Double-loop sliding mode control of reentry hypersonic vehicle with RCS

In order to solve the problem of insufficient aerodynamic moment caused by thin air in the re-entry stage of hypersonic vehicle, this paper establishes an attitude angle model of hypersonic vehicle with reaction control system (RCS), and derives its affine linear model to decoupled the internal and external loop. According to the dead zone and saturation characteristics of RCS thruster, a control method to convert continuous moment into discrete switching instruction using pulse width modulation (PWM) is proposed. Since the number of thrusters is usually redundant, the installation matrix of thrusters in the body coordinate is established, and the command moment is coordinately distributed to the individual thrusters. Then a double-loop sliding mode controller (DSMC) is designed to achieve attitude stability and trajectory tracking. Finally, the simulation results show that DSMC has higher maneuverability, fewer thruster switches and stronger robustness to interference

Spray-combustion synthesis: Efficient solution route to high-performance oxide transistors

Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations

Structural analysis of scorpion a [alpha]- and a [alpha]-like toxins that bind to Na⁺ channels

M.S. (Master of Science

Starting and Regulating Characteristics of Electric Pump Feed System for LRE under Different Schemes

Liquid rocket engines (LREs) are essential power sources for access to space. Electric pump feed systems have received noteworthy attention because of their high efficiency, convenient regulation, and simple structure. In this study, an oxidant feed system with two pumps in parallel was established. The centralized parameter method and the distributed parameter method were used for modeling. The dynamic characteristics of different starting schemes and regulating schemes were obtained. The results show that the asynchronous opening of two pumps led to a pressure peak from the second stage to the third stage. Under the low operating conditions, the pump speed of the asynchronous scheme was about 13,300 r/min, the pump speed of the synchronous scheme was about 12,100 r/min, and the pump speed of the joint adjustment scheme was about 24,800 r/min. The joint adjustment of pump speed and valve opening could increase the pump speed by a factor of one-third, while maintaining the efficiency at a high level. The optimal scheme could be selected according to a genetic algorithm-based calculation process, together with the curves of the flow rate and pressure with pump speed and valve opening. This study can contribute to the application of electric pumps for liquid rocket propulsion

Starting and Regulating Characteristics of Electric Pump Feed System for LRE under Different Schemes

Liquid rocket engines (LREs) are essential power sources for access to space. Electric pump feed systems have received noteworthy attention because of their high efficiency, convenient regulation, and simple structure. In this study, an oxidant feed system with two pumps in parallel was established. The centralized parameter method and the distributed parameter method were used for modeling. The dynamic characteristics of different starting schemes and regulating schemes were obtained. The results show that the asynchronous opening of two pumps led to a pressure peak from the second stage to the third stage. Under the low operating conditions, the pump speed of the asynchronous scheme was about 13,300 r/min, the pump speed of the synchronous scheme was about 12,100 r/min, and the pump speed of the joint adjustment scheme was about 24,800 r/min. The joint adjustment of pump speed and valve opening could increase the pump speed by a factor of one-third, while maintaining the efficiency at a high level. The optimal scheme could be selected according to a genetic algorithm-based calculation process, together with the curves of the flow rate and pressure with pump speed and valve opening. This study can contribute to the application of electric pumps for liquid rocket propulsion

Optimization of combustion organization scheme for pre-combustion chamber of pre-cooled engine

Abstract Pre-cooled engines, in which the incoming air is cooled by a pre-cooler before it enters the subsequent components for operation, are one of the important developments in combined power solutions. Therefore, how to optimize the gas temperature uniformity of the high temperature gas stream at the outlet of the pre-combustion chamber to achieve higher efficiency of the pre-cooled engine will be the main research content. In this paper, grid partitioning was performed on the pre combustion chamber model, and the k-omega model and EDC model were used to simulate the internal flow field of the pre combustion chamber. And verify the correctness of the simulation through engine hot testing. Explored the changing trends of the internal velocity and temperature fields of the engine under different secondary injection structures. The larger the secondary injection flow rate, the more obvious the obstruction to high-temperature gas, and the better the uniformity of gas temperature. However, in experiments, the secondary injection components often cannot withstand a large flow rate ratio. Ultimately, the gas temperature uniformity is best when the secondary injection flow rate ratio is 65%. Circumferential deflection will cause the gas to spin, and the spinning process will make the gas temperature at the same radius more uniform. However, due to the decrease in radial velocity, the obstruction effect on the overall high-temperature gas is weakened. When the gas is deflected towards the head by 30°, the velocity of the incoming gas and the velocity of the secondary injection gas are combined and perpendicular to the axis. At this time, the gas temperature uniformity is the best

The Influence of Thrust Chamber Structure Parameters on Regenerative Cooling Effect with Hydrogen Peroxide as Coolant in Liquid Rocket Engines

Liquid rocket engines with hydrogen peroxide and kerosene have the advantages of high density specific impulse, high reliability, and no ignition system. At present, the cooling problem of hydrogen peroxide engines, especially with regenerative cooling, has been little explored. In this study, a realizable k-epsilon turbulence model, discrete phase model, eddy dissipation concept model, and 10-step 10-component reaction mechanism of kerosene with oxygen are used. The increased rib height of the regenerative cooling channel causes the inner wall temperature of the engine increases, the average temperature of the coolant outlet decreases slightly, and the coolant pressure decreases. The overall wall temperature decreases as the rib width of the regenerative cooling channel increases. However, in the nozzle throat area, the wall temperature increases, the average coolant outlet temperature decreases, and the coolant pressure drop increases. A decrease in the inner wall thickness of the regenerative cooling channel results in a significant decrease in the wall temperature and a small increase in the average coolant outlet temperature. These findings contribute to the further development of the engine with hydrogen peroxide and can guide the design of its regenerative cooling process

Annulated Thienyl-Vinylene-Thienyl Building Blocks for π‑Conjugated Copolymers: Ring Dimensions and Isomeric Structure Effects on π‑Conjugation Length and Charge Transport

A series of annulated thienyl-vinylene-thienyl (<b>ATVT</b>) building blocks having varied ring sizes, isomeric structures, and substituents was synthesized and characterized by spectroscopic, electrochemical, quantum chemical, and crystallographic methods. It is found that <b>ATVT</b> ring size and isomeric structure critically affect the planarity, structural rigidity, optical absorption, and redox properties of these new π-units. Various solubilizing substituents can be introduced on the annulated hydrocarbon fragments, preserving the <b>ATVT</b> planarity and redox properties. The corresponding π-conjugated copolymers comprising <b>ATVT</b> units and electron-deficient units were also synthesized and characterized. The solubility, redox properties, and carrier transport behavior of these copolymers also depend remarkably on the annulated ring size and the <b>ATVT</b> unit isomeric structure. One of the copolymers composed of an <b>ATVT</b> with five-membered rings (<b>1</b>), (<i>E</i>)-4,4′,5,5′-tetrahydro-6,6′-bi­(cyclopenta­[<i>b</i>]­thiophenylidene), and a naphthalenediimide (<b>NDI</b>) unit exhibits a broad UV–vis–NIR absorption with an onset beyond 1100 nm both in solution and in the film state, and thin films exhibit n-type semiconducting properties in field-effect transistors. These results are ascribed to the extended main chain π-conjugation length and the low HOMO–LUMO bandgap. Other π-conjugated copolymers containing unit <b>1</b> also exhibit characteristic red-shifted UV–vis–NIR absorption. A diketopyrrolopyrrole-based copolymer with unit <b>1</b> serves as an electron donor material in organic photovoltaic devices, exhibiting broad-range external quantum efficiencies from the UV to beyond 1000 nm

Annulated Thienyl-Vinylene-Thienyl Building Blocks for π‑Conjugated Copolymers: Ring Dimensions and Isomeric Structure Effects on π‑Conjugation Length and Charge Transport

A series of annulated thienyl-vinylene-thienyl (<b>ATVT</b>) building blocks having varied ring sizes, isomeric structures, and substituents was synthesized and characterized by spectroscopic, electrochemical, quantum chemical, and crystallographic methods. It is found that <b>ATVT</b> ring size and isomeric structure critically affect the planarity, structural rigidity, optical absorption, and redox properties of these new π-units. Various solubilizing substituents can be introduced on the annulated hydrocarbon fragments, preserving the <b>ATVT</b> planarity and redox properties. The corresponding π-conjugated copolymers comprising <b>ATVT</b> units and electron-deficient units were also synthesized and characterized. The solubility, redox properties, and carrier transport behavior of these copolymers also depend remarkably on the annulated ring size and the <b>ATVT</b> unit isomeric structure. One of the copolymers composed of an <b>ATVT</b> with five-membered rings (<b>1</b>), (<i>E</i>)-4,4′,5,5′-tetrahydro-6,6′-bi­(cyclopenta­[<i>b</i>]­thiophenylidene), and a naphthalenediimide (<b>NDI</b>) unit exhibits a broad UV–vis–NIR absorption with an onset beyond 1100 nm both in solution and in the film state, and thin films exhibit n-type semiconducting properties in field-effect transistors. These results are ascribed to the extended main chain π-conjugation length and the low HOMO–LUMO bandgap. Other π-conjugated copolymers containing unit <b>1</b> also exhibit characteristic red-shifted UV–vis–NIR absorption. A diketopyrrolopyrrole-based copolymer with unit <b>1</b> serves as an electron donor material in organic photovoltaic devices, exhibiting broad-range external quantum efficiencies from the UV to beyond 1000 nm

Annulated Thienyl-Vinylene-Thienyl Building Blocks for π‑Conjugated Copolymers: Ring Dimensions and Isomeric Structure Effects on π‑Conjugation Length and Charge Transport

A series of annulated thienyl-vinylene-thienyl (<b>ATVT</b>) building blocks having varied ring sizes, isomeric structures, and substituents was synthesized and characterized by spectroscopic, electrochemical, quantum chemical, and crystallographic methods. It is found that <b>ATVT</b> ring size and isomeric structure critically affect the planarity, structural rigidity, optical absorption, and redox properties of these new π-units. Various solubilizing substituents can be introduced on the annulated hydrocarbon fragments, preserving the <b>ATVT</b> planarity and redox properties. The corresponding π-conjugated copolymers comprising <b>ATVT</b> units and electron-deficient units were also synthesized and characterized. The solubility, redox properties, and carrier transport behavior of these copolymers also depend remarkably on the annulated ring size and the <b>ATVT</b> unit isomeric structure. One of the copolymers composed of an <b>ATVT</b> with five-membered rings (<b>1</b>), (<i>E</i>)-4,4′,5,5′-tetrahydro-6,6′-bi­(cyclopenta­[<i>b</i>]­thiophenylidene), and a naphthalenediimide (<b>NDI</b>) unit exhibits a broad UV–vis–NIR absorption with an onset beyond 1100 nm both in solution and in the film state, and thin films exhibit n-type semiconducting properties in field-effect transistors. These results are ascribed to the extended main chain π-conjugation length and the low HOMO–LUMO bandgap. Other π-conjugated copolymers containing unit <b>1</b> also exhibit characteristic red-shifted UV–vis–NIR absorption. A diketopyrrolopyrrole-based copolymer with unit <b>1</b> serves as an electron donor material in organic photovoltaic devices, exhibiting broad-range external quantum efficiencies from the UV to beyond 1000 nm