• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.2
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• pp.220-228
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• 2012

In this paper, we explained the design technique about Ka-band active limiter for protecting the receiver of a millimeter wave seeker. To implement low flat leakage power, we proposed the control circuit of active limiter to control limiter voltage with PRF(Pulse Repetition Frequency) signal and input power. This active limiter consisted of the conventional 2 stage passive limiter, a feedback circuit with a directional coupler, detector, non-inverting amplifier and over-current protection resistance. As the test result of the fabricated Ka-band limiter, it had 1 GHz bandwidth, 3.5 dB insertion loss at the small input power and -7.5 dBm flat leakage at the 4 W RF input power, respectively.

• Journal of Mushroom
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• v.1 no.1
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• pp.34-43
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• 2003

This study was carried out to determine the proper pin-heading induction time(spawn running time) when different incubation temperature were applied to Pleurotus ostreatus(Chunchu 2ho, Suhan 1ho, Heukpyung). Incubation period was 17 days at 23 and 21 days at 17 for Chunchu 2ho, 17 days at 23 and 26 for Heukpyung, and 22~23 days at 17~23 for Suhan 1ho. Incubation period for Suhan 1ho was not significantly affected by incubation temperature. The time required for initial pin-heading was 4~5 days at 17, 20, 23 and 26 for Chunchu 2ho as well as Heukpyung, and was 3 days at 17, 20, 23 and 5~6 days at 26 for Suhan 1ho. As the incubation period became longer, the available fruit-bodies at Chunchu 2ho were made more but they were short. The yield of Chunchu 2ho and Heukpyung increased when incubated for 22~27 days at 20~23 and that of Suhan 1ho also increased when incubated for 22~23 days at 17~23.

• Transactions of Materials Processing
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• v.25 no.2
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• pp.96-101
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• 2016

The current study was conducted to elucidate the effect of cementite morphology and matrix-ferrite microstructure on sliding wear behavior in spheroidized high carbon (1wt. % C) steel. The high carbon steel was initially heat treated to obtain a full pearlite or a martensite microstructure before the spheroidization. The spheroidizing heat treatment was performed on the full pearlitic steel for 100 hours at 700℃ and tempering was performed on the martensitic steel for 3 hours at 650℃. A spheroidized cementite phase in a ferrite matrix was obtained for both the full pearlite and the martensite microstructures. Sliding wear tests were conducted using a pin-on-disk wear tester with the heat treated steel as the disk specimen. An alumina(Al₂O₃) ball was used as the pin counterpart during the test. After the spheroidizing heat treatment and the tempering, both pearlite and martensite exhibited similar microstructures of spheroidized cementite in a ferrite matrix. The spheroidized pearlite specimens had lower hardness than the tempered martensite; however, the wear resistance of the spheroidized pearlite was superior to that of the tempered martensite.

• The Research Journal of the Costume Culture
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• v.7 no.3
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• pp.1-16
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• 1999

This study in concerned with the costume accessories appeared in Sam Kuk Sa ki. The accessories of both sexes were analized. Results of this research can be summarized as follows : It was appeared that names of accessories of men were fewer in number than those of women. Men\`s accessories such as a hat, bok-du, a belt,boots, shoes, and sock were mentioned in Sam Kuk Sa Ki. Women\`s accessories appeared such as a hat, a comb, a hair pin, a belt, shoes, and sock. A bok-du, boots, and a hared belt were used exclusively by men, while a hat, kwan(冠), a comb, a hair pin, a scarf, pyo( ) were worn exclusively by women. All men from different classes including true bone class as well as the common class wore bok-du, a hat, a hard belt, boots, sock ; however, class distinctions were made from materials used for those items. Also women\`s accessories were used as means of differentiating social status of the wearer by means of materials employed for each item. Especially, woman\`s hat and scarf were a symbol of the noble class. Only two classes of women from the true-bone class and women from the sixth du-pum class entited to wear hats. Wearing a scarf was not allowed to women from the common class. Class dirrernetiations were made by the materials used for hats and scarves. Materials for a scarf such as gold and silver leaf, pecock tail, and king fisher fly feather were restricted to women from true-bone class. Such as man\`s hat bok-du( 頭), use of women\`s comb and hair pin, scarf, leggings were items drived from Tang China. It clearly showed that costume accessories of Silla were heavily influenced by the Chinese. At the same time the costume accessories were sued to make sex difference among the people of Silla. Woman wore a soft belt made of cloth while man wore a hard belt. Woman\`s hat, a scarf, a comb, a hair pin, a belt or sash for a shirt, and leggings were woman\`s sex symbol. Thus, costume accessories of Silla appeared in Sam Kum Sa Ki functioned as means of differentiating social status of the wearer such as sex,class and rank in the society. Also, they showed that Silla kingdom had close cultural relationship with Tang China.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3516-3525
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• 2022

The high capture cross-section (𝜎_c) of Gadolinium (Gd-155 and Gd-157) causes reactivity penalty and swing at the initial stage of fuel burnup in Pressurized Water Reactor (PWR). The present study is concerned with the feasibility of the combination of mixed burnable poison with both low and high 𝜎_c as an approach to minimize these effects. Two considered reference designs are fuel assemblies with 24 IBA rods of Gd₂O₃ and Er₂O₃ respectively. Models comprise nuclear fuel with a homogeneous mixture of Er₂O₃, AmO₂, SmO₂, and HfO₂ with Gd₂O₃ as well as the coating of PaO₂ and ZrB₂ on the Gd₂O₃ pellet's outer surface. The infinite multiplication factor was determined and reactivity was calculated considering 3% neutron leakage rate. All models except Er₂O₃ and SmO₂ showed expected results namely higher values of these parameters than the reference design of Gd₂O₃ at the early burnup period. The highest value was found for the model of PaO₂ and Gd₂O₃ followed by ZrB₂ and HfO₂. The cycle burnup, discharge burnup, and cycle length for three batch refueling were calculated using Linear Reactivity Model (LRM). The pin power distribution, energy-dependent neutron flux and Fuel Temperature Coefficient (FTC) were also studied. An optimization of model 1 was carried out to investigate effects of different isotopic compositions of Gd₂O₃ and absorber coating thickness.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.756-768
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• 2023

Neutron transport calculations are extremely challenging due to the high computational cost of large and complex problems. A multilevel octree grid algorithm (MLTG) of discrete ordinates method was developed to improve the modeling accuracy and simulation efficiency on 3-D Cartesian grids. The Balakovo-3 VVER-1000 neutron dosimetry benchmark is calculated to verify and validate this numerical technique. A simplified S₂ synthetic acceleration is used in the MLTG calculation method to improve the convergence of the source iterations. For the triangularly arranged fuel pins, we adopt a source projection algorithm to generate pin-by-pin source distributions of hexagonal assemblies. MLTG provides accurate geometric modeling and flexible fixed source description at a lower cost than traditional Cartesian grids. The total number of meshes is reduced to 1.9 million from the initial 9.5 million for the Balakovo-3 model. The numerical comparisons show that the MLTG results are in satisfactory agreement with the conventional S_N method and experimental data, within the root-mean-square errors of about 4% and 10%, respectively. Compared to uniform fine meshing, approximately 70% of the computational cost can be saved using the MLTG algorithm for the Balakovo-3 computational model.

• Journal of the Korean institute of surface engineering
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• v.38 no.5
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• pp.202-206
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• 2005

Nitriding treatments were conducted on tool steel (SKD 61) at a temperature of $500^{\circ}C$ for 5 hr using high vacuum direct current (DC) plasma, with ammonia and argon as source gases. The structural and compositional changes produced in the nitrided layers by applying different ratios of Ar to $NH_{3}\;(n_{Ar}/n_{NH3}) were investigated using glancing x-ray diffraction (GXRD), optical microscopy, atomic force microscopy (AFM), micro-Vickers hardness testing, and pin-on-disc type tribometer. Nitriding case depths of around of $50{\mu}m$ were produced, varying slightly with different ratios of $n_{Ar}/n_{NH3}. It was found that the specimen surface hardness was 1150 Hv with $n_{Ar}/n_{NH3}=1, increasing to a maximum value of 1500 Hv with $n_{Ar}/n_{NH3}=5. With a further increase in ratio to $n_{Ar}/n_{NH3}=10, the surface hardness of the specimen reduced slightly to a value of 1370 Hv. These phenomena were caused by changes of the crystallographic structure of the nitride layers, i.e the $\gamma'-Fe_{4}N$ phase only was observed in the sample treated with $n_{Ar}/n_{NH3}$=1, and the intensity of the $\gamma'-Fe_{4}N$ phase were reduced but new phase of $\varepsilon'-Fe_{3}N$, which was known as a high hardness, with increasing $n_{Ar}/n_{NH3}. Also, the relative weight loss of counterface of the pin-on-disc with unnitrided steel was 0.2. And that of nitrided steel at a gas mixture ($n_{Ar}/n_{NH3}) of 1, 5, 7, and 10 was 0.4, 0.7, 0.6, and 0.5 mg, respectively. This means that the wear resistance of the nitrided samples could be increased by a factor of 2 at least than that of unnitrided steel.

• Journal of Veterinary Clinics
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• v.25 no.3
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• pp.218-220
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• 2008

A 1.4 kg adult great homed owl was presented to the University of Missouri-Columbia Veterinary Teaching Hospital after being found by the side of the highway. Physical examination revealed soft tissue injuries to the left wing and leg, and good body condition (body score 4/5). The radiographs revealed comminuted fracture of the diaphysis of the left tibiotarsus (severe) and ulna (mild). Closed reduction of the fracture was performed to the left tibiotarsus and ulna. System combining an intramedually (IM) Kirschner pin, IM Kirschner pin for external skeletal fixation, and polymethylmethacrylate was used for fracture repair. At 13 weeks, radiographs revealed that bridging callus was well formed over cortices of the fracture area. No physical, behavioral, or other assessable impairment was found during the rehabilitation period.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.149-157
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• 2000

Tool wear in the shearing process such as blanking, piercing and trimming is very important, because it has great effects on the dimensional accuracy, working efficiency and economy. Most of tools in the shearing process have the coated layer at surface fur good wear and corrosion resistance. When the surface of tool is teated, the wear Phenomena of coated surface layer and inner layer may be different. This paper describes a computer modelling technique by the finite element method in order to investigate the wear mechanism and to predict the wear profile of Ti-N coated tool in piercing process according to the volume of Production. Wear coefficients of the coated layer and inner layer are obtained through Pin-on-Disk wear test, respectively. To verify the effectiveness of the suggested technique, the technique is applied to wear analysis in piercing recess of piston pin and simulation results are compared with experimental ones.

• 한국기계연구소 소보
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• s.15
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• pp.91-103
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• 1985

In this paper, temperature distribution and thermal stress are investigated considering engine peak pressure and the time average temperature distribution in the piston under running conditions for the diesel engine. The induced stress are calculated by the Finite Element Method(FEM). The results obtained are summerized as follows. 1) The results calculated by the FEM present good agreement with other numerical solution in literature. 2) It is confirmed that maximum compressive stress are induced in the part of outside wall between the piston crown and the pin bush. 3) In the axial direction, the hoop stresses are changed its sigh at the portion of crown near the inner wall side 4)Large gradient of temperature is shown in the piston crown near the side wall in the axial direction, in the part between the piton crown and the pin bush in radical direction 5)in case of stress distribution of piston wall surface in the axial direction, the hoop stress is a little greater than axial stress, and the latter is greater than the radial stress