3,212 research outputs found
Active rc networks of low sensitivity for integrated circuit transfer function
Active RC network is capable of extremely high Q performance with exceptional stability and has independently adjustable zeros and poles. The circuit consists of two integrators and two summers that are interconnected to produce a complete second-order numerator and a second-order denominator
MHD Turbulence Revisited
Kraichnan (1965) proposed that MHD turbulence occurs as a result of
collisions between oppositely directed Alfv\'en wave packets. Recent work has
generated some controversy over the nature of non linear couplings between
colliding Alfv\'en waves. We find that the resolution to much of the confusion
lies in the existence of a new type of turbulence, intermediate turbulence, in
which the cascade of energy in the inertial range exhibits properties
intermediate between those of weak and strong turbulent cascades. Some
properties of intermediate MHD turbulence are: (i) in common with weak
turbulent cascades, wave packets belonging to the inertial range are long
lived; (ii) however, components of the strain tensor are so large that, similar
to the situation in strong turbulence, perturbation theory is not applicable;
(iii) the breakdown of perturbation theory results from the divergence of
neighboring field lines due to wave packets whose perturbations in velocity and
magnetic fields are localized, but whose perturbations in displacement are not;
(iv) 3--wave interactions dominate individual collisions between wave packets,
but interactions of all orders make comparable contributions to the
intermediate turbulent energy cascade; (v) successive collisions are correlated
since wave packets are distorted as they follow diverging field lines; (vi) in
common with the weak MHD cascade, there is no parallel cascade of energy, and
the cascade to small perpendicular scales strengthens as it reaches higher wave
numbers; (vii) For an appropriate weak excitation, there is a natural
progression from a weak, through an intermediate, to a strong cascade.Comment: 25 pages, to appear in The Astrophysical Journa
Design, development and delivery of one /1/ breadboard and three /3/ production units of a 75 VA integrated static inverter Monthly progress report no. 11, Mar. 1966
Breadboard model development of integrated static inverte
Design, development and delivery of one /1/ breadboard and three /3/ production units of a 75 VA integrated static inverter Monthly report no. 15
Flip-flop arrays, power transistors, epitaxial stress, and other technological developments in integrated static inverter progra
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Trauma ICU Prevalence Project: the diversity of surgical critical care.
Background:Surgical critical care is crucial to the care of trauma and surgical patients. This study was designed to provide a contemporary assessment of patient types, injuries, and conditions in intensive care units (ICU) caring for trauma patients. Methods:This was a multicenter prevalence study of the American Association for the Surgery of Trauma; data were collected on all patients present in participating centers' trauma ICU (TICU) on November 2, 2017 and April 10, 2018. Results:Forty-nine centers submitted data on 1416 patients. Median age was 58 years (IQR 41-70). Patient types included trauma (n=665, 46.9%), non-trauma surgical (n=536, 37.8%), medical (n=204, 14.4% overall), or unspecified (n=11). Surgical intensivists managed 73.1% of patients. Of ICU-specific diagnoses, 57% were pulmonary related. Multiple high-intensity diagnoses were represented (septic shock, 10.2%; multiple organ failure, 5.58%; adult respiratory distress syndrome, 4.38%). Hemorrhagic shock was seen in 11.6% of trauma patients and 6.55% of all patients. The most common traumatic injuries were rib fractures (41.6%), brain (38.8%), hemothorax/pneumothorax (30.8%), and facial fractures (23.7%). Forty-four percent were on mechanical ventilation, and 17.6% had a tracheostomy. One-third (33%) had an infection, and over half (54.3%) were on antibiotics. Operations were performed in 70.2%, with 23.7% having abdominal surgery. At 30 days, 5.4% were still in the ICU. Median ICU length of stay was 9 days (IQR 4-20). 30-day mortality was 11.2%. Conclusions:Patient acuity in TICUs in the USA is very high, as is the breadth of pathology and the interventions provided. Non-trauma patients constitute a significant proportion of TICU care. Further assessment of the global predictors of outcome is needed to inform the education, research, clinical practice, and staffing of surgical critical care providers. Level of evidence:IV, prospective observational study
Formation of nanoporous InP by electrochemical anodization
Porous InP layers can be formed electrochemically on (100) oriented n-
InP substrates in aqueous KOH. A nanoporous layer is obtained
underneath a dense near-surface layer and the pores appear to propagate
from holes through the near-surface layer. In the early stages of the
anodization transmission electron microscopy (TEM) clearly shows
individual porous domains which appear to have a square-based pyramidal
shape. Each domain appears to develop from an individual surface pit
which forms a channel through this near-surface layer. We suggest that the
pyramidal structure arises as a result of preferential pore propagation
along the directions. AFM measurements show that the density of
surface pits increases with time. Each of these pits acts as a source for a
pyramidal porous domain. When the domains grow, the current density
increases correspondingly. Eventually, the domains meet forming a
continuous porous layer, the interface between the porous and bulk InP
becomes relatively flat and its total effective surface area decreases
resulting in a decrease in the current density. Numerical models of this
process have been developed. Current-time curves at constant potential
exhibit a peak and porous layers are observed to form beneath the
electrode surface. The density of pits formed on the surface increases with
time and approaches a plateau value
Nanoporous domains in n-InP anodized in KOH
A model of porous structure growth in semiconductors based on propagation of pores along the A directions has been developed. The model predicts that pores originating at a surface pit lead to porous domains with a truncated tetrahedral shape. SEM and TEM were used to examine cross- sections of n-InP electrodes in the early stages of anodization in aqueous KOH and showed that pores propagate along the A directions. Domain outlines observed in both TEM and SEM images are in excellent agreement with the model. The model is further supported by plan-view TEM and surface SEM images. Quantitative measurements of aspect ratios of the observed domains are in excellent agreement with the predicted values
Effect of electrolyte concentration on anodic nanoporous layer growth for n-InP in aqueous KOH
The surface morphology and sub-surface porous structure of (100) n-InP following anodization in 1 - 10 mol dm-3 aqueous KOH were studied using linear sweep voltammetry (LSV) in combination with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). LSV of n-InP in 10 mol dm-3 KOH showed a single anodic current peak at 0.41 V. As the concentration of electrolyte was decreased, the peak increased in current density and charge and shifted to more positive potentials; eventually individual peaks were no longer discernable. Porous layers were observed in SEM cross-sections following linear potential sweeps and the porous layer thickness increased significantly with decreasing KOH concentration, reaching a maximum value at ~2.2 mol dm-3. At concentrations less than 1.8 mol dm-3 the layer thickness decreased sharply, pore diameters became wider and pore walls became narrower until eventually, at 1.1 mol dm-2 or lower, no porous layers were observed. It was also observed that the pore width increased and the inter-pore spacing decreased with decreasing concentration. It is proposed that preferential pore propagation occurs along directions, contrary to previous suggestions, and that the resulting anoporous domains, initially formed, have triangular cross-sections when viewed in one of the {110} cleavage planes, ‘dove-tail’ crosssections viewed in the orthogonal {110} cleavage plane and square profiles when viewed in the (100) plane of the electrode surface
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