• Journal of Oral Medicine and Pain
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• v.31 no.3
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• pp.265-274
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• 2006

Temporomandibular joint (TMJ) internal derangement, especially disc displacement with reduction (DDwR) is the most common TMJ arthropathy and has been thought to do some effects on masticatory performance. Measuring of maximal bite force has been widely used as objective and quantitative method of evaluating masticatory performance, but previous studies showed various results due to various characteristics of subjects and different measuring devices and techniques. In a few studies about the correlation of bite force and temporomandibular disorders (TMD), some authors reported that bite force and masticatory performance would be reduced in patients with TMD because of pain. But the correlation of changes in structure of articular disc and masticatory performance has not been well investigated yet. In this study, to investigate the influences of non-painful disc change on the masticatory performance, we measured the value of maximal bite force, occlusal contact area and occlusal pressure of 39 patients with non-painful DDwR of the TMJ using pressure sensitive film, and compared it with that of 59 controls. The results are summarized as follows: 1. The maximal bite force (P<0.01) and the occlusal contact area (P < 0.05) of the DDwR patients were greater than the controls. 2. There was no significant difference in occlusal pressure between the DDwR patients and the controls (P > 0.05). 3. The maximal bite force of the male group was greater than that of the female group (P < 0.05). However, the occlusal contact area and the occlusal pressure between the male and the female group didn't show significant difference (P > 0.05). From the results above, we can suggest that DDwR could be a factor of changing bite force, but more controlled, large scaled and EMG related further study is needed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.121-123
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• 2002

The design of an air seat cushion for preventing decubitus ulcer includes many design factors such as the even distribution of interface pressure, the minimization of mean and peak interface pressure values, and the reduction of interface shear force and pressure gradient. It involves the anatomic condition of plegia's buttock as well as air pressure in air cells of cushion. As a result, a suitable design of the cushion satisfying the all requirements is a difficult problem. Therefore, an appropriate and effective numerical tool to develop an air cushion orthosis is required. The purpose of the present study was to develop an air seat cushion orthosis having optimized air cells for evenly distributed interface pressure between the buttock and cushion surface. For the purpose, an advanced finite element (FE) model for the design of air cushion was developed. Since the interface pressure and shear force behavior, as well as stress analyses were primary concern, a FE air cell model was developed and verified by the experiments. Then, the interactions of two cells were checked. Also, the human part of the developed numerical model includes every material property and geometry related to buttock and femoral parts. For construction of dimension data of buttock and femoral parts, CT scans were performed. A commercial FE program was employed for the simulation representing the seating process on the orthosis. Then, sensitive analyses were performed with varying design parameters. A set of optimal design parameters was found satisfying the design criteria of the orthosis. The results were utilized to produce a prototype of the orthosis. Experimentally, the buttock interface pressure distributions from the optimized and previous ones were compared. The new seat orthosis showed a significantly improved interface pressure characteristics compared to the most popular one in the market. The new orthosis will be used for the development of the AI(artificial intelligent) controlled seat orthosis fur prevention of decubitus ulcer fur various plegic patients and the elderly.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.5
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• pp.812-817
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• 2013

This study demonstrates the diffusion bonding process between a tungsten carbide shank (K30) and tungsten carbide (DX5) for micro WC-PCD tool fabrication. A type of nickel alloy was used as the filler met alto improve the bond ability between K30 and DX5. The bonding pressure, time, and surrounding conditions were kept constant. In particular, the normal pressure was controlled precisely under buckling analysis. Diffusion bonding was performed at various operation temperatures (1170-1770 K) by using a specially designed jig. The microstructure on the localized bonded surface was analyzed using scanning electron microscopy and optical microscopy. In the case of diffusion bonding of WCat 1370-1770K, the filler metal melted completely and diffused between the two base metals, and they were bonded more tightly on both sides than at temperatures below 1370 K. Our results demonstrated the importance of sensitive temperature dependence of diffusion bonding.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.303-311
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• 2012

In this study, we introduce a dynamic process model as well as the design methodology of optimized fuzzy controller for its efficient application to vacuum production system to produce a semiconductor, solar module and display and so on. In a vacuum control field, PID control method is widely used from the viewpoint of simple structure and preferred performance. But, PID control method is very sensitive to the change of environment of control system as well as the change of control parameters. Therefore, it's difficult to get a preferred performance results from target system which has a complicated structure and lots of nonlinear factors. To solve such problem, we propose the design methodology of an optimized fuzzy PID controller through a following series of steps. First a dynamic characteristic of the target system is analyzed through a series of experiments. Second the process model is built up and its characteristic is compared with real process. Third, the optimized fuzzy PID controller is designed using genetic algorithms. Finally, the fuzzy controller is applied to target system and then its performance is compared with that of other conventional controllers(PID, PI, and Fuzzy PI controller). The performance of the proposed fuzzy controller is evaluated in terms of auto-tuned control parameters and output responses considered by ITAE index, overshoot, rise time and steady state time.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.6
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• pp.757-770
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• 1998

A Navier-Stokes code with a low Reynolds number k-.epsilon. turbulence model was tested to investigate its predictability for the unsteady transitional boundary layer flow due to rotor-stator interaction. A preliminary calculation with three different numbers of time steps 300, 600, and 1000 for a rotor wake passing period was carried out to see the effects of time steps on the unsteady flow and pressure fields due to rotor-stator interaction. Numerical solutions showed that unsteady pressure was much more sensitive to the number of time steps and over 600 time steps should be used to get a numerical solution independent of the number of time steps for a rotor wake passing period. The original low Reynolds number k-.epsilon. turbulence model showed very poor prediction of the unsteady transitional boundary layer flow due to rotor-stator interaction. This was due to the excessive production of turbulent kinetic energy near the leading edge. A modification suggested by Launder was incorporated and the modified model captured well the wake induced transitional strip. Present solutions also showed improved prediction over previous Euler/boundary layer solution in terms of the onset of unsteady transition and its extent.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.647-655
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• 1997

The purpose of present study is to investigate the influence of a spinal gamma-aminobutyric acid B($GABA_B$) receptor on a central regulation of blood pressure(BP) and heart rate(HR), and to define its mechanism in the spinal cord. In urethane-anesthetized, d-tubocurarine-paralyzed and artificially ventilated male Sprague-Dawley rats, intrathecal administration of drugs were carried out using injection cannula(33-gauge stainless steel) through the guide cannula(PE 10) which was inserted intrathecally at lower thoracic level through the puncture of a atlantooccipital membrane. Intrathecal injection of an $GABA_B$ receptor agonist, baclofen(30, 60, 100 nmol) decreased both BP and HR dose-dependently. Pretreatment with 8-bromo-cAMP(50 nmol), a cAMP analog, or glipizide(50 nmol), a ATP-sensitive $K^+$ channel blocker, attenuated the depressor and bradycardic effects of baclofen(100 nmol), but not with 8-bromo-cGMP(50 nmol), a cGMP analog. These results suggest that the $GABA_B$ receptor in the spinal cord plays an inhibitory role in central cardiovascular regulation and that this depressor and bradycardic actions are mediated by the decrease of cAMP via the inhibition of adenylate cyclase and the opening of $K^+$ channel.

• Journal of computational fluids engineering
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• v.13 no.1
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• pp.35-40
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• 2008

Generally flight vehicles have many cavities such as wheel wells, bomb bays and windows on their external surfaces and the flow around these cavities makes separation, vortex, shock and expansion waves, reattachment and other complex flow phenomenon. The flow around the cavity makes abnormal and three-dimensional noise and vibration even thought the aspect ratio (L/D) is small. The cavity giving large effects to the flow might make large noise, cause structural damage or breakage, harm the aerodynamic performance and stability, or damage the sensitive devices. In this study, numerical analysis was performed for cavity flows by the unsteady compressible three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Wilcox's $\kappa-\omega$ turbulence model. The MPI(Message Passing Interface) parallelized code was used for calculations by PC-cluster. The cavity has the aspect ratios of 2.5, 3.5 and 4.5 with the W/D ratio of 2 for three-dimensional cavities. The Sound Pressure Level (SPL) analysis was done with FFT to check the dominant frequency of the cavity flow. The dominant frequencies were analyzed and compared with the results of Rossiter's formula and Ahuja& Mendoza's experimental datum.

• Korean Journal of Clinical Pharmacy
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• v.7 no.1
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• pp.33-39
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• 1997

Cardiac and antihypertensive effects of BMS-180448, a cardiac-selective ATP-sensitive potassium channel opener, and its newly synthesized derivatives KR-31281, KR-31282 and KR-31299 were evaluated in isolated perfused rat hearts (25 min global ischemia/30 min reperfusion) and conscious rats. Three new compounds $(10\;{\mu}M)$ induced positive inotropism as evidenced by increased LVDP (left ventricular developed pressure) and RPP (Rate-Pressure Product) in nonischemic rat heart. HR-31299 increased CF (coronary flow) and HR (heart rate) but the other two had no effects. KR-31282, KR-31281 and HR-31299 had a tendency to increase reperfusion LVDP and RPP compared with vehicle, while the latter two significantly reduced reperfusion EDP with a tendency to inclose TTC (time to contracture). All three KR-compounds had very weak effects on MBP and HR in conscious rats. These results indicate that KR-31281 and HR-31299 may have some cardioprotective effects, although weaker than BMS-180448, and their mode of action different from that of BMS-180448, despite the similarity in major structural moeity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.155-158
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• 2003

The effects of Mn, V addition on the behavior of structure and the effects of cooling rate of S20C steel for use of Tn housing and valve for automotive parts have been investigated. Transformation start temperature measured from inflection point of cooling curves has been found out to decrease with increasing cooling rate and to be more sensitive to Mn contents when cooling rate is fast. It was therefore shown that the grain was refined. If there is a big compacting pressure, it is indicated that hardness becomes much greater at surface than inside.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3135-3147
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• 1993

A numerical method is presented which can solve the steady flow and heat transfer from a rotating and heated circular cylinder in a uniform flow for a range of Reynolds number form 5 to 100. The steady response of the flow and heat transfer is simulated for various spin parameter. The effects on the flow field and heat transfer characteristics known as lift, drag and heat transfer coefficient are analyzed and the streamlines, velocity vectors, vorticity, temperature distributions around it were scrutinized numerically. As spin parameter increases the region of separation vortex becomes smaller than upper one and the lower region will vanish. The lift force, a large part is due to the pressure force, increases as the Reynolds number and it increases linearly as spin parameter increases. The pressure coefficient changes rapidly with spin parameter on the lower surface of the cylinder and the vorticity is sensitive to the spin parameter near separation region. As spin parameter increases the maximum heat coefficient and the thin thermal layer on front region are moved to direction of rotation. However, with balance between the local increase and decrease, the overal heat transfer coefficient is almost unaffected by rotation.