共查询到20条相似文献，搜索用时 15 毫秒
1.
Monolithic integration of resonant tunneling diodes (RTDs) and high electron mobility transistors (HEMTs) is an important development direction of ultra-high speed integrated circuit. A kind of top-RTD and bottom-HEMT material structure is epitaxied on InP substrate through molecular beam epitaxy. Based on wet chemical etching, metal lift-off and air bridge interconnection technology, RTD and HEMT are fabricated simultaneously. The peak-to-valley current ratio of RTD is 7.7 and the peak voltage is 0.33 V at room temperature. The pinch-off voltage is -0.5 V and the current gain cut-frequency is 30 GHz for a 1.0 μm gate length depletion mode HEMT. The two devices are conformable in current magnitude, which is suitable for the construction of various RTD/HEMT monolithic integration logic circuits. 相似文献
2.
We present a new sense amplifier circuit for EEPROM memory. The topology of the sense amplifier uses a voltage sensing method, having low cost and low power consumption as well as high reliability. The sense amplifier was implemented in an EEPROM realized with an SMIC 0.35-μm 2P3M CMOS embedded EEPROM process. Under the condition that the power supply is 3.3 V, simulation results showed that the charge time is 35 ns in the proposed sense amplifier, and that the maximum average current consumption during the read period is 40 μA. The novel topology allows the circuit to function with power supplies as low as 1.4 V. The sense amplifier has been implemented in 2-kb EEPROM memory for RFID tag IC applications, and has a silicon area of only 240 μm^2. 相似文献
3.
Inhabited by women with male characteristics and men possessing female features, the Dunnet Landing in Sarah Orne Jewett’s masterpiece The Country of the Pointed Firs is depicted as a harmonious land of beauty, from which Jewett’s preference of androgyny is fully expressed. In this novel, androgyny is used as a means by Jewett to achieve her feministic idea of the equality between men and women and that neither of the sex has prejudice upon the other in this combination. Through a detailed textual analysis, this paper reveals the androgyny elements in this novel and discusses about the possibility of androgyny as a way out for feminism. 相似文献
4.
This paper concerns with modeling and design of an algorithm for the portfolio selection problems with fixed transaction costs and minimum transaction lots. A mean-variance model for the portfolio selection problem is proposed, and the model is formulated as a non-smooth and nonlinear integer programming problem with multiple objective functions. As it has been proven that finding a feasible solution to the problem only is already NP-hard, based on NSGA-II and genetic algorithm for numerical optimization of constrained problems (Genocop), a multi-objective genetic algorithm (MOGA) is designed to solve the model. Its features comprise integer encoding and corresponding operators, and special treatment of constraints conditions. It is illustrated via a numerical example that the genetic algorithm can efficiently solve portfolio selection models proposed in this paper.This approach offers promise for the portfolio problems in practice. 相似文献
5.
Seyed Javad Mirabedini Mohammad Teshnehlab M. H. Shenasa Ali Movaghar Amir Masoud Rahmani 《浙江大学学报(A卷英文版)》2008,9(12):1666-1675
We propose a novel approach called adaptive fuzzy ant-based routing （AFAR）, where a group of intelligent agents （or ants） builds paths between a pair of nodes, exploring the network concurrently and exchanging obtained information to update the routing tables. Routing decisions can be made by the fuzzy logic technique based on local information about the current network state and the knowledge constructed by a previous set of behaviors of other agents. The fuzzy logic technique allows multiple constraints such as path delay and path utilization to be considered in a simple and intuitive way. Simulation tests show that AFAR outperforms OSPF, AntNet and ASR, three of the currently most important state-of-the-art algorithms, in terms of end-to-end delay, packet delivery, and packet drop ratio. AFAR is a promising alternative for routing of data in next generation networks. 相似文献
6.
Published in 1923, Cane, the representative work of Jean Toomer has been widely studied by critics. Among which,one of perspectives is to analyze the biblical metaphors in the novel. A closer reading of the book shows that the Cain allusion is an unifying theme, for the author once refers Cane as Cain, and most of the characters in the novel are blacks who are believed to be descendant of Cain because of the color of their skin as well as the same suffering of isolation and alienation. Here a study of the Cain allusion in the novel is presented with focus on Karintha’s story in the first part of Cane. 相似文献
7.
The indirect boundary element method (IBEM) is used to study the surface motion of an alluvial valley in layered half-space for incident plane P-waves based on Wolf’s theory. Firstly, the free field response can be solved by the direct stiffness method, and the scattering wave response is calculated by Green’s functions of distributed loads acting on inclined lines in a layered half-space. The method is verified by comparing its results with literature and numerical analyses are performed by taking the amplification of incident plane P-waves by an alluvial valley in one soil layer resting on bedrock as an example. The results show that there exist distinct differences between the wave amplification by an alluvial valley embedded in layered half-space and that in homogeneous half-space and there is interaction between the valley and the soil layer. The amplitudes are relatively large when incident frequencies are close to the soil layer’s resonant frequencies. 相似文献
8.
Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential phase shift. Based on the unique dispersion property of the composite right/left-handed (CRLH) metamaterial structure, a new configuration is presented in this paper for fabricating the broadband differential phase shifter, which employs a novel CRLH metamaterial structure as one of the differential phase-shift arms, instead of the conventional coupled line. The new circuit can achieve a phase shift of 90° in an operational bandwidth as broad as one octave and its phase deviations are quite small. An original design of the novel broadband phase shifter is presented, in which the artificial CRLH structure was implemented by microstrip quasi-lumped elements. Both the simulated and measured results of the 90° broadband differential phase shifter are presented. 相似文献
9.
Darra Pace Diane Schwartz 《美中教育评论》2008,5(12):20-26
The inclusion of students with disabilities at the university is a relatively new occurrence in the field of special education. Although legislation in the United States has supported the acceptance of students with disabilities at the post-secondary level, it has only provided minimal support with the emphasis on the learner rather than the curriculum. Now we are looking for multiple ways for students to access learning and demonstrate mastery. Universal Design for Learning （UDL） is currently seen as a means to reconceptionalize curriculum. This study examines the experience of four professors and their effort to use a Classroom Performance System （CPS） as part of reformatting their courses using UDL. The Center for Applied Special Technology, CAST （2001） states that the goal of Universal Design for Learning is to develop teaching methods that enable all students with diverse learning needs, including those with disabilities and cultural differences, to have equal access to classroom curriculum. This paradigm shift echoes the move in special education from a deficit model to a minority rights model put forward by Hahn （1989）, and which is the basis of inclusive educational philosophy. Together inclusion and UDL create learning environments that strive to serve all students. This research describes the implementation of clickers as part of the CPS program in college courses in a special education teacher preparation program. The case study demonstrates how technology can provide access for all learners with positive outcomes such as increased participation and application of knowledge. It also illustrates some of the difficulties in making this pedagogical paradigm shift particularly in the use of technology, and the value of overcoming the existing barriers in place. 相似文献
10.
A high speed column-parallel CDS/ADC circuit with nonlinearity compensation is proposed in this paper.The correlated double sampling (CDS) and analog-to-digital converter (ADC) functions are integrated in a threephase column-parallel circuit based on two floating gate inverters and switched-capacitor network.The conversion rate of traditional single-slope ADC is speeded up by dividing quantization to coarse step and fine step.A storage capacitor is used to store the result of coarse step and locate the section of ramp signal of fine step,which can reduce the clock step from 2 n to 2 (n/2+1).The floating gate inverters are implemented to reduce the power consumption.Its induced nonlinear offset is cancelled by introducing a compensation module to the input of inverter,which can equalize the coupling path in three phases of the proposed circuit.This circuit is designed and simulated for CMOS image sensor with 640×480 pixel array using Chartered 0.18μm process.Simulation results indicate that the resolution can reach 10-bit and the maximum frame rate can reach 200 frames/s with a main clock of 10MHz.The power consumption of this circuit is less than 36.5μW with a 3.3V power supply.The proposed CDS/ADC circuit is suitable for high resolution and high speed image sensors. 相似文献
11.
Single-acting double-stator multi-pumps and multi-motors 总被引：4，自引：0，他引：4
We investigated a series of novel motors and pumps with a new structure called double-stator. Double-stator can be used as pump or motor just for the working condition on demand. A certain amount of pumps or motors are formed in one shell and these subpumps or submotors can work alone or in company without influence on other pumps or moters. This kind of double-stator pumps （motors） are called multi-pumps （multi-motors）. Through the analysis of multifarious connection modes of single-acting double-stator multi-pumps and multi-motors, the mathematical expressions of output flow rate, rotational speed and torque are acquired. The results indicate that different flow rates can be provided by one fixed displacement double-stator multi-pump system under the condition of an unalterable driven speed. Likewise, under the terms of a fixed input flow and without complex variable mechanisms, the functions of double speeds, multiple speeds and even differential connection can be realized by a double-stator multi-motor system with various output rotational speeds and torques. 相似文献
12.
HEYulin ZHENGTaixion 《重庆大学学报(英文版)》2002,1(1):7-10
Virtual environment has been widely applied in scientific research and considered as an important tool of exploring science.But constructing a real virtual environment is rather difficult.The difficulty cannot be compared with developing general software,It has a high demand for sofware technology,Obviously traditional methods are not competent for the job.Fortunately with the development of agent-oriented technologies ,all problems seem to be solved.By classifying a virtual environment into four layers corresponding with real world and considering it as a collection of agents,the virtual objects can be mapped into agents and an agent model can be designed.Based on the idea that the state change of a system is caused by that of in dividuals and the mutual effect among them,a theory of agent behavior driven by event and belief is put for ward.Such agent-oriented modeling method can cope with the demand for handling multi-dimension information.It is an effective technique for constructing a large and complex virtual environment. 相似文献
13.
Vacuum interrupter, high reliability component of distribution switches, circuit breakers and contactors 总被引：1，自引：0，他引：1
SLADE Paul G LI Wang-pei MAYO Stephen SMITH R. Kirkland TAYLOR Erik D 《浙江大学学报(A卷英文版)》2007,8(3):335-342
The use of vacuum interrupters(VIs)as the current interruption component for switches,circuit breakers,reclosers and contactors operating at distribution voltages has escalated since their introduction in the mid-1950’s.This electrical product has developed a dominating position for switching and protecting distribution circuits.VIs are even being introduced into switching products operating at transmission voltages.Among the reasons for the VI’s popularity are its compactness,its range of application,its low cost,its superb electrical and mechanical life and its ease of application.Its major advantage is its well-established reliability.In this paper we show how this reliability has been achieved by design,by mechanical life testing and by electrical performance testing.We introduce the“sealed for life”concept for the VI’s integrity.We discuss this in terms of what is meant by a practical leak rate for VIs with a life of over 30 years.We show that a simple high voltage withstand test is an easy and effective method for monitoring the long-term vacuum integrity.Finally we evaluate the need for routine inspection of this electrical product when it is used in adverse ambient environments. 相似文献
14.
15.
CHEN Xiao-fei ZOU Xue-cheng LIN Shuang-xi LIU Zheng-lin JIN Hai 《浙江大学学报(A卷英文版)》2007,8(8):1346-1350
An integrated laser diode driver(LDD) driving an edge-emitting laser diode was designed and fabricated by 0.35 μm BiCMOS technology. This paper proposes a scheme which combines the automatic power control loop and temperature com-pensation for modulation current in order to maintain constant extinction ratio and average optical power. To implement tem-perature compensation for modulation current,a novel circuit which generates a PTAT current by using the injecting base current of a bipolar transistor in saturation region,and alternates the amplifier feedback loop(closed or not) to control the state of the current path is presented. Simulation results showed that programmed by choice of external resistors,the IC can provide modu-lation current from 5 mA to 85 mA with temperature compensation adjustments and independent bias current from 4 mA to 100 mA. Optical test results showed that clear eye-diagrams can be obtained at 155 Mbps,with the output optical power being nearly constant,and the variation of extinction ratio being lower than 0.7 dB. 相似文献
16.
Epstein-Barr virus(EBV),a human gammaherpesvirus carried by more than 90% of the world’s population,is associated with malignant tumors such as Burkitt’s lymphoma(BL),Hodgkin lymphoma,post-transplant lymphoma,extra-nodal natural killer/T cell lymphoma,and nasopharyngeal and gastric carcinomas in immune-compromised patients.In the process of infection,EBV faces challenges:the host cell environment is harsh,and the survival and apoptosis of host cells are precisely regulated.Only when host cells receive sufficient survival signals may they immortalize.To establish efficiently a lytic or long-term latent infection,EBV must escape the host cell immunologic mechanism and resist host cell apoptosis by interfering with multiple signaling pathways.This review details the apoptotic pathway disrupted by EBV in EBV-infected cells and describes the interactions of EBV gene products with host cellular factors as well as the function of these factors,which decide the fate of the host cell.The relationships between other EBV-encoded genes and proteins of the B-cell leukemia/lymphoma(Bcl) family are unknown.Still,EBV seems to contribute to establishing its own latency and the formation of tumors by modifying events that impact cell survival and proliferation as well as the immune response of the infected host.We discuss potential therapeutic drugs to provide a foundation for further studies of tumor pathogenesis aimed at exploiting novel therapeutic strategies for EBV-associated diseases. 相似文献
17.
刘莹 《读与写:教育教学刊》2012,(3):8+19
The traditional teaching approach has long been concerned with imparting knowledge,and many college teachers still opt for this method in their practice In English class teachers choose to emphasize ma the language points,ignoring that English language mainly functions as a tool of communication.On the other hand,for students the purpose of learning English is to pass the examination.This traditional approach fails to cultivate students’ communicative ability in English.In recent years,however,the general shift from a knowledge-based education to an ability-oriented one makes it an imperative to reform the traditional teaching methods.As a new kind of teaching theory and teaching activity,task-based approach(TBA) has been introduced and applieded by English teachers in China,especially those engaged in English teaching in higher vocational colleges. 相似文献
19.
A Method for Reducing Noise Radiated from Structures with Vibration Absorbers by Using an Accelerated Neural Network 总被引：2，自引：0，他引：2
A method for reducing noise radiated from structures by vibration absorbers is presented. Since usual design method for the absorbers is invalid for noise reduction, the peaks of noise power in the frequency domain as cost functions are applied. Hence, the equations for obtaining optimal parameters of the absorbers become nonlinear expressions. To have the parameters, an accelerated neural network procedure has been presented.Numerical calculations have been carried out for a plate-type cantilever beam with a large width, and experimental tests have been also performed for the same beam. It is clarified that the present method is valid for reducing noise radiated from structures. As for the usual design method for the absorbers, model analysis has been given, so the number of absorbers should be the same as that of the considered modes. While the nonlinear problem can be dealt with by the present method, there is no restriction on the number of absorbers or the model number. 相似文献
20.
The strabismus conception of masculinity and power with its manipulation as reflected in the consequences of actions endorsed and demonstrated by leaders, followers, citizens as individuals and groups at different times in the past, and present has been a major source of the seemingly quiescence and underdevelopment in Africa. Masculinity has often been associated with being athletic, breadwinner, objective, sexually aggressive, unemotional, dominating, etc.; while power is frequently construed as a tool of dominance, authority, superiority, influence, and governance. This inapt perception was borne out of Africa＇s nictitating and ignorance. The consequences of the misconception include abuse of power, intolerance, intimidation, militancy, humiliation, insecurity, inadequate dialogic tools and opportunities, etc. These result in the Climate of Fear as being experienced in the Niger-Delta of Nigeria, Kenya, and other parts of Africa. Thus, this paper examines the concepts of masculinity and power with exemplification from Africa with Wole Soyinka＇s Climate of Fear. The research methodology employs a combination of critical discourse analysis and Halliday＇s systemic functional theory of grammar with sociolinguistics approaches for the analysis. The study posits that the root of the problems that abound in Africa is traceable to the lack of precise socio-cultural, political and philosophical ideologies by Africans. The research opines that these fundamental problems of Africa can be resolved through orientation with education for all, which is one of the challenges of the millennium development goals. Thus, the paper examines the contrivance of open distance learning and its role in the education of African citizenry. It concludes on the ground that open distance learning as a recent and welcomed information technological development in Africa, if properly channeled and adequately funded would enhance sustainable development in Africa by its elimination of some of the aforementioned obstacles. 相似文献