Preparation and Anti⁃arc Erosion Property of Ag Matrix Electrical Contact Material Reinforced by Novel Ti_(2)Cd

Due to their outstanding electrical contact properties,Cd-containing silver-matrix electrical contact materials can meet the requirements of high stability and long life for military defense and aerospace applications.In order to further reduce the Cd content under the premise of meeting the high-performance requirements,in this study,high-purity intermediate Ti_(2)Cd powder of MAX phase(Ti_(2)CdC)was synthesized with a pressureless technique and then applied to reinforce the Ag matrix.The Cd content of the as-prepared Ag/Ti_(2)Cd composites was actually reduced by 38.31%compared with conventional Ag/CdO material.Based on the systematic study of the effect of heat treatment temperature on the physical phase,morphology,interface and comprehensive physical properties of Ag/Ti_(2)Cd composites,the preferred samples(heat treated at 400°C for 1 h)showed high density(97.77%),low resistivity(2.34μΩ·cm),moderate hardness(90.8HV),high tensile strength(189.9 MPa),and exhibited good electrical contact performance after 40000 cycles of arc discharging under severe conditions(DC 28 V/20 A).The results of microscopic morphological evolution,phase change and elemental distribution of the electrical contact surface show that the combination of high stability of Ti_(2)Cd reinforcing phase,good interfacial bonding with Ag matrix and improved melt pool viscosity in the primary stage of arc erosion,results in low and stable contact resistance(average value 13.20 mΩ)and welding force(average value 0.6 N),low fluctuation of static force(2.2-2.5 N).The decomposition and absorption energy of Ti_(2)Cd and the arc extinguishing effect of Cd vapor are the main reasons for the stable arcing energy and arcing time of electric contacts in the late stage of arc erosion.

Diagnostic implications of neutrophil-to-lymphocyte ratio,platelet-tolymphocyte ratio,and systemic immune-inflammatory index for gastric carcinoma

BACKGROUND The diagnosis of gastric carcinoma(GC)is essential for improving clinical outcomes.However,the biomarkers currently used for GC screening are not ideal.AIM To explore the diagnostic implications of the neutrophil-to-lymphocyte ratio(NLR),platelet-to-lymphocyte ratio(PLR),and systemic immune-inflammatory index(SII)for GC.METHODS The baseline data of 133 patients with GC and 134 patients with precancerous gastric conditions admitted between January 2022 and December 2023 were retrospectively analyzed.The information on peripheral blood platelet,neutrophil,and lymphocyte counts in each patient was collected,and the NLR,PLR,and SII levels of both groups were calculated.Additionally,multivariate logistic regression analysis was conducted,and the diagnostic implications of NLR,PLR,and SII in differentiating patients with precancerous gastric conditions,compared with those with GC,were analyzed through receiver operating characteristic(ROC)curves.RESULTS The data indicated that NLR,PLR,and SII had abnormally increased levels in the patients with GC.Gender and body mass index were risk factors for the occurrence of GC.ROC data revealed that the areas under the curve of three patients with precancerous gastric conditions,who were differentiated from those with GC,were 0.824,0.787,and 0.842,respectively.CONCLUSION NLR,PLR,and SII are all abnormally expressed in GC and have diagnostic implications,especially when used as joint indicators,in distinguishing patients with precancerous gastric conditions from those with GC.

Preoperative serum total bilirubin-albumin ratio as a prognostic indicator in patients with hepatitis-related cirrhosis after splenectomy

BACKGROUND Splenectomy is an effective yet invasive intervention for alleviating portal pressure in patients with hepatitis cirrhosis.However,the current prognostic indicators for predicting long-term overall survival of these patients have several limitations.AIM To assess the potential of preoperative total bilirubin-albumin(B/A)ratio as a prognostic indicator for patients with hepatitis cirrhosis undergoing splenectomy.METHODS A total of 257 patients diagnosed with hepatitis cirrhosis were retrospectively enrolled in the study.Normality test,t-test,Wilcoxon test,χ2 test,or Fisher’s exact test was employed to analyze the intraoperative and postoperative conditions of the patients.Receiver operating characteristic(ROC)curve analysis was utilized to depict the 10-year overall survival rate.RESULTS During the follow-up period,85.99%of the patients survived,with a median survival time of 64.6 months.Multivariate analysis revealed that total serum B/A ratio was an independent risk factor for overall survival(P=0.037).ROC curve analysis demonstrated that a B/A ratio of 0.87 was the optimal cut-off value.Consequently,the patients were categorized into two groups:High B/A group(n=64)and low B/A group(n=193).The median follow-up time for the high B/A group and low B/A group was 56.8 months and 67.2 months,respectively(P=0.045).Notably,the high B/A group exhibited a significantly lower 10-year overall survival compared to the low B/A group(P<0.001).Patients with hepatocellular carcinoma(HCC)had lower overall survival rates.Patients with a high B/A ratio exhibited a lower overall survival than those with a low B/A rate in the overall cohort and the subgroups of patients with HCC or not,early Child-Pugh grade,low albumin-bilirubin grade,and model for end-stage liver disease score≥10(log-rank test,P<0.001 for all).CONCLUSION The B/A ratio can serve as an effective prognostic indicator for overall survival in patients with hepatitis B virusrelated cirrhosis following splenectomy,and a higher B/A ratio may suggest a poorer prognosis.

Prognostic value of preoperative fibrinogen to albumin ratio in predicting postoperative outcomes in patients with gallbladder cancer

BACKGROUND Gallbladder cancer(GBC)is known for its poor prognosis and challenging management.The preoperative fibrinogen to albumin ratio(FAR)has been proposed as a potential prognostic marker for predicting postoperative outcomes in GBC patients,but its efficacy and prognostic value remain underexplored.AIM To evaluate the prognostic value of preoperative FAR in GBC outcomes.METHODS This retrospective cohort study included 66 patients who underwent curative surgery for GBC at our institution from January 2018 to January 2022.Preoperative FAR values were obtained within one week prior to surgery.Patients were followed through outpatient visits or telephone interviews,with overall survival(OS)as the primary endpoint.Statistical analyses,including receiver operating characteristic curve analysis and Kaplan-Meier survival estimates,were performed using SPSS software(version 27.0).RESULTS The cohort consisted of 36 male and 30 female patients,with a mean age of 61.81±8.58 years.The optimal FAR cut-off value was determined to be 0.088,with an area under the receiver operating characteristic curve of 0.7899,sensitivity of 68.96%,and specificity of 80.01%.Patients with FAR≤0.088 showed significantly better survival rates(1-year:60.5%,2-year:52.6%,3-year:25.9%)and a median OS of 25.6 months(95%confidence interval:18.8-30.5 months),compared to those with FAR>0.088 who had a median OS of 10.8 months(95%confidence interval:6.3-12.9 months).CONCLUSION Lower preoperative FAR is associated with longer OS in GBC patients,confirming its potential as a valuable prognostic indicator for improving outcome predictions and guiding patient management strategies in gallbladder cancer.

A Novel Ideal Ohmic Contact SiGeC/Si Power Diode with Graded Doping Concentration

A novel structure of ideal ohmic contact p^＋ （SiGeC）-n^- -n^＋ diodes with three-step graded doping concentration in the base region is presented, and the changing doping concentration gradient is also optimized. Using MEDICI, the physical parameter models applicable for SiGeC/Si heterojunction power diodes are given. The simulation results indicate that the diodes with graded doping concentration in the base region not only have the merit of fast and soft reverse recovery but also double reverse blocking voltage,and their forward conducting voltage has dropped to some extent,compared to the diodes with constant doping concentration in the base region. The new structure achieves a good trade-off in Qs-Vf-Ir ,and its combination of properties is superior to ideal ohmic contact diodes and conventional diodes.

EFFECT OF INVOLUTE CONTACT RATIO ON THE DYNAMIC PERFORMANCE OF SPUR GEAR WITH NOTOOTH PROFILE MODIFICATION

The effect of involute contact ratio on the torsional vibration behavior ofspur gear-pair is studied analytically through a mass-spring model. The tooth stiffness in model notonly has a relation with time, as many prior studies presented, but, more important, with involutecontact ratio (ICR) as well. The ICR embodies its impact on the spur gear's dynamic performancethrough changing the proportion of tooth stiffness when there are n+1 teeth in contact to toothstiffness when there are n teeth in contact. A couple of curves about impact of ICR on the gear'sdynamic performance are presented, and they clearly demonstrate that the model can accuratelydescribe the effects of ICR on dynamic transmission error. Finally, some conclusions useful toreduce vibration and noise of gear-pair are proposed.

基于改进Ratio统计量的重尾AR(p)时间序列均值变点检验

文章提出两个改进的Ratio统计量来研究重尾AR(p)时间序列均值变点检验问题,在原假设下推导了统计量的渐近分布,且在备择假设下证明了其一致性。由于重尾指数未知且难以估计,因此结合Wild Bootstrap重抽样方法来确定渐近分布的临界值;在均值变点存在的情形下,给出了变点位置的一致估计量。数值模拟结果表明:统计量的临界值均不受重尾指数和自回归系数的影响,其经验水平和经验势均取得满意的效果;尤其在原假设下,积分型Ratio统计量的经验水平表现出更好的稳健性,而在备择假设下,最值型Ratio统计量则具备更好的显著性。最后,基于一组股票数据,从实际应用角度进一步阐明所提方法的有效性和可行性。

COMMON DEFINITION FOR END-SURFACE CONTACT RATIO OF GEARS AND ITS APPLICATIONS

Common definition and calculating expressions of end-surface contact ratiofor all type of gears are put forward, and with calculation expressions for involute gears,micro-segments profile gears, and sine-curved profile gears being discussed. The end-surface contactratio of gears is defined as the ratio of the action angle (the rotation angle of gear from gear-into gear-out for one pair of teeth) to the rotation angle per pitch (or central angle per tooth).According to the theory of gearing, equation of the meshing line can be deduced from the toothprofiles of basic rack. Having obtained the equation of the meshing line, and being given theaddendum outline of the gears, the contact ratio can be calculated with the calculation expressions.For the involute gears, this definition has same effect as the well-known definition: ratio of thecontact line to the base pitch. This definition of contact ratio is also suitable to othernon-involute gears, such as micro-segments profile gears, sine-curved profile gears, and can givemore reliable results.

Arc erosion of AgSnO_2 electrical contacts at different stages of a break operation

Arc erosion studies are conducted on AgSnO2 contact materials at different stages in the break operation. A resistive load arrangement is used with up to 42 V DC at 24 A and a constant contact opening velocity. The arc current is terminated at different stages as the arc is drawn between the contacts enabling a study of the arcing phenomena up to that point. Surface profiling of the contacts is conducted to determine the extent of erosion at the different stages as the arc is drawn. Spectral analysis is also conducted on the arc and then related to the extent of erosion. The results show that particular features occur at different stages as the arc is drawn. As the arc is initially established, it goes through an ＂Arc Generation＂ regime where the arc roots are small and immobile on both the anode and the cathode. Material transfer occurs mainly from anode to cathode. The spectral analysis indicates that Sn and O species dominate the arc followed by the Ag species. As the arc is drawn further and enters the ＂Arc Degeneration＂ regime, the anode undergoes significantly larger erosion than the cathode. Also, both contacts indicate that multiple arc roots have formed, which are highly mobile in the later stages of the discharge. The spectral analysis indicates that Ag and N species are in high concentrations compared to other species. The mechanisms of erosion and deposition are discussed in relation to the species within the arc discharge. For the complete break operation, it is found that the anode undergoes major erosion, and it is thought that the gaseous ions species do not dominate the arc under these conditions of short arcs and voltage 〈42 V to cause cathode erosion.

Preparation and microstructure characterization of a nano-sized Ti^(4+)-doped AgSnO_2 electrical contact material

A Ti^4＋-doped nano-structured AgSnO2 material was prepared using sol-gel method and characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, and scanning electron microscopy （SEM）. The results show that Ti^4＋ cations are successfully doped into the crystal lattice of SnO2, and thus significantly improve the electrical conductivity of the sample. Furthermore, the coating of Ag on Ti^4＋-doped SnO2 nano-sized particles enhances the surface wettability and enables the resulting AgSnO2 material to have better mechanical properties.

Experiment and finite element method analysis mass erosion and transfer of Ag/La_2NiO_4-based electrical contacts during operation

A uniform transient temperature field model of electrical contacts operation was found by analyzing the process of closing arc constriction resistance Joule heat ~ breaking arc. Essential parameters of Ag/La2NiO4 electrical contact material for transient temperature field calculation were obtained through tests of electrical contact experimental instrument under 18 V DC in different cur- rents, other correlation experiments, and calculation anal- ysis. The finite element method was applied to solve the transient temperature field, and the features and distribution of the transient temperature field were obtained. The condition of material erosion and mass transfer can be forecasted by those calculation results. It is beneficial to research about the lifetime of Ag/La2NiO4 electrical material.

Effect of contact angle and helix angle on slide-roll ratio under the accelerated motion state of ball screw mechanism

To study the effect of the contact angle and helix angle on slide-roll ratio at the ball contact points under the accelerated motion state of ball screw mechanisrm(B S M),the curve theory in differential geometry a d the homogeneous transformation matrix ae used to establish the acceleration kinematics model of BSM.The model can be used to describe the accelerated motion relationships among the screw,balls and nut,calculate the acceleration of relative motion at the contact points between the balls and raceways,and analyze five accelerated motion rules between the balls and raceways.It also conducts a simulation analysis of the slide-roll ratio relationship between the accelerations at the ball center and the contact point of ball under different contact angles and helix angles.As shownby the analysis,with the increase in the BSM’s contact angle,the slide-roll ratio at the contact points decreases,and the contact angle has a relatively significant effect on the slide-roll ratio.However,with the decrease in the BSM’helix angle,the slide-roll ratio at the contact points decreases,and the helix angle has a relatively insignificant effect on the slide-roll ratio.By measuring the accelerations of both the screw and nut under the accelerated motion state,it also verifies the existence of the slide-roll mixed motion at the ball contact point A between the ball and the screw racewayand pure rolling at the ball contact point B between the ball and the nut raceway during the accelerated motion.

Aberration changes of the corneal anterior surface following discontinued use of rigid gas permeable contact lenses

AIM: To record aberrations with a corneal topographic device on the anterior surface of the cornea at different time-points prior to wearing and following discontinued use of rigid gas permeable (RGP) contact lenses. The effect of wearing RGP on the anterior surface of the cornea was discussed to provide guidance for clinical refractive error correction.METHODS: The study objects were 24 eyes from 24 patients. All patients underwent identical examination procedures prior to lens use, as well as afterwards, including slit-lamp examination, non-contact tonometer measurement, computer optometry and corneal curvature measurement, subjective refraction test, and corneal topography analysis. The patients wore contact lenses everyday for 1 month and then discontinued. Corneal topographies were recorded at certain time points of 30 minutes, 1 day, 3, 7 and 14 days following use.RESULTS: Total corneal aberration at each time point following discontinued use of RGP contact lenses was less than the time point prior to use. Detailed results were as follows: root mean square (RMS) (pre)=(1.438± 0.328)μm, RMS (30 minutes) =(1.076 ±0.355)μm, RMS (1 day) =(1.362 ±0.402)μm, RMS (3 days) =(1.373 ±0.398)μm, RMS (7 days) =(1.387 ±0.415)μm, and RMS (14 days) = (1.430±0.423)μm. Results showed that at 30 minutes after discontinued use of RGP contact lenses, almost all 2 ndand 3 rd-order aberrations change. Quadrafoil Z10 and spherical Z12 of the 4 th-order were also changed. Alterations to Z5, Z6, and Z12 at 1 day after discontinued use were significant differences compared with the time period prior to RGP use: Z5 and Z6 decreased, and Z12 increased slightly. Z5 and Z6 remained decreased at 3 days after discontinued use, but Z9 and Z10 continued to increase and Z12 returned to levels prior to RGP use. At 14 days after discontinued use, all aberrations were notsignificantly different from the values prior to use.CONCLUSION: The use RGP contact lenses greatly reduced total aberration of the anterior surface of the cornea. Changes to 2 ndand 3 rd-order aberrations (including Z3, Z4, Z5, Z6, Z7, and Z8) were more significant. Following discontinued use of RGP contact lenses, the majority of lower order aberrations returned to original levels in a short period of time. During this process, a transient higher order aberration appeared, but all changes disappeared within 14 days after discontinued use of RGP contact lenses.

Mechanism of contact angle saturation and an energy-based model for electrowetting

Electrowetting,as a well-known approach to increasing droplet wettability on a solid surface by electrical bias,has broad applications.However,it is limited by contact angle saturation at large voltage.Although several debated hypotheses have been proposed to describe it,the physical origin of contact angle saturation still remains obscure.In this work,the physical factors responsible for the onset of contact angle saturation are explored,and the correlated theoretical models are established to characterize electrowetting behavior.Combination of the proper 3-phase system employed succeeds in dropping the saturating contact angle below 25？,and validates that the contact angle saturation is not a result of devicerelated imperfection.

Migration of Some Elements and Radionuclides across aGranite-Granite Contact Zone: A Natural Analoguefor Safe Disposal of High-Level Radwastes

Abstract Elements and natural radionuclides in the contact zone of two granites with different ages would migrate from one to the other because of the difference in their chemical contents and later water-rock interactions. This migration could serve as an analogue for the near-field process of radwastes in a high-level radwaste deep geological disposal repository.

Spin Polarization at Organic-Ferromagnetic Interface： Effect of Contact Configuration

Based on ab initio theory, the interracial spin polarization of a benzene-dithiolate molecule vertically adsorbed on a nickel surface is investigated by adopting different microscopic con- tact configurations. The results demonstrate a strong dependence of the interfacial spin polarization on the contact configuration, where the sign of spin polarization may vary from positive to negative with the change of contact configuration. By analyzing the projected density of states, an interracial orbital hybridization between the 3d orbital of the nickel atom and the sp3 hybridized orbital of the sulfur atom is observed. We also simulated the interracial adsorption in mechanically controllable break junction experiments. The magne- toresistance obtained from Julliere model is about 27% based on the calculated interracial spin polarization, which is consistent with experimental measurement.

Comparation of effectiveness of silicone hydrogel contact lens and hydrogel contact lens in patients after LASEK

AIMTo conduct a comparative study of effectiveness of silicone hydrogel contact lens and hydrogel contact lens, which are used in patients after laser-assisted subepithelial keratomileusis (LASEK).METHODSSixty-three patients (121 eyes) with a spherical equivalent ≤-5.0 D were chosen after undergoing LASEK in 2012 at Guangdong General Hospital. They were randomly divided into 2 groups. The silicone hydrogel group included 32 cases (61 eyes) that wore silicone hydrogel contact lenses for 4-6d after the operation, while the hydrogel group included 31 cases (60 eyes) who wore hydrogel contact lenses for 4-6d after the operation. Patients' self-reported postoperative symptoms (including pain, photophobia, tears, and foreign body sensation) were evaluated. The healing time of the corneal epithelium, the visual acuity of patients without contact lens after epithelial healing, and the incidence of delayed corneal epithelial shedding were also assessed. The follow-up time was 1mo.RESULTSPostoperative symptoms were milder in the silicone hydrogel group than in the hydrogel group. There were significant differences in pain, foreign body sensation, and photophobia between the 2 groups (P<0.05), although there was no significant difference in postoperative tearing (P>0.05). The healing time of the corneal epithelium in the silicone hydrogel lens group was markedly shorter than that in the hydrogel group (4.07±0.25 vs 4.33±0.82d, t=2.43, P=0.02). Visual acuity without contact lenses after healing of the corneal epithelium was better in the silicone hydrogel group compared with the hydrogel group (χ2=7.76, P=0.02). There was no significant difference in the occurrence of delayed corneal epithelial shedding between the 2 groups (P>0.05).CONCLUSIONPatients with LASEK using silicon hydrogel contact lenses had less discomfort and shorter corneal epithelial healing time compared with those using hydrogel contact lenses, suggesting that silicon hydrogel contact lenses may be considered to be a better choice of bandage contact lens after LASEK.

Comparison of the effects of first and second generation silicone hydrogel contact lens wear on tear film osmolarity

AIM:To compare the effects of first and second generation silicone hydrogel(SiH) contact lens wear on tear film osmolarity.METHODS:The healthy subjects who have never used contact lenses before were enrolled in the study.Tear film osmolarity values of 16 eyes(group 1) who wore first generation SiH contact lenses were compared with those of 18 eyes(group 2) who wore second generation SiH contact lenses after three months follow-up.RESULTS:Beforecontactlenswear,tearfilmosmolarity of groups 1 and 2 were 305.02±49.08 milliosmole(mOsm) and 284.66±30.18mOsm,respectively.After three months of contact lens wear,osmolarity values were found 317.74±60.23mOsm in group 1 and 298.40±37.77mOsm in group 2.Although osmolarity values for both groups of SiH contact lens wear after three months periods were slightly higher than before the contact lens wear,the difference was not statistically significant. CONCLUSION:Contact lens wear may cause evaporation from the tear film and can increase tear film osmolarity leading to symptoms of dry eye disease.In the current study,there is a tendency to increase tear film osmolarity for both groups of SiH contact lens wear,but the difference is not statistically significant.

Determination of the Normal Contact Stiffness and Integration Time Step for the Finite Element Modeling of Bristle-Surface Interaction

In finite element modeling of impact,it is necessary to define appropriate values of the normal contact stiffness,Kn,and the Integration Time Step(ITS).Because impacts are usually of very short duration,very small ITSs are required.Moreover,the selection of a suitable value of Kn is a critical issue,as the impact behavior depends dramatically on this parameter.In this work,a number of experimental tests and finite element analyses have been performed in order to obtain an appropriate value of Kn for the interaction between a bristle of a gutter brush for road sweeping and a concrete surface.Furthermore,a suitable ITS is determined.The experiments consist of releasing a steel bristle that is placed vertically at a certain distance from a concrete surface and tracking the impact.Similarly,in the finite element analyses,a beam is modeled in free fall and impacting a surface;contact and target elements are attached to the beam and the surface,respectively.The results of the experiments and the modeling are integrated through the principle of conservation of energy,the principle of linear impulse and momentum,and Newton’s second law.The results demonstrate that,for the case studied,Kn and the impact time tend to be independent of the velocity just before impact and that Kn has a very large variation,as concrete is a composite material with a rough surface.Also,the ratio between the largest height of the bristle after impact and the initial height tends to be constant.

Separation of contact stress components by moire interferometry

A hybrid technique of combining moire measurement and analytical solution is developed to separate the normal and the tangential components of distributed contact stresses between two co-plane bodies. The moire interfe-rometry offers the displacement fields near the deformed contact zone, from which the tangential strains and boundary slopes of the deformed configurations can be evaluated. Those experimental results provide boundary conditions for the discrete integration of Flamant＇s solutions, to inversely compute the separated components of the contact stresses.