cẩn thận khi dùng lò vi sóng
Sử dụng lò vi sóng
... - 10:06 AM Lò nấu vi sóng Lò Vi sóng (Microwave oven - sóng cực ngắn) hiện nay đã ngự trị trong bếp của nhiều gia đình cũng như tại công sở, trường học…. Dân giầu có thì sắm một lò gắn vào tường ... chạy lò khi không có thực phẩm trong lò. - Luôn luôn có nước hoặc thực phẩm ướt khi dùng lò, để tránh cho ống magnetron khỏi bị hư hao. - Khi món ăn quá khô, có thể để một ly nước trong lò. ... cũng như cách dùng lò sao cho hiệu quả và đúng hướng dẫn. Lịch sử lò vi sóng Nhiều phát minh khoa học là kết quả của nhận xét tình cờ. Kháng sinh Penicillin được tìm ra khi nhà vi trùng học...
Ngày tải lên: 17/09/2013, 20:10
NGUOI CAO TUOI PHAI RAT CAN THAN KHI DUNG THUOC
... hãy dùng thuốc theo sự chỉ định của bác sĩ, theo sự hướng dẫn của dược sĩ. - Khi bác sĩ cho đơn thuốc, phải dùng đúng thuốc theo đơn đó, không tự ý dùng thêm hoặc thay đổi thuốc, thậm chí dùng ... diễn kinh nghiệm dùng thuốc ở người trẻ tuổi cho NCT. - Lưu ý các thuốc tránh dùng cho NCT nói chung và NCT đang mắc một bệnh lý nào đó. Cần lưu ý có những dạng thuốc nên tránh dùng cho NCT đang ... một bệnh như: - Không dùng dạng thuốc sủi bọt đối với người bị bệnh tăng huyết áp, suy tim (dùng dạng thuốc sủi bọt luôn chứa muối natri sẽ làm bệnh nặng thêm). - Không dùng thuốc chẹn bêta đối...
Ngày tải lên: 27/09/2013, 06:10
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P1)
... wavelengths between 1 m (10 –6 m) and 1 mm. Beyond the infrared spectrum is the visible optical spectrum, the ultraviolet spectrum, and x-rays. Below the microwave frequency spectrum is the radio ... tuning. Here the costs for the design and tuning can be reduced greatly by using CAD, which can provide more accurate design with less design iterations, leading to first-pass or tuneless filters. ... developments in this area are cer- tainly being stimulated by increasing computer power. Another driving force for the developments is the requirement of CAD for low-cost and high-volume production. In...
Ngày tải lên: 24/10/2013, 16:15
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P2)
... ports of the network NЈЈ ; and all the S submatrices con- tain the corresponding S parameters. Obviously, p + c = M 1 and q + c = M 2 . It is [aЉ] q [aЉ] c [SЉ] qc [SЉ] cc [SЉ] qq [SЉ] cq [bЉ] q [bЉ] c [aЈ] p [aЈ] c [SЈ] pc [SЈ] cc [SЈ] pp [SЈ] cp [bЈ] p [bЈ] c b i ᎏ a j a 1 a 2 Ӈ a M S 1M S 2M Ӈ S MM ... at port 2 of the network NЈ and port 1 of the network N Љ when SЈ mn and SЉ mn are evaluated individually. 2.8 NETWORK PARAMETER CONVERSIONS From the above discussions it can be seen that for ... composite network is given simply by the sum of the short-circuit admittance matrices of the individual networks. Analogously, the networks of Figure 2.3(b) are connected in series at both their input...
Ngày tải lên: 24/10/2013, 16:15
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P3)
... the same 3 pole Butterworth lowpass prototype as that used previously in Section 3.3.1, Figure 3.15(b) illustrates a bandpass having a passband from 1 to 2 GHz obtained using the element transformation. 3.3.4 ... = 1 to n (3.24) g n+1 = 1.0 For convenience, Table 3.1 gives element values for such filters having n = 1 to 9. As can be seen, the two-port Butterworth filters considered here are always sym- metrical ... be chosen. 3.2.2 Chebyshev Lowpass Prototype Filters For Chebyshev lowpass prototype filters having a transfer function given in (3.9) with a passband ripple L Ar dB and the cutoff frequency...
Ngày tải lên: 28/10/2013, 23:15
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P4)
... previous expressions for re are obtained based on the quasi-TEM or quasistatic approximation, and therefore are rigorous only with DC. At low microwave frequencies, these expressions provide ... expressions also provide accuracy better than one percent. If more accurate values are needed, an iterative or optimization process based on the more accurate analysis models described previously can ... 4.10(h). These microstrip patch resonators can be analyzed as waveguide cavities with mag- netic walls on the sides. The fields within the cavities can be expanded by the TM Z nm0 modes, where z is perpendicular...
Ngày tải lên: 28/10/2013, 23:15
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P5)
... Semilumped Lowpass Filters Having Finite-Frequency Attenuation Poles The previous two types of microstrip lowpass filter realize the lowpass prototype filters having their frequencies of infinite ... can only be electrically equivalent to the combline filter in the vicinity of the mid- band frequency, and its stopband behavior is different from that of the combline fil- ter. Similar to the ... inductances L 1 , L 3 , and L 5 block transmission by having infinite series reactance, whereas the capacitance C 6 shorts out transmission by having infinite shunt susceptance. A microstrip filter...
Ngày tải lên: 07/11/2013, 21:15
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P6)
... design this type of filter, let us consider the design of an op- timum distributed highpass filter having a cutoff frequency f c = 1.5 GHz and a 0.1 dB ripple passband up to 6.5 GHz. Referring to Figure ... = 1 to n where b i are the susceptance slope parameters of series parallel resonators. It is obvious that for a chosen lowpass prototype, with known element values, the desired reactance/susceptance ... relative dielectric constant of 10.8 and a thickness of 1.27 mm. The bandstop filter is designed to provide an RF rejection better than 40 dB over an operating frequency band from 3.5 GHz to 5.5 GHz....
Ngày tải lên: 07/11/2013, 21:15
Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P7)
... (MEMS) provide a class of new devices and com- ponents which display superior high-frequency performance and enable new system capabilities. For a general definition, a MEMS is a miniature device ... ability to effectively improve filter selectivity. Therefore, it does not constitute a particularly attractive choice for achieving frequency selectivity. Never- theless, it may be of interest ... production. The change in permittivity as a func- tion of electric field is the key to a wide range of applications. Frequency-agile filters are among many other device applications of ferro- electrics....
Ngày tải lên: 07/11/2013, 21:15
Tài liệu Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P8) doc
... of S 11 in (8.76) is always equal to 1. This is because in the vicinity of resonance, the parallel res- onator of Figure 8.11 behavior likes an open circuit. However, the phase response of S 11 changes ... of Kirchhoff’s two circuit laws and states that the algebraic sum of the currents leaving a node in a network is zero, with a driving or external current of i s the node equa- tions for the circuit of Figure ... resonator Y in = j C + = j 0 C – (8.74) Note that 0 = 1/͙L ෆ C ෆ is the resonant frequency. In the vicinity of resonance, say, = 0 + ⌬ , (8.74) may be simplified as Y in = j 0 C· (8.75) where...
Ngày tải lên: 15/12/2013, 06:15
Tài liệu Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P9) doc
... filter synthesis by optimization is a three-pole cross-cou- pled resonator filter having asymmetrical frequency selectivity. The desired filter response will exhibit a single finite frequency attenuation ... are violated. 9.3 OPTIMIZATION 287 minimize ⌬⌽,⌬⌰ Ή R b (⌽ + ⌬⌽, ⌬⌰) – R a (⌽)Ή where ⌬⌽ denotes the modifications to the physical design parameters for compensating the characteristic deviation ... the initial decomposition design, the filter is decomposed into individual cascaded sections, where reference planes of each individual section are represented by circuit nodes and the discontinuities...
Ngày tải lên: 15/12/2013, 06:15
Tài liệu Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P10) pptx
... the improvement in selectivity over the Chebyshev filter is evident. The closer the atten- uation poles to the cut-off frequency (⍀ = 1), the sharper the filter skirt and the higher the selectivity. ⍀ a FBW ... rejection bandwidths are 100 MHz and 120 MHz, respectively, which obviously does not meet the rejection require- ments. Having determined the design parameters, the nest step is to find the physical ... communications systems, flat group delay of a bandpass fil- ter is demanded in addition to its selectivity. In order to achieve a flat group delay characteristic, two approaches are commonly used. The...
Ngày tải lên: 15/12/2013, 06:15
Tài liệu Microstrip bộ lọc cho các ứng dụng lò vi sóng RF (P11) ppt
... even without the via hole grounding. Thus, it would seem that the voltage and current distributions would not change much in the vicinity of the midband fre- quency, even though the via holes are ... “New high temperature superconductive microstrip lines and resonators,” Applied Supercon- ductivity, Inst. Phys. Conf. Ser. 148, 1995, 1995, 1195–1198. [7] J S. Hong and M. J. Lancaster, “Novel ... is associated with the necessity of using low-value characteristic impedance lines ț High sensitivity to small variations in physical dimensions ț Excitation of higher-order modes ț Difficulty...
Ngày tải lên: 15/12/2013, 06:15