• 소성∙가공
• /
• 제31권3호
• /
• pp.124-128
• /
• 2022

NdFeB magnets have been positioned as the core materials in advanced technologies such as MRI (magnetic resonance imaging), FA (factory automation system), robot, motors, and so on based on the highest magnetic properties. To effectively improve the refined microstructure, the plastic deformation has been known as the good alternatives by the recrystallization. However, it has been regarded as being impossible because of the few slip systems in the RE-Fe-B magnets at room temperature. The purpose of this study was to investigate the possibility of control of grain refinement and magnetic anisotropy of NdFeB alloy powder by the severe plastic deformation. The NdFeB magnet powder was fabricated by gas atomization process, and the powder was pre-compacted at high temperature. The pre-compacted billets were deformed by HPT (high pressure torsion), and then the deformed billets were observed microstructure and magnetic properties. After the HPT process at room temperature, the grain size decreased with increasing because of the melted Nd-rich phase, and the anisotropy of Nd₂Fe₁₄B phase was formed after the HPT process.

• 한국빅데이터학회지
• /
• 제2권1호
• /
• pp.5-15
• /
• 2017

6시그마는 지난 20여 년간 제조 및 서비스 등의 산업에서 프로세스 개선을 위하여 꾸준히 적용되어왔다. 그럼에도 불구하고 6시그마는 Define 단계에서 의미있는 프로젝트를 계속 발굴하기 힘들고 Control 단계에서 지속적인 측정 및 통제가 쉽지 않다는 문제가 지적되었다. 이를 해결하기 위하여 개선 프로세스의 지속적인 통제와 관리를 원활히 할 수 있는 체계가 요구되며, 비즈니스 프로세스 관리(BPM) 시스템이 효과적 대안이 될 수 있다. 본 연구에서는 프로세스 운영 및 분석에서 누적된 데이터를 중심으로 지속적 프로세스 개선을 실현하기 위한 목적으로 6시그마와 BPM의 통합 모형을 제시하고, 프로젝트 수행을 위하여 상호 데이터기반으로 프로세스를 분석, 개선, 모니터링하는 과정을 설명한다. 이를 통하여 6시그마와 BPM의 장점을 결합하여, 지속적으로 업무를 개선하고 관리함으로써 전사적인 경영성과를 극대화할 수 있을 것으로 기대한다.

• 한국전기전자재료학회논문지
• /
• 제25권7호
• /
• pp.531-536
• /
• 2012

We herein present results of flat and uniform polymer-blended small molecular semiconductor thin films. Which were produced for organic thin film transistors (OTFTs), using a simple pre-metered horizontal dipping process. The organic semiconducting thin films were composed of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) composite blended with a polymer binder of poly(${\alpha}$-methylstyrene) (PaMS). We show that the pre-metered horizontal-dip-coating(H-dip-coating) process allowed the critical control of the thickness of the blended TIPS-PEN:PaMs thin film. The fabricated OTFTs using the TIPS-PEN:PaMs films exhibited maximum field-effect mobility of $0.22\;cm^2\;V^{-1}\;s^{-1}$. These results demonstrated that H-dip-coated TIPS-PEN:PaMS films show considerable promise for the production of reliable, reproducible, and high-performance OTFTs.

• 한국전기전자재료학회논문지
• /
• 제29권9호
• /
• pp.552-558
• /
• 2016

Goethite, ${\alpha}$-FeOOH have various applications such as absorbent, pigment and source for magnetic materials. Goethite particles were synthesized in a two step process, where $Fe(OH)_2$ were synthesized in nitrogen atmosphere using $FeSO_4$ as a raw material in the first process, and after that acicular goethite particles were obtained in an air oxidation process of $Fe(OH)_2$ in highly alkaline aqueous solution. Their phase and microstructure were investigated with XRD and FE-SEM. It was found that the morphology of goethite and the ratio of length-to-width (aspect ratio) of acicular goethite are dependent on the some factors such as R value ($OH^-/Fe^{2+}$), air flow rate and pH conditions. In particular, R value has the strongest influence on the synthesized goethite morphology. It is considered that the optimal value R is 4.5 because X-ray diffraction peaks of goethite have the highest intensity at that value. Morphology of goethite particles was controlled by air flow rates, showing that their size and aspect ratio are getting smaller and decrease, respectively as air flow rate increases. The largest goethite particle obtained is about 1,500 nm in length and 150 nm in diameter.

• Journal of Advanced Marine Engineering and Technology
• /
• 제24권4호
• /
• pp.470-477
• /
• 2000

The states of control loops in existing actual systems are changed according to time varying conditions of controllest process and other system components. Adjusting control parameters properly at site which is performed generally by Ziegler & Nichols mthod is important for safe and efficient operation, but the method may require much time to adjust and not easy to inexperienced engineers. This study is aimed to propose more handy method to adjust control parameters by plotting operating conditions on the space of adjusting parameters. One loop of model control system without perturbation condition has been adopted and its stability limit was plotted on the coordinates of Gain and Integral time which was acquired after analyzing Nyquist diagrams and time domain responses. The result showed that the sets of adjusting parameters according to critical stability and proper stability could be acquired reasonably through both responses and the curves on parameter space revealed available patterns for the purpose of easy maintenance of control characteristics.

• Tribology and Lubricants
• /
• 제31권6호
• /
• pp.239-244
• /
• 2015

Chemical mechanical polishing (CMP) is one of the most important processes for enabling sub-14 nm semiconductor manufacturing. Moreover, post-CMP defect control is a key process parameter for the purpose of yield enhancement and device reliability. Due to the complexity of device with sub-14 nm node structure, CMP-induced defects need to be fixed in the CMP in-situ cleaning module instead of during post ex-situ wet cleaning. Therefore, post-CMP in-situ cleaning optimization and cleaning efficiency improvement play a pivotal role in post-CMP defect control. CMP in-situ cleaning module normally consists of megasonic and brush scrubber processes. And there has been an increasing effort for the optimization of cleaning chemistry and brush scrubber cleaning in the CMP cleaning module. Although there have been many studies conducted on improving particle removal efficiency by brush cleaning, these studies do not consider the effects of brush contamination. Depending on the process condition and brush condition, brush cross contamination effects significantly influence post-CMP cleaning defects. This study investigates brush cross contamination effects in the CMP in-situ cleaning module by conducting experiments using 300mm tetraethyl orthosilicate (TEOS) blanket wafers. This study also explores brush pre-treatment in the CMP tool and proposes recipe effects, and critical process parameters for optimized CMP in-situ cleaning process through experimental results.

• 대한금속재료학회지
• /
• 제50권11호
• /
• pp.817-822
• /
• 2012

Nano powders of $Al_2O_3$ and $TiO_2$ compounds made by high energy ball milling were pulsed current activated sintered for studying their sintering behaviors and mechanical properties. The advantage of this process is that it allows very quick densification to near theoretical density and inhibition of grain growth. Nano-structured $Al_2TiO_5$ with small amount of $Al_2O_3$ and$TiO_2$ was formed by sintering at $1300^{\circ}C$ for 5 minute, in which average grain size was about 96 nm. Hardness and fracture toughness of the nano-structured $Al_2TiO_5$ compound with a small amount of $Al_2O_3$ and$TiO_2$ were $602kg/mm^2$ and $2.6MPa{\cdot}m^{1/2}$, respectively.

• Geomechanics and Engineering
• /
• 제14권2호
• /
• pp.161-174
• /
• 2018

The present study investigates the soil-structure interaction (SSI) effects on the seismic performance of smart base-isolated structures. The adopted control algorithm for tuning the control force plays a key role in successful implementation of such structures; however, in most studied carried out in the literature, these algorithms are designed without considering the SSI effect. Considering the SSI effects, a linear quadratic regulator (LQR) controller is employed to seismic control of a smart base-isolated structure. A particle swarm optimization (PSO) algorithm is used to tune the gain matrix of the controller in both cases without and with SSI effects. In order to conduct a parametric study, three types of soil, three well-known earthquakes and a vast range of period of the superstructure are considered for assessment the SSI effects on seismic control process of the smart-base isolated structure. The adopted controller is able to make a significant reduction in base displacement. However, any attempt to decrease the maximum base displacement results in slight increasing in superstructure accelerations. The maximum and RMS base displacements of the smart base-isolated structures in the case of considering SSI effects are more than the corresponding responses in the case of ignoring SSI effects. Overall, it is also observed that the maximum and RMS base displacements of the structure are increased by increasing the natural period of the superstructure. Furthermore, it can be concluded that the maximum and RMS superstructure accelerations are significant influenced by the frequency content of earthquake excitations and the natural frequency of the superstructure. The results show that the design of the controller is very influenced by the SSI effects. In addition, the simulation results demonstrate that the ignoring the SSI effect provides an unfavorable control system, which may lead to decline in the seismic performance of the smart-base isolated structure including the SSI effects.

• 한국정밀공학회지
• /
• 제29권4호
• /
• pp.433-440
• /
• 2012

Various studies to improve the physical abilities of the human have been steadily continued from the past to the present. Only recently such technology has been realized, and those are expected to replace or complement human beings in large part. In this paper, the current status of developed wearable robots is investigated and studies were conducted in order to apply the types of robots in industry spot. In order to apply wearable exoskeleton robot to industry which enhances human physical capability, driving range of the robot's degrees of freedom were selected by analyzing working motion, and augmentative exoskeleton structure design process is presented by analyzing require torque and power during selected working motion. At the end of this paper, the designed mock-up is introduced to validate the feasibility of designed robot.

• 대한예방한의학회지
• /
• 제4권2호
• /
• pp.193-204
• /
• 2000

In this study, advanced model for quality control of oriental medicine and methods for practice was suggested through literature inspection, analysis of foreign system such as China and Japan, survey analysis on the current system, quality analysis of randomly selected oriental medicine samples, and intensive discussions among oriental medicine specialists 1. The quality of oriental medicine should be consistently controlled by Ministry of Health and Welfare form its cultivation or import to its circulation process to final consumer 2. All oriental medicines should be circulated as standardized goods which should be marked by lot numbers. The packing material and Packing size should be liberalized. The qualify should be differentialized though free competition among makers. 3. Realistic standards for pesticide, heavy metal and decolorant should be established though long-term monitoring process according to each oriental medicine's origin, therapeutic part, cultivation area, harvesting time, and cultivation method. 4. Ministry of Health and Welfare should educate oriental medicine's quality control personnel regularly or on demand, and establish specialist pool. Ministry of Health and Welfare should also establish oriental medicine information system to provide informations about quality of domestic or foreign oriental medicinal raw materials. 5. The government should provide information about foreign of oriental medicine market to importers. Quality of imported oriental medicine should be inspected before its customs clearance, and all imported oriental medicine should be circulated by standardized oriental medicine makers. 6. Oriental medicine's pharmacopoeia should be Published to provide quality standard of oriental medicine and improve it.