Main Runner Research Articles

In memory of Kelvin Kiptum: a reflection on his record-breaking marathon and the future outlook for a sub 2-h race from a drafting perspective.

Drafting is a common technique to reduce the drag experienced by elite runners on races, leading to faster finish times. The tactic has been successfully used in previous marathon world records. In the 2023 Chicago Marathon, Kenyan runner Kelvin Kiptum broke the marathon record after a 2:00:35 finish. This feat is impressive considering the lack of use of drafting, despite the availability of two pacers for the majority of the race. In this study, the drag faced by Kiptum and his pacers during the race is calculated by means of computational fluid dynamics (CFD). The performance of each runner is evaluated from an energetic standpoint, and the analysis is extended to include more efficient drafting formations. Running in proper formations results in drag reductions in excess of 70% for the main runner. Our results indicate that, by properly using the advantages of drafting, Kiptum could have finished the race at a staggering 1:57:34, a full three minutes better than his own record and 215s better than the previous world record. Proper use of drafting does indeed improve the energetic performance of a runner, allowing for lower race times and potentially helping elite runners in breaking the 2-h barrier for a marathon.

Design and Simulation of Hydraulic Integrated Valve based on SLM Technology

Intelligent robots put forward the need for miniaturization and integration of hydraulic systems. Based on SLM technology, this paper designs a hydraulic integrated valve, integrates flow channels, adapters and other facilities on the valve body, replaces the original linear movement scheme with a rotating spool scheme, studies parameters such as runner diameter and minimum wall thickness, and simulates and analyzes the flow performance of liquid when the main control runner and a single valve work. The results show that the integrated valve has the advantages of light weight, small size and good performance.

Corrosion mechanisms of Al2O3-SiC-C refractory castables by iron and slag based on post-mortem analysis of industrial samples

The Al2O3-SiC-C or ASC castables are used in the main runners of blast furnaces. Most of the papers published to date focus on laboratory corrosion tests because access to the post-mortem samples of ASC castables is difficult. However, investigation of post-mortem samples is crucial in reducing the wear of ASC castables. The main runner is divided into the turbulence, middle, and non-turbulence zones. The microstructures of post-mortem samples located in working linings of different zones were investigated by SEM/EDS technique. The thermodynamic simulations were carried out in different systems, such as slag/refractory and iron/refractory, using the FactSage software. The SEM/EDS results showed the formation of phases with low melting points, such as gehlenite and anorthite, together with spinel solid solutions in the matrix and calcium dialuminate near the alumina aggregates. The thermodynamic simulations showed that slag and iron tend to react with alumina and silicon carbide, respectively.

Numerical Analysis of the Flow by Using a Free Runner Downstream the Francis Turbine

The current requirements of industrialized countries require the use of as much renewable energy as possible. One significant problem with renewable energy is that the produced power fluctuates. Currently, the only method available for energy compensation in the shortest time is given by hydroelectric power plants. Instead, hydroelectric power plants (especially the plants equipped with hydraulic turbines with fixed blades) are designed to operate in the vicinity of the optimal operating point with a maximum ±10% deviation. The energy market requires that hydraulic turbines operate in an increasingly wide area between −35% to 20% from the optimum operating point. Operation of hydraulic turbines far from the optimum operating point involves the appearance downstream of the turbine of a decelerated swirling flow with hydraulic instabilities (known in the literature as the vortex rope). The main purpose of this paper is to investigate numerically a new concept by using a free runner downstream on the main hydraulic runner turbine more precisely in the draft tube cone. The free runner concept requires rotations at the runaway speed with vanishing mechanical torque. The main purpose is to redistribute the total pressure and the moment between the shaft and the periphery. In addition, the free runner does not modify the operating point of the main hydraulic turbine runner.

Frequency‐Sensitivity of the seismic damage to suspended ceilings

AbstractSeismic damage to suspended ceilings was frequently reported even in minor to moderate earthquakes and caused problems to immediate occupancy and quick recovery of buildings. While peak floor acceleration (PFA) has been exclusively used as an intensity measure for suspended ceilings, this study introduces a shake table test on minimum subassemblies of suspended ceilings under sinusoidal excitation to critically assess the rationality of this practice. The test results show a significant frequency‐sensitivity of the ceiling damage that, depending on the dominant frequencies, an excitation of a lower PFA might cause much severer damage than that of a higher PFA. A numerical model that captures the nonlinear interaction of the individual components in a suspended ceiling, that is, the main and cross runners, ceiling panels, a hanger, and enclosure angles, is established and calibrated to simulate the frequency‐sensitive behavior observed in the shake table tests. The model is then extended for suspended ceilings of realistic dimensions. Three‐dimensional fragility spectra of suspended ceilings under sinusoidal excitations are proposed to relate the extent of seismic damage with not only the PFA but also the excitation frequency. Boundaries of damage limit states can be defined by taking two‐dimensional sections on the fragility spectra, based on which, the influence of key factors on ceiling damage characteristics is illustrated.

Auditory interaction between runners: Does footstep sound affect step frequency of neighboring runners?

This study aimed to investigate the effect of footsteps of a neighboring runner (NR) on the main runner's step frequency (SF), heart rate (HR), and rating of perceived exertion (RPE). The participants were male long-distance runners belonging to a university track and field team. Two experiments were conducted in which the main runner (participant) and NR (examiner) ran with the same running speed on two adjacent treadmills separated by a thin wall. The participants were instructed that the experimental purpose was to investigate the HR when running with others and running alone. In Experiment 1, NR performed three trials of changing the footstep tempo in 5 bpm (beat per minute) faster (+5bpmFS), 5 bpm slower (-5bpmFS), or no footsteps (NF) conditions. The results showed that the footstep condition affected the variability of the SF but not the mean SF. Next, Experiment 2 was conducted by increasing the footstep tempo condition. NR performed seven trials of changing the footstep tempo by ±3 bpm, ±5 bpm, ±10 bpm, or no footstep. The results showed that the footstep condition affected the mean SF and the SF decreased at -10bpmFS compared to NF. There were no differences in the HR and RPE between conditions. These results indicated that the footsteps of NR could influence the SF, although it was unclear whether footsteps were involved in the synchronization between runners. Overall, our findings emphasize the environmental factors that influence running behavior, including the NR's footsteps.

Toward a better understanding of synchronous vibrations in hydroelectric turbines

Runner–casing interactions are known to be major stress contributors during turbine operation in nominal regimes. These synchronous vibrations must be properly understood to ensure reliable long-term turbine operation. It is widely accepted in the hydro community that rotor–stator interactions (RSI) are the main runner–casing mechanisms. In this study, the authors demonstrate that casing non-uniformities can induce a wide range of synchronous vibrations in a hydroelectric turbine, that are not predicted by the standard RSI theory. The mathematical background that generalizes RSI concept is first derived and then the theory is verified using recorded data from two different hydroelectric Francis runners. The suggested framework is able to explain unexpected resonances between rotating speed harmonics and structural modes observed during runner transient operations.

Experimental Investigation of a Free Runner Concept Downstream of Francis Turbines

The main purpose of the paper is to investigate experimentally a new concept by using a free runner downstream of the main hydraulic runner turbine to increase the flexibility in operation. The free runner concept supposes that rotates at the runaway speed with vanishing mechanical torque. The main purpose is to redistribute between the shaft and the periphery the total pressure and the moment of momentum, such that the flux of total pressure and the moment of momentum are not altered. Moreover, the free runner does not modify the operating point of the main hydraulic turbine runner. The experimental investigation focuses on velocity profiles measurements with the LDV system and the unsteady pressure measurements downstream the free runner, in the draft tube cone.

Reconstruction of the Francis 99 main runner blade using a hybrid parametric approach.

The runner blade shape has been described as a set of discrete sections joining hub and shroud, resulting in such 3D free geometrical forms of considerable complexity that the search for an appropriate parametric approach for its reconstruction and optimization is still a matter of research field. For this reason, the main purpose of this study has been to reconstruct a real and twisted runner blade with a required accuracy through a methodology that uses several algorithms to combine sections and surfaces parametric approaches. Using the surface approach, the free-form shape of the 3D camber surface was defined by a multi-directional interpolation procedure. Using the section approach a Direct Profiling method was tested to fitting the hydrofoil section to the real one. For the blade reconstruction, ten profiles were stacked along the spanwise direction of the real blade to obtain by interpolation the pressure and suction sides using a lofting procedure, thus achieving an acceptable continuous and smooth surface definition. We assume that this methodology could be efficient to reconstruct a damaged and worn free-form blade, especially when the original surface geometry implies sections with different Thickness Distribution along the spanwise direction.

Research and Evaluation of the Influence of the Construction of the Gate and the Influence of the Piston Velocity on the Distribution of Gases into the Volume of the Casting

Distribution of gasses to the cast volume and volume of pores can be maintained within the acceptable limits by means of correct setting of technological parameters of casting and by selection of suitable structure and gating system arrangement. The main idea of this paper solves the issue of suitability of die casting adjustment—i.e., change of technological parameters or change of structural solution of the gating system—with regards to inner soundness of casts produced in die casting process. Parameters which were compared included height of a gate and velocity of a piston. The melt velocity in the gate was used as a correlating factor between the gate height and piston velocity. The evaluated parameter was gas entrapment in the cast at the end of the filling phase of die casting cycle and at the same time percentage of porosity in the samples taken from the main runner. On the basis of the performed experiments it was proved that the change of technological parameters, particularly of pressing velocity of the piston, directly influences distribution of gasses to the cast volume.

Aerodynamic effects and performance improvements of running in drafting formations

Drafting as a process to reduce drag and to benefit from the presence of other competitors is applied in various sports with several recent examples of competitive running in formations. In this study, the aerodynamics of a realistic model of a female runner is calculated by computational fluid dynamics (CFD) simulations at four running speeds of 15 km h−1, 18 km h−1, 21 km h−1, and 36 km h−1. Aerodynamic power fractions of the total energy expenditure are found to be in the range of 2.6%-8.5%. Additionally, four exemplary formations are analysed with respect to their drafting potential and resulting drag values are compared for the main runner and her pacers. The best of the formations achieves a total drag reduction on the main runner of 75.6%. Moreover, there are large variations in the drag reduction between the considered formations of up to 42% with respect to the baseline single-runner case. We conclude that major drag reduction of more than 70% can already be achieved with fairly simple formations, while certain factors, such as runners on the sides, can have a detrimental effect on drag reduction due to local acceleration of the passing flow. Using an empirical model for mechanical power output during running, gains of metabolic power and performance predictions are evaluated for all considered formations. Improvements in running economy are up to 3.5% for the best formation, leading to velocity gains of 2.3%. This translates to 154 s (≈2.6 min) saved over a marathon distance. Consequently, direct conclusions are drawn from the obtained data for ideal drafting of long-distance running in highly packed formations.

Performance Analysis of Booster based Gravitational Water Vortex Power Plant

Gravitational Water Vortex Power Plant (GWVPP) is a power generation system that suits for ultralow head streams of water with low flow rate. Due to the simple design, compact structure, and the possibility of local fabrication, it can benefit rural areas for off-grid supply. The purpose of this research is to study the potential of booster based GWVPP. Previous researches concluded the best position of turbine in GWVPP is actually not the maximum head position which eventually does not extract all possible head. This research explores the possibility of adding an extra runner (booster runner) below the main runner in the existing set up for additional power generation. The performance of the booster runner, modelled in CATIA V5R21 was studied computationally using ANSYS 18.1 FLUENT for various boosters with varieties of number of blades, blade inclination angle, height of booster, rotational speed and the blade profile so as to obtain the most suitable design of the booster runner, which was then verified experimentally in a model set up using four different booster runners. The research showed an increase of 3.84W in the miniaturized model which corresponds to the increase in efficiency of 20.4% from a total of 63.55% by main runner alone. This implies that the power generation can be increased by the addition of the booster runner in the existing set up.

Безопасная эксплуатация эскалаторов: современное состояние и взгляд в будущее

The article contains an overview of the main trends of the escalators future development and innovative trends in ensuring an integrated system of their safe operation. The relevance of the study of the problem is based on the creation of a system for monitoring and diagnosing the technical condition of the escalator equipment in order to minimize the damage due to failures while ensuring a standardized reliability indicator for the tunnel escalators. They are related to hazardous objects, which entails special requirements for safety of the escalator equipment. Currently, many countries adopted an effective proactive service model using digital doubles, which accurately monitor the real state of technology based on the smart sensors. Data are collected in the cloud service store to analyze the received information.  A promising area of research includes monitoring and diagnostics of the technical condition of the escalator equipment, analysis of the results of vibration diagnostics using the envelope method (data of State Unitary Enterprise «Petersburg Metro»). The assessment of efficiency and commercialization of the monitoring project is presented in the article. The main system of project indicators, including a positive economic effect, will be achieved thanks to the use of advanced technologies of a proactive approach with monitoring of the vibration state of the main gear box and bearing units of the escalator drive motor, as well as the main and auxiliary runners of the escalator stages in order to identify dangerous defect. The growth of development of critical irreversible processes will be reduced, that will increase the probability of failure-free operation in relation to downtime, and, reduce the accident rate.

Degating of AlSi10Cu2Fe High-Pressure Die Casting Component Using Resonance Vibration Technique

The high-pressure die casting process is meant for high volume production rate mainly used in the automotive industry. An efficient method to separate the die-cast components from the main sprue and runner system is crucial to improving the productivity of the manufacturing processes. Conventionally casting components are often separated with the use of a grinding wheel machine, trimming machine or pneumatic hammer. Often these techniques require customized machine design in trimming the cast part as each die casting gate design might be different from one another, especially when there is a change in production cast model. This may incur higher set-up cost and additional configuration time. It is unfavourable in the manufacturing production line that handles small batch high variation of casting model in the small/medium casting industry. Thus, this paper introduced an alternative degating technique with the use of a shaker machine to match the resonance of the casting component natural frequency to separate the die-cast component from the casting tree. The proposed method can overcome the drawback of the conventional method by eliminating the additional configuration time required when there is a change in different casting part design. Die casting parts employed in this study were constructed by AlSi10Cu2Fe aluminium alloy. Experimental modal analysis was performed to verify the natural frequency calculated through finite element analysis. The correlated finite element model was then employed for harmonic response analysis to compute the frequency response of input excitation location against output stress response at the gate. The results from the analysis showed that the first natural frequency mode could induce a bending mode at the gate and created the highest stress concentration at the location. Next, an experiment was carried out by exciting the first natural frequency to the casting part using a shaker machine. In the experiment, the die-cast components were able to break away within 0.31 s at its first natural frequency. This observation was found to be in agreement with the simulation results, whereby the degating time of 0.27 s was obtained. Therefore, the present study has shown that an efficient degating of casting components process can be achieved via introducing a correct mode of vibration excitation.

Shaking table tests on seismic response of backdrop metal ceilings

In recent earthquakes, the failure of ceiling systems has been one of the most widely reported damage and the major cause of functionality interruption in some buildings. In an effort to mitigate this damage, some scholars have studied a series of ceiling systems including plaster ceilings and mineral wool ceilings. But few studies have involved the backdrop metal ceiling used in some important constructions with higher rigidity and frequency such as the main control area of nuclear power plants. Therefore, in order to evaluate its seismic performance, a full-scale backdrop metal ceiling system, including steel runners and metal panels, was designed, fabricated and installed in a steel frame in this study. And the backdrop metal ceiling system with two perimeter attachments variants was tested: (i) the ends of the runners were connected with the angle steel to form an effective lateral constraint around the backdrop metal ceiling, (ii) the perimeter attachments of the main runner were retained, but the perimeter attachments of the cross runner were removed. In the experiments, different damage of the backdrop metal ceiling system was observed in detail under various earthquakes. Results showed that the backdrop metal ceiling had good integrity and excellent seismic performance. And the perimeter attachments of the cross runner had an adverse effect on the seismic performance of the backdrop metal ceiling under earthquakes. Meanwhile, a series of seismic construction measures and several suggestions that need to be paid attention were proposed in the text so that the backdrop metal ceiling can be better applied in the main control area of nuclear power plants and other important engineering projects.

Purification and Characterization of Naturally Occurring Post-Translationally Cleaved Ara h 6, an Allergen That Contributes Substantially to the Allergenic Potency of Peanut

The 2S albumin Ara h 6 is one of the most important peanut allergens. A post-translationally cleaved Ara h 6 (pAra h 6) was purified from Virginia type peanuts, and the cleavage site was mapped using high-resolution mass spectrometry. Compared to intact Ara h 6, pAra h 6 lacks a 5-amino acid stretch, resembling amino acids 43-47 (UniProt accession number Q647G9) in the nonstructured loop. Consequently, pAra h 6 consists of two chains: an N-terminal chain of approximately 5 kDa and a C-terminal chain of approximately 9 kDa, held together by disulfide bonds. Intermediate post-translationally cleaved products, in which this stretch is cleaved yet still attached to one of the subunits, are also present. The secondary structure and immunoglobulin E (IgE) binding of pAra h 6 resembles that of intact Ara h 6, indicating that the loss of the nonstructured loop is not critical for maintaining the protein structure. Commercially available monoclonal and polyclonal immunoglobulin G (IgG) antibodies directed to Ara h 6 react with both intact Ara h 6 and pAra h 6, suggesting that the involved epitopes are not located in the area that is post-translationally cleaved. No differences between intact Ara h 6 and pAra h 6 in terms of IgE binding were found, suggesting that the area that is post-translationally cleaved is not involved in IgE epitopes either. For all main cultivars Runner, Virginia, Valencia, and Spanish, intact Ara h 6 and pAra h 6 occur in peanut at similar levels, indicating that pAra h 6 is a consistent and important contributor to the allergenic potency of peanut.

Analytical Study of Large-Area Suspended Ceilings

ABSTRACTDue to the complex and heterogeneous construction of suspended ceiling systems, current standards provide only limited guidance for their seismic design. Simplified uniaxial numerical models of suspended ceiling systems are developed based on the experimental observation. Main runners with tributary ceiling area and grid connections in the longitudinal direction are modeled using lumped-masses and nonlinear connection springs. The proposed numerical models can be used as simple computational tools to explore the dynamic behavior and to estimate the design forces. Possible changes to the current standard design that suggest a more rational distribution of ceiling inertia forces are also discussed.

Archaeometallurgical Investigations of the Early Iron Age Casting Workshop at Kamieniec. A Preliminary Study

Abstract This preliminary study characterizes the bronze metalworking on a defensive settlement of the Lusatian culture in former Kamieniec (Chełmno land, Poland) as it is reflected through casting workshop recovered during recent excavations. Among ready products, the ones giving evidence of local metallurgy (e.g. casting moulds and main runners) were also identified. With the shrinkage cavities and dendritic microstructures revealed, the artifacts prove the implementing a casting method by the Lusatian culture metalworkers. The elemental composition indicates application of two main types of bronzes: Cu-Sn and Cu-Pb. Aside these main alloying additions, some natural impurities such as silver, arsenic, antimony and nickel were found which may be attributed to the origin of the ore and casting technology. The collection from Kamieniec was described in terms of its structure and composition. The investigations were made by means of the energy dispersive X-ray fluorescence spectroscopy (ED-XRF), scanning electron microscopy (SEM) coupled with an energy dispersive X-ray analysis system (EDS) and optical microscopy (OM). In order to fingerprint either local or non-local profile of the alloys, the ED-XRF data-set was statistically evaluated using a factor analysis (FA).

Capacity Evaluation of Suspended Ceiling-Perimeter Attachments

AbstractReported frequently in recent earthquakes, failure of the ceiling perimeters in suspended ceiling systems leads to propagation of damage to the rest of the system. Therefore, the need to understand how ceiling systems perform around their perimeters during an earthquake is becoming increasingly important. In this study, a series of component-level experiments was designed at the University of Nevada, Reno to estimate the ceiling-perimeter capacities. Test specimens were constructed from cross tees and main runners, which were then connected to a portion of gypsum–stud partition wall using either pop rivets or seismic clips. The test specimens were subjected to monotonic and cyclic loading to obtain their failure capacities. Then, several fragility curves were developed for ceiling joints based on available experimental data. In addition to the experimental studies, a series of analytical models for ceiling-perimeter joints was developed and calibrated using component experimental data.

Arc Movement Inside an AC/DC Circuit Breaker Working With a Novel Method of Arc Guiding: Part II—Optical Imaging Method and Numerical Analysis

This paper aims at understanding the design concept and behavior of the ionized gases inside a new electrical contactor. The switching device is designed for ac and dc operations up to 3.5 kV and nominal currents up to 800 A. The contactor consists of five electrodes: two anodes, two cathodes, and a moving electrode or bridge which works as an anode and a cathode simultaneously. In order to increase the safety, the electrical contactor includes two contact points. The line current can be diverted into an arc between the electrode and the bridge and an arc between the runner electrodes. The movement of the ionized gases is controlled by two permanent magnets and two coils installed near the electrodes. The arc plasma itself feeds the coils with current. The arc plasma velocity increases if more current is allocated in the arc plasma. The dynamics of ionized gases in the contactor is analyzed using two optical methods, viz., optical imaging method and high-speed camera (HSC). The optical imaging software has been developed to generate dynamic images of the high-speed ionized gases at a rate of 50 000 frames/s. The results of this method have been compared with those obtained using an HSC. A transient numerical model has been developed to simulate the arc plasma inside the main runner for the case of dc current. The properties of the air plasma are considered variable with temperature and pressure. The calculation shows the position and temperature of the arc plasma as a function of time.