• Journal of the Korean Wood Science and Technology
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• 제51권1호
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• pp.23-37
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• 2023

One type of biomass that has promising potential for bio pellet production is spent coffee grounds (SCGs). However, previous studies have shown that SCGs in bio pellets cause a lot of smoke. Therefore, they need to be mixed with a material that has a higher calorific value to produce better quality pellets. One material that can be used is pine wood because it has a natural resin content that can increase the calorific value. The aim of this study was to examine the quality of bio pellets produced with SCGs and pine wood charcoal at different particle sizes. The charcoal was ground using either a hammer mill (HM) or a ball mill (BM). Pine wood charcoal was mixed with SCGs at ratios of SCGs to pine wood charcoal of 4:6 and 6:4 by weight, respectively, and the adhesive used a tapioca with a composition ratio 5% of the raw material. The bio pellets were produced using a manual pellet press. The quality of the bio pellets was assessed based on Indonesian National Standard (SNI) 8021-2014, and the physical observations include flame length, burning rate, and compressive strength. The average water content, ash content, and calorific value of the bio pellets were in accordance with SNI 8021-2014, but the density and ash content values were below the standard values. The BM variation of bio pellets had a higher compressive strength than the HM variation, and the 4:6 BM variation had the longest burning time compared with 4:6 HM.

• 한국정밀공학회지
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• 제10권2호
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• pp.114-125
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• 1993

In the present study the newly developed CAD/CAM system is applied to the process of the molding design, machining for mini-sized and precise processive die, and the production of press-stamped parts. When the design of a die was completed by means of CAD, wire cut NC data were generated with the aid of a design drawing in the CAD system and then inputed into the wire cut machine, and with the aid of a hole chart which had been made for this purpose, all the data were classified into the categories of CNC milling, jig boring, jig grinding, and machine center, and then developing a program of generating NC data, errors in process were reduced and programming time was shortened. The program was developed by using Autolisp language which was built-in the CAD, and realizing the intergation of designing a die, generating and processing NC data directly by a designer, designing time and machinery processing time were shorted. And the traditionally required working time for design. NC program required 6 days of work becomes 4 days of work by using the developed CAD/CAM system so that the efficiency shows 150% of the reduction working time. The prpgram of the design of the automation a progressive die mold was developed in the PC-Class Autocad system, therefore development expense could be reduced, and the integration of the CAD/CAM of the progressive die mold with the standard DB being built could be realized.

• 한국재료학회지
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• 제33권8호
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• pp.337-343
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• 2023

3Y-TZP (3 mol% yttria-stabilized tetragonal zirconia polycrystals) ceramics have excellent mechanical properties including high fracture toughness, good abrasion resistance as well as chemical and biological stability. As a result, they are widely used in mechanical and medical components such as bearings, grinding balls, and hip implants. In addition, they provide excellent light transmittance, biocompatibility, and can match tooth color when used as a dental implant. Recently, given the materials' resemblance to human teeth, these ceramics have emerged as an alternative to titanium implants. Since the introduction of CAD/CAM in the manufacture of ceramic implants, they've been increasingly used for prosthetic restoration where aesthetics and strength are required. In this study, to improve the surface roughness of zirconia implants, we modified the 3Y-TZP surface with a biocomposite of hydroxyapatite and forsterite using room temperature spray coating methods, and investigated the mixed effect of the two powders on the evolution of surface microstructure, i.e., coating thickness and roughness, and biological interaction during the in vitro test in SBF solution. We compared improvement in bioactivity by observing dissolution and re-precipitation on the specimen surface. From the results of in vitro testing in SBF solution, we confirmed improvement in the bioactivity of the 3Y-TZP substrate after surface modification with a biocomposite of hydroxyapatite and forsterite. Surface dissolution of the coating layer and the precipitation of new hydroxyapatite particles was observed on the modified surface, indicating the improvement in bioactivity of the zirconia substrate.

• 한국전기전자재료학회논문지
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• 제36권3호
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• pp.214-225
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• 2023

Piezoelectric actuators, which utilize piezoelectric crystals or ceramics, are commonly used in precision positioning applications, offering high-speed response and precise control. However, the use of low-performance ceramics and expensive single crystals is limiting their versatile use in the actuator market, necessitating the development of both high-performance and cost-effective piezoelectric materials capable of delivering higher forces and displacements. The use of textured Pb (lead)-based piezoelectric ceramics formed by so-called templated grain growth method has been identified as a promising strategy to address the performance and cost issue. This review article provides insights into recent advances in texturing Pb-based piezoelectric ceramics for improved performance in actuation applications. We discussed the relevant issues in detail focusing on current challenges and emerging trends in the textured piezoelectric ceramics for their reliability and performance in actuator applications. We discussed in detail focusing on current challenges and emerging trends of textured piezoelectric ceramics for their reliability and performance in actuator applications. In conclusion, the article provides an outlook on the future direction of textured piezoelectric ceramics in actuator applications, highlighting the potential for further success in this field.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2022년도 추계학술대회
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• pp.300-300
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• 2022

Wheat (Triticum spp.) is an important source of food worldwide and the focus of considerable efforts to identify new combinations of genetic diversity for crop improvement. In particular, wheat starch composition is a major target for changes that could benefit human health. Starches with increased levels of amylose are of interest because of the correlation between high amylose content and elevated levels of resistant starch, which has been shown to have beneficial effects on health for combating obesity and diabetes. In this study, high amylose wheat germplasms from other countries were collected and cultivated in Korea, and then the content of amylose was evaluated, we examined amylose content in 614 wheat germplasm. Furthermore, amylose content was validated using several milling processes such as roller, hammer, and grinding mill. As a result, the amylose content distribution was divided into five groups. The range of the amylose levels in whole wheat flour was 18.3% to 29.6%. In addition, the mutant lines were screened for high amylose, and two mutant lines (WX-1046 and WX-1074) exhibited a comparable amylose content to Keumkang whole wheat (19.6%). It has been established that high amylose indicated SS IIa null and necessitate GBSS. Based on these findings, it may be helpful to develop high amylose wheat germplasm and production techniques, particularly in Korea.

• 한국분말재료학회지
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• 제30권5호
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• pp.409-414
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• 2023

YSZ (Y₂O₃-stabilized zirconia)-based ceramics have excellent mechanical properties, such as high strength and wear resistance. In the application, YSZ is utilized in the bead mill, a fine-grinding process. YSZ-based parts, such as the rotor and pin, can be easily damaged by continuous application with high rpm in the bead mill process. In that case, adding WC particles improves the tribological and mechanical properties. YSZ-30 vol.% WC composite ceramics are manufactured via hot pressing under different pressures (10/30/60 MPa). The hot-pressed composite ceramics measure the physical properties, such as porosity and bulk density values. In addition, the phase formation of these composite ceramics is analyzed and discussed with those of physical properties. For the increased applied pressure of hot pressing, the tetragonality of YSZ and the crystallinity of WC are enhanced. The mechanical properties indicate an improved tendency with the increase in the applied pressure of hot pressing.

• 대한치과기공학회지
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• 제45권4호
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• pp.87-94
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• 2023

Purpose: This study aimed to observed changes in the shape of dental barrels based on application time. Machinability measures the angle of alloy specimens. Polishing performance measures the surface roughness of alloy specimens. Methods: The dental barrel polishing equipment used in this study was a Snow Barrel (DK Mungyo). Three types of cobalt-chromium alloys for partial dentures were used as specimens (BC CAST R [BP]; Bukwang, Vera PDI [VP]; Aalbadent, and GM 800+ [GP]; Dentaurum). Specimens were prepared in the form of plates (10 mmx10 mmx2 mm). Dental barrel polishing was performed at 450 rpm for 60 minutes with intervals of 5 minutes. The processing angle was measured using a microscope (SZ61; Olympus). Results: For the angle measurement, the VPC specimen was measured at 78.64°, 36.00° for the VP60 specimen, 79.57° for the BP control (BPC) specimen, 28.07° for the BP60 specimen, 75.01° for the GPC specimen, and 39.92° for the GP60 specimen. For the surface roughness measurements, the average surface roughness of the VPC and VP15 specimens were 1.09 ㎛ and 0.26 ㎛, respectively. The average surface roughness of the BPC and BP20 specimens were 1.77 ㎛ and 0.29 ㎛, respectively. The average surface roughness of the GPC and GP15 specimens were 1.08 ㎛ and 0.27 ㎛. Conclusion: The results were excellent after about 20 minutes of dental barrel polishing conditions presented in this study.

• 한국건설순환자원학회논문집
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• 제12권1호
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• pp.72-81
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• 2024

이 연구에서는 DEIPA를 사용하여 바텀애시를 미분말화하고, 이를 활용하여 바텀애시 치환 시멘트를 개발했다. partial or no-known crystal structure 방법을 X-선 회절 정량 분석에 적용하여 비결정질인 바텀애시와 C-S-H의 양을 분리하여 정량화 할 수 있었다. DEIPA를 첨가하지 않은 배합에서는 바텀애시가 거의 반응하지 않았으며, 이에 따라 압축강도도 낮게 발현되었다. 그러나 DEIPA를 첨가한 배합에서는 시멘트의 수화 거동을 변화시켰을 뿐만 아니라 바텀애시와 수산화칼슘 사이의 포졸란 반응도 향상시켜서 추가적인 C-S-H를 생성하였고, 재령 초기 뿐만 아니라 후기에도 높은 압축강도를 얻을 수 있었다. 따라서 바텀애시를 분쇄할 때 극소량의 DEIPA를 첨가하더라도 바텀애시의 반응성을 충분히 증진시킬 수 있었기에 바텀애시 치환시멘트 개발에 도움이 될 것으로 사료된다.

• 자원리싸이클링
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• 제33권2호
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• pp.37-45
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• 2024

몰리브덴은 높은 내열성, 내부식성에 의해 다양한 산업에 적용되어, 우리나라의 핵심광물로 선정된 중요한 금속이다. 그러나 최근 몰리브덴 광맥의 저품위화로 인해 생산에 어려움을 겪고 있어, 몰리브덴 선광 공정에 대한 효율 향상이 필요하다. 본 연구에서는 국내 몰리브덴광 선광 공정의 효율 향상을 위한 기초 선광 특성 평가 연구를 수행하였다. 기초 선광 특성은 광물학적 분석, 분쇄일지수, 부유선별 속도 분석으로 평가되었다. 분석 결과, 단체분리가 가능한 몰리브덴광의 입자 크기는 ~100 ㎛였으며, 분쇄 일지수는 14.57 kWh/t로 산출되었다. 또한 부유선별 속도 분석을 통해, 부유선별 단위 공정 각각의 최적 부유선별 시간을 제공함으로써 최적화를 위한 운영 조건을 확립하였다. 마지막으로 본 연구에서 제공한 몰리브덴광 기초 선광 특성 정보는 향후 산업 규모의 몰리브덴 선광 플랜트의 분쇄 및 부유선별 공정을 진단하는 데 활용될 예정이다.

• 자원리싸이클링
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• 제33권2호
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• pp.24-36
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• 2024

리튬이온전지 재활용 공정은 직접 재활용, 습식제련공정, 건식제련공정으로 분류되어 왔으며, 습식제련공정 기반 상용공정은 해체, 파분쇄, 열처리, 선별 등으로 구성된 전처리 공정으로 블랙매스를 생산하고 습식제련공정으로 각 금속을 회수한다. 개발 중인 모든 리튬이온전지 재활용공정은 전구체 원료 제조를 위해 전처리공정 후 침출 등의 습식제련공정을 진행하기 때문에 이 글에서는 재활용공정의 전처리공정에 따른 분류법을 제시하였다. 현재 개발 중인 주요 공정은 황산염배소, 탄소열환원, 합금제조 등이며, 전처리공정에서 미이용 부산물의 활용이 가능할 경우 리튬이온전지 재활용 공정의 경제성 향상이 가능하리라 판단된다.