The Behavior of the Centrally Pivoted Thrust Bearing Pad with Hydrostatic Recesses Pressurized by a Constant-Rate Flow

The tilting behavior of the centrally pivoted, externally pressurized tilting thrust pad is investigated. The pressure distribution in the oil film is obtained by solving the Reynolds' equation which takes into account the external pressurization induced by a constant-rate flow. The relation between the size of the hydrostatic recess and the tilt angle of the pad is described. Calculations show that a pad with pressure recesses may have a negative tilt angle, depending on the size of the recess. The pressure variation around the hydrostatic pressure recess causes the moment to force the pad to tilt backward. At high shaft rotational speeds, the pad tilts backward too much and eventually fails to support the load. The hydrostatic pressure recess that is utilized to avoid the metal contact may cause this. The result was confirmed by experiments.     

Radical polimerization of methyl α-crotonyloxymethyl) acrylate to soluble polymer bearing pendant double bonds

Methyl α-(crotonyloxymethyl)acrylate (MCRMA) of which the α-substituted acryloyl and crotonyl groups are sterically hindered and reluctant to homopolymerize, respectively, was synthesized and polymerized. The polymerization of MCRMA primarily took place through homopolymerization of the α-(substituted methyl)acryloyl group to yield a soluble polymer bearing a large number of the pendant crotonyloxy groups. The ratio of the rate constants for the inter- and intramolecular additions of the propagating radical to form the linear and cyclic repeating units, respectively, indicates that this monomer exhibits an exceptionally low possibility of cyclopolymerization because of the sterically hindered intramolecular addition of the crotonyloxymethyloyl radical to the crotonyl group. Crosslinking by the reaction of the pendant double bond slowly proceeded due to an extremely low reactivity of the crotonyloxy group towards poly-[α-(crotonyloxymethyl)acrylate] radical. Received: 1 October 1999/Accepted: 2 November 1999     

Thermodynamic Behavior of Stable Carbon Isotopic Compositions of Individual Polycyclic Aromatic Hydrocarbons Derived from Automobiles

Concentrations, molecular compositions, and compound-specific stable carbon isotopic compositions ( i 13 C) of polycyclic aromatic hydrocarbons (PAHs) in gasoline exhaust particles (GEPs) and diesel exhaust particles (DEPs) were investigated in this study. i 13 C of PAHs in GEPs ranged from m 13.3 to m 26.8, and that in DEPs ranged from m 21.7 to m 26.3. The interspecies i 13 C variations in each sample were 5.3 - 2.2 in GEPs and 2.6 - 1.3 in DEPs. PAHs in GEPs show larger interspecies i 13 C variation than those in DEPs; hence, a degree of carbon isotopic fractionation during the conversion from fuel to PAH seems to be larger in gasoline engines than that in diesel engines. Pyrene series PAHs, which consist of only hexagonal rings, in almost all GEP samples show strong negative correlation between the H/C ratio and i 13 C whereas fluoranthene series PAHs, which contain a pentagonal ring, show less systematic isotopic behavior in GEP samples. A kinetic isotope effect in thermal cracking of organic macromolecules may be minor for PAH formation in vehicle engines. We suggest that the isotopic trend of pyrene series in GEPs can be explained by a thermodynamic isotope effect, and that disturbance from isotopic equilibrium may cause a weak correlation between the isotopic behavior and the H/C ratio among the interspecies PAHs.     

Fast redox of composite electrode of nitroxide radical polymer and carbon with polyacrylate binder

For organic radical batteries, poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) has been reported as a promising positive electrode material. The PTMA/C composite electrode prepared with polyacrylate binder demonstrated the fast redox performance for the application to aprotic secondary batteries. When the variation in discharge capacities of the PTMA/C composite electrode was tested galvanostatically at 20C rates, the electrode retained 96% of the initial capacity after 1000 cycles. This is attributed to the fact that the redox of PTMA is a simple reaction to form the oxoammonium salt doped with ClO₄^? anions in the electrolyte. When the PTMA/C composite electrode was discharged at different C rates, the electrode retained 81% of the theoretical capacity even at 50C rates. This remarkably high rate capability originates from the fast electron-transfer kinetic of the 2,2,6,6-tetramethylpiperidine-N-oxyl (so-called TEMPO) radical, partially jelled polyacrylate binder, and the improved conductivity throughout the electrode by thoroughly mixing with carbon.     

Direct ortho‐Hydroxylation of 2‐Phenylpyridines using Palladium(II) Chloride and Hydrogen Peroxide

Direct functionalization of the ubiquitous C H bond is receiving much attention because complex structures can be formed from simple precursors. This paper reports a useful method for the direct hydroxylation of 2‐phenylpyridines using palladium(II) chloride and aqueous hydrogen peroxide. In this method, hydrogen peroxide, which has high atom efficiency, is employed as the oxidant and phenol derivatives are generated via C H activation.

     

Simulation results of a hexahedron-octahedron based spherical stepping motor

The simulation results of a novel stepping motor based on a pair of a regular hexahedron and a regular octahedron (call “6-8 spherical stepping motor” afterward) are presented. The 3D electromagnet and motion coupled simulation program “Magnet 6” is used for the simulation. As the conditions of simulation, the excitation current and frequency is 1 A and 5.3 Hz, respectively. Three phase sinusoidal excitation currents are applied to two pairs of three coils of the stator individually at 120 deg intervals. The simulation results show that the rotor rotates along the rotating magnetic field and the output torque is 0.04 Nm. The simulation results prove the correctness of the 6–8 spherical motor driving method. The developed 6–8 spherical stepping motor is air-core type without back yoke for avoiding the cogging torque. When using iron core with back yoke, the proposed motor will be a high-torque spherical motor. The 6–8 spherical stepping motor was tested and the experimental results were compared with the simulation results. Then, the simulation program was used for optimum design of the 6–8 spherical stepping motor.     

A comparative study on co-combustion performance of municipal solid waste and Indonesian coal with high ash Indian coal: A thermogravimetric analysis

In recent years there has been an increasing utilization of coal blends in the Indian power industry, with Indonesian coal, due to high ash content and shortages in domestic coal production. On the other hand, rapid economic growth is aggravating the municipal solid waste (MSW) related environmental problems. In this study, an attempt has been made to compare the co-combustion characteristics of hydrothermally treated MSW and Indonesian coal with high ash Indian coal, so as to replace the Indonesian coal with MSW. The effect of blending Indonesian coal and hydrothermally treated MSW with Indian coal on ignition behavior was studied. MSW blends of 10%, 20%, 30% and 50% (in wt.%), and an Indonesian blend of 10% with Indian coal were tested in a thermogravimetric analyzer (TGA) in the temperature from ambient to 700 °C with a temperature increase of 10 °C/min. From the results, at 10% of blend, ignition and carbon burnout were similar for Indonesian and MSW blend, analogous to coal combustion and even better than the Indonesian coal blend, which indicated the feasibility for replacing Indonesian coal with hydrothermally treated MSW. Further, the results show a scope to increase the MSW blend in Indian coal up to 20%, as the constituents behave as a single fuel.     

Development of multilayer laminar-type diffraction gratings to achieve high diffraction efficiencies in the 1-8 keV energy region

W/C and Co/SiO(2) multilayer gratings have been fabricated by depositing a multilayer coating on the surface of laminar-type holographic master gratings. The diffraction efficiency was measured by reflectometers in the energy region of 0.6-8.0 keV at synchrotron radiation facilities as well as with an x-ray diffractometer at 8.05 keV. The Co/SiO(2) and W/C multilayer gratings showed peak diffraction efficiencies of 0.47 and 0.38 at 6.0 and 8.0 keV, respectively. To our knowledge, the peak efficiency of the W/C multilayer grating is the highest measured with hard x rays. The diffraction efficiency of the Co/SiO(2) multilayer gratings was higher than that of the W/C multilayer grating in the energy range of 2.5-6.0 keV. However, it decreased significantly in the energy above the K absorption edge of Co (7.71 keV). For the Co/SiO(2) multilayer grating, the measured diffraction efficiencies agreed with the calculated curves assuming a rms roughness of approximately 1 nm.     

High‐Pressure Synthesis of Tantalum Nitride Having Orthorhombic U2S3 Structure

Among binary compounds, there is a high potential for discovery of novel members (polymorphic phases or compounds) of the nitrides of transition metals group due to a pronounced dependence of the oxidation state of the metals (M) on pressure. The power of high pressure–high temperature (HP‐HT) route for synthesis of binary nitrides has already been demonstrated by the discovery of cubic nitrides of the group 4 and 14 elements, of crystalline polymorphs of P₃N₅, and by reports on formation of four noble metal nitrides. It is anticipated that such HP products exhibit, in addition to enhanced elastic and mechanical behavior, other functional properties making them interesting for industrial applications. Here, HP–HT synthesis research is extended to nitrides of group 5 elements, resulting in the discovery of a novel hard tantalum nitride, exhibiting U₂S₃ structure: η‐Ta₂N₃ (Pbnm, a = 8.1911(17) Å, b = 8.1830(17) Å, c = 2.9823(3) Å). The stoichiometry is supported by two independent means, verifying that η‐Ta₂N₃ is the first thermodynamically stable transition metal nitride with a N:M ratio exceeding 4:3. Due to its high hardness and peculiar texture (needle‐like and granular crystallites), η‐Ta₂N₃ may find practical applications as a hard fracture resistant material.