• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.1-8
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• 2023

Power transmission shafts in rotary wing aircraft use a hollow shaft to reduce weight. We can apply linear elastic fracture mechanics to predict crack propagation behavior. This paper predicted crack growth life of a hollow shaft with a circumferential through-type crack by finite element analysis. A 2D finite element model was created by applying a torsion and forming elements considering cracks. We defined the initial crack length and performed the finite element analysis by increasing the crack length to derive stress intensity factor at crack tips. We defined the length just prior to the stress intensity factor exceeding the fracture toughness as the crack limit length. We calculated the crack limit length using a handbook and numerically integrated the crack growth rate equation to derive growth life of each crack. The growth life of each crack was compared to verify the proposed finite element analysis method.

• Spatial Information Research
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• v.23 no.5
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• pp.41-52
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• 2015

MOLIT (Minister of Land, Infrastructure and Transport) authorized Indoor Spatial Information as Basic spatial information in 2013. It became a legal evidence for constructing and managing Indoor Spatial Information. Although it has a little advantage to utilize as service level that Indoor Spatial Information by laser scan or measurement, it has a lot of problems such as consuming many resources, requiring additional progresses for inputting Object Information. In conclusion, it is inefficient to utilize for the maintenance and domestic AEC/FM field. The purposes of this study is to output Indoor Spatial Information by operating IFC model which based on open BIM and to improve availability of Indoor Spatial Information with data visualization. The open-sources of IFC Exporter, a inner program of Revit (Autodesk Inc), is used to output Indoor Spatial Information. Directs 3D Library is also operated to visualize Indoor Spatial Information. It is possible to inter-operate between XML format and the objects of Indoor Spatial Information. It can be utilized in various field as well. For example COBie linkage in facility management, construction of geo-database using air-photogrammetry of UAV (Unmaned Areal Vehicle), the simulation of large-scale military operations and the simulation of large-scale evacuation. The method that is purposed in this study has outstanding advantages such as conformance with national spatial information policy, high level of interoperability as indoor spatial information objects based on IFC, convenience of editing information, light level of data and simplifying progress of producing information.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.1
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• pp.89-95
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• 2024

Nowadays, the competitiveness of a company depends on the ability of all organizational members to share and utilize the organizational knowledge accumulated by the organization. As if to prove this, the world is now focusing on ChetGPT service using generative AI technology based on LLM (Large Language Model). However, it is still difficult to apply the ChetGPT service to work because there are many hallucinogenic problems. To solve this problem, sLLM (Lightweight Large Language Model) technology is being proposed as an alternative. In order to construct sLLM, corporate data is essential. Corporate data is the organization's ERP data and the company's office document knowledge data preserved by the organization. ERP Data can be used by directly connecting to sLLM, but office documents are stored in file format and must be converted to data format to be used by connecting to sLLM. In addition, there are too many technical limitations to utilize office documents stored in file format as organizational knowledge information. This study proposes a method of storing office documents in DB format rather than file format, allowing companies to utilize already accumulated office documents as an organizational knowledge system, and providing office documents in data form to the company's SLLM. We aim to contribute to improving corporate competitiveness by combining AI technology.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.543-550
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• 2007

As an emerging materials in construction fields, FRP(fiber reinforced polymer) has been used in many area of civil engineering for its light weight and high strength. In this study we chose the 2nd Jindo-Bridge as a prototype, and evaluate effect of replacing steel components to FRP components through simplified 3D linear analysis. Static and modal analysis are done and the analysis results are compared with steel case analysis. From the static analysis results, the maximum stress of each component and maximum displacement of middle span are compared. Due to the reduction of deadload, the FRP structure causes less deflection than the original steel structure and from the reduced section (cable) analysis we confirmed the previous result. The occurrence wind velocity of flutter is compared by the frequency ratio.

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.69-75
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• 2012

The purpose of this paper is to study comparative analysis of cable dome structures by reinforcement effect with bracing and fabric. Tensegrity systems are stable structures which are reticulated spatial structures composed of compressive straight members, struts, and cables. Tensegrity structures need to be introduced to the initial stress for the self-equilibrated system to have a stable state. In this paper, the effect of reinforcement resisting the in-plan twisting is investigated for the Geiger-type and Zetlin-type models reinforced by bracing and fabric. The effect of initial imperfection is also studied because the structural instabilitity phenomenon of shell-like structures is very sensitive according to the initial condition. We study a more exact analysis concerning the structural instability of tensegrity structures using nonlinear analysis program. Then, two types of tensegrity models will be analysed and compared.

• Journal of Industrial Convergence
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• v.20 no.6
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• pp.37-45
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• 2022

With the development of the Internet of Things (IoT), related network infrastructures require new technologies to protect against threats such as external hacking. This study proposes an L-PBFT consensus algorithm that can protect IoT networks based on a blockchain consensus algorithm. We designed a blockchain (private) model suitable for small networks, tested processing performance for ultra-small/low-power IoT devices, and verified stability. As a result of performance analysis, L-PBFT proved that at least the number of nodes complies with the operation of the consensus algorithm(minimum 14%, maximum 29%) and establishes a trust network(separation of secure channels) different from existing security protocols. This study is a 4th industry convergence research and will be a foundation technology that will help develop IoT device security products in the future.

• Korean Journal of Remote Sensing
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• v.39 no.5_4
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• pp.1165-1172
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• 2023

Recently, Korea has declared carbon neutrality by 2050. The Korea Forest Service is promoting the precision and high technology of forest resource surveys. As such, the demand for forest resource management is increasing, and the need to build a digital twin of forest space is increasing. However, to date, digital twin has only built and provided virtual city services, which are city and nationwide digital twin environments. Three-dimensional digital twin services targeting forest space are not operated and provided. Therefore, in this study, we aimed to implement a forest digital twin environment to provide 3D forest spatial information services corresponding to vertical information such as tree-level height and thorax diameter. By lightweighting realistic 3D tree models and applying 3D Tiles, we confirmed the feasibility of implementing a forest digital twin environment for 3D forest spatial information services. Through continuous research, we plan to implement a forest digital twin that can deploy and service 3D tree models for trees nationwide, including street trees in urban areas. This is expected to enable the development of forest digital twin services for forest resource management.

• Composites Research
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• v.30 no.2
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• pp.158-164
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• 2017

The fiber metal laminate is a type of hybrid materials laminated thin metallic sheets with fiber reinforced plastic sheets. The laminate has been researched or applied in automotive and aerospace industries due to their outstanding impact absorbing performance in view of light weight aspect. Specially, the replacement of side-impact beam as the fiber reinforced plastic has been researched actively. The objective of this paper is the primitive investigation in the development of side-door impact beam using the fiber metal laminate. First, the three-point bending simulations were conducted to decide the shape of impact beam using the numerical analysis. Next, two cases impact beam (pure DP 980 and fiber metal laminate) were installed in the side-door, and then the bending tests (according to FMVSS 214S) were simulated using the numerical analysis. It is noted that the side-door impact beam can be replaced with the fiber metal laminate sufficiently based on the numerical analysis results.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.137-142
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• 2016

A two-step open system(TOS) was proposed to relay between a healing platform and a repository of personal health documents. TOS was designed by taking into consideration the pubsub service based on large scale connections to monitor a provider's access/request process for health documents in real time. TOS, however, uses WebSocket as a communication protocol in case of pubsub. Given the operational environment of low quality wireless networks for mobile devices that are user terminals in a healing platform, there is a need to add a messaging protocol to support QoS as well as a transmission protocol. As a light messaging protocol optimized for mobile devices, MQTT defines reliable messaging QoS to consider a wireless network situation of low speed/low quality. This study designed an MQTT protocol-based message broker to support QoS in case of large scale connections and pubsub by taking into consideration mobile devices that are user terminals in a healing platform. After designing a model between TOS and MQTT message broker, the study implemented a prototype based on the proposed design and compared it with its counterparts from previous studies based on the performance indicators in a load-test with the MQTT client tool.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.939-946
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• 2011

In thermal power generation companies, the recycling of refined ash (LOI < 6%) obtained from a PC-firing furnace is beneficial for the companies, e.g., it can be used for making lightweight aggregates. However, ash having a high LOI, which cannot be reused, is still buried in the ground. To obtain refined ash, the re-burning of high-LOI ash (LOI > 6%) in a PC-firing furnace can be an alternative. In this study, a numerical analysis was performed to demonstrate the effects of ash re-burning. An experimental constant value was decided by TGA (thermo-gravimetric analysis), and a DTF (drop-tube furnace) was used in the experiment for calculating the combustion of ash. On the basis of the trajectory of the moving particles of coal and ash, it was concluded that supplying ash near the burner, which is located high above the ground, is appropriate. On the basis of numerical results, it was concluded that an ash supply rate of 6 ton/h is suitable for combustion, without affecting the PC-firing boiler.