Multiple Loops Research Articles

A Multi-Correlation Peak Phase Deblurring Algorithm for BeiDou B1C Signals in Urban Environments

With the widespread global application of BeiDou navigation, BeiDou B1C signaling based on Quadrature Multiplexed Binary Offset Carrier (QMBOC) modulation is expected to be extensively used in urban environments due to its wider signal bandwidth, smaller code pseudorange measurement errors, and stronger multipath capabilities. Despite offering higher positioning accuracy and secondary modulation characteristics of the BeiDou, B1C signals introduce the challenge of multiple peaks in the autocorrelation function. This leads to phase ambiguity during signal acquisition and tracking, resulting in positioning deviations of tens or even hundreds of meters. In urban environments, such deviations give rise to significant practical application issues. To address this problem, we have designed a multi-loop structure for the synchronous tracking of B1C signals and proposed a multi-peak phase-deblurring algorithm specifically tailored for the BeiDou B1C signal in urban environments. This algorithm considers the coupling relationship between the code and the carrier loops, and by matching the structural design of multiple loops, it achieves a precise and unambiguous phase estimation of the pseudocode, enabling the stable tracking of the entire loop for the BeiDou B1C signal. Simulation and actual testing demonstrate that the algorithm exhibits an error less than 0.03 for chip intervals when the signal-to-noise ratio is greater than −20 dB. Additionally, the accuracy can be improved by adjusting the set conditions, making it suitable for urban environments.

194 An uncommon cause of small bowel obstruction with perforation after a caesarean section

Abstract The incidence of small bowel obstruction after any abdominal surgery is 9%, whereas it is only 0.1% after a C-Section. Small bowel obstruction secondary to herniation of a segment of the small bowel beneath the intact rectus sheath and between the rectus muscle is extremely rare. Reviewing the literature revealed that less than five cases were reported. Here we present a 39-year-old female six days post caesarean section presented with abdomen pain, distension, and not opening bowels. The blood investigations showed White blood cells 15.42x109/L and C-reactive protein 286mg/L. She was hypotensive and tachycardic. On clinical examination, the abdomen was distended and peritonitic. The Computed tomography of the abdomen and pelvis with contrast showed there is small bowel obstruction with multiple loops of proximal dilated bowel with a transition point within the pelvis and in midline a small inferior umbilical or incisional hernia containing a knuckle of small bowel with a moderate amount of pneumoperitoneum and free fluid. She underwent an emergency laparotomy and was found to have four quadrants of purulent peritonitis. In addition, a 3cm defect in the midline peritoneum allowed herniation of approximately 30cm of small bowel into preperitoneal space between the recti with ischaemia and perforation at the neck of the hernia. She had small bowel resection anastomosis, and the peritoneal defect was formally closed to prevent re-herniation of bowel loops. The NICE guidelines recommend not closing the peritoneum during the c-section. However, this case is an example of severe postoperative morbidity, which could be avoided by peritoneal closure.

Stable and meta-stable contract networks

This paper studies a multilateral matching market in which each participant can sign contracts with any other agents. This market subsumes the two-sided matching and the roommate problem as special cases. We consider a hypergraph (I,C), with possible multiple (hyper)edges and loops, in which the vertices i∈I are interpreted as agents, and the edges c∈C as contracts that can be concluded between agents. The preferences of each agent i are given by a choice functionfi possessing the so-called path independent property. In this general setup we consider the notion of stable contract network.The paper contains two main results. The first one is that a general stable contract problem for (I,C,f) can be reduced to a special one in which preferences of the agents are given by weak orders, or, equivalently, by utility functions. However, stable contract systems may not exist. Trying to overcome this trouble, we introduce a weaker notion of meta-stability for contract systems. Our second result is that meta-stable systems always exist. A proof of this result relies on an appealing theorem on the existence of the so-called compromise function.

MiR34a-5p impedes CLOCK expression in chronodisruptive C57BL/6J mice and potentiates pro-atherogenic manifestations.

Altered circadian rhythms underlie manifestation of several cardiovascular disorders, however a little is known about the mediating biomolecules. Multiple transcriptional-translational feedback loops control circadian-clockwork wherein; micro RNAs (miRNAs) are known to manifest post transcriptional regulation. This study assesses miR34a-5p as a mediating biomolecule. 8-10-week-old male C57BL/6J mice (n = 6/group) were subjected to photoperiodic manipulation induced chronodisruption and thoracic aortae were examined for miRNA, gene (qPCR) and protein (Immunoblot) expression studies. Histomorphological changes were assessed for pro-atherogenic manifestations (fibrillar arrangement, collagen/elastin ratio, intima-media thickening). Computational studies for miRNA-mRNA target prediction were done using TargetScan and miRDB. Correlative in vitro studies were done in serum synchronized HUVEC cells. Time point based studies were done at five time points (ZT 0, 6, 12, 18, 24) in 24h. Chronodisruption induced hypomethylation in the promoter region of miR34a-5p, in the thoracic aortae, culminating in elevated miRNA titers. In a software-based detection of circadian-clock-associated targets of miR34a-5p, Clock and Sirt1 genes were identified. Moreover, miR34a-5p exhibited antagonist circadian oscillations to that of its target genes CLOCK and SIRT1 in endothelial cells. Luciferase reporter gene assay further showed that miR34a-5p interacts with the 3'UTR of the Clock gene to lower its expression, disturbing the operation of positive arm of circadian clock system. Elevated miR34a-5p and impeded SIRT1 expression in a chronodisruptive aortae exhibited pro-atherogenic changes observed in form of gene expression, increased collagen/elastin ratio, fibrillar derangement and intimal-media thickening. The study reports for the first time chronodisruption mediated miR34a-5p elevation, its circadian expression and interaction with the 3'UTR of Clock gene to impede its expression. Moreover, elevated miR34a-5p and lowered SIRT1 expression in the chronodisruptive aortae lead off cause-consequence relationship of chronodisruption mediated proatherogenic changes.

A testbed for studying the interactions between human operators and advanced control systems

Industrial chemical processes are operated under closed-loop control while being supervised by human operators. The low-level regulatory controllers are often supplemented by advanced multivariate control such as Model Predictive Control (MPC). Since MPC is complex, its control actions can be non-intuitive to the operator. The operator may turn off any controller if they suspect the control actions triggered by it. Hence, it is imperative to understand the operator's interaction with automation. In this work, we develop a testbed with the potential to understand the operator's confidence in MPC through a human factors approach. The testbed consists of a multi-unit chemical process instrumented with various sensors, multiple low-level SISO control loops, and a high-level MPC. The testbed is instrumented with a mechanism to record keystrokes, mouse movements, and mouse clicks to observe the operators’ interactions with the process (during various fault scenarios) through the provided Human Machine Interface.

Robust Single-Loop Control Strategy for Four-Level Flying-Capacitor Converter Based on Switched System Theory

For the four-level flying capacitor converter (FFCC), it is required to simultaneously control the output voltage and balance the flying-capacitor voltages. Existing control methods for the FFCC always employ multiple control loops, where for every controlled voltage variable an independent control loop is to be designed. However, such a control structure of multiple loops leads to a complex coupling effect among these loops. Due to the coupling, it is difficult to achieve a coordinated design of a large number of control parameters and demonstrate the control system stability. To simplify the control design and the implementation, this article proposes a single-loop control strategy by using the switched system theory. All the voltages are driven towards their desired values with a single control loop, instead of using several individual controllers. Thus, the issue of devoting efforts to dealing with the couplings among multiple control loops is bypassed. Moreover, the system's large-signal stability is ensured in a straightforward manner, thereby simplifying the stability analysis. In the design process, the system parameter uncertainties are also considered. Comparative experiments demonstrate the good transient performance and the strong robustness of the proposed control strategy.

Integration of feedforward and feedback control in the neuromechanics of vertebrate locomotion: a review of experimental, simulation and robotic studies.

Animal locomotion is the result of complex and multi-layered interactions between the nervous system, the musculo-skeletal system and the environment. Decoding the underlying mechanisms requires an integrative approach. Comparative experimental biology has allowed researchers to study the underlying components and some of their interactions across diverse animals. These studies have shown that locomotor neural circuits are distributed in the spinal cord, the midbrain and higher brain regions in vertebrates. The spinal cord plays a key role in locomotor control because it contains central pattern generators (CPGs) - systems of coupled neuronal oscillators that provide coordinated rhythmic control of muscle activation that can be viewed as feedforward controllers - and multiple reflex loops that provide feedback mechanisms. These circuits are activated and modulated by descending pathways from the brain. The relative contributions of CPGs, feedback loops and descending modulation, and how these vary between species and locomotor conditions, remain poorly understood. Robots and neuromechanical simulations can complement experimental approaches by testing specific hypotheses and performing what-if scenarios. This Review will give an overview of key knowledge gained from comparative vertebrate experiments, and insights obtained from neuromechanical simulations and robotic approaches. We suggest that the roles of CPGs, feedback loops and descending modulation vary among animals depending on body size, intrinsic mechanical stability, time required to reach locomotor maturity and speed effects. We also hypothesize that distal joints rely more on feedback control compared with proximal joints. Finally, we highlight important opportunities to address fundamental biological questions through continued collaboration between experimentalists and engineers.

Narrow linewidth fiber laser with multiple unpumped EDF fiber loops and self-injection feedback

In this paper, we proposed a narrow linewidth single-longitudinal-mode (SLM) fiber laser, which was realized by employing a triple-cascaded unpumped erbium doped fiber (EDF) Sagnac loops structure with Rayleigh backscattering (RBS) feedback. Narrow linewidth SLM laser output can be achieved by using the unpumped EDF loops. However, it is generally difficult to achieve laser emission with a linewidth below 1 kHz and a power of tens of milliwatts. In this paper, we propose a fiber laser with multiple unpumped Er-doped fiber loops and self-injection feedback. The cascade of multi-unpumped Er-doped fiber rings is employed to reduce the linewidth of the laser, while the self-injection feedback based on RBS is used to improve the stability of the laser and further compress the laser linewidth. By only utilizing three unpumped Er-doped fiber rings cascaded, we obtain an output beam with a linewidth of 723.05 Hz and laser power of 21.52 mW with 0.30 dB fluctuation during a period time of 30 min at the pump power of 170.6 mW. After introducing the feedback mechanism based on RBS into the fiber laser, an output laser with a linewidth of 530.11 Hz and a laser power of 8.57 mW with 0.23 dB fluctuation in 30 min can be obtained at the pump power of 268.68 mW. Compared with the fiber laser with one unpumped Er-doped fiber ring, the linewidth is reduced more than two times.

Multi-Zone Integrated Iterative-Decoupling Control of Temperature Field of Large-Scale Vertical Quenching Furnaces Based on ESRNN

Temperature uniformity within a large vertical quenching furnace is the key factor to determine the properties of aluminum workpieces. The existing temperature control method for quenching furnaces cannot overcome the influence of multi-zone coupling issues, which lead to unstable product performance and a lack of key performance. Based on a workpiece temperature field model, a spatial-temporal dimensional extrapolation method is proposed to realize fast and accurate solving of the temperature model. In view of the over-burning and under-burning problems during the temperature rising period, a self-incentive nonparametric adaptive iterative control algorithm is presented, which realizes consistent temperature rising of multiple heating zones. Aiming at the strong coupling problem of the multi-zone heating manner during the temperature holding period, the decoupling problem of multiple control loops is converted into a multi-loop integrated control optimization problem. An eigenvector self-update recurrent neural network (ESRNN) is constructed to determine the Jacobian information and tune the control parameters of each loop controller in real time, thereby realizing the integrated intelligent decoupling control of multiple heating loops. Simulation and industrial results verify the superiority of the proposed method, which can realize high-precision and high-uniformity control of a large-scale temperature field and effectively improve the quality and performance of aluminum alloy workpieces.

A New Approach to Selecting Optimal Parameters for the Sliding Mode Algorithm on an Automotive Suspension System

Stimuli from the road surface cause car vibrations. The suspension system ensures the vehicle’s stability and smoothness when moving. In this research, the author introduces the use of active suspension with a hydraulic actuator to improve the comfort of cars. Car oscillations are described based on a quarter-dynamics model with five state variables. Besides, the nonlinear system’s SM (sliding mode) control algorithm is used to control the system. The SM algorithm’s parameters are optimally selected using the multiple loop algorithm. The multiple loop algorithm allows the values to vary within a predefined limit and provides an optimal parameter based on the vehicle’s vibration conditions. This is a new point in the paper compared to previous studies. The output of the simulation problem includes displacements and accelerations of both the sprung and unsprung masses. In addition, the change of dynamics force at the wheel is also considered when evaluating the interaction between the wheel and the road surface. According to the paper’s results, the vehicle body’s acceleration and displacement values are strongly reduced when using the SM algorithm, compared with cars with only traditional suspension. In addition, the change in dynamics force at the wheel is not significant when using this algorithm. As a result, the car’s smoothness has been improved while the vehicle’s stability has not been lost. The phenomenon of “chattering” still occurs in some cases; however, its effect is negligible.

From actin waves to mechanism and back: How theory aids biological understanding

Actin dynamics in cell motility, division, and phagocytosis is regulated by complex factors with multiple feedback loops, often leading to emergent dynamic patterns in the form of propagating waves of actin polymerization activity that are poorly understood. Many in the actin wave community have attempted to discern the underlying mechanisms using experiments and/or mathematical models and theory. Here, we survey methods and hypotheses for actin waves based on signaling networks, mechano-chemical effects, and transport characteristics, with examples drawn from Dictyostelium discoideum, human neutrophils, Caenorhabditis elegans, and Xenopus laevis oocytes. While experimentalists focus on the details of molecular components, theorists pose a central question of universality: Are there generic, model-independent, underlying principles, or just boundless cell-specific details? We argue that mathematical methods are equally important for understanding the emergence, evolution, and persistence of actin waves and conclude with a few challenges for future studies.

A Novel MIMO Control for Interleaved Buck Converters in EV DC Fast Charging Applications

This brief proposes a new multiple input multiple output (MIMO) control for off-board electric vehicle (EV) dc fast chargers. The proposed feedback matrix design avoids multiple tuning of controllers in multiple and interconnected loops while improving the performance of interleaved dc buck converters over classical PI/PID controls. The innovative features of the presented strategy are the reference current monotonic tracking from any initial state of charge with an arbitrarily fast settling time and the fast compensation of both load variations and imbalances among the legs. Numerical results validate the performance improvements of the proposed discrete-time MIMO algorithm for interleaved buck converters over classical PI/PID controls. Full-scale hardware-in-the-loop (HIL) and scaled-down prototype experimental results prove the feasibility and effectiveness of the proposal.

A New Method to Improve the Detection Sensitivity of Differential Magnetic-Field Probe for Near-Field Scanning

In this article, a new method is proposed to improve the detection sensitivity of the differential magnetic-field probe for near-field scanning. In order to prove the rationality of this method, two differential magnetic-field probes (Probes A and B) with multiple parasitic loops are investigated. First, a conventional differential magnetic-field probe is theoretically analyzed and studied. Second, a pair of parasitic loops are introduced into a differential magnetic-field probe (Probe A) to enhance the detection sensitivity. Third, two pairs of parasitic loops are inserted into the differential magnetic-field probe (Probe B). The corresponding analysis is also given and discussed. Moreover, in order to verify the performance of these probes (Probes A and B), two of the simulated models are printed and manufactured based on six-layered and eight-layered printed circuit boards (PCBs), respectively. A standard microstrip line is applied for calibrating and characterizing these probes. The measured and simulated results reveal that the proposed method could significantly improve the detection sensitivity of differential magnetic-field probes.

Disturbance Rejection in MIMO Systems With Emotional-Learning-Based Controller: Application to Variable Rotor-Speed Helicopters

This manuscript proposes a Pareto-optimal approach toward designing an estimator for rejecting disturbances with an emotional-learning-based control (ELBC) administered MIMO system. Contrary to the conventional high-gain-based ELBC design, this approach employs a disturbance estimate augmented stimulus which is not prone to excitation of mechanical resonance. Furthermore, in contrast to the existing SISO-based methods of estimator design, this approach considers key attributes, such as disturbance rejection, noise sensitivity, control signal chattering, and loop interaction associated with multiple loops of an MIMO system in an integrated manner. The parameters of the estimator are realized by minimizing a performance index that is representative of the weighted sensitivity and complementary sensitivity functions of the MIMO system. The approach is illustrated with four popular disturbance estimators. Experimental results on a laboratory-scale helicopter under dynamic wind gusts demonstrate its efficacy with respect to nominal ELBC design.

Toward an ethics of autopoietic technology: Stress, care, and intelligence

The relationship between humans and technology has attracted increasing attention with the advent of ever stronger models of artificial intelligence. Humans and technology are intertwined within multiple autopoietic loops of stress, care, and intelligence. This paper suggests that technology should not be seen as a mere tool serving humans’ needs, but rather as a partner in a rich relationship with humans. Our model for understanding autopoietic systems applies equally to biological, technological, and hybrid systems. Regardless of their substrates, all intelligent agents can be understood as needing to respond to a perceived mismatch between what is and what should be. We take this observation, which is evidence of intrinsic links between ontology and ethics, as the basis for proposing a stress-care-intelligence feedback loop (SCI loop for short). We note that the SCI loop provides a perspective on agency that does not require recourse to explanatorily burdensome notions of permanent and singular essences. SCI loops can be seen as individuals only by virtue of their dynamics, and are thus intrinsically integrative and transformational. We begin by considering the transition from poiesis to autopoiesis in Heidegger and the subsequent enactivist tradition, and on this basis formulate and explain the SCI loop. In an acknowledgment of Maturana’s and Varela’s project, our findings are considered against the backdrop of a classic Buddhist model for the cultivation of intelligence, known as the bodhisattva. We conclude by noting that SCI loops of human and technological agency can be seen as mutually integrative by noticing the stress-transfers between them. The loop framework thus acknowledges encounters and interactions between humans and technology in a way that does not relegate one to the subservience of the other (neither in ontological nor in ethical terms), suggesting instead integration and mutual respect as the default for their engagements. Moreover, an acknowledgment of diverse, multiscale embodiments of intelligence suggests an expansive model of ethics not bound by artificial, limited criteria based on privileged composition or history of an agent. The implications for our journey into the future appear numerous.

Modelling, experimental validation and analysis of a multiple stage PC-PMF Sagnac loop interferometer with spectral shape versatility using an optimized fitting algorithm

Here we experimentally demonstrate a multi-stage Sagnac loop with high spectral shape versatility by employing a serial sequence of different polarization controllers (PC) and Polarization-Maintaining Fibres (PMF), and we develop a general mathematical model to simulate it for N PMF stages inside of its loop using the Jones formalism. Our model is then validated for the cases of 2 and, for the first time, 3 stages by comparing the numerical simulation results with the experimental data, achieving a very small Root Mean Squared Error (RMSE) of around 10−4. Additionally, we propose a heuristic optimization capable of retrieving physical information from the measured spectra about the polarization states inside the loop, opening up the possibility of the use of such modelling as an interrogation tool for sensing applications. Finally, we perform a brief analysis of the interferometric pattern curves obtained in order to further understand its versatility. This spectral flexibility makes such interferometers interesting candidates for use as tunable optical filters and quasi-distributed sensors.

Magnetic characteristics of the ferrimagnetic bilayer MXene-like nanostructure with interlayer exchange interactions: Monte Carlo study

Monte Carlo simulations are used to investigate the magnetic properties of the nanostructured spin-7/2 and spin-1 ferrimagnetic bilayers within interlayer exchange interactions. The effects of nonmagnetic layers thickness, magnetic coupling and the crystal field on the blocking temperature, magnetization and hysteresis loops are studied. It is found that the blocking temperature decreases when increasing the magnetic coupling between layers and/or increasing the thickness of the magnetic layer. Besides, the model exhibits multiple hysteresis loops for which the area decreases when increasing the thickness of the magnetic layer, the crystal field and/or the temperature. Moreover, the effect of temperature on the behavior of the partial and the total magnetization and the total susceptibility are also as investigated.

A 12-Bit 2 GS/s Single-Channel High Linearity Pipelined ADC in 40 nm CMOS.

This paper presents a single-channel 12-bit, 2 GS/s pipelined analog-to-digital converter (ADC) for wideband sampling receivers. The design adopts a novel source follower input buffer with multiple feedback loops to improve sample linearity and extend bandwidth. Additionally, an improved two stages charge pump amplifier topology is introduced, which doubles the Gain Bandwidth Product (GBW) without consuming additional power. To address the back-end ADC and background calibration, a multi-level dither strategy is employed, utilizing a new high-speed and low-cost uniform distribution pseudorandom code generator. The prototype ADC fabricated in 40 nm CMOS process achieves 68.24 dB SFDR up to Nyquist frequency with a sampling rate of 2 GS/s. Measurement results demonstrate a bandwidth exceeding 5 GHz, resulting in a Schreier FOMs of 152.4 dB.

A clinical case of small intestinal intussusception caused by metastatic melanoma

Intestinal obstruction is observed in about 9.0 % of patients with acute surgical pathology of the abdominal cavity. The disease occurs at any age, but more often between 25–50 years. Mixed intestinal obstruction is only 3–7 %. The most common form of mixed intestinal obstruction is intestinal invasion. The most common cause of intussusception in adults is an intestinal tumor. Early diagnosis and the optimal amount of surgical treatment are the main components of successful treatment of the patient.
 Aim: to familiarize practitioners with a rare case of intestinal obstruction in adults and its management strategies in a surgical hospital.
 Materials and methods. The patient was treated in the surgical department of the Communal Non-Profit Enterprise “City Hospital No. 7” Zaporizhzhia City Consul. The patient underwent preoperative preparation and surgical intervention.
 Results. The patient underwent an emergency median laparotomy under total intravenous anesthesia with artificial lung ventilation. During the examination of the abdominal cavity, multiple distended loops of the small intestine were visualized. During the revision, at a distance of 1.5 meters from the ligament of Treitz, a volumetric formation of the small intestine of dense-elastic consistency, represented by small-intestinal invasion, up to 10 cm long, was detected. The proximal sections of the small intestine are distended, light purple in color. The sections of the small intestine that were distal to the site of invasion were inflamed. Manual disinvagination of the small intestine was performed. The visual examination showed that the intestine was viable. There was a tumor was found on the antrumeral margin, measuring 1.8 × 2.5 cm, dense in consistency, finely tuberculated, dark purple heterogeneous in color, infiltrating and deforming the wall of the small intestine. Resection of the invaded area of the small intestine with the tumor was performed with the imposition of a small-small intestinal anastomosis “side to side” with two-row nylon sutures.
 Conclusions. In this clinical case, it was possible to establish the final diagnosis and determine further surgical strategy only intraoperatively. Only early diagnosis of melanoma will allow avoiding the complications identified in this patient.

Continuous-flow simulation of manufacturing systems with assembly/disassembly machines, multiple loops and general layout

Performance evaluation methods are important to design and control manufacturing systems. Approximate analytical methods are fast, but they may be limited by the restrictive assumptions on the system. On the contrary, simulation has not specific limitations in its applicability, but the time to model and analyse a manufacturing system can increase as the level of detail addressed by the model increases. The main contribution of this study is presenting a computationally efficient methodology to simulate single-part continuous-flow manufacturing systems with assembly/disassembly machines, multiple loops, general layout and general inter-event time distributions. By using graph theory, a new method is presented to identify the machines causing slowdown, blocking and starvation in a general layout and determine the time before the occurrence of a state transition for each machine and the time before the fulfilment or depletion of each buffer. By advancing the time clock to the next event-time accordingly, the number of discrete events needed to be simulated is decreased compared to a discrete-event simulation with discrete flow of parts. As a result, the proposed method is on average 15 times faster than DES methods in the analysis of discrete-flow systems, and 110 times faster on average in the analysis of continuous-flow systems. The low computational time of the proposed method allows to simulate systems under general assumptions and in a very short time.