Journal articles: 'Modulation angulaire'

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Bertho, A., M. Dos Santos, A. François, and F. Milliat. "Histoire de la prise en charge des cancers bronchopulmonaires non à petites cellules de stade précoce : de la chirurgie à la radiothérapie stéréotaxique." Radioprotection 55, no. 3 (May 20, 2020): 165–72. http://dx.doi.org/10.1051/radiopro/2020050.

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Avant le début du XXe siècle, le cancer bronchopulmonaire était une maladie rare. Aujourd’hui, c’est le quatrième cancer le plus fréquent en France et concerne, chaque année, près de 50 000 patients. Si à travers l’histoire, la pierre angulaire de la prise en charge thérapeutique du cancer bronchopulmonaire reste la chirurgie, la radiothérapie en est un des piliers, notamment chez les patients à haut risque chirurgical. La radiothérapie est apparue quelques mois après la découverte des rayons X en 1896 et, rapidement, des protocoles standardisés ont été mis au point par les premiers radiobiologistes. Ces protocoles sont ceux que nous connaissons encore aujourd’hui : 2 Gy par fraction et 5 fractions par semaine sur une durée totale de 5 à 8 semaines. Si les protocoles ont peu changé en un siècle, la technique et la balistique ont connu de grandes avancées. Ces améliorations ont mené à un bouleversement profond des protocoles. Les améliorations techniques de délivrance de dose, par l’optimisation de l’imagerie, de la précision du positionnement des patients et dans la modulation de la géométrie des faisceaux ont conduit au développement de la radiothérapie en conditions stéréotaxiques ou radiothérapie stéréotaxique. Aujourd’hui, la radiothérapie stéréotaxique est utilisée pour la prise en charge des tumeurs bronchopulmonaires de stade précoce comme alternative à la chirurgie.

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Wang, Huan, Jiajun Linghu, Xuezhi Wang, Qiyi Zhao, and Hao Shen. "Angular-Dependent THz Modulator with Hybrid Metal-Graphene Metastructures." Nanomaterials 13, no. 13 (June 23, 2023): 1914. http://dx.doi.org/10.3390/nano13131914.

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The coupling effects of surface plasmon resonance (SPR) from metamaterials induce variation in both the frequency and intensity of plasmonic modes. Here, we report an angular-dependent THz modulator with hybrid metal–graphene metastructures. The metastructures composed of the period gold split-rod arrays on top of a monolayer graphene, which show redshift modulation in the THz region with an increasing incident angle due to the strong out-of-plane magnetic flux introduced by the clockwise circular current at the oblique incidence. By utilizing graphene-based actively tunable conductor with ion-gel electrical gating, the THz transmission can be significantly modified. The modulation depth of the hybrid metal–graphene metastructure modulator can reach ~37.6% at 0.62 THz with a gate voltage of −3 V. The theoretical modeling of transmitted dependency on frequency and incident angle is demonstrated at different Fermi energies, which fits well with the experimental results. This hybrid device can offer a useful method for THz applications (such as angle sensors or angular-resolved spectroscopy), where angle-dependent modulation is needed.

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Liu, Peijun, Yanan Fu, Xi Xie, Changjun Min, Yuquan Zhang, and Xiaocong Yuan. "High-efficiency monolayer metallic metasurface for modulation of orbital angular momentum." Chinese Optics Letters 20, no. 12 (2022): 123601. http://dx.doi.org/10.3788/col202220.123601.

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Huang Xianming, 黄先明, 王飞 Wang Fei, 陆宝乐 Lu Baole, and 白晋涛 Bai Jintao. "基于轨道角动量交换实现巨克尔非线性效应调控." Acta Optica Sinica 42, no. 22 (2022): 2219002. http://dx.doi.org/10.3788/aos202242.2219002.

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Wang, Jian, Jun Liu, Shuhui Li, Yifan Zhao, Jing Du, and Long Zhu. "Orbital angular momentum and beyond in free-space optical communications." Nanophotonics 11, no. 4 (December 14, 2021): 645–80. http://dx.doi.org/10.1515/nanoph-2021-0527.

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Abstract Orbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting, N-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.

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Liu, Jun, Shuang Zheng, Shi Chen, Long Zhu, Shimao Li, Shengqian Gao, Heyun Tan, Xinlun Cai, and Jian Wang. "High-speed spatial light modulation based on photon dimension mapping assisted by an integrated mode multiplexer." Applied Physics Letters 120, no. 13 (March 28, 2022): 131103. http://dx.doi.org/10.1063/5.0076652.

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Photon dimension mapping provides an efficient way to learn from each other's strengths to offset their own weaknesses in a variety of applications. By mapping the conventional amplitude modulation to spatial mode modulation and employing an integrated orbital angular momentum (OAM) mode multiplexer, we present an integrated approach to break the spatial light modulation speed limit and implement the high-speed silicon-chip-assisted OAM encoding information transfer. The silicon chip is formed by a multi-mode micro-ring resonator with angular grating embedded in the inner wall and two bus waveguides with different widths for OAM mode multiplexing. Using the fabricated silicon-based OAM mode multiplexer (OAM+1 and OAM-14), we demonstrate 15-Gbit/s amplitude-to-OAM modulation mapping in the experiment, which is far beyond the achievable low-speed OAM encoding information transfer with a conventional spatial light modulator (SLM). The observed optical signal-to-noise ratio (OSNR) penalties at a bit-error rate (BER) of 2 × 10−3 are about 1.0 dB, and the OSNR penalty is improved by about 1.4 dB with the balanced detection. The demonstrations with favorable performance may open up added opportunities in more spatial-mode-enabled applications by photon dimension mapping with silicon chips.

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Buzzelli, A., P. de Bernardis, S. Masi, N. Vittorio, and G. de Gasperis. "Optimal strategy for polarization modulation in the LSPE-SWIPE experiment." Astronomy & Astrophysics 609 (January 2018): A52. http://dx.doi.org/10.1051/0004-6361/201730754.

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Context. Cosmic microwave background (CMB) B-mode experiments are required to control systematic effects with an unprecedented level of accuracy. Polarization modulation by a half wave plate (HWP) is a powerful technique able to mitigate a large number of the instrumental systematics. Aims. Our goal is to optimize the polarization modulation strategy of the upcoming LSPE-SWIPE balloon-borne experiment, devoted to the accurate measurement of CMB polarization at large angular scales. Methods. We departed from the nominal LSPE-SWIPE modulation strategy (HWP stepped every 60 s with a telescope scanning at around 12 deg/s) and performed a thorough investigation of a wide range of possible HWP schemes (either in stepped or continuously spinning mode and at different azimuth telescope scan-speeds) in the frequency, map and angular power spectrum domain. In addition, we probed the effect of high-pass and band-pass filters of the data stream and explored the HWP response in the minimal case of one detector for one operation day (critical for the single-detector calibration process). We finally tested the modulation performance against typical HWP-induced systematics. Results. Our analysis shows that some stepped HWP schemes, either slowly rotating or combined with slow telescope modulations, represent poor choices. Moreover, our results point out that the nominal configuration may not be the most convenient choice. While a large class of spinning designs provides comparable results in terms of pixel angle coverage, map-making residuals and BB power spectrum standard deviations with respect to the nominal strategy, we find that some specific configurations (e.g., a rapidly spinning HWP with a slow gondola modulation) allow a more efficient polarization recovery in more general real-case situations. Conclusions. Although our simulations are specific to the LSPE-SWIPE mission, the general outcomes of our analysis can be easily generalized to other CMB polarization experiments.

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Belousov, Igor, Veniamin Samoseiko, and Alecsandr Saushev. "Assessment of filtering properties of asynchronous electric drive with pulse width modulation." E3S Web of Conferences 363 (2022): 01025. http://dx.doi.org/10.1051/e3sconf/202236301025.

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The process of pulse-width modulation in the converter-motor system is considered. It is noted that the main task of pulse width modulation of voltage formed by the electronic key converter in the converter-motor system is to reduce current pulsations during the modulation period. It is established, that the dynamic process of current change in the electric machine during the period of pulse-width modulation can be approximated by R, L filter. It is shown, that the most important task of pulse-width modulation is minimization of modulation error by current in electric motor. The analysis of possible criteria of estimation of modulation process quality in control systems of electric drive is carried out. It is noted that as a criterion of optimality to assess the quality of modulation in the converter-electromotor system, it is advisable to use the integral quadratic criterion of relative error, called the local variance of the current, as well as the average value of the local variance of the current at the period of the modulating function, called the integral variance of current. The process of estimating the filtering ability of electric machines as part of the electric drive is considered. A system of basic values based on nominal values of electric motor stator voltage, its nominal angular speed and nominal stator current has been selected. The index of filtering properties of the load considering introduction of basic values has been proposed. The equations of an asynchronous electric machine with constant coefficients in the complex form of writing are given. The dependency of the real part of roots of the characteristic equation for an asynchronous machine as a function of angular speed of the rotor rotation is constructed. An analytical expression for the estimation of the filtering properties of asynchronous machines is obtained. The comparison of different types of electric machines according to this parameter is made.

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Zhang, Chenming, Jie Li, Xiaoqiao Yuan, Xi Zhang, Xiaokai Wei, Kaiqiang Feng, Chenjun Hu, Debiao Zhang, and Yubing Jiao. "Optimal Rotational Angular Velocity Determination Method Based on Compound Rotary Semi-Strapdown Inertial Navigation System." Sensors 22, no. 12 (June 17, 2022): 4583. http://dx.doi.org/10.3390/s22124583.

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Single-axis rotation modulation (SRM) still accumulates errors in the roll axis direction, which leads to the navigation accuracy not meeting the requirements of guided missiles. Compound rotation modulation (CRM) superimposes one-dimensional rotation on the basis of SRM, so that the error of the projectile in the direction of the roll axis is also modulated. However, the error suppression effect of CRM is not only affected by the error of the IMU itself, but also related to the modulation angular velocity. In order to improve the accuracy of rotary semi-strapdown inertial navigation system (RSSINS), this paper proposes an optimal rotation angular velocity determination method. Firstly, the residual error in CRM scheme is analyzed; then, the relationship between the incomplete modulation error and the modulation angular velocity in CRM is discussed; finally, a method for determining the optimal modulation angular velocity is proposed (K-value method). The analysis of the results shows that the navigation accuracy of the guided projectile is effectively improved with the rotation scheme set at the modulation angular velocity determined by the K-value method.

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Kushiro, Keisuke, Mingjia Dai, Mikhail Kunin, Sergei B. Yakushin, Bernard Cohen, and Theodore Raphan. "Compensatory and Orienting Eye Movements Induced By Off-Vertical Axis Rotation (OVAR) in Monkeys." Journal of Neurophysiology 88, no. 5 (November 1, 2002): 2445–62. http://dx.doi.org/10.1152/jn.00197.222.

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Nystagmus induced by off-vertical axis rotation (OVAR) about a head yaw axis is composed of a yaw bias velocity and modulations in eye position and velocity as the head changes orientation relative to gravity. The bias velocity is dependent on the tilt of the rotational axis relative to gravity and angular head velocity. For axis tilts <15°, bias velocities increased monotonically with increases in the magnitude of the projected gravity vector onto the horizontal plane of the head. For tilts of 15–90°, bias velocity was independent of tilt angle, increasing linearly as a function of head velocity with gains of 0.7–0.8, up to the saturation level of velocity storage. Asymmetries in OVAR bias velocity and asymmetries in the dominant time constant of the angular vestibuloocular reflex (aVOR) covaried and both were reduced by administration of baclofen, a GABAB agonist. Modulations in pitch and roll eye positions were in phase with nose-down and side-down head positions, respectively. Changes in roll eye position were produced mainly by slow movements, whereas vertical eye position changes were characterized by slow eye movements and saccades. Oscillations in vertical and roll eye velocities led their respective position changes by ≈90°, close to an ideal differentiation, suggesting that these modulations were due to activation of the orienting component of the linear vestibuloocular reflex (lVOR). The beating field of the horizontal nystagmus shifted the eyes 6.3°/ g toward gravity in side down position, similar to the deviations observed during static roll tilt (7.0°/ g). This demonstrates that the eyes also orient to gravity in yaw. Phases of horizontal eye velocity clustered ∼180° relative to the modulation in beating field and were not simply differentiations of changes in eye position. Contributions of orientating and compensatory components of the lVOR to the modulation of eye position and velocity were modeled using three components: a novel direct otolith-oculomotor orientation, orientation-based velocity modulation, and changes in velocity storage time constants with head position re gravity. Time constants were obtained from optokinetic after-nystagmus, a direct representation of velocity storage. When the orienting lVOR was combined with models of the compensatory lVOR and velocity estimator from sequential otolith activation to generate the bias component, the model accurately predicted eye position and velocity in three dimensions. These data support the postulates that OVAR generates compensatory eye velocity through activation of velocity storage and that oscillatory components arise predominantly through lVOR orientation mechanisms.

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Van Leeuwen, Moira, Sjoerd Bruijn, and Jaap Van Dieën. "Mechanisms that stabilize human walking." Brazilian Journal of Motor Behavior 16, no. 5 (December 15, 2022): 326–51. http://dx.doi.org/10.20338/bjmb.v16i5.321.

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In this paper we review what mechanisms are used to stabilize human bipedal gait. Based on mechanical reasoning, potential mechanisms to control the body center of mass trajectory are modulation of foot placement, stance leg control consisting of modulation of ankle moments and push-off forces, and modulations of the body’s angular momentum. The first two mechanisms and especially the first are dominant in controlling center of mass accelerations during gait, while angular momentum control plays a lesser role, but may be important to control body alignment and orientation. The same control mechanisms stabilize both steady-state and perturbed gait in both the mediolateral and antero-posterior directions. Control is at least in part active and is affected by proprioceptive, visual and vestibular information. Results support that this reflects a feedback process in which sensory information is used to obtain an estimate of the center of mass state based on which foot placement and ankle moments are modulated. These active feedback mechanisms suggest training approaches for populations at risk of falling, such as augmenting their effective use by means of augmented feedback, or using their complementary nature to train one mechanism by constraining the other mechanisms.

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Maneiro-Catoira, Roberto, Julio Brégains, José A. García-Naya, and Luis Castedo. "Dual-Beam Steerable TMAs Combining AM and PM Switched Time-Modulation." Sensors 22, no. 4 (February 11, 2022): 1399. http://dx.doi.org/10.3390/s22041399.

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Wireless sensor networks (WSN) are increasingly requiring directional antennas that not only provide higher capacity, security, transmission range or robustness against interference, but also contribute with smart antenna capabilities such as adaptive beamforming or multi beam radiation patterns. Standard phased arrays provide these features, but employing feeding networks based on digitally controlled variable phase shifters (VPSs) which have the disadvantage of high cost and limited angular resolution. Instead, time-modulated arrays (TMAs) use switched feeding networks governed by digital periodic sequences which allow harmonic patterns to be radiated and endows (TMAs) with attractive multifunctional capabilities. In this paper, we analyze and properly combine (TMA) switched feeding networks capable of time-modulating an antenna array with discretized amplitude modulation (AM) and phase modulation (PM) waveforms. The advantages of the proposed innovative dual-beam (TMA) with respect to the competing architectures are, on the one hand, its power efficiency and beamsteering (BS) phase sensitivity and, on the other, its hardware simplicity, which allows for an excellent relative cost advantage.

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Kolesnyk, Vadym, and Mykola Chernyak. "Autonomous Instrumental Error Correction for a Strapdown Inertial Navigation System." MECHANICS OF GYROSCOPIC SYSTEMS, no. 45 (May 15, 2023): 85–97. http://dx.doi.org/10.20535/0203-3771452023293127.

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Microelectromechanical systems (MEMS)-based strapdown navigation systems offer advantages such as small size, low cost, and minimal power consumption. However, MEMS sensors are prone to significant low-frequency noise and poor bias repeatability, which can lead to navigational errors over time. These errors make them unsuitable for autonomous navigation applications, even with frequent recalibration. One way to solve this problem is the rotation modulation method. This approach is widely recognized but has only been successful with precise laser and fiber optic gyroscopes equipped with precise rotating platforms. This article focuses on the potential of adapting the rotation modulation method for the case of inexpensive MEMS sensors that can significantly improve navigation performance while maintaining the benefits of microelectromechanical technologies. Potential issues of implementation were discussed, and corresponding requirements were formulated. The proposed optimal computation scheme was verified during static tests of the developed inertial measurement unit (IMU). The rotation of the IMU is capable of harmonically modulating the quasi-static errors of inertial sensors, which are practically eliminated during the navigational algorithm processing estimation, which paves the way for a significant reduction of its navigation errors and increases its autonomous operation time. The static tests conducted in laboratory conditions confirmed the research method's high technical potential. It has been shown that the proposed method is effective for various spatial orientations of the rotational modulation axis. Installing an IMU on a non-steering car wheel allows for abandoning an artificial rotational motion source while preserving the proposed method's advantages. The proposed implementation's main limitation is that the IMU's output data update frequency becomes a multiple of the frequency of the modulating rotation. Accordingly, this frequency should be at least twice the maximum frequency of body manoeuvres to ensure their observability. Additionally, a critical issue is the compensation of the angular velocity of modulation from gyroscope readings. However, despite the mentioned considerations, such an implementation of IMU modulation by rotation still has enormous potential for application in terrestrial navigation.

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Liu Haida, 刘海达, 黑小兵 Hei Xiaobing, 杨洋 Yang Yang, 谢元昊 Xie Yuanhao, 盖磊 Gai Lei, 顾永建 Gu Yongjian, 肖芽 Xiao Ya, and 李文东 Li Wendong. "用于水下光通信高维调制与解调的轨道角动量叠加态." Laser & Optoelectronics Progress 60, no. 9 (2023): 0901001. http://dx.doi.org/10.3788/lop220952.

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Liu, Weihang, Chao Feng, Yi Jiao, and Sheng Wang. "A coherent harmonic generation method for producing femtosecond coherent radiation in a laser plasma accelerator based light source." Journal of Synchrotron Radiation 28, no. 3 (March 22, 2021): 669–80. http://dx.doi.org/10.1107/s1600577521002745.

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The electron beam generated in laser plasma accelerators (LPAs) has two main initial weaknesses – a large beam divergence (up to a few milliradians) and a few percent level energy spread. They reduce the beam brightness and worsen the coherence of the LPA-based light source. To achieve fully coherent radiation, several methods have been proposed for generating strong microbunching on LPA beams. In these methods, a seed laser is used to induce an angular modulation into the electron beam, and the angular modulation is converted into a strong density modulation through a beamline with nonzero longitudinal position and transverse angle coupling. In this paper, an alternative method to generate microbunching into the LPA beam by using a seed laser that induces an energy modulation and transverse–longitudinal coupling beamlines that convert the energy modulation into strong density modulation is proposed. Compared with the angular modulation methods, the proposed method can use more than one order of magnitude lower seed laser power to achieve similar radiation performance. Simulations show that with the proposed method a coherent pulse of a few microjoules pulse energy and femtosecond duration can be generated with a typical LPA beam.

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Zhang, Jiayu, Jie Li, Xiaorui Che, Xi Zhang, Chenjun Hu, Kaiqiang Feng, and Tingjin Xu. "The Optimal Design of Modulation Angular Rate for MEMS-Based Rotary Semi-SINS." Micromachines 10, no. 2 (February 10, 2019): 111. http://dx.doi.org/10.3390/mi10020111.

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In previous studies, the semi-strapdown inertial navigation system (SSINS), based on microelectromechanical system (MEMS) sensors, had realized cross-range measurement of attitude information of high-spinning projectiles through construction of a “spin reduction” platform of the roll axis. However, further improvement of its measurement accuracy has been difficult, due to the inertial sensor error. In order to enhance the navigational accuracy, a periodically rotating method is utilized to compensate for sensor error, which is called rotation modulation. At present, the rotation scheme, as one of the core technologies, has been studied by a lot of researchers. It is known that the modulation angular rate is the main factor affecting the effectiveness of error modulation. Different from the long-endurance and low-dynamic motion characteristics of ships, however, the short-endurance and high-dynamic characteristics of the high-spinning projectile not only require the modulation angular rate to be as fast as possible but, also, the influence of the rotation speed error caused by rotating mechanism errors cannot be ignored. Combined with the rotation speed error of the rotating mechanism, this paper explored the relationship between modulation angular rate, device error, and the navigation error, and then proposed a design method for optimal modulation angular rate. Experiments were carried out to validate the performance of the method. In addition, the proposed method is applicable for rotation modulation systems with different types of motors as the rotating mechanism.

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Jing, Zhengyao, Jie Li, Xi Zhang, Kaiqiang Feng, and Tao Zheng. "A Novel Rotation Scheme for MEMS IMU Error Mitigation Based on a Missile-Borne Rotation Semi-Strapdown Inertial Navigation System." Sensors 19, no. 7 (April 9, 2019): 1683. http://dx.doi.org/10.3390/s19071683.

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In previous research, a semi-strapdown inertial navigation system (SSINS), based on micro-electro-mechanical system (MEMS) sensors, was able to realize over-range measurement of the attitude information of high-rotation missiles by constructing a single axis “spin reduction” platform. However, the MEMS sensors in SSINS were corrupted by significant sensor errors. In order to further improve SSINS measurement accuracy, a rotational modulation technique has been introduced to compensate for sensor errors. The ideal modulation angular velocity is changed sharply to achieve a constant speed, while in practical applications, the angular rate of the rotating mechanism’s output needs to go through an acceleration-deceleration process. Furthermore, the stability of the modulation angular rate is difficult to achieve in a high-speed rotation environment. In this paper, a novel rotation scheme is proposed which can effectively suppress the residual error in the navigation coordinate system caused by the modulation angular rate error, including the acceleration-deceleration process and instability of angular rate. The experiment results show that the position and attitude accuracy of the new rotation scheme was increased by more than 56%. In addition, the proposed scheme is applicable to navigation accuracy improvement under various dynamic conditions.

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ZHANG, Chao, and Lu MA. "Trellis Coded Orbital Angular Momentum Modulation." IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences E99.A, no. 8 (2016): 1618–21. http://dx.doi.org/10.1587/transfun.e99.a.1618.

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Basar, Ertugrul. "Orbital Angular Momentum With Index Modulation." IEEE Transactions on Wireless Communications 17, no. 3 (March 2018): 2029–37. http://dx.doi.org/10.1109/twc.2017.2787992.

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Wu, Fuping, Yuanfei Hui, Zhiwei Cui, and Ju Wang. "Reflection Characteristics of Airy Beams Impinging on Graphene-Substrate Surfaces." International Journal of Optics 2022 (January 3, 2022): 1–10. http://dx.doi.org/10.1155/2022/5319174.

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In this work, we analytically and numerically investigate the reflection characteristics of the airy beams impinging on graphene-substrate surfaces. The explicit analytical expressions for the electric and magnetic field components of the airy beams reflected from a graphene-substrate interface are derived. The local-field amplitude, Poynting vector, and spin and orbital angular momentum of the reflected airy beams with different graphene structure and beam parameters are presented and discussed. The results show that the reflection properties of the airy beams can be flexibly tuned by modulating the Fermi energy of the graphene and have a strong dependence on the incident angle and polarization state. These results may have potential applications in the modulation of airy beams and precise measurement of graphene structure parameters.

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Khosravi, Shahram, Amirabbas Ghazizadeh, and Shant Baghram. "21-cm power spectrum and ionization bias as a probe of long-mode modulated non-Gaussian sky." Monthly Notices of the Royal Astronomical Society 488, no. 4 (August 21, 2019): 5941–51. http://dx.doi.org/10.1093/mnras/stz2037.

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ABSTRACT The observed hemispherical power asymmetry in cosmic microwave background radiation can be explained by long-wavelength mode (long-mode) modulation. In this paper, we study the possibility of detecting this effect in the angular power spectrum of the 21-cm brightness temperature. For this task, we study the effect of the neutral hydrogen distribution on the angular power spectrum. This is done by formulating the bias parameter of the ionized fraction to the underlying matter distribution. We also discuss the possibility that the long-mode modulation is accompanied by a primordial non-Gaussianity of local type. In this case, we obtain the angular power spectrum with two effects of primordial non-Gaussianity and long-mode modulation. Finally, we show that the primordial non-Gaussianity enhances the long-mode modulated power of the 21-cm signal via the non-Gaussian scale-dependent bias up to four orders of magnitude. Accordingly, observations of the 21-cm signal with upcoming surveys, such as the Square Kilometer Array (SKA), will probably be capable of detecting hemispherical power asymmetry in the context of long-mode modulation.

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Жиленко, Д. Ю., and О. Э. Кривоносова. "Синхронизация в турбулентном сферическом течении Куэтта под действием неравномерного вращения." Журнал технической физики 89, no. 7 (2019): 992. http://dx.doi.org/10.21883/jtf.2019.07.47786.391-18.

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Turbulent flows of viscous incompressible fluid in rotating spherical layer in the presence of synchronization are under consideration. Numerical results are presented. Synchronization of turbulent flow is due to the action of periodical modulation of the angular velocity of inner spherical boundary. The angular velocity of outer spherical boundary is constant. Obtained results were compared with experimental data. The interval of modulation amplitudes was determined where synchronization is followed by intermittency “chaos – chaos”.

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Hadar, O., A. Dogariu, and G. D. Boreman. "Angular dependence of sampling modulation transfer function." Applied Optics 36, no. 28 (October 1, 1997): 7210. http://dx.doi.org/10.1364/ao.36.007210.

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Sherstukov, S. A., A. N. Buravtsova, D. S. Tolstykh, and S. S. Pechnikov. "Operation algorithms and application of functional converters modulating voltage for generation of precision radio signals with angular modulation." IOP Conference Series: Materials Science and Engineering 919 (September 26, 2020): 052008. http://dx.doi.org/10.1088/1757-899x/919/5/052008.

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Li, Zhaohui, and Wenying Xue. "Measuring the orbital angular momentum mode of vortex beam based on phase matching sequence." Journal of Physics: Conference Series 2209, no. 1 (February 1, 2022): 012006. http://dx.doi.org/10.1088/1742-6596/2209/1/012006.

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Abstract Measuring the orbital angular momentum(OAM) mode of vortex beams is of great significance in applications based on vortex beams.we propose a method of phase matching characteristics of vortex beams to measure the OAM mode. The method first use a high-speed spatial light modulator(SLM) to sequentially load a set of helical phase sequence images, so that the vortex beam is modulated by this SLM. Then obtain the modulated optical field through pinhole filtering, and then the synchronized tilt phase modulation is performed by the 4f system and high-speed SLM. When the OAM mode of vortex beam is opposite to the topological charge of helical phase image, that is, the incident vortex beam degenerates to the fundamental Gaussian mode beam,and through our optical system, the output plane obtained a indicating spot with the position related to the OAM mode. The Simulation and experimental results show that the method obtains a clear OAM mode indicating spot on the final output plane, which verifies the theoretical derivation.

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Miranda, Martin, Nobuyuki Takei, Yuki Miyazawa, and Mikio Kozuma. "Multi-Harmonic Modulation in a Fiber-Optic Gyroscope." Sensors 23, no. 9 (May 1, 2023): 4442. http://dx.doi.org/10.3390/s23094442.

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Optimizing the bias modulation of a fiber-optic gyroscope is crucial to improving its precision. In this study, we propose and demonstrate the use of multiple harmonics of sinusoidal modulation as an intermediate alternative to the widely used modulation methods: sinusoidal and square-wave modulation. We show that this alternative integrates the advantages of each modulation method by providing a smooth modulation that produces a clean, spike-free output and a satisfactory signal-to-noise ratio. By using three harmonics of modulation in combination with a high frequency to reduce thermal phase noise, we obtained an angular random walk of 5.2(2)μdeg/h and a bias instability of ∼10μdeg/h. This is the highest performance ever reported for fiber-optic gyroscopes.

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Kadry, Haysam M., Mohammad Alhawari, and Dimitrios L. Sounas. "Angular-Momentum Biased Circulator With Locally Generated Modulation." IEEE Transactions on Microwave Theory and Techniques 69, no. 1 (January 2021): 551–65. http://dx.doi.org/10.1109/tmtt.2020.3034322.

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Ren, Zhijun, Jinping He, and Yile Shi. "Generation of Mathieu beams using angular pupil modulation." Chinese Physics B 27, no. 12 (December 2018): 124201. http://dx.doi.org/10.1088/1674-1056/27/12/124201.

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Tardini, G., J. Ferreira, P. Mantica, A. G. Peeters, T. Tala, K. D. Zastrow, M. Brix, C. Giroud, and G. V. Pereverzev. "Angular momentum studies with NBI modulation in JET." Nuclear Fusion 49, no. 8 (July 17, 2009): 085010. http://dx.doi.org/10.1088/0029-5515/49/8/085010.

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Bespalov, E. S. "Models for a sinusoidal angular modulation index meter." Measurement Techniques 49, no. 3 (March 2006): 233–37. http://dx.doi.org/10.1007/s11018-006-0096-6.

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Bai, Xudong, Fuli Zhang, Li Sun, Anjie Cao, Chong He, Jin Zhang, and Weiren Zhu. "Dynamic millimeter-wave OAM beam generation through programmable metasurface." Nanophotonics 11, no. 7 (February 17, 2022): 1389–99. http://dx.doi.org/10.1515/nanoph-2021-0790.

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Abstract Millimeter-wave (mmWave) and orbital angular momentum (OAM) multiplexing are two key technologies for modern wireless communications, where significant efforts have been devoted to combining these two technologies for extremely high channel capacities. Recently, programmable metasurfaces have been extensively studied for stimulating dynamic multi-mode OAM beams, owing to their ability of subtle dynamic modulation over electromagnetic waves in a digital manner. However, programmable metasurfaces for mmWave OAM stimulation are rarely mentioned, due to the requirement of extremely high processing precision for mmWave applications. In this paper, a programmable metasurface is presented to stimulate dynamic multi-mode mmWave vortex beams. The proposed metasurface is composed of electronically reconfigurable units, which is obtained through configuration integration of a PIN diode within each radiation patch for modulating the unit resonant property. Both low reflection losses and stabilized inverse phase states are obtained for the binary unit coding states within the operation band. Through modulating the real-time coding distribution on the metasurface by programmable bias circuit, the generation of mmWave OAM beams with mode numbers l = 0, l = +1, l = +2, and l = +3 are numerically designed and experimentally verified. Our study paves a new perspective for the cross amalgamation of both mmWave and multi-mode OAM technologies.

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Papadakis, Antonios E., and John Damilakis. "Evaluation of an organ-based tube current modulation tool in pediatric CT examinations." European Radiology 30, no. 10 (May 20, 2020): 5728–37. http://dx.doi.org/10.1007/s00330-020-06888-5.

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Abstract Objectives To investigate the effect of an organ-based tube current modulation (OTCM) technique on organ absorbed dose and assess image quality in pediatric CT examinations. Methods Four physical anthropomorphic phantoms that represent the average individual as neonate, 1-year-old, 5-year-old, and 10-year-old were used. Standard head and thorax acquisitions were performed with automatic tube current modulation (ATCM) and ATCM+OTCM. Dose calculations were performed by means of Monte Carlo simulations. Radiation dose was measured for superficial and centrally located radiosensitive organs. The angular range of the OTCM exposure window was determined for different tube rotation times (t) by means of a solid-state detector. Image noise was measured as the standard deviation of the Hounsfield unit value in regions of interest drawn at selected anatomical sites. Results ATCM+OTCM resulted in a reduction of radiation dose to all radiosensitive organs. In head, eye lens dose was reduced by up to 13% in ATCM+OTCM compared with ATCM. In thorax, the corresponding reduction for breast dose was up to 10%. The angular range of the OTCM exposure window decreased with t. For t = 0.4 s, the angular range was limited to 74° in head and 135° for thorax. Image noise was significantly increased in ATCM+OTCM acquisitions across most examined phantoms (p < 0.05). Conclusions OTCM reduces radiation dose to exposed radiosensitive organs with the eye lens and breast buds exhibiting the highest dose reduction. The OTCM exposure window is narrowed at short t. An increase in noise is inevitable in images located within the OTCM-activated imaged volume. Key Points • In pediatric CT, organ-based tube current modulation reduces radiation dose to all major primarily exposed radiosensitive organs. • Image noise increases within the organ-based tube current modulation enabled imaged volume. • The angular range of the organ-based tube current modulation low exposure window is reduced with tube rotation time.

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Shi, Chengzhi, Marc Dubois, Yuan Wang, and Xiang Zhang. "High-speed acoustic communication by multiplexing orbital angular momentum." Proceedings of the National Academy of Sciences 114, no. 28 (June 26, 2017): 7250–53. http://dx.doi.org/10.1073/pnas.1704450114.

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Long-range acoustic communication is crucial to underwater applications such as collection of scientific data from benthic stations, ocean geology, and remote control of off-shore industrial activities. However, the transmission rate of acoustic communication is always limited by the narrow-frequency bandwidth of the acoustic waves because of the large attenuation for high-frequency sound in water. Here, we demonstrate a high-throughput communication approach using the orbital angular momentum (OAM) of acoustic vortex beams with one order enhancement of the data transmission rate at a single frequency. The topological charges of OAM provide intrinsically orthogonal channels, offering a unique ability to multiplex data transmission within a single acoustic beam generated by a transducer array, drastically increasing the information channels and capacity of acoustic communication. A high spectral efficiency of 8.0 ± 0.4 (bit/s)/Hz in acoustic communication has been achieved using topological charges between −4 and +4 without applying other communication modulation techniques. Such OAM is a completely independent degree of freedom which can be readily integrated with other state-of-the-art communication modulation techniques like quadrature amplitude modulation (QAM) and phase-shift keying (PSK). Information multiplexing through OAM opens a dimension for acoustic communication, providing a data transmission rate that is critical for underwater applications.

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Kim, Eunhee, Sunghwan Sohn, Hyunwook Moon, Jun Hyeok Choi, and Kiwon Lee. "Linear Frequency Modulation and Orthogonal Code Modulation for Co-Located Multiple-Input Multiple-Output High-Frequency Surface Wave Radar." Remote Sensing 16, no. 1 (December 26, 2023): 104. http://dx.doi.org/10.3390/rs16010104.

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A high-frequency surface wave radar (HFSWR) is the only sensor that provides inexpensive surveillance for up to 200 nautical miles (NM) of the exclusive economic zone in the 3–5 MHz band. However, because of its long wavelength, its angular resolution is low. Multiple-input multiple-output (MIMO) technology is an attractive method to improve angular resolution. This paper proposes MIMO waveforms and their processing that can be used in HFSWR systems. This dual modulation method applies linear frequency modulation to each pulse and orthogonal polyphase codes for a few consecutive pulses to enable MIMO processing. The proposed method can effectively remove the correlation of mutual interference and exhibits excellent performance in removing multiple-time-around echoes.

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Viktorov, D. S., and E. V. Plastinina. "The mathematical description of the functional transformations of a signal with angular modulation in sequentially the connected quantizers of a phase and tension." Spacecrafts & Technologies 2, no. 1 (2018): 38–46. http://dx.doi.org/10.26732/2618-7957-2018-1-38-46.

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The most important constituent of the modern terrestrial stations of satellite communication are digital synthesizers of signals. With their help various composite signals indicators. The interest of developers in use in the created and perspective terrestrial stations of satellite communication of digital synthesizers of signals is caused by a number of the objective reasons: – digital synthesizers of signals, in comparison with analog, have high stability of parameters of the formed signals and low level of phase noise; – the combination of broad functionality to high speed of switching and a small step of reorganization on the frequency (a share of hertz) allows to form with use of the same device signals of various frequency with a high precision of installation and speed of switching; – the quick action of the modern element base allows to form heterodyne signals in the wide working range of frequencies making hundreds of megacycles. Enough scientific works is devoted to a research of methods and devices of digital formation of different types of signals. Digital synthesizers of signals with angular modulation are considered in them insufficiently fully, as a rule, separately from each other, without identification of common for them regularities and features of the analysis. The analysis of transformations of the digital signal with angular modulation in digital synthesizers of signals presented by function of several variables, as a rule, is based on numerical methods. For its carrying out it is necessary to receive the mathematical description of transformations of signals with angular modulation in an analytical look. The functional dependences describing transformations of signals with angular modulation in sequentially the connected quantizers of a phase and tension with use of a method of display of signals and a method of planimetric integrals are presented in article. The received dependences allow to estimate distortions of the formed signal by means of spectral and correlation analysis.

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Qin, Xiujuan, Xinzhu Sang, Hui Li, Rui Xiao, Chongli Zhong, Binbin Yan, Zhi Sun, and Yu Dong. "High Resolution Multiview Holographic Display Based on the Holographic Optical Element." Micromachines 14, no. 1 (January 6, 2023): 147. http://dx.doi.org/10.3390/mi14010147.

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Limited by the low space-bandwidth product of the spatial light modulator (SLM), it is difficult to realize multiview holographic three-dimensional (3D) display. To conquer the problem, a method based on the holographic optical element (HOE), which is regarded as a controlled light element, is proposed in the study. The SLM is employed to upload the synthetic phase-only hologram generated by the angular spectrum diffraction theory. Digital grating is introduced in the generation process of the hologram to achieve the splicing of the reconstructions and adjust the position of the reconstructions. The HOE fabricated by the computer-generated hologram printing can redirect the reconstructed images of multiview into multiple viewing zones. Thus, the modulation function of the HOE should be well-designed to avoid crosstalk between perspectives. The experimental results show that the proposed system can achieve multiview holographic augmented reality (AR) 3D display without crosstalk. The resolution of each perspective is 4K, which is higher than that of the existing multiview 3D display system.

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Liu, Tuo, and Tongyang Shi. "Loss-induced multiple modal coalescences in an acoustic ring cavity." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 268, no. 8 (November 30, 2023): 444–49. http://dx.doi.org/10.3397/in_2023_0077.

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Chiral exceptional points refer to a class of non-Hermitian degeneracies where two counter-propagating whispering-gallery-like eigenmodes coalesce into one travelling eigenmode, which have been utilized to create orbital angular momentum in various wave systems. However, most studies in this field have so far focused on the modal coalescence for a specific azimuthal order. In this work, we investigate the eigenmodes evolution of an acoustic ring cavity under complex spatial modulation of refractive index along the azimuthal direction. We show that a careful engineering of the complex modulation, possibly realized with acoustic metamaterials, can lead to multiple modal coalescences to produce a series of travelling eigenmodes with different orbital angular momentum orders. These coalesced eigenmodes can be directly excited by a simple source at their resonant frequencies. Our work provides a straightforward approach to the generation and manipulation of acoustic orbital angular momentum.

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Filion-Côté, Sandrine, Feriel Melaine, Andrew G. Kirk, and Maryam Tabrizian. "Monitoring of bacterial film formation and its breakdown with an angular-based surface plasmon resonance biosensor." Analyst 142, no. 13 (2017): 2386–94. http://dx.doi.org/10.1039/c7an00068e.

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Vahidinia, Vahideh, Mahmoud Atashbar, and Shahram Hosseinzadeh. "Orbital angular momentum and mode multiplexing based index modulation." Physical Communication 48 (October 2021): 101407. http://dx.doi.org/10.1016/j.phycom.2021.101407.

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Lee, Hyuk. "Polarization-independent acoustooptic light modulation with large angular aperture." Applied Optics 27, no. 5 (March 1, 1988): 815. http://dx.doi.org/10.1364/ao.27.000815.

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Hyuk Lee. "Acoustooptic Light Modulation with Large Bandwidth and Angular Aperture." IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 34, no. 4 (July 1987): 485–86. http://dx.doi.org/10.1109/t-uffc.1987.26971.

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Bian, Zichao, Soliman Alhudaithy, Zhe Wang, Zibang Zhang, Kaikai Guo, Liheng Bian, Yuji Tomizawa, Peter Satonick, Kazunori Hoshino, and Guoan Zheng. "Angular light modulator using optical blinds." Optics Express 24, no. 25 (November 30, 2016): 28467. http://dx.doi.org/10.1364/oe.24.028467.

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Rogers, Brian, Suzanne Martin, and Izabela Naydenova. "Study of the Effect of Methyldiethanolamine Initiator on the Recording Properties of Acrylamide Based Photopolymer." Polymers 12, no. 4 (March 25, 2020): 734. http://dx.doi.org/10.3390/polym12040734.

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The use of Holographic Optical Elements (HOEs) in applications, such as in light shaping and redirection, requires certain characteristics such as a high Diffraction Efficiency, low angular selectivity and stability against UV damage. In order to maximize the performance of the HOEs, photosensitive materials are needed that have been optimised for the characteristics that are of particular importance in that application. At the core of the performance of these devices is the refractive index modulation created during holographic recording. Typically, a higher refractive index modulation will enable greater light Diffraction Efficiency and also operation with thinner devices, which in turn decreases the angular selectivity and the stability of the refractive index modulation introduced during recording, which is key to the longevity of the device. Solar concentrators based on volume HOEs can particularly benefit from thinner devices, because, for a solar concentrator to have a high angular working range, thinner photopolymer layers with a smaller angular selectivity are required. This paper presents an optimisation of an acrylamide-based photopolymer formulation for an improved refractive index modulation and recording speed. This was achieved by studying the effect of the concentration of acrylamide and the influence of different initiators in the photopolymer composition on the diffraction efficiency of holographic gratings. Two initiators of different molecular weights were compared: triethanolamine (TEA) and methyldiethanolamine (MDEA). A fivefold increase in the rate of grating formation was achieved through the modification of the acrylamide concentration alone, and it was also found that holograms recorded with MDEA as the initiator performed the best and recorded up to 25% faster than a TEA-based photopolymer. Finally, tests were carried out on the stability of the protected and unprotected photopolymer layers when subjected to UV light. The properties exhibited by this photopolymer composition make it a promising material for the production of optical elements and suitable for use in applications requiring prolonged exposure to UV light when protected by a thin melinex cover.

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Keny, Swapnil M. "Trends in Guided Growth for Correction of Angular Deformities around the Knee: Past, Present, and Future." Journal of Clinical Orthopaedics 8, no. 2 (2023): 57–61. http://dx.doi.org/10.13107/jcorth.2023.v08i02.600.

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The principles of guided growth have been followed in orthopaedics since historic times . The bent tree braced to a stake to make it grow upward and straight is the first reference to the principles of growth modulation in the annals of orthopaedic history Keywords: Guided Growth, Epiphysiodesis, Hemiepiphysiodesis, growth modulation, eight plates, genu varum, genu valgum, deformity correction, pediatric orthopaedics, growth plate

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Feng, Xin-di, Yin Wang, Li-juan Shi, Hong-yu Zou, Yu-jing Lu, Ding Jia, Yong Ge, et al. "Mode converter of vortex beams by phase-gradient acoustic metagratings." Journal of Applied Physics 133, no. 3 (January 21, 2023): 034502. http://dx.doi.org/10.1063/5.0130015.

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Recently, acoustic vortices with orbital angular momentum (OAM) have attracted great attention and interest owing to their extensive applications. Based on the generalized Snell’s law (GSL), acoustic vortex beams can be observed by constructing different types of acoustic metasurfaces immersed into cylindrical waveguides. However, owing to the restrictions of the phase gradient of metasurface structures and the critical order of propagating vortex beams, there exist great challenges in realizing complex modulation of vortex beams and designing advanced multifunctional sound devices. Here, we theoretically study and experimentally demonstrate the extended GSL in designing a mode converter of vortex beams based on phase-gradient acoustic metagratings (AMs). We demonstrate that the extended GSL can not only accurately predict the transmitted or reflected orders of vortex beams created by a series of AMs with arbitrary phase gradient ξ, but also effectively overcome the limitations of both the phase gradient and the critical order. More importantly, we design a type of mode converter of vortex beams and realize the mode conversion of output vortex beams by simply modulating the orders of input vortex beams. To present it, we experimentally demonstrate the switch between the output vortex beams with the orders of −2 and 2 through the same phase-gradient AM by using the input vortex beams with the orders of 1 and −1, respectively, which can be separately predicted by the GSL and the extended GSL. Our work paves a way for the complex modulation of acoustic vortex beams and the design of multifunctional OAM-based sound devices with practical applications.

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Volkov, A. A., and M. S. Morozov. "Improving Noise Immunity of Digital Radio Systems with Angular Modulation." World of Transport and Transportation 17, no. 1 (September 13, 2019): 90–99. http://dx.doi.org/10.30932/1992-3252-2019-17-1-90-99.

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Maitland, Calum, Daniele Faccio, and Fabio Biancalana. "Modulation instability of discrete angular momentum in coupled fiber rings." Journal of Optics 21, no. 6 (May 28, 2019): 065504. http://dx.doi.org/10.1088/2040-8986/ab18eb.

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Danino, B., R. Rödl, J. E. Herzenberg, L. Shabtai, F. Grill, U. Narayanan, E. Segev, and S. Wientroub. "Growth modulation in idiopathic angular knee deformities: is it predictable?" Journal of Children's Orthopaedics 13, no. 3 (June 2019): 318–23. http://dx.doi.org/10.1302/1863-2548.13.190033.

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Purpose To evaluate the temporal and spatial sequence of events following temporal hemiepiphysiodesis in idiopathic knee varus/valgus. Methods This is a retrospective multicentre study on 372 physes in 206 patients. The average rate of correction (ROC) was calculated; univariate and multivariate analysis were performed. Results In all, 92% of the femoral physes were followed for more than one year/reached skeletal maturity. Of those, 93% were corrected to a mechanical lateral distal femoral angle (mLDFA) of 85° to 89°; 2% did not, while 5% were over-corrected. A total of 92% of the tibial physes were followed for more than one year/reached skeletal maturity. Of those, 92% were corrected to a mechanical medial proximal tibial angle (mMPTA) of 85° to 89°; 2% did not, while 6% were over-corrected. Factors significantly influencing success and ROC were age, direction and magnitude of deformity. Femoral ROC was significantly faster than tibial ROC: 0.85° versus 0.78°/month, respectively (p = 0.05). Femoral valgus ROC was significantly faster than varus ROC: 0.90° versus 0.77°/month, respectively (p = 0.04). A constant was derived to calculate the amount of correction. Significant correlation was found between calculated and actual mLDFA in valgus deformity during the first year (r = 0.58 to 0.87, p < 0.01). Calculated mLDFA of varus deformity did not correlate with actual mLDFA. Significant correlation was found when calculating mMPTA correction in all deformities. Conclusions Femur corrects faster than tibia; valgus femoral deformities are corrected faster than varus. Valgus correction in the distal femur/proximal tibia as well as varus correction in the tibia in idiopathic patients is highly predictable. The constant derived is the first tool which enables predicting and monitoring amount of correction in hemiepiphysiodesis when correcting angular deformities around the knee. Level of Evidence IV

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Zotov, Sergei A., Alexander A. Trusov, and Andrei M. Shkel. "High-Range Angular Rate Sensor Based on Mechanical Frequency Modulation." Journal of Microelectromechanical Systems 21, no. 2 (April 2012): 398–405. http://dx.doi.org/10.1109/jmems.2011.2178116.

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Park, SW, C.-S. Lee, HR Kang, HS Pak, and A. Wilkins. "Visibility of the phantom array effect according to luminance, chromaticity and geometry." Lighting Research & Technology 52, no. 3 (September 23, 2019): 377–88. http://dx.doi.org/10.1177/1477153519867115.

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Light-emitting diode-based lighting systems are now applied in both general lighting and automotive lighting. Time-modulated control methods such as pulse width modulation are frequently applied as a dimming method. This paper presents the characteristics of the visibility of the phantom array effect according to luminance, chromaticity and angular field of view. The threshold frequency of the visibility of the phantom array increases in proportion to the logarithm of the luminance of the light source. As the angular field of view of the light source increases, the threshold frequency of the visibility of the array decreases exponentially over a range from 0.125° to 4° in our experimental conditions. The threshold frequency at which the array is visible depends on chromaticity at high light source modulation frequencies. When designing time-modulated light sources, our findings can be applied so as to minimize the phantom array effect.

Journal articles on the topic 'Modulation angulaire'

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