• Communications of the Korean Mathematical Society
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• v.36 no.2
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• pp.209-227
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• 2021

In this paper, we deal with the question that what kind of properties does a ring gain when it satisfies symmetricity or reversibility by the way of nilpotent elements? By the motivation of this question, we approach to symmetric and reversible property of rings via nilpotents. For symmetricity, we call a ring R middle right-(resp. left-)nil symmetric (mr-nil (resp. ml-nil) symmetric, for short) if abc = 0 implies acb = 0 (resp. bac = 0) for a, c ∈ R and b ∈ nil(R) where nil(R) is the set of all nilpotent elements of R. It is proved that mr-nil symmetric rings are abelian and so directly finite. We show that the class of mr-nil symmetric rings strictly lies between the classes of symmetric rings and weak right nil-symmetric rings. For reversibility, we introduce left (resp. right) N-reversible ideal I of a ring R if for any a ∈ nil(R), b ∈ R, being ab ∈ I implies ba ∈ I (resp. b ∈ nil(R), a ∈ R, being ab ∈ I implies ba ∈ I). A ring R is called left (resp. right) N-reversible if the zero ideal is left (resp. right) N-reversible. Left N-reversibility is a generalization of mr-nil symmetricity. We exactly determine the place of the class of left N-reversible rings which is placed between the classes of reversible rings and CNZ rings. We also obtain that every left N-reversible ring is nil-Armendariz. It is observed that the polynomial ring over a left N-reversible Armendariz ring is also left N-reversible.

• International journal of advanced smart convergence
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• v.8 no.2
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• pp.109-115
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• 2019

Currently, LPWA(Low Power Wide Area) communication technology is widely used due to the development of IoT(Internet of Things) technology. Among the LPWA technologies, LoRaWAN(Long Range Wide Area Network) is widely used in many fields due to its wide coverage, stable communication speed, and low-cost modem module prices. In particular, LoRa(Long Range) can easily construct LoRaWAN with a dedicated gateway. So many organizations are building their own LoRaWAN-based networks. The LoRaWAN Gateway receives the LoRa packet transmitted from an End-device installed in the adjacent location, converts it into the Internet protocol, and sends the packet to the final destination server. Current LoRa Gateway uses a single-hop method, and each gateway must include a communication network capable of the Internet. If it is the mobile communication(i.e., WCDMA, LTE, etc.) network, it is required to pay the internet usage fee which is installed in each gateway. If the LoRa communication is frequent, the user has to spend a lot of money. We propose an idea on how to design a multi-hop protocol which enables packet routing between gateways by analyzing the LoRaWAN communication method implemented in its existing single-hop way in this paper. For this purpose, this paper provides an analysis of the standard specification of LoRaWAN and explains what was considered when such protocol was designed. In this paper, two gateways have been placed based on the functional role so as to make the multi-hop protocol realized: (i) hopping gateway which receives packets from the end-device and forwards them to another gateway; and (ii) main gateway which finally transmits packets forwarded from the hopping gateway to the server via internet. Moreover, taking into account that LoRaWAN is wireless mobile communication, a level-based routing method is also included. If the protocol proposed by this paper is applied to the LoRaWAN network, the monthly internet fee incurred for the gateway will be reduced and the reliability of data transmission will be increased.

• The Journal of the Korea Contents Association
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• v.22 no.4
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• pp.284-291
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• 2022

People use various tools to present themselves including Social Network Services(SNS hereafter). This study categorized three types of presentation of self, which are genuine, ideal, and social self, and based on Goffman's Impression Management Framework, investigated if these types of presentations have any patterns related to SNS posting styles. Especially, we focused on the styles of hashtags including if hashtags are used in the main tests, if hashtags are hidden, and what kinds of words are used for hashtags. Using 450 posting data uploaded to the Instagram, we found that the posting presenting ideal self show very high rate of using hidden hashtags(98%) and using common expressions(97%), which are not the case for genuine and social self types. This results imply that people concern more about their impressions especially when they present their ideal self on SNS, partially confirming Goffman's Impression Management Framework.

• Clinical and Experimental Pediatrics
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• v.49 no.9
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• pp.937-945
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• 2006

The population of adult patients with congenital heart disease(CHD) has increased dramatically because of improved survival of infants and children with CHD. There are still a substantial number of adults with unrepaired CHD. Many adult patients do not know the possible problems of their disease such as ventricular dysfunction, arrhythmia, and what they should pay attention to. They often consider themselves "cured" or "healthy" if only they don't have overt symptoms, and visit hospitals only after deterioration of their problems. Some patients are neglected because they cannot be corrected surgically although careful medical support can improve their survival and quality of life. It is, therefore, essential that the patients, their families, and physicians understand the potential problems of CHD and need for regular follow-up. In this paper we will take a brief review for common medical problems of repaired or unrepaired CHD and also mention a few specific diseases which are common in adults.

• Korean System Dynamics Review
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• v.8 no.2
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• pp.25-49
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• 2007

An important assumption of the classical linear regression model is that the disturbances appearing in the population regression function are homoskedastic; that is, they all have the same variance. If we persist in using the usual testing procedures despite heteroskedasticity, what ever conclusions we draw or inferences we make be very misleading. The contribution of this paper will be to the concrete procedure of the proper estimation when the heteroskedasticity does exist in the data, because the quality of dependent variable predictions, i.e., the estimated variance of the dependent variable, can be improved by giving consideration to the issues of regional homogeneity and/or heteroskedasticity across the research area. With respect to estimation, specific attention should be paid to the selection of the appropriate strategy in terms of the auxiliary regression model. The paper shows that by testing for heteroskedasticity, and by using robust methods in the presence of with and without heteroskedasticity, more efficient statistical inferences are provided.

• Korean Institute of Interior Design Journal
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• no.16
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• pp.91-97
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• 1998

We have been taught designing process throughout the long period of education. Nevertheless it is hard to make a quick response to actual project However if we are faced with the actual project as a design professionals it is hard to cope with the project at once nothing but ambiguous idea. Also most of designers concemed with the project do not recognize who are responsible for what. Consequently this attitude delays the entire operation causing waste of time and resources and leads to the unacceptable result. This research is designed therefore to come up with the projects control process that is practical enough to encourage interior designers as well as design firms to face actual projects with shrewd response. There is of course no single right answer to certain design projects. But at least there should be a guideline which shows designers more reasonale systematic ways to control design project lest they should waste time and cost : a guideline as an assistance for successful design result.

• Journal of Korean Physical Therapy Science
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• v.6 no.3
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• pp.83-89
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• 1999

We are approaches various painful diseases in clinic. Although same disease, it is different to acute, subacute and chronic stage of disease. Therefore, to understanding of tissue anatomy, pathology and physiology is necessary to under-standing pattern of diseases. It is duty work that choice of hot or ice, electrotherapy, choice of adaptable frequency and mathod of exercise therapy etc. During treatment it is important method to choose to treat the client. As treating the client by exercising or treating when the client is resting and seeing if anything else is a problem etc. So what I have approached some of the treatment that a physical therapist could miss during treatment.

• MALSORI
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• no.50
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• pp.71-83
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• 2004

Recently, broadcast news speech recognition has become one of the most attractive research areas. If we can transcribe automatically the broadcast news and store their contents in the text form instead of the video or audio signal itself, it will be much easier for us to search for the multimedia databases to obtain what we need. However, the desirable speech signal in the broadcast news are usually affected by the interfering signals such as the background noise and/or the music. Also, the speech of the reporter who is speaking over the telephone or with the ill-conditioned microphone is severely distorted by the channel effect. The interfered or distorted speech may be the main reason for the poor performance in the broadcast news speech recognition. In this paper, we investigated some methods to cope with the problems and we could see some performance improvements in the noisy broadcast news speech recognition.

• The Journal of Korean Institute for Practical Engineering Education
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• v.1 no.1
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• pp.38-43
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• 2009

In the study of differential equation the most obstacle is that you have to spend lots of times and the plots of solutions are not easy by hand. If we do not solve these kinds of problem, it is difficult to achieve the goal of the object which is the understanding and the practical use of the differential equation. In this paper we explain what should be Maple's usefulness in the method of removing these obstacles, and introduce the stepwise executing codes of Maple which is developed for student's easy application.

• English Language & Literature Teaching
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• v.18 no.1
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• pp.153-169
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• 2012

This study reviews an English enhancement course implemented for medical and nursing college students of 2011 to improve their standardized English test scores. A total of 117 first-year students underwent the pre-test and the post-TOEIC in November 2011. After the pre-test, lectures on listening enhancement strategies and problem solving tactics on reading comprehension were supplemented with 4 times of enhancement-tests. Their pre- and post-TOEIC results were compared to see if such enhancement strategies were effective to improve their TOEIC scores. It was further to investigate, through survey questionnaires, how the subjects felt about a number of pre-test-type TOEIC exercise with what-to-listen and how-to-infer listening strategies and pattern-drill practices for reading comprehension. It was found that the scores of listening comprehension improved significantly for both major students whereas reading scores showed slight decrease among nursing majors. It is concluded that administering numerous pre-test-type-TOEIC exercise is effective for students to improve their listening scores supplemented with listening strategies Also, students' response showed positive toward the enhancement course.