• Macromolecular Research
• /
• v.12 no.2
• /
• pp.145-155
• /
• 2004

Facilitated transport membranes for the separation of olefin/paraffin mixtures have long been of interest in separation membrane science because olefins, such as propylene and ethylene, which are important chemicals in petrochemical industries, are currently separated by energy-intensive cryogenic distillation processes. Recently, solid polymer electrolyte membranes containing silver ions have demonstrated remarkable performance in the separation of olefin/paraffin mixtures in the solid state and, thus, they can be considered as alternatives to cryogenic distillation. Here, we review recent progress, and critical issues affecting in the use of facilitated olefin transport membranes; in particular, we provide a general overview with reference to carrier properties, transport mechanisms, and separation performance.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.6
• /
• pp.98-111
• /
• 2009

The objective of this study is to revise the related regulations and laws of intelligent transport systems performance tests and methods. This study improves the reliability of present traffic information, reduce public discontent by systematic reforms and reduce national and social costs through the analysis of intelligent transport system performance tests'current status and problems. This study will maximize the investment profits and efficiency of ITS system as the reliability of transportation information which is created through the maintenance of ITS equipment and center, systemization of work responsibility through close analysis of ITS performance test and overall evaluation of role of ITS performance assessment organization will improve and new level of service will be born.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.9
• /
• pp.1283-1294
• /
• 1993

The conventional transport protocols, developed on top of the low-bandwidth high-error network services, exhibit poor performances when operating in the new high-bandwidth low-error networks. A new transport protocol HSTP(High Speed Transport Protocol) was proposed to take advantage of the new network environment. This paper gives a performance evaluation by simulation technique of the proposed HSTP and conventional TP4(Transport Protocol class 4) in their data trans-fer characteristics. The performance variation by HSTP and TP4 are investigated when their various error control techniques are employed, three different techniques for HSTP, and two for TP4. The performance enhancement in HSTP is also evaluated when the rate control technique is used as part of the flow control mechanisms.

• Journal of information and communication convergence engineering
• /
• v.7 no.3
• /
• pp.241-246
• /
• 2009

Advances in mobile and wireless networking technologies have enabled mobile ad hoc networks applicable to a wide range of areas. Many cases of even such ad hoc networks demand to be accessible to the global network. Owing to be diversified in features depending on applications, however, some those networks may consist of devices or nodes which do not facilitate all the same transport protocols. This results in unreachable situations of establishing ad hoc network: such as non-existence of all required access points, faults or contention in a path of particular protocol communication. Interworking between different transport protocols can alleviate such problems. This paper proposes an interworking scheme to improve data transport performance and network accessibility, especially in such a mobile ad hoc network that is applicable to data communications among ships or user's convenient u-health services. Modeling and simulation analysis are used to verify the improvement.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.1
• /
• pp.60-66
• /
• 2009

A service network in the future ubiquitous environment can consist of a variety of elements, which include different protocols of the network transport. Interwoking different transport protocols can alleviate such problems occurred in accessing network as poverty of facilities, faults, and contention in a path of particular protocol communication. This paper schemes to improve performance of the network constituted of different protocols for the network transport. Interposing an interwork element, like SDR (Software Defined Radio), in the network can raise availability of transport paths, and then improve transport performance of the overall network Simulation analysis justifies such a scheme and this paper presents simulation results.

• Journal of KIISE:Information Networking
• /
• v.33 no.1
• /
• pp.28-37
• /
• 2006

Recently, transport layer mobility supporting approaches based on SCTP, which is a new standard transport layer protocol, are proposed. In this paper, the handover performance and overheads of these transport layer mobility supporting approaches are compared to those of the traditional network layer mobility supporting approaches. Through the simulation results, it is shown that the handover performance of the transport layer mobility supporting approaches is better or at least similar to that of the plain MIPv6, which is the representative network layer mobility supporting approach. With respect to the amount of control packet, the transport layer approaches impose less overhead than any of the network layer approaches.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.7
• /
• pp.92-98
• /
• 1995

In the cluster tool, it is necessary to precisely control the vacuum pressure for the wafer transportation between transport module and cassette or process modules with the range of 1*10$^{-4}$ to 5*10$^{-5}$ torr. So we have designed the pressure control system for the transport module of the cluster tool and have evaluated its performance. Digital PID is utilized with the weighted sum of both three previous errors and one current error. The feedback signal is put into the nitrogen mass flow controller using the transport module controller. This pressure control system can prevent the transport module from the particle generation and backstreaming of hazardous process gases of the process chamber.

• Computers and Concrete
• /
• v.31 no.6
• /
• pp.485-499
• /
• 2023

Both damage and unsaturated conditions accelerate the transport of erosive media inside concrete. However, their combined effects have not been fully investigated. A multiscale mortar model using representative volume elements is developed, capturing the number and distribution in each phase. Afterwards, mortar damage microstructure evolution is simulated in the tensile process. Finally, the unsaturated mortar transport is predicted and analysed. The results indicate that damage significantly affects the diffusion process in the early stage, while the transport performance is weakened due to the obstruction of the nontransport phase in the later stage. The higher the saturation and the more connected pores, the faster the diffusion rate of chloride ions. Chloride ions spread around the cracks in a tree-like manner along. The model can very well predict the chloride ion transport performance of unsaturated and damaged mortar.

• Journal of Distribution Science
• /
• v.15 no.11
• /
• pp.59-72
• /
• 2017

Purpose - This paper evaluated the efficiency performance of the three major maritime transport markets and examined the determinants of the performance. The firms' revenue fluctuates with the changes of the economic cycle; hence it is important for them to set up business strategies to improve efficiencies. A lack of efficiency measurements for shipping firms leads to a significant gap in determining their overall performance. Research design, data, and methodology - Each of DEA scores was adopted for the evaluation and panel regression was used to examine the impact of determinants on the performance. The analysis included 50 shipping firms from three maritime transport markets as follows; 15 firms of container liners, 18 firms of bulk carrier and 17 firms of tanker carriers, and its period was from 2010 to 2016. Results - In the CCR model, container liners were the highest, tanker carriers were the second, and bulk carriers were the lowest in operation efficiency and financial efficiency. By region, operation efficiency and financial efficiency was high in the order of America, Asia, and Europe. Conclusions - This study suggests business strategies for maritime transport companies based on the analytical results of determinants of operational and financial efficiency.

• Nuclear Engineering and Technology
• /
• v.54 no.10
• /
• pp.3766-3777
• /
• 2022

It is essential to ensure the safety of spent nuclear fuel (SNF) transport cask in drop situation that is included in transport accident scenarios. The safety of the drop situation is affected by the impact absorption performance of impact limiters. Therefore, when designing an impact limiter, the uncertainty in the material properties that affect the impact absorption performance must be considered. In this study, the material properties of the wood inside the impact limiter were selected as the variables for a parametric study. The sensitivity analysis of the drop response of the SNF transport cask with impact limiter was performed. The minimum wood strength required to prevent a direct collision between the cask and floor was derived from the analysis results. In addition, the plastic strain response was analyzed and strain-based evaluation was performed. Based on this result, the critical values of wood properties that change the impact dynamic characteristics were investigated. Finally, the optimal material properties of wood were obtained to secure the structural safety of the SNF transport cask. The results of this study can contribute to the development of SNF transport cask, thereby ensuring safety in transport accident conditions.