• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.192-198
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• 2001

We consider an interpolation problem with nonuniform rational B-spline curves given ordered data points. The existing approaches assume that weight for each point is available. But, it is not the case in practical applications. Schneider suggested a method which interpolates data points by automatically determining the weight of each control point. However, a drawback of Schneiders approach is that there is no guarantee of avoiding undesired poles; avoiding negative weights. Based on a quadratic programming technique, we use the weights of the control points for interpolating additional data. The weights are restricted to appropriate intervals; this guarantees the regularity of the interpolating curve. In a addition, a knot placement is proposed for pleasing interpolation. In comparison with integral B-spline interpolation, the proposed scheme leads to B-spline curves with fewer control points.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.3
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• pp.491-498
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• 2016

The software defined networks implement a software network control plane, which is physically separated from the data plane. For wide area software defined network deployments, multiple controllers are required, and the placement of these controllers influences importantly the performance of the software defined networks. This paper proposes a Tabu search algorithm, which is one of the meta heuristic algorithms, for an efficient controller placement in software defined networks. In order to efficiently obtain better results, we propose new neighborhood generating operations, which are called the neighbor position move and the neighbor number move, of the Tabu search algorithm. We evaluate the performances of the proposed algorithm through some experiments in terms of the minimum latency and the execution time of the proposed algorithm. The comparison results show that the proposed algorithm outperforms the existing genetic algorithm and random method under various conditions.

• Korean Journal of Computational Design and Engineering
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• v.20 no.4
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• pp.348-356
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• 2015

It is important to devise methods for assisting dentists to consistently determine implant positions and directions and to accurately perform drilling tasks during dental implant surgery. In this paper, we propose a novel approach to tooth implant placement planning which deals with the determination of the positions and directions of multiple implant fixtures for a set of missing mandibular teeth and suggests the selection of the sizes and types of the implant fixtures. We combine Korean standard data in the sizes and positions of human teeth with the patient specific 3D models of mandibular jawbones, nerve curves, and neighboring teeth around the missing teeth in order to determine the positions and directions of the implant fixtures for the missing teeth. Using the geometric and spatial information of the jawbones, the teeth and the implant fixtures, we can construct the 3D models of surgical guide stents which are crucial to perform drilling tasks with ease and accuracy. Adopted in 3D simulation of dental implant placement, the approach can provide surgeon students with good educational contents. We also expect that, with further work, the approach can be used as a useful tool to plan for dental implant surgery.

• Investigative and Clinical Urology
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• v.59 no.6
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• pp.371-375
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• 2018

Purpose: To compare patients with sepsis due to obstructive urolithiasis (Sep-OU) and underwent drainage by percutaneous nephrostomy (PCN) or a double-J (DJ)-ureteral stent and to identify predictive risk factors of DJ stent failure in these patients. Materials and Methods: We reviewed our records from January 2013 to July 2018 and identified 286 adult patients with Sep-OU out of which 36 had bilateral involvement, thus total 322 renal units were studied. Urologic residents in training carried out both ureteral stenting and PCN tube placement. Demographic data and stone characteristics were recorded along with Charlson comorbidity index. For predicting risk factors of DJ stent failure, those variables that had a p-value <0.1 in univariate analysis were combined in a multinomial regression analysis model. Results: The patients with PCN placement were significantly older than those with DJ stent placement (p=0.001) and also had significant number of units with multiple calculi (p=0.018). PCN was also placed more frequently in those patients with a upper ureteric calculi (p<0.05). On multinomial regression analysis multiple calculi (p=0.014; odds ratio [OR], 4.878; 95% confidence interval [CI], 1.377-17.276) and larger calculi size (p=0.040; OR, 0.974; 95% CI, 0.950-0.999) were the significant predictors of DJ stent failure. Conclusions: In patients with sepsis from obstructive urolithiasis due to larger and multiple calculi a PCN placement might be better suited although this data requires further prospective randomized studies to be extrapolated.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.91-108
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• 2000

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.101-114
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• 2007

Dowel bars in the jointed concrete pavement are used to both provide load transfer across pavements joints and prevent the joint faulting leading to longer service life. On the contrary, the misplacement of dowel bar can provide negative results including the joint freezing(locking) that may cause the joint spatting and unexpected mid-slab cracking. The dowel bar can be placed using the assembly or dowel bar inserter (DBI) during the concrete pavement construction. In the domestic practice of the concrete pavement construction, the dowel bar is placed using the assembly method. This study primarily focuses on the comparison of these two dowel placement methods using the field data from the KHC test road in which both dowel placement methods have been applied to a certain length of the concrete pavement. The field data regarding the alignment of the dowel bars placed by both methods was collected using MIT-SCAN2, a nondestructive measuring equipment, and processed to compute Joint Score and Running Ave. Joint Score which are used as indicators of the dowel bar performance. The comparison of the methods for the dowel bar placement using these indicators shows that the DBI method provided much better alignment of the dowel bars reducing the risk of joint freezing than the assembly method. In order to improve the quality of the dowel bar placement using the assembly method, the current weak points of the assembly method including the fabrication, storage, and installation of dowel bar assembly were investigated and the solution was suggested. The improved dowel bar sets based on the suggested solution have been applied to an actual practice of the concrete pavement construction. The field data shows that the improved assembly method suggested in this study can highly reduce the risk of joint freezing.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.4
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• pp.9-16
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• 2010

In the health monitoring of civil engineering structures, the optimal sensor placement has a major influence on the quality of the results. This paper considers the problem of locating sensors with the aim of maximizing the data information so that structural parameters or damage of structures can be assessed. An proposed technique using a genetic algorithm is introduced to find the optimal placement of sensors. The sensitivity on modal vectors by structural parameters and the orthogonality of modal vectors have been taken as the fitness function of the genetic algorithm. A simple tower structure is used for example analyses to investigate the feasibility and applicability of the proposed approach. The example analyses show the way how the modal sensitivity and the modal orthogonality in the fitness function have influence on the optimal sensor placement. It is shown that the present method using the proposed fitness function can provide the reliable results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.542-549
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• 2004

The compressive strength of concrete is commonly used criterion in producing concrete. However, the tests on the compressive strength are complicated and time-consuming. More importantly, it is too late to make improvement even if the test result does not satisfy the required strength, since the test is usually performed at the 28th day after the placement of concrete at the construction site. Therefore, accurate and realistic strength estimation before the placement of concrete is being highly required. In this study, the estimation of the compressive strength of concrete was performed by probabilistic neural network (PNN) on the basis of concrete mix proportions. The estimation performance of PNN was improved by considering the correlation between input data and targeted output value. Adaptive probabilistic neural network (APNN) was proposed to automatically calculate the smoothing parameter in the conventional PNN by using the scheme of dynamic decay adjustment algorithm. The conventional PNN and APNN were applied to predict the compressive strength of concrete using actual test data of a concrete company. APNN showed better results than the conventional PNN in predicting the compressive strength of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1035-1040
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• 2003

This research investigates the actual data and construction technology of the massive bottom slab placed by $23,000m^3$ concrete quantity in site of the in-ground type LNG receiving terminal having 20,000kl storage capacity. The purpose of this study is to determine the optimum mix design and control the actual concreting procedures including concrete production, transportation, placement, vibrating and curing in site. For this purpose, the optimum mix design using ternary blended cement(furnace slag cement＋fly ash) and under piping method having 11 gates and 7 distributors are selected. As test results of actual construction, concrete placement is finished during 68hours with good success and obtained the good quality of the fresh and hardened concrete including slump, air contents, no-segregation, compressive strength and low hydration heat. Also, actual data for all of concrete procedures are proved successful and satisfied with our specifications.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.43-46
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• 1990

A general scheme for a discrete adaptive observer having exponetial weighting properties is presented for a single-input single-output linear system. In this scheme, all the past measurement data are weighted esponetially both with the weighting factor and the stable matrix F. This observer is then implemented in the design of an indirect adaptive pole placement contoller. To increase nemerical stability in getting the controller parameter, a recusive algorithm is introduced. It is shown that the overall control scheme is globally stable with the persistent excition