Perfect Case Research Articles

A numerical investigation of freshwater and sediment discharge variations of Poyang Lake catchment, China over the last 1000 years

The Poyang Lake catchment, an important sub-catchment of Changjiang, experienced ‘Little Ice Age’ (LIA) and accelerating intensity of human activities during the last 1000 years. As such, the area and time period serve as a perfect case to study the variations in water and sediment discharge under combined natural and anthropogenic impact. Simulation results of the model HydroTrend indicate that the annual average cumulative water discharge of the five rivers entering Poyang Lake over the last 1000 years is 103.65 ± 1.80 km3, and climate change is the dominating factor determining water discharge variations over time. Influenced by the LIA (AD 1451–1850), the total water discharge of the five rivers was reduced by 10%. Sediment load discharging into Poyang Lake by the five rivers was only 9.21 ± 0.43 Mt yr−1 between AD 1000 and 1700, when the anthropogenic impact on the landscape was still low. However, with the human activities accelerating during the past 300 years, the sediment load entering Poyang Lake underwent a drastic change. Because of intensified soil loss, the total sediment load entering Poyang Lake during AD 1800–1950 increased by 58.7%, compared with AD 1000–1700. After AD 1950, the sediment load variation is mainly reflected by the combined impact of dam emplacement and soil erosion. As sediment interception by dams continuously increased over time, the total sediment load entering Poyang Lake during AD 1990–2000 is only 60.9% of that of the highest riverine sediment flux during AD 1951–1980, which is almost equal to that of the lowest level during AD 1000–1700. The sediment load of many rivers in the world exhibited similar variation trends as that of Poyang Lake under combined impact of climate change and human activities. Better understanding the mechanisms of these variation trends is helpful to analyzing the formation and evolution of an estuary-shelf sedimentary system over the Holocene.

Robust amplify‐and‐forward relay beamforming for security with mean square error constraint

In this study, security schemes at the physical layer are proposed for an amplify-and-forward relay system in the presence of a passive eavesdropper. We focus on maximising the transmit power of the artificial noise (AN) to degrade the minimum mean square error (MMSE) level at the eavesdropper, while achieving MMSE constraint for the desired receiver. Assuming that the desired receiver and the passive eavesdropper possess perfect channel state information (CSI), AN is designed to lie in the null space of legitimate channels. However, the available CSI is impossible to be perfect in practice. Therefore the authors present a robust beamforming scheme which maximises the worst-case transmit power of the AN under the condition of imperfect CSI and recovers a large fraction of the performance in the perfect CSI case. A classical alternating optimisation algorithm is proposed to obtain the relay beamforming weights, and simulation results show the benefit of proposed schemes.

Robust Joint Source-Relay-Destination Design Under Per-Antenna Power Constraints

This paper deals with joint source-relay-destination beamforming (BF) design for an amplify-and-forward (AF) relay network. Considering the channel state information (CSI) from the relay to the destination is imperfect, we first aim to maximize the worst case received SNR under per-antenna power constraints. The associated optimization problem is then solved in two steps. In the first step, by revealing the rank-one property of the optimal relay BF matrix, we establish the semi-closed form solution of the joint optimal BF design that only depends on a vector variable. Based on this result, in the second step, we propose a low-complexity iterative algorithm to obtain the remaining unknown variable. We also study the problem for minimizing the maximum per-antenna power at the relay while ensuring a received signal-to-noise ratio (SNR) target, and show that it reduces to the SNR maximization problem. Thus the same methods can be applied to solve it. The differences between our result and the existing related work are also discussed in details. In particular, we show that in the perfect CSI case, our algorithm has the same performance but with much lower cost of computational complexity than the existing method. Finally, in the simulation part, we investigate the impact of imperfect CSI on the system performance to verify our analysis.

Performance Analysis of IA Techniques in the MIMO IBC With Imperfect CSI

In this work we consider the multiple-input multiple-output (MIMO) interference broadcast channel (IBC) and analyse the performance of interference alignment (IA) under imperfect channel state information (CSI), where the variance of the CSI error depends on the signal-to-noise ratio (SNR). First, we derive an upper bound on asymptotic mean loss in sum rate compared to the perfect CSI case and then we quantify the achievable degrees of freedom (DoF) with imperfect CSI. Both sum rate loss and achievable DoF are found to be dependent on the number of cells in the system and the amount of users per cell, in addition to the CSI error parameters themselves. Results show that when error variance is inversely proportional to SNR, full DoF are achievable and the asymptotic sum rate loss is bounded by a derived value. Additionally if the CSI imperfection does not disappear for asymptotically high SNR, then the full DoF gain promised by IA cannot be achieved; we quantify this loss in relation to the CSI mismatch itself. The analytically derived bounds are validated via system simulation, with the cellular counterparts of the maximum signal-to-interference-plus-noise ratio (Max-SINR) and the minimum weighted leakage interference (Min-WLI) algorithms being the IA techniques of choice. Secondly, inspired by the CSI mismatch model used to derive the bounds, we present a novel Max-SINR algorithm with stochastic CSI error knowledge (Max-SINR-SCEK) for the MIMO IBC. Simulations show that the proposed algorithm improves performance over the standard one under imperfect CSI conditions, without any additional computational costs.

Finding Bronies – The accidental audience of My Little Pony: Friendship is Magic

Abstract The practice of audience segregation, demographic profiling and manufactured viewerships has become common practice in the television industry since the turn towards niche programming and narrowcasting in an increasingly multichannel environment. While much critical scholarship has been devoted to the way that media companies undertake extensive market research to target their products to specific demographic segments, this article concentrates on the way that untargeted and unexpected viewers have coalesced around certain television programmes, and become the ‘accidental audience’. ‘Bronies’ have become the most well-known accidental audience in recent years, and are a perfect case study by which this phenomenon can be examined. The article therefore explores the way that accidental audiences develop, and how they offer both opportunity and threat to the managed selling of media brands. This article will also engage with the issues surrounding identifying and responding to these accidental audiences. Using the ‘Brony’ fandom of My Little Pony: Friendship is Magic, this article asks how accidental audiences develop and how, in particular, the Internet serves to shape and cultivate them.

Distributed Detection of Binary Decisions with Collisions in a Large, Random Network

We consider the problem of distributed detection in a large network of sensors. A random number of sensor nodes are randomly deployed. Sensor nodes perform local detection tests and communicate detections over a multiple-access channel to a fusion center. The fusion center can recognize both successful communications and communication collisions in the channel. We derive decision rules for both perfect communications and a delay-constrained communications protocol, and show that each are functions of count statistics only. We derive analytical expressions that characterize the performance of the system in terms of detection performance. We analyze performance with respect to sensor density and with respect to communications delay. Simulation examples validate theoretical predictions with numerical results. We show that the detection performance improves with network density despite increasing communication collisions. In addition, we show that detection performance using the protocol model, with imperfect communications, rapidly converges to the perfect communications case as the number of communication slots increase.

Improved HDRG decoders for qudit and non-Abelian quantum error correction

Hard-decision renormalization group (HDRG) decoders are an important class of decoding algorithms for topological quantum error correction. Due to their versatility, they have been used to decode systems with fractal logical operators, color codes, qudit topological codes, and non-Abelian systems. In this work, we develop a method of performing HDRG decoding which combines strengths of existing decoders and further improves upon them. In particular, we increase the minimal number of errors necessary for a logical error in a system of linear size L from to for any We apply our algorithm to decoding quantum double models and a non-Abelian anyon model with Fibonacci-like fusion rules, and show that it indeed significantly outperforms previous HDRG decoders. Furthermore, we provide the first study of continuous error correction with imperfect syndrome measurements for the quantum double models. The parallelized runtime of our algorithm is for the perfect measurement case. In the continuous case with imperfect syndrome measurements, the averaged runtime is for Abelian systems, while continuous error correction for non-Abelian anyons stays an open problem.

A Generic Measurement Setup for Implementation and Performance Evaluation of Spectrum Sensing Techniques: Indoor Environments

Spectrum sensing is the preeminent task of both cognitive radios and next generation wireless networks. There are various spectrum sensing techniques and methods presented in the literature. Performance evaluation of these techniques and methods is an important issue from the perspective of both the receiver and system design. In this regard, experimental studies that involve implementation, measurement, and performance evaluation of these methods under realistic conditions are of paramount importance, along with the relevant theoretical work. Therefore, in this paper, a generic measurement methodology is proposed to implement various spectrum sensing techniques and evaluate their performances. Mobile and immobile scenarios; line-of-sight and non-line-of-sight conditions; and presence/absence of perfect spectral knowledge cases are all investigated for both energy detector (first-) and second-order statistical receivers. Results are presented along with relevant discussions. Future directions are outlined as well.

On the Local Tb Theorem: A Direct Proof under the Duality Assumption

AbstractWe give a new direct proof of the local Tb theorem in the Euclidean setting and under the assumption of dual exponents. This theorem provides a flexible framework for proving the boundedness of a Calderón–Zygmund operator, supposing the existence of systems of local accretive functions. We assume that the integrability exponents on these systems of functions are of the form 1/p + 1/q ⩽ 1, the ‘dual case’ 1/p + 1/q = 1 being the most difficult one. Our proof is direct: it avoids a reduction to the perfect dyadic case unlike some previous approaches. The principal point of interest is in the use of random grids and the corresponding construction of the corona. We also use certain twisted martingale transform inequalities.

Quadrupole collectivity in neutron-rich Cd isotopes

The proximity to the closed shells at Z = 50 and N = 82 makes the neutron-rich Cd isotopes a perfect test case for nuclear theories. The energy of the first excited 2+-state in the even 122-128 shows an irregular behaviour as the Cd isotopes exhibit only a slight increase for 122Cd to 126Cd and even a decrease from 126Cd to 128Cd. This anomaly can so far not be reproduced by shell model calculations. Only beyond mean field calculations with a resultant prolate deformation are capable to describe this anomalous behaviour. In order to gain more information about the neutron-rich Cd isotopes a Coulomb excitation experiment was performed with MINIBALL at REX-ISOLDE, CERN. The extracted transition strengths B (E2,0+gs → 2+1) for 122,124,126,128Cd agree with beyond mean field calculations. The spectroscopic quadrupole moments Qs (2+1) are compared with measurements on odd neutron-rich Cd isotopes.

Transport regimes in nitrogen-doped carbon nanotubes: Perfect order, semi-random, and random disorder cases

The electronic structure and the transport properties of nitrogen-doped carbon nanotubes are investigated using a tight-binding model and a real-space Kubo-Greenwood approach, respectively. The transport regimes of various axial and helical doping configurations, from perfectly periodic to fully random disordered cases, are examined through the time dependence of the diffusivity. By varying the degree of disorder, a rich set of transient regimes is predicted going from persisting quasiballistic to momentarily localized regimes. A spectacular long-time ballistic regime is also observed for a specific semi-random disorder doping configuration owing to symmetry effects.

Outage-Constrained Beamforming for Two-Tier Massive MIMO Downlink with Pilot Reuse

Massive multiple-input multiple-output (MIMO) systems and small cell networks are both regarded as promising candidates to meet the exponential growth of mobile data traffic for the next generation (5G) wireless communications. Hence, a new kind of multitier networks which combine massive MIMO macro cells with a secondary tier of small cells is proposed to resolve the contradiction of large network coverage and high data rate. In such multitier networks, it is inevitable to allocate nonorthogonal uplink pilot sequences to user equipment (UE) due to the large number of users. We propose a pilot reuse scheme by exploiting the unique architecture of this networks and analyse the special mixed channel state information (CSI) yielded by the pilot reuse scheme. Based on the mixed CSI, we formulate a downlink transmit beamforming problem of minimizing the total power consumption while satisfying the quality of service (QoS) requirements with outage constraints. After decomposing the original problem into simpler subproblems, we provide an efficient algorithm to combine these subproblems and solve them iteratively for generating the beamforming vectors. Monte Carlo simulations show that the average power consumption of the proposed pilot reuse scheme and its associated beamforming algorithm is close to that of the perfect CSI case.

Dual-Element PIFA Design with Dual Shorting Pins for Multiband Communication Devices

A low profile multiband resonant, dual-element array antenna is proposed for use in handheld communication devices. The proposed antenna comprises two dual shorting pin planar inverted-F antennas and a folded ground plane which operates as a perfect electric conductor case. The feeding scheme adopted for the proposed design produces a fixed phase difference between two antenna elements of the design to achieve an ultrawide bandwidth and a flexible radiation pattern. The proposed antenna design is simulated with commercially available software, which is based on the finite element method. The resonant frequency bands covered are GSM850/900, DCS1800, PCS1900, UMTS2100, and LTE2300/2600 MHz. Details of the design considerations for the proposed antenna are described and the simulated and measured results are presented and discussed, which are in agreement.

Whose Voice, Whose Interests?

This paper looks at whose voice is heard and whose interests are protected in the making of finance-related laws in China. To ensure its accuracy, the paper focuses on a real-life case study of the making of bankruptcy laws in 1986 and 2006. Laws provide a set of incentives and constraints on their intended users and beneficiaries. In the context of bankruptcy law this means determining who shall bear the risk of corporate failure, whose interests shall be prioritized in corporate exit or reorganization, and who shall be the mediator/decision-maker in a case of conflict. Exploring bankruptcy law-making process in China sheds light on the interaction between and pressures exerted by the various stakeholders, which in turn informs the debate of representation and participation in China’s legislative process. While it is generally accepted that the key and dominant player is the Party-state whose representatives prepare, debate, vote on and promulgate the law, I propose that that is not a complete picture. The Party-state is subject to multiple internal influences and interests they wish to protect. These internal motives are influenced by certain powerful external users and stakeholders of the proposed law who try to protect their own interests. Although the Party-state is the ultimate law-maker, it allows deliberations and interjections by the interested parties. As a result, the interests and motivations of the two groups interact and affect each other leading to a compromise formulation of the new law. The discussion in this paper is informed by what we know about the passage of the 2006 bankruptcy law. The experience with making the older 1986 law will also be included where relevant. Thanks to the fundamentally opposed interests at play it took many years, numerous drafts and uniquely bumpy and disharmonious legislative run to reach an acceptable compromise each time which makes the bankruptcy law a perfect case study of the interests at play in corporate law-making in China and in transition from plan to market in general. The key clashes included ideology, the position and adequate protection of workers, the role and rights of financial creditors (as represented by the banks) and the admissibility of international pressure and experience. In other words, the key to passing the 1986 and 2006 laws was whether and to what extent should the ingrained demand for worker protection and social welfare provision be compromised to accommodate the need for further economic growth and how far to accommodate the demands of the increasingly powerful and independent financial creditors (i.e. mostly private companies and banks) and the international community. Although the paper focuses on bankruptcy law, the findings may be applicable to a variety of corporate finance-related laws since it uncovers the process and mechanisms used in law-making more broadly.

Performance Analysis of Interference Alignment Under CSI Mismatch

With interference alignment (IA), the achievable degrees of freedom (DoFs) in wireless networks can be linearly scaled up with the number of users. However, to attain the full DoF, the availability of perfect network channel state information (CSI) is mandatory, which is not pragmatic in general. In this paper, we quantify the performance of IA under CSI mismatch where the variance of the CSI measurement error depends on the signal-to-noise ratio (SNR). We show that when this error variance is proportional to the inverse of the SNR, the full DoF is achievable, and an upper bound on asymptotic mean loss in sum rate compared with the perfect CSI case is derived. We also derive a bound on the achievable DoF when the CSI error variance is proportional to the inverse of the SNR to a power of a constant. Furthermore, we investigate the effect of CSI mismatch on the performance of the maximum signal-to-interference-plus-noise ratio (Max-SINR) algorithm. We show that with perfect CSI, the Max-SINR algorithm outperforms interference leakage minimization algorithms, but with the presence of imperfect CSI, its comparative improvement becomes negligible. We then propose an adaptive Max-SINR algorithm that can notably improve the performance of the original Max-SINR algorithm under CSI mismatch.

Geology and gravity modeling of the Logrosán Sn–(W) ore deposits (Central Iberian Zone, Spain)

Sn–(W) granite-hosted ore deposits are characterized by the occurrence of pegmatites, stockworks and quartz veins within a granitic cupola and its surrounding host-rocks. A regional exploration tool for these deposits consists of targeting syn- to late-orogenic specialized S-type hidden shallow granites by geophysical methods. However, gravity as a tool for “brownfield type” exploration in a mature granite-related ore setting has not been widely used. The Logrosán area (Central Iberian Zone) provides a perfect case scenario with Sn–W endo- and exogranitic ore deposits within a relatively small-scale realm. We suggest that the understanding of the subsurface of the Logrosán area provides a key tool to develop a more comprehensive geological and metallogenic model for the ore deposits. In addition, a better explanation for the mineral evolution and the Sn–W ore precipitation can be achieved, by comparing the chemical and textural features of ores from several of the Logrosán deposits. Field gravity and geologic data allowed the modeling of the hidden granite bodies. Combining this information with detailed mineralogical, geochemical data and ore deposit modeling has allowed a definition of targets for probable new Sn–(W) deposits, all within a few kilometers of the main intrusion center.

Capacity Analysis of Interference Alignment With Bounded CSI Uncertainty

Interference alignment (IA) has been demonstrated to achieve the degree-of-freedom (DoF) of an interference channel given perfect global channel state information (CSI). In this letter, we consider the case of imperfect CSI with bounded errors and derive a capacity lower bound of the channel using IA. We show that this lower bound is within 1 bps/Hz of the capacity of the perfect CSI case up to a certain signal-to-noise ratio (SNR) which we refer to it as the saturating SNR. Further, we introduce a new metric called modified DoF (mDoF) in order to characterize the multiplexing performance of IA with imperfect CSI at finite SNR. Simulation results for the 3-user case are provided to illustrate the region within which the actual capacity of IA falls.

Feedback‐error‐resistant and reduced feedback‐rate orthogonal space‐time block coding scheme employing single transmit antenna selection

A novel and generic transmit diversity scheme that employs combined single transmit antenna selection (TAS)/orthogonal space-time block coding (OSTBC) scheme with reduced feedback-rate and robust error performance in the presence of feedback errors (FEs) is introduced in this paper. Statistical expressions and performance metrics related to the post-processing signal-to-noise ratio of the proposed scheme are derived for Nakagami-m fading channels considering that the channel estimation process is error-free and the feedback information is delivered to the transmitter side with no delay. Exact expressions for outage probability and bit/symbol error rates of M-ary signals are presented to examine the system performance in the presence of FEs extensively. Also, the asymptotic analysis is provided to explore the asymptotic diversity order and the asymptotic coding gain of the proposed scheme that is compared with that of the conventional TAS/OSTBC scheme from different perspectives. The proposed scheme is shown to provide not only full-diversity order as the conventional scheme for perfect feedback case but also superior error performance in the presence of FEs. Moreover, the error performances of both schemes and the superiority of the modified scheme are examined by considering an error-correcting structure in the feedback link.

Quotations, References, etc. A Glance on the Writing Habits of a Late Mīmāṃsaka

Rāmānujācārya’s Tantrarahasya, a philosophical treatise mainly dedicated to the hermeneutics and epistemology of the Pūrva Mīmāṃsā School, might be considered hardly more than a jigsaw of reused passages, since (at least) one third of it has a direct source, and (at least) a further third has its roots in interlanguage usage. It is thus a perfect case study for investigating the compositional habits of philosophical authors in pre-modern śāstra literature. The article analyses the formal aspects of textual reuse by Rāmānujācārya and draws some general conclusions regarding the author’s intellectual affiliation to Prābhākara Mīmāṃsā on the basis of the way he reuses his school’s texts as compared to the reuse of other schools’ texts. A final section discusses the possibility of generalising these results to the approach to textual reuse of the whole Pūrva Mīmāṃsā.

Buckling and post-buckling of gradient and nonlocal plasticity columns experiencing softening

The buckling and the post-buckling behaviors of a perfect axially loaded column are analytically investigated through a global bilinear moment–curvature elastoplastic constitutive law. Three plasticity cases are studied, namely the linear hardening plasticity law, the perfect elastoplastic case and the softening case. The applications of such a study can be found in various structural engineering problems, including reinforced concrete, steel, timber or composite structures. It is analytically shown that for all kinds of elastoplastic behaviors, the plasticity phenomena lead to a global softening branch in the load–deflection diagram. The propagation of the plasticity zone during the post-buckling process is analytically characterized in case of linear hardening or softening plasticity laws. However, it is shown that the unphysical elastic unloading solution necessarily occurs in presence of local softening moment–curvature constitutive law. A nonlocal plasticity moment–curvature softening law is then used to control the localization branch in the post-buckling stage. This nonlocal plasticity law includes the explicit and the implicit gradient plasticity law. Higher-order plasticity boundary conditions are derived from an extended variational principle. Some parametric studies finally illustrate the main findings of this paper, including the plasticity modulus effect on the post-buckling behavior of these plasticity structural systems.