827 research outputs found
Sum-Rate Maximizing Cell Association via Dual-Connectivity
This paper proposes a dual-connectivity (DC) profile allocation algorithm, in
which a central macro base station (MBS) is underlaid with randomly scattered
small base stations (SBSs), operating on different carrier frequencies. We
introduce two dual-connectivity profiles and the differences among them. We
utilize the characteristics of dual-connectivity profiles and their applying
scenarios to reduce feasible combination set to consider. Algorithm analysis
and numerical results verify that our proposed algorithm achieve the optimal
algorithm's performance within 5 \% gap with quite low complexity up to
times.Comment: 10 pages, 5 figures, conferenc
PDPD: Packet Delivery Prediction-based Data Forwarding to Moving Targets in Vehicular Networks
Department of Electrical EngineeringVehicular Ad hoc Network (VANET) is one of technologies to realize various ITS services that provide safe driving and efficient traffic condition. VANET consists of moving nodes, and hence its topology frequently changes. In VANETs, multi-hop data delivery is complicated by the fact that vehicular networks are highly mobile and frequently disconnected. In this thesis, we develop a novel forwarding scheme that accounts for the vehicle density, and delivers packets in a reliable and timely manner. We pay attention to the encounter event between two vehicles and the probability of successful transmission at the encounter place to guide forwarding decision. The proposed forwarding scheme uses traffic statistics to predict vehicle encounters, and optimize forwarding decision by taking into consideration the quality of wireless communications. We verify the results through simulations and show that our proposed scheme achieves reliable data transmission in VANET.ope
Essays on Economic Development and Gains from Trade
In each of the three essays, I investigate gains from trade originating at three sources: i) vertical specialization through intermediate goods trade, ii) improving allocation of resources across heterogeneous firms, and iii) developing countries\u27 technological advancement towards particular factors of production, either skilled labor or unskilled labor. I develop three models of trade, featuring multi-stage production, micro-distortions with endogenous entry and exit, and directed technical change. First, I show quantitatively that trade barriers play an important role in hindering the integration of poor countries in global market through trade in intermediate goods. Second, I find that the substantial impact of trade is to improve allocation on the extensive margin by forcing out less productive firms and replacing those with more productive firms. Third, I prove that gains from trade are magnified due to endogenously directed technical change.
In the first chapter, I investigate whether the gains from trade are systematically related to the level of development. This chapter argues that we need to consider a multi-stage production process to answer the questions. I develop a Ricardian trade model which features two stages of production. At each stage, gains from trade can be measured by the home trade share, a measure of market integration.Looking at each stage\u27s home trade shares across countries, I find different specialization patterns: rich countries are integrated at each stage whereas most poor countries are not integrated. Measured gains from trade are more than ten times larger for the 10 richest countries than for the 10 poorest countries. For the rich countries, two-thirds of the gains are accounted for by second stage trade. Poor countries\u27 small gains from trade are accounted entirely by first stage trade. I argue that difference in trade barriers between rich countries and poor countries, particularly in the second stage of production, limit trade gains for poor countries.
Second chapter studies the impact of international trade on sectoral total factor productivity (TFP). Misallocation of resources across heterogeneous firms impacts negatively on TFP. In this chapter, I study trade liberalization as a source of reducing misallocation across firms, thus leading to higher TFP. Misallocation is reduced on the extensive margin by forcing out less productive firms and replacing those with more productive firms. Using firm-level panel data on Chinese manufacturing, I measure distortions across firms and over time as in Hsieh and Klenow (2009). I find that the allocation of factors improves more in industries that experience a higher reduction in tariff rates. Less productive firms are more likely to exit in sectors that experience a higher tariff reduction. In addition, entrants in more liberalized sectors are more productive relative to entrants in less liberalized sectors. Reducing misallocation on the extensive margin has quantitatively large effect on TFP.
In the third chapter, I analyze how technical change is directed towards particular factors of production in international trade between the North and the South. Typical assumption in the literature is that either technologies are exogenously given or technical change is allowed only in the North. I present a model of international trade with endogenous growth by allowing the South to direct their technology. This chapter studies the implications of the technical change for the gains from trade and the skill premium. Main result shows that more R&D is directed towards skill-augmenting technology in the North than in the South in sectors with the same skill-intensity. Technical change induced by lowering trade costs can increase the skill premium in both the North and the South.Gains from trade are magnified due to endogenous directed technical change. This results in larger gains from trade compared with the model where technical change is either not allowed or allowed only in the North
Mechanical Seal Failure in the Oil Flooded Compressor
Case StudiesWe consistently experienced mechanical seal failure of the oil–flooded screw compressor in the refrigeration system. The first seal failure happened on July, 2015, which is a year passed since start-up. This seal failure was repeated 4 times every 3 months. All the seal failures were caused by the oil
carbonization. These phenomena happened on the outboard seal only and all seal failures’ phenomena were almost same. We finally solved this problem by adjusting the seal face flatnes
Online home appliance control using EEG-Based brain-computer interfaces
Brain???computer interfaces (BCIs) allow patients with paralysis to control external devices by mental commands. Recent advances in home automation and the Internet of things may extend the horizon of BCI applications into daily living environments at home. In this study, we developed an online BCI based on scalp electroencephalography (EEG) to control home appliances. The BCI users controlled TV channels, a digital door-lock system, and an electric light system in an unshielded environment. The BCI was designed to harness P300 andN200 components of event-related potentials (ERPs). On average, the BCI users could control TV channels with an accuracy of 83.0% ?? 17.9%, the digital door-lock with 78.7% ?? 16.2% accuracy, and the light with 80.0% ?? 15.6% accuracy, respectively. Our study demonstrates a feasibility to control multiple home appliances using EEG-based BCIs
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