Modifikasi Pengujian Kekuatan Lekat Lapisan Hvof Thermal Spray Dengan Serbuk Wc Pada Nosel Roket

Modification of Bonding Strength Test of WC HVOF Thermal Spray Coating on Rocket Nozzle. One way toreduce structural weight of RX-100 rocket is by modifying the nozzle material and processing. Nozzle is the main targetin weight reduction due to the fact that it contributes 30 % to the total weight of the structur. An alternative for this is bysubstitution of massive graphite, which is currently used as thermal protector in the nozzle, with thin layer of HVOF(High Velocity Oxy-Fuel) thermal spray layer. This paper presents the characterization of nozzle base material as wellas the modification of bonding strength test, by designing additional jig to facilitate testing processes while maintaininglevel of test accuracy. The results showed that the material used for RX-100 rocket nozzle is confirmed to be S45Csteel. Modification of the bonding strength test was conducted by utilizing chains, which improve test flexibility andmaintains level of accuracy of the test

Social–environmental drivers inform strategic management of coral reefs in the Anthropocene

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages—the foundation species of coral reef ecosystems. Here, we compiled coral abundance data from 2,584 Indo-Pacific reefs to evaluate the influence of 21 climate, social and environmental drivers on the ecology of reef coral assemblages. Higher abundances of framework-building corals were typically associated with: weaker thermal disturbances and longer intervals for potential recovery; slower human population growth; reduced access by human settlements and markets; and less nearby agriculture. We therefore propose a framework of three management strategies (protect, recover or transform) by considering: (1) if reefs were above or below a proposed threshold of >10% cover of the coral taxa important for structural complexity and carbonate production; and (2) reef exposure to severe thermal stress during the 2014–2017 global coral bleaching event. Our findings can guide urgent management efforts for coral reefs, by identifying key threats across multiple scales and strategic policy priorities that might sustain a network of functioning reefs in the Indo-Pacific to avoid ecosystem collapse

Cloud computing security: from single to multi-clouds

The use of cloud computing has increased rapidly in many organizations. Cloud computing provides many benefits in terms of low cost and accessibility of data. Ensuring the security of cloud computing is a major factor in the cloud computing environment, as users often store sensitive information with cloud storage providers but these providers may be untrusted. Dealing with "single cloud" providers is predicted to become less popular with customers due to risks of service availability failure and the possibility of malicious insiders in the single cloud. A movement towards "multi-clouds", or in other words, "interclouds" or "cloud-of-clouds" has emerged recently. This paper surveys recent research related to single and multi-cloud security and addresses possible solutions. It is found that the research into the use of multi-cloud providers to maintain security has received less attention from the research community than has the use of single clouds. This work aims to promote the use of multi-clouds due to its ability to reduce security risks that affect the cloud computing user

Efektivitas Model Pembelajaran Group Investigation Terhadap Kemampuan Menulis Teks Anekdot Pada Siswa Kelas X Smk Sultan Iskandar Muda Medan Tahun Pelajaran 2018/2019

Penelitian ini bertujuan untuk mengetahui masalah pada siswa dalam kemampuan menulis teks anekdot yang masih sangat rendah, beberapa faktor penyebabnya adalah penggungaan model pembelajaran yang kurang tepat. Penelitian dilakukan untuk mengetahui efektivitas model pembelajaran group investigation terhadap kemampuan menulis teks anekdot siswa kelas X SMK Sultan Iskandar Muda Medan tahun pelajaran 2018/2019. Untuk dilasanakan penelitian ini sampel terlebih dahulu diambil dari kelas X-MM1 dan X-MM2 yang berjumlah 62 siswa. Sebagai alat pengumpulan data dalam penelitian ini digunakan tes pilihan berganda sebagai alat pengumpul data. Hipotesis dalam penelitian ini adalah hasil belajar menulis teks anekdot dengan menggunakan model pembelajaran group investigation lebih baik dari pada hasil belajar dengan menggunakan model ceramah. Data penelitian ini dianalisis dengan menggunakan rumus uji ”t” karena demikian  2,00 <  7,2 >  2,00. Maka, hipotesis nol () ditolak dan hipotesis () diterima. Berdasarkan analisis data maka dapat disimpulkan bahwa terdapat efektivitas yang signifikan atas penggunaan  model group investigation terhadapt kemampuan menulis teks anekdot pada siswa kelas X SMK Sultan Iskandar Muda Medan Tahun Pelajaran 2018/201

Euclid preparation. TBD. Galaxy power spectrum modelling in real space

We investigate the accuracy of the perturbative galaxy bias expansion in view of the forthcoming analysis of the Euclid spectroscopic galaxy samples. We compare the performance of an Eulerian galaxy bias expansion, using state-of-art prescriptions from the effective field theory of large-scale structure (EFTofLSS), against a hybrid approach based on Lagrangian perturbation theory and high-resolution simulations. These models are benchmarked against comoving snapshots of the Flagship I N-body simulation at $z=(0.9,1.2,1.5,1.8)$, which have been populated with H$\alpha$ galaxies leading to catalogues of millions of objects within a volume of about $58\,h^{-3}\,{\rm Gpc}^3$. Our analysis suggests that both models can be used to provide a robust inference of the parameters $(h, \omega_{\rm c})$ in the redshift range under consideration, with comparable constraining power. We additionally determine the range of validity of the EFTofLSS model in terms of scale cuts and model degrees of freedom. From these tests, it emerges that the standard third-order Eulerian bias expansion can accurately describe the full shape of the real-space galaxy power spectrum up to the maximum wavenumber $k_{\rm max}=0.45\,h\,{\rm Mpc}^{-1}$, even with a measurement precision well below the percent level. In particular, this is true for a configuration with six free nuisance parameters, including local and non-local bias parameters, a matter counterterm, and a correction to the shot-noise contribution. Fixing either tidal bias parameters to physically-motivated relations still leads to unbiased cosmological constraints. We finally repeat our analysis assuming a volume that matches the expected footprint of Euclid, but without considering observational effects, as purity and completeness, showing that we can get consistent cosmological constraints over this range of scales and redshifts