• Journal of Drive and Control
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• v.19 no.1
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• pp.51-61
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• 2022

This paper presents a model-free system based on a framework of a backstepping sliding mode control (BSMC) with a radial basis function neural network (RBFNN) and adaptive mechanism for electro-hydraulic systems (EHSs). First, an EHS mathematical model was dedicatedly derived to understand the system behavior. Based on the system structure, BSMC was employed to satisfy the output performance. Due to the highly nonlinear characteristics and the presence of parametric uncertainties, a model-free approximator based on an RBFNN was developed to compensate for the EHS dynamics, thus addressing the difficulty in the requirement of system information. Adaptive laws based on the actor-critic neural network (ACNN) were implemented to suppress the existing error in the approximation and satisfy system qualification. The stability of the closed-loop system was theoretically proven by the Lyapunov function. To evaluate the effectiveness of the proposed algorithm, proportional-integrated-derivative (PID) and improved PID with ACNN (ACPID), which are considered two complete model-free methods, and adaptive backstepping sliding mode control, considered an ideal model-based method with the same adaptive laws, were used as two benchmark control strategies in a comparative simulation. The simulated results validated the superiority of the proposed algorithm in achieving nearly the same performance as the ideal adaptive BSMC.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.4_2
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• pp.991-999
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• 2024

This study is based on research on a magnetic induction amplification power generation system using quantum fluctuations, and aims to confirm the similarity to the meissner effect through quantum analysis using magnets and suggest the possibility of utilizing alternative energy. Research was conducted on increasing the efficiency of motors based on the similarity between magnetic quantum array experimental devices and the superconductor phenomenon. It was confirmed that the experimental device that arranged the quantum of magnetism rotated by canceling out the magnetism by having a resistance value of "0", which is not a general characteristic of magnetism that generates attractive force. This is an observation of the similarity between the superconductor phenomenon and the meissner effect, and it was confirmed that material synthesis or temperature had little effect. This study confirmed that the efficiency is more than 20 times that of existing power on average. Therefore, this study suggests that there is a possibility of commercialization of an Energy Harvesting System (EHS) that can produce and store energy.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.311-312
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• 2008

This paper try to show that the method for maintaining link stability by fast reporting the status PDU to RLC layer in MAC layer. The proposed method is implemented based on the mechanism of reordering processing in MAC-ehs entity in HSPA evolution system.

• International Journal of Computer Science & Network Security
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• v.24 no.6
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• pp.153-160
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• 2024

Information technology plays an important role in healthcare. The cloud has several applications in the fields of education, social media and medicine. But the advantage of the cloud for medical reasons is very appropriate, especially given the large volume of data generated by healthcare organizations. As in increasingly health organizations adopting towards electronic health records in the cloud which can be accessed around the world for various health issues regarding references, healthcare educational research and etc. Cloud computing has many advantages, such as "flexibility, cost and energy savings, resource sharing and rapid deployment". However, despite the significant benefits of using the cloud computing for health IT, data security, privacy, reliability, integration and portability are some of the main challenges and obstacles for its implementation. Health data are highly confidential records that should not be made available to unauthorized persons to protect the security of patient information. In this paper, we discuss the privacy and security requirement of EHS as well as privacy and security issues of EHS and also focus on a comprehensive review of the current and existing literature on Electronic health that uses a variety of approaches and procedures to handle security and privacy issues. The strengths and weaknesses of some of these methods were mentioned. The significance of security issues in the cloud computing environment is a challenge.

• Journal of Hydrogen and New Energy
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• v.29 no.1
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• pp.111-116
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• 2018

The environmental impacts of a 1 kW polymer electrolyte membrane fuel cell (PEMFC) system are quantitatively assessed by performing a Life Cycle Assessment (LCA) study. A PEMFC system produces electricity and heat simultaneously, so an appropriate allocation of associated inputs and outputs is performed between the electricity and heat produced. The environmental impacts of the PEMFC system on the impact categories such as global warming (GW), abiotic depletion (AD), acidification (AC), and eutrophication (EU) are assessed from the life cycle impact assessment. The impact indicator results of the impact assessment on these impact categories are obtained as $3.70E-01kg\;CO_2\;eq./kWh$, 1.86E-03 kg Sb eq./kWh, $4.09E-04kg\;SO_2\;eq./kWh$, and $1.88E-05kg\;PO_4{^{3-}}/kWh$, respectively. For all impact categories studied the most influential stage is the operation stage, which accounts for 98.8%, 98.7%, 70.3%, and 62.3% of the total impact on GW, AD, AC, and EU, respectively. For the impact categories of AD, AC, and EU, most of the environmental impacts during the operation stage is attributed to the production of city gas. However, for the impact category of GW, $CO_2$ emission from the reforming process of city gas is the main reason for the largest contribution of the operation stage to the total impact results.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.4
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• pp.447-454
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• 2023

Objective: This study aims to investigate the impact of changes in working conditions on job-related stress and musculoskeletal disorders using the results of seven surveys conducted at a single workplace from 2004 to 2022 regarding factors hazardous to the musculoskeletal system. Additionally, the study aims to propose alternative methods of investigating factors hazardous to the musculoskeletal system. Methods: A car parts manufacturing plant where the same survey was taken seven times from 2004 to 2022 was selected and the survey data was analyzed. The main contents of the survey were weekly working hours, Borg's scale, work intensity, job-related stress, and the prevalence of musculoskeletal symptoms. The statistical analysis was performed using SAS (version 9.4). Results: The results of this study are as follows. Firstly, changes in working conditions have an impact on job-related stress. Secondly, changes in working conditions have an impact on work intensity indicators. Thirdly, changes in working conditions have an impact on the prevalence of musculoskeletal symptoms. Fourthly, even with an increase in age and length of service, job-related stress and musculoskeletal symptoms were alleviated when working conditions were improved. Conclusions: In order for measures to reduce musculoskeletal disorders to be successful, working conditions must not deteriorate, and it is necessary to demand revisions to regulations, etc. to reflect these points in the investigation of hazardous factors to the musculoskeletal system.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.3
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• pp.266-273
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• 2021

Objective: The objective of this study was to suggest improvement methods for investigations and systems through a review of musculoskeletal risk factor investigation reports conducted in the workplace. Methods: A total of 34 reports on musculoskeletal risk factor investigations were reviewed. To confirm the appropriateness of the evaluation, reevaluation was conducted through a field investigation using other evaluation tools. In order to understand the effectiveness of the improvement plan, a survey was conducted with those in charge of tasks with ergonomic burdens. Results: As a result of performing a field survey using the work sampling method recommended by the KOSHA (Korea Occupational Safety and Health Agency) for ten tasks, eight tasks were determined to pose an ergonomic burden. When 30 tasks were evaluated with RULA (rapid entire body assessment), 90% of them were evaluated at a higher level than the results of the workplace survey. Among the improvement measures, only 36% of the field workers affirmed them, and in only 19% of the workplaces were actual improvements made. Conclusions: In order to improve the ergonomic investigation system for risk factors in the ergonomic burden task, it is necessary to secure the objectivity of the evaluation performed by the institution and enable the active participation of workers in improvement activities.

• Journal of the Korean Institute of Gas
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• v.28 no.2
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• pp.47-55
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• 2024

More than 100 liquefied hydrogen tanks are expected to be introduced in Korea by 2030. Since liquefied hydrogen is stored in a vacuum insulation structure tank at -253℃, there is a possibility of a major disaster in which the tank bursts if there is a problem with insulation. Therefore, the law stipulates that PRV should be installed as the last bastion. It is important to note that in the case of liquefied hydrogen, it becomes useless if the pressure drop of the pipe is ignored and the capacity is calculated incorrectly. In CGA S-1.3, the pressure drop rate of the PRV inlet and outlet pipes is set to less than 3% and less than 10%, respectively. However, there is an interdependence between the amount of pressure drop and the flow rate of the pipe, making it impossible to calculate these values at once. Therefore, we developed a simulator that calculates the pressure loss rate of PRV system using MATLAB/Simulink and evaluated the sensitivity of the pressure drop rate to design elements.

• Journal of Advanced Marine Engineering and Technology
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• v.15 no.2
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• pp.73-83
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• 1991

A tracking controller which can improve the performance of nonlinear electrohydraulic position control systems is designed and implemented. The method is based on augmenting the system with both compensated integrator and additional integrator, obtaining the feedback control law which stabilizes the linear part of the original nonlinear system, and then readjusting the feedback gains using the describing function method to eliminate the limit cycle in the steady-state. The proposed control law is implemented using OP amplifiers and electronic components, and step and ramp response tests are carried out in the electrohydraulic servomechanism EHS-160. The results show the improvement in both transient and steady-state responses.

• Journal of Environmental Health Sciences
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• v.47 no.3
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• pp.205-226
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• 2021

Objectives: Biomonitoring programs have been widely implemented in the field of environmental health, both in Korea and worldwide. Recently, it has been suggested that the storage, management, and utilization of biosamples collected from biomonitoring programs should be organized based on a biobank system. Therefore, we attempted to review the current status of representative biomonitoring programs and biobank systems that have been implemented in Korea and in other countries. Methods: We searched for bio-samples collected in domestic and foreign biomonitoring programs and their applications. For this, we referred to research papers, homepages hosted by biomonitoring programs, and project reports. We also checked information for biobanks related with biomonitoring programs, including the operating systems, facilities, technologies, and regulations of biobanks. Results: We summarized six domestic and 32 foreign biomonitoring programs. These biomonitoring programs collected bio-samples to determine the relationship between environmental chemicals and diseases. Domestically, bio-samples from KoNEHS, KorSEP, MOCEH, KoCHENS, and KorEHS-C were stored at -80℃ in a deep freezer at the National Institute of Environmental Research, while KNHANES samples were stored at Korea Biobank, which has a stabilized biobanking system with a well-established database. Nine foreign biomonitoring programs (JECS, China-NHBP, CKB, CHMS, NHANES, GerES, Germaan ESB, MoBa, and UK Biobank) were ongoing for large populations. Among them, CKB, GermanESB, and UK biobank have been maintained for at least 10 years with their own biomonitoring programs as well as advanced systems for the safe storage of bio-samples. Conclusion: Currently on-going biobanks have devoted considerable efforts to managing bio-samples for public purposes. The preceding domestic and foreign biomonitoring programs and biobanks will be great references for constructing biobank facilities and systems for environmental public health in Korea in the future.