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Scientific Reports Feb 2021Development of a magnetic nozzle radiofrequency (rf) plasma thruster has been one of challenging topics in space electric propulsion technologies. The thruster typically...
Development of a magnetic nozzle radiofrequency (rf) plasma thruster has been one of challenging topics in space electric propulsion technologies. The thruster typically consists of an rf plasma source and a magnetic nozzle, where the plasma produced inside the source is transported along the magnetic field and expands in the magnetic nozzle. An imparted thrust is significantly affected by the rf power coupling for the plasma production, the plasma transport, the plasma loss to the wall, and the plasma acceleration process in the magnetic nozzle. The rf power transfer efficiency and the imparted thrust are assessed for two types of rf antennas exciting azimuthal mode number of [Formula: see text] and [Formula: see text], where propellant argon gas is introduced from the upstream of the thruster source tube. The rf power transfer efficiency and the density measured at the radial center for the [Formula: see text] mode antenna are higher than those for the [Formula: see text] mode antenna, while a larger thrust is obtained for the [Formula: see text] mode antenna. Two-dimensional plume characterization suggests that the lowered performance for the [Formula: see text] mode case is due to the plasma production at the radial center, where contribution on a thrust exerted to the magnetic nozzle is weak due to the absence of the radial magnetic field. Subsequently, the configuration is modified so as to introduce the propellant gas near the thruster exit for the [Formula: see text] mode configuration and the thruster efficiency approaching twenty percent is successfully obtained, being highest to date in the kW-class magnetic nozzle rf plasma thrusters.
PubMed: 33531602
DOI: 10.1038/s41598-021-82471-2 -
Pulmonary Therapy Dec 2023There is increasing pressure to prefer propellant-free inhaler devices over pressurized metered-dose inhalers (pMDI) due to environmental considerations. In this work,...
INTRODUCTION
There is increasing pressure to prefer propellant-free inhaler devices over pressurized metered-dose inhalers (pMDI) due to environmental considerations. In this work, we present results from three life cycle assessments (LCAs) on Easyhaler dry powder inhaler product portfolio and assess the changes in environmental impact and carbon footprint (CF) of the products over time.
METHODS
Three cradle-to-grave LCAs were conducted in 2019, 2021, and 2023. The 2019 assessment covered four products while 2021 and 2023 assessments included all six products in the portfolio. LCA for the protective cover sometimes used with Easyhaler was conducted in 2023. In addition to CF, nine other environmental impact categories were assessed to ensure that no burden shifting occurs.
RESULTS
During the study period, the non-weighted average CF of the Easyhaler decreased by 11.2%. For individual products, the decrease varied from 5.0 to 6.8% between the assessments. In the latest assessment, the average CF of Easyhaler was 547 gCOe with a range of 452-617 gCOe. The LCA of the protective cover was assessed for the first time in 2023 and had a CF of 66 gCOe.
CONCLUSIONS
Our results show that the climate impact of pharmaceutical products can be reduced without making changes to the product itself. The CF of Easyhaler products is in agreement with the lower end of the CF range previously reported for dry powder inhalers. Climate impact from the protective cover was one-tenth compared to the climate impact from the product itself.
PubMed: 37749379
DOI: 10.1007/s41030-023-00239-7 -
ACS Omega Feb 2022Maintaining the structural integrity of solid rocket propellant charges has been widely concerned by scholars around the world. The introduction of a polyester...
Maintaining the structural integrity of solid rocket propellant charges has been widely concerned by scholars around the world. The introduction of a polyester transition layer between the propellant and the liner is a new and effective method used to improve the interfacial bonding properties of the solid propellant charge and inhibit the migration of high-energy plasticizers. Uniaxial tensile pull-off specimens and accelerated aging experiments at multiple temperatures were used to study the interfacial bonding properties of propellant charges and the migration properties of plasticizers, respectively. The influence of the polyester structure on the two properties was also discussed in detail, and a targeted antimigration mechanism was proposed based on the molecular structure of the plasticizer. In addition, the Weibull model was used to fit the plasticizer migration behavior, and the plasticizer migration master curve in the charge system was obtained based on the principle of time-temperature superposition, which broadens the application field of the model and is important from an application perspective.
PubMed: 35224395
DOI: 10.1021/acsomega.1c06929 -
Optics Express Sep 2021This manuscript presents an ultrafast-laser-absorption-spectroscopy (ULAS) diagnostic capable of providing calibration-free, single-shot measurements of temperature and...
Ultrafast-laser-absorption spectroscopy in the mid-infrared for single-shot, calibration-free temperature and species measurements in low- and high-pressure combustion gases.
This manuscript presents an ultrafast-laser-absorption-spectroscopy (ULAS) diagnostic capable of providing calibration-free, single-shot measurements of temperature and CO at 5 kHz in combustion gases at low and high pressures. Additionally, this diagnostic was extended to provide 1D, single-shot measurements of temperature and CO in a propellant flame. A detailed description of the spectral-fitting routine, data-processing procedures, and determination of the instrument response function are also presented. The accuracy of the diagnostic was validated at 1000 K and pressures up to 40 bar in a heated-gas cell before being applied to characterize the spatiotemporal evolution of temperature and CO in AP-HTPB and AP-HTPB-aluminum propellant flames at pressures between 1 and 40 bar. The results presented here demonstrate that ULAS in the mid-IR can provide high-fidelity, calibration-free measurements of gas properties with sub-nanosecond time resolution in harsh, high-pressure combustion environments representative of rocket motors.
PubMed: 34614743
DOI: 10.1364/OE.435506 -
Polymers Nov 2022Energetic oxetanes, a group of energetic binders (EBs), are the focus of this review. We briefly introduce the role of binders and the difference between EBs and... (Review)
Review
Energetic oxetanes, a group of energetic binders (EBs), are the focus of this review. We briefly introduce the role of binders and the difference between EBs and traditional "non-energetic" polymer binders, followed by a discussion of the synthesis and key properties of polyoxetanes. Priority is given to recent works, but a long-term perspective is provided where necessary, to illustrate the development of this field and the most relevant emerging trends. New reports on methods of obtaining oxetane polymers are presented; concerning the possibility of using a new catalyst, water: Al(CH), or the ratio of comonomers on the properties of the obtained binders. The synthesis of copolymers with the use of polymers with an oxetane ring and polyethers, polybutadiene terminated with hydroxyl groups and poly (3-difluoroaminomethyl-3-methyloxetane) is discussed. The latest developments in crosslinking reactions and crosslinking agents used are also described. The primary challenges faced by the field are identified and a perspective on the future development of polyoxetane EBs is presented.
PubMed: 36365643
DOI: 10.3390/polym14214651 -
IEEE Aerospace Conference. IEEE... 2021Multi-Reward Proximal Policy Optimization, a multi-objective deep reinforcement learning algorithm, is used to examine the design space of low-thrust trajectories for a...
Multi-Reward Proximal Policy Optimization, a multi-objective deep reinforcement learning algorithm, is used to examine the design space of low-thrust trajectories for a SmallSat transferring between two libration point orbits in the Earth-Moon system. Using Multi-Reward Proximal Policy Optimization, multiple policies are simultaneously and efficiently trained on three distinct trajectory design scenarios. Each policy is trained to create a unique control scheme based on the trajectory design scenario and assigned reward function. Each reward function is defined using a set of objectives that are scaled via a unique combination of weights to balance guiding the spacecraft to the target mission orbit, incentivizing faster flight times, and penalizing propellant mass usage. Then, the policies are evaluated on the same set of perturbed initial conditions in each scenario to generate the propellant mass usage, flight time, and state discontinuities from a reference trajectory for each control scheme. The resulting low-thrust trajectories are used to examine a subset of the multi-objective trade space for the SmallSat trajectory design scenario. By autonomously constructing the solution space, insights into the required propellant mass, flight time, and transfer geometry are rapidly achieved.
PubMed: 35028651
DOI: 10.1109/aero50100.2021.9438267 -
Molecules (Basel, Switzerland) Mar 2024The combustion behavior of various propellant samples, including double-base propellants, pressed nitramine powders, and modified double-base propellants containing...
The combustion behavior of various propellant samples, including double-base propellants, pressed nitramine powders, and modified double-base propellants containing nitramine, was examined using OH-PLIF technology. The combustion process took place within a combustion chamber, and images capturing the flame at the moment of stable combustion were selected for further analysis. The distribution and production rate of OH radicals in both the double-base propellant and the nitramine-modified double-base propellant were simulated using Chemkin-17.0 software. The outcomes from both the experimental and simulation studies revealed that the concentration of OH radicals increased with a higher content of NG in the double-base propellant. In the modified double-base propellant containing RDX, the OH radical concentration decreased as the RDX content increased, with these tendencies of change aligning closely with the simulation results.
PubMed: 38474686
DOI: 10.3390/molecules29051175 -
Annals of Translational Medicine Jan 2021The management of chronic refractory pain (non-neoplastic and cancer-related pain) remains a therapeutic challenge. The continuous intrathecal (IT) administration of... (Review)
Review
The management of chronic refractory pain (non-neoplastic and cancer-related pain) remains a therapeutic challenge. The continuous intrathecal (IT) administration of drugs may play an important role in the possible management options. Intrathecal drug delivery devices (IDDDs) may be effective for patients with refractory chronic pain. Therefore, they may be adopted for non-oncologic pain in patients with compression fractures, spondylolisthesis, spondylosis, back surgery failure syndrome and spinal stenosis. Oncologic patients can benefit from these treatments in a variable way according to tumor characteristics, prognosis, periprocedural imaging and risk of disease progression. In this review, we describe the most commonly used drugs (opioids and non-opioids), their pharmacokinetic and pharmacodynamic features and indications of use. The most used drugs are morphine, hydromorphone, fentanyl, methadone, bupivacaine, clonidine, and ketamine. Patient evaluation before the device implantation should be based on clinical examination, medical records assessment and psychometric evaluation. The infusion pumps available on the market are both non-programmable (with continuous IT deliver of drugs) and programmable (with variable deliver of drugs according to their flow rate). Moreover, we describe the procedure of implantation and the potential complications of IT drug delivery (such as bleeding, infection, loss of cerebrospinal fluid, wound seroma, loss of catheter pump propellant).
PubMed: 33569488
DOI: 10.21037/atm-20-3814 -
Molecules (Basel, Switzerland) Apr 2023Boron powder is a kind of metal fuel with high gravimetric and volumetric calorific values, which has been widely used in military fields such as solid propellants,... (Review)
Review
Boron powder is a kind of metal fuel with high gravimetric and volumetric calorific values, which has been widely used in military fields such as solid propellants, high-energy explosives, and pyrotechnics. However, the easily formed liquid oxide layer can adhere to the surface of boron powder and react with the hydroxyl (-OH) group of hydroxyl-terminated polybutadiene (HTPB) binder to form a gel layer that is detrimental to propellant processing and restricts the complete oxidation of boron powder. Therefore, to improve the combustion efficiency of boron powder, the ignition and combustion mechanisms of boron powder have been studied, and surface coating modification strategies have been developed by researchers worldwide, aiming to optimize the surface properties, improve the reaction activity, and promote the energy release of boron powder. In this review, recent studies on the ignition and combustion mechanisms of boron powder are discussed. Moreover, the reported boron powder coating materials are classified according to the chemical structure and reaction mechanism. Additionally, the mechanisms and characteristics of different coating materials are summarized, and the mechanism diagrams of fluoride and metal oxide are provided. Furthermore, promising directions for modification methods and the potential application prospects of boron powder are also proposed.
PubMed: 37049973
DOI: 10.3390/molecules28073209 -
Chemical Science Mar 2022Hybrid rocket propulsion can contribute to reduce launch costs by simplifying engine design and operation. Hypergolic propellants, igniting spontaneously and...
Hybrid rocket propulsion can contribute to reduce launch costs by simplifying engine design and operation. Hypergolic propellants, igniting spontaneously and immediately upon contact between fuel and oxidizer, further simplify system integration by removing the need for an ignition system. Such hybrid engines could also replace currently popular hypergolic propulsion approaches based on extremely toxic and carcinogenic hydrazines. Here we present the first demonstration for the use of hypergolic metal-organic frameworks (HMOFs) as additives to trigger hypergolic ignition in conventional paraffin-based hybrid engine fuels. HMOFS are a recently introduced class of stable and safe hypergolic materials, used here as a platform to bring readily tunable ignition and combustion properties to hydrocarbon fuels. We present an experimental investigation of the ignition delay (ID, the time from first contact with an oxidizer to ignition) of blends of HMOFs with paraffin, using White Fuming Nitric Acid (WFNA) as the oxidizer. The majority of measured IDs are under 10 ms, significantly below the upper limit of 50 ms required for functional hypergolic propellant, and within the ultrafast ignition range. A theoretical analysis of the performance of HMOFs-containing fuels in a hybrid launcher engine scenario also reveals the effect of the HMOF mass fraction on the specific impulse ( ) and density impulse ( ). The use of HMOFs to produce paraffin-based hypergolic fuels results in a slight decrease of the and compared to that of pure paraffin, similar to the effect observed with Ammonia Borane (AB), a popular hypergolic additive. HMOFs however have a much higher thermal stability, allowing for convenient mixing with hot liquid paraffin, making the manufacturing processes simpler and safer compared to other hypergolic additives such as AB.
PubMed: 35432883
DOI: 10.1039/d1sc05975k