Value Of VR Research Articles

Effects of Partial-Body, Continuous/Pulse Irradiation at Dose Rates from FLASH to Conventional Rates on the Level of Surviving Blood Lymphocytes: Modeling Approach. I. Continuous Irradiation.

A mathematical model developed by Cucinotta and Smirnova is extended to describe effects of continuous, partial-body irradiation at high doses D and at dose rates N from FLASH to conventional rates on the level of surviving blood lymphocytes in humans and small laboratory animals (mice). Specifically, whereas the applicability of the model is limited to the exposure times shorter than a single cardiac cycle T0, the extended model is capable of describing such effects for the aforementioned and longer exposure times. The extended model is implemented as the algebraic equations. It predicts that the level of surviving blood lymphocytes in humans and mice increases with increasing the dose rate from N= D/T0 to FLASH rates and approaches the upper limiting level of 1-vR, where vR is the fraction of blood volume in the irradiated part of the blood circulatory system. Levels of surviving blood lymphocytes computed at doses from 10 Gy to 40 Gy and at dose rates N, which equal or exceed 40 Gy/s for humans and 400 Gy/s for mice, are nearly indistinguishable from the upper limiting level. In turn, the level of surviving blood lymphocytes in humans and mice decreases with decreasing the dose rate from N= D/T0 to conventional rates and approaches a lower limiting level. This level strongly depends on the dose D (it is smaller at larger values of D) with a slight dependence on the dose rate N. The model with the parameters specified for mice (together with the model of the dynamics of lymphopoietic system in mice after partial-body irradiation) reproduce, on a quantitative level, the experimental data, according to which the concentration of blood lymphocytes measured in mice in one day after continuous, partial-body irradiation at a high dose and conventional dose rate is smaller at the larger value of vR. Additionally, the model predicts at the same high dose (>10 Gy) a faster restoration of the blood lymphocyte population in humans exposed to continuous, partial-body irradiation at a FLASH dose rate compared to a conventional dose rate.

Multi-environment phenotyping of linseed (Linum usitatissimum L.) germplasm for morphological and seed quality traits to assemble a core collection

Linseed or flax (Linum usitatissimum L.) is one of the most ancient industrial crops domesticated for oilseed and natural fiber. India is one of the two proposed centers of origin of linseed and harbours high genetic diversity. The Indian Council of Agricultural Research-National Bureau of Plant Genetic Resources (ICAR-NBPGR) conserves one of the largest base collections of Linum with around 2800 germplasm accessions at National Genebank, of which 2576 are the unique accessions of cultivated linseed and were characterized for 10 qualitative and 26 quantitative traits and the resultant multi-environment data along with passport information was used to develop a multipurpose core collection. Initially, five different core sets were derived using the core collection assembler tool ‘Core Hunter 3’ by optimization of average genetic distances between each accession and nearest entry in the core (A-NE) and the average distance between each entry and nearest neighbouring entry (E-NE). These five core sets were subjected to different quality evaluation indices to select one set that best represents the maximum genetic diversity and representativeness present in the entire tested collection. The Core collection-4, developed with weightage of E-NE and A-NE in the ratio of 0.7–0.3 was chosen as the best core collection as it exhibited desirable genetic distance, variance difference percentage (VD; 85%), coincidence rate of range (CR; 91.66%) and variable rate of coefficient of variance (VR; 117.76%), which were more than threshold value of VD (80%), CR (80%), and VR (100%) required for an optimally good core collection. Several summary statistics, Kullback-Leibler distance and Shannon Weaver diversity index indicated similar trait distribution patterns among the chosen core set and the entire collection. Correlogram and principal component analysis revealed that trait associations and their magnitude were conserved for most of the traits in the chosen best core collection. The development of this multipurpose core collection is expected to cater to the needs of linseed breeders and germplasm curators to pave the way for expedited access to genetically diverse and agronomically important material for trait introgression.

Application Of VR In the Field of Education

VR in virtual reality and augmented reality technology is a new technology applied in the field of education in recent years. This paper combs and analyses the educational application research from three aspects: educational games, art education and political education. First, starting from education, the author expounds that virtual reality education is based on the teaching concept of "interesting" games and takes education and teaching objectives as the design concept. Then, it introduces the performance of virtual reality technology in the field of art. This part explains the important role of virtual reality technology in the field of art education. It mainly expounds the practical exploration of VR in teaching, the value of VR in art design teaching, the content of VR in the new path of art design curriculum reform, and the innovation of VR teaching. Finally, the application of virtual reality technology in ideological and political education is proposed. At the end of this paper, the application of VR in these three aspects is summarized and prospected.

Research on the Application of VR in Education and Gaming

VR in virtual reality technology is a new technology applied in the field of education and gaming in recent years. This article describes the current development of VR in the field of education and games, and demonstrates the diversity of VR technology applications to promote a better understanding of VR technology. First of all, starting with education, this paper expounds that virtual reality education is designed based on educational and teaching objectives. we introduce the performance of virtual reality technology in the field of education. This section describes the important role of virtual reality technology in the field of medical education and classroom education. The challenges in the field of education were discussed. Then it expounds the practical exploration of VR in games and the value of VR in game development. Finally, we analyse some advantages and characteristics of VR games. The article concludes with a summary and outlook for the full text.

Association between ventilatory ratio and ICU mortality in interstitial lung disease patients on mechanical ventilation: A retrospective study

BackgroundVentilatory ratio (VR) is a simple bedside index of ventilatory efficiency. Interstitial lung disease (ILD) is a diverse group of diseases that causes fibrosis or inflammation of the pulmonary parenchyma, and the main clinical manifestation is hypoxemia. To date, no study has explored ventilation efficiency in patients with ILD. ObjectivesThis study aimed to explore the features of VR in mechanically ventilated patients with ILD and their relationship with intensive care unit (ICU) mortality. MethodsIn this retrospective analysis, we included mechanically ventilated patients with ILD in the ICU of West China Hospital, Sichuan University, from 2013 to 2021. Demographic data and mechanical ventilation (MV) parameters within 24 h of intubation were collected. The characteristics of VR and their relationships with ICU mortality were also analyzed. Results224 patients were included in the final analysis. There were 146 males (53.9%), and the median age was 65 years (interquartile range [IQR]54∼74). The mean value of VR was 2.22, and VR was significantly higher in nonsurvivors than in survivors (1.79 vs 2.32, P < 0.001). A high VR value was an independent risk factor for ICU mortality (odds ratio=1.602, P = 0.038) after adjustment. A high value of VR was associated with a shorter survival time after admission to ICU (hazard ratio=1.485, P = 0.006) ConclusionsVR in patients with ILD on MV was increased, and the VR of nonsurvivors within 24 h of intubation was higher than that of survivors. The high VR value within 24 h of intubation was an independent risk factor for ICU mortality after adjusting for other factors.

Ventilatory ratio, dead space, and venous admixture in patients with acute respiratory distress syndrome

BackgroundVentilatory ratio (VR) has been proposed as an alternative approach to estimate physiological dead space. However, the absolute value of VR, at constant dead space, might be affected by venous admixture and CO2 volume expired per minute (VCO2). MethodsThis was a retrospective, observational study of mechanically ventilated patients with acute respiratory distress syndrome (ARDS) in the UK and Italy. Venous admixture was either directly measured or estimated using the surrogate measure PaO2/FiO2 ratio. VCO2 was estimated through the resting energy expenditure derived from the Harris–Benedict formula. ResultsA total of 641 mechanically ventilated patients with mild (n=65), moderate (n=363), or severe (n=213) ARDS were studied. Venous admixture was measured (n=153 patients) or estimated using the PaO2/FiO2 ratio (n=448). The VR increased exponentially as a function of the dead space, and the absolute values of this relationship were a function of VCO2. At a physiological dead space of 0.6, VR was 1.1, 1.4, and 1.7 in patients with VCO2 equal to 200, 250, and 300, respectively. VR was independently associated with mortality (odds ratio [OR]=2.5; 95% confidence interval [CI], 1.8–3.5), but was not associated when adjusted for VD/VTphys, VCO2, PaO2/FiO2 (ORadj=1.2; 95% CI, 0.7–2.1). These three variables remained independent predictors of ICU mortality (VD/VTphys [ORadj=17.9; 95% CI, 1.8–185; P<0.05]; VCO2 [ORadj=0.99; 95% CI, 0.99–1.00; P<0.001]; and PaO2/FiO2 (ORadj=0.99; 95% CI, 0.99–1.00; P<0.001]). ConclusionsVR is a useful aggregate variable associated with outcome, but variables not associated with ventilation (VCO2 and venous admixture) strongly contribute to the high values of VR seen in patients with severe illness.

Detailed Spectroscopy of Post-AGB Supergiant GSC 04050–02366 in IRAS Z02229+6208 IR Source System

In the optical spectra of the cold post-AGB supergiant GSC 04050$-$02366, obtained with the 6-meter BTA telescope with a spectral resolution of R$\ge$60000 on arbitrary dates over 2019$\div$2021, a radial velocity variability is found. Heliocentric Vr based on the positional measurements of numerous absorptions varies from date to date with a standard deviation of $\Delta$Vr$\approx$1.4 km/s about the average value of Vr=24.75 km/s, which may stem out of the low-amplitude pulsations in the atmosphere. The spectra of the star are purely absorption type, there are no obvious emissions. Intensity variability of most of absorptions and Swan bands of the C$_2$ molecule was discovered. A slight asymmetry of the H$\alpha$ profile is observed at some observation dates. The position of H$\alpha$ absorption core varies within 27.3$\div$30.6 km/s. Splitting into two components (or asymmetry) of strong low-excitation absorptions (YII, ZrII, BaII, LaII, CeII, NdII) was found. The position of the long-wavelength component coincides with the position of other photospheric absorptions, which confirms its formation in the atmosphere of the star. The position of the shortwave component is close to the position of the rotational features of Swan bands, which indicates its formation in the circumstellar envelope expanding at a velocity of about Vexp=16 km/s.

Phenotypic Characterization, Genetic Diversity Assessment in 6,778 Accessions of Barley (Hordeum vulgare L. ssp. vulgare) Germplasm Conserved in National Genebank of India and Development of a Core Set.

The entire collection of cultivated barley germplasm accessions conserved in the Indian National Genebank (INGB) was characterized for nine qualitative and 8 quantitative traits to assess the nature and magnitude of prevailing genetic variability and to develop a core set. A wide range of variability was observed for days to spike emergence (51–139 days), days to physiological maturity (100–152 days), plant height (45.96–171.32 cm), spike length (3.44–13.73 cm), grain number/spike (10.48–82.35), and 100-grain weight (1.20–6.86 g). Initially, seven independent core sets were derived using 3 core construction tools– MSTRAT, PowerCore, and Core Hunter 3 by employing the maximization method, heuristic sampling, and optimisation of average genetic distances, respectively. The core set-3 generated by Core Hunter 3 by simultaneous optimisation of diversity and representativeness, captured maximum genetic diversity of the whole collection as evident from the desirable genetic distance, variance difference percentage (VD; 87.5%), coincidence rate of range (CR; 94.27%) and variable rate of coefficient of variance (VR; 113.8%), which were more than threshold value of VD (80%), CR (80%), and VR (100%) required for good core collection. The coefficient of variation and Shannon–Weaver diversity indices were increased in the core set as compared with the whole collection. The low value of Kullback-Leibler distance (0.024–0.071) for all traits and quantile-quantile plots revealed a negligible difference between trait distribution patterns among the core set and entire assembly. Correlogram revealed that trait associations and their magnitude were conserved for most of the traits after sampling of the core set. The extraction of the INGB barley core set and identification of promising accessions for agronomically important traits in different genetic backgrounds will pave the way for expedited access to genetically diverse and agronomically important germplasm for barley breeding.

3D Virtual Reality Imaging of Major Aortopulmonary Collateral Arteries: A Novel Diagnostic Modality.

BackgroundMajor aortopulmonary collateral arteries (MAPCAs), as seen in patients with pulmonary atresia, are arteries that supply blood from the aorta to the lungs and often require surgical intervention. To achieve complete repair in the least number of interventions, optimal imaging of the pulmonary arterial anatomy and MAPCAs is critical. 3D virtual reality (3D-VR) is a promising and upcoming new technology that could potentially ameliorate current imaging shortcomings.MethodsA retrospective, proof-of-concept study was performed of all operated patients with pulmonary atresia and MAPCAs at our center between 2010 and 2020 with a preoperative computed tomography (CT) scan. CT images were reviewed by two congenital cardiac surgeons in 3D-VR to determine additional value of VR for MAPCA imaging compared to conventional CT and for preoperative planning of MAPCA repair.Results3D-VR visualizations were reconstructed from CT scans of seven newborns where the enhanced topographic anatomy resulted in improved visualization of MAPCA. In addition, surgical planning was improved since new observations or different preoperative plans were apparent in 4 out of 7 cases. After the initial setup, VR software and hardware was reported to be easy and intuitive to use.ConclusionsThis study showed technical feasibility of 3D-VR reconstruction of children with immersive visualization of topographic anatomy in an easy-to-use format leading to an improved surgical planning of MAPCA surgery. Future prospective studies are required to investigate the clinical benefits in larger populations.

Provider experiences of virtual reality in clinical treatment.

BackgroundVirtual reality (VR) has proven effective in the treatment of specific phobias and trauma particularly when in-vivo exposure therapy might be costly (e.g. fear of flying, combat scenes). Similarly, VR has been associated with improvement of chronic pain and of acute pain during medical procedures. Despite its effectiveness as a healthcare tool, VR technology is not well-integrated into common practice. This qualitative study aims to explore the provider perception of the value of VR and identify barriers to VR implementation among healthcare providers.MethodsA 66-item self-report survey was created to examine application of VR to clinical practice, perceived value of this treatment, ease of learning the technology, billing considerations, and other obstacles. 128 providers (MDs and PhDs) who were located in the United States and had used VR as a therapeutic tool in the past year were identified through research papers, as well as user lists and news articles from VR application websites. Of the 128 providers contacted, 17% (22) completed our online self-report measure. Of these, 13% of respondents (N = 17) completed greater than 75% of the questionnaire and were considered completers. Provider responses were collected over a one-month period and qualitatively analyzed.ResultsThe majority of providers were from an academic institution (n = 12, 70.6%), and all providers practiced in the outpatient setting. Providers most commonly reported using VR for the treatment of acute pain and/or anxiety related to medical procedures (n = 11, 64.7%), followed by specific phobia (n = 6, 35.3%) and social phobia (n = 6, 35.3%). All providers agreed VR is a valuable tool they would recommend to colleagues. The majority (n = 15, 93.8%) believed VR helped their patients progress in treatment, compared with other methods. Providers cited the ability to individualize treatment (n = 14, 87.5%) and increase patient engagement (n = 15, 93.8%) as main benefits of VR. A minority reported negative feedback from patients about content (n = 4, 25%) or about the technology in general (n = 6, 37.5%), whereas all reported some form of positive feedback. The slight majority (n = 10, 58.8%) of providers did not find transitioning to VR difficult. Of those who did, cost was the most commonly cited barrier (n = 6). Regarding reimbursement, only 17.6% (n = 3) of providers reported the ability to bill for VR sessions. Most providers (n = 15, 88.2%) received training on their VR platform which they found beneficial. Comparing the trained and untrained groups found no significant difference in VR comfort level (p = 0.5058), the value of VR in practice (p = 0.551) or whether providers would recommend VR to others (p = 0.551), though sample sizes were small.ConclusionsIn corroboration with previous research, this study demonstrates that VR is well-received by patients and providers, allowing increased patient engagement and treatment individualization. However, associated costs, including an inability to bill for this service, can present a barrier to further implementation. These findings will guide further development of virtual reality as a standardized tool in psychiatry and pain management.

Perceptions and experiences of virtual reality in public libraries

PurposeVirtual reality (VR) is becoming a more available technology including in public spaces like libraries. The value and role of VR as a tool for learning and social engagement are unclear. The purpose of this paper is to explore the ways in which library patrons and librarians perceive VR and experience VR through library drop-in programs.Design/methodology/approachThis paper is based on research conducted in seven Washington State Libraries where VR was adopted for drop-in programming for the first time. Data was collected between March and June 2018 and involved interviews with librarians and patrons, a patron user experience survey, and observational field notes from researchers on site during library programs.FindingsFindings are presented in relation to user perceptions of VR compared to their actual VR experiences, and in relation to informal learning and social engagements. The authors frame the analysis and discussion in relation to sociotechnical imaginaries – culturally situated ideas about the relationship between society and technology, and considering the larger cultural landscape that informs collective views about the present and future.Social implicationsThe paper discusses pending and potential inequalities related to gender, race and class in conversation with technology industry and VR. Issues discussed include unequal access to technology in public libraries and representation of minoritized groups in VR.Originality/valueThis work takes a critical perspective considering the inequities in relation to mainstreaming VR through public spaces like libraries.

School's Back

Social virtual reality (social VR) is an emerging technology that has the potential to support unique social experiences for groups of older adults. In this paper we explore the use of social VR to support group reminiscence, an activity that has been shown to have a positive impact on the lives of older adults. We developed School Days, a bespoke social VR application that enables groups of geographically dispersed older adults to meet in a virtual environment to reminisce about their school experiences. We conducted a user study over the course of 5 months with 16 participants aged 70--81 to evaluate how School Days supported reminiscence. In this paper, we focus on how the use of reminiscence scaffolding features in School Days impacted on the older adults' ability to participate more fully in the reminiscence activities. Our results illustrate the value of social VR for connecting older adults over distance, and contribute new knowledge of how virtual environments can be designed to scaffold reminiscence; how techniques such as 3D conversation starters and individual artefacts can be used to scaffold reminiscence; and how pre-recorded holographic stories (Avacasts) can be used to introduce new perspectives and prompt self-reflection. We contribute five design reflections aimed at guiding the design of future reminiscence tools in social VR.

A Liquid Metal Based Multimodal Sensor and Haptic Feedback Device for Thermal and Tactile Sensation Generation in Virtual Reality

AbstractVirtual reality (VR) has been widely used for training, gaming, and entertainment, and the value of VR is continually increasing as a contact‐free technology. For an immersive VR experience, measuring finger movements and providing appropriate feedback to the hand are as important as visual information, given the necessity of the hands for activities in daily life. Thus, a hand‐worn VR device with motion sensors and haptic feedback is desirable. In this paper, a multimodal sensing and feedback glove is developed with soft, stretchable, lightweight, and compact sensor and heater sheets manufactured by direct ink writing (DIW) of liquid metal, eutectic gallium‐indium (eGaIn). In the sensor sheet, ten sensors and three vibrators are embedded to measure finger movements and provide vibro‐haptic feedback. The other heater sheet provides thermo‐haptic sensation in accurate and rapid manner via model‐based feedback control even under stretched conditions. The multimodal sensing and feedback glove allows users to feel the contact status and discriminate materials with different temperature. Performance of the proposed multimodal glove is verified under VR environments including touching and pushing two blocks of different materials and grabbing a heated metal ball submerged in hot water.

Sterile neutrino dark matter in left-right theories

SU(2)L× SU(2)R gauge symmetry requires three right-handed neutrinos (Ni), one of which, N1, can be sufficiently stable to be dark matter. In the early universe, WR exchange with the Standard Model thermal bath keeps the right-handed neutrinos in thermal equilibrium at high temperatures. N1 can make up all of dark matter if they freeze-out while relativistic and are mildly diluted by subsequent decays of a long-lived and heavier right-handed neutrino, N2. We systematically study this parameter space, constraining the symmetry breaking scale of SU(2)R and the mass of N1 to a triangle in the (vR, M1) plane, with vR = (106− 3 × 1012) GeV and M1 = (2 keV–1 MeV). Much of this triangle can be probed by signals of warm dark matter, especially if leptogenesis from N2 decay yields the observed baryon asymmetry. The minimal value of vR is increased to 108 GeV for doublet breaking of SU(2)R, and further to 109 GeV if leptogenesis occurs via N2 decay, while the upper bound on M1 is reduced to 100 keV. In addition, there is a component of hot N1 dark matter resulting from the late decay of N2→ N1ℓ+ℓ− that can be probed by future cosmic microwave background observations. Interestingly, the range of vR allows both precision gauge coupling unification and the Higgs Parity understanding of the vanishing of the Standard Model Higgs quartic at scale vR. Finally, we study freeze-in production of N1 dark matter via the WR interaction, which allows a much wider range of (vR, M1).

Understanding Users’ Engagement and Responses in 3D Virtual Reality: The Influence of Presence on User Value

AbstractVirtual reality (VR) provides new opportunities for businesses to gain competitive advantages by enabling them to innovatively engage customers. Based on presence theory, this study aims to test the influences of two major components of presence, social presence and spatial presence, on users’ perceptions of hedonic value, utilitarian value and engagement in the VR environment. An experiment was conducted on two conditions of a VR application (low vs. high social presence) to test the hypotheses proposed in the research model. The results reveal that social presence and spatial presence can improve the hedonic value of VR. However, inconsistent with previous studies, our findings reveal a negative relationship between spatial presence and engagement. Theoretical and practical implications and future research directions are subsequently discussed.

Echocardiograms Estimated the Severity of Aorticstenosis (AS) Accompanied with Tachycardiac Arrhythmia (AATA)

patients accompanied with tachycardiac arrhythmia (Frequent premature ventricular arrhythmia, supraventricular tachycardia,atrial fibrillation, etc), estimated the severity of aorticstenosis under transthoracic echocardiography (TTE), using the methods as below: continuous-wave (CW) Doppler echocardiography estimated aortic jet speed (VAV) and across valve mean pressure difference (△Pmean), Doppler echocardiography estimated the effective aortic valve area (AVAeffective) and velocity ratio (VR=VLVOT/VAV) by using the continuity equation, 2D echocardiography estimated aortic valve geometric area in anatomy (AVAanatomy). And compared the stability, accuracy and clinical value of these methods. This was a review of 11 AATA cases that were diagnosed in our institution between November 2016 and January 2017. At the condition of tachycardiac arrhythmia, estimating VAV, △Pmean, AVAeffective, VR and AVAanatomy under TTE. At the condition of normal arrhythmia under cardiopulmonary bypass during the surgery, estimating VAV, △Pmean, AVAeffective, VR and AVAanatomy once more under transesophageal echocardiography (TEE). And also, estimating AVAanatomy intraoperative exploration. In order to decrease the measurement error, we measured every values at lest three times and choose the mean value. Compared with the values estimated under normal arrhythmia, at the condition of AATA (with the severity of AS at moderately to severely), the value of VAV and △Pmean have differences (P < 0.05), easy to underestimate the severity of AS; the value of AVAeffective and VR have differences (P < 0.05), easy to overestimate the severity of AS; the value of AVAanatomy, which often greater than the value of AVAeffective, has no obvious difference and has good consistency with the geometric area of aortic measured intraoperative exploration. When estimating the severity of AS at the condition of AATA under TTE, the methods of assessment by Doppler echocardiography often instability, easy to underestimate or overestimate because of the affection of the ventricular rate. While the method of assessment by 2D echocardiography seemed to be less sensitive to the ventricular rate, so that could be a more reliable method in estimating the severity of AS at AATA and have clinical significance, although it has some differences with the value of AVAeffective.

Study on Aging Resistance Properties of Natural Rubber Dried by Microwave

In this work, thermogravimetry (TG) and Wallace plastometer were used to study the thermal-oxidative aging resistance properties of natural rubber (NR) dried by microwave and hot-air. Showed from the results, thermal degradation temperature, primary thermal-oxidative degradation temperature, the value of P0, PRI and VR for NR dried by microwave were higher than those of NR dried by hot-air; the thermal-oxidative aging resistance properties of NR vulcanizes dried by microwave improved significantly, and the rate of change for elongation at break (-26.76%) and tensile strength (-38.6%) of NR vulcanizes dried by microwave before and after aging were apparently higher than those of NR vulcanizes dried by hot-air, which were (-60.29%) and (-82.11), respectively.

Numerical investigation of two-degree-of-freedom vortex-induced vibration of a circular cylinder in oscillatory flow

Two-degree-of-freedom (2dof) vortex-induced vibration (VIV) of a circular cylinder in oscillatory flow is investigated numerically. The direction of the oscillatory flow is perpendicular to the spanwise direction of the circular cylinder. Simulations are carried out for the Keulegan–Carpenter (KC) numbers of 10, 20 and 40 and the Reynolds numbers ranging from 308 to 9240. The ratio of the Reynolds number to the reduced velocity is 308. At KC=10, the amplitude of the primary frequency component is much larger than those of other frequency components. Most vibrations for KC=20 and 40 have multiple frequencies. The primary frequency of the response in the cross-flow direction decreases with the increasing reduced velocity, except when the reduced velocity is very small. Because the calculated primary frequencies of the response in the cross-flow direction are multiple of the oscillatory flow frequency in most of the calculated cases, the responses are classified into single-frequency mode, double-frequency mode, triple frequency mode, etc. If the reduced velocity is in the range where the VIV is transiting from one mode to another, the vibration is very irregular.For each KC number the range of the reduced velocity can be divided into a cross-flow-in-phase regime (low Vr), where the response and the hydrodynamic force in the cross-flow direction synchronize, and a cross-flow-anti-phase regime (high Vr), where the response and the hydrodynamic force in the cross-flow direction are in anti-phase with each other. The boundary values of Vr between the cross-flow-in-phase and the cross-flow-anti-phase regimes are 7, 9 and 11 for KC=10, 20 and 40, respectively. For KC=20, another cross-flow-anti-phase regime is found between 15≤Vr≤19. Similarly the in-line-in-phase and the in-line-anti-phase regimes are also identified for the response in the in-line direction. It is found that the boundary value of Vr between the in-line-in-phase and the in-line-anti-phase regimes is greater than that in the cross-flow direction. They are 14 and 26 for KC=10 and 20, respectively. Maximum amplitude occurs at the boundary value of the reduced velocity between in-phase regime and anti-phase regime in both the x- and the y-directions.

Numerical Study on Motions of Rolls in Hot Rolling of Titanium Alloy Large Rings

Abstract Titanium alloy is sensitive to strain rate, so motions of rolls are crucial to the hot rolling process of titanium alloy large rings. In the study, firstly, the relative velocity vr was proposed to synthesize motion parameters of rolls, including the rotational velocity of the driver roll n1 and the feed rate of the idle roll v, and then the reasonable range of vr was determined analytically based on the stable forming condition. Secondly, a reliably coupled thermo-mechanical 3D-FE model of the process was developed in the dynamic explicit code ABAQUS/Explicit. Finally, the effect of vr on the process was studied using FE simulation. The results obtained show that although increasing vr by two different ways, i.e., by decreasing n1 or by increasing v, makes the feed amount per revolution Δhi increase, not all of their effects on the process are in agreement, such as for the nonuniformity of strain distribution. An appropriately larger value of vr is helpful to improve the end-plane quality and make strain and temperature distributions in a deformed ring more uniform, but has an adverse influence on the roll force.

The Research on Relationship between Heat Generation and Crosslinking Density of Vulcanized Rubber

Crosslinking density of vulcanized rubber which was filled with carbon black and silica was experimentally researched, and its corresponding heat generation, dynamic lag loss (tanδ) and loss modulus ( E″) were also studied. Based on these tests, the model of the relationship among them was established. The results showed that the characteristic value of crosslinking density Vr almost showed downward trend as a straight line when the quantity of silica increased, but temperature rise, loss modulus E″ and tanδ increased obviously. Silane coupling agent Si-69 could improve the crosslink density and dynamic performance. In the drawing, linear correlation was good in linear fitting between temperature rise and loss modulus, as well as between temperature rise and tanδ. Keywords: vulcanized rubber; crosslingking density; heat generation; hysteresis