Influence Of Negative Pressure Research Articles

Safety Evaluation of Plain Concrete Lining Considering Deterioration and Aerodynamic Effects

With an increase in the service time of high-speed railway tunnels, various defects caused by construction-quality defects in the secondary lining begin to appear. How to evaluate the safety of such tunnels and take countermeasures is very important for the safe operation of tunnels. Based on the load-structure method and a numerical simulation, this paper studied the short-term and long-term safety of the missing section of anti-crack reinforcement mesh in the plain concrete lining of a high-speed railway mountain tunnel. The short-term safety evaluation considered the influence of negative pressure caused by aerodynamic effects. The long-term safety evaluation considered the combined influence of the surrounding rock and concrete deterioration and the negative pressure and concrete fatigue damage caused by aerodynamic effects. The results showed that under the negative pressure generated by aerodynamic effects, the minimum tensile safety factor of the lining in the defective section increased by 3.8%, while the minimum compressive safety factor of the lining decreased by 7.9%. The negative pressure generated by the aerodynamic effects had little impact on the short-term safety of the lining in the defective section. During the long-term safety evaluation, the overall safety of the defective section decreased significantly, and the minimum tensile and minimum compressive safety factors of the lining decreased by 59.4% and 66.8%, respectively. The calculation results for the initial design do not meet the long-term design requirements and cannot guarantee the long-term safe operation of the tunnel. Finally, two new strengthening methods of galvanized steel mesh-short bolts and galvanized corrugated steel plate-short bolts were proposed to strengthen the defective section of the concrete lining, so as to improve the ultimate bearing capacity and toughness of the plain concrete lining structure.

Influence of negative pressure on changes in blood supply in donor zones of perforant flaps formation

Our study is based on the establishment of normative indicators of the effect of negative pressure on the skin of the thigh. To do this, a group of healthy volunteers was examined – 35 people: 17 women and 18 men aged 19 to 58. The study was conducted on the clinical basis of the burn centre in 2020-2021. The local vacuum was created using a negative pressure device “AGAT-Dnepr” by applying a silver-containing polyurethane sponge directly on the front surface of the thigh. The pressure (P) – 110-160 mmHg has been applied for 30 minutes. Tissue perfusion was monitored by laser Doppler flowmetry and thermal imaging research. Measurements were performed before vacuum, immediately after the end of the application of negative pressure, for three days at the same time at a constant temperature. According to the results of the cluster analysis, based on the effect of negative pressure on the thigh skin, patients with three types of reactions were identified – low, medium and high perfusion changes. The perfusion level of tissue volume per unit time increased the most rapidly: in the group of high perfusion by 45.56 (95% CI 42.09-51.96) PU; in the group of average perfusion – by 22.49 (95% CI 19.93-28.99) PU; in the low perfusion group – by 22.43 (95% CI 15.90-25.13) PU. The number of erythrocytes per unit tissue changed at a medium rate: in the high perfusion group by 57.77 (95% CI 53.05-62.48) AU; in the group of average perfusion – by 55.86 (95% CI 49.62-65.06) PU; in the low perfusion group – by 34.85 (95% CI 13.19-53.55) PU. Among those surveyed, 12 people were included in the low perfusion group (34.29%), 16 people in the medium perfusion group (45.71%) and 7 people in the high perfusion group (20.0%). Before VAC-action the ascending level of thigh skin temperature T1 ranged from 28.60 to 32.90°C and averaged 31.46 (95% CI 30.97-31.95)°C. Immediately, after the offset of the negative pressure the area of the fields of local skin temperature rise increased, the average temperature level ranged from 30.60 to 35.0°C and the average T2 was 33.59 (95% CI 33.16-34.01)°C. The temperature rise occurred on average by 2.13 (95% 1.72-2.54)°C, which corresponded to an increase of 6.77% with significant (p<0.001) statistical differences. Only 1 examined had a slight decrease in the tem­perature of the thigh skin from 31.9 to 31.6°C, in the rest of the examined the rise was by 6.4°С maximally, from 28.6 to 35.0°С, there was a temperature rise by 2°С or more degrees among 9 people (25.71%). After 24 hours there was a rise in local body temperature among all examined (100%), after 48 hours – among 25 (71.43%), and after 72 hours – among 21 examined (60.0%). When choosing a donor site of the perforant flaps, we recommend relying on areas which will belong to the group of indicators with high perfusion. According to the analysis, the group of high perfusion will include patients with an initial average level of perfusion in the donor areas per unit time of 15.84 (14.47-17.21) PU, the number of erythrocytes per unit tissue – 58.73 (53.44-64.02) AU and skin temperature – 29.23 (28.65-29.80)°С; to the average according to F rates – 14.36 (13.0-15.73) PU, C rates – 45.37 (39.74-51.0) AU, T rates – 28.17 (27.74-28.60)°С; to the group of low perfusion, respectively, according to F rates – 12.38 (10.74-14.0) PU, C rates – 43.89 (40.18-47.61) AU, T rates – 29.79 (29.17-30.40)°С. In general, the effect of negative pressure contributes to increased perfusion and local microcirculation in tissues, as evidenced by dynamic infrared thermography: increased “hot” skin fields, increased temperature with a temperature gra­dient ∆T2.1=2.13 (95% 1.72-2.54)°C and for indicators of laser Doppler flowmetry – increase in perfusion by 2.42 times (p<0.001).

Influence of Negative Pressure on Clogging of Submerged Entry Nozzle for Continuous Casting

Influence of Negative Pressure on Clogging of Submerged Entry Nozzle for Continuous Casting

Gas seepage characteristics of loaded coal under negative suction pressure

ANSYS was used in this study to simulate the change in permeability of loaded coal under negative pressure. The ANSYS transient structural module was employed to simulate the coal loading conditions and to calculate the coal volumetric strain and coal porosity change. In the ANSYS Fluent module, the porosity of the porous medium was changed to replace the coal deformation, and the outlet pressure was changed to simulate the change of negative pressure. By using 1stOpt software, the relationships among the negative pressure, effective stress, and permeability of coal were fitted, and the binary nonlinear function of permeability varying with effective stress and negative pressure was obtained, and the correlation coefficient was excellent. Results showed that the coal permeability had a negative exponential relationship with effective stress. Hence, the permeability decreased with the increase of the effective stress. The change in stress loading mode caused a sudden change in porosity and permeability. The coal permeability had an approximately linear relationship with negative pressure. Hence, permeability increased with an increase in negative pressure. However, with the increase of effective stress, the influence of negative pressure on coal permeability was gradually weakened.

The two-phase flow simulation and experimental research on the formation of solder voids in power module

This paper focuses on the formation of solder voids in the large-area die-attach (DA) in power modules. The finite volume simulation method was used to study the motion behaviors of bubbles in molten liquid solder. The experiments were carried out by changing the reflow atmosphere. The voids distribution in DA was characterized by X-Ray detection. Results suggest that vacuuming the molten solder can significantly reduce the void rate of the DA. The bubbles only need a short stroke to escape from the molten solder under the influence of negative pressure. From a mechanical point of view, the collapse of the solder during the phase change is one of the main forces for driving the bubble to coalesce and move horizontally, but it may also lead to an increase in void ratio due to the reduction of BLT (Bond Layer Thickness). Solders with larger wall contact angles tend to have a larger void rate due to the increase in viscous resistance. The nitrogen atmosphere has a positive effect on reducing the void rate by reducing the wall contact angle of liquid solder. Besides, the wall adhesion plays a leading role in the movement of the bubble, and the influence of the buoyancy is small.

The Influence of Negative Pressure and of the Harvesting Site on the Characteristics of Human Adipose Tissue-Derived Stromal Cells from Lipoaspirates.

Background Adipose tissue-derived stromal cells (ADSCs) have great potential for cell-based therapies, including tissue engineering. However, various factors can influence the characteristics of isolated ADSCs. Methods We studied the influence of the harvesting site, i.e., inner thigh (n = 3), outer thigh (n = 3), outer thigh (n = 3), outer thigh (Results We revealed higher initial cell yields from the outer thigh region than from the abdomen region. Negative pressure did not influence the cell yields from the outer thigh region, whereas the yields from the abdomen region were higher under high negative pressure than under low negative pressure. In the subsequent passage, in general, no significant relationship was identified between the different negative pressure and ADSC characteristics. No significant difference was observed in the characteristics of thigh ADSCs and abdomen ADSCs. Only on day 1, the diameter was significantly bigger in outer thigh ADSCs than in abdomen ADSCs. Moreover, we noted a tendency of thigh ADSCs (i.e., inner thigh+outer thigh) to reach a higher cell number on day 7. Discussion. The harvesting site and negative pressure can potentially influence initial cell yields from lipoaspirates. However, for subsequent in vitro culturing and for use in tissue engineering, it seems that the harvesting site and the level of negative pressure do not have a crucial or limiting effect on basic ADSC characteristics.in vitro culturing and for use in tissue engineering, it seems that the harvesting site and the level of negative pressure do not have a crucial or limiting effect on basic ADSC characteristics.

Computational Model of Unsteady Hydromechanics of Large Amplitude Gerstner Waves

The computational experiments in the ship fluid mechanics involve the nonstationary interaction of a ship hull with wave surfaces that include the formation of vortices, surfaces of jet discontinuities, and discontinuities in the fluid under the influence of negative pressure. These physical phenomena occur not only near the ship hull, but also at a distance where the waves break as a result of the interference of the sea waves with waves reflected from the hull. In the study reported here we simulate the wave breaking and reflection near the ship hull. The problem reduces to determining the wave kinematics on the moving boundary of a ship hull and the free boundary of the computational domain. We build a grid of large particles having the form of a parallelepiped and, in the wave equation instead of the velocity field we integrate streams of fluid represented by functions as smooth as the wave surface elevation field. We assume that within the boundaries of the computational domain the waves do not disperse, i.e. their length and period stay the same. Under this assumption, we simulate trochoidal Gerstner waves of a particular period. This approach allows to simulate the wave breaking and reflection near the ship hull. The goal of the research is to develop a new method of taking the wave reflection into account in the ship motion simulations as an alternative to the classic method which uses added masses.

APPLICATION OF VAC-THERAPY IN THE TREATMENT OF DIABETIC FOOT

The aim. To substantiate the effectiveness of the use of VAC-therapy in the treatment of wounds in patients with diabetic foot syndrome. Materials and methods. The patient with a complicated form of diabetic foot syndrome was examined. The monitoring of the course of the wound process is supplemented by clinical, cytological, microbiological and morphological criteria. In the treatment of patients we used vacuum therapy apparatus. Vacuum wound therapy was performed in negative pressure regimens in the range of 80–125 mm Hg. Results. In the pattern of morbidity in economically developed countries, diabetes mellitus (DM) occupies one of the first places. Its prevalence is 1.5–6 %. The number of patients with diabetes in Ukraine is likely to reach 14 million by 2020. Lesions of the lower extremities of different genesis occur in 30–80 % of people with impaired carbohydrate metabolism. Most often, these lesions are complicated by the development of chronic peptic ulcer defects, which, when untimely diagnosed and inadequate treatment, leads to amputation of the affected limb. Even when radical surgery is avoided, the long and costly treatment of trophic disorders of the soft tissues of the feet and legs leads to huge costs of both material resources and time for medical staff. In 15 % of patients with DM, trophic ulcers of the lower extremities are diagnosed. Recent studies have focused on such important aspects of the study of this issue as the early diagnosis of soft tissue lesions in individuals with DM, the development of treatment aimed at preventing amputations, facilitating the further rehabilitation of patients. Vacuum therapy is one of the new methods of treating wound defects, including in patients with diabetic foot syndrome. Topical application of vacuum therapy has already become an integral therapeutic option for wound debridement in patients with diabetic foot syndrome. However, when applying the classic vacuum therapy technique, these patients have the problem of delaying the outflow of tissue exudate and lysis detritus to the vacuum system. Conclusions. Optimization of the technique of the influence of negative pressure on the wound by applying forced drainage with irrigation of the wound with an antiseptic can maintain a constantly high concentration of antimicrobial agent in the wound, increase the speed of wound dialysis and prevent clogging of pores of the sponge and the bacterial colonies in it. The application of this technique avoids high amputation, accelerates the time of wound healing, and retains the supporting function of the lower extremity.

The influence of negative pressure during gas extraction in low-permeability coal seams on the effect of gas extraction

In order to improve the extraction method of gas extraction in coal seams with low permeability, the quadratic polynomial formula between the amount of extracted pure gas and negative pressure during gas extraction (NPGE) can be deduced based on the basic theory of oil and gas seepage mechanics in porous media and the pressure function theory of distribution of gas pressure. By using the measurement of orifice flowmeter, the formula of the amount of extracted mixed gas can be acquired and then the expression between the gas extraction concentration (GEC) and NPGE is deduced. Thus, the equation set concerning gas extraction effect is composed of three equations: the equation between the amount of extracted pure gas and NPGE, the formula for calculating the amount of extracted mixed gas, and the formula of relationship between the GEC and NPGE. According to the equation set, the GEC and the amount of extracted pure gas are calculated to further draw the scatter diagram and trend line of function. Afterwards, by analyzing the calculation result and trend line of functions, it can be seen that the increase amplitude of GEC is limited by improving the NPGE. By observing the on-site NPGE of the 20109 Wangjialing Coal mine (Shanxi Province, China), it can be speculated that with increasing NPGE, the increase trends of the GEC and the amount of extracted pure gas were consistent with that deduced theoretical formula for calculating the amount of extracted pure gas. It was basically shown as a quadratic polynomial relation in which the amount of extracted pure gas insignificantly increased. Therefore, it is infeasible to improve the gas extraction in coal seams with low permeability only relying on increasing the NPGE, and other technology methods are necessary.

A novel technique to prevent intra-operative pneumothorax in awake coronary artery bypass grafting: biomaterial neo-pleura☆

Pneumothorax caused by damaged pleura represents the biggest obstacle in awake coronary artery bypass grafting. In order to safely perform this surgery, a new technique was developed to close the damaged pleura. A rub-and-spray method was employed using polyglycolic acid nonwoven fabric and fibrin glue. At first, some fibrinogen solution was rubbed on the edge of the pleural defect and then the PGA fabric was placed and the fibrinogen and thrombin solutions were sprayed. Using a thorax model, the burst pressure caused by positive pressure and the influence of negative pressure, moisture, time, continuous respiratory movement and pleural defect size were examined. In an animal experiment using pigs, the duration spent on repair was measured and any air leakage from the pleura was also identified. In the thorax model, the burst pressure was 355.9+/-55.8 mmHg with positive pressure and no significant difference in negative pressure, moisture, time and respiratory moment was identified. However, there was a significant difference in the defect size. In the animal model, repair was easily achieved regardless of the defect size or location and air leakage was not seen after repair. The average duration of repair was 21.0s. The present method achieved a strong closure with sufficient durability. Since the fabric is soft and flexible and suturing is not required, moving and fragile pleura can be easily repaired regardless of the defect location and size. Once established, the present method may be used in other forms of awake thoracic surgery or reconstruction of the thorax.

Influence of negative pressure when harvesting adipose tissue on cell yield of the stromal–vascular fraction

Adipose tissue is the standard autologous filling material used in plastic surgery today. At the same time it is also a source of mesenchymal stem cells, situated in the Stromal-Vascular Fraction (SVF) and easy to obtain in large quantities. The method of harvesting adipose tissue is an important stage for cell survival. So far, comparative studies on harvesting techniques have only concerned MTT cell viability of mature adipocytes. The aim of our study was to determine the influence of pressure on the yield of SVF cells in relation to the syringe aspiration technique which is the standard technique in plastic surgery. For this, six different harvesting conditions were tested on 3 patients. For each condition, a sample was taken from the trochanter region with the help of a 3 mm cannula, manual aspiration by a 10 ml syringe; wall suction; the traditional pump suction at -350 and -700 mmHg; the power assisted liposuction at -350 and -700 mmHg. Cell yield with a pressure of -350 mmHg, assisted or not, was greater than that obtained at -700 mmHg and significantly superior to aspiration with a syringe (p<0.05). At -350 mmHg, the use of power-assisted liposuction gave better results for two out of three patients when compared to non-power-assisted liposuction. Negative pressure is a factor influencing the number of SVF cells harvested.

Bass-reflex speaker assembly

To provide a bass-reflex speaker assembly having superior water resistance and which can be mounted on a motorcycle, while not being subjected to the influence of negative pressure due to wind during travel and which is capable of maintaining superior sound quality. A resonant duct projects downwards at an incline at a bottom surface of a speaker enclosure. It is therefore difficult for rain water to enter because the duct opens downwards and water that may enter temporarily can be easily discharged from the same duct. Furthermore, when speakers are positioned within the cowling of the motorcycle, negative pressure occurring due to wind when the vehicle is travelling acts not only on the front surfaces of paper cones of the speakers, but also on the rear surfaces via the ducts. Therefore, superior sound quality can be maintained without the influence of negative pressure being incurred and a bass-reflex speaker assembly suited to motorcycles is therefore possible.

Studies on the Blood Capillaries under the Influence of Negative Pressure (VII)

Studies on the Blood Capillaries under the Influence of Negative Pressure (VII)

Studies on the Blood Capillaries under the Influence of Negative Pressure (VIII)

Studies on the Blood Capillaries under the Influence of Negative Pressure (VIII)

Studies on the Blood Capillaries under the Influence of Negative Pressure (VI)

Studies on the Blood Capillaries under the Influence of Negative Pressure (VI)

Studies on the Blood Capillaries under the Influence of Negative Pressure (IV)

Studies on the Blood Capillaries under the Influence of Negative Pressure (IV)

Studies on the Blood Capillaries under the Influence of Negative Pressure (III) : On the dilatation of capillaries and the relation between the dilatation and the edema.

Studies on the Blood Capillaries under the Influence of Negative Pressure (III) : On the dilatation of capillaries and the relation between the dilatation and the edema.

Studies on the Blood Capillaries under the Influence of Negative Pressure (II) : On the edema

Studies on the Blood Capillaries under the Influence of Negative Pressure (II) : On the edema

Studies on the Blood Capillaries under the Influence of Negative Pressure : (I) The variation on normal blood capillaries

The author devised and made a certain suction apparatus which is able to observe the Capillaries during the whole time of the application of negative pressure. Applicaling-200mmHg with this apparatus. he investigated the changes of capillaries on 50 normal adults, and obtained the following results. Whole the capillaries were expanded, blood filling was increased, base colour Avas strengthened, blood flow was delayed or stopped, and the edema appeared on all Cases. Also observed the capillary bleedings and the increase of number of visible capillaries on some cases.

The Influence of Negative Pressure in the Sphenoid on the Optic Nerve

The Influence of Negative Pressure in the Sphenoid on the Optic Nerve