Azma Putra

Characterization of activated carbons from oil-palm shell by CO2 activation with no holding carbonization temperature.

Activated carbons can be produced from different precursors, including coals of different ranks, and lignocellulosic materials, by physical or chemical activation processes. The objective of this paper is to characterize oil-palm shells, as a biomass byproduct from palm-oil mills which were converted into activated carbons by nitrogen pyrolysis followed by CO2 activation. The effects of no holding peak pyrolysis temperature on the physical characteristics of the activated carbons are studied. The BET surface area of the activated carbon is investigated using N2 adsorption at 77 K with selected temperatures of 500, 600, and 700°C. These pyrolysis conditions for preparing the activated carbons are found to yield higher BET surface area at a pyrolysis temperature of 700°C compared to selected commercial activated carbon. The activated carbons thus result in well-developed porosities and predominantly microporosities. By using this activation method, significant improvement can be obtained in the surface characteristics of the activated carbons. Thus this study shows that the preparation time can be shortened while better results of activated carbon can be produced.

Biomass from Paddy Waste Fibers as Sustainable Acoustic Material

Utilization of biomass for green products is still progressing in the effort to provide alternative clean technology. This paper presents the utilization of natural waste fibers from paddy as acoustic material. Samples of sound absorbing material from paddy waste fibers were fabricated. The effect of the fiber density, that is, the fiber weight and the sample thickness, and also the air gap on the sound absorption coefficient is investigated through experiment. The paddy fibers are found to have good acoustic performance with normal incidence absorption coefficient greater than 0.5 from 1 kHz and can reach the average value of 0.8 above 2.5 kHz. This result is comparable against that of the commercial synthetic glass wool. Attachment of a single layer of polyester fabric is shown to further increase the absorption coefficient.

Investigation on natural waste fibers from dried paddy straw as a sustainable acoustic absorber

The use of synthetic materials as acoustic absorbers is still applied extensively in building industry. These non-biodegradable materials do not only cause pollution to the environment, but also contribute significantly in increasing the CO2 causing the effect of global warming. Therefore researchers have now driven their attentions to find sustainable and eco-friendly materials to be an alternative sound absorber. This paper discusses the use of natural fibers from dried paddy straw as a fibrous acoustic material. Since this is one of common natural waste materials found across South East Asia, the usage will also minimize the production cost. A panel sound absorber from paddy straw is fabricated and its acoustic properties are investigated through experiment. Good acoustic performance is found particularly above 2000 Hz and is comparable against that from the classical synthetic absorber.

Normal Incidence of Sound Transmission Loss of a Double-Leaf Partition Inserted with a Microperforated Panel

A double-leaf partition in engineering structures has been widely applied for its advantages i.e. in terms of its mechanical strength as well as its lightweight property. In noise control, the double-leaf also serves to be an effective noise barrier. Unfortunately at low frequency, the sound transmission loss reduces significantly due to the coupling between the panels and the air between them. This paper studies the effect of a micro-perforated panel (MPP) inserted inside a double-leaf partition on the sound transmission loss performance of the system. The MPP insertion is proposed to provide a hygienic double-leaf noise insulator replacing the classical abrasive porous materials between the panels. It is found that the transmission loss improves at the troublesome mass-air-mass resonant frequency if the MPP is located closer to the solid panel. The mathematical model is derived for normal incidence of acoustic loading.

Prediction of waste heat energy recovery performance in a naturally aspirated engine using artificial neural network

The waste heat from exhaust gases represents a significant amount of thermal energy, which has conventionally been used for combined heating and power applications. This paper explores the performance of a naturally aspirated spark ignition engine equipped with waste heat recovery mechanism (WHRM). The experimental and simulation test results suggest that the concept is thermodynamically feasible and could significantly enhance the system performance depending on the load applied to the engine. The simulation method is created using an artificial neural network (ANN) which predicts the power produced from the WHRM.

Normal Incidence of Sound Transmission Loss from Perforated Plates with Micro and Macro Size Holes

his paper studies the sound transmission loss of perforated panels and investigates the efect of the hole diameter on the sound insulation performance under normal incidence of acoustic loading. he hole diameters are distinguished into micro (submillimeter) and macro (millimeter) sizes. In general, the transmission loss reduces as the perforation ratio is increased. However, by retaining the perforation ratio, it is found that the transmission loss increases as the hole diameter is reduced for a perforate with micro holes due to the efect of resistive part in the hole impedance, which is contrary to the results for those with the macro holes. Both show similar trend at high frequency where the luid behavior inside the hole is inertial. Simple analytical formulae for engineering purpose are provided. Validation of the models with measurement data also gives good agreement.

A Combined Softening and Hardening Mechanism for Low Frequency Human Motion Energy Harvesting Application

This paper concerns the mechanism for harvesting energy from human body motion. The vibration signal from human body motion during walking and jogging was first measured using 3-axes vibration recorder placed at various places on the human body. The measured signal was then processed using Fourier series to investigate its frequency content. A mechanism was proposed to harvest the energy from the low frequency-low amplitude human motion. This mechanism consists of the combined nonlinear hardening and softening mechanism which was aimed at widening the bandwidth as well as amplifying the low human motion frequency. This was realized by using a translation-to-rotary mechanism which converts the translation motion of the human motion into the rotational motion. The nonlinearity in the system was realized by introducing a winding spring stiffness and the magnetic stiffness. Quasi-static and dynamic measurement were conducted to investigate the performance of the mechanism. The results show that, with the right degree of nonlinearity, the two modes can be combined together to produce a wide flat response. For the frequency amplification, the mechanism manages to increase the frequency by around 8 times in terms of rotational speed.

On a simple technique to measure the airborne noise in a car interior using substitution source

From various methods of measuring noise in a motor vehicle, a technique to separate the airborne and structure-borne noise is of interest as an important measure to improve the noise control treatment. This paper proposes a simple technique to measure the contribution of the airborne noise in a vehicle cabin using substitution source method. A cone loudspeaker was used as the substitution source and the airborne transfer function was measured. The technique has successfully separated the airborne transmission with the intersection frequency at roughly 400 Hz with the structure-borne noise. It is found that this is independent of the engine speed.

TRANSMISSIBILITY OF A LAMINATED RUBBER-METAL SPRING A PRELIMINARY STUDY

This paper discusses the isolation performance of a laminated rubber-metal spring. A multi-degree-of-freedom-system model using mass-damper-spring components is developed to calculate its transmissibility due to only axial vibration in the spring. The results show the embedded layers of metal plate can improve the transmissibility at high frequency.

Analysis of Axial Vibration in the Laminated Rubber-Metal Spring

The laminated rubber-metal spring is well known in application as the vibration isolator for earthquake protection. The spring is therefore designed to be able to sustain the vibration waves from horizontal direction. This paper discusses the possibility of the laminated spring to be employed for other applications where the excitation mainly comes from axial direction, such as to isolate vibration transmission from heavy engine. The model is first developed for a simple finite rod to simulate the effect of internal resonances at high frequency when the wavelength is much smaller than the length of the rod. The effect of metal plates inserted in the rubber is then modelled using the lumped parameter system. The results are presented in terms of the vibration transmissibility.