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Abstract An equivalent circuit modelling methodology for the ball‐grid‐array (BGA) transition is proposed and validated with full‐wave electromagnetic simulation and measurement results. The BGA transitions modelled with the proposed methodology are validated to have a good accuracy up to 40 GHz. Unlike the existing BGA modelling methodologies which cannot model the BGA transition with short transmission lines within the anti‐pad region, the proposed methodology is developed from the practical BGA modelling scenario and models the irregular‐shape solder pads with transmission lines within the anti‐pad region. The BGA transitions modelled with the proposed methodology can be used for accurate and fast signal integrity simulations, analyses, and optimizations on 2.5D and 3D packaging. Additionally, factors impacting the accuracy of the equivalent circuit model are revealed by the proposed methodology.

Abstract Nearly four decades have passed since IBM scientists pioneered atomic force microscopy (AFM) by merging the principles of a scanning tunneling microscope with the features of a stylus profilometer. Today, electrical AFM modes are an indispensable asset within the semiconductor and nanotechnology industries, enabling the characterization and manipulation of electrical properties at the nanoscale. However, electrical AFM measurements suffer from reproducibility issues caused, for example, by surface contaminations, Joule heating, and hard‐to‐minimize tip drift and tilt. Using as experimental system nanoscale Schottky diodes assembled on oxide‐free silicon crystals of precisely defined surface chemistry, it is revealed that voltage‐dependent adhesion forces lead to significant rotation of the AFM platinum tip. The electrostatics‐driven tip rotation causes a strain gradient on the silicon surface, which induces a flexoelectric reverse bias term. This directional flexoelectric internal‐bias term adds to the external (instrumental) bias, causing both an increased diode leakage as well as a shift of the diode knee voltage to larger forward biases. These findings will aid the design and characterization of silicon‐based devices, especially those that are deliberately operated under large strain or shear, such as in emerging energy harvesting technologies including Schottky‐based triboelectric nanogenerators (TENGs).

Abstract Silicon (Si) content in plant tissues is considered a functional trait that can provide multiple morpho‐physiological benefits to plant individuals. However, it is still unclear whether and how these individual benefits extend to plant community processes and ecosystem functioning. Here we investigated how plant Si content is associated with plant community properties and the ecosystem structure of herbaceous communities in Israel. We sampled 15 sites across the Mediterranean and desert ecosystems and built models to evaluate how plant silicon content (community‐weighted mean and standard variation) is associated with variables such as species richness, biomass production, plant cover, and functional diversity. Finally, we used model selection techniques to test whether models depicting plant Si content perform better than models using data on soil Si instead. Sites with lower susceptibility to drought had significantly more Si‐accumulating grass species and higher soils Si content. Models with plant Si content instead of soil Si, always performed better, although those considering Si content variation had overall stronger associations with community properties than only mean Si content. For instance, up to 51% of plant Si content variation was explained by climate, biomass production, and species richness, combined. Still, mean plant Si content and plant cover combined explained up to 42% of plant functional diversity. Our results suggest the that plant Si content serves as a proxy for understanding the ecological properties and functioning of arid and Mediterranean ecosystems. Nevertheless, the significance of Si has not been fully explored in other ecosystem types, where its influence may be less pronounced compared with the ecosystems examined in this study. In light of various global change scenarios, enhancing our understanding of Si as a plant functional trait could help bridge existing knowledge gaps and improve ecological modeling, thus enabling more accurate forecasts of changes in plant distributions.

Abstract Biomaterials encounter considerable challenges in extensive bone defect regeneration. The amelioration of outcomes may be attainable through the orchestrated modulation of both innate and adaptive immunity. Silicon‐hydroxyapatite, for instance, which solely focuses on regulating innate immunity, is inadequate for long‐term bone regeneration. Herein, extra manganese (Mn)‐doping is utilized for enhancing the osteogenic ability by mediating adaptive immunity. Intriguingly, Mn‐doping engenders heightened recruitment of CD4+ T cells to the bone defect site, concurrently manifesting escalated T helper (Th) 2 polarization and an abatement in Th1 cell polarization. This consequential immune milieu yields a collaborative elevation of interleukin 4, secreted by Th2 cells, coupled with attenuated interferon gamma, secreted by Th1 cells. This orchestrated interplay distinctly fosters the osteogenesis of bone marrow stromal cells and effectuates consequential regeneration of the mandibular bone defect. The modulatory mechanism of Th1/Th2 balance lies primarily in the indispensable role of manganese superoxide dismutase (MnSOD) and the phosphorylation of adenosine 5′‐monophosphate‐activated protein kinase (AMPK). In conclusion, this study highlights the transformative potential of Mn‐doping in amplifying the osteogenic efficacy of silicon‐hydroxyapatite nanowires by regulating T cell‐mediated adaptive immunity via the MnSOD/AMPK pathway, thereby creating an anti‐inflammatory milieu favorable for bone regeneration.

Abstract Two‐dimensional dopant layers (δ‐layers) in semiconductors provide the high‐mobility electron liquids (2DELs) needed for nanoscale quantum‐electronic devices. Key parameters such as carrier densities, effective masses, and confinement thicknesses for 2DELs have traditionally been extracted from quantum magnetotransport. In principle, the parameters are immediately readable from the one‐electron spectral function that can be measured by angle‐resolved photoemission spectroscopy (ARPES). Here, buried 2DEL δ‐layers in silicon are measured with soft X‐ray (SX) ARPES to obtain detailed information about their filled conduction bands and extract device‐relevant properties. This study takes advantage of the larger probing depth and photon energy range of SX‐ARPES relative to vacuum ultraviolet (VUV) ARPES to accurately measure the δ‐layer electronic confinement. The measurements are made on ambient‐exposed samples and yield extremely thin (< 1 nm) and dense (≈1014 cm−2) 2DELs. Critically, this method is used to show that δ‐layers of arsenic exhibit better electronic confinement than δ‐layers of phosphorus fabricated under identical conditions.

Abstract Silica‐aluminium composite powders are important precursors for the preparation of sealant coatings by supersonic flame spraying. Micron‐scale silica‐aluminium composite powders can be prepared using a planetary ball mill, but powder agglomeration often leads to composite failure. Using relevant modelling software to build the 3D modelling of the ball mill jar, which based on the discrete element method, using the Hertz–Mindlin contact model and after specifying the simulation boundary conditions, the ball mill process was simulated and analysed. Visualise the influence of important process parameters such as frequency, size and diameter of milling balls and ball‐to‐powder weight ratio, and systematically analyse the microscopic morphology and composite condition of the agglomerated and dispersed powders. The results show that the ball motion during the ball milling process is mainly divided into three representative types: ball–ball impact, ball crushing motion against the jar wall and ball–wall impact. The energy transfer efficiency of the milling balls to the powder system is highest when the ratio of the three types of motion is uniform. SEM images and EDS spectra showed that the aluminium powder was sufficiently crushed, with an average particle size below 1 μm. The aluminium powder was uniformly distributed on the surface of the silicon powder, and the particle size of the composite silicon aggregates was sufficiently reduced.

Abstract Si, as a narrow bandgap semiconductor with a broadband absorption for sunlight, is considered to be a very competitive photoelectrode material for solar‐driven photoelectrochemical (PEC) water splitting. However, there are major barriers in construction of efficient and stable Si‐based PEC cell, including low photovoltage, sluggish reaction kinetics, and poor stability in electrolytes. This review focuses on the strategies to solve these issues and summarizes recent progress. The working principles of PEC water splitting are first introduced. Then the strategies for improving Si‐based photoelectrode performances are discussed, including (1) the regulation of Si surface morphology for enhancing light harvesting, (2) band structure engineering strategies to reduce recombination of photogenerated carriers, and (3) modification of protection layers for long stability and loading cocatalysts on Si‐based photoelectrodes for accelerating water splitting. Lastly, we have presented some issues of Si‐based photoelectrode materials, which should be addressed in future research.

Abstract Silicon (Si)‐based negative electrodes have attracted much attention to increase the energy density of lithium ion batteries (LIBs) but suffer from severe volume changes, leading to continuous re‐formation of the solid electrolyte interphase and consumption of active lithium. The pre‐lithiation approach with the help of positive electrode additives has emerged as a highly appealing strategy to decrease the loss of active lithium in Si‐based LIB full‐cells and enable their practical implementation. Here, the use of lithium squarate (Li2C4O4) as low‐cost and air‐stable pre‐lithiation additive for a LiNi0.6Mn0.2Co0.2O2 (NMC622)‐based positive electrode is investigated. The effect of additive oxidation on the electrode morphology and cell electrochemical properties is systematically evaluated. An increase in cycle life of NMC622||Si/graphite full‐cells is reported, which grows linearly with the initial amount of Li2C4O4, due to the extra Li+ ions provided by the additive in the first charge. Post mortem investigations of the cathode electrolyte interphase also reveal significant compositional changes and an increased occurrence of carbonates and oxidized carbon species. This study not only demonstrates the advantages of this pre‐lithiation approach but also features potential limitations for its practical application arising from the emerging porosity and gas development during decomposition of the pre‐lithiation additive.

Abstract For next‐generation powering batteries, silicon with high energy density is considered the most promising anode material. However, the low rate performance and limited cycling life of silicon anode confines its commercial application. Porous interface constructed on the silicon‐based anode could provide relatively short electrolyte pathways, high transport rate of both lithium ions and electrons, and more stabilized surfaces, which are considered as one of the effective ways to maintain both high energy density and fast charging ability. Here, with a focus on porous interface construction and highlighting the advantages of surface coating, we aim to point out how porous interface affect the fast charging ability for silicon anode.

Abstract A photonic crystal ring resonator‐based 6 × 6 router has been designed and reported. The router is designed using silicon pillars with a refractive index of 3.47 perforated in the air background of refractive index 1 in a square lattice with a lattice constant of a = 562 nm. The router is designed to operate in the third optical window wavelength which has low loss and most widely used in optical communication systems and networks. Plane‐wave expansion and finite difference time domain method has been used to obtain the bandgap and performance of the designed router, which exhibits acceptable performance such as low insertion loss, low propagation delay, and low crosstalk. These routers will find applications in the photonic integrated circuit that paves a path to all‐optical networks.

Abstract The human brain's neural networks are sparsely connected via tunable and probabilistic synapses, which may be essential for performing energy‐efficient cognitive and intellectual functions. In this sense, the implementation of a flexible neural network with probabilistic synapses is a first step toward realizing the ultimate energy‐efficient computing framework. Here, inspired by the efficient threshold‐tunable and probabilistic rod‐to‐rod bipolar synapses in the human visual system, a 16 × 16 crossbar array comprising the vertical form of gate‐tunable probabilistic SiOx memristive synaptic barristor utilizing the Si/graphene heterojunction is designed and fabricated. Controllable stochastic switching dynamics in this array are achieved via various input voltage pulse schemes. In particular, the threshold tunability via electrostatic gating enables the efficient in situ alteration of the probabilistic switching activation (PAct) from 0 to 1.0, and can even modulate the degree of the PAct change. A drop‐connected algorithm based on the PAct is constructed and used to successfully classify the shapes of several fashion items. The suggested approach can decrease the learning energy by up to ≈2,116 times relative to that of the conventional all‐to‐all connected network while exhibiting a high recognition accuracy of ≈93 %.

Purpose: The objective of the present work was to test the feasibility of in vivo imaging of hyperpolarized 50-nm silicon-29 ( 29 Si) nanoparticles., Methods: Commercially available, crystalline 50-nm nanoparticles were hyperpolarized using dynamic polarization transfer via the endogenous silicon oxide-silicon defects without the addition of exogenous radicals. Phantom experiments were used to quantify the effect of sample dissolution and various surface coating on T 1 and T 2 relaxation. The in vivo feasibility of detecting hyperpolarized silicon-29 was tested following intraperitoneal, intragastric, or intratumoral injection in mice and compared with the results obtained with previously reported, large, micrometer-size particles. The tissue clearance of SiNPs was quantified in various organs using inductively coupled plasma optical emission spectroscopy., Results: In vivo images obtained after intragastric, intraperitoneal, and intratumoral injection compare favorably between small and large SiNPs. Improved distribution of small SiNPs was observed after intraperitoneal and intragastric injection as compared with micrometer-size SiNPs. Sufficient clearance of nanometer-size SiNPs using ex vivo tissue sample analysis was observed after 14 days following injection, indicating their safe use., Conclusion: In vivo MRI of hyperpolarized small 50-nm SiNPs is feasible with polarization levels and room-temperature relaxation times comparable to large micrometer-size particles., (© 2024 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Abstract Titanium diboride (TiB2) is an extremely hard ceramic which has excellent heat conductivity, oxidation stability, and resistance to mechanical erosion. Broader application of this material is inhibited by economic factors, particularly the cost of densifying a material with a high melting point. In this study, reaction bonded TiB2 (RB‐TiB2) composites are fabricated by the reactive infiltration of molten Si into preforms of TiB2 plus carbon. Microstructure analysis indicates uniform distribution of TiB2 particles in the composites. RB‐TiB2 composites with fine particles show higher flex strength and fracture toughness, while composites with larger particles have higher thermal conductivity, measured to be 120 W/(m K) at room. The coefficient of thermal expansion (CTE) of the composites is insensitive to the particle size and can be controlled in the range of 4.0‐5.2 ppm/K (room temperature). RB‐TiB2 shows the potential to be used for electronics thermal management applications with a combination of matching CTE, good thermal conductivity, high melting point, and attractive mechanical properties.

Abstract To address the issues of large volume change and low conductivity of silicon (Si) materials, carbon coatings have been widely employed as surface protection agent and conductive medium to encapsulate the Si materials, which can improve the electrochemical performance of Si‐based electrodes. There has been a strong demand to gain a deeper understanding of the impact of efficient carbon coating over the lithiation and delithiation process of Si materials. Here, we report the first observation of the extended two‐phase transformation of carbon‐coated Si nanoparticles (Si/C) during electrochemical processes. The Si/C nanoparticles were prepared by sintering Si nanoparticles with polyvinylidene chloride precursor. The Si/C electrode underwent a two‐phase transition during the first 20 cycles at 0.2 C, but started to engage in solid solution reaction when the ordered compact carbon coating began to crack. Under higher current density conditions, the electrode was also found to be involved in solid solution reaction, which, however, was due to the overwhelming demand of kinetic property rather than the breaking of the carbon coating. In comparison, the Si/C composites prepared with sucrose possessed more disordered and porous carbon structures, and presented solid solution reaction throughout the entire cycling process.

Abstract Magnesiothermic reduction has received attention as a method to produce silicon retaining the morphology of the silicon dioxides that serve as the starting materials of the reduction. We performed the reduction of silica glass substrates with magnesium deposited on them under various conditions, including changing the reaction temperature from 500 to 700°C, changing the reaction time from 15 to 420 minutes, and changing the thickness of the deposited magnesium film from 6.6 to 12.1 μm. Crystalline products and their amounts were investigated using X‐ray diffraction. In these reactions, the silica glass substrates were reduced to silicon and/or magnesium silicide depending on the conditions. Under the conditions where the reaction temperature is higher, the reaction time is longer, and the thickness of the magnesium is thinner, silicon was generated more predominantly than magnesium silicide, and vice versa. Under the intermediate conditions, both crystalline silicon and magnesium silicide were generated. Furthermore, it was revealed that the magnesium silicide was rapidly generated within 15 minutes at temperatures higher than 600°C. Then, as the reaction continued, the amount of magnesium silicide gradually decreased, and that of silicon increased. From these results, a two‐step reaction model was proposed: At first, silicon dioxide is reduced to magnesium silicide with the complete consumption of the deposited magnesium; and subsequently, the magnesium silicide reacts with unreacted silicon dioxide and silicon in the intermediate oxidation states to produce silicon. Based on this model, silicon and magnesium silicide were selectively prepared under well‐controlled conditions.

Abstract The Si surface coating by carbon is an appealing strategy to improve both the electronic conductivity and to stabilize the solid electrolyte interphase (SEI). In the present study, the electrochemical performance comparison of three nanocrystalline silicon‐based electrodes confirms the advantage brought by the carbon presence either as coating or in a composite, to improve their performance in Li‐ion batteries (LIBs). To rationalize this behavior, a full study of the electrode/electrolyte interface was achieved through the analysis of the cumulated relative irreversible capacity and the impedance and X‐ray photoelectron spectroscopies measurements. The study highlighted that the carbon coating leads to more efficient and less resistive SEI than that formed on silicon or on the native oxide surface. The pitch carbon matrix offers the same advantages and avoids moreover the isolation of particles. The control of the Si/electrolyte interface has a crucial role in the performance of Si‐based electrodes as negative electrodes for LIB.

Abstract Silicon (Si) has been attracting extensive attention for rechargeable lithium (Li)‐ion batteries due to its high theoretical capacity and low potential vs Li/Li+. However, it remains challenging and problematic to stabilize the Si materials during electrochemical cycling because of the huge volume expansion, which results in losing electric contact and pulverization of Si particles. Consequently, the Si anode materials generally suffer from poor cycling, poor rate performance, and low coulomb efficiency, preventing them from practical applications. Up‐to‐date, there are numerous reports on the engineering of Si anode materials at microscale and nanoscale with significantly improved electrochemical performances. In this review, we will concentrate on various precisely designed protective layers for silicon‐based materials, including carbon layers, inorganic layers, and conductive polymer protective layer. First, we briefly introduced the alloying and failure mechanism of Si as anode materials upon electrochemical reactions. Following that, representative cases have been introduced and summarized to illustrate the purpose and advancement of protective coating layers, for instance, to alleviate pulverization and improve conductivity caused by volume expansion of Si particles during charge/discharge process, and maintain the surface stability of Si particles to form a stable solid‐electrolyte interphase layer. At last, possible strategies on the protective coating layer for stabilizing silicon anode materials that can be applied in the future have been indicated.

Abstract Silicon (Si) is beneficial to plants since it increases photosynthetic efficiency, and alleviates biotic and abiotic stresses. In the most highly weathered and desilicated soils, plant phytoliths make up the reservoir of bioavailable Si. The regular removal of crop residues, however, substantially decreases this pool. Si supply may therefore be required to sustain continuous cropping. Available Si fertilizers are costly and usually poor in soluble Si. Biochar produced from the pyrolysis of phytolith‐rich biomass is thus a promising alternative Si source for plants. Taking into account the challenges of increasing food demand and environmental concerns, we evaluate the global potential of biochar produced from major crop residues and manures in terms of phytogenic Si (PhSi) supply. Crop residues contribute to 80% of the global production of biomass dry matter (8,201 Tg/year) of which 3,137 Tg/year are potentially available after pyrolysis, giving a potential application rate of 1.7 T ha−1 year−1 for highly weathered soils in the tropics. The potential PhSi supply from crop biochar amounts to 102 Tg Si/year. On its own, rice straws produce 57.7 Tg PhSi/year, accounting for 56.6% of the potential annual PhSi production. The Si release from crop biochar depends on inter altere feedstock type, pyrolysis temperature, soil pH, and buffer capacity. Furthermore, the amplitude of plant Si uptake and mineralomass depends on plant species, soil properties, and processes. These factors interact and can exert a decisive influence on the effectiveness of phytolithic biochar in releasing Si into highly weathered soils. We conclude that the use of phytolithic biochar as a Si fertilizer offers undeniable potential to mitigate desilication and to enhance Si ecological services due to soil weathering and biomass removal. This potential must be explored, as well as the conditions for using biochar in the field.

Abstract Increasing the energy density of conventional lithium‐ion batteries (LIBs) is important for satisfying the demands of electric vehicles and advanced electronics. Silicon is considered as one of the most‐promising anodes to replace the traditional graphite anode for the realization of high‐energy LIBs due to its extremely high theoretical capacity, although its severe volume changes during lithiation/delithiation have led to a big challenge for practical application. In contrast, the co‐utilization of Si and graphite has been well recognized as one of the preferred strategies for commercialization in the near future. In this review, we focus on different carbonaceous additives, such as carbon nanotubes, reduced graphene oxide, and pyrolyzed carbon derived from precursors such as pitch, sugars, heteroatom polymers, and so forth, which play an important role in constructing micrometer‐sized hierarchical structures of silicon/graphite/carbon (Si/G/C) composites and tailoring the morphology and surface with good structural stability, good adhesion, high electrical conductivity, high tap density, and good interface chemistry to achieve high capacity and long cycling stability simultaneously. We first discuss the importance and challenge of the co‐utilization of Si and graphite. Then, we carefully review and compare the improved effects of various types of carbonaceous materials and their associated structures on the electrochemical performance of Si/G/C composites. We also review the diverse synthesis techniques and treatment methods, which are also significant factors for optimizing Si/G/C composites. Finally, we provide a pertinent evaluation of these forms of carbon according to their suitability for commercialization. We also make far‐ranging suggestions with regard to the selection of proper carbonaceous materials and the design of Si/G/C composites for further development.

Abstract Agricultural residues, such as straw, offer an opportunity to produce biofuels and chemicals in biorefineries without compromising food production. The ideal “dual‐purpose cultivar” would have high yield of grain and straw. In addition, the straw should be easy to process in a biorefinery: It should have good degradability, high concentration of carbohydrates, and low concentration of ash. Nitrogen (N) is an essential nutrient important for plant growth, crop yield and grain quality. However, N production and application comes with a high cost and high environmental footprint. The N application should consequently be based on an economical optimum. Limited knowledge exists on how N application affects the potential of straw for biorefining, for example, straw yield and quality. This study, conducted over three cropping seasons, investigated the effect of N supply on the biorefining potential and included 14 wheat cultivars and one triticale cultivar. The N supply directly affected the yield of straw and grain. In addition, the protein concentration in grain and straw increased, but the composition of the straw with respect to carbohydrates and lignin was largely unaffected by N supply. The only significant change was a lower silicon concentration at increasing N application rate, which could be beneficial for lignin valorization in biorefineries. Likely due to the negligible changes in cell wall composition, the effect of N application rate on straw degradability was not significant. N application should therefore primarily be optimized with respect to grain quality and overall yield of grain and straw. Differences between cultivars were also minor with respect to their performance in a biorefinery process. From a breeding and agronomic perspective, focus should therefore be put on maximizing the biomass output from the field, that is, selecting the cultivar with highest grain and straw yield and optimizing the application of fertilizer to get optimum N use efficiency.

Abstract Incorporating active materials into metamaterials is expected to yield exciting advancements in the unprecedented versatility of dynamically controlling optical properties, which sheds new light on the future optoelectronics. The exploration of emerging semiconductors into terahertz (THz) meta‐atoms potentially allows achieving ultrafast nanodevices driven by various applications, such as biomedical sensing/imaging, ultrawide‐band communications and security scanners. However, ultrafast optical switching of THz radiation is currently limited to a single level of tuning speed, which is a main hurdle to achieve multifunctionalities. Here, a hybrid metadevice which can realize the pump‐wavelength controlled ultrafast switching response by the functionalization of double photoactive layers is demonstrated experimentally. A whole cycle of electromagnetically induced transparency switching with a half‐recovery state changes from 0.78 ns to 8.8 ps as pump wavelength varies from near infrared to near ultraviolet regions. The observed pump‐color selective switching speed changing from nanosecond scale to picosecond scale is ascribed to the wavelength‐dependent penetration length of Ge and the contrasting defect states between noncrystalline Ge and epitaxial Si layers. It is believed that the schemes regarding pump‐color controllable ultrafast switching behavior introduced here can inspire more innovations across the field of ultrafast photonics and can boost the reconfigurable metamaterial applications.

Marx generator is a voltage boosting device for power pulse compression, in which its capacitors are charged in parallel and discharged in series. To get a higher voltage boost ratio, high-voltage silicon stacks have been applied to substitute the isolated inductances in this study. Experiments with two isolation modes in the Marx generator have been carried out. Experimental results reveal that the high-voltage silicon stacks with the parameters of 50 kV/1 kA used in the Marx generator can increase the voltage step-up ratio to 168.6:1, up from 141:1 and 162.9:1 when isolating inductances and silicon-stacks with parameters of 50 kV/3 kA are applied, respectively. Moreover, the silicon stack-isolating-type Marx generator can almost eliminate the pre-pulse existing on the load if the isolated inductances employed. Therefore, it is crucial to choose appropriate high-voltage silicon stacks as the isolating devices in the Marx generator designed in this study.

Abstract Grazing‐induced changes in plant quality have been suggested to drive the negative delayed density dependence exhibited by many herbivore species, but little field evidence exists to support this hypothesis. We tested a key premise of the hypothesis that reciprocal feedback between vole grazing pressure and the induction of anti‐herbivore silicon defenses in grasses drives observed population cycles in a large‐scale field experiment in northern England. We repeatedly reduced population densities of field voles (Microtus agrestis) on replicated 1‐ha grassland plots at Kielder Forest, northern England, over a period of 1 year. Subsequently, we tested for the impact of past density on vole life history traits in spring, and whether these effects were driven by induced silicon defenses in the voles’ major over‐winter food, the grass Deschampsia caespitosa. After several months of density manipulation, leaf silicon concentrations diverged and averaged 22% lower on sites where vole density had been reduced, but this difference did not persist beyond the period of the density manipulations. There were no significant effects of our density manipulations on vole body mass, spring population growth rate, or mean date for the onset of spring reproduction the following year. These findings show that grazing by field voles does induce increased silicon defenses in grasses at a landscape scale. However, at the vole densities encountered, levels of plant damage appear to be below those needed to induce changes in silicon levels large and persistent enough to affect vole performance, confirming the threshold effects we have previously observed in laboratory‐based studies. Our findings do not support the plant quality hypothesis for observed vole population cycles in northern England, at least over the range of vole densities that now prevail here.

This article presents an integrated design of active phased array for low-altitude detection radar. Integrated design is an important method to realise miniaturisation and low cost. The multifunctional integrated chip technology is used to design the tile-type transmit/receive module. The whole array is divided into subarrays for modularisation. In addition, in order to be integrated with active circuits, a wide-beam and silicon-based antenna is proposed and verified.

This study designs a micro-machined BCB-cavity patch antenna and two types of four-element micro-machined antenna arrays at 100 GHz. The patches are fabricated on Benzocyclobutene (BCB) polymer material. The silicon substrate is selective lateral etched under the patch antenna to fabricate a cavity surrounded by metal and filled with BCB material. The BCB-cavity under patches can reduce the excitation of surface waves and enhance the radiation on performance. A single large BCB-cavity is designed to implement the four-element antenna arrays under the consideration of mutual coupling. The proposed single antenna has a 2.8 GHz impedance bandwidth. At 100 GHz, the simulated maximum gain is 6.7 dBi for the single antenna and 13 dBi for the four-element antenna arrays.

A silicon-based phased-array transmitter working at 100 GHz is proposed in this study. Planar array ferroelectric film phase shifters (FPSs) are realised with patch antennas, DC bias lines, microstrip lines and power dividers on a monolithic silicon substrate. The system enables full process compatibility and avoids loss caused by multichip interconnection. The isolation layer uses benzocyclobutene polymer film with low permittivity and low loss tangent, providing large thickness physical isolation. The FPS has a compact length of 0.45 mm, and simulation results show that its phase shift degree at 100 GHz is 125.7° with 3.95 dB insertion loss and 11.4 dB reflection loss. The patch antenna shows that the maximum simulated radiation gain of the single antenna is 4 dBi and the four-element antenna array is 9.7 dBi at 100 GHz. The beam can be steered to ±10°. The proposed system lays an important foundation for the realisation of silicon-based system-on-chip radar RF front-end system.

The interest in hybrid electric aircraft has invigorated research into superconducting power networks and superconducting electrical machines. Underpinning this is the ability to control the flow of electrical current at cryogenic temperatures, using power electronic devices. The authors have, for the first time, directly compared the performance of technologically relevant semiconductor materials for the realisation of high-performance cryogenic power devices using a bulk resistivity model. By validating the model using both computational and experimental results, the performance of technologically relevant semiconductors has been calculated down to a temperature of 20 K where the freeze out of dopants is shown to be the major limiting factor in determining the performance of power electronic devices. Both Ge and GaAs are predicted to have a superior conductivity in comparison to the industrial standards Si and 4H-SiC due to greater carrier mobilities and lower dopant ionisation energies.

The clamping force is the most important parameter of Press Pack IGBTs (PP IGBTs) as it not only affects the electrical, thermal, and mechanical characteristic, but also the long lifetime reliability. Too little clamping force increases the contact resistance and junction temperature. Too much clamping force makes the silicon chips mechanical damage. However, it is quite complex and time-consuming to obtain the influence of the clamping force on the long-time reliability through the power cycling test because that many tests are needed to execute under a large range of clamping forces. Here, a single IGBT chip sub-module is proposed to simulate the long lifetime reliability through the finite element method under various clamping forces. Both the thermal contact resistance within different contact interfaces that affects the junction temperature of silicon chips a lot and the elastic-plastic model that affects the lifetime of specific material layers are considered in this finite element model to make it more accurate. The combination of Coffin–Mason and Basquin model is proposed to obtain the power cycling lifetime of the sub-module based on simulation results. A clamping force range is obtained and this also gives a guideline for the power cycling test.

A kind of silicon-and-boron-modified phenolic–formaldehyde resin (SBPF) with excellent thermal stability was fabricated via a simple two-step method and used for the matrix of ablation materials. The structure and thermal stability of the modified phenolic–formaldehyde resins (PFs) were characterised. The results showed that boron and silicon elements have been incorporated into SBPF in the form of a chemical bond. Meanwhile, the cured products showed an increase in graphite structure and a decrease in disordered structure due to the incorporation of boron and silicon. Compared with the ordinary phenolic resin, the initial thermal degradation temperature and charring yield at 800°C of SBPF increased by 73°C and 15 wt%, respectively. Further, the modified PFs, nano-Al(2)O(3) powders, glass powders and vitreous silica fibres were used to obtain a novel ceramizable phenolic moulding composite. The morphology, chemical composition and ablative characteristics of the composites were explored. The results showed that a compact and homogeneous SiO(2)–Al(2)O(3) layer formed on the ablated surface and protected the carbonised matrix and fibres from further oxidation. Compared with the ordinary PF composites, the SBPF composites showed a highly decreased linear/mass ablation rates, indicating the synergistic effect of boron and silicon modification on the enhanced ablation property.