• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.429-433
• /
• 1997

High-speed and high-precision are trendy at present in the development of machine tools which are required for various fields of industry such as semiconductor, automobde, mold fabricat~on and so on. High damping capacity of the structure is an iniportant factor to ohtain precise products without vibration during manufacturing caused by rapid trarisportatm and rotation of spindle unit Resin concrete have high potential for machine tool bed due to its good damping characteristics. In this study, the statlc and dynamic characteristics of the machine tool bed were analysed. Also, the hybrid machine tool bed, made of steel base and polyester resin concrete material, was manufactured and its good dynamic characteristics were proved experimentally.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.8 no.4
• /
• pp.76-82
• /
• 2009

A worm screw is widely used in a geared motor unit for motion conversion from rotation to linear motion. For mass production of a high quality worm, the current roll forming process is substituted with the milling cutter process. Since the milling cutter process enables the integration of all machining operations of worm manufacturing on a CNC(Computer Numerical Control) lathe, productivity can be remarkably improved. The tooling system for side milling cutter on the CNC lathe to improve machinability is developed. However, the runout of spindle and cutting tips are important factors to be considered for producing high quality worms because the tooling system has multiple tips. In this study, surface roughness variations accuracy according to runout was investigated in side milling cutter for worm screw. The result shows by simulation and experiment.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.1
• /
• pp.163-172
• /
• 1988

An off-line Geometric Adaptive Control Scheme is applied to the milling machine to identify its guideway errors. In the milling process, the workpiece fixed on the bed travels along the guideway while the tool and spindle system is fixed onto the machine. The scheme is based on the exponential smoothing of post-process measurements of relative machining errors due to the tool, workpiece and bed deflections. The guideway error identification system consists of a gap sensor, a, not necessarily accurate, straightedge, and the numerical control unit. Without a priori knowledge of the variations of the cutting parameters, the time-varying parameters are also estimated by an exponentially weighted recursive least squares method. Experimental results show that the guideway error is well identified within the range of RMS values of geometric error changes between machining passes disregarding the machining conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.65-69
• /
• 2004

The small form factor optical data storage devices are developing rapidly nowadays. Since it is designed for portable and compatibility with flash memory, its components such as disk, head, focusing actuator, and spindle motor should be assembled within 5 m thickness. The thickness of focusing actuator is within 2 mm and the total working range is $+/-100{\mu}m$, with the resolution of less than $1{\mu}m$. Since the thickness is limited tightly, it is hard to place the yoke that closes the magnetic circuit and hard to make strong flux density without yoke. Therefore, Halbach array is adopted to increase the magnetic flux of one side without yoke. The proposed Halbach array type focusing actuator has the advantage of thin actuation structure with sacrificing less flux density than conventional magnetic array. The optical head unit is moved on the swing arm type tracking actuator. Focusing coil is attached to swing arm, and Halbach magnet array is positioned at the bottom of deck along the tracking line, and focusing actuator exerts force by the Fleming's left hand rule. The working range and resolution of focusing actuator are analyzed with FEM and experiment.

• Journal of Veterinary Clinics
• /
• v.40 no.5
• /
• pp.323-329
• /
• 2023

Peripheral blood-derived mesenchymal stem cells (PB-MSCs) have shown promise in cell-based therapy, as they can be harvested with ease through minimally invasive procedures. This study aimed to isolate PB-MSCs from foals and mares and to compare the proliferation and cellular characteristics of the PB-MSCs between the two groups. Six pairs of mares and their foals were used in this study. MSCs were isolated from PB by direct plating in a tissue culture medium, and cell proliferation (population doubling time [PDT], and colony-forming unit-fibroblast assay [CFU-F]), and characterization (morphology, plastic adhesiveness, colony formation, trilineage differentiation) were examined. There was no significant difference in the PB-MSC yield, CFU-F, and PDT between the mares and foals. PB-MSCs from both mares and foals showed typical MSC characteristics in terms of spindle-shaped morphology, plastic adhesive properties, formation of colonies, trilineage differentiation. These results suggest that PB-MSCs isolated from horses, both adult horses, and foals, can be used for equine cell-based therapy.

• 제어로봇시스템학회:학술대회논문집
• /
• 2004.08a
• /
• pp.1732-1737
• /
• 2004

This paper proposes Internet-based checking technique for machine-tools with variant CNC (Computerized Numerical Controller). According to the architecture of CNC, CNC is classified into two types such as CAC (Closed Architecture Controller) which is conventional CNC, and OAC (Open Architecture Controller) which is a recently introduced PC-based controller. CAC has a closed architecture and it is dependent on CNC vender specification. Because of this, it has been very difficult for users to implement an application programs in CNC domain. Therefore, an additionally special module is required for Internet-based application such as remote checking. In this case, web I/O embedded module can be efficiently applied for Internet-based checking. The module is directly attached to TCP/IP network for communication. In order to obtain the monitoring data of CNC machines, the I/O signals of the module are assigned to PLC (Programmable Logic Controller) input and output (I/O) signals within CNC domain. On the other hand, OAC has a PC-based open architecture and an additional module is not necessary for the connection with external site. Because of this, a simple DAU is just used for signal sensing and data acquisition without additional communication modules. For Internet-based remote checking of machine-tools with OAC, a user-defined daemon and application programs are implemented as the form of internal function within the PC-based controller. Internet communication is performed between the daemon program in CNC domain and web script programs in external server. Checking points defined in this research are classified into two categories such as structured point and operational point. The formal includes the vibration of bearing, temperature of spindle unit and another periodical management. And the latter includes oil checking, clamp locking/unlocking and machining on/off status.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.10 no.4
• /
• pp.279-285
• /
• 2016

Reliable recording and analysis of peripheral nerve activity is important to recognize the user's intention for controlling a neuro-prosthetic hand. In this paper, we present a peripheral nerve recording system that consisted of an intrafascicular multi-electrode array, an electrode insertion device, and a multi-channel neural amplifier. The 16 channel multi-electrode array was stably implanted into the sciatic nerve of the rat under anesthesia using the electrode insertion device. During passive movements and mechanical stimuli, muscle and cutaneous afferent signals were recorded with the multi-channel neural amplifier. Furthermore, we propose a spike sorting method to isolate individual neuronal unit. The muscle proprioceptive units were classified as muscle spindle afferents or Golgi tendon organ afferents, and the skin exteroceptive units were categorized as slow adapting afferents or fast adapting afferents. Experimental results showed that the proposed method could be applicable to record and analyze peripheral nerve activity in neuro-prosthetic systems.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.6
• /
• pp.69-74
• /
• 2017

In the current machining industry, machining precision is necessary and machining is being carried out. In this ultra-precision machining industry, the fixation of the workpiece is very important and the degree of machining depends on the degree of fixation of the workpiece. In ultra-precision machining, various methods, such as using a vise chuck or the like and using bolt nut coupling, are used for fixing a workpiece to an existing machine tool. In particular, when the precision gripping force of the jig is insufficient during machining of the ultra-precision mold parts, the machining material shakes due to the vibration or friction, and the machining precision is lowered. In the ultra-precision machining of power transmission parts, such as gears, the accuracy of the product is then determined. In addition, the amount of heat generated during machining has a significant effect on the machining accuracy. This is because the vibration value changes according to the grasp force of the jig that fixes the workpiece, and the change in the calorific value due to the change in the main shaft rotation speed of the ultra-precision machining. The increase in the spindle rotation speed during machining decreased the heat generation during machining, and the machining accuracy was also good, and it was confirmed that the machining heat changed according to the fixed state of the workpiece and the machining accuracy also changed. In this study, we try to optimize the driving part of the power vise by using structural analysis, rather than the power vise, using the basic mechanical-type power unit.

• Journal of the Korean Institute of Gas
• /
• v.21 no.4
• /
• pp.70-75
• /
• 2017

This paper presents the FEM analysis results on the deformation behavior safety of automatic cut-off horizontal and conventional vertical gas valves. Based on the FEM analysis, the primary maximum deformation of $4.4{\mu}m$ was formed on the right end side of a valve body when the internal gas pressure was supplied on the screw port and gas discharge port of an automatic cut-off horizontal gas valve. And the secondary maximum deformation of $2.9{\mu}m$ was formed on the end side of safety valve port. This small deformation of an automatic cut-off horizontal gas valve is strongly related to the balanced design of a horizontal gas valve main body, which is composed of a screw part, gas outlet port, port for a stem and spindle shaft assembly, and safety valve port. But, the primary maximum deformation of 0.076mm was formed on the upper part of a conventional automatic cut-off vertical gas valve when the internal gas pressure was supplied on the screw port and gas discharge port. And the secondary maximum deformation of 0.055mm was formed on the left end side of a gas outlet port. This may effect on the sealing clearance of o-ring that is inserted on the groove of an automatic cut-off unit. Thus, this paper recommends an automatic cut-off horizontal gas valve compared with that of a conventional gas valve for a gas leakage free mechanism of a LPG cylinder valve.

• The Korean Journal of Zoology
• /
• v.33 no.3
• /
• pp.276-296
• /
• 1990

This study attempts to investigate several enteroendocrine cells in the gastrointestinal epithelia of the Korean snakes (Dinodon rufozonatum rufozonotum Rhabdophis tigrina tigrina, Enhydris rufodorsata, Agkistrodon blomhoffii brevicaudus, Agkistrodon saxatilis, Agkistodon calginosus). For a light-microscopical examination of immunocytochemistry, the paraffin sections (5 $\mu$ m) of tissue specimens taken from the various parts of the gastrointestinal tract were stained immunocytochemically by PAP procedure with 10 antisera. The frequency of enteroendocrine cells per unit area (mm$^2$) of each mucosa were counted and the shapes of the cells were observed. In Dinodon rufozonatum rufozonatum, Rhobdophis tigrina tigrina, Enhydris rufodorsata, Agkistrodon saxatilis and Agkistrodon caliginosus, cholecystokinin (CCK)-8, gastrin, pancreatic polypeptide (PP) and serotonin cells were observed. But the freuqency of these immunoreactive cells differ trom each portion of gastrointestinal tracts of all species, respectively. In Agkistrodon blomhoffii brevicaudus, CCK-8, gastrin and serotonin cells were observed. CCK-8 and serotonin cells were found in whole gastrointestinal tracts and gastrin cells were observed in pylorus and mucosa of small intestine. The frequency of these cells was different from each portion. The shapes of CCK-8, gastrin, PP and serotonin cells were pyramidal or oval and closed type in stomach. A large number of these cells were spindle in shape and open type in small intestine and anterior pant of large intestine, whereas some cells were closed type. In posterior part of large intestine and rectum, these cells were oval in shape and closed type.