• International Journal of Internet, Broadcasting and Communication
• /
• v.14 no.1
• /
• pp.10-18
• /
• 2022

Since High Sierra, APFS has been used as the main file system. It is a well-established file system that has been used stably thus far. From the perspective of digital forensics, there are still many areas to be investigated. Apple File System Reference is provided to the apple developer site, but it is not satisfactory to fully analyze APFS. Researchers know more about the structure of APFS than before, but they have not yet fully analyzed its structure to a perfect level about it. In this paper, we develop APFS object identification tool for digital forensics. The most basic and essential object identification and analysis of the APFS filesystem will be conducted with the tool. The analysis in this study serves as the background for an analysis of the checkpoint operation principle and structure, including the more complex B-tree structure of APFS. There are several options for the developed tool, but the results of two use cases will be shown here. Based on the implemented tool, it is hoped that more functions will be added to make APFS a useful tool for faster and more accurate analyses.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.10
• /
• pp.109-114
• /
• 2004

A combined optimal design problem of structural and control systems is discussed by taking a 3-D flexible structure as an object. We consider a minimum weight design problem for structural system and disturbance suppression problem for the control system. The conditions for the existence of controller are expressed in terms of linear matrix inequalities (LMI). By minimizing the linear sum of the normalized structural objective function and control objective function, it is possible to make optimal design by which the balance of the structural weight and the control performance is taken. We showed in this paper the validity of combined optimal design of structural and control systems.

• Coupled systems mechanics
• /
• v.12 no.5
• /
• pp.461-479
• /
• 2023

The paper deals with the finite element modelling of the free vibration and structural behavior of a particular four-floor reinforced concrete structure subjected to static equivalent seismic loads and supported by a shallow foundation system called SNSF (Spider Net System Footing). The two FE models are a simple 2D Matlab model and a detailed 3D model based on solid elastic elements using Altairworks (Hypermesh and Optistruct). Both models can simulate the soil structure interaction. We concentrate on the behavior of a representative cell involving two columns on five levels. The influence of the boundary conditions on the external vertical planes of the domain are duly studied. The Matlab model appears relevant for a primary estimation of frequencies and stiffness of the whole structure under vertical and lateral loads.

• Journal of IKEEE
• /
• v.23 no.1
• /
• pp.112-119
• /
• 2019

In this paper, we propose a deep learning structure suitable for embedded system. The flame detection process of the proposed deep learning structure consists of four steps : flame area detection using flame color model, flame image classification using deep learning structure for flame color specialization, $N{\times}N$ cell separation in detected flame area, flame image classification using deep learning structure for flame shape specialization. First, only the color of the flame is extracted from the input image and then labeled to detect the flame area. Second, area of flame detected is the input of a deep learning structure specialized in flame color and is classified as flame image only if the probability of flame class at the output is greater than 75%. Third, divide the detected flame region of the images classified as flame images less than 75% in the preceding section into $N{\times}N$ units. Fourthly, small cells divided into $N{\times}N$ units are inserted into the input of a deep learning structure specialized to the shape of the flame and each cell is judged to be flame proof and classified as flame images if more than 50% of cells are classified as flame images. To verify the effectiveness of the proposed deep learning structure, we experimented with a flame database of ImageNet. Experimental results show that the proposed deep learning structure has an average resource occupancy rate of 29.86% and an 8 second fast flame detection time. The flame detection rate averaged 0.95% lower compared to the existing deep learning structure, but this was the result of light construction of the deep learning structure for application to embedded systems. Therefore, the deep learning structure for flame detection proposed in this paper has been proved suitable for the application of embedded system.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.11
• /
• pp.135-146
• /
• 1997

This paper describes fault diagnosis method in complex system with hierachical structure similar to human body structure. Complex system is divided into unit, item and component. For diagnosing this hierarchical complex system, it is necessary to implement special neural network. Fault diagnosis system can forecast faults in a system and decide from current machine state signal information. Comparing with other diagnosis system for single fault, the developed system deals with multiple fault diagnosis comprising Hierarchical Neural Network(HNN). HNN consists of four level neural network, first level for item fault symptom classification, second level for item fault diagnosis, third level for component symptom classification, forth level for component fault diagnosis. UNIX IPC(Inter Process Communication) is used for implementing HNN wiht multitasking and message transfer between processes in SUN workstation with X-Windows(Motif). We tested HNN at four units, seven items per unit, seven components per item in a complex system. Each one neural newtork operate as a separate process in HNN. The message queue take charge of information exdhange and cooperation between each neural network.

• Earthquakes and Structures
• /
• v.4 no.1
• /
• pp.63-84
• /
• 2013

A semi-active mass damping (SMD) system with magnetorheological (MR) dampers focusing on low- and mid-rise buildings is proposed in this paper. The main purpose of this study is to integrate the reliable characteristics of the traditional tuned mass damper (TMD) and the superior performance of the active mass damper (AMD) to the new system. In addition, the commonly seen solution of deploying dense seismic dampers throughout the structure nowadays to protect the main structure is also expected to switch to the developed SMD system on the roof with a similar reduction performance. In order to demonstrate this concept, a full-size three-story steel building representing a typical mid-rise building was used as the benchmark structure to verify its performance in real life. A numerical model with the interpolation technique integrated was first established to accurately predict the behavior of the MR dampers. The success of the method was proven through a performance test of the designated MR damper used in this research. With the support of the MR damper model, a specific control algorithm using a continuous-optimal control concept was then developed to protect the main structure while the response of the semi-active mass damper is discarded. The theoretical analysis and the experimental verification from a shaking table test both demonstrated the superior mitigation ability of the method. The proposed SMD system has been demonstrated to be readily implemented in practice.

• Structural Engineering and Mechanics
• /
• v.20 no.2
• /
• pp.191-207
• /
• 2005

Time delay exists inevitably in active control, which may not only degrade the system performance but also render instability to the dynamic system. In this paper, a novel active controller is developed to solve the time delay problem in flexible structures. By using the independent modal space control method, the differential equation of the controlled mode with time delay is obtained from the time-delay system dynamics. Then it is discretized and changed into a first-order difference equation without any explicit time delay by augmenting the state variables. The modal controller is derived based on the augmented system using the discrete variable structure control method. The switching surface is determined by minimizing a discrete quadratic performance index. The modal coordinate is extracted from sensor measurements and the actuator control force is converted from the modal one. Since the time delay is explicitly included throughout the entire controller design without any approximation, the system performance and stability are guaranteed. Numerical simulations show that the proposed controller is feasible and effective in active vibration control of dynamic systems with time delay. If the time delay is not explicitly included in the controller design, instability may occur.

• World Technopolis Review
• /
• v.4 no.2
• /
• pp.46-61
• /
• 2015

There is an implicit assumption in most regional innovation policy studies that once a policy has been made the policy will be implemented. This assumption is not valid for regional innovation policies formulated in many countries. This assumption rests upon certain political and organization conditions. It is frequently said that regional innovation system in Korea is one of the successful cases because of properly established institution for the implementation of innovation policies. The components of institution for innovation are defined in this article. For the analysis of institution for regional innovation system in Korea, three aspects such as organization, policies & programs, and governance structure were taken into account. Institution for regional innovation system in Korea is analyzed with three aspects: (1) organization for policy implementation, (2) innovation policy, and (3) governance structure. Firstly, organizations for innovation in Korea are composed of three categories such as organizations for policy formulation, organizations for policy implementation and agencies for coordination. Secondly, there are two categories of policies for innovation: (1) policies for the enhancement of national competitiveness and policies for the regional innovation capacity building, and (2) policies for fostering manpower and policy for regulatory reform. Thirdly, innovation governance in Korea is composed of three layer structure: (1) top level governance which is composed of two committee, three ministries and two agencies, (2) local level governance such as one innovation related offices and one center for regulatory reform, and (3) one category of agency for coordination as a regional platform.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2003.09a
• /
• pp.571-574
• /
• 2003

This research is aimed to automate the generating process of the database from paper based table forms like this work. The registration table has so complicate table structures, ana in this research we used the registration tables as an example of general table structure understanding. We propose a table structure understanding system for some table types, and it has some steps. The first step is that the document images on paper are read from the image scanner. The second step is that a document image segments into some tables. In the third step, the character strings is extracted using image processing technology and the property of the character strings is determined. And the structured database is generated automatically. The proposed system consists of two systems. "Master document generation system" is used for the table form definition, and it doesn′t include the handwritten characters. "Structure analysis system for complete d table" is used for the written form, and it analyzes the table form filled in the handwritten character. We implemented the system using MS Visual C＋＋ on Windows, and it can get the correct extraction rate 98％ among 51 registration tables written by the different students.

• Journal of Mechanical Science and Technology
• /
• v.16 no.10
• /
• pp.1229-1238
• /
• 2002

In this paper, a method to obtain the sensitivity of eigenvalues and the random responses of the structure with uncertain parameters is proposed. The concept of the proposed method is that the perturbed equation of each uncertain substructure is obtained using the finite element method, and the perturbed equation of the overall structure is obtained using the mode synthesis method. By this way, the reduced order perturbed equation of the uncertain system can be obtained. And the response of the uncertain system is obtained using probability method. As a numerical example, a simple piping system is considered as an example structure. The damping and spring constants of the support are considered as the uncertain parameters. Then the variations of the eigenvalues, the correlation function and the power spectral density function of the responses are calculated. As a result, the proposed method is considered to be useful technique to analyze the sensitivities of eigenvalues and random response against random excitation in terms of the accuracy and the calculation time.