EFFECTS OF SOME PHENYLETHYNYLSILICON COMPOUNDS ON HEAT-CURABLE SILICONE RUBBER Ⅲ 1, 1, 3, 3-TETRAMETHYL-1, 3-DIPHENYLETHYNYL-DISILOXANE

We have shown that some phenylethynylsilicon compounds are good cure crosslinkersof heat-curable silicone rubber(HCSR). In this paper the effects of 1, 1, 3, 3-tetramethyl-1, 3-diphenylethynyldisiloxane (TMDPDS) as a crosslinker on HCSR were studied. Thevulcanizates with fine mechanical properties could be obtained with suitable amounts ofTMDPDS. Sol fractions, and crosslinking density of vulcanizates and vulcanizationretardation effect of TMDPDS on hydrosilation curing silicone rubber were also discussed.

EFFECIS OF TEMPERATURE AND OVERLOAD RETARDATION ON CORROSION FATIGUE CRACK GROWTH OF HIGH STRENGTH STEEL

The fatigue crack growth rate (CGR) of ultra high strength steel 30CrMnSiNi2A in distilled water at 18,35 and 55℃ were measured.It was confirmed that the temperature is strongly af- fected on the corrosion fatigue CGR of ultra high strength steel.An expression concerning the effects of Δ K and temperature on the CGR was proposed.The fact that the apparent activation energy (36.6 kJ/mol) resulted from regressive analysis of CGR data was similar to the activation energy of hydrogen diffusion in γ-Fe,strongly supporting the theory of hydrogen-assisted crack growth.The overload retardation effect was greatly reduced in cor- rosion fatigue crack growth,especially at lower frequency,e.g.,0.1 Hz.This phenomenon might be due to the increase of the SCC component of CGR after an overload.

Effect of the lenticles on moisture migration in capillary zone of tailings dam

Small-particle interlayers(lenticles)show some characteristic hydraulic properties and can affect the movement of unsaturated water.In this study,we developed a novel online capillary-water-absorption monitoring device and conducted three groups of comparison tests to simulate lenticle positions and thicknesses with respect to the capillary rise.The results show that the characteristic wetting front exhibits a fast rise in the early stage,a slow rise in the middle stage,and stability in the later stage.The motion of the capillary water in the lenticle is mainly transversal,with the upward curve being"flat,"and the longer is"flat,"the longer is the time needed for the water to move.The interlayer can form a capillary stagnation zone with moisture content close to saturation.The high interlayer may form a discontinuous corrugated capillary zone.Thus,when the wetting front reaches the"coarse-grain(lower)-fine-grain(upper)"interface,the"anti-capillary barrier effect"results in more moisture in the upper layer.Thus,when the wetting front of the capillary water reaches the"fine-grain(upper)-coarse-grain(lower)"interface,the"capillary barrier effect"causes the moisture content of the upper tailings to decreases sharply because of the horizontal movement of the water in the fine medium.It is clear that the presence of lenticles can retard the rise of capillary water by storing water.

Investigation of the effects of humic acid and H_(2)O_(2) on the photocatalytic degradation of atrazine assisted by microwave

A solution of atrazine in a TiO_(2)suspension,an endocrine disruptor in natural water,was tentatively treated by microwave-assisted photocatalytic technique.The effects of mannitol,oxygen,humic acid,and hydrogen dioxide on the photodegradation rate were explored.The results could be deduced as follows:the photocatalytic degradation of atrazine fits the pseudo-first-order kinetic well with k=0.0328 s–1,and·OH was identified as the dominant reactant.Photodegradation of atrazine was hindered in the presence of humic acid,and the retardation effect increased as the concentration of humic acid increased.H_(2)O_(2)displayed a significant negative influence on atrazine photocatalysis efficiency.Based on intermediates identified with gas chromatography-mass spectrometry(GC-MS)and Liquid chromatography-mass spectrometry(LC-MS/MS)techniques,the main degradation routes of atrazine are proposed.

Flame-retardant Wrapped Ramie Fibers towards Suppressing “Candlewick Effect” of Polypropylene/Ramie Fiber Composites

In this work, a flame-retardant polypropylene（PP）/ramie fiber（RF） composite was prepared. The ramie fibers were wrapped chemically by a phosphorus- and nitrogen-containing flame retardant（FR） produced via in situ condensation reaction so as to suppress their candlewick effect. Fourier transform infrared spectroscopy（FTIR）, X-ray photoelectron spectroscopy（XPS） and scanning electron microscopy（SEM） demonstrated that the ramie fibers wrapped chemically by FR（FR-RF） were obtained successfully. Thermogravimatric test showed that the PP/FR-RF composite had more residue and better thermal stability at high temperatures than the PP/RF composite. Cone calorimeter（CC） results indicated that the peak of heat release rate（PHRR） and total heat release（THR） correspondingly decreased by 23.4% and 12.5% compared with the values of neat PP/RF. The PP/FR-RF composite created a continuous and compact char layer after the combustion. Combining FTIR analysis of char residue after CC test with heat conduction coefficient results, it could be concluded that the charring of FR on RF greatly weakened the candlewick effect of RF, and more char residue in the RF domain facilitated the formation of more continuous and compact char layer in the whole combustion zone, consequently protected PP composites during combustion, resulting in the better flame retardancy of PP/FR-RF composite than that of PP/RF composite.

A giant atom with modulated transition frequency

Giant atoms are known for the frequency-dependent spontaneous emission and associated interference effects.In this paper,we study the spontaneous emission dynamics of a two-level giant atom with dynamically modulated transition frequency.It is shown that the retarded feedback effect of the giant-atom system is greatly modified by a dynamical phase arising from the frequency modulation and the retardation effect itself.Interestingly,such a modification can in turn suppress the retarded feedback such that the giant atom behaves like a small one.By introducing an additional phase difference between the two atom-waveguide coupling paths,we also demonstrate the possibility of realizing chiral and tunable temporal profiles of the output fields.The results in this paper have potential applications in quantum information processing and quantum network engineering.

Rigorous spectral representation of relativistic random phase approximation for finite nuclei

By using the rigorous spectral representation of relativistic random phase approximation, the low-lying excitation of finite nuclei and its longitudinal response function for quasielastic electron scattering are calculated in the σ-ω model of quantum hadrodynamics. It is shown that the reproduction of the correct order of the 1- and 3- excitation states of 16O is due to the contribution of the exchange vertex. There is no significant influence of the retardation effect on the low-lying excitation states. In contrast, the retardation effect plays an important role in the electron scattering process of nuclei. The theoretical longitudinal responses of 12C and 40Ca, including the contributions of the exchange vertex and the retardation effect, are suppressed and reproduce the experimental data better than the results excluding them.

Nucleophilic Substitution Reaction of p-Dinitrobenzene by a Carbanion: Evidence for Electron Transfer Mechanism

On the basis of investigation of cyclic voltammetry, EPR spectroscopy and competition experiments, the nucleophilic substitution reaction of p- dinitrobenzene with the sodium salt of ethyl α-cyanoacetate carbanion in dimethyl sulfoxide giving ethyl α-cyano-α- (p-nitrophenyl) acetate is shown to take place via the intermediacy of p-dinitrobenzene radical anion. The reaction rate goes faster than that between p-nitrohalobenzenes and the same sodium salt of ethyl α-cyanoacetate carbanion. There is an evidence for a single electron transfer mechanism.