Commodity Components Research Articles

Sodium oleate potentiates the concurrent overproduction of lipids and carotenoids in Chlorella vulgaris towards biofuel and nutraceutical applications

Microalgal metabolites have emerged as potential commodity components due to their notable beneficial nutritional and economic properties, and thus, their overproduction is of paramount importance to combat the existing ecological and dietary issues. However, the production titer of these metabolites by the algal systems at optimal cultivation conditions is inadequate to meet the burgeoning global demand for those metabolites. Therefore, a pressing demand remains to concurrently co-produce valuable metabolites without compromising cellular biomass production. Here, we report an effective strategy that simultaneously overproduces lipids, biomass and carotenoids in Chlorella vulgaris by providing sodium oleate (NaOL) in the cultivation medium. Supplement of sodium oleate at the optimal concentration (50 µg/mL) at increased light intensity enhances cellular growth rate in a dose-dependent manner. Total lipid content was quantified, which showed that lipid content was significantly increased in the NaOL-treated cells by 2.08-fold than that of the control cells. Interestingly, spectrophotometric determination of total carotenoids showed that carotenoid content was increased by 2.48-fold in the T5 (50 µg/mL) NaOL treated cells compared to the control. Interestingly antioxidant analysis showed that NaOL provision alleviated the antioxidant potential of the algal cells. Together, this report exemplifies the potential strategy to preclude the existing intricacies of co-producing metabolites in C. vulgaris by supplementing NaOL, thereby highlighting the viable chemical engineering approach for the biological production of commercially essential metabolites in microalgae.

HV-SNSP: A Low-Overhead Data Recovery Method Based on Cross-Checking

The failure of a single unreliable commodity component is very common in large-scale distributed storage systems. In order to ensure the reliability of data in large-scale distributed storage systems, many studies have emerged one after another. Among them, Erasure Codes are widely used in actual storage systems, such as Hadoop Distributed File System (HDFS), which provides high fault-tolerance with lower storage overhead. However, usually the recovery of erasure-coded storage system when encountering node failure results in severe cross-node and cross-rack bandwidth consumption, which affects the efficiency of failure recovery and wastes additional resources. In this paper, we improve the erasure coding storage strategy in distributed storage systems, and propose a low-overhead data recovery method based on cross-checking, namely HV-SNSP. In HV-SNSP, horizontal and vertical cross parity checking is realized by adding RS parity inside the data node, that is, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}^{\mathrm {RS(n, k)}}$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}^{\mathrm {RS(n', \textrm {}k')}}$ </tex-math></inline-formula> storage architecture. Based on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{H}^{\mathrm {RS(n, \textrm {}k)}}$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{V}^{\mathrm {RS(n', k')}}$ </tex-math></inline-formula> , a low-cost supply node selection strategy, namely SNSP, is designed, and nodes with shorter network distance and lower load are selected to participate in recovery. This strategy can effectively reduce the amount of data transmission, shorten the recovery time, and improve the recovery efficiency. The experimental results show that compared with traditional RS, HV-SNSP can reduce the amount of cross-rack data transmission by 62.5% during data recovery, and can shorten the recovery time by up to 42.41%; Compared with D3, HV-SNSP can reduce the occupation of cross-rack bandwidth by 25% and shorten the recovery time by 36.58%.

SkiMon: A Wireless Body Area Network for Monitoring Ski Flex and Motion during Skiing Sports.

Monitoring and gathering data on sporting activities holds significant promise for athletes, equipment developers, and physical fitness clinicians. Wireless Body Area Networks are being used in sporting environments as a means of gathering data, providing feedback, and helping to gain understanding of athletic activities. Applying WBANs to skiing situations, which have higher vibration, velocities, and damp environments than many other sports, can open up opportunities to understand the dynamics of skiing equipment behaviors, skiing routes on mountains, and how individuals react when skiing. To support these outcomes, a prototype WBAN-style off the shelf component system called SkiMon was proposed, implemented, and tested. The SkiMon system uses inexpensive ESP8266, Raspberry Pi, and sensor devices to gather high quality motion and location tracking data on skiers in real-world skiing conditions. By using IEEE 802.11b/g/n wireless networks, SkiMon is able to sample data at a minimum of 50 Hz, which is enough to model most ski vibration behaviors. These data results are shown to reflect ground truth 3D maps and the acceleration data comports with earlier works on ski vibration testing. Overall, a WBAN-based commodity components solution shows promise as a high quality sensor platform for tracking and modeling skiing activities.

Equity-Driven Sensing System for Measuring Skin Tone-Calibrated Peripheral Blood Oxygen Saturation (OptoBeat): Development, Design, and Evaluation Study.

Many commodity pulse oximeters are insufficiently calibrated for patients with darker skin. We demonstrate a quantitative measurement of this disparity in peripheral blood oxygen saturation (SpO2) with a controlled experiment. To mitigate this, we present OptoBeat, an ultra-low-cost smartphone-based optical sensing system that captures SpO2 and heart rate while calibrating for differences in skin tone. Our sensing system can be constructed from commodity components and 3D-printed clips for approximately US $1. In our experiments, we demonstrate the efficacy of the OptoBeat system, which can measure SpO2 within 1% of the ground truth in levels as low as 75%. The objective of this work is to test the following hypotheses and implement an ultra-low-cost smartphone adapter to measure SpO2: skin tone has a significant effect on pulse oximeter measurements (hypothesis 1), images of skin tone can be used to calibrate pulse oximeter error (hypothesis 2), and SpO2 can be measured with a smartphone camera using the screen as a light source (hypothesis 3). Synthetic skin with the same optical properties as human skin was used in ex vivo experiments. A skin tone scale was placed in images for calibration and ground truth. To achieve a wide range of SpO2 for measurement, we reoxygenated sheep blood and pumped it through synthetic arteries. A custom optical system was connected from the smartphone screen (flashing red and blue) to the analyte and into the phone's camera for measurement. The 3 skin tones were accurately classified according to the Fitzpatrick scale as types 2, 3, and 5. Classification was performed using the Euclidean distance between the measured red, green, and blue values. Traditional pulse oximeter measurements (n=2000) showed significant differences between skin tones in both alternating current and direct current measurements using ANOVA (direct current: F2,5997=3.1170 × 105, P<.01; alternating current: F2,5997=8.07 × 106, P<.01). Continuous SpO2 measurements (n=400; 10-second samples, 67 minutes total) from 95% to 75% were captured using OptoBeat in an ex vivo experiment. The accuracy was measured to be within 1% of the ground truth via quadratic support vector machine regression and 10-fold cross-validation (R2=0.97, root mean square error=0.7, mean square error=0.49, and mean absolute error=0.5). In the human-participant proof-of-concept experiment (N=3; samples=3 × N, duration=20-30 seconds per sample), SpO2 measurements were accurate to within 0.5% of the ground truth, and pulse rate measurements were accurate to within 1.7% of the ground truth. In this work, we demonstrate that skin tone has a significant effect on SpO2 measurements and the design and evaluation of OptoBeat. The ultra-low-cost OptoBeat system enables smartphones to classify skin tone for calibration, reliably measure SpO2 as low as 75%, and normalize to avoid skin tone-based bias.

When to Lock the Volatile Input Price? Procurement of Commodity Components Under Different Pricing Schemes

Problem definition: We study a two-stage supply chain, where the supplier procures a key component to manufacture a product and the buyer orders from the supplier to meet a price-sensitive demand. As the input price is volatile, the two parties enter into either a standard contract, where the buyer orders just before the supplier starts production, or a time-flexible contract, where the buyer can lock a wholesale price in advance. Moreover, we consider three selling-price schemes: Market Driven, Cost Plus, and Profit Max. Academic/practical relevance: This problem is motivated by real practices in the cloud industry. Our model and optimization approach can address similar problems in other industries as well. Methodology: We assume that the input price follows a geometric Brownian motion. To determine the optimal ordering time, we propose an optimization approach that is different from the classic approach by Dixit et al. ( 1994 ) and Li and Kouvelis ( 1999 ). Our approach leads to deeper analytical results and more transparent ordering policy. Through a numerical experimentation, we compare profitability of different parties under different contracts, pricing schemes, and market conditions. Results: The buyer’s ordering policy is determined by a threshold policy based on the current time and input price; the optimal threshold depends on not only the drift and volatility of the input price but also, their relative magnitude. The supplier’s optimal procurement time should be determined by analyzing a trade-off between the holding cost of storing the components and the future input-price movement. Managerial implications: Under the Profit-Max and the Cost-Plus pricing schemes, the time-flexible contract is a Pareto improvement compared with the standard contract, whereas under the Market-Driven pricing scheme, the supplier may be better off under the standard contract. Moreover, although the most favorable scenario for the buyer is under the Profit-Max pricing scheme, the most favorable scenario for the supplier oftentimes is under the Cost-Plus pricing scheme. Furthermore, this study provides valuable insights into impacts of various characteristics of the component market, such as the trend and volatility of the input price, on the expected profit of the supply chain and its split between the two parties.

Sense Your Power

Energy-constrained sensor nodes can adaptively optimize their energy consumption if a continuous measurement is provided. This is of particular importance in scenarios of high dynamics such as with energy harvesting. Still, self-measuring of power consumption at reasonable cost and complexity is unavailable as a generic system service. In this article, we present ECO, a hardware-software co-design that adds autonomous energy management capabilities to a large class of low-end IoT devices. ECO consists of a highly portable hardware shield built from inexpensive commodity components and software integrated into the RIOT operating system. RIOT supports more than 200 popular microcontrollers. Leveraging this flexibility, we assembled a variety of sensor nodes to evaluate key performance properties for different device classes. An overview and comparison with related work shows how ECO fills the gap of in situ power attribution transparently for consumers and how it improves over existing solutions. We also report about two different real-world field trials, which validate our solution for long-term production use.

Зона свободной торговли ЕАЭС–Индия: параметры и потенциал

In 2017, negotiations on the free trade area between India and the EAEU countries entered an active phase. The directions of the negotiation process cover the issues of import tariff liberalization, and the elimination of non-tariff restrictions. The study aims at quantifying the potential impact of mutual tariff liberalization on the dynamics of bilateral trade between Russia and India, in order to develop key principles for Russia's negotiating position (as part of the EAEU), taking into account its strategic priorities. The research methodology bases on the SMART partial equilibrium model and a qualitative analysis of contemporary trends in import demand and the degree of India’s trade protectionism towards imports from the EAEU countries. The study found that the symmetric bilateral tariff liberalization may result in the higher potential increase in Russian exports to India than in the corresponding effects on imports, which will increase the bilateral trade surplus. This is in the interests of Russia, but it hardly meets the strategic interests of India due to its chronic trade deficit. The free trade area may lead to the diversification of the commodity component of Russian exports due to the growing export supplies of Russian coal, to a lesser extent – of metals (aluminum, copper and articles thereof). However, the opportunities to increase the share of high-tech products in the structure of Russian exports remain limited. The free trade area can become an important tool for strengthening Russian exporters of fertilizers, as well as certain categories of agricultural products. In turn, Indian exporters can strengthen their positions on the Russian market of medicines, as well as increase the share of textile products, jewelry and certain categories of agricultural products. The results can serve for developing the position of Russia (as a EAEU member) in multilateral negotiations.

Low-Complexity Design and Validation of Wireless Motion Sensor Node to Support Physiotherapy.

We present a motion sensor node to support physiotherapy, based on an Inertial Measurement Unit (IMU). The node has wireless interfaces for both data exchange and charging, and is built based on commodity components. It hence provides an affordable solution with a low threshold to technology adoption. We share the hardware design and explain the calibration and validation procedures. The sensor node has an autonomy of 28 h in operation and a standby time of 8 months. On-device sensor fusion yields static results of on average ° with a drift of 2° per half hour. The final prototype weighs 38 g and measures ø6 cm × cm. The resulting motion sensor node presents an easy to use device for both live monitoring of movements as well as interpreting the data afterward. It opens opportunities to support and follow up treatment in medical cabinets as well as remotely.

Design Flow for Active Interposer-Based 2.5-D ICs and Study of RISC-V Architecture With Secure NoC

Interposer-based 2.5-D integrated circuits (ICs) enable the chip-level reuse of hard intellectual properties (IPs), also known as chiplets. Such system-level integration shortens the design cycle considerably for large-scale and heterogeneous chips. Besides traditional interposers, which only provide passive elements and routing, active interposers are furthermore comprised of logic components. When implemented carefully using a dedicated electronic design automation (EDA) flow, an active interposer can significantly improve the design quality and flexibility for 2.5-D ICs. In this article, we present a complete EDA flow and design strategies targeting, such active interposer-based 2.5-D ICs. Our key contributions include the coanalysis of power, performance, signal and power integrity, and the related co-optimization of chiplets and the active interposer. Our benchmark is a 64-core RISC-V architecture, organized into multiple chiplets and interconnected by a system-level network-on-chip (NoC). For efficiency, we embed the NoC routers and integrated voltage regulators (IVRs) into the active interposer. Moreover, we integrate security monitors into the interposer-based NoC to protect the system and its shared memories against adversarial traffic. The simple yet powerful benefit of this implementation is to offer security by construction, as it is based on a clear physical separation between critical and trusted components (the system-level NoC) versus commodity components (the chiplets). We contrast our active, secured design to a passive, unsecured design baseline of the same RISC-V benchmark and find that the active design reduces the silicon area by 18.5%, power by 3.2%, and IR drop by 73.7%.

Biotechnological perspectives to augment the synthesis of valuable biomolecules from microalgae by employing wastewater

Increasing population and urbanization bring along depletion of water resources with notable discharge of industrial and municipal wastewater which is rich in nutrients. Microalgae hold great promise for assimilating the nutrient compounds, particularly the intricate nitrogen (N) and phosphorus (P) compounds from wastewater, resulting in algal biomass enriched with various valuable biomolecules. However, development of strategies involving the cultivation of microalgae for wastewater treatment and production of commodity components is still in its infancy. In this review, the current status of microalgae-mediated wastewater treatment, the existing technological bottlenecks that hamper the effective use of photosynthetic microalgae, and innovative solutions to obviate the shortcomings are discussed. Also, this article highlights the potential use of genetic engineering technologies in overproducing algal biomolecules without impeding cellular biomass accumulation by regulating critical metabolic targets for the development of engineered algal strains. In this context, adaptive laboratory evolution (ALE) could be the promising tool to further empower the engineered strains to mitigate the adverse effect from the wastewater cultivation medium. In summary, this review provides novel insights into the application of genetic engineering strategies for overproducing algal biomass and valuable biomolecules such as lipids and polyunsaturated fatty acids using wastewater in a cost-effective manner.

Deterministic Data Distribution for Efficient Recovery in Erasure-Coded Storage Systems

Due to individual unreliable commodity components, failures are common in large-scale distributed storage systems. Erasure codes are widely deployed in practical storage systems to provide fault tolerance with low storage overhead. However, random data distribution (RDD), commonly used in erasure-coded storage systems, induces heavy cross-rack traffic, load imbalance, and random access, which adversely affects failure recovery. In this article, with orthogonal arrays, we define a Deterministic Data Distribution (D 3 ) to uniformly distribute data/parity blocks among nodes, and propose an efficient failure recovery approach based on D 3 , which minimizes the cross-rack repair traffic against a single node failure. Thanks to the uniformity of D 3 , the proposed recovery approach balances the repair traffic not only among nodes within a rack but also among racks. We implement D 3 over Reed-Solomon codes and Locally Repairable Codes in Hadoop Distributed File System (HDFS) with a cluster of 28 machines. Compared with RDD, our experiments show that D3 significantly speeds up the failure recovery up to 2.49 times for RS codes and 1.38 times for LRCs. Moreover, D 3 supports front-end applications better than RDD in both of normal and recovery states.

Affordable and robust phenotyping framework to analyse root system architecture of soil-grown plants.

The phenotypic analysis of root system growth is important to inform efforts to enhance plant resource acquisition from soils; however, root phenotyping remains challenging because of the opacity of soil, requiring systems that facilitate root system visibility and image acquisition. Previously reported systems require costly or bespoke materials not available in most countries, where breeders need tools to select varieties best adapted to local soils and field conditions. Here, we report an affordable soil-based growth (rhizobox) and imaging system to phenotype root development in glasshouses or shelters. All components of the system are made from locally available commodity components, facilitating the adoption of this affordable technology in low-income countries. The rhizobox is large enough (approximately 6000cm2 of visible soil) to avoid restricting vertical root system growth for most if not all of the life cycle, yet light enough (approximately 21kg when filled with soil) for routine handling. Support structures and an imaging station, with five cameras covering the whole soil surface, complement the rhizoboxes. Images are acquired via the Phenotiki sensor interface, collected, stitched and analysed. Root system architecture (RSA) parameters are quantified without intervention. The RSAs of a dicot species (Cicer arietinum, chickpea) and a monocot species (Hordeum vulgare, barley), exhibiting contrasting root systems, were analysed. Insights into root system dynamics during vegetative and reproductive stages of the chickpea life cycle were obtained. This affordable system is relevant for efforts in Ethiopia and other low- and middle-income countries to enhance crop yields and climate resilience sustainably.

Natural resources based integrated agricultural system for the sustainable plantation industry

Crop production is the management of plant environmental factors to achieve maximum and sustainable production. Thus the production of crops in an integrated agricultural system must be capable not only to integrate and to harmonize between commodity components, various species of crops and livestock, but also to integrate and harmonize these commodity components with various elements in every environmental factor, both biotic and abiotic. The integration and harmonizasion based on renewable natural resources is an effort to realize a sustainable plant production (for profit, for people and for planet). Two groups of environmental factors grow plants, namely Abiotics: Climate and Edafik (land), and Fire; And Biotics: Disruptive organisms (pests, diseases and weeds), beneficial organisms (land caverage vegetations, bacteria and non-pathogenic fungi, symbiotic). Climate and soil factors are the two main factors interacting with the changing environmental factors of crops as a result of climate change, whether global, local, or micro. These changes have been identified to be environmental stresses for plants. Abiotic stresses of temperature, water and nutrients provide a weakening condition, thereby increasing the vulnerability of plants to biotic stress. Various efforts need to be continued to develop integrated agricultural production technology that utilizes local natural resources to enable plants to adapt to environmental stress. Below, Integrated agriculture system will be describe into on-farm subsystem (horizontal diversification) and off-farm subsystem (vertical diversification).

Cloud computing

Cloud computing is a mode of acquisition of infrastructure where a cloud service provides on demand computing and on-demand storage, accessible over the web, with a matching business model, namely pay-per-use. Lower cost, sometimes a factor of five, is achieved by automating operations in warehouse-sized data centres, sharing the hefty burden of cooling, physical security, and power backup, and the use of commodity components. As access to storage managed by cloud service providers gained market acceptance, the phrase “the cloud” came into use to refer to the location of information stored with a cloud service provider to be shared (business documents and photos) or copied for backup (against losing a phone or deleting information on a laptop). Security, and to a lesser extent privacy, concerns are the major barriers to the adoption of cloud computing, but the leading cloud service providers have responded to the point that sensitive information, such as medical records and credit-card-holder data, is now held in the cloud.

Dynamic Stable Supplier Coalitions and Invariance in Assembly Systems with Commodity Components

Assembly systems are composed of suppliers selling components to an assembler, who configures a final product for sale to the market. This is commonplace in many supply chains, such as healthcare and automobiles for example. Suppliers in such systems often form coalitions to enhance their bargaining power as well as for economies of scale. In the paper titled “Dynamic Stable Supplier Coalitions and Invariance in Assembly Systems with Commodity Components,” the authors show some interesting findings—how payoff allocation among coalition members can affect outcomes and when such outcomes are robust to allocation rules.

An integrated cyber-physical system for automatic identification of massive discs

Optical discs can reliably preserve massive data for long-term in low-cost. When querying these accumulative data, it is necessary to quickly obtain the query results, and to seek the physical location of the corresponding optical disc. To this end, it demands each disc have a unique identifier in both the cyber and physical worlds, make massive data be managed effectively, conveniently, and credibly. This paper designs a batch-disc automatic identification system, which integrates common optical disc recorders, printers, and cameras, automatically to print physical label and to burn logical identification on each disc. Consider that each commodity component has its own internal independent timing control and a specific external interface. This study designed and developed a customized mechanical structure, as well as a global software scheduling mechanism to coordinate physical behavior and logical control. The experimental results show that the system can continuously identify 200 discs at once, averaging 2 minutes per disc.

The U.S. Shale Oil Revolution and the Behavior of Commodity Prices

The United States is committed to technological improvements in horizontal drilling and hydraulic fracturing in its drive of toppling the world's leading oil producers by the mid-2020s and evolving into a net oil exporter by 2030. Consequently, these technological innovations revolutionized the U.S. oil sector and the international oil market with increasing relevance of the shale oil and attendant shock spillovers to financial and commodity markets. Upon these attractions and consistent with evidence in the literature, we trace the oil price and commodity price dynamics to the shale oil revolution using a recursive structural VAR model of the shale supply shocks. In line with the standard practice of ensuring sensitivity of results, we conduct analyses such as impulse responses, forecast-error variance decomposition, and historical decompositions to accommodate energy and nonenergy commodity components. We show, in addition to the popular view in the extant literature, that the shale oil revolution is not only associated with the recent oil price plunge, but also responsible for the tumble in the total energy-based commodity prices with crude oil price being just a component.

Harmonium

We introduce Harmonium , a novel ultra wideband (UWB) RF localization architecture that achieves decimeter-scale accuracy indoors. Harmonium strikes a balance between tag simplicity and processing complexity to provide fast and accurate indoor location estimates. Harmonium uses only commodity components and consists of a small, inexpensive, lightweight, and FCC-compliant UWB transmitter or tag , fixed infrastructure anchors with known locations, and centralized processing that calculates the tag’s position. Anchors employ a new frequency-stepped narrowband receiver architecture that rejects narrowband interferers and extracts high-resolution timing information without the cost or complexity of traditional UWB approaches. In a complex indoor environment, 90% of position estimates obtained with Harmonium exhibit less than 31 cm of error with an average of 9 cm of inter-sample noise. In non-line-of-sight conditions (i.e., through-wall), 90% of position error is less than 42 cm. The tag draws 75 mW when actively transmitting, or 3.9 mJ per location fix at the 19 Hz update rate. Tags weigh 3 g and cost $4.50 USD at modest volumes. Furthermore, VLSI-based design concepts are identified for a simple, low-power realization of the Harmonium tag to offer a roadmap for the realization of Harmonium concepts in future integrated systems. Harmonium introduces a new design point for indoor localization and enables localization of small, fast objects such as micro quadrotors, devices previously restricted to expensive optical motion capture systems.

Robust and Probabilistic Failure-Aware Placement

Motivated by the growing complexity and heterogeneity of modern data centers, and the prevalence of commodity component failures, this article studies the failure-aware placement problem of placing tasks of a parallel job on machines in the data center with the goal of increasing availability. We consider two models of failures: adversarial and probabilistic. In the adversarial model, each node has a weight (higher weight implying higher reliability) and the adversary can remove any subset of nodes of total weight at most a given bound W and our goal is to find a placement that incurs the least disruption against such an adversary. In the probabilistic model, each node has a probability of failure and we need to find a placement that maximizes the probability that at least K out of N tasks survive at any time. For adversarial failures, we first show that (i) the problems are in Σ 2 , the second level of the polynomial hierarchy; (ii) a variant of the problem that we call R obust F ap (for Robust Failure-Aware Placement) is co-NP-hard; and (iii) an all-or-nothing version of R obust F ap is Σ 2 -complete. We then give a polynomial-time approximation scheme (PTAS) for R obust F ap , a key ingredient of which is a solution that we design for a fractional version of R obust F ap . We then study H ier R obust F ap , which is the fractional R obust F ap problem over a hierarchical network, in which failures can occur at any subset of nodes in the hierarchy, and a failure at a node can adversely impact all of its descendants in the hierarchy. To solve H ier R obust F ap , we introduce a notion of hierarchical max-min fairness and a novel Generalized Spreading algorithm, which is simultaneously optimal for every upper bound W on the total weight of nodes that an adversary can fail. These generalize the classical notion of max-min fairness to work with nodes of differing capacities, differing reliability weights, and hierarchical structures. Using randomized rounding, we extend this to give an algorithm for integral H ier R obust F ap . For the probabilistic version, we first give an algorithm that achieves an additive ϵ approximation in the failure probability for the single level version, called P rob F ap , while giving up a (1 + ϵ) multiplicative factor in the number of failures. We then extend the result to the hierarchical version, H ier P rob F ap , achieving an ϵ additive approximation in failure probability while giving up an (L + ϵ) multiplicative factor in the number of failures, where L is the number of levels in the hierarchy.

CPLC: Visible Light Communication based on Circularly Polarized Light

Direction communication between smart devices has been extensively studied, while VLC is a promising method, because of wide bandwidth and low implementation cost. However, existing VLC methods rely on the high flash frequency to avoid human discomfort, imposing high cost at the devices. To address this issue, we propose CPLC (circularly polarized light communication), which utilizes the circular polarized light with orientation free. By doing this, our method is applicable to various smart devices (e.g., smartwatch), as long as they are equipped with a tiny light sensor. Specifically, CPLC has the following contributions: 1) Large range of modulation rate from 0 to 2 kHz. 2) Receiver mobility at low flash frequency without light flicker. 3) Ultra-low power consumption and tiny size. These features not only differentiate CPLC from previous VLC methods, but also ensure that CPLC is beneficial to various smart devices. We implement CPLC system with commodity components and develop a prototype. The extensive evaluation on this prototype demonstrates that the CPLC system can provide a wide range of modulation rate from 0 to 2 kHz with 0.5mW power consumption and 5mm diameters size in receiver side.