The characterization of volatile molecular substances

1993 ◽  
Vol 443 (1918) ◽  
pp. 313-332 ◽  
Keyword(s):  
Subjective Evaluation ◽  
Sensor Arrays ◽  
Intrinsic Property ◽  
Wide Range ◽  
The Laplace Transform ◽  
Molecular Substances ◽  
Definition Of ◽  
Enclosed Space

Diffusion for gaseous sources comprising more than one type of substance is examined to show how relative concentrations change with time and distance. The large variations which are predicted make nonsense of the popular assumption that odour or smell is an intrinsic property of the source material. However, some characterization of volatile chemical substances is needed. It is shown that this is possible by creating a uniform and stable atmosphere after the relapse of sufficient time by introducing the gas mixture into an enclosed space. In this investigation the situation is analysed for a spherical enclosure using Fourier analysis techniques for the long timescale behaviour and the Laplace transform for the short timescale solution. The measurement of odours via the response of sensor arrays within a spherical enclosure is considered and a proposal is made for utilizing such an enclosure in a definition of volatile molecular substances (analogous to biological ‘smell’). The conditions for optimum compatibility between an array of sensors and a set of calibrands are discussed and the practical means of effecting such measurements are considered in relation to known types of sensor. It is concluded that the quality of volatile molecular substances is definable and measurable down to very low gas concentrations in air: probably below 10 parts per billion for a wide range of gas mixtures unconstrained by such limitations associated with a biological nose such as toxicity, temperature and subjective evaluation.

scholarly journals The Calibration Home Base for Imaging Spectrometers

2016 ◽  
Vol 2 ◽  
Author(s):  
Johannes Felix Simon Brachmann ◽  
Andreas Baumgartner ◽  
Peter Gege
Keyword(s):  
Wavelength Range ◽  
Stray Light ◽  
Third Party ◽  
Home Base ◽  
Geometric Calibration ◽  
Wide Range ◽  
Along Track ◽  
Near Future

The Calibration Home Base (CHB) is an optical laboratory designed for the calibration of imaging spectrometers for the VNIR/SWIR wavelength range. Radiometric, spectral and geometric calibration as well as the characterization of sensor signal dependency on polarization are realized in a precise and highly automated fashion. This allows to carry out a wide range of time consuming measurements in an ecient way. The implementation of ISO 9001 standards in all procedures ensures a traceable quality of results. Spectral measurements in the wavelength range 380–1000 nm are performed to a wavelength uncertainty of +- 0.1 nm, while an uncertainty of +-0.2 nm is reached in the wavelength range 1000 – 2500 nm. Geometric measurements are performed at increments of 1.7 µrad across track and 7.6 µrad along track. Radiometric measurements reach an absolute uncertainty of +-3% (k=1). Sensor artifacts, such as caused by stray light will be characterizable and correctable in the near future. For now, the CHB is suitable for the characterization of pushbroom sensors, spectrometers and cameras. However, it is planned to extend the CHBs capabilities in the near future such that snapshot hyperspectral imagers can be characterized as well. The calibration services of the CHB are open to third party customers from research institutes as well as industry.

TESTING AS A METHOD OF CONTROL AND ASSESSMENT OF THE FORMATION OF COMPETENCIES

2021 ◽  
Vol 23 (1) ◽  
pp. 18-23
Author(s):  
Belalov R.М.
Keyword(s):  
Educational Practice ◽  
Testing System ◽  
Test Results ◽  
Present Stage ◽  
Research Issues ◽  
Test Items ◽  
Wide Range ◽  
Level Of Knowledge ◽  
Definition Of

At the present stage, pedagogical tests are one of the most accessible and developed methods for assessing students' knowledge. Evaluation of the results of global research on testing problems showed that the developers of test items pay special attention to the form and their standardization, the processing of test results and the interpretation of the data obtained, methods of automatic test formation. The goal is to study the possibility of using testing to assess the formation of students' competencies. Materials and methods. Theoretical: a review of psychological and pedagogical literature on research issues, analysis, synthesis, generalization, systematization. Results. Testing characterizes a number of properties, the main of which is the objectivity of the assessment of results, the definition of "gaps" in knowledge. The result of testing is obtaining objective information about the quality of knowledge and skills, determining the sections that are the worst learned by the students. All of the above makes it possible to adjust the course of training. Test control can be external, when the subjects are offered a dichotometric range, which contains both completed and unfulfilled tasks on a wide range of issues. During the testing process, students have the opportunity to independently identify gaps in their own knowledge. The study confirms the possibility of using testing in assessing the formation of students' competencies and ultimately provides an increase in the level of knowledge. Conclusion. At the present stage, the introduction of tests into educational practice is an inevitable process, therefore, efforts should be directed to the development of a theoretical platform for the testing system, which will entail an increase in the efficiency of using tests as a form of control.

scholarly journals Effects of gas–wall interactions on measurements of semivolatile compounds and small polar molecules

2019 ◽  
Vol 12 (6) ◽  
pp. 3137-3149 ◽  
Author(s):  
Xiaoxi Liu ◽  
Benjamin Deming ◽  
Demetrios Pagonis ◽  
Douglas A. Day ◽  
Brett B. Palm ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Transmission Efficiency ◽  
Polar Molecules ◽  
Ionization Mass ◽  
Atmospheric Measurements ◽  
Wide Range ◽  
Teflon Tubing ◽  
Gas Interactions

Abstract. Recent work has quantified the delay times in measurements of volatile organic compounds (VOCs) caused by the partitioning between the gas phase and the surfaces of the inlet tubing and instrument itself. In this study we quantify wall partitioning effects on time responses and transmission of multifunctional, semivolatile, and intermediate-volatility organic compounds (S/IVOCs) with saturation concentrations (C∗) between 100 and 104 µg m−3. The instrument delays of several chemical ionization mass spectrometer (CIMS) instruments increase with decreasing C∗, ranging from seconds to tens of minutes, except for the NO3- CIMS where it is always on the order of seconds. Six different tubing materials were tested. Teflon, including PFA, FEP, and conductive PFA, performs better than metals and Nafion in terms of both delay time and transmission efficiency. Analogous to instrument responses, tubing delays increase as C∗ decreases, from less than a minute to >100 min. The delays caused by Teflon tubing vs. C∗ can be modeled using the simple chromatography model of Pagonis et al. (2017). The model can be used to estimate the equivalent absorbing mass concentration (Cw) of each material, and to estimate delays under different flow rates and tubing dimensions. We also include time delay measurements from a series of small polar organic and inorganic analytes in PFA tubing measured by CIMS. Small polar molecules behave differently than larger organic ones, with their delays being predicted by their Henry's law constants instead of their C∗, suggesting the dominance of partitioning to small amounts of water on sampling surfaces as a result of their polarity and acidity properties. PFA tubing has the best performance for gas-only sampling, while conductive PFA appears very promising for sampling S/IVOCs and particles simultaneously. The observed delays and low transmission both affect the quality of gas quantification, especially when no direct calibration is available. Improvements in sampling and instrument response are needed for fast atmospheric measurements of a wide range of S/IVOCs (e.g., by aircraft or for eddy covariance). These methods and results are also useful for more general characterization of surface–gas interactions.

Hitting-Time Densities of a Two-Dimensional Markov Process

1992 ◽  
Vol 6 (4) ◽  
pp. 561-580
Author(s):  
C. H. Hesse
Keyword(s):  
Global Analysis ◽  
First Passage Time ◽  
Type Equation ◽  
Passage Time ◽  
Two Dimensional ◽  
First Passage ◽  
Wide Range ◽  
The Laplace Transform ◽  
Mean And Variance

This paper deals with the two-dimensional stochastic process (X(t), V(t)) where dX(t) = V(t)dt, V(t) = W(t) + ν for some constant ν and W(t) is a one-dimensional Wiener process with zero mean and variance parameter σ2= 1. We are interested in the first-passage time of (X(t), V(t)) to the plane X = 0 for a process starting from (X(0) = −x, V(0) = ν) with x > 0. The partial differential equation for the Laplace transform of the first-passage time density is transformed into a Schrödinger-type equation and, using methods of global analysis, such as the method of dominant balance, an approximation to the first-passage density is obtained. In a series of simulations, the quality of this approximation is checked. Over a wide range of x and ν it is found to perform well, globally in t. Some applications are mentioned.

Demand for cosmetology procedures in accordance with psychological aspects of personality

2019 ◽  
Vol 4 (2) ◽  
pp. 11-26
Author(s):  
Екатерина Задионченко ◽  
Ekaterina Zadionchenko ◽  
Полина Казакова ◽  
Polina Kazakova
Keyword(s):  
Subjective Evaluation ◽  
Mass Market ◽  
Social Trends ◽  
Physiological Processes ◽  
Anonymous Questionnaire ◽  
Psychological Behavior ◽  
Wide Range ◽  
Important Quality ◽  
High Motivation

An increased number of cosmetic institutes and cosmetologists as well as a wide range of service in this field is explained by natural physiological processes in our body, whichsteadily lead to decline of its functions, i.e. aging. Fashion for bright, young and successful look makes a great contribution to psychological behavior of a modern woman making her conform to social trends. The presence of various skin diseasesresulting from pathological aspects, disruption of hormonal status, bad ecology, and stress entails early appearance of aesthetic drawbacks that makes a person call upon specialists of aesthetic and cosmetology fields, or even dermatologists, in some severe cases. We were interested people of what age and with what problems address cosmetologists. The object of our research was men and women older than 18, dissatisfied with their appearance or having some skin problems. We did not take into account people who visit cosmetologists on instructions of their parents (average age of such patients is 12±1,8 years old). Anonymous questionnaire was held among 163 people, among whom there were 37 men (average age is 28±1,9 years old) and 125 women (average age is 33±1,7 years old). All the respondents were asked to answer the questions of a prepared questionnaire (pic.1; pic.2): about multiplicity of visits to a cosmetologist, about the reasons of visiting a cosmetologist, types of cosmetology service, and to evaluate (subjectively) the efficiency of mass-market cosmetics and professional cosmetics, and to point out the qualities that a cosmetologist should possess. By analyzing the obtained data we learnt that men (75,3%) almost do not visit a cosmetologist, but women vice versa visit a cosmetologists on a regular basis (70,9%). However, 22,1% of women carry out procedures more often than 1-2 times a month, and the others (6,6%) – 1-2 times a week. It happened that the most popular procedure is depilation (34,4%). A facial (21,6%) and massage (21,6%) are less in demand.It was revealed that women almost equally use mass-market cosmetics and professional cosmetics while men (85%) do not differentiate between these them and do not use any of them. According to a subjective evaluation, in 46,4% of the cases the use of professional cosmetics was more popular than cosmetics made of simple home ingredients that was bought in ordinary shops. 93,1% of respondents pointed out that the most important quality of a cosmetologist is medical education. Despite high motivation of women to visit a cosmetologist, according to the questionnaire, high prices of procedures limits the quantity of visits, 34,2% of respondents told this.

scholarly journals Effects of Gas-Wall Interactions on Measurements of Semivolatile Compounds and Small Polar Molecules

2019 ◽  
Author(s):  
Xiaoxi Liu ◽  
Benjamin Deming ◽  
Demetrios Pagonis ◽  
Douglas A. Day ◽  
Brett B. Palm ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Transmission Efficiency ◽  
Polar Molecules ◽  
Ionization Mass ◽  
Atmospheric Measurements ◽  
Wide Range ◽  
Teflon Tubing ◽  
Gas Interactions

Abstract. Recent work has quantified the delay times in measurements of volatile organic compounds (VOCs) caused by the partitioning between the gas phase and the surfaces of the inlet tubing and instrument itself. In this study we quantify wall partitioning effects on time responses and transmission of multi-functional, semivolatile and intermediate-volatility organic compounds (S/IVOCs) with saturation concentrations (C*) between 100 and 104 µg m−3. The instrument delays of several chemical ionization mass spectrometer (CIMS) instruments increase with decreasing C*, ranging from seconds to tens of minutes, except for the NO3−-CIMS where it is always on the order of seconds. Six different tubing materials were tested. Teflon, including PFA, FEP, and conductive PFA, performs better than metals and Nafion in terms of both delay time and transmission efficiency. Analogous to instrument responses, tubing delays increase as C* decreases, from less than a minute to > 100 min. The delays caused by Teflon tubing vs. C* can be modeled using the simple chromatography model of Pagonis et al. (2017). The model can be used to estimate the equivalent absorbing mass concentration (Cw) of each material, and to estimate delays under different flow rates and tubing dimensions. We also include time delay measurements from a series of small polar organic and inorganic analytes in PFA tubing measured by CIMS. Small polar molecules behave differently than larger organic ones, with their delays being predicted by their Henry’s law constants instead of their C*, suggesting the dominance of partitioning to small amounts of water on sampling surfaces as a result of their polarity and acidity properties. PFA tubing has the best performance for gas-only sampling, while conductive PFA appears very promising for sampling S/IVOCs and particles simultaneously. The observed delays and low transmission both affect the quality of gas quantification, especially when no direct calibration is available. Improvements in sampling and instrument response are needed for fast atmospheric measurements of a wide range of S/IVOCs (e.g., by aircraft or for eddy covariance). These methods and results are also useful for more general characterization of surface/gas interactions.

scholarly journals Interface Refinement of Low-to-Medium Resolution Cryo-EM Complexes using HADDOCK2.4

2021 ◽  
Author(s):  
Tim Neijenhuis ◽  
Siri C. van Keulen ◽  
Alexandre M.J.J. Bonvin
Keyword(s):  
Protein Complexes ◽  
Protein Assemblies ◽  
Cellular Processes ◽  
Protein Interfaces ◽  
Density Maps ◽  
Medium Resolution ◽  
Wide Range ◽  
Multimeric Protein

A wide range of cellular processes require the formation of multimeric protein complexes. The rise of cryo-electron microscopy (cryo-EM) has enabled the structural characterization of these protein assemblies. The produced density maps can, however, still suffer from limited resolution, impeding the process of resolving structures at atomic resolution. In order to solve this issue, monomers can be fitted into low-to-medium resolution maps. Unfortunately, the produced models frequently contain atomic clashes at the protein-protein interfaces (PPIs) as intermolecular interactions are typically not considered during monomer fitting. Here, we present a refinement approach based on HADDOCK2.4 to remove intermolecular clashes and optimize PPIs. A dataset of 14 cryo-EM complexes was used to test eight protocols. The best performing protocol, consisting of a semi-flexible simulated annealing refinement with restraints on the centroids of the monomers, was able to decrease intermolecular atomic clashes by 98% without significantly deteriorating the quality of the cryo-EM density fit.

scholarly journals Scientific approaches to the system of concepts of "national security": international legal aspect

2020 ◽  
Vol 7 (12) ◽  
pp. 70-77
Author(s):  
А. Альван
Keyword(s):  
National Security ◽  
Legal Aspect ◽  
The State ◽  
Constitutional Rights ◽  
External Threats ◽  
Wide Range ◽  
Single Well ◽  
Definition Of ◽  
The Individual

Scientific approaches to the concept of "national security" are systematized in the article. The author substantiates that there are four main approaches to the concept of "national security". The first group - works devoted to the terminological characterization of national security. Another group - the authors define national security because of the state of protection of vital interests, the individual, society and the state against all kinds of threats. The third group is studies that analyze the types of national security, in particular: economic, environmental, financial, personnel, financial, social, etc. These characteristics reflect their socio-political nature, trace the unity of personal, public and state security, developing political and other processes. The fourth group of studies are those that pay attention to problems related to the correct use of the concept of "national security" and the possibility of its replacement. Fifth group - analyzes the interaction and correlation of threats and security.There is no single, well-defined definition of national security today. No matter what approach the authors use, there are different approaches, and in some cases, complications or simplifications of this category.In our opinion, national security should be understood as a state of protection of the individual, society and state against a wide range of internal and external threats, which ensure the realization of citizens' constitutional rights and freedoms, decent quality and standard of living, sovereignty, independence, state and territorial integrity. , sustainable socio-economic development of the state.

Emission and Laser-Induced Fluorescence Spectroscopy of Laser-Ablated Titanium Plume

1999 ◽  
Author(s):  
Schubert S. Chu ◽  
Costas P. Grigoropoulos
Keyword(s):  
Time Of Flight ◽  
Laser Induced Fluorescence ◽  
Spectroscopic Techniques ◽  
Wide Range ◽  
Optical Time ◽  
Background Gas ◽  
Spectrally Resolved ◽  
Deposited Film

Abstract Pulsed laser deposition (PLD) of thin films has evolved into a well-recognized technique for a wide range of materials and in a variety of devices. There is great interest in the energy characterization of the ablated plume because this is a key parameter in determining the quality of the deposited film. Spectroscopic techniques, such as optical time-of-flight (TOF,) emission spectroscopy, and laser-induced-fluorescence (LIF) are excellent methods for this purpose since they offer temporal and spatial resolution as well as the capability of distinguishing different species. The effects of laser fluence and background gas pressure on the kinetic energies of the ablated species were found by the optical time-of flight technique and by emission imaging. Furthermore, laser-induced-fluorescence was employed for spectrally resolved imaging. The results provide additional data on the kinetic energy and the distribution of neutral titanium. The axial velocity of neutral titanium was found to be as high as 2 × 104 m/s. The distribution of species within the plume was also determined.

Features of Fabrication Technology and Properties of Wicks of Heat Pipe Receivers for Solar Dish/Stirling Systems

Solar Energy ◽  
2005 ◽  
Author(s):  
Volodymyr Baturkin ◽  
Vladylen Zaripov ◽  
Charles E. Andraka ◽  
Timothy A. Moss
Keyword(s):  
Heat Pipe ◽  
Thermal Power ◽  
Substrate Material ◽  
Future Application ◽  
Stainless Steel 316L ◽  
Two Phase ◽  
Extensive Program ◽  
Definition Of

Elaboration of robust and reliable capillary systems for solar energy heat pipe receivers is the important step for future application of this product for systems with thermal power of 30–80 kW. The paper considers a new approach to fabrication of capillary structure of heat pipe receivers on the basis of discrete metal fibers with diameter of 30 microns made of stainless steel 316L, and describes some of methods of wicks characterization as well. This technology has been demonstrated by fabrication of porous 4 mm thick wicks with bulk porosity about 0.82 applied to convex surfaces of dome-shaped receivers with radius 178 mm/height 119 mm (thermal power 36 kW) and radius 247 mm/height 173 mm (thermal power 68 kW) and for inner surface of tube with length 450 mm and diameter 73 mm (thermal power 14 kW). The distinction of the proposed technology is in the use of discrete fibers, which are felted on the curved surface in a special way and in the combination of procedures of the felt formation and their sintering to the surface (substrate material is Haynes Alloy 230). Execution of an extensive program of experimental characterization of a wick layer attached to the substrate has been developed and completed. The characterization of applied wicks determines a definition of their structural (local porosity, thickness of porous layer), mechanical (quality of wick bonding to substrate) and hydrodynamic properties (pumping diameter, one-phase and two-phase permeability). Initial estimation of wick performance was performed on the basis of methods developed at the National Technical University of Ukraine for two main modes of receiver operation — with return of sodium to a point on the dome (reflux) and without it. Prediction of receiver thermal performance, when they operate as a part of solar concentration assembly, was determined by specialized heat pipe performance software /Sandia National Laboratories, C. Andraka, 1999/.

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