Tension variation reduction in high speed cone winding

The research work was concened with the design of tension compensators for spinning-winding machines for the purposes of reducing winding tension variation during high speed cone winding. Initially, the research was directed to investigating the 'winding error', i.e. the difference between yarn supply and demand, which was the main cause of winding tension variation. Mathematical models were established to analyse the winding velocity variation and yarn path length variation. Several methods have been investigated to reduce winding tension variation and to develop tension compensators. These include using a servo motor to keep constant winding velocity and using a curved distribution bar to keep constant path length. Two promising tension compensators were selected for detailed investigation. they were a mechanical compensator and a mechatronic compensator.Based on the analysis of 'winding error', A multiple bar mechanism was devised, analysed and optimised to provide tension compensation. Further consideration has been given to a microprocessor controlled mechanism, that works according to predetermined look-up tables and sensor signals to reduce winding tension variation. The computer simulation of yarn winding process, the software design for the optimisation of mechanical compensator and the control of mechatronic compensator, and the results of winding tension experimentation are also presented in the thesis

Systematic Evaluation of Two Classical Receptor Models in Source Apportionment of Soil Heavy Metal(loid) Pollution Using Synthetic and Real-World Datasets

Due to the lack of a priori knowledge on true source makeup and contributions, whether the source apportionment results of Unmix and positive matrix factorization (PMF) are accurate cannot be easily assessed, despite the availability of built-in indicators for their goodness of fit and robustness. This study systematically evaluated, for the first time, the applicability and reliability of these models in source apportionment of soil heavy metal(loid)s with synthetic datasets generated using known source profiles and contributions and a real-world dataset as well. For eight synthetic datasets with different pollution source characteristics, feasible Unmix solutions were close to the true source component compositions (R2 > 0.936; total mean squared errors (MSEs) < 0.04), while those of PMF had significant deviations (R2 of 0.484–0.998; total MSEs of 0.04–0.16). Nonetheless, both models failed to accurately apportion the sources with collinearity or non-normal distribution. Unmix generally outperformed PMF, and its solutions showed much less dependence on sample size than those of PMF. While the built-in indicators provided little hint on the reliability of both models for the real-world dataset, their sample-size dependence indicated that Unmix probably yielded more accurate solutions. These insights could help avoid the potential misuse of Unmix and PMF in source apportionment of soil heavy metal(loid) pollution

Ion-Imprinted Mesoporous Silica for Selective Removal of Uranium from Highly Acidic and Radioactive Effluent

It is strategically important to recycle uranium from radioactive liquid wastes for future uranium supply of nuclear energy. However, it is still a challenge to adsorb uranium selectively from highly acidic and radioactive waste. In this paper, we report a novel strategy for effective uranium removal from highly acidic and radioactive media by surface ion-imprinted mesoporous silica sorbent. The sorbent was successfully synthesized by a co-condensation method with uranyl as the template ion and diethylphosphatoethyltriethoxysilane as the functional ligands. The pseudo-second-order model and Langmuir model showed better correlation with the sorption kinetic and isotherm data, and the sorption equilibrium could be reached within 40 min, the maximum adsorption capacity from Langmuir model was 80 mg/g in 1 mol/L nitric acid (HNO₃) solution at 298.15 K. The sorbent showed faster kinetics and higher selectivity toward uranium over other ions compared with nonimprinted mesoporous and other previous sorbents. Furthermore, the ion-imprinted materials exhibited remarkable radioresistance stability and could be regenerated efficiently after five cycles. This work may provide a new approach for highly efficient sorption of uranium from strong HNO₃ and radioactive media

Surface Ion-Imprinted Polypropylene Nonwoven Fabric for Potential Uranium Seawater Extraction with High Selectivity over Vanadium

Uranium seawater extraction is strategically important to guarantee the future supply for nuclear power generation. However, it is still a challenge to selectively capture uranium over vanadium in seawater. In this paper, we propose a new method for potential uranium seawater extraction with high selectivity over vanadium. Specifically, surface ion-imprinted polypropylene nonwoven fabric is prepared by copolymerization of 4-vinylbenzyl chloride and 1-vinylimidazole in the presence of uranyl tricarbonate complex. The sorption follows the pseudo-second-order model and can reach the equilibrium with a large capacity of 133.3 mg/g within 15 h at pH 8.0 and 298.15 K. The imprinted fabric shows excellent selectivity toward uranium over vanadium and the other coexisting ions in seawater. In addition, it exhibits good salt-resistant stability and can be regenerated efficiently after five cycles. This work indicates that the imprinted fabric may be a promising sorbent for potential uranium seawater extraction

Photoinduced Palladium-Catalyzed Radical Heck-Type Coupling of Cyclobutanone Oxime Esters with Vinyl Arenes

A palladium-catalyzed radical Heck-type coupling reaction of cyclobutanone oxime esters with olefins under visible-light irradiation has been developed. The cyanoalkyl/Pd(I) hybrid species generated by selected ring-opening C–C bond cleavage of imino/Pd(I) species reacted smoothly with vinyl arenes, delivering the cyanoalkylation olefins under mild conditions. This elegant strategy has a broad scope and functional group tolerance. Subsequently, late-stage functionalization of bioactive molecules and synthetic transformations of the product further confirm the practicality

Photoinduced Desaturation of Amides by Palladium Catalysis

A photoinduced palladium-catalyzed desaturation method that is suitable for converting the linear amides to their α,β-unsaturated counterparts is reported. The reaction does not require strong base/acid or sulfur/selenium and oxidant reagents and can be carried out at room temperature through a simple one-step operation. The protocol exhibits great scalability and functional group tolerance. The reaction mechanism has been investigated through deuterium labeling experiments, radical clock, radical capture, and kinetic studies. Mechanistic studies suggested a radical pathway involving aryl/alkyl Pd-radical intermediates

Logistic regression results showing risk of suicidal behaviors associated with specific stressors in school life.

<p>Note. ORs were adjusted for all school life stressors as well as demographic variables listed in the table.</p

Effects of gender, region, school life stressors and childhood adversities on risk for suicidal ideation and for suicide attempt.

<p>Notes: Model I: analyses without any adjustment; Model II: only adjusted for gender and region; Model III: adjusted for all variables listed in the table.</p

Prevalence of suicidal ideation and suicide attempts in the study population.

<p>Note. In the study population, 56 students did not report gender information and 3 students did not report the region of permanent family residence. .</p

Logistic regression results showing risk of suicidal behaviors associated with specific adverse experiences in childhood.

<p>Note. ORs were adjusted for all childhood adversities as well as demographic variables listed in the table.</p