• Title/Summary/Keyword: hybrid evaluation

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A Study on the Certification Standard Analysis and Safety Assurance Method for Electric Propulsion System of the Urban eVTOL Aircraft (도심용 eVTOL 항공기 전기추진시스템 기준 분석 및 안전성 확보 방안에 관한 연구)

  • Kim, Juyoung;Yoo, Minyoung;Gwon, Hyukrok;Gil, Ginam;Gong, Byeongho;Na, Jongwhoa
    • Journal of Aerospace System Engineering
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    • v.16 no.3
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    • pp.42-51
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    • 2022
  • An eVTOL aircraft, which is required to operate with low pollution/low noise in urban environments, mostly use battery-powered electric propulsion systems as power sources, not traditional propulsion systems such as reciprocating or turbine engines. Accordingly, certification preparation for the electric propulsion system and securing the safety of the electric propulsion system, are important issues. In the U.S., special technical standards equivalent to FAR Part 33 were issued to certify electric engines, and in Europe, various special conditions were established to certify electric propulsion systems. Thus, in Korea, the technical standards for the electric propulsion system for eVTOL aircraft must also be prepared in line with the U.S. and Europe. In this paper, SC E-19, the technical standard of the electric/hybrid propulsion system (EHPS) in special conditions, was analyzed. Additionally, securing the safety of the electric propulsion system of the aircraft are proposed, through the collaboration of SC E-19 technical standards with the existing aircraft safety evaluation procedure ARP 4761. Finally, through a case study of the Ehang 184 electric propulsion system, it has been confirmed that the proposed safety assurance method is applicable at the aircraft level.

Fabrication of Radar Absorbing Shells Made of Hybrid Composites and Evaluation of Radar Cross Section (하이브리드 복합재를 이용한 레이더 흡수 쉘의 제작 및 레이더 단면적 평가)

  • Jung, Woo-Kyun;Ahn, Sung-Hoon;Ahn, Bierng-Chearl;Park, Seoung-Bae;Won, Myung-Shik
    • Composites Research
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    • v.19 no.1
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    • pp.29-35
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    • 2006
  • The avoidance of enemy's radar detection is very important issue in the modem electronic weapon system. Researchers have studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), 'C'-type shell and 'U'-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

Evaluation of Bonding Performance of Hybrid Materials According to Laser and Plasma Surface Treatment (레이저 및 플라즈마 표면처리에 따른 이종소재 접합특성평가)

  • Minha Shin;Eun Sung Kim;Seong-Jong Kim
    • Composites Research
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    • v.36 no.6
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    • pp.441-447
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    • 2023
  • Recently, as demand for high-strength, lightweight materials has increased, there has been great interest in joining with metals. In the case of mechanical bonding, such as bolting and riveting, chemical bonding using adhesives is attracting attention as stress concentration, cracks, and peeling occur. In this paper, surface treatment was performed to improve the adhesive strength, and the change in adhesive strength was analyzed. For the adhesive strength test were conducted with Carbon Fiber Reinforced Plastic(CFRP), CR340(Steel), and Al6061(Aluminum), and laser and plasma surface treatment were used. After plasma surface treatment, the adhesive strength improved by 7.3% and 39.2% in CFRP-CR340 and CFRP-Al6061, respectively. CR340-Al6061 was improved by 56.2% in laser surface treatment. Surface free energy(SFE) was measured by contact angle after plasma treatment, and it is thought that the adhesion strength was improved by minimizing damage through a chemical reaction mechanism. For laser surface treatment, it is thought that creates a rough bonding surface and improves adhesive strength due to the mechanical interlocking effect. Therefore, surface treatment is effect to improve adhesive strength, and based on this paper, the long-term fatigue test will be conducted to prevent fatigue failure, which is a representative cause of actual structural damage.

A Study on Public Interest-based Technology Valuation Models in Water Resources Field (수자원 분야 공익형 기술가치평가 시스템에 대한 연구)

  • Ryu, Seung-Mi;Sung, Tae-Eung
    • Journal of Intelligence and Information Systems
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    • v.24 no.3
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    • pp.177-198
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    • 2018
  • Recently, as economic property it has become necessary to acquire and utilize the framework for water resource measurement and performance management as the property of water resources changes to hold "public property". To date, the evaluation of water technology has been carried out by feasibility study analysis or technology assessment based on net present value (NPV) or benefit-to-cost (B/C) effect, however it is not yet systemized in terms of valuation models to objectively assess an economic value of technology-based business to receive diffusion and feedback of research outcomes. Therefore, K-water (known as a government-supported public company in Korea) company feels the necessity to establish a technology valuation framework suitable for technical characteristics of water resources fields in charge and verify an exemplified case applied to the technology. The K-water evaluation technology applied to this study, as a public interest goods, can be used as a tool to measure the value and achievement contributed to society and to manage them. Therefore, by calculating the value in which the subject technology contributed to the entire society as a public resource, we make use of it as a basis information for the advertising medium of performance on the influence effect of the benefits or the necessity of cost input, and then secure the legitimacy for large-scale R&D cost input in terms of the characteristics of public technology. Hence, K-water company, one of the public corporation in Korea which deals with public goods of 'water resources', will be able to establish a commercialization strategy for business operation and prepare for a basis for the performance calculation of input R&D cost. In this study, K-water has developed a web-based technology valuation model for public interest type water resources based on the technology evaluation system that is suitable for the characteristics of a technology in water resources fields. In particular, by utilizing the evaluation methodology of the Institute of Advanced Industrial Science and Technology (AIST) in Japan to match the expense items to the expense accounts based on the related benefit items, we proposed the so-called 'K-water's proprietary model' which involves the 'cost-benefit' approach and the FCF (Free Cash Flow), and ultimately led to build a pipeline on the K-water research performance management system and then verify the practical case of a technology related to "desalination". We analyze the embedded design logic and evaluation process of web-based valuation system that reflects characteristics of water resources technology, reference information and database(D/B)-associated logic for each model to calculate public interest-based and profit-based technology values in technology integrated management system. We review the hybrid evaluation module that reflects the quantitative index of the qualitative evaluation indices reflecting the unique characteristics of water resources and the visualized user-interface (UI) of the actual web-based evaluation, which both are appended for calculating the business value based on financial data to the existing web-based technology valuation systems in other fields. K-water's technology valuation model is evaluated by distinguishing between public-interest type and profitable-type water technology. First, evaluation modules in profit-type technology valuation model are designed based on 'profitability of technology'. For example, the technology inventory K-water holds has a number of profit-oriented technologies such as water treatment membranes. On the other hand, the public interest-type technology valuation is designed to evaluate the public-interest oriented technology such as the dam, which reflects the characteristics of public benefits and costs. In order to examine the appropriateness of the cost-benefit based public utility valuation model (i.e. K-water specific technology valuation model) presented in this study, we applied to practical cases from calculation of benefit-to-cost analysis on water resource technology with 20 years of lifetime. In future we will additionally conduct verifying the K-water public utility-based valuation model by each business model which reflects various business environmental characteristics.

Comparison of Agronomic Characteristics, Yield and Feed Value of Different Corn Hybrids for Silage (국내육성 사일리지옥수수의 일반생육특성 및 사료가치의 품종간 비교)

  • Son Beom-Young;Moon Hyeon-Gui;Jung Tae-Wook;Kim Si-Ju;Kim Jong-Duk
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.51 no.3
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    • pp.233-238
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    • 2006
  • This study was conducted to evaluate growth characteristics, yield and feed value of newly bred domestic silage corn hybrids compared to foreign imported corn hybrid. Days to silking were $78{\sim}86$ days and longer than that of P3394 (Control). Kwangpyeongok, Cheonganok, and Cheongsaok were resistant to lodging. Such trait of stay-green of Kwanganok, Kwangpyeongok, Cheonganok, Cheongsaok, and Suwon159 was not different from that of P3394. Duruok, Kwangpyeongok, and Suwon159 were more resistant to Bipolaris maydis (southern corn leaf blight) than P3394. All of the silage corn hybrids were resistant to Exserohilum turcicum (northern corn leaf blight) and Smut. Ear ratios to total dry matter (%) of Cheonganok was similar to P3394. Ear lengths of domestic hybrids were similar or longer than that of P3394. Dry matter yield of domestic hybrids except Suwon19 and Jangdaok were similar to that of P3394. Total digestible nutrient (TDN) yields, Duruok, Kwangpyeongok, Cheonganok, and Cheongsaok were similar to P3394, but Kwanganok, Suwon19, Jangdaok and Suwon159 were lower than P3394. Acid detergent fiber(ADF), Suwon19 was lowest among all hybrids, and all hybrids except Suwon19 had values ranging from 44.7 to 49.0%, similarly with P3394. Neutral detergent fiber (NDF) values of the hybrids were similar to that of P3394, and ranged from 68.1 to 72.8%, except for Duruok which was lowest. Relative feed values (RFV) of Duruok, Kwangpyeongok, Cheonganok, Jangdaok, and Suwon159 had values ranging from 71.0 to 75.7 and were not significantly different from P3394. ADF was significantly negatively correlated with number of days to silking, number of days to maturity, and fresh matter yield, but was significantly positively correlated with resistance to corn borer. RFV showed a significantly positive correlations with no. of days to maturity and fresh matter yield, but significantly negative correlation with resistance to European corn borer. Therefore, indices for evaluation of feed value as well as production were important to select corn hybrids for silage. It is concluded that domestic hybrids tested in this study have high feed value as well as high production similar to those of imported corn hybrid.

Recommender system using BERT sentiment analysis (BERT 기반 감성분석을 이용한 추천시스템)

  • Park, Ho-yeon;Kim, Kyoung-jae
    • Journal of Intelligence and Information Systems
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    • v.27 no.2
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    • pp.1-15
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    • 2021
  • If it is difficult for us to make decisions, we ask for advice from friends or people around us. When we decide to buy products online, we read anonymous reviews and buy them. With the advent of the Data-driven era, IT technology's development is spilling out many data from individuals to objects. Companies or individuals have accumulated, processed, and analyzed such a large amount of data that they can now make decisions or execute directly using data that used to depend on experts. Nowadays, the recommender system plays a vital role in determining the user's preferences to purchase goods and uses a recommender system to induce clicks on web services (Facebook, Amazon, Netflix, Youtube). For example, Youtube's recommender system, which is used by 1 billion people worldwide every month, includes videos that users like, "like" and videos they watched. Recommended system research is deeply linked to practical business. Therefore, many researchers are interested in building better solutions. Recommender systems use the information obtained from their users to generate recommendations because the development of the provided recommender systems requires information on items that are likely to be preferred by the user. We began to trust patterns and rules derived from data rather than empirical intuition through the recommender systems. The capacity and development of data have led machine learning to develop deep learning. However, such recommender systems are not all solutions. Proceeding with the recommender systems, there should be no scarcity in all data and a sufficient amount. Also, it requires detailed information about the individual. The recommender systems work correctly when these conditions operate. The recommender systems become a complex problem for both consumers and sellers when the interaction log is insufficient. Because the seller's perspective needs to make recommendations at a personal level to the consumer and receive appropriate recommendations with reliable data from the consumer's perspective. In this paper, to improve the accuracy problem for "appropriate recommendation" to consumers, the recommender systems are proposed in combination with context-based deep learning. This research is to combine user-based data to create hybrid Recommender Systems. The hybrid approach developed is not a collaborative type of Recommender Systems, but a collaborative extension that integrates user data with deep learning. Customer review data were used for the data set. Consumers buy products in online shopping malls and then evaluate product reviews. Rating reviews are based on reviews from buyers who have already purchased, giving users confidence before purchasing the product. However, the recommendation system mainly uses scores or ratings rather than reviews to suggest items purchased by many users. In fact, consumer reviews include product opinions and user sentiment that will be spent on evaluation. By incorporating these parts into the study, this paper aims to improve the recommendation system. This study is an algorithm used when individuals have difficulty in selecting an item. Consumer reviews and record patterns made it possible to rely on recommendations appropriately. The algorithm implements a recommendation system through collaborative filtering. This study's predictive accuracy is measured by Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE). Netflix is strategically using the referral system in its programs through competitions that reduce RMSE every year, making fair use of predictive accuracy. Research on hybrid recommender systems combining the NLP approach for personalization recommender systems, deep learning base, etc. has been increasing. Among NLP studies, sentiment analysis began to take shape in the mid-2000s as user review data increased. Sentiment analysis is a text classification task based on machine learning. The machine learning-based sentiment analysis has a disadvantage in that it is difficult to identify the review's information expression because it is challenging to consider the text's characteristics. In this study, we propose a deep learning recommender system that utilizes BERT's sentiment analysis by minimizing the disadvantages of machine learning. This study offers a deep learning recommender system that uses BERT's sentiment analysis by reducing the disadvantages of machine learning. The comparison model was performed through a recommender system based on Naive-CF(collaborative filtering), SVD(singular value decomposition)-CF, MF(matrix factorization)-CF, BPR-MF(Bayesian personalized ranking matrix factorization)-CF, LSTM, CNN-LSTM, GRU(Gated Recurrent Units). As a result of the experiment, the recommender system based on BERT was the best.

Equivalent Circuit Modeling of Aperture-Coupled Microstrip-to-Vertically Mounted Slotline Coupler (개구면을 통한 마이크로스트립-수직 슬롯 라인 결합 구조의 회로망 해석과 모델링)

  • Nam, Sang-Ho;Kim, Jeoung-Phill
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.20 no.4
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    • pp.357-365
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    • 2009
  • A general analysis of a microstrip-to-vertically mounted slotline(VMS) coupler is presented with a view to developing an equivalent circuit, and the efficient evaluation of the related circuit element values. Based on this theory, the effects of frequency and structure parameters such as aperture length and VMS width on the characteristics of the coupler are studied. In order to check the validity of the proposed analysis and design theory, a C-band linearly tapered slot antenna fed by an aperture-coupled back-to-back microstripline-to- VMS coupling structure is optimally designed using a hybrid genetic algorithm. Moreover, the computed characteristics from the network analysis is compared to the measurement and simulation results. The obtained results fully validate the efficiency and accuracy of the proposed network model.

Gene flow from herbicide resistant genetically modified rice to conventional rice (Oryza sativa L.) cultivars

  • Han, Sung Min;Lee, Bumkyu;Won, Ok Jae;Hwang, Ki Seon;Suh, Su Jeoung;Kim, Chang-Gi;Park, Kee Woong
    • Journal of Ecology and Environment
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    • v.38 no.4
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    • pp.397-403
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    • 2015
  • Rice (Oryza sativa L.) is an important feeding crop in Asia, and utilization of genetically modified (GM) rice is highly demanding. For co-existence of GM rice and non-GM rice, the proper confinement measures should be provided. Thus, we surveyed gene flow from herbicide resistant GM rice to the conventional rice cultivars in the field tests. Gene flow frequency decreased with increasing distance between the pollen donor and recipients and did not exceed more than 1% even at the nearest distance. In single recipient model plot, a maximum gene flow frequency was observed at the shortest distance and hybrid was detected up to 12 m from the pollen donor. The direction of gene was coincided with the dominant wind direction. Gene flow assessment to multiple recipient plots was conducted under the high raining season by chance, and abrupt decline of gene flow frequency and maximum distance were resulted. According to the survey results, current regulation for isolation distance is reasonable for environmental safety or for general crop production. However, we suggest an alternative measure for GM rice cultivation that should be supplemented to overcome the out of estimation and in the environment asking higher security levels.

Implant supported prosthesis with high performance polymers using a double scanning method (Double Scanning에 의한 고성능 중합체를 이용한 임플란트 지지 고정성 보철물 수복 증례)

  • Kang, Kyeong-Hwan;Park, Jin-Hong;Lee, Jeong-Yol;Shin, Sang-Wan
    • The Journal of Korean Academy of Prosthodontics
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    • v.55 no.3
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    • pp.305-310
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    • 2017
  • Nowadays, the development of dental scanner and CAD/CAM technology can facilitate the fabrication of hybrid prosthesis. Double scanning technique, scanning a trial prosthesis and master model, made it possible to realize virtual design and simplify the laboratory work. Instead of using the metal or zirconia framework with composite, ceramic or denture tooth, the new high performance polymer Polyetherketoneketone (Pekkton, Cendres+$M{\acute{e}}taux$, Biel, Switzerland) as a framework with Polymethyl methacrylate (PMMA) veneering teeth (Visio-lign, Bredent, Senden, Germany) was used in this case. This case report showed an acceptable treatment outcome and satisfaction of patient using Pekkton and Visio-lign. However, long term clinical evaluation is needed.

Static Homogeneous Multiprocessor Task Graph Scheduling Using Ant Colony Optimization

  • Boveiri, Hamid Reza;Khayami, Raouf
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.11 no.6
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    • pp.3046-3070
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    • 2017
  • Nowadays, the utilization of multiprocessor environments has been increased due to the increase in time complexity of application programs and decrease in hardware costs. In such architectures during the compilation step, each program is decomposed into the smaller and maybe dependent segments so-called tasks. Precedence constraints, required execution times of the tasks, and communication costs among them are modeled using a directed acyclic graph (DAG) named task-graph. All the tasks in the task-graph must be assigned to a predefined number of processors in such a way that the precedence constraints are preserved, and the program's completion time is minimized, and this is an NP-hard problem from the time-complexity point of view. The results obtained by different approaches are dominated by two major factors; first, which order of tasks should be selected (sequence subproblem), and second, how the selected sequence should be assigned to the processors (assigning subproblem). In this paper, a hybrid proposed approach has been presented, in which two different artificial ant colonies cooperate to solve the multiprocessor task-scheduling problem; one colony to tackle the sequence subproblem, and another to cope with assigning subproblem. The utilization of background knowledge about the problem (different priority measurements of the tasks) has made the proposed approach very robust and efficient. 125 different task-graphs with various shape parameters such as size, communication-to-computation ratio and parallelism have been utilized for a comprehensive evaluation of the proposed approach, and the results show its superiority versus the other conventional methods from the performance point of view.