Gas-Sensitive Performance Study of Metal (Au, Pd, Pt)/ZnO Heterojunction Gas Sensors for Dissolved Gases in Transformer Oil.

An oil-immersed transformer is a critical electrical device for power delivery. Online monitoring of transformer operation is the key to ensuring the regular operation of power systems. This paper proposes Au/ZnO, Pd/ZnO, and Pt/ZnO heterojunctions as new gas-sensitive materials and investigates their gas-sensitive performance to dissolved gases (C2H4, CO, and H2) in transformer oil. Upon theoretical density functional theory (DFT) calculations, the analysis of the total density of states (TDOS), partial density of states (PDOS), molecular orbital theory, and charge deformation density reveals that Au, Pd, and Pt form heterojunctions with ZnO, which enhance the electrical conductivity of the system. Meanwhile, intrinsic ZnO is unsuitable for gas detection and adsorption, while the Au/ZnO heterojunction suits C2H4 detection. In contrast, the Pd/ZnO heterojunction is suitable for H2 detection, and the Pt/ZnO heterojunction is suitable for C2H4 and CO detection. The electrical conductivity of the adsorption models is changed to varying degrees after gas adsorption. The different change rate electrical conductivity just serves as a theoretical foundation for determining the type and concentration of dissolved gases in transformer oil. The research results act as a theoretical foundation for constructing gas sensors with a ZnO-based material.

Unraveling the correlations between microbial communities and metabolic profiles of strong-flavor Jinhui Daqu with different storage periods.

Daqu is a saccharification agent required for fermenting Baijiu, a popular Chinese liquor. Our objective was to investigate the relationships between physicochemical indices, microbial community diversity, and metabolite profiles of strong-flavor Jinhui Daqu during different storage periods. During different storage periods of Jinhui Daqu, we combined Illumina MiSeq sequencing and non-target sequencing techniques to analyze dynamic changes of the microbial community and metabolite composition, established a symbiotic network and explored the correlation between dominant microorganisms and differential metabolites in Daqu. Fungal community diversity in 8d_Daqu was higher than that in 45d_Daqu and 90d_Daqu, whereas bacterial community diversity was higher in 90d_Daqu. Twelve bacterial and four fungal genera were dominant during storage of Daqu. Bacillus, Leuconostoc, Kroppenstedtia, Lactococcus, Thermomyces and Wickerhamomyces decreased as the storage period increased. Differences of microbiota structure led to various metabolic pathways, and 993 differential metabolites were found in all Daqu samples. Differential microorganisms were significantly related to key metabolites. Major metabolic pathways involved in the formation of amino acids and lipids, such as l-arogenate and hydroxyproline, were identified. Interactions between moisture, acidity, and microbes may drive the succession of the microbial community, which further affects the formation of metabolites.

Direct nonlinear parameter estimation method for a phase generated carrier position sensor.

Phase generated carrier (PGC) is widely applied in interferometric phase estimation for distance, vibration and velocity measurements. However, traditional PGC methods suffer from nonlinear effects, causing limitations to demodulation of signal. Modified PGC methods, such as ellipse fitting algorithm (EFA), resolves these issues, but usually requires additional phase shift. With our proposed method in this paper, only one period of signal and one test point is required to attain accurate depth of phase modulation and phase. We use a photodiode to calibrate light intensity in data acquisition, and develop a Levenburg-Marquadt algorithm to estimate values of PGC parameters. An improved algorithm is also proposed to avoid local optimization based on prior information to ensure measurement stability. Less than 5 × 10-3 rad phase measurement uncertainty and over 55 dB Signal to Noise and Distortion Ratio (SINAD) is obtained in experiment.

Automated design of freeform imaging systems for automotive heads-up display applications.

The freeform imaging system is playing a significant role in developing an optical system for the automotive heads-up display (HUD), which is a typical application of augmented reality (AR) technology. There exists a strong necessity to develop automated design algorithms for automotive HUDs due to its high complexity of multi-configuration caused by movable eyeballs as well as various drivers' heights, correcting additional aberrations introduced by the windshield, variable structure constraints originated from automobile types, which, however, is lacking in current research community. In this paper, we propose an automated design method for the automotive AR-HUD optical systems with two freeform surfaces as well as an arbitrary type of windshield. With optical specifications of sagittal and tangential focal lengths, and required structure constraints, our given design method can generate initial structures with different optical structures with high image quality automatically for adjusting the mechanical constructions of different types of cars. And then the final system can be realized by our proposed iterative optimization algorithms with superior performances due to the extraordinary starting point. We first present the design of a common two-mirror HUD system with longitudinal and lateral structures with high optical performances. Moreover, several typical double mirror off-axis layouts for HUDs were analyzed from the aspects of imaging performances and volumes. The most suitable layout scheme for a future two-mirror HUD is selected. The optical performance of all the proposed AR-HUD designs for an eye-box of 130 mm × 50 mm and a field of view of 13° × 5° is superior, demonstrating the feasibility and superiority of the proposed design framework. The flexibility of the proposed work for generating different optical configurations can largely reduce the efforts for the HUD design of different automotive types.

Freeform mirror array design for concentrating sunlight onto a CPV solar cell.

In a concentrating photovoltaic (CPV) system, realizing an illumination spot consistent with the photosensitive area of the CPV cell while maintaining high optical performances is a challenging but rewarding issue. For instance, uniform irradiance distribution not only reduces the risk of damage to CPV cells due to the local heat accumulation, but also improves photoelectric conversion efficiency; free chromatic aberration ensures that a wide solar spectrum can be regulated; a high concentration ratio helps reduce the usage of CPV cells, and so on. Here, we propose a method to design a freeform mirror array to concentrate sunlight and generate a square light pattern with uniform irradiance distribution on the photovoltaic cell. Each freeform mirror can produce a uniform illumination pattern on the CPV cell. We demonstrate the effectiveness of the proposed method with several design examples, and a series of factors affecting the optical performance is also analyzed.

Freeform illumination optics design for extended LED sources through a localized surface control method.

Freeform illumination optics design with extended light sources to realize an accurate light control is very important, but still remains a challenging issue. Here, we propose a new method to design compact and efficient freeform lenses for extended sources. We employ a localized surface control strategy to directly modify the freeform surface to redistribute the light rays emitted from the extended LED source in a desired manner. By the combination of basic radiometry calculation and backward ray tracing, we obtain the irradiance distribution on the target plane and estimate the localized freeform surface to be modified. The optimization function with a Gaussian form is adopted to modify the localized surface. The smoothness of the freeform surface is taken into account in the optimization process to guarantee the processability of the freeform optics. We demonstrate the effectiveness of the proposed method with three design examples.

Automatic design of an extreme ultraviolet lithography objective system based on the Seidel aberration theory.

In this paper, a method is proposed to solve the initial optical structure of an off-axis multimirror system for an extreme ultraviolet lithography (EUVL) application. By tracing the characteristic rays, the primary aberration can be expressed as a function of the distance and curvature based on the Seidel aberration theory. The initial structure with a favorable aberration performance is calculated when the function value is 0. We solve two different initial structures with an off-axis, six-mirror configuration with different optical powers. The NA of the finally optimized optical system is 0.25, the wavefront aberration rms value is less than 0.04λ, and the absolute distortion is below 1.2 nm.

Secretory carcinoma of the sinonasal cavity and pharynx: A retrospective analysis of four cases and literature review.

Secretory carcinoma (SC) is a recently recognized type of salivary gland tumor characterized by t(12;15) (p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. Most SCs are located in a main salivary gland, and primary sinonasal secretary carcinoma is rare. We describe three cases of primary SC in the sinonasal cavity with high-grade transformation (HGT) in one case, and the first case in the pharynx. All tumors comprised slightly atypical cells with solid, tubular, microcystic growth patterns. The case with HGT included two components with distinct sharp boundaries and comedo necrosis, high mitotic figures and obvious cellular atypia. Tumor cells were positive for vimentin, S100, and Gata-3 and negative for p63 and DOG-1. Three cases showed nuclear staining of pan-TRK and one showed cytoplasmic staining. All cases harbored ETV6 gene rearrangement, and ETV6-NTRK3 gene fusion was detected in three cases. Most patients were treated with radical resection and adjuvant therapy. After excision, all remained tumor-free for 65-164 months (medium 98.5 months). SC in the sinonasal cavity and pharynx is a low-grade malignant tumor with histologic features overlapping those of other salivary gland tumors. Immunohistochemical analysis and fluorescence in situ hybridization are useful techniques for its differential diagnosis.

Developing an innovative raw wheat Qu inoculated with Saccharopolyspora and its application in Huangjiu.

BACKGROUND: Mechanized Huangjiu is a stable product, is not subject to seasonal production restrictions, and markedly reduces labor intensity compared to traditional manual Huangjiu. However, the bitterness of mechanized Huangjiu impedes its further development. RESULTS: Based on process optimization, when the fermentation temperature was 45 °C and the fermentation time was 122 h, the inoculation amount of Saccharopolyspora was 5%, the amount of added water was 26%, and the glucoamylase and amylase activities of wheat Qu increased by 27% and 40% respectively, compared with those before optimization. Huangjiu fermented by raw wheat Qu inoculated with Saccharopolyspora rosea F2014 showed a significant (P < 0.05) decrease in bitter amino acid content (1.24 vs. 2.86 g L-1 , a decrease of 56%), which attenuated its bitterness. CONCLUSION: An innovative fermentation process of inoculating Saccharopolyspora into raw wheat Qu was developed for the first time. Such a process could be used to control bitterness based on raw wheat Qu inoculated with Saccharopolyspora rosea F2014, instead of traditional wheat Qu in Huangjiu fermentation. © 2022 Society of Chemical Industry.

Least-squares ray mapping method for freeform illumination optics design: erratum.

We provide corrections of the author list as well as Eq. (12) and (13) in our previous publication [Opt. Express28, 38113811 (2020)10.1364/OE.385254].

Freeform illumination optics for 3D targets through a virtual irradiance transport.

Freeform illumination optics design for 3D target surfaces is a challenging and rewarding issue. The current researches on freeform illumination optics are mostly involved in planar targets, especially for the cases where the targets are perpendicular to the optical axis. Here, we propose a general method to design freeform optics for illuminating 3D target surfaces for zero-étendue sources. In this method, we employ a virtual observation plane which is perpendicular to the optical axis and transfer the irradiance on the 3D target surface to this virtual plane. By designing freeform optics to generate the transferred irradiance distribution, the prescribed irradiance distribution on the 3D target can be realized automatically. The influence of the freeform optics size is considered in the optics design process, which makes it possible to design illumination system for near-field configuration where the influence of the freeform optics size cannot be ignored. We demonstrate the robustness and elegance of the proposed method with three design examples.

Compact freeform illumination optics design by deblurring the response of extended sources.

Freeform illumination design for extended sources is a very challenging but rewarding issue that can benefit a wide range of illumination systems. Here, we propose a method that can achieve compact and highly efficient illumination lenses by deconvolving the blur caused by the extent from light sources. We combine the illumination calculation with the mathematical model of spatially variant convolution and develop a direct computational scheme to calculate the blur kernel without approximations. Two design examples with high optical performances are presented to demonstrate the effectiveness of the proposed method.

Design of a high-throughput telescope based on scanning an off-axis three-mirror anastigmat system.

A high-throughput optical system possesses a large field of view (FOV) and high resolution. However, it is a major challenge to design such a telescope with these two conflicting specifications. In this paper, we propose a method to design a high-throughput telescope based on the classical off-axis three-mirror anastigmat (TMA) configuration by introducing a scanning mechanism. We derive the optimum initial design for the TMA system with no primary aberrations through characteristic ray tracing. During the design process, a real exit pupil is necessitated to accommodate the scanning mirror. By gradually increasing the system's FOV during the optimization procedure, we finally obtained a high-throughput telescope design with an F-number of 6, a FOV of 60∘×1.5∘, and a long focal length of 876 mm. In addition, a tolerance analysis is also conducted to demonstrate the instrumentation feasibility. We believe that this kind of large rectangle FOV telescope with high resolution has broad future applications in the optical remote sensing field.

Variable-diameter beam-shaping system design with high zoom ratio containing aspheric optical components.

Recently, the optical design of refractive beam-shaping systems has been extensively studied, although such study remains focused on two optical surfaces. Designing a beam-shaping system with variable output beam sizes and prescribed irradiance profiles remains a challenging but rewarding task. Here, we present a design framework, including calculation of the initial system and optimization process, to achieve variable-diameter beam-shaping systems with high zoom ratios. We introduce the whole process of designing a compact 8× zoom system of superior optical performance by transforming a Gaussian beam into flat-top beams with different magnifications. We also present a design of a zoom beam-shaping system transforming a Gaussian beam into variable beams with inverse Gaussian distributions to demonstrate the robustness and efficiency of the proposed method.

Relativistic Artificial Molecules Realized by Two Coupled Graphene Quantum Dots.

Coupled quantum dots (QDs), usually referred to as artificial molecules, are important not only in exploring fundamental physics of coupled quantum objects but also in realizing advanced QD devices. However, previous studies have been limited to artificial molecules with nonrelativistic Fermions. Here, we show that relativistic artificial molecules can be realized when two circular graphene QDs are coupled to each other. Using scanning tunneling microscopy (STM) and spectroscopy (STS), we observe the formation of bonding and antibonding states of the relativistic artificial molecule and directly visualize these states of the two coupled graphene QDs. The formation of the relativistic molecular states strongly alters distributions of massless Dirac Fermions confined in the graphene QDs. Moreover, our experiment demonstrates that the degeneracy of different angular-momentum states in the relativistic artificial molecule can be further lifted by external magnetic fields. Then, both the bonding and antibonding states are split into two peaks.

Robust atomic-structure of the 6 × 2 reconstruction surface of Ge(110) protected by the electronically transparent graphene monolayer.

Wafer-scale growth of the unidirectional graphene monolayer on Ge surfaces has rejuvenated the intense study of the surfaces and interfaces of semiconductors underneath graphene. Recently, it was reported that the Ge atoms in the Ge(110) surface beneath a graphene monolayer underwent a rearrangement and formed an ordered (6 × 2) reconstruction. However, a plausible atomic model related to this (6 × 2) reconstruction is still lacking. Here, by using scanning tunnelling microscopy/spectroscopy (STM/S) and density functional theory (DFT) calculations, we deeply investigated the structural and electronic properties of the Ge(110) (6 × 2) surface encapsulated by a graphene monolayer. The (6 × 2) surface reconstruction was confirmed for the post-annealing-graphene-covered Ge(110) surface via STM, and was found to be quite air-stable, owing to the protection of the graphene monolayer against surface oxidation. Our study disclosed that the topographic features of the topmost graphene monolayer and the Ge(110) surface could be selectively imaged by utilizing suitable scanning biases. According to the STM results and DFT calculations, a rational ball-and-stick model of the (6 × 2) reconstruction was successfully provided, in which an elemental building block comprising two Ge triangles and two isolated Ge atoms adsorbed on the unreconstructed ideal Ge(110) surface. Local density of states of the graphene/Ge surface was explored via scanning tunneling spectroscopy (STS), presenting four well-defined differential conductance (dI/dV) peaks, protruding at energies of 0.2, 0.4, 0.6 and 0.8 eV, respectively. The four peaks predominantly originated from the surface states of the reconstructing adatoms and were well reproduced by our theoretical simulation. This result means that the Ge surface is very robust after being encapsulated by the epitaxial graphene, which could be advantageous for directly fabricating graphene/Ge-hybrid high-speed electronics and optoelectronics based on conventional microelectronics technology.

Recommended optical system design for the SSST.

The Southern Spectroscopic Survey Telescope (SSST) is a planned multi-wavelength space survey telescope by China located in Chile. In this paper, we present a feasible optic system design based on wide-field Cassegrain corrector configuration for the SSST of China. Our recommended design has a large field of view (FOV) of $ {2.4^ \circ } \times {2.4^ \circ } $2.4∘×2.4∘ with its image spot size less than 0.3 arcsec in diameter for its full FOV in 80% encircled energy. The atmospheric dispersion effect and actual science requirements are taken into consideration. In addition, a trade-off study is presented. This paper can also provide a reference to the next generation of spectroscopic survey telescopes.

Method for absolute measurement of flat surface.

Interferometry is a relative measurement method for optical surface testing, and thus its testing accuracy depends on the accuracy of the reference surface. Absolute measurement is one of the most effective methods to improve the testing accuracy in interferometry. We present an efficient absolute measurement method based on Zernike polynomial fitting algorithms. With our proposed method, the profiles of both the test surface and the reference surface can be calculated simultaneously. We further carried out simulation analysis to scientifically evaluate the test accuracy of the proposed method. Finally, we conducted actual experiments to demonstrate the feasibility and practicability of our method.

Experimental study on hybrid compensation testing of an off-axis convex ellipsoid surface.

Aspherical surfaces can provide significant benefits to a wide variety of optical systems, but manufacturing high-precision aspherical surfaces has historically been limited by the ability to measure them. Null testing has always been the ideal method in aspherical measurement. However, in many cases, it is hard to realize null testing for complex surfaces, especially for convex surfaces in complicated forms. In this paper, we propose a hybrid compensation method combining a spherical mirror and a computer generated hologram (CGH) to achieve the null testing of the convex aspherical surface. Firstly, we introduce our self-developed mathematical models in the hybrid compensation method, including optics alignment model, distortion correction model and spherical surface error removing model. Then the performance of our proposed method is analyzed by a null testing experiment of an off-axis convex ellipsoid mirror. The experimental result shows that the proposed method can accomplish the hybrid compensation testing of convex aspherical surfaces effectively, and it can also bring much to the application of our method in convex aspherical surface testing.

Double freeform surfaces design for beam shaping with non-planar wavefront using an integrable ray mapping method.

We propose a method to design double smooth freeform surfaces applied in beam shaping with a ray mapping method in the paper. We couple the calculation of ray mapping and the construction of freeform surfaces to approach the surface normal field integrability condition based on the symplectic flow mapping scheme. In this paper, the incident beam wavefront is not limited to be planar or spherical. Several challenging design examples are presented that include transforming a circular Gaussian beam to an unconventional beam with variously shaped contour, and transforming an elliptic beam to a convergent beam with complex irradiance distribution in non-paraxial regime. The results show the high efficiency and feasibility of the proposed method in designing freeform optics for beam shaping applications.