Fast Lean Erasure-Coded Atomic Memory Object

In this work, we propose FLECKS, an algorithm which implements atomic memory objects in a multi-writer multi-reader (MWMR) setting in asynchronous networks and server failures. FLECKS substantially reduces storage and communication costs over its replication-based counterparts by employing erasure-codes. FLECKS outperforms the previously proposed algorithms in terms of the metrics that to deliver good performance such as storage cost per object, communication cost a high fault-tolerance of clients and servers, guaranteed liveness of operation, and a given number of communication rounds per operation, etc. We provide proofs for liveness and atomicity properties of FLECKS and derive worst-case latency bounds for the operations. We implemented and deployed FLECKS in cloud-based clusters and demonstrate that FLECKS has substantially lower storage and bandwidth costs, and significantly lower latency of operations than the replication-based mechanisms

ARES: Adaptive, Reconfigurable, Erasure coded, atomic Storage

Atomicity or strong consistency is one of the fundamental, most intuitive, and hardest to provide primitives in distributed shared memory emulations. To ensure survivability, scalability, and availability of a storage service in the presence of failures, traditional approaches for atomic memory emulation, in message passing environments, replicate the objects across multiple servers. Compared to replication based algorithms, erasure code-based atomic memory algorithms has much lower storage and communication costs, but usually, they are harder to design. The difficulty of designing atomic memory algorithms further grows, when the set of servers may be changed to ensure survivability of the service over software and hardware upgrades, while avoiding service interruptions. Atomic memory algorithms for performing server reconfiguration, in the replicated systems, are very few, complex, and are still part of an active area of research; reconfigurations of erasure-code based algorithms are non-existent. In this work, we present ARES, an algorithmic framework that allows reconfiguration of the underlying servers, and is particularly suitable for erasure-code based algorithms emulating atomic objects. ARES introduces new configurations while keeping the service available. To use with ARES we also propose a new, and to our knowledge, the first two-round erasure code based algorithm TREAS, for emulating multi-writer, multi-reader (MWMR) atomic objects in asynchronous, message-passing environments, with near-optimal communication and storage costs. Our algorithms can tolerate crash failures of any client and some fraction of servers, and yet, guarantee safety and liveness property. Moreover, by bringing together the advantages of ARES and TREAS, we propose an optimized algorithm where new configurations can be installed without the objects values passing through the reconfiguration clients

RADON: Repairable Atomic Data Object in Networks

Erasure codes offer an efficient way to decrease storage and communication costs while implementing atomic memory service in asynchronous distributed storage systems. In this paper, we provide erasure-code-based algorithms having the additional ability to perform background repair of crashed nodes. A repair operation of a node in the crashed state is triggered externally, and is carried out by the concerned node via message exchanges with other active nodes in the system. Upon completion of repair, the node re-enters active state, and resumes participation in ongoing and future read, write, and repair operations. To guarantee liveness and atomicity simultaneously, existing works assume either the presence of nodes with stable storage, or presence of nodes that never crash during the execution. We demand neither of these; instead we consider a natural, yet practical network stability condition N1 that only restricts the number of nodes in the crashed/repair state during broadcast of any message. We present an erasure-code based algorithm RADON_{C} that is always live, and guarantees atomicity as long as condition N1 holds. In situations when the number of concurrent writes is limited, RADON_{C} has significantly improved storage and communication cost over a replication-based algorithm RADON_{R}, which also works under N1. We further show how a slightly stronger network stability condition N2 can be used to construct algorithms that never violate atomicity. The guarantee of atomicity comes at the expense of having an additional phase during the read and write operations

Dynamic marketing capabilities, foreign ownership modes, sub-national locations and the performance of foreign affiliates in developing economies

Purpose – The purpose of this paper is to examine the role of dynamic marketing capabilities (DMC), foreign ownership modes and sub-national locations on the performance of foreign owned affiliates (FOAs) in developing economies. Design/methodology/approach – Based on a sample of 254 FOAs in Indian manufacturing sector (covering the period of 2000-2008 leading to 623 firm-year observations), the empirical paper adopts the panel data regression approach. Findings – The study confirms the significant importance of DMC to assist FOAs to gain better sales performance in an emerging market such as India. The findings indicate that Wholly Owned Foreign Affiliates (WOFAs) have better sales performance than International Joint Venture (IJV), and Majority-owned IJV (MAIJV) perform better than Minority-owned IJV (MIIJV) in the Indian manufacturing sector. The results confirm that effective deployment of DMC leads to better sales performance in WOFAs and to some extent in MAIJVs compared to MIIJVs. Perhaps the most interesting finding is that developing DMC in non-Metropolitan areas is associated with higher sales growth than in Metropolitan locations. Originality/value – The study contributes to the literature by examining the impact of DMC on performance of FOA by considering the organised manufacturing sector in a large and fast growing developing economy. In addition, the results for the moderating effects provide novel evidence of the conditions under which DMC of FOA interacts with different ownership modes and influence firm performance

Aerosol control on depth of warm rain in convective clouds

Aircraft measurements of cloud condensation nuclei (CCN) and microphysics of clouds at various altitudes were conducted over India during CAIPEEX (Cloud Aerosol Interaction and Precipitation Enhancement Experiment) phase I and II in 2009 and 2010 respectively. As expected, greater CCN concentrations gave rise to clouds with smaller drops with greater number concentrations (Nc). The cloud drop effective radius (re) increased with distance above cloud base (D). Warm rain became detectable at the tops of growing convective clouds when re exceeded 12 µm with appreciable liquid water content (> 0.01 g/Kg). The re is determined by the number of activated CCN, Nad, and D. The Nad can be approximated by the maximum measured values of Nc. Higher Nc resulted in greater D for reaching the re threshold for onset of warm rain, re, denoted as D. In extreme cases of highly polluted and moist air that formed the monsoon clouds over the Indo-Gangetic plains, D exceeded 6 km, well above the 0{degree sign}C isotherm level. The precipitation particles were initiated there as supercooled rain drops at a temperature of -8{degree sign}C. Giant CCN reduced re and D, by initiating raindrops at warmer temperatures. This effect was found mainly in dusty air masses over the Arabian Sea. Besides, the aerosol effect on D, D was found to decrease with increase in cloud water path

Comparative Analysis of Different Control Schemes for DC-DC Converter: a Review

DC-DC converters are some power electronic circuits that convert the DC voltage from one level to another. They have a very large area of applications ranging from computing to communication. They are widely used in appliance control transportations and high-power transmission. Its increasing demand is based on its capability of electrical energy conversion. The basic topologies of DC-DC converter are Buck converter and Boost converter, other topologies are derived from these two basic topologies. Mathematical modelling of both Buck converters is done. Some of the control schemes are summarized in this paper. Current mode control (CMC), PID, Sliding Mode (SM) control including their advantages and disadvantages are highlighted in this paper

Comparative Analysis of Different Control Schemes for DC-DC Converter

DC-DC converters are some power electronic circuits that convert the DC voltage from one level to another. They have a very large area of applications ranging from computing to communication. They are widely used in appliance control transportations, and high-power transmission. Its increasing demand is based on its capability of electrical energy conversion. The basic topology of DC-DC converter are Buck converter and Boost converter, other topologies are derived from this two-basic topology. In this paper mathematical modelling of both Buck and Boost converters has been done. Some of the control schemes are summarized in this paper. Current mode control (CMC), PID, control including their advantages and disadvantages are highlighted in this paper

Scale interactions near the foothills of Himalayas during CAIPEEX

Scale interactions associated with small scale (<100 km) dynamics might play a crucial role in the distribution of aerosol in the Himalayan foothills region. Turbulence measurements from a horizontal flight path during Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) are used to illustrate the scale interactions in the vertically sheared flow below the high-level subtropical westerly jet, which is important in the transport of pollution. Data analysis reveals the three dimensional property of large eddies that scale 10-12 km near the slopes, which could bring pollution from the valley to the Tibetan Plateau through a circulation adhering to the slopes. This circulation has a subsidence region away from the slopes and may also contribute to the buildup of pollution in elevated layers over the Plains. The vertical velocity and temperature spectra from research flight data showed clear indications of (-5/3) slope in the mesoscale range. The isotropic behavior of the velocity spectra was noticed for cloud-free traverses, while this behavior is distorted for cloudy conditions with the enhancement of energy at smaller scales as well as with low frequency gravity wave generation. A high-resolution cloud allowing model simulation over the flight path is used to examine the representation of these dynamical interactions in the numerical model. Based on the analysis of observational data and model inferences, a conceptual understanding of the flow in the region close to the foot hills and its role in the distribution of aerosol and cloud condensation nuclei is presented