| 1. |
- Jiang, Bing-Xin, et al.
(author)
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Fabrication and bonding of In bumps on Micro-LED with 8 μ m pixel pitch
- 2024
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In: ENGINEERING RESEARCH EXPRESS. - 2631-8695. ; 6:2
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Journal article (peer-reviewed)abstract
- Indium (In) is currently used to fabricate metal bumps on micro-light-emitting diode (Micro-LED) chips due to its excellent physical properties. However, as Micro-LED pixel size and pitch decrease, achieving high-quality In bumps on densely packed Micro-LED chips often presents more challenges. This paper describes the process of fabricating In bumps on micro-LEDs using thermal evaporation, highlighting an issue where In tends to grow laterally within the photoresist pattern, ultimately blocking the pattern and resulting in undersized and poorly dense In bumps on the Micro-LED chip. To address this issue, we conducted numerous experiments to study the height variation of In bumps within a range of photoresist aperture sizes (3 mu m -7 mu m) under two different resist thickness conditions (3.8 mu m and 4.8 mu m). The results showed that the resist thickness had a certain effect on the height of In bumps on the Micro-LED chip electrodes. Moreover, we found that, with the photoresist pattern size increasing under constant resist thickness conditions, the height and quality of the bumps significantly improved. Based on this finding, we rationalized the adjustment of the photoresist pattern size within a limited emission platform range to compensate for the height difference of In bumps caused by different resist thicknesses between the cathode and anode regions. Consequently, well-shaped and dense In bumps with a maximum height of up to 4.4 mu m were fabricated on 8 mu m pitch Micro-LED chips. Afterwards, we bonded the Micro-LED chip with indium bumps to the CMOS chip, and we found that we could successfully control the CMOS chip to drive the Micro-LED chip to display specific characters through the Flexible Printed Circuit (FPC). This work is of significant importance for the fabrication of In bumps on Micro-LED chips with pitches below 10 mu m and subsequent bonding processes.
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| 2. |
- Zhu, Zhaolong, et al.
(author)
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Enhancing face-milling efficiency of wood–plastic composites through the application of genetic algorithm–back propagation neural network
- 2024
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In: Wood Material Science & Engineering. - 1748-0272 .- 1748-0280.
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Journal article (peer-reviewed)abstract
- Wood–plastic composites (WPCs) have advanced physicochemical properties and are widely applied in various fields. How to achieve high-efficiency, high-quality machining of WPC is a pressing issue that WPC manufacturing enterprises need to address. To this end, this research focused primarily on improving the machinability of WPC with end milling experiments. In this work, a single-factor method was used to analyse the impact of axial milling depth, spindle speed, and tool rake angle on resultant forces and surface roughness. Main effects analysis was applied to explore the degree of influence of axial milling depth, spindle speed, and tool rake angle on cutting forces and surface roughness. Furthermore, three-dimensional characterisation techniques were utilised to analyse the surface morphology characteristics of WPC during end milling. Finally, a genetic algorithm–back propagation neural network was applied to develop prediction models for resultant force and surface roughness, and optimal milling conditions were identified as axial milling depth of 0.50 mm, spindle speed of 7841 r/min, and rake angle of 15°; these produced the lowest resultant force and surface roughness. The findings of this work are proposed as a guide for better cutting performance in the industrial production of WPC.
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| 3. |
- Lin, Xian Qi, et al.
(author)
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Electromagnetically induced transparencies in a closed waveguide with high efficiency and wide frequency band
- 2012
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:9, s. 093502-
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Journal article (peer-reviewed)abstract
- We propose an effective method to alleviate the conflict between large group delay and wide frequency band in electromagnetically induced transparency (EIT) design. Two kinds of electrically induced transparency (E-IT) and magnetically induced transparency (M-IT) are proposed, respectively. Then an EIT with wide transparency window is developed by combining the independent E-IT and M-IT structures. All of the transparencies are designed in a closed waveguide system, and high efficiency is obtained at the same time. One sample is fabricated and the bandwidth is increased to more than 3 times without decrease of the group delay and increase of the size.
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| 4. |
- Lin, Xian Qi, et al.
(author)
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Understand and realize an "invisible gateway" in a classical way
- 2013
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In: Progress In Electromagnetics Research. - 1070-4698 .- 1559-8985. ; 141, s. 739-749
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Journal article (peer-reviewed)abstract
- We create an invisible gateway simply by putting electric and magnetic superscatterers in a metallic waveguide. The characteristics of the electric and magnetic resonators are analyzed in a metallic hollow waveguide, and the dual-mode superscattering property is discussed in detail to broaden the bandwidth of the invisible gateway. Good agreement is achieved between the simulation and measurement for such an invisible gateway. The present work help readers understand easily how an invisible gateway works (or makes sense) in a classical way without using any complex metamaterial or complicated method of transformation optics.
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| 5. |
- Shao, Jun, et al.
(author)
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Photoluminescence probing of interface evolution with annealing in InGa(N)As/GaAs single quantum wells
- 2015
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In: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 118:16, s. 165305-
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Journal article (peer-reviewed)abstract
- The effects of thermal annealing on the interfaces of InGa(N)As/GaAs single quantum wells(SQWs) are investigated by excitation-, temperature-, and magnetic field-dependent photoluminescence(PL). The annealing at 750 °C results in more significant blueshift and narrowing to the PLpeak than that at 600 °C. Each of the PL spectra can be reproduced with two PL components: (i)the low-energy component (LE) keeps energetically unchanged, while the high-energy component(HE) moves up with excitation and shows at higher energy for the In0.375Ga0.625As/GaAs butcrosses over with the LE at a medium excitation power for the In0.375Ga0.625N0.012As0.988/GaAsSQWs. The HE is broader than the corresponding LE, the annealing at 750 °C narrows the LE andHE and shrinks their energetic separation; (ii) the PL components are excitonic, and the InGaNAsshows slightly enhanced excitonic effects relative to the InGaAs SQW; (iii) no typical S-shape evolutionof PL energy with temperature is detectable, and similar blueshift and narrowing are identifiedfor the same annealing. The phenomena are mainly from the interfacial processes. Annealingimproves the intralayer quality, enhances the interfacial In-Ga interdiffusion, and reduces the interfacialfluctuation. The interfacial interdiffusion does not change obviously by the small N contentand hence similar PL-component narrowing and blueshift are observed for the SQWs after a nominallyidentical annealing. Comparison with previous studies is made and the PL measurementsunder different conditions are shown to be effective for probing the interfacial evolution in QWs.
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| 9. |
- Jiang, Shangsong, et al.
(author)
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Cutting Force and Surface Roughness during Straight-Tooth Milling of Walnut Wood
- 2022
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In: Forests. - : MDPI. - 1999-4907. ; 13:12
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Journal article (peer-reviewed)abstract
- Walnut (Juglans regia L.) is widely used in wood furnishings, and machinability is a key factor for improving product quality and enterprise benefits. This work focused on the influence of the rake angle, depth of cut, and cutting speed on the cutting force and machined surface roughness during the straight-tooth milling of walnut. On the basis of the experimental findings, a mathematical model was created using a response surface methodology to determine the relationship between the cutting force and the cutting conditions, as well as the relationship between the surface roughness and the cutting conditions. Variance analysis was used to study the significant contributions of the interactions of various factors and two-level interactions to the cutting force and surface roughness. The optimized combination of milling conditions, resulting in lowest cutting force and surface roughness, was determined to be a rake angle of 5°, a depth of cut of 0.6 mm, and a cutting speed of 45 m/s.
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| 10. |
- Lin, Qi, et al.
(author)
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Subject-adaptive Loose-fitting Smart Garment Platform for Human Activity Recognition
- 2023
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In: ACM transactions on sensor networks. - : Association for Computing Machinery (ACM). - 1550-4867 .- 1550-4859. ; 19:4
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Journal article (peer-reviewed)abstract
- The ability to recognize and detect changes in human posture is important in awide range of applications such as health care and human-computer interaction. Achieving this goal using loose-fit garments instrumented with sensors is particularly challenging, due to the complex interaction between garments and human body. Herein we present a method to detect and recognize human posture with casual loose-fitting smart garments integrated with highly sensitive, stretchable, optical transparent, and low-cost strain sensors. By attaching these sensors to an off-the-shelf casual jacket, we developed a smart loose-fitting sensing garment that enables posture recognition using a deep learning model, domain-adaptive Convolutional Neural Networks-Long Short-Term Memory (CNN-LSTM). This deep learning model overcame the noise and variation due to the complex interaction between loose-fitting garments and human body. Considering that users' labeled data are usually not available in the training stage, an additional domain discriminator path on the conventional CNN-LSTM model has been introduced to further improve the adaptability. To evaluate the potential of this loose-fitting smart garment, three case studies were conducted under realistic conditions: recognitions of human activities, stationary postures with random hand movements and slouch. Our results demonstrate the potential of the proposed smart garment system for practical applications.
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