Double Loop Research Articles

Terahertz ultra-wideband antenna with tunable band-notch creation using resonant/non-resonant graphene loop

The state of graphene loop applied in the slotted antenna radiator is converted from non-resonant to resonant to achieve the tunable band-notch characteristics in an ultra-wideband (UWB) antenna. In the non-resonant state, the graphene loop with value of chemical potential as 0 eV acts as a parasitic element and does not contribute to radiation. Increasing the chemical potential of graphene starts converting the state of graphene loop from non-resonant to resonant. The graphene surface starts confining the localized surface plasmons with the increment in chemical potential and hence the multiple higher order resonances are formed. The higher order resonance with the destructive effect provide the band-notch characteristic in UWB response. The variation in chemical potential can tune the created notched band over frequency. Also, conversion of state of graphene loop from non-resonant to resonant deteriorates the far-field radiation parameters and radiation efficiency of antenna drastically. A trade-off can be set to find the required value of gain and radiation efficiency and frequency of the created band notch. Moreover, another technique of utilizing the double graphene loops with less surface area has also been studied, which allows one to attain the higher radiation efficiency of antenna along with the band-notch characteristics.

DL-EPR vs. LSV-KOH: from simple detection of deleterious phases to analysis of morphology and high accuracy on determination of sigma phase in UNS S32750 stainless steel

ABSTRACT An optimised electrochemical technique, linear sweep voltammetry (LSV) in KOH solution (LSV-KOH) was confronted with the double loop electrochemical Potentiokinetic reactivation (DL-EPR) to verify which is the best technique to quantify deleterious phases (DP) in a UNS S32750 super duplex stainless steel. DL-EPR presented an error in determination of deleterious phases in the range of 6.9–100%. LSV-KOH show a better accuracy in quantification of deleterious phases volume fractions, the error range for LSV-KOH was 2.4–26.2%. When the morphology of sigma changes from lamellar to divorced, was observed modifications on LSV-KOH voltammograms. In specimens where lamellar morphology is present, the voltammograms show two peaks curve. Meanwhile, in specimens where occurred also divorced precipitation of sigma the voltammograms changes to a 3 peaks curve. This feature is due to the dissolution of sigma phase boundaries which has different compositions according to the form of sigma precipitation.

Enhanced modified reliability index approach for efficient and robust reliability‐based design optimization

AbstractThe reliability index approach (RIA) is one of the effective tools for solving the reliability‐based design optimization (RBDO) probabilistic model, which models the uncertainties with probability constraints. However, its wide application in engineering is limited due to low efficiency and convergence problems. The RIA‐based modified reliability index approach (MRIA) appears to be very robust and accurate than RIA but yields inefficient for the most probable point (MPP) search with highly nonlinear probabilistic constraints. In this study, an enhanced modified reliability index approach (EMRIA) is developed to improve the efficiency and robustness of searching for MPP and is utilized for RBDO. In the EMRIA, an innovative active set using rigorous inequality is applied to construct the region of exploring for MPP, where the unnecessary probabilistic constraint could be eliminated adaptively during the iterative process. Moreover, the double loop strategy (DLS) is integrated into the EMRIA to strengthen the efficiency and robustness of large‐scale RBDO problems. Two numerical examples demonstrated that the EMRIA is an efficient and robust method for MPP search in comparison with current first‐order reliability methods. Six RBDO problems quoted also indicate that DLS‐based EMRIA has good performance to solve complex RBDO problems.

Compensated Deadbeat Predictive Current Control Considering Disturbance and VSI Nonlinearity for In-Wheel PMSMs

In this article, a compensated deadbeat predictive current control (CDPCC) based on composite sliding mode disturbance observer (CSMDO) is proposed in response to the detrimental disturbance. Above all, the parameter variation and external load change are regarded as a lumped disturbance to build the PMSM mathematical model. Based on this model, a CSMDO is constructed to estimate the lumped disturbance in both speed and current loops. Then, the estimated disturbances are applied as compensations for the double loops to increase the speed robustness and current tracking accuracy. Furthermore, a voltage space vector compensation method is introduced to reduce the current distortion resulting from the added dead time in the three-phase full-bridge voltage source inverter. In the end, the effectiveness of the CDPCC method is validated by experiments through an in-wheel PMSM drive.

Norman window slot antenna with sectoral feed backed by linear phase reflector for ultra wideband applications

An ultra wideband (UWB) slot antenna is proposed, developed, and experimentally validated in this article. The Norman window-shaped UWB slot antenna demonstrates stable radiation characteristics in both directions—zenith (θ = 0°) and nadir (θ = 180°) over the entire UWB frequency range (3.1–10.6 GHz) as observed in both simulations and experiments. A linear phase reflecting UWB frequency selective surface (FSS) is proposed by printing two orthogonal layers of pair of double rectangular loops on the same side of dielectric substrate as a merged frequency selective surface (MFSS). The UWB MFSS is then loaded with the slot antenna and the impact of MFSS on the impedance and radiation characteristics in different configurations of antenna and MFSS together is studied. One configuration with optimum solution is developed for experimental validations followed by the analysis of its radiation characteristics. The proposed antenna demonstrates a directional radiation pattern due to suppression of back lobe radiation when integrated with the UWB MFSS. The proposed antenna demonstrates maximum gain of 7.86 dB with a gain enhancement of 3.6 dB in boresight (θ = 0°) direction when MFSS is applied as a reflector to opposite side of the antenna slot.

Sigmoid Formation through Slippage of a Single J-shaped Coronal Loop

A well-known precursor of an imminent solar eruption is the appearance of a hot S-shaped loop, also known as a sigmoid, in an active region (AR). Classically, the formation of such an S-shaped loop is envisaged to be implemented by magnetic reconnection of two oppositely oriented J-shaped loops. However, the details of reconnection are elusive due to weak emission and subtle evolution during the preeruptive phase. In this paper, we investigate how a single J-shaped loop transforms into an S-shaped one through the slippage of one of its footpoints in NOAA AR 11719 on 2013 April 11. During an interval of about 16 minutes, the J-shaped loop slips through a low-corona region of strong electric current density in a bursty fashion, reaching a peak apparent speed of the slipping footpoint as fast as 1000 km s−1 and over. The enhancement of electric current density, as suggested by nonlinear force-free field modeling, indicates that the “nonidealness” of coronal plasma becomes locally important, which may facilitate magnetic reconnection. The loop segment undergoing slipping motions is heated; meanwhile, above the fixed footpoint coronal emission dims due to a combination effect of the lengthening and heating of the loop; the latter of which is manifested in the temporal variation of dimming slope and of emission measure. These features together support an asymmetric scenario of sigmoid formation through slipping reconnection of a single J-shaped loop, which differs from the standard tether-cutting scenario involving a double J-shaped loop system.

Approximate Laplace importance sampling for the estimation of expected Shannon information gain in high-dimensional Bayesian design for nonlinear models

One of the major challenges in Bayesian optimal design is to approximate the expected utility function in an accurate and computationally efficient manner. We focus on Shannon information gain, one of the most widely used utilities when the experimental goal is parameter inference. We compare the performance of various methods for approximating expected Shannon information gain in common nonlinear models from the statistics literature, with a particular emphasis on Laplace importance sampling (LIS) and approximate Laplace importance sampling (ALIS), a new method that aims to reduce the computational cost of LIS. Specifically, in order to centre the importance distributions LIS requires computation of the posterior mode for each of a large number of simulated possibilities for the response vector. ALIS substantially reduces the amount of numerical optimization that is required, in some cases eliminating all optimization, by centering the importance distributions on the data-generating parameter values wherever possible. Both methods are thoroughly compared with existing approximations including Double Loop Monte Carlo, nested importance sampling, and Laplace approximation. It is found that LIS and ALIS both give an efficient trade-off between mean squared error and computational cost for utility estimation, and ALIS can be up to 70% cheaper than LIS. Usually ALIS gives an approximation that is cheaper but less accurate than LIS, while still being efficient, giving a useful addition to the suite of efficient methods. However, we observed one case where ALIS is both cheaper and more accurate. In addition, for the first time we show that LIS and ALIS yield superior designs to existing methods in problems with large numbers of model parameters when combined with the approximate co-ordinate exchange algorithm for design optimization.

Investigation of intergranular stress corrosion cracking in a failed 347H stainless steel furnace tube

A 347H stainless steel tube of a furnace of a hydroprocessing unit was cracked during operation shortly after the last shutdown. Both internal and external surfaces of the tube were exposed to sulfur compounds. Material characterization methods including tensile test, double loop electrochemical potentiodynamic reactivation test and fractography were used to investigate the failure causes. Based on stereo investigations, the external surface of the tube was identified as the crack initiation location. The microstructure evaluation and DL-EPR test showed that sensitization with a high DOS value of 18 occurred in the tube material. The sensitization has resulted in a dramatic reduction in the elongation parameter. Fractography examination exhibited a brittle fracture with presence of sulfide corrosion products on the fracture surface. Finally, due to the combination of the obtained results and additional observations including corrosion within grain boundaries and intergranular cracking, polythionic stress corrosion cracking was determined as the failure mechanism.

Design and characterisation of a dual probe with double‐loop structure for simultaneous near‐field measurement

In this study, a near-field dual probe with a double-loop structure is designed and characterised. The high-performance, low-loss Rogers material and four-layer printed circuit board are applied to design the double detection loop structure, which increases the detection area and effectively improves the frequency response of the probe. The key parameters of the probe, including the frequency response, calibration factor, sensitivity, spatial resolution, isolation and differential electric field suppression are characterised by a microstrip line. Compared with other dual probes, the proposed probe has better frequency response and higher sensitivity. The magnetic field sensitivity is −90.88 dB A/m/ H z $\sqrt{\mathrm{H}\mathrm{z}}$ and the electric field sensitivity is −46.89 dB A/m/ H z $\sqrt{\mathrm{H}\mathrm{z}}$ at 1 GHz.

The effect of acceptor dopant on the memory effect of BaTiO3 ceramics

In the present study, BaTi(1-x)MxO3 (x = 0.005, 0.01, 0.015; M is Mn, Fe, and Co) ceramics were prepared by the conventional solid-state reaction method. Four distinct and independently addressed memory states were experimentally obtained based on the double hysteresis loop, which was achieved by acceptor doping in BaTiO3 ceramics. Moreover, this study indicated that for acceptor-doped BaTiO3 ceramics, larger electronegativity and smaller ionic radius of acceptor ions benefitted the more significant memory effect and better fatigue resistance. All these results could provide a promising solution for multi-state memory applications.

Record high-Tc and large practical utilization level of electric polarization in metal-free molecular antiferroelectric solid solutions

Metal-free antiferroelectric materials are holding a promise for energy storage application, owing to their unique merits of wearability, environmental friendliness, and structure tunability. Despite receiving great interests, metal-free antiferroelectrics are quite limited and it is a challenge to acquire new soft antiferroelectric candidates. Here, we have successfully exploited binary CMBrxI1-x and CMBrxCl1-x solid solution as single crystals (0 ≤ x ≤ 1, where CM is cyclohexylmethylammonium). A molecule-level modification can effectively enhance Curie temperature. Emphatically, the binary CM-chloride salt shows the highest antiferroelectric-to-paraelectric Curie temperature of ~453 K among the known molecular antiferroelectrics. Its characteristic double electrical hysteresis loops provide a large electric polarization up to ~11.4 μC/cm2, which endows notable energy storage behaviors. To our best knowledge, this work provides an effective solid-solution methodology to the targeted design of new metal-free antiferroelectric candidates toward biocompatible energy storage devices.

Fetal-maternal incompatibility in the Rh system. Rh isoimmunization associated with hereditary spherocytosis: case presentation and review of the literature.

Next to A and B antigens, agglutinogen D exhibits the highest immunogenicity. Following the transfusion of D-positive red blood cells (RBCs), almost 80% of D-negative recipients develop anti-D antibodies (Abs). Subsequently, anti-D immunization further promotes the synthesis of Abs towards other blood group antigens in or outside the Rh system. The D antigen is also involved in 95% of cases of hemolytic disease of the newborn. Transfusions, hemotherapy, grafts, and obstetric history (abortions, ectopic pregnancy, births) are all risk factors for Rh isoimmunization. In the case of ABO compatibility between mother and fetus, Rh-positive fetal RBCs that have reached the maternal bloodstream are not destroyed by group agglutinins, and Rh antigenic sites are not hidden by the maternal immune system. But a Rh-negative mother with a homozygous Rh-positive husband will certainly have a Rh-positive fetus. As it has an irreversible evolution, the Rh isoimmunization once installed cannot be influenced in the sense of decreasing the Ab titer, therefore, injectable globulin has no effect. A particular case was that of a newborn with Rh system incompatibility associated with hereditary spherocytosis The clinical balance at birth reflects the severe jaundice of the female newborn of 3140 g, gestational age 38∕39 weeks, extracted by lower-segment transverse Caesarean section, with a double loop nuchal cord, Apgar score 8. Because the jaundice was severe and atypical (face and upper chest), we considered the possibility of coexistence of hemolytic disease of the newborn by Rh blood group incompatibility associated with hereditary spherocytosis, as it turned out to be true and mentioned. Changes in genes encoding proteins in the structure of the RBC membrane have amplified hemolysis induced by maternal-fetal isoimmunization in the Rh system. Massive hemolysis accentuated by congenital spherocytosis, confirmed later, imposed blood transfusion and dynamic monitoring.

Hybrid uncertainty propagation and reliability analysis using direct probability integral method and exponential convex model

Uncertainty propagation and reliability evaluation, being the crucial parts of engineering system analysis, play vital roles in safety assessment. How to reasonably consider the complex multisource uncertainty behavior in both static and dynamic systems is paramount to ensuring their safe operation. However, there is a significant lack of research on aleatory and epistemic uncertainties for both static and dynamic systems. To this end, a new hybrid exponential model is proposed by combining probabilistic and non-probabilistic exponential models, which aims to accurately measure the uncertainty propagation and reliability evaluation problem with aleatory and epistemic uncertainties for static and dynamic systems. The proposed hybrid exponential model consists of nested double optimization loops. The outer loop performs a probabilistic analysis based on the direct probability integral method, and the inner loop performs a non-probabilistic computation. Then, a new hybrid exponential probability integral method is developed to effectively perform uncertainty propagation and reliability analysis. Finally, four examples, including two static and two dynamic examples with complex performance functions, are tested. The results indicate that the proposed hybrid exponential model offers a universal tool for uncertainty quantification in static and dynamic systems. Moreover, the hybrid exponential probability integral method can accurately and efficiently obtain the upper and lower bounds of the probability density function and cumulative distribution function.

Performance evaluation of a PMDC motor with battery storage control and MPPT based solar photovoltaic system

This paper analyzes and demonstrates the performance of a solar photovoltaic (SPV)-fed permanent magnet DC (PMDC) motor under various operating conditions. In this configuration, a 5HP PMDC is coupled to a SPV system and a boost converter has been interfaced between them to regulate the DC output voltage acquired from the SPV system. The switching pulse to the converter has been provided by the maximum power point tracking (MPPT) controller (P&O and INC) in order to acquire maximum and desired power across the DC link with varying irradiance. A battery energy storage system (BESS) is often used in association with this configuration caused by the non-linear nature of the SPV system and to overcome the volatility of the DC connection affected by environmental effects. For this purpose, a double loop PI controller is analyzed, and examined the DC link. Additionally, the operation of bidirectional DC-DC converter in buck and boost mode during battery charging and discharging is also performed. This operation ensures maintaining a constant and continuous power across the DC link to regulate the PMDC motor consistently. A comparison of results has also been presented for both incremental and conductance (INC) and P&O controllers. The mathematical modeling of configuration has been performed in MATLAB/Simulink software. The results and key findings have been tabulated and even elaborated graphically.

Signal amplification in growth cone gradient sensing by a double negative feedback loop among PTEN, PI(3,4,5)P3 and actomyosin

Axon guidance during neural wiring involves a series of precisely controlled chemotactic events by the motile axonal tip, the growth cone. A fundamental question is how neuronal growth cones make directional decisions in response to extremely shallow gradients of guidance cues with exquisite sensitivity. Here we report that nerve growth cones possess a signal amplification mechanism during gradient sensing process. In neuronal growth cones of Xenopus spinal neurons, phosphatidylinositol-3,4,5-trisphosphate (PIP3), an important signaling molecule in chemotaxis, was actively recruited to the up-gradient side in response to an external gradient of brain-derived neurotrophic factor (BDNF), resulting in an intracellular gradient with approximate 30-fold amplification of the input. Furthermore, a reverse gradient of phosphatase and tensin homolog (PTEN) was induced by BDNF within the growth cone and the increased PTEN activity at the down-gradient side is required for the amplification of PIP3 signals. Mechanistically, the establishment of both positive PIP3 and reverse PTEN gradients depends on the filamentous actin network. Together with computational modeling, our results revealed a double negative feedback loop among PTEN, PIP3 and actomyosin for signal amplification, which is essential for gradient sensing of neuronal growth cones in response to diffusible cues.

Biosynthesis of ZnO Nanoparticles using Lime Leaf Extract (Citrus auraantifolia) for Identification of Latent Fingerprints

<p>Fingerprints are an identification tool in forensic science because of their unique properties. Unfortunately, some of the chemicals used in fingerprint powders are toxic and pose a potential health hazard. This study was conducted to analyze the ability of ZnO nanoparticles to identify latent fingerprints. ZnO nanopowder was synthesized with lime leaf extract using the green synthesis method with double-distilled water solvent and characterized by FT-IR at a wavenumber of 4000-400 cm<sup>-1</sup> and SEM-EDX analysis to provide information about the morphology and to detect the elemental composition nanoparticles. The average particle diameter through SEM was around 173.4 nm and formed a spherical with a rough surface with beige color. Identification of latent fingerprints using the powder dusting method on various porous surfaces (craft paper and greaseproof paper) and non-porous surfaces (glass preparations, aluminium foil, and compact disk) shows visualization with the characteristics of the ridges that look good and clear. The study showed the highest frequency of loops (47%), followed by double loops (20%), plain whorls (30%), and central pocket whorls pattern (3%) from 30 fingerprint samples consisting of 14 men and 16 women. Development identification fingerprints using TiO<sub>2</sub> show visualization more clearly because color contrast from bright white color and detail ridges is shown better with ZnO nanopowder.</p>

Large electric-field induced strain in new ternary lead-free piezoelectric solid solution Na0.5Bi0.5TiO3-BaTiO3-Sr (Ta0.5Al0.5) O3

Ternary lead-free piezoelectric ceramics Na0.5Bi0.5TiO3-BaTiO3-Sr(Ta0.5Al0.5)O3 were synthesized via conventional solid-phase synthesis. All samples exhibited pure perovskite structure, indicating that Sr(Ta0.5Al0.5)O3 can be solidified into the Na0.5Bi0.5TiO3-BaTiO3 perovskite structure. The remanent polarization Pr and coercive field EC of the undoped Na0.5Bi0.5TiO3-BaTiO3 ceramic were Pr∼35.23µC/cm2 and EC∼42.46 kV/cm, respectively. The introduction of Sr(Ta0.5Al0.5)O3 sharply affected the ferroelectric properties of the substrate Na0.5Bi0.5TiO3-BaTiO3 ceramics. Increase in the content of Sr(Ta0.5Al0.5)O3 induces transition of this ternary system from a ferroelectric phase to an antiferroelectric-like phase, accompanied by double hysteresis loops in the 0.003SAT, 0.005SAT, and 0.01SAT components. The high dielectric constant ε′∼4300 was obtained for the 0.005SAT composition. The 0.015SAT composition yielded the maximum bipolar electric-field strain S (%) ∼0.53 % and high-field piezoelectric strain coefficient d33*∼ 996 pm/V. This result shows that a ternary Na0.5Bi0.5TiO3-BaTiO3-Sr(Ta0.5Al0.5)O3 solid solution is a promising alternative to lead-based piezoelectric materials in the field of high-performance actuators.

Geometrical Effects of Two Different Space Closing Loops and Its Forces and Moments—A FEM Study

Objective To evaluate the geometrical effects of double keyhole loop (DKHL) and T-loop and its forces and moments during en mass space closure using finite element method. Materials and Methods A 3-dimensional finite element model of maxillary arch was created and stimulated for first premolar extraction case with 0.022 slot Roth prescription bracket. DKHL and T-loop arch wire were created using 19×25 stainless steel and was opened 1 mm for activation using 2 different methods. The study was divided into 2 groups based on the loop design, method of activation, and degree of Gable bend. The stress distribution, tooth displacement, and moment-force ratio were calculated. Result The overall stress distribution was more or less uniform in all the groups. However, maximum von Mises stress was observed in the second premolar region for both the groups. There was greater torque and vertical control in the anterior segment and better anchorage control in posterior segment with increase in degree of Gable bend for both the loops activated using ligature tie. Moment-force ratio of 8-10 was achieved for both the loops. Conclusion Therefore, DKHL was as efficient as T-loop in producing the desirable biomechanical properties during en mass space closure.

Ardisiawhitmorei (Primulaceae-Myrsinoideae), a new species from north east of Peninsular Malaysia.

Ardisiawhitmorei Julius & Utteridge, sp. nov. (Primulaceae-Myrsinoideae), a member of ArdisiasubgenusStylardisia on account of the style protruding from the closed petals prior to anthesis, is herein described and illustrated as a new species. This new species is easily distinguished by the combination of the inflorescences with a slender rachis branched to two orders, the corolla lobes are abaxially glabrous with usually up to only two gland-dots near the apex and the brochidrodromous secondary veins with double loops near the margin.

Antiferroelectric-like double hysteresis loops in Ag-doped K0.5 Na0.5NbO3 ceramics

In this work, we report the effect of Ag+ doping on the microstructure, dielectric, ferroelectric, piezoelectric, and energy storage properties of the K0.5Na0.5NbO3 (KNN) ceramics for which (K0.5Na0.5)(1-x)AgxNbO3 (KNN-xAg) ceramics with x = 0, 0.01, 0.02 and 0.03 were prepared by the conventional solid-state method. The substitution of Ag+ changes the microstructure of KNN from inhomogeneous bimodal grain distribution to homogeneous densely packed grains with an average grain size of 0.5–2.25 μm. The phase transition (TC) of KNN shifts towards the lower temperature side with Ag+ doping. Antiferroelectric-type double PE loops were observed in Ag-doped KNN ceramics at room temperature, which has improved the energy storage and piezoelectric properties of KNN. For ceramics poled at 2 kV/mm for 30 min, a d33 value of ∼149 pC/N and kp ∼0.41 were obtained. These enhanced properties in Ag-doped KNN are due to the occurrence of double polarization hysteresis loops.