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This paper presents a numerical analysis of various sensing features of a hollow-core photonic crystal fiber-based milk sensor in the terahertz (THz) frequency range (e.g., 1.0 THz ≤ f ≤ 3.0 THz). The performance of this proposed sensor was evaluated by COMSOL Multiphysics, a commercial program that uses the finite element approach. The computational results indicate that the relative sensitivity is 97.984, 97.696, and 97.586% respectively, at f = 2.2 THz, for several types of cow milk, camel milk, and water; and the corresponding effective areas are 187,210, 187,870, 186,170 μm2. In addition, it has been explained that the effective material loss for water, cow, and camel milk is 0.0066172, 0.0066961, and 0.0066991 cm−1, respectively. Moreover, the proposed sensor also has low confinement losses are 1.86 × 10–13, 1.89 × 10–13, 1.891 × 10–13 dB/m a high numerical aperture (0.37), and birefringence is 4.5 × 10–04 under ideal geometry and operational circumstances compared to the previous research work. This sensor may be produced using standard manufacturing techniques, and due to its enhanced detecting capabilities, it can be a crucial part of milk sensing devices implemented in real life such as industry fields related to milk sensing by fabrication using the 3D printing method. [ABSTRACT FROM AUTHOR]

Although it has been shown that using recycled concrete aggregate in new structural concrete is economical and sustainable, the use of this material for such applications is still not widespread. One of the reasons is that manufacturers, designers, engineers, owners, and other market players are not familiar with specifying and utilizing this material—although standards are starting to incorporate provisions for recycled aggregate concrete, successful, practical example projects are needed. The current paper describes the results of a partnership between universities and a precast concrete manufacturer of hollow core slabs. Seven hollow core slabs with volumetric replacement ratios of natural aggregate with recycled aggregate from 0% to 60% were tested to failure in both bending and shear, and then undamaged portions of the slabs were subjected to punching shear until failure. The results showed only mild differences in strength, with different replacement percentages of recycled aggregate under the various loading scenarios. Numerical simulations performed in Abaqus demonstrated the feasibility of analyzing recycled aggregate concrete structural elements and provided important insights into their behavior. [ABSTRACT FROM AUTHOR]

AbstractHollow-core precast prestressed reinforced concrete (HCPPRC) slabs have been widely available since the 1980s in different structures due to many advantages. Since no shear reinforcement is arranged in HCPPRC slabs before casting, concrete itself provides the shear resistance, especially in the zones close to the supports, which are the most popular regions for shear failure. This experimental study aims to investigate some shear strengthening techniques for HCPPRC slabs, including using carbon fiber reinforced polymer (CFRP) sheets, concrete topping, filling 50% of the slab voids in shear zones with concrete, filling all shear zone voids with concrete, steel through anchors in shear zones, and mixing between filling 50% of the slab shear zone voids in addition to using steel anchors. The experimental program consists of two control specimens and six shear-strengthened specimens that were tested using two-line loads up to failure. Cracking load, cracking deflection, ultimate load, maximum deflection, and failure mode are recorded and discussed for all specimens. The results show that filling 50% and 100% of shear voids with concrete increases slab concrete strength by about 79% and 61.45%, respectively, while using steel through anchors decreases slab concrete strength. Moreover, filling 50% of the shear voids is the best technique for strengthening the shear capacity of HCPPRC slabs due to increasing the cross-section area of the slab’s shear strength. In contrast, using screws with nuts only is not preferred for shear strengthening of HCPPRC slabs.

The present study is focused on wall panels exposed to fire, with the construction building elements we used being made of wood and gypsum board materials. This type of configuration forms hollow core wood due to the constructive process. The aim is to present a numerical study to approach the calculation of the temperature inside hollow core wood elements and measure their fire resistance. The temperature evolution inside the cavities will be obtained with recourses to obtain the heat effect by convection and radiation through the wall elements. A numerical model, previously validated by the authors, will be used to carry out this process. The methodology includes the use of the finite element method in thermal and transient analysis with nonlinear materials to calculate temperature. To measure the fire resistance of the constructive model, the thermal insulation criterion, defined by the EN 1363-1:2020 standard, will be applied. Different results will be presented to discuss and ensure the verification of these fire-resistant elements. [ABSTRACT FROM AUTHOR]

In the present study, a photonic crystal fiber with a simple design and low losses in the range of terahertz broadband pulse was designed. The proposed structure of this study consisted of a large central air core arranged by three rings of air holes in a regular hexagonal pattern in a uniform Teflon matrix. The refractive index of Teflon, which was made of polymer, was 1.44. The conduction in this fiber was achieved using photonic band gap (PBG) only for a certain range of non-zero values. The simulation results showed that at the wavelength of 174 µm with a central hole diameter of 2.9Ʌ (Ʌ = 300 µm), the lowest confinement losses equal to 0.2 dB/m occurred and the dispersion parameter was 1.2 ps/nm km. [ABSTRACT FROM AUTHOR]

The present study is focused on wall panels exposed to fire, with the construction building elements we used being made of wood and gypsum board materials. This type of configuration forms hollow core wood due to the constructive process. The aim is to present a numerical study to approach the calculation of the temperature inside hollow core wood elements and measure their fire resistance. The temperature evolution inside the cavities will be obtained with recourses to obtain the heat effect by convection and radiation through the wall elements. A numerical model, previously validated by the authors, will be used to carry out this process. The methodology includes the use of the finite element method in thermal and transient analysis with nonlinear materials to calculate temperature. To measure the fire resistance of the constructive model, the thermal insulation criterion, defined by the EN 1363-1:2020 standard, will be applied. Different results will be presented to discuss and ensure the verification of these fire-resistant elements.

The hollow-core fiber-based sensor has garnered high interest due to its simple structure and low transmission loss. A new hollow-core negative-curvature fiber (HC-NCF) sensor based on the surface plasmon resonance (SPR) technique is proposed in this work. The cladding region is composed of six circular silica tubes and two elliptical silica tubes to reduce fabrication complexity. Chemically stable gold is used as a plasmonic material on the inner wall of the sensor structure to induce the SPR effect. The proposed sensor detects a minor variation in the refractive indices (RIs) of the analyte placed in the hollow core. Numerical investigations are carried out using the finite element method (FEM). Through the optimization of structural parameters, the maximum wavelength sensitivity of 6000 nm/RIU and the highest resolution of 2.5 × 10−5 RIU are achieved in the RI range of 1.31 to 1.36. In addition, an improved figure of merit (FOM) of 2000 RIU−1 for Y-polarization and 857.1 RIU−1 for X-polarization is obtained. Because of its simple structure, high sensitivity, high FOM, and low transmission loss, the proposed sensor can be used as a temperature sensor, a chemical sensor, and a biosensor. [ABSTRACT FROM AUTHOR]

The construction industry has been broadly developed and improved over the last decades. One of the functional innovations in this sector is the employment of steel fibers. This work assesses the impacts of using Steel Fiber Reinforced Concrete (SFRC) on the properties of hollow-core slabs. The hollow core slab (HCS) is considered in this research. Also, this study explored the influence of utilizing some SFRC fractions on the characteristics of hollow-core slabs. Four case studies were addressed, including (A) Conventional concrete, (B) Concrete with Type 1 SFRC, (C) Concrete with Type 2 of SFRC with a ratio of 0.5%, and (D) Concrete with Type 2 with a portion of 1%. ANSYS software package was used to guide numerical analysis and modeling of HCS and identify major parameters that affect the HCS performance with the help of Finite Element Analysis (FEA). Depending on the numerical results, it was found that using SFRC between 0.5% and 1% in concrete tubes tested numerically provided significant rates of durability, minimized deflection, and enhanced the mechanical behavior of concrete. Furthermore, the work outcomes confirmed that optimum displacement was attained when the SFRC ratio was 1.5%, corresponding to load values of 25 kN to 200 kN. Besides, the findings affirmed that using the first type of SFRC accomplished a considerable decline in the deflection of concrete. Deflection reduction ratios of 4.16% and 6.23% were obtained after adding the first and second types of SFRC into the reinforced hollow concrete core, respectively. Meanwhile, adding the first and second types of SFRP into non-reinforced hollow concrete core accomplished a reduction portion of 12.2% and 20.39%, respectively. [ABSTRACT FROM AUTHOR]

This study presents the dependence of strain sensitivity on cavity length in conventional Fabry–Perot (F‐P) sensors. A high number of F‐P sensors were required and to ensure their reproducibility, a manufacturing process was developed to obtain similar sensors but with different types of lengths. A hollow‐core silica tube was used to fabricate several F‐P cavities by fusion splicing it between two sections of SMF28 fiber. The fabricated F‐P has a varying length ranging from 15 to 2500 μm. The cavities were measured under a microscope and the reflected spectrum was acquired for each one. Strain measurements were performed for a maximum strain of 1000 με. The strain sensitivity showed a highly linear correlation with ∆λFSR. Small length variations for short cavities heavily affect the FSR value. The smallest and longest cavities present sensitivities of 8.71 and 2.68 pm/με, respectively. Thermal characterization for low‐ and high‐temperature regimes was also performed and is constant for tested sensors. [ABSTRACT FROM AUTHOR]

Chemicals like acetone, ethanol, hexane, isopropanol, and hexanol are essential components of our daily routines, serving critical functions in various industries and medical settings. Therefore, it is essential to perform thorough examinations to identify any contamination in these substances, which is crucial for preserving their high quality and confirming their appropriateness for different uses. The detection of these chemicals is done using a novel approach utilizing ultra-short pulses passed through Hollow-Core-Photonic Crystal Fiber based sensor. The fiber characteristics including the non-linear and dispersion parameters are used to sense the change in shape of the ultra-short pulse as the pulse travels through the HC-PCF. By implementing this approach, we've attained distinctive levels of compression sensitivity and power upsurge for the samples tailored to each specific input setup. A minimum compression sensitivity has been recorded as 24.5 % when the input power was 600W, resulting in an outstanding power upsurge of 719 W. • Unique Approach for detecting Pure Solvent (Alcohol, Hexanol, Isopropanol etc.) which is computationally efficient and simpler. • Design and Optimization of Hollow core Photonic crystal fiber which is unique in shape. • Minimum compression sensitivity has been recorded as 24.5 % when the input power was 600W, resulting in an output power of 1319.33W and power upsurge of 719W • Wide range of tunability in case of input power, Pulse duration. [ABSTRACT FROM AUTHOR]

Photonic Crystal Fibers (PCF) are flexible in its structural dimensions such as core radius, cladding hole radii and pitch. This flexibility permits the researcher to optimize the fiber to its best performance for desirable applications. Therefore, the objective of this paper is to propose an optimized Hollow Core Photonic Crystal Fiber (HCPCF) by investigating the optical parameters of the fiber. In addition to this, the manuscript intends to provide a brief comparative analysis of conventional Single Mode Fiber (SMF) and proposed HCPCF. Major parameters for study are taken as confinement factor, confinement loss, dispersion and birefringence. Based on these optical parameters, efficiency of the design is judged, where all the structural entities are chosen and investigated sequentially. The optimized value for pitch, radius of air-holes of core and cladding region of HCPCF are calculated as 3.8 µm, 18.01 µm and 1.2 µm, respectively. On comparison of HCPCF and conventional SMF, it is observed that the CF for the proposed HCPCF is higher than conventional SMF. On the other hand, confinement loss is lower for the conventional SMF. Thus, it is inferred that this optimized HCPCF can be used for high power small distance communication or sensing based optical applications.

This paper has modelled and numerically analyzed an inimitable hollow-core PCF-based biosensor. The modelled sensor comprises an elementary arrangement of circular holes. This biosensor is specifically designed to detect cow milk and camel milk efficiently. The sensor has been simulated and numerically analyzed in the THz band ranging from 1 to 2 THz. Numerical analysis unfolds multiple optical parameters considered as PCF-based sensors performance indices. The proposed sensor has maintained about 79.26%, 78.82%, and 77.23% relative sensitivity for cow milk, camel milk, and water, respectively, at the optimum point of 1.5 THz. The values of numerical apertures are 0.266, 0.2683, and 0.2768 at the same operating point for the same sequence of analytes. The proposed sensor has also shown negligible effective material and confinement loss. Besides, the use of only circular holes enhances the implementation feasibility of this model practicing the prevailing fabrication strategies.

The hollow-core fiber-based sensor has garnered high interest due to its simple structure and low transmission loss. A new hollow-core negative-curvature fiber (HC-NCF) sensor based on the surface plasmon resonance (SPR) technique is proposed in this work. The cladding region is composed of six circular silica tubes and two elliptical silica tubes to reduce fabrication complexity. Chemically stable gold is used as a plasmonic material on the inner wall of the sensor structure to induce the SPR effect. The proposed sensor detects a minor variation in the refractive indices (RIs) of the analyte placed in the hollow core. Numerical investigations are carried out using the finite element method (FEM). Through the optimization of structural parameters, the maximum wavelength sensitivity of 6000 nm/RIU and the highest resolution of 2.5 × 10−5 RIU are achieved in the RI range of 1.31 to 1.36. In addition, an improved figure of merit (FOM) of 2000 RIU−1 for Y-polarization and 857.1 RIU−1 for X-polarization is obtained. Because of its simple structure, high sensitivity, high FOM, and low transmission loss, the proposed sensor can be used as a temperature sensor, a chemical sensor, and a biosensor.

In this article, an antiresonant nodeless hollow core fiber having nested hybrid cladding elements is proposed without having large distance between core and jacket capillary. The presented anisotropic construction (elliptical nesting in circular tube) with optimized curvature factor, strut thickness, and gap between adjacent tubes lead to extremely low loss over wide band compared to existing structures (circular, circular nested, elliptical, elliptical nested). The results show the lowest confinement loss of 0.0007 dB/km at 1.06 $\mu$ m with maintaining a loss of less than 0.003 dB/km over 670 nm (0.90 $\mu$ m to 1.57 $\mu$ m) bandwidth. In addition, the lowest surface scattering loss of 0.01 dB/km is achieved along with better bending stability and effective single mode operation. The proposed fiber may have potential opportunity in optical communication systems for its low-loss transmission over wideband region. [ABSTRACT FROM AUTHOR]

In this manuscript, a squared hollow-core photonic crystal fiber-sensor is introduced, which can be used for efficient amino acid investigations using THz waves. Amino acid identification is crucial in medical science, particularly in the drug discovery. The performance analysis has been conducted using the finite element method (FEM) based the COMSOL MULTIPHYSICS software package, and important waveguide properties have been assessed elaborately for five essential amino acids in a wide range of THz frequencies at different core dimensions. The analysis shows that the proposed model exhibits an extraordinarily high sensitivity of 99.98% and remarkably low confinement loss of 4.72 × 10–22 cm−1 for tryptophan, the rarest of the essential amino acids found in proteins. The excellent sensing capabilities are achieved by introducing two hollow square air cavities surrounded by four rectangular air channels in the cladding. The fabrication of the sensor is achievable using the extrusion technique with 3D printing, which is also discussed in detail. [ABSTRACT FROM AUTHOR]

Hollow-core concrete columns are widely used as structural members to reduce the cost and self-weight of concrete structures. This study investigates the axial load–axial deformation behavior of glass fiber-reinforced polymer (GFRP) bar- and helix-reinforced hollow-core circular concrete columns. Four specimens of 214-mm outer diameter and 56-mm circular inner hole diameter with a height of 850 mm were tested under axial compression. One specimen was reinforced with steel bars and steel helices, and the remaining three specimens were reinforced with GFRP bars and GFRP helices. It was found that, for a similar amount of longitudinal and transverse reinforcements, the GFRP bar-reinforced specimen achieved 15% and 4% higher effectiveness of confinement reinforcement and ductility, respectively, than the steel bar-reinforced specimen. The effectiveness of confinement reinforcement and ductility of the GFRP bar-reinforced specimen was higher for the smaller pitch of GFRP helices. The GFRP bar-reinforced specimen with helices of 30 mm pitch achieved 46% and 66% higher effectiveness of confinement reinforcement and ductility, respectively, than the GFRP bar-reinforced specimen with helices of 90 mm pitch. [ABSTRACT FROM AUTHOR]

This article numerically offers and analyses a hollow core circular shaped photonic crystal fiber-based surface plasmon resonance (CH-PCF-SPR) biosensor. The biosensor sensitivity is analyzed with applying a mode solver built finite element method (FEM) incorporating multi-physics software “COMSOL”. A nano film of silver is coated as sensing layer on the external surface for easy sensing and more practical realization. The biosensor unveils the highest wavelength sensitivity valued 21000 nm/RIU and amplitude sensitivity valued 2456 RIU−1, and corresponding wavelength resolution of 4.76 × 10−6 RIU and amplitude resolution of 4.07 × 10−6 RIU, respectively, using wavelength interrogation technique (WIT) and technique of amplitude interrogation (AIT), in detecting effective refractive index range 1.33 RIU and 1.42 RIU. Besides, the consequence of changing structural parameters like – pitch, diameter of air hole, various plasmonic metals and silver (Ag) layer thickness are also resulted in results section. The sensitivity of the offered sensor is analyzed to examine the means of spectral loss depth, resolution and amplitude sensitivity. In arrears to the modest scheme, highly sensitive and resolution nature, the offered design can be precisely applied in detection of bio molecular analytes

In this article, a kind of conical cup-stacked carbon nanotubes (CSCNTs) grown by the microwave irradiation of the mixture of ferrocene and carbon black nanoparticles is reported. They are characterized by the long-cone shape, the nearly unchanged wall thickness and the huge hollow core. SEM and TEM analyses reveal that they are formed by the stacking of the truncated conical graphene layers precipitated from the surfaces of catalysts. The motions and coalescences of catalysts result in the increase of catalyst size during reaction. At the same time, the inner diameter of the truncated conical graphite layer precipitated from the surface of catalyst can increase with the catalyst size continuously. As a result, the as-grown CSCNTs have the conical hollow core and almost unchanged wall thickness. To the best of our knowledge, this kind of conical CSCNTs has been reported for the first time. [ABSTRACT FROM AUTHOR]

In this work, we report an efficient method to produce pure hollow silica spheres (HSS) using phenyltrimethoxysilane (PTMS) compound. The production of HSS was carried out via hydrolysis of PTMS in the aqueous media and followed by a condensation reaction to form silica spheres with phenyl groups. The product was then calcined to remove phenyl groups and obtain pure silica spheres with >95% fine structure. The chemical nature of pure silica was confirmed by Fourier transforms infrared spectroscopy. The calcined HSS were stable beyond the temperature of 900 °C as confirmed by thermal gravimetric analysis (TGA). The calcined spheres preserved their spherical appearance and hollow core as shown by SEM and TEM micrographs. Interestingly, the average size of the spheres was reduced significantly after calcination from 760 to 510 nm, confirming further the removal of phenyl groups. The calcined HSS offered much higher surface area (A s) when analysed by BET; A s for calcined product was ∼406 and mere ∼4.8 m2/g for uncalcined HSS. Finally, drug release study of cisplatin/HSS showed over 45% of steady cumulative release for 72 h. The prepared HSS can be dispersed in water opening the possibility of many novel bio/non-bio applications. [ABSTRACT FROM AUTHOR]

Lightweight sandwich composites mainly utilize hollow textile preforms as their reinforcement. The production of such structures with desired mechanical properties requires monitoring of its repeat unit weight and fibre volume fraction (FVF) from designing stage itself. In this work, mathematical expressions have been developed using fabric geometrical parameters which can calculate the areal density and FVF of a repeat unit of 3D hollow woven structures. Five samples each of trapezoidal and rectangular spacer configurations were produced with different cell structural parameters and materials to validate the model. It was found that the computed results for both the weight and FVF were in good correlation with experimental results, with prediction accuracy being more than 90% in all cases. It was also found that with increase in the cell dimensions, the FVF of the expanded fabric decreases. [ABSTRACT FROM AUTHOR]

This research dealt with the linear elastic behavior of hollow core slabs resting on a linear Winkler type foundation. A finite difference method was used to model the slabs as wide beams and the foundation as elastic springs. The finite element method was also used to model the problem using ABAQUS 6.10 software program. A comparison between the method proposed in this paper and methods from previous studies was made to check the accuracy of the solutions. Several important parameters were incorporated in the analysis, viz. the hollow core size and shape, subgrade reaction and slab depth, to trace their effects on deflections, bending moments and shear forces. A computer program coded in Fortran was developed for the analysis of hollow core slabs on an elastic foundation. It was found that the maximum difference in deflection between the present study and the exact solution was 3% for the finite difference and 7% for the finite element method. [ABSTRACT FROM AUTHOR]

Highlights • We present a novel hollow-core fiber, guide light in subwavelength-diameter holes. • The propagation mechanism of low-index hole is studied by evanescent field coupling. • Properties of high birefringence, two-zero dispersion in hollow fiber are obtained. • They have characteristics of solid fibers and can be applied as hollow fibers. Abstract We present a novel hybrid hollow-core photonic crystal fiber, which can confine and guide light in subwavelength-diameter air holes of core. The propagation mechanism of low-refractive-index hole is studied by evanescent field coupling and electromagnetic theory of optical waveguide transmission. The unique transmission characteristics in the novel fiber with new propagation mechanism are shown. The evanescent-field power fraction in the core holes can be changed flexibly between 10% and 50%. The confinement loss is very low in the broadband wavelength range 1–1.8 μm, which is not limited by surface modes and photonic bandgap effect appearing in hollow-core photonic bandgap fibers. The excellent characteristics of matching mode area, high birefringence, single polarization and single mode in hollow-core fiber are obtained. The two-zero dispersion, broadband flattened dispersion and dispersion compensation properties of hollow-core fiber are also presented. The novel hybrid photonic crystal fiber has the characteristics of solid core fibers and is suitable for the application as hollow core fibers. [ABSTRACT FROM AUTHOR]

A terahertz sensor based on a hollow core photonic crystal fiber has been proposed in this paper for chemical analyte detection in the terahertz frequency range. The Zeonex-based asymmetrical hollow core is filled with an analyte and surrounded by a number of asymmetrical rectangular air holes bounded by a perfectly matched layer with absorbing boundary conditions. The performance of the proposed sensor is numerically investigated by using finite element method-based COMSOL software. It is found that a hollow core provides a high relative sensitivity as well as low transmission loss. Moreover, simplicity in design facilitates manufacturability, making it practical for a number of different biological and industrial applications. [ABSTRACT FROM AUTHOR]

In some novel warheads, the explosive charge is not compactly filled within the cylindrical casing but has a hollow core instead. However, most existing formulas can only predict the fragment velocity of warheads fully filled with explosive charge. In this work, through theoretical analysis and numerical simulations, a new formula was proposed to predict the initial fragment velocity of novel warheads with hollow core. The formula was built on top of the Gurney formula and made use of a correctional function to account for the effects of the rarefaction wave from the hollow core of the explosive charge on the fragment velocity. The formula showed good agreement with the experimental results in the validation tests. Hence, the proposed formula is suitable for predicting the initial fragment velocity of warheads with hollow core. [ABSTRACT FROM AUTHOR]