Link Performance Research Articles

Seismic Performance of IWF Flexural Link in Inverted-V Eccentrically Braced Frames With Different Stiffener Spaces

Resistant structures, such as Eccentrically Braced Frames (EBFs), are required to be established in earthquake-hazard areas. In EBFs, an essential beam component, known as link, plays a crucial role in determining the performance of these structures. As the seismic energy dissipator, link experiences failure to prevent heavy damage to other EBFs members, such as beams and columns. Although several studies have been carried out to enhance the seismic performance of link, there is still limited regarding these elements. Therefore, this study aimed to investigate several IWF flexural links constructed in FE models of Inverted-V EBFs. A total of three flexural links with different stiffener spaces were considered namely non-spacing, 250 mm, and 100 mm stiffener spacing links. To assess their performance, cyclic loading with yield displacement control was used in EBFs models. Observations were mainly conducted on EBFs performances consisting of strength, stiffness, and dissipation energy. The results showed that the best seismic performance was specified on a 100 mm-stiffener spacing link by presenting the largest and most stable hysteresis curve. Based on these results, the configuration of the narrow space stiffener in the link element was recommended to improve the seismic performance of EBFs.

Pre-Coded Inter-Satellite Routing Algorithm with Load Balancing for Mega-Constellation Networks

In order to achieve global multiple seamless coverage, space-based internet usually adopts low Earth orbit (LEO) mega-constellation networks structure, which has the characteristics of high network topology dynamics, limited on-board computing and storage capacity, and uneven distribution of ground traffic. Such features may cause problems such as high transmission delay, network congestion and link interruption. Establishing a stable, efficient and balanced satellite communication link can effectively alleviate the performance of the transmission delay, load balancing, and network throughput. Taking advantage of the regularity of network topology, a pre-coded inter-satellite routing algorithm with load balancing is proposed, which includes 3 parts: (a) the routing sequence coding method and the concept of gateway satellite Service Region (GSSR) are proposed; (b) the initial routing sequence of GSSR is generated based on the maximum network flow method under the ideal situation of uniform satellite traffic distribution; (c) aiming at the uneven distribution of traffic, the Sinkhorn algorithm is used to improve the load balancing performance of inter-satellite links. Simulation results show that, for the Starlink Group-4 constellation, the proposed method can maintain a low transmission delay and improve the load balancing together with the network throughout performance with minimal hops and low time complexity.

Research on commercially electric wheelchairs and improving the running performance of passive link of joystick-type 6-wheel electric wheelchairs on uphill and downhill roads Part 1

Research on commercially electric wheelchairs and improving the running performance of passive link of joystick-type 6-wheel electric wheelchairs on uphill and downhill roads Part 1

Application of multi-source remote sensing technology in UAV communication control system

Abstract Unmanned aerial vehicles (UAVs) are crucial in various sectors but face challenges in communication reliability. This paper introduces a cutting-edge UAV communication control system, designed using time-series synthetic aperture radar interferometry (InSAR) technology and support vector machine (SVM) classification. Our findings reveal exceptional communication link performance across multiple flight scenarios, notably achieving a bit error rate (BER) of 0.001% in cruising mode. Additionally, the system demonstrated remarkable reception sensitivity, closely aligning with theoretical predictions at −81.1 dBm. This innovative approach utilizes multi-source remote sensing to significantly enhance UAV communication, offering a novel strategy for addressing UAV communication dilemmas.

Emulation and Testbed Prototyping of Laser Beam Propagation Characteristics through Atmospheric Turbulence for Optical Satellite Feeder Links

Two classical scenarios in space communications can be examined to evaluate the link performance of free space optical communications (FSO). These scenarios include the downlink and uplink between earth ground stations and near earth geostationary (GEO) satellites, as well as between the earth and spacecraft that are located a significant distance from the earth (i.e., one or more astronomical units (AU) away). Deep space is often defined as being more than 0.01 AU, or around 1,500,000 km, from Earth. In the first part of this analytical research, various practical system characteristics for optical lasers, telescopes, transmitters, receivers, and atmospheric disturbances, including absorption and scintillation, are taken into consideration. The simulation outcomes were compared to significant experimental data from DLR & JAXA’s OICETS/Kirari-Japan to validate the extended simulation model. Additionally, this work will propose a synthetic effects-based optical turbulence generator in order to deeply investigate atmospheric turbulence disturbances in free-space optical communication systems and support the advancement of artificial intelligence processing-based mitigation solutions. Worth mentioning, the initial outcomes and analytical comparisons demonstrate the preliminary viability of the simulation model for the link budget and scintillation estimation for FSO investigations, which can give deep insight into the development of the proposed testbed prototyping, machine learning-based laboratory measurement system, and enhancement possibility for FSO project design and execution for longand medium-term space mission planning.

A development of mobile application satellite link budget calculator – SATELEC

Link Budget is a calculation of gains and losses during transmission from transmitter to receiver in each communication system. In satellite communication, the main purpose of calculating link budget is to analyse the satellite system performance. One of the parameters to measure the satellite link performance is the Carrier to Noise ratio (C/N). There are a few satellite link calculators were developed using MATLAB/GUI and website. However, there are no available apps to help student to compare the calculated satellite link budget calculator for self-study. Therefore, a mobile apps called SATELEC was developed to calculate satellite link budget parameters. By using this satellite link budget calculator apps, all parameters such as Effective Isotropic Radiated Power (EIRP), Power Flux Density, Path Loss, Antenna Gain and Power Received can be calculated. After the value of power received is obtained, the value of Carrier to Noise ratio (C/N) can be determined by taking into account the noise in the communication. Results shows values obtained from the mobile is reliable after comparison with calculated value.

A SYSTEMS APPROACH TO PRACTICE TRANSFORMATION FOR BRAIN HEALTH INTEGRATION INTO COMMUNITY HEALTH CENTER SERVICES

Abstract Community Health Centers are America’s largest and most successful primary care system, providing access to quality healthcare services to more than 30 million Americans through more than 14,000 service delivery locations regardless of patients’ ability to pay. The National Association of Community Health Centers (NACHC) provides the training and education that health centers need to advance practice transformation and improve care delivery models to succeed in value-based care and meet the needs of patient populations. Through the Value Transformation Framework (VTF), NACHC provides an approach to support health center systems change, organizes and distills evidence-based interventions, provides knowledge, tools and resources, and links performance to the Quintuple Aim – improved health outcomes, patient and staff experience, reduced costs, and equity. NACHC guides health centers in the application of the VTF through a nation-wide learning community, Elevate. Health center participation in Elevate is linked to improved performance on clinical quality measures, improved patient and staff experiences, and reduced costs. Within the Elevate, NACHC successfully implemented a learning track focused on brain health, offering health center-specific guidance on a clinical introduction to Dementia early detection/risk reduction; incorporating Dementia early detection/risk reduction into care management workflows and leveraging reimbursement opportunities; and strengthening community linkages and partnerships to support Dementia early detection/risk reduction. Evaluation data from this learning track indicates health center interest in continuing education related to brain health integration into health center services. This topic is especially relevant considering the increasing population segment of older adult patients that health centers serve.

Emerging Data-Driven Calibration Research on an Improved Link Performance Function in an Urban Area

The reliability of urban transportation systems is crucial for ensuring smooth traffic flow and minimizing disruptions caused by external factors. This study focuses on improving the stability and efficiency of transportation systems through the calibration of a refined link performance function while building upon the U.S. Bureau of Public Roads (BPR) model. To achieve this, we propose three customized algorithms—Newton’s method, Bayesian optimization, and the differential evolutionary algorithm—to calibrate the key parameters. Additionally, we conducted a sensitivity analysis to assess the influences of the model parameters on link performance. Numerical experiments conducted in Yuyao City demonstrate the applicability and efficacy of the proposed model and solution algorithms. Our results reveal that the Newton approach is notably more efficient than the Bayesian optimization algorithm and the differential evolutionary algorithm.

Experimental study on seismic performance of two-segment replaceable link with separated splicing plates

Traditional I-beam sections connected with end plates face challenges related to end bolts and excessive residual deformation. In response to these challenges, this study introduces an innovative concept: two-segment replaceable links with separated splicing plates. Two variations of replaceable links have been designed - one with separated splicing plates featuring standard bolt holes, and another with short slotted bolt holes. Cyclic loading tests has been conducted to study their seismic performance. The test results reveal that the failure modes of the links include flange buckling and tearing at the welds connecting the flange and end plate. The hysteresis curves of the specimens are complete and stable. The average overstrength coefficient of the links is 1.75, meeting the specified limit requirement for an overstrength coefficient greater than 1.5 for the link. The ultimate plastic rotation reaches up to 0.19 rad. Notably, specimens with short slotted bolt holes exhibit a relatively significant energy dissipation ratio due to bolts slip during test and they demonstrate optimal replaceability in terms of minimized replacement time and residual shear rotation. Furthermore, the two-stage design method for high-strength bolts in splicing plate is proposed considering bolts slip.

Enhanced Charging/Discharging Process in Perovskite Active Light Source for High‐Speed Visible‐Light Communication

AbstractMetal halide perovskites are promising light source materials for visible light communication (VLC) due to their excellent photoelectric properties and small resistance‐capacitance time constant. However, previous reports mainly used perovskites as the passive light sources, which not only makes it susceptible to posterior excitation light sources, but also complex in the integration process. Herein, the quasi‐2D PEA2Csn‐1PbnBr3n+1 perovskite light–emitting diodes (PeLEDs) as an active light source in VLC link is demonstrated. It is found that the charging/discharging process of PeLEDs is an important factor governing the ‐3 dB bandwidth (f‐3 dB) of the VLC. To improve this, 3‐sulfopropyl methacrylate potassium salt (SMPS) molecules are introduced into perovskite to simultaneously passivate deep and shallow energy level defects at grain boundaries. Additionally, the multiple quantum wells structures of PEA2Csn‐1PbnBr3n+1 are modified to be flat. At the optimal SMPS concentration, the maximum external quantum efficiency of PeLEDs reaches 21.5%. Meanwhile, the VLC achieves 3.2 MHz f‐3 dB with data transmission of 18.6 Mbps, which is the highest f‐3 dB in PeLEDs with the same active area. Hence, it provides a versatile method to improve the performance of VLC links based on active light sources and advances toward the goal of high‐speed, energy‐efficient and secure free communication.

Estimating network flow and travel behavior using day-to-day system-level data: A computational graph approach

To estimate network flow and travel behavior under recurrent traffic conditions, we leverage computational graphs and multi-source system-level data and solve a single-level optimization problem consistent with stochastic user equilibrium under logit assignment (SUELOGIT). Our model learns time-specific O-D matrices and utility functions and network flow parameters such as link flows, path flows, and travel times. To increase the model’s representational capacity for reproducing observed link flows and travel times, the parameters of the link performance functions are assumed link-specific. More importantly, the utility function in the route choice model is enriched with (i) link-specific parameters to capture the effect of unobserved attributes on route choices and (ii) period-specific parameters weighting the observed features in the utility function to capture the heterogeneity of travelers preferences among periods of the day. Experiments on synthetic data show that the parameters of the models can be consistently recovered and that the solution of the model satisfies the SUELOGIT conditions with high accuracy. The estimation procedure is also robust to random noise in both the observed traffic flow and travel time, and it requires very few hyperparameter tuning. Subsequently, the algorithm is deployed at a large scale using real-world multi-source data in Fresno, CA, with hourly data collected during the morning and afternoon peak periods of October 2019. The utility function includes link-specific effects and attributes such as travel time, the standard deviation of travel time, the number of traffic incidents, and socio-demographic information obtained from the US Census. We obtain estimates for the total trips and travelers’ utility function by hour of the day and for the average values of the link performance parameters that are reasonable and informative on the demand and supply characteristics of the transportation network.

Rainbow link beamforming technology and relevant analysis

In the 5G era, millimeter wave has been mentioned as an important position. Millimeter wave has some problems that cannot be ignored: the free space path loss and atmospheric attenuation. To overcome these problems, millimeter wave systems rely on beamforming to overcome losses. Traditional techniques utilize phase antenna arrays for beamforming, which can cause delays in the time consumption and beam scheduling, and due to limited beams, this technology can only be connected to a limited number of devices, and each transmission occupies the entire bandwidth. This paper introduces a new technology called rainbow link, which is implemented by a new true time delay (TTD) array structure. This technology can achieve the allocation of different subcarriers to a large number of users in the corresponding beamforming direction. Users only need to select appropriate frequency resources. In this work, we calculate the performance of rainbow link with different parameters, and our results show that given 1 GHz bandwidth using 64 element antenna arrays, a rainbow-link cell achieves 1ms latency and 0.6M symbols per second with 0.03 active user rate.

Two-way differential strategy for wireless sensor networks

In this paper, a novel optimal two-way amplify and forward (AF) differential beamforming method for wireless sensor network is proposed. The proposed method is an advanced signal processing technique used to enhance the performance and reliability of the communication link by exploiting the diversity provided by multiple antennas. Unlike current state-of-the-art methods which require the knowledge of channel state information (CSI) at both transmitting and receiving antennas or at least at the receiving antennas, the suggested method does not need CSI at any transmitting or receiving antenna. Moreover, the proposed method enjoys high error performance with high diversity and coding gain and has a very low encoding and decoding complexity. Through our simulations, the proposed method is proved to outperform the best known non-coherent multi-antenna methods.

Outage Performance of Uplink Pre-Amplified FSO Links Over Turbulence, Beam Wander, and Pointing Errors

Outage Performance of Uplink Pre-Amplified FSO Links Over Turbulence, Beam Wander, and Pointing Errors

Joint Power Control and Resource Allocation for Optimizing the D2D User Performance of Full-Duplex D2D Underlying Cellular Networks

D2D communication is a promising technology for enhancing spectral efficiency (SE) in cellular networks, and full-duplex (FD) has the potential to double SE. Due to D2D’s short-distance communication and low transmittance power, it is natural to integrate FD into D2D, creating FD-D2D to underlay a cellular network to further improve SE. However, the residual self-interference (RSI) resulting from FD-D2D and interference arising from spectrum sharing between D2D users (DUs) and cellular users (CUs) can restrict D2D link performance. Therefore, we propose an FD-D2D underlying cellular system in which DUs jointly share uplink and downlink spectral resources with CUs. Moreover, we present two algorithms to enhance the performance experience of DUs while improving the system’s SE. For the first algorithm, we tackle an optimization problem aimed at maximizing the sum rate of FD-DUs in the system while adhering to transmittance power constraints. This problem is formulated as a mixed-integer nonlinear programming problem (MINLP), known for its mathematical complexity and NP-hard nature. In order to address this MINLP, our first algorithm decomposes it into two subproblems: power control and spectral resource allocation. The power control aspect is treated as a nonlinear problem, which we solve through one-dimensional searching. Meanwhile, spectral resource allocation is achieved using the Kuhn–Munkres algorithm, determining the pairing of CUs and DUs sharing the same spectrum. As for the second algorithm, our objective is to enhance the individual performance of FD-DUs by maximizing the minimum rate among them, ensuring more uniform rate performance across all FD-DUs. In order to solve this optimization problem, we propose a novel spectral resource allocation algorithm based on bisection searching and the Kuhn–Munkres algorithm, whereas the power control aspect remains the same as in the first algorithm. The numerical results demonstrate that our proposed algorithm effectively enhances the performance of DUs in an FD-D2D underlying cellular network when compared to the sum rate maximization design.

Adaptive Precoding for Aeronautical Communication Systems in Public Channels

The family of aeronautical communication systems is considered as one of the core technologies for the beyond-the-fifth-generation (B5G) networks, thus attracting rapidly increasing attention from both industry and academia. In this paper, a new multiple-input multiple-output (MIMO) precoding scheme is proposed for aeronautical communication systems, where the transmit power for the aerial user equipment (UE) approaching the target cell is maximized based on the direction information. Specifically, we first transform the precoding optimization problem into a linear programming problem, and then develop two algorithms to derive the precoders for two transmission modes, namely the multi-stream and single-stream transmissions. For the multi-stream case, an algorithm based on manifold optimization is proposed, which guarantees the equal power allocation for each antenna. For the single-stream case, we derive a precoder by a numerically stable algorithm that extends the Newton-Raphson method. Simulation results show that the proposed precoding schemes can improve the link performance of the UEs with known directions, while ensuring that the performance of the UEs with unknown directions can still be close to that achievable by conventional schemes.

Column Link Behavior in Eccentrically Braced Composite 3-Dimensional Frames

Eccentrically braced frames are renowned for their capacity to absorb seismic forces while offering greater adaptability. These frames incorporate bracings that are joined to the beams with an intentional offset, forming a connection within the beams. Nevertheless, there are drawbacks associated with implementing these beam connections when renovating frames. This paper seeks to enhance the design approach by introducing an eccentric link within the column of a composite structure. Eccentric braced frames (EBFs) are hybrid systems that offer both ductility in moment resisting frames (MRFs) and lateral stiffening in the concentrically braced system. The study examines composite frames with 5, 10, and 15 stories using eccentric X- and V-type bracings with an eccentricity of 0.5 m and 1 m. Three different earthquake zones are considered, based on Indian seismic code provisions: zone 3, zone 4, and zone 5. The structures are analyzed computationally by nonlinear time history analyses. The lateral load-resisting behavior of the structure with the same eccentricity in beam links and column links is compared. Then, the structure is subjected to a pushover analysis to study the performance characteristics such as capacity curve, lateral displacement, inter-storey drift, and plastification of the structure. As anticipated, compared to conventional moment resisting frames (MRFs) and concentrically braced frames (CBFs), eccentrically braced frames have better energy dissipation. Furthermore, the behavior of X-braced column links is found to be similar to the performance of beam links, but V-braced frames showed better performance in column link frames than in beam link frames. Also, the increase of the link length played a major role in the ductility of the frames.

Generation and free-space transmission characterization of bottle vortex beam

Vortex beams carrying orbital angular momentum (OAM) with the doughnut-shaped intensity distribution can be employed in free-space optical (FSO) communication links to circumvent obstructions. However, the size of the receiver aperture is proportional to the size of obstructions, which seriously constrains the application of OAM beams in this scenario. In this paper, we propose a method to generate bottle vortex beams (BVBs) with a parabolic trajectory by manipulating the radial phase distribution of conventional OAM beams. Meanwhile, the trajectory of BVBs generated are highly compatible with the predesigned trajectory by using this method. Moreover, we evaluate the free-space transmission performance of BVBs under atmospheric turbulence and limited receiving aperture. The results show that BVBs have better OAM FSO communication link performance compared with conventional OAM beams and Bessel beams. In addition, the performance of the BVBs circumventing obstructions is further investigated. The simulation results show that when setting the atmospheric turbulence strength D/r0 = 2 and the obstruction size of 40 mm, the average received optical power of the BVBs captured by a limited receiving aperture diameter (d = 40 mm) is improved about 7 dB and 3 dB compared to conventional OAM beams and Bessel beams, respectively.

Unified performance parameters for IM/DD techniques over gamma-gamma fading channel with pointing errors

In this paper, we discuss the performance of different intensity modulation direct detection techniques (IM-DD) used in free space optical systems (FSO) under different channel impairments such as path loss, atmospheric turbulence, and pointing errors. We derived unified formulas for each of the average symbol error rate (SER) bounds and outage probability for different modulation techniques: OOK, MPPM, and LMPPM. The accuracy of the obtained formulas is validated through comparison with MC-simulation results. Finally, we investigate the effect of system parameters on FSO link performance.

Performance analysis of underwater vertical wireless optical communication links using selection combining.

In this paper, we have investigated the performance of underwater vertical wireless optical communication (UVWOC) links employing on-off key modulation for selection combining based receive diversity schemes in the presence of underwater turbulence, pointing errors, and attenuation losses. Due to variations in temperature and salinity along the ocean's depth, turbulence-induced fading affects the performance of the underwater vertical wireless optical link. The vertical link of the underwater medium influenced by a strong turbulence regime is modeled using cascaded gamma-gamma distribution considering multiple non-identical layers along with attenuation losses and pointing errors. We have derived closed-form expressions for the average bit error rate (BER) and outage probability (OP) for the link employing multiple detectors at the receiving end. The accuracy of all of the closed-form expressions derived in this paper has been validated using Monte Carlo simulations.