Absorption Rate Research Articles

Recent Research Progress on Surface Modified Graphite Carbon Nitride Nanocomposites and Their Photocatalytic Applications: An Overview

Semiconductors with visible light catalytic characteristics can realize the degradation of pollutants, CO2 reduction, and hydrogen preparation in sunlight. They have huge application value in the fields of environmental repair and green energy. Graphite phase nitride (g-C3N4, CN) is widely used in various fields such as photocatalytic degradation of pollutants due to its suitable gap width, easy preparation, low cost, fast visible light response, and rich surface activity sites. However, the absorption rate of ordinary CN on visible light is low, and the carriers are easy to recombination, making the lower optical catalytic activity. Therefore, in order to improve the photocatalytic characteristics of the CN, it is necessary to make the surface modification. This article first introduces several main methods for the current surface modification of CN, including size regulation, catalyst embedding, defect introduction, heterostructure construction, etc., and then summarizes the optical catalytic application and related mechanisms of CN. Finally, some challenges and development prospects of CN in preparation and photocatalytic applications are proposed.

Magnetic Nanoparticles with On-Site Azide and Alkyne Functionalized Polymer Coating in a Single Step through a Solvothermal Process.

Background/Objectives: Magnetic Fe3O4 nanoparticles (MNPs) are becoming more important every day. We prepared MNPs in a simple one-step reaction by following the solvothermal method, assisted by azide and alkyne functionalized polyethylene glycol (PEG400) polymers, as well as by PEG6000 and the polyol β-cyclodextrin (βCD), which played a crucial role as electrostatic stabilizers, providing polymeric/polyol coatings around the magnetic cores. Methods: The composition, morphology, and magnetic properties of the nanospheres were analyzed using Transmission Electron and Atomic Force Microscopies (TEM, AFM), Nuclear Magnetic Resonance (NMR), X-ray Diffraction Diffractometry (XRD), Fourier-Transform Infrared Spectroscopy (FT-IR), Matrix-Assisted Laser Desorption/Ionization (MALDI) and Vibrating Sample Magnetometry (VSM). Results: The obtained nanoparticles (@Fe3O4-PEGs and @Fe3O4-βCD) showed diameters between 90 and 250 nm, depending on the polymer used and the Fe3O4·6H2O precursor concentration, typically, 0.13 M at 200 °C and 24 h of reaction. MNPs exhibited superparamagnetism with high saturation mass magnetization at room temperature, reaching values of 59.9 emu/g (@Fe3O4-PEG6000), and no ferromagnetism. Likewise, they showed temperature elevation after applying an alternating magnetic field (AMF), obtaining Specific Absorption Rate (SAR) values of up to 51.87 ± 2.23 W/g for @Fe3O4-PEG6000. Additionally, the formed systems are susceptible to click chemistry, as was demonstrated in the case of the cannabidiol-propargyl derivative (CBD-Pro), which was synthesized and covalently attached to the azide functionalized surface of @Fe3O4-PEG400-N3. Prepared MNPs are highly dispersible in water, PBS, and citrate buffer, remaining in suspension for over 2 weeks, and non-toxic in the T84 human colon cancer cell line, Conclusions: indicating that they are ideal candidates for biomedical applications.

Numerical analysis of multistage ultrasonic atomization enhanced ammonia-water falling film absorption

The absorption refrigeration system is a widely used system that utilizes waste heat and is environmentally friendly. However, many current systems still suffer from challenges such as large volume, and high initial investment. Meanwhile, optimizing the absorber is crucial for enhancing system performance as it is one of the main components. In this study, a novel absorber model is proposed and its influencing factors of performance are comprehensively analyzed. In this model, the traditional falling film absorber is divided into multiple stages, with an ultrasonic atomizer (UA) installed in each stage to enhance absorption. In each stage, falling film and atomization absorption occur simultaneously, and their outputs are combined and weighted at the exit to maintain continuous droplet absorption, effectively utilizing the entire absorber volume. In this process, the vapor–liquid contact area is increased through atomization, and simultaneously, generated heat is removed by the cooling water during mixing. As a result, the absorber’s absorption capacity increases, and the outlet solution temperature decreases. The results demonstrate that compared to the traditional falling film absorber, the proposed absorber, when divided into two stages with a droplet diameter of 50 μm and an atomization rate x = 0.7, shows a 60.64 % increase in ammonia absorbed rate. Additionally, compared to double-stage absorber, triple-stage absorber increases the ammonia absorption by 9.52 %. As the number of stages increased, the strengthening effect persisted, albeit with a gradually diminishing rate of increase. Scaling up to ten stages results in a 152.63 % absorption rate increase and a size optimization of 60.43 %. In this paper, multi-stage ultrasonic atomization is innovatively introduced into the falling film absorber, which enhances ammonia absorption and reduces the volume of the absorber. Additionally, the multi-stage atomization offers an innovative method to improve the droplet absorption process.

Multifunctional plasmonic metamaterial absorber in the middle infrared range for polarization detection

It is significant to enhance the absorption rate, extend bandwidth and obtain the polarization information of electromagnetic radiation for detection technology. Here, we design and propose the simulation model of broadband and highly polarization-sensitive mid-IR metamaterial absorber by regulating the light field with the plasmonic response. The absorber is based on a simple subwavelength metal grating construction. Its absorption response can cover the 3–5 μm infrared atmospheric window. Detection technology in the mid-IR range has a strong ability to detect objects at high temperatures. In this waveband, the maximum absorption rate can reach more than 98% for TM polarization radiation. In comparison, it is less than 2% for TE polarization radiation, and the extinction ratio of 50 is concurrently achieved. The absorption spectrum can be broadened to the high and low-frequency direction by reasonably adding nanostrips in the unit cell. We also investigate the relationship between incident angle and spectral absorption and clarify the absorption stability of the absorber under oblique incidence. By integrating with the infrared focal plane detector, the device can make the infrared photodetector integrate and develop from a single sensor to multi-dimensional information and promote the development of polarization detector to miniaturization, high efficiency and high integration.

Synergistic effect of graphdiyne (C2H2n-2) based hollow spherical Cu2O/GDY and NiS dual cocatalysts boosting photocatalytic hydrogen evolution

The control of carrier separation morphology and efficiency is a key strategy for preparing high-performance photocatalysts. In this study, Cu2O/graphdiyne was introduced into NiS in the form of hollow nanospheres, creating a novel composite material. This method improved upon the traditional graphdiyne fabrication processes that typically use copper foil. Through the hollow spherical structure, both internal and external surface light scattering and reflection were significantly enhanced, indirectly enhancing the light absorption rate of the photocatalyst and photocatalytic activity. Ultraviolet-visible spectroscopy and photoelectrochemical results showed that using NiS as the external cocatalyst and Cu2O as the internal cocatalyst are the driving factors for the hydrogen evolution reaction, with a synergistic effect that accelerated the reaction. Such synergistic catalytic effects are rare in traditional photocatalytic systems, indicating their potential application value in enhancing catalytic efficiency. The overall performance was more than 22 times that of Cu2O/graphdiyne alone and more than 2.6 times that of NiS. Additionally, the electronic band structures and reaction mechanisms can be elucidated through Density Functional Theory (DFT) calculations, Ultraviolet Photoelectron Spectroscopy (UPS) and UV-Vis spectroscopy. These findings not only offer practical guidance but also underscore the significance of precisely manipulating the components of composite catalysts to optimize performance.

Characterization of Humic Acid Salts and Their Use for CO2 Reduction

The European Union aims to be climate neutral by 2050. To achieve this ambitious goal, net greenhouse gas emissions must be reduced by at least 55% by 2030. Post-combustion CO2 capture methods are essential to reduce CO2 emissions from the chemical industry, power generation, and cement plants. To reduce CO2, it must be captured and then stored underground or converted into other valuable products. Apromising alternative for CO2 reduction is the use of humic acid salts (HASs). This work describes a process for the preparation of potassium (HmK) and ammonium (HmA) humic acid salts from oxidized lignite (leonardite). A detailed characterization of the obtained HASs was conducted, including elemental, granulometric, and thermogravimetric analyses, as well as 1H-NMR and IR spectroscopy. Moreover, the CO2 absorption capacity and absorption rate of HASs were experimentally investigated. The results showed that the absorption capacity of the HASs was up to 10.9 g CO2 per kg. The CO2 absorption rate of 30% HmA solution was found to be similar to that of 30% MEA. Additionally, HmA solution demonstrated better efficiency in CO2 absorption than HmK. One of the issues observed during the CO2 absorption was foaming of the solutions, which was more noticeable with HmK.

Optimization of starch foam extrusion through PVA polymerization, moisture content control, and CMCS incorporation for enhanced antibacterial cushioning packaging

Melt strength and moisture content are critical parameters in starch foam extrusion, as they dictate bubble expansion dynamics, which subsequently determine the foam's properties. Despite continuous advancements in the development and application of starch foams, challenges such as water resistance, mechanical strength, and antibacterial activity remain unresolved. This research investigates the influence of polyvinyl alcohol (PVA) polymerization and moisture content on the properties of extruded foam while also exploring the potential for enhancing antimicrobial functionality by incorporating carboxymethyl chitosan (CMCS) into conventional starch foams. The findings underscore the significance of melt strength and intermolecular entanglements in shaping foam characteristics, confirming that bioactive components effectively improve hydrophobicity, foaming characteristics, and antibacterial capabilities. Moreover, by precisely regulating PVA polymerization and moisture content, it became feasible to optimize foam properties and achieve the desired performance. Specifically, foam with a moisture content of 12 % and a PVA polymerization degree of 1700 exhibited exceptional performance, including the highest foaming ratio of 45.62, the minimal water absorption rate of 6.31 %, and the greatest recovery rate of 88.95 %. Furthermore, increasing CMCS concentrations substantially enhances the antibacterial properties of the foam, demonstrating its potential for application in antibacterial cushioning packaging and emphasizing its versatility and practicality.

Investigation of microstructure, hydrogen storage performance of Re-Mg-based alloy modified by RE2O3 (RE = Dy, Er, Yb)

In order to further study the hydrogen storage mechanism of Mg-based hydrogen storage materials, Mg90Ce5Y5 alloy was used as the basis, and three kinds of heavy rare earth oxides were doped into the alloy by ball milling technology. The microstructure and hydrogen storage properties were characterized by XRD, SEM, TEM and PCI. The results show that the hydrogen absorption rate and discharge rate of modified Mg90Ce5Y5 alloy are significantly increased, and the performance is Er2O3 > Dy2O3 > Yb2O3. The hydrogen storage capacity of Er2O3 catalyzed samples is 5.02 wt%, which is higher than 4.82 wt% and 4.80 wt% of Dy2O3 and Yb2O3 catalyzed samples. The hydrogen absorption saturation rate of the sample catalyzed by Er2O3 for 2 min is ∼90 %, the complete release of hydrogen only takes 50 min at 573 K, and the dehydrogenation activation energy is 76.9 kJ/mol. The hydrogen absorption and emission rate is fast, and the dehydrogenation activation energy is slightly lower than that of the other two catalysts. In the process of hydrogen absorption and desorption, the three catalysts exhibit different phase transitions, namely DyH2↔DyH3, ErH2↔ErH3 and irreversible YbH2. DyH2↔DyH3, ErH2↔ErH3 phase transitions have the "hydrogen pump" effect, which can effectively improve the hydrogen absorption and desorption kinetic rate of Mg90Ce5Y5 alloy. Some nano-rare earth compounds and phase transformation significantly improve the kinetic properties of the alloy. However, the enthalpy change of all three catalytic alloys is around 76 kJ/mol H2, which is considered only a slight improvement in thermodynamic properties.

An eco-friendly strategy of cell wall stapling: In situ crosslinking of acrylic acid emulsion impregnated in thermally treated poplar wood

Traditional wood modification methods often result in the release of harmful substances and energy wastage. This study proposes an efficient and environmentally friendly modification strategy for fast-growing poplar wood. The approach involves polymerizing organic linear molecules within the cell wall to form stitches, thereby enhancing the dimensional stability and mechanical properties of wood and increasing its ability to withstand various environments. Poplar wood specimens were treated via a method that combines heat treatment with acrylic emulsion impregnation. The research findings indicated an improvement in the mechanical properties of poplar wood following the combined treatment. Moreover, poplar wood subjected to this treatment approach exhibited a 35.24 % lower water absorption rate after a 7-day water immersion test, and tangential and radial swelling rates of the wood were reduced by 29.66 % and 45.68 %, respectively. Scanning electron microscopy revealed excellent penetration of acrylic emulsion into wood cells; the emulsion infiltrated the wood and adhered to the cell walls, forming a crosslinked network structure. Analysis of the modification mechanism through X-ray diffraction, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy showed that the successful infusion of acrylic emulsion compensated for the lower mechanical properties of thermally treated wood, thus improving the utilization value of poplar. The acrylic emulsion is an environmentally friendly and harmless modifier, making the modified wood suitable for various applications, including indoor furniture, logistics, and outdoor facilities. This modification strategy enables efficient resource utilization and provides valuable insights for the sustainable development of the timber industry.

Performance improvement of a U-tube heat exchanger based hydrogen storage reactor by phase change materials

Solid-state hydrogen storage technology using metal hydrides as carriers has great application prospects. This study aims to optimize the heat transfer resistance and absorption kinetics issues encountered in practical applications of LaNi5-H2 storage materials in storage reactors. A mathematical model for the hydrogen absorption process in the reactors based on U-tube and straight-tube heat exchangers was built, and the advantages of U-tube structure and the flow characteristics of the heat transfer fluid on its heat transfer and absorption performance were analyzed. To further enhance the U-tube based reactor's performance, phase change materials (PCM) were subsequently introduced as an auxiliary heat transfer medium, while the amount of PCM and the thermal conductivity of the reaction bed were optimized. The results showed that the appropriate PCM dosage could overcome the inherent defects of the U-tube heat exchanger and significantly improve heat dissipation and reaction rates of the reactor, and the H2 absorption completion time was shortened by 1.4 times. In addition, the increased thermal conductivity of reaction beds is equally important for the enhancement of heat transfer and absorption rate. Nevertheless, further increase of PCM's thermal conductivity has a limited effect on the improvement of the performance.

Design of air-stabilized Mg-Sc alloy with enhanced hydrogen storage properties via in-situ formation of Sc-hydride in Sc dissolved phase

Severe surface oxidation and slow kinetic rates are the main obstacles which limit the industrial application of Mg-based hydrogen storage alloys. In this work, an attempt is carried out to design and develop the highly active and air-stabilized Mg-Scx (x = 1, 2 and 3 at.%) alloys via an inexpensive and efficient method. The Sc atoms are completely dissolved in the Mg matrix to form single-phase solid solution alloy. At 325 °C and 2.0 MPa hydrogen pressure, Mg-Sc2 alloy exhibits the rapidest absorption rate with the hydrogen capacity of 6.25 wt%. The synergism of lattice distortion induced by Sc-doping and the in-situ formed ScH2 nanoparticles enhance the de/hydrogenation kinetics. After exposed to air for 800 h, almost no MgO can be detected and the hydrogen storage capacity is only reduced by 0.11 wt%, maintaining the initial total capacity more than 98 %. Sc can protect Mg-based alloys from O2 and H2O pollution, which is ascribed to the formation of an oxygen atoms exclusion zone around the solute atoms caused by valence electrons transfer.

Carbon nanotube heat absorber for efficient direct-heating of liquid tin in a solar receiver

A new approach that use vertically-aligned carbon nanotubes (VACNT) as heat absorbers is proposed for efficient direct solar heating of liquid tin in a solar receiver integrated with beam-down optics. Plate-type CNT heat absorbers were prepared by adjusting the concentration of CNTs in the processing solvent m-cresol. The prepared CNT absorber exhibited an increase in bulk density and the formation of a densely packed nanotubes skeleton with a higher CNT concentration in m-cresol. Thermal conductivity, a key design factor for solar absorbers, showed a stronger correlation with skeletal density than with bulk density. Heat absorption characteristics of the solar liquid tin receiver (50 mm-i.d., 60 mm-high) with the CNT absorbers integrated with a Fresnel lens (0.98 m i.d.) were determined. The tin temperature in the receiver with the CNT absorber reached a maximum of 728 °C. Bare tin exhibited system efficiency of 27.7 % and receiver efficiency of 38.3 %, but tin heating through the CNT plates exhibited system efficiency of up to 48.4 % and receiver efficiency of 64.3 %, showing a system heat absorption rate 1.75 times higher. The thermal absorption efficiency was proportional to the skeletal density of the plates, and the thermal absorption of the system was dominated by the efficient transfer of absorbed heat in the energy absorption region. The energy flow and heat loss in the receiver system were analyzed. Although the bare tin receiver exhibited a high heat loss of 27.1 % owing to the low emissivity or high reflectivity of the tin surface, the heat loss in the CNT absorber plates with high absorptivity was only 0.9 %. The flat plate-shaped transmission window in the receiver caused significant reflective heat loss and convective heat loss owing to head-on wind. Based on the energy flow analysis, improvement approaches for enhancing the thermal efficiency of the proposed receiver system are suggested.

Experimental investigation on low‐velocity impact performance of carbon fiber reinforced polyether ether ketone thermoplastic composite materials in room and elevated temperature

AbstractCarbon fibers woven‐ply reinforced polyether ether ketone (C/PEEK) thermoplastic composites are widely used in aerospace and high‐tech industries because of their exceptional resistance to low‐velocity impact. In this paper, experimental investigation is carried out to determine the low‐velocity impact performance of C/PEEK laminates at room temperature (RT) and high temperature (90°C and 150°C) environments. Both macroscopic and microscopic analyses are applied to examine the influence of temperature on the mechanical response and damage mode of the material. The attention of this investigation is on impact parameters such as maximum contact force, energy absorption rate, indentation depth, and damage mode. The findings show significant changes in material stiffness, rate of energy absorption, and indentation depth with rising temperature. Temperature variations have a notable effect on the PEEK matrix plasticity, C/PEEK composite interlaminar properties, crack initiation and propagation, and damage mode at the overlaps of warp and weft fibers, resulting in a transition from brittle to ductile failure.Highlights Experimental investigation is carried out to study the low‐velocity impact performance of C/PEEK. The effects of impact energy and environmental temperature on the low‐velocity impact performance of C/PEEK are investigated. The mechanism of how environmental temperature affects the damage mode of C/PEEK is investigated.

Low-methoxy-pectin and chlorogenic acid synergistically promote lipolysis and β-oxidation by regulating AMPK signaling pathway in obese mice

Chlorogenic acid (CGA) displays various biological activities in preventing high-calorie diet-induced metabolic complications. The absorption efficiency of CGA in the stomach and small intestine is relatively low, with approximately 70 % of CGA being metabolized by colonic microorganisms before it enters the bloodstream. In this study, we successfully developed CGA-LMP (Low-methoxy-pectin) conjugates to improve the absorption rate of CGA. C57BL/6J mice were fed high-fat diets (HFD) supplemented with CGA, LMP, or CGA-LMP conjugates for a duration of eight weeks. The results demonstrated that the CGA, LMP, or CGA-LMP conjugates prevented HFD-induced hyperlipidemia, inflammation, liver steatosis, and adipocyte hypertrophy in obese mice. Notably, the CGA-LMP conjugates demonstrated superior efficacy in alleviating obesity compared to CGA or LMP alone. Further studies revealed that the primary mechanism of weight loss was the activation of the AMPK signaling pathway, which facilitates lipolysis and lipid β-oxidation. These findings highlight that the enhanced the anti-obesity effectiveness of CGA-LMP conjugates, expanding their potential applications in the field of functional nutrition and foods.

Triple Fixed-dose combination of Dapagliflozin, Sitagliptin, and Metformin for People with Type 2 Diabetes in Indian Settings

Objective: This study assessed the bioequivalence of a fixed-dose combination (FDC) therapy containing extended-release Metformin (Metformin XR), Dapagliflozin, and Sitagliptin for treating type 2 diabetes (T2D). The objective was to compare the absorption rate and extent of the FDC with two reference products: Sitagliptin 100mg tablets (R1) and a combination of Dapagliflozin 10mg plus Metformin 1000mg extended-release tablets (R2) in healthy adult males under fed conditions. Methods: An open-label, randomized, cross-over study was conducted with 24 healthy male participants. Each participant received a single dose of the test FDC and the reference products, with blood samples collected over 72 hours to evaluate pharmacokinetic parameters (Cmax, AUC0-t, AUC0-inf, Tmax, Kel, AUC_% Extrap_obs, and t1/2). Bioequivalence was determined based on the 90% confidence intervals (CIs) of the geometric mean ratios for AUC0-t and Cmax, within a predefined range of 80.00%-125.00%. Safety and tolerability were also assessed. Results: Pharmacokinetic analysis was performed on 22 subjects. The geometric mean ratios for the FDC compared to the reference products were within the predefined bioequivalence range, indicating that the absorption profiles of the FDC and the reference products were similar. The mean plasma concentration-time curves for Dapagliflozin, Sitagliptin, and Metformin XR were almost identical between the FDC and reference products, demonstrating consistent drug release and absorption. No significant differences were observed in Tmax, t1/2, or other pharmacokinetic parameters, further supporting bioequivalence. Additionally, the FDC was well-tolerated, with no serious adverse events reported, and all subjects completed the study without complications. Conclusion: The study confirmed that the FDC of Dapagliflozin, Sitagliptin, and Metformin XR is bioequivalent to the reference products in healthy adult males under fed conditions. This bioequivalence supports the use of the FDC as an effective treatment option to improve glycemic control in adults with T2D, particularly in the Indian context, promoting the benefits of combined therapy in managing diabetes. Keywords: Bioequivalence, Fixed-dose combination (FDC), Type 2 diabetes (T2D), Pharmacokinetics, Dapagliflozin, Metformin XR, Sitagliptin

362 Nutrikinetic evaluation and modeling of 25-hydroxyvitamin D3 in beef cattle

Abstract The objective of this study was to evaluate serum 25-hydroxyvitamin D3 [25(OH)D3] status in beef cattle when 1) fed diets with supplemental 25(OH)D3 or calcidiol (HyD, dsm-firmenich, Plainsboro, NJ), and 2.) a single dose of calcidiol was administered to cannulated heifers on nutrikinetic evaluation and predictive modeling simulations. In experiment 1, crossbred heifer calves [n = 96, initial body weight (BW) = 222 ± 12.4 kg] were assembled from auction markets near Dickson, TN and transported ~1,069 km to Manhattan, KS. Heifers (n = 12 per pen) were stratified by BW and randomly allocated to a corn-based receiving diet with one of four dietary treatments: 1) No supplemental D3 or calcidiol (CON, n = 24), 2) 3,000 IU supplemental D3·heifer⁻¹·d⁻¹ (D3, n = 24), 3.) 0.5 mg calcidiol/h/d (Hy D Low, n = 24), or 4.) 1.0 mg calcidiol·heifer⁻¹·d⁻¹ (Hy D High, n = 24) for 60 d. Blood samples were collected from each heifer prior to transport (d -1), on arrival (d 0) and on d 14, 31, and 60 of dietary treatment period. Data were analyzed using the GLIMMIX procedure of SAS using animal as experimental unit and treatment as fixed effect. HyD High calves had greater (P < 0.001) serum 25(OH)D3 concentrations than HyD Low at d 14 and 31 (Figure 1 and 2). At d 14, 31 and 60, HyD High and HyD Low calves had greater (P < 0.001) serum 25(OH)D3 concentrations than CON or D3 treatments. In experiment 2, cannulated crossbred heifers (n = 8, initial BW = 289 ± 44.9 kg were randomly assigned to one of two treatments: 1.) 3 mg/272 kg BW calcidiol, or 2.) 5 mg/272 kg BW calcidiol in a single dose administered via rumen cannula at h 0. Serial blood samples were collected at baseline out to 70 d post-dose. Serum 25(OH)D3 concentrations were analyzed via HPLC coupled with tandem MS (dsm-firmenich, Belvidere, NJ). Predictive modeling simulations of serum 25(OH)D3 concentrations used non-parametric superposition (Certara Phoenix WinNonlin 64, St. Louis, MO) from applying non-compartmental analysis with the assumptions of linearity, independent calcidiol dose response, and the rate of absorption and the average systemic clearance were consistent for each calcidiol dosing interval. The elimination half-life (t1/2) of calcidiol was determined to be an average of 7.1 d and area under change in concentration-time curve time 0 to the last time point that measured above baseline concentration post dose (AUC0-last) averaged of 32.6 d (Table 1). Non-parametric dosing simulations using nutrikinetic parameters from experiment 2 suggest that administration of two 5 mg oral doses of calcidiol with daily feeding of 1 mg would result in a rapid and sustained increase in serum 25(OH)D3. However, simulations should be confirmed in vivo before implementation.

Compact Ultra-Wide Band Two Element Vivaldi Non-uniform Slot MIMO Antenna for Body-Centric Applications

This work presents a novel compact two-port Vivaldi Non-uniform Slot MIMO Antenna (VNSMA) to overcome the challenges of traditional ultra-wideband (UWB) antennas, such as large size, limited bandwidth (BW), high mutual coupling, and suboptimal performance in wearable devices. Designed based on Vivaldi non-uniform slot profile antenna (VNSPA) theory, this antenna offers superior performance metrics and significantly advances wearable antenna technology. The novelty of this work is investigating different positions for the two compact UWB VNSA to get better performance with smaller sizes, wider impedance matching BW, and lower mutual coupling (MC) where side by side at an angle of 180ᵒ is determined to be the best configuration. Detailed parametric studies were performed on this configuration for better performance, where the MC was further reduced by etching the ground plane with a vertical slot between the two antennas and L slots around the Microstrip to Slot (M/S) transition, respectively. Furthermore, BW and gain enhancements were obtained by etching exponential tapered and triangular slots at its two edges. Using the Finite Integration Technique (FIT), Computer Simulation Technology (CST) software is used for the simulations in this work. The VNSMA is tested on a CST Gustav human phantom and gives excellent results with low specific absorption rate (SAR) values at several UWB frequencies. The proposed VNSMA provides good, measured outcomes of S11 < -11.08 dB with wide BW of 12.5 GHz (2.33–14.83 GHz) covering high isolation of -23 dB (for most of frequency band), moderate-high gain of 5.89 dBi, radiation efficiency of 66-90%, low Envelope Correlation Coefficient (ECC) of 0.002 and high diversity gain (DG) of 9.99 dBi, stable radiation patterns, and average group delay of 1.2 ns. This innovative design, which optimizes antenna positioning and incorporates ground plane modifications, achieves remarkable improvements in BW, which covers multiple bands, including WLAN (2.4–2.485 GHz), X-band (8-12 GHz), and part of Ku band (12-18 GHz). The findings demonstrate the antenna's potential for various high-resolution microwave imaging applications, particularly in medical diagnostics like breast and brain cancer detection, showcasing its impact in wearable technology and healthcare.

Design a metamaterial based applicator for hyperthermia cancer treatment

This research describes a metamaterial-based applicator with and without water bolus for cancer treatment. The metamaterial based applicator consists of a double spiral antenna and a slotted square shape artificial magnetic conductor (SSA) structure. The antenna is designed on a low-cost FR4 substrate with dimensions of 32 × 32 × 3.27 mm3, and the SSA unit cell which behaves as a metamaterial, is designed on an RT-duroid substrate with dimensions of 15 × 15 × 0.76 mm3 (size of the unit cell). The 4 × 4 unit cells of the SSA structure are optimized to direct the maximum field toward the cancer tissue. The proposed applicator (antenna + SSA structure) is tested for hyperthermia treatment using a heterogeneous phantom (skin, fat, and muscle layers) and the human-mimicked model with an air medium and a water bolus layer. The applicator’s performance is evaluated in terms of specific absorption rate (SAR), penetration depth (PD), and effective field size (EFS). Further, thermal analysis is performed, with 1.5 W of input power at the antenna port, and the maximum temperature rise of 44 0C is obtained. The cancer tissue (tumor) temperature ranges between 41 °C to 45 °C, sufficient for effective hyperthermia therapy. Finally, the suggested metamaterial based applicator is built and tested in the presence of a phantom and head tissue simulating liquid.

High-efficiency GaAs TFSC based on Ti plasma enhancement

This study proposed a performance enhancement scheme for GaAs thin-film solar cell (TFSC) based on Ti plasma enhancement. It aims to enhance the light absorption ability of the cell by using surface plasmon excitations of metal nanoparticles, and to predict and optimize the performance of the TFSC using the FDTD method. By introducing Ti nanosphere and pyramid structures on the upper and lower surfaces of the cell, the reflection and transmission losses of light are effectively reduced. This increases the interaction between the cell materials and light, and significantly improves the cell's ability to absorb light. It is shown that Ti nanosphere and pyramid structures can localize the electric field near the metal surface, which greatly enhances the absorption of light on the upper and lower surfaces of the cell. In the wavelength range of 380–1200 nm, the absorption of all bands reaches more than 93 %, with an average absorption rate as high as 97.60 %, and is close to perfect absorption in the wavelength range of 700–900 nm. Meanwhile, the photoelectric conversion efficiency (PCE) of the cell reaches 32.72 %, which significantly improves the overall performance of the cell and provides a compelling design solution for the innovation and development of GaAs TFSC technology.

Interdigitated resonator based frequency selective rasorber with high selectivity

Abstract This paper investigates a highly selective Frequency Selective Rasorber (FSR) utilizing interdigitated resonators, characterized by a passband exhibiting low insertion loss and the introduction of a second-order passband response in the lossless layer enhances selectivity on both sides of the passband. The lossy unit is implemented by inserting interdigitated resonators on an octagonal ring loaded with lumped resistors, while the lossless layer is constructed with a five-layer structure. Simulation results demonstrate a low Insertion Loss&amp;#xD;(IL) value of 0.78 dB at 3.5 GHz. At vertical incidence, the S21&gt;-3 dB bandwidth ranges from&amp;#xD;3.41 to 3.67 GHz, and the S11&lt;-10 dB range spans from 2.2 to 8.2 GHz, obtaining two absorption bands on either side of the passband, with absorption rates exceeding 80%. The operating frequency bands are 1.95-3.27 GHz and 3.8-8.4 GHz. The designed FSR exhibits polarization insensitive. To validate simulation results, a prototype FSR was fabricated and tested, with experimental data aligning with simulation results.&amp;#xD;