• The korean journal of orthodontics
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• v.52 no.3
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• pp.201-209
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• 2022

Objective: To compare the removal torque of microimplants upon post-use removal and post-retention removal and to assess the influencing factors. Methods: The sample group included 241 patients (age, 30.25 ± 12.2 years) with 568 microimplants. They were divided into the post-use (microimplants removed immediately after use or treatment) and post-retention (microimplants removed during the retention period) removal groups. The removal torque in both groups was assessed according to sex, age, placement site and method, and microimplant size. Pearson correlation and multiple linear regression analyses were performed for evaluating variables influencing the removal torque. Results: The mean period of total in-bone stay of microimplants in the post-retention removal group (1,237 days) was approximately two times longer than that in the post-use removal group (656.28 days). The removal torques in the post-retention removal group (range, 4-5 N cm) were also higher than those in the post-use removal group. The mandible and pre-drilling groups demonstrated higher placement and removal torques than did the maxilla and no-drilling groups, respectively. In the no-drilling post-use removal group, the placement torque and microimplant length positively correlated with the removal torque. In the post-retention removal group, unloading in-bone stay period and microimplant diameter positively correlated with the removal torque in the no-drilling and pre-drilling methods, respectively. Conclusions: The removal torques differed according to the orthodontic loading and removal time of microimplants. With prolonged retention of microimplants inserted using the no-drilling method, the removal torque was clinically acceptable and positively correlated with the unloading in-bone stay period.

• The korean journal of orthodontics
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• v.39 no.4
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• pp.203-212
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• 2009

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion in a self-drilling manner. Methods: A 3D finite element method was used to simulate the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) into 1 mm thick cortical bone. The shape and dimension of thread groove in the center of the cortical bone produced by the cutting flute at the apical of the microimplant was obtained from animal test using rabbit tibias. A total of 3,600 analysis steps was used to calculate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, were observed in the peri-implant bone along the whole length of the microimplant. Level of strains in the vicinity of either the screw tip or the valley part were similar. Conclusions: Bone strains from a microimplant insertion in a self-drilling manner might have a negative impact on the physiological remodeling of cortical bone.

• Korean Journal of Plant Resources
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• v.11 no.3
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• pp.296-300
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• 1998

When medicinal mushroom, Poria cocos, is cultured , inoculation method of spawn is cross slice inoculation of which the both sides of pine tree were peeled and spawn of P.cocos was inoculated. However, this method required lots of inoculation amount. This study was carried out to improve the culturing method of P. cocos. A good growth of P.cocos was observed in MCM(mushroom complete medium), showing proper mycelia growth and density. In inoculation amount, conventional method(cross slice inoculation) requires 20 bottles of spawn. In contrast, short log method required 8 bottles of spawn and drilling inoculation method 2~3 bottles, which could save by 60% and 85-90% respectively. In the selectrion of tree species, pine and larch had better condition for spawn culture and sclerotia formation condition.In terms of yield , pine was 33.7kg/3.3$m^2$. In the yield of pine, conventional method was 23.4kg/3.3$m^2$, drilling inoculation 29.4kg/3.3$m^2$, short log inoculation 31.7kg/3.3$m^2$, therefore drilling inoculation could increase by 25% and short log inoculation 35%, In addition, management cost was also saved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.181-182
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• 2007

• Journal of The Korean Society of Grassland and Forage Science
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• v.16 no.3
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• pp.199-207
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• 1996

This experiment was canied out to determine the effects of seeding method and seeding ratio in mixed cropping of forage rye and red clover on dry matter yield, nutritional yield and chemical characteristics of soil. The main treatment was two seeding methods(drilling and broadcasting) and the sub treatment was six seeding ratios between rye and red clover(T1; 150kg : 0 kg/ha, T2; 120 : 3, T3; 90 : 6, T4; 60 : 9, T5; 30 : 12, T6; 0 : 15). The experiment was performed at the College of Natural Science of Kon-Kuk University in Chungju in 1992. The results were summarized as follows; 1. Protein content was increased by increasing the seeding ratio of red clover, but content of NDF and ADF were decreased. 2. The seeding method did not affects significantly the dry matter yield, but broadcasting showed higher dry matter yield than drilling in the same seeding ratio. Especially, T3 of broadcasting was the highest yield of 13, 172 kg/ha The T3 of broadcasting and T4 of drilling showed hlghly crude protein yield of 1, 268 kgha and 1, 252 kg/ha, respectively. 3. Comparing the each seeding ratio of two seeding method, total nitrogen yield of shoot and root of drilling were higher than broadcasting. Especially, T2 and T4 of drilling were the highest in total nitrogen yield. 4. There were more increase in organic matter and nitrogen contents but decrease in K, Ca of soil by increasing the seeding ratio of red clover than soil before experiment. In the seeding methods, broadcasting was an effect of soil improvement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.867-875
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• 2004

In order to inspect burr geometry and hole quality in micro-drilling processes, a cost-effective method using an image processing and shape from focus (SFF) methods on the machine tool is proposed. A CCD camera with a zoom lens and a novel illumination unit is used in this paper. Since the on-machine vision unit is incorporated with the CNC function of the machine tool, direct measurement and condition monitoring of micro-drilling processes are conducted between drilling processes on the machine tool. Stainless steel and hardened tool steel are used as specimens, as well as twist drills made of carbide are used in experiments. Validity of the developed system is confirmed through experiments.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.133-140
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• 2004

Recently reduction of industrial products in size and weight has been increased by application of micro-drills in gadgets of high precision and a great interest of a micro-drilling has been raised. Due to the lack of tool stiffness and the chip packing, the micro-drilling requires not only the robust tool structure which has not affected by vibration but also effective drilling methods designed to prevent tool fracture from cutting troubles. This paper presents an optimum design shape of a 0.15 mm micro-drill associated with a new manufacturing process to improve the production rate and to lengthen the tool life and suggestions on the micro-drilling characteristic properties associated with the tool life and workpiece quality.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.993-998
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• 2002

watches, air bearings and printed circuit hoards (PCB). However, it is not easy to determine optimum cutting conditions since the micro drilling process is very sensitive to various disturbances. Also, undesirable characteristics to optimize the micro drilling are small signal-to-noise ratios, drill wandering motions and high aspect ratios. Thus, in this study, experimental design methods are applied to determine optimum cutting conditions. Suing the methods, three cutting parameters, fred, step and curving speed are optimized to minimize thrust forces. Obtained conditions are verified through required experimental works. As the results, it is shown that the experimental methods can be applied to micro drilling processes to determine Optimum Cutting Conditions.

• Journal of Advanced Marine Engineering and Technology
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• v.7 no.2
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• pp.29-35
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• 1983

In general, for measuring residual stresses in plane stress state, two principal stresses {\sigma}_1 , {\sigma}_2$ and their directions .theta., should be determined. Naturally, for deciding three unknowns ${\sigma}_1, {\sigma}_2, ${\theta}$-three informations are necessary and therefore three strain gages are required for determining residual stresses at one point. In this paper, we tried to measure the residual stresses of one point with only two strain gages by drilling twice the hole of different diameters at the point and by detecting relaxation strains for each hole-drilling. We present also the formulas for determining the residual stresses from relaxation strains detected by strain gages in each hole-drilling. We carried out experiment, determining principal stresses and their directions of specimens applied specified uniform stress, and compared experimental results with the values calculated by formulas presented in this paper. The values calculated by formulas presented in this paper are always a little greater than the experimental results.

• Laser Solutions
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• v.10 no.3
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• pp.11-14
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• 2007

A trepanning optics is the optical system which makes focus laser beam rotate and incline to the material processing surface. The trepanning optics is used in order to improve the quality of laser drilling process and control the taper of drilling diameter. In order to make trepanning optics, we can use the eccentricity of lens, scanner using two mirror, dove prism, or wedge. Among these method, in this paper wedge is used for trepanning optics. The wedge trepanning optics has advantage on the high speed of rotation. In this paper, we design the wedge trepanning optics using ray tracing. ements and engine design variables of system to satisfy the customer's requirements.