Essential oils of Zingiber officinale var. rubrum Theilade and their antibacterial activities

The essential oils obtained by hydrodistilation of the leaves and rhizomes of Zingiber officinale var. rubrum Theilade were analysed by capillary GC and GC–MS. Forty-six constituents were identified in the leaf oil, while 54 were identified in the oil from the rhizomes. The leaf oil was clearly dominated by β-caryophyllene (31.7%), while the oil from the rhizomes was predominantly monoterpenoid, with camphene (14.5%), geranial (14.3%), and geranyl acetate (13.7%) the three most abundant constituents. The evaluation of antibacterial activities using the micro-dilution technique revealed that both the leaf and rhizome oils were moderately active against the Gram-positive bacteria Bacilluslicheniformis, Bacillus spizizenii and Staphylococcus aureus, and the Gram-negative bacteria Escherichia coli, Klebsiella pneumoniae and Pseudomonas stutzeri.     

An effective differential harmony search algorithm for the solving non-convex economic load dispatch problems

Solving the non-convex economic load dispatch (ELD) problem with evolutionary algorithms has gained increasing research in recent years. In this paper, a differential harmony search (DHS) algorithm is proposed by combining the mechanisms of both differential evolution and harmony search. In the DHS, the pitch adjustment operation is cooperated with the different mutation operation to enhance the exploitation ability of harmony search, and both the memory consideration and the pitch adjustment are used to enhance the exploration ability of evolution search. In addition, a repair procedure and three simple selection rules are proposed for constraint handling. Numerical simulations are carried out based on different kinds of testing problems with various constraints including valve point effects, multi-fuels, ramp rate limit and prohibited operation zones. Simulation results and comparisons with the some existing algorithms demonstrate the effectiveness, efficiency and robustness of the proposed DHS algorithm. Finally, the effect of parameter setting on the DHS is investigated as well.     

The sun rises in the east (of Africa): A comparison of the development and status of solar energy markets in Kenya and Tanzania

This paper describes, compares and analyses the historical development and current status of Kenya's and Tanzania's emerging solar energy markets. The analysis is based on an extensive literature survey and 25 in-depth personal interviews with experts on the East African solar power market. Kenya's solar market is found to be one of the world's leading markets for off-grid solar uses, with a current installed capacity of over 10 MWp and more than 320,000 solar home systems. Having developed much later than the Kenyan market, Tanzania’s market still remains smaller than its neighbour’s, with an installed capacity of around 4 MWp and at least 40,000 solar home systems, but is in the process of catching up. In addition to solar home systems, other applications of solar energy technologies, such as in social institutions, telecoms and tourism, are covered. Major differences and similarities between the Kenyan and Tanzanian solar markets are identified and reasons for these are analysed. Initial policy implications regarding the regulation and promotion of solar energy in East Africa suggest that awareness, availability and affordability are major drivers that all need to be present to enable the widespread adoption of off-grid solar technologies in emerging markets.     

A review of nanofluid heat transfer and critical heat flux enhancement—Research gap to engineering application

As a novel strategy to improve heat transfer characteristics of fluids by the addition of solid particles with diameters below 100 nm, nanofluids exhibit unprecedented heat transfer properties and are being considered as potential working fluids to be used in high heat flux systems such as electronic cooling systems, solar collectors, heat pipes, and nuclear reactors. The present paper reviews the state-of-the-art nanofluid studies on such topics as thermo-physical properties, convective heat transfer performance, boiling heat transfer performance, and critical heat flux (CHF) enhancement. It is indicated that the current experimental data of nanofluids thermal properties are neither sufficient nor reliable for engineering applications. Some inconsistent or contradictory results related to thermo-physical properties, convective heat transfer performance, boiling heat transfer performance, and CHF enhancement of nanofluids are found in data published in the literature. No comprehensive theory explains the energy transfer processes in nanofluids. To bridge the research gaps for nanofluids' engineering application, the urgent work are suggested as follows. (1) Nanofluid stability under both quiescent and flow conditions should be evaluated carefully; (2) A nanofluid database of thermo-physical properties, including detailed characterization of nanoparticle sizes, distribution, and additives or stabilizers (if used), should be established, in a worldwide cooperation of researchers; (3) More experimental and numerical studies on the interaction of suspended nanoparticles and boundary layers should be performed to uncover the mechanism behind convective heat transfer enhancement by nanofluids; (4) Bubble dynamics of boiling nanofluids should be investigated experimentally and numerically, together with surface tension effects, by considering the influences of nanoparticles and additives if used, to identify the exact contributions of solid surface modifications and suspended nanoparticles to CHF enhancement in boiling heat transfer. Once we acquire such details about the above key issues, we will gain more confidence in conducting application studies of nanofluids in different areas with more efficiency.     

Thermal conductivity and dynamic mechanical analysis of NiZn ferrite nanoparticles filled thermoplastic natural rubber nanocomposite

The effect of NiZn ferrite nanoparticles on the thermal behaviour of thermoplastic natural rubber (TPNR) composite is investigated. Melt blending technique was employed to prepare TPNR matrix, which comprised of natural rubber (NR), liquid natural rubber (LNR) and high-density polyethylene (HDPE) in a ratio of 20:10:70. Dynamic mechanical analysis results show that the thermal stability of the nanocomposites enhanced with increasing filler loading. Moreover, thermal conductivity of the nanocomposites increased with filler content until 8 wt%, which is believed to be the optimum loading that formed the suitable percolated network for phonon conduction facilitation.     

Study of the martensitic transformation in NiTi–epoxy smart composite and its effect on the overall behavior

In this work, the effect of wire phase transformation on the overall thermo-mechanical behavior of NiTi–epoxy composites has been investigated. The shape memory wire received in as drawn condition was subjected to three heat treatments which results to different transformation characteristics. Composite specimens were manufactured by casting followed by curing and post curing process. The mechanical behavior of samples has been determined using standard tensile test. The effect of wire volume fraction and test temperature was investigated as well.It is found that the martensitic transformation occurring in the wire affects the mechanical behavior of the composite specimens. In this way, using the wire with higher transformation stress improves the composite tensile strength. This is achieved either by increasing the test temperature or by using the wires heat treated at lower temperatures. From the experimental results, the martensitic transformation can change the debonding mode. It seems that on the constraint of matrix, the transformation occurs simultaneously at several points in wires that result in regular debonded/undebonded pattern.     

Effect of manifold injection of hydrogen gas in producer gas and neem biodiesel fueled CRDI dual fuel engine

The high flammability of hydrogen gas gives it a steady flow without throttling in engines while operating. Such engines also include different induction/injection methods. Hydrogen fuels are encouraging fuel for applications of diesel engines in dual fuel mode operation. Engines operating with dual fuel can replace pilot injection of liquid fuel with gaseous fuels, significantly being eco-friendly. Lower particulate matter (PM) and nitrogen oxides (NO_x) emissions are the significant advantages of operating with dual fuel.Consequently, fuels used in the present work are renewable and can generate power for different applications. Hydrogen being gaseous fuel acts as an alternative and shows fascinating use along with diesel to operate the engines with lower emissions. Such engines can also be operated either by injection or induction on compression of gaseous fuels for combustion by initiating with the pilot amount of biodiesel. Present work highlights the experimental investigation conducted on dual fuel mode operation of diesel engine using Neem Oil Methyl Ester (NeOME) and producer gas with enriched hydrogen gas combination. Experiments were performed at four different manifold hydrogen gas injection timings of TDC, 5°aTDC, 10°aTDC and 15°aTDC and three injection durations of 30°CA, 60°CA, and 90°CA. Compared to baseline operation, improvement in engine performance was evaluated in combustion and its emission characteristics. Current experimental investigations revealed that the 10°aTDC hydrogen manifold injection with 60°CA injection duration showed better performance. The BTE of diesel + PG and NeOME + PG operation was found to be 28% and 23%, respectively, and the emissions level were reduced to 25.4%, 14.6%, 54.6%, and 26.8% for CO, HC, smoke, and NO_x, respectively.     

Storage of luminescent nanoparticles in porous silicon: Toward a solid state “golden fleece”

Meso-porous silicon layers and free-standing membranes are studied as solid-state safe storing matrixes for luminescent Si and 3C–SiC nanoparticles. The porous silicon “fleece” is shown to soak efficiently and easily a great number of luminescent nanoparticles from ethanol solution. Incorporation of the nanoparticles inside the meso-pores after ethanol evaporation was illustrated by photoluminescence and reflection spectroscopies. Numerous reproducible extractions of the nanoparticles from the meso-porous network can be ensured by controlled adding a few drops of pure ethanol.     

Ion conduction in vanadium-substituted LiSn<Subscript>2</Subscript>P<Subscript>3</Subscript>O<Subscript>12</Subscript> electrolyte nanomaterials

LiSn₂P_3 − y V _y O₁₂ powders with y = 0.2, 0.4, 0.6, and 0.8 are prepared by mechanochemical milling method. The pellets of the compounds are heat treated at temperatures between 700 to 1,000 °C for sintering period of 8 h. X-ray diffraction analysis indicates that all samples consist of rhombohedral crystalline LiSn₂P₃O₁₂ phase. Energy dispersive X-ray analysis confirmed that V⁵⁺ has been successfully substituted into LiSn₂P₃O₁₂ crystalline phase. The conductivities of the pellets are determined using impedance spectroscopy. Impedance analysis shows enhancement in both bulk and grain boundary conductivities with increase in y. The enhancement in bulk conductivity is due to decrease in bulk activation energy reflecting an increase in ion mobility as a result of an increase in bottleneck size. Enhancement in grain boundary conductivity is attributed to increase in the number of conducting pathways due to an increase in crystallite homogeneity.