非平衡态/不可逆过程的热力学理论(Ⅱ)

<正> 7 解的唯一性 如果不考虑非平衡态和不可逆性,则等能密度理论中的基本命题与经典弹性理论中的在形式上完全相同。无论整个系统的动能是大还是小,图6中(sumform)_o上的面力T_i和在(sumform)_c和在的位移u_i将始终在空间坐标系x_i和时刻i下给出。与一般力学中相同,必须知道有关位移u_i及其时间导数的初始条件。它们的影响则可通过(38)和(39)向等能面转化,从而得到     

Dithienylethene-Based Single Molecular Photothermal Linear Actuator

By employing a mechanically controllable break junction technique, we have realized an ideal single molecular linear actuator based on dithienylethene (DTE) based molecular architecture, which undergoes reversible photothermal isomerization when subjected to UV irradiation under ambient conditions. As a result, open form (compressed, UV OFF) and closed form (elongated, UV ON) of dithienylethene-based molecular junctions are achieved. Interestingly, the mechanical actuation is achieved without changing the conductance of the molecular junction around the Fermi level over several cycles, which is an essential property required for an ideal single molecular actuator. Our study demonstrates a unique example of achieving a perfect balance between tunneling width and barrier height change upon photothermal isomerization, resulting in no change in conductance but a change in the molecular length, which results in mechanical actuation at the single molecular level.     

Intramolecular hydroamination of aminoalkynes with silver-phenanthroline catalysts

Intramolecular hydroamination of several aminoalkynes catalyzed by silver-phenanthroline complexes is reported. This catalyst system complements previous protocols by employing air- and moisture-stable complexes without compromising activity or reaction control. Some of the hydroamination products are subject to a useful aerobic oxidation. Silver-phenanthroline complexes have successfully demonstrated efficacy in the desymmetrization of a prochiral diyne.     

Binaural detection with narrowband and wideband reproducible noise maskers. III. Monaural and diotic detection and model results

A single-interval, yes-no, tone-in-noise detection experiment was conducted to measure the proportion of "tone present" responses to each of 25 reproducible noise-alone and tone-plus-noise waveforms under narrowband (100 Hz), wideband (2900 Hz), monotic, and diotic stimulus conditions. Proportions of "tone present" responses (estimates of the probabilities of hits and false alarms) were correlated across masker bandwidths and across monotic and diotic conditions. Two categories of models were considered; one based on stimulus energy or neural counts, and another based on temporal structure of the stimulus envelope or neural patterns. Both categories gave significant correlation between decision variables and data. A model based on a weighted combination of energy in multiple critical bands performed best, predicting up to 90% of the variance in the reproducible-noise data. However, since energy-based models are unable to successfully explain detection under a roving-level paradigm without substantial modification, it is argued that other variations of detection models must be considered for future study. Temporal models are resistant to changes in threshold under roving-level conditions, but explained at most only 67% of the variance in the reproducible-noise data.     

Development and application of a high-performance liquid chromatography method using monolithic columns for the analysis of ecstasy tablets

A rapid and selective HPLC method using monolithic columns was developed for the separation and quantification of the principal amphetamines in ecstasy tablets. Three monolithic (Chromolith RP18e) columns of different lengths (25, 50 and 100 mm) were assessed. Validation studies including linearity, selectivity, precision, accuracy and limit of detection and quantification were carried out using the Chromolith SpeedROD, RP-18e, 50 mm x 4.6 mm column. Column backpressure and van Deemter plots demonstrated that monolithic columns provide higher efficiency at higher flow rates when compared to particulate columns without the loss of peak resolution. Application of the monolithic column to a large number of ecstasy tablets seized in Ireland ensured its suitability for the routine analysis of ecstasy tablets.     

Azimuthal correlations and Bose Einstein effects in the reaction K+p → K+p2π+2π− AT 16 GeV/c

Azimuthal distributions between all possible particle pairs are studied in the reaction K⁺p → K⁺p2(π⁺π^?) at 16 GeV/c. It is shown that the hypothesis of uncorrelated transverse momenta at fixed rapidities of the final-state particles, is sufficient to describe the main features of the data. An interesting exception occurs for identical particle pairs where a genuine short-range correlation, attributed to Bose-Einstein symmetrization, is observed. The correlation length of this effect is shown to be related to the impact parameter distribution of the produced pions.     

Vibration of edge reinforced annular plates

The free transverse vibration of annular plates reinforced by circular rings along the simply supported outer and free inner boundaries is analyzed. A closed form solution is obtained by applying the appropriate forces, moments and motions of the circular edge-beams as boundary conditions on the differential equation for the free transverse vibration of plates. A study of the resulting natural frequencies compared with previous results for unreinforced edges indicates that edge-beams with even a relatively small stiffness have a significant effect upon the natural frequencies of the system.     

Novel Approaches to the Synthesis of Some Heterocycles Containing Nitrogen

Some syntheses of heretofore unknown pyrimidines, tetrahydroquinazolines, and quinazolines are described. These methods are uniquely simple one- or two-step reactions, general and versatile in scope, and give high yields. Some interesting chemistry associated with these heterocyclic systems is discussed.     

Energy-dissipation characteristics of steel tubes

This paper presents the results of an experimental investigation of the energy-dissipation characteristics of steel tubes subjected to large deformations under both quasistatic and impact diametrical loading conditions. Recently, such structural elements have been employed in the design of several impact attenuation systems used in highway-safety applications. The importance of considering the effects of different boundary conditions, strain-rate effects, and the influence of inertia in predicting the response of such systems is demonstrated. Under impact conditions it is shown that a cluster of such tubes is subjected to a shock wave which travels through the system. These experimental results compare favorably with numerical-structural shock-wave-theory predictions.