Analytical Simulation Research Articles

Development of Space Charge Limited Electron Gun Employing Virtual Cathode Position Simulation

The design and development of the electron gun for vacuum electronic devices is a critical and challenging task having a profound impact on device performance. Current state-of-the-art electron gun simulation codes employ the concept of a virtual cathode for the simulation of space charge-limited electron guns, where the virtual cathode distance is to be provided as an input by the user. In this report, an approach to calculate the virtual cathode position through analytical formulation and simulation is presented. The effect of inaccurate virtual cathode on gun parameters is studied through simulation and its repercussions are explained. The approach has been applied in the simulation using three-dimensional tracking solver to design a 50 kV, 10 Amp electron gun, which is to be used in a C-band Klystron. Based on the design, a Gun-Collector-Test-Module (GCTM) has been developed and hot-tested for experimental validation. A good agreement between the simulated and measurement results validates the design approach of the electron gun.

Wireless power transfer system for capsule robot designed by radial square transmitting coil pair with novel ferrite structure.

Wireless power transmission for capsule robots has always posed challenges due to the unpredictable postures. A radial transmitting coil with a novel ferrite structure is proposed, which consists of two parts with the function of converging magnetic induction lines and reducing magnetic leakage. To improve the flux density, uniformity, and shielding effectiveness, the design parameters are discussed and optimized on the basis of analytical calculations and simulation analysis. The proposed ferrite structure improves the power transfer efficiency from 2.78% to 5.21%. Additionally, the power transfer stability showed a slight improvement from 76.4% to 77.6%, while magnetic leakage was reduced by 84%. Finally, the human tissue safety is also discussed and verified. The wireless power transfer system is shown to be feasible and safe.

An Adaptive Meta-Modelling Approach for Multi-Dimensional Correlated Flow Field Responses

ABSTRACT It has become common practice to build inexpensive surrogate models to supplant time-consuming numerical simulations. By gradually increasing the number of training samples, the efficiency of model construction can be significantly improved. This study proposes an adaptive meta-modelling approach for multi-dimensional correlated responses within the framework of proper orthogonal decomposition (POD) and the Kriging model. The algorithm begins with the adaptive sampling algorithm for each reduced-dimension response, which integrates the prediction variance, distances between samples, and sensitivity indicator of each parameter. The adaptive sampling criterion for each reduced-dimension response is weighted by the energy of the modal, forming the adaptive sampling algorithm for multi-dimensional correlated responses. Tests on an analytical function and M6 wing simulation show that, under the same number of training samples, the proposed adaptive algorithm results in a model with lower prediction error than the random sampling algorithm, offering a more efficient model for flow field prediction.

Flow pattern dependent model for airlift pumps performance: Analytical simulation and experimental verification

Airlift pumps are widely applied in different industries largely for flow recirculation purposes such as in petroleum exploration, deep-sea mining, wastewater and sewage treatment, and chemical processing industries. Their performance is significantly dependent on the two-phase flow patterns within their riser pipe and difficult to be accurately predicted. Most previous studies have developed mathematical models to predict lifted liquid flow rate and pumping efficiency of these pumps assuming one flow pattern in the pump riser. However, several flow patterns such as bubbly, slug, churn, and annular flow patterns can exist in the pump riser. Furthermore, most of the current models are developed and validated for use with small-diameter riser pipes, mainly tested in laboratory settings, while industrial applications usually utilize larger pump sizes. To address these limitations, the present study aims at developing a mechanistic model that is applicable for use across a wide range of airlift pump sizes. To verify the proposed model, a series of experiments was conducted under a wide range of operating and geometrical conditions. An airlift pump with a riser diameter of 3.175 cm (small pump) was tested in the lab for an adjustable submergence ratio (0.5, 0.7, and 0.9) at inlet air flow rates up to 20 kg/hr. High-speed imaging was carried out to visualize flow pattern within the riser pipe and instantaneous void fraction data was collected using a capacitance sensor to identify flow patterns and transitions. Four large airlift pumps, featuring riser pipe diameters of 5.08, 10.16, 15.24, and 20.32 cm—dimensions commonly encountered in industrial settings—were tested on-site at an industrial facility, with inlet air flow rates of up to 100 kg/hr. The model showed ∓20% agreement with experimental results of both small and large size pumps. The proposed model was also used to analytically simulate the impact of riser pipe diameter and length as well as submergence ratio on an airlift pump’s performance.

Assessment of Physicochemical and Microbiological Characteristics of Honey in Southwest Ethiopia: Detection of Adulteration through Analytical Simulation

This study aimed to evaluate the quality of honey in the supply chain from the Gera district to Jimma town in southwest Ethiopia and develop a predictive model to detect adulteration. A preliminary survey revealed that poor handling practices and adulteration negatively impacted honey's physicochemical and microbial quality. For laboratory analysis, 268 honey samples were collected from households, cooperatives, chira markets, Agaro markets, and Jimma markets. They were mixed separately to create composite samples representing different value chain actors. Laboratory results indicated that honey samples from supply chain actors confirmed significant differences (p < 0.05) in physicochemical and microbial quality. The study found that the extent of adulteration and physicochemical quality loss increased from producers to Jimma retailers, indicating multiple-stage adulteration along the supply chain that could pose a risk to the safety and quality of the product. The physicochemical quality parameters of the honey samples in the study varied within the following ranges: moisture (18.35–19.42%), water activity (0.48–0.61), viscosity (7.45–10.28 Pas), pH (3.41–4.0), titratable acidity (34.01–36.03 meq/kg), ash (0.1–0.23%), electrical conductivity (0.25–0.39 mS/cm), Total Soluble Solid (75.9–77.5 °Brix), Water insoluble Solid (0.16–2.48 g/100 g), Diastase Activity (6–14 DN), and Hydroxymethylfurfural (0.2–27.7 mg/kg). Microbiological analyses showed that total aerobic bacterial and fungal load ranged from 2.7 × 101–2.29 × 102 and 3.2 × 101–4.57 × 102, respectively. A predictive model was developed using adulteration indicator parameters, showing good linearity (R2>90%) and predictive capacity for detecting adulteration with sugar syrup.

Load Modulation Feedback in Adaptive Matching Networks for Low-Coupling Wireless Power Transfer Systems

This paper explores the use of load modulation feedback (LMF) in adaptive matching networks (MN) for low-coupling inductive wireless power transfer systems, with an emphasis on its use in implantable medical devices. After deriving the handy expressions of link efficiency and modulation depth in the case of LMF in the case of loose coupling, a brief overview of the most common capacitive resonance networks is presented. In particular, the MN employing two capacitors in Series–Parallel and in Parallel–Series configurations allow adaptivity with a wide range of load conditions. Then, the authors describe an effective design procedure of an adaptive matching network with LMF for an inductive wireless power transfer system, exploring the trade-off between power efficiency and modulation depth. Analytical and electrical simulations show that the proposed simple modulation strategy can successfully achieve high power transfer efficiency while maintaining steady back telemetry under varying loading conditions.

Microporomechanics of quasi-brittle rocks: Theoretical formulations and analytical simulations

Hydromechanical coupling is one of the essential theoretical and practical issues in rock mechanics and rock engineering. In geological context, it is critically important to incorporate the effect of pore pressure into the constitutive equations with full account of cracking-induced material anisotropies and friction-related plastic deformation. Focus here is put on poromechanical formulations for quasi-brittle rocks weakened by microcracks and saturated with pore fluid pressure. The linear homogenization method applied to derive the effective properties and system free energy is combined with the irreversible thermodynamics and the problem decomposition. Constitutive derivations include the determination of the system free energy, state equations associated with and evolution laws of the internal variables, closed-form failure criterion, etc. Inherent coupling between anisotropic unilateral damage, friction-induced plastic deformation and the fluid pressure constitutes one of significant novelties of the work. Continuities required for the total free energy, macroscopic stress and the global porosity are guaranteed at any opening-closure transition of cracks. Through strength and deformation coupling analyses, the effects of fluid pressure on material strength and deformation are elucidated and also validated by experiments we performed upon a sandstone.

Feature selection based machine learning models for 5G network slicing approximation

The development of 5G networks is expected to introduce novel concepts and challenges in domains such as technology, security, and customer demands due to advancements in mobile internet and communication services. The three main services that the 5G network provides are enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable low-latency communication (URLLC). Network slicing is the practice of dividing a single physical network into many virtual networks in order to facilitate the delivery of multiple services across that network. These slices improve the network’s reliability and make it possible to provide more customized services. This article provides an overview of 5G network slicing, discussing its layers and overall architecture. Additionally, the paper proposes a machine learning network slicing model based on feature selection, comprising three main components. Firstly, data collection involves gathering two different datasets from various sources. Secondly, feature selection algorithms are applied to choose the most relevant set of features, as the collected datasets may contain numerous unnecessary attributes and values. Lastly, various classification models are utilized on the selected features to predict the optimal network slice, thereby improving the efficiency of the 5G network. The analytical results and simulation models demonstrate that the proposed machine learning models with feature selection perform exceptionally well and accurately predict 5G network slices.

Novel simulator designed for grounded negative inductance with lossless characteristics incorporated with single OTRA

This article introduces a novel design of a simulator for grounded lossless negative inductance by using an active element -single Operational Trans Resistance Amplifier (OTRA) and four passive components. Without interrupting the condition of realization of inductance, the value of the simulated inductance can be independently administered by a MOS based resistor. For validation of the analytical elucidation PSPICE simulation results are used. Moreover, sensitivity analysis, Monte-Carlo simulation, temperature analysis, and % of total harmonic distortion (%THD) are also investigated to verify the functionality of the proposed circuit. As an application claim of the projected configuration, an inductance nullification circuit is also implemented that exposes that the proposed negative inductance simulator may be used to cancel or reduce the effective inductance in a circuit. The Analog Design Environment tool of Cadence Virtuoso is employed for designing the layout of the OTRA.

Reliability modeling of wave energy converters based on pelamis technology

Wave generators, as renewable sources, are increasingly applied for power generation in developed electric networks. With the development of wave generator technologies, large-scale devices such as oscillating water columns, pelamis, wave-dragon, oyster, buoy, sea wave slot cone converter, and tapchan have been invented to extract electrical power from wave energies. The output of wave generators relies on the height and period of waves, and because of the wide variation in these quantities, the produced power from them changes widely. Therefore, in electric networks incorporating large wave generators, reliability is influenced and should be analyzed. In this paper, for the first time, the reliability modeling of pelamis, as a kind of commercial-scale wave generator, is executed. In the proposed multi-state reliability model of pelamis, failures of composed components and changes in the production of power are addressed. To obtain the optimal number of power states in the model, the XB factor is computed. Then, to reduce the number of power states in the model, the fuzzy c-means clustering methodology is applied. The obtained model is used to examine the adequacy assessment of an electric network containing a pelamis farm. Numerical results show that wave converters can improve the reliability performance of electric systems. However, wave period and height affect the reliability indices of the power system. The effectiveness of the proposed method is validated by comparing the outcomes obtained by the analytical and Sequential Monte Carlo Simulation methods.

Different glassy characteristics are related to either caging or dynamical heterogeneity.

Despite the enormous theoretical and application interests, a fundamental understanding of the glassy dynamics remains elusive. The static properties of glassy and ordinary liquids are similar, but their dynamics are dramatically different. What leads to this difference is the central puzzle of the field. Even the primary defining glassy characteristics, their implications, and if they are related to a single mechanism remain unclear. This lack of clarity is a severe hindrance to theoretical progress. Here, we combine analytical arguments and simulations of various systems in different dimensions and address these questions. Our results suggest that the myriad of glassy features are manifestations of two distinct mechanisms. Particle caging controls the mean, and coexisting slow- and fast-moving regions govern the distribution of particle displacements. All the other glassy characteristics are manifestations of these two mechanisms; thus, the Fickian yet non-Gaussian nature of glassy liquids is not surprising. We discover a crossover, from stretched exponential to a power law, in the behavior of the overlap function. This crossover is prominent in simulation data and forms the basis of our analyses. Our results have crucial implications on how the glassy dynamics data are analyzed, challenge some recent suggestions on the mechanisms governing glassy dynamics, and impose strict constraints that a correct theory of glasses must have.

Bifurcations, chaotic dynamics, sensitivity analysis and some novel optical solitons of the perturbed non-linear Schrödinger equation with Kerr law non-linearity

This study introduces an analysis of bifurcations, chaotic dynamics, and sensitivity using the Galilean transformation applied to the perturbed non-linear Schrödinger equation (NLSE) with Kerr-law nonlinearity. Additionally, we employ the efficient Sardar sub-equation (Sse) method to derive various optical soliton solutions. Initially, we outline the general framework of the Sse method proposed. Next, we utilize a traveling wave transform on the NLSE, transforming it into a system of nonlinear ordinary differential equations (NLODEs) which are further separated into their real and imaginary components. Furthermore, we apply this method to derive new optical solitons for the NLSE equation with Kerr law. We perform exact analytical simulations of these optical soliton solutions and investigate the effects of different parameters on the soliton waves.

COVID-19 cases prediction with negative group delays digital function

The negative group delay (NGD) is an uncommon function enabling to propagate arbitrary waveform signals with time-advance behavior. The counterintuitive NGD function was initially experimented for anticipating typically fast and short duration electronic signals in micro- and milli-second time scale. The application of NGD function to large time scale signal attracts more and more the attention of data processing engineer. This paper aims to investigate on the ability of NGD function to predict time- dependent social data with someday time-advances. As practical case of study, an innovative application of NGD function for predicting disease cases is treated. The digital circuit theory enabling to understand the low-pass (LP) NGD canonical TF and the characterization approach is established. It is shown in which condition the first order difference equation represents a LP-NGD circuit. Then, the design method of typical LP-NGD predictor as numerical circuit is introduced in function of the expected time-advance. The NGD predictor time-variation property is theoretically initiated. The NGD time-advance varied from -7 days to -1/2 days is investigated with deterministic data prediction processing from 5-months bi- exponential waveform data. The predicted data with time-advance of about -4 days was confirmed by analytical computation and simulation. The LP-NGD digital predictor feasibility is validated with monthly COVID-19 randomly arbitrary data by computed and virtually tested results. It was investigated with sensitivity analysis that the prediction performance is better when the input signal is smoothed enough. As expected, prediction result showing very good correlation with input data is demonstrated.

Modulation of intramolecular charge transfer in D-A functionalized pyrrolopyrazine and their application in luminescent solar concentrators

In this study, we fabricated LSCs using pyrrolopyrazine-based organic fluorophore (PP2) with an intramolecular charge transfer (ICT) function and aggregation-induced emission. PP2 incorporates unique features, including an intramolecular charge transfer (ICT) function and aggregation-induced emission. The pyrrolopyrazine core of PP2 is decorated with an electron-rich dimethylamine group and two electron-poor cyano groups, enhancing its potential for light harvesting in LSC applications. In the polymethylmethacrylate (PMMA) matrix, PP2 showed strong absorption near ultraviolet (395 nm–406 nm), emitted green-colored visible light (474 nm–478 nm), and exhibited a photoluminescence quantum efficiency (PLQY) of 67%. The external photon efficiency (ηext) and internal photon efficiency (ηint) of the fabricated LSC under AM 1.5G illumination (1 sun) were 3.36% and 39.1%, respectively. Subsequently, we conducted an analytical simulation to estimate the ηext and the ηint as the dimensions of the LSC were scaled up. In addition, the photovoltaic performance measurement under 1 sun showed a power conversion efficiency (ηPCE) of 1.074% with a scattering background and 0.633% without a scattering background. Thus, this research introduces PP2 as a novel fluorophore with promising prospects for advancing the field of LSC technology.

Analytical solution on temperature evolution in three-layer barrier high-level radioactive waste repository and required pre-cooling time determination

An analytical model of the temperature field in a high-level radioactive waste (HLW) disposal repository containing three-layer barrier of bentonite blocks, bentonite pellets and surrounding rock was established, and a series of mathematical methods were used to obtain a fully analytical solution for the model, which can visually represent the relationships between temperature and various parameters and provide a reference for designing repository. Through comparisons to other existing analytical and numerical simulation results, the validity of our solution was verified. Subsequently, temperature evolution analyses of one-canister and one-panel conditions were performed using the derived solution. Additionally, the temperature evolution at the point where peak temperatures are expected (i.e., mid-height of central canister's side surface in one disposal panel) was investigated with different geometric design dimensions, and it was observed that temperature remains virtually unchanged when the tunnel spacing exceeds 40 m. The required pre-cooling times for four types of HLW under different geometric and thermal parameters were analyzed using the obtained solution, with all canisters considered in one disposal panel.

Perancangan Mata Pisau pada Traktor Pemanen Jagung Menggunakan Solidwork

Corn is one of the plants in agriculture that is needed in the lives of people in West Sumatra. Based on data in 2020 the need for corn is in the range of 1.2 million tons. But what can be produced is 939,466 tons. Traditional corn harvesting technology is a problem that causes corn production is not maximized. Corn harvesting tractor is one of the innovations in agricultural technology. The most important unit of the harvesting machine is the blade. The success of the machine in the harvesting process is determined by the shape and strength of the blade. Experimental testing is expensive and time consuming. Therefore, this study examines the design and simulation of blade strength on corn harvesting tractors with Solidwork software. The simulation carried out is a static analytic structural simulation. The simulation results include von-mises stress, displacement and factor of safety. Stress on the crossbar design has a maximum value of 2.168e+07 N/m^2 at the shaft connection and the inside of the bearing, maximum displacement on the side of the blade tip with a value of 1.953e-01 mm and FoS with a value of 5.553e+04. In design S the maximum stress is 2.476e+07 N/m^2, the displacement on the side of the blade tip is 2.199e-01 mm and the FoS is 1.052e+04. Both designs were given the same material AISI 1045, a force load of 87.05 N and a torque load of 41.5 Nm. The design that is suitable for use is the S shape design based on the results of the simulation and the shape that is more suitable for the harvesting process.

Mechanical characterization of human skin—A non-invasive digital twin approach using vibration-response integrated with numerical methods

This paper proposes an innovative approach to identify elastic material properties and mass density of soft tissues based on interpreting their mechanical vibration response, externally excited by a mechanical indenter or acoustic waves. A vibration test is performed on soft sheets to measure their response to a continuous range of excitation frequencies. The frequency responses are collected with a pair of high-speed cameras in conjunction with 3-D digital image correlation (DIC). Two cases are considered, including suspended/fully-free rectangular neoprene sheets as artificial tissue cutout samples and continuous layered human skin vibrations. An efficient theoretical model is developed to analytically simulate the free vibrations of the neoprene artificial sheet samples as well as the continuous layered human skins. The high accuracy and validity of the presented analytical simulations are demonstrated through comparison with the DIC measurements and the conducted frequency tests, as well as a number of finite element (FE) modeling. The developed analytical approach is implemented into a numerical algorithm to perform an inverse calculation of the soft sheets' elastic properties using the imported experimental vibration results and the predicted system's mass via the system equivalent reduction/expansion process (SEREP) method. It is shown that the proposed frequency-dependent inverse approach is capable of rapidly predicting the material properties of the tested samples with high accuracy.

Physics based numerical model of a nanoscale dielectric modulated step graded germanium source biotube FET sensor: modelling and simulation

This paper proposes a novel dielectric modulated step-graded germanium source biotube FET for label-free biosensing applications. Its integrated structure and unique design combine the benefits of the gate stack, germanium source, triple-gate architecture, and a step-graded biotube channel, resulting in superior performance over existing biosensors. A compact two-dimensional analytical model for channel potential, drain current, threshold voltage, and subthreshold swing has been formulated and agrees well with the simulated results. The comprehensive investigation of different device parameters, including doping and bias, offers valuable insights into optimizing the biosensor’s performance. The proposed biosensor exhibits remarkable sensitivity, achieving up to 263 mV and 1495.52 nA for certain biomolecules, which has been validated by a compact analytical model and simulations performed on the SILVACO TCAD simulator. Several parameters are employed to assess the biosensor’s effectiveness: threshold voltage, ION/IOFF ratio, subthreshold swing, off-current, peak trans-conductance, and on-current. Furthermore, the biotube channel design enables lightweight and cost-efficient biosensors, enhancing the biosensor’s practicality. This work also includes an analysis of the effect of temperature on the biosensor’s performance and characteristics, providing insights into practical applications. High sensitivity of the biosensor signifies a significant advancement in biosensing technology, suggesting a wide range of potential applications in biomedical field.

Impact of holes in an interdigital parallel folded coupled line‐based wideband bandpass filter for X‐band applications

AbstractIn this paper, a study on the effects of strategically implemented holes in a miniaturized wideband bandpass filter (BPF) utilizing interdigital folded coupled lines is presented. First, the BPF is designed to produce the passband by introducing a fold in the coupled lines. The passband is centered at 9.3 GHz (X‐band), catering to radar applications. Coupled lines connected to a modified U‐shaped transmission line comprise the filter's design configuration. The novelty of the design resides in incorporating drilled holes along the coupled lines, which generate perturbations and resonant effects, resulting in enhanced impedance variations and improved filter performance. With the aid of electromagnetic analysis and simulation software, the coupled lines, U‐shaped transmission lines, and drilled hole diameters are all optimized. Vector Network Analyzer performs all the measurements and draws the comparisons. An increment of 22.58% is seen in return loss as it increases from −24 to −32 dB, and the insertion loss shows an increase of 16.74%. The proposed filter has been subjected to analytical study, simulation, and implementation, which have confirmed its exceptional return loss, favorable insertion loss, and compact dimensions. The research results make a valuable contribution to the development of miniaturized wideband BPFs, specifically focusing on their use in radar systems. In such systems, the ability to accurately and efficiently filter signals is paramount. The design insights and performance improvements presented in this study have significant implications for broader applications in microwave engineering and communication systems.

General Closed-Form Transfer Function Expressions for Fast Filter Bank

The existing literature focuses on the applications of fast filter bank due to its excellent frequency responses with low complexity. However, the topic is not addressed related to the general transfer function expressions of the corresponding subfilters for a specific channel. To do this, in this paper, general closed-form transfer function expressions for fast filter bank are derived. Firstly, the cascaded structure of fast filter bank is modelled by a binary tree, with which the index of the subfilter at each stage within the channel can be determined. Then the transfer functions for the two outputs of a subfilter are expressed in a unified form. Finally, the general closed-form transfer functions for the channel and its corresponding subfilters are obtained by variables replacement if the prototype lowpass filters for the stages are given. Analytical results and simulations verify the general expressions. With such closed-form expressions lend themselves easily to analysis and direct computation of the transfer functions and the frequency responses without the structure graph.