Multi-objective optimization using improved NSGA-II for integrated process planning and scheduling problems in a machining job shop for large-size valve.

This paper studied an integrated process planning and scheduling problem from a machining workshop for large-size valves in a valve manufacturing plant. Large-size valves usually contain several key parts and are generally produced in small-series production. Almost all the parts need to be manufactured in the same workshop at the same time in the plant. Facilities have to handle various items in one order, including different models, sizes, and types. It is a classical NP-hard problem on a large scale. An improved NSGA-II algorithm is suggested to obtain satisfactory solutions for makespan and manufacturing costs, which involve large optimization parameters and interactions. A two-section encoding method and an inserting greedy decoding method are chosen to enable the algorithm. The dynamic population update strategy based on dynamic population update and the adaptive mutation technique depending on the population entropy changing rate are selected for enhancing both the solution quality and population diversity. The methodology was successfully implemented in a real-life case at a major valve machining workshop operated by Yuanda Valve Company in China. By taking into account realistic factors and restrictions that have been identified from a real-world manufacturing setting, this technique aids in bridging the knowledge gap between present IPPS research and practical valve production implementations.

Designing Advanced Amorphous/Nanocrystalline Alloys by Controlling the Energy State.

Amorphous alloys, also known as metallic glasses, exhibit many advanced mechanical, physical, and chemical properties. Owing to the nonequilibrium nature, their energy states can vary over a wide range. However, the energy relaxation kinetics are very complex and composed of various types that are coupled with each other. This makes it challenging to control the energy state precisely and to study the energy-properties relationship. This brief review introduces the recent progresses on studying the enthalpy relaxation kinetics during isothermal annealing, for example, the observation of two-step relaxation phenomenon, the detection of relaxation unit (relaxun), the key role of large activation entropy in triggering memory effect, the influence of glass energy state on nanocrystallization. Based on the above knowledge, a new strategy is proposed to design a series of amorphous alloys and their composites consisting of nanocrystals and glass matrix with superior functional properties by precisely controlling the nonequilibrium energy states. As the typical examples, Fe-based amorphous alloys with both advanced soft magnetism and good plasticity, Gd-based amorphous/nanocrystalline composites with large magnetocaloric effect, and Fe-based amorphous alloys with high catalytic performance are specifically described.

Enhancing the Consistency and Performance of Graphene-Based Devices via Al Intermediate-Layer-Assisted Transfer and Patterning.

Graphene has garnered widespread attention, and its use is being explored for various electronic devices due to its exceptional material properties. However, the use of polymers (PMMA, photoresists, etc.) during graphene transfer and patterning processes inevitably leaves residues on graphene surface, which can decrease the performance and yield of graphene-based devices. This paper proposes a new transfer and patterning process that utilizes an Al intermediate layer to separate graphene from polymers. Through DFT calculations, the binding energy of graphene-Al was found to be only -0.48 eV, much lower than that of PMMA and photoresist with graphene, making it easier to remove Al from graphene. Subsequently, this was confirmed through XPS analysis. A morphological characterization demonstrated that the graphene patterns prepared using the Al intermediate layer process exhibited higher surface quality, with significantly reduced roughness. It is noteworthy that the devices obtained with the proposed method exhibited a notable enhancement in both consistency and sensitivity during electrical testing (increase of 67.14% in temperature sensitivity). The low-cost and pollution-free graphene-processing method proposed in this study will facilitate the further commercialization of graphene-based devices.

Evolutionary and developmental specialization of foveal cell types in the marmoset.

In primates, high-acuity vision is mediated by the fovea, a small specialized central region of the retina. The fovea, unique to the anthropoid lineage among mammals, undergoes notable neuronal morphological changes during postnatal maturation. However, the extent of cellular similarity across anthropoid foveas and the molecular underpinnings of foveal maturation remain unclear. Here, we used high-throughput single-cell RNA sequencing to profile retinal cells of the common marmoset (Callithrix jacchus), an early divergent in anthropoid evolution from humans, apes, and macaques. We generated atlases of the marmoset fovea and peripheral retina for both neonates and adults. Our comparative analysis revealed that marmosets share almost all their foveal types with both humans and macaques, highlighting a conserved cellular structure among primate foveas. Furthermore, by tracing the developmental trajectory of cell types in the foveal and peripheral retina, we found distinct maturation paths for each. In-depth analysis of gene expression differences demonstrated that cone photoreceptors and Müller glia (MG), among others, show the greatest molecular divergence between these two regions. Utilizing single-cell ATAC-seq and gene-regulatory network inference, we uncovered distinct transcriptional regulations differentiating foveal cones from their peripheral counterparts. Further analysis of predicted ligand-receptor interactions suggested a potential role for MG in supporting the maturation of foveal cones. Together, these results provide valuable insights into foveal development, structure, and evolution.

Elucidation and Pharmacologic Targeting of Master Regulator Dependencies in Coexisting Diffuse Midline Glioma Subpopulations.

Diffuse Midline Gliomas (DMGs) are universally fatal, primarily pediatric malignancies affecting the midline structures of the central nervous system. Despite decades of clinical trials, treatment remains limited to palliative radiation therapy. A major challenge is the coexistence of molecularly distinct malignant cell states with potentially orthogonal drug sensitivities. To address this challenge, we leveraged established network-based methodologies to elucidate Master Regulator (MR) proteins representing mechanistic, non-oncogene dependencies of seven coexisting subpopulations identified by single-cell analysis-whose enrichment in essential genes was validated by pooled CRISPR/Cas9 screens. Perturbational profiles of 372 clinically relevant drugs helped identify those able to invert the activity of subpopulation-specific MRs for follow-up in vivo validation. While individual drugs predicted to target individual subpopulations-including avapritinib, larotrectinib, and ruxolitinib-produced only modest tumor growth reduction in orthotopic models, systemic co-administration induced significant survival extension, making this approach a valuable contribution to the rational design of combination therapy.

[Orthopaedic robot assisted femoral neck dynamic cross fixation system for the treatment of femoral neck fractures].

OBJECTIVE: To explore and compare the clinical efficacy of orthopedic robot assisted femoral neck system （FNS） and traditional manual FNS in the treatment of femoral neck fractures in middle-aged and young people. METHODS: The clinical data of 62 consecutive patients with femoral neck fracture and age less than 65 years old admitted to the Intelligent Orthopaedic Department of Beijing Jishuitan Hospital from June 2021 to June 2022 were retrospectively analyzed. According to whether orthopedic robot-assisted surgery the patients were divided into two groups：30 patients aged 34 to 56 years old were treated with orthopedic robot assisted FNS internal fixation after closed or limited open reduction（experimental group）； 32 patients aged 33 to 54 years old underwent FNS internal fixation after closed or limited open reduction（control group）. The age, gender, time from injury to admission, average hospital stay, surgical duration, intraoperative bleeding volume, and intraoperative fluoroscopy frequency of two groups of patients were analyzed and compared. The hip joint function in both groups of patients was evaluated using the Harris hip joint scoring standard at 6 months after surgery. RESULTS: All 62 patients with femoral neck fractures successfully completed the surgery. There was no significant difference（P>0.05） between the experimental group and the control group in terms of baseline data such as age, gender, time from injury to admission, time from admission to surgery and the intraoperative bleeding. The surgical duration of the experimental group was significantly shorter than that of the control group [42.1（28.5, 50.7）min vs. 53.4（36.9, 62.5） min, Z=-2.338, P=0.019]. The intraoperative X-ray fluoroscopy frequency of the experimental group was significantly lower than that of the control group[8.0 （6.0, 11.0） times vs. 15.0（13.0, 17.0） times, Z=-5.960, P<0.001]. In terms of postoperative hip joint function, there was no significant difference in Harris score between the two groups of patients at 6-month follow-up（P>0.05）. CONCLUSION: Compared with manual operation of FNS, orthopedic robot assisted FNS in the treatment of femoral neck fractures can help shorten surgical time, reduce intraoperative fluoroscopy frequency, and have similar therapeutic effects on long-term hip joint function recovery.

Remediation of polycyclic aromatic hydrocarbons polluted soil by biochar loaded humic acid activating persulfate: performance, process and mechanisms.

The remediation for polycyclic aromatic hydrocarbons contaminated soil with cost-effective method has received significant public concern, a composite material, therefore, been fabricated by loading humic acid into biochar in this study to activate persulfate for naphthalene, pyrene and benzo(a)pyrene remediation. Experimental results proved the hypothesis that biochar loaded humic acid combined both advantages of individual materials in polycyclic aromatic hydrocarbons adsorption and persulfate activation, achieved synergistic performance in naphthalene, pyrene and benzo(a)pyrene removal from aqueous solution with efficiency reached at 98.2%, 99.3% and 90.1%, respectively. In addition, degradation played a crucial role in polycyclic aromatic hydrocarbons remediation, converting polycyclic aromatic hydrocarbons into less toxic intermediates through radicals of ·SO4-, ·OH, ·O2-, and 1O2 generated from persulfate activation process. Despite pH fluctuation and interfering ions inhibited remediation efficiency in some extent, the excellent performances of composite material in two field soil samples (76.7% and 91.9%) highlighted its potential in large-scale remediation.

Effects of depth of straw returning on maize yield potential and greenhouse gas emissions.

Appropriate straw incorporation has ample agronomic and environmental benefits, but most studies are limited to straw mulching or application on the soil surface. To determine the effect of depth of straw incorporation on the crop yield, soil organic carbon (SOC), total nitrogen (TN) and greenhouse gas emission, a total of 4 treatments were set up in this study, which comprised no straw returning (CK), straw returning at 15 cm (S15), straw returning at 25 cm (S25) and straw returning at 40 cm (S40). The results showed that straw incorporation significantly increased SOC, TN and C:N ratio. Compared with CK treatments, substantial increases in the grain yield (by 4.17~5.49% for S15 and 6.64~10.06% for S25) were observed under S15 and S25 treatments. S15 and S25 could significantly improve the carbon and nitrogen status of the 0-40 cm soil layer, thereby increased maize yield. The results showed that the maize yield was closely related to the soil carbon and nitrogen index of the 0-40 cm soil layer. In order to further evaluate the environmental benefits of straw returning, this study measured the global warming potential (GWP) and greenhouse gas emission intensity (GHGI). Compared with CK treatments, the GWP of S15, S25 and S40 treatments was increased by 9.35~20.37%, 4.27~7.67% and 0.72~6.14%, respectively, among which the S15 treatment contributed the most to the GWP of farmland. GHGI is an evaluation index of low-carbon agriculture at this stage, which takes into account both crop yield and global warming potential. In this study, GHGI showed a different trend from GWP. Compared with CK treatments, the S25 treatments had no significant difference in 2020, and decreased significantly in 2021 and 2022. This is due to the combined effect of maize yield and cumulative greenhouse gas emissions, indicating that the appropriate straw returning method can not only reduce the intensity of greenhouse gas emissions but also improve soil productivity and enhance the carbon sequestration effect of farmland soil, which is an ideal soil improvement and fertilization measure.

The ubiquitin-proteasome system in the plant response to abiotic stress: Potential role in crop resilience improvement.

The post-translational modification (PTM) of proteins by ubiquitination modulates many physiological processes in plants. As the major protein degradation pathway in plants, the ubiquitin-proteasome system (UPS) is considered a promising target for improving crop tolerance drought, high salinity, extreme temperatures, and other abiotic stressors. The UPS also participates in abiotic stress-related abscisic acid (ABA) signaling. E3 ligases are core components of the UPS-mediated modification process due to their substrate specificity. In this review, we focus on the abiotic stress-associated regulatory mechanisms and functions of different UPS components, emphasizing the participation of E3 ubiquitin ligases. We also summarize and discuss UPS-mediated modulation of ABA signaling. In particular, we focus our review on recent research into the UPS-mediated modulation of the abiotic stress response in major crop plants. We propose that altering the ubiquitination site of the substrate or the substrate-specificity of E3 ligase using genome editing technology such as CRISPR/Cas9 may improve the resistance of crop plants to adverse environmental conditions. Such a strategy will require continued research into the role of the UPS in mediating the abiotic stress response in plants.

Size Dependent Phase Transformation of Liquid Gallium.

As the most popular liquid metal (LM), gallium (Ga) and its alloys are emerging as functional materials due to their unique combination of fluidic and metallic properties near room temperature. As an important branch of utilizing LMs, micro- and submicron-particles of Ga-based LM are widely employed in wearable electronics, catalysis, energy, and biomedicine. Meanwhile, the phase transition is crucial not only for the applications based on this reversible transformation process, but also for the solidification temperature at which fluid properties are lost. While Ga has several solid phases and exhibits unusual size-dependent phase behavior. This complex process makes the phase transition and undercooling of Ga uncontrollable, which considerably affects the application performance. In this work, extensive (nano-)calorimetry experiments are performed to investigate the polymorph selection mechanism during liquid Ga crystallization. It is surprisingly found that the crystallization temperature and crystallization pathway to either α -Ga or ß -Ga can be effectively engineered by thermal treatment and droplet size. The polymorph selection process is suggested to be highly relevant to the capability of forming covalent bonds in the equilibrium supercooled liquid. The observation of two different crystallization pathways depending on the annealing temperature may indicate that there exist two different liquid phases in Ga.

Strain-driven Kovacs-like memory effect in glasses.

Studying complex relaxation behaviors is of critical importance for understanding the nature of glasses. Here we report a Kovacs-like memory effect in glasses, manifested by non-monotonic stress relaxation during two-step high-to-low strains stimulations. During the stress relaxation process, if the strain jumps from a higher state to a lower state, the stress does not continue to decrease, but increases first and then decreases. The memory effect becomes stronger when the atomic motions become highly collective with a large activation energy, e.g. the strain in the first stage is larger, the temperature is higher, and the stimulation is longer. The physical origin of the stress memory effect is studied based on the relaxation kinetics and the in-situ synchrotron X-ray experiments. The stress memory effect is probably a universal phenomenon in different types of glasses.

Evolutionary and Developmental Specialization of Foveal Cell Types in the Marmoset.

In primates, high-acuity vision is mediated by the fovea, a small specialized central region of the retina. The fovea, unique to the anthropoid lineage among mammals, undergoes notable neuronal morphological changes during postnatal maturation. However, the extent of cellular similarity across anthropoid foveas and the molecular underpinnings of foveal maturation remain unclear. Here, we used high throughput single cell RNA sequencing to profile retinal cells of the common marmoset ( Callithrix jacchus ), an early divergent in anthropoid evolution from humans, apes, and macaques. We generated atlases of the marmoset fovea and peripheral retina for both neonates and adults. Our comparative analysis revealed that marmosets share almost all its foveal types with both humans and macaques, highlighting a conserved cellular structure among primate foveas. Furthermore, by tracing the developmental trajectory of cell types in the foveal and peripheral retina, we found distinct maturation paths for each. In-depth analysis of gene expression differences demonstrated that cone photoreceptors and Müller glia, among others, show the greatest molecular divergence between these two regions. Utilizing single-cell ATAC-seq and gene-regulatory network inference, we uncovered distinct transcriptional regulations differentiating foveal cones from their peripheral counterparts. Further analysis of predicted ligand-receptor interactions suggested a potential role for Müller glia in supporting the maturation of foveal cones. Together, these results provide valuable insights into foveal development, structure, and evolution. Significance statement: The sharpness of our eyesight hinges on a tiny retinal region known as the fovea. The fovea is pivotal for primate vision and is susceptible to diseases like age-related macular degeneration. We studied the fovea in the marmoset-a primate with ancient evolutionary ties. Our data illustrated the cellular and molecular composition of its fovea across different developmental ages. Our findings highlighted a profound cellular consistency among marmosets, humans, and macaques, emphasizing the value of marmosets in visual research and the study of visual diseases.

[Adsorption Performance of Walnut Green Husk Biochar for Heavy Metals].

The biochars of WP300, WP500, and WP700 were prepared by pyrolyzing walnut green husk under 300℃, 500℃, and 700℃ with the oxygen-free condition for removing Pb2+, Cu2+, and Cd2+ in an aqueous solution. The results revealed that WP500 prepared under the medium pyrolysis temperature achieved the best adsorption performance for heavy metals, and the highest removal efficiency was reached when the solution pH was 8, in which the removal efficiency of Pb2+, Cu2+, and Cd2+ were 97.87%, 99.78%, and 71.15%, respectively. The required biochar dosage for heavy metal removal varied under different adsorption conditions. In the single-metal system, the optimal dosage for WP500 in the Pb2+, Cu2+, and Cd2+ solutions was 1.3 g·L-1, 2.1 g·L-1, and 1.9 g·L-1, respectively, whereas in the pollution metals system, the optimal biochar dosage was 5.1 g·L-1. In addition, the adsorption capacity of WP500 for the three heavy metals followed the order of Pb2+>Cu2+>Cd2+ under the single and combined-metals system, indicating that there were no synergistic or antagonistic effects among these three adsorbates. The fitting results of the adsorption isotherm model suggested that various immobilization methods existed in adsorption process between WP500 and Pb2+, Cu2+, and Cd2+. The kinetic fitting results suggested that the main reaction between WP500 and Pb2+, Cu2+, and Cd2+ was chemical adsorption. The mechanisms of WP500 for heavy metals involved pore-filling, electrostatic attraction, ion-exchange, mineral precipitation, complexation, and π-π electron donor-accepter interaction. To conclude, this study offered a new insight for the resource utilization of the waste walnut green husk.

[Effectiveness of proximal femur bionic nail for intertrochanteric fracture in the elderly].

Objective: To evaluate effectiveness of proximal femur bionic nail (PFBN) in treatment of intertrochanteric fractures in the elderly compared to the proximal femoral nail antirotation (PFNA). Methods: A retrospective analysis was made on 48 geriatric patients with intertrochanteric fractures, who met the selection criteria and were admitted between January 2020 and December 2022. Among them, 24 cases were treated with PFBN fixation after fracture reduction (PFBN group), and 24 cases were treated with PFNA fixation (PFNA group). There was no significant difference in baseline data such as age, gender, cause of injury, side and type of fracture, time from injury to operation, and preoperative mobility score, American Society of Anesthesiologists (ASA) score, Alzheimer's disease degree scoring, self-care ability score, osteoporosis degree (T value), and combined medical diseases between the two groups ( P>0.05). The operation time, intraoperative blood loss, number of blood transfusions, transfusion volume, length of hospital stay, occurrence of complications, weight-bearing time after operation, and postoperative visual analogue scale (VAS) score, walking ability score, mobility score, self-care ability score were recorded and compared between the two groups. And the radiographic assessment of fracture reduction quality and postoperative stability, and fracture healing time were recorded. Results: The operations in both groups were successfully completed. All patients were followed up 6-15 months with an average time of 9.8 months in PFBN group and 9.6 months in PFNA group. The operation time was significantly longer in PFBN group than in PFNA group ( P<0.05), but there was no significant difference in intraoperative blood loss, number of blood transfusions, transfusion volume, length of hospital stay, change in activity ability score, and change in self-care ability score between the two groups ( P>0.05). The weight-bearing time after operation was significantly shorter in PFBN group than in PFNA group ( P<0.05), and the postoperative VAS score and walking ability score were significantly better in PFBN group than in PFNA group ( P<0.05). Radiographic assessment showed no significant difference in fracture reduction scores and postoperative stability scores between the two groups ( P>0.05). All fractures healed and there was no significant difference in fracture healing time between the two groups ( P>0.05). The incidence of complications was significantly lower in PFBN group (16.7%, 4/24) than in PFNA group (45.8%, 11/24) ( P<0.05). Conclusion: Compared with PFNA, PFBN in the treatment of elderly intertrochanteric fractures can effectively relieve postoperative pain, shorten bed time, reduce the risk of complications, and facilitate the recovery of patients' hip joint function and walking ability.

Influence of psychological capital on core competency for new nurses.

BACKGROUND: The development of core competency is crucial for the success of new nurses, enabling them to deliver high-quality care. Psychological capital (PsyCap), encompassing self-efficacy, optimism, hope, and resilience, significantly influences individuals' abilities and achievements across various professions. However, limited research has specifically examined the impact of PsyCap on the core competency of new nurses. This study aims to bridge this gap by investigating the relationship between PsyCap and core competency development in new nurses, providing valuable strategic insights for improving PsyCap and promoting core competence acquisition. METHODS: 142 new nurses were chosen for the investigation using a convenient cluster sampling method. The questionnaire included components on socio-demographic characteristics, the Competency Inventory for Registered Nurses (CIRN), and the PsyCap Questionnaire-24 (PCQ-24). The t-test, One-Way ANOVA, Pearson correlation analysis and hierarchical multiple regression were used for statistical analysis. RESULT: The number of valid questionnaires was 138, and the effective return rate was 97.2%. The overall mean score for core competencies was 171.01 (SD 25.34), and the PsyCap score was 104.76(SD 13.71). The PsyCap of new nurses was highly correlated with core competency, with a correlation coefficient of r = 0.7, p < 0.01. Self-efficacy of PsyCap is a significant independent predictor of core competency (adjust R2 = 0.49). CONCLUSION: Self-efficacy in PsyCap is an important predictor of new nurses' core competency. Nursing managers should pay sufficient attention to the cultivation and development of new nurses' PsyCap, with particular emphasis on enhancing self-efficacy to improve their core competency.

Salt altered rhizosphere fungal community and induced soybean recruit specific species to ameliorate salt stress.

Different crop genotypes showed different adaptability to salt stress, which is partly attributable to the microorganisms in the rhizosphere. Yet, knowledge about how fungal communities of different genotypes in soybean respond to salt stress is limited. Here, qPCR and ITS sequencing were used to assess the response of rhizobial fungal communities of resistant and susceptible soybean to salt stress. Moreover, we isolated two fungal species recruited by resistant soybeans for validation. The assembly of fungal community structure might be strongly linked to alterations in fungal abundance and soil physicochemical properties. Salt stress derived structural differences in fungal communities of resistant and susceptible genotypes. The salt-resistant genotype appeared to recruit some fungal taxa to the rhizosphere to help mitigating salt stress. An increase of fungal taxa with predicted saprotrophic lifestyles might help promoting plant growth by increasing nutrient availability to the plants. Compared with the susceptible genotypes, the resistant genotypes had more stronger network structure of fungi. Lastly, we verified that recruited fungi, such as Penicillium and Aspergillus, can soybean adapt to salt stress. This study provided a promising approach for rhizospheric fungal community to enhance salt tolerance of soybean from the perspective of microbiology and ecology.

Detecting the exponential relaxation spectrum in glasses by high-precision nanocalorimetry.

Nonexponential relaxations are universal characteristics for glassy materials. There is a well-known hypothesis that nonexponential relaxation peaks are composed of a series of exponential events, which have not been verified. In this Letter, we discover the exponential relaxation events during the recovery process using a high-precision nanocalorimetry, which are universal for metallic glasses and organic glasses. The relaxation peaks can be well fitted by the exponential Debye function with a single activation energy. The activation energy covers a broad range from α relaxation to ß relaxation and even the fast γ/ß' relaxation. We obtain the complete spectrum of the exponential relaxation peaks over a wide temperature range from 0.63Tg to 1.03Tg, which provides solid evidence that nonexponential relaxation peaks can be decomposed into exponential relaxation units. Furthermore, the contribution of different relaxation modes in the nonequilibrium enthalpy space is measured. These results open a door for developing the thermodynamics of nonequilibrium physics and for precisely modulating the properties of glasses by controlling the relaxation modes.

Safety and effectiveness of fluorescence laparoscopy in precise hepatectomy: A meta-analysis.

BACKGROUND: To perform a systematic review of the safety and effectiveness of fluorescence laparoscopy-guided precise hepatectomy. METHODS: We searched the PubMed, Embase, Web of Science, and Cochrane Library databases from inception to December 1, 2022, using the search terms "indocyanine green," "ICG," "infracyanine green," "laparoscopy," "liver resection," and "hepatectomy." After performing a methodological quality assessment of the included studies, the overall results were subjected to meta-analysis using Review Manager 5.3. RESULTS: After screening, the meta-analysis included a total of 13 articles. The studies included 1,115 patients who were grouped into the fluorescence laparoscopy (490 patients) and conventional laparoscopy (625 patients) groups. All articles included in the meta-analysis were of high quality. The results of the meta-analysis revealed that compared to the conventional laparoscopy group, the fluorescence laparoscopy group had a higher R0 resection rate (odds ratio=4.03, 95% confidence interval [1.50, 10.83], P = 0.006), lower blood transfusion rate (odds ratio=0.46, 95% confidence interval [0.21, 0.97], P = 0.04) and lower blood loss (mean difference=-36.58; 95% confidence interval [-59.75, -13.41], P = 0.002). However, the length of hospital stay, operative time, and incidence of postoperative complications did not differ significantly between both groups (P>0.05). CONCLUSION: Compared to conventional laparoscopy, fluorescence laparoscopy provides better application effects in hepatectomy. The surgical procedure has demonstrated good safety and feasibility, which make it worthy of popularization.

The Design of a Novel 2-42 GHz MEMS True-Time Delay Network for Wideband Phased Array Systems.

This article presents the design method of a compact MEMS switched-line true-time delay line (TTDL) network over a wide frequency range extending from 2 to 42 GHz using TTDL units. The TTDL units, namely the cascading radio frequency micro-electromechanical system (RF MEMS) switches and GCPW, were employed in the proposed TTDL network to improve the delay-bandwidth product (DBW) while maintaining its compact size and low delay variation (DV). For comparison, a theoretical analysis of the RF MEMS switch was performed while observing the switch performance with various top electrodes. The MEMS TTDL network has a compact size of 5 mm × 5 mm, with a maximum delay of 200 ps and a minimum of 30 ps. The maximum insertion loss of 9 states is 10 dB, and the in/out return loss is better than 20 dB across 2-42 GHz. The group delay variations are within ±2.5% for all the delay states over the operating frequency range. To the best of our knowledge, the proposed TTDL network obtains the most control bits among the TTDL networks offered to date.