Analysis of curtailment at The Geysers geothermal Field, California

Geothermal energy has traditionally been viewed as a baseload energy source, but the rapid growth of intermittent renewable energy has led to a need for more flexibility in power generation to avoid mandatory curtailment imposed by grid operators. This study of curtailment at The Geysers provides insights into the magnitude, duration, frequency, temporal and spatial distribution, and potential causes of curtailment events between 2013 and 2018. Annual levels of curtailment range during this period from 9 to 47 GW h, representing 0.15 to 0.81 % of the net generation. Most curtailments occurred at the power plants connected to a lower capacity transmission line and may result from transmission constriction. There is a clear link between negative pricing and economic curtailment, especially when solar production is higher. Economic curtailment events tend to be only a few hours and vary in magnitude up to almost 300 MW, whereas transmission-related curtailment events can be up to several weeks in duration. It is likely that curtailment of geothermal power will be an increasing concern, and could be mitigated by flexible generation strategies and increases in energy storage. It is critical to know the nature of curtailment events so that flexible generation options can be assessed properly

A Novel Beamformed Control Channel Design for LTE with Full Dimension-MIMO

The Full Dimension-MIMO (FD-MIMO) technology is capable of achieving huge improvements in network throughput with simultaneous connectivity of a large number of mobile wireless devices, unmanned aerial vehicles, and the Internet of Things (IoT). In FD-MIMO, with a large number of antennae at the base station and the ability to perform beamforming, the capacity of the physical downlink shared channel (PDSCH) has increased a lot. However, the current specifications of the 3rd Generation Partnership Project (3GPP) does not allow the base station to perform beamforming techniques for the physical downlink control channel (PDCCH), and hence, PDCCH has neither the capacity nor the coverage of PDSCH. Therefore, PDCCH capacity will still limit the performance of a network as it dictates the number of users that can be scheduled at a given time instant. In Release 11, 3GPP introduced enhanced PDCCH (EPDCCH) to increase the PDCCH capacity at the cost of sacrificing the PDSCH resources. The problem of enhancing the PDCCH capacity within the available control channel resources has not been addressed yet in the literature. Hence, in this paper, we propose a novel beamformed PDCCH (BF-PDCCH) design which is aligned to the 3GPP specifications and requires simple software changes at the base station. We rely on the sounding reference signals transmitted in the uplink to decide the best beam for a user and ingeniously schedule the users in PDCCH. We perform system level simulations to evaluate the performance of the proposed design and show that the proposed BF-PDCCH achieves larger network throughput when compared with the current state of art algorithms, PDCCH and EPDCCH schemes

DAILY KNEE JOINT LAXITY IN FEMALES ACROSS A MENSTRUAL CYCLE AND MALES ACROSS A CALENDAR MONTH

Increased athletic participation of females has resulted in a high occurrence of anterior cruciate ligament (ACL) injuries. Excessive knee joint laxity during hormonal peaks of endogenous sex hormones during the follicular, ovulatory, and luteal phases of the menstrual cycle has been associated with ACL injury risk. The purpose of this study was to determine the effect of gender and menstrual phase on knee joint laxity over the full course of a normal menstrual cycle in females and across a calendar month in males. A repeated measures ANOVA revealed no interaction effect between gender and phase, no main effect for gender, but a statistically significant main effect for phase. Since male participants demonstrated a similar inclination between phases, the significance of this trend should be interpreted as a possible random occurrence

Effect of retempering with retarding admixture on properties of concrete subjected to prolonged mixing

In situations like delivery of concrete from central mixing plant, in road construction, in constructing lengthy tunnels, in transportation of concrete by manual labor, in hilly terrain long hauling of concrete is required. Loss of workability and undue stiffening of concrete may take place at the time of placing on actual work site1. In such situations engineers at site, many a time reject the concrete partially set and unduly stiffened due to the time elapsed between mixing and placing. Mixed concrete is a costly material and it cannot be wasted without any regard to cost. It is required to see whether such a stiffened concrete could be used on work without undue harm with use of retarding admixtures. The process of remixing of concrete, if necessary, with addition of just the required quantity of water is known as ‘retempering’ of concrete1. Sometimes, a small quantity of extra cement is also added while retempering. In the site sometimes the concrete has to wait for some time to enter in the formwork after it is mixed. This may be due to some break down in the conveyance or quarrel between the labors. In such situations the concrete looses its plasticity. But since the quantity is enormous2, such concrete cannot be wasted. In such situations addition of small quantity of cement and water along with retarding admixture can bring back the plasticity to concrete. Thus retempering becomes important in such odd situations2. In this paper an attempt is made to study the strength characteristics of concrete containing retarding admixture at retempering time of 15min upto 90 min. The tests are conducted to evaluate the strength characteristics of concrete like compressive strength, tensile strength, flexural strength for different retempering times

An analytical model to determine fundamental frequency of rectangular plate having rectangular array of circular perforations

In the current study an analytical model to determine fundamental frequency of perforated plate with circular perforation is formulated. Circular holes are replaced by equivalent square hole and non homogeneity in Young’s modulus and density due to equivalent square perforation is expressed by using unit step functions. Analytical formulation is based on Rayleigh-Ritz method. In present study boundary condition considered is clamped at all edges. The deflected middle surface of the plate is approximated by a function which satisfies the boundary conditions. Proposed approach is validated by comparing numerical analysis results with Finite Element Method (FEM) modal analysis results

Analytical model to determine fundamental frequency of free vibration of perforated plate by using unit step functions to express non-homogeneity

In the current study an analytical model to determine fundamental frequency of perforated plate is formulated. Non-homogeneity in Young’s modulus and density due to perforation is expressed by using unit step function in Rayleigh’s Quotient. In the present analysis the boundary condition considered is clamped at all edges. Perforated plate is considered as plate with uniformly distributed mass and holes are considered as nonhomogeneous patches. The deflected middle surface of the plate is approximated by a function which satisfies the boundary conditions. The proposed approach is validated by comparing results with finite element method modal analysis

SCREENING OF CELLULOLYTIC BACTERIA FOR PRODUCING CELLULASE UNDER SOLID STATE FERMENTATION USING WATER HYACINTH AS A SUBSTRATE

Objective: The infestation of water hyacinth in the aquatic system produces serious environmental problems. In our study, we have used the water hyacinth as a substrate for the production of cellulase enzyme from bacteria isolated from decayed water hyacinth.Methods: The bacterial isolates were morphologically and biochemically characterized and the bacterial cultures were identified as Proteus vulgaris and Serratia ficaria respectively. The effect of various process parameters such as pH, temperature, substrate concentration and fermentation time on cellulase production by Proteus vulgaris were optimized.Results: Out of twenty five isolates, two bacteria viz. AK1 and AK2 grew well on CMC agar media. Cellulase enzyme activity was found to be higher (4.07 U/ml) in case of Proteus vulgaris compared to Serratia ficaria. Cellulase production by Proteus vulgaris was optimized as pH 7, 35 °C temperature, 30% of water hyacinth and 24 h of incubation time. Cellulase produced under optimum condition was purified using dialysis and ion exchange chromatography. The molecular weight and specific activity of completely purified cellulase was found to be 33 KDa and 361.25 U/mg respectively.Conclusion: It can be concluded that the water hyacinth can be used as a potential substrate for production of cellulase by Proteus vulgaris which is isolated from decayed water hyacinth

Plant Leaf Disease Detection Using Efficient Image Processing and Machine Learning Algorithms

India is often described as a country of villages, where a majority of the population depends on agriculture for their livelihood. The landscape of Indian agriculture is approximately 159.7 million hectares. Agriculture plays a pivotal role in India's Gross Domestic Product (GDP), accounting for about 18% of the nation's economic output. Diseases and pests can have detrimental effects on crops, leading to reduced yields. These challenges can include the spread of plant diseases, infestations by insects or other pests, and the overall degradation of crop health. Early detection of diseases in crops is crucial for several reasons. Detecting diseases at an early stage allows for prompt intervention, such as applying appropriate pesticides or taking preventive measures. The main aim of this study is to develop a highly effective method for plant leaf disease detection using computer vision techniques. Here, leaf disease detection comprises histogram equalization, denoising, image color threshold masking, feature descriptors such as Haralick textures, Hu moments, and color histograms to extract the salient features of leaf images. These features are then used to classify the images by training Logistic Regression, Linear Discriminant Analysis, K-nearest neighbor, decision tree, Random Forest, and Support Vector Machine algorithms using K-fold validation. K-fold validation is used to separate the validation samples from the training samples, and the K indicates the number of times this is repeated for the generalization. The training and validation processes are performed in two approaches. The first approach uses default hyperparameters with segmented and non-segmented images. In the second approach, all hyperparameters of the models are optimized to train segmented datasets. The classification accuracy improved by 2.19% by utilizing segmentation and hyperparameter tuning further improved by 0.48%. The highest average classification accuracy of 97.92% is achieved using the Random Forest classifier to classify 40 classes of 10 different plant species. Accurate detection of plant disease leads to the sustained growth of plants throughout the growing span of the plants