Compact Size Research Articles

A review of single flow, flow boiling, and coating microchannel studies

Abstract The objective of this review article is to provide a comprehensive analysis of the latest research on microchannel heat sinks, with a particular focus on single-phase flow, flow boiling, and coating microchannels. The review aims to highlight the progress made in this field and identify the challenges that need to be addressed to promote the widespread adoption of microchannel heat sinks. The review article examines the research on microchannel heat sinks and analyzes the findings related to single-phase flow, flow boiling, and coating microchannels. The analysis of single-phase flow in microchannels covers the impact of various parameters, including channel size, fluid properties, and flow conditions, on the heat transfer rate. The analysis of flow boiling in microchannels includes the identification of the potential advantages and challenges associated with this technique, as well as the strategies developed to mitigate these issues. The analysis of coating microchannels examines the effects of surface coatings on flow behavior and heat transfer performance. The review finds that microchannel heat sinks have gained significant attention due to their potential for high heat transfer rates in a compact size. The analysis of single-phase flow reveals that the heat transfer rate is proportional to the channel diameter and inversely proportional to the fluid viscosity. Increasing the flow rate results in higher heat transfer rates and pressure drops. The analysis of flow boiling reveals that this technique can significantly increase the heat transfer rate compared to single-phase flow. However, it can also lead to flow instability, wall superheat, and premature drying. The review identifies strategies to mitigate these issues, including using different surface coatings, enhancing nucleation, and optimizing channel geometry. The analysis of coating microchannels shows that coatings can alter the surface energy, wettability, and roughness of the channel walls, affecting the flow behavior and heat transfer performance. Coatings made from materials such as metals, polymers, and self-assembled monolayers have been investigated, and their effects on the flow of boiling heat transfer have been analyzed. The review highlights the need for further research to address the challenges associated with microchannel heat sinks, including flow instability and premature drying. Additionally, the review suggests that there is a need for more comprehensive studies on the effects of different surface coatings on flow behavior and heat transfer performance. Future research can also explore the potential of other materials for coating microchannels and investigate new strategies to optimize channel geometry and enhance nucleation. The review article concludes that the progress made in understanding microchannel heat transfer is significant, but further research is necessary to realize the full potential of microchannel heat sinks.

Design and Development of a Package Delivery Robot

This research focuses on the design and development of a package delivery robot, comprising an electronic housing and a storage unit. The robot is remotely controlled through a website, equipped with obstacle detection capabilities, and capable of unlocking the storage unit. However, movement is limited when the storage unit is installed on the electronic housing. The objective of this project was to build a package delivery robot that could operate in organised environments, such as universities and estates. The project commenced with extensive research on existing delivery robots, analysing their strengths and weaknesses. Based on this analysis, a set of design requirements was formulated, emphasising compact size, lightweight construction, and user-friendly operation. A custom control system was developed, enabling robot navigation, while sensors were integrated to facilitate obstacle avoidance and pedestrian safety. The first chassis of the robot was constructed using lightweight sheet metal, but turned out to be too heavy for the motors to drive, so the chassis was reconstructed using corrugated cardboard. To evaluate its performance, the robot underwent rigorous testing in a simulated urban environment. The robot has a speed of 0.5 m/s, and receives commands at a speed of 0.0068 nano seconds. It also consumes a power of 120 watts. While the robot demonstrated below-average performance in these aspects, limitations were identified, such as the inability to make left or right turns due to the shaft that connects the tyre and the motor being short. In conclusion, this research introduces a package delivery robot that has the potential to significantly enhance the customer delivery experience in urban environments. The robot represents progress in delivery system development and provides valuable insights into the challenges and opportunities within the field of mechatronics. The introduction, methodology, results, and conclusion framework used in this project offers a comprehensive understanding of the research and development process, the robot's performance, and its impact on the field.

A Wideband Circularly Polarized Dipole Antenna with Compact Size and Low-Pass Filtering Response.

This paper presents a compact wideband circularly polarized cross-dipole antenna with a low-pass filter response. It consists of two pairs of folded cross-dipole arms printed separately on both sides of the top substrate, and the two dipole arms on the same surface are connected by an annular phase-shifting delay line to generate circular polarization. A bent metal square ring and four small metal square rings around the cross-dipoles are employed to introduce new resonant frequencies, effectively extending the impedance and axial-ratio bandwidth. Four square patches printed on the middle substrate are connected to the ground plane by the vertical metal plates in order to reduce the antenna height. Thus, a compact wideband circularly polarized antenna is realized. In addition, a transmission zero can be introduced at the upper frequency stopband by the bent metal square rings, without using extra filter circuits. For verification, the proposed model is implemented and tested. The overall size of the model is 90mm×90mm×33mm (0.37λ0×0.37λ0×0.14λ0; λ0 denotes the center operating frequency). The measured impedance bandwidth and 3 dB axial-ratio (AR) bandwidth are 53.3% and 41%, respectively. An upper-band radiation suppression level greater than 15 dB is realized, indicating a good low-pass filter response.

An ultra‐low‐power low‐noise amplifier using a combination of current reuse and self‐forward body bias techniques for biomedical applications

SummaryLow‐power low noise amplifiers (LNAs) are critical block in the radio frequency (RF) front‐end of medical device radiocommunications service (MedRadio) receivers for amplifying weak received signals while introducing minimal noise. Despite the inherently low transconductance of MOS transistors, it is possible to achieve low noise, high gain, and good linearity in low power LNAs. This paper presents a combination of techniques to realize an ultra‐low‐power LNA with a compact size and high performance. The proposed LNA utilizes multiple gm‐boosting and self‐forward body bias techniques, with certain transistors operating in weak inversion. Additionally, the Multi‐Objective Inclined Planes System Optimization algorithm is employed to determine the optimal values of the circuit components, thereby achieving the best compromise among the various performance parameters. The proposed LNA with buffer is designed and simulated using an 180 nm CMOS process over the frequency band of 0.3–1 GHz. Simulated results show that the proposed LNA achieves a gain of 19.6 dB, a noise figure of 5.1 dB, good input matching (S11 < −10 dB), and a third‐order intermodulation intercept point (IIP3) of 3.8 dBm. Additionally, it consumes 320 μW (without buffer) from a 1 V power supply, and the chip area is 235 μm × 372 μm. The simulated results demonstrate that the proposed ultra‐low power LNA is a promising candidate for biomedical applications.

Broadband Quad-Element MIMO Antenna with Enhanced Isolation for Sub-6 GHz and Sub-7 GHz 5G Applications

In this manuscript, a broadband quad-element MIMO antenna with enhanced isolation for n77, n78, and n79 bands of Sub-6 GHz and the n46 and n96 bands of Sub-7 GHz under 5G applications is designed. The designed antenna element is a rectangular monopole antenna comprising a semi-circular cut and a semi-circle embedded to obtain a wide bandwidth. These four-element antennas are aligned orthogonally to achieve the compact size and high isolation features of MIMO performance. The overall area of MIMO antenna is 40×40x1.6 mm3. MIMO antenna has a high isolation of <- 21 dB, an envelope correlation coefficient (ECC<0.002), a high diversity gain (DG> 9.99), an MEG gain of -3 dB, and a peak gain of 5.08 dBi.The results of the experiment are satisfactory with the S-parameter simulation results According to the results, a broadband quad-element MIMO antenna is a suitable candidate for Sub-6 GHz and Sub-7 GHz 5G applications.

Laser-induced micro-cavity on a fiber end with a harmonic-Vernier effect for salinity sensing

In this paper, a fiber optic salinity sensor based on Fabry–Perot interference (FPI) with a harmonic-Vernier effect is suggested. An open cavity and a resin solid cavity are grown at the end of the fiber by a unique fiber-end photopolymerization and integration (FEPI) technique. When seawater fills the open cavity, it changes the optical path length (OPL) of the interferometer directly. While the OPL of the reference interferometer is hardly impacted by the seawater. The insertion of the harmonic envelope shifts greatly with salinity. Tunable sensing performances are achieved by adjusting the cavity length ratio(CLR) according to a theoretical model. The maximum sensitivity of 6.53 nm/‰is attained in the range of 25 ‰to 45 ‰when its CLR approaches 1.18. In addition, the measuring accuracy, consistency, and temperature compensation method are also experimentally investigated. The suggested sensor is a prospective competitor in the field of measuring the salinity of seawater due to the advantages of high sensitivity, compact size, large dynamic range, and adjustable capabilities.

Generative Model for Dual-Band Filters Based on Modified Complementary Split-Ring Resonators

This article presents a generative model for the inverse design of dual-band filters based on a type of modified complementary split-ring resonator (CSRR). It consists of a series of convolutional neural networks that incorporate the conditional deep convolutional generative adversarial network (GAN) technique. The filters are designed by etching the modified CSRRs on the surface of substrate-integrated waveguides. This design allows us to achieve two passbands with a compact size. In this GAN-based generative model, the CSRRs are represented as two-dimensional matrices. Each matrix corresponds to a training sample of the designed filter, and its S-parameters are extracted through an HFSS simulation. Both the matrices and the S-parameters are fed into the model as the training datasets. Different CSRRs with various sizes are employed for a wider applicable frequency band. Normalized matrices and normalized S-parameters are utilized to simplify the complex generative model resulting from the variations in CSRR sizes. The effectiveness of the generative model is validated through four design examples of dual-band filters, with their center frequencies located within 5 to 18 GHz. The inference time for each design is approximately 18.5 min. The measurement results of the fabricated filters are in good agreement with the simulation ones.

Sol–gel derived ceramic nanoparticles as an alternative material for microstrip patch antenna in WLAN applications

In the fast-evolving realm of communication technology, microstrip patch antennas (MPAs) are in high demand owing to their compact size, lightweight, inexpensive, ease of integration, and compatibility with modern electronic devices. This research focuses on the synthesis of ZnAl2O4Ca (ZAC) ceramic nanoparticles using an economical sol–gel method suitable for microstrip patch antenna applications. The structural analysis study of ZAC nanoparticles confirmed the polycrystalline nature with 8.1 nm of crystallite size whereas an investigation of functional groups showed the corresponding vibration modes. Morphological investigation revealed the spherical grains having their mean diameter of 12.32 nm. The dielectric property’s examination, revealed the dielectric permittivity of 13, loss tangent of 0.02, and conductivity of 67 μΩ−1 cm−1. Furthermore, a prototype patch antenna fabricated using ZAC ceramics demonstrated a dual-band performance at frequencies 2.8 GHz and 4.8 GHz, with return losses of − 25.78 dB and − 28.5 dB, respectively. This work suggests the suitability of ZAC ceramic nanoparticles for use in WLAN applications.

A wide-band high gain beamsteerable variable patch reflectarray antenna for THz applications

This article proposed a compact size, high gain, wideband reflectarray antenna for THz and 6 G applications. To enhance the aperture efficiency and gain, a single layer L-shape delay line-based unit cell with a size of 0.45λ0 is adopted. The λ0 is the free space wavelength at 1.35 THz. The SiO2 substrate is sandwiched between L- shape delay line and the ground plane of gold. The unit cell, equivalent parallel RLC circuit modelled with gap coupled capacitance is also presented which is validated through the Ansys-High Frequency Structure Simulator (HFSS) and Advanced Design System (ADS). The dimension of the RA is 3 mm having 610 elements. It is excited by the pyramidal horn antenna at an optimum distance (F/D =1.21). The optimum ratio (F/D) is calculated with the help of the cosq model at −10 dB edge taper. The operating bandwidth is obtained 46.15 % from 1 to 1.6 THz. The reflection phase and magnitude are 500° and 3.93 dB at 1.35 THz. It is adjusted by varying the length of the delay line. The maximum aperture efficiency and realized gain are 35 % and 28 dBi respectively. The Side lobe level is −15.5 dB and the Co-Cross polarization level is below −30 dB.

Maize Leaf Disease Recognition Based on Improved Convolutional Neural Network ShuffleNetV2.

The occurrence of maize diseases is frequent but challenging to manage. Traditional identification methods have low accuracy and complex model structures with numerous parameters, making them difficult to implement on mobile devices. To address these challenges, this paper proposes a corn leaf disease recognition model SNMPF based on convolutional neural network ShuffleNetV2. In the down-sampling module of the ShuffleNet model, the max pooling layer replaces the deep convolutional layer to perform down-sampling. This improvement helps to extract key features from images, reduce the overfitting of the model, and improve the model's generalization ability. In addition, to enhance the model's ability to express features in complex backgrounds, the Sim AM attention mechanism was introduced. This mechanism enables the model to adaptively adjust focus and pay more attention to local discriminative features. The results on a maize disease image dataset demonstrate that the SNMPF model achieves a recognition accuracy of 98.40%, representing a 4.1 percentage point improvement over the original model, while its size is only 1.56 MB. Compared with existing convolutional neural network models such as EfficientNet, MobileViT, EfficientNetV2, RegNet, and DenseNet, this model offers higher accuracy and a more compact size. As a result, it can automatically detect and classify maize leaf diseases under natural field conditions, boasting high-precision recognition capabilities. Its accurate identification results provide scientific guidance for preventing corn leaf disease and promote the development of precision agriculture.

Investigation on the Torsional–Flexural Instability Phenomena during the Bending Process of Hairpin Windings: Experimental Tests and FE Model Validation

Modern electric motors developed for the automotive industry have an ever higher power density with a relatively compact size. Among the various existing solutions to improve torque and power density, a reduction in the dimensions of the end-windings has been explored, aiming to decrease volume, weight, and losses. However, more compact end-windings often lead to complex shapes of the conductors, especially when preformed hairpin windings are considered. The rectangular cross-section of hairpin conductors makes them prone to deviating out of the bending plane during the forming process. This phenomenon, known as torsional–flexural instability, is influenced by the specific aspect ratio of the cross-section dimensions and the bending direction. This study focuses on understanding this instability phenomenon, aiming to identify a potential threshold of the cross-section aspect ratio. The instability makes it difficult to predict the final geometry, potentially compromising the compliance with the geometric tolerances. A finite element model is developed to analyse a single planar bend in a hairpin conductor. Various cross-section dimensions with different aspect ratios are simulated identifying those that experience instability. Moreover, an experimental campaign is conducted to confirm the occurrence of instability by testing the same single planar bending. The experimental data obtained are used to validate the finite element model for the tested dimensions. The aim is to provide designers with a useful tool to select hairpin geometries that are more suitable for the folding process, contributing to successful assembly and improving the overall design process of preformed hairpin conductors.

Rational Design of Pyrido[3,2-b]indolizine as a Tunable Fluorescent Scaffold for Fluorogenic Bioimaging.

Novel fluorescent scaffolds are highly demanding for a wide range of applications in biomedical investigation. To meet this demand, the pyrido[3,2-b]indolizine scaffold was designed as a versatile organic fluorophore. With the aid of computational modeling, fluorophores offering tunable emission colors (blue to red) were constructed. Notably, constructed fluorophores absorb lights in the visible range (>400 nm) despite their small sizes (<300 g/mol). Among the fluorophores was discovered a highly fluorogenic fluorophore with a unique turn-on property, 1, and it was developed into a washing-free bioprobe for visualizing cellular lipid droplets in living cells. Furthermore, motivated by the core's compact size and structural analogy to indole, unprecedented tryptophan-analogous fluorogenic unnatural amino acids were constructed and incorporated into fluorogenic peptide probes for monitoring peptide-protein interactions.

50 GHz Four-Port Coupling-Reduced Probe Card Utilizing Pogo Pins Housed in Custom Metallic Socket.

A design for a pogo-pin probe card featuring a metallic socket is proposed to eliminate signal leakage and coupling loss in a multi-port environment. The proposed metallic pogo-pin socket includes a metal wall structure between adjacent pogo pins, ensuring complete isolation. This metal wall offers an advantage in removing coupling issues between pogo pins that can occur with typical dielectric pogo-pin sockets. The designed probe card is fabricated as a prototype and verified for its performance. Measurement results using a test through line show that coupled power is minimized, providing a low-loss transmission performance of -2.14 dB to an RF chip at 50 GHz, all within a compact size. Although the dielectric spacer used to secure the pogo pins allows for some leakage, it can maintain a low coupling performance of under -15 dB in the millimeter-wave band. The prototype probe card can deliver an RF signal to a 5G circuit with a low loss of -0.7 dB at 28 GHz and -1.9 dB at 39 GHz frequency. The designed probe card is capable of transmitting multiple RF signals to the RF system without signal distortion in a multi-port environment.

Fluorescent Probe-Based Fiber Optic Sensor for Real-Time Monitoring of Chloride Ions in Coastal Concrete Structures.

Coastal concrete structures, such as cross-sea bridges and tunnels, are susceptible to the penetration of chloride ions, which can lead to the deterioration of the passive film on the rebar surface, consequently accelerating the corrosion process. Conventional methods for monitoring chloride ions typically require in situ drilling for sample collection, thereby compromising efficiency and accuracy. Additionally, real-time monitoring and early warning cannot be achieved. To address these challenges, this work introduces a fluorescent-probe-based fiber optic sensor for monitoring chloride levels in concrete structures. Quinine sulfate was chosen as the fluorescent material due to its exceptional sensitivity to chloride ions and its stability in concrete environments. The proposed sensor was manufactured using sol-gel and 3D-printing techniques. Tests were conducted using concrete simulation fluid and cement mortar specimens. The results demonstrate that the sensitivity of the proposed sensor is greater than 0.01 M, and its accuracy in penetration depth measurement is better than 3 mm. The findings confirm that the designed fiber optic sensor based on quinine sulfate enables real-time monitoring of chloride ions in concrete structures, offering high sensitivity (0.1% in concentration and 2.7 mm in terms of penetration depth), unique selectivity (as it is immune to other ions whose concentrations are 10 times higher than those of Cl-), and a compact size (10 × 20 mm). These attributes render it promising for practical engineering applications.

EfficientSkinSegNet: a lightweight convolutional neural network for accurate skin lesion segmentation

Accurate segmentation of skin lesions is crucial for the early detection and treatment of skin cancer. In this study, we propose EfficientSkinSegNet, a novel lightweight convolutional neural network architecture specifically designed for precise skin lesion segmentation. EfficientSkinSegNet incorporates efficient feature extraction encoders and decoders, leveraging multi-head convolutional attention and spatial channel attention mechanisms to extract and enhance informative features while eliminating redundant ones. Furthermore, a multi-scale feature fusion module is introduced in the skip connections to facilitate effective fusion of features at different scales. Experimental evaluations on benchmark datasets demonstrate that EfficientSkinSegNet outperforms state-of-the-art methods in terms of segmentation accuracy while maintaining a compact model size. The proposed network shows promise for practical clinical diagnostic applications, providing a balance between segmentation performance and computational efficiency. Future research will focus on evaluating EfficientSkinSegNet’s performance on diverse semantic segmentation tasks and optimizing it for medical image analysis.

Development and Comprehensive Evaluation of TMR Sensor-Based Magnetrodes.

Due to their compact size and exceptional sensitivity at room temperature, magnetoresistance (MR) sensors have garnered considerable interest in numerous fields, particularly in the detection of weak magnetic signals in biological systems. The "magnetrodes", integrating MR sensors with needle-shaped Si-based substrates, are designed to be inserted into the brain for local magnetic field detection. Although recent research has predominantly focused on giant magnetoresistance (GMR) sensors, tunnel magnetoresistance (TMR) sensors exhibit a significantly higher sensitivity. In this study, we introduce TMR-based magnetrodes featuring TMR sensors at both the tip and midsection of the probe, enabling detection of local magnetic fields at varied spatial positions. To enhance detectivity, we designed and fabricated magnetrodes with varied aspect ratios of the free layer, incorporating diverse junction shapes, quantities, and serial arrangements. Utilizing a custom-built magnetotransport and noise measurement system for characterization, our TMR-based magnetrode demonstrates a limit of detection (LOD) of 300pT/ at 1 kHz. This implies that neuronal spikes can be distinguished with minimal averaging, thereby facilitating the elucidation of their magnetic properties.

U-shaped and V-shaped tuned liquid column dampers in vibration reduction of earthquake-induced buildings: A comparative study

The comparative study of a V-shaped tuned liquid column damper (VTLCD) and a U-shaped tuned liquid column damper (UTLCD) to minimize the dynamic response of a building under seismic loadings is investigated in this paper. A VTLCD is an improved form of a traditional UTLCD, in which the V-shaped liquid column of a VTLCD replaces the horizontal liquid column of a UTLCD. The equations of motion of an earthquake-excited MDOF building equipped with a VTLCD or UTLCD are established in this study. The operating conditions and geometric constraints of VTLCD and UTLCD are analyzed to build optimization problems. Herein, two main targets of optimization problems are considered, including the maximum relative displacement used to assess structural safety and the maximum absolute acceleration used for the purpose of human safety. Next, configurations of VTLCD and UTLCD are optimized based on data from the El Centro earthquake, with the peak ground acceleration (PGA) being 0.5 g, corresponding to each target mentioned above. Then, these configurations are tested under ten random earthquakes with different peak ground accelerations (PGAs). The present work results show that VTLCD has a more compact size compared with UTLCD. Furthermore, the vibration reduction capacity of VTLCD is higher than that of UTLCD (having the same mass as VTLCD) when the system is subjected to earthquake loads with different PGAs, especially for earthquakes with a high PGA.

A Multi-Parameter Tunable and Compact Plasmon Modulator in the Near-Infrared Spectrum

To keep pace with the demands of modern photonic integration technology, the electro-optic modulator should feature multi-parameter tunable components and a compact size. Here, we propose a hybrid structure that can modulate the multi-parameters of surface plasmon polaritons (SPPs) simultaneously with a compact size by controlling the electron concentration of indium tin oxide (ITO) in the near-infrared spectrum. The length, width and height of the device are only 15 μm, 5 μm and 9 μm, respectively. The numerical results show that when the electron concentration in ITO changes from 7.5 × 1026 m−3 to 9.5 × 1026 m−3, the variation in amplitude, wavelength and phase are 49%, 300 nm and 347°, respectively. The demonstrated structure paves a new way for multi-parameter modulation and the realization of ultracompact modulators.

High-sensitivity robust Mach-Zehnder interferometer sensor in ultra-compact format

A new type of fiber sensor called the mini-two-path Mach-Zehnder interferometer (MTP-MZI) sensor has been proposed and demonstrated for high-sensitivity curvature and temperature detection. The sensor is created by fusing two sections of single-mode fibers (SMFs) with an electric-arc technology. In the curvature experiment, the maximum intensity sensitivity is 112.6 dB/m−1 when the curvature changes from 0.005224 m−1 to 0.052245 m−1. As far as our knowledge, it has the highest sensitivity with the same scale in the MZI fiber sensors. Additionally, a temperature sensing performance has been measured within the range from 30 °C to 70 °C, and the maximum temperature sensitivity is 162 pm/°C. Compared with the two-path MZI with traditional meter-scale, the proposed MZI has the advantages of robustness, compact size, easy preparation, and packaging, which can open up new avenues for MZI in the application of multi-dimensional and multi-parameter sensing.

Topological Edge State Ring Resonator for Mid-Infrared(MI) Refractive Indices Biosensor for detection of Brain Tumors

The unique properties of light underlie the perspectives of quantum photonic technologies, optical interconnects, and a wide range of new sensors.Some of the most dangerous and deadly diseases are tumors, cancers, and brain lesions, which are expensive to detect and treat. Therefore, a low-cost and accurate method to diagnose them can prevent and treat the progress of this disease. In this work, we used the precise topological valley photonic crystal (TVPC) method for detection. TVPC is an important method for transmitting and controlling light in the optical device. The valley-spin locking in the topology state provides robust transfer and low propagation loss at the desired path.In order to design, by finding the edge band within the first bulk band gap of 146.4 THz–155.9 THz, the model and design of the topological ring resonator (TRS)were realized. We proposed a topological biosensorbyusing the hexagonal lattice air holes in the silicon slab with a compact size of 22.95 μm × 10 μm. the quality factor and sensitivity at best value are 2.905 × 104 and 9021 nm RIU−1 respectively. This design can be implemented on the Complementary Metal-Oxide-Semiconductor (CMOS) technology as a high-sensitivity optical device.