Development of novel methodologies for utilising low-cost sensors for ambient Particulate Matter measurement

There is increasing concern about the impact of ambient Particulate Matter (PM) exposure on human health. Existing ambient air quality monitoring networks, because of their sparseness, are not able to capture the spatial-temporal variation of ambient PM concentration. Recent studies have shown that although low-cost PM monitors, such as Optical Particles Counters (OPCs), can be utilised for both personal exposure and high-density sensor network applications, these sensors can be subject to several limitations such as relative humidity (RH) interferences, the inability to measure smaller (e.g. ultrafine) particles and the assumption made about the constant aerosol density value used in the conversion from number concentration to mass concentration. Water can condense on aerosol particles resulting, if uncorrected for, in particle size growth and thus overestimation of the measured PM concentration in a manner which depends on both RH and the chemical composition of particles. In contrast, failing to account for particles below the sensors’ size detection limit leads to potentially large underestimations of PM concentrations. To account for changes in the aerosol density values assumed by OPCs, the PM readings calculated from the particle size and concentration measurements require the application of an additional, often empirical, factor. Not accounting for this factor, results in a poor agreement between PM measurements from an OPC and a reference gravimetric instrument. To address these issues, this work describes the development, application and assessment of a three-stage correction process which allows low-cost sensors to provide quantitative PM measurements. The first step is to account for the particle hygroscopic growth under high RH conditions. This led to the development of two correction methodologies: 1) a particle size distribution correction algorithm (based on κ-Köhler theory) which corrects for the particle hygroscopic growth after the measurements, and 2) a prototype particle drying system (consisting of a heated inlet) which dries the particles before measuring their size. Results from field studies across winter and summer are presented to show the feasibility and accuracy of the two methodologies. The application of the correction algorithm resulted in a significant improvement in the determination of the correct particle size and concentration, with the overestimation of PM measurements (calculated in the size range of the low-cost sensor) reduced from a factor of 4.60±0.10 to 1.00±0.10. Similarly, the implementation of the particle drying system provided comparable results with the overestimation of PM measurements reduced from a factor of 1.90±0.20 to 0.90±0.10. However, the performance of the correction algorithm is dependent on the correct assumption of the particle chemical composition as opposed to the application of a heated tube on the sensor inlet which ensures drying of the particles. The second step is to estimate and include the contribution of particles below the low-cost sensor size detection limit in the calculation of PM concentrations. An algorithm to determine the concentration of particles below 300 nm diameter based on the particle size distribution of reference measurements between the low-cost sensor and the reference instrument size detection limits was developed. The application of the estimation algorithm resulted in a reduction for the underestimation of the total PM concentrations from a factor of 0.40±0.10 to a factor of 1.10±0.10. Finally, optical reference instruments try to exploit a semi-empirical correction factor to scale the calculated PM values to match the reference gravimetric methods measurements. This work investigated the possibility of applying a similar correction factor to low-cost sensor measurements. It was shown that, by exploiting the ratio between PM2.5 and PM1 measurements, an equivalent correction factor for low-cost sensors can be derived, thus enabling the Alphasense OPC-N2 PM measurement to be accurate within 25% relative to the certified reference equivalent data. This work shows that, when appropriate corrections are applied, portable low-cost sensor can provide PM measurements which are comparable with readings from reference standard instruments. Finally, a conceptual design to exploit the dependence of PM on RH for chemical composition derivation is also included. Even though the sensor used in this work is the Alphasense OPC-N2, the presented methodologies are generally applicable to all OPC-based PM sensors.Thanks to Alphasense Ltd. for fully funding my PhD programme

On quantum and relativistic mechanical analogues in mean field spin models

Conceptual analogies among statistical mechanics and classical (or quantum) mechanics often appeared in the literature. For classical two-body mean field models, an analogy develops into a proper identification between the free energy of Curie-Weiss type magnetic models and the Hamilton-Jacobi action for a one dimensional mechanical system. Similarly, the partition function plays the role of the wave function in quantum mechanics and satisfies the heat equation that plays, in this context, the role of the Schrodinger equation in quantum mechanics. We show that this identification can be remarkably extended to include a wide family of magnetic models classified by normal forms of suitable real algebraic dispersion curves. In all these cases, the model turns out to be completely solvable as the free energy as well as the order parameter are obtained as solutions of an integrable nonlinear PDE of Hamilton-Jacobi type. We observe that the mechanical analog of these models can be viewed as the relativistic analog of the Curie-Weiss model and this helps to clarify the connection between generalised self-averaging and in statistical thermodynamics and the semi-classical dynamics of viscous conservation laws.Comment: Dedicated to Sandro Graffi in honor of his seventieth birthda

Riemannian geometry of Hartogs domains

Let D_F = \{(z_0, z) \in {\C}^{n} | |z_0|^2 < b, \|z\|^2 < F(|z_0|^2) \} be a strongly pseudoconvex Hartogs domain endowed with the \K metric $g_F$ associated to the \K form $\omega_F = -\frac{i}{2} \partial \bar{\partial} \log (F(|z_0|^2) - \|z\|^2)$. This paper contains several results on the Riemannian geometry of these domains. In the first one we prove that if $D_F$ admits a non special geodesic (see definition below) through the origin whose trace is a straight line then $D_F$ is holomorphically isometric to an open subset of the complex hyperbolic space. In the second theorem we prove that all the geodesics through the origin of $D_F$ do not self-intersect, we find necessary and sufficient conditions on $F$ for $D_F$ to be geodesically complete and we prove that $D_F$ is locally irreducible as a Riemannian manifold. Finally, we compare the Bergman metric $g_B$ and the metric $g_F$ in a bounded Hartogs domain and we prove that if $g_B$ is a multiple of $g_F$, namely $g_B=\lambda g_F$, for some $\lambda\in \R^+$, then $D_F$ is holomorphically isometric to an open subset of the complex hyperbolic space.Comment: to appear in International Journal of Mathematic

Microprocessor fault-tolerance via on-the-fly partial reconfiguration

This paper presents a novel approach to exploit FPGA dynamic partial reconfiguration to improve the fault tolerance of complex microprocessor-based systems, with no need to statically reserve area to host redundant components. The proposed method not only improves the survivability of the system by allowing the online replacement of defective key parts of the processor, but also provides performance graceful degradation by executing in software the tasks that were executed in hardware before a fault and the subsequent reconfiguration happened. The advantage of the proposed approach is that thanks to a hardware hypervisor, the CPU is totally unaware of the reconfiguration happening in real-time, and there's no dependency on the CPU to perform it. As proof of concept a design using this idea has been developed, using the LEON3 open-source processor, synthesized on a Virtex 4 FPG

Performance analysis of a common-rail Diesel engine fuelled with different blends of waste cooking oil and gasoil

An experimental campaign was performed to study the behavior of a common-rail Diesel engine in automotive configuration when it is fuelled with blends of Diesel fuel (DF) and waste cooking oil (WCO). In particular the tested fuels are: B20 blend, composed of 20% WCO and 80% DF; B50, composed of 50% WCO and 50% DF; WCO 100% and 100% DF. In order to fuel the engine with fuel having a similar viscosity, this quantity, together with density, has been meas-ured at temperature ranging from rom to about 80 °C. According to these measurements, before fuelling the engine B20 was heated up to 35 °C and B50 to 75 °C. An in-house software was developed to acquire the data elaborated by the electronic control unit. Results show the trend in torque and global efficiency at different gas pedal position (gpp) and different engine speed. The experiments show that larger discrepancies are measured at smaller gpp values, while at larger ones dif-ferences become smaller. A similar trend is noticed for engine global efficiency

The bisymplectomorphism group of a bounded symmetric domain

An Hermitian bounded symmetric domain in a complex vector space, given in its circled realization, is endowed with two natural symplectic forms: the flat form and the hyperbolic form. In a similar way, the ambient vector space is also endowed with two natural symplectic forms: the Fubini-Study form and the flat form. It has been shown in arXiv:math.DG/0603141 that there exists a diffeomorphism from the domain to the ambient vector space which puts in correspondence the above pair of forms. This phenomenon is called symplectic duality for Hermitian non compact symmetric spaces. In this article, we first give a different and simpler proof of this fact. Then, in order to measure the non uniqueness of this symplectic duality map, we determine the group of bisymplectomorphisms of a bounded symmetric domain, that is, the group of diffeomorphisms which preserve simultaneously the hyperbolic and the flat symplectic form. This group is the direct product of the compact Lie group of linear automorphisms with an infinite-dimensional Abelian group. This result appears as a kind of Schwarz lemma.Comment: 19 pages. Version 2: minor correction

Thermo-economic assessment of a olive pomace gasifier for cogeneration applications

A thermo-economic analysis of a combined heat and power (CHP) plant fed by syngas produced through the gasification of dry olive pomace is presented. The plant is composed by a 800 kWtdowndraft gasifier, a gas clean-up system, a 200 kWemicroturbine (MGT) and a heat recovery system to cogenerate hot water. Surplus heat is used to dry olive pomace from 50% to 17% wb moisture content. The plant is modeled in ASPEN Plus. Real data from experimental tests are used to calibrate the gasifier model, while the technical specification and performance of the CHP plant are collected from commercial plants in operation and data from manufacturers. Mass and energy balances are reported throughout the paper. The thermodynamic simulation of the biomass gasifier coupled to the MGT, the thermal and electrical conversion efficiency and temperature of cogenerated heat available are also presented. A thermo-economic assessment is then proposed, to investigate the economic profitability of this small scale CHP plant in the Italian energy policy scenario and considering the subsidies available for renewable electricity in the form of feed-in tariffs. For this purpose, the case study of base load CHP plant operation and heat supplied to different typologies of energy end user is assumed. The results allow quantifying the most influencing economic and technical factors that affect the performance and profitability of such investment and the bottlenecks that should be faced to facilitate a broader implementation of such CHP schemes for on site generation

Basic fibroblast growth factor mediates carotid plaque instability through metalloproteinase-2 and –9 expression

OBJECTIVE(S): We hypothesized that basic fibroblast growth factor (bFGF) may exert a role in carotid plaque instability by regulating the expression of matrix metalloproteinases (MMP). METHODS: Plaques obtained from 40 consecutive patients undergoing carotid endarterectomy were preoperatively classified as soft or hard. Serum bFGF was pre- and postoperatively measured. The release of MMP-2 and MMP-9 in the blood serum, and the activity, production and expression in the carotid specimens was analyzed. Specific anti-bFGF inhibition tests were performed in vitro on human umbilical artery smooth muscle cells (HUASMC) to evaluate the role of bFGF in the activity, production and expression of MMP-2 and -9. RESULTS: Twenty-one (53%) patients had a soft carotid plaque and 19 (48%) a hard plaque. Preoperative bFGF serum levels were higher in patients with soft plaques [soft=34 (28-39) pg/mL and hard=20 (17-22) pg/mL-p&lt;0.001] and postoperatively returned to normal values (when compared to 10 healthy volunteers). The serum levels of MMP-2 in patients' with soft plaques were higher than those in patients' with hard plaques [soft=1222 (1190-1252) ng/mL and hard=748 (656-793)ng/mL-p&lt;0.0001]. MMP-9 serum values were 26 (22-29) ng/mL for soft plaques and 18 (15-21) ng/mL for hard plaques (p&lt;0.0001). We found increased activity, production and expression of MMP-2 and -9 in soft plaques compared to hard plaques (p&lt;0.001). In vitro inhibition tests on HUASMC showed the direct influence of bFGF on the activity, production and expression of MMP-2 and -9 (p&lt;0.001). CONCLUSIONS: bFGF seems to exert a key role in carotid plaque instability regulating the activity, production and expression of MMP thus altering the physiologic homeostasis of the carotid plaque