scispace - formally typeset
Search or ask a question
Author

Ubaidillah Ubaidillah

Bio: Ubaidillah Ubaidillah is an academic researcher from Sebelas Maret University. The author has contributed to research in topics: Magnetorheological fluid & Materials science. The author has an hindex of 9, co-authored 52 publications receiving 274 citations. Previous affiliations of Ubaidillah Ubaidillah include Sunan Kalijaga Islamic University & Islamic University.

Papers published on a yearly basis

Papers
More filters
Journal ArticleDOI
TL;DR: In this article, the effect of different types of multiwall carbon nanotubes (MWCNTs) on the morphological, magnetic and viscoelastic properties of magnetorheological elastomers (MREs) are studied.
Abstract: The effect of different types of multiwall carbon nanotubes (MWCNTs) on the morphological, magnetic and viscoelastic properties of magnetorheological elastomers (MREs) are studied in this work. A series of natural rubber MRE are prepared by adding MWCNTs as a new additive in MRE. Effects of functionalized MWCNT namely carboxylated MWCNT (COOH-MWCNT) and hydroxylated MWCNT (OH-MWCNT) on the rheological properties of MREs are investigated and the pristine MWCNTs is referred as a control. Epoxidised palm oil (EPO) is used as a medium to disperse carbonyl iron particle (CIP) and sonicate the MWCNTs. Morphological and magnetic properties of MREs are characterized by field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM), respectively. Rheological properties under different magnetic field are evaluated by using parallel plate rheometer. From the results obtained, FESEM images indicate that COOH-MWCNT and CIP have better compatibility which leads to the formation of interconnected network in the matrix. In addition, by adding functionalized COOH-MWCNT, it is shown that the saturation magnetization is 5% higher than the pristine MWCNTs. It is also found that with the addition of COOH-MWCNT, the magnetic properties are improved parallel with enhancement of MR effect particularly at low strain amplitude. It is finally shown that the use of EPO also can contribute to the enhancement of MR performance.

46 citations

Journal ArticleDOI
13 Jun 2019
TL;DR: In this article, the effect of good corporate governance and corporate social responsibility on firm value with financial performance as a moderating variable was investigated in banking companies listed in the IDX for 2011-2015.
Abstract: Good corporate governance and corporate social responsibility can assist the company in facing the challenges and risks as a strategy in increasing the firm value by building the right image from the stakeholders’ view. This study aims to determine the effect of good corporate governance and corporate social responsibility on firm value with financial performance as a moderating variable. The population of this research is banking companies listed in Indonesia Stock Exchange (IDX) for 2011–2015. The sample consisted of 23 companies which were selected by purposive random sampling. This data is analyzed by using Partial Least Square approach. The results of this study indicate that good corporate governance has an insignificant positive effect on firm value; otherwise corporate social responsibility has a significant negative impact on firm value. Financial performance has significantly strengthened the relationship between good corporate governance and corporate social responsibility on firm value.

32 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the response of a magnetorheological brake (MRB) system under the free move inertial mass and provided a linear second order differential equation to model the stopping time and braking torque behaviors.
Abstract: The study is objected to investigate the response of a magnetorheological brake (MRB) system under thefree move inertial mass. The disk-type MRB comprises of a rotating disk immersed in magnetorheological fluids (MRFs) and surrounded by an electromagnet coil. The magnetized coil causes a solidification of the MR fluid so that the shear stress between the moving part and static part increases resulting in the decrement speed of the moving parts. The shear stress can be varied by applying different electric current to the coil. The study began with the part design using the3D modeling software, followingbythe magnetostatic analysis. The flux density across the magnetorheological fluid could be predicted through this finite element magnetic simulation. The quantity of magnetic flux was then used to predict the shear stress between static and moving parts. The fabricated MRB was integrated onto a test rig which employs load cell and speed sensor as well as completely instrumented with data acquisition.Since the MRB test rig performed a simple free rotation system, a linear second order differential equation was derived to model the stopping time and braking torque behaviors. The equation of motion was built in a Simulink model, and the simulation results were compared to the real measurement. The achievable braking torque was also presented based on theaverage value from the load cell.

28 citations

Journal ArticleDOI
TL;DR: The analysis implied that the effectiveness of the MRE was associated with the use of the SO, and the closed-loop mold helped enhance the absolute modulus up to 0.8 MPa, which could be potentially useful in industry applications, particularly as vibration absorbers, which require a high range of stiffness.
Abstract: The existing mold concept of fabricating magnetorheological elastomer (MRE) tends to encounter several flux issues due to magnetic flux losses inside the chamber. Therefore, this paper presents a new approach for enhancing particle alignment through MRE fabrication as a means to provide better rheological properties. A closed-loop mold, which is essentially a fully guided magnetic field inside the chamber, was designed in order to strengthen the magnetic flux during the curing process with the help of silicone oil (SO) plasticizers. The oil serves the purpose of softening the matrix. Scanning electron microscopy (SEM) was used to observe the surface morphology of the fabricated MRE samples. The field-dependent dynamic properties of the MREs were measured several ways using a rheometer, namely, strain sweep, frequency sweep, and magnetic field sweep. The analysis implied that the effectiveness of the MRE was associated with the use of the SO, and the closed-loop mold helped enhance the absolute modulus up to 0.8 MPa. The relative magnetorheological (MR) effects exhibited high values up to 646%. The high modulus properties offered by the MRE with SO are believed to be potentially useful in industry applications, particularly as vibration absorbers, which require a high range of stiffness.

25 citations


Cited by
More filters
01 Jan 2014
TL;DR: A portfolio of technologies now exists to meet the world's energy needs over the next 50 years and limit atmospheric CO2 to a trajectory that avoids a doubling of the preindustrial concentration.
Abstract: Humanity already possesses the fundamental scientific, technical, and industrial know-how to solve the carbon and climate problem for the next half-century. A portfolio of technologies now exists to meet the world's energy needs over the next 50 years and limit atmospheric CO2 to a trajectory that avoids a doubling of the preindustrial concentration. Every element in this portfolio has passed beyond the laboratory bench and demonstration project; many are already implemented somewhere at full industrial scale. Although no element is a credible candidate for doing the entire job (or even half the job) by itself, the portfolio as a whole is large enough that not every element has to be used.

269 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the present of a number of promising cathode materials for Li-ion batteries and summarized the very recent research progress focusing on the surface coating strategies, mainly including the coating materials, the coating technologies, as well as the corresponding working mechanisms for cathodes.

234 citations

Journal ArticleDOI
TL;DR: Magnetorheological elastomers (MREs) are a class of recently emerged smart materials whose moduli are largely influenced when exposed to an external magnetic field as mentioned in this paper.
Abstract: Magnetorheological elastomers (MREs) are a class of recently emerged smart materials whose moduli are largely influenced when exposed to an external magnetic field. The MREs are particulate composites, where micro-sized magnetic particles are dispersed inside a non-magnetic polymeric matrix. These elastomers are known for changing their mechanical and rheological properties in the presence of a magnetic field. This change in properties is widely known as the magnetorheological (MR) effect. The MR effect depends on a number of factors such as type of matrix materials, type, concentration and distribution of magnetic particles, use of additives, working modes, and magnetic field strength. The investigation of MREs’ mechanical properties in both off-field and on-field (i.e. absence and presence of a magnetic field) is crucial to deploy them in real engineering applications. The common magneto-mechanical characterization experiments of MREs include static and dynamic compression, tensile, and shear tests in both off-field and on-field. This review article aims to provide a comprehensive overview of the magneto-mechanical characterizations of MREs along with brief coverage of the MRE materials and their fabrication methods.

150 citations

01 Jul 2011
TL;DR: In this paper, the authors analyzed 130 German companies' CSR disclosures (470 firm-year observations) to investigate the determinants of these voluntary disclosure activities and found that, consistent with the political cost theory, companies' disclosures of all CSR issues are affected by their visibility, shareholder structure, and relationship with their US stakeholders.
Abstract: textCurrently, companies spend a great deal of effort on Corporate Social Responsibility (CSR) disclosures. CSR disclosure relates to the provision of information on companies' environmental and social performance. From an economic perspective, companies might disclose this information to avoid or decrease potential political costs. We construct a CSR disclosure index based on the Global Reporting Initiative (GRI) guidelines. Using content analysis, we analyze 130 listed German companies' CSR disclosures (470 firm-year observations) to investigate the determinants of these voluntary disclosure activities. Our results show that, consistent with the political cost theory, German companies' disclosures of all CSR issues are affected by their visibility, shareholder structure, and relationship with their US stakeholders. In addition, higher profitability is associated with more environmental disclosures. Finally, size and industry membership affect the amount of CSR disclosure.

147 citations