Analysis of residuals in daily solar radiation time series

The Box-Jenkins approach is applied to daily solar radiation data from four different locations in Malaysia. The deterministic annual component is obtained by Fourier analysis. The stochastic component of the time series is fitted to three models, ARMA (1,0), ARMA (2,0) and ARMA (1,1). Random shocks from these models are tested by Box-Pierce statistic and Ljung-Box for whiteness of residuals. Skewness and kurtosis coefficients are tested for normality

Review of materials for adsorption refrigeration technology

Purpose: During the last 20 years, interest in the closed adsorption heat pump and refrigeration systems has increased steadily. In this paper, consideration is given to aspects of adsorption refrigeration in terms of existing materials used in adsorption refrigeration, heat transfer characteristics of materials, and cost of materials and manufacturing. Design/methodology/approach: The paper is a general review of adsorption refrigeration technology. Findings: In recent years several papers have been published in this area and many aspects of the system have been addressed. Much effort has been devoted to enhance materials properties. Originality/value: The paper provides information of value to those involved with heat pump and refrigeration systems technology

Conceptual design of a hybrid thermal and photovoltaic receiver of an FMDF collector

The optical characteristic of a Fixed Mirror Distributed Focus (FMDF) solar collector is used as a basis for the design of an hybrid thermal and photovoltaic (PV) receiver. The result provides another variation in energy conversion that an FMDF solar collector can conveniently perform

Application of probability models to Malaysian sunshine data

A 10-year Malaysian sunshine data of four stations were fitted to three models, namely the Bendt, Hollands and Huget and Saunier models. Distribution parameters of the models were determined from the values of the observed mean of the sunshine data. The Kolmogorov–Smirnov test was applied to determine the goodness of fit. It was found that the Saunier model was suitable for the Petaling Jaya and Subang stations while the Hollands and Huget model well suited the Bayan Lepas and Kota Bharu stations. The Bendt model did not give a good fit for all stations. It was also found that for the months that have the same observed mean but different observed standard deviations the distribution models were able to fit well only if the estimated standard deviations were close in value to the observed standard deviations

Kinetics of cellulase production by Aspergillus terreus at various levels of dissolved oxygen tension in a stirred tank bioreactor

In this study the effect of different levels of dissolved oxygen tension (d.o.t) on the production of three main components of extracellular cellulases (FPase, CMCase and β-glucosidase) at a fixed agitation speed by Aspergillus terreus was investigated. Growth of A. terreus and cellulase production were modeled based on logistic and Luedeking-Piret equations. The results from the model fit well with the experimental data, confirming that the models were appropriate for describing and representing growth and cellulase production at various d.o.t levels. The models showed that the production of FPase and CMCase were growth-associated processes. Cell growth and cellulase production were approximately two-fold higher in a stirred tank bioreactor compared with a shake-flask culture. At a d.o.t of 55% air saturation, cell growth and cellulase production were higher than at low d.o.t (40% air saturation) or high d.o.t (80% air saturation). The highest activities of FPase (2.33 U ml-1), CMCase (51.10 U ml-1), and β-glucosidase (16.18 U ml-1) were obtained at a d.o.t of 55% air saturation, yielding overall productivities of 19.40, 425.00, and 67.40 U l.h-1, respectively

Optimization of cellulase production by Aspergillus terreus under submerged fermentation using response surface methodology

Oil palm empty fruit bunch (OPEFB) is one of the most important wastes from the oil palm industry which can be treated and utilized as a main carbon source in fermentation. The ability of newly isolated Aspergillus terreus to produce cellulases in submerged fermentation with OPEFB fibre as carbon source was investigated. Response surface methodology based on central composite design (CCD) was chosen to optimize the composition of four medium constituents viz, OPEFB fibers (5-15 g/L), yeast extract (3-9 g/L), CaCl2 (1-5 mM), MgSO4 (3-7mM) and to optimize the level of two environmental condition agitation speed (200-300 rpm) and temperature (28-32°C). A second order model was proposed to assess the effect of these 6 variables. Based on the proposed model, the optimized conditions for the maximum cellulase production was 13.90 g/L OPEFB fiber, 8 g/L yeast extract, 3.5 mM CaCl2, 7 mM of MgSO4, 225 rpm of agitation and 29°C temperature. The optimized values obtained by the statistical analysis gave 14.25U/ml of CMCase, 1.13 U/ml of FPase, and 9.86 U/ml of β-glucosidase and 5.2 g/l of Cell concentration. In fermentation using the optimized conditions, the fungi cell concentration, CMCase, FPase and β-glucosidase activity was 5.2 g/l, 14.25 U/ml, 1.13 U/ml and 9.86 U/ml, respectively

Improved cellulase production by Aspergillus terreus using oil palm empty fruit bunch fibre as substrate in a stirred tank bioreactor through optimization of the fermentation conditions

Response surface methodology (RSM) was performed to evaluate the effects of dissolved oxygen tension (DOT) and initial pH on the production of carboxymethyl cellulase (CMCase), filter-paper hydrolase (FPase), and β-glucosidase by Aspergillus terreus in a 2 L stirred tank bioreactor. Delignified oil palm empty fruit bunch (OPEFB) fibre was used as the main substrate under submerged fermentation. Growth of A. terreus and the production of three main components of cellulase were optimized by central composite design (CCD) design. Statistical analysis of results showed that the individual terms of these two variables (DOT and pH) had significant effects on growth and the production of all components of cellulase. Maximum growth (13.07 g/L) and cellulase activity (CMCase = 50.33 U/mL, FPase = 2.29 U/mL and β-glucosidase = 15.98 U/ml) were obtained when the DOT and initial culture pH were set at 55% and 5.5, respectively. A high proportion of β-glucosidase to FPase (8:1) in cellulase of A. terreus could be beneficial for efficient hydrolysis of cellulosic materials. The use of OPEFB as a main substrate would reduce the cost of fermentation for the production of cellulase

Efficient and Stable Routing Algorithm Based on User Mobility and Node Density in Urban Vehicular Network

Vehicular ad hoc networks (VANETs) are considered an emerging technology in the industrial and educational fields. This technology is essential in the deployment of the intelligent transportation system, which is targeted to improve safety and efficiency of traffic. The implementation of VANETs can be effectively executed by transmitting data among vehicles with the use of multiple hops. However, the intrinsic characteristics of VANETs, such as its dynamic network topology and intermittent connectivity, limit data delivery. One particular challenge of this network is the possibility that the contributing node may only remain in the network for a limited time. Hence, to prevent data loss from that node, the information must reach the destination node via multi-hop routing techniques. An appropriate, efficient, and stable routing algorithm must be developed for various VANET applications to address the issues of dynamic topology and intermittent connectivity. Therefore, this paper proposes a novel routing algorithm called efficient and stable routing algorithm based on user mobility and node density (ESRA-MD). The proposed algorithm can adapt to significant changes that may occur in the urban vehicular environment. This algorithm works by selecting an optimal route on the basis of hop count and link duration for delivering data from source to destination, thereby satisfying various quality of service considerations. The validity of the proposed algorithm is investigated by its comparison with ARP-QD protocol, which works on the mechanism of optimal route finding in VANETs in urban environments. Simulation results reveal that the proposed ESRA-MD algorithm shows remarkable improvement in terms of delivery ratio, delivery delay, and communication overhead

Gravitational search algorithm optimization for PID controller tuning in waste-water treatment process

This paper presents a new approach of optimization technique in the controller parameter tuning for waste-water treatment process (WWTP) application. In the case study of WWTP, PID controller is used to control substrate (S) and dissolved oxygen (DO) concentration level. Too many parameters that need to be controlled make the system becomes complicated. Gravitational Search Algorithm (GSA) is used as the main method for PID controller tuning process. GSA is based on Newton's Law of Gravity and mass interaction. In this algorithm, the searcher agents survey the masses that interact with each other using law of gravity and law of motion. For WWTP system, the activated sludge reactor is used and this system is multi-input multi-output (MIMO) process. MATLAB is used as the platform to perform the simulation, where this optimization is compared to other established optimization method such as the Particle Swarm Optimization (PSO) to determine whether GSA has better features compared to PSO or vice-versa. Based on this case-study, the results show that transient response of GSA-PID was 20%-30% better compared to transient response of the PSO-PID controlle