• Progress in Superconductivity and Cryogenics
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• v.8 no.4
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• pp.1-7
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• 2006

This paper reviews AC loss characteristics of high $T_c$ superconductors. The mechanisms of AC loss generation are explained briefly, and AC losses are classified by the magnetic field components which generate them. A couple of analytical formulae of AC losses, which are useful for simple and rough AC loss estimations, are presented. AC loss characteristics of single BSCCO multifilamentary conductors and single YBCO coated conductors are reviewed based on previous experimental and numerical studies. AC loss characteristics of those two types of practical high $T_c$ superconductors are compared with each other.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.spc1
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• pp.215-219
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• 2006

Artemisia spp. collections, AC60, AC67, and AC77, that showed the high levels of antioxidant activities and had good growth characters and productivity, were cultivated for mass production. Using selected excellent ones, AC60, AC67, and AC77, after mass production, mugwort teas were made through rubbing and drying processes. Total phenolic compound content, nitrite scavenging ability, and SOD-like activity in mugwort teas and commercial teas were compared. Total phenolic compound content was the highest in AC67 with 109.6 mg/100 ml. Nitrite scavenging ability of AC67 tea was relatively high with 92.5% at pH 1.2 and Jasmine (98.1%), Persimmon Leaf Tea (96.4%), Green tea (98.5%), and Jakseolcha (98.7%) were very high as well. In SOD-like activity, mugwort teas, AC67 (91.7%) and AC77 (93.7%), were high as well as those of Seolrokcha (92.1%) and Rooibos Tea (93.8%). This suggests that AC60, AC67, and AC77 could be used fur making high quality teas as well as Seolrokcha, Jasmine, Green tea, Jakseolcha, Rooibos Tea, Peppermint Herb Tea.

• Asian-Australasian Journal of Animal Sciences
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• v.8 no.1
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• pp.43-50
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• 1995

This study was carried out to investigate the effects of activated carbon (AC) on growth, ruminal charateristics, blood profiles and feed digestibility in sheep, using roughage-based or concentrate-based diets. Twelve Suffolk breed of sheep of similar age and weight were distributed into 4 groups in a $2{\times}2$ factorial design. Two groups were fed a roughage-based diet with (R + AC) and without AC (R - AC), while the other two were fed a concentrate-based diet with (C + AC) and without AC (C - AC), respectively. The addition of 0.3% AC was based on dry matter of feed offered to animals. The incorporation of AC in roughage and concentrate based diets had no marked effects on feed intake, daily gain and feed conversion of the animals within experimental diets. The results obtained might be due to the low level of AC added in the diet. The animal on both concentrate-based diets were higher than the roughage-based diets in terms of daily gain and feed conversion ratio. However, it was observed that the animals provided with AC in the concentrate-based diet did not suffer from diarrhea and easily adjusted to high concentrate feeding. Further, the pH value for all diets before feeding was noted to be similar. After feeding, however, pH was shown to be higher in R + AC (p < 0.05) than in C + AC diet. Rumen protozoa number was decreased after feeding for both + AC diets, but in C - AC diet it was higher than in the roughage-based diets. For ammonia-nitrogen, C - AC was found to be higher than C + AC diet and the roughage-based diets before feeding. Total volatile fatty acid concentration, propionate and valerate molar ratios for both diets and time of collection were not affected. However, acetate, butyrate and valerate molar ratios were observed to be affected by diets and time of collections. The diets with AC increased (p < 0.05) before feeding for acetate molar ratio, but not different within diet, however, the roughage diets were found to be higher (p < 0.05) in acetate than the concentrate diet. In the blood parameters, the glutamic pyruvic transaminase (GPT), red and white blood cell (RBC, WBC) counts and packed cell volume (PCV) did not differ within and among the diets. Likewise, the WBC differential count in both diets with either - AC or + AC were similar in trend. However, lymphocyte count was noted to be increased in R + AC than the R - AC diet. The addition of AC in both diets did not affect nutrient digestibilities within diets.

• Journal of Korean Ophthalmic Optics Society
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• v.11 no.3
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• pp.267-273
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• 2006

For this study, we measured heterophoria, Calculated AC/A, Gradient AC/A of pre & post LASIK operation. In case of heterophoria, the results showed that orthophoria 2.78% decreased, exophoria 2.78% increased on pre & post op distance phoria and exophoria 5.55% increased, esophoria 5.55% decreased on pre & post op near phoria. In case of AC/A, Calculated AC/A significantly decreased as 0.36 at AC/A and accommodation decreased as 1.25D (p<0.05). It showed that Gradient AC/A decreased 0.34 and PC/A increased 0.09 but they didn't show significant difference.

• Journal of the Korean Society of Radiology
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• v.84 no.3
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• pp.666-675
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• 2023

Purpose This study aimed to determine whether the attenuation coefficient (AC) from attenuation imaging (ATI) was correlated with visual US assessment in patients with hepatic steatosis. Moreover, it aimed to assess whether the patient's blood chemistry results and CT attenuation were correlated with AC. Materials and Methods Patients who underwent abdominal US with ATI between April 2018 and December 2018 were included in this study. Patients with chronic liver disease or cirrhosis were excluded. The correlation between AC and other parameters, such as visual US assessment, blood chemistry results, liver attenuation, and liver-to-spleen (L/S) ratio, were analyzed. AC values according to visual US assessment grades were compared using analysis of variance. Results A total of 161 patients were included in this study. The correlation coefficient between US assessment and AC was 0.814 (p < 0.001). The mean AC values for the normal, mild, moderate, and severe grades were 0.56, 0.66, 0.74, and 0.85, respectively (p < 0.001). Alanine aminotransferase levels were significantly correlated with AC (r = 0.317, p < 0.001). The correlation coefficients between liver attenuation and AC and between L/S ratio and AC were -0.702 and -0.626, respectively (p < 0.001). Conclusion Visual US assessment and AC showed a strong positive correlation with the discriminative value between the groups. Computed tomography attenuation and AC showed a strong negative correlation.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2317-2323
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• 2017

Recently, linear compressors of cooling systems such as refrigerators, which have a free piston driven by a linear motor, have attracted much attention because of their high efficiency. For structural reasons, linear compressors applied in refrigerators should use an AC capacitor to ensure stable control. However, AC capacitors are expensive and bulky. In this paper, we propose a new method to realize stable control without a real AC capacitor by implementing a virtual AC capacitor with software. To realize a virtual AC capacitor, a pure integral is calculated. Nonetheless, if an offset current exists, the calculation may diverge to infinity. To solve this problem, a high-pass filter is applied and the compensation for the phase angle and magnitude are realized with a new method. Finally, a virtual AC capacitor enables variable frequency operations. Hence, in case of a lack of voltage, we can compensate by running the linear compressor in high-frequency operations. To improve efficiency, we may optimize the operation frequency. The validity of a virtual AC capacitor has been verified through simulations and experimental results.

• 한국가스학회:학술대회논문집
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• 2001.10a
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• pp.45-57
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• 2001

An alternating current (AC) corrosion using coupon has been studied. Coupons were applied in terms of AC voltage from high value to low value through the survey of AC voltages on buried gas transmission pipeline over the country. Parameters such as AC current density of coupon, AC voltage, cathodic protection potential, soil resistivity and frequency were monitored continually. Corrosion induced by AC was observed even under cathodically protected condition that met cathodic protection criterion(: below -850mv vs. CSE). Corrosion rate was affected mainly not by AC voltage but by both of frequency and AC current density. An experimental corrosion rate relationship could be obtained statistically, in which AC corrosion rate increased linearly with effective AC current density and its slope was 0.619.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.749-753
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• 2003

This paper presents an output voltage regulation system using PWM Buck-Boost AC-AC converter for power qualify improvement of custom power. This paper proposes dynamic modeling of the system for control object and in addition, a controller design example. Therefore, system state equation is derived whereby the transfer function could be obtained. The paper shows a regulation controller for tracking the output voltage to the reference under specific operating point. Finally, this paper shows validity and practical applicability of the proposed modelling and system design by experimental results.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.315-319
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• 2003

This paper presents modeling and analysis of static and dynamic characteristics in PWM Boost AC-AC converter used for input voltage sag compensation of custom power. Especially, using circuit DQ transformation technique, an equivalent circuit in fundamental frequency domain is obtained which has all the system characteristics. Moreover, voltage gain and input power factor is analytically induced and linearized state equation at the specific operating point is given. Finally, simulation results show the validity of the proposed modelling and analyses.

• Journal of the Korean Chemical Society
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• v.8 no.3
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• pp.103-108
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• 1964

A rapid method of daughter free Ac$^{227}$ tracer preparation was studied. Through two stage extraction by HDEHP and TBPO, essentially daughter free Ac$^{227}$ tracer can be prepared. Possible loss of Ac$^{227}$ activity during the process was estimated. Milking of Th$^{227}$ from Ac$^{227}$ was also studied.