Effect of rotation direction of a rotary tiller on draft and power requirements in a Bangkok clay soil

Experiments were conducted in a Bangkok clay soil to evaluate the performance of a rotary tiller equipped with reverse or conventional blades. The conventional rotary tiller was equipped with C-type blades whereas the reverse-rotary tiller had new types of blades. Tests were conducted on wet land as well as in dry land. Tests were conducted at tractor forward speeds of 1.0, 1.5 and 2.0 km/h. A power-take-off (PTO) power consumed was calculated from the PTO torque and speed. The results indicated that the PTO power consumption was less for the reverse-rotary tiller compared to the conventional tiller for all passes and forward speeds. For both rotary tillers, power consumption decreased as the number of passes increased, whereas power consumption increased when the forward speed was increased. At all forward speeds, the power consumption was the highest during the first pass and lowest during the third pass. The maximum difference of PTO power requirement was after the first pass at 1.0 km/h forward speed. The reverse-rotary tiller consumed about 34% less PTO power under this condition.     

Evaporator critical heat flux in the double-wall artery heat pipe

The fact that heat is transferred into a heat pipe through the liquid-saturated evaporator wick gives rise to the so-called boiling limit on the heat pipe capacity. The composite nature of the double-wall artery heat pipe (DWAHP) wick structure makes the prediction of the evaporator superheat (Δ T_crit) and the critical radial heat flux (q_r) very difficult. The effective thermal conductivity of the wick, the effective radius of critical nucleation cavity, and the nucleation superheat, which are important parameters for double-wall wick evaporator heat transfer, have been evaluated based on the available theoretical models. Empirical correlations are used to corroborate the experimental results of the 2 m DWAHP. A heat choke mounted on the evaporator made it possible to measure the evaporator external temperatures, which were not measured in the previous tests. The high values of the measured evaporator wall temperatures are explainable with the assumption of a thin layer of vapor blanket at the inner heating surface. It has been observed that partial saturation of the wick (lean evaporator) causes the capillary limit to drop even though it may be good for efficient convective heat transfer through the wick. The 2 m long copper-water heat pipe had a peak performance of 1850 W at 23 W/cm² with a horizontal orientation.     

Synthesis of New Hybrid Structured Magnetite Crosslinked Poly Ionic Liquid for Efficient Removal of Coomassie Brilliant Blue R-250 Dye in Aqueous Medium

In this work, new crosslinked pyridinium poly ionic liquid and its magnetite hybrid structured composite were prepared and applied to remove the toxic dye Coomassie Brilliant Blue (CBB-R250) from aqueous solutions. In this respect, vinyl pyridine, maleic anhydride, and dibromo nonane were used to prepare crosslinked quaternized vinyl pyridinium/maleic anhydride ionic liquid (CQVP-MA). Furthermore, a linear copolymer was prepared by the reaction of vinyl pyridine with bromo nonane followed by its copolymerization with maleic anhydride in order to use it as a capping agent for magnetite nanoparticles. The monodisperse MNPs were incorporated into the crosslinked PIL (CQVP-MA) by ultrasonication to prepare CQVP-MA/Fe₃O₄ composite to facilitate its recovery using an external magnetic field and enhance its adsorption capacity. The chemical structures, thermal stabilities, zeta potential, particle size, EDS, and SEM of the prepared CQVP-MA and CQVP-MA/Fe₃O₄ were investigated. Adsorption kinetics, isotherms, and mechanisms of CB-R250 elimination from aqueous solutions using CQVP-MA and CQVP-MA/Fe₃O₄ were also studied, and the results revealed that the pseudo second-order kinetic model and the Langmuir isotherm model were the most suitable to describe the CBB adsorption from an aqueous solution. The adsorption capacities of CQVP-MA and CQVP-MA/Fe₃O₄ were found to be 1040 and 1198, respectively, which are more than those for previously reported material in the literature with reasonable stability for five cycles.     

Ab initio study of tautomerism and hydrogen bonding of β-carbonylamine in the gas phase and in water solution

All the possible conformations of the three tautomeric isomers of simple β-carbonylamine were fully optimized at ab initio MP2/6-31G** and B3LYP/6-31G** levels in order to determine the conformational equilibrium and the energies of the O—H···N and O···H—N hydrogen bridges. For the most interesting conformations, further calculations in water solution were also carried out. It was found that carbonylamine is the most stable tautomer, followed by enolimine and carbonylimine. This order of stability does not change in solution. O—H···N is the strongest hydrogen bridge, but in solution its energy as well as that of the O···H—N one are dramatically lowered. The deprotonation energy was also calculated and discussed. Received: 16 September 1999 / Accepted: 3 February 2000 / Published online: 5 June 2000     

Discrete Fourier Transform with Denoise Model Based Least Square Wiener Channel Estimator for Channel Estimation in MIMO-OFDM

Multiple-input Multiple-Output (MIMO) systems require orthogonal frequency division multiplexing to operate efficiently in multipath communication (OFDM). Channel estimation (C.E.) is used in channel conditions where time-varying features are required. The existing channel estimation techniques are highly complicated. A channel estimation algorithm is needed to estimate the received signal’s correctness. In order to resolve this complexity in C.E. methodologies, this paper developed an Improved Channel Estimation Algorithm integrated with DFT-LS-WIENER (ICEA-DA). The Least Square (L.S.) and Minimum Mean Square Error (MMSE) algorithms also use the Discrete Fourier Transform (DFT)-based channel estimation method. The DFT-LS-WIENER channel estimation approach is recommended for better BER performance. The input signal is modulated in the transmitter module using the Quadrature Phase Shift Keying (QPSK) technique, pulse modeling, and least squares concepts. The L.S. Estimation technique needs the channel consistent throughout the estimation period. DFT joined with L.S. gives higher estimation precision and limits M.S.E. and BER. Experimental analysis of the proposed state-of-the-art method shows that DFT-LS-WIENER provides superior performance in terms of symbol error rate (S.E.R.), bit error rate (BER), channel capacity (CC), and peak signal-to-noise (PSNR). At 15 dB SNR, the proposed DFT-LS-WIENER techniques reduce the BER of 48.19%, 38.19%, 14.8%, and 14.03% compared to L.S., LS-DFT, MMSE, and MMSE-DFT. Compared to the conventional algorithm, the proposed DFT-LS-WIENER outperform them.     

A Proficient approach to enhance heat transfer using cupric oxide/silica hybrid nanoliquids

Journal of Thermal Analysis and Calorimetry - High performance cooling anticipated in smaller size heat transfer equipment is the most significant challenge in many industries including CPU...     

Self‐Supported Chiral Titanium Cluster (SCTC) as a Robust Catalyst for the Asymmetric Cyanation of Imines under Batch and Continuous Flow at Room Temperature

A robust heterogeneous self‐supported chiral titanium cluster (SCTC) catalyst and its application in the enantioselective imine‐cyanation/Strecker reaction is described under batch and continuous processes. One of the major hurdles in the asymmetric Strecker reaction is the lack of availability of efficient and reusable heterogeneous catalysts that work at room temperature. We exploited the readily hydrolyzable nature of titanium alkoxide to synthesize a self‐supported chiral titanium cluster (SCTC) catalyst by the controlled hydrolysis of a preformed chiral titanium‐alkoxide complex. The isolated SCTC catalysts were remarkably stable and showed up to 98 % enantioselectivity (ee) with complete conversion of the imine within 2 h for a wide variety of imines at room temperature. The heterogeneous catalysts were recyclable more than 10 times without any loss in activity or selectivity. The robustness, high performance, and recyclability of the catalyst enabled it to be used in a packed‐bed reactor to carry out the cyanation under continuous flow. Up to 97 % ee and quantitative conversion with a throughput of 45 mg h^?1 were achieved under optimized flow conditions at room temperature in the case of benzhydryl imine. Furthermore, a three‐component Strecker reaction was performed under continuous flow by using the corresponding aldehydes and amines instead of the preformed imines. A good product distribution was obtained for the formation of amino nitriles with ee values of up to 98 %. Synthetically useful ee values were also obtained for challenging α‐branched aliphatic aldehyde by using the three‐component continuous Strecker reaction.     

The Proton NMR Assignment of 1-Aminocyclo-propane-1-carboxylic Acid

The two sets of diastereomeric hydrogen atoms cis and trans to the carboxylate of 1-aminocyclopropane-1-carboxylic acid (ACC) were differentiated by a ¹H-nmr study. The measurement of the ¹H-nmr spectrum of ACC at pH 3.8 during the successive addition of non-chiral lanthanide reagents such as Eu(NO₃)₃, Pr(NO₃)₃ or Gd(NO₃)₃ demonstrated that the hydrogen atoms cis to the carboxylate function of ACC resonate at δ=1.42 and that the hydrogen atoms trans to the carboxylate function of ACC resonate at δ=1.20. The mono-substituted cyclopropanes, cyclo-propanecarboxylic acid (CPC) and cyclopropyl-amine (CPA) were used in complementary lanthanide-reagent shift titrations along with the back titration of an ACC-Eu⁺⁺⁺ complex with DCl to further substantiate the assignment. This assignment allows for the non-destructive, nonisotopic diluting analysis of various biosynthetically derived deuterated ACC's formed from the corresponding deuterated S-adenosyl-L-methionine.     

Effect of paramagnetic doping on an inorganic polymer triaquadipotassiumbis(malonato)zincate: spectroscopic investigation

Spectroscopic investigations on Mn(II)-doped triaquadipotassiumbis(malonato)zincate [K₂(H₂O)₃] [Zn(mal)₂], an inorganic polymer, have been carried out at room temperature using single crystal electron paramagnetic resonance (EPR), ultraviolet–visible, FT-IR and powder XRD techniques. Single crystal rotations along the three orthogonal axes show more than 30 lines of patterns in EPR spectra, indicating the presence of two sites, one with a large D value and the other with a smaller D value. The calculated spin-Hamiltonian parameters are as follows. Site 1: g _xx =2.099, g _yy =2.092, g _zz =1.988, A _xx =9.77, A _yy =9.71, A _zz =8.96 mT, D _xx =?29.09, D _yy =?11.90, D _zz =40.99 mT; Site 2: g _xx =2.040, g _yy =1.995, g _zz =1.924, A _xx =9.51, A _yy =9.09, A _zz =8.80 mT, D _xx =?11.94, D _yy =?7.51 and D _zz =19.45 mT. The direction cosines of g/A/D do not match with the direction cosines of Zn–O bonds in the host lattice for either site, suggesting that both the Mn(II) sites entered the lattice interstitially. Optical results indicate a strong covalent bonding between the metal ion and ligands, with site symmetry being primarily octahedral. The FT-IR and powder XRD data confirm the retention of the crystal structure, even after incorporating a paramagnetic probe. Various admixture coefficients, bonding and optical parameters have also been calculated.