Search Results (11)

Accurate trajectory control during atmospheric entry is critical for the success of Mars landing missions, where strong non-linearities and uncertain dynamics pose significant challenges to conventional control strategies. This study develops a computational framework that integrates fuzzy parameter-varying models with Lyapunov-based analysis to achieve robust trajectory stabilization of Mars entry vehicles. The non-linear longitudinal dynamics are reformulated via sector-bounded approximation into a Takagi–Sugeno fuzzy parameter-varying model, enabling systematic gain-scheduled controller synthesis. To reduce the conservatism typically associated with quadratic Lyapunov functions, a fuzzy Lyapunov function approach is adopted, in conjunction with the Full-Block S-procedure, to derive less restrictive stability conditions expressed as linear matrix inequalities. Based on this formulation, several controllers are designed to accommodate the variations in atmospheric density and flight conditions. The proposed methodology is validated through numerical simulations, including Monte Carlo dispersion and parametric sensitivity analyses. The results demonstrate improved stability, faster convergence, and enhanced robustness compared to existing fuzzy control schemes. Overall, this work contributes a systematic and less conservative control design methodology for aerospace applications operating under severe non-linearities and uncertainties. Full article

In this contribution, we address quantum transport in long periodic arrays whose basic cells, localized potentials $U\left(x\right)$, display certain particular features. We investigate under which conditions these “local” special characteristics can influence the tunneling behavior through the full structure. As the building blocks, we consider two types of $U\left(x\right)$s: combinations of either Pöschl–Teller, $U_0/{cosh}^2\left[\alpha x\right]$, potentials (for which the reflection and transmission coefficients are known analytically) or Gaussian-shaped potentials. For the latter, we employ an improved potential slicing procedure using basic barriers, like rectangular, triangular and trapezoidal, to approximate $U\left(x\right)$ and thus obtain its scattering amplitudes. By means of a recently derived method, we discuss scattering along lattices composed of a number, N, of these $U\left(x\right)$s. We find that near-resonance energies of an isolated $U\left(x\right)$ do impact the corresponding energy bands in the limit of very large Ns, but only when the cell is spatially asymmetric. Then, there is a very narrow opening (defect or rip) in the system conduction quasi-band, corresponding to the energy of the $U\left(x\right)$ quasi-state. Also, for specific $U_0$’s of a single Pöschl–Teller well, one has 100% transmission for any incident $E>0$. For the $U\left(x\right)$ parameters rather close to such a condition, the associated array leads to a kind of “reflection comb” for large Ns; $|T_N{\left(k\right)|}^2$ is not close to one only at very specific values of k, when $|T_N{|}^2\approx 0$. Finally, the examples here—illustrating how the anomalous transport comportment in finite but long lattices can be inherited from certain singular aspects of the $U\left(x\right)$s—are briefly discussed in the context of known effects in the literature, notably for lattices with asymmetric cells. Full article

In this paper, we investigate a novel T-S fuzzy parameter varying system with Markov jump, in which parameters depend not only on a Markov chain but also on linear parameter varying elements that take values in convex polytopic sets. Stable conditions and the gain-scheduling controller design method for this system are obtained. Applying Lyapunov function depending on the operation mode and full block S-procedure lemma, we obtain stochastic stabilization conditions. We find that this novel system has two distinct advantages. On the one hand, it inherits the advantages of traditional T-S fuzzy systems in handling nonlinear objects under the frame of T-S fuzzy systems; on the other, it obtains the advantages of dealing with time-varying characteristics from the point of linear parameter varying (LPV) systems. Finally, the theory results are illustrated via numerical simulation. Full article

To evaluate point-of-care testing (POCT) for the potential early detection of biomarkers of Parkinson’s disease, a systematic investigation of portable and low-cost platforms is performed based on the Proton-enzyme-linked immunosorbent assay (Proton-ELISA) methodology. The detection of the α-synuclein antigen was first presented by biotin-relative linkers, and glucose substrate solution was first performed with a systematic experimental design to optimize the sensing results. All materials in this study are commercially available. Three different experiments with the partitional check were performed to investigate the Proton-ELISA platform, including proton catalyzed efficiency, blocking efficiency, and full Proton-ELISA procedure. The response time was selected as 15 min by the time-dependent curves of a full reaction. The limit of detection of conventional ELISA kits is 0.169 ng/mL, which is much lower than the Proton-ELISA results. The final response of the full Proton-ELISA procedure to pH changes was approximately 0.60 and 0.12 for α-synuclein antigen concentrations of 100 ng/mL and 4 ng/mL, respectively. With the partitional check, pH changes of pure glucose substrate and conjugated oxidase and interference of the nonspecific binding are 1.7 and 0.04, respectively. The lower pH changes far from the partitional check results can be concluded for the properties of glucose oxidase conjugation, including the isoelectric point and binding affinity modification by the testing environment. This preliminary guideline can be used as a lesson learnt to speed up following studies of the evaluation and optimization of other antigen detection. Therefore, Proton-ELISA can be suggested for some special applications with the help of custom-designed conjugation in the environment with less degradation or interference and a proper detection concentration range. Full article

For transient stability analysis of a multi-machine power system, the Extended Equal Area Criterion (EEAC) method applies the classic Equal Area Criterion (EAC) concept to an approximate One Machine Infinite Bus (OMIB) equivalent of the system to find the critical clearing angle. The system-critical clearing time can then be obtained by numerical integration of OMIB equations. The EEAC method was proposed in the 1980s and 1990s as a substitute for time-domain simulation for Transmission System Operators (TSOs) to provide fast, transient stability analysis with the limited computational power available those days. To ensure the secure operation of the power system, TSOs have to identify and prevent potential critical scenarios through offline analyses of a few dangerous ones. These days, due to increased uncertainties in electrical power systems, the number of these critical scenarios is increasing, substantially, calling for fast, transient stability analysis techniques once more. Among them, the EEAC is a unique approach that provides not only valuable information, but also a graphical representation of system dynamics. This paper revisits the EEAC but from a modern, functional point of view. First, the definition of the OMIB model of a multi-machine power system is redrawn in its general form. To achieve fast, transient stability analysis, EEAC relies on approximate models of the true OMIB model. These approximations are clarified, and the EAC concept is redefined with a general definition for instability, and its conditions. Based on the defined conditions and definitions, functions are developed for each EEAC building block, which are later put out together to provide a full-resolution, functional scheme. This functional scheme not only covers the previous literature on the subject, but also allows to introduce several possible new EEAC approaches and provides a detailed description of their implementation procedure. A number of approaches are applied to the French EHV network, and the approximations are examined. Full article

This paper presents the results of experimental and numerical tests on angle members connected by one leg with a single row of bolts. This study was designed to determine which failure mode governs the resistance of such joints: net section rupture or block tearing rupture. Experimental tests were insufficient to completely identify the failure modes, and it was necessary to conduct numerical simulations. Finite element analysis of steel element resistance based on rupture required advanced material modelling, taking into account ductile initiation and propagation of fractures. This was realised using the Gurson–Tvergaard–Needleman porous material model, which allows for analysis of the joint across the full scope of its behaviour, from unloaded state to failure. Through experimental testing and numerical simulations, both failure mechanisms (net section and block tearing) were examined, and an approach to identify the failure mode was proposed. The obtained results provided experimental and numerical evidence to validate the strength function used in design standards. Finally, the obtained results of the load capacity were compared with the design procedures given in the Eurocode 3′s current and 2021 proposed editions. Full article

Fifth generation Vehicular Cloud Computing (5G-VCC) systems support various services with strict Quality of Service (QoS) constraints. Network access technologies such as Long-Term Evolution Advanced Pro with Full Dimensional Multiple-Input Multiple-Output (LTE-A Pro FD-MIMO) and LTE Vehicle to Everything (LTE-V2X) undertake the service of an increasing number of vehicular users, since each vehicle could serve multiple passenger with multiple services. Therefore, the design of efficient resource allocation schemes for 5G-VCC infrastructures is needed. This paper describes a network slicing scheme for 5G-VCC systems that aims to improve the performance of modern vehicular services. The QoS that each user perceives for his services as well as the energy consumption that each access network causes to user equipment are considered. Subsequently, the satisfactory grade of the user services is estimated by taking into consideration both the perceived QoS and the energy consumption. If the estimated satisfactory grade is above a predefined service threshold, then the necessary Resource Blocks (RBs) from the current Point of Access (PoA) are allocated to support the user’s services. On the contrary, if the estimated satisfactory grade is lower than the aforementioned threshold, additional RBs from a Virtual Resource Pool (VRP) located at the Software Defined Network (SDN) controller are committed by the PoA in order to satisfy the required services. The proposed scheme uses a Management and Orchestration (MANO) entity implemented by a SDN controller, orchestrating the entire procedure avoiding situations of interference from RBs of neighboring PoAs. Performance evaluation shows that the suggested method improves the resource allocation and enhances the performance of the offered services in terms of packet transfer delay, jitter, throughput and packet loss ratio. Full article

The Fitbone^® motorized nail system has been used to correct limb length discrepancies (LLD) for several years. This study focuses on its application in posttraumatic limb lengthening surgery, its outcome and challenges. Materials and methods: A prospective, single center study was conducted between 2010 and 2019 in patients treated with motorized lengthening nails. The inclusion criteria were symptomatic LLD of 20 mm or more. An imaging analysis was done using TraumaCad^® software (Brainlab AG, Munich, Germany) to compare frontal alignment angles and limb length discrepancy (LLD) on preoperative and latest follow-up radiographs of the lower limbs. Results: Thirty-four patients were included with a mean age of 28.8 ± 9.7 years, a mean follow-up of 27.8 ± 13 months and a mean hospital stay of 4.4 ± 1.7 days. The mean LLD was 44 ± 18 mm in 29 femoral and 32 ± 8 mm in 4 tibial cases, which was reduced to less than 10 mm in 25/34 (74%) patients. The mean healing index was 84.6 ± 62.5 days/cm for femurs and 92 ± 38.6 days/cm for tibias. The mean time to resume full weight-bearing without walking aids was 226 days ± 133. There was no significant difference between preoperative and final follow-up alignment angles and range of motion. The mechanical lateral distal femoral angle (mLDFA) was corrected in the subgroup of 10 LLD patients with varus deformity of the femur (preoperative 95.7° (±5.0) vs. postoperative 91.5° (±3.4), p = 0.008). According to Paley’s classification, there were 14 problems, 10 obstacles and 2 complications. Discussion: Six instances of locking screw pull out, often requiring reoperation, raise the question of whether a more systematic use of blocking screws that provide greater stability might be indicated. Lack of compliance can lead to poor outcomes, patient selection in posttraumatic LLD patients is therefore important. Conclusion: Limb lengthening with a motorized lengthening nail for posttraumatic LLD is a relatively safe and reliable procedure. Full patient compliance is crucial. In-depth knowledge of lengthening and deformity correction techniques is essential to prevent and manage complications. Full article

The present short communication described a new procedure for the reconstruction of the horizontal severely resorbed edentulous maxilla with custom-made deproteinized bovine bone block, fabricated using three-dimensional imaging of the patient and computer-aided design/computer-aided manufacturing (CAD/CAM) technology. The protocol consisted of three phases. In the diagnosis and treatment planning, cone-beam computed tomographic scans of the patient were saved in DICOM (digital imaging and communication in medicine) format, anatomic and prosthetic data were imported into a dedicated diagnostic and medical imaging software, the prosthetic-driven position of the implants, and the graft blocks perfectly adapted to the residual bone structure were virtually planned. In the manufacturing of customized graft blocks, the CAD-CAM technology and the bovine-derived xenohybrid composite bone (SmartBone^® on Demand - IBI SA - Industrie Biomediche Insubri SA Switzerland) were used to fabricate the grafts in the exact shape of the 3D planning virtual model. In the surgical and prosthetic procedure, the maxillary ridge augmentation with custom-made blocks and implant-supported full-arch screw-retained rehabilitation were performed. The described protocol offered some advantages when compared to conventional augmentation techniques. The use of deproteinized bovine bone did not require additional surgery for bone harvesting, avoided the risk of donor site morbidity, and provided unlimited biomaterial availability. The customization of the graft blocks reduced the surgical invasiveness, shorting operating times because the manual shaping of the blocks and its adaptation at recipient sites are not necessary and less dependent on the clinician’s skill and experience. Full article

So-called “Type IX” chute spillways with impact baffle blocks have been used successfully around the globe for over 50 years. A key advantage of the chute spillway is the elimination of a costly stilling basin allowing for a more simplistic outlet works design. The current design process is based upon physical models developed in the 1950s and observation of completed projects over the last 50 years. The design procedure is empirical and provides the designer with a range of workable layouts, baffle heights, and baffle spacing. Unfortunately, this approach may not be optimal. This first study of a longer research effort focus uses Monte Carlo simulations and computational fluid dynamics (CFD) to examine the design methodology and physical model basis for the current design procedure. Initially, the study examined the design procedure with a Monte Carlo simulation to explore the range of acceptable designs that can be realized. Then, using CFD, full-scale prototype (located in Gila, Arizona USA) physical model results that were a key basis for the current design procedure were recreated. The study revealed that a wide range of acceptable chute designs can result from following the current design procedure but that some of these may be better than others. The study also outlines future research efforts needed to revise the current design methodology. Full article

No studies are available that evaluate the retention of disilicate crowns according to different cementation procedures. The purpose of this study was to measure the retention of lithium disilicate crowns cemented using two different cementation systems. Twenty extracted mandibular premolars were prepared. Anatomic crowns were waxed and hot pressed using lithium disilicate ceramic. Teeth were divided into two groups (n = 10): (1) self-curing luting composite and (2) glass-ionomer cement (GIC). After cementation, the crowns were embedded in acrylic resin block with a screw base. Each specimen was pulled along the path of insertion in Universal Testing Machine. Failure load in Newtons (N) and failure mode were recorded for each specimen. Failure mode was classified as decementation or fracture. Failure load data were analyzed using one-way analysis of variance (ANOVA). Failure modes were compared using Pearson’s Chi-square test. Mean failure load was 306.6(±193.8) N for composite group and 94.7(±48.2) N for GIC group (p = 0.004). Disilicate crown cemented with luting composite most often failed by fracture; otherwise, crown cemented with glass-ionomer cement most often failed by decementation (p = 0.02). Disilicate full crown cemented with luting composite showed higher failure load compared with conventional cementation with glass-ionomer cement. Full article