PV Value Research Articles

Moisture adsorption behaviour of biscuit during storage investigated by using a new Dynamic Dewpoint method

The changes in moisture adsorption isotherms of commercial biscuits during storage were investigated by means of a rapid Dynamic Dewpoint Isotherms (DDIs) method. Moreover, the relationships between the changes in moisture content and some quality characteristics of biscuits (moisture, aw, peroxide value – PV and texture) were studied during 92days of storage at 35°C. GAB model was used to fit the experimental sorption behaviours. During storage, moisture content and aw of biscuits increased and the obtained isotherms showed modifications in behaviour and shape. Significant changes were observed in PV values and texture, particularly during the first 40days of storage.The monolayer moisture content, obtained by the BET equation, significantly increased during storage from 1.473 to 2.080gwater100gdb−1, probably because of the increase in the active sites for water binding due to the chemical and physical changes of the main components, induced by product ageing.

TEHL analysis of high-speed and heavy-load roller bearing with quasi-dynamic characteristics

In this paper, the aero-engine mainshaft roller bearing D1842926 under typical operating conditions is taken as a case study, a new integrated numerical algorithm of quasi-dynamics and thermal elastohydrodynamic lubrication (TEHL) is put forward, which can complete the bearing lubricated analysis from global dynamic performance to local TEHL state and break out of the traditional analysis way carried out independently in their own field. The 3-D film thickness distributions with different cases are given through integrated numerical algorithm, meanwhile the minimum film thickness of quasi-dynamic analysis, integrated numerical algorithm and testing are compared, which show that integrated numerical results have good agreements with the testing data, so the algorithm is demonstrated available and can judge the lubrication state more accurately. The parameter effects of operating and structure on pv value, cage sliding rate, TEHL film pressure, thickness and temperature are researched, which will provide an important theoretical basis for the structure design and optimization of aero-engine mainshaft roller bearing.

Experimental investigation on the friction and sealing characteristics of narrow end-face seal ring with spiral grooves for wet clutch

Purpose – The purpose of this paper is to investigate the friction and sealing characteristics of narrow end face seal ring with spiral grooves for wet clutch by experiment. Design/methodology/approach – The shallow spiral grooves are machined in the end face of narrow seal ring by laser, and all of other parameters of specimens are the same with the actual production. The investigation of friction and sealing characteristics are carried out by comparing the experiment results of end face seal ring with spiral grooves with the conventional seal ring without spiral grooves through friction coefficient test, volume leakage rate test and pv value test. Findings – Comparing with conventional seal ring without spiral grooves, seal ring with spiral grooves experiences boundary lubrication, mixed lubrication and fluid film lubrication with the increase of rotation speed, whereas the conventional seal ring only experiences mixed lubrication. Besides this, the volume leakage rate is slightly larger, but the pv value is much larger than that of conventional seal ring. Originality/value – Effect of spiral grooves on the friction and sealing characteristics of narrow end face seal ring for wet clutch is investigated. The improved lubrication performance can be achieved by shallow spiral grooves even if the distance of radius difference used to machine grooves is very small.

Effects of turbulent flow field on wavefront aberration in liquid-convection-cooled disk laser oscillator

A liquid-convection-cooled Nd:YAG disk laser oscillator with an output power of 30.7 W and a slope efficiency of 14.1 % is built. By using large-eddy simulation model, the wavefront aberration induced by the turbulent flow is numerically calculated. In the experiment, a Shack–Hartmann wavefront sensor is used to measure the wavefront aberration and the laser intensity distribution. The RMS values and PV values of the beam wavefront and the phase stability of three feature points have been investigated. The experimental results prove that the turbulent flow with high flow velocity and high turbulent intensity can reduce the aberration of the flow field.

Production and characterization of refined oils obtained from Indian oil sardine (Sardinella longiceps).

Crude Sardinella longiceps oil was refined in different stages such as degumming, neutralization, bleaching, and deodorization. The efficiency of these processes was evaluated on the basis of free fatty acid (FFA), peroxide (PV), p-anisidine (pAV), total oxidation (TOTOX), thiobarbituric acid reactive species (TBARS) values, Lovibond CIE-L*a*b* color analyses, and (1)H NMR or GC-MS experiments. The utilities of NMR-based proton signal characteristics as new analytical tools to understand the signature peaks and relative abundance of different fatty acids and monitoring the refining process of fish oil have been demonstrated. Phosphoric acid (1%) was found to be an effective degumming reagent to obtain oil with the lowest FFA, PV, pAV, TOTOX, and TBARS values and highest color reduction. Significant reduction in the contents of hydrocarbon functionalities as shown by the decrease in proton integral in the characteristic (1)H NMR region was demonstrated by using 1% H3PO4 during the course of the degumming process. A combination (1.25:3.75%) of activated charcoal and Fuller's earth at 3% concentration for a stirring time of 40 min was found to be effective in bleaching the sardine oil. This study demonstrated that unfavorable odor-causing components, particularly low molecular weight carbonyl compounds, could successfully be removed by the refining process. The alkane-dienals/alkanes, which cause unfavorable fishy odors, were successfully removed by distillation (100 °C) under vacuum with aqueous acetic acid solution (0.25 N) to obtain greater quality of refined sardine oil, a rich source of essential fatty acids and improved oxidative stability. The present study demonstrated that the four-stage refinement process of sardine oil resulted in a significant improvement in quality characteristics and nutritional values, particularly n-3 PUFAs, with improved fish oil characteristics for use in the pharmaceutical and functional food industries.

Analysis of the Surface Shape Effect on Optical Homogeneity Measurement of Large Calibre Optical Materials

Optical homogeneity is an important measurement of the optical materials, directly affects wavefront quality of the refractive optical system, changes the system wavefront aberration. As the traditional direct measurement method requires high precision surface shape machining for optical material (PV value < 0.1λ), it was gradually replaced by the method of Fizeau interferometer four step, which requires lower surface shape. This article used 600mm diameter Fizeau interferometer, a four step method tested the optical homogeneity of the same 500 mm diameter fused quartz material with a front surface shape respectively 3.719 λ and 0.427 λ (λ = 632.8nm). Comparison of the test results showed that the PV difference of optical homogeneity between the two was only 0.036 λ, △n inaccuracy was 10-7, and the homogeneity morphology matched exactly. To further analyze the factors affecting the optical homogeneity, the front surface shape of the other sample was sliced ​​in a predetermined direction. This artical analyzed the effect of morphology upon the slicing line on optical homogeneity. The conclusion was that the direct affecting factor on optical homogeneity was the slope of surface morphology, rather than the overall PV value.

The Communication Research between PLC and PID Temperature Controller

In this paper, the communication between PLC and PID temperature controller are researched. The asynchronous communication protocol of E909 is used to protect the data that transformed among the bus. The process of speaking, reading and writing of PV and SV value as well as the PID temperature controller communication combine no protocol communications is designed in this paper. At last the models are realized by programming. Experiments show the project we proposed can finish the data transformation in real-time without damage and lost.

Lung ventilation volumetry with same-breath acquisition of hyperpolarized gas and proton MRI.

The purpose of this work was to assess the reproducibility of percentage of ventilated lung volume (PV) measured from hyperpolarized (HP) (3)He and (1)H anatomical images acquired in the same breath-hold when compared with PV measured from (3)He and (1)H images from separate breath-holds. Volumetric (3)He ventilation and (1)H anatomical images of the same resolution were acquired during the same breath-hold. To assess reproducibility, this procedure was performed twice with a short gap between acquisitions. In addition, (1)H images were also acquired in a separate breath for comparison. PV ((3)He ventilated volume divided by (1)H total lung volume) was calculated using the single-breath-hold images (PV(single)) and the separate-breath-hold images (PV(separate)). Short-term reproducibility of PV measurement was assessed for both single- and separate-breath acquisitions. Dice similarity coefficients (DSCs) were calculated to quantify spatial overlap between (3)He and (1)H segmentations for the single- and separate-breath-hold acquisitions. The efficacy of using the separate-breath method combined with image registration was also assessed. The mean magnitude difference between the two sets of PV values (±standard deviation) was 1.49 ± 1.32% for PV(single) and 4.19 ± 4.10% for PV(separate), with a significant difference (p < 0.01). The mean magnitude difference between the two PV values for the registered separate-breath technique (PV(sep-registered)) was 2.27 ± 2.23%. Bland-Altman analysis showed that PV measured with single-breath acquisitions was more repeatable than PV measured with separate-breath acquisitions, regardless of image registration. DSC values were significantly greater (p < 0.01) for single-breath acquisition than for separate-breath acquisition. Acquisition of HP gas ventilation and (1)H anatomical images in a single breath-hold provides a more reproducible means of percentage lung ventilation volume measurement than the previously used separate-breath-hold scan approach, and reduces errors.

Scanning Mirror Topology Optimization of the Imaging Spectrometer

In order to obtain high dynamic RMS performance of the scanning mirror in the working condition, the topology optimization method based on the constrain of dynamic deformation was carried out. Effective simplifications are implemented to reduce the complexity of the calculation. With the topology method, a lightweight form of the scanning mirror was generated on the dynamic working condition. The result shows that the lightweight ratio of the optimized structure is 47.4%, the PV value is 19.36nm and the RMS value is 5.65nm, which is improved by 18.46% and 17.41%, respectively. Besides, the first order frequency has increased by 113.8Hz. The results illustrate that the proposed method for the optimization of the scanning mirror is reasonable and practically.

Dry friction and wear characteristics of impregnated graphite in a corrosive environment

Tribological properties of impregnated graphite are greatly influenced by preparation technology and working conditions and it’s highly susceptible to corrosion environmental impacts, but the experimental research about it are few. In this paper, three kinds of impregnated graphite samples are prepared with different degree of graphitization, the tribological properties of these samples in the dry friction environment and in a corrosive environment are analyzed and contrasted. The tribo-test results show that the friction coefficient of samples is reduced and the amount of wear of samples increase when the graphitization degree of samples increases in dry friction condition. While in a corrosive environment (samples are soaked N2O4), the friction coefficient and amount of wear are changed little if the graphitization degree of samples are low. If the degree of graphitization increase, the friction coefficient and amount of wear of samples increase too, the amount of wear is 2 to 3 times as the samples tested in the non-corrosive environment under pv value of 30 MPa · m/s. The impregnated graphite, which friction coefficient is stable and graphitization degree is in mid level, such #2, is more appropriate to have a work in the corrosion conditions. In this paper, preparation and tribological properties especially in corrosive environment of the impregnated graphite is studied, the research conclusion can provide an experimental and theoretical basis for the selection and process improvement of graphite materials, and also provide some important design parameters for contact seal works in a corrosive environment.

Fabrication of small aspheric moulds using single point inclined axis grinding

Single point inclined axis grinding techniques, including the wheel setting, wheel–workpiece interference, error source determination and compensation approaches, were studied to fabricate small aspheric moulds of high profile accuracy. The interference of a cylindrical grinding wheel with the workpiece was analysed and the criteria for selection of wheel geometry for avoiding the interference was proposed. The grinding process was performed with compensation focused on two major error sources, wheel setting error and wheel wear. The grinding results showed that the compensation approach was efficient and the developed grinding process was capable to generate small aspheric concave surfaces on tungsten carbide material with a profile error of smaller than 200nm in PV value after two to three compensation cycles.

Variation in photosynthetic and nonphotosynthetic vegetation along edaphic and compositional gradients in northwestern Amazonia

Abstract. Tropical forests vary substantially in aboveground properties such as canopy height, canopy structure, and plant species composition, corresponding to underlying variations in soils and geology. Forest properties are often difficult to detect and map in the field, however, due to the remoteness and inaccessibility of these forests. Spectral mixture analysis of Landsat imagery allows mapping of photosynthetic and nonphotosynthetic vegetation quantities (PV and NPV), corresponding to biophysical properties such as canopy openness, forest productivity, and disturbance. Spectral unmixing has been used for applications ranging from deforestation monitoring to identifying burn scars from past fires, but little is known about variations in PV and NPV in intact rainforests. Here we use spectral unmixing of Landsat imagery to map PV and NPV in northern Amazonia, and to test their relationship to soils and plant species composition. To do this we sampled 117 sites crossing a geological boundary in northwestern Amazonia for soil cation concentrations and plant species composition. We then used the Carnegie Landsat Analysis System to map PV and NPV for these sites from multiple dates of Landsat imagery. We found that soil cation concentrations and plant species composition consistently explain a majority of the variation in remotely sensed PV and NPV values. After combining PV and NPV into a single variable (PV–NPV), we determined that the influence of soil properties on canopy properties was inseparable from the influence of plant species composition. In all cases, patterns in PV and NPV corresponded to underlying geological patterns. Our findings suggest that geology and soils regulate canopy PV and NPV values in intact tropical forests, possibly through changes in plant species composition.

Lubricating characteristics and motion characteristics of a rolling piston for rotary compressors in air conditioners

To investigate the lubricating characteristics between the rolling piston and the vane, as well as the characteristics of rotating motion of the rolling piston in a rotary compressor, we perform a numerical analysis of the rolling piston and vane motion. The analysis considers mixed lubrication of the vane sliding surface to calculate the friction force between the vane and the vane slot. We find that the relative sliding velocity between the rolling piston and the vane can be reduced by reducing the rolling piston weight, and that the maximum PV value during one crank revolution between the rolling piston and the vane decreases due to the increased vane slot length in high-rotating-frequency regions.

Spherical mirror estimation with phase diversity method

In order to verify the phase diversity wavefront detector system by using its own light source to complete the wavefront estimation task independently, this paper sets up estimation spherical mirror shape of experiment platform with the method of phase diversity. Phase diverisity method collects shorter exposure image at the same time in the focal plane and away from the focal plane, calculates the distribution of wavefront solutions and recovers the target based on known defocus, so as to realize the estimation of large mirror aberration. In order to further validate the phase diversity measurement method, the phase diversity measurement results with high accuracy ZYGO interferometer measurement results are compared. Experimental results demonstrate that agreement is obtained among the errors distribution, PV value and RMS value of ZYGO interferometer, so the phase diversity method can effectively estimate the mirror aberration, which shows the feasibility and accuracy of phase diversity method.

Influence of roasting conditions on fatty acid composition and oxidative changes of cocoa butter extracted from cocoa bean of Forastero variety cultivated in Togo

Cocoa butter is responsible for physico-chemical, rheological and sensory properties of chocolates. Forastero cocoa beans are rich in cocoa butter. Roasting of cocoa beans is an essential step of their processing, giving rise to many desirable transformations. On the other hand, it causes changes in certain valuable ingredients including also cocoa butter. This article studies the influence of roasting conditions, i.e. temperature, humidity and flow velocity of roasting air, on the fatty acid composition, peroxide value and content of conjugated dienes and trienes in cocoa butter extracted from cocoa beans. Generally, in most cases roasting did not increase the peroxide value. In the constant conditions due to obtained results of PV, CD and CT values it is recommended to roast cocoa beans at the temperature of 150°C, 1m/s air velocity and 5% relative humidity. In the variable conditions lower values of PV, CD and CT were achieved when cocoa beans were roasted in variants with changing temperature from 150°C to 135°C or with changing air velocity from 1 to 0.5m/s. Generally, the roasting process substantially did not change the content of each fatty acid, regardless of the applied conditions.

Microstructure and Tribological Properties of WC-CeO2/Ni- base Alloy Composite Coatings

The Ni-base alloy composite coatings synergistically reinforced by WC and CeO2 particles were prepared on the surface of 7005 aluminum alloy by the plasma spray technique. The microstructures and the tribological properties of the composite coatings were researched. The results show that with the addition of CeO2 particles, the microstructure of the composite coating is refined; meanwhile, the WC reinforcing particles change from round to irregular polygon and their decarburization are alleviated. The friction coefficients and the wear losses of the composite coatings are lower than those of the WC/Ni-base alloy composite coatings and the Ni-base alloy coatings at different PV values. When the PV values are smaller than 3.36 N·m/s, the maximum contact stress of the composite coating is lower than its elastic limit contact stress, the wear mechanisms of which are mainly micro-cutting wear and fatigue wear. As the PV values are bigger than 3.36 N·m/s, the maximum contact stress exceeds the elastic limit contact stress of the composite coating and the contact temperature sharply increases to 648 °C, obvious plastic deformation and desquamation traces appear on the worn surface and the wear mechanisms turn into multi-plastic deformation wear, abrasive wear and adhesive wear accompanied with oxidative wear.

Design and analysis of radial support for a large-aperture rotating mirror

Effective support ways can contribute to the good performance of a large-scale optical system. An adjustable three-segment surface-contact radial support way is proposed to facilitate the movement process of a large-scale rotating mirror. Under a most dangerous working condition, the supporting angle is optimized by a two-step optimization method, which makes the maximum PV value reduce by 10.26% relative to that before optimization and that the maximum von Mises stress has a very little increase. Moreover, the coupling analysis of thermal stress in the rotating mirror caused by some thermal factors, such as motor heat, is carried out to validate the assembly design. The supporting way, as an effective radial mounting for dynamic optical elements, can be valuable for the reference of similar opto-mechanical design.

Stability of rice bran oil extracted by SFE and soxhlet methods during accelerated shelf-life storage

Supercritical fluid high oryzanol (SFE HO) and supercritical fluid low oryzanol (SFE LO) rice bran oils were obtained and compared with that extracted by the Soxhlet (SOX) method. Their composition and stability during storage were determined. The amount of unsaponifiable matter and gamma oryzanol of SFE samples were significantly (p < 0.05) higher than SOX. While the amount of tocopherol in SOX (4.0 mg·g-1) was higher than that reported in SFE HO and SFE LO, at 3.2 and 2.6 mg·g-1, respectively. After storage for 42 days at 70 °C the PV, FFA%, conjugated diene and p-anisidine values of SOX were higher than those of SFE HO, and SFE LO. The SFE samples showed better stability than SOX under successive heating and the addition of BHA decreased PV, FFA%, conjugated diene and p-anisidine levels in all samples.

Contrastive Analysis on Thermal Deformation of Thrust Bearing Pad with Two Kind of Supporting

In order to solve thermal deformation, the finite element numerical simulation of two kind of tilting pad thrust bearing is made for the same pad surface, and thermal deformation is made to analyze comparatively. The results show that the temperature field, the deformation field and the values of pad are similar for two different supported thrust bearing (point, line support) under the same operating condition. The pad temperature and deformation will increase with the increasing of pv values. According to the calculation conditions, the temperature field rose about 1°C, and the thermal deflection increased 0.002mm with pv value increased by 10%.

Theoretical and Experimental Research on a Pressure-Reducing Valve for a Water Hydraulic Vane Pump

In order to control the high PV value between the vanes and the cam ring in a water hydraulic vane pump, a pressure-reducing valve with a constant pressure ratio was developed in this study. The pressure and leakage characteristics of the valve were theoretically analyzed by simulation and the experiments were also conducted based on the valve prototype. The theoretical analysis agrees well with the experimental results. Further, these results reveal that the pressure ratio of the valve decreases to the design value with the increasing working pressure. Additionally, the leakage of the valve rises simultaneously with the increasing working pressure and can be reduced significantly by decreasing the clearance between the valve body and the spool. The presented research not only proves the successful development of the pressure-reducing valve but also lays a foundation for the investigation of a high-pressure water hydraulic vane pump.