Lock Technique Research Articles

Factors influencing the retention of dowels

A technique for assessing the axial retention of dowels has been developed. This method uses whalebone instead of extracted teeth. Threaded dowels appear to have better resistance to axial displacement than other types. Resistance of threaded dowels to torsional forces can be significantly improved by a rotation lock technique.

A Stabilized Oscillator for the Radar Ranging System

This paper discusses the salient features of a stabilized crystal oscillator, which makes use of the phase lock techniques. Experimental results are given.

Simple method for measuring conductance changes to one part in 106 at MHz frequencies

A phase lock technique for the measurement of small conductance changes at MHz frequencies is described. The method requires a stable Q meter having an analog output proportional to the Q and a lock-in detector. The sensitivity is excellent, with changes as small as one part in 106 having been easily observed.

Two-Stage Self-Limiting Series Mode Type Quartz-Crystal Oscillator Exhibiting Improved Short-Term Frequency Stability

A simplified model of the transistor sustaining stage employed in common quartz-crystal oscillators is presented. Examination of the model, including associated noise sources, provides an explanation for general differences observed in the output-frequency spectra of several types of widely used self-limiting crystal oscillator circuits. A self-limiting quartz-crystal oscillator circuit configuration is described that has been specifically designed to exhibit simultaneously each of the three important circuit characteristics necessary for improved oscillator short-term frequency/phase stability: large value of oscillator resonator loaded Q, adequate suppression of 1/f flicker-of-phase type noise, and improvement in oscillator ultimate signal-to-noise ratio. Several models of the oscillator circuit have been constructed employing high quality third overtone 5-MHz AT- and BT-cut quartz resonators. Measurement of oscillator short-term frequency stability using conventional phase lock and sampling techniques confirm attainment of substantial improvement in oscillator short-term frequency stability when compared to conventional self-limiting oscillator circuits.

A System for the Precise Calibration of Air Navigational Receivers

A new RF signal generator for the calibration of very high frequency omnidirectional radio (VOR) and instrument landing system (ILS) navigational receivers is presented. This new instrument improves the calibration accuracy of VOR angle and glide slope and localizer angle deviation by an order of magnitude over the calibration systems used up to now. The same order of magnitude improvement applies to the precision of AM level, phase angle settings, RF level, etc., and the stability of the simulated RF carrier in order to make the improved accuracy realizable. A new frequency lock technique allows to cover the RF frequency ranges continuously and still obtain a stability close to frequency synthesizer performance. The two major contributions to the improved performance are a linear and flat carrier amplitude demodulator using a two-diode voltage comparator and a new digital frequency lock technique. The carrier and modulation specifications are discussed which are necessary to achieve the improved accuracies. Measurement techniques are shown which are used to verify these accuracies along with the measurement results.

Uterine closure with unlocked suture in cesarean section: Safety and Quality.

Objective: Comparing locked and unlocked uterine closure techniques in terms of bleeding control and uterine incision healing. Methods: The patients undergoing cesarean section in Sifa University Hospital between May - October 2012 were accepted to this prospective controlled study. Primarily, safety was evaluated. The hemoglobin count (HC) and serum creatine kinase (CK) levels of the patients in the locked (n = 47) and unlocked (n = 35) groups were measured just before and 24 hours after operation. Hemoglobin deficit, increase in CK and the additional hemostatic sutures were compared. Secondly, uterine scar healing was evaluated three months later. Scar thickness, niche and percentage of thinning of the scar region of the locked (n = 27) and unlocked (n = 32) groups were calculated and compared. Results: The hemoglobin deficit was similar in two groups. CK rise was less in the unlocked group but it was not significant (P = 0.082). Unlocked group needed more additional sutures (P = 0.016). The thickness of the niche and the percentage of thinning of the scar region were significantly less in the unlocked group (P= 0.002, P=0.000). Conclusions: Unlocked uterine closure technique is safe and has less damage to the myometrium.

Inter-Diffusion of Li-Isotopes in Liquid Lithium Metal

The inter-diffusion coefficient of 6Li and 7Li in liquid Li metal has been measured by a capillaryreservoir vacuum lock technique and by mass spectrometric analysis. For the temperature interval 195—450 °C and near-normal isotopic composition, the results can be represented by D= (1.41 ±0.12) ·10-3 exp[— (2825 ± 90)/ (R T)]. Theoretical relations connecting diffusion and viscosity are well obeyed. Fair agreement is obtained with the COHEN-TURNBULL free volume theory, if Li* is the diffusing species.