Input Power Changes Research Articles

Optic-fiber communications: Nonlinear-transformation group

A new method for finding solutions of the nonlinear Schrodinger equation is proposed. A comutative multiplicative group of nonlinear transformations, which operate on stationary localized solutions, enables a consideration of fractal subspaces in the solution space, stability, and deterministic chaos. An increase of the transmission rate in the optic-fiber communications can be based on new forms of localized stationary solutions, without significant change of input power. The estimated transmission rate is 50 Gbit/s, for certain available soliton transmission systems.

A Pressure Control Valve Using MR Fluid

A novel control valve using MR fluid (MR valve) is proposed for fluid control systems. The MR or Magneto-Rheological fluid is a newly developed functional fluid whose apparent viscosity is controlled by the applied magnetic field intensity wider than that of Electro-Rheological fluid. The MR valve consists of a flow channel between a pair of magnetic poles and the differential pressure is controlled by the applied magnetic field intensity. It features simple, compact and reliable structure without moving parts.An MR valve is fabricated. The magnetic poles have 20mm×3Omm in face size and 3mm in gap length and are connected to an electromagnet. Through experiments on the static characteristics, it is found that the differential pressure is controlled by the applied magnetic field intensity under little influence of the flowrate, which corresponds to a pressure control valve. The differential pressure and output power changes of 0.68MPa and 20W are obtained with the input current and power changes of 710A-turns and 1.9W at the flowrate of 30cm3/s (1.8L/min).

Design of variable reflectivity mirrors and unstable resonators for Nd:YAG lasers with high average power

Positive branch as well as negative-branch unstable resonators in different quadrants of the stability diagram were examined both theoretically and experimentally. Variable reflectivity mirrors (VRM) Were used as outcoupling elements. The resonators comprised up to three Nd:YAG rods (6* 3/8 inch) with a maximum input power of 12 kW each. This system provided a maximum output power of 550 W per rod using a symmetric flat resonator. A novel design of unstable resonator (near-concentric unstable resonator NCUR), showed to be quite insensitive to input power changes within the complete range: the round trip magnification only changed by a factor of 3, resulting in a nearly constant slope efficiency and a very much reduced shift of the focal spot. With one rod, 420 W maximum laser power with a beam parameter product of 2.3 mm mrad (two rods: 680 W, 7 mm mrad) was obtained. Kirchhoff-integral based numerical calculations indicate smaller beam parameter products. This deterioration is caused by spherical aberration of the thermal lens and by differences of refractive power for r- and phi -polarizations. The VRMS Were produced at FLI's coating laboratory. An industrial evaporation machine equipped with the two electron-beam heated crucibles and a planetary drive was used. Thin-film designs with only one shaped layer yield reflectivity profiles of nearly any super-Gaussian shape with peak reflectivities of up to 90%. If an additional layer is inserted, one obtains apodized apertures. The phase shift of the reflected beam is similar to that of single-layer VRM. With a geometric model, the production parameters of the fixed mask method, such as aperture diameter and distance to the substrate, can be estimated as before. The damage threshold is 10-16 3 cm-2 (15 ns).

The NIST 30 MHz Linear Measurement System.

An automated linear measurement system (LMS) has been developed to determine the nonlinearity of a tuned 30 MHz power detector over a 6.021 dB range. This detector uses a single thermistor bead design with thermal isolation to obtain nearly linear tracking over a 4:1 change in input power. The nonlinear correction for this change, determined by the LMS, is on the order of 1.00030 (+130 μB) for the detector presently in use. Initial experiments indicate an expanded uncertainty of ±0.138% (±598 μB), which is based upon Type A and Type B components.

An experimental investigation of the transient response of a water heat pipe

Experiments were performed to investigate the transient response of a water heat pipe to step changes in input power at different cooling rates. The copper heat pipe employs a double-layered, 150 mesh copper screen wick and its evaporator section was uniformly heated while the condenser section was convectively cooled. The time constants of the vapor temperature and the effective power throughput, for both heat-up and cool-down transients, were determined as functions of the electric power input and the water mass flow rate in the cooling jacket of the condenser section. Both the vapor and wall temperatures were measured at ten axial locations along the heat pipe.

Axial radio frequency electric field intensity and ion density during low to high mode transition in argon electron cyclotron resonance discharges

To investigate the transition from the low density mode to the high density mode in an electron cyclotron resonance (ECR) discharge, a Langmuir probe and an E field probe were used to measure ion density and E field intensity as functions of axial position and power. The experiments were performed in argon at 0.13 Pa in a 7.9 cm diam cyclindrical source chamber propagating TE11 mode 2.45 GHz microwave power. Low mode was characterized by a standing wave throughout the plasma chamber and minimal power absorption. High mode exhibited nearly complete power absorption and no standing wave past the ECR zone. A sliding short (ss) was used to determine if the position of an E field null in the source chamber affected the transition between these two modes for various magnetic field configurations. The ss position had little effect on mode transition, relative power absorption or ion density when positioned downstream from a broad, large volume resonance zone (resonance near the mirror midplane). However, the plasma could not be ignited if the short was placed at or upstream from the large volume resonance zone. If the magnetic field was adjusted to yield a sharp, small volume resonance zone (resonance midway between the midplane and the throat), then positioning the ss to force an E field null at the resonance zone would prevent plasma ignition, even at 800 W forward power. The ion density exhibited a hysteresis (i.e., a direct jump from no plasma to a plasma density observed at other sliding short positions for that same forward power, thereafter following the ion density versus forward power dependence observed at nearby ss positions) on power cycling when the sliding short was within ∼1 cm of the broad resonance zone or within ∼1 cm of forcing a null in the sharp resonance zone caes. The ion density versus power curve for the broad volume case exhibited a change in slope over the transition region (Pforward ≊40 W) when the ion density at the resonance zone was ≊1×1011 cm−3. For the narrow zone cases, a region of bistability (i.e., rapid plasma density fluctuations between low and high mode with little or no change in external input power) was observed for which the ion density fluctuated between a value near 5×1010 cm−3 in low mode and 5×1011 cm−3 in high mode. Similar transitions were observed in a 14.6 cm diam ECR source with a TM01 mode, indicating that the effect is not solely dependent on the microwave field structure in the ECR chamber.

Dynamic properties of transverse-magnetic wave injected semiconductor lasers

Dynamic responses of optical polarization bistability and self-sustained pulsation in transverse-magnetic (TM) wave injected semiconductor lasers are analyzed. Due to the TM wave injection, laser amplification of TM wave and laser oscillation in the transverse-electric (TE) mode simultaneously occurs in the laser. The calculated dynamic responses of optical polarization bistability are compared with measured responses. The upper limit of the switching time and the repetition frequency are clarified from calculations. The self-sustained pulsation triggered by a change of TM input power is found in the course of the calculation. The conditions needed for the pulsation are discussed. >

Intensity-dependent Phase Shifts in Nonlinear Coupling Devices

Abstract For nonlinear coupling devices, general solutions using Stokes parameters fail to give complete information of phase shifts, as they only provide the phase-shift difference between the two outputs of coupling waveguides (or two cores for fibre coupling devices). Thus the standard Stokes parameter formulation is not sufficient for some applications in which the nonlinear phase shifts through the devices are of great concern. The analysis given here presents complete and exact solutions for nonlinear phase shifts in optical coupling devices for the first time. This reveals unusual behaviour of the nonlinear phase shifts because, in a certain input power range, a small change of input power can bring about a large change in the nonlinear phase shift. Some basic characteristics of the nonlinear phase shifts and their potential influence on application of coupling devices to all-optic signal processing are discussed.

Secondary Flow Due to the Tip Clearance at the Exit of Centrifugal Impellers

The velocity distribution was measured at the exit of two different types of un-shrouded centrifugal impeller under four different tip clearance conditions each; one with 20 radial blades and inducers and the other with 16 backward-leaning blades. The effect of tip clearance on input power was also measured. By increasing the tip clearance, the input power was hardly changed in the radial blade impeller and was reduced in the backward-leaning blade impeller. The velocity distribution normalized by the passage width between hub and shroud wall was hardly changed at the exit of the radial blade impeller by varying the tip clearance. On the other hand, the relative flow angle was reduced significantly and monotonously by an increase of tip clearance in the backward-leaning blade impeller. The change in input power due to the tip clearance was clearly related to the change of flow pattern at the exit of impeller due to the secondary flow. This is most likely caused by the component, normal to the blade, of the shear force to support the fluid in the clearance space against the pressure gradient in the meridional plane without blades.

Secondary flow due to the tip clearance at the exit of centrifugal impellers. 2nd report. Relationship between secondary flow and slip coefficient.

The velocity distributions measured at the exit of two different types of unshrouded centrifugal impellers respectively under four different tip clearance conditions were reexamined with respect to the shroud wall surface. By increasing the tip clearance, the hub-to-shroud velocity distribution was hardly changed at the exit of the radial blade impeller, by contrast, the relative flow angle was reduced significantly and monotonously in the backward-leaning blade impeller. The change in input power due to the tip clearance was clearly related to the change of flow pattern at the exit of the impeller due to the secondary flow, which must be induced by the component, normal to the blade, of the shear force to support the fluid in the clearance space against the pressure gradient in the meriodional plane without blades.

The rf input power dependence of chromium excited state level populations in the inductively coupled plasma

Excited state level populations have been measured for Cr(I) and Cr(II) in the inductively coupled plasma. The measurement was carried out using a 4096 pixel linear photodiode array spectrometer to detect emission intensities from 16 atomic and 16 ionic lines. The effect of changes in rf input power on the level populations was studied over the power range 0.75-1.75 kW. The results are consistent with a p-LTE model of excitation and ionization.

1.25-MHz attenuation measurement system

A system has been developed to make highly accurate measurements of nominally 6-dB increments of attenuation at 1.25 MHz. Initial experiments indicate a typical systematic error of 5 μB (1 μB = 0.00001 dB) with a resolution of 1 μB. A special linearity measurement system (LMS) using NBS-constructed linear tuned hybrids and power detectors has been used to determine the nonlinearity of a tuned 1.25-MHz power detector. This detector utilizes a single thermistor bead design with thermal isolation to obtain nearly linear tracking of a 4:1 change in input power. The nonlinear correction for this change, determined by the LMS, is on the order of 13 μB for the detector presently in use. This calibrated detector and another of similar design are used in the attenuation measurement system (AMS) to make power ratio measurements to determine the change in attenuation of the device under test (DUT). It is anticipated that changes of approximately 6 dB can be measured with initial insertion loss of up to 100 dB with an accuracy of 0.001 dB. A special design consideration will be required for units used for calibration in order to keep mismatch errors from significantly degrading the accuracies estimated above.

Multi-Input and Multi-Output Control of AC Generator Driven by Windmill or Turbine

Multi-input and multi-output control problem for an alternating current synchronous generator (ACG) driven by windmill or turbine is considered. Controlled variables of this system are the frequency and the magnitude of the output voltage. A system not being connected into the infinite bus is considered, which means that both the controlled variables easily vary with load change and input power change, While in usual case the frequency of the AC generator connected into the existing power system remains constant because of large capacity of the interconnected power system. The state equations for the system are derived by means of two methods; physical consideration and mathematical identification technique. Two kinds of control systems are synthesized; full state feedback control system utilizing all the state variables and output feedback control system utilizing only output variables. These control systems are synthesized by means of a proposed improved optimal regulator theory. Simulation and experimental studies are carried out and good results are reported.

Potential Hydraulic Input Power Changes in the Left Pulmonary Arterial Circulation at Birth

We studied hydraulic input power and input impedance changes in the left pulmonary arterial circulation (LPAC) before and after birth because they account for the relative importance of pulsatile and steady power and provide insight into the physiologic mechanisms of accomodating to each. Pulsatile pressure and flow were measured by a Millar micromanometer and electromagnetic flowmeter in 5 near term fetal lambs. Instantaneous power (IP) was calculated as the product of pressure and flow with time. The apparent power was calculated as the root mean square (RMS) of IP after the steady power was subtracted. Input impedance analysis allowed partitioning of pulsatile apparent power into average and reactive (RMS) components. Power values were calculated from 4 epochs of 48 seconds before and after birth in each animal.

On the Pressure Losses Due to the Tip Clearance of Centrifugal Blowers

The pressure distribution along the shroud is measured for three types of centrifugal impeller at seven different values of tip clearance each. The change of input power due to a change of tip clearance is related to the effective blockage at the impeller tip. Since the change of input power is little for the test cases, the variation of local pressure gradient along the shroud is mostly attributed to the change of local pressure loss. The local pressure loss is related to the local tip clearance ratio and to the local pressure gradient based on the deceleration of relative velocity in the impeller. Since the local pressure gradient is largest near the throat of the impeller, for many impellers the clearance ratio at the throat is used as the representative value. The tip clearance loss is related to the clearance ratio and the pressure rise based on the deceleration of relative velocity in the impeller. A good correlation is observed in all cases at various flow rate.