Safety Guaranteed Control for Spacecraft Inspection Mission

This paper investigates the safety guaranteed problem in spacecraft inspection missions, considering multiple position obstacles and logical attitude forbidden zones. In order to address this issue, we propose a control strategy based on control barrier functions, summarized as "safety check on kinematics" and "velocity tracking on dynamics" approach. The proposed approach employs control barrier functions to describe the obstacles and to generate safe velocities via the solution of a quadratic programming problem. Subsequently, we design a proportional-like controller based on the generated velocity, which, despite its simplicity, can ensure safety even in the presence of velocity tracking errors. The stability and safety of the system are rigorously analyzed in this paper. Furthermore, to account for model uncertainties and external disturbances, we incorporate an immersion and invariance-based disturbance observer in our design. Finally, numerical simulations are performed to demonstrate the effectiveness of the proposed control strategy.Comment: 22 pages, 9 figures, submitted to JGC

Adaptive Reduced-Attitude Control for Spacecraft Boresight Alignment with Safety Constraints and Accuracy Requirements

This paper investigates the boresight alignment control problem under safety constraints and performance requirements, involving pointing-forbidden constraint, attitude angular velocity limitation, and pointing accuracy requirement. Meanwhile, the parameter uncertainty issue is taken into account simultaneously. To address this problem, we propose a modified composite framework integrating the Artificial Potential Field (APF) methodology and the Prescribed Performance Control (PPC) scheme. The APF scheme ensures safety, while the PPC scheme is employed to realize an accuracy-guaranteed control. A Switched Prescribed Performance Function (SPPF) is proposed to facilitate the integration, which monitors various constraints and further establishes compatibility between safety and performance concerns by leveraging a special PPC freezing mechanism. To further address the parameter uncertainty, we introduce the Immersion-and-Invariance (I\&I) adaptive control technique to derive an adaptive APF-PPC composite controller, further guaranteeing the closed-loop system's asymptotic convergence. Finally, numerical simulations are carried out to validate the effectiveness of the proposed scheme.Comment: Submitted to T-AE

Status and progress of China SKA Regional Centre prototype

The Square Kilometre Array (SKA) project consists of delivering two largest radio telescope arrays being built by the SKA Observatory (SKAO), which is an intergovernmental organization bringing together nations from around the world with China being one of the major member countries. The computing resources needed to process, distribute, curate and use the vast amount of data that will be generated by the SKA telescopes are too large for the SKAO to manage on its own. To address this challenge, the SKAO is working with the international community to create a shared, distributed data, computing and networking capability called the SKA Regional Centre Alliance. In this model, the SKAO will be supported by a global network of SKA Regional Centres (SRCs) distributed around the world in its member countries to build an end-to-end science data system that will provide astronomers with high-quality science products. SRCs undertake deep processing, scientific analysis, and long-term storage of the SKA data, as well as user support. China has been actively participating in and promoting the construction of SRCs. This paper introduces the international cooperation and ongoing prototyping of the global SRC network, the construction plan of the China SRC and describes in detail the China SRC prototype. The paper also presents examples of scientific applications of SKA precursor and pathfinder telescopes completed using resources from the China SRC prototype. Finally, the future prospects of the China SRC are presented.Comment: T. An, et al. Status and progress of China SKA Regional Centre prototype. Sci. China-Phys. Mech. Astron. 65: 129501 (2022

One Embedder, Any Task: Instruction-Finetuned Text Embeddings

We introduce INSTRUCTOR, a new method for computing text embeddings given task instructions: every text input is embedded together with instructions explaining the use case (e.g., task and domain descriptions). Unlike encoders from prior work that are more specialized, INSTRUCTOR is a single embedder that can generate text embeddings tailored to different downstream tasks and domains, without any further training. We first annotate instructions for 330 diverse tasks and train INSTRUCTOR on this multitask mixture with a contrastive loss. We evaluate INSTRUCTOR on 70 embedding evaluation tasks (66 of which are unseen during training), ranging from classification and information retrieval to semantic textual similarity and text generation evaluation. INSTRUCTOR, while having an order of magnitude fewer parameters than the previous best model, achieves state-of-the-art performance, with an average improvement of 3.4% compared to the previous best results on the 70 diverse datasets. Our analysis suggests that INSTRUCTOR is robust to changes in instructions, and that instruction finetuning mitigates the challenge of training a single model on diverse datasets. Our model, code, and data are available at https://instructor-embedding.github.io.Comment: Accepted in ACL2023 Finding

Widespread aggregation of mutant VAPB associated with ALS does not cause motor neuron degeneration or modulate mutant SOD1 aggregation and toxicity in mice

Background: A proline-to-serine substitution at position-56 (P56S) of vesicle-associated membrane protein-associated protein B (VAPB) causes a form of dominantly inherited motor neuron disease (MND), including typical and atypical amyotrophic lateral sclerosis (ALS) and a mild late-onset spinal muscular atrophy (SMA). VAPB is an integral endoplasmic reticulum (ER) protein and has been implicated in various cellular processes, including ER stress, the unfolded protein response (UPR) and Ca^(2+) homeostasis. However, it is unclear how the P56S mutation leads to neurodegeneration and muscle atrophy in patients. The formation of abnormal VAPB-positive inclusions by mutant VAPB suggests a possible toxic gain of function as an underlying mechanism. Furthermore, the amount of VAPB protein is reported to be reduced in sporadic ALS patients and mutant SOD1G93A mice, leading to the hypothesis that wild type VAPB plays a role in the pathogenesis of ALS without VAPB mutations. Results: To investigate the pathogenic mechanism in vivo, we generated human wild type (wtVAPB) and mutant VAPB (muVAPB) transgenic mice that expressed the transgenes broadly in the CNS. We observed robust VAPB-positive aggregates in the spinal cord of muVAPB transgenic mice. However, we failed to find an impairment of motor function and motor neuron degeneration. We also did not detect any change in the endogenous VAPB level or evidence for induction of the unfolded protein response (UPR) and coaggregation of VAPA with muVAPB. Furthermore, we crossed these VAPB transgenic mice with mice that express mutant SOD1G93A and develop motor neuron degeneration. Overexpression of neither wtVAPB nor muVAPB modulated the protein aggregation and disease progression in the SOD1G93A mice. Conclusion: Overexpression of VAPBP56S mutant to approximately two-fold of the endogenous VAPB in mouse spinal cord produced abundant VAPB aggregates but was not sufficient to cause motor dysfunction or motor neuron degeneration. Furthermore, overexpression of either muVAPB or wtVAPB does not modulate the course of ALS in SOD1G93A mice. These results suggest that changes in wild type VAPB do not play a significant role in ALS cases that are not caused by VAPB mutations. Furthermore, these results suggest that muVAPB aggregates are innocuous and do not cause motor neuron degeneration by a gain-of-toxicity, and therefore, a loss of function may be the underlying mechanism

Lemur: Harmonizing Natural Language and Code for Language Agents

We introduce Lemur and Lemur-Chat, openly accessible language models optimized for both natural language and coding capabilities to serve as the backbone of versatile language agents. The evolution from language chat models to functional language agents demands that models not only master human interaction, reasoning, and planning but also ensure grounding in the relevant environments. This calls for a harmonious blend of language and coding capabilities in the models. Lemur and Lemur-Chat are proposed to address this necessity, demonstrating balanced proficiencies in both domains, unlike existing open-source models that tend to specialize in either. Through meticulous pre-training using a code-intensive corpus and instruction fine-tuning on text and code data, our models achieve state-of-the-art averaged performance across diverse text and coding benchmarks among open-source models. Comprehensive experiments demonstrate Lemur's superiority over existing open-source models and its proficiency across various agent tasks involving human communication, tool usage, and interaction under fully- and partially- observable environments. The harmonization between natural and programming languages enables Lemur-Chat to significantly narrow the gap with proprietary models on agent abilities, providing key insights into developing advanced open-source agents adept at reasoning, planning, and operating seamlessly across environments. https://github.com/OpenLemur/Lemu

The association between normal BMI with central adiposity and proinflammatory potential immunoglobulin G N-Glycosylation

Background: The mechanism by which normal body mass index (BMI) with central adiposity (NWCA) increases the risk of the diseases has not been completely elucidated. The inflammatory role of immunoglobulin G (IgG) N-glycosylation in obesity defined by BMI or central adiposity defined by waist-to-hip ratio (WHR) was reported, respectively. We undertook this three-center cross-sectional study to determine the association between the IgG N-glycans and NWCA. Methods: The participants were categorized into four different phenotypes: normal BMI with normal WHR (NW), normal BMI with central adiposity (NWCA), obesity with normal WHR (ONCA) and obesity with central adiposity (OCA). The IgG N-glycans were analyzed using ultra-performance liquid chromatography analysis of released glycans, and differences among groups were compared. Results: In total, 17 out of 24 initial IgG N-glycans were significantly different among the four groups (NW, ONCA, NWCA and OCA) (P\u3c0.05/6*78=0.0001). The changes of IgG glycans in central obesity (12 GPs) were more than those in obesity (3 GPs). In addition, lower galactosylation and bisecting GlcNAc and higher fucosylation were associated with increased risk of NWCA. Conclusion: Central obesity was involved in more changes of IgG N-glycosylation representing stronger inflammation than obesity, which might make a greater contribution to the risk of related disorders. NWCA was associated with an increased pro-inflammatory of IgG N-glycosylation, which was accompanied by the development of central obesity and other related disorders

Interactions between the jet and disk wind in a nearby radio intermediate quasar III Zw 2

Disk winds and jets are ubiquitous in active galactic nuclei (AGN), and how these two components interact remains an open question. We study the radio properties of a radio-intermediate quasar III Zw 2. We detect two jet knots J1 and J2 on parsec scales, which move at a mildly apparent superluminal speed of $1.35\,c$. Two $\gamma$-ray flares were detected in III Zw 2 in 2009--2010, corresponding to the primary radio flare in late 2009 and the secondary radio flare in early 2010. The primary 2009 flare was found to be associated with the ejection of J2. The secondary 2010 flare occurred at a distance of $\sim$0.3 parsec from the central engine, probably resulting from the collision of the jet with the accretion disk wind. The variability characteristics of III Zw 2 (periodic radio flares, unstable periodicity, multiple quasi-periodic signals and possible harmonic relations between them) can be explained by the global instabilities of the accretion disk. These instabilities originating from the outer part of the warped disk propagate inwards and can lead to modulation of the accretion rate and consequent jet ejection. At the same time, the wobbling of the outer disk may also lead to oscillations of the boundary between the disk wind and the jet tunnel, resulting in changes in the jet-wind collision site. III Zw 2 is one of the few cases observed with jet-wind interactions, and the study in this paper is of general interest for gaining insight into the dynamic processes in the nuclear regions of AGN.Comment: accepted by Ap