Internal and net roof pressures for a dynamically flexible building with a dominant wall opening

Rajnish N Sharma 한국풍공학회 2013 Wind and Structures, An International Journal (WAS Vol.16 No.1

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.

Crystallization kinetics for carbon dioxide gas hydrate in fixed bed and stirred tank reactor

Rajnish Kumar,Asheesh Kumar,Dishant Khatri,Ju-dong Lee 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.6

The phase change from germ nuclei to growth nuclei and subsequent volume transformation in a crystallization process was modeled by Avrami equations. The phase change during the hydrate formation was fitted with the classical Avrami model by utilizing gas uptake data. The idea is to understand the difference in growth behavior of hydrate crystals when in small pores compared to a stirred tank reactor which does not pose any physical restrictions to hydrate growth. The parameters n and k of the Avrami equation were determined explicitly for CO2 hydrate formation.

A novel CdTe/Eu-MOF photoanode for application in quantum dot-sensitized solar cell to improve power conversion efficiency

Rajnish Kaur,Amit L. Sharma,김기현,Akash Deep 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-

The quantum dots (QDs) and metal-organic frameworks (MOFs) have emerged as the efficient nanomaterials for light harvesting, photocatalysis, and photovoltaic applications. Here, the application of a composite of CdTe QDs with a europium-MOF was demonstrated as a novel photoanode to achieve the improvement in the short circuit current density from 19.8 (CdTe QD) to 28.45 mA/cm2 (CdTe QD/Eu- MOF). So does power conversion efficiency (PCE) between the former (1.67%) and the latter (3.02%). This 1.35% of difference (or absolute enhancement) in the PCE can be attributed to an enhanced surface area and increased photon absorption capacity.

Aerodynamics of an intercity bus

Rajnish Sharma,Daniel Chadwick,Jonathan Haines 한국풍공학회 2008 Wind and Structures, An International Journal (WAS Vol.11 No.4

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package CFX™ was used. It has been found that dramatic reductions in coefficient of drag (CD) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended

Scaling methods for wind tunnel modelling of building internal pressures induced through openings

Rajnish N Sharma,Simon Mason,Philip Driver 한국풍공학회 2010 Wind and Structures, An International Journal (WAS Vol.13 No.4

Appropriate scaling methods for wind tunnel modelling of building internal pressures induced through a dominant opening were investigated. In particular, model cavity volume distortion and geometric scaling of the opening details were studied. It was found that while model volume distortion may be used to scale down buildings for wind tunnel studies on internal pressure, the implementation of the added volume must be done with care so as not to create two cavity resonance systems. Incorrect scaling of opening details was also found to generate incorrect internal pressure characteristics. Furthermore, the effective air slug or jet was found to be longer when the opening was near a floor or sidewall as evidenced by somewhat lower Helmholtz frequencies. It is also shown that tangential flow excitation of Helmholtz resonance for off-centre openings in normal flow is also possible.

An Empirical Study on Business Ethics in Manufacturing Sector

Rajnish Ratna,Saniya Chawla,Isha Arora 강원대학교 경영연구소 2013 Asia-Pacific Journal of Business Vol.4 No.2

Ethics involves distinguishing between what is right or wrong thereby making a correct choice. An organization should treat its internal as well as external stakeholders ethically. This research gives valuable insights on the prevailing ethical climate and potential organizational challenges in nstitutionalizing ethics and its management in the manufacturing sector. The present study is designed to analyze four parameters of ethical climate in the manufacturing sector with reference to different managerial levels, to identify the critical factor of the ethical code of conduct and to find correlations between four parameters of ethical climate. Descriptive research has been used and data are collected from 200 employees of three Indian companies of manufacturing sector using a well designed questionnaire. Analyzing data with SPSS, It has been found that overall good number of people believe that MBE (Management of Business Ethics) process is well implemented. People are well aware and trained and involved in the ethical process. Senior management is very much committed to promote the ethical environment in the organization and thus company values are well communicated to the employees. Concern resolution mechanism is well established in the organization. MBE in the organization is more prevalent in higher-level employees. Senior management commitment and reinforcement is very critical for CoC (code of conduct). Correlation between all the 4 parameters is positive and significant. But the parameters are not highly correlated with each other. Organizations need to work upon these parameters to promote an ethical climate in the organization by awarding or felicitating exemplary ethical behavior. More emphasis should be given on senior management commitment and reinforcement of the ethical behavior across all levels.

Another New Complexity Metric for Object-Oriented Design Measurement

Kumar Rajnish 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.2

Recent advances in the photovoltaic applications of coordination polymers and metal organic frameworks

Kaur, Rajnish,Kim, Ki-Hyun,Paul, A. K.,Deep, Akash The Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.11

<▼1><P>Coordination polymers and metal organic frameworks (CPs/MOFs) have attracted a great deal of attention in a variety of scientific fields due to their unique and intriguing structural properties.</P></▼1><▼2><P>Coordination polymers and metal organic frameworks (CPs/MOFs) have attracted a great deal of attention in a variety of scientific fields due to their unique and intriguing structural properties. Photovoltaic applications of these porous polymers belong to a relatively new area of research. The current status of research on this subject amply highlights the usefulness of CPs/MOFs in improving the properties of next-generation photovoltaic devices (<I>e.g.</I>, dye-sensitized solar cells). This review article was written to cover the recent advancements that have been achieved in this rapidly expanding area of research. It also compares and contrasts the energy conversion efficiencies in photovoltaic applications using different MOFs and other systems.</P></▼2>

Aerodynamics of an intercity bus

Sharma, Rajnish,Chadwick, Daniel,Haines, Jonathan Techno-Press 2008 Wind and Structures, An International Journal (WAS Vol.11 No.4

A number of passive aerodynamic drag reduction methods were applied separately and then in different combinations on an intercity bus model, through wind tunnel studies on a 1:20 scale model of a Mercedes Benz Tourismo 15 RHD intercity bus. Computational fluid dynamics (CFD) modelling was also conducted in parallel to assist with flow visualisation. The commercial CFD package $CFX^{TM}$ was used. It has been found that dramatic reductions in coefficient of drag ($C_D$) of up to 70% can be achieved on the model using tapered and rounded top and side leading edges, and a truncated rear boat-tail. The curved front section allows the airflow to adhere to the bus surfaces for the full length of the vehicle, while the boat-tails reduce the size of the low pressure region at the base of the bus and more importantly, additional pressure recovery occurs and the base pressures rise, reducing drag. It is found that the CFD results show remarkable agreement with experimental results, both in the magnitude of the force coefficients as well as in their trends. An analysis shows that such a reduction in aerodynamic drag could lead to a significant 28% reduction in fuel consumption for a typical bus on intercity or interstate operation. This could translate to a massive dollar savings as well as significant emissions reductions across a fleet. On road tests are recommended.

Internal and net roof pressures for a dynamically flexible building with a dominant wall opening

Sharma, Rajnish N. Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.16 No.1

This paper describes a study of the influence of a dynamically flexible building structure on pressures inside and net pressures on the roof of low-rise buildings with a dominant opening. It is shown that dynamic interaction between the flexible roof and the internal pressure results in a coupled system that is similar to a two-degree-of-freedom mechanical system consisting of two mass-spring-damper systems with excitation forces acting on both the masses. Two resonant modes are present, the natural frequencies of which can readily be obtained from the model. As observed with quasi-static building flexibility, the effect of increased dynamic flexibility is to reduce the first natural frequency as well as the corresponding peak value of the admittance, the latter being the result of increased damping effects. Consequently, it is found that the internal and net roof pressure fluctuations (RMS coefficients) are also reduced with dynamic flexibility. This model has been validated from experiments conducted using a cylindrical model with a leeward end flexible diaphragm, whereby good match between predicted and measured natural frequencies, and trends in peak admittances and RMS responses with flexibility, were obtained. Furthermore, since significant differences exist between internal and net roof pressure responses obtained from the dynamic flexibility model and those obtained from the quasi-static flexibility model, it is concluded that the quasi-static flexibility assumption may not be applicable to dynamically flexible buildings. Additionally, since sensitivity analyses reveal that the responses are sensitive to both the opening loss coefficient and the roof damping ratio, careful estimates should therefore be made to these parameters first, if predictions from such models are to have significance to real buildings.