Loss Of Vacuum Research Articles

The Use of Vacuum‐Assisted Closure Therapy for the Treatment of Distal Extremity Wounds in 15 Dogs

To evaluate clinical outcome after vacuum-assisted closure (VAC) therapy in dogs with traumatic wounds located in the distal extremities and report our early experience with VAC. Retrospective study. Dogs (n=15) with traumatic distal extremity wounds. Medical records (1999-2003) of dogs with traumatic injuries to the distal extremities managed by VAC were evaluated. Data included signalment, location of wound, time until surgical intervention, wound reconstruction methods, orthopedic procedures, outcome, complications associated with VAC, and length of hospitalization. The mean number of days until reconstruction was 4.6 days (range, 2-7 days). Reconstructive surgery was successful in all cases. Mean hospitalization was 9.7 days (range, 6-16 days). Complications included dermatitis at the wound margin and loss of vacuum causing wound desiccation. VAC therapy can be used to achieve adequate management of traumatic distal extremity wounds. VAC provides an effective method of securing skin grafts over the wound bed. VAC therapy can be used as an ancillary treatment for distal extremity wounds in dogs before surgical repair as well as a method for securing skin grafts to the wound bed.

Heat conductivity metamorphoses in narrow gaps using the example of vacuum-processed glass packs

An analysis is performed of the formulas available in the literature to calculate the rarefied gas heat conductivity, and the dependencies are revealed of the coefficients of the glass pack thermal resistance against the heat transfer and their constituents on the pressure and the degree of the glass blackness in order to determine the necessary parameter values to meet the requirements of the 1991 ASTM International Standard. The possibility is noted of vacuum losses due to gas or fluid desorption from the internal surfaces of the glass pack, thus, causing a significant increase in the heat conductivity.

Effect of powdered activated carbon on Chinese traditional medicine wastewater treatment in submerged membrane bioreactor with electronic control backwashing

Chinese traditional medicine wastewater, rich in macromolecule and easy to foam in aerobic biodegradation such as Glycosides, was treated by two identical bench-scale aerobic submerged membrane bioreactors (SMBRs) operated in parallel under the same feed, equipped with the same electronic control backwashing device. One was used as the control SMBR (CSMBR) while the other was dosed with powdered activated carbon (PAC) (PAC-amended SMBR, PSMBR). The backwashing interval was 5 min. One suction period was about 90 min by adjusting preestablished backwashing vacuum and pump frequency. The average flux of CSMBR during a steady periodic state of 24 d (576 h) was 5.87 L/h with average hydraulic residence time (HRT) of 5.97 h and that of PSMBR during a steady periodic state of 30 d (720 h) was 5.85 L/h with average HRT of 5.99 h. The average total chemical oxygen demand (COD) removal efficiency of CSMBR was 89.29% with average organic loading rate (OLR) at 4.16 kg COD/(m 3-d) while that of PSMBR was 89.79% with average OLR at 5.50 kg COD/(m 3-d). COD concentration in the effluent of both SMBRs achieved the second level of the general wastewater effluent standard GB8978–1996 for the raw medicine material industry (300 mg/L). Hence, SMBR with electronic control backwashing was a viable process for medium- strength Chinese traditional medicine wastewater treatment. Moreover, the increasing rates of preestablished backwashing vacuum, pump frequency, and vacuum and flux loss caused by mixed liquor in PSMBR all lagged compared to those in CSMBR; thus the actual operating time of the PSMBR system without membrane cleaning was extended by up to 1.25 times in contrast with the CSMBR system, and the average total COD removal efficiency of PSMBR was enhanced with higher average OLR.

Control and Performance Characteristics of Eight Different Suction Biopsy Devices

To determine the control and performance characteristics of eight different suction biopsy devices. Physician control of the syringe and needle was measured precisely with the validated linear displacement method during the aspiration phase and during five biopsy passes. The visual analog scale was used to measure operator difficulty in the following domains: (i) attachment to the needle, (ii) generation of vacuum, (iii) detection of loss of vacuum, (iv) release of the vacuum, and (v) clearing of the sample from the needle. Performance in various phases of the biopsy procedure varied widely among the biopsy devices tested. Unintended forward penetration (ie, loss of control in the forward direction) was significant with the reverse aspiration syringe (31.5 +/- 1.7 mm), three-ringed control syringe (25.4 +/- 4.1 mm), BioSuc-C7 syringe (28.3 +/- 1.9 mm), conventional syringe with a plunger lock (6.1 +/- 1.5 mm), syringe pistol (9.2 +/- 2.4 mm), and conventional syringe (3.8 +/- 2.9 mm) but was significantly less for the reciprocating procedure device (RPD; 0.7 +/- 0.7 mm; P </= .001) and RPD syringe holder (0.6 +/- 0.6 mm; P </= .001). The mean performance rankings were the best for the RPD (3.42 +/- 2.57) and RPD syringe holder (4.29 +/- 2.50) and worst for the conventional syringe (6.14 +/- 2.67; P </= .001) and conventional syringe with a plunger lock (6.86 +/- 3.80; P </= .001). Each of the suction biopsy devices has unique advantages and disadvantages. Suction biopsy devices with the least favorable overall performance were the conventional syringe and the conventional syringe with a plunger lock. The highest overall performance was seen with the RPD and RPD syringe holder.

IMPROVING THE QUALITY OF PORK HAM BY PULSED VACUUM COOLING IN WATER

ABSTRACT Vacuum cooling of pork ham with water, or immersion vacuum cooling, is a successful method to compensate the high mass loss of traditional vacuum cooling. In order to further optimize vacuum cooling with water, pulsed vacuum cooling was designed to study the effect of different cycles on the quality of pork ham, i.e., in one cycle, four cycles and eight cycles. The result indicated that increasing pulse cycles during vacuum cooling of pork ham with water would reduce the cooling loss with compatible cooling time. Tests on the physical properties of pork ham disclosed that tenderness and water‐holding capacity could be improved by increasing pulse cycles during vacuum cooling with water. However, There was no significant difference observed between pork ham in 4 pulse cycles and 8 pulse cycles (P &gt; 0.05). Therefore, treatment of 4 pulse cycles was adopted for future research related to vacuum cooling of pork ham with water.

Dust mobilization by high-speed vapor flow under LOVA

In the safety analysis on the International Thermonuclear Experimental Reactor (ITER), the ingress of coolant (ICE) event and the loss of vacuum (LOVA) event are considered as one of the most serious accident. On the assumption of LOVA occurring after ICE, it is inferable that activated dusts are under the wet condition. Transport behavior of in-vessel activated dusts under the wet condition is not well understood in comparison with the dry case. In this study, we experimentally investigated the entrainment behavior of dust under LOVA after ICE. We measured dust entrainment by high-speed humid airflow with phase change. Graphite dusts and glass beads are used as substitutions for mobile inventory. The relations among the relative humidity, the entrainment of particles in the exhaust gas flow and the adhesion rate of dust particles on the pipe wall have been made clear, as has the distribution profile of dust deposition on the pipe wall. The entrainment ratio decreased as the relative humidity increased and increased as the initial pressure difference increased.

ARIES-AT safety design and analysis

ARIES-AT is a 1000 MWe conceptual fusion power plant design with a very low projected cost of electricity. The design contains many innovative features to improve both the physics and engineering performance of the system. From the safety and environmental perspective, there is greater depth to the overall analysis than in past ARIES studies. For ARIES-AT, the overall spectrum of off-normal events to be examined has been broadened. They include conventional loss of coolant and loss of flow events, an ex-vessel loss of coolant, and in-vessel off-normal events that mobilize in-vessel inventories (e.g., tritium and tokamak dust) and bypass primary confinement such as a loss of vacuum and an in-vessel loss of coolant with bypass. This broader examination of accidents improves the robustness of the design from the safety perspective and gives additional confidence that the facility can meet the no-evacuation requirement under average weather conditions. We also provide a systematic assessment of the design to address key safety functions such as confinement, decay heat removal, and chemical energy control. In the area of waste management, both the volume of the component and its hazard are used to classify the waste. In comparison to previous ARIES designs, the overall waste volume is less because of the compact design.

Response of an urban bus flywheel battery to a rapid loss-of-vacuum event

The University of Texas at Austin Center for Electromechanics (UT-CEM) has developed a 2 kW-hr flywheel battery for energy management on a hybrid electric urban bus. The battery recovers braking energy and stores excess energy generated by the prime mover (e.g., internal combustion engine). The flywheel rotor, fabricated from high-strength composites, spins at 40,000 rpm at full charge (∼900 m/s tip speed), and is housed in a vacuum enclosure to minimize windage drag. Also integrated into the enclosure is a composite containment system that has been prooftested to provide additional safety. Ensuring flywheel safety is a major issue that must be addressed in using flywheels for transportation applications. A large leak caused by a service failure of the vacuum system could damage the flywheel before the energy dump system has time to act. A rapid loss-of-vacuum test on a rotor similar to that planned for the urban bus flywheel was conducted. Instrumentation, during the flywheel spin test recorded increasing flywheel surface temperature (>316°C or 600°F) following an intentional and abrupt loss of vacuum. No severe damage was noted on the surface of the flywheel, which was later retested to a higher speed to assess structural integrity. This paper provides an analysis of the data from that test and discusses the experimental results as they pertain to safety of the bus flywheel.

Numerical modeling of gland seal erosion in a geothermal turbine

Excessive erosion of the low-pressure rotor end gland seal of a 25 MWe geothermal turbine produced a partial loss of turbine vacuum that degraded cycle efficiency. This study used computational fluid dynamics (CFD) to identify the causes of erosion and the optimal steam seal system flow conditions for reducing the erosion problem. The predictions were based upon a numerical calculation using a commercial CFD code (Adapco Star-CD) to model the rotor end gland seal with a steam flow containing hard solid particles. The results confirmed that flow conditions play a major role in rotor gland seal erosion. By changing steam seal flow pressures to vary flow, it was confirmed that there is a threshold seal flow condition below which erosion does not occur, or is minimized. Optimizing the rotor end gland seal supply pressure and intercondenser pressure reduced the turbulent flow kinetic energy by 49%, with a corresponding decrease in the erosion rate of the rotor gland seal surface. The erosion rate is related directly to the particle velocity and turbulent flow kinetic energy. Recommendations are provided for adjusting the rotor end gland seal system to avoid erosion.

Development of a pilot system for converting sweet potato starch into glucose syrup.

Sweet potato has been chosen as one of NASA's crops to support human beings in future space missions. One of the possible uses is to make syrup that can be used as a general sweetener. In this work a simple engineering system for converting sweet potato starch into glucose syrup was studied on a laboratory scale. The system comprises the following main units: a blender, continuous stirred tank reactor (CSTR), centrifugal and vacuum filters, deionization column and vacuum evaporator. The system was tested by carrying out conversion processes from fresh sweet potato roots. The roots were pealed, sliced, homogenized, heated and hydrolyzed by diastase of malt and Dextrozyme C (Novo Nordisk BioChem, North America, Inc.) enzymes in the CSTR. After hydrolysis the slurry was filtered, de-ionized and concentrated to get glucose syrup. The performance of the system was evaluated based on the quality of the conversion. The main factor was the level of reducing sugars except for the deionization where ash content and color were the main factors. Through careful control of the system units, good heating performance in the CSTR was obtained and the hydrolysis process attained sufficient conversion. The filtration process that incorporated the centrifuge was faster than when it was by-passed to the vacuum filter but losses in sugars were higher. Deionization removed more than 90% of the ash and reduced pigmentation, with probable insignificant losses in sugars during the deionization process. Recovery levels when the centrifuge was used and when it was by-passed could reach about 65% and 78%, respectively. These correspond to reducing sugar concentration of 259 and 310 mg/ml in 150-ml syrups from 300 g of sweet potatoes in each process. However, from concentration trials, syrups with volumes of 100 and 70 ml with the respective dextrose equivalence of 281 and 213 mg/ml were obtained. The syrups obtained were brownish in color and the process that employed centrifugal filtration gave a product with color that resembled the original color of the sweet potatoes. Further work is required to improve the overall system performance.

Interaction of plasma-facing materials with air and steam

In the design of ITER-FEAT, several candidate materials are foreseen for plasma-facing components of the divertor (tungsten, carbon fibre-reinforced composites (CFC), molybdenum) and the first wall (beryllium). In the view of accidental scenarios such as a loss of coolant accident or a loss of vacuum accident the reaction between these materials and steam or air remains a safety concern. To provide kinetic data, describing the chemical reactivity of plasma-facing materials in air and steam, we used coupled thermogravimetry/quadrupole mass spectrometry. In this paper we present the results of a screening investigation that compares the oxidation rates of tungsten, molybdenum, CFC and beryllium in the temperature range 300–700 °C. From the thermogravimetry and mass spectrometry results we obtained the reaction rates as a function of temperature. For the metals tungsten, molybdenum and beryllium, a transition is observed between protective oxidation at lower temperatures and non-protective oxidation at higher temperatures. This transition temperature lies in the range 500–550 °C for tungsten and molybdenum, which is lower than for beryllium. At above temperatures 550 °C, the oxides formed on molybdenum and tungsten volatilise. This increases the oxidation rate dramatically and can lead to mobilisation of activation products in a fusion reactor. We also performed experiments on both undoped CFC and CFC doped with 8–10% silicon. The influence of silicon doping on the chemical reactivity of CFC's in air is discussed.

Failed Vacuum Extraction: Maternal Risk Factors and Pregnancy Outcome

Vacuum extraction, more widely used than forceps for operative vaginal delivery in Europe, is said to have failed when it is unduly difficult or there are more than two cup disengagements. This retrospective study of singleton, vertex deliveries at more than 36 weeks' gestation sought to identify obstetrical risk factors for a failed trial of vacuum extraction. A total of 211 trials taking place in the years 1990-1998 were reviewed; 5.4% of attempts (113) failed, leading to cesarean delivery within 15 minutes. Extraction was done only when the cervix was completely dilated, the membranes had ruptured, and the fetal head was engaged. Traction was done slowly and was stopped if there was any loss of vacuum. Pressure was limited to 0.8 kg/cm 2 . Only two reapplications of the metal cup were permitted. Three instances of lost suction were construed as method failure. Failed vacuum extraction was significantly and linearly associated with high birth weights; these infants were likelier to be large for gestational age and to weigh more than 4000 g. A lack of prenatal care also correlated with a higher rate of failed extraction. On multiple logistic regression analysis, both deficient prenatal care and a birth weight greater than 4000 g were independent risk factors for failed vacuum extraction. Women in whom extraction failed had significantly more cervical and uterine tears than when the procedure succeeded, and the relationship with uterine rupture persisted after adjusting for previous cesarean delivery, Failed extraction correlated with postpartum anemia and also with higher rates of intrapartum and postpartum fetal death (odds ratios: 35.9 for intrapartum fetal death and 9.1 for postpartum death). Both maternal and neonatal outcomes are compromised by a failed trial of vacuum extraction. An estimated fetal weight exceeding 4000 g should be viewed as a relative contraindication, particularly for women who have not received adequate prenatal care.

Polyaniline thin film optical waveguides for integrated optics and VLSI prepared by vacuum evaporation technique

Polyaniline is emerging as an important polymer material which offers challenging opportunities for both fundamental research and new technological applications in waveguides. Metal doped polyaniline has been prepared initially in the form of powder by a solution growth technique. The emeraldine salt with doped metal was also prepared by solution growth technique. This powder was used for vacuum evaporation on optically flat glass substrate. The dark green doped (Fe, Al) polyaniline thin films were prepared by vacuum evaporation technique (10−4 torr). Deposited waveguide thin films have been characterized structurally, using X-ray diffraction (XRD), optically etc. Effective refractive index of the thin film waveguide was also calculated theoretically and experimentally. Waveguide parameters, namely refractive index, propagation loss and depth of vacuum deposited polyaniline thin films optical waveguide have been determined. The optical spectra and structure and waveguide parameters of vacuum deposited polyaniline thin films are strongly affected by the type of doping. It is possible to reduce the losses by addition of Fe to the vacuum deposited polyanine thin film and modify the effective refractive index (Oeff) according to particular requirements. Results are compared with the results in the literature. Copyright © 2002 John Wiley & Sons, Ltd.

Abrupt Outflow of Boiling Liquid

Analysis is performed of heat and mass transfer and dynamic processes under conditions of abrupt loss of vacuum of the liquid circuit with subsequent adiabatic vaporization. Two stages of unsteady-state outflow are treated, namely, the propagation of a pressure wave along the circuit and the transition to the steady-state mode. The phase velocities, interphase heat and mass transfer, and the interphase forces due to the velocity disequilibrium and the effect of associated masses are taken into account and directly calculated at both stages.

Compact gate valve for UHV

A compact gate valve for UHV is described. The valve was designed to allow isolation of the ion source volume of an ion gun used in a surface analysis system. Therefore, filaments can be replaced without ultra-high vacuum loss in the analysis chamber. Other applications for this valve are suggested. The valve has been built inside a DN40CF flange. Operation of the valve is done by a linear actuator. Differential pumping is possible with the use of a Tee in the actuator connection. The construction details are described and the testing results are presented.

Safety and Environment Assessment of ARIES-AT

ARIES-AT is a 1000 MWe conceptual fusion power plant design with a very low projected cost of electricity. The design contains many innovative features to improve both the physics and engineering performance of the system. From the safety and environmental perspective, there is greater depth to the overall analysis than in past ARIES studies. For ARIES-AT, the overall spectrum of off-normal events to be examined has been broadened. They include conventional loss of coolant and loss of flow events, an ex-vessel loss of coolant, and in-vessel off-normal events that mobilize in-vessel inventories (e.g. tritium and tokamak dust) and bypass primary confinement such as a Loss of Vacuum and an in-vessel loss of coolant with bypass. This broader examination of accidents improves the robustness of the design from the safety perspective and gives additional confidence that the facility can meet the no-evacuation requirement. We also provide a systematic assessment of the design to address key safety functions such as confinement, decay heat removal, and chemical energy control. In the area of waste management, waste is classified by both the volume of the component and its hazard. In comparison to previous ARIES designs, the overall waste volume is less because of the compact design.

Vacuum preloading consolidation of Yaoqiang Airport runway

Yaoqiang Airport is an international airport serving the city of Jinan, China. The soil on the site consists of alternate layers of silty sand, silty clay, silt and clay. An under-consolidated soft clay layer approximately 4 m thick is located at between 7·5 m and 11·5 m depth above a silty clay layer. Soil improvement was proposed to consolidate the site prior to the construction of a runway to eliminate excessive settlement under static and dynamic loads on the runway. The results from field pilot tests for both surcharge preloading and vacuum preloading under the same consolidation pressure of 80 kPa are presented. Soil settlement in the range 20–30 cm was achieved in 80–90 days. For the vacuum treatment, in-situ deep mixing slurry cut-off walls were installed to control vacuum loss in a shallow silty sand layer. Data from the successful full-scale vacuum treatment of the site are also presented

Oxidation and volatilization of TZM alloy in air

The excellent high temperature strength and thermal conductivity of molybdenum-base alloys provide attractive features for components in advanced magnetic and inertial fusion devices. Refractory metal-base alloys react readily with oxygen and other gases, and molybdenum alloys are susceptible to losses from highly volatile molybdenum trioxide (MoO 3) species. Transport of radioactivity by the volatilization, migration and re-deposition of MoO 3 during a potential accident involving a loss of vacuum or inert environment represents a safety issue. We have experimentally measured the oxidation, volatilization and re-deposition of molybdenum from TZM in flowing air between 400°C and 800°C. Calculations using chemical thermodynamic data for vapor pressures over pure MoO 3 and a vaporization mass transfer model correlate well with the experimental data between 600°C and 800°C. Partial saturation of (MoO 3) gas species accounts for influences of flow rate at 700°C. Some anomalies in oxidation rate below 650°C suggest that other phases, e.g., MoO 2 or other non-stoichiometric oxides may influence oxidation and volatilization processes under some limited conditions.

Numerical analysis on thermal-hydraulic and dust transport behavior in fusion reactors at loss-of-vacuum events

Thermal-hydraulic and dust transport behavior in a fusion reactor during a loss-of-vacuum (LOVA) event was analyzed numerically using a newly developed 3-D analysis code under a compressible flow and 3-D cylindrical coordinates conditions from the viewpoint of the thermofluid safety of the fusion experimental reactors. After the LOVA event occurs, air will flow from the outside of a vacuum vessel (VV) through a breach into the inside and the activated dust accumulated in the VV may be blown up from the floor and spread throughout the whole area of the VV. From the predicted results, velocity, pressure and temperature distributions in the VV at the LOVA event were clarified quantitatively by 3-D computations. The predicted average pressures inside the VV were in good agreement with the experimental results from vacuum to atmospheric pressure. In addition, the dust transport behavior in the VV at LOVA conditions was visualized numerically. A cluster of dust particles was initially set on the floor of the VV and the breach was suddenly opened. The dust particles were transported from the floor to the inside of the VV by the external fluid through the breach. Almost all of the dust were deposited on the wall over a long period of time, but some of those were entrained to the outside of the VV as a result of the exchange flow and the rest was deposited onto the side walls and penetrations in the VV.

Vacuum integrity and protection systems at JET

Vacuum integrity and the reliable operation of related protection systems are essential at JET, both for the protection of expensive equipment and for the safety of personnel. High integrity vacuum interlocks and protection systems were required to satisfy the `Safety Case', which was established for the UK regulatory authorities to permit JET to commence tritium operations. The continuing retention of tritium within the torus dictates that the integrity of the vacuum systems needs to be maintained. The requisite integrity is achieved with passive and active designs and complemented by various systems of work. The designs of a number of pressure interlocks are outlined. Solutions to air and coolant leaks, since the start of tritium operations, are given. Although it has not been possible to eliminate the occasional loss of vacuum by air and coolant leaks, it is concluded that the consequences of these failures can be minimised.