• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1120-1131
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• 2011

Researches using time reversal acoustics(TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of a plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric(PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.418-429
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• 2011

Researches using time reversal acoustics (TRA) for impact localization have been paid attention to recently. Dispersion characteristics of Lamb waves, which restrict the utility of classical nondestructive evaluation based on time-of-flight information, can be compensated through the application of TRA to Lamb waves on a plate. This study investigates the spatial focusing performance of time reversal Lamb waves on a plate using finite element analysis. In particular, the virtual sensor effect caused by multiple wave reflections at the boundaries of the plate is shown to enable the spatial focusing of Lamb waves though a very small number of surface-bonded piezoelectric (PZT) sensors are available. The time window size of forward response signals, are normalized with respect to the number of virtual active sensors. Then their effects on the spatial focusing performance of Lamb waves are investigated.

• Asian-Australasian Journal of Animal Sciences
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• v.5 no.3
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• pp.469-473
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• 1992

Data on the birth weight, 8 week body weight and ewe body weight of an unselected random mating Romney Marsh sheep flock are analyzed to study the influence of various environmental factors. The average birth weight of lambs was 5.06 kg. Sex of lamb, birth type and dam age contributed significant variation in lamb birth weight (p < 0.05). Males were significantly heavier than females (p < 0.05) and singles were significantly heavier than multiples (p < 0.05) at birth. Birth weight of lamb increased with the progress of dams' age. The overall average 8 week body weight of lambs was 20.84 kg. Effect of birth weight, sex, birth type and dam age was significant on 8 week body weight of lamb. Eight week body weight increased with the increase of lamb birth weight (b=1.285 kg). Ewes' body weight taken before tupping was affected by ewes' age, year of performance and their weight at birth. It was concluded that performance data on lamb birth weight, 8 week body weight and ewe body weight should be corrected for the above relevantly significant environmental factors in any genetic calculation in the United Kingdom Romney March sheep.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.3
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• pp.227-233
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• 2011

The ultrasonic guided wave phased array using magnetostrictive patch transducers is proposed. The magnetostrictive transducer has received much attention because it is cost-effective and capable to generate ultrasonic waves with a simple configuration. However, it has not been used for ultrasonic guided wave phased array applications until now. In this paper, we propose a magnetostrictive transducer based phased array system consisting of a multi-channel function generator, power amplifiers and Lamb wave magnetostrictive transducers. To check the performance of the ultrasonic guided wave phased array, several Lamb wave focusing experiments were carried out in an aluminum plate. The results demonstrated the capability of the developed array to focus the Lamb waves at specific target points.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.722-725
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• 2014

The spatial focusing of time reversal Lamb waves on a plate has attracted considerable attention for identifying the location of an input source. This study investigates the spatial focusing performance on a plate with respect to the number of piezoelectric (PZT) sensors for varying locations of input sources. In particular, a small number of PZT sensors produce spatial focusing through the virtual sensor effect due to reflection of Lamb waves at plate edges. The spatial focusing performance with respect to the number of PZT sensors is quantified in terms of signal to noise ratio through numerical simulation and its implication is discussed.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.8
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• pp.1209-1215
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• 2015

Since lamb is a commodity, producers cannot control the price of the product they sell. Therefore, managing production costs is a necessity. We explored the study of elasticities as a tool for basing decision-making in sheep production, and aimed at investigating the composition and elasticities of lamb production costs, and their influence on the performance of the activity. A representative sheep production farm, designed in a panel meeting, was the base for calculation of lamb production cost. We then performed studies of: i) costs composition, and ii) cost elasticities for prices of inputs and for zootechnical indicators. Variable costs represented 64.15% of total cost, while 21.66% were represented by operational fixed costs, and 14.19% by the income of the factors. As for elasticities to input prices, the opportunity cost of land was the item to which production cost was more sensitive: a 1% increase in its price would cause a 0.2666% increase in lamb cost. Meanwhile, the impact of increasing any technical indicator was significantly higher than the impact of rising input prices. A 1% increase in weight at slaughter, for example, would reduce total cost in 0.91%. The greatest obstacle to economic viability of sheep production under the observed conditions is low technical efficiency. Increased production costs are more related to deficient zootechnical indexes than to high expenses.

• Asian-Australasian Journal of Animal Sciences
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• v.30 no.9
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• pp.1270-1277
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• 2017

Objective: The present study aimed to determine the impact of ewe body condition score (BCS) (over a range of 2.0 to 3.0) and nutritional treatments (consisting of differing herbage masses) during very late pregnancy and lactation and their potential interaction on the performance of twin-bearing ewes and their lambs to weaning. Methods: On day 142 of pregnancy, twin-bearing ewes with a BCS of 2.0, 2.5, or 3.0 were allocated to a "Moderate' or 'Unrestricted' nutritional treatment until day 95 of lactation (weaning). The nutritional treatments aimed to achieve average herbage masses of 1,200 to 1,300 kg dry matter (DM)/ha (Moderate) and 1,500 to 1,800 kg DM/ha (Unrestricted). Results: There were no three-way interactions between ewe BCS group, nutritional treatment and time for any ewe or lamb parameter. The nutritional treatments had no effect (p>0.05) on lamb birth or weaning weight. Lambs born to Moderate ewes had greater survival and total litter weight at weaning (p<0.05). Regardless of BCS group, Unrestricted treatment ewes had greater body condition and back-fat depth at weaning than Moderate treatment ewes (p<0.05). Ewes of BCS 2.0 group reared lighter lambs to weaning (p<0.05) and tended to have a lower total litter weight (p = 0.06) than BCS 3.0 group ewes. Conclusion: This study suggests farmers should aim to have all ewes with a BCS of 2.5 or 3 in late pregnancy for optimal lamb weaning performance. Furthermore, there is no benefit to lamb production of offering ewes pasture masses >1,200 kg DM/ha during very late pregnancy and lactation.

• Asian-Australasian Journal of Animal Sciences
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• v.9 no.2
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• pp.211-213
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• 1996

A study was undertaken to investigate the effect of feeding early weaning diets based on different vegetable protein sources fed to Afghani lambs. Three isonitrogenous and isocaloric complete formula diets viz., A, B and C were prepared having cottonseed meal, soybean meal and canola meal; respectively as major source of protein. Eighteen 30-35 days old Afghani male lambs were randomly allotted to three experimental diets. Lambs were fed individually twice a day for a period of 60 days. Daily feed intake and weekly weight gain was recorded. Results indicated that weight gain was significantly(p<0.05) higher(282 g/lamb/day) in lambs fed diet B as compared to lamvs fed on diets A(231 g/lamb/day) and C(242 g/lamb/day). No significant difference was found in feed intake among the diets. Significant difference(p<0.05) were noticed in feed efficiency in lambs fed on diets A(6.88), B(5.41) and C(6.17).The economic efficiency was observed to be the best on diet B as compared to diets A and C. It was concluded that Afghani lambs(30-35 days) can be reared on early weaning diets and soybean meal was found comparatively better protein source for early weaning diet.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.3
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• pp.262-267
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• 2007

Detection of gas leak from a tube is a very important issue in the quality control of machines such as the heat exchanger of an air-conditioner, because leakage of operating gas directly reduces the performance of machines. The acoustic emission (AE) method is a common way to detect leak of gas, however its application under the environment of mechanical vibration is restricted since most AE detectors are very sensitive to external vibration noise. In order to overcome this problem, we propose a method based on the mode analysis of the Lamb wave. In this method, the dominant Lamb mode and its frequency are found first, and then a proper band-pass filter is used to retain only this frequency component. In this way, we could improve the SNR (signal-to-noise ratio) of AE signal generated by gas leak from the tube even under vibratory environment.

• Asian-Australasian Journal of Animal Sciences
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• v.4 no.2
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• pp.183-186
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• 1991

Lamb fed 2% urea treated sago fibre and corn at 1.5 : 1 ratio (sago fibre + corn) and supplemented with fishmeal at 0, 50, 100, 150 g/head/day, gained 68.6, 139.6, 158.6 and 166.3 g/day, respectively. A simple feed cost analysis indicated that the sago with supplementation of fishmeal at 50 g/head/day could be an efficient and economic diet for sheep. The result showed that energy and protein supplements are necessary for reasonable performance of the sheep fed on urea treated sago fibre.