scholarly journals A method of measuring the effective resistance of a condenser at radio frequencies, and of measuring the resistance of long straight wires

1932 ◽  
Vol 137 (831) ◽  
pp. 116-133 ◽  
Keyword(s):  
Energy Loss ◽  
Resonance Method ◽  
Effective Resistance ◽  
Circular Disc ◽  
Solid Dielectric ◽  
Thermal Method ◽  
Thermal Methods ◽  
Elegant Method ◽  
Air Condenser ◽  
Total Capacity

When the effective resistance of a high frequency circuit is measured by a resonance method, it is usual to find that the resistance exceeds the calculated resistance of the coil. Some of the discrepancy may be due to energy loss in the condenser, and it is desirable to have some means of measuring this loss. The energy loss in high power condensers is now measured regularly by thermal methods and may be as small as 0·025 per cent. of the volt ampere product. But a thermal method is impracticable for the small condensers used in a laboratory because the power absorbed would be less than 0·1 W. Most of the energy loss in an air condenser is presumably due to the dielectric supporting the plates and to poor contacts between the plates. Dye has developed ma very elegant method for measuring the energy loss in a condenser, which presumes that all the loss occurs in the solid dielectric. In his method there is a special condenser which consists of two capacities in parallel, and screened from one another. One portion of this compound condenser contains the insulating supports for the second portion. Accordingly the second portion contains no solid dielectric and is a pure air condenser and is presumed to have no loss. This condenser consists of a single circular disc, which may have one of three sizes, contained within a cylindrical box; the plate hangs from a metal stem which is supported on quartz blocks contained in a chamber above the cylindrical box. The total capacity may be considered to be in two parts. One between the metal stem and the case and having a dielectric which is partly quartz and therefore imperfect; the other between the circular disc and the case and having no dielectric except air and therefore being perfect. The condenser to be tested can be connected in parallel with the special condenser and its capacity is adjusted to be equal to that between the circular disc and the case. The disc can be detached from the stem and so leave only the imperfect portion of the special condenser. The condenser under test is then placed in parallel with the imperfect portion, resulting in a total capacity unchanged by the substitution process. But the substitution has replaced a capacity without loss for an equal capacity with loss. The total circuit resistance is measured by a resonance method before and after the substitution and the difference of value is ascribed to the loss in the condenser under test. Since the special condenser is provided with three different discs the resistance of the condenser under test could be measured at three different settings.

scholarly journals On the construction of a standard high-frequency inductive resistance and its measurement by a thermal method

1925 ◽  
Vol 109 (751) ◽  
pp. 508-522
Keyword(s):  
Radio Frequency ◽  
Direct Current ◽  
High Frequency ◽  
Wheatstone Bridge ◽  
Effective Resistance ◽  
Thermal Method ◽  
Thermal Methods ◽  
Direct Current Resistance ◽  
Complete Circuit ◽  
Parasitic Currents

The ordinary methods of measuring the radio-frequency resistance of inductance coils depend on the measurement of the resistance of a complete circuit, containing, usually, the coil, a thermo-ammeter, a condenser and leads. The lack of knowledge of the effective resistance of the circuit outside the coil, of the losses induced in the surrounding objects, and of the distribution of parasitic currents, leave some doubt on the reliability of the value of the resistance obtained by these methods. To obtain reliable measurements it is necessary to fall back on some thermal method by means of which the power lost in the coil itself can be measured quite independently of the circuit and neighbouring bodies. The method described in this paper was carried out essentially as a check to the usual methods of measurement. A number of investigators have used thermal methods to measure the effective resistance of coils. Amongst them may be mentioned T. P. Black, L. W. Austin, H. Abrahams, Gr. W. O. Howe, and L. Lehrs. T. P. Black (1) compared the effective resistance of long solenoids with the effective resistance of straight wires, employing a method resembling that of J. A. Fleming (2) for measuring the high-frequency resistance of straight wires by means of a differential air thermometer. L. W. Austin (3) compared the heat given out by a coil when current at radio frequencies and direct current were passed through two similar coils. The coils were immersed in oil, and the equality of temperature noted by thermo-junctions connected in opposition in the two vessels. H. Abrahams (4) compared the rise of temperature of coils after passing radio-frequency current and then direct current by quickly finding the change in the direct-current resistance measured by a Wheatstone bridge. G. W. O. Howe (5) found the rise of temperature of long solenoids by means of a thermojunction placed near the centre, and compared the effect of direct and highfrequency currents. He thus assumed that the loss is uniformly distributed along the coil, an assumption which will hold only if the coil is long. L. Lehrs (6) enclosed the coil in a vessel connected to a very sensitive manometer, and adjusted the alternating and direct currents so that no change could be observed on switching from one to the other.

scholarly journals Assessment of Nanocalcite Synthesis Routs on Green Biodiesel Production: Comparative Study

2020 ◽  
Vol 10 (5) ◽  
pp. 6139-6147
Keyword(s):  
Fossil Fuel ◽  
Sol Gel ◽  
Biodiesel Production ◽  
Thermal Method ◽  
Thermal Methods ◽  
Cooking Oil ◽  
The Past ◽  
Similar Vein ◽  
Egg Shell ◽  
Forward Process

There has been a large demand for producing and utilizing eco-friendly fuel during the past few decades. In this regard, proposing an alternative to fossil fuel has to be judged based on its availability, and sustainability. Biodiesel is one of the realistic candidates to be a fossil fuel substitute. Albeit, biodiesel production is not straight forward process as it involves a chemical reaction that necessitates the use of a catalyst. In current research, we synthesized calcite (CaCO/CaCO3) nanocatalysts were prepared using two common methods, namely, sol-gel and thermal method. The findings revealed that synthesized nanocatalyst by sol-gel method enhanced the biodiesel yield to 93% compare to 98% for nanocatalyst synthesized from egg shell by the thermal method. In a similar vein, the nanocatalysts manufactured by sol-gel and thermal methods were tested for their reusability and showed a 81%, and 88%, biodiesel yield respectively. Furthermore, the Cetane Index (CI) was measured to confirm the efficiency of the produced biodiesel which was within a recommended range of (45-54), suggestive that CaCO/CaCO3 nanocatalyst might be a good candidate for efficient and reasonably clean biodiesel production from cooking oil waste.

Role of thermoxidation and depolymerisation in the ageing of systems paper/gum arabic/historical ink

2014 ◽  
Vol 68 (4) ◽  
Author(s):  
András Peller ◽  
Milena Reháková ◽  
Michaela Ciglanská ◽  
Peter Šimon
Keyword(s):  
Reaction Path ◽  
Gum Arabic ◽  
Thermal Ageing ◽  
Accelerated Ageing ◽  
Thermal Method ◽  
Reaction Paths ◽  
Thermal Methods ◽  
Iron Gall ◽  
A Minor ◽  
Whatman Paper

AbstractThe aim of this study was to assess the role and proportional representation of depolymerisation and thermoxidation reaction paths in the systems paper/gum arabic (GA)/historical ink during various accelerated ageing methods. The historical inks under study are iron-gall, bistre, and sepia. The results indicate that thermoxidation represents only a minor reaction path in the ageing of paper/GA/ink systems except for the iron-gall ink and the light-thermal method of accelerated ageing. The iron-gall ink accelerates both reaction paths of ageing, i.e. thermoxidation and depolymerisation; in this case, thermoxidation might become the prevailing degradation reaction path. For the sepia ink, an anti-depolymerisation stabilising effect in thermal methods of ageing has been detected. Considering the thermoxidation reaction path, the results even suggest that a compound preventing thermoxidation is formed during the thermally accelerated ageing in air and in 100 mg L−1 of NO2. In the light-thermal ageing, the most stable sample is the Whatman paper (W)/GA/bistre ink.

scholarly journals Influence of Mode of Power Source on the Mechanical Properties of Vibratory Weld Joints

2019 ◽  
Vol 9 (2) ◽  
pp. 2919-2922
Keyword(s):  
Mechanical Properties ◽  
Steel Specimen ◽  
Alternate Current ◽  
Power Source ◽  
Modern Technology ◽  
Thermal Method ◽  
Thermal Methods ◽  
Heating And Cooling ◽  
Hardness Property ◽  
The One

Welding plays a major role in modern technology. During welding, a portion of the specimen is subjected to heating. Because of different heating and cooling cycles of the specimen, residual stresses induced in the specimen i.e., mechanical properties gets reduced. To enhance the mechanical properties there are different techniques are available i.e., thermal and non-thermal methods. Vibratory welding is the one of the non-thermal method; mechanical properties of steel specimens are analyzed under with and without vibrations under different power source condition. In this paper input parameters which are considered is straight polarity, reverse polarity and alternate current. Tensile and hardness property of the steel specimen are analyzed and compared with the without vibratory condition.

scholarly journals Determining the temperature values on the surface of complex curvilinearly bent agricultural machine parts during the formation of powder coatings by thermal methods

2021 ◽  
Vol 845 (1) ◽  
pp. 012139
Author(s):  
E V Pukhov ◽  
V L Sidorenkov ◽  
I V Shchegolev
Keyword(s):  
Surface Preparation ◽  
Total Power ◽  
Maximum Temperature ◽  
Thermal Method ◽  
Powder Materials ◽  
Back Side ◽  
Thermal Methods ◽  
Agricultural Machine ◽  
Average Temperature ◽  
Machine Parts

Abstract The development of modern technologies for the restoration and hardening of agricultural machine parts require the development of a mathematical apparatus that simulates the involved processes. For this purpose, the models should take into account the technological features of the process of hardening and restoration of machine parts, including: cleaning; determination of geometric indicators; surface preparation; choice of technology; subsequent machining of the resulting surface; surface quality control. One of the priority directions in the development of technologies for the restoration and hardening of parts is the formation of coatings on machine parts using powder materials applied by the gas-thermal method. One of the most important conditions for obtaining high-quality coatings is temperature control on the surface of the part. In this regard, it is of scientific interest to study the effect of the distance from the surface of the part to the flame nozzle when applying self-fluxing powder on the time-average temperature at the point of coating, the maximum temperature on the back side of the part, and the total power transferred to the part by the gas burner. This paper presents a mathematical model for determining the above-mentioned influence, and also presents the results obtained using a computer program. The novelty of the model is the ability to use it to study temperature values for complex curved-bent machine parts (crankshafts and camshafts of agricultural machines). To check the reliability of the dependences obtained, experiments were carried out and the convergence with theoretical developments was confirmed.

scholarly journals Simulação Numérica de Escoamento não Isotérmico em Reservatório de Óleo com Poços Aquecedores

2018 ◽  
Vol 3 (2) ◽  
Author(s):  
Relber Bernardo Lopes
Keyword(s):  
Oil Recovery ◽  
Reservoir Simulation ◽  
Heavy Oil ◽  
Finite Differences ◽  
Operator Splitting ◽  
Water Injection ◽  
Thermal Method ◽  
Thermal Methods ◽  
Finite Differences Method

<p>A recuperação aprimorada de reservatórios de óleo pesado só ocorre mediante um método de suplementação de energia, tal como a injeção de água ou a aplicação de um procedimento térmico. Para procedimento térmicos, tradicionalmente há injeção de vapor, injeção de água quente e combustão {\it in-situ}. No entanto, os procedimento térmicos denominados não convencionais, como o aquecimento eletromagnético, formam um novo grupo de técnicas de recuperação de óleo. Neste trabalho, utilizamos simulação numérica de reservatórios para estudar um procedimento térmico não convencional usando os chamados aquecedores de poços. Consideramos um fluxo monofásico não-isotérmico bidimensional de óleo ligeiramente compressível. Para determinar a pressão e a temperatura do reservatório, empregamos o método das diferenças finitas, além de um esquema numérico totalmente implícito e um fracionamento de etapas. Os resultados mostram que a técnica de aquecimento considerada pode ser usada para melhorar a recuperação de petróleo pesado, mantendo a pressão do reservatório alta por um longo período em comparação com as outras estratégias.</p><p><strong>Palavras-chave</strong>: Método das diferenças finitas, fluxo não-isotérmico, fracionamento de etapas, simulação de reservatório, aquecedores de poços.</p><p>===========================================================================</p><p>Enhanced recovery for heavy oil reservoirs only occurs using a method of energy supplementation, like water injection or a thermal method. For thermal methods, traditionally there are steam injection, hot water injection and the {\it in-situ} combustion. However, thermal methods named non-conventional, such as electromagnetic heating, form a new group of oil recovery methods. In this work, we use numerical reservoir simulation in order to study a non-conventional thermal method using the so-called well heaters. We consider a two-dimensional non-isothermal single-phase flow of slightly compressible oil. In order to determine the pressure and temperature of the reservoir, we employ the finite differences method, a totally implicit numerical scheme, and an operator splitting. The results show that the heating technique considered can be used to enhance heavy oil recovery by maintaining the reservoir pressure high for a long period when compared to the other strategies.</p><p><strong>Key words</strong>: Finite differences method, non-isothermal flow, operator splitting, reservoir simulation, well heaters.</p>

Inelastic Electron-Matter Interactions

1978 ◽  
Vol 36 (3) ◽  
pp. 259-267
Author(s):  
J. Silcox
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Chemical Structure ◽  
Inelastic Electron ◽  
Primary Concern ◽  
Unique Probe ◽  
Introductory Paper ◽  
Elastic Processes ◽  
Experimental Level ◽  
Inelastic Processes

In this introductory paper, my primary concern will be in identifying and outlining the various types of inelastic processes resulting from the interaction of electrons with matter. Elastic processes are understood reasonably well at the present experimental level and can be regarded as giving information on spatial arrangements. We need not consider them here. Inelastic processes do contain information of considerable value which reflect the electronic and chemical structure of the sample. In combination with the spatial resolution of the electron microscope, a unique probe of materials is finally emerging (Hillier 1943, Watanabe 1955, Castaing and Henri 1962, Crewe 1966, Wittry, Ferrier and Cosslett 1969, Isaacson and Johnson 1975, Egerton, Rossouw and Whelan 1976, Kokubo and Iwatsuki 1976, Colliex, Cosslett, Leapman and Trebbia 1977). We first review some scattering terminology by way of background and to identify some of the more interesting and significant features of energy loss electrons and then go on to discuss examples of studies of the type of phenomena encountered. Finally we will comment on some of the experimental factors encountered.

Data Acquisition and Handling Unit for a Quantitative Use of Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 232-233 ◽  
Author(s):  
P. Trebbia ◽  
P. Ballongue ◽  
C. Colliex
Keyword(s):  
Electron Microscope ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Single Channel ◽  
Detection System ◽  
Surface Barrier ◽  
Solid State Detector ◽  
Electrostatic Mirror ◽  
Electron Energy Loss

An effective use of electron energy loss spectroscopy for chemical characterization of selected areas in the electron microscope can only be achieved with the development of quantitative measurements capabilities.The experimental assembly, which is sketched in Fig.l, has therefore been carried out. It comprises four main elements.The analytical transmission electron microscope is a conventional microscope fitted with a Castaing and Henry dispersive unit (magnetic prism and electrostatic mirror). Recent modifications include the improvement of the vacuum in the specimen chamber (below 10-6 torr) and the adaptation of a new electrostatic mirror.The detection system, similar to the one described by Hermann et al (1), is located in a separate chamber below the fluorescent screen which visualizes the energy loss spectrum. Variable apertures select the electrons, which have lost an energy AE within an energy window smaller than 1 eV, in front of a surface barrier solid state detector RTC BPY 52 100 S.Q. The saw tooth signal delivered by a charge sensitive preamplifier (decay time of 5.10-5 S) is amplified, shaped into a gaussian profile through an active filter and counted by a single channel analyser.

Trends in Electron Energy Loss Spectroscopy

1977 ◽  
Vol 35 ◽  
pp. 228-229
Author(s):  
C. Colliex ◽  
P. Trebbia
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Materials Science ◽  
Analytical Technique ◽  
Recent Developments ◽  
Quantitative Results ◽  
Electron Microscopes ◽  
Electron Energy Loss ◽  
Primary Electrons

The physical foundations for the use of electron energy loss spectroscopy towards analytical purposes, seem now rather well established and have been extensively discussed through recent publications. In this brief review we intend only to mention most recent developments in this field, which became available to our knowledge. We derive also some lines of discussion to define more clearly the limits of this analytical technique in materials science problems.The spectral information carried in both low ( 0<ΔE<100eV ) and high ( >100eV ) energy regions of the loss spectrum, is capable to provide quantitative results. Spectrometers have therefore been designed to work with all kinds of electron microscopes and to cover large energy ranges for the detection of inelastically scattered electrons (for instance the L-edge of molybdenum at 2500eV has been measured by van Zuylen with primary electrons of 80 kV). It is rather easy to fix a post-specimen magnetic optics on a STEM, but Crewe has recently underlined that great care should be devoted to optimize the collecting power and the energy resolution of the whole system.

Scattering-angle dependence of signal/background ratio of inner-shell electron excitation loss in EELS

1983 ◽  
Vol 41 ◽  
pp. 390-391
Author(s):  
T. Oikawa ◽  
M. Inoue ◽  
T. Honda ◽  
Y. Kokubo
Keyword(s):  
Energy Loss ◽  
Electron Excitation ◽  
Heavy Elements ◽  
Background Intensity ◽  
Light Elements ◽  
Energy Analyzer ◽  
High Background ◽  
Scattering Angle ◽  
Angle Dependence ◽  
Shell Electron

EELS allows us to make analysis of light elements such as hydrogen to heavy elements of microareas on the specimen. In energy loss spectra, however, elemental signals ride on a high background; therefore, the signal/background (S/B) ratio is very low in EELS. A technique which collects the center beam axial-symmetrically in the scattering angle is generally used to obtain high total intensity. However, the technique collects high background intensity together with elemental signals; therefore, the technique does not improve the S/B ratio. This report presents the experimental results of the S/B ratio measured as a function of the scattering angle and shows the possibility of the S/B ratio being improved in the high scattering angle range.Energy loss spectra have been measured using a JEM-200CX TEM with an energy analyzer ASEA3 at 200 kV.Fig.l shows a typical K-shell electron excitation edge riding on background in an energy loss spectrum.

Sign in / Sign up

Export Citation Format

Share Document