Spatial impact of the digital economy on low-carbon logistics efficiency in RCEP countries.

A thorough study of the spatial impact of the digital economy on low-carbon logistics efficiency would be greatly significant for Regional Comprehensive Economic Partnership (RCEP) countries to improve low-carbon logistics efficiency and achieve sustainable cooperation. This study constructs a theoretical framework from the perspective of spatial effects on the impact of the digital economy on low-carbon logistics efficiency in RCEP countries. The entropy method was used to measure the level of digital economic development. The super-efficiency SBM model was used to measure low-carbon logistics efficiency. Spatial feature analysis was conducted using kernel density estimation and Moran's index, followed by empirical analysis using spatial econometric models to examine the spatial impact of the digital economy on low-carbon logistics efficiency in RCEP countries. The results indicate that in RCEP countries, both low-carbon logistics efficiency and the level of digital economic development exhibit significant spatial positive correlation. Furthermore, the digital economy can promote low-carbon logistics efficiency in economically neighboring countries through spatial spillover effects. The improvement of domestic low-carbon logistics efficiency can also promote low-carbon logistics efficiency in neighboring countries. This conclusion was supported by endogeneity tests and a convergence analysis. Additionally, the mechanism analysis revealed that improving the level of green energy can enhance the spatial spillover effects of the digital economy and promote low-carbon logistics efficiency. Finally, countermeasures and suggestions was proposed to improve the low-carbon logistics efficiency of RCEP countries through the digital economy.

Wide-field-of-view auto-coupling optical antenna system for high-speed bidirectional optical wireless communications in C band.

Due to a great many superior features of infrared light communication (ILC), like high capacity and strong privacy, ILC is considered a potential candidate for serving the high demands of beyond fifth-generation/sixth-generation (B5G/6 G) communication systems. However, the terminal's limited field-of-view (FOV) induces great difficulty in establishing line-of-sight (LoS) link between the transceiver and the terminal. In this paper, we propose a wide-FOV auto-coupling optical antenna system that utilizes a wide-FOV telecentric lens to collect incident infrared beams and automatically couple them into a specific single-mode-fiber (SMF) channel of fiber array and optical switch. The performance of this optical antenna system is assessed through simulation and manual alignment operation, and validated by automatic alignment results. A coupling loss of less than 10.6 dB within a FOV of 100° for both downstream and upstream beams in C band is demonstrated by the designed system. Furthermore, we establish a bidirectional optical wireless communications (OWC) system employing this antenna and a fiber-type modulating retro-reflector (MRR) system in the terminal. Both 10-Gbps on-off keying (OOK) downstream and upstream transmissions are successfully realized with the FOV of up to 100° in C band where the measured bit-error-rate (BER) is lower than 3.8 × 10-3. To the best of our knowledge, this is a brand-new auto-coupling optical antenna system with the largest FOV in ILC automatic alignment works in terminals that have ever been reported.

Elimination of the fundamental mode hybridization on an x-cut lithium-niobate-on-insulator by using a densely packed bent waveguide array.

Lithium niobate (L i N b O 3, LN) is a promising material for integrated photonics due to its natural advantages. The commercialization of thin-film LN technology has revitalized this platform, enabling low-loss waveguides, micro-rings, and compact electro-optical modulators. However, the anisotropic birefringent nature of X-cut LN leads to mode hybridization of TE and TM modes, which is detrimental to most polarization-sensitive integrated optical waveguide devices. A novel structure, to the best of our knowldege, utilizing a densely packed bent waveguide array is presented in this paper to eliminate mode hybridization. The refractive index is modulated in a manner that eliminates the avoided crossing of the refractive index curves of the TE and TM fundamental modes; thus, mode hybridization is prevented. The structures are readily accessible in the full range of commercially available LN film thicknesses from 400 to 720 nm and in any etching depth. The proposed structures give a polarization extinction ratio of -30d B across all bend radii, while simultaneously maintaining low excess loss of less than -1d B after reaching a 100 µm bend radius.

LiNbO3 waveguide with embedded Ag nanowire and 3L MoS2 for strong light confinement and ultra-long propagation length in the visible spectral range.

A vertical slot LiNbO3 waveguide with an Ag nanowire and 3L MoS2 embedded in the low-refractive index slot region is proposed for the purpose of improving light confinement. We find that the proposed waveguide has a novel dielectric based plasmonic mode, where local light field is enhanced by the Ag nanowire. The mode exhibits an extremely large figure of merit (FoM) of 6.5×106, one order of magnitude larger than that the largest FoM of any plasmonic waveguide reported in the literature to date. The waveguide also has an extremely long propagation length of 84 cm in the visible wavelength at 680 nm. Furthermore, the waveguide has a low sub-micro bending loss and can be directly connected to all-dielectric waveguides with an extremely low coupling loss. The proposed vertical slot LiNbO3 waveguide is a promising candidate for the realization of ultrahigh integration density tunable circuits in the visible spectral range.

Mathematical Modeling of COVID-19 Control and Prevention Based on Immigration Population Data in China: Model Development and Validation.

BACKGROUND: At the end of February 2020, the spread of coronavirus disease (COVID-19) in China had drastically slowed and appeared to be under control compared to the peak data in early February of that year. However, the outcomes of COVID-19 control and prevention measures varied between regions (ie, provinces and municipalities) in China; moreover, COVID-19 has become a global pandemic, and the spread of the disease has accelerated in countries outside China. OBJECTIVE: This study aimed to establish valid models to evaluate the effectiveness of COVID-19 control and prevention among various regions in China. These models also targeted regions with control and prevention problems by issuing immediate warnings. METHODS: We built a mathematical model, the Epidemic Risk Time Series Model, and used it to analyze two sets of data, including the daily COVID-19 incidence (ie, newly diagnosed cases) as well as the daily immigration population size. RESULTS: Based on the results of the model evaluation, some regions, such as Shanghai and Zhejiang, were successful in COVID-19 control and prevention, whereas other regions, such as Heilongjiang, yielded poor performance. The evaluation result was highly correlated with the basic reproduction number (R0) value, and the result was evaluated in a timely manner at the beginning of the disease outbreak. CONCLUSIONS: The Epidemic Risk Time Series Model was designed to evaluate the effectiveness of COVID-19 control and prevention in different regions in China based on analysis of immigration population data. Compared to other methods, such as R0, this model enabled more prompt issue of early warnings. This model can be generalized and applied to other countries to evaluate their COVID-19 control and prevention.

Overwater light-sheet Scheimpflug lidar system for an underwater three-dimensional profile bathymetry.

The feasibility of an overwater light-sheet Scheimpflug lidar system for underwater three-dimensional (3D) profiling is considered. Corrections for the refraction at the air-water interface are proposed. Applications for profiling marine ecosystems are explored in distance up to several meters, and millimeter precision is accomplished. The experimental results demonstrate that our system is suitable for underwater 3D profiling and has great potential in marine biological detection.

All-optical NRZ wavelength conversion based on a single hybrid III-V/Si SOA and optical filtering.

We demonstrate all-optical wavelength conversion (AOWC) of non-return-to-zero (NRZ) signal based on cross-gain modulation in a single heterogeneously integrated III-V-on-silicon semiconductor optical amplifier (SOA) with an optical bandpass filter. The SOA is 500 µm long and consumes less than 250 mW electrical power. We experimentally demonstrate 12.5 Gb/s and 40 Gb/s AOWC for both wavelength up and down conversion.

5 x 20 Gb/s heterogeneously integrated III-V on silicon electro-absorption modulator array with arrayed waveguide grating multiplexer.

We present a five-channel wavelength division multiplexed modulator module that heterogeneously integrates a 200 GHz channel-spacing silicon arrayed-waveguide grating multiplexer and a 20 Gbps electro-absorption modulator array, showing the potential for 100 Gbps transmission capacity on a 1.5x0.5 mm² footprint.

Ultracompact tapered coupler for the Si/III-V heterogeneous integration.

An ultracompact tapered coupler, which is suitable for mode transformation between a 220 nm high silicon wire waveguide and a Si/III-V hybrid waveguide, is proposed for Si/III-V heterogeneous integration. The tapered coupler is composed of three sections. Since the tapered coupler avoids exciting the unwanted high-order modes in the III-V waveguide, the length of the tapered coupler can be dramatically shortened. In the proposed structure, the total length of the trisectional tapered coupler can be as short as 8 µm with a fundamental mode-coupling efficiency of over 95% in a bandwidth of over 100 nm. The alignment tolerance of the proposed structure is also analyzed.

Suspended ultra-small disk resonator on silicon for optical sensing.

An ultra-small disk resonator consisting of a suspended silicon disk with a submicron bending radius sitting on an SiO(2) pedestal is demonstrated experimentally. An asymmetrical suspended rib waveguide is integrated as the access waveguide for the suspended submicron disk resonator, which is used to realize an ultra-small optical sensor with an improved sensitivity due to the enhanced evanescent field interaction with the analyte. The present optical sensor also has a large measurement range because of the ultra-large free-spectral range of the submicron-disk resonator. As an example, a suspended submicron disk sensor with a bending radius of 0.8 µm is designed, fabricated, and characterized. The concentration of NaCl aqueous solution and organic liquids is measured with the suspended submicron-disk sensor, and the measured sensitivity is about 130 nm/RIU, which agrees well with the simulation value.

Nonlocal effects in a hybrid plasmonic waveguide for nanoscale confinement.

The effect of nonlocal optical response is studied for a novel silicon hybrid plasmonic waveguide (HPW). Finite element method is used to implement the hydrodynamic model and the propagation mode is analyzed for a hybrid plasmonic waveguide of arbitrary cross section. The waveguide has an inverted metal nano-rib over a silicon-on-insulator (SOI) structure. An extremely small mode area of~10⁻6λ² is achieved together with several microns long propagation distance at the telecom wavelength of 1.55 µm. The figure of merit (FoM) is also improved in the same time, compared to the pervious hybrid plasmonic waveguide. We demonstrate the validity of our method by comparing our simulating results with some analytical results for a metal cylindrical waveguide and a metal slab waveguide in a wide wavelength range. For the HPW, we find that the nonlocal effects can give less loss and better confinement. In particular, we explore the influence of the radius of the rib's tip on the loss and the confinement. We show that the nonlocal effects give some new fundamental limitation on the confinement, leaving the mode area finite even for geometries with infinitely sharp tips.

Inhibitory kinetics of bromacetic acid on beta-N-acetyl-D-glucosaminidase from prawn (Penaeus vannamei).

beta-N-Acetyl-D-glucosaminidase (NAGase, EC.3.2.1.52), a composition of chitinases, cooperates with endo-chitinase and exo-chitinase to disintegrate chitin into N-acetylglucosamine (NAG). NAGase from prawn (Penaeus vannamei) is involved in digestion and molting processes. The investigation of enzymatic properties, functional groups and catalytic mechanism is an essential mission to its commercial application. Bromacetic acid (BrAc) is a specific modifier for the histidine residue in specific condition. In this paper, the effect of BrAc on prawn NAGase activity for the hydrolysis of pNP-NAG has been investigated. The results showed that BrAc can reversibly and non-competitively inhibit the enzyme activity at appropriate concentrations and the value of IC(50) was estimated to be 17.05+/-0.65 mM. The inhibition kinetics of the enzyme by BrAc has been studied using the kinetic method of the substrate reaction. And the inhibition model was set up and the microscopic rate constants for the reaction of the inhibitor with free enzyme and the enzyme-substrate complexes were determined for inactivation and reactivation. The rate constant of the forward inactivation (k(+0)), which is 1.25 x 10(-3)s(-1), is about eight times as much as that of the reverse reactivation (k(-0)), which is 1.64 x 10(-4)s(-1). Therefore, when the BrAc concentration is sufficiently large, the enzyme is completely inactivated.