• Journal of the Korean Operations Research and Management Science Society
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• v.15 no.2
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• pp.45-61
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• 1990

This study examines shareholder wealth effects in tender offers and attempts to explain abnormal return variations of bidding and target firms at announcement of takeovers using the free cash flow hypothesis of Jensen. On average, bidders with large free cash flows pay higher premia (apparently more than fair market value) to targets than do other bidders with no free cash flows. Thereby, these bidders experience negative wealth effects on announcement of tender offers. Cross-sectional regression analysis suggests that for the subsample of takeover bids where bidders have large free cash flows, the increase in the debt ratio resulting from takeover has a significant positive wealth effect for bidding firm shareholders, while it has no effect in other subsamples. The evidence is consistent with the free cash flow hypothesis.

• Knowledge Management Research
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• v.20 no.4
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• pp.39-55
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• 2019

Although Firms have been increasing their information security significantly to handle increased security risks, the effects of information security were not well understood. This study aims to investigate the market value of information security by employing the event study methodology. Our research also explores how market responses vary depending on the type of information security announcements. We collected 177 firm-level information security announcements between 2001 and 2017 in South Korea. For all samples, our results indicate that the stock market positively reacts to information security announcements. We also conducted subsample analysis and found that while information security certification announcement has a positive impact on the stock market, information security activities (e.g. award, information security system) announcement had no impact on the stock market. Our study adopted a novel approach (i.e. event study) for investigating the effects of information security and found that information security investment positively affects firm value. Our results allow managers to measure the effects of information security investment and help them make right decisions on information security investment.

• Communications for Statistical Applications and Methods
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• v.16 no.6
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• pp.1031-1036
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• 2009

Under recent dramatic declines in response rates, various procedures have been considered among survey practitioners to reduce nonresponse in order to avoid its potential impairment to the inference. In the random digit dialing telephone surveys, substantial efforts are often required to obtain the initial contact for the screener interview. To reduce a burden with higher data collection costs, refusal conversion can be administered only to a random portion of the sample, reducing nonresponse (bias) with an expense of sample variability increment due to the associated weight adjustment. In this paper, we provide ways to determine the optimal subsampling rate using a linear cost model. Our approach for refusal subsampling is to predetermine a random portion from the full sample and to apply refusal conversion efforts if needed only to the subsample.

• International Journal of Reliability and Applications
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• v.10 no.1
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• pp.1-15
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• 2009

Even though the impact of manufacturing quality to reliability is not considered much as well as that of design area, a major cause of an early failure of the product is known as manufacturing problem. This research applies two different types of neural network algorithms, the Back propagation (BP) algorithm and Learning Vector Quantization (LVQ) algorithm, to identify and classify the nonrandom variation pattern on the control chart based on knowledge-based diagnosis of dimensional variation. The performance and efficiency of both algorithms are evaluated to choose the better pattern recognition system for auto body assembly process. To analyze hundred percent of the data obtained by Optical Coordinate Measurement Machine (OCMM), this research considers an application in which individual observations rather than subsample means are used. A case study for analysis of OCMM data in underbody assembly process is presented to demonstrate the proposed knowledge-based pattern recognition system.

• Journal of the Korea Society of Computer and Information
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• v.21 no.11
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• pp.151-158
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• 2016

This study analyzes the stock market reaction of disclosure of technological information using events which are collected in the Korean stock market for the thirteen-year period between January 2002 and December 2014. We find that abnormal return on the disclosure day of full sample firms is positive and statistically significant. However, abnormal return of high R&D intensity subsample is a larger positive number than that of the low one. Using a longer window, it shows that low R&D intensity negatively decreases the long term performance after the adoption of new technological information. The empirical evidence of the studying is expected to serve as a good judging guide-line for the investors.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.20 no.43
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• pp.205-209
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• 1997

One objective of the u control chart is to detect changes of mean nonconformities per unit occurred owing to various causes. This paper shows the detection probability using the Poisson distribution for various parameters, that is, subsample size n, mean nonconformities per unit $u_o$, and $u_o's$ change ratio k. We find that (1) as $u_o$ increases the smaller n is required for the same detection probability and the same change ratio; (2) as k gets away from 1 the smaller n is required; (3) the bigger n is required for the bigger detection probability. Several tables are given from our findings and are hoped to be used as guidelines for u chart users.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.41.3-42
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• 2018

Redshift space distortion (RSD) is known as a powerful cosmological probe. The large-scale RSD has been detected by various redshift surveys and continues to be a major target of ongoing surveys. On the other hand, the small-scale RSD, called finger-of-god (FoG) effect, also has cosmological information, because different cosmological parameters cause different halo mass functions and viriarized velocities. We define the "length" of FoG and examine its dependence on cosmological parameters using the Multiverse simulation. We also use the SDSS DR7 data to see how strong constraints current data sets could provide. It is found that the volume-limited subsample D5, consisting of ~100,000 galaxies at z~0.08, yields $\Delta \Omega_m ~ 0.02$.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.69.1-69.1
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• 2021

We present preliminary results of the VLA archival HI data of local AGN hosts. The sample consists of the galaxies selected from the Swift-BAT hard X-ray survey. The main goal is to probe the gas environment of the sample in order to verify the role of gas accretion as one of the major AGN triggering mechanisms. HI, as a mostly diffuse and extended gas component in many galaxies, is a sensitive tracer to explore the impact of the surroundings on galaxies. In this work, we therefore probe the HI imaging data of a subsample of BAT-BASS AGN hosts, starting with the cases for which relatively high HI fluxes have been reported from the past single-dish observations. Based on their resolved HI properties, we will discuss the possibility of gas accretion and its role in powering AGNs in these examples.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.12 no.1
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• pp.133-144
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• 2017

This study investigates firm-specific financial variables that determine investment or speculative grades from the viewpoint of firms, which are one of the major stakeholders related to the credit rating. We employ an ordered probit model for our analysis with the sample data from 1999 to 2015 for listed firms in the Korean stock markets. For investment grades, operating margin, sales, market-to-book, dividend payment, capital expenditure ratio, and tangible asset ratio have a significantly positive impact on credit ratings. In the subsample for speculative grades, the coefficients of the dividend payment, retained earnings ratio, and capital expenditure ratio are significantly positive while short-term debt ratio and R&D expenditures have a significantly negative impact on credit ratings. For the analysis before and after 2009, when the Credit Information Use and Protection Act was strengthened after the global financial crisis, the coefficients of the capital expenditure ratio, cash ratio, and tangible asset ratio are significantly positive in the subsample for investment grades before 2009, but not significant after 2010. The coefficient of the long-term debt ratio is more significantly negative than that of the short-term debt ratio before 2009, for speculative grades, but short-term debt ratio has a more negative effect on ratings than long-term debt ratio after 2010. Surprisingly, the coefficient of the R&D expenditures is significantly negative in both investment and speculative grades since 2010. Our findings are inconsistent with the conjecture that the increase in R&D expenditures enhances the possibility of creating cash-flow by raising the investment growth opportunity, and thus affects positively the credit rating.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.77.2-77.2
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• 2015

Galaxies are known to evolve passively in the cluster environment. Indeed, much evidence for HI stripping has been found in cluster galaxies to date, which is likely to be connected to their low star formation rate. What is still puzzling however, is that the molecular gas, which is believed to be more directly related to star formation, shows no significant difference in its fraction between the cluster population and the field galaxies. Therefore, HI stripping alone does not seem to be enough to fully understand how galaxies become passive in galaxy clusters. Intriguingly, our recent high resolution CO study of a subsample of Virgo spirals which are undergoing strong ICM pressure has revealed a highly disturbed molecular gas morphology and kinematics. The morphological and kinematical peculiarities in their CO data have many properties in common with those of HI gas in the sample, indicating that strong ICM pressure in fact can have impacts on dense gas deep inside of a galaxy. This implies that it is the molecular gas conditions rather than the molecular gas stripping which is more responsible for quenching of star formation in cluster galaxies. In this study, using multi transitions of 12CO and 13CO, we investigate the density and temperature distributions of CO gas of a Virgo spiral galaxy, NGC 4402 to probe the physical and chemical properties of molecular gas and their relations to star formation activities.