5,124 research outputs found

    Intensity dependences of the nonlinear optical excitation of plasmons in graphene

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    Recently, we demonstrated an all-optical coupling scheme for plasmons, which takes advantage of the intrinsic nonlinear optical response of graphene. Frequency mixing using free-space, visible light pulses generates surface plasmons in a planar graphene sample, where the phase matching condition can define both the wavevector and energy of surface waves and intraband transitions. Here, we also show that the plasmon generation process is strongly intensity-dependent, with resonance features washed out for absorbed pulse fluences greater than 0.1 J m−2. This implies a subtle interplay between the nonlinear generation process and sample heating. We discuss these effects in terms of a non-equilibrium charge distribution using a two-temperature model.Peer ReviewedPostprint (author's final draft

    Prinsip Kehati-hatian Pejabat Pembuat Akta Tanah dalam Pengurusan Peralihan Tanah “Letter C”

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    Penulisan jurnal ini membahas mengenai salah satu permasalahan tentang Prinsip Kehati-Hatiaan Pejabat Pembuat Akta Tanah Dalam Pengurusan Peralihan Tanah “Letter C”. Permasalahan yang muncul adalah Prinsip Kehatian-hatian PPAT hanya dijelaskan dalam Pasal 22 PP No. 37 Tahun 1998 bahwa Akta PPAT harus dibacakan/dijelaskan isinya kepada para pihak dengan dihadiri oleh sekurang-kurangnya 2 (dua) orang saksi sebelum ditandatangani seketika itu juga oleh para pihak, saksi-saksi dan PPAT. Sementara dalam pengurusan peralihan tanah Letter C seharus-nya seorang PPAT tidak hanya memastikan bahwa para pihak menghadap dengan PPAT sebagai Pejabat yang membacakan dan menjelaskan akta akan tetapi sesuai prinsip kehati-hatian PPAT dapat menghindari dan mencegah terjadinya kesalahan yang menyebabkan munculnya permasalahan dalam pengurusan peralihan Letter C. karena dalam praktek pengurusan Letter C, PPAT tidak membacakan dan menjelaskan isi akta yang mana para pihak tidak hadir di hadapan PPAT. Sehingga PPAT tidak hati-hati dalam menjalankan jabatannya. Selain itu dalam Pasal 23 Ayat (1) dijelaskan mengenai prinsip kehati-hatian yakni “PPAT dilarang membuat akta, apabila PPAT sendiri, suami atau istrinya, keluarganya sedarah atau semenda, dalam garis lurus tanpa pembatasan derajat dan dalam garis ke samping sampai derajat kedua, menjadi pihak dalam perbuatan hukum yang bersangkutan, baik dengan cara bertindak sendiri maupun melalui kuasa, atau menjadi kuasa dari pihak lain.” Sementara dalam praktiknya PPAT dalam pengurusan Letter C menjadi pihak dengan membuat kuasa pengurusan Letter C. Tujuan penelitian ini untuk Mengkaji dan menganalisis kedudukan dan kekuatan hukum Letter C sebagai alat bukti kepemilikan tanah dan Mengkaji dan Menganalisis bentuk pelaksanaan prinsip kehati-hatiaan PPAT dalam pengurusan peralihan tanah Letter C. dengan menggunakan metode penelitian pada jenis adalah penelitian hukum normatif. Penelitian hukum normatif adalah memecahkan masalah hukum secara normatif yang pada dasarnya bertumpu pada analisa dan mendalam terhadap bahan-bahan pustaka dan dokumen-dokumen hukum yang relevan dengan permasalahan hukum yang dikaji. Penelitian melalui metode normatif dalam penulisan ini adalah Prinsip Kehati-Hatiaan Pejabat Pembuat Akta Tanah Dalam Pengurusan Peralihan Tanah “Letter C”

    Hot phonon decay in supported and suspended exfoliated graphene

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    Near infrared pump-probe spectroscopy has been used to measure the ultrafast dynamics of photoexcited charge carriers in monolayer and multilayer graphene. We observe two decay processes occurring on 100 fs and 2 ps timescales. The first is attributed to the rapid electron-phonon thermalisation in the system. The second timescale is found to be due to the slow decay of hot phonons. Using a simple theoretical model we calculate the hot phonon decay rate and show that it is significantly faster in monolayer flakes than in multilayer ones. In contrast to recent claims, we show that this enhanced decay rate is not due to the coupling to substrate phonons, since we have also seen the same effect in suspended flakes. Possible intrinsic decay mechanisms that could cause such an effect are discussed.Comment: 4 pages, 3 figure

    Reinforcing Value of Information Technical Report No. 65-1

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    Psychology experiment to show if information is reinforcing and if negative discriminative stimulus is both positively and negatively reinforcin

    Non-linear resistivity and heat dissipation in monolayer graphene

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    We have experimentally studied the nonlinear nature of electrical conduction in monolayer graphene devices on silica substrates. This nonlinearity manifests itself as a nonmonotonic dependence of the differential resistance on applied DC voltage bias across the sample. At temperatures below ~70K, the differential resistance exhibits a peak near zero bias that can be attributed to self-heating of the charge carriers. We show that the shape of this peak arises from a combination of different energy dissipation mechanisms of the carriers. The energy dissipation at higher carrier temperatures depends critically on the length of the sample. For samples longer than 10um the heat loss is shown to be determined by optical phonons at the silica-graphene interface.Comment: 4 pages, 4 figure

    Finite element analysis applied to redesign of submerged entry nozzles for steelmaking

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    The production of steel by continuous casting is facilitated by the use of refractory hollow-ware components. A critical component in this process is the submerged entry nozzle (SEN). The normal operating conditions of the SEN are arduous, involving large temperature gradients and exposure to mechanical forces arising from the flow of molten steel; experimental development of the components is challenging in so hazardous an environment. The effects of the thermal stress conditions in relation to a well-tried design were therefore simulated using a finite element analysis approach. It was concluded from analyses that failures of the type being experienced are caused by the large temperature gradient within the nozzle. The analyses pointed towards a supported shoulder area of the nozzle being most vulnerable to failure and practical in-service experience confirmed this. As a direct consequence of the investigation, design modifications, incorporating changes to both the internal geometry and to the nature of the intermediate support material, were implemented, thereby substantially reducing the stresses within the Al2O3/graphite ceramic liner. Industrial trials of this modified design established that the component reliability would be significantly improved and the design has now been implemented in series production
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