Excess Density Research Articles

Molecular dynamics simulation of laser assisted grinding of GaN crystals

Gallium nitride crystal is a typical difficult-to-machine material due to its distinct anisotropy, high brittleness, and high hardness. The molecular dynamics simulations of traditional grinding and laser assisted grinding of GaN single crystals with a single grit were performed, and the influences of the laser power density on grinding force, stress distribution, material damage mechanism, subsurface damage depth, and abrasive wear were systematically studied. The results demonstrated that dislocations, stacking faults, hexagonal-to-cubic phase transition, and amorphous transition were generated during both traditional grinding and laser assisted grinding processes. Compared with the traditional grinding, laser assisted grinding with an appropriate laser power density reduced the grinding force, stress distribution, phase transition percentage, dislocation loop length, subsurface damage depth, and wear damage of the abrasive. However, excessive laser power densities caused deeper subsurface damage depth and severer amorphous damage for the rake face of the abrasive particle, which seriously deteriorated the integrity of the ground surface and subsurface. The results not only enhance the understanding of material removal and damages under the coupling actions of the laser and abrasive machining, but also provide a theoretical basis for parameter optimization during the machining of GaN single crystals.

THE IMPACTS OF URBANIZATION AND ECONOMIC COMPONENTS ON PUBLIC HEALTH IN TURKEY: 2014-2018 PANEL DATA ANALYSIS / Türkiye’de Kentleşme Ve Ekonomik Bileşenlerinin Toplum Sağlığı Üzerindeki Etkileri: 2014-2018 Panel Veri Analizi

Covid-19 Pandemi süreci sonrasında ekonomi ve kentleşme alanındaki akademik çalışmaların odak noktasını toplum sağlığı üzerinde etkili olan iktisadi ve sosyopolitik bileşenler ve bu konuda karşılaşılan temel açmazlar oluşturmaktadır. Toplum sağlık harcamaları üzerinde doğrudan ya da dolaylı olarak kentsel dinamikler, ekonomik kalkınma girişimler ve ekolojik kısıtlar belirleyici olmaktadır. Bu kapsamda çalışmanın temel amacı kentleşme ve çevresel unsurlar ile ilişkili olarak iktisadi ve sosyopolitik parametrelerin toplum sağlık harcamaları arasındaki ilişkiyi analiz etmektir. Bu amaçla çalışmada Türkiye’deki 2014 ile 2018 yılları arasında 30 büyükşehir için toplum sağlığı harcamaları üzerindeki etkisi olan unsurları belirlemek için Panel EGLS modeli kullanılmıştır. Çalışma sonucunda plansız kentleşmenin sebep olduğu nüfus yoğunluğu, hava kirliliği, hijyen koşullarının yetersizliği, atıklar, kişi başına düşen yeşil alan miktarının yetersiz olması gibi bileşenlerin toplum sağlığını koruma ve geliştirme maliyetlerini arttırdığı tespit edilmiştir. Benzer şekilde enerji kullanımının artması, yüksek eğitim seviyesi ve yaşlı nüfus oranı gibi parametrelerin toplum sağlık hizmetlerine olan talebi artırdığı sonucuna ulaşılmıştır.

Investigation of Affinity and Preservation Ability of Trehalose Glycopolymer toward α-Amylase

Trehalose is a well-known preservation agent for various biomolecules, but the mechanism by which it achieves this function remains unclear. Trehalose glycopolymers with various sugar densities were utilized for affinity analysis and preservation assays with α-amylase. Strong affinity and weak preservation ability were observed when glycopolymers with excess sugar density were applied. In contrast, weak affinity and strong preservation abilities were observed when glycopolymers featuring appropriate sugar densities were used. These results indicated that the affinity was not correlated with preservation ability under heated conditions. It was important for the trehalose glycopolymer to form a densely packed trehalose glycocluster, regardless of affinity, to achieve preferable preservation properties.

Effectiveness of roux-en-Y gastric bypass vs sleeve gastrectomy on lipid levels in type 2 diabetes: a meta-analysis

Abstract Introduction Obesity and its co-morbidities, including type 2 diabetes (T2DM) and dyslipidemia, are accompanied by excess cardiovascular morbi-mortality. Aside from excess low density lipoprotein-cholesterol (LDL-C), atherogenic dyslipidemia (AD), mainly characterized by elevated triglycerides and decreased high density lipoprotein-cholesterol (HDL-C) levels, is often present in T2DM obese patients. Bariatric surgery, such as Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), has become a reference treatment in that population. However, the respective effects of RYGB vs SG on lipid metabolism in T2DM patients have been rarely studied. Methods A meta-analysis of randomized controlled trials, comparing the effects of RGYBG vs SG on lipid metabolism 12 months after surgery in T2DM patients, was performed. Results Four studies including a total of 298 patients (151 patients in the RYGB and 147 patients in the SG group) were examined. Despite a greater decrease in body mass index and greater improvement in glycaemic control in RYGB compared to SG. RYGB vs SG was more effective in reducing total cholesterol, LDL-C and non-HDL-C levels (mean difference [MD] −24.10 mg/dL, 95% CI −33.76 to −14.44, p<0.00001; [MD] −23.24 mg/dL, 95% CI −34.84 to −11.63, p<0.00001 and MD 31.70 mg/dL, 95% CI −46.00 to −17.40, p<0.00001, respectively). Conclusions The superiority of RYGB vs SG in reducing LDL-C, with an effect comparable to a moderate-intensity statin, suggests RYBG should be favoured in hypercholesterolemic T2DM patients in order to further reduce cardiovascular risk. Funding Acknowledgement Type of funding sources: None.

In situ study on plastic deformation mechanism of Al0.3CoCrFeNi high-entropy alloys with different microstructures

Al0.3CoCrFeNi high-entropy alloys (HEAs) have attracted the attention of researchers owing to their excellent mechanical properties. In this study, Al0.3CoCrFeNi HEAs with typical grain microstructures were fabricated and subjected to tensile tests, along with in situ scanning electron microscopy–electron backscatter deformation (SEM–EBSD), to determine the relationship between the grain microstructure, plastic deformation, and mechanical properties. The in situ EBSD analysis showed that the HEA sample with fine grains (FGs) exhibited more significant grain boundary deformation than that with coarse grains (CGs). The FG sample had a more uniform dislocation density distribution than the CG sample, and no noticeable excessive dislocation density was observed inside the grain. This indicates that the plastic deformation of the FG sample could be distributed more homogeneously without a prominent local stress concentration. Based on the grain structures from EBSD scans, crystal plasticity finite element modeling (CPFEM) and analysis were conducted to analyze the grain-level stress and strain heterogeneities. The results showed that during the tensile process, high stress was initially distributed near the B2 phase and subsequently at the grain boundaries of the HEA with increase in tensile deformation. The local stress distribution in the matrix was significantly affected by the B2 phase. Although high stress was distributed near the B2 phase during plastic deformation, the probability of crack initiation at the phase boundaries was low. This can be partly attributed to the formation of deformation twins at the junction of the B2 phase and FCC matrix, which releases the stress.

Evolution of structure of rail steel lamellar pearlite under compression deformation

The article presents the results of analysis of evolution of the defective substructure of rail steel pearlite with lamellar morphology under deformation by uniaxial compression. The strain hardening of the studied steel under such deformation has a multistage character. Deformation of steel is accompanied by fragmentation of pearlite grains, which intensifies as the degree of deformation increases and reaches 0.4 of the studied foil volume at ε = 50 %. Fragments formed in ferrite plates are separated by low-angle boundaries. It was established that the average sizes of ferrite plate fragments decrease from 240 nm (ε = 15 %) to 200 nm (ε = 50 %) with an increase in the deformation degree. Fragmentation of cementite plates was revealed. It was found that the size of the fragments varies within 15 – 20 nm and weakly depends on the degree of steel deformation. Fracture of cementite lamellae, proceeding by their dissolution and cutting by mobile dislocations, was discovered. Carbon atoms that have passed from the crystal lattice of cementite to dislocations are carried out into the interlamellar space and form particles of tertiary cementite, the size of which is 2 – 4 nm. In the process of steel deformation, an inhomogeneous dislocation substructure is formed, which is due to the deceleration of dislocations by cementite particles. It was found that an increase in the deformation degree is accompanied by a decrease in the scalar and excess density of dislocations, which may be due to the escape of dislocations into low-angle boundaries, as well as their annihilation. It was established that the sources of internal stress fields are the interfaces between pearlite grains and colonies, cementite plates in pearlite grains, particles of the second phase located in the volume of ferrite plates.

Effects of Process Parameters on Density of GH5188 High-temperature Alloy after Selective Laser Melting

GH5188 high-temperature alloy specimens were fabricated by selective laser melting (SLM) and influencing laws of laser power, laser velocity and laser energy density on density of specimens were researched. The results shows that along with the laser energy density increases from 73.02 J/mm3 to 88.18 J/mm3, porosity in specimens decrease and relative density increases from 98.86% to 99.75%. However, as the laser energy density increase further, the density begins to decrease continuously. The main causes that effects relatively density including: the powder is not fused at low energy density, as well as the powder splash and gasification at higher energy density. Neither inadequate nor excessive laser energy density is conducive to improvement of density of specimens. As the increase of laser velocity and laser power, density of specimens increases firstly and then decreases. The variation trend of relative density is similar with that of laser energy density and there are reasonable ranges of laser velocity and laser power. However, influencing laws of laser velocity and laser power on density of specimens are different.

N -body simulations, halo mass functions, and halo density profile in f(T) gravity

We perform N-body simulations for $f(T)$ gravity using the ME-Gadget code, in order to investigate for the first time the structure formation process in detail. Focusing on the power-law model, and considering the model-parameter to be consistent within 1$\sigma$ with all other cosmological datasets (such as SNIa, BAO, CMB, CC), we show that there are clear observational differences between $\Lambda$CDM cosmology and $f(T)$ gravity, due to the modifications brought about the latter in the Hubble function evolution and the effective $Newton\prime s$ constant. We extract the matter density distribution, matter power spectrum, counts-in-cells, halo mass function and excess surface density (ESD) around low density positions (LDPs) at present time. Concerning the matter power spectrum we find a difference from $\Lambda$CDM scenario, which is attributed to about 2/3 to the different expansion and to about 1/3 to the effective gravitational constant. Additionally, we find a difference in the cells, which is significantly larger than the Poisson error, which may be distinguishable with weak-lensing reconstructed mass maps. Moreover, we show that there are different massive halos with mass $M>10^{14}M_{\odot}/h$, which may be distinguishable with statistical measurements of cluster number counting, and we find that the ESD around LDPs is mildly different. In conclusion, high-lighting possible smoking guns, we show that large scale structure can indeed lead us to distinguish General Relativity and $\Lambda$CDM cosmology from $f(T)$ gravity.

Nitrogen rates and plant density interactions enhance radiation interception, yield, and nitrogen use efficiencies of maize

The contributions of the different leaf layers to maize yields identified as middle leaf > lower leaf > upper leaf, where the vertical photosynthetically active radiation (PAR) in the canopy gradually decreases. We hypothesized that the allocation of more PAR and nitrogen (N) to the highest contributing leaves will would be beneficial for higher yields and N use efficiencies. The N application rate and plant density effectively regulated the canopy light and N distribution. We evaluated the interactive effects of N rate and plant density on the agronomic and ecophysiological characteristics of leaves at different orientations in a 2019/2020 field experiment. In this study, an N application rate of 180 kg ha–1 coupled with a plant density of 82,500 plants ha–1 achieved the highest yield and N recovery efficiency (NRE). In contrast to the traditional farming practices in northern China, the density was increased and N rate was reduced. Densification from 52,500 to 82,500 plants ha–1 increased the population leaf area index (LAI) by 37.1% and total photosynthetically active radiation (TPAR) by 29.2%; however, excessive density (from 82,500 to 97,500 plants ha–1) drastically reduced the proportion of TPAR by 28.0% in the lower leaves. With increased density, the leaf areas and angles of the upper leaves decreased much more than those of the other leaves, which allowed the middle and lower leaves to access more light, which manifested a smaller extinction coefficient for light (KL). A high yield (>1,000 kg ha–1) of maize could be achieved simultaneously with higher NRE; however, it was negatively correlated with internal N use efficiency (IEN). Higher N concentrations and lower total performance index (PItotal) in the lower leaves may be an important rationale for the reduction of IEN in high-yielding maize. Additionally, decreased N rate without yield reduction under higher densities was primarily attributed to the more uniform vertical N distribution [a smaller extinction coefficient for N (KN)]. These results suggest that the N fertilizer rate can be moderately reduced without a reduction in maize yield under high plant densities in northern China.

An in situ study of abyssal turbidity-current sediment plumes generated by a deep seabed polymetallic nodule mining preprototype collector vehicle

An in situ study to investigate the dynamics of sediment plumes near the release from a deep seabed polymetallic nodule mining preprototype collector vehicle was conducted in the Clarion Clipperton Zone in the Pacific Ocean 4500-m deep. The experiments reveal that the excess density of the released sediment-laden water leads to a low-lying, laterally spreading turbidity current. At the time of measurement, 2 to 8% of the sediment mass were detected 2 m or higher above the seabed and were not observed to settle over several hours, with the remaining 92 to 98% below 2 m and some fraction of that locally deposited. Our results suggest that turbidity current dynamics sets the fraction of sediment remaining suspended and the scale of the subsequent ambient sediment plume. The implications of this process, which is characteristically overlooked in previous modeling efforts, are substantial for plume modeling that will lie at the heart of environmental impact statements for regulatory consideration.

Bulk viscosity of hard sphere fluids by equilibrium and nonequilibrium molecular dynamics simulations.

The bulk viscosity, ηb, of the hard sphere (HS) fluid is computed by equilibrium and nonequilibrium molecular dynamics (NEMD) simulations, the latter using an adaptation of the time-stepping method for continuous potential systems invented by Hoover et al. [Phys. Rev. A 21, 1756 (1980)], which employs an imposed cyclic density variation on the system by affine scaling of the particle coordinates. The time-stepping method employed for HS is validated against exact event-driven hard sphere methodology for a series of equilibrium quantities over a wide density range, including the pressure, singular parts of the hard sphere viscosities, and the nonsingular parts of the shear viscosity time correlation functions. The time steps used are typically only a little smaller than those employed in continuous potential simulations. Exact pressure tensor fluctuation expressions are derived for the singular (or infinite limiting frequency) equilibrium parts of the viscosities, which were employed in the simulations. The values obtained agree well with the predictions of the Enskog theory for all densities considered. The bulk viscosity obtained by NEMD is shown to be noticeably frequency dependent for densities in excess of ∼0.8, decaying approximately exponentially to the Enskog and equilibrium simulation values at all densities considered for frequencies in excess of ∼5 in hard sphere units. Temperature profiles during the cycle and the effects of strain amplitude on the computed frequency dependent bulk viscosity are presented. The bulk viscosity increases with the maximum density amplitude.

Potential reductions in ultra-processed food consumption substantially improve population cardiometabolic-related dietary nutrient profiles in eight countries

Background and aimsThe negative effect on dietary nutrient profiles is the most obvious mechanism explaining the higher risk of cardiometabolic diseases associated with increased dietary share of UPF observed in large cohort studies.We estimate the proportion of diets with excessive energy density, excessive free sugars or saturated fat contents and insufficient fiber that could be avoided, if UPF consumption was reduced to levels among lowest consumers across eight countries, as well as the proportion of diets with multiple inadequacies. Methods and resultsUsing nationally-representative cross-sectional surveys from Brazil (2008–09), Chile (2010), Colombia (2005), Mexico (2012), Australia (2011–12), the UK (2008–16), Canada (2015), and the US (2015–16), inadequate energy density (≥2.25 kcal/g) or contents of free sugars (>10% of total energy intake), saturated fats (>10% of total energy intake) and fiber (<25 g/2000 kcal) population attributable fractions were quantified.Substantial reductions in nutrient inadequacies would be observed ranging from 50.4% in Chile to 76.8% in US for dietary energy density, from 15.5% in Colombia to 68.4% in Australia for free sugars, from 9.5% in Canada to 35.0% in Mexico for saturated fats, and from 10.3% in UK to 37.9% in Mexico for fiber. Higher reductions would be observed for diets with multiple nutrient inadequacies: from 27.3% in UK to 77.7% in Australia for ≥3 and from 69.4% in Canada to 92.1% in US, for 4 inadequacies. ConclusionsLowering dietary contribution of UPF to levels among country-specific lowest consumers is a way to improve population cardiometabolic-related dietary nutrient profiles.

Static Dielectric Constants, Densities, Refractive Indices and Related Properties of Binary Mixtures at Various Temperatures Under Atmospheric Pressure

Experimental dielectric constants at (293.15, 298.15, 303.15) K, densities and refractive indices at 293.15 K are reported for water- ethanol and water- n-butanol binary mixture systems over the entire volume fraction range and atmospheric pressure. From the experimental dielectric data, the excess dielectric constant, effective Kirkwood correlation factor, Bruggeman factor and from density and refractive index data various parameters and their excess properties like excess density, excess refractive index, excess molar polarization, and excess molar volume were estimated and reported in the study. The static dielectric constant of the studied binary mixtures decreases with increase in temperature and volume fraction of the solutes. The density values are decreasing and refractive indices are increasing with increasing volume fraction of ethanol and n-butanol in water. Excess molar volumes values of ethanol and n-butanol are negative over the entire volume fraction range shows the presence of intermolecular interaction and hydrogen bonding in both the binary mixtures.

Degradation of Edge‐Defined Film‐Fed Silicon Glass–Glass Modules on Florida Rooftop After 22 Years

Thin silicon () adoption can provide significantly lower cost. Kerfless technologies provide thin wafers while preventing material from being wasted. Understanding how this family of processing influences module reliability is important. A set of four edge‐defined film‐fed growth (EFG) silicon modules from a ten‐module system in Florida is measured after 22 years of exposure. Power loss rates of 0.58–0.78% year−1 are measured for three modules, while a rate of 1.32% is measured for a module with severe delamination and corrosion. Short‐circuit current degrades between 10.7% and 13.1% for all modules. The losses are primarily optical and recombination based; however, series and shunt resistance effects play a non‐negligible role. Pre‐existing recombination losses exist but are exacerbated via degradation. Optical losses in short‐circuit current are due in part to encapsulant yellowing. Electroluminescence (EL) images display the effects of processing on bulk quality by clearly showing lines of alternating brightness along the wafer length. To the authors’ knowledge, this is the first article displaying suns– data, effective lifetime versus excess carrier density data, and module EL images for EFG silicon‐based modules.

Piezoelectricity across 2D Phase Boundaries.

Piezoelectricity in low-dimensional materials and metal-semiconductor junctions has attracted recent attention. Herein, a 2D in-plane metal-semiconductor junction made of multilayer 2H and 1T' phases of molybdenum(IV) telluride (MoTe2 ) is investigated. Strong piezoelectric response is observed using piezoresponse force microscopy at the 2H-1T' junction, despite that the multilayers of each individual phase are weakly piezoelectric. The experimental results and density functional theory calculations suggest that the amplified piezoelectric response observed at the junction is due to the charge transfer across the semiconducting and metallic junctions resulting in the formation of dipoles and excess charge density, allowing the engineering of piezoelectric response in atomically thin materials.

Band Gap Opening in Bilayer Graphene-CrCl3/CrBr3/CrI3 van der Waals Interfaces.

We report experimental investigations of transport through bilayer graphene (BLG)/chromium trihalide (CrX3; X = Cl, Br, I) van der Waals interfaces. In all cases, a large charge transfer from BLG to CrX3 takes place (reaching densities in excess of 1013 cm-2), and generates an electric field perpendicular to the interface that opens a band gap in BLG. We determine the gap from the activation energy of the conductivity and find excellent agreement with the latest theory accounting for the contribution of the σ bands to the BLG dielectric susceptibility. We further show that for BLG/CrCl3 and BLG/CrBr3 the band gap can be extracted from the gate voltage dependence of the low-temperature conductivity, and use this finding to refine the gap dependence on the magnetic field. Our results allow a quantitative comparison of the electronic properties of BLG with theoretical predictions and indicate that electrons occupying the CrX3 conduction band are correlated.

Subgrain Coalescence Simulation by Means of an Advanced Statistical Model of Inelastic Deformation

The development of technological methods for processing and manufacturing of functional (with a priori targeted properties) polycrystalline materials and products made of these materials still remains an acute problem. A multilevel modeling approach offers researchers the opportunity to describe inelastic deformation by applying internal variables that give an effective characterization of the material structure at different structural scale levels. High temperature plastic deformation is accompanied by these processes, which leads to a significant rearrangement of the meso- and microstructure of the material. The most substantial contribution to changing the properties of polycrystals is made by the evolution of grain and defect structures at the expense of dynamic recrystallization, which significantly depends on dynamic recovery. In this paper, we consider the problem of the coalescence of subgrains undergoing rotation during inelastic hot deformation. This process is called subgrain coalescence, and it is one of the dynamic recovery mechanisms responsible for changes in the fine subgrain structure. Under applied thermomechanical loads, the coalescence process promotes the formation of recrystallization nuclei and their subsequent growth, which can greatly change the grain structure of a polycrystal. The problem was solved in terms of the advanced statistical model of inelastic deformation, modified to describe the subgrain coalescence process. The model takes into account the local interactions between contacting structural elements (subgrains). These have to be considered so that the grain coalescence caused by a decrease in subboundary energies during their progressive merging can be adequately analyzed. For this purpose, a subgrain structure quite similar to the real structure was modeled using Laguerre polyhedra. Subgrain rotations were investigated using the developed model, which relies on the consideration of the excess density edge component of the same sign dislocations on incidental subgrain boundaries. The results of modeling of a copper polycrystal are presented, and the effects of temperature and strain rate on the subgrain coalescence process is demonstrated.

Optimizing the Thickness and Diameter of Dual Structure Patterned Media Dots for Heat-Assisted Magnetic Recording

Dual structure bit patterned media were optimized for heat-assisted magnetic recording (HAMR). Each dot contained two discrete recording structures and was therefore able to store two bits of information. The optimized parameters were the dot diameter and the thicknesses of the recording structures. Analysis of the thermal stability of the magnetization at elevated temperatures suggested a design with a thicker recording structure on the bottom, where the head field was weaker, and a thinner structure on the top. Recording simulations showed that the optimal design could lead to user areal recording densities in excess of 9 Tbit/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

The effect of the molecular structure of alkyl ether carboxylate surfactants on the oil–water interfacial tension

• OPLS-AA is not applicable to study surfactants at the alkane-water interface. • Trappe-UA and OPLS-AA underestimate the effect of surfactants on the IFT. • The adsorption limit decreases with the increase in the surfactant headgroup length. • Doubling the tailgroup length leads to a small decrease in the adsorption limit. • The effect of a surfactant molecule size on the adsorption limit is asymptotical. Alkyl ether carboxylate surfactants at the alkane–water interface are explored experimentally through interfacial tension measurements with the spinning drop method and molecular dynamics simulations. The experimental interfacial tension dependence on bulk surfactant concentration is interpreted with the Redlich-Peterson adsorption model, which fits the experiments well. The critical micelle concentrations obtained from the experimental isotherms agree reasonably with published data on other surfactants of the same class. The length of the ethylene oxide hydrophilic segment significantly influences the dependence of the CMC and the interfacial tension at CMC on temperature. The excess surface density of the surfactant at the decane-water interface is calculated with the Redlich-Peterson model and compared with the molecular dynamics simulations, which are performed with two different forcefields. The simulations showed only semiquantitative agreement with the experiments: surfactants interfacial concentrations corresponding to a particular value of tension are systematically higher than the values derived from the experiments, for both forcefields by a certain factor that appears constant. Simulations of surfactants with different lengths of the alkyl tail and ethylene oxide head segments revealed general tendencies related to the surfactants interactions in the layer. Initially, the ethylene oxide segment elongation decreases the monolayer density and increases the effective elasticity. However, as the number of ethylene oxide monomers exceeds approximately eight, the density and compressibility become invariant of the length, which is likely explained by the dominance of electrostatic forces between the charged carboxylate groups that decay with the distance slower than the steric repulsion between the ethylene oxide chains.

Fusion of optical and SAR images based on deep learning to reconstruct vegetation NDVI time series in cloud-prone regions

The normalized difference vegetation index (NDVI) is crucial to many sustainable agricultural practices such as vegetation monitoring and health evaluation. However, optical remote sensing data often suffer from a large amount of missing information due to sensor failures and harsh atmospheric conditions. The synthetic aperture radar (SAR) offers a new approach to filling in missing optical data based on its excessive revisit density and its potential to image without interference from clouds and rain. Due to the difference in imaging mechanisms between SAR and optical sensors, it is very difficult to fuse the data. This paper developed an advanced deep learning Spatio-temporal fusion method, i.e., Transformer Temporal-spatial Model (TTSM), to synergize the SAR and optical time-series to reconstruct vegetation NDVI time series in cloudy regions. The proposed multi-head attention and end-to-end architecture achieved satisfactory accuracy (R2 greater than 0.88), outperforming the existing deep learning solutions. Extensive experiments were carried out to evaluate the TTSM method on large-scale areas (the spatial scale of megapixels) in northeast China with the main vegetation types of crops and forests. The R2, SSIM, RMSE, NRMSE, and MAE of our prediction results were 0.88, 0.80, 0.06, 0.16, and 0.05, respectively. The influence of training sample size was investigated through a transfer learning study, and the result indicated that the model had good generalizability. Overall, our proposed method can fill in the gap of optical data at an extensive regional scope over the vegetated area using SAR.