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Article

Peng Sun, Naiguang Lu, Mingli Dong, Xiaoping Lou and Zexiang Tan

Geometric structure error of parabolic trough concentrator (PTC) frame affects the installation accuracy of mirrors and absorber tubes and thus decreases the solar energy…

Abstract

Purpose

Geometric structure error of parabolic trough concentrator (PTC) frame affects the installation accuracy of mirrors and absorber tubes and thus decreases the solar energy concentrating efficiency. Until now, there is no effective method to instruct the assembly and regulation of PTC frames. This paper aims to propose a vision guided method for fast and accurate regulation of mirror and absorber supports to improve the geometric quality of PTC frames.

Design/methodology/approach

The PTC frame support regulating system consists of a general-purpose online photogrammetry system, frame support measurement adaptors and data analyzing software. First, the positions and angles of all the supports are measured in real time by the online photogrammetric system. Then, the measured positions and angles are aligned to the design reference frame through the transformation calculated by an absorber position constrained nonlinear optimization so as to get the geometric errors and regulating amounts. Finally, a graduated pseudo-color-based visualization method is proposed to assist the manual or automated regulation of PTC frame supports in site.

Findings

The proposed method does not need to construct a reference system nor specify the rotation attitude of the PTC frame, and it is capable of conducting efficient and accurate regulation on PTC frame assembly line. The method is applied to manual regulation of a light type PTC frame structure. After regulation, the maximum position and angle errors of supports are reduced to less than 0.15 mm and 0.15° respectively and the intercept factor is increased to 97%, which meets the requirement for a qualified PTC concentrator.

Originality/value

To the authors’ knowledge, this paper is the first to propose a vision guided assembly or regulation method for PTC frame structures. The research uses online photogrammetry system to provide real-time geometric quality information feedback, elaborates the data analysis algorithm and provides the visualization method for accurate and efficient in site regulation. Furthermore, this paper also provides theories, methods and experiences for other applications that use vision guidance for attitude regulation and digital flexible assembly of large equipment.

Details

Industrial Robot: the international journal of robotics research and application, vol. 46 no. 6
Type: Research Article
ISSN: 0143-991X

Keywords

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Article

Bushra Rahim

Devolution of fiscal and administrative autonomy to public schools is a global phenomenon now. Various models of school autonomy have been adopted both in developing and…

Abstract

Purpose

Devolution of fiscal and administrative autonomy to public schools is a global phenomenon now. Various models of school autonomy have been adopted both in developing and developed countries. The purpose of this paper is to explore the impact of devolution of fiscal autonomy to public primary schools through Parent–Teacher Councils (PTCs) on retention of primary school children in the Khyber Pakhtunkhwa (KP) province, Pakistan.

Design/methodology/approach

Two sources of data were used to analyze the research question: Education Management Information System for the years 2006–2011 and 2007–2012, and a specially designed survey questionnaire used to compile information about PTCs from 222 public primary schools in the KP Province. Multiple linear regressions were conducted to examine whether PTC reforms are related to retention rates. An education production function approach was used to examine the effect of “inputs” (PTC reform) on “outputs” (retention).

Findings

The regression results indicate that reforms in procedural mechanisms to spend PTC budget and schools with separate classrooms for each grade level are significant in improving retention to the last grade of primary. The results also indicate that retention in all-girls’ schools tend to be significantly lower compared to all-boys’ schools.

Research limitations/implications

First, the integration of data sets resulted in a small sample size, 361 schools, out of which the researcher could visit only 222 schools (10 schools per district) due to time and financial constraints. There may be a probability that with a larger sample size the author findings may look slightly different. However, this is the only current data set collected by the researcher in KP, Pakistan. Second, an ideal way of calculating retention is to track each and every child enrolled in a school over a period of five years and to calculate retention at the end of Grade 5 called true cohort model. However, due to unavailability of such kind of data, a more commonly used method, called reconstructed cohort method, is employed. In this method, data on enrollment by grade are used for six consecutive years, with an assumption that the student flow rates will remain unchanged over time and across grades.

Practical implications

The findings of this study provide vital policy input to the Government of Pakistan in particular and other developing countries in general. The study reveals that PTCs have critical impacts on educational outcomes, school productivity and return on public sector educational investment thus providing an impetus for further strengthening of PTC and community participation. Besides, this study offers significant implications as to how school-based management programs will lead to outcomes under resource scarcity in developing countries.

Social implications

The paper has implications for the role of school leadership and community participation and for how to engender community involvement in marginalized areas where communities often do not have the time, resources or confidence to participate in their schools. Besides, community participation in parent–teacher meetings means that the school budget is spent transparently and with consensus. Hence, the chances of misuse of funds are minimized to a considerable extent, a dilemma faced by many developing countries. Finally, the collection of PTC-related data regularly especially details about budget allocated, spent and, the unutilized budget may result in better record keeping, which was found lacking during the visit.

Originality/value

The uniqueness and originality of this paper can be gauged from the fact that no systematic study exists with regards to the impact of school autonomy on students’ retention to the last grade of primary in KP province – a poor and conflict-ridden region in a low-income country (Pakistan). Also, the data collection from primary and secondary sources was not an easy task. However, the researcher as a civil servant has to use personal contacts to collect primary and secondary data. Hence, this study is unique and first of its kind in nature. No such research has been conducted so far by any researcher, especially in KP.

Details

International Journal of Educational Management, vol. 33 no. 7
Type: Research Article
ISSN: 0951-354X

Keywords

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Case study

Robert C. Wolcott

The case presents a $1+billion technology company seeking new growth through the introduction of a radically new product platform. During its first ten years, PTC

Abstract

The case presents a $1+billion technology company seeking new growth through the introduction of a radically new product platform. During its first ten years, PTC Corporation grew faster than Microsoft did during the similar period of its evolution. By the late 1990s PTC was faced with intensified competition and saturation in its core markets. To maintain growth, the company introduced a completely new product platform. While PTC focused on developing and selling the product, it failed to recognize that this new product was so different from its traditional offerings that it required a new organizational structure, sales capabilities, support processes, and market strategy. The case traces the company's evolution from development and launch of Windchill through the four-year period post-launch, during which its founding CEO was forced out and the company transformed. Ultimately, Windchill became a top seller for PTC, but not until after significant internal change.

The PTC case illustrates what it means to build a new business within the context of an existing, successful firm. It can also be used to explore what it takes to accomplish a successful new product launch for a substantially new product platform. Sales and channel strategy also figures prominently in the case.

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Article

Aik-Chuan Teo, Garry Wei-Han Tan, Keng-Boon Ooi, Teck-Soon Hew and King-Tak Yew

The purpose of this paper is to uncover the effects of perceived transaction convenience (PTC) and perceived transaction speed (PTS) on unified theory of acceptance and…

Abstract

Purpose

The purpose of this paper is to uncover the effects of perceived transaction convenience (PTC) and perceived transaction speed (PTS) on unified theory of acceptance and use of technology (UTAUT) in the context of m-payment.

Design/methodology/approach

A predictive analysis approach was used to examine the PTC and PTS using a two-stage partial least square (PLS) and neural network (NN) analyses.

Findings

The findings reveal that only effort expectancy (EE) and facilitating conditions (FC) were discovered to significantly influence BI. More importantly, PTC was found to have positive significant relationship with EE and performance expectancy (PE). Moreover, PTS also supported the positive relationship with BI and EE.

Practical implications

The findings of the study provided further insights to mobile payment service providers, online banking industry players, and all decision makers and stakeholders involved.

Originality/value

Despite of many attempts devoted to understand m-payment adoption, the effects of PTC and PTS on m-payment are not well understood.

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Article

Marko Hrovat, Darko Belavič, Jaroslaw Kita, Janez Holc, Silvo Drnovšek, Jena Cilenšek, Leszek Golonka and Andrzej Dziedzic

Aims to evaluate different thick‐film materials for use in strain sensors and temperature sensors on low‐temperature co‐fired ceramic (LTCC) substrates.

Abstract

Purpose

Aims to evaluate different thick‐film materials for use in strain sensors and temperature sensors on low‐temperature co‐fired ceramic (LTCC) substrates.

Design/methodology/approach

LTCC materials are sintered at the low temperatures typically used for thick‐film processing, i.e. around 850°C, The thick‐film resistor materials for use as strain and temperature sensors on LTCC tapes are studied. Thick‐film piezo‐resistors in the form of strain‐gauges are realised with 10 kΩ/sq. 2041 (Du Pont)and 3414‐B (ESL), resistor materials; thick‐film temperature‐dependent resistors were made from PTC 5093 (Du Pont), and NTC‐4993 (EMCA Remex) resistor materials.

Findings

The X‐ray spectra of the 2041 and 3414‐Bb low TCR resistors after drying at 150°C and after firing display more or less the same peaks. The electrical characteristics of 2041 resistors fired on alumina and LTCC substrates are similar indicating that the resistors are compatible with the LTCC material. After firing on LTCC substrates the sheet resistivities and TCRs of the 3414‐B resistors increased. Also, there is a significant increase in the GFs from 13 to over 25.

Originality/value

Investigates the compatibility of thick‐film materials and the characteristics of the force and temperature sensors.

Details

Microelectronics International, vol. 23 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

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Article

Mohamed Chebaani, Amar Goléa, Med Toufik Benchouia and Noureddine Goléa

Direct Torque Control (DTC) of induction motor drives is a well-established technique owing to features such as fast dynamic and insensibility to motor parameters…

Abstract

Purpose

Direct Torque Control (DTC) of induction motor drives is a well-established technique owing to features such as fast dynamic and insensibility to motor parameters. However, conventional DTC scheme, based on comparators and the switching table, suffers from large torque and flux ripples. To improve DTC performance, this study aims to propose and implement a sensorless finite-state predictive torque control using extended Kalman Filter in dSPACE environment.

Design/methodology/approach

This paper deals with the design of an extended Kalman filter for estimating the state of an induction motor model and for sensorless control of systems using this type of motor as an actuator. A complex-valued model is adopted that simultaneously allows a simpler observability analysis of the system and a more effective state estimation.

Findings

Simulation and experimental results reveal that the drive system, associated with this technique, can effectively reduce flux and torque ripples with better dynamic and steady state performance. Further, the proposed approach maintains a constant switching frequency.

Originality/value

The proposed speed observer have been developed and implemented experimentally under different operating conditions such as parameter variation, no-load/load disturbances and speed variations in different speed operation regions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Ebenezer Adaku, Kwasi Amoako-Gyampah, Seth Nii Anang Lomotey, Charles Teye Amoatey and Samuel Famiyeh

The Pension Trust Company (PTC) in Ghana is the sole agency responsible for the management of the first-tier pension scheme as well as processing of claims submitted by…

Abstract

Purpose

The Pension Trust Company (PTC) in Ghana is the sole agency responsible for the management of the first-tier pension scheme as well as processing of claims submitted by beneficiaries for this scheme. The claim processing system at PTC was wrought with significant delays resulting in severe customer dissatisfaction and hardship to retirees. Hence, a new system – Age 54+ project – was developed to address the problems related to claims processing. The purpose of this paper is to report on the efficiency gains from the new claim processing system implemented at PTC and to use the philosophies behind the lean operations concept to explain the results.

Design/methodology/approach

Data for this study were obtained from the benefits system of PTC for the period 2009–2013. The data consist of a series of benefits processing time for two groups of 56,000 claimants – those cleared under the Age 54+ project and those cleared under the old processing system. The processes of the two claim processing systems were analysed and their processing times compared.

Findings

The new system – Age 54+ – decreased the average processing time for new claims by 20 per cent. The new system is a simple approach which is driven by a “Let’s Start in Time” idea.

Originality/value

The operations management literature suggests that process redesign approaches and the implementation of continuous improvement techniques represent mechanisms for achieving performance improvements at governmental agencies. This study shows and discusses the redesign of a social security scheme process using a lean operation concept of waste elimination method and application of kanban to deliver performance improvement.

Details

International Journal of Productivity and Performance Management, vol. 67 no. 7
Type: Research Article
ISSN: 1741-0401

Keywords

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Article

Ab Kasaeian, Reza Daneshazarian, Fathollah Pourfayaz, Sahar Babaei, Mojgan Sheikhpour and Shima Nakhjavani

Because of its increased absorptance in fluid and reduced heat loss, direct absorption nanofluid (DANF) is receiving intense interest as an efficient way to harvest solar…

Abstract

Purpose

Because of its increased absorptance in fluid and reduced heat loss, direct absorption nanofluid (DANF) is receiving intense interest as an efficient way to harvest solar energy. This work aims to investigate, for the first time, the application of DANF in parabolic trough collectors (PTC), a promising collector for solar thermal systems.

Design/methodology/approach

A representative flow and heat transfer study of different fluids in a straight tube is conducted, and the basic energy equation and radiative transfer equations are numerically solved to obtain the fluid temperature distribution and energy conversion efficiency. Ethylene glycol (EG) and different concentrations of (i.e., 0.1-0.6 per cent) multi-wall carbon nanotubes (MWCNT) in EG are used as sample fluids. Four cases are studied for a traditional PTC (i.e., using metal tube) and a direct absorption PTC (i.e., using transparent tube) including a bare tube, a tube with an air-filled glass envelope and a tube with vacuumed glass envelop. The numerical results are verified by an experimental study using a copper-glass absorber tube, which reveals the good potential of DANFs.

Findings

Compared with a conventional PTC, using DANF shows an increase of 8.6 per cent and 6.5 K, respectively, in thermal efficiency and outlet temperature difference at a volume fraction (0.5 per cent) of nanoparticles. The results also show that the improvement in solar efficiency increases with increasing particle concentrations, and the vacuum insulated case has the highest efficiency.

Originality/value

In all previous studies, an important section was missing as the effect of photons on the direct solar absorption trough collector, which is considered in this study. This paper proposes a new concept of using direct solar absorption nanofluids for concentrated solar collectors and analyzes the performance of both absorptance and transmittance efficiency considerations. To reveal the potential of the new concept, an analytical model based on energy balance is developed, and two case studies are performed.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Thomas Maeder, Caroline Jacq, Ludivine Ammon and Perer Ryser

The purpose of this paper is to study tuneable positive temperature coefficient (PTC) effect in polymer-wax-carbon composite resistors. The resistivity dependence on…

Abstract

Purpose

The purpose of this paper is to study tuneable positive temperature coefficient (PTC) effect in polymer-wax-carbon composite resistors. The resistivity dependence on temperature of composite resistors made of carbon fillers dispersed in an organic matrix is known to be strongly affected by the matrix thermal expansion. High PTC effects, i.e. essentially switching from resistive to quasi-insulating behaviour, can be caused by phase changes in the matrix and the assorted volume expansion, a behaviour that has been previously shown with both simple organic waxes and semi-crystalline polymers. However, waxes become very liquid on melting, possibly resulting in carbon sedimentation, and tuneability of semi-crystalline polymers is limited.

Design/methodology/approach

The authors therefore study a ternary polymer-wax-conductor (ethylcellulose-octadecanol-graphite) composite resistor system, where polymer and wax fuse to a viscous liquid on heating, and re-solidify and separate by crystallisation of the wax on cooling.

Findings

It is shown that with appropriate formulation, the resulting resistors exhibit strong PTC effects, linked with the melting and crystallisation of the wax component. The behaviour somewhat depends on sample history, and notably cooling speed.

Research limitations/implications

The phase equilibria and transformation kinetics of the polymer-wax system (including possible wax polymorphism), as well as the exact mechanism of the conductivity transition, remain to be investigated.

Originality/value

As many compatible polymer-wax systems with different melting/solidification behaviours are available, ternary polymer-wax-conductor composite PTC resistors allow a high tuneability of properties. Moreover, the high viscosity in the liquid state should largely avoid the sedimentation issues present with binary wax-conductor systems.

Details

Microelectronics International, vol. 31 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

Abstract

Details

Aircraft Engineering and Aerospace Technology, vol. 72 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

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