Search

Land models, which have been developed by the modeling community in the past two decades to predict future states of ecosystems and climate, have to be critically evaluated for their performance skills of simulating ecosystem responses and feedback to climate change. Benchmarking is an emerging procedure to measure and evaluate performance of models against a set of defined standards. This paper proposes a benchmarking framework for evaluation of land models. The framework includes (1) targeted aspects of model performance to be evaluated; (2) a set of benchmarks as defined references to test model performance; (3) metrics to measure and compare performance skills among models so as to identify model strengths and deficiencies; and (4) model improvement. Component 4 may or may not be involved in a benchmark analysis but is an ultimate goal of general modeling research. Land models are required to simulate exchange of water, energy, carbon and sometimes other trace gases between the atmosphere and the land-surface, and should be evaluated for their simulations of biophysical processes, biogeochemical cycles, and vegetation dynamics across timescales in response to both weather and climate change. Benchmarks that are used to evaluate models generally consist of direct observations, data-model products, and data-derived patterns and relationships. Metrics of measuring mismatches between models and benchmarks may include (1) a priori thresholds of acceptable model performance and (2) a scoring system to combine data-model mismatches for various processes at different temporal and spatial scales. The benchmark analyses should identify clues of weak model performance for future improvement. Iterations between model evaluation and improvement via benchmarking shall demonstrate progress of land modeling and help establish confidence in land models for their predictions of future states of ecosystems and climate. [ABSTRACT FROM AUTHOR]

Abstract: In the tropics, daylighting from a side window requires shading to intercept direct sunlight from the window whilst allowing penetration of daylight from sky. In this paper, daylighting from a double-pane glazed window with enclosed horizontal slats (slat window) was investigated for which it is situated on either north or south wall of a room. Full-scale experiments and simulations were conducted to characterize distribution of the interior daylight from the slat window under a real tropical climate. Performance of the slat window was evaluated in terms of the “useful daylight illuminance” (UDI), interior daylight availability and light power density (LPD) of an integrated dimmable lighting system. Empirical formulas were developed for determining annual average LPD values of the dimmable lighting system over its served area. The LPD value can be used with a reduced form of the energy equation of Thailand's building energy code to evaluate the reduced annual electrical energy consumption for accreditation of the daylight use in a building. The analysis of life cycle cost proved that the daylighting from the slat window integrated with the dimmable lighting system is cost effective. [Copyright &y& Elsevier]

Abstract: Glulam structures in service may exhibit considerable moisture induced stresses perpendicular to grain that may affect the load-bearing capacity. An option to enhance the low tensile strength of glulam perpendicular to grain is the use of self-tapping screws, which has shown promising results in constant climates. In varying climates, however, the performance of such screw reinforcements is currently not well understood. The present paper reports results of both experiments and numerical simulations investigating the effect of self-tapping screws on moisture induced stresses arising in glulam exposed to single wetting and drying climate changes. It is shown that during wetting, the screw reinforcement significantly reduces the maximum tensile stresses arising in the cross section centre. With screw distances from 70 to 210mm, stress reductions by 70–30% are achieved (compared to unreinforced glulam beams). The tensile stresses arising between the reinforcing screws depend not only on the screw distance, but also strongly on the cross section width and the annual ring pattern of the laminates. During drying, the additional restraint caused by the reinforcing screws resulted in a slight increase of the tensile stresses at the cross section border. These were, however, rather low compared to the tensile stresses arising during wetting. [Copyright &y& Elsevier]

Abstract: Many parameters have been used to evaluate the thermal performance of envelope wall/roofs, most of them for air-conditioned buildings. In this paper, the interest is focused on parameters to assess the thermal performance of envelope wall/roofs for non air-conditioned buildings. Five groups of parameters, some previously used and some newly proposed, have been analyzed. To test the evaluation parameters, numerical simulations of the periodic heat transfer through five different roof configurations have been carried out. This research shows the suitability of the energy transferred through the wall/roof during a day, the decrement factor, the discomfort degree hours, and the hot (or cold) thermal performance index to be used for thermal evaluation of wall/roofs in non air-conditioned buildings. The sensitivity of these parameters with climatic conditions and with the outdoor surface solar absorptance is analyzed. Additionally, it has been shown that the steady-state thermal transmittance, the thermal admittance modulus, the periodic thermal transmittance modulus, and the surface decrement factor, calculated with surface temperatures, are not suitable parameters to evaluate wall/roofs in non air-conditioned buildings. [Copyright &y& Elsevier]