• Journal of Korean Society of Transportation
• /
• v.27 no.1
• /
• pp.143-155
• /
• 2009

A dynamic traffic assignment (DTA) has recently been implemented in many practical projects. The core of dynamic model is the inclusion of time scale. If excluding the time dimension from a DTA model, the framework of a DTA model is similar to that of static model. Similar to static model, with given exogenous travel demand, a DTA model loads vehicles on the network and finds an optimal solution satisfying a pre-defined route choice rule. In most DTA models, the departure pattern of given travel demand is predefined and assumed as a fixed pattern, although the departure pattern of driver is changeable depending on a network traffic condition. Especially, for morning peak commute where most drivers have their preferred arrival time, the departure time, therefore, should be modeled as an endogenous variable. In this paper, the authors point out some shortcomings of current DTA model and propose an alternative approach which could overcome the shortcomings of current DTA model. The authors substitute a traditional definition for time-dependent OD table by a new definition in which the time-dependent OD table is defined as arrival time-based one. In addition, the authors develop a new DTA model which is capable of finding an equilibrium departure pattern without the use of schedule delay functions. Three types of objective function for a new DTA framework are proposed, and the solution algorithms for the three objective functions are also explained.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.16 no.5
• /
• pp.653-658
• /
• 2013

For towing the new type armored vehicle and maintaining the close support, the armored recovery vehicle(ARV) with winch and crane has been developed. In case of crane, it is mainly used to salvage heavy objects by rotational and vertical motion. Especially, the crane bracket is very important parts due to fixing the ARV's body and rotary joint and preventing the force rotation of crane. Therefore, the crane bracket needs to have an enough strength to endure the high load and it is very important to analyze the stress distribution under loads. In the present work, the experimental and analytical investigation on structural integrity evaluation of crane bracket were carried out. The simulation of three-dimensional finite element method(FEM) was compared with experimental datum. From the numerical results, the FEM simulations corresponded well with th experimental results and the structural safety was confirmed by safety factor.

• Microbiology and Biotechnology Letters
• /
• v.32 no.1
• /
• pp.11-15
• /
• 2004

Embryonic stem (ES) cells are derived from the inner cell mass of the blastocyst-stage embryos that can be propagated indefinitely and, at the same time, can be differentiated into all the cell types that constitute the body. Current research using ES cells is mainly focused on the efficient generation of specific cell types by employing optimal differentiation conditions, which often requires the genetic manipulation of ES cells. As a way of developing an efficient system to regulate foreign gene expression in ES cells, we have inserted the gene encoding Corynebacterium diphtheria toxin-A (DTA) into an autonomously induced plasmid under positive doxycycline control ('Tet-on' system). In this study, we demonstrate that this system can lead to the cell death of mouse ES cells by the induction of DTA expression when exposed to the tetracycline derivative, doxycycline. MTT assay showed that this induction resulted in the apoptosis of ES cells.

• Journal of Korean Public Health Nursing
• /
• v.22 no.1
• /
• pp.121-130
• /
• 2008

Purpose: Immunization is one of the simplest and most effective approaches for protecting the health of children from preventable infectious disease. This study assessed the immunization statuses of children presenting to childcare centers in Korea and compared the sociodemographic factors of children with age-appropriate immunization for DTaP4 with those with delayed immunization for DTaP4. Method: A national mail survey was used to collect data on the children's immunization history and sociodemographic information. A total of 248 mothers returned completed questionnaires for their children. Results: The overall immunization coverage for HepB, a series of DTaP and polio and varicella was above 95%. However, the percentage of age-appropriate immunizations of vaccines ranged from 45.3% to 69.0% depending on the vaccines. Only the age of the child was a significant factor for delayed immunization for DTaP4. Conclusion: To fully protect children from vaccine-preventable disease, childcare providers can playa role in monitoring the immunization statuses of children in their care centers to ensure that they all receive all childhood immunizations on time.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.7
• /
• pp.774-780
• /
• 2016

In this paper noise source and transfer path of tactical vehicle are analyzed with partial coherence function and spectrum analysis. Engine, transmission, structure panel and aerodynamic are main source of cabin noise. To reduce cabin noise, identifying transfer path of sources and analyzing their contribution is important. With modeling of transfer path and partial coherence function, transfer path and principal noise source can be identified. Engine/transmission and structural resonance are principal source of low frequency noise and by adding stiffener and sound absorbing material, resonance of vibration and inflow air problem can be solved.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.26 no.4
• /
• pp.365-374
• /
• 2016

The underwater radiated noise can be reduced by decreasing the structure borne noise of the on-board equipment. Therefore, the structure borne noise of the onborad installed equipment is strongly restricted by ROK navy with MIL-Std 740-2. Usually, the vibration transmissibility from the equipment to the hull of the ship is dependent on its mount characteristics. Even though the double mount structure is proper to apply for ship board application rather than single mount, it is not widely applied due to the weight and volume resriction of the ship. Therefore, in this research, the base using sandwitch panel which can act as double mount structure is suggested and its noise reduction capacity is verified with analytic calculation as well as experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.803-808
• /
• 2011

The shipboard working environment of navy vessel is very inferior to the ground working environment. For this reason, the crew of a navy vessel suffer from an occupational disease such as lumbar pain, hearing loss, etc. Although standard for navy vessel's environmental vibration is applied, the criterion of the environmental vibration is too high. So it doesn't help to improve habitability of crew. In this study, for improving its habitability of crew, the current vibration level of navy vessel was examined and the standard of navy vessel's environmental vibration was investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.10a
• /
• pp.797-802
• /
• 2011

Vibration of diesel engines in naval vessels causes structure vibration which is significant under water radiating noise source under CIS (Cavitation Inception Speed). So managing the vibration level of diesel engine is important for survivability and also durability of naval vessels. Therefore, in this research, a vibration criterion which is applied for Korean naval vessels are reviewed. It is compared with the DNV, ABS and merchant ship's diesel engine criteria. And also vibration data of three Korean naval vessels are analyzed. As a result, reasonable criteria of diesel engine vibration and shipbuilding standards are suggested.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.5
• /
• pp.407-413
• /
• 2014

The diesel engine and reduction gear combination is one of the common propulsion system in a naval vessel. Since the diesel engine has torsional vibration caused by reciprocating motion of the mass and gas pressure force of the cylinder, high cycle torsional fatigue can be occurred. Therefore, ROK navy restricts the maximum stress of the propulsion shaft according to MIL G 17859D. In this paper, the root cause for the failure of the diesel engine and reduction gear connecting shaft occurred in typical naval vessel is investigated based on the measured bending and torsional moment according to MIL G 17859D procedure.

• Polymer Science and Technology
• /
• v.4 no.5
• /
• pp.387-397
• /
• 1993