钢丝绳捻制中预变形器和后调直器的研制

以捻制8×19S-13电梯用钢丝绳为例,对8/450合绳设备的预变形器和后调直器进行重新设计和制造,将预变形器改为卧式锥形结构,后调直器由5轮3组改为7轮4组。工艺工装改进后,进行样品试验和批量生产,检测显示各项技术指标较改进前有较明显的提高。

建筑结构逆作区一柱一桩工程施工技术

介绍上海仲盛商业中心逆作区桩基工程中一柱一桩的施工技术和施工质量保证措施,以及对一些不足之处进行改进的设想。

A Low Noise,High Linearity CMOS Receiver for 802.11b WLAN Applications

A 2.4GHz monolithic CMOS receiver with direct-conversion architecture is presented. This quadrature receiver is designed for 802.11b wireless LAN applications at the maximum data rate of 11Mbps as a low-cost solution. Five key blocks,i, e., a low noise amplifier （LNA）, a down-conversion mixer, a variable gain amplifier, a low pass filter, and a DC- offset cancellation circuit,are designed based on system design and low noise high linearity considerations. The necessary auxiliary circuits are also included. Fabricated in SMIC 0.18μm 1p6m RF CMOS process, the receiver＇s performance is measured as：4. 1 dB noise figure, - 7.5dBm input third order intercept point （IIP3） for LNA ＆ mixer at high gain setting, - 14dBm IIP3 for the whole receiver,53dBc @30MHz offset of adjacent channel power rejection,and less than 5mV out- put DC-offset. The receiver consumes 44mA under a 1.8V power supply with I,Q two paths.

Design of a CMOS Current-Adjustable Charge-Pump Circuit Insensitive to Power Supply and Temperature

A CMOS charge-pump circuit with adjustable current is presented.A bandgap voltage reference,a low drop-out regulator,and a capacitive DC-DC voltage-booster are used to generate supply voltage for the current reference.This generated voltage is insensitive to the changes of external power supply voltage and temperature,while the current reference itself is insensitive to temperature.The circuit is designed in 0.18μm 1.8V standard digital CMOS process.The simulated results show that the performance of the circuit is satisfied.

EFFECTIVE DOUBLE LOOP CONTROL FOR A SQUARE WAVE BRUSHLESS DC MOTOR

A new type of brushless DC motor has been developed by using a square wave rare earth permanent magnet synchronous motor with its double loop control circuit. The double loop control scheme of the drive system yields a combination of desired characteristics including simplified control structure, small ripple torque, high speed accuracy, wide operating speed range, and fast dynamic response. Experimental results confirm excellent characteristics of the motor.

A new dimmer for alternating-current directly driven light-emitting-diode lamp

A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method. Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage. Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer. The experimental result shows that the proposed PWM dimmer has good performances.

Amplitude modulation measurement of symmetrical microwave power sensor

In order to reduce the mismatch error, a direct current （DC） calibration method is introduced when the modulated microwave signal is measured. The microwave power is input to the left section of the power sensor, and the DC power is input to the right of the power sensor. Due to the existence of parasitic loss and electromagnetic coupling, the microwave power results in a mismatch error. However, the DC power does not have the mismatch error. So the DC power applied in the right section can calibrate the mismatch error of the microwave power in the left section. The calibration factor is measured at different modulation rates and modulation depths.The measurement results show that the carrier frequency is the major factor influencing the measurement results. After calibration, the carrier frequency and the modulation rate have little effect on the output voltage. The frequency response becomes relatively flat in the frequency range up to 20 GHz, and the sensitivity on average is enhanced by about 0.12 mV/dBm. Therefore, the DC calibration method has a certain reference value for the terminal-type microwave power sensor.

Mathematical Description of Acousto-Optic Tunable Filter Orthogonal Polarizing Method

The transfer function of the optical splitting system of the acousto-optic tunable filter （AOTF） is deduced to be a reference to optical design. The characteristic matrix （ transfer function） of AOTF is used to describe quantitatively the characters of polarization elements in the orthogonal polarizing system. According to the characteristic matrix, the included angle of polarizer＇s transmission direction and polarization analyzer＇s transmission direction should be 90°. As a result the signal to noise ratio increased about 20 times though the light intensity was reduced to 54.3%,because both the transmittances of polarizer and polarization analyzer are 0. 74, which is an intrinsic character. The orthogonal polarizing method is an effective method to get rid of the influence of zero order light and improve the spectrum resolution and signal-to-noise ratio.

Experimental Study on the Effectiveness of TLDs under Wave Loading

The objective of this study is to experimentally investigate the effectiveness of Tuned Liquid Dampers (TLDs) for suppressing the dynamic response of a platform structure subjected to wave loading and to explore the applicability of TLDs for suppressing the structural vibration of fixed offshore platforms. The experimental model is scaled according to a full size platform by matching its dynamic properties. Rectangular and circular TLDs of various sizes and water depths are examined. The experiments were performed in a 2-D wave flume. The effectiveness of TLDs is evaluated based on their response reduction. By observing the performance and the behavior of TLDs through laboratory experiments, the effects of a number of parameters including container shape, container size, number of dampers, frequency ratio, mass ratio, and incident wave characteristics are investigated.

Power-line Modem over the Low Voltage Grid Using Direct Sequence Spread Spectrum Techniques

Power-line networks are designed to deliver electricity. They reach most of the domiciles and other buildings nowadays, so most of the people have access to it. On the other hand the backbone for the communications networks is not available in all countries especially the developing ones. A high cost and changing the design for the networks may be needed to construct this backbone. If data can be transmitted over the power-line networks, a recognized cost and time save can be achieved. In Egypt, the infrastructure is not always available for constructing a communications network backbone due to the already designed buildings before the need for these backbones. In this paper, we overcome this problem by designing a reliable Power-line Modem that operates safely on the low voltage grid. The modem is based on the Direct Sequence Spread Spectrum technique. It uses the mains zero crossing as an efficient way for the synchronization between the transmitter and the receiver. The Modem takes into account the problems of the Power-line including noise, attenuation and impedance dismatching.

Novel transmitter of dark RZ signal based on external modulator

A novel transmitter to generate a dark RZ signal with tunable duty cycle and extinction ratio is proposed, by modifying the process of preceding, modulating and coding, A dark RZ signal is generated simply by using one dual-arm Mach-Zehnder LiNbO3 modulator. We demonstrate experimentally that this optical dark RZ signal can be directly measured by a conventional binary intensity modulation direct detection （IM-DD） receiver. When different values of duty cycles at 2.5 Gbit/s are adjusted, the experimental results show different BER curves and eye diagrams of the optical dark RZ signal.

Commissioning of Dragon-Ⅰ Linear Induction Accelerator

This paper describes the subsystems commissioning process of Dragon-Ⅰ which include the injector,the pulsed power system,the transport system and the Bremsstrahlung target.The experimental results and further work are presented.

Preliminary Design of Compact FEL Terahertz Radiation Source

A new type of compact terahertz (THz) radiation source using free electron laser (FEL) is discussed in this paper.The concept machine consists of an independently tunable cell thermionic RF gun (ITC-RF Gun),an accelerating structure with symmetry RF-incoupler and a coaxial load RF-outcoupler,an undulator combined with an optical resonance cavity of hole-coupling mode.Withoutα-magnet and other bunch compressors,the size of this machine is decreased.The conceptual design and numerical simulation are presented.

High-Consistency Behavior Modeling of a Switched-Capacitor Sigma-Delta Modulator in SIMULINK

To improve the simulation accuracy of SIMULINK, a novel inclusive behavior model of an integrator is proposed that introduces the effects of different circuit nonidealities of a switched-capacitor sigma-delta modulator into SIMULIK simulation. The nonlinear DC gain and nonlinear settling process are introduced into the op-amp module. The signaldependent charge injection and nonlinear resistance are introduced into the switch module. In addition, the noise source including flicker and thermal noise is introduced into system as an independent module. The novel model is verified by SIMULINK behavioral simulations. The results are compared with results from circuit level simulation in Cadence SPICE using TSMC 0.35μm mixed signal technology. It shows that the novel model succeeds in introducing the influences of the nonidealities into behavior simulation to more realistically describe the circuit performances and increase the accuracy of SIMULINK simulation.

Bandgap-tunable lateral and vertical heterostructures based on monolayer Mo1-xWxS2 alloys

The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.

Transient mode competition in directly modulated DFB semiconductor laser

A new effect of transient mode competition in directly modulated DFB laser based on equivalent phase-shift （EPS） technique is presented and studied. Since there are multi-order reflections in EPS structure and if the 0th order subgrating is properly de- signed, the transient lasing of 0th order will occur during the rising time of the injection current. As a result, transient mode competition between -lst order （main mode） and 0th order will occur accordingly. This can consume redundant carrier and suppress the transient relaxation oscillation, which may be applied in some areas like on-off switching modulation of DFB semiconductor lasers. As an example, an equivalent n phase shift （n-EPS） is carefully designed to realize the effect. In such a laser the 0th order wavelength is in the margin of the material gain region and the -1st order wavelength is around the gain peak, while the stable single longitudinal mode （SLM） operation of the -lst order is guaranteed. The simulation investigation is performed. Good results with suppressed relaxation oscillation and 1.25 Gb/s directly on-off modulation （32 dB extinction ratio） are demonstrated. We believe it provides a new kind of method for on-off switching with high extinction ratio and weak relaxation oscillation.