人造金刚石与硬质合金复合材料的研制

 本实验选用TiH₂及其它微量元素做粘结剂，在DS-029B型六面顶压机上烧结人造金刚石与硬质合金复合材料。实验中，采取TiH₂脱氢与金刚石净化同时进行的工艺，在高真空和一定温度下脱氢，得到高活性的新鲜钛，使其具有更强的粘结作用，以获得高磨耗比的金刚石复合材料。实验中比较了不同净化温度对磨耗比的影响；同一种粘结剂不同含量与磨耗比之间的关系；同时还测试了其耐热性及时间极限。结果表明，这种复合材料在850 ℃下，加热3 min，磨耗比没有明显改变。     

In-situ observations and acoustic measurements upon fragmentation of free-floating intermetallics under ultrasonic cavitation in water

Grain refinement in alloys is a well-known effect of ultrasonic melt processing. Fragmentation of primary crystals by cavitation-induced action in liquid metals is considered as one of the main driving mechanisms for producing finer and equiaxed grain structures. However, in-situ observations of the fragmentation process are generally complex and difficult to follow in opaque liquid metals, especially for the free-floating crystals. In the present study, we develop a transparent test rig to observe in real time the fragmentation potential of free-floating primary Al₃Zr particles under ultrasonic excitation in water (an established analogue medium to liquid aluminium for cavitation studies). An effective treatment domain was identified and fragmentation time determined using acoustic pressure field mapping. For the first time, real-time high-speed imaging captured the dynamic interaction of shock waves from the collapsing bubbles with floating intermetallic particles that led to their fragmentation. The breakage sequence as well as the cavitation erosion pattern were studied by means of post-treatment microscopic characterisation of the fragments. Fragment size distribution and crack patterns on the fractured surface were then analysed and quantified. Application of ultrasound is shown to rapidly (<10 s) reduce intermetallic size (from 5 mm down to 10 μm), thereby increasing the number of potential nucleation sites for the grain refinement of aluminium alloys during melt treatment.     

Optical Channel Selection Avoiding DIPP in DSB-RFoF Fronthaul Interface

The paper presents a method of selecting an optical channel for transporting the double-sideband radio-frequency-over-fiber (DSB-RFoF) radio signal over the optical fronthaul path, avoiding the dispersion-induced power penalty (DIPP) phenomenon. The presented method complements the possibilities of a short-range optical network working in the flexible dense wavelength division multiplexing (DWDM) format, where chromatic dispersion compensation is not applied. As part of the study, calculations were made that indicate the limitations of the proposed method and allow for the development of an algorithm for effective optical channel selection in the presence of the DIPP phenomenon experienced in the optical link working in the intensity modulation–direct detection (IM-DD) technique. Calculations were made for three types of single-mode optical fibers and for selected microwave radio carriers that are used in current systems or will be used in next-generation wireless communication systems. In order to verify the calculations and theoretical considerations, a computer simulation was performed for two types of optical fibers and for two selected radio carriers. In the modulated radio signal, the cyclic-prefix orthogonal frequency division multiplexing (CP-OFDM) format and the 5G numerology were used.     

Computational studies on the thermal decomposition of the CH2FOCHFO radical

Theoretical studies have been carried out on the kinetics and thermochemistry of the thermal decomposition of the CH₂FOCHFO radical formed during the photo-oxidation of CH₂FOCH₂F (HFE-152E) using the dual-level method of obtaining the optimised structure at DFT(M06-2X)/6-311++G(d,p) followed by a single-point energy calculation at the G3 level of theory. The rate constant for different reaction channels involved during the decomposition processes of CH₂FOCHFO is evaluated at 298 K and 1 atm using canonical transition-state theory. The results point out that the C–H bond scission is the dominant path involving an energy barrier of 9.5 kcal mol^?1 determined at the G3 level of theory. A potential energy diagram is constructed and the results are compared with the data available from the literature for a structurally similar molecule.     

Franck–Condon Factors and r‐Centroids for the B–, C–, F–, and G–X Band Systems of YF Molecule

The Franck–Condon factors and r‐centroids, which are very closely related to relative transition probabilities, have been evaluated by a more reliable numerical integration procedure for the B¹π–X¹Σ⁺, C¹Σ⁺–X¹Σ⁺, F¹Σ⁺–X¹Σ⁺, and G¹π–X¹Σ⁺ band systems of the YF molecule, using suitable potentials.     

Rotational Analysis of the 1–4 Band of the B 2Σ+–X 2Σ+ System of 14C16O+

ABSTRACT

High-resolution emission spectrum of the 1–4 band of the B ²Σ⁺–X ²Σ⁺ transition of ¹⁴C¹⁶O⁺ was observed for the first time by conventional emission spectroscopy. The band spectrum was excited in a water-cooled Geissler lamp filled with commercial gaseous carbon monoxide enriched in about 80% of the radiocarbon ¹⁴C. A rotational analysis has been carried out and obtained molecular constants have been merged with previously published data for the B ²Σ⁺–A ²Π_i and A ²Π_i–X ²Σ⁺ transitions. The principal equilibrium constants for the ground X ²Σ⁺ state obtained from this work are ω_e = 2121.7726(98), ω_e x _e = 13.9055(27), B _e = 1.815290(30), α_e = 1.6594(33) × 10^?2, and γ_e = ? 0.377(73) × 10^?4 cm^?1. Also, presently known experimental equilibrium molecular constants of the X ²Σ⁺ states of the CO⁺ isotopic molecules are summarized and isotopic dependence of the B _e and ω _e constants is discussed.     

Partitioning of atmospheric carbon dioxide over Central Europe: insights from combined measurements of CO 2 mixing ratios and their carbon isotope composition

Regular measurements of atmospheric CO ₂ mixing ratios and their carbon isotope composition (¹³C/¹²C and ¹⁴C/¹²C ratios) performed between 2005 and 2009 at two sites of contrasting characteristics (Krakow and the remote mountain site Kasprowy Wierch) located in southern Poland were used to derive fossil fuel-related and biogenic contributions to the total CO ₂ load measured at both sites. Carbon dioxide present in the atmosphere, not coming from fossil fuel and biogenic sources, was considered ‘background’ CO ₂. In Krakow, the average contribution of fossil fuel CO ₂ was approximately 3.4%. The biogenic component was of the same magnitude. Both components revealed a distinct seasonality, with the fossil fuel component reaching maximum values during winter months and the biogenic component shifted in phase by approximately 6 months. The partitioning of the local CO ₂ budget for the Kasprowy Wierch site revealed large differences in the derived components: the fossil fuel component was approximately five times lower than that derived for Krakow, whereas the biogenic component was negative in summer, pointing to the importance of photosynthetic sink associated with extensive forests in the neighbourhood of the station. While the presented study has demonstrated the strength of combined measurements of CO ₂ mixing ratios and their carbon isotope signature as efficient tools for elucidating the partitioning of local atmospheric CO ₂ loads, it also showed the important role of the land cover and the presence of the soil in the footprint of the measurement location, which control the net biogenic surface CO ₂ fluxes.     

Nuklearpharmaka — Ihre Entwicklung,Präparation und Anwendungsmöglichkeiten

Radioaktiv markierte Präparate haben in denletzten Jahren in schnell zunehmendem Maße Eingang in die klinische Medizin gefunden. Sie sind beieiner Reihe von Indikationen schon jetzt außerordentlich wertvolle Hilfsmittel bei der Diagnose, besonders bei der Prüfung von Organfunktionen.     

Radioaktive und stabile Isotope bei der Lösung pflanzenphysiologischer Probleme

Es werden neuere Ergebnisse von Untersuchungen zur Biosynthese einiger Alkaloide und zum Stoffwechsel von Herbiziden mitgeteilt und diskutiert, die unter Verwendung von ¹⁴C, ³H und ¹⁵N durchgeführt wurden.