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Driving simulators have boosted the vehicle design with the introduction of human beings in the simulation loop. For a realistic functioning, the steering system must provide an accurate behaviour, since the hand wheel is a crucial human interface. Despite a large diffusion of steering models, this paper deals with the creation of a specific solution for real-time applications, characterized by precise features as numerical stability and low computational cost. The proposed model is based on a physical structure and considers all the key phenomena, such as the system elasticities, the power steering effects and friction hysteresis, making the model more accurate in terms of steering wheel torque and lateral acceleration than other angle-driven models. Its two degrees of freedom design allows a proper behaviour of the power steering sub-model; another key aspect is the friction model: the use of the LuGre formulation greatly improves accuracy and stability in comparison to the lookup table friction models. Compared to the literature reference torque-driven model, it does not need the use of a torque sensor when implemented in driving simulators having an angle-driven formulation (the input of the steering wheel is its angle and the torque needed is its output), hence it is cheaper to implement; nevertheless, its accuracy is close to state-of-art reference. An original parametrization procedure is proposed since a generalized one is not available in literature; using a steering test-rig, all the model variables are defined. The validation phase combines offline and online simulations, assessing objectively and subjectively the model’s capabilities and showing accurate results in terms of steering wheel torque, lateral acceleration and steering feeling. In addition, a minor contribution of this paper shows how different analyses (steering effort evaluation, experimental data comparison or simulator feedback computation) require different output torques.

By means of time-resolved photoluminescence (TR-PL) spectroscopy, we present a detailed investigation of the carrier relaxation dynamics in a CsPbBr3bulk sample and microcrystal ensemble at cryogenic temperature on a picosecond time scale. We provide evidence of a long temperature-dependent cooling rate for the excitons and free carriers population, with an initial cooling time constant of a few tens of picoseconds. A relaxation bottleneck in the thermalization process was found that cannot be explained by the Auger effect or hot phonon population, since we address a very low excitation regime, not commonly investigated in literature, where such processes are not effective. Adding a continuous wave optical bias to the picosecond excitation, we probed the photoinduced PL decrease of the localized states and the photoinduced PL increase of the population in the high energy states. A long recovery time from the photoinduced PL decrease was found for localized states and quite significant differences were detected, depending on the resonance/off resonance bias used in the experiment.

The performance of semi-active differential systems is deeply influenced by the way in which they are actuated. Conventional semi-active systems are actuated by pressure-controlled hydraulic actuators that, despite their good dynamical behaviour, are relatively inefficient. In this work, the authors propose an innovative controlled hydraulic pump solution that is able to drastically improve the efficiency and to reduce the overall encumbrances, maintaining very high performance in terms of dynamical behaviour and corresponding frequency response. The authors investigate design criteria of the proposed solution, describe a simulation model and validate design and simulation models with experimental data.

IMPORTANCE: Predictors of lethal arrhythmic events (LAEs) after a pediatric diagnosis of hypertrophic cardiomyopathy (HCM) are unresolved. Existing algorithms for risk stratification are limited to patients older than 16 years because of a lack of data on younger individuals. OBJECTIVE: To describe the long-term outcome of pediatric-onset HCM and identify age-specific arrhythmic risk factors. DESIGN, SETTING, AND PARTICIPANTS: This study assessed patients with pediatric-onset hypertrophic cardiomyopathy diagnosed from 1974 to 2016 in 2 national referral centers for cardiomyopathies in Florence, Italy. Patients with metabolic and syndromic disease were excluded. EXPOSURES: Patients were assessed at 1-year intervals, or more often, if their clinical condition required. MAIN OUTCOMES AND MEASURES: Lethal arrhythmic events (LAEs) and death related to heart failure. RESULTS: Of 1644 patients with HCM, 100 (6.1%) were 1 to 16 years old at diagnosis (median [interquartile range], 12.2 [7.3-14.1] years). Of these, 63 (63.0%) were boys. Forty-two of the 100 patients (42.0%) were symptomatic (defined as an New York Heart Association classification higher than 1 or a Ross score greater than 2). The yield of sarcomere gene testing was 55 of 70 patients (79%). During a median of 9.2 years during which a mean of 1229 patients were treated per year, 24 of 100 patients (24.0%) experienced cardiac events (1.9% per year), including 19 LAEs and 5 heart failure–related events (3 deaths and 2 heart transplants). Lethal arrhythmic events occurred at a mean (SD) age of 23.1 (11.5) years. Two survivors of LAEs with symptoms of heart failure experienced recurrent cardiac arrest despite an implantable cardioverter defibrillator. Risk of LAE was associated with symptoms at onset (hazard ratio [HR], 8.2; 95% CI, 1.5-68.4; P = .02) and Troponin I or Troponin T gene mutations (HR, 4.1; 95% CI, 0.9-36.5; P = .06). Adult HCM risk predictors performed poorly in this population. Data analysis occurred from December 2016 to October 2017. CONCLUSIONS AND RELEVANCE: Pediatric-onset HCM is rare and associated with adverse outcomes driven mainly by arrhythmic events. Risk extends well beyond adolescence, which calls for unchanged clinical surveillance into adulthood. In this study, predictors of adverse outcomes differ from those of adult populations with HCM. In secondary prevention, the implantable cardioverter defibrillator did not confer absolute protection in the presence of limiting symptoms of heart failure.

We study both theoretically and experimentally the luminescence in non-intentionally but heavily p-doped GaAs quantum wells of 55 and 150A width. At T=2K the PL spectra under cw excitation present an excitonic peak and a broad acceptor band. Time-resolved optical pumping of the acceptor line allows us to measure the free electron spin relaxation time. We have investigated its temperature dependence in the 4-40K range. The experimental findings are interpreted in the framework of the D'Yakonov-Perel' mechanism for the electron gas.

We show that the initial dynamics of resonantly-excited excitons in quantum wells is controlled by several processes such as radiative recombination, spin relaxation of excitons, electrons and holes, and scattering between different in-plane momentum states of excitons. We present a unifïed analysis of the results, which provides quantitative information about these important rates, and a good physical understanding of the initial dynamics of nonequilibrium excitons. In particular, we show that the enhanced radiative recombination rate of excitons makes an important contribution to the early decay of the photoluminescence.

AbstractThe selective growth of InAs quantum dot chains self-ordered at mesoscopic distances on a rippled GaAs(001) substrate is obtained by tuning the direction of the As flux at high temperature and high As/In flux ratio. Microphotoluminescence experiments demonstrate that such isolated quantum dot chains show single quantum dot emission properties.

Base‐catalysed condensation reactions of nitroacetic esters with dipolarophiles to give isoxazole derivatives proceed faster, and often with higher yields, in the presence of water than in organic solvents such as chloroform. Kinetic profiles show that induction times are greatly reduced when the reaction is performed “in water” or “on water”. Any specificity of the base related to H‐bonding ability observed in chloroform is lost in water: all bases either organic or inorganic give the same result that is simply depending on concentration. A 0.1 molar ratio of base to nucleophile gives the best conversion, whereas addition of one equivalent of base or strong acid prevents the reaction from occurring. These results fit into a reaction sequence in which reversible addition to a dipolarophile is followed by acid‐catalysed irreversible dehydration of the cycloadduct. This is a remarkable example of a condensation reaction occurring in water because of irreversible acid‐catalysed water elimination. The reaction has been successfully applied to dipolarophiles containing a wide variety of functional groups, including carboxylic acids and ammonium salts, under mild conditions. This new click‐style reaction is expected to be compatible with biological environments.

Time-resolved photoluminescence experiments in high quality InAs/GaAs quantum dots clearly show the interplay between radiative recombination and thermalization processes. In particular from temperature dependent PL spectra, we prove that the carrier recombination dynamics is ruled by the thermal population in optically inactive exciton states, related to the population of the first excited hole levels. Moreover time-resolved spectra do not show any relaxation bottleneck, indicating an efficient carrier capture and a fast energy relaxation of the photogenerated carriers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present a detailed experimental study on the exciton dynamics in InGaAsN/GaAs quantum well structures after picosecond excitation. Time-resolved photoluminescence (PL) data are reported for samples grown in the very same conditions but differing for the nitrogen content. By varying the excitation density and the lattice temperature, we show that the PL from samples with nitrogen arises from localized excitons. Besides, the emission from localized states saturates even at low excitation power with a broadening of the PL band on the high energy side. No major quenching of the quantum yield is observed upon temperature increase. This indicates that the recombination dynamics is affected by non-radiative channels, which do not strongly depend on temperature. The similar dynamics observed in nitrogenated and not-nitrogenated samples suggest the dominance of non-radiative channels due to the highly-strained host matrix.

Vertically aligned InAs/GaAs quantum dot structures were investigated. They were grown by atomic layer molecular beam epitaxy, with 10 layers and wedged spacer thickness d varying between 7.7 and 12.5 nm at steps of 0.2 nm. The effects of electronic coupling on the fundamental transition energy and decay dynamics were studied by time-resolved and continuous-wave photoluminescence (PL). The energy of the PL peak position decreases with increasing d, while the corresponding lifetime increases with d. This is attributed to the interplay of the electronic delocalization along the column and the Coulomb interaction between electrons and holes. Furthermore, a bell-shaped behaviour of the PL lifetime as a function of emission energy was observed inside the inhomogeneously broadened PL band.

We present a detailed investigation of the exciton and free-carrier dynamics in high quality GaN/AlGaN MBE-grown quantum wells under different experimental conditions. In particular time-resolved photoluminescence spectra clearly indicate a major role played by the photoinduced screening of the internal electric field in the carrier recombination. Resonant and non-resonant time-resolved spectra are compared, suggesting a more efficient screening of the field when the carriers are created in the well. Experimental data are analyzed in the framework of a model based on the self-consistent solution of both Schrödinger and Poisson equations and a rate-equation for the time evolution of the carrier dynamics.

In this paper we performed steady-state and time-resolved near-field scanning optical spectroscopy on GaN/AlN quantum dot (QD) structures and InGaN/GaN multiple quantum wells (MQWs). The morphology of the QD sample is composed of islands in the 500–1000 nm range on the top of which dots nucleate. These islands are separated by slightly smaller structures showing less intense luminescence. Time-resolved photoluminescence mapping (spatially and spectrally resolved) of InGaN/GaN MQW structures revealed bright and dark spots with nearly constant peak energy and time decay. The results suggest that the bright and dark spots of the samples correspond to islands with higher and lower absolute number of QD-like regions where the excitons are localized.

We show that either a blueshift or a redshift of the fundamental transition energy can be observed in vertical arrays of InAs/GaAs quantum dots, depending on the spacer thicknesses, and explained by including strain, indium segregation, and Coulomb effects.

We have investigated the photoluminescence properties of GaN quantum dots with sub-micron lateral resolution by means of Near-Field Scanning Optical Microscopy (SNOM) operating in illumination mode. The analyzed sample consists of several stacked planes of GaN/AlN quantum dots grown by molecular beam epitaxy on Si(111) substrate. A clear correlation between the surface topography measured by Atomic Force Microscopy on uncapped samples and the SNOM luminescence maps has been found.

We present an experimental study of the exciton and phonon replica dynamics in high quality GaN epilayers and AlGaN/GaN quantum wells (QW) by means of picosecond time-resolved photoluminescence (PL) measurements. A non-exponential decay is observed both at the zero phonon line (ZPL) and at the n = 1 LO replica. Time-resolved spectra unambiguously assign the replica to the free exciton A recombination. Optical migration effects are detected both in the epilayer and the QWs samples and disappear as the temperature increases up to 60–90 K. Even though the sample quality is comparable to state-of-the-art samples, localization effects dominate the exciton dynamics at low temperature in the studied GaN based strucures.

Optical techniques, in particular photoluminescence (PL) spectroscopies, are currently used as a probe of the sample properties in semiconductor physics. The information obtained from the combined study of the near band-edge radiative recombination, i.e. of the free-carrier, free exciton (FE) and bound exciton PL, by means of both spectrally-resolved and time-resolved photoluminescence allows a reconstruction of the carrier dynamics and provides a good test of the sample device quality. The present availability of laser sources delivering femtosecond pulses with a photon energy greater than 5.5 eV, i.e. of the diamond indirect band-edge, allows now the application of such techniques to the characterisation of diamond samples. In fact good quality CVD diamond films exhibit a free-exciton recombination which can be used as a probe of their quality. The technique has been used in the present study for the characterisation of virgin and neutron irradiated CVD diamond samples.

Diamond films are extensively studied for applications as functional material for UV photoconductors. CVD-grown polycrystalline diamond films show very interesting performances, but their complete exploitation is actually limited by a slow time response if compared to other materials, by a relatively high concentration of structural defects, impurities and grain boundaries, which may affect the collection length of photogenerated charges. High-quality single crystal diamonds could solve some of these problems. The absence of grain boundaries can produce longer collection lengths. The nitrogen and impurity contents can be reduced and then large type-IIa diamond single-crystals can be obtained. In this work, a detailed structural and functional characterization of type Ib HPHT diamond crystals has been carried out and the results have been compared to similar characterizations of CVD films to evaluate the different behavior, taking also into account that these high pressure high temperature (HPHT) diamond crystals contain several tens ppm of nitrogen.

We present a detailed study of the angular pattern of the coherent emission from a semiconductor microcavity, under normal incidence excitation. Experimental results obtained by means of interferometric correlation measurements with subpicosecond resolution and by means of frequency and angle resolved cw spectra are compared. We show that a clear distinction between reflectivity and resonant Rayleigh scattering can be very difficult, as interference effects between the two coherent emissions play an important role. The frequency spectra of several RRS speckles have been measured for both the upper and lower polariton branches, denoting a long coherence time and a relevant role played by the microcavity wedge.

The coherent and incoherent components of the resonant secondary emission from GaAs quantum well structures after ultrashort excitation have been studied as a function of the excitation density and inhomogeneous broadening. We find that the coherent emission saturates with the excitation power in good agreement with a simple model taking into account the exciton inhomogeneous broadening and the excitation induced dephasing.

We present the first experimental study of the exciton spin relaxation dynamics in InGaN/GaN multiple quantum well structures after quasi-resonant picosecond excitation with linearly polarized light. Whereas short spin-relaxation times are generally expected in GaN-based bulk structures, for multiple quantum well structures we found long spin-relaxation times, around 100 ps, when the indium content was not too high. Our results suggest that the energy relaxation toward the radiative state can preserve the linear polarization of the exciton.

The relevance of resonant elastic light scattering to the relaxation of optically induced coherence in semiconductor structures is discussed. It is shown that important information on the intrinsic dephasing time of the optical excitation can indeed be extracted from the resonant Rayleigh scattering signal even in the case of inhomogeneously broadened transitions. Finally, a time-resolved technique is illustrated that is capable of yielding direct access to the coherence relaxation times in both bulk and quantum-confined semiconductor structures as long as the excitation is chosen so as to be resonant with the material transition.

We present a detailed investigation of the anti-Stokes (AS) luminescence which originates from exciton recombination when below gap excitation is used, in a set of high quality quantum well structures. We observe strong excitonic resonances in the AS signal as measured from photoluminescence and photoluminescence excitation spectra. We demonstrate that neither the electromagnetic coupling between the wells nor the morphological disorder can explain this up-conversion effect. Time-resolved luminescence data after ps excitation and fs correlation spectroscopy results provide clear evidence of the occurrence of a two-step absorption which is assisted by the exciton population resonantly excited by the first photon.

We report on the carrier dynamics in n-type double-barrier quantum well structures in an electric field. Both the intersubband and interband photocurrents, excited by long-wavelength (4μm) and short-wavelength (0.5μm) radiation, respectively, show a photovoltaic asymmetry with respect to the applied field. This asymmetry arises from an internal field due to an asymmetric dopant distribution with respect to the well centers. Time-dependent photoluminescence measurements allow us to determine the field dependence of the electron and hole capture times.

By nonlinear mixing of IR and visible radiation,i.e.coherent Raman scattering by polaritons driven by a CO2laser, it has been possible to get high-resolution spectra for theF-modes of a NaClO3crystal in the region (907÷957) cm−1, where several isotopic modes are present. The obtained independent measurement of the refractive index and absorbance allows an accurate determination of the polariton dispersion curve and its width inq-space. The experimental data confirm the existence of a localized isotopic mode at 931 cm−1and a strongly damped isotopic mode near 960 cm−1. Finally, an accurate measurement of the dispersion of the second-order nonlinear polarizability in the same energy region has been obtained for the first time. Usando tecniche di mescolamento non lineare di radiazione visibile e IR, cioè diffusione Raman coerente da polaritoni pompati da un laser a CO2, è stato possibile ottenere spettri ad alta risoluzione dei modiFdi un cristallo di NaClO3nella regione (907÷957) cm−1, dove sono presenti piú modi isotopici. La misura così ottenuta, in modo indipendente, dell'indice di rifrazione e dell'assorbanza del cristallo permette una determinazione accurata della curva di dispersione e della sua larghezza nello spazio dei momentiq. I dati sperimentali confermano l'esistenza ci un modo isotopico localizzato a 931 cm−1e di un modo fortemente smorzato intorno a 960 cm−1. Infine, è stata ottenuta per la prima volta una misura accurata della dispersione della polarizzabilità non lineare del second'ordine nella stessa regione di energie. Используя технику нелинейного смешивания инфракрасного и видимого излучений, т.е. когерентное рамановское рассеяние на поляритонах, образованных CO2лазером, оказывается возможным получение спектров с высоким разрешением дляF-мод кристалла NaClO3в области (907÷957) см−1, где имеется несколько изотропных мод. Проведенное независимое измерение показателя преломления и поглощения позволяет нам аккуратно определить дисперсионную кривую и ее ширину вq-пространстве. Экспериментальные данные подтверждают существование локализованной моды при 931 см−1и сильно затухающей моды вблнзи 960 см−1. В заключение, впервые проведено точное измерение дисперсии нелинейной поляризуемости второго порядка в той же области энергий.

AimTo investigate morphological changes in Enterocytozoon bieneusi and the duration of symptomatic relief after combination treatment with furazolidone and albendazole in AIDS patients.MethodsFour severely immunocompromised AIDS patients with symptomatic E bieneusi infection of the gut received an 18 day course of combined furazolidone and albendazole (500 + 800 mg daily). All patients were monitored for parasite shedding in stool by light microscopy at the end of treatment and monthly during follow up. At the end of treatment, duodenal biopsy specimens obtained from three patients were studied by transmission electron microscopy by two pathologists blind to the patients' treatment or clinical outcome. Duodenal biopsy specimens obtained from one of the patients two months after completion of treatment were also studied electronmicroscopically.ResultsAll patients had long lasting symptomatic relief, with a major decrease--or transient absence--of spore shedding in stools from completion of treatment. After treatment, changes in faecal spores were persistently found by light microscopy in all cases, and there was evidence of both a substantial decrease in parasite load and ultrastructural damage in the parasite in all biopsy specimens. The treatment was well tolerated, and no patient had clinical or parasitological relapse during follow up (up to 15 months).ConclusionsThe long lasting symptomatic relief observed in all four treated patients correlated with the persistent decrease in parasite load both in tissue and in stool, and with the morphological changes observed in the life cycle of the protozoan. These data suggest that combined treatment with furazolidone and albendazole is active against E bieneusi and may result in lasting remission even in severely immunocompromised patients.

Picosecond-resolved and steady-state photoluminescence at LHe temperature in low-energy ion-gun hydrogenated GaAs/GaAlAs heterostructures are reported. The exciton in the GaAs layer shows an increase in lifetime — up to a factor of 3 — for moderate hydrogenation, followed by a sharp decrease below the value for the untreated sample, for higher H doses. Luminescence efficiency shows a consistent behavior. Incorporation of H generates a strong D-A band falling  ̃64 meV below the gap energy. The behavior for heavy hydrogenation indicates the formation of a new type of deep defect, not ascribed to surface damage, because of the protective GaAlAs layer, plus the fact that the excitonic emission of the latter shows no variation.

Ge-on-Si substrates, made by a thin Ge relaxed layer with a low threading dislocation density and reduced surface roughness deposited on Si, are capable of accommodating the mismatch between GaAs and Si substrate and can be used for the growth of high quality AlGaAs/GaAs layers and of GaAs nanostructures by droplet epitaxy, while maintaining a low thermal budget compatible with the integration of CMOS devices.

We have studied different strained InGaAs/GaAs ultrathin quantum wells grown on vicinal surfaces for various terrace lengths and In contents. From photoluminescence experiments we observe an enhancement of the continuum density of states of quantum wells with large In content (x=0.35). We associate this behavior with the localization of carriers in regions of quasi one-dimensional confinement which are induced by fluctuations in the lateral periodicity of the strained layers. This assumption is supported by time resolved measurements as well. Copyright 1993, 1999 Academic Press

indicate that the Eu3+ions occupy two different sites of low symmetry of the host structure.