Frequency Values Research Articles

Palladium‐Silver Alloys Deposited on Different Carriers for Dehydrogenation of Formic Acid

AbstractHydrogen (H2) is recognized as a clean energy carrier with great potential for the future energy systems. Given the existing challenges in direct H2 storage and delivery, the current option for utilizing hydrogen energy is to produce hydrogen from its storage carriers on‐site, and the development of a highly active, highly selective, and highly stable catalyst for H2 production is an important part of this. Herein, PdAg alloy was deposited on mesoporous carbon nitride (mpg‐C3N4) as a catalyst for the dehydrogenation of the formic acid (FA). The synergistic effect of Pd and Ag metals for catalysis was explored. The role of the supports on the catalytic performance was also demonstrated by depositing PdAg alloy on several carriers of Silica@Resorcinol‐Formaldehyde Spheres, Carbon Flower Particles and SBA‐15. Pd1Ag1/2/mpg‐C3N4 showed a considerable activity during FA dehydrogenation with a turnover frequency (TOF) value of 887 h−1 at 333 K, demonstrating that carbon nitride as a carrier has a significant enhancement on the catalytic hydrogen production from formic acid.

Synthesis of Co-Cr(0) and Co-Cr-B catalysts from bean pods extract by the green synthesis method and their application in sodium borohydride hydrolysis

AbstractIn this study, the effect of Co-Cr(0) and Co-Cr-B nanocatalysts on sodium borohydride hydrolysis was investigated. The extract obtained from the pods of the bean plant was produced using the environmentally friendly green synthesis method, along with the chemical reduction method as the production procedure for the catalysts. The analyses used to study the structure and surface morphology of catalysts are SEM, TEM, EDX, XRD, FTIR, and XPS. From the SEM and TEM pictures, the shape of the catalysts comprises of tiny spheres and has a porous nanostructure, and the particle size is 35–40 nm. The XRD investigation revealed that the catalysts had an amorphous structure. The catalysts’ structure has been confirmed to include the components Co, Cr, and B using EDX and XPS analyses. It was examined how different amounts of catalyst, different NaBH4/NaOH concentrations, and different solution temperatures affected the hydrolysis of sodium borohydride. The n-th order kinetic model was utilized to determine the activation energies of Co-Cr(0) and Co-Cr-B nanocatalysts, which were found to be 24.39 kJ/mol and 43.09 kJ/mol, respectively. Also, the turnover frequency (TOF) values of synthesized nanocatalysts Co-Cr(0) and Co-Cr-B at 60 °C were calculated as 19,210 mLmin− 1g− 1 and 12,410 mLmin− 1g− 1, respectively. The repeatability of catalysts in NaBH4 hydrolysis showed high activity even after the fifth use. Graphical Abstract

Thermoelectric performance of newly discovered LiHfPdZ (Z= Al, Ga, and In) quaternary Heusler compounds: A DFT study

Li-based quaternary Heusler LiHfPdZ (Z = Al, Ga, and In) compounds have been investigated for their electronic properties, structural stability, phonon spectra, and thermoelectric performance. Band structure calculations based on Density Functional Theory, show the indirect semiconductor nature of LiHfPdZ (Z = Al, Ga, and In) compounds with band gaps of 0.73 eV, 0.79 eV, and 0.58 eV, respectively. We obtained flat Hf-5d bands (without dispersion) in the vicinity of Fermi energy (EF), resulting in a high value of Seebeck coefficient. The positive values of frequencies in the phonon dispersion curve confirm the dynamic stability of these compounds. The computed elastic properties suggested that the studied compounds are mechanically stable. The calculated values of melting points of this compounds are around 1500 ± 300 K, which ensures the stability of these compounds at high temperatures. We obtained a maximum value of the figure of merit 0.72, 0.68 and 0.67 for LiHfPdAl, LiHfPdGa and LiHfPdIn compounds respectively, which is higher than other Li based QH compounds of same kind i.e. LiHfCoSn (0.59) and LiHfCoGe (0.61) obtained by Singh et al. at same temperature. Overall, a comparatively high and stable value of ZT above 600 K is obtained only in LiHfPdAl, which suggests that it is the most suitable candidate as TE material for high-temperature applications.

Structural response of half-scale pumice concrete masonry building: shake table/ambient vibration tests and FE analysis

Seismic performance evaluation of masonry structures is of paramount importance for ensuring the safety and resilience of buildings in earthquake-prone regions. There are limited number of studies on pumice elements in the literature. In addition, there are almost no studies investigating the earthquake behavior of pumice masonry building as a whole structure. In this context, a comprehensive understanding of their seismic response and dynamic characteristics has been lacking. To address this knowledge gap, a shake-table experimental campaign was undertaken, wherein half-scale pumice masonry building was exposed to simulated seismic forces. To enhance the experimental findings, numerical simulations were performed to confirm and expand our comprehension of how the pumice masonry structure responds to dynamic forces. Integrating both experimental and numerical outcomes provides a holistic understanding of how pumice masonry buildings behave during seismic events. At the end of the experimental study, the frequency values of the pumice model were observed to decrease up to 23.5% in the modes compared to the undamaged state. In the numerical model, this value decreases up to 19.85%. For the undamaged and damaged model, the first three experimental mode shapes were similar to the numerical mode shapes. Both experimental and numerical results show that the expected damages occur in the same regions. These results show that nonlinear FE models can be helpful in determining potential damage model locations. The findings have implications for the seismic design and retrofitting of similar traditional masonry buildings, facilitating the development of resilient and sustainable engineering solutions in seismic-prone regions.

Spectrogram Analysis for Lovebird Voice Characterization Based on Age

Lovebirds are known to be energetic and active birds. The chirps produced by these birds are also known to be very melodious. This study aims to analyze the sound characterization of lovebirds of various age ranges such as the amplitude and frequency produced. The method used in this research is a qualitative analysis non-experiment. This research uses spectrogram analysis in the process of processing existing data. The results obtained in this study are the frequency values at the age of 1 month, 2 months, 4 months, and 7 months in a row, namely 3257.81 Hz, 3416.01 Hz, 3533.20 Hz, and 3937.50 Hz. In addition, the amplitude values obtained at the age of 1 month, 2 months, 4 months, and 7 months were 2.96 Pct FS, 2.99 Pct FS, 3.29 Pct FS, and 8.45 Pct FS, respectively. This shows that the increase in frequency and amplitude values is proportional to the increase in age. Then it is also obtained that the frequency value produced in the age range of one to seven months is in the range of 3000 Hz - 4000 Hz.

Comparative Study of TLP250 and IR2132 Driver-Based Inverter for Induction Motor Driving

As time progresses, electric motors are used for industrial or commercial purposes. The need for a motor that is robust, simple, and easy to maintain has been answered by creating an induction motor that can handle the purpose. At the beginning of its use, induction motors were more often used at constant speeds. Using an inverter becomes one of the solutions at hand to control the induction motor. Nowadays, most inverters are controlled by the SPWM (Sinusoidal Pulse Width Modulation) method. This method can adjust the output voltage and frequency by setting the carrier signal's frequency value and the reference signal's amplitude. A driver circuit is needed to implement an SPWM-based inverter. This driver circuit is needed to isolate the power circuit from the controller. Moreover, this circuit is also used to increase the microcontroller output signal to trigger the IGBT gate switch. The IR2132 and TLP250 drivers are often used in three-phase inverter applications. These drivers have advantages and disadvantages. This paper discusses the capabilities of these two drivers when applied to a three-phase inverter that functions as an induction motor drive. This inverter-controlled induction motor is advantageous because it can be rotated at a nominal speed and frequency.

Evaluation of Awareness Levels of Family Violence in Accordance with Some Variables of Adult Individuals

In this study, the comparison of domestic violence awareness based on various socio-demographic variables (age, gender, education level, marital status, number of children, family structure, income level, employment status, place of residence, region of residence, previous exposure to violence) intended. For this purpose, a questionnaire was applied to 753 people, 508 women (67.5%) and 245 men (32.5%), aged 18 and over, living in Turkey. The "Domestic Violence Awareness Scale" (AİŞFÖ), the reliability and validity of which was studied by Özyürek and Kurnaz (2019), was used in the questionnaire form. In addition, the socio-demographic information of the participants was included. The research is based on examining domestic violence awareness based on demographic variables. In this context, quantitative approach and cross-sectional design were preferred while conducting the research. The model of the research was designed in the scanning model. The data obtained as a result of the research were analyzed in the SPSS-25 statistical program. In the analysis of the data; Shapiro-Wilk and Kolmogorov-Smirnov test, frequency and percentage values, t test and anova tests were applied. As a result of the analyzes made; It was determined that the awareness of domestic violence showed a significant difference according to the gender and working status of the participant group.

The Sportsman Ship Orientation of Generation Z

In the research, it is purposed to analyze the sportsmanship orientation of the Z generation individuals born between 2000-2004 in terms of some variables. This research is a study that aims to examine some demographic characteristics (gender, age, sports club membership, regular exercise) and sportsmanship orientation of the Z generation individuals born between 2000-2004. The sample of the study consists of 233 Z generation individuals, 115 female and 118 men. As it is a means of collected information in the research; Developed by Vallerand, Briere, Blanchart and Provencher (1997), the original Development and Validation of the Multidimensional Sportspersonship Orientations Scale (MSOS) and the Turkish adaptation of Gülfem Sezen Balçıkanlı (2010) was applied. The obtained data were examined by using the SPSS 22 package program. Percentage, frequency and mean values were used in the descriptive analyzes of the demographic characteristics of the participants in our study. “T-Test” was used for samples in the analysis of paired groups, one-way analysis of variance (ANOVA) tests were used in the comparative analysis of three or more groups, and Post-Hoc tests were used to determine which groups the differences originated from. As a result of the tests, it was seen that the sportsmanship orientation of the Z generation individuals born between the years 2000-2004 was at the "Medium" (79,36) level. In the base dimensions of "conforming to social norms, obedience to rules and management and showing respect for the other competitors", "Medium" sportsmanship orientations of the Z generation individuals were observed, and "High" level of sportsmanship orientation was observed in the "responsibility in sports" sub-dimension.

Turkish Language Prospective Teachers’ Perceptions of Metaphors Regarding Artificial Intelligence

The concept of Artificial Intelligence (AI) initially emerged as a term in the field of computer science. In the subsequent years, this concept transcended its origins and became relevant across various domains of human life. Nowadays, it’s possible to encounter AI in nearly every aspect of human life. In this context, it’s considered noteworthy to examine individuals’ metaphorical perceptions of AI. Accordingly, the purpose of the research is determined as the investigation of Turkish prospective teachers’ metaphorical perceptions of AI. Phenomenology, a qualitative research method, is employed in the study. The study group consists of 115 voluntary Turkish prospective teachers, 94 of whom are female and 21 are male, studying at the Faculty of Education at Artvin Çoruh University. Among the prospective teachers, 36 are first-year students, 37 are second-year students, 26 are third-year students, and 16 are fourth-year students. Data for the research are collected through semi-structured interview forms prepared by the researchers. Content analysis method is used for data analysis, and the data are presented by tabulating them along with frequency values. The analysis reveals that 115 Turkish language prospective teachers produced a total of 110 metaphors. Among these metaphors, 21 belong to male prospective teachers, while 89 belong to female prospective teachers. Metaphors such as human (f19), robot (f10), future (f4), ocean (f3), storm (f2), spring (f2), assistant (f4) are found to be generated by both female and male prospective teachers. In addition to positive metaphors, Turkish language prospective teachers also generated negative metaphors like threat (f2), massacre (f1), monster (f1), etc., concerning AI. Consequently, although Turkish language prospective teachers developed some negative metaphors, it’s observed that their perceptions of AI are predominantly positive.

DIVERSITY OF MANGROVES AND ASSOCIATED PLANTS IN MANDANGISIAO ESTUARY, MISAMIS ORIENTAL, PHILIPPINES

The study aimed to assess the diversity status of mangroves and associates. Four transect lines were established perpendicular to the shoreline, ranging from 20 to 100 meters based on mangrove stand size. Along these transects, three 10 m × 10 m quadrat plots were set up to evaluate mangrove trees, and within each quadrat, a 2 m × 2 m regeneration plot was established. The study calculated the di-versity indices, such as relative frequency, relative density, and relative dominance to determine the species im-portance value. A total of four mangrove species and two associated plants were identified, representing three mangrove families and three genera, as well as three plant families and three genera for associated plants. The record-ed species included Avicennia marina, Nypa fruticans, Rhizophora mucronata, Sonneratia caseolaris, Acanthus ebrac-teatus, and Acrostichum speciosum. The overall diversity value of the mangroves and associated plants was 0.87, indi-cating relatively low species richness. The true mangroves, Rhizophora mucronata exhibited the highest values for relative density (68.07%), while Nypa fruticans is the highest in terms of relative dominance (42.20%). Both have the same highest value in relative frequency (32.43%). All in all, the highest species importance value for true mangroves is Rhizophora mucronata with 126.23%. In associated plants, highest value of relative density and relative frequency belongs to Acanthus ebracteatus with 58% and 60%, respectively. Subsequently, the highest species importance value for associated plants is 118% for Acanthus ebracteatus. The study concluded that the Mandangisiao Estuary in Jasaan, Misamis Oriental has a limited species diversity, contrary to the initial hypothesis. Furthermore, the mangrove forest in the estuary faces potential threats from garbage dumping, tree cutting, boat mooring, and human encroachment, despite all the recorded species having a Least Concern conservation status.

An Adversarial Example Method Based on Dropping Information to Improve Attack Capability

At present, deep neural network has been widely used in many research fields. However, with the in-depth research on artificial intelligence research, it is found that artificial intelligence technology based on deep neural networks bringsconvenience coming with potential security risks. For example, an attacker may misguide the image classification model to output a wrong result with high confidence by adding slight perturbations to a clean image via the adversarial example method. Compared with the previous methods of adding additional information to the images to generate adversarial examples, Ranjie Duan et al. proposed the AdvDrop algorithm. In this algorithm, adversarial examples are generated by deleting the existing information of the images, which is realized by adjusting the quantization step. However, in the quantization process, the AdvDrop algorithm does not consider the different effects of different gradient values of the quantization table on the adversarial effect. In this regard, AdvDrop+ is proposed, that is, in each iteration, the quantization tables are updated according to the gradient numerical values scaled with a factor. To find the proper scaling factor, we find the gradient value of the highest frequency in the gradient histogram and compute its logarithm and the final result is the scaling factor. The experiments show that AdvDrop+ has better attack performance than AdvDrop under the setting of target attack with nearly the same image distortion. At the same time, AdvDrop+ retains the characteristic of AdvDrop, which can drop information.

Comparison of TEVA vs. PRAAT in the Acoustic Characterization of the Tracheoesophageal Voice in Laryngectomized Patients.

Background: Previous studies have assessed the capability of PRAAT for acoustic voice analysis in total laryngectomized (TL) patients, although this software was designed for acoustic analysis of laryngeal voice. Recently, we have witnessed the development of specialized acoustic analysis software, Tracheoesophageal Voice Analysis (TEVA). This study aims to compare the analysis with both programs in TL patients. Methods: Observational analytical study of 34 TL patients where a quantitative acoustic analysis was performed for stable phonation with vowels [a] and [i] as well as spectrographic characterization using the TEVA and PRAAT software. Results: The Voice Handicap Index (VHI-10) showed a mean score of 11.29 ± 11.16 points, categorized as a moderate handicap. TEVA analysis found lower values in the fundamental frequency vs. PRAAT (p < 0.05). A significant increase in shimmer values was observed with TEVA (>20%). No significant differences were found between spectrographic analysis with TEVA and PRAAT. Conclusions: Tracheoesophageal speech is an alaryngeal voice, characterized by a higher degree of irregularity and noise compared to laryngeal speech. Consequently, it necessitates a more tailored approach using objective assessment tools adapted to these distinct features, like TEVA, that are designed specifically for TL patients. This study provides statistical evidence supporting its reliability and suitability for the evaluation and tracking of tracheoesophageal speakers.

Feature engineering mediated machine learning prediction of high-frequency property of soft magnetic thin films

High-frequency applications including magnetic write heads, inductors, transformers and sensors etc, demand thin films with tremendous soft magnetic properties. In this regard, the resonance frequency of the soft magnetic thin films is of crucial importance which has a direct relation with material properties. Meanwhile, machine learning (ML) has recently evolved as an efficient tool for material designing tasks including material-property relationship. For an ML algorithm to efficiently perform such tasks, feature engineering is implemented, in which a set of descriptors is designed that can best represent the data. Here, we employ the ML technique, combined with data augmentation and feature engineering, for the estimation of the resonance frequency (f r) value of thin films for high-frequency applications from different sets of theoretical and experimental features. Among the selected experimental features, when anisotropy field is combined with saturation magnetization, the ML model’s performance is improved, which is in line with the Kittel’s expression for f r estimation. Finally, it is shown that the data augmentation can improve the training score, and reduce the mean squared error as well as bias of the models. The outcomes of this work are of key importance in paving the way for ML implementation in material-property analysis and time and cost-effective high-frequency device designing.

Analisis Kerentanan Gedung Menara FMIPA UNM Berdasarkan Pengukuran Mikrotremor Dengan Metode FSR (Floor Spectra Ratio)

Research has been conducted on vulnerability analysis of Gedung Menara FMIPA UNM based on microtremor measurements using the FSR (Floor Spectra Ratio) method. The purpose of this study was to analyze the data from microtremor measurements using the FSR (Floor Spectra Ratio) method so that natural frequency, amplification, and vulnerability values of Gedung Menara FMIPA UNM were obtained. The measurements were made using a set of portable measuring instruments TDL 303 S Seismograph to record vibrations. Measurements were made at 37 points in the building and 3 points in the area around the building. Recording data is processed using Geopsy with FSR method. The results of the study obtained the natural frequency of the Gedung Menara FMIPA UNM for each component was 1.3047 Hz to 2.3823 Hz in the NS component and 1.0556 Hz to 2.4355 Hz in the EW component. The amplification of the Gedung Menara FMIPA UNM for each component is 306.8593 to 2850.7233 in NS components and 360.975 to 4783.54 in EW components. The vulnerability value of the Gedung Menara FMIPA UNM for each component is to in NS component and to in EW component. Gedung Menara FMIPA UNM has complied with SNI 1726-2002. The 12nd floor is the part with the highest building vulnerability.

Cation vacancy modulated Cu3P-CoP heterostructure electrocatalyst for boosting hydrogen evolution at high current densities and coupling Zn-H2O battery

Exploiting highly efficient, cost-effective and stable electrocatalysts is key to decreasing hydrogen evolution reaction (HER) kinetics energy barrier. Herein, the alkaline HER kinetics energy barrier can greatly reduce by the joint strategies of the cation vacancy and heterostructure engineering, which is seldom explored and remains ambiguous. In this study, an efficient and stable copper foam-supported Cu3P-CoP heterostructure electrocatalyst with cation vacancy defects (defined as Cu3P-CoP-VAl/CF) was designed for HER via the successive coprecipitation, electrodeposition, alkali etching and phosphorization treatments. As anticipated, the as-obtained Cu3P-CoP-VAl/CF electrocatalyst reveals a remarkable catalytic activity for HER with a low overpotential of 205 mV at a current density of 100 mA·cm−2, a high turnover frequency value of 1.05 s−1 at an overpotential of 200 mV and a small apparent activation energy (Ea) of 9 kJ·mol−1, while shows superior long-term stability at large current densities of 100 and 240 mA·cm−2. Systematic experiment and characterization data demonstrate that the formed cation vacancy could optimize the Ea, leading to the decrease of the kinetic barriers of Cu3P-CoP/CF heterostructure, as well as the established heterogeneous interface induced a synergistic effect between biphasic components on boosting the kinetics toward HER. The results of density functional theory disclose that the synergistic effect of Cu3P-CoP heterostructure could decrease the energy barrier and optimize Gibbs free energy of hydrogen adsorption, resulting in the enhancement of intrinsic catalytic activity of Cu3P-CoP-VAl/CF. More significantly, the alkali-cell assembled by Cu3P-CoP-VAl/CF (cathode) and RuO2/CF (anode) behaves outstanding water splitting performance, delivering a current density of 10 mA·cm−2 at a relatively small applied voltage of 1.58 V, along with encouraging long-term durability. In addition, the alkaline Zn-H2O battery with Cu3P-CoP-VAl/CF as the cathode has been fabricated for the simultaneous generation of electricity and hydrogen, which displays a large power density of up to 4.1 mW·cm−2. The work demonstrates that rational strategy for the design of competent electrocatalysts can effectively accelerate the kinetics of HER, which supplies valuable insights for practical applications in overall water splitting.

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction.

Water electrolysis is one promising and eco-friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2-xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best-performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe-based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2-xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large-scale and sustainable hydrogen gas generation.

Elevated Water Oxidation by Cation Leaching Enabled Tunable Surface Reconstruction

AbstractWater electrolysis is one promising and eco‐friendly technique for energy storage, yet its overall efficiency is hindered by the sluggish kinetics of oxygen evolution reaction (OER). Therefore, developing strategies to boost OER catalyst performance is crucial. With the advances in characterization techniques, an extensive phenomenon of surface structure evolution into an active amorphous layer was uncovered. Surface reconstruction in a controlled fashion was then proposed as an emerging strategy to elevate water oxidation efficiency. In this work, Cr substitution induces the reconstruction of NiFexCr2‐xO4 during cyclic voltammetry (CV) conditioning by Cr leaching, which leads to a superior OER performance. The best‐performed NiFe0.25Cr1.75O4 shows a ~1500 % current density promotion at overpotential η=300 mV, which outperforms many advanced NiFe‐based OER catalysts. It is also found that their OER activities are mainly determined by Ni : Fe ratio rather than considering the contribution of Cr. Meanwhile, the turnover frequency (TOF) values based on redox peak and total mass were obtained and analysed, and their possible limitations in the case of NiFexCr2‐xO4 are discussed. Additionally, the high activity and durability were further verified in a membrane electrode assembly (MEA) cell, highlighting its potential for practical large‐scale and sustainable hydrogen gas generation.

MeNPs-PEDOT Composite-Based Detection Platforms for Epinephrine and Quercetin.

The development of low-cost, sensitive, and simple analytical tools for biomolecule detection in health status monitoring is nowadays a growing research topic. Sensing platforms integrating nanocomposite materials as recognition elements in the monitoring of various biomolecules and biomarkers are addressing this challenging objective. Herein, we have developed electrochemical sensing platforms by means of a novel fabrication procedure for biomolecule detection. The platforms are based on commercially available low-cost conductive substrates like glassy carbon and/or screen-printed carbon electrodes selectively functionalized with nanocomposite materials composed of Ag and Au metallic nanoparticles and an organic polymer, poly(3,4-ethylenedioxythiophene). The novel fabrication method made use of alternating currents with controlled amplitude and frequency. The frequency of the applied alternating current was 100 mHz for the polymer deposition, while a frequency value of 50 mHz was used for the in situ electrodeposition of Ag and Au nanoparticles. The selected frequency values ensured the successful preparation of the composite materials. The use of readily available composite materials is intended to produce cost-effective analytical tools. The judicious modification of the organic conductive matrix by various metallic nanoparticles, such as Ag and Au, extends the potential applications of the sensing platform toward a range of biomolecules like quercetin and epinephrine, chosen as benchmark analytes for proof-of-concept antioxidant and neurotransmitter detection. The sensing platforms were tested successfully for quercetin and epinephrine determination on synthetic and real samples. Wide linear response ranges and low limit-of-detection values were obtained for epinephrine and quercetin detection.

The ambiguity of frequency determination in digital microwave frequency discriminators

Instantaneous frequency measurement devices are designated for very fast measurements of the current frequency value of microwave signals, even if they are very short in the time domain. Fast measurements of frequency temporary values may be based on the evaluation of the phase difference of signal propagating through the microwave transmission lines with unequal, but known, lengths. This paper presents the principle of determination of temporary values of the microwave signal frequency using the digitalized signals and the binary value of them eventually. In the purpose of increase the frequency discrimination resolution, additional tracks with lines with a larger length are proposed. For the system with elements with analytical model transmission characteristics it is typical that bands of ambiguity of frequency measurement occurs. To tackle this problem in addition to 4 x 4 Butler matrix implementation the method of using combination sine and cosine signals is proposed.

Mechanical, vibration damping and acoustics characteristics of hybrid aloe vera /jute/polyester composites

The development of biodegradable hybrid fibre composites is gaining pace in the automotive and construction industries due to their lightweight structural applications, which offer considerable benefits for the environment. In this present investigation, hybrid bio composites were fabricated using a compression molding machine with plain woven jute and aloe vera mats along with polyester resin as the matrix. Six types of hybrid biocomposite laminates were prepared by varying the stacking arrangement of jute and aloe-vera mats to analyse the impact of stacking arrangements on vibration damping and acoustic behaviour of these hybrid bio composites. From the results, it is concluded that the maximum value of natural frequency is obtained from the JJAJ type of composite. i.e., 157, 326, and 370 Hz for Modes I, II, and III respectively, due to good interlacing of fibres in the weft and warp directions. J/J/A/J (AJ3) hybrid bio composite has highest sound absorption coefficient of 0.47 at 3000 Hz, and a better transmission loss i.e 19.84 dB, according to the results of the acoustic research. The comparison of experimental and theoretical analysis was carried out, and found that experimental and theoretical values are closely related to each other.