• Journal of Power Electronics
• /
• v.14 no.1
• /
• pp.48-60
• /
• 2014

Multilevel inverters have been widely used for high-voltage and high-power applications. Their performance is greatly superior to that of conventional two-level inverters due to their reduced total harmonic distortion (THD), lower switch ratings, lower electromagnetic interference, and higher dc link voltages. However, they have some disadvantages such as an increased number of components, a complex pulse width modulation control method, and a voltage-balancing problem. In this paper, a novel nine-level reduced switch cascaded multilevel inverter based on a multilevel DC link (MLDCL) inverter topology with reduced switching components is proposed to improve the multilevel inverter performance by compensating the above mentioned disadvantages. This topology requires fewer components when compared to diode clamped, flying capacitor and cascaded inverters and it requires fewer carrier signals and gate drives. Therefore, the overall cost and circuit complexity are greatly reduced. This paper presents modulation methods by a novel reference and multicarrier based PWM schemes for reduced switch cascaded multilevel inverters (RSCMLI). It also compares the performance of the proposed scheme with that of conventional cascaded multilevel inverters (CCMLI). Simulation results from MATLAB/SIMULINK are presented to verify the performance of the nine-level RSCMLI. Finally, a prototype of the nine-level RSCMLI topology is built and tested to show the performance of the inverter through experimental results.

• Phonetics and Speech Sciences
• /
• v.4 no.3
• /
• pp.59-73
• /
• 2012

This study attempts to investigate the contribution of prosody to the foreign accent in Chinese speakers' English production by examining the synthesized speech of crossing native and non-native talkers' prosody and segments. For the stimuli of the foreign accent ratings, we transplanted gender-matched native speakers' prosody onto non-native talkers' segments and vice versa, utilizing the TD-PSOLA algorithm. Eight English native listeners participated in judging foreign accent and comprehensibility of the transplanted stimuli. Results showed that the synthesized stimuli were perceived as stronger foreign accent regardless of speakers' proficiency when English speakers' prosody was crossed with Chinese speakers' segments. This suggests that segments contribute more than prosody to native listeners' evaluation of foreign accent. When transplanted with English speakers' segments, Chinese speakers' prosody showed a difference in duration rather than pitch between high and low proficiency such that stronger foreign accent was detected when low proficient Chinese speakers' duration was crossed with English speakers' segments. This indicated that prosody, more specifically duration, plays a role though the prosodic role is not overall as significant as segments. According to the post acoustic analysis, the temporal features contributing to making the duration parameter prominent as opposed to pitch were found out to be speaking rate, pause duration and pause frequency. Finally, foreign accent and comprehensibility showed no significant correlation such that native listeners had no difficulty listening to highly foreign accented speech.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.12
• /
• pp.195-210
• /
• 2020

This study describes the structure of the capital markets for small- and medium-sized enterprises (SMEs) and startup companies in Korea, which is an emerging market that has experienced drastic changes. The overall capital market can be divided into private and public capital markets. In the private capital market, most of the demand for capital comes from non-listed private firms, including startups and SMEs. In the case of SMEs and startups, the KOSDAQ, the Korea New Exchange (KONEX), and primary collateralized bond obligations (P-CBOs) are part of the public capital market. SMEs and startups are generally incapable of raising sufficient capital owing to their low credit ratings, and they largely have limited access to primary markets to issue shares and borrow money. The Korean government has developed a systematic financial aid program to provide funds to these companies. The fund for SMEs has significantly contributed to the development of the venture capital market. Many Korean banks provide substantial lending to SMEs, but this lending is available only because of the Korean government's loan recovery guarantee. Furthermore, SMEs can issue corporate debt in the form of primary collateralized bond obligations through government guarantees, but such debt issuances have placed increasing pressure on public guarantee institutions.

• Journal of the Ergonomics Society of Korea
• /
• v.30 no.2
• /
• pp.297-302
• /
• 2011

Many WMSDs(work-related-musculoskeletal disorders) have been reported in diverse industries and have also attracted much attention in recent years. Neck-related MSD is generally known as one of common WMSDs, especially it happens to workers who are working at the automobile assembly plants and/or shipyards. The awkward posture is considered as a main cause of neck-related MSDs. A neck supporter was developed to prevent neck-related MSDs, and 10 males were recruited to evaluate the newly developed neck supporter by measuring subjective discomfort ratings of whole body, shoulder, neck and neck-muscle activities. Muscle activities from four neck muscle groups(left/right sternocleidomastoid and upper/middle trapezius) were measured while simulating an automobile assembly task. Results showed that the neck supporter help to significantly improve subjective discomfort for whole-body, shoulder as well as neck body parts. The analyses of muscular activities also showed that the activities of left/right sternocleidomastoid muscles were statistically decreased with the neck supporter in this study. The muscle activities of upper/middle trapezius in case of wearing the neck supporter were not significantly different with the muscle activities in case of no-wearing the neck supporter. Overall findings verified that the neck supporter might help to prevent neck-related MSDs based on the current study.

• Journal of Power Electronics
• /
• v.15 no.5
• /
• pp.1318-1328
• /
• 2015

The photovoltaic (PV) power conditioning system for small-scale applications has gained significant interest in the past few decades. However, the standalone mode of operation has been rarely approached. This paper presents a two-stage multi-level micro-inverter topology that considers the different operation modes. A multi-output flyback converter provides both the DC-Link voltage balancing for the multi-level inverter side and maximum power point tracking control in grid connection mode in the PV stage. A modified H-bridge multi-level inverter topology is included for the AC output stage. The multi-level inverter lowers the total harmonic distortion and overall ratings of the power semiconductor switches. The proposed micro-inverter topology can help to decrease the size and cost of the PV system. Transient analysis and controller design of this micro-inverter have been proposed for stand-alone and grid-connected modes. Finally, the system performance was verified using a 120 W hardware prototype.

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

• The Plant Pathology Journal
• /
• v.25 no.4
• /
• pp.422-428
• /
• 2009

Studies were conducted to identify the sources of resistance in mungbean recombinant inbred lines (RILs) in Thailand against mungbean yellow mosaic disease (MYMD). 146 mungbean RILs in $F_8$ series were evaluated in a field including resistant parent NM-10-12-1 and susceptible parent KPS 2 during summer 2008 under high inoculum pressure. The RILs were subsequently scored for disease symptom severity ratings (DSSR) using a new scale. Observations regarding DSSR and % disease index (%DI) showed that the tested RILs responded differently to the disease. A large number of RILs (132) were found highly susceptible, 12 were susceptible, 3 were tolerant and one was resistant. Overall screening results showed that three RILs, viz. line no. 30, 100 and 101 had minimum DSSR and % disease index thus they are good source of resistance to MYMD in spite of high disease pressure and can therefore be used directly as varieties to manage the disease in Thailand.

• The Journal of the Acoustical Society of Korea
• /
• v.24 no.2
• /
• pp.111-116
• /
• 2005

This study deals with a subjective assessment to investigate the preferred acoustic conditions and determine the important acoustical parameters in concert halls. A subjective test was carried out using dummy head recorded sounds made in actual halls in Australia (referred to as Hall A and Hall B) to evaluate the acoustic performance of two halls. The results of subjective tests were then correlated with measured acoustical parameters to investigate the significant determinants for the preference judgements. The listeners show a stronger Preference for seats in the Hall B than those in the Hall A. The low preferences for seats in the Hall A are in agreement with live performance ratings assessed by musicians. It is found that the sound level is the most significant acoustical parameter for evaluating the overall acoustic preference in the two halls.

• Journal of Power Electronics
• /
• v.9 no.3
• /
• pp.464-471
• /
• 2009

This paper introduces a new Motion-$SPM^{TM}$ (Smart Power Modules) module in Single In-line Package (SIP), which is a fully optimized intelligent integrated IGBT inverter module for up to 1kW low power motor drive applications. This module offers a sophisticated, integrated solution and tremendous design flexibility. It also takes advantage of pliability for the arrangement of heat-sink due to two types of lead forms. It comes to be realized by employing non-punch-through (NPT) IGBT with a fast recovery diode and highly integrated building block, which features built-in HVICs and a gate driver that offers more simplicity and compactness leading to reduced costs and high reliability of the entire system. This module also provides technical advantages such as the optimized cost effective thermal performances through IMS (Insulated Metal Substrate), the high latch immunity. This paper provides an overall description of the Motion-$SPM^{TM}$ in SIP as well as actual application issues such as electrical characteristics, thermal performance, circuit configurations and power ratings.

• Journal of Fisheries and Marine Sciences Education
• /
• v.22 no.3
• /
• pp.374-387
• /
• 2010

This study presumed that pre-service elementary teachers' stereotypical attitude toward foreign groups is critical factor to be considered in the context of Korean multicultural education. 422 pre-service elementary school teachers rated repeatedly seven ethnic groups on thirteen semantic differential scales which consist of four factors; attractiveness-unattractiveness, superiority-inferiority, rationality-irrationality, and aggressiveness-compliance. A series of repeated measure MANOVAs were used to test variability in pre-service elementary school teachers' stereotypical attitude across foreign groups. They rated Japanese the most positive, but Chinese the most negative, and others more or less positive in overall attitude. Their ratings of each ethnic group also varied across four attitude factors. Japanese and Whites were classified into the most attractive and superior, and moderately rational and aggressive groups. In contrast, Chinese were rated as the most unattractive, inferior, irrational, and moderately aggressive one. Southeast Asians were rated as attractive, compliant, and inferior one. In contrast, Arabians were rated as unattractive, aggressive, and moderately superior one. Finally, North Koreans were rated moderately superior, the most aggressive and irrational one. All these findings were discussed in terms of multicultural education in Korea.