• 한국기계가공학회지
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• 제18권1호
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• pp.24-30
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• 2019

The deck floor of a the cargo truck becomesis damaged and aged due to the continuous loading of the loading cargo and external environmental factors. Floor boards made of wood and metal are often used. In the case of wood, the cost is high due to the use of imported wood, and the strength is easily deterioratesd due to environmental factors. In the case of metal materials, the durability is higher than that of wood, but problems are raised due to the effect of major factors that hinder the weight reduction, and the effects of corrosion. In order to replace this stucturestructural design, this study proposed a wood fiber composite using natural raw materials. Woody composites are being used as environmentally and friendly exterior materials with the combined advantages of plastic, and wood,; low cost and low density. However, due to the nature of the woody composites, the properties are differentdiffer depending on the contents of the matrix, reinforcing agent, additives, compatibilizer, etc. In this study, we investigate these problems through analysis of the microstructure and mechanical properties according to proper content and injection molding conditions. As a result, it is considered that the wood deck composite can replaced the current Deck Floor Boardreplace current deck floor boards through continuous continued research and results of this study.

• Advances in environmental research
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• 제10권1호
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• pp.59-86
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• 2021

Landfilling is the most commonly adopted method for a large quantity of waste disposal. But, the main concern related to landfills is the generation of leachate. The leachate is high strength wastewater that is usually characterized by the presence of high molecular recalcitrant organics. Several conventional methods are adopted for leachate treatment. However, these methods are only suitable for young leachate, having high biodegradability and low toxicity levels. The mature and stabilized leachate needs advanced technologies for its effective treatment. Advanced oxidation processes (AOPs) are very suitable for such complex wastewater treatment as reported in the literature. After going through the literature survey, it can be concluded that Fenton-based approaches are effective for the treatment of various high/low strength wastewaters treatment. The applications of the Fenton-based approaches are widely adopted and well recognized due to their simplicity, cost-effectiveness, and reliability for the reduction of high chemical oxygen demand (COD) as reported in several studies. Besides, the process is relatively economical due to fewer chemical, non-sophisticated instruments, and low energy requirements. In this review, the conventional and advanced Fenton's approaches are explained with their detailed reaction mechanisms and applications for landfill leachate treatment. The effect of influencing factors like pH, the dosage of chemicals, nature of reaction matrix, and reagent ratio on the treatment efficiencies are also emphasized. Furthermore, the discussion regarding the reduction of chemical oxygen demand (COD) and color, increase in biodegradability, removal of humic acids from leachate, combined processes, and the pre/post-treatment options are highlighted. The scope of future studies is summarized to attain sustainable solutions for restrictions associated with these methods for effective leachate treatment.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.411-428
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• 2022

This paper presents the Campbell diagram analysis of the rotordynamic system using the full order model (FOM) and the reduced order model (ROM) techniques to determine the critical speeds, identify the stability and reduce the computational time. Due to the spin-speed-dependent matrices (e.g., centrifugal stiffening matrix), several model order reduction (MOR) techniques may be considered, such as the modal superposition (MS) method and the Krylov subspace-based MOR techniques (e.g., Ritz vector (RV), quasi-static Ritz vector (QSRV), multifrequency quasi-static Ritz vector (MQSRV), multifrequency/ multi-spin-speed quasi-static Ritz vector (MMQSRV) and the combined Ritz vector & modal superposition (RV+MS) methods). The proposed MMQSRV method in this study is extended from the MQSRV method by incorporating the rotational-speed-dependent stiffness matrices into the Krylov subspace during the MOR process. Thus, the objective of this note is to respond to the question of whether to use the MS method or the Krylov subspace-based MOR technique in establishing the Campbell diagram of the shaft-disc-blade assembly systems in three-dimensional (3D) finite element analysis (FEA). The Campbell diagrams produced by the FOM and various MOR methods are presented and discussed thoroughly by computing the norm of relative errors (ER). It is found that the RV and the MS methods are dominant at low and high rotating speeds, respectively. More precisely, as the spinning velocity becomes large, the calculated ER produced by the RV method is significantly increased; in contrast, the ER produced by the MS method is smaller and more consistent. From a computational point of view, the MORs have substantially reduced the time computing considerably compared to the FOM. Additionally, the verification of the 3D FE rotordynamic model is also provided and found to be in close agreement with the existing solutions.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.292-307
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• 2022

The study presents kinetics of degradation and mineralization of an anti-epileptic drug Lamotrigine (LAM) in the aqueous matrix by electrochemical advanced oxidation process (EAOP) on Ti/DSA (Ta₂O₅-Ir₂O₅) and Stainless Steel (SS) anodes using sodium sulphate as supporting electrolyte. On both the anodes, kinetic behaviour was pseudo-first-order for degradation as well as mineralization of LAM. On Ti/DSA anode, maximum LAM degradation of 75.42% was observed at an associated specific charge of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 100 ppm Na₂SO₄ concentration. Maximum mineralization attained was 44.83% at an associated specific charge of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 50 ppm concentration of Na₂SO₄ with energy consumption of 2942.71 kWh/kgTOC. Under identical conditions on SS anode, a maximum of 98.92% LAM degradation was marked after a specific charge (Q) of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 100 ppm concentration of Na₂SO₄. Maximum LAM mineralization on SS anode was 98.53%, marked at a specific charge of 3.1 (Ah/litre) at a current density of 1.38 mA/cm² and 75 ppm concentration of Na₂SO₄, with energy consumption of 1312.17 kWh/kgTOC. Higher Mineralization Current Efficiency (MCE) values were attained for EAOP on SS anode for both degradation and mineralization due to occurrence of combined electro-oxidation and electro-coagulation process in comparison to EAOP on Ti/DSA anode due to occurrence of lone electro-oxidation process.

• Advances in nano research
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• 제15권1호
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• pp.49-57
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• 2023

As composite materials are used in many applications, the modern world looks forward to significant progress. An overview of the application of composite fiber materials in sports equipment is provided in this article, focusing primarily on the advantages of these materials when applied to sports equipment, as well as an Analysis of the influence of sports equipment of fiber-reinforced composite material on social sports development. The present study investigated surface morphology and physical and mechanical properties of S-glass fiber epoxy composites containing Al₂O₃ nanofillers (for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%). A mechanical stirrer and ultrasonication combined the Al₂O₃ nanofiller with the matrix in varying amounts. A compression molding method was used to produce sheet composites. A first physical observation is well done, which confirms that nanoparticles are deposited on the fiber, and adhesive bonds are formed. Al₂O₃ nanofiller crystalline structure was investigated by X-ray diffraction, and its surface morphology was examined by scanning electron microscope (SEM). In the experimental test, nanofiller content was added at a rate of 1, 2, and 3% by weight, which caused a gradual decrease in void fraction by 2.851, 2.533, and 1.724%, respectively, an increase from 2.7%. The atomic bonding mechanism shows molecular bonding between nanoparticles and fibers. At temperatures between 60 ℃ and 380 ℃, Thermogravimetric Analysis (TGA) analysis shows that NPs deposition improves the thermal properties of the fibers and causes negligible weight reduction (percentage). Thermal stability of the composites was therefore presented up to 380 ℃. The Fourier Transform Infrared Spectrometer (FTIR) spectrum confirms that nanoparticles have been deposited successfully on the fiber.

• 한국환경농학회지
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• 제41권4호
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• pp.288-309
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• 2022

BACKGROUND: The objective of this study was to develop a comprehensive and simple method for the simultaneous determination of 59 veterinary drug residues in livestock products for safety management. METHODS AND RESULTS: For sample preparation, we used a modified liquid extraction method, according to which the sample was extracted with 80% acetonitrile followed by incubation at -20℃ for 30 min. After centrifugation, an aliquot of the extract was evaporated to dryness at 40℃ and analyzed using liquid chromatography combined with tandem mass spectrometry. The method was validated at three concentration levels for beef, pork, chicken, egg, and milk in accordance with the Codex Alimentarius Commission/Guidelines 71-2009. Quantitative analysis was performed using a matrix-matched calibration. As a results, at least 52 (77.6%) out of 66 compounds showed the proper method validation results in terms of both recovery of the target compound and coefficient of variation required by Codex guidelines in livestock products. The limit of quantitation of the method ranged from 0.2 to 1119.6 ng g-1 for all matrices. CONCLUSION(S): This method was accurate, effective, and comprehensive for 59 veterinary drugs determination in livestock products, and can be used to investigate veterinary drugs from different chemical families for safety management in livestock products.

• 한국해양학회지:바다
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• 제13권3호
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• pp.237-245
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• 2008

우리는 해저 연약지반 주행차량과 주행차량의 상부에 결합되어 있는 유연관의 연성거동 동력학 해석 기법을 개발하였다. 연약지반 주행차량은 1개의 강체로 모델링되었으며, 질량집중매개변수 기법을 이용한 이산화기법을 적용하여 유연관을 모델링하였다. 강체 무한궤도 주행차량의 운동방정식과 유연관의 3차원 비선형 지배방정식을 결합시켰으며, 4개의 오일러 매개변수를 이용하여 주행차량과 유연관의 자세를 표현하였다. 주행차량과 유연관의 비선형 연성거동 동력학 방정식의 해를 구하기 위해, 증분-반복법을 이용하였다. 시간영역 수치적분을 위해 $Newmark-\beta$기법을 이용하였다. 증분-반복법을 적용하여 연성 운동방정식에 대한 자코비안 행렬을 유도하였다. 동적거동 동력학 해석 기법을 통해 유연관의 동적거동과 연약지반 위를 주행하는 무한궤도 차량의 동적거동 사이의 상호작용을 시간영역에서의 관찰하였다.

• 산업경영시스템학회지
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• 제47권3호
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• pp.202-216
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• 2024

In today's rapidly changing business environment, rapid decision making and effective project management are essential for business growth. This study examines how project manager competencies and organizational structures affect business performance. Successful project execution depends on the strategic use of project managers' skills and organizational resources to maximize performance. An empirical study was conducted with 475 participants from the construction and engineering sectors. The applied analyses included multiple regression analysis and two-way ANOVA to assess how project manager competencies and organizational types affect business performance. The results of the study show that project manager competencies significantly improve business performance, especially when combined with appropriate organizational types. Effective use of organizational frameworks leads to better financial results, increased market competitiveness, and greater innovation. The results of the study are as follows: First, project manager competencies were found to have a significant positive effect on business performance. Second, the use of functional, project, and matrix organizations had a significant positive effect on business performance. This suggests that aligning organizational structures with business objectives is important for achieving optimal performance. Overall, this study provides valuable insights into the academic literature and practical applications of project management and organizational research. In addition, if we can select organizational members based on the learning effects of previous projects when operating new projects in the future, it will help reduce risks. Ultimately, it will improve the project manager's competency level, promote the individual abilities and knowledge sharing of team members, and provide opportunities for the company to build efficient new systems. This will be evaluated as a valuable study in terms of academic and practical productivity.

• 지능정보연구
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• 제25권1호
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• pp.219-239
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• 2019

개인에게 맞춤형 서비스를 제공하는 것이 중요해지면서 개인화 추천 시스템 관련 연구들이 끊임없이 이루어지고 있다. 추천 시스템 중 협업 필터링은 학계 및 산업계에서 가장 많이 사용되고 있다. 다만 사용자들의 평점 혹은 사용 여부와 같은 정량적인 정보에 국한하여 추천이 이루어져 정확도가 떨어진다는 문제가 제기되고 있다. 이와 같은 문제를 해결하기 위해 현재까지 많은 연구에서 정량적 정보 외에 다른 정보들을 활용하여 추천 시스템의 성능을 개선하려는 시도가 활발하게 이루어지고 있다. 리뷰를 이용한 감성 분석이 대표적이지만, 기존의 연구에서는 감성 분석의 결과를 추천 시스템에 직접적으로 반영하지 못한다는 한계가 있다. 이에 본 연구는 리뷰에 나타난 감성을 수치화하여 평점에 반영하는 것을 목표로 한다. 즉, 사용자가 직접 작성한 리뷰를 감성 수치화하여 정량적인 정보로 변환해 추천 시스템에 직접 반영할 수 있는 새로운 알고리즘을 제안한다. 이를 위해서는 정성적인 정보인 사용자들의 리뷰를 정량화 시켜야 하므로, 본 연구에서는 텍스트 마이닝의 감성 분석 기법을 통해 감성 수치를 산출하였다. 데이터는 영화 리뷰를 대상으로 하여 도메인 맞춤형 감성 사전을 구축하고, 이를 기반으로 리뷰의 감성점수를 산출한다. 본 논문에서 사용자 리뷰의 감성 수치를 반영한 협업 필터링이 평점만을 고려하는 전통적인 방식의 협업 필터링과 비교하여 우수한 정확도를 나타내는 것을 확인하였다. 이후 제안된 모델이 더 개선된 방식이라고 할 근거를 확보하기 위해 paired t-test 검증을 시도했고, 제안된 모델이 더 우수하다는 결론을 도출하였다. 본 연구에서는 평점만으로 사용자의 감성을 판단한 기존의 선행연구들이 가지는 한계를 극복하고자 리뷰를 수치화하여 기존의 평점 시스템보다 사용자의 의견을 더 정교하게 추천 시스템에 반영시켜 정확도를 향상시켰다. 이를 기반으로 추가적으로 다양한 분석을 시행한다면 추천의 정확도가 더 높아질 것으로 기대된다.

• 지능정보연구
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• 제21권2호
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• pp.1-18
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• 2015

협업 필터링은 학계나 산업계에서 우수한 성능으로 인해 많이 사용되는 추천기법이지만, 정량적 정보인 사용자들의 평가점수에만 국한하여 추천결과를 생성하므로 간혹 정확도가 떨어지는 문제가 발생한다. 이에 새로운 정보를 추가로 고려하여, 협업 필터링의 성능을 개선하려는 연구들이 지금까지 다양하게 시도되어 왔다. 본 연구는 최근 Web 2.0 시대의 도래로 인해 사용자들이 구입한 상품에 대한 솔직한 의견을 인터넷 상에 자유롭게 표현한다는 점에 착안하여, 사용자가 직접 작성한 리뷰를 참고하여 협업 필터링의 성능을 개선하는 새로운 추천 알고리즘을 제안하고, 이를 스마트폰 앱 추천 시스템에 적용하였다. 정성 정보인 사용자 리뷰를 정량화하기 위해 본 연구에서는 텍스트 마이닝을 활용하였다. 구체적으로 본 연구의 추천시스템은 사용자간 유사도를 산출할 때, 사용자 리뷰의 유사도를 추가로 반영하여 보다 정밀하게 사용자간 유사도를 산출할 수 있도록 하였다. 이 때, 사용자 리뷰의 유사도를 산출하는 접근법으로 중복 사용된 색인어의 빈도로 산출하는 방안과 TF-IDF(Term Frequency - Inverse Document Frequency) 가중치 합으로 산출하는 2가지 방안을 제시한 뒤 그 성능을 비교해 보았다. 실험결과, 제안 알고리즘을 통한 추천, 즉 사용자 리뷰의 유사도를 추가로 반영하는 알고리즘이 평점만을 고려하는 전통적인 협업 필터링과 비교해 더 우수한 예측정확도를 나타냄을 확인할 수 있었다. 아울러, 중복 사용 단어의 TF-IDF 가중치의 합을 고려했을 때, 단순히 중복 사용 단어의 빈도만을 고려했을 때 보다 조금 더 나은 예측정확도를 얻을 수 있음도 함께 확인할 수 있었다.