Based on the characteristics of the variable pivot gait during the human load-carrying, this paper proposes a double-leg coordination assistance principle for load-carrying: assisting support of the guiding leg at the heel-pivot stage by the spring to reduce the collision, which can reduce the ankle moment of the following leg that is performing the push-off at the toe-pivot stage. A novel unpowered load-carrying exoskeleton (ULE) with a double-support closed-chain configuration is designed, and the theoretical verification is carried out. Five subjects participate in the load-carrying and metabolic cost experiments for assisting and energy-saving effect evaluation, and the angle and moment of human joints, plantar pressure, spring compression and human net metabolic rate are analyzed. Compared with carrying load by the human alone, wearing the novel ULE with spring reduces the human peak ankle moment performing the push-off by up to 11.9 ± 1.6% (Mean±SE, 10 kg), average ankle moment over the support phase by up to 36.8 ± 9.1% (Mean±SE, 5 kg) and the average vertical plantar pressure by up to 8.1 ± 1%% (Mean±SE, 15 kg). Meanwhile, wearing the novel ULE reduces the human net metabolic rate by 5.6 ± 0.5% (Mean±SE, 10 kg), 4.1 ± 0.7% (Mean±SE, 15 kg) and 5.9 ± 1.6% (Mean±SE, 20 kg). The results show that the novel ULE can provide support and joint moment assistance over the whole support phase while reducing human net metabolic rate. This study can also be applied to the powered load-carrying exoskeleton, providing a new avenue.

Human–machine compatibility and collaborative control for stroke patients utilizing lower limb rehabilitation robots have attracted considerable research attention. As a highly human–machine-coupled system, ensuring adequate compliance and safety is fundamental to efficient and comfortable rehabilitation. Therefore, this paper first quantifies human–machine contact interactions, proposes a human–machine coupling dynamics modeling method, and identifies the robot’s dynamic inertia parameters and human lower limb parameters. Second, a dual closed-loop controller for the rehabilitation robot is designed. Based on the bottom position control, an adaptive admittance control algorithm is proposed that employs the root-mean-square propagation (RMSprop) algorithm to tune the adaptive gain. In rehabilitation training, the controller can adaptively adjust the admittance parameters according to the human–machine interaction force to achieve responsiveness to the dynamic changes of the human–machine system. The experimental results of the control system show that the human–machine cooperative control performance is significantly improved, the maximum joint angle error is reduced by more than 40.9%, and the maximum human–machine interaction force is reduced by more than 19.4%.

High gain greater than 106 is crucial for the preamplifiers of joule-class high-energy lasers. In this work, we present a specially designed compact amplifier using 0.5%Nd,5%Gd:SrF2 and 0.5%Nd,5%Y:SrF2 crystals. The irregular crystal shape enhances the gain length of the laser beam and helps suppress parasitic oscillations. The amplified spontaneous emission (ASE) induced by the high gain is analyzed through ray tracing. The balance between gain and ASE is estimated via numerical simulation. The gain spectral characteristics of the two-stage two-pass amplifier are examined, demonstrating the advantages of using different crystals, with bandwidths up to 8 nm and gains over 106. In addition, the temperature and stress distributions in the Nd,Gd:SrF2 crystal are simulated. This work is expected to contribute to the development of high-peak-power ($\ge$terawatt-class) high-energy (joule-class) laser devices.

We are concerned with the following coupled Schrödinger system with a Hardy potential in the critical case

\begin{align*}\begin{cases}-\Delta u_{i}-\frac{\lambda_{i}}{|x|^2}u_{i}=|u_i|^{2^*-2}u_i+\sum_{j\neq i}^{3}\beta_{ij}|u_{j}|^{\frac{2^*}{2}}|u_i|^{\frac{2^*}{2}-2}u_i, ~x\in \mathbb{R}^N,\\u_i\in D^{1,2}(\mathbb{R}^N),\,\, N\geq 3,\,\, i=1,2,3,\end{cases}\end{align*}

$2^*=\frac{2N}{N-2}$

$\lambda_i\in (0,\Lambda_N), \Lambda_N:= \frac{(N-2)^2}{4}$

$\beta_{ij}=\beta_{ji}$

$\beta_{ij} \gt 0$

$\beta_{i_{1}j_{1}} \gt 0$

$\beta_{i_{2}j_{2}} \lt 0$

$(i_{1}, j_{1})$

$(i_{2}, j_{2})$

$\beta_{ij}\ge0$

$N\ge5$

$\beta_{ij} \gt 0$

$N=3,4$

$N=3, 4$

$N\geq 5$

$N\geq 5$

$N\ge5$

This paper introduces an equivalent series mechanism model to improve ankle rehabilitation robots’ ability to recurrence the complex movements of the anthropo-ankle and enhance human-machine locomotion compatibility. The model emulates the true anatomical architecture of the ankle joint and is integrated with a parallel rehabilitative mechanism. The rehabilitative robot includes dual virtual motion centers to mimic the ankle joint’s intricate motion, accommodate individual patient variations, and address the rehabilitation requirements of both right and left feet. Firstly, a serial equivalence model of anthropo-ankle is developed based on the kinematic and anatomical characteristics of the human ankle. The type design for the 4-degree of freedom (4-DOF) parallel ankle rehabilitative robot is then conducted on the basis of the kinematical and restrictive properties of the anthropo-ankle equivalence kinematic model. Secondly, the mechanism’s motion properties allow it to be equivalent to a series branch chain, enabling the establishment of an inverse kinematics model. The kinematical performance of the mechanisms is analyzed using the transmissibility and constrainability indices, followed by workspace analysis and dimensional optimization of the rehabilitative mechanism. Finally, a human-machine coupled rehabilitative simulation model is developed using OpenSim biomechanics software to evaluate the recovery effect.

Machine learning has already shown promising potential in tiled-aperture coherent beam combining (CBC) to achieve versatile advanced applications. By sampling the spatially separated laser array before the combiner and detuning the optical path delays, deep learning techniques are incorporated into filled-aperture CBC to achieve single-step phase control. The neural network is trained with far-field diffractive patterns at the defocus plane to establish one-to-one phase-intensity mapping, and the phase prediction accuracy is significantly enhanced thanks to the strategies of sin-cos loss function and two-layer output of the phase vector that are adopted to resolve the phase discontinuity issue. The results indicate that the trained network can predict phases with improved accuracy, and phase-locking of nine-channel filled-aperture CBC has been numerically demonstrated in a single step with a residual phase of λ/70. To the best of our knowledge, this is the first time that machine learning has been made feasible in filled-aperture CBC laser systems.

In an effort to alleviate the issue of knee joint fatigue and injury during lower limb ambulation, a novel passive assisted exoskeleton robot with human–machine interaction is investigated to assist the movement of the human knee joint. The design of the exoskeleton configuration takes into consideration the physiological structure and gait function of the knee joint, ensuring that it satisfies the requirements for motion, force, and gait function of the knee joint. To explore the interaction between the wearer and the exoskeleton, a human–machine kinematic model after wearing exoskeleton is established, which is instrumental in analyzing the integration motion of the wearer and exoskeleton. In addition, the dynamic and static models of the knee joint after wearing the exoskeleton are established, utilizing the Newton–Euler method and force polygon method, respectively, to evaluate the effectiveness of the exoskeleton. Moreover, the size parameters and spring stiffness of the exoskeleton are optimized, using both human body kinematic model and mechanic model. Furthermore, the effectiveness of the exoskeleton in proving assistance is evaluated through human body simulation, using OpenSim. The results indicate that the exoskeleton significantly reduces the knee joint torque by 48.42%.

A low-energy proton accelerator named pulsed synchronous linear accelerator (PSLA) is proposed and developed at the Institute of Fluid Physics, which is driven by unipolar-pulsed high voltages. Pulsed-accelerating electric fields and low-energy ion beams are precisely synchronized on temporal and spatial positions for continuous acceleration. The operating mode and the features of the PSLA are introduced. At present, the feasibility of a low-energy proton PSLA has been verified in principle. An average accelerating gradient up to 3 MV/m for protons is achieved.

Based on the path encoding pulse compression teleology, a novel method for obtaining high-power microwave (HPM) pulse with ultrahigh repetition frequency is proposed in this paper. The mechanism of the path encoding pulse compression teleology is first introduced. And then, the obtained HPM pulse is analyzed. Theoretical analysis shows that the peak power of MW level and the repetition frequency of MHz level for the generated HPM pulse can be easily reached. To demonstrate the effectiveness of this method for obtaining HPM pulse with ultrahigh repetition frequency characteristic, a HPM-obtaining experiment was carried out based on an S-band microwave source. The HPM pulses with the width of 1 ns, 2 ns, and 3 ns are studied, respectively. The measured results show that the HPM pulse with the power higher than 100 kW and the repetition frequency of 250 kHz at the frequency of 2.856 GHz is easily obtained. The repetition frequency of the generated HPM pulse can be easily changed. Because the pulse with the power higher than 100 kW and the repetition frequency of several hundreds of kHz is obtained for the first time, this type of pulse will have a broad prospect of application in the communication, radar, and electronic countermeasure fields. In addition, the effect experiment of interfering communication and control links was carried out by utilizing the ultrahigh repetition frequency characteristic of the generated HPM pulse. Also, the experiment results show the feasibility of this pulse for interfering the communication and control links.

Aerospace represents the development of national science and technology. It is an important foundation for exploring space and an important guarantee for the construction of aerospace power. There are many large workpieces in the aerospace field. The box insulation layer of large workpieces is an important processing problem. A new thick processing equipment is proposed to process the box insulation layer of large workpieces. The thick processing equipment consists of the XYZ shaft long guide rail and five degrees of freedom (5-DOF) RAPA. The mechanical structure of the 5-DOF RAPA is a redundantly actuated parallel mechanism (RAPM). Meanwhile, this paper proposes a new method to design 5-DOF redundantly actuated parallel mechanisms (RAPMs) with large output rotational angles. Based on configuration evolution and Li group, two articulated moving platforms (AMPs) and four kinds of limbs are designed, and a series of 3T2R (T represents translation, R represents rotation) RAPMs and 2T3R RAPMs are synthesized. To verify the designed RAPMs with large angle, an example of RAPMs, 4UPS-{2UPR}-R is analyzed. To ensure that the RAPM has no mechanism vibration impact in movement, this paper represents the RAPM adopts a newly proposed trajectory planning method. The results show that the 4SPU-(2UPR)R mechanism possesses large angles and verifies the efficiency of the new proposed trajectory planning method in simplified trajectories. This work lays the foundation for processing the box insulation layer of large workpieces with straight lines and arcs paths.

This paper proposes a linear quadratic approximation approach to dynamic nonlinear rationally inattentive control problems with multiple states and multiple controls. An efficient toolbox to implement this approach is provided. Applying this toolbox to five economic examples demonstrates that rational inattention can help explain the comovement puzzle in the macroeconomics literature.

The Schrödinger–Poisson system describes standing waves for the nonlinear Schrödinger equation interacting with the electrostatic field. In this paper, we are concerned with the existence of positive ground states to the planar Schrödinger–Poisson system with a nonlinearity having either a subcritical or a critical exponential growth in the sense of Trudinger–Moser. A feature of this paper is that neither the finite steep potential nor the reaction satisfies any symmetry or periodicity hypotheses. The analysis developed in this paper seems to be the first attempt in the study of planar Schrödinger–Poisson systems with lack of symmetry.

The Huangshaping deposit is unique in southern Hunan Province, China, as it hosts economic reserves of both W–Mo and Pb–Zn mineralization, which are usually associated with granite and granodiorite porphyry in this area, respectively. This study reports results of in situ LA-MC-ICP-MS sulphur isotopic composition analyses conducted on sulphides from both W–Mo and Pb–Zn mineralization from the Huangshaping deposit with the aim of constraining ore genesis for this deposit. All samples from the proximal W–Mo mineralization have relatively uniform and high δ34S values (8.7 ‰ to 16.0 ‰), close to the range for carbonate sediments in this deposit (13.8 ‰ to 18.1 ‰). These patterns suggest that the granite porphyry in this deposit was the sulphur source for W–Mo mineralization, and that the assimilation of evaporite from the carbonate sediments led to the high δ34S values of the granite porphyry. Sulphides from the Pb–Zn mineralization have δ34S values (2.2 ‰ to 10.3 ‰) lower than those of the W–Mo mineralization, and generally increase in this paragenetic order, with the lowest δ34S values being similar to those of the basement (3.8 ‰ to 7.7 ‰). These patterns indicate that the original sulphur for the Pb–Zn mineralization was most likely derived from the basement, with input of sulphur from the carbonate sediments increasing during the evolution of ore-forming fluids. On the basis of the measured sulphur isotopic compositions, it is suggested that the ore-forming materials for the W–Mo mineralization were derived from the granite porphyry, whereas ore-forming materials extracted from the basement dominated the Pb–Zn mineralization.

At present, the study on autonomous unmanned ground vehicle navigation in an unstructured environment is still facing great challenges and is of great significance in scenarios where search and rescue robots, planetary exploration robots, and agricultural robots are needed. In this paper, we proposed an autonomous navigation method for unstructured environments based on terrain constraints. Efficient path search and trajectory optimization on octree map are proposed to generate trajectories, which can effectively avoid various obstacles in off-road environments, such as dynamic obstacles and negative obstacles, to reach the specified destination. We have conducted empirical experiments in both simulated and real environments, and the results show that our approach achieved superior performance in dynamic obstacle avoidance tasks and mapless navigation tasks compared to the traditional 2-dimensional or 2.5-dimensional navigation methods.

Experimental studies suggest that abnormal levels of Ca, Mg and phosphorus are implicated in pancreatic carcinogenesis. We investigated the associations between intakes of these minerals and the risk of pancreatic cancer in a case-control study conducted in 1994–1998. Cases of pancreatic cancer (n 150) were recruited from all hospitals in the metropolitan area of the Twin Cities and Mayo Clinic, Minnesota. Controls (n 459) were randomly selected from the general population and frequency matched to cases by age, sex and race. All dietary variables were adjusted for energy intake using the residual method prior to data analysis. Logistic regression was performed to evaluate the associations between intake of three nutrients examined and the risk of pancreatic cancer. Total intake of Ca (936 v. 1026 mg/d) and dietary intake of Mg (315 v. 331 mg/d) and phosphorus (1350 v. 1402 mg/d) were significantly lower in cases than in controls. After adjustment for confounders, there were not significant associations of total and dietary intakes of Ca, Mg and phosphorus with the risk of pancreatic cancer. In addition, no significant interactions exist between intakes of these minerals and total fat on pancreatic cancer risk. In conclusion, the present study does not suggest that intakes of Ca, Mg and phosphorus were significantly associated with the risk of pancreatic cancer.

Managerial networking with political actors has long been recognized as a crucial co-option strategy to navigate the challenging institutional environment in emerging economies. However, we know much less about what drives the variation of political networking investment by private ventures. Drawing on resource dependence theory, we unpack the dyadic business-government relations and identify the key organizational and environmental factors that shape the power dependence relationships between private ventures and the government. By examining power imbalance and mutual dependence in this dyadic relationship and considering both the necessity and the capability of political networking, we develop hypotheses regarding the ways in which size-, connection-, and location-based dependencies affect firms’ political networking intensity. These hypotheses are tested through a unique survey of Chinese private ventures. Our study finds that political networking intensity (1) has an inverted U-shaped relationship with firm size, (2) is negatively associated with the presence of embedded political ties while positively associated with that of achieved political connections, and (3) is smaller when the focal firm is located in business development zones. This research bears rich implications for our understanding of corporate political activity in emerging economies from a resource dependence lens.

Data on average iodine requirements for the Chinese population are limited following implementation of long-term universal salt iodisation. We explored the minimum iodine requirements of young adults in China using a balance experiment and the ‘iodine overflow’ hypothesis proposed by our team. Sixty healthy young adults were enrolled to consume a sequential experimental diet containing low, medium and high levels of iodine (about 20, 40 and 60 μg/d, respectively). Each dose was consumed for 4 d, and daily iodine intake, excretion and retention were assessed. All participants were in negative iodine balance throughout the study. Iodine intake, excretion and retention differed among the three iodine levels (P < 0·01 for all groups). The zero-iodine balance derived from a random effect model indicated a mean iodine intake of 102 μg/d, but poor correlation coefficients between observed and predicted iodine excretion (r 0·538 for μg/d data) and retention (r 0·304 for μg/d data). As iodine intake increased from medium to high, all of the increased iodine was excreted (‘overflow’) through urine and faeces by males, and 89·5 % was excreted by females. Although the high iodine level (63·4 μg/d) might be adequate in males, the corresponding level of 61·6 μg/d in females did not meet optimal requirements. Our findings indicate that a daily iodine intake of approximately half the current recommended nutrient intake (120 μg/d) may satisfy the minimum iodine requirements of young male adults in China, while a similar level is insufficient for females based on the ‘iodine overflow’ hypothesis.