Quantum frequency conversion and single-photon detection with lithium niobate nanophotonic chips

In the past few years, the lithium niobate on insulator (LNOI) platform has revolutionized lithium niobate materials, and a series of quantum photonic chips based on LNOI have shown unprecedented performances. Quantum frequency conversion (QFC) photonic chips, which enable quantum state preservation during frequency tuning, are crucial in quantum technology. In this work, we demonstrate a low-noise QFC process on an LNOI nanophotonic platform designed to connect telecom and near-visible bands with sum-frequency generation by long-wavelength pumping. An internal conversion efficiency of 73% and an on-chip noise count rate of 900 counts per second (cps) are achieved. Moreover, the on-chip preservation of quantum statistical properties is verified, showing that the QFC chip is promising for extensive applications of LNOI integrated circuits in quantum information. Based on the QFC chip, we construct an upconversion single-photon detector with the sum-frequency output spectrally filtered and detected by a silicon single-photon avalanche photodiode, demonstrating the feasibility of an upconversion single-photon detector on-chip with a detection efficiency of 8.7% and a noise count rate of 300 cps. The realization of a low-noise QFC device paves the way for practical chip-scale QFC-based quantum systems in heterogeneous configurations.Comment: 8pages, 6 figures, 1 tabl

Determination of statistical homogeneity by comprehensively considering the discontinuity information

Statistička homogenost stijenske mase oduvijek je važno pitanje u inženjerstvu stijenske mase. U ovom je radu analizirana stijenska masa podzemnog skladišta nafte na otoku Huang usmjerena na raspodjelu statistički homogenog područja. Duljina rasprostiranja je osnovni element za određivanje karakteristika pukotina. Stijenska masa različitih duljina rasprostiranja pukotina uvelike se razlikuje kad se radi o mehaničkim i karakteristikama deformacije. Ovaj rad obuhvaća podatke o duljini rasprostiranja u podjeli statistički homogenog područja i razmatra vrijednosti varijance i srednje vrijednosti uzoraka pukotina odvojeno u različitim područjima F-testom i T-testom kako bi se utvrdilo imaju li uzorci statistički slične podatke o duljini rasprostiranja. Potrebni su brojni uzorci pukotina da bi se dobilo statistički homogeno područje. U ovom je radu primijenjen Watsonov test za određivanje statistički homogenog područja i razmatrani su podaci o pojavi pukotina u svrhu dobivanja manjeg broja uzoraka za usporedbu pojave pukotina. Podaci o postojanju pukotina i duljini rasprostiranja analiziraju se uvođenjem F-testa, T-testa i Watson-testa kako bi se dobili osnovni podaci o pukotinama i objektivni i prihvatljivi rezultati za statističku homogenost.The statistical homogeneity of rock mass has always been an important issue in rock mass engineering. The rock mass of national underground oil storage in Huang Island is analyzed in this study with focus on the division of a statistically homogeneous area. Trace length is a basic element in determining crack features. The rock mass of different track lengths differs widely in terms of mechanics and deformation characteristics. This study includes trace length information in the division of a statistically homogeneous area and considers the variances and mean values of crack samples in different regions separately by F-test and T-test to determine if the samples have statistically similar trace length information. Numerous crack samples are required to divide a statistically homogeneous area. This study adopts the Watson test to divide a statistically homogeneous area and considers data on crack occurrence to achieve the purpose of obtaining fewer samples for occurrence comparison. Crack occurrence and trace length information are considered by integrating F-test, T-test, and Watson test to gather adequate basic information on cracks and obtain objective and reasonable results for statistical homogeneity

Determination of statistical homogeneity by comprehensively considering the discontinuity information

Statistička homogenost stijenske mase oduvijek je važno pitanje u inženjerstvu stijenske mase. U ovom je radu analizirana stijenska masa podzemnog skladišta nafte na otoku Huang usmjerena na raspodjelu statistički homogenog područja. Duljina rasprostiranja je osnovni element za određivanje karakteristika pukotina. Stijenska masa različitih duljina rasprostiranja pukotina uvelike se razlikuje kad se radi o mehaničkim i karakteristikama deformacije. Ovaj rad obuhvaća podatke o duljini rasprostiranja u podjeli statistički homogenog područja i razmatra vrijednosti varijance i srednje vrijednosti uzoraka pukotina odvojeno u različitim područjima F-testom i T-testom kako bi se utvrdilo imaju li uzorci statistički slične podatke o duljini rasprostiranja. Potrebni su brojni uzorci pukotina da bi se dobilo statistički homogeno područje. U ovom je radu primijenjen Watsonov test za određivanje statistički homogenog područja i razmatrani su podaci o pojavi pukotina u svrhu dobivanja manjeg broja uzoraka za usporedbu pojave pukotina. Podaci o postojanju pukotina i duljini rasprostiranja analiziraju se uvođenjem F-testa, T-testa i Watson-testa kako bi se dobili osnovni podaci o pukotinama i objektivni i prihvatljivi rezultati za statističku homogenost.The statistical homogeneity of rock mass has always been an important issue in rock mass engineering. The rock mass of national underground oil storage in Huang Island is analyzed in this study with focus on the division of a statistically homogeneous area. Trace length is a basic element in determining crack features. The rock mass of different track lengths differs widely in terms of mechanics and deformation characteristics. This study includes trace length information in the division of a statistically homogeneous area and considers the variances and mean values of crack samples in different regions separately by F-test and T-test to determine if the samples have statistically similar trace length information. Numerous crack samples are required to divide a statistically homogeneous area. This study adopts the Watson test to divide a statistically homogeneous area and considers data on crack occurrence to achieve the purpose of obtaining fewer samples for occurrence comparison. Crack occurrence and trace length information are considered by integrating F-test, T-test, and Watson test to gather adequate basic information on cracks and obtain objective and reasonable results for statistical homogeneity

A Bidirectional Scoring Strategy-Based Transformation Matrix Estimation of Dynamic Factors in Environmental Sensing

Simultaneous localization and mapping (SLAM) is the technological basis of environmental sensing, and it has been widely applied to autonomous navigation. In combination with deep learning methods, dynamic SLAM algorithms have emerged to provide a certain stability and accuracy in dynamic scenes. However, the robustness and accuracy of existing dynamic SLAM algorithms are relatively low in dynamic scenes, and their performance is affected by potential dynamic objects and fast-moving dynamic objects. To solve the positioning interference caused by these dynamic objects, this study proposes a geometric constraint algorithm that utilizes a bidirectional scoring strategy for the estimation of a transformation matrix. First, a geometric constraint function is defined according to the Euclidean distance between corresponding feature points and the average distance of the corresponding edges. This function serves as the basis for determining abnormal scores for feature points. By utilizing these abnormal score values, the system can identify and eliminate highly dynamic feature points. Then, a transformation matrix estimation based on the filtered feature points is adopted to remove more outliers, and a function for evaluating the similarity of key points in two images is optimized during this process. Experiments were performed based on the TUM dynamic target dataset and Bonn RGB-D dynamic dataset, and the results showed that the added dynamic detection method effectively improved the performance compared to state of the art in highly dynamic scenarios

Effect of Powder Size on Microstructure and Mechanical Properties of 2A12Al Compacts Fabricated by Hot Isostatic Pressing

This paper studied the effects of powder size on densification, microstructure, and mechanical properties of the hot isostatic-pressed 2A12 aluminum alloy powder compact. The results show that the near-fully dense powder compact can be successfully achieved and the smaller the powder is, the higher the relative density is. In addition, as the powder size decreases, the precipitated phases in the powder compact change from continuously point-like distribution at the junctions among powder particles to the concentrated distribution at the three-way intersections. Compared with the large powder, the tensile strength, yield strength, and elongation of the compact with the small powder were improved by 14%, 30.8%, and 48.6%, respectively

Local Analysis Method on Gross Error of Multidimensional Adjustment Problem

As demonstrated by an example of a leveling network,existing methods of correcting gross errors based on residuals have a few shortcomings including the dependence on the location of gross errors within the leveling network.To address these problems,local analysis method(LAM) is proposed.In multidimensional adjustment problem,an observed quantity usually can be expressed as function of other observed quantities.Then it can be obtained a group of indepen-dent observed values of the observed quantity,which includes observed value corresponding to the observed quantity and functions of other observed values.And an approach to search functions based on the design matrix is given.So it can be determined according to number of independent observed values whether the observed value can tolerate gross error.A method based on LAM is also developed to detect gross errors.Finally,the detection method and LAM are detailed in an example of a goniometric network

A Depression-Based Index to Represent Topographic Control in Urban Pluvial Flooding

Extensive studies have highlighted the roles of rainfall, impervious surfaces, and drainage systems in urban pluvial flooding, whereas topographic control has received limited attention. This study proposes a depression-based index, the Topographic Control Index (TCI), to quantify the function of topography in urban pluvial flooding. The TCI of a depression is derived within its catchment, multiplying the catchment area with the slope, then dividing by the ponding volume of the depression. A case study is demonstrated in Guangzhou, China, using a 0.5 m-resolution Digital Elevation Model (DEM) acquired using Light Detection and Ranging (LiDAR) technology. The results show that the TCI map matches well with flooding records, while the Topographic Wetness Index (TWI) cannot map the frequently flooded areas. The impact of DEM resolution on topographic representation and the stability of TCI values are further investigated. The original 0.5 m-resolution DEM is set as a baseline, and is resampled at resolutions 1, 2, 5, and 10 m. A 1 m resolution has the smallest TCI deviation from those of 0.5 m resolution, and gives the optimal results in terms of striking a balance between computational efficiency and precision of representation. Moreover, the uncertainty in TCI values is likely to increase for small depressions

Benchtop 19F nuclear magnetic resonance spectroscopy enabled kinetic studies and optimization of the synthesis of carmofur

Carmofur, a 5-fluorouracil derivative, was initially developed as an antineoplastic agent to treat colorectal cancer. Through drug repurposing efforts, it has been identified as a potent covalent inhibitor of the main protease of SARS-CoV-2 (Mpro), making it a promising therapeutic agent against COVID-19. However, previous synthetic procedures suffer from low yields, or long reaction times. In this study, benchtop 19F nuclear magnetic resonance spectroscopy (NMR) enables the real-time quantitative monitoring and characterization of the synthesis of carmofur by providing kinetic insight. Furthermore, its proton lock capabilities no longer require the use of deuterated solvents, and has enabled convenient, and rapidly scalable synthesis of our compound. Here, we present the application of benchtop 19F NMR as an efficient method for optimizing the synthesis of carmofur and its future application in the synthesis of related 5-FU analogs