Dynamic whole system testing of combined renewable heating systems : the current state of the art

Objective: For the evaluation of the energetic performance of combined renewable heating systems that supply space heat and domestic hot water for single family houses, dynamic behaviour, component interactions, and control of the system play a crucial role and should be included in test methods. Methods: New dynamic whole system test methods were developed based on “hardware in the loop” concepts. Three similar approaches are described and their differences are discussed. The methods were applied for testing solar thermal systems in combination with fossil fuel boilers (heating oil and natural gas), biomass boilers, and/or heat pumps. Results: All three methods were able to show the performance of combined heating systems under transient operating conditions. The methods often detected unexpected behaviour of the tested system that cannot be detected based on steady state performance tests that are usually applied to single components. Conclusion: Further work will be needed to harmonize the different test methods in order to reach comparable results between the different laboratories. Practice implications: A harmonized approach for whole system tests may lead to new test standards and improve the accuracy of performance prediction as well as reduce the need for field tests.

Kinetics of interface state-limited hole injection in alpha-naphthylphenylbiphenyl diamine (alpha-NPD) thin layers

Injection-limited operation is identified in thin-film, alpha-NPD-based diodes. A detailed model for the impedance of the injection process is provided which considers the kinetics of filling/releasing of interface states as the key factor behind the injection mechanism. The injection model is able to simultaneously account for the steady-state, current-voltage (J-V) characteristics and impedance response. and is based on the sequential injection of holes mediated by energetically distributed surface states at the metal-organic interface. The model takes into account the vacuum level offset caused by the interface dipole, along with the partial shift of the interface level distribution with bias voltage. This approach connects the low-frequency (similar to 1 Hz) capacitance spectra, which exhibits a transition between positive to negative values, to the change in the occupancy of interface states with voltage. Simulations based on the model allow to derive the density of interface states effectively intervening in the carrier injection (similar to 5 x 10(12) cm(-2)), which exhibit a Gaussian-like distribution. A kinetically determined hole barrier is calculated at levels located similar to 0.4 eV below the contact work function. (C) 2008 Elsevier B.V. All rights reserved.

Convergence towards asymptotic state in 1-D mappings: a scaling investigation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Interaction of the meso-tetrakis (4-N-methylpyridyl) porphyrin with gel and liquid state phospholipid vesicles

The interaction of the cationic meso-tetrakis 4-N-methylpyridyl porphyrin (TMPyP) with large unilamellar vesicles (LUVs) was investigated in the present study. LUVs were formed by mixtures of the zwitterionic 1,2-dipalmitoyl-sn-glycero-phosphatidylcholine (DPPC) and anionic 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) phospholipids, at different DPPG molar percentages. All investigations were carried out above (50 degrees C) and below (25 degrees C) the main phase transition temperature of the LUVs (similar to 41 degrees C). The binding constant values, K-b, estimated from the time-resolved fluorescence study, showed a significant increase of the porphyrin affinity at higher mol% DPPG. This affinity is markedly increased when the LUVs are in the liquid crystalline state. For both situations, the increase of the K-b value was also followed by a higher porphyrin fraction bound to the LUVs. The displacement of the vesicle-bound porphyrins toward the aqueous medium, upon titration with the salt potassium chloride (KCl), was also studied. Altogether, our steady-state and frequency-domain fluorescence quenching data results indicate that the TMPyP is preferentially located at the LUVs Stern layer. This is supported by the zeta potential studies, where a partial neutralization of the LUVs surface charge, upon porphyrin titration, was observed. Dynamic light scattering (DLS) results showed that, for some phospholipid systems, this partial neutralization leads to the LUVs flocculation. (C) 2012 Elsevier Inc. All rights reserved.

Impact of the Manaus urban plume on trace gas mixing ratios near the surface in the Amazon Basin: Implications for the NO-NO2-O-3 photostationary state and peroxy radical levels

We measured the mixing ratios of NO, NO2, O-3, and volatile organic carbon as well as the aerosol light-scattering coefficient on a boat platform cruising on rivers downwind of the city of Manaus (Amazonas State, Brazil) in July 2001 (Large-Scale Biosphere-Atmosphere Experiment in Amazonia-Cooperative LBA Airborne Regional Experiment-2001). The dispersion and impact of the Manaus plume was investigated by a combined analysis of ground-based (boat platform) and airborne trace gas and aerosol measurements as well as by meteorological measurements complemented by dispersion calculations (Hybrid Single-Particle Lagrangian Integrated Trajectory model). For the cases with the least anthropogenic influence (including a location in a so far unexplored region similar to 150 km west of Manaus on the Rio Manacapuru), the aerosol scattering coefficient, sigma(s), was below 11 Mm(-1), NOx mixing ratios remained below 0.6 ppb, daytime O-3 mixing ratios were mostly below 20 ppb and maximal isoprene mixing ratios were about 3 ppb in the afternoon. The photostationary state (PSS) was not established for these cases, as indicated by values of the Leighton ratio, Phi, well above unity. Due to the influence of river breeze systems and other thermally driven mesoscale circulations, a change of the synoptic wind direction from east-northeast to south-southeast in the afternoon often caused a substantial increase of ss and trace gas mixing ratios (about threefold for sigma(s), fivefold for NOx, and twofold for O-3), which was associated with the arrival of the Manaus pollution plume at the boat location. The ratio F reached unity within its uncertainty range at NOx mixing ratios of about 3 ppb, indicating "steady-state" conditions in cases when radiation variations, dry deposition, emissions, and reactions mostly involving peroxy radicals (XO2) played a minor role. The median midday/afternoon XO2 mixing ratios estimated using the PSS method range from 90 to 120 parts per trillion (ppt) for the remote cases (sigma(s) < 11 Mm(-1) and NOx < 0.6 ppb), while for the polluted cases our estimates are 15 to 60 ppt. These values are within the range of XO2 estimated by an atmospheric chemistry box model (Chemistry As A Box model Application-Module Efficiently Calculating the Chemistry of the Atmosphere (CAABA/MECCA)-3.0).

Testing the TICT State Hypothesis: an Investigation into the Solvatochromic Behavior of 2-Naphthalenylmethylene Malononitrile

Towards the goal of investigating the possible Twisted Intramolecular Charge Transfer (TICT) state mechanism of fluorescence emission, two aromatic dicyanovinyl compounds, 2-(naphthalene-2-ylmethylene) malononitrile (DCN) and a rigidified analogue, 3,4-dihydrophenanthren-1(2H)-ylidene)malononitrile (RDCN) were synthesized and their absorption and steady-state fluorescence emission spectra characterized. The spectral characterization was divided into two studies: first, DCN and RDCN were characterized in liquid solvents of increasing polarity; second, DCN and RDCN were characterized in viscous solvents and rigid glass media. The absorption spectra for both DCN and RDCN in all solvents demonstrated little to no solvatochromism. Emission results for DCN and RDCN in liquid solvents of increasing polarity showed DCN possessing strong solvatochromism while RDCN showed much less solvatochromism. Using the Lippert-Mataga equation, the difference between the ground and excited state dipole moment for DCN was estimated to be 8.4 + 0.4 Debye and between ~3.0 to 5.0 Debye for RDCN. Quantum yield measurements for DCN and RDCN in hexane, diethyl ether and acetonitrile were less than 0.01 and independent of polarity for both both solvents, with DCN generally possessing a quantum yield 3-4 times greater than RDCN. Experiments in glass media for DCN and RDCN showed a lessening of their solvatochromic character in both polar and non-polar glasses. These data provide strong evidence for a link between molecular flexibility and solvatochromism. However, while these data are consistent with a TICT state hypothesis for the emission mechanism, an alternative mechanism proposed by Maroncelli et al.10 involving rotation about the dicyanovinyl double bond in the excited state remains a possibility as well.

A Model to quantify Disease state based on the ayurvedic concept of Tridosa

The ancient Indian system of Ayurveda revolves around the concept of tridosha namely vata, pitta and kapha. The disturbance in the steady state of these three factors is said to be the starting point of the development of diseases. Even though the diseases and their associated symptoms are well- described in the medical system, no mention is directly made in the basic texts about the quantification. We offer here a specific protocol to quantify a disease in terms of ayurvedic principles

An analysis of variance type method to describe and compare steady states in clinical data

Identifying and comparing different steady states is an important task for clinical decision making. Data from unequal sources, comprising diverse patient status information, have to be interpreted. In order to compare results an expressive representation is the key. In this contribution we suggest a criterion to calculate a context-sensitive value based on variance analysis and discuss its advantages and limitations referring to a clinical data example obtained during anesthesia. Different drug plasma target levels of the anesthetic propofol were preset to reach and maintain clinically desirable steady state conditions with target controlled infusion (TCI). At the same time systolic blood pressure was monitored, depth of anesthesia was recorded using the bispectral index (BIS) and propofol plasma concentrations were determined in venous blood samples. The presented analysis of variance (ANOVA) is used to quantify how accurately steady states can be monitored and compared using the three methods of measurement.

Space-state robust control of a Buck converter with amorphous core coil and variable load

Pulse-width modulation is widely used to control electronic converters. One of the most frequently used topologies for high DC voltage/low DC voltage conversion is the Buck converter. These converters are described by a second order system with an LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core rather than an air core permits the design of smaller converters. If high switching frequencies are used to obtain high quality voltage output, then the value of the auto inductance L is reduced over time. Robust controllers are thus needed if the accuracy of the converter response must be preserved under auto inductance and payload variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a switching frequency that is not too high is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results and a comparison with a standard PID controller are also presented.

Multipartite entanglement and quantum state exchange

We investigate multipartite entanglement in relation to the process of quantum state exchange. In particular, we consider such entanglement for a certain pure state involving two groups of N trapped atoms. The state, which can be produced via quantum state exchange, is analogous to the steady-state intracavity state of the subthreshold optical nondegenerate parametric amplifier. We show that, first, it possesses some 2N-way entanglement. Second, we place a lower bound on the amount of such entanglement in the state using a measure called the entanglement of minimum bipartite entropy.

Overexpressed Ca-v beta 3 inhibits N-type (Ca(v)2.2) calcium channel currents through a hyperpolarizing shift of "ultra-slow" and "closed-state" inactivation

It has been shown that P auxiliary subunits increase current amplitude in voltage-dependent calcium channels. In this study, however, we found a hovel inhibitory effect of beta3 Subunit on macroscopic Ba2+ currents through recombinant N- and R-type calcium channels expressed in Xenopus oocytes. Overexpressed beta3 (12.5 ng/ cell cRNA) significantly suppressed N- and R-type, but not L-type, calcium channel currents at physiological holding potentials (HPs) of -60 and -80 mV At a HP of -80 mV, coinjection of various concentrations (0-12.5 ng) of the beta3 with Ca,.2.2alpha(1) and alpha(2)delta enhanced the maximum conductance of expressed channels at lower beta3 concentrations but at higher concentrations (>2.5 ng/cell) caused a marked inhibition. The beta3-induced Current suppression was reversed at a HP of - 120 mV, suggesting that the inhibition was voltage dependent. A high concentration of Ba-2divided by (40 mM) as a charge carrier also largely diminished the effect of P3 at -80 mV Therefore, experimental conditions (HP, divalent cation concentration, and P3 subunit concentration) approaching normal physiological conditions were critical to elucidate the full extent of this novel P3 effect. Steady-state inactivation curves revealed that N-type channels exhibited closed-state inactivation without P3, and that P3 caused an similar to40 mV negative shift of the inactivation, producing a second component with an inactivation midpoint of approximately -85 mV The inactivation of N-type channels in the presence of a high concentration (12.5 ng/cell) of P3 developed slowly and the time-dependent inactivation curve was best fit by the sum of two exponential functions with time constants of 14 s and 8.8 min at -80 mV Similar ultra-slow inactivation was observed for N-type channels Without P3. Thus, P3 can have a profound negative regulatory effect on N-type (and also R-type) calcium channels by Causing a hyperpolarizing shift of the inactivation without affecting ultra-slow and closed-state inactivation properties.

Entangled-state cycles from conditional quantum evolution

A system of cascaded qubits interacting via the one-way exchange of photons is studied. While for general operating conditions the system evolves to a superposition of Bell states (a dark state) in the long-time limit, under a particular resonance condition no steady state is reached within a finite time. We analyze the conditional quantum evolution (quantum trajectories) to characterize the asymptotic behavior under this resonance condition. A distinct bimodality is observed: for perfect qubit coupling, the system either evolves to a maximally entangled Bell state without emitting photons (the dark state) or executes a sustained entangled-state cycle-random switching between a pair of Bell states while emitting a continuous photon stream; for imperfect coupling, two entangled-state cycles coexist, between which a random selection is made from one quantum trajectory to another.

The steady performance of a porous and compliant aerostatic thrust bearing

Recent developments in aerostatic thrust bearings have included: (a) the porous aerostatic thrust bearing containing a porous pad and (b) the inherently compensated compliant surface aerostatic thrust bearing containing a thin elastomer layer. Both these developments have been reported to improve the bearing load capacity compared to conventional aerostatic thrust bearings with rigid surfaces. This development is carried one stage further in a porous and compliant aerostatic thrust bearing incorporating both a porous pad and an opposing compliant surface. The thin elastomer layer forming the compliant surface is bonded to a rigid backing and is of a soft rubber like material. Such a bearing is studied experimentally and theoretically under steady state operating conditions. A mathematical model is presented to predict the bearing performance. In this model is a simplified solution to the elasticity equations for deflections of the compliant surface. Account is also taken of deflections in the porous pad due to the pressure difference across its thickness. The lubrication equations for flow in the porous pad and bearing clearance are solved by numerical finite difference methods. An iteration procedure is used to couple deflections of the compliant surface and porous pad with solutions to the lubrication equations. Comparisons between experimental results and theoretically predicted bearing performance are in good agreement. However these results show that the porous and compliant aerostatic thrust bearing performance is lower than that of a porous aerostatic thrust bearing with a rigid surface in place of the compliant surface. This discovery is accounted to the recess formed in the bearing clearance by deflections of the compliant surface and its effect on flow through the porous pad.

Elevated Hypercoagulability Markers In Hemoglobin Sc Disease.

Hemoglobin SC disease is a very prevalent hemoglobinopathy, however very little is known specifically about this condition. There appears to be an increased risk of thromboembolic events in hemoglobin SC disease, but studies evaluating the hemostatic alterations are lacking. We describe a cross-sectional observational study evaluating coagulation activation markers in adult hemoglobin SC patients, in comparison with sickle cell anemia patients and healthy controls. A total of 56 hemoglobin SC and 39 sickle cell anemia patients were included in the study, all in steady state, and 27 healthy controls. None of the patients were in use of hydroxyurea. Hemoglobin SC patients presented a significantly up-regulated relative expression of tissue factor, as well as elevations in thrombin-antithrombin complex and D-dimer, in comparison to controls (p<0.01). Hemoglobin SC patients presented lower tissue factor expression, and thrombin-antithrombin complex and D-dimer levels when compared to sickle cell anemia patients (p<0.05). Endothelial activation (soluble thrombomodulin and soluble vascular cell adhesion molecule-1), and inflammation (tumor necrosis factor-alpha) markers were both significantly elevated in hemoglobin SC patients when compared to controls, being as high as the levels seen in sickle cell anemia. Overall, in hemoglobin SC patients, higher hemolytic activity and inflammation were associated with a more intense activation of coagulation, and hemostatic activation was associated with two very prevalent chronic complications seen in hemoglobin SC disease: retinopathy and osteonecrosis. In summary, our results demonstrate that hemoglobin SC patients present a hypercoagulable state, although this manifestation was not as intense as that seen in sickle cell anemia.

Key Endothelial Cell Angiogenic Mechanisms Are Stimulated By The Circulating Milieu In Sickle Cell Disease And Attenuated By Hydroxyurea.

As hypoxia-induced inflammatory angiogenesis may contribute to sickle cell disease manifestations, we compared the angiogenic molecular profiles of plasma from sickle cell disease individuals and correlated these with in vitro endothelial cell-mediated angiogenesis-stimulating activity and in vivo neovascularization. Bioplex demonstrated that plasma from steady-state sickle cell anemia patients presented elevated concentrations of pro-angiogenic factors (Angiopoietin-1, basic fibroblast growth factor, vascular endothelial growth factor, vascular endothelial growth factor-D and placental growth factor) and displayed potent pro-angiogenic activity, significantly augmenting endothelial cell proliferation, migration and capillary-like structure formation. In vivo neovascularization of Matrigel plugs was significantly greater in sickle cell disease mice, compared with non-sickle cell disease mice, consistent with an upregulation of angiogenesis in the disease. In plasma from patients with hemoglobin SC disease without proliferative retinopathy, anti-angiogenic endostatin and thrombospondin-2 were significantly elevated. In contrast, plasma from hemoglobin SC individuals with proliferative retinopathy displayed a pro-angiogenic profile and had more significant effects on endothelial cell proliferation and capillary formation than plasma of patients without retinopathy. Hydroxyurea therapy was associated with significant reductions in plasma angiogenic factor profile, in association with an inhibition of endothelial cell-mediated angiogenic mechanisms and neovascularization. Thus, sickle cell anemia and retinopathic hemoglobin SC individuals present a highly angiogenic circulating milieu, capable of stimulating key endothelial cell-mediated angiogenic mechanisms. Combination anti-angiogenic therapy for preventing progression of unregulated neovascularization and associated manifestations in sickle cell disease, such as pulmonary hypertension, may be indicated; furthermore, the benefits and drawbacks of the potent anti-angiogenic effects of hydroxyurea should be clarified.