Effect of Porous Copper Pore Density on Joint Interface: Microstructure and Mechanical Analysis

The effect of the pore density of porous copper (Cu) on brazed Cu/porous Cu was investigated. A filler with a composition of Cu-9.0Sn-7.0Ni-6.0P (Sn: Tin; Ni: Nickel; P: Phosphorus) and porous Cu with pore densities of 15 pores per inch (PPI), 25 PPI, and 50 PPI were employed. The joint strength of Cu/porous Cu was evaluated with shear tests at different brazing temperatures. Characterizations of the joint interface and fractured surface were achieved with scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The micro-hardness test of Cu/porous Cu joint interface showed a high hardness value (HV) for 50 PPI porous Cu. This result was in line with its low shear strength. It was proved that the joint strength of Cu/porous Cu is dependent on the pore density of the porous Cu structure and brittle phases of Cu₃P and Ni₃P in the brazed interface.     

Study of intrinsic white light emission and its components from ZnO-nanorods/<Emphasis Type="Italic">p</Emphasis>-polymer hybrid junctions grown on glass substrates

We report white-light luminescence from ZnO-organic hybrid light emitting diodes grown on glass substrate by low temperature aqueous chemical growth. The configuration used for the hybrid white light emitting diodes (HWLEDs) consists of two-layers of polymers (PEDOT:PSS/PFO) on glass with top ZnO nanorods. Electroluminescence spectra of the HWLEDs demonstrate the combination of emission bands arising from the radiative recombination in polymer and ZnO nanorods. In order to distinguish emission bands we used a Gaussian function to simulate the experimental data. The emitted white light was found to be the superposition of a blue line at 454 nm, a green emission at 540 nm, orange line at 617 nm, and finally a red emission at 680 nm. The transitions causing these emissions are identified and discussed in terms of the energy band diagram of the hybrid junction. Color coordinates measurement of the WLED reveals that the emitted light has a white impression with 70 color rendering index and correlated color temperature 5500 K. Comparison between ITO and aluminum top contacts and its influence on the emitted intensity is also discussed.     

Trends of solar radiation effects on the temperature of vertical surfaces of a modern terrace house

This is a study done to investigate the effects of solar radiation on the wall surface temperature of a modern terrace house. It involves the analysis of the thermal fluctuations of common building materials used for walls or vertical surface areas such as the bricks, glass of the window, and metal doors. A thermal imager and data logging system was used in collecting the data for the Southeast and Northwest façades of the house. The imager gave resourceful data on the thermal heat trend of the walls and their surface temperature. The results show that a lighter wall surface color reduces the temperature of the surface. Furthermore, the bricks, which have a higher density hence a higher absorptivity due to their high capacity for storage of heat, decrease the flow of heat. However, the use of tinted glass on windows increases the surface temperature of the glass area of the wall surface. The metal also shows a high similarity with glass in terms of its thermal performance. In conclusion, the types of material used on wall surfaces have a significant impact on the wall temperature.     

Air and oxy-fuel combustion behaviour of petcoke/lignite blends

The pyrolysis and combustion behaviour of a petroleum coke (petcoke), an indigenous lignite and their 70/30 wt.% blend in air and oxy-fuel conditions were investigated by using non-isothermal thermo-gravimetric method (TGA) coupled with Fourier transform infrared (FTIR) spectrometer. Blend samples were prepared by mixing lignite, which has low calorific value, high ash and moisture contents with petcoke that has high calorific value, low ash and moisture content, in the proportion of 70:30. Pyrolysis tests were carried out in nitrogen and carbon dioxide environments which are the main diluting gases of air and oxy-fuel environments, respectively. Pyrolysis curves of parent fuels and their blend reveal close resemblance up to 700 °C in both N₂ and CO₂ environments. At higher temperatures, further weight loss taking place in N₂ and CO₂ atmospheres is attributed to calcite decomposition and CO₂-char gasification reaction, respectively. Gasification reaction leads to significant increase in CO and COS formation as observed in FTIR evolution profiles. Almost identical experimental and theoretical pyrolysis profiles of the blend samples show that there is no synergy between the parent fuels of the blend in both pyrolysis environments. Combustion experiments were carried out in four different atmospheres; air, oxygen-enriched air environment (30% O₂–70% N₂), oxy-fuel environment (21% O₂–79% CO₂) and oxygen-enriched oxy-fuel environment (30% O₂–70% CO₂). Combustion experiments show that replacing nitrogen in the gas mixture by the same concentration of CO₂ leads to delay in combustion (lower maximum rate of weight loss and higher burnout temperatures). Overall comparison of derivative thermogravimetry (DTG) profiles shows that effect of oxygen content on combustion characteristics is more significant than that of diluting gas in the combustion environment. At elevated oxygen levels, profiles shift through lower temperature zone, peak and burnout temperatures decrease, weight loss rate increases significantly and complete combustion is achieved at lower temperatures and shorter times. Theoretical and experimental combustion profiles of the blend mainly display different trends, which indicate synergistic interactions between lignite and petcoke during their combustion in different environments.     

The Economic Benefits of Generation Revenue and Demand Payment Assessment in Pool-based Market Model: The Case of Malaysia

In Malaysia, as the Power Purchased Agreement is coming toward the end, pool market model is recognized as a conceivable model to overcome the shortcomings of the single buyer market. However, there are issues on the welfare of the generators involved. In context of Malaysian Electricity Supply Industry, this paper proposes a model, a pool hybrid introducing the minimum capacity payment involving the efficiency of the generators and base load sharing approaches. Under single auction power pool, a case study is conducted for the generators in Peninsular Malaysia for an economic analysis to highlight the merits of the proposed model compared with other pool-based market models in terms of generation revenue and demand payment. The load demand curves, the details of the MW-installed capacity, energy prices, capacity prices, and efficiency of the generators are the parameters taken into account in carry out analysis on each generator revenue. Results have shown that pool hybrid market ensures the intermediate value of generation revenue with all Independent Power Producers participation even at the lowest demand and decreased the demand payment.     

Effects of Dilute Acid Pretreatment on Chemical and Physical Properties of Kenaf Biomass

In the current research, kenaf represents an agricultural biomass that possesses enormous potential for industrial applications. Because of its complex structure, which is composed of cellulose, hemicellulose, and lignin, pretreatment process was conducted. Here, dilute acid pretreatment process was conducted, statistically using the response surface method, which included three parameters: mass of biomass (g), temperature (°C), and time (min). About 2 g of kenaf biomass was treated with 2% dilute sulphuric acid, and it was found to have higher glucose conversion (25.3%) when the process was conducted for 60 min at the temperature of 180°C. The main aim of the current research is to investigate the chemical and physical changes of kenaf biomass before and after the pretreatment. The changes could be clearly seen in the cellulose, hemicellulose, and lignin composition before and after the pretreatment, which were evaluated via TAPPI standard test methods. Morphological observation under scanning electron microscope confirmed the changes that took place on the kenaf biomass from complex to simple surface structure. Fourier transform infrared analysis confirmed the presence of cellulose, hemicellulose, and lignin contents of the kenaf biomass before and after pretreatment. Crystallinity of the treated kenaf biomass also increased from 46.6% to 70.0%, as evidenced from X-ray diffractometer analysis.     

Stability of Silica‐ and Enzyme‐Treated Palm Oil Under Deep Frying Conditions

The oxidative and thermal stability of low diglycerides palm oil produced via silica treatment (sPO) and enzymatic treatment (ePO) compared with standard quality palm oil (SQ) and premium quality palm oil (PQ) was investigated. Both of the oils displayed better oxidative stability compared with SQ as well as significantly higher (P < 0.05) thermal resistance and oxidative strength than SQ and PQ due to lower amounts of partial glycerides. Although the initial induction periods (IPs) of sPO and ePO were significantly lower compared with SQ and PQ, both the oils showed slower drops in their IP values. The darkening effect after frying was significantly (P < 0.05) slower in sPO compared with SQ, PQ, and ePO. Besides, there is no difference p > 0.05 in the rate of FFA formation between sPO and PQ. The anisidine value and peroxide values were lowest in sPO, followed by ePO, PQ, and SQ.     

Optimization of isoflavone production from fermented soybean using response surface methodology

This study was conducted to investigate the interaction effects among process variables during isoflavone production and optimized the yield of isoflavone. A response surface methodology (RSM) was employed to study the relationships of fermentation temperature, time, and starter culture on daidzin and daidzein as an isoflavone product. The experiments were designed using central composite by applying 2⁴ factorial designs with 2 center points. Fermented soybean produced a maximum of 1,284.14 μg/g daidzin at an optimum temperature of 29.39°C, fermentation duration at 32.06 h and starter culture content of 0.96%(w/w). Meanwhile, an optimum daidzein (1,663.85 μg/g) was obtained at 35°C and 48 h fermentation process with 0.5%(w/w) starter culture. Validation study showed the observed and predicted values were in compliance with 5% level of significance. The RSM was successful in identifying the optimum conditions for the isoflavone production.     

Comparison of analytical techniques for dynamic trace metal speciation in natural freshwaters

Several techniques for speciation analysis of Cu, Zn, Cd, Pb, and Ni are used in freshwater systems and compared with respect to their performance and to the metal species detected. The analytical techniques comprise the following: (i) diffusion gradients in thin-film gels (DGT); (ii) gel integrated microelectrodes combined to voltammetric in situ profiling system (GIME-VIP); (iii) stripping chronopotentiometry (SCP); (iv) flow-through and hollow fiber permeation liquid membranes (FTPLM and HFPLM); (v) Donnan membrane technique (DMT); (vi) competitive ligand-exchange/stripping voltammetry (CLE-SV). All methods could be used both under hardwater and under softwater conditions, although in some cases problems with detection limits were encountered at the low total concentrations. The detected Cu, Cd, and Pb concentrations decreased in the order DGT > or = GIME-VIP > or = FTPLM > or = HFPLM approximately = DMT (>CLE-SV for Cd), detected Zn decreased as DGT > or = GIME-VIP and Ni as DGT > DMT, in agreement with the known dynamic features of these techniques. Techniques involving in situ measurements (GIME-VIP) or in situ exposure (DGT, DMT, and HFPLM) appear to be appropriate in avoiding artifacts which may occur during sampling and sample handling.