Values Of Lambda Research Articles

Kernelized Normalizing Constant Estimation: Bridging Bayesian Quadrature and Bayesian Optimization

In this paper, we study the problem of estimating the normalizing constant through queries to the black-box function f, which is the integration of the exponential function of f scaled by a problem parameter lambda. We assume f belongs to a reproducing kernel Hilbert space (RKHS), and show that to estimate the normalizing constant within a small relative error, the level of difficulty depends on the value of lambda: When lambda approaches zero, the problem is similar to Bayesian quadrature (BQ), while when lambda approaches infinity, the problem is similar to Bayesian optimization (BO). More generally, the problem varies between BQ and BO. We find that this pattern holds true even when the function evaluations are noisy, bringing new aspects to this topic. Our findings are supported by both algorithm-independent lower bounds and algorithmic upper bounds, as well as simulation studies conducted on a variety of benchmark functions.

Uniformly convergent extended cubic B-spline collocation method for two parameters singularly perturbed time-delayed convection-diffusion problems

This work proposes a uniformly convergent numerical scheme to solve singularly perturbed parabolic problems of large time delay with two small parameters. The approach uses implicit Euler and the exponentially fitted extended cubic B-spline for time and space derivatives respectively. Extended cubic B-splines have advantages over classical B-splines. This is because for a given value of the free parameter lambda the solution obtained by the extended B-spline is better than the solution obtained by the classical B-spline. To confirm the correspondence of the numerical methods with the theoretical results, numerical examples are presented. The present numerical technique converges uniformly, leading to the current study of being more efficient.

Utility of anti-immunoglobulin IgA, IgG, IgM, Kappa, Lambda - FITC (conjugate) cocktail in routine renal pathology practice

BackgroundImmunofluorescence studies on frozen sections are an essential component in the evaluation of renal biopsies. The basic panel in most centres constitutes IgG, IgA, IgM, C3c, C1q, Kappa and Lambda light chain antibody testing. The purpose of this panel is to detect immunoglobulin or complement deposits and further subclassify the disease based on the location, intensity and pattern of immunoglobulin and complement staining. However, there are a substantial proportion of nephropathies that do not show any obvious immune-deposits on immunofluorescence. We currently, do not have any evidence-based alternative immunofluorescence panel to rule out these conditions. This study aims to evaluate the utility of anti-immunoglobulin IgA, IgG, IgM, Kappa, Lambda - FITC cocktail immunofluorescence on renal biopsy frozen sections with emphasis on its role as a primary screening panel in conjunction with C3c and C1q.MethodsAnti-immunoglobulin IgA, IgG, IgM, Kappa, Lambda light chain - FITC cocktail immunofluorescence was performed on 593 consecutive native renal biopsies along with the routine panel comprising of the individual FITC labelled IgG, IgA, IgM, C3c, C1q, Kappa and Lambda light chain immunofluorescence stains.ResultsIn 235 (39.6%) cases immune deposits (immune-complex mediated and monoclonal gammopathy-related) were present and the rest 354 (59.7%) cases were negative for immunoglobulin or complement deposits. Overall, the sensitivity, specificity, positive predictive value and negative predictive values of anti-immunoglobulin IgA, IgG, IgM, Kappa and Lambda - FITC cocktail in distinguishing immune-complex/immunoglobulin-mediated glomerulopathies from non-immune complex/immunoglobulin-mediated glomerulopathies were 100% each.ConclusionAnti-immunoglobulin IgA, IgG, IgM, Kappa and Lambda - FITC cocktail when used in conjunction with C3c and C1q, can be an effective first line investigation in all native renal biopsies. Further, testing with the individual FITC labelled IgG, IgA, IgM, Kappa and Lambda light chain immunofluorescence can be performed, depending on the initial screening as described above. Overall, this algorithmic approach can save valuable resources.

Topological black holes in higher derivative gravity

We study static black holes in quadratic gravity with planar and hyperbolic symmetry and non-extremal horizons. We obtain a solution in terms of an infinite power-series expansion around the horizon, which is characterized by two independent integration constants – the black hole radius and the strength of the Bach tensor at the horizon. While in Einstein’s gravity, such black holes require a negative cosmological constant Lambda , in quadratic gravity they can exist for any sign of Lambda and also for Lambda =0. Different branches of Schwarzschild–Bach–(A)dS or purely Bachian black holes are identified which admit distinct Einstein limits. Depending on the curvature of the transverse space and the value of Lambda , these Einstein limits result in (A)dS–Schwarzschild spacetimes with a transverse space of arbitrary curvature (such as black holes and naked singularities) or in Kundt metrics of the (anti-)Nariai type (i.e., dS_2times S^2, AdS_2times H^2, and flat spacetime). In the special case of toroidal black holes with Lambda =0, we also discuss how the Bach parameter needs to be fine-tuned to ensure that the metric does not blow up near infinity and instead matches asymptotically a Ricci-flat solution.

Shear layers in two-stage compound channels investigated with LS-PIV

Flow experiments are conducted in a two-stage compound open-channel, with varying intensity of the velocity difference between the main channel (deep part) and the floodplain (shallower part), using a large-scale free surface PIV technique (LS-PIV). For all investigated flows, a shear layer develops at the interface between main channel and floodplain, characterised by a peak of turbulent shear stress. Yet, two different kinds of shear layer could be identified. The first kind is characterised by the presence of large-scale quasi-periodic structures of Kelvin-Helmholtz type which are growing in downstream direction, whereas the second kind is characterised by smaller-scale vortical structures without quasi-periodicity and which do not grow in downstream direction. The shear parameter lambda =(U_2-U_1)/(U_2+U_1), where U_1 and U_2 are defined as the velocities outside the shear layer, is identified as a key parameter to distinguish between these two types of shear layers, supporting a result from Proust et al. (Water Resour Res 53: 3387–3406, 2017). A physical interpretation of the lambda-criterion is proposed, based on the inhibiting effect of ambient turbulence (the turbulence level outside the shear layer) on the emergence of Kelvin-Helmholtz structures. Accordingly, the threshold value of lambda, above which large-scale structures can develop, is dependent on the level of the ambient turbulence. Despite their very different behaviours, the two types of shear layer have the same efficiency to generate turbulent shear stress for a given velocity difference across the shear layer, except for lambda-values close to the threshold value.

Retracted: Exact solutions of the Schrödinger equation using extended Nikiforov-Uvarov formalism for generalized pseudo-harmonic oscillator

The Schrodinger equation with generalized pseudo-harmonic oscillator (GPHO) is transformed into a form that is compatible with extended Nikiforov-Uvarov (ENU) formalism, and its exact solutions are obtained in three and N-dimensions using this formalism. The energy spectrum for the GPHO was obtained in closed form, and the wave function was determined using the biconfluent Heun differential equation. Special cases are deduced, and some numerical results are shown to illustrate the behaviour of the bound state energies at different quantum states for various values of potential parameter; lambda. In addition, the thermodynamic property expressions for GPHO are obtained in closed form, and their variation with temperature-dependent parameters is discussed extensively for various values of lambda. Our results agree with those obtained in the literatures.

Symmetries of Non-Linear ODEs: Lambda Extensions of the Ising Correlations

This paper provides several illustrations of the numerous remarkable properties of the lambda extensions of the two-point correlation functions of the Ising model, shedding some light on the non-linear ODEs of the Painlevé type they satisfy. We first show that this concept also exists for the factors of the two-point correlation functions focusing, for pedagogical reasons, on two examples, namely C(0,5) and C(2,5) at ν=−k. We then display, in a learn-by-example approach, some of the puzzling properties and structures of these lambda extensions: for an infinite set of (algebraic) values of λ these power series become algebraic functions, and for a finite set of (rational) values of lambda they become D-finite functions, more precisely polynomials (of different degrees) in the complete elliptic integrals of the first and second kind K and E. For generic values of λ these power series are not D-finite, they are differentially algebraic. For an infinite number of other (rational) values of λ these power series are globally bounded series, thus providing an example of an infinite number of globally bounded differentially algebraic series. Finally, taking the example of a product of two diagonal two-point correlation functions, we suggest that many more families of non-linear ODEs of the Painlevé type remain to be discovered on the two-dimensional Ising model, as well as their structures, and in particular their associated lambda extensions. The question of their possible reduction, after complicated transformations, to Okamoto sigma forms of Painlevé VI remains an extremely difficult challenge.

Effectiveness of Science Learning Model Containing Balinese Local Wisdom in Improving Character and Science Literacy of Junior High School Students

The current situation is the low character of students, so brawls and violence often occur in various layers of society. The present study is aimed at analyzing the effectiveness of the science learning model in improving the character and scientific literacy of junior high school students. The research is a quasi-experimental design in the form of a posttest-only control design. The study sample was 158 people. A questionnaire and test were used for the character and scientific literacy variable data collection. Descriptive analysis and inferential analysis were used to analyze the post-test data. The descriptive analysis involved the mean, standard deviation, and variance. Inferential statistical analysis was done with the MANOVA test. The analysis results showed that the F value for Pillae Trace, Wilk Lambda, Hotelling Trace, and Roy's Largest Root had significantly less than 0.001, which means all are significant. Therefore, the study indicates that the science learning model containing Balinese local wisdom is effective on character and scientific literacy. Thus, this learning is recommended as a solution that can be used as an innovative learning model.

From monocular photograph to angle lambda: A new clinical approach for quantitative assessment

ABSTRACT Angle lambda assessment is essential in pediatric and strabismus practice. An abnormal angle lambda will modify the visual appearance of a strabismus or mimic one. Currently, angle lambda can be assessed by corneal topographs. Unfortunately, the use of these devices remains limited in the context of a strabismus clinic. Herein, we propose an easy, low cost, and reproducible method for angle lambda quantification, based on monocular photographs. Monocular pictures were taken by using a camera with a ring flash, centered by a fixation point. A digital evaluation analyzed the position of the corneal reflex on the pupil diameter. Using a trigonometric formula, the resulting ratio was converted into the value of angle lambda. This method was tested on 20 healthy eyes, on two successive couples of pictures, to evaluate its repeatability. Assessment using Pentacam was performed for comparison. The mean value of angle lambda was +2.61° ± 2.92° and 2.63° ± 2.85° in both picture series, respectively, and Lin’s repeatability coefficient was 0.99 – with a systematic deviation of −0.071° compared to Pentacam assessment. Angle lambda distribution was in range with values from the literature. This new method allows for angle lambda assessment without requiring a specific device and can be used in strabismus and pediatric clinics.

Renormalizing the vacuum energy in cosmological spacetime: implications for the cosmological constant problem

The renormalization of the vacuum energy in quantum field theory (QFT) is usually plagued with theoretical conundrums related not only with the renormalization procedure itself, but also with the fact that the final result leads usually to very large (finite) contributions incompatible with the measured value of Lambda in cosmology. As a consequence, one is bound to extreme fine-tuning of the parameters and so to sheer unnaturalness of the result and of the entire approach. We may however get over this adversity using a different perspective. Herein, we compute the zero-point energy (ZPE) for a nonminimally coupled (massive) scalar field in FLRW spacetime using the off-shell adiabatic renormalization technique employed in previous work. The on-shell renormalized result first appears at sixth adiabatic order, so the calculation is rather cumbersome. The general off-shell result yields a smooth function rho _{mathrm{vac}}(H) made out of powers of the Hubble rate and/or of its time derivatives involving different (even) adiabatic orders sim H^N (N=0, 2,4,6,ldots ), i.e. it leads, remarkably enough, to the running vacuum model (RVM) structure. We have verified the same result from the effective action formalism and used it to find the beta -function of the running quantum vacuum. No undesired contributions sim m^4 from particle masses appear and hence no fine-tuning of the parameters is needed in rho _{mathrm{vac}}(H). Furthermore, we find that the higher power sim H^6 could naturally drive RVM-inflation in the early universe. Our calculation also elucidates in detail the equation of state of the quantum vacuum: it proves to be not exactly -1 and is moderately dynamical. The form of rho _{mathrm{vac}}(H) at low energies is also characteristic of the RVM and consists of an additive term (the so-called ‘cosmological constant’) together with a small dynamical component sim nu H^2 (|nu |ll 1). Finally, we predict a slow (sim ln H) running of Newton’s gravitational coupling G(H). The physical outcome of our semiclassical QFT calculation is revealing: today’s cosmic vacuum and the gravitational strength should be both mildly dynamical.

Remarks on the black hole shadows in Kerr-de Sitter space times

This work is geared towards analysis of shadows cast by Kerr-de Sitter (KdS) and Kerr-de Sitter Revisited (RKdS) black holes. Considering observers in the vicinity of the static radius, we derive the impact parameters defining the apparent positions of the shadows. Such observers are of interest to our work because embedding diagrams have shown that de Sitter space-time is analogous to an asymptotically flat one in the vicinity of the static radius. We also perform a comparative analysis between our result with that in Ref. [1]. Furthermore, we numerically obtain the radii of curvature, vertical diameters and horizontal diameters of the shadows. We find that for Lambda =1.11times 10^{-52} ,, m^{-2}, M87* observations cannot distinguish a RKdS black hole shadow from that of a Kerr black hole. Additionally, for the same value of Lambda , KdS and RKdS black hole shadows are, in practise, indistinguishable. Previously, it has also been shown that when Lambda =1.11times 10^{-52} ,, {text {m}}^{-2}, KdS and Kerr black hole shadows are indistinguishable. Utilizing the 2017 EHT observations of M87* on the allowed range of the characteristic radius of the shadow, we obtain constraints on both black holes. When, a/M>0.812311, we observe that large angles of inclination (theta >30.5107^{circ }) do not pass the constraints for both KdS and RKdS black holes.

Differential gray matter connectivity correlates of CSF biomarkers: Results from the EPAD Cohort

AbstractBackgroundGray matter network (GMN) disruptions correlate with amyloid burden in the earliest stages of Alzheimer’s Disease (AD) pathology in cognitively unimpaired individuals. However, it remains unknown if and how hyperphosphorylated tau (p‐tau) influences GMNs. Here, we investigated the relation between GMNs and cerebrospinal fluid (CSF) p‐tau181 levels in non‐demented individuals from the European Prevention of Alzheimer Dementia (EPAD) cohort and evaluated whether this relationship is mediated by amyloid and Clinical Dementia Rating (CDR) status.MethodWe included 1198 participants from the EPAD v1500.0 release, who had both CSF biomarkers and structural MRI available. The cut‐off for amyloid‐β positivity (A+) was defined at <1000 pg/mL. Single‐subject network properties were extracted from 3D‐T1w MRI (Figure 1). Regional values were computed for 117 AAL atlas regions. Linear models were used to investigate main effects and interactions between amyloid status and p‐tau181 levels on global GMN measures. A three‐way interaction with CDR was modeled. Age, sex, site, total intracranial volume, and network size were included as covariates. Analyses were repeated for local network properties across AAL regions and FDR‐adjusted.ResultSample characteristics are provided in Table 1. A+ individuals had lower degree, clustering, gamma, and small world coefficients, and higher betweenness centrality (Figure 2). Higher p‐tau181 levels were associated with lower values of degree, betweenness centrality, lambda, and path length (Figure 3). Lambda, path length, and clustering showed an interaction effect of amyloid status and CDR on their relationship with p‐tau181 levels: A‐ individuals with CDR 0 had lower path length and lambda in association with tau, while A+ CDR 0.5 individuals with lower clustering coefficient values showed higher p‐tau181 (Figure 4). No associations were found for other GMN measures. Regional analysis showed a relationship of p‐tau181 with local path length in the precuneus (Figure 5).ConclusionGMN alterations show distinct associations with p‐tau181 levels, partially affected by amyloid and CDR status. Non‐amyloid related alterations of path length might be linked to axonal tau‐related changes. Clustering alterations seem instead to be linked to amyloid deposition and resulting local synaptic disconnectivity.

Holographic colour superconductors at finite coupling with NJL Interactions

We study a bottom-up holographic description of the QCD colour superconducting phase in the presence of higher derivative corrections. We expand this holographic model in the context of Gauss–Bonnet (GB) gravity. The Cooper pair condensate has been investigated in the deconfinement phase for different values of the GB coupling parameter lambda _{G B}, we observe a change in the value of the critical chemical potential mu _c in comparison to Einstein gravity. We find that mu _c grows as lambda _{G B} increases. We add four fermion interactions and show that in the presence of these corrections the main interesting features of the model are still present and that the intrinsic attractive interaction can not be switched off. This study suggests to find GB corrections to equation of state of holographic QCD matter.

The effect of air-fuel ratio on tailpipe exhaust emission of motorcycles

This article presents the actual AFR of the vehicular emission from the tailpipe data of motorcycles with petrol engine in Southwest Nigeria. It also presents the ratio between the actual air-fuel ratio (AFRactual) and the ideal/stoichiometric air-fuel ratio (AFRideal) known as the equivalence air-fuel ratio or lambda (λ). This was compared with the expected value for lambda by the catalytic technology for exhaust gases emission, which is 1 (± 5%). In this study, over 95% of the sampled motorcycles have higher lambda values than expected, thereby emitting very high concentrations of carbon monoxide (CO), hydrocarbon (HC), and carbon dioxide (CO2). The Portable, Hand-Held, battery-operated Kane automotive 4-gas analyser with detector tube (Model Auto 4-1) was used to measure the automobile emissions. The air-fuel ratio is a significant indicator and very important measure for gasoline engine performance controlling and tuning, and anti vehicles exhaust emissions pollution reasons [1]. Internal combustion (IC) gasoline fuelled engines exhaust gases emission depend heavily and mainly on the air-fuel ratio. For a gasoline fuelled engine, carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) exhaust gases emission are significantly influenced by air-fuel ratio. CO and HC are majorly generated or produced with rich air–fuel mixture, while NOx with lean air-fuel mixtures which mean that there is no fixed air-fuel mixture for which it can obtain the minimum for all exhaust gases emission [2]. This study can help in reducing fuel consumption, improving the quality of fuel combustion and reducing vehicle exhaust emissions in Nigeria.

Developing a Clinical Prediction Model for Failed Nonoperative Management of SLAP Tears (220)

Objectives:Patients with a superior labral anterior to posterior (SLAP) tear of the shoulder are often initially treated non-operatively, but many do not respond and require surgery. Identifying patients who are likely to fail non-operative management and would benefit from early surgical intervention can shorten time of disability and limit resources utilized on unsuccessful treatments. The purpose of this study is to create a clinical prediction model to determine which patients are likely to fail non-operative treatment of SLAP tears and require surgical intervention.Methods:This was a case-control study consisting of patients treated at a single institution for isolated, non-degenerative SLAP tears. Patients with concomitant rotator cuff tears were excluded from this analysis. Patients were retrospectively surveyed using the Research Electronic Data Capture (REDCap) system regarding clinical features of their shoulder injury, non-operative treatments that they received, and key functional outcomes during their post-injury period. Responders underwent additional medical record review to identify other variables related to the clinical presentation and treatment of their shoulder injury.In order to simplify the predictive model and optimize its interpretability, the lasso (least absolute shrinkage and selection operator) method of penalized logistic regression analysis was used to identify the characteristics that were most closely associated with failure of nonoperative treatment. The data was randomly split into a training set and test set. Using the training set, the value of lambda which minimized cross-validation prediction error rate was determined (Figure 1). The final lasso model was then computed. The predictive accuracy of the final model was assessed using the test data set.Results:Overall, 189 patients were contacted and included in the analysis. The mean age of included patients was 29.9 +/- 6.7 years. Thirty-eight patients (20.1%) were female. One hundred and six patients (56.1%) failed non-operative management and required surgical intervention.The final lasso model identified a total of 9 variables that were significantly associated with failure of non-operative management of SLAP tears (Table 1). These predictors included pre-injury overhead sports participation, presence of specific symptoms, severity of pain, and the type of non-operative treatment modalities used. Injury to the dominant extremity, history of prior shoulder injury, patient age, use of NSAIDs, and occupation involving manual labor or overhead work were not associated with failure of nonoperative treatment. The predictive accuracy of the model was 70.3% (95% CI 53.0%, 84.1%). Sensitivity of the model was 81.0% and specificity was 56.3%.Conclusions:A clinical prediction model consisting of variables describing patient characteristics, specific symptoms, and the type of non-operative treatment modalities utilized was found to predict failure of non-operative management of SLAP tears with moderate accuracy. Further refinements of this prediction model, including the inclusion of additional physical examination and imaging variables, will be required before future iterations are tested in clinical practice.

Existence and Nonexistence of Positive Solutions for Singular (p,\xa0q)-Equations with Superdiffusive Perturbation

We consider a nonlinear Dirichlet problem driven by the (p, q)-Laplacian and with a reaction which is parametric and exhibits the combined effects of a singular term and of a superdiffusive one. We prove an existence and nonexistence result for positive solutions depending on the value of the parameter lambda in overset{circ }{{mathbb {R}}}_+=(0,+infty ).

Moving the epidemic tipping point through topologically targeted social distancing

The epidemic threshold of a social system is the ratio of infection and recovery rate above which a disease spreading in it becomes an epidemic. In the absence of pharmaceutical interventions (i.e. vaccines), the only way to control a given disease is to move this threshold by non-pharmaceutical interventions like social distancing, past the epidemic threshold corresponding to the disease, thereby tipping the system from epidemic into a non-epidemic regime. Modeling the disease as a spreading process on a social graph, social distancing can be modeled by removing some of the graphs links. It has been conjectured that the largest eigenvalue of the adjacency matrix of the resulting graph corresponds to the systems epidemic threshold. Here we use a Markov chain Monte Carlo (MCMC) method to study those link removals that do well at reducing the largest eigenvalue of the adjacency matrix. The MCMC method generates samples from the relative canonical network ensemble with a defined expectation value of lambda _{text {max}}. We call this the “well-controlling network ensemble” (WCNE) and compare its structure to randomly thinned networks with the same link density. We observe that networks in the WCNE tend to be more homogeneous in the degree distribution and use this insight to define two ad-hoc removal strategies, which also substantially reduce the largest eigenvalue. A targeted removal of 80% of links can be as effective as a random removal of 90%, leaving individuals with twice as many contacts. Finally, by simulating epidemic spreading via either an SIS or an SIR model on network ensembles created with different link removal strategies (random, WCNE, or degree-homogenizing), we show that tipping from an epidemic to a non-epidemic state happens at a larger critical ratio between infection rate and recovery rate for WCNE and degree-homogenized networks than for those obtained by random removals.

Development of a prognostic model for hepatocellular carcinoma using genes involved in aerobic respiration.

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide. Currently, recent risk stratification has only focused on liver function and tumor characteristics. Thus, the purpose of this study was to develop a prognostic model based on genes involved in aerobic respiration. Matched tumor and normal tissues from TCGA and ICGC cohorts were analyzed to identify 15 overlapping differential expressed genes. Cox univariate analysis of the 15 genes in the TCGA cohort revealed they were all associated with disease-specific survival (DSS) in HCC patients. Using LASSO estimation and the optimal value for penalization coefficient lambda 12 genes were selected for the prognostic model, and then HCC patients in the TCGA cohort were dichotomized into low-risk and high-risk groups. Univariate and multivariate Cox analysis demonstrated patients in low-risk group had better survival. Validation of the risk score model with the ICGC cohort produces results consistent with those of the TCGA cohort. In conclusion, this study developed and validated a prognostic model of HCC through a comprehensive analysis of genes involved in aerobic respiration. This model may help develop personalized treatments for patients with HCC.

Reconstrução de curvas paramétricas por meio de uma abordagem probabilística

Este trabalho trata da reconstrução de curvas paramétricas utilizando funções de densidade de probabilidade para gerar uma amostragem de pontos no domínio da curva e aproximado-a em um intervalo específico. Existem várias abordagens para amostrar curvas paramétricas, que permitem que a mesma esteja de acordo com a curvatura ou comprimento de arco. Em geral, estas técnicas estão baseadas em heurísticas, e não conseguem dar soluções ótimas. Neste artigo, pretendemos usar uma abordagem probabilística, de modo que a amostragem de pontos resultante esteja de acordo com alguma função de densidade definida no domínio da curva, colocando mais pontos onde esta densidade é maior. Por ser mais geral, esta abordagem inclui os casos mencionados acima como casos particulares. Em geral, aproximar curvas planas com base na Distribuição Uniforme se revelou mais eficiente do que tomando como referência a Distribuição Exponencial. O valor de lambda na Distribuição Exponencial interfere na aproximação de algumas curvas, sendo necessário encontrar um valor de lambda adequado para chegar a uma boa aproximação da curva. Aproximar a curva com base na sua curvatura é um método usado quando se deseja gerar mais amostras onde a curvatura é maior. Porém, esse método só pode ser usado em casos especiais uma vez que a integral da função curvatura, na maioria das vezes, é muito difícil de ser calculada.

The Environmental Safety of the Fiat 0.9 TwinAir Compressed Natural Gas Engine

The article presents the results of measurements of concentrations of selected exhaust components of the Fiat 0.9 TwinAir spark-ignition engine operating according to load characteristics. The tested engine has an indirect, multi-point petrol supply system and has been retrofitted with an indirect CNG injection system. The results of the tests are a comparison of selected economic, ecological and energetic indicators of engine operation obtained when fuelled with CNG and 95 octane petrol. The operation of the engine fuelled with gaseous fuel was preceded by autocalibration of the controller of the fuelling system. The article presents the results of tests of concentrations of harmful components of exhaust gases: carbon dioxide CO2, carbon monoxide CO, nitrogen oxides NOx and HC hydrocarbons. Moreover, the values of lambda λ air excess coefficient are presented and fuel consumption is compared. The obtained results of the tests of the engine fuelled with CNG gas show a significant decrease in the value of the obtained torque in comparison to the engine torque when fuelled with petrol. The engine fuelled with compressed natural gas contributed to the improvement of its ecological properties and a reduction of fuel consumption, which are important factors of ecological and energy safety. Exhaust gas analysis showed a reduction in the concentration of harmful components of exhaust gases, mainly hydrocarbons and nitrogen oxides. A positive effect of the operation of the engine powered by CNG was also a significant reduction of carbon dioxide in the exhaust gases compared to the engine powered with gasoline.