bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study of the Effect of Drag Reduction Agents on the Performance of Jet Pumps
Authors: Gazzar M. El. , Meakhail T , Mikhail S 
Published: June 2006

The overall efficiency of the jet pump is low compared with most of the other types of pumps. The majority of previous investigations concentrated on the effect of its geometric ratios on its performance. To the best of the authors’ knowledge, there are no previous investigations on the effect of adding drag reduction agents to the fluid passing on its performance, which is the objective of the present investigation. The mixing process in this case is that of two streams: the primary stream is water (Newtonian fluid), whereas the secondary stream is a solution of certain polymer (considered to be non-Newtonian). Tests are carried out to study the effect of different concentrations of additives (carboxy methyl cellulose (CMC)) on the performance of the jet pump. The experimental results include characteristic curves for different area ratios, with different concentrations of CMC, as well as the wall static pressure distributions along the mixing chamber, diffuser, and outlet pipe. The results show that the concentration have a pronounced effect on the overall efficiency. The efficiency increases with the increase in concentration, up to a certain value, then decreases at higher value of concentration. Further, the maximum overall efficiency increases with the decrease in values of area ratio ( R).
Influence of Harmonic Surface Roughness on the Fatigue Life of Elastohydrodynamic Lubricated Contacts
Authors: Chapkov A. D. , Colin F , Lubrecht A. A. 
Published: June 2006

In recent years, owing to the increase in transmitted power, increase in temperature, and decrease in viscosity, elastohydrodynamic lubricated (EHL) contact conditions have become extremely severe. Consequently, roughness and surface features become increasingly important when compared with the lubricant film thickness, which can induce wear. Moreover, local pressure variations increasingly cause surface-induced fatigue. Therefore, the understanding of roughness behaviour in EHL contact performance has become important. Three decades ago, a widely used tool to predict contact performance was proposed by Dawson and Tallian. It is based on the central film thickness to composite roughness ( h3/σ) ratio. However, engineering fatigue life models require the stress level and the stressed volume to study the contact life reduction, and neither can be extracted directly from the h3/σ ratio. This article extends the amplitude reduction analysis. It proposes a new dimensionless parameter including central film thickness, roughness wavelength, and amplitude. It is shown that the pressure fluctuations depend solely on this parameter and that the fatigue life depends mainly on this parameter.
Effect of elastohydrodynamic film thickness on a wear model for worm gears
Authors: Sharif K. J. , Evans H. P. , Snidle R. W. , Barnett D , Egorov I. M. 
Published: June 2006

Worm gears used for power transmission commonly consist of a steel worm running against a bronze or phosphor bronze worm wheel. The wheel teeth are usually manufactured using an ‘oversize’ hob so that the initial elastic contact between the teeth is in the form of an ellipse with lubricant entrainment predominantly in the major axis direction. As a result of this unfavourable contact geometry, the lubricant film generated between the worm and wheel teeth is relatively thin. The kinematic configuration is close to that of simple sliding as the velocity of the wheel tooth surface relative to the nominal contact point is very low in comparison with that of the worm. The combination of poor film forming, high sliding and a soft gear material (to avoid scuffing) leads to the continuous wear seen in these gears. The article presents results obtained using a model for the prediction of wear for this configuration based on the well-known Archard wear law extended to take the variation of pressure and film thickness over the contact area into account in determining the wear rate. The pressure and film thickness distributions are obtained from elastohydrodynamic lubrication (EHL) modelling of the contact over the meshing cycle. Wear patterns are presented corresponding to different film thickness sensitivities in the wear formula, and these predictions, together with the calculated increase in backlash due to wear, give a basis for calibrating the model against experimental wear tests.
Wear effects and mechanisms of soot-contaminated automotive lubricants
Authors: Green D. A. , Lewis R , Dwyer-Joyce R. S. 
Published: June 2006

A study has been carried out to investigate the influence of soot-contaminated automotive lubricants in the wear process of a simulated engine valve train contact. Previous research on this topic has been mainly performed from a chemical point of view in fundamental studies, with insufficient relevance to real engine conditions, i.e. load and geometry. This study investigates the conditions under which wear occurs through specimen testing. The objective of the work was to understand the wear mechanisms that occur within the contaminated contact zone, to help in future development of a predictive wear model to assist in the valve-train design process. The effects of soot in lubricants have been tested using a reciprocating test-rig specifically designed for this application, where a steel disc is held in a bath of oil and a steel ball (replicating a valve train contact) is attached to a reciprocating arm. The materials, contact geometry and loading conditions are all related to specific conditions experienced within an engine's valve train. The testing was carried out under various contact conditions, using carbon black as a soot simulant. Wear measurements were taken during the tests and wear scar morphology was studied. The results have revealed how varying lubrication conditions changes the wear rate of engine components and determines the wear mechanism that dominates for specific situations.
Prediction of losses in belt-type continuously variable transmission due to sliding between belt and disc
Authors: Poll G , Kruse T , Meyer C 
Published: June 2006

The efficiency of belt-type continuously variable transmission (CVT) - apart from the power consumption of auxiliary systems such as hydraulics - predominantly depends on the energy dissipated during sliding at the belt-disc contacts. These sliding motions are a consequence of elastic deformations and misalignments because of clearances, resulting in a so-called spiral path of the belt elements on the discs and hence tangential and radial sliding motions. The performance of such systems can be predicted through an iterative computation by numerically solving a set of differential equations for the forces and motions coupled with a finite-element computation of the deformations. A comparison with elaborate measurements of deflections, belt motions, and losses shows that a relatively simple modified Coulomb type friction model with a steep gradient through the origin delivers sufficiently accurate results. The computations reveal the existence of ‘locked’ zones with extremely low ‘creeping’ motions. Thus, the mechanisms of power transmission in belt-type CVT are better understood and designers have a validated tool to optimize shaft and disc geometry concerning maximum efficiency.
Lubrication in refrigeration systems: Numerical model for piston dynamics considering oil-refrigerant interaction
Authors: Grando F. P. , Priest M , Prata A. T. 
Published: June 2006

Piston dynamics plays a fundamental role in several processes related to the operation of hermetic reciprocating compressors used in refrigeration. For example, the refrigerant leakage through the radial clearance between piston and cylinder, which reduces compressor pumping efficiency, and also the viscous friction associated with the lubricant film in the radial clearance, which is related to energy consumption. It is important to optimize such variables, ensuring at the same time smooth operation of the piston in its reciprocating motion, minimizing wear and increasing lifetime. In this context, numerical models studying piston dynamics provide a useful tool for engineering design. These models usually consider an oil film filling the piston-cylinder clearance and operating in the hydrodynamic regime. Determining cavitation conditions occurring along the ringless piston represents an additional difficulty in modelling. As refrigerant is present in the compressor environment, it inevitably interacts with the oil, changing lubricant characteristics. The refrigerant can dissolve in the oil at higher pressures, reducing viscosity, and can be released at lower pressures, leading to a two-phase flow. This work explores how the interaction of oil and refrigerant affects piston dynamics, using a numerical model that considers as the lubricant a mixture of oil and refrigerant with variable properties. Comparing the results with simulations where pure oil is considered as the lubricant and a cavitation criterion is adopted, significant differences were observed in predicting piston trajectory and power consumption along the cycle.
Bio-tribology and bio-mimetics in the operating environment
Authors: Dowson D , Neville A 
Published: June 2006

The main objectives of this review are to draw attention to some of the interesting and exciting studies of human and animal tribology and to introduce the growing field of bio-mimetics. Studies of natural and total replacement synovial joints are widely known and spectacular progress has been reported in both fields. However, it is becoming ever more important to link engineering and biology and to apply sound tribological principles in the further development of long-lasting total joint replacements. In this article, accounts will be given for a wider range of fascinating tribological features of biological systems, embracing friction, lubrication, and wear. These include animal locomotion, swimming, adhesion and attachment to adjacent surfaces, oral tribology, skin and ocular tribology. Bio-mimetic approaches to engineering problems, in which lessons have been learned from comparable solutions in the natural world, have been impressive, but they have not yet been widely applied in tribology. The challenge remains with prospects of ever closer association between bio-tribology and bio-mimetics.
Development of a Three-Dimensional Substructure Search Program for Organic Molecules
Authors: Kato Hiroaki , Takahashi Yoshimasa 
Published: June 2006

Abstract
A computer program, called SS3D, has been developed for the three-dimensional substructure searching of organic molecular structures. Our approach is based on a clique-finding algorithm that compares chemical graphs containing edges labelled with inter-atomic distances. The program allows one to specify some allowance of the distance for the geometrical matching of 3D-substructures; it also allows one to define some constraints for the query substructure or for the geometrical pattern to be used in the search. The details concerning the program are discussed and several illustrative examples are given.
Preparation and Chemical Properties of a Novel Layered Cerium(IV) Phosphate
Authors: Tsuhako Mitsutomo , Danjo Mayumi , Baba Yoshinobu , Murakami Masahiko , Nariai Hiroyuki , Motooka Itaru 
Published: June 2006

Abstract
A synthetic method of a novel cerium(IV) bis(hydrogenphosphate) dihydrate, Ce(HPO4)2·2H2O, hereafter referred to as CeP·2H2O, has been established by the hydrothermal reaction of cerium(IV) oxide with phosphoric acid in an autoclave. The preparation of CeP·2H2O was significantly affected by the reaction conditions: the mixing ratio (P2O5/CeO2) of CeO2 and phosphoric acid, heating temperature and time, and water vapor pressure. The optimum condition for the preparation of CeP·2H2O was the mixing ratio of 1.5—2.0, heating temperature 175—200 °C, heating time 5 h, and water vapor pressure 5.0—7.0 atm.
The results of X-ray powder diffraction, fluorescent X-ray analysis, differential thermal analysis and thermogravimetry (DTA-TG), IR spectrum, and phase transition showed that CeP·2H2O is a novel crystalline layered cerium(IV) phosphate having a interlayer distance d = 18.0 Å, longer than any layered phosphates (zirconium(IV), titanium(IV), and tin(IV) phosphates) so far reported.
The reversible phase transition of CeP·2H2O occurred as follows, when exposed to various relative humidities:

CeP·2H2O dissolved slightly in distilled water and hydrochloric acid, and much more in aqueous sodium hydroxide and aqueous ammonia. CeP·2H2O effectively adsorbed ammonia in an aqueous solution and ammonia gas.
Molecular Structures of HMPA-Coordinated Samarium(II) and Ytterbium(II) Iodide Complexes. A Structural Basis for the HMPA Effects in SmI2-Promoted Reactions
Authors: Hou Zhaomin , Zhang Yugen , Wakatsuki Yasuo 
Published: June 2006

Abstract
The reaction of ytterbium(II) iodide (YbI2) with 4.5 equiv of hexamethylphosphoric triamide (hmpa) in tetrahydrofuran (thf) gave [Yb(hmpa)4(thf)2]I2 (1) as yellow crystals. A similar reaction of SmI2 with hmpa afforded black-purple [SmI2(hmpa)4] (2) after recrystallization from toluene. When 10 equiv of hmpa were used in the reaction with SmI2, [Sm(hmpa)6]I2 (3) was obtained as purple blocks. Complexes 1—3 have been structurally characterized by crystallographic studies. The structural data of these complexes satisfactorily explain the hmpa effects observed in SmI2-promoted reactions, and also provide a guideline for the use of HMPA in these reactions.
Modified Borohydride Agents, (1,4-Diazabicyclo[2.2.2]octane)(tetrahydroborato)zinc Complex [Zn(BH4)2(dabco)]. A New Ligand Metal Borohydride as a Stable, Efficient, and Versatile Reducing Agent
Authors: Firouzabadi Habib , Zeynizadeh Behzad 
Published: June 2006

Abstract
(1,4-Diazabicyclo[2.2.2]octane)(tetrahydroborato)zinc complex is a stable compound which has been used for the selective reduction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyloins and acyl chlorides to their alcohols and aldehydes in THF or CH2Cl2/hexane at room temperature or under reflux conditions.
Side-Chain Liquid-Crystalline Polyoxetanes with a Spacer-Separated Azobenzene Moiety. II. Preparation and Characterization of Polyoxetanes Derived from 4-(4-Alkoxyphenylazo)phenyl 4-[7-(3-Methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates
Authors: Ogawa Hiroshi , Hosomi Tetsuya , Kosaka Toshiaki , Kanoh Shigeyoshi , Ueyama Akihiko , Motoi Masatoshi 
Published: June 2006

Abstract
A series of polyoxetanes were prepared by the cationic ring-opening polymerization of 4-(4-alkoxyphenylazo)phenyl 4-[7-(3-methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates using 0.08 molar amount of THF·BF3 in dichloromethane at 20 to 30 °C. Although the product polymers indicated GPC-average molecular weights of around 9000 to 23000, in most cases, they did not have an unimodal molecular weight dispersity. The liquid-crystalline mesophases of the polymers were examined by differential scanning calorimetry and polarized optical microscopy; these textures were observed due to nematic and/or smectic mesophases over a wide temperature range from about 250 °C to room temperature. The benzoate moiety, the longer p-substituted alkoxy tails, and the oxetane main chain play important roles in maintaining highly ordered, stable mesophases.
N,N,N′,N′-Tetraalkyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamides: Novel Chiral Auxiliaries for Asymmetric Simmons–Smith Cyclopropanation of Allylic Alcohols and for Asymmetric Diethylzinc Addition to Aldehydes
Authors: Kitajima Hiroshi , Ito Katsuji , Aoki Yuko , Katsuki Tsutomu 
Published: June 2006

Abstract
The newly introduced title compounds were found to be efficient chiral auxiliaries for the asymmetric Simmons–Smith cyclopropanation of allylic alcohols and for asymmetric addition of diethylzinc to aldehydes. For example, Simmons-Smith cyclopropanation of cinnamyl alcohol in the presence of N,N,N′,N′-tetraethyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamide (1b) proceeded with high enantioselectivity of 94% ee and addition of diethylzinc to benzaldehyde in the presence of N,N,N′,N′-tetraisopropyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamide (1e) proceeded with enantioselectivity of 99% ee. Although the reaction mechanism of these reactions is still nuclear, a monomeric seven-membered 2,2′-dihydroxy-1,1′ -binaphthyl-3,3′-dicarboxamide (1)–Zn complex is considered to be an active species which catalyzes the above reactions, on the basis of NMR experiments.
Oxidative Anion Metatheses in Diaryliodonium Iodides and Chlorides
Authors: Kazmierczak Pawel , Skulski Lech 
Published: June 2006

Abstract
Oxidative anion metatheses in the crude title iodides and chlorides produced the corresponding pure hydrogensulfates, nitrates, tetrafluoroborates, triflates, tosylates, as well as bromides and chlorides (only from the iodides) in 54—86% yields. These procedures are easier and shorter than earlier methods. By using modified oxidative metatheses in the title iodides (in the presence of HBr or HCl) it was possible either to isolate, or to detect only, the intermediate dihaloiodates(I), [Ar2I]+[IX2]− (X = Br or Cl). A complex Ph2I+Cl−·1/2I2 was also obtained in 56% yield. Tetraethylammonium iodide was similarly converted into pure tetrafluoroborate or dibromoiodate(I) in 75 and 76% yields, respectively.
Manganese-Catalyzed Silylmagnesiation of Acetylenes and 1,3-Dienes
Authors: Tang Jun , Shinokubo Hiroshi , Oshima Koichiro 
Published: June 2006

Abstract
The treatment of 4-benzyloxy-1-butyne with PhMe2SiMgMe in the presence of a catalytic amount of MnCl2 gave a monosilylated product, (E)-PhCH2OCH2CH2CH=CHSiMe2Ph, selectively after an aqueous workup. Meanwhile, the reaction of isoprene with PhMe2SiMgMe under manganese catalysis and the subsequent addition of iodomethane afforded 4-dimethylphenylsilyl-2,3-dimethyl-1-butene in good yield.
Highly Efficient Energy Transfer from Tryptophans in Avidin Tetramer to Biotin-Linked Pyrenylalanine
Authors: Kuragaki Masahiro , Sisido Masahiko 
Published: June 2006

Abstract
Highly efficient energy transfer from tryptophan units of an avidin tetramer to biotin-linked pyrenylalanine was observed. The energy transfer efficiency reached 85% when two of the four subunits were occupied with biotin-linked pyrenylalanine. The transfer efficiency vs. pyrenylalanine/binding site curve was simulated taking the distribution of the biotin derivatives among the four binding sites and the difference of Förster’s r0 values for polar and nonpolar tryptophans, into account. The results showed a qualitative agreement with the experimental data.
Excited State Intramolecular Proton Transfer Reactions in 2-(2-Hydroxyphenyl)benzimidazole in Micellar Solutions
Authors: Das Somes Kumar , Bansal Ashish , Dogra Sneh Kumar 
Published: June 2006

Abstract
Spectral characteristics of 2-(2-hydroxyphenyl)benzimidazole (HPBI) have been studied in solutions containing different compositions of dioxane–water mixtures, aqueous sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (HTAB), and Triton X-100 (TX-100). The correlation curve between the fluorescence band maxima () and the dielectric constant of dioxane–water solutions provides a better rule than the pure solvents to find the polarity at the binding site of the fluorophore in micelles. The effective dielectric constant at the binding sites of SDS, HTAB, and TX-100 are found to be 40, 20, and 20, respectively. The values of the binding constants of HPBI to these micelles conform to the above results. pKa values for various proton transfer reactions were determined at different concentrations of SDS, HTAB, and TX-100, both in the ground and singlet states, and these are discussed.
Physical and Donor–Acceptor Properties of 3-Propyl-4-ethylsydnone
Authors: Handa Minoru , Kataoka Mayumi , Wakaumi Makoto , Sasaki Yukio 
Published: June 2006

Abstract
The physical properties of 3-propyl-4-ethylsydnone at various temperatures were investigated by dielectric constant (ε), refractive index (nD), density (ρ), and viscosity (η) measurements. The dielectric constant of 3-propyl-4-ethylsydnone was very high compared with those of many organic solvents. For example, it was found to be 64.6 at 25 °C, close to that of propylene carbonate (64.9), a typical nonaqueous polar solvent with a high dielectric constant. The refractive index and density for 3-propyl-4-ethylsydnone decreased linearly with increasing temperature. The viscosity of 3-propyl-4-ethylsydnone at 25 °C was 11.2 cP (1 cP = 10−3 N s m−2). This was larger than those of many organic solvents and close to that of phenol (11.6 cP at 20 °C). From a line for log η vs. 1/T, the activation energy (Eη) for the viscosity of 3-propyl-4-ethylsydnone was found to be 29.7 kJ mol−1. The estimation of donor (DN) and acceptor (AN) numbers for 3-propyl-4-ethylsydnone were also done from 29Si and 13C NMR spectroscopies, respectively. Donor number of 3-propyl-4-ethylsydnone was about 25, and its acceptor number was approximately about 20. Both numbers were large in many organic solvents. Both physical and donor–acceptor properties were influenced by alkyl substituent groups in the 3-, 4-positions of the sydnone ring.
A Unified Theory of Uniaxially- and Biaxially-Stretched Film Methods: Three-Dimensional Reduced Spectra of Perylene
Authors: Kobayashi Michio , Yuan Xinghai , Shinbo Norio , Watanabe Masashi , Matsumoto Masunori , Miura Masanori , Yoshioka Ikuko , Tanizaki Yoshie 
Published: June 2006

Abstract
A unified theory of uniaxially- and biaxially-stretched film methods has been proposed. This theory allows the decomposition of the electronic absorption spectrum into three-dimensional reduced spectra polarized along the molecular orientation axes. A transformation theory has also been proposed to transform these reduced spectra to the three-dimensional reduced spectra polarized along the molecular axes, assuming that there exist a pure band and an overlapping band in the spectrum. These theories were applied to get the three-dimensional reduced spectra of perylene.
Thermochromism of the Crystals of 2,3-Bis(phenylthio)-1,4-naphthoquinone
Authors: Tanaka Masashi , Hayashi Hisahiro , Matsumoto Shingo , Kashino Setsuo , Mogi Kouichi 
Published: June 2006

Abstract
The crystals of 2,3-bis(phenylthio)-1,4-naphthoquinone have the dimorphs of red and violet forms. The crystal structures of a monoclinic form (violet form) and an orthorhombic form (red form) have been determined by the X-ray diffraction method. In the orthorhombic form, two phenylthio groups are located on the same side of the naphthoquinone plane, while in the monoclinic form one phenylthio group is located on the naphthoquinone plane and the other phenylthio group is located under the plane. The violet form changes to the red form upon heating. The thermochromism of these crystals was studied, based on the crystal structures of the dimorphs and the solid state CP-NMR and IR and visible absorption spectra and the differential scanning calorimetry together with the theoretical analysis of the data of IR and visible absorption spectra.
Highly Efficient and Selective Membrane Transport of Silver(I) Ion by a Cooperative Carrier Composed of Aza-18-crown-6 and Palmitic Acid
Authors: Shamsipur Mojtaba , Akhond Morteza 
Published: June 2006

Abstract
A given mixture of aza-18-crown-6 and plamitic acid was found to be an excellent cooperative carrier for the efficient transport of Ag+ ions through a bulk liquid membrane. In the presence S2O32− ion, as a suitable metal ion acceptor in the receiving phase, the amount of silver transported across the liquid membrane after 90 min was 93.6 ± 1.5%. The selectivity and efficiency of silver transport from aqueous solutions containing other cations such as Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, and Fe2+ ions were investigated. In the presence of diphosphate as a suitable masking agent in the source phase, the interfering effect of Cd2+ ion was eliminated.