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This is Part 3 of a trio of papers that unify in a natural way the two historically distinct parallel discrete event synchronization paradigms, optimistic and conservative, combining the best properties of both into a single framework called Unified Virtual Time (UVT). In this part, we survey the synchronization effects that can be achieved by restricting to corner cases the relationships permitted among the control variables, GVT, CVT, TVT, and LVT, which were defined in Part 1. We also survey various throttling policies from the literature and describe how they can be implemented in UVT by controlling the value of TVT, including policies that can take advantage of rollback in addition to LP blocking. A significant result is a new category of efficient and higher precision throttling algorithms for optimistic execution that are based on optimistic lookahead, defined in a way that is symmetric to what we now call the conservative lookahead information that is traditionally used for conservative synchronization. Finally, we present a novel algorithm allowing the choice between lazy and aggressive cancellation to be made on a message-by-message basis using either external logic expressed in the model code, or policy code internal to the simulator, or a mixture of both. [ABSTRACT FROM AUTHOR]

Buzz is an unwanted and inevitable phenomenon occurring due to the subcritical operation of intake which needs a comprehensive understanding. The buzz pattern in axisymmetric intakes differs from 2D counterpart and requires further investigation. The current study emphasizes the ways of buzz formation and its sustenance at supersonic speeds. In the present study URANS simulations have been done for various throttling ratios to simulate the engine demand conditions. It has been found that the onset of intake buzz happens for anything above the throttling ratio of 0.54. An active flow control technique using plasma actuator was used here to mitigate the influence of buzz. The study also emphases on the impact of plasma power densities on the intake performance. [ABSTRACT FROM AUTHOR]

Buzz is an unwanted and inevitable phenomenon occurring due to the subcritical operation of intake which needs a comprehensive understanding. The buzz pattern in axisymmetric intakes differs from 2D counterpart and requires further investigation. The current study emphasizes the ways of buzz formation and its sustenance at supersonic speeds. In the present study URANS simulations have been done for various throttling ratios to simulate the engine demand conditions. It has been found that the onset of intake buzz happens for anything above the throttling ratio of 0.54. An active flow control technique using plasma actuator was used here to mitigate the influence of buzz. The study also emphases on the impact of plasma power densities on the intake performance.

Using the vortex-resolving RANS/ILES method, the flow in a paired model supersonic air intake (SAI) of mixed compression with a boundary layer (BL) bleed system is investigated. The influence of the type of BL bleed system and throttling of each of the SAI on the flow characteristics, the level and spectra of pressure pulsations in the neighboring SAIs is analyzed. Cases with the same and different throttling in each of the SAIs, as well as a common and individual bleed system for neighboring SAIs, are considered. A brief description of the calculation method and boundary conditions is given. The levels of OASPL in the SAI are presented depending on the degree of throttling. The influence of throttling of one of the SAIs on the flow and features of the 1/3-octave spectra of pressure pulsations in the neighboring SAI is revealed. [ABSTRACT FROM AUTHOR]

A quasi-one-dimensional numerical model is developed to provide the internal ballistics information of a throttling segregated fuel-oxidizer system (SFOS). The present throttling SFOS is capable of regulating its thrust by adjusting the opening radius of a throttle valve mounted between the head-end fuel-rich chamber and the aft-end oxygen-rich chamber. The numerical model employs a simplified reaction mechanism to describe the chemical non-equilibrium processes and considers mass addition, wall friction, and propellant surface regression in the combustion chambers. With this numerical model, the internal flow parameter distributions and the performance of the throttling SFOS are demonstrated. The steady operation results show that when the throttle valve opening radius is adjusted from 10.5 mm to 1.4 mm, the motor thrust can be increased from 121.82 N to 250.60 N, which is a 206% thrust promotion. It validates the conception of throttling SFOS. The flow parameters also suggest that the function of the throttle valve can only be manifested when the valve opening radius is quite small. The dynamic operation results reveal that the performance histories of the throttling SFOS experience slight anti-regulations at the end of the valve actuation, which deserves extra protective measures. A theoretical prediction of the thrust regulation ability of the throttling SFOS is provided. It suggests that the thrust regulation ability is limited by the fuel-rich chamber pressure and the initial mass flow rate ratio, and a compromise has to be made among multiple parameters to achieve a reasonable thrust regulation ratio. Finally, the grain arrangement is tentatively discussed. It shows that, based on the present modeling conditions, the fuel-oxygen grain arrangement is superior in its thrust regulation ability than the reversed oxygen-fuel grain arrangement. [ABSTRACT FROM AUTHOR]

Investigating the throttling characteristics of Rocket-Based Combined Cycle (RBCC) engines in ejector mode is crucial for adapting to varied flight mission demands. This study employs validated RANS numerical methods to investigate throttling effects on an experimental kerosene-fueled RBCC engine under two representative flight conditions: ground take-off (Mach 0) and supersonic flight (Mach 2.0). Results indicate that, at Mach 0, throttling reduces the entrained secondary stream and increases mixing efficiency, but exacerbates mixing losses, which cannot be offset by the thrust produced by the secondary stream due to its weak working capacity. Therefore, specific impulse performance deteriorates during throttling. Moreover, the optimum mixture ratio remains at 2.4, consistent with conventional rockets. Conversely, at Mach 2.0, throttling mitigates the primary stream’s squeezing effect to augment the entrained secondary stream. Simultaneously, throttling enhances mixing efficiency to improve the utilization of residual fuel. Consequently, the optimum mixture ratio shifts from 2.4 to below 1.4, which contributes to harnessing the work capacity of the secondary stream generated by ram effects, and significantly improves specific impulse performance. This study emphasizes the distinct throttling characteristics at different Mach numbers and provides pivotal insights for developing more efficient RBCC engines in ejector mode.

The fractures of the hyoid bone in the neck are one of the important indicators of any pressure over the neck. The present study includes a huge sample size of mechanical asphyxiation deaths (791 cases) to study the incidence of hyoid bone fractures in hanging, ligature strangulation, and throttling. Fractures of the hyoid bone were noticed in a total of 12 cases, 9 male and 3 female with 33.33% incidence in the 41-50 years age group. Throttling dominated the strangulation group in our study with a share of 42.85%. A total of 6 (5 male, 1 female) cases showed hyoid bone fractures in the strangulation group wherein the predominant incidence is seen in 41-50 years(50%). In our study, right cornu fractures are frequent in hanging and throttling. Except for one outward compression fracture in a hanging instance, all of the fractures identified in our investigation are inward compression fractures. The present study adds to the existing literature that hyoid bone fractures are less common in hanging than throttling and any fracture of hyoid bone is common after the age of 40 years because of calcification. [ABSTRACT FROM AUTHOR]

The most common solutions for rocket engines are the single operation point (thrust level) units. Oxidiser and fuel mass flow rates and the oxidiser-to-fuel mass flow rate ratio (OFR) are some of the determinants of the thrust level. Based on these, planetary ascent and descent; space rendezvous; orbital manoeuvring, including orientation and stabilisation in space; hovering, hazard avoidance during planetary landing; and ballistic missile trajectory control propulsion systems could use throttleable liquid engines. Several engine throttling methods, such as supply pressure variation and variable injector area, can be applied. Among others, a cavitating venturi propellant regulatory valve is one of the most promising throttling method. This type of valve can provide steady mass flow, despite the downstream pressure disturbance (i.e. from the combustion chamber), which sustains a stable engine thrust as the mass flow is kept. The article presents the valve sizing method, design and prototype test results of the cavitating venturi valve that has potential for utilisation in a deep throttling rocket engine. Mass flow stability and repeatability are presented for valve operating points in the 10%–110% nominal mass flow range. Valve design optimisation, based on CFD, to sustain cavitation for a higher downstream-to-upstream pressure ratio is shown. [ABSTRACT FROM AUTHOR]

By analysis of an open shell, the design of a damping elastic kinematic joint in the lever mechanism of controllable dampers, precision robots, and manipulators is considered. Control by the maximum principle is established in terms of the gas flow rate to the spring cavity. The relation of the spring kinematics is investigated in relation to the cross-sectional profile of the spring and the gas filling. Optimal speed control of the joint is described. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the parameters of an installation for heating a coolant using liquid forcing through throttle openings. A scheme of a full-size experimental stand has been developed and the principles of operation are described in detail. For visual observation of the state of the liquid at different angular speeds of rotation of the rotor, a transparent drum model is made. The influence of the shape of the rotor skirt and the depth of its immersion in the liquid on the filling capacity of the rotor cavity at an angular velocity from 42 to 314 rad/s has been determined. The optimal parameters of the depth of immersion of the drum skirt with a diameter of 0.5 m in the liquid, at low rotor speeds of 16, 24, 32 rad/s, were obtained. The angle of inclination is calculated and it is experimentally proved that for a conical shape it is 5 degrees. It was found that at angular velocities of the rotor more than 100 rad/s, the shape and depth of immersion of the skirt in the liquid do not affect the filling of the rotor, since the feed is higher than its flow through the throttle openings. It is shown that the use of rotational forces to heat the liquid allows using an electric motor with less power, since it is spent only on unwinding the rotor with the liquid. The calculated dependence of the liquid pressure on the side walls of the rotor, the liquid heating temperature on the angular velocity of rotation of the rotor and on two values of the area of the throttle openings, at 31.4·10–6 m² and 64.34·10–6 m², is obtained. When the total area of the throttle openings is doubled, the temperature of the liquid heating at the same angular velocities increases from 35.6 °C to 82.5 °C. The above installation parameters allow you to get hot water when using small shell-and-tube heat exchangers [ABSTRACT FROM AUTHOR]

The main application of high-flow Ranque–Hilsch three-flow vortex tubes (TVT) is the low-temperature separation (LTS) of natural gas with vortex tubes used as cold generators and direct separators. In this study, we compare the purification efficiencies of TVT and the throttle at the LTS unit used at the Beregovoye field characterized by a low degree of gas expansion (pressure drop from 85 bar to 60 bar). We observed that the gas temperature and its dew point temperature was lower for TVT compared to that for the throttle used at the LTS. Moreover, use of TVT increased the degree of gas purification even at low degrees of gas expansion. This ensured the implementation of Gazprom Company standard 089–2010 for the summer conditions. [ABSTRACT FROM AUTHOR]

This is Part 2 of a trio of works intended to provide a unifying framework in which conservative and optimistic synchronization for parallel discrete event simulations can be freely and transparently combined in the same logical process on an event-by-event basis. In this article, we continue the outline of an approach called Unified Virtual Time (UVT) that was introduced in Part 1, showing in detail via two extended examples how conservative synchronization can be refactored and combined with optimistic synchronization in the UVT framework. We describe UVT versions of both a basic time windowing algorithm called Unified Simple Time Windows and a refactored version of the Chandy-Misra-Bryant Null Message algorithm called Unified CMB. [ABSTRACT FROM AUTHOR]

Algorithms for synchronization of parallel discrete event simulation have historically been divided between conservative methods that require lookahead but not rollback, and optimistic methods that require rollback but not lookahead. In this paper we present a new approach in the form of a framework called Unified Virtual Time (UVT) that unifies the two approaches, combining the advantages of both within a single synchronization theory. Whenever timely lookahead information is available, a logical process (LP) executes conservatively using an irreversible event handler. When lookahead information is not available the LP does not block, as it would in a classical conservative execution, but instead executes optimistically using a reversible event handler. The switch from conservative to optimistic synchronization and back is decided on an event-by-event basis by the simulator, transparently to the model code. UVT treats conservative synchronization algorithms as optional accelerators for an underlying optimistic synchronization algorithm, enabling the speed of conservative execution whenever it is applicable, but otherwise falling back on the generality of optimistic execution. We describe UVT in a novel way, based on fundamental invariants, monotonicity requirements, and synchronization rules. UVT permits zero-delay messages and pays careful attention to tie-handling using superposition. We prove that under fairly general conditions a UVT simulation always makes progress in virtual time. This is Part 1 of a trio of papers describing the UVT framework for PDES, mixing conservative and optimistic synchronization and integrating throttling control. [ABSTRACT FROM AUTHOR]

An energy method was used to describe a size-dependent distribution of cavitation bubbles when throttling the flow of a fluid in a control valve assembly comprising a cylindrical separator and a butterfly locking device. The parameters having a significant impact on the throttling of the working medium were distinguished among numerous process variables. An analysis of the stochastic pattern of variations in the intensity of cavitation bubble formation, obtained taking the distinguished parameters into account, showed that the transition from the initial stage of throttling toward the full opening of the valve is associated with a reduction in the number of cavitation bubbles by 1.06 times, provided that their sizes are reduced by 1.36 times. [ABSTRACT FROM AUTHOR]

This article explores the throttling aspect of the hybrid rocket motor through experiments using a lab-scale motor. The lab-scale motor utilizes a wax-Al based fuel and compressed air as the oxidizer. The oxidizer flow rate was modulated using a PID controller to study the closed-loop thrust control performance of the motor. Numerical simulations and cold flow tests were carried out to identify the suitable gains for the PID control algorithm. Pressure feedback was used in the control algorithm to obtain the closed-loop thrust control. The resultant closed-loop system followed the reference pressure accurately during the step input response test of the system. The maximum error in the observed chamber pressure was 1.86 % for a reference pressure of 4.69 bar, which corresponds to a reference thrust of 117.6 N. The response of the system for a ramp input, with linear thrust variation from 78.4 N to 127.4 N, showed that the measured thrust followed the desired ramp profile with a root-mean-square error of 1.99 N. A ramp-down test with the same thrust range produced a root-mean-square error of 6.2 N. [ABSTRACT FROM AUTHOR]

The Government of the Russian Federation has set the task of expanding the field of application of gaseous fuels in the national economy. In accordance with this task, an agreement of June 17, 2016 was developed on cooperation between PJSC Gazprom, JSC Russian Railways, JSC Sinara Group, JSC Transmashholding in the use of natural gas as a motor fuel, which provides for the production of shunting gas locomotives and mainline diesel locomotives and gas turbine locomotives. This work is a continuation of the work begun in the 1990s to create, fine-tune and test diesel locomotives using natural gas as a motor fuel. The conversion of diesel locomotives to gaseous fuel can be carried out in two ways: creation of diesel locomotives with gas piston engines and the modernization of diesel locomotives of the existing fleet by converting the diesel engines of these locomotives to use the gas-diesel cycle. A comparison of these options is given and solutions are proposed that allow using gas-diesel cycle on diesel locomotives. Mathematical models for calculating the performance indicators of a gas-diesel generator plant in operating modes and separately for the fuel supply process are presented, their features and some calculation results are presented. The experimentally determined reasons for the impossibility of operation of the power plant in the gas-diesel cycle of a shunting diesel locomotive based on TEM18 below the fourth position of the driver's controller are theoretically substantiated. The minimum required structural changes to the standard fuel equipment are determined, which are necessary to ensure stable operation of a diesel locomotive on gaseous fuel. A comparative assessment of the efficiency of converting diesel locomotives to gaseous fuel is carried out and the cost of fuel consumed per hour of operation is determined, depending on the degree of fuel replacement with gas when the locomotive is operating in average operating modes.

Thermal-induced two-phase flow instabilities could badly slow the runtime performance of two-phase systems, such as boiling water reactor core, and even endanger the safe operation. Hence, many researchers have carried out numerous researches on flow instability characteristics, but few publications cover the effects of local throttling on two-phase flow instabilities in open-channel systems such as coolant rod bundle subchannel with spacer grids in the nuclear reactor core. This paper provides a numerical study on the effects of local throttling on two-phase flow instabilities in a simplified typical coolant open-channel system in a nuclear reactor core by using the NUSOL-SYS code. The effects of local throttling ratio, throttling position, and other throttling parameters on the stability of the boiling channel system were carried out. The results show that usually in uniformly distributed throttling conditions, the stability of the system and high throttling ratio are positively correlated. In fixed throttle ratio conditions, the stability of the system is positively correlated with the distance from the throttling region to the entrance and local void fraction. If throttling regions are uniformly arranged along the heating channel with a certain value, the number of throttle regions will enhance the instability of the system. Besides, this paper preliminarily proposed a criterion function f(n, RT, α) to study the complicated throttling effects on flow instability which could provide technical reference for the safe design and operation of two-phase systems, especially, the reactor core. [ABSTRACT FROM AUTHOR]

• Two stage launch vehicle powered by semi-cryogenic engine for circular orbit and GTO. • Lift off mass reduction of the order of 42% for circular and 16% for GTO. • Totally eliminates the 3 stage launch vehicle with solid rocket booster stages. • Thrust throttling ranges from 33% to 100%. This paper explores in detail the design and optimization of the ascent trajectory for a two-stage liquid rocket capable of providing variable thrust. Thrust and steering profiles play an essential role in designing a launch vehicle mission. Variable thrusting or throttling requirement arises in the thrust profile of a liquid rocket due to structural, aerodynamic and mission-related constraints. The current study investigates this aspect for two-stage liquid rockets, which deliver a 500 kg payload to 500 km circular orbit and 180 × 36000 km Geostationary Transfer Orbit (GTO). As payload mass is kept constant in both cases, the lift-off mass varies. The study found that for both missions mentioned earlier, the required variation of thrust (throttling) is in the range of 100% to 33% for the first stage to achieve an optimal trajectory. For the second stage, a considerable requirement for throttling is absent. Optimal trajectory with throttling capability reduced the lift-off mass of the launch vehicle for a mission to circular orbit by 41.6% and to the GTO by 16.3% compared to the constant thrusting cases. Also, a two-stage liquid rocket using semi cryogenic engines with variable thrusting capability and stage structural factors as low as 0.1 can replace a three-stage rocket which delivers the same payload to the 500 km circular orbit. Kulasekharapattinam and Sriharikota were the launch sites considered for the circular orbit and GTO. The study did not consider spent stage impact constraints. Canonical Differential Evolution based solver is used for global optimization. Thrust profile, steering profile and lift-off mass are the outputs of the optimization strategy. [ABSTRACT FROM AUTHOR]

In order to solve the problem of single well without liquid phase measurement in Sulige Gas Field under the process mode of interwell series connection and wellhead wet gas measurement, a method of combining throttle flowmeter and vortex flowmeter to measure wet gas-liquid two-phase flow was proposed. The overall structure of flowmeter was simplified by integrating two kinds of flowmeter measuring tubes and adopting differential pressure static pressure, frequency and temperature integrated sensors. The indoor air-water two-phase flow experimental platform was used to test the measurement accuracy of the wet gas flowmeter. The results show that when the instantaneous liquid volume is 0.05-4 m3/h, the gas and liquid measurement errors of the combined wet gas flowmeter are within 5% and 20% respectively. The measurement accuracy of the wet gas flowmeter was tested at the wellhead of the gas well by using the separation metering device. The results show that the average error of gas and liquid phase measurement in the bubble exhaust well is less than 5% and 20% respectively, which can accurately reflect the liquid production law of the gas well and guide the optimization of the bubble discharge and filling system; the gas phase measurement error in the plunger gas lift well is less than 8%, and the liquid phase measurement error is large, but it can accurately reflect the liquid production characteristics of the plunger gas well, which could provide the basis for working condition diagnosis and production system optimization of plunger gas well.

Using the RANS/ILES method, we analyze the effect of throttling of one of the modules in a three-module high-speed model air intake on the flow, level, and spectra of pressure pulsations in each of the modules. A brief description of the calculation method and the boundary conditions used is given. The OASPL levels in air intake modules are obtained depending on the type of flow deceleration. The effect of the throttling of one of the modules on the flow and features of 1/3-octave spectra in adjacent modules is revealed. [ABSTRACT FROM AUTHOR]

The article presents the results of installing a charge flow stabilizer in the loading devices of sintering machines of the Magnitogorsk Iron & Steel Works (MMK) Sinter Plant No. 5. While previous stabilizer installation studies mainly focused on how minimizing the discreteness of the charge flow at the exit of the drum feeder affects the structure and bulk density of the sintered charge layer, the present study considers the influence of charge flow stabilization in the loading device on the gas-dynamic and thermal operation of sintering machines. The installation of a charge flow stabilizer at the sintering machines of the Magnitogorsk Iron & Steel Works allowed the sintering machine production rate to be increased by 3.4% and the charge ignition and specific power natural gas consumption to be reduced by 9–10 and 1.4–2.8%, respectively. [ABSTRACT FROM AUTHOR]

Due to the increase in the cost of diesel fuel, much attention is paid to the use of alternative types of fuel on diesel locomotives. Variants of using fuel obtained from coal, plants, gas fields and hydrogen are considered. Natural gas is the cheapest and most accessible today. The use of specially designed gas-piston engines on diesel locomotives, operating when the gas-air mixture is ignited from an external source, is the most attractive option. However, this approach has certain disadvantages:• it is necessary to create a new engine, since the modernization of existing engines requires serious structural changes;• gas piston engine operates essentially according to the Otto cycle and has lower efficiency and power indicators as compared to a diesel engine;• when modernizing existing diesel locomotives, switching to the Otto cycle excludes the possibility of using diesel fuel.Conversion of diesel locomotives to gas fuel must be carried out using the gas-diesel cycle. This approach is most acceptable for the modernization of diesel locomotives of the existing fleet, since it preserves the thermal performance of the engine and makes it possible to transfer diesel locomotives back to operation on diesel fuel. The main obstacle to the transfer of diesel locomotives to the gas-diesel cycle is the low degree of replacement of diesel fuel with gas. This circumstance is determined by the significant difficulties in ensuring the operation of the engine in the gas-diesel cycle at low loads and idling. It is necessary to ensure a stable supply of ignition fuel in these modes and guaranteed ignition of the gas-air mixture from it. The solution to this problem is ensured by maintaining a given stoichiometric ratio in the gas-air mixture and a temperature sufficient to ignite the ignition portion of the fuel.The main way to regulate the stoichiometric ratio is to reduce the amount of air entering the cylinders by throttling it at the engine inlet. This article discusses the methodology for calculating the performance of the engine when throttling the air inlet.

In the present study, 11 cases were belongs to 21 to 30 year age group followed by 9 cases belongs to 31-40 year age group. Among patients studied, 54% were males and 46 % were females, in 80% of the cases manner of death was hanging and in 4% of cases was strangulation and 6% of cases was throttling, out of 20 cases of hanging hyoid bone fracture (Anteroposterior compression fracture) was seen in 2 cases and out of 2 cases of strangulation hyoid bone fracture was not found and out of 3 cases of throttling, hyoid bone fracture (Inward compression fracture) was found in all cases. [ABSTRACT FROM AUTHOR]

This paper describes the performance of a combustion-controllable solid-propellant microthruster using laser heating. Conventional solid propellant thrusters are relatively compact and reliable because the thrusters require neither tanks nor valves and never present the risk of propellant leakage during storage. On the other hand, interruption and restart of thrust production are difficult because the combustion is autonomously sustained once the propellant is ignited. Therefore, solid propellant thrusters have never been applied to orbit maintenance or attitude control. Hence, we have developed the solid propellants in which combustion is sustained only while the heat was supplied to the burning surface and proposed a throttleable solid propellant microthruster using semiconductor laser as a heat source. In our previous study, in a prototyped thruster, a laser head was moved by a linear traverser such that laser beam followed the regressing burning surface. The thruster interrupted and restarted thrust production by switching laser. However, the use of a linear traverser increased thruster weight. Hence, we redesigned a prototype, which maintained the gap between the burning surface and the laser-introducing window to prevent laser-beam attenuation due to the combustion products. Thrust measurement showed that the prototyped microthruster successfully yielded a thrust 0.06 N, Isp of 70.3 s, and ignition delay of 0.9 s. [ABSTRACT FROM AUTHOR]

This article explores the throttling aspect of the hybrid rocket motor through experiments using a lab-scale motor. The lab-scale motor utilizes a wax-Al based fuel and compressed air as the oxidizer. The oxidizer flow rate was modulated using a PID controller to study the closed-loop thrust control performance of the motor. Numerical simulations and cold flow tests were carried out to identify the suitable gains for the PID control algorithm. Pressure feedback was used in the control algorithm to obtain the closed-loop thrust control. The resultant closed-loop system followed the reference pressure accurately during the step input response test of the system. The maximum error in the observed chamber pressure was 1.86% for a reference pressure of 4.69 bar, which corresponds to a reference thrust of 117.6 N. The response of the system for a ramp input, with linear thrust variation from 78.4 N to 127.4 N, showed that the measured thrust followed the desired ramp profile with a root-mean-square error of 1.99 N. A ramp-down test with the same thrust range produced a root-mean-square error of 6.2 N.

The thrust produced by a hybrid rocket motor (HRM) can be controlled by varying the oxidizer flow rate to the combustion chamber. This feature is useful in shaping motor thrust profiles and optimizing a vehicle flight trajectory, but propellant throttling in solid-fuel hybrids is limited to the liquid component only, complicating the control scheme and potentially destabilizing combustion in the motor. While hybrid motor throttling ability remains a subject of considerable interest, there has been little investigation of throttling in motors that use high regression rate, liquefying fuels such as paraffin wax. This article describes the development and implementation of a closed loop thrust control scheme for a laboratory-scale paraffin wax/nitrous oxide HRM using a low-cost ball valve as the controlling hardware element. A model of motor performance is first developed from which proportional-integral-derivative (PID) controller constants are obtained through experimental testing. The control scheme is demonstrated through closed loop hot fire tests of a laboratory-scale motor in which thrust tracks a set-point value with feedback provided through a load cell. Upon reaching the setpoint, the motor remains throttled within ± 2.4% of the maximum thrust of the motor. Constant and ramping thrust profiles are demonstrated.

Zero forcing can be described as a graph process that uses a color change rule in which vertices change white vertices to blue. The throttling number of a graph minimizes the sum of the number of vertices initially colored blue and the number of time steps required to color the entire graph. Positive semidefinite (PSD) zero forcing is a commonly studied variant of standard zero forcing that alters the color change rule. This paper introduces a method for extending a graph using a PSD zero forcing process. Using this extension method, graphs with PSD throttling number at most t are characterized as specific minors of the Cartesian product of complete graphs and trees. A similar characterization is obtained for the minor monotone floor of PSD zero forcing. Finally, the set of connected graphs on n vertices with throttling number at least n − k is characterized by forbidding a finite family of induced subgraphs. These forbidden subgraphs are constructed for standard throttling. [ABSTRACT FROM AUTHOR]

Managing Advertisers' Budgets in Online Advertising Platforms Most online advertising platforms sell ad placements using repeated auctions. Platforms often provide budget-management strategies that allow advertisers to control their cumulative expenditures: Advertisers declare the maximum daily amount they are willing to pay, and the platform adjusts allocations and payments to guarantee that cumulative expenditures do not exceed budgets. Many strategies can be used to accommodate budget constraints, and each one, when applied to all budget-constrained advertisers simultaneously, drives the system toward a different equilibrium. For example, platforms can modify the advertisers' bids or the auctions' allocation and payment rules. In "Budget-Management Strategies in Repeated Auctions," Balseiro, Kim, Mahdian, and Mirrokni compare the equilibrium outcome of a range of budget-management strategies used in practice. They study the impact of budget-management strategies on the trade-off between the seller's profit and buyers' utility and shed light on the incentive properties of budget-management strategies. In online advertising, advertisers purchase ad placements by participating in a long sequence of repeated auctions. One of the most important features that advertising platforms often provide and advertisers often use is budget management, which allows advertisers to control their cumulative expenditures. Advertisers typically declare the maximum daily amount they are willing to pay, and the platform adjusts allocations and payments to guarantee that cumulative expenditures do not exceed budgets. There are multiple ways to achieve this goal, and each one, when applied to all budget-constrained advertisers simultaneously, drives the system toward a different equilibrium. Our goal is to compare the "system equilibria" of a range of budget-management strategies. In particular, we consider six different budget-management strategies, including probabilistic throttling, thresholding, bid shading, reserve pricing, and two versions of multiplicative boosting. We show that these methods admit a system equilibrium, study their incentive properties, prove dominance relations among them in a simplified setting, and confirm our theoretical findings using real ad auction data from a sponsored search. Our study sheds light on the impact of budget-management strategies on the trade-off between the seller's profit and buyers' utility and may be of practical relevance for advertising platforms. [ABSTRACT FROM AUTHOR]

Consider a discrete-time process on a graph G where a set B of initial vertices are chosen to be colored blue (the remainder being white) and then a time step consists of every currently blue vertex forcing all of its neighbors to become blue; this process stops when every vertex of the graph is blue, and the process is called full forcing. The full throttling number of G is then defined to be the minimum sum of the cardinality of B and the number of time steps needed to complete the forcing process. On trees, the full throttling number is equivalent to the throttling numbers of several other graph processes, such as positive-semidefinite zero forcing, the game of cops and robbers, and the distance domination number (alternately, the k -radius) of a graph. For all of these, it is known that maximum possible throttling number for a tree on n vertices is somewhere between 1.4502 n and 14 2 n , with the former exhibited by a family of spiders. After introducing some new ideas and methods for working with throttling on trees, this paper determines the exact full throttling number of all balanced spiders (trees with equal-length paths extending from a center vertex), and proves that their full throttling numbers are bounded above by that of paths of the same order n , which are known to have full throttling number ⌈ 2 n − 1 2 ⌉. [ABSTRACT FROM AUTHOR]

Problems of ensuring the high efficiency of steam turbines during operation in partial modes are considered. It is noted that the decrease of steam throttling losses in the control valves has the greatest impact on the efficiency when operating in such modes. A brief overview of known techniques for increasing the efficiency of turbines by optimizing the operating modes of the control stage and the steam admission system, which consist in obtaining additional throttleless modes due to the combined operation of control stage nozzle boxes with different number of nozzles, is given. However, when implementing such techniques in dynamics, problems and limitations arise associated with the need for abrupt switching of control valves. A promising method (algorithm) for controlling the control valves of a steam turbine that ensures the optimization of the operating mode of the control stage and the minimum throttling losses in the control valves is proposed. The technology for implementation of the proposed control method, its advantages over the traditional one, and development prospects are stated. On the example of the T-295/335-23.5 turbine, the results of calculating the efficiency of the control stage with sequential and optimized steam admission, carried out by the proposed control method, are presented. The tests of optimized steam admission implemented by two methods, traditional and proposed one, are carried out on the mathematical model of T-295/335-23.5 turbine. The test results are presented in the form of graphs of transient processes. It is shown that, due to the optimization of steam admission by the proposed control algorithm for control valves, the disadvantages inherent in the implementation of the traditional method are eliminated, namely, the quality of transient processes is increased, there are no abrupt switching of control valves, the amplitude of steam temperature fluctuations in the nozzle boxes decreases, and it becomes possible to control the rate of their heating during optimization. [ABSTRACT FROM AUTHOR]

Reliability, along with energy efficiency, is an important characteristic of pump units in various applications. In practical pump applications, it is important to strike a balance between reliability and energy efficiency. These indicators strongly depend on the applied control method of the pump unit. This study analyzes a trade-off method for regulating a system with three parallel pumps equipped with only one frequency converter (multi-pump single-drive system). A typical operating cycle of a pumping system with variable flow rate requirements is considered. The proposed trade-off method is compared with the traditional regulation, when a change in the operating point of the pump is achieved only by changing the rotation speed, and with the method for maximum reliability. It is shown that the proposed trade-off method makes it possible to ensure sufficient reliability of the multi-pump system operation without a significant increase in energy consumption.

Valves control the fluid flow and pressure in a system or a process. Globe valves have good throttling ability, which permits its use in regulating flows. Detailed understanding of flow in Globe valve with cage apertures of various shapes and its impact on the flow characteristics and optimization was carried out. The computational study was carried out using FLUENT, a finite volume based code. Grid sensitivity test were done and the results validated experimentally. The effect of aperture configuration on flow characteristics and valve coefficient was studied to arrive at optimum value. Valve coefficient was found to be dependent on aperture shape and is maximum for the valve with triangular shaped aperture. Methodology to improve flow performance of a globe valve with highest valve coefficient is established.

The attractive features such as low static power and high density exhibited by the Non-Volatile Memory (NVM) technologies makes them a promising candidate in the memory hierarchy, including caches. However, the limited write endurance with the write variations governed by the access patterns and the applied replacement policies reduce the chance of NVMs as a successor of SRAM. These write variations are of concern as they not only breakdown the NVM cells but also reduce the effective lifetime. This paper proposes efficient techniques to mitigate the intra-set write variation to improve the lifetime of the NVM cache. Our first two techniques partition the cache into windows of equal size and distribute the writes uniformly across the cache set by employing the window as write-restricted or read-only. The selection of the window in these techniques is by rotation or with the help of counters. In our third technique, different cache ways are employed as a write-restricted over the period of execution to distribute the writes uniformly. Experimental results using full system simulation show the significant reduction in intra-set write variation along with improvement in the cache lifetime. [ABSTRACT FROM AUTHOR]

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Abstract Zero forcing is a process on a graph that colors vertices blue by starting with some of the vertices blue and applying a color change rule. Throttling minimizes the sum of the size of the initial blue vertex set and the number of the time steps needed to color the graph. We study throttling for positive semidefinite zero forcing. We establish a tight lower bound on the positive semidefinite throttling number as a function of the order, maximum degree, and positive semidefinite zero forcing number of the graph, and determine the positive semidefinite throttling numbers of paths, cycles, and full binary trees. We characterize the graphs that have extreme positive semidefinite throttling numbers. [ABSTRACT FROM AUTHOR]