NUMERICAL INVESTIGATION OF IMPINGEMENT HEAT TRANSFER USING LINEAR AND NONLINEAR TWO-EQUATION TURBULENCE MODELS

This article concerns development of a prediction method for turbulent impingement heat transfer. An investigation of a single round unconfined impinging air jet under different flow and geometrical conditions is carried out to assess the performance of linear and nonlinear two-equation turbulence models. The results show that these models may be used for impinging jet heat transfer predictions with reasonable success, but application of an ad hoc realizability constraint is necessary to avoid overprediction of the stagnation zone heat transfer. The constitutive relationship of the nonlinear models is shown to be dominated by the linear part for the present problem. Inclusion of quadratic and cubic level strain terms does not significantly affect predictions and the coupling to streamline curvature appears weak. The major effect of using an anisotropic formulation of the turbulent heat fluxes has been shown to reduce stagnation zone heat transfer rates.     

On reaction coupled transport phenomenon in reformer ducts

In compact steam reformer the probability of component degradation and failure depends strongly on the local temperature gradients coupled by various transport processes and chemical reactions in multi-functional materials. In this paper, the modeling and analysis of coupled mass transport and heat transfer processes are conducted for compact design steam reformer duct, which consists of a porous layer for the reforming reactions of methane, the fuel gas flow duct and solid plate. A fully three-dimensional computational fluid dynamics (CFD) approach is applied to calculate transport processes and effects of thermal conductivities of the involved multi-functional materials on reforming reaction rates and heat transfer/temperature distributions, in terms of surface temperatures/heat fluxes and Nusselt numbers. The steam reformer conditions such as mass balances associated with the chemical reactions and gas permeation to/from the porous layer are implemented in the calculation. The results reveal that a small thermal conductivity of the porous layer and solid plates promote high reforming reaction rates, and the convective heat transfer at the top interface varies more significantly along the main flow reformer duct.     

The radon risk in buildings

Recent research has revealed a potential health risk from building materials and sites which have a degree of radioactivity. Radium, in the form of radon gas and of ‘radon daughters’ particles, especially when emitting gamma radiation, is the main threat. It has caused much controversy in Sweden, leading to an interim report by the Radon Commission, which is discussed here by a member of the Building Climatology and Installations Division of the National Building Research Institute of Sweden.     

Cost-efficient operation of a denitrifying activated sludge process

In this paper, the choice of optimal set-points and cost minimizing control strategies for the denitrification process in an activated sludge process are treated. In order to compare different criterion functions, simulations utilizing the COST/IWA simulation benchmark are considered. By means of operational maps the results are visualized. It is found that it is easy to distinguish set-point areas where the process can be said to be efficiently controlled in an economic sense. The characteristics of these set-point areas depend on the chosen effluent nitrate set-point as well as the distribution of the different operating costs. It is also discussed how efficient control strategies may be accomplished.     

Encapsulating Elastically Stretchable Neural Interfaces: Yield,Resolution, and Recording/Stimulation of Neural Activity

A high‐resolution elastically stretchable microelectrode array (SMEA) for interfacing with neural tissue is described. The SMEA consists of an elastomeric substrate, such as poly(dimethylsiloxane) (PDMS), elastically stretchable gold conductors, and an electrically insulating encapsulating layer in which contact holes are opened. We demonstrate the feasibility of producing contact holes with 40 μm × 40 μm openings, show why the adhesion of the encapsulation layer to the substrate is weakened during contact hole fabrication, and provide remedies. These improvements result in greatly increased fabrication yield and reproducibility. An SMEA with 28 microelectrodes was fabricated. The contact holes (100 μm × 100 μm) in the encapsulation layer are only ～10% the size of the previous generation, allowing a larger number of microelectrodes per unit area, thus affording the capability to interface with a smaller neural population per electrode. This new SMEA is used to record spontaneous and evoked activity in organotypic hippocampal tissue slices at 0% strain before stretching, at 5% and 10% equibiaxial strain, and again at 0% strain after relaxation. Stimulus–response curves at each strain level are measured. The SMEA shows excellent biocompatibility for at least two weeks.     

Role of Water Activity of Liquid in Controlling Evaporation Rate of Low-Viscosity Liquids

Viscosity of liquid is normally the most critical factor when operating an evaporator in an industrial process. This study shows that the dewatering capacity during evaporation for a low-viscosity peptone solution was reduced 40% for water activity (a _w ) = 0.8 and 80% for a _w  = 0.45. Designers of evaporators should be aware of this phenomenon if the aim is to get a high degree of dry matter concentration in the liquid.     

Targeting Signaling Pathways in Epithelial Ovarian Cancer

Ovarian carcinoma (OC) is the most lethal gynecological malignancy. Response to platinum-based chemotherapy is poor in some patients and, thus, current research is focusing on new therapy options. The various histological types of OC are characterized by distinctive molecular genetic alterations that are relevant for ovarian tumorigenesis. The understanding of these molecular pathways is essential for the development of novel therapeutic strategies.

Purpose

We want to give an overview on the molecular genetic changes of the histopathological types of OC and their role as putative therapeutic targets.

In Depth Review of Existing Data

In 2012, the vascular endothelial growth factor (VEGF) inhibitor, bevacizumab, was approved for OC treatment. Bevacizumab has shown promising results as single agent and in combination with conventional chemotherapy, but its target is not distinctive when analyzed before treatment. At present, mammalian target of rapamycin (mTOR) inhibitors, poly-ADP-ribose polymerase (PARP) inhibitors and components of the EGFR pathway are in the focus of clinical research. Interestingly, some phytochemical substances show good synergistic effects when used in combination with chemotherapy.

Conclusion

Ongoing studies of targeted agents in conjunction with chemotherapy will show whether there are alternative options to bevacizumab available for OC patients. Novel targets which can be assessed before therapy to predict efficacy are needed. The assessment of therapeutic targets is continuously improved by molecular pathological analyses on tumor tissue. A careful selection of patients for personalized treatment will help to reduce putative side effects and toxicity.     

Identification and analysis of possible splits for azeotropic mixtures. 2. Method for simple columns

A new method for the design of distillation units based on the behaviour of the mode of infinitely sharp split is presented. The method is non-iterative, fail free and fast. It can lead to the creation of more optimised process flow sheets, and can automate the design process. The first step of the method consists of fast delimitation of the product regions in the concentration simplex and the identification of the ends of the pinch branches at each section. In this way a qualitative evaluation of the arrangement of the pinch branches and the bundles of trajectories can be obtained as the bundles of trajectories depend only on the relations between the values of the coefficients of the phase equilibrium of components at certain points in the concentration simplex. This first step of the method was described in a previous article. In the present article, the second step is described, namely the identification of the possible splits in simple two-sectional columns. If some split is possible, trajectories of both sections intersect each other. The simple, necessary and sufficient condition of the separability has been established: trajectories of both sections intersect each other if pinch branches of both sections have common terminals (ending points). The check-up of this simple condition does not request the calculation of pinch branches and trajectories. The identification of the possible splits is the basis for any algorithm in the synthesis of flowsheets. An algorithm for the identification of one interactive bundle at each section among many is presented here. The interactivity of bundles depends on the location of the point of products. This information about the interactive bundles will be used for subsequent steps of designing e.g. for the calculation of minimal reflux and necessary trays for given reflux.     

An improved dynamic test method for solar collectors

A comprehensive improvement of the mathematical model for the so called transfer function method is presented in this study. This improved transfer function method can estimate the traditional solar collector parameters such as zero loss coefficient and heat loss coefficient. Two new collector parameters t and m_fC_f are obtained. t is a time scale parameter which can indicate the heat transfer ability of the solar collector. m_fC_f can be used to calculate the fluid volume content in the solar collector or to validate the regression process by comparing it to the physical fluid volume content if known. Experiments were carried out under dynamic test conditions and then test data were processed using multi-linear regression method to get collector parameters with statistic analysis. A comparison of the collector parameters obtained from the improved transfer function (ITF) method and the quasi-dynamic test (QDT) method is carried out. The results show that the improved transfer function method can accurately obtain reasonable collector parameters. The influence of different averaging time intervals is investigated. Based on the investigation it is recommended to use on line calculation if applicable for the second-order differential term with 6–9 min as the best averaging time interval. The measured and predicted collector power output of the solar collector are compared during a test of 13 days continuously both for the ITF method and the QDT method. The maximum and averaging error is 53.87 W/m² and 5.22 W/m² respectively of the ITF method while 64.13 W/m² and 6.22 W/m² of the QDT method. Scatter and relative error distribution of the measured power output versus the predicted power output is also plotted for the two methods. No matter in either error analysis or scatter distribution, the ITF method is more accurate than the QDT method in predicting the power output of a solar collector.In conclusion, all the results show that the improved transfer function method can accurately and robustly estimate solar collector parameters and predict solar collector thermal performance under dynamic test conditions.