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1
Kondratiev, Alexander S., e Pavel P. Shvydko. "Analysis of collisions of precipitating solid particles with a wall in a viscous liquid". Izvestiya MGTU MAMI 17, n. 3 (25 dicembre 2023): 233–39. http://dx.doi.org/10.17816/2074-0530-501750.
Testo completoAbstract (sommario):
BACKGROUND: When calculating velocities of free precipitation of solid particle in a viscous Newtonian liquid, it is assumed that influence of incoming vessel head can be neglected. Necessity of considering this factor grows with a vessel head getting closer and with decrease of particles’ geometrical size.
AIMS: Development of the method of calculating solid particles’ precipitation rate in a Newtonian fluid considering the incoming vessel head and definition the limits of its application.
METHODS: The known analytical model of motion of precipitating disperses solid particles when approaching a vessel head is analyzed. It is shown that the known model of calculation of solid particles’ precipitation rate near the vessel head needs to be refined.
RESULTS: The proposed modification of the analytical model of definition the solid particles’ precipitation rate considering the existence of a vessel head helps to ensure more credible results from physical standpoint. Recommendations regarding the influence of the Brownian motion of fluid’s molecules on motion of precipitating solid particles are given.
CONCLUSION: Practical value of the study lies in ability to calculate solid particles’ precipitation rate near to a vessel head.
2
Povar, Igor, e Oxana Spinu. "Correlation between global thermodynamic functions and experimental data in multicomponent heterogeneous systems". Canadian Journal of Chemistry 94, n. 2 (febbraio 2016): 113–19. http://dx.doi.org/10.1139/cjc-2015-0411.
Testo completoAbstract (sommario):
The correlation between global thermodynamic functions and such experimental data, which quantitatively characterize the precipitation–dissolution processes of sparingly soluble compounds, as the degree of precipitation and residual concentrations of the solid-phase components in saturated solutions under real conditions, taking into account the complex formation reactions, has been deducted. The paper intends also to introduce widely formal thermodynamic methods for forecasting the conditions of mutual transformation of solid phases through chemical synthesis by precipitation methods, optimization of coprecipitation methods, fractional precipitation from homogeneous solutions, and separation and analysis of chemical compounds. Within the method of residual concentrations, the thermodynamic parameters of the process of precipitating cadmium ions with potassium decanoate from acid and alkaline solutions for different temperatures were investigated. On the basis of the experimentally determined degree of precipitation and its dependence on temperature, the temperature coefficients and overall thermodynamic characteristics of the precipitation process ([Formula: see text], [Formula: see text], and [Formula: see text]) were determined. The optimum conditions of the investigated process of precipitation have been established.
3
Thériault, Julie M., Nicolas R. Leroux e Roy M. Rasmussen. "Improvement of Solid Precipitation Measurements Using a Hotplate Precipitation Gauge". Journal of Hydrometeorology 22, n. 4 (aprile 2021): 877–85. http://dx.doi.org/10.1175/jhm-d-20-0168.1.
Testo completoAbstract (sommario):
AbstractAccurate snowfall measurement is challenging because it depends on the precipitation gauge used, meteorological conditions, and the precipitation microphysics. Upstream of weighing gauges, the flow field is disturbed by the gauge and any shielding used usually creates an updraft, which deflects solid precipitation from falling in the gauge, resulting in significant undercatch. Wind shields are often used with weighing gauges to reduce this updraft, and transfer functions are required to adjust the snowfall measurements to consider gauge undercatch. Using these functions reduces the bias in precipitation measurement but not the root-mean-square error (RMSE). In this study, the accuracy of the Hotplate precipitation gauge was compared to standard unshielded and shielded weighing gauges collected during the WMO Solid Precipitation Intercomparison Experiment program. The analysis performed in this study shows that the Hotplate precipitation gauge bias after wind correction is near zero and similar to wind corrected weighing gauges. The RMSE of the Hotplate precipitation gauge measurements is lower than weighing gauges (with or without an Alter shield) for wind speeds up to 5 m s−1, the wind speed limit at which sufficient data were available. This study shows that the Hotplate precipitation gauge measurement has a low bias and RMSE due to its aerodynamic shape, making its performance mostly independent of the type of solid precipitation.
4
Zhang, Lele, Lin Zhao, Changwei Xie, Guangyue Liu, Liming Gao, Yao Xiao, Jianzong Shi e Yongping Qiao. "Intercomparison of Solid Precipitation Derived from the Weighting Rain Gauge and Optical Instruments in the Interior Qinghai-Tibetan Plateau". Advances in Meteorology 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/936724.
Testo completoAbstract (sommario):
Due to the light precipitation and strong wind in the cold season, it is hard to get credible solid precipitation on the Qinghai-Tibetan plateau (QTP). To address this issue, two kinds of optical instruments, the Thies Laser Precipitation Monitor (LPM) and OTT laser-optical Particle Size Velocity (Parsivel), were used on QTP. The measured precipitation was compared with the precipitation derived from Geonor T-200B precipitation gauge (Geonor). The results showed that Geonor was hard to catch light precipitation (precipitation amount was less than 1 mm during a single event) when the wind speeds were higher than 3.5 m/s. Even when the wind speeds were smaller than 3.5 m/s, about 44% of such light precipitation events were not recorded by Geonor. The optical instruments had much better performance in recording light precipitation. Three methods were used to correct Geonor measurements of daily solid precipitation and the corrected values were set as reference for assessing the performance of LPM and Parsivel; the results showed that LPM had good performance in measuring the solid precipitation but Parsivel overestimated the precipitation amount. Methods for correcting Geonor’s hourly solid precipitation and recalculating Parsivel’s solid precipitation amount were also proposed in this paper.
5
Sheppard, B. E., e P. I. Joe. "Performance of the Precipitation Occurrence Sensor System as a Precipitation Gauge". Journal of Atmospheric and Oceanic Technology 25, n. 2 (1 febbraio 2008): 196–212. http://dx.doi.org/10.1175/2007jtecha957.1.
Testo completoAbstract (sommario):
Abstract The Precipitation Occurrence Sensor System (POSS) is a small X-band Doppler radar originally developed by the Meteorological Service of Canada for reporting the occurrence, type, and intensity of precipitation from Automated Weather Observing Stations. This study evaluates POSS as a gauge for measuring amounts of both liquid and solid precipitation. Different precipitation rate estimation algorithms are described. The effect of different solid precipitation types on the Doppler velocity spectrum is discussed. Lacking any accepted reference for high temporal resolution rates, the POSS precipitation rate measurements are integrated over time periods ranging from 6 h to one day and validated against international and Canadian reference gauges. Data from a wide range of sites across Canada and for periods of several years are used. The statistical performance of POSS is described in terms of the distribution of ratios of POSS to reference gauge amounts (catch ratios). In liquid precipitation the median of the catch ratio distribution is 82% and the interquartile range was between −12% and 19% about the median. In solid precipitation the median is 90% and the interquartile range is between −17% and 24% about the median. The underestimation in both liquid and solid precipitation is shown to be a function of precipitation rate and phase. The effects of radome wetting, raindrop splashing, wind, and the radar “brightband” effect on the estimation of precipitation rates are discussed.
6
Grünebaum, T., e E. Dorgeloh. "Biological Phosphorus Elimination Combined with Precipitation and Flocculation". Water Science and Technology 25, n. 4-5 (1 febbraio 1992): 219–24. http://dx.doi.org/10.2166/wst.1992.0498.
Testo completoAbstract (sommario):
As interactions between chemical precipitation and biological wastewater treatment are well known, biological phosphate removal should be considered for advanced nutrient removal. A combination of biological phosphate removal and chemical precipitation treatment is sensible and economic, when the precipitation step is used for removal of residual amounts of phosphate. Improved biological phosphate removal and simultaneous precipitation both give increase in dry solids phosphate content. Assuming a concentration of 0.05 gP/gSS and an effluent suspended solids concentration of 20 mg/l the solids contribution accounts for a Ptot-discharge of 1 mgP/l wastewater. Efficient solid/liquid separation is therefore vital in achieving Ptot-limit values.
7
Lara-Serrano, Marta, Daniela M. Sboiu, Silvia Morales-delaRosa e Jose M. Campos-Martin. "Selective Fragmentation of Lignocellulosic Biomass with ZnCl2·4H2O Using a Dissolution/Precipitation Method". Applied Sciences 13, n. 5 (25 febbraio 2023): 2953. http://dx.doi.org/10.3390/app13052953.
Testo completoAbstract (sommario):
Lignocellulosic biomass dissolution in an inorganic salt hydrate (ZnCl2·4H2O) and its subsequent precipitation with water for the separation of its main compounds were investigated. For this purpose, different dissolution times and temperatures were studied, where 24 h and 70 °C were found to be the optimal choice. Three solids were obtained, which were analyzed and identified by XRD, SEM, NMR, and FTIR spectroscopy. Solid I is the undissolved part of the starting material, and it consists of lignin, which does not react with the inorganic salt hydrate and the unreacted cellulose. Solid II is a cellulose-rich solid with a low portion of hemicellulose and lignin, and Solid III is mainly pure lignin as the characterization results showed. Hemicellulose is mainly dissolved and hydrolyzed in the dissolution treatment and the amount present in all solids was very small. The reactivity of Solid I and Solid II in a hydrolysis reaction was tested (0.2 M/L H2SO4, 5 h, and 140 °C), where a significant improvement in the conversion and the yield of sugars was obtained with respect to the untreated samples in both cases. Solid II yields a large amount of total reducing sugars, with a % selectivity of 78–88%, depending on the starting biomass.
8
Liu, Jie, Bensheng Huang, Liangxiong Chen, Jingxue Yang e Xiaohong Chen. "Evaluation of GPM and TRMM and Their Capabilities for Capturing Solid and Light Precipitations in the Headwater Basin of the Heihe River". Atmosphere 14, n. 3 (24 febbraio 2023): 453. http://dx.doi.org/10.3390/atmos14030453.
Testo completoAbstract (sommario):
Obtaining accurate precipitation data in mountainous regions is important but challenging. In ungauged areas, remotely sensed precipitation products are useful supplements and alternatives to measured precipitation products. However, their ability to detect solid precipitation and light precipitation in mountain areas is still unclear. The primary objective of this study is to evaluate two satellite precipitation products, Global Precipitation Measurement (GPM) and Tropical Precipitation Measuring Mission (TRMM), in the headwaters of an inland river on the northeastern Tibetan Plateau (the Heihe river basin), with a specific focus on their performance regarding light precipitation and solid precipitation. The achieved results reveal that both GPM and TRMM perform poorly over the Heihe river basin, with low Correlation Coefficient value and Critical Success Index value, particularly in winter. Based on the coupled Time-Variant Gain Model-Degree Day Factor Model (TVGM-DDF) initiated in this paper, the GPM is more applicable in terms of running hydrological models. With the aim of detecting solid precipitation, the GPM is more capable of detecting solid precipitation but still unsatisfactory at two stations. In the case of light precipitation, both products underestimate light precipitation. In general, the performance of the two products in the Heihe river basin is not satisfactory and should be enhanced in upcoming explorations. This study provides a strong foundation for choosing alternate precipitation data for related research in the mountain basin.
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Hynčica, Martin, e Radan Huth. "Long-term changes in precipitation phase in Czechia". Geografie 124, n. 1 (2019): 41–55. http://dx.doi.org/10.37040/geografie2019124010041.
Testo completoAbstract (sommario):
Long-term changes in precipitation phase are investigated at ten stations in Czechia. Trends are calculated from 1983 to 2018 for the period between November and April. Daily SYNOP reports and daily precipitation totals are used at every station, where number and occurrence of specific codes in SYNOP report determine daily precipitation totals as solid, combined (which represents, to a large extent, category of mixed precipitation), or liquid. Thereafter, it is possible to calculate trends of all precipitation phases as well as the proportion of solid to total precipitation (S/P; in %). The average S/P trend over all Czech stations is significantly negative (−0.60%·year-1) and accompanied by a sharp decrease in solid precipitation (−1.66 mm·year-1) and an increase in combined precipitation (1.50 mm·year-1). Thus, our results show a ship of precipitation phase from solid to combined. Because of the dependence of S/P on air temperature, we suppose that the current S/P decline is a manifestation of rising air temperatures in the past decades.
10
Wolff, Mareile, Ketil Isaksen, Ragnar Brækkan, Eli Alfnes, Asgeir Petersen-Øverleir e Erik Ruud. "Measurements of wind-induced loss of solid precipitation: description of a Norwegian field study". Hydrology Research 44, n. 1 (30 luglio 2012): 35–43. http://dx.doi.org/10.2166/nh.2012.166.
Testo completoAbstract (sommario):
Precipitation measurements have a well-documented and mostly wind-dependent bias which is especially apparent during solid precipitation events. The resulting inaccuracy in precipitation data remains an area of concern in quantifying regional and global climate trends. As a high-latitude country, Norway has many solid precipitation events often accompanied by high wind speeds where the current adjustment functions have only limited validity. The presented study aims at improving the quality of solid precipitation data. In a comprehensive field experiment, precipitation data of standard automatic gauges are compared with data of a reference gauge surrounded by a double fence construction to minimize wind impact. Additional meteorological parameters are measured at the test site, allowing for an in-depth analysis of high-temporal-resolution precipitation data. The goal is to develop new adjustment functions for solid precipitation measurements which account for Norway's typical climate and are suitable for automated measurements. Measurements began in winter 2010/2011 at the alpine test site in southern Norway (chosen after a pre-study in 2009/2010) and will continue for two more winters. In this paper, the test site and its instrumentation are described and preliminary results are presented.
11
Kochendorfer, John, Rodica Nitu, Mareile Wolff, Eva Mekis, Roy Rasmussen, Bruce Baker, Michael E. Earle et al. "Testing and development of transfer functions for weighing precipitation gauges in WMO-SPICE". Hydrology and Earth System Sciences 22, n. 2 (27 febbraio 2018): 1437–52. http://dx.doi.org/10.5194/hess-22-1437-2018.
Testo completoAbstract (sommario):
Abstract. Weighing precipitation gauges are used widely for the measurement of all forms of precipitation, and are typically more accurate than tipping-bucket precipitation gauges. This is especially true for the measurement of solid precipitation; however, weighing precipitation gauge measurements must still be adjusted for undercatch in snowy, windy conditions. In WMO-SPICE (World Meteorological Organization Solid Precipitation InterComparison Experiment), different types of weighing precipitation gauges and shields were compared, and adjustments were determined for the undercatch of solid precipitation caused by wind. For the various combinations of gauges and shields, adjustments using both new and previously existing transfer functions were evaluated. For most of the gauge and shield combinations, previously derived transfer functions were found to perform as well as those more recently derived. This indicates that wind shield type (or lack thereof) is more important in determining the magnitude of wind-induced undercatch than the type of weighing precipitation gauge. It also demonstrates the potential for widespread use of the previously developed transfer functions. Another overarching result was that, in general, the more effective shields, which were associated with smaller unadjusted errors, also produced more accurate measurements after adjustment. This indicates that although transfer functions can effectively reduce measurement biases, effective wind shielding is still required for the most accurate measurement of solid precipitation.
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Jia, Yufeng, Zhongqin Li, Chunhai Xu, Shuang Jin e Haijun Deng. "A Comparison of Precipitation Measurements with a PWS100 Laser Sensor and a Geonor T-200B Precipitation Gauge at a Nival Glacial Zone in Eastern Tianshan, Central Asia". Atmosphere 11, n. 10 (10 ottobre 2020): 1079. http://dx.doi.org/10.3390/atmos11101079.
Testo completoAbstract (sommario):
Precipitation is a key process in the hydrologic cycle. However, accurate precipitation data are scarce in high mountainous areas, mainly restricted by complex topography, solid precipitation and sparse recording stations. In order to evaluate the quality of precipitation measurement, this study conducted a comparison campaign of precipitation measurements with the PWS100 laser sensor and the Geonor T-200B rain gauge for an entire year from 30 April 2018 to 1 May 2019 at an elevation of 3835 m in a nival glacial zone in eastern Tianshan, Central Asia. The results show that the daily precipitation values recorded by Geonor T-200B and PWS100 are well correlated and the annual precipitation amounts recorded by the two instruments differ by 7%, indicating good capabilities of both instruments in solid precipitation measurement. However, the amount of precipitation measured by Geonor T-200B was 36 mm lower in June to August and 120 mm higher in the remaining months compared with the values measured by PWS100. Our study indicated that Geonor T-200B is more efficient than PWS100 in terms of catching solid precipitation measurements. According to the PWS100 data, the experiment site was dominated by solid precipitation particles, accounting for 60% of total precipitation particles. Based on the precipitation particle and in-situ air temperature measurements, a set of temperature thresholds were established to discriminate rain, sleet and snow. The threshold temperature of rainfall and snowfall is −1.5 and 8 °C, respectively. When air temperature ranges from −1.5 to 8 °C, sleet occurs, meanwhile the ratio of rain to snow depends on air temperature.
13
Smith, Craig D., Eva Mekis, Megan Hartwell e Amber Ross. "The hourly wind-bias-adjusted precipitation data set from the Environment and Climate Change Canada automated surface observation network (2001–2019)". Earth System Science Data 14, n. 12 (30 novembre 2022): 5253–65. http://dx.doi.org/10.5194/essd-14-5253-2022.
Testo completoAbstract (sommario):
Abstract. The measurement of precipitation in the Environment and Climate Change Canada (ECCC) surface network is a crucial component for climate and weather monitoring, flood and water resource forecasting, numerical weather prediction, and many other applications that impact the health and safety of Canadians. Through the late 1990s and early 2000s, the ECCC surface network modernization resulted in a shift from manual to automated precipitation measurements. Although many advantages to automation are realized, such as enhanced capabilities for monitoring in remote locations and a higher frequency of observations at lower cost, the increased reliance on automated precipitation gauges has also resulted in additional challenges, especially with data quality and homogenization. The automated weighing precipitation gauges used in the ECCC operational network have an increased propensity for wind-induced undercatch of solid precipitation. One outcome of the World Meteorological Organization (WMO) Solid Precipitation Intercomparison Experiment (SPICE) was the development of transfer functions for the adjustment of high-frequency solid precipitation measurements made with gauge/wind shield configurations used in the ECCC surface network. Using the SPICE universal transfer function (UTF), hourly precipitation measurements from 397 ECCC automated climate stations were retroactively adjusted for wind undercatch. The data format, quality control, and adjustment procedures are described here. The hourly adjusted data set (2001–2019; version v2019UTF) is available via the ECCC data catalogue at https://doi.org/10.18164/6b90d130-4e73-422a-9374-07a2437d7e52 (ECCC, 2021). A basic spatial impact assessment shows that the highest relative total precipitation adjustments occur in the Arctic, where solid precipitation has an overall higher annual occurrence ratio. The highest adjustments for solid precipitation are shared by the Arctic, Southern Prairies, and the coastal Maritimes, where stations tend to be more exposed and snowfall events occur at higher wind speeds.
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Bournane, M., M. Nedjar e A. F. Sirenko. "Precipitation in solid solutions of Al-Mg". Scripta Materialia 40, n. 3 (gennaio 1999): 375–82. http://dx.doi.org/10.1016/s1359-6462(98)00397-2.
Testo completo
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LINDELOFF, NIELS, ROBERT A. HEIDEMANN, SIMON I. ANDERSEN e ERLING H. STENBY. "A THERMODYNAMIC MIXED-SOLID ASPHALTENE PRECIPITATION MODEL". Petroleum Science and Technology 16, n. 3-4 (marzo 1998): 307–21. http://dx.doi.org/10.1080/10916469808949785.
Testo completo
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Pu, Kang, Xichuan Liu, Hongbing He, Yu Sun, Shuai Hu e Yi Wu. "Microphysical Characteristics of Winter Precipitation in Eastern China from 2014 to 2019". Water 12, n. 3 (24 marzo 2020): 920. http://dx.doi.org/10.3390/w12030920.
Testo completoAbstract (sommario):
To improve solid precipitation monitoring in the hydrology and meteorology field, 1-min precipitation data observed by the PARticle SIze VELocity (PARSIVEL) disdrometer in Nanjing, eastern China, from February 2014 to February 2019 for all days with solid precipitation, were used to study the microphysical characteristics of winter precipitation. In this study, the empirical V-D (velocity–diameter) relationships and observed surface temperature are used for matching precipitation types, and the precipitation data are divided into rain, graupel, wet snow and dry snow. The results show that dry snow and wet snow have maximum Dm (mass-weighted mean diameter) and minimum log10Nw (normalized intercept parameter), while rain shows the opposite. Additionally, the μ-Λ (shape parameter–slope parameter) curve of dry snow and wet snow is very close, and the μ value of dry snow and wet snow is higher than that of graupel and higher than that of rain for the same Λ value. Furthermore, the Ze-S (equivalent reflectivity factor–precipitation intensity) relationships among different types of precipitation are significantly different. If only the Ze-S relationship of rain is used for quantitative precipitation estimation (QPE), then, for small precipitation intensity, solid precipitation will be overestimated, while, for large precipitation intensity, it will be underestimated.
17
Janowicz, J. R., S. L. Stuefer, K. Sand e L. Leppänen. "Measuring winter precipitation and snow on the ground in northern polar regions". Hydrology Research 48, n. 4 (6 aprile 2017): 884–901. http://dx.doi.org/10.2166/nh.2017.059.
Testo completoAbstract (sommario):
Measuring winter precipitation in cold and windy regions is recognized as a difficult task. Nonetheless, the accurate measurement of solid precipitation provides important input data for predicting snowmelt floods and avalanche danger and for monitoring climate change. The difficulties in measuring solid precipitation are associated with environmental factors and technological issues. Environmental factors that contribute to measurement errors include wind, freezing rain, rime, and a large range of solid particle shapes and sizes. Technological issues include gauge configuration, the need for remote, low-power-consumption operation, and difficult conditions for data transmission and retrieval. The objectives of this study were to review currently used gauges for measuring solid precipitation and snow on the ground, to summarize the positive and negative characteristics of each gauge, and to provide a discussion of best practices and design and performance criteria that might be used to stimulate research on new and/or improved precipitation gauges in Northern Research Basin (NRB) countries.
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Urazgildeeva, Aleksandra V., Pavel N. Sviashchennikov, Boris V. Ivanov, Ketil Isaksen, Eirik J. Frland e Ragnar Brkkan. "Comparative analysis of Russian and Norwegian precipitation gauges, measurements in Barentsburg, Western Spitsbergen". Czech Polar Reports 7, n. 1 (1 gennaio 2017): 45–51. http://dx.doi.org/10.5817/cpr2017-1-5.
Testo completoAbstract (sommario):
Comparative analysis of records of two gauges with different wind shields (Tretyakov gauge and Geonor T200-B) were done, based on time series of parallel measurement in Barentsburg settlement, Svalbard, during two winter times in period from September 2014 to July 2016. All collected data of solid precipitation were divided into two ranges with different wind speed conditions. As it was known from earlier papers, Tretyakov gauge measurements tend to underestimate solid precipitation in case when precipitation is not intensive and wind speed is less than 5 m s-1. Opposite results were obtained for blizzard conditions (wind speed is more than 6 m s-1): Tretyakov gauge shows greater values for amount of solid precipitation than Norwegian sensor. Preliminary results in Barentsburg cannot be described as conclusive ones. Estimation of solid precipitation on Spitsbergen measured by different gauges needs further and more detailed research, which includes fieldwork in Barentsburg in spring, such as detailed snow surveys in the settlement.
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Lempio, G. E., K. Bumke e A. Macke. "Measurement of solid precipitation with an optical disdrometer". Advances in Geosciences 10 (26 aprile 2007): 91–97. http://dx.doi.org/10.5194/adgeo-10-91-2007.
Testo completoAbstract (sommario):
Abstract. A study about measurements of solid precipitation using an optical disdrometer is presented. The optical disdrometer is an improved version of the ODM 470 disdrometer. It allows to measure hydrometeors within a size range of 0.4 to 22 mm in diameter. The main advantage of this instrument is its ability to estimate accurately precipitation even under strong wind conditions (Großklaus, 1996). To measure solid precipitation a geometrical model was developed to determine the mean cross-sectional area of snow crystals for different predefined shapes and sizes. It serves to develop an algorithm, which relates the mean cross sectional area of snow crystals to their maximum dimension, liquid water content, and terminal velocity. The algorithm was applied to disdrometer measurements during winter 1999/2000 in Uppsala/Sweden. Resulting precipitation was compared to independent measurements of a Geonor gauge and to manual measurements. In terms of daily precipitation the disdrometer shows a reliable performance.
20
Li, Yanwei, Weiwei Wang, Xin Qin e Gerrit de Leeuw. "Microphysical Processes of a Cold Vortex during Its Movement to the East: A Case Study". Atmosphere 11, n. 10 (11 ottobre 2020): 1083. http://dx.doi.org/10.3390/atmos11101083.
Testo completoAbstract (sommario):
A cold vortex is an important weather system that can cause low temperatures and large amounts of rainfall. Many scientific studies have focused on the climatological features of the cold vortex along with its formation, maintenance, structure, circulation features and precipitation distribution from a synoptic perspective. However, not many studies have been conducted related to the microphysical processes in a cold vortex. In this paper, a model study is presented on the microphysical features in a cloud system associated with a cold vortex system which lasted for four days. The system formed, strengthened, split into two and dissipated while it moved towards the east and brought extensive precipitation to the influenced area. The type and amount of precipitation were not evenly distributed: liquid precipitation covered the whole area influenced by the cloud system, while solid precipitation mainly covered high latitudes north of 48° N. In this case, the cloud system was very cold and the 0 °C; level was very low, with the result that the microphysical features were dominated by cold cloud processes. The mixing ratio of liquid particles was very small, and liquid particles only covered limited areas in the clouds. Due to the low temperature, there were insufficient cloud droplets throughout the whole system for the efficient production of rain droplets by coalescence. The snow mixing ratio was largest, and ice and snow covered the whole cloud area, with very little graupel, which occurred in only a small area. The distribution of the solid particles was influenced by their growth through aggregation, the Bergeron process or accretion, resulting in many snow particles. There were insufficient liquid particles to support the formation of very large particles such as graupel. Liquid precipitation was primarily caused by the melting of snow particles precipitating out of the clouds; solid precipitation was also primarily caused by snow particles that did not melt, along with some graupel.
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Jimeno-Sáez, Patricia, David Pulido-Velazquez, Antonio-Juan Collados-Lara, Eulogio Pardo-Igúzquiza, Javier Senent-Aparicio e Leticia Baena-Ruiz. "A Preliminary Assessment of the “Undercatching” and the Precipitation Pattern in an Alpine Basin". Water 12, n. 4 (8 aprile 2020): 1061. http://dx.doi.org/10.3390/w12041061.
Testo completoAbstract (sommario):
Gauges modify wind fields, producing important systematic errors (undercatching) in the measurement of solid precipitation (Ps), especially under windy conditions. A methodology that combines geostatistical techniques and hydrological models to perform a preliminary assessment of global undercatch and precipitation patterns in alpine regions is proposed. An assessment of temperature and precipitation fields is performed by applying geostatistical approaches assuming different hypothesis about the relationship between climatic fields and altitude. Several experiments using different approximations of climatic fields in different approaches to a hydrological model are evaluated. A new hydrological model, the Snow-Témez Model (STM), is developed including two parameters to correct the solid (Cs) and liquid precipitation (Cr). The procedure allows identifying the best combination of geostatistical approach and hydrological model for estimating streamflow in the Canales Basin, an alpine catchment of the Sierra Nevada (Spain). The sensitivity of the results to the correction of the precipitation fields is analyzed, revealing that the results of the streamflow simulation are improved when the precipitation is corrected considerably. High values of solid Cs are obtained, while Cr values, although smaller than the solid one, are also significant.
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Smith, Craig D., Amber Ross, John Kochendorfer, Michael E. Earle, Mareile Wolff, Samuel Buisán, Yves-Alain Roulet e Timo Laine. "Evaluation of the WMO Solid Precipitation Intercomparison Experiment (SPICE) transfer functions for adjusting the wind bias in solid precipitation measurements". Hydrology and Earth System Sciences 24, n. 8 (20 agosto 2020): 4025–43. http://dx.doi.org/10.5194/hess-24-4025-2020.
Testo completoAbstract (sommario):
Abstract. The World Meteorological Organization (WMO) Solid Precipitation Intercomparison Experiment (SPICE) involved extensive field intercomparisons of automated instruments for measuring snow during the 2013/2014 and 2014/2015 winter seasons. A key outcome of SPICE was the development of transfer functions for the wind bias adjustment of solid precipitation measurements using various precipitation gauge and wind shield configurations. Due to the short intercomparison period, the data set was not sufficiently large to develop and evaluate transfer functions using independent precipitation measurements, although on average the adjustments were effective at reducing the bias in unshielded gauges from −33.4 % to 1.1 %. The present analysis uses data collected at eight SPICE sites over the 2015/2016 and 2016/2017 winter periods, comparing 30 min adjusted and unadjusted measurements from Geonor T-200B3 and OTT Pluvio2 precipitation gauges in different shield configurations to the WMO Double Fence Automated Reference (DFAR) for the evaluation of the transfer function. Performance is assessed in terms of relative total catch (RTC), root mean square error (RMSE), Pearson correlation (r), and percentage of events (PEs) within 0.1 mm of the DFAR. Metrics are reported for combined precipitation types and for snow only. The evaluation shows that the performance varies substantially by site. Adjusted RTC varies from 54 % to 123 %, RMSE from 0.07 to 0.38 mm, r from 0.28 to 0.94, and PEs from 37 % to 84 %, depending on precipitation phase, site, and gauge configuration (gauge and wind screen type). Generally, windier sites, such as Haukeliseter (Norway) and Bratt's Lake (Canada), exhibit a net under-adjustment (RTC of 54 % to 83 %), while the less windy sites, such as Sodankylä (Finland) and Caribou Creek (Canada), exhibit a net over-adjustment (RTC of 102 % to 123 %). Although the application of transfer functions is necessary to mitigate wind bias in solid precipitation measurements, especially at windy sites and for unshielded gauges, the variability in the performance metrics among sites suggests that the functions be applied with caution.
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Chimani, B., R. Böhm, C. Matulla e M. Ganekind. "Development of a longterm dataset of solid/liquid precipitation". Advances in Science and Research 6, n. 1 (28 febbraio 2011): 39–43. http://dx.doi.org/10.5194/asr-6-39-2011.
Testo completoAbstract (sommario):
Abstract. Solid precipitation (mainly snow, but snow and ice pellets or hail as well), is an important parameter for climate studies. But as this parameter usually is not available operationally before the second part of the 20th century and nowadays is not reported by automatic stations, information usable for long term climate studies is rare. Therefore a proxy for the fraction of solid precipitation based on a nonlinear relationship between the percentage of solid precipitation and monthly mean temperature was developed for the Greater Alpine Region of Europe and applied to the existing longterm high resolution temperature and precipitation grids (5 arcmin). In this paper the method is introduced and some examples of the resulting datasets available at monthly resolution for 1800–2003 are given.
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Pierre, Amandine, Sylvain Jutras, Craig Smith, John Kochendorfer, Vincent Fortin e François Anctil. "Evaluation of Catch Efficiency Transfer Functions for Unshielded and Single-Alter-Shielded Solid Precipitation Measurements". Journal of Atmospheric and Oceanic Technology 36, n. 5 (maggio 2019): 865–81. http://dx.doi.org/10.1175/jtech-d-18-0112.1.
Testo completoAbstract (sommario):
AbstractSolid precipitation undercatch can reach 20%–70% depending on meteorological conditions, the precipitation gauge, and the wind shield used. Five catch efficiency transfer functions were selected from the literature to adjust undercatch from unshielded and single-Alter-shielded precipitation gauges for different accumulation periods. The parameters from these equations were calibrated using data from 11 sites with a WMO-approved reference measurement. This paper presents an evaluation of these transfer functions using data from the Neige site, which is located in the eastern Canadian boreal climate zone and was not used to derive any of the transfer functions available for evaluation. Solid precipitation measured at the Neige site was underestimated by 34% and 21% when compared with a manual reference precipitation measurement for unshielded and single-Alter-shielded gauges, respectively. Catch efficiency transfer functions were used to adjust these solid precipitation measurements, but all equations overestimated amounts of solid precipitation by 2%–26%. Five different statistics evaluated the accuracy of the adjustments and the variance of the results. Regardless of the adjustment applied, the catch efficiency for the unshielded gauge increased after the adjustment. However, this was not the case for the single-Alter-shielded gauges, for which the improvement of the results after applying the adjustments was not seen in all of the statistics tests. The results also showed that using calibrated parameters on datasets with similar site-specific characteristics, such as the mean wind speed during precipitation and the regional climate, could guide the choice of adjustment methods. These results highlight the complexity of solid precipitation adjustments.
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Kochendorfer, John, Michael E. Earle, Daniel Hodyss, Audrey Reverdin, Yves-Alain Roulet, Rodica Nitu, Roy Rasmussen, Scott Landolt, Samuel Buisán e Timo Laine. "Undercatch Adjustments for Tipping-Bucket Gauge Measurements of Solid Precipitation". Journal of Hydrometeorology 21, n. 6 (giugno 2020): 1193–205. http://dx.doi.org/10.1175/jhm-d-19-0256.1.
Testo completoAbstract (sommario):
AbstractHeated tipping-bucket (TB) gauges are used broadly in national weather monitoring networks, but their performance for the measurement of solid precipitation has not been well characterized. Manufacturer-provided TB gauges were evaluated at five test sites during the World Meteorological Organization Solid Precipitation Intercomparison Experiment (WMO-SPICE), with most gauge types tested at more than one site. The test results were used to develop and evaluate adjustments for the undercatch of solid precipitation by heated TB gauges. New methods were also developed to address challenges specific to measurements from heated TB gauges. Tipping-bucket transfer functions were created specifically to minimize the sum of errors over the course of the adjusted multiseasonal accumulation. This was based on the hypothesis that the best transfer function produces the most accurate long-term precipitation records, rather than accurate catch efficiency measurements or accurate daily or hourly precipitation measurements. Using this new approach, an adjustment function derived from multiple gauges was developed that performed better than traditional gauge-specific and multigauge catch efficiency derived adjustments. Because this new multigauge adjustment was developed using six different types of gauges tested at five different sites, it may be applicable to solid precipitation measurements from unshielded heated TB gauges that were not evaluated in WMO-SPICE. In addition, this new method of optimizing transfer functions may be useful for other types of precipitation gauges, as it has many practical advantages over the traditional catch efficiency methods used to derive undercatch adjustments.
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Li, Lan, Yuan Yuan Song, Guang Ren Geng e Fu Tian Liu. "Preparation of Zirconium Sol by Precipitation Method". Solid State Phenomena 281 (agosto 2018): 52–57. http://dx.doi.org/10.4028/www.scientific.net/ssp.281.52.
Testo completoAbstract (sommario):
Zirconium sol was prepared using precipitation method. In the process, ZrO(OH)2 precipitate was firstly obtained through the addition of strong base into the zirconium ions, and then was washed to remove the chloride ion. Lastly, the obtained ZrO(OH)2 precipitate was dissolved in nitric acid solution to obtain the white mixed solution. The clear and transparent zirconium sol can be obtained after heated the white mixed solution in a water bath. In this study, the effects of three precipitating agents on the properties of zirconium sol were studied. Zirconium sol prepared by using ammonia as precipitating agent is easy to peptize, while its viscosity is very high. On the other hand, zirconium sol prepared by using urea as precipitating agent exhibits low solid content. Notably, the performance of zirconium sol prepared using ammonia and NH4Cl solution as precipitating agent is best due to its low viscosity and high solid content. In addition, zirconium sol, xerogel and zirconium dioxide powder prepared using ammonia and NH4Cl solution as precipitating agent were systematically characterized by SEM, viscometer, XRD, FTIR. The optimal zirconium sol was synthesized using a peptizing time of 8 h under a peptizing temperature was 80 °C, and the dried amorphous xerogel was converted to tetragonal ZrO2 after calcined at 600 °C, while monoclinic at 1000 °C.
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Dobrowolski, Adrian, Damian Pieloth, Helmut Wiggers e Markus Thommes. "Electrostatic Precipitation of Submicron Particles in a Molten Carrier". Pharmaceutics 11, n. 6 (13 giugno 2019): 276. http://dx.doi.org/10.3390/pharmaceutics11060276.
Testo completoAbstract (sommario):
Recently, submicron particles have been discussed as a means to increase the bioavailability of poorly water-soluble drugs. Separation of these small particles is done with both fibre and membrane filters, as well as electrostatic precipitators. A major disadvantage of an electrostatic precipitator (ESP) is the agglomerate formation on the precipitation electrode. These agglomerates frequently show low bioavailability, due to the decreased specific surface area and poor wettability. In this work, a new melt electrostatic precipitator was developed and tested to convert submicron particles into a solid dispersion in order to increase the bioavailability of active pharmaceutical ingredients. The submicron particles were generated by spray drying and transferred to the ESP, where the collection electrode is covered with a melt, which served as matrix after solidification. The newly developed melt electrostatic precipitator was able to collect isolated naproxen particles in a molten carrier. A solid naproxen xylitol dispersion was prepared, which showed a reduction of the dissolution time by 82%, and a release of 80% of the total drug, compared to the physical mixture.
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Kochendorfer, John, Tilden P. Meyers, Mark E. Hall, Scott D. Landolt, Justin Lentz e Howard J. Diamond. "A new reference-quality precipitation gauge wind shield". Atmospheric Measurement Techniques 16, n. 22 (22 novembre 2023): 5647–57. http://dx.doi.org/10.5194/amt-16-5647-2023.
Testo completoAbstract (sommario):
Abstract. Gauge-based precipitation measurements suffer from undercatch due to the effects of wind, with solid-precipitation measurements especially susceptible to such errors. When it is snowing and windy, unshielded precipitation gauges can catch less than half of the amount of precipitation of a gauge that is protected from the wind. For this reason, the US Climate Reference Network (USCRN) developed a large, double-layer, wooden wind shield called the Small Double Fence Intercomparison Reference (SDFIR). In past studies, the SDFIR has been demonstrated to be the most effective wind shield in use in any weather or climate network, reducing solid-precipitation undercatch to less than 10 % in wind speeds up to 8 m s−1. However, the wooden SDFIRs are subject to decay, they are difficult to replace and maintain, and they hinder access to maintaining the gauge. For these reasons, a new precipitation gauge wind shield called the Low Porosity Double Fence (LPDF) has been developed for use in the USCRN. Tested at three separate sites chosen for prevalent windy and snowy weather, the precipitation measurements recorded within the LPDF compared well to the SDFIR. After more than 2 years of measurements, the total precipitation recorded by the LPDF at each individual site differed by ±1.2 %, and the total LPDF accumulation from all sites was 0.03 % greater than the SDFIR accumulation. For the measurement of solid precipitation, the LPDF-shielded measurements were statistically indistinguishable from those in the SDFIR shield, and the time series of accumulation from precipitation gauges shielded by the SDFIR and the LPDF were almost identical. This new wind shield is much smaller and easier to install and maintain than any other reference-quality wind shield for the measurement of solid precipitation and may be of use within other meteorological, hydrological, and climate networks. It could also serve as a secondary reference precipitation measurement for precipitation intercomparisons held in remote locations where the construction of a full-sized Double Fence Intercomparison Reference (DFIR) shield is not feasible.
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Osypov, Valeriy, Andrii Bonchkovskyi, Andrii Oreshchenko, Dmytro Oshurok e Natalia Osadcha. "Quantifying wind-induced undercatch in the precipitation measurements at Ukrainian weather stations". Visnyk of V.N. Karazin Kharkiv National University, series Geology. Geography. Ecology, n. 55 (1 dicembre 2021): 204–15. http://dx.doi.org/10.26565/2410-7360-2021-55-15.
Testo completoAbstract (sommario):
Literature overview. Precipitation measurements include random and systematic errors. Systematic errors increase in the following order: evaporation loss, wetting loss, and wind-induced undercatch (World Meteorological Organization, 2008). The last one occurs because of the aerodynamic blockage under the precipitation gauge collector (Baghapour et al. 2017; Sevruk & Nespor, 1994). Field experiments have shown that wind-induced undercatch reaches 14% for rain and 40% for snow for the Tretyakov wind-shielded gauge (Goodison et al., 1998). In Ukraine, precipitation records omit wind-induced undercatch correction. This study aims to calculate true precipitation values at Ukrainian weather stations, evaluate existing methodologies for precipitation measurements correction, and create the digital archive of corrected precipitation values based on sub-daily observations. Material and methods. We used four methods to quantify wind-related errors for the Tretyakov gauge with wind shield proposed by Golubev (Konovalov et al., 2000), Bryazgin (Aleksandrov et al., 2005), Norway meteorological institute (Forland et al., 1996), and Yang (Yang et al., 1995). Sub-daily records were requested from Central Geophysical Observatory named after Boris Sreznevsky covering 207 stations between 1976 and 2019; 187 stations had more than 20 years’ period. Results. For the Tretyakov gauge, annual wind-induced undercatch ranges from 5 to 9.5%, depending on correction methodology. The highest bias is observed for the solid precipitation – from 17.7 to 27.4%. The precipitation loss increases along with annual wind speed at the weather station (correlation coefficient r = 0.89). Conclusions. We suggest that Golubev’s and Yang’s methodologies estimate precipitation wind-induced undercatch more accurately at stations where blizzards are often observed, we recommended using the Golubev’s methodology because it takes into account “false” precipitations. The precipitation loss equals 0.2–4% according to the Golubev’s method at covered weather stations and reaches 13–19% at the bare mountain regions or seashore. Solid precipitation is more sensitive to the influence of wind – snow loss averages 17.3% according to the Golubev methodology or 21% according to the Yang methodology, while rain loss – 2.6% or 6.7%, respectively. The obtained database with corrected precipitation comprises sub-daily and daily records from 207 Ukrainian stations between 1976 and 2019. It could be used for hydrological and climatological research.
30
Pishchalnikova, E. V., e E. V. Akilov. "PHASE STATE OF ATMOSPHERIC PRECIPITATION IN THE PERM REGION". Bulletin of Udmurt University. Series Biology. Earth Sciences 30, n. 2 (30 luglio 2020): 200–206. http://dx.doi.org/10.35634/2412-9518-2020-30-2-200-206.
Testo completoAbstract (sommario):
The phase state of precipitation is one of the significant climatic indicators in conditions of global warming. The distribution of the temporal frequency of precipitation forms gives an idea of the changes occurring in the environment. This article discusses the spatial and temporal distribution of precipitation, taking into account their morphological classification. A tendency to a decrease in the amount of precipitation falling in solid form has been established. The prevalence of the liquid phase of precipitation over solid in the annual amount by 3 % on average against the background of a greater repeatability of solid precipitation was revealed. Based on cluster analysis, zoning of the territory of the Perm region was carried out according to the prevailing forms of precipitation. Three zones have been distinguished: northeast, center and south. Particular attention is paid to certain types of precipitation: mixed and supercooled, as the most difficult to predict and having complex formation mechanisms. Favorable synoptic situations were determined: a warm sector of a cyclone and a hollow with a warm front. An analysis of the thermal state of the lower troposphere made it possible to establish the thickness of the warm layer (if any), the height of the zero isotherm, and the prevailing surface air temperature.
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Køltzow, Morten, Barbara Casati, Thomas Haiden e Teresa Valkonen. "Verification of Solid Precipitation Forecasts from Numerical Weather Prediction Models in Norway". Weather and Forecasting 35, n. 6 (dicembre 2020): 2279–92. http://dx.doi.org/10.1175/waf-d-20-0060.1.
Testo completoAbstract (sommario):
AbstractAssessing the quality of precipitation forecasts requires observations, but all precipitation observations have associated uncertainties making it difficult to quantify the true forecast quality. One of the largest uncertainties is due to the wind-induced undercatch of solid precipitation gauge measurements. This study discusses how this impacts the verification of precipitation forecasts for Norway for one global model [the high-resolution version of the ECMWF Integrated Forecasting System (IFS-HRES)], and one high-resolution, limited-area model [Applications of Research to Operations at Mesoscale (MEPS)]. First, the forecasts are compared with high-quality reference measurements (less undercatch) and with more simple measurement equipment commonly available (substantial undercatch) at the Haukeliseter observation site. Then the verification is extended to include all Norwegian observation sites: 1) stratified by wind speed, since calm (windy) conditions experience less (more) undercatch; and 2) by applying transfer functions, which convert measured precipitation to what would have been measured with high-quality equipment with less undercatch, before the forecast–observation comparison is performed. Results show that the wind-induced undercatch of solid precipitation has a substantial impact on verification results. Furthermore, applying transfer functions to adjust for wind-induced undercatch of solid precipitation gives a more realistic picture of true forecast capabilities. In particular, estimates of systematic forecast biases are improved, and to a lesser degree, verification scores like correlation, RMSE, ETS, and stable equitable error in probability space (SEEPS). However, uncertainties associated with applying transfer functions are substantial and need to be taken into account in the verification process. Precipitation forecast verification for liquid and solid precipitation should be done separately whenever possible.
32
Fan, Kai, Feng Liu, Wei Yang, Gencang Yang e Yaohe Zhou. "Analysis of soft impingement in nonisothermal precipitation". Journal of Materials Research 24, n. 12 (dicembre 2009): 3664–73. http://dx.doi.org/10.1557/jmr.2009.0434.
Testo completoAbstract (sommario):
The effects of soft impingement on precipitation are considered. A physically realistic analytical treatment of soft impingement has been developed for solid-state precipitation in a nonisothermal heating/cooling process following the basic assumptions (i.e., a two-stage transformation including site saturation of nucleation, isotropic growth and linear approximation for a concentration gradient in front of the precipitate/matrix interface). Furthermore, both one- and three-dimensional precipitations have been described using a compact expression which is analogous to Zener’s model but with a temperature-dependent growth coefficient. A detailed description for the model parameters has been given for the model application. Good agreement with published experimental data, for example, the decomposition of austenite in a 0.038–0.30wt%Mn plain carbon steel, has been achieved.
33
Cai, Xiao Hui, Zhen Yu Liu e Guo Dong Wang. "Cooling Process for Precipitation Strengthening of Vanadium in Ferrite". Materials Science Forum 706-709 (gennaio 2012): 2078–83. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2078.
Testo completoAbstract (sommario):
The precipitation of vanadium takes place mainly in ferrite by interphase precipitation or nucleation on dislocation line, which makes sense for the industry production due to the precipitation strengthening. The objective is to analysize the cooling process of V-steels to exert the precipitation strengthening of vanadium. The steels with 0.09%C-0.055%N/0.0107%N/0.0168%N/0.0193%N-0.08%V/0.085V steel are the researched steel grades. Using solid solubility products model and thermodynamic equation, the full solid solution temperature, nucleation rate curve and PTT curve of precipitation process are calculated. The effect of nitrogen on the precipitation behaviour of V(C,N) in γ and the precipitation of V(C,N) in α are simulated. Based on the calculation results the trial process is determined. The laboratorial trials are carried out with ultra fast cooling. The precipitate particles are observed by TEM. The solid solution amount increases monotonously and the size of precipitate particle decreases with the nitrogen content. The solid solution temperature of 0.055%N, 0.0107%N, 0.0168%N and 0.0193%N are 977.0°C, 1028.0°C, 1062.3 and 1078.9°C respectively. The laboratorial trial results shows that the tensile strength is improved about 100 MPa due to the precipitation strengthening. The relationship between the coiling temperature and the strength is parabolic curve downward and the relationship between the coiling temperature and the elongation is parabolic curve upward. This calculation can determine both the proper nitrogen content and the optimal cooling process. The trial results proves this method is feasible and efficiency.
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Sonali, Dalwadi, Soni Tejal, Thakkar Vaishali e Gandhi Tejal. "Silymarin-solid dispersions: Characterization and influence of preparation methods on dissolution". Acta Pharmaceutica 60, n. 4 (1 dicembre 2010): 427–43. http://dx.doi.org/10.2478/v10007-010-0038-3.
Testo completoAbstract (sommario):
Silymarin-solid dispersions: Characterization and influence of preparation methods on dissolution The influence of preparation methodology of silymarin solid dispersions using a hydrophilic polymer on the dissolution performance of silymarin was investigated. Silymarin solid dispersions were prepared using HPMC E 15LV by kneading, spray drying and co-precipitation methods and characterized by FTIR, DSC, XRPD and SEM. Dissolution profiles were compared by statistical and model independent methods. The FTIR and DSC studies revealed weak hydrogen bond formation between the drug and polymer, while XRPD and SEM confirmed the amorphous nature of the drug in co-precipitated solid dispersion. Enhanced dissolution compared to pure drug was found in the following order: co-precipitation > spray drying > kneading methodology (p < 0.05). All preparation methods enhanced silymarin dissolution from solid dispersions of different characteristics. The co-precipitation method proved to be best and provided a stable amorphous solid dispersion with 2.5 improved dissolution compared to the pure drug.
35
Sims, Elizabeth M., e Guosheng Liu. "A Parameterization of the Probability of Snow–Rain Transition". Journal of Hydrometeorology 16, n. 4 (29 luglio 2015): 1466–77. http://dx.doi.org/10.1175/jhm-d-14-0211.1.
Testo completoAbstract (sommario):
Abstract When estimating precipitation using remotely sensed observations, it is important to correctly classify the phase of precipitation. A misclassification can result in order-of-magnitude errors in the estimated precipitation rate. Using global ground-based observations over multiple years, the influence of different geophysical parameters on precipitation phase is investigated, with the goal of obtaining an improved method for determining precipitation phase. The parameters studied are near-surface air temperature, atmospheric moisture, low-level vertical temperature lapse rate, surface skin temperature, surface pressure, and land cover type. To combine the effects of temperature and moisture, wet-bulb temperature, instead of air temperature, is used as a key parameter for separating solid and liquid precipitation. Results show that in addition to wet-bulb temperature, vertical temperature lapse rate affects the precipitation phase. For example, at a near-surface wet-bulb temperature of 0°C, a lapse rate of 6°C km−1 results in an 86% conditional probability of solid precipitation, while a lapse rate of −2°C km−1 results in a 45% probability. For near-surface wet-bulb temperatures less than 0°C, skin temperature affects precipitation phase, although the effect appears to be minor. Results also show that surface pressure appears to influence precipitation phase in some cases; however, this dependence is not clear on a global scale. Land cover type does not appear to affect precipitation phase. Based on these findings, a parameterization scheme has been developed that accepts available meteorological data as input and returns the conditional probability of solid precipitation.
36
Peng, Jun, Liang Niu, Yong Guo, Li Xia Liu e Sheng Li An. "Effect of V, Ti, and Ce on Structure and Performance of NM400". Advanced Materials Research 1094 (marzo 2015): 311–15. http://dx.doi.org/10.4028/www.scientific.net/amr.1094.311.
Testo completoAbstract (sommario):
To improve the performance of NM400, V, Ti and Ce were added in NM400. The effect of alloy on grain size, precipitation, hardness and toughness was studied. The result shows that V and Ti can improve the performance by grain refiner and dispersion-strengthening. By further adding Ce, the size of grain and precipitations of V and Ti is significantly reduced, the solid solution quantity of V and Ti and the amount of precipitation are increased, and the precipitation shape transforms from cube to sphere. Therefore the hardness and toughness of steel are greatly improved. In this study, 0.2% V and 0.2% Ti were added into NM400. As a result, the precipitation of V and Ti, in form of carbide and nitride, was the smallest and dispersed, and the grain size was the smallest, which leaded to the best performance. The conclusion is that, to ameliorate the performance of NM400, the optimal additive amount of V and Ti is 0.2% no matter whether adding Ce or not.
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Mityaev, Maksim V., Marina V. Gerasimova, Elena I. Druzhkova, Tatyana G. Ishkulova e Maria Yu Menshakova. "Solid atmospheric precipitation in Murmansk and its environs". Transactions of the Kоla Science Centre. Series: Natural Sciences and Humanities 2, n. 3/2023 (26 giugno 2023): 51–67. http://dx.doi.org/10.37614/2949-1185.2023.2.3.007.
Testo completoAbstract (sommario):
In the period from January 2, 2018 to December 30, 2022, a comprehensive study of solid atmospheric precipitation was carried out in Murmansk and its environs. Data were obtained on the concentration in freshly fallen snow of solid insoluble particles (9.19±0.51 mg/l) and their components: heavy metals (zinc – 60.1±9.8 ng/g, copper – 11.0±2.6 ng/g, lead – 3.28±0.18 ng/g, cadmium – 0.859±0.096 ng/g), nutrients (nitrates – 79±11 µg-at/l, nitrites – 1.02±0.14 µg-at/l, phosphates – 4.64±0.67 µg-at/l, silicates – 25±5 µg-at/l) and organic matter (21.2±2.2 mg/l), as well as the amount of polymer particles (fragments – 7766±1401 particles per liter, micro-fibers – 638±134 threads per liter, macro-fibers – 29±4 threads per liter). The relationship between the number of insoluble particles and the direction of air masses inflow was revealed. Air masses coming from the Barents Sea brought solid precipitation with less insoluble aerosols (including heavy metals, polymer particles and organic matter) than air masses coming from the continent. The amount of biogenic elements in solid atmospheric precipitation does not depend on the direction of inflow of air masses.
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Ma, Siyi, Ruiming Su, Kaining Wang, Lei Wang, Yingdong Qu e Rongde Li. "Influence of laser pre-precipitation on the corrosion resistance of Al-Zn-Mg-Cu alloy with deep cryogenic treatment". Metallurgical Research & Technology 119, n. 1 (2022): 118. http://dx.doi.org/10.1051/metal/2022009.
Testo completoAbstract (sommario):
A recently developed AA7075 was subjected to solid solution, high temperature laser surface treatment, deep cryogenic treatment, and artificial aging. The microstructure evolution and precipitation behavior were examined, and their effects on corrosion behaviour were analyzed. The results showed that coarse η phases disappeared and a large number of smaller η phases were formed after high temperature laser surface treatment. Most of the phases dissolved into Al matrix during solution and fine η phases precipitated in laser treatment. η′ phases appeared in the high temperature laser surface treatment samples. Mg element precipitated in deep cryogenic treatment. It was concluded that the precipitation of AA7075 during heat treatment followed the sequence of solid solution → GPI (Guinier Preston) zones → metastable η′ → stable η. Reasonable laser scanning power owned the best corrosion resistance. The reasonable sample which the laser power was 1000 W showed much better corrosion resistance due to the coarsening and separation of grain boundary precipitations.
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Zeynalov, A. N. "Precipitation of solid body particles in the suspension". Construction of Oil and Gas Wells on Land and Sea, n. 8 (2019): 11–13. http://dx.doi.org/10.30713/0130-3872-2019-8-11-13.
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Nourtier-Mazauric, E., B. Guy, B. Fritz, E. Brosse, D. Garcia e A. Clément. "Modelling the Dissolution/Precipitation of Ideal Solid Solutions". Oil & Gas Science and Technology 60, n. 2 (marzo 2005): 401–15. http://dx.doi.org/10.2516/ogst:2005024.
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Virkar, Anil V. "Kinetics of Precipitation from a Dilute Solid Solution". Journal of the American Ceramic Society 68, n. 1 (gennaio 1985): C—11—C—12. http://dx.doi.org/10.1111/j.1151-2916.1985.tb15254.x.
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Garisto, Frank. "Solid dissolution: Effect of mass transport-precipitation coupling". Chemical Engineering Science 41, n. 12 (1986): 3219–22. http://dx.doi.org/10.1016/0009-2509(86)85060-6.
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Ronchi, C. "On diffusion and precipitation of gas-in-solid". Journal of Nuclear Materials 148, n. 3 (maggio 1987): 316–23. http://dx.doi.org/10.1016/0022-3115(87)90025-0.
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Novak, Craig F., Robert S. Schechter e Larry W. Lake. "Diffusion and solid dissolution/precipitation in permeable media". AIChE Journal 35, n. 7 (luglio 1989): 1057–72. http://dx.doi.org/10.1002/aic.690350702.
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Alonzo, David E., Yi Gao, Deliang Zhou, Huaping Mo, Geoff G. Z. Zhang e Lynne S. Taylor. "Dissolution and Precipitation Behavior of Amorphous Solid Dispersions". Journal of Pharmaceutical Sciences 100, n. 8 (agosto 2011): 3316–31. http://dx.doi.org/10.1002/jps.22579.
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Yükselici, M. H., e Ç. Allahverdi. "Solid-phase precipitation of CdTe nanoparticles in glass". physica status solidi (b) 236, n. 3 (aprile 2003): 694–701. http://dx.doi.org/10.1002/pssb.200301560.
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Heidemann, Robert A., Jesper Madsen, Erling H. Stenby e Simon I. Andersen. "Wax precipitation modeled with many mixed solid phases". AIChE Journal 51, n. 1 (2004): 298–308. http://dx.doi.org/10.1002/aic.10292.
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Bondarenko, Yu O., N. F. Voronina e O. A. Shmatko. "Kinetic and Thermodynamic Precipitation Parameters of the Pb-Sn Solid Solutions". Defect and Diffusion Forum 277 (aprile 2008): 193–98. http://dx.doi.org/10.4028/www.scientific.net/ddf.277.193.
Testo completoAbstract (sommario):
Stages of cellular precipitation for the supersaturated Pb-Sn solid solutions were analyzed. This was done for almost the whole homogeneity interval. Literary heritage as well as the data of the present authors concerning kinetic and thermodynamic parameters of cellular precipitation for these solid solutions were compared and summarized. It was shown that the segregation factor, which characterizes the impurity atoms behavior at the grain boundary, decreases with solid solution supersaturation increase.
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Milkereit, Benjamin, Marco J. Starink, Paul A. Rometsch, Christoph Schick e Olaf Kessler. "Review of the Quench Sensitivity of Aluminium Alloys: Analysis of the Kinetics and Nature of Quench-Induced Precipitation". Materials 12, n. 24 (6 dicembre 2019): 4083. http://dx.doi.org/10.3390/ma12244083.
Testo completoAbstract (sommario):
For aluminium alloys, precipitation strengthening is controlled by age-hardening heat treatments, including solution treatment, quenching, and ageing. In terms of technological applications, quenching is considered a critical step, because detrimental quench-induced precipitation must be avoided to exploit the full age-hardening potential of the alloy. The alloy therefore needs to be quenched faster than a critical cooling rate, but slow enough to avoid undesired distortion and residual stresses. These contrary requirements for quenching can only be aligned based on detailed knowledge of the kinetics of quench-induced precipitation. Until the beginning of the 21st century, the kinetics of relevant solid-solid phase transformations in aluminium alloys could only be estimated by ex-situ testing of different properties. Over the past ten years, significant progress has been achieved in this field of materials science, enabled by the development of highly sensitive differential scanning calorimetry (DSC) techniques. This review presents a comprehensive report on the solid-solid phase transformation kinetics in Al alloys covering precipitation and dissolution reactions during heating from different initial states, dissolution during solution annealing and to a vast extent quench-induced precipitation during continuous cooling over a dynamic cooling rate range of ten orders of magnitude. The kinetic analyses are complemented by sophisticated micro- and nano-structural analyses and continuous cooling precipitation (CCP) diagrams are derived. The measurement of enthalpies released by quench-induced precipitation as a function of the cooling rate also enables predictions of the quench sensitivities of Al alloys using physically-based models. Various alloys are compared, and general aspects of quench-induced precipitation in Al alloys are derived.
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Van De Berg, W. J., M. R. Van Den Broeke, C. H. Reijmer e E. Van Meijgaard. "Characteristics of the Antarctic surface mass balance, 1958–2002, using a regional atmospheric climate model". Annals of Glaciology 41 (2005): 97–104. http://dx.doi.org/10.3189/172756405781813302.
Testo completoAbstract (sommario):
AbstractTemporal and spatial characteristics of the Antarctic specific surface mass balance (SSMB) are presented, including its components solid precipitation, sublimation/deposition and melt. For this purpose, we use the output of a regional atmospheric climate model (RACMO2/ANT, horizontal resolution of ~55 km) for the period 1958–2002. RACMO2/ANT uses European Centre for Medium-Range Weather Forecasts (ECMWF) 40 year re-analysis (ERA-40) fields as forcing at the lateral boundaries. RACMO2/ANT underestimates SSMB in the high interior of East and West Antarctica and overestimates SSMB on the steep coastal slopes. Otherwise, the modeled spatial pattern of SSMB is in good qualitative agreement with recent compilations of in situ observations. Large-scale patterns, like the precipitation shadow effect of the Antarctic Peninsula, are well reproduced, and mesoscale SSMB patterns, such as the strong precipitation gradients on Law Dome, are well represented in the model. The integrated SSMB over the grounded ice sheet is 153mmw.e. a–1 for the period 1958–2002, which agrees within 5% with the latest measurement compilations. Sublimation and melt remove 7% and <1% respectively of the solid precipitation. We found significant seasonality of solid precipitation, with a maximum in autumn and a minimum in summer. No meaningful trend was identified for the SSMB, because the time series of solid precipitation and SSMB are affected by an inhomogeneity in 1980 within the ERA-40 fields that drive RACMO2/ANT. Sublimation, melt and liquid precipitation increase in time, which is related to a modeled increase in 2m temperature.