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Rapid and facile self-assembly coatings play a crucial role in surface functionalization of materials. In this study, a safe, fast, and environmentally friendly method is proposed to form a metal-phenolic network (MPN) through the assembly of gallic acid (GA) and iron ions ([Fe.sup.3+]), which is used for the in situ polymerization coating of l,3,5,7-tetranitro-l,3,5-7-tetrazacyclooctane (HMX). The surface of the modified HMX crystals become visibly roughened. Thermoplastic polyurethane (TPU) was coated on the surface of modified HMX by water suspension method to form HMX@MPN@TPU double-layer core-shell energetic composite material. Compared with the raw material HMX, the [beta]-[delta] phase transition temperature of the double-layer core-shell structure composite increased by 12.36[degrees]C, the impact sensitivity and friction sensitivity decreased, and the compressive strength increased by 38%, which effectively improved its mechanical properties. Highlights * It has been demonstrated that metal-phenolic networks can self-assemble on the surface of crystals. * A water suspension method was employed to prepare energetic material powder into a polymer-bonded explosive (PBX). * The modified PBX showed significant improvements in various properties, indicating that metal-phenolic networks can serve as excellent modifying materials. KEYWORDS bilayer core-shell energetic composite, HMX, in situ polymerization method, metal-phenolic network, 1 | INTRODUCTION Energetic materials have the advantages of high energy density, high combustion speed, and high explosiveness, so they have attracted wide attention in the military field. (1-3) Among [...]

In the past decades, explosive numbers of Internet of Things (IoT) devices (objects) have been connected to the Internet, which enable users to access, control, and monitor their surrounding phenomenons at anytime and anywhere. To provide seamless interactions between the cyber world and the real world, Digital twins (DTs) of objects (IoT devices) are key enablers for real time monitoring, behaviour simulations, and predictive decisions on objects. Compared to centralized cloud computing, mobile edge computing (MEC) has been envisioning as a promising paradigm for low latency IoT applications. Accelerating the usage of DTs in MEC networks will bring unprecedented benefits to diverse services, through the co-evolution between physical objects and their virtual DTs, and DT-assisted service provisioning has attracted increasing attention recently. In this article, we consider novel DT placement and migration problems in an MEC network with the mobility assumption of objects and users, by jointly considering the freshness of DT data and the service cost of users requesting for DT data. To this end, we first propose an algorithm for the DT placement problem with the aim to minimize the sum of the DT update cost of objects and the total service cost of users requesting for DT data, through efficient DT placements and resource allocation to process user requests. We then devise an approximation algorithm with a provable approximation ratio for a special case of the DT placement problem when each user requests the DT data of only one object. Meanwhile, considering the mobility of users and objects, we devise an online, two-layer scheduling algorithm for DT migrations to further reduce the total service cost of users within a given finite time horizon. We finally evaluate the performance of the proposed algorithms through experimental simulations. The simulation results show that the proposed algorithms are promising. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Vehicles (UAVs) have gained increasing attention by both academic and industrial communities, due to their flexible deployment and efficient line-of-sight communication. Recently, UAVs equipped with base stations have been envisioned as a key technology to provide 5G network services for mobile users. In this article, we provide timely services on the data streams of mobile users in a UAV-aided Mobile Edge Computing (MEC) network, in which each UAV is equipped with a 5G small-cell base station for communication and data processing. Specifically, we first formulate a flow-time minimization problem by jointly caching services and offloading tasks of mobile users to the UAV-aided MEC with the aim to minimize the flow time, where the flow time of a user request is referred to the time duration from the request issuing time point to its completion point, subject to resource and energy capacity on each UAV. We then propose a spatial-temporal learning optimization framework. We also devise an online algorithm with a competitive ratio for the problem based upon the framework, by leveraging the round-robin scheduling and dual fitting techniques. Finally, we evaluate the performance of the proposed algorithms through experimental simulation. The simulation results demonstrate that the proposed algorithms outperform their comparison counterparts, by reducing the flow time no less than 19% on average. [ABSTRACT FROM AUTHOR]

A new type of energetic composite with a double-coating structure was constructed by in-situ polymerization of dopamine and water suspension method. Using CL-20 with a particle size of 200–500 nm as the main explosive, the core–shell structured CL-20-p (CL-20@PDA) was prepared via self-polymerization of dopamine on the surface of the CL-20. After that, thermoplastic polyurethane (TPU, Estane5703) was used as the binder, the CL-20-p was coated by water suspension method, and finally CL-20-p/Estane5703 composite was prepared. The structure and properties of the samples were characterized by SEM, AFM, FTIR, XPS, Raman, XRD, DSC and mechanical sensitivity test. The test results show that the CL-20-p is successfully coated by Estane5703, and the coating degree is high. Compared with the CL-20, the crystal phase transition temperature of CL-20/Estane5703 is significantly increased, and the mechanical sensitivity is greatly reduced. The CL-20-p/Estane5703 is superior to CL-20-p and CL-20/Estane5703 in enhanced thermal stability and reduced mechanical sensitivity. [ABSTRACT FROM AUTHOR]

Flexible wearable strain sensors are crucial in human–machine interfaces, electronic skins, and human movement detection. However, simultaneously achieving high sensitivity and a large response range persists as a significant issue, and trade-offs often exist between them. In this work, thermoplastic polyurethane (TPU) fibrous membranes are prepared by utilizing electrospinning technology and used as a flexible substrate. Silver nanoparticles (AgNPs) are securely sputtered on the TPU fibrous membrane by magnetron sputtering, which enhances the sensitivity due to their small dimensions. Meanwhile, CNTs were anchored through ultrasonication to serve as an additional conductive layer to expand the response range due to their large aspect ratio. The obtained TPU/Ag/CNT fibrous membrane possesses exceptional mechanical properties (stress up to 10.44 MPa, strain up to 606.7%). The TPU/Ag/CNT-based strain sensor exhibits remarkable sensing properties of high sensitivity (gauge factor up to 6834), a large response range (up to 604% strain), and fast response and recovery times (response time is 122 ms, recovery time is 164 ms), along with an extremely low detection limit (0.1%). Moreover, it shows remarkable cycling stability, maintaining its performance for over 1000 cycles. Due to these outstanding advantages, TPU/Ag/CNT strain sensors have exceptional capacity to detect human movement and demonstrate a certain potential in the development of flexible strain sensors. [ABSTRACT FROM AUTHOR]

Background: To investigate the distribution pattern of V1+2d in the left superior pulmonary vein and its clinical significance. Methods: A retrospective analysis was conducted using three‐dimensional computed tomographic bronchography and angiography (3D‐CTBA) data from 500 lung cancer patients. Statistical analyses were performed to evaluate the incidence and drainage patterns of the three sub‐branches of V1+2d, namely V1+2d1, V1+2d2 and V1+2d3. Furthermore, clinical data from 10 patients' lesions involving V1+2d were reviewed to illustrate the impact of adjacency to V1+2d on the surgical approach. Results: The incidences of V1+2d1, V1+2d2 and V1+2d3 were 100%, 76.4% and 100% respectively. The relative interlobar distribution sizes of B3a and B1+2c and the left upper division (LUD) vein type influenced the incidence of V1+2d2 (p < 0.05; p < 0.001). V1+2d2 predominantly occurred in B3a = B1+2c and B1+2c > B3a patterns. V1+2d2 was entirely absent in the B3a > B1+2c pattern. V1+2d2 exhibited a higher incidence in both the central vein (CV) type and the noncentral vein (NCV) type when compared to the semi‐central vein (SCV) type (100% vs. 100% vs. 64.8%). The most prevalent venous drainage pattern was the three sub‐branches of V1+2d constituting a major trunk to drain (41.2%). All 10 cases with lesions involving V1+2d successfully underwent sublobar resection with no complications, and the surgical margin was ≥2 cm. Conclusions: The three sub‐branches of V1+2d exhibit a high incidence with diverse distribution patterns, yet a discernible pattern exists. For inter‐ or multi‐intersegmental nodules involving V1+2d, combined segmentectomy and subsegmentectomy or combined subsegmentectomy can ensure the safe margin. [ABSTRACT FROM AUTHOR]

Enhancing the safety performance of conventional polymer‐bonded explosives (PBX) has been a hot topic of research in the field of energy‐containing materials. For this purpose, this paper proposes a green and simple method to apply tannic acid (TA) to PBX by in situ polymerization. A two‐layer core‐shell composite with HMX as the core, TA as the inner shell, and fluoroelastomer F2602 as the outer shell was designed without changing the total binder content. The composites were analyzed by various tests and the goal of improving safety and mechanical strength was accomplished in the prepared TA‐modified PBX. Compared with the raw material HMX, the β‐δ phase transition temperature of PBX with double‐layer core‐shell structure is increased by 15.3 °C. In addition, the combination of TA coating and fluoropolymer allows the PBX to reduce impact and friction sensitivity. It also has excellent performance in enhancing the mechanical performance of PBX. The simplicity and scalability of the described method provide new ideas for the design and fabrication of high‐energy composites with higher safety and mechanical properties. [ABSTRACT FROM AUTHOR]

Background: Segmentectomy has been recommended for ground glass opacity (GGO)‐dominant small‐sized non–small cell lung cancer (NSCLC) or those with GGO component. Pure solid NSCLC is a special sub‐type and has an inferior prognosis. Whether segmentectomy could achieve comparable long‐term outcomes with lobectomy for pure solid small‐sized NSCLC remained controversial. This study aimed to compare the prognosis of segmentectomy and lobectomy for pure solid NSCLC. Methods: NSCLC patients with a pure solid nodule (≤2 cm) who received segmentectomy or lobectomy between January 2010 and June 2019 were retrospectively screened. Log‐rank test, univariable, and multivariable Cox regression analyses were used for prognostic comparison. Further, the propensity score matching analysis was adopted to yield a matched cohort. Results: After screening, 344 pure solid NSCLC patients with a median follow‐up time of 56 months were reserved. Among them, 98 patients underwent segmentectomy and the other 246 subjects received lobectomy. The lobectomy group had a larger tumor size, a higher rate of lymph node metastasis than the segmentectomy arm. Generally, patients with segmentectomy had a better disease‐free survival (DFS) (p = 0.011) and overall survival (OS) (p = 0.028) than those with lobectomy. However, the multivariable Cox regression analysis indicated that no significant survival difference existed between segmentectomy and lobectomy after adjusting the potential confounding factors (DFS: hazard ratio [HR], 0.72; 95% confidence interval [CI], 0.30–1.77, p = 0.476; OS: HR, 0.36; 95% CI, 0.08–1.59, p = 0.178). Consistently, in the propensity score matched cohort, segmentectomy (n = 74) yielded similar DFS (p = 0.960) and OS (p = 0.320) with lobectomy (n = 74). Conclusions: Segmentectomy could achieve comparable oncological outcomes with lobectomy for pure solid small‐sized NSCLC. [ABSTRACT FROM AUTHOR]

Background: Tumor size and consolidation‐to‐tumor ratio (CTR) are crucial for non–small cell lung cancer (NSCLC) prognosis. However, the optimal CTR cutoff remains unclear. Whether tumor size and CTR are independent prognostic factors for part‐solid NSCLC is under debate. Here, we aimed to evaluate the prognostic impacts of CTR and tumor size on NSCLC, especially on part‐solid NSCLC. Methods: We reviewed 1366 clinical T1 NSCLC patients who underwent surgical treatment. Log‐rank test and Cox regression analyses were adopted for prognostic evaluation. The "surv_cutpoint" function was used to identify the optimal CTR and tumor size cutoff values. Results: There were 416, 510, and 440 subjects with pure ground‐glass opacity (pGGO), part‐solid, and pure solid nodules. The 5‐year overall survival (disease‐free survival) for patients with pGGO, part‐solid, and pure solid nodules were 99.5% (99.5%), 97.3% (95.8%), and 90.4% (78.9%), respectively. Multivariate Cox regression analysis indicated that CTR was an independent prognostic factor for the whole patients, and the optimal CTR cutoff was 0.99. However, for part‐solid NSCLC, CTR was not independently associated with survival, even if categorized by the optimal cutoffs. The predicted optimal cutoffs of total tumor size and solid component size were 2.4 and 1.4 cm for part‐solid NSCLC. Total tumor size (HR = 6.21, 95% CI: 1.58–24.34, p = 0.009) and solid component size (HR = 2.27, 95% CI: 1.04–5.92, p = 0.045) grouped by the cutoffs were significantly associated with part‐solid NSCLC prognosis. Conclusions: CTR was an independent prognostic factor for the whole NSCLC, but not for the part‐solid NSCLC. Tumor size was still meaningful for part‐solid NSCLC. [ABSTRACT FROM AUTHOR]

Wide‐range DC/DC converters are widely used in telecommunications, electric vehicles, and e‐bikes. In this paper, the operation characteristics of the wide‐range cascaded buck converter with two duty cycles are investigated. The operation principle of switched‐capacitor and switched‐inductor is analyzed to ensure that there are no current or voltage spikes in the system and no additional control is required for them. Based on the volume and efficiency performance indexes, the optimal operating region of the converter should be selected to the left side of the minimum sum point of the two duty cycles. The small signal model of the converter is established, then a control strategy is proposed that the first‐stage duty cycle is directly given based on the optimal operating region, and the second‐stage duty cycle is determined by double closed‐loop control, which has good control performance, economy, and simplicity. The prototype achieved the conversion of 32 to80 V to 5 V/6 A with peak efficiencies of 92.4%/80 V, 93.8%/48 V, 94.5%/32 V. The results proved that the control strategy enables the converter to realize high efficiency and rapid dynamic regulation even in the condition of high voltage gain and wide input range. [ABSTRACT FROM AUTHOR]

Unbalanced ac voltages drastically deteriorate the performance of five-level flying capacitor (FC) rectifiers. Without introducing an extra buffering circuit to absorb the second-order oscillating power, it is an incompatible contradiction for realizing both negative-sequence current reduction and second-order voltage ripple suppression. In this article, based on the idea of using FCs in the rectifier to absorb the oscillating power, a second-order voltage ripple suppression strategy for unbalanced ac voltage conditions is proposed. Reducing the negative-sequence currents and suppressing the dc voltage ripples can be simultaneously realized. Simulations and experimental results verified the effectiveness and performance of the proposed scheme well. [ABSTRACT FROM AUTHOR]

Provisioning reliable network services for mobile users in edge computing environments is the top priority of network service providers, as unreliable services will result in tremendous losses of revenues and customers. In this paper, we study a novel service reliability augmentation problem in a mobile edge computing (MEC) network, where mobile users request network services with service function chain (SFC) and reliability expectation requirements. To enhance the service reliability of user requests, it is a common practice to make use of redundant virtualized network function (VNF) instance placement in case the primary VNF instance fails. We aim to augment the service reliability of each admitted request to its specified reliability expectation, subject to computing capacity on each cloudlet. To this end, we first formulate a novel service reliability augmentation problem for each request with an SFC and a reliability expectation requirement, by augmenting its reliability through redundant VNF instance deployment. We then show that the problem is NP-hard, and provide an admission framework of user requests by placing primary VNF instances of network functions in the SFC to different cloudlets. We then deal with the service reliability augmentation problem of an admitted request under the assumption that all secondary VNF instances of each primary VNF instance must be placed into the cloudlets no more than $l$ l hops from the cloudlet of its primary VNF instance for a fixed $l$ l with $1\leq l \leq n-1$ 1 ≤ l ≤ n - 1 , where $n$ n is the number of cloudlets in the network, for which we formulate an integer linear program solution, and develop a randomized algorithm with a good approximation ratio and high probability, at the expense of moderate resource constraint violations. We also devise a deterministic heuristic for the problem without any resource violation. We third study the service reliability augmentation problem for a set of admitted requests by extending the proposed algorithm for the service reliability augmentation problem for a single request admission. We finally evaluate the performance of the proposed algorithms through experimental simulations. Experimental results demonstrate that the proposed algorithms are promising, and their empirical results are superior to their analytical counterparts. [ABSTRACT FROM AUTHOR]

Five-level flying capacitor (5L-FC) rectifier is advantageous in unidirectional power applications due to its less power devices, higher power density, better reliability, etc. To further improve the efficiency, discontinuous PWM (DPWM) methods are preferred. This article investigates a carrier-based implementation of DPWM for the 5L-FC rectifier to reduce the switching losses. Since there is always a pair of redundant switching modes that have opposite effects on the neutral point (NP) in each region of the space-vector diagram, the NP voltage regulation can be easily realized by selecting suitable clamping modes in each control period, even with unbalanced dc loads. The generated PWM sequences based on the phase disposition PWM are also optimally redistributed to realize minimal switching loss with FC voltage balancing in two consecutive carrier periods. In addition, the permissible range of unbalanced dc loads is theoretically deduced. Finally, simulations and experiments are conducted to verify the performance of the proposed carrier-based DPWM scheme. [ABSTRACT FROM AUTHOR]