longitudinal direction was twice as large as that in the transverse direction. The highest strain in the longitudinal sensitivity direction was about four times the strain of the transverse direction.

International audience; Important challenges remain in the development of ultrafast laser writing inside semiconductor materials because the properties of narrow gap materials cause strong propagation distortions to intense infrared light. Here, we introduce a simple and robust imaging method for high-dynamic-range investigations of the laser-matter interactions in bulk semiconductors. Supported by measurements in gallium arsenide and silicon, we show how z-scan imaging of the band-to-band radiative recombination enables quantitative reconstruction of the three-dimensional distributions of free-carriers generated by nonlinear ionization with ultrashort pulses. The validity is confirmed by comparisons with ultrafast transmission microscopy (shadowgraphy) images. The superior sensitivity of the zero-background luminescence method allows the measurement of local carrier densities as low as approximate to 10(16) cm(-3) inside GaAs that is inaccessible by shadowgraphy. It provides the first direct evidence of the low density plasma generated far prior to the focus that causes the previously reported intensity clamping phenomenon. The potential of this non-coherent 3D imaging method to assess complex beam distortion features is also exemplified by real-time pre-compensation of aberration for an intense interacting beam. Published under an exclusive license by AIP Publishing.

The Ganjiang River, one of eight major tributaries of the Yangtze River, located in the western hinterland of the Cathaysia Block, SE China, has a length of 823 km and a drainage area of 82 809 km2, whose detrital zircons provide a valuable means to trace sediment provenances of the river and explore the crustal growth and evolution of the Cathaysia Block. In the current study, 389 concordia zircon U–Pb age spots and rare earth element (REE) contents, in combination with 201 Lu–Hf isotope analyses, have been determined. Oscillatory zoning, high Th/U ratios and REE distribution patterns indicate that most detrital zircon grains are of magmatic origin. The age can be further divided into seven groups: 130–185 Ma with a peak at 153 Ma (7 %); 217–379 Ma with a peak at 224 Ma (16 %); 390–494 Ma with a peak at 424 Ma (37 %); 500–698 Ma with a peak at 624 Ma (5 %); 716–897 Ma with a peak at 812 Ma (10 %); 902–1191 Ma with a peak at 976 Ma (13 %); and 2232–2614 Ma with a peak at 2471 Ma (5 %). The sources of almost all the zircon age groups can be found from the exposed rocks. In particular, Yanshanian, Hercynian to Indosinian, Pan-African, Grenvillian and Palaeoproterozoic–Archaean zircons can be mainly sourced from the northern Guangdong – southern Jiangxi – western Fujian region, while Caledonian zircons come from southern and central Jiangxi, and Jinningian zircons are from central and northern Jiangxi. Most determined zircon grains exhibit negative εHf(t) values and TDM2 ages of 797 to 4016 Ma with a wide peak at 1500–2100 Ma and a keen peak at 1824 Ma, suggesting that most zircons are sourced from the reworked ancient crustal materials or crust–mantle mixing. The zircon Hf model age cumulative probability diagram shows that rapid crustal growth took place at the Palaeo- to Mesoproterozoic and that about 90 % of the crust of the Cathaysia Block was formed before 1.5 Ga.

This research work reports on development and characterization of polyvinylidene fluoride (PVDF) thin films by intercalation of graphene during direct ink writing process with auxiliary electric potential (voltage). The effects of graphene additive on the crystallinity and β-phase transformation in PVDF thin films are studied. The results show that small amount of graphene additive in the writing ink promotes the crystalline nucleation, and the micro electric fields among graphene sheets also promote the formation of the folded β-PVDF chains and prevent the spherulite growth. When 0.05 wt% amount of graphene was added in the writing ink, the crystallinity of the thin film was about twice higher than that of the pure PVDF thin film, and the β-phase content in the thin film reached 67.30%. The sensitivity of the PVDF/graphene composite film is also much higher than that of the pure PVDF piezoelectric film.

Low-rank or sparse tensor recovery finds many applications in computer vision and machine learning. The recently proposed regularized multilinear regression and selection (Remurs) model assumes the true tensor to be simultaneously low-Tucker-rank and sparse, and has been successfully applied in fMRI analysis. However, the statistical performance of Remurs-like models is still lacking. To address this problem, a minimization problem based on a newly defined tensor nuclear-l1-norm is proposed, to recover a simultaneously low-Tucker-rank and sparse tensor from its degraded observations. Then, an M-ADMM-based algorithm is developed to efficiently solve the problem. Further, the statistical performance is analyzed by establishing a deterministic upper bound on the estimation error for general noise. Also, under Gaussian noise, non-asymptotic upper bounds for two specific settings, i.e., noisy tensor decomposition and random Gaussian design, are given. Experiments on synthetic datasets demonstrate that the proposed theorems can precisely predict the scaling behavior of the estimation error.

Femtosecond laser direct writing is widely exploited in surface periodic structures processing. However, this technique still faces challenges in obtaining high surface homogeneity and flexible morphology controllability. In this study, a flexible and efficient approach has been proposed to fabricate highly homogeneous and controllable nanogratings on silicon via chemical etching-assisted femtosecond laser modification. By precisely manipulating the laser-material interaction process, alternating amorphous-crystalline nanofringes are generated when employing femtosecond laser scanning over a Si sample, with almost no material removal. Following auxiliary chemical etching, highly homogeneous nanograting structures are obtained, and the morphology of the nanogratings can be flexibly managed through precisely controlling the duration of the etching process. Complex cross-scale patterns with remarkable structural colors that are visible under indoor light illumination are readily achieved on the sample surfaces exploiting our method. In addition, compared with traditional methods for laser-induced periodic surface structures, the fabrication efficiency is considerably improved. Our processing procedure offers potential applications in the fields of optics, nanoelectronics, and mechatronics.

We report the influence of temporally decreasing pulse trains on femtosecond laser-induced chemical etching (FLICE) of fused silica. A systematic comparison of the unshaped pulse and decreasing pulse trains of femtosecond laser for FLICE was conducted, and the differences were interpreted using a plasma model. The results revealed that the decreasing pulse trains not only affected the etching efficiency but also affected the morphology of the etched crater. When an etched crater was pre-irradiated by decreasing pulse trains, it presented a funnel-like shape at the early stage of the etching process, which contrasted with the one pre-irradiated by unshaped pulse. At the later stage of the etching process, the funnel-like shape gradually disappeared, and the crater increased in size. Compared with the unshaped pulse under the same processing conditions, the decreasing pulse trains enhanced the etched crater volume by approximately 18 times. Theoretical calculations based on the plasma model indicated that the free-electron density generated using the unshaped pulse was much higher than that generated by the decreasing pulse trains in skin layer of the sample during the first few hundred femtoseconds. The high free-electron density increased the reflectivity in skin layer of the sample; thus, the tail part of the incident pulse was strongly reflected. Consequently, the laser energy deposition into the fused silica sample decreased, eventually led to a low etching efficiency.

Changing morphology and chemical compositions of electrode active sites is an effective approach to enhance the performance of supercapacitors. Herein, a novel method has been proposed to prepare 3D porous copper oxides electrodes of supercapacitors. CuO flowers were directly grown on copper foam by the combination of femtosecond laser processing and electrochemical anodization. A femtosecond laser was used to create micro/nanoprotrusions served as the precursors for the following anodization. During anodization, the morphology and performance of the electrodes were optimized by controlling current densities and anodization times. The grown CuO flowers acted as the active materials of binderless and additive free supercapacitor electrodes. Benefiting from the unique morphology, providing plentiful redox active sites and enabling electrolyte ion access easily, a high specific capacitance of 3348.57 mF cm−2 at the current density of 1 mA cm−2 was achieved. The specific capacitance of the electrode is superior to that of electrochemical anodization. The electrode exhibits excellent rate capacity (82.5%), good cycle ability (120%), and superior coulombic efficiency (97%) during 1400 cycles. In addition, the electrode also delivers a high energy density of 56.97 μWh cm−2 at the power density of 175 μW cm−2. These results indicate that this versatile combined fabrication process is suitable for improving the electrochemical performances of copper oxides–based 3D electrodes, which have promising applications in commercial devices.

In recent decades, the invasion of saltmarsh plant Spartina alterniflora (S. alterniflora) over a large part of coastal wetlands in China, including the Yellow River Estuary (YRE) as a regional economic hub and global ecosystem services hotspot, has caused increasing concern because of its serious threats to native ecosystems. During the same period, local authorities have implemented a Water-Sediment Regulation Scheme (WSRS) in the Yellow River for flood mitigation and delta restoration purposes. The altered hydrological regime has resulted in unintended changes to estuarine ecosystem. However, the direct consequence of the WSRS on the expansion of S. alterniflora remains unclear. In this study, quantitative relationship between the inter- and intra-annual expansion patterns of S. alterniflora represented by relevant landscape metrics and indicators that quantify the concurrent variations of river and sediment discharges as the proxy of the WSRS impacts were analysed over the period of Year 2011–2018, and the analyses were performed on the YRE as a whole and on five different zones subdivided based on the invasion sequence. The results showed that there was no significant difference in the inter-annual area variation of S. alterniflora between the years with and without WSRS. Compared with the years without WSRS (2016–2017), the intra-annual (monthly) increment of the various landscape metrics [i.e., NP (number of patches), CA (class area), LPI (largest patch index) and AI (aggregation index] were found to be significantly higher in the initial stage of peak growing season (June-July) than in the mid- and late stages (July-September) in the years with WSRS (2011–2015, 2018) in the subregion located close to the south bank of YRE as the most prominent impact zone. In addition, F (mean flow), Ff (number of high flow pulses), Tf (Julian date of maximum flow) and D (duration of WSRS) were identified as the explanatory variables for the intra-annual vegetation landscape pattern changes, and their relative contributions to resultant changes were also assessed. Our results broaden the understanding of estuarine hydrological disturbance as a potential driver regulating the saltmarsh vegetation, and also have implications for S. alterniflora invasion control at estuaries under changing environment.

Vortex beams carrying orbital angular momentum (OAM), which featuring helical phase front, have been regarded as an alternative spatial degree of freedom for optical mode coding and multiplexing. For most reported OAM-based mode coding schemes, data information is only encoded by different OAM mode states. In this paper, we introduce a novel design technique to construct vortex array phase grating (VAPGs) for the flexible generation of vortex arrays, and employ the proposed VAPGs to realize multi-dimensional space/mode/amplitude coding/decoding. By designing VAPGs with different parameters and loading them on to a single spatial light modulator (SLM), we successfully generate vortex array with different mode states and relative power in the experiments. Moreover, a 10-bit multi-dimensional space/mode/amplitude data coding/decoding scheme for image transfer in free-space link with a zero bit-error-rate is experimentally demonstrated, which confirm the feasibility of our proposed VAPG-based coding/decoding scheme.

This study was conducted to investigate the speciation, bioavailability and environmental risk of heavy metals (HMs) in chicken manure (CM) and water-washed swine manure (WSM) and their biochars produced at different pyrolysis temperatures (200 to 800 °C). As the pyrolysis temperature increased, the remaining proportion, toxicity characteristic leaching procedure (TCLP), HCl and diethylenetriamine pentaacetic acid (DTPA) of HMs gradually declined. This result proved that the speciation of HMs in chicken manure biochars (CMB) and water-washed swine manure biochars (WSMB) was influenced by pyrolysis temperature. The proportions of stable fractions were enhanced with increased pyrolysis temperature and weakened the HM validity for vegetation at 800 °C. Finally, the results of the risk assessment showed that the environmental risk of HMs in CMB and WSMB decreased with increasing pyrolysis temperature. Therefore, pyrolysis at 800 °C can provide a practical approach to lessen the initial and underlying heavy metal toxicity of CMB and WSMB to the environment.

International audience; By combining and synchronizing pulses of different durations from 170 fs to 5 ns, we benchmark the appropriate temporal characteristics of laser pulses for 3D writing applications inside silicon.

Brassica napus L. (oilseed rape) was grown with daikon and white lupin in a polyvinyl chloride split pot experiment (with no barrier between the compartments or by a nylon mesh barrier (37 μm) to license partial root interaction, or a solid barrier to stop any root interactions) to examine the effect of rhizosphere interaction on the cadmium uptake. The results showed that shoot and root biomasses of oilseed rape were 40.66% and 26.94% less than that of the monocropped treatment (solid barrier) when intercropping with daikon under the rhizosphere complete interaction. However, the intermingling of roots between oilseed rape and white lupin notably enhanced the dry biomass of oilseed rape by 40.23% and decreased with the reduction of root contact. Oilseed rape intercropping with daikon enhanced the shoot Cd concentration of oilseed rape. The shoot Cd concentration (44.8 mg/kg) of oilseed rape when intercropped white lupin under complete rhizosphere interaction were greater than those of other treatments. Additionally, the intermingling of roots played a positive role in the content of citric and malic acids when intercropping with white lupin. In all systems, the BCF values of oilseed rape >5. Therefore, intercropping with white lupin may contribute to higher biomass and increased uptake Cd by oilseed rape. We can toward sustainable positive effects on phytoremediation that based on a better understanding of rhizosphere processes.

We report a facile top-flat square nanosecond (ns) laser direct writing ablation technique in a thin silver film substrate to fabricate the silver square-shaped cell structure of flexible transparent electrodes. Square silver cell structures feature smooth surface morphology, excellent edge definition, mechanical stability, strong adhesion to the substrate, and favorable resistance and transparency. In particular, this strategy enables fabrication of a high square-shaped cell areal density (ablated square cell to the total area) Ag mesh, substantially improving transparency ( > 85 % ) without considerably sacrificing conductivity ( < 5 Ω s q − 1 unit of resistance). Consequently, the proposed metallic square-shaped structure shows compatibility with a polyethylene naphthalate flexible substrate for silver-based wearable electronic devices without any protective layer over the electrodes.

Hydroponic experiments with different cadmium (Cd) concentrations were conducted to explore the impacts of nutrient allocation on the Cd enrichment of Bermuda grass. The results demonstrated with the Cd concentration increase, the accumulation of nitrogen (N), phosphorus (P) and potassium (K) in roots, stems and leaves increased first and then decreased, while the accumulation of Cd had no significant difference. The biomass and N, P and K accumulation of CD1 and CD2 were significantly different from those of CD3 and CD4, but there was no significant difference in Cd accumulation. The root N, P and K distribution ratio of CD4 increased by 47.9%, 114.3% and 64.3% compared with those of CD2 treatment, the values of stem decreased by 29.4%, 22.4% and 17.2%, and the values of leaves increased by 15.8%, 19.8% and 23.6% respectively. The K ratio of root and leaf increased and that of stem decreased. Cd reduced N and K distribution ratio of stem and increased N and K distribution ratio of root and leaf. Pearson correlation analysis showed that the accumulation of N, P and K in stems was positively correlated with the accumulation of Cd in stems, and the accumulation of N, P and K in roots, stems and leaves were positively correlated with the Cd accumulation in leaves. Bermuda grass can schedule the nutrient allocation to adapt to the Cd absorption and enrichment in different organs under different Cd concentrations. In conclusion, nutrient allocation might affect the Cd accumulation of Bermuda grass.

By introducing 3-mode and 6-mode FMF photonic lanterns, we present modes diversity receive scheme for FSOC system under random angular jitter with high efficiency. The coupling efficiency improved 30.77% and 50.23%, when the radial offset is 7 µm. © 2020 The Author(s)

Based on an NMR-guided method, one new monoterpenoid glycoside (1) was isolated from Anhua dark tea, together with five known compounds (2–6). The structure of the new compound was determined as 3-(5,5-dimethyltetrahydrofuranyl)-1-buten-3-ol primeveroside, and trivially named anhuaterpenoside A (1), on the basis of detailed spectroscopic analyses, and acidic hydrolysis. Compound 1 exhibits cytotoxic activity against MDA-MB-231 and SH-SY5Y cell lines with IC50 value of 23.26 μM and 18.57 μM, respectively.

International audience; Three-dimensional laser writing inside silicon remains today inaccessible with the shortest infrared light pulses unless complex schemes are used to circumvent screening propagation nonlinearities. Here, we explore a new approach irradiating silicon with trains of femtosecond laser pulses at repetition rates up to 5.6 THz that is order of magnitude higher than any source used for laser processing so far. This extremely high repetition rate is faster than laser energy dissipation from microvolume inside silicon, thus enabling unique capabilities for pulse-to-pulse accumulation of free carriers generated by nonlinear ionization, as well as progressive thermal bandgap closure before any diffusion process comes into play. By space-resolved measurements of energy delivery inside silicon, we evidence changes in the interplay between detrimental nonlinearities and accumulation-based effects. This leads to a net increase on the level of space-time energy localization. The improvement is also supported by experiments demonstrating high performance for 3D laser writing inside silicon. In comparison to repeated single pulses, irradiation with trains of only four-picosecond pulses with the same total energy leads to an apparent decrease of the energy threshold for modification and drastic improvements on the repeatability, uniformity, and symmetricity of the produced features. The unique benefits of THz bursts can provide a new route to meet the challenge of 3D inscription inside narrow bandgap materials.

Many kinds of real-world data, e.g., color images, videos, etc., are represented by tensors and may often be corrupted by outliers. Tensor robust principal component analysis (TRPCA) servers as a tensorial modification of the fundamental principal component analysis (PCA) which performs well in the presence of outliers. The recently proposed TRPCA model [12] based on tubal nuclear norm (TNN) has attracted much attention due to its superiority in many applications. However, TNN is computationally expensive, limiting the application of TRPCA for large tensors. To address this issue, we first propose a new TRPCA model by adopting a factorization strategy within the framework of tensor singular value decomposition (t-SVD). An algorithm based on the non-convex augmented Lagrangian method (ALM) is developed with convergence guarantee. Effectiveness and efficiency of the proposed algorithm is demonstrated through extensive experiments on both synthetic and real datasets.

International audience; The advent of ultrafast infrared lasers provides a unique opportunity for direct fabrication of three-dimensional silicon microdevices. However, strong nonlinearities prevent access to modification regimes in narrow gap materials with the shortest laser pulses. In contrary to surface experiments for which one can always define an energy threshold to initiate modifications, we establish that some other threshold conditions inevitably apply on the pulse duration and the numerical aperture for focusing. In an experiment where we can vary continuously the pulse duration from 4 to 21 ps, we show that a minimum duration of 5.4 ps and a focusing numerical aperture of 0.85 are required to successfully initiate modifications. Below and above thresholds, we investigate the pulse duration dependence of the conditions applied in matter. Despite a modest pulse duration dependence of the energy threshold in the tested range, we found that all pulse durations are not equally performing to achieve highly reproducible modifications. Taken together with previous reports in the femtosecond and nanosecond regimes, this provides important guidelines on the appropriate conditions for internal structuring of silicon.

International audience; We generate and apply trains of infrared femtosecond pulses at the highest achievable repetition-rates. This gives unique multi-timescale control parameters used for improved energy deposition and reliable 3D laser writing deep inside silicon.

We numerically compare the performance of different OAM-based mode diversity schemes under different atmosphere turbulence. The numerical results show that SIMO modes diversity scheme is more preferable under moderate-to-strong turbulence, while MISO is more appropriate under weak turbulence. © 2020 The Author(s)

With the growing use of renewable energy sources, the stability of electrical power systems can be seriously affected by fluctuations in the available power. As one of the potential solutions for this new challenge, the energy flexibility of buildings has become a focus for research and technological development. Most studies have focused on single buildings, with only a few studies on building clusters in which the building models were usually oversimplified in that they did not consider different building types or their thermal characteristics, their occupancy or their occupants’ behaviour. In this paper, we describe a data driven approach to simulating a generic building cluster that could resemble any mix of building archetypes and occupancy. The energy flexibility potential of apartment building clusters was estimated by using data from surveys and available statistics in Denmark for the worst case scenario, i.e. when the end users do not allow any disturbance when they are at home, so that energy flexibility is only available when residents are not at home. In this scenario, no energy flexibility is assumed when buildings are occupied, which yields a conservative estimation. The uncertainty of the energy flexibility potential due to uncertain occupancy and various archetypes was quantified for different scales of building cluster. The resulting hybrid-model is a combination of a building model and an occupancy model and includes the different factors that influence the potential energy flexibility of buildings. The results show that the uncertainty of the energy flexibility decreases when the aggregated number of buildings increases. The uncertainty of energy flexibility was less than 10%, when about 700 households were aggregated. This approach can be used to simulate building energy flexibility for district or even regional level energy planning when the intention is to use the available flexibility to address the challenges caused by fluctuation in the power available from renewable energy sources.

We demonstrate, for the first time, an ultra-low-noise mode-division multiplexed transmission with eight wavelength-division multiplexed channels over a 100-km few-mode fiber based on a second-order few-mode Raman amplifier. To minimize the mode dependent gain, two backward depolarized pumps at the wavelengths of 1455 nm (75 mW) and 1360 nm (1890 mW) are equally launched both into the LP11a and LP11b modes. The Raman on–off gains of the LP01 and LP11 modes are both above 8 dB and the mode dependent gain is less than 0.7 dB. An amplified spontaneous emission noise improvement of 1.8 dB is achieved in the second-order few-mode Raman amplifier, with respect to the first-order Raman amplification. The effective noise figure of the second-order few-mode Raman amplifier is about –3 dB, which is ∼1.4 dB lower than that in the first-order pumping case. In the transmission experiments, a single-mode transmission over LP01 mode and a mode-division multiplexed transmission over LP11a and LP11b modes are performed separately. The bit-error-rates for all the transmission channels are significantly improved due to the low-noise figure amplification of the second-order few-mode Raman amplifier.

The hysteresis of piezoelectric ceramics plays an important role in determining errors when they are applied in actuators. However, the relationships between the hysteresis characteristic, preparation process of the piezoelectric ceramic, and displacement error of the actuator have rarely been systematically studied. In this study, 0.9625(K 0.48 Na 0.52 )(Nb 0.6 Sb 0.4 )O 3 -0.0375Bi 0.5 (Na 0.82 K 0.18 ) 0.5 ZrO 3 (KNNS-BNKZ) ceramics were prepared via a solid-state reaction and sintered at 1140 °C, 1160 °C, and 1180 °C. Subsequently, the influence of sintering temperatures on the phase composition, microstructure, piezoelectric properties, and ferroelectric properties of the samples was studied. Furthermore, the factors affecting the hysteresis characteristics were systematically analyzed. The results showed that the ceramic sintered at 1140 °C possessed the smallest hysteresis with H max = 25% owing to its phase composition and microstructure. Additionally, linear regression of the displacement versus voltage was carried out and the corresponding equations were obtained. Finally, the hysteresis model of the ceramic sintered at 1140 ℃ was established and its error was determined to be less than 1.81%, which renders these ceramics suitable for application in high-precision actuators.

The analysis was performed to research the speciation and bioavailability of heavy metals in manures and the biochars obtained from pyrolysis of swine and goat manures. Manures were pyrolyzed at different temperatures (200–800 °C). The concentrations of heavy metals in biochars were found to be higher than those in manures. The remaining ratios of heavy metals in biochar decreased with increasing pyrolysis temperature. Our results demonstrated that heavy metal speciation in biochar was strongly impacted by pyrolysis temperature. The bioavailable heavy metal fractions (acid soluble/exchangeable fraction and reducible fraction) were transformed into the relatively stable fraction (oxidizable fraction) and very stable fraction (residual fraction) during pyrolysis. Moreover, the data of diethylenetriamine pentaacetic acid (DTPA), HCl extraction, and toxicity characteristic leaching procedure (TCLP) in biochar indicated that bioavailability and toxicity of heavy metals in biochar were greatly reduced after pyrolysis. In summary, the pyrolysis process at 500 °C can provide a practical way to decline the bioavailability of heavy metals in manure. Biochar obtained from manure pyrolyzed at 800 °C may minimize the direct and potential heavy metal toxicities of biochar to the environment.

We propose, design, fabricate and characterize a subwavelength grating slot (SWGS) waveguide on silicon platform at short-wave infrared (SWIR) wavelength of 2 μm. The mode guiding mechanism, i.e. SWGS mode, is a combination of surface-enhanced supermode and Bloch mode. We also design and fabricate a low-loss strip-to-SWGS mode converter. We further demonstrate chip-scale direct modulation data transmission at 2 μm through the fabricated SWGS waveguides. Favorable operation performance is achieved in the experiment.

Ultrafast laser pulse temporal shaping has been widely applied in various important applications such as laser materials processing, coherent control of chemical reactions, and ultrafast imaging. However, temporal pulse shaping has been limited to only-in-lab technique due to the high cost, low damage threshold, and polarization dependence. Herein we propose a novel design of ultrafast laser pulse train generation device, which consists of multiple polarization-independent parallel-aligned thin films. Various pulse trains with controllable temporal profile can be generated flexibly by multi-reflections within the splitting films. Compared with other pulse train generation techniques, this method has advantages of compact structure, low cost, high damage threshold and polarization independence. These advantages endow it with high potential for broad utilization in ultrafast applications.

In Han and Wang (2020), a 2D diffeomorphic image registration model is proposed to eliminate mesh folding. To solve the 2D diffeomorphic model, a diffeomorphic fractional-order image registration algorithm (DFIRA for short) is proposed in Han and Wang (2020). DFIRA achieves a satisfactory image registration result but it costs too much CPU time. To accelerate DFIRA, we propose a fast multi grid algorithm for 2D diffeomorphic image registration model in this paper. This algorithm achieves a satisfactory image registration result by using only one-tenth CPU time of DFIRA. At the same time, no mesh folding occurs in proposed algorithm. Furthermore, convergence analysis of the proposed algorithm is also presented. Moreover, numerical tests are also performed to show that the proposed algorithm is competitive compared with some other algorithms.

Zero-dimensional MoS2 quantum dots (QDs) possess distinct physical and chemical properties, which have garnered them considerable attention and facilitates their use in a broad range of applications. In this study, we prepared monolayer MoS2 QDs using temporally shaped femtosecond laser ablation of bulk MoS2 targets in water. The morphology, crystal structures, chemical, and optical properties of the MoS2 QDs were characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, UV–vis absorption spectra, and photoluminescence spectra. The analysis results show that highly pure, uniform, and monolayer MoS2 QDs can be successfully prepared. Moreover, by temporally shaping a conventional single pulse into a two-subpulse train, the production rate of MoS2 nanomaterials (including nanosheets, nanoparticles, and QDs) and the ratio of small size MoS2 QDs can be substantially improved. The underlying mechanism is a combination of multilevel photoexfoliation of monolayer MoS2 and water photoionization–enhanced light absorption. The as-prepared MoS2 QDs exhibit excellent electrocatalytic activity for hydrogen evolution reactions because of the abundant active edge sites, high specific surface area, and excellent electrical conductivity. Thus, this study provides a simple and green alternative strategy for the preparation of monolayer QDs of transition metal dichalcogenides or other layered materials.

In this study, based on the Dirac–Bogoliubov–de Gennes equation, we theoretically investigate the interaction effect between the anisotropic d-wave pairing symmetry and the spin orbit interaction (the Rashba spin orbit interaction (RSOI) and the Dresselhaus spin orbit interaction (DSOI)) in a graphene superconducting heterojunction. We find that the spin orbit interaction (SOI) plays a critical role on the tunneling conductance in the pristine case, but minimally affecting the tunneling conductance in the heavily doped case. As for the zero bias state, in contrast to the keep intact feature in the heavily doped case, it exhibits a distinct dependence on the RSOI and the DSOI in the pristine case. In particular, the damage of the zero bias state with a slight DSOI results in the disappearance of the zero bias conductance peak. Moreover, the tunneling conductances also show a qualitative difference with respect to the RSOI when both the RSOI and the DSOI are finite. These remarkable results suggest that the SOI and the anisotropic superconducting gap can be regarded as a key tool for diagnosing the specular Andreev reflection.

Surfaces with hierarchical micro/nanostructures have been widely fabricated for their extensive applications in self-cleaning, antireflection, etc. However, a flexible and highly efficient method for obtaining such surfaces remains a great challenge, especially for metals. In this paper, we propose a simple and tunable approach for fabricating a dual-functional surface with patterned hierarchical micro/nanostructure arrays. A femtosecond laser was used to remove the SiO2 thin film, coated on the Cu substrate, masklessly and selectively. Then the arrays of micro-protrusions decorated with nanoneedles were synthesized successfully through thermal oxidation. We demonstrate that the morphology of the micro-protrusions remarkably affects the surface properties, which can be flexibly tuned by controlling femtosecond laser parameters. By optimizing the laser parameters (e.g. scanning mode and laser fluence), we can achieve high performances with respect to superhydrophobicity, with a maximum contact angle of 161° and extremely low adhesion with a minimum sliding angle of less than 1.7°, thus demonstrating its self-cleaning function. In addition, antireflection properties with a minimum reflectance of less than 1% at a wavelength range of 700–800 nm can be achieved and the total reflectance can be steadily below 6% over a broad wavelength range of 600–1150 nm.

Ultratrace molecular detections from a limited amount of highly diluted solutions can offer unprecedented benefits in the biomedical/analytical fields, such as in precancer diagnosis, forensic analysis, and food safety. However, huge difficulties exist in completely concentrating the target molecules within a sensitive area and thereby enhancing the detection sensitivity. Herein, we report the ultratrace molecular detection using a low-adhesive superhydrophobic surface-enhanced Raman spectroscopy (LAS-SERS) substrate fabricated by femtosecond laser ablation. The LAS-SERS substrate has good characteristics, including a contact angle as high as 154°, a contact angle hysteresis below 5°, and a simulated Raman signal enhancement factor of up to 6 × 106. Compared to the previously developed superhydrophobic SERS (S-SERS) methods, the low-adhesive nature of the LAS-SERS method can greatly reduce the final contact area, thus significantly enhancing the detection limit. In our experiments, the final contact area of the LAS-SERS substrate was reduced by 19.5 times, corresponding to an 88.1 times increase in the concentration effect, as compared to the highly adhesive S-SERS substrates fabricated using the same technique. The enhanced condensation effect led to a detection limit as low as 10−14 M, which shows an obvious improvement compared to that of the other non-photolithography methods. The method reported herein offers a facile and efficient approach to the cost-effective fabrication of a high-performance LAS-SERS substrate for ultratrace molecular detection.

Bendable light beams have recently seen tremendous applications in optical manipulation, optical imaging, optical routing, micromachining, plasma generation and nonlinear optics. By exploiting curved light beams instead of traditional Gaussian beam for line-of-sight light communications, here we propose and demonstrate the viability of free-space data-carrying bendable light communications along arbitrary trajectories with multiple functionalities. By employing 39.06-Gbit/s 32-ary quadrature amplitude modulation (32-QAM) discrete multi-tone (DMT) signal, we demonstrate free-space bendable light intensity modulated direct detection (IM-DD) communication system under 3 different curved light paths. Moreover, we characterize multiple functionalities of free-space bendable light communications, including bypass obstructions transmission, self-healing transmission, self-broken trajectory transmission, and multi-receiver transmission. The observed results indicate that bendable light beams can make free-space optical communications more flexible, more robust and more multifunctional. The demonstrations may open a door to explore more special light beams enabling advanced free-space light communications with enhanced flexibility, robustness and functionality.

In the power system, the large-capacity double water inner cooled turbine generators and synchronous condensers occupy a certain market share. Their normal operation is the key upon the safe and stable operation of the power system. Therefore, mastering the faults types, faults causes and faults characteristics of the double water inner cooled synchronous machines is of great significance for ensuring their safe and stable operation and reasonable arrangement of operation and maintenance. Based on the structural characteristics of the double water inner cooled synchronous machines, this paper studies mainly the common faults locations and types of synchronous machines, the causes and characteristics of the faults, the physical quantity to be monitored, etc., which provides a reference for the maintenance and repair of the synchronous machines.

Due to the superiority in exploiting the ubiquitous "spatial-shifting" property in modern multi-way data, the recently proposed low-tubal-rank model has been successfully applied for tensor recovery in signal processing and computer vision. In this paper, we define the generalized tensor Dantzig selector to recover a low-tubal-rank tensor from noisy linear measurements. Algorithmically, we develop an efficient algorithm based on the ADMM framework. Statistically, we establish non-asymptotic upper bounds on the estimation error for the problems of tensor completion and compressive sensing. Numerical experiments illustrate that our bounds can predict the scaling behavior of the estimation error. Experiments on realword datasets show the effectiveness of the proposed model.

Tensor completion arouses much attention in signal processing and machine learning. The tensor train (TT) decomposition has shown better performances than the Tucker decomposition in image and video inpainting. In this paper, we propose a novel tensor completion model based on a newly defined latent Schatten TT norm. Then, the statistical performance is analyzed by establishing a non-asymptotic upper bound on the estimation error. Further, a scalable algorithm is developed to efficiently solve the model. Experimental results of color image inpainting demonstrate that the proposed norm has promising performances compared to other variants of Schatten norm.

Temperature sensitivity (Q10) is important to reveal carbon decomposition responding to climate change. It’s remains limited to understand how Q10 of anaerobic soil organic matter (SOM) decomposition is regulated by soil property in various wetlands with distinct hydrological characteristics. In the present study, samples of soil at the depths of 0–10 cm, 10–20 cm and 20–30 cm were collected in three typical Phragmites australis marshes, including a freshwater marsh (FPa), a no-tidal salt marsh (NTPa) and a tidal salt marsh (TPa), in the Yellow River estuary. The soil samples were incubated at 10 °C, 20 °C and 30 °C, respectively, to determine the rates of anaerobic CO2 production, Q10 values, and their relations to soil properties. Over 70-d incubation, temperature rise significantly increased the mean rates by 70%–136% (from 10 °C to 20 °C) and 64%–142% (from 20 °C to 30 °C) among the marshes, with the mean Q10 values ranging from 1.61 to 2.66. The rates of CO2 production and Q10 values were significantly affected by wetland type and soil depth. Among marshes, the Q10 of the FPa and NTPa soils was higher than that of the TPa soil (for 0–10 cm and 10–20 cm but for 20–30 cm); along soil depths, the Q10 of the top soil was higher than that of the subsoil (for FPa and NTPa but for TPa). Q10 was affected by total organic carbon (TOC), salinity and pH, and the effects were different with marshes. TOC was a main factor regulating Q10 for the freshwater and the no-tidal salt marshes, while salinity and pH were main factors for the tidal salt marsh. The findings highlight an interactive mechanism of soil property and tidal underlying the response of SOM decomposition to temperature change in estuarine wetlands.

Twisted light carrying orbital angular momentum (OAM), which features helical phase front, has shown its potential applications in diverse areas, especially in optical communications. For OAM-based free-space optical (FSO) links, a significant challenge is the power fading induced by atmospheric turbulence. In this paper, we experimentally demonstrate the mitigation of atmospheric turbulence effects with an OAM-based transmitter mode diversity scheme. By designing multi-OAM phase patterns, we successfully generate multiple OAM modes (OAM-1,0,1, OAM+2,+3,+4, OAM+5,+6,+7) carrying the same data stream for transmitter diversity without adding system complexity. An intensity-modulated direct-detection (IM-DD) system with 39.06 Gbit/s discrete multi-tone (DMT) signal is employed to confirm the feasibility of the OAM-based transmitter mode diversity scheme under atmosphere turbulence. The obtained experimental results show that the received power fluctuation and average bit-error rate (BER) are decreased under moderate to strong turbulence compared to the traditional single OAM mode transmission. In addition, the required transmitted power at 10% interruption probability is relaxed by nearly 2 dB under moderate to strong turbulence.

In recent years, the biomass was directly used extensively in agriculture due to its low cost and convenience. Increasingly serious soil pollution of heavy metals may pose threats and risks to human health. Directly addition of biomass to soil may affect the bioavailability and content of heavy metals. Here, we reviewed the impact of direct application of oil cake, manure, sewage sludge, straw and municipal waste to soil on the form and concentration of heavy metals in soil, and also emphasized the role of biomass in soil heavy metals remediation. Heavy metals can be activated in a short term by the content of heavy metals in biomass, the production of low-molecular-weight organic acids by biomass application, and the oxidation of sulfides (except for ammoniation). However, heavy metals in soil can be immobilized by humic substances. These can be produced by biomass during a long-term application to soil. Moreover, the degree of immobilization depended on the kind of biomass. Biomass contaminated by heavy metals cannot be returned to the field directly. Therefore, Mitigating the activation of heavy metals in the early stage of biomass application is meaningful, especially for application of these biomass such as straw, sewage sludge and municipal waste. Future researches should focus on the heavy metal control on direct use of biomass in agricultural.

We demonstrated a method for computer-generated holograms fabricated by using a femtosecond Bessel beam. A high-efficiency point-by-point process was used to fabricate a longitudinal modified array with a period of 10 μm and a modified area with diameter of approximately 1.5 μm on transparent glass. Tuning the modified length of each area by changing the relative positions of the Bessel beam and sample allowed the phase profile of the incident light to be flexibly adjusted to generate an arbitrary far-field pattern. The approach was verified by inscribing a designed phase hologram in borosilicate glass. Twin images were eliminated by high-level modulation.

With ultrashort pulse durations and ultrahigh peak intensities, ultrafast lasers can create different types of micro/nano-structures to functionalize the processed surface with new properties. However, the applications of this method on freeform surfaces are still limited by the short length of a laser focusing spot and complex control of the 3D moving trajectory in the fabrication process. In this paper, we overcome this problem by shaping the on-axis intensity along the propagation axis using the spatial light modulator. By designing the phase mask, we increased the length of the stable-intensity zone (intensity fluctuation < 10%) by more than 3 times compared to that of an unshaped Bessel beam. The energy deposition was also optimized to be less than 2% fluctuation based on simulations. Using this method, we fabricated micro/nano structures on 3D surfaces at different fluences and demonstrated various properties including colorization, anti-reflection, and hydrophobicity in large height range. We demonstrated the applications of the proposed method in creating hydrophobicity on complex freeform syringe tip surfaces. This improved the minimum manipulatable volume of a liquid droplet to 2 times smaller compared with untreated syringe, thus greatly extending its performance for micro-droplet manipulation. This method offers an alternative approach for reliable and affordable freeform curved-surface processing.

We developed a novel method for fabricating microlenses and microlens arrays by controlling numerical aperture (NA) through temporally shaped femtosecond laser on fused silica. The modification area was controlled through the pulse delay of temporally shaped femtosecond laser. The final radius and sag height were obtained through subsequent hydrofluoric acid etching. Electron density was controlled by the temporally shaped femtosecond laser, and the maximum NA value (0.65) of a microlens was obtained in the relevant studies with femtosecond laser fabrication. Furthermore, the NA can be continuously adjusted from 0.1 to 0.65 by this method. Compared with the traditional methods, this method exhibited high flexibility and yielded microlenses with various NAs and microlens arrays to meet the different demands for microlens applications.

The mechanisms of intercropping increasing plant biomass, cadmium accumulation, and organic acids secreted in rhizosphere soil are still unclear. Oilseed rape and intercrops were grown in boxes separated either with no barrier between the compartments or by a nylon mesh barrier (37 μm) to license partial root interaction, or a solid barrier to stop any root interactions. Two intercropping systems (oilseed rape-faba bean and oilseed rape-ryegrass) were carried out in soil with Cd content of 5 mg/kg. The intermingling of roots between oilseed rape and faba bean enhanced the biomass of oilseed rape. However, the biomass was negatively affected implying the higher nutrient apportionment to the ryegrass than oilseed rape. Oilseed rape intercropping with both faba bean and ryegrass played a positive role in the shoot Cd concentration of oilseed rape. The intermingling of roots played a positive role in the citric and malic acids when intercropping with faba bean. A remarkable increase in water-soluble Cd and DTPA-Cd content was observed during oilseed rape-faba bean complete root interaction treatment, up to 175.00% and 46.65%, respectively, which compare with the monoculture treatment. In both systems, the translocation factor values were higher for oilseed rape (O–F system) than for the other test plants and were always >1. Thus the Cd removal potential of oilseed rape can be further improved in the future by optimizing agronomic practices and intercropping with faba bean.

The physico-chemical characteristics of N fertilizers remain poorly understood with respect to their use with rape (Brassica napus L.) to remediate Cd-contaminated soil. In this work, eight types of fertilizer (comprising physico-chemical alkaline, neutral, and acidic N fertilizers) were employed to assess the effect of soil remediation via rape at different levels of Cd contamination (0, 5, and 10 mg kg−1 Cd). The results show that the pH of rhizosphere soils was significantly higher under physico-chemical alkaline N fertilizer treatments than under physico-chemical acidic and neutral N fertilizer treatments. The physico-chemical characteristics of N fertilizers affected the rhizosphere soil pH and promoted Cd phytoextraction and accumulation by rape. In the 5 mg kg−1 Cd-contaminated soil, the Cd accumulation and bioconcentration factor value in the shoots and the Cd translocation factor value were highest with the addition of NH4Cl, a physico-chemical acidic N fertilizer. Among the physico-chemical alkaline N fertilizers, Ca(NO3)2 enabled the highest accumulation of Cd in rape shoots when soil was contaminated with 10 mg kg−1 Cd. Thus, administering physico-chemical acidic N fertilizer to soils with lower Cd concentrations provides better remediation effects by rape, whereas physico-chemical alkaline N fertilizers are more effective in soils with higher Cd concentrations. These results show that physico-chemical N fertilizers can be employed to enhance the remediation of Cd-contaminated soil by rape and simultaneously improve the yield of this crop, with implications for environmental health and sustainable agricultural development.

Geothermal energy is one of the keys for understanding the mechanisms driving the plate tectonics and mantle dynamics. The surface heat flux, as measured in boreholes, provides limited insights into the relative contributions of primordial versus radiogenic sources of the interior heat budget. Geoneutrino, electron antineutrino that is produced from the radioactive decay of the heat producing elements, is a unique probe to obtain direct information about the amount and distribution of heat producing elements in the crust and mantle. Cosmochemical, geochemical, and geodynamic compositional models of the Bulk Silicate Earth (BSE) individually predict different mantle neutrino fluxes, and therefore may be distinguished by the direct measurement of geoneutrinos. Due to low counting statistics, the results from geoneutrino measurements at several sites are inadequate to resolve the geoneutrino flux. However, the JUNO detector, currently under construction in South China, is expected to provide an exciting opportunity to obtain a highly reliable statistical measurement, which will produce sufficient data to address several vital questions of geological importance. However, the detector cannot separate the mantle contribution from the crust contribution. To test different compositional models of the mantle, an accurate a-priori estimation of the crust geoneutrino flux based on a three-dimensional (3-D) crustal model is important. This paper presents a 3-D crustal model over a surface area of 10° × 10° grid surrounding the JUNO detector and a depth down to the Moho discontinuity, based on the geological, geophysical and geochemical properties. This model provides a distinction of the thickness of the different crustal layers together with the corresponding Th and U abundances. We also present our predicted local contribution to the total geoneutrino flux and the corresponding radiogenic heat. Compared to previous studies where the surface layer is subdivided into a few geologic units and each of them is considered to have the same geochemical property, our method has provided an effective approach to reduce the uncertainty of geoneutrino flux prediction by constructing the composition of the surface layer through cell by cell which are independent to each other.

Marine submerged aquatic angiosperms (seagrasses) are declining globally. The species Zostera japonica Asch. & Graebn. is endangered in its native range in Asia, but has been successfully introduced to North America. A large area (1031.8 ha) of Z. japonica meadow has recently been discovered in the intertidal zone of Yellow River Delta, China. This seagrass occurs along both sides of the river mouth, forming dense meadows in turbid water conditions. Seasonal investigations over two years were conducted to examine the distribution, biomass, seed reproduction, seed bank, and population recruitment of the seagrass meadows at three sites in the intertidal zone. The meadows generally showed relatively high coverage, biomass, reproductive effort, and seed production in August. The seed bank was found to be large and contributed to population recruitment. There were significant inter-annual variations overall, and at individual sites. These variations are likely due to winter temperatures, which determine the abundance of overwintering shoots and seedling success. Differences in micro-topography may also play a role in producing variations in seedling success between sites. Microsatellite analysis revealed a high genetic exchange between the two sides of the river mouth. The results indicate that the seagrass bed in the Yellow River Delta shallow waters is in good condition, which can be attributed to its location within a national nature reserve. Establishment of protected areas might act as an effective way to mitigate the anthropogenic disturbance, conserve the seagrass meadows, and then enhance critical ecosystem functions.