Low Resistance Research Articles

Sputter Deposited Crystalline MoO2 Films as a High-Capacity and Stable Electrode Material for Supercapacitors: Mechanistic/Electrochemical Insights

In this work, we have optimized and fabricated pristine molybdenum dioxide (MoO2) electrodes over the Silicon (Si) substrate and examined the impact of various ion-loaded aqueous electrolytes on their electrochemical behavior. The sputtered electrodes exhibited a high crystalline structure and a very low resistivity. These highly conductive electrodes were tested in three different aqueous electrolytes (acidic, neutral, and alkaline) to establish a relation between the electrode and the nature of the electrolyte to achieve optimal electrochemical performance and cyclability. The electrochemical kinetics showed that the charge storage mechanism was unique for all the electrolytes. The capacitive current was dominant in the neutral electrolyte, whereas it was diffusive dominant in alkaline and 70% capacitive in the acidic electrolyte. Our findings indicated that the MoO2@Si electrode exhibited superior electrochemical activity in an acidic electrolyte. The electrode showed a voltage window of 0.6 V with an areal capacity of 24 mF/cm2 at 0.1 V/s scan rate. Moreover, the electrode also demonstrated excellent cyclability and capacitance retention (∼145%) till 5000 cycles. These results highlighted that the binder-free MoO2@Si electrode showed outstanding electrochemical activity and stability, which makes it suitable for sulfuric acid electrolyte-based energy storage systems.

Effect of Cetyl Trimethyl ammonium bromide (CTAB) amount on the Nanoindentation creep behaviour of Sn-cu-Y2O3 nanocomposite Lead-free solder

Sn-Cu-Y2O3 nanocomposite solder is synthesized from a citrate bath by pulse electrodeposition route. Y2O3 powder is synthesized from a sol-gel assisted combustion route. Different techniques such as SEM, XRD, and TEM are used to characterize Y2O3 powder. The particle size of Y2O3 powder is found to be 27 nm. The effect of adding cetyl trimethyl ammonium bromide (CTAB) on the synthesis of Sn-Cu-Y2O3 nanocomposite lead-free solder is studied. The amount of CTAB is varied for a particular amount of Y2O3 powder. It is carried out to find the exact ratio of CTAB for better dispersion of Y2O3 powder in the electrolytic bath. Because the distribution of reinforcement in the matrix which is associated with the dispersion of Y2O3 powder in the electrolyte is as important as the amount of reinforcement in the solder matrix. For the synthesis of nanocomposite solder, the optimum ratio of CTAB to Y2O3 is found to be 1:1. After the synthesis of nanocomposite solder, the influence of Y2O3 powder on the melting temperature of the solder is also studied. Incorporating Y2O3 has little effect on the melting point of the nanocomposite solder. Nanoindentation creep test results showed that the deposit at 0.2 A/cm2 (monolithic solder) has a lower creep resistance than the nanocomposite solders. Additionally, the creep resistance of the nanocomposite with a CTAB to Y2O3 ratio of 1:1 was higher.

Enhancing heat transfer performance of aluminum-based vapor chamber with a novel bionic wick structure fabricated using additive manufacturing

Given the lightweight nature and excellent thermal conductivity of aluminum, it offers significant potential for light-weighting of phase-change cooling components. To further enhance the thermal performance of aluminum-based vapor chambers, this study utilized selective laser melting (SLM) to design and integrally manufacture the slightly oleophilic wick for the condenser of the aluminum-based vapor chamber, along with three different superoleophilic wick structures for the evaporator: the gyroid bionic composite porous wick vapor chamber (GBCPVC), the groove composite porous wick vapor chamber (GCPVC), and the uniform porous wick vapor chamber (UPVC). A water-cooling experimental setup was established, and the effects of wick structure, cooling water flow rate, and cooling water temperature on the maximum heat load, temperature uniformity, and thermal resistance of vapor chambers were systematically investigated. The results indicated that the gyroid bionic porous wick structure significantly enhanced the thermal performance of the vapor chamber. Under the same conditions, GBCPVC exhibited lower thermal resistance and superior temperature uniformity, achieving a higher heat load than GCPVC and UPVC. When the cooling water temperature was decreased, its maximum heat load significantly increased. Specifically, at 15 °C, the maximum heat load for GBCPVC reached 300 W, an increase of 33.33 % and 53.33 % compared to 25 °C and 35 °C, respectively. Conversely, a rise in cooling water temperature enhanced the temperature uniformity and reduced thermal resistance of CBCPVC. At 35 °C and a heat load of 120 W, GBCPVC achieved a minimum thermal resistance of 0.034 K/W and a maximum temperature difference of 1.46 °C. Additionally, an increased flow rate enhanced the maximum heat load of GBCPVC, and under high heat loads, it could also reduce the thermal resistance and improve temperature uniformity. This study provides new insights and solutions for the thermal management of phase-change cooling components in aerospace electronic devices.

Experimental and numerical investigation on heat transfer analysis of square slotted pin-fin heat sinks

This paper introduces two novel designs of pin-fin heat sink (PHFS), namely the inline slotted pin-fin (ISP) and the V-shaped slotted pin-fin (VSP), to address rapid heat dissipation for one central/graphics processing unit (CPU/GPU) in a single-phase liquid cooling system. Experimental and numerical investigations are conducted to observe the effect of heat transfer for non-slotted and slotted pin-fin heat sinks under different Reynolds numbers (225-720) and heating powers (90-120 W). Parameters such as average wall temperature, Nusselt number, thermal resistance, pressure drop, and hydrothermal performance factor are evaluated. Comparative analyses show that the slotted pin-fin heat sinks exhibit higher Nusselt numbers (Nu) and lower thermal resistance (Rth) levels than that in the non-slotted pin-fin heat sinks, particularly at lower Reynolds numbers. At the Reynolds number 225 and power of 120 W, the inline and V-shaped slotted pin-fin heat sinks experience a 13.98% and 19.69% increase in Nu and a 12.65% and 15.41% reduction in Rth compared to the non-slotted one, respectively. The V-shaped slotted pin-fin heat sink achieves more than 5 ∘C reduction in the maximum wall temperature than the non-slotted one. The slotted structure reduces pressure drop losses by minimizing dead flow areas on one hand. On the other hand, the inclined slots generate vortices behind the fins, increase shear-induced mixing and thus improve the force convection cooling performance.

23.6 % Efficient perovskite-organic tandem photovoltaics enabled by recombination layer engineering

Recombination layers are crucial in achieving high power conversion efficiency (PCE) in tandem solar cells. Here, we report the development and optimization of recombination junctions for high PCE perovskite-organic tandem solar cells (PO-TSCs). We choose a wide bandgap perovskite (1.79 eV) for the front subcell and a narrow bandgap (1.36 eV) organic bulk heterojunction (BHJ) for the rear subcell. The optimal thicknesses of the perovskite and organic layers were determined to be 260 and 100 nm, respectively, based on the analysis of Transfer-Matrix optical simulations. Our results demonstrate that the optimal recombination layer consists of an ultrathin layer of indium zinc oxide IZO (∼ 2 nm) deposited on MoOx/2PACz, which delivers a PCE of 23.6 %. This high PCE is attributed to the high transparency of the recombination layer in the NIR spectra region and the low sheet resistance of IZO. Furthermore, we provide a theoretical analysis of the potential efficiency of PO-TSCs as a function of front and rear subcells and predict a maximum theoretical PCE value of more than 36 %. Our work highlights the importance of selecting the proper recombination layer design for achieving high-performance PO-TSCs.

Spray freeze dried cannabidiol with dipalmitoylphosphatidylcholine (DPPC) for inhalation and solubility enhancement

Pulmonary delivery is an efficient route of administration to deliver cannabidiol (CBD) due to the high bioavailability and fast onset of action. The major formulation challenge is the poor aqueous solubility of CBD. This study aimed to produce inhalable CBD powders with enhanced solubility and characterise their solid-state properties. CBD was spray freeze dried with mannitol or trehalose dihydrate with and without dipalmitoylphosphatidylcholine (DPPC). All four powders had acceptable yields at > 70 % with porous and spherical particles. The two crystalline mannitol powders contained less residual solvent than both amorphous trehalose ones. The addition of DPPC did not affect the crystallinity and residual solvent level of the powders. Instead, DPPC made the particles more porous, decreased the particle size from 19-23 µm to 11–13 µm, and increased CBD solubility from 0.36 µg/mL to over 2 µg/mL. The two DPPC powders were dispersed from a low resistance RS01 inhaler, showing acceptable aerosol performance with emitted fractions at 91–93 % and fine particle fractions < 5 µm at 34–43 %. These formulations can be used as a platform to deliver CBD and other cannabinoids by inhalation

Antimicrobial Resistance Patterns of Common Gram-Negative Microorganisms Isolated from Patients with Lower Respiratory Tract Infections in a Teaching Hospital in Vietnam.

This cross-sectional study investigated the antimicrobial resistance (AMR) patterns of gram-negative pathogens isolated from 4,789 hospitalized patients with lower respiratory tract infections (LRTIs). Of the collected specimens, 1,325 (27.7%) tested positive for gram-negative bacteria. Acinetobacter baumannii (38.6%), Pseudomonas aeruginosa (33.5%), Klebsiella pneumoniae (18.7%), Escherichia coli (5.6%), and Klebsiella aerogenes (3.5%) were the most prevalent isolates. AMR analysis revealed high resistance rates (79.9%-100%) of A. baumannii isolates to multiple classes of antibiotics except amikacin, trimethoprim/sulfamethoxazole, and colistin. P. aeruginosa displayed low resistance to colistin (< 10%) but high resistance to other antibiotics. K. pneumoniae displayed high resistance rates of 90.0%-100.0% to most penicillins, whereas resistance rates were notably lower for colistin (7.1%) and amikacin (16.7%). K. aerogenes exhibited high resistance to various antibiotics and sensitivity to amikacin (95.1%), ampicillin (100.0%), and colistin (100.0%). E. coli isolates exhibited resistance to ampicillin (96.9%) and maximum sensitivity to several antibiotics. Our study identified significant AMR trends and highlighted the prevalence of multidrug-resistant strains (93.6% for K. aerogenes and 69.1%-92.4% for other isolates). These findings emphasize the urgent need for appropriate antibiotic management practices to combat AMR in gram-negative pathogens associated with LRTIs.

The burden of lymphatic filariasis and its control strategies in Sierra Leone: A literature review

Lymphatic filariasis (LF) poses a significant health burden in Sierra Leone, with considerable socio-economic implications. LF, caused by parasitic worms transmitted through mosquito bites, leads to lymphedema, elephantiasis, and hydrocele, severely affecting individuals’ quality of life. Sierra Leone, with its tropical climate and inadequate healthcare infrastructure, faces unique challenges in combating lymphatic filariasis. This review explores the epidemiological landscape of LF in Sierra Leone, highlighting endemic regions, its impact, and control strategies. In 2005, epidemiological coverage of high-dose medications, like ivermectin and albendazole, exceeded 65% annually across 12 districts in Sierra Leone. By 2013, eight districts were eligible for transmission assessment surveys (TAS). After three additional rounds of mass drug administration (MDA), four districts became eligible for pre-TAS assessments in 2017. Despite efforts to control LF through mass drug administration (MDA) programs, challenges such as low treatment coverage, logistical constraints, and community resistance persist. Moreover, the impact of the Ebola outbreak on healthcare delivery has further impeded LF control efforts. This literature review adds to our understanding of LF control in Sierra Leone, providing valuable insights into the epidemiology, impact, challenges, and potential strategies for enhancing LF elimination efforts. It contributes to the broader discourse on neglected tropical diseases and public health interventions, emphasizing the need for context-specific approaches and interdisciplinary collaboration to achieve sustained progress towards LF elimination and improves public health outcomes.

Characterization of manufacturing material and carbon nanohybrid for renewable energy and storage systems

Scientists are exploring advanced energy alternatives to compete with rising fossil fuel consumption and CO2 emissions due to population growth and technological advancements. Supercapacitors are highly efficient systems for storing energy due to their specific capacitance and power density, meeting modern energy storage demands. Perovskite and carbon-based materials have emerged as the most effective materials in this respect. In this work, SrSnO3/rGO nanohybrid is chosen as the supercapacitor electrode material for the very first time and a range of characterization techniques are employed to ascertain the structural and textural characteristics of the composite. The physicochemical properties of the SrSnO3 included rGO are shown to have a greater surface area, excellent electrical conductivity and a lower resistance. It is demonstrated that the rGO improved quicker ion diffusion channels for the increased redox performance in the SrSnO3/rGO nanohybrid. Additionally at 1 A/g, the SrSnO3/rGO nanohybrid has an elevated specific capacitance of 1385 F/g along with energy and power density of 66 Wh/kg and 293 W/kg, respectively in a three-electrode system. During the two electrode observations, the revealed Cs of SrSnO3/rGO nanohybrid was 122 F/g at 1 A/g with 66 Wh/kg and 293 W/kg of energy density and power density, respectively. The SrSnO3/rGO nanohybrid has exceptional functionality, as demonstrated by its 65 h stability examination via chronoamperometry and a modest drop in its CV polarization curve area after the 5000th cycle of the CV stability analysis. These evaluated results point to the nanohybrid's promising future.

DXA-derived lumbar bone strain index corrected for kyphosis is associated with vertebral fractures and trabecular bone score in acromegaly.

The bone strain index (BSI) is a marker of bone deformation based on a finite element analysis inferred from dual X-ray absorptiometry (DXA) scans, that has been proposed as a predictor of fractures in osteoporosis (i.e., higher BSI indicates a lower bone's resistance to loads with consequent higher risk of fractures). We aimed to investigate the association between lumbar BSI and vertebral fractures (VFs) in acromegaly. Twenty-three patients with acromegaly (13 males, mean age 58 years; three with active disease) were evaluated for morphometric VFs, trabecular bone score (TBS), bone mineral density (BMD) and BSI at lumbar spine, the latter being corrected for the kyphosis as measured by low-dose X-ray imaging system (EOS®-2D/3D). Lumbar BSI was significantly higher in patients with VFs as compared to those without fractures (2.90 ± 1.46 vs. 1.78 ± 0.33, p = 0.041). BSI was inversely associated with TBS (rho -0.44; p = 0.034), without significant associations with BMD (p = 0.151), age (p = 0.500), BMI (p = 0.957), serum IGF-I (p = 0.889), duration of active disease (p = 0.434) and sex (p = 0.563). Lumbar BSI corrected for kyphosis could be proposed as integrated parameter of spine arthropathy and osteopathy in acromegaly helping the clinicians in identifying patients with skeletal fragility possibly predisposed to VFs.

Vertically aligned ReS2 on MOF deorived CoS2–C hybrid as core-shell catalyst for promoting overall water splitting

The rational design of a core-shell structured electrocatalyst is important to improve the efficiency of electrocatalytic hydrogen production through water splitting. Herein, the catalyst is composed of rhenium disulfides (ReS2) vertically grown on cobalt sulfides/carbon hybrid by hydrothermal and activation treatment (CoS2–C@ReS2/CFP). The core-shell structure is constructed by sulfurizing the cobalt-based metal-organic framework, preventing the restacking of the ReS2 nanosheet, exposing more active sites, and facilitate electrolyte ion diffusion. Moreover, the CoS2–C@ReS2/CFP catalyst shows exceptional performance during the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) process in an alkaline electrolyte. At ·10 mA cm−2, the overpotentials of the CoS2–C@ReS2/CFP catalyst are 85 and 257 mV during the HER and OER processes with the small Tafel slope, low charge transfer resistance and exceptional catalytic stability. The combination of the CoS2 core and ReS2 shell is designed to adjust the adsorption energy of water molecules, promoting water dissociation, and enhancing the catalytic activity of CoS2–C@ReS2/CFP catalyst. This work provides an efficient strategy for developing the core-shell structured catalysts, potentially advancing the practical application into water splitting for hydrogen production.

Microwave-transparent metallic metamaterials for autonomous driving safety.

Maintaining the surface transparency of protective covers using transparent heaters in extreme weather is imperative for enhancing safety in autonomous driving. However, achieving both high transmittance and low sheet resistance, two key performance indicators for transparent heaters, is inherently challenging. Here, inspired by metamaterial design, we report microwave-transparent, low-sheet-resistance heaters for automotive radars. Ultrathin (approximately one ten-thousandth of the wavelength), electrically connected metamaterials on a millimetre-thick dielectric cover provide near-unity transmission at specific frequencies within the W band (75-110 GHz), despite their metal filling ratio exceeding 70 %. These metamaterials yield the desired phase delay to adjust Fabry-Perot resonance at each target frequency. Fabricated microwave-transparent heaters exhibit exceptionally low sheet resistance (0.41 ohm/sq), thereby heating the dielectric cover above 180 °C at a nominal bias of 3 V. Defrosting tests demonstrate their thermal capability to swiftly remove thin ice layers in sub-zero temperatures.

Enhanced low-temperature resistance of lithium-ion batteries based on methyl propionate-fluorinated ethylene carbonate electrolyte.

Low temperature has been a major challenge for lithium-ion batteries to maintain satisfied electrochemical performance, as it leads to poor rechargeability and low capacity retention. Commercial electrolytes of lithium-ion battery rely heavily on ethylene carbonate (EC), and its high melting point (36.4 °C) severely limits the use of batteries below 0 °C. In this work, we demonstrate that using the low melting point carboxylate of methyl propionate (MP) and vinyl fluorocarbonate (FEC) based electrolyte can overcome the low-temperature cycle limitation. Compared with carbonate electrolytes, MP has lower binding energy with Li+, which is essential to improve the low-temperature performance of the battery, and FEC is an effective component to inhibit the side reaction with the electrode of lithium metal. The carefully formulated MP-based electrolyte can generate a solid electrolyte interface with low resistance and rich in inorganic substances, which is conducive to the smooth diffusion of Li+, allowing the battery to successfully cycle at a high rate of 0.5 C at -20 °C, and giving it a reversible capacity retention rate of 65.3% at -40 °C. This work designs a promising advanced electrolyte and holds the potential to overcome limitations of lithium-ion batteries in harsh conditions.

A Method to Quantitative Compare Obfuscating Ttransformations

The paper considers the problem of quantitative comparison of potency and resistance of practically applied obfuscating transformations of program code. A method is proposed to find the potency and resistance of transformations by calculating the «comprehensibility» of the obfuscated and deobfuscated versions of a program, respectively. As a measure of program comprehensibility, it is proposed to use the similarity of this program to the approximation of its «most comprehensible» version. Based on the proposed method a model to assess potency and resistance was built, the main elements of which are: a set of investigated obfuscating transformations, a similarity function, a method to approximate the most comprehensible version of the program and a deobfuscator. To implement this model 1) obfuscating transformations provided by Hikari obfuscator are chosen; 2) 8 similarity functions are constructed by machine learning methods using static characteristics of programs from CoreUtils, PolyBench and HashCat sets; 3) the smallest program version was chosen as an approximation of the most comprehensible program version (found among the versions obtained using optimization options of GCC, Clang and AOCC compilers); 4) a program deobfuscation scheme based on the optimizing compiler from LLVM was built and implemented. The results of the potency and resistance for sequences of transformations of lengths one, two and three were experimentally obtained. These results showed consistency with the results of independent potency and resistance evaluations obtained by other methods. In particular, it was found that the highest potency and resistance are demonstrated by sequences of transformations starting with transformations of the control flow graph, and the lowest resistance and potency are generally demonstrated by sequences that do not contain such transformations.

Understanding how junction resistances impact the conduction mechanism in nano-networks

Networks of nanowires, nanotubes, and nanosheets are important for many applications in printed electronics. However, the network conductivity and mobility are usually limited by the resistance between the particles, often referred to as the junction resistance. Minimising the junction resistance has proven to be challenging, partly because it is difficult to measure. Here, we develop a simple model for electrical conduction in networks of 1D or 2D nanomaterials that allows us to extract junction and nanoparticle resistances from particle-size-dependent DC network resistivity data. We find junction resistances in porous networks to scale with nanoparticle resistivity and vary from 5 Ω for silver nanosheets to 24 GΩ for WS2 nanosheets. Moreover, our model allows junction and nanoparticle resistances to be obtained simultaneously from AC impedance spectra of semiconducting nanosheet networks. Through our model, we use the impedance data to directly link the high mobility of aligned networks of electrochemically exfoliated MoS2 nanosheets (≈ 7 cm2 V−1 s−1) to low junction resistances of ∼2.3 MΩ. Temperature-dependent impedance measurements also allow us to comprehensively investigate transport mechanisms within the network and quantitatively differentiate intra-nanosheet phonon-limited bandlike transport from inter-nanosheet hopping.

Magnetohydrodynamics simulation of magnetic reconnection process based on the laser-driven Helmholtz capacitor-coil targets

Magnetic reconnection is an important rapid energy release mechanism in astrophysics. Magnetic energy can be effectively converted into plasma kinetic energy, thermal energy, and radiation energy. This study is based on the magnetohydrodynamics simulation method and utilizes the FLASH code to investigate the laser-driven magnetic reconnection physical process of the Helmholtz capacitor-coil target. The simulation model incorporates the laser driving effect, and the external magnetic field consistent with the Helmholtz capacitor-coil target is written in. This approach achieves a magnetic reconnection process that is more consistent with the experiment. By changing the resistivity, subtle differences in energy conversion during the evolution of magnetic reconnection are observed. Under conditions of low resistivity, there is a more pronounced increase in the thermal energy of ions compared to other energy components. In simulations with high resistivity, the increase in electrons thermal energy is more prominent. The simulation gives the evolution trajectory of magnetic reconnection, which is in good agreement with the experimental results. This has important reference value for experimental research on the low-β magnetic reconnection.

Matching of Water Breakthroughs in a Low-Resistivity Oil Reservoir Using Permeability Anisotropy

In a mature middle and lower Gharif field in Oman, uncertainties surrounding initial water saturation and early water breakthroughs of unknown sources and paths suggest the presence of significant bypassed oil. In order to determine the areas with remaining oil, petrophysical and logging data of seven wells were processed using Techlog software and imported into Petrel software for modelling and simulation. Porosity was calculated using the Electric Propagation Time log and was utilized to evaluate the presence of oil, particularly in the upper tight zone of the formation. Despite the low resistivity readings in the highly porous layers, caused by good network connectivity and high formation water salinity, the resistivity contrast was sufficient to differentiate them from the oil zone. However, the calculated water saturation (Sw) in the tight top oil zone was high, consistent with the observed water production in the field. To improve the match between production data and simulation results, sensitivity analyses were conducted on various permeability anisotropy and relative permeability values within the model. The analyses showed that core-derived permeability anisotropy (vertical to horizontal ratio of 1:1) yielded a better history match for water production compared to the conventionally used value of 1:10. Water saturation maps were generated at the start and the end of production to highlight saturation distribution within the reservoirs. The maps revealed that in the lower porous part, the oil was fully depleted around the wells but remained trapped in the undrilled areas.

Development and mechanism research of hydrophobic associative polymer drag reducing agents

ABSTRACT The challenge of insufficient proppant transportation capacity in slick water remains unresolved. To tackle this concern, a hydrophobically associating water-soluble polymer (HAWP), characterized by a low molecular weight (MW) of 8.11 × 105 g/mol, was successfully synthesized via a photo-initiation method. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The drag reduction mechanism of the material was characterized through nuclear magnetic resonance and rheological performance testing. The results show that in comparison to conventional drag reducers in slick water with an average MW of approximately 1 × 107 g/mol, HAWP demonstrates significantly reduced MW. The rheological test results indicate that upon addition of sodium dodecyl benzene sulfonate (SDS, 200 mg/L) to the HAWP solution (0.3 wt%), the storage modulus experienced a substantial increase from 0.14 Pa to 7.42 Pa, demonstrating enhanced mechanical properties. Meanwhile, drag reduction (DR) tests showed that the efficiency of drag reduction achieved by the polymer system (PS) drag reducer was comparable to that of conventional linear polymers. This research achievement effectively addresses the challenges of low molecular weight and resistance reduction encountered in previous endeavors.

Novel electrochemical ZnO/MnO2/rGO nanocomposite-based catalyst for simultaneous determination of hydroquinone and pyrocatechol.

An innovative electrochemical sensing method is introduced for dihydroxy benzene (DHB) isomers, specifically hydroquinone (HQ) and pyrocatechol (PCC), employing a zinc-oxide/manganese-oxide/reduced-graphene-oxide (ZnO/MnO2/rGO) nanocomposite (NC) as an electrode modifier material. Comprehensive characterization confirmed well-dispersed ZnO/MnO2 nanoparticles on rGO sheets. Electrochemical analysis revealed the ZnO/MnO2/rGO-NC-based modified electrode possesses low electrical resistance (126.2 Ω), high electrocatalytic activity, and rapid electron transport, attributed to the synergies between ZnO, MnO2 and rGO. The modified electrode demonstrated exceptional electrochemical performance in terms of selectivity for the simultaneous detection of HQ and PCC. Differential pulse voltammetry studies validated the proposed sensor's ability to detect HQ and PCC within linear response ranges of 0.01-115 μM and 0.03-60.53 μM, with detection limits of 0.0055 µM and 0.0053 µM, respectively. Practical validation using diverse water samples showcased excellent percent recovery of HQ and PCC using the ZnO/MnO2/rGO-based electrochemical sensor, underscoring the sensor's potential for real-world applications in environmental monitoring.

Simulation investigation of effects of substrate and thermal boundary resistance on performances of AlGaN/GaN HEMTs

The temperature distributions and thermal resistances of the GaN HEMTs fabricated on different substrates (sapphire, Si, SiC and diamond) with Mo/Au interlayers were calculated and analyzed by numerical simulation. The results show that the GaN HEMT on the diamond substrate exhibits the lowest channel temperature and thermal resistance, and the thermal resistance rises with the increase of the thermal boundary resistance (TBR) for all the GaN HEMTs with the different substrate materials. Meanwhile, the high TBR (2 × 10−7 m2·K/W) severely hinders the heat exchange between the GaN layer and the substrate, which makes it difficult for the heat flux to pass through the barrier. Even diamond with high thermal conductivity can hardly reduce the channel temperature of the device. Therefore, TBR must be reduced so that the heat flux can be dissipated through a high thermal conductivity substrate. In addition, the Mo/Au interlayer generates a lower thermal boundary resistance, which has little effect on the channel temperature, thermal resistance and interfacial temperature discontinuity of GaN HEMTs.