Despite
the great potential in fabrication of biodegradable and
eco-friendly air filters by electrospinning poly(lactic acid) (PLA)
membranes, the filtering performance is frequently dwarfed by inadequate
physical sieving or electrostatic adsorption mechanisms to capture
airborne particulate matters (PMs). Here, using the parallel spinning
approach, the unique micro/nanoscale architecture was established
by conjugation of neighboring PLA nanofibers, creating bimodal fibers
in electrospun PLA membranes for the enhanced slip effect to significantly
reduce the air resistance. Moreover, the bone-like nanocrystalline
hydroxyapatite bioelectret (HABE) was exploited to enhance the dielectric
and polarization properties of electrospun PLA, accompanied by the
controlled generation of junctions induced by the microaggregation
of HABE (10–30 wt %). The incorporated HABE was supposed to
orderly align in the applied E-field and largely promote the charging
capability and surface potential, gradually increasing to 7.2 kV from
the lowest level of 2.5 kV for pure PLA. This was mainly attributed
to HABE-induced orientation of PLA backbone chains and CO
dipoles, as well as the interfacial charges trapped at the interphases
of HABE–PLA and crystalline region–amorphous PLA. Given
the multiple capturing mechanisms, the micro/nanostructured PLA/HABE
membranes were characterized by excellent and sustainable filtering
performance, e.g., the filtration efficiency of PM0.3 was
promoted from 59.38% for pure PLA to 94.38% after addition of 30 wt
% HABE at a moderate airflow capacity of 32 L/min and from 30.78 to
83.75% at the highest level of 85 L/min. It is of interest that the
pressure drop was significantly decreased, mainly arising from the
slip effect between the ultrafine nanofibers and conjugated microfibers.
The proposed combination of the nanostructured electret and the multistructuring
strategy offers the function integration of efficient filtration and
low resistance that are highly useful to pursue fully biodegradable
filters.
Polylactic acid (PLA) composites parts obtained by fused deposition modeling (FDM) three-dimensional (3D) printing have obvious fusion interfaces. The printed parts have low strength and poor plastic toughness, limiting their application in clinical degradable load-bearing implants. In this article, first, the nano-hydroxyapatite (n-HA) was modified by PLA to obtain a core-shell structure with PLA coating. The micron chopped carbon fiber (CF) was modified by nitric acid to obtain a rich oxygen-containing functional group structure. Second, the above two modified materials of n-HA and CF were coated on the surface of the PLA filament by ultrasonic impregnation to obtain the PLA/n-HA/CF composite filament. Finally, tensile samples were manufactured by FDM 3D printing with the PLA/n-HA/CF composite filament, and the tensile test was conducted. The results show that the surface-modified n-HA particles form a regular spherical core-shell structure with good dispersibility. It can be combined with a matrix of PLA filament by the PLA coating
Background
Listening is an important responsibilities of human resource managers, whether it will bring role stress to human resource managers, or lead to the risk of job burnout. This study aims to analyze the impact of listening competency on job burnout among human resource managers, and examine the mediating effect of role stress.
Methods
This study adopted a cross-sectional method to randomly select 500 human resource managers from China’s top ten human resource management cities to conduct an online questionnaire survey, and 232 valid samples were obtained. Descriptive statistical and one-way ANOVA were used to explore the status of job burnout among human resource managers in China. Correlation analysis, multiple linear regression and mediating effect analysis were employed to test the relationship between listening competency and job burnout, as well as the mediating effect of role stress.
Results
(1) 34.5% of the respondents reported mild burnout, while 3.0% respondents showed serious burnout. Emotional exhaustion was the most serious. (2) Those are good at listening could easily avoid job burnout. Among them, listening skills were conducive to reducing the degree of depersonalization of human resource managers, and empathy was more conducive to improving their personal sense of accomplishment. (3) The role stress had a significant mediating role in the relationship between listening competency and job burnout. Which means that listening competency can avoid job burnout by reducing role stress of human resource managers.
Conclusions
This study revealed the current situation of job burnout among human resource managers in China, and explored the influence of listening competency on job burnout. This study enriched the research content of job burnout, and provided references for preventing and intervening job burnout of human resource managers.
The friction-reducing performance of surfaces with regular nanotextures is a key topic in surface engineering research. This paper presented a simple, easily controlled method for fabricating regular nanotextures on an electrodeposited Ni-Co alloy. The electronic controlling on the friction performance of a nanotexured surface was investigated by AFM. The results showed that the frictional force of a nanotexured surface can be controlled by an external electric field. Before laser processing, the friction initially increased with the bias voltage and then decreased after the bias voltage exceeded 1.0 V. Its friction forces can be changed more than 2 times under the different external electric field. After laser processing, the trend of the frictional force was reversed and its friction forces changed more than 12 times for the laser-processed sample with 0.18 J/cm 2 laser power. The results also showed that the friction force decreased when using different nanotextures in an external electric field.
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