In this study, a novel kinematic calibration method is proposed to improve the absolute positioning accuracy of 6R robot. This method can achieve indirect compensation of the 25 parameters of modified Denavit–Hartenberg (MDH). The procedures of the method are threefold. Firstly, the 25-parameter errors model of MDH is initially established. However, only the errors of 10 parameters can be directly compensated in the 25-parameter errors model, since the inverse kinematics algorithm has to meet Pieper criterion. Subsequently, a calibration method is proposed to improve accuracy of the absolute position, which uses the Newton–Raphson method to transform the 25-parameter errors into 10-parameter errors (namely T-10 parameter model). Finally, the errors corresponding to 10 parameters in the T-10 parameters model are identified through the least square method. The calibration performances of T-10 parameters model are comprehensively validated by experimentation on two ER6B-C60 robots and one RS010N robot. After kinematic calibration, the average absolute positioning accuracy of the three robots can be improved by about 90%. The results indicate that the proposed calibration method can achieve more precise absolute positioning accuracy and has a wider range of universality.

Shott (2022, American Antiquity 87:794–815) argues that making inferences from ceramic data requires first inferring use lives of vessels—something that is difficult to do. This comment argues that the problem of differential use life becomes more tractable if the assemblage, rather than the vessel, is the unit of analysis. Aside from empirical reasons, theoretical considerations also favor the assemblage as the appropriate unit.

The text of the US Constitution appears to require that individual states, to the extent that they are ever allowed to conclude agreements with foreign governments, must obtain congressional approval. In practice, however, states conclude many agreements with foreign governments, including with Canada and its provinces, and they almost never seek congressional approval. This practice is an illustration of both the importance of federalism in US foreign relations and the significant role played by historical practice in informing US constitutional interpretation. The phenomenon of state international agreements assumed new prominence in 2019 when the Trump administration sued to challenge a climate change agreement that the state of California had made with Québec. Despite this challenge, for the most part, neither Congress nor the executive branch has resisted the growth in state international agreements. This acquiescence could change as countries like China target US states in an effort to work around strained relations with the US national government and as states become more assertive in resisting the national government’s foreign policies. In any event, the practice of state international agreements unapproved by Congress rests in part on a distinction between binding and non-binding agreements that deserves greater scrutiny under both domestic and international law.

In this article, we prove that the Riemann hypothesis implies a conjecture of Chandee on shifted moments of the Riemann zeta function. The proof is based on ideas of Harper concerning sharp upper bounds for the $2k$th moments of the Riemann zeta function on the critical line.

The notion that popular vigilance is central to safe-guarding democratic freedoms is a key pillar of republican political thought. Yet, this conception does not translate well to postcolonial contexts without some reconceptualization. In this article, I take up the ways in which two African statesmen and political theorists, Julius Nyerere and Thomas Sankara, reconceptualize the practice of vigilance in the postcolonial context. Both theorists demonstrate that the collective exercise of vigilance is a qualitatively different political practice in the postcolonial context because citizens must simultaneously target internal domination from elites and external domination from international institutions and former colonial powers. Furthermore, they underscore that a shared political vision in the form of a national ethic is crucial for generating and guiding mass practices of vigilance. Doing so, Nyerere and Sankara articulate a distinct tradition of postcolonial republicanism that better conceptualizes the challenges of stabilizing state–society relations in postcolonial Africa.

While the functioning of the postal system in Iran before 1500 and after 1800 has been studied, this article analyzes, based entirely on primary sources, the operation and characteristics of the Iranian postal system between 1500 and 1800 for the very first time. Such a study enables scholars to better understand the functioning of communication between both government officials and private individuals in Safavid, Afshari, and Zand Iran. During this time, there were two types of messengers: express-mounted couriers (chapar) for official business and foot messengers (shaters) for both official and private mail. The designation of qased was rarely used to denote mail foot messengers.

Sandwich composites are widely used in aerospace materials thanks to their low weight and high strength properties. The purpose of this study is to observe the effects of polyurethane foam filling on honeycomb core structures produced by additive manufacturing in terms of mechanical strength and moisture absorption properties. Within the scope of the study, honeycomb structures were produced by a 3D printer using polylactic acid (PLA) filament. Then, the honeycomb core was filled with polyurethane foam, which is supplied in liquid form. After the core material was given its final form, it was combined with an epoxy and carbon fibre facesheet material using the vacuum infusion technique. After the sandwich composite production was completed, in-plane compression, three-point bending, shear, and moisture absorption tests were applied. The polyurethane foam filling greatly increased the mechanical strength, but slightly more moisture absorption occurred in this structure compared to a hollow honeycomb structure.

This article presents and analyzes a newly discovered petroglyph from Tetzcotzinco (mun. Texcoco, Mexico) in the form of arranged pecked dots. Based on what is known about Mesoamerican divinatory systems, calendars, and the perception of space, the interpretation takes into account both the encoded numerical values and the layout of the dots. The main argument is that this and similar representations’ function was not limited to simple counting of days or serving as a kind of astronomical marker, in which the arms of the cross indicated, for example, equinoxes, which is by far their most common interpretation in academic literature. Instead, it represented calendrical cycles through the numbers, as suggested by some scholars. Based on this hypothesis, the article explores the possible connection between numbers registered in Tetzcotzinco's “pecked cross” and specific diagrams from indigenous divinatory books. Therefore, the plausible interpretation of the symbolism of this petroglyph is that it either expressed a series of meanings related to the agrarian period(s) and rain god(s) or less-known Mesoamerican calendrical cycles, such as half trecenas or seven- and nine-day periods.

We used a strand-specific RT-qPCR to evaluate viral replication as a surrogate for infectiousness among 242 asymptomatic inpatients with a positive severe acute respiratory coronavirus virus 2 (SARS-CoV-2) admission test. Only 21 patients (9%) had detectable SARS-CoV-2 minus-strand RNA. Because most patients were found to be noninfectious, our findings support the suspension of asymptomatic admission testing.

Through the collateral channel for entrepreneurs, a positive housing demand shock in Liu et al. [(2013) Econometrica 81, 1147–1184.] increases land prices and business investment, but consumption decreases on impact and there is thus a comovement problem. This paper improves Liu et al. [(2013) Econometrica 81, 1147–1184.] by adding general household preferences with broader intratemporal and intertemporal substitutions Bayesian estimation of our structural model based on aggregate US data suggests that the intratemporal substitution is larger than unity and the intertemporal substitution is smaller than unity. Our impulse responses show that a positive housing demand shock increases land prices, business investment, and consumption, which resolves the comovement problem. Moreover, the strength of the collateral channel linking land prices and business investment in our Bayesian DSGE model is larger than that in Liu et al. [(2013) Econometrica 81, 1147–1184.]. Housing demand shocks explain 39−43% of the variance of output and 41−47% of the variance of investment in our model, but the same shocks explain only 17−31% of the variance of output and 30−41% of the variance of investment in Liu et al. [(2013) Econometrica 81, 1147–1184.]. Variance decomposition reveals that housing demand shocks account for a larger share of the fluctuations in land prices, investment, employment, and output than other shocks. Using the marginal data density as the measure of fit for models, we find that our model can better explain the same US aggregate data.

We study the $R_\beta$-positivity and the existence of zero-temperature limits for a sequence of infinite-volume Gibbs measures $(\mu_{\beta}(\!\cdot\!))_{\beta \geq 0}$ at inverse temperature $\beta$ associated to a family of nearest-neighbor matrices $(Q_{\beta})_{\beta \geq 0}$ reflected at the origin. We use a probabilistic approach based on the continued fraction theory previously introduced in Ferrari and Martínez (1993) and sharpened in Littin and Martínez (2010). Some necessary and sufficient conditions are provided to ensure (i) the existence of a unique infinite-volume Gibbs measure for large but finite values of $\beta$, and (ii) the existence of weak limits as $\beta \to \infty$. Some application examples are revised to put in context the main results of this work.