• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.65 no.3
• /
• pp.171-177
• /
• 2016

Noise problem that occurs in living environment is a big trouble in the economic, social and environmental aspects. In this paper, the filtered-X LMS algorithms, the adjoint LMS algorithms, and the robust adjoint LMS algorithms will be introduced for applications in active noise control(ANC). The filtered-X LMS algorithms is currently the most popular method for adapting a filter when the filter exits a transfer function in the error path. The adjoint LMS algorithms, that prefilter the error signals instead of divided reference signals in frequency band, is also used for adaptive filter algorithms to reduce the computational burden of multi-channel ANC systems such as the 3D space. To improve performance of the adjoint LMS ANC system, an off-line measured transfer function is connected parallel to the LMS filter. This parallel-fixed filter acts as a noise controller only when the LMS filter is abnormal condition. The superior performance of the proposed system was compared through simulation with the adjoint LMS ANC system when the adaptive filter is in normal and abnormal condition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.1
• /
• pp.94-101
• /
• 2000

In this paper, a multi-channel active noise control(ANC) system using subband hybrid control techniques is proposed. Subband techniques could reduce computational burden and improve the performance of ANC systems by dividing several frequency subband and adjusting adaptive filter coefficients. So it can effectively cancel noises at wanted frequency range and use lower order adaptive filter than the existing algorithms. The adjoint LMS algorithm, which prefilter the error signals instead of the divided reference signals in frequency band, is also used for adaptive filter algorithms to reduce the computational burden of the subband adaptive systems. To improve performance of the ANC system, a weighted hybrid control technique, which has weightily properties of feedforward control systems and feedback control systems, is applied. This algorithm shows higher stability and good noise attenuation property in broad band ANC systems. Computer simulations were performed to show the effectiveness of the proposed algorithm.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.38 no.2
• /
• pp.107-114
• /
• 2014

This paper proposes a common rail pressure control algorithm for passenger car diesel engines. For handling the parameter-varying characteristics of common rail systems, the quantitative feedback theory (QFT) is applied to the design of a robust rail pressure control algorithm. The driving current of the pressure control valve and the common rail pressure are used as the input/output variables for the common rail system model. The model parameter uncertainty ranges are identified through experiments. Rail pressure controller requirements in terms of tracking performance, robust stability, and disturbance rejection are defined on a Nichols chart, and these requirements are fulfilled by designing a compensator and a prefilter in the QFT framework. The proposed common rail pressure control algorithm is validated through engine experiments. The experimental results show that the proposed rail pressure controller has a good degree of consistency under various operating conditions, and it successfully satisfies the requirements for reference tracking and disturbance rejection.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.3
• /
• pp.88-97
• /
• 2013

This paper presents a robust air-to-fuel ratio (AFR) control algorithm for managing exhaust gas recirculation (EGR) systems. In order to handle production tolerance, deterioration and parameter-varying characteristics of the EGR system, quantitative feedback theory (QFT) is applied for designing the robust AFR control algorithm. A plant model of EGR system is approximated by the first order transfer function plus time-delay (FOPTD) model. EGR valve position and AFR of exhaust gas are used as input/output variables of the plant model. Through engine experiments, parameter uncertainty of the plant model is identified in a fixed engine operating point. Requirement specifications of robust stability and reference tracking performance are defined and these are fulfilled by the following steps: during loop shaping process, a PID controller is designed by using a nominal loop transmission function represented on Nichols chart. Then, the frequency response of closed-loop transfer function is used for designing a prefilter. It is validated that the proposed QFT-based AFR control algorithm successfully satisfy the requirements through experiments of various engine operating points.

• Membrane Journal
• /
• v.25 no.3
• /
• pp.276-286
• /
• 2015

The effects of relaxation and backwashing on fouling in ultrafiltration were investigated using full-scale membrane bioreactors (MBRs) which operated at a constant flux of 30 LMH. This paper also estimated the feasibility of using intermittent aeration strategies for minimizing the hydraulic resistance to filtration in comparison with the continuous aeration for running MBRs. Multiple cycles of filtration (14.5 min each) and relaxation (0.5 min each) were repeated. Similarly, a backwash was conducted by replacing a relaxation after each filtration cycle for the comparative performance test. The attached cake thickness on the membrane rapidly increased, caused by subsequent no aeration leading to easier combining with gel layer and the formation of heterogeneous layer on the membrane surface. During periodic backwashing, it is expected that gel and thin cake layer might sufficiently be removed by heterogeneous layer. After periodic backwashing, subsequent cake layer formation during time of no aeration was rapid than frequent no aeration, acting as a prefilter and preventing further irreversible fouling. Based on the Pearson correlation analysis, overall period fouling (dTMP/min) and average of all cycles (dTMP/min) were strongly correlated with the on-off period of aeration for operating MBRs.

• Proceedings of the Membrane Society of Korea Conference
• /
• 1997.06a
• /
• pp.207-231
• /
• 1997

The use household water purifier is continuously increasing due to the distrust of the piped, rap water, which may be caused by the deterioration of water quality and water supply facilities in Korea. The water purifier distributing in the domestic market is the membrane type that composes of membrane as a basic filter, sediment filter as a prefilter and activated carbon filter instead of one purifying water system. The membrane type using as a water cleaning system is mainly the method of micro filtration(NIF) as well as ultra filtration(UF) and reverse osmosis(RO). The types of MF and UF are using to remove suspended solids and virus, and RO is using to remove ionic compound in chemical organic compounds. At the beginning the household water purifier was imported as end-product or assembled by only importing module from small businesses in Korea. Therefore, people was hard to confide in the product quality because the sales policy and management of water purifier by small business were not effectively organized. However, the defects of water purifier having up to now ate improving by the efforts of special branches of water purifier and large enterprises, and new great products are developing and producing. To develop the best quality product of water purifier in Korea, it should be considered seasonal water characteristrics rather than any other condition. For example, the water purifier can be affected by the water temperature change, increase of suspended solids in the rainy season and inflow of raw water having concentration in a dry season. The subject we have to investigate in the future is to develop the water purifying system adaptable in Korea which can treat the water quality using close analyses of local and seasonal water characteristics.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.3
• /
• pp.523-533
• /
• 2000

A two-phase anaerobic reactor with submerged membrane system was developed for increasing acidogen concentration and methane recovery. The membrane used was mixed esters of cellulose of $0.5{\mu}m$ pore size and $0.8m^2$ of effective surface area. The methanogenic reactor comprised of UASB (Upflow Anaerobic Sludge Blanket) and AF (Anaerobic Filter). COD removal efficiency was 70~80% and the methane content in the biogas increased up to 90% for the submerged membrane system in the anaerobic reactor. As the cake resistance of membrane caused a serious problem, stainless steal prefilters (40, 53, $63{\mu}m$) and air backwashing methods were applied to minimize the cake resistance effectively. Among the tested prefilters. the $63{\mu}m$ prefilter showed the best performance for reduction of cake resistance and a successful long-tern operation. By cleaning with alkali first and acidic solution later. the permeate flux decreased by long term operation was recovered to 89% of that with a new membrane.

• Tuberculosis and Respiratory Diseases
• /
• v.59 no.3
• /
• pp.279-285
• /
• 2005

Background : Ambient particles during Asian dust events are usually less than $10{\mu}m$ in size, and known to be associated with the adverse effects on the general population. There is little evidence linking Asian dust to adverse effects on the airways. In 2002, the authors found that particulate matter during Asian dust events had an effect on the symptoms and pulmonary function of patients with bronchial asthma. An aggravating factor might be that of a viral infection, but this remains unclear. Conversely, it has been speculated that African dust may carry the virus responsible for foot and mouth disease. Asian dust events are also likely to be responsible for transporting viruses, some of which are pathogenic, and common in many environments. Therefore, in this study, air samples were screened for the presence of viruses. Methods : Air samples were collected 20 times each during Asian dust events and under non-dust conditions, for at least 6 hours per sample, using a high volume air sampler (Sibata Model HV500F), with an airflow rate of 500L/min, between April and August 2003, and between April and August 2004. The samples were then screened for the presence of targeted viruses (Influenza A, B, Hog cholera virus, and Aphthovirus) using a polymerase chain reaction method. Results : One Asian dust event occurred between April and August 2003, and 3 between April and August 2004, with a 24 hour average PM10 level of $148.0{\mu}g/m^3$. The 24 hour average PM10 level was $57{\mu}g/m^3$. There was a significant difference in the PM10 concentration between dusty and clear days. No viruses (Influenza virus, Aphthovirus, and Hog cholera virus) were identified in the air samples obtained during the dusty days. Conclusions : Although no virus was detected in this study, further studies will be needed to identify suspected viruses carried during Asian dust events, employing more appropriate virus detection conditions.