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排序方式: 共有98条查询结果,搜索用时 31 毫秒
1.
Golam Haider Krishna Sampathkumar Tim Verhagen Lukáš Nádvorník Farjana J. Sonia Václav Valeš Jan Sýkora Peter Kapusta Petr Němec Martin Hof Otakar Frank Yang-Fang Chen Jana Vejpravová Martin Kalbáč 《Advanced functional materials》2021,31(29):2102196
Recent advancements in isolation and stacking of layered van der Waals materials have created an unprecedented paradigm for demonstrating varieties of 2D quantum materials. Rationally designed van der Waals heterostructures composed of monolayer transition-metal dichalcogenides (TMDs) and few-layer hBN show several unique optoelectronic features driven by correlations. However, entangled superradiant excitonic species in such systems have not been observed before. In this report, it is demonstrated that strong suppression of phonon population at low temperature results in a formation of a coherent excitonic-dipoles ensemble in the heterostructure, and the collective oscillation of those dipoles stimulates a robust phase synchronized ultra-narrow band superradiant emission even at extremely low pumping intensity. Such emitters are in high demand for a multitude of applications, including fundamental research on many-body correlations and other state-of-the-art technologies. This timely demonstration paves the way for further exploration of ultralow-threshold quantum-emitting devices with unmatched design freedom and spectral tunability. 相似文献
2.
3.
Jose Andre Morales Peter J. Clarke Yi Deng B. M. Golam Kibria 《Journal in Computer Virology》2008,4(3):221-234
New viruses spread faster than ever and current signature based detection do not protect against these unknown viruses. Behavior
based detection is the currently preferred defense against unknown viruses. The drawback of behavior based detection is the
ability only to detect specific classes of viruses or have successful detection under certain conditions plus false positives.
This paper presents a characterization of virus replication which is the only virus characteristic guaranteed to be consistently
present in all viruses. Two detection models based on virus replication are developed, one using operation sequence matching
and the other using frequency measures. Regression analysis was generated for both models. A safe list is used to minimize
false positives. In our testing using operation sequence matching, over 250 viruses were detected with 43 subsequences. There
were minimal false negatives. The replication sequence of just one virus detected 130 viruses, 45% of all tested viruses.
Our testing using frequency measures detected all test viruses with no false negatives. The paper shows that virus replication
can be identified and used to detect known and unknown viruses. 相似文献
4.
Mohammad M. Hailat Ahsan Mian Zariff A. Chaudhury Golam Newaz Rahul Patwa Hans J. Herfurth 《Microsystem Technologies》2012,18(1):103-112
In this paper continuous laser welding of two dissimilar materials, aluminum and copper, was investigated. The aluminum and
the copper utilized were Al3003-H14 and Cu110-H00, respectively. Two different sets of samples were laser welded; one in which
a filler material, tin foil alloy (S-bond 220), was sandwiched between the aluminum and the copper and another set in which
the aluminum and copper were directly welded without any filler. The foil alloy was utilized to enhance the compatibility
of the two metals; aluminum and copper, reducing the brittleness of the intermetallic compound that may form and, subsequently,
enhance the mechanical properties. The welding was carried out using an IPG 500 SM fiber laser. The length of the laser joint
produced was 20 mm and the width was about 200 μm. The strength of the joint was evaluated by conducting the lap shear stress
test. Samples in which filler foil was used exhibited a better performance in the lap shear stress test (an average of 780 N)
than the samples without tin foil (an average of 650 N). The improvement in the lap shear test could be attributed to the
positive effects of the filler on enhancing the compatibility of the intermetallic compound formed via diffusion. The fracture
surface of both types of joints (with and without filler) was characterized using scanning electron microscope equipped with
energy-dispersive X-ray (EDAX). To understand the failure initiation and propagation of the samples under tension, a finite
element (FE) model was developed for the samples created with no filler material. The failure mechanism predicted from the
FE model matches reasonably well with the experimental observations from EDAX analysis. 相似文献
5.
Mohammad Maududul Huq Md. Robiur Rahman Masnun Naher Mohammad Mizanur Rahman Khan Mostafa Kamal Masud Golam Mohammad Golzar Hossain Nianyong Zhu Yih Hsing Lo Muhammad Younus Wai-Yeung Wong 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(6):1243-1252
Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (1H, 13C and 31P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh3, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S1 → S0) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts. 相似文献
6.
A. K. M. Fazle Kibria Young Hwan Mo Min Hee Yun Moon J. Kim Kee Suk Nahm 《Korean Journal of Chemical Engineering》2001,18(2):208-214
Multi-wall carbon nanotubes (MWNTs) were synthesized by catalytic decomposition of acetylene over Fe, Ni and Fe-Ni bimetallic
catalysts supported on alumina under various controlled conditions. The growth density and diameter of CNTs were markedly
dependent on the activation time of catalysts in H2 atmosphere, reaction time, reaction temperature, flow rate of acetylene, and catalyst composition. Bimetallic catalysts were
apt to produce narrower diameter of CNTs than single metal catalysts. For the growth of CNTs at 600 ‡C under 10/100 seem flow
of C2H2/H2 mixture, the narrowest diameter about 20 nm was observed at the reaction time of 1 h for 20Fe : 20Ni : 60Al2O3 catalyst, but at that of 1.5 h for 10Fe : 30Ni : 60Al2O3 catalyst. It was considered that the diameter and density of CNTs decreased with the increase of the growth time mainly due
to hydrogen etching. The growth of CNTs followed the tip growth mode. 相似文献
7.
Md. Golam Mostofa J. H. Noh H. Y. Kim J. H. Ahn D. B. Kang 《Journal of Mechanical Science and Technology》2010,24(8):1623-1629
PMMA optical components that are used as one of the most important parts of high precision equipments and machines are increasingly
replacing the glass due to the various advantages of PMMA. Especially in Light Guide Panels, the PMMA sheet that is used in
Liquid Crystal Displays plays an important role in scattering the incident light and requires very fine machining as the sheet
is directly related to the optical characteristics of the panels. The High Speed End milling and High Speed Shaping processes
that are widely adopted and applied to the precise machining of Light Incident Plane still have quality problems, such as
cracks, breakages, poor waviness, and straightness. This paper presents the tooling device design for machining a Light Incident
Plane through vibration-assisted High Speed Shaping for increasing the optical quality by minimizing the above-mentioned problems.
The cutting tool and the tool post presented in this paper are designed by the authors to increase the magnitude of the cutting
stroke by adopting the resonant frequency without weakening the stiffness and to reduce vibrations during even high speed
feeding. The dynamic characteristics of the cutting tool and the tool post are evaluated through simulation and experiment
as well. The results reveal very appropriate dynamic characteristics for vibration-assisted High Speed Shaping. 相似文献
8.
9.
Jose Andre Morales Peter J. Clarke Yi Deng B. M. Golam Kibria 《Journal in Computer Virology》2006,2(2):135-147
The widespread use of personal digital assistants and smartphones gives securing these devices a high priority. Yet little attention has been placed on protecting handheld devices against viruses. Currently available antivirus software for handhelds is few in number. At this stage, the opportunity exists for the evaluation and improvement of current solutions. By pinpointing weaknesses in the current antivirus software, improvements can be made to properly protect these devices from a future tidal wave of viruses. This research evaluates four currently available antivirus solutions for handheld devices. A formal model of virus transformation that provides transformation traceability is presented. Two sets of ten tests each were administered; nine tests from each set involved the modification of source code of two known viruses for handheld devices. The testing techniques used are well established in PC testing; thus the focus of this research is solely on handheld devices. Statistical analysis of the test results show high false negative production rates for the antivirus software and an overall false negative production rate of 47.5% with a 95% confidence interval between 36.6% and 58.4%. This high rate shows that current solutions poorly identify modified versions of a virus. The virus is left undetected and capable of spreading, infecting and causing damage. 相似文献
10.
Fracture in particulate composites 总被引:1,自引:0,他引:1
Golam M. Newaz 《Journal of Materials Science Letters》1986,5(1):71-72