• Title/Summary/Keyword: internal capability

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Attitude Control for Agile Spacecraft Installed with Reaction Wheels (리액션휠 기반 고기동 위성 자세제어 기법 연구)

  • Kim, Taeho;Mok, Sung-Hoon;Bang, Hyochoong;Song, Taeseong;Lee, Jongkuck;Song, Deokki;Seo, Joongbo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.11
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    • pp.934-943
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    • 2018
  • In these days, demand for agile spacecraft is gradually increasing, due to the fact that agile spacecraft can improve mission capability. In this paper, an attitude control logic based on reaction wheels that can enhance agility of spacecraft is proposed. Three methods are suggested, and all three or part of them can be integrated to the existing attitude control system. First, a feedforward/feedback controller is introduced, and its pros and cons are provided, compared to the conventional feedback controller. Second, an attitude command generation method that fully utilizes torque/momentum capacities of reaction wheels is proposed. Third, a torque (current) control mode for internal wheel control is introduced. Numerical results verify that the settling time can be significantly reduced by employing the feedforward/feedback control method, especially for large angle maneuver.

Effects of Knowledge Management Activities on Financial Performance: Focusing on the Mediating Effects of Enterprise-level Resilience (기업의 지식경영활동이 재무적 성과에 미치는 영향: 기업 회복역량의 매개효과를 중심으로)

  • Kang, Yeonsil;Cho, Booyun
    • Knowledge Management Research
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    • v.22 no.1
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    • pp.139-154
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    • 2021
  • As environmental impacts on business management rapidly rise, the importance of resilience has been emphasized ever. Resilience can be defined as the capability to quickly return to daily operational levels after external shocks. Thus, we suggest and empirically verify a conceptual model using enterprise-level resilience in knowledge management. Based on previous studies, sub-components of resilience have been distinguished into R4(i.e., Robustness, Redundancy, Resourcefulness, and Rapidity) and the internal and external knowledge management activities of companies have been identified as prior factors. Considering resilience as mediating variables, firms' knowledge management activities are assumed to affect a firms' performance. We collected data with the structured survey which had been developed from the stepwise approach to verify the structural model that leads to knowledge management activities, resilience, and performance. In further research, we request exploratory research on independent variables that can increase the firms' resilience and on dependent variables that would be influenced by the enterprise-level resilience.

Case Studies and Lessons Learned from Launch Environmental Test for Nanosatellites (나노급 초소형위성 발사환경시험 사례 및 교훈)

  • Kim, Min-Ki;Kim, Hae-Dong;Choi, Won-Sub;Kim, Jin-Hyung;Kim, KiDuck;Kim, Ji-Seok;Cho, Dong-Hyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.50 no.6
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    • pp.423-433
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    • 2022
  • This paper introduces the case studies of launch environmental test for cube nanosatellites and lessons learned of the design and integration from those. Generally, nanosatellites are launched and deployed in space while being contained in nanosatellite deployers, mechanical loads of launch are transferred through the deployer. This characteristic make nanosatellites under larger loads and higher possibilities of mechanical failure. This study represents guidelines of the design and the integration of the nanosatellites by showing the cases of launch environmental test of nanosatellite system. Moreover, it is suggested that the modern nanosatellite deployer with the capability of fixing the internal nanosatellite be preferable to conventional deployer by comparing the test results with those deployers.

A multi-layer approach to DN 50 electric valve fault diagnosis using shallow-deep intelligent models

  • Liu, Yong-kuo;Zhou, Wen;Ayodeji, Abiodun;Zhou, Xin-qiu;Peng, Min-jun;Chao, Nan
    • Nuclear Engineering and Technology
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    • v.53 no.1
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    • pp.148-163
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    • 2021
  • Timely fault identification is important for safe and reliable operation of the electric valve system. Many research works have utilized different data-driven approach for fault diagnosis in complex systems. However, they do not consider specific characteristics of critical control components such as electric valves. This work presents an integrated shallow-deep fault diagnostic model, developed based on signals extracted from DN50 electric valve. First, the local optimal issue of particle swarm optimization algorithm is solved by optimizing the weight search capability, the particle speed, and position update strategy. Then, to develop a shallow diagnostic model, the modified particle swarm algorithm is combined with support vector machine to form a hybrid improved particle swarm-support vector machine (IPs-SVM). To decouple the influence of the background noise, the wavelet packet transform method is used to reconstruct the vibration signal. Thereafter, the IPs-SVM is used to classify phase imbalance and damaged valve faults, and the performance was evaluated against other models developed using the conventional SVM and particle swarm optimized SVM. Secondly, three different deep belief network (DBN) models are developed, using different acoustic signal structures: raw signal, wavelet transformed signal and time-series (sequential) signal. The models are developed to estimate internal leakage sizes in the electric valve. The predictive performance of the DBN and the evaluation results of the proposed IPs-SVM are also presented in this paper.

Highly Flexible Piezoelectric Tactile Sensor based on PZT/Epoxy Nanocomposite for Texture Recognition (텍스처 인지를 위한 PZT/Epoxy 나노 복합소재 기반 유연 압전 촉각센서)

  • Yulim Min;Yunjeong Kim;Jeongnam Kim;Saerom Seo;Hye Jin Kim
    • Journal of Sensor Science and Technology
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    • v.32 no.2
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    • pp.88-94
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    • 2023
  • Recently, piezoelectric tactile sensors have garnered considerable attention in the field of texture recognition owing to their high sensitivity and high-frequency detection capability. Despite their remarkable potential, improving their mechanical flexibility to attach to complex surfaces remains challenging. In this study, we present a flexible piezoelectric sensor that can be bent to an extremely small radius of up to 2.5 mm and still maintain good electrical performance. The proposed sensor was fabricated by controlling the thickness that induces internal stress under external deformation. The fabricated piezoelectric sensor exhibited a high sensitivity of 9.3 nA/kPa ranging from 0 to 10 kPa and a wide frequency range of up to 1 kHz. To demonstrate real-time texture recognition by rubbing the surface of an object with our sensor, nine sets of fabric plates were prepared to reflect their material properties and surface roughness. To extract features of the objects from the detected sensing data, we converted the analog dataset to short-term Fourier transform images. Subsequently, texture recognition was performed using a convolutional neural network with a classification accuracy of 97%.

Geminocystis urbisnovae sp. nov. (Chroococcales, Cyanobacteria): polyphasic description complemented with a survey of the family Geminocystaceae

  • Elena Polyakova;Svetlana Averina;Alexander Pinevich
    • ALGAE
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    • v.38 no.2
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    • pp.93-110
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    • 2023
  • Progress in phylogenomic analysis has led to a considerable re-evaluation of former cyanobacterial system, with many new taxa being established at different nomenclatural levels. The family Geminocystaceae is among cyanobacterial taxa recently described on the basis of polyphasic approach. Within this family, there are six genera: Geminocystis, Cyanobacterium, Geminobacterium, Annamia, Picocyanobacterium, and Microcrocis. The genus Geminocystis previously encompassed two species: G. herdmanii and G. papuanica. Herein, a new species G. urbisnovae was proposed under the provision of the International Code of Nomenclature for algae, fungi, and plants (ICN). Polyphasic analysis was performed for five strains from the CALU culture collection (St. Petersburg State University, Russian Federation), and they were assigned to the genus Geminocystis in accordance with high 16S rRNA gene similarity to existing species, as well as because of proximity to these species on the phylogenetic trees reconstructed with RaxML and Bayes methods. Plausibility of their assignment to a separate species of the genus Geminocystis was substantiated with smaller cell size; stenohaline freshwater ecotype; capability to complementary chromatic adaptation of second type (CA2); distinct 16S rRNA gene clustering; sequences and folding of D1-D1' and B box domains of the 16S-23S internal transcribed spacer region. The second objective pursued by this communication was to provide a survey of the family Geminocystaceae. The overall assessment was that, despite attention of many researchers, this cyanobacterial family has been understudied and, especially in the case of the crucially important genus Cyanobacterium, taxonomically problematic.

Permeability of the Lateral Air Flow through Unstructured Pillar-like Nanostructures (비정형 기둥 형상을 가진 나노구조에서의 가스 투과성 실험 연구)

  • Hyewon Kim;Hyewon Lim;Jeong Woo Park;Sangmin Lee;Hyungmo Kim
    • Tribology and Lubricants
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    • v.39 no.5
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    • pp.197-202
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    • 2023
  • Recently, research on experimental and analytical techniques utilizing microfluidic devices has been pursued. For example, lab-on-a-chip devices that integrate micro-devices onto a single chip for processing small sample quantities have gained significant attention. However, during sample preparation, unnecessary gases can be introduced into the internal channels, thus, impeding device flow and compromising specific function efficiency, including that of analysis and separation. Several methods have been proposed to mitigate this issue, however, many involve cumbersome procedures or suffer from complexities owing to intricate structures. Recently, some approaches have been introduced that utilize hydrophobic device structures to remove gases within channels. In such cases, the permeability of gases passing through the structure becomes a crucial performance factor. In this study, a method involving the deposition and sintering of diluted Ag-ink onto a silicon wafer surface is presented. This is followed by unstructured nano-pattern creation using a Metal Assisted Chemical Etching (MACE) process, which yields a nanostructured surface with unstructured pillar shapes. Subsequently, gas permeability in the spaces formed by these surface structures is investigated. This is achieved by experiments conducted to incorporate a pressure chamber and measure gas permeability. Trends are subsequently analyzed by comparing the results with existing theories. Finally, it can be confirmed that the significance of this study primarily lies in its capability to effectively evaluate gas permeability through unstructured pillar-like nanostructures, thus, providing quantitative values for the appropriate driving pressure and expected gas removal time in practical device operation.

Quantitative detection of Pythium porphyrae and Pythium chondricola (Oomycota), the causative agents of red rot disease in Pyropia farms in China

  • Jie Liu;Sudong Xia;Huichao Yang;Zhaolan Mo;Jie Li;Yongwei Yan
    • ALGAE
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    • v.39 no.3
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    • pp.177-186
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    • 2024
  • Red rot disease is one of the notorious algal diseases that threaten the cultivation of Pyropia in China, and two Pythium pathogens, i.e., Pythium porphyrae and P. chondricola, have been reported as causative agents. To monitor the pathogens, a fluorescent quantitative polymerase chain reaction (PCR) method was developed to quantitatively detect their abundance. Using overlapping PCR and pathogen-specific primer pairs, two pathogen-specific fragments were concatenated to construct an internal standard plasmid, which was used for quantification. For zoospores of known numbers, the results showed that this method can detect as less as 100 and 10 zoospores mL-1 in a 200 mL solution for P. porphyrae and P. chondricola, respectively. Using monthly collected seawater at 10 sites in Haizhou Bay, a typical aquaculture farm in China, a significantly higher temperature and a significantly lower salinity were determined in December 2021. P. porphyrae was determined to be more abundant than P. chondricola, though with similar temporal distribution patterns from December 2021 to February 2022. When a red rot disease occurred in December 2021, the two pathogens were significantly more abundant at two infected sub-sites than the uninfected sub-site within both seawater and sediment, though they were all significantly more enriched in sediment than in seawater. The present method provides the capability to quantify and compare the abundance of two pathogens and also has the potential to forecast the occurrence of red rot disease, which is of much significance in managing and controlling the disease.

A survey on the perception of the role of public health doctors of Korean medicine due to regional health care gaps (지역 의료공백에 따른 공중보건한의사의 역할 관련 인식 조사)

  • Eunyoung Choi;Hyein Jeong;Harin Kwon;Soobo Shim;Hyelim Lee;Kyeong Han Kim
    • The Journal of Korean Medicine
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    • v.45 no.3
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    • pp.168-180
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    • 2024
  • Objectives: This study aims to understand the current state of regional healthcare services and explore the role of public health doctors of Korean medicine (PHDKMs) in addressing healthcare disparities. Methods: An online survey was conducted among 951 PHDKMs registered with the Korean Public Health Korean Medicine Doctors Association from July 15 to July 19, 2024. A total of 266 responses were collected, and after removing 2 insincere responses, 264 responses were used for analysis. The survey included questions on the provision of healthcare services and the role of PHDKMs in local healthcare crisis. Results: Out of 264 responses, 85 community health centers and branches (32.2%) lacked public health doctors (PHDs). The traveling clinics were the most common alternative in these cases. Centers without PHDs received 46 complaints (54.1%) about healthcare gaps, while centers with PHDs received 70 complaints (39.1%), showing statistically significant differences. The most common complaints involved consultation and management of chronic elderly diseases. PHDKMs reported being capable of providing musculoskeletal and internal medicine treatments, but identified a need for improvement in emergency response, basic and inflammatory treatments, consultation and management of chronic elderly diseases, administration of medications, and vaccinations. They expressed a high willingness and perceived capability to perform minor medical tasks. Conclusion: The decline in PHDs is adversely affecting regional healthcare. PHDKMs can help address these gaps through expanded roles and additional training. Policymakers should consider better integrating PHDKMs into the public healthcare system to ensure continuous and comprehensive healthcare services in underserved areas.

Predictive Factors of Health promotion behaviors of Industrial Shift Workers (산업장 교대근무 근로자의 건강증진행위 예측요인)

  • Kim, Young-Mi
    • Korean Journal of Occupational Health Nursing
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    • v.11 no.1
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    • pp.13-30
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    • 2002
  • Industrial shift workers feels suffer mental stresses which are caused by unfamiliar day sleep, noisy environment, sleeping disorder by bright light, unusual contacts with family, difficulty in meeting with friends or having formal social meetings and other social limitations such as the use of transportation. Such stresses influence health of the workers negatively. Thus the health promotion policy for shift workers should be made considering the workers' ways of living and shift work specially. This study attempted to provide basic information for development of the health promotion program for industrial shift workers by examining predictive factors influencing health promotion behaviors of those workers. In designing the study, three power generation plants located in Pusan and south Kyungsang province were randomly selected and therefrom 280 workers at central control, boiler and turbine rooms and environmental chemistry parts whose processes require shift works were sampled as subjects of the study. Data were collected two times from September 17 to October 8, 1999 using questionnaires with helps of safety and health managers of the plants. The questionnaires were distributed through mails or direct visits. Means for the study included the measurement tool of health promotion behavior provided by Park(1995), the tool of self-efficacy measurement by Suh(1995), the tool of internal locus of control measurement by Oh(1987), the measurement tool of perceived health state by Park(1995) and the tool of social support measurement by Paek(1995). The collected data were analyzed using SPSS program. Controlling factors of the subjects were evaluated in terms of frequency and percentage ratio Perceived factors and health promotion behaviors of the subjects were done so in terms of mean and standard deviation, and average mark and standard deviation, respectively. Relations between controlling and perceived factors were analyzed using t-test and ANOVA and those between perceived factors and the performance of health promotion behaviors, using Pearson's Correlation Coefficient. The performance of health promotion behaviors was tested using t-test, ANOVA and post multi-comparison (Scheffe test). Predictive factors of health promotion behavior were examined through the Stepwise Multiple Regression Analysis. Results of the study are summarized as follows. 1. The performance of health promotion behaviors by the subjects was evaluated as having the value of mean, $161.27{\pm}26.73$ points(min.:60, max.:240) and average mark, $2.68{\pm}0.44$ points(min.:1, max.:4). When the performance was analyzed according to related aspects, it showed the highest level in harmonious relation with average mark, $3.15{\pm}.56$ points, followed by hygienic life($3.03{\pm}.55$), self-realization ($2.84{\pm}.55$), emotional support($2.73{\pm}.61$), regular meals($2.71{\pm}.76$), self-control($2.62{\pm}.63$), health diet($2.62{\pm}.56$), rest and sleep($2.60{\pm}.59$), exercise and activity($2.53{\pm}.57$), diet control($2.52{\pm}.56$) and special health management($2.06{\pm}.65$). 2. In relations between perceived factors of the subjects(self-efficacy, internal locus of control, perceived health state) and the performance of health promotion behaviors, the performance was found having significantly pure relations with self-efficacy (r=.524, P=.000), internal locus of control (r=.225, P=.000) and perceived health state(r=.244, P=.000). The higher each evaluated point of the three factors was, the higher the performance was in level. 3. When relations between the controlling factors(demography-based social, health-related, job-related and human relations characteristics) and the performance of health promotion behaviors were analyzed, the performance showed significant differences according to marital status (t=2.09, P= .03), religion(F=3.93, P= .00) and participation in religious activities (F=8.10, P= .00) out of demography-based characteristics, medical examination results (F=7.20, P= .00) and methods of the collection of health knowledge and information(F=3.41, P= .01) and methods of desired health education(F=3.41, P= .01) out of health-related characteristics, detrimental factors perception(F=4.49, P= .01) and job satisfaction(F=8.41, P= .00) out of job-related characteristics and social support(F=14.69, P= .00) out of human relations characteristics. 4. The factor which is a variable predicting best the performance of health promotion behaviors by the subjects was the self-efficacy accounting for 27.4% of the prediction, followed by participation in religious activities, social support, job satisfaction, received health state and internal locus of control in order all of which totally account for 41.0%. In conclusion, the predictive factor which most influence the performance of health promotion behaviors by shift workers was self-efficacy. To promote the sense, therefore, it is necessary to develop the nursing intervention program considering predictive factors as variables identified in this study. Further industrial nurses should play their roles actively to help shift workers increase their capability of self-management of health.

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