Strain analysis on the micro-nano-scale embedded asperities in the grinding process

Konstruiran je mikro-nano model za brušenje s fraktalnom površinom, kojim se razmatraju oštećenja materijala zbog istrošenosti i adhezivni učinci u postupku dodira. Dinamički se razmatraju i promjene u deformaciji hrapavosti tijekom brušenja. Za simuliranje područja deformacije u postupku brušenja primijenjena je metoda konačnih elemenata. Pokazano je da što je veća smična čvrstoća na graničnoj površini na istoj udaljenosti brušenja, to je veća ekvivalentna plastična deformacija, a gruba površina se lakše izlaže trošenju i kidanju. Maksimalna točka plastične deformacije određuje početno mjesto pojave pukotine, bilo na površini ili na nekoj udaljenosti od površine. Isto tako, što je veće jednako raspoređeno normalno opterećenje, to je veća maksimalna plastična deformacija hrapavosti na početku dodira, a to određuje i raniju pojavu inicijalnih pukotina. Nadalje, što je veća brzina brušenja, to je veća udaljenost na kojoj se dvije interaktivne dodirne površine počinju trošiti. Analizirajući raspodjelu područja deformacije ugrađene hrapavosti, istražuju se stvarni uzroci brušenja i trošenja materijala u mikro-nano mjerilu.A two-dimensional micro-nano grinding model with the fractal surface is constructed, which considers the wear-out failures of the materials and the adhesive effects in the contact process. Also, the strain changes of the asperity during the grinding are dynamically discussed. The finite element method is employed to simulate the strain field in the process of grinding. It is indicated that the larger the interfacial shear strength is, at the same grinding distance, the greater its equivalent plastic strain is, the easier the rough solid is prone to wear and tear. The maximum point of the plastic deformation determines the first place where the first cracks occur, either on the surface or at a certain distance from the surface. Also, the larger the normal even-distributed load is, the larger the maximum plastic deformation of the asperity at the initial contact time is, which determines an earlier occurrence time of the initial cracks. Furthermore, the greater the grinding rate is, the longer the distance that two interactively contacting asperities start to wear is. By studying the distribution of the strain field of the embedded asperities, the real causes why the materials are ground and worn at the scale of micro-nano are explored

SalienTime: User-driven Selection of Salient Time Steps for Large-Scale Geospatial Data Visualization

The voluminous nature of geospatial temporal data from physical monitors and simulation models poses challenges to efficient data access, often resulting in cumbersome temporal selection experiences in web-based data portals. Thus, selecting a subset of time steps for prioritized visualization and pre-loading is highly desirable. Addressing this issue, this paper establishes a multifaceted definition of salient time steps via extensive need-finding studies with domain experts to understand their workflows. Building on this, we propose a novel approach that leverages autoencoders and dynamic programming to facilitate user-driven temporal selections. Structural features, statistical variations, and distance penalties are incorporated to make more flexible selections. User-specified priorities, spatial regions, and aggregations are used to combine different perspectives. We design and implement a web-based interface to enable efficient and context-aware selection of time steps and evaluate its efficacy and usability through case studies, quantitative evaluations, and expert interviews.Comment: In Proceedings of the CHI Conference on Human Factors in Computing Systems (CHI'24), May 11-16, 2024, Honolulu, HI, US

Single-crystal elastic moduli, anisotropy and the B1-B2 phase transition of NaCl at high pressures: Experiment vs. ab-initio calculations

Single-crystal elastic moduli, Cij, and the B1-B2 phase transition of NaCl were investigated experimentally, using time-domain Brillouin scattering (TDBS), and theoretically, via density-functional-theory (DFT), to 41 GPa. Thus, we largely extended pressure range where Cij and elastic anisotropy of the solid are measured, including the first experimental data for the high-pressure B2 phase, NaCl-B2. NaCl-B1 exhibits a strong and growing with pressure anisotropy, in contrast to NaCl-B2. Theoretical values obtained using different advanced DFT functionals were compared with our measurements but no one could satisfactorily reproduce our experimental data for NaCl-B1 and NaCl-B2 simultaneously. For all available DFT results on the principal shear moduli and anisotropy, the deviation became pronounced when the degree of compression increased significantly. Similar deviations could be also recognized for other cubic solids having the same B1-type structure and similar bonding, such as CaO, MgO, or (Mg1-x,Fex)O. Furthermore, the available experimental data suggest that the B1-B2 phase transition of NaCl and the above mentioned compounds are governed by the Born stability criterion C44(P) - P > 0.Comment: 15 pages and 5 figures for the Manuscript, 10 pages and 7 figures for the Supplemen

Simultaneous Determination of Six Active Compounds in Yixin Badiranjibuya Granules, a Traditional Chinese Medicine, by RP-HPLC-UV Method

In this study, a sensitive, precise, and accurate HPLC-UV method was developed and validated to simultaneously determine the six analytes (luteolin-7-O-β-D-glucuronide, apigenin-7-O-β-D-glucuronide, diosmetin-7-O-β-D-glucuronide, acacetin-7-O-β-D-glucuronide, tilianin, and rosmarinic acid) in Yixin Badiranjibuya Granules, in which five analytes (i.e., luteolin-7-O-β-D-glucuronide, apigenin-7-O-β-D-glucuronide, diosmetin-7-O-β-D-glucuronide, acacetin-7-O-β-D-glucuronide, and rosmarinic acid) were determined for the first time in Yixin Badiranjibuya Granules, the content of tilianin in Yixin Badiranjibuya Granules was reported in other literatures, and the content of tilianin in our work was higher than that of the literature reports. The quality of 11 batch samples from four different manufacturers was evaluated using the proposed determination method. The contents of the six analytes were largely different among samples from various manufacturers. Therefore, this determination method can provide a scientific basis for quality evaluation and control of Yixin Badiranjibuya Granules

A new unsupervised pseudo-siamese network with two filling strategies for image denoising and quality enhancement

Digital image noise may be introduced during acquisition, transmission, or processing and affects readability and image processing effectiveness. The accuracy of established image processing techniques, such as segmentation, recognition, and edge detection, is adversely impacted by noise. There exists an extensive body of work which focuses on circumventing such issues through digital image enhancement and noise reduction, but this work is limited by a number of constraints including the application of non-adaptive parameters, potential loss of edge detail information, and (with supervised approaches) a requirement for clean, labeled, training data. This paper, developed on the principle of Noise2Void, presents a new unsupervised learning approach incorporating a pseudo-siamese network. Our method enables image denoising without the need for clean images or paired noise images, instead requiring only noise images. Two independent branches of the network utilize different filling strategies, namely zero filling and adjacent pixel filling. Then, the network employs a loss function to improve the similarity of the results in the two branches. We also modify the Efficient Channel Attention module to extract more diverse features and improve performance on the basis of global average pooling. Experimental results show that compared with traditional methods, the pseudo-siamese network has a greater improvement on the ADNI dataset in terms of quantitative and qualitative evaluation. Our method therefore has practical utility in cases where clean images are difficult to obtain

Study on pressure relief and permeability enhancement effect of cutting coal seam with diamond-bead wire saw

In order to explore the pressure relief and permeability enhancement effect around coal seam slot cut by diamond-bead wire saw, firstly, the mechanical model of a doubly clamped roof beam based on the stress of the slot roof was established to analyze the force characteristics of the roof beam and the characteristics of the sinking contact bottom of slot roof (referred to as the contact bottom). Besides, the self-designed physical similarity simulation test platform was used to carry out various similar simulation tests to analyze the stress and displacement changes of coal and rock strata above and below the slot after cutting the seam using wire saw with different process parameters. Finally, based on the FLAC3D numerical simulation and the development of a coal seam gas permeability calculation program, the distribution characteristics and periodic evolution laws of stress and permeability of coal and rock mass around the advancing slot of the coal working face were analyzed. The research shows that the wire saw cuts seams, which makes the stress around the slot redistribute, and the slot roof passes through three evolution forms of roof hanging, roof contact with the bottom, and continuous sinking with the advancement of the working face. When the roof does not touch the bottom, the upper and lower parts of the slot form a ‘U’-type pressure relief zone. The maximum deflection is at the center of the roof, which is also the first part to contact the bottom. After the roof contacts the bottom, the stress recovery occurs in the middle of the slot, which weakens the pressure relief and permeability enhancement effect of the slot. The larger the diameter of the diamond-bead wire saw is, the larger the ultimate span of the roof bottom is, the later the slot contacts the bottom, and the better the pressure relief effect is. With the same slot diameter, the second slot is added, and the pressure relief zone of the two slots is connected. The pressure relief effects promote each other, which weakens the stress recovery under the action of the two slots and increases the pressure relief range. When the slot advancing distance is long enough, due to the roof contacting the bottom, the pressure relief and permeability enhancement effect on both sides of the slot is better. The influence range of pressure relief is divided into stress concentration zone, pressure relief zone, stress recovery zone, pressure relief zone and stress concentration zone from left to right. The corresponding pressure relief zone and stress recovery zone have a better permeability enhancement effect

Frailty in hypertensive population and its association with all-cause mortality: data from the National Health and Nutrition Examination Survey

ObjectivesThis study aimed to investigate the relationship between frailty and all-cause mortality in hypertensive population.MethodsWe used data from the National Health and Nutrition Examination Survey (NHANES) 1999–2002 and mortality data from the National Death Index. Frailty was assessed using the revised version of the Fried frailty criteria (weakness, exhaustion, low physical activity, shrinking, and slowness). This study aimed to evaluate the association between frailty and all-cause mortality. Cox proportional hazard models were used to evaluate the association between frailty category and all-cause mortality, adjusted for age, sex, race, education, poverty–income ratio, smoking, alcohol, diabetes, arthritis, congestive heart failure, coronary heart disease, stroke, overweight, cancer or malignancy, chronic obstructive pulmonary disease, chronic kidney disease, and taking medicine for hypertension.ResultsWe gathered data of 2,117 participants with hypertension; 17.81%, 28.77%, and 53.42% were classified as frail, pre-frail, and robust, respectively. We found that frail [hazard ratio (HR) = 2.76, 95% confidence interval (CI) = 2.33–3.27] and pre-frail (HR = 1.38, 95% CI = 1.19–1.59] were significantly associated with all-cause mortality after controlling for variables. We found that frail (HR = 3.02, 95% CI = 2.50–3.65) and pre-frail (HR = 1.35, 95% CI = 1.15–1.58) were associated with all-cause mortality in the age group ≥65 years. For the frailty components, weakness (HR = 1.77, 95% CI = 1.55–2.03), exhaustion (HR = 2.25, 95% CI = 1.92–2.65), low physical activity (HR = 2.25, 95% CI = 1.95–2.61), shrinking (HR = 1.48, 95% CI = 1.13–1.92), and slowness (HR = 1.44, 95% CI = 1.22–1.69) were associated with all-cause mortality.ConclusionThis study demonstrated that frailty and pre-frailty were associated with an increased risk of all-cause mortality in patients with hypertension. More attention should be paid to frailty in hypertensive patients, and interventions to reduce the burden of frailty may improve outcomes in these patients