Transmission Coefficients Research Articles

A study on water resonance between double baffle under oblique waves

This work investigates the interactions between oblique waves and a partially immersed double baffle. An analytical solution to this problem, based on the linear potential flow theory, has been found by utilizing the eigenfunction matching method. The resonance issues between the double baffle under the action of oblique waves is primarily investigated using this model, considering various relative widths, 2B/L (2B is the distance between the two baffles, L is the wave length), and the relative submergence, kD (k is the wavenumber, D is the submergence of the baffles). When resonance occurs, the transmission coefficient will rapidly increase to 1. By analyzing the relationship between the transmission coefficient and the relative width 2B/L, it is found that there are different resonance points and modes. The resonance points and modes depend on the submergence of baffles kD. This study provides a formula for calculating the resonance points. For a normal incident wave, when kD is below 1.0, the 1st-order resonance occurs in the small 2B/L region, resulting in a piston motion. High-order modes exhibit different forms, with standing waves occurring for kD ≥ 0.8, progressive waves for kD ≤ 0.48, and resonant modes ranging between standing and progressive waves for 0.48 <kD < 0.8. The effects of the incident angle on the resonance point and mode under oblique waves have also been investigated. The incident angle wave affects the interval between the two neighboring resonance points, which increases to 1/cosα times of the normal incidence for an angle of α. The resonance motion under oblique waves is nearly identical to that under the normal incident waves in the transverse plane. The difference is that there is a progressive wave in the longitudinal plane under the action of oblique waves.

A semi-analytical fracture high-conductivity location diagnostic method for vertically fractured wells in multilayered reservoirs: field case study

Deep multilayered reservoirs are usually developed using multilayered fracturing techniques; however, the non-uniform placement of proppant causes uneven distribution of fracture conductivity. This study introduces a semi-analytical well test model for hydraulically fractured wells in multilayered reservoirs, accounting for varying fracture conductivity within the hydraulic fracture. The model is built upon the point source function, boundary element method, Duhamel theorem, and pressure superposition principle. Verification tests are conducted to ensure calculation accuracy. Sensitivity analysis is performed on key parameters, encompassing the transmissibility factor, storativity factor, fracture extension, and fracture conductivity. The findings indicate that 1) Increased heterogeneity among layers correlates with a more pronounced pressure drop; 2) Poorly-propped fracture conductivity influences the duration of bilinear flow, becoming negligible after linear flow; 3) The model’s applicability extends to other multilayered reservoirs (e.g., carbonate reservoirs) with minor adjustments. Lastly, a case study from Xinjiang oilfield is presented to demonstrate that the proposed method can derive reservoir and fracture properties for each layer individually. This study contributes to a deeper understanding of the potential of pressure data in characterizing multilayered reservoirs.

BaO-doped Na2O–CaO–P2O5 bioactive glasses: A closer look at radiation attenuation properties for medical applications

This study investigates the nuclear radiation attenuation characteristics of bioactive glasses with the system (26-x)Na2O-xBaO-29CaO–45P2O5, where x represents the molar percentage of BaO (0, 5, 10, 15). For this purpose, several parameters of shielding gamma radiation, such as the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff), atomic cross-section (ACS), electronic cross-section (ECS), equivalent atomic number (Zeq), and transmission factor (TF) were calculated. The calculations were performed across different photon energy ranges (0.015–15 MeV) using Phy-X/PSD software and validated using the WinXCOM program. The results obtained from both the software platforms exhibited a high degree of agreement. Among the investigated glasses, the BNCP-15 glass, which had the highest BaO concentration, demonstrated the highest values for MAC, LAC, Zeff, Neff, ACS, ECS, and Zeq, while displaying the minimum values for HVL, TVL, MFP, and TF. For example, the LAC values at 15 MeV were found to be 0.056, 0.063, 0.070, and 0.077/cm for BNCP-0, BNCP-5, BNCP-10, and BNCP-15, respectively. Consequently, the BNCP-15 glass exhibited superior radiation attenuation performance in comparison to the other BNCP glasses examined in this study.

Assesment risk factor for tuberculosis transmission among children: Case study in Medan

Assesment risk factor for tuberculosis transmission among children: Case study in Medan

The Effect of Fibrillation, Semi-Dry Pressing, and Surface Treatment on the Barrier Properties of Water Molecules and Oxygen on Food Packaging Paper.

The characteristics of fiber morphology and paper structure are critical to the barrier properties of food packaging paper. Herein, this study aimed to use pulp fibrillation, paper semi-dry pressing and carboxymethyl starch (CMS) coating to flatten the fibers, which were formed on the paper surface with good barrier properties due to the tight bond between fibers. The results showed that the permeability of paper was reduced by 87.56%, from 81.44 μm/Pa·s to 10.13 μm/Pa·s after the pulp fibrillation treatment (60 °SR). Moreover, semi-dry pressing treatment contributed to decreasing the water vapor transmission coefficient (WVP) by 50.98% to 2.74 × 10-10 g/m·s·Pa, and the oxygen permeation coefficient (OP) decreased by 98.04% to 1.93 × 10-14 cm3·cm/cm2·s·Pa. After coating the paper surface with titanium dioxide (TiO2) and CMS, the WVP of the paper was further reduced to 1.55 × 10-10 g/m·s·Pa, and OP was reduced to 0.19 × 10-14 cm3·cm/cm2·s·Pa. These values were 72.27% and 99.8% lower than those of the original paper, respectively. Therefore, through pulp fibrillation, semi-dry pressing of paper, TiO2 filling, and surface coating with CMS, there is no need to use synthetic polymer surface film-forming agents to achieve the high barrier properties that are required for low water and oxygen molecules permeation in food packaging paper.

Experimental investigation on hydrodynamic performance of submerged floating tunnel under the protection of a new floating energy dissipation and anti-vibration device

This study describes an efficient and applicable approach to decrease the hydrodynamic response of a submerged floating tunnel (SFT). A new type of floating energy dissipation and anti-vibration device is proposed, mainly consisting of a floating box superstructure with water and a polyvinyl chloride porous media substructure. The experimental model of an SFT with the present protection device is designed and conducted in a wave–current flume. The wave–current attenuation mechanisms for the present protection device are experimentally investigated. The sensitivity analysis for the key parameters, e.g., structure type and wave–current parameter, is conducted to investigate the hydrodynamic performance of the SFT with the present protection device. The results show that the present protection device has excellent wave–current attenuation capacity, and the transmission coefficients and the current–velocity attenuation coefficient reach 0.2 and 0.15, respectively. The sway, heave, roll, and typical cable tension from the SFT with the protection are, respectively, about 8, 6, 8, and 3 times smaller than that from without the protection. The results show that the SFT with the present protection device has excellent anti-vibration performance, which is beneficial for its safety and stability. This study has important theoretical and practical values to the anti-vibration design of SFTs serviced in complicated ocean environments.

Meander Structure Analysis Techniques Using Artificial Neural Networks

Typically, analyses of meander structures (MSs) for transfer characteristics are conducted using specialized commercial software based on numerical methods. However, these methods can be time-consuming, particularly when a researcher is seeking to perform a preliminary study of the designed structures. This study aims to explore the application of neural networks in the design and analysis of meander structures. Three different feedforward neural network (FFNN), time delay neural network (TDNN), and convolutional neural network (CNN) techniques were investigated for the analysis and design of the meander structures in this article. The geometric dimensions or top-view images of 369 different meander structures were used for training an FFNN, TDNN, and CNN. The investigated networks were designed to predict such electrodynamic parameters as the delay time (td), reflection coefficient (S11), and transmission coefficient (S21) in the 0–10 GHz frequency band. A sufficiently low mean absolute error (MAE) was achieved with all three methods for the analysis of MSs. Using an FFNN, the characteristic td was predicted with a 3.3 ps average MAE. The characteristic S21 was predicted with a 0.64 dB average MAE, and S11 was predicted with a 2.47 dB average MAE. The TDNN allowed the average MAEs to be reduced to 0.9 ps, 0.11 dB, and 1.63 dB, respectively. Using a CNN, the average MAEs were 27.5 ps, 0.44 dB, and 1.36 dB, respectively. The use of neural networks has allowed accelerating the analysis procedure from approximately 120 min on average to less than 5 min.

Optimum design of a novel Ku-band rasorber for RADAR warfare systems using ML neural network

The design, fabrication, and testing of a conformal Frequency Selective Rasorber (FSR) operating at A-T-A mode is designed for RADAR warfare systems. In the design of a miniaturized single-layer FSR element, multiple parameters influencing the absorption and transmission characteristics need to be optimized. This simulation using conventional methods consumes more simulation time. Thus, the geometrical parameters are optimized and predicted using supervised machine learning (ML) techniques to expedite the process. The multiple output regression neural network (MORNN) is used to generate multiple input and output features from the dataset. The ML algorithm is trained using the datasets generated from the electromagnetic solver using which a scalable FSR is synthesized. The reflection coefficient, (|S11|), and transmission coefficient (|S21|) are used as input data, and the dimension of the FSR unit cell for the user input frequency requirements are derived as output data. The extracted dimensions of the FSR offered a small mean square error (MSE) of 0.02 between the desired and observed results. The designed FSR offers absorption at 11.5 GHz and 18.9 GHz while the transmission window extends from 15.02 GHz to 16.09 GHz. The neural network results are endorsed using the EM simulation tool and validated by experimental measurements.

Design of single layer bowtie wide band-stop frequency selective surface with angular stability for C-band applications

This paper presents the design and analysis of a single-layer wide band-stop frequency selective surface (FSS) tailored for C-band applications. The proposed FSS design employs a modified bow-tie unit cell structure that enhances band stop characteristics, resulting in improved performance compared to traditional FSS geometry. The design process involves numerical simulations and optimization techniques to achieve the desired frequency response. A modified bowtie element with FR4 substrate comprises the proposed FSS which exhibits a resonant frequency of 6.0 GHz with a wide bandwidth of 4.84–6.96 GHz (35.93 %) and act as a band stop filter. The FSS is analyzed in terms of its transmission coefficients, providing insight into its filtering properties. In addition, parametric studies of the unit cells are done. Furthermore, the angular stability of the proposed FSS is simulated with incident waves at various angles between 0° to 60° for both TE and TM modes. The proposed FSS presents C-band applications of WLAN, ISM/WiMAX, satellite communications, radar systems, shielding and communication devices, also enhancing filtering capabilities and system performance. The simulation results are well correlated with measurement results.

Influence of stiffeners on acoustic emission monitoring of ship structures

Naval vessels are valuable assets that are expensive to build and maintain. Predictive maintenance is crucial to enhance efficiency and operability and to extend the service life of these structures. Fatigue is regarded as one of the main damage modes affecting the structural integrity of ship structures. Fatigue cracks can develop at the intersections of stiffeners and other structural elements, without being detected until they substantially grow, introducing a degree of uncertainty in the estimation of the fatigue damage. Acoustic emission (AE) is a passive ultrasound method for the detection and localization of different types of damage. AE is sensitive to crack propagation and can cover large areas, making it suitable for structural health monitoring of ship hulls. However, for accurate fatigue crack detection via AE it is crucial to understand how ultrasound waves interact with structural members i.e. stiffeners and longitudinal frames. Dispersion, scattering, reflection, and multimodality have so far hindered the application of AE in this context. This study aims to assess ultrasound wave behavior in ship structures in the presence of structural elements such as stiffeners and longitudinal/transversal frames. It investigates the ultrasound wave transmission dependence on source frequency and angle of incidence using spectral finite element (SEM) simulations and experimental measurements. The experimental setup includes a 10mm thick steel plate with a stiffener and a longitudinal beam (Figure 1). Pairs of sensors are placed on each side of the stiffener to record the incoming and transmitted waves, and to determine the transmission coefficient. By combining the results of both simulation and experiments, an expression for the transmission coefficient as a function of different frequencies and angles is presented. The results of this study can be used to maximize the coverage of AE monitoring systems and enhance their sensitivity for detection of fatigue cracks on ship structures.

Полосковый резонатор СВЧ с объемным кристаллом: экспериментальные характеристики и определение эффективной диэлектрической проницаемости

The paper presents the results of an experimental study and modeling of the frequency characteristics of a resonator in the form of two strip vibrators, separated by a large gap and covered with a bulk lithium niobate crystal. A metal electrode with a floating potential is installed on the upper surface of the crystal. The frequency dependences of the scattering matrix coefficients of a stripline resonator were measured in the frequency range up to 3 GHz. Electrodynamic analysis was carried out in the COMSOL Multiphysics numerical simulation environment. A comparison was made of experimental and numerical results, which showed good qualitative agreement between the transmission coefficients and reflection coefficients. Resonant oscillations were obtained at two or three frequencies depending on the location and orientation of the crystal. It has been established that at the first resonant frequency the electrode acts as a screen. The absence of an electrode leads to the disappearance of resonance. The simulation carried out in COMSOL made it possible to estimate the effective dielectric constant of the resonator corresponding to the values of the resonant frequencies. The calculation of electromagnetic fields made it possible to establish the types of waves corresponding to resonant frequencies. Knowing the type of waves and estimating the relative dielectric constant made it possible to construct an algorithm for a refined iterative procedure for calculating the values of the resonant frequencies and the effective dielectric constant of the resonator. The possibility of using resonators as single-link bandpass filters with a passband of about 1%, insertion loss of –1.1 dB and minimal return loss of –28 dB at the center frequency is shown.

Stenotrophomonas maltophilia Bloodstream Infection Outbreak in an Acute Care Hospital — Alameda County, California 2022–2023

Background: Stenotrophomonas maltophilia is an opportunistic pathogen found in healthcare settings. During April–September 2022, nine S. maltophilia bloodstream infections (BSIs) were identified among intensive care unit (ICU) patients at a hospital in Alameda County, California. Whole genome sequencing found isolates to be highly related. Despite implementation of infection prevention and control (IPC) interventions, four additional S. maltophilia BSIs were identified during June–September 2023. We investigated to identify risk factors for infection and stop transmission. Methods: We conducted a matched case-control study. A case was defined as S. maltophilia isolated from a blood culture from an ICU patient with a fever during April 2022–September 2023; control-patient subjects were patients admitted to the ICU during the same period with hospital stay greater than or equal to their matched case. Three control subjects were matched to each case. We extracted information on risk factors for infection from medical charts and observed IPC practices in hospital locations of interest. We collected environmental samples from the ICU, radiology unit, and emergency department. Results: Among 13 cases and 39 control subjects, patients exposed to iodinated contrast Omnipaque-300 (odds ratio [OR]: 5.7; 95% CI: 1.2–28.0), injectable propofol (OR: 12.2; 95% CI: 1.5–101.4), or fentanyl (OR: 9.2; 95% CI: 1.8–Inf.) were more likely to have a S. maltophilia BSI, compared with control-subjects. IPC deficiencies included improper cleaning and storage of medical equipment, including the contrast injection system, and patient care supplies. The outbreak strain of S. maltophilia was not isolated from environmental samples. Conclusions: Although a point-source was not identified, S. maltophilia was likely transmitted through improper IPC practices involving injectable contrast or anesthesia. Recommendations on proper cleaning and disinfection of the contrast injection system and proper storage, preparation, and administration of medications were made to reduce risk for contamination.

Profile of HIV/AIDS Patients with Neurological Manifestations in The Tertiary Referral Hospital in Bali

Background: Neurological manifestations in approximately half of Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) patients are related to high morbidity and mortality worldwide. Therefore, there is a need for epidemiological data on HIV/AIDS patients with neurological manifestations in Bali, as an international tourism destination. Objective: This study aimed to describe the clinical profile of neurological manifestations among patients with HIV/AIDS in the tertiary referral hospital for Bali and Nusa Tenggara region. Methods: A descriptive-retrospective study was conducted on HIV/AIDS patients presenting with neurological manifestations hospitalized in the Neurology Department of Prof. Dr. I.G.N.G Ngoerah Hospital Denpasar from January 2018 to December 2021. Results: Among the 227 subjects included in this study, the majority were male (69.9%) and HIV positive newly diagnosed (69.2%). Furthermore, out of 126 subjects who had CD4 data, the majority were with CD4 &lt;200 cells/mm3 (85.7%) and 53.1% were &lt;50 cells/mm3, with ages ranging from 18 to 67 years old, at a median of 36 years old. The most common neurological signs and symptoms found were paresis/paralysis (61.7%), headache (54.6%), decreased consciousness (52.9%), and cranial nerve palsy (52%). Cerebral toxoplasmosis (67.4%) and tuberculous meningoencephalitis (20.3%) were the prevalent opportunistic infections, while the mortality rate was 39.6% with sepsis as the major cause. Conclusions: Neurological manifestations are common initial symptoms in diagnosing HIV infection. Therefore, better awareness and earlier detection are required among people with risk factors of HIV transmission, particularly in groups of young and productive age with signs of immunocompromised condition as well as neurological manifestations.

Epidemic spreading on spatial higher-order network

Higher-order interactions exist widely in mobile populations and are extremely important in spreading epidemics, such as influenza. However, research on high-order interaction modeling of mobile crowds and the propagation dynamics above is still insufficient. Therefore, this study attempts to model and simulate higher-order interactions among mobile populations and explore their impact on epidemic transmission. This study simulated the spread of the epidemic in a spatial high-order network based on agent-based model modeling. It explored its propagation dynamics and the impact of spatial characteristics on it. Meanwhile, we construct state-specific rate equations based on the uniform mixing assumption for further analysis. We found that hysteresis loops are an inherent feature of high-order networks in this space under specific scenarios. The evolution curve roughly presents three different states with the initial value change, showing different levels of the endemic balance of low, medium, and high, respectively. Similarly, network snapshots and parameter diagrams also indicate these three types of equilibrium states. Populations in space naturally form components of different sizes and isolations, and higher initial seeds generate higher-order interactions in this spatial network, leading to higher infection densities. This phenomenon emphasizes the impact of high-order interactions and high-order infection rates in propagation. In addition, crowd density and movement speed act as protective and inhibitory factors for epidemic transmission, respectively, and depending on the degree of movement weaken or enhance the effect of hysteresis loops.

A highly sensitive modified triple split ring metamaterial-based sensor for blood sample detection based on dielectric property alteration

This research paper demonstrates a metamaterial (MTM) based sensing technique to detect various blood samples by analyzing their dielectric properties. The performance of this MTM-based sensor is evaluated with the help of mimicked human blood samples that closely resemble the dielectric properties of actual human blood samples. Moreover, the ISM band frequency of 2.4 GHz is chosen as one of the reference resonance frequencies due to its various industrial and medical applications. The resonating patch is developed on the FR-4 substrate with a dimension of 10 × 20 mm2 that provides sharp reference resonances of 2.4 and 4.72 GHz for the spectra of the transmission coefficient with a good quality factor (Q-factor). The MTM sensor can detect the mimicked blood samples with a maximum frequency deviation of up to 650 MHz at 2.4 GHz and up to 850 MHz at 4.72 GHz, with maximum sensitivity of 0.917 and 0.707, respectively. The measured results using the prototype of the sensor support the simulation result with good agreement, indicating high sensing capability. Due to its high sensitivity, figure of merit (FoM), and frequency shifting with dielectric property changes in blood samples, the developed MTM-based sensor can be implemented effectively for quick sensing of infected blood samples and biomedical applications.

Star shape symmetric engineered meta surface to sense food additives (benzoic acid/copper sulfate) at terahertz spectrum

This research proposed a technique for detecting the sensitivity of benzoic acid (C6H5COOH) and copper sulfate (CuSO4), which is excessively used in foods. The novelty of this work is that it detects the sensitivity of two food additives with the same metasurface. Although it offers the benefits of miniaturization, minimal sample consumption, and cost-efficiency, it is an easier, faster, and nondestructive detection method than other traditional approaches. The proposed design is based on a polyimide substrate with an aluminum resonator that forms a star shape on the substrate. The transmission frequency of the metasurface was determined at 0.91 THz with a transmission coefficient of 36.6 dB. The metasurface sensor is insensitive to polarization and has a large angle of incident. The transmission spectrum shows that the amplitude of the transmission peaks usually changes with variations in the refractive index of the analytes. The proposed sensor effectively detects benzoic acid (C6H5COOH) with a sensitivity of 0.175 THz/RIU and, the sensitivity of the Copper Sulfate (CuSO₄) is 0.225 THz/RIU with the Q factor values of 12 and 10.55 respectively. These sensitivity results and transmission intensities of different analyte thicknesses show that this proposed THz metasurface sensor can be used to detect additives in foods.

ПІДВИЩЕННЯ ЕНЕРГЕТИЧНОЇ ЕФЕКТИВНОСТІ РЕГУЛЬОВАНОГО ЕЛЕКТРОПРИВОДУ ОДНОЦИЛІНДРОВОГО ПОРШНЕВОГО КОМПРЕСОРА

The peculiarities of the operation of closed systems of adjustable electric drives of single-cylinder reciprocating compressors due to the presence of a non-linear dependence between the motor load torque and the angular movement of its rotor are considered. The method of synthesis of the regulator of the amplitude of the supply voltage of an induction motor of such an electric drive at a fixed value of the supply frequency is proposed. According to the results of research, it was found that the effect of increasing energy efficiency (reducing the difference in efficiency for constant and periodic loads) due to the use of a voltage regulator increases with a decrease in the power supply frequency. It is shown that the optimization of the transmission coefficient of the voltage regulator of electric drives with a non-linear dependence between the motor load torque and the angular movement is expedient to be carried out according to the criterion of maximum efficiency. References 25, figures 10, table 1.

Analysis of the influencing factors of transmission coefficients based on ZnSe/BeTe heterojunction

Analysis of the influencing factors of transmission coefficients based on ZnSe/BeTe heterojunction

Saturation and absorption effects on the transmission properties of Kerr-type nonlinear layers

The effects of absorption and saturation on soliton states in Kerr-type nonlinear layers are theoretically investigated. In addition to the usual gray and bright soliton structures observed in nonlinear slabs, a flat soliton, i.e., a particular soliton excitation with electric field amplitude independent of the position within the layer, is researched in cases of self-defocusing and self-focusing nonlinearities. Effects caused by the combination of absorption and saturation, such as the shift and extinction of the flat soliton peak, the decrease in the amplitude of the electric field within the nonlinear layer, and the suppression of the multistable behavior of the transmission coefficient in the vicinity of the soliton peaks, are discussed. The present theoretical results are compared and found in good quantitative agreement with previous experimental measurements.Graphical

Does Green Entrepreneurial Orientation Improve the Sustainable Performance of Agribusiness? Evidence from China

Agribusinesses play an important role in the process of green and low-carbon transformation of China’s economy. It is extremely necessary to explore how to promote green entrepreneurship in agribusiness to promote a win-win situation for the environmental and economic and social performance to achieve the sustainable development goals of agribusinesses. Based on intellectual capital theory and natural resource-based theory, this study introduces green intellectual capital (GIC) and sustainable business model innovation (SBMI) as chain mediators to build a theoretical model for exploring the impact mechanism of green entrepreneurial orientation (GEO) on sustainable performance (SP) of agribusinesses. Through the empirical analysis of 621 agribusinesses’ research data, the results show that (1) GEO has a positive impact on SP of agribusinesses; (2) GIC and SBMI are important transmission factors for the transformation of green entrepreneurial orientation into the sustainable performance of enterprises, and play a mediating role in the relationship between GEO and SP of agribusinesses; and (3) GEO promotes SBMI through the accumulation of GCI, which in turn enhances SP of agribusiness. This study not only enriches the theoretical scope of green entrepreneurship research in terms of subdimensions, but also provides theoretical references and practical guidance for agribusinesses to improve their sustainable performance.