The Role of Counties in Building a Rural Regional Innovation System

Community/Rural/Urban Development,

Continuum-based models and concepts for the transport of nanoparticles in saturated porous media: A state-of-the-science review

Environmental applications of nanoparticles (NP) increasingly result in widespread NP distribution within porous media where they are subject to various concurrent transport mechanisms including irreversible deposition, attachment/detachment (equilibrium or kinetic), agglomeration, physical straining, site-blocking, ripening, and size exclusion. Fundamental research in NP transport is typically conducted at small scale, and theoretical mechanistic modeling of particle transport in porous media faces challenges when considering the simultaneous effects of transport mechanisms. Continuum modeling approaches, in contrast, are scalable across various scales ranging from column experiments to aquifer. They have also been able to successfully describe the simultaneous occurrence of various transport mechanisms of NP in porous media such as blocking/straining or agglomeration/deposition/detachment. However, the diversity of model equations developed by different authors and the lack of effective approaches for their validation present obstacles to the successful robust application of these models for describing or predicting NP transport phenomena. This review aims to describe consistently all the important NP transport mechanisms along with their representative mathematical continuum models as found in the current scientific literature. Detailed characterizations of each transport phenomenon in regards to their manifestation in the column experiment outcomes, i.e., breakthrough curve (BTC) and residual concentration profile (RCP), are presented to facilitate future interpretations of BTCs and RCPs. The review highlights two NP transport mechanisms, agglomeration and size exclusion, which are potentially of great importance in controlling the fate and transport of NP in the subsurface media yet have been widely neglected in many existing modeling studies. A critical limitation of the continuum modeling approach is the number of parameters used upon application to larger scales and when a series of transport mechanisms are involved. We investigate the use of simplifying assumptions, such as the equilibrium assumption, in modeling the attachment/detachment mechanisms within a continuum modelling framework. While acknowledging criticisms about the use of this assumption for NP deposition on a mechanistic (process) basis, we found that its use as a description of dynamic deposition behavior in a continuum model yields broadly similar results to those arising from a kinetic model. Furthermore, we show that in two dimensional (2-D) continuum models the modeling efficiency based on the Akaike information criterion (AIC) is enhanced for equilibrium vs kinetic with no significant reduction in model performance. This is because fewer parameters are needed for the equilibrium model compared to the kinetic model. Two major transport regimes are identified in the transport of NP within porous media. The first regime is characterized by higher particle-surface attachment affinity than particle-particle attachment affinity, and operative transport mechanisms of physicochemical filtration, blocking, and physical retention. The second regime is characterized by the domination of particle-particle attachment tendency over particle-surface affinity. In this regime although physicochemical filtration as well as straining may still be operative, ripening is predominant together with agglomeration and further subsequent retention. In both regimes careful assessment of NP fate and transport is necessary since certain combinations of concurrent transport phenomena leading to large migration distances are possible in either case

Systém aktivního chlazení fotovoltaických panelů pro zvýšení jejich účinnosti

The work was divided into two main parts. The first one dealt with the analysis of the problem of influencing the performance of photovoltaic panels by active cooling. Based on the results of the analysis, an optimal system for active cooling was designed with respect to the performance enhancement but also to the damage elimination possibilities. The parameters for the implementation of the system were specified depending on the analysis performed. This analysis provided answers to the choice of the appropriate technology and to the technical design of the whole system. The second part of the work presented the actual technical solution. In the form of its design, construction, programming and testing of the resulting system

Moral reasoning and leadership style

A growing body of theory and research from the fields of leadership and cognitive moral development suggests that dimensions of leadership style and moral reasoning may be related social phenomena. Analogous paradigms appear within the literature from each field which support the proposition that personality facets may function as antecedents of certain attitudes. These attitudes can in turn serve as important predictors of behavior. This study addressed the first of the two constructions within the model, namely, the interrelationship of the personality facet of moral reasoning as assessed by the Defining Issues Test and attitudes associated with the act of leading as assessed by the Leadership Opinion Questionnaire. The sample for the study consisted of 173 graduate students in Business Administration who reported having leadership experience in formal work settings. Under investigation were the relationships among measures of moral reasoning, specifically, Principled thinking (P) and an overall developmental index (D), and two general attitudinal dimensions of leadership style, Consideration (C) and Structure (S) and/or nine theoretical aspects represented therein, including (1) Supportive, (2) Equalitarian, (3) Flexible/Receptive to Change, (4) Non-punitive, (5) System Maintaining, (6) Production Oriented, (7) Directive, (8) Flexible/Innovative, and (9) Autocratic/Punitive. Analytic techniques employed toward this end included zero order correlation, simple and multiple regression, principal component analysis, two common factor analyses and canonical correlation. Results. (1) The P score of the DIT was inversely related to the Structure dimension of leadership style across analytic methods. (2) Attempts to cross validate the relationships were unsuccessful. (3) The P score of the DIT was positively related to the Equalitarian aspect of Consideration and inversely related to Directive and Autocratic/Punitive aspects of Structure. Conclusions. The general proposition that maturity of moral thinking is related to attitudinal dimensions of leadership style among subjects with leadership experience was moderately supported. Thus, minimal progress was made toward empirical substantiation of the first construction of the paradigm linking personality facets with attitudes and attitudes with behavior

Pathogen and chemical transport in the karst limestone of the Biscayne aquifer: 3. Use of microspheres to estimate the transport potential of Cryptosporidium parvum oocysts

[1] The vulnerability of a municipal well in the Northwest well field in southeastern Florida to potential contamination by Cryptosporidium parvum oocysts was assessed in a large‐scale, forced‐gradient (convergent) injection and recovery test. The field study involved a simultaneous pulse introduction of a nonreactive tracer (SF6, an inert gas) and oocyst‐sized (1.6, 2.9, and 4.9 μ m diameter) carboxylated polystyrene microspheres into karst limestone of the Biscayne aquifer characterized by a complex triple (matrix, touching‐vug, and conduit) porosity. Fractional recoveries 97 m down gradient were inversely related to diameter and ranged from 2.9% for the 4.9 μ m microspheres to 5.8% for 1.6 μ m microspheres. Their centers of mass arrived at the pumping well approximately threefold earlier than that of the nonreactive tracer SF6 (gas), underscoring the need for use of colloid tracers and field‐scale tracer tests for these kinds of evaluations. In a modified triaxial cell using near in situ chemical conditions, 2.9 and 4.9 μ m microspheres underestimated by fourfold to sixfold the attachment potential of the less electronegative 2.9–4.1 μ m oocysts in the matrix porosity of limestone core samples. The field and laboratory results collectively suggested that it may take 200–300 m of transport to ensure even a 1‐log unit removal of oocysts, even though the limestone surfaces exhibited a substantive capability for their sorptive removal. The study further demonstrated the utility of microspheres as oocyst surrogates in field‐scale assessments of well vulnerability in limestone, provided that differences in attachment behaviors between oocysts and microspheres are taken into account

Modeling Microorganism Transport and Survival in the Subsurface

An understanding of microbial transport and survival in the subsurface is needed for public health, environmental applications, and industrial processes. Much research has therefore been directed to quantify mechanisms influencing microbial fate, and the results demonstrate a complex coupling among many physical, chemical, and biological factors. Mathematical models can be used to help understand and predict the complexities of microbial transport and survival in the subsurface under given assumptions and conditions. This review highlights existing model formulations that can be used for this purpose. In particular, we discuss models based on the advection-dispersion equation, with terms for kinetic retention to solid-water and/or air-water interfaces; blocking and ripening; release that is dependent on the resident time, diffusion, and transients in solution chemistry, water velocity, and water saturation; and microbial decay (first-order and Weibull) and growth (logistic and Monod) that is dependent on temperature, nutrient concentration, and/or microbial concentration. We highlight a two-region model to account for microbe migration in the vicinity of a solid phase and use it to simulate the coupled transport and survival of species under a variety of environmentally relevant scenarios. This review identifies challenges and limitations of models to describe and predict microbial transport and survival. In particular, many model parameters have to be optimized to simulate a diversity of observed transport, retention, and survival behavior at the laboratory scale. Improved theory and models are needed to predict the fate of microorganisms in natural subsurface systems that are highly dynamic and heterogeneous