Mirror Structure Research Articles

High-Luminance Mid-Air Image Display for Outdoor Viewing by Focusing Sunlight

The mid-air image is a very powerful method for presenting computer graphics in a real environment, but it cannot be used in bright locations owing to the decrease in brightness during the imaging process. Therefore, to form a mid-air image with a high-brightness light source, a square pyramidal mirror structure was investigated, and the sunlight concentration was simulated. We simulated the tilt angle and combination angle of the condenser as parameters to calculate the luminance of the surface of a transparent liquid crystal display. The light collector was installed at 55∘ from the horizontal plane and mirror. A high level of illumination was obtained when these were laminated together at an angle of 70∘. To select a suitable diffuser, we prototyped and measured the brightness of the mid-air image with an LED lamp to simulate sunlight in three settings: summer solstice, autumnal equinox, and winter solstice. The maximum luminance of the mid-air image displayed by collecting actual sunlight was estimated to be 998.6 cd/m2. This is considerably higher than the maximum smartphone brightness to allow for outdoor viewing, and it can ensure fully compatible visibility.

Sociology, Genetics, and the Coming of Age of Sociogenomics

Recent years have seen the birth of sociogenomics via the infusion of molecular genetic data. We chronicle the history of genetics, focusing particularly on post-2005 genome-wide association studies, the post-2015 big data era, and the emergence of polygenic scores. We argue that understanding polygenic scores, including their genetic correlations with each other, causation, and underlying biological architecture, is vital. We show how genetics can be introduced to understand a myriad of topics such as fertility, educational attainment, intergenerational social mobility, well-being, addiction, risky behavior, and longevity. Although models of gene-environment interaction and correlation mirror agency and structure models in sociology, genetics is yet to be fully discovered by this discipline. We conclude with a critical reflection on the lack of diversity, nonrepresentative samples, precision policy applications, ethics, and genetic determinism. We argue that sociogenomics can speak to long-standing sociological questions and that sociologists can offer innovative theoretical, measurement, and methodological innovations to genetic research.

Organic Current Mirror PUF for Improved Stability Against Device Aging

Physically unclonable functions (PUFs) are important primitives in the field of hardware security. Their applications can be further broadened if PUFs are fabricated using organic thin-film transistors (OTFTs). Examples include smart packaging that proves authenticity of a contained product and privacy protection for information gathered by organic sensors. This paper proposes an organic current mirror PUF (OCM-PUF) that can be fabricated on a flexible substrate. The proposed OCM-PUF adapts a current mirror structure to achieve self-compensation of the device performance degradation of OTFTs, which is unavoidable in most organic materials. Two types of OCM-PUFs were designed using a low supply voltage OTFT to evaluate the metrics as a PUF. The fabricated OCM-PUFs maintained a reliability of nearly 95% over few weeks, thereby showing that the proposed PUF achieved a high tolerance against response changes caused by device aging.

Flexibly tunable surface plasmon resonance by strong mode coupling using a random metal nanohemisphere on mirror

Abstract We propose a unique random metal nanohemisphere on mirror (NHoM) structure to tune the surface plasmon (SP) resonance in a flexible manner. The SP resonance peak was split into two peaks owing to the strong coupling between the SP mode in the metal nanohemisphere and the mirror image mode generated in the metal substrate. This phenomenon is based on the fact that the strong coupling and the induced electromagnetic effects are similar to those pertaining to the Rabi splitting, Fano resonance, and electromagnetically induced transparency, thus providing quantum effect analogies. These phenomena have recently attracted increased attention and have been studied with nanocavities fabricated with top-down nanotechnologies. Compared with previous reports, NHoM structures can be fabricated in a much easier manner and are tunable in rather wider wavelength regions without nanofabrication technologies. The SP resonance peaks were enhanced, sharpened dramatically, and tuned flexibly, based on the optimization of the thickness of the spacer layer between the metal hemisphere and metal substrate. Experimental results were reproduced and were explained based on finite difference time domain (FDTD) simulations. These phenomena have never been observed previously on similar nanosphere on mirror (NSoM) because nanohemispherical structures were required. The NHoM nanocavity structure has a quality factor >200 that is surprisingly high for the localized SP mode of nanoparticles. Flexible tuning of the SP resonance with the use of NHoM is envisaged to lead to the development of new applications and technologies in the field of plasmonics and nanophotonics.

Optimization method for universal NOLM-based phase-preserving amplitude regenerator with application to Att-NALM scheme

We theoretically investigate the conditions of achieving phase-preserving amplitude regeneration for the universal nonlinear optical loop mirror (NOLM) structure and present a method of determining the optimal working point for amplitude shaping. A normalized amplitude-phase transfer parameter is introduced to measure the phase-preserving performance at the working points of multilevel regeneration. Then, a new NOLM (so-called Att-NALM) structure, consisting of an optical attenuator and a bidirectional optical amplifier, is taken into account by the optimization method. The optimal working point can respectively be designed on the first or second plateau of the optical power transfer function for phase-preserving and amplitude regeneration of QPSK/8PSK or two-amplitude 8QAM signal. Our simulation shows that, the corresponding error vector magnitude (EVM) has a maximal reduction with the noise reduction ratio of 5.44dB, 4.7dB and 3.7dB for only amplitude noise, and 1.86dB, 1.58dB and 1.4dB for simultaneous amplitude and phase noise, respectively. We also list the design parameters of the existing NOLM structures for phase-preserving amplitude regeneration.

Plasma β Dependence of Density, Temperatures, and Magnetic-field Correlations of Mirror Structures: Observation and Theory

Abstract The mirror structures identified by the depressed or enhanced magnetic field associated with the enhanced or depressed plasma density are widely observed in the solar system plasma. These structures are generated by the mirror instability as a result of sufficiently large temperature anisotropy of T ⊥ > T ∥. Here, T ⊥ and T ∥ are, respectively, to be the temperatures perpendicular and parallel to the magnetic field and β = p/(B 2/2μ 0). Two important observed characteristics are the uneven density-magnetic field compressibility, defined as , among the various mirror events, and the anticorrelation between the temperatures and magnetic field. This study first shows two mirror structures observed in the magnetosheath with distinct β and . Specifically, β ∼ 6.67, and β ∼ 1.44, . The linear kinetic theory is adopted to derive the phase relations for the mirror instability which show an inverse relation between and , which are negative for various parameter values, and β. While the correlation may be negative or positive for the mirror unstable and stable parameter regimes, respectively. The theoretical analyses are consistent with the observational results that δT ⊥ δB < 0 for both events and δT ∥ δB < 0 is more pronounced for the high β case. The statistical analysis results are summarized by the relationships between , , , and β for six mirror wave events that show high agreements between the observations and theory.

Observations of the Source Region of Whistler Mode Waves in Magnetosheath Mirror Structures

AbstractIn the magnetosheath, intense whistler mode waves, called “Lion roars,” are often detected in troughs of magnetic field intensity in mirror mode structures. Using data obtained by the four Magnetospheric Multiscale (MMS) spacecraft, we show that reversals of gradient of magnetic field intensity along the magnetic field correspond to reversals of the field‐aligned component of Poynting flux of whistler mode waves in the troughs. Such a characteristic is consistent with the idea that the whistler mode waves are effectively generated near the local minima of magnetic field intensity because of the smallest cyclotron resonance velocity and propagate toward regions of larger magnetic field intensity along the magnetic field lines on both sides. We use the reversal of the Poynting flux as an indicator of wave source regions. In these regions, we find that pancake or an outer edge of butterfly electron distributions above ~100 eV are good candidates for wave generation. Unclear correlations of phase difference and amplitude variations of whistler mode waves in cases of ~40 km spacecraft separation indicate that a simple plane wave approximation with a constant amplitude is not valid at this spatial scale that is much smaller than the ion gyroradius. The whistler mode waves consist of small coherent wave packets from multiple sources with spatial scales smaller than tens of electron gyroradii transverse to the background magnetic field in a mirror mode structure.

Baboons (Papio papio) Process a Context-Free but Not a Context-Sensitive Grammar

Language processing involves the ability to master supra-regular grammars, that go beyond the level of complexity of regular grammars. This ability has been hypothesized to be a uniquely human capacity. Our study probed baboons’ capacity to learn two supra-regular grammars of different levels of complexity: a context-free grammar generating sequences following a mirror structure (e.g., AB | BA, ABC | CBA) and a context-sensitive grammar generating sequences following a repeat structure (e.g., AB | AB, ABC | ABC), the latter requiring greater computational power to be processed. Fourteen baboons were tested in a prediction task, requiring them to track a moving target on a touchscreen. In distinct experiments, sequences of target locations followed one of the above two grammars, with rare violations. Baboons showed slower response times when violations occurred in mirror sequences, but did not react to violations in repeat sequences, suggesting that they learned the context-free (mirror) but not the context-sensitive (repeat) grammar. By contrast, humans tested with the same task learned both grammars. These data suggest a difference in sensitivity in baboons between a context-free and a context-sensitive grammar.

Optimization of a lightweight mirror with reduced sensitivity to the mount location.

Due to optical performance requirements, the primary mirror assembly must be unaffected by environmental influences. These environmental influences include gravity, axial assembly error, flatness error of mounting interface, and thermal change, which can degrade the mirror surface's accuracy. The flexure mounts can be used to isolate the load transfers to the mirror in case of a flatness error and thermal change. The mirror surface's accuracy will degenerate significantly when the flexure mounts have deviations from the optimum axial mount location due to mirror fabrication and a testing error at the center of gravity. These two error terms introduce an accuracy of mount locations on the order of millimeters. In this paper, we describe a method to reduce the sensitivity of a lightweight mirror to the mount location. First, we introduce a design criterion that determines the sensitivity. Then, the topology and parametric optimization are used to specify selective reinforcement of the mirror structure in which the design criterion is taken as the objective function. With our method, the lightweight ratio of a 2 m mirror has been improved from 86.8% to 88.5%, and its sensitivity to the mount location has been reduced from ${1}\;{\rm nm/} \pm {1}\;{\rm mm}$1nm/±1mm to $ {0.6}\;{\rm nm/} \pm {1}\;{\rm mm} $0.6nm/±1mm.

A micro monolithic integrated force-torque sensor with piezoelectric tuning mechanism

A novel micro force-torque sensor with tuning mechanism is presented in this paper. The sensor is designed and fabricated based on monolithic integrated method, including planar graphic manufacturing and lamination process. The sensing element is composed of cross-shaped double cantilever beams which will deform when loading force and Torque. The process of sensor is divided into two parts. The structure-circuit integration process is proposed to realize the planar structure of sensor, which integrates flexible printed circuit (FPC) in the graphic multi-layer materials. The assembly of force-torque sensor is realized by the design of foldable mirror structure with each component connected by flexible limited hinges, which can form and lock at 90°. By bring in piezoelectric (PZT) composite cantilever beams as tuning mechanism, the position of the sensor can be further tuned, so that the system precision can be significant improved. According to the result of calibration and experiments, the sensor prototype has a force sensitivity of 0.29 μm/mN, a torque sensitivity of 0.33 μm/μNm and a bandwidth of 481.44 Hz, the range of force and torque measurement is – 7~7 mN and – 14~14 μNm respectively. And the linear-adjustment sensitivity of PZT composite cantilever beam is 24.69 nm/V.

Comparison of EMI effects on different current mirror structures using a post-processing framework

In this paper the use of a simulation framework for comparing the effects of electromagnetic interference (EMI) on different current mirror structures is demonstrated. This is done with the help of an existing tool that is extended by specific, newly developed Python® scripts. The Cadence Design System and Spectre are used as simulation environment. The resulting outputs obtained by DC and transient simulations serve as an input for the next post-processing steps. The investigated current mirror topologies are well-described in literature and are already analyzed with respect to their EMI robustness. This paper focuses on simplifying the comparison of these structures and reducing the need of mathematical derivations. The script results are displayed directly in the schematic by using a heatmap and annotations for voltage nodes and current terminals. Mainly, two analyses are performed, whereas one part deals with EMI-induced DC offset shifts and the other part deals with the propagation of disturbance frequencies to the output current. Finally, the analytic results are compared with the graphical ones in order to check the feasibility of using the presented framework and the newly developed scripts and procedures.

Electrostatic metallic glass micro-mirror fabricated by the self-aligned structures

In this work, an electrostatic comb-drive micro-mirror with the Pd-based metallic glass torsion bar and the self-aligned structures was proposed and developed. The self-aligned structure of the comb-drive micro-mirror is achieved avoiding the comb structure alignment process. The fixed combs of the top mirror wafer were lifted by the bottom activation post for making the comb height difference. The height difference between the fixed combs and moving combs could effectively increase the torque to the mirror structure. The static tilting angle of 16° was achieved when the input voltage is 45.6 V. In the resonant mode, the scanning angle of 40.5° was achieved when the input voltage is 30 Vpp at 95 Hz. According to the measurement results and comparing with other silicon torsion bar micro-mirrors, the driving voltage could be decreased 50% and the tilting angle could be increased around four times for the proposed micro-mirror.

Rearview Mirror Rainbow: An Optics Investigation

When driving on a sunny day, one can sometimes observe a small solar spectrum in the rearview mirror of a vehicle. The formation of this “rainbow” results from the prism-like structure of the rearview mirror. Our investigation of this phenomenon reveals that the resulting spectrum is formed in a manner similar to the way a rainbow is formed by a water droplet. We suggest a demonstration that you can perform so that your students can observe this phenomenon. All that is required is a sunny day, a ring stand, a clamp holder, and rearview mirror.

In-orbit robotic assembly mission design and planning to construct a large space telescope

We investigate the conceptual design and in-orbit assembly mission planning problem of a large space telescope (LST). The segmented mirror design has been proposed, and the robotic assembly concept considering the manipulator work space coverage is developed. To reduce the in-orbit assembly period and protect the fragile mirror structure, the assembly paths of the robots are optimized by several new algorithms. First, a mapping between the assembly path and the assembled piece number is established to rapidly generate the candidate solution to the optimization problem. Second, the two-level hybrid optimization framework that combines the ant-colony-inspired algorithm and the genetic algorithm is proposed. The hybrid optimization method is designed to be able to converge rapidly to a solution that is close to the global optimal point. The proposed models and algorithms are verified by simulation, and the results show that the methods developed can dramatically increase the in-orbit assembly mission efficiency of an LST.

Support structure and optical alignment technology of large-aperture secondary mirror measured by back transmission method

The diameter of secondary mirror measured by back transmission method in the on-orbit assembly space telescope validation prototype with a 1-meter aperture is Φ322 mm, and the distance between secondary mirror and mounting surface is 2.5 m. The requirements for supporting structure are as follows: surface figure error caused by supporting structure should be better than 3.88 nm, the tilt stability of secondary mirror is better than 2 ", and the displacement error in the direction of optical axis is 0.04 mm.According to the above requirements, the supporting structure and alignment method of the secondary mirror are illustrated in detail, and the physical testing is completed. Firstly, the size parameters are optimized by the method of Orthogonal Optimization and Finite Element Analysis (FEA),based on the optimized result, the supporting structure is designed, the bonding mode of the mirror body, the flexible structure to release stress and the implementation method of 4-DOF precise adjustment are emphasized, the results simulated by FEA show that the optical axis displacement of the secondary mirror is 5.2um and the error of the surface figure accuracy is 3 nm under the temperature range of 4℃ and gravity load. Finally, the alignment process and steps without the primary mirror as the benchmark are described in detail. the stability of the supporting structure is tested, and the test period is 14 days. The results and practice indicate that surface figure accuracy is 0.01 λ(λ = 632.8 nm), structure remains stable to excellent levels that the tilt is 1″and the displacement is 0.02 mm under gravity and thermal loading, all of them meet the requirements of the optical system for the supporting structure, the design is reasonable, the effect is good.

Highly-Dispersive Mirrors With Advanced Group Delay Dispersion

We report on a novel starting design structure of highly-dispersive mirror (HDM) which combines quarter-wavelength structure and multi-cavities, introducing more wavelength-dependent storage times of incident radiation and group delay (GD). Based on such structure, a HDM with new advanced group delay dispersion (GDD) of −20 000 fs2 in the wavelength range of 1035–1045 nm is designed, fabricated and characterized. Our proposed initial multilayer structure is instructive in designing HDM aiming at introducing large GDD. Our HDM further pushes the maximum negative GDD allowed by the design’s total physical thickness to its limitation. It offers an ideal trade-off between GDD and total mirror thickness. The HDM has been applied in a fiber-chirped system, providing a considerable compensation of GDD reaching −200 000 fs2 with only 10 reflections between two mirrors, and laser pulse compression from 2.8 ps to 213 fs is realized.

Dual-Band Diffusive Metasurface-Based Reflector With Low Out-of-Band Backscattering

This article describes a dual-band diffusive metasurface-based reflector, with a specular reflection band together with two sidebands which exhibit low radar cross-section (RCS). A rhombus-shaped patch-ring type of polarizer with dual-band characteristics is chosen as the fundamental unit cell. The polarizer and its mirror structure have opposite phases in the polarization-rotating bands, while their phase is the same in the reflection band, which is juxtaposed in-between the middle of the two polarization-rotating bands. The designed metasurface is constructed, based on the phase cancellation theory, by arranging arrays of these two unit cells in a two-dimensional pattern. The measured results show that the realized metasurface-based reflector achieves a high-efficiency specular window from 26.2 to 38.8 GHz together with two low-RCS sidebands from 18.18 to 24.6 GHz and 40.61 to 56.4 GHz. The proposed diffusive metasurface can be potentially used as a reflector for reflector antennas, which provides a highly efficient in-band radiation together with low backscattering out-of-band.

深低温SiC空间反射镜背部与侧面支撑结构对比

深低温SiC空间反射镜背部与侧面支撑结构对比

Study of Restrained Network Structures for Wasserstein Generative Adversarial Networks (WGANs) on Numeric Data Augmentation

Some recent studies have suggested using GANs for numeric data generation such as to generate data for completing the imbalanced numeric data. Considering the significant difference between the dimensions of the numeric data and images, as well as the strong correlations between features of numeric data, the conventional GANs normally face an overfitting problem, consequently leads to an ill-conditioning problem in generating numeric and structured data. This paper studies the constrained network structures between generator G and discriminator D in WGAN, designs several structures including isomorphic, mirror and self-symmetric structures. We evaluates the performances of the constrained WGANs in data augmentations, taking the non-constrained GANs and WGANs as the baselines. Experiments prove the constrained structures have been improved in 17/20 groups of experiments. In twenty experiments on four UCI Machine Learning Repository datasets, Australian Credit Approval data, German Credit data, Pima Indians Diabetes data and SPECT heart data facing five conventional classifiers. Especially, Isomorphic WGAN is the best in 15/20 experiments. Finally, we theoretically proves that the effectiveness of constrained structures by the directed graphic model (DGM) analysis.

空间引力波望远镜主反射镜系统的结构设计优化

The structure and supporting components of the primary mirror system of space gravitational wave telescope were designed and optimized. The side three-point support was used to restrain the mirror body with the primary mirror, and the selection and layout of support points were studied. The mirror adopted a semi-enclosed structure with back drill holes, which can achieve large bending stiffness. The lightweight structure of the mirror was optimized by finite element calculation combined with multi-objective genetic algorithm. The lightweight ratio of the mirror structure reached 74% without reducing the surface accuracy. An adjustable bi-axis bipod flexure hinge structure composed of two non-barrier series flexibility elements was designed, which can compensate the surface error of the mirror. The mathematical model of the flexible hinge parallel mechanism acting on the mirror was established, and the parameters were analyzed based on MATLAB. The parameters were corrected by finite element method. Finally, the analysis of mirror shape under space thermal load was carried out. The results show that the error of mirror shape is better than λ/60, which meets the design requirements.