Influence of cast versus wrought microstructure on the processing map for hot working of stainless steel type AISI 304

Processing maps for hot working of as-cast and wrought stainless steels of type AISI 304 have been developed in the temperature range 600 to 1250°C and strain rate range 0.001 to 100 s−1. The domain of dynamic recrystallization (DRX) in as-cast material occurs at higher temperatures (1250°C) and lower strain rates (0.001 s−1) than in the wrought steel (1100°C and 0.01 s−1). The effect is explained in terms of enhanced nucleation rate of DRX due to the carbide, ferrite particles, stable oxides/nitrides and second-phase intermetallics in the as-cast microstructure. The DRX domain is wider in the wrought material although the peak efficiency is less (32%) than in the as-cast case (40%). The flow instability regime is not significantly affected by the initial microstructure

Interferometry with a novel composite material

An interesting application of optical phase conjugation is phase conjugate interferometry. We report here a new approach to real-time interferometry which combines the high phase conjugate efficiency of photorefractive crystals and the fast response times offered by dye-doped polymer films by using a composite structure. The ability of this material to generate two independent but overlapping phase conjugate waves. which can interfere to reveal the phase changes in a test object, is discussed and demonstrated with a specific example.

Kinetics of ceric ion oxidation of naphthalene and its derivatives. Formation of the radical cation intermediate in the rate limiting step

Ceric ammonium sulfate, CAS, oxidizes naphthalene to 1,4-naphthoquinone in essentially quantitative yield in CH3CN-dil. H2SO4. Stoichiometric studies indicate that 6 mol of CAS are required for the oxidation of 1 mol of naphthalene to 1,4-naphthoquinone. Kinetic investigations reveal that the reaction takes place through initial formation of a 1:1 complex of naphthalene and cerium(IV) in an equilibrium step followed by slow decomposition of the complex to naphthalene radical cation. Kinetic results on the effects of acid strength, polarity of the medium, temperature and substituents are in accordance with this mechanism. Further conversion of the radical cation into 1,4-naphthoquinone takes place in fast steps involving a further 5 mol of cerium(IV) and 2 mol of H2O.

Asemakaavoitus Helsingin seudun kasvun hallinnassa

Many Finnish municipalities need to control their growth. In this research growth is understood as developments of land utilisation and also as a wide range of other changes that have mainly ap-peared as a result of a long term growth in population. The development growth control contains four areas: 1. adequate productivity of town planning, 2. stationing the growth to needs led and for sustainable developments, 3. quality of the developing environment, and 4. producing growth with communicative and transparent process. The aim of the research is to represent connection between town planning and development growth control. Research defines the role of town planning in the municipalities development growth control. In addition research focuses on links between town planning and development growth control in history, present and in the development work for the future. According to the hypothesis the extensive examination of town planning enables better growth control and promotes appropriate response to municipal changes regarding housing delivery. As an example there are five outskirt municipalities in the Helsinki region. They are called Kirkkonummi, Vihti, Nurmijärvi, Tuusula and Sipoo. The decision was to use examples based on a contingence theory. According to the theory there is no one correct way to operate. Therefore development should be based on individual municipal needs. In the research, municipality s needs were collected by 20 semi- structured interviews from municipal officials. In addition there were group interviews in Uusimaa Regional Council and in Uusimaa Regional Environmental Centre. There was also secondary material collected from official papers and statistics. Operationalisation was the analysis tool between empiric and literature reviews. The role of town planning has evolved during the 20th century from a more simple town plan level to operative stage in town planning hierarchy. Outskirt municipalities town planning was established during the 1960s. Since then one of the most important aims in the town planning has been to produce growth and building possibilities. Currently the challenge is to reach the satisfying rate of productivity and to meet increased housing demand. Other challenges include locating the appropriate geographical areas for growth; and the balance between required developments and planning permission decisions. Findings concluded that town planning should be more viable and it should have better ability to co-operate and operate in the changing operational environment. Municipality s ability to receive growth can increase and growth control can advance by planned and workable town planning. It is essential to take wide perspective of the each municipality's unique needs to improve productivity rather than to focus simply on productivity.

Processing map for hot working of as cast magnesium

The constitutive flow behaviour in hot working of as cast magnesium has been studied with the help of a processing map developed in the temperature range 300-550°C and strain rate range 0·001-100 s−1. The map, interpreted using the dynamic materials model, revealed that the material undergoes dynamic recrystallisation at 425°C and 0·3 s−1, which are the optimum parameters for hot working. Ai temperatures higher than 450°C and strain rates lower than about 0·1 s−1, wedge cracking occurs in as cast magnesium. The wedge cracking domain has a high efficiency of power dissipation (60%), whereas the dynamic recrystallisation domain has a value of 34%. At temperatures below 450°C and strain rates above 10 s−1, the material exhibits flow instability in the form of mechanical twinning. At higher temperatures and strain rates, instability is manifested by flow localisation.

Processing map for hot working of stainless steel type AISI 316L

Processing and instability maps using a dynamic materials model have been developed for stainless steel type AISI 316L in the temperature range 600-1250-degrees-C and strain rate range 0.001-100 s-1 with a view to optimising its hot workability. Stainless steel type AISI 316L undergoes dynamic recrystallisation, with a peak efficiency of 35% at 1250-degrees-C and 0.05 s-1, which are the optimum parameters for hot working this material. The material undergoes dynamic recovery at 900-degrees-C and 0.001 s-1. The increase in the dynamic recrystallisation and dynamic recovery temperatures in comparison with stainless steel type AISI 304L is attributed to the presence of a backstress caused by the molybdenum additions. These results are in general agreement with those reported elsewhere on stainless steel type 316 deformed in hot extrusion and hot torsion. At temperatures < 850-degrees-C and strain rates > 10 s-1, the material exhibits flow localisation owing to adiabatic shear band formation, whereas at higher temperatures (> 850-degrees-C) and strain rates (> 10 s-1) mechanical twinning and wavy slip bands are observed. (C) 1993 The Institute of Materials.

Processing maps for hot working of Cu-Ni-Zn alloys. Part I - Alpha-nickel silver

The constitutive behaviour of agr — nickel silver in the temperature range 700–950 °C and strain rate range 0.001–100 s–1 was characterized with the help of a processing map generated on the basis of the principles of the ldquodynamic materials modelrdquo of Prasadet al Using the flow stress data, processing maps showing the variation of the efficiency of power dissipation (given by 2m/(m+1) wherem is the strain-rate sensitivity) with temperature and strain rate were obtained, agr-nickel silver exhibits a single domain at temperatures greater than 750 °C and at strain rates lower than 1s–1, with a maximum efficiency of 38% occurring at about 950 °C and at a strain rate of 0.1 s–1. In the domain the material undergoes dynamic recrystallization (DRX). On the basis of a model, it is shown that the DRX is controlled by the rate of interface formation (nucleation) which depends on the diffusion-controlled process of thermal recovery by climb. At high strain rates (10 and 100s–1) the material undergoes microstructural instabilities, the manifestations of which are in the form of adiabatic shear bands and strain markings.

Processing maps for hot working of Cu-Ni-Zn alloys Part II Alpha-Beta nickel silver

The constitutive behaviour of agr-beta nickel silver in the temperature range 600�850 °C and strainrate range 0.001�100s�1 was characterized with the help of a processing map generated on the principles of the dynamic materials model. On the basis of the flow-stress data, processing maps showing the variation of the efficiency of power dissipation (given by [2m/(m+1)], wherem is the strain-rate sensitivity) with temperature and strain rate were obtained, agr-beta nickel silver exhibits a single domain at temperatures greater than 700 °C and at strain rates lower than 1 s�1 with a maximum efficiency of power dissipation of about 42% occurring at about 850 °C and at 0.1 s�1. In the domain, the agr phase undergoes dynamic recrystallization and controls the deformation of the alloy, while the beta phase deforms superplastically. Optimum conditions for the processing of agr-beta nickel silver are 850 °C and 0.1 s�1. The material undergoes unstable flow at strain rates of 10 and 100 s�1 and in the temperature range 600�750 °C, manifestated in the form of adiabatic shear bands.

Structural refinement using high-resolution powder X-ray diffraction data of Ca0.5Ti2P3O12, a low-thermal-expansion material

The structures of Ca0.5Ti2P3O12 and Sr0.5Ti2P3O12, low-thermal-expansion materials, have been refined by the Rietveld method using high-resolution powder X-ray diffraction (XRD) data. The assignment of space group R[3 with combining macron] to NASICON-type compounds containing divalent cations is confirmed. 31P magic-angle spinning nuclear magnetic resonance (MASNMR) data are presented as supporting data. A comparison of changes in the polyhedral network resulting from the cation distribution, is made with NaTi2P3O12 and Nb2P3O12. Factors that may govern thermal expansion in this family of compounds are discussed.

Adaptive Keeper Design for Dynamic Logic Circuits Using Rate Sensing Technique

The increasing variability in device leakage has made the design of keepers for wide OR structures a challenging task. The conventional feedback keepers (CONV) can no longer improve the performance of wide dynamic gates for the future technologies. In this paper, we propose an adaptive keeper technique called rate sensing keeper (RSK) that enables faster switching and tracks the variation across different process corners. It can switch upto 1.9x faster (for 20 legs) than CONV and can scale upto 32 legs as against 20 legs for CONV in a 130-nm 1.2-V process. The delay tracking is within 8% across the different process corners. We demonstrate the circuit operation of RSK using a 32 x 8 register file implemented in an industrial 130-nm 1.2-V CMOS process. The performance of individual dynamic logic gates are also evaluated on chip for various keeper techniques. We show that the RSK technique gives superior performance compared to the other alternatives such as Conditional Keeper (CKP) and current mirror-based keeper (LCR).

Influence of Substrate Temperature and Deposition Rate on Structural and Mechanical Properties of Shape Memory NiTi Films

NiTi thin films deposited by DC magnetron sputtering of an alloy (Ni/Ti:45/55) target at different deposition rates and substrate temperatures were analyzed for their structure and mechanical properties. The crystalline structure, phase-transformation and mechanical response were characterized by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Nano-indentation techniques, respectively. The films were deposited on silicon substrates maintained at temperatures in the range 300 to 500 degrees C and post-annealed at 600 degrees C for four hours to ensure film crystallinity. Films deposited at 300 degrees C and annealed for 600 degrees C have exhibited crystalline behavior with Austenite phase as the prominent phase. Deposition onto substrates held at higher deposition temperatures (400 and 500 degrees C) resulted in the co-existence of Austenite phase along with Martensite phase. The increase in deposition rates corresponding to increase in cathode current from 250 to 350 mA has also resulted in the appearance of Martensite phase as well as improvement in crystallinity. XRD analysis revealed that the crystalline film structure is strongly influenced by process parameters such as substrate temperature and deposition rate. DSC results indicate that the film deposited at 300 degrees C had its crystallization temperature at 445 degrees C in the first thermal cycle, which is further confirmed by stress temperature response. In the second thermal cycle the Austenite and Martensite transitions were observed at 75 and 60 degrees C respectively. However, the films deposited at 500 degrees C had the Austenite and Martensite transitions at 73 and 58 degrees C, respectively. Elastic modulus and hardness values increased from 93 to 145 GPa and 7.2 to 12.6 GPa, respectively, with increase in deposition rates. These results are explained on the basis of change in film composition and crystallization. (C) 2010 Published by Elsevier Ltd

Thermophilic fungi: An assessment of their potential for growth in soil

An attempt has been made to forecast the potential of thermophilic fungi to grow in soil in the laboratory and in the field in the presence of a predominantly mesophilic fungal flora at usual temperature. The respiratory rate of thermophilic fungi was markedly responsive to changes in temperature, but that of mesophilic fungi was relatively independent of such changes. This suggested that in a thermally fluctuating environment, thermophilic fungi may be at a physiological disadvantage compared to mesophilic fungi. In mixed cultures in soil plates, thermophilic fungi outgrew mesophilic fungi under a fluctuating temperature regime only when the amplitude of the fluctuating temperatures was small and approached their temperature optima for growth. An antibody probe was used to detect the activity of native or an introduced strain of a thermophilic fungus, Thermomyces lanuginosus, under field conditions. The results suggest that although widespread, thermophilic fungi are ordinarily not an active component of soil microflora. Their presence in soil most likely may be the result of the aerial dissemination of propagules from composting plant material.

The scratch hardness and friction of a soft rigid-plastic solid

The paper describes an experimental and analytical study of the normal and scratch hardnesses of a model soft rigid-plastic solid. The material known as ‘Plasticine’, a mixture of dry particles and a mineral oil, has been deformed with a range of rigid conical indentors with included angles of between 30° and 170°. The sliding velocity dependence of the computed scratch hardness and friction has been examined in the velocity range 0.19 mm/s to 7.3 m/s. Data are also described for the time dependence of the normal hardness and also the estimated rate dependence of the intrinsic flow stress. The latter values were estimated from data obtained during the upsetting of right cylinders. Three major conclusions are drawn from these data and the associated analysis. (1) A first-order account of the scratching force may be provided by adopting a model which sums the computed plastic deformation and interfacial sliding contributions to the total sliding work. This is tantamount to the adoption of the two-term non-interacting model of friction. (2) For this system during sliding, at high sliding velocities at least, the interface shear stress which defines the boundary condition is not directly related to the bulk shear stress. The interface rheological characteristics indicate an appreciable dependence on the imposed strain or strain rate. In particular, the relative contributions of the slip and stick boundary conditions appear to be a function of the imposed sliding velocity. (3) The computed normal and scratch hardness values are not simply interrelated primarily because of the evolving boundary conditions which appear to exist in the scratching experiments.

Mass transfer and shear rate in baffled surface aerator

The scale up or scale down of the process variables in a surface aerator requires information about the shear rate prevailing in the system. In fact, the performance of surface aerator depends upon the shear rate. Shear rate affects the mass transfer operation needed by the surface aerator. Theoretical analysis of shear rate suggests a nonlinear behavior with rotational speed of the impeller, which has been shown in the present work. Present work also shows that in a geometrically similar system of baffled surface aerator, shear rate can be used as a governing parameter for scaling up or down the mass transfer phenomena.