Modeling of a constant Voltage transformer

This paper presents a comprehensive nonlinear model of the controlled constant voltage transformer also known as the ferroresonant transformer. Saturation is a normal mode of operation for this device. This paper derives an equivalent electrical circuit that relates to the physical structure of a typical design. The level of detail includes winding resistances, continuously nonlinear magnetizing inductances, tapped windings, and leakage inductances. The paper describes methods to extract the winding resistances, leakage inductances, and hysteresis loops of the transformer and how to fit the latter into single-valued nonlinear functions. The paper compares computer simulation results of the model with those obtained analytically and experimentally. The results show that the derived circuit will be very useful for designers of the ferroresonant transformer, which is used in uninterruptible power supplies.     

Treatment of acute lateral ankle ligament ruptures. A prospective 9-13-year follow-up study of three different therapies in 79 patients

In a prospective study of 79 patients with arthrographically verified acute ruptured lateral ankle ligaments we have evaluated the long-term results of three different treatments: operation and walking-cast, walking-cast alone and elastic bandage. The average follow-up period was 11 (9-13) years, and 32 parameters concerning interview, clinical and radiographic examinations were statistically analysed. The three kinds of treatment were found to be equal, since only one parameter showed significant difference at a 5% level using Fisher's exact and the Mann-Whitney test, and no difference by using the Kruskal-Wallis test for homogeneity. Residual disabilities and late complications, such as instability, pain on activity, and the number of secondary ligament reconstructions and talocrural arthroses were low. It was concluded that nonoperative treatment provided adequate results even after a decade.     

On the coupling characteristics of coplanar waveguides andmicrostrip lines to multilayer dielectric media

The spectral-domain technique is utilized to optimize the coupling of coplanar waveguides and microstrip lines to lossy dielectric media. It is shown that to enhance the coupling, higher frequencies should be used, the dielectric constant of the substrate should be small (∈=2.56), and the width of the center conductor and gaps should be as large as possible. The dielectric constant of the superstrate should be low if a leaky-wave type of coupling is desired or large if a strong coupling by the transverse-field components is desired. It is shown that the quasi-static TEM and TM₀ modes will be excited if a superstrate is present between a high dielectric lossy media and the coplanar waveguide     

Kinetik der polykondensation von natriumsulfidhydrat und 1,4-dichlorbenzol zu poly(thio-1,4-phenylen)

The kinetics of the polycondensation of sodium sulfide hydrate and 1,4-dichlorobenzene to poly(thio-1,4-phenylene) in 1-methyl-2-pyrrolidone as solvent was studied in a differential scanning calorimeter at temperatures between 220 and 280°C. This polycondensation shows an autocatalytic behavior and the kinetics can be modelled by a first order reaction up to complete conversion. This is explained by the low solubility of sodium sulfide in l-methyl-2-pyrrolidone. The concentration of sodium sulfide is regarded as being constant during the whole course of the reaction. The autocatalytic effect can be explained by the increase of the condensation rate constant at the beginning of polycondensation due to the higher reactivity of the oligomers compared to the monomers. The number- and the weight-average molecular weight of the products formed during the course of the polycondensation can be modelled by means of stochastic methods. A simple model with only two different rate constants of the condensation process is assumed. The concentration of sodium sulfide in the reactive phase is found to be 2–5% of the value of dichlorobenzene at the beginning of the reaction and remains constant nearly until the end of polycondensation.     

Hearing loss after erythromycin therapy

We describe the case of a patient who developed bilateral loss of hearing during intravenous treatment with erythromycin. Predisposing factors may have been reduced renal and hepatic function and treatment with diuretics and aminoglycosides. Recovery was late, but hearing was probably restored to almost pre-treatment level. Patients receiving high doses of erythromycin should, as a routine, be questioned about hearing loss and tinnitus.     

A Study of Surface Deformation during Wire‐Rod Rolling of High Speed Steels using Experimental and Computational Techniques

The evolution of surface defects during shape rolling of high‐speed steel billets is studied using longitudinal surface defects prepared by machining and welding. The reduction of the defects during rolling in a production mill is compared to the total area reduction of the billets. Samples are collected after pass 4, 6, 8, 14, 19 and the final pass, 28, representing the finished 5.5mm wire. By inspecting the cross sections, the rotation of the billets from pass to pass is evaluated. Results from FE simulations on solid billets are compared to the experimental results. Generally, simulations predict less reduction than observed experimentally. In most cases cracks reduce most effectively followed by carbon steel welds and stainless steel welds.     

Real-time evaluation and visualization of learner performance in a mixed-reality environment for clinical breast examination

We investigate the efficacy of incorporating real-time feedback of user performance within mixed-reality environments (MREs) for training real-world tasks with tightly coupled cognitive and psychomotor components. This paper presents an approach to providing real-time evaluation and visual feedback of learner performance in an MRE for training clinical breast examination (CBE). In a user study of experienced and novice CBE practitioners (n = 69), novices receiving real-time feedback performed equivalently or better than more experienced practitioners in the completeness and correctness of the exam. A second user study (n = 8) followed novices through repeated practice of CBE in the MRE. Results indicate that skills improvement in the MRE transfers to the real-world task of CBE of human patients. This initial case study demonstrates the efficacy of MREs incorporating real-time feedback for training real-world cognitive-psychomotor tasks.