水陆两栖飞机典型横截面入水撞击实验研究

选取当今世界几种水陆两栖飞机典型横截面为研究对象,通过进行不同投放高度和不同质量的楔形体入水冲击实验,动态测量楔形体入水冲击过程中的压力并记录自由液面变化情况,研究了不同实验件的自由液面变化、冲击压力随时间变化及局部压力分布规律等。通过对比分析,发现带舭弯的弧形横截面型式有利于降低水陆两栖飞机在复杂海况下的着水冲击载荷,可作为水陆两栖飞机设计的参考线型。     

Investigation of structural and electronic properties by pnictogen substitution in the layered oxypnictides (LaO)ZnPn (Pn = P,As, Sb)

We study the structural and electronic properties of p-type layered oxypnictides (LaO)ZnPn (Pn = P, As, Sb), calculated by first principles. Pn substitution from P to Sb increases D_2d-type local symmetry distortions at ZnPn₄ and OLa₄ tetrahedra. (LaO)ZnP and (LaO)ZnAs exhibit direct band gaps (Γ → Γ) of 0.621 eV and 0.528 eV, respectively, while (LaO)ZnSb exhibits an indirect band gap (Γ → 0.2Λ) of 0.029 eV. The band gaps come from valence Pn p _x/p _y and conduction Zn 4s states. Moreover, the substitution increases split-off energy at Z and Γ points. We find localized valence degeneracy-lifted Zn 3d states because of the possible second-order Jahn-Teller effect, which induces the local symmetry distortions. The localized Zn 3d states are followed by minor bonding s-p hybridization of Zn and Pn. Above them, we show major bonding s-p hybridization; O 2p states in electron-blocking [LaO]⁺ layers, which are essential for thermoelectricity; and nonbonding Pn p states near Fermi level. In the conduction band, antibonding s-p hybridization is found. Our result shows new insights and findings of structural and electronic properties, which explain previous experimental results, as the focus of this study is related to inorganic chemistry. This study is important for future functional device applications.     

Metal‐Ion Permeation in Congested Nanochannels: The Exposure Effect of Ag+ Ions on the Phosphorescent Properties of a Gold(I)–Pyrazolate Complex that is Confined in the Nanoscopic Channels of Mesoporous Silica

An organometallic/silica nanocomposite of a 1D cylindrical assembly of a trinuclear gold(I)–pyrazolate complex ([Au₃Pz₃]) that was confined inside the nanoscopic channels of hexagonal mesoporous silica ([Au₃Pz₃]/silica_hex), emitted red light with a luminescence center at 693 nm upon photoexcitation at 276 nm owing to a Au^I? Au^I metallophilic interaction. When a film of [Au₃Pz₃]/silica_hex was dipped into a solution of Ag⁺ in tetrahydrofuran (THF), the resulting nanocomposite material (Ag@[Au₃Pz₃]/silica_hex) emitted green light with a new luminescence center at 486 nm, which was characteristic of a Au^I? Ag^I heterometallic interaction. Changes in the emission/excitation and XPS spectra of Ag@[Au₃Pz₃]/silica_hex revealed that Ag⁺ ions permeated into the congested nanochannels of [Au₃Pz₃]/silica_hex, which were filled with the cylindrical assembly of [Au₃Pz₃].     

A Urea Precursor to Synthesize Carbon Nitride with Mesoporosity for Enhanced Activity in the Photocatalytic Removal of Phenol

A urea precursor was used for the first time to prepare mesoporous carbon nitride (MCN) by a thermal polymerization process with silica nanospheres as a hard template. Although the prepared MCN samples have similar structures and optical properties, it was revealed that the specific surface area, pore‐size distribution, and morphology of the MCN samples depend on the initial mass ratio of urea to silica. Compared to the bulk carbon nitride (BCN) that only gave 20 % phenol removal (6 h of irradiation), the activities can be enhanced up to 74 % on MCN samples for photocatalytic removal of phenol under visible‐light irradiation. The highest conversion was obtained on MCN with an initial mass ratio of urea to silica of 5, which has high surface area of 191 m² g^?1 and a nanoporous structure with uniform pore‐size distribution of 7 nm. In addition to the high activity, the MCN sample also showed high photocatalytic stability.     

Physical and Optical Properties of Calcium Zinc Borophosphate Glasses Doped with Manganese Ions

This article reports on the physical and optical properties, absorption, and luminescence spectra in the visible region, of calcium zinc borophosphate glasses doped with manganese ions. The manganese composition was varied up to 10 mol%. The aim of this work was to investigate the effect of the luminescence properties when the glasses were doped with different compositions of manganese ions. X-ray diffraction profiles confirmed their glassy nature. The optical absorption spectrum showed bands characteristic of manganese ions in octahedral symmetry. Both excitation and emission spectra were recorded for these glasses to understand their optical performances. The emission spectrum showed a single broad band (green region) in octahedral symmetry at 582 nm as a result of transition from the upper ⁴T_1g state to the ⁶A_1g ground state of manganese ions. As the concentration of manganese ions increased, the emission band increased from 582 nm (green-light emission) to 650 nm (red-light emission). Apart from the spectral analysis, different physical properties of these glasses were also analyzed. Based on the physical and optical properties, we found the samples to be more promising for their use as novel luminescent optical materials.     

Evaluation of Antibacterial and Antifungal Properties of Low Molecular Weight Chitosan Extracted from Hermetia illucens Relative to Crab Chitosan

This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (M_w) of 6–21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan’s origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.     

The Future of Carica papaya Leaf Extract as an Herbal Medicine Product

Carica papaya (papaya) leaf extract has been used for a long time in a traditional medicine to treat fever in some infectious diseases such as dengue, malaria, and chikungunya. The development of science and technology has subsequently made it possible to provide evidence that this plant is not only beneficial as an informal medication, but also that it has scientifically proven pharmacological and toxicological activities, which have led to its formal usage in professional health care systems. The development of formulations for use in nutraceuticals and cosmeceuticals has caused this product to be more valuable nowadays. The use of good manufacturing practice (GMP) standards, along with the ease of registering this product facilitated by policies of the national government, will absolutely increase the value of papaya leaf extract as a vital nutraceutical and cosmeceutical products in the near future. In this article, we review the potential of papaya leaf extract to be a high-value commodity in terms of its health effects as well as its industrial benefits.