Hash Environment Research Articles

Thermo Structural Analysis of Biomass Combustion Steam Generation Heat Exchangers Using Three Dimensional Numerical Modelling

Biomass with all its positive characteristics contains some elements and compounds that react negatively with stainless which are known for its usage in high temperature, corrosive prone and, hash environment. Therefore, it is pertinent to comparatively study the strength of various corrosive resistance metals to be able to have an alternative to stainless steel. The purpose of this study is to model and simulate a three-dimensional steam generating boiler plant heat exchanger for a biomass firing process. In the study, inlet temperature and operating temperature of shell and tube sides are taken as input parameters with a square pitch bundle arrangement. The heat transfer analysis is done by considering hot flue gas inside the tubes and steam on shell side to determine the thermal stress, strain and deformation distributions in the tubes and shell of the heat exchanger. The study also presented time-history analysis of the both shell and tubes to ascertain the material reactions within the specified time range. The comparison of deformations and the equivalent strain rate between the two designs indicated an excellent performance of the AL6XN over the 306L stainless steel. The strain amplitude for PMX110 and WKX110 sequentially dropped from 903 to 496 and 621 to 332 between the temperature range of 100 – 10000C respectively. The maximal equivalent strain values for the shells and tubes were 2.238e-003 and 1.294e-004 for PMX110 and 1.490e-003 and 3.212e-004 for WKX110 respectively. The highest deformation in both PMX110 and WKX110 were estimated as 6.729e-004 and 6.131e-004 for the shells and 1.441e-004 and 1.328e-004 for tubes respectively.

A novel superhydrophilic hyperbranched polysiloxane grafted membrane for oil-in-water emulsion separation

Oily wastewater, posing serious environmental and social issues, has aroused widespread concerns. Membrane separation is regarded as an excellent candidate to solve the problem of oily wastewater, although membrane pollution is inevitable in the process of separation. The construction of hydrophilic surface reported so far can effectively mitigate membrane pollution. Herein, we reported a novel hyperbranched polysiloxane grafted polyvinylidene fluoride membrane (HBPSi-g-PVDF), which was prepared through grafting amino-terminated hyperbranched polysiloxanes onto the PVDF membrane surface via an amidation reaction. The HBPSi-g-PVDF membrane possessed superhydrophilic/underwater superoleophobic properties and excellent resistance to oil droplet adhesion. Meanwhile, the resulting membrane presented favorable water permeance (16924 L∙m−2∙h−1∙bar−1) and permeance recovery ratio (99.0 %). In addition, the HBPSi-g-PVDF membrane displayed satisfactory separation efficiency (>99.1 %) for diverse oil-in-water emulsions having over 6000 L∙m−2∙h−1∙bar−1 permeance. Furthermore, HBPSi-g-PVDF membrane also showed excellent environmental durability and recyclability, maintaining stable performance in hash environments, highlighting its great future for the disposal of oily wastewater.

A 3D printable and self‐healing polydimethylsiloxane elastomer

AbstractSilicone elastomers are broadly used in various fields because of their unique properties, such as flexibility, durable dielectric insulation, and excellent stability in hash environments. As a result, three‐dimensional (3D) printing of silicone elastomers is frequently required to construct personalized structures. However, existing 3D‐printing of silicone elastomers are less accurate, difficult to maintain shape, or require doping modification with thixotropic agents. Moreover, common 3D‐printable silicone elastomers do not have self‐healing capability, so they have to be discarded upon damaging. Herein, by introducing hydrogen bonds to improve the shape retention ability and induce network reversibility, we have developed a self‐healing polydimethylsiloxane elastomer, which can be readily 3D‐printed by fused deposition modeling (FDM) technology. We believe that this new silicone elastomer would be useful in the field of biomedical materials, flexible electronics, medical inserts, soft robots and so on.

Bioinspired Environment-Adaptable and Ultrasensitive Multifunctional Electronic Skin for Human Healthcare and Robotic Sensations.

Multifunctional electronic skins (e-skins) that can sense various stimuli have demonstrated increasing potential in many fields. However, most e-skins are human-oriented that cannot work in hash environments such as high temperature, underwater, and corrosive chemicals, impairing their applications, especially in human-machine interfaces, intelligent machines, robotics, and so on. Inspired by the crack-shaped sensory organs of spiders, an environmentally robust and ultrasensitive multifunctional e-skin is developed. By developing a polyimide-based metal crack-localization strategy, the device has excellent environment adaptability since polyimide has high thermal stability and chemical durability. The localized cracked part serves as an ultrasensitive strain sensing unit, while the non-cracked serpentine part is solely responsible for temperature. Since the two units are made of the same material and process, the signals are decoupled easily. The proposed device is the first multifunctional e-skin that can be used in harsh environments, therefore is of great potential for both human and robot-oriented applications.

Selection and Validation of Reference Genes for qRT-PCR Gene Expression Analysis in Kengyilia melanthera.

Kengyilia is a newly established genus. Most species in this genus survive in hash environment, which might be an indicator of an acquirement of stress resistance genes and the potential for molecular breeding in Triticeae species. Quantitative real-time PCR (qRT-PCR) is a widely used technique with varied sensitivity heavily dependent on the optimal level of the reference genes. K. melanthera is a typical psammophyte species which has high drought resistance. The reference genes of K. melanthera are not yet reported. This study aims to evaluate the expression stability of 14 candidate reference genes (EF1A, GAPDH, ACT1, UBI, TUBB3, TIPRL, CACS, PPP2R1B, TUBA1A, EIF4A1, CYPA3, TCTP, ABCG11L, and FBXO6L) under five treatments (drought, heat, cold, salt, and ABA) and find the most stable and suitable one even upon stressed conditions. The software NormFinder, GeNorm, BestKeeper, and RefFinder were used for data analysis. In general, the genes CACS and PPP2R1B are concluded to have the best overall performance under the various treatments. With the ABA treatment, TCTP and TIPRL show the best stability. CACS and TCTP, as well as TIPRL and CYPA3, were most stable under the treatments of cold and salt, respectively. CACS and FBXO6L were ranked the highest with the heat treatment and drought treatment, respectively. Finally, the Catalase-1 (CAT1) gene was used to verify the reliability of the above reference genes. Accordingly, CAT1’s expression pattern remained unchanged after normalization with stable reference genes. This study provides beneficial information about the stability and reliability of potential reference genes for qRT-PCR in K. melanthera.

Isolation and molecular identification of obligate thermophiles from hot springs in Ba Ria – Vung Tau and Khanh Hoa provinces, Vietnam

Environments with temperatures from 50°C to 80°C are rare in nature and are almost exclusively associated with geothermal regions including hot springs, solar-heated soils and volcanic areas. Thermophilic bacteria already exist and prefer in such habitats. Since innate tolerance to thermal environment and potential chassis for extracellular enzymes such as lipase, protease and amylase, which are utilized widely in the industrial fermentation, thermophilic bacteria have been becoming one of the objects for microbiologists worldwide, recently. This study aimed to isolate and identify thermophilic bacteria from hot springs in several provinces in Vietnam such as Ba Ria - Vung Tau and Khanh Hoa. In the results, six moderate thermophilic bacterial strains (namely BM7, BS5, NS1, NS3, NS4, and NW6) that could grow at 55oC were purified from the hot spring ecosystems. All micro morphology of isolates were recorded as rod-shaped, Gram positive, and endospore forming. The results of 16S rDNA sequencing and phylogenetic analysis showed that these isolate belonged to group I of Bacillus genus (the thermophilic group). The isolated strains NS1, NS3, NS4, BS5, NW6 and BM7 were identified to belong to the Bacillus genus, species as Bacillus sp. Resulting strains are potential candidates for industrial applications due to its stable fitness in a hash environment, particularly at high temperature. In addition, this study provides a useful insight into the diverse community of thermophilic bacteria (Bacillus spp.) in several hot springs of Vietnam, that can be applied as bacterial cell factories to produce biomaterials, biofuels, or valuable compounds in the future.

Robust ultrathin nanoporous MOF membrane with intra-crystalline defects for fast water transport

Rational design of high-performance stable metal–organic framework (MOF) membranes is challenging, especially for the sustainable treatment of hypersaline waters to address critical global environmental issues. Herein, a molecular-level intra-crystalline defect strategy combined with a selective layer thinning protocol is proposed to fabricate robust ultrathin missing-linker UiO-66 (ML-UiO-66) membrane to enable fast water permeation. Besides almost complete salt rejection, high and stable water flux is achieved even under long-term pervaporation operation in hash environments, which effectively addresses challenging stability issues. Then, detailed structural characterizations are employed to identify the type, chemical functionality, and density of intra-crystalline missing-linker defects. Moreover, molecular dynamics simulations shed light on the positive atomistic role of these defects, which are responsible for substantially enhancing structural hydrophilicity and enlarging pore window, consequently allowing ultra-fast water transport via a lower-energy-barrier pathway across three-dimensional sub-nanochannels during pervaporation. Unlike common unfavorable defect effects, the present positive intra-crystalline defect engineering concept at the molecular level is expected to pave a promising way toward not only rational design of next-generation MOF membranes with enhanced permeation performance, but additional water treatment applications.

Inner changes of Portland cement and metakaolin-based geopolymer in the high-temperature environment

The inner structure of cementitious materials is crucial for the intelligent design and construction in civil engineering. In this work, two kinds of samples made from Portland cement and metakaolin-based geopolymer respectively were prepared to be exposed in high-temperature environment. In the experiments, the samples were placed on a heater with a 400°C surface for 40 minutes. A high-energy X-ray computed tomography (CT) facility was used to detect the macroscopic inner structure of the samples. In addition, the infrared-ray morphology of samples was also tested and compared. Results show that metakaolin-based geopolymer was relatively more resistant to heat compared with Portland cement. However, the cracks development of metakaolin-based geopolymer was severer due to the shrinkage in the high-temperature environment. In addition, based on the X-ray CT images, a method to show the distribution of pores' sizes was proposed. It was found the distribution of pores' volumes and area surfaces can be fitted by power laws which are straight lines in the logarithmic coordinates, and the geopolymer samples have relatively higher goodness of fit. Moreover, a lower intercept of the fitting line indicates the frequency of larger pores in the sample is lower, and a lower slope indicates a tighter distribution range of the pores' sizes. These findings may provide insight for future intelligent design of digital cementitious materials used in hash environment.

Femtosecond laser point-by-point inscription of an ultra-weak fiber Bragg grating array for distributed high-temperature sensing.

Ultra-weak fiber Bragg grating (UWFBG) arrays are key elements for constructing large-scale quasi-distributed sensing networks for structural health monitoring. Conventional methods for creating UWFBG arrays are based on in-line UV exposure during fiber drawing. However, the UV-induced UWFBG arrays cannot withstand a high temperature above 450 °C. Here, we report for the first time, to the best of our knowledge, a new method for fabricating high-temperature-resistant UWFBG arrays by using a femtosecond laser point-by-point (PbP) technology. UWFBGs with a low peak reflectivity of ∼ - 45 dB (corresponding to ∼ 0.0032%) were successfully fabricated in a conventional single-mode fiber (SMF) by femtosecond laser PbP inscription through fiber coating. Moreover, the influences of grating length, laser pulse energy, and grating order on the UWFBGs were studied, and a grating length of 1 mm, a pulse energy of 29.2 nJ, and a grating order of 120 were used for fabricating the UWFBGs. And then, a long-term high-temperature annealing was carried out, and the results show that the UWFBGs can withstand a high temperature of 1000 °C and have an excellent thermal repeatability with a sensitivity of 18.2 pm/°C at 1000 °C. A UWFBG array consisting of 200 identical UWFBGs was successfully fabricated along a 2 m-long conventional SMF with an interval of 10 mm, and interrogated with an optical frequency domain reflectometer (OFDR). Distributed high-temperature sensing up to 1000 °C was demonstrated by using the fabricated UWFBG array and OFDR demodulation. As such, the proposed femtosecond laser-inscribed UWFBG array is promising for distributed high-temperature sensing in hash environments, such as aerospace vehicles, nuclear plants, and smelting furnaces.

Observed Dispersal of Invasive Yellow Flag Iris (Iris pseudacorus) through a Saline Marine Environment and Growth in a Novel Substrate, Shell Hash

Invasive in North America, Iris pseudacorus is commonly considered a freshwater species; however, I. pseudacorus can tolerate some saltwater, and is observed in brackish coastal habitats such as estuaries and marshes. Despite this tolerance, saltwater depresses I. pseudacorus reproduction, growth, survival, and dispersal ability. This raises the question of whether I. pseudacorus can spread through a marine environment and establish away from sources of freshwater. This study reports the observation of 104 established juvenile I. pseudacorus individuals in coastal habitat on two islands in southern British Columbia, Canada. Two islands that are devoid of aboveground freshwater sources such as streams, rivers, or lakes that connect to marine habitats. Individuals were also observed growing in a novel substrate, shell hash (fragments of bivalve and gastropod shells that accumulate in areas of low hydrological energy). To the best of our knowledge, this is the first confirmed case of I. pseudacorus growing in a high salinity (30 PSU) shell hash environment. Despite the need for more study, this observation suggests that a broader range of coastal habitat may be susceptible for invasion by I. pseudacorus than previously thought.

Design of flexible multi‐level topography for enhancing mechanical property

AbstractRobust mechanical property is fundamentally significant for applications of nano‐materials, such as micro‐fluidic, sensor, superhydrophobic/ icephobic, and crush‐resistant functions. However, the nano‐materials used in the applications are always easily ruined due to the poor adhesion and weak mechanical properties. To enhance the nano‐materials’ duration in hash environment, a strategy of robust nano‐topography protection is studied in this paper. In our experiment, a series of multi‐level sub‐mm topography with nano‐materials are fabricated by integrating the methods of soft lithography, and crystal growth. The mechanical properties of nano‐materials are quantitatively studied, and the nano‐material can be protected by the designed flexible multi‐level topography, which significantly decreases the strain and stress of the nano‐structure. To investigate the mechanism of this performance, a series of simulations are performed, and a mechanical model is established to explain this phenomenon. This work uncovers the multi‐level principles for nano‐materials protection and gives a guideline to design the nano‐materials’ surfaces.

High-performance thermosets with heat resistant properties derived from methacrylated isosorbide and epoxy-based vinyl ester

Styrene (ST) is a common volatile petroleum-based diluent in epoxy-based vinyl ester (VE) resin system. In recent years, a number of renewable molecules, such as eugenol, have been methacrylated and products behaved lower volatility property than ST. However, these renewable resin systems exhibited decreased thermal performance, especially glass transition temperature (Tg). Therefore, these resin systems cannot be used in hash environment. In our work, we used isosorbide to react with methacrylic anhydride and the synthesized monomer was mixed with VE resin to produce new bio-based resin system-MIVE. Volatility, viscosity and thermomechanical properties of MIVE and VE/ST resin were examined. The results indicated that MIVE had excellent low volatility property and Tg of MIVE can achieve 210 °C. Furthermore, we discussed the approach to improve heat resistant property of resin system. Acrylates with vinyl groups, including hydroxyethyl methacrylate (HEMA), pentaerythritol triacrylate (PETA) and dipentaerythritol pentaacrylate (DPHA), was grafted to MIVE respectively. Dynamic thermomechanical analysis (DMA), heat distortion temperature (HDT) and thermogravimetric (TGA) tests were used to measure thermal performance of grafted resin systems. The results showed Tg of grafted MIVE ranged from 210 to 240 °C, HDT ranged from 160 to 230 °C and initial decomposition temperature (IDT) (5% weight loss) were over 400 °C. Overall, studies showed that grafting acrylates with vinyl groups to VE was an effective way to improve the heat resistant properties of bio-based resin systems.

Sound source localization based on Michelson fiber optic interferometer array

Abstract Sound source localization is of high attention and importance. Microphone array is one of the most common technologies in acoustic source localization. In this paper, a fiber optic array acoustic sensor based on Michelson interferometer is proposed, which can be applied for sound source localization in hash environments. Sound source localization is realized through this array system. The experiment results show that the array has a high sensitivity, and the localization accuracy can be up to 0.01 m.

Investigation of Shot Peening Effect on Titanium Alloy Affecting Surface Residual Stress and Roughness for Aerospace Applications

Titanium (Ti) alloys are used in aviation industry such as engine parts, air frames etc. The main advantage of using Ti alloy is to combat chemical attack in corrosive and hash environment as well as fatigue resistance under cyclic loading conditions. This investigation mainly focuses on how to improve the fatigue resistance of a component thereby the life improvement is envisaged. One of the methods employed is shot peening process, which is a surface phenomenon and introduces compressive residual stress so that the properties like stress corrosion cracking, forming operations, strength get enhanced. The design and experimental work involves the various shot peening parameters such as impact angle, coverage area, Almen intensity levels affecting the surface roughness as well as surface and sub-surface residual stresses. Further, design of experiments involving Taguchi’s technique has been discussed at length. The shot peening parameters have been correlated with residual stress and surface roughness parameters. It is also observed that microstructure of the titanium alloy is having the features to support the fatigue properties. Finally the work has been summarized to arise at optimization of these parameters to achieve higher residual stress from the point of higher fatigue life.

High sensitivity strain sensor based on twin hollow microspheres

AbstractA sensor based on 2 hollow core microspheres is proposed. Each microsphere was produced separately through fusion splicing and then joined. The resultant structure is a Fabry‐Perot interferometer with multiple interferences that can be approximated to a 4‐wave interferometer. Strain characterization was attained for a maximum of 1350 με, achieving a linear response with a sensitivity of 3.39 ± 0.04 pm/με. The fabrication technique, fast and with no chemical hazards, as opposed to other fabrication techniques, makes the proposed sensor a compelling solution for strain measurements in hash environments.

Optical fiber sensor encapsulated by polyurethane

Fiber Bragg gratings (FBGs) are ideally suited for monitoring strain in civil structures, aircrafts, ocean engineering due to their low cost, reliable and high accuracy. A new encapsulation technology for FBG using polyurethane is proposed to help the sensor withstand large displacement in hash environment. This paper aims to provide experimental packaging procedures, calibration and field tests of developed FBG sensors for strain measurement. The principles, basic chemical reaction processes and prepare procedures of polyurethane are demonstrated. Suitable protective encapsulation to the bare fiber by polyurethane ensures that there is no relative slip at the interface. The encapsulated FBG sensor has good linearity from the result of calibration test conducted on a universal testing machine. Further the sensor is embedded into the freezing soil to evaluate the performance in severe environment.

Indirect measurement and extreme learning machine based modelling for flux linkage of doubly salient electromagnetic machine

Doubly salient electromagnetic machines (DSEMs), which are characterised with fault tolerance, low cost, high reliability, and de-excitation ability, are gaining more and more attention in safety-critical and hash environment applications, such as the aircraft generation systems. Nevertheless, the non-linear and strong coupled characteristics of the flux linkage is the obstruct crux in DSEM modelling. The DSEM model is the critical part of the system model, which is the foundation of theoretical analysis, control strategy developing, and stability analysis. This study is aimed to demonstrate the feasibility of indirect flux linkage measurement method, as well as the effectiveness of the extreme learning machine (ELM)-based flux linkage modelling method. The basic principles of the indirect measurement are analysed and the measurement processes excluding rotor-clamping devices are proposed. The ELM is employed to high-precision flux linkage modelling with high efficiency. A three-phase 12/8-pole DSEM is tested to confirm the validity of the proposed modelling method. Both finite element analysis and experimental results are presented, verifying the effectiveness of the indirect flux linkage measurement and the ELM-based modelling method.

Redundant information processing techniques comparison for differential vibratory gyroscope

Advantages of differential Coriolis vibratory gyroscope of the new type with two measuring channels of angle rate with opposite signs that provides redundant measuring information about angle rate are analyzed. Comparative analysis of four different techniques of redundant signals processing including technology of “virtual” gyro signals processing in application to the differential vibratory gyroscope is carried out. Importance of creation of redundant information processing techniques is caused by distinction of the differential vibratory gyroscope from other micro­electro­mechanical gyros, for example, tuning fork gyro, in that it has two output signals, which come from the single resonator and correspond to angle rates with opposite signs. As a result redundant output information processing techniques were obtained. This information comes from the differential vibratory gyroscope output and is formed by subtracting of two measuring channel signals. The algorithm of “virtual” gyro redundant output information processing was modified. The algorithm differs from known ones by calculation of inter­channel correlation matrix in on­line manner. This leads to decrease of angle rate measuring random error and to decrease overshoot in conditions of abrupt change of angle rate. The obtained results are important and useful for application of differential vibratory gyroscopes in stabilization systems and angular motion control. This is caused by high requirements to accuracy and ability to function in hash environment.

Energy-Efficient Power Control Scheme for Device-to-Device Communications

Device-to-device (D2D) communication permits direct communication between devices and thereby it provides performance gain for the traditional cellular network. In this paper, the problem how to allocate the transmission power efficiently is investigated and a distributed power control scheme is proposed for D2D communications. In this scheme, D2D user equipment (UE) can determine its transmission power dynamically for optimizing the link performance of the D2D link. To achieve this goal, firstly, an upper bound for the D2D transmitter density is derived based on which D2D UE determines its transmission power is on or off to avoid excess interferences and guarantee that each D2D link can achieve the link quality of service (QoS) on generally. In addition, for those D2D UEs transmitting data, the optimal transmission power is derived for a random D2D link which can optimize the successful transmission probability according to the link quality and the interference environment with few signalling exchange. Finally, some non-supported D2D links under hash environment are appropriately removed to reduce unnecessary interferences on other links and guarantee that an optimal power allocation solution exists for each D2D link. Simulation results show that compared with the fixed power scheme and the closed loop power control scheme, the proposed distributed power control scheme can improve the successful transmission probability under different wireless environments. Furthermore, compared with the closed loop power control scheme, the power consumption is reduced significantly (e.g. transmission powers for half of UEs can be reduced by above 84 %) by the proposed scheme.

Group Key Management Technique based on Logic- Key Tree in the Field of Wireless Sensor Network

In the recent times the concept of group key management is found to be one of the very essential issues in the field of wireless sensor network. Because of the dual impact limitations and various operations in open and hash environment the security and confidentiality which are considered as very challenging issues in WSN. The main issues which are associated with securing the sensor network have more complexity when the group communication of the network is considered. This paper addresses the security issues associated with the Group key management techniques and ensures some significant conclusions for group key management in cluster tree WSNs. A group is defined as a set of sensor nodes present in cluster based tree network and shares some sensory information such as temperature, pressure, etc. The main objective of the paper is to highlights some of the significant issues which are associated with the authentication of the group key data exclusively for the members who have a secure access to the group information. This study contributes an overview of secure an efficient group management mechanisms for cluster tree networks and in between group members. In order to focus on the various issues and limitations a comparative analysis of various key management techniques have been done and evaluated. The schemes are allowed to maintain multiple groups and rekey desperately. This paper focuses on the various group key management issues that outperforms conventional techniques of group key management.