Assessment of transmission of the shear stress in potted anchors for composite rods 1. Sleeve of constant thickness

The key problem facing the application of fiber-reinforced polymer (FRP) stay cables and tendons is the anchorage. Potted (bond-type) anchors have been used more extensively than anchors of any other type. The main aim in the design of anchors is to minimize the peak shear stress at the FRP rod-pottant interface. To this end, parametric analyses of the stress state in the anchors are carried out. Since parametric studies can not be easily performed by the finite-element method, an analytical model of the anchor is proposed. The model involves significant simplifying assumptions and allows one to obtain a relatively simple analytical solution for shear-stress distributions at the FRP rod-pottant interface. The use of this solution at various boundary conditions and various geometrical and mechanical parameters of anchor components enables one to search for and evaluate, at least qualitatively, different methods for decreasing the peak interfacial shear stress in the anchor. In this part of the investigation, an anchor consisting of a sleeve of constant thickness is considered. Russian tanslation published in Mekhanika Kompozitnykh Materialov, Vol. 45, No. 3, pp. 321-346, May-June, 2009.     

Short shots and industrial case studies: Understanding fluid flow and solidification in high pressure die casting

The geometric complexity and high fluid speeds involved in high pressure die casting (HPDC) combine to give strongly three dimensional fluid flow with significant free surface fragmentation and splashing. A simulation method that has proved particularly suited to modelling HPDC is Smoothed Particle Hydrodynamics (SPH). Materials are approximated by particles that are free to move around rather than by fixed grids, enabling more accurate prediction of fluid flows involving complex free surface motion. Three practical industrial case studies of SPH simulated HPDC flows are presented; aluminium casting of a differential cover (automotive), an electronic housing and zinc casting of a door lock plate. These show significant detail in the fragmented fluid free surfaces and allow us to understand the predisposition to create defects such as porosity in the castings. The validation of flow predictions coupled with heat transfer and solidification is an important area for such modelling. One powerful approach is to use short shots, where insufficient metal is used in the casting or the casting shot is halted part way through, to leave the die cavity only partially filled. The frozen partial castings capture significant detail about the order of fill and the flow structures occurring during different stages of filling. Validation can occur by matching experimental and simulated short shots. Here we explore the effect of die temperature, metal super-heat and volume fill on the short shots for the casting of a simple coaster. The bulk features of the final solid castings are found to be in good agreement with the predictions, but the fine details appear to depend on surface behaviour of the solidifying metals. This potentially has significant implications for modelling HPDC.     

Effects of polymerization method on structure and properties of thermoplastic polyurethanes

The effects of the dynamic polymerization method and temperature on the molecular aggregation structure and the mechanical and melting properties of thermoplastic polyurethanes (TPUs) were successfully clarified. TPUs were prepared from poly (ethylene adipate) glycol (M_n = 2074), 4,4′‐diphenylmethane diisocyanate and 1,4‐butanediol by the one‐shot (OS) and the prepolymer (PP) methods in bulk at dynamic polymerization temperatures ranging from 140 to 230 °C. Glass‐transition temperatures (T_gs) of the soft segment and melting points (T_ms) of the hard segment domains of OS‐TPUs increased and decreased, respectively, with increasing polymerization temperatures, but those of PP‐TPUs were almost independent of the polymerization temperature. T_gs of the soft segment and T_ms of the hard segment domains of these TPUs polymerized above 190 °C were almost the same regardless of the polymerization method. Solid‐state nuclear magnetic resonance spectroscopy (NMR) analyses of OS‐ and PP‐TPUs showed that the relative proton content of fast decay components, which corresponds to the hard segment domains, in these TPUs decreased with increasing polymerization temperatures. These results clearly show that the degree of microphase separation becomes weaker with increasing polymerization temperatures. The temperature dependence of dynamic storage modulus and loss tangent of OS‐TPUs coincided with those of PP‐TPUs at polymerization temperature above 190 °C. The apparent shear viscosity for OS‐ and PP‐TPUs polymerized above 190 °C approached a Newtonian behavior at low shear rates regardless of the polymerization method. These results indicate that TPUs polymerized at higher temperatures form almost the same molecular aggregation structures irrespective of the dynamic polymerization method. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 800–814, 2007     

Hydrophile Polymergele mit reaktiven Gruppen, 3. Mitt.: Chelatharze mit Formazan-Ankergruppen auf Basis von Saccharosemethacrylaten

The preparation and properties of hydrophilic chelating resins containing formazans as functional groups are described. Sucrosemethacrylat-gels with primary aromatic amino groups were diazotised and coupled with various substituted phenylhydrazones yielding gels with formazans as chelating anchor groups. The capacities of the gels were max. 1,6 mmol/g. The recycle of adsorption and elution was found to be satisfactory for Co²⁺ and Pb²⁺ whereas only 60% of the bonded Hg^2– could be recovered reversibly.

     

Modelling the temporal intensity distribution of laser ablation inductively coupled plasma mass spectrometry in single shot mode

A transport model is proposed that describes the temporal intensity distribution observed in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) in single-shot mode using quantitative signal equations. Calculations aim on the deduction of the dispersion function describing the time-dependent part of the signal equation.

The dispersion function depends on transport time in the centre of the transport tube, as related to carrier gas flow rate and tube volume and on the relation between carrier gas flow rate and ablation chamber volume. The equations describing the signal shape standardize signals from different systems and allow quantitative optimization of the ablation chamber, the transport tube and the detector.

Application of the model to ICP-MS shows that only a part of the area filled by the transported vaporization product and thus only a part of the transported vaporization product can be observed at the detector. The model is able to quantify both fractions.

As was calculated, the observed fraction of analyte is always higher than the observed fraction of the sample containing cross section and depends on the chosen transport parameters characterising the dispersion function. Thus, the determination of the signal integrals in the usual way can lead to systematic errors if the parameters influencing the dispersion function are variable.

Therefore, a different method of analysis based on signal equations is proposed and demonstrated. By this method of data treatment, all important system parameters influencing the dispersion function could be calculated and matched with theoretical ones. Furthermore, a complete integral of the transient signal including its statistical variation can be generated from a limited number of measurement points. For example, this can be applied to signals detected incompletely because of detector saturation and enables the use of high-abundance elements as internal standards.

Furthermore, the method can be used to monitor system performance, to identify the flow regime inside the ablation chamber, to take into account the sample volume for quantitative analysis and finally, to detect anomalous signal distributions that would lead to systematic errors. The prospects and limitations of the model are discussed for LA-ICP-MS in single shot mode.     

Hydrophile Polymergele mit reaktiven Gruppen, 2. Mitt.: Chelatharze auf Basis von Glucose- und Saccharosemethacrylaten

A widely applicable method for the preparation of chelating resins based on glucose- and sucrosemethacrylate-gels is described. Primary aromatic amino groups were bonded to the carrier by esterification with 4-nitrobenzoylchloride and subsequent reduction of the nitro groups with sodium dithionite. Diazotation and coupling with various chelating ligands (8-hydroxyquinoline, dithizone, anthranilic acid, salicylic acid and pyrogallol) afforded chelating resins with capacities of max. 1.7 mmol/g. Sucrosemethacrylate-gels were etherified with 4-nitrobenzylchloride, epichlorohydrin, 4-nitrophenyl glycide ether (IIb), acrylonitrile and 4-nitrophenylacrylamide (IVb). Reaction of the gels with IIb or IVb and subsequent reduction of the nitro groups yielded reactive carriers with ether-linked primary aromatic amino groups. Diazotation and coupling with 8-hydroxyquinoline yielded chelating resins. The capacities of the gels were 0.6–0.7 mmol/g and these resins were extremely stable to changes inpH.

     

Hydrophile Polymergele mit reaktiven Gruppen, 4. Mitt.: Chelatharze mit schwefelhaltigen Ankergruppen auf Basis von Saccharosemethacrylaten

Chelating resins with thioglycolate anchor groups have been synthesized by reaction of sucrosemethacrylate gels with thioglycolic acid. The capacities of the gels were found to be extremely high for Ag⁺ (5,3 mmol/g) and Hg²⁺ (4,9 mmol/g). About 1 mmol Hg²⁺/g could be recovered from the gel reversibly by treatment with hydrochloric acid. The removal of Hg²⁺ from aqueous 3M alkalichloride solutions was possible with capacities of 1 mmol/g.Sucrosemethacrylate gels with primary aromatic amino group were reacted with CS₂/NH₃ to yield gels with dithiocarbamate groups. Gels with thiorea groups were prepared by reaction of the amino groups with NH₄SCN/HCl. Diazotation of the amino groups, subsequent reaction with potassium xanthogenate and hydrolysis afforded gels with thiol groups. Thiol containing gels were synthesized also by reaction of the diazotised gels with Na₂S₂ and subsequent reduction with Na₂S. Reaction of the diazotised gels with mercaptans yielded resins with thioether anchor groups. The capacities of the sulfur containing gels were found to be max. 4,1 mmol/g for Hg²⁺ and 5,9 mmol/g for Ag⁺. About 35% of the bonded Hg²⁺ could be eluted resersibly with 3N-HCl.

     

On nonlinear structure of electrical noise generated by slow discharge

Nonlinear structure of electrical noise of slow electrochemical discharge is analyzed within theory of integral random homogeneous fluxes with independent increments. It is shown that the degree of deviation of a flux of elementary acts from the Poissonian flux is defined by the magnitude of the factor of symmetry of slow discharge. An equation that links polyspectra of slow discharge of first, second, and third orders is derived.     

非稳散粒噪音相位依赖特性的实验研究

为了抑制相位调制引起的散粒噪音，实验研究了通过调制二极管激光器输出光强度，使用相位解调技术得到的不同解调相位下非稳散粒噪音的功率谱.在最小散粒噪音处，得到了相比于无调制情况下的散粒噪音减小3 dB的灵敏测量结果.实验结果表明，选择合适的调制相位可以在一定程度上抑制散粒噪音.研究结果与理论分析一致.     

Shot noise in nano-electronic systems under the perturbation of ac fields

Current noise exists in circuits and electronic devices generally, and it exhibits specific features as the system reaches nanometer size. The noise in the nano-system where external ac fields are applied plays an important role, since the properties of the fields and the nano-system together govern the resulting noise. In this paper, we present the derivation of shot noise by employing the non-equilibrium Green’s function technique. The more general formulas for the current correlation and noise spectral density are given. The system is composed of a central nanosystem coupled to electrodes, and the obtained noise formulas are related to the Green’s functions of detailed central regime and the terminals. As an example, we have performed the numerical calculation on a system with a toroidal carbon nanotube coupled to normal metal leads. The noise and Fano factor show intimate relation with the structure of the system and ac fields. The Aharonov-Bohm-like behaviors on the shot noise spectral density and Fano factor are observed to exhibit oscillation structures with period of quantum flux.