Comparative performance of HgCdTe photodiodes for heterodyne application

Photodiodes used as photomixers in heterodyne applications display quantum efficiencies that are lower than the dc quantum efficiency of the device. Measurement techniques used to obtain dc quantum efficiencies, midband heterodyne quantum efficiencies, and frequency roll off characteristics are described. Measurement results for two HgCdTe photodiodes are given and discussed. It is recommended that photodiodes used in heterodyne applications be tested for heterodyne quantum efficiency over the frequency band of interest for the particular application

Comparative performance of HgCdTe photodiodes for heterodyne application

The use of photodiodes as optical photomixers in laser heterodyne spectroscopy systems is discussed. The quantum efficiency of the photodiodes is reported with the emphasis on its effect on the system's signal to noise ratio. The measurement techniques used to determine photodiode dc and heterodyne quantum efficiencies are described. The theory behind the measurements as well as actual measurements data for two HgCdTe photodiodes are presented

Kat\v{e}tov order between Hindman, Ramsey, van der Waerden and summable ideals

A family I of subsets of a set X is an ideal on X if it is closed under taking subsets and finite unions of its elements. An ideal I on X is below an ideal J on Y in the Katetov order if there is a function $f:Y\to X$ such that $f^{-1}[A]\in J$ for every $A\in I$. We show that the Hindman ideal, the Ramsey ideal and the summable ideal are pairwise incomparable in the Katetov order, where * the Ramsey ideal consists of those sets of pairs of natural numbers which do not contain a set of all pairs of any infinite set (equivalently do not contain, in a sense, any infinite complete subgraph), * the Hindman ideal consists of those sets of natural numbers which do not contain any infinite set together with all finite sums of its members (equivalently do not contain IP-sets that are considered in Ergodic Ramsey theory), * the summable ideal consists of those sets of natural numbers such that the series of the reciprocals of its members is convergent. Moreover, we show that in the Katetov order the above mentioned ideals are not below the van der Waerden ideal that consists of those sets of natural numbers which do not contain arithmetic progressions of arbitrary finite length

A unified approach to Hindman, Ramsey and van der Waerden spaces

For many years, there have been conducting research (e.g. by Bergelson, Furstenberg, Kojman, Kubi\'{s}, Shelah, Szeptycki, Weiss) into sequentially compact spaces that are, in a sense, topological counterparts of some combinatorial theorems, for instance Ramsey's theorem for coloring graphs, Hindman's finite sums theorem and van der Waerden's arithmetical progressions theorem. These spaces are defined with the aid of different kinds of convergences: IP-convergence, R-convergence and ordinary convergence. The first aim of this paper is to present a unified approach to these various types of convergences and spaces. Then, using this unified approach, we prove some general theorems about existence of the considered spaces and show that all results obtained so far in this subject can be derived from our theorems. The second aim of this paper is to obtain new results about the specific types of these spaces. For instance, we construct a Hausdorff Hindman space that is not an \I_{1/n}-space and a Hausdorff differentially compact space that is not Hindman. Moreover, we compare Ramsey spaces with other types of spaces. For instance, we construct a Ramsey space that is not Hindman and a Hindman space that is not Ramsey. The last aim of this paper is to provide a characterization that shows when there exists a space of one considered type that is not of the other kind. This characterization is expressed in purely combinatorial manner with the aid of the so-called Kat\v{e}tov order that has been extensively examined for many years so far. This paper may interest the general audience of mathematicians as the results we obtain are on the intersection of topology, combinatorics, set theory and number theory

Spivak and Rethinking the Agency of Disabled Children

Disability as a marginalised subject position is not conspicuous in Postcolonial Studies, although it does constitute a material presence and is a lived experience in the Global South. Disability Studies in the Global North often downplays social inequality and diversity that is a direct result of inequalities perpetuated by centuries of colonialism. This is problematic for indigenous populations that are disabled, as their ‘agency’ is left out in both the postcolonial and the disability narrative. This article examines the position of the subaltern that exists within subalternity, through the works of Professor Gayatri C. Spivak, and further aims to examine whether the space occupied by the subaltern is characteristically similar as a disenfranchised group to that of disabled people. Spivak’s method of affirmative sabotage and deconstruction in postcolonial studies will be used to rethink the position of disabled children to conclude that the subaltern and the experience of impairment are similarly ‘disabling’, and that disabled subaltern in treaties such as the UN Convention on the Rights of the Child cannot actually speak. </p

Squalicum Creek re-route

Squalicum Creek is one of the largest independent drainages in Whatcom County, draining most of Northern Bellingham. The creek originates in the Cascade foothills and empties into Bellingham Bay. Squalicum Creek has the highest potential for high water quality and productive fish habitat within the Bellingham city limits. The location of the creek is shown in Figure 1 with the reach addressed in this document highlighted as the Project Area. Current conditions within the project area impede fish passage and provide few spawning areas. In addition, Bug Lake and Sunset Pond currently create the highest thermal loading in Squalicum Creek. The creek also fails to meet water quality standards for dissolved oxygen (DO) and fecal coliform. The proposed action will improve water quality and native fish habitat as well as reduce predation by non-native species. This report examines three possible outcomes: the proposed action, an alternative action and a no-action alternative. The proposed action involves creating a new stream channel to route the creek around Sunset Pond. The creek will maintain its route through Bug Lake, however, it will be partially filled to create wetlands and a narrower and more complex stream channel. Increased riparian zones and installations of large woody debris (LWD) in the creek will improve water quality, stream complexity, and provide resting spaces for fish. This plan also includes the modification of existing and construction of new in-stream structures to improve fish passage by enabling salmon to out-migrate as juveniles and move upstream to spawning grounds as adults. The alternative action proposes to fill in large portions of both Bug Lake and Sunset Pond, leaving a narrow channel and transforming the remaining pond areas from manmade aqueducts to riparian areas and emergent wetlands. Riparian planting would also be added around the current stream channel between the lakes and fish passage barriers improved to facilitate fish migration. The no-action alternative would leave the creek in its current condition, leaving habitat issues unresolved. Adverse impacts from the proposed project include increased sediment loading and stormwater pollution from surrounding current and future development as well as disruption of some existing wetland areas. Water quality benefits from the lakes during high flows would also be lost. Temporary impacts as a result of infrastructure and channel improvements would be mitigated by the addition of engineered wetlands as well as continued monitoring, adaptive management strategies and education and outreach efforts to prevent further contamination via stormwater. Short term increased sediment loading during construction cannot be completely mitigated and will have potential significant adverse effects such as increased turbidity, temperature, and lowered dissolved oxygen levels which could be harmful to fish remaining in the stream. Long term goals of the project will improve these temporarily decreased water quality parameters. Impacts of the alternative action would be similar to the proposed action. There are additional potential impacts from non-native soils and even more sediment loading during construction from filling in the ponds. The alternative does not improve floodplain conveyance, though increased wetlands will help manage high-flow conditions. This alternative requires very little new infrastructure. Some supporters of the proposed Bay to Baker Trail disapprove of the current Squalicum Creek re-route because the new channel would follow the old Burlington Northern Railroad grade, which was the original location for the Bay to Baker Trail. If the re-route is completed, then the trail would have to circumvent the bridge by following James Street to the nearest intersection at McLeod Rd. These supporters claim that the Bay to Baker Trail deserves priority since that project\u27s development began years ago. In addition, some members of the community disagree over the future recreation use of Sunset Pond

A study of concept options for the evolution of Space Station Freedom

Two conceptual evolution configurations for Space Station Freedom, a research and development configuration, and a transportation node configuration are described and analyzed. Results of pertinent analyses of mass properties, attitude control, microgravity, orbit lifetime, and reboost requirements are provided along with a description of these analyses. Also provided are brief descriptions of the elements and systems that comprise these conceptual configurations