108 research outputs found
Performance analysis on the effect of stoichiometric air fuel ratio and ignition strength for spark ignition engine / Azhan Ab Rahman
No full textAn approach for control of the spark ignition on the advance / retard and also the
spark voltage with air fuel ratio for a model of carburetor engine is proposed. The
amount of air to fuel ratio is one of the well-known problems in an engine
management system design. It is one of the most critical parameter to the analysis of
engine performance, torque and fuel consumption. It is common in the production
plant as well as in the market use a greater diameter of high-tension cable that is
expected to provide a proportional power with the increase amount of spark intensity
to achieve the desired engine performance with stoichiometric air fuel ratio. A
manually voltage control coils before the high tension cable is used to vary the spark
strength in the combustion chamber in order to measure the power, torque and fuel
consumption. Sets of experiments were conducted and results obtained were
presented in term of graphs
Current concepts on oxidative/carbonyl stress, inflammation and epigenetics in pathogenesis of chronic obstructive pulmonary disease
No full textChronic obstructive pulmonary disease (COPD) is a global health problem. The current therapies for COPD are poorly effective and the mainstays of pharmacotherapy are bronchodilators. A better understanding of the pathobiology of COPD is critical for the development of novel therapies. In the present review, we have discussed the roles of oxidative/aldehyde stress, inflammation/immunity, and chromatin remodeling in the pathogenesis of COPD. An imbalance of oxidants/antioxidants caused by cigarette smoke and other pollutants/biomass fuels plays an important role in the pathogenesis of COPD by regulating redox-sensitive transcription factors (e.g., NF-κB), autophagy and unfolded protein response leading to chronic lung inflammatory response. Cigarette smoke also activates canonical/alternative NF-κB pathways and their upstream kinases leading to sustained inflammatory response in lungs. Recently, epigenetic regulation has been shown to be critical for the development of COPD because the expression/activity of enzymes that regulate these epigenetic modifications have been reported to be abnormal in airways of COPD patients. Hence, the significant advances made in understanding the pathophysiology of COPD as described herein will identify novel therapeutic targets for intervention in COPD
Environmental toxicity, redox signaling and lung inflammation:the role of glutathione
No full textGlutathione (gamma-glutamyl-cysteinyl-glycine, GSH) is the most abundant intracellular antioxidant thiol and is central to redox defense during oxidative stress. GSH metabolism is tightly regulated and has been implicated in redox signaling and also in protection against environmental oxidant-mediated injury. Changes in the ratio of the reduced and disulfide form (GSH/GSSG) can affect signaling pathways that participate in a broad array of physiological responses from cell proliferation, autophagy and apoptosis to gene expression that involve H(2)O(2) as a second messenger. Oxidative stress due to oxidant/antioxidant imbalance and also due to environmental oxidants is an important component during inflammation and respiratory diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and asthma. It is known to activate multiple stress kinase pathways and redox-sensitive transcription factors such as Nrf2, NF-kappaB and AP-1, which differentially regulate the genes for pro-inflammatory cytokines as well as the protective antioxidant genes. Understanding the regulatory mechanisms for the induction of antioxidants, such as GSH, versus pro-inflammatory mediators at sites of oxidant-directed injuries may allow for the development of novel therapies which will allow pharmacological manipulation of GSH synthesis during inflammation and oxidative injury. This article features the current knowledge about the role of GSH in redox signaling, GSH biosynthesis and particularly the regulation of transcription factor Nrf2 by GSH and downstream signaling during oxidative stress and inflammation in various pulmonary diseases. We also discussed the current therapeutic clinical trials using GSH and other thiol compounds, such as N-acetyl-l-cysteine, fudosteine, carbocysteine, erdosteine in environment-induced airways disease
Efficiency for photovoltaic inverter: a technological review
No full textIt is recognized that a small percentage difference in the efficiency of a photovoltaic (PV) inverters causes a substantial variation in their cost. This is understandable because a PV inverter is expected to be in service for a good number of years (possibly as long as the PV modules themselves) and therefore the total energy yield that can be extracted using the inverter need to be considered in the initial investment calculation. However, there appears to be confusion on the real meaning of the term “inverter efficiency”. Unfortunately, there is no single documented reference available that can adequately describe the significant of these efficiencies and how are they related to each other. In most cases, the user only relies on the efficiency numbers stamped on the inverter nameplate as a guide during PV system dimensioning. Such approach may result in a non-optimized solution. This critical review paper is an attempt to clarify these confusions by gathering, organizing and analyzing the scattered information available around from various literatures. It is hoped that the information assembled in this paper can be a valuable guidelines for PV practitioners as well as researchers to kick start their research in this field
Formulation of photovoltaic inverter weighted conversion efficiency for equatorial climate
No full textThe system energy yield (Esys) is a performance indicator used by the installer to predict the energy output generated by a photovoltaic (PV) system. From the Esys estimation, the return of investment (ROI) for the installation can be approximated. The Esys equation consists of several elements, in which one of them is the PV inverter efficiency. The peak or maximum efficiency (ηmax) value from the inverter data sheet is usually used, but this practice is inaccurate because the PV inverters rarely operate at the peak power. Alternatively, the weighted efficiency is more preferable as it essentially considers the power conversion characteristics of the inverter when subjected to varying solar irradiance. Currently, the European weighted efficiency (ηEURO) is the most recognized and widely accepted. This is because, historically, European countries (particularly Germany) used to be the largest exporter and consumer of PV inverters throughout the world. Since ηEURO is developed based on a specific European irradiance profile, it is suspected that its value may not be suitable for inverters installed in different climatic conditions, particularly the equatorial region. Thus, the first objective of this work is carried out to prove this hypothesis. A one-year dataset from a weather station located at Universiti Teknikal Malaysia Melaka is collected with adherence to the IEC 61724 Standard. This irradiance profile is injected into a PV array simulator (PVAS) and tested on four PV inverters with different sizes and technologies. It is found that the recalculated ηEURO does not conform to the value stated in the respective inverter’s datasheet, thus confirming the above hypothesis. This finding inspires the formulation of a new weighted efficiency formula for the equatorial climate (ηEQUA). Three methods have been utilized, namely the IEC 61683 Standard, Response Surface Methodology (RSM) and Equatorial Irradiance-Duration Curve. The outcomes revealed that the last approach is the most practical solution to formulate ηEQUA. The newly developed formula is validated by the measured data from the field. It is demonstrated that the prediction of Esys using ηEQUA closely matched the Esys of a real 3 kW PV system, with only 0.16% difference between the two. It is envisaged that the usage of ηEQUA instead of ηmax (or ηEURO) will results in more accurate Esys and ROI predictions for PV system installed in the equatorial region
Simulation on simulink AC4 model (200HP DTC induction motor drive) using fuzzy logic controller
No full textClassical direct torque control (DTC) has advantage in absence of coordinate transform and voltage modulator block. However, it may have disadvantage in controlling electromagnetic torque. DTC produces high ripple in electromagnetic torque as it is not directly controlled. High torque ripple causes vibrations to the motor which may lead to component lose, bearing failure or resonance. Thus, Fuzzy Logic controller is applied to reduce electromagnetic torque ripple. This paper presents the simulation analysis of Fuzzy Logic Direct Torque Controller (FLDTC) of induction machine drives. However, only the design of the controller using built in DTC induction motor drive model of Simulink AC4 will be discussed in this paper. Using FLDTC, the resulting electromagnetic torque from produced less ripple than classical DTC
Simulation on Simulink AC4 model (200hp DTC induction motor drive) using Fuzzy Logic controller
No full textSumbangan dato\u27 Haji Muhammad Nor bin Haji Ibrahim kepada bidang tafsir dan pengajian Al-Qur\u27?n
No full textThis article discusses the biography of Muhammad Nor and his contributions in the field of Tafsir and Quranic Studies. The books that are discussed are Ramuan Rapi Dari Erti Surah al-Kahfi, Tafsir Pimpinan al-Rahman Kepada Pengertian al-Qur\u27?n and Mustika Hadith. At the same time, the author thoughts towards al-Qadar which was misinterpreted by many people are also discussed
Thruster Modelling for Underwater Vehicle Using System Identification Method
No full textThis paper describes a study of thruster modelling for a remotely operated underwater vehicle (ROV) by system identification using Microbox 2000/2000C. Microbox 2000/2000C is an XPC target machine device to interface between an ROV thrusters with the MATLAB 2009 software. In this project, a model of the thruster will be developed first so that the system identification toolbox in MATLAB can be used. This project also presents a comparison of mathematical and empirical modelling. The experiments were carried out by using a mini compressor as a dummy depth pressure applied to a pressure sensor. The thruster model will thrust and submerge until it reaches a set point and maintain the set point depth. The depth was based on pressure sensor measurement. A conventional proportional controller was used in this project and the results gathered justified its selection
Records as strategic resource in the Malaysian public sector / Mohammad Azhan Abdul Aziz ... [et al.]
No full textRecords may be used to ensure transparency, to keep individuals and organisations responsible for their acts and responsibilities, and to show that organisations have met legal or regulatory standards or accepted best practices. Records appear as a medium to improve the effectiveness and efficiency of the organisation, it becomes a strategic resource that provides information for future use. This study aims to describe how public records are managed and used among officers in departments and ministries of the Malaysian government. The respondents and key informants engaged in this study are Diplomatic Administer Officers (PTD) from different position grades starting from grade M44 to JUSA because they are categorized as top management that acts as administer, policymaker, decision-maker, etc. in the organisation. The respondents were randomly selected from twelve ministries and one department of the Malaysian public sector in Putrajaya. The study conducted is quantitative method. Findings show that all hypotheses are accepted. Records users were found to have a significant and positive relationship with the strategic use of records. Records value was also found to have a significant and positive relationship with strategic use of records same as the relationship between records user and records value. Moreover, the records’ value is hypothesized as a mediator between the records user and strategic use of records also indicates the same result. The results of the study have contributed to the development of a research model and theory for using records as a strategic resource, especially, in the government sector. Government servants especially PTD must use records as one of the strategic resources in carrying out their daily affairs
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