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Operation of the safety gears is the last means of protecting passengers in a high-speed or even freely falling lift car. EN81-20 stipulates that the average retardation when the safety gears are engaged should lie between 0.2 g n and 1.0 g n while g n is the gravitational acceleration. Decades ago, in Hong Kong, to conduct a formal test on the safety gears, the car was fully loaded and the machine brake was manually released to allow the car fall freely until the overspeed governor triggered the engagement of the safety gears. This test was rather vigorous to both the gear jaws and the guiderails. Recently, tests have been conducted with 125% in-car load while the car travels under an inspection (or levelling) speed and the governor is manually triggered. Such a revised test, though much less vigorous, may not be able to verify the average retardation as required. Even a test with full load and free-falling may not reveal the whole truth by merely measuring the resulting contact scratches on the guiderails because a majority of the retardation could have been assisted by the counterweight via the suspension ropes. A method that involves an empty car traveling downward at 1 m/s with the governor manually triggered was first developed in Germany. This method has been improved to form a comprehensive procedure as detailed in this article so that a no-load rated speed, or slightly reduced speed, test is conducted, which is almost non-invasive or much less vigorous. By calculation, the average retardation when all suspension ropes are broken can be estimated. Cross-checking in our experiments revealed the validity of this procedure. The procedure also involves a test to verify the validity of parameters used to perform the estimation and takes care of some modern overspeed governors which cannot be manually triggered. It is hoped that this procedure could encourage maintenance professionals carry out safety gears tests more often to ensure a high safety standard. Practical application : This comprehensive procedure could encourage more frequent tests on the car safety gears, which is almost non-invasive for manually triggerable overspeed governors or less vigorous for non-triggerable ones. An empty car traveling downward at rated speed, or at slightly reduced speed, is tested by manually triggering the governor while a partially loaded free-falling car is tested if the governor is not manually triggerable. Results can be used to estimate the average retardation of the lift car when all suspension ropes are broken. A pre-test is included to validate critical parameters necessary for the estimation. Experiments conducted so far were on the safety gears of low- to medium-speed lifts. For high-speed lifts beyond 4 m/s, that may be considered in the next stage of research. Although the title of this article includes the city where the procedure was developed, there is no reason why this testing procedure could not be extensively applicable to any traction lift systems around the world at such speed levels. [ABSTRACT FROM AUTHOR]

CaBi2Nb2O9 ceramics were fabricated via the solid-state reaction method by the addition of B2O3 as a sintering aid at lower sintering temperatures than that prepared without B2O3. Ferroelectricity, piezoelectricity, and resistivity can be still greatly enhanced when the sintering temperature is decreased from 1075 °C for CaBi2Nb2O9 to 975 °C for CaBi2Nb2O9–0.25 wt. % B2O3. The high resistivity and weak c-axis texture ensure that the ceramics can be fully polarized in a high enough electric field. The increased spontaneous ferroelectric and remanent polarization result in a significant enhancement in the piezoelectric properties of CaBi2Nb2O9–0.25 wt. % B2O3. The sample sintered at 975 °C possesses a high piezoelectric coefficient d33 of ∼15.0 pC/N and resistivity of 1.4 × 106 Ω cm (at 600 °C) along with a high ferroelectric Curie temperature TC of ∼954 °C. This work is beneficial for the preparation of high-temperature piezoelectric ceramics with excellent electrical properties at a low sintering temperature. [ABSTRACT FROM AUTHOR]

Theaflavin-3'-gallate was synthesised using polyphenol oxidase (PPO) from gallocatechin (EGC) and epicatechin gallonic acid (ECG). Using PPO, Box-Behnken design, and single factor test, the optimal reaction conditions were determined: ECG/EGC ratio of 3:7, magnetic stirring speed of 200 rpm, reaction temperature of 37°C, and enzyme concentration of 20 mg/100 mL. Under these conditions, the yield of TF-3'-G was 18.1%. These parameters represent the optimal conversion conditions for theaflavin-3'-monogallate. [ABSTRACT FROM AUTHOR]

Microstructural evolution and compressive properties of two-phase Nb-Fe binary alloys based on the C14 Laves phase NbFe2 were characterized at both the hypo- and hypereutectic compositions. The experimental results indicated that the microstructures of the two alloys consisted of fully eutectics containing Fe and NbFe2 phases at the bottom of the ingots corresponding to the largest solidification rates. With the decrease of solidification rate, the microstructures developed into primary Fe (NbFe2) dendrites plus eutectics in the middle and top parts of the ingots. The microstructural evolutions along the axis of the ingots were analyzed by considering the competitive growth between the primary phase and eutectic as well as using microstructure selection models based on the maximum interface temperature criterion. Furthermore, the compressive properties of the two alloys were measured and the enhancements were explained in terms of the second Fe phase and halo toughening mechanisms.

BiFe0.93Mn0.07O3-0.82BiFe0.975Ti0.025O3-0.18CaTiO3 thin films were prepared on Pt/Si substrate by chemical solution deposition. The microstructure, ferroelectric and piezoelectric properties of the composite films under different annealing temperature were studied systematically. The thin film annealed at 500 °C possesses the maximum remanent polarization and piezoelectric coefficient of 112.6 µC/cm2 and 878.2 pm/V, respectively, which is comparable to most of BiFeO3-based orientated films. The results can be ascribed to the dense and uniform grain distribution in the surface morphology, and coexistence of rhombohedral twisted perovskite symmetrical structure (R3c space group) and pseudo-cubic structural phase. This work provides a feasible way to prepare high-quality lead-free composite ferroelectric films at low-cost. [ABSTRACT FROM AUTHOR]

Objective Explore the mental health status and its influencing factors of local community residents under the post-epidemic era of coronavirus disease 2019 (COVID-19) in China. Methods The basic information scale, self-rating depression scale and self-rating anxiety scale were used to carry out an online questionnaire survey among community residents in Jiangsu Province, China, and the influencing factors of depression and anxiety were analyzed by multivariate logistic regression. Results A total of 993 residents completed the mental health survey. It was found that the incidence of depressive and anxiety symptoms was 37.06% and 22.86%. Multivariate logistic regression analysis showed that women [odds ratio (OR) 95% confidence interval (95% CI) = 26.239 (14.743–46.698)], college degree and above [OR (95% CI) = 1.843 (1.085–3.130)] and ordinary residents [OR (95% CI) = 2.222 (1.441–3.425)] were risk factors for depressive symptoms, urban residents had lower risk [OR (95% CI) = 0.655 (0.394–0.829)]. Women [OR (95% CI) = 33.595 (15.812–71.381)] and ordinary residents [OR (95% CI) = 3.017 (1.602–5.680)] were risk factors for anxiety symptoms while the incidence was reduced in professional and technical personnel [OR (95% CI) = 0.271 (0.123–0.597)], workers [OR (95% CI) = 0.383 (0.168–0.876)], soldiers or policemen [OR (95% CI) = 0.200 (0.042–0.961)], married residents [OR (95% CI) = 0.463 (0.230–0.931)] and urban residents [OR (95% CI) = 0.531 (0.251–0.824)]. Conclusion The incidence of symptoms of depression and anxiety among residents was relatively high under the post-epidemic era of COVID-19, which could be affected by various factors. [ABSTRACT FROM AUTHOR]