• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.7-17
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• 2006

In this paper, we proposed an optical true time-delay (TTD) for planar phased array antennas (PAAs), which is composed of a wavelength-dependent optical true time delay (WDOTTD) followed by a wavelength-independent optical true time delay (WIOTTD). The WDOTTD is a fiber Bragg gratings (FBGs) Prism and the WDOTTD is a fiber delay-lines matrix of which each component consists of a certain length of fiber connected to cross-ports of a 2${\times}$2 MEMS switch. A 10-GHz 2-bit${\times}$4-bit two-dimensional optical TTD has been fabricated by cascading a WDOTTD with a maximum time delay of 810 ps to a WIOTTD of $\pm$50 ps. Time delay and insertion loss for each radiation angle have been measured. Time delay error for the WIOTTD has been measured to be less than $\pm$1 ps. We have also designed a two-dimensional 10-GHz PAA composed of 8${\times}$8 microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation and analyzed.

• Journal of the Korean Data and Information Science Society
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• v.22 no.2
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• pp.189-196
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• 2011

In this study, we perform a simulation study to compare frequently used standardization methods for interview scores based on trimmed mean, rank mean, and z-score mean. In this simulation study we assume that interviewer's score is influenced by a weighted average of true interviewee's true score and independent noise whose weight is determined by the professionality of the interviewer. In other words, as interviewer's professionality increases, the observed score becomes closer to the true score and if interviewer's professionality decreases, the observed score becomes closer to the noise instead of the true score. By adding interviewer's tendency bias to the weighed average, final interviewee's score is assumed to be observed. In this simulation, the interviewers's cores for each method are computed and then the method is considered best whose rank correlation between the method's scores and the true scores is highest. Simulation results show that when the true score is from normal distributions, z-score mean is best in general and when the true score is from Laplace distributions, z-score mean is better than rank mean in full interview system, where all interviewers meet all interviewees, and rank mean is better than z-score mean in half split interview system, where the interviewers meet only half of the interviewees. Trimmed mean is worst in general.

• The Journal of Korean Academy of Prosthodontics
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• v.24 no.1
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• pp.17-26
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• 1986

The purpose of this study was to investigate true hinge axis location with different times (8:00-9:00 A.M.,2:00-3:00 P.M.) and with experienced and inexperienced groups. 25 subjects, 23-27 years of age , with functionally acceptable occlusion, and no clinical signs of temporomandibular joint dysfunction were participated in this study. In this study arbitrary hinge axis point was located 13 mm anterior to the posterior margin of the tragus on a line from the center of the tragus to the outer canthus of the eye and then the true hinge axis point was located with T.M.J. hinge axis locator. The discrepancies of distance and the direction between true hinge axis point and arbitrary hinge axis point were studied according to times and two groups. The results obtained were as follows : 1. The mean distance from arbitrary hinge axis point to the true hinge axis point on the right and left sides was as follows : Experienced group: linear distance: $1.228{\pm}3.145mm$, vertical distance: $-1.128{\pm}2.515mm$, horizontal distance: $-0.484{\pm}1.806mm$. Inexperience group: linear distance: $1.628{\pm}3.158mm$, vertical distance: $-1.169{\pm}2.090mm$, horizontal distance: $-1.133{\pm}2.367mm$. Horizontal distance between experienced and inexperienced groups was significant statistically. (P<0.1) 2. True hinge axis points located within 5 mm of arbitrary hinge axis point were 86.7% in the experienced group and 84% in the inexperienced group. 3. For experienced operator A with time, the mean distance from arbitrary hinge axis point to true hinge axis point was as follows: Horizontal distance: AM: $-0.613{\pm}1.966mm$, PM: $-0.860{\pm}2.156mm$. Vertical distance: AM: $-0.886{\pm}2.518mm$, PM : $-1.226{\pm}2.660mm$. True hinge axis points had tendency to be located posterior-inferiorly to tragus-canthus line in the afternoon than in the morning, but there was not significant statistically. (P>0.1)

• Investigative Magnetic Resonance Imaging
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• v.26 no.1
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• pp.10-19
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• 2022

Purpose: To evaluate whether the added value of contrast leakage information from dynamic susceptibility contrast magnetic resonance imaging (DSC MRI) is a better prognostic imaging biomarker than the cerebral blood volume (CBV) value in distinguishing true progression from pseudoprogression in glioblastoma patients. Materials and Methods: Forty-nine glioblastoma patients who had undergone MRI after concurrent chemoradiotherapy with temozolomide were enrolled in this retrospective study. Twenty features were extracted from the normalized relative CBV (nCBV) and extraction fraction (EF) map of the contrast-enhancing region in each patient. After univariable analysis, we used multivariable stepwise logistic regression analysis to identify significant predictors for differentiating between pseudoprogression and true progression. Receiver operating characteristic (ROC) analysis was employed to determine the best cutoff values for the nCBV and EF features. Finally, leave-one-out cross-validation was used to validate the best predictor in differentiating between true progression and pseudoprogression. Results: Multivariable stepwise logistic regression analysis showed that MGMT (O⁶-methylguanine-DNA methyltransferase) and EF max were independent differentiating variables (P = 0.004 and P = 0.02, respectively). ROC analysis yielded the best cutoff value of 95.75 for the EF max value for differentiating the two groups (sensitivity, 61%; specificity, 84.6%; AUC, 0.681 ± 0.08; 95% CI, 0.524-0.837; P = 0.03). In the leave-one-out cross-validation of the EF max value, the cross-validated values for predicting true progression and pseudoprogression accuracies were 69.4% and 71.4%, respectively. Conclusion: We demonstrated that contrast leakage information parameter from DSC MRI showed significance in differentiating true progression from pseudoprogression in glioblastoma patients.

• Asian-Australasian Journal of Animal Sciences
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• v.21 no.5
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• pp.701-706
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• 2008

The aim of the present study was to determine the apparent and true digestibilities of amino acids of maize, low tannin sorghum, pearl millet and finger millet in adult caecectomized cockerels. Adult cockerels (n = 60), 25-weeks old, were used in this study of which 30 birds were caecectomized as per a standard method. The apparent digestibilities of amino acids of sorghum were not affected by caecectomy, but were higher for maize, finger millet and pearl millet in caecectomized cockerels. Caecectomy had no influence on the true digestibilities of amino acids of maize, but higher digestibilities were observed for most of the amino acids of sorghum and finger millet in caecectomized cockerels. Caecectomy lowered the true digestibility of cystine, threonine and serine of pearl millet. The apparent digestibilities of amino acids of maize, finger millet and pearl millet were underestimated in intact cockerels. The true digestibilities of most of the amino acids of sorghum and finger millet were underestimated, while those of cystine, threonine and serine of pearl millet were overestimated in intact cockerels. The findings suggest that the amino acid digestibility values of cereal grains determined using caecectomized cockerels might be appropriate and reliable for poultry diet formulations. Moreover, the digestibilities of amino acids of finger millet were inferior to other cereal grains, while those of pearl millet were comparable to maize and sorghum.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.1
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• pp.83-92
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• 2010

Emergence of high-resolution digital aerial cameras and airborne laser scanners have made innovative progress in photogrammetry and spatial information technology. The purpose of this study is to generate true orthoimage by recovering occlusion areas. The orthoimages were generated patch-based transformation. The occlusion areas were mutually corrected by using multiple aerial images. This study proposed a novel method of building roof based orthoimage generation and an effective method of occlusion area detection and recovery. The proposed methods could be efficient to generate true orthoimages in urban areas where occlusion areas are problematic.

• ETRI Journal
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• v.42 no.4
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• pp.518-526
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• 2020

This paper presents an efficient hardware random-number generator based on a beta source. The proposed generator counts the values of "0" and "1" and provides a method to distinguish between pseudo-random and true random numbers by comparing them using simple cumulative operations. The random-number generator produces labeled data indicating whether the count value is a pseudo- or true random number according to its bit value based on the generated labeling data. The proposed method is verified using a system based on Verilog RTL coding and LabVIEW for hardware implementation. The generated random numbers were tested according to the NIST SP 800-22 and SP 800-90B standards, and they satisfied the test items specified in the standard. Furthermore, the hardware is efficient and can be used for security, artificial intelligence, and Internet of Things applications in real time.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.3 no.5
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• pp.444-460
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• 2009

In this paper, we propose an expanded patching technique in order to reduce the server network bandwidth requirements to support true VoD services in VoD Systems. Double Patching, which is a typical multicast technique, ensures that a long patching stream delivers not only essential video data for the current client but also extra video data for future clients. Since the extra data may include useless data, it results in server network bandwidth wastage. In order to prevent a server from transmitting useless data, the proposed patching technique uses a new kind of stream called a linking stream. A linking stream is transmitted to clients that have received short patching streams, and it plays a linking role between a patching stream and a regular stream. The linking stream enables a server to avoid transmitting unnecessary data delivered by a long patching stream in Double Patching, so the server never wastes its network bandwidth. Mathematical analysis shows that the proposed technique requires less server network bandwidth to support true VoD services than Double Patching. Moreover, simulation results show that it has better average service latency and client defection rate compared with Double Patching.

• The Mathematical Education
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• v.51 no.2
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• pp.161-171
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• 2012

Generally mathematics is regarded as a subtle subject to grasp their true meaning. And teacher's personal conceptions of mathematics influence greatly on the teaching and learning of mathematics. More over often teachers confess their difficulties in explaining the true nature of mathematics. In this paper, applying the theory of epistemology, we tried to search factors that must be counted important when trying to understand the true nature of mathematics. As results, we identified five characteristics of mathematical knowledge such as logical reasoning, abstractive concept, mathematical representation, systematical structure, and axiomatic validation. Next, we tried to investigate math education major students' conception of mathematics using these items. To proceed this research we asked 51 students from three Universities to answer their opinion on 'What do you think is mathematics?'. Analysing their answers in the light of the above five items, we got the following facts. 1. Only 38% of the students regarded mathematics as one of the five items, which can be considered to reveal students' low concern about the basic nature of mathematics. 2. The status of students' responses to the question were greatly different among the three Universities. This shows that mathematics professors need to lead students to have concern about the true nature of mathematics.

• The Korean Journal of Health Service Management
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• v.7 no.3
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• pp.193-202
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• 2013

This study aimed to investigate and compare the perception of personal protective equipments and instrument sterilization of students who are in attendance at colleges and universities and which have bedside training as a regular subject in their curriculum for third-year students. 'Completely True' is the highest response to the question about the importance of wearing gloves, mask and medical gown from all groups. 'Completely True' is the highest response to the question about the necessity for replacement of gloves from all groups. 'Moderate True' is the highest response to the question about the necessity for replacement of mask from the group without practical training and 'Completely True' is the highest response to the question about the importance of hair cleanliness from all groups regardless of practical training experience. For the question about the perception of instrument disinfection and sterilization, the group with inside and outside practical training showed the highest perception level. Consequently, the right education for prevention of infection by setting inclusive guidelines to enhance the level of perception and practice seems continuously necessary.