• Transactions of the Korean Society of Mechanical Engineers
• /
• v.14 no.3
• /
• pp.513-525
• /
• 1990

This paper presents Adaptive Robust Servocontrol(ARSC) scheme, which is an explicit(or indirect) pole-assignment adaptive algorithm with the property of "robustness". It guarantees asymptotic regulation and tracking in the presence of finite parameter perturbations of the unknown plant(or process) model. The controller structure is obtained by transforming a robust control theory into an adaptive control version. This controller structure is combined with the model estimation algorithm which includes a dead-zone for bounded noise. It is proved theoretically that this combination of control and identification is globally convergent and stable. It is also shown, through a real-time simulation study, that the desired closed-loop poles of the augmented system can be assigned directly, and that the adjustment mechanism of the scheme tunes the controller parameters according to the assigned closed-loop poles.oop poles.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.24 no.1
• /
• pp.57-65
• /
• 2008

Purpose: Misfit of implant components was very important in terms of prosthodontics. they has been linked to prosthetic complications such as screw loosening and fracture. Although there are many results about rotational freedom or machining tolerance between fixture and abutments, the data about domestic implant systems are lacking. The aim of this in vitro study was to evaluate the rotational freedom of domestic external and internal connection implant systems between their fixtures/anlaogs and abutments comparing imported systems. Materials and Methods: Rotational freedom between abutments and fixtures/analogs was investigated by using digitalized rotational angle measuring device. (1) 1 domestic external connection system(Neobiotec) and 2 imported external connection systems(Nobel Biocare, Anthorgyr), (2) 1 domestic internal connection system(Dentium) and 4 imported external connection systems(Nobel Biocare, Anthorgyr, Straumann, Frident Dentsply), and (3) 1 domestic zirconia external connection abutment(ZirAce) were evaluated. Each group has 3 samples. Mean values for each group were analyzed. Results: The differences relative to rotational freedom between domestic and imported implant systems were observed but domestic external connection implant system showed about 2.67 degrees(in case of fixture) and internal connection system showed about 4.3 degrees(in case of fixture). Domestic zirconia abutment showed less than 3 degrees of rotational freedom in a situation where the abutment was connected to an implant fixture egardless of domestic or imported systems. Conclusion: Newly developed digitalized rotational angle measuring device has high measuring resolution. The rotational freedom of domestic implant systems were similar to imported implant systems.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.283-287
• /
• 1997

공작기계의 가공정도는 공작기계의 운동기구가 가지고 있는 기하오차와 절작작업시 발생하는 진동, 열,절삭력에 의해서 공작기계의 구조계,주축계,이송계의 변형에 의해서 직접적인 영향을 받는다. 또 가공정도는 제품의 정밀도 및 품질에 직접적인 영향을 미치기 때문에 가공정도를 향상시키기 위한 방법으로 공작기계의 오차를 측정/해석하는 방법이 연구되고 있다. 일반적으로,공작기계의 오차는 Quasi-static 오차와 Dynamic오차로 구분할수 있다. Dynamic 오차는 기계의 진동,채터 및 스핀들의 진동에 의해서만 발생하는 오차이며,Quasi-static 오차는 공작기계 구성요소인 안내면,칼럼,볼스크류등의 기하오차와 온도변화에 의한 열변형오차에 의해서 발생한다. 특히,공작기계 및 절삭가공중에 발생하는 열원에 의한 열변형 오차는 공작기계의 기하오차에 비해서 가공정도에 큰 영향을 미치며[1,2],발생오차의 약 40~70% 정도가열변형 오차에 기인한 것으로 알려져 있다[1]. 실제 많은 실험결과를 볼 때 CNC공작기계이 경우는 열변형에 의한 오차는 기하오차에 비해서 매우 크게 나타났다. 이러한 열변형 오차는 공작기계 주위 온도와 공작기계 구성요소(칼럼,이송유니크,스핀들유니트)의 비선형적인 온도 특성에 의해서 주로 발생하고, Time-variant특성을 가지고 있기 때문에 작업중에 발생하는 온도특성에 따른 열변형 오차를 최소화 할 수 있는 방법이 필요하다. 스핀들유니트는 냉각방식을 사용하여 온도변화를 줄이고 있으나 반복적인 작업과 스핀들의 고속회전으로 인해서 복합 적인 온도변화를 발생시킨다. 또, 볼스크류의 지지방식이 양쪽 고정단 형태이기 때문에 조립시 예압(pre-load)을 주어서 열팽창을 보상하고 있으나 공작기계의 반복적인 이송으로 인해서 발생하는 온도변화에 의한 열오차를 보상하는데는 어려움이 있다.됩니다. 생리적 저항력이 없는 어린이들은 이러한 공해와 생활조건의 제일희생자가 되는 것입니다. 엄마들이 "얘는 감기, 비염, 편도선을 달고 삽니다...." "얘는 코감기, 목감기 번갈아 가면서 하도 앓고 있어서 양약율 중지하고 현재 한약을 먹고 있습니다." 이러한 역경은 극복할 수 있는가\ulcorner 질병의 메카니즘은 어떻게 작용되는가\ulcorner 등등을 육미회 센타에서 체험한 사례를 가지고 말씀드리고자 합니다..ell layer (PCL)와 glia에 SOD-1이 강하게 염색되었다. APT 병용 투여로 상당수의 경련이 일어나지 않은 흰쥐는 해마의 DG에 FRA가 경미하게 염색되었고, PCL에 SOD-1도 경미하게 나타났으나, 경련이 나타난 쥐에서는 KA만을 투여한 흰쥐와 구별되지 않았다. 이상의 APT의 항산화 효과는 KA로 인한 뇌세포 변성 개선에 중요한 인자로 작용할 것으로 사료되나, 보다 명확한 APT의 기전을 검색하고 직접 임상에 응응하기 위하여는 보다 다양한 실험 조건이 보완되어야 찰 것으로 생각된다. 항우울약들의 항혈소판작용은 PKC-기질인 41-43 kD와 20 kD의 인산화를 억제함에 기인되는 것으로 사료된다.다. 것으로 사료된다.다.바와 같이 MCl에서 작은 Dv 값을 갖는데, 이것은 CdCl$_{4}$$^{2-}$ 착이온을 형성하거나 ZnCl$_{4}$$^{2-}$ , ZnCl$_{3}$$^{-}$같은 이온과 MgCl$^{+}$, MgCl$_{2}$같은 이온종을 형성하기 때문인것 같다. 한편 어떠한 용리액에서던지 NH$_{4}$$^{+}$의 경우 Dv값이 제일 작았다. 바. 본 연구

• Membrane Journal
• /
• v.8 no.4
• /
• pp.203-209
• /
• 1998

The cutting oil emulsion microfiltration was carried out on dead-end call and crossflow systems equipped with 0.22 $\mu$m GVHP Millipore and 0.2 m stainless steel Mott microfiltration membranes, respectivdy. The oil drop size in the emulsion was varied from 0.07 to 0.22 $\mu$m. Cake filtration(CFM) and standard pore blocking models(SPBM) were applied to predict the permeation flux. The permeation fluxes of 0.01 vol% oil emulsion followed CFM for dead-end system very well under the condition of 400 rpm and below 100 kPa. The SPBM was, however, suitable for the permeation flux at 400 rpm and above 150 kPa. The oil layer on the membrane surface was destroyed and reproduced repeatedly as operating pressure was suddenly changed from 60 to 200 kPa, and then returned to 60 kPa. Also, we estimated the critical entry pressure(CEP) which is changed from CFM to SPBM, and CEP for dead-end system was around 100 kPa. The CEP increased from around 100 to 150 kPa for the crossflow system as the oil concentration increased from 0.01 to 0.03 vol% when Reynolds number was 7080.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.44 no.3
• /
• pp.384-389
• /
• 2017

The resistance to dentistry is as old as the history of dentistry. Historically, dental treatment techniques have continued to evolve to minimize pain with effective treatment, but the negative perception of dentistry has not been reduced as much as the development of technology. Particularly, children have a lack of resistance to external stimuli, mental development and patience, and the degree of cooperation with dental care is reduced due to changes in parenting methods including parental influence, so can experience DFA(dental fear and anxiety) and DBMP(dental behavior management problem). Among the various stimuli experienced by the child in the dentist, psychological factors affecting the dentist, dental clinic, and social factors affect the formation of the relationship with the dentist. Especially in recent years, the addiction related to smartphone is emerging as a social problem, and the effects of smartphone addiction on the oral cavity and the effects on dental behavior are examined.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.29 no.2
• /
• pp.183-193
• /
• 2013

The characteristics of dental treatment makes the dental staff frequently contact with patient directly. Also the daily use of high-handpieces, sharp instruments, and needles often causes bleeding on oral cavity. Therefore, the risk of cross transmission grows up. The pathogen from dental practice could spread on not only the practice itself but also the dental laboratory with contaminated impressions and prosthesis. Dental clinic staffs (dentists, dental hygienists and dental technicians) should recognize all the patients have a possibility of cross contamination, and try to prevent the transmission of infection by proper infection control. In this study, we review the articles about disinfection methods and chemical infection agents used for dental impressions, and try to figure out the suitable and effective infection control system of dental impressions.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.30 no.3
• /
• pp.406-414
• /
• 2003

Chemomechanical approach to caries removal was introduced in order to preserve the maximum amount of sound tooth structure. The efficacy of chemomechanical caries removal was assessed using microcomputed tomography which offers 3 dimensional data without destroying the tooth, and the V works program. In group 1, the density values of the sound dentin, carious dentin, and remaining dentin after chemomechanical treatment were analyzed. In group 2, the density values of the sound dentin, cavity wall prepared using high speed bur, and the remaining dentin after additional $Carisolv^{TM}$ gel application on the same cavity were analyzed. The results were as follows; 1. The density value of the remaining dentin after the $Carisolv^{TM}$ treatment was 81.8% of the sound dentin(p < 0.001). 2. The density value of the remaining dentin after the conventional rotary instrument showed no statistically significant difference from that of the sound dentin(p = 0.234).

• Journal of Dental Rehabilitation and Applied Science
• /
• v.37 no.1
• /
• pp.1-15
• /
• 2021

Additive manufacturing (AM) for dental materials can produce more complex forms than conventional manufacturing methods. Compared to milling processing, AM consumes less equipment and materials, making sustainability an advantage. AM can be categorized into 7 types. Polymers made by vat polymerization are the most suitable material for AM due to superior mechanical properties and internal fit compared to conventional self-polymerizing methods. However, polymers are mainly used as provisional restoration due to their relatively low mechanical strength. Metal AM uses powder bed fusion methods and has higher fracture toughness and density than castings, but has higher residual stress, which requires research on post-processing methods to remove them. AM for ceramic use vat polymerization of materials mixed with ceramic powder and resin polymer. The ceramic materials for AM needs complex post-processing such as debinding of polymer and sintering. The low mechanical strength and volumetric accuracy of the products made by AM must be improved to be commercialized. AM requires more research to find the most suitable fabrication process conditions, as the mechanical properties and surface of any material will vary depending on the processing condition.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.38 no.3
• /
• pp.127-137
• /
• 2022

Zirconia is fabricated through various processes. Each element in fabricating process can affect the physical properties of the definitive prosthesis. In particular, both the milling process and the sintering process can affect the final integrity of the zirconia prosthesis. Most of the milling machines adopt the ultra-precision 5-axis machining method, and the results vary depending on which milling method was used and how the milling equipment was managed. Milling blocks are selected according to cutting efficiency and aesthetic reproducibility. The sintering method can affect the grain growth and optical properties, and an accurate evaluation can be made only with additional research on the recent speed sintering procedure. Not only the sintering temperature but also the temperature holding time can affect the quality of definitive prosthesis.

• The korean journal of orthodontics
• /
• v.27 no.5 s.64
• /
• pp.791-800
• /
• 1997

Sixty premolars extracted for orthodontic treatment were divided into four groups, and the residual resin was removed with four different rotary finishing instruments at a fixed speed of $18,500{\pm}300 rpm$ on the low speed handpiece. The instruments were G1; No.169L carbide fissure bur, G2: No.2 round bur, G3; No.4 round bur, G4: No.8 round bur. Then, the enamel received a S-second polishing with a rubber cup and a pumice. To find the extent of loss on the enamel at this point, prophylaxis was done with the rubber cup and pumice prior to bonding of the bracket(P1) and removal of residual resin by means of appropriate procedure applicable to each respective group(P2) followed. The final polishing was done with the rubber cup and pumice(P3), and the enamel surface roughness was measured each by the surface measuring instrument. The whole process was observed under a scanning electron microscope to gain the following results: At P2, the enamel surface roughness in G1 showed most smoothly with $2.60{\pm}0.55{\mu}m;\;in\;G2,\;3.24{\pm}0.80{\mu}m;\;in\;G3,\;3.44{\pm}0.94{\mu}m;\;in\;G4,\;3.89{\pm}0.54{\mu}m$, the roughest. G2 and G3 showed no statistical significance(P>0.05). At P3, the enamel surface roughness in G1 showed most smoothly with $2.29{\pm}0.47{\mu}m;\;in\;G2,\;2.44{\pm}0.56{\mu}m;\;in\;G3,\;2.44{\pm}0.56{\mu}m;\;in\;G4,\;2.92{\pm}0.43{\mu}m$, the roughest. G1 vs G2, G3, and G2 vs G3 had no statistical significances(p>0.05). In all groups, P2 and P3 showed rougher in surface roughness than P1, and P2 rougher than P3(p<0.01). In a case of 5-second prophylaxis with the rubber cup and the pumice on a virgin, normal enamel, fine scratches were found under the scanning electron microscope. In all four groups, unremovable gouges remained even after polishing with the ubber and pumice; residual resin was not observed with naked eye when finished with the rubber and pumice, but the resin debris was observed under the scanning electron microscope.