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This review article provides the state-of-art research and developments of the rectenna device and its two main components – the antenna and the rectifier. Furthermore, the history, efficiency trends, and socioeconomic impact of its research are also featured.
The rectenna (RECTifying antENNA), which was first demonstrated by William C. Brown in 1964 as a receiver for microwave power transmission, is now increasingly researched as a means of harvesting solar radiation. Tapping into the growing photovoltaic market, the attraction of the rectenna concept is the potential for devices that, in theory, are not limited in efficiency by the Shockley–Queisser limit. In this review, the history and operation of this 40-year old device concept are explored in the context of power transmission and the ever increasing interest in its potential applications at terahertz frequencies, through the infrared and visible spectra. Recent modeling approaches that have predicted controversially high efficiency values at these frequencies are critically examined. It is proposed that to unlock any of the promised potential in the solar rectenna concept, there is a need for each constituent part to be improved beyond the current best performance, with the existing nanometer scale antennas, the rectification and the impedance matching solutions all falling short of the necessary efficiencies at terahertz frequencies. Advances in the fabrication, characterization, and understanding of the antenna and the rectifier are reviewed, and common solar rectenna design approaches are summarized. Finally, the socioeconomic impact of success in this field is discussed and future work is proposed.
III-V on Si multijunction solar cells represent an alternative to traditional compound III-V multijunction cells as a promising way to achieve high efficiencies. A theoretical study on the energy yield of GaAs/Si tandem solar cells is performed to assess the performance potential and sensitivity to spectral variations. Recorded time-dependent spectral irradiance data in two locations (Singapore and Denver) were used. We found that a 4-terminal contact scheme with thick top cell confers distinctive advantages over a 2-terminal scheme, giving a yield potential 21% higher than the 2-terminal scheme in Singapore and 17% higher in Denver. The theoretical energy yield benefit of a 4-terminal device emphasizes the need for further technology development in this design space.
I continue my argument that Millian qualitative superiorities are infinite superiorities: one pleasant feeling, or type of pleasant feeling, is qualitatively superior to another in Mill's sense if and only if even a bit of the superior is more pleasant (and thus more valuable) than any finite quantity of the inferior, however large. This gives rise to a hierarchy of higher and lower pleasures such that a reasonable hedonist always refuses to sacrifice a higher for a lower irrespective of the finite amounts of each. Some indication of why this absolute refusal may be reasonable is provided in the course of outlining the content of the Millian hierarchy. It emerges that Mill's hedonistic utilitarianism has an extraordinary structure because it gives absolute priority over competing considerations to a code of justice that distributes equal rights and correlative duties for all. His utilitarianism also recognizes that certain aesthetic and spiritual pleasures may be qualitatively superior even to the pleasant feeling of security associated with the moral sentiment of justice. Thus, for instance, a noble individual may reasonably choose to waive his own rights so as to perform beautiful supererogatory actions that provide great benefits for others at the sacrifice of the right-holder's own vital interests.
J. S. Mill evidently accepts that society and government may legitimately use coercive measures to prevent individuals from behaving in ways that pose a risk of direct and immediate harm to other people without their genuine consent and participation. The most important thing a society can do to promote the general welfare, he makes clear in the fifth chapter of Utilitarianism, is to establish laws and customs that distribute weighty equal rights not to suffer unprovoked violence, undue discrimination, and other grievous harms. These rules of justice might sanction unusually harsh punishment for wrongdoers – whether members of the popular majority or a minority – who make a show of harming others merely because the others are perceived as belonging to alien races, religions, or ethnic backgrounds.
But Mill also gives the impression that he draws a sharp distinction between actions and speech. In the second chapter of On Liberty, he argues that mature individuals – people capable of rational persuasion, which excludes children and delirious, insane, or otherwise incompetent adults – ought to be absolutely free to form and discuss any opinions they wish: “there ought to exist the fullest liberty of professing and discussing, as a matter of ethical conviction, any doctrine, however immoral it may be considered” (CW XVIII, 228n. [11, 1n.]). He “altogether condemn[s]” even the practice of referring to “the immorality or impiety of an opinion” as such (CW XVIII, 234 [11, 11]).
Utilitarians and their critics commonly assume that maximizing utilitarianism necessarily aggregates over cardinal comparable personal utility rankings that are homogeneous in quality independently of their sources or objects, whether utility is conceived in terms of pleasure or preference satisfaction. Although familiar versions of utilitarianism, crude or sophisticated, do make such rich homogeneous utility information part of the very meaning of the doctrine, utilitarian philosophy loses credibility as a result. A more credible version of maximizing utilitarianism along John Stuart Mill's lines relies instead on plural kinds of ordinal non-comparable personal utilities that are heterogeneous in quality. One kind of utility is qualitatively superior to another if and only if the higher kind is more valuable than the lower kind irrespective of quantity. Given that the kind of utility associated with the moral sentiment of justice is qualitatively superior to any competing kinds, Mill's pluralistic ordinal utilitarianism gives absolute priority to a social code of equal rights and duties over competing considerations. Some key practical implications of this extraordinary utilitarianism are discussed with reference to various examples of the sort discussed in the literature.
Arrhenius and Rabinowicz (henceforth, AR) have argued that Millian qualitative superiorities are possible without assuming that any pleasure, or type of pleasure, is infinitely superior to another. But AR's analysis is fatally flawed in the context of ethical hedonism, where the assumption in question is necessary and sufficient for Millian qualitative superiorities. Marginalist analysis of the sort pressed by AR continues to have a valid role to play within any plausible version of hedonism, provided the fundamental incoherence that infects AR's use of such analysis is removed. But what AR call ‘Millian superiorities’ are never genuine qualitative superiorities in Mill's sense. Mill scholars need to appreciate this point and recognize that the interpretation of qualitative superiorities as infinite superiorities is the only interpretation which is compatible with the text of Mill's Utilitarianism. The continuing failure to appreciate the possibility of infinite superiorities has precluded any adequate understanding of the extraordinary structure of Mill's pluralistic hedonistic utilitarianism.
Liberals typically claim that equal rights and liberties should have suitable moral priority over competing values. Rawls (1971, 1993), for example, argues that social justice properly limits permissible conceptions of the good life in a democratic culture and that, within justice as he conceives it, a first principle of equal basic liberties has absolute priority over a second two-part principle. Political rights are given a special place within his first principle, in that they (unlike other basic rights) must have roughly equal worth (or “fair value”) for all persons (1993, pp. 5–6, 324–331, 356–362). The rationale for this special treatment seems to be the allegedly essential role that exercise of the political liberties plays in “preserving the other liberties” (Rawls, 1993, p. 299). Thus, individuals must have a fair opportunity to exercise their basic political rights “because it is essential in order to establish just legislation and also to make sure that the fair political process specified by the constitution is open to everyone on a basis of rough equality” (Rawls, 1993, p. 330).
A major aim of Rawls in particular, and of liberal theorists more generally, has been to provide a more secure foundation than utilitarianism seems to provide for the suitable priority of equal basic rights. As Rawls puts it, the “first task” of his political theory is “to provide a more secure and acceptable basis for constitutional principles and basic rights and liberties than utilitarianism seems to allow” (1985, p. 226). It is open to doubt whether this “first” task has been accomplished by Rawls or any other antiutilitarian.