Fabrication and Interface Structural Behavior of Mg/Al Thickness-Oriented Bonding Sheet via Direct Extrusion

Lei Gao,Feng Li,Ye Wang,Xing Mao Xiao,Peng Da Huo 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

Solid-state bonding of heterogeneous materials is one of the effective ways to achieve light weight. An extrusion formingprocess for Mg/Al thickness-oriented bonding sheet was carried out. Due to triaxial compressive stress in the extrusion container,the AZ31 and AA6061 billets were deformed and the bonding and forming of Mg/Al thickness-oriented sheet can berealized by this method. The observation results of the bonding position by using XRD, SEM and EDS showed that: at theforming temperature with 360–420 °C, it had a good bonding interface, and the width of the transition layer increased withthe increase of the forming temperature. The presence of brittle intermetallic compounds in the transition layer indicated thatmetallurgical bonding had occurred at the interface. Considering all factors comprehensively, when the forming temperaturewas 390 °C, the bonding quality was appropriate. Its tensile-shear strength was 42 MPa, the width of the interface transitionlayer was about 10 μm, and the microhardness was about 164.3 HV. This method provided scientific guidance and technicalreserves for green forming of Mg/Al sheets.

Whole-process Bond Characteristics of FRP-to-concrete Joint under Pressure

Lei Gao,Feng Zhang,Jia-qi Liu,Xiao-rui Lu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.12

Lateral anchoring can effectively inhibit the premature debonding of FRP (Fiber-Reinforced Polymer) plate bonds to concrete. To effectively improve the efficiency of reinforcement, the bond characteristics of FRP-to-concrete joints under pressure through the entire debonding process were analyzed via a theoretical model, experimental evaluation, and parameter studies. The results show that the load-slip behavior of a bonded joint features an elastic stage, an elastic-softening stage, an elastic-softening-residual stage, a softening-residual stage and a residual stage. Moreover, the trilinear bond-slip model reveals changes in interface bonding properties under pressure. The experimental analysis of the load-slip relationship and bond stress distribution prove the accuracy of the theoretical model. Both load capacity and slip increase with increasing bond length or lateral pressure, while increasing the plate stiffness results in an increased load capacity and a reduction in ductility.

2007 개정 중학교 과학 교과서에 나타난 21세기 글로벌 과학적 소양의 탐색

Gao, Lei,김은진,문공주,김성원,Krajcik, Joseph 이화여자대학교 교과교육연구소 2012 교과교육학연구 Vol.16 No.2

Science education focuses on improving the scientific literacy of students; this is a primary goal in the twenty-first century. Recently, scientific literacy has been re-conceptualized for the twenty-first century. There are five dimensions: habits of mind, character and values, science as a human endeavor, meta-cognition, and scientific knowledge. Each dimension consists of three sub-dimensions. This study explored the content of Korean, middle school science textbooks from the view point of twenty-first century scientific literacy. We used a twenty-first century, scientific literacy rubric. The rubric involved three dimensions: habits of mind, character and values, and science as a human endeavor. The authors applied the rubric to twelve (six from Grade 1 and another six from Grade 2), Korean, middle school, science textbooks. As a result, it was noted that most of the Korean, middle school textbooks involved content concerning the 'habits of mind'; this included communication, collaboration, and information management. There was not, however, sufficient content concerning 'character and values' and science as a human endeavor, except in one publication. As twenty-first century citizens, students need to gain 'character and values' and 'science as a human endeavor' training in the science curriculum for daily life. It is suggested, therefore, that, as twenty-first century citizenship educators and researchers, we have to emphasis and develop curricula and teaching materials that consider all dimensions for the re-conceptualization of scientific literacy, and not focus only on knowledge and problem-solving. (234 words) 21세기의 과학 교육은 미래 시민을 양성하기 위하여 과학적 소양을 함양하는 것을 목표로 하며 Choi et al.(2011)은 이를 재개념화하여 21세기 과학적 소양(21st scientific literacy)을 제안하였다. 21세기에 필요한 글로벌 과학적 소양은 과학 지식, 과학적 사고습관, 과학에서의 가치관, 과학 본성의 이해, 초인지 사고와 자기주도의 다섯 가지 영역으로 구조화되어있으며, 각 영역은 3가지 하위 영역을 포함한다. 본 연구는 21세기 과학적 사고습관, 과학에서의 가치관, 과학 본성의 이해의 3 가지 영역을 중심으로 2007 개정 교육과정에 따른 출간된 중학교 1,2 학년 각 6종, 총 12권의 과학교과서를 분석하였다. 중학교 과학교과서에는 토론․토의․논의, 발표 및 제안과 같은 활동, 그리고 정보 처리 능력에 포함되는 활동 등 과학적 사고습관에 포함되는 요소가 가장 두드러지게 나타났다. 또한 과학 본성의 이해 영역 중 과학 지식의 생성 및 특성을 알리고 과학적 호기심을 자극하는 내용 역시 상당수 포함되어 있음을 알 수 있었다. 이에 반해 과학과 관련된 사회문제를 다루며 행동변화에 영향을 주는 과학에서의 가치관 영역은 매우 적게 다루는 것을 볼 수 있다. 이러한 연구 결과에 바탕을 두고 앞으로 실제 현장에서 사용되는 교과서 외의 수업자료와 실제 수업현장 녹화 등을 통해 과학적 소양의 함양을 위한 교육이 실제 이루어지고 있는지 평가해야 할 것이며, 이러한 평가를 바탕으로 지속적으로 발전된 교육의 방향의 모색을 제언하였다.

Effect of Different Tumbling Marination Treatments on the Quality Characteristics of Prepared Pork Chops

Gao, Tian,Li, Jiaolong,Zhang, Lin,Jiang, Yun,Ma, Ruixue,Song, Lei,Gao, Feng,Zhou, Guanghong Asian Australasian Association of Animal Productio 2015 Animal Bioscience Vol.28 No.2

The effect of different tumbling marination treatments (control group, CG; conventional static marination, SM; vacuum continuous tumbling marination, CT; vacuum intermittent tumbling marination, IT) on the quality characteristics of prepared pork chops was investigated under simulated commercial conditions. The CT treatment increased (p<0.05) the pH value, $b^*$ value, product yield, tenderness, overall flavor, sensory juiciness and overall acceptability in comparison to other treatments for prepared boneless pork chops. The CT treatment decreased (p<0.05) cooking loss, shear force value, hardness, gumminess and chewiness compared with other treatments. In addition, CT treatment effectively improved springiness and sensory color more than other treatments. However, IT treatment achieved the numerically highest (p<0.05) $L^*$ and $a^*$ values. These results suggested that CT treatment obtained the best quality characteristics of prepared pork chops and should be adopted as the optimal commercial processing method for this prepared boneless pork chops.

Experimental research on local buckling of BS700 high-strength steel thin-walled box-section members under axial compression

Lei Gao,Fei Shao,Linyue Bai,Xingkun Xie,Xiaohui He 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

In this study, the ultimate bearing capacity and local buckling failure mode of members were investigated, and the results were compared to the predicted values of the existing steel structures design code. The results indicated that the failure mode of the specimen was local buckling. Finite element model is verified using experimental results. FE model is capable of predicting the behaviour of specimens and it is used for further numerical analyses. Experimental results are compared with recommendations of the steel structures design code of GB50017-2017, ANSI/AISC 360-16 and Eurocode 3. It is observed that the 83.3 % of the test bearing capacity are slightly higher than the predictions of existing codes with a variance of 5 %. It is concluded that the provisions of existing codes can meet the design requirements. However, the number of tests is limited and further related experimental and FE numerical studies are required.

Spatio-Temporal Variability and Temporal Stability of Profile Soil Moisture at a Hillslope Scale

Lei Gao,Xinhua Peng,Hu Zhou 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Observation of Ga Metal Droplet Formation on Photolithographically Patterned GaAs (100) Surface by Droplet Epitaxy

Lei Gao,Hirono, Y.,Ming-Yu Li,Jiang Wu,Sangmin Song,Sang-Mo Koo,Eun-Soo Kim,Wang, Z. M.,Jihoon Lee,Salamo, G. J. IEEE 2012 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.11 No.5

<P>A sharp contrast on the density and size of Ga metal droplets is observed on various photolithographically patterned GaAs (100). As clearly evidenced by high-resolution scanning electron microscope, Ga metal droplet density and size surprisingly differ on etched and unetched surfaces under an identical growth condition. The apparent contrast on the density and size of droplets is clearly observed at the interface between etched and unetched areas. Ga droplets exhibit much higher density and the size is much smaller on etched surface; meanwhile, the density is an order of magnitude lower and the size is much larger on unetched surface. Along different directions, [011] and [01-1], due to anisotropic surface diffusion, the density is about twice higher along [011] for the same strip pattern.</P>

Study on Metallurgically Prepared Copper-Coated Carbon Fibers Reinforced Aluminum Matrix Composites

Meilian Gao,Pingping Gao,Yu Wang,Yu Wang,Ting Lei,Chun Ouyang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

Carbon materials, like carbon fiber, carbon nanotubes and graphene, were widely used as promising reinforcements tostrengthen aluminum matrix composites (AMCs). The dispersion of reinforcement in matrix and interface wettability betweenmatrix and reinforcing phase have been key factors affecting AMCs properties. In this study, electroless copper-coatedcarbon fibers reinforced aluminum (Cu-Cf/Al) composites were prepared by spark plasma sintering processing followedby heat treatment. Microstructure and mechanical properties were investigated. Microstructure observation indicated thatfibers distributed uniformly in the composites containing up to 9 wt% copper-coated carbon fibers (Cu-Cf). In addition, aninterfacial layer of 50 nm thickness was formed between the fiber and Al matrix due to mutual diffusion of Cu and Al atoms. Vickers hardness, tensile strength and bending strength of 9 wt% Cu-Cf/Al composite increased from 40 to 93 HV, 59 to190 MPa and 110 to 326 MPa, respectively, compared to Al matrix. The improved mechanical properties are ascribed to thesynergistic effect of dispersion, precipitation and solution strengthening. However, the elongation of composite decreased ascompared to that of Al matrix. Moreover, Cu-Cf/Al composite exhibits superior corrosion resistance over uncoated carbonfiber/Al composite but less than Al matrix.

Effect of Different Tumbling Marination Treatments on the Quality Characteristics of Prepared Pork Chops

Tian Gao,Jiaolong Li,Lin Zhang,Yun Jiang,Ruixue Ma,Lei Song,Feng Gao,Guanghong Zhou 아세아·태평양축산학회 2015 Animal Bioscience Vol.28 No.2

The effect of different tumbling marination treatments (control group, CG; conventional static marination, SM; vacuum continuous tumbling marination, CT; vacuum intermittent tumbling marination, IT) on the quality characteristics of prepared pork chops was investigated under simulated commercial conditions. The CT treatment increased (p<0.05) the pH value, b* value, product yield, tenderness, overall flavor, sensory juiciness and overall acceptability in comparison to other treatments for prepared boneless pork chops. The CT treatment decreased (p<0.05) cooking loss, shear force value, hardness, gumminess and chewiness compared with other treatments. In addition, CT treatment effectively improved springiness and sensory color more than other treatments. However, IT treatment achieved the numerically highest (p<0.05) L* and a* values. These results suggested that CT treatment obtained the best quality characteristics of prepared pork chops and should be adopted as the optimal commercial processing method for this prepared boneless pork chops.

Chemical composition and in vitro digestibility of corn stover during field exposure and the fermentation characteristics of silage prepared with microbial additives

Jun Lei Gao,Peng Wang,Chang-Hai Zhou,Ping Li,Hong Yu Tang,Jiabao Zhang,Yimin Cai 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.12

Objective: To effectively use corn stover resources as animal feed, we explored the chemical composition and in vitro digestibility of corn stover during field exposure and the fermentation characteristics of silage prepared with lactic acid bacteria (LAB) and cellulase. Methods: Corn ears including the cobs and shucks were harvested at the ripe stage. The corn stover was exposed in the field under natural weather conditions. Silages were prepared after 0, 2, 4, 7, 15, 30, and 60 d of exposure. Corn stover was chopped into approximately 1 to 2 cm lengths and then packed into 5 liter plastic silos. The ensiling density was 550.1±20.0 g/L of fresh matter, and the silos were kept at room temperature (10°C to 25°C). Silage treatments were designed as follows: without additives (control), with LAB, with cellulase, and with LAB+ cellulase. After 45 d of fermentation, the silos were opened for chemical composition, fermentation quality and in vitro digestion analyses. Results: After harvest, corn stover contained 78.19% moisture, 9.01% crude protein (CP) and 64.54% neutral detergent fiber (NDF) on a dry matter (DM) basis. During field exposure, the DM, NDF, and acid detergent fiber (ADF) contents of corn stover increased, whereas the CP and water-soluble carbohydrate contents and in vitro digestibility of the DM and CP decreased (p<0.05). Compared to the control silage, cellulase-treated silage had lower (p<0.05) NDF and ADF contents. The pH values were lower in silage treated with LAB, cellulase, or LAB+cellulase, and lactic acid contents were higher (p<0.05) than those of the control. Silage treated with cellulase or LAB+cellulase improved (p<0.05) the in vitro DM digestibility (IVDMD) compared to that of the control or LAB-treated silage. Conclusion: Corn stover silage should be prepared using fresh materials since stover nutrients are lost during field exposure, and LAB and cellulase can improve silage fermentation and IVDMD.