• Journal of the Korean Society for Precision Engineering
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• v.23 no.9 s.186
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• pp.54-60
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• 2006

Fitting process carried out in automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that heats gear to a suitable range under the tempering temperature and squeezes it toward the outer diameter of shaft. Its stress depends on the yield strength of gear. Press fitting is a method that generally squeezes gear toward that of shaft at room temperature by press. Another method heats warmly gear and safely squeezes it toward that of shaft. Warm shrink fitting process for automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by this process produced dimensional changes of gear profile in both radial and circumferential directions. So that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of warm shrink fitting process, in which design parameters are involved; contact pressure according to fitting interference between outer diameter of shaft and inner diameter of gear, fitting temperature, and profile tolerance of gear. In this study, an closed form equation to predict contact pressure and fitting load was proposed in order to develop optimization technique of warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, that is, thermal-structural coupled field analysis. Actual loads measured in the field have a good agreement with the results obtained by theoretical and finite element analysis and also the expanded amounts of the gear profile in both radial and circumferential directions are within the limit tolerances used in the field.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.4
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• pp.69-76
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• 2005

In this paper, a 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has a 100MHz bandwidth at the center frequency of 14.5GHz(Ku-band) and the response of the filter is the Chebyshev function. The cavity filter uses two orthogonal $TM_{113}$ modes and one $TM_{012}$ mode. The coupling between the adjacent cavityes(intercavity coupling) results in a Chebyshev response and is accomplished by only H-filed component of If modes. The size and location of intercavity slot is determined by the coupling equation from E-and H-field of TE and TM resonant modes in circular cavity. The 2-stage 6-pole triple-mode cavity BPF has the insertion loss of 2.4dB and the reflection loss of 15dB in the passband. The triple-mode BPF proposed in this thesis can be used as channel filters for satellite payload system and can minimize filter assembly in general wireless communication system.

• Asian-Australasian Journal of Animal Sciences
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• v.26 no.4
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• pp.455-462
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• 2013

NLR family pyrin domain containing 3 (NLRP3) is a key component of the inflammasome, whose assembly is a crucial part of the innate immune response. The aim of the present study was to evaluate the association between exon 3 polymorphisms of NLRP3 and the susceptibility to digestive disorders in rabbits. In total, five coding single-nucleotide polymorphisms (cSNPs) were identified; all of which are synonymous. Among them, c.456 C> and c.594 G> were further genotyped for association analysis based on case-control design (n =162 vs n =102). Meanwhile, growing rabbits were experimentally induced to digestive disorders by feeding a fiber-deficient diet, subsequently they were subjected to mRNA expression analysis. Association analysis revealed that haplotype H1 (the two cSNPs: GT) played a potential protective role against digestive disorders (p<0.001). The expression of NLRP3 in the group $H1HX_1$ ($H1HX_1$ is composed of H1H1, H1H3 and H1H4) was the lowest among four groups which were classified by different types of diplotypes. Those results suggested that the NLRP3 gene was significantly associated with susceptibility to digestive disorders in rabbit.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.1-18
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• 2007

This study is about an arrangement method of trapezoidal pre-cast segment lining that can be applied in shield tunnel construction. Trapezoidal segment lining is formed by assembling tapered pre-cast concrete segments taking advantage of the tapered shape of pre-cast segments upon delivery on site. By calculating tapering of the segments manufactured in single type and rotating the segments when putting them together, a variety of tunnel alignments can be arranged in the most efficient way. Once the design criteria and tunnel alignment (straight or curved) is analyzed, the sequence of assembling trapezoidal segments in compliance with tunnel alignment will be computed. On site an operator can utilize the softwareto automatically determine sequential arrangement of trapezoidal segments. When the actual arrangement of segmental lining is different from the computed output, the operator can input the actually measured values to coincide the computerized calculation with the real status of assembly. Then the adjustment will be the basis of subsequent arrangement of segments, thus the continuity of work can be guaranteed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1235-1240
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• 2010

Wire-woven Bulk Kagome (WBK) is fabricated by assembling helically formed wires in six directions. To date, WBK samples have been assembled manually. For industrial application, the assembly process must be automated. Furthermore, if WBK is to be fabricated using flexible wires that cannot maintain their helical shape during fabrication, a specialized automatic machine, i.e., a loom needs to be developed. In this work, we designed and constructed a loom for fabricating WBKs using flexible wires. This loom is operated by one rotation of the upper plate, two translations of the insertion device, and insertion of wires. So-called "comb devices" are placed between multiple layers of Kagome nets to prevent the wires that are already in place from getting entangled with those that are being inserted. This loom can be also used to fabricate semi-WBKs composed of helically formed wires and rigid straight wires.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.27-34
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• 2011

This study is making a product for the development of one process worm wheel of making a shape for gear for worm wheel without hobbing manufacturing process. Because of removing a hobbing process, plastic worm wheel for increased productivity and equivalent quality is produced in the result. As the result, this product is selling to Hyundai Mobis, Mando, TRW, KOYO/NSK/Showa(Japan), Delphai(America). The core technology and different strategy are as follows. The technology protection for molding of worm whee is currently patent process "Molding process of helical gear(No. 10-2008-0105908). Further patent procedure for "molding system for positioning decision of inserting boss is currently prepared. As gear molding procedure in hobbing machine without gear machining procedure, most of all, core development technology which is making a gear tooth is main topic. So that, in case of currently developed worm wheel, because core and mold base are not developed in the first procedure, gear is machining in hobbing M/C as the second procedure. In the later, patent for mold base structure will be prepared in this study results.

• Journal of the Korean Society of Clothing and Textiles
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• v.34 no.9
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• pp.1546-1557
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• 2010

This study analyzes the status of foreign direct investment in Korean textiles and fashion firms and investigates the factors determining their performance. A total of 1,251 cases (including 1,116 manufacturers and 135 of distributors from the 2009/2010 Korean Overseas Business Directory published by KOTRA) were used. The results of this study are as follow: 1) In the case of manufacturers, China was the most heavily invested in country, and the Asian region that included China, Vietnam, Indonesia and Bangladesh consisted of 80% total investment. In cases of distributors, China was also the first ranking country and other countries, that included Vietnam, United States, and Japan are major ones. 2) In terms of the foreign entry mode, wholly-owned subsidiaries represented 90% of total cases. As the index of the degree of localization, the ratio of local employees was very high. 3) Different countries were utilized by year, type of business, and area of process. In manufacturers, Indonesia, China, and Vietnam were the most heavily utilized countries in the 1980s, 1990s, and 2000s, respectively. For distributors, China was the major market ill the 1980s and 1990s but Vietnam has emerged as the biggest market in the 2000s. In terms of area of process, China was for manufacturing fibers and fabrics, Vietnam was for most items, Indonesia was for assembly, knit, accessories, and Bangladesh was for embroidery and accessories. 4) The determining factors of the age of foreign business as the proxy index and performance of foreign business entry, were different by the type of business. For manufacturers, four factors including the dollar amount of investment, number of local employees, the mode of foreign direct investment, and entry to China were significant. On the other hand, only two factors including the dollar amount of investment and entry (other than China) were significant distributors.

• Journal of Broadcast Engineering
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• v.2 no.1
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• pp.8-15
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• 1997

In this paper, a real-time operating Motion Picture Experts Group-1 (MPEG-1) audio encoder system is implemented using a TMS320C31 Digital Signal Processor (DSP) chip. The basic operation of the MPEG-1 audio encoder algorithm based on audio layer-2 and psychoacoustic model-1 is first verified by C-language. It is then realized using the Texas Instruments (Tl) assembly in order to reduce the overall execution time. Finally, the actual BSP circuit board for the encoder system is designed and implemented. In the system, the side-modules such as the analog-to-digital converter (ADC) control, the input/output (I/O) control, the bit-stream transmission from the DSP board to the PC and so on, are utilized with a field programmable gate array (FPGA) using very high speed hardware description language (VHDL) codes. The complete encoder system is able to process the stereo audio signal in real-time at the sampling frequency 48 kHz, and produces the encoded bit-stream with the bit-rate 192 kbps. The real-time operation capability of the encoder system and the good quality of the decoded sound are also confirmed using various types of actual stereo audio signals.

• Progress in Superconductivity
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• v.13 no.1
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• pp.40-46
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• 2011

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. A 10 kWh class flywheel energy storage system (FESS) has been developed to evaluate the feasibility of a 35 kWh class SFES with a flywheel $I_p/I_t$ ratio larger than 1. The 10 kWh class FESS is composed of a main frame, a composite flywheel, active magnetic dampers (AMDs), a permanent magnet bearing, and a motor/generator. The flywheel of the FESS rotates at a very high speed to store energy, while being levitated by a permanent magnetic bearing and a pair of thrust AMDs. The 10 kWh class flywheel is mainly composed of a composite rotor assembly, where most of the energy is stored, two radial and two thrust AMD rotors, which dissipate vibration at critical speeds, a permanent magnet rotor, which supports most of the flywheel weight, a motor rotor, which spins the flywheel, and a central hollow shaft, where the parts are assembled and aligned to. The stators of each of the main components are assembled on to housings, which are assembled and aligned to the main frame. Many factors have been considered while designing each part of the flywheel, stator and frame. In this study, a 10 kWh class flywheel energy storage system has been designed and constructed for test operation.

• Tribology and Lubricants
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• v.32 no.5
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• pp.154-159
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• 2016

This paper presents an experimental study of the leakage performance and endurance performance of a mechanical face seal in the 7-ton-class turbopump of the Korea Space Launch Vehicle 2 third-stage engine. We install a mechanical face seal between the fuel pump and turbine to prevent the mixing of the fuel and turbine gas. We design and manufacture a prototype mechanical face seal, which has two parts, namely, a bellows seal assembly and mating ring. We set up a test facility to measure the leakage and endurance of the mechanical face seal. For the similarity tests, we use water under real operating conditions such as high rotational speed, high temperature, and high pressure. Through investigation of the leakage and carbon wear rate, it is possible to evaluate the performance of the mechanical face seal. The results of the leakage and endurance performance test demonstrate the absence of any leakage from the prototype mechanical face seal after a trial run and clarify that the acceptable wear rate fully satisfies the turbopump requirements. Finally, we install a qualified mechanical face seal in a 7-ton-class turbopump and perform a validation test in the turbopump real-propellant test facility in the Korea Aerospace Research Institute. The test results confirm that the mechanical face seal works well under real operating conditions.