• Ruby on Rails' Big Place in Marketplace Development

      How do you know that it’s time for you to launch your online marketplace? When do you see the necessity to provide the ultimate clear and fast “brand – consumer” communications? The point of an online marketplace is to grow customers loyalty by offering them an ever-expanding range of products.


      A brand, whether online or not, must use its reputation and expertise to make its marketplace successful.


      Let's take a look at the benefits of marketplaces and the reliability of Ruby on Rails as the strongest development tool.

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    • «Augmentation» eyes: what do we build into it today, and what else will remain under it

      • Translation

      In surgery, the term «augmentation» is used for a specific type of intervention, for example, hardening (building) the skeleton of an organ. We will talk about the empowerment of biological vision at the expense of implants.

      You can not just take out a piece of tissue from the eye, as during laser correction, but also insert something new there. For example, an implant that allows you to see at night. Or DVR. Or — what is being done now — just an internal contact lens made from a biocompatible polymer.

      Therefore, when you read about new opportunities for contact lenses, remember — all this can be built into a person. Of the most promising technologies — transfer images from your eyes to a computer and vice versa. If you are lucky, in 10 years you will be able to search for a given word in a paper book, as you are now looking for on a web page.

      But let's still go back to the real world and talk about phakic lisch, corrective vision for those who can not help the laser.
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    • Diamond inheritance problem is not a problem, that's a tricky feature

      General


      Before discussing the topic I’d like to start with a general suggestion not to use multiple inheritance and especially diamond unless you are strongly forced to. You may use e.g. composition or aggregation instead.


      Well, “Diamond inheritance problem” is some kind of steady expression which formed many years ago. You can easily find a lot of articles suggesting usage of “virtual public” to avoid the ambiguity and so on. For instance, https://en.wikipedia.org/wiki/Multiple_inheritance


      image


       That is not wrong as for the problem stated but anyway it is quite one-side statement.
       Below you can find:


      • difference in memory allocation and initialization order between public and public virtual inheritance (examples 1, 2),
      • examples of practical usage of both public and public virtual inheritance (examples 3, 4).
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    • Guide for entrepreneurs to launch an on-demand grocery delivery app amid the coronavirus pandemic



        After the onset of the coronavirus pandemic, Instacart, a popular online grocery platform, hired 300,000 workers to meet the demands of the people. In addition, they are planning to hire 250,000 more. Such is the demand for online grocery platforms nowadays. People are in self-isolation with restricted outdoor movements. The fear of contracting the disease is so high that people are looking for alternative ways even to access essential services. As a result, smartphone applications are gaining increased attention from people all over the world.
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      • Approach to calculating individual risk in COVID-19

          In February 2020, when the disease came to Europe, it became apparent to me that our timid hopes that the epidemics would subside and be finally buried in the China's soil were ruined. It was already evident from the Chinese statistics that the virus is lethal enough to scare and mild enough to pass unnoticed in many cases and, thus, to guarantee its effective dissemination. The question was when it reaches each next country.




          Another question was the individual risks, especially the risk of lethal outcome if one contracts the virus. The average figure of around 5% was circulated by late January and early February. It was known that males were more susceptible to fatal outcomes. By February, it was also evident that the virus doesn't lead to death only in the elderly — the middle age was significantly affected, as well.

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        • Parallelism in PostgreSQL: treatment of trees and conscience



            Database scaling is a continually coming future. DBMS get improved and better scaled on hardware platforms, while the hardware platforms themselves increase the performance, number of cores, and memory — Achilles is trying to catch up with the turtle, but has not caught up yet. The database scaling challenge manifests itself in all its magnitude.

            Postgres Professional had to face the scaling problem not only theoretically, but also in practice: through their customers. Even more than once. It's one of these real-life cases that this article
            will discuss.
            Many thanks to Elena Indrupskaya for the translation. Russian version is here.
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          • 11 Agile Project Management Best Practices

              The Agile method of project management focuses on the repetitive development of the product. Each iteration starts with better input. Although initially intended for software development, the Agile methodology is now being adopted rapidly in other industries too.


              At the core of the Agile methodology are sprints or cycles, which are small development time frames focusing on the continuous improvement of the development process and/or product. It involves sub-tasks that must be completed within the specified time period.


              Since the project management industry is going gaga over the Agile methodology, it is an apt time to learn the Agile methodology. Agile best practices help in further enhancing the effectiveness of the project management technique. Here are 11 of the best ones:


              1. Employ Relevant Project Management Software


              This goes without saying, using project management tools surely benefit a project no matter what the methodology or methodologies involved are. They can take care of everything ranging from file management and feedback collection to tracking progress and reporting.

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            • AdBlock has stolen the banner, but banners are not teeth — they will be back

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            • Why we love and choose Ruby instead of Node.js?

                Choosing between Node.js and Ruby on Rails, when choosing a development platform, is a core decision. That affects how the project unfolds over time, and how much server resources will be needed. Both languages can support web applications of high complexity, but each has its advantages and disadvantages. Knowledge of these pros and cons will help to choose the best solution for the proposed project. Let's analyze in more detail and tell you about our choice and experience.

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              • WebGL tutorial: image processing

                In this tutorial you will learn how to use WebGL for image processing. We will cover basic stuff like initialization, texture loading, and simple fragment shaders. I will try to cover all aspects of interaction with WebGL but you should have decent understanding of vanila javascript. If you want more in depth explanations, there is a good book called "Learn WebGL", check it out.

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              • FAQ about laser correction ReLEx SMILE: yes, in Russia there is, but no, in Russia there isn’t

                • Translation


                — Are small-invasive laser vision correction operations done in Russia using the Small Incision Lenticule Extraction method?

                Yes, about 10 years already. Every year, more and more at conferences of ophthalmologists, questions arise not at the level of “What is this?”, But at specific practical nuances of technology. VisuMax lasers exist in several clinics in Russia, but it is much less used under ReLEx SMILE than under femtoLASIK. Historically, it happened in Russia that this technology is little used in the central part and is actively used beyond the Urals.

                — What is the story with licenses for specific operations?

                Zeiss sells cones with licenses. A cone — a replacement part adjacent to the eye — is purchased with a license to use a laser procedure, usually in batches of 10 or 100 operations. For example, 10 cones and 10 licenses are received. Licenses are driven through the laser menu, and it allows you to use the appropriate cones for the appropriate program types. Licenses for SMILE separately, for femtoLASIK separately, for FLEX, rings and additional corrections are also separate licenses. Most manufacturers of femtosecond and some excimer lasers have a similar situation. Licenses for excimer operations are not needed, perhaps, except on models of about 5 years old and older.

                — And you can not get such a license for SMILE?

                Easily. Firstly, this module in the laser is as an expensive option, so the device itself without the SMILE option is cheaper. Secondly, if this option is available, then licenses to carry out the operation ReLEx SMILE can be acquired only after conducting 5–10 test runs on pig eyes, then performing at least 10 femtoLASIK operations on patients, then 50 FLEX operations, and only after that Buy a SMILE license for a specific surgeon.
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              • Programming as an endless educational pursuit

                  When one embarks on the journey to master the craft of programming, they come to the realisation that it has no finish line. No matter how good you are, there are still things to learn, solutions to explore.

                  Today, we’ll talk about the importance of remaining a lifelong student, language adoption trends according to StackOverflow and why programming itself might not be what you end up learning to become better.

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                • How to Deploy Hyperledger Fabric 1.4 to AWS

                    Hyperledger Fabric is an open-source blockchain platform from the Linux Foundation. With its help, you can create blockchain applications and control access and permissions for data in the blockchain. The most popular reason to use Hyperledger Fabric is to create a private blockchain network or set restrictions on what transactions each side can see.

                    The documentation of Hyperledger Fabric describes the creation of a blockchain network on one machine using Docker, where each member of the network is a separate container. But the process of setting up a network on several physical or virtual machines is not well described. Therefore, we decided to discuss this in the article.

                    Our blockchain application is a service for storing the medical data of school and preschool children. The data must remain unchanged. It will be presented in the form of information on vaccination and on the patient's agreement with a particular doctor. The members of the network include Parents (an organization that represents the interests of parents), Hospital (a hospital which represents pediatricians with whom parents can enter into an agreement to care for their children) and Kindergarten (a kindergarten that can request health and vaccinations reports of a child from the hospital).
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                  • A couple more unobvious things that you might not be told before laser vision correction

                    • Translation

                    Today, without the «tin», as you asked

                    There is already a post about how the laser cuts by creating millions of cavitation bubbles in the cornea layer of the eye, and analyzing telemetry from the real operation in seconds with comments of the surgeon's actions.

                    Now FAQ about various related things


                    — If I look away while the laser is running, what will happen?

                    You simply will not work. In fact, immediately after anesthesia, the eye is pressed against a special pneumocapture. To blink at you too will not leave because of fixing (it is not long and not for long). The only moment where it is possible to seriously disrupt the course of the operation is to pull the head down strongly, pulling it out of the headrest by a serious willed effort. In this case, the operation will instantly stop. More precisely, it will stop even before the loss of capture (details below).

                    — How should an operating room be prepared?

                    In general — as a normal operating room, that is, a room with a clean area (air filtration, overpressure to prevent contamination from the outside after cleaning). It is important for the procedure that microparticles of dust flying in the air do not fall between the laser lens and the eye.
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                  • Bcache against Flashcache for Ceph Object Storage


                      Fast SSDs are getting cheaper every year, but they are still smaller and more expensive than traditional HDD drives. But HDDs have much higher latency and are easily saturated. However, we want to achieve low latency for the storage system, and a high capacity too. There’s a well-known practice of optimizing performance for big and slow devices — caching. As most of the data on a disk is not accessed most of the time but some percentage of it is accessed frequently, we can achieve a higher quality of service by using a small cache.

                      Server hardware and operating systems have a lot of caches working on different levels. Linux has a page cache for block devices, a dirent cache and an inode cache on the filesystem layer. Disks have their own cache inside. CPUs have caches. So, why not add one more persistent cache layer for a slow disk?
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                    • Powershell way to exclude folder from Defender list

                      • Tutorial
                      To exclude some folder from the defender list can be used cmdlet Set-MpPreference
                      Manly, now you can stop reading, go to the PowerShell and update excludes:)
                      But if you are want to see how to perform this in more detail — welcome under the habrcut.

                      UPD: Added a script to add selected folder to excluded Defender locations (at the end of the post)
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                    • Four Ways Quantum Computing Will Change Artificial Intelligence Forever

                        If science were a dating app, quantum physics and machine learning probably wouldn’t be a match. They’re from completely different fields and often require completely different backgrounds and skills. But, throw in a little quantum computing and, suddenly, that science-matchmaking app becomes Tinder and the attraction between the two is palpable.

                        image

                        (Credit: cmo.adobe.com/articles/2017/5/how-will-artificial-intelligence-impact-business-tlp-ptr.html#gs.5zlifl)

                        Even though the extent of change that quantum computing will unleash on AI is up for debate, many experts now more than suspect that quantum computing will definitely alter AI at some level. Analysts from bank holding company BBVA, for example, point toward the natural synergy between quantum computing and AI as reasons why quantum machine learning will eventually best classical machine learning.

                        “Quantum machine learning can be more efficient than classic machine learning, at least for certain models that are intrinsically hard to learn using conventional computers,” says Samuel Fernández Lorenzo, a quantum algorithm researcher who collaborates with BBVA’s New Digital Businesses area. “We still have to find out to what extent do these models appear in practical applications.”
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                      • Laser telemetry for vision correction: a complete operation with comments (not for the faint of heart)

                        • Translation
                        Now I will show what doctors usually never show to patients. More precisely, it shows everything in the form of a beautiful render, from which it does not follow at all that a piece of metal will stick up in your cornea for a couple of minutes. Fortunately, you will not feel this because of the anesthetic premedication, you will not know and do not remember, because the piece of iron will be out of focus.



                        So, watch the video, and I will show the frames with comments. This is a real operation on a patient in a German clinic, the recording was made on a device like the “black box” of the VisuMAX device. In this case, the patient has agreed to use the recording for training purposes, usually access to such records is strictly limited.
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                      • Your company life before and after accounting automation

                          The manual work of the accountant went into oblivion. Today everyone makes machines, but, of course, controlled by a specialist. Although in our last project we have carefully worked on the topic of artificial intelligence and some accounting operations can already occur with little or no human intervention. Let's look at what systems we attracted, and what exactly was done to save time on daily routine operations.

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