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On-chip optical switches have emerged as a new class of photonic components for high-performance optical communication networks and on-chip interconnects, in which the all-optical configuration without the incorporation of other control-means is highly desired. While two-dimensional (2D) ultrathin materials demonstrate their great potential in developing ultrafast all-optical switches owing to their unique light–matter interaction, such investigations have so far been limited to the fiber optic platform or free space. Here, we realize an all-optical on-chip switch from a silicon waveguide-based asymmetric Mach–Zehnder interferometer (MZI) structure enabled by 2D ultrathin Ga2S3. Upon the visible light excitation at 532 nm, excessive photocarriers in Ga2S3 cause a change of the refractive index and subsequently a phase variation between MZI arms at the 1550 nm operation wavelength, triggering on the optical switch. On the other hand, the switch is off without the visible light stimulation, as the phase variation is recovered due to the ultrafast photo-exciton relaxation behavior of Ga2S3. The Ga2S3-enabled all-optical switch is driven at an extremely small optical power density of 0.12 W cm−2 and exhibits a response and recovery time of 26.3 and 43.5 μs, respectively, which as a combination is superior to those of fiber optic-based all-optical switches enabled by 2D materials. This work may provide a viable approach to develop on-chip all-optical photonic components for practical integrated photonic chips.

The burgeoning research into two-dimensional (2D) materials opens a door to novel photonic and optoelectronic devices utilizing their fascinating electronic and photonic properties in thin-layered architectures. The hybrid integration of 2D materials onto integrated optics platforms thus becomes a potential solution to tackle the bottlenecks of traditional optoelectronic devices. In this paper, we present the recent advances of hybrid integration of a wide range of 2D materials on integrated optics platforms for developing high-performance photodetectors, modulators, lasers, and nonlinear optics. Such hybrid integration enables fully functional on-chip devices to be readily accessible researchers and technology developers, becoming a potential candidate for next-generation photonics and optoelectronics industries.

Fiber-optic gas sensors have been considered a low-cost, effective, and robust approach for monitoring nitrogen dioxide (NO

Floating energy pile groups subjected to thermal cycles have rarely been tested, resulting in a limited understanding of their performance at the serviceability state. Centrifuge modelling of an elevated 2 × 2 floating energy pile group with a rigid cap was conducted in saturated Toyoura sand. Under a constant vertical working load, only one of the piles within the group was applied ten two-way thermal cycles with an amplitude of 7°C. The results show that the energy pile group experienced a ratcheting accumulation of irreversible tilting at a reducing rate with continued cycles. The axial load sustained by the non-energy piles was observed to increase by about 30%.

The detection of cancer cells at the single-cell level enables many novel functionalities such as next-generation cancer prognosis and accurate cellular analysis. While surface-enhanced Raman spectroscopy (SERS) has been widely considered as an effective tool in a low-cost and label-free manner, however, it is challenging to discriminate single cancer cells with an accuracy above 90% mainly due to the poor biocompatibility of the noble-metal-based SERS agents. Here, we report a dual-functional nanoprobe based on dopant-driven plasmonic oxides, demonstrating a maximum accuracy above 90% in distinguishing single THP-1 cell from peripheral blood mononuclear cell (PBMC) and human embryonic kidney (HEK) 293 from human macrophage cell line U937 based on their SERS patterns. Furthermore, this nanoprobe can be triggered by the bio-redox response from individual cells towards stimuli, empowering another complementary colorimetric cell detection, approximately achieving the unity discrimination accuracy at a single-cell level. Our strategy could potentially enable the future accurate and low-cost detection of cancer cells from mixed cell samples.

Energy storage needs to account for the intermittence of solar radiation if solar energy is to be used to answer the heat demands of buildings. Energy piles, which embed thermal loops into the pile body, have been used as heat exchangers in ground source heat pump systems to replace traditional boreholes. Therefore, it is proposed to store solar thermal energy underground via energy piles. To investigate the performance of such systems, a laboratory-scale coupled energy pile-solar collector system was built for this study. Experiments were performed to evaluate the effects of various controlling parameters on the short-term performance of the system. These include the degree of saturation of the soil, the flowrate of the heat-carrying fluid, the intensity of solar radiation, and their interaction. The results showed that under abundant solar radiation, the daily average rate of energy storage per unit pile length increases by about 150 W/m when the soil condition changes from being dry to saturated, with a maximum value of about 200 W/m. As the intensity of solar radiation drops, it becomes the dominant factor. Compared to the laminar flow, the turbulent flow contributes more to the underground solar energy storage as the soil is more saturated. This suggests a technique to minimise the electricity consumption by the system and thus optimise its performance through regulating the flowrate. In addition, a mathematical model of the coupled energy pile-solar collector system was validated against the measurements. Long-term simulations in prototype using the validated model further confirm the above conclusions.

Nanoporous plasmonic nanostructures based on noble metals have received extensive attention on the high-performance detection of chemical analytes. However, the size of such pores is rarely at the angstrom scale given the limitation of current fabrication methods. This leads to a relatively poor performance in the detection of ions. Here, we demonstrate the formation of angstrom-scale pores in ultra-thin plasmonic ammonium doped molybdenum oxide through crystal nucleation. The molybdenum oxide octahedra assemble into hexagonal rings, in which dopants fill in parts of the rings to stabilize the crystal structure and simultaneously generate a broad plasmon resonance across the visible to near-infrared regions. As a result, the unfilled centers of the rings effectively become angstrom-scale pores. Na+ ion sensing capability is investigated by integrating plasmonic ammonium doped molybdenum oxide onto D -shaped optical fibers. The ions are facilely accommodated within the pores and induce a charge re-distribution in the host. This alters the plasmon resonance behavior and modulates the optical output of the fiber transducing platform, through a strong light-matter interaction. The structure is sensitive to a wide concentration range of Na+ ions from subnanomolar (sub-nM) to submolar (sub-M) with the limit of detection (LOD) of ~5 fM, and high selectivity in both the aqueous solution and simulated serum conditions, which is a superior sensitivity over other reported optical ion sensors. This work demonstrates the strong potential of angstrom-scale porous plasmonic materials for chemical detection, and the possibility of being integrated with popular optical transducing platforms for practical high-performance sensing.

As a result of cyclic heating and cooling around the ambient temperature under drained conditions, normally consolidated and lightly overconsolidated fine-grained soils experience accumulation of irreversible volumetric contraction. Most existing thermomechanical models were developed for one heating–cooling cycle and are not suitable for multiple thermal cycles. An approach is proposed to simulate the volume change of fine-grained soil induced by thermal cycles. In the proposed approach, a thermal stabilization line is introduced to control the stabilized volumetric contraction under thermal cycles. Comparison with experimental results shows that the proposed approach can reproduce well the cumulative feature of volumetric contraction of fine-grained soil subjected to thermal cycles.

Horizontal stress changes of semi-floating energy piles subjected to cyclic thermal loading are investigated through finite element analysis adopting the hypoplastic model. By using the validated finite element model, a parametric study is carried out, considering effects of amplitude of thermal cycles, pile diameter, pile length and relative density of sand. It is revealed that due to volumetric contraction of sand (loose or dense) at the interface under temperature induced cyclic shearing, a reduction of horizontal stress occurs. The degree of reduction in horizontal stress is most affected by the amplitude of thermal cycles and the pile diameter.

Energy piles serve as supporting structures and heat-exchange elements. They can provide thermal comfort much more efficiently than traditional air-sourced systems as the ground offers high thermal conductivity and a stable temperature below a certain depth. Energy piles are commonly installed as bored piles (replacement); however, driven (displacement) energy piles are also used in practice. A direct comparison of the performance of these two different types of energy piles subjected to thermal cycles is rarely explored not fully understood. In this study, two centrifuge energy model piles, one wished-in-place at one gravity (i.e. at low stress, simulating bored pile) and the other pile was jacked in at elevated gravity were constructed in saturated Toyoura sand. After construction, they were subjected to five heating and cooling cycles (7–37°C) under a constant working load. Cumulative settlement with a ratcheting pattern was observed for the ‘bored’ energy pile after five thermal cycles. In contrast, a slight heave was recorded for the jacked-in energy pile. The observed heave can be attributed to the densification effect and particle crushing of soil when the pile was jacked in, reducing or even eliminating thermal-induced contraction of sand and hence decreasing the reduction of horizontal stress during thermal cycles.

Experimental studies on behavior of T-stubs connected using thread-fixed one-side bolts (TFOSBs) under monotonic and cyclic loads were presented. Three failure modes, which were the complete flange yielding failure, the bolt failure, and the flange yielding accompanied by hole thread failure, were observed in both tests. Effects of the cyclic load on the behavior of T-stubs were discussed from aspects of the deformation, the load transfer mechanism, the stiffness degradation and the tension yield strength. Compared to the monotonic tests, the cyclic load caused stiffness degradation and made threads on the bolt hole wall become more vulnerable to fail. In addition, comparisons showed that available design methods applied to predict the behavior of T-stubs under monotonic load also were applicable to predict that under cyclic load.

Test results on S teel R einforced C oncrete C olumn with W elded S tirrups (SRCC-WS) were presented and a simplified design method was proposed. The SRCC-WS had no longitudinal steel bars to reduce the labor forces and avoid the difficulty in connecting longitudinal bars at construction site, and stirrups were welded directly to the steel reinforcement to ensure they worked together. Five SRCC-WSs were tested under axial compression; and two traditional Steel Reinforced Concrete Columns (SRCCs) were tested for comparison. Failure modes, load-displacement curves, and strain evolution curves measured from tests were presented. Test results showed that the ultimate axial compression strength and ductility of a SRCC-WS was a little higher than that of a SRCC having the same overall steel ratio. A simplified design method for calculating the effective lateral confined pressure on the core concrete provided by the combined action of welded stirrups and steel reinforcement flanges was proposed. The calculated yield compression strength of a SRCC-WS based on the proposed concrete model agreed better with the experimental value than that calculated by the method in Eurocode 4.

Yield line patterns of T-stubs connected by thread-fixed one-side bolts (TFOSBs) are investigated when they fail due to complete flange yielding under tension using finite element analysis. Parametric studies are carried out to compare T-stubs connected by TFOSBs and those connected by nut-fixed bolts. Effects of the flange width, the flange thickness, the bolt middle distance, the bolt end distance and the bolt diameter on the yield line patterns and yield tensile strengths are presented. Analysis results show that the yield tensile strength of T-stubs connected by TFOSBs is slightly lower than that of T-stubs connected by nut-fixed bolts. The flange width is the main factor that affects the yield line patterns of T-stubs connected by TFOSBs. For T-stubs having flange width to length ratios within the range studied here, with the increase in flange width, the yield line pattern gradually changes from a double curvature yield line pattern to a non-circular end yield line pattern, then to a circular individual end yield line pattern, and eventually to a bolt hole circular yield line pattern. And for T-stubs having flange width to length ratios within the range studied here, effects of bolt end distance e on the yield line pattern depends on the flange width L. The current design method gives a reasonably conservative estimation of the tensile strengths of T-stubs connected by TFOSBs.

This paper presented numerical investigations on the behavior of a Bolted Castellated Steel Beam (BCSB) with octagonal web openings. Instead of welding the upper and the lower Tee-sections of a Castellated Steel Beam (CSB) together in the factory, they were connected using high strength bolts at the construction site. Thus, the upper and the lower Tee-sections can be transported separately, especially being convenient for a castellated steel beam with great section height. The residual stresses in the web-post induced by welding could also be avoided. The shear buckling behavior of the web-post in a BCSB with octagonal openings was studied using a verified finite element model. The buckling mode and the buckling strength of the web-post in a BCSB were compared with those of a traditional Welded Castellated Steel Beam (WCSB). Research results showed that web-posts in a BCSB with octagonal web openings had as good structural performance as those in a WCSB. Studied parameters of the BCSB included the bolt diameter, the width-to-thickness ratio of the web-post and the bolt layout. To increase the buckling strength of the web-post, a BCSB using stiffened connection plate was proposed. The Strut Model for predicting the buckling strength of the web-post in a traditional WCSB was employed for calculating that in a BCSB. Comparisons of buckling strengths obtained by Strut Model predictions and finite element simulations showed that the Strut Model could be used to predict the web-post buckling strength of a BCSB.

Vierendeel failure of castellated steel beams (CSBs) with fillet corner web openings is investigated by the Finite Element Method. Compared to beams with circular openings, CSBs with the proposed fillet corner web openings need only one cut along the web centerline. Therefore the fabrication cost can be reduced. Effects of opening dimensions and opening shapes on the Vierendeel failure of web-perforated members are investigated in this paper. Numerical results indicate that CSBs with the proposed fillet corner web openings enjoy a higher load bearing capacity than those with traditional rectangular or hexagonal openings on condition that they have the same opening height. The M – V interaction method for predicting the load bearing capacity of CSBs with fillet corner web openings is proposed. Predictions obtained from the proposed M – V interaction equation agree well with numerical results.

The elastic buckling and nonlinear post-local buckling behavior of a stiffened plate with slot holes is different to that of a solid plate. As results of systematic parameter studies, design equations for calculating the elastic buckling stress of a solid plate is modified for design a stiffened plate with slot holes. Numerical simulation shows that in the post-local buckling phase, the slots cause the membrane stress redistribution and help the non-slotted region developing into a much higher stress state, which may lead to the increase in the load bearing capacity of the slotted plate. Through studying the longitudinal stress distribution along the plate width, the effective width design equation for the solid plate is also modified to account for effects of the slots. Comparisons of the effective width factor obtained from the proposed equations, previous research results and the numerical simulation show that they agree well with each other.