Superconducting fault current limiters (SFCL) are designed to protect the electrical grid from faults that result from lightning strikes, downed power lines and other system interruptions. The rapid ...increase of impedance of the SFCL reduces the short current in the circuit. Several coreless constructions of inductive SFCLs have been tested. The space between the windings is the thick of the polyimide film kapton insulation to increase the coupling and reduces the leakage reactance. Both primary and secondary windings have been immersed in liquid nitrogen. The presented solutions reduce the size and the weight of the device. A few limiters based on HTS 1G and HTS 2G tapes has been described, tested and compared.
The aim of this study was to compare the frequency of the occurrence of lip and/or palate cleft (CL/CP) in new-borns of two breeds, Pugs and Chihuahuas, and to measure the folic acid blood levels in ...bitches during gestations both with and without folic acid oral supplementation. Bitches of 13 Pugs and 17 Chihuahuas with CL/CP cases were used in the study. In trial 1, the animals of the experimental group (n=25) were given additional folic acid from the onset of heat till the 40th day of gestation. The females of the control group (n=12) were fed a traditional diet. From all the animals blood was collected at the onset of heat, 14 days later and on the 30th day of the gestation to estimate folic acid concentration. In trial 2, the prevalence of CP/CL cases in litters from pregnancies before and after supplementation was compared. The percentage of puppies with CL/CP after supplementation decreased in both Pugs and Chihuahua puppies (10.86% and 15.78% vs. 4.76% and 4.8% respectively). On Day 0, the concentrations of folic acid were at a low physiological level (around 8 ng/ml) in all the animals. In bitches of the experimental group the blood level of folic acid on day 14th and 30th of the treatment showed an increase in both breeds (13.65 +/- 4.27 ng/ml in Pugs, 10.79 +/- 2.84 ng/ml in Chihuahuas, and 14.94 +/- 3.22 ng/ml in Pugs, 12.95 +/- 3.58 in Chihuahuas, respectively) while in the control group, this level decreased with time of gestation both in Pugs and in Chihuahuas (around 6 ng/ml). Folic acid supplementation seems to be a simple, effective preventive method to reduce the risk of CL/CP, especially in the predisposed breeds.
The aim of this study was to compare progesterone concentrations in bitches during ovulation with a different course of follicular collapse as determined by ultrasonography. The study was conducted ...on 36 animals of different breeds, from 2 to 7 years old, and from 2 to 44 kg of body weight. Ultrasound examinations of ovaries were conducted in the peri-ovulatory period until ovulation was detected. Based on USG scans the animals were divided into two groups: group A with fast follicular collapse within 1 day, and group B with gradual follicular collapse within 2-3 days. Progesterone measurements were performed in both groups on the day when the beginning of ovulation was diagnosed by USG. Follicular collapse in group A was observed in 27.8% of animals (n = 10) and in group B in 72.2% (n = 26). There were no statistical differences (p < 0.05) in progesterone concentrations between groups A and B (6.68 +/- 0.92 ng/ml and 6.81 +/- 0.57 ng/ml respectively). From 31 bred bitches (natural mating or insemination) pregnancy was confirmed in 29 females (93.5%). These results provide information about the sufficient stability of progesterone concentration during ovulation regardless of the follicular collapse speed. Ultrasonography during the peri-ovulatory period combined with progesterone measurements allows progress in ovulation management.
Recently developed 2G superconducting tapes with high resistivity in the normal state at a temperature of 77 K allow us to build transformers with high short-circuit strength. High resistance of the ...HTS windings in the normal state causes the limitation of short-circuit current to the level depend on the value of that resistance. Rapid limitation of the short-circuit current can be achieved and the steady-state fault current can be limited to a value resulting mainly from the parameters of HTS tapes used. The required reduction of prospective fault current in a power grid can be achieved by installing in it a superconducting transformer with a winding made of 2G HTS tape only if the tape provides proper resistance-per-length in normal state at a temperature of 77 K. This article presents the results of an experimental investigation of a 1-phase model of a superconducting transformer, with special regard to the possibility of limiting the short-circuit current by the superconducting winding, according to the parameters of the HTS tapes used, in particular their resistivity in normal state at a temperature of 77 K.
The fault current limiting feature of the SC transformer with the HTS 2G windings provide protection and significantly reduce wear and tear for circuit breakers and other substation power equipment. ...A comparison of the short circuit currents of the 64 MVA transformer wound with copper and YBCO 2G HTS tapes is made in this paper. The results of the analysis show that the YBCO 2G tapes enable to built the superconducting transformer with the ability to limit the short-circuit currents. The superconducting windings require special considerations for the induced electromagnetic forces in order to limit them below the allowable tensile stresses. Strongly anisotropic Y-123 tape used in the winding of the transformer will be exposed to different orientations and amplitudes of the local magnetic field. If the transformer is going to act also as a fault current limiter, the uniformity of the transition of the transformer winding is crucial to avoid sectional responses of the transformer. Therefore it is essential to conduct systematic current-magnetic field measurements to define `constant current domain' for the conductor at a given operating temperature.
Inrush Current of Superconducting Transformer Wojtasiewicz, G.; Komarzyniec, G.; Janowski, T. ...
IEEE transactions on applied superconductivity,
06/2013, Letnik:
23, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
Inrush current in superconducting transformers is a little-known phenomenon. Because of its high values and long time, it may lead to loss of superconductivity in transformer's windings. In the ...article, we present results of inrush current measurements in two superconducting transformers of the same power but different winding geometries. The results were confronted with inrush current registered for a transformer with copper windings. The results suggest different parameters of inrush current for superconducting transformers as compared to transformers with copper windings. This article is an introduction to a series of studies on the phenomenon of superconducting transformer inrush current.
In clinical practice, the parturition date in bitches is calculated on the basis of the established ovulation date, using determination of the level of LH and P4. Additionally cytological examination ...of vaginal smears makes it possible to establish the onset of diestrus, from which the delivery occurs after about 57 days. The latest method used in bitches for this purpose is foetal biometry. Measurements of the inner chorionic cavity diameter (ICC) and biparietal diameter (BP) with formulas published by Luvoni and Grioni have been popularized and the most practically useful. In a group of six bitches the effectiveness obtained with the use of ICC was 66.67% with an accuracy of 1 day and 100% with an accuracy of 2 days. BP measurements gave better results, as the accuracy was respectively 83.33% and 100%. The effectiveness of predicting the delivery date on the base of method consisting in determining the LH surge was 66.67% with an accuracy of 1 day and 100% with an accuracy of 2 days. The best effectiveness was obtained while using the method based on P4 level determination (100% both with an accuracy of 1 day, as well as of 2 days). The lowest accuracy was obtained while using the cytological method. Generally, a comparison of the methods used for predicting the date of delivery in bitches confirms practical usefulness of fetometry. Its effectiveness was not lower than traditional methods used so far, while its advantage lies in the ease of performance and the long term of application during gestation. However, full confirmation of the practical usefulness of this method requires further research on a larger number of animals.
Performance of SMES System With HTS Magnet Kozak, J; Majka, M; Kozak, S ...
IEEE transactions on applied superconductivity,
06/2010, Letnik:
20, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
The SMES system with superconducting magnet cooled by SRDK-408 crycooler has been described in this paper. The superconducting magnet consist of 7 double-pancake coils made of Bi-2223 HTS tape with ...the inner and outer diameters 210 mm, 315 mm respectively and height of 191 mm. The inductance of the magnet is about 1 H. The superconducting magnet is fabricated and tested. In the paper the design and the performance results of the SMES magnet were reported.
Information on the prevalence of subclinical endometritis and its mechanism in repeat breeding cows is very limited. The aims of this study were: a) to evaluate the incidence of this disorder with ...cytobrush cytology b) to analyze mRNA expression of tumor necrosis factor alpha (TNFalpha) and inducible nitric oxide synthase (iNOS) in endometrial biopsy samples collected from repeat breeding cows with and without subclinical endometritis. Two experiments were carried out. In experiment 1,112 (12.4%) repeat breeding cows (inseminated at least 3 times and not pregnant) were selected out of 902 cows from 8 dairy herds. Cytobrush cytology was performed on these cows, using the threshold of 10% PMNs in uterine smears. The results showed that 45 out of the 112 cows (40.2%) were diagnosed as having subclinical endometritis. In experiment 2, uterine biopsy samples were taken from repeat breeding cows with subclinical endometritis (n = 10) and without this disorder (n = 10). Using reverse transcription-PCR, the mRNA expression of TNFalpha and iNOS was determined. A statistically significant increase in expression of both substances was measured in the group of cows with subclinical endometritis (p <0.05). These results provide evidence for a high prevalence of subclinical endometritis in repeat breeding cows as well as the involvement of TNFalpha and iNOS pathways in the regulation of this pathological condition.
To determine the impact of cytologically determined endometritis (CE) diagnosed according to three different cytological thresholds in the 4th and 6th week postpartum (p. p.) on the subsequent ...reproductive performance in dairy cows.
Dairy cows (n = 222) were clinically examined in the 4th week (Exam I) and in the 6th week (Exam II) p. p. and endometrium samples were collected for cytological examination using the cytobrush method. Three cytological thresholds (percent of polymorphonuclear leucocytes to epithelial cells) were used for categorization of cows: 1) > 18% at Exam I and > 10% at Exam II; 2) > 8% at Exams I and II; 3) > 5% at Exams I and II. The animals were categorized as endometritis positive (CE+) or negative (CE-) according to all cytological thresholds at Exams I and II. For all six experimental groups the following reproductive parameters were calculated: first insemination pregnancy rate, number of services per conception, intercalving period, and total pregnancy rate on day 300 p. p.
According to different thresholds prevalence of CE ranged from 48.0% to 65.9% at Exam I and from 26.0% to 34.7% at Exam II. The first insemination pregnancy rate was statistically lower in all CE positive groups at Exam I. Number of inseminations per conception was higher (p < 0.05) in each CE positive cows with exception of group CE+ at Exam II. Intercalving periods were longer in CE cows, and significant (p < 0.05) difference was found for groups ICE+ and ICE- at Exam I. Overall pregnancy rates were similar in cytologically determined endometritis and control cows.
Impaired fertility at herd level may concern only particular reproductive indices. It seems that each herd with subclinical endometritis needs to be evaluated and managed individually, according to the different housing, feeding, and environmental conditions. The first of three thresholds used to cytologically diagnose endometritis seems to be the most reliable when applied in the 4th week p. p.
