Recently, there has been growing interest in water‐assisted injection molding (WAIM) not only for its advantages over gas‐assisted molding (GAIM) and conventional injection molding (CIM), but also ...for its great potential advantages in industrial applications. To understand the formation mechanism of water penetration induced fiber orientation in overflow water‐assisted injection molding (OWAIM) parts of short glass fiber‐reinforced polypropylene (SGF/PP), in this work, the external fields and water penetration process within the mold cavity were investigated by experiments and numerical simulations. The results showed that the difference of fiber orientation distribution in thickness direction between WAIM moldings and CIM moldings was mainly ascribed to the great external fields generated by water penetration. Besides, fiber orientation depended on the position both across the part thickness and along the flow direction. Especially in the radial direction, fiber orientation varied considerably. The results also showed that the melt temperature is the principal parameter affecting the fiber orientation along the flow direction, and a higher melt temperature significantly facilitated more fibers to be oriented along the flow direction, which is quite different from the results as previously reported in short‐shot water‐assisted injection molding (SSWAIM). A higher water pressure, shorter water injection delay time, and higher melt temperature significantly induced more fibers to be orderly oriented in OWAIM moldings, which may improve their mechanical performances and broaden their application scope.
The formation mechanism of fiber orientation in OWAIM parts of short glass fiber‐reinforced polypropylene (SGF/PP) was analyzed through an in‐depth understanding of the flow fields within a mold cavity. Water penetration significantly induces the fiber to be orientated, which may improve the mechanical performances of WAIM moldings and broaden their application scope.
water penetration length and fiber orientation (along the melt flow direction) are important indicators for water‐assisted injection molding products of the fiber‐reinforced polymer. The effects of ...melt short shot size, water injection delay time and water injection pressure on these two important indexes are analyzed theoretically and experimentally. The study found that with the increase of the melt short shot size, the extension of the water injection delay time and the increase of the water injection pressure, the water penetration length changed from 216 to 96 mm, 170 to 210 mm, and 215 to 180 mm, respectively. Therefore, it can be known that melt short shot size has the greatest influence on water penetration length, followed by water injection delay time, and finally water injection pressure. Meantime, due to the fiber orientation and change degree of water‐assisted injection‐molded products along the melt flow direction, the fiber orientation in the water channel layer along the melt flow direction has the highest and lowest change degree, followed by the wall layer and finally the core layer. It can be known that the melt short shot size has the greatest influence on the fiber orientation and the degree of change along the melt flow direction, followed by the water injection delay time, and finally the water injection pressure.
It is a critical requirement to have an insight into the mechanism of flow‐induced fiber orientation in short‐shot water‐assisted injection molding (SSWAIM) of fiber‐reinforced polymer for improving ...the structural rigidity and service life of molded parts. However, this mechanism is still unclear, which stunts the development of SSWAIM. In this work, the mechanism of flow‐induced fiber orientation in SSWAIM parts of short‐glass‐fiber‐reinforced polypropylene (SGF/PP) was clarified through numerical research and experimental verification. The results showed that the difference of fiber orientation distribution at different positions both in the radial direction and along the flow direction between SSWAIM parts and conventional injection molding (CIM) parts was mainly due to the strong flow field caused by the high‐pressure water penetration in SSWAIM. Moreover, fiber orientation in the SSWAIM part depended not only on its position both in the radial direction and along the flow direction, but also on the processing parameters. At the front of SSWAIM part, fiber orientation changed greatly in the radial direction and presented an obvious “shell layer‐core layer‐water channel layer” hierarchical structure across the part thickness, whereas this phenomenon became more inconspicuous with increasing the distance of the selected position from the water injection inlet. Short‐shot size is the principal parameter affecting the fiber orientation, and within the range of investigated processing parameters, smaller short‐shot size, shorter water injection delay time, higher water pressure, and lower melt temperature could significantly facilitate fiber orientation across the part thickness.
The flow fields generated by water penetration could significantly facilitate more fibers to be orderly oriented in SSWAIM parts, which may improve the mechanical properties of final molded parts and promote the industrialization process of SSWAIM process.
The development of security-aware mobile devices using wide-input-output (IO) nonvolatile memory (NVM) is hindered by high peak current, large area overhead for high read bandwidth (BWR), and ...considerable energy consumption for data movement between NVM and logic blocks. Furthermore, data stored in NVM are vulnerable to reverse-engineering attacks. This work presents a high BWR security-aware near-memory-computing spin-transfer torque magnetic random-access memory (STT-MRAM) macro using a multi-bit current-mode sense amplifier (MB-CSA) to reduce peak current and energy consumption for wide-IO access, a near-memory shift-and-rotate functionality (NSRF) in conjunction with the MB-CSA to reduce area overhead and enable the completion of read and logic operations within a single cycle, and a reverse-engineering-proof XOR-based memory data protector to protect data stored in NVM against reverse-engineering attacks. A 1-Mb 1024-b read STT-MRAM macro with data protector fabricated using foundry embedded 22-nm STT-MRAM. This work achieved 42.67 GB/s for BWR and 0.23 pJ/b. Inclusion of the NSRF circuit reduced area overhead by 33.3% while increasing latency by only 170 ps.
Water‐assisted injection molding of polymer matrix composites effectively combines the advantages of both the materials and technique and is now emerging into the limelight. Pipe hole length and pipe ...thickness are important indices of the products of this process and can be used to describe the water penetration behavior. In this paper, the sensitivity of water penetration behavior on the main process parameters was studied. The study shows that the water penetration behavior is most sensitive to the melt injection volume percent. For example, as the melt injection volume percent is increased, the pipe hole length is decreased from 231 mm to 116 mm, and its fluctuation is increased from 0.9% to 7.1%. The pipe thickness shows a significant change in the rear parts of the main cavity, followed by the water pressure and delay time, and, finally, the melt temperature. Furthermore, the pipe thickness in the middle of the main cavity is found to be the most sensitive to these process parameters. The above results provide certain guidance for adjusting the process parameters of the short‐shot method.
In this paper, a navigation control method is proposed for an Ackermann steering robot. In the proposed method, light detection and ranging (LiDAR) sensors are used to obtain the distance between an ...Ackermann steering robot and objects in an unknown environment. In accordance with the distances obtained by the LiDAR sensors, the navigation control system uses a behavior manager to switch between two types of behavior control, namely, toward-goal behavior control and wall-following behavior control (WFBC). If a wall or an obstacle is detected in the current path toward the target position, the behavior manager adopts WFBC to avoid the obstacle. To achieve WFBC, a fuzzy logic controller with three subfuzzy logic controllers-namely, a straight-based fuzzy logic controller, a right-based fuzzy logic controller, and a left-based fuzzy logic controller-is adopted. Switching between these three subcontrollers is achieved in accordance with the distance and angle between the robot and a wall (or an obstacle). The input signal of the proposed fuzzy logic controller is the distance between the robot and wall (or obstacle), which is determined by a LiDAR sensor at different angles, and the output of this controller is the steering angle of the Ackermann steering robot, which can move along a wall and avoid collisions with walls (or obstacles) in an environment. Experimental results indicated that the proposed fuzzy logic controller successfully implemented navigation control in two unknown environments.
In this paper, a novel chaos-based cryptosystem is proposed to ensure the communication security of video/audio streaming in the network environment. Firstly, by the proposed synchronization ...controller for the master and slave chaotic systems, respectively, embedded in the transmitter and receiver, the cryptosystem can generate the synchronized and dynamic chaotic random numbers at the transmitter and receiver simultaneously. Then integrating the chaotic random numbers with SHA3-256 (Secure hash algorithm 3), the design of synchronized dynamic key generators (SDKGs) is completed. Continuously, we can apply the SDKGs to encrypt/decrypt streaming audio/video data. In our design, we introduce the AES CFB (Advanced encryption standard cipher feedback) encryption algorithm with SDKGs to encrypt the video/audio streaming. Then the cipher-text is transmitted to the receiver via the network public channel and it can be fully decrypted with the dynamic random keys synchronously generated at the receiver. A duplex audio/video cryptosystem is realized to illustrate the performance and feasibility of this proposed research. Finally, many tests and comparisons are performed to stress the quality of random sequences generated by proposed SDKGs.
