Search Results (72)

Pancreatic cancer is an aggressive malignancy, with a current 5-year survival rate in the United States of approximately 13.3%. Although the current standard for resectable pancreatic cancer most commonly includes neoadjuvant chemotherapy prior to a curative resection, surgery, in the majority of patients, has historically been palliative. The latter interventions include open or laparoscopic bypass of the bile duct or stomach in cases of obstructive jaundice or gastric outlet obstruction, respectively. Non-surgical interventional therapies started with percutaneous transhepatic biliary drainage (PTBD), both as a palliative maneuver in unresectable patients with obstructive jaundice and to improve liver function in patients whose surgery was delayed. Likewise, interventional radiologic techniques included the placement of plastic and ultimately self-expandable metal stents (SEMSs) through PTBD tracts in patients with unresectable cancer as well as percutaneous cholecystostomy in patients who developed cholecystitis in the context of malignant obstructive jaundice. Endoscopic retrograde cholangiopancreatography (ERCP) and stent placement (plastic/SEMS) were subsequently used both preoperatively and palliatively, and this was followed by, or undertaken in conjunction with, endoscopic gastro-duodenal SEMS placement for gastric outlet obstruction. Although endoscopic ultrasound (EUS) was initially used to cytologically diagnose and stage pancreatic cancer, early palliation included celiac block or ablation for intractable pain. However, it took the development of lumen-apposing metal stents (LAMSs) to facilitate a myriad of palliative procedures: cholecystoduodenal, choledochoduodenal, gastrohepatic, and gastroenteric anastomoses for cholecystitis, obstructive jaundice, and gastric outlet obstruction, respectively. In this review, we outline these procedures, which have variably supplanted surgery for the palliation of pancreatic cancer in this rapidly evolving field. Full article

Objectives: To investigate the diagnostic value of various lymphatic imaging techniques for thoracic duct (TD) outlet obstruction in patients with chylous leakage. Methods: A retrospective analysis was conducted on 23 patients with chylous leakage who were radiologically diagnosed with a TD outlet obstruction and underwent a TD exploration and reconstruction between January 2022 and February 2025. Non-enhanced magnetic resonance lymphangiography (MRL), ⁹⁹Tc^m-DX lymphoscintigraphy, and intranodal lymphangiography were employed to detect abnormalities in the central lymphatic vessels. The Receiver Operating Characteristic (ROC) curve was utilized to analyze the diagnostic performance of these imaging methods for TD outlet obstruction in lymphatic disorders. Results: Twenty-three patients (fifteen males and eight females) with chylous leakage were included in this study, with an average age of 59.78 ± 13.08 years. Non-enhanced MRL, ⁹⁹Tc^m-DX lymphoscintigraphy, and intranodal lymphangiography revealed TD outlet obstructions in 13, 17, and 18 patients, respectively. Twenty patients exhibited findings consistent with preoperative imaging during TD explorations; the intraoperative microscopic visualization demonstrated the difficulty of white chyle entering the bloodstream for these patients. The ROC curve analysis indicated that “at least two imaging modalities were positive” and had the highest Area Under the Curve (AUC) value (0.90); “intranodal lymphangiography” and “non-enhanced magnetic resonance lymphangiography” followed closely with respective AUC values of 0.76 and 0.73, and ⁹⁹Tc^m-DX lymphoscintigraphy exhibited a lower AUC value 0.63. Conclusions: The combined utilization of multimodal lymphatic imaging techniques demonstrated a high diagnostic accuracy in identifying TD outlet obstruction in patients with chylous leakage. Full article

To address uneven airflow distribution and pesticide deposition coverage in orchard pesticide application, we developed a double-flexible duct spraying device. Utilizing FLUENT 2022 software for airflow field simulation, we analyzed various structural parameters to identify optimal configurations for the air duct type, diameter, and nozzle outlet diameter. The results indicated that the nozzle outlet diameter most significantly influences wind field uniformity, followed by the air duct diameter and type. The optimal settings were identified as follows: C-Type air duct, 100 mm duct diameter, and 50 mm nozzle outlet diameter. Validation tests confirmed these settings, with simulated and actual wind speed measurements, showing no more than a 10% relative error, affirming the simulation’s accuracy. Field tests demonstrated an average droplet density of 35.38 droplets/cm² within tree canopies, indicating strong penetration ability. Droplet distribution followed a lower > middle > upper pattern in the canopy’s vertical direction, fulfilling technical requirements for high spindle-shaped fruit trees and providing a foundation for achieving a uniform canopy coverage. Full article

A thermal-hydraulic test facility is designed to explore the thermal-hydraulic characteristics inside a fuel assembly under normal operating conditions, thereby providing data for validating computer codes for a novel gas-cooled micro reactor (GMR). The primary loop supplies helium at a prototypic temperature and pressure to the test section containing a full-size fuel assembly. The experimental procedure and the test conditions were elaborated. Pre-test simulations using the COMSOL Multiphysics 5.0 software yield detailed 3D distributions of the temperature and flow fields inside the test section, which were employed to guide the positioning of thermocouples. The maximum temperature and its locus, the pressure drop of the coolant through the test section, and the helium temperature at the outlet duct were determined. The simulation indicates that the “mixer” component can effectively enhance the mixing of helium in the rear plenum and reduce the outlet helium temperature. The measured data of preliminary tests at the facility agree well with the predicted values, which proves the accuracy and reliability of the thermocouples. An unheated section at the end of the heating rods leads to a relatively large deviation of the results on the last measuring plane. Full article

Based on the Daozhen–Wulong Zimuyan tunnel, the distance from the outlet of the air duct to the tunnel face and the diameter of the air duct are studied through an orthogonal experimental design. Aiming at the influence of the position of the air duct of the axial flow fan in the tunnel on the ventilation flow field, the improved TOPSIS theory is adopted for detailed data analysis, and the flow field characteristics are thoroughly checked to identify the optimal working condition configuration. The results show that with the increase in the distance between the air duct and the tunnel face, the local CO concentration will first decrease and then increase, indicating that too large or too small a distance will weaken the effective CO emission ability of the tunnel face, and the distance between the air duct outlet and the tunnel face is the best scheme; by combining the TOPSIS theory, entropy weight method, and analytic hierarchy process, the optimization scheme is obtained. When the distance between the outlet of the air duct and the working face is 15 m, the side wall of the air duct is 4 m away from the air, the diameter of the air duct is 1.8 m, the flow field in the tunnel shows a high degree of stability, the wind speed is significantly increased, and the vortex area that may hinder the air flow is effectively eliminated. The ventilation efficiency is greatly improved and the overall stability of the tunnel is enhanced. Full article

This study analyzed and validated a 1 MW hydropower turbine system using computational fluid dynamics (CFD) in conjunction with field test data. The fluid domain of the hydropower system includes the runner blade, vane, duct, and both inflow and outflow free surface flows. An implicit unsteady flow solver and the SST k-ω turbulence model were employed. The rotational motion of the rotor blade was simulated using the moving reference frame (MRF) method. To handle a non-conformal mesh among the intake, runner, and outlet domains, an internal interface boundary condition was applied. System performance was evaluated by adjusting the guide vane opening ratio and the runner blade pitch angle. A free surface model was also developed to accurately represent the water level. The results show that the CFD analysis predicted the turbine’s power output with a maximum deviation of 1.7% from field test measurements under different tide conditions. The numerical analysis also confirmed the influence of the runner blade pitch angle, with a 1° change in pitch angle leading to a 68 kW variation in power output. The accuracy of the CFD analysis was verified by comparing it to performance data from actual field tests. Full article

In order to study the influence of ventilation parameters on gas movement in large sections of highway tunnels, a mathematical model of gas movement in tunnels is established based on the Yijin Expressway’s Kahaluo No. 1 three-lane tunnel project in Sichuan Province, by using Fluent numerical simulation software to simulate gas tunnel construction. The space–time distribution characteristics of the gas concentration in tunnel construction are obtained, and the influence of ventilation parameters on gas movement is analyzed, the ventilation parameters of the tunnel construction site were optimized. The results show that after ventilation for 20 min, the flow field in the tunnel gradually developed and stabilized, and the gas concentration developing area finally extended to the 45 m position behind the working face, and the gas in the 9 m area behind the face mainly accumulated at the different side of the arched feet of the air duct. Ultimately, the internal flow field structure of the tunnel is mainly composed of a vortex zone (within 10 m in front of the tunnel), a development zone (10–50 m in front of the tunnel), and a stable zone (50–200 m in front of the tunnel). Under the background of the project, the optimal ventilation parameters are as follows: wind velocity 12 m/s, duct diameter 2.0 m, distance from outlet to working face 8 m, and distance from outlet to secondary lining trolley 24 m. According to the optimal ventilation parameter combination, the ventilation system of Cahalo No. 1 tunnel was optimized. It was found that the gas concentration in the tunnel decreased obviously with the increase in ventilation time. The above research further improves the gas tunnel ventilation study, which is of great significance in guiding the site to optimize the ventilation system and guaranteeing the sustainable development of the tunnel ventilation system. Full article

Endoscopic ultrasound (EUS)-guided interventions have revolutionized the management of malignant biliary obstruction (MBO) and gastric outlet obstruction (GOO), providing minimally invasive alternatives with improved outcomes. These procedures have significantly reduced the need for high-risk surgical interventions or percutaneous alternatives and have provided effective palliative care for patients with advanced gastrointestinal and bilio-pancreatic malignancies. EUS-guided biliary drainage (EUS-BD) techniques, including hepaticogastrostomy (EUS-HGS), choledochoduodenostomy (EUS-CDS), and antegrade stenting (EUS-AS), offer high technical and clinical success rates, with a good safety profile particularly when Endoscopic Retrograde Cholangiopancreatography (ERCP) is not feasible. EUS-HGS, which allows biliary drainage by trans-gastric route, is primarily used for proximal stenosis or in case of surgically altered anatomy; EUS-CDS with Lumen-Apposing Metal Stent (LAMS) for distal MBO (dMBO), EUS-AS as an alternative of EUS-HGS in the bridge-to-surgery scenario or when retrograde access is not possible and EUS-guided gallbladder drainage (EUS-GBD) with LAMS in case of dMBO with cystic duct patent without dilation of common bile duct (CDB). EUS-guided gastroenterostomy (EUS-GE) has already established its role as an effective alternative to surgical GE and enteral self-expandable metal stent, providing relief from GOO with fewer complications and faster recovery times. However, we do not yet have strong evidence on how to combine the different EUS-guided drainage techniques with EUS-GE in the setting of double obstruction. This comprehensive review aims to synthesize growing evidence on this topic by randomized controlled trials, cohort studies, and case series not only to summarize the efficacy, safety, and technical aspects of these procedures but also to propose a treatment algorithm based essentially on the anatomy and stage of the neoplasm to guide clinical decision-making, incorporating the principles of personalized medicine. This review also highlights the transformative impact of EUS-guided interventions on the treatment landscape for MBO and GOO. These techniques offer safer and more effective options than traditional approaches, with the potential for widespread clinical adoption. Further research is needed to refine these procedures, expand their applications, and improve patient care and quality of life. Full article

The characterization of passive area sources, emitting odours due to wind-driven convection, poses significant challenges. The present experimental study aims to evaluate the performance, in terms of fluid dynamics and mass transfer, of a recently developed wind tunnel, with a more compact design and reduced weight, compared to the one proposed by the Italian regulations. The results show that the new design outperforms the Italian standard in several aspects. From a fluid dynamic point of view, the new wind tunnel exhibits a slightly more homogenous and uniform velocity distribution, and it does not reveal airflow preferential channels inside the central body. The pressure tests highlight that the presence of fillers in the new wind tunnel does not significantly alter the pressure inside the hood and therefore the gas–liquid equilibrium conditions; actually, the slight overpressure may help to prevent the infiltration of external air. Finally, mass transfer tests on the standard device show a vertical concentration gradient along the outlet duct, highlighting concentration values that differ up to a factor of two depending on the measurement point. The new design has almost completely solved this issue, thanks to the use of fillers that promote mixing of the outlet flow. Full article

It is important to determine the ventilation required in the construction of deep and long tunnels and the variation law of tunnel temperature fields to reduce the numbers of high-temperature disasters and serious accidents. Based on a tunnel project with a high ground temperature, with the help of convection heat transfer theory and the theoretical analysis and calculation method, this paper clarifies the contribution of various heat sources to the air demand during tunnel construction, and reveals the important environmental parameters that determine the ventilation value by changing the construction conditions. The results show that increasing the fresh air temperature greatly increases the required air volume, and the closer the supply air temperature is to 28 °C, the more the air volume needs to be increased. The air temperature away from the palm face is not significantly affected by changes in the supply air temperature. Adjusting the wall temperature greatly accelerates the rate of temperature growth. The supply air temperature rose from 15 to 25 °C, while the tunnel temperature at 800 m only increased by 1.5 °C. Over a 50 m range, the wall temperature rose from 35 to 60 degrees Celsius at a rate of 0.0842 to 0.219 degrees Celsius per meter. The total air volume rises and the surface heat transfer coefficient decreases as the tunnel’s cross-section increases. For every 10 m increase in the tunnel diameter, the temperature at 800 m from the tunnel face drops by about 0.5 °C. Changing the distance between the air duct and the tunnel face has little influence on the temperature distribution law. The general trend is that the farther the air duct outlet is from the tunnel face, the higher the temperature is, and the maximum difference is within the range of 50 m~250 m from the tunnel face. The maximum difference between the air temperatures at 12 m and 27 m is 0.79 °C. The geological structure and geothermal background have the greatest influence on the temperature prediction of high geothermal tunnels. The prediction results are of great significance for guiding tunnel construction, formulating cooling measures, and ensuring construction safety. Full article

The basic national condition that is dominated by coal will not alter in the foreseeable future. Coal-fired boiler is the main equipment for coal utilization, and cyclone burner is a practical type of burner. There is a cyclone formation, a primary air duct inside the center air duct, and a secondary air duct. Introducing a small stream of pulverized coal gas or oil mist stream or gas directly into the reflux zone in the center duct ignites first a stable combustion and a small fluctuation of ignition pressure. In this paper, the variation of furnace temperature for cyclone pulverized coal burner corresponding to different excess air factors and the composition of gases such as O₂, CO, CO₂, and NO_X produced by combustion were investigated using fluent software. A single cyclone pulverized coal burner from an actual coal-fired boiler is used, and a combustion zone applicable to the study of a single pulverized coal burner is established to study the actual operation of a single pulverized coal burner at different excess air coefficients. The findings indicate that the ignition position of pulverized coal combustion advances with decreasing α (Excess Air Factors); however, the length of the produced high-temperature flame gets shorter. As the value of α decreases, the burnout in the furnace decreases and the CO emission concentration increases, with a maximum CO mole fraction of 0.38% at α = 1.2 and a maximum CO mole fraction of 3.13% at the axial position when α decreases to 0.8. The furnace’s concentration of NO_X, the NO_X emission level decreases significantly with decreasing α. The NO_X mole mass increases gradually with increasing α, and in the bottom portion of the primary combustion zone, more NO_X is produced. The concentration of NO_X in the chamber changes significantly after α exceeds 1.0, and the NO_X at the outlet surges from 417.25 ppm to 801.07 ppm, which is attributed to the increase in the average temperature of the chamber, which promotes the generation of thermophilic NO_X. The distribution pattern of O₂ mole fraction along the furnace height cross-section at different excess air factors is basically the same, with a maximum at the burner inlet and a gradual decrease in the O₂ content as it enters the combustion chamber to react with the pulverized coal in a combustion reaction. The value of α = 0.8 when the air supply is obviously insufficient, the fuel cannot be fully combusted, and only a small amount of CO₂ is produced. Full article

Intake is not only the main air supply component of an aircraft, but also one of the forward radar scattering sources. The aerodynamic and stealth performance of intake is critical to the serviceability of advanced fighter aircrafts. The effects of baffle boards with different configurations on the performance of the caret intake with a double S-duct diffuser are presented in this article. The multi-level fast multipole method (MLFMM) and the SST k-ω turbulence model were respectively used to calculate the surface current and the flow field. It was found that the average RCS value of intake can be effectively reduced by installing the baffle board with vertical orientation in the front diffuser, with the DC60 value and the loss of outlet total pressure both increased slightly. The boundary layer separation and the RCS characteristics of intake were closely related to the configuration of the corrugated baffle board. Compared with the traditional curved board, by installing the corrugated board with optimized corrugation number and shape, the stealth performance of intake can be further improved, and the loss of aerodynamic performance can be also reduced. Full article

The special large-slope V-shaped structure of underwater tunnels changes the ventilation characteristics during tunnel construction, making the traditional experience limited. Therefore, it is urgent to study the influence of the special structure on the safety of the air environment during construction. In this paper, a series of small-scale experiments were conducted to investigate the ventilation characteristics of V-shaped tunnels. The coupled effects of ventilation parameters (distance of duct outlet from working face $L_0$, air velocity at the duct outlet $u_0$) and structural characteristics (digging length $L_d$, slope of the uphill section $\theta$) were considered. The extreme slope of the V-shaped tunnel of 8% was considered. The flow field and pollutant transport law were determined by using CO as a tracer in the experiments. The results show that $u_0$ has a positive impact on the air return velocity, while $L_d$ has a negative impact, and neither of the other two factors has a significant effect. The transport characteristics of CO in V-shaped tunnels differ from those in flat tunnels, with the former tending to cause unconventional areas of high pollutant concentrations in the horizontal sections. Furthermore, the correlations between CO concentration and distance, ventilation time, and the influence factors discussed in this paper are derived from the experimental results. The conclusions provide guidance for the construction of V-shaped tunnels to prevent air pollution in the construction environment and to improve the working conditions of laborers. Additionally, it can also enrich the ventilation experience in tunnel construction. Full article

A high temperature is the key factor limiting the safe development of deep mine tunnels. By confronting the phenomenon of serious heat exchange between airflow and the surrounding rocks in the tunnel excavation area, a conceptual model of coupled cooling of auxiliary ventilation and partial thermal insulation is proposed. The performance of a coupled cooling system was investigated and optimized by using the scale model test with a 1:10 geometric scale and the orthogonal test. The results suggest that the average temperatures of the work zone and its central point decrease by 1.5 °C and 3.3 °C, respectively, while partial insulation layers are used. According to the sensitivity analysis for a single factor, as the ventilation duct outlet (VDO) moves away from the working face (WF), the temperature gradually increases, leading to a local high temperature area. When the ventilation duct height is arranged in the middle of the insulation layer, the cooling effect is optimal and the highest average temperature difference is 4.4 °C. The thermal equilibrium temperature can be further decreased by lengthening and thickening the insulation layer. In addition, the range analysis shows that the ventilation velocity has a greater impact on the thermal environment of the tunnel working area than the ventilation duct location and insulation layer length. The coupled cooling method can save on cooling capacity and effectively alleviate the high-temperature problems of the tunnel excavation area. Full article

In operating theaters, ventilation systems are designed to protect the patient from airborne contamination for minimizing risks of surgical site infections (SSIs). Ventilation systems often produce an airflow pattern that continuously pushes air out of the area surrounding the operating table, and hence reduces the resident time of airborne pathogen-carrying particles at the patient’s location. As a result, patient-released airborne particles due to the use of powered tools, such as surgical smoke and insufflated CO₂, typically circulate within the room. This circulation exposes the surgical team to airborne infection—especially when operating on a patient with infectious diseases, including COVID-19. This study examined the flow pattern of functional ventilation configurations in view of developing ventilation-based strategies to protect both the patient and the surgical team from aerosolized infections. A favorable design that minimized particle circulation was deduced using experimentally validated numerical models. The parameters adapted to quantify circulation of airborne particles were particles’ half-life and elevation. The results show that the footprint of the outlet ducts and resulting flow pattern are important parameters for minimizing particle circulation. Overall, this study presents a modular framework for optimizing the ventilation systems that permits a switch in operation configuration to suit different operating procedures. Full article