Higher-order composition of short- and long-period effects for improving analytical ephemeris computation

The construction of an analytic orbit theory that takes into account the main effects of the Geopotential is notably simplified when splitting the removal of periodic effects in several stages. Conversely, this splitting of the analytical solution into several transformations reduces the evaluation efficiency for dense ephemeris output. However, the advantage is twofold when the different parts of the mean-to-osculating transformation are composed into a single transformation. To show that, Brouwer's solution is extended to the second order of the zonal harmonic of the second degree by the sequential elimination of short- and long-period terms. Then, the generating functions of the different transformations are composed into a single one, from which a single mean-to-osculating transformation is derived. The new, unique transformation notably speeds up the evaluation process, commonly improving evaluation efficiency by at least one third with respect to the customary decomposition of the analytical solution into three different parts

Stability Boundaries in Laterally-Coupled Pairs of Semiconductor Lasers

The dynamic behaviour of coupled pairs of semiconductor lasers is studied using normal-mode theory, applied to one-dimensional (slab) and two-dimensional (circular cylindrical) real index confined structures. It is shown that regions of stable behaviour depend not only on pumping rate and laser separation, but also on the degree of guidance in the structures. Comparison of results between normal-mode and coupled-mode theories for these structures leads to the tentative conclusion that the accuracy of the latter is determined by the strength of self-overlap and cross-overlap of the symmetric and antisymmetric normal modes in the two lasers

Dynamics of laterally-coupled pairs of spin-VCSELs

A newly-developed normal mode model of laser dynamics in a generalised array of waveguides is applied to extend the spin-flip model (SFM) to pairs of evanescently-coupled spin-VCSELS. The effect of high birefringence is explored, revealing new dynamics and regions of bistability. It is shown that optical switching of the polarisation states of the lasers may be controlled through the optical pump and that, under certain conditions, the polarisation of one laser may be switched by controlling the intensity and polarisation in the other

Simulasi Dinamis pada Kereta Penumpang Stainless Steel New Generation menggunakan Metode Multibody Dynamic System

Stainless steel passenger coach is the most operated passenger coach in Indonesia. Because it has better facilities, cheap, and offering more operation hour. Stainless steel passenger coach fabricated by PT.Industri Kereta Api (PT.INKA) and always improve and keep innovate from generation to generation. At this time, This passenger coach being upgraded to reach the speed more than 120 Km/h and keep the ride quality and ride comfort index and called as stainless steel new generation (SS-NG) passenger coach. To reach the target one of the method is re-design the structure of bogie. The purpose of this research is to analyzing design of the SS-NG bogie, on SS-NG passenger coach using multibody dynamic simulation to studying rolling stock dynamic and compare it with existence bogie dynamic of SS-2018 passenger coach. The result of the simulation show the SS-NG bogie design give vertical and lateral ride  comfort index appropriate  to Sperling comfort index on center of carbody, center of front and rear bogie while operating at 240 Km/h.Kereta penumpang stainless steel merupakan jenis kereta yang paling banyak beroperasi di Indonesia. Hal ini karena kereta ini memberikan fasilitas lengkap, berbiaya ekonomis, dan menawarkan jam operasi yang lebih banyak. Kereta penumpang stainless steel difabrikasi oleh PT. Industri Kereta Api (PT. INKA) dari generasi pertama hingga sekarang, dan terus mengalami perkembangan inovasi. Kereta ini sedang dikembangkan agar mencapai kecepatan lebih dari 120 Km/jam dengan tetap menjaga tingkat keamanan dan kenyamanan, serta disebut sebagai kereta penumpang stainless steel new generation (SS-NG). Untuk mencapai hal tersebut, salah satu caranya adalah dengan mendesain ulang struktur bogie kereta. Penelitian ini bertujuan untuk menganalisis desain bogie pada rangkaian kereta SS-NG dengan metode simulasi system multibody dynamic untuk mengkaji dinamika kereta serta membandingkannya dengan dinamika kereta existing, yakni SS-2018. Hasil simulasi menunjukkan bahwa desain bogie kereta SS-NG memberikan tingat kenyamanan pada arah vertikal dan lateral sesuai dengan Sperling comfort index pada pusat carbody, pusat bogie depan dan belakang saat kereta beroperasi pada kecepatan 240 Km/jam

LPP3 mediates self-generation of chemotactic LPA gradients by melanoma cells

Melanoma cells steer out of tumours using self-generated lysophosphatidic acid (LPA) gradients. The cells break down LPA, which is present at high levels around the tumours, creating a dynamic gradient that is low in the tumour and high outside. They then also migrate up this gradient, creating a complex and evolving outward chemotactic stimulus. Here we introduce a new assay for self-generated chemotaxis, and show that raising LPA levels causes a delay in migration rather than loss of chemotactic efficiency. Knockdown of the lipid phosphatase LPP3 - but not its homologues LPP1 or LPP2 - diminishes the cell's ability to break down LPA. This is specific for chemotactically active LPAs, such as the 18:1 and 20:4 species. Inhibition of autotaxin-mediated LPA production does not diminish outward chemotaxis, but loss of LPP3-mediated LPA breakdown blocks it. Similarly, in both 2D and 3D invasion assays, knockdown of LPP3 diminishes melanoma cells' ability to invade. Our results demonstrate that LPP3 is the key enzyme in melanoma cells' breakdown of LPA, and confirm the importance of attractant breakdown in LPA-mediated cell steering

The Paradigm of Islamization of Knowledge According to SMN Al-Attas (From Islamization of Science to Islamic Science)

This article examines the idea of Islamization of knowledge as a variant of the issue of integration between science and Islam, to view the possibility of engendering to new science not only scientific but also religious, which is not only religious but scientific at once. With the framework of the philosophy of science, this study will bring the issue of Islamization of science more than just ideas and discourse but must forge it as a scientific paradigm, which is the paradigm of Islamization of Science. Therefore, the scientific paradigm is examined in advance, before it can be used as a perspective in reading Islamization of Science and also functionalize it in generating new knowledge. There are at least nine fundamental elements of the paradigm that must rediscover their competence with Islamic sciences, ranging from basic assumptions, values, studied issues, models, main concepts, methods of research, methods of analysis, the result of analysis or theory, and representation/ethnography. The success of this study became a large contribution to the intellectual movement that focuses on the engender of new science-based Islam or called by Islamic sciences

The Overlap Factor Model of Spin-Polarised Coupled Lasers

A general model for the dynamics of arrays of coupled spin-polarised lasers is derived. The general model is able to deal with waveguides of any geometry with any number of supported normal modes. A unique feature of the model is that it allows for independent polarisation of the pumping in each laser. The particular geometry is shown to be introduced via ’overlap factors’, which are a generalisation of the optical confinement factor. These factors play an important role in determining the laser dynamics. The model is specialised to the case of a general double-guided structure, which is shown to reduce to both the spin flip model in a single cavity and the coupled mode model for a pair of guides in the appropriate limit. This is applied to the particular case of a circular-guide laser pair, which is analysed and simulated numerically. It is found that increasing the ellipticity of the pumping tends to reduce the region of instability in the plane of pumping strength versus guide separation

Dynamics of Evanescently-Coupled Laser Pairs With Unequal Pumping: Analysis Using a Three-Variable Reduction of the Coupled Rate Equations

The five coupled rate equations used to describe laterally-coupled pairs of lasers with weak coupling and unequal pumping are reduced to a new system of three equations. This enables approximate closed-form steady-state solutions and explicit expressions for the boundaries between regions of stable and unstable dynamics to be found. The results of applying these approximations to specific cases of coupled laser pairs are shown to be in good agreement with results obtained from numerical solutions of the original set of five equations as well as earlier results from the literature. In addition the approximations based on the reduced set of equations allow a systematic investigation of the effects of material, device and operating conditions on trends and novel features in the dynamics of laterally-coupled laser pairs. The algebraic results give insight into trends with parameters without the need for extensive numerical computation and should therefore be of use in modelling two-element VCSEL arrays for numerous potential applications