Liquefaction of coal by SRC-II process: Part V: Dynamic thermal behavior of the reactor

Criteria for identification of the unstable or stable nature of the steady state based on the reactor temperature response to step changes in feed temperature, and a dynamic thermal simulation of SRC-II reactors are developed. These are used in the analysis of a dynamic SRC-II reactor experiment to confirm its unstable operation under normal process conditions. The simulation is used further to study the sensitivity of reactor temperature to changes in feed temperature and to variations in the total heat capacity of the reactor vessel and insulation materials. It is shown that, under normal SRC-II process conditions, it would take about an hour for the reactor temperature to change by ± 10°C, if no controls were used. With quench gas manipulation, the reactor temperature could be maintained within ± 1°C even for a sustained small perturbation in the process conditions. Therefore, in spite of its unstable character, the SRC-II reactors can be readily operated with quench gas manipulation without incurring any major temperature control problems.     

Experimental studies of the force to extrude a rate sensitive material

Distinctions are drawn between three mean strain rates in extrusion: those averaged over the accumulated strain, the distance travelled through the die, and the elapsed time. It is shown that when the strain rate varies, the mean strain rate based on strain is always the greatest, and the mean strain rate based on time the smallest. Three further mean strain rates are introduced, which are root mean power (RMP) values of the above strain rates. Conventional estimates of the extrusion pressure for frictionless, homogeneous flow are based on rate insensitive analyses and lead to pressures proportional to the mean strain rate based on time. When the rate sensitivity during flow is taken into account, the calculated pressure is shown to be a function of the RMP strain rate based on accumulated strain, which is considerably greater than the mean strain rate based on time. Experiments are described in which ice was extruded by the indirect process, leading to nearly frictionless, homogeneous flow. Extrusion ratios of 4, 9, 25, 81, and 144 were used. In the first series of experiments, the ram velocity was adjusted to give the samerate insensitive (i.e. time-based) mean strain rate for all the dies. In the second series of experiments, the ram velocity was adjusted to give the samerate sensitive (i.e. RMP) mean strain rate for all the dies. In all cases the extrusion pressure was proportional to the RMP strain rate and not to the time-based strain rate. The rate sensitivity correction factor is also described.     

Stepwise Formation of Some Bivalent Metal Chelates with Sodium Alizarin Sulphonate

The stepwise protonation constants of the ligand and the stability constants of Alizarin Red S with some bivalent metal ions, Pb²⁺, Cu²⁺, Zn²⁺, and Hg²⁺ have been determined at 30° and at various ionic strengths viz. 0.02, 0.05, 0.15 and 0.20, maintained by sodium perchlorate solution. The formation of the chelate is evident from the shift between the (i) ligand and (ii) ligand and metal titration curves. From the values of the stepwise protonation constants and metal ligand stability constants at various ionic strengths, thermodynamic formation constants were evaluated by extrapolation to zero ionic strength. The order of stability constants was found to be: Cu > Pb > Zn > Hg     

Performance of piezoelectric fiber-reinforced composites for active structural-acoustic control of laminated composite plates

This paper deals with the active structural acoustic control of thin laminated composite plates using piezoelectric fiber-reinforced composite (PFRC) material for the constraining layer of active constrained layer damping (ACLD) treatment. A finite element model is developed for the laminated composite plates integrated with the patches of ACLD treatment to describe the coupled structural-acoustic behavior of the plates enclosing an acoustic cavity. The performance of the PFRC layers of the patches has been investigated for active control of sound radiated from thin symmetric and antisymmetric cross-ply and antisymmetric angle-ply laminated composite plates into the acoustic cavity. The significant effect of variation of piezoelectric fiber orientation in the PFRC layer on controlling the structure-borne sound radiated from thin laminated plates has been investigated to determine the fiber angle in the PFRC layer for which the structural-acoustic control authority of the patches becomes maximum.     

Microfluorometric detection of catecholamines with multiphoton-excited fluorescence

We demonstrate sensitive spatially resolved detection of physiological chromophores that emit in the ultraviolet (<330 nm). An atypical laser source (a visible wavelength femtosecond optical parametric oscillator), and an unconventional collection geometry (a lensless detector that detects the forward-emitted fluorescence) enable this detection. We report the excitation spectra of the catecholamines dopamine and norepinephrine, together with near-UV emitters serotonin and tryptophan, in the range of 550-595 nm. We estimate the molecular two-photon action cross section of dopamine, norepinephrine, and serotonin to be 1.2 mGM (1 GM, or Goppert Mayor, is equal to 10(-58) m4 s(-1) photon(-1)), 2 mGM, and 43 mGM, respectively, at 560 nm. The sensitivity achieved by this method holds promise for the microscopic imaging of vesicular catecholamines in live cells.     

Influence of thermophysical properties on pool boiling heat transfer of refrigerants

The correct prediction of the heat transfer performance of the boiling liquid within the evaporator of a refrigeration unit is one of the essential features for the successful operation of the whole unit. A theoretically consistent calculation method for the heat transfer coefficient α in nucleate boiling, which should be based on the physical phenomena connected with vapour bubbles growing, departing and sliding on the wall and with the interactions of bubbles and of neighbouring nucleation sites within the microstructure of the heating surface, does not yet exist, despite the increasing number of papers on the subject in the recent past. Instead, the predictive methods for α available at present are empirical or semiempirical, especially for heat transfer conditions relevant in practice. Many of these correlations have been established in the form of power laws in which the relative influences of the main groups of variables on α are treated by separate factors. One of these may stand for the influence of the thermophysical properties of the boiling liquid or these properties will be included in several of the factors.New experimental results are presented for pool boiling heat transfer from a single horizontal copper tube (8 mm OD) to HFC-refrigerants (R32, 125, 134a, 143a, 152a, 227ea) and hydrocarbons (propane, i-butane). The results are compared to experimental data from the literature, and methods are discussed, how to incorporate the data in semiempirical correlations to describe the influence of the thermophysical properties of the fluids on the heat transfer performance.     

Effect of copper chromite and copper chromitecopper oxide mixture catalysts on the thermal decomposition of ammonium perchlorate and composite solid propellant

Thermal decomposition of powdered ammonium perchlorate (AP), polystyrene (PS) and $\text{AP}\text{PS}$ propellant, catalysed by freshly-prepared CuCr₂O₄ and mixtures of CuCr₂O₄ and CuO, has been studied with a low concentration (1% by mass) of the catalysts. It appears that decomposition is increased due to heterogeneous catalysis. The kinetics of thermal decomposition of AP in the presence of CuCr₂O₄ in the orthorhombic region of AP have also been studied.     

Comparison of phase noise simulation techniques on a BJT LC oscillator

The phase noise resulting from white and flicker noise in a bipolar junction transistor (BJT) LC oscillator is investigated. Large signal transient time domain SPICE simulations of phase noise resulting from the random-phase flicker and white noise in a 2 GHz BJT LC oscillator have been performed and demonstrated. The simulation results of this new technique are compared with Eldo RF and Spectre RF based on linear circuit concepts and experimental result reported in the literature.