• Journal of the Korean Statistical Society
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• v.29 no.1
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• pp.45-62
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• 2000

Rotation design is a sampling technique to reduce response burden and to estimate the population characteristics varying in time. Park and Kim(1999) discussed a generation of one-level rotation design which is called as {{{{r_1^m ~-r_2^m-1}}}} design has more applicable form than existing before. In the structure of {{{{r_1^m ~-r_2^m-1}}}} design, we derive the exact variances of generalized composite estimators for level, change and aggregate level characteristics of interest, and optimal coefficients minimizing their variances. Finally numerical examples are shown by the efficiency of alternative designs relative to widely used 4-8-4 rotation design. This is continuous work of Part Ⅰ studied by Park and Kim(1999).

• Journal of the Korean Statistical Society
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• v.35 no.4
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• pp.343-353
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• 2006

The two-way balanced one-level rotation design, $r_1^m-r_2^{m-1}$, and the three-way balanced multi-level rotation design, $r_1^m(\iota)-r_1^{m-1}$, were discussed (Park et al., 2001, 2003). Although these rotation designs enjoy balancing properties, they have a restriction of $r_2=c{\cdot}r_1$ (c should be a integer value) which interferes with applying these designs freely to various situations. To overcome this difficulty, we extend the $r_1^m(\iota)-r_1^{m-1}$ design to new one under the most general rotation system. The new multi-level rotation design also satisfies tree-way balancing which is done on interview time, rotation group and recall time. We present the rule and rotation algorithm which guarantee the three-way balancing. In particular, we specify the necessary condition for the extended three-way balanced multi-level rotation sampling design.

• Journal of the Korean Statistical Society
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• v.32 no.3
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• pp.245-259
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• 2003

The 2-way balanced one-level rotation design has been discussed (Park et al., 2001), where the 2-way balancing is done on interview time in monthly sample and rotation group. We extend it to 3-way balanced multi-level design to obtain more information of the same sample unit for one or more previous months. The 3-way balancing is accomplished not only on interview time in monthly sample and rotation group but also on recall time as well. The 3-way balancing eliminates or reduces any bias arising from unbalanced interview time, rotation group and recall time, and all rotation groups are equally represented in the monthly sample. We present the rule and rotation algorithm which guarantee the 3-way balancing. In particular, we specify the necessary and sufficient condition for the 3-way balanced multi-level rotation design.

• Journal of the Korean Statistical Society
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• v.29 no.1
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• pp.29-44
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• 2000

In this paper, we consider one-level rotation designs with finite rotation groups such that the design satisfies two basic requirements: all rotation groups are included in any given survey period, and overlapping rates depend only on the time lag. First we present the necessary number of rotation groups and a rule for the length of time the sample units are to be in or out of the sample to satisfy the requirements. Second, an algorithm is presented to put rotation groups to proper positions in a panel in order to include all finite rotation groups for any survey period. Third, we define an one-level rotation pattern which is invariant in the survey period and has useful properties in practical sense.

• Proceedings of the Korean Statistical Society Conference
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• 2002.05a
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• pp.19-24
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• 2002

The two-way balanced one-level rotation design has been discussed (Park, Kim and Choi, 2001), where the two-way balancing is done on interview time in monthly sample and rotation group. We extend it to three-way balanced multi-level design under the most general rotation system. The three-way balancing is accomplished on interview time not only in monthly sample and rotation group but also in recall time. We present the necessary condition and rotation algorithm which guarantee the three-way balancing. We propose multi-level composite estimators (MCE) from this design and derive their variances and mean squared errors (MSE), assuming the correlation from the measurements of the same sample unit and three types of biases in monthly sample.

• Proceedings of the Korean Association for Survey Research Conference
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• 2002.11a
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• pp.255-274
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• 2002

We classify rotation sampling designs into two classes. The first class replaces sample units within the same rotation group while the second class replaces sample units between different rotation groups. The first class is specified by the three-way balanced design which is a multi-level version of previous balanced designs. We introduce an extended generalized composite estimator (EGCE) and derive its variance and mean squared error for each of the two classes of design, cooperating two types of correlations and three types of biases. Unbiased estimators are derived for difference between interview time biases, between recall time biases, and between rotation group biases. Using the variance and mean squared error, since any rotation design belongs to one of the two classes and the EGCE is a most general estimator for rotation design, we evaluate the efficiency of EGCE to simple weighted estimator and the effects of levels, design gaps, and rotation patterns on variance and mean squared error.

• Journal of the Korean Statistical Society
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• v.34 no.3
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• pp.219-233
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• 2005

The 3-way balanced multi-level rotation design has been discussed (Park Kim and Kim, 2003), where the 3-way balancing is done on interview time, in monthly sample and rotation group and recall time. A greater advantage of 3-way balanced design is accomplished by an estimator. To obtain the advantage, we generalized previous generalized composite estimator (GCE). We call this as l-step GCE. The variance of the l-step GCE's of various characteristics of interest are presented. Also, we provide the coefficients which minimize the variance of the l-step GCE. Minimizing a weighted sum of variances of all concerned estimators of interest, we drive one set of the compromise coefficient of l-step GCE's to preserve additivity of estimates.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.132-138
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• 2008

Recently, mastering processes for high density optical disc such as Blu-ray disc rely on electron beams, which are operable in only vacuum. In the mastering process, one of the most important tasks is to design precision stages for providing precise positioning of the works with respect to the source in a high vacuum environment. In this paper, we have developed a precision rotation table usable in the electron beam mastering. The rotation table adopted air bearings for a high positioning repeatability and velocity stability. The air leakage from the air bearings has been minimized by employing the differential exhaust scheme using three steps of air drain. The design parameters such as diameters of exhaust lines, seal lengths, and pumping speeds were decided according to the optimization method using genetic algorithm. The performance on the vacuum level of the rotation table was evaluated experimentally and theoretically. The results indicate that a vacuum level of $10^{-4}$ Pa is achieved with operation of air bearings in a vacuum chamber, which is sufficient for the electron beam mastering.

• PNF and Movement
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• v.14 no.3
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• pp.185-193
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• 2016

Purpose: The purpose of this study was to investigate the effects of neck patterns in proprioceptive neuromuscular facilitation (PNF) for neck movement and the neck disability index (NDI) among adults with forward head posture. Methods: Thirty-nine subjects were randomly assigned into two groups. Subjects in the proprioceptive neuromuscular facilitation exercise group (PNFG, n = 20) received 20 minutes of PNF neck pattern (flexion-Rt. lateral flexion-Rt. rotation followed by extension-Lt. lateral flexion-Lt. rotation) 3 times weekly for 4 weeks. Outcomes were measured using absolute rotation angle (ARA), anterior weight bearing (AWB), range of flexion and extension motions (RFEM), and neck disability index (NDI) methods before and after the 4-week intervention period. Results: There were significant effects for the PNFG, pre- and post-intervention, in ARA, AWB, RFEM, and NDI. There were significant differences in ARA, AWB, RFEM, and NDI compared with CG. Conclusion: The results of this study suggest the PNF neck pattern could be beneficial for adults with forward head posture.Purpose: This study investigates how abdominal muscular exercise based on proprioceptive neuromuscular facilitation (PNF) can affect chronic low back pain patients in terms of their pulmonary function, pain, and functional disability indexes. Methods: Fourteen target subjects with chronic low back were randomly assigned to the control group (n = 7) that performed abdominal muscle exercises and the experimental group (n = 7) that performed PNF abdominal muscular exercises. The exercises were performed five times a week for six weeks. To check the change in pulmonary function, the forced expiratory volume at one second (FEV1) and visible analogue scale (VAS) were measured to check the pain level. The disability level caused by back pain was measured by the Oswestry Disability Index (ODI). A paired t-test was applied to compare the differences between the groups before and after the intervention, and an independent t-test was used to compare the differences between the groups. The level of statistical significance was set as ${\alpha}=0.05$. Results: Before and after the intervention, the experimental group showed a significant change in FEV1 (p < 0.01), and both the experimental and the control groups showed significant changes in VAS and ODI (p < 0.01). A comparison of the differences between the groups indicated that the experimental group showed more significant changes in FEV1 (p < 0.05). Conclusion: According to the study results, PNF abdominal muscular exercise effectively improved pulmonary function, pain, and functional disability indexes in subjects with chronic back pain. The proposed program can be applied to chronic back pain patients as a useful therapy.

• The korean journal of orthodontics
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• v.51 no.6
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• pp.375-386
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• 2021

Objective: To evaluate the accuracy of a one-piece bracket jig system fabricated using computer-aided design and manufacturing (CAD/CAM) by employing three-dimensional (3D) digital superimposition. Methods: This in vitro study included 226 anterior teeth selected from 20 patients undergoing orthodontic treatment. Bracket position errors from each of the 40 arches were analyzed quantitatively via 3D digital superimposition (best-fit algorithm) of the virtual bracket and actual bracket after indirect bonding, after accounting for possible variables that may affect accuracy, such as crowding and presence of the resin base. Results: The device could transfer the bracket accurately to the desired position of the patient's dentition within a clinically acceptable range of ± 0.05 mm and 2.0° for linear and angular measurements, respectively. The average linear measurements ranged from 0.029 to 0.101 mm. Among the angular measurements, rotation values showed the least deviation and ranged from 0.396° to 0.623°. Directional bias was pronounced in the vertical direction, and many brackets were bonded toward the occlusal surface. However, no statistical difference was found for the three angular measurement values (torque, angulation, and rotation) in any of the groups classified according to crowding. When the teeth were moderately crowded, the mesio-distal, bucco-lingual, and rotation measurement values were affected by the presence of the resin base. Conclusions: The characteristics of the CAD/CAM one-piece jig system were demonstrated according to the influencing factors, and the transfer accuracy was verified to be within a clinically acceptable level for the indirect bracket bonding of anterior teeth.