Analysis of minimum clamping force

Our objective is to determine the minimum clamping force that keep the workpiece stable during the metal cutting process. In analyzing the stability of the workpiece, one usually proves that no instant center of motion can occur on the clamping plane. However, previous search algorithms for the instant center of motion either lack theoretical sufficiency or computational efficiency. This paper presents a new method derived from the correlation between cutting force and clamping moment. This method increases the search efficiency by pruning inadequate search directions. In addition, examples are provided to illustrate minimum clamping force analysis under different fixturing conditions.     

Direct computational approaches to a magnetohydrodynamic model system

Summary The magnetohydrodynamic model system is integrated numerically as an initial-value problem. The system is integrated using two-different numerical methods. The first uses a special finite difference scheme introduced byBellman. The second makes use of the classical method of converting a partial differential equation into an infinite system of ordinary differential equations. The formulation for each computational scheme is discussed and numerical example presented.With 10 Figures     

Thermal Conductivity of a Particulate-Diamond-Reinforced Cordierite Matrix Composite

The effect of 15 vol% particulate diamond reinforcement on the thermal conductivity of a cordierite matrix was studied as a function of diamond particle size from room temperature to 700°C. The thermal conductivity was found to increase with increasing particle size to a maximum increase of about 75% for a mean particle size of 50 μ. The particle size effect was found to be more pronounced at the lower temperatures than at the higher temperatures. The observed effect of particle size and temperature was attributed to the existence of an interfacial thermal barrier, possibly resulting from interfacial phonon scattering, with a positive temperature dependence of the interfacial thermal conductance. The magnitude of this conductance suggested strong adhesion between the diamond and cordierite.     

K-band MMIC active band-pass filters

Two K-band active band-pass filters using 0.15-/spl mu/m GaAs pHEMT technology, with one fixed-frequency and the other tunable, are designed, fabricated, and tested. The fixed-frequency filter has its central frequency at 22.6 GHz, with 900-MHz bandwidth (4%). The tunable filter can be tuned from 19.5 to 21.5 GHz with the same bandwidth. Both circuits have a common size of 1 mm /spl times/ 1 mm. To our knowledge, the tunable filter is the highest frequency tunable active filter ever reported.     

Superresolution frequency estimation by alternating notchperiodogram

A novel periodogram-based maximum-likelihood algorithm is proposed for a frequency estimation problem. It is called an alternating notch-periodogram algorithm (ANPA), since the original multidimensional maximum likelihood problem is decomposed into a sequence of much simpler one-dimensional problems of finding the peaks of notch periodograms. The ANPA achieves superresolution and a very low SNR threshold and can be computed and implemented in several efficient ways. First, with FFT and a concurrent Gram-Schmidt procedure using Schur's recursions, the notch periodogram can be computed without any costly eigendecomposition and matrix inversion. This approach can further lead to a mapping of the notch periodogram onto a VLSI architecture consisting mainly of a highly pipelined notch processor and two FFT processors. Second, without degrading the excellent performance of ANPA, the notch periodogram can be simplified and approximated to provide further computational reduction and implementational simplicity     

Abrasive wear study of bainitic nodular cast iron

The abrasive wear properties of the bainitic nodular cast iron under different austenitizing and isothermal transformation temperature and time were studied in the present paper. Using Optimol Schwingung reibung verschleiß wear tester, the point contact is adopted to compare the effect of those various heat-treatment conditions on wear properties. The weight loss, wear-scar diameter and friction coefficient were measured to evaluate the wear properties. Using scanning electron microscopy, the wear mechanisms can be understood by observing the worn surface. From the results of weight loss, wear-scar diameter and friction coefficient, it can be concluded that the wear resistance increased with increasing austenitizing temperature and the most suitable austempering temperature of the material used in the present study is from 270–300 °C for 4 h.     

Experimental strategy in three-dimensional structure determination of crotoxin complex thin crystal

Electron images and diffraction patterns of crotoxin complex thin crystals contain high-resolution structural information in projection at both room and low temperatures. This paper outlines our strategy for collecting three-dimensional amplitude and phase data from these uniquely well-ordered toxin thin crystals. Preliminary experiments in support of the feasibility of this approach are presented.     

Suppression of substance P biosynthesis in sensory neurons of dorsal root ganglion by prodrug esters of potent peptidylglycine alpha-amidating monooxygenase inhibitors

Substance P as well as many other neuropeptides are synthesized as glycine-extended precursors and converted to the biologically active C-terminal amides by posttranslational modification. The final step of posttranslational processing is catalyzed by peptidylglycine alpha-amidating monooxygenase (PAM). In a previous study, N-substituted homocysteine analogs were found to be potent inhibitors of PAM partially purified from conditioned medium of cultured rat medullary thyroid carcinoma CA-77 cells. These compounds, however, were only modest inhibitors of substance P production in cultured dorsal root ganglion cells, possibly because of poor cell penetration. Several ester derivatives of hydrocinnamoyl-phenylalanyl-homocysteine, one of the most potent PAM inhibitors, were prepared to increase the intracellular accessibility of these compounds. Hydrocinnamoyl-phenylalanyl-(S-benzoyl-homocysteine) benzyl ester was identified as the most potent compound, inhibiting substance P biosynthesis in dorsal root ganglion cells with an IC50 of 2 microM. Inhibition of PAM resulted in a concomitant increase in the glycine-extended substance p (substance P-Gly) precursor peptide. In the presence of 3 microM benzyl ester derivative, the intracellular substance P-Gly level was 2.4-fold higher while the substance P level was 2.1-fold lower than the corresponding peptides in control cells. These results suggest that PAM inhibition represents an effective method for suppression of substance P biosynthesis and, therefore, may have therapeutic utility in conditions associated with elevated substance P levels. Furthermore, PAM inhibition may also prove useful in decreasing other amidated peptides.     

Containment system for the preparation of vitrified-hydrated virus specimens

A guillotine-type quick freezing device and a bio-hazard containment box have been designed, constructed, and used to prepare vitrifiedhydrated specimens of viruses in their native environment. Special design considerations include the preservation of the specimen in its natural state in vitrified ice, prevention of virus aerosols escape, and control of the potentially explosive air-coolant vapor mixtures.