Yong-Seok Choi

Autopilot Design for Agile Missile Using Time-Varying Control Technique

Abstract This paper is concerned with control allocation strategies with two time scale dynamic inversion which generate nominal control input trajectories. In addition, an robust flight control design method is proposed by using a time-varying control technique which is time-varying version of the pole placement of linear time invariant system for an agile missile with aerodynamic fin, thrust vectoring control, and side-jet thruster. The control allocation algorithms proposed in this paper are capable of extracting the maximum performance by combining each control effector. The time-varying control technique for the autopilot design enhances the robustness of the tracking performance for the wide angle of attack range. The main results are validated through the nonlinear simulations with aerodynamic data.

Morphometric analysis for evaluating the relation between incisal guidance angle, occlusal plane angle, and functional temporomandibular joint shape variation

Abstract Objective: The correlations between morphology of the temporomandibular joint structure, the anterior guidance angle, and occlusal plane were investigated. Materials and methods: A cone beam computed tomography analysis was performed in 158 patients (86 women and 72 men). 3D software was employed to obtain the coordinates of the shape of the incisal guidance angle, occlusal guidance angle, articular fossa, and mandibular condyle. Generalized Procrustes analysis including principal components analysis (PCA) were performed and produced principal components (PCs) scores of each shape and their centroid size (CS). Results: A significant Pearson correlation coefficient of 0.3451 (p < .001) was observed between the incisal guidance angle and occlusal plane. The CS also showed a correlation with the incisal guidance angle, but not with the occlusal plane angle. The PCA results revealed that there were no significant correlations between the temporomandibular joint structure (TMJ) shape (fossa and condyle) and the incisal guidance angle. Conclusions: Incisor guidance angle and occlusal plane angle were correlated. In addition, there was a correlation between CS and incisal guidance angle. In the PCA, It can be concluded that the size is more related to the incisor guidance angle than the morphological factors of the constituent components of the TMJ.

Preliminary Study to Determine the Reference Plane of Patients With a Unilateral Cleft Lip and Palate

Objective The objective of this study was to determine the three-dimensional midsagittal reference planes for unilateral cleft lip and palate (UCLP) patients that can be easily applied in a clinical setting. Design This was a retrospective analysis. Patients There were 35 UCLP patients (25 men, 10 women; 28.1 ± 6.9 years old) in this study. Methods With landmarks three-dimensional coordinates obtained from cone-beam computed tomography, the symmetric midsagittal reference planes were calculated by applying the ordinary Procrustes superimposition method using the original and mirror images. Procrustes analysis was also used to find the closest landmarks to the calculated symmetric midsagittal reference plane and test its compatibility with the symmetrical midsagittal reference plane. Main Outcome Measure The three nearest landmarks to the symmetric midsagittal reference plane were Opisthion, Basion, and Nasion. Results The averages of the sums of the squared Euclidean distance and squared Procrustes distance differences between the two configurations and shapes fabricated by the symmetrical and landmark-based midsagittal reference planes, respectively, were calculated as 1.836 ± 3.295 and 1.519 × 10–5 ± 2.351 × 10–5. Conclusion It was confirmed that the midsagittal reference planes from these selected landmarks for UCLP patients were compatible with symmetric midsagittal reference planes from the Procrustes analysis and the asymmetric measurements.

Qualitative correlation between postoperatively increased vertical dimension and mandibular position in skeletal class III using partial-least-square path modeling

BackgroundThis study constructed a partial-least-square path-modeling (PLS-PM) model and found the pathway by which the postsurgical vertical dimension (VD) affects the extent of the final mandibular setback on the B point at the posttreatment stage for the skeletal class III surgery-first approach (SFA).MethodsThis study re-analyzed the data from the retrospective study by Lee et al. on 40 patients with skeletal class III bimaxillary SFA. Variables were obtained from cone beam computed tomography (CBCT)-generated cephalograms. Authors investigated all variables at each time point to build a PLS-PM model to verify the effect of the VD on the final setback of the mandible.ResultsFrom PLS-PM, an increase in VD10 was found to decrease the absolute value of the final setback amount of the mandible, which reflects the postsurgical physiological responses to both surgery and orthodontic treatment, which, in turn, can be interpreted as an increase in postoperative mandibular changes.ConclusionsTo resolve the issue of collinear cephalometric data, the present study adopted PLS-PM to assess the orthodontic treatment. From PLS-PM, it was able to summarize the effect of increased postsurgery occlusal vertical dimension on the increased changeability of the B point position at the posttreatment stage.

The estimation of skeletal maturity of patients with cleft lip and palate using statistical shape analysis: a preliminary study

OBJECTIVES To propose a skeletal maturity assessment method by developing a statistical regression analysis model through the integration of lateral and axial images of the cervical vertebrae of patients with cleft lip and palate obtained through CBCT. METHODS 49 patients with cleft lip and palate (28 females, 21 males; age range, 4-16 years) underwent CBCT examination, and the hand-wrist radiographic data were selected. With coordinates of landmarks from lateral and axial images of the cervical vertebrae, Procrustes analysis and principal component (PC) analysis yielded PC scores of each cervical vertebra, with the centroid size as the size factor. The meaningful PC scores from these were used for multiple regression models. RESULTS When both axial and lateral cervical vertebrae were used together, there was a 6.7% increase in the Sempé maturation level explanatory power for skeletal maturation estimation in females and an 11.4% increase in males compared with that when only the chronological age was used. CONCLUSIONS This study improved the estimating regression models using statistical shape analysis with lateral and axial cervical vertebral shapes. The obtained models had improved explanatory power for skeletal maturity estimation than previous studies with healthy people.

HExDB: a database for epigenetic changes occurring after horse exercise

DNA methylation is an essential biochemical modification that regulates gene expression. Exercise induces changes in gene expression that adapt as metabolic changes in the blood. We provide a database for the epigenetic changes after horse exercise (http://www.primate.or.kr/hexdb). Horse Exercise Epigenetic Database (HExDB) explicates the change in genome-wide DNA methylation patterns after exercise. Exercise changes the genome-wide epigenetic patterns, and understanding the regions that change is important for confirming exercise physiological mechanisms. For this purpose, our database provides information on differentially methylated regions after exercise that pass a set threshold. A total of 784 genes based on NCBI RefSeq were identified as differentially methylated in equines after exercise. Our database provides clues for the study of exercise-related epigenetic pathways in the thoroughbred horse.

HEpD: A database describing epigenetic differences between Thoroughbred and Jeju horses

With the advent of next-generation sequencing technology, genome-wide maps of DNA methylation are now available. The Thoroughbred horse is bred for racing, while the Jeju horse is a traditional Korean horse bred for racing or food. The methylation profiles of equine organs may provide genomic clues underlying their athletic traits. We have developed a database to elucidate genome-wide DNA methylation patterns of the cerebrum, lung, heart, and skeletal muscle from Thoroughbred and Jeju horses. Using MeDIP-Seq, our database provides information regarding significantly enriched methylated regions beyond a threshold, methylation density of a specific region, and differentially methylated regions (DMRs) for tissues from two equine breeds. It provided methylation patterns at 784 gene regions in the equine genome. This database can potentially help researchers identify DMRs in the tissues of these horse species and investigate the differences between the Thoroughbred and Jeju horse breeds.

Visualizations of Asymmetric Multidimensional Scaling

Distances or dissimilarities among units are assumed to be symmetric in most cases of multidimensional scaling(MDS); consequently, it is not an easy task to deal with asymmetric distances. Current asymmetric MDS still face difficulties in the interpretation of results. This study proposes a simpler asymmetric MDS that utilizes the order statistic of an asymmetric matrix. The proposed Web method demonstrates that some influences among objects are visualized by direction, size and shape of arrow to ease the interpretability of users.

Robust mixed control with aerosurface and side thruster using LTV control technique

Abstract This paper is concerned with a mixed control with aerodynamic fin and side thrusters applied to an agile missile using two-time scale dynamic inversion and linear time-varying control technique. The nonlinear dynamic inversion method with the weighting function allocates the desired control inputs (aerodynamic fin and side thrusters) to track a reference trajectory, and the time-varying control technique guarantees the robustness for the uncertainties. Closed-loop stability is achieved by the assignment of the extended-mean of these linear time-varying eigenvalues to the left half complex plane. The proposed schemes are validated by nonlinear simulations