Experiment on Activated Carbon Manufactured from Waste Coffee Grounds on the Compressive Strength of Cement Mortars

In this paper, we performed an experiment with activated carbon manufactured from waste coffee grounds on the compressive strength of normal cement mortars. The activated carbon reinforcement was manufactured from waste coffee grounds, and the collected coffee grounds were then transformed into activated carbon granules through the physical activation process. The activated carbon/cement composites were prepared by mixing cement with activated carbon granules with the weight fractions of 0.5%, 1%, 1.5%, 5%, and 10% cement. The experimental results show that adding activated carbon up to 1.5 wt% increased the early strength of cement mortars. Furthermore, we found that the composites incorporated with a small amount of activated carbon (≤1.5 wt%) had higher compressive strength over the curing period than the normal cement without activated carbon. We believe that these results would potentially have commonalities with morphological symmetry phenomena that occur on the surfaces of activated carbon granules

Liquidity Premium, Credit Costs, and Optimal Monetary Policy

I study how monetary policy affects firms' external financing decisions. More precisely, I study the transmission mechanism of monetary policy to credit costs in a general equilibrium macroeconomic model where firms issue corporate bonds or obtain bank loans, and corporate bonds are not just stores of value but also serve a liquidity role. The model shows that an increase in the nominal policy rate can lower the borrowing cost in the corporate bond market, while increasing that in the bank loan market, and I provide empirical evidence that supports this result. The model also predicts that a higher nominal policy rate induces firms to substitute corporate bonds for bank loans, which is supported by the existing empirical evidence. In the model, the Friedman rule is suboptimal so that keeping the cost of holding liquidity at a positive level is socially optimal. The optimal policy rate is an increasing function of the degree of corporate bond liquidity

Quantifying surface morphology of manufactured activated carbon and the waste coffee grounds using the Getis-Ord-Gi* statistic and Ripley’s K function

Activated carbon can be manufactured from waste coffee grounds via physical and/or chemical activation processes. However, challenges remain to quantify the differences in surface morphology between manufactured activated carbon granules and the waste coffee grounds. This paper presents a novel quantitative method to determine the quality of the physical and chemical activation processes performed in the presence of intensity inhomogeneity and identify surface characteristics of manufactured activated carbon granules and the waste coffee grounds. The spatial density was calculated by the Getis-Ord-Gi* statistic in scanning electron microscopy images. The spatial characteristics were determined by analyzing Ripley’s K function and complete spatial randomness. Results show that the method introduced in this paper is capable of distinguishing between manufactured activated carbon granules and the waste coffee grounds, in terms of surface morphology

Essays on Asset Liquidity and Its Macroeconomic Effects

The financial sector influences the macroeconomy in many aspects. Monetary policy affects firms' external financing and investment decisions through its impact on credit costs in financial markets. Institutional reform in financial markets can affect this monetary policy transmission. Safe assets are an important part of an economy. They are demanded by agents who look for a safe store of value, and how safe they are and how large their supply is affect the liquidity property of those assets and welfare of the economy. Financial crises, like the Great Recession, are not only costly in terms of output and investment in the short run, but they also cause productivity slowdown in the longer horizon through their impact on research and development (R&D). This dissertation contributes to the understanding of these issues. Chapter One studies how monetary policy affects credit costs in financial markets and firms' external financing decisions. I study this transmission mechanism of monetary policy in a general equilibrium macroeconomic model where firms issue corporate bonds or obtain bank loans, and corporate bonds are not just stores of value but also serve a liquidity role. The model shows that an increase in the nominal policy rate can lower the borrowing cost in the corporate bond market, while increasing that in the bank loan market, and I provide empirical evidence that supports this result. The model also predicts that a higher nominal policy rate induces firms to substitute corporate bonds for bank loans, which is supported by the existing empirical evidence. In the model, the Friedman rule is suboptimal so that keeping the cost of holding liquidity at a positive level is socially optimal. The optimal policy rate is an increasing function of the degree of corporate bond liquidity. Chapter Two, joint work with Athanasios Geromichalos and Lucas Herrenbrueck, studies the relationship between an asset's safety and liquidity. Recently, a lot of attention has been paid to the role "safe and liquid assets" play in the macroeconomy. Many economists take as given that safer assets will also be more liquid, and some go a step further by practically using the two terms as synonyms. However, they are not synonyms: safety refers to the probability that the (issuer of the) asset will pay the promised cash flow, and liquidity refers to the ease with which an asset can be sold if needed. Mixing up these terms can lead to confusion and wrong policy recommendations. In this chapter, we build a multi-asset model in which an asset's safety and liquidity are well-defined and distinct from one another, and examine the relationship between an asset's safety and liquidity in general equilibrium. We show that the commonly held belief that "safety implies liquidity" is generally justified, but there may be exceptions. We then describe the conditions under which a relatively riskier asset can be more liquid than its safe(r) counterparts. Finally, we use our model to rationalize the puzzling observation that AAA corporate bonds are considered less liquid than (the riskier) AA corporate bonds.Chapter Three studies how financial crises affect R&D activities, which is one of the key determinants of productivity. Recent literature documents the slow recovery and the productivity slowdown in the aftermath of financial crises. Several theoretical papers propose models to rationalize this. Some attribute it to a decline in the level of R&D, while others to a decline in the effectiveness of R&D. Which channel is more empirically relevant is an important question in guiding theoretical works. This chapter contributes to the literature by answering this question. Using data on 30 OECD countries over the years 1981-2016, I estimate the responses of R&D upon recessions and financial crises, using local projections. While recessions are bad times for output and investment in general, most of the responses are coming from the non-R&D part of investment. R&D is overall unresponsive to recessions, even to financial crises. This result suggests that a decline in R&D efficiency is a more empirically relevant channel to the productivity slowdown

Drone-Assisted Image Processing Scheme using Frame-Based Location Identification for Crack and Energy Loss Detection in Building Envelopes

This paper presents improved methods to detect cracks and thermal leakage in building envelopes using unmanned aerial vehicles (UAV) (i.e., drones) with video camcorders and/or infrared cameras. Three widely used contour detectors of Sobel, Laplacian, and Canny algorithms were compared to find a better solution with low computational overhead. Furthermore, a scheme using frame-based location identification was developed to effectively utilize the existing approach by finding the current location of the drone-assisted image frame. The results showed a simplified drone-assisted scheme along with automation, higher accuracy, and better speed while using lower battery energy. Furthermore, this paper found that the cost-effective drone with the attached equipment generated accurate results without using an expensive drone. The new scheme of this paper will contribute to automated anomaly detection, energy auditing, and commissioning for sustainably built environments

Experiment on Activated Carbon Manufactured from Waste Coffee Grounds on the Compressive Strength of Cement Mortars

In this paper, we performed an experiment with activated carbon manufactured from waste coffee grounds on the compressive strength of normal cement mortars. The activated carbon reinforcement was manufactured from waste coffee grounds, and the collected coffee grounds were then transformed into activated carbon granules through the physical activation process. The activated carbon/cement composites were prepared by mixing cement with activated carbon granules with the weight fractions of 0.5%, 1%, 1.5%, 5%, and 10% cement. The experimental results show that adding activated carbon up to 1.5 wt% increased the early strength of cement mortars. Furthermore, we found that the composites incorporated with a small amount of activated carbon (≤1.5 wt%) had higher compressive strength over the curing period than the normal cement without activated carbon. We believe that these results would potentially have commonalities with morphological symmetry phenomena that occur on the surfaces of activated carbon granules

Analysis of Cross-Association between mRNA Expression and RNAi Efficacy for Predictive Target Discovery in Colon Cancers

The availability of large-scale, collateral mRNA expression and RNAi data from diverse cancer cell types provides useful resources for the discovery of anticancer targets for which inhibitory efficacy can be predicted from gene expression. Here, we calculated bidirectional cross-association scores (predictivity and descriptivity) for each of approximately 18,000 genes identified from mRNA and RNAi (i.e., shRNA and sgRNA) data from colon cancer cell lines. The predictivity score measures the difference in RNAi efficacy between cell lines with high vs. low expression of the target gene, while the descriptivity score measures the differential mRNA expression between groups of cell lines exhibiting high vs. low RNAi efficacy. The mRNA expression of 90 and 74 genes showed significant (p < 0.01) cross-association scores with the shRNA and sgRNA data, respectively. The genes were found to be from diverse molecular classes and have different functions. Cross-association scores for the mRNA expression of six genes (CHAF1B, HNF1B, HTATSF1, IRS2, POLR2B and SATB2) with both shRNA and sgRNA efficacy were significant. These genes were interconnected in cancer-related transcriptional networks. Additional experimental validation confirmed that siHNF1B efficacy is correlated with HNF1B mRNA expression levels in diverse colon cancer cell lines. Furthermore, KIF26A and ZIC2 gene expression, with which shRNA efficacy displayed significant scores, were found to correlate with the survival rate from colon cancer patient data. This study demonstrates that bidirectional predictivity and descriptivity calculations between mRNA and RNAi data serve as useful resources for the discovery of predictive anticancer targets

Rapid and Effective Electrical Conductivity Improvement of the Ag NW-Based Conductor by Using the Laser-Induced Nano-Welding Process

To date, the silver nanowire-based conductor has been widely used for flexible/stretchable electronics due to its several advantages. The optical nanowire annealing process has also received interest as an alternative annealing process to the Ag nanowire (NW)-based conductor. In this study, we present an analytical investigation on the phenomena of the Ag NWs’ junction and welding properties under laser exposure. The two different laser-induced welding processes (nanosecond (ns) pulse laser-induced nano-welding (LINW) and continuous wave (cw) scanning LINW) are applied to the Ag NW percolation networks. The Ag NWs are selectively melted and merged at the junction of Ag NWs under very short laser exposure; these results are confirmed by scanning electron microscope (SEM), focused-ion beam (FIB), electrical measurement, and finite difference time domain (FDTD) simulation