• Korean Journal of Materials Research
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• v.34 no.2
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• pp.116-124
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• 2024

In this study, we investigated the microstructure and piezoelectric properties of 0.96(K_0.456Na_0.536)Nb_0.95Sb_0.05-0.04Bi_0.5(Na_0.82K_0.18)_0.5ZrO₃ (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 ℃. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d₃₃ = 506 pC/N for one-step specimen sintered at 1,100 ℃ (one-step 1,100 ℃ specimen). However, for one-step 1,115 ℃ specimen, a slight decrease in d₃₃ was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 ℃ specimen, the two-step specimen exhibited higher piezoelectric coefficients (d₃₃ = 574 pC/N and k_p = 0.5) than those of the one-step 1,100 ℃ specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and two-step specimens showed that despite having a higher g₃₃, the magnetoelectric composite with the one-step 1,100 ℃ specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest k_p. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.

• Journal of Life Science
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• v.31 no.4
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• pp.385-388
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• 2021

Anther cultivation for crop breeding is a method of rapid production of homozygosities by greatly reducing the time required for at least six generations to develop new varieties using conventional breeding methods. This technique of producing anther culture provides an opportunity to obtain more green plants from a methodological point of view, and the techniques that save time and effort in anther culture are also important because they increase the efficiency of culture. This study compared the callus induction rate and green plant regeneration rate of a one-step and a two-step culture that differ in their culture media and culture methods. One-step culture allows callus induction and plant regeneration in one medium, whereas two-step culture requires induction and plant regeneration in two different media. In this study, we compared the callus induction and plant regeneration rates of rice anthers as one-step and two-step cultures. The callus formation rate was 13.0% for one-step cultures and 8.6% for two-step cultures, so the rate was 4.4% higher for one-step cultures than for two-step cultures. The plant regeneration rate was 1.0% in one-step cultures and 3.0% in two-step cultures, so the regeneration rate was three times higher for the two-step cultures than for one-step cultures. This suggests that the two-step cultures are more efficient than the one-step cultures for haploid production.

• Transactions of Materials Processing
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• v.20 no.5
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• pp.357-361
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• 2011

A beryllium copper alloy(C1720) sheet was stretch-drawn using different processes. A hemispherical punch was first used and the forming behavior was examined. Then, cylindrical cups with a hemispherical head were produced by either one-step drawing or two-step forming(sequential stretch forming-drawing). The one-step drawing showed the better formability than two-step forming. However, the two-step forming was the superior process in terms of attaining shape accuracy.

• Journal of the Korean Wood Science and Technology
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• v.44 no.6
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• pp.913-922
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• 2016

This study attempted to measure molecular weight (MW) of melamine-urea-formaldehyde (MUF) resins prepared by two different synthesis methods: the one-step MUF resins were synthesized in one batch procedure, while the two-step MUF resins were prepared by a physical mixing of urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized in a separate procedure. The properties of medium density fiberboard (MDF) panels bonded with two types of MUF resins were also investigated. MWs of these MUF resins were measured using gel permeation chromatography (GPC). In addition, this study measured the MWs of one-step MUF resin during its synthesis procedure. The performance of two types of MUF resins was evaluated by determining properties of MDF panels prepared in laboratory. As the synthesis procedure progressed, both number average MW ($M_n$) and weight average MW ($M_w$) of one-step MUF resin gradually increased, while the polydispersity index (PDI) decreased. And low Mw species of the resin predominantly decreased as the synthesis step progressed. The one-step MUF resin showed greater $M_n$ and $M_w$ than those of the two-step ones even though the PDI values of both resins were very similar each other. As expected, the one-step MUF resin resulted in better properties of MDF panels than those of two-step resins. In particular, the one-step MUF resin provided better internal bond (IB) strength and thickness swelling (TS) with MDF panels than those of two-step ones, indicating better water resistance of the one-step resin. These results suggest that the preparation method of MUF resins have a great impact on the MW and final panel properties.

• Textile Coloration and Finishing
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• v.16 no.5
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• pp.1-7
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• 2004

Because acid dyes and reactive dyes require acidic condition for adsorption and alkaline condition for fixation respectively, it is difficult to dye nylon/cotton blends in one-bath one-step dyeing method. In this paper we tried to find out the suitable dye and dyeing condition for one-bath one-step dyeing of nylon/cotton blends. MNT type reactive dyes showed higher exhaustion on cotton as compared with MCT type dyes at neutral pH, which means that the MNT type reactive dyes are preferable for one-bath one-step dyeing method. The optimum condition for one-bath one-step dyeing of nylon/cotton blends was found to be pH 7. Wash fastness of fabrics dyed with half-milling type acid dyes was superior to that of fabrics dyed with levelling type acid dyes, when MNT type reactive dyes were used together.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.339-346
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• 2003

Stainless steel wire has been used in industry, dental and medical parts. Especially, it has been used widely for the dental orthodontic materials. The orthodontic wire requires good mechanical properties, such as elastic strength, combined with a high resistance to corrosion. To increase elastic strength and good corrosion resistance, drawing methods(one-step and two-step drawing) have been used and the electrochemical characteristics of drawed wire have been researched using potentiodynamic method in 0.9％NaCl and field emission scanning electron microscope. The one-step drawed wire showed the formation of rough surface. The hardness and tensile strength of two-step drawed wire increased. For the case of two-step drawed wire, the corrosion resistance and pitting potential increased compared with one-step drawed wire due to the drawing induced small surface roughness, such as scratch. The passivation and active current density decreased as the reduction in area for drawing increased.

• Fashion & Textile Research Journal
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• v.7 no.3
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• pp.339-345
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• 2005

It is difficult to dye nylon/viscose rayon mixture fabrics by one-bath one-step dyeing method, because acid dyes and reactive dyes require acidic dyebath for adsorption and alkaline dyebath for fixation respectively. In order to overcome the disadvantage of the conventional two bath two step dyeing method of nylon/viscose rayon mixture fabric, it was pretreated with cationizing agent containing chlorohydrine group in aqueous solution of sodium hydroxide. The pretreated nylon/viscose rayon mixture fabrics produced cationized fabrics that could be dyed with acid dyes and reactive dyes under neutral condition. This study was carried out to investigate dyeing possibilities, surface reflectance spectra and color characteristics of cationized nylon/viscose rayon mixture fabrics with acid dyes and reactive dyes in a non-electrolytic and neutral dyebath by one bath one step dyeing method.

• Journal of the Korean Society of School Health
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• v.1 no.1
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• pp.148-159
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• 1988

For the evaluation of physical assessment by school nurses, this study was designed in two steps physical assessment. The first step is the primary health screening by school health nurses. The second step is the Physicians' physical examination of ill health students selected by school nurses. This study was conducted on a total of 3,525 students of three primary schools located in urban, township, and rural area during the period from May to June, 1987, all data were collected through direct observation & survey method. The main findings are as follows 1. The number of ill health students selected by two step method was more than that of one step method by the physician. 2. The types of ill health students selected by two step method had more diversity than that of one step method by the physician. 3. Budgets and time consumption for two step method were more reductive than that of one step method by the physician.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.49-54
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• 2006

During most of manufacturing processes of auto-body panels, the trimming line should be designed in advance prior to flanging. It is an important task to find a feasible trimming line to obtain a precise final part shape after flanging. This paper proposes a new fast method to find feasible trimming line based on one-step analysis. The basic idea of the one-step analysis is to seek for the nodal positions in the initial blank from the final part, and then the distribution of strain, stress and thickness in the final configuration can be calculated by comparing the nodal position in the initial blank sheet with the one of the final part. The one-step analysis method is able to predict the trimming line before flanging since the desired product shape after flanging can be defined from the final configuration and most of strain paths are simple during the flanging process. Finally, designers can obtain a discrete trimming line from the boundary of the developed meshes after one-step analysis and import it into CAD system in the early design stage. The proposed method has been successfully applied to two basic curve flanging processes demonstrating many advantages.

• Textile Coloration and Finishing
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• v.11 no.5
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• pp.7-12
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• 1999

The objective of this study is to apply water repellent and flame retardant finishes simultaneously to the fabric used for automobile. Both two step and one step methods were tried to apply the finishing agent to the fabric. In the two step method, water repellent agent was treated first, and flame retardant agent was applied next. The reverse finishing process was also attempted. In the one step method, flame retardant agent and water repellent agent treated to the fabric in one bath. The results of two step method revealed that the finishing effect was better when the water repellent agent was treated first than when flame retardant agent was treated first. In one step method, fluoro water repellent agent was superior to silicon water repellent agent.