A Broadband Graphene-Based THz Coupler with Wide-Range Tunable Power-Dividing Ratios

A wide-band coupler based on the graphene with inherent DC-block function and adjustable power-dividing ratios is proposed. This coupler uses three sections of the two-line coupled lines, four sections of the three-line coupled lines, and four graphene stubs (two U-shaped stubs and two rectangular stubs). The graphene stubs allow the coupler to own dynamic surface conductivity, which could be tuned by altering the chemical potentials. The tunable power-dividing ratios could be achieved by varying the chemical potentials applied to the U-shaped graphene stubs and the rectangular graphene elements, respectively. In addition, the widths of two-line coupled lines in the proposed coupler are analyzed to affect the power-dividing ratios in detail. Finally, the power-dividing ratios of the proposed coupler have a variation range from 5.4 to 9.56 dB at 1.75 THz with a flat 90° phase shift. The minimum −10 dB impedance bandwidth is 44 % from 1.47 to 2.3 THz, thus indicating a wide-band performance

Preliminary Functional-Structural Modeling on Poplar (Salicaceae)

Poplar is one of the best fast-growing trees in the world, widely used for windbreak and wood product. Although architecture of poplar has direct impact on its applications, it has not been descried in previous poplar models, probably because of the difficulties raised by measurement, data processing and parameterization. In this paper, the functional-structural model GreenLab is calibrated by using poplar data of 3, 4, 5, 6 years old. The data was acquired by simplifying measurement. The architecture was also simplified by classifying the branches into several types (physiological age) using clustering analysis, which decrease the number of parameters. By multi-fitting the sampled data of each tree, the model parameters were identified and the plant architectures at different tree ages were simulated

The Causative Agent of FMD Disease

Foot-and-mouth disease (FMD) is an acute infection of cloven-hoofed animals caused by foot-and-mouth disease virus (FMDV). It is one of the most serious infectious diseases affecting animal husbandry and a major impediment to international trade in livestock and their products. Foot-and-mouth disease virus (FMDV), a member of the Picornaviridae family of Aphthovirus, is an icosahedral virus without envelope, 25–30 nm in diameter, containing about 8.4 kb of positive-sense single-stranded RNA. The virus exists in seven different serotypes: A, O, C, Asia1, SAT1, SAT2, and SAT3, but a large number of subtypes have evolved in each serotype. This chapter reviews the genome, structure, serotype, and epidemiology of FMDV, which will help people to further explore the mechanism of the interaction between foot-and-mouth disease virus and host and provide reference for scientific prevention and control of FMDV

Graphene-based Yagi-Uda antenna with reconfigurable radiation patterns

This paper presents a radiation pattern reconfigurable Yagi-Uda antenna based on graphene operating at terahertz frequencies. The antenna can be reconfigured to change the main beam pattern into two or four different radiation directions. The proposed antenna consists of a driven dipole radiation conductor, parasitic strips and embedded graphene. The hybrid graphene-metal implementation enables the antenna to have dynamic surface conductivity, which can be tuned by changing the chemical potentials. Therefore, the main beam direction, the resonance frequency, and the front-to-back ratio of the proposed antenna can be controlled by tuning the chemical potentials of the graphene embedded in different positions. The proposed two-beam reconfigurable Yagi-Uda antenna can achieve excellent unidirectional symmetrical radiation pattern with the front-to-back ratio of 11.9 dB and the10-dB impedance bandwidth of 15%. The different radiation directivity of the two-beam reconfigurable antenna can be achieved by controlling the chemical potentials of the graphene embedded in the parasitic stubs. The achievable peak gain of the proposed two-beam reconfigurable antenna is about 7.8 dB. Furthermore, we propose a four-beam reconfigurable Yagi-Uda antenna, which has stable reflection-coefficient performance although four main beams in reconfigurable cases point to four totally different directions. The corresponding peak gain, front-to-back ratio, and 10-dB impedance bandwidth of the four-beam reconfigurable antenna are about 6.4 dB, 12 dB, and 10%, respectively. Therefore, this novel design method of reconfigurable antennas is extremely promising for beam-scanning in terahertz and mid-infrared plasmonic devices and systems

Growth and development simulation based on functional-structural model GreenLab for poplar (Salicaceae)

International audiencePoplar (salicaceae) is one of the widest planted fast-growing trees in the world. It is not only used for timber, but also used as windbreak and ecological protection of forest widely. The architecture of poplar has direct impact on poplar's growth and applications, but poplar's architecture still has not been discussed deeply in previous poplar models because of the difficulties raised by measurement, data processing and parameterization. This paper aimed to collect the biomass and architecture data of poplars of different ages, and construct the functional-structural model of poplar based on GreenLab. The selected poplar variety was poplar 107 (Populus × euramericana cv. Neva). The biomass and architecture data were collected from four trees with 3, 4, 5 and 6 years old, respectively. The architecture was simplified by classifying the branches into several types (physiological age) according to the length and size. Based on GreenLab model, some parameters were obtained and some strong correlation coefficients were got. The comparison between the measured and simulated results was given for the trunk data of all trees. The topological structures of poplar at different tree ages were reconstructed. This paper was a exploration of poplar growth simulation based on GreenLab model, and was a good reference in the Functional-Structural model construction of complex trees

The Impact of Heterogeneous Shared Leadership in Scientific Teams

Leadership is evolving dynamically from an individual endeavor to shared efforts. This paper aims to advance our understanding of shared leadership in scientific teams. We define three kinds of leaders, junior (10-15), mid (15-20), and senior (20+) based on career age. By considering the combinations of any two leaders, we distinguish shared leadership as heterogeneous when leaders are in different age cohorts and homogeneous when leaders are in the same age cohort. Drawing on 1,845,351 CS, 254,039 Sociology, and 193,338 Business teams with two leaders in the OpenAlex dataset, we identify that heterogeneous shared leadership brings higher citation impact for teams than homogeneous shared leadership. Specifically, when junior leaders are paired with senior leaders, it significantly increases team citation ranking by 1-2%, in comparison with two leaders of similar age. We explore the patterns between homogeneous leaders and heterogeneous leaders from team scale, expertise composition, and knowledge recency perspectives. Compared with homogeneous leaders, heterogeneous leaders are more adaptive in large teams, have more diverse expertise, and trace both the newest and oldest references

Adsorption Behavior of Iodine by Novel Covalent Organic Polymers Constructed Through Heterostructural Mixed Linkers

The efficient capture and storage radioactive iodine (129I or 131I) formed during the extensive use of nuclear energy is of paramount importance. Therefore, it is a great deal to design and empolder new adsorbents for effectively disposing of iodine from nuclear waste. In this work, we presented a novel covalent organic polymer (JLUE-COP-3) constructed through heterostructural mixed linkers with perforated porousness, plenty of π-conjugated phenyl rings and functional –CO–NH– and –SO3H groups to iodine adsorption process. After fully characterizing the morphology and structure, the adsorption behavior of iodine by the resultant polymers were explored in detail. The external adsorption behavior was determined to obey the pseudo-second order kinetic model according to the kinetic analysis. The maximum liquid adsorption capacity was obtained to reach 153.85 mg/g at 298 K, which was evaluated by the Langmuir isotherm model. In addition, the negative attributes of ΔG° as well as the positive attributes of ΔH° and ΔS° at three temperatures indicated the nature of the iodine adsorption over JLUE-COP-3 was spontaneous and endothermic. The current study could look forward to making great contributions to the facile fabrication of late-model three-component POP materials and their applications in treatment of nuclear waste

Neutron scattering studies of heterogeneous catalysis

Understanding the structural dynamics/evolution of catalysts and the related surface chemistry is essential for establishing structure–catalysis relationships, where spectroscopic and scattering tools play a crucial role. Among many such tools, neutron scattering, though less-known, has a unique power for investigating catalytic phenomena. Since neutrons interact with the nuclei of matter, the neutron–nucleon interaction provides unique information on light elements (mainly hydrogen), neighboring elements, and isotopes, which are complementary to X-ray and photon-based techniques. Neutron vibrational spectroscopy has been the most utilized neutron scattering approach for heterogeneous catalysis research by providing chemical information on surface/bulk species (mostly H-containing) and reaction chemistry. Neutron diffraction and quasielastic neutron scattering can also supply important information on catalyst structures and dynamics of surface species. Other neutron approaches, such as small angle neutron scattering and neutron imaging, have been much less used but still give distinctive catalytic information. This review provides a comprehensive overview of recent advances in neutron scattering investigations of heterogeneous catalysis, focusing on surface adsorbates, reaction mechanisms, and catalyst structural changes revealed by neutron spectroscopy, diffraction, quasielastic neutron scattering, and other neutron techniques. Perspectives are also provided on the challenges and future opportunities in neutron scattering studies of heterogeneous catalysis