Decrement Method Research Articles

Integration decrement method for measuring Q of microwave resonators

The integration of the exponential decay curve of the damped oscillating microwave resonator is proposed as a tool to measure the resonator quality factor. This modification of the decrement method was verified experimentally in the X-band test Set.

CYSTIC FIBROSIS IN DENMARK IN THE PERIOD 1945‐1981 EVALUATION OF CENTRALIZED TREATMENT

Nielsen, O. H. and Schiøtz, P. O. (Paediatric Department TG, Rigshospitalet, Copenhagen, Denmark). Cystic fibrosis in Denmark in the period 1945‐1981. Acta Paediatr Scand 1982; suppl 301: 107‐119. — The present study gives a re‐evaluation of the course of the prognosis for cystic fibrosis (CF) in Denmark in the period January 1, 1945 — September 15, 1981. A total of 490 patients fulfilled the criteria of entry.Despite a rather constant annual incidence, the number of surviving CF patients is highly increasing: thus 31 patients were alive as on December 31, 1960, 119 as on December 31, 1970, and 223 as on December 31, 1980. The survival was further evaluated using the decrement method, where the patients are entered by time of birth or time of diagnosis, and the Warwick & Monson method, where the patients are entered by time of diagnosis. It applies to both methods that the underlying patient populations did not include patients with meconium ileus and patients with a retrospective or autopsy diagnosis. The probability of reaching the age of 10 years was 52% for CF patients treated exclusively in departments other than the CF centre as compared to 84% for the CF centre patients.We conclude that the centralized treatment should be preserved for a so relatively uncommon disease as CF, both because our survival curves demonstrated the prognosis to be by far the better in the patients treated at the national CF centre and because centralized treatment alone can offer appropriate research conditions.

Comparison Decrement Method for Microwave Resonator Q Measurements

The sensitivity of resonator quality-factor measurements using the decrement method can be improved by the comparison of the decay curve of a measured resonator with that of a reference standard resonator. The decay curves are compared using the integral of the function given as difference between decay curves. The comparison method, to be proposed, also has the advantage that the calibration of neither time base nor power scale is needed. Some results of the experimental verification are presented.

Asymptomatic Cerebral Aneurysm

In view of the widely divergent opinions regarding the necessity for operation in cases of asymptomatic and multiple cerebral aneurysms, an attempt is made to derive the true lifetime risk of rupture for a cerebral aneurysm in the asymptomatic patient. Prevalence data from autopsy and angiographic studies are utilized to derive a lifetime incidence for the rupture of such asymptomatic aneurysms. A decremental life table analysis method is used. The case of multiple asymptomatic aneurysms in a patient with another symptomatic aneurysm must be considered separately. Implications of these calculations are drawn regarding operation for unruptured or incidental aneurysms.

Measurement of Large Damping

Damping is an elementary factor to be considered in designing vibration isolators. So measurement of damping coefficient or damping ratio is of great importance. Usually, these values are calculated by logarithmic decrement or resonance method. These are convenient methods, if a system possesses light damping. The accuracy of these methods, however, is not satisfactory in a large damping system. In this paper, two new methods to calculate large damping with high accuracies are proposed. One is a method utilizing a phase angle between input and output, called "phase method", and the other is one utilizing the gravitational acceleration, called "gravity method". Damping coefficients of the oil damper were measured by the methods mentioned above. As the results, it is made clear that the measured values obtained by the phase method and the gravity method show higher degree of accuracy than the ones obtained by the resonance method.

Risk of spontaneous abortion following legally induced abortion.

Using the registration of all pregnant women living within a particular geographical district of Copenhagen the risk of spontaneous abortion has been calculated by means of a decremental method. A total of 3,042 pregnancies were registered and the total risk of spontaneous abortion was calculated at 10 per cent. In 431 women the previous pregnancy had been terminated by a legally induced abortion. Increased risk of spontaneous abortion could not be demonstrated in this group, where the cumulative risk of spontaneous abortion was 12 per cent. In particular, the risk of late abortion was not seen to increase.

A study of the electroplastic effect in metals

Abstract : The effects of high density, direct current pulses (100 to 1000 A/sq. mm for periods of 55-120 microsecs) on the flow stress determined in an Instron tensile testing machine were studied in a number of polycrystalline metals representing various crystal structures (Pb, Sn, Fe and Ti), with most attention being focused on Ti. The current pulses produced a decrease in the flow stress delta (o sub p) in all four metals. The work on Ti indicated that delta (o sub p) contains a contribution in addition to heating and pinch effects. This contribution (the electroplastic effect) increased significantly with current density, interstitial content and temperature (77-300K), to a lesser degree with strain, but no change was detected for a 25 fold increase in strain rate. Computer calculations of the dynamic stress changes associated with the approximately sinusoidal current-time pulses employed here yielded a contribution due to the electron-dislocation interaction (for a current density of 5000 A/sq mm at 300K) which was 32% of delta (o sub p). A model is proposed for the electroplastic effect which is based on theoretical considerations that the current flow exerts a force on the dislocations which adds to the applied force pushing a dislocation against obstacles. Complementary studies were performed on: (a) the decremental unloading method for determining the internal stress in metals, (b) the effects of temperature, gain size and interstitial content on the flow stress of Ti and (c) plastic instability in Ti sheet. (Author)

Severe arterial hypertension (grade III and IV).

The aim of this study was to evaluate the number, outcome, survival time, and causes of death of patients with severe arterial hypertension who were admitted to the Department of Medicine at Landspitalinn (National Hospital) in Reykjavik during the years 1957 to 1971. During this period 117 patients were found to have severe arterial hypertension (12.6% of all cases of hypertension diagnosed) according to the grading of Keith and Wagener, 20 patients with grade IV retinopathy and 97 patients with grade III. The case histories were analysed according to age and sex distribution, blood urea, electrocardiographic changes, heart size by X-ray at the time of diagnosis and final outcome. The survival calculations were done by the decrement method (life tables) and aim taken from patient age 65 years and less. Relatively fewer patients with severe arterial hypertension were admitted during the last five year period (1967-1971) than during the two previous five year periods. The main causes of death were cerebrovascular accidents (26.6%), myocardial infarctions (22.8%), and renal failure (22.8%). Approximately 50% of the men and 60% of the women survived five years. Elevated blood urea values and signs of left ventricular hypertrophy on ECG at the time of diagnosis carried a more sinister prognosis.

Measurements of the Q of a Loosely Coupled Cavity by the Decrement Method

In the decrement method, the Q-factor and the coupling constant s of a loosely coupled cavity can be obtained by measuring the calibrated reflection signal rather than the radiation signal.

A New Method for Measuring the Low-Temperature Dielectric Property of a Low-Loss Material with a Superconducting Resonant Cavity

A superconducting 6.5 GHz cylindrical TE011 mode cavity was used to measure the small dielectric loss of polytetrafluoroethylene at liquid helium temperature. First, the Q value and the resonance frequency of the unperturbed niobium cavity was measured by the decrement method. Then a thin cylindrical rod sample, suspended from the magnetic loop, was inserted into it through the coupling port. By the use of a gate valve and a vacuum by-pass the sample can be drawn out and reassembled without introducing air into the cavity. From the decrease of the Q value and the shift of the resonance frequency, the complex dielectric constant was obtained (ε'/ε0=1.9 and ε''/ε0=4.4×10-6 at 1.3 K). Loss tangent tan δ was estimated as 2.4×10-6.

Q Capability Indications from Infrared Absorption Measurements for Na2CO3Process Cultured Quartz

A group of 5 MHz 5th overtone quartz crystal resonators made from Na2C03 process, slow grown cul- tured quartz were measured for their extinction coefficients at 3500 cm.-' (0~~~~~'s) and Q's by the amplitude decrement method at room temperature. Alphas ranged from 0.02 to 0.3 cm-' (kO.01 reproducibility) and the Q's from 3,000,000 to 500,000 (k3% reproducibility). A smoothed curve approximating the data is given by: lo6 -_ - 0.1 14 + 7.47~1- 0.450~. Q It is roughly parallel to, but offset toward higher alphas (in the low alpha range only) from the one reported by Fraser, Dodd, Rudd and Carroll (3) for room temperature Q in NaOH process fast-grown quartz for alphas ranging up to 2.0 cm-'

Investigation of the Q of a superconducting microwave cavity

The cavity, constructed of Cu with a surface deposit of the superconductor being tested, was fastened directly to the bottom of a liquid He reservoir. It was about 14 cm in diameter, 14 cm in length, and was resonant at 2856 Mc in the TE/sub 011/ mode. An important feature was a variable coupling mechanism consisting of a ciosed wire loop suspended by a moveable dielectric arm, which extends into the cavity through a small hole in the cavity end plate. The Q of the cavity was measured by the decrement method. Measurements were made on an unpolished electroplated lead surface and on several types of tin surfaces. A curve shows variation of cavity Q with temperature. A table shows values of surface resistivity obtained. (A.G.W.)

Measurement of High Q Cavities at 10,000 Megacycles

Known methods of measuring Q in high Q resonant cavities, together with their accuracies and sources of error are discussed. For relatively low values of Q and of frequency, it is shown that band width methods are more accurate than decrement methods. For values of Q above 30,000 at frequencies above 3,000 megacycles the reverse is true. The significant feature of the present method, the wide range heterodyne decrement method, is that the accuracy is improved by observing the decay over a relatively long interval of time. An absolute accuracy of plus or minus three per cent and a relative accuracy of plus or minus two per cent are achieved. Design features and performance are discussed and constructional details are presented.