Exit Area Research Articles

Pola Morfologi dan Perkembangan Kecamatan Natar

The development of a city takes place rapidly due to its attractiveness from both economic and non-economic sides. Rural conditions that are inversely proportional to urban areas drive urbanization. Natar District, part of the Bandar Lampung Metropolitan Area and adjacent to Bandar Lampung City, has undergone changes in morphological patterns. Identifying the morphology of a city area is critical for its development to avoid morphological defects or urban sprawl. This research used a deductive approach, referring to Smailes’ theory, identifying morphology using 3 components: road network patterns, land use and building patterns and densities. In 2012, the morphological pattern in Natar District was linear beaded with the Lintas Sumatra Road as a linear line and Radin Inten II Airport Area, Rejosari Station, Natar Traditional Market, and Hajimena Village as beads (morphological core). In 2022, the morphological pattern in Natar District has developed, still having beaded linear pattern, but there are an additional 2 beads as the core morphology, namely the office, trade and services areas Merak Batin and Natar Toll Exit Area. The development of Natar District is influenced by external factors such as its position adjacent to Bandar Lampung City and internal factors such as facilities and infrastructure.

Investigation on the suitability of conventional film hole under pulsed detonation incoming flow conditions

As a novel and efficient engine, the pulse detonation engine will increasingly demand advanced cooling technology. Film cooling, widely utilized in conventional aero engines, is also anticipated to be employed in pulse detonation engines. However, further investigation is required to assess the suitability of conventional film holes for pulse detonation engines. This study determines the cooling characteristics of a plate with a single film hole in a pulse detonation engine operating at a frequency of 30Hz through numerical calculations. The types of film holes considered include cylindrical, fan-shaped, laid-back, laid-back fan-shaped, and converging-slot holes, all of which have a diameter of 1 mm and an inclination angle of 30°. The single pulse detonation period is divided into stages: initiation and detonation wave propagation, gas exhaust, and refilling. During the initiation and detonation wave propagation stage, the film hole exhibits a significant backflow phenomenon, with the magnitude of gas backflow positively correlated with the outlet area of the film hole. Notably, the converging-slot hole experiences the least amount of gas backflow, with an exit area 33 % smaller than that of cylindrical holes and a corresponding 18 % reduction in backflow enthalpy. Throughout the initiation and detonation wave propagation stage, the backflow gas carries an enthalpy ranging from 0.43 J to 0.63 J into each individual film hole. In the gas exhaust stage, the blowing ratio increases over time as the mainstream pressure decreases, leading to a rapid decline in the film cooling effectiveness of the cylindrical and laid-back holes. The converging-slot holes have the largest film covering area, thus exhibiting the highest film cooling effectiveness, which is 53 % higher than that of the cylindrical hole. In the refilling stage, the mainstream temperature reaches the same level as the secondary flow temperature, rendering the consideration of the cooling characteristics of the film hole unnecessary. Under the conditions of this study, the converging-slot hole is found to be most suitable for cooling the pulse detonation engine.

Evacuation dynamics of heterogeneous crowds: The role of helping others

To investigate the influencing mechanism of helping behavior on evacuation dynamics of heterogeneous crowds, a revised social force model that incorporates the helping behavior is proposed in this paper. The influence factors including following strategy, assisted proportion, exit angle, exit position and width, initial distribution and body size of assisted person, etc. on evacuation process are systematically analyzed. Simulation results indicate that the helping behavior has a significant impact on the evacuation process. The helping relation is vulnerable to be broken at the exit area and individuals that need assistance are more likely to be stuck under this circumstance. Besides, it is found that the proper change of exit parameters such as exit position, exit width and exit angle can alleviate the negative effect of helping behavior on the evacuation efficiency. Furthermore, the motion ability, initial position and body size of difficult person are also crucial to the evacuation outcome.

Isolator shape transition impact on hypersonic internal waverider intake flow distortion

This paper examines the impact of scramjet isolator shape transition on hypersonic internal waverider (IWR) intake. The IWR intake is designed using the osculating axisymmetric flows and streamline-tracing methods. The new Internal Conical Flow “M” basic flowfield is utilized to provide the flow information for the design method. The intake is equipped with three isolators: one with a constant cross section and two with variable cross sections with circular and rectangular exits. The entrance shape and area of the three isolators are fixed to the intake throat shape and area. The exit area of the three isolators is maintained as the entrance one. Numerical computations of three-dimensional configurations reveal that the isolators with variable cross section shapes demonstrate a higher uniformity index than those with constant cross section shape. Thus, the isolator shape transition has decreased the flow distortion of the hypersonic IWR intake system. The three isolators exhibit varied wall pressure distribution depending on the isolator cross section shape, and the total pressure recovery ratios at the three isolators' exit planes are similar. The wall pressure distributions and key performance parameters at the intake throat section, including total pressure recovery, compression ratio, and Mach number, remained consistent across the first part of the intakes. Therefore, changing the cross section shape of the isolator while keeping the area constant could enhance the flow uniformity of compressed air without negatively impacting the intake system's performance. This allows a separate shape selection of the IWR intake throat and the scramjet combustor entrance to fulfill their special requirements.

A comprehensive investigation of the effect of hole diameter and number on film cooling performance of rotating blade leading edge

The combined effect of film hole number and diameter on the film cooling were investigated on the rotating blade leading edge by using experimental and numerical methods. The film cooling performance was obtained by pressure sensitive paint technique under rotational condition. To better understand the experimental results, the flow fields obtained from numerical simulation were also analyzed. The effects of hole length-to-diameter ratio (L/d = 2.5/5/7.5), hole number (N = 7/9/10/11/13), hole diameter(d = 0.64∼1.26 mm), Hole to hole pitch, (P/d = 6.3∼9.2) and hole exit area (Ahole/ALE=4 %-14 %) on the film cooling performance are investigated. Five blowing ratios are also employed (M = 0.5 to 2.0). The results indicate that the hole length-to-diameter ratios (L/d = 2.5∼7.5) have a negligible influence on the film cooling effectiveness. Both the film hole number (N = 10/13) and the hole diameter (d = 0.64/0.75 mm) monotonically affect the film cooling performance under each blowing ratios. However, a comprehensive study indicates that there is a significant quadratic correlation between the area-averaged cooling effectiveness and the total film hole exit area for different combinations of hole number and diameter. Meanwhile, there is an optimal film hole exit area on the leading edge and it increases as the blowing ratio or mass flow rate increases.

Effects of Non-Uniform Center-Flow Distribution and Cavitation on Continuous-Type Pintle Injectors

In this paper, the flow characteristics of a continuous-type liquid–liquid pintle injector are described, focusing on the differential impact of a non-uniform center-flow distribution on single- and bi-injection methodologies as well as the cavitation effect on the spray angle. Using cold-flow experiments, jet-type flows of the center propellant caused by a non-uniform flow distribution were observed during a single injection. This resulted in an augmented pressure drop, as opposed to the flow characteristics of uniform single-film injection. By contrast, bi-injection modalities exhibited a substantial reduction in the pressure drop of the center propellant, underscoring a more equitable flow distribution. Moreover, the occurrence of cavitation in the center propellant was found to markedly affect the spray angle. By considering the injection exit area reduction caused by cavitation, the spray-angle prediction accuracy increased. The findings of this study are expected to reveal the interplay between flow distribution and pressure drop as well as that between cavitation and the spray angle in pintle injectors. Through this understanding, this study provides crucial considerations for the development of more efficient propulsion systems.

Architecture of the flagellar apparatus and related structures in Kolkwitziella acuta: Towards a fine-structural characterization of pallium-feeding dinoflagellates (Protoperidiniaceae)

The fine-structural organization of the protoperidiniacean Kolkwitziella acuta was examined by SEM and TEM. Serial sections of five cells of K. acuta were used to study the architecture of basal bodies and associated roots, the pusular system, and the feeding apparatus. The basal bodies were inserted 1 µm apart at an angle of ca. 80°, and displayed the typical peridinioid features of associating with two roots each and having a layered connective linking the longitudinal microtubular root to the transverse striated root. The transverse flagellar canal was associated with a ‘sac pusule’, while the longitudinal flagellar canal was linked, via a pusule canal surrounded by a conspicuous layer of striated material, to a collecting chamber from which ca. 40 pusular tubes radiated. An extruded pallium was present, associated with a microtubular strand (the MSP) that extended anteriorly and progressively separated into six or seven groups of microtubules, with electron-opaque vesicles present along the MSP. A prominent striated collar surrounded the exit area of the pallium and was connected to the striated collars of both the transverse and longitudinal flagellar canals. The partial nuclear-encoded LSU rDNA sequence confirmed the identification as K. acuta. The currently known fine-structural features of pallium-feeding Protoperidiniaceae are summarized.

A comprehensive comparison of film cooling characteristics of shaped holes on the leading edge of rotating blade

This study numerically investigates the cooling characteristics and flow features of various hole geometries on the rotating blade leading edge. A comprehensive comparison of cooling effectiveness, heat transfer coefficients, net heat flux reduction, and discharge coefficients is conducted among laidback fan-shaped, fan-shaped, laidback, cone holes, and cylindrical holes with two different diameters. Detailed flow and thermal field analysis reveals the impact of geometry on cooling performance. The blade rotational speed is 600 rpm, with a Reynolds number of 12.4 × 104, blowing ratios from 0.5 to 2.0, and fixed injection and spanwise angles at 90° and 30°. Shaped holes share a uniform hole exit-to-inlet area ratio, and cylindrical holes match their inlet or exit areas. The RANS equations were closed using the SST k-ω turbulence model coupled with the Gamma Theta transition model, and an unstructured grid of 13.0 million cells was employed to attain relatively accurate predictive results. Results show that the lateral expansion on the leading edge significantly enhances cooling performance, with fan-shaped holes outperforming others, especially at high blowing ratios. Additionally, cooling effectiveness and discharge coefficient on the leading edge correlate strongly with hole geometric parameters. Shaped holes with equal area ratios show similar discharge coefficients. Cooling effectiveness at high blowing ratios is proportional to the effective exit width, provided that the coolant flows smoothly without severe lift-off.

Supporting driver performance in closely spaced tunnel-interchange structure: Traffic control devices and effects on driving behavior

Objectives With the rapid development of expressways in the mountainous regions of southwestern China, closely spaced tunnel-interchange structures have inevitably emerged due to topographical constraints and environmental limitations. Given the unfavorable road geometry and rapid cross-section transitions, drivers face significant safety concerns. This study aims to investigate drivers’ safety performance at closely spaced tunnel-interchange sections and determine how safety risks can be mitigated through improved traffic control devices design. Methods Thirty-nine participants conducted an experimental study in a fixed-base simulator. The test scenario was modeled on the Xingyan Freeway-S3801 and accurately reproduced in the simulator. For each safety performance metric, the driving simulator experiments yielded a dataset with 780 observations. To address the idiosyncratic variation due to individual driver differences, a series of linear mixed effects models (LMM) were developed to analyze drivers’ behavior responses. Results In closely spaced tunnel-interchange sections, a general impairment of both longitudinal and lateral performance was observed. This study identified potential critical impact variables in traffic control device systems. According to the LMM results: (a) Removing the 0.5 km interchange ramp exit advance guide sign located in the tunnel exit area reduces dangerous behavior in the corresponding impact area. (b) Replacing the 0.5 km interchange ramp exit advance guide sign with arrow pavement markers as an information source supports improved driver performance, promoting driver safety. (c) Adding tunnel exit distance signs within tunnels is recommended to enhance situation awareness for drivers. Conclusions This study addresses the scientific issues related to traffic control devices setup for closely spaced tunnel-interchange sections, focusing on identifying potential critical impact variables. The findings provide guidance on the design of traffic control devices for such sections and support revisions to national engineering standards.

Ski slopes as an unrecognized source of human impact on vegetation

Various anthropogenic activities, e.g. construction, soil disturbance, and introducing artificial plant mixtures on newly-created ski slopes after forest clearing are significant interventions in ecosystems. These drastic acts influence the species composition of vegetation cover in the landscape. Although synanthropic species are typically infrequent in mountainous areas, they tend to flourish in disturbed environments; ski slopes are no exception to this pattern. Here we assessed the composition of vascular plants in three distinct ski slope habitats across 30 Slovak ski resorts: the ski lift entrance areas, the ski lift exit areas, and the central areas of the ski slopes. To gain insights into the dynamics of the spreading of synanthropic species on ski slopes, we used selected species traits, synanthropization indices for both flora and vegetation, and considered specific disturbance criteria. The outcomes of our study confirmed that the highest richness of synanthropic species was observed in plots located at the ski lift entrance areas, while the lowest in the central areas of the ski slopes. This difference could be attributed to the proximity of anthropogenically-disturbed zones, which act as propagule sources for synanthropic species into these mountainous habitats. At the same time, elevation also plays an important role in limiting spread of synanthropic plants on ski slopes. The study of synanthropic plant species distribution on ski slopes provides valuable insights into the complex interactions between human activities and the environment.

Experimental study on backward erosion piping of a double-layer dike foundation under variable exit geometries

Double-layer dike foundation is composed of a weakly permeable overlying clay layer and a highly permeable underlying sand layer, which is one of the most common stratum types in dike engineering with the highest probability of catastrophic damage, and the main danger is backward erosion piping. Existing research on backward erosion piping of double-layer dike foundation has not fully considered the influence of the exit on the erosion process. Therefore, a self-designed test device is used to assess the influences of the size, position and type of different exits, and the circular exit is connected with the slot exit via the exit area to explore the critical identification conditions and the pipe development mechanism toward the upstream direction under different exit geometry conditions. The results show that both the local and global hydraulic gradients borne by the exit are inversely proportional to the exit area and are less notably affected by the location of the exit. The development process of slot exit pipes differs from that of circular exit pipes, and pipes are usually developed alternately at the two corners of the exit near the upstream end and then converge into one pipe. The average pipe depth and width are proportional to the exit size and the seepage length. With increasing average pipe area of the slot exit, pipes develop more rapidly after head enhancement, and the damage to the dike foundation increases.

Exploring the causes of frequent accidents at highway tunnel exits: Coupling analysis of the slack effect and white hole effect in extra-long tunnels

In this paper, the causes of frequent traffic accidents at the exits of highway tunnels are investigated. This study recruited 34 subjects to conduct vehicle experiments using an illumination meter, eye tracker, Smarter Eye and OBD to measure the illumination, eye movement characteristics, driving trajectory, and speed while driving in a tunnel exit. A questionnaire was used to investigate drivers’ subjective feelings while driving. The change trend of each indicator in the area near the tunnel exit was analyzed, and the relationships among the light environment, driver physiology, driving behavior, and driver psychology were explored. The psychological and physiological inconsistency phenomenon and abnormal acceleration behavior were observed at the tunnel exit, and the slack effect was verified. As the tunnel exit area is driven through, with the rapid increase in illumination, the rate of change of the driver’s pupil area increases, and the distance between the vehicle and the tunnel sidewall increases. It is unreasonable that in a tunnel exit with a poor traffic environment, some drivers experience psychological slack and tend to increase their speed and accelerate out of the tunnel. The slack effect is observed in most drivers, approximately 79.4% of the total. The white hole effect interferes with drivers’ vision and reduces their ability to obtain traffic information. The slack effect reduces drivers’ attention and increases vehicle speed. A coupling effect exists between the white hole and slack effects, which together threaten traffic safety at the tunnel exit.

Numerical Simulation of the OFA Effect on Combustion in a 600 MWe Boiler with Centrally Fuel Rich Burners

ABSTRACT With the rapid development of renewable energy, the traditional coal-fired power generation plays an important role in peak regulation, which requires the boilers to operate at low load or even ultra-low load. In order to investigate the effect of over-fire air (OFA) ratio on the flow, temperature and component concentration distribution and the furnace exit parameters for utility boilers at ultra-low loads, a 600 MWe utility boiler with centrally fuel rich (CFR) burner technology is taken as the object of study, and numerical simulations are carried out for five operating conditions with different OFA ratios (0%–40%) at 25% of the boiler’s maximum continuous rating (BMCR) load. The results show that no obvious high-temperature region is formed in the furnace and the flow field distribution in the furnace exit area is not conducive to the stable combustion of pulverized coal when the OFA ratio is 0% and 10%. When the OFA ratio is 30%, the area of the high-temperature region in the furnace reaches its maximum. When the OFA ratio is 40%, the furnace exit NO concentration is only 94.54 ppm. With the increase of the OFA ratio from 0% to 40%, the temperature of the flue gas at the furnace exit decreases by more than 100 K, which may affect the stable operation of the Selective Catalytic Reduction (SCR) denitrification equipment. Taking into consideration the flow in the furnace, the combustion, the NO x emission, and other factors, the recommended OFA ratio is 20% ~30%.

Effect of expressway exit deceleration markings on distracted drivers in China

Expressway exit areas experience traffic diversion and complex road conditions, making them accident-prone areas. In this study, transverse and fishbone visual illusion deceleration markings were selected to optimize the induction facilities at expressway exits. The research aims to investigate the impact of these markings on the driving behavior, cognitive load, and physiological characteristics of drivers in various distracted scenarios at expressway exit areas. Furthermore, a comprehensive evaluation of each experimental scheme is conducted using the Matter-Element Extension Model. The study found that the implementation of deceleration markings can effectively enhance driver alertness and lane change awareness, enabling drivers to reduce their speed to near the speed limit in exit areas without compromising driving comfort. Compared to the situation without markings, drivers begin to decelerate approximately 600 m earlier and exit the ramp when markings are present. Fishbone deceleration markings, in contrast to transverse markings, result in lower vehicle speeds, smoother deceleration, and more effectively stimulate drivers' intention to change lanes, guiding them to make the final lane change earlier. Based on the comprehensive evaluation results, it is recommended that transverse or fishbone deceleration markings be considered in engineering practice. These markings have not produced significant effects on driver visual fatigue and driving load, with fishbone markings demonstrating superior comprehensive evaluation outcomes. These research findings can provide valuable insights for future expressway exit area marking design schemes, further enhancing driver safety.

Experimental evaluation of the influence of the diffuser inlet to nozzle exit cross sectional area ratio on pressure oscillation in a high-altitude test facility

The ratio of diffuser inlet to nozzle exit area (Ad/Ae) is one of the most important parameters in designing and evaluating the performance of a high-altitude test facility (HATF). Typically, at motor pressures near start or operating pressure of the diffuser, the vacuum chamber pressure oscillates at a high Ad/Ae, which may be dangerous for the HATF. In the present study, the effect of the Ad/Ae on the starting and breakdown performance of a second throat exhaust diffuser (STED) has been investigated experimentally using a HATF supplied by high-pressure cold air apparatus. Upon examining the overall performance of the diffuser, it is observed that with an increase in Ad/Ae, the oblique sealing shock wave at the diffuser inlet undergoes significant changes in location and strength. This leads to a further reduction of the flow total pressure and a stronger separation of the flow along the diffuser. Consequently, flow instability arises during starting or breakdown phases near the STED starting or operating pressure. By frequency analysis, it is observed that as Ad/Ae increases, the number of oscillatory modes of the vacuum chamber pressure increases and the dominant frequency of the oscillations in these transient situations becomes larger. Additionally, there is a significant decrease in nozzle pressure related to the onset of pressure oscillations. Furthermore, with an increase in Ad/Ae from 1.27 to 7.81, the minimum starting pressure and breakdown pressure of STED increase by 20.33% and 28.47%, respectively. Also, the hysteresis range in performance of STED vanishes at high Ad/Ae values.

EFFECTS OF CONTINUOUS AND FRACTURED RIBS PLACED AT THE ENDWALL SURFACE UPSTREAM OF THE TURBINE-VANE LEADING-EDGE

Total pressure loss, chaotic and heavy flow downstream of the turbine passage exit area are a few effects of the desired increase in inlet temperature input at the upstream part of the turbine vane passage. Huge amount of energy from the cross-flows near the middle of the vane actual chord are transported downstream by this chaotic flow which often results in aerodynamic loss and differential heat penalties. To compare the different arrangement, comparisons of the two geometries, the impact of adding various rib configurations upstream are studied for heat augmentation efficacies. The leading-edge rib(s) effects at the mid-stream of the vane passage are quantitatively examined in this work using computational fluid dynamics (CFD) technique. With the employment of Reynolds Averaged Navier-Stoke energy equations, the geometries are modelled choosing the appropriate boundary conditions. Polyhedral mesh is used with fifteen prism layer mesh at the endwall and vane surfaces to capture the flow physics close to the endwall area. Although the two configurations employed showed relative reduction in the total pressure loss coefficient, however, the fractured ribs produced superior outcomes of Nusselt number reduction of over 10% along the passage exit region. The data demonstrate a considerable difference in the overall pressure loss between the two configurations.

Why frequent traffic accidents at highway tunnel exit? – An experimental analysis of the slack effect

This study analyzes the causes of frequent traffic accidents at the exit areas of highway tunnels. Vehicle experiments were conducted to collect data on the light environment, vehicle speed, and driver eye movement. The distribution patterns of the illumination, vehicle speed, and gaze location occupancy were analyzed, and highway tunnels of different lengths were compared. The tunnel exit area is divided into the transition, exit, and departure zones. It was observed that there was an obvious white-hole effect at the exit zone, with drastic changes in the light environment. The presence of abnormal acceleration behavior in the transition zone and decreased attention in the departure zone demonstrate the existence of psychological and physiological slack in drivers. Additionally, the tunnel length positively correlates to the slack effect, which is stronger in extra-long tunnels than in the short and medium tunnels. Multiple control scenarios were established and driving simulation experiments were conducted to further analyze the impact of the slack effect on the traffic safety. The experimental results demonstrated that the slack effect of the extra-long tunnels exhibited an evident lag which was still present after leaving the tunnel exit. The average vehicle speed and trajectory offset were larger and more discrete in the post-tunnel zone than on an ordinary open road. The speed of the curve in the post-tunnel zone is 5.1 % higher than that of the curve in the ordinary road, and the maximum trajectory offset is 54.3 % higher. Thus, this study reveals the slack effect at tunnel exits and explains the abnormal phenomenon of relatively good traffic environments but high traffic accident rates in the transition and departure zones of tunnel exits. These results present considerable practical significance for the safe operation of highway tunnels, particularly extra-long tunnels.

Safety Evaluation and Influential Factor Analysis of Urban Expressway Diversion Areas Based on Non-Stationary Conflict Extremes

To evaluate the safety conditions of expressway exit areas with different exit forms, a safety analysis method based on the conflict extreme model is proposed. Based on video data from four typical urban expressway diversion areas, longitudinal conflicts and lateral conflicts were identified using time to collision and cross time to collision methods, respectively, and traffic parameters such as traffic flow were extracted. A Bayesian hierarchical conflict extreme model for joint conflict types was constructed by integrating the peak over threshold and Bayesian hierarchical approach. The threshold for conflicts was determined using the mean residual life plot and the threshold stability plot. Subsequently, a logarithmic link function for the scale parameter was established by combining different covariates. Then, the model parameters were estimated using the Markov chain Monte Carlo simulation method. Finally, based on the fitted distribution, a comprehensive safety evaluation and influential factor analysis were conducted for each diversion area. The results show that an increase in traffic flow and the ratio of large vehicles leads to a higher probability of traffic accidents. However, an increase in the average speed reduces the probability of traffic accidents. The construction form of the diversion area and the number of off-ramp lanes do not demonstrate an explicit relationship with the probability of traffic accidents. The research conclusion indicates that the Bayesian hierarchical extreme model can effectively utilize short-term observed conflicts for long-term crash estimation, and it has the potential to be applied in the field of safety evaluation.

Comparative analysis of spatial transport characteristics of spring cold-front-type sandstorms in the Hexi Corridor

In this study, we investigate the spatial transport characteristics of cold-front-type sandstorms with different intensities in the Hexi Corridor based on the hourly observation data from 13 ground-based meteorological stations in the Hexi Corridor, the data in the upper and lower layers from the Meteorological Information Comprehensive Analysis And Process System, and the three-dimensional aerosol observation data of the Vertical Feature Mask product obtained from the Cloud-Aerosol Lidar with Orthogonal Polarization of the United States. The results show that the influence range and horizontal transport distance of cold-front-type sandstorms in the Hexi Corridor are determined by the intensity, thickness and width of the upper-level troughs and the intensity of cold fronts. Generally, cold fronts pass through the Hexi Corridor from noon to evening and stay in this region for a long time or move slowly, which is favorable to the horizontal long-distance transport of sandstorms. The intensity of the 200 hPa upper-level jets is directly proportional to both the influence range and transport distance of sandstorms which primarily occur on the left side of the exit area of an upper-level jet. The strengthening of upper-level jets induces the formation of the vertical circulation cell at middle and low levels. The ascending branch of the circulation cell lifts sand-dust particles from the surface to the upper layers, and the descending branch transports upper-level momentum to the near-surface. This circulation situation increases the near-surface wind speed and forms sandstorms. The occurrence time and descending branch of the secondary circulation cell caused by upper-level jets are important indicators for predicting the occurrence time and falling area of sandstorms. Dust aerosols are mainly concentrated at a height of 2–6 km,.,and they can reach the height of 12 km. When the dust is concentrated at the height of 2–8 km, and the wind speed of 500 hPa and 300 hPa reaches 28 and 32 m s− 1 or above respectively, the cold front sandstorm can realize the long distance transport of thousands of kilometers.

Termination without global capture: electrocardiographic and anatomical characteristics using 3D-electroanatomical mapping system in reentrant ventricular tachycardia

Abstract Background Termination without global capture (TWGC) is the phenomenon which a pacing stimulus applied during ventricular tachycardia (VT) terminates the tachycardia without generating a QRS complex, and is considered as an indicator for the critical component of the circuit. The details of the electrocardiographic and anatomical characteristics of the site using a 3D-electroanatomical mapping system (3D-EAM) remain unknown. Purpose This study aimed to retrospectively analyze the cases that showed TWGC during VT mapping and ablation, and to investigate the electrocardiographic characteristics and relationship with the substrate identified by 3D-EAM. Methods Of 632 cases of VT associated with structural heart disease from July, 2019 to July, 2023 at a university hospital and a university medical center, cases with TWGC were analyzed. Results TWGC was observed in 10 patients (median age 61 years, 9 males, 5 ischemic cardiomyopathy, median LVEF 31%) at least once (12 times) in 11 locations. Local capture was observed in 6. The QRS morphology generated by continued pacing after TWGC matched the clinical VT in only 5 VTs (42%). Five showed decremental conduction of stimulus to QRS interval following the TWGC. In 11 locations, 4 corresponded to scar area (<0.1 mV) in the voltage map, 6 to border zone (0.1-1.5 mV), and 1 had no information on 3D-EAM. Of 12 times of TWGC, 3 were at the entrance, 1 at the central isthmus, and 1 at the exit. Acute elimination of clinical VT was successful in 7 of 10. Conclusions More than half of the sites with TWGC were located at the border zone in 3D-EAM. TWGC also occurred in the central or exit area, and local capture was observed frequently.Termination without global capture