solidot此次改版内容包括服务器更新、编程语言、网站后台管理的优化、页面和操作流程的优化等。

信息流

•   08-13 15 muxueqz 22393

为什么要自己动手写一个静态博客？ 众所周知，随着Github Pages这样的服务越来越流行，现在像Hexo、Hugo、Pelican这样的静态博客越来越多， 像我以前就是用Pelican的，但因为Pelican的依赖比较多（其实是想自己造轮子）， 自从见过Nim就一直很想自己写一个静态博客，但总是觉得比较麻烦， 直到看到 [Writing a small static site generator](https://blog.thea.codes/a-small-static-site-generator/) ， 才发现原来写一个静态博客竟如此简单。 废话不多说，那我们就开始动手做吧！

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•   05-29 LWN 11022

Finding a way for applications to do atomic writes to files, so that either the old or new data is present after a crash and not a combination of the two, was the topic of a session led by Christoph Hellwig at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). Application developers hate the fact that when they update files in place, a crash can leave them with old or new data—or sometimes a combination of both. He discussed some implementation ideas that he has for atomic writes for XFS and wanted to see what the other filesystem developers thought about it.

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•   05-29 LWN 9975

Debian Linux and its family of derivatives (such as Ubuntu) are partly characterized by their use of .deb as the packaging format. Packages in this format are produced not only by the distributions themselves, but also by independent software vendors. The last major change of the format internals happened back in 1995. However, a discussion of possible changes has been brought up recently on the debian-devel mailing list by Adam Borowski.

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• An annual contest challenges programmers to create 8-bit games of intrigue and adventure

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•   05-29 Slashdot 19714

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•   05-29 MIT Technology 20191

Taking down the ‘drunk ’ Pelosi video could set a precedent for censoring political satire or dissent.

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•   05-29 LWN 9678

Ted Ts'o led a discussion on storage testing and, in particular, on his experience getting blktests running for his test environment, in a combined storage and filesystem session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit. He has been adding more testing to his automated test platform, including blktests, and he would like to see more people running storage tests. The idea of his session was to see what could be done to help that cause.

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•   05-29 Hacker News 19994

iPhone apps share data with trackers, ad companies and research firms

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• The physical memory in a computer system is a precious resource, so a lot of effort has been put into managing it effectively. This task is made more difficult by the complexity of the memory architecture on contemporary systems. There are several layers of abstraction that deal with the details of how physical memory is laid out; one of those is simply called the "memory model". There are three models supported in the kernel, but one of them is on its way out. As a way of understanding this change, this article will take a closer look at the evolution of the kernel's memory models, their current state, and their possible future.

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•   05-28 MIT Technology 19788

A look at historical case studies shows us how we handle the liability of automated systems.

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•   05-28 OSnews 19303

We are developers and designers making apps for the GNOME platform. We take pride in our craft and work hard to make sure our applications are a great experience for people. Unfortunately, all our efforts designing, developing, and testing our apps are made futile by theming in many cases. This is insanity – even if they claim it only applies to distribution makers. Their argument basically comes down to certain themes making certain applications look bad, and that theming removes branding from applications. First, theming making applications look bad is either an issue with the theme that needs to be fixed or an issue with Gtk+/GNOME being bad at theming, and second, your branding is irrelevant on my computer, or on my distribution. I use KDE, and one of the main reasons I do so is to ensure I can make my desktop and its applications look exactly the way I want them to look.

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•   05-28 LWN 19112

The stable tree was the topic for a plenary session led by Sasha Levin at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). One of the main areas that needs attention is testing, according to Levin. He wanted to discuss how to do more and better testing as well as to address any concerns that attendees might have with regard to the stable tree.

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•   05-27 MIT Technology 36247

And how it might even be a good thing.

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• An analogy framework between wiretap channels (WTCs) and state-dependent point-to-point channels with non-causal encoder channel state information (referred to as Gelfand-Pinker channels (GPCs)) is proposed. A good sequence of stealth-wiretap codes is shown to induce a good sequence of codes for a corresponding GPC. Consequently, the framework enables exploiting existing results for GPCs to produce converse proofs for their wiretap analogs. The analogy readily extends to multiuser broadcasting scenarios, encompassing broadcast channels (BCs) with deterministic components, degradation ordering between users, and BCs with cooperative receivers. Given a wiretap BC (WTBC) with two receivers and one eavesdropper, an analogous Gelfand-Pinsker BC (GPBC) is constructed by converting the eavesdropper's observation sequence into a state sequence with an appropriate product distribution (induced by the stealth-wiretap code for the WTBC), and non-causally revealing the states to the encoder. The t

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• Wi-Fi technology has strong potentials in indoor and outdoor sensing applications, it has several important features which makes it an appealing option compared to other sensing technologies. This paper presents a survey on different applications of Wi-Fi based sensing systems such as elderly people monitoring, activity classification, gesture recognition, people counting, through the wall sensing, behind the corner sensing, and many other applications. The challenges and interesting future directions are also highlighted.

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•   05-25 OSnews 20336

More or less anyone using modern PCs has to wonder: why does Windows use backslash as a path separator when the rest of the world uses forward slash? The clear intermediate answer is “because DOS and OS/2 used backslash”. Both Windows 9x and NT were directly or indirectly derived from DOS and OS/2, and certainly inherited much of the DOS cultural landscape. That, of course, is not much of an answer. The obvious next question is, why did DOS use backslash as a path separator? When DOS 2.0 added support for hierarchical directory structure, it was more than a little influenced by UNIX (or perhaps more specifically XENIX), and using the forward slash as a path separator would have been the logical choice. That’s what everyone can agree on. Beyond that, things get a bit muddled. A fascinating bit of sleuthing, and the author comes to an interesting theory. What’s fascinating to me is that I don’t even consciously realise the MS-DOS is the odd one out here – I just adapt t

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•   05-24 LWN 19104

Several new system calls have been proposed for addition to the kernel in a near-future release. A few of those, in particular, focus on memory-management tasks. Read on for a look at process_vm_mmap() (for zero-copy data transfer between processes), and two new APIs for advising the kernel about memory use in a different process.

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• In an interesting video interview, Canonical founder Mark Shuttleworth shares his thoughts on desktop Linux. Some of his most prominent statements include: “I think the bigger challenge has been that we haven’t invented anything in the Linux that was like deeply, powerfully ahead of its time” and, “if in the free software community we only allow ourselves to talk about things that look like something that already exists, then we’re sort of defining ourselves as a series of forks and fragmentations.”

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•   05-23 LWN 19562

One thing that is known about using transparent huge pages (THPs) for filesystems is that it is a hard problem to solve, but is there a solid first step that could be taken toward that goal? That is the question Song Liu asked to open his combined filesystem and memory-management session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). His employer, Facebook, has a solid use case for using THPs on files in the page cache, which may provide a starting point.

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•   05-23 LWN 20055

The linux-kernel mailing list has recently seen more than the usual amount of traffic proposing new system calls. LWN is endeavoring to catch up with that stream, starting with a couple of proposals for the management of file descriptors. pidfd_open() is a new way to create a "pidfd" file descriptor that refers to a process in the system, while close_range() is an efficient way to close many open descriptors with a single call.

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•   05-23 LWN 19635

The LWN.net Weekly Edition for May 23, 2019 is available.

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•   05-23 LWN 10985

Amir Goldstein has a use case for a feature that could be called a "lazy file reflink", he said, though it might also be described as "VFS-level snapshots". He went through the use case, looking for suggestions, in a session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). He has already implemented parts of the solution, but would like to get something upstream, which would mean shifting from the stacked-filesystem approach he has taken so far.

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•   05-22 LWN 19330

The "guarantees" that existing filesystems make with regard to persistence in the face of a system crash was the subject of a session led by Amir Goldstein at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). The problem is that filesystem developers are not willing to make much in the way of guarantees unless applications call fsync()—something that is not popular with application developers, who want a cheaper option.

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•   05-22 Hacker News 19930

Zork and the Z-Machine: Bringing the Mainframe to 8-Bit Home Computers

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•   05-22 Ars Technica 20295

Local health officials say cheap charlatans are likely using contaminated equipment.

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•   05-22 Hacker News 19611

ZetaSQL – A SQL Analyzer Framework from Google

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•   05-22 Ars Technica 20614

We can now see the Neogene period in color.

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•   05-22 LWN 19238

The relationship between SUSE and the openSUSE community is currently under discussion as the community considers different options for how it wants to be organized and governed in the future. Among the options under consideration is the possibility of openSUSE setting up an entirely independent foundation, as it seeks greater autonomy and control over its own future and operations.

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•   05-22 Ars Technica 20188

Unless you explicitly want it installed, you probably won't get this update.

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•   05-22 LWN 11011

The openSUSE project has announced the release of openSUSE Leap 15.1. "Leap releases are scalable and both the desktop and server are equally important for professional’s workloads, which is reflected in the installation menu as well as the amount of packages Leap offers and hardware it supports. Leap is well suited and prepared for usage as a Virtual Machine (VM) or container guest, allowing professional users to efficiently run network services no matter whether it’s a single server or a data center."

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•   05-22 IEEE 19959

Cybersecurity experts and data wranglers are in high demand

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•   05-22 LWN 10470

The cost of fsync() is well known to filesystem developers, which is why there are efforts to provide cheaper alternatives. Ric Wheeler wanted to discuss the longstanding idea of adding an asynchronous version of fsync() in a filesystem session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM). It turns out that what he wants may already be available via the new io_uring interface.

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•   05-21 LWN 19586

Damien Le Moal and Naohiro Aota led a combined storage and filesystem session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit (LSFMM) on filesystem work that has been done for zoned block devices. These devices have multiple zones with different characteristics; usually there are zones that can only be written in sequential order as well as conventional zones that can be written in random order. The genesis of zoned block devices is shingled magnetic recording (SMR) devices, which were created to increase the capacity of hard disks, but at the cost of some flexibility.

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•   05-21 IEEE 19192

The wonder crystal could yield imagers that are far more sensitive than commercial detectors

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•   05-21 OSnews 19524

Android is now at the point where sRGB color gamut with 8 bits per color channel is not enough to take advantage of the display and camera technology. At Android we have been working to make wide color photography happen end-to-end, e.g. more bits and bigger gamuts. This means, eventually users will be able to capture the richness of the scenes, share a wide color pictures with friends and view wide color pictures on their phones. And now with Android Q, it’s starting to get really close to reality: wide color photography is coming to Android. So, it’s very important to applications to be wide color gamut ready. This article will show how you can test your application to see whether it’s wide color gamut ready and wide color gamut capable, and the steps you need to take to be ready for wide color gamut photography.

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•   05-21 LWN 19706

In a combined filesystem and storage session at the 2019 Linux Storage, Filesystem, and Memory-Management Summit, Avri Altman wanted to discuss the "turbo-write" mode that is coming for Universal Flash Storage (UFS) devices. He wanted to introduce this new feature to assembled developers and to get some opinions on how to support this mode in the kernel.

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•   05-20 LWN 19444

By the time Linus Torvalds released the 5.2-rc1 kernel prepatch and closed the merge window for this development cycle, 12,064 non-merge changesets had been pulled into the mainline repository — about 3,700 since our summary of the first "half" was written. Thus, as predicted, the rate of change did slow during the latter part of the merge window. That does not mean that no significant changes have been merged, though; read on for a summary of what else has been merged for 5.2.

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•   05-18 MIT Technology 20334

It might have been less exuberant than last year, but crypto hype isn’t going away anytime soon—and there’s still clearly big money to be made

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•   05-18 LWN 19348

The ever-increasing complexity of the software stacks we work with has given testing an important role. There was a recent intersection between the automated testing being done by the Yocto Project (YP) and a bug introduced into the Linux kernel that gives some insight into what the future holds and the potential available with this kind of testing.

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•   05-14 OSnews 19981

A vulnerability in the messaging app WhatsApp has allowed attackers to inject commercial Israeli spyware on to phones, the company and a spyware technology dealer said. WhatsApp, which is used by 1.5bn people worldwide, discovered in early May that attackers were able to install surveillance software on to both iPhones and Android phones by ringing up targets using the app’s phone call function. The malicious code, developed by the secretive Israeli company NSO Group, could be transmitted even if users did not answer their phones, and the calls often disappeared from call logs, said the spyware dealer, who was recently briefed on the WhatsApp hack. I never answer phone calls from telephone numbers I am not familiar with, let alone when the incoming callers his their number blocked. Apparently, though, not even protects you from attacks such as these.

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• Engineers have designed a scheme to let thousands of brain implants talk at up to 10 megabits per second

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•   04-25 Ars Technica 21989

Freedom of Information Act seems to be latest weapon to fight climate misinformation.

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•   04-25 Slashdot 20887

Researchers have found an explanation for why many drivers act out toward cyclists: They are actually dehumanizing people who ride bikes, according to an April study by Australian researchers in the journal Transportation Research. From a report: And this dehumanization -- the belief that a group of people are less than human -- correlates to drivers' self-reported aggressive behavior. Since 2010, cyclist fatalities have increased by 25 percent in the US. A total of 777 bicyclists were killed in crashes with drivers in 2017, and 45,000 were injured from crashes in 2015. Data compiled by the League of American Bicyclists also suggests that, in some states, bicyclists are overrepresented in the number of traffic fatalities. "The idea is that if you don't see a group of people as fully human, then you're more likely to be aggressive toward them," said Narelle Haworth, a professor and director of the Centre for Accident Research and Road Safety at Queensland University of Technology, one

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•   04-25 Hacker News 12450

Enterpriseification

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• We introduce a family of quasi-Banach spaces - which we call wave packet smoothness spaces - that includes those function spaces which can be characterised by the sparsity of their expansions in Gabor frames, wave atoms, and many other frame constructions. We construct Banach frames for and atomic decompositions of the wave packet smoothness spaces and study their embeddings in each other and in a few more classical function spaces such as Besov and Sobolev spaces.

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• Recently the authors introduced lecture hall tableaux in their study of multivariate little $q$-Jacobi polynomials. In this paper, we enumerate bounded lecture hall tableaux. We show that their enumeration is closely related to standard and semistandard Young tableaux. We also show that the number of bounded lecture hall tableaux is the coefficient of the Schur expansion of $s_\lambda(m+y_1,\dots,m+y_n)$. To prove this result, we use two main tools: non-intersecting lattice paths and bijections. In particular we use ideas developed by Krattenthaler to prove bijectively the hook content formula.

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• We employ the proximal averaged Newton-type method for optimal control (PANOC) to solve obstacle avoidance problems in real time. We introduce a novel modeling framework for obstacle avoidance which allows us to easily account for generic, possibly nonconvex, obstacles involving polytopes, ellipsoids, semialgebraic sets and generic sets described by a set of nonlinear inequalities. PANOC is particularly well-suited for embedded applications as it involves simple steps, its implementation comes with a low memory footprint and its fast convergence meets the tight runtime requirements of fast dynamical systems one encounters in modern mechatronics and robotics. The proposed obstacle avoidance scheme is tested on a lab-scale autonomous vehicle.

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• We study the equivariant elliptic characteristic classes of Schubert varieties of the generalized full flag variety $G/B$. For this first we need to twist the notion of elliptic characteristic class of Borisov-Libgober by a line bundle, and thus allow the elliptic classes to depend on extra variables. Using the Bott-Samelson resolution of Schubert varieties we prove a BGG-type recursion for the elliptic classes, and study the Hecke algebra of our elliptic BGG operators. For $G=GL_n(C)$ we find representatives of the elliptic classes of Schubert varieties in natural presentations of the K theory ring of $G/B$, and identify them with the Tarasov-Varchenko weight function (a.k.a. elliptic stable envelopes for $T^*G/B$). As a byproduct we find another recursion, different from the known R-matrix recursion for the fixed point restrictions of weight functions. On the other hand the R-matrix recursion generalizes for arbitrary reductive group $G$.

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• A device-independent dimension test for a Bell experiment aims to estimate the underlying Hilbert space dimension that is required to produce given measurement statistical data without any other assumptions concerning the quantum apparatus. Previous work mostly deals with the two-party version of this problem. In this paper, we propose a very general and robust approach to test the dimension of any subsystem in a multiparty Bell experiment. Our dimension test stems from the study of a new multiparty scenario which we call prepare-and-distribute. This is like the prepare-and-measure scenario, but the quantum state is sent to multiple, non-communicating parties. Through specific examples, we show that our test results can be tight. Furthermore, we compare the performance of our test to results based on known bipartite tests, and witness remarkable advantage, which indicates that our test is of a true multiparty nature. We conclude by pointing out that with some partial information about

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• Artin's representation is an injective homomorphism from the braid group $B_n$ on $n$ strands into $\operatorname{Aut}\mathbb{F}_n$, the automorphism group of the free group $\mathbb{F}_n$ on $n$ generators. The representation induces maps $B_n\to\operatorname{Aut}C^*_r(\mathbb{F}_n)$ and $B_n\to\operatorname{Aut}C^*(\mathbb{F}_n)$ into the automorphism groups of the corresponding group $C^*$-algebras of $\mathbb{F}_n$. These maps also have natural restrictions to the pure braid group $P_n$. In this paper, we consider twisted versions of the actions by cocycles with values in the circle, and discuss the ideal structure of the associated crossed products. Additionally, we make use of Artin's representation to show that the braid groups $B_\infty$ and $P_\infty$ on infinitely many strands are both $C^*$-simple.

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• This research considers the ranking and selection (R&S) problem of selecting the optimal subset from a finite set of alternative designs. Given the total simulation budget constraint, we aim to maximize the probability of correctly selecting the top-m designs. In order to improve the selection efficiency, we incorporate the information from across the domain into regression metamodels. In this research, we assume that the mean performance of each design is approximately quadratic. To achieve a better fit of this model, we divide the solution space into adjacent partitions such that the quadratic assumption can be satisfied within each partition. Using the large deviation theory, we propose an approximately optimal simulation budget allocation rule in the presence of partitioned domains. Numerical experiments demonstrate that our approach can enhance the simulation efficiency significantly.

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• In this paper we study the draw-down related Parisian ruin problem for spectrally negative L\'{e}vy risk processes. We introduce the draw-down Parisian ruin time and solve the corresponding two-sided exit time via excursion theory. We also obtain an expression of the potential measure for the process killed at the draw-down Parisian time. As applications, new results are obtained for spectrally negative L\'{e}vy risk process with dividend barrier and Parisian ruin.

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• We prove decay with respect to some Lebesgue norms for a class of Schr\"odinger equations with non-local nonlinearities by showing new Morawetz inequalities and estimates. As a byproduct, we obtain large-data scattering in the energy space for the solutions to the systems of $N$ defocusing Choquard equations with mass-energy intercritical nonlinearities in any space dimension and of defocusing Hartree-Fock equations, for any dimension $d\geq3$.

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• A hyperbolic polynomial (HP) is a real univariate polynomial with all roots real. By Descartes' rule of signs a HP with all coefficients nonvanishing has exactly $c$ positive and exactly $p$ negative roots counted with multiplicity, where $c$ and $p$ are the numbers of sign changes and sign preservations in the sequence of its coefficients. For $c=1$ and $2$, we discuss the question: When the moduli of all the roots of a HP are arranged in the increasing order on the real half-line, at which positions can be the moduli of its positive roots depending on the positions of the sign changes in the sequence of coefficients?

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• The differential evolution algorithm is applied to solve the optimization problem to reconstruct the production function (inverse problem) for the spatial Solow mathematical model using additional measurements of the gross domestic product for the fixed points. Since the inverse problem is ill-posed the regularized differential evolution is applied. For getting the optimized solution of the inverse problem the differential evolution algorithm is paralleled to 32 kernels. Numerical results for different technological levels and errors in measured data are presented and discussed.

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•   04-24 Ars Technica 20657

Qubit avoids quantum wrecking ball, silicon may be future for quantum computers.

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• Let $k$ be a field containing an algebraically closed field of characteristic zero. If $G$ is a finite group and $D$ is a division algebra over $k$, finite dimensional over its center, we can associate to a faithful $G$-grading on $D$ a normal abelian subgroup $H$, a positive integer $d$ and an element of $Hom(M(H), k^\times)^G$, where $M(H)$ is the Schur multiplier of $H$. Our main theorem is the converse: Given an extension $1\rightarrow H\rightarrow G\rightarrow G/H\rightarrow 1$, where $H$ is abelian, a positive integer $d$, and an element of $Hom(M(H), k^\times)^G$, there is a division algebra with center containing $k$ that realizes these data. We apply this result to classify the $G$-simple algebras over an algebraically closed field of characteristic zero that admit a division algebra form over a field containing an algebraically closed field.

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• A Deza graph with parameters $(v,k,b,a)$ is a $k$-regular graph on $v$ vertices in which the number of common neighbors of two distinct vertices takes two values $a$ or $b$ ($a\leq b$) and both cases exist. In the previous papers Deza graphs with parameters $(v,k,b,a)$ where $k-b = 1$ were characterized. In the paper we characterise Deza graphs with $k-b = 2$.

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• Semi-analytic expressions for the static limit of the $T$-matrix for electromagnetic scattering are derived for a circular torus, expressed in both a basis of toroidal harmonics and spherical harmonics. The scattering problem for an arbitrary static excitation is solved using toroidal harmonics, and these are then compared to the extended boundary condition method to obtain analytic expressions for auxiliary $Q$ and $P$-matrices, from which $\mathbf{T}=\mathbf{P}\mathbf{Q}^{-1}$ (in a toroidal basis). By applying the basis transformations between toroidal and spherical harmonics, the quasi-static limit of the $T$-matrix block $\mathbf{T}^{22}$ for electric-electric multipole coupling is obtained. For the toroidal geometry there are two similar $T$-matrices on a spherical basis, for computing the scattered field both near the origin and in the far field. Static limits of the optical cross-sections are computed, and analytic expressions for the limit of a thin ring are derived.

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• We study a wireless ad-hoc sensor network (WASN) where $N$ sensors gather data from the surrounding environment and transmit their sensed information to $M$ fusion centers (FCs) via multi-hop wireless communications. This node deployment problem is formulated as an optimization problem to make a trade-off between the sensing uncertainty and energy consumption of the network. Our primary goal is to find an optimal deployment of sensors and FCs to minimize a Lagrange combination of the sensing uncertainty and energy consumption. To support arbitrary routing protocols in WASNs, the routing-dependent necessary conditions for the optimal deployment are explored. Based on these necessary conditions, we propose a routing-aware Lloyd algorithm to optimize node deployment. Simulation results show that, on average, the proposed algorithm outperforms the existing deployment algorithms.

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• The well-known plastic number substitution gives rise to a ternary inflation tiling of the real line whose inflation factor is the smallest Pisot-Vijayaraghavan number. The corresponding dynamical system has pure point spectrum, and the associated control point sets can be described as regular model sets whose windows in two-dimensional internal space are Rauzy fractals with a complicated structure. Here, we calculate the resulting pure point diffraction measure via a Fourier matrix cocycle, which admits a closed formula for the Fourier transform of the Rauzy fractals, via a rapidly converging infinite product.

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• The aim of this paper is to study the asymptotic properties of the maximum likelihood estimator (MLE) of the drift coefficient for fractional stochastic heat equation driven by an additive space-time noise. We consider the traditional for stochastic partial differential equations statistical experiment when the measurements are performed in the spectral domain, and in contrast to the existing literature, we study the asymptotic properties of the maximum likelihood (type) estimators (MLE) when both, the number of Fourier modes and the time go to infinity. In the first part of the paper we consider the usual setup of continuous time observations of the Fourier coefficients of the solutions, and show that the MLE is consistent, asymptotically normal and optimal in the mean-square sense. In the second part of the paper we investigate the natural time discretization of the MLE, by assuming that the first N Fourier modes are measured at M time grid points, uniformly spaced over the time inte

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• By allowing a mobile device to offload computation-intensive tasks to a base station, mobile edge computing (MEC) is a promising solution for saving the mobile device's energy. In real applications, the offloading may span multiple fading blocks. In this paper, we investigate energy-efficient offloading over multiple fading blocks with random channel gains. An optimization problem is formulated, which optimizes the amount of data for offloading to minimize the total expected energy consumption of the mobile device. Although the formulated optimization problem is non-convex, we prove that the objective function of the problem is piecewise convex, and accordingly develop an optimal solution for the problem. Numerical results verify the correctness of our findings and the effectiveness of our proposed method.

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• We study the bounded endomorphisms of $\ell_{N}^2(G)=\ell^2(G)\times \dots \times\ell^2(G)$ that commute with translations, where $G$ is a discrete abelian group. It is shown that they form a C*-algebra isomorphic to the C*-algebra of $N\times N$ matrices with entries in $L^\infty(\widehat{G})$, where $\widehat{G}$ is the dual space of $G$. Characterizations of when these endomorphisms are invertible, and expressions for their norms and for the norms of their inverses, are given. These results allow us to study Riesz systems that arise from the action of $G$ on a finite set of elements of a Hilbert space.

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• Math is widely considered as a powerful tool and its strong appeal depends on the high level of abstraction it allows in modelling a huge number of heterogeneous phenomena and problems, spanning from the static of buildings to the flight of swarms. As further proof, Gardner's and Carroll's problems have been intensively employed in a number of selection methods and job interviews. Despite the mathematical background, these problems are based on, several solutions and explanations are given in a trivial way. This work proposes a thorough investigation of this framework, as a whole. The results of such study are three mathematical formulations that express the understood mathematical relationship in these well-known riddles. The proposed formulas are of help in the formalization of the solutions, which have been proven to be less time-taking when compared to the well-known classic ones, that look more heuristic than rigorous.

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•   04-22 LWN 19988

The election for the Debian project leader has concluded; the leader for the next year will be Sam Hartman. See this page for the details of the vote.

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•   04-03 Hacker News 20945

Implementing API Billing with Stripe

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•   04-03 MIT Technology 21370

A look at the data shows that despite the crypto market’s long downturn, VCs are still betting big.

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•   04-03 Ars Technica 21702

Intel wants to sell you more than just some CPUs for your servers.

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•   04-03 Slashdot 22182

Two new studies reaffirm every computer dunce's worst fears: IT professionals blame the employees they're bound to help for their computer problems -- at least when it comes to security. From a report: One, courtesy of SaaS operations management platform BetterCloud, offers grim reading. 91 percent of the 500 IT and security professionals surveyed admitted they feel vulnerable to insider threats. Which only makes one wonder about the supreme (over-)confidence of the other 9 percent. [...] Yet now I've been confronted with another survey. This one was performed by the Ponemon Institute at the behest of security-for-your-security company nCipher. Its sampling was depressingly large. 5,856 IT and security professionals from around the world were asked for their views of corporate IT security. They seemed to wail in unison at the lesser and more unwashed. Oh, an objective 30 percent insisted that external hackers were the biggest cause for concern. A teeth-gritting 54 percent, however, s

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•   04-03 Ars Technica 21663

Impact of weapon on satellite threw some debris into orbits that could strike space station.

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•   04-03 Ars Technica 21658

Kotaku report cites 19 sources from various BioWare studios to explain what went wrong.

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• Lego Education, the education-focused arm of the veteran Denmark company, is making its biggest product debut in three years, unveiling Spike Prime, a new kit that aims to mix the company's familiar bricks with motors, sensors and introductory coding lessons. The company is targeting kids aged between 11 to 14. From a report: Lego Mindstorms have been around for years. The Mindstorms EV3 robotics kit remains a staple of many learning centers and robotics classrooms. Lego's newest kit looks more like Lego Boost, a programmable kit that aimed to win over families in 2017 and was compatible with regular Lego bricks. It's compatible with Lego Boost, Lego Technic sets and classic Lego pieces, but not with Lego's previous Mindstorms accessories. Lego Mindstorms EV3 is remaining alongside Lego Spike Prime in Lego Education's lineup, and looks like it's aiming more at the high school crowd, while Lego Spike Prime could bridge to that higher-end projects. The Spike Prime set is created specif

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•   04-03 Hacker News 21653

K-Means Clustering: Unsupervised Learning Applied on Magic:The Gathering

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•   04-03 Slashdot 21850

An anonymous reader writes: Microsoft today announced that Visual Studio 2019 for Windows and Mac has hit general availability — you can download it now from visualstudio.microsoft.com/downloads. Visual Studio 2019 includes AI-assisted code completion with Visual Studio IntelliCode. Separately, real-time collaboration tool Visual Studio Live Share has also hit general availability, and is now included with Visual Studio 2019.

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• Starting today, Microsoft is ending all ebook sales in its Microsoft Store for Windows PCs. "Previously purchased ebooks will be removed from users' libraries in early July," reports The Verge. "Even free ones will be deleted. The company will offer full refunds to users for any books they've purchased or preordered." From the report: Microsoft's "official reason," according to ZDNet, is that this move is part of a strategy to help streamline the focus of the Microsoft Store. It seems that the company no longer has an interest in trying to compete with Amazon, Apple Books, and Google Play Books. It's a bit hard to imagine why anyone would go with Microsoft over those options anyway. If you have purchased ebooks from Microsoft, you can continue accessing them through the Edge browser until everything vanishes in July. After that, customers can expect to automatically receive a refund. According to a newly published Microsoft Store FAQ, "refund processing for eligible customers start rol

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• At its Data-Centric Innovation Day, Intel today announced its Cascade Lake line of Xeon Scalable data center processors. From a report: The second-generation lineup of Xeon Scalable processors comes in 53 flavors that span up to 56 cores and 12 memory channels per chip, but as a reminder that Intel company is briskly expanding beyond "just" processors, the company also announced the final arrival of its Optane DC Persistent Memory DIMMs along with a range of new data center SSDs, Ethernet controllers, 10nm Agilex FPGAs, and Xeon D processors. This broad spectrum of products leverages Intel's overwhelming presence in the data center, it currently occupies ~95% of the worlds server sockets, as a springboard to chew into other markets, including its new assault on the memory space with the Optane DC Persistent Memory DIMMs. The long-awaited DIMMs open a new market for Intel and have the potential to disrupt the entire memory hierarchy, but also serve as a potentially key component that ca

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•   04-03 OSnews 21297

This account of Anthem’s development, based on interviews with 19 people who either worked on the game or adjacent to it (all of whom were granted anonymity because they were not authorized to talk about Anthem’s development), is a story of indecision and mismanagement. It’s a story of technical failings, as EA’s Frostbite engine continued to make life miserable for many of BioWare’s developers, and understaffed departments struggled to serve their team’s needs. It’s a story of two studios, one in Edmonton, Alberta, Canada and another in Austin, Texas, that grew resentful toward one another thanks to a tense, lopsided relationship. It’s a story of a video game that was in development for nearly seven years but didn’t enter production until the final 18 months, thanks to big narrative reboots, major design overhauls, and a leadership team said to be unable to provide a consistent vision and unwilling to listen to feedback. Perhaps most alarming, it’s a story about a studio in crisis. Do

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• We study the $L_p$ discrepancy of digital NUT sequences which are an important sub-class of digital $(0,1)$-sequences in the sense of Niederreiter. The main result is a lower bound for certain sub-classes of digital NUT sequences.

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•   04-02 IEEE 21191

Get Keysight’s Basic Instruments Flyer Featuring the New 1000 X-series Scopes

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