Search

In order to determine the characteristic flavor of Jingyang Fu brick tea, a national geographical indication product, the volatile compounds of Jingyang Fu brick tea, Anhua Fu brick tea and four other dark teas were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) in this study. The results showed that in total 154 compounds were identified by GC-IMS and HS-SPME-GC-MS, and the flavor composition of Jingyang Fu brick tea was clearly distinguished from that of Anhua Fu-brick tea and that of the other dark teas. Totally 12 characteristic substances of Jingyang Fu brick tea were obtained by comparative analysis with the other dark tea, seven of which were validated by GC-IMS, including 1-octen-3-one, n-hexanol, guaiacol, β-pinene, methyl butyrate, n-propanol and 2-heptanone, and the remaining five were characterized by HS-SPME-GC-MS based on aroma activity values, including hexanal, decanal, (E,E)-3,5-octadien-2-one, methyl salicylate and α-viologenone. The identification of characteristic flavor substances can provide a theoretical basis for the identification, origin tracing and processing optimization of Jingyang Fu brick tea.

Electromagnetic performance regulation in mid‐infrared (MIR) and microwave (MW) spectrums is crucially significant, which can be achieved by heterophase introduction and structural manufacturing. In this work, Si‐O amorphous phase is introduced into Pt film by magnetron co‐sputtering technique, the film thickness is optimized by adjusting deposition time. After annealing treatment, a double‐layered structure is constructed with the migration and growth of Pt crystals, in which the lower layer is composed of Pt coarse grains while the upper layer is Si‐O amorphous phase with embedded Pt fine grains. Furthermore, due to the thickness difference, diverse kinds of structural patterns (arrays or mesh) can be obtained with the solid‐state dewetting of the lower layer. According to the increasing thickness, the infrared emissivity can decrease from 0.67 to 0.25 (8–14 μm), demonstrating a great decline of apparent temperature of 162.9 °C when the background is 300 °C. And the microwave transmissivity also exhibits tremendous variation over 90% (from 96% to 5%), realizing the transformation from transmitting to shielding. [ABSTRACT FROM AUTHOR]

Bulk metallic glasses (BMGs) display excellent strength, high hardness, exceptional wear resistance and corrosion resistance owing to its amorphous structure. However, the manufacturing of large-sized and complex shaped BMG parts faces significant difficulties, which seriously hinders their applications. Laser powder bed fusion (LPBF) is a typical additive manufacturing (AM) technique with a cooling rate of up to 108 K/s, which not only allows for the formation of amorphous structures but also solves the forming problem of complex-shaped BMG parts. In recent years, a large amount of work has been carried out on the LPBF processing of BMGs. This review mainly summarizes the latest progress in the field of LPBF additively manufactured BMGs focusing on their mechanical properties. We first briefly review the BMG alloy systems that have been additively manufactured using LPBF, then the mechanical properties of LPBF-fabricated BMGs including the micro- and nano-hardness, micropillar compressive performance, and macro-compressive and tensile performance are clarified. Next, the relationship between the mechanical properties and microstructure of BMGs produced via LPBF are analyzed. Finally, the measures for improving the mechanical properties of LPBF-fabricated BMGs are discussed. This review can provide readers with an essential comprehension of the structural and mechanical properties of LPBF-manufactured BMGs. [ABSTRACT FROM AUTHOR]

L-ascorbic acid (vitamin C, VC), an essential nutrient obtained from the diet to maintain various vital signs for the human body, is a crucial indicator of food quality and nutritional value. Herein, high-performance liquid chromatography with electrochemical detection (HPLC-ECD) was developed and validated with the advantages of higher sensitivity, simpler operation processes, and more rapid detection in measuring VC levels in honey samples when compared with the common methods (titration, spectrophotometric, and HPLC-DAD methods). The results of the HPLC-ECD methodological validation showed that the limit of detection (LOD) was 0.0043 µg mL−1; the relative standard deviations (RSDs) of the intra- and inter-day values were between 2.51% and 5.15%, and the regression coefficient was >0.999 in the linear range of 0.1 to 20 µg mL−1. The validated HPLC-ECD method was also successfully utilized to evaluate the VC levels in different varieties of honey samples with various storage durations as well as in fruit and biological samples. This study provided a perspective for the further accurate determination of VC content in food and biological samples. [ABSTRACT FROM AUTHOR]

In this paper, in order to study the dynamic behavior of the three-body interaction, the generalized Kuramoto model with bimodal frequency distribution under the joint interaction of two-body and three-body is proposed. The comparative numerical results of the phase synchronization paths of the three-body interaction under different coupling strengths show that the three-body interaction can transform the continuous transition process into the first-order transition process. Interestingly, the change from continuous to discontinuous transition due to the variation of the coupling strength of the three-body interaction is similar to the shape of the bimodal distribution of the natural frequency. The critical coupling strength of the two-body interaction of synchronous transition is derived from the Ott–Antonsen–Ansatz method. The numerical results are consistent with the theoretical ones. The findings help our understanding of the transformation process from being continuous to discontinuous. [ABSTRACT FROM AUTHOR]

Summary: The metro‐induced vibrations and seismic safety are both big issues for historical buildings in modern cities. This paper proposed a novel hybrid vibration bearing (HVB) to isolate horizontal earthquakes and mitigate vertical metro‐induced vibrations. The HVB consists of lead rubber bearing and thick rubber bearing with decoupled horizontal and vertical behaviors. The mechanical model of HVB is developed, and a new vertical stiffness formula of thick rubber bearing is proposed to calculate the compression stiffness, without conducting test. A static test of the prototype HVB and a dynamic experiment of an SDOF system were performed. The bearing has stable behavior under different pressures and lateral deformations. The bidirectional test confirmed the decoupling characteristics. The isolation design and retrofitting of an overtrack historical building was conducted. After retrofitting, the average maximum vibration level and the average subfrequency vibration level decreased 25% and 18%, respectively. The horizontal accelerations of isolated structure were 65% to 70% of the input, and the shear strains of bearings were smaller than 200% under rare earthquakes. Finally, case study of structures with different types of foundations is introduced. The vibration mitigation efficiency of different structures is confirmed. [ABSTRACT FROM AUTHOR]

Nano‐heterointerface engineering has been demonstrated to influence interfacial polarization by expanding the interface surface area and constructing a built‐in electric field (BEF), thus regulating electromagnetic (EM) wave absorption. However, the dielectric‐responsive mechanism of the BEF needs further exploration to enhance the comprehensive understanding of interfacial polarization, particularly in terms of quantifying and optimizing the BEF strength. Herein, a “1D expanded 2D structure” carbon matrix is designed, and semiconductor ZnIn2S4 (ZIS) is introduced to construct a carbon/ZIS heterostructure. The cross‐dimensional nano‐heterointerface design increases interface coupling sites by expanding the interface surface area and induces an increase in the Fermi level difference on both sides of the interface to modulate the distribution of interface charges, thereby strengthening the BEF at the interface. The synergistic effect leads to excellent EM absorption performance (minimum reflection coefficient RCmin = −67.4 dB, effective absorption bandwidth EAB = 6.0 GHz) of carbon/ZIS heterostructure. This work introduces a general modification model for enhancing interfacial polarization and inspires the development of new strategies for EM functional materials with unique electronic behaviors through heterointerface engineering. [ABSTRACT FROM AUTHOR]