Sunday, June 11, 2017


Samsung Galaxy 











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There's an "Infinity Display" that runs from edge to edge


Samsung is known for having some of the best displays in the business. It steps up the game this year with a new display that runs almost the full length of the smartphone. The company calls this an "Infinity Display" and indeed believes it will usher in a new era of "Infinity smartphones." It supports the latest video standards that have so far only been limited to televisions, including HDR, for a more accurate picture.
Since the display stretches nearly to the bottom of the smartphone, where a home button used to live, Samsung employed special technology that allows the user to press into the display. This serves as the actual home button, returning users to the main screen whenever it's pressed.


CNBC: Galaxy S8 3




It can recognize your face



The Galaxy S8 and Galaxy S8+ are chock full of biometric technology. There's a fingerprint reader on the back, an option that has become standard on even the most affordable smartphones. There's an iris scanner on the front, a feature that was also present on the ill-fated Galaxy Note 7. Finally, there's a new face scanner, which Samsung hopes folks will use to quickly unlock their smartphones.

  • There's an "Infinity Display" that runs from edge to edge

    Samsung is known for having some of the best displays in the business. It steps up the game this year with a new display that runs almost the full length of the smartphone. The company calls this an "Infinity Display" and indeed believes it will usher in a new era of "Infinity smartphones." It supports the latest video standards that have so far only been limited to televisions, including HDR, for a more accurate picture.
    Since the display stretches nearly to the bottom of the smartphone, where a home button used to live, Samsung employed special technology that allows the user to press into the display. This serves as the actual home button, returning users to the main screen whenever it's pressed.
    CNBC: Galaxy S8 6
    Devin Hance | CNBC
  • It can recognize your face

    The Galaxy S8 and Galaxy S8+ are chock full of biometric technology. There's a fingerprint reader on the back, an option that has become standard on even the most affordable smartphones. There's an iris scanner on the front, a feature that was also present on the ill-fated Galaxy Note 7. Finally, there's a new face scanner, which Samsung hopes folks will use to quickly unlock their smartphones.
    CNBC: Galaxy S8 2
    Devin Hance | CNBC


Monday, January 5, 2015

power

power


p=vi
i=Imsin(2πft) and v= Vmsin(2πft+θ)


p=VmImsin(2πft)sin(2πft+θ)
p=VIcosθ(1- cos2πft)+ VIsinθ(sin2πft)

For a purely resistive circuit 

pR=VIcos(0°)(1 cos 2πft) +VIsin(0°) sin 2πft 
     =VI(1- cos 2πft)+ 0 or
     =VI -VIcos 2πft 

Sunday, August 31, 2014

ohm's law




Ohm's law





Equation (4.2) is known as Ohm’s law in honor of Georg Simon Ohm (Fig. 4.1). The law clearly reveals that for a fixed resistance, the greater the voltage (or pressure) across a resistor, the more the current, and the more the resistance for the same voltage, the less the current. In other words, the current is proportional to the applied voltage and inversely proportional to the resistance. By simple mathematical manipulations, the voltage and resistance can be found in terms of the other two quantities:

.

voltage




Voltage




      Pictorially, if one joule of Energy (1 J) is required to move the one coulomb (1 C) of charge of Fig. 2.10 from position xto position y,the potential difference or voltage between the two points is one volt (1 V). If the energy required to move the 1 C of charge increases to 12 J due to additional opposing forces, then the potential difference will increase to 12 V. Voltage is therefore an indication of how much energy is involved in moving a charge between two points in an electrical system. Conversely, the higher the voltage rating of an energy source such as a battery, the more energy will be available to move charge through the system. Note in the above discussion that two points are always involved when talking about voltage or potential difference. In the future, therefore, it is very important to keep in mind that a potential difference or voltage is always measured between two points in the system. Changing either point may change the potential difference between the two points under investigation. Ingeneral,the potential difference between two points is determined by

.

current




 Current


    If 6.242x 10^18 electrons drift at uniform velocity through the imaginary circular cross section  in 1 second,the flow of charge, or current,is said to be 1 ampere(A) in honor of André Marie Ampère . This is an enormous number of electrons passing through the surface in 1 second. The Current associated with only a few electrons per second would be inconsequential and of little practical value. To establish numerical values that permit immediate comparisons between levels, a coulomb(C) of charge was defined as the total charge associated with  6.242x 10^18 electrons. The charge associated with one Electron can then be determined from





Sunday, February 23, 2014

operational amplifier

Operational Amplifier 運算放大器

這是一個結合放大加減運算比較等功能的微型電路, 內裡由多個 bipolar junction transistor  所組成。

Operational Amplifier的好處

只要外接幾個電阻就可以實現功能;
無需計算反向或正向偏壓;
方便地計算放大倍數;
價格便宜;
比自己設計电路更慳位和節省用電量。


線路圖



Vcc+ 和 Vcc- 是電源一邊是正電壓另一邊是負電壓;
輸入可以是 differential, non-inverting, inverting;
Offset 腳外接線路用來調整輸出 0,條件是在輸入腳空接的時候。

等效電路




最理想是開路放大倍數無限大Aol,
rd等如無限大,
ro等如 0 ,



反相操作



之前我們所講的是開路放大倍數Aol, 
A=vo/v1
現在的是閉路放大倍數G, 因為輸出腳巳連接到輸入腳 1形成一個閉路。
G=vo/v1
由於理想放大倍數是無限大所以輸入電壓v1等於零
v2-v1=vo/A=0
也即是說v1=v2
這就是虛擬的短路, 由於 v 2 接地所以 v1 同樣是0v