Operational Performance Parameters Research Articles

A Hierarchical Reliability Control Method for a Space Manipulator Based on the Strategy of Autonomous Decision-Making

In order to maintain and enhance the operational reliability of a robotic manipulator deployed in space, an operational reliability system control method is presented in this paper. First, a method to divide factors affecting the operational reliability is proposed, which divides the operational reliability factors into task-related factors and cost-related factors. Then the models describing the relationships between the two kinds of factors and control variables are established. Based on this, a multivariable and multiconstraint optimization model is constructed. Second, a hierarchical system control model which incorporates the operational reliability factors is constructed. The control process of the space manipulator is divided into three layers: task planning, path planning, and motion control. Operational reliability related performance parameters are measured and used as the system’s feedback. Taking the factors affecting the operational reliability into consideration, the system can autonomously decide which control layer of the system should be optimized and how to optimize it using a control level adjustment decision module. The operational reliability factors affect these three control levels in the form of control variable constraints. Simulation results demonstrate that the proposed method can achieve a greater probability of meeting the task accuracy requirements, while extending the expected lifetime of the space manipulator.

Coherent optical transients observed in rubidium atomic line filtered Doppler velocimetry experiments

We report the first successful results from our novel Rubidium Atomic Line Filtered (RALF) Doppler velocimetry apparatus, along with unanticipated oscillatory signals due to coherent optical transients generated within pure Rb vapor cells. RALF is a high-velocity and high-acceleration extension of the well-known Doppler Global Velocimetry (DGV) technique for constructing multi-dimensional flow velocity vector maps in aerodynamics experiments [H. Komine, U.S. Patent No. 4,919,536 (24 April 1990)]. RALF exploits the frequency dependence of pressure-broadened Rb atom optical absorptions in a heated Rb/N2 gas cell to encode the Doppler shift of reflected near-resonant (λ0 ≈ 780.24 nm) laser light onto the intensity transmitted by the cell. The present RALF apparatus combines fiber optic and free-space components and was built to determine suitable operating conditions and performance parameters for the Rb/N2 gas cells. It yields single-spot velocities of thin laser-driven-flyer test surfaces and incorporates a simultaneous Photonic Doppler Velocimetry (PDV) channel [Strand et al., Rev. Sci. Instrum. 77, 083108 (2006)] for validation of the RALF results, which we demonstrate here over the v = 0 to 1 km/s range. Both RALF and DGV presume the vapor cells to be simple Beer's Law optical absorbers, so we were quite surprised to observe oscillatory signals in experiments employing low pressure pure Rb vapor cells. We interpret these oscillations as interference between the Doppler shifted reflected light and the Free Induction Decay (FID) coherent optical transient produced within the pure Rb cells at the original laser frequency; this is confirmed by direct comparison of the PDV and FID signals. We attribute the different behaviors of the Rb/N2 vs. Rb gas cells to efficient dephasing of the atomic/optical coherences by Rb-N2 collisions. The minimum necessary N2 buffer gas density ≈0.3 amagat translates into a smallest useful velocity range of 0 to 2 km/s, which can readily be extended to cover the 0 to 10 km/s range, and beyond. The recognition that coherent optical transients can be produced within low pressure vapor cells during velocimetry experiments may offer new insights into some quantitative discrepancies reported in earlier DGV studies. Future plans include “line-RALF” experiments with streak camera detection, and two-dimensional surface velocity mapping using pulsed laser illumination and/or gated intensified CCD camera detection.

Financial Value Creation: A Comparative Study of VC-Backed IPOs and Non-VC-Backed IPOs in India

As financial investors in portfolio companies, venture capital (VC) firms are expected to add value through continuous monitoring and sustained involvement. Such an effort is expected to give VC-backed IPO firms (VC IPOs) an edge over those IPO firms not backed by VCs. We examine such value additions use a comparative analysis of operating and stock performance data of VC IPOs against three groups of non-VC POs. We identified a set of 92 VC IPOs and 182 non VC IPOs. The 182 non-VC IPOs were further subdivided into industry and size groups. While Wilcoxon tests were used to compare the medians of operating and stock performance, panel data regression models were used to establish the impact of VC on those differential performances. We find that the medians of VC IPOs on most operating performance parameters are better than non-VC IPO groups. But the relational tests could not attribute the better performance to VC influence. We conclude that this could be indicative of VCs’ superior ability to identify promising ventures and push them toward their maximum potential. This study is one of the pioneering efforts in exploring VC value creation in the Indian context. We also extend the capital market research in accounting to a VC context.

Cost-Effective Isolation of a Process Impurity of Pregabalin.

Cost-effective isolation methods were developed on preparative HPLC, flash LC, and simulated moving bed (SMB) to prepare the process impurity, 3-(aminomethyl)-5-methylhex-4-enoic acid (4-ene impurity), of pregabalin. By a thorough experimental study on the different isolation techniques available, it was concluded that SMB was the most cost-effective. Hence, it was a continuous chromatography that utilized the advantage of SMB so that a high quantity of the impurity was generated in a short period of time. SMB was equipped with eight reversed-phased columns and was used to separate the process impurity of pregabalin. The effects of flow rate in zone 2 (Q2) and 3 (Q3), as well as switching time, on the operating performance parameters like purity, productivity, and desorbent consumption were studied. Operating conditions leading to more than 90% purity in the raffinate outlet stream were identified, together with those achieving optimal performance. All of these developed methods are novel, cost-effective, and can be applied to the isolation of other process- and stability-related impurities of pregabalin.

Mathematical modeling for the performance and emission parameters of dual fuel diesel engine using hydrogen as secondary fuel

In this work, mathematical models were developed to correlate the brake thermal efficiency, un-burnt hydrocarbons, carbon monoxides and oxides of nitrogen by varying engine parameters like Load and Gaseous (H2) fuel substitution. The developed models can be used to predict the important performance and emission parameters for diesel-hydrogen operation in various combinations at different loads within the experimental domain. Response surface methodology (RSM) has been applied for developing the models using the techniques of design of experiments and multi linear regression analysis. General factorial design was used to plan the experiments. Second order response surface models were found to be the most suitable in the present work. Analysis of variance (ANOVA) of the experimental results at 95% confidence level revealed that the developed models are significant. Comparison of experimental output with those predicted by the developed models showed close proximity having high correlation coefficients R2 for the various response variables.

Study of slagging and fouling mechanisms in a lignite-fired power plant

A significant proportion of the electrical power requirements of Greece are covered by lignite-fired power plants. Greek lignite is characterized by a high water and ash content and a low heating value. Slagging and fouling are common inside the power units and severely affect the performance of the power plants (reduced efficiency, steam leakage in the superheaters and water walls whereas the high temperature of the exhaust gases leads to the mal-functioning of the electrostatic filters). In addition excessive interior pollution cause the units to stop for cleaning resulting in a reduced production and increased maintenance costs.In this paper the results from a measurement campaign in a steam boiler affected by excessive deposits are presented and compared against the manufacturer's operating data. A number of differences were found between the two sets of data and were attributed to the particulars of excessive amount of deposits in the boiler. In addition, the present study investigates the chemical composition and behavior of the slagging and fouling deposits that occur in units of the Kardia power plant as well as of a bottom ash and a fly ash sampled from the same unit. The steam path of the unit was simulated using the DNA software in order to model the effect of the contamination on the global performance parameters of the power plant and the results were compared against the experienced operational performance parameters. In addition, a number of practices are proposed and assessed for reducing the levels of boiler contamination and extending the time between successive maintenance stoppages.

Collision risk-capacity tradeoff analysis of an en-route corridor model

Flow corridors are a new class of trajectory-based airspace which derives from the next generation air transportation system concept of operations. Reducing the airspace complexity and increasing the capacity are the main purposes of the en-route corridor. This paper analyzes the collision risk-capacity tradeoff using a combined discrete–continuous simulation method. A basic two-dimensional en-route flow corridor with performance rules is designed as the operational environment. A second-order system is established by combining the point mass model and the proportional derivative controller together to simulate the self-separation operations of the aircrafts in the corridor and the operation performance parameters from the User Manual for the Base of Aircraft Data are used in this research in order to improve the reliability. Simulation results indicate that the aircrafts can self-separate from each other efficiently by adjusting their velocities, and rationally setting the values of some variables can improve the rate and stability of the corridor with low risks of loss of separation.

High-stability time-domain balanced homodyne detector for ultrafast optical pulse applications

Low-noise, efficient, phase-sensitive time-domain optical detection is essential for foundational tests of quantum physics based on optical quantum states and the realization of numerous applications ranging from quantum key distribution to coherent classical telecommunications. Stability, bandwidth, efficiency, and signal-to-noise ratio are crucial performance parameters for effective detector operation. Here we present a high-bandwidth, low-noise, ultra-stable time-domain coherent measurement scheme based on balanced homodyne detection ideally suited to characterization of quantum and classical light fields in well-defined ultrashort optical pulse modes.

Adaptive frequency compensation for maximum and constant bandwidth feedback amplifiers

We present an adaptive frequency compensation technique providing maximum bandwidth closed-loop amplifiers. The approach exploits an auxiliary variable gain amplifier to implement an electrically tunable compensation capacitor proportional to the feedback factor. In this manner, the closed-loop bandwidth is kept ideally constant irrespective of the closed-loop gain. The proposed method can be applied to any amplifier adopting dominant-pole compensation. As an example, we designed a CMOS amplifier providing 66-dB direct current gain and 310-MHz gain-bandwidth product. For closed-loop gains ranging from 1 to 10, the closed-loop bandwidth was found never lower than 401 MHz (noinverting configuration) and 229 MHz (inverting configuration). A similar amplifier with equal gain-bandwidth product, but adopting the traditional fixed compensation approach, would exhibit a closed-loop bandwidth reduced to 33 MHz (noninverting) and 30 MHz (inverting) when the gain magnitude is set to 10. The enhanced frequency performance is obtained with a 48% increase in current consumption, whereas the other main operational amplifier performance parameters remain almost unchanged compared with the standard solution. Copyright © 2011 John Wiley & Sons, Ltd.

A SASE free electron laser optimization based on new generation in-vacuum undulators

Optimization studies for an accelerator based light source, namely self-amplified spontaneous emission (SASE) free electron laser (FEL), based on new generation in-vacuum hybrid and superconducting undulator configurations, are compared and discussed. It is shown that the FEL wavelength should be down to soft X-rays ( ∼ 3 nm ) part of the spectrum while keeping the same linear accelerator (linac) energy about 1 GeV. On the other hand, numerical calculations and simulation results of the main performance parameters for SASE operation (1D gain length, saturation power and saturation length), are optimized. Finally, technological advantages and challenges for both cases, are briefly mentioned.

The Computerized Simulation Software Development of the Bidirectional Pneumatic Hammer

During the construction for solving geological hazard of landslide, there often existed the accidents of sticking pipe and burying drilling caused by borehole collapse. It resulted that drilling tool couldn’t be pulled out, and scraped the drilling tool and borehole. So it was necessary to research a kind of pneumatic hammer which could realize drilling at normal work, and push out the drilling tool by reverse impact when the formation collapse caused sticking pipe and bury drilling. In order to research profoundly the pneumatic hammer work mechanism and describe piston movement laws in detail, physical model was established according to the actual conditions, finite difference method was adopted, thermodynamics and kinematics were applied. Using object-oriented programming, the bidirectional pneumatic hammer software was developed whose integrated development environment was VB. The software could calculate acceleration, velocity, displacement, pressure, temperature of the front and back air chamber at any time and the operating performance parameters of the pneumatic hammer. Not only the bidirectional pneumatic hammer, but also the unidirectional pneumatic DTH hammer and the no-dig impactor were designed by the software.

Optimization considerations for a SASE free electron laser based on a superconducting undulator

A self amplified spontaneous emission (SASE) free electron laser (FEL) based on a new generation superconducting planar undulator, is optimized. It is shown that the laser wavelength should be down to soft X-rays range (∼2–3nm) of the spectrum via a dedicated undulator driven by a 1GeV electron linear accelerator (linac). Numerical calculations and simulation results of the three main performance parameters for SASE operation, namely 1D gain length (LG,1D), saturation power (Psat) and saturation length (Lsat), are compared and discussed.

The Computerized Simulation Software Development of the Pneumatic DTH

Designing the pneumatic DTH by the method of anology, experience and actual test, the investment is large, the cycle is long, and it is difficult to achieve the optimization. In order to research profoundly the DTH work mechanism and describe piston movement laws in detail, physical model is established according to the actual conditions, finite difference method is adopted, thermodynamics and kinematics are applied. Using object-oriented programming, the pneumatic DTH computerized simulation software is developed whose integrated development environment is VB. The software can calculate acceleration, velocity, displacement, pressure, temperature of the front and back air chamber at any time and the operating performance parameters of the pneumatic DTH. The law of many factors influencing on the pneumatic DTH performance can be found and the optimization of the pneumatic DTH structure parameter can be achieved by the ergodic method. Not only the pneumatic DTH but also the no-dig impactor is designed by computerized simulation.

Performance, emission and combustion evaluation of soapnut oil–diesel blends in a compression ignition engine

Soapnut ( Sapindus mukorossi) oil, a nonedible straight vegetable oil was blended with petroleum diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and soapnut oil (10%, 20%, 30% and 40%) fuel blends were used to conduct short-term engine performance and emission tests at varying loads in terms of 25% load increments from no load to full loads. Tests were carried out for engine operation and engine performance parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (smoke, CO, UBHC, NO x , and O 2) were recorded. Among the blends SNO 10 has shown a better performance with respect to BTE and BSEC. All blends have shown higher HC emissions after about 75% load. SNO 10 and SNO 20 showed lower CO emissions at full load. NO x emission for all blends was lower and SNO 40 blend achieved a 35% reduction in NO x emission. SNO 10% has an overall better performance with regards to both engine performance and emission characteristics.

A parabolic dish/AMTEC solar thermal power system and its performance evaluation

This paper proposes a parabolic dish/AMTEC solar thermal power system and evaluates its overall thermal–electric conversion performance. The system is a combined system in which a parabolic dish solar collector is cascaded with an alkali metal thermal to electric converter (AMTEC) through a coupling heat exchanger. A separate type heat-pipe receiver is selected to isothermally transfer the solar energy from the collector to the AMTEC. To assess the system’s overall thermal–electric conversion performance, a theoretical analysis has been undertaken in conjunction with a parametric investigation by varying relevant parameters, i.e., the average operating temperature and performance parameters associate with the dish collector and the AMTEC. Results show that the overall conversion efficiency of parabolic dish/AMTEC system could reach up to 20.6% with a power output of 18.54 kW corresponding to an operating temperature of 1280 K. Moreover, it is found that the optimal condenser temperature, corresponding to the maximum overall efficiency, is around 600 K. This study indicates that the parabolic dish/AMTEC solar power system exhibits a great potential and competitiveness over other solar dish/engine systems, and the proposed system is a viable solar thermal power system.

Feasibility of blending karanja vegetable oil in petro-diesel and utilization in a direct injection diesel engine

Karanja ( Pongamia pinnata) oil, a non-edible high viscosity (27.84 cSt at 40 °C) straight vegetable oil, was blended with conventional diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and karanja oil fuel blends (5%, 10%, 15%, and 20%) were used to conduct short-term engine performance and emission tests at varying loads (0%, 20%, 40%, 60%, 80%, and 100%). Tests were carried out over the entire range of engine operation and engine performance parameters such as fuel consumption, thermal efficiency, exhaust gas temperature, and exhaust emissions (smoke, CO, CO 2, HC, NO x , and O 2) were recorded. The brake specific energy consumption (BSEC), brake thermal efficiency (BTE), and exhaust emissions were evaluated to determine the optimum fuel blend. Higher BSEC was observed at full load for neat petro-diesel. A fuel blend of 10% karanja oil (KVO10) showed higher BTE at a 60% load. Similarly, the overall emission characteristics were found to be best for the case of KVO10 over the entire range of engine operation.

Collaborative knowledge sharing in Composite New Product Development: An aerospace study

New Product Development (NPD) in the commercial aerospace industry focuses on producing products, which reduce operating and service costs, emissions and weights, while increasing operating performance parameters. There is an increasing use of Composite materials in aerospace NPD projects to achieve these goals due to the advantageous properties of increased strength and reduced weight. A key constraint in developing Composite capability in aerospace NPD is the development of appropriate diagnostic and manufacturing capability requiring new knowledge within aerospace organisations. The aim of this paper is to explore the acquisition, embedding and use of new knowledge from multiple sources in Composites NPD using a case analysis of a leading international aerospace prime. In particular, the study focuses on the need for new diagnostic testing capabilities and knowledge within the Composites NPD process as a source of competitive advantage. Data sources include multi-level semi structured interviews ( n=20) with internal and external stakeholders involved in the NPD process and focus groups ( n=5) comprised of the Composites NPD team members. The findings show that in addition to traditional internal and external knowledge sources, out of sector knowledge (in this case from Healthcare Diagnostics) can be used to inform specialist NPD technologies. Furthermore, it is essential that knowledge from multiple sources is effectively integrated within the NPD process using a designated knowledge portal.

Separation of phosphatidylcholine from soybean phospholipids by simulated moving bed

A simulated moving bed (SMB), equipped with eight silica-gel columns, was used to separate phosphatidylcholine (PC) from soybean phospholipids. The effects of flow rate in Sections 2 (Q(2)) and 3 (Q(3)), switching time, feed flow rate and feed concentration on the operating performance parameters: purity, recovery, productivity and desorbent consumption were studied. Operating conditions leading to more than 90% purity in both outlet streams have been identified, together with those achieving optimal performance. Regions leading to complete separation are observed and explained theoretically. As the mass-transfer effect was not considered, the triangle theory only gives initial guesses for the optimal operating conditions.

Modeling, Simulation of a Simulated Moving Bed for Separation of Phosphatidylcholine from Soybean Phospholipids

A rate model, which considers axial dispersion, external mass transfer, intraparticle diffusion and nonlinear isotherms, and ports periodic switching is adopted to simulate the simulated moving bed (SMB) process. The effects of flow rate in Sections 2 and 3 and switching time on the operating performance parameters: purity, recovery, productivity and desorbent consumption are studied. A simulation approach is applied to simulate the operation and performance of the SMB. The model predicts the performance of the transient and cyclic steady state behavior to a reasonably good extent, and provides guidance operation condition of the SMB process.

PERFORMANCE ANALYSIS OF FORECAST DRIVEN VENDOR MANAGED INVENTORY SYSTEM

Vendor Managed Inventory (VMI) is a centralized link between suppliers and customers that enables faster, less complex transactions without creating individual lines of communication for every business relationship. The current scenario necessitates the effective integration of forecasting with VMI to maintain its efficient inventory level with less safety stock. Concerning the above, this paper proposes a Forecast Driven Vendor Managed Inventory Model (FDVMI) in which a suitable forecasting model, which has minimum error and which satisfies Tracking Signal, is selected to predict the demand. The operational control and performance parameters are estimated for the partners under VMI mode of operation. The proposed model is analyzed with a case problem of M/s Nerolac stock point, Madurai with all performance parameters. The analysis reveals that the adaptation of FDVMI guarantees tangible benefits such as increase in buyer profit, vendor profit, decrease in sales price and contract price and intangible benefits such as reduced inventory, replenishments and stock outs. However, the validity of the results depends on the various factors such as sales-demand relationship, order and carrying costs of vendor and buyer in the Existing Operation (EO), combined order and carrying costs of vendor in VMI system and so on.