Electrical Capacitance Method Research Articles

Effect of Grease Filling on the Film Thickness in Deep-Groove Ball Bearings

Determining the film thickness during the bleeding phase of grease lubrication in a bearing is difficult due to the various replenishment and loss mechanisms involved. An additional factor that could influence the film thickness is the amount of grease in the bearing. In this study, film thickness is measured in deep-groove ball bearings using two different greases, each with initial grease filling percentages of 7.5%, 15%, and 30% of the bearing’s free volume. Film thickness is measured during the early stage of the bleeding phase at various loads and speeds using the electrical capacitance method. Results show that, after churning, values of temperature and film thickness are similar for the three different filling quantities. This indicates that bulk grease flow or oil bleed from the reservoirs formed in the unswept region does not impact the lubricant film thickness in the early stage of bearing operation.

Measuring Film Thickness in Starved Grease-Lubricated Ball Bearings: An Improved Electrical Capacitance Method

Presented in this article is a new method to measure the film thickness in a rolling bearing running under starved conditions, such as in grease-lubricated bearings, using the electrical capacitance method. The method was used to study the impact of speed on film thickness. Results show that fully flooded conditions prevail at lower speeds where the film thickness increases with increasing speed. At higher speeds, where grease-lubricated bearings run under starved lubrication conditions, this increase is less pronounced. At even higher speeds, the film thickness becomes almost independent of the speed.

Electrical Capacitance versus Minirhizotron Technique: A Study of Root Dynamics in Wheat-Pea Intercrops.

This study evaluated the concurrent application and the results of the root electrical capacitance (CR) and minirhizotron (MR) methods in the same plant populations. The container experiment involved three winter wheat cultivars, grown as sole crops or intercropped with winter pea under well-watered or drought-stressed conditions. The wheat root activity (characterized by CR) and the MR-based root length (RL) and root surface area (RSA) were monitored during the vegetation period, the flag leaf chlorophyll content was measured at flowering, and the wheat shoot dry mass (SDM) and grain yield (GY) were determined at maturity. CR, RL and RSA exhibited similar seasonal patterns with peaks around the flowering. The presence of pea reduced the maximum CR, RL and RSA. Drought significantly decreased CR, but increased the MR-based root size. Both intercropping and drought reduced wheat chlorophyll content, SDM and GY. The relative decrease caused by pea or drought in the maximum CR was proportional to the rate of change in SDM or GY. Significant linear correlations (R2: 0.77–0.97) were found between CR and RSA, with significantly smaller specific root capacitance (per unit RSA) for the drought-stress treatments. CR measurements tend to predict root function and the accompanying effect on above-ground production and grain yield. The parallel application of the two in situ methods improves the evaluation of root dynamics and plant responses.

Genotypic Differences in Root System Size in White Mustard in Relation to Biomass Yield and Soil Nitrogen Content

Growing catch crops is one of the possible strategies to decrease erosion and nitrogen loss from soil profiles. Biomass yield and root system size have significant impacts on the soil nitrogen content. a three‑year field experiment with eight varieties of white mustard (Sinapis alba L.) was established to evaluate the effects of genotype and environment on biomass yield, soil nitrogen content and rooting parameters. Significant effects of genotype were found for root length density (RLD), root surface density (RSD) and specific root length (SRL) in the plow layer (0 – 20 cm) and for root system size (RSS), measured by electrical capacitance method, during three phenological phases. Higher biomass yield in varieties with higher RLD and RSD values during ripening and a larger RSS during flowering were found in dry conditions. Relationship of the root system and biomass yield to nitrate and ammonia nitrogen content varied in different environments. We found a significant relation between the RSS and ammonia nitrogen content in more fertile environment on average over the three years. The nitrate nitrogen content was related to the RLD, RSD and SRL in favorable year at shallow soil depths (0 – 20 cm).

Moisture monitoring experience in the old town of Genoa (Italy)

Abstract The paper describes the monitoring process, which was conducted in an important and valuable religious building in Genoa: St Matteo Abbey. It has had serious problems with rising damp both in the hall, where the damage is particularly evident on the walls of the lateral aisles, and in the space below the crypt. In 2012, the Abbot decided to use an active system of wall dehumidification, which works with electromagnetic waves. The monitoring activities were carried out simultaneously and independently by Ecodry Italia and the University, under the supervision of both Superintendence (administrative architectural heritage body) and Curia (religious administrative body). During the days agreed for monitoring, measurements were taken independently by both parties in the same points with different equipment. There were four types of moisture measurements: environmental, superficial (Electrical Resistance method), sub-superficial (Electrical Capacitance method) and deep measurements (Gravimetric method). The paper includes the results of the moisture monitoring performed from 2012 to 2016. During the monitoring process, 6 survey campaigns were carried out, which, each time, investigated the same points and parameters to obtain values comparable to each other, in order to evaluate the actual effectiveness of the installed devices. The case study revealed critical issues regarding the structure of the Abbey that should have discouraged the choice of the dehumidification equipment and that inevitably reflected negatively on the outcome of the monitoring. It is therefore not possible to deduce, from such a complex case, a univocal result that proves that the installed dehumidification system is effectively decreasing the amount of moisture present in the walls of the Abbey of St Matteo, hall, and the room under the crypt.

Application of Electrical Capacitance Method for Prediction of Plant Root Mass and Activity in Field-Grown Crops.

The root electrical capacitance (CR) method is suitable for assessing root growth and activity, but soil water content (SWC) strongly influences the measurement results. This study aimed to adapt the method for field monitoring by evaluating the effect of SWC on root capacitance to ensure the comparability of CR detected at different SWC. First a pot experiment was conducted with maize and soybean to establish CR–SWC functions for the field soil. Ontogenetic changes in root activity were monitored under field conditions by simultaneously measuring CR and SWC around the roots. The CR values were normalized using SWC data and experimental CR–SWC functions to obtain CR*, the comparable indicator of root activity. The effect of arbuscular mycorrhizal fungi (AMF) inoculation on the CR* and biomass of field-grown soybean was investigated. The pot trial showed an exponential increase in CR with SWC. CR–SWC functions proved to be species-specific. CR showed strong correlation with root dry mass (R2 = 0.83–0.87). The root activity (CR*) of field-grown crops increased until flowering, then decreased during maturity. This was consistent with data obtained with other methods. AMF inoculation of soybean resulted in significantly higher CR* during the late vegetative and early flowering stages, when destructive sampling concurrently showed higher shoot biomass. The results demonstrated that the root capacitance method could be useful for time course studies on root activity under field conditions, and for comparing single-time capacitance data collected in areas with heterogeneous soil water status.

Application of electrical capacitance measurement for in situ monitoring of competitive interactions between maize and weed plants

Applicability of root electrical capacitance (EC) measurement for monitoring of crop–weed competition was studied in a pot experiment. Maize (Zea mays L.) was grown both alone and with Echinochloa crus-galli or Abutilon theophrasti in different densities with regular measurement of root EC. Plants were harvested 42 days after planting to determine above- and belowground biomass. Depending on weed density, E. crus-galli-A. theophrasti interaction reduced the root EC of maize by 22–66% and 3–57%, respectively. Competitive effect of crop on weeds and intraspecific competition among weeds could also be detected by EC values: E. crus-galli was less sensitive both to the presence of maize and to intraspecific competition than A. theophrasti. Strong linear correlations between root dry mass and root EC for crop and weeds (with R2 from 0.901 to 0.956) were obtained by regression analyses at the end of the experiment. EC monitoring informed us on the emergence time of competition: E. crus-galli interfered with maize root growth a week earlier then A. theophrasti, and increasing weed densities accelerated the emergence of competition. In conclusion, the simple, non-destructive EC method should be considered a potential in situ technique for pot studies on crop–weed competition, which may partially substitute the intrusive techniques commonly used in agricultural researches.

Modification of the tree root electrical capacitance method under laboratory conditions.

For many years, scientists have been searching for nondestructive methods for the measurement of plant root system parameters. The measurement of electrical capacitance (EC) across the root has been proposed as one such nondestructive method. This article presents a study on the determination of relationships between EC measurement and the shape and size of the electrodes immersed in medium that are used for measurement. Measurement of EC and the parameters characterizing root systems of 1-year-old seedlings of the common beech Fagus sylvatica L. was conducted under laboratory conditions. The measurements of EC were performed between seedling root systems and two different electrodes in the form of a cylinder or a rectangular plate. Statistically significant correlations were found between the capacitance and root system parameters in both the variants; however, the correlations were higher in the case of the flat rectangular plate. Correlation coefficient (r) between EC and total root length was 0.688 for cylindrical electrode and 0.802 for rectangular plate, for total root area 0.641 and 0.818, and for dry weight of root system 0.502 and 0.747. The best-fitted linear regression relationships between the EC and the measured parameters were characterized by low determination coefficients in variants with cylindrical electrodes, and higher with flat rectangular plate electrodes. The results indicated that a two-dielectric media concept is a better model than Dalton's model when attempting to interpret the behavior of root and soil capacitance. The different electrodes probably allow root capacitance measurements to be interpreted from different aspects. However, this hypothesis requires further verification.

On the Film Thickness of Grease-Lubricated Contacts at Low Speeds

The contribution of the thickener to the thickness of the lubricating film in grease-lubricated contacts is investigated. Four different types of greases were tested in a ball/spherical roller-on-disc machine, where the film thickness was measured using the interferometry method, varying the temperature, load, and slip. The test results show that there are two lubrication regimes. Below a transition speed the grease thickener plays an important role where the film thickness increases with decreasing speed. At higher speeds the film thickness is primarily governed by the base oil. This transition speed is a function of the temperature and not of the load and slip. At higher speeds the grease film thickness can be calculated using the base oil viscosity. The electrical capacitance method was applied to measure the film thickness at ultralow speed in a real bearing, showing that the single contact results are indeed applicable to a full rolling bearing.

The static dielectric permittivity of ionic liquids

The static dielectric permittivity εS (“static dielectric constant”) is an important quantity for characterizing the solvation capability of a solvent. The past two decades have seen the advent of ionic liquids — low-melting organic salts — as intriguing alternatives to volatile organic solvents. While for non-conducting media εS is readily measured by electrical capacitance methods, such methods fail for electrical conductors because the samples are short-circuited by their intrinsic electrical conductivity. In dielectric theory εS is defined as the zero-frequency limit of the real part of the frequency-dependent complex dielectric permittivity. This definition provides a recipe to determine εS by dielectric relaxation spectroscopy. The paper reviews the achievements in characterizing and understanding the static dielectric constant of Ionic Liquids with particular focus on work in the author's laboratory.

Testing New In-Kiln Meter for Monitoring Lumber Moisture Content during Drying

The objective of this study was to test a new in-kiln sensor for monitoring lumber moisture content during industrial drying. The theoretical foundation of the technology was already known, because it is based on electrical conductivity, but the mechanism of implementation was new and required validation. For this reason, the technology was compared with two other widely used methods for assessing lumber moisture content, namely, the oven-drying and electrical capacitance methods. The tests were performed in a 120-m3 industrial kiln operated by a sawmill in the eighth region of Chile, and the results showed that the average moisture content at the end of drying was satisfactorily determined by the new in-line sensor. As predicted by theory, the sensor was not able to accurately measure moisture content above 25%, but it was still able to provide the equivalent of a drying curve for monitoring of the drying process.

Electrical capacitance as a rapid and non-invasive indicator of root length

Measurement of tree root systems by conventional methods is a Herculean task. The electrical capacitance method offers a rapid and non-destructive alternative, but it has largely been restricted to herbaceous species. The Dalton Model has been the main concept for understanding equivalent root circuitry; it proposed that roots were cylindrical capacitors with epidermis and xylem being the external and internal electrodes. Capacitance (C) therefore varied in proportion to root surface area (A), mass (M), length (L) and relative permittivity of the plant tissue ε(r). We used the capacitance method on forest and plantation trees (13 to circa 100 y.o.) in situ to test hypotheses derived from implicit assumptions about tree-root-soil circuitry. We concluded: C was not confounded by intermingled root systems; C was strongly related to diameter at breast height (DBH); C was less strongly related to DBH for multiple species at the same site; and C was a poor indicator of DBH, M and L across species, ages and sites. We proposed that ε(r) was proportional to root tissue density ρ and fitted a model with P < 0.05 and R(2) = 0.70 when the three immature (13 y.o.) trees were excluded. There was no significant difference (P = 0.28) between the parameters of the tree model (excluding the immature trees) and one of the same form fitted to data from bean (Vicia faba L.; R(2) = 0.55). Together, the data sets suggested (R(2) = 0.94; n = 26) that there may exist a general relationship of this form applied over two orders of magnitude of L.

Electrical impedance and capacitance method: A new approach for detection of functional aspects of arbuscular mycorrhizal colonization in maize

Applicability of root electrical impedance (EI) and electrical capacitance (EC) measurements for the detection of arbuscular mycorrhizal fungal (AMF) colonization was studied. AMF-inoculated and non-inoculated maize plants were compared whilst growing them under well-watered and drought-stressed condition with regular measurement of root EI and EC. AMF-colonized maize plants showed lower EI and higher EC than control counterparts independently of moisture condition, indicating an enhanced root–soil interface. Root scanning revealed lower root surface area in mycorrhizal plants than in non-mycorrhizal ones growing under well-watered condition, while in plants exposed to drought no significant difference between root surface areas was detected. Since fungal colonization didn't provoke an increase in root surface area, the higher root–soil interface showed by EI and EC values was apparently due to the increased absorption surface area caused by the growth of AMF hyphae. Consequently, the simple, non-destructive EI and EC method is considered an appropriate technique for in situ investigation of AMF-colonization and function, which may partially substitute the intrusive techniques commonly used in mycorrhizal research.

Exposing drying patterns: using electrical resistivity tomography to monitor capillary rise in sandstone under varying drying conditions

Rising damp and other moisture movements through porous stone and rock are known to cause weathering and deterioration, as noted in a range of recent field and laboratory studies. However, relatively little is known about the behaviour of moisture within a porous stone under realistic conditions because of lack of suitable monitoring methods. This paper has two main aims: firstly, to evaluate different electrical (resistivity and capacitance) methods to monitor subsurface and surface moisture regimes and, secondly, to use these methods to monitor the movement of water by capillary rise in a sandstone block under (a) conditions of constant moisture ingress at the base and (b) an enhanced drying regime with and without constant moisture ingress at the base. Our results indicate that, for electrical resistance tomography (ERT) measurements on a sandstone block, medical electrodes provide more reliable contact with the stone than spring-loaded pointed metal electrodes, and that the combination of ERT and handheld moisture meters gives a realistic picture of moisture movements within the block. The capillary rise and drying experiments reveal complex moisture movement over time and space. Under conditions of constant moisture supply, accelerated drying results in maintained or enhanced capillary rise. These findings are presented to further our understanding of the behaviour of moisture within porous sandstone.

Monitoring of herbicide effect in maize based on electrical measurements

Monitoring of herbicide effect in maize based on electrical measurements The effect of the herbicide acetochlor on root growth was studied by a non-destructive electrical impedance and capacitance method in pot experiments on maize. Acetochlor was applied both as single active ingredient and mixed with safener AD-67 in two dosages. Without safener addition, acetochlor had a permanent inhibiting effect on plant root expansion. The safener AD-67 was capable of providing protective effect against herbicide application. High correlations between root electrical impedance or capacitance and the root dry mass or surface area under our laboratory conditions were confirmed by plant harvest method. Root electrical impedance and capacitance measurements proved to be valid for monitoring the effect of the herbicide influencing root development and for distinguishing plant groups subjected to different stress conditions.

A nondestructive method for estimating the root mass of young peach trees after root pruning using electrical capacitance measurements

The objective of this study was to estimate the root mass of young ornamental peach seedlings using nondestructive measurements of electrical capacitance (EC). We measured the root mass of peach seedlings to determine the relationship between EC and the root mass. Ornamental peach seedlings grown the field in Andosol showed good linear correlations between EC and root dry mass (R2=0.896), and EC and fresh mass (R2=0.897). Similar correlations (R2=0.806 for dry mass) were observed in an experiment with Japanese pear rootstocks. A study of the root mass and the root EC before and after root pruning treatment showed that this technique can detect the reduction in root mass in young peach trees (R2=0.669). The study results also indicate that the EC method may be a feasible, repeatable, and useful nondestructive means of estimating the root mass (fresh or dry) of peach trees.

Estimating root mass in maize genotypes using the electrical capacitance method

A two-year field hydroponic study was conducted on root mass of maize (Zea mays L.) using the root electrical capacitance (Croot) method. The primary objective of the study was to test the utility of the Croot method in estimating root mass of maize (on a fresh and dry weight basis), and to determine any influence of maize genotype on this relationship. Secondary objectives were: (i) To determine if the volume of the Turface®-filled hydroponic containers had an effect on root mass-Croot relationships, and (ii) to determine if the number of plants/container affected the Croot measurements of individual plant root systems. Firstly, it was concluded that different maize genotypes appeared to have uniquely different root dry mass vs. Croot relationships. Secondly, the massing of the maize plant roots at the bottom of smaller (20-litre) pails seemed to frequently have a negative effect on the strength of the root mass-Croot relationship. Thirdly, multiple plants could be regarded as a single experimental unit in Croot studies when their root electrical capacitance was measured simultaneously. The predictive capability of the equations developed from this hydroponic study was reasonably good, but research is needed on similar genotype-specific relationships under field soil conditions to determine if they might have some utility in broader agronomic field applications.

Relationships between skin properties and environmental parameters

Many authors have written about skin physiological parameters and their changes according to different environmental conditions. Nevertheless, the literature puts in evidence disagreement among different studies due to the great variability in these parameters and due to the difficulty in comparing the results obtained under different working conditions. Hence, the aim of this work is to attempt to clarify the relationship between some skin properties, such as transepidermal water loss (TEWL), skin hydration and mean skin temperature (T(sk)), and the environmental parameters of ambient temperature (T(a)) and relative humidity (RH), with the help of a climatic chamber to make the environment reliable. This work must be considered as the preliminary step of a wider project dealing with textile engineering: the results will be used in identifying criteria for textile design with the aim of producing more comfortable clothing. Experiments were carried out in a climatic chamber with independently controlled T(a) and RH. All the combinations between three levels of T(a) (20 degrees C, 25 degrees C and 30 degrees C) and four levels of RH (25%, 45%, 65% and 85%) were used on a panel of six young female subjects. The assessments made were: skin surface hydration using an electrical capacitance method, TEWL using a Tewameter and T(sk) using a set of thermistors. The results showed a significant correlation between TEWL and T(a), while the RH had a weaker effect on TEWL in the temperature range under investigation. Also, T(sk) showed a higher correlation with T(a) compared with RH. Finally, skin surface hydration was found to be strongly affected by both environmental parameters. The analysis of experimental data resulted in the elaboration of some easy empirical models useful to evaluate the changes in TEWL, skin hydration and T(sk) in different climatic conditions. These relationships must be considered to be valid only in a restricted range of T(a) (20-30 degrees C) and RH (25-85%) for young female subjects (25-35 years old).

Electrical capacitance of roots in relation to plant electrodes, measuring frequency and root media

The electrical capacitance method was applied for the examination of living root systems in a pot experiment. The measured root capacitances gave an unambiguous indication of the development of root mass and length. The root capacitances measured using needle and clamp plant electrodes were closely similar when the roots of whole plants were placed in water, while increasing differences were observed with a decrease in soil water saturation. The difference in capacitance between the plant electrodes is outlined by interpreting the action mechanism of the clamp electrode. The capacitance and electrical impedance spectra (30 Hz-1 MHz) were determined for roots in soil, for pieces of roots washed free of soil, and for the soil itself. The root capacitance was smaller than that of the soil and higher than that of root pieces at 1 kHz, while the capacitance of the soil became equal to that of roots in soil at about 2 kHz. This calls attention to the importance of the measuring frequency when determining root capacitance. A capacitor model with two dielectric media is proposed besides Dalton's model in order to interpret the behaviour of root and soil capacitances. However, its validity requires further verification.

Effect of surface roughness on elastohydrodynamic traction: Part 1

The effect of surface roughness on traction performance was experimentally studied using a two-roller tester. The nature of the contact was investigated using electrical resistance and electrical capacitance methods. Increased shear stress was observed in the viscous region, which could be attributed to a higher average shear rate and to greater viscosity under EHD contact conditions due to pressure fluctuations caused by the surface texture.