Balder W. Holst

Hello there!

My name is Balder and this is my personal website. Here i write down what i learn to maybe help others some day. For now i will just act like people are reading my articles, and make them for fun.

This website has three main sections:

I write these articles for fun, and even though i try to make sure that they are correct, i am not a perfect human and there are sure to be mistakes. Below is a list of most recent articles in all categories.

Recent Posts

The Heat Equation
The Heat Equation How heat distributed in a rod changes over time. Each point tends towards the average of its neighbours. This also works for multiple dimensions. $$\frac{\partial u}{\partial t} = \alpha \cdot \nabla^{2} u, \s \alpha = \frac{k}{c\rho}$$ $t$: Time $u$: Temperature as a function of position and time. $k$: Thermal conductivity $c$: Specific Heat Capacity $\rho$: Density Video
0001/01/01 · Notes
The OSI model
The OSI model Open system interconnection model. Layers Physical layers Electrical layer and Physical connections Physical addressing Logical addressing Transport 4. Transport layer User layers 5. Communication management 6. Data encoding, compression and encryption. 7. Application It also defines timing and endures reliability.
0001/01/01 · Notes
The Wave Equation
The Wave Equation $$u_{tt} = c^{2}u_{\mathbf{xx}} = c^{2} \nabla^{2} u_{}$$ $c$: Wave speed $u$: Amplitude Example lektion10
0001/01/01 · Notes
Thevenin Ækvivalens
Thevenin Ækvivalens Beregn det Thevenin-ækvivalente kredsløb. Find $R_T$ “nulstil” alle strømkilder (nulling) Regn den ækvivalente modstand Find $V_T$ Sæt $i$ (slut-strømmen) til $0$. Find spændingen
0001/01/01 · Notes
Thread Deadlocks
Thread Deatdocks Hold and Wait No Preemption Circular Wait
0001/01/01 · Notes
Transformation Matrices
Transformation Matrices Transformation from $\set{A}$ to ${\set B}$. $$^A_BT = \left( \begin{array}{cccc} r_{11} & r_{12} & r_{13} & p_x \ r_{21} & r_{22} & r_{23} & p_y \ r_{31} & r_{32} & r_{33} & p_z \ w_x & w_y & w_z & s \ \end{array} \right) $$ In kinematics we only interested in rotation and translation. Shering and scaling is therefore disabled. $$ \left( \begin{array}{cccc} r_{11} & r_{12} & r_{13} & p_x \ r_{21} & r_{22} & r_{23} & p_y \ r_{31} & r_{32} & r_{33} & p_z \ 0 & 0 & 0 & 1 \ \end{array} \right) = \left( \begin{array}{cc} ^A_BR & ^Ap_{org} \ 0^{3 \times 1} & 1 \ \end{array} \right) $$
0001/01/01 · Notes
Transient Respons
Transient Respons “Transiente kredsløb dør ud” - Jan Man kan ikke snakke om impedans I spoler og kondensatorer er det forskellige størrelser, der ikke kan ændre sig momentant. Kondensator $$I_C(0_{+}) = I_C(0_{-})$$ Spoler $$V_L(0_{+}) = V_L(0_{-})$$
0001/01/01 · Notes
Transistorer
Transistorer En lille strøm styrer en meget større strøm Kan forstærke strømme hvor operationsforstærkere forstærker spænding. Karakteristikker Ideel Praktisk Storsignal Typer Transistorer Bipolar Junktion Transistor - BJT $$I_{E} = I_{B} + I_{C}$$ $L_{E}$ : Emitter strømmen $I_{B}$ : Base strømmen $I_{C}$ : Collector strømmen Arbejdsområder Aktiv $$\beta = \frac{I_{C}}{I_{B}} \arrows I_{C} = \beta \cdot I_{B}$$ $\beta$ : Forstærkningen (af strømmen) Det hvor transistoren fungerer som en diode.
0001/01/01 · Notes
Transmission
Transmission Signal Impairment Attenuation: Loss of energy $$dB = 10 \cdot \log_{10}\left(\frac{P_{2}}{P_{1}}\right)$$ $P_{1}$: Initial power $P_{2}$: Final power $$dB = 20 \cdot \log_{10}\left(\frac{V_{2}}{V_{1}}\right)$$ $V_{1}$: Initial Voltage $V_{2}$: Final Voltage Distortion Different frequencies will be warped (in phase) differently as the signal travels. Therefore the receiver signal will be distorted. Noise Thermal noise: From random movements of electrons in the conductor. Induced noise: Electromagnetic (motors, machines…) Crosstalk: Another wire affects this line Impule noise: lightning, thunderstorms… Signal-to-Noise ratio $$SNR=\frac{\text{average signal power}}{\text{average noise power}}$$ $$SNR_{dB} = 10 \cdot \log_{10}(SNR)$$ Data rate limit Depends on three factors
0001/01/01 · Notes
Transport Layer
Transport Layer See slides. Protocols stop-and-wait Only one packet in the channel at a time Reliable but inefficient just go-back-N where N=1 go-back-N: Idea: acknowledge more than one packer at a time We still have to resend correctly received packets if the sender times out selective-repeat Only resend corrupted packets Always same ACK as received number TCP Reliable Connection Oriented UDP Unreliable Connectionless Continuous data stream No flow control No error control We can use piggybacking in bidirectional communication.
0001/01/01 · Notes