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This paper considers deep visual recognition on long-tailed data. Under the long-tailed distribution, a small portion of the classes (head classes) occupy most training samples and the most classes (tail classes) only occupy relatively few samples. We observe that such long-tailed distribution significantly distorts the deeply-learned feature space, which consequentially compromises the deep visual recognition. Specifically, during training, each head class is prone to a relatively wide spatial distribution in the deep feature space, while each tail class is prone to a relatively small spatial distribution. In another word, the tail classes usually have much smaller spatial distribution than the head classes, distorting the overall feature space. In response, we propose to explicitly inflate the distribution of each tail class in the deep feature space, so that the tail classes will have comparable distribution range as the head classes. To this end, we replace each tail feature vector with a set of feature vectors on the fly. These feature vectors follow a probabilistic distribution learned from the head classes and yield a “feature cloud” surrounding the original tail feature. We show that the feature cloud effectively transfers the within-class diversity from the head classes onto the tail classes, maintaining an effect of probabilistic feature augmentation. An important advantage of the proposed feature cloud is that it is capable to bring general improvement to long-tailed visual recognition on two fundamental tasks, i.e., deep classification and deep representation learning, in spite of the significant differences between them. Extensive experiments on both deep metric learning benchmarks and deep image classification benchmarks validate the effectiveness of the proposed feature cloud.

In recent years, the air material transportation system has played an increasingly important role in many fields. However, traditional laboratory management methods cannot meet the requirements for real-time and high-level supervision capabilities of air material transportation laboratories. In order to solve this problem, the real-time database and cloud computing technology are used in this paper to design and improve laboratory management system. The paper discusses the feasibility of the real-time database and cloud computing technology and outlines the three aspects of the design: the overall architecture, network topology and data flow. According to the actual situation of an air material transportation laboratory, the real-time database architecture is designed to manage the massive test data, personnel information, and on-site monitoring equipment of the laboratory. Finally, the project realizes the functions of the system and makes laboratory management more intelligent.

Aiming at the problem that the traditional monitoring mode of power generation can’t monitor the normative behavior of operators as well as realize the comprehensive monitoring and intelligent decision-making analysis of power generation safety, this paper applies cloud platform, real-time database, OpenPose and TensorFlow to the power generation safety management system to monitor and manage the operation process of staff. The research shows that the application of cloud computing and deep learning technology in power generation safety monitoring system can significantly improve the compatibility, real-time performance and supervision ability of the system, and ensure the accuracy and recognition rate of data. And the application of human posture recognition can improve the safety of staff daily operations.

With the increase of city air monitoring sites and monitoring project, monitoring instruments and monitoring data are increasing rapidly. When using the traditional relational database in processing huge real-time data, the throughput and timeliness of monitoring system has been unable to meet the needs of the business. In order to solve this problem, this paper introduces the real-time database into the air quality automatic monitoring system. According to the design principles, the paper outlines the four aspects of the design: the composition of the system, the overall structure of the system, the data flow and the network topology. Aim at assembling the embedded system architecture, distributed system, database technology, network browser/server computing mode, client/server network computing technology, and large-scale computer application system of virtual private network connection based on public network. In the specific design, this paper design substation and central station architecture based on the real-time databases and complete the function of field data collection and storage, equipment control, data transmission, human-computer interaction, data exchange interface with third party system and other function. Finally, according to the observation results of the city air quality automatic monitoring system, the project realizes the functions of the system and improve the real-time quality of environmental air monitoring and the capacity of instrument supervision.

Introduction:Epithelioid hemangioendothelioma (EHE) of the bone is a very rare malignant vascular neoplasm, with biologic behavior between that of locally aggressive epithelioid hemangioma and malignant epithelioid angiosarcoma. We report a case of a patient with EHE who underwent bone scint

A novel class of thermosetting resins based on allylated and transesterified epoxidized soybean oil (AE-ESBO) curable by radical mechanism was developed. The AE-ESBO was prepared from ESBO by oxirane ring-opening and then transesterification with allyl alcohol. A family of rubbery to glassy resins was prepared by radical copolymerization of AE-ESBO with different concentrations of maleic anhydride (MA). Glass transition temperatures (Tg) of these resins ranged from below room temperature to about 130°C based on the amount of MA. In spite of the presence of anhydride groups, water absorption was low

A new class of biopolymers based on plant oils with allylic double bonds was prepared from vegetable oils by oxirane ring-opening. Investigation of model systems revealed that the main side reactions during ring-opening were formation of intramolecular cyclic ethers in epoxidized linoleic fatty ester and oligomerization. Side reactions in the epoxidized oleic fatty ester were insignificant. Allyl alcohol ring-opened epoxidized soybean oil (AESBO) was then copolymerized with maleic anhydride (MA) to prepare thermosetting resins by free radical polymerization and esterification. In the best case, high gel content (99%), low water absorption (∼1%), and low swelling ration in toluene (∼4%) were achieved. Glass transition temperatures of these resins ranged from below room temperature to about 123 °C depending on the loading of MA. Tensile modulus varied from few MPa to 1.1 GPa, with the highest tensile strength of 29 MPa.

Thermoplastic urethanes based on polyricinoleic acid soft segments and MDI/BD hard segments with varied soft segment concentration were prepared. Soft segment concentration was varied from, 40 to 70 wt%. Biodegradation was studied by respirometry. Segmented polyurethanes with soft segments based on polyricinoleic acid degrade relatively slow losing about 11% carbon after 30 days, but faster than corresponding petrochemical polyesterurethanes. Since biodegradation proceeds mainly through the soft segments, higher soft segment content polymers displayed slightly higher biodegradation. Polyurethanes with dispersed hard domains in the soft phase displayed slightly faster biodegradation than those with co-continuous morphology. Polyester diol degrades slower than castor oil but significantly faster than the polyurethanes with built in soft segments from the same diol. Castor oil biodegrades slower than soybean oil.

To our knowledge, this is the first description of the material properties of a high molecular weight linear polyester prepared from the methyl ester of 9-hydoxynonanoic acid (HNME). The HNME of high purity was prepared by ozonolysis of castor oil, followed by methanolysis of triglycerides. High molecular weight polyester prepared in bulk by transesterification was a highly crystalline material with limited solubility in chlorinated solvents. The polyester is an analogue of polycaprolactone (PCL), but the longer hydrocarbon chain between ester groups imparted intermediate properties between polyesters and polyethylene, characterized by a higher melting point, higher Tg, better thermal stability, and lower solubility in chlorinated solvents than PCL. Differential scanning calorimetry showed only a single transition-melting at 70 °C with melting enthalpy of 95 J/g. Properties of the material were strongly dependent on the molecular weight. Lower molecular weight material was brittle with low mechanical stre...

In our previous publication on the structure–property behavior of segmented polyurethanes based on castor oil [Petrovic ZS, Xu Y, Zhang W. Polymer Preprints 2007;48(2):852–3.], the results showed that these materials which possessed a soft segment weight concentration (SSC) of 70% have both low tensile strength and elongation at break. This behavior is distinctly different from segmented polyurethanes of comparable soft segment content obtained from petrochemical polymeric diols that possess terminal hydroxyl groups. The poor elastic properties of these segmented polyurethanes were ascribed to the low molecular weight of the polymers as well as due to the presence of the six-carbon “dangling chain”, which may influence the morphology of the resulting segmented polyurethanes. To further understand this behavior, four segmented polyurethanes with the SSC of 70, 60, 50, and 40%, respectively, were synthesized from a polyricinoleate diol with an Mn of 2580, diphenylmethane diisocyanate (MDI) and butanediol. The objective of this work was to study the effect of SSC on the morphology of the resulting polyurethanes, and to correlate the morphology with the properties of these bio-based segmented polyurethanes. Polymers were characterized by GPC, viscometry and spectroscopic methods. Thermal and mechanical properties of the polymers indicated good microphase separation. Microphase morphology was also noted by SAXS and AFM. Finally, “spherulitic-like” superstructures were noted in the solution cast films that are believed to arise from the nucleation and crystallization of the hard segments.

Carbon nanofiber (CNF) and carbon nanotube (CNT) composites have enhanced mechanical and electrical properties that make these composites desirable for antistatic and electronic dissipation technology. These applications require a homogenous dispersion of CNFs within a polymer matrix. To improve the compatibility/dispersability of CNFs within a polymer matrix, a hyperbranched polyol CNF composite was synthesized by the chemical modification of oxidized CNFs with glycidol and boron trifluoride diethyl etherate. The resulting polyol CNFs were characterized by TGA, FTIR, TEM/SEM and XPS. The hydroxyl groups were reacted with heptafluorobutyryl chloride to determine the amount of oxidized groups in the sample. The resulting composite was characterized by FTIR and elemental analysis. The amount of hydroxyl groups increased by 550% for the polyol CNFs as compared to the oxidized CNFs and an improvement in dispersion ability was observed.

Poly(ethyl acrylate) (PEA)/poly(methyl methacrylate) (PMMA) emulsion blends that were combined with unmodified montmorillionite (MMT) to improve the physical properties via nanocomposite formation. We prepared a cationic PEA/PMMA latex and used a heterocoagulation process to create a homogeneous dispersion of the clay platelets in the matrix. The cationic PEA/PMMA emulsion blends were prepared using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous slurry of MMT. The PEA/PMMA–MMT nanocomposites could be processed at low temperatures. Low temperature processing prevented the commonly observed discoloration associated with many thermoplastic nanocomposites. DSC, SAXS, TEM and AFM were used to study the dispersion of MMT and morphology of PEA/PMMA–MMT nanocomposites. Tensile stress, elongation at break and Young's modulus demonstrated a significant reinforcing effect of clay.

Polyacrylate-clay nanocomposites were prepared by an in situ polymerization method followed by heterocoagulation. In the heterocoagulation method, a cationic polyacrylate emulsion was prepared by emulsion polymerization using a cationic initiator in the presence/absence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous clay slurry. WAXD results and TEM images suggest that morphologies of these nanocomposites depend on preparation method, mixing method, and the amount of free surfactant. TG-DTG analyses demonstrate the improvement in thermal stability of these nanocomposites, while DSC results indicate no significant changes in glass transition temperature of these nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3850–3855, 2006

Polystyrene–carbon nanofiber (CNF) nanocomposites have been synthesized by a ‘bottom-up’ method through electrostatic assembly. First, a cationic polystyrene (PS) latex was synthesized by conventional emulsion polymerization. The latex was mixed with an aqueous suspension of oxidized CNF. PS–CNF nanocomposites were obtained by heterocoagulation due to the electrostatic interaction between cationic PS latex and anionic CNF. Thermal properties were characterized by DSC and TGA, while morphologies of the nanocomposites were studied by SEM. Electrical resistivity results showed that the percolation threshold in our PS–CNF nanocomposites was below 2 wt% (1 vol%). This low percolation threshold is related to the dispersion, and thus a superior network formation of CNF in PS matrix.

Poly(methyl methacrylate) (PMMA)–clay nanocomposites were prepared by a heterocoagulation method. A cationic PMMA emulsion was prepared by emulsion polymerization using a cationic initiator in the presence of free surfactant, cetyl trimethylammonium bromide (CTABr), followed by mixing with an aqueous clay slurry. Clays used in present research included montmorillonite (MMT), synthetic hectorites and fluorohectorites (with two different sizes). WAXD results and TEM images indicate that the morphologies of these nanocomposites depend on clay colloid stability as well as clay loadings. WAXD and TEM results also indicate the good morphology preservation of the nanocomposites during solution and melt processing. Thermal stability of these nanocomposites was studied by TG–DTG analyses; the mechanism of thermal stability improvement is discussed based on experimental results.

1,3-Dioxepane was polymerized with triflic acid as an initiator in the presence of acetic acid (AA) and hexane diacid. The structure of the poly(1,3-dioxepane) (polyDOP) obtained was characterized by 1H NMR spectra and gel permeation chromatography. The molecular weights (MWs) were determined by vapor pressure osmometry. The results obtained in both systems were completely different from those in which low-MW polyols were used as chain-transfer agents. When the molar ratio of carboxylic acid to triflic acid was low, high-MW polyDOP with a controlled MW and narrow MW distribution was obtained. The content of the ester group in the final product depended greatly on the molar ratio of AA to triflic acid. The polymerization mechanism is discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1232–1240, 2000

Styrene underwent the ATRP process using an asymmetric difunctional initiator, 2-hydroxylethyl 2′-bromobutyrate in combination with CuBr and 2,2′-bipyridine (bpy). Polystyrene with hydroxyl and bromine groups at each end of the polymer (HO-PSt-Br) was obtained, and used as a chain-transfer agent in the cationic ring-opening polymerization of 1,3-dioxepane with triflic acid as initiator. The structures of the polymerization products were analyzed by 1H NMR and GPC analyses, indicating the formation of block copolymer. The molecular weight distribution of the block copolymer was relatively narrow and the molecular weight of the polyDOP block was high. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 436–443, 2000

Polystyrene (PSt) with end-terminal bromine (Br-PSt-Br) was synthesized by the atom transfer radical polymerization of styrene with the difunctional initiator 1,2-bis(2′-bromobutyryloxy)ethane in combination with CuBr and bipyridine. The Br-PSt-Br reacted with silver perchlorate at −78 °C, and the resulting macromolecular initiator was used to initiate the polymerization of tetrahydrofuran. Triblock poly(tetrahydrofuran)-polystyrene-poly(tetrahydrofuran) (PTHF-PSt-PTHF) diol was obtained after propagation at −15 °C. The conversion of the polymerization was measured by gas chromatography. The structures of the triblock copolymer PTHF-PSt-PTHF diol were characterized by 1H NMR and gel permeation chromatography. The mechanism of cationic ring-opening polymerization is discussed. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 337–344, 2000

Poly (1,3-dioxepane) [PDOP] triol was prepared by cationic ring-opening polymerization with [C 2 H 5 C(CH 2 OCH 2 CH 2 CO + ClO - 4 ) 3 ], trioxocarbenium perchlorate, as an initiator. The structures of the PDOP triols obtained were verified by 1 H-NMR, FTIR, and GPC results. Initiation, propagation, and termination mechanisms were discussed based on the structural analysis of the polyacetal polyols. The results of GPC, NMR, and IR measurements showed that the PDOP triols obtained had similar branch chain lengths. Number-average molecular weights were determined by vapor pressure osmometry (VPO), end group titration and 1 H-NMR.

New oxocarbenium perchlorates, [(C2H5)(4-n)C(CH2OCH2CH2CO+ClO)n, n = 3, 4] were synthesized and used in the preparation of poly (tetrahydrofuran) (PTHF) polyols. The structures of PTHF polyols and corresponding hydrolysis products were determined by 1H-NMR and FTIR. GPC curves showed that the amount of cyclic oligomers was negligible. The polymerization process was followed by gas chromatography. Kinetic studies showed no termination reaction. The mechanism of the polymerization was discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3391–3399, 1999

A new four-armed poly(1,3-dioxepane) tetraol was prepared by cationic ring-opening polymerization of 1,3-dioxepane (DOP) in the presence of 6,6-bis(5-hydroxyl-2-oxapentyl)-4,8-dioxaundecanediol1,11 (THA) with triflic acid(I) as initiator. The structure of the poly(DOP) tetraol obtained was characterized by 1 H and 13 C NMR spectra. The molecular weights of the obtained tetraols were controlled by the mole ratio of DOP consumed to initial THA, and it was found that each macromolecule contains only one THA unit on the average. GPC studies showed that the cyclic oligomers in the products were negligible.

Starting from a bio-based polyol through modification of soybean oil, BIOH™ X-210, two series of bio-based polyurethanes-clay nanocomposite foams have been prepared. The effects of organically-modified clay types and loadings on foam morphology, cell structure, and the mechanical and thermal properties of these bio-based polyurethanes-clay nanocomposite foams have been studied with optical microscopy, compression test, thermal conductivity, DMA and TGA characterization. Density of nanocomposite foams decreases with the increase of clay loadings, while reduced 10% compressive stress and yield stress keep constant up to 2.5% clay loading in polyol. The friability of rigid polyurethane-clay nanocomposite foams is high than that of foam without clay, and the friability for nanofoams from Cloisite® 10A is higher than that from 30B at the same clay loadings. The incorporation of clay nanoplatelets decreases the cell size in nanocomposite foams, meanwhile increases the cell density; which would be helpful in terms of improving thermal insulation properties. All the nanocomposite foams were characterized by increased closed cell content compared with the control foam from X-210 without clay, suggesting the potential to improve thermal insulation of rigid polyurethane foams by utilizing organically modified clay. Incorporation of clay into rigid polyurethane foams results in the increase in glass transition temperature: the Tg increased from 186 to 197 to 204 °C when 30B concentration in X-210 increased from 0 to 0.5 to 2.5%, respectively. Even though the thermal conductivity of nanocomposite foams from 30B is lower than or equal to that of rigid polyurethane control foam from X-210, thermal conductivity of nanocomposite foams from 10A is higher than that of control at all 10A concentrations. The reason for this abnormal phenomenon is not clear at this moment; investigation on this is on progress.

Encapsulants and underfills are polymeric materials containing some levels of low molecular mass chemicals which turn into volatiles during heat exposure. It is of interest to know what and when the volatiles undergo thermal desorption and are released during high temperature exposure such as solder reflow or environmental testing. Moisture turning to steam is not the only vapor present during solder reflow. With the push towards lead-free and higher reflow temperatures, this outgassing behavior is of particular significance to assist in the improvement of manufacturing yields. Using evolved gas analysis with gas chromatography and mass spectrometry, vapors found from epoxy mold compounds are carbon dioxide, moisture, methyl alcohol, benzene, isobutyl methyl ketone, triphenyl phosphine and occasionally, siloxanes from stress releasing agents. Gases reflecting curing byproducts or unreacted products are observed. For underfills, these gases are either absent or much reduced. Both underfills and encapsulants show some signs of polymer chain decomposition at higher temperatures for lead-free applications. Gas evolution rate increased directly with temperature for both encapsulants and underfills.