• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.4
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• pp.324-335
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• 2013

This article presents the design, control, and implementation of a small quad-rotor system under the practical limitation of being cost effective for private use, such as in the cases of control education or hobbies involving radio-controlled systems. Several practical problems associated with implementing a small quad-rotor system had to be taken into account to satisfy this cost constraint. First, the size was reduced to attain better maneuverability. Second, the main control hardware was limited to an 8-bit processor such as an AVR to reduce cost. Third, the algorithms related to the control and sensing tasks were optimized to be within the computational capabilities of the available processor within one sampling time. A small quad-rotor system was ultimately implemented after satisfying all of the above practical limitations. Experimental studies were conducted to confirm the control performance and the operational abilities of the system.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.104-112
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• 2002

Controllers for acoustic noise reduction in disk drives have been developed but they have slower seek time performance than time-optimal controllers. We propose a new seek servo controller that has acoustic noise reduction benefit and faster seek time performance than conventional controllers. The proposed controller is designed to make sure that head is moved with maximized acceleration and deceleration under the voltage limitation imposed on head-positioning motor and so it provides faster seek time than conventional controllers designed by considering the current limitation. The experimental results using a commercially available disk drive confirm that the use of the proposed controller results in foster seek time than conventional controllers for acoustic noise reduction.

• Journal of the Semiconductor & Display Technology
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• v.8 no.1
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• pp.39-42
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• 2009

In this paper an attempt for realizing a storage system which works as a part of human brain has been discussed. The system is expected to be able to coordinate with human brain. And current storage may have inherent problem due to an intrinsic attribute of storage, exclusiveness. Directory structure in it must be a source of confusion, if it used out side of the range of limitation. Adapting multidimensional annotation of file name extension and directory-less file system, a new storage system able to associate and coordinate with human brain may be available near future. This paper showed that the limitation of current storage system clearly exists, because of human brain limitation to memorize directory name.

• Proceedings of the Korea Information Processing Society Conference
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• 2014.11a
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• pp.215-217
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• 2014

In Software Defined Network (SDN), data plane and control plane are decoupled. Dummy switches on the data plane simply forward packet based on the flow entries that are stored in its flow table. The flow entries are generated by a centralized controller that acts as a brain of the network. However, the size of flow table is limited and it can conduct a security issue related to Distributed Denial of Service (DDoS). Especially, it related to resource attack that consumes all flow table resource and consumes controller resources. In this paper, we will analyze the impact of flow table limitation to the controller. Then we propose an approach that is called Flow Table Management to handle flow table limitation.

• 한국노년학
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• v.40 no.3
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• pp.543-563
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• 2020

As people age and their physical functions are declined, they stay longer in the home, thus being more affected by the home environment. Many studies have shown the association between the home environment and health. However, little is known about the effect of the home environment on disability and depression of older people with functional limitation. This study, therefore, aimed to examine the moderating effect of the home environment on the pathway between walking limitation and instrumental activity of daily living(IADL) disability, and the relationship between IADL disability and depression. We performed logistic regression and multiple linear regression analyses with data on 3,027 participants from the 2018 Seoul Aging Survey. As results, first, older people who lived home with poor conditions showed a higher risk of walking limitation(OR=1.487, 95% CI: 1.250 - 1.770), IADL disability(OR=1.594, 95% CI: 1.303 - 1.949), and depression(OR=1.943, 95% CI: 1.553 - 2.430). Second, the home environment moderated the relationship between walking limitation and IADL disability. Older people with walking limitation who lived in poor housing condition experienced more IADL disability than others. Third, after controlling for walking limitation, the home environment had significant moderating effect on the relationship between IADL disability and depression. Elderly with IADL disability living in poor home experienced higher risk of depression. Based on these results, the study suggests the necessity of home modification intervention targeting functional limitation of older adults as strategy for preventing disability and depression, and enabling aging in place.

• Journal of Korean Society of Transportation
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• v.23 no.6 s.84
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• pp.41-53
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• 2005

The effective utilization of an airport is considerably influenced by natural features and man-made structures inside and outside its boundary. These obstacles affect the airspace available for approaches and departures and the weather minima which dictates the necessary weather conditions for aircraft to be allowed to take-off or land. Certain areas of the airspace near airports must be regarded as the integral parts of the airport system. The availability of the required airspace is as important as are the runway and their associated strips to the safe and efficient use of the airport. For these reasons, ICAO and the member states have established the standards regarding the obstacle limitation surfaces and regulated the construction of the man-made structures in and beyond the surfaces. Existing objects that extend above a obstacle limitation surfaces should as for as practicable be removed except when, in the opinion of the appropriate authority, an objects is shielded an existing immovable objects, or after aeronautical study it is determined that the object would not adversely affect the safety or significantly affect the regularity of operations of airplanes. However, Korea's aviation law does not specified the outer horizontal surface in the obstacle limitation surfaces, while ICAO and most member states do. The absence of the outer horizontal surface regulation has created legal disputes between regulating agencies and private parties. The case study in this paper found that a skyscraper planned beyond Korea's obstacle limitation surfaces does affect the flight safety and the efficient use of an airport. Therefore, in areas beyond the obstacle limitation surfaces. those objects which extend to a height of 150m or more above ground elevation should be regarded as obstacle, unless a special aeronautical study indicates that they do not constitute a hazard to airplanes. We proposed low alternative regulatory schemes for resolving the issues raised in this paper, and we recommended to adopt ICAO's standards and recommended practices.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.210-218
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• 2016

Recently, as service design was introduced to improve the quality of public service, there have been many attempts to improve various public service. In the process, various stakeholders including general citizens are participating in the design improvement activity through a method of design service but the parties are facing a difficulty in the progress because of a limitation of time and budget and a lack of professionalism among the member while the parties are planning the process and activities based on the professional service design method. Persona method that is usually used in the process of service design is encountering a limitation as well. Also, there are continuous attempts to understand the limitation of persona and apply an alternative research method among service and UX designers. For this reason, this thesis is to recognize the limitation in deduction method of traditional persona and suggests a fast and economical production method of Rapid Persona speaking for the goal of users and overcoming the limitation. Furthermore, by applying the suggested method of making Rapid Persona to an actual public service design project of National Statistical Office, the test through an empirical study was conducted. This was conducted with the purpose of progressing a discussion in the respect of actual application beyond a banal discussion. Through the research method suggested in this study, it is expected to overcome the limitation of time and a lack of professionalism and, based on these, can be used in the process of various service design and UX design as establishing persona in a fast and easy way.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.2
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• pp.251-258
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• 2019

Objective: Chronic obstructive pulmonary disease(COPD) is characterized by persistent airflow limitations associated with chronic inflammatory response due to noxious particles or gases in the lung. Inflammation and oxidative stress are associated with COPD. The aim of this study was to evaluate the relationship among inflammation, oxidative stress, and airflow limitation severity in retired miners with COPD. Methods: The levels of serum high-sensitivity C-reactive protein(hsCRP) as a biomarker for inflammation, degree of reactive oxygen metabolites(dROMs) and biological antioxidants potential(BAP) in plasma as biomarkers for oxidative stress were measured in 211 male subjects with COPD. Degree of airflow limitation severity as determined by spirometry was divided into three grades grouped according to the classification of the Global Initiatives for Obstructive Lung Disease(GOLD)(1, mild; 2, moderate; $3{\leq}$, severe or more) using a fixed ratio, post- bronchodilator $FEV_1/FVC$ < 0.7. Results: Mean levels of dROMs significantly increased in relation to airflow limitation severity(GOLD 1, 317.8 U.CARR vs. GOLD 2, 320.3 U.CARR vs. GOLD $3{\leq}$, 350.9 U.CARR, p=0.047) and dROMs levels were correlated with serum hsCRP levels(r=0.514, p<0.001). Mean levels of hsCRP were higher in current smokers(non-smoker, 1.47 mg/L vs. smoker, 2.34 mg/L, p=0.006), and tended to increase with degree of airflow limitation severity(p=0.071). Mean levels of BAP were lower in current smokers(non-smoker, $1873{\mu}mol/L$ vs. smoker, $1754{\mu}mol/L$, p=0.006). Conclusions: These results suggest that inflammation and oxidative stress are related to airflow limitation severity in retired miners with COPD, and there was a correlation between inflammation and oxidative stress.

• 전기의세계
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• v.17 no.2
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• pp.6-10
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• 1968

The conversive limitation of electric energy for the thyristor inverter is analysed under the boundary conditions which the term of a negative inverse voltage is longer than that of the turn off time of the thyristor under commutation. It is clear that the maximum electric energy conversion is affected by the turn off time of the thyristor, the reactance of a commutation reactor, the capacity of a commutation condenser and the voltage of Direct current source. It is useful for design the thyrister invertor and the motor speed control to apply the above conclusion.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.61-64
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• 2001

Levitation force of a new magnetic levitation system using a super-conducting bulk magnet(SBM) and a permanent magnet(PM) was numerically calculated. The non-linear J-E relation of a SBM was modeled using a critical state model and iteration method, and demagnetization of a PM was considered using a demagnetization curve of a real PM. The maximum limitation of levitation force was found according to increasing the trapped field in a SBM. Finite element method was used for numerical calculation.