Molecular simulation of alkene adsorption in zeolites

The adsorption isotherms of various alkenes and their mixtures in zeolites such as silicalite-1 (MFI-type), theta-1 (TON-type), and deca-dodecasil 3R (DDR-type) were calculated using the grand canonical Monte Carlo (GCMC) approach. Additionally, the adsorption of alkene–alkane mixtures was simulated. The GCMC approach was combined with the configurational-bias Monte Carlo (CBMC) method. Effective Lennard–Jones parameters for the interaction between the oxygen atoms of all-silica zeolites and the sp²-hybridized groups of linear alkenes were determined using a united atom force field. They were adjusted to the experimental adsorption data of silicalite-1 (MFI). The inflection behaviour of the 1-heptene isotherm was investigated in detail. It is shown that, in the inflection region, the 1-heptene molecules alter their end-to-end length depending on their location. The occurrence of a maximum in the mixture adsorption isotherms is attributed to two effects: entropic effects and non-ideality effects. From the mixture simulations some general conclusions concerning the separation of hydrocarbons with silicalite-1 can be drawn. The transferability of the Lennard–Jones parameters to other zeolites was investigated. Simulations of adsorption isotherms in the zeolites theta-1 and DD3R and their comparison with experimental data indicate the possibility of transferring the parameters to other all-silica zeolites.     

Whistles of small groups of Sotalia fluviatilis during foraging behavior in southeastern Brazil

Whistle emissions were recorded from small groups of marine tucuxi dolphins (Sotalia fluviatilis) in two beaches located in an important biological reserve in the Cananéia estuary (25 degrees 03'S, 47 degrees 58'W), southeastern Brazil. A total of 17 h of acoustic data was collected when dolphins were engaged in a specific feeding foraging activity. The amount of 3235 whistles was recorded and 40% (n=1294) were analyzed. Seven acoustic whistle parameters were determined: duration (ms), number of inflection points, start and end frequency (kHz), minimum and maximum frequency (kHz), and frequency range (kHz). Whistles with up to four inflection points were found. Whistles with no inflection points and rising frequency corresponded to 85% (n=1104) of all analyzed whistles. Whistle duration varied from 38 to 627 ms (mean=229.6+/-109.9 ms), with the start frequency varying between 1 and 16 kHz (mean=8.16+/-3.0 kHz) and the end frequency between 2 and 18 kHz (mean=14.35+/-3.0 kHz). The importance of this study requires an accurate measurement of the whistles' emissions in an unusual foraging feeding behavior situation on two beaches where several tucuxis, mostly mother-calf pairs, are frequently present. These two beaches are located in a federal and state environment Environmental Protected Area threatened by the progressive increase of tourism.     

X射线法测量的ICF靶丸参数的图像分析

 在ICF靶丸参数测量中，采用接触X射线显微辐射照相法获得靶核的X射线吸收底片图像，将该底片放置于显微镜下并用CCD获得了数字化图像。基于该数字化图像信息，编写了一套完整的计算机算法来计算靶参数。采用辐向平均法标定出靶中心，采用图像强度函数对半径的二阶微分来确定出靶层分界位置，计算精度约为0.2pixels。     

Non-homogeneous SiGe-on-insulator formed by germanium condensation process

Ge condensation process of a sandwiched structure of Si/SiGe/Si on silicon-on-insulator （SOI） to form SiGe-on- insulator （SGOI） substrate is investigated. The non-homogeneity of SiGe on insulator is observed after a long time oxidation and annealing due to an increased consumption of silicon at the inflection points of the corrugated SiGe film morphology, which happens in the case of the rough surface morphology, with lateral Si atoms diffusing to the inflection points of the corrugated SiGe film. The transmission electron microscopy measurements show that the non-homogeneous SiGe layer exhibits a single crystalline nature with perfect atom lattice. Possible formation mechanism of the non-homogeneity SiGe layer is presented by discussing the highly nonuniform oxidation rate that is spatially dependent in the Ge condensation process. The results are of guiding significance for fabricating the SGOI by Ge condensation process.     

Characteristics of whistles from rough-toothed dolphins (Steno bredanensis) in Rio de Janeiro coast, southeastern Brazil

There is no information about the whistles of rough-toothed dolphins in the South Atlantic Ocean. This study characterizes the whistle structure of free-ranging rough-toothed dolphins recorded on the Rio de Janeiro coast, southeastern Brazil, and compares it to that of the same species in other regions. A total of 340 whistles were analyzed. Constant (N = 115; 33.8%) and ascending (N = 99; 29.1%) whistles were the most common contours. The whistles recorded had their fundamental frequencies between 2.24 and 13.94 kHz. Whistles without inflection points were frequently emitted (N = 255; 75%). Some signals presented breaks or steps in their contour (N = 97; 28.5%). Whistle duration was short (347 ± 236 ms and 89.7% of the whistles lasted <600 ms). Seventy-eight whistle contour types were found in the total of whistles analyzed, and 27 (7.9%) of these occurred only once. Most of the whistle types were unique to a particular recording session (N = 43). The signals emitted by the rough-toothed dolphins in southeastern Brazil were characterized by low frequency modulation, short duration, low number of inflection points, and breaks. Differences in the mean values of the whistle parameters were found between this and other studies that recorded Steno bredanensis, but as in other localities, whistles above 14 kHz are rare.     

Experimental simulation of hydrodynamic flow noises in an autonomous marine laboratory

The spectral characteristics of turbulent pressure pulsations arising from the flow around an autonomous marine laboratory have been measured. The autonomous marine laboratory is an upgraded Dolphin buoyant device, equipped with modern digital facilities for autonomous recording, which extends the frequency range of the signals under study up to 50–60 kHz. The power spectra and cross spectra of turbulent pressure pulsations have been measured at different points of the measuring section by point pressure transducers 1.3 or 20 mm in diameter at a speed of the autonomous marine laboratory of 8–22 m/s. The measurements have revealed unexpected behavioral features of the spectra (their inflection points) at high frequencies. An analysis is performed to explain these features. In particular, it is shown that the correction function based on the more complex cross spectrum model (in comparison with the Corcos cross spectrum model) developed by Smol’yakov in 2006 predicts a monotonic (without inflection points) decrease in the spectral levels at high frequencies for reconstructed (corrected) spectra.     

立式升温型溴化锂吸收式热泵的设计与变工况研究

本文对立式升温型溴化锂吸收式热泵循环和各部件建立了数学模型,并设计了85℃热水驱动产110℃热水的立式降膜升温型溴化锂吸收式热泵,吸收器输出功率为50 kW。然后对其在热源热水温度和流量变化、冷却水入口温度和流量改变等非设计工况下的工作特性进行了计算与分析研究,得到变工况对于机组性能系数,效率和机组负荷的影响关系图。发现在我们的研究范围内,热源水参数的变化对机组性能的影响要大于冷却水。并且在热源水参数变化过程中,机组性能存在性能急剧变化的拐点,实际运行中应当避免。     

Effect of electron irradiation on the oxidation of indium

The oxidation kinetics of indium is studied for two cases, namely, during continuous electron irradiation (E _p = 1800 eV) and without electron irradiation, as a function of the time of exposure to an oxygen medium at a partial oxygen pressure of 10⁻⁴ Pa and room temperature. The initial oxygen exposure was 50 L. The kinetic curves recorded upon continuous electron irradiation have two inflection points, and they can be attributed to the following three states of oxidation: physical adsorption, chemisorption with the formation of a nonstoichiometric oxide layer, and the growth of a homogeneous oxide layer. Only the first inflection point is observed during oxidation without electron irradiation, and further exposure does not lead to the second inflection point within the experimental time.     

Superfluidity and magnetism in multicomponent ultracold fermions

We study the interplay between superfluidity and magnetism in a multicomponent gas of ultracold fermions. Ward-Takahashi identities constrain possible mean-field states describing order parameters for both pairing and magnetization. The structure of global phase diagrams arises from competition among these states as functions of anisotropies in chemical potential, density, or interactions. They exhibit first and second order phase transition as well as multicritical points, metastability regions, and phase separation. We comment on experimental signatures in ultracold atoms.     

On the characteristics of solar activity and galactic cosmic ray intensity at the solar cycle maximum and inflection points

The correlation between the characteristics (sunspot area and galactic cosmic ray intensity) at inflection points and at the solar cycle maximum is discussed. Probable characteristics in the forthcoming maximum of cycle 24 are considered.     

Statistical properties of a wave with random frequency modulation in a dispersive medium

The probability distributions of frequency, intensity, and other parameters of a wave with random frequency modulation propagating in a dispersive medium are determined and studied. In particular, the probability distributions for photon density are found for the limiting cases of linear and quadratic medium dispersion characteristics. It is demonstrated that in the latter case the photon density probability distribution has a singularity produced by the absence of time focusing of the wave in the vicinity of dispersion curve inflection points. The statistics of wave frequency in a multifrequency regime are considered in detail.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 12, pp. 1797–1802, December, 1978.The authors thank A. N. Malakhov for his interest in the study.     

Kinetics of stimulated polariton scattering in planar microcavities: evidence for a dynamically self-organized optical parametric oscillator

Strong temporal hysteresis effects in the population kinetics of pumped and scattered lower polaritons (LPs) have been observed in a planar semiconductor microcavity under a nanosecond-long pulsed resonant excitation (by frequency and angle) near the inflection point of the LPs' dispersion. The hysteresis loops have a complicated shape due to the interplay of two instabilities. The self-instability (bistability) of the nonlinear pumped LP is accompanied by a strong parametric instability which causes an explosive growth of the scattered LPs' population over a wide range of wave vectors. Finally, after a 30-500 ps period, a three-mode scattering pattern forms, thereby demonstrating a dynamically self-organized regime of the optical parametric oscillator. Stability is maintained by the presence of numerous weak "above-condensate" modes; the whole system therefore appears to be highly correlated.     

Global Rainbow Thermometry for Mean Temperature and Size Measurement of Spray Droplets

Global rainbow thermometry is a new technique for measuring the average size and temperature of spray droplets. For data inversion a global rainbow pattern is employed, which is formed by constructive interference of laser light scattered by an ensemble of spherical droplets. The non‐spherical droplets and liquid ligaments provide a uniform background and hence do not influence the interference pattern from which average size and temperature are derived. This is a large improvement with respect to standard rainbow thermometry, investigated since 1988, which is strongly influenced by particle shape. Moreover, the technique is applicable to smaller droplets than the standard technique because the global pattern is not spoiled by a ripple structure. Data inversion schemes based on inflection points, minima and maxima are discussed with respect to spray dispersion and droplet flux. The temperature derivation from inflection points appears to be independent of spray dispersion. Preliminary measurements in a heated water spray are reported. The mean diameter obtained from the rainbow pattern is smaller than the arithmetic mean diameter measured by phase‐Doppler anemometry. The accuracy of the temperature measurement by global rainbow thermometry is shown to be a few degrees Celsius.     

Morphology and Growth of Single Crystals of Isotactic Polypropylene from the Melt

Isolated single crystals of isotactic polypropylene (iPP) grown from the melt were studied by optical microscopy and atomic force microscopy (AFM). The single crystals had a well-known rectangular shape when crystallized at high temperatures (T_c) above 155°C. The width increased with decreasing T_c, and the shape became hexagonal below 130°C. The single crystals were sectored with thickness difference between them. The growth rate along the a*-axis, G_a*, agreed well with the growth rate of spherulites, as expected. G_a* had two inflection points on the plots against (TΔT)^?1. The lower temperature inflection corresponds to the regime II-III transition, and the higher temperature one is accompanied by an inflection of the growth rate in the b-axis direction, G_b, which has been measured for the first time. The inflection of G_b at the lower inflection temperature of G_a* was much smaller than that of G_a* and may not exist. The crystals are basically surrounded with flat surfaces and no indications of kinetic roughening in the regime III were recognized in the AFM images. The inflections of G_a* and G_b caused a complicated shape change of the aspect ratio, having a minimum at around 135°C.     

Gedanken experiments at high-order approximation: nearly extremal Reissner-Nordström black holes cannot be overcharged

Phenomenologically interesting scalar potentials are highly atypical in generic random landscapes. We develop the mathematical techniques to generate constrained random potentials, i.e. Slepian models, which can globally represent low-probability realizations of the landscape. We give analytical as well as numerical methods to construct these Slepian models for constrained realizations of a full Gaussian random field around critical as well as inflection points. We use these techniques to numerically generate in an efficient way a large number of minima at arbitrary heights of the potential and calculate their non-perturbative decay rate. Furthermore, we also illustrate how to use these methods by obtaining statistical information about the distribution of observables in an inflationary inflection point constructed within these models.     

On the most accurate measurements of the wavelengths of X-ray spectral lines

The paper discusses the influence of statistical errors in measuring the intensity of a spectral line on the exact determination of its wavelength. Using simplifying assumptions, it is shown that the relative error in measuring the wavelengths of spectral lines of the same type, caused by the statistical character of X-ray intensity measurements and by the influence of the true width of the spectral line, is practically constant under the same conditions, i.e. it is independent of the lattice parameters of the crystals used and of the wavelength of the spectral line. It seems that the latest exact measurements of Bearden confirm this result.The greatest care should therefore be devoted to the neighbourhood of inflection points of the curve representing the spectral line profile when making exact measurements of the spectral position of the lines.The author heartily thanks Professor M. A. Blochin for valuable remarks on this work.     

基于宽频带温度脉动仪的大气温度起伏谱测量

常用温度脉动仪测量湍流的频谱, 频谱范围多在20Hz以下, 无法呈现大气温度起伏的高频特征。介绍一种宽频带低噪声温度脉动仪的设计方法, 研制出相应的仪器, 并进行了真实大气温度起伏测量实验。结果表明, 大气温度起伏具有丰富的高频信息, 温度起伏功率谱在更宽的频率范围内存在幂率不变性, 部分温度谱在高频部分出现拐点, 以更陡的幂率下降, 湍流谱的形状以及拐点出现的位置和湍流强度有一定的关系。拓宽了温度起伏功率谱的研究范围, 为光波传输的理论研究和技术应用提供了高频湍流谱信息, 为非Kolmogorov湍流研究提供了测量手段。     

Convexity and tadpoles

We show that it is possible to produce a convex effective potential using the tadpole method of calculation, both at zero temperature and in real time finite-temperature quantum field theory. We point out, however, that this does not evade the failure of the loop expansion in a theory with a non-convex classical potential at a temperature where the minima of the effective potential have moved in to the classical points of inflection.     

Nonuniversal ordering of spin and charge in stripe phases

We study the interplay of topological excitations in stripe phases: charge dislocations, charge loops, and spin vortices. In two dimensions these defects interact logarithmically on large distances. Using a renormalization-group analysis in the Coulomb-gas representation of these defects, we calculate the phase diagram and the critical properties of the transitions. Depending on the interaction parameters, spin and charge order can disappear at a single transition or in a sequence of two transitions (spin-charge separation). These transitions are nonuniversal with continuously varying critical exponents. We also determine the nature of the points where three phases coexist.     

Search for a reliable methodology for PSD determination based on a combined molecular simulation-regularization-experimental approach: The case of PHTS materials

We present here a methodology for searching a robust pore size distribution (PSD) for adsorbent materials. The method is based on a combination of individual adsorption isotherms, obtained from Grand Canonical Monte Carlo simulations, a regularization procedure to invert the adsorption integral equation (Tikhonov regularization solved by singular value decomposition), and the needed experimental adsorption isotherm. The selection of several parameters from the available choices to start the procedure are discussed here: the size of the kernel (number of individual pores and number of experimental adsorption points to be included), the fulfillment of the Discrete Picard condition, and the L-curve criteria, all leading to find a reliable and robust PSD. The procedure is applied to plugged hexagonal templated silicas (PHTS), synthesized, and characterized in our laboratory.