How would you redesign and revamp the city transit system?

Suppose we have a very crowded city. 118.29 sq mile and population 7.001 million. Now the government made you the prime architect of the city and have to solve the extreme traffic jam problem. We cannot build subway underneath the ground because land is muddy and wet deep underneath.

There are lots of buildings and densely situated and no space inside the city to build a pillar for metro or LRT (Light Railway Transit) or no space for Maglev. There are a couple of highways and flyovers but they are jam-packed. The main transit is rickshaws, taxis, buses, cars, vans, and private cars. If you were an architect of that city how would you have solved that traffic jam problem?

Right now the city is centralized. Would you decentralize each city in each province and build independent and best hospitals, schools, colleges, universities, clinics in those cities of each province so people don’t have to come to the city frequently?

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Correlate two different zone system records

I am working with two data sets from different sources that represent the same phenomena and have a challenging point.

Both data sets represent demographic attributed of the population [ person id, age, gender, income , … ] and records are matched to the zone number with no specific Location. So I can only map them to the center of the zone.

My question is, what algorithm, method, technique is suitable to find a common grid system for both zones for comparison? They should represent a high correlation as they are for the same population.

I use postgis, QGIS, Python and Java

two zone systems overlaid

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inverse() vs pinv() which one good for linear system

I have a linear system A*x=b. Here x value is unknown. So I have to find out the value of x. A is sparse matrix whose diagonal and off diagonal element have some value. Others are zero or tense to zero.

I am using matlab to solve it. I have two option

  1. x= inv(A)*b

  2. x=Ab

    But both give me same result NaN. I know this will happen because A is a sparse matrix. So, I am trying pinv() which is pseudo inverse. Now I get some value.

    I create this thread to take a opinion from stackoverflow community that is it good when inverse failed to produce result take a help of pseudo inverse? What type of result pseudo inverse produce? Is it authentic or it is a form of error?

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How do you find the phase portrait of a second order non linear system?

If given something like

$ddot x + dot x +x+ x^3 = 0$

What are the steps to sketching the phase portrait by hand? I know there is some software that can do it, but I do not understand the intuition behind it. Also, What exactly is a phase portrait? From what I see it is a plot of $x$ versus $dot x$, but I dont understand how because for any constant of $x$, $dot x$ will be $0$.

I must be missing some key linear algebra/differential equations intuition…

Thank you

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Is this proof system stronger than resolution?

Consider the proof system where the certificate is a sequence $(c_1,c_2,cdots,c_n=bot)$ in which each $c_i$ is either an input clause or a clause derived from the input clauses and the clauses $c_1,cdots,c_{i-1}$ by a trivial derivation (Definition 8). This certificate can be efficiently checked using the RUP (Reverse Unit Propagation) (Proposition 3) property of the clauses.

My intuition is that the length of the proof in this proof system can be shorter than the length of the resolution proof since the former allows to skip some intermediary clauses that are required in the resolution proof.

Is this proof system stronger than resolution?

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When a Certain Operating System Structure is Better Than the Others

I realize this may be a question that could be open to debate because Operating Systems(OSs) will have different needs depending on what they are needed for and they are almost all Hybrid; However, I want to know what is better to use in certain situations because I need to create a simple OS.

But I’d like to know if it is possible and worthwhile to quantitatively and conditionally compare these 4 OS Structures. I have been enjoying reading a book and a website that I credit for sparking this question in my mind.

Operating System Concepts 9th Edition

By Abraham Silberschatz and Greg Gange

Page 78, Section 2.7

link to website


1 = best
4 = worst

Size – The space it takes in an address, cache, memory, or storage

Execution – The speed of the software architecture when it is running.

Extendable – How much of the kernel code depends on each other. For example, the more extendable the easier it is to add a new device to interface and work with the OS. Things that share kernel and user space by nature will be harder to extend.

Security – the better the lower chance of system failure. Much of comes from programming mistakes because the earlier OS Structures shared kernel and userspace. The more prone to crashes the worse the security

Code – The amount of code required that is required. NOT how much skill is required to code it and how much work it takes to change it.

table, th, td {
    border: 1px solid black;
OS Structures Microkernel Monolithic Layered Modules
Basic Description User and kernel services done in seperate space User and kernel services done in same space Layer 0 => hardware Layer n => user interface More modern. Kernel can optimize for these processes taking over CPU
Size 1 3 ? ?
Execution 3 1 if small amount of processes 4 1 if large amount of processes
Extendible 2 4 3 1
Security 2 4 3 1
Code 3 1 ? ?
Example MacOS DOS Having trouble finding one Red Hat and MacOS
Debugging 3 4 1 2

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After instalation, boot error message: can not find any operational system

After a clean installation of Elementary Loki, there is an error message during the booting that does not allow me run Elementary. “Cannot find any operational system”. As I am not an expert, the only solution I found was change Legacy instead of UEFI inside the BIOS, and wallah! is working now.

However, although is working now I suppose something is wrong with my GRUB and I should fix it to be able to boot Elementary with UEFI. I would really appreciate any orientation about how to fix it.

This question it was already posted here Force UEFI installation? but unfortunately did not find a real solution.

*Some additional information: Elementary is the only OS I’m running in my laptop right now. However, previously the laptop was using Windows 10 that came in for default. My laptop is a Sony Vaio, S series.

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logon.exe: windonws seven Ultimate italian system. error: computer is not locked. nothing to do

I am working in a windows 7 italian system. I have set a login method with user and password.

I have done a scheduled task to automatically start the logon.exe -u test -p passtest (no “-k key1 key2”)(perhaps I need but I do not know what to write).

It is not working.

The log file tell me always “computer is not locked. nothing to do.”

Can you give me some advice? many thanks

PS: from Auto-Logon without registry hack in Windows 7 with Domain Account

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A system of equations in $mathbb{R}^n$


begin{cases}x_{1}+ldots +x_{n}=n\
x^{2}_{1}+ldots +x^{2}_{n}=nend{cases}

$$left( x_{1},ldots ,x_{n}right) in mathbb{R} ^{n}$$

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PHP – Função exec, shell_exec e system não funcionam corretamente

Executando o exemplo da documentação no próprio site funciona.


echo exec('whoami');

$output = shell_exec('ls -l');
echo "


O meu códgio não difere tanto dos exemplos descritos na documentação, o que desejo fazer é apenas executar uma outra aplicação com o seguinte comando:

Meu código/exemplo:

exec(“python3 caminho/”)

E agora pessoal!?

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