Hengtong Optoelectronic (China)

ABSTRACT Reliable high‐voltage direct current (HVDC) cable insulation requires suppressed DC conductivity and stable charge transport at elevated temperatures. This study investigates charge transport mechanisms in crosslinked polyethylene‐polystyrene (XLPE‐PS) polymeric alloys, emphasizing the effects of structural evolution from unalloyed to alloyed states. XLPE‐PS composites were prepared via controlled processing at 150°C (unalloyed) and 220°C (polymeric alloy), and DC conduction was measured over 30°C–90°C and 10–60 kV/mm using a three‐terminal electrode system. Thermally stimulated depolarization current (TSDC) analysis shows that molecular‐level dispersion of PS and enhanced interfacial crosslinking redistribute trap states, reduce space‐charge accumulation, and stabilize carrier trapping/detrapping dynamics. As a result, charge transport in XLPE‐PS transitions from hopping conduction at low fields, to space‐charge‐limited conduction over intermediate ranges, and to Poole‐Frenkel conduction only under combined high field and temperature. Compared with conventional XLPE, the polymeric alloy exhibits significantly reduced DC conductivity and enhanced electrical stability. The mechanism map developed here links microstructural modifications, trap regulation, and conduction behavior, providing a rational framework for designing next‐generation HVDC cable insulation with superior performance.

Infrastructure development in permafrost regions continues to face growing challenges from frost heaves and thaw settlement. The traditional frost heave theory considers that soil freezing is caused by the migration of liquid water in the soil; however, existing engineering practice shows that the migration of water vapor during the freezing process cannot be neglected. Based on the hydrothermal–air migration theory of unsaturated soils and their frost heave mechanism, this study established a coupled hydrothermal–air frost heave model for unsaturated silty clay under unidirectional freezing conditions. The computational model was verified through indoor modelling tests. The entire process of water vapor migration, moisture accumulation, and condensation-induced ice formation in unsaturated silty clay was comprehensively reproduced by numerical simulation. The results showed that the moisture field is redistributed during the freezing process of unsaturated soil. The increase in volumetric ice content in the frozen zone is due mainly to the migration of water vapor. Liquid water and water vapor in the unfrozen zone migrate towards the freezing edge driven by the temperature gradient, where they accumulate, leading to a decrease in the unsaturated pore space and a decrease in the equivalent vapor content. This study’s results can provide theoretical support for frost damage prevention in unsaturated silty clay in permafrost regions.

In practical applications, Super absorbent polymers (SAP) can have certain adverse effects on concrete. Incorporation of SAP could lead to changes in the pore structure, thereby affecting strength. At the same time, SAP could also present cost challenges. To address these issues, a specific modifier can be incorporated into the SAP internally curing concrete. In this paper, the mechanical properties of nano-SiO2 and fly ash composite modified SAP internal curing concrete were investigated. The mechanical properties of the composite modified SAP were reflected through compressive strength and tensile strength tests as well as porosity mutual verification. The results indicate that nano-SiO2 and fly ash increase the strength of the modified SAP internal curing concrete and reduce the porosity. When the maximum content of nano-SiO2 reaches 3 %, the modification effect is more favourable. Under the combined effect of nano-SiO2 and fly ash, both the strength and porosity of SAP internal curing concrete are improved.

A loopback interconnect datacenter optical network is proposed for Intra- and Inter-Pod switching with commercial devices. Its feasibility was demonstrated by experiments since the filtering performance is similar at loopback and common ports.

Abstract Real‐time terahertz passive imaging systems are highly demanded in security checking application. In this paper, two four‐pixel receiver arrays for 340 and 250 GHz passive imaging systems are presented. As the core device of the front‐end of the receiving array, the low noise terahertz mixer is realized based on the enhanced Schottky diode model and low‐loss circuit structure. The minimum double side band (DSB) noise temperature of the separated 340 and 250 GHz mixers is 900 and 580 K, respectively, within the operational band‐width. Without considering fluctuation in the power gain, the calculated temperature sensitivity of 340 GHz receiver is 0.8 K with 40 GHz RF band. Finally, based on all‐solid‐state millimeter‐wave drive front end and reflector optics, a passive terahertz imaging system is completed. Less than 1 cm space resolution is achieved for 1–3 m object distances, and the distinct imaging to hidden threats is produced and made contrast among the two receiver arrays. The perfect imaging performances of the system verify the low noise characteristic of terahertz mixer. The Schottky solid‐state receiver array provides a cheap and feasible option for personal security screening.

This paper proposes an intelligent reflecting surfaces (IRSs)-assisted Petahertz mobile communication system. The IRSs are utilized in this system to assist the base station for beam tracking and reduce the impact of obstacles by path replanning and real-time power distribution. The scheme of auxiliary beam deflection and tracking is purposed based on the working principle of phase controlled IRSs. Since signals can be deflected freely among multiple IRSs, two multi-path power allocation schemes for optimal system performance are also proposed. Experiments and simulation are presented for verification.

Ultra-low loss (ULL) fibers allow high-quality signal transmission and are expected to become important candidates for new deployment of fiber links in an optical network. In our previous study, we investigated strategies for selecting network links to be deployed with ULL fibers in a single stage, subject to an annual operational budget. As a step further, this study considers such deployment in multiple stages, which corresponds to a scheduling problem of ULL fiber deployment. To this end, we cannot simply adopt a repetition of our previous single-stage deployment approach since it cannot tell which set of links are to be deployed with ULL fibers in each stage. Rather, we need to jointly consider the set and the order of links to be deployed in each stage so as to get a maximum overall gain in terms of time-weighted frequency slot (FS) usage. Also, the time taken for deploying each fiber link and the interval between neighboring deployment stages should be considered. To achieve a global optimization, we develop a mixed integer linear programming (MILP) model and look at three scheduling strategies which are physical length (PL), shortest route traversed (SRT), and maximum deployment gain (MDG) based strategies. We evaluate the performance of these strategies through simulations and find that the proposed MDG strategy performs best in terms of the total time-weighted FS usage. Results also show that there is an optimal number of deployment stages which provides maximum gain of spectrum usage while requiring few network re-optimizations.

After the upgradation of new ultra-low loss (ULL) fibers for network links, some optical amplifiers on these links can become redundant. We consider rearranging these amplifiers for a lower system cost while not significantly degrading optical signal transmission performance. Different rearrangement strategies are proposed and evaluated.

We propose a new method to discriminate and identify the modulation format of signals based on an unsupervised neural network named convolutional Gaussian-Bernoulli restricted Boltzmann machine (CGBRBM). Tests are performed to demonstrate how the proposed method works and to evaluate the discrimination/identification accuracy for different input combinations. Signals of five modulation formats are used to test the CGBRBM-based algorithm including QPSK, 8QAM, 16QAM, 32QAM, and 64QAM. The results indicate the performance of the proposed method when dealing with various application scenarios and reveal the relation between discrimination accuracy and identification accuracy.