Clearance-induced orientation uncertainty of spherical linkages

This paper proposes a kinematic model to evaluate the orientation uncertainty range of spherical linkages caused by the joint clearances. Based on the concepts of imaginary clearance link, spherical N-bar rotatability laws, and the invariant link rotatability, the uncertainty of the output angle can be treated as a mobility problem. And the uncertainty region of the end-effector is treated as a workspace problem for the remodeled linkage. The paper highlights the orientation error by isolating the kinematic effects of joint clearance from other error factors. The discussion is carried out through spherical four-bar linkages and five-bar linkages. Numeric examples are presented to demonstrate the uncertainty range of the output angle and the uncertainty region of the end-effector. The result shows that, in the worst case, the error of each joint clearance will be magnified in a closed-loop structure compared with linearly adding all the clearance error. This implies that from a kinematics point of view, closed-loop spherical linkages or parallel manipulators will lead to a greater deviation on the end-effector than its open-loop counterpart. Using more passive joints in the manipulator may result in more error possibilities.

3HSP J095507.9+355101: A flaring extreme blazar coincident in space and time with IceCube-200107A

The uncertainty region of the highly energetic neutrino IceCube200107A includes 3HSP J095507.9+355101 (z = 0.557), an extreme blazar, which was detected in a high, very hard, and variable X-ray state shortly after the neutrino arrival. Following a detailed multiwavelength investigation, we confirm that the source is a genuine BL Lac. This new detection differs from TXS 0506+056, which is thus far the first source associated with IceCube neutrinos, and is considered a “masquerading” BL Lac. As in the case of TXS 0506+056, 3HSP J095507.9+355101 is also way off the so-called blazar sequence. We consider 3HSP J095507.9+355101 a possible counterpart to the IceCube neutrino. Finally, we discuss some theoretical implications in terms of neutrino production.

Functional Location-Scale Model to Forecast Bivariate Pollution Episodes

Predicting anomalous emission of pollutants into the atmosphere well in advance is crucial for industries emitting such elements, since it allows them to take corrective measures aimed to avoid such emissions and their consequences. In this work, we propose a functional location-scale model to predict in advance pollution episodes where two pollutants are involved. Functional generalized additive models (FGAMs) are used to estimate the means and variances of the model, as well as the correlation between both pollutants. The method not only forecasts the concentrations of both pollutants, it also estimates an uncertainty region where the concentrations of both pollutants should be located, given a specific level of uncertainty. The performance of the model was evaluated using real data of SO 2 and NO x emissions from a coal-fired power station, obtaining good results.

Orbital dynamics of 2020 AV2: the first Vatira asteroid

ABSTRACT Vatira-class near-Earth objects (NEOs) have orbits entirely interior to the orbit of Venus with aphelia 0.307 < Q < 0.718 au. Recently discovered asteroid 2020 AV2 by the Zwicky Transient Facility on 2020 January 4 is the first known object on a Vatira orbit. Numerical integrations of 2020 AV2’s nominal orbit show it remaining in the Vatira region for the next few hundred kyr before coupling to Venus and evolving onto an Atira orbit (NEOs entirely interior to Earth’s orbit with 0.718 < Q < 0.983 au) and eventually scattering out to Earth-crossing. The numerical integrations of 9900 clones within 2020 AV2’s orbital uncertainty region show examples of Vatira orbits trapped in the 3:2 mean-motion resonance with Venus at semimajor axis a ≈ 0.552 au that can survive on the order of a few Myr. Possible 2020 AV2 orbits also include those on Vatira orbits between Mercury and Venus that only rarely cross that of a planet. Together, the 3:2 resonance and these rarely-planet-crossing orbits provide a meta-stable region of phase space that is stable on time-scales of several Myr. If 2020 AV2 is currently in this meta-stable region (or was in the past), that may explain its discovery as the first Vatira and may be where more are discovered.

Performance Analysis of PN Code Acquisition with MIMO Scheme for an UWB TH/CDMA System

This paper presents performance and its simulation results of pseudonoise (PN) code acquisition scheme with MIMO scheme for an ultra-wideband time-hopping/code-division-multiple-access (UWB TH/CDMA) system. The transmission channel is modelled as a frequency selective lognormal fading channel. In almost practical PN code acquisition system, the existence of more than two synchronous cells in the uncertainty region of the search process is possible due to multipath effect. Therefore, based on deriving the detection probability, false alarm rate, miss detection probability, and mean acquisition time, the acquisition performance is analyzed under the hypothesis of multiple synchronous states (cells) in the uncertainty region of the PN code. And the code acquisition performance is evaluated when the correlator outputs are noncoherently combined by using equal gain combining (EGC) scheme. In this procedure, the closed form for the conditional probability of decision variable is derived using the Gauss-Hermite quadrature formula. The performance comparison of the scheme mentioned above shows that the code acquisition performance with the diversity combining technique, especially when increasing the number of antenna, is more robust than that using no diversity. And code acquisition performance comparison also shows that if the detection threshold is set inappropriately, the performance might be degraded, even if an antenna diversity method is applied. It is also shown that Tx diversity can improve the acquisition performance but not as much as Rx diversity does. And Rx diversity can be applied to the acquisition system for additional diversity gain if the complexity of the receiver can be accepted.

The Parsing Syllable Envelopes Test for Assessment of Amplitude Modulation Discrimination Skills in Children: Development, Normative Data, and Test–Retest Reliability Studies

Intensity peaks and valleys in the acoustic signal are salient cues to syllable structure, which is accepted to be a crucial early step in phonological processing. As such, the ability to detect low-rate (envelope) modulations in signal amplitude is essential to parse an incoming speech signal into smaller phonological units.The Parsing Syllable Envelopes (ParSE) test was developed to quantify the ability of children to recognize syllable boundaries using an amplitude modulation detection paradigm. The envelope of a 750-msec steady-state /a/ vowel is modulated into two or three pseudo-syllables using notches with modulation depths varying between 0% and 100% along an 11-step continuum. In an adaptive three-alternative forced-choice procedure, the participant identified whether one, two, or three pseudo-syllables were heard.Development of the ParSE stimuli and test protocols, and collection of normative and test–retest reliability data.Eleven adults (aged 23 yr 10 mo to 50 yr 9 mo, mean 32 yr 10 mo) and 134 typically developing, primary-school children (aged 6 yr 0 mo to 12 yr 4 mo, mean 9 yr 3 mo). There were 73 males and 72 females.Data were collected using a touchscreen computer. Psychometric functions (PFs) were automatically fit to individual data by the ParSE software. Performance was related to the modulation depth at which syllables can be detected with 88% accuracy (referred to as the upper boundary of the uncertainty region [UBUR]). A shallower PF slope reflected a greater level of uncertainty. Age effects were determined based on raw scores. z Scores were calculated to account for the effect of age on performance. Outliers, and individual data for which the confidence interval of the UBUR exceeded a maximum allowable value, were removed. Nonparametric tests were used as the data were skewed toward negative performance.Across participants, the performance criterion (UBUR) was met with a median modulation depth of 42%. The effect of age on the UBUR was significant (p < 0.00001). The UBUR ranged from 50% modulation depth for 6-yr-olds to 25% for adults. Children aged 6–10 had significantly higher uncertainty region boundaries than adults. A skewed distribution toward negative performance occurred (p = 0.00007). There was no significant difference in performance on the ParSE between males and females (p = 0.60). Test–retest z scores were strongly correlated (r = 0.68, p < 0.0000001).The ParSE normative data show that the ability to identify syllable boundaries based on changes in amplitude modulation improves with age, and that some children in the general population have performance much worse than their age peers. The test is suitable for use in planned studies in a clinical population.

VIBRAÇÃO MECÂNICA EM UM TRATOR AGRÍCOLA ENSAIADO EM PISTA PADRONIZADA

Uma das principais variáveis que afetam o rendimento produtivo dos operadores de tratores agrícolas e que pode causar sérios problemas de saúde é a vibração gerada durante o funcionamento dessa máquina. Este trabalho teve como objetivo avaliar a vibração que incide sobre o corpo inteiro do operador através do assento de um trator agrícola mediante ensaio em pista de vibração padronizada. Empregou-se um trator de 92 kW de potência em quatro condições de lastragem: completamente lastrado, empregando somente lastro sólido, somente lastro líquido e completamente sem lastros, em quatro velocidades de deslocamento: 1,19 m s-1; 1,47 m s-1; 1,75 m s-1 e 2,08 m s-1, com pressões de inflação nos rodados traseiros e dianteiros de 137,85 kPa e 165,47 kPa respectivamente. Utilizou-se um acelerômetro de três eixos (eixos x, y e z), fixado sobre o assento do trator para avaliação do efeito da vibração no corpo do operador. A aquisição foi feita com o aparelho HVM – 100 e software BLAZE® 6.1.1, sendo obtidos os parâmetros aceleração média resultante, valor da dose de vibração, fator de crista e projeção de dose para 8 horas de trabalho. Realizou-se a análise de variância e separação de médias para todos os componentes analisados. Todas as análises estatísticas foram feitas com o teste de Tukey a 5% de probabilidade (p<0,05). As menores velocidades de deslocamento do trator resultaram nas melhores condições de conforto, enquanto as maiores velocidades geraram as piores condições de trabalho. A lastragem máxima do trator ocasionou as condições menos prejudiciais ao operador quando combinada com as menores velocidades de deslocamento do trator. Os níveis e tipos de lastragem na velocidade V1 e a lastragem máxima (L1) na velocidade V2 apresentaram valores de dose de vibração abaixo do nível de ação, enquanto os demais tratamentos geraram valores acima do nível de ação ou na região de incerteza, sem chegar ao limite de exposição. Na projeção de dose para oito horas de trabalho, todos os tratamentos se encontraram acima do nível de ação ou na região de incerteza. Tanto para a aceleração média resultante quanto para o valor de dose de vibração os valores de vibração ocasionados no sentido do eixo y foram os principais responsáveis pelo comportamento dos dados.PALAVRAS-CHAVE: Mecanização agrícola, segurança do trabalho, conforto, insalubridade, ergonomia. MECHANIC VIBRATION IN A FARM TRACTOR TESTED ON A STANDARDIZED TRACK ABSTRACT: One of the main variables that affect the productive performance of agricultural tractors operators and can cause serious health problems is the vibration generated during operation. This study aimed to evaluate the vibration that comes over the entire body of the operator through the seat of a tractor by standardized test vibration track. A tractor of 92 kW of power was used in four conditions of ballasting: fully ballasted, using only solid ballast, liquid ballast and completely ballasts in four travel speeds, 1.19 m s -1; 1.47 m s-1; 1.75 ms-1 and 2.08 ms-1 with inflation pressures in the front and rear axles of 137.85 kPa to 165.47 kPa respectively. A three-axis accelerometer (x, y, and z) was fixed to the tractor seat to evaluate the effect of vibration on the body of the operator. The request was made with the HVM unit - 100 and BLAZE® software 6.1.1, which obtained the average resultant acceleration parameters, vibration dose value, crest factor and dose projection for 8 hours of work. Analysis of variance and average separation were performed for all analyzed components. All statistical analyzes were performed using the Tukey test at 5% probability (p <0.05). Tractor smaller travel speeds resulted in the best conditions of comfort, while the highest speeds generated the worst working conditions. Maximum tractor ballasting caused the least harmful conditions to the operator when combined with the smaller tractor travel speeds. The levels and types of ballasting in the V1 speed and the maximum ballasting (L1) in the V2 speed showed vibration doses values below the level of action, while the other treatments generated values above the action level or the uncertainty region, without reaching the exposure limit. At the dosage projection for eight hours of work, all treatments resulted on values above the action level or on the uncertainty region. For both the average resultant acceleration as to the vibration dose value, vibration values caused to the axis y were the main responsible for the behavior of the data.KEYWORDS: Agricultural mechanization; work safety, confort, unsanitary conditions, ergonomics.