• Journal of the Society of Naval Architects of Korea
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• v.60 no.3
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• pp.202-211
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• 2023

The profile shops in shipyards produce section steels required for block production of ships. Due to the limitations of shipyard's production capacity, a considerable amount of work is already outsourced. In addition, the need to improve the productivity of the profile shops is growing because the production volume is expected to increase due to the recent boom in the shipbuilding industry. In this study, a scheduling optimization was conducted for a parallel welding line of the profile process, with the aim of minimizing tardiness and the number of set-up changes as objective functions to achieve productivity improvements. In particular, this study applied a dynamic scheduling method to determine the job sequence considering variability of processing time. A Markov decision process model was proposed for the job sequence problem, considering the trade-off relationship between two objective functions. Deep reinforcement learning was also used to learn the optimal scheduling policy. The developed algorithm was evaluated by comparing its performance with priority rules (SSPT, ATCS, MDD, COVERT rule) in test scenarios constructed by the sampling data. As a result, the proposed scheduling algorithms outperformed than the priority rules in terms of set-up ratio, tardiness, and makespan.

• Restorative Dentistry and Endodontics
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• v.46 no.1
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• pp.1.1-1.13
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• 2021

Objectives: The aim of this study was to evaluate the dystrophic mineralization deposits from 3 calcium silicate-based cements (Micro-Mega mineral trioxide aggregate [MM-MTA], Biodentine [BD], and EndoSequence Root Repair Material [ESRRM] putty) over time after subcutaneous implantation into rats. Materials and Methods: Forty-five silicon tubes containing the tested materials and 15 empty tubes (serving as a control group) were subcutaneously implanted into the backs of 15 Wistar rats. At 1, 4, and 8 weeks after implantation, the animals were euthanized (n = 5 animals/group), and the silicon tubes were removed with the surrounding tissues. Histopathological tissue sections were stained with von Kossa stain to assess mineralization. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) were also used to assess the chemical components of the surface precipitates deposited on the implant and the pattern of calcium and phosphorus distribution at the material-tissue interface. The calcium-to-phosphorus ratios were compared using the non-parametric Kruskal-Wallis test at a significance level of 5%. Results: The von Kossa staining showed that both BD and ESRRM putty induced mineralization starting at week 1; this mineralization increased further until the end of the study. In contrast, MM-MTA induced dystrophic calcification later, from 4 weeks onward. SEM/EDX showed no statistically significant differences in the calcium- and phosphorus-rich areas among the 3 materials at any time point (p > 0.05). Conclusions: After subcutaneous implantation, biomineralization of the 3-calcium silicate-based cements started early and increased over time, and all 3 tested cements generated calcium- and phosphorus-containing surface precipitates.

• Journal of Cardiovascular Imaging
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• v.31 no.2
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• pp.71-82
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• 2023

BACKGROUND: Cardiac magnetic resonance fingerprinting (cMRF) enables simultaneous mapping of myocardial T1 and T2 with very short acquisition times. Breathing maneuvers have been utilized as a vasoactive stress test to dynamically characterize myocardial tissue in vivo. We tested the feasibility of sequential, rapid cMRF acquisitions during breathing maneuvers to quantify myocardial T1 and T2 changes. METHODS: We measured T1 and T2 values using conventional T1 and T2-mapping techniques (modified look locker inversion [MOLLI] and T2-prepared balanced-steady state free precession), and a 15 heartbeat (15-hb) and rapid 5-hb cMRF sequence in a phantom and in 9 healthy volunteers. The cMRF_5-hb sequence was also used to dynamically assess T1 and T2 changes over the course of a vasoactive combined breathing maneuver. RESULTS: In healthy volunteers, the mean myocardial T1 of the different mapping methodologies were: MOLLI 1,224 ± 81 ms, cMRF_15-hb 1,359 ± 97 ms, and cMRF_5-hb 1,357 ± 76 ms. The mean myocardial T2 measured with the conventional mapping technique was 41.7 ± 6.7 ms, while for cMRF_15-hb 29.6 ± 5.8 ms and cMRF_5-hb 30.5 ± 5.8 ms. T2 was reduced with vasoconstriction (post-hyperventilation compared to a baseline resting state) (30.15 ± 1.53 ms vs. 27.99 ± 2.07 ms, p = 0.02), while T1 did not change with hyperventilation. During the vasodilatory breath-hold, no significant change of myocardial T1 and T2 was observed. CONCLUSIONS: cMRF_5-hb enables simultaneous mapping of myocardial T1 and T2, and may be used to track dynamic changes of myocardial T1 and T2 during vasoactive combined breathing maneuvers.

• Steel and Composite Structures
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• v.52 no.2
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• pp.199-215
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• 2024

The Caynarachi Bridge is a 130 m long posttensioned steel-concrete composite bridge built in Peru. The structural performance of this bridge under construction loads is reviewed in this paper using numerical simulation. Hence, a numerical model using shell finite elements to trace its deformational behavior at service conditions is proposed. The geometry and boundary conditions of the superstructure are updated according to the construction schedule. Firstly, the adequacy of the proposed model is validated with the field measurements obtained from the static truck load test. Secondly, the study of other scenarios less explored in research are performed to investigate the effect of some variables on bridge performance such as time effects, sequence of execution of concrete slabs and type of supports conditions at the abutments. The obtained results show that the original sequence of execution of the superstructure better behaves mechanically in relation to the other studied scenarios, yielding smaller stresses at critical cross sections with staging. It is also demonstrated that an improper slab staging may lead to more critical stresses at the studied cross sections and that casting the concrete slab at the negative moment regions first can lead to an optimal design. Also, the long-term displacements can be accurately predicted using an equivalent composite resistance cross section defined by a steel to concrete modulus ratio equal to three. This article gives some insights into the potential shortcomings or advantages of the original design through high-fidelity finite element simulations and reinforces the understating of posttensioned composite bridges with staging.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.549-556
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• 2017

This study investigated the importance of social cognitive intervention and the cognitive rehabilitation intervention by comparing the difference and examining the relationship between neurological cognitive function and social cognitive function of stroke patients in the acute phase and chronic stroke before returning to the community. LOTCA, cartoon intention inference task, and social behavior sequence task were performed on 30 acute stroke inpatients and 30 chronic stroke patients from May 2015 to June 2016. A two sample t test was conducted to examine the differences between the groups. The Pearson's correlations test was performed to examine the correlation among the variables in each group. As a result, there were statistically significant differences between the neurological cognitive function and social cognitive function of acute stroke patients and chronic stroke patients who were undergoing rehabilitation training before returning to the community (p<0.05). A linear relationship was found between the thinking operation and social behavior sequence task in the acute stroke group (r=0.539, p<0.05). In the chronic stroke group, visual perception (r=0.530, p<0.05), visual motor organization (r=0.655, p<0.05) and thinking operation (r=0.534, p<0.05) were correlated with the cartoon intention inference task. In addition, the social behavior sequence task were correlated with visual organization (r=0.534, p<0.05) and thinking operation (r=0.764, p<0.05). As a result of multiple regression analysis, the neurological cognitive functions influencing the social cognitive function in the cartoon task was found to be the thinking operation (B = 0.431) in acute stroke patients and the thinking operation (B=0.272) and visuomotor organization (B = 0.218) in the case of chronic stroke. In addition, the results of the social behavior sequence task revealed the thinking operation (B=0.417) in the acute stroke patients, and thinking operation (B=0.267), visual motor organization(B=0.274) and visual perception(B=151) in chronic stroke patients to be significant. According to this result, there is a difference in the neurological and social cognitive levels between the two groups. Therefore, the social cognition is strongly related to the high level cognitive function as thinking operation of the neurological cognitive function. Therefore, in further research, it would be necessary to determine if there is a change in higher cognitive function in neurological cognitive function after applying a social cognition intervention program for stroke.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.99-103
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• 2017

As a development test of the 75-tonf LOx/Kerosene liquid rocket engine for KSLV-II first Stage Engine, hot firing test of 75-tonf engine are performed. The current status of development test on first stage 75-tonf engine system including combustion chamber, turbopump, gas generator, propellant supply system are presented. During the 75tonf engine test campaign, the development of startup sequence of LOx-Kerosene engine system, engine startup using pyrostarter, ignition of gas generator, steady operation and engine shutdown is successfully performed. As a passenger test during engine hot firing tests, Thrust Vector Control system (TVC) of the engine are also evaluated during engine hot firing test. The results of hot firing test of 75-tonf thrust engine system will be used for the design confirmation and performance evaluation of 75 tonf engine system for KSLV-II first Stage.

• Journal of the Korea Computer Graphics Society
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• v.15 no.4
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• pp.1-11
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• 2009

In this paper, we present a prism-based mesh culling method to improve effectiveness of continuous collision detection which is a major bottleneck in a simulation using polygonal mesh models. A prism is defined based on two matching triangles between a sequence of times m a polygonal model. In order to detect potential colliding set(PCS) of prism between two polygonal models in a unit time, we apply the visibility test based on the occlusion query to two sets of prisms which are defined from two polygonal models in a unit time. Moreover, we execute the narrow band culling based on SAT(Separating Axis Test) to define potential colliding prism pairs from PCS of prisms extracted as a result of the visibility test. In the SAT, we examine one axis to be perpendicular to a plane which divides a 3D space into two half spaces to include each prism. In the experiments, we applied the proposed culling method to pairs of polygonal models with the different size and compared the number of potential colliding prism pairs with the number of all possible prism pairs of two polygonal models. We also compared effectiveness and performance of the visibility test-based method with those of the SAT-based method as the second narrow band culling. In an experiment using two models to consist of 2916 and 2731 polygons, respectively, we got potential colliding prism pairs with 99 % of culling rate.

• International Journal of Highway Engineering
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• v.12 no.3
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• pp.79-85
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• 2010

This paper presents a preliminary study of roller types for chip seals based on aggregate retention performance. Chip seal test sections composed of single seals of granite 78M aggregate and CRS-2 emulsion were constructed using three different roller types: the pneumatic tire roller, steel wheel roller, and combination roller. In order to investigate the performance of these rollers effectively, it is critical to test chip seal samples obtained directly from field construction. Therefore, test sections were constructed on New Sandy Hill Church Road near Bailey, North Carolina. Chip seal samples obtained from these sections were used for laboratory testing. The aggregate retention performance was evaluated using the flip-over test (FOT), Vialit test, and the third-scale Model Mobile Loading Simulator (MMLS3). Based on the test results and visual observation, both the pneumatic roller and the combination roller used together are recommended to improve chip seal performance with the sequence of the pneumatic roller rolling first followed by the combination roller.

• Journal of muscle and joint health
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• v.6 no.1
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• pp.22-36
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• 1999

The purpose of the study was to identify disease characteristics and behavior pattern of treatment for patients with Fibromyalgia. This study was carried out between May to Aug. in 1998 through direct interview in Rheumatism clinic at H. University Hospital and subject in this study were 125 outpatients diagnosed with Fibromyalgia. Collected data were analyzed by descriptive statistics and t-test, ANOVA using SPSS Window program. The results of this study are as follows. 1. General Characteristics : All of the persons with Fibromyalgia were female who were mostly in their forties(37.5%). A third of them(38.4%) were graduated from high school. The greatest part of them(54.4%) were christians but little part of them(16.8%) were employed 2. Disease Characteristics : They have struggled with Fibromyalgia for 10 years on an average. About half of them(56.9%) suffered from Fibromyalgia only but the others had another diseases which were in greatest part occupied by Osteoarthritis. The number of tender point which is a feature of Fibromyalgia differed according to measuring criteria. Yunus criteria. however, was proved to be the most proper measuring criteria than any other method as it showed high correlations between symptoms and physical activities. The most serious symptoms that complained the patients among subjective symptoms are pain, sleep disorder, and fatigue in sequence, and activities most hard to do among physical activities are washing by hand, scrubbing by hand, and shopping in sequence. 3. Behavior Pattern of Treatment : The largest part of them(42.4%) had received medical treatment after they were determined to have the disease and most of them were taking medicine as prescribed by physician(88.8%) or other medicines(16.8%), Of them, two thirds stated that the medicine they took were effective. Around a third of them took exercises mostly composed of swimming. The medical institution they visited in the past were orthopedic surgical department, Oriental hospital, physical therapy department in sequence and, in a slight percent(11.4%), psychiatric department. 4. Relations between Disease Characteristics and Behavior pattern of Treatment : It shows that number of tender point and level of symptom are significantly different according to duration of disease and medical intervention. As a results, it can be suggest that persons with Fibromyalgia need to take exercises and medicine continually regardless of medical treatment as it is a chronic disease whose symptoms are hardly mitigated.

• Journal of KIISE:Software and Applications
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• v.29 no.12
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• pp.883-894
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• 2002

Classical deterministic testing controls the execution of concurrent programs based on the equivalence between specifications and programs. However, it is not directly applicable to a situation in which synchronization sequences, being valid but infeasible, are taken into account. To resolve this problem, we had proposed automata-based deterministic testing in our previous works, where a concurrent program is executed according to one of the sequences accepted by the automaton recognizing all sequences semantically equivalent to a given sequence. In this paper, we present the automata-based testing environment for Java multi-thread programs, and we design and implement "Deterministic Executor" in the testing environment. "Deterministic Executor" transforms a Java multi-thread program by applying automata-based deterministic testing, the transformed program presents testing results. "Deterministic Executor" uses "Automata Generator", which generates an equivalent automaton of a test sequence, and "Replay Controller", which controls the execution of programs according to the sequence accepted by the automaton. By illustrating automata-based testing procedures with a gas station example, we show how the proposed approach does works in a Java multi-threaded program.roach does works in a Java multi-threaded program.