Quasi-steady State Methods Research Articles

Experimental analysis of indoor temperature of residential buildings as an input for building simulation tools

The Energy Performance of Buildings Directive (EPBD) requires Member States to assess the energy use of buildings. However, the results heavily depend on the correct implementation of building properties and boundary conditions. This paper challenges the average indoor temperature assumed in Quasi Steady State methods and proposes a temperature profile to improve the accuracy of the simulation. This temperature profile is derived from in-situ measurements of the indoor temperature in nine terraced houses and is characterised by the energy performance of the building, the outdoor climate and the user behaviour. Applying this new temperature profile in the energy simulation model decreases the energy performance gap between simulated and actual energy use.

Application of quasi-steady state methods to molecular motor transport on microtubules in fungal hyphae

We consider bidirectional transport of cargo by molecular motors dynein and kinesin that walk along microtubules, and/or diffuse in the cell. The motors compete to transport cargo in opposite directions with respect to microtubule polarity (towards the plus or minus end of the microtubule). In recent work, Gou et al. (2014) used a hierarchical set of models, each consisting of continuum transport equations to track the evolution of motors and their cargo (early endosomes) in the specific case of the fungus Ustilago maydis. We complement their work using a framework of quasi-steady state analysis developed by Newby and Bressloff (2010) and Bressloff and Newby (2013) to reduce the models to an approximating steady state Fokker–Plank equation. This analysis allows us to find analytic approximations to the steady state solutions in many cases where the full models are not easily solved. Consequently, we can make predictions about parameter dependence of the resulting spatial distributions. We also characterize the overall rates of bulk transport and diffusion, and how these are related to state transition parameters, motor speeds, microtubule polarity distribution, and specific assumptions made.

Explicit integration of extremely stiff reaction networks: quasi-steady-state methods

A preceding paper demonstrated that explicit asymptotic methods generally work much better for extremely stiff reaction networks than has previously been shown in the literature. There we showed that for systems well removed from equilibrium explicit asymptotic methods can rival standard implicit codes in speed and accuracy for solving extremely stiff differential equations. In this paper we continue the investigation of systems well removed from equilibrium by examining quasi-steady-state (QSS) methods as an alternative to asymptotic methods. We show that for systems well removed from equilibrium, QSS methods also can compete with, or even exceed, standard implicit methods in speed, even for extremely stiff networks, and in many cases give somewhat better integration speed than for asymptotic methods. As for asymptotic methods, we will find that QSS methods give correct results, but with non-competitive integration speed as equilibrium is approached. Thus, we shall find that both asymptotic and QSS methods must be supplemented with partial equilibrium methods as equilibrium is approached to remain competitive with implicit methods.

Research on Security Assessment Index System for Operating Reserve in Large Interconnected Power Grid

Optimization and placement of spinning reserve is an important issue in power system planning and operation. Systematic way for security assessment of operating reserve needs to study. A security assessment index system for operating reserve in large interconnected power grids is presented in this paper. Firstly, classification and determination methods of operating reserve at home and abroad are investigated, and operating reserve is divided into transient state operating reserve and quasi-steady state operating reserve from the view of security assessment. Secondly, assessment indexes and optimization methods for transient state operating reserve are studied. Thirdly, optimization model, deterministic and probabilistic optimization methods for quasi-steady state operating reserve are explored. Finally, some principles for determination of operating reserve are suggested, and a security assessment index system is put forward. The proposed index system, considering both transient and quasi-steady state, both deterministic and probabilistic methods, provides a systematic way to assessment and arrangement of operating reserve.

Silicon solar cell under electromagnetic wave in steady state: effect of the telecommunication source's power of radiation

The characterisation of minority carriers' recombination parameters is important to design any optoelectronic component, since they play an important role in the device performance. Many diagnostic techniques, steady state, quasi-steady state, transient and modulation methods for both the experimental and theoretical measurement have been developed for the determination of single or several recombination parameters. Many studies on recombination and electrical parameters of solar cells under constant magnetic field and / or electric field in the bulk due to carrier concentration have been proposed with one or three dimensional approach. In previous works, we study the effects of electromagnetic waves on silicon solar cell recombination parameters by changing the distance between the 2 MW power of radiation AM antenna and the solar cell. This work presents a one dimensional study of the influence of telecommunication source's power of radiation on a silicon solar cell illuminated by a white light in steady state. The telecommunication sources which can be an AM radio antenna or a FM radio antenna radiate electromagnetic waves. Electric field intensity depends on the power of radiation and the distance between the electric field intensity measurement point and the antenna. The magneto transport equations of excess minority carriers are solved with new boundary conditions. New analytical expressions of minority carriers' density, photo-current density, back surface recombination velocity, intrinsic junction recombination velocity and photo voltage depending on electromagnetic field intensity are established. The effects of electromagnetic field on photo-current density, back surface recombination velocity, intrinsic junction recombination velocity and photo- voltage by making vary the antenna power of radiation are then analysed. We analyze also the effects of electromagnetic field on the electric power delivered by the solar cell to an external charge. Thus, using the maximum of electric power delivered by the solar cell to an external charge, we deduce the solar cell conversion efficiency. The analysis of electromagnetic field effects on the silicon solar cell put out the influence of AM radio antenna or FM radio antenna on recombination parameters.

On the evaluation of diffusivities in gels using the diffusion cell technique

Modeling of the gel-immobilized cell system requires accurate measurement of diffusion coefficients. Three methods of the quasi-steady-state (QSS) method, the time-lag (TL) method and a variant quasi-steady-state (VQSS) method were critically assessed and compared for the evaluation of diffusivities using the diffusion cell technique. Experimental data from our laboratory were used for the analysis of the influence of crucial theoretical assumptions not being fulfilled in each method. The results highlighted a risk in obtaining highly variable diffusion coefficients by not validating the QSS and the accuracy of the measurements. In the TL method, the estimation of diffusivities based on the plot intercept that was mostly used in the literature, results in a many fold lower value when compared to that based on the plot slope. The comparison with the QSS and VQSS methods confirmed similar diffusivity obtained by the TL method based on the plot slope. It thus suggested that the correct estimation of diffusivities by the TL method could be based on the plot slope only. Furthermore, the errors associated with the solute mass in the gel, the sample withdrawal and the non-negligible concentration changes in the chambers were also discussed. It is concluded that diffusion cell technique has to be employed cautiously for a correct evaluation of diffusivities.

Anodic oxidation of hydrazine and its derivatives: Part IV. The oxidation of methylhydrazine (MH) on gold electrodes in acid solution

The electrooxidation of methylhydrazine on a gold electrode in H 2 SO 4 has been studied. Linear sweep, steady state and quasi steady-state methods were used to evaluate the various parameters for the oxidation process and a mechanism is proposed. It involves two fast de-electronation reactions and the rate-determining step is an activated desorption step.

Anodic oxidation of hydrazine and its derivatives Part IV. The oxidation of methylhydrazine (MH) on gold electrodes in acid solution

The electrooxidation of methylhydrazine on a gold electrode in H2SO4 has been studied. Linear sweep, steady state and quasi steady-state methods were used to evaluate the various parameters for the oxidation process and a mechanism is proposed. It involves two fast de-electronation reactions and the rate-determining step is an activated desorption step.

Use of Transient Excitation in the Dynamic Analysis of Structures

In recent years many methods have been proposed for the measurement of the frequency response of linear systems but the method most often used in the study of structures is the steady state vector response method, the natural frequencies and damping ratios being measured from the resulting vector diagrams. This method is tedious and time consuming and often cannot be readily applied outside the laboratory. Some effort has been directed in the past to employ quasi-steady state methods such as the slow frequency sweep technique but errors are introduced because the response at resonance is less than the steady state maximum and the frequency at which the maximum occurs is shifted in the direction in which the excitation frequency is changing. Additional errors are introduced in the analysis of the system response because of the necessary averaging time of the function analyser used to derive the vector diagrams. Some refinements in technique have been proposed by Reed who developed the “λ Law” frequency sweep in which the percentage change in frequency per cycle is constant. This offers some reduction in test time when compared with logarithmic and linear frequency sweeps but a knowledge of the minimum damping likely to be encountered at any resonant frequency within the sweep range is essential so that the method may be employed advantageously.