Dependence Of Resistance Research Articles

Umklapp electron-electron scattering in bilayer graphene moiré superlattice

Recent experimental advances have been marked by the observations of ballistic electron transport in moir\'e superlattices in highly aligned heterostructures of graphene and hexagonal boron nitride (hBN). Here, we predict that a high-quality graphene bilayer aligned with an hBN substrate features ${T}^{2}$-dependent resistivity caused by umklapp electron-electron (Uee) scattering from the moir\'e superlattice, that is, a momentum kick by Bragg scattering experienced by a pair of electrons. Substantial Uee scattering appears upon $p$ doping of the bilayer above a characteristic threshold, and its contribution towards the resistivity grows rapidly with hole density, until it reaches a peak value, then falling off by an order of magnitude. This rapid, nonmonotonic dependence of resistivity, in the density range where the system is otherwise highly conductive, suggests the possibility of a nonconventional field-effect transistor operation. We also analyze the influence of an electrostatically induced interlayer asymmetry (and the associated band gap) in the bilayer and trigonal warping on the electron-electron umklapp scattering.

Evidence of multi-band superconductivity in non-centrosymmetric full Heusler alloy LuPd2Sn

In this work, evidence of multi-band superconductivity and presence of mixed parity states in full Heusler alloy LuPd2Sn is investigated using the x-ray diffraction, temperature and field dependent resistivity, temperature dependent magnetization, and heat capacity measurements. Our studies reveal that LuPd2Sn is a type II superconductor and undergoes superconducting transition below 2.5 K. Above 2.5 K, the temperature and field dependence of resistivity indicate to the presence of multiple bands and inter-band phonon assisted scattering. The upper critical field, H C2 (T) exhibits linear behaviour and deviates from Werthamer, Helfand and Hohenberg model over the measured temperature range. Additionally, the Kadowaki–Woods ratio plot supports the unconventional superconductivity in this alloy. Moreover, a significant deviation from the s-wave behaviour is noted, which is studied using phases fluctuation analysis. It indicates the presence of spin triplet along with spin singlet component arising due to antisymmetric spin orbit coupling.

Nature of polaronic hopping conduction mechanism in polycrystalline and nanocrystalline Gd0.5Sr0.5MnO3 compounds

In the present study, we have investigated the structural, electrical and magneto-transport properties of polycrystalline and nanocrystalline Gd0.5Sr0.5MnO3 compounds. The variation of transport properties is modified by tuning the grain size of the material. In the high temperature semiconducting region, temperature dependent resistivity data can be well explained by non-adiabatic small polaron hopping (SPH) mechanism. In addition, the resistivity data for all compounds in the low-temperature paramagnetic region can also be well explained by the variable range hopping (VRH) model. The parameters obtained from SPH and VRH mechanisms are found to be reasonable. In the case of nanocrystalline compounds, there is an overlapping temperature range where both SPH and VRH models are valid simultaneously, and a new conduction mechanism - variable range hopping of small polaron s(VR-SPH) is satisfactorily valid for the whole temperature range of these compounds. However, for the polycrystalline compound, the overlapping temperature region between VRH and SPH models does not exist and the VR-SPH mechanism is not valid here. Thus, polarons play a leading role in selecting different conduction mechanisms in different temperature ranges.

Magnetic and Magnetotransport Properties of the Magnetic Topological Nodal‐Line Semimetal TbSbTe

AbstractThe magnetic properties, magneto‐resistivity, Hall resistivity, Seebeck coefficient, and heat capacity are investigated for a magnetic topological nodal‐line semimetal TbSbTe. The calculated energy‐band structures of TbSbTe show two nodal rings on the kx‐ky planes, and the Fermi surface possesses one electron pocket with an enclosure of one hole pocket around the Γ point. The multiple magnetic phase transitions are induced at critical magnetic fields of Hc1 ≈ 10.5 kOe, Hc2 ≈ 20.8 kOe, and Hc3 ≈ 38.2 kOe at 2 K for the H // ab plane. Temperature dependence of electrical resistivity displays a hump‐like feature around 240 K, a general positive slope above TN = 6 K but a negative slope below TN. The magnetoresistance exhibits a conversion from the semi‐classical H2 dependence at weak fields to the linear‐field dependence at high fields, indicating the presence of a Dirac linear energy dispersion. TbSbTe may provide an ideal platform for studying topological physics and designing devices based on topological quantum materials.

Influence of Bi3+ substitution on the structural and magnetic properties of Pr0.6Sr0.4MnO3 ceramics

We report the structural and magnetic phase transition induced in Pr0.6Sr0.4MnO3 as Pr3+ ions are replaced by Bi3+. Analysis of Rietveld refinement of the X-ray diffraction data reveals a change in crystal symmetry from orthorhombic, space group Pnma for x ≤ 0.20 to Imma for x > 0.50. Across intermediate Bi3+ substitution (0.25 ≤ x ≤ 0.40), a structural phase coexistence of Pnma and Imma symmetry is found. Based on the combined studies of electrical and magnetic properties, a magnetic phase diagram for Bi substituted Pr0.6Sr0.4MnO3 samples is proposed here. The electrical resistivity and magnetization studies for partial Bi3+ substituted samples x ≤ 0.10 indicate samples to be ferromagnetic metallic with TC = 310 K and 290 K for x = 0.0 and 0.10 respectively. As Bi3+ concentration increases, TC decreases, and the system transforms to be antiferromagnetic insulating with TN = 158 K for x = 0.60 accompanied by a spin glass like state below 10 K. For samples with intermediate Bi3+ concentrations i.e., 0.25 ≤ x ≤ 0.40, field induced metamagnetic magnetization loops (M vs. H) imply the competitive coexistence of ferromagnetic and antiferromagnetic interactions in the same matrix. Also, the open loops in field dependent resistance curves (MR vs. H) for 0.20 ≤ x ≤ 0.40, specify the field induced transition from insulating to metallic state. The magnetoresistance improves on increasing Bi3+, with MR% reaching a maximum of 100% for 0.20 ≤ x ≤ 0.30 samples.

Thickness-tunable magnetic and electronic transport properties of the quasi-two-dimensional van der Waals ferromagnet Co0.27TaS2 with disordered intercalation

The intercalation of magnetic elements in nonmagnetic van der Waals (vdW) materials is an effective way to design different (quasi) 2D magnets and produce exotic properties. More specifically, how exactly the intercalator is distributed within the synthetic crystal can also affect the physical properties substantially. In contrast to conventional $3d$ transition-metal intercalates of niobium and tantalum dichalcogenides, which commonly have $2\ifmmode\times\else\texttimes\fi{}2$ or $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}$ type ordered intercalation, we report a disordered intercalation of Co atoms between the vdW gaps of $2H$-tantalum disulfide ($2H\text{-Ta}{\mathrm{S}}_{2}$). The obtained quasi-vdW ferromagnet ${\mathrm{Co}}_{0.27}\mathrm{Ta}{\mathrm{S}}_{2}$ shows both perpendicular magnetic anisotropy and thickness-tunable magnetic properties. More interestingly, the temperature dependence of electrical resistivity shows a semiconductorlike behavior, in contrast to the metallic feature of other analogs in this material family. This unexpected phenomenon can be understood through a variable-range hopping mechanism, which is due to highly disordered intercalation. Moreover, ${\mathrm{Co}}_{0.27}\mathrm{Ta}{\mathrm{S}}_{2}$ shows a side-jump scattering dominated anomalous Hall effect, which can also be related to the disordered distribution of Co intercalators.

Magnetoelastic coupling with inverse magnetocaloric effect observed in Sr2YRuO6

Sr2YRuO6, a 4d transition metal, Ru ion based double perovskite crystallizes in monoclinic structure with Y and Ru octahedra ordering alternately. The relevance of lattice distortion to complex magnetic ground state is investigated from structural, vibrational, magnetic, transport and thermal properties. Raman modes due to monoclinic distortions are observed. From the temperature dependent magnetization studies, a magnetic transition is observed at 25 K and below that the presence of weak ferromagnetic contribution is noticed. A magnetic frustration parameter of six is evaluated from the magnetic results that suggest the presence of spin frustration on the Ru octahedra leading to geometric frustration in SYRO. Isothermal magnetization measurements are carried out for several temperatures from 8 K to 70 K in small temperature intervals to determine the magnetocaloric effect of Sr2YRuO6. The change in magnetic entropy around the Neel temperature, 25 K and Inverse magnetocaloric effect is observed in the system around this temperature. The change in isothermal magnetic entropy results indicates a canted AFM structure as the ground state. Neutron diffraction data refined using propagation vector, k = (0.5,0.5,0) reveal antiferromagnetic ordering at temperatures below 30 K down to 2 K. Variation of the lattice parameters with temperature from the neutron powder diffraction result signifies the presence of magnetoelastic coupling around 25 K. From the temperature dependent resistivity measurements, a small polaron hopping like conductivity is observed in the system. Activation energy reduces with the increase in temperature. Temperature dependent specific heat data shows no ordering, the absence of peak around magnetic transition along with magnetic contribution well above transition temperature is consistent with magnetic frustration in this system.

High-performance non-Fermi-liquid metallic thermoelectric materials

Searching for high-performance thermoelectric (TE) materials in the paradigm of narrow-bandgap semiconductors is hampered by a bottleneck. Here we report on the discovery of metallic compounds, TiFexCu2x−1Sb and TiFe1.33Sb, showing the thermopower exceeding many TE semiconductors and the dimensionless figure of merits zTs comparable with the state-of-the-art TE materials. A quasi-linear temperature (T) dependent electrical resistivity in 2–700 K and the logarithmic T-dependent electronic specific heat at low temperature coexist with the high thermopower, highlighting the strong intercoupling of the non-Fermi-liquid (NFL) quantum critical behavior of electrons with TE transports. Electronic structure analysis reveals a competition between the antiferromagnetic (AFM) ordering and Kondo-like spin compensation as well as a parallel two-channel Kondo effect. The T-dependent magnetic susceptibility agrees with the quantum critical scenario of strong local correlation. Our work demonstrates the correlation among high TE performance, NFL quantum criticality, and magnetic fluctuation, which opens up directions for future research.

Phase field theory for pressure-dependent strength in brittle solids with dissipative kinetics

A phase field theory of fracture mechanics is formulated to address dependence of material strength on stress state, noting that brittle solids are usually more fracture resistant when mean stress is compressive. Fracture is addressed via a dissipative kinetic law which instills rate dependence and viscous resistance to propagation. A dependence of kinetic viscosity on triaxiality for locally compressive stress states is proposed. Solutions are derived to one-dimensional problems for an isotropic material, linear or nonlinear elastic, under different loading protocols: uniaxial stress extension, uniaxial stress compression, and uniaxial strain compression. Analytical results enable determination of parameters and verification of finite element predictions. Three-dimensional simulations of polycrystalline microstructures are enacted under similar loading protocols. Results provide insight into effects of crystalline microstructure and anisotropy for different stress states. With increasing confinement, the ratio of macroscopic pressure to shear stress increases, and influences of microstructure and anisotropy on average stress and ductility are reduced.

Correlation between electron-phonon coupling and superconductivity of Sn2+ ion irradiated MgB2-thin films

This study investigates the impact of 2 MeV Tin ion (Sn2+) irradiation with doses from 2E12 to 7E13 on the Raman spectroscopy and superconductivity properties of MgB2-thin films samples. Raman spectroscopy has been used to examine the behavior of electron-phonon coupling (EPC). For the superconductivity properties, the temperature dependence resistivity, R(T), and the magnetic field-dependent magnetization, M(H), were measured. The import of EPC, which is related to the change in critical temperature (Tc), was calculated using the McMillan-formula modified by Allen–Dynes, using the phonon frequency of the middle peak center ω2(E2g). Raman spectroscopy showed that the value of EPC decreased from 1.113 (Pristine) to 0.969 (7E13). Although the critical temperature (Tc) decreased with increasing Sn2+ ion doses, the values of the in-field critical current density (Jc) and upper critical field (Hc2) increased and reached a maximum for the 5E13 sample. In addition, the magnetic penetration depths of the pristine and optimal dose (5E13) samples were measured using magnetic force microscopy (MFM), providing the thermodynamic critical field (Hc) in the MgB2 films.

Predictors of steroid dependence and resistance in patients with ulcerative colitis

AIM: detection of steroid dependence and steroid resistance predictors in patients with ulcerative colitis (UC).PATIENTS AND METHODS: a retrospective study was conducted. The medical documentation of 1105 patients, who underwent inpatient treatment in Ryzhikh National Medical Research Center of Coloproctology from 2018 to 2021, were analyzed. 69% of patients (n=762) received systemic steroid therapy for UC. In accordance with inclusion and non-inclusion criteria, the medical documentation of 170 patients was selected for statistical analysis. Depending on the steroid status of patients, three groups were identified: group 1 (n=56) with steroid dependence, group 2 (n=56) with steroid resistance and group 3 - control (n=58), who were prescribed systemic GCS without the further development of steroid dependence and resistance.RESULTS: the incidence of steroid dependence was 23.4% (n=259), and steroid resistance was 15.2% (n=168). We identified the following predictors and risk factors of steroid dependence: age of the disease onset <30 y.o. (AOR=0,960, 95%CI= 0,928-0,993, p=0,019), start dose of prednisolone <60 mg (AOR=2,369, 95%ДИ= 1,030-5,441, p=0,042), prescription of systemic GCS ≥2 courses per year (AOR=2,988, 95%ДИ= 1,349-6,619, p=0,007), Mayo Index Score <10 (AOR=0,631, 95%ДИ=0,492-0,809, p<0,001). The risk of steroid resistance statistically significant when Mayo Index Score ≥10 (AOR=2,573, 95%ДИ=1,094-6,050, p=0,030), albumin level <37,1 g/l (AOR=4,571, 95%ДИ=1,567-13,330, p=0,005), CRP ≥47,1 mg/l (AOR=2,641, 95%ДИ=1,102-6,328, p=0,029).CONCLUSION: it is rational to predict an individual response to GCS in patients with UC. With a high risk of developing steroid dependence and steroid resistance, it is advisable to consider early appointment of biological and target therapy, avoiding represcription of GCS.

How do three-layer surgical masks prevent SARS-CoV-2 aerosol transmission?

The three-layer surgical mask was recognized by the World Health Organization as an effective-protection tool for reducing SARS-CoV-2 transmission during the COVID-19 pandemic; however, the contribution of each layer of this mask to the particle size–dependent filtration performance resistance remains unclear. Here, both experimental work and numerical simulation were conducted to study the role of each mask layer in particle size–dependent filtration and respiratory resistance. By using scanning electron microscopy images of a commercial three-layer mask, composed of two spun-bond and one melt-blown nonwoven polypropylene fabric layers, four representative models were constructed, in which the computational fluid dynamics of multiphase flow were performed. The pressure drop of all models under different flow conditions was measured next. Numerical simulation was then verified by comparing the experimental results in the present study and other theoretical works. The filtration efficiency of the spun-bond polypropylene nonwoven fabric layer was much lower than that of the melt-blown nonwoven polypropylene fabric layer for the particle diameter in the range of 0.1–2.0 μm. Both the spun-bond and melt-blown nonwoven polypropylene fabric layers demonstrated extremely low filtration efficiency for particles was<0.3 μm in diameter, with the maximum filtration efficiency being only 30%. The present results may facilitate rational design of mask products in terms of layer number and structural design.

Signs of the presence of an ordered phase in the Cu-5.9 at.% Pd alloy after its long-term annealing at a moderate temperature

The structure and electrical properties of the Cu-5.9 at.% Pd alloy were studied after its annealing for two months at 250°C. As a result of such a long-term thermal treatment, in the XRD patterns taken from the alloy one can observe a weak superstructural (100) reflection, which seems abnormal, since the alloy can only be in the state of a disordered single-phase solid solution (as it follows from the generally accepted Cu-Pd phase diagram). Quantitative analysis of the X-ray diffraction patterns reveals the presence of two new phases with different contents of Pd. An assumption is made that L12 superstructure can be formed in the Pd-enriched phase. The specific features observed in the temperature dependence of electrical resistivity, as well as the TEM results, confirm this set-forth hypothesis of ours. Using the resistometric method, the temperature of the order-disorder phase transition in the alloy was estimated as Tc ≈ 340°С. It is concluded that the position of the A1-(A1 + L12) phase boundary in the Cu-Pd phase diagram requires more precise definition in the region of compositions on the side of the low Pd content.

Transient multilayer analytical model of a line heat source probe for in-pile thermal conductivity measurements

In-pile measurements of nuclear fuel properties is of critical importance for the design, performance, and safety considerations of next generation nuclear reactors and can be difficult due to the high temperature and high neutron flux environment. Real-time data for thermal conductivity is currently lacking due to the difficulty in deploying advanced instrumentation for thermal properties measurements in situ during nuclear operations. This limitation hinders our understanding of the mechanisms responsible for these changes. In this study, we have developed analytical models, utilizing the quadrupoles method, for in-pile thermal conductivity measurements using a novel line heat source. This probe uses Joule heating of a single wire to induce a temperature gradient and heat flow in surrogate fuel samples, while simultaneously leveraging the temperature dependent resistance of the wire as a thermometer to monitor the temperature rise of the sample for thermal conductivity extraction. The analytical models have been verified against more computationally intensive finite element models and experimental results were obtained from Teflon (PTFE) and aluminum samples. Coefficient of determination (R2) values for the measurements were 0.995, 0.987, and 0.992 for 10, 20, and 30 mm PTFE respectively and 0.983, 0.992, and 0.960 for 10, 20, and 30 mm aluminum respectively. Further complimenting the fits, sensitivity parameter studies were conducted on the 10 and 30 mm PTFE and aluminum highlighting the potential of our approach for rapid in-pile thermal conductivity measurements.

Electronic transport properties of GeS single crystals grown by vapor transport from molten GeS source

The electrical properties of GeS single-crystal are determined by the Van der Pauw method as a function of the temperature, thus establishing for the first time the dependence of electrical resistivity on both carrier concentration and mobility. This was possible after the repeated growth of GeS by vapor transport from molten GeS so that high-purity (low concentration of Fe and Na impurities) and high-crystalline (XRC FWHM = 2 min.) GeS single-crystals could be obtained. An extraordinary high electrical conductivity is observed between 180 and 450 K, ranging from 1.1 x10-2 to 3.7 x10-5 Ω−1 cm−1. Acceptors are activated over the whole temperature range, while donor activation takes place above 280 K, partially compensating the hole carrier concentration. In contrast, the mobility is proportional to T−2.4 over the whole temperature range, indicating the predominance of lattice scattering. At room temperature the electrical conductivity is as high as 6.7 × 10-3 Ω−1 cm−1, originating from a hole concentration of 1.7 × 1015 cm−3 and mobility of 25 cm2/Vs.

N-hydroxypipecolic acid induces systemic acquired resistance and transcriptional reprogramming via TGA transcription factors.

N-hydroxypipecolic acid (NHP) accumulates in pathogen-inoculated and distant leaves of the Arabidopsis shoot and induces systemic acquired resistance (SAR) in dependence of the salicylic acid (SA) receptor NPR1. We report here that SAR triggered by exogenous NHP treatment requires the function of the transcription factors TGA2/5/6 in addition to NPR1, and is further positively affected by TGA1/4. Consistently, a tga2/5/6 triple knockout mutant is fully impaired in NHP-induced SAR gene expression, while a tga1/4 double mutant shows an attenuated, partial transcriptional response to NHP. Moreover, tga2/5/6 and tga1/4 exhibited fully and strongly impaired pathogen-triggered SAR, respectively, while SA-induced resistance was more moderately compromised in both lines. At the same time, tga2/5/6 was not and tga1/4 only partially impaired in the accumulation of NHP and SA at sites of bacterial attack. Strikingly, SAR gene expression in the systemic tissue induced by local bacterial inoculation or locally applied NHP fully required functional TGA2/5/6 and largely depended on TGA1/4 factors. The systemic accumulation of NHP and SA was attenuated but not abolished in the SAR-compromised and transcriptionally blocked tga mutants, suggesting their transport from inoculated to systemic tissue. Our results indicate the existence of a critical TGA- and NPR1-dependent transcriptional module that mediates the induction of SAR and systemic defence gene expression by NHP.

Therapeutic effect of gedatolisib, a pan-PI3K/mTOR inhibitor, on prostate cancer models with PI3K or PTEN mutational status.

149 Background: Metastatic castration-resistant prostate cancer (mCRPrC) is characterized by a loss of androgen receptor (AR) sensitivity and oncogenic activation of the PI3K, AKT, and mTOR (PAM) pathway. Loss of the PI3K regulator, PTEN, is frequent during prostate cancer (PrC) initiation, progression, and therapeutic resistance. Co-targeting PAM/AR pathways is a promising PrC treatment strategy but hampered by complex PAM-AR pathway crosstalk driving either reciprocal negative feedback inhibition or feedback relief. Most PAM inhibitors (PAM-i) selectively spare (or weakly inhibit) one or more key PAM pathway components, potentiating drug resistance depending on the PAM mutation status of patients. AKT-i demonstrated limited efficacy in PTEN-deficient PrC and even less efficacy in PTEN-wild type (wt) in recent clinical studies, suggesting that more comprehensive inhibition of the PI3K isoforms and mTOR may be required. We posited that gedatolisib, a well-tolerated and potent inhibitor of all Class I PI3K isoforms, mTORC1, and mTORC2, would be effective in both PTEN-wt and PTEN-deficient PrC. Methods: A panel of PrC cell lines with different PI3K or PTEN status ( wt: 22RV1, MDA-PCa-2b, DU145; null: LNCaP, PC3, C4-2) were assayed under different conditions for their sensitivity to gedatolisib and other PAM-I ( PI3K: alpelisib, copanlisib; AKT: capivasertib, ipatasertib; mTOR: everolimus; pan-PI3K/mTOR: samotolisib, gedatolisib). A combination of cell viability, growth rate, cytotoxicity and phospho-FACS analytical assays were used. Xenograft studies evaluating gedatolisib with a subset of these models were also performed in castrated mice. Results: We confirmed that AKT-i is more effective in PTEN-null than PTEN-wt PrC. In contrast, the two pan-PI3K/mTOR-i evaluated were effective independent of PI3K or PTEN status. Gedatolisib exhibited superior potency and efficacy compared to each of the other PAM-i for cell proliferation, death, or PAM pathway activation. In vivo, gedatolisib substantively inhibited tumor growth regardless of PTEN or PI3K status. Conclusions: We demonstrated that gedatolisib exerts superior activity regardless of PI3K or PTEN status in all PrC cell lines evaluated compared to the other PAM pathway inhibitors evaluated. Our results indicate potent and simultaneous blockade of all Class I PI3K isoforms, mTORC1, and mTORC2 could circumvent PTEN dependent resistance. Gedatolisib as a single agent and in combination with other therapies reported promising preliminary efficacy and safety in various solid tumor types. In light of the PrC findings reported here, development of gedatolisib may be warranted in PrC patients regardless of their PTEN or PI3K status.

Bias dependent NDR in TiO2/NiO heterojunction diodes

TiO2/NiO thin film heterojunction diodes are fabricated using electron beam evaporation and DC sputtering techniques. Three different thicknesses of NiO (58, 82, and 160 nm) are combined with a TiO2 film of about 80 nm thick. The common device configuration is FTO/TiO2/NiO/Au with a 4 mm sq. device area. The thickness dependent diode I-V characteristics were analyzed; with the increase in thickness, the diode knee voltage, series resistance, and ideality factor have reduced. All the devices exhibit a high diode ideality factor, which means the diode currents are not limited by drift, diffusion, or recombination at the space charge region. The high ideality factor points to the presence of interface states, spatial inhomogeneities, or tunneling in the devices. Further, the bias dependent negative differential resistance (NDR) in I-V characteristics and the presence of an anomalous peak in C-V characteristics were analyzed, which claimed the presence of interfacial trap states, defects, or tunneling in the diodes. The Fowler-Nordheim tunnel model was applied to the devices and the field enhancement factors were calculated as −14.3, −9.3, and −9.2 for the diodes in the increasing order of thickness. The tunneling phenomenon was confirmed as trap-assisted indirect tunneling. Also, the temperature dependence of NDR was studied.

Conductive Additive Manufactured Acrylonitrile Butadiene Styrene Filaments: Statistical Approach to Mechanical and Electrical Behaviors.

Additive manufacturing is a process in which digital three-dimensional (3D) design data are used to build a component in layers by accumulating materials. There are many materials used in additive manufacturing technology. The most basic features that distinguish these materials are their strength and electrical behavior. They can be strong or flexible, resistant to abrasion, depending on the application used. Recently, 3D printing filament and polymeric composite materials combined with carbon nanostructures with electrical conductivity have been used. In this study, acrylonitrile butadiene styrene (ABS), a carbon black-filled conductive material with high strength and hardness, was preferred. The aim in this study is to focus on the mechanical and electrical behavior of the material processed in filament form. Fabrication of samples was done using a fused deposition modeling-based printer that controls filament orientation. Different experimental studies were conducted: (1) mechanical tests to determine the maximum tensile strength values of the samples; and (2) electrical tests to analyze the electrical resistances of the samples. In the design of the first experiment, infill volume, layer height, infill type, and printing direction were determined as factors affecting strength. In the design of the second experiment, the length, nozzle temperature, and measurement temperature were determined as the factors affecting the electrical resistance. Statistical analysis of the measured data was performed to evaluate the overall result of the experiments. Finally, a prediction model of real-time tensile strength and resistance values was created using machine learning algorithms. These algorithms are Gaussian Process Regression and Support Vector Machine. The results confirmed the known linear dependence of electrical resistance on the length of the 3D-printed conductive ABS samples and showed how changing the fabrication settings affected the strength values.

The Effect of Opto-Electronic Transition Type on the Electric Resistivity of Cr-Doped Co3O4 Thin Films

Cr-doped Co3O4 thin films were prepared by spray pyrolysis on soda-lima glass. The structure and morphology of the prepared samples were characterized by grazing incidence X-ray diffraction (GIXRD), Fourier-transform infrared spectroscopy (FTIR) and Scanning electron Microscopy (SEM). The results indicated the formation of a single cubic spinel phase with a crystallite size of about 6 nm. Different electronic transitions and estimations of the band gap structure were determined from the optical absorption spectra. The dependence of electrical resistivity on Cr content was investigated. It was found that the resistivity increased by increasing the Cr content. In addition, the effect of photon excitation on the electrical properties showed that the electrical resistivity decreased under visible illumination (λvis. = 532 nm) and increased under infrared illumination (λIR = 780 nm). The relative change in resistivity (sensitivity) under both light illuminations was enhanced by increasing the Cr content. Therefore, this work introduces a new application for Co3O4 material as a light detector.