Sometimes you are needed to maintain power supply for your device for some time when the main source fails. It can be alarm system or some light source or digital clock. Of course if source interrupts are very short, there can be capacitor with big capacity connected, but it is not reliable. Better use backup battery and diode. This solution is very simple and cheap. The diode protects the back current float to battery. This doesn’t take much space to implement as the main bigger part is battery. As there just backup source it is not necessary to use rechargeable battery.
Most of physical and chemical experiments can be described with a finite number of rules. In physiological processes everything can be tied to laws of nature. Good model can be as a guideline to new experiments. Usually model and experiment has iterative connection. In order to understand ho to investigate any material there is model needed (block 1). First we need abstract understanding about what we are investigating (block 2). Abstracts are transformed into mathematical model (block 3). There we can use formulas and solve them using computer. The results you get shows, what experiments have to be done and what to expect from them. This loop system is resistive to irregularities in mathematical model. In other words, this is the purifier of experiments and models. How to model blood vessels There can be many modeling ways of them. This is because, that every model has its own benefits and …
There was a time, when all IC’s were only TTL type. They were marked as 74LS or 74ALS. But then there came CMOS types of semiconductor. They are usually marked CDxx. And lately there appeared combined semiconductors who are compliant to both types. They usually are marked as 74HC or 74HCT. TTL are faster than CMOS, but they sink more power. They are powered from 5V source. To diminish the power consumption, the CMOS were developed. They can work with supplied voltages in range 3 to 15V. The main disadvantage is that they are static sensitive. So you always have to be grounded when working with CMOS. Now both types of semiconductors are widely used. Sometimes there is as dilemma to connect TTL to CMOS. You cannot connect directly TTL to CMOS as there are different supply voltages. So you need some compliance circuit. The simplest can be bipolar transistor …
I found on Matlab very handy tool which allows easily to trace boundaries of objects in a picture. So I adopted it to skin lesions. This can be used for automatic detection of skin irregularities and used to calculate lesion properties like asymmetry of shape, or border irregularities, who can help in detecting melanoma. There are numerous of investigations done, so I only put few examples on how it looks like. I will give you my source code, so you can try it by your own. Look at my results: 1) And it also finds center of mass:
To improve diagnostic accuracy the ABCD rule of lesion screening is widely used based on asymmetry (A), border (B), color (C), and differential structure (D) measuring. • A total dermatoscopic value (TDV) results from the calculation TDV = A·1,3 + B·0,1 + C·0,5 + D·0,5 • This score contributes to the differentiation between benign and malignant lesions: 1,00 – 4,75 – benign skin lesion 4,75 – 5,45 – suspicious More than 5,45 – melanoma Asymmetry A – Asymmetry of Shape, Structure and Color. The lesion is divided in four regions and there is symmetry inspected across x or y axis. If asymmetry is only by one axis it gives 1 point and if on both axis there are 2 points calculated. So for shape, structure and color, there can be 6 points maximum.
There are many skin image capture methodologies developed and used. Here are short review of them: Dermatoscopic photography The deepest layer of skin can be reached – Papillary dermis Resolution – depends on optical system View of skin – Horizontal The main disadvantage is reflections of light from skin surface – stratum cornea. Dermatoscopic oil immersion photography The deepest layer of skin can be reached – Papillary dermis Resolution – depends on optical system View of skin – Horizontal Reflections of light from skin surface are smaller because of oil used between camera optics and skin.
I used simple lamp directed to glossy table surface. One polarizer is in front of lamp and other is in front of lens of digital camera. Both polarizes are perpendicularly oriented to each other. How does this work? There is a theory about an angle on which the incident polarized electromagnetic waves turn reflects from surface with polarization plane turned in 90 degrees. When light going through polarizer towards the surface, the light is polarized in one direction and when it reflects from surface it is turned by 90 degrees and those waves are filtered by another perpendicular polarizer in front of lens.