• Transactions of the Korean Society of Automotive Engineers
• /
• v.24 no.3
• /
• pp.345-351
• /
• 2016

This study was carried out to determine an optimal lean $NO_x$ trap (LNT) regeneration condition based on a $NO_x$ storage fraction. The LNT regeneration was performed by an in-cylinder post fuel injection method. A $NO_x$ storage fraction is defined by the ratio of current cumulated $NO_x$ amount in the LNT to the $NO_x$ storage capacity: 0 means empty and 1 fully loaded. In this study five engine operating conditions were chosen to represent the New European Driving Cycle. With various $NO_x$ storage fractions each engine operating condition, the LNT regeneration was executed and then $NO_x$ conversion efficiency, additional fuel consumption, CO and THC slip, peak catalyst temperature were measured. The results showed that there exist an optimal condition to regenerate the LNT, eg. 1500 rpm 6 bar BMEP with below 0.7 $NO_x$ storage fraction in this experimental constraint.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.2
• /
• pp.60-66
• /
• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.6
• /
• pp.64-71
• /
• 2013

In this study we designed a lean $NO_x$ trap (LNT) model with $GT-POWER^{TM}$ program and then the LNT model was compared to the bench flow reactor test results. This model consists of 9 kinetic reactions to represent the main steps of NO oxidation, $NO_x$ adsorption, $NO_x$ release and then its reduction. The comparison was performed on the operating conditions at the space velocity of 50,000 1/hr and 80,000 1/hr with the temperature range of $200^{\circ}C{\sim}500^{\circ}C$ with the even spaced temperature step of $50^{\circ}C$. The experimental results show that the $NO_x$ conversion efficiency was enhanced by the temperature up to $350^{\circ}C$ and then decayed at higher temperatures. The LNT model predicts the similar trend of the $NO_x$ conversion efficiency to the experimental results below $350^{\circ}C$, but overestimates above $350^{\circ}C$. This overestimation comes from the higher reduction efficiency which was obtained by the different reduction gas composition such as $C_3H_6$ in the model to replace $CH_4$, $C_2H_4$ in the bench test.

• Journal of the Korean Society of Tobacco Science
• /
• v.20 no.2
• /
• pp.166-171
• /
• 1998

In order to improve the efficiency of F$_1$ hybrid seeds production(KF 114), some experiments were carried out in a greenhouse this year. Mother plant(MSNC567) and pollen plant(NC) were grown in some pots (30 x 30cm, WxH). The gathered pollens were mixed with celite, pollen deluent dusts and stored in refrigerator at l$0^{\circ}C$ before pollination. To establish the critical range of the mixed rate and the storage period of pollens, the change in a percent of capsule set, number of seed and seed weight per capsule, weight of 1000 seeds and germination percent of seed resulted of pollination with pollen deluent dusts were investigated. The results are as follows; Percent of capsule set showed the mixed rate 1:5 resulted in no difference and those of 1:10 and 1:20 decreased about 5 ～15% when compared with trials using pollen alone. There was no difference among duration of storage in a same mixed rate. Numbers of seed per capsule showed a significant difference among the mixed rates and among durations of storage. Numbers of seed per capsule were decreased about 55 ～ 90 % as the mixed rate increase, about 2 ～ 28 % as the duration of storage increase. Weight of seed per capsule decreased about 16 ～ 23 % as the duration increase and decreased about 3 ～ 89 % as the mixed rate increase when compared with trials using pollen alone. Weight of 1000 seeds showed non significant difference among duration of storage but were higher than trials used pollen alone as the mixed rate increase.

• Korean Journal of Digital Imaging in Medicine
• /
• v.7 no.1
• /
• pp.33-38
• /
• 2005

Modern hospitals have been greatly facilitated with information technology (IT) such as hospital information system (HIS). One of the most prominent achievements is medical imaging and image data management so-called Picture Archiving and Communication Systems (PACS). Due to inevitable use of diagnostic images (such as X-ray, CT, MRI), PACS made tremendous impact not only on radiology department but also nearly all clinical departments for exchange and sharing image related clinical information. There is no doubt that better use of PACS leads to highly efficient clinical administration and hospital management. However, due to rapid and widespread acceptance of PACS storage and management of digitized image data in hospital introduces overhead and bottleneck when transferring images among clinical departments within and/or across hospitals. Despite numerous technical difficulties, financing for installing PACS is a major hindrance to overcome. In addition, a mirroring or a clustering backup can be used to maximize security and efficiency, which may not be considered as cost-effective approach because of extra hardware expenses. In this study therefore we have developed a new based on grid of distributed PACS in order to balance between the cost and network performance among multiple hospitals.