Stability Field Research Articles

The urban in ecology: a quantitative textual analysis of the scientific literature over a century

Many authors have described ‘urban ecology’ as a subfield of ecology that emerged in the 1990s and has expanded exponentially. We propose to take a step further and analyse the expansion of the ‘urban’ in ecology with a novel quantitative approach, with the aim to better understand the relationship between ecology and the urban. Previous quantitative assessments of the urban in ecology have focused on short to medium time spans (5 to 40 years) and on research coined as ‘urban ecology’, and have rarely considered the content of publications (e.g., vocabulary and topics) using quantitative methods. In this paper, we conduct a bibliometric assessment and an in-depth quantitative textual data analysis of a corpus of 960 articles published from 1922 to 2018 in 10 leading English-language journals in ecology and conservation biology. We address the following questions: (1) When and how have urban environments been integrated into ecological research during the past century? (2) What urban research topics have been investigated in ecology during the same period? (3) How have these research topics changed through time? Our results show that the urban was never entirely absent from publications in ecology. The quantitative analyses highlight three turning points (1970s, 1990s and 2000s) in the relationship between ecology and the urban. Moreover, they help visualize the shift from particularly scattered publications at the beginning of the period to publications characterized by a more homogeneous vocabulary, reflecting the stabilization of a research field focused on the urban in ecology.

Robotic purse-string suture technique for intracorporeal anastomosis using double-stapling technique in robotic resection of rectal and sigmoid colon cancer: a propensity score-matched analysis

BackgroundRobotic three-dimensional magnified visual effects and field of view stabilization have enabled precise surgical operations. Intracorporeal anastomosis in right-sided colorectal cancer surgery is expected to shorten operation times, avoid paralytic ileus, and shorten wound lengths; however, there are few reports of intracorporeal anvil fixation for intestinal anastomosis in left-sided colorectal cancer surgery. Herein, we introduce a simple, novel procedure for using robotic purse-string suture (RPSS) in intracorporeal anastomosis with the double-stapling technique in rectal and sigmoid cancer surgery and report short-term outcomes.MethodsFrom September 2022 to April 2024, 105 consecutive patients underwent robotic surgery with double-stapling technique anastomosis for rectal or sigmoid colon cancer at our institution. Their data were retrospectively analyzed. Intracorporeal anastomosis with the double-stapling technique using RPSS was performed in 26 patients (the RPSS group), while the double-stapling technique anastomosis with extracorporeal anvil fixation was performed in 79 patients (the EC group). A 1:1 propensity score-matched analysis was performed (matching criteria: sex, age, body mass index (BMI), tumor location and tumor size) using a caliper 0.3.In the RPSS group, after tumor-specific or total mesorectal excision, specimens were extracted from the umbilical wound with simultaneous anvil placement in the body cavity. The oral colonic stump was robotically excised and robotically circumferentially stitched with 3–0 Prolene in all layers. After anvil insertion into the stump, the bowel wall of the colon was completely sewn onto the central rod of the anvil. Reconstructions were anastomosed using the double-stapling technique.ResultsThe matched cohort contained 23 patients in each group. The RPSS group had significantly less bleeding than the EC group (p = 0.038). Super-low anterior resection (SLAR) in the RPSS group had shorter total operative times than those in the EC group (p = 0.045). The RPSS group experienced no perioperative complications greater than Clavien–Dindo grade III or any anastomosis-related complications.ConclusionsThe RPSS technique can be performed safely without any anastomosis-related complications and reduces the total operative times in SLAR and blood loss through total robotic surgery. This may be a useful modality for robotic colorectal surgery.

A full-bridge flux pump using two switches: numerical model and experimental prototype

Abstract High-temperature superconducting (HTS) magnets are promising in high field applications. However, due to inevitable joint resistance and flux creep, HTS magnets still face challenges in maintaining field stability in their closed-loop operation. HTS flux pumps can charge closed HTS magnets wirelessly, thus allowing lower cryogenic loading and more flexible arrangements in HTS magnet systems. In this work, a full-bridge flux pump using two AC field-controlled switches is proposed, which can charge HTS magnets during whole cycles. Therefore, the charging speed of the proposed full-bridge flux pump is at least one time larger than half-bridge flux pumps. A numerical model and an experimental prototype are developed to verify the working principle of the proposed full-bridge flux pump. Simulation and experimental tests are carried out to investigate the working characteristics of the proposed flux pump. The proposed flux pump has huge potential in the application scenarios where high charging speed is required.

The Effect of External Magnetic Field on Electron Scale Kelvin–Helmholtz Instability

We use particle-in-cell, fully electromagnetic, plasma kinetic simulation to study the effect of external magnetic field on electron scale Kelvin–Helmholtz instability (ESKHI). The results are applicable to collisionless plasmas when, e.g., solar wind interacts with planetary magnetospheres or a magnetic field is generated in AGN jets. We find that as in the case of magnetohydrodynamic (MHD) KHI, in the kinetic regime, the presence of an external magnetic field reduces the growth rate of the instability. In the MHD case, there is a known threshold magnetic field for KHI stabilization, while for ESKHI this is to be analytically determined. Without a kinetic analytical expression, we use several numerical simulation runs to establish an empirical dependence of ESKHI growth rate, Γ(B 0)ω pe, on the strength of the applied external magnetic field. We find the best fit is hyperbolic, Γ(B0)ωpe=Γ0ωpe/(A+BB¯0) , where Γ0 is the ESKHI growth rate without an external magnetic field and B¯0=B0/BMHD is the ratio of external and two-fluid MHD stability threshold magnetic field, derived here. An analytical theory to back up this growth rate dependence on the external magnetic field is needed. The results suggest that in astrophysical settings where a strong magnetic field pre-exists, the generation of an additional magnetic field by the ESKHI is suppressed, which implies that nature provides a “safety valve”—natural protection not to “over-generate” magnetic field by the ESKHI mechanism. Remarkably, we find that our two-fluid MHD threshold magnetic field is the same (up to a factor γ0 ) as the DC saturation magnetic field, previously predicted by fully kinetic theory.

The sensitivity of lowermost mantle anisotropy to past mantle convection

It is widely believed that seismic anisotropy in the lowermost mantle is caused by the flow-induced alignment of anisotropic crystals such as post-perovskite. What is unclear, however, is whether the anisotropy observations in the lowermost mantle hold information about past mantle flow, or if they only inform us about the present-day flow field. To investigate this, we compare the general and seismic anisotropy calculated using Earth-like mantle convection models where one has a time-varying flow, and another where the present-day flow is constant throughout time. To do this, we track a post-perovskite polycrystal through the flow fields and calculate texture development using the sampled strain rate and the visco-plastic self-consistent approach. We assume dominant slip on (001) and test the effect of the relative importance of this glide plane over others by using three different plasticity models with different efficiencies at developing texture. We compare the radial anisotropy parameters and the anisotropic components of the elastic tensors produced by the flow field test cases at the same location. We find, under all ease-of-texturing cases, the radial anisotropy is very similar (difference <2%) in the majority of locations and in some regions, the difference can be very large (>10%). The same is true when comparing the elastic tensors directly. Varying the ease-of-texture development in the crystal aggregate suggests that easier-to-texture material may hold a stronger signal from past flow than harder-to-texture material. Our results imply that broad-scale observations of seismic anisotropy such as those from seismic tomography, 1-D estimates and normal mode observations, will be mainly sensitive to present-day flow. Shear-wave splitting measurements, however, could hold information about past mantle flow. In general, mantle memory expressed in anisotropy may be dependent on path length in the post-perovskite stability field. Our work implies that, as knowledge of the exact causative mechanism of lowermost mantle anisotropy develops, we may be able to constrain both present-day and past mantle convection.

Corundum-quartz metastability: the role of silicon diffusion in corundum

The synthesis of the Al2SiO5 polymorphs kyanite, sillimanite and andalusite in a pure Al2O3–SiO2–H2O (ASH) system has long been known to be impeded. In order to decipher individual aspects of the reaction: corundum + SiO2aq, which repeatedly fails to produce thermodynamically stable Al2SiO5, we conducted experiments within the stability fields of kyanite and sillimanite (500–800 ℃; 0.2–1 GPa) with the aim of forming reaction coronas on corundum. Results showed that metastable corundum + quartz assemblages form persistently in pure ASH, even in Al2SiO5 seeded experiments, despite the presence of catalyzing fluid and evidence of fast reaction kinetics. Coronas on corundum spontaneously formed when additional components (Na, K, N, and Mg) were added to the experiment. In a similar experiment with baddeleyite (ZrO2) instead of corundum in silica saturated water, a zircon corona formed readily. This implies that nucleation and growth of Al2SiO5 is obstructed under conditions of Al and Si saturation in aqueous fluid, while both corundum and quartz saturated aqueous fluid are willing participants in other reactions towards stable corona formation. Instead of Al2SiO5 precipitation, an unexpected fluid-aided silica diffusion process into corundum was documented. The latter included the formation of nanometer wide hydrous silicate layers along the basal plane of the corundum host, which enhanced the silica diffusion rate drastically, leading to silica supersaturation in the host mineral, and ultimately to precipitation of quartz inside corundum. We conclude that the natural metastable assemblage of quartz and corundum is not necessarily the result of dry or fluid absent conditions, given that the aqueous fluid in experiments does not promote Al2SiO5 formation, but rather seems to support the formation and preservation of a metastable assemblage.

Characteristic Analysis of Electromagnetic Force in an HTS Field Coil Using a Performance Evaluation System

A performance evaluation system (PES) can experimentally test the structural stability and magnetic field effects of HTS coils against high magnetic fields and electromagnetic forces before mounting the HTS coils on a large-capacity rotating machine. This paper deals with the characteristic analysis of electromagnetic force in an HTS field coil for a 10 MW Class HTS Wind Power Generator using PES. Based on the designed 10 MW class HTS wind power generator, the HTS coils are manufactured and installed in the PES by a support structure, which is designed considering the electromagnetic force (torque) and heat loads in the HTS coil. To check the stress and deformation in the support structure caused by the electromagnetic force generated from the coil, strain gauge sensors were attached to the support structure and measured under full-load conditions. As a result, the maximum magnetic field and electromagnetic force are 2.8 T and 71 kN, respectively. Compared to the analysis results, the magnetic field and generated electromagnetic force in the HTS coil were the same under no-load and full-load conditions. These results will be effectively used to study and fabricate high magnetic field coils for HTS applications, as well as the PES being fabricated.

Enthalpy-based cascaded lattice Boltzmann method for conjugate heat transfer

Lattice Boltzmann (LB) methods for conjugate heat transfer are widely studied because of the simplicity and efficiency in dealing with complex boundary conditions. Recently, cascaded (or central-moments-based) LB (CLB) method has shown the potential to improve the stability of LB method. For conventional CLB method which is constructed through the continuous equilibrium distribution function, the temperature-based energy equation is recovered and solved. The continuity of temperature and heat flux at conjugate interface is unable to be accurately enforced without special treatment. To circumvent this deficiency, an enthalpy-based CLB method for conjugate heat transfer is developed in this work. In the proposed method, the enthalpy-based formulation of equilibrium moments is directly designed in the central-moment space, and the macroscopic quantity solved is converted from temperature to enthalpy. As demonstrated by the Chapman-Enskog multiscale analysis, the enthalpy-based energy equation can be recovered by the CLB equation. Compared with the conventional CLB method, the continuity condition for temperature and heat flux on the conjugate interface can be enforced automatically without special treatment. In addition, the proposed CLB method provides a new way to develop a CLB equation that can recover to a general convection-diffusion equation. Finally, the accuracy and stability of the temperature field are validated by benchmarks for the proposed enthalpy-based CLB method.

P-T evolution of HP migmatitic paragneiss from the Beni Bousera metamorphic unit (internal Rif, Northern Morocco) constrained by phase equilibria modelling and melt reintegration

ABSTRACT The high-pressure (HP) migmatitic paragneiss of the Beni Bousera metamorphic unit (BBMU) from the Beni Bousera Massif underwent granulite-facies metamorphism. They mainly consist of garnet, biotite, kyanite, sillimanite, cordierite, spinel, quartz, plagioclase, K-feldspar, rutile, ilmenite and graphite. These minerals form a sequence of metamorphic assemblages corresponding to five metamorphic events (M1, M2, M3, M4, and M5). The first three events correspond to a latest Carboniferous-earliest Permian metamorphic evolution, while the last two are retrograde and Alpine in age. The p-T conditions of these metamorphic events were estimated using pseudosection calculations in the MnNCKFMASTHO system. Following prograde stage conditions of 9.3–10.9 kbar and 630–665°C (M1 stage), the p-T evolution culminates in melting of the paragneiss which occurred mainly at HP conditions, within the kyanite stability field, at 11.8–14.2 kbar and 820–845°C (M2 pressure-peak); anatexis then continued at high to medium pressure (HMP), within the sillimanite stability field, at 9.9–11 Kbar and 840–860°C (M3 thermal-peak), accompanied by the production of very small proportions of melt. The prograde p-T segment of the inferred clockwise path is characterized by a pressurization related to a post-Variscan collisional event triggered by the closure of the Paleotethys Ocean, and is followed by the exhumation of the granulitic unit to mid-crustal depth, with slight coeval heating. The retrograde Alpine evolution is coeval with the final exhumation of the migmatitic paragneiss and underlying peridotites during back-arc extension related to the westward retreat of the Alpine subduction. It occurred under sub-solidus conditions from 9.5–10.7 kbar and 818–848°C (M4) to 4.9–5.85 kbar and 710–785°C (M5) and corresponds to a near-isothermal and strongly decompressive metamorphic evolution (ΔP ≈ 5 Kbar).

Co-incineration of multiple inorganic solid wastes towards clean disposal: Heat and mass transfer modeling, pollutant generation, and machine learning based proportioning

The co-disposal of solid waste by industrial kilns is presently attracting increasing attention. In this study, we investigate the co-disposal of solid waste, i.e. converter ash (CA), sintered ash (SA), blast furnace bag ash (BA), and municipal solid waste incineration fly ash (MSWIFA), under simulated blast furnace ironmaking conditions. The results show that it is feasible to use blast furnace to treat MSWIFA, but the stability of temperature field should be controlled in the process of co-disposal. With the increase of temperature, the conversion rate of NO decreased to 16.4%, and ZnFe2O4 became the main mineral composition, accounting for 75.53%. Corresponding to the flue gas corrosion condition of solid waste treatment, it is found that the corrosion resistance of the furnace material TH347H is better than 20G. Finally, based on the experimental data, the nested optimization algorithm of machine learning model is established to achieve the reverse output of optimal conditions. Overall, the study provides theoretical support and methodology guidance for the co-disposal of solid waste in blast furnaces in providing support for the further development of co-disposal of solid waste in industrial kilns.

Improved stabilization of loess soil using magnesium oxysulfate cement-based ecological composite binder

The technology of loess solidification plays a crucial role in addressing issues such as soil erosion, with the key material in this process being the loess stabilizer. To tackle the high energy consumption problem associated with traditional loess stabilizers primarily composed of Portland cement, this study employed a more ecological sustainable alternative by incorporating solid waste coal gangue and magnesium oxysulfate (MOS) cement as a binding agent for consolidating loess. The alterations in bulk density, porosity, mineral structure, and microstructure of the consolidated soil with different MOS content were systematically investigated and validated. The pore size of MOS-solidified loess decreased significantly to a range of 0.04–3.60 μm compared to 0.80–3.88 μm for pure loess. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and thermogravimetric (TG/DTG) analysis revealed that the addition of MOS binder generated hydrated magnesium silicate (M-S-H), Mg(OH)2, and a small amount of 5Mg(OH)2·MgSO4·7H2O phase which filled the gaps between soil particles and bonded them together effectively. When the proportion of MOS binder added reached 11 %, the compressive strength of stabilized loess after curing for 28 days increased up to 9.4 MPa. After immersion in water for 24 h, the strength only decreased by 5.3 %, with a softening coefficient of 94.7 %. The test results consistently indicate that the enhancement in mechanical properties can be attributed to the binding effect facilitated by MOS. The ecological composite binder based on coal gangue and MOS demonstrates great potential in the field of soil stabilization.

Successful subduction of oceanic plate after failed attempts in the Late Archean: Petrological and geochemical constraints

When and how plate tectonics started and evolved to the style as we know it today is a fundamental yet highly controversial question. Numerical geodynamic modelling predicts that the transition into plate tectonics in the Archean was episodic with possible alternation between success and failure of subduction. However, direct geological evidence for failed subduction is scarce. While this possibility has been suggested by numerical modelling, it is still lack of geological evidence. Here we present a combined study of zircon U-Pb ages and Hf-O isotopes, as well as whole-rock major and trace elements, for meta-igneous rocks from the Alxa Block in the westmost North China Craton (NCC). Two periods of Late Archean magmatism ca. 2.75 Ga and 2.5 Ga are identified to occur surrounding a pre-3.0 Ga continental nucleus. Geochemical analyses of the ca. 2.75 Ga meta-mafic and meta-felsic igneous rocks show two different modes of tectonic regime. The felsic rocks resemble typical Archean TTG (tonalite-trondhjemite-granodiorite) in composition, with variable εHf(t) values from -2.8 to 11.0 and δ18O values from 4.3 ‰ to 7.9 ‰. Petrogenetic modelling suggests that their magmatic source was the ca. 3.1–2.75 Ga oceanic crust that was hydrothermally altered at different temperatures and then mixed with the older continental crust and partially melted in lower crust in the garnet stability field. This requires tectonic accretion of the oceanic crust to the continental nucleus, signifying an attempted or failed subduction. On the contrary, the meta-mafic rocks exhibit arc-like trace element patterns and calc-alkaline evolution trend, indicating a metasomatic mantle source due to successful subduction of the oceanic slab to subarc depths. Taken together, the present results provide robust constraints on the behavior of oceanic slab at the Archean convergent margin, where successful oceanic subduction would be achieved after several failed attempts. Such failure-success processes of oceanic subduction may be applicable to the whole NCC and other cratons elsewhere in the world, reflecting the gradual maturation of plate tectonics in the Archean, consistent with predictions of numerical modelling.

Polydopamine-functionalized polyethersulfone membrane: A paradigm advancement in the field of α-amylase stability and immobilization

Biocatalytic membranes have great potential in various industrial sectors, with the immobilization of enzymes being a crucial stage. Immobilizing enzymes through covalent bonds is a complex and time-consuming process for large-scale applications. Polydopamine (PDA) offers a more sustainable and eco-friendly alternative for enzyme immobilization. Therefore, surface modification with polydopamine as mussel-inspired antifouling coatings has increased resistance to fouling. In this study, α-amylase enzyme was covalently bound to a bioactive PDA-coated polyethersulfone (PES) membrane surface using cyanuric chloride as a linker. The optimal activity of α-amylase enzyme immobilized on PES/PDA membrane was obtained at temperature and pH of 55°C and 6.5, respectively. The immobilized enzyme can be reused up to five reaction cycles with 55 % retention of initial activity. Besides, it maintained 60 % of its activity after being stored for five weeks at 4°C. Additionally, the immobilized enzyme demonstrated increased Michaelis constant and maximum velocity values during starch hydrolysis. The results of the biofouling experiment of various membranes in a dead-end cell demonstrated that the PES membrane’s water flux increased from 6722.7 Lmh to 7560.2 Lmh after PDA modification. Although α-amylase immobilization reduced the flux to 7458.5 Lmh due to enhanced hydrophilicity, compared to unmodified membrane. The findings of this study demonstrated that the membrane produced through co-deposition exhibited superior hydrophilicity, enhanced coating stability, and strong antifouling properties, positioning it as a promising candidate for industrial applications.

Dexmedetomidine versus labetalol for induced hypotension during functional endoscopic sinus surgery: a randomized, double-blind study

Background &amp; Objective: Functional endoscopic sinus surgery (FESS) is a surgical procedure for treating sinus diseases. Bleeding is a common concern during FESS, so maintaining hemodynamic stability and ensuring quality surgical field visibility is crucial for achieving the best outcomes. The present study compared the time taken to achieve target mean arterial pressure (MAP) when using dexmedetomidine or labetalol during FESS and assessed the quality of the surgical field to establish the better choice of the two. Methodology: The study was conducted as a prospective, randomized, double-blinded clinical study. Sixty patients classified as American Society of Anesthesiologists grade I or II, undergoing FESS under general anesthesia, were divided into two groups, each with 30 patients. Group D patients received dexmedetomidine and Group L received labetalol. The study aimed to maintain the mean arterial pressure (MAP) between 60-70 mmHg. The operative field visibility was assessed using the Fromme and Boezaart scoring system. Emergence time and postoperative first analgesic request time were also recorded. Results: The time taken to achieve target MAP (60-70 mmHg) was less in Group D (15.1 ± 0.2 min) than in Group L (18.2 ± 0.5 min), and it was statistically significant (P &lt; 0.05). Although insignificant, lower MAP were observed in the Group D than Group L. A significantly lower heart rate was observed at defined intervals in Group D than in Group L. The visibility of the surgical field in both groups has comparable results. The first analgesic request time was considerably longer in Group D (52.2 ± 1.9) compared to Group L (10.2 ± 2.1) (P &lt; 0.05). Conclusion: Dexmedetomidine provided better hemodynamic stability and operative field visibility than Labetalol during FESS. Abbreviations: FESS - Functional endoscopic sinus surgery; MAP - Mean arterial pressure; EtCO2 - end-tidal carbon dioxide Keywords: Dexmedetomidine; Labetalol; Controlled Hypotension; Mean Arterial Pressure Citation: Gupta S, Yadav I, Saxena A, Bagla RK, Nazir N. Dexmedetomidine versus labetalol for induced hypotension during functional endoscopic sinus surgery: a randomized, double-blind study. Anaesth. pain intensive care 2024;28(4):652−657; DOI: 10.35975/apic.v28i4.2507 Received: May 19, 2024; Reviewed: June 08, 2024; Accepted: June 08, 2024

The estrous cycle modulates hippocampal spine dynamics, dendritic processing, and spatial coding.

Histological evidence suggests that the estrous cycle exerts a powerful effect on CA1 neurons in mammalian hippocampus. Decades have passed since this landmark observation, yet how the estrous cycle shapes dendritic spine dynamics and hippocampal spatial coding in vivo remains a mystery. Here, we used a custom hippocampal microperiscope and two-photon calcium imaging to track CA1 pyramidal neurons in female mice over multiple cycles. Estrous cycle stage had a potent effect on spine dynamics, with heightened density during periods of greater estradiol (proestrus). These morphological changes were accompanied by greater somatodendritic coupling and increased infiltration of back-propagating action potentials into the apical dendrite. Finally, tracking CA1 response properties during navigation revealed enhanced place field stability during proestrus, evident at the single-cell and population level. These results establish the estrous cycle as a driver of large-scale structural and functional plasticity in hippocampal circuits essential for learning and memory.

Construction Stability Analysis and Field Monitoring of Shallowly Buried Large-Section Tunnels in Loess Strata

Construction Stability Analysis and Field Monitoring of Shallowly Buried Large-Section Tunnels in Loess Strata

Excellent low-E energy storage and fluorescence temperature sensing features in Bi0.5Na0.5TiO3-based transparent ceramics

Transparent dielectric ceramics with ultrafast discharge rates and gigantic power densities are ideal candidates for transparent pulse capacitors (TPCs). However, the requirement of a high external electric field and inferior temperature stability hinder practical applications. (Bi0.5Na0.5)TiO3-based ceramics exhibit large polarization and two characteristic dielectric peaks, easy to obtain high energy-storage density under low electric fields (low-E) and maintain stable energy-storage performance (ESP) within a wide temperature range. However, their low optical transmittance (T%) limits their development into TPCs. In this work, to concurrently obtain high T% and excellent ESP and stability under low-E conditions, we propose a collaborative optimization strategy for determining the regulations of grain size, bandgap energy and domain structure. The results show that the pellucidity and energy-storage characteristics improve with decreasing grain and domain sizes. A relatively high T% of 45.6 % (at 710 nm) and recoverable energy-storage density (Wrec ∼ 3.46 J cm−3 at 197 kV cm−1) are obtained for the (1-x)[0.85(Bi0.5-3yNa0.5-yYb3yHoyTiO3)-0.15SrZrO3]-xBaHfO3 ceramics. Additionally, the dielectric temperature stability also results in splendid storage temperature stability (ΔWrec/Wrec < 3.1 % in the range of 0–200 °C). Importantly, codoping Ho/Yb in the ceramics induces excellent fluorescence temperature sensing feature. The multifunctional TPCs have application potential in the field of search and rescue signal transmission, providing ideas for developing novel optoelectronic devices.

Separation and Evaluation of the Gradient Relaxation in the Atomic Comagnetometer

AbstractIn the atomic comagnetometer, nuclear spin relaxation is a core parameter that affects the magnetic field suppression ability and stability, and is influenced by various gradient fields. It is necessary to measure and separate the effects of different gradients on nuclear spin, which helps to effectively suppress them separately. This article proposes a periodic optical pumping method for separating and measuring polarization gradient relaxation and magnetic field gradient relaxation, considering the effects of pump light and applied magnetic field. The comprehensive influence model for pump light on transverse nuclear spin relaxation is established, and the measurement steps and parameter selection criteria for the proposed method considering signal decay characteristics are provided. Furthermore, the proportion of various gradient relaxations is quantified. This work provides an evaluation method for gradient relaxation suppression, supporting the improvement of the measurement sensitivity and stability of the atomic comagnetometer.

Evaluation Method of Magnetic Field Stability for Robotic Arc Welding Based on Sample Entropy and Probability Distribution

In this study, we analyzed the arc magnetic field to assess the stability of the arc welding process, particularly in robotic welding where direct measurement of welding current is challenging, such as under water. The characteristics of the magnetic field were evaluated based on low-frequency fluctuations and the symmetry of the signals. We used double-wire pulsed MIG welding for our experiments, employing Q235 steel with an 8.0 mm thickness as the material. Key parameters included an average voltage of 19.8 V, current of 120 A, and a wire feeding speed of 3.3 m/min. Our spectral analysis revealed significant correlations between welding stability and factors such as the direct current (DC) component and the peak power spectral density (PSD) frequency. To quantify this relationship, we introduced a novel approach using sample entropy and mix sample entropy (MSE) as new evaluation metrics. This method achieved a notable accuracy of 88%, demonstrating its effectiveness in assessing the stability of the robotic welding process.

Field stability of an Alvarez-type drift tube linear accelerator with small drift tubes

This study presents theoretical, simulation and experimental investigations of the field stability of a 7 MeV Alvarez-type drift tube linear accelerator (DTL) with small drift tubes (DTs). Although technical advances in permanent magnet quadrupoles make smaller DTs possible, resulting in higher shunt impedance, it is widely recognized that the DT-to-wall spacing must lie between ∼0.90 and ∼1.03 times a quarter wavelength (λ/4) to achieve field stability through post couplers (PCs). To enhance the shunt impedance of a DTL cavity, we decrease the outer diameter of the DTs and increase the inner diameter of the cavity, resulting in a DT-to-wall spacing of 1.16 times λ/4. A low-power experiment confirms that when the global tilt sensitivity slope is zero, the PC-to-DT distance is larger and there exists a stronger coupling between the PCs, resulting in a disturbed distribution of PC modes, where the frequencies of lower-order modes are overwhelmed by higher-order modes. The observed result is consistent with the analysis result given by the equivalent circuit theory and three-dimensional simulation. After field tuning by the trial-and-error method, the relative error of the axial electric field is within ±1.9% and the tilt sensitivity is within ±70%/MHz.