• Journal of Communications and Networks
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• v.15 no.4
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• pp.383-397
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• 2013

In this paper, the sensitivity of massive antenna arrays and digital beamforming to radio frequency (RF) chain in-phase quadrature-phase (I/Q) imbalance is studied and analyzed. The analysis shows that massive antenna arrays are increasingly sensitive to such RF chain imperfections, corrupting heavily the radiation pattern and beamforming capabilities. Motivated by this, novel RF-aware digital beamforming methods are then developed for automatically suppressing the unwanted effects of the RF I/Q imbalance without separate calibration loops in all individual receiver branches. More specifically, the paper covers closed-form analysis for signal processing properties as well as the associated radiation and beamforming properties of massive antenna arrays under both systematic and random RF I/Q imbalances. All analysis and derivations in this paper assume ideal signals to be circular. The well-known minimum variance distortionless response (MVDR) beamformer and a widely-linear (WL) extension of it, called WL-MVDR, are analyzed in detail from the RF imperfection perspective, in terms of interference attenuation and beamsteering. The optimum RF-aware WL-MVDR beamforming solution is formulated and shown to efficiently suppress the RF imperfections. Based on the obtained results, the developed solutions and in particular the RF-aware WL-MVDR method can provide efficient beamsteering and interference suppressing characteristics, despite of the imperfections in the RF circuits. This is seen critical especially in the massive antenna array context where the cost-efficiency of individual RF chains is emphasized.

• 대한생식의학회:학술대회논문집
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• 2003.12a
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• pp.21-30
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• 2003

As a result of the technological advance provided by intracytoplasmic sperm injection (ICSI) in 1992, the evaluation and treatment of the infertile male has changed significantly. Many men who were previously thought to be irreversibly infertile have the potential to initiate their own biologic pregnancy. However, not all men having impaired semen parameter are ideal candidates for ICSI for numerous reasons including a lack of addressing the underlying problem causing the male infertility, unknown genetic consequences, and cost-effectiveness issues. In this era of ICSI, the fundamental approach to the male with suspected subfertility is unchanged and is based on a history, physical examination, and focused laboratory testing. The urologist should approach the patient with an intent to identify remediable causes of subfertility given the specific clinical situation. For instance, should a gentleman have his varicocele repaired or vasectomy reversed, or should he proceed directly with ICSI? If no factors can be improved in a timely manner, then ICSI should be considered using the available sperm. Examples of recent advances include the diagnosis and treatment of ejaculatory duct obstruction, indications and techniques for performing testis biopsy, and technique for sperm harvesting. In addition, potential genetic causes of male subfertility should be diagnosed and discussed with the patient. Cystic fibrosis gene mutation, karyotype abnormallities, and Y-chromosome microdeletions all have recently been identified as causative for male infertility in otherwise phenotypically normal men. With recently evolved diagnostic and therapeutic techniques now available for the infertile couple, even the most severe male factor problems in patients previously considered irreversibly infertile are now potentially treatable. The physician should be aware of the availability and limitations of these new and exciting reproductive technologies because they will allow him to provide timely and more effective therapy for the infertile couple. An understanding of these advances by all physicians is important as we progress into the $21^{st}$ century

• Journal of Ocean Engineering and Technology
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• v.19 no.5 s.66
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• pp.16-25
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• 2005

The effect of vertical riser support system on the dynamic behaviour of a classical spar platform is investigated. Spar platform generally uses buoyancy-can riser support system, but as water depth gets deeper the alternative riser support system is required due to safety and cost issues. The alternative riser support system is to hang risers off the spar platform using pneumatic cylinders rather than the buoyancy-can. The existing numerical model for hull/mooring/riser coupled dynamics analysis treats riser as an elastic rod truncated at the keel (truncated riser model), thus, in this model, the effect of riser support system can not be modeled correctly. Due to this reason, the truncated riser model tends to overestimate the spar pitch and heave motion. To evaluate more realistic global spar motion, mechanical coupling among risers, guide frames and support cylinders inside of spar moon-pool should be modeled. In the newly developed model, the risers are extended through the moon-pool by using nonlinear finite element methods with realistic boundary condition at multiple guide frames. In the simulation, the vertical tension from pneumatic cylinders is modeled by using ideal-gas equation and the vertical tension from buoyancy-cans is modeled as constant top tension. The different dynamic characteristics between buoyancy-can riser support system and pneumatic riser support system are extensively studied. The alternative riser support system tends to increase spar heave motion and needs damper system to reduce the spar heave motion.

• Journal of Food Hygiene and Safety
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• v.33 no.2
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• pp.146-150
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• 2018

Red pepper is one of the most important spices popularly utilized in Korea. Because of the differences in tariff rates between red pepper powder and seasoned red-pepper sauce, seasoned red-pepper sauce is often therefore imported by consumers, then dried, ground, and added to red pepper powder for cost effective purposed to use the product the most effectively. In this study, we combined species-specific polymerase chain reaction (PCR) assays (for red pepper, garlic, onion, spring onion, and ginger) with whole-genome amplification (WGA). Thirty-nine red pepper powders were well in accordance with their labels. However, six red pepper powder and five seasoned red-pepper sauce products failed to meet their compliance requirements. As a consequence, our monitoring results revealed that the overall mislabeling rate detected in this study was identified at 22%. Thus, our findings showed that the species-specific PCR in conjunction with WGA was an ideal method to identify raw materials that are used in the manufacturing of red pepper powder and seasoned red-pepper sauce.

• Journal of the Korea Institute of Construction Safety
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• v.2 no.1
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• pp.21-27
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• 2019

Hybrid & Integrated Beam (HI-BEAM), one of the composite systems, appears to have the advantage of high rigidity of reinforced concrete structures and long span of steel structures. In addition, because HI-BEAM makes the ends of beams from reinforced concrete, it is able to construct ideal composite construction method for effectively joining with reinforced concrete columns and can produce high-quality concrete structures without completing them in the field. Existing studies on the HI-BEAM method are mostly studies on structural aspects or epidemiological characteristics, or studies on the productivity and cost analysis of different structures through case studies, and analysis of actual construction methods is based on actual construction sites. In this study, the economic feasibility of the HI-BEAM method is verified by comparing the productivity and construction costs of the RC-BEAM method (RC-BEAM) method and the HI-BEAM method.

• Smart Structures and Systems
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• v.29 no.5
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• pp.661-675
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• 2022

In this paper, an electric vehicle drives with efficient control and low cost hardware using four quadrant DC converter with Permanent Magnet Direct Current (PMDC) motor fed by DC boost converter is presented. The main idea of this work is to improve the energy efficiency of the conversion chain of an electric vehicle by inserting a boost converter between the battery and the four quadrant-DC motor chopper assembly. Consequently, this method makes it possible to maintain the amplification gain of the 4 quadrant chopper constant regardless of the battery voltage drop and even in the presence of a fault in the battery. One of the most important control problems is control under heavy uncertainty conditions. The higher order sliding mode control technique is introduced for the adjustment of DC bus voltage and mechanical motor speed. To implement the proposed approach in the automotive field, experimental tests were carried out. The performances obtained show the usefulness of this system for a better energy management of an electric vehicle and an ideal control under different operating conditions and constraints, mostly at nominal operation, in the presence of a load torque, when reversing the direction of rotation of the motor speed and even in case of battery chamber failure. The whole system has been tested experimentally and its performance has been analyzed.

• Journal of Internet Computing and Services
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• v.16 no.4
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• pp.131-139
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• 2015

With the request for the advent of new engine toward economic growth, the issue regarding public-owned data disclosure has been increasing. The Korean governments are forced to open public-owned data and to utilize them in solving the various social problems and in promoting the welfare for the people. In contrast, due to the distrust of the effectiveness for the policy, many public owned organizations hesitate to open the public-owned data. However, in spite of communication gap between the government and public organizations, Ministry of Government Administration and National Information Society Agency recently planned to accelerate the information disclosure. The study aims to analyze the perception of the public organization for public data utilization and to provide proper recommendations. This research identified mutual weights that the organization recognize in opening and sharing the public data, based on benefit, opportunity, cost, and risk. ANP decision making tool and BOCR model were applied to the analyses. The results show that there are significant differences in perceiving risk and opportunity elements between the government and public organizations. Finally, the study proposed the ideal alternatives based on four elements. The study will hopefully provide the guideline to the public organizations, and assist the related authorities with the information disclosure policy in coming up with the relevant regulations.

• Korean Journal of Construction Engineering and Management
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• v.13 no.6
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• pp.3-12
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• 2012

The slowdown of private building industry resulted in growth of remodeling market as a way to improve energy performance. Remodeling is considered more cost-effective and eco-friendly approach for energy efficient building than new construction. Since 2008, Seoul has promoted Building Retrofit Project (BRP) preponderantly to attract energy-saving renovation by supporting building owners to switch building system into energy-saving system when they remodel their old buildings. According to 2012 press release, 254 Private sectors participated in this green building project and annually reduced 41000ton of greenhouse gas emission, 14000TOE, which also result in 7.5 billion won energy cost savings per year. The paper focuses on the building envelope remodeling as a way to improve energy efficiency. Different components of the building envelope such as wall insulation, window, and shading, were applied to the baseline model and the comparison was analyzed to come up with the ideal solution. This study only assesses the building envelope as to suggest the way to redesign the better energy performing building. Offering solution focusing on the architectural feature is essential because it will provide basic information and standard when remodeling a building for energy efficiency, especially, for the nonresidential buildings used as rental offices.

• Ocean and Polar Research
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• v.34 no.4
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• pp.365-384
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• 2012

Microalgae are photosynthetic microorganisms that are highly productive in the presence of basic renewable natural sources (light, $CO_2$, water and nutrients). They can synthesize lipids, carbohydrates and proteins in a small number of days. Subsequently, these carbon-captured products can be processed into both biofuels and valuable co-products. Additionally, microalgae would be an ideal feedstock for replacing land-based food crops with cellular products as high energy density transportation fuels. These microscopic organisms could contribute a significant amount of renewable energy on a global scale. In Korea, microalgae biofuel research was common in the early 1990s. The research activities were unfortunately stopped due to limited governmental funds and low petroleum prices. Interest in algal biofuels in Korea has been growing recently due to an increased concern over oil prices, energy security, greenhouse gas emissions, and the potential for other biofuel feedstock to compete for limited agricultural resources. The high productivity of microalgae suggests that much of the Korean transportation fuel requirements can be met by biofuels at a production cost competitive with the increasing cost of petroleum seen in early 2008. At this time, the development of microlalgal biomass production technology remains in its infancy. This study reviewed microalgae culture systems and biomass production, harvesting, oil extraction, conversion, and technoeconomical bottlenecks. Many technical and economic barriers to using microalgal biofuels need to be overcome before mass production of microalgal-derived fuel substitutes is possible. However, serious efforts to overcome these barriers could become a large-scale commercial reality. Overall, this study provides a brief overview of the past few decades of global microalgal research.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1512-1512
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• 2001

The University of Cordoba conducts since 1991 a breeding program to obtain new olive cultivars from intraspecific crosses. The objective is to obtain new early bearing and high-quality cultivars. In plant breeding, many seedlings must be tested to increased the chance of getting desirable genotypes. Therefore, fast, cheap and accurate methods of analysis are necessary. The conventional laboratory techniques are costly and time-consuming. Near Infrared Spectroscopy (NIRS) can satisfy the characteristics requested by plant breeders and offers many advantages such as the simultaneous analysis of many traits and cheap cost. The objective of this work was to asses the performance of NIRS to estimate oil fruit components (fruit weight, flesh moisture, flesh/stone ratio and oil flesh content in dry weight basis) and fatty acid composition in olive fruit. Genotypes from reciprocal crosses between ‘Arbequina’, ‘Frantoio’ and ‘Picual’ cultivars have been used in this study. A total of 287 samples, each from a single plant, were scanned using a DA-7000 Diode Array VIS/NIR Analysis System (Perten Instruments), which covers the visible and NIR range from 400-1700 nm. All samples were analysed for fatty acid composition (gas chromatography) and 220 for oil fruit components (oil content by nuclear magnetic resonance), 70% and 30% of samples were randomly assign for the calibration and validation sets respectively. The preliminary results shows that calibration for palmitic, oleic and linoleic acids were highly accurate with calibration and validation values of $r^2$ from 0.85 to 0.95 and 0.76 to 0.91 respectively. Calibration for palmitoleic and estearic acids were less accurate, probably because of the narrow range of variability available for these fatty acids. For the oil fruit components, calibration were high accurate for flesh moisture and oil flesh content in dry weight basis ($r^2$ higher than 0.90 in both calibration and validation sets) and less accurate for the other characteristics evaluated. The first results obtained indicate that NIRS analysis could be an ideal technique to reduce the cost, time and chemical wasted necessary to evaluate a large number of genotypes and it is accurate enough to use for pre-selecting genotypes in a breeding program.