Optimal Placement Research Articles

A model of task-level human stepping regulation yields semistable walking.

A simple lateral dynamic walker, with swing leg dynamics and three adjustable input parameters, is used to study how motor regulation affects frontal plane stepping. Motivated by experimental observations and phenomenological models, we imposed task-level multiobjective regulation targeting the walker's optimal lateral foot placement at each step. The regulator prioritizes achieving step width and lateral body position goals to varying degrees by choosing a mixture parameter. Our model thus integrates a lateral mechanical template, which captures fundamental mechanics of frontal-plane walking, with a lateral motor regulation template, an empirically verified model of how humans manipulate lateral foot placements in a goal-directed manner. The model captures experimentally observed stepping fluctuation statistics and demonstrates how linear empirical models of stepping dynamics can emerge from first-principles nonlinear mechanics. We find that task-level regulation gives rise to a goal equivalent manifold in the system's extended state space of mechanical states and inputs, a subset of which contains a continuum of period-1 gaits forming a semistable set: perturbations off of any of its gaits result in transients that return to the set, though typically to different gaits.

Optimizing the location of vaccination sites to stop a zoonotic epidemic

Mass vaccinations are crucial public health interventions for curbing infectious diseases. Canine rabies control relies on mass dog vaccination campaigns (MDVCs) that are held annually across the globe. Dog owners must bring their pets to fixed vaccination sites, but sometimes target coverage is not achieved due to low participation. Travel distance to vaccination sites is an important barrier to participation. We aimed to increase MDVC participation in silico by optimally placing fixed-point vaccination locations. We quantified participation probability based on walking distance to the nearest vaccination site using regression models fit to participation data collected over 4 years. We used computational recursive interchange techniques to optimally place fixed-point vaccination sites and compared predicted participation with these optimally placed vaccination sites to actual locations used in previous campaigns. Algorithms that minimized average walking distance or maximized expected participation provided the best solutions. Optimal vaccination placement is expected to increase participation by 7% and improve spatial evenness of coverage, resulting in fewer under-vaccinated pockets. However, unevenness in workload across sites remained. Our data-driven algorithm optimally places limited resources to increase overall vaccination participation and equity. Field evaluations are essential to assess effectiveness and evaluate potentially longer waiting queues resulting from increased participation.

Symmetry, separation, and stability: Physical properties for effective dosimetric space with a stabilized hyaluronic acid spacer.

The proximity of the rectum to the prostate in radiation therapy (RT) for prostate cancer presents a significant dosimetric challenge, leading to high rectal doses and resulting in detrimental side effects. Perirectal tissue spacing reduces rectal dose and gastrointestinal toxicities by mechanically separating these organs. A variety of materials have been explored for use as rectal spacers, most recently, a stabilized hyaluronic acid (HA) gel, which can be formed into deliberate a shape, and retains the definition of that shape, while remaining flexible, unlike polyethylene glycol (PEG) hydrogels. This study evaluates the dosimetric impact of the spacer, including shape symmetry, the degree of separation at different locations, and the temporal stability of the space. Our goal is to provide physics-informed guidance on the optimal use of this sculptable spacer. A secondary analysis was performed on data from a 13-center prospective randomized trial (NCT04189913), involving 136 patients with centrally-reviewed treatment plans conducted on CT/MR simulation scans before and after receiving HA spacer implants. Patients were treated with 60Gy in 20 fractions to the prostate. For this study, python software was utilized for automated processing of DICOM RTstruct and RTdose files, facilitating detailed analysis of the spacer's impact on anatomical displacement and dosimetric outcomes. Complete dose-volume histograms (DVHs) were reconstructed, and combined into composite population DVHs before and after implant, verified against trial-reported dose points. Patients were divided into similar groups of separation and symmetry, and differences in their composite DVHs were tested for significance. Stability of the spacer was studied by comparing serial MRI images and by computing the distance between contours at four axial planes, at simulation and 3-month follow-up, post RT. The introduction of the HA spacer significantly enhanced rectal sparing, as evidenced by a reduction in the mean rectal integral dose by over 6Gy. High rates of implant symmetry(>95%) were observed, indicating nearly optimal lateral spacer placement. In superior-inferior coverage, this study like many others, saw the spacing largest at the superior extent but becoming more variable inferiorly at the level of the prostate apex. This allowed study of the apex as a specific area for dosimetric concern. Stability assessments confirmed that the spacer maintained its position and dimensions between the simulation and the 3-month post-RT, implying stable geometry during treatment, with only minimal separation changes observed. Statistical analysis using the Kruskal-Wallis test revealed significant correlations of larger separations at the inferior and apical planes with improved dosimetric outcomes, including rV30Gy. The use of a stabilized HA spacer in prostate RT effectively enhances prostate-rectum separation, leading to significant rectal sparing without undesirable dose compromises. This study underscores the role of strategic placement and shape, specifically including>1cm separation from the base down to the prostate apex. When combined with the treatment planning techniques used in the trial to create a steep dosimetric gradient across the spacer, these findings elucidate the dosimetric outcomes that can be expected in the clinical implementation of HA spacer. This is particularly relevant in the evolution of hypofractionated treatment regimens for prostate cancer therapy.

Comparison of feasibility and effectiveness of tunneled dialysis catheter placement with or without DSA guidance: a propensity score-matched cohort study

Background In some resource-limited regions, the placement of tunneled dialysis catheters (TDC) is often preferred under ultrasound guidance rather than fluoroscopy. This study compared ultrasound-and digital subtraction angiography-guided (DSA)-guided TDC in renal replacement therapy. Methods This retrospective cohort study included all TDC placements performed at our hospital between January 2020 and October 2022. We utilized 1:1 propensity score matching (PSM) to balance the demographic and clinical characteristics of the DSA-guided and ultrasound-guided groups. Dialysis prescriptions and actual dialysis completion were assessed using intraclass correlation coefficients (ICC). Multivariable logistic regression analyses determined the risk factors for early termination of dialysis. The differences in adverse events, catheter function, and catheter tip position were evaluated between the two groups. Results The study included 261 patients (142 in the DSA-guided group and 119 in the ultrasound-guided group). After PSM, 91 patients were included in each group, with no significant baseline differences (p > .1). Both groups achieved adequate catheter blood flow and ultrafiltration volumes without deviations from dialysis prescriptions (ICC ≥ 0.75). The DSA-guided group had fewer early dialysis terminations than the ultrasound-guided group (3.3 vs. 12.0%, p = .026). The position of the catheter tip in the right atrium was more consistent in the DSA-guided group (100 vs. 74.2%, p < .001). Conclusion Hemodialysis catheters inserted under DSA guidance exhibited superior performance compared to those inserted under ultrasound guidance, primarily due to more accurate catheter tip positioning. DSA guidance is recommended when ensuring optimal catheter tip placement.

Leveraging Optimal Sparse Sensor Placement to Aggregate a Network of Digital Twins for Nuclear Subsystems

Nuclear power plants (NPPs) require continuous monitoring of various systems, structures, and components to ensure safe and efficient operations. The critical safety testing of new fuel compositions and the analysis of the effects of power transients on core temperatures can be achieved through modeling and simulations. They capture the dynamics of the physical phenomenon associated with failure modes and facilitate the creation of digital twins (DTs). Accurate reconstruction of fields of interest (e.g., temperature, pressure, velocity) from sensor measurements is crucial to establish a two-way communication between physical experiments and models. Sensor placement is highly constrained in most nuclear subsystems due to challenging operating conditions and inherent spatial limitations. This study develops optimized data-driven sensor placements for full-field reconstruction within reactor and steam generator subsystems of NPPs. Optimized constrained sensors reconstruct field of interest within a tri-structural isotropic (TRISO) fuel irradiation experiment, a lumped parameter model of a nuclear fuel test rod and a steam generator. The optimization procedure leverages reduced-order models of flow physics to provide a highly accurate full-field reconstruction of responses of interest, noise-induced uncertainty quantification and physically feasible sensor locations. Accurate sensor-based reconstructions establish a foundation for the digital twinning of subsystems, culminating in a comprehensive DT aggregate of an NPP.

Oblique Lumbar Interbody Fusion Combined with Posterior Percutaneous Pedicle Screw Internal Fixation: Does Variability in Cage Position Influence Clinical Outcomes?

The study investigates how cage positions in oblique lumbar interbody fusion (OLIF) combined with posterior percutaneous pedicle screw internal fixation (PPSF) affect lumbar canal and foraminal decompression and postoperative outcomes, providing guidance for optimal placement and efficacy assessment. This investigation assesses radiologic outcomes and follow-up data in relation to cage position variability among 80 patients who underwent L4/5 single-segment OLIF+PPSF from 2018 to2022. In the study involving 80 participants, the combination of OLIF and PPSF significantly improved lower back and leg symptoms in patients, leading to positive clinical outcomes during follow-up. The intervertebral disk height increased from an average of 8.10±2.79mm before surgery to 11.75±2.14mm after surgery (P<0.001). Additionally, this surgical technique notably increased the FH (P<0.001) and expanded the DCSA from 68.81±53.89mmˆ2 before surgery to 102.91±60.46mmˆ2 after surgery (P<0.001). Linear results suggest that changes in the position of the cage do not affect spinal imaging parameters. There is no significant difference in the correction of spinal parameters or prognosis whether the cage is back, middle, ahead. In the OLIF+PPSF procedure, strict requirements for cage position are not necessary to achieve predetermined spinal biomechanical parameters. The practice of repeated fluoroscopy to adjust cage position postimplantation does not provide added clinical benefits to the patient.

EHMI on the Vehicle or on the Infrastructure? A Driving Simulator Study

Automated vehicles (AVs) may require the implementation of an external human-machine interface (eHMI) to communicate their intentions to human-driven vehicles. The optimal placement of the eHMI, either on the AV itself or as part of the road infrastructure, remains undetermined. The current driving simulator study investigated the effect of eHMI positioning on human driving behavior, during the approach and execution of right turns at T-intersections. Forty-three participants drove under three conditions: absence of eHMI, eHMI on the AV (eHMIv), and eHMI integrated into the infrastructure (eHMIi). Participants encountered AVs that either yielded or did not yield to their vehicles. The results regarding the placement of the eHMI showed that both concepts are advantageous, but for different reasons. eHMIv was appreciated because implicit and explicit communication are congruent, although the AV must first be visually identified to respond to it. eHMIi was appreciated because a familiar cue is always at a known location in the environment; as a result, participants braked earlier for the intersection and came less close to the AV (which can be interpreted as a safety advantage or efficiency disadvantage). Although there are limitations to a driving simulator study like this, this research provides important insights into the fundamental question of how information placement affects drivers’ visual attention demands and driving behavior, topics that are important in view of the development of future cities.

Integrating Operations Research into Very Large-Scale Integrated Circuits Placement Design: A Review

The placement stage of the physical design of very large-scale integrated circuits (VLSI) specifies the arrangement and order of standard cells and devices within an area, and the effectiveness of the placement result directly affects the chip’s performance. The advancement of process standards and reduction in the size of features size have dramatically increased the complexity of placement design. The realization of placement algorithms to deal with millions of cells has thus become an important issue in the automation of integrated circuit electronic design. In this paper, we first segment the digital integrated circuits into VLSI design styles and review them from the perspectives of practical placement problems, placement design ideas, and placement optimization methods. The discussion around traditional circuits focuses on the essence of the placement problem, placement steps, and classification of placement algorithms. In modern circuit placement, the discussion focuses on the impact of technical constraints on design. After identifying the essence of the placement problem, solutions to the packing problem are reviewed, and we then summarize our representative placement algorithms. Finally, based on the development of VLSI placement design, the optimization bottlenecks of existing placement design are summarized, and suggestions for future research are made based on the latest research topics and methodologies.

Optimizing capacitor size and placement in radial distribution networks for maximum efficiency

As distribution systems continue to expand, they face challenges such as increased system losses and inadequate voltage regulation. To address these issues, shunt capacitors are being deployed in distribution networks. These capacitors offer reactive power compensation, enhance power factor, improve voltage profiles, promote system stability, and significantly reduce losses. However, determining the appropriate capacitor sizes and their optimal placements requires careful consideration of both technical and economic factors. The nonlinear nature of optimal capacitor placement and sizing, leveraging optimization techniques becomes crucial in identifying the best locations and values for capacitors. This paper demonstrates the effective utilization of Particle Swarm Optimization (PSO) and Real Coded Genetic Algorithm (RCGA) optimization techniques for capacitor placement and selection. The optimization techniques are applied to a 33-bus IEEE standard radial distribution system, to reduce the real power loss and to improve the voltage profile considering both constant and variable loads. Both PSO and RCGA algorithms identify suitable locations for the placement of capacitors for reactive power compensation within the distribution system. By optimizing the objective function associated with capacitor placement costs and maximizing annual cost savings, the PSO and RCGA techniques yield promising results. After implementing the optimal capacitor placements at the identified candidate nodes, a significant reduction in losses within the radial distribution system is observed. Moreover, the cost savings achieved through optimal placement and sizing are substantial.

Distal Positioning of the Ulnar Shortening Plate Increases Symptomatic Removal: A Comparative Analysis of Ulnar Shortening Osteotomy Plate Positioning and Symptomatic Hardware Removal

Abstract Background Ulnar shortening osteotomy (USO) is a common procedure to treat symptomatic ulnar-sided wrist symptoms in patients with positive ulnar variance who fail nonoperative management. Plate placement on the volar, dorsal, or subcutaneous border of the ulna has been described. There remains debate regarding the optimal plate placement to minimize soft tissue irritation and the need for plate removal. The goal of this study is to determine whether plate position along the volar cortex versus along the subcutaneous border, as well as the distance of the plate from the ulnar styloid, affects the risk of symptomatic hardware requiring removal. Methods In total, 112 USO procedures on 107 patients performed between 2017 and 2023 were retrospectively reviewed. The position of the plate on the ulna and the distance of the plate from the ulnar styloid were assessed radiographically. Demographic information, visual analog scale pain scores, disability of the arm, shoulder, and hand scores, and incidence of hardware removal were collected and compared between plate location groups. Results The overall symptomatic hardware removal rate was 79%. There was no difference in the rate of symptomatic hardware removal between volar (80%) and subcutaneous (77%) plate locations (p = 0.69) at a mean follow-up time of 26 months. The mean distance from the distal plate to the ulnar styloid was higher in cases in which hardware was retained (p = 0.03). Conclusion We found no difference in hardware removal rates based on volar versus subcutaneous plate placement after USO. Cases in which hardware was not removed had a higher mean distance from the distal plate to the ulnar styloid. Further prospective studies are warranted to determine optimal plate positioning to minimize hardware irritation after USO.

Enhanced distribution system performance through optimal placement of hybrid dynamic voltage restorer

Enhanced distribution system performance through optimal placement of hybrid dynamic voltage restorer

Optimization of UAV base station placement for D2D content delivery network

Optimization of UAV base station placement for D2D content delivery network

Intrajejunal levodopa in Parkinson's disease: Optimization of PEG application

The various forms of Percutaneous Endoscopic Gastrostomy (PEG) are highly relevant in neurology, as pump-administered intrajejunal levodopa application is one of the indispensable forms of therapy in advanced Parkinson's disease. Optimal PEG placement and follow-up are therefore significant for the success of the therapy. However, the standard intrajejunal administration of levodopa gel via a JET-PEG, i. e. a PEG with an internal catheter inserted into the jejunum, is not without problems for various reasons. In particular, the considerable cumulative complication rates demand a reconsideration of the situation. The very limited absorption area of the drug in the region of the flexura duodenojejunalis must also be taken into account. Causes of complications are predominantly a non-optimal application technique of PEG and internal catheter as well as the frequent lack of an adequate follow-up. In this paper, the details of a modified and optimized application technique compared to the conventional techniques are presented. These new methods have proved their usefulness in clinical applications for years, and additionally a new application form, the Hybrid-PEG, is presented. However, many of the details derived from anatomical/physiological, surgical and endoscopic aspects must be strictly observed during the application in order to reduce or avoid minor and major complications. In particular, problems are caused by local infections in the area of the insertion point of the PEG including peritonitis, leaks and buried bumper syndrome (BBS). The relatively frequent dislocations of the internal catheter also prove to be particularly troublesome. These can ultimately be avoided by clip fixation of the catheter tip down in the jejunum. In particular, the use of the newly developed Hybrid-PEG, a combination of endoscopically controlled gastropexy with three sutures and subsequent central thread-pull-through of the PEG tube, can significantly reduce the complication rate and thus achieve a decisive improvement for patients. The aspects discussed here are highly relevant for all those involved in the therapy of advanced Parkinson's disease. Trustful interdisciplinary collaboration between neurology and endoscopy/surgery/gastroenterology is a prerequisite for good clinical outcomes.

OptiLoc: Integrating SCSO and DV-Hop for wireless sensor network localization with application to disease forecasting in cattle farm monitoring

Disease prediction and management in cattle farming present significant challenges due to the complex interplay of environmental factors, disease transmission dynamics and the need for accurate localization of disease-carrying cattle. Traditional approaches often fall short in optimizing anchor node selection and accurately forecasting disease occurrences. To address these limitations, we propose OptiLoc, a novel framework that integrates advanced optimization techniques and disease forecasting algorithms. The proposed OptiLoc framework leverages Enhanced Sand Cat Swarm Optimization (SCSO) for optimizing anchor node selection within the farm area network. By dynamically adjusting the exploration rate and incorporating an opposition-based memory mechanism, OptiLoc ensures thorough exploration of the search space while preventing premature convergence. Furthermore, the multi-objective optimization aspect of SCSO considers factors such as coverage, energy efficiency, and connectivity, resulting in optimal anchor node placement. Additionally, OptiLoc integrates disease forecasting capabilities using logistic regression classifiers with dictionary learning. By extracting meaningful features from sensor data and training linear classifiers, OptiLoc predicts disease outbreaks among the cattle population. These predictions are seamlessly integrated into the optimization process through an expanded fitness function, which considers disease-related parameters alongside traditional optimization objectives. Furthermore, OptiLoc enhances disease management and control efforts by localizing sensor nodes using the DV-Hop method. By estimating sensor node positions based on hop distances to anchor nodes and dynamically calibrating hop distances based on real-time data on disease prevalence and environmental factors, OptiLoc achieves precise localization results. The proposed OptiLoc framework offers several advantages over traditional approaches. It optimizes anchor node placement, accurately forecasts disease outbreaks, and enhances localization accuracy, thereby empowering farmers with actionable insights to safeguard the health and well-being of their livestock. Performance evaluation reveals for the anchor nodes, it measures a mean localization error of 3.2% to 9.1% with a mean error of 5.91%. Similarly, for the sensor nodes, the mean localization error is 3.45% to 8.25% with a mean error of 5.445%. The AUC of the logistic regression classifier with dictionary learning is 0.97. Through its comprehensive approach, OptiLoc represents a significant advancement in optimizing WSNs in agricultural environments.

Optimising the hydraulic performance of a jet impingement sprinkler by varying elevation angle: A Comparative study with a non-impingement sprinkler

A novel jet impingement sprinkler was designed to replace the additional water-dispersing devices usually used in rotating sprinklers to adapt performance for low-pressure conditions. Utilising the asymmetric impingement mode of primary and secondary jets, the design prioritises the secondary nozzle elevation angle. Theoretical expressions were establish between the primary and secondary jet momentum rates. Hydraulic performance experiments, were conducted under intermediate and low-pressure conditions, examining water application rate, wetted radius, and Christiansen's uniformity coefficient at various elevation angles. High-speed photography (HSP) experiments elucidate differences in hydraulic performance, revealing that the impingement jet generally featured a lower maximum water application rate but a smoother distribution compared to its non-impingement counterpart. Using the CRiteria Importance Through Intercriteria Correlation (CRITIC) method, comprehensive scores highlight an optimal arrangement with a 34.5° secondary nozzle elevation angle, illustrating superior performance under low pressure. Comparative analyses between the wetted radius and Christiansen's uniformity coefficient uncover a trade-off, with jet impingement sacrificing wetted radius for increased uniformity. However, this efficiency diminished as jet impingement effects intensify. HSP experiments validate theoretical calculations, with a relative error of less than 4% for jet deflection angle and jet breakup length. Non-linear curve fitting establishes relationships between jet breakup length, mean observed jet deflection angle, operating pressure, and wetted radius. Calculated and measured values exhibited a relative error within 5%, affirming the applicability of the developed equation for predicting wetted radius in jet impingement sprinklers.

A segmented conformal surface for ultrawideband monostatic and bistatic RCS reductions

In this paper, a segmented cylindrical metal surface based on an optimal arrangement is proposed to achieve ultrawideband and wide-angle radar cross section (RCS) reduction. Firstly, a multi-stage semi-cylindrical surface that uses the difference in radius between each cylinder to achieve phase cancellation is designed. The PSO algorithm is used to obtain the best length of each cylinder. Then, each semi-cylinder is equally divided into a certain number of sub-surfaces. Subsequently, in the axial direction, the sequence of these sub-surfaces with different radii is disrupted according to the optimal arrangement to form discontinuous surface reflection phases. A 10-dB RCS reduction under normal incidence is achieved from 4.36 to 20.6 GHz, and the bandwidth ratio reaches 4.72:1. The theoretical analysis and simulated results are in good agreement with the measured results, and the design has an important reference value for ultrawideband monostatic and bistatic RCS reductions for cylinder-like targets.

Optimal allocation of solar photovoltaic distributed generation for performance enhancement of electrical distribution networks considering optimal volt‐var regulation under uncertainty and high load variation

AbstractThis article proposes an optimal placement and sizing of photovoltaic (PV) power systems based distributed generation (DG) in radial electrical distribution networks considering the capability of PV inverters to regulate the voltage by optimal injecting and absorbing reactive power at the point of common coupling (PCC) using honey badger algorithm (HBA), as a recent and efficient optimization algorithm to solve the complicated optimal allocation. Several objective functions are achieved for distribution system performance enhancement: minimizing the power loss and the voltage deviation index (VDI) and maximizing the voltage stability index (VSI). Based on historical data and probabilistic models, seasonal hourly solar irradiance, ambient temperature, and load variation curves have been modeled, which simultaneously consider the light, normal, and heavy load demand. The essential components of distribution power systems have been characterized. To investigate the validity of the proposed approach, IEEE 33 and IEEE 69 BUS radial distribution test systems have been considered for power flow (PF) analyses, where Newton's Raphson method has been applied to solve the PF issue. The simulation results of different numerical scenarios have shown the effectiveness and validity of the newly proposed method to solve the optimal allocation problem considering optimal volt‐var regulation control of PV inverters compared to several valid and robust optimization algorithms.

Optimal Arrangement and Rearrangement of Objects on Shelves to Minimize Robot Retrieval Cost

Optimal Arrangement and Rearrangement of Objects on Shelves to Minimize Robot Retrieval Cost

Automating cloud virtual machines allocation via machine learning

Automating cloud virtual machines allocation via machine learning

Simulation-based Optimal Sensor Placement in Tunnel Structures considering Uncertain in-situ Conditions and Multiple Loading Scenarios

The expansion of the underground infrastructure and the necessity to maintain the full functionality of the existing tunnels highlights the role of structural health monitoring in keeping track of the behaviour of the structure over time. In the study, the focus is on segmental tunnel lining for deep and long tunnels. The aim of this research is to investigate the best position for sensor placement based on the potential loading scenarios that might insist on the tunnel structure. Since for the evaluation of the lining safety we are interested in the maximum stresses reached in the structure, which might lead to durability critical cracking or crushing of concrete, a method is presented to suggest optimal positions for strain gauges. Due to uncertain geological conditions, multiple loading configurations acting on the tunnel structure are simulated using a finite element model. The results are employed to better identify the sensor locations, on the basis of where damage is prone to occur and where maximum information about the stress state in the structure can be inferred. The results obtained by the framework are discussed in light of a practical engineering perspective and the advantages as well as the limitations of the proposed approach are expounded.