• Journal of the Korean Operations Research and Management Science Society
• /
• v.17 no.1
• /
• pp.67-75
• /
• 1992

In this paper, by using perturbation analysis method, We find the sensitivity of the mean busy cycle with respect to means interrival time in M/M/1 Queue. We show that the Perturbation analysis estimate can be expressed as a sum of the infinitesimal perturbation analysis (IPA) estimate and the effect caused by changes in transition probabilities, thus explaining why IPA estimates are not consistent in general.

• Korean Chemical Engineering Research
• /
• v.57 no.1
• /
• pp.133-141
• /
• 2019

High specific surface area zirconia with acid-basic property was synthesized by precipitation using reflux method or hydrothermal synthesis method using ammonium hydroxide solution as precipitant in the range of pH of Zr solution from 2 to 10. The prepared zirconia was characterized by the nitrogen adsorption, X-ray diffraction (XRD), isopropanol temperature programmed desorption (IPA-TPD), scanning electron microscopy and X-ray photoelectron spectroscopy, and the catalytic activity in the IPA decomposition reaction was correlated with the acid-basic properties. When using reflux method, high pH of Zr solution was required to obtain high fraction of tetragonal zirconia, and pure tetragonal zirconia was possible at pH 9 or higher. High pH was required to obtain high specific surface area zirconia, and the hydrous zirconia synthesized at pH 10 had high specific surface area zirconia of $260m^2g^{-1}$ even after calcination at $600^{\circ}C$. However, hydrothermal synthesis with high pressure under the same conditions resulted in very low specific surface area below $40m^2g^{-1}$ and monoclinic phase zirconia was synthesized. High pH of the solution was required to obtain high specific surface area tetragonal phase zirconia. In hydrothermal synthesis requiring high pressure, monoclinic zirconia was produced irrespective of the pH of the solution, and the specific surface area was relatively low. Zirconia with high specific surface area and tetragonal phase was predominantly acidic compared to basicity and only propylene, which was observed as selective dehydration reaction in IPA decomposition reaction, was produced.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.15 no.1
• /
• pp.52-65
• /
• 2016

The electronic toll collection system(ETCS), is globally used in about 40 countries. In Korea, the Korea Expressway Corporation led the nationwide introduction of the ETC system in 2007 under the brand name of the Hi-pass. Since then, Hi-pass, with its rate of average daily use reaching about 70%, has become an essential facility in Korean expressways. To identify users' perception on Hi-pass (satisfaction, preference, etc.), this study conducted a Modified Importance-Performance Analysis (M-IPA). With this, this study attempted to identify the kind of efforts necessary to enhance current Hi-pass users' convenience and satisfaction. According to the result of M-IPA, the items including "non-stop payment" and "toll discount" are identified as key items that require further improvement. For improvement in the "non-stop payment" item, operations of Hi-pass toll booths appropriate for the demand for Hi-pass use and the selection of Hi-pass booths' locations in consideration of entry and exit lanes need to be improved. In addition, with regard to the "toll discount" item, although toll discount is currently provided to Hi-pass users, thus, PR thereof will have to be strengthened. It is expected that this study will be used as basic data to devise methods of enhancing Hi-pass usage through improvement of Hi-pass users' satisfaction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.14 no.3
• /
• pp.223-227
• /
• 2001

In this paper, the authors present the fabrication of high-yield Si thin-membranes by electrochemical etch-stop in tetramethyl ammonium hydroxide (TMAH): isopropyl alcohol (IPA):pyrazine solutions. The current-voltage (I-V) characteristics of n- and p-type Si in TMAH:IPA;pyrazine solutions were analysed, repsectively. Open circuit potential (OCP)and passivation potential (PP) of n- and p-type Si, respectively, were obtained and applied potential was selected between n- and p-type Si PPs. The electrochemical etch-stop method was applied to the fabrication of 801 micro-membranes with 20.0 $\mu\textrm{m}$ thickness on a 5" Si wafer. The average thickness of fabricated 801 micro-membranes on one wafer 20.03$\mu\textrm{m}$ and the standard deviation was ${\pm}$0.26$\mu\textrm{m}$. The Si surface of the etch-stopped micro-membranes was extremely flat with no noticeable taper or nonuniformity. The results indicate that use of the electrochemical etch-stop method for the etching of Si in TMAH:IPA;pyrazine solutions provides a powerful and versatile alternative process for fabricating high-yield Si micro-membranes.

• Korean Journal of Materials Research
• /
• v.16 no.2
• /
• pp.99-105
• /
• 2006

This paper reports an improved bonding method using the IPA (isopropyl alcohol) assisted low-temperature bonding process for the PMMA (polymethylmethacrylate) micro CE (capillary electrophoresis) chip. There is a problem about channel deformations during the conventional processes such as thermal bonding and solvent bonding methods. The bonding test using an IPA showed good results without channel deformations over 4 inch PMMA wafer at $60^{\circ}C$ and 1.3 bar for 10 minutes. The mechanism of IPA bonding was attributed to the formation of a small amount of vaporized acetone made from the oxidized IPA which allows to solvent bonding. To verify the usefulness of the IPA assisted low-temperature bonding process, the PMMA micro CE chip which had a $45{\mu}m$ channel height was fabricated by hot embossing process. A functional test of the fabricated CE chip was demonstrated by the separation of fluorescein and dichlorofluorescein. Any leakage of liquids was not observed during the test and the electropherogram result was successfully achieved. An IPA assisted low-temperature bonding process could be an easy and effective way to fabricate the PMMA micro CE chip and would help to increase the yield.

• Transactions on Electrical and Electronic Materials
• /
• v.2 no.2
• /
• pp.21-25
• /
• 2001

This paper presents the effect of pyrazine on tetramethylammonium hydroxide (TMAH):isopropyl alcohol (IPA) single-crystal silicon anisotropic etching properties. With the addition of IPA to TMAH solutions, etching characteristics are exhibited an improvement in flatness on the etching front and a reduction in undercutting, but the etch rate on (100) silicon is decreased. The (100) silicon etch rate is improved by the addition of pyrazine. An etch rate on (100) silicon of 0.8 ${\mu}{\textrm}{m}$/min, which is faster by 13% than a 20 wt.% solution of pure TMAH, is obtained using 20 wt.% TMAH: 0.5 g/100 ml pyrazine solutions, but the etch rate on (100) silicon is decreased when more pyrazine is added. With the addition of pyrazine to a 25 wt.% TMAH solution, variations in flatness on the etching front are not observed and the undercutting ratio is reduced by 30~50%. These results indicate that anisotropic etching technology using TMAH:IPA:pyrazine solutions provides a powerful and versatile method for realizing of microelectromechanical systems.

• Transactions on Electrical and Electronic Materials
• /
• v.2 no.2
• /
• pp.26-31
• /
• 2001

This paper presents the electrochemical etch-stop characteristics of single-crystal Si(001) wafers in tetramethyl ammonium hydroxide(TMAH):isopropyl alcohol(IPA):pyrazine solutions. The addition of pyrazine to TMAH:IPA solutions increased the etch rate of (100) Si, thus the etching time required by the etch-stop process shortened. The current-voltage(I-V) characteristics of n- and p-type Si in TMAH:IPA:pyrazine solutions were obtained, respectively. Open circuit potential(OCP) and passivation potential(PP) of n- and p-type Si, respectively, were obtained and applied potential was selected between n- and p-type Si PPs. The electrochemical etch-stop method was used to fabricate 801 microdiaphragms of 20 ${\mu}{\textrm}{m}$ thickness on a 5-inch Si wafer. The average thickness of fabricated 801 microdiaphragms on one Si wafer was 20.03 ${\mu}{\textrm}{m}$ and the standard deviation was $\pm$0.26 ${\mu}{\textrm}{m}$. The Si surface of the etch-stopped microdiaphragm was extremely flat with no noticeable taper or nonuniformity.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.3
• /
• pp.1522-1530
• /
• 2014

High-rise residential complex type is getting important as new town development and urban regeneration in the downtown area. However, literature review of high-rise residential complex and research on satisfaction analysis of real residents are lack. Therefore, this paper is analyzing environmental friendly planning elements of high-rise building as housing subdivision, inside of building, facility, and maintenance by a survey on experts. The purpose of this paper is to suggest improvement method of environmental-friendly planning elements of high-rise residential complex by M-IPA. First, as a result, the part of housing subdivision has to keep complex land utilization, environmental-friendly transportation. Second, the part of inside of building shows that ecological housing subdivision, indoor air environment urgent and indoor temperature environment keeps maintaining. Finally, the part of facility/maintenance shows that material and facility, and index of energy management are urgently needed.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.36 no.1
• /
• pp.70-77
• /
• 2013

The theory of two-dimensional quality, in particular, the Kano model that is developed by the analogy with the M-H theory, has been applied in various industry fields for more than three decades. Importance-Performance Analysis (IPA) assumes that the degree of physical fulfilment of quality attributes and the satisfaction of that attribute is linear, and therefore, it is applicable to the traditional one-dimensional attribute, not other quality types defined in the Kano's model such as attractive or must-be attribute. To solve this problem, the current study suggests a new importance-satisfaction analysis using a modified IPA in accordance with the three quality types and a diagonal method introduced by Slack (1999) to determine improvement priority. For this, I investigated 19 smartphone's quality attributes and conducted a survey of 334 university students for the results of Kano's model, which adopted from Song and Park (2012)'s study, and the importance/satisfaction of the quality attributes and the results of the priority for improvement of the 19 quality attributes. The results show that the proposed I-S priority model is better than the conventional IPA based on the comparison results of determination coefficient from the regression analysis of the two models.

• Journal of the Korean Institute of Educational Facilities
• /
• v.24 no.5
• /
• pp.11-18
• /
• 2017

An university dorm has significant implications in terms of providing residential, living, and learning spaces. With its supportive function, a dorm enables each university to provide higher level of education. The operation & maintenance(O&M) condition of the dorm has a decisive effect on the students' satisfaction. Accordingly, high levels of O&M services should be performed for students. However, Korean dorms are being operated and maintained by their own O&M guidelines without the consideration of spatial characteristics of dorm facilities and the comprehensive and systematic understanding on effective O&M processes. Given the fact that dorm facility can be a crucial factor in determining the entire quality of university and its O&M condition is closely related to the satisfaction of students, it is imperative that we need to pay more attention to the O&M condition and services. Therefore, the main objective of this research is to improve dorm students' satisfaction levels by applying different O&M method, preventive maintenance rather than reactive maintenance which has been performed so far. In ordering for doing it, 'Facility Management(FM) Standard' from KS, 'Facility Performance Indicator(FPI)' from APPA: Leadership in educational facilities and 'Building O&M Inspection Manual' from Korean Ministry of Land, Infrastructure and Transport were analyzed to come up with 15 significant O&M factors. After extracting O&M factors, the survey was conducted to determine importance rate and performance rate of each O&M factor. Using the Important-Performance Analysis(IPA), the priority of 15 O&M factors was established. The result of this research will be helpful for the efficient dorm facility O&M services and for facility managers to appropriately allocate the limited resources and human power.