Small Space Research Articles

Tolerance analysis of slat gear rotary actuator in civil aircraft

Abstract The slat gear rotary actuator of civil aircraft needs to meet the requirements of small space and large transmission ratio. The planetary gear system based on triple teeth is a common actuator design, and the design structure is complex, so its tolerance control is also strict. In order to meet the design requirements of its internal structure, this paper presents a deviation analysis method for the internal structure design of a typical civil aircraft slat gear rotary actuator. The results of preliminary tolerance distribution and improved tolerance distribution are analyzed using the Jacobi-based assembly deviation model. By comparing the standard deviation of the analysis results, the validity of this deviation analysis method is verified, which proves that this method can be used to analyze the internal structure deviation of the rotary actuator of slat gear in civil aircraft.

A triangle decomposition method for the mobility control of mecanum wheel-based robots

Mobile robots are used in a variety of applications including research, education, healthcare, customer service, security and so on. Based upon the application, the robots employ different locomotion systems for their mobility. When it comes to rolling locomotion, the wheels used to provide mobility to robots can be categorized as: tracks, omnidirectional wheels, and unidirectional wheels with a steering system. The ability of omnidirectional wheels to drive machines in small spaces makes them interesting to use. Among the types of omnidirectional wheels, mecanum wheels are widely used due to their inherent benefits. With the right control strategy, robots equipped with mecanum wheels can move freely, in all possible directions. In this study, a triangle decomposition approach is employed for controlling omnidirectional mecanum wheel-based robots. The method consists of breaking down any path into a set of linear motions that can be horizontal, vertical, or oblique. Furthermore, the oblique paths are divided into smaller segments that can be resolved into a horizontal and vertical component in a right-angle triangle. The suggested control method is tested and proved on a simple scenario using Webots simulation software.

Feasibility of using CubeSats and small detectors for in-situ space debris and cosmic dust flux measurement

Impacts on spacecraft by mm-sized debris in Earth orbit can have severe consequences including loss of a spacecraft and generation of more debris. This hazard and potential mitigation are discussed herein, and the risk of an impact (the product of flux and damage) is found vs. size. Reduction of the future flux of mm-sized debris by de-orbiting life-expired space vehicles, only reduces, not eliminates, this hazard. It is thus vital that the flux of mm-sized objects in orbit is well defined, but this requires on-orbit determination. To provide statistically meaningful debris flux data, large detection areas are traditionally required. CubeSats could host debris detectors, but only have small surface areas, and the data from many would be required. Accordingly, flux data from historic small space exposed surfaces are compared herein to MASTER flux model predictions, with good agreement for exposure times of just a few years, demonstrating a viable method to determine the debris flux. The cost of a network of CubeSat mounted impact detectors is also estimated found, and, for fleets of order 100 CubeSats, is comparable to the traditional single large satellite mounted instrument.

A study on factors influencing the spatial oppressiveness in small courtyard spaces within university residential areas

ABSTRACT A number of obstacles in terms of the growing demand for residential spaces for students in China's education industry. Changing urban development patterns often lead to densely populated, unpleasant university residential neighborhood, posing threats to the well-being of university personnel. This study addresses the limitations of past research, focusing on a real campus's enclosed high-rise student apartment courtyard. Using three key design variables (courtyard area, building height and ground-level interface transparency), 27 sample scenarios were developed for psychological experiments. The findings indicate that while visual scene complexity has minimal impact on oppression to confined environments, building exposure and sky visibility do. People's perception of openness is determined by building exposure, sky visibility, and visual complexity. Higher visual complexity and greater sky visibility enhance the sense of openness. Satisfaction is primarily influenced by sky visibility. The study also conducts a multiple linear regression of spatial and psychological indicators and discusses the tolerance threshold for spatial oppressiveness and the spatial oppressiveness under various spatial types of samples.

SIMPLE: Efficient Temporal Graph Neural Network Training at Scale with Dynamic Data Placement

Dynamic graphs are essential in real-world scenarios like social media and e-commerce for tasks such as predicting links and classifying nodes. Temporal Graph Neural Networks (T-GNNs) stand out as a prime solution for managing dynamic graphs, employing temporal message passing to compute node embeddings at specific timestamps. Nonetheless, the high CPU-GPU data loading overhead has become the bottleneck for efficient training of T-GNNs over large-scale dynamic graphs. In this work, we present SIMPLE, a versatile system designed to address the major efficiency bottleneck in training existing T-GNNs on a large scale. It incorporates a dynamic data placement mechanism, which maintains a small buffer space in available GPU memory and dynamically manages its content during T-GNN training. SIMPLE is also empowered by systematic optimizations towards data processing flow. We compare SIMPLE to the state-of-the-art generic T-GNN training system TGL on four large-scale dynamic graphs with different underlying T-GNN models. Extensive experimental results show that SIMPLE effectively cuts down 80.5% ~ 96.8% data loading cost, and accelerates T-GNN training by 1.8× ~ 3.8× (2.6× on average) compared to TGL.

A Reliability Assessment Method for Complex Systems Based on Non-Homogeneous Markov Processes.

The Markov method is a common reliability assessment method. It is often used to describe the dynamic characteristics of a system, such as its repairability, fault sequence and multiple degradation states. However, the "curse of dimensionality", which refers to the exponential growth of the system state space with the increase in system complexity, presents a challenge to reliability assessments for complex systems based on the Markov method. In response to this challenge, a novel reliability assessment method for complex systems based on non-homogeneous Markov processes is proposed. This method entails the decomposition of a complex system into multilevel subsystems, each with a relatively small state space, in accordance with the system function. The homogeneous Markov model or the non-homogeneous Markov model is established for each subsystem/system from bottom to top. In order to utilize the outcomes of the lower-level subsystem models as inputs to the upper-level subsystem model, an algorithm is proposed for converting the unavailability curve of a subsystem into its corresponding 2×2 dynamic state transition probability matrix (STPM). The STPM is then employed as an input to the upper-level system's non-homogeneous Markov model. A case study is presented using the reliability assessment of the Reactor Protection System (RPS) based on the proposed method, which is then compared with the models based on the other two contrast methods. This comparison verifies the effectiveness and accuracy of the proposed method.

Colour Perception in Camper Van Interior Design Using Virtual Reality Technology

Virtual reality (VR) technology has been developing progressively and rapidly in the past decades. VR technology is used to create 3D models of rooms and spaces, which can be used to create more accurate and detailed designs. Colours used in interior design have the ability to create specific moods, create harmony, and change the perception of how large or small a space may look or feel. The purpose of this study is to explore the application of virtual reality technology in the interior design of a camper van considering the role of colour perception. We aim to determine the effect of colour on the interior design creating professional-looking 3D camper van layout. The results show that any non-professional in 3D design can design a functional and comfortable living space in the camper van using Vanspace 3D software. It was found that light colours and shades create the feeling of space, light, comfort and cosiness. When choosing colours for the interior design of a small limited space, as is the case with a camper van, it is advisable to combine warm earth colours, white and beige colours.

Heat exchange performance of an energy-pile group in a hybrid GSHP system and effects of pile spacing

In long-term operations, seasonal imbalance in the thermal load may adversely affect the heat transfer performance of the energy piles, potentially resulting in thermal accumulation within the ground and eventual system failure. The heat transfer performance of energy pile systems during long-term operation under unbalanced thermal loads must be investigated. Moreover, the design parameters of energy piles are usually constrained by the requirements of foundation structural design, resulting in energy piles being densely arranged. Hence, the influence of pile spacing on the heat exchange performence of energy piles must be comprehensively understood. In this study, two- and three-dimensional energy-pile heat transfer models were established and innovatively coupled based on an engineering project currently under design. Numerical simulations were performed to investigate the heat transfer behavior of energy-pile groups subjected to unbalanced thermal loads and the effect of pile spacing on their heat exchange performance. Furthermore, design recommendations regarding the determination of the proportion of thermal loads to be borne by the energy piles in a hybrid GSHP system were provided. The results indicate that the proposed 2D-3D coupled modeling approach is able to simulate the heat exchange performance of large-scale energy pile groups. Pile spacing considerably affects the long-term thermal performance of energy-pile groups, especially in cases with small pile spacings. The influence of pile spacing on the heat exchange capacity of energy piles can be considered in the design phase by incorporating a group effect coefficient η, which are calculated to be 0.165, 0.470, 0.732, and 1 for pile spacings of 2 m, 4 m, 6 m, and 10 m, respectively.

Pigeonhole Design: Balancing Sequential Experiments from an Online Matching Perspective

Practitioners and academics have long appreciated the benefits of covariate balancing when they conduct randomized experiments. For web-facing firms running online A/B tests, however, it still remains challenging in balancing covariate information when experimental subjects arrive sequentially. In this paper, we study an online experimental design problem, which we refer to as the online blocking problem. In this problem, experimental subjects with heterogeneous covariate information arrive sequentially and must be immediately assigned into either the control or the treated group. The objective is to minimize the total discrepancy, which is defined as the minimum weight perfect matching between the two groups. To solve this problem, we propose a randomized design of experiment, which we refer to as the pigeonhole design. The pigeonhole design first partitions the covariate space into smaller spaces, which we refer to as pigeonholes, and then, when the experimental subjects arrive at each pigeonhole, balances the number of control and treated subjects for each pigeonhole. We analyze the theoretical performance of the pigeonhole design and show its effectiveness by comparing against two well-known benchmark designs: the matched-pair design and the completely randomized design. We identify scenarios when the pigeonhole design demonstrates more benefits over the benchmark design. To conclude, we conduct extensive simulations using Yahoo! data to show a 10.2% reduction in variance if we use the pigeonhole design to estimate the average treatment effect. This paper was accepted by George Shanthikumar, data science. Supplemental Material: The online appendix and data files are available at https://doi.org/10.1287/mnsc.2023.02184 .

Enhancing Urban Development Control Through the Warsaw Natural System: A Case Study in Warsaw, Poland

This study delves into the Warsaw Natural System (WNS) in Warsaw, Poland, and its efficacy in regulating urban development within the city. The paper is divided into three main sections, each addressing a distinct aspect of urban development control. Firstly, the paper examines how WNS effectively manages outward urban expansion through the strategic use of wedge-shaped green spaces. Empirical evidence demonstrates the WNS's success in curbing urban sprawl and maintaining a balanced spatial layout. Secondly, the study investigates how the WNS controls inward urban over-development by employing small urban green spaces interconnected throughout the city. The analysis highlights the effectiveness of this approach in creating fragmented urban development, and preventing excessive density. Thirdly, the paper explores how the WNS contributes to the resilience of urban development by enhancing functional diversity within urban green spaces, and how this diversity enriches the lives of urban residents and sustains the WNS's spatial pattern, offering long-term control over urban space development. In addition to its strengths, the study also identifies existing shortcomings within the WNS and proposes recommendations for future improvement, aiming to enhance its effectiveness in controlling urban development. This research provides valuable insights into sustainable urban planning practices and underscores the importance of adaptable green infrastructure in shaping cities for the future.

A 3D in vitro model for assessing the influence of intraocular lens: Posterior lens capsule interactions on lens epithelial cell responses

Posterior Capsule Opacification (PCO), the most frequent complication of cataract surgery, is caused by the infiltration and proliferation of lens epithelial cells (LECs) at the interface between the intraocular lens (IOL) and posterior lens capsule (PLC). According to the “no space, no cells, no PCO” theory, high affinity (or adhesion force) between the IOL and PLC would decrease the IOL: PLC interface space, hinder LEC migration, and thus reduce PCO formation. To test this hypothesis, an in vitro hemisphere-shaped simulated PLC (sPLC) was made to mimic the human IOL: PLC physical interactions and to assess their influence on LEC responses. Three commercially available IOLs with different affinities/adhesion forces toward the sPLC, including Acrylic foldable IOL, Silicone IOL, and PMMA IOL, were used in this investigation. Using the system, the physical interactions between IOLs and sPLC were quantified by measuring the adhesion force and interface space using an adhesion force apparatus and Optical Coherence Tomography, respectively. Our data shows that high adhesion force and tight binding between IOL and sPLC contribute to a small interface space (or “no space”). By introducing LECs into the in vitro system, we found that, with small interface space, among all IOLs, acrylic foldable IOLs permitted the least extent of LEC infiltration, proliferation, and differentiation (or “no cells”). Further statistical analyses using clinical data revealed that weak LEC responses are associated with low clinical PCO incidence rates (or “no PCO”). The findings support that the in vitro system could simulate IOL: PLC interplays and predict IOLs’ PCO potential in support of the “no space, no cells, no PCO” hypothesis.

Low-Order Modeling of Stacked Rotor Performance in Hover

Coaxial, corotating (stacked) rotors have shown improved performance compared to conventional rotors, but the optimum configuration is highly sensitive to the rotor parameters. This paper reports the development of a low-order model, blade interaction prediction (BLIP), to efficiently predict the thrust and power of closely spaced rotor blades and quantify the effects of rotor geometry on total and individual stacked rotor performance. BLIP couples a vortex panel method and blade element momentum theory to combine the effects of bound circulation and rotor inflow. A cascade effect in the two-dimensional vortex panel method was implemented to incorporate the effect of airfoils rotating in a circle. Validation was performed with measurements of a 1.108-m-radius fixed-pitch stacked rotor with variable axial and azimuthal spacing, and excellent correlation was observed. It was found that small azimuthal angles and axial spacings are most effective in varying total thrust. The variation of thrust and power with azimuthal spacing was found to be a result of bound circulation, while the variation with axial spacing is due to rotor inflow interactions.

Upper gastrointestinal endoscopic submucosal dissection using an ultrathin endoscope: a retrospective, single-center evaluation.

Recent studies have reported the therapeutic use of endoscopic submucosal dissection (ESD) using an ultrathin endoscope for targeting pharyngeal and distal side lesions in the stenosis or as a less invasive treatment via the nasal route. However, the effectiveness and safety of these treatments remain undetermined. Therefore, this study aimed to review treatment outcomes and discuss the advantages and precautions of the treatments based on our experience. This study included 13 patients with 14 lesions who underwent 14 sessions of upper gastrointestinal ESD using an ultrathin endoscope between December 2021 and August 2023. The outcome measures included lesion background, en bloc resection rate, en bloc complete resection rates, and incidence of adverse events (including post-operative bleeding, intraoperative perforation, and delayed perforation). The lesions in the esophagus, stomach, and duodenum were eight, three, and three, respectively, and the median length (range) of each located lesion was 16.5 (6-26), 17 (9-36), and 10 (4-16) mm, respectively. En bloc resection and en bloc complete resection rates were 100 and 92.9%, respectively. The only adverse event was an intraoperative perforation observed during duodenal ESD, resulting from the assistant's inadvertent expansion of the SOUTEN at the final dissection stage. Our results demonstrate that ESD with an ultrathin endoscope effectively reaches lesions in difficult locations and enables treatment within a small working space. Therefore, ESD using an ultrathin endoscope is a treatment option for lesions located distally to gastrointestinal stenosis, highly fibrotic lesions, and duodenal tumors.

Differences between Stable and Unstable Architectures of Compact Planetary Systems

We present a stability analysis of a large set of simulated planetary systems of three or more planets based on architectures of multiplanet systems discovered by Kepler and K2. We propagated 21,400 simulated planetary systems up to 5 billion orbits of the innermost planet; approximately 13% of these simulations ended in a planet–planet collision within that time span. We examined trends in dynamical stability based on dynamical spacings, orbital period ratios, and mass ratios of nearest-neighbor planets as well as the system-wide planet mass distribution and the spectral fraction describing the system’s short-term evolution. We find that instability is more likely in planetary systems with adjacent planet pairs that have period ratios less than 2 and in systems of greater variance of planet masses. Systems with planet pairs at very small dynamical spacings (less than ∼10–12 mutual Hill radii) are also prone to instabilities, but instabilities also occur at much larger planetary separations. We find that a large spectral fraction (calculated from short integrations) is a reasonable predictor of longer-term dynamical instability; systems that have a large number of Fourier components in their eccentricity vectors are prone to secular chaos and subsequent eccentricity growth and instabilities.

The Boundedness of Generalized Fractional Integral Operators on Small Morrey Spaces

The small Morrey space is the set of locally Lebesgue integrable functions with norm defined supremum over radius of ball . This paper aims to prove the boundedness properties of the generality of fractional integral operators in small Morrey spaces using Hedberg-type inequality. The first, in this paper will be discuss to prove Hedberg-type inequality on small Morrey spaces using dyadic decomposition, H lder inequality, and doubling condition. Furthermore, by using the inequality, it can be proven that the boundedness of generalized fractional integral operators on small Morrey spaces.

Is a direct numerical simulation (DNS) of Navier-Stokes equations with small enough grid spacing and time-step definitely reliable/correct?

Turbulence is strongly associated with the vast majority of fluid flows in nature and industry. Traditionally, results given by the direct numerical simulation (DNS) of Navier-Stokes (NS) equations that relate to a famous millennium problem are widely regarded as ‘reliable’ benchmark solutions of turbulence, as long as grid spacing is fine enough (i.e. less than the minimum Kolmogorov scale) and time-step is small enough, say, satisfying the Courant-Friedrichs-Lewy condition (Courant number < 1). Is this really true? In this paper a two-dimensional sustained turbulent Kolmogorov flow driven by an external body force governed by the NS equations under an initial condition with a spatial symmetry is investigated numerically by the two numerical methods with detailed comparisons: one is the traditional DNS, the other is the ‘clean numerical simulation’ (CNS). In theory, the exact solution must have a kind of spatial symmetry since its initial condition is spatially symmetric. However, it is found that numerical noises of the DNS are quickly enlarged to the same level as the ‘true’ physical solution, which finally destroy the spatial symmetry of the flow field. In other words, the DNS results of the turbulent Kolmogorov flow governed by the NS equations are badly polluted mostly. On the contrary, the numerical noise of the CNS is much smaller than the ‘true’ physical solution of turbulence in a long enough interval of time so that the CNS result is very close to the ‘true’ physical solution and thus can remain symmetric, which can be used as a benchmark solution for comparison. Besides, it is found that numerical noise as a kind of artificial tiny disturbances can lead to huge deviations at large scale on the two-dimensional Kolmogorov turbulence governed by the NS equations, not only quantitatively (even in statistics) but also qualitatively (such as spatial symmetry of flow). This highly suggests that fine enough spatial grid spacing with small enough time-step alone could not guarantee the validity of the DNS of the NS equations: it is only a necessary condition but not sufficient. All of these findings might challenge some of our general beliefs in turbulence: for example, it might be wrong in physics to neglect the influences of small disturbances to NS equations. Our results suggest that, from physical point of view, it should be better to use the Landau-Lifshitz-Navier-Stokes (LLNS) equations, which consider the influence of unavoidable thermal fluctuations, instead of the NS equations, to model turbulent flows.

Solar Photo Voltaic Connected Quasi Z Source Inverter for Grid and utility Application

This paper discusses the use of quasi-Z-source inverters, in utility grid systems. These inverters enhanced dependability and one-stage buck and boost abilities make them appropriate for photovoltaic power conditioning applications. The small signal sate space method utilized for the proposed system using Quasi ZSI for utility and grid integration application. Shoot through state also implemented on dc side to enhanced the voltage gain. The Controlling of dc side and ac side also implemented in MATLAB using state space transfer function. A two-stage controlling technique implemented on two level 6 switch inverters with SPWM with P &amp; O MPPT and PI controller. The proposed system has solar PV array rating of 5.5kW and utilized in distribution purpose. A simple boost controlling technique has been implemented to obtained the desired gain and less ripples are present in the current due to the presence of inductor in the QZSI impedance network. During light loading the surplus power injected to the grid with the help of PLL system and when load demand increases the power take from the grid smoothly without loss of synchronism. The system has better stability and fast dynamic response during transient. The THD has been observed at the inverter and load side with LC filter, THD within the permissible limit as per IEEE std 1547.

Impact of Flexible Furniture on Small Spaces in Residential Apartment with Smart Solutions

Impact of Flexible Furniture on Small Spaces in Residential Apartment with Smart Solutions

Real‐time topology optimization via learnable mappings

AbstractIn traditional topology optimization, the computing time required to iteratively update the material distribution within a design domain strongly depends on the complexity or size of the problem, limiting its application in real engineering contexts. This work proposes a multi‐stage machine learning strategy that aims to predict an optimal topology and the related stress fields of interest, either in 2D or 3D, without resorting to any iterative analysis and design process. The overall topology optimization is treated as regression task in a low‐dimensional latent space, that encodes the variability of the target designs. First, a fully‐connected model is employed to surrogate the functional link between the parametric input space characterizing the design problem and the latent space representation of the corresponding optimal topology. The decoder branch of an autoencoder is then exploited to reconstruct the desired optimal topology from its latent representation. The deep learning models are trained on a dataset generated through a standard method of topology optimization implementing the solid isotropic material with penalization, for varying boundary and loading conditions. The underlying hypothesis behind the proposed strategy is that optimal topologies share enough common patterns to be compressed into small latent space representations without significant information loss. Results relevant to a 2D Messerschmitt‐Bölkow‐Blohm beam and a 3D bridge case demonstrate the capabilities of the proposed framework to provide accurate optimal topology predictions in a fraction of a second.

Proliferating inverted follicular keratosis of genital skin: Case series of a challenging variant.

Inverted follicular keratosis (IFK) is a benign cutaneous epithelial tumor typically presenting as a small papule on the head and neck. We have encountered deep endophytic tumors on genital skin with some characteristics of IFK but also atypical features, raising concern for squamous cell carcinoma (SCC). Four such tumors were identified in our database. Histopathologic analysis and ancillary studies were performed. All patients were young women who presented with a solitary 0.5-1.0 cm lesion on the vulva, perineum, or inner buttock. Each showed a squamous proliferation arising from the epidermis, with endophytic growth that was deep and bulbous but not infiltrative. The tumor lobules contained eosinophilic keratinocytes, forming numerous squamous eddies. Small irregular spaces and dyskeratotic cells were frequently found. Nuclear pleomorphism was minimal to absent. All demonstrated wild-type p53 expression and lack of p16 block positivity. In situ hybridizations for human papillomavirus were negative. None of the three cases with follow-up data showed evidence of recurrence. The absence of infiltrative growth or significant pleomorphism, the presence of numerous squamous eddies, the reassuring immunoprofile, and the lack of evidence of recurrence support a variant of IFK and speak against SCC. We propose the term "proliferating IFK" to highlight the florid squamous proliferation. Recognition of this unusual variant would avoid overdiagnosis of SCC.