• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.5
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• pp.437-444
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• 2020

This study was focused on the stabilization of surge motions of a moored vessel under irregular head seas. A two-point moored vessel shows strong non-linearity even in regular sea, owing to its inherent non-linear restoring force. A long-crested irregular wave is subjected to the vessel system, resulting in more complex nonlinear behavior of the displacement and velocities than in the case of regular waves. Sliding mode control (SMC) is implemented in the moored vessel to control both surge displacement and surge velocity. The SMC can provide a closed-loop system with performance and robustness against parameter uncertainties and disturbances; however, chattering is the main drawback for implementing SMC. The goal of minimizing the chattering and state convergence with accuracy is achieved using a quasi-sliding mode that approximates the discontinuous function via a continuous sigmoid function. Numerical simulations were conducted to validate the effectiveness of the proposed control algorithm.

• Journal of Environmental Science International
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• v.18 no.4
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• pp.463-471
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• 2009

A study on vegetation in the Mangyeong River and Dongjin River basins and the surrounding regions of the Saemangeum Reclaimed Land was conducted in a series of efforts to determine the expected ecological changes in the salt marshes, to restore their vegetation, to explore the restoring force of halophyte, to examine the community mechanism and, ultimately, to rehabilitate marshy land vegetation along the lakeside, coastal dune and salt marshes of the Saemangeum Project Area. The findings of the study may be summed up as follows: Five species such as Suaeda japonica, Salicornia herbacea, Atriplex gmelini, Aster tripolium and Suaeda asparagoides that are mostly distributed in the estuary of the Saemangeum Reclaimed Land were analyzed to examine the mechanism of halophyte to maintain their community. To find out the strategies of plants for survival and the cause of forming community structure, a research was made as for appearance ratio of biomass, root lengths and germination. With regard to biomasses of halophyte, the biomass of Suaeda japonica increases rapidly, while Salicornia herbacea adopts a strategy of unstable growth pattern by which the biomass increases slowly in parallel with its slow speed of growth since initial appearance of young sapling. In contrast, Suaeda asparagoides, Atriplex gmelini and Aster tripolium choose to adapt themselves to environment promptly by being transformed into life form of annual or biennial plant, a pattern that is presumed to be favorable and stable for survival in the later stage of growth. In short, there is a sharp distinction among the 5 species: i.e. Suaeda japonica that begins to grow fast in the length of surface and underground section but slows down from the mid-stage on; Salicornia herbacea that grows slowly in the beginning step but starts to step up from the middle onward; Atriplex gmelini and Aster tripolium growing slowly in the initial stage but fast later on; and Suaeda asparagoides that turns from the constant growth in the beginning to rapid growth in the later period. The outcomes of the analysis into status of growth and influencing factors of Suaeda japonica in the sowing field that is most widely prevalent in the Saemangeum Reclaimed Land as a sort of ecological pioneer in the salt marshes showed that the average size of grass lands, density and number of individuals increase in the natural sowing field as well as in the plowing field regardless of their physical as well as physico-chemical features of the soil as the season progresses from June to October of a year.

• Journal of Korean Academic Society of Home Health Care Nursing
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• v.2
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• pp.5-18
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• 1995

While the socioeonomic status of Koreas has been dramatically increasing in recent years, chronic and geriatric diseases have also been on the rise, bringing about many changes in our health care system. The basic goals of the home health care are to reduce health care costs, to increase the attrition rate in general hospitals, and to care for patients effectively and conveniontly at home. The purpose of this paper is to review and examine the current status of the home health care in Korea throughout the reports, surveys, other informations and education system of home health nurse. We identified the various types of home health care services programs, such as hospital-based home health care operated in public sector(demonstration project) and community-based home health care in health centers or in private sector, that is, Korean Nurse Association. Hospital based home heatlh care model was established as an alternative to traditional in-patiet services. Quality assurance and client satisfaction is an important measure of care received and establishment of payment and reimbursement for home health care services is important in promotng the home health care. We found out a fee-per-visit system composed of three kinds of fees : a basic service fee(16,000 Won), a travel fee(5,000 Won), and per-service fees (variables). Like fees paid for in-patient care, insureds pay 20% and insurers pay 80% of the basic and per-service fee. The travel fee is borne totally by the insured. Home health care continues to be viewed as not only the most preferred way to provide care to clients, but also the most cost effective. Home health care is that component of a continuum of comprehensive health care whereby health services are provided to individuals and families in their places of residence for the purpose of promoting, maintaining, or restoring health, or of maximizing the level of independence, while minimizing illness. Services appropriate to the needs of the individual patient and family should be planned and provided, nursing is to be a force for positive change and enhanced the nursing professionalism. Whatever type of involvement of home health care, it is essential to remember that home health care is highly service-oriented and highly touch health car deilvery system.

• The Journal of the Korea Contents Association
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• v.15 no.3
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• pp.78-87
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• 2015

Recently, Police integrity has been issued on the media, which cause discredit of police organization. Although high level of morality and integrity are required compared to other occupational groups due to their authority to exert legal force to the citizens and a variety of policies have been enforced by the National Police Agency for the purpose of uplifting the integrity of the officers, in reality, corruption had not yet been eradicated. At this point in time, this study attempted to draw implications for uplifting integrity by utilizing domestic and foreign preceding studies and statistical data related to police corruption and uplifting integrity. The inspection system through whistle-blowing was pointed out as a problem in the institutional framework that hinders uplifting integrity of the police officers and the perception in which police officers are regarded as potential criminals was also pointed out as a problem. Also, vague standards of disciplinary action in examining an offense of a police officer and lack of care for those who were disciplined in the past which affects loyalty to the organization were presented as problems. Based on such suggested concerns, policies for uplifting integrity and restoring citizens' trust in the policies officers were proposed. The proposed agenda were warning the police officers by presenting clear and specific category of corruptive behaviors, expressing the necessity of devising a system that prevents the officers from committing serious crimes by discovering problematic officers earlier through introduction of Early Warning System(EWS) of US and Australian police in order to break away from exposure-oriented inspection system, and reinforcing the testing of integrity in the new employment process.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.87-96
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• 1999

To analyze the dynamic behavior of structure, direct integration and mode superposition may be utilized in time domain analysis. As finite number of frequencies can give relatively exact solutions, mode superposition is preferable in analyzing structural behavior. In non-linear analysis, however, mode superposition is seldom used since time-varying element stiffness changes stiffness matrix, and the change of stiffness matrix leads to the change of essential constants - natural frequencies and mode shapes. In spite of these difficulties, there are some attempts to adopt mode superposition because of low cost compared to direct integration, but the result is not satisfactory. In this paper, a method using mode superposition in non-linear analysis is presented by separating local element stiffness from global stiffness matrix with the difference between linear and non-linear restoring forces to the external force vectors included. Moreover, the hysteresis model changing with the relative deformation in each floor makes it possible to analyze non-linear behavior of structure. The proposed algorithm is applied to shear beam model and the maximum displacement is compared with the result using direct integration method.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.140-145
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• 2018

This paper deals with the dynamical analysis of a two-point mooring vessel under surge excitations. The characteristics of nonlinear behaviors are investigated completely including bifurcation and limit cycle according to particular input parameter changes. The strong nonlinearity of the mooring system is mainly caused by linear and cubic terms of restoring force. The numerical simulation is performed based on the fourth order Runge-Kutta algorithm. The bifurcation diagram and several instability phenomena are observed clearly by varying amplitudes as well as frequencies of surge excitations. Stable periodic solutions, called the periodic windows, can be obtained in succession between chaotic clouds of dots in case of frequency ${\omega}=0.4rad/s$. In addition, the chaotic region is unexpectedly increased when external forcing amplitude exceeds 1.0 with the angular frequency of ${\omega}=0.7rad/s$. Compared to the cases for ${\omega}=0.4$, 0.7rad/s, the region of chaotic behavior becomes more fragile than in the case of ${\omega}=1.0rad/s$. Finally, various types of steady states including sub-harmonic motion, limit cycle, and symmetry breaking phenomenon are observed in the two-point mooring system at each parameter value.

• Journal of Practical Agriculture & Fisheries Research
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• v.17 no.1
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• pp.57-71
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• 2015

This study was conducted to develop the fertigation system with a peristaltic hose pump and brushless DC motor. The fertigation system was consisted of sensor, main controller, motor control unit, peristaltic pump, water supply pump, control panel, and filter. The peristaltic pump discharges liquid by squeezing the tube with rollers. Rollers attached to the external circumference of the rotor compresses the flexible tube. The fluid is contained within a flexible tube fitted inside a circular pump casing. The developed fertigation system has no mixing tank but instead injects directly a concentrated nutrient solution into a water supply pipe. The revolution speed of the peristaltic pump is controlled by PWM (Pulse width modulation) method. When the revolution speed of the peristaltic pump was 300rpm, the flow rate of the 3.2, 4.8, 6.3mm diameter tube was 202, 530, 857mL/min, respectively. As increasing revolution speed, the flow rate of the peristaltic pump linearly increased. As the inner diameter of a tube larger, a slope of graph is more steep. Flow rate of three roller was more than that of four roller. Flow rate of a norprene tube with good restoring force was more than that of a pharmed tube. As EC sensor probe was installed in direct piping in comparison with bypass piping showed good performance. After starting the system, it took 16~17 seconds to stabilize EC. The maximum value of EC was 1.44~1.7dS/m at a setting value of 1.4dS/m. The developed fertigation system showed ±0.06dS/m deviation from the setting value of EC. In field test, Cucumber plants generally showed good growth. From these findings, this fertigation system can be appropriately suitable for fertigation culture for crops.