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•Artificial Neural Networks (ANNs) are used to predict comfort parameters.•Hourly indoor air temperature and relative humidity in building were predicted one day to one month in ...advance in hot-humid region.•ANN model performances are characterized by mean square error and the coefficient of correlation.•The experimental building is built with cement hallow block in the town of Douala-Cameroon.
The prediction of the air temperature (IT) and relative humidity (IH) in a building can help to reduce energy consumption for air conditioning. The purpose of this work was to apply the artificial neural network (ANNs) for an hourly prediction, 24–672h in advance of (IT) and (IH) in buildings found in hot-humid region. The inputs used in the model are 12 last values of indoor and outdoor air temperature and relative humidity. The experimental building is built with cement hallow block in Douala-Cameroon. IT and IH were collected for 24 months. The experimental data were used to determine the optimal ANN structure with levenberg-marquardt algorithm using Matlab software. The optimal structure was the multilayer perceptron (MLP) with 36 input variables, 10 hidden neurons and two neurons in the output layer. The activation functions were respectively the hyperbolic tangent in the hidden layer and the linear function in the output layer. Moreover, the IT and IH results simulated by using the ANN model were strongly correlated with the experimental data, with the coefficient of correlation of 0.9850 for IT and 0.9853 for IH. These results testified that ANN can be used for hourly IT and IH prediction.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Data presented on this paper are from the collection on the experimental site during a 12 months period, corresponding to the two seasons of the year. The site is located in the city of Douala in ...Cameroon, in a hot and humid zone. The experimental premises are located above the ground floor of a storey-building. They are built of 20 cm thick hollow breezeblocks with interior and exterior cement plastering, and they consist of the following: an open uninhabited room; a closed uninhabited room; and an inhabited room. The data acquisition system was achieved by the thermo-hygrometers and the anemometer placed in the rooms in accordance with the ASHRAE 55 standard 1, on instruments for measuring thermal comfort parameters in buildings. Collected data consists of the following: temperature, relative humidity and air velocity outside the site; the temperature and relative humidity inside the different rooms. These parameters are collected with a one-hour time step. The matlab software is used to calculate the maximum, minimum, average and standard deviation for each measured parameter. several areas are used for data processing: the search for causal links between the climatic parameters of the site, and those of the indoor environments of the buildings; data prediction on a one year's history basis; the impact of each experimental scenario on the thermal behaviour of the room; the assessment of the heat transfer in the room; the evaluation of the potential for energy savings in the room.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Modelling and simulation of a habitat sample lead to a model which the average resultant dry temperature is of 28.30 °C at the peak hours during the periods of occupation of the house. This result is ...within the acceptable and tolerable thermal comfort zone in humid tropical climate. It thus arises from this study, that housing with the following specifications: cement floor, wall with mixed hollow concrete block and wood plank, and roof with aluminium sheet is thermally well adapted for the Douala climate. Optimization of the thermal behaviour of this housing consists of bringing vegetation around it in order to reduce the thermal loads due to solar heat gain, improving the air replacement and taking into account the thermal inertia of its walls.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
La présente étude est consacrée à l’obtention du confort thermique dans l’habitat par une utilisation judicieuse des matériaux de construction. La particularité de cette étude est qu’elle intègre un ...volet socioculturel par la prise en compte des matériaux entrant dans les habitudes architecturales de la population en comparaison aux habitats ‘modernes’ en parpaing aggloméré creux en zone chaude. Les simulations des habitats sont effectuées avec le logiciel Pléiades+Comfie et les réponses thermiques de leurs enveloppes sont analysées. Au cours de cette simulation thermique, des comparaisons sont effectuées entre les matériaux traditionnels disponibles dans chaque zone climatique comme le bois, la brique de terre, la terre battue et les matériaux modernes, tels que le parpaing de ciment. Les résultats de ces simulations ont montré qu’en fonction des climats, le bois et la brique de terre sont meilleurs par rapport au parpaing de ciment, car l’habitat traditionnel représente parfois une réponse directe aux contraintes climatiques et est spécifique à chaque région. L’analyse des résultats montre aussi que l’on peut obtenir un bon niveau de confort thermique, avec les matériaux locaux en améliorant un choix de la forme de l’habitat, son orientation et les dimensions des ouvertures.
This work is an application of experimental temperature data previously collected in a residential building in Douala, Cameroon, in order to analyze thermal discomfort. The data was collected ...according to three occupancy scenarios over 12 month period using thermohygrometer sensors. The temperature data are analysed in comparison with the comfortable temperature range from 24°C to 28°C. The degree hour (DH) method was used to assess the severity of thermal discomfort in a hot and humid climate. The results reveal that the open C1, closed C2 and inhabited C3 rooms corresponding to scenarios C1, C2 and C3 respectively, have 7270.6°H, 9063.9°H and 10023°H. The inhabited room C3 has the largest DH and although the room C1 has the smallest DH, the latter largely exceeded the tolerable limit value of 1250°H set by the RE2020 Environmental Regulations. Results from this work can serve in building modelling for researchers and architects to act for the alleviation of thermal discomfort in regions with hot and humid climate.
The aim of this paper is to study the influence of drying temperature on the active ingredients of medicinal plants: the case of total alkaloids of Alstonia boonei Wild. Barks of Alstonia boonei, ...collected on one stem, were cut and dried in the fresh air, and in an electric dryer at 40 ° C, 50 ° C and 60 ° C. Samples from the several drying methods and others of a fresh bark were then subjected to a phytochemical analysis in order to do a quantitative and qualitative study of alkaloids contained in barks. The study revealed that the alkaloid content of the bark of Alstonia boonei decreases when the drying temperature increases. The decay rate of the extraction yield of total alkaloids compared to the samples is 0.00091% for an increase of one degree Celsius. Thus, the extraction yield of total alkaloids is 0.0436% for the fresh sample, 0.0430% for drying at open air and 0.0174% for a drying temperature at 60 ° C. Natural drying of bark at the fresh air or at room temperature limit the losses of alkaloids. PUBLICATION ABSTRACT
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper uses the central tool of an investment-savings and monetary-policy model with an augmented Philips curve and presents a few extensions of that model to analyze the multiplier effects of ...macroeconomic policies in the United States. In doing so, the authors incorporate realistic assumptions in the model related to the recent financial characteristics of the global economy. The monetary policy reaction function embeds a new augmented Taylor-rule incorporating housing and stock prices and the credit lending rate. And the household consumption and firm investment decisions incorporate housing and stock assets and the credit market frictions. The equilibrium income is derived and compared with the actual nominal gross domestic product of the United States for the period 1990 to 2009. More importantly, fiscal and trade multipliers are derived and discussed. The main finding is that government spending, tax cut, and trade multipliers are relatively smaller in size when more realistic features are incorporated in the model. The model simulation shows that the model can track actual gross domestic product reasonably well. The model should be further improved before it could be used for policy exercises.
Objectives To evaluate if subcutaneous continuous glucose monitoring (sCGM) is feasible in cardiac surgery and if reliable glucose values are reported under hypothermic extracorporeal circulation. ...Design Feasibility trial. Setting University hospital. Participants Ten consecutive patients undergoing coronary artery bypass grafting. Interventions Prior to surgery, during hypothermic extracorporeal bypass, and 48 hours postoperatively, arterial blood glucose samples were compared with sCGM every 30 minutes. Statistical analysis utilized Clarke´s error grid and Bland-Altman plot. Measurements and Main Results Three hundred fifty-one pairs of glucose measurements were recorded including 59 during hypothermic extracorporeal circulation. Agreement between these measurements was acceptable, with a regression line slope of 0.88 and an offset of 17.4 (p = 0.87). Error grid analysis indicated a safe margin of 99.1% within zone A (no clinical action needed) or zone B (values would not lead to inappropriate treatment). Only 0.9% were plotted in zone D (potentially dangerous failure). Measurements during hypothermic extracorporeal circulation were comparable. Correlation coefficient was 0.760. The offset regression line was more pronounced (50.9) with a flatter slope (0.640). Within the error grid all plot values were in zone A or B. Conclusions sCGM compared with arterial blood gas glucose monitoring under hypothermic extracorporeal circulation appears to be feasible and reliable.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Le traitement des conflits intercommunautaires ne peut plus se réduire aux seules querelles foncières, politiques et agropastorales. Au-delà de ces causes traditionnelles, il faut désormais saisir le ...rôle joué par les forces et groupes armés, ainsi que d’autres formes d’allégeances transfrontalières, dans l’incitation et l’exploitation des lignes de fractures préexistantes en leur faveur. Une perspective encore marginale au Cameroun, que cette recherche vise à explorer. Elle montre comment les conflits armés se superposent aux rivalités intercommunautaires comme une nouvelle grammaire de la conflictualité.
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