• Korean Journal of Food Science and Technology
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• v.40 no.3
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• pp.349-353
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• 2008

This study was performed to determine the adherence rates of standard type Salmonella Typhimurium (ST) and wild type Salmonella spp.(WT) in pork after the following contact types and times at $10^{\circ}C$: pork meat (2, 6, 24 hr), conveyer belt (2, 6 hr), stainless steel (2, 6 hr), and cutting board (2, 6 hr). After 6 hr of pork meat to meat fat contact, the adherence rates for ST and WT were approximately 4.21 and 26.87%, respectively, and after 6 hrs of pork meat to red meat contact they were 16.40 and 27.48%, respectively. However, after 24 hr of both types of contact, ST and WT showed 100% adherence rates. The adherence rates for ST after 2 hr and 6 hr of pork meat to conveyer belt contact were 1.34 and 0.60%, respectively, while the adherence rate for WT was 5.14% after 6 hr of contact. After pork meat to stainless steel contact, ST showed adherence rates of zero and 1.59% after 6 and 24 hr of contact, respectively, while the adherence rates for WT ranged from 0.17% after 2 hr to 5.01% after 6 hr. On the other hand, neither ST nor WT offered adherence data following pork meat to cutting board contact. These results suggest that the adherence rates of ST and WT after pork meat to pork meat contact or pork meat to processing surface contact were significantly affected by the contact time and WT presented much higher adherence rates for both types of transmission than ST.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.67-75
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• 2019

The diaphragm used for CFT columns has a small amount of steel to be used, but has a disadvantage that welding is difficult and openings are required because the steel tube and four sides must be welded. The improved diaphragm to be examined in this study was cut into four corners by cutting the center hole for concrete filling. In the improved diaphragm, the width of the center hole is the same as that of the previous diaphragm, but the width of the diaphragm contacting the steel tube is reduced, thereby reducing the welding length by about 70% compared to the previous diaphragm. The in-plane strain of each specimen was analyzed when the same load was applied to the interior diaphragm through a simple tensile test. Using the general FEM program(ANSYS 19.2), the analysis was performed under the same conditions as the actual simple tensile test, and the load transfer between the improved diaphragm and the previous diaphragm was compared. When the width of the diaphragm is equal to or smaller than the flange width, stress is concentrated from the end of the diaphragm, and when the flange width is larger, stress is concentrated at the center.

• The Journal of the Convergence on Culture Technology
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• v.5 no.3
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• pp.345-349
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• 2019

In Korea, the mountainous area occupies more than 70% of the whole country, cutting of earth slope that cuts a part of the ground surface is widely used when building infrastructures such as road, railroad, and industrial complex construction. In recent years, regulations on environmental damage have become more strict, and various methods have been developed and applied. Among them, Concrete-Panel Retaining Wall technique is actively applied. Concrete-Panel Retaining Wall is a method to resist horizontal earth pressure by forming a wall by attaching a precast retaining wall to the front of the support material and increasing the shear strength of the disk through reinforcement of the support material. Soil nailing, earth bolt, and ground anchor are used as support material. Among them, ground anchor is a more aggressive reinforcement type that introduces tensile load in advance to the steel wire, and a large concentrated load acts on the front panel. This concentrated load is a factor that creates cracks in the concrete panel and reduces the durability of the retaining wall itself. In this study, steel pipe sleeves and reinforcements were purchased at the anchorage of the panel to prevent cracks, and by applying bumpy shear keys to the end of the panel, the weakness of the individual behavior of the existing grout anchors was improved. The problem of degraded landscape by exposure to front concrete of retaining wall and protrusion of anchorage was solved by the production of natural stone patterns and the construction of sections that do not protrude the anchorage. In order to verify the effectiveness of anti-crack sleeves and reinforcements used in the null, indoor testing and three-dimensional numerical analysis have been performed, and the use of steel pipe sleeves and reinforcements has demonstrated the overall strength increase and crack suppression effect of panels.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.195-214
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• 2000

The high-speed steel (shorten as HSS) consists of Fe and several kinds of transition metal carbides. The cutting tools or wear-resistant materials made from HSS experience relatively high thermal shock because a coolant such as water or oil is flowed over the surface of heated HSS. The purpose of this research is to increase the hardness, strength, fracture toughness and thermal shock resistance of HSS. A possible strategy is to incorporate a hard ceramic material with high strength in HSS matrix. This paper describes the processing, microstructure and mechanical properties of the oriented unidirectional mullite fiber/HSS composite. The unidirectional mullite fibers of 10${\mu}{\textrm}{m}$ diameter were dispersed by the ultrasonic irradiation of 38 kHz in an ethylenglycol suspension containing HSS powder of 11${\mu}{\textrm}{m}$ median size. The dried green composites with 4-68 vol% fibers were hot-pressed for 2h at 100$0^{\circ}C$ in Ar atmosphere under a pressure of 39 MPa. The higher density was achieved in the composite with a lower content of fibers. The oriented unidirectional fibers were well dispersed in the HSS matrix. The average distance between the center of fibers in the cross section was close to the value calculated from the fiber fraction. No reaction occurred at the interfaces between HSS and mullite fibers in the composites. The composite with 13.6 vol% fibers showed 100 MPa of four point flexural strength at room temperature. The thermal expansion of composite with heating was influenced by the orientation of mullite fibers.

• Journal of the Society of Disaster Information
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• v.16 no.2
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• pp.411-419
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• 2020

Purpose: This study is intended to improve the performance of traffic signs corroded by aging, to ensure maintenance efficiency, a water-hardened coating solution was developed. Performance tests were then used to determine the optimal component scale. Method: For research purposes, the results were analyzed by conducting corrosion resistance assessment, physical properties evaluation, storage safety assessment, etc. on coating solutions of various magnifications. Results: The analysis results showed that there was little hearing in the cutting area in the liquid with added magnesium, so the method effect was excellent. And there was little blister occurrence, which was analyzed at the highest magnification. Conclusion: Enhancements to future new component scale experiments are needed for water-hardened coating solutions that have been recognized for their performance through this study. And institutional improvement efforts are needed to expand the enforcement of traffic sign maintenance using coating solutions.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.4
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• pp.472-481
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• 2015

Objectives: Welding is a major task in shipbuilding yards that generates welding fumes. A significant amount of welding in shipbuilding yards is done on steel. Inevitably, manganese is present in the base metals being joined and the filler wire being used and, consequently, in the fumes to which workers are exposed. The objective of this work was to characterize manganese exposure associated with work area, total and particle size-selective mass concentration, and compare the mass concentrations obtained using a three-piece cassette sampler, size-selective impactor sampler and blood manganese concentrations. Materials: All samples were collected from the main work areas at one shipbuilding yard. We used a three piece cassette sampler and the eight stage cascade impactor sampler for the airborne manganese mass concentration of total and all size fractions, respectively. In addition, we used the results of health examination of workers sampled for airborne manganese. Results: The oder of high concentration of airborne manganese in shipbuilding processes was as follows; block assembly, block erection, outfitting installation, steel cutting, and outfitting preparation. The percentages of samples that exceeded the OES of the ministry of employment and labor by the cassette sampling method was 12.5%, however 59.1% of sampled workers by the impactor sampling method exceeded the TLV of the ACGIH. Conclusions: Even though the manganese concentrations in blood of workers exposed to higher airborne manganese concentration were higher than among those exposed to lower concentrations, there was no difference in blood manganese concentrations among work duration. The data analyzed here by characterizing size-selective mass concentrations indicates that the inhaled manganese of welders in shipbuilding yards could be mostly manganese-containing respirable particle sizes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.4
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• pp.72-79
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• 1997

A study is a experiment which is figure out to optimum discharge cutting condition of the surface roughness, electronic discharging speed and electrode wear ration with Ton , Toff and V(voltage) as an input condition according to the current(Ip) in an electric spark machine : 1) Electrode is utilized Cu and Graphite. 2) Work piece is used the material of carbon steel. The condition of experiment is : 1) Current is varied 0.7(A) to 50(A) and the time of electric discharging to work piece in each time is 30(min) to 60(min). 2) After the upper side of work piece was measured in radius(5$\mu$m) of stylus analyzed the surface roughness to ade the table and graph of Rmax by yielding data. 3) Electro wear ratio is : \circled1Cooper was measured ex-machining and post-machining by the electronic balance. \circled2The ex-machining of graphite measured by it, the post-machining was found the data from volume $\times$specific gravity and analyzed to made its table and graph on ground the data. 4) In order to keep the accuracy of voltage affected to the work piece was equipped with the A.V. R and the memory scope was sticked to the electric spark machine. 5) In order to preserve the precision of current, to get rid of the noise occured by internal resistance of electric spark machine and to force injecting for the discharge fluid , it made the fixed table for a work piece to minimize the work error by means of one's failure during the electric discharging.

• Journal of Powder Materials
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• v.19 no.2
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• pp.117-121
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• 2012

Tool steels serve a large range of applications including hot and cold workings of metals and injection mouldings of plastics or light alloys. The high speed steels (HSS) are specifically used as cutting tools and wear parts because it has high strength, wear resistance and hardness along with appreciable toughness and fatigue resistance. From the view of HSS microstructure, it can be described as metallic matrix composites formed by a ferrous with a dispersion of hard and wear resistant carbides. The experimental specimens were manufactured using the PIM with T42 powders (50~80 vol.%) and polymer (20~50 vol.%). The green parts were debinded in n-hexane solution at $60^{\circ}C$ for 8 hours and thermal debinded at an $N_2-H_2$ mixed gas atmosphere for 8 hours. Specimens were sintered in high vacuum ($10^{-5}$ Torr) and various temperatures.

• Steel and Composite Structures
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• v.27 no.3
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• pp.337-353
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• 2018

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.1
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• pp.29-40
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• 2005

Formation of nanocrystalline ferrite was investigated using milled powders obtained by planetary ball milling of chips, which were made by high speed mechanical cutting of a low carbon steel(0.15%C-1.1%Mn-0.01%Ti). After 4 hour milling the chips were changed to powders of $50{\mu}m$ in average size, and with increasing milling time the powders were refined to about $3{\mu}m$ for 128 hour and showed more equiaxed shapes. Nanocrystalline(nc) region appeared in the surfaces of powders milled for 1 hour, and the 4 hour milled powders were almost filled with nc region. Hardness of nc region was much higher than that of work-hardened(WH) region. With increasing milling time, ferrite and cementite in pearlite were severely deformed and lamellar spacing was decreased, and then cementites began to disappear after 4 hour milling due to dissolution into ferrite. Deformation bands formed in lightly work-hardened region showed large width and similar crystallographic orientations. Spacing of deformation bands was decreased with deformation and the layered microstructure consisting of narrow deformation bands subdivided into variously oriented small grains was formed by more deformation, and eventually this structure seemed to be evolved to the nc structure by further deformation. It is also conjectured the growth of nc ferrite grains occurred through the coalescence of nanocrystalline ferrites rather than the nucleation and growth of recrystallized grains.