Slot Length Research Articles

Study on the Influence of Structural Parameters of Microwave Heating Device on the Heating Effect of Natural Gas Hydrate Reservoir

Abstract The investigation into microwave heating technology for enhancing gas production from hydrate reservoir has attracted wide attention. However, the initial microwave heating device structure still has limitations of low average temperature and uneven temperature distribution in the reservoir during microwave heating. This study has established the microwave heating simulation model, which is validated by the reservoir microwave heating experiment results. Based on the simulation results of microwave heating model, the optimized structure parameters of microwave heating device are obtained: the slots distribution method is cross-distribution, the slot shape is rectangle, the slot angle is 75°, and the slot length is 30 mm. Following microwave heating with the optimized structure for 10 hours, the average temperature within the 1-meter radius of the reservoir rises from 2 °C to 9.52 °C, the maximum temperature in the reservoir is 58.21 °C, and the temperature standard deviation is 9.15 °C. The results mentioned above indicate that the optimized structure can well increase the temperature in the gas hydrate reservoir and the temperature distribution is uniform. This study will further promote the application of microwave heating technology in the actual exploitation of natural gas hydrate.

A 2.4-7GHz Dual Band Microstrip Patch Antenna (DBMPA)

We designed a 2.4-7GHz dual-band microstrip patch antenna DB-MPA using electromagnetic field simulation and transmission characteristic (S21) measurements. Optimizing the slot length of the patch surface increased the directional antenna gain at 7 GHz by 3.5 dB compared to 2.48 GHz, reducing the effect of the higher spatial propagation loss of 9 dB at 7 GHz. A transmission system simulation with an antenna component model incorporating S21 data measured with the 2.4-7GHz DB-MPA from 1 to 8 GHz was conducted at a spatial propagation distance of 5 to 40 m to verify the practicality of the 2.4-7GHz DB-MPA

Slot-Loaded Vivaldi Antenna for Biomedical Microwave Imaging Applications: Influence of Design Parameters on Antenna's Dimensions and Performances.

This paper demonstrates the design steps of a slot-loaded Vivaldi antenna for biomedical microwave imaging applications, showing the influence of the design parameters on the antenna's dimensions and performances. Several antenna miniaturization techniques were taken into consideration during the design: reduction in the electromagnetic wavelength by using a high-permittivity substrate material (relative permittivity ϵr=10.2), the placement of the antenna inside a coupling medium (ϵr=23), and the elongation of the current path by etching slots on each side of the radiator to reduce the antenna's lowest resonant frequency without increasing its physical dimensions. Moreover, an analysis of different antenna slot design scenarios was performed considering different slot lengths, inclination angles, positions, and numbers. Considering the frequency range of microwave imaging (i.e., about 500 MHz-5 GHz) and the array arrangement typical of microwave imaging, the best design was chosen. Finally, the antenna was fabricated and its performances in the coupling medium were characterized. The simulation and measurement results showed good agreement between each other. In comparison with literature antennas, the one developed in this work shows wide bandwidth and compact dimensions.

Performance of length limits to sustain a data- and capacity-limited fishery

Length limit regulations are widely recommended to sustain fish biomass and fishery yields, particularly for data- and capacity-limited fisheries. However, previous findings were generally derived from equilibrium conditions, used hypothetical fisheries, and/or did not explicitly quantify the performance of length limits under a combination of implementation levels, increasing fishing effort, and discard mortality. Here, we apply the management strategy evaluation (MSE) framework to test the performance of three length-limit management procedures (MPs)—maturity and high maturity length limits (i.e., minimum length limits set at and above the length at maturity, respectively) and slot length limit (i.e., excludes both immature and very large fish from retention)—in Iran's largely unregulated, data- and capacity-limited kingfish fishery. We subject these MPs to different conditions, including strong and weak implementations, discard mortality, and an expansion in future fishing efforts, and quantify their overall performance in terms of fishing mortality, biomass, and yield. Our results show that strong implementation of length limits results in the largest gains: the lowest future long-term fishing mortality and the highest biomass and yields relative to the maximum sustainable yield (MSY) level. When illegal-sized fish are selected but discarded with high discard mortality under strong implementation, or retained under weak implementation, the benefits of length limits are severely reduced. Still, length limits are projected to result in much lower fishing mortality and maintain biomass and fishery yields near MSY levels compared to the current fishery's selectivity and retention. Over the entire projection period, the high maturity length limit provided the highest probability of sustainable biomass and the highest mean relative yield under weak implementation and a growing future fishing effort. Our results underscore the benefits of implementing length limit regulation in sustaining data- and capacity-limited fisheries, particularly if current fishing conditions involve selecting and retaining small and immature fish under a high and growing fishing mortality rate.

Second harmonic generation enhancement based on quasi-BICs in centrosymmetric materials

In centrosymmetric optical materials, the second-order nonlinear polarization of the bulk electric dipolar contribution is zero. More effective utilization of the contribution of the surface term is one of the key methods to efficiently obtain second-order nonlinear responses on these materials. Herein, a design of densely packed slotted nanopillar arrays based on quasi-bound states in the continuum (quasi-BICs) is proposed. The quasi-BICs are analyzed by using the finite element method as an example of silicon and the second harmonic generation (SHG) process is simulated. In the structure, normal-incidence linearly polarized light excites magnetic dipole-like quasi-BICs with a high quality factor which effectively promotes light-matter interactions. Increasing the nanopillar radius or decreasing the lattice constant within a certain range can cause the distribution of quality factors in k-space of the ky direction to contract toward the Γ point, which leads to a quasi-BIC with higher quality factors at the Γ point. By conjunctively adjusting the nanopillar radius and lattice constant or changing the slot azimuth, the resonance wavelength can be adjusted over a wide range (about several hundred nanometers) or finely (within about one nanometer) while maintaining high quality factors. When the symmetry perturbation introduced by the slot is small, it is calculated that the SHG conversion efficiency is about 10−6∼10−5 at an incident light power density of 1 MW/m2, and the SHG power is about 107∼108 times enhancement compared with the structure without slots. As the slot width decreases, higher SHG conversion efficiency with more significant SHG enhancement can be achieved at a specific slot length. The results provide new insights into the modulation of the resonant wavelength and quality factor of quasi-BICs, as well as the control of second-order nonlinear effects in centrosymmetric materials.

An improved sensing data cleaning scheme for object localization in edge computing environment

Abstract Radio frequency identification (RFID) is widely applied due to its fast identification speed and non-contact detection. However, the identification process of RFID tags is susceptible to interference from other tags and environmental factors, resulting in inaccurate identification data. To overcome these problem, this paper proposes an improved sensing data cleaning scheme for object localization in edge computing environment. In tag level data cleaning, we use adaptive sliding window and further consider dynamic tags and read rate in continuous reading cycle to adjust the window size timely and appropriately. In the reader level data cleaning, we estimate the tag number based on Chebyshev’s inequality through Markov chain for cyclic control and optimize different time slot lengths to improve the recognition rate. We build an edge computing environment and combine the proposed tag-level cleaning method and reader-level cleaning method to form a comprehensive RFID data cleaning process. Comparative experimental results show that the RFID data cleaning method proposed in this paper can effectively reduce redundant and missing data and improve the accuracy of tag recognition.

Multiple boundary layer suction slots technique for performance improvement of vertical-axis wind turbines: Conceptual design and parametric analysis

Vertical-axis wind turbines (VAWTs) are gaining attention for urban and offshore applications. However, their development is hindered by suboptimal power performance, primarily attributable to the complex aerodynamic characteristics of the blades. Flow control techniques are expected to regulate the flow on the blade surface and improve blade aerodynamics. In the present study, an effective active flow control technique, multiple boundary layer suction slots (MBLSS), is designed for VAWTs performance improvement. The impact of MBLSS on the aerodynamic performance of VAWTs is examined using high-fidelity computational fluid dynamics simulations. The response surface methodology is employed to identify the relatively optimal configuration of MBLSS. Three key parameters are considered, i.e., number of slots (n), distance between slots (d), and slot length (l), which vary from 2 to 4, 0.025c to 0.125c, and 0.025c to 0.075c, respectively. The results show that MBLSS positively affects the power performance and aerodynamics of VAWTs. Parameter n has the most significant effect on VAWT power performance and the importance of d and l is determined by tip speed ratios (TSRs). Tight and loose slot arrangements are recommended for high and low TSRs, respectively. The relatively optimal configuration (n = 2, d = 0.025c, l = 0.05c) results in a remarkable 31.02% increase in the average net power output of the studied TSRs. The flow control mechanism of MBLSS for VAWT blade boundary layer flow has also been further complemented. MBLSS can prevent the bursting of laminar separation bubbles and avoid the formation of dynamic stall vortices. This increases the blade lift-to-drag ratio and mitigates aerodynamic load fluctuations. The wake profiles of VAWTs with MBLSS are also investigated. This study would add value to the application of active flow control techniques for VAWTs.

Investigation of a hybrid two-layered channel-jet heat sink for air cooling

With the miniaturization and deep integration of electronics, the challenges associated with high-power heat dissipation technology have increased. Combining the features of jet cooling technology and microchannel cooling technology, a hybrid two-layered channel-jet heat sink is designed for general consumer CPUs. The heat sink performance is investigated experimentally. Since the CPU generation power is 120 W, the heat sink can control the CPU excess temperature below 60 °C with an air volume less than 20 m3/h and a pressure drop less than 20 Pa. The different geometric parameters of the heat sink are numerically calculated. Increasing the channel width and reducing the channel height and slot length can enhance the heat transfer but also increase the pressure drop. Orthogonal tests are employed to optimize the design by evaluating the performance of various heat sink structures. The performance evaluation criterion (PEC) is selected as the evaluation index. Under standard conditions with a cross-sectional airflow velocity of 1.5 m/s, the optimal structure is a 2 mm channel width, 12 mm channel height and 50 mm slot length.

A neighbor discovery protocol with adaptive collision alleviation for wireless robotic networks

Recently, several movement control algorithms have been proposed to move robots to the desired locations and complete various collaborative tasks. These algorithms usually require information exchange among robots, which in turn relies on efficient neighbor discovery. However, neighbor discovery of robots is a challenging problem due to limited communication range and beacon collision. Here, how to set the time slot length and contention window to alleviate the beacon collisions is a major issue: too large or too small slot length and contention window values cannot achieve good performance in the robotic network. Therefore, we propose a neighbor discovery protocol with an adaptive collision alleviation mechanism, i.e. ND-ACA. ND-ACA adopts a simple mechanism to detect and avoid potential collisions before sending beacon, and adaptively adjusts both slot length and backoff window according to the number of historical beacon collections and beacon collisions. Extensive simulation results show the efficiency of our proposed approach. To the best of our knowledge, this is the first work in the literature that explore the joint implementation effects that simultaneously consider the robot mobility model and neighbor discovery.

Intrusion detection in machine learning based E-shaped structure with algorithms, strategies and applications in wireless sensor networks

In the everyday world of computer applications, from the cloud to the Internet of Things, distributed sensor networks are essential (IoT). These computer application devices are often connected to Arduino network connection and microcontrollers such sensors and actuators. Thus, a defensive network with an IDS serves as the need for contemporary networks. The intrusion detection system has unavoidably evolved throughout the years, but despite this, it remains a difficult study topic since the current intrusion detection system uses signature-based approaches rather than anomaly detection. Therefore, improving the current intrusion detection system is challenging since it is difficult to find zero-day attacks in IoT networks when dealing with varied data sources. Filtered Deep Learning Model for Intrusion Detection with a Data Communication Approach is presented in this study. The five steps that make up the suggested model are Initialization of Sensor Networks, Cluster Formation and Head Selection, Connectivity, Attack Detection, and Data Broker. It was discovered that the suggested model for intrusion detection outperformed both the current Deep Learning Neural Net and Artificial Neural Network. In comparison to the most popular algorithms, experimental findings revealed a superior result of 96.12 % accuracy. The E-shaped patch antenna is a brand-new single-patch wide-band microstrip antenna that is presented in this research. A microstrip antenna's patch has two parallel slots built into it to increase its bandwidth. Investigating the behaviour of the currents on the patch allows for the exploration of the wide-band mechanism. A broad bandwidth is achieved by optimising the slot's length, breadth, and location. Finally, a 40.3 % E-shaped patch antenna is developed, made, and tested to resonate at 7.5 and 8.5 GHz for wireless communications. Additionally displayed are the reflection coefficient, VSWR, radiation pattern and directivity.

Percolation of straight slots on a square grid.

This work is devoted to the emergence of a connected network of slots (cracks) on a square grid. Accordingly, extensive Monte Carlo simulations and finite-size scaling analysis have been conducted to study the site percolation of straight slots with length l measured in the number of elementary cells of the grid with the edge size L. A special focus was made on the dependence of the percolation threshold p_{C}(l,L) on the slot length l varying in the range 1≤l≤L-2 for the square grids with edge size in the range 50≤L≤1000. In this way, we found that p_{C}(l,L) strongly decreases with increase of l, whereas the variations of p_{C}(l=const,L) with the variation of ratio l/L are very small. Consequently, we acquire the functional dependencies of the critical filling factor and percolation strength on the slot length. Furthermore, we established that the slot percolation model interpolates between the site percolation on square lattice (l=1) and the continuous percolation of widthless sticks (l→∞) aligned in two orthogonal directions. In this regard, we note that the critical number of widthless sticks per unit area is larger than in the case of randomly oriented sticks. Our estimates for the critical exponents indicate that the slot percolation belongs to the same universality class as standard Bernoulli percolation.

Simulation and experimental study of notched cantilever beam for improved vibration energy harvesting

This research paper addresses the design and analysis of a Notched Cantilever Beam Energy Harvester (NCBEH) aimed at enhancing vibration energy harvesting. The voltage output from Lead Zirconate Titanate (PZT) piezoelectric material is directly related to the strain it experiences. Therefore, numerical simulations using ANSYS were conducted to investigate the variations in natural frequency and stress–strain distribution with respect to slot length in a slotted cantilever beam. Additionally, a notch was introduced into the beam to further enhance strain distribution. The study found that, with precise PZT placement, an NCBEH with a 55 mm slot length can generate 15% more voltage output at lower natural frequencies compared to existing Piezoelectric Cantilever Beam Energy Harvesters (PCEH) [1]. Experimental tests were also conducted to compare the voltage output response of the NCBEH and the PCEH, with the results showing good agreement with the numerical simulation findings.

Numerical study of the induction of intratumoral apoptosis under microwave ablation by changing slot length of microwave coaxial antenna.

Recent advances in technology have led to an increase in the detection of previously undetected deep-located tumor tissue. As a result, the medical field is using a variety of methods to treat deep-located tumors, and minimally invasive treatment techniques are being explored. In this study, therapeutic effect of microwave ablation (MWA) on tumor generated inside liver tissue was analyzed through numerical analysis. The distribution of electromagnetic fields in biological tissues emitted by microwave coaxial antenna (MCA) was calculated through the wave equation, and the thermal behavior of the tissue was analyzed through the Pennes bioheat equation. Among various treatment conditions constituting MWA, tumor radius and the slot length inside the MCA were changed, and the resulting treatment effect was quantitatively confirmed through three apoptotic variables. As a result, each tumor radius has optimal power condition for MWA, 2.6W, 2.4W, and 3.0W respectively. This study confirmed optimal therapeutic conditions for MWA. Three apoptotic variables were used to quantitatively identify apoptotic temperature maintenance inside tumor tissue and thermal damage to surrounding normal tissue. The findings of this study are expected to serve as a standard for treatment based on actual MWA treatment.

An Experimental Study on the Seismic Performance of a Replaceable Steel Link System Acting as a Structural Fuse

This study investigated the seismic performance of reinforced concrete columns retrofitted with Replaceable Steel Links (RSLs), focusing on the effects of varying sliding slot lengths and torsional loads. The RSL system, known for its simple construction and effective seismic performance, was analyzed to assess the feasibility of substituting damaged steel links post-earthquake, using the system as a structural fuse. The experimental results highlighted the role of sliding slot lengths in delaying the initiation of shear cracks, especially under eccentric lateral loads. The RSL system exhibited notable torsional resistance, showing only a 10% decrease in maximum load capacity, even with a two-fold increase in the eccentric distance. Furthermore, with an increase in sliding slot length, the difference in cumulative energy dissipation attributable to augmented eccentric distances reached approximately 50%, indicating a notable impact of sliding slot length on the system’s ability to resist torsion. Consequently, it is recommended that the length of the sliding slot be based on the specific seismic design objectives when employing the RSL system as a structural fuse. The post-experiment inspection revealed no deformation in the steel plates, and the buckled steel links could be effortlessly replaced by loosening the high-tensile bolts in the slots. These findings demonstrate the RSL system’s efficiency as a structural fuse.

Experimental and numerical study on flow characteristics of dual‐cavity die based on multi‐objective optimization

AbstractSlot die coating is a common method of manufacturing electrodes for lithium‐ion batteries. In this paper, a multi‐objective optimization research on the geometry of dual‐cavity die is investigated based on the numerical simulation of lithium battery anode slurry flow combined with the surface response optimization method. First, we use the Plackett–Burman test method to screen the geometric parameters significantly affecting the optimization objective. Then, based on the Box–Behnken response surface analysis method, we determine the optimal combination of parameters. The results show that the inner cavity radius and slot gap are the main structural variables affecting exit‐velocity uniformity and die deformation. The slot gap and slot length mainly affect the inlet pressure. The coefficient of deviation of exit velocity uniformity and average inlet pressure of the optimized die structure decreased by 51.3% and 7.6%, respectively. This research provides theoretical guidance for the design of slot coating dies.Highlights Screening significant geometric parameters using Plackett–Burman test methodology. Box–Behnken response surface analysis to determine optimal parameters. Velocity uniformity and inlet pressure increased by 51.3% and 7.6%, respectively.

Model of slot antenna for MPECVD of carbon nanostructure

A model of a slotted waveguide antenna for microwave plasma enhanced chemical vapor deposition (MPECVD) of carbon nanostructures at low pressure is developed. The performance of two slot applicator for the production of dense plasma in the working gas (argon) at a frequency of 2.45 GHz is investigated by EM field simulator. Results show that dimensions of the symmetrical slots (length l ≤ λg/2, width of d = 6-10 mm) and optimized angle (φ=32° with respect to the waveguide central line) have a strong influence on the impedance matching of the waveguide to the dielectric window and plasma column (1.5 < SWR < 2.5), and on the radiation efficiency. The dielectric plate and plasma column density were taken into account in the model in the optimisation of the dimensions of the slots. The mode structure of standing surface waves in the plasma column is investigated at three values of plasma density and results for the radial (n=1) and azimuthal wave numbers (m=3, 4, 5) are in agreement with experimental results.

Predicting slot lengths of MRI exams to decrease observed discrepancies between planning and execution

This retrospective study aimed to reveal discrepancies between planned (Tplan) and actual (Tact) slot lengths of abdomen MRI exams, and to improve Tplan by predicting slot lengths via a machine learning algorithm. Tplan and Tact were retrieved from RIS and modality logfiles, respectively, covering 3038 MRI exams of 17 protocols performed at an abdomen department. Comparisons showed that 30% of exams exceeded planned slot lengths. On the other hand, exams completed within planning failed to manifest good adherence to schedule, as many of them were assigned with an unnecessarily long slot. While adjusting the planned exam duration by a fixed amount of time for each protocol could move Tplan closer to the mean or median Tact, the large spread of Tact would still be unaffected. This is why this study goes one step further, introducing a method to predict the required slot length not only per protocol, but for each individual exam. A Random Forest Regression model was trained on historic data to predict individual slot lengths (Tpred) based on patient and exam context. The correlation between Tpred and Tact was found to be better than that of Tplan and Tact, with Pearson correlation factors of 0.66 and 0.50, respectively. The overall adherence to schedule was also improved by the prediction, as seen by a reduction of both the root mean squared error (–28%) and the standard deviation (–16%) of the differences between planned/predicted slot times and Tact. To provide further insights into the discrepancies between planning and execution of MRI exams, nineteen exams from the Liver protocol with verified clinical information were selected. This case study showed that patient conditions, diagnostic purposes and the selection of sequences during exams could explain some variations of exam durations, but the potential for improving the exam time prediction by including this additional context is limited.

ВЛАСНІ КОЛИВАННЯ В ПЛАНАРНО-КІРАЛЬНИХ ДВОШАРОВИХ ОБ’ЄКТАХ ПОРОДЖУЮТЬ ШТУЧНУ ОПТИЧНУ АКТИВНІСТЬ

Subject and Purpose. The research focuses on how the resonance frequencies, the Q-factor of resonances, and the polarization plane rotation ability are influenced by the topology of individual components of a planar-chiral double-layer object consisting of a pair of con- jugated irises having rectangular slots and accommodated in a circular waveguide. Methods and Methodology. All the numerical results are obtained by the mode-matching technique (MMT) and the transverse reso- nance method on the basis of our own proprietary MWD-03 software package. Results. By the waveguide example, it has been shown that the internal structure of individual components and dihedral symmetry of the conjugated bilayer allow all the conclusions of the spectral theory (theory of eigen-oscillations) to be carried over to all the objects of the type. On the other hand, these objects behave as symmetric two-port waveguide components with conventionally "symmetric" and "antisymmetric" eigen-oscillations. The mutual coupling of these eigen-oscillations depends on the bilayer parameters. Where the frequen- cies of these eigen-oscillations are close enough, the polarization plane rotation and the transmission bandwidth reach their highest. It has been demonstrated that as a slot number increases, the resonance frequency decreases. The theoretical results have been confirmed by the measurements at the X range of frequencies for pairs of conjugated irises with various numbers of rectangular slots. Conclusions. A pair of conjugated chiral irises can rotate the polarization plane. The iris topology, iris spacing, and the mutual ro- tation angle alter resonance frequencies. The resonance frequencies can be reduced by increasing the rectangular slot length and/or slot number. Even though they have not longitudinal symmetry, such objects have properties of two-port waveguide components. In particular, the phase shift of their reflection and transmission coefficients is modulo 90. Besides, a possibility exists to divide eigen-oscillations into conventionally "symmetric" and "antisymmetric" based on the proximity of their fields to those whose type of symmetry is known before- hand. This makes it possible to approximate the reflection and transmission coefficients through corresponding eigenfrequencies.

O-Shape Fractal Antenna Optimized Design with Broad Bandwidth and High Gain for 6G Mobile Communication Devices

Optimization of antenna parameters is important for achieving the best design that has higher results for gain and bandwidth while also having a smaller size. One such antenna design is numerically investigated and presented in this research. The antenna is optimized to an O-shape fractal design from a square patch design. The antenna is created by etching a slot of a square patch and making an O-shape fractal metamaterial patch antenna that operates on the THz band. The THz patch antenna is also investigated for its metamaterial properties. The optimization of the THz patch antenna is carried out for substrate height, slot length, and slot width. The optimized design has a size of 65 × 65 µm2. The highest bandwidth of 31.4 THz (138%) and the highest gain of 11.1 dBi is achieved. The optimized design is then investigated for multiple elements. The two-element MIMO antenna design using an O-shape patch is investigated to observe its performance and compare it with an O-shape single-element design. The two-element MIMO antenna design gives two bands with a bandwidth of 18 THz (113%) and 21 THz (56%). The gain of this design is 5.18 dBi and the size is 130 × 65 µm2. A comparison between the O-shape single-element fractal design, two-element fractal MIMO design, and other published designs is carried out. The compact, broadband, and high gain design presented can be used for 6G high-speed mobile communication devices.

Multi-objective optimization of a compact wideband antenna using grey relational analysis

In this article, a wide bandwidth along with compactness is achieved using a multi-objective optimization technique in a simple X-band antenna structure. The grey relational analysis is used to predict S11, bandwidth and gain for specific combinations of corner-cut length (lc), slot length (ls), and slot width (wst) of the proposed antenna. The effect of corner-cut length, slot length, and slot width on S11, −10 dB bandwidth, and antenna gain is also analyzed. This paper discusses a slotted patch antenna that can cover the X-band frequency range. The modifications involve adding four corner-cut and a parallelogram-shaped slot to the rectangular patch along with a tapered feedline, resulting in a wide bandwidth of 1.55 GHz (9.7 GHz to 11.25 GHz). The proposed compact antenna (23 mm × 32 mm × 1.575 mm) has a peak gain of 8.8 dBi at 10 GHz and can be used in radar communication. An equivalent circuit analysis is done and S11 of the circuit is matched with simulated and measured results. It is appropriate for use as a unit element in an antenna array due to its clear and straightforward design.