Thermal ionization mass spectrometry (TIMS) is the workhorse for lead isotopic ratio analysis due to its excellent precision. Silica gel as ionization activator on Re filament is proved to the best ...emitter that can provide excellent sensitivity even small Pb sample size. However, the price of Re filament is three times that of Ta filament that leads to high experimental cost for TIMS laboratory. Here, we first present a novel silicon nitride (β-Si3N4) emitter on the Ta filament with good sensitivity for Pb isotopic ratio measurements. Hence, the cost of filament material is cut down ∼70%. The β-Si3N4 emitter can yield stable and long-life Pb+ signal, about 2–3 V 208Pb and 0.65–0.90 V 208Pb for 20 ng and 5 ng NIST SRM981 sample size that is applicable to the most geological materials for bulk analysis. A suite of silicate reference materials were analyzed to verify the reliability and accuracy of our method. For 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotope ratios of geological samples, excellent internal precisions (2 SE) of ±0.005%–0.013% are achieved. Replicate digestions and analyses of the basalt standard BCR-2 and coal fly ash standard GBW08401 demonstrate that good external precision is obtainable that is 0.10–0.18% (n = 6, 2 SD) for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios.
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•A low-cost and sensitive of β-Si3N4 emitter is presented for Pb isotope analysis.•This method is economy of materials that cut down (∼70%) the cost of the filaments.•β-Si3N4 emitter yields stable and high intensity Pb + signal for 5–20 ng NIST SRM981.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Sm–Nd isotopic system, one of the important techniques for dating and geochemical tracing, has been widely used in geosciences. Precise and accurate measurements of Nd isotopic ratios are more ...difficult to achieve for microsamples that contain less than 50
ng
Nd, when routine Nd
+ technique is applied on thermal ionization mass spectrometer (TIMS). Compared to Nd
+ technique, the NdO
+ technique, owing to more efficient ionization, is a better choice for high precision measurements of Nd isotopic ratios of micro- or low-content samples. This study presents measurement results of sub-nanogram size samples of standard reference solution and rock-powder using NdO
+ technique on the latest TIMS (GV product IsoProbe-T). Sixteen rock-powder references and four reference solutions were measured both by NdO
+ and Nd
+ techniques for an evaluation of accuracy and precision of measurements obtained by the NdO
+ technique. Results show that analytical precision and reproducibility of NdO
+ measurements of sub-nanogram Nd is comparable with those obtained by the Nd
+ measurements of samples containing 200
ng
Nd. Internal precision of the
143Nd/
144Nd ratios achieved with both techniques is better than 0.003%. Our results show that the microsample NdO
+ technique is a very promising method for high resolution Sm–Nd geochronology and isotopic tracing.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The most recent studies on the applications of nanostructured carbon materials, including carbon nanotubes, carbon nanofibers, and graphene oxides, in constructions are presented. First, the ...preparation of nanostructured carbon/infrastructure material composites is summarized. This part is mainly focused on how the nanostructured carbon materials were mixed with cementitious or asphalt matrix to realize a good dispersion condition. Several methods, including high speed melting mixing, surface treatment, and aqueous solution with surfactants and sonication, were introduced. Second, the applications of the carbon nanostructured materials in constructions such as mechanical reinforcement, self-sensing detectors, self-heating element for deicing, and electromagnetic shielding component were systematically reviewed. This paper not only helps the readers understand the preparation process of the carbon nanostructured materials/infrastructure material composites but also sheds some light on the state-of-the-art applications of carbon nanostructured materials in constructions.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Direct dating of petroleum systems by hydrocarbon or associated authigenic minerals is crucial for petroleum system analysis and hydrocarbon exploration. The precipitation of authigenic pyrite in ...petroliferous basins is commonly genetically associated with hydrocarbon generation, migration, accumulation, or destruction. Pyrite rubidium-strontium (Rb-Sr) isotope dilution thermal ionization mass spectrometry (ID-TIMS) is a well-developed technique, and its successful application for high-temperature ore systems suggests that this dating method has the potential to directly date key processes in the low-temperature petroleum systems. Rb-Sr data for pyrites in two Ordovician carbonate rock specimens collected from ~4952 m in the YD-2 well in the Yudong region, northern Tarim Basin (NW China), yield two identical isochron ages within analytical uncertainties: 206 ± 13 (2σ) and 224 ± 28 Ma (2σ). SEM investigations demonstrate that Rb and Sr atoms mainly reside in the crystal lattice of the pyrites due to the absence of fluid and mineral inclusions. The rigorous Rb-Sr isochron relations documented in the samples indicate that such residency can result in sufficient Rb/Sr fractionation and initial Sr isotopic homogenization for geochronology. In addition, the closure temperature (227–320 °C) for the Rb-Sr isotope system in pyrite is higher than the precipitation temperature for pyrite in petroleum-related environments (below 200 °C), suggesting that the Rb-Sr age of pyrite was not overprinted by post-precipitation alteration. Integrating the lead-strontium-sulfur isotopes of the pyrites with burial history analysis, the ages are interpreted as the timing of alteration of the paleo-oil pool by a hydrothermally-triggered thermochemical sulfate reduction process. This study, for the first time, demonstrates that Rb-Sr pyrite geochronology, combined with radiogenic and stable isotopic analyses, can be a useful tool to evaluate the temporal evolution of oil pools. This approach bears great potential for dating of petroleum systems anywhere else in the world.
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CEKLJ, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Complete sample digestion is a prerequisite for acquiring high-quality analytical results for geological samples. Closed-vessel acid digestion (bomb) has typically been used for the total digestion ...of refractory geological samples. However, the long digestion time (4–5 days) and insoluble fluoride complexes still pose challenges for digesting refractory geological samples using this approach. In this study, an efficient and simplified digestion technique combining ultrafine powders from planetary ball milling with bomb digestion was developed for trace element analysis of refractory geological samples: peridotite and granitoid. The method shows two significant improvements compared with previous approaches. (1) By performing dry planetary ultrafine milling, the initial 200 mesh peridotite (<74 μm) could be reduced to 800 mesh (<20 μm) in 6 min at a ball-to-powder mass ratio of approximately 15 using 3 mm tungsten carbide milling balls. (2) Complete peridotite and granitoid dissolution were achieved in approximately 2 h, 60 times faster than what is achievable using previous methods (2 h vs 120 h). Moreover, ultrafine powders effectively suppressed insoluble fluoride formation during bomb digestion. A suite of peridotite and granitoid reference materials were measured to evaluate the stability of this method. This efficient, simple, and reliable sample digestion method could benefit geological, food, environmental, and other fields requiring solid sample decomposition via wet acid, fusion, combustion, or dry ashing.
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IJS, KILJ, NUK, PNG, UL, UM
Thermal ionization mass spectrometry is considered as the “gold standard” for obtaining precise 87Sr/86Sr isotopic ratios. However, the conventional TIMS technique is laborious because it requires ...the purification of Sr using expensive and complex resin column techniques to overcome severe 87Rb isobaric interference on 87Sr and inhibition on ionization of Sr originating from matrix elements. To overcome this issue, we have developed a hydrofluoric acid coprecipitation method specifically designed for red wine samples. This method effectively captures Sr while eliminating 87Rb isobaric interference and removing the majority of matrix element inhibition for red wine samples. Notably, our method offers several advantages, including low cost, rapidity, simplicity, and high sample throughput. We have applied this method to analyze nine red wine samples sourced from China, Spain, Chile, Argentina, France, Italy, and Australia. Our method greatly simplified the sample preparation process for red wine samples without compromising the analytical accuracy and precision.
Thermal ionization mass spectrometry is considered as the "gold standard" for obtaining precise
87
Sr/
86
Sr isotopic ratios. However, the conventional TIMS technique is laborious because it requires ...the purification of Sr using expensive and complex resin column techniques to overcome severe
87
Rb isobaric interference on
87
Sr and inhibition on ionization of Sr originating from matrix elements. To overcome this issue, we have developed a hydrofluoric acid coprecipitation method specifically designed for red wine samples. This method effectively captures Sr while eliminating
87
Rb isobaric interference and removing the majority of matrix element inhibition for red wine samples. Notably, our method offers several advantages, including low cost, rapidity, simplicity, and high sample throughput. We have applied this method to analyze nine red wine samples sourced from China, Spain, Chile, Argentina, France, Italy, and Australia. Our method greatly simplified the sample preparation process for red wine samples without compromising the analytical accuracy and precision.
Thermal ionization mass spectrometry is considered as the "gold standard" for obtaining precise
87
Sr/
86
Sr isotopic ratios.
The structure of photovoltaic power plant changes from time to time, which leads to nonlinear, time-invariant charateristics of the mathematical model of the photovoltaic power plant. The automatic ...generation control system based on PID control algorithm with constant parameters can't cope with them well. To improve the performance of the automatic generation control system, its control algorithm is studied. For photovoltaic plants, a discrete adaptive control algorithm is designed based on Popov superstability theory. In a 50 MW photovoltaic plant, the perfomances of the automatic generation control system based on this adaptive control algorithm and that based on PID algorithm with constant parameters are compared. The simulation proved the superiority and feasibility of the automatic generation control system based on this adaptive algorithm.
Natural characteristics of thin-wall pipe of the compressor under uniformly distributed pressure were presented in this paper based on a cylindrical shell model. In the traditional method, the beam ...model was usually used to analyze the pipe system. In actual fact, the pipe segment of the compressor was always broken in the form of a long crack or a partial hole and the phenomenon was hardly explained by beam model. According to the structure characteristic of compressor pipe segment, whose radius is large and thickness is little, shell model shows the advantage in this kind of pipe problem. Based on Sanders’ shell theory, the vibration differential equation of pipe was established by applying the energy method. The influences of length to radius ratio (
L
/
R
), thickness to radius ratio (
h
/
R
), circumferential wave number (
n
) and pressure (
q
) on the natural frequencies of pipe were analyzed. The study shows: Pressure and structural parameters have a great effect on the natural characteristics of the pipe. Natural frequency increases as the pressure increases, especially for the higher mode. The sensitivity of natural frequency on pressure becomes stronger with
h
/
R
ratio increases; when
L
/
R
ratio is greater than a certain critical value, the influence of the pressure on natural frequency will no longer be obvious. The value of
n
corresponding to the minimum natural frequency also depends on the value of pressure. In the end, analysis of the forced vibration of a specific pipeline model was given and the modal shapes were illustrated to understand the break of the pipe. The research here will provide the theory support for the dynamic design of related pressure pipe and further experiment study should be employed.
A novel micro-slip friction modeling approach based on real pressure distribution is presented for simulating the interface friction behavior of blades with dovetail joints in aircraft engines. ...Considering the influence of rotational speed and stagger angle on the true pressure distribution of the dovetail joint, an asymmetric pressure density function was established and applied to the Iwan friction model. The pressure distribution at the tenon joint interface is obtained through finite element modeling. And the pressure distribution function is obtained through dimensionality reduction and data fitting. Under the framework of the Iwan model, a new tangential friction displacement relationship at the tenon interface was obtained by changing the critical slip force density function. On this basis, a dynamic model of the dovetail blade was established and the contact characteristics of the interface were analyzed. The results indicate that under the influence of uneven pressure distribution, the width and length directions of the contact interface exhibit different friction behaviors, and the nonlinear response of the blades is affected.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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