Position Operators Research Articles

Minimal lengths in 3D via the generalized uncertainty principle

We investigate an extension of the Generalized Uncertainty Principle (GUP) in three dimensions by modifying the three dimensional position and momentum operators in a manner that remains coordinate-independent and retains as much of the standard position-momentum commutators as possible. Moreover, we bound the physical momentum which leads to an effective minimal length in every coordinate direction. The physical consequences of these modified operators are explored in two scenarios: (i) when a spherically-symmetric wave function is ‘compressed’ into the smallest possible volume; (ii) when the momentum is directed in a single direction. In case (ii), we find that the three dimensional GUP exhibits interesting phenomena that do not occur in one dimension: the minimal distance in the direction parallel to a particle's momentum is different from the minimal distance in the orthogonal directions.

Quantizing the quantum uncertainty

The spread of the wave-function, or quantum uncertainty, is a key notion in quantum mechanics. At leading order, it is characterized by the quadratic moments of the position and momentum operators. These evolve and fluctuate independently from the position and momentum expectation values. They are extra degrees of quantum mechanics compared to classical mechanics, and encode the shape of wave-packets. Following the logic that quantum mechanics must be lifted to quantum field theory, we discuss the quantization of the quantum uncertainty as an operator acting on wave-functions over field space and derive its discrete spectrum, inherited from the sl2 Lie algebra formed by the operators xˆ2, pˆ2 and xp̂. We further show how this spectrum appears in the value of the coupling of the effective conformal potential driving the evolution of extended Gaussian wave-packets according to Schrödinger equation, with the quantum uncertainty playing the same role as an effective intrinsic angular momentum. We conclude with an open question: is it possible to see experimental signatures of the quantization of the quantum uncertainty in non-relativistic physics, which would signal the departure from quantum mechanics to a QFT regime?

Technique Tips: A Reflection on Mouth Mirrors: Types, Usage and Modifications

The mouth mirror is an essential tool in the dental armamentarium. Among its many functions, the most significant is being able to visualize aspects of the oral cavity that are not accessible visually with an appropriate operator posture. Various mouth mirrors are available and can differ in their design, head size and reflective surface. While in use, clinicians may encounter multiple circumstances that can hamper the quality of the reflected image. This in turn can negatively influence the diagnosis and treatment delivered. Hence, the purpose of this Technique Tip is to provide information on various designs of mouth mirrors as well as to provide solutions to counter the challenges associated with the use of mouth mirrors. Clinical relevance: Sharp, bright, reflected images may be provided for dental clinicians using simple methods and other equipment associated with the mouth mirror.

X-Ray Imaging in the Simulated Microgravity Environment of Parabolic Flight.

INTRODUCTION: The advancement of human spaceflight has made urgent the need to develop medical imaging technology to ensure a high level of in-flight care. To date, only ultrasound has been used in spaceflight. Radiography has multiple advantages over ultrasound, including lower operator dependence, more rapid acquisition, typically higher spatial resolution, and characterization of tissue with acoustic impedance precluding ultrasound. This proof-of-concept work demonstrates for the first time the feasibility of performing human radiographs in microgravity.METHODS: Radiographs of a phantom and human subject's hand, knee, chest, cervical spine, and pelvis were obtained aboard a parabolic flight in microgravity and simulated lunar gravity with various subject and operator positions. Control radiographs were acquired with the same system on the ground. These radiographs were performed with a Food and Drug Administration-approved ultra-portable, wireless, battery-powered, digital x-ray system.RESULTS: The radiographs of the phantom acquired in reduced gravity were qualitatively and quantitatively compared to the ground controls and found to exhibit similar diagnostic adequacy. There was no statistically significant difference in contrast resolution or spatial resolution with a spatial resolution across all imaging environments up to the Nyquist frequency of 3.6 line-pairs/mm and an average contrast-to-noise ratio of 2.44.DISCUSSION: As mass, power, and volume limitations lessen over the coming decades and the miniaturization of imaging equipment continues, in-flight implementation of nonsonographic modalities will become practical. Given the demonstrated ease of use and satisfactory image quality, portable radiography is ready to be the new frontier of space medical imaging.Lerner D, Pohlen M, Wang A, Walter J, Cairnie M, Gifford S. X-ray imaging in the simulated microgravity environment of parabolic flight. Aerosp Med Hum Perform. 2023; 94(10):786-791.

Aerial Gaze Target Recognition Based on Head and Eye Movements

Aerial gaze target recognition is an important step in aerial eye control interaction. In order to achieve accurate aerial gaze target recognition, the VT4LM recognition algorithm was constructed in this paper. By this algorithm, the facial images containing the eyes of the flight operators were first inputted into Vision Transformer (ViT) to extract the local features, and the head posture of the flight operators was inputted into four LSTMs to extract the global features. Then, the local and global features of the flight operators were inputted into three fully connected layers, two dropout layers and one softmax classifier. Finally, the recognition result of aerial gaze target was obtained. In this paper the effectiveness of the VT4LM recognition algorithm was verified through the identification of four aerial line-of-sight gaze targets named Head-up display, Accelerator push rod, Control lever and Rudder by four flight operators during simulated flight. The experimental results showed that the accuracy of the VT4LM algorithm for aerial gaze target recognition reached 89.29% and the Cross Entropy Loss was 1.45. Compared to the other three recognition methods, the VT4LM algorithm had the highest recognition accuracy and minimum loss. When using the VT4LM algorithm to detect four simulated flight operators staring at four aerial gaze targets, the recognition accuracy was all higher than 85.00%. It could be seen that the VT4LM algorithm had a good performance in aerial gaze target recognition.

Solusi Alternatif Pada Bilangan Tiga Digit Kuadrat

Some of the mistakes made by students when working on math problems in square numbers included misapplied material concepts and not being careful in the calculation process which resulted in wrong final results. This study aims to provide alternative solutions in calculating square numbers. In addition, this research required an understanding of previously studied mathematical concepts. By used the literature study method, namely the method of collected data by understood and studied theories from various literature related to research. The results of the study obtained an alternative formulation of three- digit square numbers. Let's say ABC is any squared of any three-digit number. Then by multiplyied the usual stacked, we got the result that ABC²= A²2AB2AC+B²2ABC² regreded the five positions that are underlined, the operations started from the last and last order to the front. If the position operation results in a number of more than one digit, then the number with the last digit is used in that position, while the remaining digits are added with the position operation in front of it. Until the position operation ends at the forefront. As a result of applied this method requires understood the concept of the operation and memorization in applied the method

Optimal positive end-expiratory pressure titration of intraoperative mechanical ventilation in different operative positions of female patients under general anesthesia

ObjectiveThis study aimed to compare the effectiveness and safety of different titrated methods used to determine individual positive end-expiratory pressure (PEEP) for intraoperative mechanical ventilation in female patients undergoing general anesthesia in different operative positions, and provide reference ranges of optimal PEEP values based on the titration. MethodsA total of 123 female patients who underwent elective open abdominal surgery under general anesthesia were included in this study. After endotracheal intubation, patients' body position was adjusted to the supine position, Trendelenburg positions at 10° and 20° respectively. PEEP was titrated from 20 cmH2O to 4 cmH2O, decreasing by 2 cmH2O every 1 min. Electrical impedance tomography (EIT), hemodynamic and respiratory mechanics parameters were continuously monitored and recorded. Optimal PEEP values and reference ranges were respectively calculated based on optimal EIT parameters, mean arterial pressure (MAP), and lung dynamic compliance (Cdyn). ResultsEIT-guided optimal PEEP was found to have higher values than those of the MAP-guided and Cdyn-guided methods for all three body positions (P < 0.001), and it was observed to more significantly inhibit hemodynamics (P < 0.05). The variable coefficients of EIT-guided optimal PEEP values were smaller than those of the other two methods, and this technique could provide better ventilation uniformity for dorsal/ventral lung fields and better balance for pulmonary atelectasis/collapse. The 95% reference ranges of EIT-guided optimal PEEP values were 4.6–13.8 cmH2O, 7.0–15.0 cmH2O and 8.6–17.0 cmH2O for the supine position, Trendelenburg 10°, and Trendelenburg 20° positions, respectively. ConclusionEIT-guided optimal PEEP titration was found to be a superior method for lung protective ventilation in different operative positions under general anesthesia. The calculated reference ranges of PEEP values based on the EIT-guided method can be used as a reference for intraoperative mechanical ventilation.

Analisis Ergonomika Pengoperasian Bagian Pencacah pada Mesin Pencacah Pakan Ternak Multiguna

The multi-purpose animal feed chopping machine is one of the feed chopping tools that many farmers use to help speed up the chopping of raw materials that will be used as animal feed. The chopping machine can be operated optimally if the machine is ergonomic so that it is safe and comfortable to operate. This study aims to analyze the ergonomics of a multi-purpose animal feed chopper in terms of anthropometry, operating workload and the level of work fatigue specifically for the chopper. This research uses quantitative methods which are supported by literature studies regarding the design of creating machine dimensions. The parameters in this study are: (1) anthropometric data consisting of Standing Finger Tip Height (TJUB), Standing Vertical Reach (JVB), and Standing Horizontal Reach (JHB); (2) the recommended weight limit that can be lifted by the operator (RWL), and (3) cardiovascular load (CVL). The research results stated that the height of the chopper hopper (100 cm) was classified as ergonomic because it was still between TJUB (66.10 cm) and JVB (183.95 cm). The operator's position from the hopper should not exceed JHB (66.00 cm). The recommended load limit (RWL) is 5.38 kg. Operation of the machine chopper section does not cause work fatigue with an average CVL of 10.71% (≤ 30%). Keywords: Anthropometry, CVL, Pulse Rate, RWL, Work Fatigue.

Thermality of the zero-point length and gravitational selfduality

It has been argued that the existence of a zero-point length is the hallmark of quantum gravity. In this paper, we suggest a thermal mechanism whereby this quantum of length arises in flat, Euclidean spacetime [Formula: see text]. For this, we consider the infinite sequence of all flat, Euclidean spacetimes [Formula: see text] with [Formula: see text], and postulate a probability distribution for each [Formula: see text] to occur. The distribution considered is that of a canonical ensemble at temperature [Formula: see text], the energy levels those of a 1-dimensional harmonic oscillator. Since both the harmonic energy levels and the spacetime dimensions are evenly spaced, one can identify the canonical distribution of harmonic-oscillator eigenvalues with that of dimensions [Formula: see text]. The state describing this statistical ensemble has a mean square deviation in the position operator, that can be interpreted as a quantum of length. Thus, placing an oscillator in thermal equilibrium with a bath provides a thermal mechanism whereby a zero-point length is generated. The quantum-gravitational implications of this construction are then discussed. In particular, a model is presented that realizes a conjectured duality between a weakly gravitational, strongly quantum system and a weakly quantum, strongly gravitational system.

Ballistic transport for limit-periodic Schrödinger operators in one dimension

In this paper, we consider the transport properties of the class of limit-periodic continuum Schrödinger operators whose potentials are approximated exponentially quickly by a sequence of periodic functions. For such an operator H , and X_H(t) the Heisenberg evolution of the position operator, we show the limit of \frac{1}{t}X_H(t)\psi as t\to\infty exists and is nonzero for \psi\ne 0 belonging to a dense subspace of initial states which are sufficiently regular and of suitably rapid decay. This is viewed as a particularly strong form of ballistic transport, and this is the first time it has been proven in a continuum almost periodic non-periodic setting. In particular, this statement implies that for the initial states considered, the second moment grows quadratically in time.

Quantum gravity, the cosmological constant, and parity transformation

One of the leading issues in quantum field theory and cosmology is the mismatch between the observed and calculated values for the cosmological constant in Einstein's field equations of up to 120 orders of magnitude. In this paper, we discuss new methods to potentially bridge this chasm using the generalized uncertainty principle (GUP). We find that if quantum gravity GUP models are the solution to this puzzle, then it may require the gravitationally modified position operator undergoes a parity transformation at high energies.

Modified 30-Degree Head-Up Tilt Park Bench Position in Semielective Posterior Fossa Surgery in a Patient with Pheochromocytoma

AbstractVon Hippel–Lindau (VHL) disease is a rare genetic disorder associated with the central nervous system and visceral organs. Pheochromocytomas occur in 10% of VHL patients, while cerebellar tumors are common tumors in VHL syndrome, with an incidence of 60%. The most common position for posterior fossa operations is the park bench or lateral decubitus position. These positions have primarily replaced the sitting position. However, the advantages of the supine position cannot be overlooked. The coexistence of pheochromocytoma and the cerebellar tumor may require modification in surgical position and anesthesia management in line with possible pathophysiological changes. We present the anesthesia management in posterior fossa surgery in patients with postponed pheochromocytoma surgery. The present case highlights the importance of a multidisciplinary team approach and anesthetic management.

Remarks on the quasi-position representation in models of generalized uncertainty principle

This note aims to elucidate certain aspects of the quasi-position representation frequently used in the investigation of one-dimensional models based on the generalized uncertainty principle (GUP). We specifically focus on two key points: (i) contrary to recent claims, the quasi-position operator can possess physical significance even though it is non-Hermitian, and (ii) in the quasi-position representation, operators associated with the position, such as the potential energy, also behave as a derivative operator on the quasi-position coordinate, unless the method of computing expectation values is modified. The development of both points revolves around the observation that the position and quasi-position operators share the same set of eigenvalues and are connected through a non-unitary canonical transformation. This outcome may have implications for widely referenced constraints on GUP parameters.

Lumbar lateral interbody fusion: step-by-step surgical technique and clinical experience.

Lateral lumbar interbody fusion (LLIF) is a minimally invasive surgical approach used to treat a variety of degenerative and deformity conditions of the lumbar spine such as advanced degenerative disease, degenerative scoliosis, foraminal and central stenosis. It has emerged as an alternative to the traditional posterior and anterior lumbar approaches with some potential benefits such as lower blood loss and shorter hospital stay. In this article, we provide our single institutional surgical experience including main indications and contraindications, a step-by-step surgical technique description, a detailed preoperative imaging assessment with a focus on magnetic resonance imaging (MRI) psoas anatomy, operative room (OR) setup and patient positioning. A descriptive surgical technical note of the following steps is provided: positioning and fluoroscopic confirmation, incision and intraoperative level confirmation, discectomy and endplate preparation, implant size selection and insertion and final fluoroscopic control, hemostasis check and wound closure along with an instructional surgical video with tips and pearls, postoperative patient care recommendations, common approach-related complications, along with our historical clinical institutional group experience. Finally, we summarize our research experience in this surgical approach with a focus on LLIF as a standalone procedure. Based on our experience, LLIF can be considered an effective surgical technique to treat degenerative lumbar spine conditions. Proper patient selection is mandatory to achieve good outcomes. Our institutional experience shows higher fusion rates with good clinical outcomes and a relatively low rate of complications.

Local projections on Einstein–Podolsky–Rosen states

The nonlocality of Einstein–Podolsky–Rosen (EPR) states is discussed in the framework of Weyl algebras. To include all possible limits of expectation values, the associated canonical cyclic representations of EPR states are considered. The momentum and position operators of individual particles do not exist in such representations, which explains the uncertainty principle in these cases. However, there are still one-to-one correspondences between the local Weyl operators associated with individual particles. The local observable algebras of individual particles are Type II1 von Neumann algebras and have numerous projection operators. The states obtained by applying local projection operations to the EPR states have perfect correlations between local subalgebras. Bell’s inequality is maximally violated by these states. The lack of atomic projections of Type II1 von Neumann algebras implies that the EPR states cannot be disentangled by local projection operations.

A Conditional Variational Auto-encoder Model for Reducing Musculoskeletal Disorder Risk during a Human-Robot Collaboration Task

In recent years, there has been a trend to adopt human-robot collaboration (HRC) in the industry. In previous studies, computer vision-aided human pose reconstruction is applied to find the optimal position of point of operation in HRC that can reduce workers’ musculoskeletal disorder (MSD) risks due to awkward working postures. However, the reconstruction of human pose through computer-vision may fail due to the complexity of the workplace environment. In this study, we propose a data-driven method for optimizing the position of point of operation during HRC. A conditional variational auto-encoder (cVAE) model-based approach is adopted, which includes three steps. First, a cVAE model was trained using an open-access multimodal human posture dataset. After training, this model can output a simulated worker posture of which the hand position can reach a given position of point of operation. Next, an awkward posture score is calculated to evaluate MSD risks associated with the generated postures with a variety of positions of point of operation. The position of point of operation that is associated with a minimum awkward posture score is then selected for an HRC task. An experiment was conducted to validate the effectiveness of this method. According to the findings, the proposed method produced a point of operation position that was similar to the one chosen by participants through subjective selection, with an average difference of 4.5 cm.

On outdoor testing procedures of large samples of PV modules

AbstractSTC power control of PV module supply requires testing large samples of modules with low uncertainty. This paper analyses the feasibility of outdoor measurements with the modules kept at their operating positions. The classical procedure of recording I‐V curves and translating them to STC in accordance with IEC‐60891:2021 using the cell temperature directly observed at a few points of the rear of the module entails expanded uncertainties larger than 3% (k = 2), which is too much for this procedure being accepted in quality controls with contractual consequences. A convenient procedure for overcoming this barrier consists in comparing the I‐V curves of a tested and a reference module of the same type, both working under the same operating conditions. The latter is mostly secured if they are in adjacent positions. However, when the procedure is applied to large samples of PV modules kept in their operating positions, the distance between both modules can reach tens of meters and significant inter‐module temperature differences can arise. A method for counterbalancing these differences consists of correcting the measured power values by considering the temperature difference observed at the back‐sheet centres of the tested and the reference modules. That also provides clues to estimating the uncertainty of the results. This procedure has been applied in seven testing campaigns, carried out at commercial PV plants. Dedicated instrumentation, based on two radio linked I‐V tracers, allowing the simultaneous measurement of the I‐V curves and of the temperature at the centres of the reference and the tested modules, has been developed for that. The resulting uncertainties are similar to those corresponding to high‐quality solar simulators and low enough for dealing, in practice, with strict quality control requirements.

Multi-objective multi-fidelity optimisation for position-constrained human-robot collaborative disassembly planning

ABSTRACT Human-robot collaborative disassembly lines are widely used by remanufacturing companies to disassemble end-of-life (EOL) products. When disassembling large-sized EOL products, each workstation on a disassembly line is generally divided into multiple operating positions, so that different operators can disassemble the same product at their respective positions at the same time, thereby greatly improving efficiency. This paper focuses on a position-constrained human-robot collaborative disassembly planning (PC-HRCDP) problem for the above-mentioned lines, including three subproblems of disassembly sequence planning, disassembly line balancing and robot path planning. A multi-objective mixed integer programming model for PC-HRCDP is developed to solve small-scale instances. Furthermore, a multi-objective multi-fidelity optimisation (MO-MFO) algorithm is proposed to solve large-scale instances. Comprehensive experiments are conducted based on 10 problem instances generated in this study. Experimental results show that the proposed MO-MFO is better than a high-fidelity optimisation algorithm in terms of running time. In addition, benefiting from the strategy of MO-MFO to allocate the limited high-fidelity computational budget to solutions in the two stages of multi-objective optimisation and optimal sampling, MO-MFO is significantly better than the existing representative multi-fidelity optimisation algorithms in terms of the hyper-volume and the inverted generational distance.

Application of intraoperative endoscopic in laparoscopic gastric cancer surgery

The application of intraoperative endoscopic in laparoscopic gastric cancer surgery can compensate for the limitations of a single laparoscopic mode that only relies only on serous vision, and work as the Chinese saying "four ounces can move a thousand pounds". Intraoperative endoscopy not only effectively helps to accurately locate the tumor boundary in real-time and achieve precise resection, but also enables real time and interactive inspection of the quality of esophagojejunal anastomosis, reduces postoperative complications such as anastomotic leakage and bleeding, and accelerates postoperative recovery. However, most centers in China do not emphasize the application of intraoperative endoscopy in laparoscopic gastric cancer surgery due to the lack of a good cooperation mechanism between the gastrointestinal surgery team and the digestive endoscopy team. Therefore, based on clinical practice experience, the author briefly discusses the application of intraoperative endoscopic in routine laparoscopic gastric cancer surgery, including pre-examination preparation operator position, endoscopic techniques, postoperative management, etc., covering application scenarios such as early tumor localization, confirmation of upper esophageal margin confirmation, anastomotic examination, biopsy of primary lesion specimens in neoadjuvant/conversion treatment cases. We hope that it will help gastroenterologists to better apply intraoperative endoscopy in laparoscopic gastric cancer surgery, and assist in precise resection and safe anastomosis of the operation.

Does the introduction of a cobot change the productivity and posture of the operators in a collaborative task?

Musculoskeletal disorders (MSDs) are the main occupational diseases and are pathologies of multifactorial origin, with posture being one of them. This creates new human-robot collaboration situations that can modify operator behaviors and performance in their task. These changes raise questions about human-robot team performance and operator health. This study aims to understand the consequences of introducing a cobot on work performance, operator posture, and the quality of interactions. It also aims to evaluate the impact of two levels of difficulty in a dual task on these measures. For this purpose, thirty-four participants performed an assembly task in collaboration with a co-worker, either a human or a cobot with two articulated arms. In addition to this motor task, the participants had to perform an auditory task with two levels of difficulty (dual task). They were equipped with seventeen motion capture sensors. The collaborative work was filmed with a camera, and the actions of the participants and co-worker were coded based on the dichotomy of idle and activity. Interactions were coded based on time out, cooperation, and collaboration. The results showed that performance (number of products manufactured) was lower when the participant collaborated with a cobot rather than a human, with also less collaboration and activity time. However, RULA scores were lower-indicating a reduced risk of musculoskeletal disorders-during collaboration with a cobot compared to a human. Despite a decrease in production and a loss of fluidity, likely due to the characteristics of the cobot, working in collaboration with a cobot makes the task safer in terms of the risk of musculoskeletal disorders.