On relative stability of linear stationary feedback control systems with time delay

A method is presented whereby the absolute and relative stabilityof linear control systems containing transport lag can be determined.As a result feedback systems with variable time delay and loopgain, may be investigated in straightforward manner.     

Ultraviolet spectroscopic study of ferric equilibria at high chloride concentrations

The equilibria among the species Fe³⁺, FeCl²⁺, FeCl₂ ⁺, FeOH²⁺ and Fe(OH)₂ ⁺ have been examined by ultraviolet absorption spectroscopy. Our results indicate that previous workers have generally overestimated the stability constant of FeCl²⁺ and that the association of Fe³⁺ and Cl^– is predominantly inner sphere. The formation constant of FeOH²⁺ obtained in 0.68 m NaCl is in good agreement with our earlier results obtained in 0.68 m NaClO₄. Our results indicate that formation of FeOHCl⁺ is much less significant than has been previously reported. Molar absorptivities for the species Fe³⁺, FeCl²⁺, FeCl₂ ⁺ and FeOH²⁺ are reported for wavelengths between 220 and 400 nanometers.     

Quantitative Approximation by Fractional Generalized Discrete Singular Operators

Results in Mathematics - In this article, we study the fractional generalized smooth discrete singular operators on the real line, the univariate and non-univariate cases, regarding their...     

Investigating the effect of the zwitterion/lactone equilibrium of rhodamine B on the cybotactic region of the acetonitrile/scCO2 cosolvent

We investigated the effect of adding acetonitrile to supercritical carbon dioxide (scCO(2)) in the presence of rhodamine B. This spectroscopic investigation of the scCO(2)/acetonitrile, rhodamine B/scCO(2), and rhodamine B/acetonitrile interactions revealed that rhodamine B, which possesses a temperature dependent equilibrium between a zwitterionic form and a neutral form, had a strong affect on the cybotactic region. To confirm that this effect was only dependent upon the rhodamine B/acetonitrile interactions and not merely due to the bulk-phase behavior of the scCO(2), we measured the compressibility of the scCO(2)/acetonitrile mixture and found it to be independent of the acetonitrile concentration to less than approximately 0.047 mol fraction. We fit the compressibility data using the Peng-Robinson equation of state because it is most appropriate for fluids in the region between 1.72 and 12.45 MPa and between 313 and 333 K.     

Role of laser-induced plasma formation in pulsed cellular microsurgery and micromanipulation

We investigate experimentally the physical processes underlying pulsed cellular microsurgery and micromanipulation using nanosecond 532- and 1064-nm laser pulses focused at high numerical aperture. We find that the laser parameters employed for many microirradiation techniques are congruent with those leading to optical breakdown in water. We determine the size and shape of the laser-induced plasma, pressure of the emitted shock wave, and size and energy of the cavitation bubble formed by the expanding plasma. We discuss implications of the results for biophysical microirradiation procedures.     

Observation of quantum coherence in mesoscopic molecular magnets

By applying a transverse magnetic field B( perpendicular) of sufficient strength to the uniaxial molecular magnets Fe8 and Mn12, the tunneling splitting Delta(t) of their S = +/-10 magnetic ground states can be made large compared to perturbations such as hyperfine and dipolar interactions. We present evidence for such a Delta(t) from magnetic specific heat data below 1 K that is consistent with coherent quantum mechanical tunneling in a "mesoscopic" system under such conditions.     

不同岩蔷薇浸膏挥发性致香成分的SED-GC-MS分析研究

岩蔷薇(cistusladaniferusL.)又名赖百当(labdanum),属半日花科。利用其树脂分泌物及枝叶,通过蒸馏、浸提和萃取等方法,可制得岩蔷薇精油、浸膏、净油、油树脂等各种香原料品种。岩蔷薇的香原料制品是膏香类的极重要品种,主要应用于日化和食品行业,在烟草行业也多有应用。因香料烟香味的主要来源是类赖百当化合物的降解,故被归为烟草的五大类香味物质之一:赖百当类、双萜烯及其降解产物类。这类物质在香料烟中的含量较高,对形成香料烟的特殊香味风格具有重要意义,且在烟草中赖百当仅存在于香料烟中,烤烟、自肋烟中均不存在。赖百当类化合物是香料烟中特有的香气物质,主要成分是冷杉醇、赖百当烯二醇,经调制和醇化转化为多种降赖百当类化合物,其中降龙涎香醚、龙涎香内酯、脱氢龙涎香内酯等都具有强烈的龙涎香香气,对增进卷烟香气和吃味有很好作用。     

Ultraviolet spectroscopic study of ferric hydroxide complexation

Ultraviolet absorbance spectra of ferric ions in 0.68m NaClO₄ were studied as a function of pH at 4.0, 14.9, and 25.0°C. The results provided an evaluation of the stability constant for the formation of FeOH²⁺ which is *₁=[FeOH ⁺][H ⁺]/[Fe ³⁺]. The enthalpy change for the reaction Fe³⁺+H₂O FeOH²⁺+H⁺ was calculated as 10.0±0.3 kcal-mole^–1. Increasing temperature was also found to promote the reaction Fe³⁺+2H₂O Fe(OH) ₂ ⁺ +2H⁺. Our results were combined with the results of other to produce an expression describing the first hydrolysis equilibrium at ionic strengths between 0 and 3m and temperatures between 4.0 and 45.0°C at 1 atm total pressure. At 25°C and 0.68m the ionic strength *₁=1.90×10^-3     

Fluoride in sea water: intercalibration study based on electrometric and spectrophotometric methods

Fluoride was shown to be a conservative constituent of sea water. Samples from the eastern tropical North Pacific, the Caribbean, the Labrador Basin, and the Reykjanes Ridge region indicated that the most probable $\text{F}\text{Cl}$ ratio in sea water is 6.71·10^-5 with an overall uncertainty of ±0.07·10^-5 based on 99% confidence limits of ±0.02·10^-5 and an allowance of ±0.05· 10^-5 for systematic error. Double-blind measurements from laboratories using electrometric and spectrophotometric methods agreed closely. Mean $\text{F}\text{Cl}$ ratios found were all within 0.7% of the most probable value.