共查询到20条相似文献,搜索用时 15 毫秒
1.
Thomas M. Koller Corina Steininger Michael H. Rausch Andreas P. Fröba 《International Journal of Thermophysics》2017,38(11):167
In this study, a simple prediction method for the surface tension of ionic liquids (ILs) as a function of temperature is developed. Based on a database of experimental surface tension values collected from the literature, first a prediction scheme for the surface tension at a reference temperature of 298.15 K using only information on the density, molar mass, and anion type of the IL is suggested. By combination of this approach with the temperature dependence of the density, an extended prediction scheme describing the temperature dependence of the surface tension of ILs is recommended. The optimized prediction model for the surface tension allows for the prediction of about 3500 temperature-dependent experimental surface tension data of 226 different ILs with a standard deviation of about 7 %. In comparison with fluid-specific prediction methods found in the literature, the developed simple empirical prediction model requires only easily accessible parameters and can be applied for ILs with arbitrary cation and anion combinations. Thus, the proposed prediction method seems to be a valuable engineering tool for the quantitative estimation of the surface tension of ILs. 相似文献
2.
Keshavarz MH 《Journal of hazardous materials》2006,138(3):448-451
A simple new procedure is introduced to predict melting point of selected class of energetic compounds containing nitramines, nitrate esters, nitrate salts and nitroaliphatics energetic compounds. The number of nitrogen and oxygen as well as the number of nitramine group and the contribution of some specific functional groups would be needed in the new method. Energetic compounds should contain at least one of the functional groups including N-NO(2), C-ONO(2) or nonaromatic C-NO(2). Calculated melting point for 33 nitramines, nitrate esters, nitrate salt and nitroaliphatics are compared with experimental data. Predicted melting points have average deviation of 5.4% for these energetic compounds. 相似文献
3.
A simple correlation has been introduced to estimate melting point of carbocyclic nitroaromatic compounds. The methodology assumes that melting point of a carbocyclic nitroaromatic compound with general formula C(a)H(b)N(c)O(d) can be expressed as a function of the number of hydrogen and nitrogen atoms as well as the contribution of some specific functional groups and the existence of ortho or para isomers in disubstituted benzene ring. Predicted melting points using the method described herein and group contribution method of Joback and Reid [K.G. Joback, R.C. Reid, Chem. Eng. Commun. 57 (1987) 233] have the average deviation of 5.0 and 37.6%, respectively, for 60 carbocyclic nitroaromatic compounds. The proposed new method clearly exhibits a much better accuracy. 相似文献
4.
D. Tomida S. Kenmochi T. Tsukada K. Qiao C. Yokoyama 《International Journal of Thermophysics》2007,28(4):1147-1160
Thermal conductivities are reported for a series of 1-alkyl-3-methylimidazolium hexafluorophosphates having butyl, hexyl,
and octyl groups, which are expressed by [bmim][PF6], [hmim][PF6], and [omim][PF6], respectively. The experimental method used was a transient short-hot-wire method. Since only a small amount of sample liquid
is required, this method was found to be effective for the thermal-conductivity measurements of ionic liquids (ILs). The experimental
temperatures ranged from 294 to 335 K at pressures up to 20 MPa. The values of the thermal conductivities of ILs at normal
pressure are similar to those of benzene. It was found that an effect of the length of the alkyl chain on the thermal conductivities
in ILs is negligible. From the data for the thermal conductivity and viscosity at 293.15 K and 0.1 MPa of ILs and normal alkanes,
a simple correlation was developed based on the Mohanty theory. From comparisons between the thermal conductivities of ILs
and those of organic liquids (n-hexane, benzene, and methanol), the temperature and pressure dependences of the thermal conductivity of ILs are relatively
weak. 相似文献
5.
Instead of being seen as alternative solvents and electrolytes for organic reactions, catalysis, separation, electrochemistry, and so on, ionic liquids (ILs) consisting of discrete cations and anions have recently emerged as versatile building blocks for advanced functional materials. A number of functional ILs and IL-containing composite materials have been realized by either chemical modification (covalent functionalization or ion-exchange metathesis) or physical integration of ILs and traditional materials. The unique structure and behavior of ILs as a platform not only provides additional opportunities to adjust the physicochemical properties of these ionic materials for task-specific applications, but also offers other attractive features such as intrinsic ionic conductivity and high thermal, chemical, and electrochemical stability. These soft materials combine the favorable features of ILs and the original chemistries of the functional groups or materials; some even possess unexpected functions resulting from synergetic interaction between these two components. Materialization of ILs is truly a novel, promising research direction for both IL chemistry and materials science. In this article, we review recent advances in IL-based functional materials, focusing on smart and sensitive materials, optical materials, energetic materials, and IL/carbon hybrid materials. 相似文献
6.
A. P. Fröba M. H. Rausch K. Krzeminski D. Assenbaum P. Wasserscheid A. Leipertz 《International Journal of Thermophysics》2010,31(11-12):2059-2077
This study reports thermal-conductivity data for a series of [EMIM] (1-ethyl-3-methylimidazolium)-based ionic liquids (ILs) having the anions [NTf2] (bis(trifluoromethylsulfonyl)imide), [OAc] (acetate), [N(CN)2] (dicyanimide), [C(CN)3] (tricyanomethide), [MeOHPO2] (methylphosphonate), [EtSO4] (ethylsulfate), or [OcSO4] (octylsulfate), and in addition for ILs with the [NTf2]-anion having the cations [HMIM] (1-hexyl-3-methylimidazolium), [OMA] (methyltrioctylammonium), or [BBIM] (1,3-dibutylimidazolium). Measurements were performed in the temperature range between (273.15 and 333.15) K by a stationary guarded parallel-plate instrument with a total measurement uncertainty of 3 % (k = 2). For all ILs, the temperature dependence of the thermal conductivity can well be represented by a linear equation. While for the [NTf2]-based ILs, a slight increase of the thermal conductivity with increasing molar mass of the cation is found at a given temperature, the [EMIM]-based ILs show a pronounced, approximately linear decrease with increasing molar mass of the different probed anions. Based on the experimental data obtained in this study, a simple relationship between the thermal conductivity, molar mass, and density is proposed for the prediction of the thermal-conductivity data of ILs. For this, also densities were measured for [EMIM][OAc], [EMIM][C(CN)3], and [HMIM][NTf2]. The mean absolute percentage deviation of all thermal-conductivity data for ILs found in the literature from the proposed prediction is about 7 %. This result represents a convenient simplification in the acquisition of thermal conductivity information for the enormous amount of structurally different IL cation/anion combinations available. 相似文献
7.
Heat Capacity of Ionic Liquids Using Artificial Neural Networks and the Concept of Mass Connectivity
José O. Valderrama Gwendolyn Martinez Claudio A. Faúndez 《International Journal of Thermophysics》2011,32(5):942-956
Artificial neural networks and the concept of mass connectivity index are used to correlate and predict the heat capacity
at constant pressure of ionic liquids (ILs). Different topologies of a multilayer feed-forward artificial neural network were
studied, and the optimum architecture was determined. Heat-capacity data at several temperatures taken from the literature
for 31 ILs with 477 data points were used for training the network. To discriminate among the different substances, the molecular
mass of the anion and of the cation and the mass connectivity index were considered as the independent variables. The capabilities
of the designed network were tested by predicting heat capacities for situations not considered during the training process
(65 heat-capacity data for nine ILs). The results demonstrate that the chosen network and the variables considered allow estimating
the heat capacity of ILs with acceptable accuracy for engineering calculations. The program codes and the necessary input
files to calculate the mass connectivity index and the heat capacity for other ILs are provided. 相似文献
8.
Fah Keen Chong Nishanth G. Chemmangattuvalappil Fadwa T. Eljack Mert Atilhan Dominic C. Y. Foo 《Clean Technologies and Environmental Policy》2016,18(4):1177-1188
Recently, ionic liquids (ILs) have been introduced as potential carbon dioxide (CO2)-capturing solvents, as a substitute to conventional amine-based solvents. Conventional amine-based solvents that are used for CO2 capture show some drawbacks, such as high solvent loss, high regeneration energy requirement, and solvent degradation. These shortcomings can be potentially overcome if IL-based solvents are considered. ILs have negligible vapour pressure, high thermal stability, and wide range of thermophysical properties. Nonetheless, using experimentation to identify suitable ILs as CO2-capturing solvents is a tedious and costly task, as there are more than a million possible combinations of cations and anions that make up the ILs. Computer-aided tools have been previously developed for targeted IL design, which often involve non-linear programming. However, non-linear programming sometimes fails to converge, due to enlarged search space for optimal solution and its complex formulations. In this paper, the authors present a simple yet systematic visual approach to design IL solvents for carbon capture. Property integration framework is employed in this approach to systematically design IL, where the design problem can be mapped from the property domain into a cluster domain through clustering technique. The advantage of the visual approach is the ability to enumerate novel IL candidates. Group contribution (GC) method is included in the framework to estimate the properties of designed ILs. By combining property integration framework and GC method, the proposed approach is able to provide a property-based platform to visualise the performance of designed ILs on a ternary diagram. A case study is presented to illustrate the validity of the proposed approach. 相似文献
9.
Harumi Veny Saeid Baroutian Mohamed Kheireddine Aroua Masitah Hasan Abdul Aziz Raman Nik Meriam Nik Sulaiman 《International Journal of Thermophysics》2009,30(2):529-541
Density data as a function of temperature have been measured for Jatropha curcas seed oil, as well as biodiesel jatropha methyl esters at temperatures from above their melting points to 90 °
C. The data obtained were used to validate the method proposed by Spencer and Danner using a modified Rackett equation. The
experimental and estimated density values using the modified Rackett equation gave almost identical values with average absolute
percent deviations less than 0.03% for the jatropha oil and 0.04% for the jatropha methyl esters. The Janarthanan empirical
equation was also employed to predict jatropha biodiesel densities. This equation performed equally well with average absolute
percent deviations within 0.05%. Two simple linear equations for densities of jatropha oil and its methyl esters are also
proposed in this study. 相似文献
10.
Nanayakkara YS Moon H Payagala T Wijeratne AB Crank JA Sharma PS Armstrong DW 《Analytical chemistry》2008,80(20):7690-7698
Water or aqueous electrolytes are the dominant components in electrowetting on dielectric (EWOD)-based microfluidic devices. Low thermal stability, evaporation, and a propensity to facilitate corrosion of the metal parts of integrated circuits or electronics are drawbacks of aqueous solutions. The alternative use of ionic liquids (ILs) as electrowetting agents in EWOD-based applications or devices could overcome these limitations. Efficient EWOD devices could be developed using task-specific ILs. In this regard, a fundamental study on the electrowetting properties of ILs is essential. Therefore electrowetting properties of 19 different ionic liquids, including mono-, di-, and tricationic, plus mono- and dianionic ILs were examined. All tested ILs showed electrowetting of various magnitudes on an amorphous flouropolymer layer. The effects of IL structure, functionality, and charge density on the electrowetting properties were studied. The enhanced stability of ILs in electrowetting on dielectric at higher voltages was studied in comparison with water. Deviations from classical electrowetting theory were confirmed. The physical properties of ILs and their electrowetting properties were tabulated. These data can be used as references to engineer task-specific electrowetting agents (ILs) for future electrowetting-based applications. 相似文献
11.
A new method of estimating the lower flammability limit (LFL) of general organic compounds is presented. The LFL is predicted at 298 K for gases and the lower temperature limit for solids and liquids from structural contributions and the ideal gas heat of formation of the fuel. The average absolute deviation from more than 500 experimental data points is 10.7%. In a previous study, the widely used modified Burgess-Wheeler law was shown to underestimate the effect of temperature on the lower flammability limit when determined in a large-diameter vessel. An improved version of the modified Burgess-Wheeler law is presented that represents the temperature dependence of LFL data determined in large-diameter vessels more accurately. When the LFL is estimated at increased temperatures using a combination of this model and the proposed structural-contribution method, an average absolute deviation of 3.3% is returned when compared with 65 data points for 17 organic compounds determined in an ASHRAE-style apparatus. 相似文献
12.
Solubility parameters for a number of drugs and related organic solids were determined from their dispersion and polar surface free energy data by means of an equation found to be valid for solvents. The relation fits quite well all solids investigated with an excellent correlation coefficient. The calculated solubility parameters, O, were checked with the ones estimated from molecular groups and fragment constants according to Fedors method, F. A similar O of 14.6 was obtained for o-hydroxybenzoic and p-hgdroxybensoic acids. The deviations from F shown in ethyl-p-aminobenzoate, benzoic acid, and aspirin were attributed to the imperfection of their vapor.
The solubility profile of hydrocortisone acetate was obtained in dioxane-water mixtures, and the solubility parameter of the drug was determined from the peak solubility in this binary solvent system. The experimental results for some drugs were compared with their solubility parameters calculated from the surface free energy data. Excellent agreement was found for hydrocortisone acetate, whereas griseofulvin and p-hydroxybenzoic agreed fairly. The “chameleonic” behavior of benzoic acid results in different experimental Solubility parameter, and the percentage deviation from O ranged from 3.4-20.8. A deviation of 11.8% was obtained for ethyl-p-aminobenzoate and was attributed to the influence of its crystal structure which would account for its low E value measured. The relation suggested was also applied to the dicarboxylic acids. The odd-even alteration seen in their melting points is not reflected on their solubility parameters. The high O calculated for these acids were related to their elongated shape. 相似文献
The solubility profile of hydrocortisone acetate was obtained in dioxane-water mixtures, and the solubility parameter of the drug was determined from the peak solubility in this binary solvent system. The experimental results for some drugs were compared with their solubility parameters calculated from the surface free energy data. Excellent agreement was found for hydrocortisone acetate, whereas griseofulvin and p-hydroxybenzoic agreed fairly. The “chameleonic” behavior of benzoic acid results in different experimental Solubility parameter, and the percentage deviation from O ranged from 3.4-20.8. A deviation of 11.8% was obtained for ethyl-p-aminobenzoate and was attributed to the influence of its crystal structure which would account for its low E value measured. The relation suggested was also applied to the dicarboxylic acids. The odd-even alteration seen in their melting points is not reflected on their solubility parameters. The high O calculated for these acids were related to their elongated shape. 相似文献
13.
Host cardinality estimation is an important research field in network
management and network security. The host cardinality estimation algorithm based on
the linear estimator array is a common method. Existing algorithms do not take memory
footprint into account when selecting the number of estimators used by each host. This
paper analyzes the relationship between memory occupancy and estimation accuracy and
compares the effects of different parameters on algorithm accuracy. The cardinality
estimating algorithm is a kind of random algorithm, and there is a deviation between the
estimated results and the actual cardinalities. The deviation is affected by some
systematical factors, such as the random parameters inherent in linear estimator and the
random functions used to map a host to different linear estimators. These random factors
cannot be reduced by merging multiple estimators, and existing algorithms cannot
remove the deviation caused by such factors. In this paper, we regard the estimation
deviation as a random variable and proposed a sampling method, recorded as the linear
estimator array step sampling algorithm (L2S), to reduce the influence of the random
deviation. L2S improves the accuracy of the estimated cardinalities by evaluating and
remove the expected value of random deviation. The cardinality estimation algorithm
based on the estimator array is a computationally intensive algorithm, which takes a lot of
time when processing high-speed network data in a serial environment. To solve this
problem, a method is proposed to port the cardinality estimating algorithm based on the
estimator array to the Graphics Processing Unit (GPU). Experiments on real-world highspeed network traffic show that L2S can reduce the absolute bias by more than 22% on
average, and the extra time is less than 61 milliseconds on average. 相似文献
14.
《Drug development and industrial pharmacy》2013,39(7):1135-1151
AbstractSolubility parameters for a number of drugs and related organic solids were determined from their dispersion and polar surface free energy data by means of an equation found to be valid for solvents. The relation fits quite well all solids investigated with an excellent correlation coefficient. The calculated solubility parameters, O, were checked with the ones estimated from molecular groups and fragment constants according to Fedors method, F. A similar O of 14.6 was obtained for o-hydroxybenzoic and p-hgdroxybensoic acids. The deviations from F shown in ethyl-p-aminobenzoate, benzoic acid, and aspirin were attributed to the imperfection of their vapor.The solubility profile of hydrocortisone acetate was obtained in dioxane-water mixtures, and the solubility parameter of the drug was determined from the peak solubility in this binary solvent system. The experimental results for some drugs were compared with their solubility parameters calculated from the surface free energy data. Excellent agreement was found for hydrocortisone acetate, whereas griseofulvin and p-hydroxybenzoic agreed fairly. The “chameleonic” behavior of benzoic acid results in different experimental Solubility parameter, and the percentage deviation from O ranged from 3.4-20.8. A deviation of 11.8% was obtained for ethyl-p-aminobenzoate and was attributed to the influence of its crystal structure which would account for its low E value measured. The relation suggested was also applied to the dicarboxylic acids. The odd-even alteration seen in their melting points is not reflected on their solubility parameters. The high O calculated for these acids were related to their elongated shape. 相似文献
15.
智能控制技术与互联网技术在房间空调系统应用的基础是对其性能的在线实时监测。本文提出一种房间空调系统性能在线监测的方法。首先将空调器布置温度测点采集到的换热器铜管表面温度和电流电压等电路参数结合,转化为制冷循环中制冷剂的状态参数;再通过压缩机流量半经验计算模型计算制冷剂的质量流量,进而得出室内机中制冷剂侧的换热量;最后结合电路参数求得的整机功率,实现房间空调系统制冷量、制热量、功率、能效的实时监测。结果表明:采用此方法计算房间空调器性能参数的最大偏差小于15%,主要误差来源为蒸发压力的计算误差。 相似文献
16.
Potential wells of metallic and intermetallic phases are constructed by ab initio calculation using the density functional theory. The potential wells are presented as a function of a characteristic length scale equivalent to the cubic root of the average atomic volume, to reflect the importance of density on binding. The results show that the characteristics of a potential well dictates the melting temperature of a crystalline solid metal or an intermetallic phase. The energetic requirement for melting is equivalent to an activation state where the slope of the potential well gets close to the positive maximum, or where the well experiences a step change in energetic state. The work offers a way to predict melting points of metallic/intermetallic phases, which is particularly useful to metastable phases, for which it is usually difficult to measure the melting points directly. Such predicted data on melting points are useful for establishing thermodynamic databases for phase diagram calculations. 相似文献
17.
L.G. Van Uitert 《Materials Research Bulletin》1977,12(4):315-320
For most cubic, ionic compounds and metals the product of the volume expansion coefficient and the melting point (in °C) tends to be a structure dependent constant. However, this does not hold for tetrahedral semiconductors (groups IV, III–V, and II–VI). For the latter, it is shown that the deviation of the measured coefficient from that expected from the product value for diamond is a function of both ionicity and bond length. 相似文献
18.
Capillary electrophoretic application of 1-alkyl-3-methylimidazolium-based ionic liquids 总被引:8,自引:0,他引:8
Ionic substances with melting points at or close to room temperature are referred to as ionic liquids. Interest in ionic liquids for their potential in different chemical processes is increasing, because they are environmentally benign and are good solvents for a wide range of both organic and inorganic materials. In this study, a capillary electrophoretic method for resolving phenolic compounds found in grape seed extracts is reported. The method, in which 1-alkyl-3-methylimidazolium-based ionic liquids are used as the running electrolytes, is simple and reproducible. The separation mechanism seems to involve association between the imidazolium cations and the polyphenols. The role of the alkyl substituents on the imidazolium cations was investigated and will be discussed. 相似文献
19.
20.
X. P. Hao J. P. Sun C. Y. Xu P. Wen J. Song M. Xu L. Y. Gong L. Ding Z. L. Liu 《International Journal of Thermophysics》2017,38(6):90
Miniature Ga and Ga–In alloy fixed points as temperature standards are developed at National Institute of Metrology, China for the in situ calibration of temperature sensors. A quasi-adiabatic vacuum measurement system is constructed to study the phase-change plateaus of the fixed points. The system comprises a high-stability bath, a quasi-adiabatic vacuum chamber and a temperature control and measurement system. The melting plateau of the Ga fixed point is longer than 2 h at 0.008 W. The standard deviation of the melting temperature of the Ga and Ga–In alloy fixed points is better than 2 mK. The results suggest that the melting temperature of the Ga or Ga–In alloy fixed points is linearly related with the heating power. 相似文献