Dynamic Rollover Prediction of Heavy Vehicles Considering Critical Frequency

Rollover of commercial heavy vehicles can cause enormous economic losses and fatalities.It is easier for such vehicles to rollover if the driver’s steering frequency is close to the critical frequency of the vehicle’s roll motion;however,the critical roll frequency has rarely been investigated.In this study,the second-order transfer function between the steering input and roll angle was developed to calculate the critical frequency of the vehicle’s roll motion.The simulated spectrum and transfer function were then used to dynamically predict the peak lateral load transfer ratio.Laboratory experiments were conducted using a scaled vehicle to verify the critical roll frequency.The results suggest that the peak value of the lateral load transfer ratio during steering can be accurately determined from the driver’s input,and the critical roll frequency has a dominant effect on the dynamic rollover of heavy vehicles.

A MODEL FOR THE VARIATIONS OF THE CRITICAL FREQUENCY OF F_2 LAYER DURING THE NEGATIVE PHASES OF IONOSPHERIC STORMS

A model for the negative phase of ionospheric storms in middle latitudes is presented. It is assumed that there will be molecule enriched air in the thermosphere above the auroral oval during the period of the main phase of a magnetic storm. The molecule enriched air is carried to the middle latitudes by thermospheric neutral wind, and at the same time it diffuses away. When the molecule enriched air arrives at the F2 layer above a station, the electron loss rate in the F2 layer increases, the electron density decreases and then the negative phase at the station begins. We have calculated the variations of the fo F2 following magnetic storms for Manzhouli （29.5°N, 117.5°E）, Freiburg （48°N, 07°E） and Billerica （43°N, 71°W） respectively. The results agree very well with typical events observed at the three stations and can be used to explain some average features of negative phase ionospheric storms in middle latitudes.

Critical flicker frequency for diagnosis and assessment of recovery from minimal hepatic encephalopathy in patients with cirrhosis

BACKGROUND:Minimal hepatic encephalopathy (MHE) impairs quality of life and predicts overt hepatic encephalopathy (HE) in cirrhotic patients.Diagnosis of MHE requires cumbersome tests.Lactulose is effective in the treatment of MHE.This study aimed to evaluate the use of critical flicker frequency (CFF) for the diagnosis of MHE in cirrhotic patients after treatment.METHODS:One hundred and ten patients were evaluated by psychometry (number connection tests A,B or figure connection tests A,B),P300 auditory event related potential (P300ERP),venous ammonia,and CFF for MHE.MHE was diagnosed by abnormal psychometry (>2SD age matched controls) and P300ERP.MHE patients were treated with lactulose for one month.Response was defined by normalization (<2SD of matched controls) of both psychometry and P300ERP.RESULTS:Of the 110 patients [Child Turcott Pugh score A:B:C 39:42:29,(age 41.6±11.6 years,M:F 82:28)],75 (68%) had abnormal results of psychometric tests,and 74 (67%) had prolonged P300ERP.Fifteen (20%) patients with abnormal results of psychometric tests had normal P300ERP.Thus sixty (54.5%) patients were diagnosed as having MHE.After treatment for one month,34 (57%) recovered while 26 (43%) continued to have abnormal resents of psychometric or P300ERP tests.CFF was <39 Hz in 72 (65.4%) patients before treatment and in 20 (33.3%) after treatment.CFF sensitivity,specificity,positive predictive value,negative predictive value,and diagnostic accuracy for the assessment of recovery of MHE were 65%,91%,85%,77% and 80%,respectively.CONCLUSION:CFF is a simple,relatively reliable,and accurate test without any dependence on age or literacy in the diagnosis and assessment of recovery of patients with MHE.

Analysis of Speeds of Cylinders of Saw Gins and Linters and Determination of Critical Frequencies for them

With an increase in the density of the seed roll in the roll box of the saw gin, the quality indicators of the fiber and seed are poor, energy consumption increases, machine breakdowns increase, and when the density decreases, the performance of the saw gin increases. Therefore, the density control of the seed roll is one of the important problems in the ginning process. The paper proposes a change in the rotation speed of the saw cylinder with a decrease in the diameter of its numerical linear speed and machine productivity. The article describes the problem of regulating the density of a seed roll in a saw gin of the DP series, provides an overview of work on regulating the operation of the machine, determines the dependence of the productivity of gins and linters on the state of the saw system in these machines, as well as changes in the linear speed of the saw by changing its diameter. Also, the critical speed of the gin and linter saw cylinder was determined to prevent resonance. In this case, the Simulation package of the SolidWorks computer program was used. The results of the study made it possible to adjust the speed of the cylinders when changing the diameter of the saws, which improved the productivity of the machine while maintaining the quality of the fiber and seed.

EFFECT OF THE GUIDES ON THE LOWEST CRITICAL ROTATIONAL FREQUENCIES OF CIRCULAR SAW

The effects of the location,number and stiffness of guide pads on the lowest critical rotational frequencies of the rotating circular saw damped at the inside and free at the perimeter are discussed by the non linear theory and the perturbation theory of structural vibration analysis The influence of the centrifugal force and the cutting temperature are considered in the course of the analysis The results of the analysis and the calculation show that the introduction of one guide does not stably raise critical rotational frequencies of the circular saw The two guides can raise lowest critical rotational frequency of the circular saw when the angle between the two guides fixed on the direction of the circumference satisfies the certain conditions

The theory of critical flicker fusion frequency and its application in cataracts

Background:Due to media opacity,it is usually difficult to accurately evaluate the postoperative visual acuity in cataracts patients.As a small and portable tool,the critical flicker fusion frequency(CFF)device reflects the temporal resolution of visual function and has been widely used in clinical research.However,poor understanding of the technique and equipment limitations have restricted its clinical application in China.Main text:There was a decrease in the CFF value in various ophthalmic diseases,indicating that the CFF is sensitive to detect visual functional changes.A number of studies have shown that the CFF test can accurately distinguish patients with simple cataracts from those with cataracts combined with fundus disease,and,as a visual test,it can more accurately predict postoperative visual acuity without being affected by media opacity.This study comprehensive reviews the basic principles of CFF and its application in ophthalmology,especially in cataracts.Conclusions:As one of the tools for dynamic visual function detection,the CFF test could help doctors to assess the possible presence of fundus disease in cataracts patients,especially in eyes with dense cataracts,and more precisely provide a reasonable visual prognosis than other available visual tests.

Behavior of a superconducting bulk in a running high-T_c superconducting maglev system(I):distribution of magnetic and electric field

A theoretical model of describing the electromagnetic and thermal dynamics of high-Tc superconducting bulks in a high-Tc superconducting Maglev system is built up.The model contains the effects of hysteresis-type loss,flux flow,flux creep,and thermal diffusion on the superconducting bulks in the Maglev system.As the first stage of this study,the behavior of magnetic and electric fields,as well as the distribution energy flow density in the superconducting bulk is studied.The results show that the flux flow and thermal diffusion affect the behaviors of the electromagnetic field in the high-Tc superconducting bulks in different ways;however,both of them contribute significantly to the energy dissipation of the superconducting bulks when they are used in the Maglev train.

Testing of new ionospheric models along the meridian 110°E over the Northern Hemisphere

Despite the continuous improvement of the widely used empirical model international reference ionosphere(IRI),the recently appeared new models must be tested worldwide.Testing along the meridians has the advantage of dealing with the latitudinal dependent parameters.This paper uses new models of parameters foF2(critical frequency),TEC(total electron content),andτ(equivalent slab thickness of the ionosphere),which are of great importance for evaluating the effects of space weather.IRI-Plas,NNT2F2,and NTSM models were tested using data from 6 ionosondes located along the meridian 110°E in March 2012.It is shown that the IRI-Plas model provides the closest values to experiment with respect toτ,while the NTSM model provides a rather limited reflection of the latitude dependence.Analyses of foF2(NNT2F2)have shown that,the NNT2F2 model provides good conformity with experimental values in this area,but it is very dependent on the TEC processing method.The latitudinal dependences of foF2 obtained with TEC and polynomial dependenceτ(Appr)showed the presence of positive deviations from medians not only during disturbances but also quiet periods,longitudinally at the meridian.

Analysis of the ionospheric anomaly at Great Wall Station,Antarctica

In this paper, we use an empirical method to derive the height of maximum electron concentration of the F2 region and the effective meridional neutral wind at Great Wall Station, Antarctica. The meridional wind is also calculated with the HWM90 model. Results can be used to explain two anomaly features of ionosphere at Great Wall Station. In summer, peak values of f0F2 appear during nighttime. In winter, especially during June and July, f0F2 decrease dramatically as compared with summer's one.Summer anomaly can be explained by combining effects of two causes:thermospheric winds and solar radiation. An important reason for the anomaly is the location of Great Wall Station, which is in both high geographic latitude and middle geomagnetic latitude.

Coupled bending-torsion vibration of a homogeneous beam with a single delamination subjected to axial loads and static end moments

Delaminations in structures may significantly reduce the stiffness and strength of the structures and may affect their vibration characteristics. As structural components, beams have been used for various purposes, in many of which beams are often subjected to axial loads and static end moments. In the present study, an analytical solution is developed to study the coupled bending-torsion vibration of a homogeneous beam with a single delamination subjected to axial loads and static end moments. Euler-Bernoulli beam theory and the ＂free mode＂ assumption in delamination vibration are adopted. This is the first study of the influences of static end moments upon the effects of delaminations on natural frequencies, critical buckling loads and critical moments for lateral instability. The results show that the effects of delamination on reducing natural frequencies, critical buckling load and critical moment for lateral instability are aggravated by the presence of static end moment. In turn, the effects of static end moments on vibration and instability characteristics are affected by the presence of delamination. The analytical results of this study can serve as a benchmark for finite element method and other numerical solutions.

Novel computerized psychometric tests as primary screening tools for the diagnosis of minimal hepatic encephalopathy

Minimal hepatic encephalopathy(MHE)is a critical neurocognitive complication of decompensated liver cirrhosis and portosystemic shunting,which results in a wide range of cognitive deficits including impairments in working attention,psychomotor speed,and executive function.Current guidelines have recommended paper-and-pencil psychometric tests for the diagnosis of MHE.Most high-risk cirrhotic patients are required to be examined;however,paperand-pencil psychometric tests are neither convenient nor rapid to perform in the clinic.Recently,novel computerized psychometric tests,including the inhibitory control test,EncephalApp Stroop App,and critical flicker frequency,have been proven to be rapid,effective,and convenient methods for screening MHE in clinical practice and for identifying high-risk cirrhotic patients for further validation using rigid neuropsychometric examinations.However,diagnostic accuracy of these tests is influenced by educational background,age,and cultural differences.This review summarizes clinical evidence of the application of novel computerized psychometric tests for screening MHE.

The clinical application of critical flicker fusion frequency in demyelinating optic neuritis

Purpose:To investigate the application of critical flicker fusion frequency(CFF)in demyelinating optic neuritis(DON).Methods:A cross-sectional study.A total of 127 eyes in 69 DON patients and 63 eyes in 33 healthy control(HC)groups were included between January 2021 to September 2021 from Department of Ophthalmology,PLA General Hospital.Patients underwent best-corrected visual acuity(BCVA),visual field,optical coherence tomography(OCT),flash visual evoked potential(F-VEP),and CFF examinations.The affected eyes were divided into aquaporins 4(AQP4-),myelin oligodendrocyte glycoprotein(MOG-),and double negative DON according to serum antibody;mild,moderate,severe degree visual impairment according to BCVA
0.5,0.1-0.5,<0.1;and 4 groups:<1,1~<3,3~<6 and>6 months according to time interval from onset to CFF examination.One-way ANOVA was used to perform above subgroup analysis.The correlations between CFF and F-VEP peak time,peak value,BCVA and mean visual filed defect(MD)were analyzed in order via Pearson correlation analysis.Results:he trichromatic values of red,green,and yellow in DON affected eyes were 21.83±9.03,23.66±10.21,24.09±10.77 Hz,respectively,which was significantly reduced compared with the HC group(t=-14.82,-14.22,-14.00;P<0.001).The subgroup analysis showed no significant difference between different antibody subtypes(P=0.914<0.848<0.604),whereas,a significant decrease of CFF trichromatic value was found in severe visual acuity impairment group(P<0.001).There was a significant difference in CFF-trichromatic values at different time points(P<0.001),to be specific,CFF fluctuated under 20Hz within 3 months after onset and tended to be stable around 24-28Hz.Correlation analysis showed that the peak time of F-VEP(r=-0.486,-0.515,-0.526;P<0.001),BVCA(r=-0.640,-0.659,-0.642;P<0.001),were negatively correlated with CFF trichromatic values,MD and CFF were positively correlated(r=0.486,0.453,0.476;P=0.003,0.006,0.004).Conclusions:A significant decrease of CFF value was found in DON-affected eyes,and it has a good correlation with BCVA,MD and latency of F-VEP,and can better reflect the impairment of visual function.

THE ANALYSIS OF INTRASEASONAL LONG ROSSBY WAVE SPEED IN THE SUBTROPICAL PACIFIC OCEAN

The analysis of the satellite altimeter data suggests that the propagating speed of intraseasonal long Rossby wave amplified in the subtropical Pacific Ocean is faster than that of first mode baroclinic free Rossby wave predicted by the liner theory and the propagating speed of intrascasonal long Rossby wave reflected in the eastern boundary of Pacific Ocean agrees basically with the liner theory speed of first mode baroelinic free P, ossby wave. If we do not distinguish the two kinds of hmg Rossby waves and estimate the Rossby wave speed in the whole basin, the phase speed is merely 25% higher than the linear theory long Rossby wave speed. The acceleration of the propagating speed of intraseasonal long Rossby wave amplified in the subtropical Pacific Ocean is due to the existence of westward thermolcline mean flow.

Mineral dust resuspension under vibration: Onset conditions and the role of humidity

The vibration of dusty surfaces inevitably causes re-entrainment of particles into the atmosphere.Given that movement of mineral dust particles deposited on a surface begins at a critical frequency (fc) and amplitude,an experimental laboratory study was conducted to determine the onset conditions for resuspension of a vibrated granular soil.We determined the resuspension state diagram as a function of frequency and amplitude of a sinusoidal vibration,the granulometry of the dust and the thickness of the soil bed.The mitigation effect of humidity was also evaluated.Critical frequencies ranged between 2.5 and 23 Hz when amplitudes were less than 12 rmm.These results were independent of bed thickness and perturbation type.For all particle sizes observed,fc decreased monotonically with A,contrasting with behavior observed for individual particles.In dry samples,fe for large size classes was markedly less when A was greater than 6 mm;while thefc for fine fractions only decreased once amplitudes reached 10 mm.Experiments with wet granular soils demonstrated that wetting above an optimum humidity did not necessarily impede movement and caused agglomeration.This study provides guidelines for managing resuspension of granular soils subjected to vibrations.