ABSTRACT
The shear stress transport turbulence model is employed to conduct a detailed study of flow characteristics at the highest efficiency point and near-stall point in a full-channel 1.5-stage compressor in this paper. The simulation results for the compressor's total pressure ratio and efficiency exhibit good agreement with experimental data. Emphasis is placed on examining the internal flow structure in the tip area of the compressor rotor under near-stall conditions. The results reveal that significant differences in flow structure primarily occur in the tip area as the compressor approaches stall. Specifically, a reduction in turbulent kinetic energy is observed in a region spanning approximately 20%-60% of the chord length on the rotor suction face near-stall conditions. Two additional peak frequencies, at 0.8 and 1.6 times the blade passage frequency, are observed, and the intricate flow phenomena are elaborated at the near-stall point. The near-stall point exhibits greater noise levels than the highest efficiency point, where the intensity of the surface source increases by more than 10 dB, peaking at 20 dB. This additional peak serves as a significant supplementary noise source near the stall point, leading to a maximum increase of 33.3 dB in the free radiated sound power. The acoustic response within the duct indicates that the compressor operating at the near-stall point continues to produce substantial noise on the actual test bench, showing an average increase of 6 dB in noise levels, and the distribution of the additional peak single-tone noise at the entrance significantly differs from that observed at the highest efficiency point.
ABSTRACT
Energy-dispersive X-ray fluorescence spectrometry (EDXRF) is a suitable analytical procedure for screening drug products for Elemental Impurities (EI) according to ICH guideline Q3D. EDXRF represents a cost-efficient, robust and standard-free alternative compared to other methodologies for trace analysis, and therefore utilization of this application should be encouraged. This study demonstrates the capability of EDXRF for EI screening of oral solid dosage drug products (OSD products) within a defined matrix range. Method development and validation focused on class 1 (Cd, Pb, As, Hg) and class 2A (Co, V, Ni) elements, as defined by ICH guideline Q3D. In order to limit validation activities, a novel cluster approach was applied, based on matrix properties. This included comprehensive characterization of method performance parameters for exemplary pharmaceutical matrices and demonstration of LOQ independence from matrix effects by using a set of limit samples representing typical matrix variations of OSD products. The methodology can be used as a limit test for class 1 and class 2A elements and is fully compliant with method validation requirements according to the European Pharmacopeia. The novelty of the present work is the application of EDXRF for a routine screening of OSD products for Elemental Impurities within the pharmaceutical industry beyond previously published feasibility studies for a limited number of pharmaceutical raw materials or products.
Subject(s)
Drug Contamination/prevention & control , Pharmaceutical Preparations/analysis , Spectrometry, X-Ray Emission/methodsABSTRACT
In this experiment, a TiO2-Ce0.9Zr0.1O2 support with core-shell structure was successfully prepared by a precipitation method and VO X /TiO2-Ce0.9Zr0.1O2 catalyst was prepared by an impregnation method, and the catalyst was used to catalyze the NH3-SCR of NO. Based on the results of HRTEM, XRD, BET, H2-TPR, NH3-TPD, XPS, Py-IR, it was speculated that due to the interaction between TiO2 and Ce0.9Zr0.1O2, more oxygen vacancies and Ce3+ are generated, which are beneficial to the existence of low-valence V by electron transfer between high valence state V and Ce3+and increase the acidic sites on the catalyst surface. The catalytic activity (>97%) of the VO X /TiO2-Ce0.9Zr0.1O2 catalyst is superior to the current commercial catalyst (V2O5-WO3/TiO2) and has a higher N2 selectivity (>97.5%) at 40 000 h-1 GHSV and 250-400 °C.
ABSTRACT
A series of V2O5-WO3/TiO2 catalysts with different vanadium loading amounts were prepared by an impregnation method and were characterized by XRD, Raman spectroscopy, XPS, DRIFTS, Py-DRIFTS, NH3-TPD, H2-TPR, etc. The results show that the catalytic activity is related to the ratio of V4+/V5+. The variation of the V4+/V5+ ratio caused by the different dispersion states of vanadia oxide leads to changes in the surface acidity and redox properties of the catalysts. As the V4+/V5+ ratio reaches the maximum value, the apparent activation energy (E a) required to form the transition state on the Brønsted acid sites is the lowest. Artificial regulation of vanadium loading to properly increase V4+/V5+ content may affect the interactions between V, W, O and Ti atoms, which enhances NH3-SCR reaction performance.
ABSTRACT
A 3D printing technique was introduced to a quartz-enhanced photoacoustic spectroscopy (QEPAS) sensor and is reported for the first time. The acoustic detection module (ADM) was designed and fabricated using the 3D printing technique and the ADM volume was compressed significantly. Furthermore, a small grin lens was used for laser focusing and facilitated the beam adjustment in the 3D-printed ADM. A quartz tuning fork (QTF) with a low resonance frequency of 30.72 kHz was used as the acoustic wave transducer and acetylene (C2H2) was chosen as the analyte. The reported miniaturized QEPAS trace gas sensor is useful in actual sensor applications.
