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This paper presents a unique design of a total-flow geothermal power generator that uses Turgo turbine and two-phase supersonic nozzles. The high-speed flashing jets are formed by high-pressure subcooled liquid from the well through the nozzles and impinge turbine blades obliquely to drive the Turgo turbine. This new generator converts geothermal power directly from the geothermal fluid without implementing any phase separator or heat exchanger, which results in a simple and easy-to-maintain system. A prototype of the total-flow geothermal power generator was built and field-tested in Yilan, Taiwan. Results show that compared to traditional Organic Rankine Cycle generators and double flash geothermal power plants, the new design has a competitive geothermal efficiency operating at moderate reservoir enthalpies.

This paper investigates the dynamic behaviour of a low pressure open natural circulation loop applied to a parabolic trough collector. An in-house experimental setup is developed to perform the test. The experiments are performed on two distinct modes: H-mode and S-mode, corresponding to single-phase and two-phase flow. Three distinct power amplitude modes viz, 250, 325, and 464.3 W with a power step number of 24, 18 and 12 having a duration of 15, 20 and 30 min are considered. A Fast Fourier Transform analysis revealed that the flow in the loops is stable with a maximum decay ratio of 0.726. Instabilities, including Density Wave Oscillation, geysering and flashing, are observed during the test. Moreover, the thermal inertia of the loop has a significant role in the initial stage of power steps. An increase in the power step size conferred a 9.1%–33.4% increase in the outlet temperature of water in H-mode. In S-mode, an increase in power step size delayed the onset of boiling and reduced the duration of boiling by 2.8–14.32% and 8.03–22.02%. The loop can generate a mass flux of 40–42.5 kgm2s−1 in H-mode and up to 400 kgm2s−1 in S-mode, which is significant.

In this paper we propose SecretSign, an interactive system which enables users of shared-mobility services to find their allocated vehicle quickly without notifying other people of the identity of the target vehicle. A light attached to the target vehicle turns on and off in conjunction with the user’s operation of a remote control device, while the lights on other vehicles blink in ‘random’ patterns created by study participants. We tested a passive approach, in which the light on the controller blinks in conjunction with the target, however we found users could identify the target faster with manual operation. We collected typical user-generated ‘random’ patterns in order to better camouflage the distinct patterns likely to be employed by users. We experimentally evaluated SecretSign in a parking lot, and verified that it is also effective in the daytime. Bystanders were rarely able to identify the user’s vehicle.

Many parts of the globe need large amounts of water for agricultural, industrial, and residential purposes. The global scarcity of fresh water is becoming more apparent. For saltwater desalination, a variety of methods are employed, some of which use energy and others which utilise mechanical energy. Multistage Flash Evaporation (MSF) techniques are commonly used. Essentially, the process involves gradually heating saline water to a maximum working temperature of (90 °C) to (130 °C), then flashing it in a series of phases under increasingly decreasing pressure. Each stage's vapour is condensed with entering feed water through a heat exchanger. The impact of the number of tube passes in a heat exchanger on the efficiency of a (MSF) plant was investigated, and the findings were compared to those of a (MSF) plant (Sirte City MSF plant in Libya).

Introduction: A large majority of pedestrian fatal crashes occurred during the nighttime. The focus of this research was to identify if the following pedestrian crossing treatments were more or less effective at night: pedestrian hybrid beacon (PHB), rectangular rapid flashing beacon (RRFB), or LED-embedded crossing warning sign (LED-Em). Method: For each treatment, two statistical evaluations were used on the staged pedestrian data: ANCOVA models that considered per site mean yield rates and logistic regression that considered the individual driver response to the crossing pedestrian. Results: For the PHB, essentially no difference was found between the very high daytime and nighttime driver yielding values. The research found RRFBs to be more effective at night, and the LED-Em to be more effective during the day. Using the results from the logistic regression evaluation, higher driver yielding was observed at LED-Em sites in the lower speed limit group (30 or 35 mph (48.3 or 56.3 kph), with 2 lanes (rather than 4 lanes), with narrow lanes of 10.5 or 11 ft (3.2 or 3.4 m) widths (rather than 11.5 or 12 ft (3.5 or 3.7 m) widths), and lower hourly volumes. The results from the ANCOVA model for LED-Ems also showed a statistically significant difference for yield lines (higher yielding when present). Conclusions: This analysis represents the only known study to date on the effectiveness of pedestrian crossing treatments at night. Practical Applications: This study provides additional support for the PHB as a treatment because the PHB was found to be highly effective during the nighttime as well as the daytime. The value of using advance yield lines was also demonstrated. The findings offer a caution regarding the use of the LED-Em treatment on higher speed, higher volume, or wider roads.

In this study, we experimentally investigate of a two-phase natural circulation loop that functions as a passive containment cooling system (PCCS). The experimental apparatus comprises two loops: a hot loop, for simulating containment under severe accidents, and a natural circulation loop, for simulating the PCCS. The experiment is conducted by controlling the pressure and inlet temperature of the hot loop in the range of 0.59–0.69 MPa (abs) and 119.6–158.8 °C, respectively. The heat balance of the hot loop is established and compared with a natural circulation loop to assess the thermal reliability of the experimental apparatus, and an additional system is installed to measure the vapor mass flow rate. Furthermore, the thermal–hydraulic characteristics are considered in terms of a temperature, mass flow rate, heat transfer coefficient (HTC), etc. The flow rate of the natural circulation loop is induced primarily by flashing, and a distortion is observed in the local HTC because of the fully develop as well as subcooled boiling. As a result, we present the amount of heat capacity that the PCCS can passively remove according to the experimental conditions and compared the heat transfer performance using Chen's and Dittus-Boelter correlation.

A thermal desalination system with a flash drum, a spray-nozzle system, and a condenser under vacuum is designed. Theoretical yield of water vapor in the vacuum flash drum has been evaluated based on conservation equations of mass and energy in the range from 0.35 % to 8.37% at temperature of saline feed water from 40 °C to 60 °C, salinity from 0.035 to 0.04 kg/kg, feed flow rate of 40000 kg/day, and supersaturation from 2 °C to 50 °C. A thermal-fluid model has been adopted to simulate the dynamics of saline water droplets for flash evaporation under vacuum. At a moderate droplet velocity, the model predicts time scales for evaporation from 0.5 s to 1 s with yield of flashing vapor from 69.24 % to 84.59 % at droplet radius from 100 μm to 150 μm. The yield increases with the increase in supersaturation and feed temperature, whereas it increases appreciably with the decrease in droplet size. The design is based on the evaporation time scale and the theoretical yield. Both droplet dynamics for flash evaporation and theoretical yield have been validated with results from the literature.

Green flash light (FG) and green countdown (GC) are the two most common signal formats applied in green-red transition that provides drivers additional alert before termination of green phase. Due to their importance and function in stop-pass decision-making process, proper use of them has become a critical issue to greatly improve the safety and efficiency of signalized intersections. Gradually e-bike riders have become more important commuters in China, however, the influence of FG or GC on them is not clear yet and need pay more attention to it. This study chooses two almost identical intersections to obtain highly accurate trajectory data of e-bike riders to study their decision-making behaviors under FG or GC. The e-bike riders’ behavior is classified into four categories and is to identify their stop-pass decision points using the acceleration trend. Two binary-logit models were built to predict the stop–pass decision behaviors for the different e-bike rider groups, explaining that the potential time to the stop-line is the dominant independent factor of the different behaviors of GC and FG. Furthermore empirical analysis of decision points indicated that GC provides the earlier stop-pass decision point and longer decision making duration on the one side while results in more complexity of decision making and greater risk of stop-line crossing than FG on the other side.

The flashing yellow arrow (FYA) signal display creates an opportunity to enhance the left-turn phase with a variable mode that can be changed on demand. This research develops an integrated general purpose data collection module that time stamps detector and phase state changes within a National Electrical Manufacturers Association (NEMA) actuated traffic signal controller to provide recommendations for the flashing yellow arrow left-turn mode on a cycle-by-cycle basis. 115 left-turn approaches at 38 intersections with locations across the State of Florida were analyzed totaling 1370 h of video data processed including off-peak and peak conditions. Video data extraction was an essential step in developing the gap thresholds for the permissive left-turn. Actual intersection field data were obtained through loop detector mapping to the controller in the lab in real-time mode using a peer-to-peer logic environment. A custom communications software was developed to retrieve instantaneous channel input data, synchronize opposing through green phase, analyze traffic information, provide the algorithm decision, and generate a real-time log recording the events to determine whether it would be optimal to switch the red arrow to a flashing yellow arrow. The algorithm determines the time interval between the successive arrivals of vehicles and computes the corresponding headway for each lane by cycle on a second-by-second basis. Peer-to-peer logic is a necessary step to verify and validate new traffic concepts prior to field-testing and offers the advantage of acquiring and analyzing real-time traffic data coupled with video feed with the benefit of a safe environment.

The majority of the collisions at grade crossings occurred at flashing-light-controlled grade crossings. Understanding drivers’ behaviors and visual performances in the process of approaching the crossings is the foundation of improving crossing safety. This study aims at utilizing driving simulation and eye tracking systems to investigate the efficacy of improved traffic signs and pavement markings (PSM) at flashing-light-controlled grade crossings. The improved signs and markings were modeled in a driving simulation system and tested with a series of flashing light trigger time (FLTT) ranging from 2 s to 6 s with 1 s interval increment. Foggy conditions and drivers’ genders and vocations were considered in experiment design. Thirty-six fully-licensed drivers between 30 and 48 years participated in the experiment. Several eye-movement and behavioral measures were adopted as reflections of the subjects’ performances, including the first fixation time on signs and signals and distance to stop line, total fixation duration, compliance rate, stop position, average speed at the stop line, maximum deceleration rate and brake response time. Results showed that compared with traditional grade crossings signs and pavement markings, drivers could perceive signs timelier and fixate on the flashing-light signal earlier in PSM, especially in the scenarios of earlier FLTTs. The improvement in fixation performance and sign design contributed to a higher stop compliance rate. Importantly, it was found that drivers would hesitate to decide whether to stop or cross facing with flashing red lights, which is similar to the dilemma zone of roadway intersections. Drivers were more likely to fall into the dilemma zones when FLTT was

The world's first Liquefied Hydrogen (LH2) Carrier which will transport LH2 from Australia to Japan has been built. At Japanese port, reducing the tank pressure will be required for the safe tank operation. However, pressure reduction will cause flashing, leading to an excess of the venting capacity or liquid leakage. Hence, the purpose of this research is to clarify the pressure reduction rate and liquid behavior through experimental and numerical approaches respectively. Pressure reduction experiment under high liquid level condition was conducted by using 30 m3 tank filled with saturated LH2. The experiment showed that the pressure recovery occurred at the beginning of depressurization, and then the pressure decreased based on the equilibrium state. From numerical analysis by VOF based in-house CFD code, it was found that the pressure recovery was caused by the boiling delay, and the tank pressure followed the saturation pressure after the liquid fully stirred.

The accidental releases of pressurized liquefied gases from tanks involve violent phase transformation, which would generate two-phase releases and flashing jets. To investigate the evolution of leakage behaviors and make an analysis of near-field jet flow characteristics, a small-scale liquefied gas release experiment has been established. Leakage holes with different length-diameter ratio (LDR) have been used to analyze interactions between the leakage holes and release behaviors. Morphological characteristics of jet expansion angles have been obtained by high-speed camera, and jet velocities have been measured by particle image velocimetry (PIV). Meanwhile, the depressurization process, variation of temperature in the tank and mass outflow rates were obtained. Results show that, despite the LDR is varying, expansion angles and jet velocities behavior in the same tendency: decreases in the initial and maintains in a stable value for a period. The stable velocity status was worked by the balanced pressure drop. Thereafter, an empirical two-phase mass outflow rate model is developed based on the experimental data, which is related to the nozzle geometric parameter and upstream pressure, 90 % of the experimental data are within ±12 % of the prediction. Therefore, the empirical two-phase model can be supported in the mass flow rate evaluation, especially for the release cases that LDR are smaller than 5.00 but larger than 2.00. The experimental data is beneficial for providing further insight into the prediction of accidental release and risk assessment for the liquefied gas transportation and storage.

Flash Joule heating (FJH), an advanced material synthesis technique, has been used for the production of high-quality carbon materials. Direct current discharge through the precursors by large capacitors has successfully converted carbon-based starting materials into bulk quantities of turbostratic graphene by the FJH process. However, the formation of other carbon allotropes, such as nanodiamonds and concentric carbon materials, as well as the covalent functionalization of different carbon allotropes by the FJH process, remains challenging. Here, we report the solvent-free FJH synthesis of three different fluorinated carbon allotropes: fluorinated nanodiamonds, fluorinated turbostratic graphene, and fluorinated concentric carbon. This is done by millisecond flashing of organic fluorine compounds and fluoride precursors. Spectroscopic analysis confirms the modification of the electronic states and the existence of various short-range and long-range orders in the different fluorinated carbon allotropes. The flash-time-dependent relationship is further demonstrated to control the phase evolution and product compositions.

Microalgae Dunaliella salina has been recognized as an effective source of β-carotene. To elevate the productivity of this species, light has been served as an important induction factor, in this regard, a new idea was inspired as designing a red-to-blue wavelength shifting system based on the growth rate and cell behavior. A photobioreactor was exposed to two panels of flashing red and blue LEDs. At the commencement of the stationary phase, the wavelength shifting was applied and red LEDs were replaced with blue ones. Maximum β-carotene content of 10 mg.g−1 was obtained; at least 300% higher than the content in the controlled system (flashing red and blue light to the end of growth).

Snow removal activities are performed by roadway agencies to enhance winter mobility and safety. Slower travel speeds during these operations, combined with low visibility and reduced pavement friction, mean that safety and collision avoidance remain a persistent concern. Many studies have implemented signing and lighting technologies to improve the visibility of snowplows. Although a few studies have evaluated the use of different colors on snowplows, there is no rigorous study that evaluates the potential impacts of using green warning lights for winter maintenance operations. This study, therefore, investigates the impacts of various warning light configurations on the visibility of snowplows, with the focus on green lights. To this end, 37 warning light configurations are designed using various color combinations (green and amber), and flashing patterns (single and quad) on the back (LED), the top (beacon), or both, of snowplows. These configurations are evaluated to identify the most effective configurations. Three sets of experiments are designed and implemented: static, dynamic, and weather to evaluate the visibility effectiveness in different contexts: day versus night, clear versus snowy weather, and static versus dynamic scenarios. Human subjects are employed to conduct the experiments and the test results are evaluated using statistical analyses. The conspicuity during the day time and glare during the night time are statistically different among various configurations. In addition, adding green lights with a single flash pattern to amber warning lights improves the conspicuity, while keeping the glare at an acceptable level relative to configurations using only amber.

Rectangular rapid flashing beacons (RRFBs) have proven to be a useful tool for improving driver yielding and pedestrians’ safety at midblock crossings. This study analyzed driver yielding at 23 RRFB-enhanced midblock crossings on three-lane roadways with and without median refuge islands in Oregon. The locations were chosen to represent a range of posted speed limits and average daily traffic that aligns with existing guidance for median and beacon installations. Sites were classified either as (a) no median refuge, RRFBs placed outside the roadway, (b) median refuge, RRFBs placed outside the roadway, (c) median refuge, RRFBs placed on the island and outside the roadway. Yielding was determined following protocols established in prior research. Two hundred seventy-six hours of video footage were analyzed, resulting in 3,065 crossing events (1,338 staged; 1,727 naturalistic) undertaken by 3,683 pedestrians. High yielding rates were observed—the average near side yielding rate was 97%, with the lowest site having a rate of 89.9%. Yielding rates were generally higher on the far side. Owing to sample size and consistently high yielding rates, it was not possible to make conclusive observations about the relationship between driver yielding and the presence of median or additional beacons for the volume and speed combinations. The results generally indicated that yielding rates increased with the addition of median beacons. The findings also suggested median refuge islands with a beacon increased yielding. The increase in yielding was statistically significant at sites with average daily traffic of 12,000 to 15,000.

The flashing green signal indicates that the green signal will end, and its application at signalized intersections is optional. This paper presents the results of the survey conducted among Belgrade drivers. The survey was conducted in order to analyze behavior, perceptions, knowledge, and attitudes towards the flashing green signal. Results showed that drivers mostly support the flashing green implementation. Also, respondents expressed an opinion that the flashing green improves traffic efficiency and safety. A third of drivers decelerate and stop when flashing green starts. In a situation where the vehicle in front of them decelerate when flashing green starts, 13% of drivers will try to change lane and pass an intersection. This result indicates that drivers of following cars can have conflicting decisions. Results showed that half of the respondents underestimate the flashing green duration while a third of them overestimate it.

Light is one of the most critical factors for the growth of microalgae; therefore, optimization and accessibility of light improve productivity and wastewater nutrient removal is important. The flashing light effect allows microalgae to use light effectively through intermittent exposure. Nutrient assimilation and membrane fouling were considered in a reciprocal membrane photobioreactor (RMPBR) and an LED flashing light was provided as a source of illumination. The objective of this study was to bridge the gap between light delivery and RMPBR performance. In this connection, we examined flashing lights with frequencies of 1 Hz and 1000 Hz at a constant duty cycle of 60% along with continuous light. Regarding the effect of the flashing light on RMPBR, the cells which acclimated to flashing light of 1000 Hz resulted in maximum removal of nitrate (97%) and phosphate (70%). However, the culture with the low frequency of 1 Hz was only able to remove nitrate and phosphate up to 68% and 47%, respectively. Furthermore, the reactor with 1-Hz flashing light frequency was fouled earlier within 84 h thereby reaching the highest pore-blocking. Proteins and carbohydrates were recognized as a major cause of fouling in the low-frequency flashing light. We conclude that high-frequency flashing light (1000 Hz) could be an effective light condition for nutrient uptake in wastewater treatment.

This work focuses on the modification and simulation of asphalt blowing unit- hot oil system of Kaduna Refining and Petrochemical Company (KRPC). The modification involves an introduction of a 10-inch bye-pass line to the hot oil drum which helps in preventing oil loss and decrease heater duty for better efficiency and cost effective system. While the original and modified units were simulated using ASPEN HYSYS withthe aim of observing the effect of temperature on the heater duty of the units and to determine the volume of hot oil lost from the hot oil drum due to flashing. After successful completion of the simulation, the amount of vapour lost per hour for the operational system was found to be 0.3853 m3, with a heater duty of 32240 kcal/hr while for the modified system is 0.3841 m3 and 11480 kcal/hr for amount of vapour loss and heater duty respectively. Prior to the modification, the oil is replenished at an interval of 48hrs which is totally avoidable. The introduction of bye-pass line helps to prevent oil loss and reduce heater duty by 64.40%.

Among the various joining technique used in the industries, welding is quite common and popular. However, at times it is a very complex process in which a large number of variables are involved governing the quality of weld and the resulting properties. In certain applications, like rolling stocks/rail coaches, the quality of the weld and mechanical properties of the joint are of paramount importance considering the fact that it may be a joint affecting the safety aspects. Keeping this in mind, experiments have been carried out to optimize the process parameters of flash butt welding of brake tension rods of a rail coach/rolling stock. In the present work only the major process parameters of flash butt welding of mild steel brake tension rod namely rate of current flow, heating time, flashing way, initial distance between the jaws was studied and effort has been made to optimize the same. The process parameters, once optimized, can reduce the rejection considerably as well as minimize the dependence upon operator’s skill.

This paper presents a numerical prediction of the transient hydraulic loads acting on the tubes and external supports of a pressurized water reactor (PWR) steam generator (SG) during blowdown following a sudden feedwater line break (FWLB). A simplified SG model was used to easily demonstrate the prediction. The blowdown discharge flow was treated as a flashing flow to realistically simulate the transient flow fields inside the SG and the connected broken feedwater pipe. The effects of the SG initial pressure or the broken feedwater pipe length on the intensities or magnitudes of transient hydraulic loads were investigated. Then predictions of the decompression pressure wave-induced impulsive pressure differential loads on SG tubes and the transient blowdown loads on SG external supports were demonstrated and the general aspects of transient responses of such transient hydraulic loads to the FWLB were discussed.

In the construction deeds, the water dramas a dominant segment and so far no substitute to water is available. Chemical limits of water for concrete, suggested by different codes of concrete signpost that non-potable-water can be cast-off as intercourse water. In this paper, mechanical property on concrete is gauged for assorted tap, grey, pond, and treated-sewage waters. In the research, in concrete we locate the probability of practice of treated, untreated-water as an unconventional to drinkable-water to accompanying research-laboratory examinations for an enhanced appreciative of fresh and hardened properties of raw and treated waste-water concrete. The strengths may vary with ingredients, purity of water, and curing time. In this approach, the effects of different water samples on the property of concrete, which were fresh and hardened strength characteristics investigated through experiments. Compressive, flexural, split tensile, and pull-off strength and its variability were elucidated by investigational that is based on rate processes. The flashing loading-level tests were conducted on different water-sample on mechanical testing under various water conditions. Concrete mixes using treated-sewage water cast at curing times of distinct days led to superior effects on mechanical strength. The design strength was recorded in compressive of 33.26 MPa, flexural of 2.77 MPa, and splitting tensile 2.21 MPa respectively for tap water. The result depicts that the mechanical properties of grey-water strength increased an amount of 2.1%, pond-water strength decreased an amount of 0.51% and similarly, treated-sewage water strength increased an amount of 6.9% as compare to tap-water. The optimum mechanical strength of treated-sewage water shows prodigious results compare to tap-water and also it insinuates that treated-sewage water properties augmented by 7.43% compare to pond-water.

A solar desalination system with flashing chamber is experimentally investigated. The main objective of the present study was lo improve the performance of a traditional single slope solar still through a design modification using step-wise water basin instead of flat basin and coupling the solar still with a spray water system. These modifications can increase the solar still capability to capture more solar energy. The effect of using the spray system for seawater is investigated experimentally at different spray water velocities, and flow rates on the productivity and efficiency of the solar still. It was found that the productivity and performance of the system were significantly positive dependent on both the mass flow rate of the impure water and the linear speed of the nozzles holder. They increase slightly with the using of a porous medium in basin of the still as a heat storage sink. There is an optimum mass flow corresponding to the holder linear speed with respect to both thermal efficiency and distilled water production. The unit daily productivity reaches 6.7 L/m2.day and the average daily thermal efficiency reaches 77.35%. The maximum accumulated productivity is obtained at 250 rpm.

Pressure Relief Valves (PRVs) are key elements of any hydraulic system in the process industry, especially in chemical plants or hydraulic power transmission systems. Their task is to maintain the system pressure beneath a prescribed maximum pressure and vent the excessive fluid in an emergency scenario. This paper addresses the static and dynamic behavior of a Direct Spring-Operated PRV of conical shape in the presence of two-phase non-flashing flow, that is, water-air mixture. First, experimental results on the force and discharge characteristics of such a valve in a wide range of the air-to-water mass fraction are presented. Our test facility includes a custom-designed PRV with 42.5 mm inlet pipe diameter, an inlet pressure up to 6.6 bar(g) and a maximum lift of 10 mm. Additionally, the empirical results on the static characteristics, notably fluid force on the valve disc and discharge coefficients are reported as a function of the liquid mass fraction and valve lift. In the second part of the paper, we present the development of a Matlab-based simulation tool that is capable of predicting the dynamics and stability of such a valve in the case of two-phase, non-flashing, frozen-mixture flow. Moreover, the effect of system parameters, such as spring stiffness and reservoir capacity are recorded. Finally, we also present results on the stability of the opening and closing the multi-phase flow influence on the stability of the blowdown process.

Flash butt weld process parameters determine the weld quality. The presence of weld defects due to inappropriate process parameters leads to entrapment of oxides in the weld causes premature failure. It was also observed that the flash butt process parameter is dependent on the chemistry of the steel that is processed. The high weight percentage of Mn and Si leads to a higher weight fraction of the oxides during welding. Altering the flashing length and upset length leads to the elimination of weld defects achieving full joint strength. Thermodynamic calculations predict the oxides to be primarily FeO, Fe2O3 (hematite), and SiO2 (cristobalite) along with the presence of MnO, Mn2O3, and Cr2O3. The presence of Mn, Al, and Ti in the oxides at the fractured surface is correlated with the chemical potential of these elements in the liquid steel. It can be inferred from the modeling and experimental results that with an increase in temperature, a more liquid slag phase is formed as compared to solid oxides. Slag is less viscous and can be easily extruded during the upsetting stage as opposed to solid inclusion which can be trapped during the welding operation.

When approaching a signalized grade crossing, drivers may run the red light due to the absence of yellow signal or neglect of the warning. Some warning countermeasures such as traffic signs and in-vehicle audio warning (IVAW) have the potential to improve drivers’ risk perception abilities and safety at grade crossings. In this study, a driving simulator-based experiment was conducted to investigate the effects of proposed signs and markings (PSM) and IVAW on driving behaviors at grade crossings with flashing light (FLGCs). A conceptual model was developed which divided the stop/go process into three successive stages, i.e., approach stage, reaction stage and action stage. Our experiment results showed the proposed warning countermeasure could significantly improve drivers’ performance of each stage by lowering driving speed and promoting drivers to take early and smooth brake actions. The findings suggest that the designed countermeasures have the potential to reduce FLGCs crashes and provide safety benefits in foggy weather. Moreover, human factors such as gender should be considered while deploying the collision-avoidance warning countermeasures.

Dallas phasing is an effective strategy for increasing the efficiency of protected-permissive left turns (PPLTs) at signalized intersections, without creating left-turn traps. The flashing yellow arrow (FYA) is the most widely used PPLT signal indication when Dallas phasing is utilized. The Highway Capacity Manual (HCM) signalized intersection methodology currently contains guidance on how to handle PPLTs with Dallas phasing. At intersections with the FYA indication, some agencies have been using a feature known as FYA delay, which delays the FYA indication, usually by 1 to 4 s. More recently, some agencies have also began using another feature, which suppresses the FYA when a conflicting pedestrian phase is active. The HCM does not contain guidance on how to handle FYA delay or suppression. This research proposed modifications to the HCM signalized intersection methodology to address these two FYA strategies. A sensitivity analysis was conducted to check the reasonableness of the proposed modifications. The sensitivity analysis showed that the proposed modifications are reasonable and produced the expected results.

To date, the effectiveness of light emitting diode (LED)-embedded pedestrian crossing signs is not understood, despite such signs being installed and used at pedestrian crossings. A recent study by Texas Department of Transportation focused on examining driver yield rates, a surrogate safety measure, for signs installed across the state. A total of 13 sites were sampled and field observations and video footage were recorded at each site for a total of 681 staged crossings. The driver yield rate ranged from 5% to 88%, with an average of 40%, indicating that other factors affect the effectiveness of the signs. Statistical modeling results supported this finding with the main contributors to driver yield rates being vehicle volume, measured at 1 min before the staged pedestrian crossing (converted to an hourly volume for the model), operational speed (85th percentile), deviation from 12-ft lane width, and presence of sidewalk. High hourly volume, speeds 45 mph and greater, lack of sidewalks, and 12-ft lanes (no deviation from baseline 12-ft lane width) were found to affect yield probability adversely. Based on the findings from this study, LED-embedded signs would be a suitable candidate treatment at sites with sidewalks, lower operating speeds and traffic volumes, and narrow lanes. Lastly, a comparison between driver yield rates for rectangular rapid flashing beacons, pedestrian hybrid beacons, and LED-embedded signs for various posted speed limits demonstrated that, of the three treatments, LED-embedded signs have the lowest driver yield rates, especially for higher posted speed limits.

Flow-accelerated corrosion (FAC), liquid droplet impingement erosion (LDIE), cavitation and flashing can cause continuous wall-thinning in nuclear secondary pipes. In order to prevent pipe rupture events resulting from the wall-thinning, most NPPs (nuclear power plants) implement their management programs, which include periodic thickness inspection using UT (ultrasonic test). Meanwhile, it is well known in field experiences that the thickness measurement errors (or deviations) are often comparable with the amount of thickness reduction. Because of these errors, it is difficult to estimate wall-thinning exactly whether the significant thinning has occurred in the inspected components or not. In the previous study, the authors presented an approximate estimation procedure as the first step for thickness measurement deviations at each inspected component and the statistical & quantitative characteristics of the measurement deviations using plant experience data. In this study, statistical significance was quantified for the current methods used for wall-thinning determination. Also, the authors proposed new estimation procedures for determining local wall-thinning to overcome the weakness of the current methods, in which the proposed procedure is based on analysis of variance (ANOVA) method using sub-grouping of measured thinning values at all measurement grids. The new procedures were also quantified for their statistical significance. As the results, it is confirmed that the new methods have better estimation confidence than the methods having used until now.

Aims In vitro evaluation of aspiration of viscous hyaluronic acid (HA) fillers through dermatologic needles, with and without a new solution for safe aspiration with a saline flashing procedure. The final objective is to be able to offer an easy-to-use device for a practitioner who injects fillers under and into the skin blindly. This device aims to protect him from an immediate and reproducible intravascular venous or arterial injection whatever the type of product used and independently of its rheological properties or the diameter of the needle used. Materials and methods We performed in vitro aspiration experiment using syringes and commonly used needle sizes (27G, 29G). We measured the time to observe a blood being aspirated through the needle with HA filler. Intervals longer than 10 seconds were considered as false results. We added a new approach of flashing a saline solution through the needle with a filler prior to aspiration. Saline solution pressurized by a syringe plunger opens a fluid path in the needle and enables the successful and efficient aspiration in 1-2 seconds through smallest needle size for 6 commercial HA fillers. Conclusion The saline flashing of the dermatological needles with HA fillers appeared to be a feasible and efficient solution for the 100% safe aspiration safety test. Results Aspiration was possible only in few trials with HA fillers for the 27G and all false for 29G needle, respectively. The aspiration with the novel saline flashing procedure is successful for 100% of cases with the two commonly used HA fillers and all needle sizes. The time to aspiration is also significantly shorter with the saline flashing.

A 3D numerical study of water spray flash evaporation occurring in a positive-pressure saturated vapor environment is conducted. The spray is non-uniform with a Rosin-Rammler droplet size distribution. The characteristics of the flashing spray and vapor flow field are obtained by calculating within the Eulerian-Lagrangian framework. The spray undergoes violent evaporation and significant temperature reduction in the beginning within the vicinity of the nozzle exit. As the spray develops downstream, evaporation becomes moderate. Smaller droplets are found to distribute in the spray central region with a comparatively higher evaporation rate and larger velocity variation. Meanwhile, larger droplets evaporate at a lower speed but cover a wider range. The vapor flow field near the nozzle exit is featured by high velocity and high turbulence intensity. Two sets of vortices with different scales and directions are observed in the upper and lower parts of the chamber.

Pressurized liquefied gases such as carbon dioxide are transported at a pressure above their saturation pressure. Therefore, if a pipeline transporting this substance ruptures, an abrupt expansion occurs, causing the flashing of the fluid. Computational tools that predict how fast a depressurization develops, help to assess the consequences of potential pipeline rupture scenarios. This paper describes the development of a 2-D full-bore rupture decompression model to simulate the transient depressurization of a pipeline transporting pure liquefied CO2, using ANSYS Fluent as CFD software. The scope of work focuses on incorporating non-equilibrium phase transition, while addressing the calculation of properties for metastable liquid. Additionally, it includes the comparison of model predictions when implementing two thermodynamic approaches: the Peng-Robinson Equation of State (EoS), and correlations developed in this work based on the Span-Wagner EoS. It was found that the thermodynamic approach is deemed to have a predominant effect on the arrival time of the decompression wave front at different locations along the computational domain, while the mass transfer coefficient in the source terms (C) governs the phase transition and the pressure plateau representing this phenomenon.

The effects of operational conditions on dissimilar Al-Cu flash welded joint quality have been studied using a series of industrial welding experiments. Macro- and microstructural analyses of dissimilar aluminum-copper joints produced by flash butt welding are performed in the present work. Various process conditions including standard and non-standard operational conditions were assessed during the welding experiments. Optical and scanning electron microscopy and electron dispersive x-ray spectroscopy are used to investigate and assess the metallurgical joints created through this process. For suboptimal process conditions, voids (5 mm wide, 1 mm deep) were observed at the joint interface. Some of the voids contained remnants of molten metal while some were empty. Al-Cu intermetallic compounds at the joint area were investigated, and their chemical compositions are determined. The profile of the joint interface was observed to be wavy which is attributed to the voids on the copper side and insufficient material flow of the copper during the upset. The effects of welding parameters on the waviness of the interfaces are investigated. The results show that the waviness of the interface increases with increasing the heat intensity (heat/joint area). No correlation was observed between the flashing speed and the waviness of the interfaces.

At present, large-scale and high-efficiency microalgal cultivation is the key to realizing the technology for carbon capture and storage (CCS) and bioresource recovery. Meanwhile, tubular photobioreactors (PBRs) have great potential for microalgal cultivation due to their high productivity. To improve the mixing performance and flashing-light effect, a novel tube PBR with the inner tube tangential to the outer tube was developed, whose radial aeration pores are situated along the length of the inner tube. The direction of aeration, aeration rate, light/dark cycle period (L/D), light-time ratio, average turbulent kinetic energy (TKE), and degree of synergy between the velocity and direction of the light field in the PBR were optimized by a computational fluid dynamics (CFD) simulation and field synergy theory. The results show that a downwards aeration direction of 30° and an aeration rate of 0.7 vvm are the most conducive to reducing the dead zone and improving the light/dark cycle frequency. Compared to the concentric double-tube PBR, the light/dark cycle frequency and light time of the tangent double-tube PBR increased by 78.2% and 36.2% to 1.8 Hz and 47.8%, respectively, and the TKE was enhanced by 48.1% from 54 to 80 cm2·s−2. Meanwhile, field synergy theory can be extended and applied to the design of tubular microalgae PBRs, and the average synergy of the light and velocity gradients across the cross-section increased by 38% to 0.69. The tangential inner tube aeration structure generated symmetrical vertical vortices between the light and dark areas in the PBR, which significantly improved the mixing performance and flashing-light effect. This novel design can provide a more suitable microenvironment for microalgal cultivation and is promising for bioresource recovery applications and improving the yield of microalgae.

Flashing green signal, as a part of the green traffic signal, indicates that the green signal is about to end. Drivers have more time to decide whether to stop or pass the intersection since they have prior information that the yellow signal will start. The application of flashing green at the end of the green signal is optional, hence, the question is how engineers could decide to use flashing green or not? The answer to the question should be based on researches on flashing green effects on traffic efficiency and safety at signalized intersections. The aim of this paper is to analyze the impact of flashing green on traffic efficiency by determining the value of effective green time. The research was conducted at two intersections in Belgrade, with and without a flashing green signal. Results indicate that effective green is shorter when flashing green is applied, due to the decreased utilization of the yellow signal.

The flashing process is a way of exposing water in a low-pressure environment by spraying it at high pressure so that the water converts into fine particles. This process is carried out to speed up the evaporation process of water. The evaporation process carried out on freshwater aims to separate the minerals and solids dissolved in water to increase its purity. In this study, the flashing process was carried out through a rotating nozzle that was proven to increase the rate of pure water production. The flashing process experiment is carried out following an experimental design based on the non-dimensional analysis of Buckingham's pi. The rate of pure water production () as the output variable in the flashing process is affected by the nozzle rotational speed (n), nozzle hole diameter (d), feedwater pressure (Pw), vacuum pressure (Pv) and feedwater temperature (T). The feedwater temperature itself can influence the behavior of the feedwater flow in the nozzle, in this case, is density (ρ) and viscosity (μ). Based on these variables, the non-dimensional analysis of Buckingham pi has produced four dimensionless numbers. The generated empirical equations from the flashing process experiments are in the form of quadratic equations. The empirical equation applies to feedwater pressure of 7.6 bar-g, the vacuum pressure of 0.4–0.6 bar-a and nozzle rotational speed of 0–134 rpm. The optimum condensation rate in the flashing experiment was successfully obtained, especially at the nozzle rotation of 27 rpm in all vacuum pressures tested. This success is inseparable from the use of mist-nozzles that convert the feedwater flow into the mist.

This paper aims to revise the critical flow criterion and flashing inception of the analytical critical flow model and to further explore the effect of upstream conditions on critical mass fluxes. ...

Vortex control is a novel two-phase convergent-divergent nozzle restrictiveness control mechanism. The flow control is achieved by adjustable nozzle inlet vortex strength. The underlying mechanism behind vortex control is still unclear. In this study, 3D CFD simulations of vortex flashing R134a flows in convergent-divergent nozzles have been conducted. Good agreement was found between the simulation and experimental results. When there is no vortex applied, the void fraction at the nozzle center remains low. When the vortex is applied, vapor bubbles are driven towards the nozzle center. The applied vortex significantly increases the interphase mass transfer near the nozzle outlet with more uniform interfacial area per unit volume and better utilization of liquid superheats at the nozzle center for evaporation. Thus, after the introduction of inlet vortex, more vapor is generated in the divergent part of the nozzle. As a result, the pressure drop across the divergent part of the nozzle is increased. There is negligible vapor content upstream of the throat even though the pressure is already below saturation pressure. When the inlet vortex is applied, with elevated pressure at the nozzle throat and constant inlet conditions, the pressure difference across the nozzle convergent part decreases and therefore the nozzle mass flow rate is reduced. The overall nozzle outflow mass flow averaged axial velocity can be increased by 30.1%, nozzle isentropic efficiency increases from 37.7% to 63.8% and nozzle mass flow rate drops from 16.0 g s−1 to 12.6 g s−1 when inlet vortex is introduced.

A thermal power plant for the East African Rift countries is under study for combined energy and freshwater generation using geothermal water, available at above 500 kPa pressure and temperature exceeding 150°C. This article presents the computational fluid dynamics (CFD) model and analysis of the two-phase turbine used for power generation in this total flow thermal plant. Flash boiling was implemented using a two-fluid multiphase model with the thermal phase-change criteria for heat, mass, and momentum transfer in the CFD solver ANSYS CFX. Initially, flashing flow in a converging–diverging nozzle was validated. This stationary nozzle model was then extended to a curved rotating nozzle reaction turbine and the results of flow and power were evaluated against available test data at 400 kPa feed water pressure under subcooled condition of 117°C and a very low backpressure of 6 kPa. Flow through this turbine was predicted within 8% deviation. An overestimate in thermodynamic power by 30–50% was predicted at speeds below 4000 rpm, while at the design speed of 4623 rpm the deviation was less than 5%. Rotor torque and hence power estimate was found to be dependent on the bubble size, bubble number density, and heat transfer parameters prescribed in the CFD model. The vapour dryness fraction at turbine exit was close to an isentropic expansion vapour quality. The isentropic efficiency was 7.5–17% for the analysed speed range.

The static correlations from RELAP5 and TRACE as well as the interfacial area transport equation (IATE) are benchmarked for flashing flow with selected cases from a recently published experimental ...

Recently, a novel population-based optimisation algorithm, namely firefly algorithm (FA), which mimics the flashing and attraction behaviour of fireflies, has shown promising performance in solving...

A photon correlation count technique has been used to determine the amount of emitting bubbles per ultrasonic cycle and the number of photons emitted from a bubble per flash of multibubble sonoluminescence in aqueous solutions of sodium chloride and sodium dodecylsulfate irradiated by 20 kHz ultrasound. The estimated number of flashing bubbles per cycle (~100) is much less than their total number in a cloud and reflects significant role of bubble dynamics in the flash generation. The estimated number of photons emitted from a bubble per flash (~10 000) is an order of magnitude lower than that for stable sonoluminescence of a single bubble.

The objective of this paper is to empirically investigate drivers’ decision zones at the onset of flashing green and yellow indication at rural high-speed intersections in China. 1122 high-resolution trajectories of the first-to-stop and the last-to-go vehicles during the phase transition time period were collected at four intersection approaches in Shanghai. Speed-Distance (S-D) diagram and Acceleration-Deceleration (A-D) diagram were then used to analyze the distribution of drivers’ decision zones in response to the onset of flashing green and yellow respectively. The former is a conventional approach based on a fundamental assumption that no drivers would accelerate to cross or make an abrupt stop. The latter is a more flexible method based on the required acceleration rate to cross and the required deceleration rate to stop which can be extracted from vehicle trajectory data. Results support that the installation of flashing green helps to reduce the dilemma zone according to the A-D diagram. There are limits when using S-D diagram to analyse the driving situations based on G.H.M model.

An integrated model between surface and sub-surface is typically done by interconnecting many process modelling platforms. PROSPER and GAP are the common steady state modelling platforms for sub-surface while VMGSim and HYSYS are typical steady state surface modelling platforms. A major issue of using multiple simulation platforms is the compatibility of thermodynamic physical properties calculations among the platforms. This situation makes the simulations difficult to converge to a consistent thermo physical properties values. This is due to different interaction parameters applied in each platform that impact flashing and the physical property values even though the same property package such as Peng Robinson is used. To overcome this convergence problem, a single simulation platform within iCON (PETRONAS’s standard process simulation software, co-developed with VMG-Schlumberger) has been developed. This allows the use of one thermodynamic package across the integrated model. PROSPER sub-surface pressure-flow relationship results were automatically correlated and connected to surface models within the iCON environment. This integrated model was validated with data from operations and yielded about 1.23% average error tolerance. Based on this validated model, an optimization envelope can be developed with all possible well lineup configurations. This envelope covers set points for the operations where CAPEX free optimization can readily be applied.