Search results

1 – 10 of over 8000
To view the access options for this content please click here
Article
Publication date: 1 August 1997

M.F. Barker

The growth in digital telecom systems around the world has led to an increase indemand for surge protection components. These components often use low ohm resistor…

Downloads
139

Abstract

The growth in digital telecom systems around the world has led to an increase in demand for surge protection components. These components often use low ohm resistor compositions in a serpentine configuration. The demands placed upon these materials during pulsing are high. Not only are the materials expected to withstand more severe pulses, they are also expected to have minimal adverse effect on the environment. To meet these increased demands, a new system of surge resistor materials has been developed. The design, manufacture and testing of these materials ensures optimum performance in high voltage surge applications. This paper describes the performance of this new surge resistor system and discusses how the performance of the resistors relates to the paste constituents, encapsulant materials and the laser trimming process.

Details

Microelectronics International, vol. 14 no. 2
Type: Research Article
ISSN: 1356-5362

Keywords

To view the access options for this content please click here
Article
Publication date: 1 September 1999

Winco K.C. Yung, J.S. Liu and H.C. Man

Diameter and depth of craters and removing efficiency of the material of RCCR (resin coated copper) used in PCB by a single pulse energy of 355nm YAG laser with a variety…

Abstract

Diameter and depth of craters and removing efficiency of the material of RCCR (resin coated copper) used in PCB by a single pulse energy of 355nm YAG laser with a variety of pulse energy, pulse width and defocus have been studied in the paper. It is shown that the ablation rates per pulse are much higher when compared with those at 248nm. The crater diameter increases monotonically with the pulse energy. However, when the pulse energy is very high and the power density is higher than 4.0 × 109W/cm2, the crater depth and removing efficiency decrease with the increase of pulse energy. The pulse width has an important influence on the crater diameter and volume when the pulse width changes from 24ns to 38ns, whereas the influence on the crater depth is little. The influences of defocus on ablation results depend on the power density of laser beam. A certain defocus can make both crater diameter and removing efficiency increase for a relatively high power density. Meanwhile, the thermal effect in the process of 355nm laser ablation of RCCR cannot be neglected.

Details

Circuit World, vol. 25 no. 3
Type: Research Article
ISSN: 0305-6120

Keywords

To view the access options for this content please click here
Article
Publication date: 1 October 2005

Takao Koshimizu, Hiromi Kubota, Yasuyuki Takata and Takehiro Ito

To clarify the physical working principle of refrigeration in basic pulse tube refrigerators (BPTRs).

Abstract

Purpose

To clarify the physical working principle of refrigeration in basic pulse tube refrigerators (BPTRs).

Design/methodology/approach

A numerical simulation was performed. Transient compressible NS equation was solved utilizing the TVD scheme coupled with energy equation.

Findings

The periodic flow and temperature field were obtained. The movement of the gas particles and heat transfer between the gas particles and wall were analyzed. These numerical results explained the mechanism of surface heat pumping (SHP) which is known as the working principle of refrigeration in BPTR.

Research limitations/implications

Pulse tube refrigerator (PTR) is classified into the third generation. BPTR is the first generation. It is needed to clarify the working principle of refrigeration in the second and third generation by analyzing heat and fluid flow in the tube.

Practical implications

A very useful source of information to understand the physical working principle of refrigeration in BPTR.

Originality/value

The mechanism of SHP was shown by analyzing the heat exchange between the gas particles and pulse tube wall.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 15 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 13 July 2021

Ranjit Singh, Ravi Pratap Singh and Rajeev Trehan

This study aims to experimentally investigate the influence of considered process parameters, i.e. pulse on time, pulse off time, peak current and gap voltage, on tool…

Abstract

Purpose

This study aims to experimentally investigate the influence of considered process parameters, i.e. pulse on time, pulse off time, peak current and gap voltage, on tool wear rate (TWR) in electrical discharge machining (EDM) of iron (Fe)-based shape memory alloy (SMA) through designed experiments. The parametric optimization for TWR has also been attempted using the desirability approach and genetic algorithm (GA).

Design/methodology/approach

The response surface methodology (RSM) in the form of Box–Behnken design has been used to scheme out the experiments. The influence of considered process inputs has also been observed through variance analysis. The reliability and fitness of the developed mathematical model have been established with test results. Microstructure analysis of machined samples has also been evaluated and analyzed using a scanning electron microscope (SEM). SEM images revealed the surface characteristics such as micro-cracks, craters and voids on the tool electrode surface. SEM images provide information about the surface integrity and type of wear on the surface of the tool electrode.

Findings

The input parameters, namely, pulse on time and pulse off time, are major influential factors impacting the TWR. High TWR has been reported at large pulse on time and small pulse off time conditions whereas higher TWR is reported at high peak current input settings. The maximum and minimum TWR values obtained are 0.073 g/min and 0.017 g/min, respectively. The optimization with desirability approach and GA reveals the best parametric values for TWR i.e. 0.01581 g/min and 0.00875 g/min at parametric combination as pulse on time = 60.83 µs, pulse off time = 112.16 µs, peak current = 18.64 A and gap voltage = 59.55 V, and pulse on time = 60 µs, pulse off time = 120 µs, peak current = 12 A and gap voltage = 40 V, correspondingly.

Research limitations/implications

Proposed work has no limitations.

Originality/value

SMAs have been well known for their superior and excellent properties, which make them an eligible candidate of paramount importance in real-life industrial applications such as orthopedic implants, actuators, micro tools, stents, coupling, sealing elements, aerospace components, defense instruments, manufacturing elements and bio-medical appliances. However, its effective and productive processing is still a challenge. Tool wear study while processing of SMAs in EDM process is an area which has been less investigated and of major concern for exploring the various properties of the tool and wear in it. Also, the developed mathematical model for TWR through the RSM approach will be helpful in industrial revelation.

Details

World Journal of Engineering, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1708-5284

Keywords

To view the access options for this content please click here
Article
Publication date: 17 June 2021

Raju Guntukula and Phanindra Goyari

This paper aims to evaluate the effects of climate variables on the mean yield and yield variability of major pulse crops in the Telangana state of India.

Abstract

Purpose

This paper aims to evaluate the effects of climate variables on the mean yield and yield variability of major pulse crops in the Telangana state of India.

Design/methodology/approach

Authors have estimated the Just and Pope (1978, 1979) production function using panel data at the district level of four major pulses in nine former districts of Telangana for 36 years during 1980–2015. A three-stage feasible generalized least squares estimation procedure has been followed. The mean yield and yield variance functions have been estimated individually for each of these study crops, namely, Bengal gram, green gram, red gram and horse gram.

Findings

Results have shown that changes in climatic factors such as rainfall and temperature have significant influences on the mean yield levels and yield variance of pulses. The maximum temperature is observed to have a significant adverse impact on the mean yield of a majority of pulses, and it is also a risk-enhancing factor for a majority of pulses except horse gram. However, the minimum temperature is positively related to the mean yields of the study crops except for Bengal gram, and it is having a risk-reducing impact for a majority of study crops. Rainfall is observed to have a negative impact on the mean yields of all pulses, but it is a risk-enhancing factor for only one crop, i.e. Bengal gram. Thus, rising temperatures and excess rainfall are not favorable to the productivity of pulses in study districts.

Research limitations/implications

The present study is based on the secondary data at the district level and is considering only one state. Season-wise primary data, including farm-specific characteristics, could have been better. The projected climate change and its impact on the mean yields and yield variance of pulses need to be considered in a future study.

Originality/value

According to the best of our knowledge, this is the first study to empirically evaluate the impact of climatic variables on the mean yields and yield variability of major pulses in Telangana using a panel data for major pulses and nine districts of 36 years time-series during 1980–2015. The study has given useful policy recommendations.

Details

Journal of Agribusiness in Developing and Emerging Economies, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2044-0839

Keywords

To view the access options for this content please click here
Article
Publication date: 17 June 2021

Yih-Lin Cheng and Tzu-Wei Tseng

Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of…

Abstract

Purpose

Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric printhead in MJ would affect droplet formation and performance, but there are very limited studies on it besides patents and know-hows by commercial manufacturers. Therefore, in this research, the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead was studied. Therefore, this research aims to study the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead.

Design/methodology/approach

Ricoh’s Gen4L printhead was adopted. A high-speed camera captured pictures of jetted droplets and droplet velocity was calculated. The waveforms included single-, double- and triple-pulse trapezoidal patterns. The effects of parameters were investigated and the suitable ones were determined based on the avoidance of satellite drops and preference of higher droplet velocity.

Findings

In a single-pulse waveform, an increase of fill time (Tf) decreased the droplet velocity. The maximum velocity happened at the same pulse width, the sum of fill time and hold time (Tf + Th). In double- and triple-pulse, a voltage difference (Vd) above zero in the holding stage was adopted except the last pulse to avoid satellite drops. Suitable parameters for the selected resin were obtained and the time-saving design process was established.

Research limitations/implications

Based on the effects of parameters and observed data trends, suggested procedures to determine suitable parameters were proposed with fewer experiments.

Practical implications

This study has verified the feasibility of suggested design procedures on another resin. The required number of trials was reduced significantly.

Originality/value

This research investigated the process of driving waveform design for the multi-nozzle piezoelectric printhead. The suggested procedures of finding suitable waveform parameters can reduce experimental trials and will be applicable to other MJ 3D printers when new materials are introduced.

Details

Rapid Prototyping Journal, vol. 27 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Content available
Article
Publication date: 9 February 2021

Mathew Abraham and Prabhu Pingali

This paper aims to understand the significant farm and market-level factors that incentivize the adoption and marketing of pulses influencing its supply response to…

Downloads
1871

Abstract

Purpose

This paper aims to understand the significant farm and market-level factors that incentivize the adoption and marketing of pulses influencing its supply response to changing demand.

Design/methodology/approach

The authors first use a modified Nerlovian supply response model using secondary data to identify the major price and non-price factors influencing the supply of pigeon pea, black and green gram in the major pulses growing states in India. Second, using primary qualitative data the authors map the pulses value chain from farm to retail to identify the how proportional and fixed transaction costs (FCTs) influence market participation of pulses growers and limit the transmission of price and quality information.

Findings

The supply response model shows some positive influence of price on area allocation for pigeon pea and black gram and some negative effects of yield and price increase of competing crops on pigeon pea acreage. However, for the most part, the area of Kharif pulses is inelastic to prices in the long run. Irrigation, rainfall and yields in the lag year are shown to have a significant influence on area allocation for pulses. The market study reveals that low yields, low landholding size and geographical disadvantages of high agro-climatic risk and poor connectivity hinder market access of pulses farmers relative to other crops. Market power in favor of buyers and poor price and quality information is a disadvantage to sellers, influencing their ability to participate in markets.

Research limitations/implications

A quantitative study would be required to identify the magnitude of farm and market-level transaction costs.

Originality/value

This study helps to understand the supply response of pulses and gives suggestions to direct policy to rectify this.

Details

Journal of Agribusiness in Developing and Emerging Economies, vol. 11 no. 4
Type: Research Article
ISSN: 2044-0839

Keywords

To view the access options for this content please click here
Article
Publication date: 3 March 2020

Toby Le and Sharareh Hekmat

This study aims to determine the probiotic potential of Lactobacillus rhamnosus GR-1 from Fiti sachets, in four widely consumed pulses, namely, black-eyed pea, pigeon pea…

Abstract

Purpose

This study aims to determine the probiotic potential of Lactobacillus rhamnosus GR-1 from Fiti sachets, in four widely consumed pulses, namely, black-eyed pea, pigeon pea, kabuli chickpea and desi chickpea. The secondary objective was to determine the viability of the fermented pulses during 21 days of storage at 4°C.

Design/methodology/approach

Each pulse sample was mixed with a Fiti sachet (one gram of freeze-dried consortium of Lactobacillus rhamnosus GR-1 and Streptococcus thermophilus C106) and fermented for up to 120 h. To assess the samples’ storage potential, they were refrigerated at 4°C for 21 days. Microbial enumerations and pH measurements were collected during fermentation and storage to determine the viability and fermentation potential of Lactobacillus rhamnosus GR-1 and Fiti, respectively.

Findings

There was a significant (p = 0.01) difference in mean microbial counts in all pulse samples throughout fermentation. At 24 h of fermentation, the mean bacterial count of Lactobacillus rhamnosus GR-1 in black-eyed pea, pigeon pea, kabuli chickpea and desi chickpea were 1.32 × 109 ± 0.11, 1.01 × 109 ± 0.16, 1.52 × 109 ± 0.14 and 0.80 × 109 ± 0.05 CFU/mL, respectively. Fermentation of pigeon pea, kabuli chickpea and desi chickpea at 48 h yielded the highest bacterial count for Lactobacillus rhamnosus GR-1 while black-eyed pea reached its highest bacterial count at 72 h of fermentation. The bacterial concentration of all pulse samples remained at around 109 CFU/mL during the refrigeration period of 21 days at 4°C. Furthermore, the pH of all pulse samples were below 4.6 during both fermentation and refrigerated storage.

Originality/value

Since 2004, the Fiti initiative has economically empowered hundreds of women in East Africa by teaching them how to produce and sell probiotic yogurt containing Lactobacillus rhamnosus GR-1. As a result, Fiti probiotic yogurt was made accessible to vulnerable populations in East Africa who face malnutrition, infectious diseases and environmental toxins. Because of recent climatic changes, milk has become more expensive and inaccessible for local communities. Furthermore, this study found that black-eyed pea, pigeon pea, kabuli chickpea and desi chickpea can be viable and non-diary probiotic alternatives to the Fiti probiotic yogurt in Eastern Africa. This is also the first study of its kind to provide preliminary evidence showing pulses as non-dairy alternatives to Fiti probiotic yogurt.

Details

Nutrition & Food Science , vol. 50 no. 6
Type: Research Article
ISSN: 0034-6659

Keywords

To view the access options for this content please click here
Article
Publication date: 6 August 2018

Rohollah Abdollahi

For direct torque controlled induction motor drives, an effective solution to eliminate harmonics is the use of multipulse alternating current (AC)-direct current (DC…

Abstract

Purpose

For direct torque controlled induction motor drives, an effective solution to eliminate harmonics is the use of multipulse alternating current (AC)-direct current (DC) converters. Many researchers have used different configurations based on 24- and 30-pulse rectifications for improved power quality. However, the total harmonic distortion (THD) of AC mains current with these topology is more than 4 per cent when operating at a light load. For mitigating the THD problems observed in the input currents, Abdollahi propose 40-, 72- and 88-pulse AC-DC converters, while the power quality enhancement was the main concern. It is known that by increasing the number of pulses further results in reduction in current harmonics, but this is accompanied by an increase in cost and complexity. In this context, the purpose of this paper is to design a new delta/hexagon transformer based 36-pulse AC-DC converter for harmonic reduction without increasing the cost and complexity.

Design/methodology/approach

The proposed converter consists of two paralleled 18-pulse AC-DC converters involving a nine-phase shifted uncontrolled diode bridges with an interphase transformer circuit.

Findings

In this paper, the proposed scheme is simulated by matrix laboratory (MATLAB)/SIMULINK considering different loading scenarios. The simulation results show that the proposed scheme improves the power quality indices and satisfies the The Institute of Electrical and Electronics Engineers (IEEE)-519 requirements at the point of common coupling. Also, a laboratory prototype is implemented using the proposed design, and the experimental results confirm the simulation results under different loading conditions.

Originality/value

The proposed solution is a tradeoff among the pulse number, the transformer platform, the complexity of the scheme and the cost. The proposed scheme has an optimized configuration in this regard.

Details

World Journal of Engineering, vol. 15 no. 4
Type: Research Article
ISSN: 1708-5284

Keywords

To view the access options for this content please click here
Article
Publication date: 1 April 2005

Frank W. Agbola and Maylene Y. Damoense

This study seeks to examine empirically import demand for total pulses, chickpeas and lentils in India based on the concept of unit root and cointegration.

Downloads
2762

Abstract

Purpose

This study seeks to examine empirically import demand for total pulses, chickpeas and lentils in India based on the concept of unit root and cointegration.

Design/methodology/approach

The Stock‐Watson dynamic OLS (DOLS) model – which is robust to small sample and eliminates simultaneity bias – is used to derive the long‐run price, income and urbanisation elasticities of import demand. The data covers the period 1970‐2000.

Findings

Results indicate that real GDP, relative price and urbanisation are the key determinants of import demand for pulses in India. The estimated long‐run elasticities of import demand with respect to income (relative price) are 0.4 (−1.7) for chickpeas, 0.56 (−0.87) for lentils and 0.36 (0.00) for total pulses. The estimated long‐run elasticities of import demand with respect to urbanisation are 9.9 for chickpeas, zero for lentils and 7.2 for total pulses. The policy implications of the results are discussed.

Originality/value

Provides evidence that the response of import demand for pulses to key determinants differ substantially from product to product.

Details

Journal of Economic Studies, vol. 32 no. 2
Type: Research Article
ISSN: 0144-3585

Keywords

1 – 10 of over 8000