Hollow Core Research Articles

Fiber design and performance analyses for optical multiplexing: terahertz optical communications

Multiplexing is the process of combining multiple signals at a single channel. Orbital Angular Momentum (OAM) is one of the main multiplexing techniques for optical data transmissions. This paper examines and suggests a hollow core with four layers of semilunar air-hole-shaped circular photonic crystal fiber (PCF) capable of transmitting terahertz (THz) OAM information-carrying modes. By using the full vector finite element method (FEM), OAM multiplexing is analyzed for the proposed fiber. All the THz OAM-based factors are analyzed at a frequency band ranging from 400 GHz to 800 GHz. For the first time, some important PCF factors such as effective refractive index difference (ERID), dispersion profile (DP), OAM purity, confinement loss (CL), effective mode area (ERA), and numerical aperture (NA) are quantitatively discussed with applications. The proposed design supports 50 OAM modes with ERID up to 10−3. The PCF has a CL of approximately 10–10 dB cm−1 and the lowest dispersion profile is 0.3581 ps/THz/cm. Furthermore, the OAM purity is around 97%. Nonetheless, the proposed design can be used in THz-OAM transmission and high optical fiber communications.

THE FLEXURAL BEHAVIOR OF SUSTAINABLE LIGHTWEIGHT CONCRETE HOLLOW CORE SLABS

Hollow slabs are reinforced concrete slabs with voids that enable less concrete to be used. To promote sustainability goals, this type of slab reduces material use and enhances insulating characteristics. This paper presents an experimental program for studying the flexural behavior of the sustainable hollow Slab elements of lightweight concrete with three different ratios of mixes using additives to choose the best ratio, which is then compared to a solid model with the same concrete mix with the best characteristics to clarify the variations in the structural behavior of voided slabs. In this investigation, hollow slabs with circular plastic tubes of 50mm diameter and 1020 mm length were used, organized as continuous voids with 30 mm spacing between the tubes. Three slabs were created, each measuring 1020 mm long, 420 mm wide, and 100 mm thick. All three slabs were tested via four-point loading. The best mix ratio was chosen and used to build a robust model. To analyse the key advantages of this technology over typical solid slabs, this solid model was compared to the best-performing model among the three hollow core slabs. Several properties such as load-carrying capability, deflection, crack patterns, and failure modes were observed in all loading steps. The results showed that using uniformly distributed uniaxial voids in the slab reduced concrete use by 23% as compared to solid slabs, Notably, the specimen with 200 kg/m3 lightweight aggregate demonstrated greater crack distribution and crack breadth.

Enhanced oxidative potential and cytotoxicity of high-temperature treated model soot particles due to carbonaceous core oxidation

When diesel soot particles experience high-temperature treatment during exhaust purification aiming to reduce emission, their physicochemical properties and toxicity would change as well. However, rare studies investigated the relationship between properties and health effects of soot under high temperatures. This study compared the physicochemical properties, oxidative potential (OP, dithiothreitol (DTT) method), and cytotoxicity of model diesel soot before and after 300°C and 500°C treatments in air. It was observed that the oxygen-containing functional groups, environmental persistent free radicals, surface area and pore volume increased a lot after the 500°C process, accompanied with the appearance of hollow core and decreased particle size in the images collected by high-resolution transmission electron microscopy, indicating the deep oxidation into carbonaceous core of soot. In addition, the enhancements of OPDTT and cytotoxicity were in accordance with the changes in physicochemical properties. The toxic increment at 500°C was the most due to core oxidation, whether it was compared with 300°C heating or the surface oxidation of light irradiation and ozone aging, implying that carbonaceous core oxidation caused worse health damage. Hence, it is necessary to consider the impact of widely used diesel exhaust treatment involving high temperatures, considering the potential toxicity of the resulting particles.

Hybrid Fabry–Perot interferometer: Polymer-induced microcavity for temperature and gas pressure measurement

Developing new Fabry–Perot interferometer (FPI) with high sensitivity has always been a focus in the field of optical fiber sensing. This work proposed and experimentally demonstrated a novel hybrid-structured FPI based on harmonic Vernier effect and traditional Vernier effect, utilizing a polydimethylsiloxane (PDMS) microcavity. The reference FPI is formed by the hollow core fiber, which is insensitive to temperature and gas pressure change. The sensing element is formed by two parts including a short single-mode fiber (SMF) and a PDMS microcavity. Due to the similar refractive index between the SMF and PDMS microcavity, there is very weak reflection at the interface. Only reflection at the interface between the PDMS microcavity and the air is observed. Additionally, five hybrid FPIs consisting of PDMS microcavity were fabricated and applied for temperature and gas pressure measurement, which exhibited high temperature and gas pressure sensitivities with maximal values of 5.49 nm/°C, and 22.97 nm/MPa, respectively.

Spectral broadening and nonlinear mode coupling in a gas-filled hollow core capillary

Spectral broadening and nonlinear mode coupling in a gas-filled hollow core capillary

Biaxial Hollow Slab Under Seismic Load

In reinforced concrete building structures, the slab is the component with the largest volume of concrete of all the superstructure components. Various innovations were carried out. Currently, the use of Hollow Core Slab (HCS) to reduce the load on building superstructures is widely used in Indonesia. Another type of slab is Biaxial Hollow Slab (BHS) as an alternative to reduce slab concrete volume. BHS is considered capable of reducing concrete consumption by up to 30% -50% of conventional concrete without reducing the performance of the slab itself. It could be reducing the load on the working superstructure can reduce the influence of seismic loads on the foundation. Indonesia is a country with an earthquake zone, so the use of BHS must be considered with seismic design categories that are appropriate to the earthquake zones in Indonesia. This research is focused on giving information about the numerical study of application BHS in 10th story building with design seismic category D. The thickness used in this study is equivalent thickness of BHS to solid slab. The absence of beams in weak axis and the present of perimeter beam by utilization BHS, gives the result BHS has sufficient capacity to carry the workload.

Innovative design of silicon-core mesoporous carbon composite for high performance anode material in advanced lithium-ion batteries

Silicon is widely recognized as an exceptionally auspicious anode material for lithium−ion batteries due to its remarkable specific capacity, suitable operational potential, and ecologically innocuous characteristics. This study presents a novel silicon@void@FC (fibrous carbon) composite anode material for lithium-ion batteries. Utilizing a one-step synthesis approach, the resulting hollow core–shell structure, combined with a mesoporous carbon shell, demonstrates exceptional electrochemical performance. The Si@Void@FC electrode exhibits remarkable cycle stability and rate performance, maintaining structural integrity over 500 cycles without observable degradation. The outer carbon shell acts as a protective layer and accommodates silicon volume expansion during cycling, preventing excessive contact with the electrolyte. The rich mesoporous structure facilitates efficient lithium-ion diffusion, enhancing lithiation and delithiation processes. The simplified one-step synthesis method further streamlines the preparation process, eliminating the need for complete silica template formation. This innovative Si@Void@FC composite material holds promise for advancing lithium-ion battery technology, addressing challenges associated with silicon-based anode materials, and offering insights into the design and synthesis of high-performance energy storage materials.

Effects of selectively thickening core wall on birefringence and loss in polarization-maintaining hollow core photonic bandgap fiber

Effects of selectively thickening core wall on birefringence and loss in polarization-maintaining hollow core photonic bandgap fiber

Anti-resonant hollow core fiber with excellent bending resistance in the visible spectral range

The development of wideband guided hollow-core anti-resonant fiber (HC-ARF) that covers the sensitive range of the human eye's visible spectrum is progressing rapidly. However, achieving low-loss wideband transmission with a small bending radius remains a challenging issue to be addressed. In light of this, we propose a novel, to our knowledge, HC-ARF with a nested double-semi-elliptical cladding structure in the visible spectral region. By employing finite element method simulations, we investigate the confinement loss, bending loss, and single-mode performance of this fiber design. The result shows that the confinement loss of this new fiber exhibits below 10−5 dB·m-1 across almost the entire visible band range, with a minimum loss of 1.55 × 10−7 dB·m-1 achieved for λ = 650 nm. Furthermore, this fiber demonstrates excellent resistance to bending and can maintain an ultra-low bending loss as low as 3 × 10−7 dB·m-1 even under extreme bending conditions with a radius of only 3 cm. Notably, its 3-dB bending radius reaches just 3.5 cm for λ = 532 nm. Additionally, it exhibits outstanding single-mode conductivity under various bending scenarios and achieves a high extinction ratio of up to 104 for higher-order modes after parameter optimization for specific wavelengths.

Design and fabrication of a tellurite hollow-core anti-resonant fiber for mid-infrared applications

The hollow core anti-resonant fibers (HC-ARFs) based on soft glass are in high demand for 3-6 µm laser delivery. A HC-ARF based on tellurite glass with 6 touching capillaries as cladding was designed and fabricated for the first time, to the best of our knowledge. A relatively low loss of 3.75 dB/m at 4.45 µm was realized in it. The effects of capillary number, core diameter, wall thickness of capillary, and material absorption loss on the loss of the HC-ARF were analyzed by the numerically simulation. The output beam quality was measured and the influence of bending on the fiber loss was discussed. The results of numerical simulation suggested that the theoretical loss of the prepared fiber can be reduced to 0.1 dB/m, indicating that tellurite HC-ARFs have great potential for mid-infrared laser applications.

Simulation of heat transport in textiles inspired by polar bear fur

The polar bear and several other Arctic mammals use fur composed of hollow-core fibers to survive in extremely cold environments. Here, we use finite element analysis to elucidate the role that the hollow core plays in regulating thermal transport. Specifically, we establish a three-dimensional model of a textile based on fibers with various core diameters and study transverse heat transport. First, these simulations revealed that textiles based on hollow-core fibers conduct significantly less heat than their solid-core counterparts with fibers with a core-to-fiber diameter ratio of 0.95, reducing thermal transport by 33%. In addition to this decrease in thermal transport, the mass per area of textiles is substantially reduced by making them hollow core. This led us to consider the performance of multi-layer textiles and to find that four-layer hollow-core textiles can exhibit a four-fold decrease in heat flux relative to single-layer solid-core textiles with the same mass per area. Taken together, these simulations show that hollow-core fibers are well suited for thermal insulation applications in which gravimetric thermal insulation is a priority.

Comparative Study of Numerical Methods for Predicting Crack Propagation in Reinforced Concrete Hollow Core Slabs

Hollow core slabs are commonly used in prefabricated building construction and are calculated and constructed using gravity loads. The dead loads of the structure are reduced by using this slab system. Different criteria, such as the initiation and propagation of cracks in the hollow core slab, are used to analyze these slabs. Fracture mechanics is the basis for studying crack propagation. The present study was conducted to analyze the propagation of cracks in hollow core slabs under common loading conditions using the finite element method and numerical modeling to analyze cracks in reinforced concrete members. This research is theoretically conducted using finite element software. This research takes into account the potential varieties of cracks in concrete slabs. Slabs should consider all three types of cracks, which are shear, flexural, and flexural-shear cracks obtained from the reference test. Two Contour integral and XFEM methods are used to analyze cracks in Abaqus software. To validate and control the modeling process, the laboratory results of the research of Ibrahim N. Najma, Raid A. Daudb, and Adel A. Al-Azzawi. December 2, 2019, has been used. The outcomes of this study showed that the probability of the formation of a flexural-shear crack in the slab is higher than in other crack forms.

Unraveling hierarchical hollow NiCo2S4/MXene/N-doped carbon microspheres via dual templates for high-performance hybrid supercapacitors

A multi-step strategy was rationally designed to fabricate hierarchical hollow core–shell microspheres of NiCo2S4MXene/N-doped carbon (NiCo2S4/MXene/NC) using dual templates of the polyethylene microspheres and metal–organic framework material of ZIF-67. The integration of MXene and N-doped carbon significantly enhances the electronic conductivity of electrode, while the construction of hollow spherical structures effectively alleviates the instability of NiCo2S4/NC during the charge–discharge cycles, leading to the excellent charge storage performance with a high specific capacitance (1786 F g−1 at 1 A g–1) and impressive cycling stability (over 100 % capacitance retention after 10,000 cycles). A corresponding hybrid supercapacitor displays a high specific capacitance (190 F g−1 at 1 A g–1) with a maximum energy density (67 Wh kg−1 at 796 W kg−1) and great cycling stability (over 80 % capacitance retention after 10,000 cycles). The charge storage mechanism of NiCo2S4/MXene/NC is elucidated, revealing a combination of pseudocapacitive and battery-like behavior. Density functional theory (DFT) calculations indicate that the participation of MXene significantly increases the state density of NiCo2S4/MXene near the Fermi level compared to NiCo2S4, affirming its superior metallic conductivity. This work provides a facile route only with room-temperature stirring and high-temperature calcination to prepare well-defined metal sulfide composite microstructures with high electrochemical performance.

Hollow core–shell Co@SiO2@PPy composites with efficient electromagnetic wave absorption

In this study, hollow Co@SiO2@PPy composites with excellent electromagnetic wave (EMW) absorption performance were successfully synthesized. The monodisperse hollow Co microspheres were prepared using a solvent-thermal method. The microspheres were then coated with an SiO2 layer by a modified Stöber method. Finally, the SiO2 layer was surface-coated by polypyrrole (PPy) through in-situ polymerization to obtain Co@SiO2@PPy composite materials with hollow core–shell structures. The prepared CSP2 composite achieved a minimum reflection loss (RLmin) of −65.83 dB at 1.86 mm, demonstrating an effective absorption bandwidth (EAB) of 4.84 GHz. The CSP3 composite achieved a widest EAB (EABmax) of 5.4 GHz at a thickness of 1.83 mm, while simultaneously maintaining the RL level at −50.70 dB. Additionally, it demonstrated an RLmin value of −61.66 dB with a thickness as thin as 1.66 mm. The observed shift of FTIR absorption peaks by 20 cm−1 in the PPy ring provides compelling evidence for the involvement of multilayered structures in polarization loss. The SiO2 layer not only enhances the interface polarization but also prevents corrosion of the Co core by acidic solutions. The exceptional EMW absorption characteristics can be attributed to the effective impedance matching and the combined effect of magnetic and dielectric losses.

Improving energy absorption and failure characteristic of additively manufactured lattice structures using hollow and curving techniques

Strut-based lattice structures of various types exhibited a common critical issue, namely, high tensile stress concentration occurred at node-to-strut sites, which often led to lowered energy absorbability as compared to triply periodic minimal surfaces structures. Therefore, this work aimed for improving the Octet-truss structure by a combined technique using hollow core and varying cross-section ratio. Firstly, test specimens were fabricated using a stereo-lithography based additive manufacturing of photopolymer hard resin. Elastic-plastic properties and damage criterion of the used polymer were experimentally determined and applied for finite element models. Validation by compressive tests of lattice samples showed deviations of stress–strain responses less than 12%, in which local deformation and subsequent damages were fairly predicted. Afterwards, finite element simulations of designed lattice structures subjected to compressive, combined shear, shear and tensile loads were performed and obtained stress–strain characteristics including total absorbed energies and deformation behaviors were studied. Under uniaxial compression and combined shear loads, modified Octet-truss structures exhibited considerable increases of energy absorptions up to 173% and 116%, respectively, and stress–strain responses were more stable. On the other hand, by tension mode peak stresses and elongations could be enhanced about 41% and 11%, accordingly. The improved performances of proposed strut-based structures were comparable to those of triply periodic minimal surfaces diamond structure. This was due to that local stress distributions in the structure became more uniform and previously dominated tensile stresses were switched to compressive stresses. Therefore, occurrences of shear bands and plastic hinges could be effectively inhibited.

A Detailed Numerical Model for a New Composite Slim-Floor Slab System.

The paper concerns the numerical modelling of a new slim-floor system with innovative steel-concrete composite beams called "hybrid beams". Hybrid beams consist of a high-strength TT inverted cross-section steel profile and a concrete core made of high-performance concrete and are jointed with prestressed hollow core slabs by infill concrete and tie reinforcement. Such systems are gaining popularity since they allow the integration of the main structural members within the ceiling depth, shorten the execution time, and reduce the use of concrete and steel. A three-dimensional finite element model is proposed with all parts of the system taken into account and detailed geometry reproduction. Advanced constitutive models are adopted for steel and concrete. Special attention is paid to the proper characterisation of interfaces. The new approach to calibration of damaged elastic traction-separation constitutive model for cohesive elements is applied to concrete-to-concrete contact zones. The model is validated with outcomes of experimental field tests and analytical calculations. A satisfactory agreement between different assessment methods is obtained. The model can be used in the development phase of a new construction system, for instance, to plan further experimental campaigns or to calibrate simplified design formulas.

Fuel quality assurance based on hybrid hexagonal circular hollow core PCF sensing through management of terahertz region operation

Fuel quality assurance based on hybrid hexagonal circular hollow core PCF sensing through management of terahertz region operation

Bi2O3/g-C3N4 hollow core–shell Z-scheme heterojunction for photocatalytic uranium extraction

Bi2O3/g-C3N4 hollow core–shell Z-scheme heterojunction for photocatalytic uranium extraction

Surface plasmon resonance temperature sensor based on the conjoined-tube hollow-core anti-resonant fiber with ultra-high temperature sensitivity

A surface plasmon resonance (SPR) temperature sensor based on the conjoined-tube hollow-core anti-resonant fiber (HC-ARF) is designed and analyzed. The conjoined-tube HC-ARF contains two connecting tubes with a cross arrangement in the cladding. The SPR temperature sensor is constructed by inserting a metal into one of the inner layer tubes and injecting a thermo-sensitive liquid into the hollow core of the HC-ARF to enhance the temperature sensitivity by exploiting the SPR effect. The effects of the structural parameters and thermo-sensitive media and metals on the sensing properties such as the temperature sensitivity, peak loss, resolution, amplitude sensitivity, and figure of merit (FOM) are analyzed systematically. Numerical analysis reveals ultra-high temperature sensitivity of 38.8 nm/°C and FOM of 673.84∘C−1, which are approximately 10 times higher than those of sensors described in the recent literature. In addition, the sensor is capable of detecting a wide temperature range from −5∘C to 60°C with good linearity. The SPR temperature sensor with high precision, a wide temperature detection range, a simple and easily modifiable structure, as well as good manufacturing tolerance has large potential in high-precision temperature monitoring in the petrochemical and biomedical industries.

Analysis of semi-molten hollow particle spreading and deformation in plasma spraying

Hollow yttrium-stabilized zirconia (YSZ) particles, which are often used to prepare high porosity coatings in industry, hit substrate at a fully molten state or semi-molten state due to the high temperature gradient of particles caused by the low thermal conductivity. Considering the hollow solid core large deformation and liquid solidification during the deposition of semi-molten hollow particles (SMHPs), a fluid-structure interaction model described by the coupled Eulerian and Lagrangian (CEL) method, is developed and validated to investigate the spreading results in thermal spraying. The empirical formula of dynamic viscosity based on the ABAQUS CEL method is proposed and verified for simulation of the liquid YSZ spreading and solidification. The compression ratio and plastic dissipation are calculated to reveal flattening and buckling phenomena of hollow solid core with different initial velocities and hollow radius. Moreover, a double-SMHP impact model is established to simulate the interaction of particle-particle-substrate, and the effect of flattening, buckling and structural self-contact on porosity is analyzed. Numerical simulation results show that hollow solid core large deformation induces instability accompanied by flattening, buckling or structural self-contact, which results in the reduction of layer porosity.