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81.
Claudia Lidia Simionescu 《International Journal of Engineering Science》1980,18(2):423-430
The aim of the present paper is to obtain solutions for the equation modeling of a Vlasov plasma from its linearized form, by means of control theory and using the author's previous results regarding optimal control problems for integro-differential equations. 相似文献
82.
Elena Hamciuc Corneliu Hamciuc Irina Bacosca Mariana Cristea Lidia Okrasa 《Polymer Composites》2011,32(5):846-855
Polyimide composite films were prepared by mixing the BaTiO3 particles into poly(amic acid) solution followed by film casting and thermal imidization under controlled temperature conditions. The poly(amic acid) was synthesized by solution polycondensation reaction of 4,4′‐oxydiphthalic anhydride with 2,6‐bis(4‐aminophenoxy)benzonitrile, using N‐methyl‐2‐pyrrolidone as solvent. The surface of BaTiO3 particles was modified by treating with an aminosilane coupling agent, 3‐aminopropyltriethoxysilane. Fourier transform infrared spectroscopy, X‐ray diffraction and scanning electron microscopy were used to characterize the structure and properties of the composites. The influence of BaTiO3 content on the composite film properties was evidenced. The films exhibited good thermal stability having the initial decomposition temperature above 520°C. They had stable dielectric properties over large intervals of temperature and frequency. The dielectric constant and the dielectric loss increased with the increase of BaTiO3 content. The dynamic mechanical analysis and dielectric spectroscopy revealed subglass transitions γ and β. At higher temperature an α‐relaxation that corresponds to the glass transition and a conductivity process were evidenced. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers 相似文献
83.
S. Sudha S. Vishnu Priya J. Herbert Mabel M. Palanichamy V. Murugesan 《Journal of Porous Materials》2009,16(2):215-226
Al-MCM-41, Fe,Al-MCM-41 and Zn,Al-MCM-41 materials with different silicon to metal ratios were synthesized hydrothermally
and characterized by XRD, BET, FT-IR, Acidity measurement by pyridine adsorbed FT-IR spectroscopy, 29Si and 27Al MAS NMR and ESR techniques. The orderly arrangement of mesoporous materials was clearly revealed from the XRD patterns.
29Si and 27Al MAS NMR established the co-ordination environment of silicon and aluminium. Electron paramagnetic resonance (EPR) study
confirmed the co-ordination environment of Fe in Fe,Al-MCM-41 framework. The catalytic activity of these materials was evaluated
in the vapour phase alkylation and acylation of ethylbenzene with ethyl acetate in the temperature range between 250 and 400 °C.
The products were found to be 1,3-diethylbenzene (1,3-DEB), 1,4-diethylbenzene (1,4-DEB), 1,2-diethylbenzene (1,2-DEB), 4-ethylacetophenone
(4-EAP) and acetophenone (AP). The reaction products revealed that activation of ethyl acetate is a convenient route for both
alkylation and acylation reactions. The order of the catalysts activity for the reaction is found to be Fe,Al-MCM-41 (50) > Fe,Al-MCM-41
(100) > Zn,Al-MCM-41 (50) > Zn,Al-MCM-41 (100) > Al-MCM-41 (50) > Al-MCM-41 (100). In addition to the density of acid sites,
the strength of acid sites is also important for this reaction. The effects of temperature, feed ratio, WHSV and time on stream
were also examined and the results are discussed. 相似文献
84.
S. Vishnu Priya J. Herbert Mabel S. Gopalakrishnan M. Palanichamy V. Murugesan 《Journal of Porous Materials》2009,16(4):419-427
MAPO-36 was synthesized hydrothermally by isomorphic substitution of Mg2+ in the framework of AlPO-36 and ion-exchanged with Fe3+, Zn2+, La3+ and Ce3+ by wet method. The materials were characterized by XRD, TGA, TPD (ammonia) and SEM-EDX. XRD revealed absence of structural
degradation after ion-exchange. TPD (ammonia) showed selective ion-exchange of strong acid sites in ion-exchanged MAPO-36.
The weight loss around 550 °C in TGA for Fe, La and CeMAPO-36 suggested conversion of M(OH)2+ to MO+. Toluene disproportionation was carried over all catalysts in which diphenyl methane derivative was suggested to be the principle
intermediate in the formation of p-xylene and other products. The time on stream study showed exclusive formation of p-xylene after 6 h. 相似文献
85.
分析了机动车排放的主要污染物,探讨了地下机动车道可借鉴应用的空气质量标准.通过分析机动车在地下车道内的运行特点,研究了地下车道的分类及不同分类下的通风量计算指标.给出了地下车道设计通风量的计算公式,通过实例论证了地下空间采用稀释污染物计算方法的必要性. 相似文献
86.
87.
BACKGROUND: The increased caloric requirements of HIV-positive individuals, undesirable side effects of treatment that may be worsened by malnutrition (but alleviated by nutritional support), and associated declines in adherence and possible increased drug resistance are all justifications for developing better interventions to strengthen the nutrition security of individuals receiving antiretroviral treatment. OBJECTIVE: To highlight key benefits and challenges relating to interventions aimed at strengthening the nutrition security of people living with HIV who are receiving antiretroviral treatment. METHODS: Qualitative research was undertaken on a short-term nutrition intervention linked to the provision of free antiretroviral treatment for people living with HIV in western Kenya in late 2005 and early 2006. RESULTS: Patients enrolled in the food program while on treatment regimens self-reported greater adherence to their medication, fewer side effects, and a greater ability to satisfy increased appetite. Most clients self-reported weight gain, recovery of physical strength, and the resumption of labor activities while enrolled in dual (food supplementation and treatment) programs. Such improvements were seen to catalyze increased support from family and community. CONCLUSIONS: These findings provide further empirical support to calls for a more holistic and comprehensive response to the coexistence of AIDS epidemics with chronic nutrition insecurity. Future work is needed to clarify ways of bridging the gap between short-term nutritional support to individuals and longer-term livelihood security programming for communities affected by AIDS. Such interdisciplinary research will need to be matched by intersectoral action on the part of the agriculture and health sectors in such environments. 相似文献
88.
Bambang Kuswandi Yudi Wicaksono Jayus Aminah Abdullah Lee Yook Heng Musa Ahmad 《Sensing and Instrumentation for Food Quality and Safety》2011,5(3-4):137-146
The development of chemical sensors and biosensors over several decades has been investigated resulting in novel and very interesting sensor devices with great promise for many areas of applications including food technology. The incorporation of such sensors into the food packaging technology has resulted what we call smart or intelligent packaging. These are truly integrated and interdisciplinary systems that invoke expertise from the fields of chemistry, biochemistry, physics and electronics as well as food science and technology. Smart packaging utilises chemical sensor or biosensor to monitor the quality & safety of food from the producers to the costumers. This technology can result in a variety of sensor designs that are suitable for monitoring of food quality and safety, such as freshness, pathogens, leakage, carbon dioxide, oxygen, pH, time or temperature. Thus, this technology is needed as on-line quality control and safety in term of consumers, authorities and food producers, and has great potential in the development of new sensing systems integrated in the food packaging, which are beyond the existing conventional technologies, like control of weight, volume, colour and appearance. 相似文献
89.
Yudi ZHANG Debiao HE Mingwu ZHANG Kim-Kwang Raymond CHOO 《Frontiers of Computer Science》2020,14(3):143803-215
Mobile devices are widely used for data access,communications and storage.However,storing a private key for signature and other cryptographic usage on a single mobile device can be challenging,due to its computational limitations.Thus,a number of(t,n)threshold secret sharing schemes designed to minimize private key from leakage have been proposed in the literature.However,existing schemes generally suffer from key reconstruction attack.In this paper,we propose an efficient and secure two-party distributed signing protocol for the SM2 signature algorithm.The latter has been mandated by the Chinese government for all electronic commerce applications.The proposed protocol separates the private key to storage on two devices and can generate a valid signature without the need to reconstruct the entire private key.We prove that our protocol is secure under nonstandard assumption.Then,we implement our protocol using MIRACL Cryptographic SDK to demonstrate that the protocol can be deployed in practice to prevent key disclosure. 相似文献
90.
María T. Colomer Lidia Zur Maurizio Ferrari Angel L. Ortiz 《Ceramics International》2018,44(11):11993-12001
Rhabdophane-type Eu3+,Tb3+-codoped LaPO4·nH2O single-crystal nanorods with the compositions La0.99999-xEuxTb0.00001PO4·nH2O (x?=?0–0.03), La0.99999-yTbyEu0.00001PO4·n′H2O (y?=?0–0.010), and La0.99999-zTbzEu0.000007PO4·n′′H2O (z?=?0–0.012) were hydrothermally synthesized with microwaves. It is shown that the Eu3+,Tb3+ codoping does not affect the thermal stability of these nanorods, which is due to the formation of substitutional solid solutions with both Eu3+ and Tb3+ replacing La3+ in the crystal lattice. Moreover, it is also shown that monazite-type Eu3+,Tb3+-codoped LaPO4 single-crystal nanorods can be obtained by calcining their rhabdophane-type Eu3+,Tb3+-codoped LaPO4·(n,n′ or n′′)H2O counterparts at moderate temperature in air, and that they are thermally stable. It is also observed that, for the same Eu3+,Tb3+-codoping content, the monazite-type Eu3+,Tb3+-codoped LaPO4 nanorods exhibit higher photoluminescent efficiency than the rhabdophane-type Eu3+,Tb3+-codoped LaPO4· (n,n′ or n′′)H2O nanorods. Moreover, it is found that the highest photoluminescence emission corresponds to the monazite-type La0.96999Eu0.02Tb0.00001PO4 nanorods for the La0.99999-xEuxTb0.00001PO4 system. However, for those compositions energy transfer from Tb3+ to Eu3+ does not occur. In addition, for an efficient energy transfer to occur, a content of at least 1?mol% Tb3+ is needed in all the studied materials. 相似文献