2,110 research outputs found
Operational performance assessment of decentralised energy and district heating systems
District heating systems can contribute to reducing the UK’s CO2 emissions. This thesis
investigates the operational performance of current district heating (DH) systems with the
existing and a possible future energy sector. The main contributions to knowledge are:
Operational, financial and exergy performance assessments of three functioning
DH systems and one decentralised energy (DE) technology
A methodology to optimise a DH system in a resource efficient and cost effective
way
The aims of DH systems are to provide heat, reduce CO2 emissions, ensure energy security by
operating in a resource efficient way and to tackle fuel poverty. However, the case studies in
this project confirm that DH systems operate poorly in the UK. This is largely because of the
heat losses from the DH network to the soil being high and the plant operation being
suboptimal.
Four case studies were analysed. The 785 room Strand Palace hotel has two 250 kWe
combined heat and power (CHP) engines set to modulate following the hotel’s electricity
consumption and providing approximately 90% of this annual demand. It was found that the
CHP engines never operate at full load throughout a full day, firstly because the plant cannot
export electricity to the grid and secondly the system is not fitted with a thermal store.
Financial analysis revealed that the hotel does not reduce its heating cost by operating the
CHP engines, but that the energy service company (ESCo) makes £77,000 net operating
income per year. Elmswell in Suffolk (UK) is a low heat density DH system that generates heat with a 2008
biomass boiler and pumps it to 26 terraced and semi-detached dwellings. It was found that
39% of its heat is lost to the soil and that the natural gas boiler generates 45% of the heating
load and operates with a seasonal efficiency of 65%. The heat losses to the soil for this system
were compared to a DH system of higher heat density, Loughborough University, with a
lower heat loss of 22% to the soil.
In August 2011, Loughborough University installed a 1.6 MWe CHP engine to operate with
four 3 MWth natural gas boilers to supply heat to its DH network. A study undertaken
demonstrated that by adding a 2 MWe CHP engine with a thermal storage instead of a 1.6
MWe CHP engine on its own could further increase the CO2 emissions savings from 8% to
12.4%.
The energy centre at Pimlico District Heating Undertaking (PDHU) includes a gas fired
cogeneration plant that supplies heat to 3 schools, 3,256 dwellings and 55 commercial units. It
also benefits from a 2,500 m3
thermal store. Every component of PDHU was investigated in
detail and its current operation was optimised and compared to a selection of new operating
scenarios. It was found that:
i) The thermal store operated with 93% thermal efficiency and was not used to
reduce the energy consumption or to enable more cogeneration,
ii) The CHP engines were undersized and generated only 18% of the required heat in
2012, iii) The boilers modulate and £ 70,000 could be saved per year by setting them to
operate at full load by making use of the thermal store,
iv) By installing an open-loop heat pump using the river Thames, PDHU could then
guarantee to comply with current and likely future policies impacts by setting the
energy plant to operate in CHP mode or as an electricity consumer at defined times
to benefit from low energy utility costs and to minimise CO2 emissions.
A comparison of selected performance metrics was then undertaken and it was found that
none of the three DH systems operate in a resource efficient way and that the heating cost
could be reduced further by optimising the operation of the systems. To do this, a new
optimisation methodology is proposed by maximising their exergy efficiency in addition to
maximising their overall energy efficiency and CO2 emissions reduction
Endocrinology: Clinical significance of invisible or partially visible luteinizing hormone
It is well known that luteinizing hormone (LH), like many other glycoproteins, is heterogeneous and presents several circulating isoforms. Recently, new sensitive immunometric assays measuring intact LH were developed. These assays have been found to underestimate or to be incapable of recognizing LH in some patients. This study was undertaken to determine the prevalence of such cases and to define their clinical characteristics. We compared three LH assays using as capture antibodies either a monoclonal antibody that reacts exclusively with intact LH (ES 600 Boehringer, Stratus Baxter) or a monoclonal antibody against the β subunit of LH (IMX Abbott). In 17% of 90 patients tested, ES 600 measured > 50% lower LH concentrations when compared with the EVIX. Moreover, in two cases LH was not detectable by ES 600 or Stratus, whereas it was normal with the EVIX. We found another five such cases and discuss here the clinical data and results of different hormone measurements in these seven cases of ‘invisible LH'. Although bioactive LH (mouse Leydig cell assay) was normal, the existence of low or even undetectable LH was clinically confusing and led to expensive complementary investigations such as gonadotrophin-releasing hormone analogue tests and magnetic resonance imaging. The uses and limitations of these assays are illustrated by different clinical situations in which the results of the different assays have been misleadin
A systematic review of infliximab in the treatment of early rheumatoid arthritis
Sophie Martin Du Pan, Cem Gabay, Axel FinckhDivision of Rheumatology, Department of Internal Medicine, University of GenevaBackground: Several health authorities have recently revised the indication of infliximab (IFX) to include the treatment of early rheumatoid arthritis (RA). The aim of this systematic review of the literature was to appraise the efficacy, safety, and cost-effectiveness of early therapy with IFX.Methods: We identified published clinical trials from 1966 to May 2006. We included randomized clinical trials (RCTs) in RA with disease duration of less than 3 years comparing the treatment of methotrexate-IFX (MTX-IFX) with methotrexate-placebo (MTX-placebo).Results: A total of 8 studies met inclusion criteria. Three studies reported redundant data regarding the vdH Sharp Score. Out of the 5 remaining studies, 4 analyzed structural joint destruction (vdH Sharp Score) and demonstrated a significant reduction in radiographic damage progression in favor of the combination of MTX-IFX compared with MTX-placebo (–4.1 vdH Sharp Score units (95% CI: 3.5; 4.6). Three studies also displayed a benefit of MTX-IFX on functional outcomes of RA (HAQ score) and disease activity measures (DAS, ACR response criteria), although less markedly.Conclusions: Although data might be skewed because of only 2 existing large studies with concordant data, results from RCTs demonstrate improved efficacy of the combination MTXIFX compared with MTX-placebo in early RA. However, many early RA patients probably do not require the addition of IFX to achieve a satisfying clinical and radiological course. So far, no evidence has established the superiority of MTX-IFX over MTX-prednisone or other combinations of traditional disease-modifying anti-rheumatic agents.Keywords: rheumatoid arthritis, antirheumatic agents, inflixima
Protection of Nonimmune Volunteers against Rubella by Intravenous Administration of Normal Human Gamma Globulin
Standard gamma globulin, treated with pepsin and injected intravenously five days after infection, conferred passive protection against rubella on five volunteers. Intravenous injection of gamma globulin is superior to intramuscular injection, because the antibodies enter the bloodstream immediately, and an amount of antibody sufficient for protection can be given. Injection of standard gamma globulin is recommended when gamma globulin hyperimmune to rubella virus is unavailabl
Finite Temperature Density Instability at High Landau Level Occupancy
We study here the onset of charge density wave instabilities in quantum Hall
systems at finite temperature for Landau level filling . Specific
emphasis is placed on the role of disorder as well as an in-plane magnetic
field. Beyond some critical value, disorder is observed to suppress the charge
density wave melting temperature to zero. In addition, we find that a
transition from perpendicular to parallel stripes (relative to the in-plane
magnetic field) exists when the electron gas thickness exceeds \AA.
The perpendicular alignment of the stripes is in agreement with the
experimental finding that the easy conduction direction is perpendicular to the
in-plane field.Comment: 4 pages, 2 eps figures. We show explicitly that a transition from
perpendicular to parallel stripes (relative to the in-plane magnetic field)
exists when the electron gas thickness exceeds \AA. The
perpendicular alignment of the stripes is in agreement with the experimental
finding that the easy conduction direction is perpendicular to the in-plane
fiel
Quantum magneto-oscillations in a two-dimensional Fermi liquid
Quantum magneto-oscillations provide a powerfull tool for quantifying
Fermi-liquid parameters of metals. In particular, the quasiparticle effective
mass and spin susceptibility are extracted from the experiment using the
Lifshitz-Kosevich formula, derived under the assumption that the properties of
the system in a non-zero magnetic field are determined uniquely by the
zero-field Fermi-liquid state. This assumption is valid in 3D but, generally
speaking, erroneous in 2D where the Lifshitz-Kosevich formula may be applied
only if the oscillations are strongly damped by thermal smearing and disorder.
In this work, the effects of interactions and disorder on the amplitude of
magneto-oscillations in 2D are studied. It is found that the effective mass
diverges logarithmically with decreasing temperature signaling a deviation from
the Fermi-liquid behavior. It is also shown that the quasiparticle lifetime due
to inelastic interactions does not enter the oscillation amplitude, although
these interactions do renormalize the effective mass. This result provides a
generalization of the Fowler-Prange theorem formulated originally for the
electron-phonon interaction.Comment: 4 pages, 1 figur
Models of turbulent dissipation regions in the diffuse interstellar medium
Supersonic turbulence is a large reservoir of suprathermal energy in the
interstellar medium. Its dissipation, because it is intermittent in space and
time, can deeply modify the chemistry of the gas. We further explore a hybrid
method to compute the chemical and thermal evolution of a magnetized
dissipative structure, under the energetic constraints provided by the observed
properties of turbulence in the cold neutral medium. For the first time, we
model a random line of sight by taking into account the relative duration of
the bursts with respect to the thermal and chemical relaxation timescales of
the gas. The key parameter is the turbulent rate of strain "a" due to the
ambient turbulence. With the gas density, it controls the size of the
dissipative structures, therefore the strength of the burst. For a large range
of rates of strain and densities, the models of turbulent dissipation regions
(TDR) reproduce the CH+ column densities observed in the diffuse medium and
their correlation with highly excited H2. They do so without producing an
excess of CH. As a natural consequence, they reproduce the abundance ratios of
HCO+/OH and HCO+/H2O, and their dynamic range of about one order of magnitude
observed in diffuse gas. Large C2H and CO abundances, also related to those of
HCO+, are another outcome of the TDR models that compare well with observed
values. The abundances and column densities computed for CN, HCN and HNC are
one order of magnitude above PDR model predictions, although still
significantly smaller than observed values
Modelling percolation in fibre and sphere mixtures: Routes to more efficient network formation
Fingerprint-based Wi-Fi indoor localization using map and inertial sensors
It is a common understanding that the localization accuracy can be improved by indoor maps and inertial sensors. However, there is a lack of concrete and generic solutions that combine these two features together and practically demonstrate its validity. This article aims to provide such a solution based on the mainstream fingerprint-based indoor localization approach. First, we introduce the theorem called reference points placement, which gives a theoretical guide to place reference points. Second, we design a Wi-Fi signal propagation-based cluster algorithm to reduce the amount of computation. The paper gives a parameter called reliability to overcome the skewing of inertial sensors. Then we also present Kalman filter and Markov chain to predict the system status. The system is able to provide high-accuracy real-time tracking by integrating indoor map and inertial sensors with Wi-Fi signal strength. Finally, the proposed work is evaluated and compared with the previous Wi-Fi indoor localization systems. In addition, the effect of inertial sensors’ reliability is also discussed. Results are drawn from a campus office building which is about 80 m×140 m with 57 access points
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