A numerical approach for the spread of gonorrhea in homosexuals

R. Rama Kishore and N. Ch. Pattabhiramacharyulu

This paper presents a simple mathematical model of gonorrhea in homosexual population. This model is characterized by a pair of non-linear first order ordinary differential equations reflecting the growth rates of promiscuous and infectives in a homosexual population and here cured infectives are separated from the main stream for further investigation. Numerical examples are given to explain the effect of cure rate and infective rate on the spread and control of the disease, and also estimated for lower cure rates.

Z-source inverter with a new space vector PWM algorithm for high voltage gain

U. Shajith Ali and V. Kamaraj

This paper presents a methodology to apply a novel space vector pulse width modulation control for three phase Z-source inverter. The space vector modulation for the conventional voltage source inverter is modified so that the additional shoot-through states are inserted within the zero states. So zero voltage time period is diminished for generating a shoot-through time, and active states are unchanged. The shoot-through states are evenly distributed to each phase within zero state. The shoot-through time is used for controlling the dc link voltage boost and hence the output voltage boost of the inverter. This new method provides a high voltage gain at higher modulation index. The proposed algorithm is verified with simulation and experiment. MatLab/Simulink is used for simulating the complete circuit with RL load. The frequency spectra of the output voltage and current are explored.

Optimisation of engine operating parameters for eucalyptus oil mixed diesel fueled DI diesel engine using Taguchi method

Tamilvendhan D., Ilangovan V. and Karthikeyan R.

The present investigation used Eucalyptus oil, distilled oil from leaf of eucalyptus as an alternate fuel for diesel fuel. Generally, Eucalyptus oil possesses low cetane number which is not sufficient to operate existing diesel engine. However, this could be admissible along with diesel fuel in the form of blends. Keeping this in mind experiments have been conducted using blends of Eucalyptus oil and diesel fuel to study its replace ability, performance and emission behaviour. As the investigation involves three parameters such as blend proportion, injection timing and injection pressure, a simultaneous optimisation method called Taguchi was used in the work. This method requires fewer numbers of trials for fixing optimum levels. This is the primary advantage of this method. As per this method nine trials were experimented and its results were used for optimisation. In addition, an ANOVA was also performed for the parameters to evaluate its percentage contribution over the desired output. The results of the taguchi experiment showed that the 40Eu blend (40% Eucalyptus oil and 60% diesel) performed better at 29°BTDC injection timing and at 180 bar injection pressure than other blends and had a capacity to cold start the engine. Using the optimum levels, a full range experiment was also conducted using 40Eu blend to compare its performance and emission behaviour with standard diesel operation. The results of the full range experiment showed that the 40Eu blend offered approximately 2.5% higher brake thermal efficiency than diesel baseline operation without much worsening the exhaust emission.

Stochastic characteristics of daily rainfall at Purajaya region

Ahmad Zakaria

Aim of this research is to study stochastic characteristics of daily rainfall series. The study was undertaken using 25 years (1977-2001) data of Purajaya region. The series of the daily rainfall data assumed was trend free. The periodic components of daily rainfall series were represented by using 253 harmonic expressions and stochastic components of daily rainfall series were presented using second order autoregressive parameters. Validation of generated daily rainfall series was done by comparing between generated with measured daily rainfall series. For periodic modeling, mean of the correlation coefficient between generated and measured daily rainfall series with the number of the data N is equal to 512 days for 25 years was found to be 0,9576. For periodic and stochastic modeling, mean of the correlation coefficient was found to be 0.9999. Therefore, developed periodic and stochastic model could be used for future prediction of daily rainfall time series.

Effects analysis of additional thermal protection for retrofitted buildings

Ioan Sârbu and Călin Sebarchievici

Abstract:

One of main research direction on the construction field is the reduction of the energy consumption, which supposes materials, technology and conception of buildings with lower specific energy need on one hand and equipment with high performances on the other hand. Proper thermal rehabilitation of a building will lead to a significant reduction of heating energy demand offering a higher degree of comfort, and better condition for hygiene. At the same time the environment is less polluted. The energy saving depends on the initial building characteristics and the thermal rehabilitation level on one hand, and on the proper adjustment and control of the heating system on the other hand. In this paper is analyzed the main effects of building thermal rehabilitation, with implications upon heating energy consumption and upon comfort of the occupants. Thus, it is developed a computational model of optimum additional insulation thickness, taking into account the investment cost to improve thermal resistance of building envelope and operational costs as heating energy consumption.

Kinetic sorption study of phenol onto activated carbon derived from fluted pumpkin stem waste (Telfairia occidentalis hook F.)

O. A. Ekpete and M. Horsfall Jnr

Abstract:

Fluted activated carbon obtained from fluted pumpkin stem waste can be harnessed as a useful adsorbent for the removal of phenol from aqueous solution. The contact time data was modeled using pseudo, first - order, pseudo second order, Elovich, intra-particle and liquid - film diffusion. The kinetic data favoured pseudo second-order with regression value of 0.950. Thermodynamic parameters ΔH^o, ΔS^o, and ΔG^o of the adsorption of phenol onto fluted activated carbon were negative which revealed exothermic nature of the sorption process, strong bond formation between the adsorbent and adsorb ate molecules and the spontaneous nature of the adsorption with a high preference for phenol.

Performance of voltage source multilevel inverter - fed induction motor drive using Simulink

Neelashetty Kashappa and Ramesh Reddy K.

This paper deals with performance of voltage source multilevel inverter-fed induction motor drive. A Voltage source inverter (VSI) is compared with multilevel inverter. A conventional Voltage Source Inverter-fed induction motor drive is modeled and simulated using Matlab/ Simulink and the results are presented. Multilevel inverter employing Selective Harmonic Elimination (SHE) method is also simulated and the corresponding results are presented. The FFT spectrum for the outputs is analyzed to study the reduction in harmonics.

Investigation on start-up characteristics of cryogenic heat pipes

M. Senthil Kumar and A. Senthil Kumar

Abstract:

Heat pipe is a device which transfers heat from one location to another with a small temperature gradient. Application includes use of cryogenic heat pipe in cooling infrared sensors, laser systems, cryocoolers, thermal control large superconducting magnets and tumor surgery. This paper deals with transient behavior of cryogenic heat pipes with wire mesh and axial grooved wick using nitrogen and oxygen as working fluid. A special liquid nitrogen cryostat has been designed and developed for evaluating the transient behavior of heat pipes at 77 K when the condenser portion is connected to the cold sink externally. In this study, the start-up characteristic of heat pipes is experimentally investigated.

Effect of wetting and drying on the geotechnical properties of lime - fly ash stabilized collapsible residual sand

F. N. Okonta and E. Govender

Abstract:

Berea Red Sands underlying most of the Kwazulu Natal midlands and coastal plain is a very recent unconsolidated, weakly cemented red to brown, collapsible sands. The effect of wetting and drying cycles on the UCS and CBR of compacted and cured samples of stabilized Berea Sands was investigated. Different sample mix were prepared with 4% and 8% Lime and 0%, 6% 12% and 18% Fly Ash, and tested after 4, 8 and 12 cycles of wetting and drying. Changes in mass of the stabilized sands were measured to facilitate the interpretation of changes in strength properties. The result showed reduction in UCS and CBR with increase in the number of wetting and drying cycles that is dependent on the amount of Lime and Fly Ash and the ratio of Lime to Fly Ash. For Given amount Fly Ash, samples stabilized with 8% Lime are more durable than samples stabilized with 4% Lime. Also durability increases with increase in Fly Ash content, for samples stabilized with 4% Lime to a maximum UCS associated with 12% Fly Ash, excess quantities of Fly Ash results in decreased durability. For samples stabilized with 8% Lime, increase in Fly Ash quantities results in an increase in durability for up to 18% Fly Ash used in this research. The process of wetting and drying results in general reduction in the mass of the test samples, and the percentage reduction in mass decreases with increase in quantities of Fly Ash. In the long term, defined by 12 cycles of wetting and drying, only the 8% lime and 18% fly ash material have adequate CBR under the operative drainage conditions to sustain the stresses applied by traffic loadings.

Impact of embedding renewable distributed generation on voltage profile of distribution system: A case study

Akash T. Davda, M. D. Desai and B. R. Parekh

Abstract:

Present scenario of Power system operation is contingency-constrained, and often associated with voltage limit violation problems. In this paper, the low voltage problems in an existing 2.2 MVA conventional electricity distribution network of a particular area of Gujarat State, India, have been identified and solved by injecting Renewable Distributed Generation at appropriate locations. The results of the simulations carried out using distribution system software were analyzed with respect to voltage at different nodes thereby identifying low voltage areas which were again studied by injecting RDGs at different locations and the results were analyzed. The final analysis revealed that there was no low voltage problem at any node on the network. It has been concluded that looking to serious environmental problems like pollution, greenhouse gas emissions, and long and over loaded lines attached to conventional electric power generation, transmission and distribution Networks, the injection of Renewable Distributed Generation can give a solution to low voltage problems. Reduction in losses and increased reserve capacity of the distribution network are the added advantages.

Studies on tribological properties of ZnO filled polymer nano composites

Naga Raju B., Ramji K. and Prasad V. S. R. K.

Abstract:

The tribological behavior of polyester filled with ZnO nano particles was studied. For this study, ZnO nano particles were synthesized and size was found to be 34nm. The synthesized ZnO nano particles organically functionalized with γ-aminopropyltriethoxysilane (APS). The functionalized ZnO nano particles are mixed with polyester resin through ultra sonication for getting uniform dispersion. The wear samples were prepared by mixing 1wt%, 2wt%, 4wt% and   6wt% ZnO nano particles with polyester resin. The wear properties are studied by using pin-on-disc apparatus. The 1% ZnO nano polyester composite has excellent wear properties when compared to pure polyester. The characteristics of ZnO nano polyester composite is also studied by using Scanning Electron Microscopy (SEM). Filling of nano ZnO particles in polyester changed the microstructure of polyester and prevented the destruction of polyester banded structure during the friction process which might be one of the anti-wear mechanisms of nano ZnO. The improved and best tribo-performance of the composite can be attributed due to particular mechanical properties of nano particles.

Mechanics of deformation during open die forging of sintered preform: comparative study by equilibrium and upper bound methods

Parveen Kumar, R. K. Ranjan and Rajive Kumar

Abstract:

The paper reports on an investigation into the various aspects of open die forging of metal powder preforms, which have been compacted and sintered from atomized metal powder.  An attempt has been made for the determination of the relative average die pressure developed for given geometries of the disc during the open die forging of sintered metal powder preform by using an upper bound and equilibrium method approach as different frictional stresses are assumed on top and bottom interfaces. The deformation characteristics of metal powder preform has been demonstrated by applying an appropriate interfacial friction law and yield criteria. The results so obtained are discussed critically to illustrate the interaction of various process parameters involved and are presented graphically.

Abstract:

LM25 aluminum alloy metal matrix composites (MMCs) reinforced with weight fractions of micro and nano Al₂O₃ particles up to10 wt.% were produced by stir casting. The composites thus produced were characterized for their mechanical properties such as hardness and tensile strength as well as for the dispersion of the micro and nano Al₂O₃ particles. The results reveal that stir casting could be an economical route for the production of nano composites. Nano particle reinforced MMCs exhibit better hardness and strength when compared to micro particles reinforced composites. Scanning electron microscopic observations of the microstructures revealed that the dispersion of the micron size particles where more uniform while nano particles led to agglomeration of the particles.  

Abstract:

There is a potentially vast world market for stand-alone power sources. In rural districts of the developing world, the energy consumption per capita is very low and basic energy needs are for water pumping, electricity supplies to small hospitals, lighting, cooling and telecommunications. Often the cost of connection to the grid in remote locations cannot be justified. Photovoltaic and wind power can meet these needs, but either source alone provides an intermittent supply and energy storage is needed to deliver a reliable supply. However, these two sources are complementary since sunny days are usually calm and strong winds are often accompanied by cloud and may occur at night. A combined plant therefore has higher availability than either individual source and so needs less storage capacity. A stand-alone electrical supply system is described which combines the output of wind a solar Photovoltaic generating systems. The experimental system comprise wind and solar collectors, each of 5 KW rating, with a lead-acid battery for storage and a 10 KW PWM inverter for the final output. The wind turbine generator is a 200 rpm, direct drive, Permanent-magnet, axial-flux machine based on the ‘Torus’ configuration. Its three-phase output is rectified to form a variable-voltage dc link. The power converter uses two dc-dc converters connected in series, each with a bypass diode which conducts continuously when the corresponding source is not available. For all load demands the levelised energy cost for PV-wind hybrid system is always lower than that of standalone solar PV or wind system. The PV wind hybrid option is techno-economically viable for rural electrification.