Nested Tubes Research Articles

“Machine micro/nano optics scientist”: Application and development of artificial intelligence in micro/nano optical design

Micro/nano optical materials and devices are the key to many optical fields such as optical communication, optical sensing, biophotonics, laser, and quantum optics, etc. At present, the design of micro/nano optics mainly relies on the numerical methods such as Finite-difference time-domain (FDTD), Finite element method (FEM) and Finite difference method (FDM). These methods bottleneck the current micro/nano optical design because of their dependence on computational resources, low innovation efficiency, and difficulties in obtaining global optimal design. Artificial intelligence (AI) has brought a new paradigm of scientific research: AI for Science, which has been successfully applied to chemistry, materials science, quantum mechanics, and particle physics. In the area of micro/nano design AI has been applied to the design research of chiral materials, power dividers, microstructured optical fibers, photonic crystal fibers, chalcogenide solar cells, plasma waveguides, etc. According to the characteristics of the micro/nano optical design objects, the datasets can be constructed in the form of parameter vectors for complex micro/nano optical designs such as hollow core anti-resonant fibers with multi-layer nested tubes, and in the form of images for simple micro/nano optical designs such as 3dB couplers. The constructed datasets are trained with artificial neural network, deep neural network and convolutional neural net algorithms to fulfill the regression or classification tasks for performance prediction or inverse design of micro/nano optics. The constructed AI models are optimized by adjusting the performance evaluation metrics such as mean square error, mean absolute error, and binary cross entropy. In this paper, the application of AI in micro/nano optics design is reviewed, the application methods of AI in micro/nano optics are summarized, and the difficulties and future development trends of AI in micro/nano optics research are analyzed and prospected.

DNA metabarcoding identifies urban foraging patterns of oligolectic and polylectic cavity-nesting bees

Urbanisation modifies natural landscapes resulting in built-up space that is covered by buildings or hard surfaces and managed green spaces that often substitute native plant species with exotics. Some native bee species have been able to adapt to urban environments, foraging and reproducing in these highly modified areas. However, little is known on how the foraging ecology of native bees is affected by urbanised environments, and whether impacts vary among species with different degrees of specialisation for pollen collection. Here, we aim to investigate the responses of native bee foraging behaviour to urbanisation, using DNA metabarcoding to identify the resources within nesting tubes. We targeted oligolectic (specialist) and polylectic (generalist) cavity-nesting bee species in residential gardens and remnant bushland habitats. We were able to identify 40 families, 50 genera, and 23 species of plants, including exotic species, from the contents of nesting tubes. Oligolectic bee species had higher diversity of plant pollen in their nesting tubes in residential gardens compared to bushland habitats, along with significantly different forage composition between the two habitats. This result implies a greater degree of forage flexibility for oligolectic bee species than previously thought. In contrast, the diversity and composition of plant forage in polylectic bee nesting tubes did not vary between the two habitat types. Our results suggest a complex response of cavity-nesting bees to urbanisation and support the need for additional research to understand how the shifts in foraging resources impact overall bee health.

Stem-nesting Hymenoptera in Irish farmland: empirical evaluation of artificial trap nests as tools for fundamental research and pollinator conservation

Insect pollinators are suffering global declines, necessitating the evaluation and development of methods for long-term monitoring and applied field research. Accordingly, this study evaluated the use of trap nests (“bee hotels”) as tools for investigating the ecology of cavity nesting Hymenoptera within Irish agricultural landscapes. Three trap nests consisting of 110 mm diameter plastic pipe containing 100 cardboard nest tubes of varying diameter were placed at eight apple orchards and eight oilseed rape sites and left in the field for five months. Sealed nest tubes occurred at 15 of the 16 sites, and in 77% of the 48 nests. However, only 7% of the 4800 individual nest tubes were sealed, and only 4% produced cavity-nesting Hymenoptera. Three cavity nesting bee species (Hylaeus communis, Osmia bicornis, Megachile versicolor) and two solitary wasp species (Ancistrocerus trifasciatus, A. parietinus) emerged from nest tubes. There were significant differences among species in terms of emergence date and the diameter of nest tubes from which they emerged, the latter allowing the calculation of niche width and niche overlap, and informing choice of tube size in future studies/conservation efforts. Trap nests, therefore, offer a valuable tool for fundamental ecological research and a model system for investigating interactions between stem-nesting species within their wider ecological networks. The ability of trap nests to actually increase farmland pollinator abundance and diversity as part of agri-environment schemes requires additional investigation. However, used in sufficient numbers, these trap nests provide valuable biogeographical data for cavity nesting Hymenoptera and offer a viable means for long term monitoring of these species in Irish farmland.

Hazel dormouse in managed woodland select for young, dense, and species-rich tree stands

In fragmented forest landscapes, population persistence of arboreal species with limited dispersal ability may strongly depend on the quality of the remaining forest habitat. Using the hazel dormouse (Muscardinus avellanarius) as a model species, we studied habitat selection at two spatial scales (home range and within home range) in intensely managed woodlands at its northern distributional range in Denmark. We modelled selection at home range level as the conditional probability of occupancy of 588 nest boxes and nest tubes in 15 managed forests relative to habitat variables measured within 25 m radius. Habitat selection within home ranges was modelled by comparing habitat variables within 3 m radius of triangulated locations by 19 radio-tracked individuals (12 M, 7 F) when active at night with regularly distributed available locations within their home ranges.At both spatial scales, hazel dormice strongly selected sites with high abundance-weighted species richness and high vegetation density of woody plants. On home range level, they furthermore selected for young tree vegetation, while they within home ranges selected for intermediate aged tree stands (maximum trunk circumference: 1.50 m). The predicted probability of presence in nest boxes or nest tubes varied from less than 1% to more than 99% as a combined function of three habitat variables. From May to October, selection for abundance-weighted species richness of woody plants of radio-tagged individuals decreased with date and body weight, suggesting that a diverse food base is particularly important early in their season of activity and for lean and small (growing) individuals. Selection for dense vegetation increased with body mass and mean available vegetation density within home ranges, indicating behavioural variability related to changes in energy expenditure and need for safety among individuals.The study demonstrates that the hazel dormouse has specific habitat requirements related to food and safety that can be accommodated with relatively simple means in managed forests.

Low bending loss few-mode hollow-core anti-resonant fiber with glass-sheet conjoined nested tubes.

A novel hollow-core anti-resonant fiber (HC-ARF) with glass-sheet conjoined nested tubes that supports five core modes of LP01-LP31 with low mode couplings, large differential group delays (DGDs), and low bending losses (BLs) is proposed. A novel cladding structure with glass-sheet conjoined nested tubes (CNT) is induced for the proposed HC-ARF which can suppress mode couplings between the LP01-LP31 modes and the cladding modes. The higher-order modes (HOMs) which are LP11-LP31 modes also have very low loss by optimizing the radius of the nested tube and the core radius. Moreover, the large effective refractive index differences Δneff between HOMs are all larger than 1 × 10-4 which contributes to a large DGD in the wavelength range from 1.3 to 1.7 µm. The bending loss of the HC-ARF is analyzed and optimized emphatically. Our calculation results show that bending losses of LP01-LP31 modes are all lower than 3.0 × 10-4 dB/m in the wavelength range from 1.4 to 1.61 µm even when the fiber bending radius of the HC-ARF is 6 cm.

Ultralow loss hollow-core negative curvature fibers with nested elliptical antiresonance tubes.

Hollow-core negative curvature fibers can confine light within air core and have small nonlinearity and dispersion and high damage threshold, thereby attracting a great deal of interest in the field of hollow core fibers. However, reducing the loss of hollow-core negative curvature fibers is a serious problem. On this basis, three new types of fibers with different nested tube structures are proposed in the near-infrared spectral regions and compared in detail with a previously proposed hollow-core negative curvature fiber. We used finite-element method for numerical simulation studies of their transmission loss, bending loss, and single-mode performance, and then the transmission performance of various structural fibers is compared. We found that the nested elliptical antiresonant fiber 1 has better transmission performance than that of the three other types of fibers in the spectral range of 0.72-1.6 µm. Results show that the confinement loss of the LP01 mode is as low as 6.45×10-6 dB/km at λ = 1.06 µm. To the best of our knowledge, the record low level of confinement loss of hollow-core antiresonant fibers with nested tube structures was created. In addition, the nested elliptical antiresonant fiber 1 has better bending resistance, and its bending loss was below 2.99×10-2 dB/km at 5 cm bending radius.

Leafcutter Bees (Hymenoptera: Megachilidae) as Pollinators of Pigeon Pea (Cajanus cajan (L.) Millsp., Fabaceae): Artificial Trap Nests as a strategy for their conservation

Solitary bees of the family Megachilidae are the key pollinators of pigeon pea. Artificial trap nests were used to study nesting parameters, such as occupancy rate, nest establishment time, and building pattern during the vegetative and flowering stages of the Cajanus cajan (Fabaceae). The installed traps were occupied by three different leafcutter bees (Megachile lanata, M. laticeps, M. disjuncta) and one parasitic bee Coelioxys sp. Bees occupied the nest tubes for 16.01 ± 2.82 and 10.23 ± 2.30 days in the vegetative and flowering stages. We recorded 38.33 and 72.50% trap occupancy rates during crop vegetative and flowering stages, respectively. The percent parasitization by Melittobia sp was significantly higher during the vegetative stage (53.67%). Brood cells were parasitized by Coelioxys sp (6.67%) during the flowering stage. Many female bees tend to occupy trap nests with active nest construction during the flowering stage (7.21 ± 2.28 bees). In contrast, male bees merely took shelter inside the traps during the vegetative stage. Thus, it is concluded that female bees possess more wing wear during the vegetative stage of the crop when compared to the flowering stage. We also observed a significant increase in the percent pod set, the number of seeds per pod, and 100 seed weight in the experimental plot compared to the control plot, proving the importance of leafcutter bees for the pollination of Cajanus cajan crop. The present study results confirmed the role of artificial trap nests in providing habitats for the solitary leafcutter bees, thereby increasing their activity and nest abundance, which favors the pollination and better yield in pigeon pea.

Detecting Hazel Dormice in the UK: what are we missing?

Multiple techniques can be used to detect the presence of Hazel Dormice and as a result, there is reasonable confidence that lack of detection means that dormice are probably absent. In the UK, ancient woodlands are frequently considered as the reservoir of Hazel Dormouse populations and are a usual starting point for surveys. However, we present evidence that this may be one of the most difficult habitats in which to detect the species. This is largely due to many of these woodlands being unmanaged, with a poorly developed shrub layer due to heavy shading. This reduces the probability of finding natural field signs such as nests and chewed hazel nuts. Similarly, because detection devices (nest boxes, nest tubes and footprint tunnels) are typically positioned no more than two metres from the ground for ease of study, there is an assumption that Hazel Dormice will leave the dense canopy to use them. We predict that there is a higher risk of false negatives in this habitat type and that more research is needed to provide better certainty of detection when surveying in high canopy woodland.

The battle about the box: competition as the main factor behind the choice for resting sites of hazel dormice

Abstract Nest boxes and nest tubes are widely used to survey and monitor hazel dormice (Muscardinus avellanarius). A two-year study was conducted in order to compare the performance of the two devices. In one year hazel dormice clearly preferred nest tubes over nest boxes but preferred nest boxes over nest tubes in the other year. The preference for one or other device was mainly influenced by competition for nest boxes with Apodemus mice, which preferred nest boxes over nest tubes during one year when they were abundant. This has to be considered when comparing performance of methods.

Mechanical properties of a novel nested tube and its application as anti-explosion layer

In order to further improve the energy dissipation capacity of regular circular tube as anti-explosion layer, a novel circular-vein branch nested tube (CVBNT) is proposed based on lotus leaf vein branched structure. The numerical simulation model of CVBNT under lateral quasi-static compression is firstly established and effectively verified. Then, the circular-triangular nested tube system and CVBNT are compared and analyzed from the aspects of response curve, energy absorption capacity and deformation mode. The introduction of the vein branch thin-walled plates affects the deformation mechanism and leads to more plastic hinges, which will greatly improve the energy absorption capacity. The blast mitigation performance of CVBNT as an anti-explosion layer is also studied. Results show that the deformation mechanism of CVBNT under explosion load is very different from that under quasi-static state. CVBNT can effectively alleviate the impact of explosive loads, which further avoids damage to the protected structure. The parametric analysis of structural parameters demonstrate that the reasonable selection of structural parameters is conducive to maximize the energy absorption capacity of CVBNT as an anti-explosion layer. The results of this study will be helpful to design novel thin-walled structure with better explosion resistance performance.

Study on the high birefringence and low confinement loss terahertz fiber based on the combination of double negative curvature and nested claddings

A novel double negative curvature nested fiber structure is designed by adding extra circular cladding tubes to enhance the birefringence and reduce the confinement loss. The fiber structure is composed of eight circular cladding tubes and two semi-elliptical nested tubes. The transmission performances of terahertz fiber, including birefringence, confinement loss, dispersion and effective mode field area, are studied by changing the parameters of cladding tubes. In the frequency range of 1.75–2.6 THz, the broad bandwidth of 850 GHz with high birefringence (above 10−4) can be achieved. The confinement loss of y-polarization mode with the frequency of 2.575 THz can be as low as 0.00231 dB cm−1. The waveguide dispersion coefficient is between ±0.188 ps (THz cm)−1 in the frequency range of 2.0–2.475 THz. The maximum effective mode field area of x-polarization mode is 2.618 × 10−6 m2 at 2.6 THz.

Built from connected nested tubes.

Built from connected nested tubes.

Ultrawide bandwidth dual sakura hollow-core antiresonant fiber polarization beam splitter

A dual sakura hollow-core antiresonant fiber (DSHC-ARF) is proposed for developing an ultrawide-bandwidth polarization beam splitter (PBS). An air gap is introduced into the fiber between dual sakura hollow cores acting as a mode-coupling channel, which determines the implementation of a DSHC-ARF-based PBS. We demonstrate the wavelength dependence of coupling length can be reduced by introducing nested tubes and investigate their impact on single-mode operation further. Through optimizing the fiber, a high-performance PBS based on a 4.42 cm long DSHC-ARF can be obtained with an ultrawide bandwidth of 460 nm ranging from 1400 to 1860 nm, good single-mode operation with a higher-order mode extinction ratio above 100, and a low fundamental mode loss below 0.543 dB.

Multimode Nested Antiresonant Hollow Core Fiber

A novel centro-symmetric nested antiresonant fiber (CNAF) design is proposed and investigated numerically for low-loss, multimode applications. Conventional single tube-lattice and nested antiresonant hollow core fibers (ARHCFs) inherently support multiple core modes, but the higher order modes are more prone to coupling to lossy cladding modes, thereby dissipating power along the length of the fiber. In the proposed CNAF design, coupling of higher order modes to leaky cladding modes is inhibited by bifurcating the airy region of the cladding capillaries with centrosymmetric nested tubes. The designed fiber is shown to support 5 to 9 spatially distinct core mode groups, having confinement loss less than 0.002 dB/m to 0.01 dB/m respectively. We present detailed numerical investigation into the multimode operation of the proposed fiber and its superiority over conventional asymmetric nested tube designs.

Energy absorption behaviour of an aluminium foam-filled circular-triangular nested tube energy absorber under impact loading

A novel aluminium foam-filled circular-triangular nested tube (AFCTNT) energy absorber was developed in this study, and its energy absorption behaviour under impact loading was experimentally and numerically studied. Drop-weight impact tests on the AFCTNT energy absorbers with different volumes of aluminium foam filler were first conducted to obtain their energy absorption parameters, force–displacement responses, and deformation modes. In addition, numerical studies on AFCTNT energy absorbers were also carried out, and the specific energy absorption of nested tubes and aluminium foam were obtained to further reveal their energy absorption performances. Experimental results indicated that the deformation modes of AFCTNT energy absorbers were evidently affected by the volume of aluminium foam filler. Moreover, the energy absorption performances of AFCTNT energy absorbers were found to be significantly improved by filling aluminium foam in terms of higher energy absorption, specific energy absorption, mean crushing force, and crushing force efficiency. Both experimental and numerical results demonstrated that the AFCTNT energy absorber with fully-filled aluminium foam outperformed the other AFCTNT energy absorbers owing to more significant interaction effect between the nested tubes and aluminium foam.

Comparative Analysis of Energy Absorption Capacity of Single and Nested Metal Matrix Composite Tubes Under Quasi-Static Lateral and Axial Loading

In this paper the behavior of nested tube systems under quasi-static compressive loading is investigated. Two nested tube systems with metal matrix composite are subjected to compressive loads so that in the system A the exterior and interior tubes are under axial and lateral loads, respectively but in the system B the exterior and interior tubes are under lateral and axial loads, respectively. Furthermore, these systems behavior are studied numerically. The results show that energy absorption capacity for both of nested tube systems is greater than the sum of energy absorption capacities of two constitutive tubes when loaded individually. Also, it is shown that the absorbed energy for system A is greater than that of system B. In this research the effects of section geometry and the condition of loading (axial or lateral)of thin-walled tubes on energy absorption capacity and the value of the peak load are studied both experimentally and numerically.

Experimental investigation on deformation behavior and energy absorption capability of nested steel tubes under lateral loading

The energy absorption behavior of nested tubes under lateral loading conditions was investigated in this study. Nested tubes are considered as an alternative to energy absorption structures used in many industries including automotive, military, and aerospace. Steel tubes with the same wall thickness and different diameters were used in the experiments. First, experiments of single tubes were carried out, and the deformation behavior of tubes under lateral load was examined in detail. Afterward, experiments were carried out on nested tube samples in which a minimum of 2 and a maximum of 6 tubes were used together in different numbers and sequences. It was seen from the experiments that the best-nested tube configuration in terms of energy absorption capacity was the sample that contains 6 tubes with 1767 J. While this sample absorbed 5% higher energy than the sample with 5 tubes, the specific energy absorption value was calculated to be 10% lower. Additionally, the sample with 6 tubes has a value of 43% in terms of energy efficiency which is 7% lower compared to that of the sample with 5 tubes. It was determined that the sample with 5 tubes yielded the most efficient design when specific energy absorption capability, work effectiveness, and energy efficiency parameters were considered.

Detecting hazel dormice Muscardinus avellanarius with nest tubes and tracking tunnels: maximising the probability of success.

Hazel dormice Muscardinus avellanarius are elusive, arboreal small mammals that are difficult to detect in a systematic manner. The fact that they are willing to construct their nests in artificial sites has led to the use of small plastic nest tubes as the principal survey technique in England and Wales. An alternative method uses tracking tunnels with similar dimensions to nest tubes, where their characteristic footprints can be recorded on suitable media. The results of a recent study are used here to calculate the probability of detection for each survey month using nest tubes and show how this is affected by habitat. We report on further studies of footprint tracking tunnels in areas of high rainfall. We provide guidance on duration of survey depending on the numbers of footprint tunnels deployed as well as suitable approaches to deployment and checking of tunnels. We also report on the effectiveness of commercially available tracking cards which can extend the interval between checks.

Deformation Pattern and Energy Absorption Characteristics of A Four-Tube Nested System Under Lateral and Oblique Loadings

Abstract The present research introduces a new configuration of thin-walled nested tube structure as a possible energy absorber subjected to lateral compression. The nested-tube structures were configured in a system comprising of four tubes arranged in different ways. All the nested systems were quasi-statically compressed in the lateral direction on a universal mechanical tester to obtain their energy absorption characteristics. Two modes of deformation, asymmetric mode referred to as “overlap” and symmetric mode referred to as “side-by-side”, were identified in the four-tubes nested systems. The specific energy absorbed by the inverted four-tubes systems was larger than that of the three-tubes nested systems by 20%. The experiments were also modelled using ABAQUSv6.13. Good correlations were obtained for the deformation modes and the corresponding lateral crush force-displacement. The validated model was thereafter used in parametric study to investigate the effectiveness of the nested system under two different boundary conditions; rotation of the specimen by different angles and impact at different angles.

A pilot study for rapid water clarification by V-shaped nested tubes

A pilot study for rapid water clarification by V-shaped nested tubes