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Connecting the Globe: Ground Terminal Competition for APRS Satellite Communication and Lessons Learned
Get PDFThis study presents the BIRDS-X Ground Terminal Competition, an initiative aimed at generating outreach for the radio amateur community and fostering communication with the Dragonfly satellite. Aligned with the objectives set by Amateur Radio Digital Communications (ARDC), this competition engages amateur radio enthusiasts and rigorously tests the APRS ground terminals (GT) under diverse conditions. Comprising three phases: orientation, communication test, and evaluation, the competition organizes regional communication schedules to optimize the satellite’s power budget. During the second phase, participants have a week-long window to establish contact with the satellite, providing log files, elevation data, and power output as evidence. The comprehensive evaluation in the final phase employs a grading system incentivizing compact, versatile, and affordable hardware, promoting accessibility to APRS technology. The established multipliers consider antenna type, station type, elevation angle, and cost. Moreover, two Reference Ground Terminals developed at Kyutech serve dual roles: facilitating performance evaluation for the APRS payload competition and offering technical insights for the Ground Terminal competition parameters. This paper highlights the significance of this competition in advancing the accessibility and performance of APRS technology in satellite communication.journal articl
Dragonfly: Unveiling the BIRDS-X 2U CubeSat, its Advancements, Flight Readiness, and Lessons Learnt
Get PDFThe BIRDS-X satellite project introduces Dragonfly, a 2U CubeSat based on the BIRDS Open-Source Bus system, with 100 × 100 × 227 mm dimensions. Developed at the Kyushu Institute of Technology by an international team of students, this satellite is dedicated to amateur radio communication, using a lean satellite approach. It aims to foster inclusivity and democratize space utilization. This paper comprehensively overviews the satellite’s subsystem developments and four primary mission advances. These missions include an Automated Packet Reporting System (APRS) payload competition in which five teams from different countries developed a payload and integrated it into the satellite, making it an accessible rideshare opportunity for their payloads to be tested in space, a Ground Terminal (GT) APRS global competition, on-orbit validation of a low-cost UHF transceiver, and a unique volcano monitoring task where while using the APRS protocol, the satellite will store and forward volcanic data for processing and posting. With the launch scheduled for February 2025, this paper presents the steps taken towards achieving the project objectives. This work also highlights its contribution to the evolving CubeSat landscape and amateur radio development while committing to safety standards and operational readiness.conference pape
A MBD-Based Dynamic Analysis Framework with a Viscoelastic Contact Model and Flexible Elements Toward Human Power Assistive Devices
Get PDFIt is important for the analysis of human movement and rehabilitation to incorporate spring-damper components, flexible materials, and contact force into the joint model considering human dynamics. In this study, the absolute nodal coordination formula (ANCF) method is introduced to the analytical model for the viscoelastic properties of the musculoskeletal system which is essential for analyzing human walking motion, and the flexible characteristics of the human body is reproduced. The consideration of a contact force model makes it possible to simulate contact actions between elements of the human body and the interaction with the environment. The proposed integrated framework is applied to multibody dynamics (MBD) based slider-crank mechanisms to demonstrate the dynamics/inverse dynamics analysis of human joint biomechanics.journal articl
Near-Linear Time Dispersion of Mobile Agents
Get PDFConsider that there are k ≤ n agents in a simple, connected, and undirected graph G = (V,E) with n nodes and m edges. The goal of the dispersion problem is to move these k agents to mutually distinct nodes. Agents can communicate only when they are at the same node, and no other communication means, such as whiteboards, are available. We assume that the agents operate synchronously. We consider two scenarios: when all agents are initially located at a single node (rooted setting) and when they are initially distributed over one or more nodes (general setting). Kshemkalyani and Sharma presented a dispersion algorithm for the general setting, which uses O(m_k) time and log(k + Δ) bits of memory per agent [OPODIS 2021], where m_k is the maximum number of edges in any induced subgraph of G with k nodes, and Δ is the maximum degree of G. This algorithm is currently the fastest in the literature, as no o(m_k)-time algorithm has been discovered, even for the rooted setting. In this paper, we present significantly faster algorithms for both the rooted and the general settings. First, we present an algorithm for the rooted setting that solves the dispersion problem in O(klog min(k,Δ)) = O(klog k) time using O(log (k+Δ)) bits of memory per agent. Next, we propose an algorithm for the general setting that achieves dispersion in O(k log k ⋅ log min(k,Δ)) = O(k log² k) time using O(log (k+Δ)) bits. Finally, for the rooted setting, we give a time-optimal (i.e., O(k)-time) algorithm with O(Δ+log k) bits of space per agent. All algorithms presented in this paper work only in the synchronous setting, while several algorithms in the literature, including the one given by Kshemkalyani and Sharma at OPODIS 2021, work in the asynchronous setting.journal articl
Mo2C regulated by cobalt components in N-doped carbon networks as pH-universal electrocatalyst for hydrogen evolution reaction
No full textDeveloping non-noble and high-performance electrocatalysts that are suitable for a wide pH range is viable for hydrogen evolution reaction (HER), whereas it has a great challenge to design suitable catalyst to overcome the slow water dissociation kinetics. Herein, we report a novel and large-scale tactics using natural kelp as a precursor by utilizing the super high water-absorption capacity to construct Co/Mo2C nanoparticles dispersed in N-doped carbon matrix with lamellar-crossing networks (Co/Mo2C@N-CKNs). Benefiting from synergistic advantages of Co-doped, Mo2C, as well as on the N-doped carbon, the Co/Mo2C@N-CKNs show superior HER performance in different pH condition with low overpotential of 63, 338 and 98mV at the current density of 10 mA·cm−2 in 0.5 M H2SO4, 0.1 M PBS and 1 M KOH respectively, and remaining stable even after 50 h of testing. This work may supply a common and hopeful strategy to realize non-noble and high-performance HER electrocatalysts with pH-universal work condition.journal articl
Antisolvent solubilization achieves simultaneous passivation of shallow and deep defects in perovskite solar cells
Get PDFResolving the inherent defects at the interfaces and grain boundaries of perovskite films is crucial for achieving highly efficient and stable perovskite solar cells (PSCs). This study introduces an antisolvent solubilization (AS) approach to enhance the solubilization of the bulk organic ammonium salt 2-Thiophenemethylammonium Iodide (ThMAI), which has limited solubility in low-polarity antisolvents. The results demonstrated that the AS approach could effectively passivate both shallow and deep defects in organic–inorganic hybrid perovskites (OIHPs). Furthermore, the ThMAI prepared using the AS method could react with excess PbI2 and facilitate the crystallization of the OIHPs, thereby improving light absorption, suppressing non-radiative recombination, and enhancing carrier extraction. As a result, PSCs prepared by using the AS method achieved a power conversion efficiency (PCE) of 23.69%, representing a 10% PCE improvement compared to normal devices. PSCs based on the AS method also demonstrated significantly improved heat and humidity stability.journal articl
Identification of Novel Antimicrobial Compounds Targeting Mycobacterium tuberculosis S-Adenosyl-L-Homocysteine Hydrolase Using Dual Hierarchical In Silico Structure-Based Drug Screening
Get PDFThe emergence of multidrug-resistant and extensively drug-resistant Mycobacterium tuberculosis (M. tuberculosis) has become a major medical problem. S-adenosyl-L-homocysteine hydrolase (MtSAHH) was selected as the target protein for the identification of novel anti-TB drugs. Dual hierarchical in silico Structure-Based Drug Screening was performed using a 3D compound structure library (with over 150 thousand synthetic chemicals) to identify compounds that bind to MtSAHH’s active site. In vitro experiments were conducted to verify whether the nine compounds selected as new drug candidates exhibited growth-inhibitory effects against mycobacteria. Eight of the nine compounds that were predicted by dual hierarchical screening showed growth-inhibitory effects against Mycobacterium smegmatis (M. smegmatis), a model organism for M. tuberculosis. Compound 7 showed the strongest antibacterial activity, with an IC50 value of 30.2 µM. Compound 7 did not inhibit the growth of Gram-negative bacteria or exert toxic effects on human cells. Molecular dynamics simulations of 40 ns using the MtSAHH–Compound 7 complex structure suggested that Compound 7 interacts stably with the MtSAHH active site. These in silico and in vitro results suggested that Compound 7 is a promising lead compound for the development of new anti-TB drugs.journal articl
里山と人の関わりの再生に向けた地域の環境政策の実践と協働に関する研究
Get PDF九州工業大学九州工業大学博士学位論文（要旨）学位記番号:工博甲第584号 学位授与年月日:令和6年3月25日thesi