• 품질경영학회지
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• 제35권2호
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• pp.106-112
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• 2007

In statistical process control, it is assumed that the process data are independent. However, most of chemical processes such as semi-conduct processes do not satisfy the assumption because of presence of autocorrelation between process data. It causes abnormal out of control signal in the process control and misleading estimation in process capability. In this study, we adopted Shore's method to solve the problem and propose an optimal subgroup size to estimate the variance correctly for AR(1) processes. Especially, we focus on finding an actual subgroup size for small samples based on simulation study.

• Journal of Electrochemical Science and Technology
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• 제8권1호
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• pp.15-24
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• 2017

A comparative study was performed on the passivating abilities of surface films generated on lithium titanate (LTO; $Li_4Ti_5O_{12}$) electrodes during pre-cycling at two different rates. The surface film deposited at a faster pre-cycling rate (i.e., 0.5 C) is irregularly shaped and unevenly covers the LTO electrode. Owing to the incomplete coverage of the protective film, this LTO electrode exhibits poor passivating ability. Additional electrolyte decomposition and concomitant film deposition occur during subsequent charge/discharge cycles. As a result of the thick surface film, severe cell polarization occurs and eventually causes cell failure. However, pre-cycling the Li/LTO cell at a slower rate (0.1 C) improves cell polarization and capacity retention; this occurs because the surface film uniformly covers the LTO electrode and provides strong passivation. Accordingly, there is no significant film deposition during subsequent charge/discharge cycling. Additionally, self-discharge is reduced during high-temperature storage.

• 한국기계가공학회지
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• 제9권6호
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• pp.101-108
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• 2010

The drum clutch investigated in this study is formed in 5 forming steps, which are 1st deep drawing, 2nd deep drawing, restriking, embossing, and $Grob^{TM}$ processes. Dimensional accuracy of the final products greatly depends upon how much more accurate pre-form is manufactured in the previous forming processes before the $Grob^{TM}$ process. The deep drawing, restriking and embossing processes in which the pre-form is formed are very important and decisive steps. Thus in some cases, excessive strain by these operations causes dimensional inaccuracy and cracks initiated from the base and wall of the product. Process variables such as the punch shapes both of 1st and 2nd deep drawing, and punch angle were selected to evaluate the deformation characteristics. The optimum parameters were determined from forming simulations using commercial FEM codes, DEFORM and Tauchi method, specifically developed for metal forming simulation. Finally, experiments for the whole drum clutch forming processes were carried out to verify the optimized forming parameters and the analytical results.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.120-123
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• 2016

The rotor of a turbomolecular drag pump is generally made of an aluminum alloy. Its surface finish is affected by various processes that the rotor itself undergoes during the manufacturing phase. The impact of different surface finishes on the pumping performances of a turbomolecular pump has been mainly investigated by Sawada et al [1]. The present work aims to broaden the previous bibliographic study to the drag stages of a turbomolecular pump by testing the impact of different surface finishes on the compression ratio of the pump. Experimental tests have been made focusing on two processes: the corundum sandblasting and the glass microspheres shot-peening. Both the processes flatten and/or physically remove EDM melted spheres; in particular, blasted surfaces obtained by glass shot-peening are generally smoother than surfaces obtained by corundum sandblasting. In order to characterize the surface texture left by such processes, preliminary surface roughness measurements have been made on the drag rotor disks of several pumps. The experimental tests conducted on both sandblasted and shot-peened rotors confirms previous results obtained on the turbo stages by Sawada et al. [1], showing that the average roughness of the surface has an impact on the compression ratio of the pump; in particular, an increment in the surface roughness causes a corresponding increment in the compression ratio of the pump and vice versa. For the tested pumps, the higher surface roughness gives a factor of increment of about 2 on the measured hydrogen maximum compression ratio of the pump.

• Bulletin of the Korean Chemical Society
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• 제16권12호
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• pp.1193-1203
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• 1995

In this work, we focused on the setup of the tools for the analysis of the final rotational state distribution of photofragments in vibrational predissociations of triatomic van der Waals molecules A-B2. We found that reflection principle used for the direct photodissociation processes can also be applied to find out the final rotational state distributions for indirect photodissociation processes. The quantity which represents the strength of rovibrational coupling between the quasi-bound state and the final state is reflected into the mirror of the classical angular momentum function, instead of the initial state before light absorption used in the reflection principle of direct processes. The sign change in the first derivative of the interaction potential with respect to the bond distance of B2 is found to be the source of the binodal structures in the final rotational distributions of photofragments in the model system studied in this work. In MQDT analysis, short range eigenchannel basis functions were found to be localized in angle, in the previous work [Lee, C.W. Bull. Korean Chem. Soc. 1995, 16, 957.] and may be called angle functions. Angle functions enjoy simple geometrical structures which have simple functional relations with the final state distributions of photofragments. Two processes take place along the angle functions which resemble the quasi-bound state and dominate over other processes. Two such angle functions are found to be not only localized angularly but also localized either one of ends of B2 in motions along the bond of B2. These dominating photodissociation processes, however, cancel each other. This cancellation causes photodissociation to depend sensitively on the interaction potential at other angles than the dominant one. Part of potential surface where much larger torque exists can now play an important role in photodissociation. MQDT also enables us to see which processes play important roles after cancellation. This is done by examining the amounts of time delayed by asymptotic eigenchannels.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.327-327
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• 2020

Increase in Earth's surface temperature, higher rainfall intensity rate, and rapid changes in land cover are just some of the most evident effects of climate change. Flooding, and river sedimentation are two inevitable natural processes in our environment, and both issues poses great risks in the dam industry when not addressed properly. River sedimentation is a significant issue that causes reservoir deposition, and thus causes the dam to gradually lose its ability to store water. In this study, the long-term effects of climate change on the sediment discharge in Yongdam Dam watershed is analyzed through the utilization of SWAT, a semi-distributed watershed model. Based from the results of this study, an abrupt increase on the annual sediment inflow trend in Yongdam Dam watershed was observed; which may suggests that due to the effects of climate change, higher rainfall intensity, land use and land cover changes, the sedimentation rate also increased. An efficient sedimentation management should consider the increasing trend in sedimentation rate due to the effects of climate change.

• Communications for Statistical Applications and Methods
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• 제7권2호
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• pp.435-446
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• 2000

Statistical process control(SPC) and engineering process control(EPC) are two strategies for quality improvement that have been developed independently. EPC seeks to minimize variability by adjusting compensatory variables in order to make the process level close to the target, while SPC seeks to reduce variability by monitoring and eliminating causes of variation. One purpose of this paper is to propose the IMA(0,1,1) model as the in-control process model. For the out-of-control process model we consider two cases; one is the case with a step shift in the level, and the other is the case with a change in the nonstationarity. Another purpose is to suggest the use of an integrated process control procedure with adjustment and monitoring, which can consider the proposed process model effectively. An integrated control procedure will improve the process control activity significantly for cases of the proposed model, when compared to the procedure of using either EPC or SPC, since EPC will keep the process close to the target and SPC will eliminate special causes.

• Communications for Statistical Applications and Methods
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• 제7권3호
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• pp.773-788
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• 2000

Statistical process control (SPC) and engineering process control (EPC) are based on different strategies for processes quality improvement. SPC reduces process variability by detecting and eliminating special causes of process variation. while EPC reduces process variability by adjusting compensatory variables to keep the quality variable close to target. Recently there has been needs for a process control proceduce which combines the tow strategies. This paper considers a combined scheme which simultaneously applies SPC and EPC techniques to reduce the variation of a process. The process model under consideration is an integrated moving average(IMA) process with a step shift. The EPC part of the scheme adjusts the process back to target at every fixed monitoring intervals, which is referred to a repeated adjustment scheme. The SPC part of the scheme uses an exponentially weighted moving average(EWMA) of observed deviation from target to detect special causes. A Markov chain model is developed to relate the scheme's expected cost per unit time to the design parameters of he combined control scheme. The expected cost per unit time is composed of off-target cost, adjustment cost, monitoring cost, and false alarm cost.

• International Journal of Safety
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• 제6권2호
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• pp.27-32
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• 2007

For last several decades with the achievement of fast economic development, the electrical fires occupies over 30 percent of total fire incidents almost every year in Korea and not decreased in spite of much times and efforts. Electrical fire cause diagnostics are to confirm a cause for the fire by examination of fire scene. Cause diagnosis methods haven't been systematized yet, because of limits for available information, investigator's biased knowledge, etc. Therefore, in order to assist the investigators and to find out the exact causes of electrical fires, required is research for an electrical fire cause diagnosis system using DB, computer programming and some mathematical tools. The electrical fire cause diagnosis system has two functions of DB and electrical fire cause diagnosis. The cause diagnosis is conducted by a case-based reasoning on a case base and rule-based reasoning on a rule base. For the diagnosis with high reliability, a mixed reasoning approach of a case-based reasoning and fuzzy rule-based reasoning has been adopted. The electrical fire cause diagnosis system proposes the electrical fire causes inferred from the diagnosis processes, and possibility of the causes as well.

• Korean Journal of Acupuncture
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• 제30권4호
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• pp.230-242
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• 2013

Objectives : DongUiBoGam is a representative medical literature in Korea. This research intends to structurally grasp how DongUiBoGam understands the human body and review the methods of acupuncture and moxibustion in the NaeGyeong chapter of it using text mining. Methods : The structure of DongUiBoGam was analyzed with specific parts of the book that described contents, major premises of understanding the human body, and processes of treatment. We analyzed characteristics of each acupoints in a relationship with causes of diseases & symptoms in the NaeGyeong chapter using a Term Frequency - Inverse Document Frequency(TFIDF). Results : Three different categories of pattern identification(PI) were formed after structural analysis of DongUiBoGam. Every causes of diseases & symptoms were transformed according to the three categories of PI. After analyzing the relationship between acupoints and causes of diseases & symptoms, 114 acupoints were visualized with TFIDF values of three PI categories. Conclusions : The selection of acupoints in NaeGyeong chapter of DongUiBoGam were linked to causes of diseases & symptoms based on the three PI categories. Through visualization of bipartite relationships between acupoints and causes of diseases & symptoms, we could easily understand characteristics of each acupoint.