Maximum Flow Research Articles

Trans-rectovesical pouch urethral-sparing robotic-assisted simple prostatectomy: A case series.

To detail a novel technique of robotic-assisted simple prostatectomy that makes handling the gland protruding into the bladder neck easier and can preserve the urethra and retain ejaculation function as much as possible. This is a prospective case series. Clinical data of 17 male patients who had large volume (>80 mL) benign prostatic hyperplasia (BPH) were enrolled to undergo trans-rectovesical pouch urethral-sparing robotic-assisted simple prostatectomy (usRASP). We adopted the approach through the space between the bladder neck and seminal vesicle to perform a usRASP that can avoid the detrusor skirt and fibrous matrix area of the retropubic prostate. Between the transitional zone and the peripheral zone of the large prostate, the hyperplastic prostatic gland tissue can be enucleated under direct vision while preserving the prostatic urethra and retaining the ejaculatory duct and bladder neck intact. All preoperative, perioperative and postoperative clinical data were collected, and descriptive analysis was performed. The median intravesical prostatic protrusion was 19.3 mm (8.5-32.2). The median operative time was 100 min (75-140), and the median estimated blood loss was 100 mL (10-500). The median time to catheter removal was 7 days (5-7), with a median postoperative hospital stay of 2 days (2-4). After at least 6-month follow-up, the median maximum urine flow rate and postvoid residual volume were 40.1 mL/s (12.7-52.4) and 15 mL (5-23), respectively; the median International Prostate Symptom Score and Quality of Life score were 0 (0-6.3) and 1 (0-3), respectively; and the median total prostate-specific antigen was 0.84 ng/mL (0.15-1.01). All patients successfully underwent usRASP. Fifty-eight percent of patients with normal ejaculation function before surgery can still retain normal ejaculation function. We described a new approach to performing usRASP. This new method remarkably improved the voiding function, maintained antegrade ejaculation and did not increase the post-operative complications.

Evaluation of the Efficacy and Safety of Bipolar and Monopolar Transurethral Prostate Resection in Geriatric Patients.

Benign prostatic hyperplasia unresponsive to medical treatment is an important problem for elderly patients. Although the gold standard surgical treatment is monopolar transurethral resection of the prostate (MTURP), postoperative complications are still a concern. The aim of this study was to determine which transurethral prostate resection (TURP) methods are more effective and safer in elderly patients. Patients who underwent TURP in our clinic between 2012 and 2021 were analyzed retrospectively and divided into three groups according to their ages. Patients were treated with MTURP (n = 169) and bipolar transurethral resection of the prostate (BTURP) (n = 1152). Pre- and post-operative data for age groups were compared according to TURP methods. The resection speed in the BTURP method was statistically significantly faster in groups 2 and 3 (P < 0.05). Although not statistically significant (P > 0.05), there was a numerically smaller decrease in hemoglobin (Hb) value in group 2 and a numerically greater decrease in post-voiding residual (PVR) volume in groups 1 and 3 in the BTURP method. The increase in maximum urine flow (Qmax) was significantly higher only in group 2 (P = 0.032), but it was numerically higher in all groups in the BTURP method. The results of this study showed that BTURP was at least as effective and safe as MTURP in geriatric patients and also better in terms of Hb decrease, resection speed, Qmax increase, and PVR volume decrease.

Commercial Adaptive Cruise control (ACC) and capacity drop at freeway bottlenecks

Vehicle automation has already become commercially available. Today’s mainstream vehicles are equipped with Adaptive Cruise Control (ACC) to automate longitudinal car-following. However, ACC’s limited detection range and delayed reaction hinder the vehicle’s ability to respond promptly to speed changes, and ACC could amplify minor disturbance into severe stop-and-go waves and form queues at bottlenecks. Consequently, the discharge flow could be lower than the maximum flow observed in absence of queues or congested conditions, also known as capacity drop. Microscopic simulation of freeway bottlenecks consisting of a single lane with reduced speed zone, multilane with an on-ramp merge, and multilane with an off-ramp diverge demonstrates that ACC vehicles lead to capacity drop at freeway bottlenecks. For the single lane reduced speed zone, the extent of capacity drop for ACC could be either less or more severe than that of human driven vehicles. However, the multilane freeway on-ramp and off-ramp bottlenecks are more susceptible to capacity drop than human driven vehicles, due to ACC significantly amplifying disturbances caused by lane changes, merging, and diverging.

Enhancing regional flood frequency analysis by integrating site-similarity measures with watershed modeling

This paper introduces and applies a novel methodology that integrates watershed modeling with the traditional regional flood frequency analysis. The methodology introduces a novel site-similarity measure that relies on hydrologic simulations and accounts for the effect of land depressions on streamflow generation. The new measure is tested along with other traditional measures for regional flood frequency analysis in the Canadian prairies. The case study is chosen carefully to critically test the new methodology. An application of 30 combinations of the new and traditional site similarity measures is assessed for pooling 109 sites. The homogeneity of the clustered groups is evaluated, and different probability distributions are applied to describe at-site and regional annual maximum flows. The results present enhanced groups’ homogeneity when the new measure is employed due to a better representation of the hydrologic similarity between the pooled sites. Furthermore, the regionally estimated quantiles are found susceptible to the chosen site similarity measures in the pooling process, which highlights the importance of considering the proposed measure that describes a key hydrologic aspect when land depressions exist.

“Component flow” conditions and its effects on enhancing production of continental medium-to-high maturity shale oil

Based on the production curves, changes in hydrocarbon composition and quantities over time, and production systems from key trial production wells in lacustrine shale oil areas in China, fine fraction cutting experiments and molecular dynamics numerical simulations were conducted to investigate the effects of changes in shale oil composition on macroscopic fluidity. The concept of “component flow” for shale oil was proposed, and the formation mechanism and conditions of component flow were discussed. The research reveals findings in four aspects. First, a miscible state of light, medium and heavy hydrocarbons form within micropores/nanopores of underground shale according to similarity and intermiscibility principles, which make components with poor fluidity suspended as molecular aggregates in light and medium hydrocarbon solvents, such as heavy hydrocarbons, thereby decreasing shale oil viscosity and enhancing fluidity and outflows. Second, small-molecule aromatic hydrocarbons act as carriers for component flow, and the higher the content of gaseous and light hydrocarbons, the more conducive it is to inhibit the formation of larger aggregates of heavy components such as resin and asphalt, thus increasing their plastic deformation ability and bringing about better component flow efficiency. Third, higher formation temperatures reduce the viscosity of heavy hydrocarbon components, such as wax, thereby improving their fluidity. Fourth, preservation conditions, formation energy, and production system play important roles in controlling the content of light hydrocarbon components, outflow rate, and forming stable “component flow”, which are crucial factors for the optimal compatibility and maximum flow rate of multi-component hydrocarbons in shale oil. The component flow of underground shale oil is significant for improving single-well production and the cumulative ultimate recovery of shale oil.

Clinical Outcomes in Patients With Hypocontractile Bladders Undergoing Holmium Laser Enucleation of the Prostate

To compare post-operative outcomes in patients who underwent holmium laser enucleation of the prostate (HoLEP) for benign prostatic hyperplasia (BPH) and had urodynamic evidence of bladder hypocontractility versus those with normocontractile bladders. We retrospectively reviewed HoLEP patients with pre-operative urodynamic studies at a single institution, categorizing them into normocontractile and hypocontractile groups based on the bladder contractility index (BCI) (hypocontractile defined as BCI < 100). Post-void residual (PVR) volume was measured at 6 weeks and 6 months. Secondary outcomes included maximum flow rate (Qmax) and catheterization status. Among 114 HoLEP patients with pre-operative urodynamic data, 49 had hypocontractile bladders. The median pre-operative PVR was 305 (202-446) ml in the hypocontractile group, higher than the median PVR of 190 (60-361) ml in the normocontractile group (p=.013). At 6 weeks post-op, the median PVR was higher in the hypocontractile compared to normocontractile group [38 (3-61) vs. 5 (0-44) ml, p=.016], but at 6 months post-op there was no significant difference [18 (0-39) vs. 12 (0-70) ml, p=.97]. Among men who were catheter-dependent pre-operatively, 98% of hypocontractile and 100% of normocontractile patients were catheter-free postoperatively. Qmax and symptom scores were similar at both follow-up time points. HoLEP can be an effective surgical option for BPH patients with hypocontractile bladders, including those who are catheter-dependent, with minimal differences in post-operative voiding parameters compared to those with normal bladder function.

Evaluation of learning curves for contact laser vaporization of the prostate using the 980 nm diode laser for benign prostatic hyperplasia.

We investigated the background of patients who underwent contact laser vaporization of the prostate (CVP) surgery and the learning curve of the operators. A total of 207 patients who underwent CVP surgery for benign prostatic hyperplasia between August 2018 and March 2023 were included in this study. Patient background, perioperative results, pre- and postoperative urinary flow tests, and complications were collected retrospectively. We enrolled 12 doctors who were divided into expert (five doctors) and novice (seven doctors) groups based on the number of TURP experiences before CVP. The median patient age was 73 years (51-92 years) and prostate volume was 56 cc (15-190 cc) with no difference between the expert and novice groups. Complications included urinary retention (eight cases), hematuria (four), urinary tract infection (four), intraoperative perforation (two), and postoperative stricture (one). Both cases of intraoperative perforation occurred in the novice group. The expert group had a significantly shorter operative time (38 vs. 66 min) and a higher operative efficacy of prostate volume divided by operative time (1.43 vs. 0.88 cc/min). Postoperatively, IPSS, quality of life scores, and postvoid residual urine volume decreased, and maximal flow rate increased; however, there was no significant difference between the groups. The expert group showed stable operative time and operative efficacy after about five to eight cases, while the novice group showed stable after about 15 cases. Our findings suggest that CVP was safely performed at our hospital, and operators with limited experience in TURP can achieve stable perioperative results.

Delimitation of the Final Pit in Open Pit Mines Using the Pseudoflow Maximum Flow Algorithm: A Comparative Analysis of 1×5 and 1×9 Arcs

Delimitation of the Final Pit in Open Pit Mines Using the Pseudoflow Maximum Flow Algorithm: A Comparative Analysis of 1×5 and 1×9 Arcs

Redesign Drainage Channel in Jetis District Mojokerto Regency

There are up to 50-centimeter-high puddles on the road due to the Jetis Road Drainage Channel in Mojokerto Regency's incapacity to handle the flood discharge from the drainage catchment area. The Jetis Road drainage channel's size and channel bed slope will be affected by the meeting point of the 1000 m long secondary channel and the Jetis Road drainage outlet. The objective of this research is to evaluate the efficiency of drainage channel design considering the implications of the drainage existing condition due to inconsistent dimension and sedimentation. The drainage channel is designed to handle a total discharge of 4.6 m3/sec during 10 years return of period. Under these circumstances, a trapezoidal channel with a width of one meter and a depth of two meters is needed. The Jetis Road drainage channel's enlarged dimensions result in a flood water level of 1.8. The Jetis Road drainage channel has a freeboard of 0.2 meters since the flood water level that occurs in the channel with its new dimensions is 1.8 meters. The flow rate in the intended channel serves as the control in this study to determine channel size. The channel's maximum flow velocity of 1.44 m/sec satisfies the 1.5 m/sec maximum flow velocity allowed in concrete channels.

Experimental investigation on the influence of gasoline injection pressure on the hydrogen knock limit and performance of a hydrogen–gasoline dual fuel engine

This study experimentally investigated the influence of gasoline injection pressure (GIP) on the performance and hydrogen knock limit of a gasoline direct-injection hydrogen–gasoline dual-fuel engine. The GIP was varied from 50 to 140 bar, and hydrogen was introduced at a step size of 2 LPM until knock onset at spark timings of 4° and 12° CA before top dead center (BTDC). The hydrogen knock limit was extended at a higher GIP, with maximum hydrogen flow rates of 10 and 16 LPM at 12° CA and 4° CA BTDC, respectively. Increasing the GIP and retarding the spark timing negatively affected brake thermal efficiency, brake mean effective pressure, and in-cylinder pressure. The CO2 and NOx emissions decreased, and the CO emissions increased with an increase in the GIP. The cyclic variation increased considerably with GIP. However, hydrogen blending exhibited a completely opposite trend to that of GIP.

Numerical simulation study on the effect of ignition position on premixed hydrogen deflagration characteristics in tunnels

To analyze the influence of different ignition positions on the propagation of deflagration characteristics and the disaster mechanism in the hydrogen deflagration process in the tunnel, this study compares and verifies the experimental data of tunnel model deflagration based on the CFD code GASFLOW-MPI. A combustion velocity model based on the accelerated separation effect is used, and the effect of heat transfer on the consequences of deflagration is considered. The propagation laws of pressure waves, fluid velocity and temperature in the tunnel are analyzed, and it is found that the changing trends of shock waves and fluid velocity in the tunnel are consistent, but completely opposite in the tunnel outside. The effects of different ignition positions on the hydrogen deflagration characteristics are compared and analyzed. The results show that when ignition occurs at different heights of the center of the premixed region, the impact on the deflagration characteristics is relatively small, while when ignition occurs at different horizontal distances in the premixed region, the impact on the deflagration characteristics is relatively large; the peak overpressure of side ignition is far lower than the case where ignition occurs in the center of the premixed region, but the maximum flow velocity is much higher than the center ignition. The impact on temperature is the smallest. In general, in areas close to the hydrogen/air premixed zone, side ignition results in more severe consequences, whereas in areas far from the premixed zone and outside the tunnel, central ignition leads to more severe consequences. This study provides theoretical support for understanding the disaster-causing mechanisms of hydrogen/air premixed gas deflagration in tunnels under different ignition positions.

Computational Fluid Dynamics-Based Optimisation of High-Speed and High-Performance Bearingless Cross-Flow Fan Designs

To enhance the fluid dynamic performance of bearingless cross-flow fans (CFFs), this paper presents a CFD-based optimisation of both rotor and static casing wall modifications. High-performance CFFs are essential in industrial applications such as highly specialised laser modules in the semiconductor industry. The goal for the investigated rotor modifications is to enhance the CFF’s mechanical stiffness by integrating reinforcing shafts, which is expected to increase the limiting bending resonance frequency, thereby permitting higher rotational speeds. Additionally, the effects of these rotor modifications on the fluid dynamic performance are evaluated. For the casing wall modifications, the goal is to optimise design parameters to reduce losses. Optimised bearingless CFFs benefit semiconductor manufacturing by improving the gas circulation system within the laser module. Higher CFF performance is a key enabler for enhancing laser performance, increasing the scanning speed of lithography machines, and ultimately improving chip throughput. Several numerical simulations are conducted and validated using various commissioned prototypes, each measuring 600mm in length and 60mm in outer diameter. The results reveal that integrating a central shaft increases the rotational speed by up to 42%, from 5000rpm to 7100rpm, due to enhanced CFF stiffness. However, the loss in fluid flow amounts to 61% and outweighs the gain in rotational speed. Optimising the casing walls results in a 22% increase in maximum fluid flow reaching 1800m3/h at 5000rpm. It is demonstrated that the performance of bearingless CFFs can be enhanced by modifying the geometry of the casing walls, without requiring changes to the CFF rotor or bearingless motors.

Influence of the yoga breathing exercise “uddiyana” on blood flow in the marginal sinus

Purpose: Studying the effect of the Uddiyana Bandha (UB) yoga breathing exercise on blood flow in the marginal sinus (MS).Materials and methods: The study involved 16 people in whom blood flow in the MS was assessed against the background of free breathing, during voluntary expiratory apnea (VEA) — 5 seconds, and during UB — 5 seconds. The maximum blood flow velocity (Vmax), the time-averaged maximum velocity Vmean, and the index phase character (IP) were recorded.Results: When recording Vmax during VEA (stage 2) for 5 seconds, it did not show significant differences compared to free breathing (stage 1); within 5 seconds of execution, the UB (stage 3) was significantly higher than the baseline (stage 1), p &lt; 0.001, and also higher than the VEA (stage 2), p &lt; 0.001. Vmean PEA (stage 2) for 5 seconds was without significant differences compared to free breathing (stage 1). During 5 seconds of UB execution (stage 3), Vmean was higher than the baseline (stage 1), p &lt; 0.001, and also higher than VEA (stage 2), p &lt; 0.009. Against the background of free breathing (stage 1) and PEA (stage 2), the values of IP and were without significant differences compared to UB (stage 3).Conclusions: The UB breathing exercise increases the maximum linear blood flow velocity Vmax and the time-averaged maximum blood flow velocity Vmean in the MS, which may indicate activation of cerebral venous outflow during the exercise.

Research on Teaching Planning and Teacher Evaluation Integrating Sustainable Development and Renewable Energy Concepts

Energy is an essential basis for human survival, social progress and economic development. With the rapid development of China's economy and the acceleration of urbanization, the problem of energy shortage is increasingly serious, and the problem of energy security is prominent. Based on stochastic power flow algorithm, this paper proposes the safety assessment and teaching planning of wind power generation in renewable energy. Firstly, the dynamic safety domain and thermal stability safety domain of wind power systems are proposed in this paper. Within the selected security domain, the key factors that are most likely to lead to the risk of a distribution network are selected by means of entropy-modified analytic hierarchy process (AHP). The incompleteness of the single weighting method is solved, and the total evaluation score of each layer of the index system is calculated from the subjective and objective perspectives to determine the weak link in the occurrence of accidents in the distribution network. The total score is less than 90 points, which is prone to failure risk. Finally, based on the safety index system, PLF is introduced into the uncertainty safety assessment of wind power systems to overcome the inefficiency of traditional uncertainty assessment methods. Methods PLF was used as a means of system state analysis to replace a lot of conventional power flow analysis in uncertain safety assessment, and related safety indexes were defined based on PLF results. The test system ST-PLF is taken as an example to verify the rationality of the proposed method. The results show that the proposed method can effectively realize the static security assessment of the system and identify the potentially vulnerable elements of the system. The evaluation time of the proposed method is 0.73 s, while that of the traditional method is 48.54 s. The evaluation speed of the proposed method is greatly improved, and the time is only 1.55% of that of Monte Carlo method.

MagnetoStalsis: Generating Peristalsis in an Artificial Bowel for Treatment of Short Bowel Syndrome

Efforts to develop an artificial intestine for treatment of short bowel syndrome have thus far failed to achieve coordinated peristalsis. To address this, we introduce an implantable, biomimetic, magnetically-actuated peristaltic pumping apparatus. The system consists of a magnetic pump surrounding an intestinal graft and a rotating external magnetic field generator that produces peristaltic motion in the graft as the field direction alternates. We performed computational finite element modeling to simulate deformation and stress concentration on the pump. We then tested the ability of the system to produce fluid flow through porcine subintestinal submucosa at actuation frequencies from 0 Hz to 4 Hz. The system achieved a maximal flow rate of 6.03 mL/min at 3 Hz actuation frequency, which is in the physiological range of human intestinal flow rates. This device represents a novel proof-of-concept for achieving untethered peristalsis in an implantable intestinal graft that is primed for preclinical testing in animal models of short bowel syndrome.

Transfer learning-based Gaussian process classification for lattice structure damage detection

This study presents a novel approach for real-time vision-based structural health monitoring, focusing on evaluating the deformation state of lattice structures. The structures are renowned for their remarkable recovery capabilities and exhibit similar mechanical responses under compressive loads. Despite these characteristics, quickly assessing the health status of the applied structure using knowledge from another related lattice structure is usually time-consuming and impractical. To address this, we propose to combine Gaussian process classification with transfer learning, termed TL-GPC, to detect damage states under compressive loads while also achieving uncertainty quantification. By employing structural deformations captured via the optical flow algorithm as inputs, the internal transfer kernel factor in TL-GPC is tailored to model knowledge transfer between source and target domain inputs. Experimental results show that the proposed TL-GPC model can deliver higher damage detection accuracy while ensuring stable uncertainty quantification in scenarios with limited and unbalanced experimental data.

Novel Comparison of Pyrocumulonimbus Updrafts to Volcanic Eruptions and Supercell Thunderstorms Using Optical Flow Techniques

AbstractConvective dynamics in a supercell thunderstorm, a volcanic eruption, and two pyrocumulonimbus (pyroCb) events are compared by computing cloud‐top divergence (CTD) with an optical flow technique called Deepflow. Visible 0.64‐μm imagery sequences from Geostationary Operational Environmental Satellites (GOES)‐R series Advanced Baseline Imager (ABI) are used as input into the optical flow algorithm. CTD is computed after post‐processing of the retrieved motions. Analysis is performed on specific image times, as well as the full time series of each case. Multiple CTD‐based parameters, such as the maximum and the two‐dimensional area exceeding a specified CTD threshold, are examined along with the optical flow‐retrieved wind speed. CTD is shown to accurately and quantitatively represent the behavior and magnitude of different deep convective phenomena, including distinguishing between convective pulses within each individual event. CTD captures updraft intensification as well as differences in convective activity between two pyroCb events and individual updraft pulses occurring within a single pyroCb event. Finally, the characteristics of high‐altitude smoke plumes injected by two separate pyroCb pulses are linked to CTD using ultraviolet aerosol index and satellite imagery. Optical flow‐derived parameters can therefore be applied to individual pyroCbs in real‐time, with potential to characterize pyroCb smoke source inputs for downstream smoke modeling applications and to facilitate future tools supporting air quality modeling and firefighting efforts.

Intra-Frame Graph Structure and Inter-Frame Bipartite Graph Matching with ReID-Based Occlusion Resilience for Point Cloud Multi-Object Tracking

Three-dimensional multi-object tracking (MOT) using lidar point cloud data is crucial for applications in autonomous driving, smart cities, and robotic navigation. It involves identifying objects in point cloud sequence data and consistently assigning unique identities to them throughout the sequence. Occlusions can lead to missed detections, resulting in incorrect data associations and ID switches. To address these challenges, we propose a novel point cloud multi-object tracker called GBRTracker. Our method integrates an intra-frame graph structure into the backbone to extract and aggregate spatial neighborhood node features, significantly reducing detection misses. We construct an inter-frame bipartite graph for data association and design a sophisticated cost matrix based on the center, box size, velocity, and heading angle. Using a minimum-cost flow algorithm to achieve globally optimal matching, thereby reducing ID switches. For unmatched detections, we design a motion-based re-identification (ReID) feature embedding module, which uses velocity and the heading angle to calculate similarity and association probability, reconnecting them with their corresponding trajectory IDs or initializing new tracks. Our method maintains high accuracy and reliability, significantly reducing ID switches and trajectory fragmentation, even in challenging scenarios. We validate the effectiveness of GBRTracker through comparative and ablation experiments on the NuScenes and Waymo Open Datasets, demonstrating its superiority over state-of-the-art methods.

Evaluation of the learning curve for Thulium fiber laser enucleation of prostate (ThuFLEP): retrospective study of a single-surgeon experience in real-world settings.

To assess the learning curve of Thulium Fiber Laser Enucleation of prostate (ThuFLEP) of a single surgeon inexperienced in laser endoscopic enucleation of prostate (EEP). We retrospectively analyzed all patients with benign prostate hyperplasia undergoing ThuFLEP at our center between January 2022 and August 2023 by one surgeon. Inclusion criteria were International Prostate Symptom Score > 7, prostate volume < 200g, and maximal urinary flow rate < 15 mL/s. The surgeon was inexperienced in laser EEP and trained by watching educational videos of ThuFLEP before starting to perform the procedure under mentoring during the first 4 cases. Procedural data (enucleation and morcellation efficiency, complications) and functional results up to 3 months were evaluated. Patients were divided into 4 cohorts of 20 consecutive cases to evaluate outcomes evolution throughout time. The mean age of the patients was 69.9 years (SD 7.8) and mean prostate volume was 89.9g (SD 25.8). Preoperative functional parameters were comparable between the groups. Mean enucleation efficiency (EE) ratio and morcellation efficiency (ME) ratio reached respectively 0.78g/min (SD 0.55) and 2.49g/min (SD 1.03) and both variables significantly increased from group 1 to group 3 (p < 0,001). Perioperative complications remained low throughout the caseload with similar significant 3-month functional improvements between all groups. This is the first study to evaluate ThuFLEP learning curve for a single surgeon inexperienced in laser EEP with limited mentoring. Under these real-world conditions, nearly 60 cases were needed to complete the learning curve with a complications rate remaining low throughout the training process.

Congestion Transition on Random Walks on Graphs.

The formation of congestion on an urban road network is a key issue for the development of sustainable mobility in future smart cities. In this work, we propose a reductionist approach by studying the stationary states of a simple transport model using a random process on a graph, where each node represents a location and the link weights give the transition rates to move from one node to another, representing the mobility demand. Each node has a maximum flow rate and a maximum load capacity, and we assume that the average incoming flow equals the outgoing flow. In the approximation of the single-step process, we are able to analytically characterize the traffic load distribution on the single nodes using a local maximum entropy principle. Our results explain how congested nodes emerge as the total traffic load increases, analogous to a percolation transition where the appearance of a congested node is an independent random event. However, using numerical simulations, we show that in the more realistic case of synchronous dynamics for the nodes, entropic forces introduce correlations among the node states and favor the clustering of empty and congested nodes. Our aim is to highlight the universal properties of congestion formation and, in particular, to understand the role of traffic load fluctuations as a possible precursor of congestion in a transport network.