Mountain-Shaped Coupler for Ultra Wideband Applications

This paper demonstrates a novel mountain-shaped design for a compact 3-dB coupler operating at ultra-wideband (UWB) frequencies from 3.1GHz to 10.6 GHz. The proposed design was accomplished using multilayer technology in which the structure is formed by three layers of conductors interleaved by a layer of substrate between each conductor layer. Simulation was carried out using CST Microwave Studio; the result was then compared with results from rectangular and star-shaped couplers that implemented the same technique. The results obtained show that the proposed new coupler has better performance compared to both rectangular and star-shaped coupler designs in terms of return loss, isolation, and phase difference. The coupler was fabricated and measured; the measurement results satisfactorily agree with the simulation results

Mangrove (Rhizophoro Apiculata) Fannins As A Potential Corrosion Inhibitor For Aluminium In Acidic Medium.

Utilisation of a green corrosion inhibitor formulated from natural, biodegradable and nontoxic organic compounds in industries has been extensively explored by a*great number of researchers. Investigation of tannins extracted from Mangrove Rhizophoro Apiculata sp. as a corrosion inhibitor for aluminum alloy has been carried out in acidic medium

Optimization of Pulsed Nd:YAG Laser Melting of Gray Cast Iron At Different Spot Sizes for Enhanced Surface Properties

This paper presents a laser surface modification process of gray cast iron using different laser spot size with an aims to eliminate graphite phase and achieve minimum surface roughness and maximum depth of molten zone and microhardness properties. The laser processing was conducted using JK300HPS Nd:YAG twin lamp laser source pulse TEM 00 mode, 50 W average power, 1064 nm wavelength and different laser spot sizes of 1.0 mm, 1.2 mm, 1.4 mm and 1.7 mm. Three controlled parameter were peak power (Pp), pulse repetition frequency (PRF) and traverse speed (v). Increasing spot size the parameter setting where peak power is increased and pulse repetition frequency and traverse speed is decreased. The modified surface of laser surface melting was characterized for metallographic study, surface roughness and hardness. Metallographic study and surface morphology were conducted using optical microscope while hardness properties were measured using Vickers scale. Surface roughness was measured using a 2D stylus profilometer. From metallographic study, the graphite phase was totally eliminated from the molten zone and formed white zone. This phenomenon affected hardness properties of the modified surface where maximum hardness of 955.8 HV0.1 achieved. Optimization of laser surface modification was conducted for minimum surface roughness and maximum depth of modified layer and hardness properties. From the optimization, the higher desirability is 0.902. The highest depth of molten zone obtain from spot size 1.4 mm at 132 µm and the highest hardness is 989 HV0.1 at laser’s spot size 1.0 mm. The surface roughness increased when the spot size increased from 3.10 µm to 7.31 µm. These finding indicate potential application of enhanced gray cast iron in high wear resistance automotive components such as cylinder liner and break disc

Technological Pedagogical Content Knowledge in Chemistry Education: A Review and Bibliometric Analysis Using VOSviewer and RStudio Applications

Technological Pedagogical Content Knowledge (TPACK) has become very important as technology has become an integral part of chemistry learning. The purpose of this study is to present a bibliometric and bibliographic review of various high-quality literature on TPACK in chemistry education. The bibliometric analysis used VOSviewer and RStudio. There were 22 literatures from the Scopus database published from 2011-2022. The results showed that publications increased slightly from 2018-2020 and decreased in 2020-2023. In 2012, 2013, 2016, and 2018 no articles were published, while citations to articles increased in 2018-2022 and tended to fluctuate in 2011-2018. There are 5 clusters. Cluster 1 (44 items), cluster 2 (39 items), cluster 3 (28 items), cluster 4 (21 items), and cluster 5 (11 items). In addition, papers were published by mostly Indonesian researchers. This study provides information for education researchers related to TPACK in chemistry education in the implementation of chemistry learning does not seem to have been done much which is expected to strengthen the topic of future researchers

Single channel magnetic induction spectroscopy technique for fetal acidosis detection

Current fetal acidosis diagnosis needs an invasive measurement which required a doctor to puncture fetal scalp to acquire blood pH. This method introduced risk to the fetal which fetal scalp may bruise and infected. This paper discusses a noninvasive method employing a single channel magnetic induction spectroscopy technique as an alternative method to diagnose acidosis in fetal without puncturing the fetal scalp. The studies are based on numerical simulation models to investigate the most feasible sensor coil that is sensitive and effective to be implemented in hardware setup as the shape of coil influences directly the sensing performance of the magnetic induction spectroscopy system. The study has found that the circular coil is more sensitive than linear coil. The system tested with different pH samples to mimic the blood pH value. The result is very promising with good correlation approaching 1 has been achieved. Therefore, magnetic induction spectroscopy technique has good opportunity to be applied as an alternative method to detect acidosis in the fetal with circular coil is performed as the best sensing coils for MIS hardware

Hidrolisis Selulosadari Bahan Pod Husk Kakao Menggunakan Asam Klorida

The aims of this experiment were to obtain the best concentration of HCl and the optimum length of boiling time in producing liquid sugar from cacao pod husk. Analysis of data of extracted cellulose (Phase I) used completely randomized design (CRD), which consisted of 3 NaOH concentrations tested namely : 10%, 12% and 14%. Each treatment was replieated 4 times, and therefore there were 12 experimental units used. Analysis of variance showing significant or highly significant effects were subsequently analysed by HSD at 5% or 1%, respectively. Experimental design used in the hydrolysis of cellulose (Phase II) was randomized block design (RBD) with four levels of hydrochloric acid (HCl) tested, namely: K1 = 1%; K2 = 1.5%; K3 = 2% and K4 = 2.5%. Treatments were grouped based on the length of pod husk cellulose hydrolysis time in hydrochloric acid solution, namely R1 = 2 hours, R2 = 4 hours, R3 = 6 hours, R4 = 8 hours, R5 = 10 hours and R6 = 12 hours. Each treatment was replicated three times in each group, and therefore there were 72 experimental units observed. Analysis of variance showing significant or highly significant effects were subsequently analysed by HSD at 5% or 1%, respectively. The best NaOH concentration was obtained at 12% and the optimum length of boiling time was 8 hours

A new approach for solving systems of fractional differential equations via natural transform

In this paper, A new method proposed and coined by the authors as the natural variational iteration  transform method(NVITM) is utilized to solve linear and nonlinear systems of fractional differential equations. The new method is a combination of natural transform method and variational iteration method. The solutions of our modeled systems are calculated in the form of convergent power series with easily computable components. The numerical results shows that the approach is easy to implement and accurate when applied to various linear and nonlinear systems of fractional differential equations

The effects of physiological biomechanical loading on intradiscal pressure and annulus Stress in lumbar spine: a finite element analysis

The present study was conducted to examine the effects of body weight on intradiscal pressure (IDP) and annulus stress of intervertebral discs at lumbar spine. Three-dimensional finite element model of osseoligamentous lumbar spine was developed subjected to follower load of 500 N, 800 N, and 1200 N which represent the loads for individuals who are normal and overweight with the pure moments at 7.5 Nm in flexion and extension motions. It was observed that the maximum IDP was 1.26 MPa at L1-L2 vertebral segment. However, the highest increment of IDP was found at L4-L5 segment where the IDP was increased to 30% in flexion and it was more severe at extension motion reaching to 80%. Furthermore, the maximum annulus stress also occurred at the L1-L2 segment with 3.9 MPa in extension motion. However, the highest increment was also found at L4-L5 where the annulus stress increased to 17% in extension motion. Based on these results, the increase of physiological loading could be an important factor to the increment of intradiscal pressure and annulus fibrosis stress at all intervertebral discs at the lumbar spine which may lead to early intervertebral disc damage

An adapted point based tracking for vehicle speed estimation in linear spacing

Vehicle velocity estimation is an important aspect of intelligent transportation systems. Normally velocity is estimated using dedicated laser speed traps and Doppler radars. Recently, the use of cameras is becoming more common for the purpose of traffic surveillance and smart surveillance system. It is thus the aim of this paper to propose a method for vehicle speed estimation using these existing video cameras. In this paper, we propose a vehicle speed estimation method from video analysis. The method proposed contains several steps; image preprocessing, centroid extraction and tracking. The proposed method transforms the 2D image points into a 3D virtual world to obtain actual vehicle position in 3D space. This is to account for perspective distortion commonly seen in images. Using these 3D points and measuring the time for displacement, the vehicle speed is obtained. Experimental results have shown that the proposed method gives accurate velocity estimation