Paper 7: Control of Variable-Discharge Pumps and Dangers of Pipeline Resonance

1966 ◽  
Vol 181 (1) ◽  
pp. 144-174
Author(s):  
B. J. Cooper ◽  
D. Hartland ◽  
R. Lawson ◽  
A. M. Stone ◽  
R. D. Tyler
Keyword(s):  
Power Input ◽  
Small Region ◽  
Significant Loss ◽  
Pump Efficiency ◽  
Positive Slope ◽  
Simple Criterion ◽  
Wide Range ◽  
Resonant Instability ◽  
Organ Pipe ◽  
Computer Studies

The discharge and power input of Deriaz mixed-flow pumps and pump turbines can be controlled over a wide range without significant loss in efficiency by movement of the blades. The attainment of the highest pump efficiency involves a small region of positive slope in the head discharge graph. This paper examines the limitations of designing pumps which do not exhibit positive slope and the problems of governing if a positive-slope region is accepted. It is shown that operation in the positive-slope region can introduce a serious organ-pipe resonant instability in the pipeline. A simple criterion to determine whether or not such oscillations will occur is given. This stability criterion involves the dynamic characteristics of both the pump and the pipeline. Finally, computer studies of a particular Deriaz pump installation are presented. These underline the severity of the situation should resonance develop and show how it can be avoided by the use of an air bottle of appropriate design.

How does sperm meet egg?--in a marsupial

1994 ◽  
Vol 6 (4) ◽  
pp. 485 ◽  
Author(s):  
WG Breed
Keyword(s):  
Acrosome Reaction ◽  
Small Region ◽  
Sperm Head ◽  
Sminthopsis Crassicaudata ◽  
Acrosomal Membrane ◽  
Wide Range ◽  
A Cell ◽  
Inner Acrosomal Membrane ◽  
Head Morphology ◽  
Range Of Variation

Australian marsupials exhibit a wide range of variation in sperm head morphology, and in thickness of the zona pellucida around the oocyte, suggesting interspecfic differences in the processes of sperm-egg interaction. The observations described here are largely based on the dasyurid Sminthopsis crassicaudata. They show that in oestrous females, after mating, a coagulum forms in the lateral vaginae and, within an hour of insemination, numerous spermatozoa congregate in the isthmus of the oviduct in which the vanguard population undergoes transformation with the head rotating on its axis with the tail to form a T-shape. Once oocytes are released, a few spermatozoa migrate to the higher reaches of the oviduct where sperm-zona binding occurs by way of the plasmalemma over the acrosomal region. The acrosome reaction takes place here and, as the egg rotates, the tail of the spermatozoon becomes parallel to the head. A small region of acrosome sometimes appears to remain intact at this time because spermatozoa with partly intact acrosomes have been found within the zona matrix. In some of these, electron-dense bridges between part of the inner and outer acrosomal membranes which may act as stabilizing structures, were also seen. The zona matrix is tightly packed around the penetrating spermatozoon, but that close to the acrosomal region becomes less electron-dense and more filamentous. Once incorporated into the egg, the spermatozoon lacks a cell membrane around the tail but vesicles close to the sperm head may, at least in part, be remnants of an inner acrosomal membrane. How generally applicable these observations are to other Australian marsupials remains to be determined.

A Stable Mode-Selectable Oscillator with Variable Duty Cycle and High-Efficiency

2015 ◽  
Vol 24 (09) ◽  
pp. 1550132 ◽  
Author(s):  
Li-Ye Cheng ◽  
Xin-Quan Lai
Keyword(s):  
Duty Cycle ◽  
High Efficiency ◽  
Dynamic Performance ◽  
Operation Mode ◽  
Charge Pump ◽  
Input Voltage ◽  
Cmos Process ◽  
Pump Efficiency ◽  
Stable Mode ◽  
Wide Range

A mode-selectable oscillator (OSC) with variable duty cycle for improved charge pump efficiency is proposed in this paper. The novel OSC adjusts its duty cycle according to the operation mode of the charge pump, thus improves the charge-pump efficiency and dynamic performance. The control of variable duty cycle is implemented in digital logic hence it provides robust noise immunity and instantaneous response. The OSC and the charge-pump have been implemented in a 0.6-μm 40-V CMOS process. Experimental results show that the peak efficiency is 92.7% at 200-mA load, the recovery time is less than 25 μs and load transient is 15 mV under 500-mA load variation. The system is able to work under a wide range of input voltage (V IN ) in all modes with low EMI.

Design of Small Centrifugal Compressors Performance Test Facility

2004 ◽  
Author(s):  
Fahad A. Al-Sulaiman ◽  
Amro M. Al-Qutub
Keyword(s):  
Performance Test ◽  
Performance Testing ◽  
Selection Procedure ◽  
Power Input ◽  
Test Facility ◽  
Design Stage ◽  
Centrifugal Compressors ◽  
Drive Unit ◽  
Actual Performance ◽  
Wide Range

Actual performance testing is a key element in the design stage, development and troubleshooting of centrifugal compressors. The present work discusses the procedure for designing the experimental setup and the selection of drive unit for variable centrifugal compressors sizes. It starts with setting criteria of selection. A survey over different types of drive units and facility setup was conducted. It was found that the electric drive unit with the aid of transmission for stepping-up the speeds is the most suitable type. This is due mainly to the excellent control property of electric motors allowing for wide range of operational speed and power. A new methodology was developed for selecting operational power and speeds of the drive unit for different sizes of impellers. The code, used for the analysis, was developed by the authors. It calculates the range of input power, input torque, and rotational speeds, as well as, the mass flow rate, total pressure and temperature ratios for different sizes of impellers. This will aid in selecting the proper instrumentation for the experiments. The code used for design methodology is based on one dimensional through flow formulation and validated with experimental results in the literature. It is expected that the present methodology will enhance selection procedure for designing compressor test facility.

Fatigue in Rubber. Part II

1939 ◽  
Vol 12 (2) ◽  
pp. 332-343 ◽  
Author(s):  
W. J. S. Naunton ◽  
J. R. S. Waring
Keyword(s):  
Carbon Black ◽  
Internal Friction ◽  
High Frequency ◽  
Strain Curve ◽  
Power Input ◽  
Viscous Resistance ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Wide Range ◽  
Rubber Part

Abstract 1. An apparatus is described for measuring the modulus and resilience of rubber over a wide range of frequencies. 2. These measurements can be made at any point in the stress-strain curve of the sample. 3. By increasing the power input, the same apparatus can be used to induce high frequency fatigue in the sample. 4. The earlier work with the torsion head apparatus has been confirmed, namely, that internal friction is greatest near zero strain. 5. High frequency resilience is more independent of degree of vulcanization than tripsometer resilience. 6. Modulus tends to increase with frequency. The effect is least with a rubber gum stock and is greater with compounds containing gas black. 7. Resilience decreases with frequency both in gum and gas black compounds. The decrease is more rapid in the gum compounds. 8. Viscous resistance decreases with frequency and becomes constant at higher frequencies. 9. The modulus of both rubber and Neoprene carbon black compounds decreases with fatigue. 10. The change in modulus with frequency in fatigued stocks is exactly analogous to the change before fatigue in rubber, but there is a slight divergence in the case of Neoprene.

scholarly journals In-Depth Analysis of the Role of the Acinetobactin Cluster in the Virulence of Acinetobacter baumannii

2021 ◽  
Vol 12 ◽  
Author(s):  
Kelly Conde-Pérez ◽  
Juan C. Vázquez-Ucha ◽  
Laura Álvarez-Fraga ◽  
Lucía Ageitos ◽  
Soraya Rumbo-Feal ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Multidrug Resistant ◽  
Significant Loss ◽  
Genetic Redundancy ◽  
Double Mutant Strain ◽  
Wide Range ◽  
Depth Analysis ◽  
High Level ◽  
Antivirulence Agents

Acinetobacter baumannii is a multidrug-resistant pathogen that represents a serious threat to global health. A. baumannii possesses a wide range of virulence factors that contribute to the bacterial pathogenicity. Among them, the siderophore acinetobactin is one of the most important, being essential for the development of the infection. In this study we performed an in-depth analysis of the acinetobactin cluster in the strain A. baumannii ATCC 17978. For this purpose, nineteen individual isogenic mutant strains were generated, and further phenotypical analysis were performed. Individual mutants lacking the biosynthetic genes entA, basG, basC, basD, and basB showed a significant loss in virulence, due to the disruption in the acinetobactin production. Similarly, the gene bauA, coding for the acinetobactin receptor, was also found to be crucial for the bacterial pathogenesis. In addition, the analysis of the ΔbasJ/ΔfbsB double mutant strain demonstrated the high level of genetic redundancy between siderophores where the role of specific genes of the acinetobactin cluster can be fulfilled by their fimsbactin redundant genes. Overall, this study highlights the essential role of entA, basG, basC, basD, basB and bauA in the pathogenicity of A. baumannii and provides potential therapeutic targets for the design of new antivirulence agents against this microorganism.

scholarly journals Epidemiología enfermera del duelo en Canarias

2020 ◽  
pp. 27-48
Author(s):  
Martín Rodríguez-Álvaro ◽  
Keyword(s):  
Protective Factors ◽  
Canary Islands ◽  
Significant Loss ◽  
Care Needs ◽  
Diagnostic Labels ◽  
Wide Range ◽  
High Prevalence ◽  
Functional Patterns ◽  
Limited Process

Grief is a natural and self-limited process of adaptation to a new reality that arises after a significant loss, real or perceived, with a wide range of manifestations that produce an impact on the health of the mourner. Objective: To know and identify, broken down by diagnostic gradient, the prevalence of mourning in the Canary Islands, as well as the needs of care before the diagnosis of mourning of the mourners. Results: Significantly, more women than men are identified in the three diagnostic labels under study. Patients with bereavement complications previously presented depression, anxiety, and risk of loneliness. The result of the pattern assessment is paradoxical. Conclusion: Grief is a multidimensional phenomenon that can hardly be assessed from a reductionist tool such as functional patterns. The high prevalence of complications in women’s grief should be studied in-depth, associating it with their previous burdens of care and vulnerability. The association between loneliness and complicated grief is evident, and the role of community nurses in these patients may be essential. Further research is needed on the care needs of bereaved persons, both complicated and uncomplicated, as well as on their predictive and protective factors.

Process characteristics of screw impellers with a draught tube for Newtonian liquids. The power input

1981 ◽  
Vol 46 (9) ◽  
pp. 2007-2020 ◽  
Author(s):  
Pavel Seichter ◽  
Jiří Dohnal ◽  
František Rieger
Keyword(s):  
Reynolds Number ◽  
Experimental Verification ◽  
Power Input ◽  
Creeping Flow ◽  
Total Power ◽  
Geometrical Parameters ◽  
Draught Tube ◽  
Process Characteristics ◽  
Wide Range ◽  
Newtonian Liquids

An expression has been proposed for the power input of a screw impeller with a draught tube in the creeping flow regime based on the analogy with extruder screws. Experimental verification has confirmed practical utility of the expression in a wide range of geometrical parameters of the impeller and for the Reynolds number for mixing below 20. The total power input of the impeller is expressed as a sum of the input inducing the drag flow and the input to create the pressure flow. The former of the inputs may be deduced from the theory of extruders while an empirical approach based on experiment has been used to formulate an expression for the latter.

Parodiella hedysari. [Descriptions of Fungi and Bacteria].

1999 ◽  
Author(s):  
P. F. Cannon
Keyword(s):  
New York ◽  
South Carolina ◽  
Geographical Distribution ◽  
Significant Loss ◽  
Lablab Purpureus ◽  
Lespedeza Cuneata ◽  
Wide Range ◽  
Photosynthetic Potential ◽  
The Tropics ◽  
Warm Temperate

Abstract A description is provided for Parodiella hedysari. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Occurs on leaves of a wide range of papilionoid Leguminosae. Recorded from Aeschynomene nyasana, Alysicarpus vaginalis, Amphicarpaea sp., Atylosia grandiflora, A. scarabaeoides, Clitoria rubiginosa, Crotalaria albida, C. calycina, C. juncea, C. mysorenis, C. ononoides, C. ovalis, C. prostrata, C. retusa, Desmodium acuminatum, D. adscendens, D. barbatum, D. canadense, D. canescens, D. gangeticum, D. laxiflorum, D. marilandicum, D. microphyllum, D. obtusum, D. paniculatum, D. scorpiurus, D. strictum, D. triflorum, Dolichos malosanus, Eriosema violaceum, Flemingia cumingiana, F. macrophyllla, F. parviflora, Gleditsia triacanthos, Hedysarum sp., Indigofera daleoides, I. prostrata, I. spicata, I. suffruticosa, I. swaziensis, I. tanganyikensis, Kotschya strigosa, Lablab purpureus, Lespedeza cuneata, L. sericea, Maprounea africana, Mucuna sp., Neorautenenia pseudopachyrhiza, Pediomelum argophyllum, P. cuspidatum, P. digitatum, Phaseolus linearis, Psoralea sp., Rhynchosia cinerea, R. R. difformis, R. reniformis, R. senna, R. tomentosa, Sesbania micrantha, Smithia bigemina, Strophostyles helvola, Tephrosia sp. and Vigna vexillata. DISEASE: Parodiella hedysari is a biotrophic parasite, which apparently causes little damage to tissues even when the leaf is completely covered in ascomata. Presumably at least a significant loss of photosynthetic potential must occur. GEOGRAPHICAL DISTRIBUTION: Very widely distributed throughout the tropics and warm temperate regions, and in North America extending almost to the Canadian border. Reported from: Argentina, Australia (Queensland), Botswana, Cameroon, Costa Rica, Grenada, Guyana, India, Jamaica, Kenya, Malawi, Malaysia, Mexico, Nigeria, Pakistan, Papua New Guinea, Philippines, Sarawak, Sierra Leone, Trinidad, Uganda, USA (Florida, Georgia, Kansas, Maryland, Mississippi, Missouri, Nebraska, New Mexico, New York, North Carolina, North Dakota, Oklahoma, South Carolina, South Dakota, Texas, Wisconsin), Zaire, Zambia and Zimbabwe. TRANSMISSION: no studies have been made, but ascospores are almost certainly wind- dispersed.

APPROXIMATE MOLECULAR ORBITALS: IV. THE 3dδg AND 4fδu STATES OF H2+

1967 ◽  
Vol 45 (8) ◽  
pp. 2533-2542 ◽  
Author(s):  
M. Cohen ◽  
R. P. McEachran ◽  
Sheila D. McPhee
Keyword(s):  
Perturbation Theory ◽  
Variational Methods ◽  
Excellent Agreement ◽  
Hydrogen Molecule ◽  
Wave Functions ◽  
Simple Criterion ◽  
Wide Range ◽  
Approximate Wave ◽  
Exact Calculations ◽  
Schrödinger Perturbation

Properties of the lowest even and odd δ states of the hydrogen molecule–ion have been calculated using approximate wave functions. These were derived using a combination of Rayleigh–Schrödinger perturbation theory and variational methods, which have been applied previously to calculate the corresponding wave functions of the lowest σ and π states. Our total molecular energies are in excellent agreement with the recent exact calculations of Hunter and Pritchard (1967). A simple criterion is suggested for judging the accuracy of the approximate orbitals, which indicates that all the molecular properties calculated will be accurate over a wide range of internuclear separations.

scholarly journals Transverse Patterns in the Bistable Resonant Tunneling Systems Under Ballistic Lateral Transport

VLSI Design ◽  
1998 ◽  
Vol 8 (1-4) ◽  
pp. 481-487
Author(s):  
V. A. Kochelap ◽  
B. A. Glavin ◽  
V. V. Mitin
Keyword(s):  
Numerical Simulations ◽  
Theoretical Investigation ◽  
Resonant Tunneling ◽  
Tunneling Current ◽  
Small Region ◽  
Variational Procedure ◽  
Lateral Transport ◽  
Double Barrier ◽  
Wide Range ◽  
Bistability Region

We report the theoretical investigation of the phenomenon of the formation of patterns transverse to the tunneling current in resonant tunneling double-barrier heterostructures in the case of wide range of bistable voltages. In contrast to the case of the patterns in the structures with small region of bistability, for pronounced bistability electron lateral transport is strongly nonlocal. We performed numerical simulations of the stationary and mobile patterns using special variational procedure. Our results revealed that though the possible types of patterns remains the same as for the structures with small bistability region, their characteristics are modified considerably.

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