Degrees Of Vacuum Research Articles

Influence of different storage atmospheres in packaging on color stability of beef.

The influence of storage atmosphere on the color development and myoglobin (Mb) redox state of beef was investigated. Beef samples were packaged in 6 different atmospheres including different degrees of vacuum, levels of oxygen, nitrogen, and a mixture with 20% CO2 and stored at 2°C for 14days. Over this time, color and reflection of the packaged samples were measured. The used method allows quick, easy, and non-invasive measurement of the packaged samples, without using time consuming chemical assays. The method could be implemented in beef production lines, with potential for automatization. The data was used to illustrate the L*a*b* values for insights regarding qualitative color changes. Quantitative color changes were analyzed by calculation of color difference ΔE2000. Additionally, the relative levels of the deoxymyoglobin (DMb), oxymyoglobin (OMb) and metmyoglobin (MMb) were calculated from reflection spectra. The most important findings are: there is a strong correlation (rsp=0.80 to 0.99 with one exception at rsp=0.69 (high vacuum), p≤0.05) between a* values and relative OMb levels. Storage atmospheres containing high oxygen concentrations lead to an attractive meat color, but a decreased overall color and Mb stability (ΔE=5.02 (synthetic air) and ΔE=2.23 (high oxygen) after 14 days of storage). Vacuum packaged samples are most stable in regards of color and Mb stability (ΔE=1.79 (high vacuum) and ΔE=1.63 (low vacuum) after 14 days of storage), but lack in the vibrant red color desired for sale. The experiments showed that color measurement can be a fast, non-invasive marker for meat quality. PRACTICAL APPLICATION: In this research article, six different storage atmospheres are compared regarding their influence on color stability and color quality of beef during storage in packaging. The results suggest which atmospheres to use in various sales-related scenarios. The method described can easily be applied in the meat industry to quickly monitor changes during storage and wet-aging without damaging the meat or opening the meat packages.

Effects of vacuum degree on the detonation characteristics and energy release laws of RDX explosive

To explore the detonation characteristics and energy release laws of RDX explosives under varying degrees of vacuum, the influence of vacuum degree on the fireball characteristic parameters, shock wave propagation laws and detonation performance of columnar RDX charges were studied using the air-blast experiments and AUTODYN simulations, and the fireball temperature distributions were mapped with the colorimetric thermometry technique. The experimental results indicated that as the degree of vacuum increased, the combustion duration and zone area size of the explosive fireball were both extended, while its temperature decay rate was slowed down, making the afterburning effect more pronounced. Furthermore, the peak overpressure and positive impulse of the explosion shock wave showed a downward trend, with the reductions of 56.1 % and 53.5 %, respectively, with the increasing vacuum degree. Numerical simulation was also used to reveal the energy release laws of RDX explosive, and the comparison between the experimental and numerical results showed a good degree of concordance with an average error of 6.45 %. The results of the study could provide a reference for expanding the explosion theory of explosives in plateau environment and improving the performance of explosion-proof equipment.

Prediction of two phase flow behavior and mixing degree of liquid steel under reduced pressure

The behavior of gas-liquid two-phase flow in a vessel under reduced pressure was evaluated, and the deviation between the theoretical and measured concentration in the ladle was measured using a water model. The fluid flow trajectory and mixing behavior between the fresh and stale solutions in the vessel under different degrees of vacuum were predicted. The flow in the up-leg changed from a dispersed bubble flow regime to a coalescence bubble flow regime as the degree of vacuum decreased. After reaching the ultimate degree of vacuum, the flow was a discrete bubble flow regime if the amount of liquid in the vacuum chamber was greater than the processing capacity of the chamber. There were many dead zones and local circulation phenomena in the ladle. Even in the best mixing case in the experiment, there was an obvious deviation between the measured and theoretical conductivity values in the upper part of the ladle, and the difference increased as the degree of vacuum decreased.

Influence of heat treatment on thermal cyclic fatigue of TBC systems

Vacuum heat treatment of engine components applied with thermal barrier coatings (TBC) is a common industrial process. However, there has been no systematic investigation explaining this practice. In this work, influences of the heat treatments under different degrees of vacuum (as sprayed, heat treated in atmosphere, 0.5 mbar and 6.67 × 10-4 mbar) on thermal cyclic fatigue lifetime of a TBC system was evaluated. Significant differences in the furnace cycle lifetime at 1135 °C of TBCs heat treated under different degrees of vacuum were found. The TBC samples treated at 6.67 × 10-4 mbar exhibited four times longer than other treatment configurations. Examinations of the thermally grown oxide (TGO) layer and EDS analysis suggest that TGOs with different characteristics formed under the different degrees of vacuum are attributed to the differences in thermal cyclic fatigue lifetime.

Fretting corrosion behavior of electrical contacts with tin coating in atmosphere and vacuum

Electrical contacts are basic components of electrical systems. They are applied in various conditions, which can influence the lifetime of the electrical contacts significantly. Fretting corrosion is one of the main failure mechanisms of electrical contacts with micro-motion. During this operation, the coating on electrical contacts is worn, generating wear debris. If the coating consists of non-noble material, for instance tin, which is a widely used coating material for electrical contacts, the wear debris will be oxidized and subsequently form an electrically highly resistant oxide layer after long-term service. Two decisive factors for the lifetime of electrical contacts are the number of cycles of motion and the time required to form this thick oxide layer. In many power semiconductor components, the housing is firstly pumped to vacuum condition, and then filled with nitrogen. The higher degree of vacuum leads to a substantially reduced amount of oxygen, a lower oxygen partial pressure and a longer mean free path of oxygen molecules, which retards the oxidation process. Therefore a remarkable improvement of fretting corrosion behavior is theoretically expected. The subject of this study is to investigate the effects of atmosphere and vacuum on fretting corrosion behavior. In order to investigate the fretting corrosion performance and the lifetime of these tin coated electrical contacts, a series of wear and fretting corrosion tests are conducted under various degrees of vacuum. The correlation between the lifetime of electrical contacts and pressure is analyzed. The results indicate that with an increasing degree of vacuum, the lifetime of electrical contacts in fretting tests is, as expected, prolonged.

Experimental results on Paschen tests on the electrical insulation of the terminal service Box of the correction coils of ITER

The insulation performance of wet wrapping of terminal service box pipework is investigated by the Paschen discharge test in this study. The test mock-up was designed with a U-shaped pipework as the fundamental structure, consisting of insulator breaks, voltage taps, and high voltage wires. In addition, the design of the test mock-up and insulation structure is studied, and the investigation method used in this study is described in detail. A high voltage test was conducted at room temperature for various degrees of vacuum. The test results demonstrated that the insulation (wet wrapping) remains undamaged, and leakage current is less than 10 μA. Further, the test results conformed to the requirements of the ITER Organization. Finally, the performance of the insulation was determined, and the feasibility of the wet wrapping process was verified indirectly.

Effects of vacuum degree on the water status, physicochemical properties and microstructure of fast frozen dumpling wrappers

SummaryVacuum mixing is a new method of dough making, and little literature is available regarding its effects on the product quality of frozen food. This research studied the effects of different degrees of vacuum (0.00, −0.02, −0.04, −0.06, −0.08 MPa) on the water state, thermal properties, cooking characteristics and microstructure of fast frozen dumpling wrappers during different storage times (0, 14 and 30 days). Vacuum mixing significantly decreased the spin–spin relaxation times (T2) and freezing water content, thus indicating that it decreased the mobility of moisture and enhanced the binding of dough components with water molecules. Furthermore, the increases in the cooking loss rate and hardness of fast frozen dumpling wrappers during storage were inhibited by vacuum mixing, especially after storage for 30 days, possibly because vacuum mixing formed a more continuous and compacted dough structure, thereby generating a smaller ice crystal structure. These results should provide a theoretical basis for the application of vacuum mixing to fast frozen dumplings.

Effects of osmotic dehydration vacuum-microwave drying on the properties of tilapia fillets

A novel drying method based on vacuum-microwave dehydration was developed to investigate the effects of different microwave gap ratios (MGR), microwave times, power densities and degrees of vacuum after osmotic pre-treatment on tilapia fillets. The results showed that the moisture value of fillets was decreased with the increased drying time, power density and vacuum degree. The shrinkage ratio, rehydration ratio and total colour change increased with elevated microwave time and power density. A high degree of vacuum was beneficial to the qualities of fillets. In conclusion, tilapia fillets retained their original quality properties after osmotically dehydrated vacuum-microwave drying (OD-VMD); optimum process parameters were MGR = 2, microwave time = 10 min, power density = 20 W/g, and vacuum degree = 0.08 MPa.

THE TOTAL ABSORPTION CAPACITY OF SPHERICAL CRYOSORPTION PUMPS

The aim of the study is to research influence of the type of adsorbent and the adsorption temperature to the adsorption capacity of the pump. Two methods were used: an approximate calculation of the average temperature and the accurate calculation by integration equation adsorption over the entire volume of the adsorbent. Research carried out at pressure corresponding to different degrees of vacuum. Accordingly were obtained analytical relative computational error – temperature in the periphery of the adsorbent dependence to the following conditions: adsorption of different gases for cooling liquid nitrogen pumps and overcooled liquid nitrogen pumps for the adsorbent with different values of the constant of the pore structure at different intake pressure.

The stability of 30-μm-diameter water jet for jet-guided laser machining

Combined water-jet process and laser machining, the water jet-guided laser processing is suitable in processing a thin and sensitive material with a high degree of precision required. Given that there are many uncertainties of the jet with lower than a 50-μm-diameter nozzle and lower velocities in the stability field of water jet-guided laser machining, a numerical model of a 30-μm water jet, considering the number of grids and the influence of meshes, has been studied to meet the requirements of micrometer order precision machining. Furthermore, the critical Reynolds number and the critical jet exit velocity of the case with a 30-μm-diameter nozzle have been presented to make a comparison between turbulence flow and laminar flow in air with different jet exit velocities from 0.2 to 500 m/s. Hence, the optimal jet exit velocity to achieve the longest stable length of water jet was found. Besides, three cases of 15 m/s jet exit velocity are simulated in different degrees of vacuum, which suggest water jets in vacuum are much more stable than those in atmospheric environment. Finally, a conjecture about water-jet simulation with a smaller diameter of nozzle is proposed as a future work.

The effects of annealing at 1000 °C for 24 h on the extrinsic properties of Pr–Fe–B and Nd–Fe–B-type sintered magnets

Recent studies have shown the effects of a post sintering heat treatment at 1000 °C for 24 h on the microstructure and magnetic properties of Pr–Fe–B/Nd–Fe–B magnets based on Nd 16Fe 76B 8 and Pr 16Fe 76B 8. In an attempt to understand the influence of environmental factors, an investigation into the effects of annealing under different degrees of vacuum for both types of sintered magnets has been carried out. The effect of annealing the Pr–Fe–B magnets at 1000 °C for 24 h resulted in a general increase in the magnetic properties, especially the intrinsic coercivity, although the degree of improvement appeared to be dependent on the initial annealing conditions (ambient pressure). Oxygen analysis of sintered and annealed magnets indicates a change in the nature of the grain boundary phases after the annealing treatment. The effect of annealing the Nd–Fe–B magnets at 1000 °C for 24 h resulted in a general decrease in the magnetic properties, especially the intrinsic coercivity.

Fabrication and testing of a non-glass vacuum-tube collector for solar energy utilization

Abstract An evacuated tubular solar collector was fabricated from acrylics for improved resistance to shattering. A plasmatron was employed to apply a thin gas-barrier coating to the surfaces of the plastic tube to prevent/alleviate gas infiltration. Experiments were conducted to investigate the effect of vacuum level on the performance of the non-glass vacuum-tube solar collector. Inserted in the evacuated tube was a finned heat pipe for solar energy collection and heat transfer to a water tank. Time variations of temperatures on the heat pipe surface and in the water tank were recorded and analyzed for different degrees of vacuum in the collector. The steady-state temperature of the non-glass collector was compared to that of a commercial glass vacuum-tube collector to assess the feasibility of the use of evacuated plastic tubes for solar energy collection. A simple analytical model was also developed to assist in understanding and analyzing the transient behavior and heat losses of the vacuum-tube solar collector.

Structure and Dielectric Properties of Barium Titanate Nanoparticles Prepared under Various Degrees of Vacuum

Structure and Dielectric Properties of Barium Titanate Nanoparticles Prepared under Various Degrees of Vacuum

Effect of Microdermabrasion on Barrier Capacity of Stratum Corneum

A new microdermabrasion system is used for peeling the stratum corneum in a controlled manner. The system uses inert corundum powders under various degrees of vacuum. The fine corundum powders ejected by suction power, being quickly in contact with the skin surface, abrade and remove a tiny fragment of stratum corneum. The fraction of the stratum corneum removed by microdermabrasion can be controlled by the operating conditions; the duration of application (L) and the degree of vacuum setting (V). The stratum corneum barrier function with respect to the rate of skin penetration is well correlated by the product of the square of the degree of the vacuum and the duration of the probe setting.

Grindablility of Crystalline Graphite by Dry Attrition Milling

ABSTRACT Natural graphite, with a high degree of crystallinity, is a very difficult material to be ground finely because of its high lubrication property, and its tendency to slip between lamellar structured layers. Dry grinding with the graphite was carried out using an attrition mill with different degrees of vacuum, and the size distribution and shapes of the ground particles were investigated in various grinding conditions. It was found that the grinding efficiency of the graphite was highly improved, and the submicron sized particles were obtained within reasonably short periods of time. The flaky graphite powders of approximately 0.8μm median size were easily prepared by the modified milling system in three hours.

Experimental studies on cool-down and mass flow characteristics of a demountable liquid nitrogen transfer line

A demountable transfer line has been designed and fabricated to carry out experimental studies on cool-down time and mass flow characteristics of a liquid nitrogen transfer line held in a horizontal position. The effects of varying degrees of vacuum in the interspace on the cool-down time and mass flow rates have been evaluated. It has been found that during the initial phase of cool-down, lines with coarse vacuum perform better than high-vacuum-insulated lines. The performances of multilayer-insulated lines and lines with interspace medium of carbon dioxide have been evaluated as well as that of bare line exposed to an ambient environment. An experimental correlation has been developed to predict the cool-down time as a function of vacuum level and supply dewar pressure.

Evidence of "flat sour" spoilage by obligate anaerobes in marketed canned drinks.

Twenty-five samples of canned drinks incubated at 55C° were examined in microbial aspects during high temperature storage. Forty spoiled cans were found in six kinds of canned coffee samples. The appearance of these was very similar to that of flat sour spoilage. Spoilage ratios ranged from 0.3 percent to 3.6 percent. pH values and degrees of vacuum of the spoiled cans were lower than those of the normal cans. The contents of spoiled cans were more whitish than the normal ones and in some cans separated into clear supernatants and precipitates, but the change of flavor was very slight. From 15 out of 40 spoiled cans some spore-forming obligate anaerobes were isolated. Among 15 isolates inoculated in normal canned coffee samples, 12 isolates caused flat sour spoilage, and there is a chance that the spores of 10 isolates survive the sterilization processes (F0: 15-20). These principal characteristics except for the failure of sulfate reduction might indicate the participation of Desulfotomaculum nigrificans. The flat sour spoilage found in this study was caused by at least 9 obligate anaerobic isolates, and called by the authors“A New Type of Flat Sour Spoilage”(O. A. Flat Sour Spoilage.).

Variation in long-term strength properties of niobium alloys in varying degrees of vacuum

Variation in long-term strength properties of niobium alloys in varying degrees of vacuum

EFFECT OF DEGREE OF VACUUM AND LENGTH OF STORAGE ON THE PHYSICAL CHARACTERISTICS OF VACUUM PACKAGED BEEF WHOLESALE CUTS

ABSTRACTWholesale beef cuts were vacuum packaged at low, intermediate or high degrees of vacuum and stored at l‐3°C for 7, 14, 21, 28 or 35 days. Purge loss, trim loss, muscle color and odor were not generally affected by degree of vacuum. Fat appearance and surface discoloration ratings for primal cuts favored the use of a high level of vacuum in three of five storage intervals. Total desirability ratings for primal cuts packaged with high vacuum were higher than those for primal cuts packaged with low vacuum at all five storage intervals. Cuts from the low vacuum treatment had consistently higher numerical values for trim loss than did cuts from intermediate or high vacuum level groups, but these differences were not statistically significant. Degree of vacuum used during storage of primal cuts did not generally affect the peripheral discoloration, surface discoloration or total desirability of subsequent retail steaks. However, among primal cuts stored for 21 days, peripheral discoloration and total desirability scores were lowest (P < 0.05) for retail cuts from the low vacuum treatment. Differences in juiciness, flavor desirability, overall satisfaction and Warner‐Bratzler shear values for retail steaks were not related to the degree of vacuum used to store primal cuts.

EFFECT OF DEGREE OF VACUUM AND LENGTH OF STORAGE ON THE MICROFLORA OF VACUUM PACKAGED BEEF WHOLESALE CUTS

ABSTRACTWholesale cuts of fresh beef were vacuum packaged at low, intermediate or high degrees of vacuum and stored at l‐3°C for 7, 14, 21, 28 or 35 days. Bacterial counts of samples after 7 and 14 days of storage were low [mean count < 104 per in.2 (6.45 cm2)] irrespective of degree of vacuum. Lactobacilli and anaerobic agar plate counts of cuts stored under high vacuum for 21‐35 days tended to be lower than those of comparable cuts stored under low or intermediate vacuum. This was also true, but much less frequently, for the psychrotrophic and mesophilic counts. Largest increases in bacterial counts occurred between 14 and 21 days of storage. Fluorescent pseudomonads represented only a small percentage of the total microbial population of vacuum packaged beef cuts. Lactobacilli and anaerobic plate counts of vacuum‐packaged cuts were very similar. The psychrotrophic bacterial population of cuts stored for 28 days consisted primarily of Lactobacillus sp., while Pseudomonas sp. and Enterobacteriaceae represented only a small percentage of the psychrotrophic microflora at that time.