Simple Precision Creation of Digitally Specified, Spatially Heterogeneous, Engineered Tissue Architectures

Complex architectures of integrated circuits are achieved through multiple layer photolithography, which has empowered the semiconductor industry. We adapt this philosophy for tissue engineering with a versatile, scalable, and generalizable microfabrication approach to create engineered tissue architectures composed of digitally specifiable building blocks, each with tuned structural, cellular, and compositional features.Paul G. Allen Family FoundationNew York Stem Cell FoundationNational Institutes of Health (U.S.)National Science Foundation (U.S.)Lincoln LaboratoryInstitution of Engineering and Technology (AF Harvey Prize

Minimal leader selection in general linear multi-agent systems with switching topologies : leveraging submodularity ratio

In multi-agent systems with leader-follower dynamics, choosing a subset of agents as leaders is a critical step in achieving the desired coordination performance. In this study, by considering consensus tracking for general linear multi-agent systems under switching topologies, we address the problem of selecting a minimum-size set of leaders by leveraging the submodularity ratio. First, using the dwell time technique, a criterion is derived to ensure that the states of all agents can converge to a reference trajectory that is directly tracked by each leader. Second, exploiting the derived consensus tracking criterion, the metrics with a structure of the Euclidean distance between specific vectors and the space spanned by an iteratively updated matrix are established to identify a set of leaders, and then the corresponding bound of the submodularity ratio is proposed. Third, combining the derived criterion and the constructed metrics, a leader selection scheme is presented together with three polynomial-time algorithms, and the related provable optimality bound of each algorithm can be obtained by leveraging the proposed bound of the submodularity ratio. Finally, illustrative examples are provided to verify the effectiveness of the proposed leader selection scheme

Distributed Voltage Regulation for Low-Voltage and High-PV-Penetration Networks With Battery Energy Storage Systems Subject to Communication Delay

The increasing penetration level of photovoltaic (PV) systems in low-voltage networks causes voltage regulation issues. This brief proposes a new voltage regulation strategy utilizing distributed battery energy storage systems (BESSs) while incorporating the inevitable communication delays. The proposed strategy ensures that the voltage regulation burden is appropriately shared among all involved BESSs in the network. The effects of communication delays on the performance of the proposed strategy are analyzed and an admissible delay bound is established. Case studies are conducted to verify the effectiveness of the proposed strategy.</p

Observations and interpretations of geomorphologic features in the Tianwen-1 landing area on Mars by using orbital imagery data

China’s first Mars exploration mission, Tianwen-1, successfully landed in southern Utopia Planitia on Mars on May 15, 2021. This work presents a detailed investigation of the geologic context of the landing area surface for this mission based on orbital remote-sensing data. We constructed a geomorphologic map for the Tianwen-1 landing area. Results of our detailed geomorphologic map show several major landforms within the landing area, including rampart craters, mesas, troughs, cones, and ridges. Analysis of materials on the landing area surface indicates that most of the landing area is covered by Martian dust. Transverse aeolian ridges are widely distributed within the landing area, indicating the surface contexts were (and still are) modified by regional winds. In addition, a crater counting analysis indicates the landing area has an absolute model age of ~3.3 Ga and that a later resurfacing event occurred at ~1.6 Ga. Finally, we outline four formational scenarios to test the formation mechanisms for the geomorphologic features on the landing area surface. The most likely interpretation to explain the existence of the observed surface features can be summarized as follows: A thermal influence may have played an important role in the formation of the surface geomorphologic features; thus, igneous-related processes may have occurred in the landing area. Water ice may also have been involved in the construction of the primordial surface configuration. Subsequent resurfacing events and aeolian processes buried and modified the primordial surface