## Which main problems could arise from adding a number to a domain name?

Consider the domains star.com and star1.com.

What could be the problems with adding number as in the second example?

I can think about the following, I speak Hebrew and in Hebrew I could say:

star one dot com סטאר וואן דוט קום 

I could also say:

star ehad dot com סטאר אחד דוט קום 

(ehad in Hebrew means one).

Either of the Hebrew phrases might confuse a listener (vocally); the listener might not be sure if either "one" or "ehad" would mean an actual number 1.

## Why does NDSolve run into problems here?

I am looking at a particle moving in a funny potential, described by the following differential equation. The solution should be just some kind of periodic trajectory, why is there a problem here?

Edit: here is the code:

k = NDSolve[{x'[t]^2 + 1/Cos[x[t]]^2 == 2, x[0] == 0},    x[t], {t, 0, 4}] 

## How Can I Find the Problems Occurred on MySQL-MariadbDB Systems?

I have built a three-node galera cluster, so it is a Master-Master replication structure. But sometimes the first node goes down and I can’t find the problem causing this. I am only looking at /var/log/syslog files. Where should I look to find the problems? Is there other log files I can look on production environment? Where the database admins looks for db errors?

## Should I remove HTTP to HTTPS redirects to fix performance problems reported by Google Pagespeed Insights?

I have created a brand new website in which I publish various computing services I suggest to potential customers.

As far as I know, no other website on the World Wide Web links to that website and today in nearly mid 2021 when people create backinks, they normally just make them "example.com" (no http:// or https:// and no www.).

After testing the website in Google Pagespeed Insights I got only one error about slow loading times due to the specific reason of four redirects:

http://example.com | 630 ms https://example.com | 480 ms http://www.example.com | 630 ms https://www.example.com | 480 ms 

While I need the www. for a CDN to protect from possible DDoS attacks and using HTTPS as a web standard, principally I would never create non HTTPS backlinks to my website and don’t worry from anyone on the planet doing that.

Given the current HTTPS culture and my site being currently backlinkless, should I remove HTTP to HTTPS redirects to fix performance problems reported by Google Pagespeed Insights?

## Update — current .htaccess redirection directives

RewriteEngine On RewriteCond %{HTTP_HOST} !^www\. RewriteRule ^(.*)$http://www.%{HTTP_HOST}/$  1 [R=301,L] 

## Problems with making Bookmark links

Good morning,
I don’t understand where the mistake is.
I can’t make bookmark links?
I have lists, I have proxies.
I think my configuration is good but I can’t make bookmark links.
Can you help me?
Cdtl Dracu

## Some problems importing *.hdf5 files in MA12.2

I’m attempting to Import datasets from a *.hdf5 file into Mathematica 12.2 in Win 7.

After looking at the syntax in the Wolfram Documentation Center and displaying the StructureGraph, I had no problem importing some of the datasets, from various levels, using Import["file.hdf5",elem]

However, the one dataset I’m really interested with, just gives me \$ Failed, with no additional explanations. Suggestions?

I can look at the data in this dataset using an app called HDFView. It looks fine, a spreadsheet similar to those in the datasets that were imported.

using Import[file, {{"Dimensions", "DataFormat"}}], I do notice one thing that is perhaps a problem? The format of one column is "bitfield". Using HDFView, this column includes values of either 01 or 00. Is this the problem and can it be solved?

Two of the other datasets in this files I also can’t import, but at least I get a warning message:

LibraryFunction::fpexc: Numeric data containing a floating point exception (NaN or Inf) encountered.

When looking at these datasets with HDFView, they indeed contain some NaN values. Is there a way to import them?

## Having problems joining table

I have the following tables and I want to know Jack’s dob, salary and the total score of that employee who who is also a player. The The relational schemas are:

Employee_Play(eid,pid,team) composite key is (eid,pid) Plays(pid, team, matchName, scores) composite key is (pid, team, matchName) Emp(empID, dob, salary) empID is pk  Players(pid, name, team) composite keys are (pid, team) 

The query that I wrote is this however I get an error because im using group by operator. Is there an alternate way that can work? Also Im not sure if im during the join right? I am not able to use the where clause as where name = ‘Jack’. It tells me ‘no column named Jack ‘

Select name, address, dob, sum(scores) From Emp e JOIN Emp_Players ep ON e.empID = ep.eid  JOIN Plays p ON p.pid = ep.pid Group by p.pid; 

I would really appreciate any help. Thanks.

## Problems With StreamPlot

I have the following vector functions:

$$E=\left\langle \cos\left[\frac{\pi x}{5}\right]\sin\left[\frac{\pi y}{4}\right], \sin\left[\frac{\pi x}{5}\right]\cos\left[\frac{\pi y}{4}\right], \sin\left[\frac{\pi x}{5}\right] \sin\left[\frac{\pi y}{4}\right] \right\rangle$$

$$B=\left\langle -\sin\left[\frac{\pi x}{5}\right]\cos\left[\frac{\pi y}{4}\right], \cos\left[\frac{\pi x}{5}\right]\sin\left[\frac{\pi y}{4}\right],0 \right\rangle$$

And I’d like to graph each of these in a different plane, so I want to know what they look like in the $$xy$$, $$xz$$, and $$yz$$ planes. Using stream plot I got a graph of the view in the $$xy$$ plane that I was happy with but with the other perspectives I’m finding them difficult to plot and I think it’s because I have to use $$x$$ and $$y$$ bounds for StreamPlot. So, I’m wondering if there is a way to graph these vector fields in the $$xz$$ and $$yz$$ plots so that I have functions that aren’t varying with respect to the $$z$$ axis? Because, for example, right now what I’m doing is just replacing the $$x$$ component with the $$z$$ component and graphing but since my $$z$$ component is in terms of $$x$$ it changes with the bounds which I don’t want it to do.

## Can Mathematica solve matrix-based parametric (convex or semidefinite) constrained optimization problems?

I have gone through Mathematica’s documentation and guides on ConvexOptimization, ParametricConvexOptimization and SemidefiniteOptimization. I am also running the latest version of Mathematica.

The kind of matrix-based, parametric, constrained optimization problems I want to solve is this:

$$$$\min_{X_j, \, L_{jk}} \text{Tr}(A L) \ \text{such that, } X_j \text{ and } L_{jk} \text{ are } 4\times4 \text{ Hermitian matrices} \ G_k \cdot X_j = \delta_{j k}\ L:=\begin{bmatrix}L_{11} &L_{12} &L_{13} \ L_{12} &L_{22} &L_{23} \ L_{13} &L_{23} &L_{33}\end{bmatrix} \succeq \begin{bmatrix} X_1 \ X_2 \ X_3 \end{bmatrix}\begin{bmatrix}X_1 &X_2 &X_3\end{bmatrix}$$$$ where the variables to be optimized over are $$X_j$$ and $$L_{jk}$$ ($$j$$ and $$k$$ run from 1 to 3), which are themselves matrices! The matrices $$G_k$$ and $$A$$ depend on some parameter $$\alpha$$ (and satisfy additional properties).

I have been able to run this kind of optimization in MATLAB, and also a much simpler version of this in Mathematica, where $$j, k=1$$ and the parameter value is fixed, using,

ConvexOptimization[   Tr[\[Rho]0 .      v11], {VectorGreaterEqual[{v11, x1}, "SemidefiniteCone"] &&       Tr[\[Rho]0 . x1] == 0  && Tr[\[Rho]1 . x1] == 1   &&      Element[x1, Matrices[{4, 4}, Complexes, Hermitian]] &&      Element[v11, Matrices[{4, 4}, Complexes, Hermitian]]} , {x1,     v11}]] 

However I simply can not get the full problem to run on Mathematica, using either ConvexOptimization[ ] (at fixed parameter values), ParametricConvexOptimization[ ], SemidefiniteOptimization[ ], or Minimize[ ].

ConvexOptimization[ ] at fixed parameter values for $$j, k = 1, 2$$ shows the warning ConvexOptimization::ctuc: The curvature (convexity or concavity) of the term X1.X2 in the constraint {{L11,L12},{L12,L22}}Underscript[\[VectorGreaterEqual], Subsuperscript[\[ScriptCapitalS], +, \[FilledSquare]]]{{X1.X1,X1.X2},{X1.X2,X2.X2}} could not be determined.

Minimize[ ] shows the error Minimize::vecin: Unable to resolve vector inequalities ...

And ParametricConvexOptimization[ ] and SemidefiniteOptimization[ ] simply return the input as output.

Has anyone got some experience with running such matrix-based optimizations in Mathematica? Thanks for your help.

EDIT 1: For the two-dimensional case ($$j, k=1, 2$$) I tried (with $$A$$ the identity matrix, and at fixed parameter value):

ConvexOptimization[  Tr[Tr[ArrayFlatten[{{L11, L12}, {L12,        L22}}]]], {VectorGreaterEqual[{ArrayFlatten[{{L11, L12}, {L12,          L22}}], ArrayFlatten[{{X1 . X1, X1 . X2}, {X1 . X2,          X2 . X2}}]}, "SemidefiniteCone"] &&  Tr[\[Rho]0 . X1] == 0  &&     Tr[\[Rho]0 . X2] == 0 && Tr[\[Rho]1 . X1] == 1  &&     Tr[\[Rho]1 . X2] == 0  && Tr[\[Rho]2 . X1] == 0  &&     Tr[\[Rho]2 . X2] == 1  &&     Element[X1, Matrices[{4, 4}, Complexes, Hermitian]] &&     Element[X2, Matrices[{4, 4}, Complexes, Hermitian]] &&     Element[L11, Matrices[{4, 4}, Complexes, Hermitian]] &&     Element[L12, Matrices[{4, 4}, Complexes, Hermitian]]  &&     Element[L22, Matrices[{4, 4}, Complexes, Hermitian]] }, {X1, X2,    L11, L12, L22}] 

and for the three-dimensional case ($$j, k = 1, 2, 3$$) with variable parameter value and $$A$$ the identity matrix, I tried

ParametricConvexOptimization[  Tr[Tr[ArrayFlatten[{{L11, L12, L13}, {L12, L22, L23}, {L13, L23,        L33}}]]], {VectorGreaterEqual[{ArrayFlatten[{{L11, L12,         L13}, {L12, L22, L23}, {L13, L23, L33}}],      ArrayFlatten[{{X1}, {X2}, {X3}}] .       Transpose[ArrayFlatten[{{X1}, {X2}, {X3}}]]},     "SemidefiniteCone"],  Tr[\[Rho]0 . X1] == 0 ,    Tr[\[Rho]0 . X2] == 0  , Tr[\[Rho]0 . X3] == 0 ,    Tr[\[Rho]1 . X1] == 1 , Tr[\[Rho]1 . X2] == 0  ,    Tr[\[Rho]1 . X3] == 0  , Tr[\[Rho]2 . X1] == 0 ,    Tr[\[Rho]2 . X2] == 1  , Tr[\[Rho]2 . X3] == 0 ,    Tr[\[Rho]3 . X1] == 0 , Tr[\[Rho]3 . X2] == 0  ,    Tr[\[Rho]3 . X3] == 1 }, {Element[X1,     Matrices[{4, 4}, Complexes, Hermitian]],    Element[X2, Matrices[{4, 4}, Complexes, Hermitian]],    Element[X3, Matrices[{4, 4}, Complexes, Hermitian]],    Element[L11, Matrices[{4, 4}, Complexes, Hermitian]],    Element[L12, Matrices[{4, 4}, Complexes, Hermitian]],    Element[L13, Matrices[{4, 4}, Complexes, Hermitian]],    Element[L22, Matrices[{4, 4}, Complexes, Hermitian]],    Element[L23, Matrices[{4, 4}, Complexes, Hermitian]],    Element[L33, Matrices[{4, 4}, Complexes, Hermitian]]}, {\[Alpha]}] 

Here, the $$\rho_{k}$$ matrices are the $$G_k$$ matrices.

## Problems with Dsolve[] and simple function

I’m trying to solve the following very simple differential equation, but it seems Mathematica cannot give me an answer,

FullSimplify[DSolve[{y''[x] == 2 A Sinh[B y[x]], y[0] == W, y[L] == W}, y[x], x]] 

Any thoughts? Thanks!