Access Scheme Research Articles

Hybrid vehicular access protocol and message prioritization for real-time safety messaging

Real-time safety services rely on the exchange of messages to enhance the operations of connected and automated vehicles (CAVs). These safety messages convey vital information about traffic conditions, enabling drivers to take necessary measures to prevent accidents. The timely and reliable delivery of these messages is essential, necessitating efficient channel access. Vehicular Deterministic Access (VDA) is employed as a channel access scheme with distinct priorities and stringent timing guidelines, particularly for urgent safety warnings. In this paper, we propose a hybrid approach that combines VDA and Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocols, along with a message prioritization algorithm, to ensure efficient and reliable communication of safety messages in vehicular networks. Our approach leverages the strengths of both VDA and CSMA/CA to avoid message collisions; VDA is more efficient under high traffic loads, while CSMA/CA is better suited for low traffic loads. Additionally, the incorporation of the message prioritization algorithm ensures strict deadline guarantees for high-priority messages, such as Decentralized Environmental Notification Messages (DENMs). We evaluate our proposed solution using the Artery simulation framework. Our results show over a 93% delivery rate for DENM exchanges while maintaining low collision probability across various traffic loads. This research provides practical guidance for the development of efficient and reliable communication systems for CAVs. It also offers a detailed analysis of the trade-offs among different access protocols and message prioritization strategies in vehicular networks.

Physical activity and social-emotional learning in Canadian children: Multilevel perspectives within an early childhood education and care setting

Early childhood education and care programs can support physical activity and socio-emotional skills development. However, limited research has investigated the longitudinal associations between these constructs and whether they vary across child-specific and classroom-wide levels of analysis. The present study evaluated three-month trajectories of social and emotional competencies, with an emphasis on associations with physical activity. Participants were children enrolled in a licensed not-for-profit early childhood education and care provider in Canada. Educators (n = 37) across 22 classrooms completed monthly assessments of children (N = 235) from January–March 2020. Intraclass correlation coefficients revealed that significant variability in socio-emotional strengths could be attributed to between- and within-classroom differences (21 % and 47 %, respectively), and change over time (32 %). In three-level random-slopes growth curve models, socio-emotional strengths increased over time, with significant between-classroom differences in initial averages and rates of change. Child-specific and classroom-average levels of physical activity were also associated with socio-emotional strengths. These findings underscore the importance of considering child and classroom differences in early learning contexts. Moreover, incorporating physical activity in these settings holds promise as an accessible strategy to support children’s social and emotional development.

Isocyanurate‐Derivative Enables Highly Compatible Poly‐Dioxane Electrolyte for Dendrite‐Free Li Metal Batteries

AbstractThe Li+ transport kinetics and electrochemical stability of advanced solid‐state Li metal batteries (SLMBs) are seriously limited by the actual electrolyte compositions. Here, a novel polyether‐based electrolyte (PTGDOX) is presented through in situ co‐polymerization by integrating 1,3‐dioxane with a multifunctional 1,3,5‐triglycidyl isocyanurate additive. The isocyanurate group in PTGDOX not only provides abundant coordinating sites for Li+ transfer and restricts the movement of anions, but also prompts a beneficial inorganic‐rich solid electrolyte interface on the Li electrode. As a result, PTGDOX exhibits a remarkably increased ionic conductivity of 0.48 mS cm−1 at 30 °C and a reasonable Li‐ion transference number of 0.68, enabling the Li||Li symmetric cells to stably cycle for over 2000 h at 1 mAh cm−2. Meanwhile, the assembled Li||LiFePO4 exhibit a 97.4% capacity retention after 700 cycles at 3 C with excellent thermal stability. Moreover, PTGDOX also demonstrates excellent interfacial compatibility with high‐voltage LiNi0.8Co0.1Mn0.1O2 cathode. As such, this work provides a facile and accessible strategy for designing interface‐stable polymer electrolytes and achieving practical dendrite‐free SLMBs.

UAV aided NOMA relaying with energy harvesting architecture: Performance analysis

In this work, we consider a dual hop Non Orthogonal Miltiple Access (NOMA) based communication network between Source S and two destination users UA , UB which is aided by an Unmanned Aerial Vehicle (UAV) relay R. The energy constrained UAV relay harvests energy from signal transmitted by the source through Power Splitting (PS) and further transmits the signal using Amplify and Forward (AF) protocol to the destination users through NOMA. For the proposed network, we derive analytical expressions for outage probability and ergodic capacity. The impact of parameters like PS ratio and UAV altitude is studied on the overall system performance. Further, the performance of the proposed system is also compared with Orthogonal Multiple Access (OMA) scheme. The results obtained show that the energy harvesting capacity of UAV is significantly affected under Linear and Non Linear EH models. The numerical analysis done is verified through Monte Carlo Simulations.

Synthesis and characterization of the dental adhesive monomer 10-MDP

Many studies have demonstrated the excellent performance of 10-MDP (10-methacryloyloxydecyl dihydrogen phosphate) as a functional monomer for dental adhesive materials and as a primer for ceramic surfaces. Although adhesive performance is affected by the purity level of 10-MDP, this parameter is rarely described, and possible byproducts have been suggested in the literature, but have not been identified to date. The present study aims to present an accessible 10-MDP synthesis strategy with easily handled reagents and address the characterization challenges, especially in identifying byproducts. 10-MDP was synthesized from 10-hydroxydecyl methacrylate and phosphorus pentoxide in acetone. The final product was characterized by nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR) and mass spectrometry MALDITOF/TOF. The main chemical groups associated with 10-MDP were identified by 1H, 31P, and 13C NMR analyses. Only mass spectrometry analyses (MALDITOF/TOF) could identify the presence of dimers as byproducts. Its proposed chemical structure indicates that the dimers were formed by the reaction between the phosphate ester groups and others formed by the reaction of the methacrylic group of 10-MDP molecules. Careful adjustment of the synthesis conditions to reduce the formation of these byproducts is also described. The results indicate that the characterization of 10-MDP batches as raw materials is an important task because, depending on the byproduct present, its ability to polymerize or acid etching capacity may be compromised.

Escalating costs of innovative medicines: perspective and proposals.

Public healthcare systems are challenged by the soaring costs of medications that require increasing resources, often at the expense of other investments. The increasing pharmaceutical budget poses a threat to the allocation of funds for essential preventive and primary healthcare services while also raising concerns about equitable access, particularly in models where patients bear part of the costs out of their own pockets. Proposals on how to ensure ongoing and long-term accessibility, efficiency, and financial stability are required. The escalating costs of medicines may be explained in part by the mismatch between the traditional value-based pricing and reimbursement frameworks and the type of clinical development of targeted therapies and precision medicine in clinical practice. New appraisal methods and managed access strategies should be adapted to therapies targeting small populations and addressing increased uncertainty. Fair pricing strategies, transparent healthcare investments based on problems and outcomes, regulatory reforms, international cooperation, and critically examining the drug acquisition model are potential solutions. Transitioning from an industry-driven pricing approach to a health-driven payment model can help align the cost of treatments with actual health outcomes, establishing a foundation for a healthcare system that addresses immediate challenges and fosters long-term well-being. Acknowledging the lack of a universally applicable solution, the practical implementation of interventions requires a reframing of the pricing and access system and adaption to the targeted therapeutic approaches. Balancing innovation with financial sustainability necessitates a collaborative, adaptive, and transparent approach, as well as transitioning toward health-driven payment models, moving the focus from the cost of medications to the well-being of populations worldwide.

How ‘Open’ is Distance Higher Education for Students with Disabilities? A Literature Review

This study attempts to answer the question of how "Open" Distance Higher Education is for Students with Disabilities (SwD) through a literature review. To this end, published books, journals, reports, and articles were examined using authoritative research sources such as Google Scholar, ResearchGate, and ERIC. In addition, laws related to Persons with Disabilities and education were also utilized. This paper is divided into four sections, where accessibility in Open and Distance Higher Education is analyzed in relation to SwD more broadly, concluding in the last section by discussing Open and Distance Higher Education and SwD in Greece. The existing literature and related research are very limited. The findings show that Distance Education offers significant opportunities for inclusive education, mainly due to the flexibility it provides. For students with mobility disabilities, Distance Higher Education offers the possibility of education without geographical limitations, especially when physical presence is impossible due to a lack of appropriate accessible building infrastructure. Furthermore, while multiform distance learning material can enhance accessibility, they can also pose barriers for SwD, as all tools and resources need to be accessible to everyone. Subtitles are an important accessibility tool, especially for deaf or hard of hearing learners. Additionally, examinations should be equally accessible to all learners, regardless of their disability. The distance learning material should be based on the principles of Universal Design for Learning. Also, assistive technologies and voice reading software play an important role, especially for visually impaired learners. Assistive technology and AI tools can help students depending on the type of disability. Under the current circumstances, the accessibility of SwD to Distance Higher Education, including in Greece, faces significant challenges. In conclusion, Distance Higher Education has the potential to support inclusive education, but it is necessary to implement appropriate accessibility standards and strategies.

Characterizing Rotational Dynamics and Heterogeneity via Single-Molecule Intensity Measurements.

Dynamic heterogeneity in glassy systems has typically been characterized at the single-molecule level by extracting rotational relaxation time scales from linear dichroism (LD) collected via two orthogonally polarized channels. However, in such measurements, localization precision is diminished due to photons lost relative to collection in a single detection channel. This poses challenges in characterizing rotational and translational dynamics simultaneously, as translational measurements require high localization precision. In this paper, we present a method for extracting rotational dynamics of glassy systems at the single-molecule level from intensity fluctuations of fluorescent probe molecules in a wide-field configuration without the use of a polarizing optical component. Through numerical analysis, we show that LD and intensity measurements probing rotational dynamics report similar, approximately second-order rotational correlation decays even at low signal to noise. Thus, within the assumptions of small, isotropic rotations, LD and intensity autocorrelation analysis should provide identical information on the time scale and heterogeneity of rotational dynamics. We then present experimental results that validate this numerical result, with direct comparison of LD and intensity-based approaches across probe molecules in both polymeric and small-molecule glass formers as well as across optical configurations. Our results demonstrate moderate correlation on a per-probe basis between rotational time scales obtained from both approaches, with deviations consistent with those expected in a dynamically heterogeneous system. We envision that this easily accessible strategy will be of use across disciplines for characterizing single-molecule rotational dynamics in limited signal situations and/or when high-precision localization is required.

Full-duplex dynamic TDMA scheme and clock synchronization and compensation method for the multi-user UWOC system.

In this Letter, we propose a full-duplex dynamic time division multiple access (FDD-TDMA) scheme for multi-user underwater wireless optical communication (UWOC). It supports full-duplex communication through wavelength division duplex (WDD) and enhances the system throughput using dynamic time resource allocation. Additionally, a clock synchronization and compensation method is proposed for precise clock synchronization without time-keeping. With the proposed FDD-TDMA scheme and the clock synchronization and compensation method, we establish a two-user UWOC system based on on-off keying (OOK) modulation. Experiments are conducted in a 10 m water pool environment. The experimental results show that the designed system can achieve a data rate of 25 Mbps without error codes and 40 Mbps with a bit error rate (BER) below the forward error correction (FEC) limit. The FDD-TDMA scheme notably improves the system throughput when communication demands among users are variable compared to the conventional time division multiple access (TDMA). Moreover, a reduction in phase deviations from microseconds to ten nanoseconds is achieved by the clock synchronization and compensation method.

Co-Creating an Inclusion, Diversity, Equity, and Accessibility Strategy: Defining approach and outcomes in a health data research network

BackgroundHealth Data Research Network Canada (HDRN) has committed to strengthening data use to improve health equity. Key this priority is has been an increased operationalization of Inclusion, Diversity, Equity, and Accessibility (IDEA) across the organization and within the data research processes HDRN Canada supports. Missing, however, was a unifying strategy for embedding IDEA within all HDRN Canada initiatives. ApproachGuided by results from an internal environmental scan and network feedback, HDRN Canada began developing an IDEA strategy in 2023. With the end goal of embedding IDEA across all internal teams and across all HDRN Canada strategic goals, collaborative participation methods were chosen to involve all levels of the organization. A process was designed that included focus groups, interviews, and roundtables. ResultsCo-creating the IDEA strategy required broad buy-in including detailing expectations of the planning process in advance. A flexible management approach that enabled the team to adhere to the defined process allowed the Project Team to manage unanticipated challenges. 4 key strategies emerged focusing on learning, data quality and research, leadership, and community engagement. Developing the strategy with co-creative methods helped to identify practical approaches for HDRN to prioritize IDEA within its complex data research initiatives. ConclusionHDRN Canada has outlined its commitment to IDEA in the health data ecosystem. The co-created strategy supports efforts towards accomplishing its organizational objectives and priorities. It is also a valuable resource for those in the health data space working to ensure data research contributes to equitable health outcomes.

Cervical Cancer Screening Barriers and Facilitators for Sexual and Gender Minority People: A Community-Engaged Feasibility Approach

The purposes of this study were to identify barriers and facilitators to cervical cancer screening (CCS) among sexual and gender minority (SGM) people and to determine strategies to facilitate increased CCS among these populations. Between August 2021 and December 2022, 33 semistructured, in-depth qualitative interviews were conducted with SGM adults in Kentucky. Interview transcripts were analyzed using inductive content analysis to identify patterns and themes. Barriers to CCS included negative experiences with CCS, negative associations with CCS, and healthcare providers’ lack of SGM population awareness. Facilitators of CCS included positive CCS experiences related to healthcare providers and positive CCS experiences related to healthcare settings. Recommended strategies to increase CCS were SGM population-targeted CCS encouragement and cervical cancer self-screening. Healthcare provider and healthcare system barriers and facilitators have a disproportionate influence on SGM individuals’ CCS behaviors. CCS must be normalized in the SGM community and presented and promoted specifically to SGM populations. Human papillomavirus self-sampling acceptability for SGM populations should be explored. There is a critical need for piloting culturally tailored, innovative interventions supported by healthcare providers, healthcare systems, and SGM community partners, underpinned with acceptable, accessible, and evidence-based cervical cancer prevention strategies for SGM populations.

Advancing Sustainable Development through the lens of Energy Efficiency: A Systematic Literature Review

The global focus on Sustainable Development (SD) encompasses social, economic, and environmental concerns. Energy efficiency plays a crucial role in this transition, defined as efforts to reduce energy consumption by lowering service demand. It is widely recognized as one of the most cost-effective, tested, and accessible strategies to achieve SD, fostering economic growth, social progress, and carbon reduction. To understand the interplay between energy efficiency and SD, a comprehensive review is needed. This study examines previous research on SD through the lens of energy efficiency, utilizing the SCOPUS database to select 46 publications from 2006 to 2022. These studies are categorized by year, publishers, journals, country, sectors, citations, data analysis methods, and sustainable dimensions. The classification helps identify gaps, such as the lack of a unified research framework. Advanced nations conducted 30.43% of the studies, with most research focusing more on environmental aspects than economic or social ones. This study expands the literature by highlighting connections between energy efficiency and SD, aiding scholars and practitioners in promoting sustainable development alongside energy efficiency. Consequently, the literature review focused on empirical research.

Performance enhancement of NOMA multi-user networks with aerial reconfigurable intelligent surfaces and aerial relay

In this article, we propose a combination of multiple aerial reconfigurable intelligent surfaces (ARISs) with an aerial relay (AR) for improving the performance of multiple users adopting the non-orthogonal multiple access (NOMA) scheme. In particular, two groups of ARIS are utilized, one for aiding ground-to-air (G2A) communication and another one for aiding air-to-ground (A2G) communication. Mathematical formulas of outage probability (OP), throughput, and achievable capacity (AC) of every user in the proposed ARISs-AR-NOMA network are derived over the Nakagami-m channel. The propagation environment recommended for the fifth generation and beyond (5G/B5G) is applied to enhance the practical behavior of the proposed network. To confirm the performance enhancement, we compare the OP, throughput, and AC of the proposed system with the conventional AR-NOMA network (i.e., without ARISs). Numerical illustrations demonstrate the great benefits of the proposed ARISs-AR-NOMA network, its transmit power is dramatically lower than that of the conventional network. Moreover, the throughput and AC of the proposed network are considerably higher than the conventional network’s. Based on the effect of key parameters and network behaviors, various effective solutions are recommended to enhance the performance of the proposed ARISs-AR-NOMA network.

Polar coded SCMA-OCDM based on chaotic scrambled SLM

In this work, the polar coded sparse code multiple access (SCMA) scheme based on chaotic scrambled selective mapping (CS_SLM) is proposed for future passive optical networks (PONs). The original bits are coded by polar and mapped into constellation symbols by sparse code. Then orthogonal chirp division multiplexing (OCDM) modulation is adopted which has better anti-interference ability than orthogonal frequency division multiplexing (OFDM). At the receiver, the joint iterative detection and decoding for polar and SCMA is used to further improve the BER performance. The CS_SLM is helpful to improve the reliability and security, while keeping high spectral efficiency of SCMA-OCDM modulation. A 49.42 Gb/s coded SCMA-OCDM PON over 2 km seven-core fiber is demonstrated in the experiment. The results show that the SCMA-OCDM scheme gets a receiver sensitivity of 0.8 dB at a bit error rate (BER) of 3.8 × 10−3, compared with SCMA-OFDM. Because of peak to average power ratio (PAPR), the polar coded SCMA-OCDM based on CS_SLM is compared with clipping and filtering (CAF) method, about 2.08 dB receiver sensitivity gain is obtained when BER is lower than 10−5. The polar coded SCMA-OCDM based on CS_SLM also takes security into the consideration, due to the downlink broadcasting of PON. It can be a promising candidate for the next generation PONs.

Active Detection and Channel Estimation Schemes for Massive Random Access in User-Centric Cell-Free Massive MIMO System

Active Detection and Channel Estimation Schemes for Massive Random Access in User-Centric Cell-Free Massive MIMO System

A Progressive Codebook Optimization Scheme for Sparse Code Multiple Access in Downlink Channels

A Progressive Codebook Optimization Scheme for Sparse Code Multiple Access in Downlink Channels

Multiple Access in Large-Scale LoRaWAN: Challenges, Solutions, and Future Perspectives

Enabling energy-efficient and long-distance wireless networking is expected by various Internet-of-Things systems and consumer electronics applications. Low Power Wide Area Networks can commendably satisfy this requirement because of their combination of low-power and long-range features. Thereinto, open-standard Long Range Wide Area Network (LoRaWAN) is the representative player with hundreds of deployment cases worldwide. Unfortunately, current multiple access (MA) strategy for LoRaWAN has been proved to incur severe wireless signal interference under large-scale deployment. This is the inherent hindrance for current LoRaWAN to support large-scale wireless networking. In this context, this article aims to provide a detailed tutorial of MA issues in large-scale LoRaWAN for the first time. We start with several practical use cases of large-scale LoRaWAN. We then explain the detailed challenges of large-scale LoRaWAN networking. Representative MA solutions for better LoRaWAN networking are then described and compared. Future research directions for enhanced MA protocol design are also discussed.

A flexible strategy to fabricate trumpet-shaped porous PDMS membranes for organ-on-chip application.

Porous polydimethylsiloxane (PDMS) membrane is a crucial element in organs-on-chips fabrication, supplying a unique substrate that can be used for the generation of tissue-tissue interfaces, separate co-culture, biomimetic stretch application, etc. However, the existing methods of through-hole PDMS membrane production are largely limited by labor-consuming processes and/or expensive equipment. Here, we propose an accessible and low-cost strategy to fabricate through-hole PDMS membranes with good controllability, which is performed via combining wet-etching and spin-coating processes. The porous membrane is obtained by spin-coating OS-20 diluted PDMS on an etched glass template with a columnar array structure. The pore size and thickness of the PDMS membrane can be adjusted flexibly via optimizing the template structure and spinning speed. In particular, compared to the traditional vertical through-hole structure of porous membranes, the membranes prepared by this method feature a trumpet-shaped structure, which allows for the generation of some unique bionic structures on organs-on-chips. When the trumpet-shape faces upward, the endothelium spreads at the bottom of the porous membrane, and intestinal cells form a villous structure, achieving the same effect as traditional methods. Conversely, when the trumpet-shape faces downward, intestinal cells spontaneously form a crypt-like structure, which is challenging to achieve with other methods. The proposed approach is simple, flexible with good reproducibility, and low-cost, which provides a new way to facilitate the building of multifunctional organ-on-chip systems and accelerate their translational applications.

Anthropometric Measures, Cardiometabolic and Hepatic Indices, and Cut-off Points for Predicting Type 2 Diabetes Mellitus in Southwest Iran: A Cross-Sectional Study from the Enrolment Phase of the Hoveyzeh Cohort Study

Background: Cut-off points for anthropometric measures associated with diabetes may vary across different ethnic groups. Objectives: This study aimed to identify the optimal cut-off values for these measures and their relationship with cardiometabolic and hepatic indices to predict type 2 diabetes mellitus (T2DM) in southwest Iran. Methods: This cross-sectional study was conducted in Hoveyzeh, Iran, and included a total of 7,300 individuals (1,607 with T2DM and 5,693 healthy participants). Anthropometric, cardiometabolic, and hepatic indices were calculated. Results: The visceral adiposity index (VAI) showed the highest correlation with cardiometabolic indices, such as the cardiometabolic index and lipid accumulation product. The conicity index (CI) had the strongest correlation with hepatic indices, including the hepatic steatosis index and the Alcoholic Liver Disease/Non-alcoholic Fatty Liver Disease (ALD/NAFLD) index. The atherogenic index of plasma was the most significant predictor of T2DM in the Hoveyzeh population for both men (OR: 3.39; CI: 2.38 - 4.81) and women (OR: 5.68; CI: 4.20 - 7.68). The optimal cut-off values for several anthropometric measures were higher in men than in women: BMI (28.0 vs. 25.48), Waist/Height ratio (0.64 vs. 0.56), Weight-adjusted waist index (11.83 vs. 10.76), CI (1.35 vs. 1.29), body roundness index (8.43 vs. 7.33), relative fat mass (44.63 vs. 28.5), and lipid accumulation product (67.23 vs. 67.04). Conversely, the cut-off values for optimal waist circumference (99.45 vs. 98.35), Waist/Hip ratio (0.99 vs. 0.96), VAI (2.22 vs. 2.19), and abdominal volume index (20 vs. 19.6) were higher in women than in men. Conclusions: The atherogenic index of plasma is a highly predictive indicator of T2DM. Our results suggest that novel anthropometric and cardiometabolic indices could serve as accessible and cost-effective strategies for assessing health outcomes related to T2DM.

Unlicensed Spectrum Access and Performance Analysis for NR-U/WiGig Coexistence in UAV Communication Systems

Unmanned aerial vehicles (UAVs) are extensively employed in pursuit, rescue missions, and agricultural applications. These operations necessitate substantial data and video transmission, requiring significant spectral resources. The unlicensed millimeter wave (mmWave) spectrum, especially in the 60 GHz frequency band, offers promising potential for UAV communications. However, WiGig users are the incumbent users of the 60 GHz unlicensed spectrum. Therefore, to ensure fair coexistence between UAV-based new radio-unlicensed (NR-U) users and WiGig users, unlicensed spectrum-sharing strategies need to be meticulously designed. Due to the beam directionality of the NR-U system, traditional listen-before-talk (LBT) spectrum sensing strategies are no longer effective in NR-U/WiGig systems. To address this, we propose a new cooperative unlicensed spectrum sensing strategy based on mmWave beamforming direction. In this strategy, UAV and WiGig users cooperatively sense the unlicensed spectrum and jointly decide on the access strategy. Our analysis shows that the proposed strategy effectively resolves the hidden and exposed node problems associated with traditional LBT strategies. Furthermore, we consider the sensitivity of mmWave to obstacles and analyze the effects of these obstacles on the spectrum-sharing sensing scheme. We examine the unlicensed spectrum access probability and network throughput under blockage scenarios. Simulation results indicate that although obstacles can attenuate the signal, they positively impact unlicensed spectrum sensing. The presence of obstacles can increase spectrum access probability by about 60% and improve system capacity by about 70%.