Strict Space Research Articles

Research on the effects of resonance tube bending in loop thermoacoustic refrigeration system

A high-power-density heat-driven loop thermoacoustic refrigeration system has the potential to meet miniaturization requirements of vehicle waste heat recovery systems. Given the strict space constraints in vehicle power compartments and the need to reduce equipment footprint, the resonance tubes need to be bent and coiled. However, the introduction of curvature may increase losses in resonance tubes. In order to evaluate the minor losses caused by bending on resonance tubes, a double-acoustic-source driven acoustic field modulation platform was constructed to experimentally investigate bent resonance tubes with different arc lengths under two common bending angles (90° and 180°) under high working pressure. Through the acoustic field reconstruction method, the acoustic field distributions of each resonance tube were obtained, and the effects of changes in bending angle and arc length on acoustic field and acoustic power dissipation were analyzed. The results indicated that the introduction of curvature leads to an increase in traveling-standing wave ratio, acoustic power, and acoustic power dissipation, with the degree of increase influenced by both curvature and arc length. Under the same bending angle, the minor loss is directly proportional to curvature, and there is an ExpAssoc function relationship between minor loss coefficient and curvature. Under the same curvature, the minor loss is not proportional to arc length, and minor loss coefficient slightly increases with the arc length doubles. The findings fill the research gap in resonance tube bending in loop thermoacoustic systems and provide guidance for the selection of resonance tube bending parameters.

Assessment of cruise ship decarbonization potential with alternative fuels based on MILP model and cabin space limitation

Alternative fuels are expected to play an increasingly crucial role in the decarbonization of the shipping industry. Previous studies have explored the possibility of ship integrated energy systems that use alternative fuels for emission reduction in a cost-efficient manner. However, the various navigation loads and strict space limitations of ships are usually overlooked when designing the ships' energy systems. To fill this gap, a two-stage optimization model is proposed for designing ship integrated energy systems that incorporate alternative fuels, which incorporates internal combustion engines, fuel cells, energy storage technologies, and other relevant equipment. The model captures the ship's volume and weight limitations for alternative fuel applications, and a large cruise ship sailing in Oceania and the Caribbean is selected as a case study. The application feasibilities of four mainstream alternative fuels, i.e., hydrogen, ammonia, methanol, and natural gas, have been compared with the conventional diesel power system considering the impact of future trends of fuel cost and emission-related policies. The results indicate that more than 60% of greenhouse gas emissions can be reduced by replacing conventional fossil fuels with alternative fuels. Meanwhile, alternative fuel applications are economically competitive when compared to conventional diesel power systems, considering the growing technology readiness level of fuel production and fuel cells. Overall, this study is expected to provide guidance for the utilization of alternative fuels for ships and to identify the optimal ship integrated energy systems solutions.

A feasibility study of the reflection readout method of Resistive-Plate Chambers

The conventional readout method of Resistive-Plate Chambers uses two sets of orthogonal readout strips placed at both sides of the detector to collect signals of opposite polarities, which can be processed to reconstruct the hit position of incident muons. A new readout method utilising the reflected signal is proposed with only one set of readout strips. This reflection readout method exploits the difference in the arrival time of the original and the reflected signal to determine the hit position. Customised transmission cables are used to extend the propagation distance of the reflected signal to ensure sufficient time separation of the two signals. Compared to the conventional readout method, this reflection readout method can increase the geometrical acceptance of the detector and reduce the number of readout channels, which is particularly appealing for experimental applications with strict space limit. A preliminary feasibility study of this new method has been conducted. Experimental setup and test results are shown in this paper, and it is demonstrated that a spatial resolution of sub-centimetre can be achieved.

Perfect Preparation.

Perfect Preparation.

A Review of Origami-Based Deployable Structures in Aerospace Engineering

Origami is a traditional art form of paper folding that originated in east Asia. In recent decades, the concept of origami has been extensively used to design deployable structures. Due to the strict space and load capacity limitations of the aircraft and spacecraft, the equipment they carried must be deployable and light in weight. The origami-based deployable structures provide the possibility for carrying more aerospace equipment. This paper is an overview of current research on origami-based deployable structures and applications in aerospace engineering, which mainly demonstrates the geometric properties, engineering implementations, advantages, and applications of origami-based deployable structures in aerospace engineering. Some of the latest origami-based space instruments are reviewed to have an insight into their basics and applications.

3-D Printed All-Dielectric GRIN Lens Antenna With an Integrated Feeder

In this paper we present the design, fabrication, and experimental verification of a new type of Graded-index (GRIN) lens antenna with an integrated feeder. The continuously varying refractive index distribution is chosen appropriately to offer the rays collimation at the lens aperture. It is practically implemented by varying the material density in a host medium, thus realizing a new type of all-dielectric high gain antenna, entirely using 3D printing. This solution can find application to high gain wireless communication and measurement systems. This GRIN lens antenna is printed in one monolithic process and does not require the feeder to be placed at a focal distance, thus complying with more strict space requirements. It accepts interchangeable feeds that can cover a wide frequency range. The directivity and gain are evaluated using near-field measurements in the Ku-band. A 40% measured aperture efficiency is achieved at 14GHz. The challenges and performance limitations that come with 3D printing, as compared to the design of idealized continuous distribution GRIN lenses are discussed.

An ANN-based generic energy model of cleanroom air-conditioning systems for high-tech fabrication location and technology assessments

The air-conditioning systems for high-tech clean fabrications are usually energy-intensive as they require strict space temperature, humidity and cleanliness controls simultaneously. Given that their energy performance is significantly affected by climate conditions and application scenarios concerning production technologies used, simple, reliable and widely-applicable energy models for effective fabrication location and technology assessments are of great value for decision-makers. However, no such model can be found in previous studies. In this paper, an ANN-based generic energy model for full climates and full application scenarios is proposed for location and technology assessments of high-tech cleanrooms at planning stage. The model is developed based on energy data of a typical cleanroom under all climates in China and all application scenarios by detailed simulations. The correlation of model parameters with climates and application scenarios is identified using a regression method and an ANN method. The model is validated in 22 worldwide cities under 420 application scenarios, showing satisfactory accuracy. A comprehensive energy assessment study on high-tech cleanrooms in 31 major Chinese cities is conducted under typical scenarios, providing clear overall energy use pictures of locating clean fabs. Results show that proper location selection could provide potential energy savings of 30% for large-scale clean fabs.

Hydrodynamic helicity polarization in relativistic heavy ion collisions

We study helicity polarization through the $(3+1)$-dimensional relativistic viscous hydrodynamic models at $\sqrt{{s}_{NN}}=200$ GeV $\text{Au}+\text{Au}$ collisions. Similar to the local spin polarization, we consider the helicity polarization beyond global equilibrium and investigate the contributions induced by thermal vorticity, shear viscous tensor, and the fluid acceleration. We find that the local helicity polarization induced by thermal vorticity dominates over other contributions. It also implies that, in low-energy collisions, the fluid vorticity as part of thermal vorticity may play the crucial role in the total helicity polarization. Such a finding could be useful for probing the local strength of vorticity in rotational quark gluon plasmas by measuring helicity polarization. Our simulation confirms the strict space reversal symmetry, whereas we also compare our numerical results with approximated relations derived from ideal Bjorken flow. Our studies also provide a baseline for the future investigation on local parity violation through the correlations of helicity polarization.

A Novel Trusted Software Base for Commercial Android Devices Using Secure TF Card

With the help of edge computing, the Internet of Things (IoT) provides users with efficient data transmission and processing capabilities. As a main control device of the IoT and the communication portal of edge computing, user terminals represented by Android devices have potential security risks in IoT. Trusted computing is a universal method to construct trusted environment for computing platforms. However, due to the strict space, cost, and power limitations, commercial Android devices would not be applicable to implement a dedicated onboard chip or the software Trusted Platform Module (TPM) by modifying its firmware. We have designed a practical Trusted Software Base (TSB) for mobile devices to enhance their security. By using the secure TF card as the hardware to provide secure storage and cryptographic capabilities, we implement the trusted boot and trust extension for applications on a commercial device to verify the feasibility of the TSB to ensure a trusted environment for users. Our implementation does not require any modification to the firmware or any additional hardware other than the secure TF card. Experimental evaluation shows that our method can provide trusted computing capability for commercial Android devices with low performance overheads.

Fine-grained parallelism framework with predictable work-stealing for real-time multiprocessor systems

Lately, parallel task models have received much attention in the development of real-time multiprocessor systems, as they allow highly compute-intensive tasks to have shorter deadlines which is very much required in modern reactive systems. However, missing modularity and portability can make parallel programming a cumbersome endeavor. As a consequence, compute-intensive sectors in the desktop and server segment have relied on parallelism frameworks such as Intel Threading Building Blocks, Cilk and OpenMP. These parallelism frameworks, however, are optimized for decent average case performance and consequently, do not meet the strict requirements imposed by real-time systems.In this paper, we present a proof-of-concept parallelism framework which was implemented in particular for soft real-time systems and having tight timing and safety requirements of such critical systems in mind. The proposed runtime system implements static memory allocation in a work-stealing environment that conforms to the strict space and tight probabilistic time bounds of work-stealing schedulers. Furthermore, we evaluate the performance of this framework by conducting multiprogrammed benchmarks on a real-time embedded multicore architecture.

Structural basis for DNA targeting by the Tn7 transposon.

Tn7 transposable elements are unique for their highly specific, and sometimes programmable, target-site selection mechanisms and precise insertions. All the elements in the Tn7 family utilize an AAA+ adaptor (TnsC) to coordinate target-site selection with transpososome assembly and to prevent insertions at sites already containing a Tn7 element. Owing to its multiple functions, TnsC is considered the linchpin in the Tn7 element. Here we present the high-resolution cryo-EM structure of TnsC bound to DNA using a gain-of-function variant of the protein and a DNA substrate that together recapitulate the recruitment to a specific DNA target site. TnsC forms an asymmetric ring on target DNA that segregates target-site selection and interaction with the paired-end complex to opposite faces of the ring. Unlike most AAA+ ATPases, TnsC uses a DNA distortion to find the target site but does not remodel DNA to activate transposition. By recognizing pre-distorted substrates, TnsC creates a built-in regulatory mechanism where ATP hydrolysis abolishes ring formation proximal to an existing element. This work unveils how Tn7 and Tn7-like elements determine the strict spacing between the target and integration sites.

Ultra-compact post-compressor on-shot wavefront measurement for beam correction at PHELIX

Abstract In order to reach the highest intensities, modern laser systems use adaptive optics to control their beam quality. Ideally, the focal spot is optimized after the compression stage of the system in order to avoid spatio-temporal couplings. This also requires a wavefront sensor after the compressor, which should be able to measure the wavefront on-shot. At PHELIX, we have developed an ultra-compact post-compressor beam diagnostic due to strict space constraints, measuring the wavefront over the full aperture of 28 cm. This system features all-reflective imaging beam transport and a high dynamic range in order to measure the wavefront in alignment mode as well as on shot.

Murine models of Duchenne muscular dystrophy: is there a best model?

Murine models of Duchenne muscular dystrophy: is there a best model?

A novel approach for the efficient modeling of material dissolution in electrochemical machining

This work presents a novel approach to efficiently model anodic dissolution in electrochemical machining. Earlier modeling approaches employ a strict space discretization of the anodic surface that is associated with a remeshing procedure at every time step. Besides that, the presented model is formulated by means of effective material parameters. Thereby, it allows to use a constant mesh for the entire simulation and, thus, decreases the computational costs. Based on Faraday’s law of electrolysis, an effective dissolution level is introduced, which describes the ratio of a dissolved volume and its corresponding reference volume. This inner variable allows the modeling of the complex dissolution process without the necessity of computationally expensive remeshing by controlling the effective material parameters. Additionally, full coupling of the thermoelectric problem is considered and its linearization and numerical implementation are presented. The model shows good agreement with analytical and experimental validation examples by yielding realistic results. Furthermore, simulations of a pulsed electrochemical machining process yield a process signature component of the surface roughness related to the specific accumulated electric charge. The numerical examples confirm the simulation’s computational efficiency and accurate modeling qualities.

DC-link current based position estimation and speed sensorless control of a BLDC motor used for electric vehicle applications

Abstract Sensors of any kind contribute to extra space and electronics when they are used in any application. Besides, the sensor noise also has the effect of altering the overall gain of the system. This is more prevalent in non-linear systems like motor control. In applications which have strict space constraints like Electric vehicles, the use of sensors must be optimized, which, in turn, gave rise to many sensorless state estimation strategies. This paper proposes a novel sensorless control technique for brushless direct current (BLDC) motor used in electric vehicle applications. The concept of sensorless control in BLDC Motor drive eliminates the hall-effect position sensor, thereby giving better performance and improves the robustness of the overall drive system. The main objective of this work is to estimate the position of the motor at standstill condition using stator saturation effect concerning the rotor, accelerate the motor from standstill so that enough back EMF is generated. This acceleration technique speeds up the motor to a stage where a self-actuating control mechanism is used to generate control signals with back EMF or line voltages. The motor can be started with a load, which is a significant constraint for electric vehicle application. The proposed method will avoid the reverse rotation of the motor. The proposed work is simulated in Matlab/Simulink software, and results obtained show that it works well under dynamic conditions of starting, acceleration and load switching. The hardware setup of the proposed work is developed using the TMS320F2812 DSP processor. Simulation and experimental results validate the effectiveness of the proposed work for electric vehicle application.

A two-site flexible clamp mechanism for RET-GDNF-GFRα1 assembly reveals both conformational adaptation and strict geometric spacing

SummaryRET receptor tyrosine kinase plays vital developmental and neuroprotective roles in metazoans. GDNF family ligands (GFLs) when bound to cognate GFRα co-receptors recognize and activate RET stimulating its cytoplasmic kinase function. The principles for RET ligand-co-receptor recognition are incompletely understood. Here, we report a crystal structure of the cadherin-like module (CLD1-4) from zebrafish RET revealing interdomain flexibility between CLD2 and CLD3. Comparison with a cryo-electron microscopy structure of a ligand-engaged zebrafish RETECD-GDNF-GFRα1a complex indicates conformational changes within a clade-specific CLD3 loop adjacent to the co-receptor. Our observations indicate that RET is a molecular clamp with a flexible calcium-dependent arm that adapts to different GFRα co-receptors, while its rigid arm recognizes a GFL dimer to align both membrane-proximal cysteine-rich domains. We also visualize linear arrays of RETECD-GDNF-GFRα1a suggesting that a conserved contact stabilizes higher-order species. Our study reveals that ligand-co-receptor recognition by RET involves both receptor plasticity and strict spacing of receptor dimers by GFL ligands.

Modelling Mass Crowd Using Discrete Event Simulation: A Case Study of Integrated Tawaf and Sayee Rituals During Hajj

Hajj is a mass gathering event that takes place annually in Makkah, Saudi Arabia. Typically, around three million people participate in the event and perform rituals that involve their movements within strict space and time restrictions. Despite efforts by the Hajj organisers, such massive crowd gathering and movement cause overcrowding related problems at the Hajj sites. Several previous simulation studies on Hajj focused on the rituals individually. Tawaf, followed by Sayee, are two important rituals that are performed by all the pilgrims at the same venue on the same day. These events have a strong potential for crowd buildup and related problems. As opposed the previous works in the literature, in this paper we study these two events jointly, rather than separately. We use ExtendSim, a Discrete Event Simulation tool, to integrate the Tawaf and Sayee rituals into one model. The validated model was applied to a wide range of scenarios where different percentages of pilgrims were allocated to the various Tawaf and Sayee areas. The effect of such allocations on the time to complete Tawaf and Sayee indicate strategies for managing these two key Hajj rituals.

A AVALIAÇÃO DOS FATORES DETERMINANTES PARA O AUMENTO DA PRODUTIVIDADE EM UMA EMPRESA PRODUTORA DE DENDÊ

Com o crescimento da população mundial, tem-se buscado cada vez mais o aumento da produtividade no setor agrícola, que cada vez mais necessita de técnicas, ferramentas e mão de obra qualificada para se chegar no nível de produção satisfatório. O presente artigo tem como objetivo analisar os fatores que podem contribuir para a elevação da produtividade em uma empresa produtora de Dendê. Caracterizado como uma pesquisa exploratória descritiva, onde a coleta de dados se deu com a aplicação de um questionário fechado, os principais resultados demonstram que a empresa investigada necessita investir em capacitação de seus supervisores e na qualidade de vida dos seus funcionários de modo que haja o cumprimento das atividades e que as mesmas sejam executadas através do melhor método, que possibilite a redução dos custos de produção. Ressalta-se ainda que baseado nos dados analisados, fazse necessário investir constantemente na melhoria de seu maquinário, com o objetivo de se manter competitiva perante o mercado. No que tange ao cultivo da Palma de Óleo, a empresa aplica padrões rígidos de adubação e espaçamento entre as mudas, além de estar geograficamente localizada em uma região com clima favorável ao cultivo

SYMMETRIC MONOIDALG-CATEGORIES AND THEIR STRICTIFICATION

AbstractWe give an operadic definition of a genuine symmetric monoidal $G$-category, and we prove that its classifying space is a genuine $E_\infty $$G$-space. We do this by developing some very general categorical coherence theory. We combine results of Corner and Gurski, Power and Lack to develop a strictification theory for pseudoalgebras over operads and monads. It specializes to strictify genuine symmetric monoidal $G$-categories to genuine permutative $G$-categories. All of our work takes place in a general internal categorical framework that has many quite different specializations. When $G$ is a finite group, the theory here combines with previous work to generalize equivariant infinite loop space theory from strict space level input to considerably more general category level input. It takes genuine symmetric monoidal $G$-categories as input to an equivariant infinite loop space machine that gives genuine $\Omega $-$G$-spectra as output.

Silanization of heat-treated halloysite nanotubes using γ-aminopropyltriethoxysilane

By X-ray diffraction, thermal analysis, diffuse reflectance infrared spectrometry, solid state nuclear magnetic resonance (1H and 29Si), and transmission/high-resolution transmission electron microscopy, silanization of heat-treated halloysite samples (300–1200 °C calcination) using γ-aminopropyltriethoxysilane through condensation reaction was investigated. Driven by calcining at higher temperatures, the crystalline structure of halloysite transformed to metahalloysite (500–900 °C), mixed phases of γ-alumina, silica, and primary mullite (~1000 °C, accompanied by an exothermic reaction), and secondary mullite (1200 °C), sequentially; while the lower calcination temperature 300 °C failed to change the crystalline structure except for dehydrating surface moisture. In the calcining processes, the tubular morphology of halloysite remained largely unchanged in the range 300–900 °C with additional surface mottling at temperatures ≥600 °C, but got damaged at higher temperatures ≥1000 °C. For the still tubular-shaped calcined samples, the hydroxyl distribution of the 300 °C-calcined sample was similar to that of raw halloysite; while for other samples from 600 to 900 °C calcination, the inner-surface Al-OH groups gradually decreased until completely diminished, and the external surface Si-OH groups reached maximum at 700 °C with decreasing trends as the temperature deviated from 700 °C. The 700 °C-calcined sample with maximum Si-OH groups acting as reactive sites was thus optimal for silanization, giving the highest silane loading of 5.87 mass %, which would depend on the main modification sites at the tube external surface without strict space limitation, and the unignorable oligomerization reaction of silane species besides their grafting reaction in this case. These results would be very helpful for surface properties optimization of halloysite nanotubes by heat-activation followed by silane modification, and hence for the development of halloysite-based advanced materials.