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排序方式: 共有190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.
Because of its self-regulating nature, immune system has been an inspiration source for usually unsupervised learning methods in classification applications of Artificial Immune Systems (AIS). But classification with supervision can bring some advantages to AIS like other classification systems. Indeed, there have been some studies, which have obtained reasonable results and include supervision in this branch of AIS. In this study, we have proposed a new supervised AIS named as Supervised Affinity Maturation Algorithm (SAMA) and have presented its performance results through applying it to diagnose atherosclerosis using carotid artery Doppler signals as a real-world medical classification problem. We have employed the maximum envelope of the carotid artery Doppler sonograms derived from Autoregressive (AR) method as an input of proposed classification system and reached a maximum average classification accuracy of 98.93% with 10-fold cross-validation method used in training-test portioning. To evaluate this result, comparison was done with Artificial Neural Networks and Decision Trees. Our system was found to be comparable with those systems, which are used effectively in literature with respect to classification accuracy and classification time. Effects of system's parameters were also analyzed in performance evaluation applications. With this study and other possible contributions to AIS, classification algorithms with effective performances can be developed and potential of AIS in classification can be further revealed. 相似文献
5.
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
6.
Noriaki Murakami Koji Arafune Tadanobu Koyama Yoshimi Momose Tetsuo Ozawa Yasunori Okano Sadik Dost Le. H. Dao Masashi Kumagawa Yasuhiro Hayakawa 《Microgravity science and technology》2005,16(1-4):79-83
The effect of gravity on dissolution of GaSb in InSb melt and growth of InGaSb was experimentally investigated. Experiments were carried out in a GaSb(seed)/InSb/GaSb(feed) sandwich system under an imposed temperature gradient. In the experiments, the GaSb feed crystal dissolved into the InSb melt to supply the required GaSb component for the growth of In0.1Ga0.9Sb crystal. Two parameters were considered: (1) the inclination angle (θ) of the sample for gravity as 0° and 53°, and (2) the sample diameter (D) as 9 mm and 5mm. When θ was 0°, the interface was almost flat, indicating that convection was axisymmetric and stable. Whereas the interface was distorted towards gravitational direction when θ was 53°, indicating that solutal convection was dominant. The decrease of growth temperature and sample diameter reduced the distortion of interface and the dissolution amount of GaSb feed. The homogeneous crystals were grown at the initial growth stage by supplying the GaSb component during growth. 相似文献
7.
This paper shows that a turned trochoidal function disturbance may lead to peripheral drops production. The resulting model is used to describe that a turned trochoidal disturbance leads to peripheral drops production on the liquid jet surface without the necessity for superimposed disturbances. The trochoid is a non-unique parametric function. Only non-unique parametric functions disturbances may lead to peripheral drops production. The trochoidal function disturbance is decomposed to Fourier series. Every Fourier element receives an amplification factor in accordance to the Rayleigh inviscid jet model. Peripheral drops are received on the jet surface. The paper shows that all trochoidal disturbance functions, prolate cycloid, cycloid and curtate cycloid have a capability of peripheral drops producing. A limited capability of peripheral drops production is introduced for the trochoidal curtate cycloid. Produced drops size are reduced for increasing the jet velocity and wave number. Smaller drops are also received by transition from the prolate cycloid to curtate cycloid disturbance. 相似文献
8.
This article presents an effective analytical model for determining the moisture diffusivities and moisture transfer coefficients for solid objects (namely, infinite slab, infinite cylinder, sphere; and also for irregularly shaped objects, by using a shape factor) subject to drying applications in a medium. The unsteady-state moisture diffusion analysis is used on the basis of two important criteria: 0·1 <Bi < 100 and Bi > 100. The drying coefficients and lag factors were employed. The analytical models are then verified using available experimental data taken from the literature. The results show that the method presented here can be used to determine the moisture diffusion coefficients and moisture transfer coefficients for such solid objects in a simple and accurate manner for a variety of drying applications. 相似文献
9.
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
10.
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