The hot compression behavior of pure copper (commercial grade) was studied in a temperature range between 843 and 993 K and in a strain rate range between 10−3 and 10 s−1. The activation energy for plastic flow was determined to be 215 kJ/mol, which is similar to the activation energy for lattice diffusion in copper ( = 197 kJ/mol). The stress exponent values associated with the plastic flow were 7–9, which are larger than the theoretical values associated with lattice-diffusion controlled dislocation climb creep (4.5–5). A comparison of the current data with the data obtained from the creep tests performed on the pure copper at low strain rates by other investigators in a similar temperature range revealed that the most of the data studied in this study belong to the regime where power-law breakdown occurs. Processing map constructed at a strain where steady-state plastic flow was observed showed that the power dissipation efficiency was low (≤21%) in the entire experimental ranges of strain rate and temperature. Discontinuous dynamic recrystallization (DDRX) associated with a single peak or multiple peaks in the stress-strain curves occurred during the first stage of plastic deformation. Dynamic recovery occurred after the DDRX activity ended, leading to the formation of a subgrains with low-and intermediate angle grain boundaries within the recrystallized grains with high-angle grain boundaries. Due to the formation of extensive substructure within DDRX grains, the fractions of high-angle grain boundaries measured after the compressive deformation were low (≤30%).
Self-supervised multi-frame monocular depth estimation relies on the geometric consistency between successive frames under the assumption of a static scene. However, the presence of moving objects in dynamic scenes introduces inevitable inconsistencies, causing misaligned multi-frame feature matching and misleading self-supervision during training. In this paper, we propose a novel framework called ProDepth, which effectively addresses the mismatch problem caused by dynamic objects using a probabilistic approach. We initially deduce the uncertainty associated with static scene assumption by adopting an auxiliary decoder. This decoder analyzes inconsistencies embedded in the cost volume, inferring the probability of areas being dynamic. We then directly rectify the erroneous cost volume for dynamic areas through a Probabilistic Cost Volume Modulation (PCVM) module. Specifically, we derive probability distributions of depth candidates from both single-frame and multi-frame cues, modulating the cost volume by adaptively fusing those distributions based on the inferred uncertainty. Additionally, we present a self-supervision loss reweighting strategy that not only masks out incorrect supervision with high uncertainty but also mitigates the risks in remaining possible dynamic areas in accordance with the probability. Our proposed method excels over state-of-the-art approaches in all metrics on both Cityscapes and KITTI datasets, and demonstrates superior generalization ability on the Waymo Open dataset.
The influence of CF4 plasma treatment of indium-tin-oxide (ITO) and polyimide (PI) on the patterning of ink-jet printed polymer is presented. Not much difference between the as-received ITO and PI surface energies was found, but a significant difference in surface energies between ITO and PI after CF4 plasma treatment was noted. It is expected that precise patterning can be achieved by using the difference in surface energies between the inside of the pixel and its surroundings. Also the effects of CF4 plasma treatment of ITO have been studied on the performance of polymer light-emitting diodes (PLEDs). X-ray photoelectron spectroscopy revealed that CF4 plasma treatment led to a decrease in the surface content of carbon contaminants and an increase in the surface content of fluorine, which in turn enhance the performance of PLEDs.
In recent years, the utilization of geothermal energy for buildings has increased significantly. Especially in growing urban areas, there is a need for supplementary research to maximize the efficiency of heat exchange in geothermal energy systems on space-restricted sites. There is currently a little research about improving the heat exchange by choice of pipe materials. Circular pipes of high-density polyethylene (HDPE) and polybutylene (PB) are commonly used as ground heat exchangers (GHEs) for convenience and cost benefit, but PB pipes, in particular, have thermal properties that do not have a favor in the heat exchange. Therefore, this paper presents the results of an experimental study on the use of annular stainless steel (STS) pipe as a GHE. Thermal response tests (TRT) were conducted to measure heat exchange rates in circular PB pipe and annular STS pipe installed in a steel box with the dimension of 5 m × 1 m × 1 m. Dry Joomunjin standard sand was used to fill the box and TRTs were performed for 30 hours to reach a steady state. As a result, the annular STS pipe showed about 9% higher heat-exchange rate (per pipe length) than did the circular PB pipe. Compared to the length of heat exchanger required under the same conditions, the annular STS pipe needed was shorter than the circular PB pipe. It is concluded that the STS pipe could be used as an efficient GHE.
본 연구의 목적은 전기방사법을 사용하여 poly(L-lactide-$co$-${\varepsilon}$-caprolactone) (PLCL)과 marine collagen (MC)이 혼합된 나노섬유를 제조하는 것이다. 전기방사된 나노섬유의 직경과 형태는 여러 공정 변수에 의해서 변화되는데, PLCL과 MC의 혼합비, 노즐과 콜렉터와의 거리, 노즐의 직경, 용액의 방출 속도 그리고 전기장의 세기 변화에 따라 나노파이버의 직경을 주사전자현미경을 통해서 분석하였다. 또한 제조된 나노파이버의 표면변화를 확인하기 위해 물과의 접촉각을 측정하였으며, 나노파이버의 세포 친화성을 평가하기 위해 MG-63을 이용하여 생존율과 흡착형태를 주사전자현미경과 형광현미경을 통해서 관찰하였다. 이와 같은 연구 결과, 방사거리, MC의 함량, 전기장의 세기가 증가할수록 제조된 나노파이버의 평균직경은 감소하는 경향을 나타냈다. 또한 MC의 함량이 증가할수록 나노파이버의 친수성이 증가하였고 세포독성은 관찰되지 않았다. 이에 따라 해양유래 생물에서 추출한 콜라겐은 조직공학용 소재에 새롭게 사용될 수 있을 것으로 예상된다. The uniform nanofibers of poly(L-lactide-$co$-${\varepsilon}$-caprolactone) (PLCL) with different contents of marine collagen (MC) were successfully prepared by electrospinning method. The effects of the major parameters in electrospinning process such as tip to target distance (TTD), voltage, nozzle size and flow rate on the average diameter of the electrospun nanofiber were investigated in generating composite nanofiber. The diameter and morphology of the nanofibers were confirmed by a scanning electron microscopy (SEM). Also, we measured a water contact angle to determine the surface wettability of the nanofibers. The average diameter of the nanofibers decreased as the value of TTD, MC contents, and voltages increased in comparison with that of pristine PLCL nanofiber. In contrast, the diameter of the nanofibers increased as the flow rate and inner diameter of nozzle increased in comparison with that of pristine PLCL. In addition, the hydrophilicity of the nanofiber and attachment of MG-63 cells on the sheets increased as incorporated collagen contents increased. Therefore, the marine collagen would be a potential material to enhance cellular interactivity of synthetic materials by mimicking the natural tissue.
In order to evaluate material characteristics (in situ modulus) of well-compacted subgrades, the portable falling weight deflectometer (PFWD) test, which simulates dynamic loads, was adopted. The falling energy was assumed as a dynamic load and a well-compacted subgrade was treated as an ideal elastic body. In addition, the static plate-bearing load test (PBLT) was used to evaluate the coefficient of subgrade reaction. The PFWD test and PBLT for a total of 22 testing points were carried out on well-compacted subgrades at two different highway construction sites (A and B). Three falling heights and weights were used to produce six different levels of dynamic loads. The test results show that there is a reasonable linear correlation between the dynamic deflection modulus and the coefficient of subgrade reaction of well-compacted subgrades. It was also found that the dynamic deflection modulus is not largely affected by variation of the falling energies. Application of the PFWD for compaction control and as an alternative method to the PBLT would lead to significant cost savings.
Abstract Polymorphing hydrogels can morph into another structure on demand with reprogrammable features. This concept extends the degree of morphing beyond that of traditional shape‐morphing hydrogels, which predetermine their morphing capabilities at the fabrication stage. However, current polymorphing hydrogels face limitations due to the need for complex, non‐sustained responsiveness or additional chemical steps for reconfigurable morphing. Here, photo‐reactive DNA‐cross‐linked polymorphing hydrogels are presented that enable polymorphing under patterned light. The photo‐reactive DNA cross‐links act as a regulator in changing the shapes of the hydrogels by adjusting the lengths of the cross‐links depending on the wavelength of light, which allows precise and dynamic morphing in a programmable way through a one‐pot reaction. The high programmability involving spatiotemporal controllability and reprogrammable features offers advanced solutions for multifunctional soft machines and applications requiring complex processes.
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