Intensity Nonuniformity Correction for Brain MR Images with Known Voxel Classes

Intensity nonuniformity in magnetic resonance (MR) images, represented by a smooth and slowly varying function, is a typical artifact that is a nuisance for many image processing methods. To eliminate the artifact, we have to estimate the nonuniformity as a smooth and slowly varying function and factor it out from the given data. We reformulate the problem as a problem of finding a unique smooth function in a particular set of piecewise smooth functions and propose a variational method for finding it. We deliver the main idea using a simple one-dimensional example first and provide a thorough analysis of the problem in a three-phase scenario in three dimensions whose application can be found in the brain MR images. Experiments with synthetic and real MR images and a comparison with a state-of-the-art method, N3, show our algorithm???s satisfactory performance in estimating the nonuniformity with and without noise. An automated procedure is also proposed for practical use.open

Image Restoration with a New Class of Forward-Backward-Forward Diffusion Equations of Perona-Malik Type with Applications to Satellite Image Enhancement

new class of anisotropic diffusion models is proposed for image processing which can be viewed either as a novel kind of regularization of the classical Perona-Malik model or, as advocated by the authors, as a new independent model. The models are diffusive in nature and are characterized by the presence of both forward and backward regimes. In contrast to the Perona-Malik model, in the proposed model the backward regime is confined to a bounded region, and gradients are only allowed to grow up to a large but tunable size, thus effectively preventing indiscriminate singularity formation, i.e., staircasing. Extensive numerical experiments demonstrate that the method is a viable denoising/deblurring tool. The method is significantly faster than competing state-of-the-art methods and appears to be particularly effective for simultaneous denoising and deblurring. An application to satellite image enhancement is also presented.open1

Transient Simulation of Secondary Loop Mobile Air Conditioning Systems

Since the conventional refrigerant R-134a is being phased down due to its high GWP, finding a suitable replacement refrigerant with low GWP and a system design is of great importance. However, most of the alternatives are either flammable or more expensive. Therefore, to ensure the safety of passenger and reduce the refrigerant charge, a secondary loop system with coolant loop on both condenser- and evaporator-side was proposed. In the secondary loop system, the evaporator and condenser exchange heat with air through cabin cooler and radiator, respectively. The secondary loop system has more advantages than the direct expansion system such as easy applicability of heat pump operation and battery thermal management. In this study, transient models were developed for both direct expansion system and secondary loop system in Dymola. The simulation results show that the coefficient of performance of the secondary loop system is lower than that of direct expansion system due to high pressure ratio and high compressor revolution speed when two types of systems provide similar cooling capacity. Moreover, the performances of the system using R-134a, R-152a, and R-1234yf were evaluated and compared to that of conventional direct expansion system using R-134a under the US06 driving cycle condition. Though large fluctuation is observed on the condenser capacity in the direct expansion system, the evaporator capacity is very stable. In overall, R-152a has better performance than R-1234yf and is a good candidate as an alternative refrigerant but the secondary system needs more efficiency enhancement options to compete with current R-134a direct expansion system

Review of Humidity Effect on Humid Air-to-Water Condensation by a Cooling Surface for Atmospheric Water Harvesting

Many atmospheric water harvesting technologies have been produced to mitigate water scarcity as an auxiliary source of water. These technologies may be described as direct and indirect water collection techniques. The direct method is to induce a phase-change turning from vapor to liquid on a cooling surface and generate condensate without interim processes. On the other hand, the indirect method has absorption or adsorption processes to take water from humid air before producing water. This paper focuses on the direct methods and discusses the effects of humidity and surface temperature on water generation rates and condensate droplet formation patterns in a macro-and micro-view with previous experimental data. In the view of water harvesting, the generation rate of condensate showed a dependency on the temperature difference between a dew point and a surface temperature. As a result of analyzing droplet formation behaviors considering the importance of the subcooling effect in the macro-view, it was investigated that droplet formation rates and the growth regimes of the condensate also had strong relationships with the humidity of air and the surface temperature. This review would be useful for further research on the modeling of condensate droplet formation and condensation enhancement for thermally driven water generation systems

UMMS: constrained harmonic and anharmonic analyses of macromolecules based on elastic network models

UMass Morph Server (UMMS) has been developed for the broad impact on the study of molecular dynamics (MD). The elastic network model (ENM) of a given macromolecule has been proven as a useful tool for analyzing thermal behaviors locally and predicting folding pathways globally. UMMS utilizes coarse-grained ENMs at various levels. These simplifications remarkably save computation time compared with all-atom MD simulations so that one can bring down massive computational problems from a supercomputer to a PC. To improve computational efficiency and physical reality of ENMs, the symmetry-constrained, rigid-cluster, hybrid and chemical-bond ENMs have been developed and implemented at UMMS. One can request both harmonic normal mode analysis of a single macromolecule and anharmonic pathway generation between two conformations of a same molecule using elastic network interpolation at