A benchmark-learning roadmap for regional sustainable development in China

Journal of the Operational Research Society - Serious environmental problems have accompanied China's remarkable economic growth for decades, which also have direct and indirect impacts on its...     

An EOQ model with process reliability considerations

The classical economic order quantity (EOQ) model assumes that items produced are of perfect quality and that the unit cost of production is independent of demand. However, in realistic situations, product quality is never perfect, but is directly affected by the reliability of the production process. In this paper, we consider an EOQ model with imperfect production process and the unit production cost is directly related to process reliability and inversely related to the demand rate. In addition, a numerical example is given to illustrate the developed model. Sensitivity analysis is also performed and discussed.     

When electron exchange is chemical exchange-assignment of 1H NMR spectra of paramagnetic cobalt(II)-2,2':6'2''-terpyridine complexes

Electron exchange between [Co(terpy)2]3+ and [Co(terpy)2]2+ can be monitored by 1H NMR exchange spectroscopy and allows the cobalt(II) spectra to be fully assigned.     

Mass spectra of N-substituted cantharidinimides

The mass spectra of a series of N-substituted cantharidinimides were examined. The feature of this series compounds is a sequential double hydrogen transfer from the oxabicycloheptane unit to either the carbonyl group of the succinimide unit or the nitrogen atom of the pyridyl or thiazolyl substituent through space. The ability of the N-substituent to accept a hydrogen atom possibly leads to the different fragmentation pathway.     

Relation between steady shear flow and dynamic rheology

Summary The relationships between steady shear flow and dynamic rheology are investigated at relatively high shear rates and frequencies. A useful empirical relationship in this region predicts that the magnitude of the complex dynamic viscosity | ^*| should be compared with the shear viscosity at equal values of frequency and shear rate (Cox-Merz-rule). Polystyrenes (PS) and Polyacrylamides (PAAm) have been investigated over a wide range of concentration and molecular weight. Only in case of PAAm/H₂O solutions we have found that the results do not coincide with Cox-Merz-rule. As far as we know this is the first time that deviations from Cox-Merz-rule were observed in a homogeneous system. A molecular interpretation is given.

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Zusammenfassung Die Beziehung zwischen der Scherviskosität und der komplexen (dynamischen) Viskosität bei relativ hohen Schergeschwindigkeiten und Frequenzen wurde untersucht. Eine geeignete empirische Beziehung in diesem Bereich sagt aus, daß der Betrag der komplexen Viskosität | ^*| mit der Scherviskosität bei gleichen Werten von Frequenz und Schergeschwindigkeit vergleichbar ist (Cox-Merz-Regel). Polystyrole (PS) and Polyacrylamide (PAAm) wurden über einen weiten Bereich der Konzentration und des Molekulargewichts untersucht. Nur im Fall der PAAm/H₂O-Lösungen wurden Abweichungen von der Cox-Merz-Regel gefunden. Soweit uns bekannt, ist es das erste Mal, daß Abweichungen von der Cox-Merz-Regel in einem homogenen System gefunden wurden. Eine molekulare Erklärung wird gegeben.

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Presented at the IUPAC 26^th International Symposium on Macromolecules, Mainz, September 17–21, 1979.

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With 4 figures and 1 table     

Hydrogels based on carboxymethyl cassava starch cross-linked with di- or polyfunctional carboxylic acids: Synthesis, water absorbent behavior and rheological characterizations

Carboxymethyl cassava starch (CMS) was synthesized and its hydrogels were prepared by cross-linking it with di- or polyfunctional carboxylic acids using glutaric (CASXGLU), suberic (CASXSUB), pimelic (CASXPIM) and butanetetracarboxylic acids (CASBTC) as the cross-linkers. The characterization of the CMS showed that its degree of substitution was 0.86, average molar mass (M_w) was 5.6 × 10⁶ g mol⁻¹ and the ¹³C NMR showed strong peak at δ = 180.42 ppm which was assigned to the CO carbon in the carboxymethyl group. The absorption under load (AUL) and free swelling capacity (FSC) studies showed that the hydrogels have fast swelling properties and that they reached equilibrium after 1 h. Furthermore, all the hydrogels were sensitive to the increasing salt concentrations and pH of the medium. Both AUL and FSC reduced in saline solution while their values increased in alkaline buffer solutions. The result indicate that the difunctional carboxylic acids produced hydrogels with stronger material functions compared with the polyfunctional carboxylic acid and the order of increases in both AUL and FSC was CASXBTC, CASXPIM, CASXSUB and CASXGLU.     

Oligo(fluorenyleneethynylenegermylene)s and their metallopolymers

Oligo(fluorenyleneethynylenegermylene)s and their polyplatinynes are synthesized and photophysically characterized; inclusion of heavy germylene bridges greatly boosts the phosphorescence decay rate in metallopolymers.     

Viscoelastic properties of liquid crystals of aqueous biopolymer solutions

The formation of aqueous, lyotropic phases of the biopolymers xanthan (M = 1.6·10⁶) and schizophyllan (M _W = 335 000) is investigated with stationary shear flow and oscillatory measurements, as well as with the aid of polarization microscopy, because these polymers show very different viscoelastic properties from coiled vinyl polymers. Xanthan and schizophyllan exhibit the same typical behavior observed in anisotropic solutions when the viscosity is plotted as a function of concentration and of shear rate. It has also been observed that the first normal stress difference for concentrated xanthan solutions shows a saturation effect at increasing shear rate. In oscillatory measurements only schizophyllan exhibits an maximum for the storage modulus. The absence of a such an elasticity maximum in the case of the xanthan solution may be attributed to the significantly higher flexibility of the xanthan helix. A comparison of the critical concentrations calculated according to Flory's theory and the experimentally determined values shows that the two-phase region is distinctly broader than the theory predicts. This deviation cannot be attributed to the flexibility of the polymer, but can, however, be explained by intermolecular interactions. In contrast to the non-charged schizophyllan the polyelectrolyte xanthan is affected in addition to the attractive interactions (H-bonds) by electrostatic repulsion forces.This paper was partly presented at the 198th ACS National Meeting in Miami Beach, Florida, Sept. 10–15, 1989 .