• Journal of Korean Society for Quality Management
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• v.33 no.3
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• pp.126-134
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• 2005

This paper proposes a selectively cumulative sum(S-CUSUM) control chart for detecting shifts in the process mean. The basic idea of the S-CUSUM chart is to accumulate previous samples selectively in order to increase the sensitivity. The S-CUSUM chart employs a threshold limit to determine whether to accumulate previous samples or not. Consecutive samples with control statistics out of the threshold limit are to be accumulated to calculate a standardized control statistic. If the control statistic falls within the threshold limit, only the next sample is to be used. During the whole sampling process, the S-CUSUM chart produces an 'out-of-control' signal either when any control statistic falls outside the control limit or when L -consecutive control statistics fall outside the threshold limit. The number L is a decision variable and is called a 'control length'. A Markov chain approach is employed to describe the S-CUSUM sampling process. Formulae for the steady state probabilities and the Average Run Length(ARL) during an in-control state are derived in closed forms. Some properties useful for designing statistical parameters are also derived and a statistical design procedure for the S-CUSUM chart is proposed. Comparative studies show that the proposed S-CUSUM chart is uniformly superior to the CUSUM chart or the Exponentially Weighted Moving Average(EWMA) chart with respect to the ARL performance.

• ETRI Journal
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• v.34 no.1
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• pp.24-34
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• 2012

In this paper, the directional carrier sense multiple access/collision avoidance (CSMA/CA) protocol in the immediate acknowledgement mode for IEEE 802.15.3c is analyzed under saturation environments. For the analysis, a sensing region and an exclusive region with a directional antenna are computed probabilistically and a Markov chain model in which the features of IEEE 802.15.3c and the effects of using directional antennas are incorporated is analyzed. An algorithm to find the maximal number of concurrently transmittable frames is proposed. The system throughput and the average transmission delay are obtained in closed forms. The numerical results show the impact of directional antennas on the CSMA/CA media access control (MAC) protocol. For instance, the throughput with a small beamwidth of antenna is more than ten times larger than that for an omnidirectional antenna. The overall analysis is verified by a simulation. The obtained results will be helpful in developing an MAC protocol for enhancing the performance of mmWave wireless personal area networks.

• Management Science and Financial Engineering
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• v.15 no.1
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• pp.1-31
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• 2009

This paper considers the value of warehousing contract under probabilistic demands. We consider a supply chain consisting of a supplier, a retailer and its third-party warehousing partner who provides the warehousing service to the retailer through an outsourcing contract. A typical contract is specified by initial space commitment and modification schedule. The retailer decides the order quantity for the supplier and space commitment for the outsourcing contract. Since there is close relationship between order quantity and space commitment to minimize the total cost including ordering cost, inventory carrying cost, shortage cost, and warehousing cost, we develop an analytical model under probabilistic demands, where the retailer can determine the optimal order size and space commitment level jointly. We found the closed-form optimum for a single-period case and the optimal conditions for a two-period case. To evaluate the value of contract flexibility for the two-period case, we compared the total cost under two policies; one with modification, under which the base commitment can be changed at the start of each period and the other without modification. From results of our numerical analysis, we showed that the modification policy is more cost-effective as the variability of demand increases.

• The Journal of Korean Physical Therapy
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• v.32 no.4
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• pp.245-249
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• 2020

Purpose: This study examined the effects of local vibration using a massage gun on the triceps surae flexibility by measuring the ankle dorsiflexion range of motion (ROM) compared to static stretching in healthy adults. Methods: Twenty healthy subjects were instructed in this study. They were allocated randomly to two groups: local vibration (LV) and static stretching (SS). The ankle dorsiflexion ROM was measured before and after the intervention in supine (open kinetic chain, OKC) and standing (closed kinetic chain, CKC). The LV group received local vibration using a massage gun for five minutes on their triceps surae, and the SS group stood on the Q board with a dorsiflexed ankle for five minutes. The ROM between pre- and post-intervention and the change in ROM between two groups were analyzed. A paired t-test was used to compare the ROM between pre- and post-intervention, while an independent t-test was used to compare the change in ROM between the two groups. Results: Both groups showed a significant difference between pre- and post-intervention in the position of both the OKC and CKC. The change in ROM, however, was not significantly different between the two groups. Conclusion: The application of local vibration using a massage gun for five minutes on the triceps surae could improve its flexibility as much as the application of static stretching. A massage gun for the application of a local vibration stimulus may be effective, simple, portable, and comfortable.

• The Journal of Korean Physical Therapy
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• v.31 no.4
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• pp.161-168
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• 2019

Most athletes with anterior cruciate ligament (ACL) ruptures undergo a surgical ACL reconstruction (ACLR) and rehabilitation. On the other hand, controversy still exists because neither a reconstruction nor rehabilitation have been proven to be superior in the management of ACL injury. This study reviewed the success rates of interventions to provide recommendations for the optimal management after an ACL injury. One of the most important considerations after an ACL injury is the timing and type of intervention. At the early stages, which involve the loss of volume and strength of quadriceps femoral muscle, weight bearing (closed kinetic chain) exercises with pain management followed by high velocity resistance exercises in an open kinetic chain environment are recommended to improve the quadriceps function. After that, it is important to apply intensive isokinetic exercise with a lower extension rate. In this case, it is important to apply overload to the muscles and to simultaneously lead the co-contraction of the hamstrings. Standards are essential because the timing and type of interventions are crucial to prevent re-injury and complications, such as osteoarthritis, as well as to confirm the successful outcome of the treatment. Different interventions recommended for ACL damage have yet to reach consensus. Further studies will be needed to observe the effects of the intervention through multidisciplinary approaches.

• Journal of the Korean Society of Clothing and Textiles
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• v.46 no.6
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• pp.1039-1057
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• 2022

The fashion system has been criticized for relying on a linear economy to reduce short-term costs and increase profits. Meanwhile, the circular economy strives to expand the value chain through a closed loop for companies, society, and the environment by separating consumption from resources. This study aims to elucidate the strategic characteristics of the technological measures that fashion companies and brands are trying to innovate into a sustainable fashion system on the basis of the circular economy concept. Thus, we conducted case studies by dividing the value chain of the fashion system into design, production, and consumption to identify the technological development of the circular fashion system from a technologization perspective that incorporates technological values. First, design appeared to strengthen emotional durability, design and process with circulation in mind, and fashion product digitalization. Second, production manifested itself as material development for the new fiber economy, improvement of non-environmental processes, and customization of demand-driven, responsive production. Third, consumption was the spread of the environmental consumption culture through the sharing economy platform, the realization of a virtual wearing experience to prevent rapid disposal, and the provision of information on sustainable consumption.

• Korean journal of communication and information
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• v.71
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• pp.194-223
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• 2015

This study explores a value chain structure of TV program including news, drama, and comedy. The purpose of this research focused on factor analysis and the relationship among viewer's program selection motivations. This research explores correlation between personal value and viewing motivation. This study was to identify the value structure of respondent on TV program(news, drama, comedy) based on means-end chain theory. The research used structured APT laddering questions and 251 data was analysed. Through such analysis, category difference by stage and relationship difference were identified and hierarchical value map was compared. There are four different value ladders: first is attributes, functional consequences, psychological consequences, and final value. The result shows that on news program the basic function is viewers are want to visual factor and quickly acquire social news and they pursue a value of personal social relationship. Whereas, on drama program, the viewers are reflected by around person, and they selected a program based on closed related person. In addition, the viewers are influenced by program's social nomination, production's brand in drama, and performer's nomination, producer and program prominence on comedy. The program selection is highly correlated on program selection's credibility, vital energetic life, and social relationship. The results shows that there was no significant difference between low involvement group and high involvement group for main category involvement group respondents.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.205-215
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• 2001

In this study, modeling and analysis procedure for the dynamic analysis of a high mobility tracked vehicle system were studied. The vehicle model used in this investigation is assumed to be consist of two kinematically decoupled subsystems. The chassis subsystem consists of chassis frame, sprocket, support rollers, road wheels, idler wheel, road wheel arms and idle wheel arm, while the track subsystem is represented as a closed kinematic chain consisting of track links and end connectors interconnected by revolute joints with bushing. Nonlinear contact force module describing the interaction between track link, and sprocket, idler wheel, road wheel, support roller, ground was used. The effects of road wheel arms and idler wheel arm due to tension adjuster are also considered.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.1
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• pp.41-48
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• 1994

The conventional resolved motion control is not applicable for the control of robots on the spacecraft on account of the floating base of the robots. When the robots perform the assembly or repair operations, the position and attitude of the base satellite are disturbed by the reaction force/moment caused by the robot motion. This reaction will cause error on the robot. motion. Therefore, we define a new type of Jacobian(Extended Jacobian) to minimize the effects of reaction on the accuracy of the robot performing assembly or repair operations. In this paper, we utilize the redundancy of the closed chain system to minimize the effects of the robot motion on the position and attitude of spacecraft. This will results in the accurate assembly and repair operations by the robot.

• Elastomers and Composites
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• v.32 no.1
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• pp.29-36
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• 1997

The change of elastic modulus(E'), loss modulus(E"), and loss $tangent(tan{\delta})$ were investigated on condition of double strain amplitude (DSA) at temperature of $-40{\sim}80^{\circ}C$ for carbon black filled natural rubber. E', E", and $tan{\delta}$ were increased as it closed to the glass transition temperature due to decrease of rubber network flexibility and carbon black agglomerate interaction. In the micro strain range, energy loss showed maximum value because of the chain slippage in rubber matrix, but the regeneration of carbon black agglomerate and rubber matrix affected decrease of energy loss over the mid-range strain. As a results of regression analysis, $E'\;_{max}$ correlation with ${\Delta}E'$ $(E'\;_{0.4%DSA}-E'\;_{2.0%DSA})$ showed linear relationship.