Transmission Channel Research Articles

Real-time full-duplex transmission experiment for an air and underwater invisible light communication system

Specifications for highly secure and large-capacity optical transceivers are necessary when wireless communication is used over different transmission channels, such as underwater and air, in shallow sea areas. We evaluated the dynamic characteristics of bidirectional real-time transmission using an LED Backhaul that can generate and process direct current-added orthogonal frequency division multiplexing signals in the 850 nm band to demonstrate the feasibility of invisibility light communication. A composite channel that is 1.2 m in water and 10 m in the air was used as an optical radio channel. This experiment is the first report on real-time and 4 K video stream transmission for a line-of-sight full-duplex optical wireless communication in the invisible light band via heterogeneous transmission channels such as shallow water and air.

Visible light visual indoor positioning system for based on residual convolutional networks and image restoration

Abstract Visible light positioning technology, with its advantages of low cost, strong anti-interference, and high precision, is widely researched and applied in various different scenarios. In this paper, for the complexity of indoor environments, considering the problem of occlusion by various obstacles that may exist in indoor spaces, which may lead to incomplete imaging of CMOS image sensors, a maximum gray value-based occlusion recovery and decoding scheme is proposed. This scheme effectively solves the problem of visible light transmission channel being blocked and accomplishes LED-ID decoding. In addition, the overflow effect due to uneven light irradiation gathered in each pixel row affects the accuracy of decoding LED-ID, which in turn leads to poor positioning accuracy. In this paper, we propose to use an adaptive gamma correction method to eliminate the influence of the overflow effect and to improve the accuracy of decoding. In order to improve the positioning accuracy, a visible light positioning algorithm based on residual convolutional network (VisiResNet) is proposed to achieve high accuracy positioning. The experimental results show that the average positioning error is 9.7 cm in a space of 9m× 3m× 3m, and a decoding accuracy of 90% within 1.4m is achieved in the face of different occlusion situations. The system can achieve centimeter-level positioning accuracy and meet the indoor positioning requirements.

ICT and energy consumption in Sub-Saharan Africa: Effects and transmission channels

This paper contributes to the literature on the relationship between information and communication technologies (ICTs) and energy consumption. Despite increasing attention on the subject, existing studies have not yet investigated the channels through which ICTs affect energy demand. We use a stochastic impact model extended to the population, wealth and technology regression model to estimate both the effect and transmission of ICTs on energy demand in 24 sub-Saharan African countries from 1995 to 2018. Empirical results show that ICT use, measured by mobile and fixed-line telephone penetration significantly reduces energy consumption. In addition, the mediation analysis reveals that ICTs not only have a direct negative effect on energy consumption but also an indirect negative effect through its impact on GDP per capita and industrial sector development and a mixed indirect effect through financial development. However, the total effect is negative and indicates that ICTs are reducing energy consumption in sub-Saharan Africa. To accentuate the negative effects of ICTs on energy consumption, Governments should design policies to improve access to credit for the private sector, reduce income inequalities among populations, promote the use of industrial development and provide financial incentives for the development of green technologies.

Effectiveness of military spending in reducing the intensity of armed conflict in Sub-Saharan Africa

Abstract This study empirically examines the effectiveness of military spending in reducing the intensity of armed conflict in Sub-Saharan Africa. We use a dynamic probit model, and the results show that military spending reduces the intensity of conflict. It significantly reduces low-intensity conflicts more than high-intensity conflicts. Additionally, the effectiveness of military spending depends on its level and the quality of institutions. Finally, the analysis of transmission channels shows that military spending affects conflict intensity mainly through the channel of military capabilities. We conducted several tests and robustness checks to ensure the validity of our results.

Battling for food security in Africa: Is climate finance the missing bullet?

AbstractAs climate change increasingly threatens food production and distribution in Africa, understanding how climate finance programs can effectively improve food security in the region has become a critical research priority. In this light, the present study investigates the effect of climate finance on food security across 37 African countries from 2012 to 2021, utilizing secondary data and employing the system generalized method of moments. Our findings consistently demonstrate that climate finance plays a significant role in reducing food insecurity in Africa. This effect remains robust across various alternative food insecurity and climate finance metrics. Furthermore, through analyses of transmission channels, we confirm the indirect pathways through which climate finance contributes to improved food security outcomes in the region. Based on the findings, the study recommends strengthening and expanding climate finance initiatives focusing on enhancing accessibility, equity, and targeted support for farmers to reduce food insecurity.

From policy to progress: do female parliamentarians influence energy justice?

ABSTRACT Women parliamentarians have been playing an increasingly important role in shaping climate policy and advocating for energy justice in recent years. As lawmakers, they have a unique opportunity to influence policy decisions and prioritize sustainable practices that can mitigate the effects of climate change. Additionally, women parliamentarians bring a unique perspective to the table, often championing issues that directly impact women, children, and marginalized communities who are disproportionately affected by climate change and energy injustices. As the composition of parliamentarians becomes more diversified with the increasing representation of women, it is crucial to investigate whether female parliamentarians influence energy justice. Based on the theory of ecofeminism, which suggests that women are relatively more concerned with environmental sustainability and environmental risks than men, this study tests the hypothesis that women parliamentarians are more likely to take action in favour of energy justice. Specifically, this paper aims to examine the causal effect of female parliamentarians in promoting energy justice in a panel of 62 countries. The study proposes three sub-indicators of energy justice namely distributive justice, procedural justice, and restorative justice. Using the two-stage instrumental variable approach, we isolate the effect of female parliamentarians and find that it is a driver of energy justice. The results of a mediation analysis highlight the role of democracy and human capital as transmission channels, explaining the indirect effect of female parliamentarians on energy justice. The study's conclusions therefore highlight the importance of supporting and empowering women parliamentarians in their efforts to combat climate change and energy injustice.

Vapor Channel Oscillations in Laser Lithotripsy.

Laser-based endoscopic procedures present special challenges to deliver energy for ablation or coagulation of target tissues. When optical fiber-target quasi-contact (< 0.5 mm distance) cannot be maintained or is undesirable, the creation of intervening vapor bubbles and channels provide for the necessary transmission of laser energy to the target. This work investigates the characteristics and the dynamics of vapor channels that directly affect ablation efficiency and ablation rate and are known to effect stone movement, all of which impact procedure efficiency and safety. A simplified, experimental model for thulium fiber laser (1940 nm) lithotripsy consists of a water-filled cuvette and a vertically oriented laser fiber (200 μm core diameter) with its tip at 9 mm for "quasi-free" bubble generation and at vapor channel working distances 1-5 mm from and centered on the transparent cuvette bottom simulating a target's surface. Laser power transmission is recorded and synchronized with video frames from a high-speed camera (24,260 frames per second) to capture the induced vapor channels' and bubbles' development. Laser-induced channel transmission from 0% to 100% for 1, 2, and 3 mm fiber-target distances undergoes oscillations with average periods of 0.32, 0.64, and 1.0 ms, respectively, for 500 W laser output power. For fixed fiber-target distances of 0.5, 1, and 2 mm, the variation of these average oscillation frequencies across laser powers from 500 to 1000 W is much smaller, not exceeding 14%. For fiber-target distances in the range of 1-5 mm, the fraction of the 500 W laser's total pulse energy delivered to the target for 1, 2, and 3 ms pulses linearly decreases from 0.78 to less than 0.2. The channel and bubble dynamics begin with a spherical seed bubble expansion centered on the distal fiber tip that evolves into a pear shape whose surface exhibits periodic irregularities attributable to laser beam interruption by water droplets within the developing bubble. The study of laser-induced channel oscillations provides quantitative information relating fiber-target distance to channel oscillation frequency and energy transmission onto a target. These oscillations directly effect ablation efficiency and ablation rates that are important parameters for the optimization of a procedure's safety and duration. Insights that may lead to further reduction in retropulsion are also presented. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.

Event-triggered iterative learning containment control for one-sided Lipschitz nonlinear singular switched multi-agent systems with multiple leaders and error quantization

In this work, under a repeatable control environment, the iterative learning containment control issue for multi-agent systems with one-sided Lipschitz nonlinear singular switched dynamics is addressed. It focuses on the output containment for one-sided Lipschitz nonlinear singular switched multi-agent systems (SWMASs) with multiple leaders, for which an event-triggered containment quantized iterative learning control (QILC) scheme is designed. Due to the limited system resources, SWMASs are often restricted in their communication capabilities and the frequency of controller updates in many applications, the proposed event-triggering mechanism can greatly restrict the use of communication and computation resources throughout the iterative learning process. When the triggering requirement is met, the event-triggered QILC input is repeatedly updated; alternatively, the control input stays unchanged. To conquer the nonidentical initial states of followers, an initial state learning with error quantization and event-triggering is also utilized. By virtue of some appropriate learning gains and sufficient convergent conditions, the containment error convergence can be accomplished for one-sided Lipschitz SWMASs. Finally, some numerical examples via Matlab are provided to demonstrate the efficacy of the event-triggered QILC scheme, it indicates that followers’ outputs can converge to the convex hull formed by leaders and the containment errors gradually converge to the 10−3 - vicinity of the origin along the iteration axis, where the communication resources can save more than 50% in the transmission channel.

Adaptive neural network event-triggered secure formation control of nonholonomic mobile robots subject to deception attacks

This paper investigates the adaptive neural network (NN) event-triggered secure formation control problem for nonholonomic mobile robots (NMRs) subject to deception attacks. The NNs are employed to approximate unknown nonlinear functions in robotic dynamics. Since the transmission channel from sensor-to-controller is vulnerable to deception attacks, a NN estimation technique is introduced to estimate the unknown deception attacks. In order to alleviate the amount of communication between controller-and-actuator, an event-triggered mechanism with relative threshold strategy is established. Then, an adaptive NN event-triggered secure formation control method is proposed. It is proved that all closed-loop signals of controlled systems are bounded and the formation tracking errors converge a neighborhood of the origin in the presence of deception attacks. The comparative simulations illustrate the effectiveness of the proposed secure formation control scheme.

Wireless Channel Propagation Model for Inland Waterway Bridge Scenario

Intelligent shipping is a crucial part of the transportation system, while inland river intelligent shipping is a major safeguard of intelligent transportation. Compared with the studies of mobile fading channels in land-based environments, less current research has focused on channel measurements and modeling for inland waterway bridge environments. In this paper, a segmenting radio channel model is proposed for inland highway and railway combined bridges. The ship's path under the bridge was divided into three phases, and the attenuation of signal strength was modelled separately for each. Hence, it shows ship-to-ship wireless channels in different areas and path loss on inland navigation bridges. A segmented model, instead of a basic path loss model, can accurately forecast path loss and provide a practical approach in ship-to-ship wireless channel transmission scenarios over bridges. Consequently, the channel measurements and modeling in the typical inland waterway are of great significance for establishing a reliable inland navigation broadband radio communication system.

Do natural resources influence E-government in developing countries? Effects and transmission channels

E-government has taken a prominent place in the political and economical debate. Despite the vast non-consensual literature, on the effects of natural resources, very little is known about the effects of these resources on the development of e-government. This study aims to fill this gap by analyzing the effect of natural resources on the development of e-government in a panel of 121 developing countries over the period 2003–2021. Through several empirical approaches, our results show that, on average, natural resource rents negatively affect the development of e-government. Distinguishing between different types of natural resources, we note that the negative effect of natural resources on the development of e-government remains, and the magnitude is more persistent for forestry, gas and oil rents. Furthermore, the mediation analysis suggests that the negative effect of natural resources on the development of e-government is influenced by trust in institutions, the size of the informal sector, corruption, and the quality of telecommunications infrastructures.

Climate pattern effects on global economic conditions

This study investigates how El Niño–Southern Oscillation (ENSO) climate patterns affect global economic conditions. Prior research suggests that ENSO phases, particularly El Niño, influence economic outcomes, but with limited consensus on their broader macroeconomic impacts. Using a novel monthly dataset from 20 economies, covering 80% of global output from 1999 to 2022, we employ a global augmented vector autoregression with local projections (GAVARLP) model. The empirical findings suggest that El Niño boosts output with minimal inflationary effects, reducing global economic policy uncertainty, while La Niña raises food inflation, which can amplify aggregate inflation as a “second-round” effect, amplifying uncertainty. These findings shed light on the transmission channels of climate shocks and highlight the significant role of ENSO in shaping global economic conditions, emphasizing why climate shocks should be a concern for policy markers.

An Intelligent Distributed Channel Selection Framework with Hybrid Mode Selection for Interference Mitigation in D2D based 5G Networks

Device-to-device (D2D) communication is an essential part of the 5G system used in cellular networks, which enables devices to communicate with each other without passing the base station BS. It is likely to aid in satisfying increasing capacity and effectively offloading traffic from the BS by distributing the transmission between D2D users from one side and cellular users and the BS from the other side. It results in improved throughput, energy efficiency, and other parameters. At the same time, the introduction of D2D communication in cellular networks creates new technical challenges to be addressed. One of the major issues is the mitigation of interference between device users (DUs) and primary users (PUs). This issue leads to performance degradation if it is not managed properly. In this paper, an intelligent distributed channel selection framework (IDCSF) in D2D communication for 5G networks with hybrid selection modes of D2D is proposed to help DUs select the best channel for transmission to mitigate interference. This channel selection framework classifies the available sensed channels using self-organizing map (SOM) learning technique into four classes considering channels with sensing errors false alarm (FalsA) and miss detection (MissD) to prevent using occupied channels. Furthermore, PU activity model is adjusted to aid in recovering from bad channel selection decisions. Moreover, fuzzy logic technique is utilized to determine the reliable channels which can help the DU along with channel selection algorithm to find channel&amp;rsquo;s weight values. The channel with highest weight value is selected as the best channel. Simulation results show that the proposed framework IDCSF enhances selecting the best channel, improves throughput and spectral utilization, and reduces average delay, interference and search time compared to other approaches.

How Banks are Impacted by and Mediate the Economic Consequences of Natural Disasters and Climate Shocks: A Review

AbstractNatural hazard shocks (such as natural disasters, extreme weather events, and climate shocks) have significant negative consequences for real economic activity. The banking sector can mitigate (or exacerbate) some of these consequences. This paper reviews the recent empirical literature on how banks are affected by such shocks, and how banks mediate the economic consequences to households and the real economy. After conceptualizing the theoretical transmission channels between the real economy and the banking sector, the review proceeds in two steps. First, it synthesises the existing literature on the direct effects of natural hazard shocks on bank stability, bank profitability, and credit supply. Then, the critical role of banking in economic recovery is analysed, including research on spillovers into unaffected regions through the banking system. Negative direct effects of natural hazard shocks on banks can be significant but are often transitory. Banking systems in less developed countries appear more vulnerable and are less able to maintain credit supply under adverse conditions. Banks that are better capitalised and that have incentives to support affected economies contribute to economic resilience. The review identifies several avenues for future research and highlights specific features and trade-offs relevant to policymakers interested in enabling the banking system to contribute to sustained economic development in the face of worsening physical climate risks.

Improving the efficiency of resource allocation in educational content delivery networks using the 1C:ESB integration bus

Learning Management Systems (LMS) play a key role in the educational process by providing students with various educational content and instructors with tools to monitor student knowledge and assess progress. However, as the number of students increases, the load on data transmission channels increases, which can lead to a decrease in the quality of learning. To solve this problem, Content Delivery Networks (CDN) are used to speed up the loading of websites and reduce the load on servers. CDN ensure the availability and security of websites and improve their scalability (resistance to smooth load growth) by distributing content across a network of servers around the world, allowing users to access content faster and more efficiently.Integration data exchange bus (Enterprise Service Bus, ESB) can be an effective tool for optimizing CDN content distribution algorithm. It allows integration of different systems and applications, enabling data exchange between them. This is particularly useful in the context of distance learning, which requires fast and reliable delivery of educational content, feedback, learning analytics, etc. Implementing an integration bus of data exchange with LMS-based distance learning system can be a key factor in ensuring an efficient and quality educational process. The article considers the properties and characteristics of the integration bus and justifies the use of the integration bus to optimize the algorithm of CDN content distribution, in particular in LMS.

The spillover and contagion effects of sovereign risk on stock markets

This study examines the spillover effects of sovereign risk on international stock markets using a dynamic spatial Durbin model (SDM) on a panel of forty countries from 2009Q1 to 2024Q2. The findings show that an increase in sovereign risk, as measured by CDS spreads, leads to a significant decrease in both local and foreign stock prices, with 0.027 percent reductions across foreign markets on average. These effects are transmitted through geographical, and economic and financial channels, with exchange rates, gross fixed capital formation, and industrial production playing crucial roles in influencing stock market performance. Additionally, the negative (positive) spillover effects from rising gross fixed capital formation and sovereign risk (industrial production) demonstrate how foreign markets are more impacted than domestic ones. The study highlights the interconnected nature of global financial markets, reinforcing the need for coordinated international policy responses to mitigate the transmission of sovereign risk across borders. These findings provide new insights into how global economic factors influence stock market volatility, particularly through specific transmission channels, underscoring the importance of multilateral collaboration in managing sovereign risk.

Were the tables of Ibn Isḥāq al-Tūnisī known in Paris c.1300?

Two Latin sources from the years around 1300 (John of Sicily’s commentary on the canons to the Toledan tables and a parchment slip documenting the astronomical activities and observations of Alard of Diest) contain brief references suggesting that Parisian scholars of this period had access to a set of astronomical tables for Tunis known as tabulae Benesac. According to the argument developed in this article, the tables in question probably corresponded to a Maghribī zīj originally created by Ibn Isḥāq al-Tūnisī in c.1222. The article goes on to discuss the possible channels of transmission that could have brought these tables to Paris as well as the potential implications of this finding for the history of Latin astronomy in the late 13th and early 14th century. Attention is also drawn to the presence of eclipse-related material from the Muqtabas zīj by Ibn al-Kammād in a Northern French manuscript of the second half of the 13th century, which was independently translated from the Arabic and accordingly does not derive from the well-known translation by John of Dumpno (Palermo, 1260).

Current-carrying low friction of hydrogenated amorphous carbon film

Hydrogenated amorphous carbon (a-C:H) films, which equip excellent low friction performance but insulated, are naturally excluded from sliding electrical contact applications. In this work, we achieved current-carrying low friction of a-C:H film by utilizing a triboelectric triggered ignition effect. Protective resistors were introduced in the circuit during run-in for effectively alleviating undesired arc ablation. A T-shape crystalline structure of graphite was observed in the wear track by transmission electron microscopy. The parallel-aligned graphite at the top surface induced low friction, while the vertical-aligned graphite in the interior formed efficient electron transmission channels. This study expands the selection range of current-carrying friction films and provides a novel insight for the design and regulation of current-carrying friction films.

Telemedicine data secure sharing scheme based on heterogeneous federated learning

The forward triage characteristic of telemedicine highlights its importance again in the COVID-19 pandemic. Telemedicine can provide timely emergency response in the case of environmental or biological hazards, and the patient’s medical privacy data generated in this process can also accelerate the establishment of models for preventing and treating infectious diseases. However, the reuse process of telemedicine user privacy data based on federated learning also faces significant challenges. Differences in regions, economic levels, and grades lead to heterogeneous data and resource-constrained environments, seriously damaging the federated learning process. Besides, the weak password authentication of medical terminals and eavesdropping attacks on transmission channels may cause illegal access to terminals and platforms and leakage of sensitive data. This paper proposed a telemedicine data secure-sharing scheme based on heterogeneous federated learning. Specifically, we proposed a heterogeneous federated learning scheme with model alignment to guide telemedicine practice through the reuse of telemedicine data; in addition, we designed an SM9 threshold identity authentication scheme to guarantee that the patient’s medical privacy data is protected from leakage during the federated learning process. We evaluated our scheme using two third-party medical datasets. The evaluation results indicate that this scheme can still assist the federated learning process in resisting data heterogeneity and resource constraints with almost no performance cost.

Regulating the Pore Structure and Heteroatom Doping of Soybean Straw Carbon Based on a Bifunctional Template Method for the High-Performance Carbon Supercapacitor.

The previous research addressed the waste problem of agriculture and forestry residues by exploring the efficient utilization of liquefied soybean straw in supercapacitor. The structures of the liquefied soybean straw were controlled by coupling microwave hydrothermal treatment with carbonization under the influence of a C3N4 bifunctional template. What's more, C3N4 could effectively regulate the pore structures and provide an effective N active site of carbon materials C3N4. The obtained N-SLR Carbon-700 possess a specific surface area of up to 1593.7 m2 g -1, and the pore size is mainly concentrated in the range of 1.8-2.5 nm, providing efficient ions transmission channels and storage space. Its specific capacitance is up to 261.5 F g-1 (current density of 0.5 A g-1), and the capacity retention is 74.04 % when the current density is expanded by 20 times. In the two-electrode system, the energy density of N-SLR Carbon-700 could reach to 31.3 W h kg-1 at a power density of 360 W kg-1, as well as the energy surface density is maintained at 69 % when the power density is increased by a factor of 20. This work enhances effectively the charging and discharging stability and capacitance value of carbon-based supercapacitor.