• Transactions of The Korea Fluid Power Systems Society
• /
• v.2 no.3
• /
• pp.12-17
• /
• 2005

This paper presents a theoretical study of the delivery flow ripple produced by a swash plate type hydraulic piston pump for the purpose of developing a computer simulation program capable of predicting the pump source flow ripple accurately at the design stage. Particular attention has been paid to the development of the theoretical model by clarifying quantitatively the design influences of key parts of valve plate such as relief groove and pre-compression/expansion.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.3
• /
• pp.50-55
• /
• 2008

In this paper, we propose a new shape compensation scheme to make up for the difference in groove radius between the formed tools and the machined bearing raceways, which inherently takes place during machining the ball bearing raceways by the turning process using conventional formed tools. The associated conventional methods of the formed tool design and its modification such as a simple depth compensation method and a graphical compensation method are introduced and the latter, which has been known to be the better of the two, is experimentally investigated in detail to reveal its drawback. The algorithm is given and it is applied to develop a formed tool design program. The program developed by the presented approach is successfully applied to design the formed turning tool for the bearing raceways.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.04b
• /
• pp.267-272
• /
• 1995

The paper describes an approach for measuring flow ripple generated by oil hydraulic axial piston pumps. Flow ripple has periodic waveforms due to the cyclic nature of a pump's operation, and interacts with the connected hydraulic systems such as pipes and components to produce a pressure ripple, also known as fluid-borne noise. It is indispensable to measure a flow ripple because increasing of vibration and noise caused by a flow ripple has become a point to be considered and has need of solving these problems. The measurement of flow ripple with high frequencies from oil hydraulic axial piston pumps is msde by using the remote instantaneous flow rate measurement method. As a result, the reverse flow through the relief groove in valve plate has an important effect upon a flow ripple generated by a pumps.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.10 s.253
• /
• pp.1019-1025
• /
• 2006

Numerical simulations were conducted on the gerotor type oil pump. Three oil pump models having different port and groove shape were considered. Firstly, two original models (baseline & variant.1 model) were simulated in order to validate the accuracy of the simulation results and to better understand the flow characteristics in the pump. It was found that the cavitation phenomenon as well as the teeth tip leakage is most important parameter on the pump performance. Based on the simulation results of the original models, final model (variant.2 model) which has improved port shape and pressure relief valve is suggested to enhance pump performance and to reduce driving torque. The volumetric efficiency and the hydraulic torque of the Variant.2 model is improved 4% and reduced 6.1% each at 2000RPM in experiment.

• 한국해양학회지
• /
• v.13 no.1
• /
• pp.1-8
• /
• 1978

A seismic reflection Survey was carried out in the offshere area between Geoje Island and Namhae Island, utilizing the echosounder with the frequency 28KHz and thd Uniboom with the filter band 800∼2000Hz. The results show the submarine topography, sedimentary layer structure and the depth distribution of the base rock. The water depth of the sea in the survey area is less than 80m; up to 40m contour line the sea bottom surface has a slight dip(about 1/1000), while in the zone deeper than 40m the bottom topography has a irregular relief. The thickness of the whole sedimentary deposit is about 20∼70m and divided into 3 layers: Upper layer(A layer) with horizontal laminae, intermediate layer(B layer) with cross-bedding and groove structure, and lower layer(C layer) not showing any sedimentary structure on the seismic reflection profile. The surface of the base rock is deeper gradually in the south-eastern part of the survey area and extends to 140m depth. The vertical sediments sequences, composed of B layer and A layer, show the type of transgressive sequences. It is interpreted that B layer was formed at one period when the sea level was lower 40∼60 than the present and ince then, following the rising of the sea level, A layer was deposited.

• Clinics in Shoulder and Elbow
• /
• v.13 no.1
• /
• pp.7-13
• /
• 2010

Purpose: Our purpose was to retrospectively analyze clinical results of subpectoral tenodesis of the proximal biceps tendon using an interference screw. Materials and Methods: We reviewed 23 cases of patients receiving tenodesis of the proximal biceps tendon between January 2008 and January 2009 for whom we had follow-up data for at least 1 year. Twenty-three cases were operated on using subpectoral tenodesis; 16 of these cases had a rotator cuff tear. The results were judged using a visual analog scale (VAS), ASES, tenderness on the biceps groove, fixation failure and the degree of deformity (BAD). Results: VAS and ASES scores were significantly improved in all patients by the time of the final observation. There were no significant complications or fixation failures. The patients without a tear of the rotator cuff had a better result than patients with a tear of the rotator cuff, but the difference between the two groups was not significant (p>0.05). Conclusion: In patients with pathology of the long head of the biceps brachii, benefits of subpectoral interference screw tenodesis include pain relief, maintenance of functional biceps, muscle strength, and cosmesis. Subpectoral biceps tenodesis using interference screw fixation appears to be a promising, reproducible, reliable technique for addressing anterior shoulder pain related to pathology of the long head of the biceps brachii.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.7 no.1
• /
• pp.33-38
• /
• 2014

Purpose: To determine the therapeutic effectiveness of ultrasound-guided medial branch block (MBB) for the herniated lumbar disc patients who did not relieve their symptoms after percutaneous epidural neuroplasty (PEN). Materials and Methods: From August 2011 to February 2013, 559 patients with herniated lumbar disc have undergone PEN. Among them, ultrasound-guided MBBs were performed for the patients who had sustained low back pain and refered pain to lower extremities. Eighty eight patients were followed at 1 month and 39 patients could be followed at 6 month. All procedures have been performed by the one operator, and 23 G, 10 cm needle was placed and 0.5% lidocaine was injected under ultrasound guide. To target medial branches from L1 to L5, the groove at the root of transverse process and the base of superior articular process has been identified on transverse scan. Patients were evaluated by Visual Analog Scale (VAS) and Oswestry Disability Index (ODI) at each follow-up. Significant pain relief was described as a 50% or more reduction in VAS and significant improvement in function was described as at least a 40% reduction in ODI. Results: VAS showed that preprocedure pain ($7.35{\pm}1.68$; $mean{\pm}SD$) significantly decreased 1 month after block ($3.36{\pm}2.98$) and 6 month ($3.05{\pm}2.27$) (p<0.05). ODI also showed that preprocedure score ($32.82{\pm}8.77$) significantly decreased at 1 month ($15.14{\pm}14.01$) and 6 month ($12.97{\pm}8.82$) (p<0.05). Significant pain relief was observed in 64.49% at 1 month and 64.10% at 6 month. Significant functional improvement in 59.81% at 1 month and 61.54% at 6 month. Conclusion: Ultrasound-guided medial branch block may sufficiently treat the facet problems secondary from disc disease.