Trong các hình sau, hình nào diễn tả đúng phương và chiều của cường độ điện trường \(\overrightarrow {\rm{E}} \), cảm ứng từ \(\overrightarrow {\rm{B}} \) và tốc độ truyền sóng \(\overrightarrow {\rm{v}} \) của một sóng điện từ?
a) b) c) d)
Trong các hình sau, hình nào diễn tả đúng phương và chiều của cường độ điện trường \(\overrightarrow {\rm{E}} \), cảm ứng từ \(\overrightarrow {\rm{B}} \) và tốc độ truyền sóng \(\overrightarrow {\rm{v}} \) của một sóng điện từ?
a) b) c) d)
Câu hỏi liên quan
Liệu pháp gene là phương pháp sử dụng gene để điều trị hoặc ngăn ngừa bệnh tật. Hình dưới đây thể hiện nguyên lí nào trong liệu pháp gene?
Read the following passage about and mark the letter A, B, C, D on your answer sheet to indicate the best answer to each of the following questions from 31 to 40.
Some people look at an equation and see a bunch of complicated numbers and symbols while others see beauty [I]. Now, thanks to a new tool created at Carnegie Mellon University, anyone can now translate the abstractions of mathematics into beautiful and instructive illustrations [II]. This exciting new tool is named Penrose after the mathematician Roger Penrose, who is famous for using diagrams and other drawings to communicate complicated mathematical ideas [III]. Penrose enables users to create diagrams simply by typing mathematical expressions and letting the software do the drawing [IV].
Unlike a graphing calculator, these aren’t restricted to basic functions, but can be complex relationships from any area of mathematics. “Some mathematicians have a talent for drawing beautiful diagrams by hand, but they vanish as soon as the chalkboard is erased,” said Keenan Crane, an assistant professor of computer science and robotics. “We want to make this expressive power available to anyone.”
Diagrams are often underused in mathematical communication, since producing high-quality illustrations is beyond the skill of many researchers and requires a great deal of time and effort. Penrose addresses these challenges by letting diagram-drawing experts turn their knowledge about creating diagrams into computer codes so that other users can access this capability using familiar mathematical language and a computer. “We started off by asking: ‘How do people translate mathematical ideas into pictures in their head?’” said Katherine Ye, a Ph.D. student in the Computer Science Department who is involved in the development of Penrose. “The secret sauce of our system is to empower people to easily ‘explain’ this translation process to the computer, so the computer can do all the hard work of actually making the picture.”
Once the computer learns how the user wants to see a mathematical object visualized – a vector represented by a little arrow, for instance, or a point represented as a dot – it uses these rules to draw several candidate diagrams. Users can then select and edit the diagrams they want from a gallery of possibilities. A special, simple-to-learn programming language was also developed so that they can easily convey the ideas in their minds to the Penrose system, Crane said. “Mathematicians can get very picky about notations,” he explained. “We let them define whatever notation they want, so they can express themselves naturally.”
The researchers will present Penrose at the SIGGRAPH 2020 Conference on Computer Graphics and Interactive Techniques, which will be held this July. “Our vision is to be able to dust off an old math textbook from the library, drop it into the computer and get a beautifully illustrated book - that way more people understand,” Crane said, noting that Penrose is a first step toward this goal.
(Adapted from sciencedaily.com)
Where in paragraph 1 does the following sentence best fit?
For many, the elegance of mathematical concepts often goes unnoticed amidst
the complexity.
Tiêu chí thứ hai đánh giá công nghệ là gì?
Tại sao uống nhiều rượu dẫn đến mất nước và khát nước?
1. Rượu làm giảm tiết ADH dẫn đến giảm hấp thụ nước ở ống thận.
2. Lượng nước không được tái hấp thụ ở thận sẽ ra ngoài theo nước tiểu.
3. Mất nước làm áp suất thẩm thấu trong máu tăng, kích thích vùng dưới đồi thị gây cảm giác khát.
4. Rượu làm giảm tiết ADH dẫn đến tăng hấp thụ nước ở ống thận.
Đáp án đúng là
Máy phát điện xoay chiều ba pha có cấu tạo gồm
- Nhiệt độ cao, lượng mưa lớn của khí hậu nước ta tạo thuận lợi cho
Ở điều kiện chuẩn. Khi phản ứng thu nhiệt thì
Anh A làm việc trong lĩnh vực công nghệ cho một công ty nước ngoài có chi nhánh đại diện ở Việt Nam. Hằng năm, tổng thu nhập anh A khoảng hơn 500 triệu đồng. Tuy nhiên cơ quan thuế phát hiện anh A chưa hoàn thành nghĩa vụ nộp thuế theo quy định của pháp luật hiện hành. Hành vi của anh A đã vi phạm Luật nào của nước ta?
Ý nghĩa nào là cơ bản nhất của cách mạng Tân Hợi (1911) ở Trung Quốc?
Lí do nào sau đây là lí do chủ yếu nhất của sự gia tăng nhu cầu tuyển dụng vị trí sửa chữa và bảo trì máy tính
Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 23 to 30.
Animals are primed to be wary through natural selection rather than scary television shows, but like humans, they often make mistakes when watching out for threats.
Identifying stealthy predators is already a difficult task. From the perspective of a songbird, a harmless crow flying overhead may look similar to a raptor. But predator identification is made more challenging by the fact that prey animals often juggle multiple activities like foraging, keeping an eye on competitors and courting mates, all at the same time.
This can be made easier by working as a group. Members of a school of fish, flock of birds or herd of antelope can share the task of watching out for predators. When an animal detects a predator, they share this information with other group members directly, by producing a warning, or inadvertently, by preparing to flee. The group as a whole can then respond by fleeing, hiding or adopting a defensive position.
But this information is not always reliable. When predators are harder to identify, perhaps because they are well camouflaged, an animal may be more likely to mistake unrelated sounds or movements for a predator. Research found that bumblebees were more likely to produce false alarms having previously been exposed to highly camouflaged goldenrod crab spiders than bees that were unaccustomed to them.
Some species are instead simply more vulnerable to predators than others. This can be because they are not fast enough to escape a close encounter or not equipped to fight a predator off. For these species, ignoring a true alarm is more likely to result in death, so it may be beneficial to follow a “better-safe-than-sorry” principle and pay the cost of being occasionally wrong. Willow tits produce alarm calls in response to most large aerial objects including planes and crows. This is because they are typically hunted in ambush attacks in which they are unlikely to escape. So the costs of alarm calling at a few planes becomes dwarfed by the threat of being killed in an attack.
(Adapted from https://www.thesouthafrican.com/animals/why-prey-animals-often-see-threats)
In which paragraph does the writer mention previous awareness of predators causes them to make mistakes?
Đâu là hình ảnh giá thể là vỏ cây thông?
Phát biểu nào sau đây là sai khi nói về năng lượng của vật dao động điều hòa?
Cho hình chóp tứ giác đều , có đáy là hình vuông tâm .
Khẳng định nào sau đây đúng?
Vai trò của phong trào Tây Sơn cuối thế kỉ XVIII là gì?
Read the following passage about Reducing Electronic Waste and mark the letter A, B, C or D on your answer sheet to indicate the option that best fits each of the numbered blanks from 18 to 22.
In today's hyper-connected world, our constant need for the newest electronic devices has led to a growing environmental crisis. Electronic waste, or e-waste, is one of the fastest-growing waste streams globally, with millions of tons discarded annually. A digital detox, (18)_________, can be an effective environmental practice that helps address this issue.
(19)_________, the current e-waste crisis might have been avoided. The devices that we carelessly discard often contain valuable materials that could be recycled and harmful components that contaminate soil and water. Many consumers replace functioning smartphones and laptops simply because newer models are available, not realizing the environmental impact of their decisions. The manufacturing process of new electronics requires significant resources and energy; (20)_________.
Practicing digital detox not only improves mental health but also decreases the demand for new products. (21)_________; however, if consumer demand decreases, production might slow down as well. Individuals who commit to using their devices for longer periods contribute significantly to waste reduction, and they often discover that older models fulfill their needs perfectly well.
The electronic waste problem requires both individual action and systemic change. We can create a world embracing sustainable principles, (22)_________, through our participation in digital detox practices and mindful consumption.
Read the passage below and choose A, B, C or D to answer each question from 641 to 645.
Cities develop as a result of functions that they can perform. Some functions result directly from the ingenuity of the citizenry, but most functions result from the needs of the local area and of the surrounding hinterland (the region that supplies goods to the city and to which the city furnishes services and other goods). Geographers often make a distinction between the situation and the site of a city. Situation refers to the general position in relation to the surrounding region, whereas site involves physical characteristics of the specific location. Situation is normally much more important to the continuing prosperity of a city. If a city is well situated in regard to its hinterland, its development is continuing prosperity of a city. If a city is well situated in regard to its hinterland, its development is much more likely to continue. Chicago, for example, possesses an almost unparalleled situation: it is located at the southern end of a huge lake that forces east-west transportation lines to be compressed into its vicinity, and at a meeting of significant land and water transport routes. It also overlooks what is one of the world’s finest large farming regions. These factors ensured that Chicago would become a great city regardless of the disadvantageous characteristics of the available site, such as being prone to flooding during thunderstorm activity.
Similarly, it can be argued that much of New York City’s importance stems from its early and continuing advantage of situation. Philadelphia and Boston both originated at about the same time as New York and shared New York’s location at the western end of one of the world’s most important oceanic trade routes, but only New York possesses an easy-access functional connection (the Hudson- Mohawk Lowland) to the vast Midwestern Hinterland. This account does not alone explain New York’s primacy, but it does include several important factors. Among the many aspects of situation that help to explain why some cities grow and others do not, original location on a navigable waterway seems particularly applicable. Of course, such characteristics as slope, drainage, power resources, river crossings, coastal shapes, and other physical characteristics help to determine city location, but such factors are normally more significant in early stages of city development than later.
What is the topic of the passage?
Trong văn phòng của một doanh nghiệp gồm 50 thiết bị khác nhau bao gồm máy tính để bàn, máy in, server. Các nhân viên cần truyền tải một lượng rất lớn dữ liệu qua lại với nhau liên tục trong mạng. Thiết bị nào sau đây là phù hợp nhất để có thể kết nối các thiết bị qua mạng trong tình huống trên?
Sự hình thành thạch nhũ trong các hang động chủ yếu là do phản ứng hóa học nào sau?
Một khung dây gồm 1 000 vòng, mỗi vòng có diện tích là 80 cm2. Khung dây được đặt trong từ trường đều sao cho vectơ cảm ứng từ vuông góc với vectơ đơn vị pháp tuyến của mặt phẳng vòng dây. Độ lớn cảm ứng từ là 0,8 T. Quay khung dây quanh trục quay vuông góc với vectơ cảm ứng từ thì trong khung dây xuất hiện suất điện động cảm ứng trung bình có độ lớn 6,4 V. Sau khoảng thời gian 1 s tính từ lúc khung dây bắt đầu quay, góc hợp bởi vectơ cảm ứng từ và mặt phẳng khung dây có thể nhận giá trị nào dưới đây?
