Small Square Research Articles

An all‐metal wideband circularly polarized single‐patch antenna based on TM11 mode

AbstractThis paper proposes an all‐metal wideband circularly polarized (CP) single‐patch antenna based on TM11 mode. The conventional square patch is divided into four small square patch units by loading metal shorting walls under the two vertical centerlines. The shorting walls are windowed to facilitate coupling between the adjacent units. When the TM11 mode is excited, the coupling windows not only distribute energy but also provide the 90° phase difference required for CP radiation. An additional feeding network is not required, and its profile is less than 0.05λ0 (λ0 is the free space wavelength at the center frequency). Three minima in the axial ratio (AR) response are present. The results show that right‐hand circularly polarized (RHCP) radiation is achieved. The measured 3 dB AR bandwidth is 6.9%, ranging from 1.52 to 1.62 GHz, and the RHCP realized peak gain is 7.72 dBic. An all‐metal construction suitable for satellite communication systems is designed that has superior performance in harsh space environments.

Towards an efficient multi-scale numerical model of the impact behavior of woven materials with global/local approach

This paper presents the global/local approach in the multi-scale modeling of woven material impact behavior. This approach optimally considers important microscopic mechanisms to accurately predict outcomes and reduce computational time. The inspiration for this approach stems from the specific behavior exhibited by woven materials under ballistic impact:(1) Zone 1 (Local) is a small square around the impact position, requiring comprehensive microscopic modeling to describe complex physical phenomena accurately.(2) Zone 2 (Global) represents the remaining fabric outside of Zone 1, exhibiting more global behavior and modeled with a mesoscopic model.Building upon a previous work's joining technique, an interface between these two zones is implemented and validated through numerical tensile testing. The proposed approach is then compared to the complete mesoscopic model already validated in the case of a 2D Kevlar KM2 woven fabric submitted to ballistic impact. The global/local approach demonstrates slightly greater flexibility due to the presence of microscopic yarns. It successfully predicts all microscopic phenomena while significantly reducing the degrees of freedom compared to full microscopic modeling along the entire yarn length.

Effect of variations hollow of octagon porous media on heat and mass transfer

This study investigates stream function, temperature distribution, and concentration distortion of porous media with three types of hollow. The key factors in conductive heat and mass transfer are the number of vanes in hollows and various hollows, including semi-circle, square, and triangle vanes, which are the novelty of this research. Furthermore, the valuable result of the present study is that hollows with semi-circle vanes had a higher conductive heat transfer than hollows with square and triangle vanes. It is a matter to analyze and study porous media in heat and mass phenomena which are used in three mutually coupled equations in FEM. The finite element approach is employed to compare concentration distribution in porous media with small and large square hollows. Based on the obtained numerical results, the most effect was in the reduction of stream function, temperature distribution, and concentration distortion related to square vanes in hollow. On the other hand, the Nusselt phenomena in the bottom wall influence extremely, and the results depended on some parameters such as ε, Diffusion, Radiation, and Rayleigh number. Finally, Stream function, temperature distribution, concentration distortion, and Nusselt phenomena of octagon porous media are analyzed to develop knowledge in conductive heat and mass transfer.

Mechanical Enhanced Involuntary Stress-Strain Characteristics and Environmental Assessment: GGBS & Silica-Fume

The research looks at the characteristics of Normal Concrete (NC) by testing small square blocks and larger cylindrical samples to see how they respond under pressure and strain. The flexibility of different Ground Granulated Blast Furnace Slag (GGBS) and silica fume mixtures is measured using the Saenz Model, and the results are shown in graphs comparing stress and strain. This study examines how substituting materials like GGBS and adding materials like silica fume to concrete affects its strength and environmental impact. Seven mix designs of M35 grade concrete were prepared to study strength, toughness, ability to stretch, and absorb energy, and how stress and strain are related. The results show that substituting 35% GGBS and adding 10% silica fume is best for improving the strength of NC when compressed. The suggested mathematical equations for how well NC can resist being compressed match up closely with the real-life test results. However, the measured factors show that incorporating 30% GGBS with 5% and 15% silica fume in the concrete causes more environmental harm. However, the NC without pozzolana shows a lower measure of its environmental impact, except for its contribution to climate change.

Structural, optical, magnetic properties and energy-band structure of MFe2O4 (M = Co, Fe, Mn) nanoferrites prepared by co-precipitation technique.

MFe2O4 (M = Co, Fe, Mn) nanoparticles were successfully formed through the chemical co-precipitation technique. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis were used to investigate samples' structural properties. The investigated structural properties included phases formed, crystallite size, cation distribution, hopping length, bond length, bond angle, edge length, and shared and unshared octahedral edge length. Scanning electron micrographs of the prepared samples demonstrated well-defined crystalline nanoparticles. The grain diameter was 15, 9, and 34 nm for CoFe2O4, Fe3O4, and MnFe2O4, respectively. The energy-dispersive X-ray analysis confirmed the existence of every element (Co, Fe, and O) and no discernible impurities in the samples. The optical properties were studied in detail through photoluminescence (PL) spectroscopy and Raman spectroscopy. The presence of active modes in Raman spectra confirmed the spinel structure of the MFe2O4 nanoparticles. The direct bandgap energy estimated through UV-visible spectroscopy was about 2.59-2.64 eV, corresponding with the energy-band structures of the octahedral site (1.70 eV) and the tetrahedral site (0.9 eV). This result was further confirmed by PL emission spectra. Based on Mie theory and UV-visible and PL spectral data, the mechanism of photothermal characterization for MFe2O4 nanoparticles was determined. Investigating the changes in temperature of magnetic parameters including coercivity, squareness ratio, and saturation magnetization for MFe2O4 samples showed the dominant influence of ion distribution and A-A, A-B, and B-B exchange interactions. This study also showed that strong anisotropy and weak dipolar interaction tended to increase the coercivity and squareness ratio of CoFe2O4. Conversely, weaker anisotropy and stronger dipolar interaction corresponded with the small coercivity and squareness ratio of Fe3O4 and MnFe2O4 samples.

High conductivity of n-type β-Ga2O3(010) thin films achieved through Si doping by mist chemical vapor deposition

Currently, β-Ga2O3 has attracted significant attention as a wide bandgap semiconductor, and numerous growth techniques are being explored to control its carrier concentration for various applications. In this study, we investigated the homoepitaxial growth of Si-doped β-Ga2O3 thin films on a Fe-doped β-Ga2O3 substrate using the mist chemical vapor deposition (CVD) technique developed in our group to obtain highly conductive thin films. Using mist CVD, we obtained highly crystalline Si-doped β-Ga2O3 thin films with a full-width at half-maximum of ∼40 arc sec for the (020) peak in the x-ray diffraction rocking curve. Atomic force microscopy studies indicated considerably smooth surfaces of the films with a small root mean square roughness (less than 0.5 nm). Furthermore, we controlled the carrier concentration in the range of 3.85 × 1018 to 2.58 × 1020 cm−3 by varying the Si concentration in the precursor solution. The film exhibits the highest conductivity of 2368 S/cm (mobility = 57.2 cm2/V s at the carrier concentration of 2.58 × 1020 cm−3). This study is expected to promote the application of β-Ga2O3 in devices.

Comparison Study between Open-Loop and Closed-Loop Identification for Industrial Hydraulics Actuator System

In control applications involving motion control, precise control of the Industrial Hydraulics Actuator (IHA) is necessary to accurately assess the position of the actuator rod. Non-recursive identification is used to model the system with an open-loop and closed-loop approach for this paper. The grey box approach is used to estimate the continuous model and parameter estimation for the system. The System Identification toolbox in MATLAB is used for the model estimation. The process starts by obtaining the input-output data from the experimental work. The input-output data validation outcome reveals a best-fit percentage for open-loop 88.91% and closed-loop 95.43%, as well as a small Root Mean Square Error (RMSE). This indicates a successful validation between the estimated model and the actual system due to a high degree of agreement. The open-loop and closed-loop identification have proven successful as there is no noteworthy disparity in the outcomes. The closed-loop system can be applied to unstable systems and any potential system.

Prognosis of Ground Surface Deformation of the Victoria Mine –Slănic Prahova Saline

The Victoria mine, from Slănic Prahova Saline operated in the period 1970-1992 and was mined with small rooms and square pillars, on 11 overstory levels, of 16 m high. It resulted in a volume of mining voids of 7.4 million m3, which led to the pronounced degradation of the resistance structures (rooms and pillars) and to the deformation of the ground surface of the saline. Systematic, annual monitoring of ground surface deformation has been carried out since 2004, through geometric levelling, on certain representative alignments. The prediction of the time evolution of ground surface subsidence was carried out with some power approximation functions of prognosis and the future ground subsidence curves were established on the analyzed alignments. Also, 3D numerical modeling was used to estimate ground surface subsidence and displacements.

Priestley Chao Estimator in Nonparametric Multivariable Kernel Regression in Estimating The Value of Indonesia’s Balance Trade

Several researchers have speculated that the model for the Indonesian Trade Balance Value uses a parametric model, but this model has not provided accurate results in determining the actual Indonesian Trade Balance Value. The estimation used is a parametric approach which assumes the data follows a certain pattern. This can result in big mistakes. We propose a nonparametric approach using Kernel functions for data that does not follow a particular pattern and has outliers. The Kernel function used for multivariables is the Gaussian Kernel function with the Priestley-Chao estimator. Analysis of Indonesia’s Trade Balance Data for 2019-2020 using the available data on Indonesia’s Trade Balance Rate, shows that this model is able to estimate with a very small Mean Square Error (MSE) of 0.98 at optimal bandwidth value are h1 =8.72 and h2 = 0.39. Optimum bandwidth selection uses minimum Generalized Cross Validation (GCV). With this bandwidth value, it gives very good estimation results. This model can be used to predict Indonesia’s Trace Balance Accurately on data that does not have a specific pattern and there are outlier data.

Archimedes’ Constant

In examining the area of a square within the area of a circle whose diagonal line bisects the square into two equal halves of the right triangles; is the diameter of that circle’s area in consideration. Clearly, transformation of a circle determines the ratio of expansion- in relation to its radius given that it is increasing by half. Thus, as the difference of the areas of the relative circles is half of pi; then subtracting the larger area of a circle from its larger relative square which is within its circumference: with that of the smaller area of a circle whose smaller square is also within its radius- results into half of pi minus half. Where then it is easier from such, to deduce the Archimedes constant.while the GDP is projected to increase from $603 billion in 2020 to $15 trillion in 2063. The military spending is projected to increase from $2.6 billion to $33.94 billion, and the trade balance is projected to increase from $15 billion in 2020 to $29.99 billion in 2063. The study concludes that the projected indicators align with the 2063 Africa Agenda and recommends policies that would foster sustainable economic growth and development in Nigeria. By understanding the trends and patterns of these socioeconomic indicators, policymakers can make informed decisions about how to allocate resources and promote sustainable development in Nigeria and beyond

A NEWCLASS OF TAN-G FAMILY OF DISTRIBUTIONS WITH PROPERTIES AND APPLICATIONS

This research article is dedicated to the exploration of a novel family of distributions that is based on a tangent transformation. The new class of distributions, which we have named the new class tan-G (NCT-G) family, has been developed using the ratio of the cumulative distribution function (CDF) G(x) and 1+G(x) of a baseline distribution. We provide an overview of the general properties of this family of distributions. To demonstrate the applicability of the NCT-G family, we have utilized the inverse Weibull distribution as a baseline and introduced a new member of the suggested family. This new distribution exhibits a reverse-J, increasing, or inverted bathtub-shaped hazard function. We have also explored some statistical properties of this distribution, as well as its associated parameters estimated through maximum likelihood estimation (MLE). To evaluate the accuracy of the estimation procedure, we have conducted a Monte Carlo simulation. We found that even for small sample sizes, biases and mean square errors decrease as the sample size increases. Additionally, we have applied the NCT-IW distribution to two real data sets. By using model selection criteria and goodness of fit test statistics, we empirically proved that our suggested model outperforms other existing models, most of which have a greater number of parameters.

Memory of incomplete phase transitions from a random squares model.

We present a simple two-dimensional model for a phase transition, then study its predictions, in particular the memory properties. The direct transformation is modeled by randomly placing small squares, "nuclei", on an initially empty surface. Then, the nuclei expand ("grow") up to finite final sizes which are randomly chosen in a given range, while keeping their square shape. An important issue is the "interaction" which forces some squares to remain at smaller sizes if the surrounding squares get in the way of their growth. Interestingly, this naturally leads to quasiequal total area covered by the squares of each size after a complete direct transformation. Next, it is shown that the system "remembers" incomplete ("arrested") reverse transformations taking place in reversed order of the squares sizes. The memory is "encrypted" in the distribution of the squares sizes after a next direct transformation and manifests as a significant imbalance between the areas covered by the "big" and "small" (relative to the arrest size) squares. We are able to also reproduce the so-called "hammer effect" and the memorizing of multiple arrest points. Our model is particularly relevant for the thermal memory effect in shape memory alloys, and we actually borrowed many features from existing thermodynamic models addressing this effect. However, here we eliminate the explicit thermodynamics and end up with a statistical geometry model, presumably easier to reproduce.

Exploring the restorative benefits of work in smart working structures on vacations in small villages.

Processes of redefinition of work, already in place in the pre-pandemic era, with the advent of COVID-19, have become widely required. A "model of work" that uses new technologies and the development of existing ones to improve workers' performance and satisfaction has emerged. Smart working has changed how people work and, as a result, spaces must also change to support them. The use of prefabricated movable buildings (PMB) could represent an opportunity to create smart (and co-) working spaces in a regenerative contest. Small villages with historical, architectural, and naturalistic elements and slow-life features are potential platforms where vacation and work could merge easily. This paper aims to establish if working in movable offices, like the PMBs, which provide a high level of visual and acoustics interaction with the surroundings, and which is positioned in small villages' squares, can affect workers' sense of restoration and working performance. In a laboratory setting, in the SENS i-Lab, a videowall and a 3D spatial audio system were used to compare, in terms of restorativeness and self-reported cognitive performance, the effects of a high-rise building context of a City Business District (CBD), i.e. the control scenario, and of two typical squares of small Italian villages with historic buildings, without (HIS) and with water elements (HIS-W). The findings of the experimental sessions showed that when working in close contact (visual and auditory) with historical or water elements, where life flows slowly, workers perceived a higher sense of restoration while job performance was unchanged. Implementing smart working policies in small villages that encourage the use of energy-efficient prefabricated movable buildings and that offer a high level of visual and acoustic interaction with the surrounding environment may represent a promising strategy to foster the development of the local economy and contrast the depopulation of small villages, improving the worker well-being and the reducing the impact of their activities of the environment.

Analysis of the Impact of Lateral Conduit and Metal Wire Mesh on Methane Explosions

To enhance the deflagration efficiency and protection level of combustible mixed gases in narrow spaces, a small square experimental pipeline system was designed. Experiments were conducted to investigate the effects of lateral vent pipes and metal wire meshes on the explosion characteristics of methane gas. This study examined the influence of changing the positions of the lateral vent pipes and metal wire meshes in the pipeline on the variation of parameters such as the flame shape, leading speed, and pressure of the methane/air premixed gas in the pipeline. The results indicated that the lateral vent pipes could effectively release part of the energy from the methane explosion, and the release effect was stronger the closer they were to the ignition end. This was significantly more effective in releasing the flame and pressure than when the vent pipes were placed in the middle or at the end of the pipeline. For lateral vent pipes close to the ignition source, their effective release of the not yet fully developed premixed flame allowed the heat absorption, wave absorption, and quenching performance of the installed metal wire mesh in the pipeline to fully exert their effects on the slow-spreading premixed flame. Furthermore, when a metal mesh was installed in the pipeline and the flame could not be extinguished, the flame penetrated the mesh structure, causing the flame front to become unstable and exhibit “irregular wrinkles”. That is, the flame front was no longer smooth, the wrinkles became more pronounced, and the degree of turbulence was enhanced.

Multi-Wavelength Path Loss Model for Indoor VLC with Mobile Human Blockage

Visible light communication (VLC) is one of the candidate technologies for the sixth generation (6G) networks. The path loss model is particularly important for link budget estimation and network planning in VLC. Due to the wideband nature and the extremely poor diffraction capacity of light, the path loss of the VLC channel is susceptible to wavelength dependence and blockage effect. In this paper, we propose a novel path loss model which can characterize the impact of wavelength dependence combined with mobile human blockage for both the single-LED (light emitting diode) and the multi-LED scenario. When there is no blockage in the channel, the multi-wavelength path loss under free space propagation is modeled with a small standard deviation of 0.262 in the single-LED scenario and a small root mean square error of 0.009 in the multi-LED scenario which indicates the high accuracy of the model. When considering the mobile human blockage, the blockage probability (BP) is modeled with full consideration of realistic human mobility and human body shadowing. The results indicate that the BP in single-LED scenario can reach 0.08, while the BP in multi-LED scenario is 0.022. This demonstrates that the distributed deployment of transmitters can effectively reduce the occurrence of the blockage state in VLC.

Linear energy transfer (LET) distribution outside small radiotherapy field edges produced by 6 MV X-rays

In modern radiotherapy with photons, the absorbed dose outside the radiation field is generally investigated. But it is well known that the biological damage depends not only on the absorbed dose but also on LET. This work investigated the dose-average LET (LΔ,D) outside several small radiotherapy fields to provide information that can help for better evaluating the biological effect in organs at risk close to the tumour volume. The electron fluences produced in liquid water by a 6 MV X-rays Varian iX linac were calculated using the EGSnrc Monte Carlo code. With the electron spectra, LΔ,D calculations were made for eight open small square fields and the reference field at water depths of 0.15 cm, 1.35 cm, 9.85 cm and 19.85 cm and several off-axis distances. The variation of LΔ,D from the centre of the beam to 2 cm outside the field’s edge depends on the field size and water depth. Using radiobiological data reported in the literature for chromosomal aberrations as an endpoint for the induction of dicentrics determined in Human Lymphocytes, we estimated the maximum low-dose relative biological effectiveness, (RBEM) finding an increase of up to 100% from the centre of the beam to 2 cm from the field's edge.

Proximate cues of flowering in a subtropical rain forest

AbstractPlants have evolved mechanisms to track seasonal variation in environmental resources, enabling them to time key life‐history events to appropriate seasons. While the proximate cues for flowering initiation are well documented in the temperate region, it is still unclear what the flowering cues are in the tropics, especially in the subtropics. Our study compared first flowering dates (FFDs) predicted by eight hypothesized proximate cues concerning photoperiod, mean and directional changes in solar irradiance and warm/cool temperature, and rainfall with flowering dates observed over 19 years of weekly monitoring for 16 species in a subtropical rain forest. We observed considerable interannual variation in the median FFDs for the study species, ranging from 21 to 101 days. The early‐spring flowering species tended to have greater interannual variation in FFDs than the summer flowering species. For 13 study species, temperature cues best explained interannual variation in FFDs. Cool temperatures in the previous fall/winter and warm temperatures in the current spring (or previous summer) might trigger the onset of flowering in these 13 species. Cues associated with photoperiod and irradiance also predicted interannual variation in FFDs with small root mean square error (<1.5 census intervals) for 12 species but generally had higher prediction errors than temperature‐related cues. Cues associated with seasonal variation in rainfall failed to predict flowering times in any species. Our results suggest that future changes in temperature may alter flowering times for most species in subtropical forests, leading to changes in ecosystem processes and biosphere feedback to the climate system.Abstract in Chinese is available with online material.

Controlling C–C coupling reactivity through pore shape engineering of B-doped graphyne family

Graphyne is an interesting carbon allotrope characterized by sp-sp2 hybridized carbon bonds, which allow for structure variability. Though there are studies evaluating the electrical and mechanical properties of various structures, studies utilizing its structural variety toward catalyst applications are minor. In electrocatalytic CO2 reduction reactions (CRR), producing valuable C2+ products, such as C2H4 or C2H5OH, under mild conditions is still challenging. The bottleneck has been assigned to the carbon-carbon (C–C) coupling reaction, such as 2*CO → *OCCO. In this reaction, one requires strong binding to the catalyst to enhance neighboring CO concentration, but at the same time, one needs to have low C–C coupling barriers making the OC-CO bond. Following our previous study, which showed B-doped γ-graphyne can be a catalyst for ethanol production, we conducted theoretical investigations on a range of B-doped graphyne families using density functional theory. Out of the 15 different structures studied, four, 4,12,2-, sR-, γ-, and 6,6,12-graphynes, show promising potential for CRR. B-doped 4,12,2-graphyne, with small square and rectangular pores, had a very low C–C coupling barrier of 0.34 eV with strong 2*CO adsorption (−2.5 eV). Furthermore, our research revealed a correlation between the heat of reaction (2*CO → *OCCO) and the average pore area around the acetylenic linker reaction site. Smaller pores give a favorable orientation of two CO molecules, resulting in low reaction barriers.

EasyEyes - A new method for accurate fixation in online vision testing.

Online methods allow testing of larger, more diverse populations, with much less effort than in-lab testing. However, many psychophysical measurements, including visual crowding, require accurate eye fixation, which is classically achieved by testing only experienced observers who have learned to fixate reliably, or by using a gaze tracker to restrict testing to moments when fixation is accurate. Alas, both approaches are impractical online as online observers tend to be inexperienced, and online gaze tracking, using the built-in webcam, has a low precision (±4 deg). EasyEyes open-source software reliably measures peripheral thresholds online with accurate fixation achieved in a novel way, without gaze tracking. It tells observers to use the cursor to track a moving crosshair. At a random time during successful tracking, a brief target is presented in the periphery. The observer responds by identifying the target. To evaluate EasyEyes fixation accuracy and thresholds, we tested 12 naive observers in three ways in a counterbalanced order: first, in the laboratory, using gaze-contingent stimulus presentation; second, in the laboratory, using EasyEyes while independently monitoring gaze using EyeLink 1000; third, online at home, using EasyEyes. We find that crowding thresholds are consistent and individual differences are conserved. The small root mean square (RMS) fixation error (0.6 deg) during target presentation eliminates the need for gaze tracking. Thus, this method enables fixation-dependent measurements online, for easy testing of larger and more diverse populations.

Modeling of small molecule's affinity to phospholipids using IAM-HPLC and QSRR approach enhanced by similarity-based machine algorithms

Immobilized artificial membrane chromatography (IAM) has been proposed as a more biosimilar alternative to classical lipophilicity measurement. Determination of small molecule's affinity to phospholipids can be supported for predicting their behavior in the human body. Therefore, a better understanding of the molecular interaction mechanism between small xenobiotics and phospholipids can accelerate drug discovery. Here, the quantitative structure-retention relationships (QSRR) approach was integrated with mechanistic descriptors calculated using Chemicalize software to propose an easy-to-interpretation QSRR model. Considering the heterogeneous character of the data set, locally weighted least squares kernel regression belonging to similarity-based machine learning methods have been applied. The results showed that lipophilicity, charge, and maximum projection area determine molecule binding to phospholipids. Full validation of the obtained model based on OECD recommendations has been performed and the applicability domain was defined using the probability-oriented distance-based approach. The high values of predictive squared correlation coefficient (Q2), and small root mean square error of prediction (RMSEP), 0.812 and 6.739, respectively, confirmed that the obtained QSRR model is not well-fitted to the training data but also showed prediction power. Additionally, only 1.5% of molecules from the training set and 2.8% from the validation test are outside the applicability domain, confirming great predictive abilities.