Abstract Here, a simple method for fabricating polymeric convex lens and controlling of its focal length in a single‐step fabrication is presented. The method utilizes electrostatic force to pull the polymer droplet to form the lens, as well as to accelerate the droplet to control the curvature of the lens simultaneously. Lenses with various diameter (ranging from 0.75 to 4.5 mm) and curvature are sequentially fabricated at the preprogrammed position on a dielectric and flexible substrate. Since a transparent dielectric flexible film is employed as a target substrate, not only the electrical short circuit in the process is prevented but also high optical transmittance is secured with superior mechanical bendability which allows transformation of the lens into a positive single‐axis meniscus. To show the functionality, the lenses are integrated into a microscope for a teleconverter, fluidic tubing for a magnifier, laser exposing for a concentrator, and LED bulb encapsulating as a light diffuser. The presented method with extremely simple fabrication step with focal length control is expected to be directly applied to a wide range of applications.
The wettability of fiber-reinforced composites plays a crucial role in both mechanical properties and the efficiency of the manufacturing process. This is particularly significant in large and intricate composite structures where any flaws can have more severe consequences. In this study, the impregnation of epoxy resin into carbon fiber (CF) mats in-situ was monitored by observing the electrical resistance (ER) behaviors of CFs without any other additional sensors. The ERs of CF and CF tows at various points were measured, while epoxy resin was applied to establish fundamental data on ER behavior during the Vacuum Assisted Resin Transfer Molding (VARTM) process. During the VARTM process, the ERs of CF mats in-situ were compared with the behaviors of micro and sub-micro CFs, along with capturing images of the front flow of epoxy resin. The ER data obtained during the VARTM process was visualized through 3D ER mapping, which allowing for real-time monitoring of the flow front. Ultimately, the resin flow front of epoxy resin into CF mats was successfully monitored using the ER behaviors of CFs themselves.
Abstract Background We report a rare case of orbital subperiosteal hematoma associated with frontal and ethmoidal sinusitis. Common concerns involving the orbital subperiosteal space include abscess, hematoma and tumor. Case presentation A patient presented to our clinic with periorbital swelling and limited extraocular muscle movement in her left eye. Computed tomography revealed a superior subperiosteal mass with frontal and ethmoidal sinusitis. We diagnosed the patient with subperiosteal hematoma and surgical evacuation was performed via superior orbitotomy. Brown serous discharge was drained and biopsy demonstrated fibrin clots. The final diagnosis was orbital subperiosteal hematoma and the patient was discharged with symptoms resolved. Conclusion Orbital subperiosteal hematoma is difficult to distinguish from abscess owing to its rarity and similar presentation. Computed tomography is helpful in diagnosis, and surgical evacuation during the early stages is essential to achieving a good outcome.
Achieving successful bone regeneration necessitates the design of scaffolds that meet diverse biological and mechanical requirements, often leading to conflicts in the design parameters. A key conflict arises between scaffold porosity and stiffness. Increasing porosity facilitates cell infiltration and nutrient exchange, promoting bone regeneration. However, higher porosity compromises scaffold stiffness, which is crucial for providing structural support in the defective region. Furthermore, appropriate scaffold stiffness is crucial for preventing stress shielding. Conventional geometry-based design methods utilizing single-phase materials have limited flexibility in resolving such conflicts. To address this challenge, we propose a voxel-based method for designing composite scaffolds composed of hydroxyapatite (HA) and polylactic acid (PLA). Our strategy involves first satisfying primary biological requirements by selecting appropriate porosity, pore shape, and size. Subsequently, scaffold stiffness requirements are met by selecting suitable phase materials and tuning their contents. The study demonstrates that the voxel-based approach effectively balances both biological and mechanical requirements in scaffold design. This method addresses the limitations of traditional designs by achieving an optimal balance between porosity and stiffness, which is crucial for scaffold performance in biomedical applications. Moreover, the scaffolds designed using this method can be manufactured using voxel-based 3D printing technology, which is emerging in the field. Future advancements in voxel-based 3D printing technology will further enhance the feasibility and practicality of this approach for bone tissue engineering applications.
This study showed the possibility of using a sub-terahertz (THz) traveling-wave tube (TWT) via measuring the transmission characteristics and TWT performance of the circuit by applying X-ray LIGA, a micro-fabrication process, to the interaction circuit. The applied circuit type, an E-bend folded waveguide, is a simple structure most suitable for lithography. A total of three applied frequencies were used the W-band, G-band, and 850 GHz. Among the manufactured circuits, the W-band circuit was applied to the TWT, one of the vacuum electronics devices (VEDs). This was done to prove the manufacturing accuracy of the circuit by comparing the nonlinear characteristics of the circuit with the prediction results. Through such testing, the small signal gain was measured as 13 ± 2 dB under the conditions of 13.96-kV and 24.2-mA electron beam energy. The frequency bandwidth was extremely wide, about 9 GHz, and showed similar characteristics to the simulation predictions. The maximum output of the device was obtained up to 1 W or more at 87.12 GHz by slightly increasing the beam current. These characteristic achievements showed the suitability of the TWT for very small circuits fabricated using the X-ray LIGA process, further suggesting the applicability of other sub-THz bands.
STES (Seasonal Thermal Energy Storage) is one of the most effective ways to improve the performance of the solar thermal system in the summer season. During the summer, the STES system stores thermal energy owing to low thermal demand and then uses in the winter when the thermal demand is high. Stratification in the storage tank can enhance the thermal efficiency of the system. In general, there are two methods for stratification; to control the flow rate and to apply devices such as diffuser and distributor. In this study, we propose a simple method which controls the flow rate and the inlet port position. Experiments and simulation were carried out to investigate the performance and effect of the proposed method. It was confirmed that the temperature reversal phenomenon can be prevented, and the stratification index and the solar fraction are improved by the combined control with a variable flow rate and a variable position controls.
탄소나노튜브(CNT)를 이용하여 신율이 뛰어난 p-DCPD를 지로 사용하여 손상감지용 고분자 필름 센서를 연구하였다. CNT를 수지에 혼합시킬 경우 중합을 방해하여 1차 개환만 진행되었다. CNT 농도에 따른 정적접 촉각을 측정하여 계면의 젖음성을 측정하였다. 높은 신율을 가지는 p-DCPD에 CNT를 혼합시킴으로써 전도성을 확보하였고, CNT 농도에 따른 인장강도 및 전기저항 분산도 평가를 실시하였을 경우 0.5 wt% CNT/p-DCPD 조건이 최적의 조건임을 확인하였다. CNT/p-DCPD 센서의 내구성을 평가하기 위해 동적 피로 실험을 실시하여 인장응력에 따른 전기저항 변화를 평가하였다. 초기 3회 사이클 동안은 전기저항 변화도와 응력간의 결과가 유사한 경향을 나타내었다. CNT/p-DCPD 센서의 활용을 위해 에폭시 기지 표면에 센서를 붙이고 기지 재료의 파괴거동을 확인하였다. 기지 파괴가 발생되기 전에 CNT/p-DCPD 센서의 전기저항 점핑 신호를 관찰할 수 있었다. 이는 기지재료에 발생된 균열에 의해 CNT/p-DCPD 센서와 기지간의 접착 파괴로 발생된 신호이며, 이러한 신호를 이용하여 기지재료의 균열 및 파괴를 예측해 볼 수 있었다. Damage sensing of polymer composite films consisting of poly(dicyclopentadiene) p-DCPD and carbon nanotube (CNT) was studied experimentally. Only up to 1st ring-opening polymerization occurred with the addition of CNT, which made the modified film electrically conductive, while interfering with polymerization. The interfacial adhesion of composite films with varying CNT concentration was evaluated by measuring the wettability using the static contact angle method. 0.5 wt% CNT/p-DCPD was determined to be the optimal condition via electrical dispersion method and tensile test. Dynamic fatigue test was conducted to evaluate the durability of the films by measuring the change in electrical resistance. For the initial three cycles, the change in electrical resistance pattern was similar to the tensile stress-strain curve. The CNT/p-DCPD film was attached to an epoxy matrix to demonstrate its utilization as a sensor for fracture behavior. At the onset of epoxy fracture, electrical resistance showed a drastic increase, which indicated adhesive fracture between sensor and matrix. It leads to prediction of crack and fracture of matrix.
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