• 자원리싸이클링
• /
• 제21권1호
• /
• pp.82-92
• /
• 2012

텅스텐카바이드는 금속절단 공구, 드릴의 날, 광산공구, 군사무기 재료, 화학원료, 촉매, 내마모성재료, 제트엔진 터빈 블레이드 등 다양한 용도로 사용된다. 요즘 경제적인 측면과 효율적인의 측면에서 텅스텐카바이드 재활용 기술이 넓게 연구되었다. 이 논문에서는 텅스텐카바이드 재활용 기술에 대하여 1969년부터 2011년까지 공개/등록된 미국, 일본, 유럽, 한국의 특허와 SCI급 논문을 조사하였다. 키워드를 이용하여 조사하였고 필터링 하여 특허와 논문을 수집하여 연도별, 국가별, 기관별, 기술별로 분석하였다.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2008년 영문 학술대회
• /
• pp.16-21
• /
• 2008

Aero-engine, as one kind of rotating machinery with complex structure and high rotating speed, has complicated vibration faults. Therefore, condition monitoring and fault diagnosis system is very important for airplane security. In this paper, a vibration data acquisition and intelligent fault diagnosis system is introduced. First, the vibration data acquisition part is described in detail. This part consists of hardware acquisition modules and software analysis modules which can realize real-time data acquisition and analysis, off-line data analysis, trend analysis, fault simulation and graphical result display. The acquisition vibration data are prepared for the following intelligent fault diagnosis. Secondly, two advanced artificial intelligent(AI) methods, mapping-based and rule-based, are discussed. One is artificial neural network(ANN) which is an ideal tool for aero-engine fault diagnosis and has strong ability to learn complex nonlinear functions. The other is data mining, another AI method, has advantages of discovering knowledge from massive data and automatically extracting diagnostic rules. Thirdly, lots of historical data are used for training the ANN and extracting rules by data mining. Then, real-time data are input into the trained ANN for mapping-based fault diagnosis. At the same time, extracted rules are revised by expert experience and used for rule-based fault diagnosis. From the results of the experiments, the conclusion is obvious that both the two AI methods are effective on aero-engine vibration fault diagnosis, while each of them has its individual quality. The whole system can be developed in local vibration monitoring and real-time fault diagnosis for aero-engine.

• 스마트미디어저널
• /
• 제8권1호
• /
• pp.59-66
• /
• 2019

하루가 다르게 방대한 데이터가 생겨나고, 데이터를 반영한 정책지원이나 콘텐츠들이 증가하면서 데이터에 대한 중요성이 주목받고 있다. 데이터의 시각화 측면에서 모든 데이터를 살펴보는 것에 제약이 따르기 때문에, 시각화의 기술적인 요소뿐만 아니라 데이터를 요약하고, 이해하기 쉽도록 돕는 시각화의 방법론적 요소가 중요하다고 할 수 있다. 본 논문에서는 현재 많이 사용되는 디자인 중심의 인포그래픽을 개선하고 데이터 중심의 인포그래픽을 제안하기 위해 데이터 시각화의 표현 방법을 정리하고, 시각화의 방법을 Tableau Public을 활용하여 데이터 분석 및 인포그래픽 제작사례를 제시고자 한다. 인포그래픽 제작을 위해 광주광역시 버스 이용자 데이터가 사용되었고, 분석결과 정류소 사용 총 승객수는 일반 승객수와는 유사한 결과를 보이지만 환승역 이용 승객, 청소년 승차 환승 승객수에 따른 정류소와는 차이를 보였다. 그래프 유형에 따라 시각적인 결과는 다르게 도출되었다. 데이터 중심의 인포그래픽 시각화는 기존의 인포그래픽의 시각적인 역할만 강조한 것에 비해 데이터를 효율적으로 전달하는 것을 물론 과학적 연구를 위한 도구로 활용될 것으로 기대한다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권12호
• /
• pp.5723-5743
• /
• 2018

The evolving internet-based services demand high-speed data transmission in conjunction with scalability. The next generation optical network has to exploit artificial intelligence and cognitive techniques to cope with the emerging requirements. This work proposes a novel way to solve the dynamic provisioning problem in optical network. The provisioning in optical network involves the computation of routes and the reservation of wavelenghs (Routing and Wavelength assignment-RWA). This is an extensively studied multi-objective optimization problem and its complexity is known to be NP-Complete. As the exact algorithms incurs more running time, the heuristic based approaches have been widely preferred to solve this problem. Recently the software-defined networking has impacted the way the optical pipes are configured and monitored. This work proposes the dynamic selection of path computation algorithms in response to the changing service requirements and network scenarios. A software-defined controller mechanism with a novel packet matching feature was proposed to dynamically match the traffic demands with the appropriate algorithm. A software-defined controller with Path Computation Element-PCE was created in the ONOS tool. A simulation study was performed with the case study of dynamic path establishment in ONOS-Open Network Operating System based software defined controller environment. A java based NOX controller was configured with a parent path computation element. The child path computation elements were configured with different path computation algorithms under the control of the parent path computation element. The use case of dynamic bulk path creation was considered. The algorithm selection method is compared with the existing single algorithm based method and the results are analyzed.

• 정보보호학회논문지
• /
• 제31권3호
• /
• pp.323-330
• /
• 2021

최근에는 양자 컴퓨터의 빠른 연산의 장점이 알려지면서 큐비트를 활용한 양자회로에 대한 관심이 높아지고 있다. 그루버 알고리즘은 n-bit의 보안 레벨의 대칭키 암호와 해시 함수를 n/2-bit 보안 레벨까지 낮출 수 있는 양자 알고리즘이다. 그루버 알고리즘은 양자 컴퓨터상에서 동작하기 때문에 적용 대상이 되는 대칭키 암호와 해시함수는 양자 회로로 구현되어야 한다. 이러한 연구 동기로, 최근 들어 대칭키 암호 또는 해시 함수를 양자 회로로 구현하는 연구들이 활발히 수행되고 있다. 하지만 현재는 큐비트의 수가 제한적인 상황으로 최소한의 큐비트 개수로 구현하는 것에 관심을 가지고 효율적인 구현을 목표로 하고 있다. 본 논문에서는 국산 해시함수 LSH 구현에 큐빗 재활용, 사전 연산을 통해 사용 큐빗 수를 줄였다. 또한, Mix, Final 함수와 같은 핵심 연산들을 IBM에서 제공하는 양자 프로그래밍 툴인 ProjectQ를 사용하여 양자회로로 효율적으로 구현하였고 이에 필요한 양자 자원들을 평가하였다.

• 산업경영시스템학회지
• /
• 제43권4호
• /
• pp.41-47
• /
• 2020

As modern industries are highly being developed, it is required that mechanical parts have to be manufactured with a high precision. In order to have precise parts, error-free designs have to be done before manufacturing with accuracy. For this intention being fulfilled, a mechanical analysis is essential for design proof. Nowadays, FEM simulation is a popular tool for verifying a machine design. In this paper, an impeller, being utilized in a compressor or an oil mixer as an actuator, is studied for an evaluation. The purpose of this study is to present a safety of an impeller for a proof of its mechanical stability. A static analysis for stress, strain, and deformation within a regular usage is examined. This simulation test shows 357.26×106 Pa for maximum equivalent stress and 0.207mm for total deformation. A fatigue test is carried to provide durability and its result shows that minimum safety factor is 3.2889, which guarantees that it runs without a fatigue failure in 106 cycles. The natural frequencies for the impeller is ranged from 228.09Hz to 1,253.6Hz for the 1st to the 6th mode. Total deformations at these natural frequencies are shown from 6.84mm to 12.631mm. Furthermore, Campbell diagram reveals that a critical speed is not found throughout regular rotational speeds. From the test results for the analysis, this paper concludes that the suggested impeller is proved for its mechanical safety and good to utilize at industries.

• 응용통계연구
• /
• 제35권2호
• /
• pp.217-227
• /
• 2022

분위수 회귀 모형은 변수에 숨겨진 복잡한 정보를 살펴보기 위한 효율적인 도구를 제공하는 장점을 바탕으로 많은 분야에서 널리 사용되고 있다. 그러나 현대의 대용량-고차원 데이터는 계산 시간 및 저장공간의 제한으로 인해 분위수 회귀 모형의 추정을 매우 어렵게 만든다. 분할-정복은 전체 데이터를 계산이 용이한 여러개의 부분집합으로 나눈 다음 각 분할에서의 요약 통계량만을 이용하여 전체 데이터의 추정량을 재구성하는 기법이다. 본 연구에서는 분할-정복 기법을 벌점화 분위수 회귀에 적용하고 베이즈 정보기준을 활용하여 변수를 선택하는 방법에 관하여 연구하였다. 제안 방법은 분할 수를 적절하게 선택하였을 때, 전체 데이터로 계산한 일반적인 분위수 회귀 추정량만큼 변수 선택의 측면에서 일관된 결과를 제공하면서 계산 속도의 측면에서 효율적이다. 이러한 제안된 방법의 장점은 시뮬레이션 데이터 및 실제 데이터 분석을 통해 확인하였다.

• Advances in materials Research
• /
• 제11권4호
• /
• pp.375-390
• /
• 2022

Carbon Fiber Reinforced Polymer (CFRP) composite provides outstanding mechanical capabilities and is therefore popular in the automotive and aerospace industries. Drilling is a common final production technique for composite laminates however, drilling high-strength composite laminates is extremely complex and challenging. The delamination of composites during the drilling at the entry and exit of the hole has a severe impact on the results of the holes surface and the material properties. The major goal of this research is to investigate contemporary industry solutions for drilling CFRP composites: enhanced edge geometries of cutting tools. This study examined the occurrence of delamination at the entry and exit of the hole during the drilling. For each of the 80°, 90°, and 118°point angle uncoated Brad point, Dagger, and Twist solid carbide drills, Taguchi design of experiments were undertaken. Cutting parameters included three variable cutting speeds (100-125-150 m/min) and feed rates (0.1-0.2-0.3 mm/rev). Brad point drills induced less delamination than dagger and twist drills, according to the research, and the best cutting parameters were found to be a combination of maximum cutting speed, minimum feed rate, and low drill point angle (V:150 m/min, f: 0.1 mm/rev, θ: 80°). The feed rate was determined to be the most efficient factor in preventing hole entry and exit delamination using analysis of variance (ANOVA). Regression analysis was used to create first-degree mathematical models for each cutting tool's entrance and exit delamination components. The results of optimization, mathematical modelling, and experimental tests are thought to be reasonably coherent based on the information obtained.

• 대한한방내과학회지
• /
• 제44권6호
• /
• pp.1118-1138
• /
• 2023

Objectives: Sarcopenia is an age-associated skeletal muscle disorder that can profoundly impact the health of elderly people. However, the efficacy of herbal medicine in sarcopenia is uncertain. This review aims to investigate evidence of the effect of herbal medicine on sarcopenia. Methods: We systematically searched 12 electronic databases for relevant randomized controlled trials (RCTs). Only trials that met the inclusion criteria were selected, and the characteristics of the included studies were extracted and synthesized in a narrative manner. The quality of the included studies was assessed using Cochrane's Risk of Bias (RoB) 2.0 tool. Results: 7 RCTs involving 672 participants with sarcopenia met the inclusion criteria. The intervention combining herbal medicine and conventional treatment (i.e., exercise, nutritional support) had a significant therapeutic effect compared with the conventional treatment, showing improvement in muscle strength (i.e., grip strength), muscle mass (i.e., appendicular skeletal muscle mass index), and physical function (i.e., gait speed, short physical performance battery, and timed up and go test). However, the methodological quality of the included RCTs was relatively low due to their high RoB, making it difficult to evaluate the efficacy of herbal medicine in sarcopenia. In terms of safety, several adverse events were reported. Conclusion: This review suggests that herbal medicine has a positive effect on muscle strength, muscle mass, and physical performance in elderly patients with sarcopenia, but there is a clear need for further research in this area.

• 대한물리의학회지
• /
• 제19권1호
• /
• pp.131-142
• /
• 2024

PURPOSE: This study was a systematic review and meta-analysis of the literature comparing the differences between task-oriented treadmill training and general treadmill training for stroke patients. METHODS: Literature published in the Cumulated Index to Nursing and Allied Health Literature (CINAHL), Embase, Physiotherapy Evidence Database (PEDro), and PubMed was reviewed. A total of 1,163 studies were initially retrieved, of which eight articles were included in the final review. A quality assessment of the included studies was conducted using the Risk of Bias (RoB) 2.0 tool, and Duval and Tweedie's trim and fill method was used to evaluate publication bias. Data analysis was performed using R studio 4.2.1. RESULTS: According to the quality assessment using RoB 2.0, three articles were evaluated as low risk, two as of some concern, and three as high risk. The overall effect size of task-oriented tradmill training was .35. Regarding gait function, the values were .76, .25, and .40, respectively, for gait endurance, gait speed, and gait pattern. According to Duval and Tweedie's trim and fill method, no publication bias was observed. CONCLUSION: Study findings indicate that task-oriented treadmill training is the most effective intervention for improving gait endurance in patients with stroke. Therefore, applying this intervention to patients with stroke in the community is recommended.