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As the most outstanding type of organic fiber in terms of the comprehensive performance, polyimide fiber is more conducive to reduce the composites weight than inorganic fibers, such as carbon fiber or glass fiber. A polyimide-fabric-reinforced polyether ether ketone (PEEK) composite was prepared by a hot-press molding process. The melt flow rate of the PEEK resin was measured to reveal its rheological behavior and guide the selection of the molding process parameters of the composite. The tensile properties of the composites were determined. The results revealed that the rheological properties of the resin manifested through the melt viscosity, which was more sensitive to pressure changes than to temperature changes. The tensile properties of the composites were affected by two competitive mechanisms. First, increases of molding temperature and duration time could facilitate the infiltration of the resin into the fiber fabric and improve the internal quality and tensile properties of the composite. Second, an excessively high molding temperature and long duration time could decrease the strength of the polyimide fiber, thereby reducing the tensile properties of the composites.

Although growth arrest-specific protein 2 (GAS2) promotes the growth of T-cell acute lymphoblastic leukemia (T-ALL) cells in culture, the effect of GAS2 on T-cell leukemogenesis has not been studied, and the mechanism remains unclear. In the present study, xenograft studies showed that GAS2 silencing impaired T-cell leukemogenesis and decreased leukemic cell infiltration. Mechanistically, GAS2 regulated the protein expression of C-X-C chemokine receptor type 4 (CXCR4) rather than its transcript expression. Immunoprecipitation revealed that GAS2 interacted with CXCR4, and confocal analysis showed that GAS2 was partially co-expressed with CXCR4, which provided a strong molecular basis for GAS2 to regulate CXCR4 expression. Importantly, CXCR4 overexpression alleviated the inhibitory effect of GAS2 silencing on the growth and migration of T-ALL cells. Moreover, GAS2 or CXCR4 silencing inhibited the expression of NOTCH1 and c-MYC. Forced expression of c-MYC rescued the growth suppression induced by GAS2 or CXCR4 silencing. Meanwhile, GAS2 deficiency, specifically in blood cells, had a mild effect on normal hematopoiesis, including T-cell development, and GAS2 silencing did not affect the growth of normal human CD3sup+/supor CD34sup+/supcells. Overall, our data indicate that GAS2 promotes T-cell leukemogenesis through its interaction with CXCR4 to activate NOTCH1/c-MYC, whereas impaired GAS2 expression has a mild effect on normal hematopoiesis. Therefore, our study suggests that targeting the GAS2/CXCR4 axis is a potential therapeutic strategy for T-ALL.

The ablation mechanism and performance of carbon fiber (CF)-reinforced poly aryl ether ketone (PAEK) thermoplastic composites were studied in this paper. The results show that the ablation damaged area is controlled by the irradiation energy, while the mass loss rate is controlled by the irradiation power density. In the ablation center, the PAEK resin and CFs underwent decomposition and sublimation in an anaerobic environment. In the transition zone, the resin experienced decomposition and remelting in an aerobic environment, and massive char leaves were present in the cross section. In the heat-affected zone, only remelting of the resin was observed. The fusion and decomposition of the resin caused delamination and pores in the composites. Moreover, oxygen appeared crucial to the ablation morphology of CFs. In an aerobic environment, a regular cross section formed, while in an anaerobic environment, a cortex–core structure formed. The cortex–core structure of CF inside the ablation pit was caused by the inhomogeneity of fibers along the radial direction and the residual carbon layer generated by resin decomposition in an anoxic environment. The description of the ablation mechanism presented in this study broadens our understanding of damage evolution in thermoplastic composites subjected to high-energy CW laser irradiation.

Emissions of greenhouse gases such as CO2 are rapidly increasing, causing the greenhouse effect, leading to global warming and serious impacts on the ecosystem, while photovoltaic power generation can reduce the large amount of pollutants and carbon emissions produced in the traditional power generation process. The article takes the photovoltaic power generation system of the national field observatory as the research object, and uses PVsyst software to design the system of two distributed photovoltaic power generation systems. After calculating and analysing the total power of the experimental equipment, the efficiency of photovoltaic power generation and the system cost of the field observatory, the scheme and scale of the photovoltaic power generation system are determined, and the construction of the photovoltaic power generation test system is completed. Finally, through the comparison and analysis of the one-year PV power generation data with the simulated data, the feasibility of the system design method is verified, which can meet the requirements of the field experimental station and create a zero-carbon field observatory to achieve green energy conservation and sustainable energy use, which is in line with the strategic development plan of carbon peaking and carbon neutrality promoted by the state and provides a design basis and useful reference for the construction of zero-carbon field experimental stations.

Spirobichroman-based polymers with high gas permeability and selectivity are promising for their applications as membranes in gas separation. In this study, three spirobichroman-based polyimides (PIs; 6FDA-FH, 6FDA-DH, and 6FDA-MH) were synthesised by the polyreaction between diamines containing different substituents (benzene ring, pyridine ring, and methyl group) and 4,4′-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA). The physical properties, gas transport behaviour, d-spacing, dihedral angle of molecules, and fractional free volume of the PIs were investigated through experiments and molecular simulations. The PIs exhibited excellent thermal stability and good solubility in common organic solvents. The gas permeability of the PIs was investigated; the results highlighted the critical role of the substituents in the enhancement of the gas separation performance of polymer membranes. Detailed analysis of the PIs showed that 6FDA-FH exhibits the highest gas permeability. This can be ascribed to the loose packing of the polymer chain owing to the increased dihedral angle between the two planes. However, the methyl substituent in 6FDA-MH disrupts the polymer chain packing rather than changing the dihedral angle between the two planes, thus enhancing the gas permeability of 6FDA-MH. Furthermore, 6FDA-DH exhibited the highest CO2/CH4 selectivity, which is attributed to the CO2 affinity of the polymer containing the pyridine unit.

The measurement of quasi-static 3-D knee joint movement is an important basis for studying the mechanism of knee joint injury. Most of the existing measurement methods make use of computed tomography (CT) and nuclear magnetic resonance (MR) imaging technology and hence have the disadvantages of invasiveness, ionizing radiation, low accuracy, and high cost. To overcome those drawbacks, this article innovatively proposes a 3-D motion measurement system for the knee joint based on the registration of CT images to ultrasound (US) images. More specifically, the lower limbs of a subject were first scanned once to acquire the CT images. A portable handheld device was designed to control a US probe for mechanically scanning the subject's lower limbs in a linear trajectory. During the movement of the subject's lower limbs, the US scanning was performed quasi-statically. The acquired US images were then registered to the CT images, and the 3-D motions of the lower limb bones could be recreated with the bones scanned in CT images. To guarantee the registration accuracy and efficiency, we used the H-shaped multiview slice assembly as the structural image content for the registration process. The experimental results show that our approach can accurately measure the 3-D motion of the knee joint and meet the needs of 3-D motion analysis of knee joint in practice.

Electrochromic (EC)/electrofluorochromic (EFC) bifunctional materials are receiving great attention because of their promising applications in optoelectronic devices. However, the development of ideal EC/EFC bifunctional materials is still a great challenge because of the poor integration of EC/EFC performances (optical contrast, response speed, and switching stability). Herein, we reported two novel diphenylamine-based mixed valence (MV) polyamides (S-HPA and P-HPA) with spirobifluorene (2,7-positions) and pyrene (1,6-positions) as bridged fluorescence units, respectively, showing impressive cyclability and fluorescence contrast with rapid switching. Through the formation of an effective electronic coupling between the two nitrogen centers using spirobifluorene/pyrene bridges, we demonstrated that different bridges have significant effects on the thermal and electrooptical characteristics of polyamides. In addition to lower fluorescence quantum yield and glass transition temperature, the S-HPA exhibited superior cyclability (contrast change

Laser joining technology with the advantages of high efficiency and good processing flexibility has the good application prospects in the connection of the Carbon Fibre Reinforced Thermoplastics Plastics (CFRTP) and aluminum alloy. Laser joining of CFRTP and 6061 aluminum alloy is investigated with various laser processing parameters. The microstructure characteristics and energy dispersive spectroscopy (EDS) results are analyzed. Besides, the fracture morphologies of the laser connection joints are studied. The results indicate that there is a partial unconnected area between the resin and the 6061 aluminum alloy due to the existence of the air bubbles, while most of the interface area is tightly connected where the mechanical anchoring effect exists.

Concurrent systems software is widely-used, complex, and error-prone, posing a significant security risk. We introduce VRM, a new framework that makes it possible for the first time to verify concurrent systems software, such as operating systems and hypervisors, on Arm relaxed memory hardware. VRM defines a set of synchronization and memory access conditions such that a program that satisfies these conditions can be mostly verified on a sequentially consistent hardware model and the proofs will automatically hold on relaxed memory hardware. VRM can be used to verify concurrent kernel code that is not data race free, including code responsible for managing shared page tables in the presence of relaxed MMU hardware. Using VRM, we verify the security guarantees of a retrofitted implementation of the Linux KVM hypervisor on Arm. For multiple versions of KVM, we prove KVM's security properties on a sequentially consistent model, then prove that KVM satisfies VRM's required program conditions such that its security proofs hold on Arm relaxed memory hardware. Our experimental results show that the retrofit and VRM conditions do not adversely affect the scalability of verified KVM, as it performs similar to unmodified KVM when concurrently running many multiprocessor virtual machines with real application workloads on Arm multiprocessor server hardware. Our work is the first machine-checked proof for concurrent systems software on Arm relaxed memory hardware.

Practical error analysis is essential for the design, optimization, and evaluation of Noisy Intermediate-Scale Quantum(NISQ) computing. However, bounding errors in quantum programs is a grand challenge, because the effects of quantum errors depend on exponentially large quantum states. In this work, we present Gleipnir, a novel methodology toward practically computing verified error bounds in quantum programs. Gleipnir introduces the (ρ,δ)-diamond norm, an error metric constrained by a quantum predicate consisting of the approximate state ρ and its distance δ to the ideal state ρ. This predicate (ρ,δ) can be computed adaptively using tensor networks based on the Matrix Product States. Gleipnir features a lightweight logic for reasoning about error bounds in noisy quantum programs, based on the (ρ,δ)-diamond norm metric. Our experimental results show that Gleipnir is able to efficiently generate tight error bounds for real-world quantum programs with 10 to 100 qubits, and can be used to evaluate the error mitigation performance of quantum compiler transformations.

Spray flash evaporation is a method for the new desalination technology driven by renewable energy. This paper studies the flash evaporation phenomenon of the seawater jet sprayed into a low-pressure chamber. A droplet flash evaporation model has been developed to enable an in-depth understanding of the flash evaporation. This model is capable of predicting the spray flash speed, the evaporated mass rate and the flashing efficiency under different working conditions. Applying this model, the effects of different operating variables on the flash evaporation process are investigated. Results from the developed model reveal a larger Jakob number, Reynolds number and Weber number all lead to the increase of the production rate. The flashing efficiency can attain values larger than 0.9 with the nozzle diameter ranging 5–14 mm when the flash chamber is 150 mm height. The flashing efficiency with nozzle diameter of 5 mm is larger than 0.9 when the flash chamber is 25 mm height. The flow velocity of 10 m/s is recommended for the current case to obtain a large production rate. A flash chamber larger than 500 mm height is needed for complete evaporation considering the presence of dissolved salt in sea water.

Cold stress limits plant growth, development and yields, and the C-repeat binding factors (CBFs) function in the cold resistance in plants. However, how pomegranate CBF transcription factors respond to cold signal remains unclear. Considering the significantly up-regulated expression of PgCBF3 and PgCBF7 in cold-tolerant Punica granatum ‘Yudazi’ in comparison with cold-sensitive ‘Tunisia’ under 4 °C, the present study focused on the two CBF genes. PgCBF3 was localized in the nucleus, while PgCBF7 was localized in the cell membrane, cytoplasm, and nucleus, both owning transcriptional activation activity in yeast. Yeast one-hybrid and dual-luciferase reporter assay further confirmed that PgICE1 could specifically bind to and significantly enhance the activation activity of the promoters of PgCBF3 and PgCBF7. Compared with the wild-type plants, the PgCBF3 and PgCBF7 transgenic Arabidopsis thaliana lines had the higher survival rate after cold treatment; exhibited increased the contents of soluble sugar and proline, while lower electrolyte leakage, malondialdehyde content, and reactive oxygen species production, accompanying with elevated enzyme activity of catalase, peroxidase, and superoxide dismutase; and upregulated the expression of AtCOR15A, AtCOR47, AtRD29A, and AtKIN1. Collectively, PgCBFs were positively regulated by the upstream PgICE1 and mediated the downstream COR genes expression, thereby enhancing freezing tolerance.

Verifying real-world programs often requires inferring loop invariants with nonlinear constraints. This is especially true in programs that perform many numerical operations, such as control systems for avionics or industrial plants. Recently, data-driven methods for loop invariant inference have shown promise, especially on linear invariants. However, applying data-driven inference to nonlinear loop invariants is challenging due to the large numbers of and magnitudes of high-order terms, the potential for overfitting on a small number of samples, and the large space of possible inequality bounds. In this paper, we introduce a new neural architecture for general SMT learning, the Gated Continuous Logic Network (G-CLN), and apply it to nonlinear loop invariant learning. G-CLNs extend the Continuous Logic Network (CLN) architecture with gating units and dropout, which allow the model to robustly learn general invariants over large numbers of terms. To address overfitting that arises from finite program sampling, we introduce fractional sampling---a sound relaxation of loop semantics to continuous functions that facilitates unbounded sampling on real domain. We additionally design a new CLN activation function, the Piecewise Biased Quadratic Unit (PBQU), for naturally learning tight inequality bounds. We incorporate these methods into a nonlinear loop invariant inference system that can learn general nonlinear loop invariants. We evaluate our system on a benchmark of nonlinear loop invariants and show it solves 26 out of 27 problems, 3 more than prior work, with an average runtime of 53.3 seconds. We further demonstrate the generic learning ability of G-CLNs by solving all 124 problems in the linear Code2Inv benchmark. We also perform a quantitative stability evaluation and show G-CLNs have a convergence rate of $97.5\%$ on quadratic problems, a $39.2\%$ improvement over CLN models.

Fluorocontaining polymers bearing special properties are unique and important materials in modern society. In this work, we focused on the phase behavior and phase diagram of poly(styrene-block-perfluorooctylethyl acrylate) with a volume fraction varying from 0.2 to 0.8. Small-angle X-ray scattering and transmission electron microscopy showed the phase formation in the sequence of hexagonally packed cylinders (HEX) to lamellar layers (LAM) to inverse hexagonally packed cylinders (iHEX) in this series of block polymers. Wide-angle X-ray diffraction experiments proved that the fluorodomains of the LAM phases and the matrix of iHEX phases contained layered structures formed by the crystallization of fluorosegments. During heating, the self-assembled lattice remained intact even after the melting of fluorodomain, with barely changed lattice parameters. Such hierarchical structural formation was understood by chain conformation and domain interaction, which may provide new insight into the molecular design of advanced materials.

This paper aims to develop a correlation for pressure undershoot and revises the hypotheses of nucleation inception in the two-phase critical flow model. The theories of rapid depressurization and isothermal bubble growth were used to construct a modified two-phase critical flow model for leak-before-break analysis. The modified model predictions exhibit strong similarities with the experimental values compared with the Moody and Henry–Fauske models, with prediction deviations of less than 8.9% in the inter-granular stress corrosion crack. The effects of the inlet conditions on the nucleation inception point, as well as the distribution characteristics of the mass quality and void fraction along the channel, were investigated to explore the mass transfer process.

To develop colorless and soluble polyimide films, a novel dianhydride containing 1,4:3,6-dianhydro-D-mannitol unit, 2,5-bis(3,4-dicarboxyphenoxy)-1,4:3,6-dianhydromannitol dianhydride (IMDA) was synthesized. And two series of polyimides were prepared via a two-step thermal imidization, PI−(1–4) were obtained from IMDA and four kinds of aromatic diamines while PI−(5–7) from IMDA and three kinds of semiaromatic diamines. All the polyimides were readily soluble in common polar solvents and could afford flexible, tough and colorless films with transparency up to 89% at 450 nm. Especially, polyimides simultaneously containing 1,4:3,6-dianhydrohexitol units in diamine and dianhydride exhibited comparable optical and soluble performance with the alicyclic fluorinated ones. Meanwhile, it was certified that 1,4:3,6-dianhydrohexitol fragment in dianhydride was more determinant in solubility and transmittance of polyimides than that in diamine. An overall investigation of these polyimides on thermal, mechanical, morphological, soluble, optical and dielectric properties was presented, and their structure-property relationships were discussed in detail.

Forests have ecological functions such as purifying the atmosphere, fixing carbon and releasing oxygen, conserving water sources, preventing wind and sand invading, and harbouring biodiversity. At the same time, they provide human beings with materials and energy, and thus are important for economic and societal development. However, in our national power grid system, trees might cause interference on power transformation lines. Furthermore, if these circumstances cannot be responded timely, huge economic losses would happen. Therefore, research of forest growth models can more accurately predict the growth and the dynamics of forests, as well as provide a reference for the power warning system. This study conducts a forecast simulation study on the growth of eucalyptus in Guangzhou province, China, proposes a multivariate statistical analysis to predict tree species growth, and then compares its performances with traditional Logistic model results. We found that our multivariate statistical model can effectively consider various environmental influencing factors, thus predict tree height excellently (R2=0.9776), so as provide new foundations for tree height prediction.

In order to prepare novel polyimides (PI) with high transparency and solubility in common solvents, three diamine monomers containing pyridine or methyl-substituted pyridine and cyclohexane, 1,1′-bis[4-(5-amino-2-pyridinoxy)phenyl]cyclohexane (IIIa), 1,1′-bis[4-(5-amino-3-methyl-2-pyridinoxy)phenyl]cyclohexane (IIIb), and 1,1′-bis[4-(5-amino-2-methyl-6-pyridinoxy)phenyl]cyclohexane (IIIc), were synthesized and characterized. The diamine monomer (IIIa) was subsequently polymerized with 3,3′,4,4′-oxydiphthalic anhydride, 4,4′-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) to obtain PIs, PI-1 and PI-2. Furthermore, PI-3 (IIIb/6FDA) and PI-4 (IIIc/6FDA) were prepared for structure–property comparison studies. The structures of the resulting PIs were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, and elemental analysis. The physical properties of the PI films were investigated by thermogravimetric analysis, differential scanning calorimetric analysis, dynamic mechanical analysis, and ultraviolet–visible spectroscopy. In general, the PIs showed excellent thermal properties and good mechanical properties. Most had good solubility in polar organic solvents such as N, N-dimethylacetamide, N, N-dimethylformamide, N-methylpyrrolidone (NMP), m-cresol, and even soluble in low boiling solvents such as tetrahydrofuran (THF) and CHCl3. The PI films also exhibited high optical transmittance of 94–97% at 500 nm and cut-off wavelength at 345–359 nm. In summary, the introduction of methyl, cyclohexane, and pyridine groups into the backbone was shown to improve the solubility and transparency of PI films.

Polyimides (PIs) with single phenyl pendant substitution were prepared based on three diamines containing phenyl pendant group, namely, 2,5-bis(4-aminophenoxy) biphenyl, 2-phenyl-4,4′-diaminodiphenyl ether, and 2,5-diaminobiphenyl (p-PDA), with the dianhydride component of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride, respectively. The physical properties of the membranes were examined, including thermal properties, fractional free volume ( FFV), solubility, and morphological structures, and were compared with the analogues without phenyl pendant. Gas transport properties of the membranes were investigated and discussed from the viewpoint of structure–property relationship. For 6FDA-derived PI membranes, gas permeability increased as the degree of PI backbone rigidity leveled up. Gas transport properties were not improved by the incorporation of phenyl pendant group for 6FDA type containing ether linkage and marginally improved as compared between PI (6FDA/p-PDA) and PI (6FDA/p-phenylenediamine (PDA)). To increase the phenyl substitution density of 6FDA/PDA-type backbone, a novel diamine bearing two phenyl pendant groups, that is, 2,6-diphenyl-1,4-diaminobenzene (p, p′-PDA) was synthesized, and PI derived from 6FDA and p, p′-PDA was prepared. The gas permeability coefficients of PI (6FDA/p, p′-PDA) were remarkably larger than those of PI (6FDA/p-PDA) and PI (6FDA/PDA).

A simple strategy is provided to construct novel shape memory polyimides with both physical and chemical crosslinks. The resulting materials exhibited an ultrahigh strain and a multiple shape memory effect without sacrificing the shape fixity and recovery, thereby presenting its potential application in the aerospace industry.

A series of polyimide (PI) membranes were prepared based on three triphenylamine-based diamines, namely 4,4′-diaminotriphenylamine, 4,4′-diamino-3′′,5′′-dimethyltriphenylamine, and 4,4′-diamino-3′′,5′′-ditrifluoromethyltriphenylamine, via thermal imidization procedure. The PI membranes displayed good thermal properties, with glass transition temperatures of 279–341°C and 5% weight loss temperatures above 515°C under a nitrogen atmosphere. The gas permeation properties of the membranes were investigated and interpreted from the viewpoint of the PI backbone structure. The gas permeation coefficients increased as the substituent pendant groups at the 3′′,5′′ positions of the triphenylamine varied from –H to –CH3 and –CF3, and the permselectivity of gas pairs (including hydrogen/nitrogen (N2), oxygen/N2, carbon dioxide (CO2)/N2, and CO2/methane) decreased in this order. The diffusion coefficients and solubility coefficients were calculated, and the results revealed the variation of the substituted triphenylamine units principally influenced the diffusion coefficients, indicating that the substituted triphenylamine affected the gas transport properties by “diffusivity-controlled” modification.

Three-dimensional ultrasonic elastic imaging is a new medical imaging technology, which aims to obtain the elastic information of human tissues and detect pathological tissues. This paper presents a 3D quasi-static ultrasound strain imaging system using a 6-DoF robotic arm. We use the robotic arm, which has 6-DoF, to control an ultrasound probe to acquire pre-deformed and post-deformed radio frequency (RF) image frames. We use a Kinect to obtain point clouds information on the surface of tissues. Then, according to the three-dimensional contour of marker pasted in the tissue, the scanning region and path can be automatically determined. Then a method based on the method vector is used to determine the attitude of the robot arm so that the probe can be perpendicular to the plane of the scanned tissues. The result of phantom and human experiments shows that the system we proposed can create high-quality 3D quasi-static ultrasound strain images. It is expected that the system we proposed has great prospects for clinical application.

Photothermal microactuators are often used as microswitches or microgrippers in micro-electromechanical systems, whereas it is difficult to fabricate three-dimensional microactuators with a high aspect ratio, since the gravity may lead to undesired deformations during printing processes. In this work, we reported a 3D printing / UV curing process flow in the support of a hydrogel to obtain a photothermal microactuator with a high-aspect-ratio polyline waveguiding structure. The waveguiding structure also served as the driving arm. The temperature parameter was investigated by the Finite Element Method while the experiment was carried out to study the temperature and displacement during the laser actuation. A demonstration showed the driving arm achieves a free-end displacement of 133.2 µm driven by 90 mW laser (46.1°C). This study helps obtain waveguiding photothermal microactuators with integrated and more complex multi-dimensional structures.

Two kinds of electrochromic and photoluminescence-active semi-aromatic polyamide and polyimide were prepared via condensation polymerization from a novel diamine, N,N-di-(4-aminophenyl)-2-amino-9,9-diphenylfluorene, with cycloaliphatic dicarboxylic acid and dianhydride, respectively. These polymers showed excellent solubility and increased thermal stability with 10% weight loss in excess of 450 °C in a N2 atmosphere. Due to the stable electrochemistry and improved solid-state fluorescence properties, the polymer films exhibited repeatable and high-contrast electroswitching in both coloration and emission (ΔT% = 80–85%, Ioff/Ion = 152.1–177.9). Especially, the polyamide still showed excellent electroswitching stability even after hundreds of cycles.

The heat transfer performance of indirect air-cooling (IDAC) towers in large power stations is sensitive to the ambient wind velocity. To ensure the economic and reliable operation of units under windy conditions, it is important to conduct research on the optimization of different wind-break structures. This paper uses computational fluid dynamics method (CFD) to simulate the heat transfer performance of a 1000 MW IDAC tower power stations with four different wind-break structures namely, cross walls, wind-break walls, cross line-screen, and louvers. The research results show that the order of the effective heat transfer improvement of four wind-break structures is the wind-break, cross wall, line-screen and louvers. The wind-break wall is the most optimal structure, but its performance is strictly influenced by the direction and velocity of the wind, and the cross walls and cross line-screen structure have similar limitation in the practice operation. The louver is installed in each sector, and it is the next best option for increasing the heat transfer performance. It can be flexibly adjusted based on the wind direction and velocity. With the decrease in the louver opening, k , there is a decrease in the heat transfer rate of the windward sectors, and a significant increase in the heat transfer rate of the leeward sectors. Thus the total heat transfer rate of the IDAC tower can be improved tremendously. Based on the analysis of heat transfer and air flow mechanisms, there is an optimal opening, k , which achieves the largest heat transfer performance in an IDAC tower at each wind velocity. This study provides an effective and practical approach to improve the efficiency of power plants in a windy area.

To achieve the superheat-resistant polymers for flexible display substrates, two new diamines, namely 6-amine-2-(4-aminobenzene)-1-methyl-benzimidazole (m-MePABZ), 5-amine-2-(4-amino-benzene)-1-methyl-benzimidazole (p-MePABZ) containing N-methyl benzimidazole (BI) were synthesized and a serials of poly(benzimidazole imide) (PBII) films were prepared through thermal imidization. Among them, the flexible polyimide (PI) film derived from m-MePABZ and pyromellitic dianhydride (PMDA) has an ultra-low coefficient of thermal expansion (CTE) down to 2.5 ppm K−1 and an outstanding high glass-transition temperature (Tg) up to 431 °C. Furthermore, the employment of N-methyl overcame an issue of the high H2O-absorption of traditional PBIIs, and the effect of “para-” and “meta-connecting” methyl on molecular packing and properties of these PIs was investigated. These data provided a useful guide to develop high performance PBIIs by incorporating N-methyl.

To investigate the effect of introducing 2,2′-dichloro substituted biphenyl linkage into the polymer backbones on the properties of polyimides (PI), 2,2′-dichloro-4,4′,5,5′-biphenyltetracarboxylic dianhydride (DCBPDA) was polymerized with aromatic diamines, including 2,2′-bis(trifluoromethyl)benzidine (TFMB) in m-cresol to obtain a series of soluble polyimides. For comparison, PI without 2,2′-dichloro substitution was prepared derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). The inherent viscosities of the DCBPDA derived polyimides were tested in the range of 0.88–2.14 dL g−1. Thermal analysis revealed DCBPDA type polyimides had coefficients of thermal expansion in the range of 15.1–29.5 ppm.K−1. Their glass transition temperatures were in the range of 355 °C–437 °C, and were higher than the BPDA derived counterpart. Additionally, the employment of DCBPDA resulted in better organo solubility and optical transparency. For example, PI(DCBPDA/TFMB) could be dissolved in acetone and ethyl acetate at room temperature, the film showed a transparent and colorless feature. The results were analyzed from the perspective of structure-property relationship, and may provide helpful knowledge for the topic of polyimide chemistry.