Two-way Valve Research Articles

Improved Digital Hydraulic Tracking Control of Water Hydraulic Cylinder Drive

AbstractA position tracking control system is implemented by utilizing parallel-connected on/off valve series. The pulse code modulation method is used to achieve stepwise flow control and four valve series, each having four two-way solenoid valves, are used. A cost function based controller is used to control simultaneously and independently flow paths from supply to cylinder chambers and from chambers to tank. It is shown that controllability can be improved especially at low velocities by allowing three or four valve series to be open simultaneously instead of using classical inflow-outflow control.

ENERGY-EFFICIENT MOTION CONTROL OF A DIGITAL HYDRAULIC JOINT ACTUATOR

This paper studies the energy efficiency of a heavily loaded cylinder drive. Pulse code modulation is used to control all four flow path independently with parallel connected on/off valves. A valve manifold with 4x5 two-way screw-in cartridge valves is used and the dimensions of the test system are such that actuator size, load force, effective inertia and natural frequency are at the same level as in joint actuators of typical medium size mobile machines. A cost function based control solution is used for online minimization of power losses. Power losses are compared with traditional proportional load-sensing system.

The Variability of Resting Metabolic Rate Measurements

1711 Resting metabolic rate (RMR) is a primary contributor to energy balance, representing up to 75% of total energy expenditure. Like any other measurement, however, its usefulness depends on its accuracy and reliability. PURPOSE: To examine the shortterm test-retest variability of RMR. METHODS: RMR was measured on 40 volunteers (20 male, 20 female). Subjects avoided exercise, caffeine, nicotine and food for three hours prior to testing. Following a 30-minute period to achieve a resting steady state, expired air was collected in Douglas bags via a mouthpiece and a two-way valve for two 10-minute intervals, with a 10-minute interval separating the assessments. Subjects remained in a supine position with minimal movement throughout the protocol. For the analysis, the lower value (LVO2) for each subject was compared to the higher values (HVO2). RESULTS: The mean RMR values for the LVO2 and HVO2 were 235 ± 54 ml/min and 246 ± 53 ml/min, respectively, with the LVO2 and HVO2 evenly distributed across the two trials. A paired t-test (α = 0.05) revealed a significant difference between the two measurements. The average absolute and relative differences between the values were 11 ± 10 ml/min and 5.0%, respectively. Regression analyses were performed to establish any trends in the variability of the RMR values in relation to time of day, body weight, Body Mass Index, age, room temperature, and average RMR value. Each parameter yielded a low R2 value, indicating that the variance in the RMR values was not due to the variance in these parameters. The most significant factor for absolute difference was body weight (R2 = 0.044), and average RMR had the largest impact on the relative difference (R2 = 0.079). A t-test also found no significant difference in the variability of male and female subjects (p = 0.721 and 0.757 for absolute and relative differences, respectively). CONCLUSION: There was a statistically significant short-term variability in RMR measurements, with an average individual difference of 5.0% for the two measurements. None of the potential influences examined demonstrated a significant effect on the variability of RMR.

Tests of Respiratory Muscle Strength In Neonates

After completing this article, readers should be able to: 1. Describe the underlying cause of respiratory failure in about 50% of preterm infants who require intubation and mechanical ventilation. 2. Compare compliance characteristics of the chest wall in infants, older children, and adults. 3. List some of the conditions seen in neonates that can adversely affect respiratory muscle function. 4. List noninvasive tests for assessing respiratory muscle strength in neonates. Chest wall mechanics of neonates and infants play an essential role in ventilation that frequently is underappreciated. Dysfunction of the respiratory muscles can cause both a disease process and an inability of the patient to compensate for it. As an example, respiratory muscle failure may be the underlying cause in about 50% of preterm infants who have ventilatory failure. (1) In this article, we detail the current understanding of the physiology of the respiratory muscles in neonates and discuss a number of tests designed to assess their function. Mechanically, the respiratory system can be thought of as being composed of two components. The first includes the respiratory muscles, the rib cage, and the anterior abdominal wall, which together make up the “pump,” whose function is to move air in and out of the lungs. The second includes the airways and lung parenchyma through which gas exchange occurs and can be referred to as the “load” on which the pump must act. For ventilation to occur, the respiratory pump must overcome both the frictional (eg, airway resistance) and tissue elastic forces (eg, lung and chest wall compliance) that create the load. The balance between the capabilities of the pump and the magnitude of the load can influence whether respiratory “success” or “failure” occurs. The chest wall, which contains muscles and skeletal structures, undergoes dramatic maturational changes over the first several years of life. In addition …

Tidal off-line exhaled nitric oxide measurements in a pre-school population.

Exhaled nitric oxide (ENO) is used as a non-invasive marker of airway inflammation. The aim of this study was to measure ENO in a pre-school population using a relatively novel method, the off-line tidal breathing method, and to investigate differences in ENO between subjects with different presentations of wheezing. ENO was measured in 129 children (median age 4.4 years, quartiles 4.0-4.8 years) through a mouth mask attached to a two-way valve with an expiratory resistance of 5 cm H(2)0. Mean tidal ENO concentration (tENO) was calculated from triplicate measurements. Mean +/- SEM tENO for 89 control subjects was 13+/-0.4 ppb (95%CI 11.8-13.7 ppb); this level was significantly different from tENO in 15 children with a history of recurrent wheezing (18.6+/-1.9 ppb; 95%CI 14.5-22.7 ppb; t-test P<0.0001). Mean tENO in 16 children with a single wheezing episode was 11.4+/-1.0 ppb (95%CI 9.2-13.6 ppb) and thus significantly different from the recurrent wheezing group (t-test P=0.0024). The off-line tidal breathing method is a feasible and appealing method for measuring exhaled nitric oxide in pre-school children. With this method, higher tidal exhaled nitric oxide levels were found in children with recurrent wheezing.

Flow injection analysis in a microfluidic format.

A microfluidic flow injection analysis system has been designed and evaluated. The system incorporates within a single two-layer poly(dimethylsiloxane) monolith multiple pneumatically driven peristaltic pumps, an injection loop, a mixing column, and a transparent window for fluorescence detection. Central to this device is an injection system that mimics the operation of a standard six-port, two-way valve used in conventional liquid chromatography and flow injection experiments. Analyte and carrier solutions continuously flow through this injection system allowing for measurements and sample changes to be performed rapidly and simultaneously. Injection volumes of 1.25 nL generated peak area reproducibility of better than 3% relative standard deviation. The flow injection device was evaluated with fluorescent dyes and demonstrated a detection limit of 400 zmol for fluorescein. A rudimentary sample selection system allowed calibration curves to be rapidly produced, often in less than 10 min. The hydrolysis of fluorescein diphosphate by alkaline phosphatase demonstrates that chemical assays can be carried out with this device in a manner characterized by short analysis times and low sample consumption.

Accurate Trajectory Tracking Control of Water Hydraulic Cylinder with Non-Ideal on/off Valves

AbstractThe aim of the work is to develop an on/off valve based trajectory tracking control solution without fast and/or continuous switching of valves. The pulse code modulation method is used to realise stepwise control of inflow and outflow of the actuator. Both inflow and outflow paths have five parallel-connected two-way solenoid valves, each having different flow capacity according to binary series, and a four-way on/off valve is used for changing direction of movement. Cost function based open-loop and closed-loop control solutions are developed and it is demonstrated how the cost function weights can be used to find a reasonable trade-off between tracking performance and pressure surges. Closed-loop results show accurate and reasonably smooth position tracking and simultaneous pressure level control. Achieved control performance is close to that of water hydraulic servo systems.

Postexercise oxygen consumption and substrate use after resistance exercise in women.

This study investigated the acute effects of 45 min of resistance exercise (RE) on excess postexercise oxygen consumption (EPOC) and substrate oxidation 120 min after exercise in moderately trained women. Ten RE trained women (age = 29 +/- 3 yr; ht = 168 +/- 8.3 cm; wt = 59 +/- 5.7 kg; VO2max = 38.3 +/- 4.7 mL.kg-1.min-1) underwent two trials: control sitting and RE. Subjects acted as their own controls in a random counterbalanced design. A 2-d nonexercise period was established between testing trials. Oxygen consumption (VO2) and respiratory exchange ratio (RER) were measured continuously by indirect calorimetry before, during, and after exercise and on a separate control day. RE consisted of 3 sets of 10 exercises at 10-repetition maximum with a 1-min rest period between each set. Fingertip samples of blood lactate concentration [BL] were collected immediately postexercise and every 30 min thereafter until [BL] returned to resting baseline values after exercise. The overall 2-h EPOC was 6.2-L (RE = 33.4 +/- 5.1 L vs control = 27.2 +/- 0.3 L), corresponding to an 18.6% elevation over the control period. RER was significantly (P < 0.01) below the control RER from minute 30 to minute 120 postexercise (RE = 0.75 +/- 0.01 vs control = 0.85 +/- 0.01). During the last 30 min of recovery, VO2 and [BL] had returned to control/baseline values and fat oxidation was significantly (P < 0.0001) higher (29.2 vs 16.3 kcal) after RE compared with the control trial. These data indicate that in young RE trained women, acute RE produces a modest increase in VO2 during a 2-h recovery period and an increase in fat oxidation.

Two-way MR fluid valve

Two-way MR fluid valve

Reproducibility of the alternating breath test of fractional inspired O2 in infants.

We conducted a reproducibility study of the alternating breath test (ABT) for assessing peripheral chemoreceptor function in infants. The ABT delivers a rapid hypoxic stimulus to the peripheral chemoreceptors with breath-by-breath alternations of the inspired O2 fraction. The reproducibility of the ABT performed on a single occasion has not been extensively studied in infants. Eight unsedated infants (postnatal age, 22+/-19 d; weight, 3.2+/-0.4 kg) were studied in standardized conditions: morning naps, supine position, room temperature 22-24 degrees C, quiet sleep, and face mask attached to a pneumotachograph connected to a two-way electric valve. Respiratory gases were analyzed by mass spectrometer. Two ABTs were performed. Each included a 2-min control run (CR) alternating between air and air, and a 2-min test run (TR) alternating between air and 0.15 O2. After data preprocessing, on average 13+/-11% of the data were rejected because of sighs, apneas, and cycles with the fraction of inspired oxygen above 0.17. Using the remaining validated breaths, the response to ABT was calculated for the CR, for all breaths in the TR (TR(T)), and for the first 50 breaths of the TR (TR50). During the ABTs oxygen saturation did not fall below 96%, and heart rate was not affected. Inspired and end-tidal CO2 fractions remained unchanged during the ABTs. FetO2 oscillated in TRs at a lower values than in CRs and differed significantly between breaths of air and hypoxic breaths of TRs. All infants responded to ABT with percentage alternation coefficients of TRs significantly greater than those of CRs for all respiratory variables. The values of the coefficients were not significantly different between both ABT, and between TR50 and TR(T). The greatest values of the coefficients were for timing variables compared with flows and volume. We conclude that the ABT is a reproducible test of peripheral chemoreceptor function under standardized conditions.

Inertial sizing of aerosol inhaled during pediatric tidal breathing from an MDI with attached holding chamber

A procedure that allows cascade impaction to be used to measure the particle size distribution of the aerosol inhaled from a holding chamber with a square wave tidal breathing pattern is described. A constant flow rate of 28.3 l/min occurs through an Anderson impactor while tidal breathing occurs through the holding chamber by using a two-way valve system and a piston connected to a computer controlled stepper motor. Replicas of infant (7 months old) and child (4 years old) faces are used to allow collection of the aerosol at the entrance to simulated nostrils during tidal breathing at flow rates and tidal volumes near predicted values for these ages. Ventolin ® and Beclovent ® MDIs with the Space-Chamber ® holding chamber (with infant or pediatric mask) are tested. Although significantly less drug ( P<0.01) is inhaled with the infant face replica than the child face replica or the adult-mouthpiece study of Finlay et al. (1997), these differences are largely due to differences in amounts inhaled in large particles, since no significant difference is found in the amount inhaled in particles <2.1 μm for salbutamol or <3.3 μm for beclomethasone between the infant, child or adult-mouthpiece results. These results indicate that caution may be needed when evaluating holding chambers using in vitro data on total mass inhaled, since differences can be caused by differences in large particles that do not contribute significantly to lung deposition.

Randomized Prospective Study of the Impact of Three Needleless Intravenous Systems on Needlestick Injury Rates

AbstractObjective:To determine the impact of three needleless intravenous systems on needlestick injury rates.Design:Randomized controlled trial.Setting:1,000-bed tertiary-care Midwestern hospital.Participants:Nursing personnel from general medical, general surgical, and intensive-care units.Interventions:From June 1992 through March 1994, a metal blunt cannula (MBC), two-way valve (2-way), and plastic blunt cannula (PBC) were introduced into three study areas, and needlestick injury rates were compared to three control areas using traditional needled devices.Results:24 and 29 needlestick injuries were reported in study and control areas. Intravenous-therapy-related injuries comprised 45.8% and 57.1% of injuries in each area. Thirty-seven percent and 20.7% of study and control area needlestick injuries were considered to pose a high risk of bloodborne infection. The 2-way group had similar rates of total and intravenous-related needlestick injuries compared to control groups. The PBC group had lower rates of total and intravenous-related needlestick injuries per 1,000 patient-days (rate ratios [RR], 0.32 and 0.24; 95°% confidence intervals [CI95], 0.12-0.81 and 0.09-0.61;P=.02 andP=.003, respectively) and per 1,000 productive hours worked (RR, 0.11 and 0.08; CI95, 0.01-0.92 and 0.010.69;P=.03 andP=.005, respectively) compared to controls.Conclusions:Needlestick injuries continued in study areas despite the introduction of needleless devices, and risks of bloodborne pathogen transmission were similar to control areas. The PBC device group noted lower rates of needlestick injuries compared to controls, but there were problems with product acceptance, correct product use, and continued traditional device use in study areas. Low needlestick injury rates make interpretations difficult. Further studies of safety devices are needed and should attempt greater control of worker behavior to aid interpretation.

CHARACTERISTICS OF NEW TYPE FLOW CONTROL CARTRIDGE VALVE USING PWM METHOD

The purpose of this study is to combine the good adaptability of PWM control to micro-processor with the adaptability of two-way cartridge valve to high power-level hydraulic systems. In this study, a special cartridge valve, called active cartridge valve, is used. The valve body is incorporated with a piston and the position of the piston, i.e. the opening of the valve, is controlled by the high speed on-off solenoid valve in the pilot circuit using PWM method. As a result the flow rate through the cartridge valve can be controlled by the high speed on-off solenoid valve. The effects of the design parameters on the characteristics of flow control cartridge valve using PWM metho are investigated.

Earplug with form-fitting fluid chambers

A bi-directionally insertable elastomeric ear plug for sealing an ear canal has an outer body defining two identical expansible and collapsible fluid chambers. A fluid, preferably air, is sealed within the outer body, and a passageway is defined between the two fluid chambers for selectively placing the chambers in fluid communication with each other. An elastically displaceable wall bounding the passageway acts as a two-way pressure responsive valve operative to close the passageway and thereby maintain an equilibrium condition with one of the chambers expanded and the other collapsed, and to temporarily open the passageway when one of the chambers is squeezed. The collapsed chamber is insertable into an ear canal with the aid of an elongated semi-rigid core member extending within the outer body. Thereafter, the expanded chamber can be squeezed to expand the collapsed chamber inside of the ear canal to obtain a comfortable yet tight form-fitting seal.

Mass spectrometer system for in-vivo monitoring of gas exchange in plants

A membrane introduction mass spectrometer system for the measurement of gases in plants is presented. Membrane inlets are coupled to a quadrupole MS (Q-300 PC, ATOMKI) via flexible capillaries and a two-way valve system. At a certain time only one probe is connected to the QMS and all the others are pumped simultaneously under high vacuum conditions. Two diffusion pumps are installed for the QMS and the idle inlets, respectively. The vacuum and valve systems as well as the QMS are computer controlled. The silicone rubber membrane probes are placed into the plant or over the surface of it. In latest experiments gas exchange of a reed is investigated, having the probes in the culms, rhizomes and in the soil. Ion monitoring in eight channels and mass scans in a preset range are available. The time-function of intensities at different masses (typically O 2, CO 2 Ar, N 2) are monitored and correlated with physical and chemical effects on the plant.

On-line buffer removal and fraction selection in gradient capillary high-performance liquid chromatography prior to electrospray mass spectrometry of peptides and proteins.

The technique for on-line removal of buffers and for fraction selection to eliminate source clogging and suppression of electrospray ionization by unwanted constituents consisted of: (i) selecting the initial mobile phase composition to retain analytes on top of a capillary high-performance liquid chromatography (HPLC) column; (ii) washing the buffer isocratically to waste, using a two-way micro dump valve; (iii) starting the gradient and switching the dump valve to introduce analytes into the source. Peptide and protein mixtures were prepared in 0.05-0.5 M phosphate and 0.55 mM tris-based buffers, and water. After buffer removal, chromatograms and electrospray spectra were indistinguishable from those of aqueous controls, down to 1 pmol (acidic fibroblast growth factor) consumed, and up to 78 kDa (bovine transferrin) molecular weight. Aided by the dump valve, 100 fmol of angiotensin could be fractionated and identified on the slope of a 10 x 10(6) fmol of leucine enkephalin HPLC peak. On-line buffer removal and fraction selection eliminate the need for additional preparation steps than can lead to excessive sample losses.

264 IMPROVED HOLDING CHAMBER FOR TREATMENT OF YOUNG ASTHMA CHILDREN WITH PRESSURIZED METERED DOSE INHALERS (P-MDI)

In vitro T½ (aerosol) was less than 10 sec in a polycarbonate holding chamber compared to a T½ (aerosol) of longer than 30 sec in a steel holding chamber. A prototype holding chamber of 220 mL was cast in steel, and was equipped with a two-way low-resistance valve with a small dead space to ensure a rectified inspiratory flow from the spacer and expiratory flow outside the spacer. This prototype was tested against a traditional 750 mL polycarbonate single-valved holding chamber for the delivery of budesonide aerosol from P-MDI to children in the age-range of 0-7 years suspected of asthma. The polycarbonate was primed with benzalkonium chloride prior to use to avoid the confounding effect of the material. Both holding chambers were equipped with closely fitted face masks for children less than 48 months old. One hundred and sixty five children suspected of asthma, equally distributed as regards age from 0 to 7 years, inhaled one dose of budesonide from one of the holding chambers for 60 seconds. A filter was interposed between the holding chamber and the face mask adsorbing all particles delivered to the child. The mean dose fraction inhaled from the prototype approximated 38% irrespective of age, whereas the large-volume holding chamber exhibited a highly significant age-related decrease from approximately 44% in the older children down to 19% in infants. The difference in the doses of aerosol delivered was significant among children less than 3 years of age.

Effect of tidal volume on the output and particle size distribution of hypertonic saline from an ultrasonic nebulizer

The purpose of the present study was to measure the output and particle size distribution of hypertonic saline from an ultrasonic nebulizer over the range of tidal volumes (VT) used in an epidemiological survey of asthma in children. A Starling pump was used to generate different VTs from 250 to 500 ml, at different respiratory rates of 12 and 20 breaths.min-1, to cover the normal range of respiratory pattern of children aged 7-14 yrs. The Starling pump was connected to a Timeter Compuneb Ultrasonic Nebulizer Model MP 500 with 24 cm of corrugated aerosol tubing, ID 2.2 cm, and a two-way non-rebreathing valve. Nebulizer output was measured by weighing the nebulizer chamber plus tubing and valve before and after each nebulization. To measure particle size distribution, a Malvern Particle Sizer M 3.0 (laser diffraction) was used, with a special adapter attached between valve and Starling pump. Nebulizer output increased linearly from 1.6 to 2.5 ml.min-1 for VT 250 to 500 ml, with little influence by the respiratory frequency. Furthermore, we found that in the range of VT = 300-500 ml the mass median aerodynamic diameter (MMAD) was 2.61 microns, with 100% of the particles less than 5 microns, whereas at VT = 150-250 ml the MMAD was 8.89 microns, with 90% larger than 5 microns. As output from this ultrasonic nebulizer correlates linearly with tidal volumes, size correction may not be necessary in hypertonic saline challenge tests in children. Above a VT of 300 ml, the MMAD is in the respirable range, with 100% of particles less than 5 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced order sliding mode control for pneumatic actuator

A new position control algorithm, based on sliding mode control, has been developed for a pneumatic cylinder. In the proposed pneumatic system, commercially available two-way on-off solenoid valves have been used. The inherent robustness property of the sliding mode controller makes it easier to select the switching gains of the controller. Moreover, approximate dynamic modeling of the system makes the controller simple. Since in sliding mode control, the states remain on the sliding surface, the motion of the piston is very smooth. This suggests the potential of pneumatic cylinders as actuators for robot manipulators. The controller is hybrid in nature, consisting of an error amplifier, data conversion devices and an 8088 microprocessor along with various digital circuit accessories. Only one feedback device (potentiometer) is used. Velocity is calculated from the sampled position signals. >

Salmeterol provides prolonged protection against exercise-induced bronchoconstriction in a majority of subjects with mild, stable asthma

In patients with asthma, exercise-induced symptoms are well recognized and frequently limiting. Currently available β 2-receptor agonists have a short duration of action and breakthrough symptoms may occur. We studied the efficacy of the recently developed long acting inhaled β 2-agonist salmeterol with respect to protection against exercise-induced bronchoconstriction. Twelve patients with mild to moderate, stable asthma were recruited (age range 21–33 years). They each underwent treadmill exercise tests, with target heart rate of approximately 90% of predicted maximu, 1, 6 and 12 h after a single dose of salmeterol 50 μg, salbutamol 200 μg and placebo. Patients breathed through a two-way valve, inspiring dry air from a compressed air cylinder via a Douglas bag to maintain constant humidity. The primary efficacy variable analysed was the maximum percentage fall in FEV 1 and FVC from pre-exercise readings within the first 30 min post-exercise. At 1 h post-dose there was significant protection in terms of fall in mean ± sem FEV 1 in response to exercise challenge after either salmeterol (0·83 ± 6·2%) or salbutamol (3·8 ± 5·5%) as compared with placebo (27·1 ± 7·3%). At 6 h post-dose, fall in FEV 1 on salmeterol was 11·3 ± 3·8% as compared with salbutamol, 28·0 ± 5·7% and placebo, 32·0 ± 7·0%. At 12 h post-dosing there was still significant protection in terms of fall in FEV 1 in the salmeterol treated group, 12·8 ± 4·9%, as compared with salbutamol, 28·7 ± 4·9% and placebo, 25·4 ± 7·3%. Similar results were found with respect to changes in FVC in these patients. We conclude that salmeterol is effective in protecting against exercise-induced bronchoconstriction in the majority of subjects with mild, stable asthma and that this effect lasts for at least 12 h.