Operational Space Research Articles

Electrical two-qubit gates within a pair of clock-qubit magnetic molecules

Enhanced coherence in HoW10 molecular spin qubits has been demonstrated by use of clock-transitions (CTs). More recently it was shown that, while operating at the CTs, it was possible to use an electrical field to selectively address HoW10 molecules pointing in a given direction, within a crystal that contains two kinds of identical but inversion-related molecules. Herein we theoretically explore the possibility of employing the electric field to effect entangling two-qubit quantum gates within a 2-qubit Hilbert space resulting from dipolar coupling of two CT-protected HoW10 molecules in a diluted crystal. We estimate the thermal evolution of T1, T2, find that CTs are also optimal operating points from the point of view of phonons, and lay out how to combine a sequence of microwave and electric field pulses to achieve coherent control within a switchable two-qubit operating space between symmetric and asymmetric qubit states that are protected both from spin-bath and from phonon-bath decoherence. This two-qubit gate approach presents an elegant correspondence between physical stimuli and logical operations, meanwhile avoiding any spontaneous unitary evolution of the qubit states. Finally, we found a highly protected 1-qubit subspace resulting from the interaction between two clock molecules.

A Trajectory Planning Approach for Delta Robots Considering Both Motion Smoothness and Dynamic Stress

Abstract By considering both motion smoothness and dynamic stress, a trajectory planning method for delta robots, with the goal of determining the two optimal normalized time factors that dominate the motion path in operation space, is presented in this article. First, based on the semianalytical elastodynamics model of parallel robots, which considers the compliance of the limbs and joints, a dynamic stress model of the kinematic chain was built. Two indices were proposed to reflect the motion smoothness and dynamic stress. A sensitivity analysis and an optimization of the normalized time factors for a modified fifth-order B-spline approach were conducted in isight and matlab. The results show that the two normalized time factors have important impacts on the motion smoothness and dynamic stress. A comparison showed that the trajectory planning approach based on the modified fifth-order B-spline reduced the dynamic stress while improving the motion smoothness. The approach proposed in this work can also be applied in trajectory planning for other parallel or hybrid robots.

A single-center study of thoracoscopic surgery in the treatment of pediatric mediastinal neurogenic tumors.

To study the feasibility, safety, and efficacy of thoracoscopic surgery in the treatment of pediatric mediastinal neurogenic tumors, and summarize the treatment experiences and surgical skills. A single-center retrospective analysis of 37 patients with pediatric mediastinal neurogenic tumors was conducted. Clinical charactersistics and postoperative complications were all analyzed. All the operations were successfully completed. There was no statistically significant difference in tumor diameter between the two groups (p> 0.05). The open surgery group had an average operation time of 96.5± 32.38 min, while the thoracoscopic surgery group had an average operation time of 78.3± 24.51 min (p< 0.05). The thoracoscopic surgery group had significantly lower intraoperative blood loss than the open surgery group (p< 0.05). In addition, the duration of the postoperative thoracic drainage tube was 5.43 ± 0.76 days in the open surgery group, which was longer than the 2.38 ± 0.87 days in the thoracoscopic surgery group (p< 0.05). Furthermore, the postoperative length of hospital stay was an average of 10.23 ± 1.43 days for the open surgery group, longer than for the thoracoscopic surgery group (4.36 ± 0.87 days) (p< 0.05). Thoracoscopic surgery has several advantages in the treatment of pediatric mediastinal neurogenic tumors and is worthy of clinical popularization and application. For giant mediastinal malignant neurogenic tumors, puncture biopsy and adjuvant chemotherapy can be performed before surgery to lessen the tumor volume and enlarge the operation space, which would reduce bleeding and complications.

Dyno-Kinematic Leg Design for High Energy Robotic Locomotion

Abstract Animal legs are capable of a tremendous breadth of distinct dynamic behaviors. As robots pursue this same degree of flexibility in their behavioral repertoire, the design of the power transition mechanism from joint to operational space (the leg) becomes increasingly significant given the limitations current actuator technology. To address the challenges of designing legs capable of meeting the competing requirements of various dynamic behaviors, this paper proposes a technique which prioritizes explicitly encoding a set of dynamics into a robot’s leg design, called dyno-kinematic leg design (DKLD). This paper also augments the design technique with a method of evaluating the suitability of an individual leg’s workspace to perform dynamic behaviors, called the effective dynamic workspace (EDW). These concepts are shown to effectively determine optimal leg designs within a set of three, increasingly complex, case studies on different robots. These new legs designs enable a 5 kg robot to climb vertical surfaces at 3 Hz, allow a 60 kg robot to efficiently perform a range of behaviors useful for navigation (including a run at 2 m/s), and endow a small quadrupedal robot with all of the necessary behaviors to produce running and climbing multimodality. This design methodology proves robust enough to determine advantageous legs for a diverse range of dynamic requirements, leg morphologies, and cost functions, therefore demonstrating its possible application to many legged robotic platforms.

Research on application of dynamic adaptive cache strategy and artificial intelligence technology in power engineering data processing

In order to improve the effect of power engineering data processing, this paper combines dynamic adaptive caching strategy and artificial intelligence technology to study power engineering data processing. This paper proposes a mechanism for the survival time of cached content. The survival time is set according to the frequency of content requests and the distance of the content node, so that the cached content of downstream nodes close to the user has a longer time. At the same time, after the content in the upstream node expires, it can free up cache space for the rollback operation. Finally, this paper tests the system model of this paper through experimental research. The research results show that the power engineering data processing system based on dynamic adaptive caching strategy and artificial intelligence technology proposed in this paper has certain effects.

Automated Detection of coronaL MAss Ejecta origiNs for Space Weather AppliCations (ALMANAC)

AbstractAlerts of potentially hazardous coronal mass ejection (CME) are based on the detection of rapid changes in remote observations of the solar atmosphere. This paper presents a method that detects and estimates the central coordinates of CME eruptions in Extreme Ultraviolet data, with the dual aim of providing an early alert, and giving an initial estimate of the CME direction of propagation to a CME geometrical model. In particular, we plan to link the Automated detection of coronaL MAss ejecta origiNs for space weather AppliCations (ALMANAC) method to the CME detection and characterization module of the Space Weather Empirical Ensemble Package, which is a fully automated modular software package for operational space weather capability currently being developed for the UK Meteorological Office. In this work, ALMANAC is applied to observations by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). As well as presenting the method, a proof of concept test is made on a limited set of data associated with 20 halo CMEs recorded by the Coordinated Data Analysis Workshop (CDAW) catalog near the activity maximum of solar cycle 24. SDO/AIA data for each event is processed at 6 min cadence to identify the on‐disk location and time of each CME. The absolute mean deviance between the ALMANAC and CDAW source event coordinates are within 37.05 ± 29.71 min and 11.01 ± 10.39°. These promising results give a solid foundation for future work, and will provide initial constraints to an automated CME alert and forecasting system.

Calculating the sustainability of products based on their efficiency and function

<h2>Summary</h2> The planetary boundaries concept has identified limits that must be preserved to ensure a safe operating space for humanity. We are threatening, and in some cases have exceeded, these limits in part through unsustainable use of products and services. Life cycle assessments of individual products, while valuable in evaluating the environmental footprint of a product, lack inherent impact targets. Here, I propose performance-weighted environmental sustainability as a numerical indicator to determine if the environmental impacts of a product are sustainable. Using the example of a washing machine, its function (laundry) was used to normalize the environmental impact of its freshwater use. The results suggest that a UK washing machine using 33 L of water per wash cycle is sustainable. This metric makes it possible to determine acceptable environmental impacts for individual products based on what they are used for and to inspire sustainable product design.

Modeling and design optimization of master manipulator for robot-assisted minimally invasive surgery

In the minimally invasive surgical robot system, the surgeon controls the movement of instruments with master manipulators, which is a typical physical human-robot interaction system. In this paper, the surgeon is fully taken into consideration for structural design optimization. The kinematics model of the surgeon’s arm was established to describe the irregular shape of surgeon’s operation space; The surgeon console model was established to describe the relative position between the master manipulators and the surgeon’s arm. To make master manipulator could behavior great dexterity in surgery, the dexterity index of surgeon operation space was proposed. Combined with the minimum gravity torque index and the redundancy index, this multi-objective optimization problem was solved by Salp Swarm optimization algorithm. Compared with the pre-optimization master manipulator, the performances of the optimized manipulator are overall improved by 10.3%, 23.0%, and 41.2% respectively in animal experiment.

An improved path planning algorithm based on artificial potential field and primal-dual neural network for surgical robot

Safety and accuracy are essential for path planning in a surgical navigation system. In this paper, an improved path planning algorithm is proposed to increase the autonomous level of spine surgery robots for higher safety and accuracy. Firstly, the dynamic gravitational constant and piecewise repulsion function are adopted to improve the traditional Artificial Potential Field algorithm to solve the common issues of path planning, including local minimum, unable to reach the target near obstacles. To better control the pose of the end-effector in an operation space, the positions of the two endpoints of the end-effector are further constrained. Secondly, an improved Primal-Dual Neural Network with multiple constraints is proposed to minimize the joint angular velocity norm. The multiple constraints are formulated according to the planned path, the obstacle avoidance of the robot and the joint limits. Moreover, a real-time planned velocity scheme is applied to prevent the accumulation of position errors. The simulation results of the pedicle screw implantation demonstrate that the robot can find the collision-free trajectory and arrive at the target position in various complicated situations. More specifically, the error between two endpoints of the end-effector and the target pose is below 0.1 mm in reaching the surgical tool pose, while the maximum position error is around 0.05 mm when performing the planned path. Moreover, two experiments are conducted in the real-world to verify the proposed algorithm is effective in practice.

The Role of Microorganisms and Carbon-to-Nitrogen Ratios for Microbial Protein Production from Bioethanol.

With industrial agriculture increasingly challenging our ecological limits, alternative food production routes such as microbial protein (MP) production are receiving renewed interest. Among the multiple substrates so far evaluated for MP production, renewable bioethanol (EtOH) is still underexplored. Therefore, the present study investigated the cultivation of five microorganisms (2 bacteria, 3 yeasts) under carbon (C), nitrogen (N), and dual C-N-limiting conditions (molar C/N ratios of 5, 60, and 20, respectively) to evaluate the production (specific growth rate, protein and biomass yield, production cost) as well as the nutritional characteristics (protein and carbohydrate content, amino acid [AA] profile) of MP production from bioethanol. Under C-limiting conditions, all the selected microorganisms showed a favorable AA profile for human nutrition (average AA score of 1.5 or higher), with a negative correlation between protein content and growth rate. Maximal biomass yields were achieved under conditions where no extracellular acetate was produced. Cyberlindnera saturnus and Wickerhamomyces anomalus displayed remarkably high biomass yields (0.40 to 0.82 g cell dry weight [CDW]/g EtOHconsumed), which was reflected in the lowest estimated biomass production costs when cultivated with a C/N ratio of 20. Finally, when the production cost was evaluated on a protein basis, Corynebacterium glutamicum grown under C-limiting conditions showed the most promising economic outlook. IMPORTANCE The global protein demand is rapidly increasing at rates that cannot be sustained, with projections showing 78% increased global protein needs by 2050 (361 compared to 202 million tonprotein/year in 2017). In the absence of dedicated mitigation strategies, the environmental effects of our current food production system (relying on agriculture) are expected to surpass the planetary boundaries-the safe operating space for humanity-by 2050. Here, we illustrate the potential of bioethanol-renewable ethanol produced from side streams-as a main resource for the production of microbial protein, a radically different food production strategy in comparison to traditional agriculture, with the potential to be more sustainable. This study unravels the kinetic, productive, and nutritional potential for microbial protein production from bioethanol using the bacteria Methylorubrum extorquens and Corynebacterium glutamicum and the yeasts Wickerhamomyces anomalus, Cyberlindnera saturnus, and Metschnikowia pulcherrima, setting the scene for microbial protein production from renewable ethanol.

A Method of Evaluating Safe Operating Space: Focus on Geographic Regions, Income Levels and Developing Pathway.

Safe and Just Space (SJS) is a framework for determining the range where the use of natural resources within the Earth’s carrying capacity can maintain human well-being. However, there has been no systematic monitoring and evaluation of their sustainability across time and space. Here we developed and applied a model and a sustainable development human safe operation space (SDHSOS) index to assess the sustainability capacity and development path of 149 countries from 2000 to 2018. The results demonstrate that (1) The overall sustainable development capacity of all countries is at the middle or lower level and that it has increased over time. (2) The sustainability of natural and socio-economic dimensions and their degree of change show obvious geographic differences and income differences. (3) The national development path divided by income is characterized by a decline in natural environment dimensions and an increase in socio-economic dimensions, which mainly reflects a traditional development path model that promotes social welfare at the expense of the natural environment. This study suggests that nations can accurately identify development characteristics, expand their comparative advantages is the key to improving sustainable development capabilities.

Effect of Welding Sequence in Angular Distortion on Butt Joint GMAW Process

Over time, the industrial use of the welding process has grown in significance and is now one of the primary methods for joining metallic parts. During the welding process, metallurgical and structural modifications occur close to the welded joint. The thermal stresses and geometric distortions are undesirable, and they are a challenge to accurately forecast. Laboratory tests were conducted utilizing the GMAW method on S235JR steel as the base material with the goal of examining the impact of the welding sequence on angular distortion in butt joints when comparing three different welding sequences. Equipment that can determine coordinates in the operational space with metrological accuracy was used to measure distortions. As a result of metrological and statistical analyses, it was found that the sequence factor is shown to substantially influence the final distortions and that the symmetrical method results in less distortions followed by a one-step method.

Model Test of Micro-Pile Group Reinforcing High Steep Landslide

High steep landslides are a major concern for infrastructure construction in the mountainous areas of Western China. The micro-pile technique has been gradually used to prevent landslides, due to convenient construction and good performance. However, the application of the micro-pile technique on landslide prevention was generally implemented on the front edge of landslides, which is not applicable for the high steep landslides due to the limited operation space. In this study, a large-scale model test on the performance of a micro steep pile group on the prevention of high steep landsides was conducted in order to implement the micro-pile on the top of landslides. The force-deformation characteristics and failure modes of the steel pipe micro-pile group reinforcing high steep landslides were investigated. The test results showed that the landslide thrusts acting on the micro-pile group showed a triangle distribution. The maximum soil earth pressure was observed near the slip surface during landsides. The resistance of the micro pole group was distributed in an inverted triangle, mainly in the upper half of the loaded section. The sliding bed resistance is unevenly distributed along the height direction, and is larger near the slip surface. Once the landslide occurred, the force distribution of each row of steel pipe micro-piles was basically the same. The bending moment of the loaded section of the steel pipe micro-pile was mostly negative, with a larger bending moment in the range of eight times the pile diameter above the slip surface. The largest bending moment value is located at two times the pile diameter on the slip surface. On the other hand, the bending moment of the embedded section of the steel pipe micro-pile is mostly positive, showing a tension state with a maximum value at four times the pile diameter under the slip surface. This implies that the role of loaded and embedded sections of the micro-pile group on the landsides is different. The failure mode of the micro-pile group was mainly attributable to the bending failure within eight times the pile diameter above and below the slip surface.

Laparoscopic intersphincteric resection vs. transanal total mesorectal excision in overweight patients with low rectal cancer.

ObjectiveAnus-preserving surgery in overweight patients with low rectal cancer has been a challenge due to the narrow operating space. Intersphincteric resection (ISR) was once a standard therapeutic option for low rectal cancer. The effectiveness of transanal total mesorectal excision (taTME) in treating this group of patients remains uncertain as a new surgical strategy. The aim of this study was to evaluate the short-term effects of taTME with ISR in overweight patients with low rectal cancer.MethodsA total of 53 patients with low rectal cancer were treated with taTME in 31 cases and ISR in 22 cases. The surgery-related data, pathological manifestations of surgical specimens, postoperative recovery, and postoperative complications were compared.ResultsPatients in both groups completed the surgery successfully. There were no significant differences in operative time, blood loss, anastomotic distance from the anal verge and ileostomy between the two groups (P > 0.05). TaTME group performed or virtually finished resection of the rectal mesentery, and no positive cases of Circumferential Resection Margin (CRM) or Distal Resection Margin (DRM) were detected in either group. The number of lymph nodes found in surgical specimens did not change significantly between the two groups (P = 0.391). In the subgroup analysis, however, more lymph nodes were detected in female patients undergoing taTME than in male patients (P = 0.028). The ISR group took less time to remove the drainage tubes (P = 0.013) and the same results were obtained in both groups of male patients in the subgroup analysis (P = 0.011). There were no statistically significant differences in time to start liquid diet, time to remove catheters, time to start flatus, time to begin ambulation, postoperative hospital stay, and readmission within 30 days after surgery between the two groups (P > 0.05). However, female patients in the taTME group were initiated ambulation earlier than males in the subgroup analysis (P = 0.034). The difference was insignificant in the occurrence of postoperative complications between the two groups (P > 0.05).ConclusiontaTME is safe and feasible for the treatment of overweight patients with low rectal cancer.

Constraint-consistent task-oriented whole-body robot formulation: Task, posture, constraints, multiple contacts, and balance

We present a comprehensive formulation to the problem of controlling a high-dimensional robotic system involving complex tasks subject to a variety of constraints, obstacles, balance, and contact challenges. Using intuitive and natural representations, the approach is initiated by establishing individual objectives for a task and its constraints. Simple independent controllers using artificial potential fields are then designed for each objective to reach goals while enforcing the constraints. Dynamically consistent projections in nullspaces associated with task and constraint representations are employed to deliver a coherent whole-body robot control. In multi-link multi-contact tasks, contact forces produce both resulting and internal forces. Internal forces play a critical role in robot balance and stability, achieved in this framework through modeling and controlling virtual linkages that explicitly describe the relationship between active/passive contact force, resultant force, controlled/uncontrolled internal force for multi-link multi-contact underactuated robots. Control of contacts with the environment involves material considerations such as friction and geometric constraints. Potential barriers direct the selection of contact forces ensuring stability and balance. This approach of dynamic projection and the Virtual Linkage Model addresses robot underactuation. In addition, the framework introduces a coordinate completion mechanism to establish a generalized coordinates representation of the task, removing redundancy and maintaining the full operational space dynamics description. This enables task-space dynamic control based on the relevant inertial properties. We present the experimental validation on a physical humanoid platform.

Safety Compliant Control for Robotic Manipulator With Task and Input Constraints

Increasingly, robots are working in close proximity with humans, and in dynamically changing environments. We present a new control architecture that guarantees safety under such conditions, while simultaneously ensuring that task goals are satisfied. Our approach combines Control Barrier Functions (to provide safety guarantees) with Rapidly Exponentially Stabilizing Control Lyapunov functions (to satisfy task constraints and ensure exponential convergence). We formulate the problem completely in the operational space, using super ellipsoids to define safe sets which are dynamically adapted to restrict the robot’s operational space in response to moving obstacles (including humans). Control barrier functions, which can be implemented in real time using quadratic programming, ensure the forward invariance of these safe sets, while minimally perturbing prescribed control trajectories. We demonstrate our approach on a seven degree-of-freedom Kuka LBR iiwa robotic manipulator, both in a physics engine-based simulation and with real hardware experiments.

Learning Stable Vector Fields on Lie Groups

Learning robot motions from demonstration requires models able to specify vector fields for the full robot pose when the task is defined in operational space. Recent advances in reactive motion generation have shown that learning adaptive, reactive, smooth, and stable vector fields is possible. However, these approaches define vector fields on a flat Euclidean manifold, while representing vector fields for orientations requires modeling the dynamics in non-Euclidean manifolds, such as Lie Groups. In this paper, we present a novel vector field model that can guarantee most of the properties of previous approaches i.e., stability, smoothness, and reactivity beyond the Euclidean space. In the experimental evaluation, we show the performance of our proposed vector field model to learn stable vector fields for full robot poses as SE(2) and SE(3) in both simulated and real robotics tasks.

Robot-Assisted Retraction for Transoral Surgery

Tissue retraction is an important task in head and neck surgery to leave space for surgical operations. Because the contact between the retractor and soft tissue is not trivial to model, the retraction operation has not been well addressed by robots in modern robot-assisted surgery. We propose a human-robot collaboration approach to assist the retraction for transoral surgery. The surgeons only need to roughly place the retractors into the oral cavity and specify the recommended retraction force. Robot manipulators will automatically retract the tissues in a safe way. In order to keep the touching force safe, we employ a force-sensing system at the distal end of the retractor. By analyzing the real-time force sensor data, we propose a control strategy which combines active retraction angle compensation and passive torque compensation to adjust the retractor, further reducing potential slippage during the retraction. The proposed method ensures the retraction is adaptive to unknown perturbations of the human anatomy. Our system requires no extra recognition or calibration of the surgical scene or the human tissue models. The approach is validated with two robot manipulators and force-sensing retractors on a physical head phantom as well as a cadaveric experiment. We show that the robots stably retract the mouth under various configurations, where the relative error of the stable retraction force does not exceed 11.8%.

Understanding and addressing the planetary crisis of chemicals and plastics

Planetary functions are destabilized by the releases of large quantities and numbers of anthropogenic chemicals, which go beyond planetary boundaries and threaten the safe operating space for humanity. Here, we call for urgent action to mitigate these threats and identify opportunities for intervention along the impact pathway of anthropogenic chemicals, including plastics.

Rising agricultural water scarcity in China is driven by expansion of irrigated cropland in water scarce regions

Rising agricultural water scarcity in China is driven by expansion of irrigated cropland in water scarce regions