• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.7
• /
• pp.1986-2009
• /
• 2024

The integration of blockchain technology with the rapid growth of Internet of Things (IoT) devices has enabled secure and decentralised data exchange. However, security vulnerabilities and performance limitations remain significant challenges in IoT blockchain networks. This work proposes a novel approach that combines transaction representation and machine learning techniques to address these challenges. Various clustering techniques, including k-means, DBSCAN, Gaussian Mixture Models (GMM), and Hierarchical clustering, were employed to effectively group unlabelled transaction data based on their intrinsic characteristics. Anomaly transaction prediction models based on classifiers were then developed using the labelled data. Performance metrics such as accuracy, precision, recall, and F1-measure were used to identify the minority class representing specious transactions or security threats. The classifiers were also evaluated on their performance using balanced and unbalanced data. Compared to unbalanced data, balanced data resulted in an overall average improvement of approximately 15.85% in accuracy, 88.76% in precision, 60% in recall, and 74.36% in F1-score. This demonstrates the effectiveness of each classifier as a robust classifier with consistently better predictive performance across various evaluation metrics. Moreover, the k-means and GMM clustering techniques outperformed other techniques in identifying security threats, underscoring the importance of appropriate feature selection and clustering methods. The findings have practical implications for reinforcing security and efficiency in real-world IoT blockchain networks, paving the way for future investigations and advancements.

• Nuclear Engineering and Technology
• /
• v.56 no.7
• /
• pp.2690-2697
• /
• 2024

With advancements in machine learning technologies, artificial neural networks (ANNs) are being widely used to improve the performance of gamma-ray spectroscopy based on NaI(Tl) scintillation detectors. Typically, the performance of ANNs is evaluated using test datasets composed of actual spectra. However, the generation of such test datasets encompassing a wide range of actual spectra representing various scenarios often proves inefficient and time-consuming. Thus, instead of measuring actual spectra, we generated virtual spectra with diverse spectral features by sampling from categorical distribution functions derived from the base spectra of six radioactive isotopes: ⁵⁴Mn, ⁵⁷Co, ⁶⁰Co, ¹³⁴Cs, ¹³⁷Cs, and ²⁴¹Am. For practical applications, we determined the optimum counting time (OCT) as the point at which the change in the Kullback-Leibler divergence (ΔKLDV) values between the synthetic spectra used for training the ANN and the virtual spectra approaches zero. The accuracies of the actual spectra were significantly improved when measured up to their respective OCTs. The outcomes demonstrated that the proposed method can effectively determine the OCTs for gamma-ray spectroscopy based on ANNs without the need to measure actual spectra.

• Proceedings of the Technology Innovation Conference
• /
• 1996.12a
• /
• pp.265-295
• /
• 1996

This paper investigates empirically the relationship between various business portfolio properties (particularly technological properties) and chaebol′s performance using data on the 50 largest chaebols in Korea. In addition to the traditional indexes to measure diversification such as entropy index we calculated inter-industry technological similarity using R&D expenditure data by industry and 1990 Input-output Table in Korea, and obtained chaebol-level technological relatedness and internal transaction proportion from chaebols′business profile, inter-industry technological similarity and 1990 input-output table. We applied factor analysis on 13 business portfolio property indexes and showed that they could be grouped into 3 dimensions, diversification scope, inter-business relatedness and degree of vertical integration. In this paper, using 50 largest chaebols′financial data (1989-1994), we analyzed empirically the effect of business portfolio properties on ROS (Return On Sales) which is conventional index for firm performance and on TFP(Total Factor Productivity) growth which is a pure measure of firm performance. To utilize the advantage of panel data, FEM(Fixed Effect Model) and REM(Random Effect Model) were used. The empirical result shows that the entropy index as a measurement of inter-business relatedness is not significant but technological relatedness index is significant. OLS estimates on pooled data were considerably different from FEM or REM estimates on panel data. By introducing interaction effect among the three variables for business portfolio properties, we obtained three findings. First, only VI (Vertical integration) has a significant positive correlation with ROS. Second, when using TFP growth as an dependent variable, both TR(Technological Relatedness) and f[ are significant and positively related to the deepened variable. Third, the interaction term between TR and VI is significant and negatively affects TFP growth, meaning that TR and VI are substitutes. These results suggest strategic directions on restructuring business portfolio. As VI is increased, chaebols will get more profit. A higher level of either TR or W will increase TFP growth rate. but increase in both TR and VI will have a negative effect on TFP growth. To summarize, certain business portfolio properties such as VI and TR can be considered "resources" themselves since they can affect profit rate and productivity growth. VI and TR have a synergy effect of change in profit rate and productivity growth. VI increases ROS and productivity growth, while TR increases productivity growth representing a technological synergy effect.

• Strategy21
• /
• s.31
• /
• pp.5-26
• /
• 2013

The South Korean society has experienced many changes since the sinking of ROKS Cheonan. The government reviewed its defense posture and adopted the 5·24 Measure in its relations with North Korea. As a result, the people of South Korea became more conscious of security situations on the Korean peninsula while North Korea's economy suffered badly. Meanwhile, the South Korean government has taken a flexible stance toward North Korea in terms of exchange and cooperation since September 2011. The flexible stance was to manage inter-Korea relations in a stable manner and relieve the hardships of the North Korean people while preserving the spirits and purposes of the 5·24 Measure. The UN Security Council adopted twenty-six resolutions and statements on North Korea since June 25, 1950. They include thirteen U.N. Security Council resolutions including those concerning nuclear weapons or missile programs, nine Presidential statements, and four press statements. Resolution 82, the first U.N. resolution on North Korea, came when the Korean War broke out. Resolution 825, the first one related to nuclear or missile programs, was adopted in response to North Korea's withdrawal from the NPT. Apart from these U.N. resolutions, the United States has imposed separate sanctions against North Korea. North Korea's nuclear weapons program can be considered in comparison with that of Iran in terms of the consequences they create for the regional security. The Security Council has adopted six resolutions on Iran so far. One should note that the resolutions on Iran have had much stronger sanctions compared to those imposed on North Korea. That is, while the North Korea case may be viewed as a more serious threat to international security from the perspective of nuclear weapons development or proliferation, tougher sanctions have been placed on Iran. There are two approaches that South Korea should take in addressing the related issues. First, we should aim to reduce the gap between sanctions imposed on Iran and North Korea. It is difficult to understand that a country with more serious problems is rewarded with lighter sanctions. We should take measures through the Security Council Sanctions Committee to make individuals and groups in North Korea that play a central role in developing nuclear weapons and missiles subject to additional sanctions. Second, we have to change. Other countries in the international community have become tired of North Korea's nuclear issue and now they look to South Korea for initiative. We should correctly understand this current situation and play a leading role within our capacity. Knowingly and unknowingly, the notion that the North Korean nuclear issue may be left to South Korea has been spread around the international community. Although the situation is grave, we should try to open a new horizon in ushering in the unification era by taking the initiative with confidence that there is a looming hope ahead of us. For these tasks, we should stop thinking in the old way that has been ossified for the last two decades. We should not be pushed around by neighboring great powers in dealing with North Korea related issues anymore; we should take the initiative with resolution that we will play our role at the center of four great powers and with confidence that we can do it. Based on the confidence that the Republic of Korea has become a country with enough capacity to take the initiative, we should establish a 'National Grand Strategy' representing South Korea's strategic vision that the unification is the ultimate solution to the problems related to North Korea's nuclear weapons program.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.3
• /
• pp.116-124
• /
• 2011

In this study, a new method to estimate the bridge deflection is developed by using Wireless Tilt Sensor. Most of evaluations of structural integrity, it is very important to measure the geometric profile, which is a major factor representing the global behavior of civil structure, especially bridges. In the past, Because of the lack of appropriate methods to measure the deflection curve of bridges on site, the measurement of deflection had been done restrictly within just a few discrete points along the bridge. Also the measurement point could be limited to locations installed with displacement transducers. So, in this study, the deflection of the structure was measured by wireless tilt sensor instead of LVDT(Linear Variable Differential Transformer). Angle change of tilt sensor shows structural behavior by the change of the resistor values which is presented to voltage. Moreover, the maximum deflection was calculated by changing the deflection angle which was calculated as V(measured voltage) ${\times}$F(factor) to deflection. The experimental tests were carried out to verify the developed deflection estimation techniques. Because the base of tilt measuring is the gravity, uniform measurement is possible independent of a measuring point. Also, measuring values were showed very high accuracy.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.9 no.2
• /
• pp.137-144
• /
• 2015

In this paper, we present an inertial sensor-based gait analysis system to measure and analyze lower-limb movements. We developed an integral AHRS(Attitude Heading Reference System) using a combination of rate gyroscope, accelerometer and magnetometer sensor signals. Several AHRS modules mounted on segments of the patient's body provide the quaternions representing the patient segments's orientation in space. And a method is also proposed for calculating three-dimensional inter-segment joint angle which is an important bio-mechanical measure for a variety of applications related to rehabilitation. To evaluate the performance of our AHRS module, the Vicon motion capture system, which offers millimeter resolution of 3D spatial displacements and orientations, is used as a reference. The evaluation resulted in a RMSE(Root Mean Square Error) of 1.08 and 1.72 degree in yaw and pitch angle. In order to evaluate the performance of our the gait analysis system, we compared the joint angle for the hip, knee and ankle with those provided by Vicon system. The result shows that our system will provide an in-depth insight into the effectiveness, appropriate level of care, and feedback of the rehabilitation process by performing real-time limb or gait analysis during the post-stroke recovery.

• Journal of East Asia Management
• /
• v.4 no.1
• /
• pp.23-51
• /
• 2023

We investigate whether the association between management overconfident tone and the level of audit effort measured by audit fees and hours differs depending on the level of earnings management. Prior studies suggest that firms led by overconfident managers are likely to initiate risky investments, report low quality financial statements, and have material weaknesses in internal control system. These characteristics, combined together, result in higher audit risk. At the same time, auditors assess audit risk based on the quality of financial reporting, measured by level of earnings management. As a result, the assess audit risk is likely to reflect the combined effect of management overconfidence and the level of earnings management. In this paper, we investigate whether auditors differentiate the effects of real earnings management (REM) and accrual-based earnings management (AEM) when they assess the audit risk related management overconfident. Using the CEO's letter published in 2018, we measure the CEO's tone representing the degree of overconfidence (i.e., activity). Based on this measure, we find that the positive association between managerial overconfident tone and audit effort is more pronounced as the level of REM is higher. However, we find that the baseline association does not vary depending on the level of AEM. These results suggest that auditors consider the managerial overconfident severer when such characteristic accompany the higher level of REM, which can be outcome of aggressive business decisions possibly leading to the higher audit risks. We further find that these results are stronger for Big 4 auditors and continuing auditors. This paper contributes to the literature and practice as follows. First, we provide contextual evidence on how auditors reflect managerial characteristics in the audit process by documenting that auditors actively increase their audit efforts only when overconfident managerial characteristics are highly likely to lead to audit risk. This result suggests that auditors conduct external auditing considering both the efficiency and effectiveness of the audit process. Second, we suggest that auditors use information obtained from a wide range of sources to identify audit risks. Our results provide evidence of how the auditing standards, which do not provide detailed guidelines for audit risk assessment, are being applied in practice. Finally, our results also enhance the understanding of how audit fees are determined. Combined with the studies related to audit pricing, we provide the important reference for discussion between the auditor and the auditee about the audit fee that has created acute tension after the enforcement of the new External Audit Act.

• Journal of Korean Society of Forest Science
• /
• v.113 no.3
• /
• pp.349-360
• /
• 2024

This study aimed to analyze the main forest environmental factors affecting the discernment of slow-moving landslide-prone areas in the Republic of Korea, based on data from a detailed landslide survey conducted from 2019 to 2021. Field survey data from 256 sites were collected covering 29 forest environmental factors in seven categories, including geology, soil, and topography. The analysis was conducted using the Random Forest model (AUC = 0.910) and XGBoost model (Accuracy = 0.808, Kappa = 0.594, F1 - measure = 0.494), which were evaluated as having high classification accuracy during the machine learning model development process. Consequently, factors with a high mean decrease Gini (MDG), representing classification importance, were identified as the presence of cracks (average MDG of both models: 22.1), peak elevation (14.8), and the presence of steps (7.0), indicating that these were significant factors in determining slow-moving landslide-prone areas. The presence of cracks and steps aligned well with the characteristics of slow-moving landslides, suggesting that their importance should be emphasized in future detailed landslide surveys. However, the influence of the peak elevation was considered somewhat overestimated due to the characteristics of the input data used in the analysis. These findings are expected to further improve the accuracy and efficiency of final judgments in detailed landslide surveys.

• Journal of the Korean Society for Library and Information Science
• /
• v.4
• /
• pp.43-71
• /
• 1975

Operations research has developed rapidly since its origins in World War II. Practitioners of O. R. have contributed to almost every aspect of government and business. More recently, a number of operations researchers have turned their attention to library and information systems, and the author believes that significant research has resulted. It is the purpose of this essay to introduce the library audience to some of these accomplishments, to present some of the author's hypotheses on the subject of library management to which he belives O. R. has great potential, and to suggest some future research directions. Some problem areas in librianship where O. R. may play a part have been discussed and are summarized below. (1) Library location. It is usually necessary to make balance between accessibility and cost In location problems. Many mathematical methods are available for identifying the optimal locations once the balance between these two criteria has been decided. The major difficulties lie in relating cost to size and in taking future change into account when discriminating possible solutions. (2) Planning new facilities. Standard approaches to using mathematical models for simple investment decisions are well established. If the problem is one of choosing the most economical way of achieving a certain objective, one may compare th althenatives by using one of the discounted cash flow techniques. In other situations it may be necessary to use of cost-benefit approach. (3) Allocating library resources. In order to allocate the resources to best advantage the librarian needs to know how the effectiveness of the services he offers depends on the way he puts his resources. The O. R. approach to the problems is to construct a model representing effectiveness as a mathematical function of levels of different inputs(e.g., numbers of people in different jobs, acquisitions of different types, physical resources). (4) Long term planning. Resource allocation problems are generally concerned with up to one and a half years ahead. The longer term certainly offers both greater freedom of action and greater uncertainty. Thus it is difficult to generalize about long term planning problems. In other fields, however, O. R. has made a significant contribution to long range planning and it is likely to have one to make in librarianship as well. (5) Public relations. It is generally accepted that actual and potential users are too ignorant both of the range of library services provided and of how to make use of them. How should services be brought to the attention of potential users? The answer seems to lie in obtaining empirical evidence by controlled experiments in which a group of libraries participated. (6) Acquisition policy. In comparing alternative policies for acquisition of materials one needs to know the implications of each service which depends on the stock. Second is the relative importance to be ascribed to each service for each class of user. By reducing the level of the first, formal models will allow the librarian to concentrate his attention upon the value judgements which will be necessary for the second. (7) Loan policy. The approach to choosing between loan policies is much the same as the previous approach. (8) Manpower planning. For large library systems one should consider constructing models which will permit the skills necessary in the future with predictions of the skills that will be available, so as to allow informed decisions. (9) Management information system for libraries. A great deal of data can be available in libraries as a by-product of all recording activities. It is particularly tempting when procedures are computerized to make summary statistics available as a management information system. The values of information to particular decisions that may have to be taken future is best assessed in terms of a model of the relevant problem. (10) Management gaming. One of the most common uses of a management game is as a means of developing staff's to take decisions. The value of such exercises depends upon the validity of the computerized model. If the model were sufficiently simple to take the form of a mathematical equation, decision-makers would probably able to learn adequately from a graph. More complex situations require simulation models. (11) Diagnostics tools. Libraries are sufficiently complex systems that it would be useful to have available simple means of telling whether performance could be regarded as satisfactory which, if it could not, would also provide pointers to what was wrong. (12) Data banks. It would appear to be worth considering establishing a bank for certain types of data. It certain items on questionnaires were to take a standard form, a greater pool of data would de available for various analysis. (13) Effectiveness measures. The meaning of a library performance measure is not readily interpreted. Each measure must itself be assessed in relation to the corresponding measures for earlier periods of time and a standard measure that may be a corresponding measure in another library, the 'norm', the 'best practice', or user expectations.

• The Journal of Information Systems
• /
• v.11 no.2
• /
• pp.1-25
• /
• 2002

This study is for the purpose of understanding User Satisfaction of Accounting Information System more closely by means of perceiving relations between Internal Controls and Quality. That is, this study is to assess Internal Controls and Quality and to connect those with User Satisfaction. This thesis is for the substantial study on whether Information Quality, System Quality, and Service Quality influenced by Internal Controls of Accounting Information System have an effect on User Satisfaction, when Internal Controls of Accounting Information System is good, The following hypothesis was made to achieve this purpose. First, Internal Controls will have an positive influence on Quality. Second, Qualify will positively affect User Satisfaction. Third, Internal Controls will positively Influence User Satisfaction. Fourth, Internal Controls will have a positive effect on User Satisfaction through Quality For the survey sample, this study gathered data on someone engaged in companies or organizations which have computer offices, and groups were differentiated between general staff and someone in charge of the computer office, and each group had different questions. In general, 622 of questions were distributed and 200 of the final valid samples were used for the substantial analysis. As the result of the study, the relations between Internal Controls and Quality are statistically significant. The relations between Quality and User Satisfaction ire also statistically significant. But the relations between Internal Controls and User Satisfaction are not statistically significant. Path Analysis was implemented to analyze the hypothesis on whether Internal Controls have an influence on User Satisfaction through Quality. When the result of analysis with Lisrel 8.5 was examined, index numbers(GFI, AGFI, RMR) representing the suitability of the model were enough to be taken and it is showed that there is the suitability of the model. Internal Controls of Accounting Information System can't have an influence on User Satisfaction with Quality. As the above hypothesis was rejected, Through Path Analysis, this study examined the influence which relations between Internal Controls and Quality, factors of User Satisfaction, have on User Satisfaction, and is very meaningful in terms of the first trial. And on the point of time when there are little studies on the effect analyses between Internal Controls and Quality, this study would be the promoter for the future. The limitation on this study is to analyze only mutual effects between factors by choosing Internal Controls, Quality, and User Satisfaction as survey variables. The study which measure items with precision which are related to each variable and understand measurement factors clearly should be implemented.