Ham Models Research Articles

Impact of semi-empirical methods implemented in heat, air, and moisture (HAM) models on predicted wind-driven rain (WDR) loads and hygrothermal responses

The amount, duration, and intensity of wind-driven rain (WDR) are instrumental to the durability and sustainability of building components. Semi-empirical methods implemented in heat, air, and moisture (HAM) models have proved to be a practical and efficient approach to quantify WDR exposure of building components and to examine WDR's influence on hygrothermal responses of building envelopes. However, specific assumptions and simplifications in the implementations can cause discrepancies in WDR calculations and hygrothermal responses. While measured datasets or computational fluid dynamics (CFD) predictions are employed to validate WDR calculations in previous studies, few address the further influence on hygrothermal responses, particularly confronted with full-scale experimental datasets. This paper starts with a general formulation of semi-empirical methods for WDR calculation and elaborates the ASHRAE and ISO standards implemented in two representative HAM models, WUFI and DELPHIN. In the first phase of simulations, two full-scale experimental datasets at Leuven (Belgium) and Eindhoven (the Netherlands) are reproduced by the two models to compare predicted WDR loads. In the second phase, the predicted and measured WDR loads are imposed as boundary conditions of different scenarios of one benchmark case to further analyze the influence on the hygrothermal responses. The results indicate that both models roughly reproduce the semi-empirical methods. Because of disparity in algorithms and implementations and differences in weather and building conditions, the simulated WDR loads show similar trends with deviations to the measured datasets. The predicted hygrothermal responses show deviations to different extents, presumably due to disparity in WDR load predictions during certain periods.

Effect of sanitizing E-beam treatment on the binding capacity of plasma powder used to manufacture restructured dry-cured ham models

The manufacture of restructured dry-cured hams involves a contamination risk with pathogens such as Listeria monocytogenes. This work studied the effect of E-beam, as sanitizing treatment, on the binding capacity of plasma powder (PP). For that, model systems of restructured boneless dry-cured hams were manufactured by adapting the conventional processing of dry-cured hams to their reduced size. They were contaminated with L. innocua as a surrogate and treated bilaterally with 2 kGy. The PP binding properties were determined using tensile tests. The microstructure of the binding area was studied by scanning electron microscopy. The results showed that the binding force increased progressively with the processing time and was not modified by the irradiation treatment. Scanning electron microscopy of the binding area showed increasingly compact and dense structures probably related to changes in proteins structure induced by the treatment.

The development of EMPD model for identifying and predicting the materials' moisture performances

Moisture excess or lack in buildings has many adverse effects on human health, structural durability and building energy consumption, and moisture design for building materials is an important and efficient measurement for creating a stable indoor climate. However, the current quick test method (e.g., moisture buffer value test) can only evaluate the materials' moisture buffering abilities roughly, and the advanced numerical prediction method (e.g., using HAM models) is hardly applicable in practices due to insufficient materials’ hygrothermal properties and its long computing time. EMPD model can calculate with less input parameters and short time without sacrificing accuracy. While this paper found existing EMPD has limited application conditions, and further proposed modified multilayer EMPD model. A new approach can be applied to identify and predict the moisture performances of building materials. In this paper, two typical building materials with diverse hygric properties were simulated. Their key parameters of the modified model was easily inversed by a 24h standard box test instead of several months of material hygrothermal properties tests, based on which, the materials' actual performances under various conditions can be predicted. The presented approach was validated by comparing the numerical predictions with HAM results in the corresponding conditions. This study provides an easy and fast way to test and predict the moisture performances of building materials and indoor moisture in practices.

Comparative Study of Bot & Ham Models of Public Private Partnership

Comparative Study of Bot & Ham Models of Public Private Partnership

Effect of hot carcass weight on the rate of temperature decline of pork hams and loins in a blast-chilled commercial abattoir123.

Adequate carcass chilling is required to optimize pork quality and food safety. The rate at which carcasses chill is dependent on their mass. Hot carcass weight has increased steadily over the years, certainly affecting the chilling rate of the average carcass in contemporary abattoirs. Therefore, the objective was to model the effect of HCW on temperature decline of a contemporary population of pork carcasses slaughtered at a commercial abattoir that used a blast-chilling method. In addition, carcasses were sorted into HCW classes, and the effect of HCW group was tested on the rate of temperature decline of the longissimus dorsi and semimembranosus. Hot carcass weight, internal temperature of the loin muscle (at the 10th rib) and ham, as well as ambient temperature, were recorded from 40 to 1,320 min postmortem (45 time points) on 754 pork carcasses. An exponential decay model based on Newton's law of cooling, T(t)=Ta+(T0-Ta)e-kt, was fit to temperature decline of the ham and loin of the whole population using PROC MODEL of SAS. The initial models for the decline of both ham and loin temperature displayed significant autocorrelation of errors based on evaluation of the autocorrelation function plots and Durbin-Watson test (P < 0.0001). Therefore, second- and third-order autocorrelation parameters were tested. Based on Durbin-Watson test, the use of second-order autocorrelation model with lags of 1 and 2 was deemed adequate and was therefore included in all subsequent models. This base model and its respective parameter estimates were all significant (P < 0.01) for the whole population. Carcasses approximating 85, 90, 95, 100, and 105 kg (± 1 kg) were selected and binned into their respective weight classes. Dummy variables were used to compare the effect of HCW class on parameter estimate of ham and loin models. The developed model significantly fit all weight classes (P < 0.01) for both ham and loin temperature decline. For both loin and ham models, estimates of the rate constant (k) generally decreased as HCW increased. For loin temperature, k estimate for 105-kg carcasses was 0.00124 less (P = 0.02) than 85-kg carcasses, with the intermediate HCW classes not differing from the 85-kg class. For ham temperature, estimates of k for 90, 95, 100, and 105 kg HCW were all significantly and successively less than the k estimate for 85 kg class. For perspective, loins of 95-kg carcasses were estimated to reach 2 °C in 17 h, whereas loins from 105-kg carcasses would not reach 2 °C until 27 h. For hams, 95-kg carcasses were projected to reach 2 °C in 21 h, whereas those from 105-kg carcasses would take 28 h. Overall, HCW significantly affects the rate of temperature decline of pork hams, but not loins from pork carcasses weighing between 85 and 100 kg.

Effect of Hot Carcass Weight on the Rate of Temperature Decline of the Longissimus Dorsi and Semimembranosus of Pigs Slaughtered in a Blast-Chilled Commercial Abattoir

ObjectivesOver the last 30 yr, the average hot carcass weight (HCW) has consistently increased by approximately 0.5 kg per yr. This trend toward increased HCW causes engineering challenges for aging facilities designed when average HCW was 85 kg, in contrasts to today’s average HCW of 95 kg. The rate of carcass chilling is among the primary concerns. Larger carcasses have a smaller surface area to volume ratio, and almost certainly do not reach desired internal temperatures at the same rate as smaller carcasses. However, differences in rate have not been routinely reported, and to the authors’ knowledge, no such model has been reported for a large-scale, blast-chilled pork abattoir. Therefore, the objective of this study was to model the effect of HCW on temperature decline of a contemporary population of pork carcasses slaughtered at a commercial abattoir that used a blast-chilling method. Additionally, carcasses were sorted into HCW classes and the effect of HCW group was tested on the rate of temperature decline of the longissimus dorsi and semimembranosus.Materials and MethodsHot carcass weight, internal temperature of the loin muscle (at the 10th rib) and ham, as well as ambient temperature, were recorded from 40 to 1,320 min postmortem (45 time points) on 754 pork carcasses. An exponential decay model based on Newton’s Law of Cooling, was fit to temperature decline of the ham and loin of the whole population using PROC MODEL of SAS (SAS Inst. Inc., Cary, NC). The initial models for the decline of both ham and loin temperature displayed significant autocorrelation of errors based on evaluation of the autocorrelation function plots and Durbin-Watson test (P < 0.0001). Therefore, second and third order autocorrelation parameters were tested. Based on Durbin-Watson tests, the use of second order autocorrelation model with lags of 1 and 2 were deemed adequate and were therefore included in all subsequent models. This base model and its respective parameter estimates were all significant (P < 0.01) for the whole population. Carcasses approximating (± 1 kg) 85, 90, 95, 100, and 105 kg were selected and binned into their respective weight classes. Dummy variables were used to compare the effect of HCW class on parameter estimate of ham and loin models.ResultsThe developed model significantly fit all weight classes (P < 0.01) for both ham and loin temperature decline. For both loin and ham models, estimates of the rate constant (k) generally decreased as HCW increased. For loin temperature, k estimate for 105 kg carcasses was 0.00124 less (P = 0.02) than 85 kg carcasses, with the intermediate HCW classes not differing from the 85 kg class. For ham temperature, estimates of k for 90, 95, 100, and 105 kg HCW were all significantly and successively less than the k estimate for 85 kg class. For perspective, loins of 95 kg carcasses were estimated to reach 2°C in 17 h; whereas, loins from 105 kg carcasses would not reach 2°C until 27 h. For hams, 95 kg carcasses were projected to reach 2°C in 21 h; whereas, those from 105 kg carcasses would take 28 h. These estimates generally agreed with observed values.ConclusionOverall, HCW significantly affects the rate of temperature decline of pork hams, but not loins from pork carcasses weighing between 85 and 100 kg. This method of analysis can be used to model temperature decline in individual facilities.

Hygrothermal risks of using exterior air barrier systems for highly insulated light weight walls: A laboratory investigation

The current paper presents the results of a detailed laboratory experiment to study the hygrothermal behaviour of vertical light weight walls with an exterior air barrier. Four independent test walls (each 2.3 m by 0.5 m) are placed between a newly developed hot and cold box, operating at controlled temperatures, humidities and air pressures. All four walls are insulated with 30 cm of standard mineral wool to which OSB is applied as interior vapour retarder. The test walls differ from each other by the physical properties of applied exterior air barrier; airtightness, moisture buffer capacity, vapour permeability and thermal resistance. An additional objective of the current investigation is to generate validation data for numerical HAM models. As a consequence, great care was given to create precise two dimensional conditions and to minimize air leakages.The results reveal that using an exterior air barrier instead of traditional interior one, may increase the moisture load as a result of buoyancy driven convection. This leads to an increased risk for mold growth and interstitial condensation against the upper position of the exterior sheathing in winter conditions.

Memory for sentences: Implications for human associative memory

This paper critically evaluates associative theories of sentence memory, taking as its starting point the model proposed by Anderson and Bower (1973) . Two sentence-memory experiments are presented. In the first it is shown that the existing data which support Anderson and Bower's model of Human Associative Memory (a model called HAM) are not general. Then the particular HAM model is generalized and a definition of the class of HAM models is presented. The second experiment shows that no member of the HAM class of models can account for sentence-memory data. Two alternative models, both incorporating configural or Gestalt information, are then presented and are shown to fit the existing data very well. Finally, a brief discussion of the information structure of memory is given.