Iridium System Research Articles

An agent-based framework for resilience analysis of service networks

Service networks made up of nodes and links inevitably suffer from performance degradation due to the negative effect of natural disasters and intentional attacks. Resilience is defined as the capability of recovering from disruptive events. Resilience analysis is of vital importance to evaluate network performance during the whole operation process. Given the dynamic characteristic of service networks, it is difficult to reflect the actual performance through static models. Moreover, resilience assessment should proceed with multiple metrics because network resilience is a multifaceted capability. To this end, an agent-based framework for resilience analysis is developed in this paper. Nodes are regarded as agents with independent decision-making to better respond to disruptions. The multi-agent negotiation mechanism is introduced to satisfy service requirements using deep Q-learning. In addition, network resilience is comprehensively assessed in terms of reliability, supportability and maintainability. A case study of Iridium system is conducted to illustrate the applicability of the agent-based framework. The results show that the developed framework can select the optimal route for task assignment and quantify resilience in the dynamic environment.

A comprehensive systematic review of privacy and security issues in Satellite Networks

The recent advancements in satellite networks have garnered significant interest due to their extensive geographic coverage and flexible deployment capabilities, offering a promising solution for global communications and transforming traditional communication methods. Despite these advancements, current satellite systems face challenges such as high propagation delays and inadequate coverage of high-latitude regions, particularly in Geostationary (GEO) systems. Low Earth Orbit (LEO) systems, which can address these issues, are primarily used for voice services, as seen in the Iridium system, but have encountered financial difficulties. This study aims to address the security issues in satellite networks, a critical concern as these networks increasingly rely on IP protocols and hybrid configurations of terrestrial nodes and satellite links. Previous works have identified various potential security attacks on satellite networks and proposed different solutions, but these solutions often lack comprehensive effectiveness and robustness. Our methodology involves analyzing the security vulnerabilities in satellite networks similar to the Iridium system, which includes inter-satellite links (ISL) and routers on each satellite. We review and evaluate existing security measures and propose enhancements to improve their effectiveness. Our results indicate significant vulnerabilities in current systems, but also show that with targeted improvements, security can be substantially enhanced. The implications of this study are profound, suggesting that more secure satellite networks can better support critical global communications and services, including broadband Internet and data services, thereby enhancing their reliability and user trust

2-Aminophenanthroline Ligands Enable Mild, Undirected, Iridium-Catalyzed Borylation of Alkyl C-H Bonds.

The catalytic, undirected borylation of alkyl C-H bonds typically occurs at high reaction temperatures or with excess substrate, or both, because of the low reactivity of alkyl C-H bonds. Here we report a new iridium system comprising 2-anilino-1,10-phenanthroline as the ligand that catalyzes the borylation of alkyl C-H bonds with little to no induction period and with high reaction rates. This superior activation and reactivity profile of 2-aminophenanthroline-ligated catalysts leads to broader reaction scope, including reactions of sensitive substrates, such as epoxides and glycosidic acetals, enhanced diastereoselectivity, and higher yields of borylated products. These catalysts also enable the borylation of alkanes, amines, and ethers at room temperature for the first time. Mechanistic studies imply that facile N-borylation occurs under the reaction conditions and that iridium complexes containing N-boryl aminophenanthrolines are competent precatalysts for the reaction.

Overcoming Energy Transfer for the Metallophotoredox Catalyzed Decarboxylative Alkenylation between Alkylcarboxylic Acids and Enol Triflates.

Herein we report on the decarboxylative alkenylation between alkyl carboxylic acids and enol triflates. The reaction is mediated by a dual catalytic nickel and iridium system, operating under visible light irradiation. Two competing catalytic pathways, from the excited state iridium photocatalyst, are identified. One is energy transfer from the excited state, resulting in formation of an undesired enol ester. The desired pathway involves electron transfer, resulting in decarboxylation to ultimately give the target product. The use of a highly oxidizing iridium photocatalyst is essential to control the reactivity. A diverse array of enol triflates and alkyl carboxylic acids are investigated, providing both scope and limitations of the presented methodology.

A genuine germylene PGeP pincer ligand for formic acid dehydrogenation with iridium.

We report an iridium system constructed around a long-tethered PGeP ligand that facilitates access to the less common germylene form, so far unreported for an 'NHC-type' Ge ligand. Its bonding is substantiated by computational studies and we have demonstrated its use for the catalytic dehydrogenation of formic acid, highlighting the potential of this underdeveloped type of ligand.

Structure-property relationships of photofunctional diiridium(II) complexes with tetracationic charge and an unsupported Ir–Ir bond

In contrast to the extensively studied dirhodium(II) complexes and iridium(III) complexes, neutral or dicationic dinuclear iridium(II) complexes with an unsupported ligand are underdeveloped. Here, a series of tetracationic dinuclear iridium(II) complexes, featuring the unsupported Ir(II)–Ir(II) single bond with long bond distances (2.8942(4)–2.9731(4) Å), are synthesized and structurally characterized. Interestingly, compared to the previous unsupported neutral or dicationic diiridium(II) complexes, our DFT and high-level DLPNO-CCSD(T) results found the largest binding energy in these tetracationic complexes even with the long Ir(II)–Ir(II) bond. Our study further reveals that London dispersion interactions enhance the stability cooperatively and significantly to overcome the strong electrostatic repulsion between two half dicationic metal fragments. This class of complexes also exhibit photoluminescence in solution and solid states, which, to our knowledge, represents the first example of this unsupported dinuclear iridium(II) system. In addition, their photoreactivity involving the generation of iridium(II) radical monomer from homolytic cleavage was also explored. The experimental results of photophysical and photochemical behaviours were also correlated with computational studies.

Assessment and Comparison of Three Dimensional Exoscopes for Near-Infrared Fluorescence-Guided Surgery Using Second-Window Indocyanine-Green.

ObjectiveCompared to microscopes, exoscopes have advantages in field-depth, ergonomics, and educational value. Exoscopes are especially well-poised for adaptation into fluorescence-guided surgery (FGS) due to their excitation source, light path, and image processing capabilities. We evaluated the feasibility of near-infrared FGS using a 3-dimensional (3D), 4 K exoscope with near-infrared fluorescence imaging capability. We then compared it to the most sensitive, commercially-available near-infrared exoscope system (3D and 960 p). In-vitro and intraoperative comparisons were performed. MethodsSerial dilutions of indocyanine-green (1–2000 μg/mL) were imaged with the 3D, 4 K Olympus Orbeye (system 1) and the 3D, 960 p VisionSense Iridium (system 2). Near-infrared sensitivity was calculated using signal-to-background ratios (SBRs). In addition, three patients with brain tumors were administered indocyanine-green and imaged with system 1, with two also imaged with system 2 for comparison. ResultsSystems 1 and 2 detected near-infrared fluorescence from indocyanine green concentrations of >250 μg/L and >31.3 μg/L, respectively. Intraoperatively, system 1 visualized strong near-infrared fluorescence from two, strongly gadolinium-enhancing meningiomas (SBR=2.4, 1.7). The high-resolution, bright images were sufficient for the surgeon to appreciate the underlying anatomy in the near-infrared mode. However, system 1 was not able to visualize fluorescence from a weakly-enhancing intraparenchymal metastasis. In contrast, system 2 successfully visualized both the meningioma and the metastasis but lacked high resolution stereopsis. ConclusionThree-dimensional exoscope systems provide an alternative visualization platform for both standard microsurgery and near-infrared fluorescent guided surgery. However, when tumor fluorescence is weak (i.e., low fluorophore uptake, deep tumors), highly sensitive near-infrared visualization systems may be required.

Catalytic asymmetric addition of an amine N–H bond across internal alkenes

Hydroamination of alkenes, the addition of the N-H bond of an amine across an alkene, is a fundamental, yet challenging, organic transformation that creates an alkylamine from two abundant chemical feedstocks, alkenes and amines, with full atom economy1-3. The reaction is particularly important because amines, especially chiral amines, are prevalent substructures in a wide range of natural products and drugs. Although extensive efforts have been dedicated to developing catalysts for hydroamination, the vast majority of alkenes that undergo intermolecular hydroamination have been limited to conjugated, strained, or terminal alkenes2-4; only a few examples occur by the direct addition of the N-H bond of amines across unactivated internal alkenes5-7, including photocatalytic hydroamination8,9, and no asymmetric intermolecular additions to such alkenes are known. In fact, current examples of direct, enantioselective intermolecular hydroamination of any type of unactivated alkene lacking a directing group occur with only moderate enantioselectivity10-13. Here we report a cationic iridium system that catalyses intermolecular hydroamination of a range of unactivated, internal alkenes, including those in both acyclic and cyclic alkenes, to afford chiral amines with high enantioselectivity. The catalyst contains a phosphine ligand bearing trimethylsilyl-substituted aryl groups and a triflimide counteranion, and the reaction design includes 2-amino-6-methylpyridine as the amine to enhance the rates of multiple steps within the catalytic cycle while serving as an ammonia surrogate. These design principles point the way to the addition of N-H bonds of other reagents, as well as O-H and C-H bonds, across unactivated internal alkenes to streamline the synthesis of functional molecules from basic feedstocks.

5G mobile communication convergence protocol architecture and key technologies in satellite internet of things system

This paper analyzes the network architecture of the Iridium system, Orbcomm system, Narrow Band-Internet of Things (NB-IoT) and Long Range Radio (Lo Ra) in the satellite 5G mobile communication system. A new Dynamic Routing based on Multi-factor Forwarding (MF-DR) protocol is proposed. This paper simulates the ladder-type data fusion algorithm in terms of energy consumption in the Wireless Sensor Network (WSN), the number of surviving nodes in the WSN, the communication traffic in the WSN, and the applicability of the ladder-type fusion algorithm. This verifies the superiority of the improved data fusion algorithm.

Technological aspects of the communication channels development for data transmission in the aircraft monitoring system

The article demonstrates that the Iridium satellite constellation is of the greatest interest for the organization of data transmission in the aircraft monitoring system, since it provides a stable connection between the aircraft and the control center. In this regard, additional interfaces are also provided to facilitate user access for some data transmission services in the Iridium system. It is found that, it is necessary to use a hardware-software complex when operating Iridium satellite communications. It allows displaying information on the aircraft location on the screen, as well as information from the object’s sensors. The authors propose an automated system for monitoring mobile and stationary objects “Navigator-S” as a basic version of such a hardware-software complex. At the same time, information is transmitted over the GSM channel monitoring the location of the aircraft and the state of the contact and parametric sensors.

Analysis of iridium‐augmented GPS positioning performance

Although the global positioning system (GPS) has a series of advantages such as global and high precision, there are still many deficiencies, in many cases, GSP cannot meet the requirements of the positioning accuracy. The iridium system is a low-orbit satellite system with a series of advantages such as global coverage, rapid geometric change, and low propagation loss, which can be combined with the GPS system to achieve the enhancement of positioning accuracy. In this study, the localisation performance of GPS system and iridium-augmented GPS system is compared using the localisation algorithm based on weighted least-squares method. The dilution of precision (DOP) values of the GPS system and the iridium-augmented GPS (iGPS) system and the positioning results before and after the iridium enhancement are calculated. The simulation results show that the iridium augment can optimise the DOP value of the GPS system, reduce the DOP value, and at the same time, when the GPS system cannot get the positioning result, a relatively accurate positioning result can still be obtained through the iridium augment, when the GPS system can get the positioning result, the iridium augment can significantly reduce the positioning error, and can makes the positioning result more accurate.

Mechanochemical Synthesis of Intermetallic Compounds in the Gallium–Iridium System

The interaction between a solid inert metal Ir and an active liquid metal Ga during mechanical activation in a high-energy planetary mill is studied by X-ray diffraction and scanning electron microscopy with high-resolution energy dispersive X-ray microanalysis. The effect of mechanical activation on the formation of GaxIry intermetallic compounds and GaxIry/Ir composites and their solubility in acids was investigated. The subsequent extraction of Ga from intermetallic compounds and composites in the mixture of concentrated acids [Formula: see text] makes it possible to produce nanoscale Ir.

Link Resource Allocation in Counter-Rotating Seam of Low-Orbit Satellite Network

This paper studies the communication problem at the counter-rotating seam of the low-orbit satellite based on the walker constellation. The counter-rotating seam has a short life cycle, low capacity, and dynamic geometric parameters. To better utilize the scarce link resources at the seam, increase network throughput, and approach the physical limits of the link throughput at the seam, an initial phase condition that maximizes the relative rotational joint link throughput is calculated. In the experimental simulation results using the Iridium system as an example, it is shown that better throughput can be obtained under the initial conditions, and the throughput is improved by about 30%.

The formation of disordered intermetallic phase during the solid-state interaction of WC with Ir

A relatively simple approach based on mixing WC and iridium powders, followed by heating to 1300–1600 °C in inert atmosphere, was proposed to synthesize refractory intermetallics in the tungsten – iridium system. The peculiarities of the solid-state interaction in the WC-Ir system were studied within the 1000–1600 °C temperature range using a set of modern analytical techniques. Intensive solid-state interaction in the WC – Ir system starts at 1300 °C. It was stated that this interaction can be described by two stages in the 1300–1600 °C temperature range. The first stage is the formation of Ir-rich disordered WxIr1-x solid solution with constant average composition W0.265Ir0.735. The second stage is the interaction of the obtained WxIr1-x solid solution with residual component (Ir or WC) that leads to the shift of the WxIr1-x phase composition on one side or the other in dependence on type of residual component. No ordered intermetallic phases are formed in the 1300–1600 °C temperature range. In the course of the solid-state reaction, free carbon is released as graphite-like phase on the surface of the intermetallic product.

Mechanochemical Synthesis of Intermetallic Compounds in the Gallium–Iridium System

The interaction between a solid inert metal (Ir) and an active liquid metal (Ga) during mechanical activation in a high-energy planetary mill is studied by X-ray diffraction and scanning electron microscopy with EDS-apparatus for high-resolution energy dispersive X-ray microanalysis. The influence of mechanical activation conditions on the formation of GaxIry intermetallic compounds and GaxIry/Ir composites and on their solubility in various acids is investigated. Being a surfactant for iridium, gallium propagates along the grain boundaries of polycrystalline iridium particles during mechanical activaiton and, hence, sharply decreases their strength. As a result of strong mechanical deformation during activation, the contact surface area between the solid and liquid metals, where the intermetallic compounds form intensely, increases sharply. As a result of treatment of the products of mechanical activaiton by a mixture of concentrated hydrochloric and nitric acids, iridium (>30%) from passes into an acid solution and forms HxIrCly complex compounds, which can interact with bases to form soluble complex salts.

Intercalation of graphene on iridium with samarium atoms

Intercalation of graphene on Ir (111) with Sm atoms is studied by methods of thermal desorption spectroscopy and thermionic emission. It is shown that adsorption of samarium at T = 300 K on graphene to concentrations of N ≤ 6 × 1014 atoms cm–2 followed by heating of the substrate leads to practically complete escape of adsorbate underneath the graphene layer. At N > 6 × 1014 atoms cm–2 and increasing temperature, a fraction of adsorbate remains on graphene in the form of two-dimensional “gas” and samarium islands and are desorbed in the range of temperatures of 1000–1200 K. Samarium remaining under the graphene is desorbed from the surface in the temperature range 1200–2150 K. Model conceptions for the samarium–graphene–iridium system in a wide temperature range are developed.

ChemInform Abstract: Enantioselective Hydroalkynylation of Non‐Polar Carbon—Carbon Double Bonds: Iridium‐Catalyzed Asymmetric Addition Reaction of Terminal Alkyne C—H Bonds to Substituted Norbornadienes.

AbstractThe hydroalkynylation of azanorbornadienes catalyzed by an iridium system is reported for the first time.

Selenourea-assisted synthesis of selenium-modified iridium catalysts: evaluation of their activity toward reduction of oxygen

Carbon-supported selenium-modified iridium nanoparticles have been synthesized using IrCl3 and selenourea serving as a precursor of selenium and nitrogen atoms. Here nanostructured iridium is chosen as model base metal for fundamental catalytic considerations because it exhibits interfacial properties resembling both platinum and ruthenium. The systems' electrocatalytic properties have been studied in sulfuric acid electrolyte toward reduction of oxygen and formation of hydrogen peroxide intermediate in comparison to bare iridium and platinum catalysts. To get insight into the reaction dynamics and mechanisms, such electrochemical diagnostic techniques as cyclic voltammetry and rotating ring-disk electrode voltammetry have been considered. To mimic operation of catalysts in real fuel cells, additional experiments utilizing gas diffusion electrode have also been performed. Materials are subjected to surface analytical, structural and microscopic characterization using X-ray photoelectron (XPS), fluorescence (EDX), and diffraction (XRD) methods as well as transmission and scanning electron microscopies. At low (optimum) coverages of selenium on surfaces of iridium nanoparticles, the reduction of oxygen tends to proceed at more positive potentials in comparison to bare iridium under analogous conditions. Apparently, strong affinity of bare iridium to form oxo groups on its surface (known as inhibiting oxygen reduction) is largely suppressed in presence of selenium or nitrogen atoms. But the optimum selenium-modified iridium system produces somewhat higher amounts of the hydrogen peroxide intermediate presumably due to partial physical blocking of iridium (metal and metal oxo) sites (that would otherwise be active toward the reduction of the H2O2 intermediate). High tolerance (during reduction of oxygen) of the optimum Ir-based catalyst (functionalized using selenourea) to the parasitic (e.g. in polymer membrane fuel cells) simultaneous oxidation of organic fuels (e.g. methanol or ethanol) should be mentioned as well.

Rhodium and Iridium Complexes of Bulky Tertiary Phosphine Ligands. Searching for Isolable Cationic MIII Alkylidenes

Cyclometalated chloride complexes of rhodium and iridium based on (η5-C5Me5)MIII fragments that result from the metalation of the xylyl substituent of a coordinated PR2(Xyl) phosphine (Xyl = 2,6-Me2C6H3) have been prepared by reaction of the appropriate metal precursor with the corresponding phosphine. For iridium, the four complexes 1a–d, derived from the phosphines PiPr2(Xyl), PCy2(Xyl), PMe2(Xyl), and PPh2(Xyl), respectively, have been prepared, whereas for rhodium only the complexes 2a,d, derived from PiPr2(Xyl) and PMe2(Xyl), respectively, have been studied. Chloride abstraction from compounds 1 and 2 by NaBArF (BArF = B(3,5-C6H3(CF3)2)4) leads to either cationic dichloromethane adducts or to cationic hydride alkylidene structures resulting from α-H elimination. The rhodium complexes investigated yield only dichloromethane adducts. However, in the iridium system the less sterically demanding phosphines PMe2(Xyl) and PPh2(Xyl) also provide dichloromethane adducts as the only observable products, where...

Hydrodeoxygenation of 2,5-Hexanedione and 2,5-Dimethylfuran by Water-, Air-, and Acid-Stable Homogeneous Ruthenium and Iridium Catalysts

The complexes [(4′-Ph-terpy)Ru(H2O)3](OTf)2 and [(4′-Ph-terpy)Ir(OTf)3] have been evaluated as catalysts for the conversion of 2,5-hexanedione and 2,5-dimethylfuran to hydrodeoxygenated products in aqueous acidic medium at elevated temperature (150–225 °C) under hydrogen gas (5.5 MPa). These two substrates form part of a value chain leading from C6 sugars to 2,5-hexanediol, 2,5-dimethyltetrahydrofuran, and hexane, which can be generated by the homogeneously acting ruthenium catalyst in up to 69%, 80%, and 10% yield, respectively, while at T > 175 °C the iridium system decomposes to a highly active but heterogeneously acting coating in the reactor defeating the premise of a homogeneous catalyst system. The deactivation and decomposition pathway of both catalysts leads to the formation of a series of isostructural complexes [M(4′-Ph-terpy)2]n+ (M = Fe, Ni, Ru, Ir; n = 2, 3) characterized by ESI-MS and single crystal X-ray crystallography, in which the source of the Fe and Ni is the 316SS reactor body.