۳ مطلب در خرداد ۱۴۰۰ ثبت شده است

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Electric cars and clean energy

When we refocus our thoughts on the world around us, and stop looking at only the things that can be changed—think about all the cars on the road right now. You may be surprised to learn that electric cars are faster than gasoline ones on a few key metrics: acceleration, top speed, braking distance, and battery capacity. So what gives?

The decades ahead will see a proliferation of electric cars as private ownership becomes the mainstream choice for personal transportation. gasoline will be largely replaced by battery-powered cars as well, though perhaps not for many decades. As a result, we will need strategies for securing long-term physical storage of our car if we want to drive on public roads when charging is not an option.

People are embracing clean energy, donating their power for use in the collective. But what you don’t hear about as much is the ethics of driving an electric car. The technology is sound, but is it ethical to use it so heavily? Or could it be exploited by people who want an edge over others?The good news is that there are plenty of people thinking about these issues and coming up with solutions that don't compromise on driving or driving well.

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Ketab Posts 1

کتاب چیست؟ مروری بر تعریف و مفهوم «کتاب»

این نوشته را اولین بخش از فصل دوم کتاب‌خوانی می‌دانم. اگرچه برخی از بخش‌های انتخابی فصل قبل هنوز مانده است.

۱- نگاهی به تعریف و تاریخ

تعاریف مختلفی از مفهوم کتاب عرضه شده است. مثلا ویکیپدیا:

کتاب مجموعه‌ای از صفحات نوشته‌شده، مصور، چاپ‌شده یا صفحات خالی (صفحه سفید و نانوشته)؛ ساخته‌شده از جوهر، کاغذ (ورق)، پوست حیوانات یا مواد دیگر (چسب، نخ و…) است که معمولاً از یک طرف یا سمت به یکدیگر محکم شده یا متصل می‌گردند. هر برگه در کتاب، ورق و هر سمت یا روی هر ورق، صفحه نامیده می‌شود.

تعاریف سایر لغت‌نامه‌ها از کتاب، در واقع تعریفی از کدکس است که در ادامه خواهد آمد.





پنج هزار سال از تاریخ شروع کتاب می‌گذرد. حدود ۴۵۰۰ سال پیش، اهالی بین‌النهرین از لوح‌های گلی برای  ثبت مسائل حکومتی یا مالی استفاده می‌شد (اغلب از نوع شمارش). فرم امروزی کتاب (که شاید بتوان نام دیروزی را نهاد با توجه به ظهور کتاب‌های الکترونیک) حدود ۱۸۰۰ سال پیش برای نوشتن متون مذهبی مسیحیان شکل گرفت.  به این صورت که نوشته‌هایی روی پاپیروس یا چرم نوشته می‌شد و سپس آن‌ها را با استفاده از ابزاری متناسب به هم می‌دوختند.





حدود ۱۴۴۰ بود که گوتنبرگ ماشین چاپ را اختراع کرد و به نوعی باعث شد به نوعی عدالت در دسترسی به متون یک مرحله به پیش رود.  فرایند آماده‌سازی کتاب چاپی حتی اکنون هم به لحاظ تکنولوژیک شبیه گذشته است. فقط ابزارها تغییر کرده‌اند. اگرچه اکنون دیگر نیازی نیست از یک کتاب هزاران جلد بزنید تا صرفه داشته باشد. می‌‌توانید حتی ۱۰ جلد کتاب را به دستگاه چاپ دیجیتال بدهید تا برای شما آن را چاپ کند و البته گاهی صحافی در خود آن دستگاه و گاهی در یک دستگاه جانبی انجام می‌شود.





اگرچه حدود ۵۰ سال پیش لامپ کاتدی اختراع شد تا بتوان تصویری از یک کتاب را در صفحه دید، اما تا پیدایش واقعی یک کتاب الکترونیکی ۳۰ سال طول کشید. تا همین چندی پیش (15سال) که ال‌سی‌دی و ال‌ای‌دی‌های امروزی نبودند، نگاه کردن بلندمدت به یک مانیتور برای دراز مدت مانند چشم‌کُشی بود!  بله سال 1999 اولین کتاب الکترونیکی به نام Nuvomedia’s Rocket شکل گرفت. توجه کنید چندین سال بعد از اینترنت، آمازون، گوگل و … از نظر خود من هم عجیب است.





















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A cell phone, short for cellular phone, cell phone or hand phone, can make and receive phone calls over a cellular radio frequency signal while the user is traveling in a phone service zone. Cell phones are used mostly by people talking on the telephone for personal purposes, but now these devices are being used by many businesses and even by the public for making phone calls. In the United States alone, there are more than three million cell phone users. That is a lot of cell phone users!

The traditional telephone systems use an Analog signal processing (ASP) system to convert voice signals into electrical pulses which are sent to the CPU via the radio transmitter. Modern telephone systems also use digital systems to process the analog signals. The modern mobile phone uses a different system using digital and analogue technologies. It is called GSM, which stands for Global System for Mobile Communication.

Digital technology allows the communication data to be processed efficiently by a demodulated analog signal processing system. This is done by the CPU by interpreting the received radio frequency signals. The advantage of a digital signal processing system is that it uses only one CPU instead of two or more processors using analogue technology. The demodulated analog signal processing systems are able to process high frequency signals at much higher bandwidths than the conventional systems. As a result they can process more data at faster speeds. The demodulated analogue system is also able to process more data in the same amount of time and for lower power consumption than the conventional systems.

There are a few factors that need to be considered in a phone's GSM / GPRS phone design before choosing the best handset. The most important factor is the data rate. A good demodulated digital signal processing system needs to be able to process signals of more than 3 Gigabits per second. The minimum rate that a phone should have is the average rate of the top five wireless networks, which is around 9 Gigabits per second.

There are three different types of cell phone technology currently, CDMA, TDMA, and GSM. CDMA is another type of cell phone technology where the cell phone has to receive the information at a preset point in time and be ready to accept it before making the call. When the two wireless companies decided to use the CDMA system, the technology has been used in many different cellular phones since then. However, there are many different brands of CDMA phones available, and users must carefully choose the best one for their personal needs and preferences. For a long time, the CDMA system remained the most popular and cheapest amongst cell phones.

The next technology, TDMA, operates very similarly to CDMA except for the fact that it does not require a base station. Instead, the user connects the cellular phone line directly to a receiver, which can determine the information that is to be sent or received. This type of technology is commonly referred to as CDMA plus, and some of the earliest CDMA phones use this system. Since TDMA phones are more expensive, they are better suited for smaller business and personal uses, and users prefer them over CDMA phones because they are easier to use and understand.

The third type of mobile phone is known as GSM. It stands for "Global System for Mobile Communication," and it was the first type of cellular phone technology to be used. GSM uses a transceiver chip that receives data at regular intervals from a Global System for Mobile Communications receiver. Once the data is received by the chip, it is converted into a digital signal that can be sent over cellular phones. Although this technology has been around for a while, it was until recently used in the global market, but it has recently been brought back into the American market. Nowadays, more people are switching back to GSM cellphone service.

As you can see, there are a variety of different types of mobile phones that you can use and not all of them will be suitable for your needs. When looking to buy a new phone or plan, you need to look at a few features first. If you do not already have a cellphone service provider, you may want to think about using a reputable one instead. Once you know exactly what features you are looking for and what you need from a mobile phone service, you can begin your search for the best deal. You may also want to check out your local phone store for more information on cellular phones. They will most likely be able to offer you a good deal on a cellphone plan or even a new cellphone.


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