Moisture Profiles Research Articles

A guide to eliminating baggy webs

Slack or baggy webs can cause misregistration, wrinkles, and breaks in printing and converting operations. Bagginess appears as non-uniform tautness in the cross direction (CD) of a paper web. The underlying cause is uneven CD tension profiles, for which there are few remedies once the paper is made. Precision measurements of CD tension profiles combined with trials on commercial paper machines have shown that uniform CD distribution of moisture, basis weight, and caliper profiles at the reel are key to avoiding bagginess. However, the most important but infrequently measured factor is the CD moisture profile entering the dryer section. Wetter areas entering the dryers are permanently elongated more than dry areas, leading to greater slackness in the finished paper. In storage, wound-in tension can amplify baggy streaks in paper near the surface of a roll and adjacent to the core. Unwrapped or poorly wrapped rolls exposed to low humidity environments may have baggy centers caused by moisture loss from the roll edges. All of the factors that impact bagginess have been incorporated in a mathematical model that was used to interpret the observations from commercial trials and can be used as a guide to solve future problems.

A PRACTICAL APPROACH TO DETERMINE THE TEMPERATURE CORRECTION FOR EC-5 MOISTURE SENSORS EMBEDDED IN VERTOSOL

Expansive soils are predominant in arid and semi-arid regions, and they are highly moisture sensitive. The investigation of the climate-ground interaction of expansive soils is extremely important to understand the hydro-mechanical responses of such soils. During the past decade, the low cost and simple methods to reliably monitor the soil volumetric water content have been popular among geotechnical practitioners. As a result, EC-5 moisture sensors have been widely used in agricultural and scientific projects due to the minimized salinity and textural effects on the final volumetric water content readings. The changes in soil volumetric water content profile can be effectively monitored using soil-specifically calibrated EC-5 sensors. However, due to the temperature sensitivity of EC-5 sensors, a suitable correction factor is essential to determine the actual volumetric water content of the expansive soil. In this study, the authors present a practical and straightforward approach to calibrate EC-5 sensors incorporating the temperature effect. This simple calibration approach enhances the accuracy of the EC-5 moisture profiling and eventually leads to safe decision-making of geotechnical practitioners.

Changes in the simulation of atmospheric instability over the Iberian Peninsula due to the use of 3DVAR data assimilation

Abstract. The ability of two downscaling experiments to correctly simulate thermodynamic conditions over the Iberian Peninsula (IP) is compared in this paper. To do so, three parameters used to evaluate the unstable conditions in the atmosphere are evaluated: the total totals index (TT), convective available potential energy (CAPE), and convective inhibition (CIN). The Weather and Research Forecasting (WRF) model is used for the simulations. The N experiment is driven by ERA-Interim's initial and boundary conditions. The D experiment has the same configuration as N, but the 3DVAR data assimilation step is additionally run at 00:00, 06:00, 12:00, and 18:00 UTC. Eight radiosondes are available over the IP, and the vertical temperature and moisture profiles from the radiosondes provided by the University of Wyoming and the Integrated Global Radiosonde Archive (IGRA) were used to calculate three parameters commonly used to represent atmospheric instability by our own methodology using the R package aiRthermo. According to the validation, the correlation, standard deviation (SD), and root mean squared error (RMSE) obtained by the D experiment for all the variables at most of the stations are better than those for N. The different methods produce small discrepancies between the values for TT, but these are larger for CAPE and CIN due to the dependency of these quantities on the initial conditions assumed for the calculation of a lifted air parcel. Similar results arise from the seasonal analysis concerning both WRF experiments: N tends to overestimate or underestimate (depending on the parameter) the variability of the reference values of the parameters, but D is able to capture it in most of the seasons. In general, D is able to produce more reliable results due to the more realistic values of dew point temperature and virtual temperature profiles over the IP. The heterogeneity of the studied variables is highlighted in the mean maps over the IP. According to those for D, the unstable air masses are found along the entire Atlantic coast during winter, but in summer they are located particularly over the Mediterranean coast. The convective inhibition is more extended towards inland at 00:00 UTC in those areas. However, high values are also observed near the southeastern corner of the IP (near Murcia) at 12:00 UTC. Finally, no linear relationship between TT, CAPE, or CIN was found, and consequently, CAPE and CIN should be preferred for the study of the instability of the atmosphere as more atmospheric layers are employed during their calculation than for the TT index.

Simultaneous x-ray and neutron 4D tomographic study of drying-driven hydro-mechanical behavior of cement-based materials at moderate temperatures

The drying of cement-based materials is intimately related to their durability, which has significant economic, social and environmental repercussions. The evolution of the saturation of the pore network and the associated drying shrinkage are in fact leading causes of cracking and of the ensuing penetration of aggressive chemicals.This process is highly heterogeneous, due to the thermo-hydric spatial gradients developing in the material from the exposed surfaces to its core and because of local effects, driven by the intrinsically heterogeneous micro-structure (e.g., by the distribution of pores and aggregates). It follows that macroscopic, sample-scale measurements cannot fully disclose the complexity of the underlying processes. In the last few decades, significant advances in full-field techniques have allowed an unprecedented insight into these local processes. For cement-based materials, x-ray and neutron tomography lend themselves as ideal, and highly complementary, tools for the study of their thermo-hydro-mechanical behavior. Notably, the high sensitivity to density variations of x-ray imaging gives access to the developments of fractures, in 4D (3D + time). On the other hand, neutron tomography allows the study of the evolution of the moisture field in 4D, thanks to its high hydrogen sensitivity. The combination of these two techniques provides a unique insight in thermo-hydro-mechanical couplings, e.g., the effect of cracks on the water content field.This contribution presents novel 5D datasets (3D tomographies along time, plus truly simultaneous x-ray and Neutron rapid acquisitions) in-operando of a cement paste and of a concrete sample heated at moderate temperatures (up to 140∘C).The analysis of this 5D data-set (once aligned in time and across modalities) allows for example a quantification of the 4D moisture profiles which were found to predict an overall water loss at hydric equilibrium coherent with the corresponding analytical analysis. In the cement paste sample, the x-ray dataset captures the evolution of an extensive cracking network, opening and propagation toward the core of the sample. A novel analysis procedure is here proposed which allows the extraction of these fractures and the analysis of their interplay with local drying as captured through neutron imaging. This for example reveals the depth of penetration of drying in the vicinity of the fractures along time, which is essential for the assessment and calibration of hydro-mechanical coupled models.

Study on the effect of conical and parabolic solar concentrator designs on hybrid solar dryers for apricots under variable conditions: A numerical simulation approach

ABSTRACT The main objective of this paper is to present a numerical model and simulation of coupled heat and mass transfer of solar dryer with various solar concentrator shapes considering the thermo-physical properties of apricot and climatic conditions of Nancy France. The resolution of the model will permit the prediction of the temperature and humidity of the solar air heater at the collector and drying chamber and also determine the moisture profile during the drying process. The thermal performance of each concentrator design was compared for best performance. A solar dryer with a non-coaxial conical concentrator presented for drying of apricot under the variable external conditions was used for the validation of the model. The numerical results showed a good agreement with experimental data determined for Elazig town Turkey. Numerically the global results were satisfying for moisture content and air temperature for the solar dryers. Parabolic concentrator had comparatively poor drying kinetics when compared with conical concentrators while co-axial design outperforming the non-coaxial design for drying kinetics. When applied in Nancy France environment to dry 30 kg of apricot with an initial moisture content of 3.5 kg/kg (db), lower energy consumption of 8.143 MJ per kg of water removed was determined for non-hybrid drying with non-coaxial conical concentrator while intermittent deployment for 2 MW electrical power consumed more energy with the higher energy of 18.668 MJ per kg of water extracted. For simulation on the environmental condition of Nancy France under the winter, summer, autumn and spring periods drying kinetic were better for drying with 1 MW continuous drying, while drying with 2 MW discontinuous drying performed better in the autumn period. Generally, non – hybrid drying performed poorly compared to others but is more energy utilization efficient compared to others.

Optimization of process parameters and numerical modeling of heat and mass transfer during simulated solar drying of paddy

Present study aims to optimize the process parameters and to develop a 3-dimensional, multi-layered finite element model for predicting moisture and temperature profile during simulated solar drying of paddy. Drying of paddy was conducted in an in-house designed photovoltaic integrated hybrid solar dryer. Design expert software was employed for optimization of drying process parameters (power level, air velocity and moisture content). Analysis of variance (ANOVA) was performed at significance level (P < 0.05) for the linear and interaction effects of the variables on various quality parameters. The simulation studies were performed using COMSOL Multiphysics platform. Optimum parameters for drying paddy were found at 700 W, 3.5 m/s and 12% moisture with optimal temperature, milling yield and drying time of 46 °C, 71.48% and 90 min, respectively, having the desirability factor of 0.92. Milling yield was observed to vary linearly with moisture content. Furthermore, the three dimensional model was successfully developed for paddy loaded in bulk as well as, accounting husk, bran and endosperm layers. Diffusion coefficient of endosperm, bran and husk was found to be 2.95 × 10−11, 8.66 × 10−12 and 6.00 × 10−12 m2/s, respectively. The optimized parameters can be successfully used to dry paddy to ensure maximum throughput and uniform quality of products in every drying batch. Additionally, the developed model was validated and can be employed for monitoring the drying parameters to standardize the hybrid solar drying process.

Comparison of statistical and machine learning approaches in land subsidence modelling

This study attempted to predict ground subsidence occurrence using statistical and machine learning models, specifically the evidential belief function (EBF), index of entropy (IoE), support vector machine (SVM), and random forest (RF) models in the Rafsanjan Plain in southern Iran to investigate 11 possible causative factors: slope percent, aspect, topographic wetness index (TWI), plan and profile curvatures, normalized difference vegetation index (NDVI), land use, lithology, distance to river, groundwater drawdown, and elevation. The Boruta algorithm was applied to determine the importance of the possible causative factors. NDVI, groundwater drawdown, land use, and lithology had the strongest relationships with land subsidence. Finally, we generated land subsidence maps using different machine learning and statistical models. The accuracy of these models was assessed using the AUC value and the true skill statistic (TSS) metrics. The SVM model had the highest prediction accuracy (AUC = 0.967, TSS = 0.91), followed by RF (AUC = 0.936, TSS = 0.87), EBF (AUC = 0.907, TSS = 0.83), and IoE (AUC= 0.88, TSS = 0.8).

Evaluation of a land-atmosphere coupling metric computed from a ground-based infrared interferometer

AbstractLand-atmosphere feedbacks are a critical component of the hydrologic cycle. Vertical profiles of boundary layer temperature and moisture, together with information about the land surface, are used to compute land-atmosphere coupling metrics. Ground based remote sensing platforms, such as the Atmospheric Emitted Radiance Interferometer (AERI), can provide high temporal resolution vertical profiles of temperature and moisture. When co-located with soil moisture, surface flux, and surface meteorological observations, such as at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site, it is possible to observe both the terrestrial and atmospheric legs of land-atmosphere feedbacks. In this study, we compare a commonly used coupling metric computed from radiosonde-based data to that obtained from the AERI to characterize the accuracy and uncertainty in the metric derived from the two distinct platforms. This approach demonstrates the AERI’s utility where radiosonde observations are absent in time and/or space. Radiosonde and AERI based observations of the Convective Triggering Potential and Low-Level Humidity Index (CTP-HIlow) were computed during the 1200 UTC observation time and displayed good agreement during both 2017 and 2019 warm seasons. Radiosonde and AERI derived metrics diagnosed the same atmospheric preconditioning based upon the CTP-HIlow framework a majority of the time. When retrieval uncertainty was considered, even greater agreement was found between radiosonde and AERI derived classification. The AERI’s ability to represent this coupling metric well enabled novel exploration of temporal variability within the overnight period in CTP and HIlow. Observations of CTP-HIlow computed within a few hours of 1200 UTC were essentially equivalent, however with greater differences in time arose greater differences in CTP and HIlow.

Physical and Chemical Characteristics of Teak (Tectona Grandis) Leaves as Food Packaging Material

Teak (Tectona grandis) leaves is commonly used as the packaging material of traditional food in Indonesia. This study aimed to determine the physical and chemical characteristics of teak leaves with various maturation stages to obtain information about the potency of teak leaves as active packaging material. The physical characteristics analysis including leaf color, thickness, and tensile strength, while chemical characteristics were moisture, fat content, fatty acid, and volatile profile. The results showed that the color, thickness, tensile strength, moisture, and fat content, were light green, 0.306±0.024 mm, 0.22±0.114 MPa, 74.93%, and 2.52% respectively for young teak leaves; while the mature has darker green, 0.388±0.001 mm, 0.36±0.163 MPa, 73.05%, and 2.54% respectively. The fatty acid profiles showed that young teak leaves contained 5 types of fatty acids, dominated by lignoceric acid; while mature teak leaves contained 9 types of fatty acids dominated by tricosanoic acid. The volatile components of young teak leaves e.g. acid and ester compounds, while the mature was dominated by acid and ether compounds. From the results, it is suggested that the use of teak leaves as active food packaging material can be scientifically justified.

Enhance Low Level Temperature and Moisture Profiles Through Combining NUCAPS, ABI Observations, and RTMA Analysis

AbstractThermodynamic information from low levels in the atmosphere is crucial for operational weather forecasts and meteorological researchers. The NOAA Unique Combined Atmospheric Processing System (NUCAPS) sounding products have been proven beneficial to fill the data gap between synoptic radiosonde observations (RAOBs). However, compared with the upper troposphere, the accuracy of NUCAPS soundings in the low levels still needs improvement. In this study, a deep neural network (DNN) is applied to fuse multiple data sources to enhance the NUCAPS temperature and moisture profiles in the lower atmosphere. The network is developed by combining satellite observations, including NUCAPS sounding retrievals and high resolution geostationary satellite observations from the Advanced Baseline Imager, and surface analysis from the Real‐Time Mesoscale Analysis (RTMA) as inputs, while collocated soundings from ECMWF re‐analysis version 5 are used as the benchmark for the training. The performance of the model is evaluated by using the independent testing data set, data from a different year, as well as collocated RAOBs, showing improvement to the temperature and moisture profiles by reducing the root‐mean‐squared‐error (RMSE) by more than 30% in the lower atmosphere (from 700 hPa to surface) in both clear sky and partially cloudy conditions. A convective event from June 18, 2017 is presented to illustrate the application of the enhanced low level soundings on high impact weather events. The enhanced soundings from fused data capture the large surface‐based convective available potential energy structures in the preconvection environment, which is very useful for severe storm nowcasting and forecasting applications.

Modeling and numerical simulation of heat and mass transfer in the cave wall of the Mogao Grottoes in China

In the Mogao Grottoes in Dunhuang, China, temperature and relative humidity (RH) fluctuations are the main causes of the observed deterioration. In this paper, we experimentally and numerically analyze hygrothermal transfer in the cave wall of the Mogao Grottoes. A coupled heat and moisture transfer 1D model is developed to simulate the hygrothermal behavior of the cave wall of the Mogao Grottoes, which adopts the temperature and water vapor pressure as driving potentials. The model is implemented in a programming. By constructing the numerical model of the wall under boundary conditions and comparing the measured data and simulation results, we validate the numerical model and analyze the hygrothermal transfer characteristics of the wall. The temperature and moisture profiles of the cave wall are experimentally measured and numerically determined. The simulation results are compared to experimental temperature and RH values, with good agreement despite the simplifying hypotheses adopted during modeling. By analyzing the heat and moisture distributions, we find that the heat and moisture transfer process in the cave wall changes in space and time. The complicated heat and moisture transfer directions vary cyclically. Additionally, moisture transfer in the cave wall reaches the steady state more rapidly than heat transfer. Hygrothermal cycling plays an essential role in the development of mural deterioration. The developed model provides theoretical support and a scientific method for the conservation of cave sites and a quantitative analysis approach to study mural relics.

Nutritional contribution of shellfish from the biodiversity of Todos os Santos Bay, Brazil

The aim of this study was to evaluate the proximate composition and fatty acid profile of shellfish native to Todos os Santos Bay, Bahia, Brazil. Samples of shellfish of the species Brachidontes exustus, Mytella guyanensis, Trachycardium muricatum and Goniopsis cruentata were collected in fishing communities and analyzed for moisture, ash, proteins, lipids and fatty acid profile. The average values ​​of proximate composition analysis had the following variations: moisture, from 76.27–85.33 g/100 g; ash, from 2.13 to 3.3 g/100 g; protein, from 9.44 to 19.75 g/100 g; lipids from 0.44 to 0.99 g/100 g; and energy value of 50.22–89.37 kcal/100 g. Among the species, Goniopsis cruentata had the highest protein content (19.75 g/100 g) and the lowest lipid content (0.44 g/100 g). As for the lipid profile, it was found that: palmitic and stearic acids stood out, among saturated; margaroleic, palmitoleic and oleic acids, among the monounsaturated; and eicosapentaenoic and docosahexaenoic acids, among polyunsaturated ones - within these groups, the unsaturated were predominant. The results show the nutritional contribution of different native species, which serve as a source of proteins and polyunsaturated lipids for the local population. In addition, they contribute to fill gaps in scientific knowledge and in national food composition tables.

Influence of extracts of different Feijoa (Acca sellowiana) leaf genotypes on the lactic fermentation performed by a mixed culture

The objective of this research was to evaluate the influence of the addition of aqueous extracts of Feijoa leaf genotypes (Acca Selowiana) (Access 2316, Alcântara, Helena, Mattos and Nonante) on the lactic fermentation performed by Streptococcus thermophilus and Lactobacillus delbrueckii subsp. Bulgaricus, in MRS broth and milk. The total content of phenolic compounds (TPC), the antioxidant activity (AA) and the antimicrobial activity were determined. For the samples fermented in MRS broth, with and without the presence of extracts, the parameters analyzed were the kinetics of cell growth, TPC, AA, pH, and bacterial microscopy. For the samples fermented in whole milk, the parameters analyzed were pH, titratable acidity, moisture, ash, protein, total solids, and sensory profile. There was inhibition of the mixed culture’s growth in the dilution of 80% of the extracts (TPC 75.82 - 110.90 mg EAG g-1), the other experiments having been performed with TPC below 70 mg EAG g-1. The kinetics of growth was 16 hours. For the fermented samples, there were changes to the TPC and antioxidant activity, except for the one fermented with the Access 2316 extract, for which activity remained the same. The microscopy showed predominance of Streptococcus thermophilus. In the fermented milks, pH decreased, and acidity increased, and the sensory profile was modified by the addition of the extracts. The addition of Feijoa leaf extracts in fermentation enriches the fermented product with phenolic compounds and antioxidant activity and can be a viable alternative for the provision of bioactive compounds.

Investigating temperature and moisture profiles of seasonally frozen soil under different land covers using actively heated fiber Bragg grating sensors

In this study, the actively heated fiber Bragg grating (AH-FBG) technique is developed to measure temperature and moisture profiles of partially frozen soil. The working principle of the AH-FBG sensing system is introduced, which employs an aluminum oxide tube sensor (AOTS). The unfrozen water contents and ice contents are estimated by combining AH-FBG with the frequency-domain reflection (FDR) technique. The feasibility of AH-FBG for soil moisture measurement is evaluated by laboratory and field tests under four different land covers, i.e., bare soil, concrete slab, plastic mulch (PM), and grass. It is found that AH-FBG can be used to capture unfrozen water contents and ice contents with high accuracy. The relationships between the thermal conductivity measured by AOTSs and the total water contents of frozen and unfrozen soils can be well fitted by the Côté and Konrad model. Both PM and concrete slab have a warming effect on the ground soil, which makes their depths of soil freezing shallower than that of bare soil, while the grassy land has a deeper freezing depth due to the inherent plant root-to-soil structure. The field monitoring results indicate that the PM can effectively block water migration channels at the ground surface and prevent water vapor exchange between the atmosphere and the soil, resulting in a “pot effect” that commonly exists under an impermeable layer.

Insights into thermo-hydro-mechanical (THM) behavior of cementitious materials by means of simultaneous neutron/X-ray tomography and 3D mesoscopic modeling.

In the last few decades, the significant advances in full-field techniques have allowed unprecedented insight into local processes. Notably, for cement-based materials, x-ray and neutron tomography lend themselves as highly complementary tools for the study of their THM behavior. In this communication, the analysis of the in-situ neutron tomography data-set has allowed for the quantification of the 4D moisture profiles thanks to a multiphase partitioning method applied at the voxel level. In addition, the analysis of the acquired simultaneous neutron/x-ray tomography of the cement paste sample (once aligned in time and across modalities) has allowed for the extraction of the extensive fracture network and for the estimate of its interplay with local drying. Finally, a CT-FE mapping scheme was proposed which consisted of extracting the mesoscale morphology of concrete (aggregates and pores) from x-ray/neutron attenuation fields and presenting it explicitly on a FE mesh. This has permitted to perform 3D multiphase THM simulation of concrete at the mesoscale.

Capillary-absorbed moisture transfer in a multiphase soil medium considering the load potential

The work presents an analytical solution to the equation of moisture permeability of structural varieties of capillary-absorbed moisture in a multiphase soil system with incomplete water saturation considering the influence of load potential. Researches were carried out and the influence of external load on the moisture profile in a multiphase system, the rate of moisture transfer of a discontinuous flow in general, and the rate of moisture propagation of the wetting boundaries have been shown. For a comparative analysis of the indicators of moisture transfer, functional relationships between the potential and pressure of the structural varieties of capillary-absorbed ground moisture are presented: capillary-gravity, proper-capillary and capillary-osmotic components of ground moisture. In the interval of incomplete water saturation, an attempt was made to create the foundations of capillary moisture transfer in the soil environment considering both the external distributed load and the own weight of the soil.

Coupled whole-tree optimality and xylem hydraulics explain dynamic biomass partitioning.

Trees partition biomass in response to resource limitation and physiological activity. It is presumed that these strategies evolved to optimize some measure of fitness. If the optimization criterion can be specified, then allometry can be modeled from first principles without prescribed parameterization. We present the Tree Hydraulics and Optimal Resource Partitioning (THORP) model, which optimizes allometry by estimating allocation fractions to organs as proportional to their ratio of marginal gain to marginal cost, where gain is net canopy photosynthesis rate, and costs are senescence rates. Root total biomass and profile shape are predicted simultaneously by a unified optimization. Optimal partitioning is solved by a numerically efficient analytical solution. THORP's predictions agree with reported tree biomass partitioning in response to size, water limitations, elevated CO2 and pruning. Roots were sensitive to soil moisture profiles and grew down to the groundwater table when present. Groundwater buffered against water stress regardless of meteorology, stabilizing allometry and root profiles as deep asc.30m. Much of plant allometry can be explained by hydraulic considerations. However, nutrient limitations cannot be fully ignored. Rooting mass and profiles were synchronized with hydrological conditions and groundwater even at considerable depths, illustrating that the below ground shapes whole-tree allometry.

Application of Spatial Time Domain Reflectometry for Investigating Moisture Content Dynamics in Unsaturated Loamy Sand for Gravitational Drainage

The strength of unsaturated soil is defined by the soil water retention behavior and soil suction acting inside the soil matrix. In order to obtain the suction and moisture profile in the vadose zone, specific measuring techniques are needed. Time domain reflectometry (TDR) conventionally measures moisture at individual points only. Therefore, spatial time domain reflectometry (spatial TDR) was developed for characterizing the moisture content profile along the unsaturated soil strata. This paper introduces an experimental set-up used for measuring dynamic moisture profiles with high spatial and temporal resolution. The moisture measurement method is based on inverse modeling the telegraph equation with a capacitance model of soil/sensor environment using an optimization technique. With the addition of point-wise soil suction measurement using tensiometers, the soil water retention curve (SWRC) can be derived in the transient flow condition instead of the static or steady-state condition usually applied for conventional testing methodologies. The experiment was successfully set up and conducted with thorough validations to demonstrate the functionalities in terms of detecting dynamic moisture profiles, dynamic soil suction, and outflow seepage flux under transient flow condition. Furthermore, some TDR measurements are presented with a discussion referring to the inverse analysis of TDR traces for extracting the dielectric properties of soil. The detected static SWRC is finally compared to the static SWRC measured by the conventional method. The preliminary outcomes underpin the success of applying the spatial TDR technique and also demonstrate several advantages of this platform for investigating the unsaturated soil seepage issue under transient flow conditions.

Study of Pumpkin Drying Through Magnetic Resonance Imaging

Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI) techniques are widely used in food science, mainly because they are non-invasive techniques. MRI, as a non-destructive technique, allows the study of intact samples and without any preparation of the samples before analysis. In food processing, the monitoring of distribution and water content is a consolidated analysis technique, frequently used on the market in order to preserve appropriate nutritional and health characteristics of food according to quality standards. In a food matrix, the variation of the water content is related to the changes in the internal structure and in the physico-chemical properties that occur during the transformation process. In this study MRI technique is used to evaluate the variation of the water content as a function of the drying time. Pumpkin samples are analyzed at four different drying temperatures of 50, 60, 65, and 70°C. The transverse relaxation time, T2, is used to assess the hydration level of the samples by comparing the information extracted from MR images with the drying kinetics measured by gravimetric method. Moreover, T2 maps are used to correlate the change in water distribution with the change in T2 values. The results show that the global weight loss curves obtained with the standard gravimetric method and with the MRI data are in excellent agreement. This work indicates that monitoring changes in the T2 profile of food (i.e., pumpkin) is a useful method for evaluating moisture profiles and changes induced on the sample during the drying process.

Comparison of Two Laboratory Methods for Measuring Soil Critical Temperature

Abstract Coupled heat and moisture transfer above a critical temperature is important in various geothermal applications (e.g., geothermal heat exchangers, buried power cables, and energy piles) because of its impact on nonsteady soil thermal properties. In this study, temperature and moisture content of seven sandy soils were measured using two laboratory approaches—vertical and radial—to evaluate the critical temperatures. The vertical approach measured temperature and moisture data from top to bottom of a soil column, and the radial method obtained the measurements from center to outside of the specimen. To validate the test results, computational modeling was also carried out in MATLAB. Although the results obtained from radial testing included rapid changes in temperature gradients near the boundaries between dry and wet zones, ambiguous temperature profiles (i.e., gradual gradients over the entire range) were observed in vertical testing possibly because of horizontal boundary heat losses. In contrast to the gradual temperature gradients, moisture content profiles showed significant variations near the transitional regime, thus the critical temperatures were determined based on both temperature and moisture profiles. Average critical temperature for seven soils was 45.8°C, and the critical temperature was dependent on the void ratio. As void ratio decreased, critical temperature increased with a corresponding decrease in the size of the dry zone. The critical temperatures obtained from radial testing were higher (up to 5.2°C higher) and took more time to reach steady-state condition (up to 9 h longer) than those obtained from vertical testing. Because there are limited data and methodology in published studies that discuss a standard methodology to measure soil critical temperature, a consistent, universally accepted, procedural-based method is needed for the measurement or determination of the critical temperature.