• Journal of Navigation and Port Research
• /
• v.28 no.1
• /
• pp.9-16
• /
• 2004

The purpose of this study is to examine the algorithm of ship collision avoidance system and to improve its performance. The study on the algorithm of ship collision avoidance system have been carried out by many researchers. We can divide the study according to the adopted theory into two category such as 'collision risk calculation method' and 'risk area method'. It is not so difficult to find heir merit and demerit in the respective method. This study suggested newly modified model, which can overcome a limit in the two method. The suggested model is based on collision risk calculation method and suggests how to solve the threshold value problem, that is, one of the unsolved issues in collision risk calculation method. To solve that problem this study proposed new system under which the users can select appropriate threshold value according to environments such as traffic situations and weathers conditions. Simulation results of new model is schematized using 'risk area method'to examine the relationships between the two method. In addition, in case of 'collision risk method', when TCPA and DCPA are used to determine collision risk, a problem happens, that is, two ships become too close in their stem area, therefore, partial function of 'risk area method'is adopted to solve the problem in suggested model.

• Korean Journal of Construction Engineering and Management
• /
• v.16 no.6
• /
• pp.41-52
• /
• 2015

The number of military facilities has been rapidly increased due to growing requirement of modernization and military welfare. However, adequate maintenance has not implemented to these facilities. As a result, they are deteriorated quickly and require performance enhancement treatments. There are two ways of performance enhancement, reconstruction and remodeling. Despite the research result that remodeling within the standard remodeling range is more economical, remodeling of military facilities is not considered equivalent to reconstruction as an option of performance improvement. Therefore, derived from the relationship between performance change during life cycle of building and range of remodeling needs, this study tries to propose Remodeling Process Model(RPM) which uses a method to choose remodeling in a Specific Point of Time(SPT) when remodeling is considered more economical than reconstruction. In addition, this study suggests practical service life and functionality evaluation standard together which require to realize the RPM. This RPM make it possible to avoid the cases that facilities which do not have any problem on structural reliability but have low level of functionality miss appropriate remodeling timing and inevitably choose reconstruction as a performance improvement option. It also present the possibility of simple reconstruction / remodeling decision-making for facility managers who administrate building having various type, compilation and elapsed time. Consequently, this process model focusing on remodeling more may contribute to reduce resource waste caused by reconstruction.

• Korean Journal of Construction Engineering and Management
• /
• v.22 no.2
• /
• pp.12-20
• /
• 2021

Unsafe working environments slow down working speed in that it takes a lot of time to respond in case of an accident, greatly reducing the productivity of construction work. Therefore, proper safety management that does not impede the productivity of construction works is a very important factor for successful construction project. However especially in mega project, the mutual effects of safety management and productivity are complex. Therefore, this study establishes a causal model between safety management and productivity influencing factors based on effectiveness metrics, and analyzes the effect of increased site congestion due to excessive personnel input, irregular safety measures and inefficient change of work schedules. The result of this study, is expected to contribute to enhancing the competitiveness of the construction industry as the basis for establishing a safety management plan that can secure appropriate productivity.

• Journal of Navigation and Port Research
• /
• v.46 no.6
• /
• pp.554-561
• /
• 2022

Technology development related to maritime autonomous surface ships (MASS) is actively progressing around the world. However, since there are still many technically unresolved problems such as communication, cybersecurity, and emergency response capabilities, it is expected that it will take a lot of time for MASS to be commercialized. In this study, we proposed a ship group navigation system in which one leader ship and several follower ship are grouped into one group. In this system, when the leader ship begins to navigate, the follower ship autonomously follows the path of the leader ship. For path following, PD (proportional-derivative) control is applied. In addition, each ship navigates in a straight line shape while maintaining a safe distance to prevent collisions. Speed control was implemented to maintain a safe distance between ships. Simulations were performed to verify the ship group navigation system. The ship used in the simulation is the L-7 model of KVLCC2, which has related data disclosed. And the MMG (Maneuvering Modeling Group) standard method proposed by the Japan Society of Naval Architects and Ocean Engineering (JASNAOE) was used as a model of ship maneuvering motion. As a result of the simulation, the leader ship navigated along a predetermined route, and the follower ship navigated along the leader ship's path. During the simulation, it was found that the three ships maintained a straight line shape and a safe distance between them. The ship group navigation system is expected to be used as a navigation system to solve the problems of MASS.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.21 no.1
• /
• pp.39-49
• /
• 2007

Rheumatoid arthritis is an autoimmune disease involving multiple joint. In order to access the suppressive effects of JTT on rheumatoid arthritis and it's effects on immune system we investigated whether JTT could suppress the disease progression of collagen-induced arthritis. DBA/1 mice were immunized with bovine type II collagen. After a second collagen immunization, mice were treated with DW, JTT (200 or 400 mg/kg) or methotrexate (MTX, 30 mg/kg) as a positive control. Oral administration of JTT significantly suppressed the progression of CIA, which extend is comparable to that of MTX. Histological examination reveled that JTT inhibited infiltration of inflammatory cells into affected paw joint and bone erosion and cartilage destruction were greatly reduced compared with control. Total cell number of spleen, lymph node and peripheral blood were significantly reduced. The absolute number of CD19$^+$, CD3$^+$/CD69$^+$, CD4$^+$/CD25$^+$ cell in spleen from JTT treated mice were significantly decreased. The absolute number of CD19$^+$, CD3$^+$, CD3$^+$/CD69$^+$, CD4$^+$, CD4$^+$/CD25$^+$ CD8$^+$, CD49b, CD3/CD49b cells in draining lymph node were significantly increased compared with control. In peripheral blood mononuclear cells of JTT treated mice, the absolute number of CD4$^+$, CD4$^+$/CD25$^+$, CD3$^+$/CD69$^+$ cells were significantly decreased compared with control, while that of CD49b$^+$ was slightly increased. Infiltration of CD3$^+$ cells and CD11b$^+$/Gr-1$^+$ cells into paw joint was significantly reduced in JTT treated mice. The levels of pathologic cytokines including TNF-a and IL-6 in serum were significantly decreased by oral treatment with JTT The levels of IFN-g in the culture supernatant of splenocyte stimulated with CD3$^+$/CD28$^+$ or collagen were dramatically decreased, while the levels of IL-4 was increased under CD3$^+$/CD28$^+$ or collagen stimulation. Rheumatoid factors including IgG, IgM and collagen specific antibody were present much lower in the serum of JTT treated mice than control. Taken together, JTT has suppressive effects on rheumatoid arthritis by modulating immune system, and has potential to use anti-rheumatic arthritic agent in human.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.6
• /
• pp.443-453
• /
• 2020

This study using the active vibration control technique attempts to alleviate numerically the airframe vibration of a UH-60A helicopter. The AVCS(Active Vibration Control System) is applied to reduce the 4/rev vibration responses at the specified locations of the UH-60A airframe. The 4/rev hub vibratory loads of the UH-60A rotor is predicted using the nonlinear flexible dynamics analysis code, DYMORE II. Various tools such as NDARC, MSC.NASTRAN, and MATLAB Simulink are used for the AVCS simulation with five CRFGs and seven accelerometers. At a flight speed of 158knots, the predicted 4/rev hub vibratory loads of UH-60A rotor excite the airframe, and then the 4/rev vibration responses at the specified airframe positions such as the pilot seat, rotor-fuselage joint, mid-cabin, and aft-cabin are calculated without and with AVCS. The 4/rev vibration responses at all the locations and directions are reduced by from 25.14 to 96.05% when AVCS is used, as compared to the baseline results without AVCS.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.51 no.5
• /
• pp.451-457
• /
• 2006

The purpose of this study is to measure fundamental data required for the prediction of rice quality and to develop regression models to predict protein, amylose, moisture and fatty acid contents, and Toyo taste meter value (TTMV) of brown and polished rice from hulled rice NIR spectra. NIR spectra of hulled rice measured in transmittance mode (850-1050 nm) and in reflectance mode (400-2500 nm) were used to predicted chemical compositions of brown rice and polished rice. For most chemicals, the transmittance spectra could provide better calibration results than the reflectance ones. Beside the Toyo taste meter value (TTMV), the hulled rice spectra could predict chemical contents with the determination coefficients higher than 0.8. Spectra of hulled rice measured in transmittance mode could be used for the prediction of chemical compositions in brown rice and polished rice precisely. However, taste value of polished rice was a constituent that was hardly to be predicted.

• The Journal of the Korea Contents Association
• /
• v.16 no.5
• /
• pp.229-241
• /
• 2016

This research has its purpose to seek, among the CEOs of social enterprises, the influence of job stress on business performance, social support inbetween them, and adjusting role of government-supported policies. CEO of social enterprise, which is established to realize its social purposes, receives the job stress due to business ethics, profitability, identity crisis, management challenges and etc. We would like to set the foundation for the enterprises to constantly conduct social purposes within the local society by raising the business performances of social enterprises through seeking the measures to resolve such job stresses of the CEOs by expressing them. This research applied the ISR Job Stress Model theroy as its main ground of theoretical background. We would like to analyze the inter-significance by setting the job stress causes and job stress influences as independent variables, business achievements as a dependent variable, and social support, government-supported policies as moderating variables. For the methods of the research, we collected, using structuralized questionnaire, from 223 social enterprise CEOs located within Korea. Data analysis used IBM SPSS Statristics 20.0 programme, and through general characteristic of sample, confidence testing, factorial analysis, correlation analysis and research hypothesis testing, drew the following results. First, job stress factor and influence were analyzed to have negative impacts on business performance. Second, social support was found to lower job stress factor and influence, and raise business performance. Third, government-supported policy was analyzed to lower job stress factor and influence, and raise business performance.

• The Journal of Engineering Research
• /
• v.3 no.1
• /
• pp.65-73
• /
• 1998

One approach to improved image restoration methods has been the incorporation of additional source information via Gibbs priors that assume a source that is piecewise smooth. A natural Gibbs prior for expressing such constraints is an energy function defined on binary valued line processes as well as source intensities. However, the estimation of both continuous variables and binary variables is known to be a difficult problem. In this work, we consider the application of the deterministic annealing method. Unlike other methods, the deterministic annealing method offers a principled and efficient means of handling the problems associated with mixed continuous and binary variable objectives. The application of the deterministic annealing method results in a sequence of objective functions (defined only on the continuous variables) whose sequence of solutions approaches that of the original mixed variable objective function. The sequence is indexed by a control parameter (the temperature). The energy functions at high temperatures are smooth approximations of the energy functions at lower temperatures. Consequently, it is easier to minimize the energy functions at high temperatures and then track the minimum through the variation of the temperature. This is the essence of a continuation method. We show experimental results, which demonstrate the efficacy of the continuation method applied to a Bayesian restoration model.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.12
• /
• pp.1301-1307
• /
• 2011

Electrosurgical knee wand (EKW) is a high-frequency thermocautery instrument and is often used for coagulation, ablation, excision, and extirpation of knee ligaments and tissues. In order to maximize the success rate, ease, and safety of knee surgery using EKW and radiofrequency ablation, it is necessary to ensure that the EKW selectively approaches the lesion with utmost accuracy and safety. The key feature of this instrument is its excellent maneuverability. Hence, the authors constructed a tensile spring model based on a shape memory alloy (SMA), which exhibits the shape memory effect. This model can be used in knee surgery as it is considered the most biocompatible femorotibial surgical actuator. The changes in external temperature with current and the thermoelectric characteristics of the SMA were investigated. The relationship between the restoring force and the typical stroke (TS) in response to the conditions in the SMA tensile spring design were evaluated. In conclusion, as the diameter of the SMA tensile spring decreased, the maximum temperature increased. The strain in the actuator caused a stable and proportional increase in the force and induced current for up to 15s, but this increase became very unstable after 30s. Moreover, the relationship between the current and the TS was more stable than that between the current and the restoring force.