Estimation of Daily Global Solar Radiation with Different Sunshine-Based Models for Some Burundian Stations

Sunshine duration (S) based empirical equations have been employed in this study to estimate the daily global solar radiation on a horizontal surface (G) for six meteorological stations in Burundi. Those equations include the Ångström-Prescott linear model and four amongst its derivatives, i.e. logarithmic, exponential, power and quadratic functions. Monthly mean values of daily global solar radiation and sunshine duration data for a period of 20 to 23 years, from the Geographical Institute of Burundi (IGEBU), have been used. For any of the six stations, ten single or double linear regressions have been developed from the above-said five functions, to relate in terms of monthly mean values, the daily clearness index () to each of the next two kinds of relative sunshine duration (RSD): and . In those ratios, G0, S0 and stand for the extraterrestrial daily solar radiation on a horizontal surface, the day length and the modified day length taking into account the natural site’s horizon, respectively. According to the calculated mean values of the clearness index and the RSD, each station experiences a high number of fairly clear (or partially cloudy) days. Estimated values of the dependent variable (y) in each developed linear regression, have been compared to measured values in terms of the coefficients of correlation (R) and of determination (R2), the mean bias error (MBE), the root mean square error (RMSE) and the t-statistics. Mean values of these statistical indicators have been used to rank, according to decreasing performance level, firstly the ten developed equations per station on account of the overall six stations, secondly the six stations on account of the overall ten equations. Nevertheless, the obtained values of those indicators lay in the next ranges for all the developed sixty equations:;;;, with . These results lead to assert that any of the sixty developed linear regressions (and thus equations in terms of and ), fits very adequately measured data, and should be used to estimate monthly average daily global solar radiation with sunshine duration for the relevant station. It is also found that using as RSD, is slightly more advantageous than using for estimating the monthly average daily clearness index, . Moreover, values of statistical indicators of this study match adequately data from other works on the same kinds of empirical equations.

Experimental and analytical study on design performance of full-scale viscoelastic dampers

Viscoelastic（VE） dampers, with their stiffness and energy dissipation capabilities, have been widely used in civil engineering for mitigating wind-induced vibration and seismic responses of structures, thus enhancing the comfort of residents and serviceability of equipment inside. In past relevant research, most analytical models for characterizing the mechanical behavior of VE dampers were verified by comparing their predictions with performance test results from small-scale specimens, which might not adequately or conservatively represent the actual behavior of full-scale dampers, especially with regard to the ambient temperature, temperature rise, and heat convection effects. Thus, in this study, by using a high-performance testing facility with a temperature control system, full-scale VE dampers were dynamically tested with different displacement amplitudes, excitation frequencies, and ambient temperatures. By comparing the analytical predictions with the experimental results, it is demonstrated that adopting the fractional derivative method together with considering the effects of excitation frequencies, ambient temperatures, temperature rises, softening, and hardening, can reproduce the design performance of full-scale VE dampers very well.

Theoretical investigation of interaction between a rectangular plate and fractional viscoelastic foundation

The interaction between plates and foundations is a typical problem encountered in geotechnical engineering. The long-term plate performance is highly dependent on the theological characteristics of ground soil. Compared with conventional linear theology, the fractional calculus-based theory is a more powerful mathematical tool that can address this issue. This paper proposes a fractional Merchant model （FMM） to investigate the time-dependent behavior of a simply supported rectangular plate on viscoelastic foundation. The correspondence principle involving Laplace transforms was employed to derive the closed-form solutions of plate response under uniformly distributed load. The plate deflection, bending moment, and foundation reaction calculated using the FMM were compared with the results obtained from the analogous elastic model （EM） and the standard Merchant model （SMM）. It is shown that the upper and lower bound solutions of the FMM can be determined using the EM. In addition, a parametric study was performed to examine the influences of the model parameters on the time- dependent behavior of the plate-foundation interaction problem. The results indicate that a small fractional differential order corresponds to a plate resting on a sandy soil foundation, while the fractional differential order value should be increased for a clayey soil foundation. The long-term performance of a foundation plate can be accurately simulated by varying the values of the fractional differential order and the viscosity coefficient. The observations from this study reveal that the proposed fractional model has the capability to capture the variation of plate deflection over many decades of time.

Derivation and conformity measurement of a popular explicit analytic Borowy 2C PV module model

A popular explicit analytic Borowy 2C PV module model is proposed for power generation prediction.The maximum power point and the open-circuit point which are calculated in this model cannot be equal to the data given by manufacturers under standard test condition(STC).The derivation of this model has never been mentioned in any literatures.The parameter forms of 2C model in this paper are more simplified,and the model is decomposed into a STC sub-model and an incremental sub-model.The STC model is derived successfully from an ideal single-diode circuit model.Relative error estimations are developed to do the conformity error measurements.The analysis results showed that though the biases at those critical points are very small,the conformity will depend on both of the two ratio values I_(m)/I_(sc) and V_(m)/V_(oc),which can be used to verify whether 2C model is applicable for the PV module produced by a particular manufacturer.

CLASSICAL VERIGIN PROBLEM AS A LIMIT CASE OF VERIGIN PROBLEM WITH SURFACE TENSION AT FREE BOUNDARY

In this paper we consider Verigin problem with surfaCe tension at freeboundary:where Ω1(t),Ω2(t) are regions of water and oil respectivelyl Γt is a free boundarybetween Ω1(t) and Ω2(t).Let Ω=Ω1(t) ∪Γt∪Ω1(t) be a bounded annular domainin R2, Ω2(t) is inside. nt is a normal of Γt, Pointing inwards Ω2(t),P1 and P2 arepressures of water and oil, μ1 and μ2 are viscosities of water and oil respectively, k isthe permeability, φ is the porosity, K and Vn are the curvature and the normal velocityof Γt in the direction of nt.We prove that the classical Verigin problem is the limit case(s-0) of Veriginproblem with surfaCe tension at free boundary.

Study on the hepatocellular carcinoma model with metastasis

Hepatocellular carcinoma(HCC)is one of the most common causes of cancerrelated death around the world due to advanced clinical stage at diagnosis,high incidence of recurrence and metastasis after surgical treatment.It is in urgent need to create appropriate animal models to explore the mechanism,patterns,risk factors,and therapeutic strategies of HCC metastasis and recurrence.However,most of the established models lack the phenotype of invasion and metastasis in patient,or have unstable phenotype.To establish HCC models with stable metastasis phenotype requires profound understanding in cancer metastasis biology and scientific methodology.Over the past 3 decades,HCC models with stable metastasis have been extensively studied.This paper reviewed the history and development of HCC animal models and cell models,focusing on the screening and maintaining of metastatic potential and phenotype.In-depth studies using these models vastly promote the understanding of cellular and molecular mechanisms and development of therapeutic strategies on HCC metastasis.

Critical flow-storm approach to total maximum daily load (TMDL) development:an analytical conceptual model

One of the key challenges in the total maximum daily load(TMDL)development process is how to define the critical condition for a receiving waterbody.The main concern in using a continuous simulation approach is the absence of any guarantee that the most critical condition will be captured during the selected representative hydrologic period,given the scarcity of long-term continuous data.The objectives of this paper are to clearly address the critical condition in the TMDL development process and to compare continuous and event-based approaches in defining critical condition during TMDL development for a waterbody impacted by both point and nonpoint source pollution.A practical,event-based critical flow-storm(CFS)approach was developed to explicitly addresses the critical condition as a combination of a low stream flow and a storm event of a selected magnitude,both having certain frequencies of occurrence.This paper illustrated the CFS concept and provided its theoretical basis using a derived analytical conceptual model.The CFS approach clearly defined a critical condition,obtained reasonable results and could be considered as an alternative method in TMDL development.

Quasielastic electron scattering in a derivative coupling model with relativistic random phase approximation

We apply the derivative coupling model with ZM and ZM3 parameters to investigate the longitudinal response function in quasielastic electron scattering in the relativistic random phase approximation. The non-spectral method is chosen to describe the nucleon Green＇s function in a finite nucleus. Some remarks have been made in conclusion.