• Title/Summary/Keyword: Spare Capacity

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A Cascaded D-STATCOM Integrated with a Distribution Transformer for Medium-voltage Reactive Power Compensation

  • Lei, Ertao;Yin, Xianggen;Chen, Yu;Lai, Jinmu
    • Journal of Power Electronics
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    • v.17 no.2
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    • pp.522-532
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    • 2017
  • This paper presents a novel integrated structure for a cascaded distribution static compensator (D-STATCOM) and distribution transformer for medium-voltage reactive power compensation. The cascaded multilevel converter is connected to a system via a group of special designed taps on the primary windings of the Dyn11 connection distribution transformer. The three-phase winding taps are symmetrically arranged and the connection point voltage can be decreased to half of the line-to-line voltage at most. Thus, the voltage stress for the D-STATCOM is reduced and a compromise between the voltage rating and the current rating can be achieved. The spare capacity of the distribution transformer can also be fully used. The working mechanism is explained in detail and a modified control strategy is proposed for reactive power compensation. Finally, both simulation and scaled-down prototype experimental results are provided to verify the feasibility and effectiveness of the proposed connection structure and control strategy.

A Case Study of Spatial Composition of Elderly Skilled Nursing Facility - Focused on 5 facilities of Jeonbuk Province of Korea - (노인 전문요양시설의 공간구성에 관한 연구 - 전라북도 소재 5개 시설을 중심으로 -)

  • 이민아;유옥순
    • Korean Institute of Interior Design Journal
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    • v.13 no.1
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    • pp.62-69
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    • 2004
  • The purpose of this study was to analyze spatial composition of elderly skilled nursing facility and to provide basic information for setting up the detail facility architectural guidelines. The results of the study were following: the residential spaces of the facilities in this study were more or less overcrowded since their capacity were more than 5 elderly residents. The dimensions of some residential spaces did not even come up to the standard of elderly welfare law in force. On the other hand, the facilities had a tendency to use a space with multiple purposes or to allocate a space but to leave it with no use. Moreover comparing with the 1st floor, which was mainly for the staffs and had enough space to spare, the upper floor which was for the elderly residents, was crowded with nursing staffs and elderly residents and had densely closed residential and public spaces. For the problem solving, law and regulation modification is needed according to the case study about the usage and using frequency of each facility space. And the crowded area for the elderly residents could be enlarged through the reduction(or combination) of the rarely used spaces and moving a few residential spaces into the 1st floor.

Analysis of Beam-column Joints in a Structure using Strut Members and Composite Section (스트럿 부재와 융합단면을 이용한 기둥-보 강결 구조물 해석)

  • Cho, Jae-Hyeung;Song, Jae-Ho
    • Journal of the Korean Society of Industry Convergence
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    • v.23 no.2_2
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    • pp.289-299
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    • 2020
  • The composition of convergence cross-section of the material is a technique that provides reasonable design and construction of structures. It is frequently used in medium-sized bridges and architectural structures. However, the structural behavioral spare capacity enhancement of the structure by the application of the convergence cross-section is still limited by the expandability due to the limiting state of each material. In order to overcome these limitations, this study reasonably analyzed the construction stages before and after the convergence cross-section constructed and developed a technique for forming multi-point boundary conditions using struts, which are compression members. Based on the existing cases, a reasonable construction step for forming the material composite section of the entire structural system of the structure was derived, and a numerical analysis model for a specific part was constructed to analyze the behavior of the strut application. As a result of this study, the effect of reducing the sectional force of 7.40% in beam-column joint and 6.31% in the center of girder was derived, and the deflection, which is a measure of the serviceability of the structure, improved by 54.41% from the installation and dismantling of strut members at each construction stage.

Cognitive Beamforming Based Smart Metering for Coexistence with Wireless Local Area Networks

  • Lee, Keonkook;Chae, Chan-Byoung;Sung, Tae-Kyung;Kang, Joonhyuk
    • Journal of Communications and Networks
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    • v.14 no.6
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    • pp.619-628
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    • 2012
  • The ZigBee network has been considered to monitor electricity usage of home appliances in the smart grid network. ZigBee, however, may suffer from a coexistence problem with wireless local area network (WLAN). In this paper, to resolve the coexistence problem between ZigBee network and WLAN, we propose a new protocol constructing a cognitive smart grid network for supporting monitoring of home appliances. In the proposed protocol, home appliances first estimates the transmission timing and channel information of WLAN by reading request to send/clear to send (RTS/CTS) frames of WLAN. Next, based on the estimated information, home appliances transmit a data at the same time as WLAN transmission. To manage the interference between WLAN and smart grid network, we propose a cognitive beamforming algorithm. The beamforming algorithm is designed to guaranteeing zero interference to WLAN while satisfying a required rate for smart metering. We also propose an energy efficient rate adaptation algorithm. By slowing down the transmission rate while satisfying an imperceptible impact of quality of service (QoS) of the receiver, the home appliance can significantly save transmit power. Numerical results show that the proposed multiple antenna technique provides reliable communications for smart metering with reduced power comparing to the simple transmission technique.

Energy-efficient Multicast Algorithm for Survivable WDM Networks

  • Pu, Xiaojuan;Kim, Young-Chon
    • Current Optics and Photonics
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    • v.1 no.4
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    • pp.315-324
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    • 2017
  • In recent years, multicast services such as high-definition television (HDTV), video conferencing, interactive distance learning, and distributed games have increased exponentially, and wavelength-division multiplexing (WDM) networks are considered to be a promising technology due to their support for multicast applications. Multicast survivability in WDM networks has been the focus of extensive attention since a single-link failure in an optical network may result in a massive loss of data. But the improvement of network survivability increases energy consumption due to more resource allocation for protection. In this paper, an energy-efficient multicast algorithm (EEMA) is proposed to reduce energy consumption in WDM networks. Two cost functions are defined based on the link state to determine both working and protection paths for a multicast request in WDM networks. To increase the number of sleeping links, the link cost function of the working path aims to integrate new working path into the links with more working paths. Sleeping links indicate the links in sleep mode, which do not have any working path. To increase bandwidth utilization by sharing spare capacity, the cost function of the protection path is defined to use sleeping fibers for establishing new protection paths. Finally, the performance of the proposed algorithm is evaluated in terms of energy consumption, and also the blocking probability is evaluated under various traffic environments through OPNET. Simulation results show that our algorithm reduces energy consumption while maintaining the quality of service.

High Efficiency Life Prediction and Exception Processing Method of NAND Flash Memory-based Storage using Gradient Descent Method (경사하강법을 이용한 낸드 플래시 메모리기반 저장 장치의 고효율 수명 예측 및 예외처리 방법)

  • Lee, Hyun-Seob
    • Journal of Convergence for Information Technology
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    • v.11 no.11
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    • pp.44-50
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    • 2021
  • Recently, enterprise storage systems that require large-capacity storage devices to accommodate big data have used large-capacity flash memory-based storage devices with high density compared to cost and size. This paper proposes a high-efficiency life prediction method with slope descent to maximize the life of flash memory media that directly affects the reliability and usability of large enterprise storage devices. To this end, this paper proposes the structure of a matrix for storing metadata for learning the frequency of defects and proposes a cost model using metadata. It also proposes a life expectancy prediction policy in exceptional situations when defects outside the learned range occur. Lastly, it was verified through simulation that a method proposed by this paper can maximize its life compared to a life prediction method based on the fixed number of times and the life prediction method based on the remaining ratio of spare blocks, which has been used to predict the life of flash memory.

Ginseng extracts modulate mitochondrial bioenergetics of live cardiomyoblasts: a functional comparison of different extraction solvents

  • Huang, Yun;Kwan, Kenneth Kin Leung;Leung, Ka Wing;Yao, Ping;Wang, Huaiyou;Dong, Tina Tingxia;Tsim, Karl Wah Keung
    • Journal of Ginseng Research
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    • v.43 no.4
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    • pp.517-526
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    • 2019
  • Background: The root of Panax ginseng, a member of Araliaceae family, has been used as herbal medicine and functional food in Asia for thousands of years. According to Traditional Chinese medicine, ginseng is the most widely used "Qi-invigorating" herbs, which provides tonic and preventive effects by resisting oxidative stress, influencing energy metabolism, and improving mitochondrial function. Very few reports have systematically measured cell mitochondrial bioenergetics after ginseng treatment. Methods: Here, H9C2 cell line, a rat cardiomyoblast, was treated with ginseng extracts having extracted using solvents of different polarity, i.e., water, 50% ethanol, and 90% ethanol, and subsequently, the oxygen consumption rate in healthy and tert-butyl hydroperoxideetreated live cultures was determined by Seahorse extracellular flux analyzer. Results: The 90% ethanol extracts of ginseng possessed the strongest antioxidative and tonic activities to mitochondrial respiration and therefore provided the best protective effects to H9C2 cardiomyocytes. By increasing the spare respiratory capacity of stressed H9C2 cells up to three-folds of that of healthy cells, the 90% ethanol extracts of ginseng greatly improved the tolerance of myocardial cells to oxidative damage. Conclusion: These results demonstrated that the low polarity extracts of ginseng could be the best extract, as compared with others, in regulating the oxygen consumption rate of cultured cardiomyocytes during mitochondrial respiration.

Ginsenosides attenuate bioenergetics and morphology of mitochondria in cultured PC12 cells under the insult of amyloid beta-peptide

  • Kwan, Kenneth Kin Leung;Yun, Huang;Dong, Tina Ting Xia;Tsim, Karl Wah Keung
    • Journal of Ginseng Research
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    • v.45 no.4
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    • pp.473-481
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    • 2021
  • Background: Mitochondrial dysfunction is one of the significant reasons for Alzheimer's disease (AD). Ginsenosides, natural molecules extracted from Panax ginseng, have been demonstrated to exert essential neuroprotective functions, which can ascribe to its anti-oxidative effect, enhancing central metabolism and improving mitochondrial function. However, a comprehensive analysis of cellular mitochondrial bioenergetics after ginsenoside treatment under Aβ-oxidative stress is missing. Methods: The antioxidant activities of ginsenoside Rb1, Rd, Re, Rg1 were compared by measuring the cell survival and reactive oxygen species (ROS) formation. Next, the protective effects of ginsenosides of mitochondrial bioenergetics were examined by measuring oxygen consumption rate (OCR) in PC12 cells under Aβ-oxidative stress with an extracellular flux analyzer. Meanwhile, mitochondrial membrane potential (MMP) and mitochondrial dynamics were evaluated by confocal laser scanning microscopy. Results: Ginsenoside Rg1 possessed the strongest anti-oxidative property, and which therefore provided the best protective function to PC12 cells under the Aβ oxidative stress by increasing ATP production to 3 folds, spare capacity to 2 folds, maximal respiration to 2 folds and non-mitochondrial respiration to 1.5 folds, as compared to Aβ cell model. Furthermore, ginsenoside Rg1 enhanced MMP and mitochondrial interconnectivity, and simultaneously reduced mitochondrial circularity. Conclusion: In the present study, these results demonstrated that ginsenoside Rg1 could be the best natural compound, as compared with other ginsenosides, by modulating the OCR of cultured PC12 cells during oxidative phosphorylation, in regulating MMP and in improving mitochondria dynamics under Aβ-induced oxidative stress.

The Physicochemical Characteristics of Marinated Beef Galbi under Different Cooking Conditions (양념 소갈비의 조리과정에서의 물리화학적 특성 평가)

  • Hong, Sang-Pil;Kim, Young-Ho;Lee, Nam-Hyouck;Heo, Yeong-Uk
    • Journal of the Korean Society of Food Culture
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    • v.28 no.1
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    • pp.78-88
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    • 2013
  • Marinated beef galbi is a traditional Korean dish cooked with soy sauce, pear juice, onion, sesame oil, and sugar. However, there are many differences in beef galbi, including flavor and physicochemical aspects, depending on cooking conditions. Therefore, the physicochemical characteristics of marinated beef galbi prepared through various recipes was evaluated for its effects on pH, texture, aging, proteolysis, heating conditions, cooking time, and flavor compounds (pyrazines, IMPs, or FAAs). There were significant differences in salt concentration (0.8~3.03%), pH (4.89~6.22), and solid soluble contents (1.34-6.31 Brix) between recipes in this study. In the Pearson assay for sensory evaluation, overall preference correlated well with texture (a well-known sensory attribute in meat evaluation). Controlling the pH of meat through soaking in lemon solution, alkali water, phosphate, and baking powder solution, improved water holding capacity as much as 9 to 15% compared with the control. The myofibril index (MFI) of marinated meat stored at $4^{\circ}C$ increased 32% with 24 hours of aging and reached 39% at 48 hours of aging, and its fragmentation was observed through microscopy. SDS-PAGE showed hydrolysis of acid-soluble collagen by the pear juice, possibly related to meat tenderness. On the basis of surface temperature, the cooking time was estimated to be 8 minutes with pan heating at $170^{\circ}C$, 6 minutes at $270{\sim}300^{\circ}C$, and 4 minutes with charcoal at $700{\sim}900^{\circ}C$. Different pyrazine compounds, such as 2-methyl-3-phenylpyrrol(2,3-b) pyrazine (the typical product of the browning reaction) was mainly detected, and IMP (one of the main taste compounds in beef) was in higher amounts with the charcoal treatment, potentially related to its flavor preference among treatments. Our results demonstrate an effective case study and cooking system for beef galbi.

An Online Scaling Method for Improving the Availability of a Database Cluster (데이터베이스 클러스터의 가용성 향상을 위한 온라인 확장 기법)

  • Lee, Chung-Ho;Jang, Yong-Il;Bae, Hae-Yeong
    • The KIPS Transactions:PartD
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    • v.10D no.6
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    • pp.935-948
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    • 2003
  • An online scaling method adds new nodes to the shared-nothing database cluster and makes tables be reorganized while the system is running. The objective is to share the workload with many nodes and increase the capacity of cluster systems. The existing online scaling method, however, has two problems. One is the degradation of response time and transactions throughput due to the additional overheads of data transfer and replica's condidtency. The other is and inefficient recovery mechanism in which the overall scaling transaction is aborted by a fault. These problems deteriorate the availability of shared-nothing database cluster. To avoid the additional overheads throughout the scaling period, our scalingmethod consists of twophases : a parallel data transfer phase and a combination phase. The parallel data transferred datausing reduces the size of data transfer by dividing the data into the number of replicas. The combination phase combines the transferred datausing resources of spare nodes. Also, our method reduces the possibility of failure throughout the scaling period and improves the availability of the database cluster.