Nonlinear dynamic response analysis of two-stage spur gear space driving mechanism with large inertia load

Large inertia load has been widely used in space driving mechanisms, but the research concerning theory is still an unexplored scientific field. Towards the problem of nonlinear disturbance in space driving mechanism with large inertia load, a 14-DOF (Degree of Freedom) nonlinear, time-varying, dynamic model of two-stage spur gear system was established, taking into consideration time-varying stiffness, backlash and transmission error. The dynamic response of the load, under large or small inertia was investigated, basing on the dynamic model. The results indicate that at starting, normal operation and braking, large inertia load system has obvious hysteresis, compared to small inertia. The factors that improve dynamic response speed under large inertia load were studied. The results indicate that improving the stiffness and damping of the output shaft and changing the material of second gear pair to titanium alloy are helpful in improving the dynamic response speed of the system. Some results enrich the research of two-stage spur gear nonlinear model and large inertia load, since they provide important reference for the actual design of the gear system

Petrogenesis of the quartz diorite from the Lietinggang-Leqingla Pb-Zn-Fe-Cu- (Mo) deposit in southern Tibet: implications for the genesis of a skarn-type polymetallic deposit in the Tibetan-Himalayan collisional orogen

publishedVersio

TVIR: a comprehensive vegetable information resource database for comparative and functional genomic studies

Vegetables are an indispensable part of the daily diet of humans. Therefore, it is vital to systematically study the genomic data of vegetables and build a platform for data sharing and analysis. In this study, a comprehensive platform for vegetables with a user-friendly Web interface—The Vegetable Information Resource (TVIR, http://tvir.bio2db.com)—was built based on the genomes of 59 vegetables. TVIR database contains numerous important functional genes, including 5215 auxin genes, 2437 anthocyanin genes, 15 002 flowering genes, 79 830 resistance genes, and 2639 glucosinolate genes of 59 vegetables. In addition, 2597 N6-methyladenosine (m6A) genes were identified, including 513 writers, 1058 erasers, and 1026 readers. A total of 2 101 501 specific clustered regularly interspaced short palindromic repeat (CRISPR) guide sequences and 17 377 miRNAs were detected and deposited in TVIR database. Information on gene synteny, duplication, and orthologs is also provided for 59 vegetable species. TVIR database contains 2 346 850 gene annotations by the Swiss-Prot, TrEMBL, Gene Ontology (GO), Pfam, and Non-redundant (Nr) databases. Synteny, Primer Design, Blast, and JBrowse tools are provided to facilitate users in conducting comparative genomic analyses. This is the first large-scale collection of vegetable genomic data and bioinformatic analysis. All genome and gene sequences, annotations, and bioinformatic results can be easily downloaded from TVIR. Furthermore, transcriptome data of 98 vegetables have been collected and collated, and can be searched by species, tissues, or different growth stages. TVIR is expected to become a key hub for vegetable research globally. The database will be updated with newly assembled vegetable genomes and comparative genomic studies in the future

ChatBBNJ: a question–answering system for acquiring knowledge on biodiversity beyond national jurisdiction

The marine biodiversity in Areas beyond national jurisdiction (ABNJ), encompassing approximately two-thirds of the global ocean, is persistently declining. In 2023, the agreement on the Conservation and Sustainable Use of Marine Biodiversity of Areas Beyond National Jurisdiction (BBNJ) was officially adopted. Implementing the BBNJ Agreement has the potential to effectively meet global needs for preserving marine biodiversity. Nevertheless, the implementation requires dealing with thousands of legal clauses, and the parties participating in the process lack adequate means to acquire knowledge connected to BBNJ. This paper introduces ChatBBNJ, a highly efficient question-answering system that combines a novel data engineering technique with large language models (LLMs) of Natural Language Processing (NLP). The system aims to efficiently provide stakeholders with BBNJ-related knowledge, thereby facilitating and enhancing their comprehension and involvement with the subject matter. The experimental results demonstrate that the proposed ChatBBNJ exhibits superior expertise in the BBNJ domain, outperforming baseline models in terms of precision, recall, and F1-scores. The successful deployment of the suggested system is expected to greatly assist stakeholders in acquiring BBNJ knowledge and facilitating the effective implementation of the BBNJ Agreement. Therefore, this is expected to contribute to the conservation and sustainable use of marine biodiversity in ABNJ

The effect of robot-assisted gait training for patients with spinal cord injury: a systematic review and meta-analysis

BackgroundWith the aging of the global population, Spinal injuries are often prone to occur and affect human health. The development of technology has put robots on the stage to assist in the treatment of spinal injuries.MethodsA comprehensive literature search were carried out in multiple databases, including PubMed, Medline (Ovid), Web of Science, Cochrane, Embase, Scopus, CKNI, Wang fang, VIP database, Sino Med, Clinical Trails until 20th, June, 2023 to collect effect of robot-assisted gait training for patients with spinal cord injury patients. Primary outcome includes any changes of gait distance and gait speed. Secondary outcomes include any changes in functions (Such as TUG, Leg strength, 10 MWT) and any advent events. Data were extracted from two independent individuals and Cochrane Risk of Bias tool version 2.0 was assessed for the included studies. Systematic review and meta-analysis were performed by RevMan 5.3 software.Results11 studies were included in meta-analysis. The result showed that gait distance [WMD = 16.05, 95% CI (−15.73, 47.83), I2 = 69%], gait speed (RAGT vs. regular treatment) [WMD = 0.01, 95% CI (−0.04, 0.05), I2 = 43%], gait speed (RAGT vs. no intervention) [WMD = 0.07, 95% CI (0.01, 0.12), I2 = 0%], leg strength [WMD = 0.59, 95% CI (−1.22, 2.40), I2 = 29%], TUG [WMD = 9.25, 95% CI (2.76, 15.73), I2 = 74%], 10 MWT [WMD = 0.01, 95% CI (−0.15, 0.16), I2 = 0%], and 6 MWT [WMD = 1.79, 95% CI (−21.32, 24.90), I2 = 0%].ConclusionRobot-assisted gait training seems to be helpful for patients with spinal cord to improve TUG. It may not affect gait distance, gait speed, leg strength, 10 MWT, and 6 MWT

The Influence of Different Parameter on the Seismic Behavior of SRUHSC Frame

The seismic behaviors of steel reinforced ultrahigh strength concrete (SRUHSC) frames with different axial compression ratios and shear span ratios are experimentally studied through the reversed cyclic loading test of four specimens. The test results reveal that the seismic response of the frame is closely related to the failure process and failure mode of the columns. Based on the results, a systematic exploration is further conducted in terms of the characteristics of the skeleton curve, hysteresis curve, strength degradation, stiffness degradation, and energy dissipation capacity of the structure. The results indicate that as the axial compression ratio increases, and the shear span ratio decreases, the failure process of the entire structure and the weakening of the beam end are accelerated. Meanwhile, a change of the failure mode is also observed, accompanied by corresponding changes in the strength, stiffness, and energy dissipation capacity of the system

Effect of Fast Loading on the Seismic Performance of SRUHSC Frame Structures

Due to the high compressive strength and durability of ultra-high-strength concrete, SRUHSC (steel-reinforced ultra-high-strength concrete) frame structures have been used extensively in super-high-rise buildings. However, the SRUHSC showed obvious brittleness. Encasing structural steel in the material was recognized to be a good way of alleviating the problem of brittleness. The purpose of this study is to investigate the effect of the axial compression ratio on the seismic performance of a single-story, single-span SRUHSC frame structure under rapid loading. The failure mode, deformation, strength and stiffness degradation, energy dissipation capacity and residual displacement of the structure were compared and analyzed. The seismic performance of a single-story single-span SRUHSC frame structure is verified under the conditions of a fast loading rate and high axial compression ratio. The results suggest that the horizontal resistance capacity of structures can be significantly improved by fast loading in the elastic and elastic–plastic ranges. The ductility coefficient of the structure increases with the same axial compression ratio under fast loading. With an increase in loading rate, the secant stiffness of the structure is improved

Exploring the Interactive Development between Population Urbanization and Land Urbanization: Evidence from Chongqing, China (1998–2016)

To promote regional sustainable urbanization strategies, this paper selected the population and land resources in the urbanization system, and used the time series-based econometric analysis method and the coordinated development degree model to empirically study the interactive relationship between population urbanization (PU) and land urbanization (LU) in Chongqing, China, from 1998 to 2016. The research results showed that: (1) The development of urbanization in Chongqing was relatively rapid, but the level of development was relatively insufficient. The phenomenon of population outflow during urban development was more serious, and the structure of land use irrational; (2) There was a long-term cointegration relationship between PU and LU; PU is the Granger cause of LU. A PU increase of 1% in the short-term will promote LU by 3.29%, and in the long-term will promote 2.28%; the contribution of population agglomeration to urbanization is more than 80%, while land expansion is only about 20%, and the urban development model, which relies on urban land expansion is not applicable; (3) LU was faster than PU, but the improvement of PU development’s quality level was greater than that of LU. The development quality of both systems increased year by year, and gradually developed into a coordinated state. It is recommended that the government strengthen land planning, delineate urban growth boundaries, and increase the level of land intensive use; furthermore, through the reformation of the land finance and the household registration systems, a system for linking population, finance, and construction land should be established to promote the coordinated development of the two systems

Non-contact actuated snap-through buckling of a pre-buckled bistable hard-magnetic elastica

Snap-through buckling of bistable structures is a classic topic in mechanics which has been widely studied and applied in various fields such as mechanical meta-materials and soft robotics. Obstacles that hinder broader applications of conventional bistable structures include the requirement of contact actuation to trigger instability and difficulty to control post-buckling configurations. In contrast, hard magnetic elastica (HME), a composite made of hard ferromagnetic particles and soft elastomer that deforms in response to an externally applied magnetic field, exhibits great potential to bring major advances in this field by allowing non-contact actuation and programmable control of snap-through buckling via magnetization distribution (M−distribution). Here, we develop a theoretical framework to trace the instability and post-buckling evolution process of snap-through buckling of a bistable HME. In contrast to the conventional snapping through end-end shortening, the design space for bistable HME includes two key parameters: the remanent magnetization density after pre-magnetization and the external magnetic field. We focus on two simple yet practical cases: a fixed amplitude of magnetization density along the HME with direction reversed at the magnetization interface (M−interface), and a uniform magnetic field with varied direction. We identify an optimal position for the single M−interface and direction for the uniform actuation field for pre-buckled beams with two-ends fixed, which can reduce the required actuation field for snapping to nearly half in comparison with the symmetric cases. Experiments and finite element analysis are performed to validate the model predictions. Our work may stimulate further studies on utilizing snap-through buckling in applications where fast and large shape transitions from one stable state to another can be actuated in a low-energy, non-contact mode through a remotely applied stimulus field.Agency for Science, Technology and Research (A*STAR)Nanyang Technological UniversityNational Research Foundation (NRF)This work is supported by the Cyber Physiochemical Interfaces (CPI) project #A18A1b0045 and the Singapore National Research Fellowship (NRF-NRFF11-2019-0004). H. Gao acknowledges a start-up grant (002479-00001) from Nanyang Technological University and Agency for Science, Technology and Research (A*STAR)

Experimental study on the effect of graphene on the thermal conductivity of natural rubber latex

Graphene is a new type of carbon material with excellent performance. It not only has good electrical, mechanical and thermal properties, but also can be used as a filler of natural latex materials to optimize the thermal conductivity of natural latex materials. Therefore, graphene is widely used in aviation, automobile, machinery and other fields. In order to study the influence of the coordination ratio of graphene and rubber materials on the thermal conductivity, the natural rubber latex was first diluted and dissolved with volatile organic solvent toluene; then 0g, 0.5g, 1g, 1.5g, 2g, and graphene were respectively mixed into 20g natural rubber latex to prepare 6 thin samples (type I, type II, type III, type IV, type V, type VI). Finally, the thermal conductivity of 6 samples was measured by fla laser thermal conductivity instrument. The results showed that with the increase of graphene dosage, the thermal conductivity of natural rubber latex sheet increased significantly; when the ratio of graphene dosage to natural rubber latex was about 1:10, the rate of improving thermal conductivity of natural rubber latex decreased