Adjustment Module Research Articles

Adjustable refractive index modulation for a waveguide with SU-8 photoresist by dual-UV exposure lithography

We present a new fabrication technique based on a two-step UV exposure lithographic process to marginally modulate the refractive index in commercial SU-8 photoresist. This technique achieves refractive index modulation as different regions undergo different thermal densification prior to UV-induced polymerization. A small refractive index contrast of 0.0008 or lower can be achieved, and this is especially useful for fabricating waveguides with a low level of propagation modes. This technique may be extended to other UV-curable epoxy photoresists and can easily be applied in the fabrication of optical elements such as optical interconnects and integrated optical sensors without the development process.

Attracting insects with an acoustic laser

It has been demonstrated that female Mediterranean fruit flies (Ceratitis capitata) are attracted to a trap by a pure tone at approximately the spectral peak (330 Hz) of the males mating call [Mankin et al., J. Econ. Entomol. 97, 1299–1309 (2004)]. Recent research [Sueur et al., ‘‘Sound radiation around a flying fly,’’ J. Acoust. Soc. Am. 118, 530–538 (2005)] suggests that a more complex tone that combines an amplitude-modulated fundamental and a second-harmonic component could produce more effective acoustic bait. We will describe a thermoacoustic sound source [S. L. Garrett and R-L. Chen, Echoes 10, 4–5 (2000)] that combines two closely tuned quarter-wavelength resonators designed to produce a beating fundamental of adjustable modulation depth. A third source produces the second harmonic. The trio of sources generates the desired signal at levels of 90 to 100 dB 1 meter from the array. Since the sound is produced from electrically heated filaments, no oscillators, amplifiers, or electro-acoustic transducers are required. When the pair of fundamental resonators are placed side-by-side, the beating occurs uniformly in space. When placed back-to-back, the dipolar radiation pattern rotates to produce the beating in time at any fixed location. We hope to have results with insect subjects by the time of the meeting. [Work supported by an endowment from United Technologies Corporation.]

Methods and an algorithm for operating the adjustment module of the Iskra-6 multibeam laser apparatus

A module of an automatic adjustment system has been developed and studied, consisting of a scaled segment of the main four-pass amplifier of the Iskra-6 128-beam laser apparatus. The adjustment methods are based on the use of small light markers, centered with the stops of the elements. The adjustment algorithm, the image-processing methods, and the adjustment accuracy and rate have been experimentally investigated. A software package has been developed for modeling radiation propagation through the optical system and the automatic adjustment of the system, and a comparison has been made with experiment. The results serve as a basis for further development of the system for automatically adjusting the laser apparatus.

Design and fabrication of adjustable red-green-blue LED light arrays for plant research

BackgroundAlthough specific light attributes, such as color and fluence rate, influence plant growth and development, researchers generally cannot control the fine spectral conditions of artificial plant-growth environments. Plant growth chambers are typically outfitted with fluorescent and/or incandescent fixtures that provide a general spectrum that is accommodating to the human eye and not necessarily supportive to plant development. Many studies over the last several decades, primarily in Arabidopsis thaliana, have clearly shown that variation in light quantity, quality and photoperiod can be manipulated to affect growth and control developmental transitions. Light emitting diodes (LEDs) has been used for decades to test plant responses to narrow-bandwidth light. LEDs are particularly well suited for plant growth chambers, as they have an extraordinary life (about 100,000 hours), require little maintenance, and use negligible energy. These factors render LED-based light strategies particularly appropriate for space-biology as well as terrestrial applications. However, there is a need for a versatile and inexpensive LED array platform where individual wavebands can be specifically tuned to produce a series of light combinations consisting of various quantities and qualities of individual wavelengths. Two plans are presented in this report.ResultsIn this technical report we describe the practical construction of tunable red-green-blue LED arrays to support research in plant growth and development. Two light fixture designs and corresponding circuitry are presented. The first is well suited for a laboratory environment for use in a finite area with small plants, such as Arabidopsis. The second is expandable and appropriate for growth chambers. The application of these arrays to early plant developmental studies has been validated with assays of hypocotyl growth inhibition/promotion and phototropic curvature in Arabidopsis seedlings.ConclusionThe presentation of these proven plans for LED array construction allows the teacher, researcher or electronics aficionado a means to inexpensively build efficient, adjustable lighting modules for plant research. These simple and effective designs permit the construction of useful tools by programs short on electronics expertise. These arrays represent a means to modulate precise quality and quantity in experimental settings to test the effect of specific light combinations in regulating plant growth, development and plant-product yield.

On the use of administrative databases to support planning activities: a comment

Sir, The paper by Fantini et al. 1 rightly stresses the importance in health care planning of identifying centres that treat more severe (complex) cases. However, in their evaluation of the ability of two software packages, Medicare Diagnosis Related Groups (Medicare DRG) and All Patient Refined Diagnosis Related Groups (APR-DRG), to achieve this objective, they omit to mention that the APR-DRG software incorporates into its risk adjustment modules discharge diagnosis codes representing all conditions treated during the hospitalization, regardless of when they occurred, and including late, ‘near death’ events.2This approach may be understandable, since the APR-DRG software, similar to most discharge …

Design and in vivo characterization of self-inactivating human and non-human lentiviral expression vectors engineered for streptogramin-adjustable transgene expression.

Adjustable transgene expression is considered key for next-generation molecular interventions in gene therapy scenarios, therapeutic reprogramming of clinical cell phenotypes for tissue engineering and sophisticated gene-function analyses in the post-genomic era. We have designed a portfolio of latest generation self-inactivating human (HIV-derived) and non-human (EIAV-based) lentiviral expression vectors engineered for streptogramin-adjustable expression of reporter (AmyS(DeltaS), EYFP, SAMY, SEAP), differentiation-modulating (human C/EBP-alpha) and therapeutic (human VEGF) transgenes in a variety of rodent (CHO-K1, C2C12) and human cell lines (HT-1080, K-562), human and mouse primary cells (NHDF, PBMC, CD4+) as well as chicken embryos. Lentiviral design concepts include (i) binary systems harboring constitutive streptogramin-dependent transactivator (PIT) and PIT-responsive transgene expression units on separate lentivectors; (ii) streptogramin-responsive promoters (P(PIR8)) placed 5' of desired transgenes; (iii) within modified enhancer-free 3'-long terminal repeats; and (iv) bidirectional autoregulated configurations providing streptogramin-responsive transgene expression in a lentiviral one-vector format. Rigorous quantitative analysis revealed HIV-based direct P(PIR)-transgene configurations to provide optimal regulation performance for (i) adjustable expression of intracellular and secreted product proteins, (ii) regulated differential differentiation of muscle precursor cell lines into adipocytes or osteoblasts and (iii) conditional vascularization fine-tuning in chicken embryos. Similar performance could be achieved by engineering streptogramin-responsive transgene expression into an autoregulated one-vector format. Powerful transduction systems equipped with adjustable transcription modulation options are expected to greatly advance sophisticated molecular interventions in clinically and/or biotechnologically relevant primary cells and cell lines.

Long-wavelength quantum-dot lasers on GaAs substrates: from media to device concepts

Recent progress in semiconductor quantum-dot (QD) lasers approaches qualitatively new levels, when dramatic progress in the development of the active medium already motivates search for new concepts in device and system designs. QDs, which represent coherent inclusions of narrower bandgap semiconductor in a wider gap semiconductor matrix, offer a possibility to extend the wavelength range of heterostructure lasers on GaAs substrates to 1.3 /spl mu/m and beyond and create devices with dramatically improved performance, as compared to commercial lasers on InP substrates. Low-threshold current density (100 A/cm/sup 2/), very high characteristic temperature (170 K up to 65/spl deg/C), and high differential efficiency (85%) are realized in the same device. The possibility to stack QDs (e.g., tenfold) without an increase in the threshold current density and any degradation of the other device parameters allow realization of high modal gain devices suitable for applications in 1.3-/spl mu/m short-cavity transmitters and vertical-cavity surface-emitting lasers (VCSELs). The 1.3-/spl mu/m QD GaAs VCSELs operating at 1.2-mW continuous-wave output power at 25/spl deg/C are realized, and long operation lifetime is manifested. Evolution of GaAs-based 1.3-/spl mu/m lasers offers a unique opportunity for telecom devices and systems. Single-epitaxy VCSEL vertical integration with intracavity electrooptic modulators for lasing wavelength adjustment and/or ultrahigh-frequency wavelength modulation is possible. Arrays of wavelength-tunable VCSELs and wavelength-tunable resonant-cavity photodetectors may result in a new generation of intelligent cost-efficient systems for ultrafast data links in telecom.

A space vector modulated CSI-based AC drive for multimotor applications

A space vector controlled channel state information (CSI) drive for multimotor applications is investigated. The multimotor operation of the drive is achieved by integrating the proposed active damping control, inverter-side DC link voltage feedforward control and pulse width modulation (PWM) index control into the conventional V/f control. The main function of the active damping control is to suppress possible LC resonances caused by the inverter filter capacitor and motor inductances. This function is essential in achieving stable operation of the drive, especially in the multimotor drive where multiple LC resonant modes exist. An additional advantage provided by the active damping control is that it makes the control system less sensitive to motor parameters. The inverter-side DC link voltage feedforward control and the adjustable PWM modulation index control are developed to improve the dynamic performance of the drive system. In addition, the proposed space vector PWM pattern features a low switching frequency (500 Hz), which makes the proposed drive system suitable for high power applications. The system stability is investigated by means of eigenvalue analysis. The theoretic analysis is verified by experiments on a digital signal processing (DSP) controlled CSI multimotor drive.

A novel three-phase AC/DC converter without front-end filter based on adjustable triangular-wave PWM technique

This paper proposes a novel three-phase AC/DC converter without a front-end filter. Because an adjustable triangular-wave pulsewidth modulation (PWM) (ATPWM) technique is adopted, not only is a front-end filter located after the three-phase rectifier is omitted, but also the size of the input AC filter and the output DC filter are reduced. In addition, this AC/DC converter has many advantages such as simpler structure, higher reliability, and better output waveform. The principle of operation, harmonics elimination, and feedback control of the novel AC/DC topology are elaborated. A thorough analysis on its performance under an unbalanced system is presented. Finally, the theoretical analysis is proved to be correct by simulations and experiments.

Improvement of Nonlinear Modulation by Cascaded Mach-Zehnder Configuration

A two-stage cascaded Mach-Zehnder modulator is employed for the linear external modulation of a laser. The modulation electric fields are applied on the first and second stages in the Z and Y directions, respectively. Because of the inherent versatility of the adjustable modulation parameters, improved modulation perfor mances with a high modulation depth and a high linear response are demonstrated. When a modulation depth of 21 % is required, the ratios of the second and third harmonic terms to the fundamental term can be simultaneously achieved as low as 104 and 86.7 dB, respectively.

The Reduction of Harmonic and Intermodulation Distortions with a Cascaded Mach-Zehnder Molulator

A cascaded two-stage Mach-Zehnder modulator is used to suppress the harmonic and intermodulation distortions simultaneously. The modulation electric fields are applied on the first and second stages in the y and z directions of z-cut lithium niobate crystal, respectively. Because of the inherent versatility of the adjustable modulation parameters, superior linear modulation response can be achieved. When —50 dB nonlinear suppression is required, the modulation depth of 7.5% can be obtained.

An intelligent controller for manufacturing cells

To meet multiple performance objectives and handle uncertainty during production, a flexible scheduling system is essential. In this study, a neural network based control system is proposed to adapt different scheduling strategies dynamically for a manufacturing cell. The proposed control system consists of an adjustment module and the associated equipment controller for each machine and the robot. At a decision point, the adjustment module will determine the relative importance for each performance measure according to the current performance levels and requirements. The equipment level controller, implemented by a neural network, will select the proper dispatching rule based on its status and the relative importance levels. The problem, which arises from the discrepancy of the user specification and what neural networks are trained by, is addressed. From the simulation results, the proposed refinement procedure could recover this problem so that the controller can perform closer to the actual requiremen...

First Step Towards Planning of Syntheses in Solid‐State Chemistry: Determination of Promising Structure Candidates by Global Optimization

AbstractA method is presented here that allows, in principle, the prediction of the existence and structure of (meta)stable solid compounds. It is based on a set of adjustable modules that are applied to the study of the energy function of the chemical system of interest. The main elements are a set of routines for global optimization and local minimization, as well as algorithms for the investigation of the phase space structure near local minima of the potential energy, and the analysis and characterization of the structure candidates. The current implementation focuses on ionic compounds, for which empirical potentials are used for the evaluation of the energy function in the first stage, and a Hartree–Fock algorithm for refinements. The global optimization is performed with a stochastic simulated annealing algorithm, and the local minimization employs stochastic quenches and gradient methods. The neighborhoods of the local minima are studied with the threshold algorithm. The results of this approach are illustrated with a number of examples: compounds of binary noble gases, and binary and ternary ionic compounds. These include several substances that have not been synthesized yet, but should stand a fair chance of being kinetically stable, for example further alkali metal nitrides besides Li3N, as well as Ca3SiBr2 or SrTi2O5.

CAD-based design and analysis system for reconfigurable fixtures in robotic assembly

Fixturing is an important requirement for many manufacturing and assembly operations. If flexible manufacturing and assembly systems (FMS and FAS) are to be truly flexible, then the fixturing must also be flexible. This article presents a system for computer-aided design and analysis of reconfigurable fixtures in robotic assembly. The fixturing system employs a number of adjustable fixture modules that are set up, adjusted and changed automatically by the assembly robot without human intervention. The design of the fixture layout is performed interactively on a commercially available computer-aided design (CAD) package. The development of a dedicated software program to perform kinematic analysis of the fixture layout, using the information retrieved from the CAD database, is presented. A strategy to build various fixture layouts to locate and hold workpieces of various shapes and sizes using the same set of fixture modules is also presented.

Silicon bipolar laser driving IC for 5 Gb/s and 45-mA modulation current and its application in a demonstrator system

The design and implementation of a 5-Gb/s silicon bipolar laser driver IC for direct modulation of a laser diode is reported. The adjustable modulation current range is 15-45 mA. The IC can drive 25- Omega laser modules via a 25- Omega transmission line. Typical power dissipation is 930 mW for a modulation current of 45 mA. Though the IC has been fabricated on a production line instead of using a laboratory technology, it is one of the fastest laser driver ICs ever implemented in silicon. The ability to drive an ohmic load is shown, as well as the performance when driving a real laser module. The circuit has been successfully operated in a demonstrator system for digital optical-fiber transmission.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Exercise countermeasure protocol management expert system

Exercise will be used primarily to countermeasure against deconditioning on extended space flight. In this paper we describe the development and evaluation of an expert system for exercise countermeasure protocol management. Currently, the system includes two major subsystems: baseline prescription and prescription adjustment. The baseline prescription subsystem is designed to provide initial exercise prescriptions while prescription adjustment subsystem is designed to modify the initial prescription based on the exercised progress. The system runs under three different environments: PC, SUN workstation, and Symbolic machine. The inference engine, baseline prescription module, prescription adjustment module are developed under the Symbolic environment by using the ART (Automated Reasoning Tool) software. The Sun environment handles database management features and interfaces with PC environment to obtain physical and physiological data from exercise units on-board during the flight. Eight subjects' data have been used to evaluate the system performance by comparing the prescription of nine experienced exercise physiologists and the one prescribed by the expert system. The results of the validation test indicated that the performance of the expert system was acceptable.

Adjustable modules for high-power (over 7.5-mW CS) coupling of diode lasers to single-mode fibers

Single-mode (SM) fiber output power of over 7.5-mW CW has been obtained in unique adjustable coupling modules. These are the highest powers ever reported coupled between diode lasers and single-mode fibers. Coupling efficiencies over 30 percent were obtained in simple butt-coupling by taking advantage of the large mode size available from RCA constricted-double-heterojunction large-optical cavity (CDH-LOC) lasers. We also observed peak fiber power of over 9 mW with 100-ns 50-percent duty cycle pulses. The minature modules provide relative transverse and lateral motion between fiber and laser with 2000-Å resolution, allowing fine tuning against long-term drifts. The coupling, while adjustable, is still stable against moderate acceleration of module and motion of fiber pigtail. The adjustments may be adapted to servo control.