• International Journal of Air-Conditioning and Refrigeration
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• v.16 no.3
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• pp.100-107
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• 2008

The heat transfer and friction characteristics of heat exchangers having convex louver fins are experimentally investigated, and the results are compared with those of wave fin counterparts. Eighteen samples (nine convex louver fin samples and nine wave fin samples) which had different fm pitches (1.81 mm to 2.54 mm) and tube rows (one to four) were tested. The convex angle was $11.7^{\circ}$. The j factors are insensitive to fin pitch, while f factors increase as fin pitch increases. The effect of fin pitch on f factor is more significant for the wave fin compared with the convex louver fin. It appears that the complex fin pattern of the convex louver fin induces intense mixing of the flow, and thus reduces the effect of fin pitch. Both the j and f factors decrease as the number of tube row increases. However, as the Reynolds number increases, the effect of tube row diminishes. Comparison of the convex louver fin j factors with those of wave fin reveals that convex louver fin j factors are 18% to 29% higher than those of wave fin. The f factors are 16% to 34% higher for the convex louver fin. The difference increases as fin pitch decreases. Existing correlation fails to adequately predict the present data. More data is needed for a general correlation of the convex louver fin geometry.

• Speech Sciences
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• v.11 no.1
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• pp.117-130
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• 2004

This paper investigates the English intonation of Korean speakers of English as a second language and compares it to that of English native speakers. The speech data of ten Korean speakers and three native speaker controls were tape recorded in an oral reading task in which the subjects were asked to read aloud the given text which was used in the study of Wennerstrom (1994). Following Pierrehumbert and Hirschberg (1990) who distinguishes the discrete units of meaning in intonation, pitch accents, phrase accents and boundary tones were measured. It was found that Korean speakers' use of phrase accents and boundary tones were relatively good compared to their use of pitch accents. That is, Korean speakers conform to native speakers' use of phrase or boundary tones for the purpose of marking the relationship between intermediate or intonational phrases. In contrast, the main difference of Korean speakers' use of intonation from that of native speakers was the use of pitch accents. That is, Korean speakers tend to have difficulty in assigning an appropriate pitch accent to signal relationships between new or contrastive information and that which is assumed to be understood or contributes little to the meaning of the utterance.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.4
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• pp.366-371
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• 2014

The neural network pitch controller using changing rate of generator speed has been suggested in this paper to regulate wind turbine power above the rated wind speed. The changing rate of generator speed is used in the suggested pitch controller as well as the difference between the rated and current generator speed. Matlab/simulink has been used for simulations and it has been shown that the suggested pitch controller regulates generator speed as the rated speed of 122.9[rad/s].

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1461-1466
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• 2003

This paper presents the effects of the fin array and pitch on the frost layer growth of a heat exchanger. The numerical results are compared with experimental data of a cold plate to validate the present model, and agree well with experimental data within a maximum error of 8%. The characteristics of the frost formation on staggered fin array are somewhat different from those of in-line array. The frost layer at the first fin of the in-line array grows rapidly, compared to second fin, whereas the difference of the frost layer growth between the fins of the staggered array is small. For fin pitch below 10 mm, the frost layer growth of second fin in the staggered array is affected by that of first fin. The frost layer growth and heat transfer of single fin deteriorate with decreasing fin pitch regardless of fin array, however, the thermal performance of a heat exchanger, considering increase of heat surface area, becomes better.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.9
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• pp.711-717
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• 2003

This paper presents the effects of the fin array and pitch on the frost layer growth of a heat exchanger. The numerical results are compared with experimental data of a cold plate to validate the present model, and agree well with experimental data within a maximum error of 8%. The frost behaviors of the staggered fin array are somewhat different from those of in-line array. The frost layer formed on the first fin of the in-line array grows rapidly, compared to second fin, whereas the difference of the frost layer growth between the fins of the staggered array is small. For fin pitch below 10 m, the frost layer growth of second fin in the staggered array is affected by that of first fin. The thickness of the frost layer and heat transfer of single fin are reduced with decreasing fin pitch regardless of fin array. However, the thermal performance of a heat exchanger is enhanced due to the increase of heat transfer surface area.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.308-312
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• 2006

The inductance difference between conducting layers of high-Tc superconducting (HTSC) power transmission cable causes the current sharing of each conducting layer to be unequal, which decreases the current transmission capacity of HTSC power cable. Therefore, the design for even current sharing in HTSC power transmission cable is required. In this paper, we investigated the current distribution of HTSC power cable with a shield layer dependent on the pitch length and the winding direction of each layer. To analyze the effect of the shield layer on the current sharing of the conducting layers of HTSC power cable, the current distribution of HTSC power cable without a shield layer was compared with the case of HTSC power cable with a shield layer. It could be found through the analysis from the computer simulations that the shield layer of HTSC power cable could be contributed to the improvement of current distribution of conducting layers at the specific pitch length and the winding direction of conducting layer. The result and discussion for the current distribution calculated for HTSC power transmission cable with a shield layer were presented and compared with the cable without a shield layer.

• Journal of Ship and Ocean Technology
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• v.11 no.3
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• pp.1-13
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• 2007

A semi-submersible drilling rig is regarded as one of the typical offshore structures operated in the field with moderate environments such as the Gulf of Mexico, Brazil, and West Africa. Its typical roll and pitch natural periods are around 30 seconds, which avoids prevailing regions of the wave energy spectrum, and their responses in waves are quite acceptable for common operation conditions. But large roll and pitch motions can be induced by wave difference frequency energy spectrum if the metacentric heights of a semi-submersible decrease to small values in some loading conditions, and it is because the roll and pitch natural periods increase and approach to the region where the spectral density of the low frequency wave drift moment has significant value. This paper describes the low frequency roll motion of a semi-submersible that are excited by the wave 2nd order difference frequency energy by a series of model experiments. From the model tests with several different initial metacentric heights (GM), it was observed that a semi-submersible can experience large roll motion due to the wave group spectrum.

• The Journal of the Korea Contents Association
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• v.9 no.12
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• pp.940-947
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• 2009

The study aims at investigating frequency of the stuttering of stutterers according to FAF pitch alternation level, examining a stuttering group. The study has collected spoken language samples by making each 10 people of a stuttering group carry out a reading and monologue task using NAF and FAF. The results of this study were as follows. In stuttering frequency, both reading and monologue task, there was significant difference of stuttering frequency according NAF and FAF pitch alternation level. But, There was significant difference of stuttering frequency according FAF pitch alternation level. NAF levels than FAF on type of stuttering decreased at the level of all the core behavior. The decrease was a lot of block, core behavior has changed as often repeated.

• Speech Sciences
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• v.14 no.1
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• pp.73-89
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• 2007

This study explored the perception of transplanted English prosody by thirty American and Korean, male and female listeners. The English utterances of various sentence types produced by Korean and American male speakers were employed to transplant the American prosody contours to Korean English utterances. Then, the thirty subjects were instructed to rate the transplanted prosodic components. Results showed that the interactions between the three factors (e.g., rater groups & transplantation types; transplantation types & sentence types; rater groups & transplantation types & sentence types) turned out to be meaningful. Both Americans and Koreans perceived the effectiveness of the combined effect of transplanted duration and pitch or duration and pitch and intensity. However, when perceiving individual prosodic components, Americans and Koreans showed different perceptual ratings. As for the overall prosody change, Americans perceived the change of intensity in a significant way but Koreans did not because intensity is not a crucial semantic factor in Korean. Americans rated the transplantation of duration alone as ineffective while Koreans rated otherwise. This was explained by the difference between English and Korean. The difference of perspective was also significant with different sentence types, especially with the three sentence types that had speech rates slower than other sentence types. A slower speech rate intensified the mismatch between the transplanted duration and the original pitch causing a negative impression on American listeners whereas this did not affect Korean listeners. Pedagogical implications of the findings are discussed.

• Proceedings of the KSPS conference
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• 2003.10a
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• pp.115-119
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• 2003

This study compared pitch range, speech rate, pause, intonation type and boundary tones of four sentences produced by five transgenders (male to female) to those of twenty normal adults. Voice analysis was done by Praat (version 4.049). Results indicated that there was a difference in pitch range, speech rate, pause, intonation type and boundary tones among the 3 groups(transgenders, normal males and normal females). Especially, transgenders indicated boundary tones more frequently than normal adults.