Search

Focus on the poor navigation precision when the aircraft suffers from the loss of satellite signals, the navigation method of the Synthetic Aperture Radar (SAR) platform based on Inertial Navigation System (INS), satellite positioning and scene matching is proposed. First, the corresponding equations of measurements are formed by the models of the INS, satellite positioning and scene matching points, respectively. And then applying the Kalman Filter (KF), the corresponding filter processes are established according to the different equations of measurements. The Extended Kalman Filter (EKF) is used to linearize the equations of satellite positioning and scene matching measurements. The proposed method can be executed when the satellites are not enough to provide the positioning information of the aircraft. In numeral simulations, when the satellite signals are partially missing, the proposed method can obtain lower absolute positioning errors than the INS and satellite-based method, and the proposed method obtains better precisian than the INS and satellite-based method when the satellite signals always exist. The simulation results prove the effectiveness and the superior performance of the proposed method.

Personality driven by Behavioral Inhibition/Activation Systems (BIS/BAS) can significantly influence self-esteem. Humans form self-esteem during social interactions; thus, social relationships may be a critical mediator. This study aims to systematically explore the role of social relationships in these relations among emerging adults. The essential social relationships of emerging adults, including mother-child, father-child, and peer relationships, were examined. Participants (N = 967, M age = 19.16, 420 females) completed self-reported measures for BIS/BAS, social relationships, and self-esteem. The results demonstrate the mediating effect of social relationships: BIS was negatively related to all social relationships, which were further related to lower self-esteem; BAS was positively related to mother-child and peer relationships, which were further related to higher self-esteem. Moreover, the mother-child relationship emerged as a mediator linking BIS/BAS and father-child and peer relationships in the two models, indicating the unique contribution of mother-child interactions in Chinese emerging adults. [ABSTRACT FROM AUTHOR]

The prevalence of media multitasking has raised concerns regarding its potential impact on cognitive abilities. Despite increasing attention given to this topic, there remains no consensus on how media multitasking is related to cognitive performance. This study aims to shed light on this issue by examining whether and how personality traits and family socioeconomic status (SES) moderate the relationship between media multitasking and reasoning performance. To this end, a large sample of university students (n = 777) completed a battery of measures, including the Raven's Advanced Progressive Matrices, the Media Multitasking Inventory, the Big Five Inventory, the Barratt Impulsiveness Scale, the Grit Scale, and the Family SES Questionnaire. Results revealed a negative correlation between media multitasking and reasoning performance. However, this relationship was substantially moderated by conscientiousness, extraversion, openness, and family SES. Specifically, media multitasking was more detrimental to reasoning performance among individuals with lower levels of conscientiousness, extraversion, openness, and family SES, whereas it was less detrimental to counterparts with higher levels of these personality traits and family SES. The proposed moderation model, for the first time, not only offers novel insights into the theoretical accounts regarding how media multitasking relates to cognitive abilities, but also identifies the protective factors that may buffer the negative impacts of media multitasking. [ABSTRACT FROM AUTHOR]

The polymer ultra‐low‐density proppants are critical to the development of slick‐water fracture technology, but which were prone to obvious deformation under high pressure in the fractures. To increase the stiffness of the styrene‐divinylbenzene copolymer (SDB) and obtain desired ultra‐low‐density (ULD) proppants, carbon dots (CDs) were introduced in‐situ considering their characteristics as the zero‐dimensional carbon nanomaterial. Taking the compressive strength and axial deflection, and so forth into consideration, the synthesis conditions of CDs modified SDB microspheres (CDs‐SDBs) were optimized. Taking the graphite modified SDBs (MG‐SDBs) as a reference, the density of CDs‐SDBs did keep almost constant at about 1.1800 ~ 1.1899 g·cm−3 with the increase of CDs amount. The CDs‐SDBs not only possess high‐peak pressure (41.5 N) but also minute axial deflection (0.090 mm). The advantages of CDs‐SDBs over MG‐SDBs become even more pronounced under higher pressure, which can withstand closure pressure of 80 MPa with a small crush ratio of 4.47%. CDs‐SDBs exhibit significant photoluminescence performances with maximum excitation and emission wavelengths of 634 nm and 554 nm. Highlights: CDs‐SDBs as ULD proppants with high strength and anti‐deformation were developed.Advantages of CDs‐SDBs become more pronounced under high‐closure pressure.With increasing of CDs amount, apparent density of CDs‐SDBs keep almost constant.Axial deflection of CDs‐SDBs is only 0.09 mm under 41.5 N.The crush ratio is only 4.47% under 80 MPa closure pressure. [ABSTRACT FROM AUTHOR]

Colocated multiple-input multiple-output (MIMO) radar can transmit a group of distinct waveforms via its colocated transmit antennas and the waveform diversity leads to several advantages in contrast to conventional phased-array radar. The performance depends highly on the degrees available, and element spacing can be deemed as another source of degrees of freedom. In this paper, we study the joint waveform and element spacing optimization problem. A joint waveform and array optimization criterion is proposed to match the transmit beampattern, the suppression range, and the angular sidelobes, under the constraints of minimal element spacing and total array aperture. Meanwhile, the effect of receive beamforming on suppressing mutual correlation between returns from different spatial directions is also incorporated into the optimization criterion. The optimization problem is solved by the sequential quadratic programming algorithm. Numerical results indicate that with more degrees of freedom from array spacings, colocated MIMO radar achieves a better transmit beampattern matching performance and a lower sidelobe level, compared with a fixed half-wavelength spaced array, but the benefits from additional degrees of freedom from array spacing optimization have a limit. [ABSTRACT FROM AUTHOR]

Ultra‐low‐density proppants are of great significant in slick water fracturing system, but the polymer composite microspheres can hardly promise the quality of oil and gas due to their poor hydrophobicity. To address the issue, we prepared several types of modified styrene‐divinyl benzene copolymer microspheres (MSDBs) with long‐term durable hydrophobicity and high strength, including O‐MSDBs (hydrophobic MSDBs), LO‐MSDBs (long‐time hydrophobic MSDBs), and CO‐MSDBs (coated O‐MSDBs) on the basis of a molecular structure of "KH570‐styrene (St)‐divinyl benzene (DVB)" copolymer. In this article, the design concept and the structure of MSDBs was clarified, and performances of MSDBs are systematically discussed and compared with commercially available hydrophobic microspheres. The O‐MSDBs, a kind of nanoparticle patterned St‐DVB copolymer microspheres, were prepared by a one‐step suspension polymerization undergoing a sol–gel process, showing strong hydrophobicity with a water contact angle up to 140.7°, but short durability in strong hydrochloric acid or hydrofluoric acid; On the contrary, LO‐MSDBs perform better in the stability and durability of hydrophobicity with a slightly lower water contact angle about 135.9°. The LO‐MSDBs were designed by coating functionalized St‐DVB copolymer microspheres with fluororesin. Similarly, CO‐MSDBs from fluororesin‐coated O‐MSDBs were designed. As expected, CO‐MSDBs have a stronger hydrophobicity (139.0°) than LO‐MSDBs and longer durability than O‐MSDBs. Moreover, the MSDBs exhibit better properties than the commercially available hydrophobic polymer and ceramic microspheres. [ABSTRACT FROM AUTHOR]