A review on saturated boiling of liquids on tube bundles

A review of recent investigation on boiling of saturated liquids over plain and enhanced tube bundles has been carried out taking the earlier review works as reference point. The experimental observations of various geometry and performance parameters studied by researchers are analyzed keeping current demand of industries in design and development of compact, efficient heat exchanging devices. The study shows that tube spacing plays an important role in determination of compactness of the heat exchanger.     

An efficient synthesis of quinolines under solvent-free conditions

An efficient synthesis of substituted quinolines has been achieved in a one-pot reaction from o-nitrobenzaldehyde and enolizable ketones using SnCl₂·2H₂O as the reductant under microwave irradiation without any solvent or catalyst     

A mixed anhydride approach to the preparation of sulfinate esters and allylic sulfones: Trimethylacetic p-toluenesulfinic anhydride

A reagent combination of toluenesulfinic acid and trimethylacetyl chloride affords a putative trimethylacetic p-toluenesulfinic anhydride. This reagent has been used to prepare a series of sulfinate esters from primary and secondary alcohols. In addition, the reagent was used to convert Baylis-Hillman substrates into allylic sulfones. Attempts to use the reagent to convert amines to sulfinamides were unsuccessful. In contrast, the use of 2-pyrrolidinone afforded N-p-toluenesulfinyl pyrrolidinone in 64% yield. The use of a chiral 4-benzyl-1,3-oxazolidinone or 4-benzyl-1,3-oxazolidine-2-thione led to the isolation of S-p-tolyl p-toluenethiosulfonate.     

Boric acid: a novel and safe catalyst for aza-Michael reactions in water

Boric acid efficiently catalyzes the conjugate addition of aliphatic amines to α,β-unsaturated compounds to produce β-amino compounds, with great alacrity and excellent yields, in water under mild conditions. Aromatic amines do not participate effectively in the reaction.     

Reactions of vanadium(V) with alkali sulphate or thiocyanate. Evidence for the formation of oxodiperoxovanadate(V) complexes containing ionic sulphate

Summary Vanadium pentoxide (1 mol) reacts with alkali sulphate (2 mol) or alkali thiocyanate (2 mol) and an excess of hydrogen peroxide at pH 7–8, maintained by the addition of the corresponding alkali hydroxide, to produce yellow oxodiperoxovanadate(V) complexes containing sulphate. The compounds were characterised by elemental analyses, molar conductance measurements, and i.r. and laser Raman spectroscopic studies. The compounds are formulated as M[VO(O₂)₂] · M₂SO₄ (M=alkali metal). The peroxide has been shown to be bonded to the vanadium(V) centre in a triangular bidentate (C _2v) manner.     

Eigenvalue bounds for Orr-Sommerfeld equation ‘No backward wave’ theorem

Theoretical estimates of the phase velocityC _r of an arbitrary unstable, marginally stable or stable wave derived on the basis of the classical Orr-Sommerfeld eigenvalue problem governing the linear instability of plane Poiseuille flow (U(z)=1−z ²,−1≤z≤+1), leave open the possibility of these phase velocities lying outside the rangeU _min<C _r <U _max, but not a single experimental or numerical investigation in this regard, which are concerned with unstable or marginally stable waves has supported such a possibility as yet,U _min andU _max being respectively the minimum and the maximum value ofU(z) forz∈[−1, +1]. This gap between the theory on one side and the experiment and computation on the other has remained unexplained ever since Joseph derived these estimates, first, in 1968, and has even led to the speculation of a negative phase velocity (or rather,C _r <U _min=0) and hence the possibility of a ‘backward’ wave as in the case of the Jeffery-Hamel flow in a diverging channel with back flow ([1]). A simple mathematical proof of the non-existence of such a possibility is given herein by showing that the phase velocityC _r of an arbitrary unstable or marginally stable wave must satisfy the inequalityU _min<C _r <U _max. It follows as a consequence stated here in this explicit form for the first time to the best of our knowledge, that ‘overstability’ and not the ‘principle of exchange of stabilities’ is valid for the problem of plane Poiseuille flow.     

Serial and parallel simulated annealing and tabu search algorithms for the traveling salesman problem

This paper describes serial and parallel implementations of two different search techniques applied to the traveling salesman problem. A novel approach has been taken to parallelize simulated annealing and the results are compared with the traditional annealing algorithm. This approach uses abbreviated cooling schedule and achieves a superlinear speedup. Also a new search technique, called tabu search, has been adapted to execute in a parallel computing environment. Comparison between simulated annealing and tabu search indicate that tabu search consistently outperforms simulated annealing with respect to computation time while giving comparable solutions. Examples include 25, 33, 42, 50, 57, 75 and 100 city problems.     

The g-value of the 2E state of K3CR(CN)6 and the lower symmetry field

The ⁴A₂ → ²E transition of potassium chromicyanide has been studied under magnetic field. It has been found that the g-value is nearly isotropic, quite unlike the case of ruby. An attempt has been made to explain the zero-field splittings of ^2E, ²T₁ and ²T₂ states and the g-value of the ²E state on the assumption that the distant ions are mainly responsible for lowering of symmetry of the crystal field from O_h. A reasonable choice of parameters can make the calculated values agree with the observed ones.