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  • Online Resource  (7)
  • MDPI AG  (7)
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  • 1
    Online Resource
    Online Resource
    A Water-Soluble Epoxy-Based Green Crosslinking System for Stabilizing PVA Nanofibers
    MDPI AG ; 2022
    In:  Molecules Vol. 27, No. 13 ( 2022-06-29), p. 4177-
    Details
    In: Molecules, MDPI AG, Vol. 27, No. 13 ( 2022-06-29), p. 4177-
    Abstract: With the ever-growing concern about environmental conservation, green production and water-based nanofibers have attracted more and more interest from both academic and industrial fields; nevertheless, the stabilization process of water-based nanofibers is primarily relying on the application of organic solvent-based crosslinking agents. In this work, we develop a green approach to fabricate water-resistant polyvinyl alcohol (PVA) nanofibers by using a water-based epoxy compound, N1, N6-bis(oxiran-2-ylmethyl) hexane-1,6-diamine (EH), as the crosslinker. This EH/sodium carbonate/sodium bicarbonate (CBS) solution system can break down large aggregates of PVA molecules into small ones and promote the uniform distribution of EH in the solution, resulting in the improved stability of crosslinked PVA nanofibers. We firstly report that the uniform dispersion of crosslinking agents in the electrospinning solution plays a vital role in improving the stability of spinning solutions and the water resistance of crosslinked PVA nanofibers by comparing crosslinking performances between water-based epoxy and conventional water-based blocked isocyanate (BI). This work could open up a novel strategy and green approach for the stabilization of water-based nanofibers.
    Type of Medium: Online Resource
    ISSN: 1420-3049
    URL: Article
    DOI: 10.3390/molecules27134177
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2008644-1
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  • 2
    Online Resource
    Online Resource
    Design of a Low-Frequency Harmonic Rotary Piezoelectric Actuator
    MDPI AG ; 2020
    In:  Actuators Vol. 10, No. 1 ( 2020-12-27), p. 4-
    Details
    In: Actuators, MDPI AG, Vol. 10, No. 1 ( 2020-12-27), p. 4-
    Abstract: Piezoelectric actuators usually operate under a high frequency driving signal. Here we report a harmonic rotating piezoelectric actuator by coupling a harmonic wave generator and a friction rotor, in which the actuator can be actuated by a low-frequency sinusoidal signal with positive bias. The harmonic wave is generated by a two-stage magnifying mechanism consisting of a displacement amplifier and a harmonic rod. Applying piezoelectricity theory, the actuator’s output characteristic equations are deduced. What is more, the output characteristics of piezoelectric actuators are tested with the established experimental system. Results show that the generated harmonic displacements can drive the actuator to work normally at a driving voltage of larger than 90 V and the maximum total harmonic displacement of the piezoelectric actuator comes up to 427.6 μm under the driving voltage of 150 V. Meanwhile, the error between the measured and calculated values of the harmonic displacement is less than 7%. Furthermore, the rotational speed of the piezoelectric actuator reaches 5.45 rpm/min at 150 V voltage and 5 Hz driving frequency.
    Type of Medium: Online Resource
    ISSN: 2076-0825
    URL: Article
    DOI: 10.3390/act10010004
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2682469-3
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Online Learning Engagement Recognition Using Bidirectional Long-Term Recurrent Convolutional Networks
    MDPI AG ; 2022
    In:  Sustainability Vol. 15, No. 1 ( 2022-12-22), p. 198-
    Details
    In: Sustainability, MDPI AG, Vol. 15, No. 1 ( 2022-12-22), p. 198-
    Abstract: Background: Online learning is currently adopted by educational institutions worldwide to provide students with ongoing education during the COVID-19 pandemic. However, online learning has seen students lose interest and become anxious, which affects learning performance and leads to dropout. Thus, measuring students’ engagement in online learning has become imperative. It is challenging to recognize online learning engagement due to the lack of effective recognition methods and publicly accessible datasets. Methods: This study gathered a large number of online learning videos of students at a normal university. Engagement cues were used to annotate the dataset, which was constructed with three levels of engagement: low engagement, engagement, and high engagement. Then, we introduced a bi-directional long-term recurrent convolutional network (BiLRCN) for online learning engagement recognition in video. Result: An online learning engagement dataset has been constructed. We evaluated six methods using precision and recall, where BiLRCN obtained the best performance. Conclusions: Both category balance and category similarity of the data affect the performance of the results; it is more appropriate to consider learning engagement as a process-based evaluation; learning engagement can provide intervention strategies for teachers from a variety of perspectives and is associated with learning performance. Dataset construction and deep learning methods need to be improved, and learning data management also deserves attention.
    Type of Medium: Online Resource
    ISSN: 2071-1050
    URL: Article
    DOI: 10.3390/su15010198
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2518383-7
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  • 4
    Online Resource
    Online Resource
    Fibroblast Upregulation of Vitamin D Receptor Represents a Self-Protective Response to Limit Fibroblast Proliferation and Activation during Pulmonary Fibrosis
    MDPI AG ; 2023
    In:  Antioxidants Vol. 12, No. 8 ( 2023-08-18), p. 1634-
    Details
    In: Antioxidants, MDPI AG, Vol. 12, No. 8 ( 2023-08-18), p. 1634-
    Abstract: Dysregulation of vitamin D receptor (VDR) is implicated in chronic obstructive pulmonary disease. However, whether VDR dysregulation contributes to the development of pulmonary fibrosis remains largely unknown. Analysis of bulk and single-cell RNA profiling datasets revealed VDR upregulation in lung fibroblasts from patients with pulmonary fibrosis or fibrotic mice, which was validated in lung fibroblasts from bleomycin-exposed mice and bleomycin-treated fibroblasts. Stable VDR knockdown promoted, whereas the VDR agonist paricalcitol suppressed lung fibroblast proliferation and activation. Gene set enrichment analysis (GSEA) showed that the JAK/STAT pathway and unfolded protein response (UPR), a process related to endoplasmic reticulum (ER) stress, were enriched in lung fibroblasts of fibrotic lungs. Stable VDR knockdown stimulated, but paricalcitol suppressed ER stress and JAK1/STAT3 activation in lung fibroblasts. The STAT3 inhibitor blocked bleomycin- or stable VDR knockdown-induced ER stress. Paricalcitol inhibited the bleomycin-induced enrichment of STAT3 to the ATF6 promoter, thereby suppressing ATF6 expression in fibroblasts. Paricalcitol or intrapulmonary VDR overexpression inactivated JAK1/STAT3 and suppressed ER stress in bleomycin-treated mice, thus resulting in the inhibition of fibroblast proliferation and activation. Collectively, this study suggests that fibroblast VDR upregulation may be a self-protective response to limit fibroblast proliferation and activation during pulmonary fibrosis by suppressing the JAK1/STAT3/ER stress pathway.
    Type of Medium: Online Resource
    ISSN: 2076-3921
    URL: Article
    DOI: 10.3390/antiox12081634
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704216-9
    SSG: 15,3
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    Online Resource
  • 5
    Online Resource
    Online Resource
    De Novo Assembly and Comparative Transcriptome Profiling of Anser anser and Anser cygnoides Geese Species’ Embryonic Skin Feather Follicles
    MDPI AG ; 2019
    In:  Genes Vol. 10, No. 5 ( 2019-05-08), p. 351-
    Details
    In: Genes, MDPI AG, Vol. 10, No. 5 ( 2019-05-08), p. 351-
    Abstract: Geese feather production and the quality of downy feathers are additional economically important traits in the geese industry. However, little information is available about the molecular mechanisms fundamental to feather formation and the quality of feathers in geese. This study conducted de novo transcriptome sequencing analysis of two related geese species using the Illumina 4000 platform to determine the genes involved in embryonic skin feather follicle development. A total of 165,564,278 for Anser anser and 144,595,262 for Anser cygnoides clean reads were generated, which were further assembled into 77,134 unigenes with an average length of 906 base pairs in Anser anser and 66,041 unigenes with an average length of 922 base pairs in Anser cygnoides. To recognize the potential regulatory roles of differentially expressed genes (DEGs) during geese embryonic skin feather follicle development, the obtained unigenes were annotated to Gene Ontology (GO), Eukaryotic Orthologous Groups (KOG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) for functional analysis. In both species, GO and KOG had shown similar distribution patterns during functional annotation except for KEGG, which showed significant variation in signaling enrichment. Anser asnser was significantly enriched in the calcium signaling pathway, whereas Anser cygnoides was significantly enriched with glycerolipid metabolism. Further analysis indicated that 14,227 gene families were conserved between the species, among which a total of 20,715 specific gene families were identified. Comparative RNA-Seq data analysis may reveal inclusive knowledge to assist in the identification of genetic regulators at a molecular level to improve feather quality production in geese and other poultry species.
    Type of Medium: Online Resource
    ISSN: 2073-4425
    URL: Article
    DOI: 10.3390/genes10050351
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2527218-4
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  • 6
    Online Resource
    Online Resource
    3D Heterogenous Integrated Wideband Switchable Bandpass Filter Bank for Millimeter Wave Applications
    MDPI AG ; 2022
    In:  Electronics Vol. 12, No. 1 ( 2022-12-30), p. 194-
    Details
    In: Electronics, MDPI AG, Vol. 12, No. 1 ( 2022-12-30), p. 194-
    Abstract: This article proposes a three-dimensional heterogenous-integrated (3DHI) switchable bandpass filter bank with two independent wideband filter channels that cover 26–40 GHz and 32.5–40 GHz, respectively. An accurate wafer-level process with a high hollowed ratio of the applied 8-inch high-resistivity-silicon (HR-Si) interposer wafers is presented to form both compact filter channels. Above the interdigital filter patterns fabricated on the bottom interposer wafer, deep cavities are etched in the cap interposer wafer to improve the quality factor of the filter bank. Besides the cavities, the cap interposer wafer is 35% hollow inside, which two bare dies of GaAs single-pole double-throw (SPDT) switches and two thin film resistors are attached to the bottom interposer after the wafer-to-wafer (W2W) bonding. To ensure good out-of-band performance, a 3D EM co-simulation of the switch layout at the chip level and filter patterns at the package level is applied. Measurement results show that the switchable filter bank achieves a high isolation of 50 dB and a competitive shape factor (BW30dB/BW3dB) of about 1.3. In addition, the size of the switchable filter bank is only 7.0 mm × 3.5 mm × 0.6 mm, and the weight is only 0.1 g.
    Type of Medium: Online Resource
    ISSN: 2079-9292
    URL: Article
    DOI: 10.3390/electronics12010194
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2662127-7
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  • 7
    Online Resource
    Online Resource
    Analysis and Modeling of Timbre Perception Features in Musical Sounds
    MDPI AG ; 2020
    In:  Applied Sciences Vol. 10, No. 3 ( 2020-01-22), p. 789-
    Details
    In: Applied Sciences, MDPI AG, Vol. 10, No. 3 ( 2020-01-22), p. 789-
    Abstract: A novel technique is proposed for the analysis and modeling of timbre perception features, including a new terminology system for evaluating timbre in musical instruments. This database consists of 16 expert and novice evaluation terms, including five pairs with opposite polarity. In addition, a material library containing 72 samples (including 37 Chinese orchestral instruments, 11 Chinese minority instruments, and 24 Western orchestral instruments) and a 54-sample objective acoustic parameter set were developed as part of the study. The method of successive categories was applied to each term for subjective assessment. A mathematical model of timbre perception features (i.e., bright or dark, raspy or mellow, sharp or vigorous, coarse or pure, and hoarse or consonant) was then developed for the first time using linear regression, support vector regression, a neural network, and random forest algorithms. Experimental results showed the proposed model accurately predicted these attributes. Finally, an improved technique for 3D timbre space construction is proposed. Auditory perception attributes for this 3D timbre space were determined by analyzing the correlation between each spatial dimension and the 16 timbre evaluation terms.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app10030789
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2704225-X
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