• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.17 no.2
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• pp.29-31
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• 2011

Hazards associated with use of wood packaging in international trade were addressed with regulations enforced. Measures to avoid spreading of pest in the trade were discussed in terms of current status and future availability.

• Advances in aircraft and spacecraft science
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• v.2 no.1
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• pp.57-76
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• 2015

We investigated complex damped modes in beams in the presence of a viscoelastic layer sandwiched between two elastic layers. The problem was solved using two approaches, (1) Rayleigh beam theory and analyzed using the Ritz method, and (2) by using 2D plane stress elasticity based finite-element method. The damping in the layers was modeled using the complex modulus. Simply-supported, cantilever, and viscously supported boundary conditions were considered in this study. Simple trigonometric functions were used as admissible functions in the Ritz method. The key idea behind sandwich structure is to increase damping in a beam as affected by the presence of a highly-damped core layer vibrating mainly in shear. Different assumptions are utilized in the literature, to model shear deformation in the core layer. In this manuscript, we used FEM without any kinematic assumptions for the transverse shear in both the core and elastic layers. Moreover, numerical examples were studied, where the base and constraining layers were also damped. The loss factor was calculated by modal strain energy method, and by solving a complex eigenvalue problem. The efficiency of the modal strain energy method was tested for different loss factors in the core layer. Complex mode shapes of the beam were also examined in the study, and a comparison was made between viscoelastically and viscously damped structures. The numerical results were compared with those available in the literature, and the results were found to be satisfactory.

• Journal of Power Electronics
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• v.12 no.4
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• pp.623-631
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• 2012

In this paper, a digital controller design procedure is presented for single-phase voltage-doubler boost rectifiers (VDBR). The model derivation of the single-phase VDBR is performed in the s-domain. After that the simplified equivalent z-domain models are derived. These z-domain models are utilized to design the input current and the output dc-link voltage controllers. For the controller design in the z-domain, the traditional K-factor method is modified by considering the nature of the digital controller. The frequency pre-warping and anti-windup techniques are adapted for the controller design. By using the proposed method, the phase margin and the control bandwidth are accurately achieved as required by controller designers in a practical frequency range. The proposed method is applied to a 2.5 kVA single-phase VDBR for Uninterruptible Power Supply (UPS) applications. From the simulation and the experimental results, the effectiveness of the proposed design method has been verified.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.148-155
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• 2008

In wireless data communication systems, retransmission of an erroneous packet is inevitable due to the harsh communication environment. In this paper, an efficient retransmission scheme using cooperation from neighboring nodes is investigated. In the cooperative retransmission scheme, an erroneous packet is transmitted to the destination by cooperative nodes which have favorable channels. This cooperative retransmission scheme requires no a priori information of neighboring nodes and has no limitation on the number of cooperating nodes. Distributed beamforming is used to accommodate multiple cooperating nodes. Phase and frequency offsets of cooperating signals are extracted from the NACK message and used to co-phase retransmitted data packets. The outage probability of the cooperative retransmission scheme is analyzed for the case of perfect synchronization and when the offsets are estimated. To reduce the impact of the residual phase and frequency offsets in cooperating signals, a low-rate feedback scheme is also investigated. It is shown that improved outage probability and reduced packet error rate (PER) performance can be achieved even for long data packets. The proposed cooperative retransmission scheme is found to outperform simple retransmission by the source as well as decode-and-forward cooperation.

• Journal of Power Electronics
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• v.11 no.6
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• pp.837-845
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• 2011

This paper proposes phase current reconstruction techniques for two-phase two-leg and two-phase four-leg inverters using a single current sensor. In the proposed methods, one phase current is sampled simultaneously with a particular branch current by using only one current sensor, and then current reconstruction algorithms are applied to extract the information on two phase currents from the sensor output. The sampled current information is periodically updated at the peak and the valley of the triangular carrier waveform in each switching cycle of pulse-width modulation (PWM). The voltage vector spaces where the phase currents can be reconstructed are evaluated. Compared to the existing method using two individual current sensors in two phases, the proposed schemes can save implementation cost since it is possible to remove one current sensor. In addition, the proposed methods are free from gain discrepancy issues between two current sensors. Simulations and experiments show excellent current reconstruction performance of the proposed methods.

• Journal of the Ergonomics Society of Korea
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• v.25 no.1
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• pp.43-49
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• 2006

A laboratory study was conducted to evaluate if two different age groups(young vs. old) had differences in walking velocity and heel contact velocity and, furthermore, if these gait characteristics could adversely influence initial friction demand characteristics(i.e. RCOF) and the likelihood of slip-initiation. Twenty eight(14 younger and 14 older adults) participated in the study. While wearing a safety harness, all participants walked at their preferred gait speed for approximately 20 minutes on the linear walking track(1.5m× 20m) consisting of two floor-mounted forced plates. During subsequent 20 cameras, respectively. The results indicated that older adults walked slower(i.e., slower whole body center-of-mass velocity), exhibited lower heel contact velocity, and produced lower initial friction demand characteristics (i.e. RCOF) in comparison to younger adults. However, ANCOVA indicated that the diferences in heel contact velocity between the two age groups were due to the effects of walking velocity. The bivariate analysis further suggested that walking velocity was correlated to RCOF and heel contact velocity, while heel contact velocity was not found to be correlated to RCOF. In conclusion, could be a better indicator for predicting initial friction demand characteristics(i.e. RCOF) not hel contact velocity.

• Journal of Construction Engineering and Project Management
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• v.9 no.2
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• pp.25-51
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• 2019

Green building certifications are being adopted widely, and existing research continues to show an array of benefits to stakeholders of green certified buildings. However, little attention has been paid thus far to the effects these buildings may have on their surrounding neighborhoods economically. This research examined the effect of LEED and/or Energy Star certification on the neighborhoods surrounding certified office buildings from an economic standpoint with spatial and statistical analyses. This research showed the unit market value of LEED and/or Energy Star certified office buildings and the parameters of LEED and/or Energy Star certification had statistically a positive impact on the median unit market value of their neighborhood areas. The findings can provide useful insights into the possibilities for additional economic benefits of their neighborhoods, encouraging a win-win approach that enhances the local real estate market.

• Asia pacific journal of information systems
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• v.31 no.4
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• pp.491-526
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• 2021

Airlines can employ a variety of quality monitoring procedures. In this study, we employ a content analysis of 8 years of online reviews for Korean airlines in contrast to other international airlines. Online airline reviews are infrequent, relative to the total number of passengers - the number of reviews is multiple orders of magnitude lower than passenger volumes - and online airline reviews are, therefore, not representative of passenger attitudes overall. Nevertheless, online reviews may be indicative of specific service issues, and draw attention to aspects that require further study by airline operators. Furthermore, significant words and phrases used in these airline reviews may help airline operators to rapidly automate filtering, partitioning, and analysis of incoming passenger comments via other channels, including email, social media posts, and call center transcripts. The current study provides insights into the contents of online reviews of Korean vs Other-International airlines, and opportunities for service enhancement. Further, we provide a set of marker words and phrases that may be helpful for management dashboards that require automated partitioning of passenger comments.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1733-1736
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• 2007

Integral floating is three-dimensional display technique which is a combination of integral imaging and floating display. In this paper, we explain and analyze the relation between the special viewing characteristics and the system factors of integral floating system. The experimental results which prove the analysis will be presented.

• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.406-415
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• 2009

Optical scanning holography (OSH) is a distinct digital holographic technique in that real-time holographic recording a three-dimensional (3-D) object can be acquired by using two-dimensional active optical heterodyne scanning. Applications of the technique so far have included optical scanning cryptography, optical scanning microscopy, 3-D pattern recognition, 3-D holographic TV, and 3-D optical remote sensing. This paper reviews some of the recent progress in OSH. Some possible further works are also discussed.