Influence of nitrogen addition on the microstructure and mechanical properties of duplex stainless steel weld metals

Duplex stainless steels find extensive applications in off‐shore, paper/pulp, refineries and petrochemical industries owing to their excellent combination of properties. Because of the thermal cycle experienced during the manufacturing/processing operations like welding, the weldment developed in this material is generally inferior in properties (mechanical and corrosion) when compared to the base material. The problem is more severe when the welding is done in the autogenous condition. The current work correlates the microstructure and property of UNS 31803 duplex stainless steel (material no. 1.4462) welded by autogenous GTA process with and without nitrogen in the shielding gas. It has been found that the nitrogen addition to the weld metal through the shielding gas mixture not only helps in achieving the proper phase balance but also improves the impact toughness of the resultant weld metal.     

Drying of hot chilli using solar tunnel drier

A mixed mode type forced convection solar tunnel drier was used to dry hot red and green chillies under the tropical weather conditions of Bangladesh. The drier consisted of transparent plastic covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using two fans operated by a photovoltaic module. The drier had a loading capacity of 80 kg of fresh chillies. Moisture content of red chilli was reduced from 2.85 to 0.05 kg kg⁻¹ (db) in 20 h in solar tunnel drier and it took 32 h to reduce the moisture content to 0.09 and 0.40 kg kg⁻¹ (db) in improved and conventional sun drying methods, respectively. In case of green chilli, about 0.06 kg kg⁻¹ (db) moisture content was obtained from an initial moisture content of 7.6 kg kg⁻¹ (db) in 22 h in solar tunnel drier and 35 h to reach the moisture content to 0.10 and 0.70 kg kg⁻¹ (db) in improved and conventional sun drying methods, respectively. The use of a solar tunnel drier and blanching of sample led to a considerable reduction in drying time and dried products of better quality in terms of colour and pungency in comparison to products dried under the sun. The solar tunnel drier and blanching of chilli are recommended for drying of both red and green chillies.     

Modelling of electrical energy recovery from urban solid waste system: The case of Dhaka city

This paper presents a system dynamics computer model to predict population growth, solid waste production, electricity generation from solid waste and percentage of total electricity demand supplied from the solid waste of Dhaka, Bangladesh. Simulated solid waste generation in Dhaka agrees well with values reported by the Dhaka City Corporation. Simulated results show that population, solid waste generation and electricity generation potential from solid waste all increase with time, but percentage of total electricity demand supplied from solid waste decreases with time. However, MSW could still supply a significant portion of the electricity demand of Dhaka. Adoption of policy for electricity recovery from urban solid waste should be dictated by the economic adoption of the technology for electricity generation from the waste and the environmental implications. The model can be used for analysing electrical energy recovery from urban solid waste management.     

Thin layer solar drying of rough rice

This paper presents a set of simple empirical equations for natural air flow solar drying of rough rice in mixed-mode type dryer, box-type dryer and open floor drying system. The moisture contents predicted by the equations were in good agreement with the observed values. The effect of drying air temperature on the drying rate constants for these three cases were found to be insignificant. The equilibrium moisture content appeared to be the most important variable controlling the drying rate. The highest drying rate was observed in case of mixed-mode dryer. The drying rate of box dryer was next to that of mixed-mode dryer. This study shows that the introduction of solar dryer for drying of rough rice is highly recommendable in Bangladesh.     

Role of lead in the growth of the highT c phase in the Bi2−x Pb x Sr2Ca2Cu3O y systems

Bi_2−x Pb _x Sr₂Ca₂Cu₃O _y superconducting samples with 0<x<0·3 have been synthesized and characterized using X-ray powder diffraction.T _c and superconducting volume fraction have been measured using a.c. magnetic susceptibility, d.c. electrical resistivity as well as X-band microwave surface resistance in the normal state. The data indicate the growth of the highT _c (2223) phase with corresponding reduction of the lowT _c (2122) phase with increasingx, up to 0·25. Beyond this value ofx there is a slight deterioration of the superconducting behaviour.     

Evidence for the Microwave Effect During Hybrid Sintering

A microwave/conventional hybrid furnace has been used to sinter three ceramics with different microwave absorption characteristics under pure conventional and a range of microwave/conventional hybrid heating regimes. The precursor powder particle size was also varied for each material. In each case it was ensured that every sample within a series had an identical thermal history in terms of its temperature/time profile. An increase in both the onset of densification and the final density achieved was observed with an increasing fraction of microwave energy used during sintering, the effect being greatest for the materials that absorbed microwaves most readily. Twenty-three percent greater densification was observed for submicron zinc oxide powder, the material with the largest microwave absorption capability, when sintered using hybrid heating involving 1 kW of microwave power compared with pure conventional power under otherwise identical conditions. For the ceramic with the lowest microwave absorption characteristic, alumina, the increase in densification was extremely small; partially stabilized zirconia, a moderate microwave absorber, was intermediate between the two. Temperature gradients within the samples, a potential cause of the effect, were assessed using two different approaches and found to be too small to explain the results. Hence, it is believed that clear evidence has been found to support the existence of a genuine "microwave effect."     

Microwave assisted synthesis of nanocrystalline YAG

Using nitrate precursors, a novel microwave assisted citrate gel process for the preparation of nanocrystalline yttrium aluminium garnet (YAG) phase has been developed. Synthesis of single phase polycrystalline YAG was achieved at temperatures as low as 600 °C using the microwave methodology whilst conventional approaches currently available require ≥1000 °C. The microwave prepared YAG powder was characterised using X-ray diffraction, FTIR spectroscopy, TEM and EDAX. The microwave method was found to yield YAG particles of ∼40 nm diameter, whilst the conventional route yielded 150 nm particles. Also substantial morphological differences were observed between the YAG particles and their agglomerates produced by the different processing methods.     

Cycles in wavelength routed optical networks

Signals in wavelength routed optical networks can oscillate in closed cycles resulting in adverse effects on network operation. In particular, amplified spontaneous emission from erbium doped fiber amplifiers can form recirculating loops that lead to amplifier saturation and oscillations. Searching, enumerating and eliminating these closed cycles becomes a problem that the network designer must address. A variety of cross-connect technologies are studied and shown to result in oscillating cycles in the network. Topological and technological approaches based on Eulerian network theory and other methods are proposed to eliminate these cycle problems