Narrow Results

The necessity for innovative biomaterials has been growing recently due to the rising cost of materials for intricate biomedical equipment. An important tactic to improve critical attributes like hemocompatibility, osseointegration potential, corrosion resistance, and antibacterial capabilities is surface modification. In this paper, an investigation has been made in the field of laser surface modification and the complex interactions between laser parameters and output performance metrics, such as contact angle and surface roughness. Surface modification by laser has been successful and, in this research, the laser parameters such as laser energy (Watts), standoff distance(mm), and frequency (kHz) along with dimple distance on the surface ($\mu$m) were considered on the output performance namely surface roughness in “$\mu$m” and contact angle in “degree”. The experiment has been carried out using the L16 orthogonal array to interpret the complex correlations between these factors and the resulting surface features. Non-dominated sorting genetic algorithm II (NSGA-II) has successfully navigated the complex parameter space and found the optimal combinations that yield the intended outcomes. The results show how important dimple distance and laser frequency are in creating hydrophobic surfaces, as well as how much of an impact they have on surface properties. It has been discovered that higher frequencies and longer standoff distances specifically reduce surface roughness, which is a crucial component in ensuring enhanced biomaterial performance. The result shows that the dimple distance and frequency of the laser have a significant effect on the development of hydrophobic surfaces. Moreover, high frequency and more standoff distance reduce the surface roughness. The predicted combination of laser parameters as per the NSGA-II is 102.91$\mu$m, 33.35W, 223.12mm, 50.01kHz, and gives a surface roughness of 0.86$\mu$m and contact angle of 158.83^∘. In essence, this study not only sheds light on the intricate dynamics governing laser-based surface modification but also paves the way for the design and development of advanced biomaterials with tailored surface properties, poised to revolutionize biomedical applications.

This paper investigates the use of straight-beam elements to simulate the vibration of curved beams that is mathematically more challenging. First, analytical solutions of the out-of-plane and in-plane dynamic responses of the curved beam are derived for reference. Then, for the straight beam approach, the elastic stiffness matrix, consistent mass matrix, consistent nodal loads, and transformation matrix are derived and included in a procedure for computing the dynamic responses of the curved beam. The effectiveness of the straight beam approach in analyzing the free vibration and forced vibration (induced by moving vehicle) of the curved beam is validated, with the results compared with the theoretical solutions and those by Abaqus. It can be concluded that the straight beam approach is a simple and efficient means for analyzing the out-of-plane and in-plane vibrations of curved beams with high precision.

Neurostimulation is a promising treatment for refractory epilepsy. We studied the effect of cortical stimulation with different parameters in the rat motor cortex stimulation model. High intensity simulation (threshold for motor response - 100 μA), high frequency (130 Hz) stimulation during 1 h decreased cortical excitability, irrespective of the interpulse interval used (fixed or Poisson distributed). Low intensity (10 μA) and/or low frequency (5 Hz) stimulation had no effect. Cortical stimulation appears promising for the treatment of neocortical epilepsy if frequency and intensity are high enough.

A solitary wavenumber-frequency formulation is suggested using an ancient Chinese arithmetic. The nonlinear Schrödinger equation is used as an example to show the effectiveness of the formulation.

In order to study the electromagnetic wave transmission characteristics in seawater under external physical effects, we present a study of seawater ionic solution and perform a theoretical basis of magnetic field on water molecules and ionic motion to investigate the variation of dielectric properties with frequency under static magnetic field (0.38 T). Seawater is a naturally multi-component electrolyte solution, the main ingredients in seawater are inorganic salts, such as NaCl, MgSO₄, MgCl₂, CaCl₂, KCl, NaHCO₃, etc. The dielectric properties of these electrolyte solutions with different salinity values (0.01–5%) were measured in frequencies ranging from 40 to 5 MHz at 12${}^{\circ }$C. The results show that the dielectric constant decreases with increasing frequencies no matter with magnetic field or without it. Frequency dependence of the dielectric constant of NaCl solution increases under magnetic field at measure concentrations. In a solution of MgCl₂ ⋅ 6H₂O, KCl and NaHCO₃ are consistent with NaCl solution, while CaCl₂ ⋅ 2H₂O solution is in contrast with it. We also find that dielectric loss plays a major role in complex permittivity. With the effect of magnetic field, the proportion of dielectric loss is reducing in complex permittivity. On this basis it was concluded that the magnetic field influences the orientation of dipoles and the variation is different in salt aqueous solution.

This paper reports the stress and frequency analysis of dynamic silicon diaphragm during the simulation of micro-electro-mechanical-systems (MEMS) based piezoresistive pressure sensor with the help of finite element method (FEM) within the frame work of COMSOL software. Vibrational modes of rectangular diaphragm of piezoresistive pressure sensor have been determined at different frequencies for different pressure ranges. Optimal frequency range for particular applications for any diaphragm is a very important so that MEMS sensors performance should not degrade during the dynamic environment. Therefore, for the MEMS pressure sensor having applications in dynamic environment, the diaphragm frequency of 280 KHz has been optimized for the diaphragm thickness of 50 $\mu$m and hence this frequency can be considered for showing the better piezoresistive effect and high sensitivity. Moreover, the designed pressure sensor shows the high linearity and enhanced sensitivity of the order of ($\sim$0.5066 mV/psi).

The temperature dependences of resistance, impedance and capacitance of semitransparent sensor having structure ITO/PTB7-Th:PC${}_{61}$BM/Graphene composite (semisurface type) were investigated. The transparency of the sensor was 58–60%. The dependences of the resistance, impedance and capacitance at different frequencies 100 Hz, 1 kHz, 10 kHz, 100 kHz and 200 kHz and temperature in the range of 23.8–80${}^{\circ }$C for the sensor were studied. It was observed that as the temperature increased from 23.8${}^{\circ }$C to 80${}^{\circ }$C, the resistance and impedance (at 1 kHz) of the samples decreased, on average, by a factor of 3.51 and 3.79, respectively. At same experimental conditions (1 kHz), the capacitances of the samples also decreased by a factor of 9.6. It was also noted that as frequency increased from 100 Hz to 200 kHz, the impedance of the sensor decreased by a factor of 21 and 12, at temperatures 24${}^{\circ }$C and 58${}^{\circ }$C, respectively. Under the same conditions, the capacitance decreased by a factor of 30 and 28, respectively. The temperature resistance coefficients were measured to be −1.31%/${}^{\circ }$C, −1.30%/${}^{\circ }$C, −1.27%/${}^{\circ }$C, −0.84%/${}^{\circ }$C, −0.72%/${}^{\circ }$C and −0.33%/${}^{\circ }$C for R, Z (100 Hz), Z (1 kHz), Z (10 kHz), Z (100 kHz) and Z (200 kHz), respectively. For capacitance measurement, the temperature capacitance coefficients were measured as −1.39%/${}^{\circ }$C, −1.38%/${}^{\circ }$C, −1.37%/${}^{\circ }$C, −1.36%/${}^{\circ }$C and −1.34%/${}^{\circ }$C, respectively. The semitransparent PTB7-Th- and PC${}_{61}$BM-based temperature sensor can be used for measurement of the temperature as a teaching aid in situations where visual control of illumination and light intensity is required.

Data processing with multiple domains is an important concept in any platform; it deals with multimedia and textual information. Where textual data processing focuses on a structured or unstructured way of data processing which computes in less time with no compression over the data, multimedia data are processing deals with a processing requirement algorithm where compression is needed. This involve processing of video and their frames and compression in short forms such that the fast processing of storage as well as the access can be performed. There are different ways of performing compression, such as fractal compression, wavelet transform, compressive sensing, contractive transformation and other ways. One way of performing such a compression is working with the high frequency component of multimedia data. One of the most recent topics is fractal transformation which follows the block symmetry and archives high compression ratio. Yet, there are limitations such as working with speed and its cost while performing proper encoding and decoding using fractal compression. Swarm optimization and other related algorithms make it usable along with fractal compression function. In this paper, we review multiple algorithms in the field of fractal-based video compression and swarm intelligence for problems of optimization.

Enhanced sensitivity, precise measurements and accuracy are the key factors to identify the performance of any sensor. In this paper, p-polycrystalline silicon micro-pressure sensor has been designed which works on the principle of piezoresistive effect. A theoretical modeling and computational simulation of the circular Si-diaphragm have been performed through the extensive study of stress and frequency response with the help of finite element method (FEM) within the framework of COMSOL. For a thin diaphragm ($\sim$50 $\mu$m), the Eigen frequency and the frequency generated in a diaphragm under the influence of pressure has been optimized within the pressure range from 1–25 kPa. The modes of vibrations generated in the diaphragm have been optimized at wide-frequency range $\sim$200–800 kHz at various pressure values. The findings of the presented research have suggested that for a $\sim$50 $\mu$m thin diaphragm, the optimized fundamental frequency is $\sim$310 kHz for showing better piezoresistive response which results into enhanced sensitivity. Moreover, the simulation results show that for the designed sensor, the pressure sensitivity of $\sim$11.51 mv/psi has been conveyed.

The dielectric properties of a material determine its response of the material to the Electromagnetic field (EM field). It comprises dielectric constant (${\epsilon }^{\prime }$), which is the ability to store energy of EM fields, and dielectric loss (${\epsilon }^{\prime \prime }$) which is the amount of dissipated Electromagnetic energy in the form of heat. Dielectric properties are affected by various factors such as frequency, temperature, bulk density, moisture content, etc. Dielectric constant and dielectric loss were determined in this study for milk powders viz. Whole Milk Powder, Skim Milk Powder, and Infant Milk Powder at various microwave frequencies (5.68, 7.45, 10.25GHz). The method used to determine dielectric properties is the Two-point Method which is implemented on a microwave bench. It became apparent that when frequency increases dielectric constant decreases and dielectric loss first decreases and then increases. It was also observed that the fat content can have an impact on the milk powders’ dielectric properties.

To facilitate future pasteurization experiments utilizing microwave energy, the dielectric properties of five dried fruits — almond (Prunus dulcis), cashew nut (Anacardium occidentale), pistachio (Pistacia vera), peanut (Arachis hypogea L.) and walnut (Juglans regia) were investigated at room temperature (28^∘C). Samples were taken in powder form to investigate the effect of increased surface-to-volume ratio on their dielectric properties, as applicable in the case of nanomaterials. The measurements were conducted at four different frequencies (3.30, 7.50, 9.30and 14.70GHz) in the microwave spectrum by using the two-point method and a MATLAB program was used for solving the transcendental equation to obtain values of dielectric constant and loss factor. The findings revealed a decreasing trend in the values of dielectric constant of the five dried fruits as the frequency increased. However, no consistent trend was observed for the dielectric loss factor of the fruits with increasing frequency. Further, the penetration depth of electromagnetic waves in all the five dry fruit samples was observed to decrease as the frequency increased. On comparing results for dielectric parameters of dry fruits in powder form with those of whole fruit kernels, no definite trends are observed for ${\epsilon }^{\prime }$ and ${\epsilon }^{″}$, but the penetration depth is found to decrease when the sample is taken in powder form.

Nanocomposite particles of silver modified CrO₂ were synthesized by a chemical CrO₃ → CrO₂ reduction in the presence of Ag⁺ in an aqueous medium whereby the half-metallic ferromagnetic particles of CrO₂ are generated within a shell of silver. The dielectric constant ε_r, AC resistivity ρ_AC, and the dielectric power loss were studied after annealing recovered Ag:CrO₂ powder (compacted as the billets), at 300°C for 2 h in air, at 10–1000 kHz frequencies (f) at room temperature. At 10 kHz, the ρ_r has as large a value as 49, with ρ_AC = 106 kΩ-cm and power loss 0.42. As f increases, all the three parameters are decreased monotonically to the values 28, 3.6 kΩ-cm, and 0.06 respectively. Almost a steady ε_r as well as ρ_AC value exists, with controlled power loss, useful for high frequency applications over f ≥ 400 kHz.

Current networks-on-chip (NoCs) may include many Intellectual Properties (IPs). As those IPs do not necessarily operate at the same clock frequency, a significant number of Phase Locked Loops (PLLs) are required. Since a PLL is very power consuming ($e.g.$, a PLL delivering a 6 GHz frequency consumes 11 mW), one needs to reduce the number of PLLs. To the best of our knowledge, only one work in literature tackled this problem. Since the interested problem is not polynomial in time, we developed heuristic-based methods and found that our work outperforms that which is described in the literature both in terms of number 30% and power consumption 25% of PLLs with less CPU time.

This paper presents a varactorless tunable active inductor-based voltage controlled oscillator (VCO) in 90nm CMOS process. The proposed VCO yields a wide tuning range of 116% with an output frequency of 1.19–4.46GHz for the tuning voltage of 0.3–1.5V. It consumes a low dc power ranging from 2.44mW to 4.79mW for the specified tuning range. The variation of phase noise ranges from $-83.03$dBc/Hz to $-78.65$dBc/Hz at 1MHz offset with the change of tuning voltage as well as tuning frequency. The proposed varactorless VCO has a maximum Figure of Merit (FOM) of $-148.85$dBc/Hz with a differential output power of 1.8dBm at tuning voltage of 0.7V. The elimination of varactor which abates the silicon area consumption and the minimization of the variation of performance parameters are the special outcomes of the proposed active inductor-based VCO. Comparing the performance parameters such as power consumption, FOM and tuning range, the proposed design outperforms most of the cited designs.

An algorithm is presented which generates pairs of oscillatory random time series which have identical periodograms but differ in the number of oscillations. This result indicates the intrinsic limitations of spectral methods when it comes to the task of measuring frequencies. Other examples, one from medicine and one from bifurcation theory, are given, which also exhibit these limitations of spectral methods. For two methods of spectral estimation it is verified that the particular way end points are treated, which is specific to each method, is, for long enough time series, not relevant for the main result.

This paper focuses on applying the octonions to explore the electromagnetic and gravitational equations in the presence of some material media, exploring the frequencies of astrophysical jets. Maxwell was the first to use the algebra of quaternions to describe the electromagnetic equations. This method encourages scholars in adopting the quaternions and octonions to study the physical properties of electromagnetic and gravitational fields, including the field strength, field source, linear momentum, angular momentum and so forth. In this paper, the field strength and angular momentum in the vacuum can be combined together to become one new physical quantity, that is, the composite field strength within the material media. Substituting the latter for the field strength in the vacuum will deduce the field equations within material media, including the electromagnetic and gravitational equations in the presence of some material media. In terms of the electromagnetic fields, the electromagnetic equations in the presence of some electromagnetic media are able to explore a few new physical properties of electromagnetic media. Especially, in case the magnetic flux density and magnetization intensity both fluctuate at a single frequency, their frequencies must be identical to each other within electromagnetic media. In some extreme cases, the electromagnetic equations within electromagnetic media will be degenerated into Maxwell’s equations in the vacuum. The above reveals that the electromagnetic equations within electromagnetic media are capable of extending the scope of application of electromagnetic theory. For the gravitational fields, there are some similar inferences and conclusions within gravitational media. Further they can be utilized to research the frequencies of astrophysical jets.

In this paper, we propose a new frequency amplitude formula for the local fractional nonlinear oscillation via local fractional calculus. It is more general than the He’s frequency amplitude formula. Several test cases of local fractional nonlinear oscillations are given to prove the feasibility of the improved formula.

The method of solving the vibration frequency of local fractional nonlinear oscillators under general initial conditions is studied by coupling the energy balance method with the Galerkin method. One test case of fractional vibration is given to prove the feasibility of this method.

This paper focuses on considering a combined method for solving a fractional oscillation equation arising from a micro/nanobeam-based micro-electromechanical system under the magnetic force. It is an efficient method based upon the fractional complex transformation and the spreading residue harmonic balance method. The fractional oscillator is transformed as the conventional oscillation system by using the fractional complex transformation. The approximated periodic solutions and frequencies are given by applying the spreading residue harmonic balance method. Sensitive analysis of the approximated frequencies concerning different amplitudes and parameters is provided, which may be helpful for realizing the system stability. Numerical comparisons with some existing methods such as Runge–Kutta method and He’s frequency formulation approach are shown to confirm the efficiency of the proposed method.

Graph-Based Data Mining (GBDM) is an emerging research topic nowadays, for the retrieval of the essential information from the graph database. There exist many algorithms that find frequent patterns in a given graph database. One such algorithm, GASTON uses support based on frequency to discover frequent patterns. The discovery phase in the Gaston algorithm is time-consuming, and the pages captured the interest of the users are ignored by the existing GASTON algorithm. This paper proposes an algorithm, Weighted-Gaston (W-Gaston) algorithm, by modifying the existing Gaston algorithm. Here, four interesting measures are developed based on the frequency, entropy, and the page duration, for the retrieval of the interesting sub-graphs. The proposed interesting measures include four types of support: (1) Support based on the page duration (W-Support), (2) Support based on the entropy (E-Support), (3) Support based on the page duration and the entropy (WE-Support), and (4) Support based on the frequency, page duration, and the entropy (FWE-Support). The simulation of the proposed work is done using the MSNBC and the weblog databases. The experimental results show that the proposed algorithm performed well as compared with the existing algorithms.