Research on Dual-Wavelength Absolute Ranging Technology Based on FMCW Laser Interference

FMCW (Frequency-Modulated Continuous Wave) interferometer can achieve high-precision displacement measurement by phase discrimination of the interference signal. The phase needs to be superimposed continuously, so the optical path cannot be interrupted in the measurement process. To solve this problem, a new absolute ranging technology - decimal comparison method is proposed in the manuscript. According to the principle of FMCW interference, two DFB lasers with different central wavelengths are used to measure the same target. The sampled interference signal is processed by digital signal processing to calculate the integer and decimal of the synthetic wavelength period. The optical path difference of the target is calculated by the established mathematical model. The experimental results show that this method not only ensures the measurement accuracy, but also realizes the absolute measurement, and expands the application range of FMCW interferometry.

Continuous monitoring of aerial density and circadian rhythms of flying insects in a semi-urban environment

Although small in size, insects are a quintessential part of terrestrial ecosystems due to their large number and diversity. While captured insects can be thoroughly studied in laboratory conditions, their population dynamics and abundance in the wild remain largely unknown due to the lack of accurate methodologies to count them. Here, we present the results of a field experiment where the activity of insects has been monitored continuously over 3 months using an entomological stand-off optical sensor (ESOS). Because its near-infrared laser is imperceptible to insects, the instrument provides an unbiased and absolute measurement of the aerial density (flying insect/m3) with a temporal resolution down to the minute. Multiple clusters of insects are differentiated based on their wingbeat frequency and ratios between wing and body optical cross-sections. The collected data allowed for the study of the circadian rhythm and daily activities as well as the aerial density dynamic over the whole campaign for each cluster individually. These measurements have been compared with traps for validation of this new methodology. We believe that this new type of data can unlock many of the current limitations in the collection of entomological data, especially when studying the population dynamics of insects with large impacts on our society, such as pollinators or vectors of infectious diseases.

Scientific knowledge as a means and a prerequisite for discovering the essential powers of the individual

Using historical-philosophical and historical-cultural material, the authors substantiate the idea that the heuristic potential of knowledge is enhanced by an in-depth analysis of its philosophical foundations. In the process of analysing knowledge in various philosophical traditions, the authors reach an activistic conception of knowledge, which includes freedom as a prerequisite for external and internal human activity. Knowledge doesn’t coincide with the absolute measurement of freedom and at the same time with the factuality of phenomenal being. It realizes itself at the point of unity of these considerations. By analyzing the sensual, empirical, and theoretical measurement of knowledge, the authors conclude that knowledge, as well as its structure, should be considered in a broad methodological and philosophical way, including the dialectic of knowledge and ignorance. Knowledge is related to the system of human activity. This system includes the object, subject, purpose and objectives of study. But the activity system also relates to nature of the operations performed. This nature is connected with the soul of a person, their inner world. The latter has to do with personal knowledge, latent knowledge. The purpose of the study is to analyze scientific knowledge as a prerequisite for discovering the essential powers of the individual.

Multiposition Rotation Interference Absolute Measurement Method for High-Precision Optical Component Surfaces

Modern optical engineering requires increasingly sophisticated interferometry methods capable of conducting subnanometer scale measurements of the large aperture, high-precision optical component surfaces. However, the accuracy of interferometry measurement is limited to the accuracy with which the surface of the reference mirror employed in the interferometer system is known, and the influence of gravity-induced deformation cannot be ignored. This is addressed in the present work by proposing a three-flat testing method based on multiposition rotation interference absolute surface measurement technology that combines the basic theory of N-position rotation with the separability of surface wavefront functions into sums of even and odd functions. These functions provide the rotational symmetric components of the wavefront, which then enables the absolute surface to be reconstructed based on the N-position rotation measurements. In addition, we propose a mechanical clamping combined with computational method to compensate for the gravity-induced deformations of the flats in the multiposition rotation absolute measurements. The high precision of the proposed absolute surface measurement method is demonstrated via simulations. The results of laboratory experiments indicate that the combination compensation method provides the high-precision surface reconstruction outcomes. The present work provides an important contribution for supporting the interferometry measurement of large aperture, high-precision optical component surfaces.

Experimental consolidation and absolute measurement of the $$^\text {nat}$$C(p,x)$$^{11}$$C nuclear activation cross section at 100 MeV for particle therapy physics

The $$^\text {nat}$$ nat C(p,x)$$^{11}$$ 11 C reaction has been discussed in detail in the past [EXFOR database, Otuka et al. (Nuclear Data Sheets 120:272–276, 2014)]. However, measured activation cross sections by independent experiments are up to 15% apart. The aim of this study is to investigate underlying reasons for these observed discrepancies between different experiments and to determine a new consensus reference cross section at 100 MeV. Therefore, the experimental methods described in the two recent publications [Horst et al. (Phys Med Biol https://doi.org/10.1088/1361-6560/ab4511, 2019) and Bäcker et al. (Nuclear Instrum Methods Phys Res B 454:50–55, 2019)] are compared in detail and all experimental parameters are investigated for their impact on the results. For this purpose, a series of new experiments is performed. With the results of the experiments a new reference cross section of (68±3) mb is derived at (97±3) MeV proton energy. This value combined with the reliably measured excitation function could provide accurate cross section values for the energy region of proton therapy. Because of the well-known gamma-ray spectrometer used and the well-defined beam characteristics of the treatment machine at the proton therapy center, the experimental uncertainties on the absolute cross section could be reduced to 3%. Additionally, this setup is compared to the in-beam measurement setup from the second study presented in the literature (Horst et al. 2019). Another independent validation of the measurements is performed with a PET scanner.

Abnormal Vision-Based Displacement Perception in Parkinson’s Disease

In this work, we investigate the effect of Parkinson’s disease (PD), and common corresponding therapies on vision-based perception of motion, a critical perceptual ability required for performing a wide range of activities of daily livings. While PD has been recognized as mainly a motor disorder, sensory manifestation of PD can also play a major role in the resulting disability. In this paper, for the first time, the effect of disease duration and common therapies on vision-based perception of displacement were investigated. The study is conducted in a movement-independent manner, to reject the shadowing effects and isolate the targeted perceptual disorder to the maximum possible extent. Data was collected using a computerized graphical tool on 37 PD patients [6 early-stage de novo, 25 mid-stage using levodopa therapy, six later-stage using deep brain stimulation (DBS)] and 15 control participants. Besides the absolute measurement of perception through a psychometric analysis on two tested position reference magnitudes, we also investigated the linearity in perception using Weber’s fraction. The results showed that individuals with PD displayed significant perceptual impairments compared to controls, though early-stage patients were not impaired. Mid-stage patients displayed impairments at the greater of the two tested reference magnitudes, while late-stage patients were impaired at both reference magnitudes. Levodopa and DBS use did not cause statistically significant differences in absolute displacement perception. The findings suggest abnormal visual processing in PD increasing with disease development, perhaps contributing to sensory-based impairments of PD such as bradykinesia, visuospatial deficits, and abnormal object recognition.