Impact of Revised Code NBC105 on Assessment and Design of Low Rise Reinforced Concrete Buildings in Nepal

Gorkha Earthquake in 2015 has impacted considerably in the design and construction of buildings in Nepal. Strength and Safety of life and constructions have become the prime concerns of the government and the public. Regulation is required to achieve the strength and safety in the constructions. Hence, a need for revision of building codes has been felt and Nepal Building Code, NBC105 has been revised. This paper presents the impact of the revised code on seismic load estimation for low rise reinforced concrete buildings. For the assessment of the impact linear and non- linear static and linear dynamic analysis of reinforced concrete residential buildings of two storey and four Storey has been taken subjected to Indian Standard Codes IS 1893: 2002, IS 1893:2016, Nepal Building Codes NBC 105: 1994 and NBC 105: 2020. The buildings were modeled and analyzed in SAP2000. The response of the buildings such as time period, base shear, drifts, and storey forces from the application of the four codes was compared. The comparison of the results shows that the structural response of the building under the revised NBC105:2020 is 60% to 65% higher compared to the previous code NBC105:1994.

An Enhanced Low Voltage Ride-Through Control Scheme of a DIFG based WTG Using Crowbar and Braking Chopper

The grid codes define low voltage ride-through (LVRT) as capability of wind turbine generator (WTG) to support the grid voltage by injecting reactive power and suppress the rise of DC-link voltage and inrush rotor current in the rotor side converter (RSC) of the doubly fed induction generator (DFIG) during a fault. Moreover, the rotor current increases significantly during severe disturbances if any protection schemes are not employed. Therefore, the protection schemes must be used to avoid the damage to the converter during a fault. This paper proposes an enhanced LVRT control scheme of a DFIG employing a crowbar in the RSC side and braking chopper across the DC-link capacitor. The DFIG is highly delicate to grid voltage fluctuation during a fault because the DFIG is directly linked to the grid via stator. During severe fault the crowbar regulates the rotor current within an acceptable range and the braking chopper discharges the DC-link capacitor via resistor within a safe limit. The proposed LVRT control scheme is performed for a 2.4-MW DFIG using a MATLAB/SIMULINK simulator. The results delineate that the proposed control scheme is able to rapidly decrease the rotor current and repress the escalation in DC-link voltage during a grid fault.

Critical Review and Improvement of Bank Protection Methods in Nepalese Rivers

This paper reviews performance of bank protection works constructed over the last decades along the major rivers in Nepal. The study reveals main reasons of early spurs failure in five major rivers - Koshi, Narayani, West Rapti, Karnali and Mahakali. The overview finds design deficiency as the main reason of failure of bank protection works. The methodology incorporates a combination of field visits and a review of design reports, master plans. The study finds bank protection works along the major rivers in Nepal consist almost exclusively of spurs often combined with revetments in between, made of gabions filled with boulders. Also, the launching aprons are constructed of gabions. The lifetime of these bank protection works is less than 10 years and often much shorter. Designs are based on standard designs from Indian standards, developed for normal alluvial rivers. The study recommends initiating a bank protection pilot project to identify the cause of failure of the bank protection works and to test remedial measures for the sustainability enhancement of river protection works in future.

Voltage Control and Braking System of a DFIG during a Fault

This paper describes a voltage control scheme of a doubly fed induction generator (DFIG) wind turbine that can inject more reactive power to the grid during a fault so as to support the grid voltage. To achieve this, the coordinated control scheme using both rotor side converter (RSC) and grid side converters (GSC) controllers of the DFIG are employed simultaneously. The RSC and GSC controllers employ PI controller to operate smoothly. In the voltage control mode, the RSC and GSC are operated. During a fault, both RSC and GSC are used simultaneously to supply the reactive power into the grid (main line) depending on voltage dip condition to support the grid voltage. The proposed system is implemented for single DFIG wind turbine using MATLAB simulation software. The results illustrate that the control strategy injects the reactive power to support the voltage stability during a fault rapidly. Also, the braking system is designed to protect the wind turbine system from over speed. For this purpose, the braking resistors are being used.

Risk Rating for Risk-Based Maintenance: A Case Study of Small Hydropower Plant in Nepal

Fourth generation maintenance philosophy and Quality management system 9001:2015, emphasis on the concept of risk based thinking. And it is one of the challenging part of maintenance department to adopt these philosophy by quantifying all the activities of the department. Risk rating based on reliability is one of the techniques to quantify the maintenance activities for those organizations, whose reliability of goods and services matter in the market. Hydropower sector is also among them whose reliability matters highly in consumer life standard. So this paper approaches to rate the risk of hydropower based on the reliability of components for the implementation of Risk-based maintenance. From the study of data recorded in log book of a small hydropower plant located in western part of Nepal, it was found that the overall reliability score of the plant was 0.9819, which was low as compared to other hydropower of Nepal, where turbine section of both the units of the plant found a higher risk score than other systems. Study adopted two tools i.e. Analytical Hierarchical based Fault Tree Analysis and Critical Analysis Technique to find the critical assets and Failure Mode and Effect Analysis for the rest of all to quantifying the risk in component level. The analysis shows that the cooling system as the critical asset for both the units and it contributes 72% and 64% in the reliability of the turbine section. The critical assets thus obtained was validated through the critical analysis technique. From which the risk score of cooling system found 90% in both the units. To analyze the risk in component level, Failure Mode and Effect Analysis of different sub component of critical assets was done. Among the sub-components of the cooling system, radial tube filter gets the highest risk score. Its components; cartridge, tube, and joints have the risk score of 450, 192, and 96 respectively. And from the critical analysis of the rest of the subsystems of uint-I and unit-II, components such as bearings, breaker of the transmission system, transmission equipment, excitation system and transformer of unit-I and breaker of the transmission system, transmission equipment and excitation system of unit-II are found to have higher critical score, hence, it is recommended to apply preventive activities on these components as per the manufacturer to reduce the risk that could be caused by their failure.

A Report on GIS Based Analysis of Landslides in Myagdi District

Lanslide have become a routine event during monsoon in Nepal which accompanies a huge social, physical and economical loss. As the number of landslide event is in increasing order each year but their proper study is still limited, this assessment is an example of simple step in landslide study. Also, the developmental activities disturb the topology and hence increase or bring new form of landslide in the region. This report is mainly a preliminary study of existing landslide in Myagdi district which is generally carried out using QGIS software and remote sensing data available from http://earthexplorer.usgs.gov and recent Google satellite image. From the analysis carried out by using the inbuilt features in QGIS, relationship between various terrain, hydrological and anthropogenic parameters with landslide was driven. Based on this approach a simple precautionary measures in development activities, disaster preparedness and mitigation activities can be carried out.

Devnagari Handwritten Characters Image Super-Resolution based on Enhanced SRGAN

The difficulty in machine learning-based image super-resolution is to generate high-frequency component in an image without introducing any artifacts. In this paper, Devnagari handwritten characters image using a generative adversarial network with a classifier is generated in high-resolution which is also classifiable. The generator architecture is modified by removing all batch normalization layers in generator architecture with a residual in residual dense block. Batch normalization is removed because it produces unwanted artifacts in the generated images. A Devnagari handwritten characters classifier is built using CNN. The classifier is used in the network to calculate the content loss. The adversarial loss is obtained from the GAN architecture and both of the losses are added to obtain total loss. Generated HR images is validated using six different evaluation metrics among which MSE, PSNR determines pixel-wise difference and SSIM compares images perceptually. Similarly, FID is used to measure the statistical similarity between the batch of generated images and its original batch. Finally, the Gradient similarity is used to assess the quality of the generated image. From the experimental results, we obtain MSE, PSNR and SSIM as 0.0507, 12.95(dB) and 0.8172 respectively. Similarly, the FID value obtained was 27.5 with the classification accuracy of image data of 98%. The gradient similarity between the generated image and the ground truth obtained was 0.9124.

Development of Polynomial Mode Shape Functions for Continuous Shafts with Different End Conditions

Common methods used to determine the solutions for vibration response of continuous systems are assumed mode method, Rayleigh-Ritz method, Galerkin Method, finite element method, etc. Each of these methods requires the shape functions which satisfy the boundary conditions. Shape functions derived in most of the classical textbooks are simple trigonometric functions for some end conditions but are very complex transcendental functions for many end conditions. It is very difficult to determine the vibration response of a continuous system analytically by using such transcendental shape functions. Hence this paper presents a method to develop polynomial shape functions required to solve the vibration of continuous shafts with different end conditions. The natural frequencies obtained from the developed polynomial shape functions are compared to those obtained from the classical transcendental shape functions and found very close for the first three modes.

High Temperature Superconductivity: A Prospective Remedy for Energy Crisis in Future

This paper summarizes the superconducting phenomenon followed by application of superconductivity devices on energy sector. High temperature superconductivity are very innovative, promising and eco-friendly alternative to mitigate the energy crisis by saving energy.

Design, Fabrication, and Performance Analysis of an Automatic Horizontal Egg Incubator

This research paper presents the design, construction, and performance testing of an automatic electrically powered egg incubator utilizing the horizontal placement of eggs. This experimental research was driven by the specific design and construction of a well-insulated rectangular egg-incubating box of dimension 400 mm × 600 mm × 500 mm and thickness 30 mm, where sample eggs were kept for experimental test analysis under the favorable temperature and humidity inside the box, which was automatically controlled. The device was made to operate under the temperature range of 37°C – 38°C, which was found to be adequate for developing embryos and also maintaining relative humidity at the range of 45–60% for the first 18 days and 60–90% for the last three days. Finally, in this machine, the egg tray was adjusted horizontally, and a motor clamped mechanism was used 5 times a day which was controlled automatically by a micro-controller for the motion of eggs up to 18 days of incubation. In conclusion, this egg-incubating machine has an efficiency and hatchability of 72.22%.