Since its inception in 1987, the Low Income Housing Tax Credit (LIHTC) program has ballooned into the largest ever source of subsidized construction of low-income housing in the United States, ...accounting for one-third of all recent multi-family rental construction. This paper examines the crowd out effects of this increasingly important source of low-moderate income housing. To do so, we analyze the impact of LIHTC construction at three different levels of geography, MSA, county, and 10-mile radius circles. This allows us to employ increasingly extensive geographic fixed effects that help to difference away unobserved factors. Political variables are also used as instruments to further facilitate identification.
In all of our models, IV estimates yield substantially greater crowd out than OLS, confirming the endogenous attraction of LIHTC development to areas ripe for new construction. Our most robust IV estimates indicate that nearly 100% of LIHTC development is offset by a reduction in the number of newly built unsubsidized rental units, although the confidence band around this point estimate allows for less dramatic assessments. Additional estimates suggest that LIHTC development has a much more moderate impact on construction of owner-occupied housing, but these estimates are imprecise. Overall, while LIHTC development may well affect the
location of low-moderate income rental housing opportunities, our estimates suggest that the impact of the program on the
number of newly developed rental housing units appears to be small.
A 3D thermoelectric numerical model is used to investigate different internal heat loss mechanisms for a thermoelectric generator with bismuth telluride p- and n-legs. The model considers all ...thermoelectric effects, temperature dependent material parameters and simultaneous convective, conductive and radiative heat losses, including surface to surface radiation. For radiative heat losses it is shown that for the temperatures considered here, surface to ambient radiation is a good approximation of the heat loss. For conductive heat transfer the module efficiency is shown to be comparable to the case of radiative losses. Finally, heat losses due to internal natural convection in the module is shown to be negligible for the millimetre sized modules considered here. The combined case of radiative and conductive heat transfer resulted in the lowest efficiency. The optimized load resistance is found to decrease for increased heat loss. The leg dimensions are varied for all heat losses cases and it is shown that the ideal way to construct a TEG module with minimal heat losses and maximum efficiency is to either use a good insulating material between the legs or evacuate the module completely, and use small and wide legs closely spaced.
•Heat losses for a thermoelectric generator of bismuth telluride are investigated.•Radiative, conductive and convective heat losses are considered.•Surface to surface radiation, as well as full fluid flow, is considered.•A good thermal conductive insulator limits the heat loss the most.•Minimize heat losses by using closely spaced small and thick legs.
This study explored whether there is a gender difference in letter-sound knowledge when children start at school. 485 children aged 5-6 years completed assessment of letter-sound knowledge, i.e., ...large letters; sound of large letters; small letters; sound of small letters. The findings indicate a significant difference between girls and boys in all four factors tested in this study in favor of the girls. There are still no clear explanations to the basis of a presumed gender difference in letter-sound knowledge. That the findings have origin in neuro-biological factors cannot be excluded, however, the fact that girls probably have been exposed to more language experience/stimulation compared to boys, lends support to explanations derived from environmental aspects.
•A two-pole magnet alternately magnetizes 13 layered regenerator beds.•A parallel flow circuit using solenoid valves controls the magnetic cooling cycle.•At a 10.3 K span, 340 W heating power with a ...heating AMR COP of 6.7 was produced.•A maximum second-law efficiency of 20.6 % was achieved.
The design of a rotary active magnetic regenerator heat pump device with a multi-bed concept is presented. Important design features are the rotating two-pole magnet assembly, the laminated iron ring, the 13 fixed tapered regenerator beds, and the dynamically adjustable parallel flow circuit. The optimized magnet design was developed with optimally shaped segments and optimum remanence for the desired magnetic field distribution oscillating between 0 and 1.44 T in the air gap. The iron ring was laminated to reduce the eddy currents, allowing the device to run at cycle frequencies up to 3 Hz. The design of the regenerator housing was optimized with respect to parasitic losses and even flow distribution in both directions. Employing 3.4 kg of La(Fe,Mn,Si)13Hy (CALORIVAC HS) refrigerant and at a hot reservoir temperature of 295 K and a cycle frequency of 0.5 Hz, the heat pump achieved a maximum second-law efficiency of 20.6 %, while providing a heating load of 340 W with a heating COP of 6.7 at a 10.3 K span. The COP values presented only consider the magnetic power and ideal pump power delivered to the AMR, neglecting the pump efficiency. At 1.2 Hz, the device produced a maximum heating power of 950 W while maintaining a 5.6 K span, resulting in a heating coefficient of performance and second-law efficiency of 7.0 and 11.6 %, respectively. The performance demonstrated in this paper could be an important milestone in the development of future magnetocaloric devices.
Display omitted
Active magnetic regenerator (AMR) refrigerators represent an alternative to vapor compression technology and have great potential in realizing cooling devices with high efficiency, which are highly ...desirable for a broad range of applications. The technology relies on the magnetocaloric effect in a solid refrigerant rather than the temperature change that occurs when a gas is compressed/expanded. This paper presents the general considerations for the design and construction of a high frequency rotary AMR device. Experimental results are presented at various cooling powers for a range of operating conditions near room temperature. The device exhibited a no-load temperature span of over 25 K and can absorb a 100 W cooling load at a 20.5 K temperature span.
► A rotary regenerator active magnetic regenerator refrigerator with operating frequencies up to 8 Hz is for the first time presented. ► A maximum no-load temperature of 25.4 K is reported, and a maximum cooling power over 1000 W when operating near zero span was measured. ► The device produces 100 W cooling at a temperature span of 20.5 K. ► The COP was measured and a value of 1.8 for at a 400 W load and an 8.9 K span is reported.
•Experimental tests of different flow profiles in a rotary multi-bed AMR device.•Study of the influence of blow fraction (fraction of cycle when fluid is flowing).•Shorter blow fractions generate ...higher temperature spans but lower COPs.•Highest second-law efficiency obtained with the largest tested blow fraction.•Blow fraction can be used to control the performance of a magnetic refrigerator.
A rotary multi-bed active magnetic regenerator (AMR) device was modified to allow testing different fluid flow waveforms, with different blow fractions (i.e., the fraction of the AMR cycle when there is fluid flow in the regenerators). The different values of blow fraction were generated using different cam rings that actuate the poppet valves at the inlet and outlet of the regenerators, controlling how long the valves stay open and the number of valves open at the same time. Results showed that smaller blow fractions yield higher values of temperature span for fixed flow rate and cooling capacity, but lower values of coefficient of performance for the same conditions. An analysis of the shaft and pumping powers showed that shorter blow fractions cause higher pressure drop and higher torque oscillations and mechanical vibrations. The highest value of second-law efficiency of 19.1% was obtained for the largest blow fraction tested (80%). Designs for magnetic refrigerators where the fluid flow waveform can change during operation are also discussed in this paper.
•Experiments show large impact of unbalanced flow in active magnetic regenerators.•Flow channel resistances inducing unbalanced flow are investigated theoretically.•Modeled flow unbalances reveal ...strong impact on multi-bed magnetic refrigerators.
Experiments with a recently constructed rotary multi-bed active magnetic regnenerator (AMR) prototype have revealed strong impacts on the temperature span from variations in the resistances of the flow channels carrying heat transfer fluid in and out of the regenerator beds. In this paper we show through numerical modeling how unbalanced flow in the beds decreases the cooling power and COP for a dual bed device. Furthermore, it is shown how resistance variations in multi-bed devices give rise to unbalanced flow in the individual beds and how this decreases cooling powers and COPs of the machines by approximately 30% and 50%, respectively.
Background
Genetic modification of allergenic foods such as apple has the potential to reduce their clinical allergenicity, but this has never been studied by oral challenges in allergic individuals.
...Methods
We performed oral food challenges in 21 apple‐allergic individuals with Elstar apples which had undergone gene silencing of the major allergen of apple, Mal d 1, by RNA interference. Downregulation of Mal d 1 gene expression in the apples was verified by qRT‐PCR. Clinical responses to the genetically modified apples were compared to those seen with the wild‐type Elstar using a visual analogue scale (VAS).
Results
Gene silencing produced two genetically modified apple lines expressing Mal d 1.02 and other Mal d 1 gene mRNA levels which were extensively downregulated, that is only 0.1–16.4% (e‐DR1) and 0.2–9.9% (e‐DR2) of those of the wild‐type Elstar, respectively. Challenges with these downregulated apple lines produced significantly less intense maximal symptoms to the first dose (Vmax1) than with Elstar (Vmax1 Elstar 3.0 mm vs 0.0 mm for e‐DR1, P = 0.017 and 0.0 mm for e‐DR2, P = 0.043), as well as significantly less intense mean symptoms per dose (meanV/d) than with Elstar (meanV/d Elstar 2.2 mm vs 0.2 mm for e‐DR1, P = 0.017 and 0.0 mm for e‐DR2, P = 0.043). Only one subject (5%) remained symptom‐free when challenged with the Elstar apple, whereas 43% did so with e‐DR1 and 63% with e‐DR2.
Conclusion
These data show that mRNA silencing of Mal d 1 results in a marked reduction of Mal d 1 gene expression in the fruit and reduction of symptoms when these apples are ingested by allergic subjects. Approximately half of the subjects developed no symptoms whatsoever, and virtually all subjects wished to consume the apple again in the future.
•Experimental results of a novel rotary active magnetic refrigerator are obtained.•Experiments are compared to predictions from a 1D numerical AMR model.•Performance is evaluated considering ...parasitic losses for a range of conditions.•A cooling power of 200W is produced at a span of 16.8K with a COP of 0.69.•The attained overall second-law efficiency is around 5%.
Performance results for a novel rotary active magnetic regenerator (AMR) and detailed numerical model of it are presented. The experimental device consists of 24 regenerators packed with gadolinium (Gd) spheres rotating inside a four-pole permanent magnet with magnetic field of 1.24T. A parametric study of the temperature span, cooling power, coefficient of performance (COP) and efficiency of the system was carried out over a range of different hot reservoir temperatures, volumetric flow rates and cooling powers. Detailed modeling of the AMR using a 1D model was performed and compared with the experimental results. An overall mapping of the thermal losses of the system was performed, and good agreement between the experimental and numerical results was found when parasitic heat losses were subtracted from the modeling results. The performance of the system was evaluated via the COP, the exergetic-equivalent cooling power (ExQ), and the overall second law efficiency, η2nd. Losses mapping indicated that friction and thermal leakage to the ambient are the most important contributors to the reduction of the system performance. Based on modeling results, improvements on the flow distributor design and reduction of the cold end thermal parasitic losses are expected to enhance the efficiency of the system. For an operating frequency of 1.5Hz, a volumetric flow rate of 400L/h, a hot reservoir temperature of 297.7K, and thermal loads of 200 and 400W, the obtained temperature spans, ΔTS, were 16.8K and 7.1K, which correspond to COPs of 0.69 and 1.51, respectively. The maximum overall second-law efficiency was 5.6% for a ΔTS of 12.9K at 500L/h and 400W.
We estimate the social benefits of homeownership using an exogenous instrument based on randomly assigned treatment status from a field experiment that subsidized saving for home purchase for ...low-income renters through Individual Development Accounts (IDAs). This approach attempts to eliminate the potential correlation present in previous analyses between unobserved individual characteristics leading to homeownership and traits leading to provision of social capital or local amenities. Consistent with previous work, we show that homeownership positively affects political engagement in simple probits. Instrumental variable probits, however, show no impact of homeownership on political involvement. IV results for other social outcomes are less conclusive. The analysis suggests that with the use of an exogenous instrument, it is possible to generate results that are different from the previous literature. Our results also suggest that being eligible to open an IDA did not spur households to provide more social capital or local amenities.
PDF
