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Articles 541 - 570 of 1147

Full-Text Articles in Mechanical Engineering

Numerical Study Of Paraffin Wax Melting In A Cavity With A Gradient Of Hot Wall Inclination, Agus Dwi Korawan Aug 2020

Numerical Study Of Paraffin Wax Melting In A Cavity With A Gradient Of Hot Wall Inclination, Agus Dwi Korawan

Makara Journal of Technology

The melting of a phase change material (PCM) in a cavity with a gradient of hot wall inclination was simulated numerically using five models, namely, Model-A, Model-B, Model-C, Model-D, and Model-E with gradients of −2, −4, ∞, 4, and 2, respectively. The PCM was paraffin wax, which was melted using an enthalpy porosity technique with a pressure-based method. Model-A was found to be the best model. For the completion of the melting process, the models were assigned with the liquid fraction of 1. Model-A required the shortest time, followed by Model-B, Model-C, Model-E, and Model-D, respectively. Compared with Model-C, Model-A …

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Analysis The Keelung Harbor Hydrodynamic Environment For The Safety Of Navigation, Hsing-Yu Wang, Dong-Taur Su, Sung-Shan Hsiao Aug 2020

Analysis The Keelung Harbor Hydrodynamic Environment For The Safety Of Navigation, Hsing-Yu Wang, Dong-Taur Su, Sung-Shan Hsiao

Journal of Marine Science and Technology–Taiwan

In this study, we simulated the hydrodynamics of the waters near the Keelung Harbor entrance and fairway before and after harbor expansion. The simulation results are used to discuss the impact of changes in the current characteristic on the inbound vessels. With reference to the fairway planning of Keelung Harbor, the simulation results before the expansion show that the current velocity with inbound fairway during the flood tide ranges from 0.08 to 1.03 m/s. Current direction was affected by the east breakwater, and a circulation occurs near the harbor entrance. After the expansion, during the flood tide, counterclockwise circulations occur …

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Experimental Investigation Into The Boundary Layer Of A Robotic Anguilliform Propulsor, Jonathan R. Eastridge Aug 2020

Experimental Investigation Into The Boundary Layer Of A Robotic Anguilliform Propulsor, Jonathan R. Eastridge

LSU New Orleans Theses and Dissertations

Boundary layer information local to three longitudinal positions has been characterized for a 130 cm long biomimetic self-propulsor known as NEELBOT-1.1 that swims with undulatory anguilliform-like motions, via analysis of stereo particle image velocimetry (PIV) measurements for key moments in the undulation cycle and for numerous combinations of swimming conditions and motion parameters, ideal and non-ideal. No obvious turbulent flow structures or indications of boundary layer separation were observed at nonzero advance speeds, and skin friction coefficients were subsequently estimated for magnitude relative to the dynamic pressure associated with operation at the design swimming speed of Uo = 0.25 …

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Alternative Material Selection For Oyster Restoration With An Emphasis On Living Docks, Bridgette Soucy Aug 2020

Alternative Material Selection For Oyster Restoration With An Emphasis On Living Docks, Bridgette Soucy

Theses and Dissertations

Oyster restoration efforts, including Living Shoreline and Living Dock projects, utilize aquaculture-grade plastic oyster mats to mitigate the decline of benthic communities. Aquaculture-grade plastic are known for strength, durability, and resilience to degradation in seawater. Over time, plastics break into microscopic segments commonly referred to as microplastics. Microplastics represent a major concern as marine organisms mistake the small particles for food. Plastics bioaccumulate in marine species, which impacts the marine food web and humans. In order to reduce further negative anthropogenic impacts, natural fibers and nature-inspired concrete mixtures were utilized across a series of experiments in order to determine an …

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Modular Cable Buoy, James J. Marinas, Gabriela Vargas, Anthony Catello, Joseph Heald Jun 2020

Modular Cable Buoy, James J. Marinas, Gabriela Vargas, Anthony Catello, Joseph Heald

Mechanical Engineering

Cable terminations are often the least reliable and most expensive components of a maritime system. These cables are suspended in water by a buoy to reduce wear at the terminations. The Naval Information Warfare Center requires a modular auxiliary float with tunable buoyancy that can be placed along such cable. Our system must be able to be deployed, adjusted, and retrieved quickly and easily during operational use. This report focuses on our team’s final design concept and includes all analysis to justify our design direction along with safety, maintenance, and repair considerations. The report further elaborates on cost analysis, manufacture …

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Compound Flooding In Coastal Areas Emanating From Inland And Offshore Events, Hamed Behzad Koochaksaraii May 2020

Compound Flooding In Coastal Areas Emanating From Inland And Offshore Events, Hamed Behzad Koochaksaraii

Dissertations

The vulnerability of urban populations to natural hazards and climate change is a major theme in many reports on coastal cities with flooding ranking highly among the climate change concerns. Flooding could occur as a result of runoff for inland rainfall that accumulates at the mouth of the estuary to the sea or it could occur due to a storm surge emanating from the ocean. The techniques for modeling the flooding from these events are very different, as they were developed in different scientific fields: hydrology and hydraulic engineering for inland rainfall versus coastal oceanography and coastal engineering for offshore …

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Design Of An Environmentally Responsive Grooming Tool To Aid In Underwater Navigation, Bruce Huntress Walker Iii May 2020

Design Of An Environmentally Responsive Grooming Tool To Aid In Underwater Navigation, Bruce Huntress Walker Iii

Theses and Dissertations

Underwater hull grooming is a proactive approach to ship hull husbandry. It has been defined as the frequent and gentle wiping of a ship hull coating to maintain it free of fouling. One of the challenges to implementing a grooming schedule is the control and navigation of the devices over the surface of the hull. This thesis presents prior research that has developed self-attaching rotating brushes as an effective method to groom fouling control coatings and the results from several years of implementation in the marine environment. The hypothesis of this thesis is that the condition of the ship hull …

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Living Docks: Structural Implications And Determination Of Force Coefficients Of Oyster Mats On Dock Pilings In The Indian River Lagoon, Ryan Christiansen May 2020

Living Docks: Structural Implications And Determination Of Force Coefficients Of Oyster Mats On Dock Pilings In The Indian River Lagoon, Ryan Christiansen

Theses and Dissertations

Brevard County, Florida, is facing rapid population growth and increased pollution entering the Indian River Lagoon (IRL), impairing water quality and damaging the ecosystem. This is problematic not only for public health and environmental stability, but also for the economy. The Living Docks initiative was created to combat environmental degrade in the lagoon and restore natural functions back to the ecosystem. With increased urbanization along coastal systems, there is opportunity for new forms of ecological engineering such as Living Docks, which attaches oyster mats to dock pilings as a means to promote the growth of filter feeding organisms. It is …

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Using The Chloride Penetration Depth Obtained From Rcpt To Assess The Permeability Of Concrete, Kang-Shiun Huang, Chung-Chia Yang Apr 2020

Using The Chloride Penetration Depth Obtained From Rcpt To Assess The Permeability Of Concrete, Kang-Shiun Huang, Chung-Chia Yang

Journal of Marine Science and Technology–Taiwan

A review of the literature on the rapid chloride permeability test (RCPT; ASTM C1202) indicates that RCPT has a few shortcomings, namely complex anions in concrete and Joule heating. The charge passed through concrete is affected by chloride ions because of the complex anions in concrete. Moreover, Joule heating influences the experimental temperature and causes an abnormal increase in the charge passed. Engineers have focused on the advance of the critical chloride front toward steel, but the charge passed in RCPT experiments has a poor relationship with the chloride penetration depth in fly ash concrete. Thus, it is risky to …

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Evaluation Of Migration Characteristics Of Opc And Slag Concrete From The Rapid Chloride Migration Test, Rues-Wen Shiu, Chung-Chia Yang Apr 2020

Evaluation Of Migration Characteristics Of Opc And Slag Concrete From The Rapid Chloride Migration Test, Rues-Wen Shiu, Chung-Chia Yang

Journal of Marine Science and Technology–Taiwan

In this study, the non-steady state chloride migration coefficient in concrete was measured using the rapid chloride migration (RCM) test. After completing the test, we established the specimen’s chloride profile by collecting concrete powder samples at predetermined, controlled depths. In order to investigate whether the RCM (NT BUILD 492) can be applied to slag concrete, we made ordinary Portland cement (OPC) concrete and slag concrete with different water binder (w/b) ratios. The combined results from the concrete chloride profile and regression analysis demonstrated that the NT BUILD 492 RCM method can be successfully applied to slag concrete. In summary, a …

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Fuzzy-Sliding-Mode-Based Robust Tracking Control Of Autonomous Underwater Vehicles, Qiaomei Sun, Jinguo Chen, Wan Yu, Huashan Su Apr 2020

Fuzzy-Sliding-Mode-Based Robust Tracking Control Of Autonomous Underwater Vehicles, Qiaomei Sun, Jinguo Chen, Wan Yu, Huashan Su

Journal of Marine Science and Technology–Taiwan

Control of an autonomous underwater vehicle (AUV) is difficult due to its nonlinear and coupled characteristics, parameter uncertainties, and unknown disturbances. This paper presents a motion control system based on an adaptive fuzzy sliding mode control (FSMC) method for trajectory tracking of an AUV. The proposed FSMC method is primarily based on a combination of sliding mode control (SMC) strategy with an adaptive fuzzy algorithm to estimate external disturbances and weaken the chattering effect. A waypoint guidance law based on a line-of-sight (LOS) algorithm is applied to the guidance system. Simulation studies confirm a good performance of the proposed controller. …

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Effects Of Collision Damage On The Ultimate Strength Of Fpso Vessels, Muhammad Zubair Muis Alie, Dian Ramasari, Taufiqur Rachman, Ristiyanto Adiputra Apr 2020

Effects Of Collision Damage On The Ultimate Strength Of Fpso Vessels, Muhammad Zubair Muis Alie, Dian Ramasari, Taufiqur Rachman, Ristiyanto Adiputra

Makara Journal of Technology

Floating production storage offloading (FPSO) vessels are movable offshore structures. These structures are designed with large dimensions, and their decks are loaded with several types of equipment. During collision damage, the hull and deck parts loaded with equipment are severely affected. Therefore, the ultimate strength of FPSO vessels should be thoroughly checked and evaluated. The objective of the present study is to analyze the ultimate strength of FPSO vessels against collision damage characterized by hogging and sagging under longitudinal bending. The cross section of an FPSO vessel is modeled with elements composed of stiffened and unstiffened plates. The vessel length …

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Ionic Conductivity And Electrochemical Properties Of Alginate–Nn4no3-Based Biopolymer Electrolytes For Edlc Application, Norfatihah Binti Mazuki, Nur Muhitul Jalilah Rasali, Bouchta Sahraoui, Ahmad Salihin Samsudin Apr 2020

Ionic Conductivity And Electrochemical Properties Of Alginate–Nn4no3-Based Biopolymer Electrolytes For Edlc Application, Norfatihah Binti Mazuki, Nur Muhitul Jalilah Rasali, Bouchta Sahraoui, Ahmad Salihin Samsudin

Makara Journal of Technology

In this work, alginate doped with various contents of ammonium nitrate (NH4NO3) as a solid biopolymer electrolyte (SBE) was prepared via casting by using distilled water as a solvent. Impedance studies on alginate–NH4NO3 SBE films were conducted via impedance spectroscopy. The lowest bulk resistance (Rb) showed that the maximum ionic conductivity of the sample containing 25 wt.% NH4NO3 at ambient temperature (303 K) was 5.56 × 10−5 S cm−1. The temperature dependence of ionic conductivity was evaluated, and results confirmed that electrolytes followed an Arrhenius behavior. The highest conducting sample was fabricated into an electrical double-layer capacitor and characterized in …

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Synthesis Of Epoxy Monoethanolamide From Bauhinia Monandra Seed Oil, Adewale Adewuyi, Rotimi A. Oderinde Apr 2020

Synthesis Of Epoxy Monoethanolamide From Bauhinia Monandra Seed Oil, Adewale Adewuyi, Rotimi A. Oderinde

Makara Journal of Technology

In this study, we synthesized epoxidised monoethanolamide (EMA) from Bauhinia monandra seed oil (BMO) via a simple reaction route. In this process, BMO was transesterified to obtain a mixture of methyl esters, which was subjected to a urea adduct complexation reaction. The unsaturated methyl esters (BME) from the urea adduct complexation reaction were then epoxidised using performic acid produced in situ in a one-pot reaction system. The epoxidised methyl esters were converted to EMA by reacting them with monoethanolamine (1:10). The progression of the reaction was monitored using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy, and the …

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Ethylene Carbonate And Polyethylene Glycol As Efficient Plasticizers In Cmc-Pva-Nh4no3-Based Polymer Electrolyte, Noor Saadiah Mohd Ali, Yuki Nagao, Ahmad Salihin Samsudin Apr 2020

Ethylene Carbonate And Polyethylene Glycol As Efficient Plasticizers In Cmc-Pva-Nh4no3-Based Polymer Electrolyte, Noor Saadiah Mohd Ali, Yuki Nagao, Ahmad Salihin Samsudin

Makara Journal of Technology

This study investigated the influence of plasticizers (polyethylene glycol [PEG] and ethylene carbonate [EC]) on the ionic conduction of CMC-PVA-NH4NO3. Blended biopolymer electrolytes (BBEs) based on carboxymethyl cellulose–polyvinyl alcohol (CMC-PVA) doped with ammonium nitrate (NH4NO3) were obtained via casting solution technique incorporated with PEG and EC, which acted as plasticizers. Electrical impedance spectroscopy (EIS) was conducted to evaluate the effect of plasticization on the ionic conduction properties. The ionic conductivity improved from 1.70 × 10−3 S/cm for un-plasticized BBEs to 3.92 × 10−3 S/cm for plasticized BBEs with EC and 3.00 × 10−3 S/cm for plasticized BBEs with PEG. The …

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Current Status Of Hydrothermal Treatment For Energy And Material Recovery Toward A Sustainable Post-Consumer Material Cycle, Baskoro Lokahita, Muhammad Aziz, Fumitake Takahashi Apr 2020

Current Status Of Hydrothermal Treatment For Energy And Material Recovery Toward A Sustainable Post-Consumer Material Cycle, Baskoro Lokahita, Muhammad Aziz, Fumitake Takahashi

Makara Journal of Technology

The demand for energy-efficient and environmentally friendly municipal solid waste (MSW) processing has increased in developing countries. The thermochemical process offers a fast and reliable solution to reutilize or reduce the volume of MSW. Hydrothermal treatment is a novel MSW treatment technology that is compatible with high-moisture-content feedstock. It involves the thermal degradation of MSW in pressurized water or steam, which promotes the disintegration of cellulosic and polymer materials. Recent advances have shown effective MSW conversion into homogenous solid hydrochar with higher energy density. Alkali and chlorine content, which causes issues in combustors, was successfully removed due to the washing …

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Liquefaction Potential Analysis Based On Nonlinear Ground Response On The Coastline Of Bengkulu City, Indonesia, Lindung Zalbuin Mase Apr 2020

Liquefaction Potential Analysis Based On Nonlinear Ground Response On The Coastline Of Bengkulu City, Indonesia, Lindung Zalbuin Mase

Makara Journal of Technology

This paper presents the study of the seismic response and liquefaction potential of the coastal area of Bengkulu City during the September 2007 Sumatra earthquake. The study is conducted by collecting site investigation data (standard penetration test) and applying input motion to observe soil response. Synthetic ground motion is generated by considering the important aspects of earthquakes, including focal depth, epicenter, earthquake source, and site classification. The synthetized ground motion is then used as the input motion in the seismic response analysis. The results of this analysis are spectral acceleration and peak ground acceleration at each depth. The resulting spectral …

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Comparison Of Phytoremediation And Filtration For Diamond-Mine-Tailings Water Treatment, M. Hafidhuddin Noor, Mijani Rahman, Akhmad Gazali, Nia Kania, Aulia Rahma, Erdina L.A. Rampun, Amalia E. Pratiwi, Muthia Elma Apr 2020

Comparison Of Phytoremediation And Filtration For Diamond-Mine-Tailings Water Treatment, M. Hafidhuddin Noor, Mijani Rahman, Akhmad Gazali, Nia Kania, Aulia Rahma, Erdina L.A. Rampun, Amalia E. Pratiwi, Muthia Elma

Makara Journal of Technology

The water pollution caused by diamond mine activities can kill aquatic life. In this work, we used phytoremediation and filtration to treat pond water polluted by the tailings of a diamond mine located in South Kalimantan, Indonesia. Einchhornia crassipes (water hyacinth) was utilized as the biomass for the phytoremediation process. Gravel (10–15 mm) and sand (0.1–1 mm) were used as filter media in the simple filtration setup, using an up-flow system (bottom to top). In the experiment, 16 L of diamond tailing water was poured into five phytoremediation reactors (each 60 L in volume), which were then tested over seven …

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Shallow Water Seafloor Geodesy: Gps On An Anchored Spar Buoy, Surui Xie Feb 2020

Shallow Water Seafloor Geodesy: Gps On An Anchored Spar Buoy, Surui Xie

USF Tampa Graduate Theses and Dissertations

Measuring seafloor motion in shallow coastal water is challenging due to strong and highly variable oceanographic effects. Such measurements are potentially useful for monitoring near-shore coastal subsidence, subsidence due to petroleum withdrawal, strain accumulation/release processes in marine shelves and submerged volcanoes, and certain fresh water applications, such as volcano deformation in caldera-hosted lakes. I participated in a project to develop a seafloor geodetic system for this environment based on an anchored spar buoy topped by high precision GPS. Orientation of the buoy is measured using a digital compass that provides heading, pitch, and roll information. The combined orientation and GPS …

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A Neural Network Approach To Estimate Buoy Mooring Line Sensor Deflection, Tom Price Jan 2020

A Neural Network Approach To Estimate Buoy Mooring Line Sensor Deflection, Tom Price

Dissertations, Master's Theses and Master's Reports

Instrumented moorings are often used to measure characteristics, such as temperature and current, over the water column. However, the moorings deflect from the effects of currents and waves, which could lead to innacurate measurements. In this work, a computationally efficient method to compensate for mooring sensor position errors is developed. The two-step process first uses a hydrodynamic model of the buoy and mooring line system to create estimated mooring line deflections in a steady current. A neural network model is trained to approximate the hydrodynamic model’s mooring line displacement given the spatial location of the buoy and current profile measurements. …

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Optimization Of Shape And Control Of Linear And Nonlinear Wave Energy Converters, Jiajun Song Jan 2020

Optimization Of Shape And Control Of Linear And Nonlinear Wave Energy Converters, Jiajun Song

Dissertations, Master's Theses and Master's Reports

In this dissertation, we address the optimal control and shape optimization of Wave Energy Converters. The wave energy converters considered in this study are the single-body heaving wave energy converters, and the two-body heaving wave energy converters. Different types of wave energy converters are modeled mathematically, and different optimal controls are developed for them. The concept of shape optimization is introduced in this dissertation; the goal is to leverage nonlinear hydrodynamic forces which are dependent on the buoy shape. In this dissertation, shape optimization is carried out and its impact on energy extraction is investigated. In all the studies conducted …

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Development Of Horizontal Axis Hydrokinetic Turbine Using Experimental And Numerical Approaches, Abdulaziz Abutunis Jan 2020

Development Of Horizontal Axis Hydrokinetic Turbine Using Experimental And Numerical Approaches, Abdulaziz Abutunis

Doctoral Dissertations

“Hydrokinetic energy conversion systems (HECSs) are emerging as viable solutions for harnessing the kinetic energy in river streams and tidal currents due to their low operating head and flexible mobility. This study is focused on the experimental and numerical aspects of developing an axial HECS for applications with low head ranges and limited operational space. In Part I, blade element momentum (BEM) and neural network (NN) models were developed and coupled to overcome the BEM’s inherent convergence issues which hinder the blade design process. The NNs were also used as a multivariate interpolation tool to estimate the blade hydrodynamic characteristics …

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Fft Phase Shift Of Water Wave Analysis, Chu-Kuan Lin, Shih-Yu Hsu, Jaw-Guei Lin Dec 2019

Fft Phase Shift Of Water Wave Analysis, Chu-Kuan Lin, Shih-Yu Hsu, Jaw-Guei Lin

Journal of Marine Science and Technology–Taiwan

The fast Fourier transform (FFT) has been accepted as a tool for signal processing. This study conducted a series of numerical experiments using Matlab. By conducting FFT analysis on designated wave trains, the FFT results revealed that an extra phase shift of ��ሺ2�� ��⁄ ሻ , with N representing the number of data points for an i-th wave component, was implicitly added to the analyzed phases during the analysis. When extra phase shifts were subtracted from the analyzed phases of each component, signals could be completely reconstructed in the time domain with an acceptable difference. This study tested component and …

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A New Synthesized Microalloys Steel Ods Of High Amplitude Ultrasonically Irradiation, Marzuki Silalahi, Hanif Abdurrahman Wicaksana, Ferhat Aziz, Syahfandi Ahda, Mohamad Riza Iskandar Dec 2019

A New Synthesized Microalloys Steel Ods Of High Amplitude Ultrasonically Irradiation, Marzuki Silalahi, Hanif Abdurrahman Wicaksana, Ferhat Aziz, Syahfandi Ahda, Mohamad Riza Iskandar

Makara Journal of Technology

Micropowders of oxide-dispersion-strengthened (ODS) steel have been synthesized using the ultrasonic irradiation method with variations in amplitude. The ultrasonic irradiation process is performed for 50 h at a frequency of 20 kHz with 40%, 50%, and 60% amplitudes in toluene solution. The formation of Fe-Cr microalloys in the preparation of Fe- 15Cr-0.5Y2O3 powder was analyzed using SEM-EDS, X-ray diffraction (XRD), and TEM-EDS. The percentage of Fe- Cr phase mass fraction of ODS steel micropowder formed during ultrasonic irradiation with 40%:50%:60% amplitude was 12.2%:34.1%:22.1%, with 25.67:77.02:38.51 nm crystallite size. The crystallite size at 50% amplitude was the largest, and the diffusion …

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Comprehensive Inspection On The Experimental Ferritic Stainless Steel By Means Of Transmission Electron Microscopy And Neutron Diffraction Techniques, Parikin Parikin, Mohammad Dani, Riza Iskandar, Aziz Khan Jahja, Andon Insani, Joachim Mayer Dec 2019

Comprehensive Inspection On The Experimental Ferritic Stainless Steel By Means Of Transmission Electron Microscopy And Neutron Diffraction Techniques, Parikin Parikin, Mohammad Dani, Riza Iskandar, Aziz Khan Jahja, Andon Insani, Joachim Mayer

Makara Journal of Technology

The field of physical metallurgy is one of the primary beacons that guide alloy developments for multipurpose materials such as the in-core structure materials for pressure vessel components and heat exchangers. The surface microstructure of new ferritic steel with significant local constituent materials was characterized by high resolution powder neutron diffractometer (HRPD) and transmission electron microscope (TEM), combined with the energy dispersive X-ray spectroscopy (EDX). The alloy contains73% Fe, 24% Cr, 2% Si, 0.8% Mn, and 0.1% Ni, in %wt. The charge materials were melted by the casting techniques. The neutron diffractograms obtained shows five dominant diffraction peaks at (110), …

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Study On Antibacterial Of Chitosan/Hydroxyapatite Doped Magnesium Composite As A Material For Bone Graft Applications, Andromeda Dwi Laksono, Teodoro A. Amatosa, Jr., Hilda Pebrianti Octaviana Sitorus, Wentika Putri Kusuma Asih, Sulistijono Sulistijono Dec 2019

Study On Antibacterial Of Chitosan/Hydroxyapatite Doped Magnesium Composite As A Material For Bone Graft Applications, Andromeda Dwi Laksono, Teodoro A. Amatosa, Jr., Hilda Pebrianti Octaviana Sitorus, Wentika Putri Kusuma Asih, Sulistijono Sulistijono

Makara Journal of Technology

Hydroxyapatite (HAp) is one of the constituent minerals of bone and teeth, that has been widely used for synthesizing bone graft. Due to the limitation on properties of the hydroxyapatite, it is doping with Magnesium (HAp-Mg). The addition of Chitosan (Chi) was expected to improve the antibacterial properties of HAp-Mg. The present research aims to study the influence of Chitosan with 0, 5, 15, and 25 wt% addition on biocompatibility properties of Chi/HAp-Mg composite. HAp-Mg was synthesized using the sol-gel method; meanwhile, Chi/HAp-Mg composite was manufactured by mixing Chitosan in acetic acid, and HAp-Mg was added into the mixture. The …

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Evaluation Of Primal-Dual Splitting Algorithm For Mri Reconstruction Using Spatio-Temporal Structure Tensor And L1-2 Norm, Mia Rizkinia, Masahiro Okuda Dec 2019

Evaluation Of Primal-Dual Splitting Algorithm For Mri Reconstruction Using Spatio-Temporal Structure Tensor And L1-2 Norm, Mia Rizkinia, Masahiro Okuda

Makara Journal of Technology

Magnetic resonance imaging (MRI) is an essential medical imaging technique which is widely used for medical research and diagnosis. Dynamic MRI provides the observed object visualization through time and results in a spatiotemporal signal. The image sequences often contain redundant information in both spatial and temporal domains. To utilize this characteristic, we propose a spatio-temporal reconstruction approach based on compressive sensing theory. We apply spatio-temporal structure tensor using nuclear norm, in addition to the wavelet sparsity regularization. The spatio-temporal structure tensor is a matrix that consists of gradient components of the MRI data w.r.t the spatial and temporal domains. For …

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Influence Of Nh4f In Dextran Based Biopolymer Electrolytes: Conductivity And Electrical Analysis, Muhamad Hafiz Hamsan, Mohd Fakhrul Zamani Kadir, Shujahadeen Bakar Aziz, Muhammad Amirul Solihin Azha, Saifful Kamaluddin Muzakir Dec 2019

Influence Of Nh4f In Dextran Based Biopolymer Electrolytes: Conductivity And Electrical Analysis, Muhamad Hafiz Hamsan, Mohd Fakhrul Zamani Kadir, Shujahadeen Bakar Aziz, Muhammad Amirul Solihin Azha, Saifful Kamaluddin Muzakir

Makara Journal of Technology

Dextran polymer host was doped with different concentrations of ammonium fluoride (NH4F) via casting technique. In this present work, dextran-NH4F film has been employed to investigate the ionic conductivity using electrochemical impedance spectroscopy from 50 to 5 MHz. The highest room temperature conductivity is achieved at (2.33 ± 0.76) × 10-3 S cm-1 with 40 wt.% NH4F. The electrolyte is found to obey Arrhenius rule at high temperature with activation energy of 0.21 eV. Dielectric analysis has been performed to obtain better understanding on the conductivity pattern. The dielectric parameters e.g. ɛreal, ɛimag, Mreal, and Mimag have been tested as …

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Acute Toxicitystudy Of Choline Based Ionic Liquids Towards Danio Rerio Fish And The Aggregation Behavior Of Their Binary Mixtures, Mansoor Ul Hassan Shah, Nasruddin Nasruddin, Suzana Bt Yusup, Muhammad Moniruzzaman Dec 2019

Acute Toxicitystudy Of Choline Based Ionic Liquids Towards Danio Rerio Fish And The Aggregation Behavior Of Their Binary Mixtures, Mansoor Ul Hassan Shah, Nasruddin Nasruddin, Suzana Bt Yusup, Muhammad Moniruzzaman

Makara Journal of Technology

Marine oil spills are effectively controlled by chemical dispersants. However, the toxicity associated with it reduce its employment in marine environment. To overcome this limitation, the acute toxicity of choline based ionic liquids was evaluated as a potential low toxic variant for oil spill remediation. Further, the aggregation behavior of the individual as well as their binary mixtures was also evaluated by employing tensiometry technique. The half-lethal concentration, LC50on zebrafish (Danio rerio) of three choline based ionic liquids showed that the studied ionic liquids (ILs) fall in the range of “practically nontoxic” ( 100-1000 mg L-1).Various micellar properties showed that …

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Neutron Diffraction Study Of Multiferroic 0.6nife2o4/0.4batio3 Composite, Engkir Sukirman, Yosef Sarwanto, Syahfandi Ahda, Andon Insani Dec 2019

Neutron Diffraction Study Of Multiferroic 0.6nife2o4/0.4batio3 Composite, Engkir Sukirman, Yosef Sarwanto, Syahfandi Ahda, Andon Insani

Makara Journal of Technology

Neutron diffraction study on the 0.6NiFe2O4/0.4BaTiO3 multiferroic composite has been carried out. The 0.6NiFe2O4/0.4BaTiO3 multiferroic composites have been synthesized by solid reaction method. In this study, 20 g of BaTiO3 (BTO) and 20 g of NiFe2O4 (NFO) compounds were prepared from the powder raw materials of BaO3 and TiO2 for BTO, and NiO and Fe2O3 for NFO. Furthermore, both BTO and NFO were each crushed for 5 hours using High Energy Milling (HEM). Then the BTO and NFO were calcined in the furnace at 950 °C/5 hours and 900 °C/5 hours, respectively. Both NFO and BTO precursors were manually mixed …

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