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Reliable observations of aerosol optical properties are crucial for quantifying the radiative forcing of climate. The simultaneous measurements of aerosol optical properties at three wavelengths for PM1 and PM10 were conducted in urban Beijing from March 2018 to February 2022. The aerosol absorption coefficient (σab) at 550 nm of PM10 and PM1 decreased by 55.0 % and 53.5 % from 2018 to 2021. The significant reduction in σab may be related to reduced primary emissions caused by effective air pollution control measures. PM2.5 mass concentration decreased by 34.4 % from 2018 to 2021. Single scattering albedo (SSA) increased from 0.89±0.04 for PM10 (0.87±0.05 for PM1) in 2018 to 0.93±0.03 for PM10 (0.91±0.04 for PM1) in 2021. Increasing SSA and decreasing PM2.5 mass concentration suggest that the fraction of absorbing aerosols decreased with improved air quality due to pollution control measures being taken. The annual average submicron absorption ratio (Rab) increased from 86.1 % in 2018 to 89.2 % in 2021, suggesting that fine particles are the main contributors to total PM10 absorption and that the contribution of fine particles to absorption became more important. The absorption Ångström exponent (AAE) in winter decreased from 2018 to 2021, implying a decreasing contribution from brown carbon to light absorption, which may relate to the reduced emissions of biomass burning and coal combustion. During the study period, aerosol radiative forcing efficiency became more negative, mainly influenced by increasing SSA and was −27.0 and −26.2 W m−2 per aerosol optical depth (AOD) for PM10 and PM1 in 2021. Higher σab and PM2.5 mass concentrations were primarily distributed in clusters 4 and 5, transported from the south and the west of Beijing each year. σab and PM2.5 corresponding to clusters 4 and 5 decreased evidently from 2018 to 2021, which may result from the control of source emissions in surrounding regions of Beijing. The 4-year data presented in this study provide critical optical parameters for radiative forcing assessment within two size ranges and are helpful for evaluating the effectiveness of clean air action.

Mineral dust is a major natural atmospheric aerosol that impacts the Earth's radiation balance. The significant scavenging process of fine particles by the strong wind during the dust provided a relatively pristine environment in which the occurrence of new particle formation (NPF) was less influenced by anthropogenic emissions. In this study, the NPF events occurring after the dust event (dust-related NPF) and other normal days (other NPF events) were classified based on the long-term particle number size distribution (PNSD) in urban Beijing in spring from 2017 to 2021. By comparing the two types of NPF events, we estimated that anthropogenic emissions could contribute approximately 50 % to the observed formation rate and 30 % to the growth rate. Anthropogenic emissions played a more important role when nucleated particles grew into the sizes above 10 nm. We also assessed a severe dust storm that originated from Mongolia and swept over northern China on March 15–16, 2021. The maximum hourly mean PM10 mass concentration reached 8000 μg m-3 during the dust storm. A downward trend of particle hygroscopicity was found during dust storms as compared with the polluted episode, resulting in an increasing trend of the critical diameter at different supersaturations (ss) where aerosols are activated as cloud condensation nuclei (CCN), although NPF occurred at approximately noon time when dust faded. The critical diameter was elevated by approximately 6 %–10 % (ss = 0.2 % and 0.7 %) during the dust storm, resulting in a lower CCN activation ratio, especially at low supersaturation. Modifications of the nucleation and growth process, as well as the particle-size distribution and hygroscopicity by the dust, provide valuable information that reveals the underlying climate and air quality effects of Asian mineral dust.

Reliable observations of aerosol optical properties are crucial for quantifying the radiative forcing of climate. The simultaneous measurements of aerosol optical properties at three wavelengths for PM1 and PM10 were conducted in urban Beijing from March 2018 to February 2022. The results showed considerable reductions in aerosol absorption coefficient (σab) at 550 nm of PM10 and PM1 by 55.0 % and 53.5 % from 2018 to 2021. SSA increased from 0.89 ± 0.04 for PM10 (0.87 ± 0.05 for PM1) in 2018 to 0.93 ± 0.03 for PM10 (0.91 ± 0.04 for PM1) in 2021. These results indicated that the absorbing aerosols were more effectively controlled than scattering aerosols due to pollution control measure-taking. The annual average submicron absorption ratio (Rab) increased from 86.1 % in 2018 to 89.2 % in 2021, suggesting that fine particles are the main contributors to total PM10 absorption and that the fine particles to absorption became more important. Absorption Angstrom exponent (AAE) in winter decreased from 2018 to 2021, implying a decreasing contribution from brown carbon to light absorption, which may relate to the decreased emissions of biomass burning and coal combustion. During the study period, aerosol radiative forcing efficiency became more negative and were −27.0 and -26.2 W m−2 AOD−1 for PM10 and PM1 in 2021, which was mainly influenced by increasing SSA. Higher σab and PM2.5 mass concentrations were mainly distributed in clusters 4 and 5 transported from the south and the west of Beijing in each year. σab and PM2.5 corresponding to clusters 4 and 5 decreased evidently from 2018 to 2021, which may result from the control of source emissions in surrounding regions of Beijing. The 4-year data presented in this study provide critical optical parameters for radiative forcing assessment within two size ranges and are helpful for evaluating the effectiveness of clean air action.

Piper nigrum L. and P. longum L. are widely used in various medicinal formulations. The dichloromethane fraction of Piper nigrum L. and P. longum L. (DF) can prevent cerebral ischemic injury although the underlying mechanisms are obscure. The aim of this study was to evaluate the potential neuroprotective effects of DF on a rat model of permanent middle cerebral artery occlusion (pMCAO) and assess the molecular mechanisms. Animals were administered with DF (50, 100, and 150 mg/kg) or nimodipine (12 mg/kg) 6 h after pMCAO for 14 consecutive days via intragastric gavage. In the vitro this study identified that DF reduced neurological severity scores and improved survival rate. Results showed that DF markedly inhibited the percentage of apoptotic cells as well as neuronal autophagy and mitigated the overall neuronal and vascular damage in the ischemic region. Western blot testing showed that at the molecular level, DF significantly suppressed ischemia-induced activated expression of LC3, Beclin1, Atg12, and Atg5. Overall, our study indicated that DF attenuated neuronal autophagy by suppressing the expression of autophagy-related proteins to generate neuroprotection effect for ischemic stroke.

A design method of compact wideband balun bandpass filter (BPF) with high selectivity based on corrugated slot is proposed here. To realize wideband balun response in compact size, metal strips are deployed parallel to the half‐mode corrugated slot (HMCS). Besides, the coupling of corrugated slot to the metal stripline provides the conversion of slot to microstrip structure at the balanced ports. By placing a pair of resonators at the balanced ports, a wideband balun BPF response with high selectivity can be realized. In addition, a U‐shaped resonator is also loaded at the end of the corrugated slot to suppress harmonics. Afterwards, a compact wideband balun BPF centred at 2.42 GHz with 3‐dB FBW of 45% is designed, fabricated, and measured. The effective size is 0.13λg × 0.39λg (λg is the guided wavelength of the centre frequency) and the measured results indicate that the magnitude imbalance is less than 0.45 dB and the phase imbalance is less than 4.8° within the operation frequency band.

We propose a method to design compact circularly polarized (CP) antenna using a novel sunshine-shaped slotted radiating patch, which exhibits slow wave and other interesting properties. The structured radiating patch introduces adjustable coupling between a pair of orthogonal modes (TM10 mode and TM01 mode) to facilitate good axial ratio (AR) and reflection parameters of the antenna simultaneously in the radiating frequency band. A $\pi $ /2 balun is employed to excite the TM10 and TM01 modes by using back feeding structure. Based on the proposed method, a compact left-hand CP antenna is designed, fabricated, and measured to verify the feasibility of the design method. The whole antenna is $0.17\lambda _{0}\times 0.17\lambda _{0}$ in dimension ( $\lambda _{0}$ is the wavelength in free space) and the measured maximum gain is 5 dBic in the working band, and 3 dB AR bandwidth is 0.4% for left-hand CP.

We present a new method to design miniaturized antennas using a corrugated microstrip (CM) line, which shows good slow wave characteristic in the required frequency band. To achieve good radiating behavior and low profile simultaneously, CM is employed as the resonating part of the antenna. The impact of the CM propagation constant on the antenna is discussed in detail. The miniaturized antenna is designed and measured to verify the feasibility of the design method. The measured results show that the proposed antenna can achieve a beamwidth of 70° in E-plane and 75° in H-plane with a gain tolerance of 3 dB, and the realized peak gain level at the central frequency is 5.15 dBi, which have good agreements to the expected designs. Such results indicate that the proposed antenna exhibits excellent radiation characteristics at the resonant mode. The effective size of the proposed miniaturized antenna is $0.16\lambda _{0}\times 0.16 \lambda _{0}\times 0.04 \lambda _{0}$ at 9 GHz, in which $\lambda _{0}$ is the wavelength of the central frequency.

The influence of relative humidity on aerosol properties and the direct radiative forcing of PM

A wide-angle broadband converter from odd-mode spoof surface plasmon polaritons (SPPs) to spatial waves is proposed using spatially gradient Vivaldi-shaped flaring structure. We first show the dispersion, Eigen mode, and effective circuit topology of the designed SPP structure and show that it can support a propagating odd mode. A conversion structure between odd-mode spoof SPPs and spatial mode has been designed to realize smooth impedance and wavenumber transition. Through the full-wave simulation method, we obtained the optimized geometric parameters, from which we fabricate the converter using the print circuit board technology. The measured results from both far field and near field show that the proposed structure has successfully excited odd-mode spoof SPPs coming from an extremely wide-angle spatial radiation. The allowed azimuthal and pitched angle ranges are larger than 72°.

We propose an efficient method to suppress the crosstalk based on the mode mismatch between spoof surface plasmon polariton (SPP) transmission line (TL) and microstrip. Since microstrip and spoof SPP TL support quasi-transverse electromagnetic (quasi-TEM) wave and transverse magnetic (TM) wave, respectively, the transmitting electromagnetic (EM) energy can hardly be coupled between these two kinds of TLs, which helps to reduce the crosstalk. For the cases of weak and strong coupling, two kinds of structures of spoof SPP TLs are designed. To verify the performance of crosstalk suppression, two samples of the coupled TLs are presented and fabricated. Simulated and experimental results show that the crosstalk of both strong and weak coupling is reduced by approximately 35 and 30 dB, respectively, by introducing the spoof SPP TL into the microstrip pair. Thus, crosstalk in traditional circuits can be alleviated by the mode mismatch between spoof SPP TLs and microstrips, which is significant for high-speed and high-density integrated systems.

The end Cartesian trajectory of space robot is planned to optimize the attitude disturbance of the satellite base during the motion of space manipulator. Before planning the end motion, first realize the end Cartesian trajectory parameterization of space manipulator, then set different optimization objectives and multiple constraint conditions, and at last obtain the optimization objective function based on constraint modification. Afterwards, the same Cartesian task is planned based on the trajectory optimization algorithm and the trapezoidal velocity method, and the simulation results of the trajectory optimization algorithm and the trapezoidal velocity method are compared from the perspective of the satellite base attitude disturbance and the joint angles of space manipulator.

The prerequisite for space robots on-orbit capturing and servicing is to inspect and track the attitude of the target satellite. However, the number of DOFs (degrees of freedom) of space robot is limited, which cannot satisfy the position and attitude tracking of space robot end and the zero disturbance of the satellite base attitude at the same time. The multi-task priority motion planning method of space robot is adopted, which can realize the attitude tracking of space robot end and the zero disturbance of the satellite base attitude, while the position tracking of space robot end can be optimized. The simulation experiment results show that the method is effective.

This paper introduces a set of ground micro-gravity experiment system to emulate the 3-dimensional motion of space robot with free-floating satellite base, which adopts the hardware-in-the-loop simulation to realize. The system can be used to verify the motion planning and control algorithm and reproduce the motion of space robot system, which includes the motion of space manipulator and that of the satellite base. The components and the realization process of ground microgravity emulation system are introduced in detail. The effectiveness verification experiments of ground micro-gravity system are carried out and the experiment results show that the system is effective.

The future wireless communications require different kinds of modulation functions to be integrated in a single intelligent device under different scenarios. Here, we propose a multi-scheme digital modulator to achieve this goal based on integrated spoof surface plasmon polaritons (SPP) in different frequency bands. By constructing switchable spoof SPP units, the propagating wave in the proposed spoof SPP waveguide can be manipulated in amplitude domain, frequency domain, and phase domain. As a proof of concept, the integrated multi-scheme digital modulator is experimentally verified to achieve at least three kinds of modulations, including amplitude shift keying, phase shift keying, and frequency shift keying, in a single digital spoof plasmonic waveguide. The simulated and measured results show that the modulator has excellent property of field confinement and is capable of frequency-domain modulation. Hence, the multi-scheme modulation property makes the proposed SPP digital modulator be an effective and reliable candidate for efficient manipulations of SPP waves and for advanced modulation technology

Purpose This paper aims to present a smooth transition adaptive hybrid impedance control for compliant connector assembly. Design/methodology/approach The dynamics of the manipulator is firstly presented with linear property. The controller used in connector assembly is inspired by human operation habits in similar tasks. The hybrid impedance control is adopted to apply force in the assembly direction and provide compliance in rest directions. The reference trajectory is implemented with an adaptive controller. Event-based switching strategy is conducted for a smooth transition from unconstrained to constrained space. Findings The method can ensure both ideal compliance behaviour with dynamic uncertainty and a smooth transition from unconstrained to constrained space. Also, the method can ensure compliant connector assembly with a good tolerance to the target estimation error. Practical implications The method can be applied in the connector assembly by “pushing” operation. The controller devotes efforts on force tracking and smooth transition, having potential applications in contact tasks in delicate environment. Originality/value As far as the authors know, the paper is original in providing a uniform controller for improving force and position control performance in both unconstrained and constrained space with dynamic uncertainty. The proposed controller can ensure a smooth transition by only adjusting parameters.

A new method of designing compact dipole antenna based on surface polarized plasmon (SPP) structure, is proposed in this paper. To realize the compact design, we take advantage of the slow wave character of the SPP to design arms of the dipole antenna. While, the radiation pattern in the operating band is not change too much against conventional dipole antenna one. The arms of the proposed dipole antenna are fed by microstrip line. Besides, the ground plane plays the role of the reflector, thus obtaining a good forward gain of the antenna. Afterwards, the antenna, whose working band is 3.54-3.57GHz is designed to verify the effectiveness of the proposed method, the simulated results show that the proposed antenna has the gain of 3dB and 40% reduction in dimension against the conventional dipole antennas.

Structured metallic surfaces, also called as plasmonic surfaces, have been proposed to support spoof surface plasmon polariton (SPP) modes, which can mimic natural SPPs at optical frequencies. Complex plasmonic surfaces can provide a large degree of freedom to engineer the characteristics of SPP dispersion. However, the analysis of complex plasmonic surfaces is difficult using the existing theoretical methods, such as the effective medium model and mode matching model. Recently, an accurate field-network-joint method has been introduced into the dispersion analysis of complex plasmonic surfaces, but it only works in the lossless case. In this communication, lossy complex plasmonic surfaces are investigated based on the modified field-network-joint method. The proposed method can predict not only the dispersion relationship between the frequency and the wavenumber, but also the lossy feature of the plasmonic surface with high efficiency and accuracy. As an example, a periodic structure with biforked slits filled by a lossy medium is fabricated and measured. The calculated attenuation constant (i.e., the imaginary part of the wavenumber) of the lossy structure is nearly identical to the measured result, demonstrating the superiority of the proposed analytical method. Ministry of Education (MOE) This work was supported in part by the National Science Foundation of China under Grant 61871127, Grant 61701246, Grant 61631007, Grant 61571117, Grant 61501112, Grant61501117, Grant 61522106, Grant 61722106, Grant 61701107, and Grant 61701108, in part by the 111 Project under Grant 111-2-05, in part by the Singapore Ministry of Education Academic Research Fund TIER 1 under Grant 2017-T1-001-239 [RG91/17 (S)], and in part by TIER 2 under Grant MOE2015-T2-1-145. (Corresponding authors: Tie Jun Cui; Yu Luo.)

In this paper, we proposed a new method to analyze the dielectric loss feature of complex structured metallic surface, which is inspired by the idea of the field-network joint method. In order to show the general method of our scheme, we first introduce the behavior of electromagnetic (EM) wave in the upper space using the field view. Meanwhile, we describe the properties of the structured metallic surface based on the view of the circuit topology of the complex structure composed of the transmission line model for continues structure and the lump model for the discontinues structure, which can obtain through the previous research. Hence, by the aid of the mature microwave theory and technology, we can show a general method to analysis the dielectric loss of complex structured metallic surface, which have not been discussed in previous research.

Motion planning of space robot approaching the target satellite is indispensable for satellite on-orbit servicing. However, many motion planning methods cannot be directly applied to practical space robot system. In order to solve this problem, we adopt the velocity-level kinematics to solve the motion planning problem of space robot in Cartesian space. During the process of space robot motion, the attitude disturbance optimization of satellite base and joint limits avoidance are key issues. For the joint limit problem, the joint threshold function optimization method is proposed. For the disturbance of the base attitude, we propose a new optimization method based on the coupling angular momentum. Finally, the results of the simulation experiment are given, which prove that the methods in this paper are valid.

Ultrathin corrugated metallic structures have been proved to support spoof surface plasmon polariton (SPP) modes on two-dimension (2D) planar microwave circuits. However, to provide stronger field confinement, larger width of strip is required to load deeper grooves, which is cumbersome in modern large-scale integrated circuits and chips. In this work, a new spoof SPP transmission line (TL) with zigzag grooves is proposed. This new structure can achieve stronger field confinement compared to conventional one with the same strip width. In other words, the proposed spoof SPP TL behaves equivalently to a conventional one with much larger size. Dispersion analysis theoretically indicates the negative correlation between the ability of field confinement and cutoff frequencies of spoof SPP TLs. Numerical simulations indicate that the cutoff frequency of the proposed TL is lower than the conventional one and can be easily modified with the fixed size. Furthermore, two samples of the new and conventional spoof SPP TLs are fabricated for experimental demonstration. Measured S-parameters and field distributions verify the ultra-strong ability of field confinement of the proposed spoof SPP TL. Hence, this novel spoof SPP structure with ultra-strong field confinement may find wide applications in microwave and terahertz engineering.

Owing to the gorgeous features of planar design, strong field confinement, and compatibility with traditional microwave devices, spoof surface plasmon polaritons (SSPPs) have been developing at a rapid pace in modern microwave technologies. Band-rejection filters, especially multi-band rejection filters, are a significant ecosystem of SSPPs to be designed. Here, we firstly propose compact multi-band rejection filters, including dual-band and triple-band, through the addition of interdigital capacitance loaded loop resonators (IDCLLRs) into the grooves of the corrugated SSPP transmission line (TL). Compared to traditional metamaterial particles like split ring resonators (SRRs) and complementary SRRs (CSRRs) with the same size, IDCLLRs possess excellent merits of lower resonant frequency, larger dynamic range, and more tunable parameters, which enable the proposed device to be more compact and have more freedom for adjusting bandwidths. Both the simulated and experimental results demonstrate the high performance of two multi-band rejection filters, which can provide wide stop-bandwidth (a maximum relative bandwidth of up to 9.5% for the dual-band filter and 8.8% for the triple-band filter) and high isolation (the isolation of both filters can be less than −30 dB and the maximum isolation of up to −60 dB for the dual-band filter and −58 dB for the triple-band filter). The compact SSPP filters with adjustable multi-band rejections may greatly advance progress towards SSPP-based devices and integrated systems.

A new method to design wide band bandpass filter (BPF) with harmonic Suppression is presented in this paper. The T shape multiple-mode resonator (MMR) is employed to realize the wideband bandpass response with one transition zero outside the passband. The better out of band suppression is achieved by adopting the new feeding structure. The feeding structure introduces a new resonate mode, which provides additional transition zero at upper stop band to realize better harmonic suppression. After wards, a microstrip filter is designed for verifying the feasibility of the design method.