• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.56-61
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• 1986

Rotor dynamic response of pumps is greatly influenced by the nature of the hydraulic forces arising from wearing seal, balance drum and impeller, etc.. Therefore, rotor dynamic analysis should be conducted during the design stage in order to aleviate some of the vibrational problems which might occur during the operational life of pumps. Previsousely, the authors have proposed the method to obtain the dynamic seal coefficients of the annular plain seal, convergent and divergent tapered seals, parallel grooved seal, spiral grooved seal and annular stepped seal. On the basis of these results, this paper presents the investigated effect of seals on the stability behavior of a centrifugal pump. The results show the effects of seal geometry, pressure difference, clearance, length/diameter ratio, on stability behavior.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.285-291
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• 2014

This paper is related to the improvement of efficiency for high performance centrifugal pumps by reducing leakage loss, which is achieved by applying the grooved seal as a non-contact seal to the pumps. Various combinations of grooved seal types, including the spiral and the parallel groove in the rotor and/or in the stator, were tested by the experiment. And the corresponding hydraulic performance and the magnitude of axial thrust were measured and calculated for ten cases. From the results, the type with the spiral groove(spiral angle : $0.98^{\circ}$) in both the rotor and the stator was found to be most effective. In this case, the head and the efficiency were improved from the original design by 2.1% and 2.3% respectively at design capacity($340m^3/h$), and the axial thrust was decreased by 10%.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.356-363
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• 2001

Piston seal is a device designed to prevent leakage in split connecctions or between relatively moving part. Contact force, critical pressure at which extrusion occurs, leakage rate, fluid film thickness and friction force have been analyzed for some design parameter such as clearance between cylinder wall piston, depth of rectangular groove and pressure of sealed hydraulic fluid. In this paper, we analyze displacement and stress of Wearing by finite element analysis to understand Contact Behaviour Characters.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.1
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• pp.94-104
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• 2021

Objectives: A number of medical institutions have been conducting fit tests to perform seal checks on masks. This study aimed to compare the differences fit factor before and after domestic N95 mask-wearing training through a fit-test. Methods: A survey of 59 healthcare workers was conducted regarding whether they had undergone a fit test or received training on mask-wearing. Further, the fit of two types of domestic N95 masks was measured before and after the training using a QNFT(Quantitative Fit test). The average fit factors before and after training were compared using a paired t-test. Additionally the differences in the fit test pass rate were analyzed using a McNemar test. Results: A statistically significant difference was seen between the fit factors in the fit tests conducted before and after the training (p=0.0015), as well as in the fit of the two types of masks tested (p<0.01). Thus, an improvement in mask fitting was seen after the training, even with differently fitted masks. Conclusions: Upon using a QNFT, a significant increase in the fit factors for N95 masks was observed after training compared with masks that were fitted as usual. This highlights the importance of training in mask-wearing, with the conclusion that training healthcare providers will improve the fit of masks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1091-1098
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• 2003

Flexure bearings have been used in linear-resonant compressors to maintain a non-contacting clearance seal between the piston and cylinder. There are two types of tangential cantilever bearing and spiral arm bearing with flexure bearings. A newly devised linear flexure bearing (KIMM-Ml) for compression refrigeration machines is disclosed having improved tight gas clearance maintaining capability for better system performance. KIMM-Ml is an integrated device comprising an axially moving diaphragm with circumferentially arranged arc-shaped flexure blades secured between rim and hub spacers, which turn out to have higher radial stiffness than the one with circumferential tangential cantilever flexure blades. It is expected for KIMM-Ml to play a key role in designing long life, special purpose compression refrigeration machines by providing frictionless, non-wearing, linear movement and radial support for the machines as well as a gas clearance seal by maintaining extremely tight clearances between piston and cylinder.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.246-250
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• 2000

The oral screen is a functional appliance, suitable for the treatment of developing malocclusion associated with aberrant muscular patterns. The better muscle balance between tongue and the buccinator mechanism can be established, and the reestablishment of normal growth and development can be achieved. The oral screen can be used for the correction of the following conditions : (1) thumbsucking, tongue thrusting and lip biting, (2) mouth breathing, (3) mild distocclusion with premaxillary protrusion, (4) open bites in deciduous and mixed dentition, and (5) incompetent lips. The patient should wear the oral screen every night and also during the day whenever possible. The effects of oral screen can be elevated through lip seal exercise : the lips should be kept in contact all the time to improve the lip seal. In the presented two cases, the patients were considered mouth breathers and to have incompetent lips, and one patient with maxillary incisal protrusion and the other with open bite. They were instructed to wear the oral screen with lip seal exercise. After wearing the appliance for 1 and 2 years respectively, mouth breathing was decreased and lip length and strength were increased, the maxillary incisors were retruded and open bite reduced.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.2
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• pp.92-101
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• 2001

This article reviewed previous studies on the 3D face recognition and anthropometric facial analysis to design suitable respirators for individuals. 3D facial anthropometric data have not been reported in Korea yet. With 3D facial data, it is possible to design and to manufacture respirators having more effective respirator-face seal and thus providing more comfortable wearing than donning of those respirators designed using 1 and 2-dimensional data. Also 3D data could be used for respirator fit-testing and selecting suitable respirator type and size by computer simulation without several steps of fit-test to each individual worker.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.404-409
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• 2002

A newly devised linear flexure bearing (KIMM-LFB) for reciprocating machines is disclosed having improved tight gas clearance maintaining capability for better system performance. KIMM-LFB is an integrated device comprising an axially moving diaphragm with circumferentially arranged arc-shaped flexure blades secured between rim and hub spacers, which turn out to have higher radial stiffness than the one with circumferential tangent cantilever flexure blades. It is expected for KIMM-LFB to play a key role in designing long life, special purpose reciprocating machines such as spacecraft borne cryogenic refrigerators (cryocoolers) by providing frictionless, non-wearing, linear movement and radial support for the machines as well as a gas clearance seal by maintaining extremely tight clearances between piston and cylinder.

• Journal of Digital Convergence
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• v.16 no.12
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• pp.571-577
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• 2018

Bicycle riders complain of many inconveniences when wearing glasses, sunglasses and masks. The disposable fine dust mask has been developed to resolve such inconveniences of bicycle riders. The scope of research is limited to the fiber which generates one-time static electricity and the shape of the mask due to the characteristic of fine dust mask. The purpose is to design and make the fine dust mask with a simple production process. The new disposable fine dust mask has secured enough space of the mask in front of the mouth by longitudinal folding and minimized stuffiness by maintaining the shape of the folded part to prevent touching the mouth even by heavy breathing. The streamlined sponge is attached at the part of nose support and the area of the cheek has been expanded to be about 2.5cm wider than ordinary masks to improve tight seal at the side. In addition, a new disposable fine dust scarf mask has been developed to block ultraviolet rays for the face and neck while filtering fine dust with the tight fine dust mask.