• Communications of Mathematical Education
• /
• v.37 no.2
• /
• pp.199-212
• /
• 2023

The purpose of this study is to find out whether there is a difference in achievement between blocked practice and interleaved practice according to the difference in domain and type of learning content in mathematics subject, and through this result, it is to confirm whether the effect of interleaved practice in mathematics learning is due to the 'Discriminative-contrast Hypothesis' or the 'Distributed-practice Hypothesis'. Although interleaved practice is more effective than blocked practice, previous studies have not shown consistent results regarding the cause. Therefore, in this study, 103 first-year middle school students were randomly assigned to blocked practice, interleaved practice, remote blocked practice, and remote interleaved practice groups had learning activities over 4 times. The results reveals that the effect of interleaved practice appeared in similar types in the same domain, but the effect of interleaved practice did not appear in different types in different domain. In addition, through this result, it was confirmed that the effect of interleaved practice was due to the 'Discriminative-contrast hypothesis' rather than the 'Distributed-practice hypothesis'. Further research topics were suggested after the issues on the research method and the findings were discussed.

• Journal of Power Electronics
• /
• v.19 no.3
• /
• pp.665-675
• /
• 2019

Renewable energy based on photovoltaic systems is beginning to play an important role to supply power to remote areas all over the world. Owing to the lower output voltage of photovoltaic arrays, high gain DC-DC converters with a high efficiency are required in practice. This paper presents a novel interleaved DC-DC boost converter with a high voltage gain, where the input terminal is interlaced in parallel and the output terminal is staggered in series (IPOSB). The IPOSB configuration can reduce input current ripples because two inductors are interlaced in parallel. The double output capacitors are charged in staggered parallel and discharged in series for the load. Therefore, IPOSB can attain a high step-up conversion and a lower output voltage ripple. In addtion, the output voltage can be automatically divided by two capacitors, without the need for extra sharing control methods. At the same time, the voltage stress of the power devices is lowered. The inrush current problem of capacitors is restrained by the inductor when compared with high gain converters with a switching-capacitor structure. The working principle and steady-state characteristics of the converter are analyzed in detail. The correctness of the theoretical analysis is verified by experimental results.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.11C
• /
• pp.1106-1112
• /
• 2009

The SC-FDMA(single carrier-frequency division multiple access) was recently adopted as the uplink multiple access scheme from 3GPP LTE(3rd Generation Partnership Project Long Tenn Evolution) due to its low PAPR (Peak-to-averaged power ratio). The bandwidth of IFDMA(interleaved FDMA), one of the sub-carrier mapping methods of SC-FDMA, gets narrower as the roll-off factor of RRC(root raised cosine) filter decreases from 1 to 0, whereas its PAPR can increase significantly. In practice, to increase the power efficiency of an amplifier, signals with high PAPR undergo the process of clipping. Clipping of signals may cause regeneration of high-frequency components as well as distortion of signals. The current paper deals with the effect of clipping on the spectrum and BER of IFDMA signals with RRC filters.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.23 no.3
• /
• pp.91-108
• /
• 1998

Automated Storage and Retrieval Systems (AS/RSs) are an important facility for modern material management. The expected benefits of these capital-intensive facilities are gained when their control policies and their physical design parameters are determined simultaneously. In this paper we present several analytical models that capture the impact of the storage assignment policy and of the rack design on the expected storage and retrieval times. Sequential and interleaved service modes are considered for sequencing the storage and retrieval requests. We further investigate the impact of the rack structure on the relative performance of the following storage assignment policies : closest open location (random), full turnover-based policy, and class-based. Our analysis clearly indicates that significant savings in crane travel time are realized when implementing full turnover-based policy, rather than random. These savings become more and more pronounced as the profile of the storage racks approaches the square-in-time shape. Furthermore, it is shown that a class-based policy, with a small number of storage classes, will capture most of these savings and be easier to manage in practice.