• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.9
• /
• pp.663-670
• /
• 2020

A study on mechanical property characterization and modeling technique was carried out to approximate the behaviour of structures with 2.5D C/SiC material. Several tensile tests were performed to analyze the behaviour characteristics of the 2.5D C/SiC material and elastic property was characterized by applying a mathematical homogenization and a modified rule of mixture. SiC matrix representing the elasto-plastic behavior approximates as a bilinear function. Then the equivalent yield strength and equivalent plastic stiffness were calculated by minimizing errors in experiment and approximation. RVE(Representative Volume Element)was defined from the fiber and matrix configuration of 2.5D C/SiC and a process of calculating the effective stiffness matrix by applying the modified rule of mixture to RVE was implemented in the ABAQUS User-defined subroutine. Finite element analysis was performed by applying the mechanical properties of fiber and matrix calculated based on the proposed process, and the results were in good agreement with the experimental results.

• Journal of Trauma and Injury
• /
• v.24 no.1
• /
• pp.12-17
• /
• 2011

Purpose: A rib fracture secondary to blunt thoracic trauma continues to be an important injury with significant complications. Unfortunately, there are no definite treatment guidelines for severe multiple rib fractures. The purpose of this study was to evaluate the result of early operative stabilization and to find the risk factors of surgical fixation in patients with bilateral multiple rib fractures or flail segments. Methods: From December 2005 to December 2008, the medical records of all patients who underwent operative stabilization of ribs for severe multiple rib fractures were reviewed. We investigated patients' demographics, preoperative comorbidities, underlying lung disease, chest trauma, other associated injuries, number of surgical rib fixation, combined operations, perioperative ventilator support, and postoperative complications to find the factors affecting the mortality after surgical treatment. Results: The mean age of the 96 patients who underwent surgical stabilization for bilateral multiple rib fractures or flail segments was 56.7 years (range: 22 to 82 years), and the male-to-female ratio was 3.6:1. Among the 96 patients, 16 patients (16.7%) underwent reoperation under general or epidural anesthesia due to remaining fracture with severe displacement. The surgical mortality of severe multiple rib fractures was 8.3% (8/96), 7 of those 8 patients (87.5%) dying from acute respiratory distress syndrome or sepsis. And the other one patient expired from acute myocardial infarction. The risk factors affecting mortality were liver cirrhosis, chronic obstructive pulmonary disease, concomitant severe head or abdominal injuries, perioperative ventilator care, postoperative bleeding or pneumonia, and tracheostomy. However, age, number of fractured ribs, lung parenchymal injury, pulmonary contusion and combined operations were not significantly related to mortality. Conclusion: In the present study, surgical fixation of ribs could be carried out as a first-line therapeutic option for bilateral rib fractures or flail segments without significant complications if the risk factors associated with mortality were carefully considered. Furthermore, with a view of restoring pulmonary function, as well as chest wall configuration, early operative stabilization of the ribs is more helpful than conventional treatment for patients with severe multiple rib fractures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.2
• /
• pp.611-618
• /
• 2020

The reliability of the results of LCC analysis is determined by accurate analytical procedures and energy data from which the uncertainty is removed. Until now, systems that can automatically measure these energy data and produce databases have not been commercialized. Therefore this paper proposes a concept model of an S-LCC platform that can automatically collect and analyze electric energy consumption data of equipment systems using the IOT, which is the core tool in the Fourth Industrial Revolution and operates the equipment system efficiently using the analyzed results. The proposed concept model was developed by the convergence of existing BLCS and IOT and was comprised of five modules: Facility Control Module, LCC Analysis Module, Energy Consumption Control Module, Efficiency Analysis Module, and Maintenance Standard Reestablishment Module. Using the results of LCC analysis deduced from this system, the deterioration condition of an equipment system can be identified in real-time. The results can be used as the baseline data to re-establish standards for the maintenance factor, replacement frequency, and lifetime of existing equipment, and establish new maintenance standards for new equipment. If the S-LCC platform is established, it would increase the reliability of LCC analysis, reduce the labor force for entering data and improve accuracy, and would also change disregarded data into big data with high potential.

• Journal of the Korean Society of Combustion
• /
• v.18 no.4
• /
• pp.37-43
• /
• 2013

The effects of preferential diffusion of hydrogen in interacting counterflow $H_2$-air and CO-air premixed flames were investigated numerically. The global strain rate was varied in the range $30-5917s^{-1}$, where the upper bound of this range corresponds to the flame-stretch limit. Preferential diffusion of hydrogen was studied by comparing flame structures for a mixed average diffusivity with those where the diffusivities of H, $H_2$ and $N_2$ were assumed to be equal. Flame stability diagrams are presented, which show the mapping of the limits of the concentrations of $H_2$ and CO as a function of the strain rate. The main oxidation route for CO is $CO+O_2{\rightarrow}CO_2+O$, which is characterized by relatively slow chemical kinetics; however, a much faster route, namely $CO+OH{\rightarrow}CO_2+H$, can be significant, provided that hydrogen from the $H_2$-air flame is penetrated and then participates in the CO-oxidation. This modifies the flame characteristics in the downstream interaction between the $H_2$-air and CO-air flames, and can cause the interaction characteristics at the rich and lean extinction boundaries not to depend on the Lewis number of the deficient reactant, but rather to depend on chemical interaction between the two flames. Such anomalous behaviors include a partial opening of the upper lean extinction boundary in the interaction between a lean $H_2$-air flame and a lean CO-air flame, as well as the formation of two islands of flame sustainability in a partially premixed configuration with a rich $H_2$-air flame and a lean CO-air flame. At large strain rates, there are two islands where the flame can survive, depending on the nature of the interaction between the two flames. Furthermore, the preferential diffusion of hydrogen extends both the lean and the rich extinction boundaries.

• Journal of Microbiology and Biotechnology
• /
• v.17 no.3
• /
• pp.496-510
• /
• 2007

This paper describes the use of a discrete mathematical model to represent the basic mechanisms of regulation of the bacteria E. coli in batch fermentation. The specific phenomena studied were the changes in metabolism and genetic regulation when the bacteria use three different carbon substrates (glucose, glycerol, and acetate). The model correctly predicts the behavior of E. coli vis-a-vis substrate mixtures. In a mixture of glucose, glycerol, and acetate, it prefers glucose, then glycerol, and finally acetate. The model included 67 nodes; 28 were genes, 20 enzymes, and 19 regulators/biochemical compounds. The model represents both the genetic regulation and metabolic networks in an integrated form, which is how they function biologically. This is one of the first attempts to include both of these networks in one model. Previously, discrete mathematical models were used only to describe genetic regulation networks. The study of the network dynamics generated 8 $(2^3)$ fixed points, one for each nutrient configuration (substrate mixture) in the medium. The fixed points of the discrete model reflect the phenotypes described. Gene expression and the patterns of the metabolic fluxes generated are described accurately. The activation of the gene regulation network depends basically on the presence of glucose and glycerol. The model predicts the behavior when mixed carbon sources are utilized as well as when there is no carbon source present. Fictitious jokers (Joker1, Joker2, and Repressor SdhC) had to be created to control 12 genes whose regulation mechanism is unknown, since glycerol and glucose do not act directly on the genes. The approach presented in this paper is particularly useful to investigate potential unknown gene regulation mechanisms; such a novel approach can also be used to describe other gene regulation situations such as the comparison between non-recombinant and recombinant yeast strain, producing recombinant proteins, presently under investigation in our group.

• Journal of the Korean Applied Science and Technology
• /
• v.37 no.4
• /
• pp.848-859
• /
• 2020

This study selected 42 domestic preceded literatures that applied exercise programs to the elderly for the past 10 years from 2010 to the first half of 2020 to analyze the characteristics of preceded research, applied period of exercise programs, configuration of exercise programs, and effectiveness of exercise programs on elderly depression, and the conclusion is as follows. First, the majority of the subjects were female and male/female elderly people in the preceding literature, and it appeared that there were no male subjects alone for any of the studies showed. The majority of the ages were over 65 years old, and the number of subjects was 50 or less. In the group, preceded research with exercise/control groups was mostly predominant, and the participated institutions and regions accounted for the majority of the residential area/public institutions and sanatorium. Second, the period of the exercise program was mostly applied for more than 12 weeks, and the frequency of exercise per week was 1-2 times and 3-4 times. Most of the preceding literature was applied with a 60-minute exercise program during the one-time exercise period. Third, most of the contents of the exercise program consisted of a aerobic exercise alone and combination of aerobic·anaerobic exercise. Fourth, it was confirmed that the effects of exercise programs were effective in physical fitness factors as well as in depression and cognitive function.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.7
• /
• pp.26-32
• /
• 2017

VOD (Video-On Demand) Services are considered to be one of the most successful data broadcasting services, along with Electronic Program Guides (EPGs). In particular, VOD services provide supplementary revenue for broadcasting companies in addition to the existing subscription fees and advertisement-based revenue. Therefore, each broadcasting company has developed its own VOD service and constantly seeks to improve it. This leads to the development of new VOD services, so developers are considering ways to effectively handle the frequent development needs. In this background, we conducted underlying research to apply the feature-oriented analysis model to the development of VOD services. The feature-oriented analysis model used in this study is the Feature-Oriented Domain Analysis (FODA) one developed by SEI of Carnegie Mellon University. FODA provides a tool for specifying the feature model of a software domain, based on which the developers can determine the configuration of the software with the customers. This study developed a feature model of the VOD service domain and devised the functionalities and test cases in an integrated manner with the feature model. Additionally, we proposed a VOD service development process utilizing the feature model, function specification, and test cases.

• Journal of KIISE:Information Networking
• /
• v.34 no.3
• /
• pp.226-238
• /
• 2007

In this paper, we present a novel fully distributed topology control protocol that can construct the multiple-ring topology of Minimal Connected Dominating Set (MCDS) as the transport backbone for mobile ad hoc networks. It makes a topology from the minimal nodes that are chosen from all the nodes, and the constructed topology is comprised of the minimal physical links while preserving connectivity. This topology reduces the interference. The all nodes work as the nodes of the distributed parallel Boltzmann machine, of which the objective function is consisted of two Boltzmann factors: the link degree and the connection domination degree. To define these Boltzmann factors, we extend the Connected Dominating Set into a fuzzy set, and also define the fuzzy set of nodes by which the multiple-ring topology can be constructed. To construct the transport backbone of the mobile ad hoc network, the proposed protocol chooses the nodes that are the strong members of these two fuzzy sets as the clusterheads. We also ran simulations to provide the quantitative comparison against the related works in terms of the packet loss rate and the energy consumption rate. As a result, we show that the network that is constructed by the proposed protocol has far better than the other ones with respect to the packet loss rate and the energy consumption rate.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.8
• /
• pp.18-25
• /
• 2020

With the development of water internet technology, data communication between objects is expanding. Research related to data communication technology between vehicles that incorporates related technologies into vehicles has been actively conducted. For data communication between mobile terminals, data stability, reliability, and real-time performance must be guaranteed. The 5 GHz Wi-Fi band, which is advantageous in bandwidth, communications speed, and wireless saturation of the wireless network, was selected as the data communications network between vehicles. This study analyzes how to design and implement a 5 GHz Wi-Fi network in a vehicle network. Considering the characteristics of the mobile communication terminal device, a continuous variable communications structure is proposed to enable high-speed data switching. We simplify the access point access procedure to reduce the latency between wireless terminals. By limiting the Transmission Control Protocol Internet Protocol (TCP/IP)-based Dynamic Host Configuration Protocol (DHCP) server function and implementing it in a broadcast transmission protocol method, communication delay between terminal devices is improved. Compared to the general commercial Wi-Fi communication method, the connection operation and response speed have been improved by five seconds or more. Utilizing this method can be applied to various types of event data communication between vehicles. It can also be extended to wireless data-based intelligent road networks and systems for autonomous driving.

• The Journal of the Korea Contents Association
• /
• v.8 no.1
• /
• pp.272-281
• /
• 2008

A layer channel, which can express effects on 3D image, is inserted to use it on application rendering effectively. The current method of effect rendering requires individual sources in storage and image processing, because it uses individual and mixed management of images and effects. However, we can save costs and improve results in images processing by processing both image and layer channels together. By changing image format to insert a layer channel in image and adding a hide function to conceal the layer channel and control to make it possible to approach image and layer channels simultaneously during loading image and techniques hiding the layer channel by changing image format with simple techniques, like alpha blending, etc., it is developed to improve reusability and be able to be used in all programs by combining the layer channel and image together, so that images in changed format can be viewed in general image viewers. With the configuration, we can improve processing speed by introducing image and layer channels simultaneously during loading images, and reduce the size of source storage space for layer channel images by inserting a layer channel in 3D images. Also, it allows managing images in 3D image and layer channels simultaneously, enabling effective expressions, and we can expect to use it effectively in multimedia image used in practical applications.