• 한국생산제조학회지
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• 제19권3호
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• pp.353-358
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• 2010

This research introduces a new and improved design for a pneumatic cylinder driven roll feeder wherein each of the principal rotating feeder parts is configured so as to have feeding accuracy and to be low manufacturing cost. The feed pitch accuracy of the proposed roll feeder was evaluated by measuring lengths of cut offs of the strip stock with a shear attached to an air press. The air press was designed, manufactured, and mounted on the same table of the proposed roll feeder such that the strip stock maintained horizontal plane until the strip stock entered into the shear. The proposed roll feeder and the air press were designed to be operated automatically by a PLC employed controller. The feed pitch accuracy of the proposed roll feeder was analyzed by setting the pitch as 10, 12.5, and 15mm. At each predetermined feed pitch, the proposed roll feeder was tested 300 times as one test set and replicated three times. The average lengths of the cut offs of the strip stock ranged from 9.98 to 10.13mm, from 12.42 to 12.57mm, and from 14.96 to 15.06mm at the predetermined 10, 12.5, and 15mm feed pitch, respectively, among the total of 900 samples of each feed pitch. Main cause of variation of the length of the cut off of the strip stock fed by the proposed roll feeder was considered to be fluctuation of the air press during recompressing period of the air compressor to pressurize the air in the air tank. The largest difference between the maximum and the minimum length of the cut off was appeared while the air compressor recompressing the air. The air compressor used for this study restricted the air delivered to the proposed roll feeder while it was still running. Thus, this air delivery restriction problem should be improved by stabilizing the air press while the proposed roll feeder is running.

• 한국가스학회지
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• 제3권3호
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• pp.58-64
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• 1999

멤브레인 방식의 저장탱크 제작에서 가장 중요한 설계 파라메타인 멤브레인 유니트의 피치에 관한 응력거동 문제를 유한요소법을 사용하여 해석하였고, 이 결과를 기존의 피치설계치수와 비교 검토하였다. 본 연구에서 고려한 링 마디식 멤브레인의 경우 피치의 길이를 어떻게 설정하든지 초대형 탱크의 경우에서는 안전성 문제가 발생하지 않았다. 그러나 반복하중에 의한 피로강도가 문제되는 선박용 멤브레인의 경우에는 피치를 짧게 설계하는 것이 유리하다는 것을 보여주고 있다. 멤브레인 주름의 변형거동을 보면 주름의 높이 방향 변형이 폭에 비하여 $15{\~}50\%$ 정도 더 크게 발생하고, $-162^{\circ}C$의 초저온에 의한 변형은 액압에 의한 변형과 비교할 때 그리 크지는 않음을 보여준다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.507-510
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• 2002

In economical points of view, AC loss of high temperature superconducting devices is considered as a serious problem that must be solved. Expecially, in case of HTS cables, HTS tapes are wound helically on the former to reduce AC loss. Critical characteristics of HTS tapes, however, are influenced by mechanical stress as well as electrical, temperature, and magnetical factors. The purpose of this study is to investigate the over current characteristics of HTS tapes given mechanical stress when they are wound on the former. We prepared HTS tapes with the pitch angle 20$^{\circ}$, length 25cm as well as tapes with pitch angle 0$^{\circ}$. When current of over 200A$\_$rms/ was applied, we found out that there are differences to the rate of resistance increase between the case of pitch angle 20$^{\circ}$and that of 0$^{\circ}$. The rate of resistance variation in HTS tapes of pitch angle 20$^{\circ}$increased more slowly than that of pitch angle 0$^{\circ}$. As a result, we concluded that if critical characteristics of HTS tapes are degraded by any external factor, when over current is applied, the current limiting characteristics in HTS tapes won't be able to be expected any more.

• International Journal of Precision Engineering and Manufacturing
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• 제5권3호
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• pp.19-25
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• 2004

Pitch measurements of 150 nm one-dimensional grating standards were carried out using a contact mode atomic force microscopy with a high resolution three-axis laser interferometer. This measurement technique was named as the 'nano-metrological AFM'. In the nano-metrological AFM, three laser interferometers were aligned precisely to the end of an AFM tip. Laser sources of the three-axis laser interferometer in the nano-metrological AFM were calibrated with an I$_2$ stabilized He-Ne laser at a wavelength of 633 nm. Therefore, the Abbe error was minimized and the result of the pitch measurement using the nano-metrological AFM could be used to directly measure the length standard. The uncertainty in the pitch measurement was estimated in accordance with the Guide to the Expression of Uncertainty in Measurement (GUM). The primary source of uncertainty in the pitch-measurements was derived from the repeatability of the pitch-measurements, and its value was about 0.186 nm. The average pitch value was 146.65 nm and the combined standard uncertainty was less than 0.262 nm. It is suggested that the metrological AFM is a useful tool for the nano-metrological standard calibration.

• 대한후두음성언어의학회지
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• 제5권1호
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• pp.11-21
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• 1994

The vocal pitch is controlled by the tension, mass, and length of the vocal fold. It is well known that cricothyroid approximation raises the vocal pitch by simulating the contraction of the cricothyroid muscle, and there were so many reports that have noted a relationship between cricothyroid distance and pitch control, but there does not seem to be any single generally accepted theory to account for this connection. It is generally known that the strap muscles are active during low and falling Fo, and the suprahyoid muscles are active during high and raising Fo. These findings can be related to a general picture of the motion of the larynx during changes in Fo, the cricothyroid joint would tend to lengthen the vocal folds, as the larynx moves up and forward, and relax them as it moves back and down. In this study, we suggest that the relationship between anterior cricothyroid distance and fundamental frequency of the larynx was so complex according to the level of larynx and vertebral curvature. The higher the level of larynx, the wider the cricothyoid distance, but there is more greater fundamental frequency even though more wide cricothyroid distance. This phono-menon seems to be due to the multifactors, especially the vertical tension of the conus elasticus or the change of cricothyroid articulation. It is generally known that the crocothyoid and vocal is muscles are very closely related to pitch elevation, but sternohyoid muscle seems to be more closely related to pitch lowering. By this electromyographic studies, the sternohyoid muscle have dual activity to pitch control, increased activity during the low fundamental frequency and falling pitch, but also increased activity during the higher fundamental frequency and raising pitch at least in this study.

• 말소리와 음성과학
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• 제7권1호
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• pp.107-116
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• 2015

The present experiment investigated the effect of word length on the length of f0 intervals for North Kyungsang children. In order to find out the lengths of the f0 intervals, the f0 values at the midpoints of vowels in words were measured. F0 estimates were computed as intervals consistent with the logarithmic scale corresponding to the number of syllables in the words. The results indicated that the mean f0 intervals in words of different lengths showed a significant difference for the HH in HH vs. HHL and the LH in LH vs. LLH for North Kyungsang children. Adult speakers from the North Kyungsang region significantly differed only within the HH in HH vs. HHL. Adult speakers made a noticeable contribution in this characteristic from the children. The result of the adult study was presented to confirm whether the children used a North Kyungsang dialect. With respect to individual speaker differences, the North Kyungsang children showed more or less consistent patterns in quantile-quantile plots for the HH vs. HHL, but for the HL vs. LHL and LH vs. LLH, there were more variations than for the HH vs. HHL. The individual speakers' variation was the largest for the HL vs. LHL and the smallest for HH vs. HHL. Considering these results, the effect of word length on f0 intervals tended to show pitch accent-type-specific characteristics in the process of prosodic acquisition.

• 말소리와 음성과학
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• 제6권4호
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• pp.67-77
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• 2014

This study investigated (1) whether Korean learners of English use discourse-level prosody in L2 production as native speakers of English do, and (2) whether discourse-level prosody is also found in the Korean language, as is evident in the prosody of native speakers of English. The study compared the production of the same 15 sentences in two types of reading materials, sentence-level and discourse-level. This study analyzed the onset pitch, sentence mean pitch and pause length to examine the paratone (intonational paragraph) realization in discourse-level speech. The results showed that in L2 discourse-level prosody, the Korean speakers were limited in displaying paratone and did not made significant difference between sentence-level and discourse-level prosody. On the other hand, in L1 discourse-level text, both English and Korean participants demonstrated paratone using pitch. However, there were differences in using prosodic cues between two groups. In using pauses, the ES group paused longer before both the orthographically marked and not marked topic sentences. The KS group paused longer only before the orthographically marked topic sentence in both L1 and L2 text reading. In the comparison of sentence-level and discourse-level prosody, the topic sentences were marked by different prosodic cues. English participants used higher sentence mean pitch, and the Korean participants used higher onset pitch.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.111-120
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• 2008

A particle image velocimetry (PIV) technique was employed to investigate the effects of blowing jet on the flow characteristics over stationary and pitch-oscillating airfoils. The Reynolds number was $7.84{\times}10^5$ based on the chord length. It was found that for stationary airfoil cases, continuous and pulsating blowing jets successfully reduced separated wake region at high angles of attack. A comparison study of two different types of jet blowing indicated that pulsating jet is more effective than continuous jet for flow separation control. Pulsating leading-edge blowing postpones flow separation and increased stall angle of attack by $2^{\circ}{\sim}3^{\circ}$. For pitch-oscillating airfoil cases, the PIV results showed that blowing jet efficiently delays the separation onset point during pitch-up stroke, whereas it does not prevent flow separation during pitch-down stroke, even at angles of attack smaller than static ones.

• 한국통신학회논문지
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• 제16권12호
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• pp.1324-1335
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• 1991

본 논문은 음절을 음소로 분리하고 각각의 특징을 추출하여 음소를 판별할 수 있는 패턴을 설정하는 실험에 관한 연구이다. 음소분리는 피치검출, 각 성문피크펄스의 폭, 포락실, 진폭의 바이어스, 발성시간 등의 파라메타를 적용한다. 최초의 피치는 성문펄스의 폭, 에너지, 정규화와 성문피크의 가변바이어스 등의 변화에 따라 모음 포라선의 봉우리 부분에서 검출, 이를 기준으로 전체의 피치구간을 추적한다. 모음은 포만트 패턴의 유동을 감소시키는 방법과 제2포만트만으로 모음의 판별이 가능함을 제시하며, 피치 고저에 무관한 압축파형을 추정한다. 자음은 포락실, 스펙트럼, 압추파형, 분석방법 등을 발음방법과 음소 상호 영향에서 패턴을 추출한다. 실험결과 모음음소 90%, 초성자음80%, 종성자음 60% 판별된다.

• Tribology and Lubricants
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• 제23권4호
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• pp.149-155
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• 2007

The CAD model of a elliptical gear for wire cutting has been developed. The rolling contact of pitch ellipses whose rotation axes coincide with their focus has been analyzed, and the perimeter of the pitch ellipse has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. The elliptical gear has been designed by imposing the master tooth on the divided points of the pitch ellipse, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of an elliptical gear is a composite curve of arcs only, and consequently NC codes for wire cutting can be easily generated. Furthermore, a computer simulation program is developed to verify the mesh of the elliptical gear.