臭氧强化电絮凝处理直接耐晒大红4BS模拟染料废水

采用臭氧强化电絮凝法处理直接耐晒大红4BS模拟染料废水,研究了染料脱色的影响因素及其COD_Cr去除动力学。考察了电流密度、溶液初始pH 值、染料初始浓度、支持电解质浓度、反应温度和臭氧流量对臭氧强化电絮凝法处理4BS染料脱色效率的影响。结果表明,电流密度15 mA·cm^-2,pH值10.0,4BS染料初始浓度100 mg·L^-1,支持电解质浓度3000 mg·L^-1,臭氧流量06 L·h^-1,20 ℃下反应50 min后4BS脱色率达94％以上。COD_Cr去除符合拟二级动力学。     

Canonical Orderings of Hexagons That: (1) Nearly Meet the Intent of Patterson's Nomenclature Rules and (2) Orient a Molecule for Purposes of Assigning a IUPAC Name

A nomenclature technique developed earlier by the author is expanded to produce an ordering of hexagons that nearly meets the original intent of Patterson's nomenclature rules in organic chemistry for a system of polycyclic aromatic hydrocarbons formed using only benzene modules. The result desired is a simple systematic method which orients a figure formed by the fusion of regular hexagonal rings so that, first, there is a maximum number of rings on a horizontal line and, second, that as many of the remaining rings as possible are above and to the right of this horizontal reference line. In the process of trying to formulate such a system, problems that are inherent in interpreting the intent of Patterson's rules and in pragmatically implementing these rules are examined. Furthermore, a minor modification of the technique produces a canonical orientation of a long molecule which can then be used to formulate the I.U.P.A.C. name for this molecule.     

The α and β structural forms of poly(tetramethylene terephthalate): a study by broad line nuclear magnetic resonance

Broad line nuclear magnetic resonance measurements have been carried out on oriented poly(tetramethylene terephthalate). The second moment was determined as a function of specimen orientation for the polymer in its unstrained state, and also under extension, where previous X-ray diffraction measurements have shown that the crystal structure changes from the α form (relaxed) to the β form (strained). The n.m.r. results for the stretched specimen are consistent with the molecular conformation being close to full extension, and agree quantitatively with the crystal structure proposed by Hall and Pass. The n.m.r. results for the unstrained material are, however, not in agreement with any of the crystal structures which have been proposed and suggest that, contrary to present conclusions, the conformation and orientation of the central methylene pairs in the glycol residue must remain substantially unchanged in the transformation from the α to the β form.     

Consideration of reaction mechanisms leading to pyrolytic carbon of different textures

A distinction between a growth and a nucleation mechanism is not sufficient to draw direct conclusions in relation to the texture of pyrolytic carbon. This is determined by the carbon formation mechanisms, which are analogous or at least similar to the mechanisms of aromatic growth. The latter mechanisms are reviewed in the first part of the paper with special consideration of structural chemical aspects. The relevance of the individual mechanisms is analyzed in the second part based on experimentally determined reaction products. Most important mechanisms are aryl-aryl combination, intramolecular dehydrocyclization and ethine addition reactions. The influence of mechanisms concerning an inhibition of the formation of five-membered rings and a transformation of five- into six-membered rings is difficult to estimate. The results indicate that a high textured carbon is formed from a gas phase exhibiting an optimum ratio of aromatic to small linear hydrocarbons (ethine). This model is called the particle-filler model (aromatic hydrocarbons: molecular particles; ethine: molecular filler).     

On the Theory of NMR Line Shapes in Amorphous Regions of Uniaxially Oriented Polymers

Abstract

A theory of NMR of protons belonging to highly-stretched polymer chains with fixed ends, e.g. tie molecules of amorphous regions of oriented semicrystalline polymers, is presented. Analysis is carried out in terms of the model of freely-jointed chains. All contributions to the line shape from the intramolecular dipole-dipole interactions (DDI) are taken into account. Expressions are derived for the residual time independent component of DDI and the second moments of the fluctuating DDI. The NMR spectra are described in terms of the Anderson-Weiss approximation. A number of spectra are calculated for polyethylene. It is shown that the linewidth of high lemperature spectrum rapidly grows with stretching and approaches that of crystallite polymer. It is demonstrated that the distribution function of tie molecules can, in principle, be obtained from the dependence of the spectra on the stretching ratio.     

絮凝剂对磷酸料浆沉降分离性能影响的实验研究

介绍了湿法磷酸料浆在加入不同剂量的聚丙烯酰胺时的重力沉降性能,通过比较A、B两种聚丙烯酰胺对实验料浆沉降性能的影响,得出的结论是:当加入B型聚丙烯酰胺,加入量为10ppm时,该料浆的沉降性能较好,且温度宜控制在60℃左右。实验结果对提高湿法磷酸料浆的分离效率以及分离机械的选型都具有重要的指导意义。     

A model for the C5a receptor and for its interaction with the ligand

A printer's error was introduced into the title of this articlewhen it was in press. The correct title is as follows. A model for the C5a receptor and for its interaction with theligand^* An omission was also made on the second line of the first columnon page 769. This and the subsequent four lines should readas follows. pairing of Cys86(B) with Cys109(C) or Cys285(G), but stronglysuggest that with either Cys293 or Cys294(G). A choice can bemade with arguments given below. Pairing with Cys285(G), forinstance, would require a vertical relative shift of two helixturns which would immerse polar side chains in the membrane.     

A study of residence time distribution in co‐rotating twin‐screw extruders. Part II: Experimental validation

In the first part of this paper, a new approach to model the residence time distribution (RTD) in a co‐rotating twin‐screw extruder was proposed. It consists of coupling a continuum mechanics approach with a chemical engineering one, yielding an RTD curve without any fitting parameter. However, the choice of ideal reactors that depict the behavior of each particular profile is not evident. In this second part, we present an experimental study based on two types of extruder (Leistritz 30–34 and Clextral BC45), different screw profiles and two measurement techniques (off‐line and in‐line). Global, partial and local RTD curves were obtained, both experimentally and by means of a deconvolution technique. This series of experiments permitted the definition of the best association between ideal reactors and screw elements. Using this association, a comparison has been made between experimental results and theoretical calculations. A good agreement was generally obtained in terms of the RTD shape, delay time, mean residence time and variance.     

Synthesis of derivatives of Naphtol AS containing polar groups and modification used for C.I. Pigment Red 57

The synthesis of derivatives of Naphtol AS containing polar groups (–COOH, –SO₃H) and factors affecting the reaction have been studied. Four derivatives of Naphtol AS containing –COOH or –SO₃H groups in the 3- or 4- position of the phenyl ring were synthesized. Derivatives of Naphtol AS as the second coupling component were used in mixed coupling and the effect of its added amount on the colour strength, hue, flowability and dispersing extent (in water) of pigments was studied.     

E.p.r. study of reduced and reductively ethylated coals

Two coals (78 and 85 wt % C) were reduced with potassium in tetrahydrofuran in the presence of naphthalene and also ethylated with ethyl iodide. The e.p.r. spectra of the coals and products consisted of two components: a narrow and a broad line. Both reduction and ethylation led to a decrease in concentration of paramagnetic centres; quenching was greater in centres related to the broad line component. A mechanism for the quenching is suggested.     

Injection and stabilization of mesophase pitch in the fabrication of carbon-carbon composites. Part I. Injection process

The fabrication of carbon-carbon composites by injection of low viscosity mesophase pitch through a fiber preform followed by stabilization and carbonization was examined. The fully transformed mesophase MOMP and AR pitches were injected through either soft or rigidized disk preforms 35 mm thick and 68 mm in diameter. Injection provided good even filling of major flow channels and fiber bundles. Flow-induced fibrous microstructures were retained by quenching and preserved by stabilization upon carbonization. A second injection cycle was effective in filling voidage created by thermal densification. A third cycle was applied, but required severe injection conditions and provided only incremental improvement. The carbon-carbon composite reached a density of 1.8 g/cm³ after three injection cycles.     

西气东输二线管道工程高压线穿越施工研究与探讨

探讨了西气东输二线东26标段GD033--GD034桩之间的管道横穿500 k V高压线施工的选择与研究,针对施工现场实际情况,通过方案必选提出该地段施工方案和施工质量安全保障措施。     

A broad line n.m.r. study of oriented poly(vinylidene fluoride)

Broadline nuclear magnetic resonance measurements have been carried out for the proton resonance in oriented poly(vinylidene fluoride). The spectra in general show two component lines with distinctly different line widths. The broad component shows a high degree of molecular orientation and can be satisfactorily assigned to the crystalline regions of the polymer. The narrow component corresponds to an oriented non crystalline phase which is sufficiently constrained to allow motion about the chain axis only. An appreciable decrease in the value of the rigid mass fraction was observed in both of the samples over the temperature range examined. Our calculations indicate that this could play an important role in the temperature dependence of the pyroelectric response of this material.     

Comparison of g.p.c. elution characteristics and diffusion coefficients of asphaltenes

A theoretical analysis of configurational effects on exclusion chromatography (g.p.c.) and diffusion rates of macromolecules is used to interpret data for the diffusion coefficients of petroleum-derived asphaltenes in tetrahydrofuran at 25 °C. If the asphaltene constituents are considered to be rigid, disc-like molecules, the theory and experiments are consistent in that both show the asphaltene diffusion coefficients to be smaller than those of g.p.c.-equivalent polystyrenes. Two conclusions result from this work: (1) polystyrene is not a good molecular model for predicting the diffusional characteristics of asphaltenes; and (2) there is a broad variation (by a factor of ten) of diffusion coefficients among the constituents of one asphaltene extract.     

Voltammetric behaviour of iron in cement. III. Comparison of iron versus reinforcing steel

The cyclic voltammetric behaviour of reinforcing steel in cured Portland cement paste was investigated and compared with that of pure iron. The cyclic volammetric behaviour of reinforcing steel in cement is very similar to that reported earlier for iron in cement, both with and without NaCl and NaNO₂ (a corrosion inhibitor) additions. This similarity confirms that the results and conclusions obtained using iron are also applicable to the behaviour of reinforcing steel. A useful method for determining true surface areas of iron or steel electrodes by linear sweep voltammetry also is described in detail.     

Hierarchical control of a train of continuous polymerization reactors

A multilayer control scheme is synthesized for a series of polymerization stirred tank reactors to control the monomer conversion over the reactor line. In this work two layers of control are implemented. In the' first level digital PI or self-tuning regulators (STR) are used to control the reaction temperature of each reactor in the series by manipulating the flowrates of the coolant streams. In the second layer, a locally linear state space model, that can predict the monomer concentration in each reactor, is derived based on steady-state energy balances. A quadratic performance index is then minimized to obtain the optimal reaction profile that will bring the monomer distribution over the reactor line to its desired target value.     

A 13C-n.m.r. study of radiation-induced racemization in isotactic polypropylene

Unexpectedly large changes in the stereochemistry of isotactic polypropylene have been observed by ¹³C-n.m.r. following γ-irradiation at 25°C up to 250 kGy. The observed G-value of 64 for the loss of isotactic triads is much higher than previously reported G-values for scission, crosslinking or hydrogen formation in irradiated polypropylene. A mechanism of initial chain scission, racemization and subsequent recombination is indicated. The pattern of pentad sequences is inconsistent with the occurrence of isolated random racemization events; this suggests that the energy released on recombination promotes a second racemization within a range of 1–3 monomer units.