Dynamics simulation study on civil aircraft planned pavement emergency landing

Engine pylon is one of the most important components of large civil aircraft, playing an essential role in structure connecting and load bearing. It is chosen as the research target, and a full sized engine-pylon-wing finite element model is established. By conducting the simulations of different landing and impacting conditions, dynamical responses and separation status of the pylon are obtained. Some main factors that affect the pylon’s separation are found out on the basis of preliminary analysis. The reasonable pylon separations for belly landing with small pitch angles and dead-stick landing are achieved. At last, further measures to improve the modeling method and achieve better pylon separations are discussed based on a comparative analysis of all the simulation results. The proposed dynamical modeling method along with the emergency landing parameters and simulation results can provide certain reference to similar studies, pylon structure designs and validation tests

SERVICE CATEGORY SYSTEM IN LOW-POWER AND LOSSY NETWORKS

Presented herein are novel techniques to resolve cache capacity issues in Low-Power and Lossy Networks (LLNs) by utilizing border router edge computing. Following deployment of a network, such as an information-centric networking (ICN) network, a border router will generate a bitmap for all support services through negotiations with a cloud service (CS) and low-power devices. The border router will then cache data that satisfies specific service criteria for low-power devices that have registered for such data. The border router will further publish the service bitmap to a sleep proxy. A given low-power device can periodically examine the service bitmap via beacons to determine whether there may be any service(s) in which it is interested and, if so, respond to the border router

Aeroacoustic testing of the landing gear components

The sound field generated by full scale landing gear components was studied in an acoustic wind tunnel. Noise characteristics were evaluated. The noise contribution of each part was investigated by removing the gear part individually. Three design parameters were also obtained to assess the noise reduction potential. Test results indicate that the noise spectrum of the component is essentially broadband and mainly dominated by some peaks corresponding to the constant St. Sound pressure level scales with the sixth power velocity law. Noise radiation from the components has obvious directivities. The main strut is the least contributor while the bogie is the largest contributor to the total noise. It is also found that the noise level increases with the gear installation angle from 0° to 16.5° while it decreases via changing the torque link layout from the front of the main strut to its back or modifying the bogie shape by filling its holes

Split Unlearning

Split learning is emerging as a powerful approach to decentralized machine learning, but the urgent task of unlearning to address privacy issues presents significant challenges. Conventional methods of retraining from scratch or gradient ascending require all clients' involvement, incurring high computational and communication overhead, particularly in public networks where clients lack resources and may be reluctant to participate in unlearning processes they have no interest. In this short article, we propose \textsc{SplitWiper}, a new framework that integrates the concept of SISA to reduce retraining costs and ensures no interference between the unlearning client and others in public networks. Recognizing the inherent sharding in split learning, we first establish the SISA-based design of \textsc{SplitWiper}. This forms the premise for conceptualizing two unlearning strategies for label-sharing and non-label-sharing scenarios. This article represents an earlier edition, with extensive experiments being conducted for the forthcoming full version.Comment: An earlier edition, with extensive experiments being conducted for the forthcoming full versio

Dataset Obfuscation: Its Applications to and Impacts on Edge Machine Learning

Obfuscating a dataset by adding random noises to protect the privacy of sensitive samples in the training dataset is crucial to prevent data leakage to untrusted parties for edge applications. We conduct comprehensive experiments to investigate how the dataset obfuscation can affect the resultant model weights - in terms of the model accuracy, Frobenius-norm (F-norm)-based model distance, and level of data privacy - and discuss the potential applications with the proposed Privacy, Utility, and Distinguishability (PUD)-triangle diagram to visualize the requirement preferences. Our experiments are based on the popular MNIST and CIFAR-10 datasets under both independent and identically distributed (IID) and non-IID settings. Significant results include a trade-off between the model accuracy and privacy level and a trade-off between the model difference and privacy level. The results indicate broad application prospects for training outsourcing in edge computing and guarding against attacks in Federated Learning among edge devices.Comment: 6 page

Reconfigurable Intelligent Surface Based Orbital Angular Momentum: Architecture, Opportunities, and Challenges

Orbital angular momentum (OAM) has gained a lot of attention due to its potential in enhancing the spectral efficiency for wireless communications. Using different OAM modes, multiple independent data streams are simultaneously transmitted by using spatial distribution of helical phase, which enables OAM as a new form of multiple access technique for wireless communications. Controlling the phases of incoming electromagnetic waves, the reconfigurable intelligent surface (RIS) is suitable for implementing OAM. In this article, an RIS-based OAM framework is introduced. The basic concepts and features of RIS and OAM are presented. Then classifications and comparisons of different RIS-based OAM schemes are summarized. Simulation results verify that RIS-based OAM transmission can achieve nearly 100 percent higher spectral efficiency of wireless communication systems compared to the conventional RIS scheme

Pass-by-Pass Ambiguity Resolution in Single GPS Receiver PPP Using Observations for Two Sequential Days: An Exploratory Study

“Pass-by-pass” or “track-to-track” ambiguity resolution removes Global Navigation Satellite System (GNSS) satellite hardware delays between adjacent undifferenced (UD) ambiguities, which is often applied in precise orbit determination (POD) for Low Earth Orbit (LEO) satellites to improve the accuracy of orbits. In this study, we carried out an exploratory study to use the “pass-by-pass” ambiguity resolution by differencing the undifferenced ambiguity candidates for two adjacent passes in sidereal days for a single Global Positioning System (GPS) receiver static Precise Point Positioning (PPP). Using the GPS observations from 132 globally distributed reference stations of International GPS Service (IGS), we find that 99.08% wide-lane (WL) and 97.83% narrow-lane (NL) double-difference ambiguities formed by the “pass-by-pass” method for all stations can be fixed to their nearest integers within absolute fractional residuals of 0.2 cycles. These proportions are higher than the corresponding values of network solution with multiple receivers with 97.39% and 91.20%, respectively. About 97% to 98% of ambiguities can be fixed finally on average. The comparison of the estimated station coordinates with the IGS weekly solutions reveals that the Root Mean Square (RMS) in East and North directions are 2-4 mm and is about 6 mm in the Up direction. For hourly data, it is found that the mean positioning accuracy improvement can achieve to about 10% after ambiguity resolution. From a dam deformation monitoring application, it shows that the fixing rate of WL and NL ambiguity can be closed to 100% and higher than 90%, respectively. The time series generated by PPP are also in agreement with the short baseline solutions

Properties of tungsten mine waste geopolymeric binder

Tungsten mine waste mud (TMWM) geopolymeric binder is a new cementitious material with a very high early age strength. It is obtained from dehydroxylated mine waste powder mix with minor quantities of calcium hydroxide and activated with NaOH and water-glass solutions. Tests on properties of TMWM binders such as workability, setting time, unrestrained shrinkage, water absorption and static modulus of elasticity were carried out and the results are reported in this paper. This is followed by comparisons with literature related data and a discussion about it. The results showed that current devices use to assess OPC fresh properties are not recommended to evaluate TMWM binders. It has also been found that traditional procedures used to evaluate unrestrained shrinkage may be responsible for misleading results when using those new binders. Water absorption data shows that TMWM has a very compacted structure. Results concerning the static modulus of elasticity are similar to the ones obtained by other authors. However the hypothesis related to modulus of elasticity decrease due to the use of high Al/Si alkali activated mixtures was not confirmed

Applying the Coulomb Failure Function with an optimally oriented plane to the 2008 Mw 7.9 Wenchuan earthquake triggering

The Coulomb failure function (CFF) quantitatively describes static stress changes in secondary faults near the source fault of an earthquake. CFF can be employed to monitor how static stress transfers and then shed some light on the probability of successive events occurring around a source fault. In this paper we focus on the CFF and particularly on optimally oriented planes. We present a unified model to determine an optimally oriented plane and its corresponding Coulomb stress, then apply the model to the 2003 Mw 6.6 Bam (Iran) earthquake and the 2008 Mw 7.9 Wenchuan (China) earthquake, thereby checking its effectiveness. Our results show that spatial correlation between positive Coulomb stress changes and aftershocks are, for the 2003 Bam earthquake, 47.06% when elastic Coulomb stress changes are resolved on uniform planes and 87.53% when these are resolved on optimally oriented planes at depth; for the 2008 Wenchuan earthquake the correlations are 45.68% and 58.20%, respectively. It is recommended that account be taken of optimally oriented planes when drawing a Coulomb stress map for analyzing earthquake triggering effects